From smart@nn.comTue Jun 13 10:30:38 1995 Date: Tue, 13 Jun 1995 12:26:09 -0500 (CDT) From: Mark Smart To: analogue@hyperreal.com Subject: Re: about the GS-300 > On Mon, 12 Jun 1995, Tosh wrote: > Did anyone ever find out whether the thing could be MIDIed or CVed? > What synthesizer is it close to sound-engine-wise? > I've always wondered.....I noticed "VCO" on the front of the unit...:-) > It's called the GR-300, not GS-300. I have one of these and recently got schematics so I can do some mods. The thing I like about it is that it's an extremely fast and accurate pitch-to-voltage converter; the disadvantage is that it's a VERY primitive, non-programmable synth. The architecture is like this. Each string can drive one or both of two sawtooth-only analog oscillators. One osc. always follows the guitar string's pitch, and the other can be set to be some fixed musical interval away from the first, up to a little over an octave in either direction. Two tunings for the second oscillator can be set with knobs and selected with footswitches called "A" and "B". A variable portamento time can make the oscillators sweep gradually from A to B instead of changing instantaneously. The oscillator(s) for each string follow the amplitude envelope of the guitar string. (no sustain function or ADSR amplitude envelope generator at all). Here's the part that really sucks: all six (or twelve) oscillators get mixed and sent through ONE lowpass VCF at the end. The filter doesn't follow the pitch of the strings (how would it know which string to follow?), but at least it does follow the sweeping from pitch A to pitch B. A primitive AD envelope generator (actually, the attack is variable, but the decay follows the envelope of the mixed guitar strings) can allow slow filter attacks for wwwwhhoosshhhhhh effects. (the GR-300 can be heard doing this at the beginning of "Secret Journey" from the Police's "Ghost In The Machine" album). In addition, the guitar has a hexaphonic fuzz unit: each string is run through a separate distortion circuit, so that when you play jazz chords, it sounds like a Queen album instead of mush. I suppose with some klooging it would be possible to control it with MIDI, but it probably wouldn't be worth it. To me the thing's strength is its incredible tracking as a guitar synth, faster than any other unit I've played, including the newest Rolands. I'm currently trying to hook it up to a real programmable analog synth to increase its sound pallette. At least the two or three sounds it can do are pretty cool. The distinctive part of its sound is that the note attacks have a kind of squeak which sorta sounds like a violin attack. You can hear this on a lot of Pat Metheny albums. Anyway, that's the basic setup. I don't think it's analogous to any Roland keyboard synths, but I could be wrong. Mark Smart