DAC chip for PCM2707

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JanErik,

PCM2707 has a system clock output as well. You can hook this directly to your PCM1792A.

An External Crystal (and 2x caps) can be hooked up to the PCM2707 for the 12MHz clock.

I don't see where you'd need the PLL17xx device. Can you let me into your thought process? :confused::)

Thanks again

Dafydd Roche (TI Audio Converter Systems Engineer).
P.S. For further reference, you may want to read some of the threads over at:
Data Converters - TI E2E Community
 
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What about using a high precision XO for the System clock of the PCM1792 (according to the table on page 15 of the datasheet) and devide it down 2 or 4 times according to the need of the 2707 using high speed D-Flip-Flops.
Did this for the combination of ES9023 and WM8804 (49,152 MHz and 12,288 MHz).
 
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Sorry, have been a bit too fast :eek: My thoughts might not apply to your setup.

According to the datasheet the PCM2707 supports 32, 44.1 and 48 kHz samplerate with SYSCK = 256Fs available at the corresponding I2S header pin (FUNC2, Pin18). You could use this as system clock for 1792. However the jitter related performance will not be very good due to 2707 using adaptive isochronous USB transfer. Could be improved using SPDIF and an aditional SPDIF receiver chip (e.g. WM8804) with reclocking, though not sure if its worth the effort.

PCM2707 quite easy to implement, but wouldn't it be better to go for other solutions like XMOS (e.g. used on USBstreamer) to get the most out of the 1792? If you are not fixed to complete DIY you could use just one of the available USB to I2S interfaces like that shown in the link. Just an idea...;)
 
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Oops, I didnt realize that it already gives the necessary clock!

I do think the USB is just fine, the PCM2705 already sounds good but I would like to use a more high-end DAC. Likely also powered over USB, despite what people may say :p

An SPDIF DAC is a separate project I am thinking of.

But I am aiming to do it totally DIY, this is hobby and there is no fun otherwise.
 
It seems to be quite old chip...? And I cant find it in any store nor to be sampled.

TDA1543 or AD1865? Or booth? Just kidding ;)
My point is... best way is to use PCM2707 in non-os configuration with some good-sounding DAC chip with I2S input (for example TDA1543) without any glue logic. Anyway, TI PCM USB chips properly implemented have also good sound by themselves without using of external DAC.
 
I meant TDA1543... and what is wrong with oversampling?
Yes, I am very satisfied already with PCM2705, but they all have worse specs than the PCM2702 that was used in the AlienDAC, and it is not available anymore.
Plus, the PCM1792 would give balanced outputs natively.
 
I meant TDA1543... and what is wrong with oversampling?
Yes, I am very satisfied already with PCM2705, but they all have worse specs than the PCM2702 that was used in the AlienDAC, and it is not available anymore.
Plus, the PCM1792 would give balanced outputs natively.

Don't know about today (because I didn't check), but few years ago I was still able to buy TDA1543 (and TDA1543A) in local shop in my country for 2 Euros/piece. Chip have very bad spec, but on other hand good sound. Only few components are needed (passive IV) for complete DAC. It is working with PCM270x I2S signal as input without problems. PCM270x is 16/44.1 USB audio device, not 24-bit.

Direction from your first post is OK, but this I will not advise to anybody, because it is much more complicated way, with possibility that final result will be worst than simple TDA1543 solution.

I build small USB bus powered board with PCM2707, that is used as USB/I2S bridge, and can be connected to any external DAC device (with I2S input) that I have.
 
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