I have noticed quite a few questions about the suitability of the store's
heat sinks for various projects, and since I have tested and documented
most of them here, I am happy to present my list of the sinks and their
respective thermal resistance numbers. Toward the bottom it lists the
wattage for a 30 deg C rise on a single side and the number of TO3-P
type packages it is drilled for.

Hi all!

My name is Walter and I'm from the Netherlands. I'm interested in DIY audio projects and hope to find answers to my questions here on diyAudio.

Amp is SST Son of Ampzilla by Bongiorno, not the latter all-new amp w/the same name and "II" suffix by Wyred4Sound/EJ Sarmento. Rated 100/200/400W @ 8/4/2-ohms, single 1k VA toroidal transformer, 100k uF PS filter, 55# net, a serious piece of kit by a person credited with creating the ubiquitous balanced differential circuit.

Can readers predict (say, within a range) the dB difference between using one SOA/Bongiorno in stereo vs. two SOA, one SOA p/c and one channel per each amp? One professional suggested 6 dB difference obviously favoring the latter, which sounds high to me.

I have a huge selection of power Rs. I have only one SOA. I considered listening to one channel of one SOA > one speaker channel and assembling a big bank of power Rs for the other unused channel, comparing the Rs to no Rs/no load. The speaker is 4-ohms nominal with a reasonable EPDR. If this is a good idea, please define the recommended R load and minimum power.

Thanks.

Dear all,

After some time I am again in DIY area, so I have (perhaps stupid) question...
I have two sparate PSU from HP, I think from some printers or scanners. Model 0957-2260, output voltage is DC 32V and output current 5625 mA, what is OK for my application. Of course, I need two of them to have symetric power supply +32 -GND- - 32V.

Question is: is it possible to connect theirs outputs to achive desired voltage or not? It means that I have to connect plus from one to a minus of another one to have central point.

Something rings in my head that someone told me that I need to do something with input connection (230VAC), but cannot remember what was warning...

Any ideas, advices?

Thank you in advance, regards,

Boris

Hi,

First post so be gentle..

I've been meaning to join this forum for a while as I almost always end up coming across great information from here. I started my interest/vocation with electronics with audio and moved onto digital/power, well, its about time I got back into the swing of analogue audio design.

My first question is about repairing a Rel Storm III sub for a neighbour. It's an older 2002 model, and by the looks of things the bipolar driver transistors for the MOSFET have blown, taking a resistor with it. After contacting Sumiko about it, I managed to convince customer support to provide the value of he burnt resistor, and I have the datasheets for the driver transistors. (BFN16 NPN, and BFN19 for PNP). As these transistors are SMT SOT89 they can't dissipate much heat, which is probably why they have failed (even with a good copper heatsink on the PCB). They added through-hole footprints on the PCB in parallel, making it easier to use TO-220's (or TO-126) for replacements, so I was thinking, MJE340's and 350's?

I am not after 'improving' sound for my neighbour as he is happy with it, so the closer I get to BFN16/19 equivilents the better, and being a sub, high end frequency response is not an issue. I picked these transistors for availability, and their higher power dissipation, along with the possibilty of adding a heatsink.

There's also the MJE15034/35, which are most expensive, higher gain, greater power dissiaption, highg frequency response etc.. but I fear the high end won't be needed for a sub, plus, perhaps the higher gain would result in a change in sound, or require a change in the values of passives.

As cheeky as this is, if anyone owns a storm III, any cance you could post a pic of the power amp PCB? Specifically the driver transistors not the MOSFET's). I read that Rel upgraded the design in 2005 due to failures (most likely of this kind) so a picture of the later model would be ideal, as I could see any changes they made. As you can guess, Rel is understandably a bit hush hush on this, as they want money for repairs, plus, its a specialists field, for qualified 'rel engineers' only.

Ultimately, despite my (somewhat limited) understanding of audio electronics, I am not trying to reinvent the wheel. Purely to get the sub working again, as close to the original sound quality as posible, but improving reliability so parts don't overheat again. Hopefully he can enjoy another 10 years of it, without having to upgrade 🙂

Cheers,

Buriedcode

Hello! Having a great time designing and building my own audio equipment!

Been working on a stereo PCB based on the Project 3A from Rod Elliot, i'm here asking you guys what do you think about this layout.
P.S. Since i can't find the exact BJTs used in the original Project, i wonder if i could use a couple of 2SC5200 and 2SA193.

I run sound at a local skating rink that has a 10,000 square foot oval skating floor that is coated concrete. Has walls on three sides with one long side open to the rest of the building.

We currently have four Yorkville 18" subs (two at one end of the rink two at the other end of the rink) which never sounded good.

We replaced three of the 14 QSC 8" two way powered speakers (only three of them actually still worked) with three of the Mackie 212 powered speaker.

Decided to look up subs and found the Rockville RBG18FA as I'm looking for the ability to reproduce bass under 40Hz and the Frequency Response spec is +/-3dB 25Hz - 120Hz which should fit the bill quite nicely.

https://www.rockvilleaudio.com/rbg18fa/

Would that be a good sub for the application and if so how many are needed and where should they be placed?

If that is not a good sub, what sub would be recommended for about $1,000 or under?

The system gets turned up a good bit once a week for four hours continuous by a local DJ who plays there.

My SMPS1200A180 (v7) (feeding a 4-channel UcD180-based amplifier) was taking progressively longer and longer time to start. Over a year or so it gradually went from seconds to minutes from the moment the power was supplied to the relay click and the actual start of the amplifiers. Today it just refused to power up. The internal fuse is fine. Disconnecting the amplifiers makes no difference.

Anyone with a similar experience? Any suggestions on the repairs? Thank you!

I've got a DBX 234XS crossover which I use in my home stereo using XLR to RCA cables I made and XLR to 1/4" balanced to connect to the USB audio interface.

Anyways when I turn off power to the power strip everything is plugged into, there is a nice pop in my speakers.

Is it normal for the 234XS to cause that sort of pop and if so can it be fixed, or does it have a problem?

Also, if it is normal and no fix can be done, what is a decent 2 way 24 dB/octave active crossover that does not produce any pop in the speakers?

Hello forum, I'm thinking of building this but using rimlock complement (EF40, ECC40, EL41/2, EZ40) just for fun I did this exact version once with very good results and since I have the valves and sockets thought of putting them into something "useful"
I know EF40 is EF86 equivalent and the pentode section of the ECL86 is almost the same as the EL41

My question is what would I need modify to fit the ECC40, accordingly to Philips the cathode and overall bias has to be changed (of course it is a completely different tube)



So, do you agree with Philips recommendation ? any comments will be appreciated.

Greetings from Dallas, TX.

I bought a pair of these from a guy who does new cinema sound installs and selling the old systems.

Link for reference is here: https://eaw.com/documentation/cb152x/



Would anyone know what model of woofer is used there? It looks like a BC 15", since one of the HF drivers is BC DE72. I took it out, bit there is no label (OEM by BC?)

I might try to take it out and make pictures, but it looks as many other 15" woofers if no one knows the replacement given by EAW. The one I took out already had its part number unreadable, will have to try the other one.

Hi all! My name is Nick and I live in San Diego.

I am an audio enthusiast and my current setup consists of:

Sources:
Luxman PD-151 Mk II turntable/Gold Note PH-1000 Lite
Gustard A26 Dac

Preamp/Amp:
BAT VK-80/Accuphase P-360 (just upgraded)

Speakers:
Scansonic MB3.5B

I use Roon and HQPlayer for streaming with both running on a Mac Mini M1 and the HQP NAA running on a RPi5.

