Any advice on building a good Envelope Modifier?

[loss1234]

I have been reading about the Maestro Envelope Modifier and it sounds like the type of thing I'd like to build, similar to an EG in a synth but for guitar. However, the Maestro circuit looks pretty transistor heavy so i was wondering if there is a better, smaller parts count way to implement an ENVELOPE onto a guitar signal.

Has anyone done a circuit that does this? Sounds like it would basically be an envelope connected to a vca of some kind that would "Shape" the guitar sound. It would be great if using a track and hold, you could even get it to artificially hold the note so you could have a "Release" control.

anyway, not sure if this exists or not.

thanks

[Mark Hammer]

"Good" envelope modification really needs a signal with characteristics more like that of an oscillator; i.e., as close to steady state as possible.  You CAN do something like that with a compressor, but realistically, you probably want something like a nicely lowpass-filtered fuzz that is capable of providing a long-sustaining tone that retains lots of harmonic content for a while.  the trouble with regular old guitar signals is that: a) by the time you can achieve some sort of audible swell the input signal has actually decayed enough that you can't hear the swell, b) the guitar doesn't sustain long enough for a decay-time control to be of any earthly use, and c) whatever swell you can hear is undermined by the fairly rapid loss of harmonic content after the initial transient.

Something like the trigger extractor circuit that Craig Anderton had in keyboard Magazine back in '83 or so, driving a simple Attack/Decay envelope generator (which in turn drives a VCA), would deliver more useful results.  Naturally, the signal that feeds the trigger extractor (which identifies that a new sweep should begin) should be clean so as to provide the most dynamics (hence, least likelihood of false triggering), and that signal needs to be fuzzed and filtered before it goes to the VCA.

[flo]

Something like what Mark suggests would be nice: Gate/trigger extraction, fuzz, attack-decay, VCA.
I can hardly believe that there is no simple schematics and layout already avalable... but I can not find it yet. If somebody knows a link to a project please post a reply. Thanks.

[loss1234]

well i have been playing a lot with sine to square conversion, triggering multiple counters, so really what i am processing with the envelope should already have plenty of sustain (although if it doesnt i have been reading a lot about track and holds, and maybe something like that could continue the end of the last note)

anyway, when you say a trigger extractor, I think ray wilson has one on his sight. so i would get a trigger from the amplitude of the sound, send that into a small Attack Release and VCA circuit? i havent ever seen that ANDERTON circuit you mention but i will look for it.

is this the principal the the MAESTRO circuit worked on?


you know a lot of what i have been doing to find FX i want, is to use my (DIY BUILT) modular synth as a testing ground. So say I want to see what my guitar would sound like filtered with a sample and hold triggering the filter, well i just patch it up. BUT obviously my modular is giant and the PCB boards are way too big to fit in a small pedal. SO i am testing the CONCEPTS in my synth but looking for stomp box type circuits on this SITE and others.


i have been poring over the EH rackmount guitar synth schematics trying to find the blocks that make up the ENV and the VCA,etc but it can be pretty hard to follow sometimes.

anyway, sorry for rambling and thanks for the advice. i think what you are saying is there is no easy magic circuit.

[Mark Hammer]

Well, there ISN'T any easy magical circuit, but that doesn't mean it has to be complicated either.  For example, a simple A/D or A/R envelope is probably sufficient for most guitar needs.  The one found here: http://hammer.ampage.org/files/Device1-2.PDF is simple and sufficient.  Pretty dang easy to perf in an evening.  The Anderton trigger extractor is posted but I need to find the link (possibly at the www,synthdiy.com archive).  Only takes a quad op-amp and some garden-variety passive components, and can provide a variable-duration gate in addition to 5V and 10V trigger pulses.  Alternatively, just go to Ray Wilson's "Sub-Commander" Guitar Synth and have at it.  At least you know you can get a single board that will include everything you need.

[loss1234]

thanks a lot for the leads!

while the ray wilson guitar synth is really cool looking, its quite a bit more than i need for now. plus i think building all this out on my own on perf or press n peel will end up teaching me a lot! i am going to get started on the A/R and i will look for that anderton circuit.

do you have any recommendations on a vca to hook to the end of this? i have had lots of bleed through problems with transistor based (chip based matched pairs) vca's in synthesis so i am wondering if i should go with an OTA...anyway.

thanks again

[flo]

I also found this. Looks interesting and seems to have all the components:
Sound Lab Mini-Synth
http://www.musicfromouterspace.com/analogsynth/SOUNDLABMINISYNTH/soundlab.html
Sound Lab Mini-Synth Guitar Trigger
http://www.musicfromouterspace.com/analogsynth/SOUNDLABMINISYNTH/guitar_trigger.html