I have a pair of Ray Lumley M-100 amps. Have used two complete sets GE 6550 for close to twenty years. Need new tubes. Which tubes would you recommend to purchase? Any knowledge of the sound character of the different models. I like the accurate/neutral type of sound versus the too valve sound.
They ranked the sound from each variant in an Air Tight Amp. Unfortunately, I can't find my copy to give you all the results, but this was a very informative article. There were a couple of current production models that rated very well. One of these is the JJ KT88 for about $50 each.
I am still using NOS GE 6550A's so I can't give you comparison form my own experience, but I will try the JJ's when the time comes to retube.