JJ el-84s; not holding their tone...?

Discussion in 'Amps and Cabs' started by JDW3, Apr 29, 2005.


  1. JDW3

    JDW3 Member

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    I ran some old RCA el-84s in my '99 Tophat CR for about 3 years. Sounded SO much better than stock. Well, I finally decided they were a bit worn and after the post "studies", I went with the JJ el-84.

    I gig pretty regularly and the first weekend they were punchy, smooth and robust. That was 3 weeks ago. Now I am looking around at my amp and wondering who turned my treble down!

    Possibly the tubes have "burned in", like a set of guitar strings? Sound more like worn out, to me. I'm kinda bummed that this has happened so soon. The amp sounded killer 2 weeks ago.

    Has anyone else noticed this? In JJ's in particular?
     
  2. Laroosco!

    Laroosco! Member

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  3. dzeitlin

    dzeitlin Member

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    I've recently found that going to Groove Tubes JJs (signified with an S), drastically reduces problems with JJs. Plus, with GT, you can choose your gain (1-10 with 1 being high gain). I have a quad of them in my Budda SD30 (#1s). I was looking for quiker breakup, and they delivered in spades. I also found that the higher the gain of there tubes, the rounder, and less trebly they are.
     
  4. Mastervolume

    Mastervolume Member

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    see my thread about EL84s I don't like the JJs at all.

    you can get better tubes for the same or cheaper.
     
  5. IPlayHamers

    IPlayHamers Member

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    If you purchase your JJ's from Bob at Eurotubes, you can also choose your gain. I have not found that my JJ's exibited any less treble after constant use.

    To the poster, If you are running your amp in Class A/B it WILL need biased with any tube change. Perhaps this is why you are experiencing the problems you do.
     
  6. wixedmords

    wixedmords Member

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    JJ's are some of the most reliable newly manufactured tubes.

    I have fantastic luck with them.

    Of course there can be duds, and you may not like their sound to begin with.
     
  7. JDW3

    JDW3 Member

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    Hey Laroosco; yep Michigan. Living up in in Grand Blanc for the past year. Used to be White Lake/Waterford area.

    I didn't bias the amp (Tophat) because I thought it was a sort of class A amp. I know there's arguements about the Tophats being class AB. Quite a few times in the past where I didn't bias el-84s. This is the first time I've experienced a loss in treble and volume. The amp isn't running hot.

    Just wondered if this is common amongst JJ el-84s.

    So what ARE the better el-84s?
     
  8. tedwoods

    tedwoods Member

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    Well,I do like JJ's but yes,I go through them pretty quickly.

    On one occassion I've experienced the same treble loss in my Mojave Coyote after two weeks of hard use although they had the same bias rating as my previous set.

    Usually though, they can last up to six months even in my Matchless which as you all know runs tubes relatively hot.

    What was the bias rating of the RCA's?That must have been optimum for the amp...but propably unmatched by "modern" standards.

    Ted
     
  9. JDW3

    JDW3 Member

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    I really don't know what the bias rating was; I just installed them! They were used at the time also. Very smooth, more grind and low end.

    The JJ's were much tighter when installed, than the RCAs, but now sound very generic and worn, like old strings basically. I used the RCAs hard for at least 3 years, I suppose thats why I am really surprised at this.

    So GT has "better" JJs at varying gain strengths? What are the other options, if any, besides NOS and EI?
     
  10. ericb

    ericb Silver Supporting Member

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    Just as a headsup , when I had a Tophat Club Royale in the 90's , I tried a variety of el84's and had a pair of Amperex labeled Mullards and they were just way better than the JJ's and EI's and Sovteks then .. I also had GE's that were nice, but the Amperex/Mullards were way more rich and juicy. Like an idiot I threw them in when I sold the amp, and the guy I sold it to sold the amp the next week.. I figgered he'd enjoy those! BUT just lost out myself on using them in another amp!!! Anyway, they're heavily recommended

    ERIC
     
  11. JDW3

    JDW3 Member

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    I just got in from the gig....man, those tubes really suck! I shouldn't have to crank the amp more every night! The cut and clarity is gone. Really disappointing...
     
  12. Blue Strat

    Blue Strat Member

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    They're probably running way to hot as in most EL84 amps.

    For some reason, most EL84 amp designers reun EL84s WAY past the maximum power dissipation (at idle) spec which leads to the early demise of EL84s. I wonder why they don't just increase the cathode resistor value.

    To find out if your EL84s are running too hot, read the section at the top of the EL84 section on my website.
     
  13. illinimax

    illinimax Gold Supporting Member

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    I've had the same experience with JJs. They do sound great when fresh, though. Try some EH El84s.
     
  14. dstengineer

    dstengineer Member

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    It's very true that even the better brand "new" tubes are quite inconsistent in quality. If you buy and use lots of tubes like we do you find this out very quickly. It's also true that A LOT of EL84 amp designs are not optimized for NEW tubes. The makers (I hesitate to say designers because so many seem to just copy old designs almost exactly), use cathode values that force modern tubes to run way to hard. This means a short life to the best of the batch and a very short life to anything that's on the low end of the quality curve. I've found that designing the output around the new tube's characteristics can go a long way towards better sound and longer life.
    Companies like Eurotube, Groovetubes etc. go to the trouble of trying to pick the best of the lot for you. And you get what you pay for. I've found that JJ's, EI's and even Sovteks can start out sounding fine but quickly loose their edge. The harsh reality is that for every 10 tube I buy only 4 usually last. The rest start to sound bad, make mechanical noises, or fail quickly. This accounts for the HIGH price of NOS tubes. I have a 40 year old set of Valvos that I take out for comparison testing with other tubes. They're amazing quality. SO are my old RCA's and even a pair of 1970 Toshiba 6BQ5 tubes. Your best bet with any new brand is to by spares and if the seeler has a 30, 60 nor 90 day gaurantee... use it.

    Bob Dettorre
    DST-Engineering
     
  15. LavaMan

    LavaMan Gold Supporting Member

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    I just got a a complete set of JJs from Bob at Eurotubes for my Mesa Mark IV. I am using the EL34 and 6L6 combintation. They are fresh now and sound great. It will be interesting to see if there is any change in sound quality in the next few weeks....I hope not, because right now my amp is sounding better than it ever has.
     

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