On the BOM and schematic, I mislabeled the compander as NE571 when it should have read NE570. The document and schematic have been corrected and re-uploaded.
http://smallbear-electronics.mybigcommerce.com/ic-ne570/ (http://smallbear-electronics.mybigcommerce.com/ic-ne570/)
while we're at it... I just had a look at the builddoc for the modulation add on and was wondering why there is a 47k for the version with external rate and depth pots, but no connection of lug 2 of the pot to the pcb. I get that the resistance will vary with the turn of the pot due to the paralleled resistance, but why is this constellation preferable to just wiring lug 2 in?
my guess would be to change the taper, but you mentioned that using a C-taper would be preferable anyways. makes me wonder, if the 47k is redundant if a C-taper is used. thanks
Yeah I had the same question for the modulation part.
And the NE571 and 570 are interchangeable right? Is the 570 supposed to be better?
The NE571/SA571 should be interchangeable with the NE570. The NE570 is a bit more common and it's what the DM-2 used. But, if you have a 571 there's no reason not to just use that, AFAIK.
As far as the Depth pot, the reason it is hooked up that way is because pins 1&2 are connected on the MOD PCB. If you were to wire lug 2 into the PCB, it would short the 47k resistor which defeats the whole purpose. The Depth control works fine if you skip the 47k and wire the pot as normal, but at the highest settings it can go too far and create noise with the modulation so the stopper resistor helps prevent that.
The C taper is a suggestion for the Rate only. B is fine for Depth and Rate, but C on the Rate offers more fine-tuning.
Thanks for the answer!
I'll use a sa571 I just ordered.
thanks for the clarification.