|
|
 |
Understanding Guitar Wiring
Understanding impedance and impedance matching
|
Updated 10/03
Any electrical
circuit has an inherent impedance, and electric guitars
or electrified instruments are no different. There are
exceptions to this rule, but most often the manufacturer
of these “different” components has designed
other components to change the system to standard high
impedance.
Magnetic (High impedance)
High impedance is the standard output for an electric
guitar. Most amplifiers and other electric gizmos that
players use are designed to work with high impedance
magnetic pickups.
Piezos (Ultra high impedance)
Transducers are ultra high impedance devices. Therefore,
to attain maximum sonic performance, a preamp/buffer
must be used. A buffer takes the ultra high impedance
signal and converts it to a standard high impedance
signal which most guitar amps, PAs and recording equipment
can handle.
Many players use a “stomp box” effects unit
between the guitar and the amp or PA, instead of an
onboard or external preamp/buffer. Since many floor
effects can accept an ultra high input impedance and
deliver a standard high impedance output, they can be
used as a buffer. Graphic or parametric equalizers are
a logical choice, as they offer frequency control and
buffering.
Magnetic (Low impedance)
The most common low impedance magnetic pickups are the
“active” pickups sold by EMG and other specialized
manufacturers. They differ from high impedance designs
in that they typically use fewer turns of a lower gauge
(thicker) magnet wire. These coils have a low DC resistance,
which translates into a very low output, but very wide
frequency response.
To compensate for the extremely low output and to buffer
the signal to high impedance, these manufacturers build
small preamps (often sealed inside the case of the pickup)
that are powered by an onboard 9-volt battery. This
is where the term “active” comes from. These
small preamps are very clean, and boost the output of
the pickup, often to very high levels. Typically, high
impedance pickups never break the 1-volt output range,
while some low impedance designs exceed 2 volts. Some
of these pickups are designed to be VERY hot, which
will drive the preamp section of a guitar amp very hard.
This is desirable for high-gain rock-n-roll.
A few makers (Alembic is the most notable) retain the
low impedance signal out of the guitar and send it to
specially designed amps, or often directly into PA boards.
PAs are designed to accept low impedance inputs, as
most good microphones—for improved frequency response—are
low impedance.
|
|
|
|
|
|
|
|
