The tweeter doesn't sound, but it works if I connect it directly bypassing the crossover. So could this fluffy resistor/capacitor be the problem?
Can I just replace that component if so where can I buy one? Falcon acoustics are out of kits...

As you might have read, I am working on designing and building a tape head tube amplifier. For this you need quite some overall gain to overcome the gain losses in the equalization filter. Like at least 200.000; reason to split it up in 3 stages. Now every stage must have following specifications to make this work (with equalization filter in between)

Gain of minimum 60x per stage (I want triodes for linear behavior)
High input impedance > 1MOhm (the filter likes little load)
Low output impedance < 1kOhm (the filter likes low source impedance)
An output of at least 10V RMS with low THD (<1%) (your ears like this)
Low noise and hum (of course…)
Bandwidth of > 50kHz (not easy with triode/high-gain/no feedback)
There are only few triode tubes who will provide such high gains. The likes of ECC83, 6SL6, WE420A and 5755 are the most common ones. I used all of them in my Phonodude designs with excellent audio performance. The downside (as there always is one) from these tubes is the typical high plate resistance. But more on this later

Certainly a proven and excellent way to achieve the above design criteria is the MU Follower. And then I had this idea of making it modular… just design a small PCB with one follower on it, which can be universally used. I already mentioned the tape head amplifier where you need three, but with two modules you could make a RIAA Phono amplifier with a passive RIAA filter between modules or just use one module as a pre amplifier? Of course that is for ONE Channel only….

the whole story is here: link to my blog site

Specially the influence of Ck (Decoupling the cathode resistor) in the Mu Follower was an eye opening and interesting aspect.

Never realized it would make sense to decouple with as little as 100nF ....

.

I will attempt to make the UCD2k Hypex amp and have two pretty simple questions.

Is one SMP3KA700 enough for 2 UCD2K modules for a stereo set up? Better still how many can it handle out of curiosity? I ask this cause the Apollo Hypex UCD2k has two power supplies for the stereo configuration but not sure if its the SMPS3KA400 or K3700

I have also read that the UCD2K runs hot and needs sufficient cooling. The heat sink runs though the middle of the module with screw holes on the top. How do I add more heatsinks to that? Of course I will leave sufficient air space to the top of the module and the case with holes to breathe but I cant imagine how more heat sinks are attached.

Lastly if anyone would please care to explain what figures I am looking at when trying to figure out how many modules fit on one power supply. Can't figure this out for the life of me, it must be some simple figure that you just look at and add together. What figures on the datasheet?

Hi folks!

I'm a TOTAL newbie when it comes to speakers.

I have a pair of ASL6115 with JBL 2226H drivers, and a pair of altec 808-8A with 511b horns.

I'd like to make a passive crossover, but have NO idea where to start. A schematic would be the best. Can I use an Altec VOT schematic even though the bass driver is not horn loaded?

Any help is very appreciated.

Looking for advice for a small record console project. This is for use by my daughter in a small apartment. I want it to all be self contained, speaker, amp, turntable, and record storage. Attached is a sketch of what I am thinking. Size about 24" wide, 20" depth. So record player under top, speaker is the middle section, record storage below. I plan to fit all electronics in the same area with speaker, I think a little chip amp will do. Looking for inexpensive speaker options.

I think for speaker I could go 2 ways, either 2 full range drivers in stereo or run mono into the amp and a pllxo to split the channels into hi pass and low pass for a mono bi-amp WAW arrangement. Basically a center fullrange flanked by two woofers. The latter appeals to me since I think it could deliver better bass and spl but I have no idea what box volume/port to setup.

Thinking of drivers in the 2-4" range and under $20 each. A little flexible around the size since height is not set. Appreciate any suggestions.

Hello, I am looking for a manual, schematic or any other information for this meter. Thanks!

Wondering if anyone knows the proper way to dial in the offset and bias on these units. I know that, when the amp is still cold, I'm aiming for ~0mv offset and 1.5mv bias.

That being said, the schematic isn't terribly clear where I am to measure for bias and offset. I can only assume it's the pairs of pins marked TP2 "Offset" and TP3 "Bias". I'm not sure what the TP1 "DC DET IN" is for...

Also when I measure across the offset pins and turn the amp on, I get a large initial value that slowly decreases over the next minute or two, and never stops fluctuating. Is this normal? Does that mean I should let the amp warm a little before performing the adjustment? Or is this just a consequence of my using a cheap multimeter?

Hello,


I have successfully constructed a 300 watt power amplifier based on Michael Chua's C300 design. It is not designed to be the best possible design given currently available components. Rather, it is designed to use the most widely available and the minimum number of types of components so that it will be more likely to be able to be continue to be built into the future. It is for educational and archival purposes as well as audio enjoyment. I have made numerous modifications and improvements. There are four PCBs available which combined can be used to construct a fairly complete amplifier unit:


1. Amplifier PCB
2. Soft Start PCB
3. Power conditioning PCB
4. Balanced to unbalanced receiver PCB


The project is at


GitHub - profdc9/PowerAmpAudio: Power Amplifier based on Michael Chua's C300 amplifier


You can download the entire project to your computer by clicking the green "Code" button and then "Download ZIP."



There are instructions on the github about the PCBs and how to build them. All the PCBs include gerbers, BOMs, and schematics. The projects are all created with Kicad so they may be modified using open source software. The project is available under the Creative Commons Attribution/Share-Alike 4.0 license which permits commercial or non-commercial use.



Special thanks to Hans Polak for his suggestion to add TPC compensation.



Pictures of the prototype have been included. Sorry for the spaghetti cable mess, it will be cleaned up.



Please let me know if you have any questions or comments.


Best,


Dan

There`s not so many threads about nested feedback round here.

There are some examples of such a design like AKSA`s "Lifeforce" and Greg BAll`s "SKA" but the schematics are not available. Everyone saying that these amps sound wonderfull.

ANyone have schematic or example?

It would be nice of someone to tell how it realy works and wath`s the trick.

Cheers!

Hiya folks - doing some cleanup of unused Allo gear. It was all in service for only ~3 weeks then shelved.

1) USBridge Signature w/ 16GB Sandisk Ultra micro SD (Volumio installed) - Sold
2) DigiOne Signature (w/ USBridge Sig Faceplate) - $230 shipped
3) Shanti - sold
4) Isolator v1.2 w/ Battery pack - $30 shipped


Thanks!

Hello all; I'm looking for some friendly advice for my speaker building project...

