[sdiy] Testing codecs

Mike Bryant mbryant at futurehorizons.com
Fri Jun 10 23:10:21 CEST 2022

The ADAU1401 (and many other ADI ADCs) has a current input so the input level structure is set purely by the external resistance of the audio source.  Not sure why you'd want to spec the A-D-A performance separately.  It's just the A-D and D-A combined.

Hadn't noticed before the DAC output is a bit low.  As it is balanced I'd have expected a good 4V pk-pk, but it's probably down to using only a 3.3V supply whereas some TI parts use a switched capacitor multiplier.

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Barry Klein via Synth-diy
Sent: 10 June 2022 18:25
To: Synth-diy at synth-diy.org
Subject: [sdiy] Testing codecs

Since we are seeing digital audio converter questions I’ll post two:
Codec specs show ADC and DAC specs but some of the codecs I am evaluating are difficult to test using the digital I/O and I have been testing audio in audio out with no DSP manipulations (SigmaDSP). I am wondering why the codecs aren’t specd for this configuration as it is likely pretty common.  
Another question is about the gain structures of the boards. Not always 1:1 in:out.  2Vrms in/900mV out on ADAU1401A  I think for example.  Do I modify results or config to compensate?
I have a QA401 and had a APx555 for a week and a half.


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