I was experimenting with point-to-point wiring with LM3886. Notice that almost full DC power supply voltage at output terminal! I thought I was losing one side of power supply but after carefully check, the power supply working correctly. Later on, I found that part of the input is not connected, after reconnect it works. I also try shorting the input to ground, there is no DC at output as well.

Why is that? Is it because incorrect input bias when disconnected?? I tried simulate on TINA-TI, and it is kinda show what I experienced.

Closed SW1 = Normal/ correct wiring. Only 1.18mV at output.


Open SW1 = Disconnected input bias circuit. Simulation show 22 V DC at output.


Please share your thoughts.
AP

Hi, is anyone using the Topping E30 II Lite dac on Mac? I have a Mac book pro i7 with OSX 10.13.6 High Sierra and I would like to purchase the Topping E30 II Lite to connect the Mac to my hifi system. Do you know if there is a need to install drives or does the Topping E30 II Lite work without it? Thank you

A recent thread discussed the internal emitter resistance of BJTs and its effects on thermal stability.

Since I was curious, I fitted a BJT model with an emitter resistor to the Vbe-versus-Ic graph in the MJ15003 datasheet. A reasonable match was produced with 40 milliohms at 25C and a 0.16 milliohm/C temperature coefficient. The Vbe sensitivity to temperature was -2.1mV/C and Is was 10^-12 A.




I am curious if anyone has similar data for other power transistors.
Ed

A little less than a year ago, I successfully completed my first tube audio project: an RIAA phono amplifier. It was a fantastic success, and my family and I have been thoroughly enjoying it. Winter is coming again here in the Rockies, so it's time to start thinking about indoor projects. At the moment, the preamp feeds into a set of computer speakers, which is pretty anticlimactic. It's time to start working on the rest of system!

I think what I want to do is an integrated amplifier (I might could be convinced to go another route) with a similar basis. I want the most minimalist circuit possible (100% tube and passives), single-ended class A, all analog (including power supply, because this is part of the fun for me), low power (pushing shelf speakers in a living room, rarely might need to compete with a vacuum cleaner), using modern, current production components (future proofing). My current setup consists exclusively of a record player, but there's an ancient Sonos that my wife uses from time to time, and I'd like to replace it with a better streamer down the road (phase three?). A third, maybe fourth channel would probably make for all the extensibility I'd need for quite a while. Aside from that, I think I don't really want much more to it than a volume control, again, for the minimalism to keep the part count to a minimum.

What thoughts or advice do people have for me? Any designs/schematics out there that fit the bill?

I made a simplified version of my STM32F723 firmware for STM32F723E-DISCO board with just I2S input (no I2S output). Should work at least at 192k/32.

It uses this board:
https://www.mouser.fi/ProductDetail/STMicroelectronics/STM32F723E-DISCO?qs=DXv0QSHKF4wBapbNjrzotQ==

Attached is the source code. It runs on FreeRTOS although this version does not really utilize it.
I used STM32F723E-DISCO board's Arduino connectors CN11 and CN13 for all I/O.
I2S signals are at CN11.1 (FS), CN13.4 (BCK) and CN13.7 (SD).
I2C2 is available at CN11.10 (SCL) and CN11.9 (SDA).
4 GPIO outputs at CN13.3, CN13.5, CN13.6 and CN13.8.
GND at CN11.7.

The source code also includes a "driver" for my AK5394 board which uses all 4 GPIO outputs. This can be used as an example of how to connect to ADC board.

STM32F723E-DISCO board is of course not optimal for running I2S as it is meant to be a showcase of various MCU capabilities. For best results a custom board dedicated to I2S should be used.

Have fun!

Well after much procrastination (and waiting for nicer weather....) the build has begun.

I own 2 atmos avrs and find both disappointing. IMO, height sounds such as aircraft, birds, thunder, rain, wind, spacecraft, rocket and other height sounds should only come through height speakers. Atmos is overhyped and basically snake-oil. There's no unique content in the heights. It's just a replication of the bed layer channels. Manufacturers are no longer making bluray players, because physical media is dead. Everyone is streaming. But streaming has a bandwidth problem. You can have quality 5.1, or compressed & lossy atmos. Since the heights are just the same data repeated, it makes sense to save the bandwidth and do the replication in the avrs instead.

I also want to boost the bass only for gunshots, thunder and explosions, and not music. And have automatic attenuation.

These are my goals...

delete

Hi first time poster.

I am restoring a '73 Minimoog synthesizer and it requires a complimentary pair (in this case 2N3904/2N3906).

I noticed in a previous post that a test circuit designed by Elvee might be the answer.



The attached is the circuit from the Minimoog service manual.

In note (4) the request is that the PNP Vbe is 10-20mV lower than the NPN at 200mA.

I'm not an engineer, but I think at that current it would deep fry the BJT's or cause thermal problems in the matching process.

Any help appreciated.

It is a quite long time now I`ve started to mod my Xonar STX. Now is finish this work. The result: you will not believe it (DIY...)
For those interest in this task, I open this thread...

Some pictures to follow...

Anyone using a mic calibrator?

Not frequency response, just level - 94 / 114 dB @ 1 kHz. I do acoustic measurements, the mic has a cal file but the sound card I have has a gain knob. So FR should be right(ish) but who knows about overall sensitivity. So, calibrated reference source to the rescue.

B&K and GRAS make expensive ones and that's great when work is paying. But for hobby projects I'm looking for something cheaper. There are a few of them for sale on Amazon for around $100. Are any of them worth while?

Let's see, here are some examples...
Reed Instruments R8090 - $179 (the expensive one!)
This silver cylinder calibrator - sold by multiple vendors - ~$111
Grey rectangle with orange band calibrator - multiple vendors - $79
Black cyl with blue LCD - $109 (sometimes this one is called ND9B, but then it's ~$200)

Anyone know?

A bummer - these all seem to be targeted at SPL meters and accomodate 1" and 1/2" mics but I think the typical FR measurement mic is smaller. I can probably 3D print an adapter, if I seal it...?

Hi ! i am watching this most unique speaker The old Allison Six



i do not understand the rationale behind this design
I guess that the cross Hz between the woofer and the tweeter should be around 2kHz ?
for a good part of its range the woofer should be directional
I wonder what the designer tried to achieve
Can anyone explain me please this design ?
I would like to replicate it but with a wideband in place of the tweeter and lowering the cross frequency
What would be the best cut ? 500Hz ? less ?
i am lost but intrigued

Never mind.

Draloric Polywatt Resistors with screw terminals:





I found them in an abandoned Lab in the University-Hospital where I work.
Never seen resistors like that before… the one in the housing is a potentiometer.

