Looking for the schematic for this preamp, anyone?

Pete B.

SOLD!

Academy Audio VCX Muses volume control, LPS9 power supply, white LED display, and remote.

Used. Purchased second hand as working, but I never installed or powered them up.

$125 shipped to continental USA.

Today I purchased a beautiful Threshold setup locally, including an S/300 Series II amp and a FET One Series II. Both units have a sticker that indicates they've been factory updated to the e/series STASIS topology. I bought them from a local audio dealer who bought them from the original owner.

The preamp has jacks for the MC inputs, but the MM input is blocked off. Inside the preamp, the circuit board looks very different from other photos of FET Ones I've seen. Mine is more similar to a FET Nine I've seen a photo of, with little daughterboards attached to the main board, which presumably host the preamp circuits. The phono preamp boards have a DIP switch nestled between them, which, if it's similar to the FET Nine, allows different impedance and capacitance settings to be selected. But I haven't managed to find a manual for this particular mod of this preamp. Do any Threshold experts here have any insight to the switch positions for the FET One Series II with e/series mod?

I've attached a couple of photos of my unit. Thanks for any help!

I have been doing off-and on DIY audio projects since the 2000s. First one was and IB subwoofer cut into my attic in ~2005 with 4 Dayton audio subwoofers. Later on built a 7.3 home theater system with modified Econowaves built into a baffle wall.
Did nothing for years. Recently built a pair of desktop speakers with the Mark Audio Pluvia and some pieces of firewood. Next projects I am planning are some 18" subs and TAD 2404 clones, and some 15" OB speakers.

I've got a pair of Advent Maestro speakers that were given to me today. They are in good condition and the woofers were refoamed a few years ago.

I already ordered new caps for the crossover.

Two things I've noticed.

1. The speaker wire terminals on both speakers has separated from the terminal cup with the crossover on it at the bottom. What should I use to secure it back down?

2. I've read where the woofer doesn't play high enough causing a hole in the frequency response near the crossover point of the woofer and midrange which is 900Hz. Listening to them, I believe I actually hear that, but will wait until the film caps come in and are installed to see if that fixes it. If I still hear the issue, what is the best way to eliminate the issue? Normally I'd just use a different inductor value for the woofer, but the inductor is part of the dish where the fuse, speaker terminals and other crossover components are and I'd have to add an inductor which would require mounting it somewhere in the cabinet.

What I should do is disconnect a midrange and test it using my DATS V3 speaker tester so I can see what the impedance of it is as in order for the 14uF cap value to be correct the midrange impedance would have to be 12.5 ohms provided the specs I found are correct. That's not exactly possible though given the speakers are at work now.

Specs of the speaker.

https://audio-database.com/ADVENT/speaker/a-1012.html

Also I will run these with a powered sub.

The response is +/- 3dB 42-23kHz

I currently have the powered sub crossover set to 40Hz, but am not that happy with it.

I can put two 160uF electrolytic caps in parallel to make a 320uF cap which based on the rated 6 ohms impedance of the speaker will give me a high pass of 82Hz.

I might try that tomorrow with the caps between the + speaker lead and + speaker terminal. If it sounds better then I may install the caps between the + speaker lead and woofer inductor (when i install the film caps) so that I don't run the risk of the caps affecting the midrange and treble.

EDIT:

Here's the crossover schematic I found.



However the response graph I found seems to suggest there is no hole in the frequency response.

Hi,

I am doing some test with my prephono gain for my MC cart. The pre phono is using Dale resistor, but the one i plan to use with 36 Kohm for each channel is not a Dale, it is a Kiwame. Do you think the Kiwame in terms of sound quality is equal to the Dale?

Tks in advance for a suggestion.

Best regards

Adelmo

I have a Hafler Iris Preamp, which I love. Probably will need a re-cap soon, but working well right now. Managed to find an Iris remote on eBay. Yes, my Iris preamp has the receiver board.

However, when batteries are put in the remote itself, the red tally light simply keeps on flashing (about 2x/second) and there is no response from the preamp to any button pushes on the remote. I believe the rcvr board in the preamp is functional, as apparently if there are issues with it the preamp won't come out of muting.

I've tried IR detection using the camera on my iPhone and there's no apparent flash from the remote. I've confirmed that I do see flashes from a known functioning remote.

Any ideas on where to start? I'm also asking on AudioKarma, as well as checking in on D. Hedin's thread here on making your own Iris remote in case mine can't be revived.

Thanks in advance!
Waldemar

I was recently gifted a Hafler IRIS pre-amp (along with a DH-200 amp). Unfortunately it does not have a remote control.
Remotes are rare and expensive. In addition one requires the internal receiver board. Cost could be $120 or more if I could find them.

I have studied the IRIS schematic and have decided to roll my own IR remote control.

My plan is as follows.
I'll be using one of these remote kits for arduino.
https://www.ebay.com/itm/373765651681

I will then interface this to an Arduino Pro micro (5v version)

I only plan to implement volume, and input selection at the first go. But I may add balance and normal/mute functionality later on.

Below is what I have figured out so far regarding the interface from the IR receiver board to the pre-amp. This connector is on the back of the display panel of the unit.

In addition there is a transparent window where the receiver phototransistor would mount near the connector.

I will mount the Arduino board on perf board and there will be an LM324 to translate the D/A output of the Arduino to create the volume/ balance 0-14v control voltages.

There will also be some 5v to 16v logic translation for the input mux and other control signals.

My first experiment will be to hook up some potentiometers and dip switches to see if I can fake the operation manually.
I will post progress in this thread. All comments and suggestions welcome.

Wish me luck...


Hafler Remote connection

Pin Name Notes
1 JAM I believe JAM is used to lock input selection when recording.
2 RMB 0-14 volts for balance setting from remote
3 RMV 0-14 volts for volume setting from remote
4 REM V/B Active high pulse to set volume, active low to select balance
5 Neg16v
6 NORM Active high pulse to select normal remote
7 MUTE Active high pulse to select mute remote
8 WARN ??
9 Pos16v
10 GROUND
11 N/C
12 I2 "C" select for Input MUX
13 I1 "B" select for Input MUX
14 I0 "A" select for Input MUX
15 I3 Believe this is pulsed high to latch the LED indicator for input and latch selection

I've successfully created three-way bookshelf speakers containing a 10" woofer, a 2" dome midrange, and a 1" tweeter per closed enclosure for years. The crossovers are tuned to have output response (nearly) summing flat as shown in this picture.



However, I've been using them with an active subwoofer. Now I plan to stop using subwoofer and would like to listen to low-frequency from the main speakers. I removed subwoofer and found the bass wasn't enough, though I reckon these speakers sound flat.

I still have a pair of the woofers unused so I thought to add them to the system. In other words, the bookshelf speakers will be converted to floor-standing from now on.

