News:

Happy Thanksgiving to GDIY'ers in the US!
Travel safely!



soundguy

Synth guys, Audio to CV?
« on: October 06, 2004, 04:36:51 PM »
Is there an easy solution to get an audio signal to generate CV?  Id like to take an electric bass and get a minimoog oscillator or something similar to track it.  There's gotta be a way to do this, any ideas?

dave

chips are good with dip...


NewYorkDave

Synth guys, Audio to CV?
« Reply #1 on: October 06, 2004, 04:47:43 PM »
A Moog CV input is volt-per-octave, right? It's been a while ;)

Here's a schematic and PCB layout for a pitch-to-CV converter:
http://www.ele4music.com/pdfs/pv1.pdf

NewYorkDave

Synth guys, Audio to CV?
« Reply #2 on: October 06, 2004, 04:59:31 PM »
...or just look for a used 360 Systems Slavedriver
http://www.modezero.com/slavedriver.htm

alk509

Re: Synth guys, Audio to CV?
« Reply #3 on: October 06, 2004, 05:05:46 PM »
Quote from: "soundguy"
Is there an easy solution to get an audio signal to generate CV?


Just do an envelope follower type dealy... shouldn't be too hard.

Quote from: "NewYorkDave"
Here's a schematic and PCB layout for a pitch-to-CV converter


That thing won't track a bass... It doesn't track that well when presented with anything other than a steady frequency, symmetrical signal. There were some attempts to process the input to make it more easily trackable, but AFAIK, nothing really worked well.

Feed it a VCO, though, and it rocks!

Peace,
Al.

Lest laziness get the best of you!

soundguy

Synth guys, Audio to CV?
« Reply #4 on: October 06, 2004, 05:10:26 PM »
how would an envelope follower address the issue?  Is there an envelope follower with a CV output?

dave

chips are good with dip...

alk509

Synth guys, Audio to CV?
« Reply #5 on: October 06, 2004, 05:12:51 PM »
Quote from: "soundguy"
how would an envelope follower address the issue?


It won't... Sorry, I thought you wanted to track amplitude, then re-read your post and forgot to delete the EF comment.

Peace,
Al.

Lest laziness get the best of you!

soundguy

Synth guys, Audio to CV?
« Reply #6 on: October 06, 2004, 05:19:56 PM »
I just want to a bass to trigger an oscillator.  There must be a way to do it, seems like hip hop people would have figured this one out a million years ago.

dave

chips are good with dip...

squib

Synth guys, Audio to CV?
« Reply #7 on: October 06, 2004, 05:22:48 PM »
many years ago i had a unit that did this very thing. From memory it used a charge pump type circuit that converted ac to a frequency dependent dc, there is a cmos chip that does this...can't recall the type number at hand. To work though, it first passed the audio through a voltage contolled low pass filter that operated just above the fundamental. The control voltage for this was derived from the frequency to dc circuit, so it is a feedback arrangement. It required a bit of setting up but worked well. It also generated a amplitude controled gate generator. I recall teaming it up with a CV and gate to midi converter and singing into a mic to control a DX7.... ah those were the days!

NewYorkDave

Synth guys, Audio to CV?
« Reply #8 on: October 06, 2004, 05:23:17 PM »
There is a way to do it. It just ain't as simple as you probably want it to be :)

soundguy

Synth guys, Audio to CV?
« Reply #9 on: October 06, 2004, 05:24:54 PM »
Id be happy to buy a premade product, I just dont even know where to start with this...

dave

chips are good with dip...


gang of elk

Synth guys, Audio to CV?
« Reply #10 on: October 06, 2004, 05:36:05 PM »
to my knowledge there aren't many devices out there that do this well.  korg made a box that went along w the MS series of synths that does this.  it has a hz/v response curve, rather than v/oct.  

my sherman filterbank tracks pitch ok but there's no physical output for the internal cv that's controlling filter cutoff.  

the best pitch-tracking circuit i've used is the input section of a schumann electronics PLL, which, as you can guess by the name, utilizes a PLL to latch onto a monophonic signal.  i've asked john make a box that can do this and spit out CV but he hasn't done so.  

also, analogue systems (UK) makes a synth module that does this.  no idea how it works though.  see here

alk509

Synth guys, Audio to CV?
« Reply #11 on: October 06, 2004, 05:47:31 PM »
Quote from: "NewYorkDave"
There is a way to do it. It just ain't as simple as you probably want it to be :)


Yeah, there's definitely a way to do it: I had an Axon AX-100 pitch to MIDI box that really tracked beautifully! I think the AX-100 uses PLL's.

