[sdiy] Analog Delay Lines (was) [common acronyms?]

[Don Tillman]

   Date: Mon, 08 Oct 2001 22:19:36 -0400
   From: harry <harrybissell at prodigy.net>

   An allpass filter network could also introduce delay... thats how
   phase shifters and old (Hammond) vibrato units work...

Hey Harry,

Perhaps we're running with different terminologies, but I believe an
allpass filter and the Hammond delay are fundamentally different
beasts.

An allpass filter, one with mirror image poles and zeroes, only offers
something approaching delay over a small frequency range.  For
instance, the delay at the high and low extremes is zero.

But the Hammond delay is different -- it's an LC model of a
transmission line, it doesn't have mirror image poles and zeroes, and
it's a pretty accurate delay over a wide frequency range.

 -- Don

-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com