Original Crumar Multiman first, then three sawtooths thru my plugin:
http://www.service-1.de/music/StringChorusCrumar.m p3
(the filter in my plugin is Solina-like, not Crumar, so it's not the same)

I was going to say that too. I love the TAL Chorus 60, or whatever it is called.

For years (back in the 80's) I used a Crumar Performer for high string lines. Of course it didn't sound like real strings, but I still miss that sound. I think I remember looking into it further and the sound was a single osc that had dividers on it to give the different notes. very similar to an old organ design. The chorus was in fact three chorus lines, each set at different rates. The thing I liked about it was that there was no perceptible beating of the three choruses.

Same here. My Performer's broken now I liked the chorus on it a lot, but even more so the 3-band filter. You could really sculpt the sound with that.

But it was 2 Osc per note, one 8' and one 16', like most of the old string synths.

IIRC...

My old Logan string melody II had 3 bbd chips - separate mod frequency and depth with internal preset pots that I liked to tweak on occasion. That ensemble as an fX would be awesome!

There was only one master oscillator + dividers, but 3 octave related footages on sliders and an additional bass footage for the lower half of the keyboard. Whatever, all notes were most definitely off the same divider set & thus totally in sync.

There seems to be some mass acceptance that string machines used sawtooth waves. If anyone knows how to get a sawtooth out of organ divider chips - I'd like to know!

Jim

They're not pure sawtooths by a long way. The harmonic content is not so different from a VCO sawtooth in some respects, but the waveform is a long way off. Paraphonic top-octave-divide oscillators and the associated circuitry have a number of interesting, and subtle, sonic characteristics which are not easily emulated. Listen to the decay phase of any string synth with a paraphonic oscillator and fully polyphonic AR envelopes for a start (any ARP string machine will do). There's a quite unlikely trick they pull to get 48 AR envelopes at an affordable price (48 VCAs in 1978? forget it...), and it shines through very distinctively in the sound, if you pay attention

I've looked at individual wave cycles from both my old Crumar and my Roland RS-202 and they do look kind of sawtoothed...but not quite.

Hi WOK, this is an effect that I've been looking for, for some time now. I love what you've done, and hope you will release this to the public. Very nice! In fact I recently bought a Korg polysix mainly for the ensemble effect... very retro! As it turns out it is a much better synth than I remember it when it was first made, and am very glad I bought it...but it would also be nice to have your effect for the VST world. Keep up the great work!

I found something on the ARP omni chorus that showed 3 BBD chips in parallel with independent modulation LFO's.

Anyone know of a service sheet resource (free!) for these things?

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A frequency divider is comprised of flip-flop circuits. The natural output is a square wave. You can modify this by gating the output with the input and have a pulse wave that's at the frequency of the output but with the pulse width of the input. Add a simple RC filter and you might have the "odd" sawtooth.
I'd love to see a schematic and see what they actually did!

Cheers
Jim

Here you are:
http://technopolitan.se/manuals/ARP/ARP%20Omni-2%2 0Service%20Manual.pdf
http://peterunderdog.com/arp/techinfo.html

Brilliant! Many thanks for the Omni service sheet.

The String "Phasor" in the Omni is shown as 3 separate BBD - and the direct sound does not appear to be used! The schematics give the nominal clock rate of each bbd, but you'd need to know how many stages the delays had to work out the 3 delay times of a stock ARP ensemble effect (512?)

The answer to the "sawtooth" is there - it's the divider squarewave filtered (simple RC) and rectified, although the rectifiers can be defeated by a switch.
The RC filtering component values differ per note - the time constant has to fit in the half cycle. Probably if you were to check every note, some saw slopes will hit the zero crossing either early or not quite reach it. Anyway, it's essentially a sawtooth with an exponential curve rather than the linear one you might expect for a saw wave. When the rectifier is active, the saw positive slope suddenly drops to zero when there isn't enough voltage to bias the diode & of course there is no negative cycle but it remains at zero until the next positive slope.

Assuming I'm right - I'm quite pleased to have cleared that up!

Jim

That's pretty much what I've seen documented for the Crumar Performer, too.

Latest sound example (simple saw from synth, no other effects):
http://www.service-1.de/music/StringChorus3.mp3

it sounds convincing to me, the instant gratification obvious sound

Listening to the previous example with the original Crumar you posted, it seems that the Crumar has more trebble, which makes it more "shiny".