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Any Mods to make 12ax7 act like ay7?

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  • Any Mods to make 12ax7 act like ay7?

    I have an EH ay7 that sounds no better than an old at7, but plenty of quiet well behaved 12ax7's. I'm aware of mods to reduce the gain of the 2nd tube, but has anyone tried making an AX7 run like an AY7 or is there something so different between these 2 tubes that it won't work?

    I'd guess a shared cathode resistor somewhere between 1.5K & 2.7K, maybe different plate resistors, and I don't know what for a bypass cap. Maybe even switch in another resistor in parallel to bring it back down as a pull-boost?

  • #2
    The easiest thing to do is pull the AX and fit another 12AY. They are different in too many ways that stop them from sounding the same.

    For a cleaner sound from the 12AX7 you might try running the cathode unbypassed, but it might kill dynamics & still won't sound like a 12AY.

    Going over 1.5K for the shared cathode might just make things sterile & stiff. Try 1K to 1.5K with a 10uf bypass cap?

    Or try a split load plate resistor to dump some gain before the coupling cap?

    Typically the EH12AY7 don't sound that bad, there are better NOS out there but not all NOS are better.

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