Amplifier Input Impedance

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.

OK. So are not some loudspeakers designed with very low impedences so that they will audition better because they are louder? (and I understand that this is not the same as sensitivity.) Does that not relate to input impedence in amplifiers?

I'm not arguing with an audio engineer--just asking?

http://www.audioholics.com/audio-amplif

The above site agrees with some above comments from Bombaywalla and others. To summarize, according to the source, high input impedence in SS causes high voltage gain which in turn causes noise. It can also cause bandwidth to decrease. And finally it can introduce DC offset.

My head is still spinning from trying to absorb what I read in 15 websites which destroyed my misconceptions.
But apparently high input impedences can cause more harm than good.

Thank you, Atmasphere. A crash course in amplfier design is clearly not going to work for me.

George,

How does noise relate to your above description of input impedence, gain, etc if at all?

Lynne