Which preamp to pair with Moon W5 amplifier?

If you can afford about $4k used, there is a sweet VAC Renaissance pre available right now.

I have a Sim Titan and the VAC Ren pre myself, and ran through 3 other pre's with very good-yet-similar results, but NOT like the Ren.

The Renaissance pre has a transformer-coupled output, just like the Supratek's, 1st Sounds and a few others. This design makes it very compatible with low-impedance solid-state amps like the Sim Moon series, and it also helps reduce hum and hiss. Where the VAC won-out over the other transformer-coupled models for me was features - Remote control (vol/mute/selector), 2 balanced ins/1 balanced out, Cinema bypass and a reasonably-sized, enclosed cabinet (compared to the Suprateks) to protect the tubes. It also has stunning build quality and an AMAZINGLY dynamic sound. The detail it dug out of my CD's is staggering.

Although like many tubed pre's it doesn't have balanced in and outputs, the Hovland HP-100 or HP-200 is a consideration. I once did an A/B comparison between the Simaudio P-5 and Hovland HP-100. No question, it just took one track of Ryan Adams Heartbreaker to realize the Hovland was much more musical and liquid in the midrange. Unfortunately, the Hovland did have a quiet hum in one channel, which has been noted by others as well. So, do have a listen !

Bbybaudio, The W-5 is a very nice amp. It's one of my favorites as it is quite fast and provides even a somewhat sweet sound which is a bit unusual for a solid state amp.

In fact, I did not know what a fast amp was until I plugged the W-5 into my system.

If you agree that the W-5 already has a somewhat sweet sound, then I would put less consideration toward a tubed preamp and just focus on a good preamp regardless of it being a tube or solid state.

I cannot remember now which preamps I had when I owned the W-5 but a few that I think may really compliment it would be a Placette Active Linestage or a Pass Labs X2.5 or X-1.

As I recall, the only questionable deficiency with the W-5 was it's bass reproduction. For this reason alone, I would stay away from a tube preamp with the W-5.

-IMO