Hi all,

I bought a small cheap amplifier from Ali, claimed to be TPA3116 (but cannot be, of course, at this price; i just hoped will be some 10W peak but is not, at least not on 4 ohms), and I did some tests. Audio speaking, appears to cough (typically overload audio interruptions) at beyond 3W peak/6 ohms (subjective, hearing only) . Current supply from 12 to 24V rises a bit from 25 to 30mA (for the whole board) . Oscilloscope output shows that the rectangles are full voltage, so is not supplied through some kind of internal buck converter. The output frequency is at 370kHz.

Peaks seen on oscilloscope appears to be at 700mA at 8 ohms and 1A at 8 ohms, irrespective of voltage (12-24V) but dynamic response is far better at 24V, audio interruptios are rarer.

Do anyone knows what chip was really used in these?

Hi guys,

I'm trying to build a circuit to match NPN and PNP transistor pairs for my SymAsym amplifier. The basis for this exercise is the paper by Ian Fritz, see https://www.dragonflyalley.com/synth/images/TransistorMatching/ianFritz-transmat0011_144.pdf

Since I need +12V and -12V I want to use my lab power supply at 24V and use a virtual GND with voltage divider.
Here is for example the circuit for PNP matching made with LTSpice:



Voltage across the leads on the right side is measured for calculating the mismatch. R4 and R5 values should be as close as possible. I want to use 1% tolerance resistors, that's why I simulate with 99k and 101k.
The NPN version looks like this:



Due to the simple voltage divider the voltages are not +12/-12V but +13.18/-10.82 V for the PNP version and +10.82/-13.18 V for the NPN version.
I don't see a problem with that, except for the difference in current at which the transistor mismatch is measured.

Will this work? Am I missing something?

Best regards,

Jonas

what do you guys think is the best regulator in terms of price/performance?

LT3042/LT3045 still seems to be the best performing for around 5/10 euro, tho im wondering if some good regulators exist that cost half as much ?

TPS7A700 is a bit cheaper

I have a matched pair of the MAOP 11 and want to built the Lhotse with them.
I already started fabricating them, nice speaker!

Hi guys,

I have an Oppo BDT-101CI, I would like to unlock the region for DVDs, I found this online
https://www.oppodigital.com.au/pages/superdisc-unlock-your-oppo-bluray-player-for-all-dvd-regions
Do you think it is compatible with my Oppo?
The site is Australian..!!
Thank you

Hi I am Christos Spanoudes , 71 YOLD , electronics engineer, building DIY since i was able to solder, designed / built / serviced mainly PSU and audio gear but also control circuits , 40 years under name of CVRC ELECTRONICS , retired , now electronics is just for fun and hobby.

my question following a relative thread on this forum :


I have an amp that output devices Originally were 2SA1302 / 2SC3281 ( BAG END 400A )

Found a good direct replacement for the output devices possibly to be MJL1302/MLJ3281

The output driver transistors were 2SC3907 and 2SA1516, and i found equivalent to be possibly 2SA1943/2SC5200,
but could one use the MJL1302/MLJ3281 ( TO264 ) or even the smaller case NJW3281/NLW1302 ( for same case ) ,
as drivers to the MJL1302/MLJ3281 ?

because the MJL1302/MLJ3281 and 2SA1943/2SC5200 have spec almost same between them , except for case and max power etc.
and the MJL1302/MLJ3281 will be more robust if they will work ok .Unless there would be a catch .

Any response welcome to start in this super nice / useful ( I found ) forum.

Hi guys i have a Panasonic ch9 . Bookshelfs are ok but amplifier is dead . It have onboard crossover . Its a pre amp if i say it right . I want to detach crossover from board and attach it directly to speakers . Can you help me about it please

hi, I am experiencing problems since a couple of weeks with scrolling in mobile view on a fully updated iOS device (18.2.1) with up to date firefox as browser (Firefox 134.1 (49636)). This started a while ago, maybe a month. I have no addons installed.

description: the scrolling does stop, and does not float. it happens either way no matter whether the finger is released from the screen, or touching will scrolling. this behavior is periodically interrupted by a normal scrolling experience.

Hi All,

I am looking to replace the balance potentiometer for the rotel ra-930 ax. Trying to work out which replacement will be most suited. I think the resistance value is 100k ohms. I'm currently looking at some options by Bourns, but it's hard to know which is the right one. Any thoughts/links to appropriate replacements would be welcome, thanks!

I thought this would fit best here, as it is more of a 'whatever we want to talk about' post vs. putting it in the build thread or the like.

First, I won a gold medal for the s l o w e s t build, I think ordered the parts 4 years ago, and due to a job change, move, life stuff, I got the power supply built/tested, then didn't progress from there. Anyway, finally got it done and running today. Everything went smooth, no issues at all (I was VERY careful and sweated the details).

My main system is a McIntosh C53 preamp and I have a MC462 (450 watt SS amp) and MC275 (75 watt tube)...I swap between the amps as I feel like. like them both for different reasons. I also have the little 2.3 watt Decware Zen amp (it has some background hum that is preventing me from falling in love with it). I'm currently using and loving a pair of Zu Audio DW6 I picked up at the factory (about 45 minutes away, my welcome to Utah gift). Also have a pair of Sonus Faber towers that are currently off to the side while I enjoy the Zu's.

The main reason I did this build was to learn and sharpen my skills. I learned a TON, not only about electronics, but the build process. I remember the first time I tried soldering vs. now, where I can 'feel' the molten metal flowing and manipulate it (but still a lifetime of learning, I'm no pro!). As such, the amp itself was more of a curiosity and side effect vs. the main attraction. Maybe it would be good, maybe not, but not really the point.

***

Holy ****... I've been listening to it all evening, and I'm still not comprehending it. OK, maybe I am just in a really good mood tonight - but need to say my personality is NOT one of a honeymoon, most things I buy (or make) I generally don't like at first, then either stay that way...or grow to like them. This amp just immediately grabbed me and had be stand to attention.

OK, as I was listening, I was trying think of ways to describe what I was hearing. Like riding a motorcycle for the first time after driving your whole life, yup. Like standing at the rim of the Grand Canyon in person after seeing a documentary on it, yup. Like listening to a set of good headphones (I really got that feeling), yup. Like playing a synthesizer vs. hearing a recording of one, yup.

The sound clear, immediate, fast, nimble, precise, liquid. It is almost like the sound is playing faster than my brain can keep up with. And on these high-sensitivity speakers, ENDLESS power and dynamics. The speakers felt like they were pulled up close to me, the imaging was wider, taller, deeper. Also on a technical note, zero background hum or hiss (something I can't say for the Decware).

I'll make a quick reality check to say I HATE bright sound - and while this amp certainly brings endless high frequency energy, not once was I wincing or wanting to turn it down for being bright or shrill. This also means a product that tries to sound 'lively' by being bright is immediately on my naughty list. I think this amp would be a disaster with a bad source, the wrong speakers.

