991 Filters

Our latest "Moog" module for eurorack:

The  991 Filter and Attenuator is a passive module (i.e. no power required) that contains a switched low pass filter, a switched high pass filter, and an attenuator.

Single PCB with easily obtainable compoenents.

May be built using vintage Mullard C280 aka "tropical fish" capacitors (as in the picture below), or with smaller modern capacitors. 

901 Voltage Controlled Oscillator

 Originally it was not my intention to build this module, but having got the 901A and 901B working this was more of an academic excercise to prove that following the Moog approach of combining a 901A and 901B in a single module actually works.

There is no Moog documentation for the 901, so some educated guesses have been made.

The 901 Voltage Controlled Oscillator module combines the two "rear" PCBs from my standard 901A and 901B modules with a new single 16HP "front" controls PCB to give a single module oscillator. 

It includes the same fixed and variable level waveform outputs as the Moog original, but I have added a "mix" output (using an in-built CP3 mixer with selectable positive or negative output), plus a pulse width modulation input.