By popular demand, here is a new thread devoted to PETTaLS flat panel speaker simulation software, developed by Dr. David Anderson. Flat panel speakers may also be referred to as bending wave speakers, or DML speakers.
Let's use this thread to discuss topics specific to the use of and improvement of this great new tool. Topics could include, but are not limited to:

• new release announcements
• questions about how to use it
• features you'd like to see
• possible bugs
• interpretation of results
• other....

The free version of the software is available here:

PETTaLSFree

Some videos about the software are here:

PETTaLS Videos

Eric

Look at these two circuits. They do the same.
The difference is the single and the dual supply.
Another difference is the capacitor C1 and C3.
Because the negative voltage at input pin C3 should be put 'upside down'.
This goes for all bipolar opamps with NPN input transistors.
And when using dual voltage supply.
If a bipolar opamp has PNP transistors input the C3 should be turned the other way.

Since I have to solder something and it's not easy, my thoughts fly to the new DAC. I know that I'm embarking on a big project, so I'm starting from scratch, from making a PCB, rectifier, regulator, analog stage, digital inputs. I already have the complete analog stage and power supply solved from previous DACs and that's no problem. The analog stage with tubes is not a problem either.
The problem is which new generation DAC to choose, AKM or ESS, ESS is easier to implement, but I've got my eye on the AKM AK4191 and AK4499EX.
And one more thing bothers me, will this be better than the old school, specifically the eight PCM1702s that I'm playing now?
This question is difficult to answer, I know. To me, the old school sound is somehow more natural and pleasant, closer to analog sources. But I also know that the new generation is often built only according to instructions from DS, I have not seen any sophisticated regulators and analog stages in practice so far.

Hi all
some years ago I built a couple of 2 way speakers based on mid-woofer SB17NRXC35-8 and a tweeter SB26STC-C000-4.
The cabinet was sealed with a volume of 15L
I enjoyed a lot them, but I feel that bass are too poor. So I decided to realize a new project 3 way that is an extension of that one.
I'm evaluating 2 sub-woofer: SB26SFCL38-8 or dayton sd270a-88 (the first one to be preferred bcause it is 8 ohm).

I designed the cabninet, all SPL response and the crossover. My only problem is that the final impedence seems too low (about 2 ohm expecially at high freq) and I'm not able to adjust it. I tried with LPAD, but I'm not so familiar and I was not able to reach good result.

Can someone help me?

Hello diyers,
I've been playing sub-less for few months but with time I realised I was really missing a clean first octave.
My boxes are not able to go very low, it's 2x 15OB350 per side in around 200 L.
They can go low with EQ of course, but they just sound better crossed around 35/30hz, lower is just noise.
Don't know if it's the drivers high fs/qts, the "still" too small boxes or maybe not strong enough, or the room placement, probably all combined.
I see them more as big mid-bass in fact.

I had in mind to upgrade the drivers at one point, for the nero-15sw800 that should better fit the needs, but even if they're not that expensive it's still four of them that I'd need. And more important I'm not 100% convinced it will be a big improvement due to the mains placement.

So before going there I have to try spread bass again, within following constrains:
1 - nice look and integration with furnitures
2 - high sensitivity
3 - critical damping if possible

#2 means big drivers, I still have my four 18sw450 from my previous dipole, why not using them?
#2 and 3 kind of go together, but against #1 for the size implied.
#3 is a way to finally decide for myself if an L/T box can really sound the same as a big natural one (and I believe not, but lets' test).

I started with what I had around and within the new room layout constrains, with a sealed um12-22 in maybe 100-120 liters (much bigger in real but with sand walls) right behind me.
Not bad at all but not enough juice, plus it's not easy to nicely integrate with the furnitures.
I couldn't try my old concrete ported one as I got rid of it few months ago (and for that I had to destroy it in place, too heavy to get out 😛). I don't regret, it stayed for years unused in the same spot, it was fun to build, but also just too bulky, and too hard to move around to test different spots.

So, I had to find a way for 2-3 subs, placed behind me, light enough to move around a bit, but big enough to not require an L/T, easy?
Thought about it few months ans was about to buy woods when… again my favorite/hated shop just launched a new serie: the rådmansö.
Beautiful pieces in my mind, I would have loved to start with these when I've built my mains, a lot of cool stuff could be built around them.
Went to see them in real, and realised even the big one could do it, this one, 159x64x46cm, 468L. :




Got one, some mdf, some valchromat and let's go.
Like previous stuff I've just built a box within a box, 18mm glued all around inside, 24mm for the back, half the baffle doubled in valchromat, bracing with scraps, kind of light. The good surprise is that the radmanso is full particle boards, no honeycomb core on this like on many others, so nearly 4cm thick particles + mdf at the end.
The baffle is removable so I could add more bracing later if needed (I already found a spot that may need it).
And I could try 1 or 2 drivers, even clamshell isobaric if the box is still not big enough 😛
It's around 330-350 L. I'm guessing. Yes I did some sims but, they're just sims…

I of course did few mistakes again, my very first move was one! While sanding the inside of each panels for better glueing, I messed up and sanded the wrong spot of the panels, the edge that would have been visible outside. So I couldn't get the recessed baffle like I initially wanted.
Damn' what an idiot. So the baffle is now flushed, I'm sure it would have looked much better with the recess (like the mains).
Maybe I'll add a fabric grill, I'll see, it's fun to see the big driver too.
Then the valchromat was finished with tung oil, for a nice dark contrast.
Some details are left for later like the right cable, neutrik connector, better driver screws, replace temp wheels once in place to decouple a bit etc.
Not sure I’ll use the original steel stand that comes with it, it’s sturdy but will add 20cm in height.




I quickly plugged one little fosi on it yesterday and it seems promising, efficient for sure.
I hope I can move it in the right place soon to measure it.
Meaning right below the diffusors behind me, where I now have a bunch of besta used for storage.

In all this I kind of try to find the same effect I had in my car years ago. I might repeat myself but it was so fun with 2x15'' at few cm right behind the head. Breathtaking was the right word, literally, and I'm not talking SPL, just air movement in your lungs even at low levels, like someone with a pump trying to empty your lungs at every beat!

Of course home environment is a total animal but if I can get 10% of this I'd be happy 😛
Will come back with measurements soon, if a success I will build another one, and maybe even 3 in total.
Cheers!

Discussions about 6KV6 and/or 6KM6 pop up here and there from time to time.
What I haven't found yet is an example of this tube being used successfully in a SE triode amp.
So what's the (preliminary) consensus on how to best use them?
Appreciate your input.

I want to buy 2 prasis crc pcb with lt4320.

This is a long thread with many twists and dead ends. Before diving in, take a look a this first:

• The documentation files of the finished Open Source Monkey Coffin loudspeaker. I am (trying to) keep this up to date!
• The notes at the end of this post, which have some useful hints to navigate the thread.

-----------------------------------------------------------

Following up on the earlier Open Source Speaker thread (part I and part II) I am starting a new thread to discuss the develpment of the "Open Source Monkey Coffin".

Here's an update of my earlier Monkey Coffin ideas. Sorry it's so long.

POINTS OF DEPARTURE (as I see them):

• The first poll says it should be a three way, and it's okay to cost more than $500 per box.
• The second poll says that the Monkey Box should be "amplifier friendly" (work well with ACAs or small tube amps, etc.), and it should not be too big (not more than 60-80 L).
• The speaker should be straight forward to make for DIY novices (we don't want to scare them, we want them to run to the hardware shop and build stuff on their kitchen table). There is no point in designing for expert builders, because they will design their own speakers anyway.

MY IMPLEMENTATION IDEAS (I admit these are partially biased by my own preferences, because I need some motivation to actually put some work into this):

• The box shoud be easy enough to make on a kitchen table. Dimensions roughly 30 x 65 x 30 cm or so (will depend on the requirements of the drivers and box tuning).
• For "weak amp compatibility" I set the efficiency target to 92 dB/2.83V/1m, with bass extension to 45 Hz (-3 dB). Achieving this will not be very easy.
• The impedance curve should be flatish and qualify as "8 Ohm". This means we can't "cheat" with the efficiency target by using low-impedance drivers.
• Use high-quality drivers/parts with the right tech specs for the task. The look of the drivers has to be "right" for a HiFi system in a home environment, but is second priority after the tech specs (people may not want to build a speaker that does not look "right").
• Woofer: The woofer will likely be the limiting factor that determines the size/bass-extension/efficiency compromise. I guess a 10" unit would be the right choice here. The earlier threads already mentioned a few units that might be interesting for this design (Fane Sovereign Pro 10-300SC, Ciare FXE 10-2.5, Volt BM251.3, some Beymas, etc.). We'll have to look at this some more.
• Midrange: Needs to keep up with the SPL requirements, so many of the conventional "HiFi" midranges are out. I have some experience with the ATC SM75-150 dome, which is VERY good, expensive, and not available to DIYers anymore. When ATC stopped selling to the DIY market, Volt released the VM752 dome, which is a very good clone of the ATC driver. I really want to use the Volt VM752 dome. It can be used from its fs (400 Hz) up to about 3 kHz or so.
• Tweeter: There are many good tweeters out there. I am a big fan of Be dome tweeters (ScanSpeak D3004/6640, SB Acoustics Satori TW29BN). I also read a bit about waveguides, which do good things. They help with matching the dispersion of the tweeter to the midrange, they reduce the effects of baffle diffraction, they increase the on-axis efficiency, and they reduce non-linear distortion of the tweeter (by reducing the drive voltage for a given SPL). At the moment I can't think of a reason why we should not use a waveguide.
• Cross over filters: the x-over frequencies will depend quite a bit on the driver choices. However, if possible, I like to set the woofer/midrange x-over frequency such that it fits the baffle-step centre frequency. This makes it easier to compensate the baffle step by fiddling with the woofer SPL vs midrange SPL. If the drivers allow, I like using 6 dB/octave filters because it's easier to get the time-domain response of the loudspeaker right. In my experiments, my ears preferred 6 dB filters over 12 dB filters.
• I will openly admit that costs are not my first priority. If the right parts cost a lot of money and there are no alternatives, so be it. The earlier threads indicated that it's ok if the parts cost is more than $500 per speaker. Some said $1000. My priority is to make this a very good speaker, and suitable parts may cost a bit of money. In the end, there will always be substantial flexibility with costs related to x-over parts and enclosure materials + finishing.

NEXT STEPS AND QUESTIONS (everyone has his/her own approach to loudspeaker design, but here's my suggestion):

• In the first step we'll have to narrow down the driver choices. This will be a forward-and-backward process between driver suggestions and model runs using these drivers, always keeping the design targets in mind. I'd suggest choosing a woofer first, because that will define the box size, bass extension, and sensitivity. Let's say the midrange is set (yes, you are allowed to complain, but... ). The tweeter comes last.
  Question: What input data do we need for these model runs? Do we need actual measurements of the drivers in their baffle/box? I am not big with modelling tools, and I tend to replace detailed model runs by measurements from prototypes. Others might be more efficient than this by using their modelling tools.
• The second step is to build an actual prototype. Now we need money to buy parts. If the design is still attractive to me (i.e., it's something that I'd like to build and use myself), I'd be willing to put in some money and go for it. I could also do measurements.
  Question: How will the funding work? Anyone experienced with raising and managing money for open source projects? Anyone willing to put some cash on the table? Who will manage the money, and how?
• The third step is to tweak the prototype. Again, this will be another forward-and-backward process. And we may need more money.

