Can anyone explain the tech of £25,000 Audiophile Pre-Amp from Mend It Mark?

[tszaboo]

It's not a problem until you realize that it requires capacitors, then it's a problem

Why is it a problem? It isn't as though the extra cost is an issue.

When you have a gain that's 1000x than a few mv offset can drive the output to the rail. Even if it doesn't your offset can change with temperature, time, humidity. Overall, it can even produce audible noise.
Also, Elko can be noisy, at least I measured them to have more noise than not having them.

[tom66]

Also, in his explanation about the noise reduction he states the signal doubles while the noise is reduced. That's also not correct.

He states that the combined noise outputs of two parallel op amps "cancel each other out" somewhat. I think this is a loose explanation because two random sources can't "cancel" each other. As I see it, if these two amps have a gain of 100, and if each has a noise level of 1mV, then the noise voltage at the summing junction would be 141mV. That's because the noise power doubles, but the voltage only increases by sqrt(2). Moreover, since the noise power is what we hear, how can this gizmo provide any measurable or detectable benefit?

I think the advantage here is that you can have four opamps at a gain of 25 summed together using resistors, so the noise gain (at the differential stage in the opamp) is lower.

[Zero999]

It's not a problem until you realize that it requires capacitors, then it's a problem

Why is it a problem? It isn't as though the extra cost is an issue.

When you have a gain that's 1000x than a few mv offset can drive the output to the rail. Even if it doesn't your offset can change with temperature, time, humidity. Overall, it can even produce audible noise.

AC coupling eliminates that, because the gain at DC is one.

Also, Elko can be noisy, at least I measured them to have more noise than not having them.

Then use polypropylene or C0G.

EDIT:
I had another look through the video. I can now see why the offset voltage needs to be low. I missed the fact the resistor values used in the non-inverting amplifiers are very low, just 1k33 and 2R2, which is presumably to keep the noise as low as possible, so 4700µF capacitors would have to be used to get a lower cut-off of 16Hz.
https://youtu.be/uJ35ufUh2Tw?t=711

[tszaboo]

It's not a problem until you realize that it requires capacitors, then it's a problem

Why is it a problem? It isn't as though the extra cost is an issue.

When you have a gain that's 1000x than a few mv offset can drive the output to the rail. Even if it doesn't your offset can change with temperature, time, humidity. Overall, it can even produce audible noise.

AC coupling eliminates that, because the gain at DC is one.

Also, Elko can be noisy, at least I measured them to have more noise than not having them.

Then use polypropylene or C0G.

Unless you have capacitors in the feedback of the opamp, turning it into a BPF with gain, the DC offset will have the same sort of gain as the AC signal. But this is not working with for example Sallen-key topology maybe with Multiple path filters. IDK, I usually don't use those as the gain is hard to adjust.
And the topology used here definitely has the same offset gain as signal gain.

[Stringwinder]

On old vinyl dynamic range was limited but no dramatic changes (improvements !?) was made to the music.
Early digital media (CD's) kept the dynamics but got rid of the vinyl noise.
Nowadays despite 24 bit/192 kHz lots of music is processed to death in mastering.
Dynamic range is completly gone in some genres, illustration shows an example.
Six decibels less dynamic range is A LOT if you are used to the full range.
"Remastered" is a foul swear word if you like the dynamics of live music.

A useful tool to see what is left of the music after smothering (also called "mastering").
https://www.lts.a.se/ljudteknik/masvis/

So now in the digital era all music sounds so much better?
(... or is it "Music in - Garbage out"?)

[Zero999]

It's not a problem until you realize that it requires capacitors, then it's a problem

Why is it a problem? It isn't as though the extra cost is an issue.

When you have a gain that's 1000x than a few mv offset can drive the output to the rail. Even if it doesn't your offset can change with temperature, time, humidity. Overall, it can even produce audible noise.

AC coupling eliminates that, because the gain at DC is one.

Also, Elko can be noisy, at least I measured them to have more noise than not having them.

Then use polypropylene or C0G.

Unless you have capacitors in the feedback of the opamp, turning it into a BPF with gain, the DC offset will have the same sort of gain as the AC signal. But this is not working with for example Sallen-key topology maybe with Multiple path filters. IDK, I usually don't use those as the gain is hard to adjust.
And the topology used here definitely has the same offset gain as signal gain.

Refer to my edit.

