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420 Stereo Power Amplifier
MONITORMODECHANNEL 2CHANNEL 1
420
STEREO POWER
AMPLIFIER
CLIP
GAIN
5
2738
GAIN
64
DUAL TRACKING
INDEPENDENT
91
100
GAIN
654
37
2
CLIP
1
10
0
8
9
MONO
STEREO
HEADPHONESCONTROLS
STEREO
SPEAKER
MUTED
ACTIVE
HE 420 STEREO POWER AMPLIFIER IS A TWO-CHANNEL POWER AMPLIFIER for
use in professional and commercial audio systems. The 420 may be operated as a two
T
channel amplifier with 20 watts (RMS) per channel, or as a single channel amplifier capable of 40
watts (RMS) output (bridged-mono mode). The 420 is intended for use in powering near-field
monitors, small reference speakers used for radio or audio for video reference, small paging
speakers, multiple pairs of headphones, or as a general purpose line driver/distribution amplifier.
The 420 is easy to install and simple to operate
as well. When used as a stereo amplifier, a
single ganged potentiometer controls the level
of both channels. As a 2-channel amp there’s
an independent level control for each channel.
In conjunction with the level controls each
channel has a bright red LED to indicate the
onset of clipping.
While the 420 is compact (1 rack space) and
low cost, one should not overlook it’s impressive performance data. Total harmonic
distortion (THD) is less than .04% at 1 watt
output (see the back of this page for complete
specifications). The 420 is truly a professional
amplifier—clean, crisp sound reproduction and
total freedom from noise. As an added feature,
the 420’s relatively low stray field emissions
A front panel MODE switch mono sums
(mixes) the two inputs. This feature is handy
for broadcast and recording engineers who
allow it to be racked next to a wide variety of
audio and video equipment without adversely
affecting the equipment’s performance.
wish to check the mono compatibility of their
signals. Commercial sound engineers can use
this feature to mix paging signals or paging and
music signals.
As with all Symetrix products the documentation accompanying the 420 is second to none.
This means you’ll be able to install and begin
using the product in no time at all. Our mean
In recording studios and other similar applications, the 420 makes an ideal headphone
amplifier. You can drive one pair of phones
from the front panel jack, or many pairs from
the rear panel terminals. In fact, the 420 will
time between failure statistics are among the
best in our industry, but should you require
applications assistance or repair you’re backed
up by a worldwide network of Symetrix
distributors and dealers. •
drive multiple professional headphone sets such
as the AKG K-240 to 122 dB SPL!
POWER
APPLICATIONS
Recording and broadcast studio
near field monitor amp
Video suite audio monitor
amplifier
Audio and video remote truck
monitor amp
Small paging system power
amplifier
Background music
amplifier
Recording and broadcast
headphone system amp
General purpose high level line
driver
FEATURES
Compact (uses only 1 rack
space)
20 watts/channel (stereo)
40 watts (mono bridged)
Symetrix Inc. Mountlake Terrace, WA, USA Tel (425)778-7728 Fax (425)778-7727 www.symetrixaudio.com
Mono mix mode
Front panel headphone jack
Front panel output mute switch
420
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420 Stereo Power Amplifier
100 WATTS MAXIMUM
MANUFACTURED IN
SEATTLE WASHINGTON,
UNITED STATES OF AMERICA
FUSE
FUSE
TIP
RING
SLEEVE
TYPICAL INPUTS
=HIGH(+)=
=LOW(-)=
=GROUND=
SLEEVE
RING
TIP
PIN 2
PIN 3
PIN 1
SPECIFICATIONS
Input/Output
Inputs XLR-Female Paralleled with TRS ¼" jacks
Outputs Two, 4 Ohms minimum impedance, #6 screw terminals
Maximum Input Level +21 dBu
Maximum Output (stereo/2-channel) 20 watts RMS, per channel, into a 4- or 8-Ohm load
Maximum Output (mono bridged) 40 watts RMS into an 8-Ohm load
Minimum Load 4 Ohms, stereo mode;
Headphone Output 100-Ohm source impedance,
Performance Data
(measured at 120V AC line voltage)
Frequency Response 20 Hz to 20 kHz (+0, -1 dB)
Crosstalk >60 dB (22 kHz bandwidth)
Sensitivity 0 dBu for 20 watts into an 8-Ohm load
Maximum Gain 27 dB
Signal to Noise >95 dB
Typical Distortion <0.04%, @ 1 kHz, 1 watt into 8 Ohms
THD+Noise <0.2%, 20 Hz to 20 kHz, @ 20 watts into 8 Ohms
Clip Indicators One per channel
10 kilohms Line-Level Balanced Bridging
Balanced CMRR greater than 55 dB @ 1 kHz
8 Ohms, monobridged mode
19V open circuit with speakers off
OUTPUTS
CHANNEL
CHANNEL
1
2
12
3
20 WATTS PER CHANNEL 8 OHMS (CLASS 2 WIRING)
Physical
Size (hwd) 1.72 x 19 x 7.25 inches, 4.37 x 48.26 x 18.415 centimeters
INPUT 2
UNBALANCED/
BALANCED
BALANCED
Specifications subject to change without notice.
INPUT 1
UNBALANCED/
BALANCED
BALANCED
Weight 7.6 lbs (3.5kg) net, 10 lbs (4.6 kg) shipping
Electrical
Power Requirements 120V nominal, 108 to 132V AC, 60 Hz, 100 watts
420 ARCHITECTS AND ENGINEERS SPECIFICATIONS
The power amplifier shall be a compact,
two input, two output, high performance, power amplifier. It shall occupy
a single rack space. (1U)
The unit shall be capable of delivering
20 watts per channel into a minimum
load of 4 Ohms. The unit shall also have
a mono-bridge mode which delivers 40
watts into a minimum load of 8 Ohms.
The inputs shall be active balanced
bridging designs terminated with 3-pin
XLR (AES/IEC standard wiring), and ¼"
TRS female. The input circuitry shall
incorporate RFI filters. The balanced
inputs shall accommodate +24 dBu
signals without distortion. Screw
terminals shall be provided for power
amplifier outputs.
THD shall not be greater than 0.04%, @
1 kHz, @ 1 watt in 8 Ohms. Signal to
noise ratio shall be greater than 95 dB.
Frequency response shall be 20 Hz to 20
kHz (+0 dB, -1 dB).
The power amplifier shall be protected
from output short-circuits. A front panel
Dual Tracking switch shall allow the
Channel 1 gain control to simultaneously
control the level of both channels. There
shall be a ¼" tip-ring-sleeve jack
mounted on the front panel for stereo
headphone output. A front panel switch
shall be provided to mute the rear panel
output connections. Another front panel
switch shall be provided to sum the two
input signals and route them to the two
gain controls.
Independent clipping indicators shall be
provided for each output channel.
The amplifier shall be capable of
operating by means of its own built-in
power supply connected to 120V
nominal AC (108 to 132V) 60 Hz.
The unit shall be a Symetrix Incorporated model 420 Stereo Amplifier.
420
Publication ©1997 Symetrix, Inc.
Symetrix Inc. Mountlake Terrace, WA, USA Tel (425)778-7728 Fax (425)778-7727 www.symetrixaudio.com