DuckMixer!!!

 It's a mixer! It can sidechain the main channels with ..... I just had the idea to normal the first mixer input to the duck-signal jack... okay that's done and I'm continuing this post so I can create a QR code linking TO this post so I can add it to the PCB before ordering it.

Anyway, this is what this will do. It's a 4 channel (stereo) or 8 channel (mono, but pairs of channels are linked) mixer. It accepts one or two signals to duck the incoming audio by envelope-following the duck-signal (adjustable decay) which illuminates an LED, which is paired with an LDR (light-dependent resistor) which shunts the incoming audio to ground. The input resistor is 100K, and the LDRs can get down to a hundred some ohms when fully illuminated (in my experience?) so it'll attenuate the incoming signal to hopefully less than 1% .

There's "max volume" attenuators on each of the 8 channels. There's four stereo sliders controlling the main level of the pairs of channels. There's a duck delay knob (controls how fast the envelope returns to zero) and each stereo pair has its own duck level knob, which controls how much current can go to each LED inside the Vactrol (LED/LDR pair).

There's a L out jack, a R out jack, a mono mixdown jack, and a stereo headphone-capable jack.

I'm proud of the headphone amp portion. It's a single DIP8 through-hole footprint into which the builder can install a bog-standard NE5532 op amp. These can put um... 25mA into a typical 32ohm headphone? Not a enough current to work well, there will be distortion and the volume will be low. But you can STACK OP AMPS as high as you want, four? five? SIX??? Probably wanna keep it at six or lower. But stack those babies and they'll happily drive 32 ohm headphones to Very Loud Volumes (beware the ears).

There's a gain/volume control for the final mixer amp, which really does set the gain so you can mix eight very hot signals without impossible-to-get-rid-of clipping.

Oh yeah, you can also mix the duck-signal into the final mix if you want. OH YEAH, there's a pair of send/return jacks for one of the channel pairs. They're post-sidechain, not sure that's the BEST choice... I love love LOVE me some monster reverb tails that are being sidechained by a kick drum. It's so cool.

Okay, now it's time to post this and go order five PCBs!!!