Gz34 Rectifier and 220uf series Filter caps...

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by JubileeMan 2555, Feb 23, 2008.

  1. JubileeMan 2555

    JubileeMan 2555 Member

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    Am I playing with fire here? I keep reading that GZ34 rects don't like to see any more than 60uf, but My super has 2x220uf filters in the first round which would make it 110uf.

    I tried it out, and the amp works fine, but is it just a ticking time bomb for my rectifier?
     
  2. slider313

    slider313 Silver Supporting Member

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    I thought it was 50uf on the GZ34 ? In any case, you're putting the tube at risk.
     
  3. phsyconoodler

    phsyconoodler Member

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    If you are talking about a Super Reverb,those filter capacitors are not stock.The Super had 70uf caps in series for the last 40 years and they add up to 35uf.I use 100uf capos in mine for a total of 50uf and have had no failures of rectifier tubes.The Gerald Weber idea of 220uf caps just makes the bass response of the Super even more woofy than it already is.My advice is to get those out of the amp and get a pair of 100uf caps.
    However,there have been almost no reports of rectifier failures related to those 220uf caps.Just too much bass.
     
  4. JubileeMan 2555

    JubileeMan 2555 Member

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    I put those 220uf caps in myself. The bass isnt woofy to me. Just nice and tight like I like it:)

    So you've never had issues with 220uf caps and a tube rect?
     
  5. Blue Strat

    Blue Strat Member

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    I highly recommend not doing this. Try a solid state rectifier instead.
     
  6. JubileeMan 2555

    JubileeMan 2555 Member

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    Thanks for the help... I think i'll just drop the 220uf down to 100uf and call it a day.

    I had found a couple of NOS Rectifiers in a broken Ocilliscope, and figured I'd have some fun. I think I dig a rect. for quieter playing and want to have the option for REct when I'm playing soft, and SS when playing loud...

    I've been using SS rectifiers. In fact, I made one myself using some UF4700 diodes. Super cheap, and they sound great!
     
  7. Lyle Caldwell

    Lyle Caldwell Member

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    If you need the high filtering (which I highly doubt) you could put in a Weber WZ34 Copper Cap, which emulates a GZ34 well but doesn't have any limitations regarding the first filter cap value.
     
  8. Trout

    Trout Member

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    The thing guys miss using excessive PS input caps is the long term effect.

    When the rectifier tube is fairly new or new, they seem to work just fine. Down the road as they age a bit, suddenly you start to get arcing inside the tube. That is generally followed by other PS related failures like blown PT's, even blown tubes and OPT's can occure.

    I have an old Seymour Duncan Convertable 100W that came stock with oversized caps. The ONLY rectifier tube that would work without arcing was a sylvania 5U4GB Black plate. Everything else would arc on every power up or flip of the standby switch.

    I finally got tired of chasing rect tubes and lowered the stock cap values. It had a pair of 200UF's as shown in the schematic on page 2.

    YMMV
    Trout
     
  9. Clutch21286

    Clutch21286 Member

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    FWIW-I have been using 80uf in my amp with a Sovtek GZ34 for about 1 year now. No problems.
     
  10. phsyconoodler

    phsyconoodler Member

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    Two eighties in series is only forty uf.Not an issue.
     
  11. Clutch21286

    Clutch21286 Member

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    Psycho, I am using 80uf it is a TW Rocket inspired amp :AOK
     
  12. BP-Plickner

    BP-Plickner Silver Supporting Member

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    on fender type ab763 and 5f6a/5f8a circuits I use 50 to 64 MFD on the first stage (plates) with a GZ34. Using a 40mfd in the next stage (screens) seems to help firm things up pretty good.
    I am surprised that the recto didn't arc with 100mfd before it!:eek:
     
  13. JubileeMan 2555

    JubileeMan 2555 Member

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    lol..actually its 110! :) Its probably a testament to the NOS Holland Tube quality.

    But again folks, not an issue. I'm either going to knock down the filtering or use a SS rect. I just wanted the option. I've never felt rectifiers as huge parts of tone.
     
  14. donnyjaguar

    donnyjaguar Member

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    FWIW, if you use a choke input filter in the power supply you can go much higher with your capacitor values. This design also regulates better. Not sure why guitar amps seldom go this route as it seems inherently more reliable.
     

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