For you techies out there...if I were to switch from 6550/KT88's to KT90's, besides the usual rebias, what changes/upgrades/tweeks/mods would have to be done to accommodate the new tube type?(this would be for the classic 60 watt bass heads, 200s, Sorado, later Sonaro, all with SS rectifier plug-ins). What advantage/enhancement do these tubes provide(I once read in a old issue of Guitar Player that they were comparable to EL34's, which, if so, isn't exactly the direction I'd want to go in relation to bass guitar tones). On the other hand, I've also read that the KT90 provides a bit more boost in power(I assume that the trannies can deal with it). I just acquired a '69 Sorado with 90's from an out of state guitar store, and when I fired it up, one of the tubes went bad, so, before I order new tubes and take it in to my amp guy for a going over, I want to consider my options. I can't be too sure that things were done properly when those tubes were installed in the first place. But, if 90's are an improvement, I might want to change over my other 60 watt heads. Thanks.
