USB audio cracked... finally!

[firedog]

54 minutes ago, PeterSt said:

 

And Alex, I have been on the verge of stipulating that we could exchange some gear so I could use the ISO-Regen for this.  But I didn't because I'd have to wait for it while I have time for this today and probably not on any other day. Well, as you know, I promised you something ... 2 years ago ? And now this day has come.

OK, my mind is set to it finally.

 

One other thing : I am not on to subjective judgments other than what many know already, similar to what a few now know about the sound of the Lush cable. So my idea it to show why a cable etc. sounds like it does and then by means of the eye diagram.

So put yourself back one year. What was the advice : put the Regen close to the DAC. That is fine and we will see why that is.

I hope.

Peter-

Tried to find info about the Lush cable and how to order. Couldn't find it. 

Can someone direct me?

[BigAlMc]

Hi @firedog

 

I'm not Peter obviously but I ordered mine by emailing Peter:

 

Sales @ phasure dotcom

 

Think the info is all on the forums at Phasure but I'm not registered over there so not sure if there's more info or a better summary. Try this thread

 

http://www.phasure.com/index.php?topic=3854.0

 

Cheers,

Alan

[Jud]

1 hour ago, PeterSt said:

And Alex, I have been on the verge of stipulating that we could exchange some gear so I could use the ISO-Regen for this.  But I didn't because I'd have to wait for it while I have time for this today and probably not on any other day.

 

...mental image of a truck with flashing lights pulling up to the door: “Special ISO Regen delivery for Mr. Peter St_____!”

[jabbr]

21 hours ago, PeterSt said:

Jud, I assume you looked at this picture :

 

and assumed the blue horizontal line to be zero. This is not so, as zero would be at the mouse pointer (just a bit under the lowest level).

The blue horizontal line is what is says : the threshold of where a 0 starts to be a 1 on the rising edge and where the 1 starts to be a 0 on the falling edge.

 

I did not look into the text, but without text and only looking at the picture, this is DC Offset.

And yes, DC Offset, which is most often not stable at all, causes jitter in this case.

 

@Jud, a few additional comments on your question regarding digital transitions and jitter:

 

1) The specific transition point depends on several factors including the specific logic family, VCC, GND. Factors such as how the logic is implemented and noise within the logic circuit itself affect the exact transition point and thus jitter.

2) USB is a differential signal which reduces the effects of common mode noise. If the GND rises and falls, and does for both signals and the receiver, this should mostly balance out.

3) What can be particularly problematic is when the VCC and GND at the receiver vary independently of the HIGH and LOW on the signal. This is why ground, signal planes and bypass are so important.

[mmerrill99]

14 minutes ago, jabbr said:

USB is a differential signal which reduces the effects of common mode noise. If the GND rises and falls, and does for both signals and the receiver, this should mostly balance out.

I think you are using the wrong term here "common mode noise" - it should be "differential (normal) mode noise"

 

CM noise is when the voltage on both differential channels are of the same polarity & therefore their summation, at a point in time, in a differential receiver will not be zero, it will be additive.

 

In contrast differential mode noise is of opposite polarity between the differential lines & the summation is zero at any point in time

[mmerrill99]

15 minutes ago, jabbr said:

@Jud, a few additional comments on your question regarding digital transitions and jitter:

 

1) The specific transition point depends on several factors including the specific logic family, VCC, GND. Factors such as how the logic is implemented and noise within the logic circuit itself affect the exact transition point and thus jitter.

2) USB is a differential signal which reduces the effects of common mode noise. If the GND rises and falls, and does for both signals and the receiver, this should mostly balance out.

3) What can be particularly problematic is when the VCC and GND at the receiver vary independently of the HIGH and LOW on the signal. This is why ground, signal planes and bypass are so important.

Apart from CM noise, I agree with the rest

The differential aspect of USB is crucial & shouldn't be taken for granted. There's a tendency to treat differential lines as immune to noise but that's not the full picture.

Remember that a differential receiver is a crossing detector - that's the primary function of the PHY part of a USB receiver.

 

[marce]

1 hour ago, Jud said:

 

Sometimes when you repeat something enough different ways, it eventually penetrates.  Thanks, marce.

