#1
Currently my JVM is making a warbling sound as well as having a "farting" type sound when using the OD channels. The bass just seems to flub out. I plugged into the fx loop directly and it seems as if the preamp tubes are good to go. It might be the power tubes. Any suggestions would be welcomed. Also, if tubes need replaced, please recommend some tubes. 

Another question would be could I replace the power tubes, currently EL34, with E34L without needing to take to a tech to rebias.

Thanks for your help!
Gibson LP traditional and DC standard, PRS S2 Custom 24, MIA Standard Strat, Charvel So Cal Pro Mod, Schecter Banshee 7
EVH 5153, Mesa DR Tremoverb combo 2-2x12's
Line 6 M13
Last edited by bobafettacheese at Jun 26, 2017,
#2
No ideas or suggestions?
Gibson LP traditional and DC standard, PRS S2 Custom 24, MIA Standard Strat, Charvel So Cal Pro Mod, Schecter Banshee 7
EVH 5153, Mesa DR Tremoverb combo 2-2x12's
Line 6 M13
#3
It sounds like Power Tubes to me.   I have no idea about needing to rebias that amp though.   Eurotubes sells the E34L and some other options for it though - http://www.eurotubes.com/store/pc/configurePrd.asp?idProduct=659
Guitars:
Jackson Kelly KE3 - MIJ (Distortion/Jazz)
Jackson DKMGT Dinky (EMG 81/85)
ESP E-II Eclipse Custom (JB/'59)
ESP LTD EC-1001FR (EMG 81/60)
Fender MIM Strat

Amps:
Mesa/Boogie Dual Rectifier Roadster 212
Laney IronHeart IRT-Studio
Peavey Vypyr 30
Peavey ReValver Amp Sims
TOOOO many T.C. Electronic Pedals. . .
#4
I'm confused, you plugged into the FX loop return (I'm assuming) and determined the preamp tubes were good... how? That is used to determine if power tubes are good to go.

As usual, if it is indeed preamp tubes, roll a known good preamp tube through each slot and play until you find one that is giving the issue, and then just replace that one.

In reference to your biasing question, assuming your amp has an adjustable bias you will need to re-bias your amp when you get new tubes even if they are the same type.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.