[Rob Watts]

@Rob Watts
While following the PSAudio DirectStream threads regarding their regular DAC firmware updates, i was surprised that several final release candidates were auditioned prior to each release - and the code was mostly functionally identical .. with only changes in signal flow, timing, parallel -vs- serial, compilation switches, etc. Yet, each variant sounded 'different' - and the final release determination was based on a compromise. What this is telling me is that we are so near the bleeding edge of silicon switching noise and ground plane disturbances affecting even a 'perfect' DAC algorithm.

I know you have a handle on the small details ... but some of the claims of M-Scaler taps and ultra-low noise floor affecting perceived sonics seem so incredulous. Is there an end to all this? Its starting to sound silly. Are humans blessed with a quantum computer in our heads that can do math at 80-bits precision in real time? Or, like the PSAudio firmware variants ...are you just shuffling around the electrons and seeing 'real' differences where there are none?
- No offence or disrespect intended, please ... i am just curious of your comments.
Thanks
Dan

I agree with you; talking of small signal errors at -350 dB upsetting depth performance is just plane crazy. Objectively, it makes no sense that the ear/brain can be so sensitive.

But... Listen to real sounds. I am typing this at dawn in the Welsh countryside. My window is ajar, and I can hear sheep 200 feet away - and it sounds 200 feet away. From the farm 2 miles away a dog barks; it clearly sounds 2 miles away. Do this on reproduced audio and things sounds comparatively flat; no-body would claim that a recording of a dog barking 2 miles away actually sounds anything like two miles distant.

Now when I listen to noise shapers, and change the performance of noise shapers, I can easily and reliably hear changes in depth perception. And when I measure the digital domain performance of the noise shaper, there is a correlation between the small signal performance of the noise shaper and depth perception; so a 200 dB noise shaper (this means it can't resolve small signals below -200 dB accurately) has poorer depth than a 220 dB noise shaper - and continuing this process on I ended up with 350 dB performance (and I could still hear improvements from 330 to 350).

Now these numbers really do not make any kind of rational sense. And when I observed this, I was convinced that the most likely explanation was that the noise shaper performance was merely a proxy for something else going on - for example an analogue aberration that was magnifying the effect of the noise shapers, for example folding down from RF frequencies (where we do not get anything like 350 dB performance).

But I soon found that idea was wrong; I use noise shapers in digital only truncators, where you are going from say 56 bits at 768 kHz down to 24 bits. So it's all digital; and again, listening to these noise shapers gave exactly the same result; 350 dB performance had better depth than 300 dB digital only noise shapers.

But these performance numbers still make me uncomfortable; but I have repeated it with different pulse array noise shapers, and truncator noise shapers about half a dozen times with different designs - and I get exactly the same result. And I can hear you saying it is confirmation bias, because the listening tests are not double blind, and I know which noise shaper I am listening too - and I can't rule that out as a possibility. But I do plenty of listening tests where I get zero difference when I am actually expecting a sound quality change as I conduct my listening tests to be as accurate as possible. Because of these multiple tests, I am convinced that these results are real.

But if indeed noise shapers are required to such accuracy, then the ADC noise shaper itself must also need this performance. So the Davina ADC project is an 11th order 104 MHz noise shaper, and is capable of better than 350 dB performance. So to test this aspect I have the ability to turn off different integrators and hence adjust the noise shaper performance. I plan to make two recordings using two Davina's from the same mic feed, with different noise shaper performances; I will then publish the files with random file names and ask people to say which file has the better depth perception. This will be a blind listening test and will give more credence to whether this effect is real or not. Of course, it may be possible that ADC noise shapers do not show this problem - then I will have a serious headache to explain why DAC noise shapers are different!

I note actually with interest your comment "Are humans blessed with a quantum computer in our heads that can do math at 80-bits precision in real time?" And that recalled an article in New Scientist about neurons. Apparently, neuron scientists do not know whether a neuron is a simple 1 bit processor (it's output dependent solely on other inputs) or whether it has internal memory and quantum processing internally, so is actually an N bit quantum processor with a 1 bit output. That's a fairly fundamental knowledge hole... And we have no idea how the brain calculates depth perception to the amazing resolution it actually has. And I am not aware of any published psycho-acoustic papers on the technical requirements for depth perception...

