[sdiy] Signal levels on modulars???

[Richard Wentk]

At 10:40 04/05/2003 -0700, Tim Ressel wrote:
>Harry,
>
>Here is the rub: I use lots of TL08x opamps, and they
>don't like getting ip close and personal with he
>rails. +/- 13 volts is about tops for them with 15
>volt rails. This is not a lot of headroom.
>
>I have two modules that are wigging out due to (I
>think) clipping issues. If I can fix those modules,
>then I'll keep the +/- 10V scheme. I need to decide
>before I due any VCO PCBs.

The way I think of it is that +/- 5V is a 10V range, which at 1V/oct is 
equal to about 1000:1. Which is nicely equivalent to the 20 - 20k audio 
range. In other words a larger voltage range will just be wasted, because 
there will be very few situations where you need a mod source range > 1000:1.

But you can always attenuate, right...?

No. If you rely on attenuators to calm down a 20V swing all you'll be doing 
most of the time is wasting half the pot's range. Which is not good.

For those few times when you want a larger swing, you can always patch in 
an amplifier. As a rule I'd allow +/10V of headroom on mod inputs, even 
though the likely active range will be half of that. But anything that 
works with audio, like a VCA or VCF, assumes +/-5V before clipping. (And 
for completeness, I assume that anything >=5V counts as a gate on gate 
inputs.)

Richard