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Re: Lo Fi Looping

I've used the ISD chip before and indeed the bandwidth is low.  Its 
designed
for telephone answering machines I believe and the bandwidth is even lower
than a telephone, also I think 8KHz  is the max sample rate.  The chips I
tried out are pretty cheap:

ISD1420PISD1420P Voice Record and Playback IC (20sec) $3.20
ISD2560PISD2560P Voice Record and Playback IC (60sec) $9.95

If I remember right, they will store a large possible number of samples 
even
on power down, and they can store many samples with very negligable seek
times.  There's a  loop playback option (don't know about glitches at the
loop point though ;), or a loop "queueing" option that will play 
consecutive
samples.  A pin goes low when the sample is finished playing so with some
simple logic it could be used to start from the beginning again for
consecutive sample playing.  There is even an input that has a built in
compressor and a mic pre, you can set the attack and release times with
resistors (potentiometers if you want).  You can chain multiple chips for
longer record/playback times too. 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.

The lo-fi isn't really what I'm going for so I didn't really persue it 
more,
but the chip has the right features for a simple cheap looper!  I would be
happy to hear more about your project, even off-list if you want.  I'm
betting you're going to want a simple micro on-board to do the control 
tasks
and user interface, but then again maybe not.  Good luck!

Jon

http://www.winbond-usa.com/products/isd_products/chipcorder/portfolio/
http://www.winbond-usa.com/products/isd_products/chipcorder/datasheets/