I am interested in a DSC2 DSD dac to replace the Gustard since I prefer to let HQP convert everything to DSD.

Thanks for reading - Nick

Brand New in boxes.
These have been sitting in my cupboard for 10 years for unfinished Boominator project. Selling to rationalise my extensive project list.

• (4x) P.Audio SN-10MB MkII 600Watt 10" Low Mid Frequency Woofer
• (4x) P.Audio PHT-407N 1 Inch Horn Loaded Super Tweeter Neodymium Driver/Horn Combination

$1000 for the lot.

https://audioxpress.com/news/the-return-of-an-icon-the-new-revox-b77-mk-iii-tape-recorder



dave

Hi folks. Long story but keeping it short. I have a CA5300 that was blowing fuses. I took it to repair and see my luck. Figured out that one channel's amp board had all the outputs shorted. Below is summary

CH1 - While amp was off, I didnt realize that wired from PS still had 80+ volts and it sparked. I then discharged the caps and then connected it. I then noticed the 253 transistor was chipped off. No burn smell through. I replaced it from other board. Swapped this from other board and when I switched it on a loud bang and before any smoke, I immediately switched it off. With these amps there is no way I can use a DLB or Variac as the protection circuit doesnt engage if it sees that I have a DLB (100V bulb) or a variac.

CH2 - I powered it on but had the magic smoke. Later I see there is a 82V zenar doide and adjacent 253 transistor was smoked. I used parts from this board to CH1 and waiting for the parts to arrive.

CH3 - Working fine

CH4 - This was the original channel that had blown outputs. So I swapped the A1294/C3263 pair of outputs. Total of 5 pairs. This time, I used all the outputs from CH2 and the amp started to work and thought I had fixed it. The sound was not fully clear when I was testing. I increased the volume and boom. went into protection mode and same original issue. It was blowing fuses. All 5 pairs of outputs went shorted within 2 mins of running. This also caused the two big CL80 thremosister (maybe a bigger one not sure) to smoke but I switched the unit off on time.

CH 5- Working fine.

I checked all the caps. For each board there are 9 of 100uf 100v. They all are measuring 89 to 92uf with .45 ohm ESR. I will be changing all the caps and will see. For the people who worked on these amps, what were the probable components that failed. The LME49810 is unobtainable and I don't know how to check if the chip is working or not. I am trying to source 10 pairs of A1294/C3263 and K-amps member was kind enough to confirm that he might have them.

So key question is what would be the cause for the pop/bang from amp board and smoke. Even if I manage to find 10 pairs, how do I validate if the amp board would work without burning any components. Any guidance that helps me. Thanks

Hello everyone

I have been gone for some time. I know there are many threads on this boards and i have them open but I have. few particuklar questions for this build and it would be very helpful to. me if i could document the progress here with p[ictures and ask my questions and hopefully get some tips and guidance.

I have these parts:
Login to view embedded media
my first question is about powering the board with +-15 VDC
would it be possible/advisable to power it with one external 15VDC power supply? i wire in the positive polarity for the +15 and i swap the positive and negative for -15
in this way i am only using one power supply and the two voltages will be mirror images so if one has a +0.03v ripple the other will have the exact voltage in opposite plarity and the two channels will have truly mirror coltages applied to them at every instant. is that electrically ok?

Hi all, I have been replacing old passive components from a tube amp and have seen that people think a polypropylene cap is better than a polyester cap and was seeing if you thought it was a good idea to replace them. They are 0.047uf 250v. I’ve included a pic of a cap that I plan on replacing and a photo of replacement. Also is there a better replacement for this polyester cap?
Thanks in advance
Matt

I've started a layout design on the Rod Elliott's Project 10, i'm seeking for you advices.

Hi!

I've built a couple of kits before, but I've just started designing and building a speaker from scratch. I’m cheating a bit though. Ganesha, my speaker, will use the same drivers and have roughly the same volume as the open-source SB Acoustics Bromo kit. So, it wouldn’t surprise me if I end up with similar port dimensions and a comparable crossover.

I've just glued up the cabinet and started to learn how to measure drivers... and I'm a bit lost so thats why I'm here. 🙂

Cheers,
Jan

I have been testing a pile of JFETs (multiple different part numbers) with multiple different instruments to find a simple DIY method for creating matches for some JFET Beast PCB builds.

I believe that matching can be accomplished simply and at a very low cost. This thread is to show my conclusion of a rig to measure each JFET.

The journey to get to this point is a discussion for another time.

The pTA consists of a connected pair of OTA's to simplify balanced input/output functions, wanting to avoid the matching of numbers of precision resistors without resorting to INA's necessarily. It takes advantage of the formidable current mirroring (shown below on the right) and the CMRR already existing in AD844 devices, adding a linearization input network using an NE5532 dual VFA op-amp. Although this pTA cannot match the minimalist distortions or CMRR capabilities of the best INA's it does an excellent job IMO without using global feedback, producing a pair of differential phase aligned output currents.

The pTA supports differential input signalling, allowing for a broad range of applications left to the imagination of anyone here to use. The NE5532 input device bypasses the non-linear transconductance of the input buffers in each of the AD844 CFA's. In so doing the pTA has much lower distortion and can generate programmable currents using a single resistor, in this case R6, in a simple calculation using Ohm's law in relation to the differential input voltage.

As this current is channeled to flow only into (or out of) the inverting terminals of opposing AD844's, the currents are equal in feeding into their respective current mirrors, being also complementary matched in the folding over with AC, a condition that generates equal amplitude differential currents phase aligned over wide frequencies. Phase alignment is of advantage in the process of converting back from differentials to single ended at the receiving end.

A basic implementation of the pTA is shown in the LTSpice screenshot below. The voltage outputs shown on the right are labelled on top, this corresponds to nodes identified on the schematic, being also colour coded to the waveforms below the labels.



In this simple example a 1 kHz 2 Volt pk/pk signal is presented from a floating source B2 that looks into a 50 kOhm load, being arbitrarily offset by 4 volts DC. The ends feed into U3 and U4 via lines N001 and N006. These appear as red and grey waveforms centered around +4 V DC. The two output signals in yellow and blue are centered around zero volts, being produced by U1 and U2 on nodes N004 and N008 respectively. The output signal voltages can easily be calculated with reference to the input Vin differential signal whereupon for the yellow sine trace has Vo = Vin(diff) x (R11/R6) or 3/4 Vin and the bottom Vo = Vin(diff) x (R2/R6) or Vo= Vin. As can be seen on the schematic the extent the 4 Volt DC is stripped from the output signal is down to 4 or 5 milliVolts, this is close to about -60dB CMRR. To obtain similar results from a resistor based network seems would require resistor tolerances in the order of 0.1%.

I would like to thank Hans Polak for his assistance in reviewing this material, for conducting simulation experiments on distortion and for assisting in the learning and using of LTSpice. I hope that the material presented is of use to anyone wanting to experiment with it... and hope that the results are shared...forget it if its negative though...quiet...no I won't!...I'm warning you...make my day punk!...stop it... people with start to think I'm crazy... I know I do...

Hi everyone!
My name is Daniel and I'm from Norway. I've recently gotten into the world of audio and found a lot of valuable information on this forum and I'm very excited to learn more!

