According to the 502P manual (or I would never have known) you're supposed to turn the bias screw all the way down when changing power tubes...I wondered what would happen if I didn't, but thanks to Jeninite24 I now know! I also bias the 120s to the 500mv spec and they tend to stay there...the LEDs are pretty accurate and you have 50mv in either direction as adjustment "headroom" anyway...when I check the bias drift from time to time (or really the neighborhood juice drift) its never moved more than .05 to .010 mv with any of the various output tubes I've used, and seems VERY stable with 120s. The LEDs seem to track the available voltage or something (without preamp signal) since they blink, stay on, all go off...whatever, all the time.
Tube upgrades for Jolida 502B?
I realize this is something that has come up before, though in searching the archives I didn't come away with a clear path forward. My amp is completely stock and came equipped with Sovtek 6550s. Using it to drive Totem Forest speakers. I contacted Jolida. They recommend KT88s. Their reply is a bit unclear but they might be suggesting Electro Harmonix. They also indicate reliability issues with Chinese KT88s. Response Audio (Jolida dealer and modder) recommends Shuguang KT88s (Chinese). The Tube Store recommended JJ Tesla KT88s on the strength of their great imaging and deep bass (more bass being something I was looking for). I was initially leaning towards SED Winged "C" 6550s. Now I am a bit more confused. I'm curious about KT88 vs 6550 sonics and reliability differences. Thanks in advance to any one willing to take the time to share their experience and preferences.
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- 47 posts total
- 47 posts total