actually, it’s the other way around, PSAudio suggests 4 miiliamps for the 12au7’s that they ship the BHK pre with and 5 milliamperes when you change to the 6 volt tubes.
My question is, and I wasn’t clear about it when I first posted the question, has anyone tried a 12au7 and increased the bias to 5 milliamperes? I don’t want to just try it if it’s possibly going to hurt the preamp. A gentleman on the PS Audio forum tried a Tungram 7dj8 which is supposedly Bascom’s (the designer and the B in BHK) favorite tube and he set the bias first to 4 milliamperes and then tried the 5 milliamperes setting and stated, and I quote, “I was amazed at how such a small increase of just 1 milliamperes can make such a big improvement”. Now I’m curious but I don’t want to blow the damn thing up to fing out. Thanks.