I will try an put together a simple guide to some of all this. Generally the rise time is pretty constant from period to period, but just as you can get ground bounce (the example you showed) you can also get supply droop, and this can cause the rise time to slow a tint tiny amount, this would then alter the switching point very slightly (Jitter). When doing signal integrity investigations you always work on a mathematically perfect waveform, you can then add amounts of deterministic and Gaussian jitter etc and see what effect it has on the overall signal. the beauty of SIV software is you see lots of pretty pictures so its easier to grasp what is going on, trying to describe it in words... well its fun.

[manisandher]

1 hour ago, firedog said:

People really need to get off Mani's case.

 

Thanks FD, I appreciate the gesture.

 

But it really is fine - just gives me a chance to retort with evidence and facts, which usually shuts them up.

 

Now back to this excellent discussion...

 

Mani.

[jabbr]

34 minutes ago, mmerrill99 said:

CM noise is when the voltage on both differential channels are of the same polarity & therefore their summation, at a point in time, in a differential receiver will not be zero, it will be additive.

 

Yes. I am using @Jud's example: ground rises and falls aka ground bounce. If everything rises and falls in perfect equilibrium, the digital transition occurs at the same point to a certain approximation. 

 

See Figure 3: https://www.maximintegrated.com/en/app-notes/index.mvp/id/2045

[manisandher]

50 minutes ago, marce said:

I will try an put together a simple guide to some of all this.

 

That would be excellent.

 

In another thread, I noticed you wrote: "...next week I'm back in sunny [sic] Winbourne  doing a 14 layer flexi rigid board and later back onto a controller board with well over 2000 components 8 layers (and we have a design with about 20,000 components on!!!)..." Does that mean you're one of the 'Ultra Electronics' guys?

 

Mani.

[marce]

18 minutes ago, manisandher said:

 

That would be excellent.

 

In another thread, I noticed you wrote: "...next week I'm back in sunny [sic] Winbourne  doing a 14 layer flexi rigid board and later back onto a controller board with well over 2000 components 8 layers (and we have a design with about 20,000 components on!!!)..." Does that mean you're one of the 'Ultra Electronics' guys?

 

Mani.

Nope, I do work for ultra PMES, down at Winbourne I am Cobham's PCB layout engineer of choice, flight refuelling. We use hybrids that Ulta do down these on some projects.

[manisandher]

5 minutes ago, marce said:

Nope, I do work for ultra PMES...

 

Oh in that case, I won't take your posts too seriously. I mean, what could you possibly know... 

 

Mani.

[marce]

 So true... lol.

[Speedskater]

7 hours ago, Speed Racer said:

We are dealing with digital data here. This isn't analog where the cable can act as a filter to color the analog signal.

A reasonable analog interconnect cable will not filter an audio signal.

[PeterSt]

9 hours ago, PeterSt said:

So ... This should be a great day;

 

Or maybe not so super great. 

DAC setup was made, scope was put forward but next I spent hours on the phone about a delivery of capacitors I am waiting for for weeks and which was finally shipped yesterday and ... delivered somewhere else. Then another delivery of flat packs (boxes) for the Lush stayed away for too long, so half of the Lushes for today were not packed and all helping hands had to leave the building leaving me with a pile of cables. Then I had to reorganize things because people who payed first had there Lushes not packed which made me feel bad. And then the almost worst part was that the flat packs were delivered with the UPS truck 2 minutes behind it. So that created psychological pressure because all I had to do was pack the remaining Lushes together with the proper paperwork ... and under pressure all becomes messy.

 

And so I have one Lush left of 70cm and one of 100cm not shipped because that 100cm ended up somewhere ... well, I don't even know.

 

The reason for this post :

Please bear with me because some of the packages really look ugly for the tape and plastic bag I had to put on it in, which things I (all so clearly) never do, let alone being in a rush. Apologies for that. and for that one which did not get out. And for the one person who probably receives 100cm instead of 70cm.

 

Peter

[elcorso]

1 hour ago, Speedskater said:

A reasonable analog interconnect cable will not filter an audio signal.

 

Nor will it add noise ...

