A PCM1704 DAC with Xmos USB interface - diyAudio
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Old 17th January 2014, 12:59 AM   #1
hllyfm is offline hllyfm  China
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Default A PCM1704 DAC with Xmos USB interface

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

For more detail, You can visit
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Here is the some picture of this DAC

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Old 17th January 2014, 01:42 AM   #2
hllyfm is offline hllyfm  China
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I use a Orava Headphone amplifier and T1 headphone with this DAC
the sound is amazing

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Old 17th January 2014, 01:57 AM   #3
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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
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Old 17th January 2014, 02:05 AM   #4
hllyfm is offline hllyfm  China
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Quote:
Originally Posted by abraxalito View Post
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
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Old 18th January 2014, 02:03 AM   #5
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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.
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Old 20th January 2014, 01:56 AM   #6
hllyfm is offline hllyfm  China
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Quote:
Originally Posted by abraxalito View Post
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
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Old 29th January 2014, 01:49 AM   #7
hllyfm is offline hllyfm  China
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The sound get better with these days' run in
New version with better chassis will be available soon
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Old 29th January 2014, 02:10 AM   #8
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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'.
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Old 13th February 2014, 11:55 PM   #9
hllyfm is offline hllyfm  China
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Originally Posted by abraxalito View Post
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
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Old 8th April 2014, 05:36 PM   #10
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Default I/V and output stage

How are you doing I/V? What about output stage?

I see your DAC is for sale at HOLO Audio, PCM1704 T.REX DAC -Ա
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