Hi,

I have a B&W PV1 that has decided to not power up properly anymore. When you turn power on now, you get a thump from both drive units, then the red LED turns blue and the electronic control display comes on, then another thump and display goes off and led goes to red again.. this then just keep cycling in this state until you remove power..

Has anyone ever come across this before and have any ideas how to fix the problem?

Thanks

Hi Folks, can anyone tell me attached circuit where the front end and driver stage SK3566 able to drive KT150, certainly I will modify t to fixed bias as - 48v.

The voltage specification for AES3/EBU is ±2V to ±7V (revised from ±2V to ±10V), this is needed for diving the cable. How could this be dropped to 0V to ±5V at the receiving end without causing damage to the signal? The drop wouldn't result in data loss, it's still a difference of ±5V, but would be more usable by μCs, FPGAs, and so on. I'm sure this is commonly done, but usually in ICs. I want to make my own receiver because every receiver IC I've used has problems/errors with it. Even the suggested pre-IC circuits are often incorrect. The specification sheets for AES3/EBU are very sparse and incomplete. Maybe a different transformer ratio (1.4?) would do the trick, but would probably need to be custom made, and for now I'm only going to be making about 10 units, so that wouldn't be an option. Maybe there's a different translator that I can use that I'm not aware of? I must use a twisted pair (CAT5) for my application, the other pairs are used for other unrelated signalling, so I can't use something like S/PDIF. Conversion to optical may be an option at the receiving device, but I think in the EBU specification, transformers are mandatory. I wonder if a galvanically isolated digital isolator qualifies as a transformer? Many can handle ±7V inputs. Some are too slow though, so if you use one instead of a transformer, take note of the speed!

I imagine that the same or similar method I'm looking for would also be applicable to "upshift" the signal for a cable driver?

Just a side note, this will be used in both consumer and professional applications (switchable).

For sale 2 NEW, NEVER USED Dayton Audio RSS390HF-4 15" Reference Series subwoofer.
Bought for a project that will never become true.

91,2 dB
Fs 18 Hz
1000W max

NEW in their original package, one was opened just for pictures. The other one was installed in a test box but never connected, played or measured.

Price for each is 350€ right now, 700€ for the pair.
I would sell the pair for 430€ +PP fees + Shipping.

I was trying to build a fullrange sealed box with the volume of 30cm*30cm*115cm.

However, I have found threads on enclosure dimensions, pointing out:

'if the length of an edge is excessively greater (3 times as a rule of thumb) than the others, the box will act as an ML-TL, instead of behaving as a sealed box.'

is this phenomenon caused from standing waves within the enclosure?

as a humble hobbyist, I am quite not sure if I have understood it correctly...

if it is, would my enclosure design work properly as a sealed box, if I put in enough stuffing, to suppress the standing waves?

judging by the Boxnotes simulation, I assume that fully (in theory, as bass absorption would be a tough task) absorbing sound waves within the enclosure from 176hz and up would eliminate any unwanted resonances caused from standing waves... but I am again unsure of whether I understand how all this works.

I was intrigued by this circuit (post #123) from forum's member Joe Berry - a novel use of Q7 (schematic below) which enables: 1) a better circlotron symmetry with single-ended input and 2) thermal stability of output HEXFETs' bias without source resistors.
And it does deliver. In my (adapted) circuit the output stage bias (set with P2) is 300 mA and it changes 20 mA for a temperature change of 40 degrees Celsius. I tested the prototype for two weeks and it behaves nicely (DC offset on the speaker is set with P1 but it wanders +/-30mV - I guess some thermal coupling should tame it).
Leaving the HEXFETs' source resistors out is really a game changer - the inevitable HEXFETs' "grain in the sound" is still there, but lower in intensity and different in character. Now it sounds like it's part of the ambient, reminds me of that analogue feeling of good vinyl and reel tape reproduction and, most important, it doesn't get in the way when listening to the music - I was able to listen to complex orchestral music for hours without complaints. Changing the OS bias to 1A brings the minuscule change in sound.

Congrats Joe Berry - your idea works lovely ! 👍

I changed the PS voltage to 2 x 20V (that's more than enough power for my needs) and the output devices are IRFP044N (Vgs=4.65V @ Id-0.3A). BF862 runs on 2.5 mA and BC560C flows the Ic of 9mA, so the values had to be adapted. I got the output stage bias of 300mA by connecting the 2k7 parallel to R1 but P2 changes it in wide range - start setting it with max. value of P2 (that gives lowest bias). It's worth mentioning that the amp is very silent - the background is pitch black, no hearable noise at all (speakers are 93dB@1W sensitive and the total PSU capacity is 64000uF - 0R1 between 22ooouF and 10000uf is not much of a filtering help but it allows easy bias measurement).

Pics show:

• schematic "as built"
• the point-to point built prototype
• 20 kHz into 4R
• 20 kHz into 1uF+4R
• 95 kHz into 4R
• hard clipped 20 kHz sine wave, into 4R

* EDIT 11-Jul-2022 :
Link to Joe's explanation of circuit's inner life, post #72

Hi everyone .
where can I find material to read to understand more about equalization ?. but something that starts from scratch because
I know very little about it , I would like to put ideas in order and remove confusion .
hardware , digital , diy , proprietary .
it's easy to get confused.
Thank you

I was sent the wrong bit the first time. I need a top bearing cutter with a 1/4" shank. Does Freud even make them in this size? An online catalog wasn't very helpful, its for a store not by Freud.

Amazon has some cheap looking one in 1/4"

Is a small 6 amp router but I only intend on cutting 1/4 plywood with it. I cut a lot thicker material with it already.

Do anyone know the oscillator frequency for the TL494 or the value for the timing capacitor (pin-5) ?
Timing resistor is 10K (103 smd - pin 6).
similar amp maybe Excursion KXA-1K.

Why does the 3.5" still sound like it's way too loud?
Is this why my EQ looks the way it does my whole life? With what I guess are flat FR speakers 🤔
I can literally just listen to a ScanSpeak 22w or 26W by itself and barely miss a mid or tweeter.

