The BAT vk60 is a great amp, and can be found for less than 2k. I don't know what your power requirements are but I had one running Martin Logans with lower sensitivity than your va's and was quite happy.
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I'm not sure what aspect of your sound you are expecting to improve with a tube amp. Tube amps do sound different from each other tonally speaking, so I would assume you are looking for liquidity and bloom, not more warmth. Personally I would be looking at some of the push pull 80wt (+/-) amps using. Look at getting one from a well known manufacturer so if you are not happy it will be easiy to resell and not loose a lot. Think CJ, ARC, VTL, etc. The CJ ll is a nice place to start. Easy to operate and easy to resell, and sounds quite nice and has adequate power. I see them selling for well under $2000.
Thanks for your input Newbee and Mthieme.
I was thinking about amps in that power range but I started to have second thoughts when I read the recommendation chart on the VTL web site. They suggest that with speakers with two 6" woofers to use the MB 185. I was thinking more along the line of their ST 85. Would a <100 watt amp have the damping factor needed to control a speaker with five drivers? The Beethovens have 2 7" woofers, 2 mids and 1 dome tweeter. They present a 4 ohm load but have 91 dB sensitivity.
FWIW I have some 4ohm speakers which I have driven with 4 different tube amps, a 35wt integrated, a 60wt triode, an 80wt pentode and a 160wt pentode. The speakers have 2 woofers, 2 midranges, and a tweeter. They are ported. They have an efficiency spec of 92db. The larger amps drive these speakers with ease at volume levels that can overload the room at 4 or 8 ohms. The smaller amp has the same capacity, volume wise, but for some reason do not sound as smooth in the mids/highs off the 4 ohm tap, which you would think the speakers should be connected, although the bass is just fine. Off the 8 ohm tap they are much smoother but the bass is just a tad soft, a little of the impact gone, but very little.
The point of all this is that some extra power can go a long way, that is the larger amps can drive the speakers better throughout the frequency range even though none of them is really max'ed out power wise. The 4 ohm speakers sound fine on the larger amps on the 8 ohm taps - as with the smaller amp the highs seem smoother. I suspect that the larger ones just have better transformers and can drive the woofers better even at a higher impedence.
Hope this helps some in your decision. FWIW 100 watts of tube power is a lot of power!
I also drove Legacy Focus 2020 with the bat with great results. They have 7 drivers if memory serves me. 3 12',2 6", 1" tweeter and a ribbon tweeter. They are very efficient(95 i believe) and are 8 ohm, and I have heard them rock with 15 watt Cary monos. But getting back to your problem, I think that you will be better served trying to hear your speakers with a similar power amp at your dealer than taking the blanket recommendation of the vtl website. 91db is pretty efficient so don't count out lower specs.
Here's an Update for tube amps with the Beethovens. I went to a dealer near me that has both VTL and Vienna Acoustics gear for sale. I listend to a VTL st85 and fell in love with the sense of air and the beauty of the mids and highs. The sparkle and liveliness were intoxicating. The bass was pretty muddy and slow though. I don't think I could live with this amp. I'll try the VTL ST 150 next. By the way I listened to a Bryston 3bsst and an Ayre V5x? in the same sitting and just thought they were boring and uninvolving compaired to the VTL, although they did do the bass very well. I've been ruined by one tube amp audition, one that didn't even make the cut!
I just received a used VTL ST150 and I am evaluating it right now. My first impressions are generally good. The bass is very good, tight fast and full bodied. This is a definite improvement over the ST 85 that I tried. The midrange doesn't have the same lush bloom that the ST85 did. I guess this is a function of using 6550 instead of el34 power tubes. This being said the midrange is still real pleasing. The high end was a little harsh at first, kind of bright, female vocals had a lot of sibilence. But this seems to be calming down now. I ordered some Mullard CV4024 to change out the input 12AT7s. The ones in there are of unknown origin. I'll post back in a few days after listening over the weekend. As of now I think this is a keeper.
Mullard to the rescue. The CV4024 are a huge improvement over whatever the 12AT7s were that came with the amp. The harsh highs are gone and have been replaced with sweet and extended highs. The high end is the biggest suprise for me with this amp. Much more detailed and extended that I thought tubes would do. I am enjoying a Mississippi John Hurt recording right now in triode mode. Very relaxed and open. Nice airy presentation with a sound stage that goes deep behind the speakers. The sound stage is not as wide as the McCormack DNA 125 but I think that is what the McCormack does better than most amps I have heard.
The width of the soundstage is about the only area that the McCormack is better than the ST 150. Don't get me wrong I really like the DNA 125 and would recomend it to anyone looking for a good reasonably priced amp. I am keeping it, just moving it to the bedroom were it will replace an Acurus A250. The ST 150 is staying in the big system for a long time.
Most reputable dealers will let you audition any type of equipment they have in house. Some will go the extra mile to accomodate. I had the pleasure of listening to the ST-150 with a pair of wilson duettes. The sound was really an experience. I have a Sonic Frontiers Power 1 with a pair of watt/puppy v.11. I will be trading it in for a VTL.
I had a pair of VA Beethovens and now have the Mahlers, but I thought that the Beethovens were actually a little power hungry. I have flipped between the 4 and 8 ohm settings, but was not certain which sounded best. I am currently driving my Mahlers off of the 4 ohm setting from my Mcintosh Mc402.
They are a great speaker though and will sound wonderful with quality tubes!