Mismatched Preamp/Amp Impedance--What Will I Hear?

There is no way it is anywhere near 100K as stated. If the preamp is tranny-coupled it could be as low as <100R. If not and has a cathode follower then ~1000R. If neither could be as high as 2-3K ohms - that is about the upper-limit.

Thanks for the responses. Hope you're right about a translation error. I found the 100K output impedance in different places on the Web, but perhaps they all result from the same translation error.

I just try it out and see what it sounds like. My other tube preamp has 400 ohms output impedance so it should serve as a good comparison.

I feel pretty certain that the specs you are looking at are wrong. 100K output impedance is a ridiculous number that makes no sense.

That said, if you connect a 100K output impedance into a 25K input impedance you would get approximately a 14db reduction in volume relative to the volume you would have if the 1 to 10 rule were satisfied. You would also get various frequency response irregularities corresponding to differences in the variations of the two impedances with frequency. That is likely to be most pronounced in the deep bass, where tube preamp output impedances tend to rise, causing the deep bass to be attenuated relative to higher frequencies.

You would also get some rolloff of the upper treble due to interaction of the output impedance with cable capacitance, even at the short one meter length, unless your cable has particularly low capacitance (e.g. 12pf/ft, such as some of the Blue Jeans cables).

Regards,
-- Al