Do I really need a preamp?

George is mostly correct here, just watch out that some solid state amps have a 10K input. 47K is not a standard.

Out of a 4V source, I have heard a Goldpoint resistor type passive preamp sound pretty good into Class A, SS monos with 100K ohm input, but still lacking depth and dynamics compared to the same amps played through my preamp, which is buffered with no gain. Into NC1200 Class D amps, the passive preamp sounds very clean, and delivers close to the same level of dynamics as I achieve through my buffered preamp. However, through my Class AB SS stereo amp with 10K ohm input, the passive preamp sounds terrible.

I also have a pair of balanced Endler attenuators, which connect directly to the amplifiers so there are no cables required after the attenuators. I cannot discern any significant difference in dynamics between those and the Goldpoint passive, from which I use a1M cable into the amps.

Marqmike, I would think first your power amp has enough gain
for a passive preamp to work very well, this would be a very
important thing. Second you must have a very good quality
passive preamp, passive preamps like active are not all
created equal. I have had high quality amplifiers that they
could carry an inferior preamp and vice a versa. Get both
right and your in for a treat. A few years ago I owned a
McCormack DNA-1 with a revision A which had plenty of gain
for a passive preamp coupled with an upgraded McCormack
passive preamp. It sounded heavenly, there was no lack of
dynamics, it was refined and transparent as hell. I miss
that combination terribly because I never thought of looking
at another active preamp with this combination.

I believe even in Stereophile John Atkinson states 47k-51k input impedance has been an unofficial input impedance standard now for over 50 years for most home audio S/S products input resistances. Since it was made the standard for MM cartridge loading way back and they followed suit with preamp and poweramps at 47k-51k.

Tube amps have even higher up to and higher than 100kohm which is even better for higher value passives like 20kohm ones.

As for the very few amps that are 10k that many tube preamps won't drive, they constitute probably less than 1%
of the market share.

Cheers George

For years I used a Preamp. Once I bought the PS Audio Direct Stream Dac and sent the output to my BSG QOL and then to my Amp, I sold my Preamp.