I have finally acquired a Counterpoint SA-11 preamplifier! It does not pass a signal except through the passive output. I am hoping someone can help me with documentation. A manual for adjusting the various potentiometers and a schematic would be wonderful. If you PM me, I'll send my email. Thank you very much!

I just made myself a high voltage regulator that I could use for my tube experiments. If you also need a high voltage regulator with good performance, or want to make use of the jellybean parts around, here's a design that is fully simulated and tested.

Features

• Ripple rejection measured at least 93dB (limited by apparatus)
• Output noise measured at most 50μVrms
• Using TL431 as voltage reference and LM317 as pass transistor
• Ability to add soft start function
• No bulky film capacitor needed (if a bit higher noise floor can be tolerated, so the PCB could be made smaller than a credit card!)

Yes, I know there's the 21st Century Maida Regulator, which is very applicable and I even built one myself. But after intense experiment I'd like to share some ways you can tune a regulator better or more suitable to your case. Perhaps I could call this regulator the 2020s Maida Regulator 😉.

Schematic


The good thing about LM317 is that it's available, reliable, and doesn't require a big output capacitor to be stable. However, the original Maida regulator suffers from poor ripple rejection because of greatly reduced loop gain especially at low frequencies, and the additional 6.9V zener doesn't help much. I found there was a mysterious 1.5Hz voltage fluctuation on my mains and the Maida regulator was almost helpless. (In fact I even tried a 100V zener. It did help a little, but for greatly increased noise and temperature coefficient.)

A TL431 driving LM317 is always seen as a form of super regulator: it has very high ripple rejection, at least IN THEORY. My regulator uses the same idea but adds protection to every low voltage part so they can regulate a higher voltage. (Q1 protects U1, Q2 protects U2, Q3 protects U3) For details of the components see the following sections.

Measurements

I tested the prototype PCB using my DIY low noise preamplifier whose input noise density is only 1.4nV/√Hz and bandwidth 0.1Hz~100kHz. (with a 10Hz HPF for the following measurements, image 02 below) All measurements use a 10kΩ load at the output unless specified. The output voltage is 451V, which is a bit off from the theoretical 2.495V/1.8k*(1.8k+330k)=460V because I used 5% resistors. However the voltage reading doesn't change when load changes to 3.3kΩ (136mA).

When C1 is 3.8μF of ceramic capacitors, the output noise is 70μVrms. When C1 is a 4.7μF film capacitor, the output noise is 50μVrms. The image 01 shows the noise waveform 1000x amplified.

According to the SPICE simulation with the most accurate 431 and 317 model I can find, PSRR reaches 160dB and the output ripple shouldn't exceed 100nVrms. (buried in noise) Reality is mostly disappointing. With an input ripple of 1.8Vrms, the output ripple measured by averaging is 40uVrms which means PSRR=93dB. However my preamp shielding isn't particularly clean and the output might have been polluted by the mains, because measuring the LT3080 version also gives around 45uVrms, which means the majority of output ripple might be mains hum coupled into the scope somewhere. Try measuring it better by yourself to determine the actual PSRR value.

Components

I assembled the prototype board with mainly SMD parts, and ignoring the unused area (which I planned for testing some other circuits) the actual size is smaller than a card. You can use THT parts of course. Here's a list of explanation for some components:

Q2: Power MOSFET used as cascoded U2 protector. I just happened to have STW11NK90Z in hand, but beefier STW12NK95 or lighter STW8NK80Z should also work.
U1: Original Maida regulator uses a Zener diode, but I found using a TL431 gives lower output noise. TL431 has another benefit which is its low output impedance compared to a Zener. This impedance acting with the Ciss of Q2 can create an unwanted pole in the cascode loop, and may cause parasitic oscillation. See Q1.
Q1: Providing bias current to U1, and isolates the Ciss of Q2 from U1. TL431 typically can only take up to 1nF (for small capacitance) from its cathode, so Q1 also acts as a buffer between U1 and the gate capacitance larger than 1nF. Also if you:

• use a resistor instead of Q1, or
• use two LND150 in series instead of CPC3980, or
• connect Q2's gate to the bottom side of R3 (suggested by The AoE Figure 9.113. To be fair they added a ferrite at the gate.)

then using a 0.5W 15V zener to drive STW11NK90Z will certainly result in oscillation and the HV transformer will shout. Interestingly, 1W zener driving STW11NK90Z (Ciss=3nF) or 0.5W zener driving STW8NK80Z (Ciss=1.32nF) is stable. Meanwhile, I highly suggest that you DO NOT include a gate stopper resistor for Q2, as it also slows Q2 down and WILL cause oscillation. These observations are highly component-dependent and I don't know if your parts will behave the same.
U3: Voltage reference and feedback amplifier. This TL431 is protected by Q3, D1, and D4. However, TL431s from different manufacturers might behave differently. See R10.
Q3: U3 protector by cascoding. I have some LND150 in hand but an enhancement MOSFET with enough voltage rating (like over 600V) should also work. If using an enhancement MOSFET, prepare another bias voltage of around 10 to 15 volts for the gate.
R4: Decrease the thermal dissipation of Q3. If you change the output voltage to be lower this is optional.
R8, R9: Feedback resistor determines the output voltage. Output voltage is 2.495V/R9*(R9+R8)
C1: Adj bypass capacitor for LM317. Can be as low as 0.22uF but the larger C1 is, the lower output noise will be. If C1 is larger than 4.7uF, during start up the output voltage will ramp up for extented period of time. This acts as a soft start. Capacitor larger than 10uF doesn't affect the output noise more but still extends the soft start. C1 also contributes to the loop stability, see R10.
C2: Used for increasing HF loop gain around U3. Maybe be optional but adding it improves PSRR and lowers noise. 0.22uF MLCC is generally enough.
R10: Tunes the HF loop gain. If C1 is larger than around 1.5uF and U3 is a TI or HTC one, then R10 can be 0Ω (shorted). If C1 is smaller, then R10 has to be made larger to ensure stability. For example, when using C1=0.22uF (MLCC), R10 has to be at least 20kΩ. Less R10 results in a noise peaking at higher frequency until the circuit oscillates, but more R10 causes excessive broadband noise at the output, so you might have to trim it for your need. Also, if U3 is from onsemi when C1=3.8uF (MLCC), then R10 has to be at least 10kΩ to be stable. (but the noise rises to 400μVrms, so not a good deal) Again, these are only the results from the batch of parts I have, and your build might behave differently.

All caps used here are rated 600V or higher. They can be polarized ones but polarized capacitor tends to take a lot of place and the value can be too large for this application.

I wish this little application note might offer some help for those who want to build a power supply. Keep safe and good luck.

Hi, sometime ago I got a kit with upc1342v and NJW0218G/ NJW0302G transistors.
There was an instruction about how to set it (I guess the quiescient current), but I lost it.

Here is the schematic


I dont quite remember what to measure when setting the 5k trimmer (the current going through the power lines?).
How much the current should be for the given power transistors?
Also, if it is dangerous if I drop half the power supply when I am measuring (as it is dangerous with some chip amps).

Hi peeps,

I have a bit of a noob question to ask.

The value for this rezistor should be 1.4 kohm, right? Or am I missing something?

Thank you.

