£25,000 Audiophile Pre-Amp repair video by Mend It Mark

[Nucleonics]

Well looks like i'm a bit late with this post, the designer had the video taken down. Not surprisingly given the user comments about the build construction.

Apparently the secret sauce, as revealed by Mark, were hand picked amp-ops that had matching characteristics (sorry i forgot which parameter it was). Loads of separate power supplies and a ton of tantalum capacitors (one of which was the source of the problem). The boards were stacked with plastic standoffs, which got knocked off during shipping.

Hope it gets unblocked since it was quite interesting. Maybe it's available somewhere.

EDIT: Removed video is now on Odysee:
https://odysee.com/The-%C2%A325,000-Pre-Amp-that-went-Wrong---Tom-Evans-Mastergroove-SR-mkIII:c

[themadhippy]

copyright infringement  myarse. My guess is the purveyor of over price audio tat was upset that someone dared to prove him wrong and manged to fix it rather easily and without damaging the stylus,depriving him of his over priced repair fee.

[Andy Watson]

I watched that video. It will be interesting to see if Mr Evans can make the copyright claim stick.

Interesting to see what 25k audiophool pounds will buy!  The tricks for reducing noise are well known - as Mark explained. The only secrret sauce was variety of op-amp used which I believe Mark only guessed at. The mechanical construction was embarrassingly flimsy, especially for something with a £25K price tag. There was obvious shielding on the top and bottom but, unless I missed something, nothing on the sides. The case appeared to be plastic.

I don't think I'll be buy one of those

[themadhippy]

The mechanical construction was embarrassingly flimsy, especially for something with a £25K price tag.

Those audiophile cardboard shims dont come cheap you know

[armandine2]

..definitely glad I watched it when I had the chance to - Mark certainly gave him something to remember 

[Nominal Animal]

I can easily understand paying £2.5k for a bespoke handmade unit to ones own specifications/needs.  But £25k?  That's exploitation, unless it was an art piece and an investment.  You know, like an unconnected tantalum cap superglued to the wall as an exhibit.

[Nucleonics]

Mark just posted a follow-up video... given the humor included i wonder if this one will be blocked too .

[mikeselectricstuff]

No way on earth there is a valid copyright claim just for showing the insides of a commercial product.
Hope the complainer gets a good spanking for making a false claim, topped with good dose of Streisand effect - what a muppet!

[madires]

Luckily I watched the video before it was taken down. I can fully understand why Mr. Evans feels embarrassed.

[themadhippy]

Now thats what i call  a follow up video

[timeandfrequency]

I also watched the first video about that preamp : absolutely amazing, and so well featured by Mark's natural humor.

The 'ultra low noise' preamp is build by cascading several DC power supplies (some of them made with 78XX, 79XX) to raise the PSRR of the whole system.

Noise floor of the preamp is improved by wiring 4 opamps in //  (so noise factor is divided by 2). Again, nothing extraordinary : the trick is known for decades.

Elektor published 30 years ago a phono preamp with 8 JFETS in // that can be build for 30 bucks. Anybody interested for $£€ 1 000 000  ?

As mentionned above, the PCB of Mr. Evans preamp are badly stacked/cobbled together with nylon spacers as you can see here : https://hackaday.com/2024/11/14/repairing-the-questionable-25000-tom-evans-audiophile-pre-amp/

And no lateral shields at all : it is well known that magnetic parasitic fields never travel horizontally.

Indeed, the Streisand effect is taking place :
https://www.audiosciencereview.com/forum/index.php?threads/repairing-the-questionable-%C2%A325-000-tom-evans-audiophile-pre-amp.58548/
https://www.lencoheaven.net/forum/index.php?topic=45691.0
https://pinkfishmedia.net/forum/threads/repairing-a-%C2%A325k-phono-stage-gulp.298363/page-5
https://forums.stevehoffman.tv/threads/tom-evans-mastergroove-sr-a-25k-embarrassment.1213315/

[thm_w]

I watched that video. It will be interesting to see if Mr Evans can make the copyright claim stick.

Interesting to see what 25k audiophool pounds will buy!  The tricks for reducing noise are well known - as Mark explained. The only secrret sauce was variety of op-amp used which I believe Mark only guessed at. The mechanical construction was embarrassingly flimsy, especially for something with a £25K price tag. There was obvious shielding on the top and bottom but, unless I missed something, nothing on the sides. The case appeared to be plastic.

The plastic case is funny, even cheap audio gear usually has spray on conductive shielding.

And the true irony is that this thing is (acording to hackaday) a record player pre-amp, which means the noise levels are near irrelevant to begin with.

[EEVblog]

This is exactly why I advocate that every Youtuber should be on other platforms like Odysee.
There is no way for us to see the video so that we can be sure what any potential issue is.

