tube amp for b&w signature 805

Gvatchna,
I agree with your points on B&W speakers other than Signature 805 as I also own Nautilus 805, which will be for sale later. I have never tried Silver Signatures using 2nd order low-pass filter, and you have never used Signature 805s using 1st order low-pass filter. In addition, my amplifiers have 4-Ohm taps. The dealer I bought my speakers from is using Classe CAM-200 to drive them. At the volume I audition them, my SETs only lost a liitle bit at macrodynamics.

My exerience was mostly with Nautilus 800's -- very little with the 805sig. However it may be useful for Glai & Bigkidz.

Gvatchna: my experience using Symphonic Line tallies with yours. On the 805's (a brief, 1hr, audition), a Kraft 250 ref slightly outclassed the RG4's in musicality, nuance and control. OTOH, the RG4 driving the 805's sounded, subjectively, ever so slightly "faster"... The differences b/ween RG4 and Kraft 250 were more than evident on the 800's: there with the Kraft we had detail and an "iron" control in the lower end -- indeed, the louder we played, the better (more open, more headroom???, more detailed) the sound became.

We also tried a tube -- a pair of KR mono's (allegedly an SET design with proprietary tubes -- huge) that drove the 805's very well. On the 800's we had a feeling that loud Mahlerian passages were a little compressed -- but that may have been an impression.

Please note that this was NOT a "critical auditioning" session -- just playing around (none of us could afford the 800's anyway) -- so after the first 2hrs or so, we ended up listening just to the 800's driven by the Kraft 250. Not that we rejected the 805's... but those belonged to a friend while the 800's to a dealer, so we grabbed the chance to play w/ the 800's :)!
Pre was a CAT Ultimate. Cheers

In term of thruth of timbre my Unico int/hybrid as done actually better than many expensive tube amps. that came my way. Another modern inexpensive classic with great timbre is Comrad Jonhson CAV 50 int. push pull. More expensive and only used would be Cary 20 LX Mono using KR 300 BLXS giving 20 in SE mode. My faved amp but could be compromised with the 805.