JJ tubes killed my Fender DRRI

Discussion in 'Glowing Bottle Tube Amp Forum' started by digitalMagnetics, May 5, 2021.

  1. TwoBear

    TwoBear Tele-Afflicted

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    So I’m guessing you replaced all the tubes? If so maybe try to put the preamp tubes all back in hopefully in the same spots. Is this a tube rectified version? As far as saying you set the bias where you liked it before, are you taking into account that the new tubes could be different (it obviously seems they are although it might be the pre’s) or are you setting them to about 70% of max dissipation? I mean if you’re just setting them to the same negative milliamps as the last tubes, that’s probably not going to be right for this amp, although we should rule out the preamp tubes first because just one shaky preamp tube can ruin the whole mix. Do you still have the old tubes right? and you did like it? Just figured it was time or whatever? That’s cool but we shouldn’t write them off quite yet.
     
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  2. TwoBear

    TwoBear Tele-Afflicted

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    That’s the part that needs “some Splaynin’’ Was it at some arbitrary number like -32 and you set it to -32 again? That wouldn’t be correct unless the two power tubes were almost exactly like the last ones. So like I said my other post I will start by putting all the preamp tubes back in the same spot they were if you could so you can weed out if they are the problem. Was there a 12at7 in the PI and did that get replaced with the same value?
     
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  3. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    https://robrobinette.com/Tube_Bias_Calculator.htm

    I find the JJ 6V6S sounds at its best when run at the hot end. When I switched to them in my Cub 10, I had to wind the bias pot all the way round to get them to ~70% whereas Ruby/Shuguang required it around halfway and the old 6p6s were somewhere close to the 'cooler' region of the pot.
    As they've gained hours of use, they've started pulling more current, why?, I don't know. They sound superb as a result. They're now sitting around ~75% at idle.
    Run cold, they weren't nice. They sounded 'cold'. Harsh, brittle and sterile. Warm 'em up.
     
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  4. guitar_paul1

    guitar_paul1 Tele-Meister

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    Bias by ear while watching the numbers to make sure they're staying in a safe range.
     
  5. kbold

    kbold Friend of Leo's

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    We talking power tubes or pre-amp tubes, or inverter (or all)?
    My response would vary wrt which tubes.
     
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  6. lathoto

    lathoto Tele-Meister

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    Run them hot! Maybe they just told you how bad a stock Fender speaker can be? I swear by them.
     
  7. rze99

    rze99 Poster Extraordinaire

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    Mine sounded best with Tung Sols but they didn’t last. I have JJ and the bias as warm as possible. Sound good but I prefer the sound of the Tung Sols.
     
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  8. jimgchord

    jimgchord Tele-Afflicted

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    Jjs are 14w tubes. You need to rebias your amp
     
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  9. omahaaudio

    omahaaudio Friend of Leo's

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    Never mind then.
     
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  10. Commodore 64

    Commodore 64 Friend of Leo's

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    I've done a LOT of tube rolling. What you say doesn't comport with my experience. The main reason I don't like JJ's is red lettering on the glass.

    Possibilities:

    1. Something amiss with tubes, but one would be operating at much different points. You see it somehow on your bias readings.
    2. Your bias needs to be set by ear, as mentioned. IMHO, of course. Make it sound good. Verify tube isn't terribly out of spec or redplating.
    3. Your tubes sound bad.
    4. Your ears are more tuned/sensitive than mine.
     
  11. Fret Wilkes

    Fret Wilkes Friend of Leo's

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    This was exactly my impression of the JJ preamp tubes when I first tried them in a HRDlxe. I went right back to the original preamps tubes. I did like the JJ 6L6 and have stuck with them in HRDlxe and 68 Twin Reverb since.
     
  12. Paul G.

    Paul G. Friend of Leo's

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    Biasing to numbers is a guide, but the JJ 6V6s are quite rugged, kinda almost a 5881. You need to get the amp biased properly taking into account the fact that they are 14W tubes (not 12W like most 6V6s). A bias probe is handy-dandy when replacing tubes with the same type, but here you need to actually get to ~60%-65% MPD, so plate voltage needs to be taken into account and bias actually calculated.

    Those DRRIs are already biased pretty cold. I'll bet with the JJs you're way below 50% so you'll sound grainy, and harsh. Distortion (if you can get there) will be thin and spiky.

