Tone changes after 20 minutes

[Gsxrbusa]

The past couple times I have played my Herbert I have noticed it sounds a bit dull and does not hit as hard during the first 15-20 minutes of playing at band volumes. Also has a slight volume drop. After 20 mimutes or so it sounds normal again, hits hard and brings the normal brutality. It never had this issue before, which leads me to believe it is a tube issue.

Could this be a power tube problem? Or something else? Thanks for the help in advance.

 

[mightywarlock]

that sounds like tube issues.
i mean, it is pretty commonly known that your tone gets better when the tubes have been warmed up awhile...

but to have it shifting around is weird.

try new ones?

 

[Peter Diezel]

Tubes

 

[Gsxrbusa]

Thanks guys. I will replace.