---------------------------------------------

Notes and updates:

Important note 31 Oct. 2019: DIYers may profit from this open-source project for their own private purposes, for example by building and enjoying a copy of the Open Source Monkey Coffin speaker. Please do not use the information developed in this open source project on a larger scale (for example by selling speakers based on the Open Source Monkey Coffin design or substantial parts of it) without written permission.

Note 4 Oct. 2018: This project has received financial support from LORDSANSUI, Paul Vancluysen, George Wright, KaffiMann, Charles Bueche, zimmer64, John Barbor, and others (anonymous) here. Thank you!

Note 10 Nov. 2019: This project has come a very long way, and the OSMC design is now completed. The design goals have been largely met, but some of the early implementation ideas have changed a bit along the way (x-over topology, woofer size, tweeter details). The full documentation of the OSMC design is here: https://github.com/mbrennwa/osmcdoc

Note 4 Oct. 2018 and 18 Nov. 2019: Final choice of drivers:

• Tweeter: ScanSpeak R2904/7000 ring radiator (post 295 and follow ups) with a custom waveguide as described in post 881 (available via group buy or by DIY 3D printing or CNC machining).
• Midrange: Volt VM752 3" textile dome
• Woofer: FaitalPRO 12PR320 12" paper cone (see post 162 and post 244).

Note 18 Nov. 2019: Final enclosure is in post 925 (drawings) and post 930 (photos, showing stuffing).

Note 18 Nov. 2019: Final x-over is in post 931.

Note 18 Nov. 2019: The polar response diagrams (horizontal and vertical) are in post 895.

Note 18 Nov. 2019: The power response is in post 901.

Note 18 Nov. 2019: The electrical impedance is in post 900.

Note 19 Feb. 2020: A bunch of graphs with test results as compiled from the documentation on GitHub (on-axis SPL response, step response, polar response, cumulative decay spectrum (CSD) are in post 917.

Note 9 May 2020: If you don't know where to look, here's a list with some shops and retailers for OSMC parts:

• diyAudio group buy for the OSMC tweeter waveguides
• Falcon (Europe): Scan 2904 tweeter, Volt VM752 midrange driver, x-over parts, etc.
• Solen (Canada, US): Scan 2904 tweeter, Volt VM752 midrange driver, x-over parts, etc.
• Audiohobby (free shipping everywhere!?): Scan 2904 tweeter, x-over parts, bass-reflex ports
• US Speaker (US): Faital 12PR320 woofer
• Blue Aran (Europe): Faital 12PR320 woofer
• Acoustical Surfaces (US): Melamine foam. Contact person: Tom Ewert +1 (952) 466-8229. They also sell in small quantities!
• Ebay: Melamine foam
• Buttinette (yes...): lambs wool
• Deer Creek Audio: Custom speaker stands

Recently @hifijim started a new project involving the Bliesma T25A tweeter, as part of the discussion I offered to see if a simple small waveguide could be simulated. Jim has decided against the use of a waveguide for perfectly understandable reasons. I don't have a T25A myself and so I haven't created a printable model of the profile to test. There was some interest shown in that thread for the waveguide profile to be posted in a separate thread, so here it is.

The Bliesma aluminium drivers are very tall and require a different profile than many modern waveguides aim for in order to avoid ugly cancellations in the very high frequency range. I tried a number of variations on a theme in Ath to see what I could get, but it was not easy to find a profile that did not have some kind of downside to it.

I've simulated many CAD drawn profiles for the T25A in the past and so that is the route I tried next. This should hardly come as news or any kind of discovery as it has been known for a long time that dome tweeters almost always work in a waveguide that uses a section of a circular radius for it's profile. This does not have as dramatic of an effect on the directivity as OS or other proflies can have, but it is that property of not doing too much that allows it to work almost as a universal profile.

It is very simple to draw in a CAD program. I use Fusion and will outline how to use that program to draw it, but the principal could be applied to any other program.

This waveguide is thin at 6mm and relatively small at 104mm in diameter, similar to a standard tweeter faceplate.

I first draw a circle on the XZ plane that represents the throat, in this case it is 29.7mm, using a slightly higher value of 30mm might be preferable depending on the properties of the material being used to print it.



A new sketch is drawn on the XY plane and the previous circle is projected into this sketch. I draw a construction line straight up at the depth of the waveguide in this case 6mm. I then draw another line across at a 90 degree angle the distance of half the overall diameter in this case 52mm. I then draw a 3 point arc between the projected throat, the outer point of the waveguide profile and the last point just needs to be below the top construction line. With practice you can place it so that tangency is already enforced, but if not use the sketch constraints to make the 3 point arc tangent to the top construction line. You can check if this has worked by extending the arc all the way around until it becomes a circle. In this case the 3 point arc as drawn has a radius of 118.01mm.




The centre point of the circle that is the radius can be see by zooming out the sketch, it is highlighted in yellow



The same principal could be used to create a deeper and larger version of the same thing, there will then be a bigger effect on the overall directivity. This may not be a good thing for the T25A, but if the same ratio is kept between depth and outer diameter I would imagine it could be scaled up without creating negative interference. I haven't tested this so I cannot say exactly what will happen.

I have attached the surface profile as a zipped step file in case anyone wants to use it as is to create their own printable model.

I have attached the simulation outputs based on Jim's baffle. It is more consistent and even than a bare driver and given the size constraints, it fit's on the same diameter as the driver or can be made to. These are non normalized and show 1500 to 15K 0 to 90 degrees in 10 degree steps. The response is pretty much within 1 or 2 dB 0 to 40 degrees and is an even 10 dB down across the board at 90 degrees vs 0.



There is diffraction on axis because this is a BEM model with fully reflective boundaries. All sharp edges and creases on the baffle of which there are a few that are also symmetric show the worst case scenario. A real wooden baffle with smoothed edges and a less symmetric profile would offset this to some extent.



By 15 degrees off axis the response is a pretty smooth downslope

Im looking at building this Class AB1 cathode biased amplifier based on this design here.
I have most of the components on hand, including a suitable power transformer and pair of OT's.
I am making a few changes, I am using an EF37A/6J7G instead of an EF86 and using 807 tubes instead of 6L6.

Few questions, is the 750pF capacitor across the CT to anode on the tube to remove oscillations? I find its odd only one half has this, ive never seen this before on such a schematic.
There is also an 820pf cap going across for the NFB loop, how critical are the values for these capacitors?
I have quite a bunch of silver mica caps on hand but nothing quite exact, ive got a few 680pF and 1000pF on hand if they will suffice.

Here is the schematic and a rough layout ive drawn of the turret board.
Another issue im unsure will be a problem is i mirrored the layout, so have to cross some wires over, not too sure if this is a worry, you will see what I mean with the channel on the left of the image.
The phase inverter was not too big of a deal, as i just swapped over each triode section.
Im unsure about the path of the heater wiring, but its just rough, I will probably move the tube sockets around some more and I have not included the power supply yet, but all the transformers will sit behind the 807 tubes at the bottom of the image. The filter choke im hoping will fit under the chassis.

I've been working on a bass 8k (power supply seems identical to MD8000.1 so I've been browsing repair posts for those as well). I've replaced IC9, IC3, and IC1 and any accompanying SMDs that needed replaced. I replaced both power supply, output fets, and gate resistors. With the rectifiers pulled to isolate the power supply I can't get it to build a square wave on powerup. IC1 builds a perfect 40khz square wave, IC3 not so much, it tries to build a very odd signal initially and then goes flat once the amp goes through it's power up cycle. While testing R150 went up in smoke. I'm running out of ideas and looking for some guidance. I will be buying Perrys book as soon as I have the funds as well

Any help is greatly appreciated, I have a lot to learn and am very appreciative of any guidance and tips. Thank you!

As the title states, this is a thread dedicated to dome midrange drivers, specifically any larger dome driver at least 50mm or 2" in diameter intended to be used in a 3 way or larger speaker design.

Being there isn't a good collection of data on this rather rare type of driver and its use, it would be nice to have it all in one thread. My goal was to give anyone interested in the successful design of a speaker using a dome midrange a solid starting place to gather or share the info necessary to design a new speaker or to modify an existing design to use them ie. xover, baffle modifications, etc.

If you have any specific or technical info (measurements, graphs, data, xover design, pictures, links etc) regarding your favorite dome midrange or a specific technical question, please feel free to share it in this thread.

Please keep your post to the point and avoid any strong subjective opinions. I was hoping this thread could accumulate as much relevant info as possible. Thanks in advance for any productive shared info.

When I was young, we spent hours on end playing what we called word game. Same rules but it was always 4 letter words.
I was introduced recently to this new sensation and tried it today. Now I know it's beginners luck, but first time out I got it in 3 words.
I think I'll try again and let it bring me back to earth.
Who else is doing this?

Does anyone have a schematic for the Foster (also called Fostex) LC300 3 way crossover? I have a pair of Goodman's speakers with the Foster crossover. I want to rewire the speaker and don't know which connections go where.
Thank you

Ian

Hello everyone,
I hope you're all doing well.
I have designed a 4-way passive crossover network and would like to kindly ask for your expert feedback and suggestions regarding my design.

Here’s a brief overview of the system:

Driver Units

• Tweeter: Accuton C25-6-158
• Midrange: Accuton C90-6-079
• Midwoofer: Accuton C173-6-191E
• Woofer: Accuton C173-6-191E (second unit)

Target Crossover Points

• Woofer: Below 370 Hz
• Midwoofer: 390 Hz to 707 Hz
• Midrange: 681 Hz to 2.8 kHz (smooth handoff)
• Tweeter: Natural extension beyond 2.8 kHz

Design Approach

• Crossover points were calculated based on classic LC filter theory.
• Fine-tuning of slopes, impedance compensation (Zobel networks), and component values was supported by AI (ChatGPT) consultation.
• Emphasis was placed on achieving smooth frequency response, phase coherence, minimized distortion, and high-end performance characteristics.

Additional Notes

• Zobel networks were applied where necessary to ensure impedance flattening and better load behavior for the amplifier.
• The goal is to create a system that combines precision, natural tonality, and audiophile-grade resolution.

I would greatly appreciate any feedback, suggestions for improvement, or critical insights you might have regarding this design.
Thank you very much for your time and expertise!

For Sale, pair Acoustic Elegance TD-12M midbass drivers in good contition with boxes.
Price 800 Euros, plus shipping. Only EU please.
https://aespeakers.com/shop/td/td12m/

So I have been playing with some "old school amps" or so I thought. A older friend of mine tells me of a Fosgate amp he has stored and ends up bringing it to me. Holly crud! I don't know old school since it sure is not around the late 80-90 range, it's the mid to late 70's!

Anyway, I took covers off and took pics and measured power and ground leads and seem plausible. The speaker outputs all measure about 42ohm and that waved a flag to me. Sounds way too low. I studied up on how to power the amp up using a current draw on the red lead and it is cycling on/off about 2 cycles second. This is just like my friend told me it was doing when he tried it on a power supply years ago. He said it would play but only would stay going if kinda loud and would cycle if played at low volume, from what I recall from speaking to him. I was in shock after all. I did not hook up to a speaker or take any voltage measurements on the speaker leads yet as I am a little nervous with this rare amp. I thought it best to just go straight for some advise.

I tried powering with both a car battery and power supply combined and same result as just my 30amp power supply.