My current and long-time “hi-end” speaker system consist of 17 year old Audio Physic Virgo III’s, which offer more inner detail and resolution, transparency, and pinpoint imaging compared to my previously owned mid-1980's Apogee Duetta’s. And while the Apogee’s could produce prodigious amounts of bass, it was not as tight as I desired (especially after hearing the Entec SW-1’s). I’m not a loud-volume listener, but because the Virgo’s have limited bass extension, I chose to run them in parallel with a pair of line-level late 1990's Velodyne 12 inch servo subwoofers which I can blend well with the main speakers in my relatively large listening room.

Years ago I thought I would pursue an improved DIY speaker project that would offer even more of the above qualities, using what were considered then to be some of the best speaker driver units available:

Scan Speak D2509/9900 Revelator tweeter
Scan Speak 18W/8545-00 mid-woofer
NHT 1259 subwoofer

Since I lacked the requisite measuring equipment, knowledge, and experience to design my own crossovers, I was going to use the 2-way Scan Speak Reference Monitor, Brennwald's ScanSpeaker, or Madisound designed crossover that had been employed for the Scan-Speak drivers, in conjunction with a pair of sealed subwoofers for the NHT 1259's powered by plate amplifiers. The general design would follow the Tony Gee Andromeda speaker, which I find quite aesthetically pleasing.

Now approaching retirement, I have been bitten by the idea of building these speakers once again. Pulling the drivers out of storage, I discovered they are pristine. But I have become aware that after 15+ years, significant advancements with speaker technology have been made. I therefore have the choice to:

1) pursue the project as originally envisioned, or

2) sell one, two, or all of these driver pairs and invest in an updated design, such as those from Troels Gravesen, who seems to have a very good reputation and obviously is both very knowledgeable and experienced.

However, I find the potential number of possibilities bewildering. Troels refuses to make any recommendations, and I don’t have the time or inclination to become a serial speaker builder. Other than frequency response and distortion graphs, and without the ability to audition a particular speaker, let alone hear it in the personal home listening environment, how does one decide between – for example – the Ekta Grande, Jensen 1071, Illuminator Monitor, Ellam FLEX paired with a suitable subwoofer, Ellipticor-1 with subwoofer, Ellipticor-3, or the ATELL-3?

Are the “classic” drivers I have still good enough that I wouldn’t hear a significant difference compared to the newer designs? Or given a specific budget, would it be best to pursue the most cutting edge drivers and designs one can afford, hoping for a significant and worthy improvement over what the classic drive units can provide? Given the few and far between reviews of DIY speaker projects by an independent reviewer (e.g. not the builder or kit seller), which direction should one move towards? I’m looking for suggestions or a methodology by which – ear-unheard – one can make any kind of informed decision.

Much thanks 🙂

Howdy All!

I have a pair of Soundcraftsmen PM860 monoblocks. They are being fed by a Don Sachs Model 1 preamp.

When I turn them on, I hear the initial rush of current, then nothing.

If I turn them off and back on again, I get about 30 seconds of music, then nothing.

Any ideas what is going on?

TIA...

Hi there all 😀

Does anyone have the schematics of a Rockford T1500.1bd amplifier?

Thanks a lot 🙂

Hello Everyone

I have been a lurker for a good while on this site, but this will be my first post. I have looking for a DIY audio project and not quite found anything that will fit my needs/desires but that also meets my minimal skills, particularly when it comes to woodworking. I have been doing a lot of reading and think I have come up with an interesting concept that I can execute but have got to the point where I have some questions that I am hoping the community might be able to help with before I plow into making a bunch of simple mistakes.

Quick bit of background, I have been keen to find a good single driver speaker solution based on a fairly efficient driver. I recently built a pair of Bottlehead's Monamour mono-block SET amps based on the 2A3 tube which are great but max out at about 6-7 watts depending on tube choice.

Of all the designs I looked at on here (and there is a ton of great information which makes for lots of fun reading) the one I was drawn to most was the BIB. With the BIB calculator provided I was quickly able to get a handle on the math and start exploring drivers and cabinet sizes that might work for me. The challenge I found was the distinct lack of WAF. I do have my own space for my speakers, but still when you get into larger drivers the BIB box does become very imposing.

I started exploring alternate box shapes that could make the BIB a bit more "interesting" while not adding too much complexity to the build. I went through a bunch of iterations of trying the fold the line in different ways but nothing really worked and just added unnecessary complexity.

Finally I settled on the idea of creating a BIB Pipe. Basically I would try to find a good match for a piece of commercially available PVC pipe and build a cone to place in the center of the pipe. With the cone expanding downwards into the pipe, I simulate a folded cone where instead of just folding around a single axis like the standard BIB, the cone folds in all directions and the line returns back up expanding at the same rate as the cone gets smaller again.

Whilst this initially may sound incredibly complex, the math is no different in my mind to the standard BIB when you have a shape of a defined line length, a defined terminus area, that is increasing in cross-sectional area linearly along it's length.

As far as construction I am planning to do most of the complex design on a computer and 3D print the more challenging components. I should perhaps also admit that I have never done any 3D printing, but again there is a ton of information in the online communities so I am sure I can get over that hurdle.

There are however some challenges. I have tried to tackle a few of them but I am at the point where I could really use some input from the community on some of these things which are more basic in terms of which principles are strict and which have some flexibility to be manipulated.

1) How precise does the line length need to be?
Based on my testing of a few different drivers, the best fit for my needs came out be the FE168EZ. Per the BIB calculator I need to shoot for a line length of 132.01". The question is how accurate does that need to be. While the base concept is quite simple there are a few elements which may influence the final line length which I may not be able to fully account for. How far out can I be in terms of line length tolerance without impact the overall output?

2) How linear does the cross sectional area expansion need to be?
There is one design element in particular, the speaker driver box which will connect the driver on the outside of the main pipe to the cone on the inside which "consumes" cross sectional area from the main pipe cavity. I have attempted to account for this by increasing the ID of the main pipe at this point, but chose to only pick a few points and make an approximation of the cross sectional area at these points. I don't expect the effect to be a significant compression of the pipe, but the expansion may be less linear in this area. Do I need to go back and really focus on ensuring the expansion is as linear as possible or is a bit of variation OK?

3) The big concern. The design call for the driver to be mounted in a box with the back of the box pinched down to match the width of the cone at the Zdriver distance. In the BIB itself the driver is fully sitting in the line, whereas in my concept the driver is sitting fully in the box which is connected to the line. My intention was to stuff the box and hope that the restriction would not cause issues either in the driver itself or the coupling between the driver and the line. The other issue I can't determine is, assuming the first point is not an issue, should I include the distance from the back of the driver to the center of the cone in my line length calcs, or do I simply treat the point where the driver box and the cone intersect as the Zdriver point and treat the whole box separately from the line. My concern is that if I take that approach, the effective output of the driver enclosed in a stuffed box may have a different effective Fr leading to a different line length requirement. But this is where my knowledge falls apart and I am frankly grasping at straws and flailing with my lack of understanding.

