I recommend against using Groove Tubes. They're all relabelled tubes from some other manufacturer, so you might as well go direct. I don't buy (literally) their 'magical' claims to a better matching system.
The Sovtek 5881 is probably better suited to Metal than your style (if I remember correctly), although in my experience, they were kinda muddy. A 6L6 will break up a bit earlier, and sound smoother when it does. They should give you a sound closer to the original Fender tone, since that's what the amp was built around. KT66 tubes would add some more headroom before breakup, and may give a tighter low end.
Eurotubes explains a bit about their JJ (formerly Tesla) offerings, that may help. That's good source for JJ tubes, and I've become quite fond of those. I use a quad of JJ KT88's in my Ampeg VT-22. And I'm doing some prototyping based around EL84 power tubes. These are small tubes, little bigger than the ones in the preamp.
BTW, I think you meant EL[u]3[/u]4 in your question. I've never used any, so I know what to expect from them.
I recommend installing JJ 6L6GC power tubes, and swapping out the first 12AX7 Normal channel preamp tube for a US-made 5751. You should find that your clean sound is smoother and warmer, while retaining the high-end sparkle. With a 12AX7 in the Bright channel, it will have all the gain you need, and the new 6L6GC's should respond nicely.
There's no need to adjust anything to accomodate different preamp tubes, but the bias
must be set for the power tubes. And since most Fender amps came out of the factory biased 'cold' to extend the tube life past the warranty period, ask your tech to set it at about 60-65% of spec plate dissipation. That won't seriously reduce the tube life, but it
will make a dramatic improvement in the tone.
Lordathestrings
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