"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?

Most "normal" equipment works on the principle that the signal is an
AC voltage of varying amplitude & frequency. Thus, you want each
device to have low output impedance and high input impedance. The high
input impedance means the downstream device doesn't draw much current
(or power) so the upstream device doesn't have to work very hard. In
other words, it's easier (takes less power) to swing a given voltage
across a higher impedance load. The low output impedance means the
upstream device can deliver some current if necessary and is
relatively immune to cable effects.

I played around with impedance ratios when I designed & built my
preamp (ladder stepped passive attenuator switchbox) and found that if
the ratio of impedances is at least 100:1 (meaning input of downstream
is at least 100 times output of upstream) then I could not detect any
sonic differences. But when the ratio got down to 20:1 then I could
hear some subtle differences.

Based on that I'd guess 50:1 to be a reasonably safe rule of thumb,
meaning anything more is probably overkill as the effects would not be
audible.