[sdiy] Paralleling lots of ADC inputs

[Tom Wiltshire]

Has anyone ever tried paralleling up lots of uP ADC inputs?

I’ve got several dsPIC processors running simultaneously producing audio (I was asking about the comms on this board the other day - I’ll show you when it’s a bit further along) and I want to add vibrato. The obvious way for me to get the same vibrato on each individual processor is to use an ADC input to vary the pitch. This has some advantages, like I can use whatever waveshape I like (and I don’t have to decide now) and I can provide a pitch modulation input. The downside is that noise can get in, but I can filter the ADC results heavily to minimise that, so I’m not too worried.

So - I need to tie together several ADC inputs. Can I just tie them together? Should I drive the tied-together-inputs with an op-amp follower or something to make sure I’ve got a nice low impedance output? Or do the inputs themselves need buffers in front of them (e.g. tied-together-signal -> opamp buffer -> ADC input). Has anyone tried anything like this?

Any experience you can offer would be appreciated.

Thanks,
Tom

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       Electric Druid
Synth & Stompbox DIY
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