The Voyager has it, the Retroverb has it, the LBB synth has it (I think), the Moogerfooger Ring Mod has it, and the WMD Geiger Counter has it.
I have all these and have never explored the possibilities of the CV ins and outs.
Can somebody explain how this works, what cables I need, and what NOT to do?
It’s exactly what it says–control voltage. It uses voltage output or input of a function of one device to control another devices function. The simplest example is using an expression pedal into a cv input. It’s basically just lke turning a knob on the Voyager, but it leaves your hands free to tweak other things.
For me, where CV really gets interesting is when you use it to sync disparate functions on multiple synths. For example, just today I was using the LFO CV out on my Ekdahl Moisurizer to control the pitch of my Voyager (simple connection with standard 1/4 cableHenson when I play the two together, anytime I increase the oscillation speed on the Ekdahl, it simultaneouly increases the pitch on the Moog. Really create for synchronizing sounds in live performance.
From an unknown and unverified source :
CV stands for “Controlus Voltagus” : a synthesizer induced illness/addiction for which there is no known cure (other than go buy yourself a couple of CP-251’s or any other device with in and out jacks).
So any cables will do…doesn’t matter if it is balanced or not right?
And are there any things to NOT do? I swear reading somewhere it can ruin things or screw them up if you hook them up wrong.
Read this : http://www.moogmusic.com/manuals/cp-251.pdf It’s all in there.
Edit : This is obviously not the same manual as my printed copy of the CP-251 manual. While the bulk of the manual still stands, there are a few anomalies in there. From page 24 (Technical Information) and on, resistance of input, output or potentiometers is often stated erroneously as 500W or 50kW (for example). These are not watts but Ohms and should read 500 Ohms or 50k Ohms.
Here is a quick rundown, about as simple as I can make it.
All sound travels in the form of waves. They have a particular shape with particular set of harmonics. How many times that wave cycles is called the Frequency.
THe Speed of the Frequency is measured in Hertz or Hz. Hz is how many times per second that wave cycles.
THe Strength of the Frequency is called Amplitude.
THe HUman ear can hear frequencies from 20 Hz to 20,000 Hz (or Kilo Hurtz or KHz) THe higher the frequency, the higher the pitch.
Now lets move on to voltages.
Voltages…
In an analog synthesizer you usually have knobs called potentiometers.
Unlike a digital synthesizer, when you turn a potentiometer, you are actually controlling the amount of electricity that is going through that circuit at a given point in time.
This is pre MIDI technology by the way.
If you have a circuit that acts in this manner, where the voltage going into it controls the amount of vibration that circuit makes, you have a Voltage COntrolled Oscillator (VCO). This is your waveshape generator. This is your sound generator. This is where Frequency and waveshapes enter the picture because this produces waveshapes.
Increasing the voltage in this type of Oscillator, increases the frequency, or pitch of the oscillator.
With Voltages, there is a voltage source and a destination. The devices you ask about have CV or Control Voltage inputs to accomodate the signal from a voltage generator.
A keyboard controller will send a voltage amount to an oscillator (like 1 volt per octave with some oscillators). This voltage from the keyboard changes the pitch of the oscillator, just as your hand physically turning the potentiometer will change the frequency. This is control voltage, an electronic hand that “turns the knob” for you.
Your Ring Modulator has voltage inputs that will allow you to connect an expression pedal that will control the Frequency, Mix, Amount or the Rate of the LFO on your Ringmod.
A VOltage Controlled Filter (VCF) acts in the same way. A Filter actually filters out the harmonics from a waveshape that an oscillator generates. a lowpass filter will allow low frequencies to pass through. This type of filter has a cutoff frequency potentiometer. Turning this knob will change the amount of high frequencies that are allowed to pass through. You can send an expression pedal to the Cutoff CV input to “turn” that potentiometer (or modulating) the cutoff frequency.
An Envelope Generator is a device that generates control voltages that evolve over a period of time. If you pluck a string, it will vibrate. it will have an Attack Decay Sustain and a Release. An Envelope Generator creates a voltage that conforms to these properties (ADSR), by putting a value to each.
A voltage controlled amplifyer (VCA) lets the sound generated by your osc to output to your speaker. Increasing and decreasing the voltages to this device will open and close the VCA, controlling your volume. A gunshot will have a very fast attack and decay, virtually no sustain with a long release as the sound dies out as the waves travel away from you. THe ocean’s surf has a slow attack and a slow release.
In summary,
If you have a device that generates voltages and has a CV OUT, hook it up to something that has a CV in, and you will have remote control over the destination normally controlled by a potentiometer.
Your LFO from your ringmod will modulate the cutoff frequency of a voltage controlled filter. If you hook that same LFO to your VCA, then it will turn up and down the volume really fast generating a tremelo effect. This is what happens to the Frequency of the Carrier Oscillator in your Ringmod when you have it switched to LO.
Any questions?
Eric
There’s a reasonably detailed primer at the back of most Moog manuals. Hop on over to “Products” then “Minimoog Voyager” (for instance) then “Old School” and click on the manuals tab.
There are sections on all of this including scenarios using the MP-251, etc.
Mostly, though… you learn from trying different things. I have a Little Phatty Tribute with newly added CV outs and I’m still learning an awful lot about how these voltages and in particular, the envelopes change the sound of my Voyager OS and my Moggerfooger pedal.
Moog also has a few training DVDs. Not sure how good or not they are… would appreciate a review from somebody out there… (the few bits on YouTube are only so-so)
The Fooger Training DVD’s show you just a few things you can do, basically just an introductory clinic, not too many really advanced things covered. They do explain what each in and output does, but as far as really creative wayt to hook them up theres not a WHOLE lot of that.
Eric
ericK “kHz or Kilo Hurtz”
That’s why in another tread I recommended hard physical exercise, Eric.
If kilos HURT, go figure what Megas and Gigas can do. Better get some strenght in the legs, arms and core before exposing oneself to KiloHurtz…
splitting hairs again? 
I think ill excercise a spell checker first next time. At least the information was sound (no pun intended).
Eric
…dont plug your junky old wurlitzer organ into the carrier input of your ring mod or it will cost you $65.75 
Why not? I can’t see anything inherently wrong with this. What happened?
ryan from moog told me the organ either had leaky caps or some voltage offst problems, and fried the op amp in the carrier input of the ring mod.
so plugging a functional organ(or any instrument?sound sorce) in yeilds great results, just not a broken one lol