The problem is I cannot easily add them without mod the crossovers. And I want to increase only low-frequency region. I finally need to convert them to 3.5-way system. In fact, I tried building them 3-way by typical way of adding the second woofer and redo the whole crossovers and found the unsatisfied result when there's no upgrading in bass SPL increasing anymore. Thus, I realized the 3.5-way system may correctly fix the problem.

Here is the simulation of the 3.5-way system that I randomly generated in simulation software.



I confess I don't have knowledge about the procedure or theory for building 3.5-way system. I simply add a second woofer with twice larger inductor on it, the 14mH coil.

And this is the comparison between 3-way and 3.5-way systems.



I would like to ask whether I did it correctly? And is the result (simulation graph) acceptable? I know the more accurate version should be from real measurement not simulation result, but this is the first step of learning. So, please try to understand.

See the attached circuit circled in red. The circuit senses a signal and provides -12V for on and +12V for off, just the opposite of ICEPower modules. I am wanting to have the circuit provide +12V for on and 0V for off. A little more complicated than a simple flip flop. Any ideas? I can build a simple circuit on a breadboard and piggyback off the +-15V to power it.

Hello, not sure if this is the best place to seek answers but this forum popped up as an option when searching the net for info about Quatre Gain Cell Series Amplifiers. Want to know how to approach powering them up for the first time in probably 6-10 years. One is a DG250C and the other a GC500 the internals in both look fairly clean although showing signs of possible repairs or up-grades... etc, and both look like fairly substantial pieces of gear with one (GC500) having the most enormous power transformer I’ve ever seen on any piece of music gear to date period. A friend of mine got them out of a storage room in a club where they were once used as the house dance pa system and I don’t even know if they work or not. Given the nature of the situation it would seem reckless to simply load the speaker out’s and just plug it into the wall due to the size of the capacitors and the adjacent delicate looking pc boards with small chips standing off the board.

I’m hoping that I could use these (or one of them) for an alternative s-state system in my home as I do enjoy the clarity and POWER of a good s-state amp as an alternative to several tube amp sound systems that I currently own and rotate periodically. I had to sell my last good s-state power amp about a year ago due to relocation cost and I miss it. It was a JBL/Urei 6260 power amp and I used it mostly to power my Altec Valencia’s that also had to go about a year prior. Anyway… enough sob story telling. Any advice on these amps? Things I should know? Like, how to control the levels as there aren’t any on the amps themselves?? And the safest way to test power them up would be greatly appreciated. Again i have 2 amplifiers… Quatre Gain Cell Series DG250C QMI and GC500 QMI.

Also: I'm a diy-er that probably should have been on this forum a long time ago and looking forward to sharing ideas and learning more about how to tweak, mod and make usable circuits.

Thanks!

Hi Guys!

I have always been fascinated by the large monitor speakers from JBL. Unfortunately, these are not cheap, so I wanted to build something like the 4367 myself.

http://www.newaudio.it/JBL/4367 JBL (1)/JBL Synthesis 4367 White Paper.pdf

15 "plus compression driver / horn was given. So I started looking for suitable drivers.
My friend Nico Germanos from Quint-Audio, Germany gave me the tip to test the new Tymphany DFM drivers and sent me a pair.
Since I don't have many horns to test, I immediately sent the drivers to my DAU buddy Christian. A few days later he sent me the measurements on the Monacor MRH-200 and I was amazed. Nico was right, the Tymphany DFM-2535s run great.



Since the MRH-200 is quite expensive, I decided on the almost identical Celestion H1 9040-P, which costs only a third.

Now I had to find a suitable candidate for the bass. Since the DFM is quite cheap despite its great measurements, I wanted to stay in a similar price range in the bass as well. Together with my friends from the DAU we discussed many possible woofers, but most of the cheap ones needed too much volume for bass reflex. In the end it was the LaVoce WSF152.50, which was kindly made available to me by the German distributor Steinigke Showtechnik.
This woofer runs very well in a closed box, which is brought to a lower cut-off frequency by a high-pass cap. Not super deep, but it will work well when the speakers placed close to the walls.



Both drivers are very well made for this price range. Since the Tymphany and the horn are smaller compared to the drivers in the JBL 4367, the crossover frequency is higher than in the original. I ended up at around 1500Hz.



The box also works very well at 15, 30 and 45 degrees horizontally off-axis (2db offset).



The crossover is an 18db high pass and a 12dB low pass plus serial notch.



The cost in Europe is less than 500 Euro for a complete pair. Certainly not much for a loudspeaker that has a surprisingly good sound and can also manage very high levels without problems.

If you want to see more designs from our small diy-group, please visit our german homepage:
Presenting DIY-HiFi Projects - The Idea behind It! - Der-Akustische-Untergrund

Greetings, Friends. I was looking at some scans of the old Vacuum Tube Valley magazine and ran across their Octal Line Stage, posted in Issue 11, Spring 1999.






I'll include the entire article at the end of the post.

It's a nice looking circuit, a cathode follower.

Looks like the 100k volume pot is acting as the grid leak resistor, don't love that. I'd add a 1M from Pin 4 to Ground.

And I guess that's a voltage doubler (?) to make 12v to allow 12S_7 tubes, don't think I'll use that. Might run the tubes on AC to start, or use a bridge rectifier with 1N5820 and CRC to make 6.3vDC.

I'd like to use some of those Vishay film caps that are so cheap now. C1 in the power supply is much too large, even with the low current demand. I'd go with 20uF, and this cap from Vishay looks very nice at $8. The 2nd cap in the power supply is spec'd at 100uF 450v, a very affordable EL cap but a rather expensive film cap. Could I use a lower-value film cap in this position without impacting the performance of the preamp?

The cap in the amp circuit is very large, 330uF 450v. The best option here from Mouser is an Audio-grade EL with a rather short lifespan. Could I use another of those 20uF film caps? As there's no film cap option for the bypass cap (330uF 35v) I'd probably use an audio-grade EL for that, and just plan to replace both caps after 2000-ish hours.

Thoughts? Thanks for taking a look!

w

My new to the forums post. I’ve actually read many discussions on this forum before but never as a member. I’ve been an electronics enthusiast for pretty much my entire life (over 40 years so far). I’m also on the HP forums as well as I tend to own and repair quite a bit of the HP gear. Thanks for having me in the forums and I hope to learn and share with you all as I can.

New poster to the forum. Been playing around with solid state and tube gear. Just got myself a Chinese PP tube amp kit, but will need some guidance! Will post over in that forum. 🙂

Hi all:

The YouTube channel Jana Loves Hi-Fi has posted a video about the building process of the Denon DL-103 MC cartridge, at the Shirakawa factory in Japan.

Login to view embedded media
FWIW, I think that the coil wire diameter used in the DL-103 is 15µm Ø.

The video skips over key areas such as the fabrication of the armature, polepieces, how the stylus is attached to the cantilever, suspension wire choices etc.
But it does discuss seldom-mentioned subjects like how the damper performance is affected by temperature, and overall is well worth watching.

