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.
take the above coment with a grain of salt- I use a highly modded Sonic Frontiers Line 3 preamp (2-chassis 65 ib beasty), along with a Sim Audio W-3 amp, and the bass is full and deep...
Stehno - Interesting comment about lack of bass, I had that problem when I bought my W5 based off the reviews. I had no BASS with my Audible Illusions L1 preamp (tube). After two weeks I returned it to the Dealer and Bought an EAD PowerMaster 2000 amplfier which solved both ends of the sonic Spectrum...
I have owned the Placette Active (single Ended) and it is an amazing preamp! it made one of the biggest improvements in my overall system. It is amazing how much a preamp can get in the way of your music
Stehno: I have had no problem with low end. In fact I pruchased W5 to replace Bryston 4BST (a bass master)based on reviews in both Sterophile and the absolute sound, both of which raved about it's phenomenal low end. In fact even in passive mode with the Adcom Pre, the low end is tremendous. I would like a little more midrange liquidity. Using Classe CDT-1 and DAC1 front end and B&W CDM7SE speakers. MIT top of the line cables all around except for illuminati balanced digital.
Bbybaudio, I purchased the W-5 when I still owned a BAT vk500 with BATPAK. The BAT had far superior bass control and definition with my Aerial 10T speakers with almost endless supply of power in comparison to the W-5.
But the W-5 was easily superior to the BAT in every other respect except the bass.
Basically what I thought I was hearing was a congested and/or compressed and ill-defined bass that simply got worse as the volume got louder. Low listening levels weren't too bad.
At the time, I was well aware of the write-ups on the W-5's bass from the mags which helped persuade me to make the purchase. But I just assumed the amp simply was not a good match for my speakers since they do demand a bit of power. I sold the W-5 for an amp that had the speed of the W-5 but it's bass was even better than the BAT.
Then a couple of years later I was on Sim Audio's web-site reading a review of the W-5 and the P-5 by Peter Moncrief of International Audio Review and although he too likes the W-5, he described the bass deficiencies that I too had experienced.
I am now on yet another amp with a bass reproduction that is simply out of this world IMO.
Still the W-5 is a wonderful amp in many ways. And I think for some to many listeners the W-5 would be quite an eye opener for the musical nuances that it reveals, speed of transient attack, and for it's overall sweet presentation.
As I said earlier, I have the Sim Titan, and never had ANY lack of the QUANTITY of bass, though it was not as tight and punchy as I wanted - UNTIL the VAC pre was added. It actually added even more depth and extension, while also firming up the bass that the Titan provided. I think this is a direct advantage of a tube pre with a transformer-coupled output design - it adds the tube mid-range qualities without sacrificing bass or treble extension, and the input impedance of the amp is far less critical.
That was after trying the Pass X2.5, Placette Active Linestage and a PSE HL-1 tube hybrid. They all seemed really good overall, but also just left the Sim with its standard bass characteristics - deep, sustained and sweet, but a just smidgen loose.
** Here's A Question for you all -
I have been wondering if, for the 2-channel listening and overall impact, would W-6 Monoblocks notably improve on what the Titan offers without changing the overall Sim 'flavor'? .....Or is it just an extra couple of power cords I have to buy.....
Any comments about the W-6's? PLEASE !?!?
Thanks for your input. My local simaudio dealer actually recommended the Audio Research LS25 MK II. In fact, he does not dislike the Adcom as long as it is in passive mode.
If you can get your hands on the P5 they go together like hand in glove! Prior to buying it I used a Proceed Pre, Classe DR6, Plinius CD LAD, and Audio Research LS15. All of them sounded pretty good because the W5 is fairly easy to mate up with. But the P5 sounds like a Krell, Levinson, and Rowland combined in one. It is built like a tank. The only negative thing that I would say is that the imbillical cord from the separate power supply is not long enough!
Your electronics outclass your speakers by a large margin. If you're looking for more midrange liquidity - I would take an encompassing look outside of B&W.