While I still like my other big amps, this one is special, and I have a LOT more listening to do.

I was not expecting this outcome, and that is not a bad thing!

Longtime lurker here but i finally got to a point where im stumped and am hoping that one of you geniuses are able to help me out. I run roughly 12 picoreplayers pumping to 3 12 channel amps for whole home audio. Prior to that i used Amazon Echo Flexes since they had a headphone jack out and that worked well. Since moving to picoreplayers (using squeeze and airplay paired with LMS or music assistant) i've run into some unique use cases that the echo's handled fine.

Basically im looking to learn more about if picoreplayer can detect different audio input from different sources (airplay from my phone, squeezelite from LMS/MASS, announcements from homeassistant, etc) and automatically switch audio renderers when a new one makes a request. The issue i have is that if i start airplay from my phone and then there is an announcement or something from home assistant (via a direct squeezelite integration or via MASS) it just turns airplay off but doesnt play the announcement.

Im hoping to find a solution that can be a controller and switch between different audio sources on the fly. I have messed with volumio and moode in the past as well. Moode was close. it actively stops the audio renderer but there were some issues with it relying on MPD as the main audio renderer vs squeeze or airplay. I am familiar with the Wiim devices and they seem to be able to do this but i am already invested with these pi's and would love to find a solution to this. TIA!

hello i have a Sonos s2 port model s23 that output audio not working was working for a year no issues but now nothing works it plays in the app also when i connect my laptop with music it wont work either ...i opened the box looked at the boards capacitors and i don't see any that look exploded looking at the RCA Qr code give me this 54303rc1mvd47c1a and the main board QR code give me 62202mb1mu7be71a.. i hopping that i could find out whats the issue im ordering a meter to test caps...if any body had this issue please let me know... thank you

By way of introduction, I have but a single question that involves a stereo board amp I want to use in bridge mode (BTL). The board/chip is a TDA7498 and info on which jumpers config for bridge mode and which output to use is very scarce. I will start a new thread elsewhere when I can, if necessary. Thanks.
Scott T.

New poster looking at restoring my old hifi gear and some recent 2nd hand additions to the collection.

Just purchased a single JBL 2205H. What iteration can this model be 'reconed' to?

Sharing pics of my build. They’re Paul Carmody’s Amigas built as bookshelves (baffle width, drivers, crossover per the design). I lost my notes for whose cabinet I copied but they’re .5 cubic foot with 2” by 5” port.

The cabs are 3/4” MDF with quarter sawn khaya veneer in a pattern inspired by this webpage…https://woodworkersinstitute.com/the-sunburst-burnett-table/

Plan A for aesthetics of the cabinets was having the burst from one corner of the baffle only with the rest painted gloss black. When my wife saw the test panel I made, she challenged me to step it up. Im happy I did. I’m not an experienced builder and this is my first try at veneer work. The finish is danish oil and lacquer.

Having some issues with a new pair of B&C 18NW100s. Both TSPs measure significantly different than the factory specs. Fs is very high on both drivers as are Qts. The driver with slightly lower Fs has been run in with a 15V 10hz sine, pushing the driver up to xmax for a total of 1hr. After that I've seen only 2 hz drop, when it should end up at about 33 hz. The other driver with higher Fs is still like it was right out of the box.

I also measured the lower Fs driver right after disconnecting it from the test amp, being 35 - 36 hz with a slightly warm motor.

The below posted measurments were after cooling down over night.

Anyone else see this on their 18NW100s?

Howdy folks! Absolute newbie here, just starting into the hobby and still very much learning.

I gotta’ say, audiophiles are both incredibly helpful with their deep knowledge of this world — and simultaneously caused me untold headaches as I tried to pick up equipment! Haha

It was an odyssey and forgive me if any of this is completely incorrect, these were just what I was seeing along the way:

I started out wanting an all-in-one player, thinking there would be quality options and otherwise… only to find out that pretty much anything with a built-in speaker was going to cause playback issues. Learned something right off the bat!

I next switched gears to a ‘set’, a turntable with separate speakers included, only to be scared off by people saying that the quality of all of these components would usually be more than lacklustre.

Ooookay, moving on, I switched to trying to look for a decent budget manual turntable — while trying to keep the budget not far off from my original all-in-one estimates — only to find that it was recommended by many posters, resources, etc for newbies to stick to fully automatic turntables until they get their sea legs.

So I narrowed it down to the usual suspects of Audio-Technica and Sony, and eventually even hit buy on the entry-level automatic Sony option. But something felt off, couldn’t say what, so I cancelled the order (I very rarely get buyers remorse so I took it as a sign).

Started doing a bit more digging and was finding a lot of ‘You’ll want to upgrade in months if you go with either of the above. The sound is going to be noticeably inferior even to a layman’ — and also that modern automatics tend to be more prone to failure because there’s more mechanics at play. Okay. Jeez. So where do I go from here, I thought?

That’s when I honed in on ‘modern’. Started researching why time and time again people kept saying they preferred the vintage stuff to modern, and that to get the same sound that even entry level vintage pieces provided often required extremely high end modern equipment. That things were built better because of the mass proliferation and competition of the turntable market in decades past.

From here I started digging into vintage Technics, found them to be reputable, reliable, and have longevity — and discovered linear tracking along the way.

After doing as much of a pre-deep dive as I could for my first turntable I ultimately decided on going the vintage automatic, linear tracking, direct drive route! Vintage build quality with new user simplicity — plus my wife would be comfortable with it as well.

I picked up a Technics SL-Q5 for $95 Canadian (around $65 USD)— vintage turntables are a little harder to find in Canada due to a smaller population and thus smaller collectors circle. It’s a bit grimy but I love the 80s styling abd it (mostly) seems to function properly, though I’m here to work through some potential issues.

And now I’m here to solicit a little guidance from people who know this technology far better than I!

Long time member, had to sign in again with new email address. Now retired, I have been an electronics tinkerer since junior high school. Have built several amps and preamps including Pass Alephs, tube phono pres and tube pres. Currently working on a Bryston 4B SST Clone.

I always understand that the sealed enclosure has a better transient response than the vented enclosure and may be in the top position compared to other enclosure types.

Recently, my friend, who is a fan of the transmission line system, told me that the TL gives overall better performance than the sealed enclosure. He described that the TL won't produce any emphasis on the bass like the sealed system, no matter how well designed it is, and the TL gives a better transient response.

Unfortunately, when I tried reading Vance Dickason's cookbook, there was little information in the TL chapter compared to the sealed and vented chapters.

All in all, Is my friend correct?

