[sdiy] Blocking/Decoupling caps on a summing op-amp mixer

[Justin Owen]

On Tue, Mar 18, 2008 at 1:15 PM, Justin Owen <juzowen at googlemail.com> wrote:

> > c) Since I'm not using dual voltage or AC - do I still need the caps anyway?

> If you're using the mixer to sum / process DC control voltages, then
actually you don't want the caps at all. You'll want decoupling caps for
mixing audio or other AC signals, but they're just to remove any DC offset
from those signals.

That's really good to know - thanks.

So - If I'm mixing the outputs from two oscillators (running at audio frequency) that are part of the same circuit as the op-amp/mixer and running from the same power supply - they would be needed - yeah?

Sorry - I porobably should have mentioned they were mixing 'internal' signals rather than 'external'.

FWIW - thes two oscillators I'm mixing the levels of are 555-based and I've decoupled Pin 5 on both of them.

Thanks again - appreciated.

J