Replacing 12ax7 tubes in Jolida 202

[Bill K Davis]

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?

[Mr Peabody]

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.

[blackraven]

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.

[dean_martin]

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.

[Happy Camper]

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.

[Bill K Davis]

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.

[Almeida100]

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.

[frenchmon]

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!