I really think if a couple of these fundamentals can be solved this could turn into a really good design. I have started doing some of the CAD work and have attached a couple of pictures of my initial designs. For context the commercial pipe will be SCH40 10" PVC and the whole finished speaker will be about 70 inches tall.

Alternatively I could be in way over my head and you all might be able to save me a bunch of wasted time and effort trying to build something which is doomed for failure from the outset.

Apologies for the incredibly long first post and thanks in advance for any and all feedback.

Phil

What do you prefer between aural compensator and loudness? AFAIK, the loudness operates by boosting low and high frequencies, while the aural compensator will reduce midrange with some attenuation on overall level at the same time. Is it a good a idea to have an aural compensator and a loudness together in the amplifier?

Anyone know what diodes these are ?

Looking for an empire tonearm in need of repair so I can do some experimenting without ruining a perfectly good arm. Mostly interested in the bearing part with the sprung tracking force weight, along with the mounting post. Have considered using others arms as a staring point, but the empires have a VTA adjustment built in, which most of the dual arms with dynamic tracking force don’t seem to have.

Let me know if you’ve got one of these for sale or trade, or something similar with dynamic/spring loaded tracking force.

If you’ve got an empire arm with interchangeable headshell for an affordable price, I’d be interested in that too, to use as is.

Thanks in advance!

Hi everyone,

the 4P10C is a forgotten Russian octal pentode with plate cup (not MO) that has a 15W dissipation with specs close to EL34 (though it looks like a KT66 having a similar size box plate but smaller plate wings).

I don't see anything in the net about it.

I do have it's detailed specs as can be found on a paper packed by the factory inside the tube box.

Any member that has tested it in a project?

Hi guys,
I have got a Positive Grid Spark practice amp. Its powered from a typical 19V power brick. Its humming so bad. There are some known issues with these units and its has got something to do with grounding issues. There are couple of suggestions that people have made and have worked for them:

1. Connect a usb cable to the unit and the other end to a properly grounded laptop/computer.
2. Attach a separate cable from the chassis of the unit to the ground pin of the mains.
3. Change the power supply to a ‘three pronged’ power brick.

I didn’t have any issues with the amp out of the box and with in a weeks time the humming began. I used option 1 and connected the USB port to a well grounded computer. It did seem to help at first but then the hum came back. Right now the usb cable remedy is not working. I tried option 2 as well by alligator clipping the chassis to the mains earth and there is no improvement/change on the hum whats so ever. My mains out are properly grounded and I have confirmed this.

I am starting to think that maybe my unit has got a failing component somewhere as the problem kept progressively deteriorating to the point where it is now.
So I was hoping to get suggestions on what to look for.

I measured the resistances between the AGND, PGND and DGND (marked on the pcb). All seems to be well connected. However I did notice that the chassis of the USB port to PGND showed resistance value jumping around before it settled to 0ohms, I am assuming that its error on my side with my probes.

Also I have got a question about the 3rd option (‘three pronged’ power brick) - how does grounding help with noise etc with an SMPS type power brick. I see with SMPS schematics that the ground is not directly connected to anything on the SMPS but sometimes through a Y type cap to com. Is that connection doing the magic?

Anyway I was hoping for more suggestions on what to look for. I have got the unit opened.

Thanks in advance.

Hello everyone!!

I have a Krell KSA 100 MK2 that has had a rough life.
Recently, the right channel blew up.

After replacing all the driver transistors (MJE 15030/15031), some resistors and couple of output transistors the amplifier came back to life.

Having went through the entire internet, I have come to a conclusion that most people, that own this Krell, adjust their bias to 500mV.

As a start, I adjusted the bias to 450mV on both channels, I was very happy with how it sounded. However, the heatsink temperature of the repaired channel had averaged around 95°C (203°F), while the left channel (also repaired at some point) had a temperature of around 70°C (158°F).

Because of such high temperature, I have dialed the bias down to about 375mV on both channels, and the left channel averages now around 60°C (140°F), while the right channel averages around 80°C (176°F).

I plan on doing a full restoration of this amplifier sometime in the future. They are wonderful amplifiers that deserve love. Until then, I'd like to try to get it working the way it should.


My questions are:

1. Can anyone tell me what is the normal temperature of the heatsinks and the recommended bias for the Krell KSA 100 MK2 ?

2. Could the high temperate be the result of the output transistors not being from the same batch? I have only replaced the bad ones, while left the working ones in place.

3. I have measured the bias by measuring the voltage across one of the 1ohm resistors next to one of the output transistors. Is that a correct way of doing that?

I really appreciate any advice you can give on how to approach this issue.
Thank you!! 🙂

I'm wondering whether the online caculators of port dimensions for vent enclosure work for bandpass enclosure? Also, if I were to build the triangular ports on the bandpass cabinet, can I use the calculator of square ports, by considering a square as two triangles? Finally, could anybody help to suggest a reliable online ports calculator, please? As I found many websites having different formulas. Thank you in advance

Hey all,

I have a Class A amp power supply on my Krell Clone - Pinkmouse boards)

Anyway, I want to change the CRC to CLC to see power supply ripple reduction.

I saw a few pics that the Pass amps have an iron core inductor (similar to Speaker crossover coils). I did find in my stash two chokes of 4.75mh and .2 ohms DCR (amp rating unknown). These look like vintage Altec Lansing Iron Core Crossover inductors - see pics... look to be 16awg wire...

I remember years ago trying this and the inductors got quite hot (I am pulling around 6A per rail) after a while, but so did the whole damn amp!.

The power supply is a 1KVA Toroid into a 25A Rectifier - 56,000uf - L - 56,000uf and rails are +/- 36VDC.

Anyway, if only .2ohms and 6 amp, 16awg, how to guess at power capabilities (weigh it?)

Whats too hot? Yes, I get that I dont wanna melt the coating...

I see crossover iron core inductors rated at 500W but only .2ohms DCR - how / why? I know there is more to this than Amp x Resistance going into the power rating...

Hello If anyone can help me wire this MC SUT. Im trying to use it with a Denon 103r 14 Ohm to a Hagerman trumpet. Im trying to load it at 470 ohms.

