Balanced Low Power Tube Monoblocks?

Balanced ... Hummmm ... (scratching my chin). If you can live without balanced, I can suggest the VAC Renaissance 70/70 (Mk. III or Signature). I started with a 70/70, then ran the monoblock "140/140" version for six years, and now I'm back to the 70/70 (Mk. III) which I alternate with a darTZeel. The 70/70 is one chassis, but completely dual mono, all the way down to two power cords and two on/off switches. A very potent 65 watts per channel (excellent output transformers and power supplies). Real quality - $14k in 1999 dollars - unlike VAC's Phi products, the Renaissance amps are all point-to-point wired. The amp autobiases the 300B's and there's a tube shut-down feature which automatically kills power to any output tube that fails - it's a zero maintenance tube amp (there aren't many of those).

I run mine from a fully balanced preamp and a 25 ft. balanced interconnect with Neutrix XLR-to-RCA adapters - sounds super. I'm using Sylvania 6SN7 GTB chrome tops for drivers and phase splitters, and the original 300B's that came with the amp.

Most people don't know what these amps are - you can pick one up for $4k/$5k.

Hi Tvad:

I have used a number of different speakers with my 70/70 and 140/140's. With the 70/70, I have used Dunlavy SC-III's, very briefly Vienna Acoustics Mahlers, Escalante Fremonts, and currently, Eben X-3's. With the 140/140's, I used the Mahlers, Ultimate Monitors, and very briefly, the Esclanates, but most of the time (4 years), Revel Salons. Roughly 75% of the music I listen to is symphonic (tending toward big symphonic), with the balance being a mix of acoustic jazz (with lots of bossa nova - the wife is Brazilian), blues/rock and French and Brazilian pop.

The Renaissance amps are a cut above the current Phi offerings, having been designed and manufactured at the height of the two-channel boom in the mid/late 90's when people were spending big money on state-of-the-art two channel gear (they were designed by Kevin Carter, incidentally). No boards - only expensive point-to-point wiring and generally outrageous parts quality. Regarding the 300B's, you are right that they are much more expensive than power pentodes. In addition, 300B's used in the Renaissance circuit have to be carefully selected, as it is a hotrodded Class A design that runs the output tubes at 95% of the WeCo 300B spec maximum voltage. That said, good 300B's are extremely hearty little beasts and have far more life than pentodes. I bought only one set for the 140's, and I went back to the original octet that came with my 70/70 when I went back to the 70/70 (I had my 140's converted into two stereo 70/70's, having sold one and kept the other). The stock VAC 300B's, which are rebadged Golden Dragons or Shunguang factory 300B's, are quite good and work very well in the amp - I've got at least 10,000 hours on this original set. Having corresponded with other owners, the amp evidently sounds best with Sofia carbon plates, which is where I will go when the current octet dies.

The 70/70 has really stiff power supplies and superb output transformers - it has 2 Ohm taps and can drive virtually any speaker (Sound by Singer was unable to drive the big Pipedreams with the VTL Brunhilde - they used a 70/70 instead - the amp is a beast). It would not be ideal on an 86 db. speaker with big orchestral in big rooms, but I understand that you will use a highly efficient speaker? If that is the case, then I would suggest the 30/30, which is generally considered to be the "honey" of the Renaissance line. It's only 32 watts/channel, but a real 32 watts - one of the shops in Manhattan (Innovative? I can't remember) hooked it up to the B&W 801N, of all speakers, just for laughs, and it drove it - not very loud, but nothing blew up.

Regarding balanced operation, my opinion is that, by the time the signal gets to the amp, most of the advantages of balanced operation have been achieved. The truly differential balanced tube amps like AtmaSphere and BAT mentioned by others in this thread are certainly well built and great sounding products, but as I have written, at the amp end, I do not believe a balanced amp is necessary. If I were going to use highly efficient speakers, I'd look at a low powered push/pull amp like to 30/30 or the Cary that uses a pair of 845's, or perhaps a high-powered single ended amp like the Lamm or Zanden. Of course, room size, musical preferences and equipment synergies are crucial.

Not sure I understand why you need monoblocks - do you have a lot of money tied up in short speaker cables made for monoblocks? I have a 1 meter pair of Jena Symphonies on ice in the closet for that reason - I bit the bullet and bought 8 ft. runs for my amps, each of which is single chassis. If monoblock operation is desired simply due to design advantages, dual mono designs are generally the same thing (again, nothing is shared in the 70/70 other than the chassis).

Hope this helps.

Understood. To make a final pitch for VAC's Renaissance amps, there is a monoblock version of the 30/30, called the "30/70", which is 65 watts per monoblock channel. They come up for sale on Audiogon from time to time, and the 30/30 can be rewired by VAC into 30/70 monoblocks for roughly $500 per amp. I find the cosmetics on the 30/30 || 30/70 to be a bit loud, but, like all of the Renaissance amps, they sound superb, being incredibly transparent, open and alive (assuming they're run with zero feedback).