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12at7 with 12ax7 tubes

Greetings and Happy Easter,

This post has probably been answered before at some point. I have a Symphonies pre V2 that uses three 12ax7 tubes along with a 6x4 rectifier. I wanted to know if I could use a pair of 12at7 tubes for the output section with no ill effects. Thanks to all and good listening.
south43
rodman99999
6,156 posts
 
The 12AT7 is interchangable with the 12AX7, but has slightly more than 30% less gain. ergo: You will have to turn the volume a bit higher to get the same SPL from your system.
gmuffley
132 posts
 
Dropping a 12AT7 in for a 12AX7 does more than reduce gain. The cathode and plate resistors should be changed to make the 12AT7 operate in the most linear fashion. The two tubes have very different transconductance and plate resistance.
sebrof's avatar
sebrof
835 posts
 
"The 12AT7 is interchangable with the 12AX7, but has slightly more than 30% less gain"

Rodman - I've heard that about the 12AX7 vs. the 5751, but never the 12AT7. Are you sure you're on track with this?
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