The part that I'm confused about is the resistors that are recommended to reduce ringing. Somewhere I read that they are not needed unless I'm trying to reduce load

I know the recommended load is 100 Ohm for cart but i don't want to reduce load unless its necessary so I was planning on listening to it at 427ohm before reducing load. Thank you all for the help

Thanks

Gary

So...

This is more for just curiosity sake, not really a problem.

I've owned these 70's beauties for years, had them checked out a couple of years ago, and they still meet factory specs. they are built like battleships). And they sound great too.

On the bottom side of the amps (under a annoyingly pain in the a$$ panel to remove), there are 2 fuses; a 5 amp and a 1 amp. The 5 amp fuse has never blown for me, but if the speaker cables touch accidently when the amp is on, the 1 amp blows.

When the 1 amp blows, the amp still outputs audio, but it is a few db lower, and highly distorted. Sounds almost worse than a blown speaker driver. It almost sounds as if one were to continue playing the amp like this, it could damage the speaker.

My question is, why the hell does this fuse being blown still allow the amp to output such a distorted signal? Why not just disable all output?


For those that are unfamiliar with these amps, they were part of Kenwood's high end line, and their (successful. IMO) attempt at competing with the best of the US high end audio products.

Here is a pair of Tube Amplifier Phase Splitting Interstage Transformers LL1660S/10mA, SE to PP.
I pulled them from a new built and were used for less then 100 hours. It was a EL34 amp that I decided to disassemble and I have no use of them right now.
They are in excellent shape. They have soldered a circuit board that allows different possible connections.
I am asking $150 plus shipping of a 5 lbs. package from 06851.

Hi everybody,


that's my first post here, but let me already thank everybody - the last few days I was working on my old Rotel RX 304 and this forum was a great resource.


What I've done so far is replacing all old electrolytic capacitors with new ones. After the recap, the amp sounds way better than before, so I'm quite happy. There is still one problem with a background noise which wasn't fixed by the recap.


Here is a bit of initial diagnosis obtained by playing around with Online Tone Generator - generate pure tones of any frequency:

- There is already auditable noise coming at very low Hz, in fact there is a tone at approximately the input frequency (so if I put in 1Hz sinus, I get a tone every second).
- This tone disappears if the volume is lowered, but the exact volume depends on the frequency: if the input signal has a higher frequency, then the noise appears already at a lower volume. It doesn't matter if the volume is controlled from the PC or by the volume button of the Rotel.
- The noise is there over the whole frequency range, even if the input signal is 20kHz (where it sounds like a tone of about 10kHz).
- The noise (at least for lower input frequencies) is not affected by the treble control, but its volume goes down linearly with the bass control (but is still there even with bass -10).

- The problem is in both channels, but slightly different. The noise in the left channel has lower amplitude of the noise (as displayed in the Watt display from the Rotel) and twice the frequency of the right channel (for 1Hz input).
- There is also a white noise at higher volume (probably not related, but if somebody has an idea how to fix that...).


I sadly don't have good equipment to measure things (not even a voltmeter), but I'm planning to go to a repair cafe and check a few things. So would like to have advice what to check. Thanks!

Hi, all.

I've obtained an old and used, but still working, pair of Spirit Absolute 4p studio monitors. They were really cheap, and, for nostalgic reasons, I wanted them. But they need some love.

They work and play, but both exhibit some hum and "tzzzzz" and they pop and click quite loudly when powering up and down.

Is this a matter of just replacing all the electrolytic capacitors? There aren't many in the amps, according to the service manual.

I've tried to manually copy/paste the schematics to .PNG's and attach them to this post.

As far as I'm able to interpret the schematics, there are no electrolytic caps in the "turn on/off mute circuit", nor are there any of interest in the woofer and tweeter protection circuits. I thinks those are based on optocouplers, that "short" the positive and negative inputs of the respective amps, thus lowering the outputs. But I could be wrong. I would suspect, however, that a any start-up delay would mute the woofer and tweeter so as to block any pops and clicks from the drivers. What could be the cause of this not working properly? Is this easily fixed (i.e. replacing a few parts)?

Hope you can help!
Thanks!

James.

I often see wonderful builds with best-of-parts (that is, the builders didn't spare anything) but the signal-wires, mostly twisted pairs, going all the way back-to-front from the RCA-plug to the selector-switch (elma 04, seiden, etc.), over to a luscious volume-control of sorts, and from there all the way back to the board.

Aren't wire-length supposed to be made the shortest possible, or is this more an esthetic problem? My head is often smoking from trying to figure out the really shortest way from input-connector to selector-switch to volume-control to the line-stage... Obsolete?

david

Thought the attached schematic might help some readers.
It's an NE5532 Buffer listed on Ebay by umpteen sellers.
NE5532 OP-AMP HIFI Audio Preamplifier Dual Preamp Board for Bluetooth Pre-amp K9 | eBay

Take care when selecting buffers - this is split supply, some others are single supply.

What is a good way to clean dirty (dust/grease-collecting) tubes without damaging the lettering/printing? I have tried water plus gentle wiping and that removes the lettering easily (at least for the tubes I am dealing with). Any tricks members would like to share? Thank you.

Q1 = Crown Electrostatic Speaker Panels RTR (upper left corner panel in google photo pictures)

Q3 = Janszen eletrostatic tweeter panels from Z zeries Z-600

Selling all four as a package.

$140 plus $20 shipping (continental U.S. sale/shipping only).


Electrostatic Panel Pictures - Google Photos

if you have circuit curiosity, check this interesting dual channel unity gain IC out:
https://www.mouser.com/ProductDetail/Texas-Instruments/P82B96P?qs=aEuGZpxfbxV0WPFsO7nJmg==

i'm curious if this is a valid IC to try making a stereo buffer for a 4 cable method-ish approach. perhaps one channel from the guitar and the other from the end of the mono drive pedal loop to the reverbs/delays/etc. then a 2nd IC for the stereo out of the stereo loop to recording interface.

thoughts on this chip?

here's the datasheet:
https://www.ti.com/lit/ds/symlink/p82b96.pdf

for sale Tribute Audio potted choke
20h 120mA

100usd

I’ve almost finished my Tube balanced preamp based on ecc82 and ecc88 in attach, but I could not slove voltage problem. When I connect one of the chaneles to power supply it is working fine, tested sound as well. When I connect both sides/channels to PS voltage started to rise after several seconds and I switched it off. The strange thing is that the heater voltage is also going up.
I have HV Power supply based on 5U4G and with Hammond transformer and choke. I also have one LV Power supply 6.3V for filament of all 4 tubes. Ecc82 supplied with 6.3 parallel. Also when I switch on PS to heaters without HV its also fine, 6.3 stable.
Does anyone experianced the same issue or got an idiea?

