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Thread: OT impedance for P-P 6L6's

  1. #1
    rf7
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    OT impedance for P-P 6L6's

    I have a OT with 5Kohm taps and 3.3K ohm taps on the primary side. What is the best tap to use for a 4 tube 100W 6L6 push pull amp? It's a Mesa Boogie Dual rectifier amp.

    My data book says effective load resistance for a Class AB1 6L6GC push pull amp is 5.6K ohms. So, for two pairs of 6L6's is the suggested impedance half of that, 2.8K ohms, since that two pairs are in parallel?

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    Senior Hollow State Tech Bruce / Mission Amps's Avatar
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    Quote Originally Posted by rf7 View Post
    I have a OT with 5Kohm taps and 3.3K ohm taps on the primary side. What is the best tap to use for a 4 tube 100W 6L6 push pull amp? It's a Mesa Boogie Dual rectifier amp.

    My data book says effective load resistance for a Class AB1 6L6GC push pull amp is 5.6K ohms. So, for two pairs of 6L6's is the suggested impedance half of that, 2.8K ohms, since that two pairs are in parallel?
    You have all kinds of possibilities there and either taps can be made to work.
    If the OT has 2,4,8 and 16 ohm taps I would use the 5k6 primary with a speaker mismatch.
    2 ohms load on the 4 ohm tap, 4 ohms load on the 8 ohm tap or 8 ohms load on the 16 ohm tap.
    If it doesn't have those secondary taps available or you don't have those speaker loads, then I would use the 3k3 primary and forget about it.
    Since the "common" primary impedance found in 4x6l6 guitar amps is around 2K, you could even use the 3k3 tap with a speaker mismatch (low load on the next higher secondary tap, as above) and probably be just fine too.
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
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  3. #3
    rf7
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    The secondary has 4, 8, and 16 ohm taps available, but the amp only has 4 and 8 ohm outputs on the back panel. So I'll roll with the 3.3K ohm tap.

    With those multiple taps on the primary, could I hook it up as an ultralinear OT?
    Last edited by rf7; 08-23-2008 at 09:38 PM.

  4. #4
    Senior Hollow State Tech Bruce / Mission Amps's Avatar
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    Quote Originally Posted by rf7 View Post
    The secondary has 4, 8, and 16 ohm taps available, but the amp only has 4 and 8 ohm outputs on the back panel. So I'll roll with the 3.3K ohm tap.

    With those multiple taps on the primary, could I hook it up as an ultralinear OT?
    Ultralinear taps would be primary taps, not secondary taps.
    If the ratio from high zed to lower zed was close enough, it could work... look up the ratios and see if the math works out.
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
    303-955-2412

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    Senior Member Old Tele man's Avatar
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    FWIW -- Fender Twin and Showman amps (4 x 6L6GC) use 2K OT's, which is exactly one-half the 2 x 6L6GC 4K OT's...and, of course, their POWER handling ratings is twice, 100W vs. 45-50W.
    Last edited by Old Tele man; 08-25-2008 at 10:01 PM.
    ...and the Devil said: "...yes, but it's a DRY heat!"

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