A guitar amp tube is basically an amplifier that employs valves or vacuum tubes to magnify the electric signals a musical instrument produces. For bass and electric guitars, pickups produce those signals – usually of the electromagnetic kind – and they go through the power tubes and preamp tubes of the amplifier prior to exiting the amp via a speaker.
So, do guitar amp tubes need to be broken in?
No, they need not. In other words, you need not play amp tubes at lower volumes for a period before you could really turn them up. There are certain tools or devices that need to have their break-in periods. The guitar amp tube is not one among them. Speakers, for instance, definitely require breaking-in. Tubes, particularly, output tubes, could require some burn-in for stabilization.
The break-in that your speakers go through is the reason why they sound noticeably different (generally better) after a period of use than you first played them fresh out of the box. To get your speakers to break in, you just need to play them extensively. If you play them for up to 10 hours total, you should be done with the break-in phase with them. Kindly note there is no break-in “process” as such. You just have to use the device normally or the way it was intended to be used.
Similar is the case with guitar amp tubes. There are some people who might believe that amp tubes have a break-in phase. And to help the tubes get through that period, all they do is play the tubes regularly. During the first few minutes of play, you would find the amp tube a bit on the stiffer side. However, things should be fine pretty soon, and you may start cranking it up in pretty much no time.
Initial Usage Recommendations
It should now be pretty clear that amp tubes do not have any “break-in” phase as such. However, like any new thing, you need to go slow when using them initially. This would be plainly to look for errors or faults that could be attributed to the tube’s manufacturing process.
When you power the amp using lower voltage, it becomes easier to look for faults (if any). If there are no issues, the voltage could be increased. If the amp tube still seems to function well, then you can safely assume that it has no major issues.
This goes for huge guitar amp stacks to small low wattage tube amps.
Manufacturers, at least the ones that mass-produce these tubes, usually burn in the amps inside a rack for some hours to identify problematic units. The faulty units are likely to break or not work during their initial few hours of usage if they were to be used by the end consumer. These initial few hours of testing is referred to as “infant mortality”. It’s not a technical term, but more of a slang phrase.
During this phase, the amp’s different components and processing errors are looked into – which include cold solders, assembling process errors, etc. If zero errors show up during this phase, then it’s highly likely that the amp would work as per expectations throughout its lifetime. By the end of the lifetime, however, the components would have aged or become too worn out, which is fine.
The takeaway is even the brand-new amp you purchase has gone through its fair share of use. But since it’s put to use inside the factory and for testing purposes, it’s not technically a “used” product. The manufacturer has done all the burning-in that needs to be done. You, the consumer, need not redo all of that at all.
Diagnosing Bad Amp Tubes
When a tube amp is cranked, pretty much nothing can surpass the authentic analog sound it makes. However, when it’s not working to its potential or as per design, the sound takes a beating. Unfortunately, most people would not be able to discern that drop in sound. Tube testers are usually able to. However, even they may not be able to paint a proper picture of the issue with those delicate tube guitar amps.
These amp tubes are essentially a group of fragile components disguised in a chassis made of vacuum-sealed glass. The performance and longevity of the tube amp hinge on different factors. These could range from the consistency with which the volume gets cranked, the level of maintenance, travel on the road, speaker vibrations, general wear and tear, etc.
When a tube amp has issues, it usually gives away the following signs:
- Unusual sounds – such as popping, crackling, humming, hissing, etc.
- The overall volume of the amps go down
- Individual tubes start glowing dimmer or brighter than others
- The amp just won’t power on
- A noticeable degradation in the amp’s tone
Some signs may be visible. In fact, before you look for any sonic issues, see if there are visible signs of a bad tube. Look out for the following.
Inspect the Glow
Inside your tubes resides a heater filament. When the amp tube works optimally, the filament illuminates with a warm orange glow. When glowing, these filaments release electrons at an increased temperature, producing necessary heat for the tube to maintain the optimal tone of the amplifiers. Based on the model or the manufacturer, the glow’s brightness levels would vary.
Notice the Illumination Color
A cloudy violet or purple glow around the innards of the different components clearly indicates that the tube has some kind of a leak. Replace the tube immediately once you learn about the leak. For optimal functioning, a sealed, airless vacuum is imperative. An air leak inside the tube produces positive ions that cause ionization in the components.
Check the Getter’s Condition
The getter’s condition is something most people overlook in their amp tubes. In case you didn’t know, a getter is basically a light grey or silver-colored metallic material that’s used in vacuum tubes or any other thing that’s sealed. They are placed close to the tubes’ top housing, although they could be coated at the bottom and their side in other types. Basically, their condition ascertains how healthy the tubes are and whether there are potential defects, such as a gradual air leak, which you should be wary of.