Hi There
I just did a recap job on the Amp a couple of days back. I put it back together last night.
The Amp is going into protect when I turn up either of the volumes. Seperately. The fans speed up aswell.
I'm only turning them up one or two notches.
They come out of protect when I turn them back down. The fans slow down too.
I'll try again tonight and see exactly what its doing. Lights etc.

I'm waiting on some BNC male plug to Banana plugs so I can use my scope leads with my multimeter.
A lot safer for testing. I can use the 10x aswell.

If anyone has the proper CA4 Schematic it might be of help. Ive got most of the other ones.
Cheers

BTW. The Amp was known to be going into protect before the recap. I just didn't test it beforehand.
I was under the impression it was in Protect full stop.

I have been an audiophile since my youth. First good diy speakers were Wharfedale Unit 5 three ways. Great with my Lenco L78 and Goodmans 110 receiver. Progressed through various speaker builds. A nice one was a Proac R2.5 clone but my favourite so far is a Falcon kit for my T27/B110 Kefs from the seventies with a matched to serial numbers crossover. Also done some amp building , SunAudio 300B and SunAudio pre amp, as well as OTLs from Bruce Rozenblit.

Here is a PDF of of the Pearl 3 from Burning amp 2023 for those of you whom already have circuit boards.





EDIT: Video presentation on Pearl 3 for BAF '23 can be found here - https://burningampfestival.com/videos/


EDIT: Build documentation "Pearl 3 Phono Build Doc-1.0d" is attached below. Version 1.0d is the most current. Download and print.


EDIT: Interview with Wayne about Pearl 3 - #881

EDIT: Modushop/ HiFi200 Chassis set available here - https://www.diyaudio.com/community/threads/pearl-3-burning-amp-2023.404054/post-7538807 https://modushop.biz/site/index.php?route=product/product&product_id=971

EDIT: Online build guide - https://guides.diyaudio.com/Guide/Pearl+3/28

EDIT: SMD soldering tutorial using Pearl 3 - Login to view embedded media

USSA-5 build and review:

Amplifier Design/layout: Fab (The Great and Powerful Ape)

Amplifer PCB Layout: Alex

PSU Design/Layout: Project16

PSU PCB Production: Prasi


I couldn't stop thinking about this amplifier. The obsession began with a few fleeting traces of it's existence. The few members that have actually completed it were mostly silenced by its greatness. When I had enquired about it, people simply said "Oh, the USSA-5? It's the best amp I've ever heard."

I had to build it. But, the great mind that designed the amp wasn't going to just give me the boards. I offered to build a children's wing at his nearest hospital in his name. He said no. I said I would make huge donations to wildlife preserves around the world. He still said no. He was like talking to Willy Wonka and I was Charlie Bucket. I needed a golden ticket....

In the end, what worked was honesty and a promise to do two things: to build the amplifier and write a review.

So, here it is.

Hey all, I have this nice Magnavox 138BB tube amp that I use as a Guitar amp (stock) and driven with a Joyo American Sound pedal/preamp. Works ok, but not very loud...so I added a LND150 Gain stage in front of it. Now plenty loud but has quite a bit of hum...sounds like 60hz... I like this setup....pushes the 6V6 nicely.

The 220 ohm source resistor leaves me with around 125vdc at drain (1/2 B+), so I think the LND150 is biased correctly....but would like to reduce the hum... any advice? Thought of reducing the R2 from 1M to 470k....

I am "stealing" B+ from the two high side of the 470k anode resistors in maggie amp.

Without the LND150 circuit, no hum at all...

I got this amp with the power supply and output sections both having blown fets. I replaced the fets and now when I power it up the power supply starts fine for the first 3 seconds Drawing .4 amps. But when the output stage kicks on the amp draws current for a tenth of a second and the output side shuts down. And keeps cycling this way

Dissected, but far from dead:
Here lies the nerve center of an essentially brand-new Technics SL-100c:



So... Where to begin?

Browsing eBay on a recent evening, I ran across a listing to the effect of, " !!PARTS!! Technics SL-100/1500 Tonearm, Platter, Motherboard, Otherboard. "

Okay, uhhh... [clicks mouse]

As advertised, the seller was parting out a "damaged in shipping" 100c that he'd purchased "as a return." After some back-and-forth, a story emerged: Apparently someone bought this $1k+ turntable on Amazon, stripped off the stock cartridge and then returned it in the original box (minus most of the original engineered packaging). As many likely know, there's sort-of a supply chain purgatory where (literally) billions of returned items languish for long periods before being either bundled and resold or trucked off to a landfill. Never did I imagine those items to include things like brand-new turntables with ultra-accurate coreless motors that hifi mags have been raving about.

According to the seller, the unit was basically loose in the box and took a beating in transit: Dustcover destroyed, tonearm badly damaged, chassis cosmetically irredeemable, and... motor working perfectly. Unable to stop myself, I bought the motor, platter and everything you see here for a few hundred bucks.

Why tho?

Well for one thing, I've since confirmed the performance: Assembled with the motor just sitting on my desk, the RPM iphone app shows the platter running at 33.34 +0.03, w/f 0.15% (and even better at 45). That DUSTS the belt-drive deck I spent a mint on five years ago (which frankly leaves me wanting in other ways as well). More than anything, I just want to get my hands into this. I lust after classic broadcast decks, and have long wanted to join the SP-10 club (yes, I've spent a lot of time on The Incredible Thread). But for a lower price-of-entry, and given the specs above, this seems like a pretty cool alternative challenge.

And before anyone asks: Yes, I'm a bit out of my depth. I know this will cost more than I think. I don't yet have all the tools I'll need. There will be massive research and a lot of trial and error. I know there's a lot I don't know, and I'm prepared for this to take a long time.

So all that said, this thread will serve as the build log.

It's getting late, but at some point over the weekend I'll post my progress so far, my overall plan, anticipated next steps, and a few questions for the forum.

Really hoping a few of Technics Heads (and other experienced folks) will vibe with this project, follow and advise.
Cheers!

The Iron Pre is now listed in the diyAudio store for anyone to purchase.

Until the 'Build Guide / Build Thread' is created, this post will contain all current schematics and notes for the Iron Pre sold through the diyAudio store. Check back frequently to ensure you have the latest files.

Sep 14 2023 - Below is what you're waiting for! See some awesome information and help from 6L6 on the SE build. A new thread and the guide using the web interface will be posted ... soon. Post #2291

Background

Hello Happy DIYers / Greedy Boyz!

I am thrilled to announce that Zen Mod's Iron Pre essentials kits will be offered in the DIYAudio store. This is not a group buy. You can learn more about the project in the thread linked below.

https://www.diyaudio.com/community/threads/whats-wrong-with-the-kiss-boy.293169/

Highlights include matched Toshiba JFETs from Nelson Pass and high-nickel CineMag transformers. 6L6 has volunteered to post one of his incredible build guides also.

If you're a Smiths fan, you may ask, How Soon Is Now? They should be available for order before the end of the year. At this time, we have enough parts sourced for 100 SE and 50 balanced kits.

The next obvious question is, how much? Costing is not final yet, but the goal is $100 for the SE kits and $125 for the balanced kits; a tremendous bargain. We have contingencies for all the parts, and we hope that this will be a permanent addition to the store. However, for now, we can only promise what we've got. Get 'em while you can.

Click the link below to see what will be included in the kit, answer a few questions about what you might like to see in the future, and get on the list.

Note - The n-channel JFETs will be 2SK370.

Quick and Dirty Startup Process

This happens after: the boards are stuffed, the AC supply is verified and connected properly, and I/O has been connected. Nothing needs to be shorted. Note the additional step for the V4 SMD version.

1. Set V+ and V-
   
   Adjust P1 and P2 for each board until V+ is +15V0 and V- is -15V0
   
   GND, V+ and V- pads are clearly marked on PCBs.
   Do not move forward if you cannot adjust the voltages to within 0V1 or if the voltage seems unstable.
   
   
2. For V4 SMD Only- Set current through JFETs
   • Set DMM to DCmV.
   • Place probes across R34 and R37 for SE or R40 and 41 for Balanced. You can also use square pads / test points near resistors.
   • Turn P4 and P6 respectively until DMM reads 14mV +- 0.05mV - See schematic.
3. Null DC offset
   • SE
     • No jumper caps in place for JP1 or JP2
     • Measure at center pin of JP1 and JP2 NOT between those two pins*
     • Turn P3 / P4 (V3 and earlier) or P3 / P5 (V4 SMD) respectively until voltage shows 0V +- 5mV
     • Cap the jumpers for your choice of gain.
   • Balanced
     • No jumper caps on JP+ or JP-
     • Measure at pin 1 of JP+ and JP- NOT between those two pins*
     • Turn P3 / P4 (V3 and earlier) or P3 / P5 (V4 SMD) respectively until voltage shows 0V +- 5mV
     • Cap the jumpers.​

Updates

4-May 2023

Edited 7-Aug 2023. All in-line photos have been removed. Please see attached files for all documentation.

5-May 2023

Updated Single-Ended BoM to correct 330R part notations in the gain stage to R28 and R29.

Attached are the Bill of Materials / Parts Lists - Note File Names for Balanced and SE

26 - May 2023

Updated SE and Balanced Bill of Materials to indicate that snubber components should not be installed.

Balanced BoM Filename - BOM_Store_Iron_Pre_Balanced_Dist_v5.pdf
SE BoM Filename - BOM_Store_Iron_Pre_SE_Dist_v5.pdf

27 - May 2023

Updated SE and Balanced Bill of Materials to correct and clearly note which diodes should be installed for input switching.

Balanced BoM Filename - BOM_Store_Iron_Pre_Balanced_Dist_v6.pdf
SE BoM Filename - BOM_Store_Iron_Pre_SE_Dist_v6.pdf

1 - June 2023

Note - No changes required. However, the packing lists some of you will receive may note LM336-5.0. That was a typo; apologies. The correct parts (as supplied and noted in the BoM) are LM336-2.5.

Removed the link to sign up indicating interest in kits. Those currently on the list will get first priority for the next round of kits. After that, they will be sold through the normal process through the store.

6 - June 2023

There are two gorgeous prototype chassis available; one designed specifically for SE, and one for Balanced. You can find some details in post #431. The depth for both chassis is 280mm. There is additional information sprinkled throughout the thread re: acceptable sizes and some potential part numbers for IECs, input / outputs etc. along with pictures of some examples. Please search first before asking chassis questions, and I'd recommend using the latest posts' information. Again, they are prototype chassis, and anything could change at any time until the design is finalized. The best source of information re: the chassis is directly from Modushop until they are sold in the diyAudio store. Timing TBD.

8 - June 2023

Added parts placement and pcb layouts for those interested.

30 - June 2023

V7 - Minor Updates to BoMs. QTY added. Ensure to check quantity per board against the quantity you need for your project. Added links to a popular online website to show examples of parts that will work for the connection between the main boards and the twister boards for input selection / LED power etc. Added generic descriptions for those that would prefer to select their own parts.

1 - July 2023

V8 - Minor Updates to BoMs. Added heatsinks for M3 if 12V relays are used.

7 - Aug 2023

I'm excited to say that more kits will be available very soon for 'round 2'. Continue checking this post (as always) and the thread overall for up to the minute updates.

In his graciousness, ZM has made some minor running changes. Changes are:

• Updated transformer snubber circuit.
• Easier positioning / mounting of the CineMag transformers in some situations.
• Changes to allow easier use of some logic circuits for input switching.

