I currently have a custom built amp which have 6V6 tubes. I think the sound is sooooo sweet that every time I plug in my Strat, my body starts to shiver :). However, recently, I bought an Ibanez JEM7V guitar. This guitar sounds better on my old amp which has EL34's. Now I am thinking about changing my tubes in my custom built to EL34, EL84 or 6L6 tubes. However, I don't know how much it will change my sound... How much will this take effect on my sound clean and driven? The only thing I notice right now with my 6V6 tubes, is that the gain doesn't crunch that much as my old amp with the EL34's. Is this only due to the tubes, or could there be an other explanation? Would it in the end be smart to change my tubes from 6V6 to either 6L6, EL34 or EL84 (or perhaps something else?)?

  • Either (1) try it, or (2) install an inline effects box. Sep 30, 2014 at 11:48
  • Presumably you're talking power amp tubes; what about the preamp?
    – jonrsharpe
    Sep 30, 2014 at 12:12
  • I was told that the preamp tubes don't make that much of a difference. It could be wrong, I don't know. Sep 30, 2014 at 12:13
  • It depends - preamp tubes will certainly dominate at lower volumes, and the power amp tubes are amplifying whatever comes out of the preamp tubes. See e.g. tdpri.com/forum/amp-central-station/…
    – jonrsharpe
    Sep 30, 2014 at 12:37
  • What's the amp? More info on your sound and the sound you are looking for would be helpful. "Better" is very subjective. Also, changing preamp tubes will make a difference- that's where the sound starts.
    – charlie
    Sep 30, 2014 at 16:16

2 Answers 2


Changing tubes requires a re-biasing. If you don't know what this means and don't have the proper equipment, then do not try anything like this. For your safety and your amp's safety. Simply being an octal power amp tube does not automatically make any two tubes 'switchable' and 'comparable'. Some amps have a built in bias switch to allow switching between el34s and 6l6s, most don't. The sound difference between the two mentioned is described, amongst other things, as being one of the defining differences between an old Fender Bassman and a first generation Marshal (not the sound you and I associate with a Marshal). Enjoy your two distinct amps! Use each for it's specialty. Get an a/b switch to choose between the two instead of trying to turn one into the other.

  • Thanks for your great advice! I didn't know that changing tubes is more than just "screwing in a light bulb". I will most likely start using both amps then. The only struggle is transportation though :P. Oct 8, 2014 at 14:24
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    Glad to help. You may want to consider playing with the preamp tubes if you are really in the mood to play around (as we all are). Most likely both amps have 12ax7 preamp tubes. But different make and company can sometimes sound different to certain ears. Or if you want to have less gain (distortion and volume) you can switch them for 12at7 12au7 or a compatible tube. This type of stuff has alot of info on the web. Too much actually: )
    – user6591
    Oct 8, 2014 at 14:56

My first move would be - on condition the valve bases are compatible - to take out the valves from one amp, and use them in the second. Of course, I'd make a recording of each, to have an A-B comparison. There is going to be a difference in the circuitry between the two, mostly in the pre-amp side, appertaining to eq. as much as anything, so a direct comparison (valve to valve) is almost impossible. Sadly, getting a set of replacement valves isn't cheap - but you'd end up with some spares.

  • Great idea in fact! Thanks for the hint! Is there a difference in buying 2 tubes separate or buying it in pairs? Somehow the pairs are more expensive at our local music store (it's huge) than buying the same twice separate... Oct 6, 2014 at 11:48
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    Tubes can be matched , so if you need more than one, get them as a matched set.
    – Tim
    Oct 6, 2014 at 12:11

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