Just arrived today

I've had a pair of Magnepan MG-12 sitting here for over a year. I have to redo the goo holding down the wires on the right panel because I'm getting some buzz out of it on bass-heavy material. While I have it apart I'm going to redo the XO and probably set them in wood frames while I'm at it, basically do the entire Peter Gunn approach. I found his original XO schematic posted on the IA/MUG forum, which was based on the SMGa. However, many of the Magnepan models had parts selected to tailor the crossover point to that particular panel, and of course the PG parts list was an ever evolving work in progress. Also, I'd like to get a clarification on the below diagram because it doesn't make sense:




First, why is the panel on the left shown as "right speaker" and vice versa? I suspect it has to do with flipping the panels but I still can't get my brain to understand it. Also, where is the resistor for the tweeter? PG quite clearly talked about using a single resistor there.

If anyone has a recent schematic and parts list appropriate to my panels please DM me.

After a quick blessing from our technical, spiritual, and menu advisor, Nelson Pass, I am glad to present the preliminary discution for the diyAudio Mosfet F6.



Cool, huh? 🙂 This is made for IRFP420, or a similar Mosfet that has a Vgs in the 4V range. This is a beautifully simple amplifier!



Member Didiet78 has done some preliminary layout, (Thanks a million! It looks wonderful!!) this is the current thinking - 2 PCB, a left and a right, in order to keep the input transformer as far back as possible on both sides, and to have the Mosfet mounted low on the heatsink. The PCB will be designed to only mount the specified Jensen transformer, but I'll look into the possibility of a second set of pads, if possible, to mount a Lundhal or something... No promises.


The diyAudio store is also looking into stocking the transformers, which would make the whole process quite easy.

The other consideration in this project is the PSU, by which a shielded transformer is going to be very necessary, mounted as far from the input transformer as possible, and possible in a screening can as well. Or, of course, a separate box for transformer, diodes and first capacitor bank. Other than that, everything is straightforward. The diode, cap and resistor bank are the 'Firstwatt vernacular', I.E., look at any Firstwatt amp and use that PSU. The diyAudio PSUv3 boards will work beautifully, as will many other PCB.

The floor is open for discussion. 😀

This is the Group Buy and Build thread for the Alpha Nirvana 39W SE Class A amplifier designed by AKSA. The technical discussion thread is here:

Alpha Nirvana 39w 8ohm Class A Amp

PCBs:


Production ones will be 2mm thick, 2oz Cu, ENIG gold finish, and Blue solder mask.

Amp module looks like this assembled:


Includes helper snubber boards to allow remote mounting of MOSFETs for flexibility and ease of installation by decoupling the installation of the PCB and the MOSFETs:


Latest Schematics and BOM will be updated soon, but current version (very close to final) is below:

I recommend use of these Fairchild MOSFETs (higher power rating than IRFP's):

FQA40N25 ON Semiconductor / Fairchild | Mouser

FQA36P15 ON Semiconductor / Fairchild | Mouser

The SLB PSU is also highly recommended - proven to work with single SLB and Antek 600VA 24v (AN-6224) trafo. Should work as dual monoblock with dual SLB and Antek 300VA 24v trafos (or equivalent). Also, a ready to run (RTR) solid state relay (SSR) DC protection is highly recommended to prevent turn on thump and provide safety net for your speakers should something fail.

Also tested to work on DIYA Store Dissipante 4Ux300mm chassis. Board is UMS compliant and I did not have to drill and tap a single hole on my UMS heatsink. Chassis temp is 57C at hottest point in 20C ambient. A 5Ux400mm would be much more generous and allow higher bias current.

Pre-Orders are now being taken in my Etsy shop for the GB.

Pricing is $37ea (includes pair of snubber boards - which cost almost as much as the PCB, hence the higher price). Thus, a stereo pair requires two boards. Free shipping in USA. Etsy calculated shipping elsewhere - circa $23 via tracked and insured USPS First Class mail.

If you place a pre-order, please add your name to a running list below with name, qnty, country. Thanks!

A huge thank you to Hugh (AKSA) for the design and JPS64 for the superb professional layout.

Here is the schematic of my amp "AS-BUILT". These values should work and clears up any ambiguous locations where multiple values are possible.


Schematic of snubber boards:


Edit Dec 26, 2019: AndyR has put together a nicely annotated BOM for both the 8ohm and 4ohm versions here:
Alpha Nirvana 39w 8ohm Class A Amp

Edit June 13, 2020: note that the feedback resistor R126 and R124 could 1% metal thin film or hand-matched carbon film as 1% not available at reasonable price. This needs to be done to get the same gain from left and right channel. It’s more important that they are matched left and right and not for absolute value. Also note that metal oxide thick film should not be used (dominant H3 and high THD). Do not use carbon composition - that is an error in the BOM. Sorry about that. Carbon film will have a slightly higher THD but more H2 vs H3. Metal thin film will have lower THD but relative H3 will be closer to H2 but H2 still dominant. Safest bet is use 0.5% metal thin film for these 2 resistors. But I personally like the carbon vs metal thin film.

Edit Feb 7, 2020: Pin diagram for Molex quick connects to MOSFETs


Edit Mar 11. 2020: helpful pin diagram for MOSFETs


Edit Apr 24, 2020 - Dual Monoblock Connection Diagram if using SLB PSU's:

What Type of Capacitor is This? Can/should this be replaced with a film cap in the speaker crossover? I'm unable to find anything that looks like it on google.

AC
TSI-8044
PXB25LR50
25uF-50VA* (* last character is obscured, assumed to be 'C')

The cap looks like this with the above markings (pic borrowed from a diyAudio post from 2011).


As used in my crossover:

Hi everyone

after years of lurking on DIYAudio I've decided to step out of the shadows and join the conversations.

After many years of being an audiofool and buying too many systems I thought it was time to design and build my own. How hard can it be?
Pretty bloody hard as I found out!

I'm interested in distributed audio, active loudspeakers and horns - a match made in theoretical heaven but practical hell. The upside of each brings great benefits but the downside is its really hard to do and hence the motivation to join diyAudio and discuss the challenges with people far more knowledgeable and experienced than me.

Currently I have a pair of Kii3 active loudspeakers that I love but am looking to replace them with my own design and build active, three-way using horns and distributed audio.

Anyway, enough about me - I'm off to the forums.

PrinceArnold

Posting the schematic of my tube preamp:

Sounds ok but when breaks up, the overdrive is too thick.

Swapped the cathode bypass caps from 22uf to 2.2uf but can't notice any difference.
Swapped the cathode resistors from 820 to 2k4 (should be towards less gain and cold/ asymmetrical clipping).

Could it be the MOSFET follower that alters the signal spectrum in a way?
F.ex. input capacitance, how it AC loads the valve, changing the harmonic distortion (f.ex. odd vs even order harmonics)
I put it so that it buffers the valve output, thus preserving all the top end and harmonics..