Gentlemen, the right channel of my AUDIO Agile Step AMP is broken.
There is only hum coming out of the right speaker, and when I look at the right channel with my scope, I see the input signal (a simple 1 KHz sinus)
oscillating around 0 VDC.

I do not have any documentation concerning the STEP AMP.
Moreover: the AUDIO Agile company does not exist anymore, and I do not find a communication ID (f.e. EMail) of its owner (?),
Mr. Björn Langlie, in the INTERNET.

Is anyone of you able to support me repairing the STEP AMP?
It would be best, if the one who says: "I will do (assist you, repair) it" lives in EUROPE.

Many thanks and best regards - keep safe from CORONA - Rudi_Ratlos

First time user and I am quite liking it and the whole idea.
WindowSwap

Pair of Macrom/Morel drivers
4 Ohm version , do think it,s the MW 162 or the 164 version .
50 euro + shipping

Here is a pair of OPTs, James JS-6226HS 20W 6.6k push-pull, 10Hz-60kHz (-1dB) and Primary current Max 90mA.
I pulled them from a new built and were used for less then 100 hours. It was a EL34 amp that I decided to disassemble and I have no use of them right now.
They are in excellent shape.
I am asking $150 plus shipping of a 17 lbs. package from 06851.

Don't know if these are any good to anyone.

Removed from a Kenwood KA3020 of 1990s vintage.

Untested. Includes the white things.

Small chip to the outer casing of one of the small C4137 things

Free including shipping.!

Hi guys,

After my journey with the right distorted channel (https://www.diyaudio.com/forums/digital-source/361410-cdp-x33es-channel-distorted.html) i thought it was time to start with the dim screen of my Sony cdp-x33es.

Any ideas where to start?

thanks!

Rubbereend

I was wondering if quad single voltage toroidal transformers are available somewhere, or are they "custom" made for amplifier companies?

Has anyone seen anything like this in ~600VA?



Here is something similar from Aliexpress, but in 220v primary and extra secondary voltages,



Or should I just split a single 36v-0-36v 600va transformer or use two 36v-0-36v transformers and stop looking for Unicorns?

Thank you,

David.

Hello,

I would like to to turn a AA764 Fender Champ Amp, into a stereo one, by simply doubling the circuit, but keeping only one power supply.



Since it is a single ended, it gives with 2 6V6 with 14W power something around 40mA per tube, and 8 mA more for the screens if we consider 10% dissipation. For the triodes it would be a 1ma for each, so a total of 4ma.

It will be a total of 92mA and if we take in consideration rectification and filtering losses it will be 20% more, something arround 110mA where a 5Y3-GT can handle 125mA.

Question, since the current will double, the intended voltage are not the same, as I tried to simulate the PSU with PSU2 tool (PSUD2)

What would you do and which resistor values would you use?

Thank you 🙂

For sale a pair of these great 3" full rangers.
Originally supplied from a European dealer, they were measured and matched and came with a print out of the FR and impedance of each driver. They were very closely matched. This was done by a company called EMES in Germany
Alas I cannot find this information.!

I have quite a few drivers and unfinished projects and I have a hankering for some PS95s so I'm letting these go

£40 plus shipping

I recently built this EL84 pp amp. But no sound came out. Is there something wrong with the design?

Hi all,

I've read lots of recommendations for the use of dual bridge rectifiers in PSUs, but have not read any clear justification for this design. Can anyone point me at a good reference or state the reasoning here?

Examples:

Diagram 3 here: http://www.tnt-audio.com/clinica/ssps1_e.html

http://www.kk-pcb.com/power-2.html


Cheers,

Dan

I've just replaced the power supply caps in my Audiolab 8000A, and I thought people might be interested in my experience.

I'd had the amp in storage for a few years, and when I got it out to set up again I found the RCA sockets had started to break as the plastic bodies crumbled - a common problem. So replacing those was my first job - I got a new set from an eBay seller for £57 (which is not cheap).

The old caps are Elna 10,000uF 50v, and looking around what was available I settled on Mundorf Mlytic 15,000uF 63v (£50 for the pair, again not cheap). One of the nice things about the Mundorfs is that they're the same size as the old Elnas - I know that's trivial, but I think it looks nice when components look as if they fit.

Today was the day I did the job, and even with a pair of modest Tannoy Mercury MX1s (and an active sub run from the pre-amp out), the difference is... not small! Without even giving it a few minutes to warm up, it's enormously improved.

Imaging is stable and a lot more precise - instruments and voices used to wander depending on the notes, and guitars seemed like they were six-feet wide. The sound stage now has a bit of depth too - it was flat 2D before.

The biggest improvement is in louder passages, which is probably not surprising. Previously a loud passage would turn mushy (if you know what I mean) and detail and imaging would smear. But now, it's smooth, powerful and far more precise.

After all that, I decided to measure the old caps to see how they rated. I had to series them up to get within the range of my meter, and they measured at only around 4,100uF apiece. It's hardly surprising the difference the new ones have made, and it's definitely money well spent.

Anyway, next job is to replace the rest of the electrolytics in the amp - probably with Elna Cerafines. My recommendation for anyone considering replacing the power supply caps in an old amp is... just do it.

Hi!

First and foremost, sorry if this is explained elsewhere. I'm working on fixing my very first tube gear. Analog electronics is pretty new to me. Reading whatever I can find, "Youtube university" etc. My background is in IT and digital logic, so some concepts I understand fine, whereas certain basics most certainly have eluded me.

Ok, so back to the question at hand - voltage levels on tubes, and how to understand the spec sheet. I'm fixing up a Conrad Johnson preamp using 6922 triodes, and discovered there were no plate voltage. Traced it back to a couple of faulty transistors (used for power regulation, I assume). Ok, fine.

However, when checking all the pins on the tube sockets, I discovered the heaters were running on everything from 45-60v. This preamp consists of dual monoblocks, so I can use the working channel as a control - and lo and behold, it was approximately in the same range.

If I check the data sheet for the 6922 (http://www.tubebooks.org/tubedata/HB-3/Receiving-Type_Industrial_Tubes/6922.PDF), it said heater voltage should be 6.3v +/- 0.6v. However, it also states that, relative to the cathode, it can be from -60v to 120v.

How should I read this? Does the tube really have such a wide tolerance? If so, why do they state 6.3v?

Apparently, the tubes work fine at ~50v for the heaters, since the working channel has no issues. I've measured relative to ground, but the cathode has about 1.3v relative to ground, so no big difference.

