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ARCHITECTÕS AND ENGINEERÕS SPECIFICATIONS
The power amplifier shall contain all solid-state circuitry, using
complementary silicon semiconductors. The amplifier shall
operate from 50-60 Hz AC power, with voltages of 100, 120, or
240 Vac. The amplifier shall operate from a normal household
AC outlet, drawing less than 900 VA when driven with random
program material at 1/8 rated power into four ohm loads. The
amplifier shall be supplied with a single molded AC cord having
an appropriate AC plug for the intended operating voltage.
The amplifier shall contain two independent channels. Each chan-
nel shall have independent protective circuitry against open cir-
cuit, short circuit, or reactive loads, and the remaining channel
shall continue to operate if one channel fails. A muting circuit
shall provide three seconds of muting after turn-on, and shall
mute within 1/4 second after turn-off or loss of power, to protect
the load against turn-on or turn-off thumps. Self resetting ther-
mal shutdown shall protect the circuitry against temperatures in
excess of 90°C, and a front panel resettable circuit breaker or
fuse shall protect against AC overloads.
Each channel of the amplifier shall have an independently
defeatable limiter. Each channel shall also have bypassable high-
pass filtering, with independently selectable -3 dB frequencies
of 30 Hz or 50Hz. The limiter and high pass filter controls shall be
on an 8-position DIP switch on the amplifierÕs rear panel.
Each channel of the amplifier shall typically be capable of meet-
ing the following performance criteria, with both channels driven
simultaneously, unless otherwise stated: Output power, 8 ohms
per channel, 20 Hz-20 kHz, less than 0.1% distortion, at least
110 watts rms per channel. Output power, 4 ohms per channel, 1
kHz, less than 1% distortion, at least 200 watts rms per channel.
Frequency response shall be 20 Hz-20 kHz + 0, - 1 dB at 1 watt
output. SMPTE IM distortion shall be less than 0.025% at rated
power, 8 ohms, and less than 0.05% at rated power, 4 ohms. IHF
damping factor shall be at least 200. Signal to noise, below rated
output, shall be at least 105 dB (A weighted). Dynamic head-
room at 8 ohms shall be at least 2 dB. The voltage gain shall be
29 dB at full gain. The input sensitivity for rated 8 ohm power
shall be 1.12 Vrms. Input impedance shall be 20 kilohms bal-
anced and unbalanced noninverting, 10 kilohms unbalanced in-
verting. Balanced, bridging input circuit shall be standard, and
the amplifier shall meet all performance criteria in the balanced
or unbalanced mode. The amplifier shall have passive cooling
for ultra-quiet operation. Each channel shall have the following
controls, indicators, and connectors: Rear mounted gain control
calibrated in dB. Clipping indicator, responding proportionally to
any distortion in excess of 0.1%. Balanced/unbalanced input
jack of the Neutrik "Combo" (combined 1/4" TRS and XLR). Bal-
anced input of the barrier strip screw terminal type. Speaker ter-
minals of the "touch proof" binding post type. In addition, the
chassis shall feature a rear mounted mono-bridging switch, front
mounted AC switch and circuit breaker or fuse in some export
locations, mounting positions on the rear for optional 70 V out-
put transformers, and built-in rack mounting ears. The chassis
shall mount in a 19" rack, occupying 3 rack spaces (5.25"). Chas-
sis depth behind the rails shall be 8.5" plus 1 in allowance for
the binding posts. Weight shall be 24 Ib. The amplifier shall be
the QSC Model USA 400.
BACK
USA 400 Specifications
OUTPUT POWER (per channel, typical)
8 ohms, 20 Hz to 20 kHz, 0.1% THD, 110 watts
8 ohms, 1kHz, 1% THD, 125 watts
4 ohms, 1 kHz, 1% THD, 200 watts
2 ohms, 1 kHz, 1% THD, 250 watts
OUTPUT POWER (bridged mono)
16 ohms, 1 kHz, 1% THD, 250 watts
8 ohms, 1 kHz, 1% THD 400 watts
DISTORTION:
SMPTE-IM, less than 0.025%
FREQUENCY RESPONSE:
20 Hz to 20 kHz, +0/-1 dB, 1 watt
DAMPING FACTOR:
Greater than 200
DYNAMIC HEADROOM: 2 dB at 8 ohms
NOISE: 105 dB below rated output (A weighted)
SENSITIVITY: 1.12 Vrms for rated power (8 ohms)
VOLTAGE GAIN: 28 (29 dB)
INPUT IMPEDANCE: 10K unbalanced, 20K balanced
CONTROLS:
Front: AC Switch, AC Circuit Breaker
Back: Stereo/Bridge Switch/Ch 1 and Ch 2 Gain Knobs
8 Position DIP Switch for Filter & Limiter
INDICATORS:
PWR-ON: Green LED
CLIP: Red LED, 1 per channel
CONNECTORS: (each channel)
Input: Barrier strip and Neutrik "Combo" 1/4" TRS and XLR, tip positive
Speakers: "Touch proof" binding posts
COOLING: Passive
AMPLIFIER PROTECTION:
Full short circuit , open circuit, ultrasonic, and RF protection. Stable into reactive or mismatched
loads.
LOAD PROTECTION:
On/off muting and DC-fault protection.
OUTPUT CIRCUIT TYPE:
Complementary linear outputs.
POWER REQUIREMENTS: 100,120, 240 Vac, 50-60 Hz
POWER CONSUMPTION:
Normal Operation: 4 ohms per channel: less than 4.4 amps, 120 Vac (900 VA)
DIMENSIONS:19.0" (48.3 cm) rack mounting
5.25" (13.3 cm) tall (3 spaces)
9.5" (24.1 cm) deep
WEIGHT: 24 Ibs (10.9 kg) net, 28 Ibs (12.7 kg) shipping
Output Averaging ª short circuit protection (US Patent 4,321,554)
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE.
1675 MacArthur Boulevard
Costa Mesa, California 92626-1468 USA
Phone: 714/754-6175 Fax: 714/754-6174
