MACKIE FRS1700 - Manual (Page 10)

10
FRS Series Amplifiers
FRS Series Amplifiers
AMP MODE
CHANNEL 2 CHANNEL 1 BRIDGED
BRIDGED
CH 1 CH 2
CLIP LIMIT
FILTER
SUBSONIC @ 30Hz
PIN
1+
1
PIN
1+
2+
1+
1
PIN
2+
2
PIN
1+
1
SPEAKER OUTPUTS
Use only class 3 wiring
POWER CONSUMPTION 2000 W
THIS DEVICE COMPLIES WITH PART 15 OF THE FCC RULES. OPERATION IS SUBJECT TO THE
FOLLOWING TWO CONDITIONS: (1) THIS DEVICE MAY NOT CAUSE HARMFUL INTERFERENCE,
AND (2) THIS DEVICE MUST ACCEPT ANY INTERFERENCE RECEIVED, INCLUDING INTERFERENCE
THAT MAY CAUSE UNDESIRED OPERATION.
AVIS: RISQUE DE CHOC ELECTRIQUE — NE PAS OUVRIR
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC
SHOCK, DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR
MOISTURE. DO NOT REMOVE COVER. NO USER SERVICEABLE
PARTS INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL.
AVIS: N'OUVREZ PAS LA COUVERTURE. N'EXPOSEZ PAS CET ÉQUIPEMENT À LA PLUIE OU À L'HUMIDITÉ.
FRS • 2800
FAST RECOVERY POWER AMPLIFIER
10. Amp Mode
This switch determines the input signal routing
within the amplifier. The stereo setting will be used in
most applications. However, some applications might
be better suited for using either the mono or the bridge
setting.
Stereo: This is the normal position used when
amplifying stereo signals. This mode accepts separate
left and right inputs (1 and 2), and routes them to the
channel 1 and channel 2 outputs. Each channel’s level
control adjusts the gain for its own channel, and each
channel is independent.
Mono: This mode (also known as dual-mono) is used
when you want to send a mono signal to both outputs.
It accepts a single input (input 1), and routes it to both
the channel 1 and channel 2 amplifiers. Each channel’s
level control adjusts the gain for its own channel.
Bridge: This mode (also known as bridged-mono)
accepts a single input (input 1), and uses both
amplifier outputs to power one speaker. Use the
channel 1 level control to adjust the gain (turn the
channel 2 level control all the way down). The
hookup diagram at the bottom of page 6 shows how
to connect a speaker in bridged mono.
WARNING: In bridged mode, both
connections to your speaker are live;
that is, neither is grounded through the
chassis (because the black binding posts are not used).
11. Clip Limit
When engaged, this switch helps to protect
loudspeakers from the effects of clipping. It is
designed to be virtually transparent, meaning you
probably won’t even notice any audible difference
when the switch is turned on.
We recommend that you leave this switch on at all
times. However, if you are working at quiet levels, or you
have already placed a compressor / limiter in the signal
path, you can leave this switch off.
The limiter senses when the amplifier is about to be
overdriven and attenuates the overall level just enough
to keep the signal from clipping. Clipping occurs when
the output voltage no longer linearly follows the input
voltage. As the amplifier output voltage increases, it will
eventually run into the internal DC power supplies and
start to flatten out. The flat tops represent a DC voltage
reaching the speakers, which interrupts the natural
movement of the speaker’s voice coil. High frequency
harmonics are also produced which can play havoc with
tweeters. Square waves sound awful, and could possibly
damage the speakers and / or your reputation.
Speakers are designed to handle good clean
continuous signals, but give them a clipped
signal and even high-power speakers can
be damaged. For example, a 100 watt amplifier that
is clipping, can damage speakers that are rated at
400 watts.
The limiter is especially handy when working with
loud output levels. Having the signal spikes (kick drum,
for instance) attenuated a bit can actually increase
the apparent loudness of the overall mix without
diminishing the “power” behind the spikes. It is also
a useful protection device for those unexpected
moments, such as the lead singer actually hitting the
right note, a mic stand or the drummer falling over,
dropping the tone arm, or an attack of killer feedback.
With the limiter engaged, the amplifier can
still be overdriven into clipping and cause
distortion. It just takes a stronger signal to
do it. So even with the limiter turned on, still pay
attention to the OL LEDs.
12. Subsonic Filter
Turn this switch on to engage a low-frequency cutoff
(high-pass) filter at 30 Hz. The frequency range below
30 Hz is attenuated.
The amplifiers can amplify signals below 20 Hz, but
most speakers can’t reproduce frequencies that low.
By engaging the subsonic filter, you allow the amplifier
to power only the frequencies you can hear. In
addition, this filter can reduce low-frequency stage
noise (footsteps) and accidental microphone pops
that could damage a loudspeaker.
Leave this off if the amplifier is powering a
subwoofer, or if the speakers can reproduce low
frequencies such as the kick drum range.
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