High Current SS amps with input impedance = 200K

Without commenting on sound, which is a subjective thing, I'd say the amps that best fit your criteria, but would have to be purchased used, would be Bel Canto Ref1000 MK I monoblocks, Belles 350A Reference stereo, or Belles 150A Reference monoblocks. You should know that the Belles amps perform best running balanced, IMO, but the 350A can be run single ended. The 150A Reference monos must be run balanced.

All these amps will drive your speakers extremely well, and they have input impedances of 50k Ohms (Belles 350A Reference) or higher, so they will work well will tube preamps.

The Belles amps run only slightly warm to the touch. The Bel Canto are stone cold.

I'd also recommend used Pass Labs X-250 or Plinius SA-250, but these run warm and are monster amps, so they don't really fit your requirements.

As far as new amps in your price range, I can't think of any at this time.

"I don't know why Mapman is reluctant to consider ARC recommendations "

Newbee, what gave you that idea?

I'm not. I would assume ARC to be a most reliable source for recommendations regarding their equipment given their considerable history, experience and reputation, and the fact that their unit has been a home run to-date in my system.

Tvad has been around with a lot of different equipment I believe and has a good attention to sound quality and technical details so I do not discount his observations in this area either.

I agree with your point about validity of apples and apples comparisons between amps based solely on input impedance differences as well, but I do not doubt that higher amp input impedances relative to pre-amp output impedance is one (of several) technically sound measurements that one can attempt to optimize along with but not at the expense of others necessarily as well.

Mapman, Note that I deleted the post you are responding to. Sorry about that. I was really responding to Tvads observations and was not at all pleased about what I was saying especially as it applied to you. I had already communicated all I could really offer to you in previous posts. And I saw no reason to continue the correspondence with Tvad although he is so serious I must admit that I do, sometimes, enjoy rocking his boat. He is a good guy and means well.

But, FWIW, if you can accept the accuracy of ARC's recomendations about amp matching with that pre amp, restricting your search for an amp based upon a desire for higher input impedence will not add to the performance of the amp/pre-amp combo. If the car takes regular gas and the tank is full, that is as good as it gets.

Hope you find the right amp for your Ohms.

Newbee, the sonic differences between a 10k Ohm and a 20k Ohm amp when used with most tube preamps would be applicable to a real live person in a real room provided the person was an audiophile with an audiophile quality system. No question about it. Not just theory. Read Atkinson. He lays it out in plain English. No technical knowledge required.

Although you just tossed out the 10k Ohm impedance spec, it is not an unrealistic number for solid state amps. McCormack amps have an input impedance of 10k Ohms, and in my experience using them (DNA-2, DNA-500), they don't work well with most tube preamps due to the input impedance issue.

Here are Stereophile's output impedance measurements for the SP16L line-stage preamp, for which the ARC specs are identical to what Mapman quoted:

http://www.stereophile.com/tubepoweramps/901/index6.html

The measurements indicate 262 ohms at mid and hi frequencies, and 549 ohms at 20Hz.

Into a 600 ohm load (sic), they measured a loss at 20Hz of only 2.5db (see Figure 1). By my calculations, into a 10K load the 549 ohm output impedance would result in a loss at 20Hz of less than 0.4db.

So the output circuit, and particularly the output coupling capacitor, of the SP16 appears to be designed more conservatively than in the case of most tube preamps. And the recommendation of a 20K minimum load appears to be conservative as well.

Regards,
-- Al