Pure mixing DIY

[Theo Verelst]

For who finds that interesting I made a little stereo mixer with probably the best (analog) audio quality OpAmp chips in the world, a simple setup adding two (or more) channels up like a pure analog addition. The schematics are similar to the one I've shown a while ago, in this video I show a bit of the bells and whistles:

 

[video:youtube]tQHu4IAPpTA

 

This sort of project for those with DIY skills isn't very expensive, but quality parts OTOH do not come overly cheap for hobby or small scale pro use: even getting input parts like jack chassis parts to clink your synth jack cables into can get relatively expensive if you want more than a few, and of the best quality. The shown prototype I made using a general-purpose circuit board can in principle add up tens of signals, costing only a (metal film) resistor per additional channel, so that's a great plus, and it has very good specs (it's transparent).

 

As an experiment I also tried to connect some outputs of equipment to the alternate use of this circuit: a "high-Z" (high impedance) input buffer amplifier stage: in fact some equipment appears to benefit from very lightly loading it's outputs.

 

Now I'll look into some very good quality balancing issues/circuits and try out which equipment is sensitive to which grounding loops and output loading issues...

 

Theo V.