Okay so a few of the members recommended this tube for the JVM...to reduce some of it's gain ... So like I tried it now for several weeks to a month at practice and at home... Didn't really notice much loss in gain...but what I did notice over time that my JVM just didn't sound right... it had this funky thing going on in the mid frequencies... and my DSL and 800 didn't have that same weird sound. Was beginning to think I had to unload the JVM cause it was just not sounding like a proper Marshall.. Then I remembered that I had put a 'JJ' preamp tube in the head...and from what I remembered in the past JJ tubes just didn't sound right to me... So I removed the JJ preamp tube and placed both and EH and Tungsol, Raytheon, Chinese 12AX7s and that killer Marshall tone came back. I especially like the BP Raytheon in V1 and the EH in V2. I love that JVM again. Preamp tubes, certain ones anyway, have a profound affect on amp tone.