#1
Hi Guys,

I have a Blackstar Studio-20 and after say 10 minutes it will begin a low rumbling sound. If I tap the chassis it stops and if you tap it again it rumbles again. It only seems to occur on the clean channel as well.

Is this a sign that I need new tubes? the amp is 2 years old from new and had no changes.
If so, how would you determine which tubes need changing, the power amp or pre-amp?

Thanks for any help!!
#2
I would replace all the tubes
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate