[sdiy] Mixer Design Question

[harrybissell at wowway.com]

I think you might want to use an Inverting Summing Amplifier
(opamp circuit) to add the six preamps. You could have output
jacks that are "normallized" so that if you do not use an individual
output(s) they will be automatically patched throuh the mixer.

If you don't want the singal inverted, you could use a second
inverting opamp, with the volume control inbetween the summer
(mixer) and the output. This would be a really good way to go as the pot
would be buffered by the second opamp.

H^) harry



On Fri, 4 Apr 2008 14:21:34 -0400, alfred.pear wrote
> Hi -
> 
> I'm relatively new to electronics building and op amps have been
> keeping me suitably occupied.
> However, I have a particular application and I can't quite wrap my
> head around the circuit design and was hoping someone would be kind
> enough to help me.
> 
> Essentially, I'd like six independent channels to use as discrete
> pre-amps, but I would also like the option of patching them into a
> single, final stage with an overall gain control.
> 
> Is there a design where I can maintain the integrity of the singular
> pre-amps, while having an overall final mix in a separate output?
> 
> Since I'm not totally at home with diodes yet, if they are necessary,
> is there a way to do this while maintaining both polarities in the
> final stage?
> 
> Thanks to all,
> Al
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Harry Bissell & Nora Abdullah 4eva