Rob

 

[514077]

I agree with you; talking of small signal errors at -350 dB upsetting depth performance is just plane crazy. Objectively, it makes no sense that the ear/brain can be so sensitive.

But... Listen to real sounds. I am typing this at dawn in the Welsh countryside. My window is ajar, and I can hear sheep 200 feet away - and it sounds 200 feet away. From the farm 2 miles away a dog barks; it clearly sounds 2 miles away. Do this on reproduced audio and things sounds comparatively flat; no-body would claim that a recording of a dog barking 2 miles away actually sounds anything like two miles distant.

Now when I listen to noise shapers, and change the performance of noise shapers, I can easily and reliably hear changes in depth perception. And when I measure the digital domain performance of the noise shaper, there is a correlation between the small signal performance of the noise shaper and depth perception; so a 200 dB noise shaper (this means it can't resolve small signals below -200 dB accurately) has poorer depth than a 220 dB noise shaper - and continuing this process on I ended up with 350 dB performance (and I could still hear improvements from 330 to 350).

Now these numbers really do not make any kind of rational sense. And when I observed this, I was convinced that the most likely explanation was that the noise shaper performance was merely a proxy for something else going on - for example an analogue aberration that was magnifying the effect of the noise shapers, for example folding down from RF frequencies (where we do not get anything like 350 dB performance).

But I soon found that idea was wrong; I use noise shapers in digital only truncators, where you are going from say 56 bits at 768 kHz down to 24 bits. So it's all digital; and again, listening to these noise shapers gave exactly the same result; 350 dB performance had better depth than 300 dB digital only noise shapers.

But these performance numbers still make me uncomfortable; but I have repeated it with different pulse array noise shapers, and truncator noise shapers about half a dozen times with different designs - and I get exactly the same result. And I can hear you saying it is confirmation bias, because the listening tests are not double blind, and I know which noise shaper I am listening too - and I can't rule that out as a possibility. But I do plenty of listening tests where I get zero difference when I am actually expecting a sound quality change as I conduct my listening tests to be as accurate as possible. Because of these multiple tests, I am convinced that these results are real.

But if indeed noise shapers are required to such accuracy, then the ADC noise shaper itself must also need this performance. So the Davina ADC project is an 11th order 104 MHz noise shaper, and is capable of better than 350 dB performance. So to test this aspect I have the ability to turn off different integrators and hence adjust the noise shaper performance. I plan to make two recordings using two Davina's from the same mic feed, with different noise shaper performances; I will then publish the files with random file names and ask people to say which file has the better depth perception. This will be a blind listening test and will give more credence to whether this effect is real or not. Of course, it may be possible that ADC noise shapers do not show this problem - then I will have a serious headache to explain why DAC noise shapers are different!

I note actually with interest your comment "Are humans blessed with a quantum computer in our heads that can do math at 80-bits precision in real time?" And that recalled an article in New Scientist about neurons. Apparently, neuron scientists do not know whether a neuron is a simple 1 bit processor (it's output dependent solely on other inputs) or whether it has internal memory and quantum processing internally, so is actually an N bit quantum processor with a 1 bit output. That's a fairly fundamental knowledge hole... And we have no idea how the brain calculates depth perception to the amazing resolution it actually has. And I am not aware of any published psycho-acoustic papers on the technical requirements for depth perception...

Rob

All I can say is that I like rlistening to people who aren't afraid to question even their questions. Thanks for the rare gift of your posts, Rob.

 

[Mython]

@Rob Watts
some of the claims of M-Scaler taps and ultra-low noise floor affecting perceived sonics seem so incredulous. Is there an end to all this? Its starting to sound silly. Are humans blessed with a quantum computer in our heads that can do math at 80-bits precision in real time?

Hmmm... interesting (and very common) assumption that all human audio perception is a function of brain activity... (scuttles away before a can of worms scatters all over the floor..!)