Hello Everyone,
I have read somewhere in the forum about tube rectification for PS of TDA 1543 ? Is that some joke since we are talking about max 8 vols at a very low current ? Is someone seeing some idea in that ?
Thanks

As I have two LL1667 5mA lying in my box, I thought of giving them a chance in the concertina, for a 15W 6B4G PPP for my 414-8A midbass 60-350Hz. With coils in opposite phase 15mA is max. Would be great if it worked as planned as there will be less problems with max swing compared with a conventinal inverted concertina with the available 270V B+. Will try to find a suitable low Cin MOSFET if the 2540 isn´t good enough. Driver before the concertina is a trioded 6E5P.

Could anyone please do a sanity check of the circuit. Sims good, but you can not see what will happen at higher frequencies. Tried to get capacitance and K figures from Lundahl, but they couldn´t help me.

Hi!

Has anybody got the PCB Gerber Files to make Giulianodes Relay–Based Interpretation of Bob Cordell's THD Analyzer Design please?

The Rotary Wafer Switch Assemblies and the wafers/screens, etc., etc., are getting very difficult to find and are a great deal more expensive than the total number of relays Member Giulianodes used!

There used to be a Dropbox link but this has been dead for years, and several other Members have said they have the files!

Chris Williams

Selling 1x ECDesigns U192ETL

USB to ElectroTOS/ Toslink converter, transport
all capacitors changed to Audio Note Kaisei BP
Including ElectroTOS cable

SOLD

Hi,

Do not ask me why, but after 10+ year an old obsession came back and I like to play with motors for turntables :- )
Maybe because I've recently acquired a Systemdek TT and want to improve.

Some 10+ years ago I wanted to play with 3 phase motors, I thought that should be the most smooth, silent but stable strong driving. Maybe THE ultimate driving. Since I had experience with DDS generators, to generate a precise, very close to sinewave (14bit, 400MSPS) what I can adjust each phase difference was not a problem.

Then I've started to search for motors. Had an expensive maxon and a lot of hard drive motors, some RC plane motors. None was good for being a TT motor, the reason was they liked to spin in high rpm, hated to spin in low rpm we need. Not only with my drive, I've acquired multiple divers too, result was the same.

A 2 phase driver derivated from that project, to drive the good old premotec/airpax/philips sycn motor - and that was great success. Especially with motors rewind to 24V. Sure it is overkill. Making 2 sinewave with 2 AD9954, than some signal conditioning and a power amp module (2x LM3886). I prefer it over the usual maxon 110191/110189 what I have to a friend.
I've used the DDSgen+LM3886 to 24V sync motor for a decade, I guess it will still win and will be my main driver, but I just can not stop playing with DC motors too, and now, I would ask YOU:

Do you have any tip, advice for a 3 phase motor suitable for TT, which may also accept (or even better is designed to) low rpm?

What is low rpm is relative I know. The sync motor spins 250 rpm, but with smaller pulley and driving on the outside of the platter we could go up somewhat (but for sure not to 3000+ RPM, where most motors started to shine what I've tested so far).

???

Thanks!
JG

Hi,
Trying to experiment for the first time. I've got some MAOP 10.2's well broken in, but currently homeless and I am considering grabbing some SB Audience 18SW450 18" subwoofers cause I've never really had "big displacement" drivers before.

Considering my first build with these to be an open baffle, cause I also haven't had an open baffle before, or even listened to one.
AND I'm also trying to design a speaker for the first time.

This is where I've gotten to currently.
Please note the shape of the baffle is a bit rough. Not deliberately wonky! Designed to be a winged OB.
1st order lowpass on SW at 100hz, 1st order highpasson MAOP at 600hz.



Without xovers:



I have a sneaking suspicion that the response on the MAOP is actually terrible. I don't believe BASTA models well above 1k though, so I'm not sure. Note the scale of the dB response.
I also don't like that the Full ranger is so far away from the SW driver (40cm).
I believe it should be within 1/4 wavelength of crossover to sum well? Which is actually kind of impossible with an 18" woofer anyway? With a non-symmetrical crossover, which should I be calculating for? The midpoint at 350hz? ~25cm

I don't actually really know what I'm looking at. I'm going through and trying to compare it all to the documentation that is online, and actually learn what I'm doing, but understanding what keywords I should be looking for in this instance, might accelerate the process significantly. I'd love anyone's tips or feedback here so I can move to my next phase of learning.

Is the peaking at the bottom end of the MAOP response "bad" or expected with OB?
What is a good goal response for the FR driver if this is actually as bad as I think?
How high in the bandwidth do I stop paying attention to BASTA's sim?
Does the SW actually look good like this with the lowpass in place?
Should I consider a H frame or U frame for the SW with a separate baffle on top for the MAOP?

Thank you for your time, I can't wait to hear your thoughts.

Dear diyAudio members and professionals!
I'm Robert, form Hungary.
I would like to join your community as an amateur electronics technician.

Hello, after looking around for options i would like to build my own volume control, relay based one seem to be one of the best and they allow me to play around with arduino again

some features im looking for

• atleast 1db steps
• 2x2 XLR Balanced Inputs
• 2x2 XLR Outputs

Microcontroller for:

• Display
• Rotary encoder
• Remote
• Mute Button
• Input Select Button
• Output Select Button
• Saving Volumes for each input

If Possible:
A "desktop unit" controlling the main unit (IR?)

imo the most flexible i stay with a relay board that basicly just contains the relays, i might do a seperate controller board (or wire it individually)

Questions i still have
1. i saw a design with 6 relais (-1db, -2db, -4db, -8db, -16db, -32db) but it seems this design has up to 6 resistors in series, isnt a shunt stepped attueuator "better" with only two resistors?
2. which type of relais/resistors? pref 0,1% precision
3. any recommendations or ideas are welcome 🙂 also when people are interested i buy a few boards more...

Hi,

I want to measure the noise the final tubes make in a PP stage. In other words, disconnected from the driver stage. With nothing connected to the finals G1 (except the negative voltage through a 100K resistor) I can hear some noise. With UL the noise is louder than in triode mode, but the nature / sound of the noise is similar.

I tried shorting both G1’s with a capacitor (0.15 uF) to ground. This resulted in quite loud pops (pop pop pop, every second) from the speaker. Then I tried both G1’s connected to each other with these capacitors, but this resulted in a high tone screaming from the speaker. There is no NFB in the amplifier, only UL mode when selected.

Do driving grids pick up noise when not shorted for AC?

I will hookup my spectrum analyzer tomorrow to get a beter view on what’s happening.

Regards, Gerrit

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Seems like there's some ideas that could be used for Audio DACs such as the divider driven LSB etc.

Hi. How can i sell my troubleshooting notes? I have been an audio Tech for over 40 years.​

Thank you

I have 4 new Talema 70065K transformers including the matching boards for sale, each for 20€ or all together for 70€.I have a few more of these 4 of these and can let a few more go as well. The Talema Transformers are very silent. The price does not include PayPal and shipping costs. PayPal is accepted, registered mail order buyer pays the additional 5% PayPal fees. With PayPal Freund the 5% does not apply and can be sent without tracking, the shipping costs within the EU are approx. 15€. Shipping within Germany €6. Outside the EU it may vary by country. Combined shipping possible. If you are interested send me a PM.

hello! i need help audison bit one processor is not turning on. Using remote turn on or audio signal turn on is not working. please give advice or somebody has a schematic at power supply side, i really appreciate.
thank you and keep safe

Hi there,
I am a guitarist and wish to take the smallest equipment to replicate my favourite guitar tone to various amateur live venues. My ideal equipment is a small ‘guitar headphone amp’. This unit plugs into my guitar and has a mini headphone jack output. Designed to practise at home. I assume I can send this into an ‘aux’ input in a venue’s mixing desk, but if they don’t have this option then how can I send it to one of the main line level inputs?

