Virtually all modern pre-power combinations work on the principle of a
constant voltage output, that is, a low output impedance driving a high
input impedance. This has the benefit that as there is very little current
flowing, the cable resistance has no bearing (not that there is any of any
consequence in short lengths), but more importantly, the cable capacitance
will have a miniscule effect on the frequency response. (again for short
"domestic" distances)

As I understand it, Krell's CAST works on a different idea, that is driving
current from a high output impedance into a low input impedance, effectively
constant current.
This was also the principle behind the unpopular DIN standard, although the
output Z wasn't very high, and the input Z wasn't very low!. Although
keeping the input impedance of the power amp very low will also avoid any
noticable low-pass filtering due to the connecting cable, I don't see any
benefit of this approach, except commerically, to ensure that Krell sell a
complete Pre-power system.

Perhaps any devotees of Krell CAST may like to explain how it's better than
the conventional approach.

Serge

"Midlant" wrote in message
...
When matching a pre-amp to a power amp what is the correct match IRT
impedences? ie: low out on pre with high in on amp or vice-verse? What
are the benefits of the design?
I have also recently read that there are three (more?) different pre-amp
design set ups that also effect how the pre is matched to the amp. Could
anyone explain this, please?
Thanks.
John