I just had my mono-block EQ square wave tested by my tech. The tracings are not as good as my amps results so there is some coloration taking place. So, my search continues for a transparent pre-amp...

So Sam, did you find the preamp you're looking for? Any update?

Soon i'll recap this almost-vintage Musical Fidelity from 80's:

Yes, I lucked into a Classe SSP-25 processor/preamp at a thrift for $40 not too long ago. OK, it is not a dedicated preamp but the performance is much better than anything I have. I had Tom I., who is my superb tech do a square wave test and the results are almost what I want with the only deficiency being slight tilting of the 20 Hz plateau. This indicates slight degradation over the duration of the tone but at least there is no rounding or other defects. The 1 kHz and 20 kHz traces look great with vertical attack and decay and flat tops. This translates to greater accuracy and musical flow.

Check out theternal construction of the SSP-25. Like a power amp, there is no substitute for a large transformer and filter caps. And, like a power amp, a preamp can run out of power which will definitely show when reproducing complex music. Anyways, the SSP-25 is a sound processor and the power supply is asked to run the processing chips (which I never use) so it is not perfect. I would like to try Classe's dedicated preamps with separate power supply. Some day...

Good stuff Clint. Are you able to quantify the before and after signal quality?

Unreal! Why can't this ever happen to me? I have made a few decent deals in the past, but never a really great deal like this. Enjoy it!

Believe me, the Classe was a lucky find even by my standards.

Sure i'll like to know for instance the preamplifier gain and sensitivity, output noise, AC-line power draw at idle, input/output polarity, and input and output impedance at 1kHz, etc... but i have not the instruments and tools to measure those items. Even though i'll trust my ears better than some specs.... I always go with the one that sounds over the one that measures better because when i listen it is to the MUSIC rather than sit and read the data telling me it should sound good. But hey, this is just me and i'm very selfish concerning my tastes after all i need only to please me.

BTW, that Classé preamp it's very good. Awesome power supply filtering.
Congrats.

My own recent journey involved a single-ended tube amp (5 watts) and no preamp. My DAC and tuner both had variable outs, so I simply swapped patchcords, and used the volume controls on the sources. Tape and Phono complicated things, so I eventually bought a Meridian 201 preamp, and I am very happy with it: clean, no obvious noise, no tone controls, no scritchy knobs, but pushbuttons thruout. It has the usual British weird ergonomics, but I can live with that.