My strategy will be to play it safe and go with a high current SS amp that doubles output into 4 and eve 2 ohms as much as possible and has a higher input impedance, along the lines of those I mention above. That will optimize electronic interfaces both in from pre-amp and out to speakers.
From there, whatever amp used will be in an optimal position to synergize with pre-amp and speakers and deliver its best performance as a result, whatever that may be, I would say.
Tvad, I'm sure I could hear the difference. That part would be a walk in the park. But I'm not so sure that I could connect the difference to the difference in impedence values as opposed to the amps design or how it interfaces with the speakers.
For Mapman, whose post follows. FWIW IMHO, the differences which may occur between the small differences, or deviation from optimum values, between amp and pre-amp that we are talking about (I'm NOT talking about gross mismatches, or even medium mis-matches) are absolutely dwarfed by the output capabilities as well as the tonal signature of the amp and the impedence curve of the speakers. But you have probably already figured out that that is my opinion. :-)
BTW, if you are looking for high power, high quality power ss amps, I'd recommend that you look at some vintage stuff, especially stuff made by Nelson Pass when he ran Threshold, especially the SA or S series stuff. Even if you had to have some recapped because of age they would still be a hell of a deal. If I ever went back to SS that is the first place I would go.
It does make sense to me optimize the electronic interface between components in a system to whatever extent possible, all other factors aside, to maximize inherent performance.
The input impedance of my current Musical Fidelity A3CR amp is ~31K.
I've seen ARC SS power amps with 150K ohm input impedance. I'm thinking that it might make sense to go with an SS amp like this from a company that has tube pre-amps as a specialty.
Other options I know of to consider are Bel Canto Ref 100m (150K ohm unbalanced input impedance, 300K ohm balanced)and Wyred 4 Sound (~60K ohm input impedance).
Stock ICE power class D amps appear to have only about 20K input impedance which would seem to make them a less desired match with many tube pre-amps.
Any other SS amps with high input impedance to consider? I doubt I would seriously consider a tube power amp for my application at this point with the big current hungry OHM 5s in my system.
Tvad, Note I said no difference at 20K or above, but I did add the words 'unlikely' and 'meaningful' to the reference to 10K. To me at least it probably wouldn't be 'meaningful'. I draw this assumption from my personal experience using ARC stuff and assorted SS and tubed amps with input impedances between 10K and 100K. I get far more wound up working out amp output and speaker impedence matching issues (as I know you do as well).
BTW, Tvad, have you actually heard the SP16 connected with a 10K amp AND an identical amp differing only in that the impedence value was increased to 20K. Im unaware of any such amps though. I think if we could find a techie who could set up such a demo by altering the output impedence of some amp in some way without otherewise changing the signal, we might then, and I think only then, know if there was a difference, meaningful or not.
But its fun thinking about all of the issues anyway. :-)
Mapman, Bob may be 'right' as Tvad sez, but the ratio is way beyond any nominal ratio you see bantered around like 10 to 1 for example. In this case it would be very close to 80 to 1.
Personally I'd tend to trust ARC when it sez a 20K imput impedence would be adequate (I actually did that without regret) and not get my panties in a knot over what the difference would be between say 20K and 47K or even 100K. I'd even take bets that in this instance even Bob couldn't tell the difference if he was listening with a stethoscope. In fact I'd take bets that it would be unlikely that he would hear any meaningful difference if the amp's input impedence was as low as 10K.
Personally I'd believe ARC. I'd even go so far as to think that their recommendation would be conservative and act accordingly, spending the copious amount of time necessary to solve these issues to insuring that the amps output impedence was a good match for the speakers to be used, to finding the right tubes to flesh out the pre-amp's tonal issues when matching it with any particular amp, or just sitting back and listening to some good music.
But hey, thats just me. I'm not very anal about all of these techie issues. :-)
FWIW I find it hard to believe that an ARC pre amp has an output impedence of 20K. 260 perhaps, with a recommendation from ARC that the amp have an input impedence of 20K.
Just a WAG - I didn't bother to research it, I'll leave that up to you. :-)
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