Archive of the former Yahoo!Groups mailing list: MOTM

--- On 5 Nov, 2000 jhaible@... wrote:

Creating delayed vibrato with envelope and VCA is ok -
many synths do this. But there is one method I like
better: That's the way it's done in Roland's Vocoder
Plus.
There you have a double-T type sine wave oscillator
that is damped such that it cannot oscillate. When a
key is depressed, a variable delay is started, and
after that delay a transistor switches the sine
oscillator to being slightly undamped. So it starts
oscillating, amplitude building up in a "natural" way
until it reaches a point where nonlinear feedback
prevents it from further growing.
Is this the same as an ordinary LFO, gated with an
exponentially rising envelope? Maybe so, but I gave
not made in depth comparisons so far. I have built it
once, as part of my JH-720 performance synth, and I
like it very much. In a way it's less flexible than a
full-blown envelope / VCA / LFO solution in that you
don't have extra control over the rise time (which is
coupled to the oscillator's own frequency). But then
again, this "natural" coupling of rise time and
modulation frequency is part of the incredibly
"natural" feel of the whole circuit. (And you still
have the delay time fully variable). And the sine
wave is very pure - you cannot accidentally start to
gate it open other than on it's zero crossing.
I for one prefer it to the "ordinary" solution by far:
I have them both side by side in the JH-720, and I'm
always using the "Vocoder Plus" option.
So what about a dedicated MOTM Delay Vibrato module ?
JH.
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Hi again, Juergen!

Hope you don't mind the long quotation; it's been a
while since you posted that, so I wanted to make sure
that you recalled everything...

Anyway, if I may pester you yet again, do you have any
schematic(s) available on your LFO Delay, either on
your website, or - dare I ask? - by e-mail?

It sounds like a Very Good solution to obtain
natural-sounding modulation.

Thank You Very Much - once again - for your
assistance!

Analogically Yours,
Dave Garfield




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