VCO in FM mode

djfill · Joined: Jan 10, 2012 Posts: 26 Location: Cardiff, Wales, UK

Has anyone tried FM synthesis using yusynth VCOs? I've tried some basic patches and compared with a digital FM synth but get different results. Although I get good results using subtractive synthesis, I'm not really sure how high to set my expectations when trying FM patches. I do get some interesting metallic sounds, but the tracking isn't consistent which causes the timbre to change between notes.

On my digital synth, if I try a basic single Modulator to Carrier patch with a 1:1 ratio and slowly increase the Mod level, I get a nice organ type sound, whereas with my VCOs I get a harsher sound. Another thing to say at this point is I have the same issue as others with tracking and stability. I get good tracking for about 3 octaves but thats about it.

Am I setting my expectations too high for the oscillators, has anyone else had much success in this area? Or should I just be happy with a great subtractive mini modular....

I'm willing to do a video demo for anyone that's interested...

Thanks, Phil

gdavis · Posted: Mon Mar 17, 2014 3:09 pm Post subject:

Ya, analog FM will never be as accurate as digital. It's very sensitive to the frequency ratios which with digital oscillators can be made absolutely perfect, but analog is never perfect. There's also the fact that digital synths labeled as "FM" aren't always technically FM (i.e. DX7 is actually phase modulation). Don't know if the difference is really audible though.

There's also a difference between log and linear FM, and if you start going into deep modulation there's through-zero FM (which the Yusynth VCO's don't do).

One thing you can do that might help a little bit is to connect the output of the carrier to the sync input of the modulator (I've been meaning to experiment with this myself but haven't gotten around to it).

There's a guy on muffwiggler who's been developing a digital modular FM oscillator that looks (and sounds) pretty darn cool.

yusynth · Joined: Nov 24, 2005 Posts: 1314 Location: France

IN order to achieve what you expect (like digital FM) you need a so called Thru Zero VCO, which is not the case of the YUSYNTH VCO. With the YUSYNTH VCO you can only achieve weird FX, you can't expect to have something in perfect tune while using the FM modulation.

djfill · Joined: Jan 10, 2012 Posts: 26 Location: Cardiff, Wales, UK

ok, thanks for the response...at least I won't be banging my head against the wall trying to achieve the unachievable...Though I did manage to get a mean sounding FM bassline within one octave and will be great for FX and oneshots.

I guess I'll let the DX7 and the Modular stick to what they do best.

dstrength · Posted: Tue Apr 01, 2014 6:46 am Post subject:

FM via analog has indeed always left me with mostly effects type sounds.

But, there's some other concepts along the same line as FM that can be fun, and do work well with an analog modular. Basically, use your VCO to clock other things that would normally take a gate or CV.

Try Amplitude Modulation: Gate your VCA with an Audio range signal.

Another is to clock your envelopes generators with an Audio signal, then use the EG as wave shaper, treating the CV output as an Audio signal.

There's an excellent 63 part series of articles in Sound on Sound titled Synth Secrets that discusses many of these techniques....and can give you some other ideas for modular patching. I remember these articles opening up some new patching ideas for me...

http://www.soundonsound.com/search?url=%2Fsearch&Keyword=%22synth+secrets%22&Words=All&Summary=Yes