Any input is greatly appreciated!

Hello, I am looking for a manual, schematic or any other information for this meter. Thanks!

With a big thanks to Koifarm for allowing copy´s and sharing, and same thanks to flancfuster for sharing his files, I had some PCB´s made.... MM Mini-Me and PSU.
My first intention was to give some away, but they ended up a little more costly than expected + they got "caught" in customs :-(.
I got 20 sets made, and I´ll let go of 15 set´s for the cost.
1 phono pcb+1psu pcb = 12Euro.
Untracked shipping in bubble envelope worldwide = 6Euro.
I also have a small stash of NOS 6N16B-V and can let go of 5 quads (unmatched) for 6Euro pr. quad.
PM me for details if interrested.
All needed info here:

Mini-Me phono preamp

The price is for PayPal "family and friends" transfer or Normal PayPal+4% for their fee (I prefer the first option) 🙂

Please have a look at my offer of four AKSA NAKSA 100 modules.

Asking 199 Euros per piece, international shipping is possible.

Link:
NAKSA 100 amp modules

I know this has probably been discussed 100 times .

But does anyone know of a good replacement for the driver ic for the outputs ?

It’s labeled ABLETEC.COM. 436P

Hello All,

I need help on this type of amplifier, schematic or service manual is much appriciated.

Thanks in advance.

Glass painter

Differential O-scope probes are still a lot of money, for some reason**, but I don't see why in a world of amazingly cheap, low-noise, precision op-amps it should be so difficult to create one - at least for audio use.

Has anyone built such a device for themselves? Are there any easy-bake recipes out there for such things? I've done a bit of search, and I may not be using the correct terms, as I get little of nothing.. but what could it require, other than possibly one or two hi-performance op-amps? I'd think that a very competent device could be built for around $25 USD - and that, with really fancy op-amps and a well-reg'd supply.

One requirement might be that it passes DC - so that might also be a hang up, but either way, even good to 10-100KHz should be fine for most all audio work.

(** might be a good one, which is why I ask, heh)

Ok im repairing a soundstream ta1.3000d it claims 3000rms@.5ohm however one of the oem u30d20d mospec rectifiers had a short the other 3 were ok but i cant find a replacement from a reputable source. After doing some research i found that the fmu 32u is very close almost identical except the (isfm)AKA peak forward surge current is 200A and the oem rectifiers peak forward surge current is 300A. Thats about the only difference i really see so my question is can i replace the Mospec u30d20d with the fmu32u and the amp perform like normal.

PICS OF PDF FILES BELOW FOR COMPARISON!

Not sure if this has been talked about before, perhaps elsewhere.

It's about the phenomenon of people, mostly younger, using excessive and overblown bass while listening to their, ahem,... music.
Particularly in their cars.

What is the deal?
As far as I can determine, it's rampant, annoying, and just plain dumb, but that's my opinion.
I don't understand the attraction, and why people choose to do it.
Is it a "power" thing, or just a fanatic thing?

Is it to make up for other shortcomings or insecurities?
Have manufacturers catered to this crowd to reap profits, at the expense of ruining people's hearing?

The average, sensible human being, surely likes a "full bodied sound" to enjoy, and since everybody's various tastes and preferences are concerned, that's perfectly fine.

But what is the attraction to brain-shaking, window-rattling, and trunk lid vibrating bass?
Setting off car alarms along the way.....

The "I don't give a crap" attitude of someone driving down a residential street at night isn't pretty to me, and I'm sure others.

Maybe someone here can toss in a few of their observations, without starting a thread-war.

My son runs a radio station online as a hobby.

We think that someone has accessed the website without authority.

The website is currently unsecured.

How can we secure the website.


Andy


.

I've been testing OB in an active 4-way configuration where the low bass is covered by two 12" sealed Rythmik subs, and the OB has two 10", an 8" for mids and a tweeter.

The twin 10" are Beyma 10G40 which I had from a previous project. I'm liking the sound, but need to cross them no lower than 70Hz and while the bass is very well defined I still miss a bit of impact. I'm thinking I might need more Sd on the midbass. Does this sound like a good diagnose?

I see most OB use 12" or 15" drivers, sometimes using two per side. I believe often those are used without subs below, though. The recommendations seem to be for drivers with low fs (30-35Hz), high Qts (Emminence Alpha 15A has 1.2), Xmax of 8-10mm.

Looking at pro drivers, the ones that satisfy the fs and Xmax criterias and have the highest Qts are 18". Using one 18" per side would allow crossing from the sub around 40-50Hz, and would almost double Sd of twin 10". But then I don't often see 18" for OB midbass so maybe I'm off. Hence the ask for help 🙂

Here are the two 18" I've narrowed down to:

• Beyma 18LX60: Qts: 0.48, Xmax: 8mm, fs: 35Hz, Sd: 1320cm2, Sensitivity@50Hz: about 89-90dB, impedance@50Hz: about 16 ohm

• Faital 18HP1010: Qts: 0.40, Xmax: 9.75mm, fs: 35Hz, Sd: 1207cm2, Sensitivity@50Hz: about 93dB, impedance@50Hz: about 27 ohm

For reference AE Dipole 18: Qts: 0.81, Xmax: 15mm, fs: 23Hz, Sd: 1218cm2, Sensitivity & impedance charts not published. AE aren't available around here and logistics would be complicated, but I use them as good reference for a driver that has been designed for dipole operation.

Today the midbass runs up to 500Hz. Would love to get input from experienced users regarding using a 18" driver vs 15" or even twin 12" for this application and if there are better suited drivers than the ones I listed. Maybe I'm giving high Qts more value than what it deserves?

Thank you!

Hi all, I was wondering if anyone has heard an Aunt Corey's Homemade Passive Buffered Preamplifier , and any opinions about them?

I started one years ago , I worked on it for a while but didn't really know what I was doing, so didn't complete it. I have the Power Supply mostly built from years ago .... I was thinking it would really good to finish mine.
Unfortunately I can't find my original BUF-03AJ's that I purchased back then. Does anyone have a pair of BUF-03AJ's that they would be willing to part with for a good cause?

Wanting opinions on weighing the credibility of DATS V3 measurements compared to the manufacturers. I realize this might be a silly question, as I bought the DATS so that I could get specs for the specific drivers I am using, I guess I just don't like what I am getting (because I wanted the smaller enclosure implied by posted specs)

I am working on making a version of Zilch's Econowave SR Compact, except I will be setting up an active crossover/amp unit that will let them travel in a small(ish) package. These will not by run with a sub, and ultimate performance in this area is not critical.