Peace,
Al.

Lest laziness get the best of you!

Steve Jones

Synth guys, Audio to CV?
« Reply #12 on: October 06, 2004, 06:01:51 PM »
To build one, perhaps you could copy the interface circuit from the Korg MS20 synthesiser - it has an external input section with a pitch to CV converter, an envelopr follower, and a trigger extractor. You would need to mod it's output from Hz/Volt to Volt per octave though.
Synthesizer technician
Sydney Australia.

http://synthrepairs.com

soundguy

Synth guys, Audio to CV?
« Reply #13 on: October 06, 2004, 11:46:07 PM »
Can you take a bass, feed it to a sherman filterbank and just output the triggered oscillator and filter with none of the bass input signal?  Thats all Im really trying to do, it would be incredibly convenient if that would work, dont know anyone with a sherman to try though...

dave

chips are good with dip...

hodad

Synth guys, Audio to CV?
« Reply #14 on: October 07, 2004, 12:02:38 AM »
Harry bissell designed a board for this purpose (may have been based on a circuit Moog designed for his theremins?)--it works pretty well.  It used to be availa ble through EFM  http://www.ele4music.com, but I don't know if it still is.  

Tom

gang of elk

Synth guys, Audio to CV?
« Reply #15 on: October 07, 2004, 12:07:07 AM »
sortof.  the sherman doesn't have 'oscillators' but during self oscillation the resonance peak becomes a sine whose cutoff freq tracks the pitch of the input source.  there are 2 filters so that's 2 sines.  they can be offset from each other w a rotary switch than sets the second filter cutoff freq at specific intervals relative to the first.  when resonance is cranked and you're in tracking mode, there's rarely a trace of the original source, so yes, you can ditch the original signal, not much of a choice really.  btw, only the sherman mk2 has this feature.  the original sherman mk1 does not have tracking. also, there's a switch for tracking -1 octave, -1quint, +1octave, +1quint, or normal.   mind you, the resulting sound is pretty aggressive and behavior is unwieldy, not at all like a typical minimoog tone, but fun as hell.

StephenGiles

Synth guys, Audio to CV?
« Reply #16 on: October 07, 2004, 08:46:13 AM »
This involves a great deal of circuitry. I suggest that you take a look at my tracing of the Electroharmonix Guitar Synth to be found on Mark Hammer's site. The library terminial I am using has right click disabled so I can't copy & paste the link. I try to find a workaround.

http://hammer.ampage.org/

There you go - it's 3 or 4 pages back.
Stephen
The best place to find a helping hand is at the end of your arm!

al_p

Synth guys, Audio to CV?
« Reply #17 on: October 08, 2004, 03:11:53 AM »
what about getting a midi pickup -> midi/CV converter -> synth? sorry no model #s off the top of my head. there are more than a few guitar midi pickups out there.

after a quick search this might do the trick. http://www.synthtopia.com/items/Roland/ROLGK2B.htm

the electro harmonics micro synth does an OK job...probably not as cut and dry as you would want though.

i've been meaning to research this more as i am really curious about doing the same thing but, with guitar...gets a bit tricky with poly i would imagine.
AL P.

alk509

Synth guys, Audio to CV?
« Reply #18 on: October 08, 2004, 07:54:43 AM »
Quote from: "al_p"
after a quick search this might do the trick. http://www.synthtopia.com/items/Roland/ROLGK2B.htm


That's not a MIDI pickup... You'd still need a V-synth box (or whatever it's called).

Peace,
Al.

Lest laziness get the best of you!

al_p

Synth guys, Audio to CV?
« Reply #19 on: October 08, 2004, 11:08:49 PM »
Quote from: "alk509"
That's not a MIDI pickup... You'd still need a V-synth box (or whatever it's called).


yes you are right. after a second look i realized. but the idea could still work...don't have time to look around right now. what do you guys think? i am curious.
AL P.


 

Related Topics

Subject / Started by Last post
Last post June 28, 2004, 07:27:36 AM
by kruz
Last post May 06, 2008, 02:27:48 PM
by barclaycon
Last post May 31, 2008, 09:35:10 AM
by mrclunk
Last post October 10, 2008, 06:13:30 PM
by Mbira
Last post March 06, 2010, 09:51:10 PM
by emorysmith