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.
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.