Since I have a multi channel Bheringer mixer which I use to mix the modular output and some synths with I thought I would not have much to contribute to this thread, but maybe this could be of interest. In my modular I use ‘intermediate’ mixers (called Mix-O-Matic) which are signal and/or CV mixers. These are very simple in construction and easy to use. I’ve been using them for a while now and like multiples and attenuverters they are sort of a staple tool to me now. They consist of TL072s (but I could have used one TL074) which are configured as an inverting summing amplifier followed by an inverter each. This results in 2 summing circuits. For one I also output the inverse sum.
My battery operated stereo micro-mixer.
4 x stereo in (one mono in with gain/drive, goes into L+R on channel 1).
Stereo AUX out - switchable aux-sends with a master pot.
Stereo mixing with master pot.
Either stereo output will drive headphones directly.
I rebuilt a mixer I first made a couple of years back…
I managed to shrink the insides by using finer gauge wiring, and got 9V battery operation + headphone direct drive by using 4 X LM386 (the 5th LM386 board is used for the mono-input, connecting to channel 1 via caps, so it won’t mono-bridge that stereo input).
I ended up using pre built boards, and modified the gain (pins 1-8) to x20 to lower the noise floor.
First version:
Images below: The first version, using LM324 and dual rail. The first outlay with pots, switches, could be re-used… but the cables I had then were way too thick. And buffered inputs was overkill:
