USB audio cracked... finally!

[mmerrill99]

24 minutes ago, PeterSt said:

Audio (as in audiophile terminology) is a totally different world for uncountable reasons. The most complex of all, perhaps

The accountable reasons are that there is a digital to analog interface - staying in the digital domain is fine for all the interfaces - transitioning to the analog domain is where the issues arise & our pattern matching processing is picking up on the issues

[PeterSt]

2 minutes ago, manisandher said:

Probably didn't get the graphs up quickly enough...

 

Nope. People might refresh the page to see them

[jabbr]

5 minutes ago, marce said:

We use signal integrity software (as well as physical checking of waveforms) and only for the hard interfaces, if USB audio is that hard why do I see NO evidence of proper signal integrity engineering...

 

Most DAC manufacturers outsource their $50 interface or depend on $5-10 SoC to do everything...

[PeterSt]

2 minutes ago, mmerrill99 said:

The accountable reasons are that there is a digital to analog interface - staying in the digital domain is fine for all the interfaces - transitioning to the analog domain is where the issues arise & our pattern matching processing is picking up on the issues

 

Not that I disagree - not at all.

But this topic is about a worse subject : that the digital domain only already matters (and a LOT) and that again only within the USB transfer (which is digital from where it leaves the PC to its I2S output).

Btw in front of that we have again a pile of digital-only, which is merely what Jud referred to. And nothing sounds the same wherever you can change elements or settings like buffer sizes etc.

 

[PeterSt]

12 minutes ago, marce said:

if USB audio is that hard why do I see NO evidence of proper signal integrity engineering...

 

Because audio in this realm is not-error-corrected digital data.

 

That it is subject to jitter - which is audible - in the D/A process is something else.

 

You have some nice headphones or more expensive speakers, right ? Just asking.

Btw, a fine turn table also suffices. 

[Jud]

22 minutes ago, marce said:

We use signal integrity software (as well as physical checking of waveforms) and only for the hard interfaces, if USB audio is that hard why do I see NO evidence of proper signal integrity engineering...

 

@marce, if you were willing, it would be very interesting for me, and hopefully others, to learn something about the following:

 

- The signal integrity software you use, if it is not internal custom stuff;

 

- Ditto for the signal integrity verification measurements you perform, and the equipment you use to do it;

 

- The more significant sorts of things you are thinking about when you mention "proper signal integrity engineering."

[marce]

33 minutes ago, PeterSt said:

 

OK, next attempt. 

 

So we have the subject of this topic - the cable. If you are certain that USB cables don't make a difference for audio, then I think it is better to stop reading.

 

Then we have my personal idea that at this moment (and for me / Phasure) the most in audio can be advanced by means of USB improvements. You may call it tweaks, but those sound only different. So improvements is key.

Of course it is (or should be) moot to you that this is my thinking. Fact is that since I think like this, the one after the other real improvement pops up (ask the customers).

 

Data integrity ? no. For many maybe yes, but not for me as the USB errors are shown in real time. They should not be there and they are not there. And *if* they are there you will hear clicks or pops or scratches, up to silence when things really fail. Btw, more USB cables fail on this than not.

Sadly, we can also say : Data integrity ? Yes. But this is more of the voodoo kind and the hope that less jitter in USB data sounds better or technical is better for the further work out of the D/A process. You may have seen me write about that I am not certain about this. Still the Phasure NOS1a/G3 too has a "femto clock" for its USB interface. Does it help ? yes, together with the remaining upgraded parts it does. On its own ? I don't think so, or it is inaudible.

 

Higher bandwidth USB ? well, this is a very indirect one, with the notice that this is about the upsampling possibility the DAC can digest (mind you, which thus the computer can spit out). Not so important ? ... only know that the filtering (which is that upsampling) "makes" the sound.

 

I'll stop for now but notice that this is all interface related only and that our interface is USB.

I do not believe cables can as as a DSP and alter the digital data to alter the sound that means the subtle changes many report changing cables, it is digital after all. never noticed many USB cables failing go some citation... Femto clocks for audio... A bloody lot of overkill... I am playing devils advocate here a bit, as I often play around with digital/analogue interfaces and we dont have half the problems that digital audio seems to have.

[marce]

13 minutes ago, Jud said:

 

@marce, if you were willing, it would be very interesting for me, and hopefully others, to learn something about the following:

 

- The signal integrity software you use, if it is not internal custom stuff;

 

- Ditto for the signal integrity verification measurements you perform, and the equipment you use to do it;

 

- The more significant sorts of things you are thinking about when you mention "proper signal integrity engineering."

I use Cadstar SIV

https://www.quadrasol.co.uk/eda/eda-products/cadstar-signal-integrity-verify/

 

I don't do the measurements the test department people for whoever I am slaving for do the measurements, variety of customers including pro audio. i tend to do a lot at Winbourne for FRL and other bespoke customers (just recently done tests boards for wavefront sensors, multi channel high speed ADC/DAC, not had half the problems some seem to have with USB audio) As mentioned on a previous thread, you also have to model the scope probes, so as well as seeing the real waveform you can add the scope loading and provide a waveform as it will be shown on the scope.

I am hearing lots of discussions on how bad USB is (and SPDIF) and have been for many moons, what I don't see is any scope shots of waveforms etc. I think we have had maybe two eye diagrams put on line in the past and that's about it... If it is such a bad interface I would have expected more investigation and information

[marce]

35 minutes ago, PeterSt said:

 

Because audio in this realm is not-error-corrected digital data.

 

That it is subject to jitter - which is audible - in the D/A process is something else.

 

You have some nice headphones or more expensive speakers, right ? Just asking.

Btw, a fine turn table also suffices. 

Er you can still do signal integrity, do a lot of real time stuff where you don't get chance to resend. Jitter is not the big problem people seem to think it is today, and can be solved at the conversion device.

[marce]

45 minutes ago, jabbr said:

 

Most DAC manufacturers outsource their $50 interface or depend on $5-10 SoC to do everything...

Yes because its a well understood and used serial interface and the devices are there where its all on chip so better for everyone.

Some of this is tickling me, I really do have some views on why some like to promote USB audio as terrible and have solutions for this...

Over and out.

[PeterSt]

23 minutes ago, marce said:

Some of this is tickling me, I really do have some views on why some like to promote USB audio as terrible and have solutions for this...

 

Of course. But we all need to make some money ?!

 

All these things sound different, up to wildly different. But being an audiophile is not your hobby, so you think it sound can not change. If audio/music *is* your hobby - and especially when it is digital audio, you automatically will seek for solutions to what your ears don't like much.

 

As for the two eye diagrams you saw, yes, you are right.

The equipment needed for this is quite unaffordable for us poor guys. Maybe you disagree ?

[89reksal]

8 hours ago, Speed Racer said:

 

You might want to reserve criticism for a product until you have a chance to hear it in action......

 

Wow! There's a novel idea.

[marce]

20 minutes ago, PeterSt said:

 

Of course. But we all need to make some money ?!

 

All these things sound different, up to wildly different. But being an audiophile is not your hobby, so you think it sound can not change. If audio/music *is* your hobby - and especially when it is digital audio, you automatically will seek for solutions to what your ears don't like much.

 

The equipment needed for this is quite unaffordable for us poor guys. Maybe you disagree ?

LOL best answer yet

 

I am an audiophile, just found proper listening tests interesting and informative so don't get to excited unless I have gnawed away at a problem and proved to myself that there is a difference present that I can hear, tenuous. There are instances where I hear differences, but I test myself firstly to determine whether I am hearing a difference or whether my perceptions are playing with me.

 

I agree for many the gear is expensive but for some of the larger concern it is not or they could hire it.

 

[marce]

1 hour ago, mmerrill99 said:

The accountable reasons are that there is a digital to analog interface - staying in the digital domain is fine for all the interfaces - transitioning to the analog domain is where the issues arise & our pattern matching processing is picking up on the issues

With digital being the best way of transporting information (remember 4-20mA interface) and the real world being analogue there are simply zillions of ADC and DAC interfaces out there, so they are well studied and most problems understood, even good old digital audio is now some 30+ years old.

