Author Topic: £25,000 Audiophile Pre-Amp repair video by Mend It Mark  (Read 18378 times)

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Offline tszaboo

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #25 on: December 09, 2024, 09:35:25 am »
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!

 :palm:

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.
X
I though it was a customer, after the manufacturer refused to repair it.
I watched the video, and the construction was obviously a joke, that "shielding" is made by someone who ahs no deeper understanding of electrical fields. If you want to shield it you build it in a mu metal enclosure for starters, or at least Aluminium, not laser cut acrylic.
The standoffs seems to be identical that you get from Aliexpress in a kit for 1.99 including shipping.
I honestly don't know why anyone would want to own this preamp. Even before it was opened and reviewed. There is one reason, and that's consultants building a system for you, and getting paid percentage, based on how much they spend on it.
 

Online mikeselectricstuff

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #26 on: December 09, 2024, 09:37:49 am »
, that "shielding" is made by someone who ahs no deeper understanding of electrical fields. If you want to shield it you build it in a mu metal enclosure for starters, or at least Aluminium, not laser cut acrylic.

mu-metal is for shielding magnetic fields, not electric - any metal will do for the latter

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Offline tszaboo

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #27 on: December 09, 2024, 10:35:50 am »
, that "shielding" is made by someone who ahs no deeper understanding of electrical fields. If you want to shield it you build it in a mu metal enclosure for starters, or at least Aluminium, not laser cut acrylic.

mu-metal is for shielding magnetic fields, not electric - any metal will do for the latter
Yes, and for an amplifier that practically claims "lowest noise ever, better than any other amplifier" shielding magnetic fields as well as electric would be a requirement. It's not magic to have this, I have a relatively Yamaha AVR that comes in bent steel chassis. This is something done by many audio gear.
You stack it on a HiFi shelf, it can pick up the magnetic field of the transformer of another amp, and it gets amplified 1000 times in a phono preamp, and you get 50Hz hum.
« Last Edit: December 09, 2024, 10:40:54 am by tszaboo »
 

Offline artag

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #28 on: December 09, 2024, 06:58:21 pm »

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

Yeah, what was that about ? Couldn't he fix it himself ? Was he trying to show Mark up with a 'difficult' repair ? Why would he do that to a genuinely nice bloke ? It was a tant shorting a power line FFS.. Mark put far more effort into documenting the amp properly than he did fixing it, which he took minutes over once he'd documented it.
 

Offline timeandfrequency

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #29 on: December 09, 2024, 07:03:27 pm »
I had completely missed the fact that the manufacturer seems to have sent the amplifier to Mark themselves with that challenge!
When I heard this, I couldn't believe it.
Does this mean Mr. Evans is incapable of repairing his lovingly-cobbled-together stuff himself?
Did he actually outsource the design and manufacturing?
 

Offline themadhippy

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #30 on: December 09, 2024, 07:39:31 pm »
could be   the owner was quoted £6k for the repair by tom evans,and when they declined they were pointed towards mark who wouldnt be able to repair it
 

Offline temperance

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #31 on: December 09, 2024, 08:00:03 pm »
could be   the owner was quoted £6k for the repair by tom evans,and when they declined they were pointed towards mark who wouldnt be able to repair it

 :-DD
 

Offline BrianHG

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #32 on: December 09, 2024, 08:02:40 pm »
If I were to make a super quiet phono pre-amp, I would make the first gain stage differential right on the RCA input connector itself cased in a copper tube, powered by a photo voltaic cell (basically acts like a combination supply and constant DC current source) being most likely a custom discrete differential bipolar transistor design.  The photo-voltaic making this stage completely separate from the mains with differential output for the next stage.  This is the place where you need to take care of the noise on the massive gain needed for a MC phono cartridge.

The later stages could be generic high quality op-amps and instead of the stupid power supplies, just a properly designed high current ultra low ripple DC regulated supply with properly LC filtered sub-division if necessary.

The 30k$ for what was illustrated was a joke.
« Last Edit: December 10, 2024, 05:34:23 am by BrianHG »
 
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Offline EEVblog

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #33 on: December 09, 2024, 09:39:41 pm »
I just noticed that at 13:19 he does show the actual schematic from what is presumably the service manual in a spiral binder.
So maybe, technically, he does have a copyright claim for that bit if the service manual is proprietary? Although it's not marked as such, at least on the page he shows.
« Last Edit: December 10, 2024, 12:45:18 am by EEVblog »
 

Offline themadhippy

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #34 on: December 09, 2024, 09:47:40 pm »
Quote
he does show the actual schematic from what is presumably the service manual in a spiral binder.
So maybe, technically, he does have a copyright claim for that bit if the service manual is proprietary?
you mean the service manual mark produced himself ?
 

Offline Andy Watson

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #35 on: December 09, 2024, 09:50:10 pm »
I just noticed that at 13:19 he does show the actual schematic from what is presumably the service manual in a spiral binder.
So maybe, technically, he does have a copyright claim for that bit if the service manual is proprietary?
If I remember correctly, Mark reverse-engineered the unit to make that "service manual". The circuits displayed were very similar to what might be found on the chip datasheets.
 

Offline Xena E

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #36 on: December 09, 2024, 09:59:10 pm »
Mark showed his own reverse engineered document, and some semi manufacturer's application notes.

TBF to Mr Evans the amp used pretty competent noise reduction techniques in the design, but not the mechanical construction... and it was built down to such a low standard that even an Amstrad looks better quality beside it... I think it's niether here nor there how much the ticket price was, it just looks like a crappy prototype lash up...

