useful ways of using AUDIO as CV source???

loss1234

I am interested in using samples, guitar, vocals etc as way to create a CV or wave (pulse, saw, square,etc) so that the audio can be manipulated BY the synth and also Control or trigger it.

I know about envelope followers, but I am looking for things that either create a tone, or a cv. I was looking at Ray wilsons guitar synth but that pcb is HUGE so id love to find some simpler circuits.

is there an easy way to get a square wave from a guitar or sample?

thanks

widdly · Posted: Mon Apr 14, 2008 11:54 pm Post subject:

You can try distortion pedals, in particular fuzz pedals to get a squarish wave. A compression pedal is handy before the fuzz pedal to flatten out the envelope.

You might like to try some of these circuits... http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

Try looking at the "simple square wave shaper made simpler", "Stupid CMOS tricks", and "PWM". It's not going to be HIFI but probably interesting. They all have a tendency to crap out on the ends of notes.

CJ Miller · Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1

I don't have a lot of modules ready for real use, but one of the first boards I successfully built years ago - and which always near my bench - is my combination envelope follower/trigger extractor/gate extractor. They are based on the designs from Barry Klein's book. They are very useful. And then, of course, you can apply any other modifications to the envelope signal... invert, bias, rectify, and any other processing which can be thought of. S&H, T&H. Depending on what audio, a dedicated preamp is also useful.

Amplitude and frequency are mainly what there is to work with here, and of course an amplitude envelope is much easier to do. I've got a few Harry Bissell/EFM/Moog pitch-to-voltage PCBs, but I haven't finished those. P2V seems like a huge design challenge but I figure even errors will still provide fun signals to play with.

Simple samplers /wavetables can be fun to work into a modular setup for waveforms, processing, and include digital domain transforms not available with an analog input. PCM bends, logic-based effects and modulation, etc. These things can all yield fun sounds, and also data which can be used for other musical purposes.

loss1234 · Posted: Tue Apr 15, 2008 3:38 am Post subject:

great advice

those P to v PCBS you mention, were those one time sales or are they still for sale?

i have that barry klein book so i will check it out!

and making a square wave with distortion is something i have thought about a bit.

cant wait to get started!

thanks

Peake · Posted: Tue Apr 15, 2008 10:28 am Post subject:

I don't know if there's a schematic out there for the Korg X-11 "guitar synth" but parts of it might prove interesting/useful.

I've heard that some folks have had luck using simple, monophonic tones with the Korg MS20's External Signal Processor, but that it takes work to get it to produce useful results under particular conditions:

http://www.synthdiy.com/show/file/?id=1690

loss1234 · Posted: Tue Apr 15, 2008 10:35 am Post subject:

thanks

it sure has a lot of opamps in a row!!

i printed it out...lots of people have being saying its useful.

ericcoleridge · Joined: Jan 16, 2007 Posts: 889 Location: NYC

loss1234 · Posted: Tue Apr 15, 2008 3:05 pm Post subject:

we are both right, there are opamps AND cmos inverters. at least that was what i saw at first glance. i need to take some time this week to study that AND what you posted. thanks btw

the EFM P to v, i think i had a thread on here about that recently BUT he specifically stated it wouldnt work for guitar without some pre processing...i wonder if he still has pcbs?

I am very intrigued by the idea that ray wilson is using, which is to somehow get a pulse wave that is at the same frequency as the guitar, which allows for a pulse and a sub ocatve of whatever you play. maybe that idea mixed with the korg idea could be useful? i DONT need precision.

just results in a brute force kind of way!

thanks

loss1234 · Posted: Fri Apr 18, 2008 9:38 pm Post subject: PWM

on this page

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

there is a circuit called PWM

it allows you to take guitar (or audio ) and square it and PWM it. its a start towards getting a vco to sync or read cv from audio

BUT

here is a problem

lets say i am syncing my vco to this guitar
and then i stop playing for a second, well suddenly my SYNC IN is no longer getting a signal. so it starts squealing at some other pitch!!

so how do i get around this? is there a way to make the sync signal sustain (with a cap or something?) hmmmm

a reverb would be too much work to add to this!!

any ideas?

widdly · Posted: Fri Apr 18, 2008 11:18 pm Post subject:

Lot's of the envelope follower schematics have Gate output. Use the gate output to feed an envelope. Feed the VCO to a VCA and use the envelope to control the output level.

loss1234 · Posted: Sat Apr 19, 2008 6:14 am Post subject:

that's it? so its just like how id do it on a modular.

i would have thought it might sound too choppy.

but the more i read about it, even the moog 107 freq pedal talks about the same concept in their pdf

thanks so much

loss1234 · Posted: Sat Apr 19, 2008 8:49 am Post subject: SAMPLES

OK

here are some samples of my progress up to date

this is the best i can get it for now

i used the PWM circuit from circuit snippets, into the SYNC IN on my ken stone cgs48

i tried using JUST the synth signal in some, and in some XORing the guitar signal AND the synth signal..also adding lfo or sample and hold in some.

Sync is a strange beast though, it seems you cant modulate the vco in the same sort of way you could if it wasnt syncing.

here they are (comments please)

vco sync 2 gtr2.mp3

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gtr sync 1.mp3

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lfo mod gtr sync.mp3

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samplehold cv ync gtr.mp3

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loss1234 · Posted: Sat Apr 19, 2008 8:51 am Post subject:

by the way, the analog systems pitch to cv is in HZ/oct.
would there be any way to convert that to v/oct?

strange they wouldnt include the conversion in the module

Inventor · Posted: Sat Apr 19, 2008 9:18 am Post subject: Re: SAMPLES

loss1234 · Posted: Sat Apr 19, 2008 9:25 am Post subject:

interesting that they sound like clipped off guitar because only ONE of them actually should have contained any guitar...three of them had the guitar SYNCING a vco, so I suppose if it sounded Like a guitar, thats a good sign? maybe? because it means the vco was tracking the guitar well enough?

let me see what the 4th one was...

loss1234 · Posted: Sat Apr 19, 2008 9:28 am Post subject:

OK

the 4th one was heavily filtered and the filter was being modulated by a sample and hold module.

and i was playing chords i think (power chords)

that last one is more what i will END UP USING this for...stuff that has more of a weird synth sound. but the other three, well they seem to show me that the VCO will sync to squared guitar.

unless (but this is unlikely as i tried it on 2 vcos) the sync is not working and the signal is just bleeding through. but i don think this is the case.

next i will try feeding counters with the signal.

Inventor · Posted: Sat Apr 19, 2008 9:43 am Post subject:

loss1234 · Posted: Sat Apr 19, 2008 10:12 am Post subject: follower?

hey can anyone recommend a good synth envelope follower that is low parts count but good performance?

i wasnt using a true follower on those samples i was just plugging the audio into the gate in of my adsr.

thanks

CJ Miller · Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1