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Re: Lo Fi Looping
> Thanks Jon. Yes, there seems to be quite
a few versions offered by ISD.
> Where did you purchase your
chips?
good question can't remember, but you can get them
here for example:
> > The big drawback as I see it is that
there
> > is no provision for overdub or feedback, but you could get
this with a two
> > chip design if you were clever.
Not that clever, but here's the gist: You
have two ISD chips which both can either record or playback. There are two
states: A and B. Lets say you have recorded a loop in
ISDchip#1. In state A, you playback the loop once on ISD1, and record
on ISD2. ISD2 takes its input from both the mic, and the output of ISD1 x
FEEDBACK. Then as soon as ISD1 signals its the end of playing the loop,
you switch to state B where ISD2 is playing back and ISD1 is recording the
mic + ISD2 x FEEDBACK. Keep going back and forth this way, and you have a
basic system with feedback and overdub. You could put a switch in to
enable the overdub function by simply turning the mic on/off. The feedback
could be a potentiometer voltage divider so it is variable. I'm pretty
sure you could do the whole thing in digital logic based on the ISD chips
outputs and inputs.
Ok, here's the one problem with this scheme - those
ISD chips have a finite number of record cycles before they die. I think
its spec'd at 100,000 cycles. So say you play a 15 second loop for 1 hour
each day. That's a little over 2 years of life before you have to change
out the chips. It all depends on the desired usage. They don't spec
a lifetime on playback, but I would assume its quite a bit many more
cycles.
If I were you I'd attempt your simple system
first. Those chips are pretty straight forward to get up and running with
if you read the datasheet carefully. Good luck and keep us
posted.
Jon