Please give the video a "like" so that more videos of this type will be made in the future 😃.

kind regards, jonathan

PS. Ariga-san has been involved in building cartridges from 1983, which is one year after I started designing them.

The beauty of this circuit deserves its own thread.

After considering Mr. Pass's 2025 Beast R2, I have tentatively settled on a 3-in-parallel J113 XEN Circlotron cell.

The triple cell attached idles at ~32.5mA and leaves class A at ~ 83 mA peak.

My plan is to have 6 of these triple cells driven by one cell for a total of 7 cells per "row" on a PCB.

A triple-in-parallel cell will have 6 resistors and 6 JFETs. The PCB layout should work out nicely as per the attached drawing.

6 "rows" will yield about 1A idle total for the output JFETs. The actual idle can be adjusted with the V_adj supply.

Peak current should be ~ 2.5A per the simulation. Actual peak current may vary.

Hi all,

I'm working on a Sansui 2000a with a bad right channel. Preamp out is good. speaker out, not so much so.

Right side volume is way down and sine wave looks, well, to much trouble to describe. Adjusting pots doesn't help, even though bias current was originally way down

The famously troublesome Q806 has ac coming out of the collector. Seems the problem has been solved. Except what is there is not a 2sc458 in that spot. It is a C631. Left side also.

Please tell me I'm making too much of this. Like at one time the C631 was a common replacement and I can just drop in a pair of KSC1845 and stop worrying about it.

So I've bought another Metcal MX500 for a spare and it doesn't want to heat the Iron (Iron has been tested ok) working through the document attached page two has voltages from working units, mine tests OK until I come to U4,

Pin 4 measures 261mv dc
Pin 5 bounces around low mv

However Pin 2 when switched on, light green and iron connected is measured at 56vdc not 18vdc like on my working unit, does this point to U4 being faulty?

any help welcomed on this

Hello everyone,

I have two questions regarding the matching of small-signal, pre-driver, or power bipolar transistors, such as the BC549/559, KSC1845/KSA992,MJE340/350, MJE15034/35, or MJL4281/4302.

1) Which quantities should be closest ? Hfe, Vbe, or VbeSat ? In what order ?

2) From what tolerance do you consider that two quantities are matched ? 5%, 1%, 0.1% ?

These questions for building a high-performance Wolverine-type amplifier.

I'm taking my measurements with a DCA75 Pro.

Thank you for your answers.
Alain

For sale four PL509 tubes, ( 3 Philips, 1 Telsa). This is what I have left from the days of my EAR 509 tube amp. The Philips ones were used but the Tesla IIRC is NIB.
40 euros + pp.

Hey guys, can anyone recommend me a class D amplifier board (also in Kit) that can replace this Chinese board with TPA3116D2?



I've read almost the entire thread on the TPA3116D2 and now I know almost more than the designers
I've also read (and translated from Japanese) all the evaluations and modifications made by CyberPit that date back to 10 years ago, in the meantime I think the technology has evolved.

Unfortunately my eyesight is no longer what it was 20 years ago and I struggle to work on SMD circuits, so I'm looking for a board that sounds good with two 8 Ohm desktop speakers like the Tannoy mercury mR Cherry and a subwoofer.
I don't need excessive power, I listen to music while working on the PC, the important thing is that it doesn't require modifications (or at least few modifications) and that it sounds good.

I don't make it a question of price, but since I already have the HiFi system it must be a modest expense.


The only limitation I have is space, I bought an aluminum case with an internal space as in the photo that must contain everything: the three channels + the tone control + the power supply.

Thanks to anyone who wants to help me

Has anyone ever seen an amp or design that uses these industrial darlingtons?
EVK71-060 75 amp
EVL311-050 100 amp
All very high voltage
Could be used for a Quasi complimentary design, and they are insulated making mounting/heatsinking easy.

Good morning!
My amp, Onix OA 21s, has no headphone out. There’s a tape out connector on the backside, but nothing switched.
Am I thinking correctly that I could plug in a HP-amp, and use this (with the Onix‘ Pot put to zero)?

I do like the Wolverine .... but it is a little too big and expensive.
Some of us use 2.1 systems with a sub , we don't need 300W/ch. It seems there aren't many small amps that have
super low distortion , either "big and dirty" or small and dirtier ?

- AMPLIFIERS - IPS/OPS

1 - Arcwelder - mini EF3 ... either a 60W or 100W output stage , just a mini "Wolverine" through-hole PCB. Tested classic Harmon - kardon output
stage with "ripple eaters" . The main VBE is "out on wires" for output device placement. (OPTO) is optional to integrate current sense protection.

2 - Arcwelder - "Beast" EF3 .... 5 pair output transistors. For big "hungry" speakers. Can do 350+ watts ! It also has integrated current sense (OPTO).

3 - Symasui V1.1 ... Hitachi type 2-stage differential (VAS). Everything is cascoded. This IPS should exceed even a Wolverine (blameless) type IPS.
Has more open loop gain at 20Khz (66db) and tremendous gain at low frequencies (120db). Simulates sub PPM (<1)consistently.

4- Spookyamp V2.1 ... SMD high voltage , low current input stage. Hawksford cascoded self-clamping "Leach amp". ...quite "bombproof".
It has a inverting servo that controls the current sources instead of through standard NFB. 3.8mA VAS is ideal for the "mini EF3". 5PPM is typical.

5- Hellraiser V1.2. This used to be the Kypton from "Slewmaster" days. It is a CFA (current feedback) based input stage with a non- inverting servo.
It is the same as the Spookyamp except for the small signal stages. 3PPM is typical @ 10-20Khz.

6 - Infidel V1. This is like the wolverine , but uses LED's for the VAS cascode and CCS. Another LED shows the LTP CCS status. 2-pole miller comp. ,
and a simple layout is presented. Perfect for a first time SMD adventure.

- POWER SUPPLIES - Other protection accessories ...

1 - Arcwelder power board. All through-hole (TH) except for the opto-isolator (OPTO). 20Kuf+ per rail , uses a 17A standard flat bridge
rectifier. On-board MOSFET's are controlled by a external trigger. Fuses and jumpers (for the MOSFET's) are standard.

2 - Arcwelder soft-start - Another "business end" board. ALL AC , dangerous inrush , relays , MOV , and "AC sense" Just a 6 pin connector
with 3 control signals and (+12/+5/ground) to connect to the MCU (control board).

3 - Arcwelder SS relay - standard DC detect , MOSFET relay and rail reference , small form factor. (The other "business end" PCB).

4 - Arcwelder main control board - Arduino NANO standard (pluggable for loading code) Integrated +/- 12V and 5V supplies.
ALL digital with no AC or rail level potentials onboard.

This is a modular audio amplifier "ecosystem". Shortly in the future there will be -
A . protection , bluetooth , and various other accessories. (power meters, etc.)

