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Emulating the Roland GR-300 waveform
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Emulating the Roland GR-300 waveform
dot matrix madness
Since I haven't found a designed sounds/patches subforum will try my luck here:
Did somebody succeed in emulating the specific waveform of the Roland guitar synth GR-300 (or its successors) using modular modules?
This particular copped/clipped sawtooth waveform is illustrated in section "4 - Square Wave to Sawtooth Wave to GR-300 Wave" here:
www.joness.com/gr300/GR-300.htm
I assume a first approach would be to mix sawtooth and pulse, whereby the pulse width is controlled by the pitch (probably scaled reverse with respect to the pitch). As far as I see that from the schematic the GR-300 uses a 4-pole low pass filter.
Any further hints to get those typical Pat Metheny sounds he uses on the record "Offramp" e.g. in the track "Are you going with me" are welcome.

Thanks in advance!
Dave Peck
The final waveform, shown as (E) at the bottom of that image, looks like a sawtooth waveform through a clipper, with the clipper only affecting the top half of the waveform. If your clipper module doesn't allow independent clipping of the top and bottom halves of the wave, add a DC offset to the sawtooth to shift the whole wave positive, which will cause the clipper to only affect the top half of the waveform.
dot matrix madness
Clipping the sawtooth is exactly what the GR-300 does. Any recommendation on clipping modules, either DIY or Eurorack?
Dave Peck
Sorry, my rig is MU so I'm not too familiar with what's available in Euro. But there are Euro modules like the Doepfer A-136 which include a clipper function along with a lot of other distortion capabilities. Maybe do some searching on ModularGrid and see what turns up there?
dot matrix madness
Dave Peck wrote:
Sorry, my rig is MU so I'm not too familiar with what's available in Euro. But there are Euro modules like the Doepfer A-136 which include a clipper function along with a lot of other distortion capabilities. Maybe do some searching on ModularGrid and see what turns up there?

The A-136 module seems indeed the designated one for this purpose.
Squattamolie
Like Dave, my rig is MU, but I did try putting a waveform through a Q130 clipper module. The first pic is with it clipping only the top of the wave, the second pic, clipping both. By the way, I bought a GR300 with a G505 new, back in the day, and really liked it. Then, like a complete ass, I traded it in when I got a GM70, thinking "oh, the GR300 doesn't have MIDI, I don't need it anymore"! waah I still have and use the GM70, but I miss the GR300.





Dave Peck
Clipping both the top & bottom of the saw will boost the ODD harmonics a lot more, making it sound more 'hollow' and closer in sound to a square wave.

A couple of things worth noting:

1. If your clipper doesn't let you clip only one side of the waveform, you can still achieve this effect by combining the raw saw wave and a +5v DC signal in a mixer module (assuming your mixer module will pass DC signals) and then send the mixer output to the clipper. Doing this causes the audio saw wave to be shifted positive by 5V, so it is not alternating between -5V and +5V, it is alternating between 0 V and +10V, and now the clipper will only chop off the top peaks and will not affect the bottom peaks.

2. Now try replacing that 5V DC signal with a slow LFO sine wave, so the output of the mixer is a saw that is slowly being 'biased' up and down, shifting from +10v / 0 V, to +5V / -5V, to 0v / -10V, over and over again. Now when you send THIS signal through the clipper, something really interesting happens - you get an effect that sounds like pulse width modulation, but it is being applied to a SAW wave instead of to a PULSE wave. As the (saw wave+LFO bias) signal passes through the clipper, the clipper will chop off only the top, then both the top & bottom, then only the bottom, etc. You may have to carefully adjust the mixer levels for the saw & LFO to get best results.

3. Note that you can apply this same type of "clipper module as PWM" effect to pretty much ANY waveform by using this trick of mixing the wave with a biasing LFO before you send the waveform to the clipper.
dot matrix madness
The schematics of the Q130 clipper module seems just what I was looking for. Thanks very much!
Dave Peck
Yes, the Q130 will do exactly what you are looking for, but keep in mind that it is an MU format module and you were asking about DIY or Euro format. So to make it work in a Euro format modular, you'll need to re-panel it so it fits in the synth and give it new Euro-sized jacks instead of the MU-style 1/4" jacks, and you will need to provide the proper +15V/-15V DC power source required by MU modules, which is different from the 12V power needed for your Euro format modules.
flo
You could get similar results with: MAX ("fuzzy OR") functions, switches, crossfaders.
dot matrix madness
Dave Peck wrote:
Yes, the Q130 will do exactly what you are looking for, but keep in mind that it is an MU format module and you were asking about DIY or Euro format. So to make it work in a Euro format modular, you'll need to re-panel it so it fits in the synth and give it new Euro-sized jacks instead of the MU-style 1/4" jacks, and you will need to provide the proper +15V/-15V DC power source required by MU modules, which is different from the 12V power needed for your Euro format modules.

I checked the schematic and it should run without changes on +/-12V. Anyhow, I will build that on vector board with a 3HE front plate (full DIY as usual).
Dave Peck
Nice! If you're into DIY module re-paneling projects, the Dotcom modules make it easy. They have all of the electronics on a PCB that is elevated on standoffs behind the panel, and all of the panel controls are connected to the PCB using short wires from the panel components to small Molex 2-pin and 3-pin latching connectors located around the edges of the board (see photos). So you just remove the board, install it behind your new panel, and reconnect the wires from the PCB connectors to the new panel components. Viola!

dot matrix madness
Dave Peck wrote:
Nice! If you're into DIY module re-paneling projects, the Dotcom modules make it easy. [...]


Well, my DIY approach is a bit more on the "yourself" side:

fixed filter bank
Dave Peck
Sweet buttery Jesus! A DIY filter bank with hand-made inductors....!!

we're not worthy
Funch
dot matrix madness wrote:
Since I haven't found a designed sounds/patches subforum will try my luck here:
Did somebody succeed in emulating the specific waveform of the Roland guitar synth GR-300 (or its successors) using modular modules?
This particular copped/clipped sawtooth waveform is illustrated in section "4 - Square Wave to Sawtooth Wave to GR-300 Wave" here:
www.joness.com/gr300/GR-300.htm
I assume a first approach would be to mix sawtooth and pulse, whereby the pulse width is controlled by the pitch (probably scaled reverse with respect to the pitch). As far as I see that from the schematic the GR-300 uses a 4-pole low pass filter.
Any further hints to get those typical Pat Metheny sounds he uses on the record "Offramp" e.g. in the track "Are you going with me" are welcome.

Thanks in advance!
curious as to the outcome in trying to get the gr300 wave. I came close with the Erica Synths Fusion VCO set to triangle wave with the waveshaper knob on 1. The waveshaper morphs from triangle to saw wave.

But it is just a close approximation mono wave for playing one note lines and (when triggered from a guitar controller) tracks no where near as good as the orignal gr300 synth. It does however mix well with the original for slow fade in, held note type stuff.

Like the wave clipped info, might have to try that.
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