Pair of LL2785CAM 60ma amorphous single ended OPT for 300b or 2a3
Only a month old. Perfect condition.
Ideal upgrade for Elekit TU-8900E.
I can confirm that these sound spectacular!

These retail for USD482 each.

Asking USD700 or 550GBP pair
These are in the UK. I can ship worldwide at cost.
Payment by WISE or bank transfer only. No Paypal.

Hi all, I love diyAudio. Learn from everyone

Hi thanks for allowing me to join this group.
My system has been working flawlessly for years but today I noticed the main amp was still powering the main speakers with the blue off , power ring button released !
Still sounds great but would appear to be permanently active .

Thanks for accepting me, I've been involved with electronics since I was just a kid in the mid-1960s, In the 1970s I built my FM receivers which for some reason were scarce here in Australia when FM transmissions began, in the mid-1980 I designed and built my own solid state amplifiers, I also built my own transmission line laud speakers, from the late 1980's work pressures moved my HiFi on hold until I retired in 2021, since then I renewed my electronics to three-way active loudspeakers, last year I put together my first streamer, based on RP4 Allo digione streamer with ES9038 DAC, running on Volumio, which really impressed me, the noise floor has pushed some distance underground, Currently I'm trying to commission my new Protodac/RP4 streamer, trying to configure on MoOde, the available instructions are vague would be an understatement.

Hi to all.
Having purchased a TA-5650 with half working Vfets, I wanted to ask the experts what modifications is necessary to make it work with only one pair of Vfets per channel, as in the 4650. The voltages for the power transistors are almost identical and it is probably only necessary to modify the values of some resistances. Thanks for the help

This originally started in this thread which asks the question "why aren't we building a bookshelf synergy monitor" and answers it with "we are" or at least "let's try and see what we get."

I got inspired back in the Trynergy thread to build a semi bookshelf point source horn

The results with the SB Acoustics SB65WBAC25-4 were very encouraging that Bushmeister went and ordered the drivers and some off the shelf waveguides to start experimenting.

So here is sort of my vision of the end goal. It's all very fluid and we try to make things smaller where possible. The reality is it might be closer to a small stand mount. Decisions of which WG to bass the system on sets overall size.



Thanks to Bushmeister for the willing spirit to tackle this project. We are going to work together to come up with a new speaker with development and plans happening in real time ad hoc. It starts with Bushmeister picking the off the shelf 18 Sound waveguide.

Here is a summary of the completed speaker built by Bushmeister.

I guess we are calling the "XBush". Post 1248

Some highlights of the XBush:

Predicted sensitivity and response before EQ using a Harsch XO at 500Hz and SB23NRXS45-8 woofers:


The business side of the horn normally not visible when boxed up:


Mounted inside cabinet:


Finished speaker:


Acoustic XO slopes for Harsch:


Harmonic distortion at 100dB and 1m (nice!). Note that this is just a 2-wa speaker with two sealed 8in drivers - that manage to produce nice deep bass extension with low distortion:


Measured acoustic phase:


Measured Horizontal Polar Directivity:


Measured Vertical Polar Directivity:


Step Response:


Measured Group Delay:



######### XRK971's XBUSH ############

Not fully up to snuff yet when compared to Bushmeister's amazing effort, but here is Xrk971's attempt which uses a Faital Pro LTH142 waveguide, dual Dayton RS180P-8 woofers, and same SB65WBAC25-4 mid/tweeter:

Internals with all 3d printed driver to horn adapters (here shown with early version using DC200-8 wofoer):


Later version with RS180P-8 woofers:


Detail of SB65 throat adapter:


CAD drawing of adapter:


All 3D files (STL) for xrk971’s Xbush are here:
A Bookshelf Multi-Way Point-Source Horn

Fitting into box for first time:


Measured Polar directivity of SB65 in LTH142 waveguide:


3d printed woofer to waveguide adapter:


3d printed woofer chamber volume reducer plug:


Polar directivity with woofer holes:




Used in stereo with uTrynergy on left and Xrk's speaker on right:


Acoustic XO slopes of Xrk's speaker:


Phase of Xrk's speaker (still working on getting it flatter and proper 55deg phase bump for Harsch):


Harmonic Distortion of Xrk's speaker (not very good - many leagues below what Bushmeister is able to do):


I suspect the higher HD has to do with a number of things including: driver choice, cabinet volume and wall material, cabinet resonance damping methods, waveguide inertness via 4kg of epoxy Bondo, and larger holes (60mm vs equiv 29mm).
All pieces and adapters on Xrk's speaker were 3d printed PLA vs hand cut and epoxy for Bushmeister's excellent effort. Sometimes low tech gives better results.

So, my speaker is still a project waiting for more work to improve the phase, the step response, and improve the harmonic distortion.

Hi all,
with JLE TPA3255 amp in the table, i am trying to shunt the input stage, which is unuseful because drived with a high level differential DAC (SMSL SU-9).
The JLE amp is design with PFFB topology.
Tried yesterday shunting input stages not working. Amp goes to FAULT.
What i had done :

• Remove SE/BAL solder jumpers
• Remove opamps from sockets
• Connect J1-1 to socket A pin 1
• Connect J1-3 to socket A pin 7
• Connect J2-1 to socket B pin 1
• Connect J2-3 to socket B pin 7

Something strange is near 2.9V DC mesured at the outputs AC blocking caps.





Another try is removing 100k input resistors to ground (RA1, RA2, RB1, RB2). Same results.

If you like it, does it matter how it measures

Hey guys,

is there a possibility to switch between the EQ presets without connecting the DSP to a laptop?

Like switching from BT to Aux via short circuiting Ground and Stop.

Thank you!

I have a recently acquired Kenwood KD-770D with a speed problem. It appears that the PLL is not working because the table runs about 54 RPM at both 33 and 45 settings. PLL lock LED doesn't engage. I'd appreciate any suggestions on troubleshooting this table, thanks.

EDIT: I'm just looking for suggestions based on prior experience with this table (or similar, e.g. KD-990). Just trying to shortcut the solution with information from someone who's already been there. Cheers.

Hello,

I have for sale a few pcbs or finished modules for this amplifier.


More info about the Gaincore can be found here.
This amp is capable of giving 25wrms/8r with very low thd using a single 29.5vdc power supply.
It accepts sits and mosfets(to247 and sot227(pucks)).

The A2Cmx-V hosts an A2Cmx filter like this one and a negative rail converter this way you need a single rail power supply.

As a minimum requirement for the choke you will need 60-70mh and 2a.

2x Gaincore pcb + 2x A2Cmx-V pcb - 40€
2x Gaincore module(without Sit) - 140€
2x A2Cmx-V module - 120€

Hello. Working into a Williamson project, kind of. I can get 100 Vdc above onto the first plate supplying the first stage with the same 400Vdc as cathodyne did with 100k plate / 1k cathode resistors. I know the original scheme used 47k/ 470 ohm suplied at 250v above to get the same current. But the swing is minimal, I drived the amp with 200mVpk without nfb applied. Does it make a dramatic difference in respect with original circuit please ? Thanks.

This is my actual circuit.