Boards that include the changes will note "2023" vs. "2021" on the silkscreen. The Twister board accompanying the 2023 boards notes V.3. Both 2021 and 2023 boards are included with 'round 2'. You cannot choose which you will receive, and you will not know which you will receive until they arrive. Do not fret if you get a kit with 2021 boards. If you need to use a particular type logic solution, there is a very easy modification previously noted in the thread, and the snubber is not necessary. The changes made were a kindness from ZM, but all 2021 boards can be made to function just like 2023 boards with a few user-tweaks described in the thread.

Note - The attachments have been packaged and note which files to choose for the respective boards. Previous attachments and in-line thumbnails / photos have been removed for clarity. The BoMs have been updated slightly for clarity.

9 - Aug 2023

There is a minor error on the silkscreen for the boards marked Iron Pre SE Zen Mod Labs 2023. The polarity notation for C11 visible when the cap is installed is incorrect. Ignore it.



13 - Aug 2023

His Mightiness created two graphics for how to wire standard pots for both SE and Balanced. Attached.

29 - Aug 2023

Minor updates to balanced BoMs. Removed reference to D15.

31 - Aug 2023

Added wiring diagram for AVC for SE. See post #2113 for context.

21 - June 2024

All testing for the Super Mega Deluxe version is complete. Kits will be back in the store 'soon'.

25 - September 2024

"Soon" is relative. 🙂. SMD kits are on sale. The schematics and files for the Super Mega Deluxe (SMD) have been attached in their appropriately named .zip files. Enjoy your builds.

26 - September 2024

A few people purchased the "completion" kits for the V3 and earlier boards and were wondering if they could be used for the V4 SMD kits. A lot of the parts are identical, but below is what you'll need in addition and to swap a few parts.

For balanced you will need:
4x additional 825R or 820R resistors - I like these Vishay BC 825R
8x 58R or 62R resistors - I like these Vishay BC 62R
4x 1R resistors - I like these Vishay BC 1R
8x 100R trimmers - I like these Bourns 3296 Series 100R Trimmers
4x 1uF film caps with 5mm or 15mm lead spacing - I like these TDK 1.0uF with 15mm Lead Spacing

For SE you will need:
2x additional 825R or 820R resistors - I like these Vishay BC 825R
4x 58R or 62R resistors - I like these Vishay BC 62R
2x 1R resistors - I like these Vishay BC 1R
4x 100R trimmers - I like these Bourns 3296 Series 100R Trimmers
2x 1uF film caps with 5mm or 15mm lead spacing - I like these TDK 1.0uF with 15mm Lead Spacing

27 - September 2024

Some potentially helpful additional parts in post #3784. If people have more helpful suggestions, I can add them.

3 - February 2025

Added diagrams for setting buffer current in V4 builds.

Dear DiYA members, I have been fomenting this speaker project for the last month and submit the premilinary XO for anyone enjoyment and constructive/destructive comments. Thank you.

Who can remember listening with friends to Mortal combat song, and the unintelligible words:

Test your might, Mortal combat, sounded like : whowwoodtlungtodwwoooo (mortal combat) tksssssss yuourrrrr migshhhhht (test your might).

I have the following phase splitter designed for a 12AU7.





What components would I need to change for it to use a 12AX7 so it can drive a quad of 6V6 in push pull parallel unless with feedback I can get a 1V input sensitivity for 25 watts out with the 12AU7?

The 6V6 has a max grid resistance of 100k when operated fixed bias so the load on each output of the phase inverter will be 50k unless it's ok to use a single 100k grid resistor for two 6V6 in parallel.

I am back again with the same amplifier, my lovely Xtant X604.
Last time I was able to recover the functionality with your help (water leak). Now I discovered that my front left tweeter is not working and making strange sound (I am bi-amping the front end). So I popped the cover off, inspected for water leaks - didn't find any but found 2 burned resistors. One is R111, the other one has no reference designator but since it sits between R108 and R110 it is likely R109. Also did a search before making this post and found the schematic for X603 posted by Perry Barin. Wonder if Perry or someone else has the same schematic without additional markings written over it. Perry was wonderful helping me fix the amp last time I had a short due to water leak that formed crater in pcb (2021). Will try to dig into this tomorrow.

I realized that I have two ears, 4 speakers, and about 16 tube amps. So I want to get rid of some. I have them listed on eBay, but am happy to kill the listing(s) and sell them directly if anybody is interested.

More info on my website pmillett.com or you can see the listings on eBay:

https://www.ebay.com/itm/1674531214...M6XS4H&hash=item26fcfbdb83:g:xkoAAOSwtTVn~U7X

https://www.ebay.com/itm/1674532051...PK9TB0&hash=item26fcfd228c:g:c40AAOSwzxRn~V7T

https://www.ebay.com/itm/1568922170...BEWVJ2&hash=item2487813ee9:g:bMEAAOSwHN1n~UhC

Pete

Hello there and thank you for giving me access and any guidance you can provide. I came across a line array design that caught my attention and I would like to make a couple of them to see how it is. It has 1 x 6.5" and 1 x 8" and a driver. It does not say the size and the design does not explain if it is 2 way or 3 way, although I personally understand that the 3 way is more complete.

Hello all, I'm currently working on a SounDigital 2400.4 EVOX. Would anyone happen to know which output fets are used?

Back story: When powered up, the amp has no power light or rail voltage and smoke comes from a few pins of the SG3525a. When I remove the output card, the amp powers up with a blue light and builds rail voltage with no issue.

So the issue seems to be a short on the output card. All output fets don't appear to be shorted when checking continuity between the gates/drain/source, so I believe the issue may be the irs2052m chips instead. But I'm planning on replacing the fets as well while I'm in there. Thanks in advance

Feel free to use this thread to post your DIY efforts.

hello folks,
here is something i have been working on for some time.
I am willing to offer the pcbs as a group guy.
let me know if there is interest.
I will share a bom to GB subscribers, all mouser based, if GB goes ahead.
regards
Prasi

Edit 1: Group buy closed for THT PCBs, but still open for SMD PCBs. More info in the below link.
Group Buy List
group list qty_new - Google Sheets
Schematic SMD LT4320 rectifier LT4320 based active rectifier
Schematic THT LT4320 rectifier LT4320 based active rectifier
Schematic LT4320 CRC PSU PCB: LT4320 based active rectifier

Edit 2: Revision in prices. (price drop!)
LT4320 based active rectifier

Edit 3: GB closed for SMD PCBs. Only last 10 pairs of THT pcbs remain.

THT BOM BY MERLIN EL MAGOO LT4320 based active rectifier

EDIT 4: New GB for LT4320 based CRC PSU PCB Started..PCB's Produced and being shipped..-Completed and closed...
1. The Design: LT4320 based active rectifier
2. The PCB design: LT4320 based active rectifier
3. Physical PCB's: LT4320 based active rectifier
4. The BoM : LT4320 based active rectifier

EDIT 5: Group buy sign up has begun for modified SMD and THT rectifier boards with ENIG finish and earlier LT4320+CRC PSU PCBs. Please sign up at the below google sheet with your DIYA username and qty required against each pcb type.
LT4320 based active rectifier
Some 3D views of how the actual PCB assembly looks like
SMD: LT4320 based active rectifier
THT: LT4320 based active rectifier
CRC PSU PCB : LT4320 based active rectifier

EDIT 5: HAVE ALOOK AT PAGE 78 AND 79 FOR ALL PCB DESIGN IMAGES, SCHEMATICS AND 3-D MODELS AT ONE PLACE.

Announcement: Audio Widget project

The Audio Widget project is open-source code and schematics for
USB based digital audio. It has functional firmware and software. And
it sounds good!

Cool? You bet! Here you can get started with USB audio without
worrying too much about the USB part of things.

Or you can contribute to a great open-source coding project. The
most important contribution we could need right now is coders for
USB Audio Class 2 drivers on Windows. But other efforts are needed
too. See below.

The code is written in C for the Atmel AT32UC3A3256 32-bit MCU. It
supports USB Audio Class 1.0 and 2.0 (UAC2). On Windows / UAC1 it
works with 24/44.1 and 24/48 with sample skip/insert. Asynchronous
USB is in progress, and we could use your help.

On Linux (>2.6.37) and OS X, using asynchronous USB, it also
supports 24/88.2, 24/96, 24/176.4 and 24/192. The open-source
firmware is in a git repository. It can be selectively compiled to run
on the three different boards. The firmware includes several UI and
display options.

There are three hardware options. The hardware is in a beta state. It
plays music very well, but there is still tweak potential.


1) A stand-alone USB-DAC with stereo audio playback functions only.
This board uses the ES9022 DAC chip. Contact
george.boudreau@YoyodyneConsulting.ca for info on how to obtain
one. More information on the this and other audio designs visit
Yoyodyne Consulting/Audio Hardware

2) USB-I2S module + Analog Board. The module has all the pinouts you
need for digital audio, GPIO, I2C, SPI, LCD display and UART debug.
The module uses 2.0mm pitch pin rows. The Analog Board uses the
module to do stereo playback with an ES9022 DAC and low-noise
VBUS-LDO based power. AB-1 is a straightforward design to begin with,
and if you're into analog tweaking we challenge you to make your own
versions! Schematics and BOM are on
Downloads - sdr-widget - Audio and Control Interface for Amateur Radio SDR and Audiophile USB-DAC - Google Project Hosting.
Go to Q N K T C USB-I2S Module and Analog Board 1 for more information. Contact
borge.strand@gmail.com to obtain a kit.

3) SDR-Widget Beta 2.0. This is the original fork of the project,
open-source HAM radio. The hardware supports both playback and
record. Contact george.boudreau@YoyodyneConsultingl.com for info
on how to obtain one. Visit
Yoyodyne Consulting/SDR-Widget
for more information of pricing and availability.

For more information, go to sdr-widget - Audio and Control Interface for Amateur Radio SDR and Audiophile USB-DAC - Google Project Hosting
and
https://groups.google.com/group/audio-widget?hl=en
This announcement is cross-posted. Please join the mailing lists of
both SDR-Widget and Audio-Widget to continue the discussion there.

SDR-Widget is the original branch, where most of the firmware
discussions take place.

Feel like contributing? We'd always like to see more hands. There's
quite a few tasks planned:

- Firmware for Asynchronous UAC1 / Windows for 44.1 and 48ksps.

- Analog tweaks. Ideas are welcome for PSU, DAC, IVC, preamp etc.
Feel free to make suggestions, or even better, your own Analog
Board for the USB-I2S module.

- Windows open-source drivers for USB Audio Class 2.0. This
protocol is supported in Linux and OS X kernels, but not yet
in Windows.

- Adding more IO control to the firmware


Cheers,
Børge

Just checking if anyone knows what i can use for a replacement for a TC4427COA that's marked C2 on a Sundown SFB 8000D?

Was donated a pair of these today, Crossover attached
The woofer (2519Aa Japan) looked promising with a low Fs & Qt, parameters:
Fs 20.75; Re 7; Qe .38; Qm 5.53; Qt .35; Vas 142.38; Sd 314; Le .84; eff 87.6
did some sims, Woofer looks good in 60L (Optimus oix is 38L), tuned to 22Hz
all this fun & I haven't listened to them yet....

The Big Q: Do I restore them to original, or 'improve' them to my own taste....???????