I bet it picks up mobile phone interference like buggery.
 

Offline Bud

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #37 on: December 09, 2024, 10:00:13 pm »
The 30k$ for what was illustrated was a joke.
Nude virgins need to be paid. And delivery from the remote island is expensive.
« Last Edit: December 09, 2024, 10:04:03 pm by Bud »
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Offline langwadt

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #38 on: December 09, 2024, 10:00:27 pm »
I just noticed that at 13:19 he does show the actual schematic from what is presumably the service manual in a spiral binder.
So maybe, technically, he does have a copyright claim for that bit if the service manual is proprietary? Although it's not marked as such, at least on the page he shows.

the page has a "Mend It Mark" logo on the footer, I assume he drew himself
 

Offline Xena E

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #39 on: December 09, 2024, 10:03:14 pm »
could be   the owner was quoted £6k for the repair by tom evans,and when they declined they were pointed towards mark who wouldnt be able to repair it

Mark said at 20 seconds in on his second video that the unit was sent him directly by the manufacturer.

What arrogance to then claim he wouldnt be able to fix it!
 

Offline Gyro

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #40 on: December 09, 2024, 10:24:52 pm »
Just a thought that it might have been a stunt to get some visibility of his 'advanced' design and manufacturing techniques (or artisan hand building), similar to a certain robot builder, only to have his balloon burst by Royal Mail, his plastic pillars and a healthy dose of reality. The unexpected result might then have prompted him to have the subsequent video taken down.

Yes it's an oddball thought, but it's also pretty arrogant for the manufacturer to send a faulty unit to a repair channel with such a challenge without expecting the internals to be seen (he can't really have expected Mark not to figure out the concealed fixings under the foot pads?).
« Last Edit: December 09, 2024, 10:34:14 pm by Gyro »
Best Regards, Chris
 
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Offline wraper

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #41 on: December 09, 2024, 10:42:07 pm »
What a piece of junk. I doubt I'd pay even $10 for that garbage to flip it afterwards because I'd feel shame for selling such piece of shit at all.
 

Offline themadhippy

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #42 on: December 09, 2024, 11:05:39 pm »
Quote
Mark said at 20 seconds in on his second video that the unit was sent him directly by the manufacturer.
He does,but he didnt say he had been asked to repair it by the manufacturer.maybe marks client  had it shipped directly from tom evans  after balking at a   £6k repair price
 
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Offline Xena E

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #43 on: December 09, 2024, 11:36:12 pm »
Quote
Mark said at 20 seconds in on his second video that the unit was sent him directly by the manufacturer.
He does,but he didnt say he had been asked to repair it by the manufacturer.maybe marks client  had it shipped directly from tom evans  after balking at a   £6k repair price

That would make more sense... but either way it all just seems so bizarre.

X
 

Online magic

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #44 on: December 09, 2024, 11:56:47 pm »
What a piece of junk. I doubt I'd pay even $10 for that garbage to flip it afterwards because I'd feel shame for selling such piece of shit at all.

There is more than $10 in there in tantalum caps alone.
Semiconductors too, but you would need to decap a few to identify them.

I'd take it for $10 ;D
 

Offline EEVblog

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #45 on: December 10, 2024, 12:45:46 am »
I just noticed that at 13:19 he does show the actual schematic from what is presumably the service manual in a spiral binder.
So maybe, technically, he does have a copyright claim for that bit if the service manual is proprietary?
If I remember correctly, Mark reverse-engineered the unit to make that "service manual". The circuits displayed were very similar to what might be found on the chip datasheets.

Ah, so it is, I stand corrected.
 

Offline showman

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #46 on: December 10, 2024, 01:27:37 am »
Looks like Louis Rossmann will reupload the video to his channel and will fight for it to not be removed again.
 
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Offline CatalinaWOW

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #47 on: December 10, 2024, 02:11:38 am »
The mechanical design is not robust, certainly not Post Office proof, and there are many things to be questioned in the electrical design.  But at least it does have decently low noise as shown in Marks final test sequences.

The copyright violation may be subtle.  In Mark's reverse engineered documentation package he appears to use the manufacturers name in the title block, stand alone in a separate box.  I am not a member of the legal profession but this may be unauthorized use.  I think it would have been better if he said something like "Reverse engineered approximation to product of ...."
 

Offline showman

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #48 on: December 10, 2024, 02:46:09 am »
The copyright violation may be subtle.  In Mark's reverse engineered documentation package he appears to use the manufacturers name in the title block, stand alone in a separate box.  I am not a member of the legal profession but this may be unauthorized use.  I think it would have been better if he said something like "Reverse engineered approximation to product of ...."
I don't see how this has anything to do with copyright. Perhaps you mean trademark, which it might have something to do with, but I doubt it as well.
 

Offline EEVblog

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Re: £25,000 Audiophile Pre-Amp repair video by Mend It Mark
« Reply #49 on: December 10, 2024, 03:23:12 am »
The copyright violation may be subtle.  In Mark's reverse engineered documentation package he appears to use the manufacturers name in the title block, stand alone in a separate box.  I am not a member of the legal profession but this may be unauthorized use.  I think it would have been better if he said something like "Reverse engineered approximation to product of ...."
I don't see how this has anything to do with copyright. Perhaps you mean trademark, which it might have something to do with, but I doubt it as well.

Yes, nothing to do with copyright. Using a Trademarked name or logo for identification purposes has been well established in trademark case law, so almost certianly not an issue. Although as is always the case in trademark law, the deepest pocket destroys the shallowest pocket.
 
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