Also: should I build:
XT25 + RS52 + SB23
or
TG9 + SB23

I was also thinking 22W (which 1 now has a dent) + TG9 (or with RS52 + XT25
or
ScanSpeak 26w + TG9
or
XT25 + SB15 + 26w (box will be big)

The TG9 is 8 ohm and the SB is 4 ohm and the TG9 is still loud.
Am I a bit silly or is almost every one else? 😳 🤣

or 22W (which 1 now has a dent) + RS52 + XT25 (pics attached, yep I got one baffle/woofer offer by 1"/25mm 🤣)

Hi guys,
Long time reader, first time poster... LoL
I have an excellent little Forte 1a amp that I keep around as a spare sense I replaced it with a Threshold SA 3.9e in the main system. BC I can get another one of these Forte amps pretty easy I got to thinking, could you convert this amp to a class A monoblocks?
I've seen some 200wpc class AB stuff get converted to 50wpc class A but I haven't seen a lot of class A stuff get converted to mono's.
I am no EE so the schematic I found for the amp looks like hieroglyphs to me so hopefully one of you smarter gents can look at it & give me your thoughts 😉
Thanks!

Channel One Sound System in England

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I got turned on to these guys at a party. Who else would like to set this up in their back yard?

This is a pretty large transformer. Probably about 400 or 500 VA. 6 secondaries which can be combined if needed. Pulled from a six-channel amplifier.

Input 120v 60hz

Output 21.4v---0---21.4v

$15 plus shipping

I need a little help deciding what values of resistance I should use for the buffering transformers, and volume/balance pot for a passive preamp.

It will be driving a 12 foot long interconnect to a modern SS amp.

My dac and phonostage have standard outputs.

What would you'all recommend?

Today I opened a mechanically broken Black Gate F,
There are two roughened and darkened aluminum foils inside, and the black tissue soaked in lytic.
How are the + / - poles determined ?
What is the rocket science here ?

Hi 🙂

Wondering if anyone may have an idea what burnt out and what I may need to solder in place, yes I am a beginner and don't understand much but always ready to have a go to learn :-o

I posted on a different forum, for advice for the fault as the item is quite old and has quite a narrow / specific use, compared to modern things these days.... but I seem to have found the fault with help! and I now assume it is back in the general analogue output area of tech knowledge...??

Any thoughts much appreciated! 🙂

Link to the forum where I posted for help:
https://forums.slimdevices.com/foru...porter-fault-any-suggestions-much-appreciated

Over the last few months, I've been working on a project inspired by Eddie Current amps. Since those are becoming more and more difficult to find (and I like DIY), I decided to make my own. Uses Monolith Magnetics nanocrystalline interstage transformers, Electraprint silver output transformers with custom tertiary winding, Wein bridge oscillator circuit for a high-frequency filament supply (~44khz VAC for the 2a3 tubes). Case was custom designed by me in Fusion and then Protocase brought it to life. PSU box has the B+ supply using EY500a rectifiers, Toroidy power transformers, Neurochrome soft start. Overall a really fun project and it sounds incredible.

What I have is a Polk XT-12 with -new box and woofer. It is 60L Vb minus my port and toroid (@ 55L). Port is 10cm X 30cm long. I found a good web calculator ....
http://www.mh-audio.nl/Calculators/BRH.html .
I don't know the T/S parameters of the Polk XT-12. It works , but I heated up the VC - I was a dummy and Xmax'ed it with my DIY plate amp. (photo 1) .
Amp worked TOO good @ 14hz , I smelled the VC after 20 minutes. I just wanted to see the worst case load for the new amp.

Using that MH-audio calculator with many Parts-Express drivers and suggestions , it seems to be valid (very close) as far as box tuning.
The NEW driver I want looks cool (a piston) and fits the box - A Dayton LS12-44. https://www.parts-express.com/Dayto...ofile-Subwoofer-Dual-4-Ohm-295-253?quantity=1
In (photo 2) I plugged in all my T/S parameters and get roughly a 32hz F3 (with the smaller Vb). I actually get gain between 40-60hz. Is that normal ?
I would not mind some free output at 45hz , I listen to classic rock mostly.
The Dayton can also be wired as a 2R in parallel , I have a 30-0-30 trafo , I'm sure my REAL amp could drive that with this lower voltage. Would running
at the lower Imp. change my T/S params ?? Running in series (8R) , I'm not too displeased . The original XT Polk driver does not seem to have much output below 30hz
with actual in-room testing, Polk says the OEM sub is usable to 26hz .... I'm not sure I even trust Polk , they make junk these days .... the original amp was a joke (failed).
Thanks...

PS- I know my port is barely sufficient for that 10mm Xmax , but the amp might not push the dayton much more than 5-7mm.
The Dayton = 250W .... my amp is a 4 output device 125W unit,

I found old German amplifiers; Braun Atelier series; A1, A2, R1, etc. have speaker set A and B wired in series when they operate in A+B mode, instead of parallel connecting like most amplifiers.

I wonder if I connect the multi-way speakers — no matter 2-way or 3-way — in “Bi-Wiring” configuration in serial connection to traditional amplifiers, are there any disadvantages compared to parallel connection?

Attached is the illustration of a view from amplifier to a 3-way system connecting in bi-wiring setup in serial connection.

rayma has suggested that we start this thread with some guidelines to choosing a good (or bad!) candidate. Usually the choice is made when something falls into your lap, but if given a choice, what brands and even models are most promising? I'll start by saying that the only thing I'd recommend for a beginner to avoid is an amplifier with 7591/7868/other last generation output valves. These were made in a time when manufacturing was at its peak and the horsepower races were too. Output valves were run hard and put up wet, and current manufacturing is unable to make really solid replacements. Other folk may differ, of course.

Hopefully, if this thread progresses well, we can include topics of safety, troubleshooting both general and specific to these old parties, test equipment including DIY and modern DAC/ADC plus software methods, and best practice dealing with aged capacitors, etc.

So, safety first last and always. There's a very lengthy sticky thread on safety that covers a lot of ground, but I'll add mine here. Keep one hand in your pocket. Better yet, attach test leads with power off, then keep both hands in your pockets. Current hand-to-hand goes through your heart, and you're a dead peckerwood. Make something to bleed down voltage AND have a dedicated DC voltmeter connected across B+ at all times. Cost about $15 - $20 and a cheap layer of protection. Keep kids, pets and impulsive friends on the other side of the door. For soldering, wear eye-pro. Make a strong habit of looking AGAIN at the unplugged end of the power cord every time you approach the patient.

Maybe enough to begin, Next!

All good fortune,
Chris

Hey everyone,

I just returned from my workbench so this is a spontaneous post, I didn't prepare it very well. I'll do my homework better if this one lacks info.

