Preamp Tube Gain Factor and Substitution Chart 12AX7 Family Tube Substitution The 12AX7 family of dual-triode preamp tubes consists of the 12AX7, 5751, 12AT7, 12AY7, 12AV7 & 12AU7. These are all pin compatible with one another, the only differences being the gain factor of each tube. A common substitution is to replace a 12AX7 with a 5751 or a 12AY7 to tame a preamp that tends to overdrive too easily, allowing you to get a better ‘clean’ sound out of your amp. Tube Gain Acceptable Substitutes 12AX7 100 5751 12AT7 12AY7 5751 70 12AX7 12AT7 12AY7 12AT7 60 5751 12AY7 12AY7 45 5751 12AT7 12AV7 12AV7 41 12AY7 12AU7 12AU7 19 12AV7 It is important to note that the above is not carved in stone and any of these tubes can be substituted for any other. For example in the 4×10 5F6-A Bassman the stock first gain preamp tube is designated as a 12AY7 which has a gain factor of 45. Replacing it with a 12AX7 that has a gain factor of 100 dramatically changes the tone and feel of the amp. Experiment and see what works best for you. 300Guitars Shop My shop is located at 1 Executive Dr Unit L Toms River, NJ 08755 Please feel free to email me if you have any questions or are in need of some tech work. Monday: 10am - 5pm Tuesday: 10am - 5pm Wednesday: Closed Thursday: 10am - 5pm Friday: 10am - 5pm Saturday 10am - 2pm. (I am in every other Saturday). I am also an Eminence, Mercury Magnetics, Mojo Musical Supply dealer. I do all the tech work myself so you deal directly with me. I am a one man shop and my hours can vary so please contact me to confirm that I will be open. Email me: firstname.lastname@example.org Call or text me: 848-218-0362 Shipping Info for all repair work: Please ship all repairs to: 1 Executive Dr Unit L Toms River, NJ 08755 I am currently offering all phases of guitar work which includes: Set-ups Fret dressing Re-fretting New hand cut custom bone nuts & saddles Electronics work And amplifier work which includes: Basic maintenance Bias adjustment Repairs and restorations Modifications And more.... Testimonials: David Nicholas - The 20watt amp is sounding fantastic! Delivered the goods at the gig and I'm finding cool tones all over the place with it. Love the cab w Emenince Tonkerlites too- perfect for my sounds! Makes the 12 string sound like a grand piano! Peter Lacis - I had an audition for something recently that was all about Led Zeppelin I -- my custom Pennalizer BLEW THE MINDS of the guys I was playing with. They couldn't believe the sounds coming out of that amp. That album was never in my mind when I came up with the idea....so that's yet another testament to the amazing work that you do. Scott Goldberg - I am very satisfied with the set-up, and the fast turn around. With the "lower" action it feels easier to play. I will definitely spread the word.