Fig. 1 - You can install the USAB Ultra Slim Acoustic Bass pickup almost anywhere under the
strings without routing.
Fig. 2 - As opposed to typical voltage-driven pickups, the passive Alumitones
use a current-driven design. Photos courtesy of Lace Musical Products.
Last month we looked at magnetic bass
pickups—their shapes and basic functionality
[“From Strings to Voltage,” August 2012].
This was an overview of historical pickups and
how they’ve evolved over time. Our next step
is to consider some guidelines that will help
you when shopping for a new pickup, if you’re
interested in experimenting with sound.
So where should you start?
You might ask yourself, what do I expect
from my pickup? Once you’ve stated your
goals, you can investigate how manufacturers
describe their products and then figure
out how your goals and these descriptions
fit together. Both tasks can be tricky: Tone
is hard to describe with words, and it’s
tough to sort through and differentiate the
huge amount of pickups on the market.
As a player, you probably prefer one of
the two main pickup categories—single-coil
or humbucker. You might even know if you
prefer active or passive pickups, and have
a sense of how they work with the musical
styles you’re into. But beyond that, the
adjectives rear their heads. As a result, most
bassists simply end up playing whatever
their hero or best friend uses.
For manufacturers, the standard
approach is to give customers a bloomy
tonal description and do some name-dropping
of both artists and musical categories.
The technical data usually comes at the end
of the catalog or is buried in a tab on the
website. Typically, the info is minimal—pickup size and DC-resistance.
DC-resistance? The common understanding
is that a low resistance creates more treble
and a lower output, while a higher resistance
produces more bass and a louder sound.
Unfortunately, this only applies if you use the
same magnets, wire, and construction. Change
one element and you’re—once again—lost.
It is absolutely beyond me why manufacturers
don’t even try to give their customers
a better impression of what to expect from
their products—and this emotional marketing
is typical for the whole industry. There’s
nothing wrong with the currently available
pickups, but the way they are marketed uses
a combination of hype and PR. The technical
info that really describes them is hidden.
“How does this pickup sound?” As a
musician interested in technical matters,
you should know this familiar question
is misleading. A pickup doesn’t sound!
It simply converts string movement into
an electric signal. For a manufacturer,
it’s relatively easy to measure electrical
response and put this into a graph. Known
as response curves, these graphs give us a
much better idea of how a certain frequency
might get translated into a signal. We see
the height and width of the resonance peak
(also known as “Q”) and can translate any
given frequency curve into a corresponding
signal—or at least its strength. It’s not the
whole picture, but it would be a beginning.
If manufacturers consistently provided
this data, customers would learn to read
and compare these curves and at least get
some useful info. Players are savvy enough
to understand that the full magic of a
good sound can’t be plotted into a 2D
diagram, while the manufacturers could up
their game by using real specs. Of course,
dealing with better-informed customers
creates a few risks: Customers might question
the current choice of pickup models
and ask for more variety.
The only way most of us choose a new
pickup is through visual appeal, a friend’s recommendation,
or personal experience. This
can be a disappointing and expensive course.
What if we learn that the electrical and tonal
differences of various pickups are not that
big? Might we then focus on other factors?
In my previous columns, we discussed
how load and capacitance have a huge influence
on pickup functionality. What about
the string-to-pickup distance, not to mention
where the pickups are placed on the body?
Let me introduce two special pickups:
One is the USAB Ultra Slim Acoustic Bass
pickup, and the other is the Alumitone,
both made by Lace Musical Products. The
USAB’s obvious feature is that it’s slim—just
around 8 mm (Fig. 1). It fits well between
the strings and body of almost any electric
bass without any routing. By playing around
with its position, you can tap into a huge
fountain of knowledge. Even if you later
decide to go with a more standard pickup
on a new instrument, this knowledge will
still serve you well because the tonal character
of a given position remains valid.
The Alumitone J and P models are
“current-driven” pickups. Most pickups are
“voltage-driven,” meaning they use a lot of
copper wire turns around the magnet to
induce a usable voltage. The passive, current-driven
Alumitones use 95 percent less copper
wire and they’re noiseless, even though
they use just one coil to pick up the string
movement. This low-voltage signal runs into
a transformer, which converts it to a higher
voltage. The principle is not new, but Lace
deserves credit for making this design available
to players again. You’ll recognize the
Alumitones’ obvious advantage when you
hold them, as they weigh about 70 percent
less than a standard voltage-driven pickup.
They also sound slightly different from
classic pickups, but I won’t try to describe the
sound with those bloomy adjectives. Whether
these two different designs produce the sound
you expect ... well, that’s another discussion.
As long as manufacturers leave customers
in the dark by offering choice without giving
facts, I’d recommend either staying with
what you have or getting prepared for some
serious experimentation. I’m sure there are
other specialized pickups out there, so feel
free to send me info on any that catch your
interest. Next time, we’ll explore non-magnetic
alternatives. See you then.
Heiko Hoepfinger is a German
physicist and long-time bassist, classical
guitarist, and motorcycle enthusiast. His
work on fuel cells for the European orbital
glider Hermes got him deeply into modern
materials and physical acoustics, and
led him to form BassLab (basslab.de)—a
manufacturer of monocoque guitars and basses. You can
reach him at
chefchen@basslab.de..