I just did a complete retube of my 5150II with JJ tubes, and have to agree with the accolades. Instant reduction in noise, and the
clean tone has undergone an
incredible improvement. My bandmate, after hearing the before & after commented "man, it's actually sounding like a clean tone now."
I replaced my v1 tube with a 12ax7 rated at 100 gain, to try and clean up the clean channel. biased up warm it really does make it sound like a different amp. High gain is less noisy and warmer as well.