I think you are going to find CF's in most of the tube preamps you go looking
for. It's not the spec I would go looking for.
fwiw, I have 2 Pass amps (30.5 and 100.5's) and I drive them with Conrad
Johnson tube preamps (ART and ACT 2.2) and neither of them have CF's. Their
output impedance "averages" 500 ohms and is not a problem for me. My Pass
amps are rated at 20K or 30k (rca or balanced).
Whatever the input impedance is of your Pass is, just look for a preamp that is
at least 1/10 of that and hopefully a little more because the output impedance
does vary at different frequencies. That spec is just an average.
for. It's not the spec I would go looking for.
fwiw, I have 2 Pass amps (30.5 and 100.5's) and I drive them with Conrad
Johnson tube preamps (ART and ACT 2.2) and neither of them have CF's. Their
output impedance "averages" 500 ohms and is not a problem for me. My Pass
amps are rated at 20K or 30k (rca or balanced).
Whatever the input impedance is of your Pass is, just look for a preamp that is
at least 1/10 of that and hopefully a little more because the output impedance
does vary at different frequencies. That spec is just an average.