Preamp Tubes Memphis

Amps & Cabs Memphis
1

The manual list 12AX7 tubes for the Memphis under the front panel. Can I use 12AT7, 12AU7, etc ???

2

Hi Stephen, The various preamp tube types are chosen by the designer of the amp for their specific gain and or tonal characteristics when determining their particular placement in the amp’s circuits. Although it may not harm the amp to try different preamp tube types in the various positions, it may cause less than desirable results depending on which tube position you are swapping. Inversely, you may like the effect of a different tube type in any given position of the amp. Take a look at the preamp tube gain info below for more detailed insight as to what you might expect from the various tube types. Cheers! Gil

The 12AX7, 12AT7, and 12AU7 are all miniature, twin triode vacuum tubes commonly used in audio amplifiers, but they differ in their amplification factor (mu) and other characteristics, affecting their suitability for various applications. The 12AX7 has the highest mu (around 100), making it ideal for high-gain preamp stages. The 12AT7 has a medium mu (around 60), often used as a grounded-grid RF amplifier or in phase inverters. The 12AU7 has the lowest mu (around 20) and higher plate current, making it suitable for applications requiring lower gain and higher power output.

Here’s a more detailed comparison:

12AX7:

  • Mu: 100
  • Characteristics: High gain, often used in the first gain stage of guitar amplifiers and other audio preamplifiers.
  • Applications: Guitar amplifier preamps, microphone preamps, effects pedals.
  • Equivalent/Substitutes: 5751 (lower gain), ECC83.

12AT7:

  • Mu: 60
  • Characteristics: Medium gain, lower noise than 12AX7, suitable for higher frequencies.
  • Applications: Phase inverters, reverb drivers, RF amplifiers.
  • Equivalent/Substitutes: ECC81.

12AU7:

  • Mu: 20
  • Characteristics: Low gain, high plate current, can handle more power than 12AX7.
  • Applications: Phase inverters, line amplifiers, some output stages.
  • Equivalent/Substitutes: ECC82, 5814A, ECC802, E82CC.
3

Thank you Gil.

I bought the combo on Thursday. Its a early one with the AR75. All the original tubes are gone. There was a 12AT7 in V1 and the reverb. I changed out V1 with a 12AX7.

I know the guy I bought it from and he had put some nice tubes in it. The V1 was a vintage GE 12AT7. A little less aggressive and a nice glass in the highs. I prefer the 12AX7 for what I do.

4

Thats cool Stephen, congrats on the amp! Experiment and enjoy!

5

Thanks

Ticket to Ride and Drive My Car, Live at Leeds, Since I’ve Been Loving You. Definitely enjoying the colors and textures. Just starting to figure out what she can do. Just brilliant the range that is available.