I want the overdriven sound not that thick and with more chime on the top end.

There is a 220k audio pot between both stages (the gain).
I think of treble bleed cap (some more top end) but it won't affect full gain setting and the general sound signature.

Selling a fully built and tested LR Phono by Pete Millett,
more info here: http://www.pmillett.com/LR_phono.html

Phono board and PSU board
for EU buyers, will throw in 2 12V batteries for those that want to try a battery supply.

SOLD

hi there, i joined this forum mostly just to post one technical question, but ill probably still stick around. i don't know too much about audio but my house has a fairly old surround sound system (yahama ns-ap1600s and yst-sw011) and i'd like to figure out how to troubleshoot/fix some of the issues i encounter. 🙂

Hi guys,
I got a high quality 23uf cap but not the 22 uf that the schematic asks for. Would this pose a problem or only be of minor concern?
Position C2

Hello, just joined and hoping to learn, maybe contribute. Even I am in US, English is not my first language so sometimes I may not be best at communicating. That being said, now about me, I have EE degree but in electrical devices, more like electronic drives, control, typical industrial stuff. I was working as electronic engineer /designer, developing power supplies and protection circuits but have no experience in audio and zero knowledge of tubes. I have basic test equipment (scopes, bench power supplies, multimeters) can read schematics so I should be able to participate in discussion. I am looking to dive deep and start tube amplifier build, will post in proper forum soon.

I have 1.6s now. Owned them for 25 years. I would like to find a used pair of 3.6s, but was thinking about new 2.7i. Anyone here own the 2.7i or the 3.7i? My local dealer, which is not very local, is no longer open on Saturdays. I know if I want a serious audition, I need to book an appointment.

General complaints now... Why is the dealer not open Saturday?!?!?!? Probably too many tire kickers. The price of 3.7s is way too much for me at this point. And don't even get me started on the X upgrade. Also, why are all the 1.7, 2.7, 3.7 models not bi-amp / bi-wire capable? I would want the crossovers external like the 3.6s. I know, these are rhetorical questions because it comes down to cost and marketing. I really want to listen to Diptyque speakers. Nothing close by and probably out of my price range. But reviewers say great things about them.

Rant finished.

I am a hobbyist based in North DFW and want to learn a thing or two about speaker cabinetry, drivers, and crossovers.

I currently have a pair of Tekton Double Impacts I am trying to "clean up" and customize for my listening space.

I am quite happy with them as is, but since I am a tinkerer and can't sit idling for more than 5 minutes, I figured I would take them on and upgrade the cabinet finish and crossover components and wiring.

I intend on beginning with a baseline of measurements and going from there. I look forward to chatting with y'all and learning a few things.

Cheers

My kids are begging me to help get them going in car stereo.

Does anyone know where to find obsolete parts, such as the balance pot on this preamp? Having issues with lost right channel and scratchiness in balance pot. Cannot restore right channel after multiple cleanings with deoxit. I think the pot is junk, feels very rough and center detent is a bit out of whack, if that makes any sense. It seems as though there are several "detents". Not sure what that means. Is it possible to match it up with a different pot as this one seems to be obsolete. I have searched everywhere and cannot find an exact match. It may be an Alps piece but not sure and if so, they don't seem to make it anymore. Any help would be appreciated. Thanks,
Bill

New member from Kansas City. Former sole broadcast/transmitter engineer for a 100Kilowatt FM College station (CE without the title) then moved on to producing and recording syndicated radio music programs for a religious world headquarters. Annual Handel's Messiah recording and broadcast (Large orchestra, 300 voice choir, 4 soloists). Hundreds of hours recording classical pipe organ. Opened RBW Records in 1990 and was self employed recording around the country, operating a struggling little e-commerce record label and designing and installing in-house video systems for call centers for data and powerpoint. Also designed custom 3 and 4 way mic transformer mic splitters for a Colorado Acoustic Design Firm that put my gear in a half dozen opera houses around the world. Also served as an RF and support tech for Arrowhead Stadium game day production from 1993 till 2005. Not great years for Chiefs football but most games were a lot of fun. Am now moving into collecting some vintage audio equipment, restoring them as necessary. Selling a few and maybe putting together a small analog/digital hybrid composition and recording home studio. I love my late 50s/early 60s Altec A7s, vintage Crown D60, D150 and D300 amps. A dozen or more great mics (Schoeps to Shure to AKG and EV), a vintage AKG BX20 reverb, various outboard gear and mic pre's. I look forward to tapping the knowledge on this list as I make my final years of life journey finding and experiencing great audio.

Hi!
Its time to change drivers in my ML-TQWT boxes. So,after looking for new drivers,im not sure wich is best choice.
So please,share your opinion. Fostex 167 with bad cone and all other problems perform very well in this boxes,and as owner od dallas II horns with fostex fe206en inside,i have faith in fostex ff165wk that will perform well. Markaudio looks better on paper,specialy PLUVIA model,but i know it not always beter sounding what looks better on paper.
So im open for sugestion and your opinion.

Looks like fun forum. Thanks.

Hello,


For my two (or three) way speaker, I have search for a 12" driver with a sensibility of 95 dB / W / M for a boxe around 100L.

Actually my design is :
- Faital Pro 12PR320, 12" drivers : 0 to 500 Hz inside 110L
- Fostex FE208EZ : 500 Hz to 20 kHz with corrective RLC inside ~8L

I have "found" the Faital Pro 12PR320 drivers, release in 2017, so relatively new. Is there any one tried it ? did you know any review or test ?

Importants datas was for me :
- sensitivity
- Fs : 42 Hz
- Mmms (low mobile stuff) : 51.4 g
- Xmax : 7.37 mm
- Vas : 98.4 L

The link : FaitalPRO | LF Loudspeakers | 12PR320

And the response from the manufacturer :

Hello!

I'm new to this forum and looking for some help with my Sennheiser PC360 headset.

The potentiometer makes a crackling sound and I've read something about bypassing the volumeknob.

I know how to solder but I don't know which wires to solder. I've included a photo of the backside of the potentiometer. I really hope anyone can help me with this 🙂

Thanks in advance 🙂

Here is a visual log of how I built my PassDIY (Designed by Wayne Colburn) Pearl 2 phono amp.

I happened into a pair of boards when I was at Burning Amp this year, and as I just finished building a Pearl 1, I was extremely interested in hearing how the new version was going to sound! I love phono preamps for some reason, and I am always interested in a good circuit.

Being at Burning Amp also gave me a chance to sit with the esteemed Mr. Colburn and pick his brain for a bit to see if I could glean any hints as how to build it successfully. In my opinion I was extremely successful. The circuit is fantastic!! Here is how I built mine ---





Thank you planet10 for redrawing the PSU schematic! 😀

I had a very nice Plitron 30v+30v 50VA transformer that I wanted to use for this project. Yes, it's a bit more voltage than required, but it's not too far off, and it's fairly easy to "throw away" a few volts when you have excess current to play with. So after posting a few question to people I came up with this plan for the unregulated powersupply.

The component choices were made as follows; MUR860 diodes because I had them, but actually because they are close to the ideal diode for a low-noise supply. They are very fast recovery and also soft recovery. Wayne did say that those attributes are quite important for a line-level (and more so for phono) PSU. They also fit the PSU PCB that I am using. If I didn't have anything on hand and need to order some diodes, I would get MUR820's --- they have more than adequate voltage ratings but are even faster!

Anyway, the 50v 6800uf caps were chosen because they were at a 'sweet spot' on size vs. cost. You could use bigger or smaller if you like, but I would have at least 10,000uf (total) per rail.

10ohm 3W dropping resistors because I had some as well, and I needed to start somewhere.

The .22uf snubber cap was a suggestion from Wayne, he did a bunch of testing and found that value to give the most benefit in a single cap. 2.2k 3W was chosen as a bleeder because (yep, you guessed it…) I had them on hand - that value is used as a bleeder in Pass power amps.


Now after all that, I must digress at this point and say that all this is necessary because I'm using the transformer with the excess voltage. If you didn't have anything in your box and needed to order a new transformer, something like this would be appropriate -- Antek - AS-0522

Also, you actually are able to mount big 'snap-in' style caps (10mm lead spacing) to the Peter Daniel board - like so;


These are 10,000uf 50v caps, BTW.


Cool! And it also could be mounted in a much smaller case if that is your style.

For reference, here is the schematic of the original schematic posted in the project.




Anyway, back to our regularly scheduled program.

I ordered a pair of Par-metal chassis for this build, model 20-12083B website here - Par-Metal (12"x8"x3")







The PSU going together -







The rectifier board is from Peter Daniel (Audiosector.com) and was actually from a gainclone board. It's compact and very well designed. A LED will be added to it later.

Now I got a pair of empty boards, without the matched jets like you get when you buy from PassDIY. So I needed to match the Jfets for Idss. Here is a good reference article - Transistor matching

It's simple - a 9v battery, DMM set to MA, a couple of clip leads and the Jfets.







Here is the assembly of the PSU enclosure --



And this photo shows the wiring around the power entry module and the ground breaker-



The connections from chassis to earth to ground are exactly is drawn in the schematic.


As I'm looking through my photos, I realize that I have no photos of the board being stuffed. (Then again, stuffing a board isn't all that exciting…) But I did need to take a photo to show where you place DMM leads to test the rail voltage.



One thing this photo does show is that although I have all the resistors installed, I don't have a jumper in the R15 spot. So, just in case you didn't see it in the article, (and I most certainly didn't see it either…) you need to put a jumper in R15.

So by this point I'm getting down to final assembly, the boards are mounted, the RCA's and other connections are in the chassis and it all need to be wired together.

One problem, the unregulated DC from the CRCRC filter is +/- 47v. That's too much to put into the regulators.


The original 10ohm resistors in the CRCRC filter were obviously not enough resistance to reduce the voltage, so I reached into my somewhat meager supply of high-wattage resistors and kludged up this -


Now the eagle-eyed of you will notice that they are not symmetrical... and that is because the (+) rail draws more current than the (-) And all I was trying to do was get the voltage at the input of the regulators somewhere between 40 and 29. Fewer than 40v as that is the maximum the 7*24 regulators can have on the input, and at least 29 because the regulators need at least 5v more than the output in order to regulate properly. They are now about 31v.



Here is the entire power supply, the power entry module has a switch and fuse, you can see the 35amp bridge isolating the PSU ground from the safety earth, the toroid, rectifier board with snubber and LED, then the CRCRC filter.
The output from the PSU, positive, negative and ground are isolated from the chassis. The umbilical is just a 3-conductor cable.

Just for reference, here is a photo of the backs of the enclosures -


The guy that I had do some machining for me screwed up the RIAA enclosure and did it upside-down. 😱 In the grand scheme of things this is not a big deal, but it did mess up my wiring, specifically where the power cable got routed. The original plan was for it to be on the other side, and the power cable about 1/2 the length that it wound up being.



Now this rat's nest is not the final wiring, but it is quiet. Very quiet. I will get around to a nicer looking routing in the near future.

Here is a quick overview of how it's grounded;

Safety Earth - only connected to the primary side of the PSU and PSU chassis.

V+, V-, Vgnd floating in both chassis.
Input and output RCA jacks floating.
Ground lug connect to chassis.
PCB starground, (a lonely, unlabeled hole under C4 and above C12) connect to ground lug.




And then the lug is connected to the chassis, I just used a longer screw in the pem nut, a tab and a metal nut to insure good conductivity.



So by this point all I needed to do was clean up the wiring.


Wiring after the clean-up. It looks better and is quieter. Awesome!! The trick is to get everything routed as close to the chassis as possible.


The stealth blue power indicator. 😀 😀 😀 On top is the umbilical.
There is a place for an LED and dropping resistor on the PSU board, and the 'light' is nothing more than an extremely small hole (>1mm) drilled in the faceplate and the LED pointing towards it. You need to look for the hole when it's off. 🙂 In the future I will probably have some CNC engraving done on the faceplates. But I do like the unassuming look of all black...

The umbilical is a 3-conductor wire from the surplus store, sheathed in techflex and terminated with '4-pin microphone connectors' from RadioShack


The completed Pearl 2. Shown with Turntable for scale.

This build is complete, it sounds fantastic and is astoundingly quiet. This is the first project I have done in a long time that was quiet (specifically PSU hum and radiant hum) from the very beginning I'm very happy with the results.

Now I need to sell off some of my random excess gear and buy a Shelter 501 cartridge... 🙂 🙂 🙂

A very special thanks to Wayne making this project available to the DIY community, and also to my buddy in California who sent me a few important parts to get this project completed. (You know who you are.) 🙂



Mouser cart for the Pearl 2 PCBs - Thank you avdesignguru!

Note: BOM does not include C7, any R20 input loading resistors or any additional input loading capacitors.

Power supply is a separate BOM that would be based on builder's preferred design.

Mouser Electronics

Hi,
I've attached the section of a project that converts speaker lever audio to line level.
It's similar to many I've seen on the net except for one detail (which I got from a schematic I also found on the net): it includes a 1uF series capacitor.
Would someone tell me why the cap is there?

