6CH Audio Mixer w/ Send/Return and sidechain compression.

6CH Audio mixer with EQ. PAN. stereo compressor
1.CHANNEL inputs & controls Channels 1-4 are mono, they have EQ, PAN, MUTE, SEND controls on each channe Channels 5&6 are stereo, L in normalled to R in, thev have mute buttons.
2.SEND\RETURN SEND: CH1-4 have pre\post fader slider switch that selects from where audio goes to SEND pot, PAN parameter do not affect on SEND pot signal so SEND outputs are monc RETURN: have volume pot and toggle switch that selects stage when signal returns to mix, selects between final mix or compressor mix in.
3. Compressor Vactrol based stereo opto compressor, CMP pot sets amount of audio signal that goes to compressor circuit SCH: sidechain signal input CH4 btn: selects how SEND pot would work, sends sianal tc send bus mix or thru compressor circuit to final mix and SEND pot sends signal to SCH input jack if nothing plugged in to it.
4. Final mix & headphones out This section have volume pot for MIX and HP outputs and peak meter for mix that takes signal before MIX volume pot.

https://www.etsy.com/listing/4515363775/6ch-audio-mixer-diy