12AX7 tubes for Counterpoint NP400


I have a Counterpoint NP400 hybrid amp (200x2 into 8 ohms), which was recently given an "ultimate" ugrade by the amp's designer, Michael Elliot. I am kind of new to tubes, but am hoping to play around with some different tubes. Any suggestions for good (great) tubes to try out. Are there any concerns with various tubes I need to be aware of? Can I just drop them in, or do I need to rebias the amp? Any advice would be greatly appreciated. Thanks
alruhl

Showing 1 response by garydf27d

I don't know about the counterpoint but I use Special quality Mullard M8137 box anode valves (Tubes)in my Art Audio Tempo Mono blocks,Art Audio VP1 Pre Amp and Sound Audio (from Hong Kong) phono stage with great success. The M8137 is a SQ version of the Mullard ECC83 (12ax7) and was produced by Mullard to the highest military spec although it was available of the industrial market. I have a Mullard Tester and the M8137s have perfectly matched halfs remarkable!! I also have various 12ax7 Telefunkens and to my ears,and importantly in my set up, the M8137s do sound "better" I would also recommend the sister Mullard M8136 which is the Box Anode High Spec ECC 82's (12au7).Look out for the Brimar "Trustworthy" range that is often overlooked again Industrial / Military spec and very fine performers. Hope this helps.