More GX-oscillator fun

[k brown]

What began as an alternate version of my earlier emulation of the Yamaha CS70M with the simple Saw/Pulse switches replaced with the multi-wave/filtered wave style oscillators like the GX-1, turned into a full-blown hybrid of the CS70M and CS-80, with the addition of GX-style oscillators.

The CS70M was Yammy's last analog synth for many years (came out just before the release of the DX7), and was almost a CS-80 with full patch memory, splitting and layering. But to get all that, it dropped a few functions.
- The series HP > LP filters (filters switched LP or HP).
- The 'Initial Level/Attack Level/ADR' filter EGs (standard ADSRs instead - some saw this as an improvement ).
- The two 'channels', I and II, are not accessible at the same time; one had to software-toggle between them and use the same panel controls - yuck!
- No Velocity and Aftertouch control of the two channels' filter cutoff and volume (Brilliance' and 'Level').
- No Velocity control of anything!
- LFO target switches rather than individual levels for each.
- No ribbon pitch controller (regular P-Bend and Mod wheels).
- No Keyboard scaling.

It did however have a few things CS-80 did not:
- A second LFO with dual outputs; one controlled by the mod wheel, the other by aftertouch (very nice).
- The other LFO had a dedicated AR envelope to sweep rate (partial stand-in for the CS-80's odd-ball Ring Mod), or be used as a direct CV for any combination of VCO, VCF, VCA or PW (also very nice). This LFO could also have it's output increased by the mod wheel.
- A built-in sequencer (yawn).
- Patch layering/unison/keyboard splitting.
- Regular P-Bend and Mod wheels.
- A butt-ugly panel.

So what I tried to do with Yumaha CS75M g (between 70 and 80, with a g on the end, get it? ), is combine most of the stuff from both synths, plus the GX-1 style oscillators (hopefully without making the GUI too crammed and cluttered), and with all controls visible on a single panel. To boot, it has a panel and slider style/colors of the CS-80.

To add the CS-80's individual level controls for each LFO target, 'ghost' half-knobs have been added to the target On'Off buttons (it's nice to be able to toggle individual modulations OnOff without disturbing their levels; something you couldn't do on the CS-80).

In addition to the GX-style oscillators, it has the GX-only capability of inverting the VCF envelopes.

Yumaha CS75M g copy.jpg (114.07 KiB) Viewed 11055 times

Yumaha CS75M_g.fsm

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The stepLFO can operate as a single 16-step or two seperate 8-steps.

Comes loaded with crude approximations of the CS-80's preset 'Tones' and a couple of my own.

I tried like blazes to give this the same keyboard split that kortezzzz ironed out for me to use in T-forTwo, but I just couldn't get it to work - my hunch is that it's to do with the two channels sharing the stepLFO, but that's just a guess.

Since I'm not a great fan of sequencer-style music, I'm thinking of doing a version of this with a long, looping (Frippertronics-style) Delay plus Martin's MVerb 7B in the panel space occupied by the stepLFO. Or maybe the Delay plus a simple graphic EQ, so one could produce something similar to Eno's Discreet Music using a single plugin?

[kortezzzz]

Hi Kevin.
Just saw it and I like it very much. I'm still learning the controls and much loved the oscillator's unique sound. This is quite complex synth so exploration time is needed. But I still don't understand why the splitting hadn't worked for you. You haven't mentioned the reason. If you have saved the schematic that failed to split, upload it too so we can try to manage it up.

[k brown]

Hey, thanks kz.

This is far as I could get it. When put in split mode, one side just goes silent; could be I'm missing something painfully obvious, but I tried everything I could think of.

Yumaha CS75M_s.fsm

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I think the only thing I didn't try is putting the stepLFO in it's own module outside of the synth engines. I fear this would require it to have a mono out; but then how do you connect it inside the synths as a mod source? But then this would also apply to the two LFOs, as the synths have those in common too? Maybe this only worked with T-forTwo because they were both entirely self-contained synths with their own LFOs.

[kortezzzz]

I can see that the keyboard does get splitted, but the signal is blocked somewhere at your blue\poly stream circuit.
It does make sense that sharing a LFO would prevent both modules working at the same time, but I realy have no idea how to manage that. Maybe adding 2 LFOs with the same controls would do the trick?

[k brown]

Yeah, that'd occurred to me but hadn't tried it.

Thanks for taking a look.