Considering tube Monos to replace SS

I am hoping for some input on compatibility issues with a possible mono block change. I am not even close to being an EE; I rely on my ears, but I also consider (and ask for help) on the more technical aspects of compatibility, of which I am no expert. At the moment my chain consists of a Manley Steelhead phono stage, into an ARC LS-27, into a pair of Bryston 28Bsst2 mono's, driving Wilson Maxx 2's. I have been considering tube monos for some time now, and am looking at swapping out the Brystons for a pair of VTL 750 mono's. My math says it works on paper (but I am not 100% certain). I am hoping some of you with much more technical expertise can offer your input. Hope Ralph or Al can chime in, as they seem to be the most respected experts in the tech end of this hobby. Thanks in advance for any info, and have a great weekend.......
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

@yogiboy  I'm sure they are fine amps, but the VTL's are available to me locally as a direct swap for my Brystons, and as I have been considering tube power for the past couple of years, it seems to be worth my consideration.

@almarg  Thank you kindly for taking the time to research the equipment in question. It gives me "food for thought". I have to give this some thought over the weekend before making my decision. As I have only ever had SS power over the years, the tube world of power will be a new experience. Now, ironically enough, as a guitar player I would never entertain the thought of playing through anything but a tube amp. Go figure......

Thanks once again Al, for taking the time.


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,
@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.

@rauliruegas  nothing wrong with the Brystons, but I have owned nothing but Bryston power since the early 80's and it's time for me to move out of my comfort zone, and experience something different.

@atmasphere  Yes, I do remember now that your amps were with the fellow from Wilson. The person that I am getting them from currently drives Watt Puppy 8's. He too is in a position where he is interested in trying new ground, so the deal works well (hopefully) for both of us. If I am correct, I believe Dave Wilson was driving the Alexandria XLF's with the VTL Siegfried's, although I could be mistaken. Ralph, all my IC's and speaker cables are short runs, between 1 - 2 meters, so no issue there at all.

I have committed to the swap, and we are trying to make arrangement to do the deed this coming weekend. I am looking forward to this step in a new direction, but must admit, after over 3 decades of dealing with the good folk over a Bryston, I'm feeling a little guilty. Almost like cheating on a spouse. I don't know what I'll say to James and Brian at the next show!!

Thanks for all the comments and advice all, and I'll chime back in after I get the VTL's up and running in my system with my thoughts.


Dear @crazyeddy: Good luck with the VTLs, at the end is you whom will live with.

Regards and enjoy the MUSIC NOT DISTORTIONS,