Hi
After multiples for my Eurorack, and wanting a good circuit for a buffered mult. There’s a lot of “noise” when you search for them, so looking for advice.
I wouldn’t mind a bank of mults that I can break into smaller groups, but think they should be buffered, as likely splitting and distributing clock signals and envelopes with them.
A circuit that can be scaled up for mega-sized mults would be interesting too…
There’s Sam’s buffered mult:
@CTorp also has a schematic/pcb(I think it’s this one anyway):
You may just get more “noise”! For clock signals and envelopes you may be able to get away with circuits that do not do well with 1 V/oct signals. For those you want gain to be unity, of course, but you also want it compatible with upstream and downstream modules. So for instance a multiple that has 1k output resistors outside the op amp feedback loop will lose 1% of signal amplitude when fed into a module with 100k input impedance. Which doesn’t sound like much but it’s 12 cents per octave mistuning, very definitely audible. Likewise if you have a 1 V/oct source with 1k output impedance feeding into a multiple with 100k input impedance, you again lose tuning accuracy. The LMNC multiple has 10M input impedance, which is more than enough — might actually be better to kick it down to 1M — and 100R output impedance. So should be good for V/oct signals. On the other hand, if you plug the wrong thing in and have a 12 V short across those 100R resistors that’s 1.44 watts, they’ll start smoking real fast…