B. At least 2 more input stages ... since it's modular !

Simple to build , NO special components , and tested to withstand fault conditions ....
Such as saturation , clipping and thermal. Low THD is not the "holy grail" , DIY projects should outperform OEM garbage.
NO China "TOP-CAP" , all Nichicon ,Wima ,ON semi - quality sourcing from trusted distributors.
Layout was tested by the Wolverine team ??? he he .... actually quite excellent !! Slewmaster was the breeding ground for most of
these designs , some of these are still performing after a decade.

Always - MORE to come !

OS

I used to have a source for stuff like this but they're not around anymore.

I need two 2 Ohm non-inductive chassis mount power resistors. Minimum I can use is a 50 Watt rating and no need for more than 200W. My first thought was Parts Express but no joy. Got any ideas on a source? Thanks.

Following on from some of the discussion on this forum about building chip amp power supplies, I am pleased to announce the addition of another page to the Gainclone section at Decibel Dungeon. I hope that it will answer many of the typical power supply questions that regularly crop up here.

I have tried to explain things both simply and comprehensively but most importantly, I have focussed on the safety aspects of building a mains fed power supply. I sincerely hope that all chip amp builders will make use of this resource and that it will keep them, and their property safe.

If you think that there is anything to add to the guide, or anything that isn't explained clearly enough, please use this thread to point that out, and I will make the necessary amendments.

A big thank you to AndrewT who took time off from his dancing) to proof-read the guide, and suggest corrections and additions.

You can find the guide here . 😉

SOLD

New Old Stock of discontinued miniDSP miniSHARC kit, complete, never used, opened only to take the photo. What's in that photo is what you get: miniSharc board, AC/DC power supply with multiple plugs, CD socket adapter, USB cable, coupon for software download from miniDSP

This was the core of the miniDSP OpenDRC series.

If you know what it is, you probably know how to use it. For everyone else, it's just a digital electronic doo-hickey. 😉

It was discontinued 3-4 years ago. The few retail shops that still list this item have it priced at 249€.

Asking US$180 (CA$250).

Less than what I paid, for sure... but it's not doing me any good, so make me an offer if you think my is price high.

Hello, I need to know more about Class H & D power amps.

Hello,
Sorry for the delay after my Ensemble Corifeo amp schematic diagram quiery,
I've contacted the amps designer monsieur frederic gautier, (Member "solen") Via this great and helpful site
Monsieur frederic gautier happily shared the Corifeo & Tiger B50 schematic diagram.
Please find the attachments

I bought these 8" coaxial Hemp Acoustics/Radians almost two years ago and am finally taking my first measurements ever! These are indoor measurements gated at 5.2ms, 1/24th smoothing at 15° intervals. I'm on a Mac, but now wish I had a windows machine for VituixCAD and the directivity plots.

Tweeters were crossed over at 800hz. Woofers played full range.

This was a very bargain purchase and I am a total novice so I'm looking for feedback on whether these drivers are usable or not. Any other pointers are welcome.

Right Mid

Right Tweeter

Left Mid

Left Tweeter

Beyma 6MCF200Nd. Matched pair. New, only opened one for measurement.
PRICE FOR A PAIR:400€
Shipping to europe is 25€, international shipping is 55€, if you want insured shipping please ask for the price. Payment by PayPal, satispay or bank transfer in advance.
my email is franco.cauda@gmail.com

So while perusing ebay for a reel to reel recorder (fingers crossed i might have nabbed one), I've been watching Terminator 2 on the telly. I stand firm that the effects hold up against any modern film and cgi peaked here. To my mind the effects in this equal Jason and the Argonauts, especially the skeleton fight, in that no modern remake could touch them for looking so good. Computers and cgi definitely have a place in cinema but I feel they've become lazy.
Discuss?

Hello. Please advise me on the regulated power supply schematic (solid state) for Frank's 6sn7 preamp.

Hey folks,

Don't know if it's too weird, but I have this idea of an line array in 3 chambers wich are connected to a transmission line. I try to figure out how to simulate this in hr but I dont get it. The chassis were 9 pcs. dayton pc83-4 in an 3p3s arrangement. The 3 parallel chambers (with 3 chassis in series) should have a port to the tml at 1/4, 1/2 and 3/4. This would normally be a backloaded horn but with an offset of the connected port and on top 3 of them. I found the ME1/2 parameter but I think I need more off a ME2/3/4 instead.

Maybe someone can give me a hint.
Thx!

3emb0t


Edit:
For better understandig, the speaker should look like this:



The acoustic circuit maybe like that:

I have the Dayton Audio DATS V3 speaker tester where the software works on a Windows 10 PC.

I went to install it on another Windows 10 PC and the software starts, but says not responding then closes.

The Windows 10 PC it works on and the one it doesn't work on:

1. Are the same model.
2. Have the same exact hardware configuration. Same model RAM, same processor, same hard drive ETC...
3. Have the same exact software configuration.

By identical I mean that I can swap hard drives between the two and the only thing I might have to do is reactivate Windows.

Also given the PCs are so identical, it should not be possible for me to be having this problem, yet I have it.

Any reason for it not to run on another identical PC?

Hi,


My name is Slava, and I currently live in Canada. I have a deep passion for both the world of audio and woodworking/cabinet-making.


I've been following diyAudio on and off for some time now and have greatly enjoyed the discussions.


A bit about my audio journey:
Since 2001, a wave of creativity has driven me to explore the joy of music creation. This passion led me to experiment with various creative aspects—DJing, music production (both live and electronic), and sound engineering. I graduated from film school specializing in sound engineering, built studios, organized events, and rented out numerous sound systems—all while running a business in construction, woodworking, and cabinet-making.


Now, I'm eager to learn even more.


My current venture:
I aim to bring high-fidelity sound to electronic music events by building a custom PA sound system.


Looking forward to sharing knowledge and learning in a supportive environment dedicated to sound reproduction.

I still have a small stash of various T.I's discontinued parts. These were purchased directly from my own company many years ago. 100% genuine guaranteed. Price is per piece. Quantity is quite generous.

+ Metal can TO-99 opamps: LME49710HA, LME49720HA, LME49713HA $8
+ OPA827AID SOIC-8 opamp: $8
+ OPA1612 SOIC-8 opamp: $4
+ Chip-amps: LM3875TF, LM3886 $9, LM4780TA $10
Shipping is calculated depending on purchased parts.

I'm looking for trading with the TDA1541A chips and the latest Amanero module.

Thank you.

this is a MIC preamp based on PGA2311, i would love suggestions about this design S2

Back in the day, I made a thread about asymmetrical Synergy horns here: https://www.diyaudio.com/community/threads/asymmetrical-synergy-horn.304489/

The idea has always been a bit fascinating to me, because:

1) asymmetrical horns can often have much better WAF. For instance, you can use asymmetrical horns on shallow loudspeakers, so that you don't have to rotate the entire enclosure.