Here's the thing: I'm breadboarding a tube amp. 6550 push pull pentode monoblocks.
I used a 21st century Maida 300V regulator for the output tubes G2 (20 mA +/-) and the preamp (30mA).
All worked fine, got a nice voltage range on the trimpot. The input voltage is 370V.

Then I decided to go fully regulated i.e. also the output tubes plates.. Settled for 350V. The regulator had to cough up 280 mA. And it said 'no'.
Reg output drops to 325V, turning the trimpot has NO effect.

I went back to the earlier situation and it worked fine again.

Somehow the reg can't handle a few hundred mA, and I have no idea why. Could someone please shed a light on this?
Thanks!

I have a high quality Swageman 16V LPS that I would like to convert (if possible) to a 5V output for use with either the LHY or PD Creative LPS upgrade for the Bluesound Node 2i. Is there a way of doing this easily? 2 options that I have researched - (1) a bucking conversion - I've seen multiple schematics from simple (a few resistors) to complex (diodes, additional filter caps etc.) or (2) what would seem easier - just purchase a new 5V transformer and replace in kind - but would this not work because of all the other ancillary components are spec'd to the current 19VA toroid.

I'm comfortable with an iron and multimeter, but not much beyond that, so any instructions keeping this in mind would be much appreciated. Thanks

I was making a tws bluetooth speakers for my travels with Tectonic TEBM36S12-4/A rectangular bmr driver and JBL charge 5 oval driver.
I noticed that the bmr sounds really good crossed over at 300hz and i mean they sound incredibly good so why not make a bigger speaker using the same bmr?
I had some reckhorn d 165i 6,5" sub drivers still in their package and I was pleasantly surprised that the sensitivities match.

While I could build fully passive set of speakers from these drivers, I rather make an active pair to give out as a xmas present.
I chose arylic plate amp to make these an active setup.
It's a two channel amp, but it has dsp. aux, bluetooth, wifi connectivity for spotify connect airplay and multi room capabilities so it might be super handy.
Power output is a bit low at 40w@4ohm, but I can suffer -3db reduction on the max spl.

Project goals:
45-20000 frequency range with max +/-2 db deviance between 100-10k
Enclosure shall be 3d printed with wooden side panels
Passive crossover
Edge difraction compensation and other eq handled by the plate amp to minimize xo cost
Project cost to stay under 500€ total

I'm currently testing the drivers in a repurposed enclosure from an old kit speaker. I just printed an adapter for the reckhorn subs and a waveguide for the bmr.

Wait a waveguide on bmr? Why?

Well it's mostly cosmetic, but it also evens out the dip at 5-7k and I tried to model it in hornresp so that the increase in sensitivity is right in the middle of the bsc correction. Also it raises the +10k region quite a lot while the driver itself has -7db slope from 10k to 20k.
Currently I have passive xo at 330hz, but I feel it's too close to the driver fs that is around 200hz when enclosed so I ordered more components to make another xo @ 500hz.
Simulated response at 330hz 12bd/o

Measured response in the repurposed enclosure.

Only passive xo and bsc as an active filter. Notice how the previously attenuated top end is now +7db emphasized. The bass boost is a characteristic of my living room acoustics.
The response is great for unfinished product! The sound is also really pleasing. It's not harsh and analytic like in gennies, but soft and pleasing. Even the reflected sound is much cleaner than on conventional speakers and that is mostly thanks to the waveguided bmr.


Render of the enclosure.

Parts used:
Tectonic TEBM36s12-4/A
Reckhorn d165i Subwoofer
Arylic up2Stream Plate amp
Coils from intertechnic
Caps from mundorf

Tools used:
Hornresp for wg and enclosure design
Vituixcad for xo design
Ender 3v2 dd modded 3d printer
XTLW Climber 8 IDEX printer
minidsp umik-1 with rew for measuring
Dayton Dats v3 for ts parameters, impedance inductance and capasitance sweeps
Handheld router for wood panel work

I will finish the cad work tomorrow and start printing these out. Hopefully they'll be ready before 25th 😀

Will keep you posted!

Gang,
Got a pair of the CineMag S217D and they look pretty nice and looking to build a line preamp with them.
https://cinemag.biz/output/output.php

So basically a 12.5K primary to 600 ohm output. The tertiary is throwing me for a bit of a loop. I see 22.2: 4.96: 1 ratio and I take it 1 = 600 puts the primary a bit higher than the specd 12.5K, (13.32K) so is the tertiary 4.96 or ~3K?

I would imagine the loading of the tertiary would effect the primary.

The Pultec seems to be the only schematic I can see using this and this is a balanced usage all the way through.

I was thinking of using a 220H loading some med mu tube and feeding back through the cathode with the tertiary with like 1-2dB of feedback. Parafeed 1.5uF blocking cap.

Thoughts? Help?
Thanks,
Gordon

Hi everyone ! I have a NOVA audio XPS1400 amplifier that 1 channel when I raise the output volume a little I have a very disturbed sine wave and shortly after it goes into protection! Does anyone have a schematic for this amp? I need it to try and get it going again

Hi, tell me, do you have spare parts for DENON DVD-2900 for sale?
Interested in a DVD drive assembly, or plastic legs and guides, and other spare parts according to the picture?
Sincerely.

I am looking to bond 8mm HDF (HD3) with 17mm Ply (BB) using green goo. Has anyone else done this? And would this provide me with constrained layer damping for my projects? (OB and sealed bass cabinet)

Once I bond the boards I will be treating it as a 'single' board and use it for cutting, routing & CNCing where necessary.

All thoughts on this are welcome, thanks 🙂

If you take a universal tool then turn out another use for it, you know?
Or make an existing tool function better that it did otherwise, a hack, you know?

As long as its mostly safe. You can sign the optional disclaimer back there <<< 😉

I turned a belt sander into a perfectly straight 90 degree bench sander with as few as a couple 2x4's and scrap plywood. But that's easy, I want to see some better ideas.

I don't have much experience with routers, but that's partly why I'm here. To learn cool router tricks 🤔😀

Similar to another post I started about abuse of horses in the racing industry, here is a similar and perhaps even worse situation.

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These horses used for tourist rides lead a terrible life and this industry also should be banned.

Whilst looking at some typical architectures for 2-stage active/passive RIAA preamps, I noticed that if the stage order [shelving gain (3180us/318us pole/zero) --> LPF (75us pole) --> gain] is chosen, the final gain stage can be configured as a 2nd order state variable filter (SVF), with the high-pass output used to implement a rumble filter, and the 75us pole incorporated into the SVF input resistor (R1 in the picture below).

This allows the rumble filter to be implemented without adding an additional stage (typically a Sallen-Key HPF) after the RIAA equalisation, and as the DC offset at the HP output of the SVF is controlled (equal to the input ofset of the SVF second opamp), no output DC-blocking capacitor is required.

State Variable Filter. The first opamp becomes the second stage of the RIAA preamplifier:



The complete circuit:



The main features are:

- The first stage implements the RIAA 3180us/318us pole/zero pair using the values originally proposed by Baxandall, which give impressive accuracy with common values. DC gain is 40dB falling to 20dB above 500Hz, so with an opamp such as the OPA2134 (characteristics shown below), the closed loop bandwidth can be seen to be >200kHz with an excess loop gain of ~30dB at 20kHz, giving good distortion attenuation.



- The RIAA 75us pole is incorporated into the input resistor of the SVF by splitting R1 into two sections, giving the exact time constant using common values. This can be done as its 2122Hz LP corner frequency will be more than 2 orders of magnitude above the <20Hz corner frequency of the rumble filter, with the inverting input of the opamp tending to a virtual earth at frequencies above this.
With a fixed gain above the HF cut-on of 19dB, again the excess loop gain is ~30dB at 20kHz.

- All resistors are E12 (if we slightly cheat and form R1 above from a pair of 1k5 in parallel - R4 above is already split into a series pair of 1k5), and capacitors E3.

Total gain is 39.2dB @ 1kHz, with a rumble filter HP corner frequency of 17.3Hz and Q = 0.71 for a Butterworth response.

Simulated frequency response (with inverse RIAA compensated input):



This has been prototyped, installed in re-purposed tuner chassis:



Measured frequency response (inverse RIAA compensated in ARTA):



Measured output noise, input shorted with 100R (measurement noise floor shown in yellow-ish):



Step response, 10mV step, and overload case, 50mV step:



1kHz sine, 6v RMS output, and overload case:



Stripboard PCB layout of one of the prototype channels:

Hi I have listed a new Twisted Pear Mux board over on ebay UK

https://www.ebay.co.uk/itm/304922283992?hash=item46fec8cfd8:g:YuUAAOSwaIdkUjEf

http://www.twistedpearaudio.com/digital/cs8416mux.aspx

Hi All! I'm working on a home theater project and am trying to reality check myself as to whether this performance stacks up, and if I ought to stand by this tweeter combination or move on to something else.

My goal is to be able to exceed 105db at one meter, allowing me to approach reference levels at about three meters. I have attached a small Peerless XT25SC40-04 ring tweeter to a DIYSG SEOS-8 waveguide, and have mated it to a Peerless HDS-830869 woofer with an active crossover for testing. The crossover on the woofer is a 4th order lowpass at 1400hz, and the tweeter has a 1st order highpass to shape the response and a 4th order highpass at 1200hz.



Overall, I think I'm getting somewhere but need better cabinet design to reduce some diffraction issues. I'm not a great woodworker and that does not come easily to me, so I'm second guessing a lot at this stage. The Peerless woofer is no longer available, so I'm looking for other options. The other options tend to cost more, so I set out this morning to answer... can this combo hang?

Here's a graph with 1 meter gated measurements stepped in 3db increments.




Here they are again with 3db offsets to lay them all on top of each other. I can't figure out how to set one as reference and the others as deviations from that- I've seen some people do it, can anybody point me in the right direction to do that too?



It seems like it comes up just short of 105db before compression is significant. Perhaps that's OK.

Now here's distortion at about 86db:



Mostly 2nd order, and over 40db down. Looks alright!

Now at about 95db:


3rd order is starting to come up, but is that level low enough? I see reviews of commercial speakers (not even very expensive) that can do better.

Finally, here's how hard I pushed it. About 107db:

Second order is pretty high, and higher order products are starting to show up, though still at fairly low level.

So, is there a better way to go? Any feedback is welcome, thanks for your time.

Hi, I've been into Quad 405's over the last 30 years or so.
I'm not saying they're the worlds best amp - but the originals are/were exceptional value, and the Chinese clones are too, with a bit of work.

The traditional criticisms of these amps are very easily overcome to make a great classic amp.
The current limiting was the major one, and lots of work rounds have been proposed. The simplest and best of which, in my opinion is to just throw the components in the bin.

I use them because I think they sound good, and have a 3 way active system with dual bass drivers. So need 4x stereo amps for my main speakers.

I've got 2 original ones, 1 original refitted with chinese boards, and 1 which I made as a student in the 1980's from boards I etched myself.

All of these, I've modified in what I consider a 'sensible' manner.
1) using recognized improvements made on later amps
2) deleting the current limiting
3) not redesigning the amp into something different
4) easily done on the existing boards, Quad or clone; don't need new boards.

The diagram is my summary of it.
Please bear in mind I'm not an Elec Eng, just a hobbyist. But I have done these exact mods to about 10 boards, and had them running well for years.

I'm searching for this RPI dac hat. I wan't to use it for a second set-up in my office. So nothing real fancy. A recaped Naim Nait 2 + some Britsh bookshelfs.
I have a RPI and a Allo Kali that i wan't to use and no need for extra power supply's. Just a simple set-up.
I have try to contact the designer, but he is not responding.
An other good option with te Kali wil be fine to.

https://www.diyaudio.com/community/threads/diy-ad1865-nos-dac-for-raspberry-pi.345225/

Hi,

I've recently upgraded my BHEL34 in order to test a special NFB loop I'm workin on.

I started by the last working point suggested on Mullard datasheet ( https://frank.pocnet.net/sheets/129/e/EL34.pdf ) for maximum power, slightly adapted.
I now run them at 460V and 44mA, on a Raa of 6.6kOhm and 23% ultralinear taps.

To improve the loadline of the phase splitter (so making it flatter) still being able to keep a good local feedback on the EL34, with the plate voltages below 300V and the cathode voltages above 0.9V even at maximum power, I've modified the 220k + 47k + 39k combo into a 330k + 33k + 27k combo to supply the two triodes.

The reduced UL tap increase the available power, lowers the driving requirements and also the input capacitance of the EL34, but the higher swing compared to the EL84 pushed me to increase the current flowing through the power drive, so to reduce the bias resistors of the PD CCS down to 100 Ohm. This allows to have more current to be able to swing more volts on the grids of tghe EL34.
I wont' repeat the calculations here, you can find them in my EL84 thread.

