Today I did some further experiments on the next little improvement to the MTG Turbo CPU for the Sequential Circuits Pro One: MIDI-to-CV. I’ve acquired a quad DAC (D/A or digital-to-analog converter) board that can be very easily hooked up to the CPU module in order to control a few more parameters in the Pro One.
For now I’ve tested controlling three parameters of the Pro One:
- Pitch (Osc 1 and/or Osc 2)
- Filter cutoff freq
- Filter resonance
- VCA ADSR/volume (I haven’t played around with this yet).
Therefore, taking input from MIDI or from within the CPU itself, here are some possible sources of data to control those parameters:
- MIDI Pitch Bend, Mod Wheel, Aftertouch, Velocity
- Other MIDI continuous controller(s)
- The internal sequencer data
- A soft-LFO that features a variety of waveforms including sample and hold (S&H)
- MIDI Clock/Sync??
Now coming up with a nice clean way for the end user to control it all — that will be a challenge.
Any other ideas or comments?
Well I don’t think the “VCA ADSR/volume” thing is going to work out.
On the bright side, Osc and Filter control is VERY easy — solder a wire and that’s pretty much it. The current firmware has some noticeable “zippering” if you move the MIDI pot controlling the filter, but theoretically I can use interpolation to smooth that out.
I already tested the S&H -> Filter cutoff and the effect is very sweet. Synching that to MIDI clock will be an awesome feature (though perhaps a little cliche).
The pitch bend is done! I added support for Pitch Bend Range adjustment (AKA Pitch Bend Sensitivity) via either SysEx or RPN 0,0.
Hi,
How about being able to control Portamento /Glide? Being able to switch it on/off and to control the time would be awsome. The Kenton midi/cv converter I use currently supports this feature…Your doing great work. Is it finished?
Hi,
No, it’s not finished. 😉 There is still some work to do on the CV stuff and other refinements. Also the CPU supports USB so it is theoretically possible to hook it to a PC without a MIDI interface, but that’s just a twinkle in my eye at the moment.
Regarding the Portamento/Glide question. Unlike external CV units, the Turbo CPU uses the existing internal DAC, so in that case it has no control over portamento. However, the optional CV board has a DAC of it’s own so it might be possible to experiment in this direction.
Hi,
I have a keyboard-less Pro-One and I was wondering if, by hooking it up with the Turbo processor and MIDI option, I would be able to use the Pro-One’s “Glide” via MIDI. The CV input on the synth actually by-passes the glide circuitry which I would like to be able to use since my MIDI-to-CV converter doesn’t have this feature built-in.
Thanks,
slalum
Yes you can. The TurboCPU uses the stock sound generation circuitry including the DAC. This allows all the original functionality plus, like you say, glide/portamento over MIDI.
Just to be clear, the stock Glide.
Good to know, thanks.
I have lots of DAC chips. Contact me at the email address at the bottom of the MTG website home page.