Ohm Walsh Micro Talls: who's actually heard 'em?

The best indicator is bass extension and response (clarity, control).

I've found that 200 ohms or lower works best with most solid state amps having 23k ohm input impedance or higher.

Most preamp manufacturers I have asked have said that an output impedance of up to 500 ohms would be fine, but what I have heard in my system has not confirmed the advice.

In all cases regarding preamp output impedance when used with a solid state preamp, lower has been better.

I have found John Atkinson's test measurements section of Stereophile reviews extremely helpful on this topic. He always addresses output impedance in preamp tests, and input impedance in amplifier tests, and he suggests impedance matching thresholds.

Tvad,

Have you found the better clarity and control extends into the upper frequency ranges as well?

Any downsides that you can identify to go along with the benefits?

This is something I'd really like to test out in my system.

Tvad,

One other question.

Certainly a low pre-amp output impedance seems to make it easier to match more amplifier input impedances, but I wonder is it the absolute value of the preamp output impedance, or the ratio or magnitude of amp input impedance to pre-amp output impedance in the end that matters?

Here's an interesting thread on the impedance matching issue:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1227661419&openflup&12&4#12

The consensus here seems to be a 10:1 amp input/pre-amp out ratio is a good target. Also that actual output impedances of pre-amps is higher at lower frequencies with can negatively impact bass response.

So for example, my case, with the ARC sp16 premap output impedance being 20K ohm, I would want an amp in the 200K input impedance range (my A3CR is only 31K).

Also, interconnects factor into the equation in regards to impedance loads presented to the pre-amp, so things get mor complicated again here.

Of the SS amps I've considered, the newer Bel Canto Ref1000m would be the best choice for me apparently, but pricey. I'll be looking to find some other options and will not rule out tube amps necessarily either.