Best Tube Based Options For B&W 803S Speakers

I drive a pair of B&W 804S with a McIntosh MC275 and love it. I used to have a Rotel 200W SS amp to drive these speakers, and at the time I was looking to upgrade amp I auditioned McIntosh MC252 (250W per channel SS) and MC275 (75W per channel tubed) with 804S, and preferred the 275.
FWIW, bass with the 275 was a lot better than with the 200W from Rotel. Let alone midrange and treble!

Generally speaking, B&W 800-series loves power and hence are usually driven by SS. I remember listening to 802D driven by $30k VTL monoblocks at the dealer and it sounded fantastic...but who would spend that much on amplification for those speakers?

Anyway, my point is with smaller 800-series such as 804S, and maybe 803S, tubes are definitely an option. I would encourage you to consider two MC275 playing as monoblocks. Of course this would not be $2.5k, but you could buy one MC275 now, see how you like tubes, and when funds permit you could buy your second 275. mC275 is also a very low maintenance amp - it is auto-biasing.

Eventually I also replaced my SS preamp with a tube pre (Lamm LL2), which I love too.
In my view, B&W aluminum tweeters and tubes play really nicely together.

Think about it!

Good input from Lewinski. I would add, though, that the output impedance of the MC275 is much lower than that of most tube amps. I had said earlier in the thread that:

Impedance curves for several other B&W models, including some that seem to have a degree of commonality with the design of the 803S, all show a rise to very high impedance values (well above 20 ohms) in the upper midrange/lower treble area, around 2 to 4 kHz or so.

The interaction of that kind of impedance variation with the relatively high output impedance of a tube amp will result in greater emphasis of those particular frequencies, relative to other frequencies, in comparison with the frequency response that would occur with a solid state amp. That would seem to be the opposite of what you are trying to accomplish, namely softening the highs.

The current Mark VI version of the MC275 has a specified damping factor of 22, which is much higher than that of most tube amps, and theoretically corresponds to unusually low output impedances (for a tube amp) of 8/22 = 0.36 ohms for the 8 ohm tap, and 4/22 = 0.18 ohms for the 4 ohm tap. John Atkinson's measurements of the Mark V version are only slightly higher than those values.

So the tonal balance effects of the interaction between the MC275's output impedance and the speaker's impedance vs. frequency characteristics will be considerably closer to those of a solid state amp than will be the case with most tube amps.

Regards,
-- Al

"07-27-14: Abrew19
Matrix 800 series tweeters were the best around at the time. The 801s and 800 were Stereophile Class A regulars and the 805 was up there too for a long time. Methinks you have something different about your ears ..."

I don't know how you come up with those tweeters being the best available at the time. That's another one I've never heard from anyone. Its possible that your hearing may be rolled off a bit, and/or have some wax buildup. I know a few people like this. They just don't hear the sibilance/harshness that most people hear. As far as Stereophile goes, I think you'll get a better sounding system doing just the opposite of what they say.

Bullitt731 hi,

This is the only impedance graph I could find, and yes it does look to be tube friendly for good push pull tubes with low output impedance.

But this graph needs to be read in conjuction with a phase angle graph as well, and there are none of these around.
If the phase angle dips to -30 or more degrees at the 3ohm to 4ohm impedance between 50hz and 700hz, which some of the later floor standing 8 series do, then this can then look to the amp as a 2ohm or even lower impedance.
And a tube, even good powerfull one may sound a bit light on in the lower mids and upper and lower bass, and therefore maybe sound too lean and bright overall.

So unless you can find a phase graph, I would stay clear of tubes and even wimpy solid state.

http://www.htguide.com/forum/showthread.php?14694-Test-in-STEREO-803s-against-803d&s=bd734233c26b3cfa17fa522d0de3e468&p=191324&viewfull=1#post191324

Cheers George

Loaned my brother my Cary SLP-05 tube preamp hooked to his SS musical fidelity amp... Got rid of any remaining sibilance on his. 804 Diamonds... Fantastic sound.