[sdiy] VCA mixer ?

[Stewart Pye]

Merlin Zener wrote:

> Hi,
>
> I had an idea, and I don't know how feasible it is, so I thought I'd ask
> you guys to comment:
> I was thinking of having a 16 input, 8 output mixer for my keyboard rig,
> and having no knobs on it, just make it in a 1RU box with a MIDI in and
> set up a panel in Cakewalk to control it.
>
> Obviously the first consideration would be the 128 VCAs - there's costs
> and noise/distortion issues to think about.

It would be a lot simpler if you just had volume control on each input 
and the use serially controlled analog muxes to do the switching. AFAIK 
(from a couple of years ago) the crosspoint switch IC's are no good if 
you want to mix the inputs. ie: have more than one input going to a 
particular output. We build audio matrix switches where I work and use 
serial control 8 input muxes (you can have more than one input 
selected). We use the MAX350. You'd need two for each output. You could 
also use serial controlled volume chips. The noise/ditortion performance 
varies on these. This way you wouldn't need a DAC but PCB layout will be 
important.

Regards,
Stewart.