Tube Sound

How much do tubes affect how your amp will sound? What makes them change the sound?

Right now I have SOVTEK 588 in my Fender Hot Rod, but I bought it used and this is what the guy put in it. I would like to switch back to the Groove Tube 6L6, EL84, or KT66-HP.(All Groove Tubes)


But if there isn't much difference between tube sounds then I won't bother.

Warmth and natural overdrive as opposed to the simulated sound you get from digital amps.

They just sound better but it's hard to describe.

Duh, they sound better, I am not debating that. I want to know what makes one sound different from the other.

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.

Is each tube associated with a different channel?

So the first preamp tube is clean, next drive, 3rd more drive? And first power tube is clean, second is drive?

So, changing a preamp tube, won't affect the others?

The power tubes are a pair which form the two halves of a push-pull circuit. This is why matching gets so much attention. I don't have a schematic for your amp, but usually the preamp tubes closest to the input jacks are the first tubes to work on the signal from your guitar. The preamp tube nearest to the power tubes is probably the phase inverter, which splits the preamp signal and sends it to the two power tubes. Any tubes in between are for the tone stack, reverb drive, tremolo oscillator, etc.

Take a look here and here for some more info.

OK, so here's what I'm thinking...

Installing JJ 6L6 GC Power Tubes and fooling around with the preamp tubes.

I want some preamp tubes to match the new 6L6's, but which ones? Right now I have 3 12AX7's.

Would changing any of the preamp tubes change the sound? (like if I only changed one and let the other stay the same). Could I mix and match the preamp tubes? Different kinds, for example 3 different tubes.