THERE ARE PERHAPS HUNDREDS OF QUALITIES THAT DISTINGUISH ONE BASS FROM ANOTHER. Yet there’s one characteristic
that divides instruments into two distinct camps:
whether or not they have passive or active electronics. The
ubiquity of active electronics over the years demands that we
all develop a keen sense of what they do, and why they do it.
Moreover, understanding active electronics could even give you
reasonable cause to avoid them, if their purpose isn’t aligned
with your sonic vision.
To understand what makes a bass “active,” it’s critical to
understand why we call some basses “passive.” In essence, the
nomenclature refers to whether or not a bass’s onboard electronics
include a source of power or not. The easiest way to
ID an active bass is to look for a battery. By including a power
source, an active bass has the ability to add gain (and more) to
the output of your pickups. Without this external power source,
the pickups are working passively. There is no additional power
available in the circuit, so any adjustment to the sound is only
ever subtractive. Most active basses provide a means of additive
An onboard preamp offers a degree of flexibility that a passive
system can’t possibly match, but don’t let that fool you
into believing it’s necessarily better to use one. It’s just a different
means of achieving sound. The first important contribution
of a preamp is related to the purpose revealed in its name.
As a preamp, the circuit onboard an active bass conditions the
signal to make it more appropriate for the much greater amplification
residing in your amp. It can boost and regulate the
overall gain of the bass, and also buffer the signal, an important
factor. Most preamps contain a buffer, and its purpose
is twofold: First, it lowers the output impedance of the bass.
Second, a well-designed buffer makes the signal less vulnerable
to interference from other components in the system. Without
going too far down Geek Lane, think of impedance specs
like a measure of the potential efficiency of a given circuit. The
ideal impedance relationship is one wherein a low-impedance
output feeds a high-impedance input. For our purposes, a buffered
bass signal is less vulnerable to impedance mismatching
(which can result in attenuated high-frequency response) and
the degradation associated with long cables.
The other advantage of an active bass is the one we most
commonly associate with onboard preamps: equalization.
EQ is just frequency-specific boosting and cutting. Through
clever design and with the help of integrated circuits designed
for this purpose, an onboard EQ allows you to add gain only
to certain ranges of the frequency spectrum. Typically, the
onboard EQ on a bass contains two or three bands, which
in total cover the breadth of the bass’s frequency response.
Whereas a passive bass can attenuate high frequencies with
its tone control, an active bass can, for example, boost the
bass, cut the mids, and boost the treble. This results in a tone
color that’s essentially unavailable through onboard manipulation
on a passive bass.
Some preamps, like models from Audere and Glockenklang,
add an additional feature: active blending. On a multi-pickup
bass, the output of each pickup is typically blended by means
of one blend potentiometer or two separate volume controls, as
on a J-style bass. This approach works well, but it does result in
interactions between the pickups as they’re blended that alter
their individual tones. An active-blended preamp avoids this,
resulting in a range of tones that more authentically reveal the
sound of each pickup’s true output, regardless of the position
of the blend control.
By this point, perhaps you’re wondering: Why aren’t all
basses active? The simple answer is that they sound different
from passive basses. We bass players are interested in sound,
and perhaps less concerned overall with the technology behind
that sound. If you know that passive basses have a different
flavor compared to active basses, then it’s easy to imagine that
they merely represent additional sounds—in the case of passive
basses, this typically means one that’s perhaps a little darker,
to summarize as simply as possible.
Whatever you think about the contrast, be encouraged that
the aftermarket is rife with options for those seeking to try out
an active system. Companies like Aguilar, Bartolini, Nordstrand,
Audere, John East, Demeter, Delano, EMG, Seymour Duncan,
and Michael Pope Designs all offer excellent onboard preamps for
you to give a whirl. And, finally, if modding your bass ain’t your
bag, understand that there’s an equally large selection of outboard
preamps (usually in form) for you to enjoy.