Re: need a digital delay that meets ridiculous requirements

[Mark Hamburg <mark_hamburg@baymoon.com>]

on 3/16/04 9:59 PM, Travis Hartnett at tiktok@sprintmail.com wrote:

> I think there's a lot of people who want delay units that smoothly
> shift pitch when you sweep the delay time, but it seems that delay
> boxes stopped doing that about ten years ago.  I forget the technical
> reason, but I think the practical explanation was "it's
> cheaper/affordable to use an effects architecture that dosn't support
> that feature".

I thought the Line6 stuff at least attempted to do that (though I haven't
tested it closely).

The following is based on a theoretical understanding rather than actual
knowledge of any specific devices...

The reason smooth pitch shift generally isn't available is that digital 
gear
these days reads the samples out at a constant rate and achieves 
differences
in delay time by changing the number of samples between the sound coming in
and the sound going out. Older bucket-brigade analog gear and probably some
old digital gear changed the rate at which it worked its way through memory
which gives you nice pitch changes but also means that fidelity goes down 
as
delay time goes up since the sample rate goes down.

If the box is capable of doing modulated delays, it has enough processing
power to produce a pitch shift while transitioning from one delay line
length to another, but it probably doesn't behave quite like the old
equipment. The Korg DL8000R, for example, will do this.

To put this all in tape terms, it's the difference between varying the 
speed
of the tape and varying the distance between the heads. Newer equipment
varies the distance between the heads.

Mark