2) I used to be fairly well known in car audio, and in car audio, nearly all of the cars running horns are using asymmetrical horns. I've long believed that it should be possible to improve on these designs, but the vast majority of them are built based on ideas from the 1960s and 1970s. Basically, car audio horns haven't evolved much since 1995 or so.

I have my last set of LU1014D amp boards which is fully built and tested. Details about the amp here - https://www.diyaudio.com/community/...d-ld1014-choke-loaded-source-follower.400792/

Built using good quality parts from either Mouser/Digikey/Newark I am expecting $165 including shipping within CONUS states.

Hi,
I've got a R&S UPD (1030.7500.05) Audio Analyzer in excellent physical shape and apparently complete with one exception: the internal hard drive is missing.

It powers up, and the BIOS boots up. Memory test is ok, but that's as far as it'll go without the hard drive.

I'd like to get this thing up and running again, but am having some trouble locating the info I need. HD type/size, OS files, System files, operating & service manuals, other repair info etc.

Can anyone out there point me in the right direction?

I can find almost NO info on the web regarding the R&S UPD (blog entries, manuals, repair info, tips, tricks etc.)

Given the UPD's capabilities, I'm very curious why there's such an apparent absence of info & interest re this tool, including here at DIYAudio.

Any helpful comments will be very much appreciated.

Cheers!

Florida International Audio Expo Feb 20 - 22, 2026 ROOM 354​

New Product: TU-8888 > Mono Block with Lumdahl LL3733


\

feel free to leave suggestions on how to make it better and stuff

Hello all. 🙂
I stumbled upon these forums while looking for information on my legacy Rohde & Schwarz UPD, that I would like to keep running as smooth and as long as possible.

My day job is full time hardware development: PCB layout, building prototypes and dealing with RMA / repairs at a small but well equipped company here in Germany. We specialise in DSP based systems including high power rack and plate amps, beam steering applications and audio management over ethernet for large building installations. This is a private account however.

In my free time I play bass guitar, repair guitar amplifiers, pedal effects and the likes.

Looking forward to meeting like-minded folks from all around.

Cheers
Kormoran

I’m Glenn from Raleigh, NC. I’m am retired and enjoying it very much. I hold a PhD in management and worked for most of my career in manufacturing and systems management.

Almost 50 years ago I built almost all the components of the Heathkit Pro Series rack audio hi-fi system. I am currently recapping the AA-1800 amp and I will be doing the preamp next. (I also built the GR-2000 TV in 1974.) I have all the components except for the AD-1702 Crossover and still enjoy listening to it.

I am looking forward to talking with other members and learning from them!

Hey guys, here we have for sale a single-Ended Tube amplifier I built a few years ago. This is the RH 84 circuit, single ended, one ECC81, and a pair of EL84, with a EZ81 rectifier. The circuit is built on a PCB I bought from a member here, the power transformer is Japanese, from tango, very high-quality with a copper flux band. Power supply capacitors are Rubicon and Chemicon, coupling capacitors are Wima film and foil. The output Transformers are from Elekit. Also, Japanese made.

Neutrik Speakon connectors, and Rca’s. What can I say, it sounds great with sensitive speakers. 4 and 8 ohm secondaries. I will include a spare set of tubes, they are all NOS.

350€ plus shipping, PayPal, friends and family or IBAN transfer.

This will be double boxed encased in hard foam. Shipping is from Vienna, Austria. It would probably be best to keep shipping inside of the EU. Let me know if you have any questions, thanks for looking.

-mac

Dear fellow forum members!
I am looking for a connector for a Sharp deck, the factory number is qcncm102fafzz.
Unfortunately, Google is not my friend, I couldn't find a really good connector. Maybe someone can help me with what kind of connector I can use here? Any JST connector? Thank you for your help!

Greetings,

I'm seeking service data for my Cayin. It uses a Sony KHM280AAA transport. Current state is on a single layer SACD it spins up and attempts to read. Then defaults to "no disc" and even ejects the drawer. Hybrids it also first says it's attempting to read the SACD layer. But then defaults to the CD layer and boots up. It reads regular CD's but has more trouble playing those back than a hybrid type.

Also both audio outputs have some odd distortions that are frequency dependant. Like a tick of sorts combined with birdies. I noticed that the playback of the hybrid CD layer has considerably less distortion than a regular CD. For some reason the distortion rises on those.

Thx,
DD

it could be posted under electronic music but hey it is dnb!
Login to view embedded media

Hi,

Not sure if I'm posting in the right section, so my apologies in advance.

Looking for a DJ controller/mixer stand/table. It does not need to be foldable/transportable as it will sit at one location only.

I was able to check this one in person and it is a little bit wobbly:

https://tinyurl.com/3ecsy2mn

Anyone tried this one?

https://tinyurl.com/mppds9sz

Or of course if you know something similar that would do the trick please let me know.

Much appreciated!

I’m fixing an older Heathkit AA-15 integrated amp for my father. It had many capacitors that were open, high esr, or highly reduced capacitance. Another major issue and the main reason I had it was that once channel had a pretty major failure. Nearly all of the transistors in the one channel were bad.



Original outputs were 40411 and are now MJ802G

Drivers were 40409 and 40410 and are now TTA004b and TTC004b

Predriver was 40408 and is now TTC004b

The two 2N3393 at the input of the amp are now 2N5551c

These were the closest replacements and were recommendations. With these changes the idle bias current is quite a bit higher than I’d like to see lol. Measuring across the 0.67 ohm emitter resistor I’m seeing close to 100 mV or just under 150 mA of current. Is it possible to put in a trimmers in order to bring that down a bit?

Thank you,
Dan

If anyone has Bendix 6888 tubes please keep me in mind. I am looking for 3 quads, matched would be better but not a hard requirement.

Hello there everyone!
I have always listen to music and prefer a good sound, but it must not cost a furtune.
Happy to be here.

Hi members.


Sharing this new proto of amplifier made with...............IGBTs. Lot of people will say "cannot works! Mosfets are better" Yes, but, why not try.


Structure used is build around TL494 working for PWM generation and high current opto drivers (TLP358) driving high speed IGBTs (GW30NC60)


At this step, with 110Vdc supply, it reach 550W (29Veff) into 1.5ohms load.



Will try to increase little more output power (to reach IGBT maximum rating).


Sound is quite good, better than some chinese amplifiers 😀



Feel free to try it.

Edit Feb. 2024: You want parts? Read this post carefully. Do what it says, all of it. Otherwise your PM might not get an answer.

This thread is for getting my big stash of tested and matched LD1014D (LU1014D) JFETs out to the DIY world!
So far I have tested and matched several hundred parts by temperature-controlled Vgs measurement and curve tracing (see details below). Additional parts will be added as testing progresses. These parts are perfect for building a DAO headphone amp, ZEN 9, F3, LuFo, SuSyLu, etc.!

