[sdiy] How the GR-300 Works

[Harry Bissell Jr]

The system is REALLY clever... by allowing the
sawtooth amplitude to vary (before the gate)...
they eliminate the need to use ANY temperature
sensitive components (like expo or log converters, or
divider circuits).

They also vary the clamp level dynamically... which
forms a crude -but-effective VCA as well.

each string only has a 1.5 octave range... so the
"spaced sawtooth" pulses have much less timbre
variation than you would imagine.

In my guitar synth, I do use a divider so I get a
true sawtooth... which can be processed to give true
PWM... and also suboctave, octave, and (woah, picture
this) FIFTH up.  I morph through all waveforms with a
single pot, or by VC.  Its probably about four times
as complex as the simple, elegant, Roland circuit.

H^) harry


--- John Mahoney <jmahoney at gate.net> wrote:

> Here's an interesting partial analysis of Roland GR
> and VG devices. 
> (I was going to CC this to Harry before I saw
> "Thanks again to Mark 
> Smart, Mike Bacich and Harry Bissell" at the bottom
> of the page. I 
> shoulda known. ;-)
> 
> http://www.joness.com/gr300/patent.htm
> 
> The "chopper gate" is an example of how a
> simple/cheap/clever design 
> can lead to a signature sound. I'm sure we could
> find many such 
> examples in the synth world.
> --
> john
> 
>