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 (978) 988-9665.

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

ONBOARD ACOUSTIC GUITAR SYSTEM

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

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

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.

FISHMAN PREFIX™ PLUS

ONBOARD ACOUSTIC GUITAR SYSTEM

CUT THROUGH

For cutting through a live band mix at high volumes.

FISHMAN PREFIX™ PLUS

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

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

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 ...

FISHMAN PREFIX™ PLUS

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.

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