See here for more information on how to find good matches from the data provided at the link below.

Test procedures:
All parts are testing and matched using PyPSUcurvetrace with calibrated power supplies, using two test methods:

• Type A test: measure the the Gate-Source voltage (Vgs) required for a Drain current (Id) of 1.5 A at Drain-Source voltage (Vds) of 2.4 V.
• Type B test: like Type A, but additionally also measure Id vs. Vds curves at Vgs = -0.6 V and -1.0 V.

Parts are measured on a temperature-controlled heaterblock at 40°C (except early Type A measurements, which were done without temperature control).
Vgs data are recorded in a list (sorted by Vgs, see link below).
Curve traces are plotted for pairs which have Vgs values that are matched to 30 mV or better (Type B only).

Prices:

• Type A parts: EUR 10 per piece
• Type B parts: EUR 15 per piece
• Shipping and handling per envelope: EUR 10 (international) or EUR 5 (Switzerland)

Matching data and part availabilities are here:

• List with Vgs data and parts availability
• Curve matching as described here
• Parameters (Vgs, gain, etc.)

How to order your parts:

1. Post a quick reply to this thread indicating your interest in getting some LD1014s.
2. Enter your details and the LD1014 part numbers in this form.
   Send me a PM with your desired LD1014 sample numbers, your full name and address (including country!), phone number (needed for shipping), and email address.
3. Wait for my reply with payment instructions.

Late 20s something year old guy from Amsterdam. Looking to build a full soundsystem used for gallery openings to raves in the distant future 🙂)). Not in a hurry, just trying to soak up as much info as I can. Right now trying to figure out my Art Welter keystone build!

I have a Schiit Saga S preamp which sits in a closet in my room with the rest of my sources.





The problem is with the closet door closed (blocks the noise of the PC and the noise of the relays in the preamp clicking) I cannot see what input on the preamp I have selected or whether the active mode is on or whether mute is on.

I use an IR extender for the remote.

That got me to thinking. Is there something I can put in front of each LED that will drive LEDs on a board mounted right outside the closet door?

Hi all,

I encountered a problem with my latest development I never had before.
As any part of the setup may be the root cause I do not really know what sub-forum fits best.

In the last years I created several variations of active speakers always based on the same approach.

A single ended ADC directly as input, a Teensy4.0 microcontroller for audio processing and 2x30W Raspberry Pi hats as amplifiers with the chassis directly connected to the amps.
The microcontroller does some equalization and the crossover calculation.
For powering that stuff switching power supplies are used.

Audio comes from a very old denon pre-amp in my home office and a Marantz AV-Receiver in my living (cinematik 😀 ) room.

The last variation has three 2x30W amps so 6 chassis connected. PSU is a 24V/220W desk PSU connected throu a DIN-4 connector to the carrier board.

The problem now is that I have high pitched noise, but only if I connect both speakers to the pre-amp and have both powered on.
I can cut the connection at any point, the audio line or the power line and everything is fine.

With a simple scope measurement I could not see anything on line.

I read a bit before come here for some advice what to do next and it feels a bit as of the PSUs lift the ground level. If the ground level even lifts some 100uV it would create a difference on the single ended ADC result. I even suspect that the PSU keeps the 24V stable. So I can not see any noise on the power line.
This lift would be at the switching frequency of the PSU. As long as only a single speaker is on, switching frequency is simply to high to change anything to the result.
But with both PSU connected it would create interferences on the ground, connecting both speakers through the pre-amp. The result would probably the differences of the switching frequencies of the PSUs and than would make it audible.

As I can command the micro controller to turn off the audio by writing zeros to the amplifiers, what kills the noise, I am somewhat sure that it happens on the analog part of the setup.

One idea I have seen somewhere in web, to add a low value resistor into the ground line to the pre-amp. As I have different audio line length in my homeoffice and my living room, I also have different levels of the noise. With the longer cables in the living room it is lower.

I already thought to switch the ADC to differential mode. But as I have a hardwire setup for the ADC it would need a complete board rework.

Another thing, where am I not sure if I remember it right, because it was before I came to the point where I accepted a general problem here, was that the setup does not had the problem as long the carrier board was not mounted to the back of the speakers. As the dayton audio chassis have a massiv magnet, could this create this behaviour?

I think I explained enough so you may have an idea what my problem is.

Any suggestion would be great.

Hi all,

Chances are low, but maybe someone out there and can help me with checking something from a local seller. Thank you!

Summary: Lots of amps produce error that can be dominated by PS ripple, including some forum favorites.

PS ripple can couple into the signal path through various paths. Some paths are capacitive (worse at HF) and some, like Early effect, are not a function of frequency.

You might think that if ingress is worse at HF than LF, then we only need to check PSRR at the treble end of the spectrum. This turns out not to be the case, since PS ripple amplitude is probably larger at LF. Let's assume a linear power supply where the rails are fed from large reservoir filter caps. And let's assume some upper bound on the amount of current flowing into or out of those caps. That puts an upper bound on the rails' slew rate, which in turn limits the amplitude of rail ripple to lower levels at HF than at LF.

If you model PS ripple as a signal that increases in level at LF -- and of course it'll have a substantial 120Hz component-- you'll find that many amps have more PS ingress at LF than at HF.

I've been simulating PSRR by modeling the rails as an AC voltage source with a large DC offset, and an AC amplitude of 333/FREQ so it's largest at LF and small at HF. (That figure assumes a 10000uF filter cap, and 20A peak charge or discharge current, which should be nearly a worst case.)

Lots of amps perform worse at LF. For example the spectrum below is the Wolverine. Its B+ rail is driven with a 40Hz ripple, amplitude 333/40 or about 8V. Its B- rail is driven with a 60Hz ripple, amplitude 333/60 or about 5.5V. There's no input signal. The output has an amplitude near 1mV peak to peak, all noise. That's not terrible, but it's a larger error than we expect from distortion, given this amp's near-ppm distortion performance. If we're driving program material at nearly full amplitude, 100V peak to peak, the 1mV error due to PS ingress is 100dB below the signal and still 20dB above the distortion floor.

Is this a real problem? Maybe not, but it's worth paying attention to, given that PS ingress can be worse than distortion. At least given assumptions that are somewhere between conservative and wildly pessimistic. :^)

(Left as an exercise: what is the actual spectrum of ripple, and is there a better way to model it in simulation?)

Probably most of the people are not interested in what I am about to write, so to save you some time:
LoCHAid stands for Low-income-countries-hearing-aid.

Why I have built has been inspired by an article referenced below and is based on cheap, ready made modules as in the article.

The disclaimer: every audiologist will tell you that a hearing aid is not merely a microphone with an amp and headphones.
Amplifiers amplify all frequencies, hearing aids amplify only what is required by a certain patient. Audiologist warn you against simple amps as they can be used too loud and cause more damage than good.
Audiologist are supposed to measure the patients hearing loss curve and set up the aid properly. This is what you are paying for. $$$ are not just for the actual device.
You have been warned.