Hello!
I just wanted to share something I found on eBay UK. Sold as base extenders, seems pretty useful to test tubes that are not pin-compatible with an existing amp or a tube tester.
Search for "McMurdo B9A Vintage Valve Base Extenders - Set of 6"

Hey guys,

my name is Chris and I'm from germany.

I have built two LF-Sat12 from a german developer (Jobst Audio) and a lonely.TH12 MKII (12 inch tapped horn) from a german developer (lonelybabe69).

Now I need some help with my DSP (NVArcher) and hopefully I'll get the needed information here.

Thank you!

I just scored a Dynaco FM-3 for $60 to complete my Dynaco system. I’m going to clean and refurbish it. Are there any common things I should look for? I’m debating on changing out all the carbon comp resistors with new metal film ones. I’m going to replace the multi cap with individual caps under the deck. I’ll also do electrolytic to form on any signal path caps. What else should I look at?

I'm building an old school distributor machine for testing vintage motorcycle ignition systems. I want to flash LEDs to indicate when the ignition pulse is happening and would like to use 12V to trigger them to avoid needing the high voltage coil and spark plug. One hurdle I'm running into is the dwell time of the ignition pulse is far too long. The LEDs stay on too long to see any timing marks.

I've been searching for edge trigger circuit designs that will work for me but every one I've in come across the minimum on time is at least as long as the trigger pulse. I can make a microcontroller see a rising or falling edge and flash the LEDs for a few microseconds but it seems to go erratic at the upper end of the RPM range.

Does anyone know of an edge trigger circuit that can have an output that's shorter than the input pulse?

This: (one of the L15D boards in my 7-channel amplifier):



Not actually sure what caused it as all I did was change an opamp in the phase inverter buffer. But it was quite exciting, with flames, noise, and magic smoke everywhere! And it even blew the VCC leg off the opamp "Is something burning?" asked my wife, "Nothing to see here, move on", I replied sheepishly 😱. Lucky I have a spare board and inverting buffer.

But I have a question. Should I have fuses between the +/-55V 500W SMPS and the L15 boards, and if so, what value fuses should I use? And should I put one fuse in the +55V rail and another in the -55V rail?

TIA, Jon.

Hello all. I'm hoping someone more knowledgeable can help me out with the electronics on my filter. I'm using a piezo tweeter in a two-way with the following filter on the piezo: a capacitor in series and a parallel (shunt) resistor across the piezo element. I'd like to know how phase is affected (if at all) by this type of arrangement. As far as I know, piezo elements also behave like capacitors in circuit.

Thanks for any help. Let me know if I should post this in a different section.

Hey everyone! I’m new here! I’ve just gotten into designing turntables and audio equipment so I’m excited to learn more about how they function!

Hello DIY audio. Very excited to explore the world of audio electronics with you!

(reposted to the correct thread bc im stupid) Howdy guys. Sorta new here. I'm really just posting this to show off what I've been working on for the past few weeks, but all tips and suggestions will be much appreciated:




The idea was to make something akin to a traditional guitar amplifier, but with a little more versatility. I had a few parts laying around: an old mini-pc, amplifier, and a Focusrite USB interface. To make use of them, I settled on using the standard 19" rackmount system to mount whatever I needed. Funny enough, there is not a single consumer-grade piece of rackmount audio equipment in there (dedicated EQ, compression, etc.) This was mostly by design. The mini-pc allows for fully digital effects (basically anything you can imagine), so there's little point in buying even a simple 1U signal processor. Moreover, more metal in the case = more weight. Portability of this system is very important. If I were to add something like that, it'd probably be an EQ, but I am full up on rack space in the front.

Anyways, I settled on a 6U rackmount flight case. 17" deep, 19" wide. It has a cover for front/back which is quite nice for portability. The covers themselves have zippers and can hold things - very nice.

From top to bottom, here are the components on the front of the rack:
1st U: Sliding tray with portable 15.something" monitor. Hold a bluetooth keyboard+touchpad combo.
2nd U: Fixed tray with Beelink s12 mini-pc, Focusrite interface (2nd gen), and a fosi audio 2.1 amplifier
3-6th U: Speaker solution. Material is either MDF or 3D-Printed (PLA). Many different speakers have been used: Marcaudio fullrangers, Fountek fullrangers, SKAR audio coaxials, woofers stolen from various studio monitors, and a Dayton audio 7" woofer (newest addition).

The back of the rack holds only the PDU. Just don't look at my solution for mounting the sliding tray. I'll probably be filling the rest of the back with a blank panel covered in acoustic foam. What do you guys think about that? Because I've just been running these speakers with the back of the rack OFF, creating a pseudo open-baffle speaker. Still sounds alright.



Signal chain: Signal sent to the interface is sent to the mini-pc which is then processed by FL Studio, and then sent back out the interface into the amplifier via RCA. Speakers are passive.

Speaker solution: The most challenging part of this was designing a "baffle" that would house speakers and sit within a standard rack. If you look up "rackmount speakers" you really don't get anything useful for this application. Why? Because this is an insane niche that never needed to be filled. What you find on google are these weird audio monitoring speakers that are very nearfield. So, I had to make my own thing. At first, I was able to get away with it by sticking a Kenwood CRS-158 on a shelf inside the rack. That worked good enough as the center speaker was exactly 17" wide, but it took up about 3.5U of rackspace, leaving lots of dead space. I started making designs on TinkerCAD and sent them to a guy who routes MDF and a co-worker that does 3D printing. So far, the only difference I've noticed between MDF and PLA is WEIGHT. My god, even with more/heavier drivers in a 3D-printed baffle, it's lighter than any MDF baffle. I'm sure there are drawbacks to PLA acoustically (not totally infilled, resonant maybe?) but my ear really hasn't heard a difference.



Drivers, how it sounds: I got a combination of full-range drivers and woofers and just started trying them out. It sounded pretty damn good in the beginning, despite the cheap/small speakers and shoddy measurements. But I quickly realized that I needed to optimize for speaker size, as a 4" speaker is NOT going to reproduce 60-70hz (I downtune my guitar), especially in this enclosure. Enthused, I went ahead and got some nicer speakers with a good cone area. These were the CHP-90s from Marcaudio and a 7" woofer from dayton audio, paired with some smaller fountek full-rangers(I also got some 4" marc audio drivers, the CHP-70s, those didn't work out very well in terms of response). Now it's sounding really nice to me. It fills to room, produces bass, and just lets me vibe out. I have yet to measure the frequency response, but I'm sure it's ****** in some way.

I settled on a 2.1 amp so that I could use a dedicated woofer if needed, reducing stress on the full-rangers. Uniquely, this allows me to run the speakers in stereo, which is actually quite noticeable, especially on my "2-way" baffle. The focusrite interface allows the system to receive two signals at a time. Some fiddling around with my DAW (fl studio) allows me to assign different inputs to different speakers, if I really wanted to. I'm also exploring ways to angle the smaller full-range drivers outwards to get a better stereo image. Basically a toe-out.

It really is more than just a guitar amplifier. As I play my guitar, you can send MIDI signals to FL Studio via USB and at the same time be using an XLR input from a vocalist for example, all while drums are looping on the playlist. And you can record it all. That is really ******* cool.
Some problems I battle:

VIBRATION: oh my god, does this thing like to vibrate. At med-low volumes, there is no issue. The moment you go past any reasonable listening level for a small room, the entire case and the contents within begin to resonate at particular frequencies. To account for this, I need to remove anything that is sitting on top of the case. Make sure that all screws are tight and even. Use many rubber washers. I've also stuck a few vibration-absorbing gels around the inside (you know, the ones drummers use on their snare), who knows if that's done anything. I guess I'm sort of asking for it, sticking speakers in a plastic enclosure which houses several different components fixed in weird ways.

