Tube Question

intangible
intangible Posts: 262
edited April 2011 in Electronics
I purchased a new (to me) 12AT7 to go in my amp, and noticed that, using this tube but not the one it replaced, one channel is five decibels or so louder than the other. I know that it is common for the two triodes in tubes of this family to not be perfectly balanced, but this seems a little far out of whack. I am very much still learning about tubes though, so I figured I would ask: is this imbalance cause for concern? I can even out the levels with my preamp, so I mainly want to know if this could be symptomatic of further problems shortly down the road.
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  • george daniel
    george daniel Posts: 12,096
    edited April 2011
    do you know if the tube was matched (sections)
    JC approves....he told me so. (F-1 nut)
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  • intangible
    intangible Posts: 262
    edited April 2011
    It was advertised as "balanced" which I took to mean the sections were matched.
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  • george daniel
    george daniel Posts: 12,096
    edited April 2011
    I don't think that it will do any harm,based upon what you said in your op--one section of the new tube is most likely weaker.I'm assuming that the AT7 is the "input "
    JC approves....he told me so. (F-1 nut)
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  • intangible
    intangible Posts: 262
    edited April 2011
    Yes, my (limited) understanding of the amp's design is that the 12AT7 serves to amplify the line level signal enough for the power tubes to be able to use it. Thank you very much for the help.
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  • F1nut
    F1nut Posts: 52,000
    edited April 2011
    Send it back for a refund or replacement.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • jaritta
    jaritta Posts: 277
    edited April 2011
    You could try to adjust you bias, If you look in the manual on how to adjust tube bias this may help with your new tube to be "ballanced" with your other tubes.
    Harman kardon signature 2.1 amp
    Denon 3312
    Epson 8700ub
    Chief mount
    Screen Innovations Performance Series 110in
    Kef q 500 (RL)
    Kef q 200 (C)
    Kef q 800 (Rear RL)
    REL T7 (SUB)
    mx 450 remote
    Sonos-Amp, Connect, Play5
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  • F1nut
    F1nut Posts: 52,000
    edited April 2011
    Bias adjustments are for power tubes, not a signal tube.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • jaritta
    jaritta Posts: 277
    edited April 2011
    My bad, didnt see that it was a signal tube not an amp... sorry
    Harman kardon signature 2.1 amp
    Denon 3312
    Epson 8700ub
    Chief mount
    Screen Innovations Performance Series 110in
    Kef q 500 (RL)
    Kef q 200 (C)
    Kef q 800 (Rear RL)
    REL T7 (SUB)
    mx 450 remote
    Sonos-Amp, Connect, Play5
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  • RuSsMaN
    RuSsMaN Posts: 17,985
    edited April 2011
    Like Jesse said, send it back. If they don't take care of you, and you just need something decent, that IS actually balanced, let me know - I'll hook it up. I've got a LOT of NOS AT7 singles here that I've tested.

    Side note, if it is vintage, clean the pins.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • intangible
    intangible Posts: 262
    edited April 2011
    I realized last night that I actually couldn't use the pre's channel levels to compensate, so I've started the process of returning it. I wiped the pins down and am waiting for them to dry, but they looked very clean both before and after, so I'm not particularly hopeful.

    Just for my future reference, are y'all suggesting I send it back, because it was not as advertised, or because it is indicative of potential future issues?

    Russman, the seller offers refunds, not exchanges, so I'll send you a PM once I get this figured out.

    Thank you all for your help.
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  • george daniel
    george daniel Posts: 12,096
    edited April 2011
    Because the sections don't match-- it ain't matched--if the seller is gonna' replace it,,have him send you a tube with closely matched sections. when I'm looking for NOS tubes,I always buy from a known seller.EX-- someone here,,or Brent Jesse,,Jim McShane,,Paul Lindemann.Good luck,let us know how it turns out.

    Just saw the note about refunds--take the money and get one from Russman or one of these

    http://www.audiotubes.com/12at7.htm
    JC approves....he told me so. (F-1 nut)
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