Bugger, just realised I left the tweeter switch out of the xover diagram, give me a few minuets....

Han anyone else thought about building a La Scala type enclosure with different dimensions? I have a Joseph Crowe ES600 horn equipped with a SB Audience 65CDN-T compression driver and was planning to build a La Scala type bin but feel the ES600 would out of place with the 24.5 inch (62cm) wide box. So I thought I could maybe build a narrower and taller box keeping the same area for the throat an mouth. What do you think? Stupid idea? 🙂

Hello all
I have fallen in love with the Pearl Acoustic Sibelius but can't afford it.
Is it possible to clone it or build something similar? Please advice

A little over a month ago I mentioned wanting to start a new PCB for the F6 that included some common and not-as-common tweaks that have found there way into the diyAudio community. This idea received positive comments and launched two new PCB designs.
https://www.diyaudio.com/community/threads/zenductor.402522/post-7469793

Mikerodrig27 created the PCB artwork for two new variants, one with the standard JFet input stage and one with the Diamond buffer. I have had the PCBs for a few weeks already. It took some extra time to rebuild an old test bed to avoid a prominent 120 Hz hum. Plus I was away on vacay for over a week. All better now.
Cutting to the chase – The performance of the new JFet PCBs has exceeded my expectations. Soldering the green LEDs into the PCB has enhanced the function of their negative temperature coefficient (NTC). There is a more pronounced boost to initial bias current while the amp is cool, then the current drops as the amp heats up. The net effect is that the amp is effectively temperature stable after a half hour, and bias current does not drift appreciably after that.

The new PCBs are built around the Jensen JT-123-FLPCH signal transformers, as standard. We could entertain a dual footprint that included the Cinemag CMOQ series, but my listening experience so far has been wonderful with the Jensens. I don't have any info yet on the lower cost signal transformer proposed for the new F6m variant. I think we may leave that for the diyAudio store.
I chose to build the JFet input version first, with IRFP048 Mosfets. This turns out to be a great combination. I can highly recommend the IRFP048 for future builds by DIY enthusiasts. The store carried these for a while, and they are inexpensive and readily available from Mouser and Digikey.

I am making further mods to the power supply of my test bed and will post more on that and the listening tests soon.

I don't know if this guy's speaker will ever be marketable but he's got a playing prototype, and I've not seen anything like it before.

If I'm understanding the concept correctly; a typical digital audio setup recreates a music signal as a mixture of pure sine waves that mix and interact via the Fourier transform principle, and the mixing occurs within a digital processor, upstream of the power amp(s) and speakers.

In contrast; in this guy's setup the mixing of the component sine waves occurs at the speaker itself. That is; driving each speaker are twenty separate signal processors feeding pure component sine waves into twenty amp channels-- discretely driving twenty drivers in each speaker. As such, the Fourier transform occurs at the speaker itself, as the separate driver outputs blend together in front of the speaker.

That's a lot of digital processors and amp channels so even if this guy succeeds in taming all the gremlins, it's a complicated and expensive setup.

Enjoy!

Login to view embedded media

Rather than muddy my other speaker post I'll ask for answers here.
If I want to play "Mix&Match" with different boxes as Jeff talked about I'll want to put the XO in a separate enclosure and either use it as a base or as a divider and sit the second box on top.

Would the components get warm enough to need a ventilated box?
I've made standalone crossovers before but I've made those in old amplifier cases so I've never had to think about heat issues

Hello everyone,
I'm very excited to join this amazing community!


I have a deep passion for high-end audio design, especially DIY loudspeakers and crossover networks.


Recently, I designed a 4-way speaker system using Accuton drivers (C25-6-158, C90-6-079, C173-6-191E x2) and carefully crafted a custom passive crossover.
With the help of AI (ChatGPT) and thorough calculations, I tuned the frequency response and phase alignment for smooth and natural sound.


I look forward to learning from all the incredible experts here and sharing my projects as I continue to improve and enjoy this wonderful hobby.


Thank you for welcoming me!

Have made a TPA3255 board thinking it would be super easy to get working 🙄

But it will not start up, and I'm a bit stuck .....

There is oscillation on OSC_IOM/IOP, see oscilloscope picture.
Had made some stupid mistakes with the reset circuit, but have replaced it with just a blue LED and the 5.6k to 12V which was already there. This means I get 2.6V on reset which should be ok. When I short the LED, bringing RESET to GND and let go again, there is short action on the output surely trying to start up, but it stops right away.
I have put red numbers on the Schematics, for the measured voltages.

Fault is low, and Clip_OTW is high.
This should mean "Overload (OLP) or undervoltage (UVP). Junction temperature lower than 125°C" .... but where is the Under voltage?
Nothing is hot.

When reset is set to GND Fault goes high.

Any suggestions?

Thanks

Ive had my hsu VTF2 Mk3 forever and I kinda wanted something new. Bringing a whole subwoofer from the US (live in Brazil) checked in on the plane is a huge hassle. I know, cause thats how I brought my hsu sub back home. After online dating with Speedwoofers I've decided that it's easier and better to just buy the driver, amp (not sure if plate or external) and assemble it here in Brazil.

I was thinking. If I get a 150ish liters box (not counting the area of the driver itself, potential amp or braces might take), would that be enough for a good response? I live in an apartment, even my hsu sub never ever reached anywhere near its potential, so I'm really not looking to reach some crazy output. My goal is to have an agile that performs very well for music and can deal with a good range (20hz+) for movies and videogames. 18 inches may sound a bit overkill, but since I can't just swap the driver cause I have to fly to America to get another one, I just don't wanna waste the trip.... does that make sense?

I cant get my hands on 0,25mm MDF here, which is pretty much equivalent to one inch thick. I was thinking maybe using the 1 inch thick MDF would make me require less bracing making the build a lot easier?
Also maybe using a external amp could make my life easier too for the assembly and maybe I could save money with a used external amp... I use a Denon 3313 CI. Do I need anything else? Or is it just the amp, woofer and enclosure?

Any thoughts? The Ultimax II 18" measurements made me really excited!!!
Help me out, and if you think something you might wanna point out is too obvious: don't. I'm stupid, go ahead and say it. I'm just an ******* with a dream here.

I have been designing another small MEH.

So far I have been designing it around the Faital Pro 2fe24 however from doing measurements the distortion is mega high at 10% THD at 10W around 600hz. It's still mega high on less power minimum 2% or 3% THD

Edit: thought I would add that this distortion is even just with a small rear chamber and no front chamber/ports/horn



This is the rear chamber I made for it: (I got the 3d file from Faital Pro and seal it with a small o ring at the top)
It is fully sealed, you can tell because the cone is harder to move than when it's free.



I'm going to borrow some peerless 830970 to try which look a bit more suitable

Does anyone know of any other good drivers that could be used in a MEH that are 2" or 2.5"?

I'm trying to push the mid up to 2.5khz at least so I need a 2" really

I have been rebuilding a pair of Quad ESL-63s and am getting close to finishing. By rebuild, I mean I have reglued stators, and replaced diaphragms in all eight drivers.

I used Gorilla clear polyurethane glue to glue the stators of only one speaker- the other stators were bonded well and would probably have broken if I tried to break them loose.

I used 3 um mylar film, stretched using a pneumatic stretcher, with resonance tuned while the film was on the stretcher to about 92Hz. The diaphragms are glued using 4693H contact cement that unlike the factory glue, actually bonds to the grid and the diaphragm.

I applied Licron Crystal to the diaphragms and tested resistivity and resonance before and after applying the Licron. Resistivities all came out at either 10^8 or 10^9 Ohms/square. Resonance dropped by about 1 Hz with the added mass of the Licron Crystal. For those who might be concerned about longevity, I have some old drivers that I worked on in the early 90s that used 4693H and Licron coating, and they are still in good shape.







You can see details of my failed and successful methods on my blog page, here.

I'll be installing the drivers back into the speakers and testing with full bias applied over the next couple days.

I’ll go first. Which one of you guys did this?

Many people say that dome midrange drivers have a sound quality which is unique and desirable. I have heard systems with dome mids that sounded very good, and others which were very ordinary. This thread discusses this topic in detail....link

For the past year, I have been thinking about the Bliesma M74A-6 driver, and simulating various options to use it effectively. To me, this driver offers an excellent way to experience the power and potential of a good dome mid in a high performance application. I like that it operates pistonically over its full range, and the first mode resonance is more than an octave above its likely pass band. This feature sets it apart from its silk and paper dome sisters. I like that it has high sensitivity and high SPL capability. I like that @HiFiCompass has measured very low harmonic and modulation distortion at high SPL. I like that the “A” aluminum dome version is considerably less expensive than the beryllium and textreme versions.

Thus, I started this project with just one primary requirement, that it use the M74A driver.

Index

Folding a new bass horn design or adjusting the dimensions of an existing design to meet a specific requirement can be somewhat of a challenge and prone to error. To make the process easier and to avoid errors as much as possible, I've created a number of different Excel workbooks that can assist with the folding process. All of them should be considered as "works in progress" as I'm continually adding new features and of course fixing the odd bugs that I come across, so always make sure to check here for the latest version before using any of these workbooks. Some of them I've actually used to design and build my own subwoofers (the best way to confirm that the workbook in question works), and in those cases I've included a link to the project sin question. If you have any questions about the spreadsheets, please post them to this thread, thanks!

The latest versions of the workbooks are available at this location:

The Subwoofer DIY Page

Since I've found these intriguing and have not seen any real discussion, I thought it might make sense to start a focused thread on them. Perhaps, they are best not labeled 'Woden Design' as all I've seen are on MarkAudio's site, but it seems appropriate.

Some Initial Questions:

1) Do these result in a similar sound field to that of the MBL RadialStrahler systems and, perhaps others similar (Manger?, Ohm Walsh?)? Without the added complexity of crossovers for omnidirectional considerations.

2) Does the need to site them around four feet from the nearest walls diminish if they are not square to the walls of a rectangular room?

3) There are quadrupole designs for three of the MA 11CM drivers (MAOP11ms, Alpair 11MS, CHN110). Each has different interior dimensions. Could the same dimensions be used for all three with adjustments to the vent length and diameter without any real compromise?

4) If I would like to be able to readily change vent length and diameter without needing to do work inside the cabinet, would using exterior mounted vents without any protrusion into the cabinet work? I'm thinking of round cylinders of wood that would attach to the cabinet with a larger hole in the cabinet, large enough to not alter the vent function.

I'm interested to see the responses and would love to know about any builds.

Skip

It uses the the bias network to do error correction. It is equivalent to CFP with MOSFET output, but it can output from rail to rail, with help of the bootstrapping.
The example below is +-14Vp into 8 Ohm with only +-15V supply voltage. You can see the distortion is low. Note that you could put opamp at the front and wrap NFB around it to reduce distortion farther.

Looking for Hypex Nilai500DIY

A new thread to discuss DIY guitar pickups.

I recently built one using six electret microphones. Every other one is wired out of phase with the adjacent mic. The set of six therefore cancel, for far field sounds. Each is arranged to be below the corresponding string, which is near field to the mic. It works pretty well - I've had it out on stage at an open mic more than half a dozen times. Other players say it sounds good. Different sound than you'd get from a piezo bridge pickup or stick-on puck.

Why microphones? I normally play classical nylon, which of course doesnt work with the magnet based embodiment shown below. I melted the hot glue and ripped out the coil, to use the plastic shell as a pre-made holder for the electret mics to start. The three low strings on this guitar are from a nylon set.

