[sdiy] mixer

[Tony Clark]

> is it enough to simply sum all of the inputs with a summing amp, or must
> each be buffered?

   I would buffer each input before your summing amp.  This way all of 
the inputs are isolated from each other "just in case".  Really, if you 
don't feel like wasting a quad op-amp chip to buffer the inputs, then it 
won't hurt.

> must all outputs be bufferes (in the case of more outs), or is the one
> summing amp enough?

   The reason to buffer is so that each line can be driven by a different 
kind of load with no ill effects on the other outputs.  Assuming that the 
input impedances are all the same, then there would be no worry about 
buffering.
   I highly recommend buffering simply because it's cheap, effective, and 
can eliminate a lot of potential headaches.

   Tony

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