Another way round this is to use a couple of op-amps as a capacitance multiplier.

https://en.wikipedia.org/wiki/Capacitance_multiplier

[themadhippy]

On old vinyl dynamic range was limited but no dramatic changes (improvements !?) was made to the music.
Early digital media (CD's) kept the dynamics but got rid of the vinyl noise.
Nowadays despite 24 bit/192 kHz lots of music is processed to death in mastering.

Hallelujah brother .compress the crap out of everything, no one will care/notice.call it a remastered super enhanced version  and  even though they've already bought it on vinyl and cd we can flog it to them a third time.

[SiliconWizard]

On old vinyl dynamic range was limited but no dramatic changes (improvements !?) was made to the music.
Early digital media (CD's) kept the dynamics but got rid of the vinyl noise.
Nowadays despite 24 bit/192 kHz lots of music is processed to death in mastering.

Yes. This is all for market reasons. A large fraction of the listeners listen to music on small gear that requires heavy compression for music to be audible.
So they do compress. A lot. And then, they add some. Like for processed food in which they add a lot of sugar and artificial sweeteners to make it taste "pleasing" when it actually just ruins food, but we still like it.

[BrianHG]

On old vinyl dynamic range was limited but no dramatic changes (improvements !?) was made to the music.
Early digital media (CD's) kept the dynamics but got rid of the vinyl noise.
Nowadays despite 24 bit/192 kHz lots of music is processed to death in mastering.

Yes. This is all for market reasons. A large fraction of the listeners listen to music on small gear that requires heavy compression for music to be audible.
So they do compress. A lot. And then, they add some. Like for processed food in which they add a lot of sugar and artificial sweeteners to make it taste "pleasing" when it actually just ruins food, but we still like it.

The problem is you just cant return an opened purchased CD if you find out the recording/mastering quality is crap.  It almost makes it worth it to pirate the source in advance, then make sure it is good, then make sure the CD you buy is a matching pressing of the pirated version you have.

I have a collection of my favorite music which were first generation CD recordings from before the mid 90's, before the loudness wars came into full bloom.  By every measure, my versions of my old favorite prog. rock and classical albums roast all the remastered garbage which came after.  In fact, way back on a private music community forum, when comparisons were done, I easily demonstrated those who purchased newly re-mastered versions of their music that all the new CD had were a +10db volume gain applied to them with a peak limiter.  Digitally lowering the volume of the new CD by 10db basically made the new CD almost sound like the old one, but worse while since some audio equipment was still hiss filled in those days at higher volumes, I instructed those to rip their old CD and add a simple +6db gain to the album and burn a new CD.  And wouldn't you know it, they were pissed beyond belief that they threw out +30$ for those remastered version which where revealed to be complete bullshit lower quality garbage.

[SteveThackery]

I easily demonstrated those who purchased newly re-mastered versions of their music that all the new CD had were a +10db volume gain applied to them with a peak limiter.  Digitally lowering the volume of the new CD by 10db basically made the new CD almost sound like the old one, but worse while since some audio equipment was still hiss filled in those days at higher volumes, I instructed those to rip their old CD and add a simple +6db gain to the album and burn a new CD.

I don't get this. Digitally lowering the volume won't undo the damage done by that peak limiter.

[coppice]

I have a collection of my favorite music which were first generation CD recordings from before the mid 90's, before the loudness wars came into full bloom.  By every measure, my versions of my old favorite prog. rock and classical albums roast all the remastered garbage which came after.  In fact, way back on a private music community forum, when comparisons were done, I easily demonstrated those who purchased newly re-mastered versions of their music that all the new CD had were a +10db volume gain applied to them with a peak limiter.  Digitally lowering the volume of the new CD by 10db basically made the new CD almost sound like the old one, but worse while since some audio equipment was still hiss filled in those days at higher volumes, I instructed those to rip their old CD and add a simple +6db gain to the album and burn a new CD.  And wouldn't you know it, they were pissed beyond belief that they threw out +30$ for those remastered version which where revealed to be complete bullshit lower quality garbage.

Was that written as a joke? On the internet its often not clear.

[BrianHG]

I easily demonstrated those who purchased newly re-mastered versions of their music that all the new CD had were a +10db volume gain applied to them with a peak limiter.  Digitally lowering the volume of the new CD by 10db basically made the new CD almost sound like the old one, but worse while since some audio equipment was still hiss filled in those days at higher volumes, I instructed those to rip their old CD and add a simple +6db gain to the album and burn a new CD.