I have old boards, with PSU onboard like for EL84, so I worked on the dropping resistors to set the voltage of the powerdrive and phase inverter CCS.
I set them to 100V and 30V for EL34 and 120V and 25V for 6550.

I've played the EL34 amp (without the new feedback) all saturday afternoon and I liked it alot.
It has alot of definition and it performs very well on many kind of music.
It pushed my Klipsch to very high levels, far beyond previos versions.

I hope to have one evening during the week to test the new feedback and report the results.
The new feedback will use an OPAMP to amplify the difference between a scaled down version of the output of the amp minus the input signal, so basically only the distortion. Simulations give ppm distortion at 1 Wrms and a Rout of 0,09 with that specific feedback, and a maximum power above 50 Wrms.
I need to find a load to test the full power in real conditions.

6550 version has only been simulated until now, and with an Raa of 4k with UL at 23%, with the same 460V B+, will give around 80Wrms.

Here below you can find the modified schematics.

Good day to all. I hope all is well and good and having good repairs this past days. I have a Focal FPP5300 5 channel all in one amp. Been troubleshooting it for a couple of day now. The issue was it is in protect mode , after troubleshooting there was an input capacitor 10uf 25volts going to the sub driver ckt. output section which was deffective, after replacing I can now see the signal after the capacitor going to the sub driver circuit but does not go through the output terminal of the sub, that means no signal coming from the sub amplifier section output, and still in protect mode. But when I connect a sub woofer on the output terminal. The amp is good and goes out of protect mode. Make an audio test and all channel are working perfectly. Removing the subwoofer from the terminal then again it goes protect mode. Can anybody have an idea why this happens? Why it needs an impedance connected to the sub output terminal on order for it to work>

I am restoring a 1966'ish vintage lab power supply that uses 5x EL34 in pentode mode for series regulation of separate plate and screen supplies up to 500Vdc (using a 620Vdc raw feed). I may well end up using valve alternatives to the EL34. I don't want to modify the existing circuitry, which is likely similar to HP’s 712B from 1954, and Fluke’s 107D from 1964, although I won't have a full schematic for another 2 weeks. I am interested to hear if anyone recalls any effort to make a solid-state equivalent (ie. valve pin compatible) of a power pentode. I think the most well known low-power ss alternative was the Feltron from the early 1970's. At the moment this post is just to reconnoitre the scene in case I've missed someone's effort.

I'm currently designing a set of compact two way desktop speakers that are bi amped, and want them to have a detachable cable.

Does anyone have any suggestions on connectors with 4 pins that might work? I was looking at the mini din connectors but it looks like they are only rated for 2 amps at 12v. I'm worried they won't handle the power as the chip amp is 24v and outputs 30 watts into each channel.

The INT25 has no DAC and no phono stage. If I buy that amp, do I also need to buy a AC and phono stage gear? If so, what is recommended?
Thanks.

I have a good friend wanting some new bookshelf speakers. He appreciates good sound, but he primarily listens to 80's punk rock so we're not talking about bass or good recordings. He will listen to folk and other stuff occasionally, but is not an audiophile in the sense of demanding the best from his gear. These will be for bedroom/small room listening, max 10 feet away and likely placed on a shelf close to a wall.

I'm thinking something up to maybe 5" size and a potentially one of the BabyLab cabinets. Is there a reasonably priced driver with decent performance in this size? I'd like to keep cost under $100usd not including the wood for the pair.

New to the forum but visited a few times and know there’s a lot of knowledge here.

I’ve got a Marantz CD63ki and I’ve got 2 issues with it. The first is that sometime when the tray is opened it shuts immediately without anything being pressed. The second is that the laser sometimes skips and this has slowly got worse. I know the transport is east to swap over but can’t seem to locate a genuine unit. There are plenty on AliExpress etc but these all look aftermarket as the motors seem smaller than the original.

Any advice would be appreciated.

Mo

So... lately I have seen with some consternation that the new "amp racks" I recently bought are already stuffed with big black boxes with a blue light out front.

It came to me that in the lab we use big programmable metrology quality power supplies. We don't put power supplies in our stuff, instead we rely on external units with voltage and current controls.

Already in some components, particularly low level and Big Pass Irons, the power supply is on a second chassis.

The next step would be to separate the power supply from ALL components... why rebuild the power supply every time the amplifier boards get redesigned?

After all, the job of the power supply is to provide a stable voltage with very little noise. We could add some current limiting as well as the cherry on top.. and for that, I can't think of anything better than what we got in the labs (or your own bench). The power supply doesn't much care if the drivers are tubes, VFETs, bipolar.... well, yeah, a tube power supply is a different thing... the amp itself might need an internal transformer to bump up the ~100VDC to ~500VDC...

How about using an instrument grade power supply instead like an HP6010/15A with ~1000 watts:

https://www.testequipmenthq.com/datasheets/Agilent-6015A-Datasheet.pdf

Sure, it will look like we brought the bench to the living room and it will require a cheat sheet not to burn up the amps... but, but.... if would be nice if it could look like this:

https://www.usaudiomart.com/details...output-tungar-dc-power-supply/images/4433276/

Something retro that looks like the stuff the Traitors Of Earth used to communicate with Ming Of Mars. Will fit nicely with the danish mid century furniture.. sort of.

Hi guys,

I'm new to this forum bit I've post the process elsewhere is anybody is curious to see.

I have change fews part and now just installed new output transistors from ON Semi(new motorola). The problem is the +30.5Vdc and -30.5Vdc from BD901 and 4 mains big caps. When I probe it to the board I have +60Vdc and -2Vdc...

I getting near to clueless about this.. when I pulled out the old output transistors and verify voltage at caps and had the +-30.5Vdc.

Left channels looks alright all over the power amp that I chech yesterday and it was before the replacement transistors. Right channel was now okay and I have to check that with new transistor.

Could the soft-clipping could make that weird voltage?

I've put attached the diagram I have put together from the manual.

Thanks for all the help in advance!!!

Hi, this is a friends amp Im trying to help diagnose. The amp powers up and fans spin then it shuts down and the protect light comes on the remote. Also, the red light on the amp flashes fast. I opened it up and looked with a magnifying glass. No signs of damage and no smell. Is anyone familiar with this amp and/or problem? Any help would be greatly appreciated. Thanks

Hi everyone,

I have a pair of 5.25" mid-woofer drivers. Their parameters are as follows:

fs = 68 Hz
Vas = 0.23 cu.ft.
Qts = 0.45
Xmax = 6 mm.
Imp. = 4 Ohms
Power = 65 W

According to Loudspeaker Cookbooks, a rule of thumb suggests that drivers with Qts of greater than 0.4 and high voice coil overhang (Xmax) be used with closed box. Nevertheless, I wonder if I use these drivers with vented box, what will be the results?

