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??
For now I’m thinking it would cost about $25 to add these features to and existing MIDI+CPU setup. And it would be very easy to install. 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,
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.
No, it’s not finished.
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.
Hey there,
I’m very interested in buying the “Turbo CPU + MIDI + CV” but I don’t see it on ebay.
Please advise.
Jeff
ps- I really believe in keeping these rare gems alive and kicking and I think this update is a dream come true.
So, I just bought this update, but realized that I may need to write you offline to talk about the CV beta. Please contact me!
best regards,
Jeff
I have lots of DAC chips. Contact me at the email address at the bottom of the MTG website home page.