Have numerous KT88s, 6550s. The Mac tube amps from the 60s used either Genelex KT88S or Tung Sol 6550s. To me, and I just recently retired my MC60s, the TS 6550s gave these amps which had tube rectifiers, the most convincing reproduction.
The new Tung Sols have great dynamics but there is definitely a haze that obscures the voices, but all in all the NOS 6550s caused the least listener fatigue. While running the MC60s, after hearing the NOS Tung Sols I rarely swapped them out.
The new Tung Sols have great dynamics but there is definitely a haze that obscures the voices, but all in all the NOS 6550s caused the least listener fatigue. While running the MC60s, after hearing the NOS Tung Sols I rarely swapped them out.