diy ADC with ADAT + SPDIF

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Well-known member
Jul 26, 2011
so I started designing a simple 8 channel ADC board to complement my Focusrite Scarlett interface.
The Scarlett can sync to external ADAT and SPDIF inputs, so I thought it would be cool to build an "extension" box with the following:
- 10x line inputs
- PCM4220/2  converters (I already have 5 of them)
- internal good quality clock
- ADAT encoder (V1401) handling 8x inputs
- SPDIF transmitter (WM8804) handling 2x inputs

I already designed the clock circuit (using two selectable low jitter oscillators) and the PCM4220 parts (using the evaluation board as example of the schematic and the layout).
I arranged the ADCs so that one of them is the master, and the rest are slaves.
Now I don't know how to connect the V1401 and the WM8804 so that they would coexist using the same clock source.
Also, I've read that jitter performances of V1401 is quite poor (and I don't want to mess with reclocking or SRC), and so I think I should sync my Focusrite to SPDIF instead of ADATso that the clock would be provided by the slave WM8804, that should perform better than the V1401 if I'm not wrong.
Does it make sense? Opinions?
thank you


Well-known member
Mar 12, 2005
Tampere, Finland
You dont have to decide yet, just build the converter box first and then experiment. You have both options available. Some PLLs can be pretty good though, don't know Focusrite's.

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