Pitch to Cv converter

[tjs2010]

Hi everyone, sorry if this is te wrong section, couldnt quite work out where it belonged. Feel free to move it if a mod spots it and it belongs elsewhere..anyway..

Im creating a pitch/ cv converter for a university project. Ideally so i can plug a guitar into an analogue synth as the input signal. I know there is a similiar (well identical thread) from 2006 but wanted to start a fresh one as im sure there are new members with knowledge on the subject, well hopefully anyway!

From my current understanding ( mainly gathered from http://www.soundonsound.c...es/synthsec.htm and bits and pieces during my studying) this is how its done...in theory at least.

My electronics knowledge is not amazing, I study a degree in audio and music technology but will be beefing up my knowledge in the next few months as the project develops.

Essentially I would like to know who has any expereance doing such a project or can point me in the right directions or any general advice would be useful

Many Thanks,
Tj.

[Jarno]

Not CV, but there is a project for a guitar-to-midi converter in Everyday Practical Electronics magazine. And there's also a very low-cost one from Sonuus.
Not sure which part you want to study, the actual electronics building, designing theoretical conversion, writing software, but you might want to choose a starting platform to narrow the scope a bit. (also not sure how much time you want to put into this).

[tjs2010]

Hi Jarno, I need to make it so that it is a frequency to cv converter as this is what i've specified im doing now so won't be using midi.

I intend to put a large amount of time into this as its outcome is essentially going to determine whether I acheive my intended grade or not.

I need to put together the circuit andunderstand how and why it works.
I have seen that there is a few microchips which could do freq - cv conversion such as the LM2917 and theres a few others.

LM2917 - Frequency to Voltage Converter

I also found this resource
http://www.national.com/an/AN/AN-C.pdf

Do you have much knowledge within this area or general electronics yourself?

Thanks for the reply aswel, any help is greatly appreciated!
Feel like I am letting myself in for a bit of a learning curve here!

Tj

[Jarno]

Just some general electronics experience myself, and just analog. I have built quite some effectspedals, but no synth stuff.

That IC looks pretty interesting, but I do wonder how well it behaves with inputs that aren't squarewaves.

[tjs2010]

My thoughts too about the IC. How would you look to go about constructing such a device? I know its a broad question, but need to gain some direction in this project!

[Enzo]

You may not intend to use MIDI, but if there are existing circuits for pitch to MIDI, and there are circuits for MIDI to CV, then that might suggest a path to success?

And may I suggest, if you are searching with google or similar, search for plain old frequency to voltage conversion, not CV or control voltage. frequency to voltage conversion is a common circuit type. CV in this context is very esoteric - the synth pitch control, and that will seriously limit the hits you get.. Once you have a working freq to voltage conversion going on, it should be simple enough to scale it to 1v per octave or whatever else you might want.

Googled for frequency voltage converter and got a lot, at least three different chip makers offer somethihng on the first page of results.

And go over to some of the old analog synth forums or newsgroups and ask about it. I doubt you are the first person to do something like this.

[neonleg]

hi!
have you tried looking at how roland & korg and other manus did it back in the day? the ms20 had a relatively reliable pitch to cv circuit but they did use hz/volt scaling. the roland gr500 and other guitar synths used pitch-cv too i think. you probably want 1v/octave scaling for this project to make it universally usable or is that not important?
heres the ms20 circuit maybe that helps?

[tjs2010]

Hi, thanks again for your replies.

Enzo, the freq - midi .. midi / cv is something I had a thought about, I'm going to see if i can avoid that route for now but at least i know i have that there as a backup and might be worth a bit of research for my write up anyway. I have been searching for as many different terms as I can think of which like you said bring up a fair few hits to microchips which operate as tachmeters ( essentaily something that converts freq into V; if im not mistaken? ) obviously there are potential problems like the squarewaves we mentioned ealier.

I think your right that I should aim first for a device which simply converts frequency into voltage, then work on the scaling after.


Neonleg, hello! Thanks for getting involved. I have stumbled accross a few synths that did such things back in the day although I dont think they were the ones you mentioned so thanks for that. Going to be spending a fair few hours checking this stuff out tomorow. I was intending to go for the 1v/octave scaling so that it can be used universially yes. As far

[Charles Darwin]

These people make one:Analogue Systems
It's the RS35 but how to actually build one I do not know.
May be if you ask them nicely and explain your situation they might be willing to help.
You will need an envelope follower as well though to make full use of its functionality.
It is included in their module. Doepfer have one in the planning stages.

[neonleg]

hi yeah there are a few vintage units that use this to varied degrees of success. i have at hand an arp avatar which derived a CV from a six string guitar by means of 6 individual frequency pickups. the ms20 of course which is monophonic too but uses a single input. the most interesting unit is the EML poly box which uses a phase locked loop circuit to act as a synthesizer "expander"
check it out Phase-locked loop - Wikipedia, the free encyclopedia
could be a good starting point..