Using a 5Y3G in place of a 5Y3GT

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Aint Life Hell?, Dec 16, 2005.


  1. Aint Life Hell?

    Aint Life Hell? Member

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    Hello,
    I have two amps that take 5Y3GT tubes in the rectifier spot. I have been thinking that I would like to try a 5Y3G (sts shaped) tube in one of those amps.
    The research that I have done has led me to believe the 5Y3G will have longer life, but I am worried about creating a problem in my amp due to voltage drop...
    Will I need to rebias the amp in order to use a 5Y3G instead of the prescribed 5Y3GT? Both amps are cathode bias...
    Any opions, both hypothetical or experiential are very much appreciated. Thank you in advance for your time and consideration.
    Best Wishes,
    MG
     
  2. Killa-B

    Killa-B Member

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    I will throw out some info and suggestions, and then I hope one of the resident tube gurus will chime in and give their take. I know a thing or two, but am no expert.

    I believe that the circuitry of the 5Y3G or 5Y3GT is identical, but the suffix just refers to the glass envelope shape. If this affects sound much, I'd be surprised.

    I really don't like 5Y3s much in general. I would much prefer to use 5V4 types as I like the response they give, and they should protect your power tubes more due to slower heat up.

    What kind of amp are you using the 5Y3s with?
     
  3. donnyjaguar

    donnyjaguar Member

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    Killa-B, it sounds like you know more about vacuum tube rectumfryers than I. Any thoughts on GZ34 vs 5U4G? It strikes me that the GZ34 takes longer to warm up (probably a good thing). In my application the voltage drop of each type of rectifier seems to be very similar and the specifications of both certainly cover off all the current I'm going to need.
     
  4. Shea

    Shea Member

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    5U4's have a bigger voltage drop than GZ34s, which also means they sag more under load. I can hear a difference between using a 5U4 and a GZ34 (after rebiasing) in a 50-watt amp, whereas I could never tell much difference between a GZ34 and solid-state rectification.

    Shea
     
  5. Aint Life Hell?

    Aint Life Hell? Member

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    Hey,
    Thank you to everyone that answered, I appreciate your assistance.
    Killa-B: I am using a 5E3 deluxe clone and an amp based on a Matchless Nighthawk. I'm not sure why he put a 5Y3 in the latter of the two, actually.
    Could I swap for a 5V4 (or 5U4) straight across, sans bias?
    Thanks again!
    Best,
    MG
     
  6. Wakarusa

    Wakarusa Member

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    5Y3G vs 5Y3GT is just ST shape vs straight glass. Careful with 5V4 as they have a much lower current rating.
     
  7. Damon

    Damon Member

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    A 5Z4G or GZ30 has pretty much the same ratings as the 5Y3 types, but with an indirectly heated cathode (like the GZ34), which means it takes awhile for high voltage to develop... generally thought to be good for the longevity of the other tubes in the circuit. Also, KCA sells a NOS Mazda 5Y3G that is indirectly heated.
     
  8. Blue Strat

    Blue Strat Member

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    Check this for the final word on rectifier swapping.
    http://kcanostubes.com/content/newsletter_details.asp?ArticleID=3
     
  9. Wakarusa

    Wakarusa Member

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    Hey Mike,
    Your rectifier swap page would be even better with some notes on current limits. Sure you can plug a 5AR4 in where a 5Y3 used to be (assuming the rest of the amp will tolerate it), but going the other way can easily lead to 5Y3 meltdown. Same goes for 5V4.

    The other tip that I'd offer is to always replace Ck when you change Rk on a cathode biased power section. The bypass cap gets a memory and can fail with a higher bias voltage.
     
  10. TheAmpNerd

    TheAmpNerd Member

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    Ta Key La really knows his chit. Don't let him fool ya
    with that I don't know BS. He's in vino country now...

    Howdy there mr tone de Max a mundo. : )

    Drink one for the gipper!:BEER
    ...
     

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