The Comparison Thread for Recovery USB Reclocker, the Regen and similar devices... (Curated Thread)

[mourip]

Just out of curiosity where did the Op go?

[The Computer Audiophile]

Just out of curiosity where did the Op go?

I think some people who didn't like him ran him out of here unfortunately.

[barrows]

from One and a half:

 

"As for what's coming down the track, crystal ball gazing here, the genie is out of the bottle here as far as controlling USB, and the traditional interface of S/PDIF is still about. Maybe DAC manufacturers may incorporate some of the inroads available externally, although my personal opinion should be to keep USB out of the DAC altogether, it's toxic since it pollutes the internal power supplies of DACs. But the market wants USB, so usually a token effort is made to include USB, using off the shelf designs. Look, a lot of these solutions work, until you isolate the signal, then the shortcomings are very obvious."

 

I do not agree that USB interfaces have to be toxic to the internal environment of a DAC. In many cases these interfaces are a problem, but with a well isolated interface, and properly separated power supplies, they need not be. The problem is that many DAC manufacturers do not really go far enough in providing isolated USB inputs. A shame, considering how to do this is well understood and not terribly expensive to implement.

[mourip]

I think some people who didn't like him ran him out of here unfortunately.

 

Sorry to hear that. Very sad.

 

I like forums to be broadly moderated but perhaps curated threads are too tempting for bullies who tend to find the control irritating?

 

I hope that he will come back as it looked like there were many who did find his posts helpful. Those who do not can always just choose to not read them.

 

Basically I would like to think that there is a place for everyone on CA...

[The Computer Audiophile]

Sorry to hear that. Very sad.

 

I like forums to be moderated but perhaps currated threads are too tempting for bullies?

Sadly I think you are correct.

[sandyk]

i agree: that part sounds silly/childish

 

Active PSU noise/ripple cancellation was used in a John Linsley Hood article that was published in Electronics Today International in April 1994.

[One and a half]

from One and a half:

 

"As for what's coming down the track, crystal ball gazing here, the genie is out of the bottle here as far as controlling USB, and the traditional interface of S/PDIF is still about. Maybe DAC manufacturers may incorporate some of the inroads available externally, although my personal opinion should be to keep USB out of the DAC altogether, it's toxic since it pollutes the internal power supplies of DACs. But the market wants USB, so usually a token effort is made to include USB, using off the shelf designs. Look, a lot of these solutions work, until you isolate the signal, then the shortcomings are very obvious."

 

I do not agree that USB interfaces have to be toxic to the internal environment of a DAC. In many cases these interfaces are a problem, but with a well isolated interface, and properly separated power supplies, they need not be. The problem is that many DAC manufacturers do not really go far enough in providing isolated USB inputs. A shame, considering how to do this is well understood and not terribly expensive to implement.

 

Apart from Exasound, do any other DAC manufacturers incorporate galvanic isolation? Sort of struggling to think of any others. I'm not talking about USB-S/PDIF converters, just DACs, it just seems so few are taking this up, maybe in time, 12 months from now, might be common place. Would be nice to add a reclocker as well. Stuff of dreams.

[audio.bill]

Bryston's BDA-2 and latest BDA-3 incorporate galvanic isolation for all electrical inputs. Quoting from their Digital Audio Brochure, "Each electrical input is galvanically isolated to completely eliminate the possibility of ground noise from the attached interconnect and device from polluting the signal." They confirmed that this includes the USB inputs on their forum. They also address reclocking - "The embedded clock signals are thrown out, and all incoming PCM data is re-clocked with our own high-precision internal master clock for the lowest possible jitter."

[Superdad]

Just to be clear, ALL DACs that use digital isolators place then AFTER the USB PHY and processor. Isolation and improved signal integrity BEFORE entering the DAC (i.e. with hub-based devices like the Recovery and REGEN, etc.--as well as galvanic isolators such as the Intona) is still effective with DACs that claim to "galvanically isolate" their USB input because once the DAC's PHY and processor generate ground-plane and packet-data noise and voltage spikes, it is very hard to get rid of the effect. Here is some more in depth on that topic from John Swenson:

 

"Isolators [after the USB input PHY and processor] help but are not nearly the panacea many people think. Let's travel through the system and look at both the power and signal and what happens to them as we go through the system.

 

So lets start with a USB receiver with bursts of high frequency noise on both the power and ground planes. This PG (power/ground) noise will modulate the data being sent to the isolators. It will slightly increase jitter and the amplitude of the pulses will vary with the noise.

 

This noisy power also goes into the driver side of the isolator. The signal going across the barrier (light, EM waves, magnetic field etc) gets modulated by this PG noise as well. The PG noise also changes the threshold of the input receivers, adding jitter to the signal.

 

On the other side of the barrier we have a couple things happening, the varying signal level, caused by the PG noise in the driver, also causes the receiver current to change, even with no signal applied. Thus the receiver causes PG noise on the "clean side" directly related to the PG noise on the "dirty side" It is definitely attenuated, but not by nearly as much as most people expect. Then we also have traditional logic noise caused by the fact the output is a normal logic signal, every time the output changes it creates noise on the PG planes on the clean side. The jitter on the signal created by the PG noise on the dirty side is still there PLUs jitter introduced by the isolation scheme. This jitter changes the spectrum of the logic noise on the PG planes on the clean side.

 

So then we feed the signal through a reclocking flop, which is supposed to get rid of all that jitter on the input. Well it helps, but no reclocking flops are completely effective. The PG noise at the flop still causes jitter to show up on it's output, PG noise changes the threshold where the flop detects the "switch" of the clock, thus increasing jitter on the output.

 

The result of this chain is that PG noise on the "dirty side" can still make it through to the "clean" side. It IS attenuated, but not completely gone.

 

Cascading such stages can theoretically help, but in order for that to work the reclocking clock has to get fed back through the isolators which significantly degrades the clock so it turns out cascading doesn't help much. (a two-stage cascade does make things better, but not by a huge amount)."

[Wyred 4 Sound]

Apart from Exasound, do any other DAC manufacturers incorporate galvanic isolation?

 

Yes, our DAC-1 LE and DAC-2 DSD/DSDse models incorporate galvanic isolation.

[One and a half]

Yes, our DAC-1 LE and DAC-2 DSD/DSDse models incorporate galvanic isolation.

 

Thank you for the reply Mr. Wyred4Sound Will add to the list. What voltage level do we need to increase to before we break the barrier?

[Superdad]

Thank you for the reply Mr. Wyred4Sound Will add to the list. What voltage level do we need to increase to before we break the barrier?

 

Hi Gary:

 

Your question does not make sense in the context that of the way digital isolators are used deep into a DAC. They are not at the input, they are AFTER both the USB PHY and processor, on the I2S/DSD lines. So voltage hits are not at all an issue that far in.

Not to say that the isolators (probably the TI capacitive ones in the W4S units) don't have a high voltage rating, it just is not a concern.

 

Now if you were looking at actual USB isolator chips (ADuM or the like; which no DAC designer uses at the input--those ADuMs are full speed only and are lousy for other reasons), then isolation voltage rating might be relevant (though ESD seems to be more of port killer in my experience).

 

Hope that helps.

 

--Alex C.