Can you run 8BQ5 tubes in a 6BQ5 amp ?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Dr. Tweedbucket, Dec 18, 2009.

  1. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    I think the heater voltage is a little different... I have a pair here that hopefully I could use.
     
  2. phsyconoodler

    phsyconoodler Member

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  3. mark norwine

    mark norwine Member

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    the first number is the filament voltage.

    I know of no guitar amps that supply 8 volts.
     
  4. Prairie Dawg

    Prairie Dawg Member

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    They were probably made for audio service in series string teevees. On the other hand if you can get 12 volts out of your filament string as some amps do you could probably cook up something or other to get them where you want to be-maybe a zener or something like that.
     
  5. Trout

    Trout Member

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    The 8BQ5 is actually a 6BQ5/EL84 with an 8 volt filament. You could always go the route the audiophiles go with their spud amps.

    Use a 12V 1.5A filament transfomer, Set it up for DC and regulate it to 8V nominal.

    10 bucks at allied electronics

    I have several of the 8BQ5's here that I saved for a headphone amp, one of those when I have time projects that will likely never get done.
     
  6. daveg777

    daveg777 Member

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    So you could damage the amp by running them? I am curious as I have run them in place of 6BQ5's in my Lightning clone with no harm, or so it seems...


    Dave
     
  7. Dr. Tweedbucket

    Dr. Tweedbucket Deluxe model available !!!11

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    Yeah, my Brother runs them in his Marshall, that's what gave me the idea. I have a few but didn't want to try it or blow anything up.


    Thanks, that's a good idea!
     
  8. Dirtydenny

    Dirtydenny Member

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    How do they sound?
     
  9. Blue Strat

    Blue Strat Member

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    Since a lot of amps with 6.3 volt filament supplies run closer to 7 volts, you can probably get away with this swap in some situations.
     
  10. Diablo1

    Diablo1 Member

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    It won't hurt the amp to run the 8BQ5. The filament heaters in the tubes just won't get as hot as they would if they saw 8 volts. Since they run cold, the emission will be low. If they sound OK, they are OK. I've used 8CG7 tubes instead of 6CG7 in an Ampeg V4. No modifications and no problems.
     
  11. Trout

    Trout Member

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    Wow,, another 2009 zombie thread Cool ;)
     
  12. Blue Strat

    Blue Strat Member

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    DOH!

    [​IMG]
     
  13. EFK

    EFK Supporting Member

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  14. donnyjaguar

    donnyjaguar Member

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    What Diablo says. I'll add that the service life of the tubes may be reduced due to emissions, although its far less likely to have a failed filament. :)

    I think I have some NOS 50L6 tubes somewhere, what a shame they are so useless! :(
     
  15. mc5nrg

    mc5nrg Supporting Member

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    Probably used in old series heater/Widowmaker amps.
     

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