Fishman PREFIX PLUS User manual

USER’S GUIDE

This fine instrument is equipped with a FISHMAN PREFIX PLUS™
ACOUSTIC GUITAR SYSTEM. Please read these instructions care-
fully. If you have any questions or problems, please call our CUS-
TOMER SERVICE LINE at [phone].
The PREFIX PLUS™ is an instrument-mounted pickup / preamp sys-
tem that offers total control of your amplified guitar sound.
THE PICKUP
The PREFIX PLUS™ ACOUSTIC GUITAR SYSTEM includes the FISH-
MAN ACOUSTIC MATRIX pickup; made with a unique co- polymer
sensing material available exclusively from Fishman. This technology
is not available from any other manufacturer. The sensing material
exhibits a sensitivity and dynamic range that far surpasses all other
known sensing materials. The ACOUSTIC MATRIX transducer is a fully
EMI shielded, multi-layer sandwich of co-polymer strips that run the
length of the pickup. This design allows the pickup to sense the motion
of the entire saddle length, providing superb string to string balance,
as well as sensitivity to both the strings and top of the instrument.
THE PREAMP
The PREFIX PLUS™ preamp module incorporates a unique "flip-top"
battery compartment for easy access. A variable NOTCH filter, shelv-
ing BASS & TREBLE , semi-parametric CONTOUR, and BRILLIANCE
controls are included for precise tone shaping and fighting feedback.
There is also a PHASE reversal switch and a low battery indicator.
The PREFIX PLUS™ can be plugged into any instrument-level audio
input with excellent results.
FISHMAN PREFIX™ PLUS
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ONBOARD ACOUSTIC GUITAR SYSTEM
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PREAMP FUNCTIONS
BATTERY COMPARTMENT
Pull the small tab at the top of the PREFIX PLUS™ toward you. The body of the preamp
will swing out, revealing the BATTERY COMPARTMENT. Insert a fresh 9V alkaline battery.
ENDPIN JACK
The PREFIX PLUS™ has no ON/OFF switch. It is turned on only when an instrument
cable is plugged into the endpin jack. To conserve the battery, remove the instrument
cable from the endpin jack when the unit is not being used.
NOTE: Plug an instrument cable into the endpin jack before you plug into the sound
equipment. Doing so will prevent loudspeaker damage.
BATTERY LOW INDICATOR
When plugging into the endpin jack, the LOW BATTERY light will flash momentarily, indi-
cating that the power is on. When the LOW BATTERY light stays on, it is time to change
the battery.
CONTROLS
NOTCH FILTER
This is a fixed level, variable-frequency filter for eliminating feedback or unwanted reso-
nance. The affected frequency is variable from 40 to 500 Hz. The NOTCH FILTER is
effectively off in the full counter-clockwise position.

FISHMAN PREFIX™ PLUS
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VOLUME CONTROL
Controls the overall gain of the PREFIX PLUS™. Goes from very quiet to very loud.
BASS CONTROL
This is a boost/cut shelving tone control. The center detent yields a flat response.
CONTOUR
This is a Wide-range semi-parametric filter. It is used to selectively shape the instru-
ment's tone.
The CONTOUR Level slider controls the amount of boost or cut applied to the selected
Contour FREQUENCY. The center detent yields a flat response.
The Contour FREQUENCY slider determines the frequency band that is boosted or cut
by the CONTOUR LEVEL control. The frequency is variable from 250 to 10 kHz.
TREBLE CONTROL
This is a boost/cut shelving tone control. The center detent yields a flat response.
BRILLIANCE CONTROL
This is a resonant style boost/cut filter. When boosted, the BRILLIANCE control can add
presence to your sound or brighten up dead strings.
PHASE SWITCH
The PHASE switch compensates for acoustic phase differences that often occur between
instrument and speaker. It can be used as a tone filter at low volume levels or a feedback
filter at high levels. The PHASE switch can correct any electrical phase difference
between the PREFIX™ system and an outboard instrument microphone. Flip the PHASE
switch several times and use your ear to find the optimum setting. The best position for
the PHASE switch may change, depending on the sound system and/or venue acoustics.