 

[musickid]

Rob's technology and its real world implementations would surely make a good topic for a PHD thesis??maybe.

 

[DaveRedRef-III]

Hi Rob
I wondered if you could update us on current progress with your new design power amps?

 

[Rob Watts]

The prototypes are being built now.

Although each block of the Power Pulse Array I have done before, I have not put all of this together before in one unit; so it's not something that I can put a realistic time line too. And who knows how many cycles of prototypes will be needed... It won't get released I am 100% happy with it, both subjectively and measurement wise.

I have been using my Dave with small loudspeakers directly, and it sounds stunning in terms of depth. So for sure I am expecting great things from this technology.

 

[JaZZ]

The prototypes are being built now.

Although each block of the Power Pulse Array I have done before, I have not put all of this together before in one unit; so it's not something that I can put a realistic time line too. And who knows how many cycles of prototypes will be needed... It won't get released I am 100% happy with it, both subjectively and measurement wise.

I have been using my Dave with small loudspeakers directly, and it sounds stunning in terms of depth. So for sure I am expecting great things from this technology.

Thanks, Rob! And don't forget to add an output for electrostatic earspeakers!

 

[DaveRedRef-III]

Jazz
(Sorry off topic Rob)
I think I recall you mentioning you built your own speakers before. I have just watched this short film by Piega on building the Coax ribbon driver. I am shocked that they haven't automated the majority of this process. It's a great product (I am a big fan) but it's like going back 60 years!

http://www.piega.info/pdf/piega_lang_mittel.mp4

Edit: I guess the low volume runs preclude the cost of automating the production of this driver

 

[Rob Watts]

Oh that was merely me as a teenager making boxes to put drive units in...

 

[DaveRedRef-III]

Oh that was merely me as a teenager making boxes to put drive units in...

I seem to recall Jazz mentioned this was a hobby of his Rob

 

[JaZZ]

Yeah, it was a great hobby, indeed – thanks, Dave, for asking and for the Piega link! Very interesting! After watching the video I can very well imagine that it's difficult (if not impossible) to produce such a «ribbon» transducer by automated processes. I've never been into the business, though, so I don't really know. My own manufacturing methods were even less automated, as I also had to make the membrane myself, including cutting and glueing the aluminum conductor traces.

The Piega drivers aren't really ribbon drivers, they're classic orthodynamic / planar magnetic drivers, in contrast to mine – which on their part lacked the necessity for a transformer, since they had an amplifier-compatible impedance of around 4 Ω thanks to the aluminum-foil traces glued on a polyester foil instead of one piece of aluminum foil. And as true ribbon transducers they also avoided the great disadvantage of planar magnetic tranducers: the magnet bars blocking/compressing/reflecting/disturbing the produced sound waves – which is clearly audible.

The first time I heard Piega speakers with coaxial drivers (of an older generation) was at a Swiss HiFi show, where I also met Kurt Scheuch, the founder of Piega. It turned out that he had bought an earlier version of my below wide-range ribbon driver (usable from 600 Hz on) from Harry Pawel, the now Swiss Stax distributor, which was interested in it and intended to distribute the final version. And he confessed that founding Piega and specializing on ribbon transducers was inspired by said prototype. Well, the great disadvantage of my design was the instability of the contacts at the current collectors which worked by mere pressure between an etched circuit board and the aluminum traces – this despite gold plating. So it was some kind of letdown despite the fascinating sound. Later I had to give up my hobby due to hearing problems (tinnitus and some kind of hyperacusis – which I have learned to live with in the meantime), while listening to headphones was barely affected. At the same time I'm also glad to have left this restless phase of my life behind.

Active membrane area: 19 x 132 mm / 25 cm²

 

[Rob Watts]

I seem to recall Jazz mentioned this was a hobby of his Rob

Mia culpa.

Actually my first experience of true High-end Hi-Fi was with my electronics teacher's system when I was 16. He had a set of loudspeakers that had the Decca ribbon tweeters - of course time is not accurate, but my recollections were of a fantastically detailed yet sweet sounding treble.

