6L6 in a Vibro Champ

Discussion in 'Amp Central Station' started by Tone Chase, Feb 29, 2020.

  1. Tone Chase

    Tone Chase Tele-Meister

    Posts:
    399
    Joined:
    Aug 20, 2014
    Location:
    Windsor ON Canada
    What needs to be done to a Vibro Champ to allow safe use of a 6L6 power tube?

    What are the pros and cons of doing this mod?

    I am only asking because every so often I read that someone has done this mod.
     
  2. Milspec

    Milspec Poster Extraordinaire Silver Supporter

    Posts:
    5,065
    Joined:
    Feb 15, 2016
    Location:
    Nebraska
    Just use the JJ 6V6 tube and you will pretty much be there.
     
  3. 2 Headed Goat

    2 Headed Goat Friend of Leo's

    Posts:
    2,150
    Joined:
    Jul 28, 2012
    Location:
    age 8
    How so?
     
  4. corliss1

    corliss1 Friend of Leo's Platinum Supporter

    Posts:
    4,143
    Joined:
    Sep 13, 2008
    Location:
    Lansing, MI
    The better question is why - just want to find out what happens? Or are you looking for something specific?
     
  5. Dacious

    Dacious Poster Extraordinaire

    Posts:
    8,389
    Joined:
    Mar 16, 2003
    Location:
    Godzone
    The Champ PT doesn't really support the heater current of the 6L6. Plugging it in might not kill the PT today but it'll make it run hotter and potentially shorten it's life.
     
    corliss1 and 2 Headed Goat like this.
  6. Milspec

    Milspec Poster Extraordinaire Silver Supporter

    Posts:
    5,065
    Joined:
    Feb 15, 2016
    Location:
    Nebraska
    The JJ 6V6 falls somewhere between the 6V6 and 6L6 design and could interchange in some amps. To many, they sound more like a 6L6 as well. I have a modded '64 Bandmaster which was originally a dual 6L6 now running quad 6V6 tubes. Only the JJ's could handle the plate voltage.
     
    Greggorios and 2 Headed Goat like this.
  7. 2 Headed Goat

    2 Headed Goat Friend of Leo's

    Posts:
    2,150
    Joined:
    Jul 28, 2012
    Location:
    age 8
    Cool, good to know - Cheers!
     
  8. stefanhotrod

    stefanhotrod Tele-Holic

    Posts:
    584
    Joined:
    Aug 27, 2016
    Location:
    germany
    Keep in mind that 6V6 are a part of the Champ tone!

    D2D737AE-4D2F-4C1D-801A-A9F009F04371.jpeg
     
    Florida Sam and Greggorios like this.
  9. telerocker1988

    telerocker1988 Tele-Afflicted

    Posts:
    1,611
    Joined:
    May 2, 2010
    Location:
    Illinois
    I absolutely run a 6L6 in my 78 Vibro Champ. The guy who put it in there is probably one of the best if not the best Fender amp repairmen of all time, the late Larry Rodgers. He said that the transformer on the Blackface/Silverface Champ and Vibro Champ is basically that of a Princeton, and it can handle it.

    It does get warm, but the tone is just night and day better. I also threw out the original Oxford and put in an Eminence 8 inch. If your baffle isn't dadoed like mine, absolutely put a 10 inch speaker in. I'm thinking of getting an aftermarket cab to put it in that I can run a 10 inch in. Makes it a mini Princeton!
     
    Tone Chase likes this.
  10. muchxs

    muchxs Doctor of Teleocity

    Posts:
    13,171
    Joined:
    Aug 14, 2004
    Location:
    New England
    There is a difference between 1970 and earlier PTs and 1971 and later.

    1970 has 70ma on the high voltage, 2 amps on the rectifier filament. There isn't a specification available on the filament current. Let's do the math:

    2x 6V6 draw most of an amp. Three 12AX7s draw most of another amp. A 12AT7 draws another .3 amp.

    Hey, ho! That's way more tubes than you'll find in a Vibro Champ. That's because we counted the tubes in a Princeton Reverb that uses the same PT.

    Classic Tone specifies 70ma on the high voltage, 3a on the rectifier, 2.25a on the filament. That means they're cutting it as close as they can for a Princeton Reverb but you can run a 5U4G rectifier.

    Don't use a 5U4G rectifier in a pre- 1971 Champ.

    By the numbers it looks like you could make it take it. In actual practice the pre- '71 PT runs hot, like melt its guts out hot. Not all of 'em run hot, maybe because the hot ones got goobered back in the '70s. I've seen a lot of Champs, Vibro Champs and Princetons with zorched PTs.


    I'd say you're o.k. to run a 6L6 if you go ahead and upgrade the transformers including the output transformer. There isn't much upside and plenty of potential downside, otherwise.
     
