Design Architecture

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rhale64l7

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Design Architecture
« on: 15 Jul 2025, 06:57 pm »
Guys I noticed not too much has been asked about this. But I have been wondering about the USB implementation. I know it is class 2 but how is it designed? Is it galvanicaly isolated? Or are you using your own design Architecture? How about the coax input? Is this all off the shelf basic stuff. I am just wondering because I want to know if any old USB cable will work? Or should I use the coax? I know about the DSP and the ADC and the DAC. And I love how it remembers volume for each input. But I am still interested in the other things that haven't been talked about.

HAL

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Re: Design Architecture
« Reply #1 on: 15 Jul 2025, 10:55 pm »
Will let the hardware designer discuss these topics. 

danvillesignal

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    • Danville Signal
Re: Design Architecture
« Reply #2 on: Yesterday at 03:16 pm »
The USB Audio Class 2 is XMOS based.

It is not galvanically isolated. I know this is sometimes touted as a feature, but really the main concern is will the USB add noise to the target? This is largely a function of how the board is routed. 
The USB doesn't affect the noise floor in the dspNexus.

Concerning S/PDIF:

Unlike USB UAC2, S/PDIF has intrinsic jitter issues. This is because the clock is part of the transmission starting at the source, A really good S/PDIF receiver, but now obsolete (WM8804/05) can get the jitter down to about 50ps.
This is still too high, but better than the likely original that might be 300ps or even worse from a TV. This is a limitation with PLL clock recovery. We do jitter attenuation in the SHARC instead and pay a lot of attention to clock circuits and routing.

I would save your money on exotic cables. Sure, its good to have reasonable quality connectors and shielding with the phono cables, maybe $10 versions. Expensive USB cables make even less sense. I would use your extra money on room treatment materials or single malt scotch. Both will likely improve your listening experience more that expensive cables.

If you are a skilled audio equipment designer, you are likely making a lot of small decisions that ultimately affect the overall performance. There really isn't one magic thing that changes everything.

Al Clark



rhale64l7

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Re: Design Architecture
« Reply #3 on: Yesterday at 05:32 pm »
Ok thank you. It does explain why I was having a hard time with the sound until last night when my son noticed a high pitched sound coming from behind my rack. It was a little switching power supply that was emitting this high frequency noise. It must be going bad but I think it was sending noise into my system. It was hideous. And it wasn't that loud. So I couldn't hear it over the music. But as soon as I fixed it the entire system sounded cleaner. It's the tiny background stuff. So subtle that you can't pinpoint. But when it's gone you know it. Couldn't pick it out in a blind test. But it is there and you can hear it. Now it's gone but I know to get those stupid things off my audio equipment. I had them gone for a while and bit on the placebo thing. I started believing the people that say they don't make a difference. So I sold all my better quality power supplies to reclaim some cash. Shouldn't have done it.