12AU7(17db) has lowest gain and 12AX7(100db) has highest -- so I would assume that 12AX7 is more volatile for upgrades.
12au7 or 12ax7
I recently purchased my first tube amp a Primaluna Prolouge 5, the previous owner said the tubes were at the end of their life. I replaced the factory KT-88's with Tung-Sol KT-120' with which I am very pleased. My questions is which would give me the biggest sonic benefit replacing the 12au7 or the 12ax7? Both will be replaced in time which do you think I should do first?
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Both will make a difference but I think the most noticeable will be the pre amp tubes. But before you change anything get used to the KT120 sound first and from there decide what if anything you want to change in the sound. For me all different manufacturers tubes have a sonic signature meaning all AU/AX tubes sound different. Brent Jessee lists some of the differences but it in the end will vary a bit depending with the topology used for the different amps. http://www.audiotubes.com/12au7.htm Good Luck |
The 12AX7 is the voltage amplifier in the amp The 12AU7 is the driver tube The 12AX7, being upstream, will have the most sonic merit. The best made were Telefunken but are nearly impossible to find NOS at this point. So if you're rolling tubes, this is the place to start. Keep in mind though that the 12AU7 is going to effect things too- whatever you hear from the 12AX7 will be passing through the 12AU7. What I always tell my customers- have at it, have fun, and don't drive yourself off the deep end. |
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