Studio Tech Tip - Keeping Your Tube Amp In The Pink, Part I
By Dr. Spot and Bill Newman

They're primitive technology, but then so is a Stradivarius. Despite technological wizardry a half-century beyond tube technology, tone purists universally agree that the fat, warm presence and gravelly distortion of a genuine tube amp can't be beat. Unfortunately, tubes can be temperamental and are far less stable and long-lived than their solid-state counterparts. Like a fine automobile, a tube amp requires a little TLC to keep it in the groove.

Warm up and Handling
Most tube amps these days have switches that let you put the amp in standby mode before you nail the tubes with a lot of juice. Hit this switch a couple of minutes or so before you begin to play. This warms up the plates slowly so you don't have hot current hitting a cold tube. Barring a standby switch, go easy on your amp when it's just waking up, and the tubes will last longer.

Solid state technology can take a lot more bumping and jostling than a tube rig. Tubes can shake loose and can be damaged by shock. So you may want to handle your tube amp yourself rather than leaving it to the drummer's kid brother.

Tubes are odd critters, sometimes if handled correctly preamp tubes in particular can last 30 years. They can grow warmer and begin to break up easier over time. Or they can go bad in a year or two and screw everything up. Generally, if you're happy with the way your amp performs, don't go messing with the tubes. But if your amp is acting up, don't assume that the tubes are not the problem just because they are relatively new.

When To Change Power Tubes
You should think of changing the power tubes in your amp (the larger tubes) the way you think of changing the oil in your car. If you run them hard and long, you'll need to change them a lot. Generally, if you play an amp a great deal you will need to change your power tubes at least once a year, considerably less if you don't play the amp much.

If your power tubes are beginning to go, you'll probably find that the amp is not as loud. If the intensity of the tone seems to sag and evince less presence, it may be a sign a power tube is going. Soon you'll be turning your amp up to 7 to get the same volume you used to get at 5.

Funky electronic noises and pops can also be a sign of power tube failure. Or sometimes power tubes can become microphonic. They may begin to emit an unpleasant, extremely high-pitched constant squealing. Next week we'll discuss preamp tube problems that can have similar effects, but if you're hearing these symptoms, chances are you'll have to bite the bullet and buy yourself a new set of power tubes.

What Tubes To Buy
When you change tubes, stick with the specific type of tube recommended by the manufacturer (i.e., the type included in the amp when it's built). Switching out types of tubes (say an EL34 for a 6L6) is a great way to destroy your amp. Tubes available directly from the manufacturer will usually be best suited to your amp. If you begin to use tubes from other companies such as GrooveTubes and Ruby, it's best to take your amp to a pro and have it biased correctly for the particular tubes you've purchased.

GrooveTubes and Ruby have reliable, realistic grading systems that let you know precisely the type of tube you're buying. So as long as you buy that exact kind of tube each time, you don't need to worry about having your amp biased again. You will want your power tubes to be matched in terms of output, so it's best to buy them in pairs or groups.

To tell whether your tubes are biased correctly, look at the color that the tubes glow when they're fired up. The tubes should glow a soft orange/amber. If they're a sort of purplish blue, they're being underdriven. If they're a harsh white/yellow, they're being overdriven. This latter condition is bad. It could really screw up your amp.

Next week we'll discuss the preamp tubes and tube amp troubleshooting. Meanwhile, play hard and play GOOD!

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