Can you help me. I want to build a 2 wire version of Buck Converter to go from 24V 4amps to 17V 4a

Hi I have a Pass Labs X1 preamp, and I’m currently facing an issue where, at volume level 3, the left channel suddenly goes to maximum loudness. During troubleshooting, I swapped the volume control board with the right channel, and the problem followed the board. This confirmed that the issue lies with the volume control board.





After further testing, I identified that Q3 on the board is the faulty component. It’s marked as “8F” and comes in an SOT-23 package. However, I haven’t been able to find much information about it. Could you help identify the exact part number for this component?

I'm offering a pair of Hartley 224 HS. They are in very nice condition, original boxed and spec sheets, only used for testing. $1250 / pair + shipping, they do not weigh too much, less than 20 lbs each, shipping shouldn't cost too much. I'm in Los Angeles. ( they are huge!)

Geoffrey

Hi everyone,

I'm just making an account to say thanks in a 10 year old post, which seems to keep being necroed ever few years due to the issue still being an issue.

Cmon sennheiser, spend the extra 3 cents...

Selling 1x pair of Lie Belin P13564 input transformers.

Lie Belin is a famous French designer and company, that made a lot of equipment and transformers for the ORTF, the French broadcasting company.

These can be used in a ratio of 1:2 or 1:4, as an input transformer for a preamp or power amplifier.
Nice sound and bandwidth, and pretty rare

SOLD

I have two Zynq based SBCs up for sale over at the EEVBlog forums, please visit my thread there for detailed information:

https://www.eevblog.com/forum/buysellwanted/fs-(eu)-zynq-fpga-boards-red-pitaya-ultra96/

(The Red Pitaya might be "sale pending" right now.)

I thought I had posted to this site years ago, but since it’s asking me to first make an introduction, I guess not.

I got into “audiophile” equipment years ago after my Sherwood receiver (c. 1981) gave up the ghost and I went to a nearby stereo repair shop that happened to also be a high-end audio dealer. While I was arranging to have my Sherwood repaired, I was offered an opportunity to audition a pair of Soundlab A1s powered by VTL monoblocks, VTL preamp, and Wadia CD player (the old BIG boxes.) I was blown away to say the least.

Since I was just a poor, 1 year out of college student, I immediately read every issue of Stereophile, Absolute Sound, and happened across a small DIY electronics print newsletter (before the internet) that walked people through the process of recapping old amps from the 60’s and making them better. I found a Lafayette KT-600, and so began my journey to better audio to listen to music the way the musician wanted you to hear it. I eventually acquired an Eico HF-89 and rebuilt it, then added another HF-89 a few years after that. My soldering iron became my favorite tool. Along with learning about different caps, culminating in my discovery of Black Gate caps, as well as a hundred other components and their good/better/best rankings inside the 80/20 rule.

I had an Aleph 5 for a few years coupled to a Classe and some other “high-end” preamp I can’t recall. I sold all of them, but a day before I was supposed to ship out my Aleph, I received my VTL 5.5 in the mail and hooked it up to the Aleph. I cryed. I should have backed out of the sale, but it was already sold, so I packed it up and shipped it out. God I miss that amp. Stupid preamps were getting in the way of magnificence.

OK, enough boring history stuff, I’ve had a pair of LX521s since 2013 and have made several upgrades along the way and now have the LX521.4 Mg ASP setup that is currently in storage. I’ve decided to sell the Genelecs I’m currently using and replace them with a pair of LXMinis, starting with building a balanced (XLR) version of the Nelson Pass ASP.

Bottom line, I love building cool things.
Mark

There have been multiple conversations on many threads about the potential benefits of removing source resistors from the AC current flow;
Nelson write in the F5Turbo article about the application of diodes for the purpose but more recently in several threads there are discussions regarding the potential use of supercapacitors for bypassing the source resistors:
F5 - `Update on Pa's new F5?', some comments in a tread on the F5m.
And of course most recently in the ACA Mini - the article itself

After some searching and reading I am curious why they are not used more often and I am hoping I could gain some enlightenment on the subject from the great and wise?

I have been reworking a germanium amplifier, and I understand the circuit below is an emitter follower (besides just the schematic saying so ), but there are some oddities about this circuit that I do not understand. I don't know anything about the transistor beyond it is germanium, obviously PNP. A pox on Magnavox for using internal numbering, and I don't have the photofact for the Magnavox A531 to look up an equivalent or whether it is even listed. Questions below . . .



Questions:

I understand R17 and R16 set the -7.2V bias voltage, but why are R15, C10 needed? Input impedance? Would not the emitter follow the base without them?

Why are R18 and C31 necessary? I'm guessing this transistor maybe cannot handle -19V on the collector, so R18 reduces the voltage drop across the transistor while C31 maintains an AC ground? But C31 (0.001uF) seems awfully small to be a bypass capacitor- maybe it is involved in a filter from the collector side somehow?

Thanks for your help!

Howdy folks! I have here a Pioneer SX-1980 receiver. The problem is that I only have one AUX input to spare, and I need another input for my Rose streamer. Since there aren’t two AUX inputs available, can I use one of the TAPE-1 & TAPE-2 for the streamer without causing any harm to the receiver? Please let me know if this is a safe alternative. 🤔

Very sought after American High-End DAC, that normally is sold out because they are not able to deliver to the high demand ... And this one has been further
upgraded in 2 important areas (Analog output and PSU).

As the name suggests this is the newest model with an AKM 4483S DAC chip, and it is about 3 months old.

It is default delivered with OPA1656 op-amps in sockets in the analog outputs. They sound good, but not nearly as good as Sparkos discrete SS2590 Pro opamps,
that in mine and many others opinion are the best op-amps on the market. The SS2590 type are originally developed for expensive studio equipment, but Sparkos
delivers adapters, so that they can be installed in 8-pin DIP sockets, and therefore also can be used in consumer equipment. But be aware that Geshelli do NOT
deliver these types from the factory. They only deliver the cheaper model SS3602 - so this is a unique offering.

As it is configured right now, it is only the RCA outputs that are running, because I have uninstalled the op-amps for the balanced outputs. But they can of course
be re-installed, if necessary.

The Sparkos SS2590 op-amps gave a large quality improvement, and the next improvement appeared by installing a powerful and noiseless linear power supply.

So if you check out videos on YT, that generally are super positive, remember to add those 2 important upgrades to the evaluation.

The DAC will be delivered in original packaging, with the upgraded PSU, and the standard PSU and 2 OPA1656 for the balanced outputs.

White alu housing with see thru plexi front and back plates. Measures: DAC: H5 x W16 x D12 cm., PSU: H5,5 x W10 x D21 cm.

The switch on the cable is installed because the linear PSU starts very slowly, and the DAC will not accept that, but will go into failure mode. But that is fixed with this switch.

The pictures might not be exceptional, but the DAC is 🙂.