Woofer: Dayton Audio PA310-8

Average measured T/S between the two drivers I have
SPL: 93.1
Re: 6.07
Fs: 33.2
Qts: 0.2935
Qes: 0.3049
Qms: 7.816
Le: 0.4852
Mms: 83.73
Vas: 110.43

Manufacture's T/S
SPL: 96.1
Re: 5.5
Fs: 39
Qts: 0.29
Qes: 0.30
Qms: 8.85
Le: 1.68 (I have found many references to these speakers measuring lower Le than this spec)
Mms: 72.8
Vas: 91.8

When working in winisd, I have been comparing with the same quasi-butterworth alignment.

The predetermined ported boxes are:

Measured specs: 1.62 cuft / 41.3 Hz tune
Manufacturer's specs: 1.1 cuft / 51.7 Hz tune

While the extra performance down low is nice, the 50% increase in box size really isn't what I wanted to see. I can certainly shrink the box down, but the port gets really long and the first port resonance really low . . . which isn't ideal . . . If I raise the tune to increase the first port resonance a bit, a definite hump in the low end response begins to show up.

When is first port resonance objectionable? I could just EQ out the hump in the Bass.

If size is pretty important, I though about maybe giving up the port but that puts F3 at 80Hz. I will be using an ADA1701 for the crossovers, and will have access to the "SuperBass" algorithm, so I can cheat here a bit . . . but I can use this with ported too.

Am I right to rely on the DATS measurements and just try to get the best out of what I have, or should I be wondering if the manufacturer is better at measuring than me?

In the attached screen cap of transfer functions, from left to right:
ported using measured T/S
ported using Manufacturer's T/S
Sealed using measured T/S

I am looking for an audio/ media player for Raspbian which is very much like runeaudio or volumio. The problem with these two is they have their own OS. and cant be installed on Raspbian. I have NAS and DNS server running on my raspberry pi. So I don't wish to dedicate Raspberry pi for that.

Both Volumio and runeaudio has remote applications where you can operate Raspberry pi headless.

Please suggest me a player.

Thanks

Hi, Gents,

I am planning on bracing the 16T X 10W X 14D two way cabinets I've just built with one side to side brace and one baffle to back brace. The cabinets are built of 3/4' Baltic birch and are of 100% mitered construction, including the top and bottom. My question is: Is it better to tie these braces to each other where they cross in roughly the center of the cabinet or keep them seperate from each other? (I know that they should be slightly off center where they butt against the panels). My hunch and one experienced speaker builder says, tie them together, but another very experienced speaker builder I respect says to keep them independent of each other. I wonder if folks who have practical experience can share their views and rationale. I'm still a beginner, this is the biggest cabinet I've built and I'd like it to be the best it can be given that it is using a very basic bracing scheme.

Best,
Jay

All transformers SOLD


I have two unused antek as 2t230 Transformers.
How about $25.00 each or two for $40.00 plus shipping.
AS-2T230 - 200VA 230V Transformer - AnTek Products Corp

This is my first DiyAudio post! I write as I'm preparing to build my first turntable plinth.

My starting point is a Micro Seiki DD-8. Micro Seiki DD-8 Direct-Drive Turntable Manual | Vinyl Engine A well-regarded direct drive table. I'll be using the motor and electronics from the DD-8 along with "upgraded" platter and tonearm. The platter is from a DD-8Z/DDL-120 (4.5kg vs 2.6kg for DD-8) and the tonearm a Micro Seiki MA-505 MkIII (vs MkI)

My hope is to take a successful table and upgrade it in a number of modest and hopefully beneficial ways. For example, the platter is bigger but still capably turned by the same motor in other Micro tables. The tonearm is an improved version of the original tonearm. I'll be moving the electronics off of the plinth and into a separate housing, much as Micro did with the DDL-120 and other higher-end tables. There will be many other variables to consider, presumably after the table is built.

The DD-8 plinth is very basic - three layers of particle board, glued together. My goal is not to build the perfect plinth, but to do "better" than the original. (And I'll say up front that I know that simply "upgrading" a few components does not guarantee success. Everything needs to work together.)

As for plinth design, the principles seem to be well agreed-upon in that the table should be sufficiently rigid, lossy, and massive - and that there are no perfect materials. So composite "sandwich" structures are often used, which blend materials in a manner that results in better damping than would otherwise occur from any one of them alone. Within that context, there are clearly different views and experiences with what works best. Of course it's important to ensure the platter bearing and tonearm are sufficiently isolated from each other and of minimizing interference from outside disruptions.

I have a masters in science, but haven't had the pleasure of applying it professionally for a long time. And I have no plinth-building knowledge of my own. So I'll probably be able to understand the technical stuff it's well-explained and I can ask follow up questions 🙂 Also I'm a capable wood worker with a garage full of tools. I don't have the ability to work with anything exotic though. (So panzerholz is out)

Again, I'm not out to build the perfect plinth. Just to do "better" via the application of simple principles and the experiences of other DIYers. And to learn a bunch in the process so I can go further next time.

Hi All,

I consider buying the following extremely budget DAC in an attempt to enjoy (if only I manage to looking at its price) SQ due to AptX-HD/LDAC:
Lusya Csr8675 Bluetooth 5.0 Wireless Receiver APTX HD/LDAC PCM5102A DAC Decoding 3.5mm RCA Output 24bit With Antenna|Digital-to-Analog Converter| - AliExpress

They seem to have 2 versions of this device as mentioned in the advert:
- APTX HD support: SBC/AAC/APTX/APTX HD
- LDAC support: SBC/AAC/APTX/LDAC

Could anyone please try explaining why choose? There are lots of CSR8675-equipped DACs out there that claim to support both Aptx-HD and LDAC, so isn't it auto selected by that BT chip itself during codec negotiation with the source? All they say is "they differ by Bluetooth version" and point at a more expensive model that states "support LDAC and APTX HD":
Lusya LDAC Bluetooth 5.0 Wireless Receiver Board PCM5102A/AK4493 DAC Decoder Board APTX HD Support 24BIT With Antenna|Digital-to-Analog Converter| - AliExpress

Could they have implemented codec specific devices in an attempt to make them cheaper than universal ones?

Many thanks in advance!

I have a Marantz PM44SE integrated amp which I’m still pretty happy with. It has served me well for many years but has developed an intermittent, though annoying, fault.

The problem is severe distortion on the left channel (both sets of speaker connectors and headphone jack) which comes and goes but tends to rear its head at some point during any listening session.