 

Roch

[Speedskater]

22 minutes ago, elcorso said:

Nor will it add noise ...

Roch

Common Impedance Coupling noise is the biggest problem with poorly chosen RCA analog interconnects.

* * * * * * * * * * * * * *

The longer the cable, the more likely it can be a problem. (under 10 feet not so much)

[elcorso]

25 minutes ago, PeterSt said:

 

Or maybe not so super great. 

DAC setup was made, scope was put forward but next I spent hours on the phone about a delivery of capacitors I am waiting for for weeks and which was finally shipped yesterday and ... delivered somewhere else. Then another delivery of flat packs (boxes) for the Lush stayed away for too long, so half of the Lushes for today were not packed and all helping hands had to leave the building leaving me with a pile of cables. Then I had to reorganize things because people who payed first had there Lushes not packed which made me feel bad. And then the almost worst part was that the flat packs were delivered with the UPS truck 2 minutes behind it. So that created psychological pressure because all I had to do was pack the remaining Lushes together with the proper paperwork ... and under pressure all becomes messy.

 

And so I have one Lush left of 70cm and one of 100cm not shipped because that 100cm ended up somewhere ... well, I don't even know.

 

The reason for this post :

Please bear with me because some of the packages really look ugly for the tape and plastic bag I had to put on it in, which things I (all so clearly) never do, let alone being in a rush. Apologies for that. and for that one which did not get out. And for the one person who probably receives 100cm instead of 70cm.

 

Peter

 

Shit happens not only in the rainforest?

 

My "Lush" is still in the customs.  I forgot that there was a holiday (very common on this side of the world). Oh, and a strike .... Now we have customs lush, but not at my house. I'll have it at home next 27, I hope.

 

Best,

 

Roch

[PeterSt]

49 minutes ago, elcorso said:

My "Lush" is still in the customs.

 

Hi Roch,

 

I assume you mean the customs underway to the rainforest ? I mean, your Lush was delivered on the 21st just outside the rainforest. 

 

Regards,

Peter

[Speed Racer]

7 hours ago, firedog said:

Not especially directed at JoeWhip, but just a comment:

 

People really need to get off Mani's case. He likes the Phasure and says so. He doesn't say other DACs suck, just that his favorite is the Phasure.  He doesn't in general talk down other DACs. He doesn't like the Schiit Yggy. His taste.

If you look around the audio based internet, there are lots of people who think the Yggy is great. There's also a not insignificant minority that thinks it really doesn't sound right.  So Mani isn't alone. 

 

I don't see why that is a problem. Other people like Lampizator, PSAudio, Mytek, etc.  Can't people express a preference either positively or negatively without getting attacked?

When someone else doesn't love a product you think is the best thing you've ever heard, they aren't attacking you personally. They're saying that for their ears and taste, they didn't like "X".

 

Grownups can handle that without going "forum crazy" on another poster or criticising him at every opportunity.

 

I don't have a problem with any of this except that Mani is almost maniacal is his distaste for Yggy. I saw this BEFORE I owned any Schiit products.....I don't give a damn if someone doesn't like what I like. What I care about about is the ferocity at which he attacks the product. Your "He doesn't like the Schiit Yggy." is just not an accurate portrayal of his presentation.

 

This attitude of his along with exaggerations regarding Phasure, for me, calls into question anything I read by him.

 

If you and all the folks that gave a reputation to this post don't see that, you are deluding yourselves.

[manisandher]

 

Deleted.

 

Mani.

[PeterSt]

8 minutes ago, Speed Racer said:

If you and all the folks that gave a reputation to this post don't see that, you are deluding yourselves.

 

I didn't when I read it at first, because it would be somewhat obvious. But I did now.

 

Anyway, I have the hope that it's now over and done with because the person who caused this (in my view) has spoken up and Mani replied.

And might it help someone, I also asked Mani to quit this one-sided, if possible. But I see already it does not help.

[PeterSt]

Mani, come on now !

 

Edit : OK, let me add a smiley. 

But it does not smile really.

 

Haha

 

[manisandher]

Deleted.

 

Mani.

[rickca]

Let's not turn this into a thread about Mani or Yggdrasil.