[sdiy] ASM1 VCO single sided PCB design tests OK

[Neil Johnson]

Magnus wrote:
> Charlie wrote:
> > ...the P supply feeding the op amps has to be "stable DC". If one rail
> > waivers in voltage relative to ground and the other stays put, the
> > oscillator seems to go out of scale.
>
> Well, the VCO core depends on the +15V to GND potential differance. AC
> signals there WILL however not only make it to the output but also cause
> modulation of the waveform.

Mmmm...that's why, when designing my little VCO core, I tied anything
related to the core to a stable (and cheap) fixed +5v reference.  The only
things that connect to the supply rails are op-amp supply pins and the
inputs to voltage references;  even the negative reference for the tune is
a cheaper zener (ok, it'll drift a bit with temperature, but way better
than letting crap in from the -ve rail).

It did surprise me when I first looked over the ASM-1 that the supply
rails were directly connected to the signal chain without any form of
referencing.

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
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