[sdiy] supply voltages and signal levels

[JH.]

> I see the supply voltage issue coming up in the OTA thread,  and in much
of
> this stuff that I've encountered it seems that 15V dual supplies are the
> norm.  Or maybe 12V,  or even 10V,  in some stuff.

Or 350V in some tube stuff (;->).
I'd say 30V (+/-15V) is a good choice to get strong signals with enough
headroom
while being save when you touch the circuit with your hands ...

> I also see signal levels quite commonly being around 10V P-P.
>
> Is this really necessary?  Are we looking at things degrading that much if
we
> were instead operating at "line level" or similar?

10Vpp *is* line level - with approx. 20dB of headroom.
That's why mixers and outboard effects mostly run from +/-15V (or anything
close to this) as well.
And that - headroom! - is why synthesizers circuits (such as VCFs) should
have excellent
SNR when you use them to process line level audio. Or a pleasant ovedrive
behaviour. (Or both.)

JH.