U
S
E
R
’
S
G
U
I
D
E
TM
ONBOARD
BLENDER
WARNING!
WE STRONGLY RECOMMEND THAT YOU FAMILIARIZE YOURSELF WITH THE
PREAMP CONTROLS BEFORE YOU ATTEMPT TO PERFORM WITH THE ONBOARD
BLENDER. FAILURE TO DO SO COULD RESULT IN WAVES OF EAR-SPLITTING
FEEDBACK AT HIGH LEVELS. (see Quick Start on page 3.)
ACOUSTIC GUITAR SYSTEM
QUICK START
To successfully combine microphone and pickup signals, it is best to start by
presetting the microphone EQ to control feedback, then mixing in the pickup.
The PREFIX™ ONBOARD BLENDER™ features three ways to control feedback;
a PHASE switch, NOTCH filter and semi-parametric CONTOUR controls.
Follow these steps to achieve a strong, feedback-free microphone response.
1. Before plugging in, set all controls as follows:
• NOTCH and VOLUME fully counter-clockwise
• All EQ sliders at center position
• BLEND slider at MIC position
2. Plug in the instrument (see THE PREAMP section) with your amplifier set as
desired.
3. Slowly increase the VOLUME until the guitar and speaker are approximately
the same level. Play the lower strings and flip the PHASE switch. Leave the
switch in the position that sounds the deepest and clearest. (See page 8)
4. Slowly increase the volume until the instrument starts to rumble or howl with
low to mid level feedback (100-200 Hz).
5. Adjust the NOTCH filter until the feedback is eliminated.
6. Slowly increase the VOLUME again, until you hear a squeal (high frequency
feedback).
7. Lower the CONTOUR Level all the way down. Slowly adjust the Contour
FREQUENCY slider until the feedback is eliminated. Raise the CONTOUR
Level slider (if possible) to just below the threshold of feedback.
8. Gradually mix in the pickup signal by adjusting the BLEND slider.
The pickup signal will add significant attack and definition to your sound.
9. Adjust the BASS and TREBLE controls as desired.
Please note that these controls will affect pickup signal only.
10. Double check the PHASE switch position until you find the clearest response.
11. Play your guitar as loud as you want.
See diagram on page 6
3
FISHMAN PREFIX™ ONBOARD BLENDER
PREAMP FUNCTIONS
BATTERY COMPARTMENT
Pull the small tab at the top
of the ONBOARD
MICROPHONE
TRIM
BLENDER™ toward you. The
body of the preamp will
swing out, revealing the BAT-
TERY COMPARTMENT.
9V BATTERY
PREFIX™ SERIES PREAMP
Insert a fresh 9V alkaline
battery.
GUITAR BODY
MICROPHONE TRIM CONTROL
A small circular potentiometer is located on the underside of the preamp just
below the battery compartment. This control is used to calibrate the microphone
gain in relation to the pickup. To use this control, set the BLEND slider to the
center position and, with a small screwdriver, adjust the potentiometer until both
the microphone and pickup levels are balanced.
ENDPIN JACK
The ONBOARD BLENDER™ 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 LED
When plugging into the endpin jack, the LOW BATTERY light will flash momen-
tarily, indicating 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 resonance. The affected frequency is variable from 50 to 900 Hz. The
4
ACOUSTIC GUITAR SYSTEM
NOTCH FILTER is effectively off in the full counter-clockwise position.
VOLUME CONTROL
The VOLUME control affects both microphone and pickup. Goes from very quiet
to very LOUD.
BASS CONTROL
This is a boost/cut shelving tone control. This control affects the pickup signal
only. The center detent yields a flat response.
CONTOUR This is a wide-range semi-parametric filter. It may be used to
shape the instrument's tone or to control feedback (see pages 6 and 7). The
CONTOUR control affects both the pickup and microphone.
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
between 250 Hz and 10 kHz.
TREBLE CONTROL
This is a boost/cut shelving tone control. This control affects the pickup signal
only. The center detent yields a flat response.
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. Whenever you play through a different
sound system or at a different venue, flip the PHASE switch several times and
use your ear to find the optimum setting.
BLEND CONTROL
This control determines the balance between microphone and pickup signals.
This control can be used as a feedback "escape hatch" if you ever need to
instantly shut off the microphone during a performance.
5
FISHMAN PREFIX™ ONBOARD BLENDER
SUGGESTED EQ SETTINGS
ANTI-FEEDBACK
50 Hz
900 Hz
QUIET
LOUD
Refer to page 3.
