A PCM1704 DAC with Xmos USB interface

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This is PCM1704 DAC with Xmos USB interface

Two PCB DAC PCB for left and right channels, and adopt good technology to make jitter lower

Also the digital receive PCB is alone and it use NOS timing & de-glitch timing technology and of course fifo is also adopted

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Here is the some picture of this DAC

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.
 
Some design related questions for you:

First - why the choice of a toroidal transformer? I'd be concerned its going to introduce mains-borne noise by virtue of its highish interwinding capacitance.

Second - you seem to have a large noise collecting loop because your digital signals enter the DAC board on one side but the power enters on another. Do you have digital/analog isolation?

Third - how are the pin1s of the XLR outputs wired?

Looks very neat work :)
 
Some design related questions for you:

First - why the choice of a toroidal transformer? I'd be concerned its going to introduce mains-borne noise by virtue of its highish interwinding capacitance.

Second - you seem to have a large noise collecting loop because your digital signals enter the DAC board on one side but the power enters on another. Do you have digital/analog isolation?

Third - how are the pin1s of the XLR outputs wired?

Looks very neat work :)

Good questions, This is only the sample DAC machine , not the final product
So first, about the transformer, there is only one toroidal transformer in this machine, I will adopt two transformer in the future, one for analog and one for digital, will have Strict isolation in the completed machine,
Second, Yes, have have digital/analog isolation in the PCB , this is 4 layer PCB
 
Going for two transformers could mean double the noise - I'd suggest getting a custom-wound EI (or R-core) trafo with the particular secondary voltages you need. Not too cost-prohibitive here in China :)

Given you're adopting isolation, what isolators are you using? Most of them introduce jitter. Since your design is an asynchronous USB one, you could put the clock on the DAC board and feed that back to the XMOS board. However you have two DAC boards (one per channel) so that's not going to be possible with the current configuration.
 
Going for two transformers could mean double the noise - I'd suggest getting a custom-wound EI (or R-core) trafo with the particular secondary voltages you need. Not too cost-prohibitive here in China :)

Given you're adopting isolation, what isolators are you using? Most of them introduce jitter. Since your design is an asynchronous USB one, you could put the clock on the DAC board and feed that back to the XMOS board. However you have two DAC boards (one per channel) so that's not going to be possible with the current configuration.

Thanks for your advice, and I will use the Aluminum chassis with CNC, just like this one:
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and I think the sound is good enough , it need good chassis
 
Machining a chassis looks cool but this is a DIY forum and by machining out a doughnut shaped hole for a toroid you make it very hard for a DIYer to fit a lower noise trafo (like EI or R-core). So 'better' here is relative to the end user - a non-DIYer will likely agree with your 'better'.
 
Machining a chassis looks cool but this is a DIY forum and by machining out a doughnut shaped hole for a toroid you make it very hard for a DIYer to fit a lower noise trafo (like EI or R-core). So 'better' here is relative to the end user - a non-DIYer will likely agree with your 'better'.

Yes, I admit it, But I think I can find good tranformer in china, such as NORATEL transformer is very good, of course the transformer core is not made in china
 
Yes, I admit it,
But I think I can find good tranformer in china, such as NORATEL transformer is very good, of course the transformer core is not made in china

Hi first of all sincere congratulations for the very nice design.
The pcbs look wonderful and i like the fact that the two channel are "treated" exactly in the same way. Very dual mono i mean.
Abut the transformer i think that the question is if toroidals are the best choice for a power supply for digital equipment.
I would say no.
Much better EI for instance like Audio Note and Schiit audio use.
Here below a very nice example ...

An externally hosted image should be here but it was not working when we last tested it.


But i have also to say that i have seen smps in high precision master clock generator units. And that are very sensitive to PS quality indeed.
So the comment was much more on the type than on the brand.
You can always place some cage around the transformer to block its EMI emission.
Very nice project anyway. Good luck !
Regards, gino
 
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