But Mike is right, it's obviously yet another abuse of the Youtube copyright system.

[coppice]

And the true irony is that this thing is (acording to hackaday) a record player pre-amp, which means the noise levels are near irrelevant to begin with.

Why would noise be irrelevant? A moving coil input is very sensitive, and they usually have some screening, to avoid pick-up from nearby things, like motors and transformers. This unit has some sheets of un-etched PCB for screening, although its pretty crudely done. I think they might not have even been grounded. In the follow up video Mark makes fun of the use of really low quality plastic spacers, rather than more robust and rigid brass ones, which would have provided a good ground path.

[langwadt]

This is exactly why I advocate that every Youtuber should be on other platforms like Odysee.
There is no way for us to see the video so that we can be sure what any potential issue is.

But Mike is right, it's obviously yet another abuse of the Youtube copyright system.

seem to me like the only times I've remember seeing those false claims a treated correctly is when someone at google in the right place follows the channel and know which buttons to push

I guess it is cheap and safe to have a bot accept all claims and deny all counter claims

[Xena E]

This is exactly why I advocate that every Youtuber should be on other platforms like Odysee.
There is no way for us to see the video so that we can be sure what any potential issue is.

But Mike is right, it's obviously yet another abuse of the Youtube copyright system.

I did see the video, it basically showed the amp as the embarasing load of badly made garbage that it is.

Mark didn't do or say anything wrong...

The manufacturer obviously didnt want that kind of publicity. I thought the folow up video from Mark was a nice middle finger salute.

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[thm_w]

And the true irony is that this thing is (acording to hackaday) a record player pre-amp, which means the noise levels are near irrelevant to begin with.

Why would noise be irrelevant? A moving coil input is very sensitive, and they usually have some screening, to avoid pick-up from nearby things, like motors and transformers. This unit has some sheets of un-etched PCB for screening, although its pretty crudely done. I think they might not have even been grounded. In the follow up video Mark makes fun of the use of really low quality plastic spacers, rather than more robust and rigid brass ones, which would have provided a good ground path.

The inherent noise floor of a record itself is already high ("-60 dB RIAA- and A-weighted with respect to 5 cm/s, 1 kHz"). Then on top of that you add the stylus noise, and pick up from nearby sources as you say.

"Tom’s shtick is that the best way to achieve true high resolution with vinyl is to lower the noise floor on the phono stage, the quieter this crucial part of the amplification chain is the wider the bandwidth and the more you will be able to hear. He advocates spending more, a lot more on the phono stage than the cartridge because no matter how good a cartridge is if the amplifier is noisy you won’t be able to hear what it’s doing."

Anyway its been discussed to death already.
https://www.diyaudio.com/community/threads/the-25-000-preamp-that-went-wrong-tom-evans-mastergroove.419907/

[magic]

Someone reuploaded it to Odysee:
https://odysee.com/The-%C2%A325,000-Pre-Amp-that-went-Wrong---Tom-Evans-Mastergroove-SR-mkIII:c

I haven't watched the whole video but the insides do look a little funny.

[coppercone2]

I have a feeling that equipment might be designated for use in EM quiet areas or housed in a shield room or something, given the price.

I am not going to comment about the electronics, but the mechanical design and wiring does look shitty, even if it was made plastic for some design reason, for the price. 

Is it some.... attempt... for vibration or dielectric constant related design?

More then likely someone got a stomach ache when they saw the cost of good standoffs and stuff lol

I Guess whatever insane margin someone contrived got blown by tantalum caps and they decided to wrap it in TP.


I am almost 100% certain that even if someone did manage some kind of enhanced specification on some audio related parameter, the 'systems engineering' basically destroyed it, even if its located in a anechoic cave on the moon.

[Towger]

A great follow-up video from Mark, unlike others who rant that YouTube is always conspiring against them.

[Xena E]

Someone reuploaded it to Odysee:
https://odysee.com/The-%C2%A325,000-Pre-Amp-that-went-Wrong---Tom-Evans-Mastergroove-SR-mkIII:c

I haven't watched the whole video but the insides do look a little funny.

The mechanical design not only made it very flimsy but everything had to be stripped completely just to replace that one poxy tantalum tick...Mr Evans could have at least used decent tantalum caps.

If Mark didn't bill that job at 10% of new cost for the amp, He sold himself short.

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[Bud]

 I'd bill 20% minimum.

[rsjsouza]

Just watched the Odysee re-post. Great work from Mark and what a terrible assembly and choice of parts for the price. 

[EEVblog]

[Xena E]

I'd bill 20% minimum.

I re watched the original video.

I had completely missed the fact that the manufacturer seems to have sent the amplifier to Mark themselves with that challenge!

 

I hope he sent it back properly packed...

...perhaps filling it with builders expanding foam to make it more rigid before giving it to the Evri van driver.
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