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Dave Platt Dave Platt is offline
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Default Mixing 4 audio channels to 3?

In article ,
DaveC newsgroups wrote:

Your drawing is wrong; signal goes to the inverting (-) inputs and the
Vcc/2 reference goes to the non-inverting (+) inputs.


Agreed.

Thanks guys. Fixed:

http://i44.tinypic.com/r1k8qa.jpg

All else looks good?


Are cap values reasonable? I added C8 & C9 out of habit of seeing in other
designs. Values for these?


I'd eliminate C9. Some op amps aren't able to drive capacitive loads
without exhibiting instability.

If you do want some noise reduction on your reference, I'd add a
small decoupling resistor (say, 47R) between U4 and C9, and perhaps
use another .1 uF for C9. If you're using a good low-noise op amp,
you can probably just omit the filtering here and feed U4's output
directly to your "common".

I'd also recommend decoupling your 16-volt power supply, with a .1 uF
located as close as practical to the V+/V- pins of each op amp.

Remember to get the polarities of C1-C7 correct when you install them
(+ to the op-amp side, - to the outside world).

--
Dave Platt AE6EO
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