CS-80 based synth with GX oscs

[k brown]

In doing a major re-vamp of my 80-vox of years ago, I decided I would upgrade the oscillators to something based on those in the CS-80's parent, the GX-1, and re-named it CS-gx. Though the basic voice structure of the CS-80 and GX-1 are nearly identical (two 'channels' of one Saw/Pulse VCO, one HP-into-LP VCF [with dedicated EG] and one VCA [with dedicated EG]) the GX-1's VCOs had additional wave/filtered-wave outputs that could be mixed with the basic Saw and Pulse. These were:
- Variable level Pulse through an adjustable freq high pass filter.
- Fixed level Saw through an adjustable freq band pass filter.
- Variable level Triangle that's shifted up an octave.
For total of five mixed signals available at each VCO output (plus Noise).
It would be very interesting to find out how they arrived at that particular combination.
For the CS-80 they simplified this to just the Saw and Pulse OnOff switches.

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CS-gx.fsm

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The other major deviance here from the basic CS-80 architecture is the supplanting of the Ring Modulator with a second LFO. Each target of both LFOs can be sent to either or both of the synth 'channels'. An additional feature from the GX-1 is the VCF Eg can be inverted.

Since not that many people have keyboards with aftertouch, I've made those functions controllable by mod wheel, footpedal, breath controller or pitch wheel.

There is no way this is going to sound like a CS-80 (no instant Vangelis here); my main reason for bothering with this is to offer something structured like a CS-80 that has the utterly unique wave/filtered-wave mixing of the GX-1 VCOs. I also wanted (for myself) a CS-80-like instrument that is simpler and less cluttered than Arturia's CS-80V, and with a much more pleasant and realistic GUI than Memorymoon's ME-80 (wonderful sounding as it is). Why on earth he opted to make the background of that GUI pitch black, when one of the most attractive aspects of the CS-80's appearance was the lovely dove grey of the panel, is beyond me.

Includes very rough approximations of the manual's factory presets, not meant to sound just like the CS-80's Tone Selector panel buttons; they're just there to provide some useful starting points. Most of them have some aftertouch applied, so if you don't have an aftertouch keyboard you'll need to turn the 'After' sliders down and re-adjust the filter cutoff to hear the preset properly.

This thing really begs to be played with a velocity plus aftertouch keyboard and a footpedal to work the Exp/Exp-Wah feature, which controls volume or both volume and filter cutoff (lacking a footpedal, this can alternately be controlled by mod/pitch wheels or breath controller).

Though the CS-80 had a built-in Chorus, I decided not to use Martin's amazing new Chorous because it's such a unique effect and doesn't do what the CS-80's chorus was meant to do which was, in combo with it's Tremolo, to simulate a Leslie speaker. Indeed I just left the chorus out; there are so many decent conventional chorus effects and Leslie sims available.

[Spogg]

Very nice Kevin!

I really do appreciate you taking extra time to supply some good presets. I really like the Pad one in particular.

As always, well done Sir!

Cheers

Spogg

[k brown]

Thanks for checkin' it out!

Just curious if very many of the 'regulars' here have aftertouch keyboards. I actually don't myself, my kbd only has velocity; but amazingly my goofy little Casio Horn generates both, and Portamento On Off mssgs as well! It's bult-in sounds are pretty naff, but as a MIDI controller they're quite something and only require the replacement of a single capacitor to keep 'em goin' as they age. Oddly they don't send breath controller mssges; I assume Casio figured the combination of velocity and aftertouch provided more expressive control.

P.S. - is it OK that I post stuff on the facebook group, or is it better that I wait to be invited to do so on a synth-by-synth basis.

[Spogg]

I don’t have a pressure sensitive keyboard either. I looked into it but they’re very costly and I’m a very poor player in any case. It seemed excessive to buy one just to test certain synths!
I looked at old ESQ synths for their poly aftertouch, but again the price put me off.

Please feel free to post any and all of your stuff on the Facebook page. It’s not very active so it’ll help to promote it. We want folk to buy FS licenses and I suspect many might be tempted when they see what you have done with it.

Cheers

Spogg

[trogluddite]

Thanks, Kevin. I've always liked synths which have envelopes and filters per oscillator like this; it adds a lot to the sound sculpting possibilities, especially being able to sculpt separate attack and sustain timbres.

Two of my three keyboards send it (Novation ReMOTE and CME Xkey [which can do mono or poly AT]), and I like using it, but often find that it takes a bit of tweaking to get the response "just so" for a patch; especially balancing it against the initial velocity response - so I appreciate having quick access to the AT settings. The patches where you've used it are good examples of how expressive it can be, I think.

[k brown]

Thanks trog - can't take credit for the patches using vel and at - they're just taken from the CS-80 manual.

Wow I didn't know anyone was making MIDI keys with poly AT. Am I correct in assuming there is no way of doing poly AT in FS?

[trogluddite]

Wow I didn't know anyone was making MIDI keys with poly AT.

The CME Xkey is a bit of a strange beast. It has keys rather like a laptop's space-bar - very thin and with very little travel. In a sense, poly-AT comes for free, as it doesn't have the usual kind of key contacts - key "velocity" also uses pressure sensors, rather than timing the interval between break and make key contacts as is usually done for a full-travel keyboard (so it's really "force" rather than "velocity"). To be honest, I expected to only use it for note "entry" and tapping out rhythms rather than for "playing"; just handy when I don't have space to carry much around with me. However, now that I've had a chance to get used to it, I've found it to be surprisingly playable.

Am I correct in assuming there is no way of doing poly AT in FS?

In principle, it can be done, but I don't think it would be particularly easy. The messages can be extracted from the MIDI stream easily enough, as they're just regular 3-byte MIDI packets; but you then have to match the AT amounts to the voices which are currently playing the corresponding notes. I think you'd probably have to keep an array/mem of the values for all 128 notes, and then read from this according to each voice's pitch value.