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Inherent Difference - 12AU7 and a 12AT7

Can anyone school me on the practical differences between a 12AU7 and a 12AT7 input tube when used in a preamp? For example, all things equal is one of these tubes quieter than the other on average, does one have greater gain than the other, and is there any characteristic 'sound' to each of these tubes?
stickman451
stickman451 OP
553 posts
 
Sorry,I meant, why don't they make a 12AU7 or a 12AT7...
br2600
7 posts
 
Same pinout, but the gain is different. A 12AU7 only has a gain of 17 or so, a 12AT7 has a gain of 60. The 12AT7 was originally designed as a VHF oscillator or mixer tube, but it can be used in audio circuits.
plangco's avatar
plangco
158 posts
 

The 12AT7 has more gain and will sound louder. Great if you want to beef up output from a DAC or preamp that normally uses 12AU7 tubes.

Because the current draw of a 12AT7 is similar to the 12AU7, in most applications a 12AT7 it can be substituted for a 12AU7 and the primary considerations are more gain (louder sound) and the perceived quality of the sound.

I used a 12AT7 in my Audio Note CD player in place of a 12AU7 and got wonderful sound from a particular Mullard that exceeded other 12AU7s that I had tried.

However, you cannot substitute a 12AX7 for either because of a huge difference in current.
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