Preamp tube recommendation for ac30

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by cap217, May 8, 2016.

  1. cap217

    cap217 Supporting Member

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    I have a lot of tubes lying around but I haven't been able to tell a big difference in tubes and positions in my ac30 amps.

    I have an ac30cc2x, Bruno ug30, z wreck that I want to retube. For power tubes I have went with mullards which I'm not happy with. The z wreck gets 7189s and I used to only use sovtek el84M tubes in everything else. I assume 7189 in everything or Ms are the best power options.

    What about preamp tubes? I am looks my for clean headroom w bass and chime. What is the significance of each tube in each position? And does v3 need to be balanced?

    I have used a lot of Jj stuff and Mullard or sovtek lps tubes but never found anything that sounded so great that I had to keep it that way.

    Any help?
     
  2. drbob1

    drbob1 Silver Supporting Member

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    My 65 AC30 has had Tung Sol reissues for 12ax7s and NOS 6P14Ps and it sounds great!
     
  3. Sunnyevan

    Sunnyevan Member

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    Got an AC30 (Korg Made in Marshall Factory) modded by Psionic Audio. I too am using Tung Sol 12ax7's. They are one of the best new production tubes out on the market. The cleans are rich and fat. The gain is thick and meaty, can get a little loose though. I have a Amperex Bugle Boy in V1, and its very harmonically rich. But the Tung Sols are close. NOS tubes aren't worth $200 a tube, theres not much difference between the Bugle Boy and the Tung Sol, my AC30 still sounds like an AC30. But, there are little harmonic nuances that do come in play. Anyways, get a Tung Sol 12ax7! Or be my guinea pig and try out a new Mullard 12ax7. I've been curious to try one of those.

    And for Power I'm using Telam/Polam EL84s. They're not NOS, but "used good tubes". Also I've tried JJ EL84. They are very haromincally rich as well. Wouldn't hesitate to use them if I ever had to.

    If I'm not mistaken V1 is the Normal/Top Boost Tube, V2 is Top Boost Tube, V3.... i forget.., V4-V6 is all tremolo/vibrato tubes.
     
  4. cap217

    cap217 Supporting Member

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    You are pretty much saying what I have been finding. The difference in tubes is small so whatever you have will work fine. I guess I'm still looking for that eye opener but it might not exist.
     
  5. pdf64

    pdf64 Member

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    The logic of specifying a balanced tube for phase splitter applications is lost on me, as it's the circuit that creates the balanced signals.
    If the triode sections within the tube have differing gains, then (within reason) the negative feedback inherent in an LTP will act to even things out.
    And for amps with a cathodyne phase splitter, only one triode section of the tube is used for that.
    As with any tube slot, if a known good spare tube doesn't sound any better, then the tube that was in there is fine.
     
  6. WillLane

    WillLane Member

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    In an AC30C2: I run JJ EL84's, have not done any experimenting with the power section and I do not feel the need too.

    NOS Tungsram in V1. V1 generally has the most impact on your tone. Tungsol in V1 if you do not want to do NOS. JJ in V2 because cathode follower positions eat up New-Sensor tubes. Tungsol 12AT7 in V3 to smooth the amp out a bit.
     

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