It can be sold for Euro 350 with the original OPA1656 op-amps installed in i both RCA and XLR outputs, but I recommend it with the SS2590 for Euro 470. It can be sent inside
the EU with GLS for Euro 30 - contact me for pricing outside EU. Payment could be PayPal to a friend, or bank transfer.

I'm new to the construction part of this. Used to service TVs back in the 70s and early 80s, and collected/fixed tube radios and TVs after as a hobby. Retired now, recovering from a brain injury (long story!) Slowly improving, and trying to relearn electronics, as my understanding of it is not what it was. I'm thinking building a simple tube amp is just the thing to help, and should, I hope, be fun.

What is the meaning of Life?
To me it seems life has no real meaning.

What do you think?
What are your goals here in life?
Other than surfing diyaudio.com 😀

Hi all,
I am ould (58) and some of my ideas are from 40 years ago. Many changed since than and I could realize one of my favorite ideas from my youth.
I registered here, I think, some years ago to get a better impression what is possible today and to find some help if I get really stuck.

I am far from experienced if it comes to PCB design and construction. I am more someone who has a good base for get things running.

Besides the hobby I still need to work for my living. In real life I earn my money as a Software-Architect/Technical Lead. So I there is some money to spend for my hobby.

Probably I need to fix my profile a bit. But that will come later.

I have a 12v power supply and a car stereo on my bench for testing amplifiers. I would like to add a 12v battery that will feed constant power to the radio so I don't have to reset all the settings every time I turn off the power supply. I would also like the power supply to charge the battery. What do I need to do?

I admit I started to buy vfet amp years ago influenced by some "internet influencers" they make me to believe they have unique sound, like no other trasistors can compare.
So, I got Yamaha b-2, Yamaha b-1, recently a Sansui ba-1000. Sure they sound similar sweet and smooth and i am satisfied.
I also found that not all vfet amp is so sweet and smooth for example hitachi ha-500f. I haven't heard one but according to kitr's review and listened to some youtube recordings I feel it sounds a little dull maybe on par with sony ta 4650. lacks some airy and live feel of ta-8650 from videos recorded in same environment. So I feel circuit design is more important.
I wonder is that true no other transistor can achieves sound like vfet? what about mosfet, high current mosfet like uhc or lapt, SiC depletion jfet? Anyone know any non-vfet amp with similar sound?
I am also curious about how vintage vfet compare to modern lowest distortiin class ab amp(
topping la90) or a GaN fet class D?

Hi everyone,

SpicyTL is online and available for download.

SpicyTL is a simulation model, based on the electrical circuit theory, which predicts the electro-acoustic behavior of transmission line loudspeaker systems. It is the evolution of the AIRDAMP model, whose development (and the principles that allow its operation) is illustrated in the article Progettare una linea di trasmissione utilizzando SPICE (Designing a Transmission Line with SPICE), published in issues 408, 409 and 410 (April, May and June 2019) of AUDIOreview. Compared to the latter, SpicyTL has a modular structure composed of several acoustic blocks and can also simulate tapered and expanding TL's.

The model, particularly suitable to design a TL damped with polyurethane foam, allows to simulate frequency response, phase response, group delay, electrical impedance, speaker cone excursion and air velocity at the TL output.

Operating instruction and download at the following address:

SpicyTL-english – Transmission Line Speakers

An in-depth look at the software, and its use for designing the Ikigai monitors, can be found in the article Progettiamo una linea di trasmissione con SpicyTL (Designing a Transmission Line with SpicyTL) on the 427th issue (January 2021) of AUDIOreview.

Kind regards,
Andrea

I have chosen to restrict access to transmissionlinespeakers.com for users from Israel. This decision is a response to the current events and human rights violations in Palestine. I strongly oppose any form of violence and injustice, and I believe this measure is necessary to express my ethical dissent.

I will post more projects that was made by me :
1. Volume controller / source selector for motor potentiometer ( like Alps blue velvet ) :
-schematics
-avr atmega8515 soft
-pcb
On atmega8515 you have to write only the fuse-bit named :
" Internal RC oscillator 8Mhz "

Hello all

Apologies if this is in the wrong section.

I have a Quad 99 pre amp and 99 CDP. I found it sounds best using RCA interconnects vs the Quadlink cable. Of course this disables the standby mode function, which is now missed.

Has anyone tried to alter a DB 15 cable so that only the necessary pin for bring in or out of standby is connected?

I've seen a few forum posts that state pin 7 is responsible for this function between the 99Pre and the 909 (but that would be the Ampbus connection), I need the pinout for the pre>CDP (Quadlink not Ampbus)

99 pre pinout




Does anyone know which pin i should be targeting?

Thanks in advance!

One channel of amp distorts when the volume is turned up. It's goes from clean to distorted around ½ power.

The voltages across r206, 207, and 208 are identical to the voltages across r306, 307 and 308.

Audio remains clean at c304 a and c201

Is there any real advantage to using single opamp in the DAC output stage?
Most of the equipment i see uses dual opamp in the output stage, would this be just to save cost and board size?

I am looking to build a new arrangement into existing pair of gifted cabinets of about 6-8ltrs. I want to run two identical (ideally 4 inch, wideband) drivers on each side in a (polk SDA-esque) crosstalk reduction arrangement. eg; LEFT; R-+, L+-. RIGHT; R+-, L-+ The drivers will be about 8-inches apart, horizontally, in each enclosure.
I have this arrangement set up in my room with 4 separate speakers and I love it. But the logistics of this are cumbersome, to say the least.
I will be running a sub from 100-150hz
I'm posting here simply to get tips and suggestions as I go through adapting the cabinets.
Any recommendations for good and affordable (ideally 4" to approximately fit the current cutouts) wideband drivers, bearing in mind cost of buying 4x
Also, my current set up uses two amps to achieve the "effect". Amp suggestions would also be useful.
I'm not particularly technical in terms of electronics/physics language.
I'm not particularly interested in a debate about the merits of xtc approach. Just hoping for experiences and tips.

Blaupunkt 5x8 voice coils melting tweeter post? I would think the coil would burn up before melting something. I measured the output for DC and it had .5v offset. It's a Chinese head unit with a (marked) TDA 75xx class AB chip. something strange going on here. Any ideas?

I am now embarking on a perilous journey on this DIY audio hobby. I am pushing the limits of my audio knowledge acquired here at DIYAudio. This project is an attempt to repurpose my pcb board intended for a CFP amp. LTSpice says the schematic will work, that is according to my understanding of how the circuit behaves.
The push pull VAS concept was taken from Keantoken's Aurum X amp with the output topology also being taken from Roender's FC-100 amp.
I ask you if anyone has made a similar design please comment your feedback. If this amp will turn out to be a firestarter 😄 I will not hesitate to toss the boards in the trash bin.

Thanks y'all!