All pass filters?

[Eli Brandt]

John Speth wrote:
> I think it's fatal to one's understanding to discuss time
> delay and phase shifting as though they're related.  Phase shifting is
> studied in terms of frequency domain analysis while time delay is not.

It's not like never the twain shall meet here -- a delay is a particular
kind of allpass filter, viz. a linear-phase one.  And I'd say it can be
useful to study delay in the frequency domain.

-- 
     Eli Brandt  |  eli+ at cs.cmu.edu  |  http://www.cs.cmu.edu/~eli/