Tube Amp Maintenance

Fender Groovetubes

Keeping a tube amp in optimum condition is relatively easy, keeping a few simple things in mind.

For those of you who travel with your amplifiers, maybe to a gig or practice, tubes can either vibrate loose while playing, or picking up and setting down the amp can jar a tube from its socket.

Many people automatically assume the tubes are bad when an amp looses performance.

Things To Look For

All amps get dirty and collect dust. Heavy dust build up will create many problems from circuit and signal failure to bad connections. The end result is poor amplifier performance. Use compressed air, the kind you would use on your computer to blow out any dust that may build up on a regular basis. Only do this knowing the amp is cooled down at least 30 minutes after playing, preferable before using.

Vintage amplifiers need proper grounding. Fluorescent lighting in most buildings can contribute to interference through the amp. Many of you have heard this annoying hiss, but it’s the nature of the beast. If you have only a 2 prong power cable, it is now time to upgrade to a 3 prong plug with the proper ground. To see if you have proper ground within your amp or checking the receptacle your amp is plugged into get a ground tester from your local hardware store. You simply plug this device into the receptacle and it will light up indicating either reverse polarity, improper ground, good ground and etc. This way you’ll know that your amp is getting good ground and eliminate this from your troubleshooting.  Other symptoms of improper grounding is when you touch the strings on your electric guitar while playing and you hear a clicking noise or feel a slight shock. First check the amp ground but secondly make sure your guitar has all of the control components grounded. Most guitars have a ground wire soldered between all of the pots and selector switch and input jack. This can easily be checked.

Stand By

Warming tubes before playing through the amp will ensure optimum output power, tone and help the life of the tubes.  In stand by mode, the speaker is disengaged. If the amp is turned on and tubes haven’t warmed properly, you don’t have full voltage yet and this is the number one thing that breaks down tubes. It is recommended to turn your amp on with stand by on for at least 2-3 minutes or more if possible. You notice when your at any concert and see all of the amps on stage, and that you see all of the red power indicators lit. These amps are on for as long as an hour before the band plays. These amps are warmed up and ready to be played at full bore. You’ll never see professionals walk on stage, turn a tube amp on and start playing loudly. Cooling down the amp is not as critical but good rule of thumb is turn stand by on so when you power up, your stand by is on and you don’t forget to allow tubes to warm.

Changing Tubes

Changing tubes can change the characteristics of the amp output. For example Fender groove tubes are available in a red, white or blue color, others us a number rating.  Basically this is telling you how soon do you want the amp to break up, or do you want it totally clean. If you use the same number rating or color tube, you will not need to re-bias the amp. Biasing is balancing amp voltage with the tubes your installing. Different brands will react differently, changing tone as well as overdrive. When changing all of your amps tubes, go with matched sets, quartets, duets, etc. Its the only way to go when achieving great tone. When your amp is biased correctly to achieve clean tone, it runs more efficiently and your tubes will last much longer. A potentiometer can be added to the circuit to manually turn up distortion. Not really recommended, will shorten the life of your tubes. The correct tube will also help with balanced harmonics and longer tube life. If unsure what to go with, look at the tube rating chart below and get your amp biased at your local independent music store and your set for the long haul.

Tube Performance Ratings

1-3 Low – Good attack with a wide range of overdrive, more distortion in the early stage of volume.

4-7 Med – Most common tube found in many production amplifiers. Great middle of the road range, performance and attack.

8-10 High – Very little break-up, mostly clean and best dynamic range.

Potentiometers

Scratchy pots should be cleaned as soon as you discover them, if so you may be able to clean them other than replacing. To do this uses compressed air and blow in and around the pot. If problem persists use a non-residue electrical contact cleaner and spray in and around thoroughly.

Now your on your way to a clean, high efficient, lean, mean, running machine