[sdiy] BBD help

[jhaible]

> Anyway... even BBDs have a limit to the clock rate you can do with them...
so
> getting
> a real short delay will still be tough.

Right. At least you work quite out of specs of most (all?) BBDs
with such a high clocking.

I think Mike Irwin has sucessfully done this, so it's actually possible
to go considerably below 1ms.


> I'd forget any delay of less than 1ms... that is the time it takes for
sound to
> travel
> 1' in air.  You will probably get NO effect a human being can notice.


OTOH, can make a nice chorus / vibrato with just 400us of delay - that's
what the Hammond scanner vibrato does in its "short" position.
And, you don't need many inductors and capacitors to build such a delay
line - much less than the 25 required for the long "Hammond" vibrato.
(I'm not talking of the 18 coupled inductors of later hammonds, but
of a fraction of the un-coupled 25 inductor version.) So you could make
a nice variable short delay from just 10 ... 15 inductors and capacitors!
(Not for extreme FX, but good enough for smooth, musical vibrato.)
You need a scanner to work with this delay line, of course, but the
good news is, with 9 positions of a scanner and an overall delay
of less than half a millisecond, you don't get much artefacts from
phase cancellation as you scan along the line. (Unlike the longer
version, which has a total delay of approx. 1ms)

JH.