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Over the holidays I acquired my first tube amplifier, a VOX VT20X. I'm not really sure whats required to keep a tube amp sounding its best for as long as possible or if they even require special treatment. what do you suggest I do for keeping it in optimal condition? Are there any circumstances or situations I should be wary of?

  • In the immortal words, "RTFM" - and then do what it says! From a quick look at the VT20X manual, it seems a fairly "user friendly" design. High power tube amps designed 50 or 60 years ago were much less "idiot proof" than modern ones. – user19146 Dec 31 '16 at 22:04
  • i did read the manual. it seemed 'too' straight forward which is why i got concerned. – Matthew Mccall Jan 1 '17 at 5:27
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There's no special treatment, just avoid mechanical shock (tubes have parts that can move under shock, and they're obviously in a glass envelope), and moisture (including beer ...), the latter of course being true for any electronic equipment. And, as a rule of thumb, never leave your tube amp anywhere where you wouldn't want to sleep, e.g., in a trunk of a car parked in the cold etc. Tubes are also especially vulnerable when they're hot, so don't move your amp too much before it has had a chance to cool down.

But in general, tube amps are more resilient than many people think. Don't worry too much, just use common sense and the above tips.

There's no need to change the tubes as long as you don't notice any strange noises, and as long as you're happy with how it sounds. You would normally change the power amp tubes much more often than the preamp tubes, because they get to do all the work. Don't forget to have your amp re-biased after changing the power amp tubes. But it may take years before you might need to change them for the first time. On average, the more often you use the amp, and the louder you play, the sooner you'll need to replace the power amp tubes.

EDIT: re-reading the question I noticed that the amp model you got is a Vox VT20X, which is actually not a conventional tube amp, but a modeling amp with only one single 12AX7 preamp tube, and no power amp tubes. Everything mentioned above remains valid, but you won't need to worry about biasing and everything else related to power amp tubes. Furthermore, chances are that throughout the whole lifetime of the amp you won't need to worry about replacing that one preamp tube.

  • Agreed that tubes amps are resilient and as such my experience is that leaving one in a car in overnight freezing temps is fine as long as you let it come up to room temp before turning it on again. Also tubes definitely degrade over time (in six months or less with daily play) so replacement is definitely an ongoing and regular consideration. Also power amp tubes last longer not shorter than preamp tubes. If the amp has a bias control it should normally only be adjusted by a tech since you have to make dangerous voltages exposed to access it. – Todd Wilcox Jan 1 '17 at 7:11
  • @ToddWilcox: Of course you can leave your amp in the car overnight, but it's better if you can avoid it. Replacing tubes is an important consideration, otherwise I wouldn't have mentioned it in my answer, but for most amateurs who don't use the amp many hours each week, it can take several years before tube replacement becomes necessary. I know that from a good friend of mine who earns his living with tube amp maintenance. – Matt L. Jan 1 '17 at 7:57
  • @ToddWilcox: Finally, you're wrong about the longevity of tubes: it is definitely the power amp tubes that must be replaced much more often than the preamp tubes. Ask any amp tech, or read this "Preamp tubes are more compact and don’t have to work as hard, so they tend to last even longer, or seemingly forever ...". This fact is also mentioned in this answer on this SE site. – Matt L. Jan 1 '17 at 7:58
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    One thing no-one has yet noted is that the capacitors will also need changing after a while. The BBC used to do it every few years, on a schedule set when the equipment was purchased. [Can't remember now whether it was every 2 or 5 years] An old Fender Vibralux we had that no amount of valve changing would fix came back to its former glory after we swapped all the old 'chewed toffees' for modern electrolytics. – Tetsujin Jan 1 '17 at 10:32
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    Tube don't have "moving parts" in the conventional sense -- yes the electrodes can move around under mechanical shock, but they don't have moving (mechanical) parts during normal operation. Also it might be a good idea to move comment about thermal shock (running the amp from a very cold state) into the body of the answer. – Dave Jan 1 '17 at 19:42

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