Considering tube Monos to replace SS

Hi Eddy,

Thank you kindly for the nice words.

I took a look at the specs on the LS-27, the 28Bsst2, the MAXX2, and the VTL MB750. I also looked at Stereophile’s reviews and measurements of the VTL and the MAXX2.

Also, BTW, I looked at the schematic for the 28Bsst2, because the input impedance spec listed in its manual was confusing. It turns out that its input impedance is actually a bit low to be optimal for use with your LS-27. The VTL would be fine in that respect.

The bottom line is that I don’t see anything that would be a showstopper if you were to replace the Bryston amp with the VTL, but there are a couple of things I would be concerned about.

Most significantly, I’m uncertain as to whether an objectionable degree of weakness might occur in the mid-bass region as a result of the interaction of the amp’s 1.3 or 1.8 ohm output impedance (depending on mode) and the challenging combinations of impedance magnitudes and impedance phase angles the MAAX2 presents in that region (see Figure 1 and JA’s comments just above it in the measurements section of Stereophile’s review).

A lesser but possibly significant concern involves gain. **If** you are presently operating the Bryston amps in their low gain mode (23 db), and **if** you were to use the VTL amp in its tetrode mode, which provides higher power and higher gain (31 db) than its triode mode, you would find yourself setting the preamp’s volume control about 8 db lower than the settings you presently use. If you are already using relatively low settings in the control’s range, and if you are already using the low gain settings of the preamp and therefore can’t make them any lower, that might result in having to use the volume control undesirably close to the bottom of its range. To provide some context, if the preamp’s volume control has its min setting at around 6:30 or 7 o’clock, and its max setting at around 5 or 5:30 o’clock, as a very rough approximation an 8 db change probably represents something like 60 degrees of rotation (although less than that near the bottom of the range, where volume changes probably occur more rapidly).

So in conclusion all I can offer in response to your question is a definite maybe :-)

Best of luck, however you decide to proceed. Regards,
-- Al

Be careful buying used VTL, they hate supporting used gear not bought from dealer....  They are the absolute worst customer service experience I've ever had.

They will need factory service at some point

Quicksilver V4 monos are awesome amps, super reliable and top notch support

Dear @crazyeddy: Problem is that the impedance and phase MAXX2 speakers is totally inadequate for tubes. Can VTL handle the Wilsons?, well it can handle but is not a good mate for the speakers. Those speakers needs the best SS amplifier you can get for can really shows at its best.

What's wrong with the Bryston, what do you want to improve? in any case my advice is to mate those speakers with SS amplifier, the speakers deserves it.

Regards and enjoy the MUSIC NOT distortions,
R.

@crazyeddy (whose moniker smacks of A Mote in God's Eye, which I read about 40 years ago...)
The Wilsons have always been easy to drive with tubes, which is why ARC and others have often showed with Wilsons at shows. The Maxxes are no exception despite the low impedance dip- even our amps which are OTLs (not noted for driving low impedances all that well) work just fine on them. The National sales manager at Wilson had our amps for quite a few years.

With a transformer coupled amp, use the 4 ohm taps and keep your speaker cables short in any event, so monoblocks are advised. Balanced inputs are nice (although the VTLs have XLR inputs, they are not balanced so no benefit accrues) if you can pull it off, which would allow you to run longer interconnect cables. If your gear sits between the speakers, this might be a non-issue.

I recommend something around 150 watts as a nice minimum, which should work fine in most rooms. So you have a wide range of amps to look at.