Best amp for KEF LS50

Still love my Rogue Cronus Magnum II with my LS50s, even more so after some careful tube rolling.

Which tubes did you end up with?

I just completed a Pass DIY amplifier project based on using NOS Sony 2SK82 and 2SJ28 VFETs as a complimentary pair in a push-pull Class A amp (https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a.html?). Even though this amp is only rated at a nominal 15 watts per channel into 8 ohms and 20 watts per channel into 4 ohms, this is one of the finest amp pairings I have heard with the KEF LS50s. This amp has a relatively high damping factor of 45, and I believe this contributes to the synergy between this amp and the LS50’s.

With my Audio Research LS7 tube line stage, I have no problems filling my living room with tonally rich music presented in a huge holographic soundstage that I previously thought was only possible with tube amps.

Combined with the spectacular imaging of the LS50’s, I am treated to very engaging music events every time I play analog or digital tracks. I listen to a wide range of music from early choral to jazz to classic rock nd blues. In fact, I was jamming to The Who’s “Live at Leeds” earlier today along with Morton Gould and His Orchestra performing Copland’s “Billy the Kid” and Grofe’s “Grand Canyon Suite.” 

Unfortunately, the Sony VFETs are near-unobtainium, but Nelson Pass does build First Watt Class A amplifiers using new production equivalent (maybe even better) Semi South Static Induction Transistors (SITs). His SIT series of First Watt amplifiers have received excellent reviews and they are worth auditioning with the KEF LS50’s in an appropriately set-up system. 

I am using Bel Canto ref1000m amps and klipsch sw-308 sub.  Very nice!

@sfseay how did the pas labs ls50 combo sound together? I have the XA25 and was considering a used pair of LS50’s.