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preamp tubes?

Discussion in 'Amps and Cabs [BG]' started by cole, May 1, 2001.

  1. cole


    Sep 14, 2000
    what determines the number of preamp tubes in an amplifier? additionally, what difference does it make? (this is in reference to tube amps, not hybrid ones)
  2. The amount of preamp tubes is determined by how much gain the amp needs before the power amp. In an old Fender Bassman, the signal runs through both triodes of a single 12AX7, then into the power amp, which also uses a 12AT7 small signal tube as the driver. There is another 12AX7 for the other channel.

    It all depends on the circuit. More tubes may mean more gain, but there may be more losses in the circuit, which would then "eat" that extra gain, like the midrange cut/boost circuit on my Ampeg V4B.

    Basically, it boils down to the fact that there are way too many variables involved to be able to make any conclusions about much of anything based on preamp tube count. You only need 1 or 2 in most basic amps. It's the rest of the circuitry in combination with the tubes that means something.


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