Arp 2600 - Envelope Follower & pre-amp

The APR 2600's envelope follower is a often ignored module.

However, its really useful and with clever patching, can greatly enhance the use of the 2600.

Found on the extreme left, the module is grouped with a pre-amp & ring modulator.

It tracks the amplitude of an incoming audio signal and generates a control voltage (CV) up to +10 V that can be used to modulate other parameters of the synthesizer.

The envelope follower is most often used with external instruments

such as using a guitar as an input signal to modulate the filter cutoff frequency of a synthesizer. By controlling the filter with the guitar's amplitude, the synthesizer can create a more expressive and responsive sound that mimics the characteristics of a guitar.

The Envelope Follower can also be used in place of an envelope generator

if you have an external signal. Thus with little more that a external sound source you have an extra envelope to modulate VCO's VCA's or filters.

The Pre-amp is important when imputing an external audio signal.

It can amplify signals up to 1000 times.

Use a guitar, mic, voice, keyboard , tablet, MP3 players, 

drum machines, Kaoss pads, etc etc 

Really versatile.

The pre-amp is normalised to the envelope follower.

Thus you don't need a cable to connect the two.

Note, that there is now no connection going from the Env Fol output

to any other part of the 2600.

In practical terms, the EF converts amplitude into voltage.

So the louder the signal, the greater the voltage.

Also, remember the EF's output is hard wired to the input of the lag processor.

Interesting! Why would you want that?

I think, if for example we plug in sounds with quick attacks like drums, we can control how responsive everything is.

Before connecting any external instruments it a good idea to check levels first.

You may want to connect your mic for example into the pre-amp input and set the 

gain to the lowest.

Patch 1

Control the pitch of a VCO with an external instrument.

Always use one of  the module's "control inputs".

Patch 2

Controlling the filter.

Remember you'll need to plug it into one of the Control inputs , not into the Audio section of inputs.

Basically, we are replacing the ADSR with a new envelope.

Patch 3

Say we want to hear the guitar / external drum but also want that instrument to impact the filter

By tweaking the envelope follower slider, you'll be able to change the effect amount on the filter.

Patch 4

VCO & filter modulation

Patch 5

Feedback & distortion

Using the Pre-amp (keep the gain down).

The pre-amp output goes into the VCA (replaces the VCF input).

In this example, Ive taken a saw waveform and plugged this into vco 2

Play around with the different knob and sliders -- pre-amp gain & filter cutoff & res is fun.

Patch 5

Voltage controlled Resonance.

1. Plug the output of the ring mod into the input of the envelope follower.

2. the output of the pre-amp is plugged into one of the inputs of voltage processor 1

3. VP (inverted) ---> ring mod input on the VCF

4. The filter output, goes into the left input of the Ring Mod.

Patch 6

Ethereal Phase-shifting on an External Source

p.96 - Original ARP 2600 patch book.

Patch 7

"Ow" on external source.

p.98 - Original ARP 2600 patch book.

Check out the 

Drum-controlled ADSR & S/H

PWM ???

p.99 - Original ARP 2600 patch book.

(I haven't tested this out myself).