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DBX 367 PreAmp with an RCA 12AU7A

Discussion in 'Preamps / Channel Strips' started by johnlaw, Nov 6, 2011.

  1. johnlaw

    johnlaw Active Member

    I just bought an RCA 12AU7A tube to replace the one in my DBX 367 which gave up.

    It doesn't work. No audio being passed or metered. I checked connections.

    Is this a wrong tube for the DBX367?
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    If this is a 376 (not a "367"), the 12AU7 is the correct tube. Are you SURE that you inserted the new tube correctly?
    Why were you replacing the original tube in the first place? Preamp tubes like that are much less likely to "go" compared to power tubes. If the original tube was going bad, there may be a power supply issue.
  3. johnlaw

    johnlaw Active Member

    It definitely is the 376 (the mic pre). I put in a 12AU7A (as opposed to a 12AU7), would that make any difference? The output with the original tube had become distorted, thin - I assumed it was the tube so I replaced it with the RCA? I understand now that paying more for the RCA tube was probably a waste of money since this such a low voltage plate, but it should at least work. I'll re-check the install (it seemed fine - the pins can only line up one way and they all settled in right to the base of the tube).

  4. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Don't discount that the RCA tube may be bad...after all it is "new old stock" at the very least. That extra "a" designation won't determine the tube's gain, shouldn't make a difference. And what you described of the original certainly does sound like it may be a bad tube.
  5. johnlaw

    johnlaw Active Member

    The RCA tube came from Tube Depot and apparently was tested before it was sent out. But I don't think its the power supply because all the other lights on the front of the unit work. Hmmm. I guess the only thing left is to check the install. Thanks again.

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