The fault seems to be related to the input selector and involves all inputs including phono. When the fault occurs, rotating the selector knob slightly usually rectifies the situation for a time. Opening the cover reveals that the input selector knob is not attached to a rotary switch but instead uses a mechanical cable linkage to a slide switch mounted on an input board separate to the main PCB (probably to keep the signal path short). I think it’s fair to assume that the fault is due to either wear or dirt in this assembly as it appears that the audio signal is routed through the multi-way switch rather than using electronic switching.

Does anyone have any experience of opening one of these switches up? If not then I’ll have a go at it. At worst I can hardwire the board to a single pair of input sockets and use an external switcher, though I’d like to preserve the phono stage if possible.

Any advice would be appreciated.

As stated in title, looking for either 2 of CA17RCY/P or failing that, CB17RCY/P

Cheers

James

Hello all,
I just saved two vumeters from a deck I saw in the scrap container (Aiwa Ad6500) and I need some advice on how to wire them up in order to use them between my computer line out and amplifier...
Since I am a noob I hope some of you can help me with a few instructions.
Attached you can find the photos (front / back) and the schematic I found over the net.
Thank you

Has anyone ever seen a sealed enclosure with an extremely low Q design, let say it has Q lesser than 0.5? Normally, Q of the sealed enclosure should be varied in 0.707 - 1.414 range, is it correct? Is it a good idea to make an extremely low Q in a sealed enclosure? Or is it simply a special design for correcting some special cases?

This is a new built and works as designed by Tom @ Neurochrome.
Specs and info could be retrieved from Modulus-86: DIY 65W power amplifier achieving -120dB (0.0001%) THD – Neurochrome and Guardian-86: High-End Speaker Protection Circuit for use in DIY Amps – Neurochrome.

I am mostly a tube guy and this amp is not a good fit for my speakers.
However, it sounds wonderful for whoever likes SS sound.

I added the Guardian-86 speaker protection and it make a nice difference at start up and peace of mind.

I am trying to recover the money I've spent on parts and materials.
Chassis is Modushop Mini Dissipante 2U 300mm, main transformer is a 225VA Hammond 1182P22.
It is setup for 20dB gain, 1.8Vrms input sensitivity

I'm asking $700 shipped to US48.

So I'm trying to use a simple current mirror to provide a voltage-independent 5mA minimum load and, like, well, I can't get it to work - I've spent more time on this than I'm willing to admit so if someone could lend a hand that'd be great.

Basically, I've got a 15V rail and a variable voltage (~0V to ~25V) rail that I want to sink 5mA from. I've tried with NPN BJTs (2N3904) and NMOS FETs (2N7000), all with the same result - everything is all good on "input" side, but the current just rises on the mirroring side, going up to 200mA in a couple seconds with the BJTs and much slower with the FETs.

Attached are schematic and a quick sketch of how I've wired them up.

What am I missing?

Wondering if this is normal or not ?

Some of the locations are loaded with gate resistors but not power supply fets and on the output side they are loaded with gate resistors and source resistors but no outputs .


Some of them look like they have never had any power supply fets in the location same with output side

Hello,

I hope you are all keeping well.

I have up for sale a new (or very nearly new) pair of Emission Labs 300B-XLS output tubes.

Asking $690.00 including shipping and PayPal fees.
That saves you at least $85. If you are in California that saves you $142.

I purchased these 3 weeks ago in celebration of a job that promised to be fairly lucrative. The job was cancelled and now these are up for sale.

I have logged roughly 12 hours on the tubes following the EML guidelines for tube break-in. Still have some hours to go for full break-in.

If you act soon, you can register these under your name for the 5 year warranty. I have not registered them yet. You have until the 25th of October, I believe. (I can send you the registration info upon payment and you can register them right away.)


REASONABLE offers will be considered.

Thanks for looking.

My home received damage during Hurricane Sally and the field adjuster wants me to replace the old school acoustic ceiling tiles in two rooms with new acoustic tiles. Problem is, I can't find any contractor in this area that install acoustic tiles.

My question for you guys is, do they actually offer any acoustic benefit over drywall?

Hello,


I'm referring to the phono preamp section of this integrated amplifer. We see a dual FET in differential mode, followed by half a 4558 dual opamp. We all know that nowadays there are so many better opamps than that one, but would the amplifier benefit sound- or noisewise from substituting it by, e.g, a NE5332 or LM833 - or an even better, faster, low-noisier one? Or is this section's characteristics mostly dominated by it's FET input what would make substituting the IC more or less useless?


Best regards!

Hello all, I would like to access the BT module on a HF-183 unit. Does anyone know if the usb port on the board can be used for this? I've read a lot of how to guides regarding soldering pigtails on other boards and using a converter/programming module but I've never found anything on this particular one that has a usb port. Thanks

Hello all

I am currently putting together a list of contents for a Third edition of Small Signal Audio Design.
Please be aware this is a very early stage in the project and it will not be hitting the bookstores for a year or more.

The Second edition was already about as large as my publishers consider practical, which is why all the phono amp material (plus a mountain of new stuff) was split off as Electronics For Vinyl in 2018. See: Electronics for Vinyl
The Third edition will have just two smallish newly-written chapters on MM and MC preamps, but nonetheless they will contain new stuff that is not in Electronics For Vinyl.

Obviously I would like to know what new stuff you would like to see in the Third edition.

Here is what is already planned:

Complete new chapter on variable gain stages.
Complete new chapter on tape machine electronics.
Complete new chapter on guitar peamplifiers.

and stuff on:

Frequency response, Frequency response of cascaded stages
Phase perception
Three-layer PCBs
Resistor accuracy: three resistor combinations
Distortion in Sallen & Key filters: 3rd & 4th-order lowpass/highpass single-stage
An improved Baxandall active volume stage with lower noise
The Newcomb and Young loudness control
Combining a Baxandall EQ stage with an active balance control
Wien fixed middle EQ: altering the Q
Improving fader offness
Balancing tracks to reduce crosstalk
The multi-function summing amplifier

Please let me know what else you would like to see.

The power supply drive section uses A1023 and C1027 drivers which I need to replace and don't have. I do have the 1220/2690 pair and the bd139/140 pair and and abundance of others.

Which would be suitable replacements for these? Normally I would just experiment but seeing as parts for this amp are not cheap I want to reduce my chances of failing.

With the recent passing of Eddie Van Halen Popular Mechanics has reposted an article by EVH about some of his hacks and a short history about how he got started in DIY.

You might enjoy reading his exploits in sound. I like his variac hack. 🙂

Eddie Van Halen Dead at 65: How the Rock Legend Hacked His Guitar