What is the best type of preamp for a class D amp?

Lots of reviews of the amp see what they liked. What you like may be quite different but I like tube pre amps with all power amps. In this situation it would seem almost a prerequisite.

The reviews that I read suggest using a tube preamp. One suggested an E.A.R. 868. So be sure to try them in your auditioning.

01-30-15: Georgelofi
Many far more technical than me say none yet can be called true hiend, as technology is not yet developed to allow the switching frequency of Class D to be high enough which then has to be filtered out at the end, and that filter not to have an audible/measureable effect on the upper mids/highs of the audio spectrum.

Interesting! I heard some has replaced their BIG BIG $$ amps with Mola Mola Kalugas and the Hypex Ncore NC1200 is a major break through in Class D.

I'm running all tubes and in the market for a SS amp to use in the hot humid summer months and can't believe I'm going to say this, including some Class D amps.

I haven't seem all that many, but it has appeared to me that many seem to have a rather low numerical impedance; which might make a difficult match for many tube pres.

Just like any amp, a pre-amp with low output impedance relative to amp input impedance is best to minimize distortion and for best dynamics. Input impedance of Class D amps run a range similar to others anywhere from 10K ohm to 200Kohm.

For a tube pre-amp 45-60kohm input amp impedance is the minimum. For lower output impedance ss amps, most any amp will likely match well in this regard.

Avoid clipping a all costs and keep noise and distortion to a minimum and audio life in general should be good.