Cycling 74 » Topic: 1v/oct from Max to control Analog Synth

1v/oct from Max to control Analog Synth

lesespejo — Sat, 12 May 2012 16:10:23 +0000

Sorry, for the noob question, i’ve been searching in the forum for something similar but only found old posts.

Well, to the point I need to send signals from Max to my analog modular synth (euro rack) to control pitch (frequency) in my oscillators, the convention in euro rack is 1 Volt per Octave.

I know i need i DC coupled audio interface, instead i use Expert Sleepers ES-3:

http://www.expert-sleepers.co.uk/es3.html

I’ve try sending many different types of signal and there is no problem, so i think is perfectly possible.

- Frequency in Max is measured in Hz
- Frequency in Euro Rack Analog Synths is measured in Volts per Octave

So I think i have to scale in some way Max’s Hz and transform them to Volts per Octave maybe multiplying, but i have try this and is not as accurate as i need. I send this patch copied from somebody in youtube which i think is pretty close to what i need, hope no body get offended, it’s made for my interface, so maybe it’ll need some tweak.

Thank you in advance for any help

– Pasted Max Patch, click to expand. –

Re: 1v/oct from Max to control Analog Synth

spectro — Sat, 12 May 2012 17:16:11 +0000

A fader at the output for a CV has a good chance of messing up your voltage scaling completely. Here is something to start with. Based on A @55hz = 1V. Edit: For some reason I can’t figure out, there now seems to be a slight offset in KSlider!?… too late to work out now. It’s past bedtime here…

– Pasted Max Patch, click to expand. –

Re: 1v/oct from Max to control Analog Synth

lesespejo — Sun, 13 May 2012 09:57:52 +0000

Spectro, maybe didn’t understand, but your patch didn’t work for me, and i forgot to say, that i don’t want to use midi, which i think, is easier to implement if you have a Midi to CV module, anyway i received some help from my fellow wigglers from the muff wigglers forum, and discovered that the maths i need are logarithms so in the new version i use log object and as you told me there are no sliders. Still no as accurate as i need but is closer.

– Pasted Max Patch, click to expand. –

Re: 1v/oct from Max to control Analog Synth

lesespejo — Sat, 19 May 2012 18:19:10 +0000

Please anyone there with any advise to do these??

I’m trying hard but i think my project needs go beyond my Max skills……….

Re: 1v/oct from Max to control Analog Synth

big_pause — Sat, 19 May 2012 22:36:35 +0000

if you want a change of 1 / octave, then what you are after is using log base 2, in max signals function, just use [log~ 2], this comes directly from the fact that the ratio of the frequencies of 2 pitches an octave apart is 2 to 1.

Re: 1v/oct from Max to control Analog Synth

oli larkin — Sun, 20 May 2012 09:50:58 +0000

get a multimeter/voltmeter and put the terminals on the tip/ring of a jack lead connected to one of your ES3 outputs. Set the multimeter to measure DC voltage.

connect a number~ or sig~ + flonum to the dac~ output that goes to the ES3 output.

gradually raise the the value you are sending out until you see 1 volt on the voltmeter – note down the value. Let’s say the value was 0.307. Now you can use the scale object to map semitones to voltage…

scale 0. 12. 0. 0.307

if your synth has good tracking, it should be reasonably in tune without using any kind of pitch tracking (like Volta or silent way does)

hope that helps,

oli

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