Tube upgrades for Jolida 502B?

Hi Tbromgard

Another Jolida JD-502P owner chiming in here. I too have Tung Sol KT-120 power tubes installed on the 502P and am very happy with them. Out of curiosity I did try the a matched quad of solid black plate Penta KT-88SC tubes. I found the bass to be less tight with the KT-88SC tubes vs the KT-120s. Mids and Highs were slightly better with the KT-120s to me. I may keep the Penta KT-88s since they don't come up for sale often or if I want a change of pace.

Now for preamp tubes here is what I've found in my system. All these notes were done with the Tung Sol KT-120 power tubes in place.

With a mellow source I found Penta Labs 12AT7 tubes and Groove Tubes 12AX7 Gold tubes make for better detail in the music without any listener fatigue.

With a source that is very forward I found The Preferred Series 7025 tubes along with Tung Sol 12AT7 tubes made the music more warm and mellow in my system with just the right amount of detail.

I also found the re-issue Mullard 12AX7s along with the EH 12AT7s made for a very mellow less detailed presentation to the music in my system. A lot of songs I was playing were really laid back. Maybe it could have been revealing the true mellowness of my source but that is what I found.

Best of luck with the search.

You might want to confirm with Jolida but to me the only difference between the 502B and the 502P is that the 502B has volume, input controls and subwoofer output. Other than that the Amplifier section is the same.

I've bought a majority of my tubes used or already burned in from the seller so it has been plug in, play and enjoy. From reading in other forums about 100 hours will do for your tubes to break-in. Enjoy. You've got quite a batch of tubes there for your Jolida. I have the Mullard CV4024 in my Jolida amp as well. The only tubes I've been swapping are the 12AX7s.

Hi Tomtab

I bought my Jolida 502P from Underwood Wally some time after Garcia got his and Walter didn't comment when I inquired about using the Tung Sol KT-120 tubes in the Jolida. I guess he is playing it safe since Jolida sends the amp with 6550 Tung Sols or KT88s. I've been using the amp for months with the KT-120s and have had no issues.

Also biasing is the same. Just put in the KT-120s and turn the screw until the LEDs light-up. I would still get the meter though to make sure you are at 500 millivolts for the KT-120s. One time I had RCA 6550 tubes in the Jolida took them out and put in the KT-120s. Turned on the 502P and after the amp was fully warmed up I checked the bias with meter and the tubes were at 723 to 865 millivolts. The LEDs were all red but I would never have known without the meter I was so way over the recommended 500 millivolts of the KT-120s.