Just a note about a change in the power tubes (KT66's) as well. A few weeks ago I started to notice that certain bass notes on the guitar were coming out with an octive lower ghost note. I was not getting a clear note but getting two notes and overtones. It was not sounding good.

Nik and others thought it was the power tubes doing that. I noticed that when I put the head on the floor and not on my cabinet, the problem seem to go away. I put the head back on the cabinet and it did it again. It seemed that the power tubes were vibrating and very microphonic. I just put in those tubes about 5 months ago and were KT66 tubes marked "Ruby" that I got from Mike at KCA. I replaced the tubes and the problem went away. I just thought that I would get a lot more life than 5 months from a set of new power tubes. I had them biased at 38. I've been wondering if anybody else has noticed short lived tubes in their JTM45 and if there were noticable improvements in which tubes they were using in both the power and preamp section of the amp??

I need to get another matched pair for a backup to take on gigs on the road.

When you were putting these different tubes in your JTM45, did you have to do something beside just change which tubes you were using??

I asked Nik when he built my JTM45 to make it available for EL34 tubes with just a bias adjustment but I wondered if it was alright to just swap tubes or not. Do you like or prefer the other power tubes over the KT66??

Also, you mentioned you have a master volume on your amp. So do I, and I've read about guys taking them out because they said that it changes the tone in a negative way. Has anybody done that and what are their experiences with the master volume on this amp??

I did change the V1 tube and the Hum did infact go away. When I got the amp a few months ago, I noticed how sensative that tube was in unwanted sound. Both by touching the tube and the chassis around the tube. Anyway, I replaced it with another JJ and the hum went away. I'll see what happens.

I have a 2 month old JTM45 built by Nik and sent to me. It has master vol. in rear of amp. The past 3 or 4 times I've turned on the amp, I've noticed a HUM that is constant with the amp on and the stand-by off. It happens with or without the guitar plugged in. This didn't happen when I first got the amp but developed over time. This is not a grounding problem.

Any syggestions to look for to fix this problem. The hum is loud enough to hear during live performances when the band stops playing or during a quiet music time and would be totally unacceptable for recording.

I'm looking for a Marshall type amp for good smooth classic tones. I've been a Fender guy for many years and want to change and maybe upgrade my sound. I'm looking for Eric Johnson, Allman Brothers, John Mayer, Santana type tones where there is breakup and overdrive but still retains a clean smooth singing tone.
I am lloking at the JTM 45 or JTM 50 but not sure about the difference. I am also looking at the Plexi 50 but I think I might want a tube rectifier for that sag so I have some questions on that. The 18 watt sounds appealing but I am affraid of not having enough even clean tone but the 36 watt which is switchable might be good option.
Any suggestions and help would be great appreaciated. The Ceriatone sight has all the models but does not really have good descriptions of the different amps and tones they deliver. I would be using a 2x12" Avitar Vintage cab with V30 speakers.