COOLING: After I added the 2.1 amplifier, thing get kinda toasty in there. I mean the pc, interface, and amplifier sit right next to each other. It hasn't necessarily become a problem yet, but I'm exploring lightweight, quiet, and unobstructive cooling solutions. I'm thinking of a 1-2U panel lined with noctua fans.

PORTABILITY: This really just means weight. This thing gets heavy quick, as rackmount equipment is almost always full metal. Any addition must pass weight consideration. Also, I definitely don't need 17" deep in my rack. I could probably get away with 12" deep, just to reduce bulk.


Let me tell you, I ******* love this thing. It gets loud, shakes my room, and is just overall so much fun to play with. I've spent so many hours modelling cabinets and playing with effects. I just got so tired of playing guitar on my "main" computer, and said screw it, I'll build something legit. And lord knows I'm not dropping $500-1000 on a decent guitar amplifier when I can drop the same amount of money to build something truly unique and more versatile. Don't get me wrong, guitar amps are cool, but this is RAD.

This is a companion amplifier to the synthesised sinewave generator, for driving low-voltage 2-phase motors.

There are many amplifier modules available, but due to the output voltage swing required, these will typically have quite a high power rating as they are intended to drive low-impedance loads, which is not needed for this application.

An Analog Devices application note shows a high-voltage amplifier which seemed promising for this application, using an op-amp with supply current sensing and a potential divider on the op-amp output to provide both a current boost and allow the high voltage rails:



A 2-channel amplifier suitable for a low-power synchronous motor based on this concept has been produced (non-inverting, zener references), using mostly non-critical parts. The TL071 op-amp proved suitable, with the only critical component being C1 for the stability of the current feedback loop:



With C1 of 1nF, step responses at 70Hz (left) and 5kHz (right) are good:



A PCB is available, Gerbers and build guide are attached to this post.



Full details also on my GitHub

Dear All,

Greetings from Poland. It has been a while since I started the journey with electronics. Started from scratch 2 years ago, learning from yt, books and forums I have had a good time with building up some diy kits.
I would like to get to know with you, sometimes to ask for a support. BUT first and foremost - to have a good time with audio I create by myself 🙂
Building some simple DAC, headphone amp and dual mono amplifier have given me a real lesson, and still does.
Currently I am working on preamp kit of Bryston clone bp26, which will be my 5th project 🙂
BEst regards to everybody!
Umetek

Does anyone happen to have the PDF of the shootout results? The original site is down.

Have a integrated Krell F.B.I sins it was new ca 2008.( but dident use it before 2011-2012 due to various reasons and health)

https://www.stereophile.com/content/krell-fbi-integrated-amplifier-specifications

And last 12 years it have been driven first my 1998 Von Schweikert VR-4 SR, and last 3 years my diy speakers 6 X Peerlees XXLS 12 inch modelnr:830847 ( 2 x 8 ohm coils, 3 per side tuned to 23 hz, in 100 liter reflex netto) each connected 16 ohm at the driver, and parallell to 5,66 ohm outside.

Active filter before amp, so Krell amp and XXLS 12 do the jobb up to 340 hz left and right ( Unother amp take midrange and top from 340 hz an upp left and right, passive xover in MTM)

Im a real high listener, mostly over 100 dB + the 15 dB peaks, so Krell amp have to work ”hard” and always get very hot on my 3-4 hours of playing now and then.

Suddenly when im listening the amp shutts down itself. (protection mode ?)

Started it up again after a few minuts, and all seems fine. Dident play as loud the rest of the listening, but it newer happend agian that night.
2 weeks after when i played as laud as i use to do it happend again, the amp” shutts down itself ( and now i begain to be worried)

Let it be for a few month ( dident have health to deal with it), and when deside to listening again i shifted the speakerconnetion so the Krell only do the mid¨s and top MTM ( for a more easy load)

It played my MTM for 2-3 secunds and then amp shutts down itself again…Grrrrr

Hade A friend brought the 55 kilo amp up from the basement & put it on my kitchen table for me, and i connected it only to 240 volt power and power it up ( no speakers or soundsourses connected) and everything seems normal (it has a 10 second start-up sequence before it goes to ready-mode)

Let it stand in ”power on mode” for an hour and them measure DC offset at the speaker terminals. The meter setting was 200 m, and both left and right speakeroutputs shows value from 010 minus to max 035 plus ( was ofted at 003)

My question is where do a go from here?

Connecting a soundsourse? Speaker ? and measure again?



Best regards John

Hey everyone! I'm a senior in college and I'm designing a turntable for my senior project. I'm interested in designing and building my own linear tracking tonearm, but I'm a beginner in audio electronics and could use some help figuring out what parts I need and how they generally work. If anyone could provide some guidance on where to begin it would be much appreciated!

Good morning from beautiful Worcester, MA!

I'm designing small bookshelves for a little media room (TV, computer, games) and my wife wants them as small as possible of course 🙄 The room is about 3 x 4 meters and I will make a subwoofer for <80 Hz later on.

I want to do a narrow baffle using the Peerless SLS-P830945 5-1/4 inch woofer with solid wood on both side aligned right to flat faces of the Peerless. So it'll be easy to make a ported 3.5 liter box with a 5 inch baffle.

For the full range, I was considering a MarkAudio driver crossed around 500 hz, first order if possible. I was considering using the Alpair 5.3, but the CHN-50 is less than half the price and seems to be very similar? Does anyone have experience with both and can clue me in to what I should be looking at to make a decision?

Obviously I haven't taken measurements yet, but playing with curves in WinPCD it seem a 1st order with the Alpair (80 uF) and a 1st order + Zobel on the Peerless (1.3 mH / 17 uF - 3 Ohm) behaves rather well. That said, I'd love your suggestions or criticisms.

Thanks

I have an earth loop which I'd prefer to leave in place and hoped wouldn't matter. Yes this problem is as old as the hills but not quite like mine. This is a long one. Perhaps you should visit the small room before proceding, and then only if you'd otherwise be bored.

No problem with line level signals but when the gain is very great - amplifying 5mV phono up to 20 Volts into speaker loads - I get low a frequency feedback howl which is so low as to be almost subsonic when the gain is turned up. This because RIAA gain is highest at low frequencies.

The situation is:
Two sets of speakers (electrostatic and dynamic) crossed switched from two amplifiers (valve and transistor). One amplifier is a stereo integrated amp and the other (valve) is a stereo power amp. Nice set-up.

Unfortunately I have to use the integrated amp's phono stage via its tape record outlets to drive the valve power amp. All signals except phono are attenuated and switched to either amp outside of both amps. Both amps are earthed to the house mains.

Here we go.... Both amplifiers' speaker minus outputs are connected to their respective mains earths - neither amp works in bridge-mode. I've commoned all speaker minus inputs and all amplifier minus outputs. That's 8 wires connected together. All live lines are switched with two DPDT switches.

[ Imagine two simple stereo two way speaker select switches mounted back to back with their commons connected together. One box switches the speakers conventionally, the other selects the amplifiers working backwards. They wouldn't need to be four pole switches because it wouldn't matter if both pairs of speakers got one of the phases provided the other phase is switched to either one of them. Maybe some good switcher boxes do it properly with a four pole double throw. Thinking abt it I reckon that would solve my problem just wouldn't be as neat as my purpose-built switch box]

Needless to say if one amp (the valve one) is simply unplugged from the mains the problem goes away.