I have two older member in the family who suffer from hearing loss (my father and my father in law).
My father in law lives in Very-high-income country and has state of the art hearing aid which he does not use very often. My father lives in a decent income country and refuses to buy a hearing aid.

The first impulse to do something for them came from the realization that my father in law listens to TV using headphones and the volume control in his TV is very cumbersome. So until recently he was listening to the sound at full volume.
I thought I can make him a small phone amp which will be used more like an attenuator. Not a hearing aid but in this case an attenuator should be beneficial. The result is here:

Then being a diyer I started looking for a diy hearing aid solution. I have found this article
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0238922

The idea is to use a small class d-amp (MAX98306) and a MAX9814 microphone module. The article contains links to a mother board pcb and a 3D printer enclosure. The authors use some high pass filters and show some results that this fits majority of the patients.

When I inspected the schematics I realised that the class d-amp used is in fact stereo so I thought I would make a stereo version. This cannot be done easily with MAX98306 because it is a "power amp" i.e. it is designed to be used with speakers and is (very) unhappy with the common ground connection in 3.5mm headphone jacks.
So instead I purchased MAX4410 which is a headphone amplifier. All the boards with MAX4410 I have seen use an on board 3.3V voltage regulator. I have decided to ditch it as I wanted to keep the whole device as small as possible - it was supposed to be powered of 2xAA batteries and all should fit in a a 4xAA battery holder.
The MAX 9814 modules can be programmed to 40,50 and 60dB gain. I ended up setting the lowest.

The device works fine. I suppose setting the volume to a level that one barely notices amplification should prevent extra hearing loss but should allow to have a decent conversation at a family table.

I will present teh device to my father next week and will inform how it was received.

PS My father in law is very happy with his headphone level attenuator.

Hi my project consists of adding 2nd order harmonics to a stereo signal to achieve a more tube like sound.
I would like to use two RCA inputs and two RCA outputs for the signals and a DSP that has enough memory and calc. power to allow me more complex operations.
I am planning to use SigmaStudio from Analog Devices as a graphical platform.

My questions:

• has anybody experience, suggestions which operations (in SigmaStudio) would likely achieve desired result of a more tube like sound ?
• I am thinking of finding a proper board based on the ADAU1466/1467 to have more memory available, has anybody a suggestion where to get a less expensive board inluding of the programmer and the RCA adapter ? AliExpress is pretty confusing, I would like to find someone who actually has experience.

Thanks
Bjoern, Singapore

Hello ,I am a new member of diyAUDIO family,I come from China.I am very interested in audio amplifier diy.

Do you know what capacitors are they black. MKP perhaps?
Also, these (1.5uF) with cream color what is the manufacturer?
They are from crossover pcb.

Why wasn't Stig Carlsson's ortho-acoustical approach more widely accepted at the time both concerning commercial products and diy projects ?
Are there a large amount of disadvantages and only a small amount of benefits ?

Some URL's concerning this approach:
https://www.carlssonplanet.com/en/speakers/produced/carlsson-oa-58/
https://www.carlssonplanet.com/en/everything-about-the-carlsson-loudspeakers/
https://www.lbtechreviews.com/news/speakers/stig-carlsson-and-the-listening-room
https://teenage.engineering/products/od-11/carlssonstory
https://minimalissimo.com/moods/sounds-of-stig-carlsson
https://www.stereophile.com/content/larsen-hifi-8-loudspeaker
https://www.stereophile.com/content/larsen-hifi-8-loudspeaker-measurements
https://www.diyaudio.com/community/threads/larsen-speakers-clone.322270/
https://www.diyaudio.com/community/threads/carlsson-speaker-sonab-oa14.23681/
https://www.diyaudio.com/community/...roject-on-ortho-acoustic-design-ideas.231571/
https://www.diyaudio.com/community/...simple-two-way-unity-corner-waveguide.315446/
https://www.larsen-speakers.de/technologie/
diy-project: posting from 2016-01-23, 17:46:
https://www.faktiskt.io/phpBB3/viewtopic.php?f=17&t=62606&start=240
https://www.diyaudio.com/community/...s-of-floor-coupled-up-firing-speakers.121385/

Thanks for comments.

I have been reading audio forums for years, in my search for more knowledge on how to build a great used stereo system. I like Marantz, NAD, and B&W equipment, that is what I use right now in my home system. I'm big on used quality and cheap used horsepower, rather than super-fine fancy 20-watt amps for the price of a car. I will need help fixing my surround sound amplifier and getting my B&W speakers in perfect order, they aren't working properly right now.
Thanks for being here, thanks for letting me read the forums, and thanks in advance for help.
Ferris

Hi all,

Trying to locate a service manual/schematics for the Mark Levinson 332 I'm currently working on. I'm able to locate the 331 service data but that is missing a few of the adjustments and TPs that are present on the 332. Any help would be much appreciated.

1. Constant loop gain for no THD both @ LF and HF,
2. No coupling capacitors at all, MC-like sound with MM cartridge thanks to
3. aperiodic non-resonant HF correcti on with lowest input capacitance.
Thanks to that, the unwanted resonance of the input circuit is shift ed far into the ultrasound region and
does not manifest itself in the audio range, and the input resistor R1 can be increased to 150 kOhm, thus
forming a "passive cooling", which reduces the input noise current in SQRT (150 kOhm / 47 kOhm) = 1.78
ti mes compared to typical Rin = 47 kOhm.
4. At the front end uses a matched pair of Dual, ultra-low noise, low-gate-current audio N-channel JFET -
the latest JFE2140 from Texas Instrument. It's allow to achieve a record IEC-A weighted signal-to-noise
rati o of 85 dBA relati ve to a standard 5 mV@1 kHz input level with an att ached 0.5 H+ MM head
equivalent. 1 kOhm
5. and THD less, then 0.00006% with fantasti c overload capacity (64 mV@1 kHz < 0.0007%).
6. The frequency response exactly corresponds to the Enhanced RIAA not with three, as usual, but with
fi ve -ti me constants, in additi on to 75 + 318 + 3180 µs, a Neumann pole compensator and a rumble -
reducing 7950 µs - IEC 98 Amendment are also implemented.
7. Double differential stages scheme : high PSRR , but stabilized bipolar +-(15-18)V power supply with low
ripple is required
The preamp board must be installed next to the tonearm to ensure the stated performance

$200​

Discussion here

MM
Frequency range: 1 Hz - 45 kHz
Ku at 1 kHz: 49 dB
Rated output voltage: 1.4V
Signal to noise rati o: >85 dBA
THD: <0.00006%
MC
Frequency range: 1 Hz - 45 kHz
Ku at 1 kHz: 68 dB
Rated output voltage: 1.4V
Signal to noise rati o: >73.9 dBA
THD: <0.0004%

Welcome to test it in Dresden, Germany

In order for the parameters of phono stages to be compared with each other, they must strictly comply
with the regulati ons established in parti cular by IEC 61938. In this case, the input of the device should not
be short-circuited, but should be loaded onto the equivalent - for MM this is a circuit consisti ng of
inductance 500 mH, in series with a 1 kOhm resistor and a capacitance of 125 pF connected in parallel to
them. For MC - 10 Ohms. The nominal input signal level for the MM is 5 mV, for the MС - 0.3 mV. Noise
parameters must be A-weighted.