Lot of updates have happened. Version 2.0 PCB has been made and group buy completed. All PCBs sold, but if you want one, PM me.

Latest schematic and build docs
Test PCB Image
Power up procedure
Distortion measurements
Gain calculations
Part I Upgrade to original design
_____________________
Original Post

Introducing the Schade Common Gate (SCG) Preamp. Signal comes in at the bottom source follower (unity voltage gain) and is then amplified by the Schade-enabled top MOSFET operated in a common gate configuration. This gets around the problem of low impedance on the gate of the Schade device.


Note: the schematics and information presented here is for personal and DIY use only and NOT for commercial use. Any other use needs my permission.

Inspiration came from George (tubelab) and Smoking-Amp, who were exploring the source-follower to common gate configuration for tube pentodes. I made a comment here that you could do this with MOSFETs too. Wrenchone and others have explored the Schade idea and Papa himself posted that really elegant Schade-enabled amplifier where the feedback connection is on the primary of the transformer to get around the problem of input impedance. I really like simplicity and elegance this circuit provides.

Here’s some of the pros of this approach:

• Gain device operates in triode mode.
• Low parts count.
• No unobtanium transistors or tubes.
• Low cost.
• No cap on the input.
• High input impedance and low output impedance (though I haven’t measured this yet).
• Preserves the phase: the source follow and common gate stages both preserve phase.

I built the resistor-loaded circuit and also a CCS loaded one (next post). It sounds excellent. It has the negative phase H2 (blue goes down when red goes up and blue goes down when red goes down), which really brings out the magic. Over the past couple of weeks, I’ve compared it to my other preamps, the 801a and the LuminAria, and it is comparable in sound.

Here are some measurements of the resistor-loaded version. I haven’t played with the load line much, but raising the load from 500R to 1k does improve things. The CCS version has almost no distortion. Subjectively though, I prefer the resistor-loaded version, it has much more of that 3D and “live” sound of LuminAria.

The build is a rats nest right now. Used the existing LuminAria setup with the Salas shunt reg. Hope to put it in its own box.

Need to get this out of my system ........

When I was a Kido, just barely moving with my first attempts of building amps and preamps from scratch, desperatelly wandering through any available printed sources ( no www yet) in search of/for Holly Grail .... my good friend just acquired specimen of which is later to be one of my all ever favorite amps - Musical Fidelity A1

(what did I knew that I'll have damn long list of my fave amps, not necesarily good ones or special in any tecnical or performance way, but heck - guy can have feelings, liking things just for liking sake )

Anyhow - not much time did pass, I had it in pieces, first to figure out schematic, and then maybe to think something clever (hell, yeah ) to make it better

Not much time after that, I had built my own, by wonder it worked right from the bat, by wonder I did guess right what output transistor are (ignore thing that I really knew just 2N3055 and needed to chase its "complementary" ..... so I had proper beginner's luck guessing right ones - 2N3055 and BDX18)

And - no wonder that I made exactly same mishaps as mishaps being implemented in original - I did use 100VA mains Iron for 80W of juiced juice, and mine also had beautiful thermal arrangement as original, resulting in oh boy!!!!!!!!!! temperature of heatsinks

Later, when we did some head to head comparison between friend's original one and my "Clone", awe was that "Clone" sounded better - simply beause I did made just power amp portion, really not being able to include preamp section in said moment, planning that to add in later time

Speak of beginner's luck, again

Conclusion - "Clone" did sound better with line level sources, preceded with just 10K pot, than original one having all bells and whistles

Then we did go wild, trying tube stage in front - finding some "modern" solution - ECC88/6DJ8 fed with humongous voltage of 30V ..... it did help some - fact that it was loaded with current source .....

What we did know that MF will follow same easy commercial pats some later, nicely feeding hordes of us ignorant imbeciles ....... in fact - nothing wrong with nice little pleasing boxes, but I later did found following Myths and Legends somewhat disgusting

Do I need to say that it sounded even better with "tube" stage, however flawed it was?


.......................................... fast rewind to www time, I started chasing Holly Grails in every possible direction, beside other things I did found some few itsybitsies about my (then) still fave amp

If you fancy some reading, see attached pic (schm , few posts down) and visit Mark Hennessy page https://www.markhennessy.co.uk/mf_a1/

M. Hennessy is getting most of facts right ....... and I have impression that he's extremely polite, whenever anything worth commenting he did comment


I'm going to be extremmmmmmely polite, not commenting anything about original commercial MF A1, neither first Gen, nor 2nd (just a gimmick, really, having USBandwhatever) nor present - 3rd or, rather, proper 2nd Gen

In last few decades, I had at least a dozen on my workbench for service and improvement, had at least 4 called "mine" ....... where last one of these 4 is still around (serving one of my friends)........... while my described clone is still somewhere around, supposedly still mine but I really need to stretch my gray cells to decipher where it is exactly .............

huh, tired of typing

First, you should know:
I am a seafarer and I spend fully half of my adult life out at sea. I'd like to say it's just a job, but it really does qualify as a life.

Second thing: I built a powered speaker system to suit my job and I'll tell you the things it needed to achieve in order to even make it aboard a ship with me.

1. Minimum weight: check in luggage has weight limits if you aren't filthy rich. I think the whole setup (2 speakers, MiniDSP Flex & cables) is around 25lbs.
2. Small box dimensions: keeping things small is actually a good way to keep weight down as well...less wood, less weight...and Small box means small suitcase witch might also weigh less.
3. Nothing stands proud of the box: it's soo much easier to protect the drive units if the surrounds or domes aren't sticking out into harms way. Just tape a protective piece of cardboard over delicate drivers and done!
4. Wide bandwidth at the expense of SPL: staterooms aboard ship are tiny so no need to get crazy loud....but I still like bass.

The completed package.

More later.

Hi,

To make a long story short, I'm working on a SET design with a slightly complex PSU design (200, 270 and 380Vdc from three separate transformer windings).
I plan to use 2x 6AU4GTA in a hybrid bridge for the 380V rail (@140mA) and I also wish to use vacuum diodes for the other two (20mA and 100mA respectively).
To keep the costs down I've been looking at russian dampers (6D14P and 6D20P) for the input and driver tube supply rails but I can't quite figure out how to interpret the heater-cathode insulation ratings in the datasheets:


Would it be safe (in long terms) to use these tubes as rectifiers up to less than 300Vdc with the heaters referenced to ground?
I could connect the heaters to the cathodes but would prefer not to if possible, no other tubes will be powered by the same heater windings though.

Transformer core size increases primary inductance which in turn is better for low frequency response.
But,-there's always a trade off. Overdoing one single parameter usually make other parameters suffer.
Any thoughts?

Folks,

At the other thread I noticed interest in what may be called a "functional clone" of the Cello palette. Please review the High End Tone Control thread for background information and the options discussed:

http://www.diyaudio.com/forums/analog-line-level/194119-high-end-tone-control.html

The Palette is best described as a Stereo Mastering EQ designed for easy and intuitive use by non-engineers (most EQ's need operators with at least two degrees and many years of experience to get suitable results). One way to describe the actions of the six controls of the Palette approximately is:

Bass [20Hz]
Drum [120Hz]
Lower Voice [500Hz]
Presence [2Khz]
Rasp [5KHz]
Air [20KHz]

Control ranges are 'weighted' so that any changes for a given rotation in for example the "presence" band are much smaller than the "bass" band, relating directly to the behaviour of the human hearing. The Palette has possibly more adjustment range than is beneficial and due to a number of factors a true clone is jut not a sensible option nor is it necessary.

Here the original:



In principle we can realise something that follows most of the Palette design brief using any technology we care to apply, so much is established.

However "Vita brevis, ars longa" dictate that we cannot spend time, effort and money on making a Palette functional clone with each and every available technology and then to let everyone choose which design suits them best.

So for starters we set the following outline for the actual EQ function:

Centre frequencies:

20Hz +/- 12 ... 18dB
120Hz +/- 6 ... 9dB
500Hz +/- 3 ... 5.5dB
2KHz +/- 3 ... 5.5dB
5KHz +/- 6 ... 9dB
20KHz +/- 12 ... 18dB

We can make bands somewhat adjustable using switches if desired.

Adjustment range is open to some debate as well.

Controls should be able to use generally available potentiometers but can be implemented also with rotary switches.

If we limit ourselves to 24-Pole switches (actually 23 Poles usable) this gives us +/- 11 positions for boost/cut.

This suggests 0.4dB steps for the innermost bands (so +/- 4.4dB), 0.8dB steps for the intermediate bands (so +/- 8.8dB) and 1.2dB steps for the extreme bands (so +/- 13.2dB).

If these items are agreeable we can proceed to select the electronic circuitry, here is where the poll comes in. If you are interested in this analogue (re)mastering EQ project, please vote in the poll on the technology to be used. the poll is multi-choice to perhaps vote 1st & 2nd choice...

Ciao T

I'm trying to decide on a push-pull amp to start building. I have most of the parts required, including transformers, and a couple of hand-me-down chassis I can use. I was thumbing through one of my old copies of the RCA Receiving Tubes manuals and found this in RC-19:



R18 and R19 (100k) take signal off the 6V6 plates to the 6AU6 driver cathodes for NFB.

R9 and R10 (330k) are a mystery to me. Simulation shows they increase the NFB a little. But how? I guess they feed a little output signal from the cathodes to the grids of the 6AU6s. That would create a little positive feedback, no?

Otherwise the design is straightforward.

I don't have a 9k or 10k OPT, but I do have a pair of 8k:VC OPTs.

The capacitor values introduce high pass filters in a couple of places that result in an infrasonic peak closed loop. I'd increase the values of C3, C4, C7, C8 to smooth that out. Otherwise the design looks well behaved, as the OPT is not within the feedback loop.

I would also improve the power supply; make it stiffer by using UF4007 diodes and bigger reservoir and first smoothing caps, and try to stabilize or regulate the 6V6 screen supply.

QUESTIONS:

• Would it be better to use plate-grid FB around the 6V6 outputs, or is the 6V6-plate to 6AU6-cathode FB basically the same thing done a little differently?
• Is the addition of R9 and R10 a good idea? I've never seen that done in any other amp designs I've looked at.
• I assume using a 6FQ7 or 6CG7 in place of the 12AU7 would be an improvement and would not require much in the way of changes. Good idea?
• I might also try this with EL84 or even 6P15P outputs instead of 6V6s. Thoughts on that? I think it would be an improvement, and they'd be easier to drive as well.

???

Folks,

Over in the other meta thread we have been discussing the TDA1541.

https://www.diyaudio.com/community/threads/building-the-ultimate-nos-dac-using-tda1541a.79452/

Based on my experiences, various articles and application notes and practical work by a number of peeps we now have a pretty decent understanding of the TDA1541 and what makes it really tick. Much of it is in line with my previous understanding, but where before I had many black boxes I now have a better feel for the internal circuits and the various implications.

---

In short:

1) The TDA1541 needs a syncronised DEM system with correctly sized DEM filter capacitors and a way of feeding the DEM Oscillator pin's that do not cause DEM switching feed trough into the substrate. Empirically 8 X DEM Clocks (352.6/384kHz) offer the best objective performance.

Very low frequency DEM oscillators with big value electrolytic capacitors are an alternative but a bit questionable insofar as it takes hours of the DAC running to get to correct operation and long term stability is highly questionable. In the end both achieve the same fundamental result in different ways.

