Everything You
Wanted to
Know About
the resultant overdrive tones sound a
little different depending on which type
of distortion is generated where. Preamp
tube distortion, as much fun as it can be,
will sound a little more fizzy and gritty,
while output tube distortion will sound
comparatively thick, rich, and dynamic (in
broad terms). Old-school tone freaks tend
to enjoy the distortion tones generated
at the output stage, which is why you see
many such players going for vintage—or
vintage-styled—amps with simple circuits,
no master volume (or one that’s bypass-able), and a minimum of bells and whistles,
ever, and you can hit the sweet spot and
still (hopefully) dodge the tinnitus until
well into late-middle age.
Be aware that many types of amps also
need to be rebiased when output tubes
are changed. This is something you can
do yourself with the help of a kit (several
types are available), or have done for you
by a qualified tech for a nominal charge.
An amp’s bias is like a car’s idle speed: it
needs to be set correctly for the amp to
operate efficiently, and an incorrect bias
setting will also seriously impede your
tone. Confusingly enough, “fixed bias”
amps are the ones that generally have
adjustable bias levels that need to be
checked and reset when you change tubes.
Cathode-biased amps, on the other hand,
which are often billed as “Class A amps,”
have a bias level that is set at the factory
with a fixed resistor. With these, you just
pop in a good, matched pair of new tubes
and away you go.
It’s also worth knowing that any new set
of output tubes, whether NOS or new
manufacture, will need some playing-in
time. They won’t sound their best until
you have put a few hours on them, and
maybe as many as forty or eighty hours
of playing time to get them into the tone
zone. Not unlike a vintage bottle of wine,
output tubes need to “breathe” a little
before they will be at their peak. Similarly,
once you uncork that prized NOS pair that
has rested on the shelf for three decades
and start playing them, they won’t last
forever. Hopefully the tonal payoff will live
up to the anticipation. Test, taste, sample,
enjoy—there’s gold in them thar tubes!
C
M
Y
CM
MY
such as channel switching and added gain
stages. Such amps aim to drive the output
tubes more than the preamp tubes, and
to generate that creamy, harmonically
saturated overdrive tone when cranked
up. This love of output-tube distortion is
also what’s leading a lot of players, touring pros included, to use smaller amps
on stage. Few players really need a big
double-stack to be heard on stage these
days, and it’s harder to push such amps
into overdrive without incurring the wrath
of the soundman and blowing your band
mates off the stage. Use a smaller fifteen
to thirty watt combo or mini-stack, how-
CY
CMY
K