Aside from the safety aspects, mitigated by bloody great labels saying "This device's earth is disconnected at the plug", Where do I put a (very high current) mains-earth path for star-earthing?

My guess, in my situation, would be to the 8 commoned heavy-wired speaker ground-lines, with a ninth connection to a dedicated mains plug with a single green and yellow conductor from its mains earth.

But OK, back to the real world, would it correctly go? To the deck/tuner, the control unit or the power amp? My guess would be to the power amp. But in any such case, you'd have signal lines carrying massive fault currents from the other components' failures.

Got it! Run everything from individual isolation transformers! Hang on, then how'd you know there was a fault......?

This is my first real post on this forum, so hopefully I'm following protocol and etiquite.
I few years ago I bought a Sumiko S.10 subwoofer. I really enjoyed it, but eventually it just stopped working. I'm far from a DIY audio guy, but was brave enough to remove the board from the back of the sub and look it over. I don't know anything about electronics, but found something that didn't look right. There is a burn mark on the board. Check it out on the bottom right of the image:



Here's a closeup of it:



I spoke with the US distributor of Sumiko. They told me they could sell me a new board, but it came with no warranty whatsoever. Given the reputation of these boards failing, that didn't sound appealing to me. I'm told I can salvage the sub just buy installing a different plate amp from Dayton or Parts Express. I don't really know what to buy, though. Also, I was under the impression there should be just a couple wires to hook up, but it appears the Sumiko has more than that. I think if I can figure out how to wire the correct aftermarket amplifier to this thing I can get it working again. A friend of mine has offered to mount it properly to the back of the sub. He works in a fabrication shop and has some experience with that sort of thing.
So here are my questions:
1. Should I buy an aftermarket amp for it?
2. If so, which one?
3. What do I need to do to wire it up properly?
I'm not afraid to spend a few extra bucks to make the amp sound at least as good as it did originally, if not even better.
Here are more pictures of the subwoofer internals that will hopefully help:




If anyone has guidance for me I would really appreciate it.

I built a modular three-way PA cabinet for Small concerts, it uses a 3 inch compression driver, a 10 inch cone, both horn loaded, and a 15 inch in a ported box.

It's working great, but it needs refining.

My main concern is about the 10 inch driver. It (and the compression driver) are out of EAW KF 650's, but new horns.

I attached a PDF of a driver which I have heard from multiple sources is virtually exactly the same as what they put in the EAW.

The difference in efficiency between the 10" and the 3" is larger than when these were in KF650's. Believe it or not, the sensitivity spec for them were the same in a kf650, and in practice I even backed off the 10" sometimes.

I'm not sure if it's due to the airtight enclosure I made behind the 10" being the wrong size, or the horn change, or something else.

Based on what I learned from helpful people on this site and reading articles, I created an airtight enclosure for the back of the 10 inch driver.

But the volume of my cavity (term?) is larger than the manufacturer specification, and I'm getting ready to address that.

Is that specification a starting point, or something to strive to match precisely? Does what kind of horn the driver is connected to influence how much volume should be behind it? Should I experiment with different volumes, and if so, what protocols/criteria should I use to assess which volume of cavity is best?

Selling:

One pair of Lundahl LL1673/10H: 140 Euros + Shipping

One pair of Lundahl LL1638/20H: 140 Euros + Shipping

Power transformer with 230V primary in reasonable conditions. Heavy and reliable, it runs very cool.

I am not using it any time soon

Open to offers, shipping to EU only

Third post from a novice builder of the Nelson Pass designed ACA Mini amplifier. My amp is built and biased, and I've spent some hours listening to it. My impressions follow the photo of my completed amp.



I have listened to the ACA Mini, well warmed up, in two systems, and now I venture to offer some impressions.

System 1 (cobbled together): WiiM Mini streamer, Schiit Modi 3 DAC, Schiit SYS (volume control), ACA Mini, PSB Alpha T20 speakers (small floorstanders, about 87 db sensitivity).

System 2 (main living room system): WiiM Pro streamer, Denafrips Ares II DAC, Schiit Saga+ hybrid preamp with a 1946 RCA gray glass 6SN7GT tube, ACA Mini (in place of Schiit Aegir), JBL Arena 170 speakers (somewhat larger floorstanders, stated sensitivity of 86 db [I think], but really more efficient than the PSBs).

Impressions: The ACA Mini has incredible clarity in the treble and high mids, with a fantastic soundstage. This is where it really stands out. What it lacks is heft in the lower midrange and bass. My thought is that it has a good skeleton but could use more muscle.

The tilt toward the treble at the expense of lower mids is particularly noticeable with vocals and instruments like acoustic guitars, where the fundamentals are in the lower midrange.

Also lacking at the low end is a degree of impact necessary for a realistic piano left hand, not to mention drums.

By contrast, the Aegir excels with lower mids and bass. It has very detailed treble, but here I could give the nod to the ACA Mini.

If my Aegir was out for service, I could easily enjoy music with the ACA Mini in its place. Not bad!

Thanks to Nelson Pass for offering this kit to us. I had a ball building it. Honestly, I felt like a teenager, learning, doing, and having fun.

I recently switched to Magnepan LRS+ with balanced F4s and this M2x I just built I won’t need. The chassis, PSU, and transformer are brand new but the boards were previously used by a friend but he needed more power so I traded for the amp back and repurposed parts. The daughter boards are all stuffed and work. 60,000uf in filtering, Vishay resistors, Nichicon caps, and covers for the Edcor transformers. Transformer is an Antek AS-4218. With near 100 db efficient Klipsch speakers the amp only has a tiny hum with my ear 1 inch from the speaker. I’m sure I could have gotten it quieter using shielded RCAs. Dissipante chassis from Modushop and Norwood boards are currently installed.

The preamp I used all parts from Academy Audio. It has the LPS9 PSU, VCX volume control, and BIB balanced input board. It has 3 balanced inputs and 2 RCA single ended outputs. The PSU is a Meanwell 5V that allows you to use your favorite power cable. I also included the standby switch that allows you to easily flip the unit to mute and you can program the VCX for another type of remote. Galaxy chassis from Modushop and remote is included. If you plan to use single ended sources, I can offer some cables for cheap that are single ended to XLR.

I’m asking $1200 for everything and I’ll ship it for free. I would love to sell these two pieces together.

In my experience 12AX7 has a tendency to microphonics and the 12AY7 is pretty resistant to it. What I would like to see is a listing of tubes that tend to be resistant to microphonics. It seems to be a a hard thing to quantify but important in some applications.

Hello there.
In the Texas Instruments application note AN-263, it describes a Wein Bridge oscillator that is enhanced by the addition of a FET. The diagram shows a 7.5V Zener diode in the circuit. Now, typical op-amp circuits presume a +/- 15 volt power supply, but I might have to use a +/- 12V Supply. It seems not unreasonable that this might affect the voltage that one would use for the zener. The scope traces on the page show the circuit using much of the 15V rails. Is there some reason that I might want to change the Zener diode voltage from what is shown?

Hi guys.
I have a JVC JR-S100. 1 channel makes a loud noise for a short time after powering up, then suddenly disappears and operates normally. This noise is independent of volume setting.
Any ideas?