Actually, I'm going to use them in passive radiator system. But, AFAIK, the PR system gives the same result as vented system, doesn't it?

Hi There,

I built a daughter board circuit that sits at the current location of SAA2770 of my Philips CD650. With it I can switch between NOS and OS mode by flipping a switch. There's no circuit modification. You can convert it back to the original hardware configuration simply by removing the daughter-board and re-inserting the SAA2770 back to its own socket.

The daughter board:


System running together:



Front Panel NOS indicator:


Mode control switch and NOS indicator wiring:


With the quick A/B listening test results, I prefer the NOS sound. It is more transparent and musical. But it's more susceptible to disc scratches as it's missing the SAA2770 interpolation to cover up the missing data.

A3K

Hello

Is someone have in stock a couple of NJL1302 by ON SEMI to sell to me ?

Thank you!

Has anyone used these grill frames from parts express? I’d like to get something simple like this.

https://www.parts-express.com/Speaker-Grill-Frame-Kit-260-346?quantity=1

I want to replace a FE103 in a 110 cm TQWT and understand from reading around this Diatone speaker is more promising for a relaxed sound than a Fostex FE166.

Right now in 2017 I see two versions of a Diatone P610 clone on Alibaba (davidlouis store), the classic one having a magnet labeled Alnico.

1) a copy of the original with an inside small alnico, a rond piece of metal, a pair costing about $ 250. Open magnet structure.



2) A copy with a different flat ferrite-like magnet, a pair costing $ 130.




The membrane and suspension look exactly the same on the pictures. Still there is a significant change in Mms. The frequency response curve are virtually the same for both products (I mean it looks like a carbon copy; this test was made in 2015/09/01)
Such a different in the measurement of Mms surprises me, seeing the same assembly. Mms is the moving mass isn't it? 😕
The second claims a higher BL but seeing the sensitivity, this fits the first one more (1,5 dB more). Chinese ads?

Anyway,

• which version is better for open baffle (for sure #1, the classic)
• which version is better for TQWT (I would expect #2)

Hi all!
I found a rather promising tube the other day.
It seems to be either an equivalent (@9V) or a close analogue of the respected and well-deserved 12GN7A.
Has anyone had experience with it?

9KX6:
Plate dissipation max - 11.5W
Transconductance - 36,000
Plate resistance - 50,000

Hello !

i have bought from the forum user "Hicoco" this alternative power supply for the UGS muse preamp project.



Due to a direction change on my project, i no longer need it. so i am here to sell to someone else that can benefit from it.

Uses 3 Hammond PCB transformer. 110-220v selectable.

Integrate 2 unregulated low-voltage output, and 4 ultrabib 1.3 regulated ones.
bipolar configuration.

all independents. So it can be useful also for other kind of projects... not just the muse-preamp.

The board is pretty big 287x287mm. 4 layer.

can accomodate all sorts of output connectors.

Asking 40€+shipping (to be calculated)
For 10€ more i can also include the 110/220v selector switch + all the needed heatsinks for the shunt's

All the docs will be supplied to who will receive the board.

Thanks !
- Michele

First Watt F4 Mockup Question

Giant 15lb heatsink would be cut in half at machine shop to make two.

Any reason I shouldn't cut these boards and do this???

DIY F4 board is too wide for my heatsink. Cut off ends to fit.


Place ends under main board and jumper together with just 4 short leads.


End result would look like this (wrong transistors shown)


Another view




Cardboard represents "1/4" Aluminum faceplate 12" x 5 7/8" (top portion of heatsink will be cut off). The total amplfier width is 17 1/2" so rack ears could be fitted. Should look great with the short fins on front and rear!


Inside area view. I'm not sure if I'll go capacitor board or screw top cans. Leaning towards screw tops. Also, one 500VA trans or two 250VA transformers?


Very large 3" heatsink "uniqe double sided"


Another view (note: double sided heatsink).


What say you?
Gary

I really need your help.

PTSD and post ChemoBrain confused on Dual ACA for mono p/s

Attempted ordering one or two AntTekl or other transformers and spacing issues.
Attempting to build one power supply chassis for both.
- struggling to use Mini Dissipante 2U --> maybe 'possible or impossible' to fit? (would be nice if anyone knows from experience)
- 3.5" x 1.5" internally available if I use the current chassis.

First question: What transformer should I purchase to power these p//s boards and two ACA mono configs; even if it will not fit in my current case?
Second question: What chassis should I purchase if I am really unable to use the 2u Dissipante?

I appreciate your seat-knowledge expertise.
John

Well

http://electricbeachaudio.com/

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So as a follow up to the 6N3/6N6 line/HP amp I created, I finally built a version using a WCF as output instead of the simple active load.

The results are nice.
Pout is 180mW from 32R to 470R.
2.4V volts out with 32R load, 9V out with 470R.
I have four boards available at the moment. 5$ each + post because I left off the 1000uF caps - just solder them across the resistor leads.

Here's the schematic. Copyleft as usual. Same dimensions as the old board.

The schematic says 6N3 because I was originally going to use them - the board is 9AJ.

I have a set of Spiral Groove Studio Ones and I have a troubled driver. I believe Joaquin Gerhard used SEAS drivers, but does anyone know the exact model, or what would be a very similar replacement? Thanks in advance.

I'm designing floor-standing speakers. They contain two separated chambers as depicted on attached. The upper chamber is passive radiator system, and the lower chamber is sealed system. Note that the midrange labeled in the picture is actually a woofer in upper chamber -- No high-pass filter applied to it.

There is no problem with the lower chamber because it's simple sealed design. The problem is the upper chamber. I tried playing with online calculators, they suggested that the PR chamber is tuned at 33Hz, while the sealed chamber is tuned at 58Hz. If they're played the same music signal, will it cause any problems? However, it's similar to car audio system where the front and rear speakers may have different tuning frequency, I think.

I just installed Daphile on a laptop and cannot get past this screen.

Any advice?

Hi !

I have noticed a strange behavior of my hi-fi set-up.