2) The TDA1541 has significant capacitive feedthrough from the digital inputs into the substrate and from there into the outputs. It is best imagined as a coupling capacitor of ~ 12pF between each digital input and the analogue outputs. 12pF does not sound like much but with MHz bit clock frequencies there is a lot of feedthrough.

Slowing down the edges of the input signals will reduce this. By using "Simultaneous Mode" we can lower the Bit Clock frequency maximally. At 192kHz Sample Rate we only have 3.072MHz Bit clock in this case. It means the edges can be slowed down much more without ill effects on the digital side, compared to I2S mode which typically has 12.288MHz Bit clock at 192kHz.

Existing "SIM" converters unfortunately (almost) all use the fallacious "stopped clock" system, which maximises the clock speed so a lot of clock feedthrough happens for a short duration and then nothing for the rest. This means we cannot slow down BCK edges too much, nor any others. So I will not consider such systems desirable.

There are debates around analogue stages and other TDA1541 related circuitry, but they are not (yet?) part of this project.

---

So, what is the project?

Make a PCB design (open sauce, free as in Free Speech and Free Beer) for a TDA1541(A) frontend that accepts an Amanero standard USB Module, incorporates an SPDIF receiver (optical, Coax and XLR) and includes an IIS to Simultaneous converter that outputs a continuous BCK at 16 X FS and the necessary LE Signal and Data and slew rate and voltage swing limiter circuitry.

Just add a TDA1541 (we might bring the IC position onto the PCB with other bits, this remains to be seen), power and analogue stage (where nobody seems to agree on anything).

As this is DIY Audio, we want to do this in discrete logic, not using CPLD or FPGA or bought in CPLD/FPGA Modules. Why no complex logic? Typically we find a few 100pS P-P additive Jitter from CPLD, FPGA or CPU's (e.g. XMOS). Ground bounce and other problems are significant. The IC cases are distinctly DIY unfriendly, a tool chain and programmer is also needed. It adds up. We can reclock to block a lot of this, but still, why?

---

With an Amanero Footprint (we can add more) the USB input is taken care of. For SPDIF the WM8804/05 series is EOL and others re unclear. So adding a CS8412(14) footprint is probably easiest, we can add suitable adapter PCB's for WM8804, CS8416/DP7416, AK4118 etc. on the PCB.

The main challenge is that we need to take a BCK of 64 X FS and a 2 X 32 Bit Data steam on one data line and output a BCK that is divided by 4 and two Data lines that have 16 Bit Per sample.

There are a number of possible approaches using shift registers, but as we need an input register to hold data from the I2S input (say 8 X 74HC595) and then an output register (say 4 X 74HC165) to hold 16 Bit that go to the TDA1541, this rapidly becomes a logic IC grave. We can find some 16 Bit Shift registers but these still account for a lot of circuitry.

On the plus side, the logic in this case becomes very transparent, obvious and easy to design and debug. Still 16 IC's or so seem a lot to me. It does remain an option.

An alternative would be to use the 74HC(T)40105 FIFO. As we have separate input and output clocks and the "elastic" FIFI we can stuff our 16 Bit into the Input side at the 64 X BCK speed and clock our data out steadily at 16 X BCK and the FIFO takes care of everything.

This would use one 40105 FIFO configured as 64 Bit Delay line with data taps at 16/32/48 and 64 Bit's so we can have the input bit's for our FIFO arrive simultaneously.

Two more 40105 FIFO handle data build as a 32 Bit X 4 FIFO. We stuff bit's into the first FIFO from where the ripple immediately to the output. We then clock out using our 16 X FS BCK. On the input side we invert MSB and only pass actual 16 Data bits, stopped input clock to block off the rest.

I think the FIFO solution is by far more elegant. An option for a secondary PLL with VCXO (or a VCLCXO) can be designed in as well.

A discussion start is here:

https://www.diyaudio.com/community/...ac-using-tda1541a.79452/page-517#post-7939329

So, if anyone wants to join into the discussion and project, feel free.

Thor

A thread to discuss how well a compression driver matches the profile of a particular horn, and how to determine that match - or mismatch.
When choosing a compression driver to go with a particular horn, what is important to know so that the two work well together? Can any driver be used with any horn? Or do some compression drivers work well certain horns and not well with others?

EDIT: April 19, 2023
Attached to this post you will find a spreadsheet, kindly provided by @marco_gea, that allows you to calculate and see the match between a given horn and driver. The spreadsheet takes the parameters of the compression driver throat and calculates an exponential horn that has an equivalent flare rate to the driver throat. With that information you can calculate and see how well a certain expo or hypex horn will match the driver's initial flare rate.
Instructions are included in the spreadsheet.

Obviously the first thing we would look at when choosing a compression driver for a horn is "are they the same size?" In other words, is it a 1", 1.4", 1.4" or 2" entrance to the horn? We normally choose a driver of the exit size as the horn throat. Also to be considered would be the mounting style, such as screw or bolts and the bolt pattern. Adapters can be used for different mount styles and even sizes. For example a common adapter is to use a 1.4" exit driver on a 2" entrance horn. PRV even make a 1" to 2" adapter. But beyond those obvious mechanical matching issues, will a certain driver work well or poorly with a different horn? And how can we determine that for a good match? How do we know the internal geometry of a particular driver?



Horns come in many shapes, sizes and profiles. We might look at a Smith horn that has no vertical expansion at all, but a wide horizontal expansion, to a Kilpsch horn with a long narrow vertical expansion and somewhat wide horizontal expansion - to a long horn that looks somewhat like a trumpet, to the Yuichi and others with mixed expansion.



I'll cite a recent example. Forum moderator @kevinkr recently went thru a good deal of trouble and expense to learn what driver works best for his new Yuichi horns. The Yuichi is a wide horn, but not very tall. In fact the horn very quickly goes to over 90° flare in the horizontal axis, while remaining with zero expansion along the vertical axis for about half its length. The horn is very much axi-asymetric, as opposed to a round horn where the expansion is axi-semetric. Is the horn a rapid expansion, narrow, or somewhere in between? What driver geometry would work best on this horn?
This is what the Yuichi looks like inside.

I have a set of Half-Chili cabinets that need new drivers. Is the Fostex FF165WK a good substitute for the FE167e in this case?

I recently was glancing at posts and someone mentioned that they had a ZEON based computer with approx 150gig of memory and it was taking several hours to render projects but this was compared to days with a weaker system. I recently was gifted several servers and about a terabyte of ram. Two of the servers can handle 4 cpus. I believe that I can set up a server with 4dies 24cores 48threads and 512gig of memory. The system is absolutely useless for me but it would be interesting to render some of the projects and see how it performs compared to other's systems.

I believe the the model that was being discussed was a wire frame stress model or some such.

At any rate I am requesting some one to tell me what software is needed and offer a project file to be rendered so that we can see the performance.

Jeremy

Here is my latest Tokin SIT amplifier. It is a DEFISIT amp (Depletion Enhancement Follower SIT) output stage based on Nelson's First Watt SIT-5 output stage. Diyers more knowledgeable than me picked apart what information Nelson provided in his SIT-5 owners' manual (https://www.diyaudio.com/community/threads/first-watt-sit5.418023/), and I rode on their coattails and came up with this version.

My build is only the output stage, and it incorporates the duo output capacitor arrangement which can be tweaked to adjust the amount of current amplification that the mosfet part of the DEFISIT push-pull output contributes to the total current amplification. This is a departure from the regular DEFISIT amplifier, where the SIT and mosfet both fully contribute to the total current amplification.

Here are a couple of LTSpice simulations. I did many simulations, but these two are what I based my design on. I chose -47VDC for one sim since I intended to build it using one of my existing amplifier chassis and power supply. I chose the -63VDC for the other since that is a reasonable voltage that will take advantage of the power capability of the THF-51S and still keep the power supply voltage reasonable for capacitor voltage and heat sink heat dissipation.

As shown in the simulation results (47VDC power supply and 2.0A Iq), the measured current through C4 connected to the SIT drain was 361mA peak, the measured current through C7 connected to the mosfet drain was 150mA, for a total of 511mA. As a check the current measured through the speaker, R8, was 509mA - close enough. So the contribution of the mosfet was 150mA/511mA = 29%.

I have not included the LTSpice screen shots of power output but the 8 Ohm power output was nearly 23W at 1% THD and 4 Ohm power output was nearly 40W at 1% THD.


63VDC PS 2A 8R 1Watt:



63VDC PS 2A AC signal current through C4, C7, and 8R Speaker:



47VDC PS 2A 8R 1Watt:



47VDC PS 2A AC signal current through C4, C7, and 8R Speaker:





As mentioned I decided to build the 47VDC version. The chassis and power supply is from my BAF2015 Amplifier - A SIT Mu Follower Revisited With Feedback (https://www.diyaudio.com/community/...t-mu-follower-revisited-with-feedback.408193/). The power supply is CLC, comprising 2x22mF - Hammond 156B - 2x22mF, and an Antek AS-3218 transformer per channel for full dual mono construction.

I put together a PCB design and sent it off to JLCPCB for fabrication. In addition to stuffing the PCB once I received it, I also changed the CLC filter from V+ supply to V- supply.



Initial power-up and subsequent Iq and SIT Vds adjustments went smoothly, and Iq and SIT Vds were stable.

Next up was testing with an 1kHz signal and distortion measurements. Unfortunately when powered up with an AC line powered 1kHz oscillator connected, the amp immediately blew the powerline fuse. So it was trouble shooting time. After checking the schematic and pcb, checking that the input capacitor was not faulty, and not finding any visible ground shorts with the meter, I was baffled.

I knew that the issue was mostly likely a grounding problem and that it only manifested itelf when an input device was connected to the amplifier. Luckily a thought came to me fairly quickly - when I changed the CLC filter from V+ to V- supply, I forgot to move the power supply connection to safety ground on the CLC filter board. The correction was made and success. Only one fuse was permanently damaged.

The dim bulb tester came in handy here as once the fuse blew, the dim bulb tester went in and I was able to probe around with power and not blow anything. In addition to using it during trouble shooting, I always use it for first power-up testing of power supplies during various stages of construction and first power-up testing of audio circuits.

As for the amplifier supply not shorting with no input device connected but shorting with an input device connected, I gave it some thought. The power supply was for V-, with V- from the supply connected as power to the amplifier circuit. V+ from the supply was connected to the amplifier circuit board as ground. The V- from the supply was ground in the previous amplifier but I forgot to change it so it was now incorrectly connected to chassis safety ground. With no input device connected to the amplifier circuit, the power to the amplifier board was floating. Although the V- was also connected to the chassis safety ground and to the powerline/IEC ground, there was no other direct connection to V+, so no short. The live from the powerline/IEC was connected to the transformer primary, which was isolated from the transformer secondary. Also the speaker and input jacks were isolated from the chassis. So with no complete direct connection of V- to V+, the current can only flow through the audio circuit. The chassis was connected to V- but there was no path for the current to flow from the chassis to power supply V+.

When the oscillator was connected to the amplifier input, the circuit was completed, current flowed, and the fuse blew. That was because the oscillator was AC powered and had a safety ground connection. So the oscillator line safety ground connected to the oscillator power supply ground, then connected to the oscillator signal ground, then connected to the amplifier signal ground, then connected to the amplifier V+. The oscillator safety ground is also connected to the amplifier safety ground through the line ground, and the amplifier safety ground is connected to amplifier V-. The net result was amplifier V+ and amplifier V- were connected together - a short circuit. There was a CL60 thermistor at the amplifier power supply ground connection. That would have limited the short circuit current: 47V/10R = 4.7A. Fuse was 2.5A slow blow.

