Will removing a power tube cut my power in half?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by loveanddag, Nov 25, 2005.


  1. loveanddag

    loveanddag Member

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    I have a hot rod deville 410. If i take out one of the power tubes will (6L6's) it cut my power in half so itll be easier to od? Ive heard of people doing this with other amps but will the circuitry in a deville be able to handle it? Theoretically, it makes sense to me it should but i figured i would ask just in case.
     
  2. slipperyfingers

    slipperyfingers Member

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    You can't remove one of your power tubes in that amp. It only has two power tubes right?. I used to have an amp with four 6L6 power tubes, and your could either pull the inside two, or the outside two...but it was still very loud.

    -SF
     
  3. loveanddag

    loveanddag Member

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    ok, im not neccesarily trying to cut volume just cut power. but yeah, its only got 2 so i guess ill just have to drive it the old fashioned way. thanks.
     
  4. VaughnC

    VaughnC Supporting Member

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    If your amp had a single ended class A output stage with 2 (or more) tubes in parallel, removing one tube would be ok because each tube is amplifying the full output signal. However, your DeVille has what's known as a class AB push-pull output stage....which means each output tube is amplifying roughly 1/2 of the output signal. So, if you remove one of your output tubes, about half of your output signal disappears, resulting in a very ugly sound.
     
  5. loveanddag

    loveanddag Member

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    O yeah, so removing one of the tubes would only give me either the top or bottom of the wave. I might just end up getting me a lower wattage amp to drive easier.
     
  6. fakeox

    fakeox Member

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    How would a switch bypassing the P.I. to 1 output tube work?
     
  7. KLB

    KLB Member

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    Kevin O'Connor covers how to get single-ended tone from a push pull amp in his "The Ultimate Tone" book series. E-mail him and ask which book to buy.
     
  8. doctord02

    doctord02 Member

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    still wouldnt work because the output transformer needs a push-pull (two tube) signal. Running a center tapped transformer as a single ended transformer is not a good idea.
    In VaughnC's reply below he specifies a two tube amp running parrallel to a single ended OT... Thats a different amp from a more common push-pull.
     
  9. fakeox

    fakeox Member

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    Thanks! Would a multi-pole switch take care of the OT problem?
     
  10. drbob1

    drbob1 Silver Supporting Member

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    I don't think that would help. What you're doing is splitting the signal into tops and bottoms and sending 1/2 thru each 1/2 of the center tapped Tx. To use it as a single ended amp you'd have to run one of the output tubes in class a and send a full spectrum signal to just one side, otherwise the non-inverted signal going to both sides would cancel itself out. Running into just one side of the OT seems likely to expose the non-used side to flyback voltages that would likely be unhealty (unless you switched in a load in place of the non-functioning tube). Regardless, if you're just looking to drop the output power of the amp you could:
    1. Add a switch for cathode bias
    2. Add a switch for "triode mode)-together they'll cut the power in 1/2
    3. Switch to yellowjacket adapters-another 50% drop
    4. Add a switchable resistance in parallel with the speakers and equal to them (another 50% drop, we're now down to about 1/2 the percieved volume) or use an attenuator that'll let you drop down to 1/4 volume or less.

    Of course all these'll change the tone and it's hard to know if you'll like the results...
     
  11. fakeox

    fakeox Member

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    Dr Bob.. Thanks kindly for the reply; great stuff but a couple of posts up i mentioned bypassing the P.I. first. My amp is not the same as loveanddag has, it is a YBA-3 with 4X6550s. Again thank You all.
     
  12. fakeox

    fakeox Member

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  13. doctord02

    doctord02 Member

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    The point being that you cant bypass the PI and run one tube thru a push-pull OT. Either the amp has a single ended OT or not. If you have a push-pull OT you cant make it behave like a single ended OT... They are different circuits and not alike.

    You definitely cannot do this with a YBA-3.
     
  14. fakeox

    fakeox Member

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