[sdiy] Phase correctors

[cheater cheater]

Hey guys,
does anyone know of any variable phase correctors?

By phase correctors I mean the things usually put in EQs that correct
the filters' phase response. Basically, the phase correctors have a
flat frequency response, and the phase shift rises (or falls) as
frequency rises (or falls).
Unfortunately, I wasn't lucky enough to find one schematic ...

Those things look interesting, though:
http://www.springerlink.com/content/g67w778950831075/
http://www.springerlink.com/content/r5537667429tu61k/

http://sound.westhost.com/pcmm.htm Look at fig 2.5 - the phase delay
drops (and becomes 'negative') with frequency rising, at a certain
rate. The idea is to be able to control this rate.

I briefly thought about just taking such a simple all-pass filter and
simply varying the 'wet' level, so the mix between the output of the
APF and the original (dry) signal, but then figured that it would just
create something to the effect of an EQ instead.

What do you guys think? Is this possible? Even by simply using
different element values (and switching between them), so not being
fully variable, but still allowing some degree of freedom.

What are your favourite designs of all-pass filters? Maybe some of
them would be more pliable for modifying the phase rolloff.

Best regards,
Damian