No. With my Mesa Baron, Triode is preferred for acoustic and smaller scale music, but adding some pentode helps a great deal with rock, orchestral, some jazz, piano and even solo guitar sometimes. and it solidifies imaging a bit. I suspect it's as we've always heard: it's all in the implementation. Unless you listen only to chamber music, there are times when pure triode is subobtimal.
Triode versus Ultralinear/Pentode
Does triode always sound better than ultralinear/pentode in circuits and parts of similar quality? I'm not really interested in SETs, but triode wiring of EL34/6550 etc. I have a CAT JL2 wired which has 6550s connected in triode and is the best amp I have ever heard in my system. I also have a Music Reference RM9 MKII with EL34s connected in ultralinear and am considering having them rewired for triode operation as I assume that is one of the reasons the CAT sound so good (those transformers may also have something to do with it). Thanks.