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  1. #1
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    Question Replacing 12ax7 tubes in Jolida 202

    My Jan Phillips 12ax7 tubes went bad on my Jolida 202. First one made what sounded like volume pot noise whenever I changed volume. Then after another month the other channel almost completely died. I wanted to be sure it was the amp ,so I switched the tubes. Instant fizzout from the tube that was almost dead(bad idea I guess).Amazing that both tubes wet out so close together.These tubes were probably about 10 years old(bought used).I ordered 2 Tung sol relacements. I have heard somewhere that you should replace all the driver tubes at once(in this case 12at7),then I read that this is an old wives tale. What do the xperts say?

  2. #2
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    If it was me I'd replace them all, especially if they all were the same age going in, if two died, the rest should be soon to follow. In addition, if the amp was used fairly regular 10 years is a good run out of those.

  3. #3
    Forum Regular blackraven's Avatar
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    I agree with Mr. P. Do a lot of research on tube brands because there could be huge differences in sound-warmth, bass, treble, transparency, detail,-you get the picture. Also, new tubes will need 10-50 hours or more of break in time to sound their best.
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  4. #4
    Can a crooner get a gig? dean_martin's Avatar
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    I have the Jolida 202a. I replaced the original 12ax7s with RCA 7025s and the 12at7s with RCAs. The 7025s went bad first which I replaced with new Mullard 12ax7s. The 12at7s are still good but I replaced them with Mullard CV4024s from upscale audio to find the right synergy. I don't think you have to replace the 12at7s when you replace the 12ax7s, unless you're not sure of their age or remaining life. It's one of those uncertainties when you buy used or new old stock.

    Another consideration is finding the right synergy between your AXs and your ATs. I liked my RCA 12at7s with the RCA 7025s, but I wasn't satisfied when the 7025s died so I tried AT replacements too.

    What power tubes are you using? I'm on my second set of winged C EL34s but they're getting harder to find and I think there may be some fakes out there. I'd like to find a reliable new production power tube.

  5. #5
    music whore Happy Camper's Avatar
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    If you don't need all the gain of an AX, consider an alternative. I used a very nice sounding GE 5 star Command series 12AY7 in place of the various AX tubes I tried in my DAC and felt it a better detailed sound than the AXs.
    d HC b

  6. #6
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    The power tubes are winged El34. I replaced the El34's about 4 years ago when one went bad because it was too close to the transformer(design flaw?),I believe. I got Pearl tube coolers and this hasn't been a problem since. Low on dough at the moment,so I'll try the Tung Sols for a month and research. Very ignorant of using something other than 12at7's. Any advice appreciated. Thanks for all the replies,guys.

  7. #7
    Can a crooner get a gig? dean_martin's Avatar
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    You really can't go wrong with the new production Tung Sols or the new Mullards.

  8. #8
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    Popped the Tung Sols in,immediately about 35% more volume,and I believe the sound is also much better. I read somewhere that you shouldn't change the driver tubes until they go bad. I now disagree with that. My volume is about 1/4 and I always used to have it 40%. Could be the Tung Sols give more juice than the Jan Phillips. I'm going to change the 12at7's next month,after this experience.Thinking of buying from audiotubes. Looking back ,I can remember that the amp lost some volume after about 1 1/2 hours of use.
    Last edited by Bill K Davis; 02-07-2013 at 06:18 AM.

  9. #9
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    I have a JOLIDA JD202A from late 1990’s and have roll the Chinese valves with JAN PHILLIPS 12AT7 (inverters), SOVTEK 12AX7LPS (drivers) and four 1999 SED Svetlana’s (“S” logo).
    With this tube set, the amp sounded better, but dynamics and middle/treble extension was a bit shy, and dynamically, this set made the amp still a bit slow.
    Than I read somewhere a review on the ERSE MPX series capacitors, and decided to change the original block capacitors for these ones.
    The “new” amp was completely different, having a stunning dynamics, pin-point imagery, with mids/treble on the bright side. Sometimes, depending on the record being played, that dynamics and bright treble seemed to my tastes somewhat aggressive. Bass was not too extended, but utterly tight, tuneful, making it very easy to follow bass lines.
    That said, I went for a change on the driver stage, and tried a 5751 tube, this time from JJ TESLA, to calm down the things. First impressions are that bass is slightly less tight and tuneful, as well as imagery is slightly less focused (and these are, for sure, strong points of the SOVTEKs 12AX7LPS), and the above mentioned aggressiveness has gone (at least hearing the same records on same chain).
    One of these days I’ll try the SOVTEK 5751s, said to be constructed the same way as the LPS’s.

  10. #10
    frenchmon frenchmon's Avatar
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    I use 5751 tubes in my preamp and very satified with them. I use KOBE TEN NOS which are very hard to find...even in Japan where they use to be made. Before you buy the Sovteks try hunting down the KOBE TEN's. Very nice tubes. I also use KOBE TEN ECC91 in my power amp. Great as well. I will be trying some Valvo NOS as well.
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  11. #11
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    Quote Originally Posted by dean_martin View Post

    What power tubes are you using? I'm on my second set of winged C EL34s but they're getting harder to find and I think there may be some fakes out there. I'd like to find a reliable new production power tube.
    Yes, unfortunately, one of the world best tube/valve factory have also closed.
    Fortunately, it is quite simple to avoid confusion with de newly produced copies of Winged C original tubes made by JSC Svetlana, at St. Petersburg factory.
    The original Svetlana tubes had no crimp holes on the plate, and carried the production date printed on the glass, below the logo (Year-Week). The tubes produced before 2001 carry an “S” logo, and the ones produced from 2001 on, carry the Winged C logo. IMO, the 1999-2000 were the most reliable tubes.
    Last edited by Almeida100; 11-18-2013 at 04:36 PM.

  12. #12
    frenchmon frenchmon's Avatar
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    I replaced the KOBE TEN ECC91 tube in the amp with a Valvo ECC91. All I can say is wow! Its like I switched in a new amp. The sound was great before, but now things are on a different planet!

    The Valvo is more 3D and holographic. better vivid sound and texture. The Valvo adds more body to everything and seems to have slowed down the performance as if I can hear every note, letting me follow alone with whatever I decided. Every note is as if its in its own space and air. Its like every album on the TT or CD in the player has new life. I love these Valvo's. I am afraid to change anything in my system, the synergy is just that good. They are great NOS tubes...and of course they are German. IF you get a chance to get some NOS Valvo, you should jump at the chance. Very traqnsparent and dynamic. Bass notes are excellent!
    Music...let it into your soul and be moved....with Canton...Pure Music


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