I don't get this. Digitally lowering the volume won't undo the damage done by that peak limiter.

No it does not, but, it made my point to the one saying that their new +30$ version of their CD was bullshit when they lowered the volume and the sound between the original and new one with a matched volume could be compared side by side as being absurdly close except for when the limiter kept kicking in during the vocals mixed with bass drum.  (Also, the waveform on the audio editor looked like some sort of puking blob compared to the original)  The guy then realized that his audio equipment amp had an audio quality issue when turning up the volume knob for the original CD to match the new one's volume.  Not that having a louder CD was actually better quality.

[BrianHG]

I have a collection of my favorite music which were first generation CD recordings from before the mid 90's, before the loudness wars came into full bloom.  By every measure, my versions of my old favorite prog. rock and classical albums roast all the remastered garbage which came after.  In fact, way back on a private music community forum, when comparisons were done, I easily demonstrated those who purchased newly re-mastered versions of their music that all the new CD had were a +10db volume gain applied to them with a peak limiter.  Digitally lowering the volume of the new CD by 10db basically made the new CD almost sound like the old one, but worse while since some audio equipment was still hiss filled in those days at higher volumes, I instructed those to rip their old CD and add a simple +6db gain to the album and burn a new CD.  And wouldn't you know it, they were pissed beyond belief that they threw out +30$ for those remastered version which where revealed to be complete bullshit lower quality garbage.

Was that written as a joke? On the internet its often not clear.

What are you getting at?
It is not a joke.
This really happened back in ~2004.
Such groups dealt exclusively with tracking CD revisions through perfect bit error free ripping tools, cheksum databases and almost exclusively using .flac file format released a few years earlier.

Maybe read my response here: https://www.eevblog.com/forum/chat/can-anyone-explain-the-tech-of-25-000-audiophile-pre-amp-from-mend-it-mark/msg5752279/#msg5752279

[Stringwinder]

If the volume control in an amplifier uses a "loudness" function to compensate
for the Fletcher Munson curves (equal loudness) there is a difference in the
sound you hear. Low input signal level (higher volume setting) gives less bass
and treble compared to higher signal level (and a lower volume control setting).
Having the same level from all sources makes it easier to do other "audio tunings"
to get a consistent result (according to your own taste).

..so I sort of agree with BrianHG on this.

[coppice]

I have a collection of my favorite music which were first generation CD recordings from before the mid 90's, before the loudness wars came into full bloom.  By every measure, my versions of my old favorite prog. rock and classical albums roast all the remastered garbage which came after.  In fact, way back on a private music community forum, when comparisons were done, I easily demonstrated those who purchased newly re-mastered versions of their music that all the new CD had were a +10db volume gain applied to them with a peak limiter.  Digitally lowering the volume of the new CD by 10db basically made the new CD almost sound like the old one, but worse while since some audio equipment was still hiss filled in those days at higher volumes, I instructed those to rip their old CD and add a simple +6db gain to the album and burn a new CD.  And wouldn't you know it, they were pissed beyond belief that they threw out +30$ for those remastered version which where revealed to be complete bullshit lower quality garbage.

Was that written as a joke? On the internet its often not clear.

What are you getting at?
It is not a joke.
This really happened back in ~2004.
Such groups dealt exclusively with tracking CD revisions through perfect bit error free ripping tools, cheksum databases and almost exclusively using .flac file format released a few years earlier.

They recompressed a huge amount of music in the 1990s, cranked up the volume, and used soft clipping algorithms to minimise the effect of the overloads. You can turn down the volume control, but you can't get the dynamic range back, and the distortion from all the clipping is still there. Lately they've been going back to the old material, running it through Melodyne, and taking away all the pitch imperfections. They just can't stop taking the music we loved, and turning it into something fresh and new and bogus and unpleasant.

[Coordonnée_chromatique]

a "loudness" function to compensate for the Fletcher Munson curves (equal loudness) there is a difference in thesound you hear.

