According to Kevin at Upscale and the PL ads you can use most any tube in combo and the auto bias circuit will make the necessary bias adjustments. BUT he doesn't say it will sound good! Just that it can work.
I don't have a PL 2. Just a PL1`, PL3 and PL5. Each of the amps sounded best with the tube type that they were originally designed to use. I ran the PL1 and the PL5 with all of the standard power tubes mentioned in the ads, in both amps. Ultimately the EL34 sounded best in the PL1, and the KT88 in the PL5. Although the 6l6 in the PL1 and the 6550 in the PL5 were quite good. More linear, not as warm.
BTW, I have run a lot of SED 6550's, KT88's, EL34's, as well as 6L6GC's and I've never had a premature failure problem. Rich's problem may have some relation to the pre-set bias points in his amp (which btw can be altered and should be if for example you decide to try 6l6's or EL34 in the PL2 - at least that was my experience).
I don't have a PL 2. Just a PL1`, PL3 and PL5. Each of the amps sounded best with the tube type that they were originally designed to use. I ran the PL1 and the PL5 with all of the standard power tubes mentioned in the ads, in both amps. Ultimately the EL34 sounded best in the PL1, and the KT88 in the PL5. Although the 6l6 in the PL1 and the 6550 in the PL5 were quite good. More linear, not as warm.
BTW, I have run a lot of SED 6550's, KT88's, EL34's, as well as 6L6GC's and I've never had a premature failure problem. Rich's problem may have some relation to the pre-set bias points in his amp (which btw can be altered and should be if for example you decide to try 6l6's or EL34 in the PL2 - at least that was my experience).