[marce]

20 minutes ago, lasker98 said:

 

Wow! There's a novel idea.

Its the interface we are discussing though, I design stuff for flight refuelling should I get a pilots license. I have done some Bluetooth PCBs for a famous Ann Summers device, should I have tried it out first to get a feel for what I am working on...). Usual come back, not required though, we can discuss theory, I know a lot don't like having to discuss things that come from a less enthusiastic viewpoint but that's the beauty of debate. The main difference between me and others is I don't trust my perceptions these days like I use to, they are to easily fooled.

[jabbr]

1 hour ago, marce said:

Yes because its a well understood and used serial interface and the devices are there where its all on chip so better for everyone.

Some of this is tickling me, I really do have some views on why some like to promote USB audio as terrible and have solutions for this...

Over and out.

 

Ground loops aren't an issue between your mouse and keyboard and hard drive  ... maybe 4K monitor? ... I got started down this track when I installed a new GPU card and 4K monitor on my workstation and my Sound Devices USBPRE2 ... which I use for recording ... let out a howl... tried a few things that didn't work ... very easiest solution was to remote the music to another room over Ethernet.

 

So I guess the issue with noise and USB DAC wasn't solved after all despite all these decades of understanding

 

The question is why? I am suggesting that its not USB per se, rather the common implementations... but nonetheless I've personally experienced noise on the USB interface, and other people hear differences depending on a number of factors and there is an industry of devices that provide USB isolation/regeneration etc. I am suggesting that these are properly placed in the DAC itself.

 

Oh and the USBPRE2 works just great with my MacBook so... hmm...

[marce]

That is noise not the interface though and I agree there is a lot of it about these days. I have posted here and there quite a bit on trying to limit noise, but as I have said it is EMC engineering, how much is done on consumer audio components I couldn't say, but from the problems probably not a lot. I use wireless streaming and have my source computer shoved away somewhere under the stairs, so its hard for the noise to get through. That said I am moving and doing a lot of modifications to my new home, so a complete home music distribution system is one of my projects... should be interesting

[jabbr]

18 minutes ago, marce said:

That is noise not the interface though and I agree there is a lot of it about these days.

 

The interface, by requiring a 5V and ground at least for handshaking, goes out of its way to beg for ground loops/leakage currents -- a.k.a capacitive coupling  and that's how the noise gets into the system... trying to decouple the power/ground starts people down a rathole of solutions... let's see the first useless product I got was the Aqvox (didn't work for me) -- at the time I didn't understand why this was actually much worse ... so I've been reading  ... and so folks can do trial and error of multitudes of "solutions" which is what we are seeing ...

 

As you note, the common isolation techniques have issues with capacitive coupling. Breaking the ground loop/leakage current issues are not entirely obvious. Other interfaces have their own issues.

 

I do think that if proper design and techniques which may be obvious to you, were widely implemented, that these problems can be mitigated.

[mmerrill99]

32 minutes ago, marce said:

With digital being the best way of transporting information (remember 4-20mA interface) and the real world being analogue there are simply zillions of ADC and DAC interfaces out there, so they are well studied and most problems understood, even good old digital audio is now some 30+ years old.

30+ years & still evolving - go figure!

Can you nominate a DAC which is immune to all this & we can check it out but not one that masks improvements in USB SI i.e not one that incorporates an ASRC in or before the DAC chip itself?

[marce]

5 minutes ago, jabbr said:

 

The interface, by requiring a 5V and ground at least for handshaking, goes out of its way to beg for ground loops/leakage currents -- a.k.a capacitive coupling  and that's how the noise gets into the system... trying to decouple the power/ground starts people down a rathole of solutions... let's see the first useless product I got was the Aqvox (didn't work for me) -- at the time I didn't understand why this was actually much worse ... so I've been reading  ... and so folks can do trial and error of multitudes of "solutions" which is what we are seeing ...

 

As you note, the common isolation techniques have issues with capacitive coupling. Breaking the ground loop/leakage current issues are not entirely obvious. Other interfaces have their own issues.

 

I do think that if proper design and techniques which may be obvious to you, were widely implemented, that these problems can be mitigated.

