5 Tube Tips
So, you finally own that amp of your
dreams—a Vox AC30, Marshall JCM800 or
a 1953 Fender Champ (we all should be so
lucky!). Or maybe you already own a couple
of great amps. I’ve talked to some players
who own well over two dozen amps in all
shapes and sizes. For many of us, the most
common denominator among the best amps
out there is that they use tubes to deliver
their magic. Of course, not all amps are tube-based—some are solid-state. But for the
most part, tubes reign supreme.
Guitar amp tubes have become so commonplace for us, yet I’m often amazed by the many
myths and misconceptions surrounding this
relatively simple technology in terms of how
to care for and extend the lifespan of these
fragile components. With so much confusion
and misunderstanding of the basics, you can
end up with an amp that isn’t living up to its
full potential. You can also spend a lot of time
and money continuously replacing tubes, or
worse—you can damage your gear. So, let’s
address some of the fundamentals of tube and
amp maintenance, which, if understood and
applied correctly, can extend the longevity of
your tubes and ultimately ensure the best possible sound out of your amp for years to come.
You can think of the bias voltage as window
blinds; you can control how much light gets
through by adjusting the blinds.
HOT Russian tubes!
With the basics out of the way, let’s take a
look at some tube tips:
before turning on the standby switch. This
step alone can greatly increase the life of your
tubes. Standby is a state of equilibrium for
your amp. The speaker remains inactive, but
preamp and power-amp tubes are given a
warm-up before being subjected to heavy use.
Basic Tube Architecture
Since most of the points I will make directly
correlate to the technology itself, the following is quick synopsis of how a tube
works (without getting too technical):
A vacuum tube, which is somewhat like a light
bulb, operates on the principle of thermionic
emission. When voltage is applied, a metal
filament coated with electrons, known as the
cathode, is heated and emits some of those
electrons. The electrons hit the plate and
become a moving electric current in a wire.
This current can do useful things, such as push
a speaker cone to make sound.
The Importance of Tube Bias
As you can imagine, there are many electrons
moving through the tube, hitting the plate
and causing it to heat up. If there are enough
electrons heating it up, it will turn red-hot,
melt the tube’s glass and the tube will be
destroyed. To prevent this from happening
we apply a “bias” voltage to the grid, which
functions like a sieve and reduces the number of electrons passing through the grid.
1. Make sure your tubes are correctly biased.
Setting the bias on your amp is analogous to
setting the idle on your car. If it’s set too high,
the car wants to run ahead, but if it’s too low
then the car will choke when you apply the
gas. In guitar terms, set the bias too high (or
“hot”) and your tubes may run over their spec
and die prematurely. Set the bias too low (or
“cold”) and your tubes may sound cold and
sterile. When working with pairs or multiples
of tubes, you also want to make sure that they
are equally biased to the same level (or to
the manufacturer’s recommended optimum
bias level) to prevent one tube from working
harder than the others, thereby shortening its
lifespan. (See figure below.)
3. Operate your amp at room temperature. This is
a “common sense” tip, but make sure your amp
tubes and components have fully adjusted to
room temperature before turning the amp on.
4. Keep all liquids and beverages away from
your amp—liquids and electricity don’t mix.
Accidental spills can not only ruin your gear
but can also cause fatal injuries!
5. Replace your tubes when needed. Tubes
turn white when they loose their vacuum,
which is a good indicator that they need to
be replaced. Another is when your tube amp
starts sounding loose and weak. Although
these are subjective terms, when you’ve
grown accustomed to your amp’s tone, you’ll
notice when this happens.
A good tube amp is designed to last for years,
and if you properly follow some of these basic
principles for maintaining your amp’s tubes,
you’ll keep your tone and peace of mind intact.
2. Turn on the main power switch first and
let the amp warm up for at least one minute
Yuval Fuchs has been an audio engineer and guitar player for 26 years. He is currently a Senior Sales Engineer
at Sweetwater Sound, and spends his free time testing
new pro audio gear and tinkering with guitar parts. He
can be reached at email@example.com.