Here is a very simple MOSFET amplifier. I don't have the name for it. The output is similar to JLH output stage, but it can actually work in class B with MOSFET. Achieve good performance with relatively small number of parts. It also has the capability of almost rail to rail voltage swing, which is the weak point of most other MOSFET designs.




[EDIT] Added constant current source for the bias. Thus, the power rail fluctuation will not affect the bias.

[EDIT] Add the protection.

Hey guys,

I have a sinus live 12 inch subwoofer, an SLW365K, and a hypex DS 4.0 plate amp and I’m trying to put together a sub for hi-fi, basically a 2.1 to go with some monitors I built.

I’m looking for some help coming up with an enclosure, I know some of you are wizards with simulation, and can point me in the right direction.

I found some TSP for the sub from Hobby hi-fi from years ago,

Fs: 31hz.
Qms: 10.4
Qes: 0.36
Qts: 0.35
Vas: 97
Mms: 135g.
Re: 3.2+3.2
Sd: 590cm2

I am assuming ported would yield better efficiency?

Can anyone help me out with coming up with a simulation for a ported box? Or point me in the right direction?

Thanks in advance for the help!

https://a.aliexpress.com/_EuLOKYC

Has anyone got experience of this preamp as I can't find any information or reviews on Google.

I specifically need balanced outputs and this board generally looks like a one stop shop for that and number of inputs.

Thanks in advance.

Hi
somebody knows what driver is inside d&b q7 top?
De900,910,914 or TN version of one of them?

Hello,

Has a push-pull regulator pleased features to power a masterclock clock ?

I know it always has a good PSRR, what has it more than some inntegated reg TS7A, ADM75xxxx/LT3042/etc.

Thanks

I built a front 2-channel surround speaker.
The drivers used are SPL Limited's LSE77-20R (4.5 USD).

Box name is MTX-0806 (TQWT with Damp-Duct).
The front is L+R, the left side is L-R, and the right side is R-L.
The surround effect varies from source to source, but the surround effect is not as good as expected.
I am wondering how to improve the surround effect in the future.

Note to moderator: I hope I have posted this in the relevant section - otherwise I apologize, and please move it.

I was interested in trying out Nelson Pass' analog XO/EQ for the LXmini (Analog XO/EQ) . However I don't have enough of the 2SK170/2SJ74 JFets, which is problematic for two reasons: they are quite hard to come by, and if you find them they are very expensive. So I tried some Fairchild J113/J176 - they are not really complementary, but they might work anyways.



In the test set-up I used matched FETs with about 12 mA Idss.

With +/-12 Volts supply it'll supply around 7 Vrms without visible clipping. Soft clipping occurs around 8 Vrms.
THD and noise is below 0.025% at about 3Vrms (I cannot supply a higher voltage distortion free).
Frequency response: Flat from DC to at least 1Mhz. 100kHz square wave shows a tiny amount of ringing, but this could probably be removed if the bandwidth is lowered.
Rise time estimated at 0.5 µS.
Output impedance is around 35 ohm. This rises to about 70 ohms if a trimmer potentiometer (100 ohms) in installed in the sources to balance out small differences between the Fets.

These specifications are, of course, far from as impressive as the Toshiba pair - but we're talking about line level signals and how audible is 0.025% THD after all?

Is there anything I have over-looked?

So I recently heard some truly superb Kroma Jovita speakers being driven by an amp from a brand I’d never heard of - Orpheus Lab. The amp was the “A Four 1200”.
The sound quality was really outstanding and I was immensely impressed. I already knew that Kroma makes great speakers so I was of course curious about the amp. I subsequently did some research and go hold of this doc which provided an overview of the topology:








I am told that some of the tech people at Orpheus are ex Goldmund and CHP and my guess is that they have brought some ideas with them . . .

Hello everyone, starting a new project. I picked up a pair of lowery organ amps. From 1958 holiday ls models. Going to run as mono blocks. Power tube are 6v6gt pp. But the power supply ran 20+ tubes in the organ. So was wondering if the PS. Would support tubes with higher output? Maybe el34s?

Thanks for your Input.

Hi everyone. I have been missing for a few weeks as everything that could happen... happened twice. So, I finally managed to get back home, and also back to tinkering and playing around with my vintage stuff (including the Citation 22 that I have not touched for the last month...). But I digress.
So,
I got a nice Nakamichi MB1 cd player, that had a bad laser, I replaced the KSS210 laser with a chinese part and that kept doing weird stuff (scratching noises in the playback, stopping altogether playing etc) although it read the TOC most of the times. . So I downloaded the service manual (of the MB2, since the MB1 manual is unobtanium), since I wanted to check eyepattern, rf and etc. maybe to adjust it.
And this is where I realize that the manual calls for an obscure object called the Nakamichi CD Test Set DA09155A, that features a few switches, BNC outputs for a scope and convenient connectors that latch on the MB.... I try to find some info on it (the MB2 manual only has a line art drawing of the thing) and find that is rarer than hen's teeth and that the one that surfaced a couple years ago went for like five times the value of the MB1 I have. Looking around, I find the manual for the Nak CD Player 2, which is basically the same thing as the MB2 in a different box, and inside, along the same drawing, there's a full schematic with part values and semiconductors of the set. First thing I realize, the thing is complex. Find the schematic below.
So I try to understand what it does, and it seems to have some oddball resistor value on many inputs, a full active filter that can select two slopes (I think), and a FET on the RF signal that I figure is amplifying the signal? Bottom line, I started designing a PCB for this and actually sourced all parts, including the op amps and the SK241 FET before asking myself: do I really need this? Is this something maybe other could be interested if it works? I know Nak used to build special a numbers of test sets for their decks to service them, that are expensive and difficult to find.
Point is, all the values and levels disclosed in the SM are relative of the signals as they come out of this box, and i have no idea how exactly the filters influence the original signal.

So here i am, can anyone hep me out? Opinions? even just to say, forget about it it's useless.
If instead it's ok, maybe this could be used to service all those Nak cd players out there, so why not, can you please help me out in making it a working set? I'd post full pcb files and BOM here.

Note, there's an error in the PCB I'm posting now, as for connections to the FET. I just need to correctly move the GSD terminals

The ones for sale on eBay and AliExpress.. are they any good?
I read a buyers' comment stating that the tubes don't fit in these (wrong holes' positions?).
Please let me know about your experience with them.
TIA!
S