It works only if the loudness response of the loudspeaker is linear within all the frequency range (in the room at the listening position)... this is perhaps why it have disappeared 

[langwadt]

I have a collection of my favorite music which were first generation CD recordings from before the mid 90's, before the loudness wars came into full bloom.  By every measure, my versions of my old favorite prog. rock and classical albums roast all the remastered garbage which came after.  In fact, way back on a private music community forum, when comparisons were done, I easily demonstrated those who purchased newly re-mastered versions of their music that all the new CD had were a +10db volume gain applied to them with a peak limiter.  Digitally lowering the volume of the new CD by 10db basically made the new CD almost sound like the old one, but worse while since some audio equipment was still hiss filled in those days at higher volumes, I instructed those to rip their old CD and add a simple +6db gain to the album and burn a new CD.  And wouldn't you know it, they were pissed beyond belief that they threw out +30$ for those remastered version which where revealed to be complete bullshit lower quality garbage.

Was that written as a joke? On the internet its often not clear.

What are you getting at?
It is not a joke.
This really happened back in ~2004.
Such groups dealt exclusively with tracking CD revisions through perfect bit error free ripping tools, cheksum databases and almost exclusively using .flac file format released a few years earlier.

They recompressed a huge amount of music in the 1990s, cranked up the volume, and used soft clipping algorithms to minimise the effect of the overloads. You can turn down the volume control, but you can't get the dynamic range back, and the distortion from all the clipping is still there. Lately they've been going back to the old material, running it through Melodyne, and taking away all the pitch imperfections. They just can't stop taking the music we loved, and turning it into something fresh and new and bogus and unpleasant.

a lot of music not only is pitch corrected and drums are aligned to a grid and sometimes replaced by samples

[coppice]

They recompressed a huge amount of music in the 1990s, cranked up the volume, and used soft clipping algorithms to minimise the effect of the overloads. You can turn down the volume control, but you can't get the dynamic range back, and the distortion from all the clipping is still there. Lately they've been going back to the old material, running it through Melodyne, and taking away all the pitch imperfections. They just can't stop taking the music we loved, and turning it into something fresh and new and bogus and unpleasant.

a lot of music not only is pitch corrected and drums are aligned to a grid and sometimes replaced by samples

The Wings of Pegasus channel on YouTube is making more and more videos bringing the extent of this to light. There doesn't seem to be anything they won't change. Even correcting singers famous for being naturally precise hitting the right pitch.

That said, I don't know any DSP engineer who has not been deeply impressed by what Melodyne can achieve. Whoever is behind that is brilliant.

[themadhippy]

[langwadt]

They recompressed a huge amount of music in the 1990s, cranked up the volume, and used soft clipping algorithms to minimise the effect of the overloads. You can turn down the volume control, but you can't get the dynamic range back, and the distortion from all the clipping is still there. Lately they've been going back to the old material, running it through Melodyne, and taking away all the pitch imperfections. They just can't stop taking the music we loved, and turning it into something fresh and new and bogus and unpleasant.

a lot of music not only is pitch corrected and drums are aligned to a grid and sometimes replaced by samples

The Wings of Pegasus channel on YouTube is making more and more videos bringing the extent of this to light. There doesn't seem to be anything they won't change. Even correcting singers famous for being naturally precise hitting the right pitch.

That said, I don't know any DSP engineer who has not been deeply impressed by what Melodyne can achieve. Whoever is behind that is brilliant.

https://youtu.be/1bZ0OSEViyo?si=gzLwmwj2MlYDZkrZ

[tszaboo]

a lot of music not only is pitch corrected and drums are aligned to a grid and sometimes replaced by samples

You mean the ones that were actually recorded, and not put together in someone's basement in the first place.

Which I'm saying a bit tongue in a cheek. I started liking Electro-swing and Synthwave, most of that were never recorded, or some is only using ~100 year old music samples, and electronic stuff.

[BrianHG]

The perfect example of progress in reverse.
For the last 2, you might as well go right down to 8bit sound.

[CatalinaWOW]

I was never much of an audiophile, and older ears have left hearing less and less.  But this is way below even my standards.  Fortunately I have older CDs and vinyl, all transcribed to mp3 for convenience.  And I have the chance to clean up the pips and snaps while I am at it

[wilfred]

Will Mend it Mark ever have the video restored to his channel? It doesn't seem fair for him to be denied the full benefit of his creative work. All these other channels re-uploading the video may help him gain audience. I hope it does. I like his channel.

I got the impression YT never actually told him what the copyright issue was.

[Stringwinder]

After finding what "Audio Science Review" had to say about his design and
copyright claims (in over 200 posts) it is rumoured that production will
be moved to Llareggub, famous from Dylan Thomas drama "Under Milkwood".