Symetrix 420 Datasheet

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 [phone] Fax [phone] www.symetrixaudio.com

Mono mix mode

Front panel headphone jack

Front panel output mute switch

420

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 [phone] Fax [phone] www.symetrixaudio.com