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Thread: Phase Inverter tube capability

  1. #1
    Join Date
    Dec 2008

    Phase Inverter tube capability

    I have a bunch of 12AT and AY7's, can I use this tube in place of a 12AX7?

    What would the differeince be? Would there be a difference?

    I've a 12AX7 that is noisy, and a don't want to fork over for tubes where I don't need to.

    Thanks in advance,


  2. #2
    Senior Member
    Join Date
    Jan 2008
    Galashiels, Scotland
    Well it may slightly lower the gain, and it may distort earlier as it won't be optimally biased, but the main problem is usually with presence controls that stop working if the gain and the feedback is lowered.
    Stick it in and give it a go!

  3. #3
    Old Timer
    Join Date
    May 2006
    Cornelius, Oregon
    The phase inverter tube is often required to supply more current than voltage, and if that is the case, the 12AU7, the 12AT7, 5751, and 12AY7 often make a better phase inverter tube than a 12AX7 for overall performance of the amplifier. Whether you will like the change or not depends as everyone hears differently. I personally like the sound of the 12AU7 and 12AY7 a lot better than the 12AX7. They are less hard sounding with more pleasing harmonics in general.


  4. #4
    Join Date
    Dec 2008
    Thanks, I found some paper on the use, but didn't really understand if it were going to cause earlier breakup, or if it would give more headroom being that it conducted more.

    I'll give it a spin, and see what it sounds like. It would most likely be less noisy being that the 12AX7 is oscilating or causing some feed back on the normal channel.

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