PHASE
BATTERY
LOW
MIC
PICKUP
BRILLIANCE
50 Hz
900 Hz
QUIET
LOUD
If you are playing through an electric
guitar amplifier or have dead strings on
the instrument, you can brighten up
your sound by setting the Contour FRE-
QUENCY slider to 10 kHz and raising
the CONTOUR Level to taste. If you
plan to play at high stage volume levels,
dial in more pickup than microphone to
avoid feedback.
PHASE
BATTERY
LOW
MIC
PICKUP
6
ACOUSTIC GUITAR SYSTEM
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.
Often the desired mid-cut will fall into
the same frequency range as potential
microphone feedback. This is your
lucky day!
50 Hz
900 Hz
QUIET
LOUD
You can also cut midrange (pickup only)
by boosting the BASS and TREBLE
sliders to realize an "implied" mid-cut at
800 Hz.
PHASE
BATTERY
LOW
MIC
PICKUP
50 Hz
900 Hz
QUIET
LOUD
FINGERSTYLE
This setting will add fullness to the bass
and definition to the treble.
PHASE
BATTERY
LOW
MIC
PICKUP
7
FISHMAN PREFIX™ ONBOARD BLENDER
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.
UPPER PEAK
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
LOWER PEAK
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.
8
ACOUSTIC GUITAR SYSTEM
WHY DO I NEED A PHASE SWITCH ?
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 mic'ed instrument faces a loudspeaker, there will be
an interactive 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 a mic'ed 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 a mic'ed 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 reso-
nance" feedback can be dealt with by putting the mic'ed 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 mic'ed 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 ...
9
FISHMAN PREFIX™ ONBOARD BLENDER
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 a mic'ed 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.
PHASE INVERTED 180°
PHASE INVERTED 180°
DISTANCE:
5’ 7"
11’ 4"
17 ’
22’ 7"
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.
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.
10
ACOUSTIC GUITAR SYSTEM
SPECIFICATIONS
Nominal Input Level:
-20 dBV
Input Overload:
Input Impedance:
Output Impedance:
Nominal Output Level:
THD:
(20 Hz - 20 kHz)-2 dBV
20 M Ohms
Less than 3.5 k Ohms
-12 dBV
Less than .04 %, -20 dBV input
Signal to Noise Ratio:
77 dB
(A weighted referred to nominal
-20 dBV input)
Current Drain:
Power Supply:
Less than 4 mA
9V Alkaline battery
(estimated 140 hours continuous use with
low battery indicator at 6.5V)
Notch Filter Range:
Bass Control Range:
50Hz - 900 Hz (-15 dB)
±
±
12 dB at 60 Hz
3 dB at 350 Hz
PICKUP ONLY
Treble Control Range:
Contour Control Range:
±
±
12 dB at 10 kHz
3 dB at 2.4 kHz
±
12dB
(adjustable from 250 Hz to 10 kHz)
Q = 0.5
All specifications subject to change without notice.
TM
ONBOARD
BLENDER
11
LIMITED WARRANTY
INSTALLATION BY A QUALIFIED PROFESSIONAL REPAIRMAN IS STRONGLY
RECOMMENDED. FISHMAN TRANSDUCERS WILL NOT BE RESPONSIBLE FOR ANY
DAMAGES THAT MAY RESULT FROM IMPROPER INSTALLATION.
The FISHMAN PREFIX™ ONBOARD BLENDER ACOUSTIC GUITAR SYSTEM is warranted
to function for a period of One (1) Year from the date of purchase. If the unit fails to function
properly within the warranty period, free repair and the option of replacement or refund in
the event that FISHMAN is unable to make repair are FISHMAN’s only obligations. This
warranty does not cover any consequential damages or damage to the unit due to misuse,
accident, or neglect. FISHMAN retains the right to make such determination on the basis of
factory inspection. Products returned to FISHMAN for repair or replacement must be
shipped in accordance with the Return Policy, as follows. This warranty remains valid only if
repairs are performed by FISHMAN. This warranty gives you specific legal rights and you
may also have other rights which may vary from state to state.
RETURN POLICY
To return products to FISHMAN TRANSDUCERS, you must follow these steps...
1. Call FISHMAN TRANSDUCERS at 978-988-9199 for a Return Authorization Number
(“RAN”).
2. Enclose a copy of the original Bill of Sale as evidence of the date of purchase, with
the product in its original packaging and a protective carton or mailer.
3. FISHMAN TRANSDUCERS’ technicians will determine whether the item is covered by
warranty or if it instead has been damaged by improper customer installation or other
causes not related to defects in material or workmanship.
4. Warranty repairs or replacements will be sent automatically free of charge.
5. If FISHMAN TRANSDUCERS determines the item is not covered by warranty, we will
notify you of the repair or replacement cost and wait for your authorization to proceed.
FISHMAN TRANSDUCERS®
340-D Fordham Road Wilmington MA 01887 USA
009-087-004 3-98
|