looking for envelope follower info

Magnus Danielson magnus at analogue.org
Sat May 9 02:32:28 CEST 1998


>>>>> "KD" == Kevin Day <kday at netcom.com> writes:

 KD> Hi all,
 KD> I would like to build an envelope follower.  I've never built any
 KD> musical electronics before, but I am reasonably handy with a soldering
 KD> iron, so a schematic using (hopefully) easily available parts might be
 KD> sufficient.  Ideally, of course, more information will be available such
 KD> as design notes, full parts list, etc.  I didn't find anything very
 KD> detailed on the net... does anyone have any suggestions?

There are several schematics available on the net. Out of my head I
recall the Korg MS-20 schematics (they are at Music Machines) as well
as part of the Moog Modular (Moog 912) schematics that where runing as
a thread a week ago or so...

You might also find similar cursuitry among the stomp-box department
and I think Jamie's got a few.

The generic design is usually:

An input amplifier with variable gain.
A precision full-wave rectifier (usually 2 diodes, 2 op-amps and a
bunch of resistors).
A lowpass filter to dampen the signal residues, this is usually
variable to change reaction time.
An output amplifier/buffer.

Then there is many variations to this of course.

It is all standard parts, 1N4148's, your favorite op-amp, some caps
and you are all set.

This is the basic envelope follower cursuit.

Cheers,
Magnus



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