I just tried a set of JJ 6V6's in my HRDx and it sounds really cool. No bias adjustment just popped them in. I had a local tech mod the tone stack to blackface specs and adjust the overdrive channels and boy the thing sounds nice with the 6L6's just loud! With the 6V6's it gets a real tweed tone almost quasi-plexi like.
been running them for a while in my HRDx, so yes they are great. If you put a dummy plug into the extension jack the amps bias will be correct, the amp needs to be 4 ohms, for the 8 ohm speaker, the amp will go to 4 ohms when you put a plug into the extension jack, really to easy, I had to do the same kind of thing with my mesa mark iv when I installed the 6v6s in it a few years ago, run off the 4 ohm jack of the amp. The 6v6s in the mark iv are also incredible.
They are some of the best 6V6 tubes ever made in my opinion and 40+ years of experience. Some may say they are not a "traditional" sounding 6V6 variant, but neither are these 10,000 hour wonders: ...if it sounds good...it is good.
