EH 16 second dly

[Haible Juergen]

	>Heh-heh... DSP digital vs. raw digital.

Needless to say that I totally agree (;->).

	>(That's my abbreviated way of saying that most modern digital delay
	>units are DSP-based with the delay process in software while the
older
	>digital delay units used some circuitry wrapped around a number of
RAM
	>chips or possibly even shift registers.  The difference really
shows
	>when you reach over and spin the delay knob.)

Given that there *is* a dedicated delay knob at all ...
What are these times when a DSP costs less than a good collet knob !

Seriously:

I wonder if there are (raw) digital delays that can be sync'ed to an
external
clock. I'm not talking about tap tempo before you start to use it, but
changing the length on the fly by resetting the adress counter with an
external
signal. I've been thinking about that for a long time, but somehow the 1sec
or 2sec delays I own are not worth the effort. I'd love to see a long "raw"
digital
delay being developed on synth-diy, with the possibility to hack each and
everything.

I won't do it myself - it's too far out of the stuff I'm normally doing, and
there's a lot
of unfinished projects on my desk. But I don't think it's too difficult:
OTA-filters on input and output, HF-VCO for clock rate, ADC and DAC, enough
RAM
for 16 seconds (maybe a few sockets to make it expandable), adress counters
of
up/down variety, up/down and reset lines as external connections, a flipflop
in the clock line for half speed. Maybe even static RAMs to avoid problems
with
refresh when not all adresses are used. Someone make a PCB and market it
like
the ASM synth ...

JH.

(And put some errors in the circuit drawings before you publish them (;->))