Moog Modular - 901 VCO

This is a 3MU module.
The Moog 901 came out in the late 1960's .. possibly 1965 to 68 ??
It's what is called a first generation VCO.
You can use this as a VCO & VCLFO (voltage controlled LFO)

It's a classic, and arguably this oscillator has influenced all VCO designs..... not just of Moog, but of synth manufacturers from around the world.

 Below are  VCOs from a ARP 2500, a Korg MS 20, and 3 Eurorack manufacturers.

 The 901 is basically a 901a + a 901b in a single panel.
I understand it was the precursor to the 901a/b/c/d (please let me know if I'm mistaken).

There are 4 fixed outs .... sine , saw, triangle, pulse. ,.... all available simultaneously.
Level of these fixed outs is 0.5V RMS (-4 db).
600 Ohms impedance.

Sine:

Saw:

Triangle:

Pulse:

There are also 4 variable level outputs... which opens the window to mixing the different waves in varing amounts and sculpturing new waveforms.
Their range is 0 to 0.5V

There are 3 CV inputs.
There is a CV span of -4V to +6V according to the manual.
I like to keep it within the range or 0 to +5V

The frequency span of the VCO is 0.1 to 15Khz
There are 6 ranges: Lo, 32", 16", 8", 4", 2"
(Lo is good for LFOs)
The tuning of these oscillators definitely drift... but it's part of their charm :-)
I've read that Wendy Carlos had to tune them again and again while recording.
 It might be the stability of the power supply ??
The manual states that keyboard tracking is a full 5 octaves... though I think maybe 2 octaves is more
reasonable. Still I love their sound.
Any temperature variations will cause large fluctuations.
Power supply requirements: -6V , +12V regulated.
                                                 -10V unregulated.

This is the view of the rear.
The PCB mates with a 22-pin connector.
(Tyco Duo-Tyne flag 22 pin edge connector)
The connections are
1. +12V
2. Ground
3. -6V
9. Sine out
11. Triangle out
12. Pulse out
14. -10V
16. Sawtooth out

Below is a pic of the 901a & a series of 901b modules
The VCOs were designed to work in banks, with a single 901A oscillator driver module.

In this pic, there are four 901b oscillators being driven by one 901a controller.
According to the manual, up to twelve 901b oscillators can be chained to one 901a controller.
The idea behind this was so just one set of CVs (from a keyboard for example) could drive a bank of 901B VCOs and they would track nicely together.

901A controller module
There are no output jacks. Only CV inputs.
There is a CV span of -4V to +6V according to the manual.
I like to keep it within the range or 0 to +5VPower supply requirements of the 901a : -6V and +12 V regulated. Max current is 25ma.

The PCB mates with a 22-pin connector.
The connections are
1. +12V
2. Ground
3. -6V
5. This connects to the corresponding number on the 901B
6. This connects to the corresponding number on the 901B ???
7. This connects to the corresponding number on the 901B
9.   Control input jacks
10. Control input jacks
11. Control input jacks
12. Control node

901-B Oscillator

Each 901B module has 4 output jacks ... one for each waveform.
Saw, tri, sine, pulse .
The amplitude of each waveform is 0.5V RMS

sAW

Sine:

Pulse

Triangular

Oscillator 901B connector  pinout.
The PCB mates with a 22-pin edge card female connector.
The connections are
1. +12V
2. Ground
3. -6V
5. This connects to the corresponding number on the 901B... "A"
6. This connects to the corresponding number on the 901B... "C"
7. This connects to the corresponding number on the 901B... "B"
9. Sine out
11. Triangle out
12. Pulse out
14. -10V
16. Sawtooth out