08/19/2025
Something I've been meaning to post for a while: How to choose new tubes for your amp. I used to do in-home retubing, where the customer played their guitar, without touching any k***s on the guitar/amp/pedals, while I swapped in tubes. I learned a lot by testing hundreds of tubes for many different ears.
An important note: don't replace every tube in a guitar amp. If someone tells you all the tubes need to be replaced, odds are you took your amp to the wrong person. If you do replace tubes, be sure to keep all the old ones, or require the tech to give you your old tubes. I've learned of dishonest techs who put in brand new tubes and kept the perfectly good and very valuable vintage tubes for themselves when a customer brought me their vintage amp, wondering why it doesn't sound as good as it used to.
This article is about trying new tubes to improve tone. If your amp needs repairs, or new capacitors, those things should be done first, as they can drastically affect tone, and might change how you feel about the new tubes you're trying. Don't change working tubes before making necessary changes to the amp.
Here's my procedure for getting the best tone without taking two steps back on an amp after I've completed repairs/recapping.
1. If you haven't already, test all the tubes with a known good tester. If any tubes fail, those will have to be replaced. Don't replace good tubes just to replace them. Don't replace good rectifier tubes to improve the tone unless you've tried all the others first, as it's unlikely to make much noticeable difference. 2. Replace the output tubes first, with a matched set of tubes (unless it only has one). The output tubes are probably 6L6, 6V6, EL34, EL84, 7591, 5881 or 6550 tubes. Ideally, try more than one set until you find one you like. 3. If your amp has a bias that can be adjusted, rebias. 4. Figure out what the rest of the tubes do. There may be multiple preamp, reverb, tremolo, and phase inverter tubes in the row. The preamp tubes are the ones that may improve your tone. Try replacing the preamp tube(s) on just one channel next. These are often 12AX7 or similar tubes. Often you can just swap these around, as long as they're good working tubes. If your amp has a "phase inverter" tube, for example, that just needs to be a good tube, it has very little to do with your tone. If your amp has more than one channel, try using a different premp tube-- you probably don't want two channels to sound identical, anyway. If your amp has multiple preamp tubes on one channel, don't stick to identical tubes. If someone is selling a "Matched" or "Balanced" preamp tube, those are only for certain hifi amps. You're better off with variety in a guitar amp. 5. If you're still not satisfied, try some more tubes. I routinely have tried 8 sets of matched output tubes and then a dozen preamp tubes before finding perfection. As a last resort, you may want to think about a new speaker after you've exhausted all the tube options, but never replace the speaker first, unless it has something wrong with it.
Hope that helps!
