Brad Robinson

Recording from Delta-Sigma DAC to PC

2 posts in this topic

Hey All,

I'm trying to record audio from classic computing shield (which I think is basically the same as the arcade shield) but just getting terrible noise.  The sound works fine when plugged into powered speakers, but plugging to sound card on my pc and recording/monitoring just gives buzzing/hissing noise.  I've tried both mic in and line in on the sound card, same result.

I'm guessing this is because of the way this kind of dac works, but wondering if there's some other reason.

Has anyone else managed to get a clean recording into a PC from one of these shields?   What am I missing?

Brad

 

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it's probably better just to stream it using a serial port at 3Mbit/s. The audio DAC relies on the speaker themselves (their inductance) to perform a low-pass filter, in both Sigma-Delta and PWM outputs. What you hear is probably switching noise and some aliasing. Alternative is for you to design such an analogue filter.

It can be technically possible to send that data over USB using a simple transceiver and isochronous transfers, but we have not done it before.

Alvie

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