Decided to swap the output valves out in my amp today. It's been used extensively for the last two-three years, mostly at gigs, and I had a spare set of JJs laying around, so thought I would pop them in just to freshen it up now that gigs are starting to happen again. The noise floor was also creeping up a bit, so I did some minor swaps in the preamp too. Good stuff.
So, the question:
I have not biased the amp after swapping the valves.
I was going to see what happened and then potentially buy a Bias Master or something so I could be sure that the mA was correct.
However, the amp is dead quiet, sounds great, I've had it up past gig volume, have looked intently at the plates etc whilst it was cranked, it's been on for about three hours and and everything looks and sounds fine. The filaments don't dim or anything like that under load. It's difficult to know whether they have that blueish glow, as it's daylight.
If I accept that the bias may be slightly hot and the valve's lifespan will be shortened a bit, or it may be slightly cold, but it sounds as good as ever, is there anything in particular to worry about? It doesn't seem like the chassis or anything is getting too warm, the valves seem to be glowing normally, and touching the valves yields them hot - but not beyond what I would expect through touching various hot output valves in the past. The amp doesn't really seem to sound or feel different after the swap. Perhaps a little more strident and punchy, but that's difficult to determine for certain.
In this scenario, is there anything to really worry about? I'll keep an eye on them at this weekend's gigs, to make sure they aren't red plating or anything daft, but everything seems to be pretty normal, and the amp seems to be running and sounding as I would expect.
(EDIT) - If anything the chassis seems a little cooler than usual, but it's currently sat outside the combo shell, so the heat from the valves is dissipating upwards rather than being directed into the top of the amp and therefore the control panel etc.