[sdiy] Audio mixers

lanterma at ece.gatech.edu lanterma at ece.gatech.edu
Fri Jun 17 05:30:15 CEST 2011


On Jun 16, 2011, at 10:25 PM, stew wrote:

> If you want a low noise mixer you'd be best off using op amp buffers for each input with a 100k input resistor to ground to set the input impedance then follow these by 5k or 10k voltage divider pots and 10k summing resistors. The lower value resistors will reduce the noise.

Doug Self's book "Small Signal Audio Design" has all sorts of tips along these lines:

http://www.amazon.com/Small-Signal-Audio-Design-Douglas/dp/0240521773

I highly recommend checking it out.

> Also use low noise op amps like the LM833 or NE5532, and the associated coupling capacitors required to combat the offset voltage caused by the bipolar input stages of the op amps. 

IIRC, I think Grant Richter is a big fan of the LM833. I seem to recall him mentioning it - or at least something with a similar number.

- Aaron




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