JJ small signal tubes are the poorest SQ I’ve ever experienced. I have multiple Rogue items but not yours. In my M180’s each has a 12AX7 and 2- 12AU7’s, the 12AX7 is the phase tube and has a pretty strong influence on gain. I currently have 12AT7’s in that slot as they have a lower Mu ( gain ). There are about 4 different tubes that you can run in the slot. 12AY7 (45), 12AT7 (60) 5751 (70), 12AX7 (100) with the corresponding mu. Your 12AU7 has a gain of 100. Rogue often recommends Mullard NOS tubes but I’m not a fan of their sound. I’m not well versed with new production 12AU7’s , but for nos in Rogue I like RCA and Tekefunken which are unfortunately expensive. I recently had my amps serviced and upgraded by Rogue. They were retubed with new production Tung Sol 5751 gold pins for the 12AX7 slot and they sound VERY NICE ! I actually preferred them over nos Telefunken. I have nos GE 5 Star and Sylvania Gold label for that slot too. I would avoid any of the JJ’s even the higher grade ones. Not sure in your amp if you would effect overall power going to a 5751 , being lower gain it imparts less noise. But with new production input tubes averaging $40-50 each I’d change them all. BTW what power tube are you running ? Happy Listening, Mike B.
I changed a Tube and…
I liked it!
Have a Rogue Audio Cronos mag lll bought it years ago as original Cronos Mag sent it in last year for the upgrade to lll . Never changed any of the original tubes .
The amp was lightly used due to my changing amps like regularly. Decided to stick with Cronos and and have really enjoyed it .
Playing vinyl for the majority of time and seem satisfied with Triode mode . Amp runs perfectly no noise at all but thought about all the threads regarding tube rolling especially the center 12au7 .
pulled out the stock JJ and found a Genalex Gold Lion ECC82/B749 (12au7) bought them 7-8 years ago .
Put the GL into center position and was thinking “am I going to really hear a difference “??? Figured I listen to a few LPs and maybe I’d notice something different good or bad Maybe ? after all it’s just one tiny tube !
Well I was blown away !, 30 seconds in listening to “two of a mind “ Desmond /Muliligan things just got a whole lot more musical 🎶. Hard to describe everything seemed improved , midrange was wow ! Soundstage was better , etc .
Went to another familiar favorite Grant Green “ Idle Moments “ Oh yes the magic is here too
Is this even possible or am I under a placebo delusion lol
Now I’m really wondering what about the other 2 12au7’s and even the 2 -12ax7’s
what else am I missing ?