    If you don't know how to calculate, get a tech. The JJs may sound a bit different (they're fine), but they won't sound "bad" properly biased.
     
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  13. Jared Purdy

    Jared Purdy Friend of Leo's

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    I had a conversation with Michael Swart about this a few years ago. When I bought my first Swart amp, they had just made the decision to switch to JJ's because the Tung Sol 6V6 would red plate, apparently. He did however say that he preferred the sound of the amp with the Tung Sol tubes.

    Because I'm not a gigging musician, and I don't tend to play for hours at a time, I took the JJ's out and put Tung Sols in. I then experimented with a set of NOS tubes, the brand of which escapes me now, and I settled on those.

    There seems to be a lot of mixed reviews about them. The Tube Store, in Hamilton, Ontario, Canada (they have a web site with a lot of US customers), carries them, but from what I have been told, they are far from preferred. The word I hear the most is "durable". And as you found out, but at what cost? I don't have any JJ's in the two amps that I have. I left the stock Fender (Groove Tubes) in. To my ears, both amps sound great. I have a lot of JJ's in a cupboard, and that is likely where they'll stay.
     
    Last edited: May 6, 2021
  14. SoK66

    SoK66 Tele-Afflicted

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    JMHO, bit in a typcal Fender BF/SF amp JJ 12AX7s sound like somone threw a blanket over the amp. In more mid range heavy amps like tweeds & Marshalls they seem the fare better. I recently acquired a new '68 Custom Deluxe Reverb that came with GT branded JJs in V1, V2 & V4, power tubes and rectifier. I relaced the preamp 12AX7 JJs with Tung-Sol RIs, the Chinese PI 12AT7 with an EH and the power tubes with a NOS set of RCA 6V6GTs. Changed the entire tonal character of the amp for the better.
     
  15. Chiogtr4x

    Chiogtr4x Doctor of Teleocity

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    I was in a Classic Country band (so, Tele> DR) as well as my own R&R/blues band ( guitar >OD/distortion pedals>DR) so the Deluxe Reverb big and clean ( not tinlky and too bright, but full!) was perfect.

    The DR is now gone, my old BJ ( blonde w/120 watt Emi Neo speaker and 9 lbs. less than the DR) has taken its place, as they both sounded similar, believe it or not

    * edit, no more Country band, though we dip into some of the music in my band
     
  16. digitalMagnetics

    digitalMagnetics TDPRI Member

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    Totally fair. I bought them as a set from Tube Depot. I really just had a bad power amp tube but figured I'd replace the whole lot to see if it upgraded the sound of the amp a bit. Later today, I'm going to put the old preamp tubes back in and start there. I'll readjust the bias if it still sounds off.

    I recently had the DRRI serviced, mainly to get reverb on the normal channel as well. At the same time, I had my guy do a total checkup on the amp and replace some of the cheaper caps with higher quality ones. The amp sounded good when I got it back! I only re-tubed when one of the 6V6s fizzed out the other day.

    Will put those old preamp tubes back in later and report back...
     
  17. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    @digitalMagnetics I don't remember if you said whether or not both channels affected. If they are both affected, try swapping V6 & V4 one at a time. Assuming you got a matched set, what are the numbers on the power tubes?
     
  18. getbent

    getbent Telefied Silver Supporter

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    I think JJ's generally are solid and reliable, but I stopped buying them, just too dark. In my tone king, when put them in, they sounded good, but just dark... I called Mark and asked if that was normal and he said that he built the amp to use EH's (which typically get negative reviews) and that I'd probably be happier with EH's, I switched, sold the JJ's and then on future changes for other amps, did likewise and was surprised at the result (positive.)

    Lots of guys swear by JJ's and I think they are rough and tough, but they wouldn't be my first choice.
     
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  19. northernguitar

    northernguitar Friend of Leo's

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    As I age, I like my amp tone to be brighter. I agree that the JJ preamp tubes add a 'warmth' or 'wooly' characteristic. My favourite is a NOS Philips tube. I just got a pair of British Mullards and need to give those a try.
     
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  20. schmee

    schmee Doctor of Teleocity Ad Free Member

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    You mean power tubes or pre tubes?
    Did you bias it?
    I love JJ 6V6's. never had a bad one.
    I hate JJ Pre tubes.
     
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