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What is the Sound of Impedence Mismatch?

As I understand it, you want your power amplifier to have an input impendence much higher than the output impedence of your preamp, at least 10x. Can anyone tell me what the sonic symptoms are of a mismatch? If I'm hovering around 10x, what might I hear that would indicate an impedence mismatch as opposed to, say, a preamp that is simply too bright or whatever?
drubin
detlof
1,899 posts
 
Dull, lifeless musical rendering, massed strings undifferentiated, often somewhat harsh, grainy sound, no bloom, lack of dynamics . Redkiwi is right to these here ears.
drubin OP
3,285 posts
 
Thank you, gentlemen.

I am playing with a First Sound Presence Deluxe tubed line stage, which has an output impedence of 1700 ohms. It's very happy with my CJ 11a at 100K ohms input impedence. But with the Pass X-150 (spec sheet says 22K balanced, not sure what it is unbalanced, which is the way I am running it), the sound is, if anything, a bit bright and over-etched. No problems with bass or dynamics, definitely not lifeless, just tilted up a little. From your descriptions, it doesn't sound like this is a technical mismatch, however. Could be a listener mismatch :)

dan
plato
1,543 posts
 
Sounds like the Presence has too much "presence". Which tubes is it using? Sometimes a simple tube swap is all that's required to restore a more pleasant tonal balance...
Of course if you are just borrowing the piece and can't change the tubes, that's another matter.
drubin OP
3,285 posts
 
No, I own the piece. To tell the truth, I don't know what tubes are in it. I'll have to open it up and check.
bob_bundus
1,834 posts
 
I've read that bass rolloff (happens due to interconnect capacitance) can be caused by such an impedance mismatch where the pre's output Z is too high for it's PA load, so you might have such an issue Drubin.
Have you experimented with different upgrade AC cords though?
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