Amplifier Input Impedance

Recently I was in the hunt for a really good set of 'muscle amps' to use on my Magnepan 20.7's and it was a little frustrating to see just how many big-name powerful SS anps have atrociously low input impedance.

Stickman451,
it's easy to levy the blame on the low impedance of the power amplifier but your Hovland HP-100 is also to blame. It's output impedance is 2500 Ohms i.e. 2.5KOhms. That's really high for a tube amp (but maybe normal??). I've seen an ARC Ref3 have a 600 Ohm output impedance, my CAT SL1 has a 100 Ohm output impedance, several Audio-Note (UK) preamps are xformer coupled to have low output impedance. SO, I know that it's very possible to have a low output impedance tube pre - the HP-100 is not one of them tho'.

Obviously you want to keep the HP-100 so it might be worth exploring a buffer stage between your pre & yet-to-be-purchased solid-state power amp?

Recently I was in the hunt for a really good set of 'muscle amps' to use on my Magnepan 20.7's and it was a little frustrating to see just how many big-name powerful SS anps have atrociously low input impedance.

can you please let the forum know which solid-state power amps you researched? And, how "atrociously low" their input impedance was?
Thanks.

The pro guys seem to handle this issue better: standard impedances.

I should keep my mouth shut because I'm ignorant, but I have read that it's hard to design a SS amp with high input impedence and still get enough power or maybe rate the amp with higher power. I know Levenson has cheated so to speak on their imput impedence ratings which are sometimes only half as high as they claim.

I have to try again. I have the same complaint on low impedence SS amps and have spent years trying to match preamp to amp. I think that the lower the input impedence, the more gain the amp has which in turn degrades sound quality. For better SQ you want low gain in amp and pre. So if company X wants to make a 200w amp, it is easier accomplished by making the amp low impedence at the input. But I don't have the technical knowledge to prove this or discuss it.

And I haven't had to deal with this issue since I got my hk990 integrated. It has a variable gain setting for the active pre which doesn't address the issue of amplifier input impedence directly (and hk doesn't say what the amp's input impedence is and hopefully hk has matched pre and amp), but it does provide a tool that affects impedence in regard to the speakers so that gain can be adjusted according to the speaker demands. If you had speakers that were 16 ohms which you could get with autoformers, a SS amp would have a lower power output.

But again I have the same complaint. Amps get gain and hence power depending on their input impedence. I'm sure someone can explain this better.