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Hz/V calibration broken for me...
MUFF WIGGLER Forum Index -> Expert Sleepers  
Author Hz/V calibration broken for me...
ringstone
Hi all

I'm having trouble calibrating my Hz/V synths with Silent Way - well, I can do so, but only over a limited range (roughly 2 octaves). I have a Korg MS-20, and Yamaha CS-15 and CS-30.

I am using a MOTU 828 which puts out a range of -2.7V to +2.7V - I calibrated my synths with this and got the above-mentioned range and felt that was fair enough given Hz/V control voltage needs to go up to about 16V to give a 5-octave range. I wanted to see whether using an ES-1 would give me a more usable range so I knocked up a prototype myself with schematics posted here. I adjusted it so I got a range of roughly -9V to +9V with the MOTU 828.

Now, while my V/Oct synths seem to calibrate OK with this circuit (I got a doubling of the range on my Future Retro XS for example) I can't for the life of me get any more range out of any of my Hz/V synths. If I use the DC output plugin I can manually get the range I want... but the Voice Controller just gives me around a 2 octave range roughly in the middle of the graph... I have tried different waveforms (I always seem to find Saw works best) different scale settings etc etc. I get a better range on my MS-20 by using the VCO mod input (which is V/Oct) than the Hz/V pitch input!

Can someone shed some light on this? Hopefully it's just some simple thing I have overlooked...

Cheers
Blair

PS On the DC capable soundcard circuit (without the rectifier) one side of the offset pot is connected to ground rather than +15V in the AC circuit. I had trouble with this until I changed it to the same as the other one...
Analog>Plugins
That is odd because using the 2408mk3 I can get 6 octaves out of my Yamaha CS-30, gives me better range than my volt/octave synths.

Not sure what to suggest really.
os
First thing - am I right in thinking that Hz/V synths generally only respond well to positive voltages? If so, you're wasting half of the resolution of the Voice Controller by having it calibrate over the whole -9V to 9V range. In the VC's Output Matrix, set the pitch scale to 0.5 and the offset to 0.5. When calibrating it should then only emit voltages from 0V to 9V.

Secondly, when you calibrate, is the Voice Controller failing to reach the full range of pitches, or is it making the synth emit the full pitch range but just failing to recognise them? If the latter, could you record audio files for me of a) the Voice Controller's pitch CV output and b) the corresponding audio coming back from the synth (i.e. they need to be recorded in sync). Then I might be able to spot why the plug-in isn't calibrating.
ringstone
That's not surprising given that the 2408 MkIII puts out almost double the voltage of an 828...

I adjusted everything a bit today and finally managed to get about 3.5 octaves from the MS-20 from the normal CV in jack. However I managed to get around 6 octaves from the VCO in (the full range of my AX-73 keyboard!) so I think I'll be using that. Can't really think of any disadvantages there.

Seems that the problem may be with the Yamaha CS-series synths, I measured the CV out across the keyboard and it only seemed to range from around 0-2V! Which means the standard output from the 828 should give me all the range I need... and testing with the DC plugin I just confirmed this.

However, even scaling the pitch output from the Voice controller plugin to 25% I am still getting the same range. It just gets to a certain pitch and the synth stops responding. Oh, I am using a "floating ring" cable as well, although it doesn't seem to matter whether I do or not, a standard mono cable seems to exhibit the same behaviour...
ringstone
Ahhhhh.... that did the trick, adding the offset doubled the available range!!!
os
Hurrah!
Analog>Plugins
Damn I did not know that the CS synths only use positive voltages, that trick should work lovely.

Love these old Yamaha synths.
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