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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Best rectifier for 5e3 build?

Discussion in 'Amp Central Station' started by t-luxe, Dec 26, 2009.

  1. t-luxe

    t-luxe Tele-Afflicted

    Nov 23, 2009
    so. cal
    Hello everyone- just finished a Mojo 5e3 kit and wonder what you guys are digging in the rectifier dept? The amp doesn't have a STANDBY switch so i'd like to use a rectifier with an indirectly heated cathode. I'm currently using an NOS 5y3 with JJ 6v6s, which gives me 376 VDC on the plates. The stock sovtek 5y3(?) gave me 406 VDC on the plates, and a new JJ 5AR4 gives me
    about 412 VDC. Will the JJs handle this OK? I noticed KCA has some NOS 5y3s with indirectly heated cathodes(I've never heard of these before) - has anyone had any experience with these? The amp sounds great at 376 VDC, but being my first build, i'm a little reluctant to run it hotter without some advice!!
     

  2. muchxs

    muchxs Doctor of Teleocity

    Aug 14, 2004
    New England
    Why not? The "ground" switch is redundant if you used a grounded cord. Everyone sticks a standby switch there.


    Yeah, the JJs will handle that.

    Yeah. They're Bendix, right?

    Try 5881s. They'll handle 412v on the plates, no sweat. A lot of guys go at this backwards, they'll build an amp that's on the edge as far as voltage and dissipation goes and then they'll go crazy trying to get the thing towards design center values.
     

  3. SirJackdeFuzz

    SirJackdeFuzz Friend of Leo's

    Age:
    44
    Jan 18, 2007
    South Africa
    I might be very wrong, but if a JJ 5U4 will fit, that is the one i will go with , as i love the socalled "valve-sag" . . . and a Texas amp builder told me they "sag" the most of all the rec. valves !

    A "sagging" 5E3 on max vol is a thing of beauty !
     

  4. ThermionicScott

    ThermionicScott Poster Extraordinaire

    Age:
    37
    Dec 3, 2005
    SW CR IA US NA PE
    Even with a directly-heated rectifier tube, there's no need for a standby switch. The signal tubes only see the B+ for a couple seconds at best before they're fully warmed up. Vibration, gas, and over-dissipation will kill them long before cathode stripping. ;)

    Given the same amount of current draw, real 5Y3s will sag the most.

    - Scott
     

  5. t-luxe

    t-luxe Tele-Afflicted

    Nov 23, 2009
    so. cal
    I like it fine with the NOS 5y3 at 376 VDC. I'd like to keep it there-Hence my question about the Bendix indirectly heated cathode NOS 5y3. I think i'll just leave it alone for now and re-wire the standby later if stripping appears to be a problem. No sense fixing it if it ain't broke! :idea:
     

  6. Chewy

    Chewy Tele-Meister

    244
    Jul 22, 2008
    NY, USA
    I haven't seen the KCA ad in question, but if it's indirectly heated, it is by nature, not a 5Y3 - even if it was some sort of revised 5Y3 with an indirectly heated cathode, the socket would probably have to be rewired to accommodate it.

    You may be able to run the amp with 5881's, but you'll be drawing more current through the transformers than most 6V6-oriented power and output transformers are spec'd for. You also may exceed the current limit of the 5Y3 (which I think is around 125 or 150 ma). But tube amps are generally pretty good about working beyond the limits of what they're designed for.

    The Sovtek 5Y3's are notorious for not being real 5Y3's and not dropping enough voltage. With one of those in your amp, you may be over-dissipating your power tubes.

    Long story short, your best bet in a 5E3 is a good NOS 5Y3.
     

  7. muchxs

    muchxs Doctor of Teleocity

    Aug 14, 2004
    New England
    Most "repro 5E3" transformers are up to the task of running 5881s, 6L6s, etc. Been there, done that. PT runs cool to the touch. Calling them "tweed Deluxe" transformers is really a stretch, they're meant to work in tweed Deluxe, Deluxe Reverb, "Marshall " 18 watt... the tweed Deluxe and the Deluxe reverb are entirely different amps. Yet the same aftermarket transformer is "correct" for both of them.

    Same deal with the OT. Most of 'em are for Deluxe / Deluxe Reverb, Deluxe Reverb is 22 watts w/ around 420v on the plates. Tweed Deluxe with 6L6s puts out around 25 watts. You'll see various power outputs quoted depending on the mood and optimism of the builder that particular day...

    BTW I wear from size 8 to size 11 boots... :lol:

    A whole bunch of '50s P.A. amp manufacturers Bogen in particular used a 5Y3 with a couple 6L6s. If it worked for Bogen it will work for me. Not my favorite rectifier but if it's what you have it will work.
     

  8. jjmantele

    jjmantele Tele-Holic

    977
    Aug 23, 2003
    New Jersey
    There is no documented case of cathode stripping in a guitar amp because of no standby. Nor even an undocumented assertion of a specific instance. At least not since the last time I checked.

    JJ 6v6 tubes can take higher voltages and higher currents than other 6v6 tubes. This has been documented. I use only NOS 5y3 tubes in 5y3 applications since the sovteks don't supply the correct voltage for a 5y3.
     

  9. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    65
    Dec 23, 2009
    Rocklin Ca.

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