When I listen to the radio through the FM tuner, preamplifier and power amplifiers get warmer than when I listen to CD/SA-CD/DVD-V or LD. In fact, in the latter case, preamp and power amp barely heat up from ambient temperature, whereas in the former, temperature of the cases is noticeably warm, especially just above the regulated power supply of the preamp.

I should add that when I listen to digital discs after the preamp+amps have got warmer after tuner listening, the case temperature of the downstream equipment cool down.

Any idea which could explain such a behavior ?

Look at the size of these things 😵

Is there a formula for calculating the coverage angle of a horn? I am unsure if I should be measuring the angle from:
a. The bottom of the throat
b. The centerline
c. The wall angle

see the attached drawing.

Hello peoples of the internet from a new member!
I have a problem and hopefully this might be the place where I could get some insights from someone smarter and more experienced then myself in these matters.
If yes; thanks in advance, if not; apologies in advance! 🙂

So, my "old trusty"® Rotel RSX-1562 has lately started having some issues. Not sure exactly how old it is, I bought it second-hand a bit over 3 years ago.
Some minutes after turning on (typically 10-20), some crackling noises start coming out of speakers, and it lasts for a good couple of minutes, then they disappear altogether.

However, noises are most audible when HDMI inputs are used (for some reason), and also most audible from center and rear speakers (I have 5.1 setup and typically use 5ch stereo audio mode). My front mains are 4ohm, all other speakers are 8ohm. Also, when audio is switched to stereo mode the crackling noises seem to down a bit, but again it might be to different impedance of the speakers.

To me it sounds like there's some static building up and then being released. It's typically higher frequencies crackling.
From other inputs (analog, coax or optical) noises are much much more quieter and harder to observe (I had to sit on the floor next to the front speakers waiting for crackling to occur) and I only heard them from HF unit (which means they are above 3kHz).

After RSX has been turned off for at least (cca) 30mins, and then turned back on, the weird sounds will reappear.

So far I've tried different computers via bunch of HDMI cables, no difference. Same issue is from my TV box as it also connects via HDMI. Since there's a 7.5m HDMI cable from my PC to RSX which passes by several other power cables and speaker cables, I thought maybe some static can accumulate in it, but wasn't able to prove it so far.
So now I think that something in RSX produces those noises when heated up. I'm in the process of obtaining a different AVR that I can connect instead of Rotel so I can take Rotel apart and check inside.

Any idea as to what might be culprit for these problems? Something inside the RSX or something completely unrelated? My plan is maybe try to replace some of the power caps?
Sorry for the maybe-not-so-coherent-text and rambling, I wrote it as things kept popping in my mind.

Thanks for any suggestions!

https://www.rotel.com/sites/default/files/rsx1562_guts.png

Markaudio MS 11 problem?
I built a pair of rough all be it in ply mid size nostromo's to run the drivers in, gentle for first 10 hours now have 20 hours on them.
The problem being they sound flat/ lifeless my chr 70.3 in a planet mini tower are running circles round them. Is it a break in issue? Company states 10 hours only for the MS, is it the cabinet? Want to get them in a MTL cabinet as they feel restrained in this box almost suffocated if that makes sense.
Bass seems fine but the mids seem stifled and no sparkle up top.

I am looking for a Buffalo-IIIsePro ES9038 board. I am not using the Tridents, but I am willing to buy those as well.

Hi. I have listed the above board on ebay uk.

New and unused

https://www.ebay.co.uk/itm/304928922854?hash=item46ff2e1ce6:g:AF8AAOSw-oFkUjVI

The question is for their later Drivecore2 amplifiers with crossover. The stereo mode offer decent flexibility, for one example you can independently set the crossover between the L and R channels. Useful with active set ups. https://www.crownaudio.com/en/products/xls-1002

Further more it will handle 2ohms in stereo no problem at all. But what if the ohms were mismatched between the two stereo channels? Meaning the Left sees 4 ohms the Right sees 2 ohms? And while doing parallel meaning two subs on one ch vs. one on the other simultaneously, equaling 2ohms ch1 4ohms ch.2. I'm thinking its okay to do so, but double checking is safer sometimes. If need be it can be in series, there should be enough useful current there to satisfy needs.

Hi,

Very quick and basic question about the miniDSP, is the following correct:

If I am using a miniDSP SHD with 2 inputs and 4 outputs, I can implement a 4 way crossover with mono outputs by routing both inputs to each output channel and then applying the crossover filters independently for each output channel?

Thanks

I'm hoping someone can help me with two questions on this simple circuit...

1) To parallel these grids I have two choices, 1. a simple series string like what is shown with one stopper or 2. each tube with its own grid stopper all terminating at a common star at the input. I'm assuming this wired series string is ok with just a single grid stopper at the beginning. (series stringing grid stopers isn't an option because the stoppers would sum across the five tubes progressively different per tube). Which would you do, like its written or star-join dedicated stoppers?

2) Do I really need 1000 uF bypass capacitors? What is the smallest Ck value do you think I can use here where the difference is inaudible from using 1000 uF? Is there a simple computation for Ck without simply always just "making them big"?

Looking for a single DIYSG Vortex-15 kit. Would buy a pair if you don't want to split. Will arrange and pay for shipping the kit(s). Box not needed but would pickup completed speaker if within a reasonable distance from southwest Missouri. Thanks

Hello!

I would like to ask for advice, regarding any improvements to these chip amps designs from the 90s. It may be that this design is already as good as it gets...

I am using these (schematics attached) amps to drive Horn mids and Horn tweeters, which use little power due to their very high efficiency. I am using max of 1-3 w/ch into 6 ohm loads at the highest listening levels. I'd say usually staying under 1 watt!




1. I need balanced inputs (already included)
2. I am willing to try different dual opamps that are designed work in this configuration. I believe it is unity gain differential application.
3. Don't need headphone out, ignore this section
4. I there are other things to try, please share your thoughts. Is anything a clear deficiency?

Happy to keep this amp "as is" but also willing to try obvious improvements.

Thanks!!

Hi All

Like many others on here i have some armstrong audio love to rekindle, i remember as a child my uncle playing his 625 receiver through some kef speakers, at that time it was so lovely to hear and look at, this was my first introduction to hifi.

Even today the looks of these amplifiers are brilliant! So i went and searched and bought these two units, the 625 and 621.






I want to rebuild the integrated 621 amplifier, the 625 was thrown in for the deal as it was damaged in transit. For me this was great as i can use it for spares, they share the same makeup right?