I have swapped power supply polarity before but had always remembered to switch the safety ground connected, until this time.

So always be careful. Electricity can kill.

Even if its from an alternative reality, just lets have dreams

Onsemi announced that KSA1381ESTU is end of life with a last order date of Jan 5, 2025. Is there any interest in a group buy for these?

My thought is to combine it with a group buy of 2SC3503E which is available from Rochester Electronics (link here), but only in large quantities (1000+). This makes for a good pairing as KSC3503 is currently only available in D grade.

Lot sizes will be 100 pieces of each device.

As this would be a large cash outlay for the initial purchase, we'd probably need to have money up front. We'd have to backorder them as both Mouser and Digikey are currently out of stock, but accepting backorders. Maybe it'll arrive in time for Christmas.

I will keep the first post updated with anyone interested in participating.

PRICING UPDATE:

Pricing factors in the price to order, taxes, shipping and repacking materials with a bit of a bump so I don't hopefully loose money on this.

Round 1: $30/100. For example, 100 x 2SC3503E and 100 x KSA1381E would be $60 + shipping.

Round 2: $30/100 for 2SC3503E and $35/100 for KSA1381E. The higher price in round 2 for KSA1381E is due to a price hike on Mouser's end.

SHIPPING:
For shipping, US will be $5. International will be $20 if the quantity is 100/100. If over this, I'll PM an estimate. This is due to the weight threshold where international shipping prices increase.

VAT: If there is VAT in your country, I understand this will be collected from the recipient, not paid by me.

TIMING UPDATE:
The Mouser order for KSA1381ESTU has been placed. Its backordered at Mouser with a restock date of 11/11/2024 (if Mousers date is accurate).
Domestic orders arrive in the second half of November.
International orders will go out via USPS international which shows shipping times of 1 to 4 weeks.

PAYMENT:
I'll send payment info once I get close to being able to ship. I have PayPal and Venmo.


ROUND 1: Closed for new participants (Shipping - UNKNOWN. Issues with Mouser)



ROUND 2: Closed for new participants (Shipping - UNKNOWN. Issues with Mouser)

Greed is killing me 🙂 I bought a used pair of DX3 with one reportedly distorting. A common thing with Lowther needing alignment methought . Yeah, right ! There is nothing to be done except $$$ replacement and I will have mismatched drivers anyway.

The TDA7293 series are underrated gems in the DIY world. This chipamp, with its modular structure, clip detector, mute-stby functions, low noise and low distortion, produced with DMOS technology, actually has the potential to compete perfectly with National/TI's LM3886. On the other hand, it is common practice to use chipamps with a buffer due to low source impedance demands and relatively high input bias currents. Likewise, with composite feedback applications, both the noise and distortion efficiency of chipamps can increase significantly. In our implementation, two matched N-channel JFETs, together with the PNP transistor, operate as a complementary feedback pair as a high-impedance, high-CMRR differential input buffer for the TDA7293. The JFE2140 / LSK389 LSK489 dual JFET combination used provides significant improvement in THD and noise compared to the use of the chipamp alone, thanks to its extremely low noise. The composite feedback rate is 26dB (20x). In this way, ~1.25v RMS input signal is sufficient for full power. On the other hand, thanks to the DC servo circuit established with TI's low-noise, low-offset opamp OPA277, the DC offset remains below 1mv.

Our inspiration for our design was Bob Cordell's LSK489 application notes and JFE2145 datasheet.
https://www.cordellaudio.com/JFETs/LSK489appnote.pdf
https://www.ti.com/lit/ds/symlink/jfe2140.pdf?ts=1717672324923&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FJFE2140
https://www.st.com/resource/en/datasheet/tda7293.pdf
https://www.ti.com/lit/ds/symlink/tps7a49.pdf?ts=1717660447218&ref_url=https%3A%2F%2Fwww.google.com%2F
https://www.ti.com/lit/ds/symlink/tps7a3001-ep.pdf?ts=1717738722969&ref_url=https%3A%2F%2Fwww.google.com%2F


The ancient 78xx 79xx series regulators, which are well known in the electronics community, have been used in audio circuits for years thanks to their stable structure, high PSRR rates and relatively low noise(?).
Measurements of 78xx-79xx ICs (even though noise values such as "0.003% Vo" are given in their datasheets) have been found to reach noise values of 500uV - 1mV in the audio band, which may disturb sensitive ears, regardless of the input noise. Of course, such a supply noise is meaningless for modern audio opamps whose PSRR is around 120dB.
However, especially in discrete applications (since PSRR efficiencies are quite low), this level of noise will be disturbing.
Although complex, discrete, parallel-hybrid low-noise solutions have been produced to solve this problem, these applications remain a troublesome alternative due to application difficulties, additional noise due to the area covered by the regulator, and the necessity of matching components in some applications.
Our application provides a good and affordable alternative to all these difficulties. TI's low-noise regulators TPS7A4901 for + rail and TPS7A3001 for – rail form the heart of our application. The effective noise amounts of these regulators in the audio band are below 15uV (RMS) level. In addition, while PSRR rates are 60dB in the 78/79 series for 100-120Hz, they are around 70dB in the TPS7As. On the other hand, load and line regulation rates and transition responses are significantly higher than the 78/79 series.
Although the input voltage of these regulators is limited to a maximum of +/-36v, input up to +/-60v can be applied thanks to the input voltage limiter used in our application.
Since the pinout of the 78/79 series is used directly, they can be used as a one-to-one replacement in applications where these regulators are used.

EPIC S

EPIC S


Positive Regulator Schematic


Negative Regulator Schematic


Final prototype measurement of EPIC S.
1K-1NF input filter
47K-4.7K NFB Resistors
4.7mA Input bias
Power: 78W 8ohm (2x42V)
Input sensivity: 1.25V
Slew Rate: 8V/uS 8ohm/1nf (JFE2140)
Slew Rate: 9V/uS 8ohm/1nf (LSK489)
Bandwidth: 5-75khz -3db
DC Offset: <500uV



EPIC S Output Noise

Hello all....

Here's my Sunday night fire sale... All prices reasonably negotiable. Will ship anywhere in the US for FREE! If outside of the US we'll work something out. Zelle is preferred, Paypal, and Venmo also ok.

I've had some medical bills that I didn't expect and need to raise some funds. Thanks everyone for looking!

Arrow Video 4K lot 9 titles: $150
The Last Startfighter
Conan The Destroyer
Conan the Barbarian
An American Werewolf In London
12 Monkeys
Witness
Silent Running
Weird Science
Narc




Beagle Bone Black Rev B unopened, and Twisted Pear Hermes-BBB Cape with extras: $75




2 TDA1540P chips with SAA7010 and SAA7030 included on CDP mainboard with 2 of Miro's TDA1540 NOS PCB's: $50



2 AD USB isolator Eval Boards. EVAL-ADUM4160EBZ (sealed) and EVAL-ADUM4165EBZ : $70



Chord Electronics Mojo DAC Complete with box, cover and cable: $150




The Beatles CD box set in Mono ! This real and was purchased at Tower Records in San Francisco. As you can see from the photos, the box, the rear paper, the inner and outer plastic sleeves are all correct. I opened this bran new still in the shrink wrap and played each disc once. : $125

I'm looking for a transformer for a Counterpoint SA-100.

Hey all,

I'm working on a new amp build - sissysit24 😉 Zen recommended a choke. I have a few questions - hoping to sort things out.

I read up on https://www.diyaudio.com/community/threads/how-do-you-calculate-choke-size-in-a-power-supply.159832/ which covers this topic but is closed so started a new one.

Assuming I did the math right on things:

1. I think the amp is 25w, need to verify that
2. I think the current draw, based on the 24v 25w would be approx 1 amp ish. ( per channel )
3. Based on the formula I think I would need a 2H choke
   1. (24 / .01)/1200 == 2
   2. I'm not sure I'm doing this right!

I'm a little unclear / hazy on where the choke would be placed. If I am understanding things correctly the choke has an in / out. I would place this choke between the dc + of the rectifier and the + in of the power supply board. Is that right?

I'm planning to use the W12 from @rhthatcher . In this configuration I would end up needing a total of 4 chokes - 2 rectifiers per channel. I think each rectifier would be passing .5 amp - is that right? ( each channel would draw aprox 1 a, dividing that evenly I think makes sense?)

When I go to look for a choke from Hammond the size / current I came up with above don't make sense to me. I think I'm either off on my calculations or just don't understand things well enough yet! If my understanding above is correct then something like Hammond 193NP would be a sensible choice?

Thoughts? Am I in the right ballpark here or off? If there is a thread / doc that covers this please let me know. I've googled and searched but not exhaustive. Most of what I found related to using chokes in tube amplifiers.

The most recent edition of my book is available on my website, ejjurich.com. I discontinued using Amazon. The old print versions were not of the best quality and were printed before text was checked for grammar. Some of the print book covers may make reference to different editions; they are all basically edition one with some updates. There are resellers selling old print copies of Vacuum Tube Amplifier Basics for ridiculously high prices. The current version of the book is available as a downloadable PDF document/eBook file for $12.00. It is also available as a PDF document/eBook on a CD for $15.00.
Why PDF?
PDF documents are readable on just about any device. Unlike standard eBook reflowable formats, content remains static. For technical documents, maintaining a static layout is best. Also, in the PDF, images are mostly color, including project circuit layouts.
Note: The CD version is only available in the US and Canada. The $15.00 price includes media postage.

I am using diyinhk es9038pro DAC board.

PCM I2S connection taked from datasheet.

Then use DSD signal: sound is mono.

I am trying to find solution to change input signal routing using i2c from amanero.

Maybe someone has experience with programming i2c outputs of amanero and can explain me how to write register values correctly in amanero?

Hi,I have a stripped Spectral DMA 100 amplifier,need help finding power supply specs for both driver and output.
I have a need to build power supplies as the chassis is missing both transformers……maybe use the chassis,I do have a Diyaudio 5U chassis new in the packing…I have been saving it for a new project,or,if the transformers needed can fit the original chassis,maybe use the Spectral case.
all outputs verified ok.
The boards appear to be prototypes,there is no serial number sticker on the back of the case….found at the Alameda Antique Fair,SanFrancisco in 2017…..
thanks,Dave Grady

Greetings.

I present the DIY FRONT END 2022.




EDIT: For current boards marked "V0R1" please find the changes and additional information in post #686 of this thread
https://www.diyaudio.com/community/threads/diy-front-end-2022.394339/page-35#post-7323986

I'm looking to build an Aleph Mini, currently trying to gather parts to order, for now I have found:

https://www.ebay.co.uk/itm/266392011176?mkevt=1&mkcid=1&mkrid=710-53481-19255-0 - the pcb
https://www.ebay.com/itm/156560013829 - mosfets
alternatively, but I'm not sure if it'd be best - https://www.ebay.com/itm/115126018088?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=wGG0QMocRHa

https://a.aliexpress.com/_EIU0SPC - enclosure

I'm also not quite sure about the PSU, what board / transformer should I use, and how to wire the potentiometer.

I need the resistor and capacitor values for the output filter.

They burned so bad that the relays are also melted and not working!