ONBOARD ACOUSTIC GUITAR SYSTEM
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SUGGESTED EQ SETTINGS
MID CUT
You can scoop out harsh midrange by setting the FREQUENCY slider slightly
above center with the CONTOUR Level cut to taste below the center detent.
You can also
cut midrange by
boosting the
BASS and TRE-
BLE sliders to
realize an
"implied" mid-
cut at 800 Hz.

FINGERSTYLE
This setting will add fullness to the bass and definition to the treble.
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ONBOARD ACOUSTIC GUITAR SYSTEM
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CUT THROUGH
For cutting through a live band mix at high volumes.

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WHAT IS PHASE?
Phase is the relationship between two signals or soundwaves originating from
the same instrument.
For our purposes, phase relationships are expressed as being either "in phase"
or "out of phase".
In phase tends to enhance, while out of phase tends to sup-
press the natural characteristics and acoustic tendencies of an instrument. A
simple way to determine the quality of phase (in or out) of two sounds is to com-
pare phase switch settings at low volumes.
IN PHASE
In phase is when the wave-
forms of two sounds originat-
ing from the same instrument
are similarly aligned in time.
Similar phase is like looking at
yourself in a mirror: your
reflection directly follows your
movement.
OUT OF PHASE
Out of phase is when the
waveforms of two sounds orig-
inating from the same instru-
ment are aligned such that the
upper peak of one wave
occurs at the same moment in
time as the lower peak of the
other. Out of phase is like
looking at yourself in a live
video monitor; the image you
see is similar, but the per-
spective is shifted. When you move to the right, the image appears to move to
your left. Continued ...

ONBOARD ACOUSTIC GUITAR SYSTEM
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PHASE, Continued from Page 8
WHAT IS THE PHASE SWITCH FOR?
The phase switch is useful for two reasons:
1. Due to the interactive and changing nature of phase, acoustic amplification
depends on maintaining optimum phase relationships between amplified
instruments, sound systems and venues.
2. Since an industry standard for polarity has not been established for all sound
equipment, the phase switch can compensate for any unintentional differences
that might occur between instrument and sound system.
APPLICATIONS
In any situation where the instrument faces a loudspeaker, there will be an inter-
active phase relationship between the two. This usually occurs with stage amps,
side fill and floor monitors at close distances.
• LOW VOLUME AMPLIFICATION
At low volumes, when an instrument and speaker are at similar levels and are
in
phase, the sound is full and solid, with the lower frequencies emphasized.
When a mic'ed instrument and speaker are
out of phase at low levels, the bass
frequencies cancel out to some extent. The resulting sound is somewhat unnat-
ural and unbalanced compared to in phase.
• HIGH VOLUME LEVELS
At high volume levels, when an instrument and speaker are in phase, the sound
pressure from the speaker will excite the instrument's sound chamber, creating a
feedback loop at the instrument's lowest octave. This "cavity resonance" feed-
back can be dealt with by putting the instrument and speaker out of phase or by
adding equalization.
A. USING THE PHASE SWITCH TO REDUCE FEEDBACK.
Inverting the PHASE switch will put the instrument and speaker
out of phase
with each other, cancelling the low frequency feedback.
If you move from your position on stage more than a few feet, you may have to
invert the PHASE switch again to maintain an
out of phase relationship
between the mic'ed instrument and speaker. Continued ...

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PHASE, Continued from Page 9
Here's why:
A typical guitar has a cavity resonance of about 100 Hz. This is the frequency
that generally feeds back when the guitar and speaker are
in phase.
100 Hz has a wavelength of about 11 feet.
Phase inverts 180° for every 1/2 a frequency's wavelength. In this case, 1/2
the wavelength is about 5 1/2 feet.
If you set your PHASE switch to eliminate cavity resonance
(out of phase) and
then move 5 1/2 feet towards or away from the speaker, you will effectively put
the mic'ed guitar/speaker relationship at 100 Hz back in phase; in the line of
fire for low frequency feedback.
B. USING THE NOTCH FILTER TO REDUCE FEEDBACK
Notching out instrument cavity resonance will eliminate the low frequency feed-
back problem completely. The advantages to using notching equalization are:
• The physical distance from the speaker will no longer be a factor for potential
low frequency feedback.
• The mic'ed instrument/speaker can remain
in phase, maintaining a more nat-
ural and balanced response.
The PHASE switch on the ONBOARD BLENDER™ in effect electronically "moves" your instrument's
position relative to the speaker by inverting the phase 180° every time you flip it.