How do you measure output impedance?

Actually, Herman, that all sounds pretty intimidating to me. I'd need a lot of hand-holding, plus a pot. Thanks for posting it, though.

Drubin, may I ask - if you feel intimidated by having to measure some voltages, why do you need it? What are you trying to achieve?

Maybe he's trying to feed a low impedence input power amp, like an Aleph, known to be tricky with unruly pre's?

Ditto, Subaruguru. I had assumed the same thing.

That's exactly right. And I had my preamp modified recently with additional resistance on one set of outputs (to lower gain) and would like to know how, if at all, this has affected the output impedance for that set of outputs.

Zoya, your question strikes me as odd. Just because the process is intimidating, why do you suspect my interest in the result?

I've been curious for some time about this issue of mismatch between pre and power amp. I'd like to have real measurements to compare with what I hear to try to get a better handle on things.