Tube Rolling | Luxman CL-38uc

I changed all of the tubes.

If you are only using certain tubes and they are the only ones you hear, then it should work.

I don't know enough technical stuff to comment on your diagram, etc.

You can change out the 12AU7s with another brand, and you might even be able to substitute a 12BH7a, but the 12AX7 has a lot more gain than a 12AU7 so I don't think those are interchangeable in that application. 

Hey, did you try rolling those tubes? I have the same amp and have been tempted to try something similar. I actually had the same questions as you regarding just changing the ones you highlighted. let me know!

Hi!

Yes, those are the right tubes :) ... only 3 would be needed if you are not using phono input or tone controls.

The only caveat is that they are placed a bit differently inside on the actual unit, so a "best guess" would be needed unfortunately on picking which ones to replace. The phono input ones are clearly distinguishable, but the others not so much :(

Haven't taken the time to do that quite yet, but will try to report back when I do.

Hope that helps!

my 2 cents

i don’t have this particular luxman pre... so this is from general knowledge and a lifetime of tube rolling

12au7 and 12ax7 are usually NOT interchangeable... vastly different gain characteristics (that is why those three tube types were designed and made in the past, despite the common 12v heater dual triode small envelope designs -- 12au7 vs 12at7 vs 12ax7 - very different gain profiles from one to the other -- 1x 3x 5x gain, thus applicable for different circuits)...you can bet that putting in a 12ax7 with 5x the gain of a 12au7 in your nice luxman will create problems

you would need to contact luxman, or a knowledgeable dealer or tech to confirm specifically which three 12au7 slots are for main amplification, not tone control buffering circuitry (what is drawn on the circuit diagram is idealized, the actual circuit board may not be laid out in exactly the same fashion)... you CAN safely swap in different 12au7 tubes in those 5 positions, but without knowing for sure, you won’t be able to assess what you are hearing in the attempt to tube roll

here is a fairly complete discussion and listing of 12au7 equivalents (these are different names for the same tube, from different parts of the world, or very very similar variants made over time i.e. improved ruggedness etc etc - with identical or very similar gain profiles) - you would be well served to read it carefully and completely

http://www.audiotubes.com/12au7.htm