    Last edited: Mar 1, 2020
  11. Tone Chase

    Tone Chase Tele-Meister

    Posts:
    399
    Joined:
    Aug 20, 2014
    Location:
    Windsor ON Canada
    I am just trying to learn. So much information on the internet, but never the full story, all in one place, with an absolute definitive answer.

    I have a 1968 Vibro Champ that is unmodified, and simply beautiful for about half my playing needs. I have several other amps that do things well, better, or different. I have no intention of altering this sweet amp.

    On the other hand, I have an modified 1974 Bronco that I picked up about 6 years ago, that had issues. I gave it to my amp tech to evaluate, and he gave me the details of what was done, resolved the issues, removed some mods, and went over the mods worth keeping, and made it simpler to use/understand them.

    I often pair both of these amps with either an ABY or a stereo effects pedal. There are many interesting options within the pairing of these two amps. They are plenty loud for at home use, and I feel that the pair could be exceptional for smaller gigging, but preferably jamming.

    At the moment, I don’t own any 6L6 based amps, and I do love the tone. It usually does not take long for the volume to get out of hand with a larger, multiple 6L6 tubed amp. I know they can be played at lower volumes, but they just entice me into continual sweeter and louder tone.

    I have considered buying a single 6L6 tube amp, but have read several times about someone using a 6L6 in a Champ type of amp. The information had always been that they use the tube, but never any information about sound, tone, highs, bottom end, wattage increase, mods necessary, which year amps might be better to try this with, etc.

    Thanks for the information so far.

    I sounds like my modded 1974 Bronco might be worth using as a test amp.

    Also the information about JJ 6V6S sounds interesting. I have a fairly large stash of new, unused JAN 6V6 tubes ranging from early ‘60’s to mid ‘70’s. So I never felt the need to try anything else.

    I am curious though, and didn’t want to damage an amp.

    I was also curious about using other rectifier tube options and what may come of that. Once again, I do not want to damage an amp.

    I welcome any worthwhile contributions of real world experience, and thanks in advance.
     
    muchxs likes this.
  12. marshman

    marshman Poster Extraordinaire

    Posts:
    5,094
    Joined:
    Feb 1, 2007
    Location:
    SE PA
    As I understand it, changing the power tube without changing the OT, your gains aren’t point to be significant. Tone might change, but power output won’t change much. But, I also seemed to understand that trying it out for an hour isn’t going to hurt anything.
     
  13. schmee

    schmee Doctor of Teleocity Silver Supporter

    Posts:
    10,879
    Joined:
    Jun 2, 2003
    Location:
    northwest
    I think you would be fine with a 6L6. Stock Champs are too anemic for me, unless you just want record with one for leads etc. . Although a little different beast, my 1x6L6 Champ 12 is a great sounding little amp and not near as ratty as a stock Champ. Big difference between 5 watts and 10 or 15. The Champ power transformer is the same as a 2 power tube Princeton right? Maybe put a plug in SS rectifier for even cleaner sound and less load on the transformer.
    One problem is you would want a 2 ohm speaker. If I was doing this I would buy a multi tap transfomer like sold by a couple places. They are I think 14 watt output transformers for single ended amps with two taps for matching to a speaker and roughly $20+. Available on Ebay and elsewhere.

    JJ 6V6 will get you just a hint of different tone, but it's not much at all. I use JJ's in all 3 of my 2 x 6V6 amps and really,.... meh, not a ton of difference. More noticeable at bedroom volume I suppose.
     
  14. muchxs

    muchxs Doctor of Teleocity

    Posts:
    13,171
    Joined:
    Aug 14, 2004
    Location:
    New England
    Your '68 has the early power transformer. Seems that's the more valuable of the two. Best leave that one alone.

    Your Bronco has the later and better PT if it still has its stock PT. Seems you could have some fun with that.

    I really like the old Allen TO11C output transformer for a single 6L6. If you go to Allen's site you'll see a TO11S, no TO11C. The old "C" was stood up to hit the mounting centers on a Champ or a Bronco chassis. I would sometimes drill an extra mounting hole and
    c o c k (stupid anti- cuss software. We're not even talkin' about little kitty cats. :rolleyes:) c o c k the transformer a couple degrees to clear the cap can.

    I usually modify old Champs and Broncos from one end to the other first by making them play loud and clean.
     
    BobbyZ likes this.
  15. Tone Chase

    Tone Chase Tele-Meister

    Posts:
    399
    Joined:
    Aug 20, 2014
    Location:
    Windsor ON Canada
    Well, I found the time to do some comparisons between my chosen 6V6, and a JJ 6L6. There were some moments and instances, but the old mid ‘60’s 6V6 just won hands down, especially when driven hard, or with the mods switched on, in the old ‘74 Bronco.

    I have several other 6L6 tubes to evaluate in the amp. There was no significant increase in volume with the first tube tried.
     
    Last edited: Mar 3, 2020
    Milspec and corliss1 like this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.