Voltage controlled 5 Band Equalizer with Feedback using cheap eq module from Ebay/Aliexpress
This is a 5 Band Equalizer Module which is already build and availiable for not much than 5 Euros, modded for eurorack, with input and output attenuators, and feedback knob for self oszillation. In addition to that, there is bipolar vactrol control over all the sliders of the EQ Module with an atteuvator and an bipolar LED for each channel! Theres even Vactrol CVable Feedback :) These parts are completely optional if you dont want them in your build... You can build this module using the schematic ive drawn, even if you buy the 10 or 15 channel versions, you just have to do the same circuit for each channel!
For the Eq Board just search: Stereo 5 Band Equalizer EQ Board on ebay or alieexpress, and go for most cheap offers!
Have Fun! Luis