So this is my plan, i would love to upgrade the boards with better components such as doing a full recap of all the boards such as the preamp, amplifier board and psu etc

I also want to change any transistors and diodes which i have read can go faulty. I would like to build this amplifier to be like brand new and to last another 20-30 years.

So my questions are:

Is it worth replacing resistors? What resistors were used (type carbon?Metal film etc) The amp board would be easy to do i could replace all the components with new parts (not to sure about the bias resistors) they look odd and special heat disspersation types.

The amp board has other tiny driver transistors, do these tend to go and would it be a good idea to replace these?


I am slowly going through the circuit diagrams to understand it all better, i also know over the many years they changed components and always upgraded or made changes.

I will start with the 621 by just replacing all the capacitors, diodes and small transistors to get it working and running as it should. The 625 will be where i play around with it and try to upgrade the components.

Any advice would be appreciated such as what the bias should be, where to measure the bias, known things that should be checked, changed, replaced etc.

One other thing is the potentiometers on the 621 are very stiff unlike the 625 which feel smooth to turn, the input selector on the 621 takes quite a bit of force to click into place, where as the 625 is smooth and doesn't take me to squeeze my fingers hard to turn it. Wondering if spraying detox in there will solve this issue.








From what i have read the 600 range were modular and share the same boards

C28 input board
A17 power board
Z20 power supply

which means i could actually swap boards from the 625 to the 621? The 625 seems to be more modern.

Also can anyone tell me good replacement parts for these parts

BC267 & BC297
BC384L transistors (would like similar or better i.e lower noise)

The bias trimmers seem old and risky to use would like to replace these with some bourns what power value would suffice here they come as 1/5w to 0.5w.

On the A17 power board there are some axial capacitors

2 x 220uf 50v and 2 x 47uf 100v which are polarised, could i replace these with non polarised (i have some which are of good quality and make).


The z20 power board has some tiny 1n4003 rectifying diodes could i replace these with something better like schottky diodes?

I also see many small eirie type capacitors of small values, thinking these would need replacing aswell? think these are Poly film types. Could i replace these with polyester, polystyrene or silver micas? lots in the tone control board!


The psu smoothing cap is 3300uf would it be ok to go slightly bigger? say 4000-6000uf? same goes for the DC speaker output caps which are 4000uf wondering if going slightly bigger has an advantage?

For further information!

The Armstrong 600 Series - Amplifier FAQ and diagrams

Yes its worth spending time and money to rebuild this back to its former glory! Any tips or things to look out for would be great.

Thanks all those interested!

My sound system is a Philips set as amp...Panasonic chip amps.
It is connected to the 3.5 mm output jack of my computer, and the computer is used as the DAC, playback etc.
Core2Duo, Gigabyte 41 series board, 2 GB RAM, Windows 7 ...it works well enough for me, I left Win 10 and came back to Win 7.

VLC player for video, Winamp 5.66 for audio.

The weird issue is there is a crackling noise when using the scroll wheel on mice, or even when using the slider on the side panel.
Checked with another mouse, and the up / down keys on the keyboard. Same result...

Any suggestions are welcome, this is a bit of a head scratcher for me.
Earthing is perfect.

$25 in very good cosmetic shape and was told it works (haven't tested). Wondering if anybody used one or have experience with this unit. The insides look like new. I need to get it on my variac. Well built, has some heft, this was used in studio. Opinions welcome.... thx

I got this one as a token of appreciation for my work on a reel-to-reel deck from my musician friend... The thing looks very nice and the build quality is just superb. Initial impressions were excellent, the headphones-out sound was well-balanced and extended. So... I thought why not hook it up to a CLC linear supply with some pre-regulation, followed by 4 x LT3045 final stage voltage regs... Well, as I've been saying... the sound of any piece of audio gear is 99% power supply... the end result was quite impressive.

I replaced one 5532 (just in front of that TPA6120) with my favourite... AD8066. This further extended the highs and lows, with even better spacing left - right, as well as between individual instruments. Good stuff.

Here are some photos... the mods are fairly straightforward... the result is simply amazing. I encourage other DIYers to do the same or similar... the mod can be easily implemented on anything that requires no more than 15V / 2A max (limited by LT3045). For dual power supply rails, there's LT3094...

Francis Monkman, founding member of rock bands Curved Air and Sky died on 12 May at age 73.

He also played synthesiser on the scores for well-known movie franchises including Star Wars, Indiana Jones, James Bond and Superman.

Hi,

was searching the forum with Google and the results seems to be unusable due to New posts -feed being indexed. This hasn't been a problem before.

Please add noindex to New posts -feed, thanks!

Fired it up for the first time and it sounds pretty nice. I noticed when I put a meter on the bias points for each EL-34 they were all seriously low. That leads me to my question. Anyone know the proper tool size for adjusting the bias. It's clearly not a flat blade screwdriver but beyond that I can't tell. Standard hex? Torx? I know the amp originally came with the tool but it's long gone now. I figures it was time to ask the braintrust.
Thanks in advance
f1jim

I saw these for sale on eBay and decided to take a punt. Very much unknown but seem to be from the XLS family although I wasn't aware of an 8". After a bit of digging I and obviously via the Mission sticker I found they are used in in some Mission active subwoofer.

Fancying trying to build a compact SLOB or just OB I thought these things might be able to be pushed a bit. If only due to the heavy surrounds.

They're were specced by the seller only as 6ohm but this appears to be a DC reading and so they're an 8ohm voice coil. Not very big a VC either...shame!

Magnet is doubled up but not very large diameter. The whole driver is quite small, only 210mm overall diameter. Effective piston about 160mm diameter. Basket is cast aluminium but quite light feeling.

So out of the box I'm a bit unimpressed with the overall sizing for an 8" 'subwoofer'. Maybe has some LT from the plate amp it would have been used with ?

Anyway I did some sweeps on it with DATS. Fs dissapointing at about 52Hz....my RS225s will probably be better! Suspension is very firm so will probably take some power there but the VC being quite small and seems a paper /cardboard type former I'm guessing heat will be an issue before anything else .

I have a board from a Luxman CD player that has TWO Burr Brown PCM1701P DAC chips on it

they work fine but the player has front panel cosmetic damage

I am selling the pair for $95 plus shipping in the USA

you get the board they are on but some other parts will be missing, you are only guaranteed to the the 1701s
you remove the 1701s yourself so you know I have not damaged them

these are highly rated DACs, see the second photo

http://vasiltech.narod.ru/files/PCM1701.pdf