Thinking about your last comment I revisited this and some other notes...

http://www.x2y.com/filters/TechDay09kr_hpa_Track2_1_Precision_Analog_Designs_Demand_GoodPCBLayouts _JohnWu.pdf

Again I wonder how much noise is affecting things... and with reference to mmerill99's comment, noise has increased greatly over the last decade, could this combined with cost based design (especially layout, its the most cost conscious part of any project) be one of the factors... Must dig out the notes on noise and rectification in op-amps, to see how that affects the signal.

[mmerrill99]

15 minutes ago, marce said:

Thinking about your last comment I revisited this and some other notes...

http://www.x2y.com/filters/TechDay09kr_hpa_Track2_1_Precision_Analog_Designs_Demand_GoodPCBLayouts _JohnWu.pdf

Again I wonder how much noise is affecting things... and with reference to mmerill99's comment, noise has increased greatly over the last decade, could this combined with cost based design (especially layout, its the most cost conscious part of any project) be one of the factors... Must dig out the notes on noise and rectification in op-amps, to see how that affects the signal.

Absolutely & this is what is mostly being addressed when talk about USB & the various add-on devices are being mentioned - it's mostly about noise - leakage currents which are far more prevalent now than in the past due to the proliferation of SMPS.

So when a system view is being taken the interconnection of the various devices in that system & the possible noise intermingling with the signal is the concern. Individual devices on their own may well test & measure exemplary

[PeterSt]

15 minutes ago, marce said:

Again I wonder how much noise is affecting things... and with reference to mmerill99's comment, noise has increased greatly over the last decade, could this combined with cost based design (especially layout, its the most cost conscious part of any project) be one of the factors..

 

Marce, maybe it is the other way around;

Noise in good audio systems has DEcreased largely (think system noise of 150dB down and better) which may make the noise you refer to more profound. That is, if you want to think in that direction.

I don't think it is about that anyway. I do have the idea though that you might think that mentioned 150dB is crazy and not necessary at all.

 

On another note, the equipment you may have in mind for (FFT) measurement will be 12bit or worse (but fast like 100gbps+) which is useless to audio because your noise line will be at -100dB only.

I think we live in different worlds, no matter your hobby is audio too.

 

Regards,

Peter

 

[jabbr]

14 minutes ago, marce said:

Thinking about your last comment I revisited this and some other notes...

http://www.x2y.com/filters/TechDay09kr_hpa_Track2_1_Precision_Analog_Designs_Demand_GoodPCBLayouts _JohnWu.pdf

 

 

Classic. Try this: how many circuit boards use X2Y caps, or low impedance caps, or bypass capacitor networks?

 

ala: http://www.intersil.com/content/dam/Intersil/documents/an13/an1325.pdf

http://www.analog.com/media/en/training-seminars/tutorials/MT-101.pdf

 

If there's just a 0.1 uF, the decoupling is suboptimal...

[marce]

I would not say SMPS's alone, in fact with the right layout they can be very quiet... PC's are one main culprit (to put PC's in perspective a basic mother board can be done on 8 layers these days and in some cases 6!!! when we do a PC for critical industrial applications we use 12-14 layers, mostly extra grounds for proper return paths and low EMC) , but also the plethora of wireless devices and other digital devices everywhere. Look at TVs once an analogue heaven, now a PC in everyone hammering away with a nice DDR interface (DDR is good for generating simultaneous switching noise.)

[marce]

11 minutes ago, PeterSt said:

 

Marce, maybe it is the other way around;

Noise in good audio systems has DEcreased largely (think system noise of 150dB down and better) which may make the noise you refer to more profound. That is, if you want to think in that direction.

I don't think it is about that anyway. I do have the idea though that you might think that mentioned 150dB is crazy and not necessary at all.

 

On another note, the equipment you may have in mind for (FFT) measurement will be 12bit or worse (but fast like 100gbps+) which is useless to audio because your noise line will be at -100dB only.

I think we live in different worlds, no matter your hobby is audio too.

 

Regards,

Peter

 

Sorry Peter I should have been more specific, I am referring to environmental noise EMI, how immune from noise is the majority of audio kit...