Then there was the full range Apogee ribbon loudspeakers in the 1980's and 90's - the 1 ohm amp killers - these had the finest timbre variations I have ever heard from a set of loudspeakers. Its a shame the company was closed in 1999.

 

[JaZZ]

Mea culpa.

Actually my first experience of true High-end Hi-Fi was with my electronics teacher's system when I was 16. He had a set of loudspeakers that had the Decca ribbon tweeters - of course time is not accurate, but my recollections were of a fantastically detailed yet sweet sounding treble.

Then there was the full range Apogee ribbon loudspeakers in the 1980's and 90's - the 1 ohm amp killers - these had the finest timbre variations I have ever heard from a set of loudspeakers. Its a shame the company was closed in 1999.

Yes, ribbon transducers are really something special. I had four pairs of Decca/Kelly ribbon tweeters for experimenting, and they were the ear-opener as to how detailed, smooth and natural treble can sound. Accidentally I was just enjoying Kim Carnes' «Bette Davis' Eyes» through the Hugo² on the balcony a few minutes ago, selected by the FiiO X5 II's shuffle algorithm – which was the key tune with the Decca ribbons (with a homemade wooden horn at that moment). I also remember well the Apogees. I liked them – but they were out of my budget, and my apartment was too small for them.

 

[DaveRedRef-III]

Yeah, it was a great hobby, indeed – thanks, Dave, for asking and for the Piega link! Very interesting! After watching the video I can very well imagine that it's difficult (if not impossible) to produce such a «ribbon» transducer by automated processes. I've never been into the business, though, so I don't really know. My own manufacturing methods were even less automated, as I also had to make the membrane myself, including cutting and glueing the aluminum conductor traces.

The Piega drivers aren't really ribbon drivers, they're classic orthodynamic / planar magnetic drivers, in contrast to mine – which on their part lacked the necessity for a transformer, since they had an amplifier-compatible impedance of around 4 Ω thanks to the aluminum-foil traces glued on a polyester foil instead of one piece of aluminum foil. And as true ribbon transducers they also avoided the great disadvantage of planar magnetic tranducers: the magnet bars blocking/compressing/reflecting/disturbing the produced sound waves – which is clearly audible.

The first time I heard Piega speakers with coaxial drivers (of an older generation) was at a Swiss HiFi show, where I also met Kurt Scheuch, the founder of Piega. It turned out that he had bought an earlier version of my below wide-range ribbon driver (usable from 600 Hz on) from Harry Pawel, the now Swiss Stax distributor, which was interested in it and intended to distribute the final version. And he confessed that founding Piega and specializing on ribbon transducers was inspired by said prototype. Well, the great disadvantage of my design was the instability of the contacts at the current collectors which worked by mere pressure between an etched circuit board and the aluminum traces – this despite gold plating. So it was some kind of letdown despite the fascinating sound. Later I had to give up my hobby due to hearing problems (tinnitus and some kind of hyperacusis – which I have learned to live with in the meantime), while listening to headphones was barely affected. At the same time I'm also glad to have left this restless phase of my life behind.

Active membrane area: 19 x 132 mm / 25 cm²

I didn't realise you had a part in what eventually developed into the Piega story. Must have been a rewarding period of your life. Not easy I am sure but rewarding nonetheless.

I intend at some point to visit Piega in Zurich for a guided tour. I certainly appreciate their tech and they are very helpful people. The coax driver in particular is an excellent driver. Very fast, detailed and natural.

 

[dmance]

@Rob Watts

There is some crazy stuff happening using deep learning and Google's open tensorflow api. Check out 'Two Minute Papers' https://www.youtube.com/user/keeroyz
for stunning advances in image interpolation from low resolution or other sample input. I know people are applying this technique to audio.
I'll keep an eye on this and ...I'm sure something akin to super high res audio interpolation from CD source is coming.
Maybe you can use a BLU2 to train the Google engine. Say ...convert 1000 tracks from CD to 16fs ...ingest data to tensorflow then see how a new track compares: BLU2 vs deep learning output. ..just an idea for an online cloud based Blu2.