SRA-120
Power Amplifier
Operating Manual
SRA-120
Stereo
Power Amplifier
Level (dB) Level (dB)
0
-1
-3
-
-6
-20
Sig.Clip
Protect
-10
Channel 1
(Mono)
-3
-6
0
-1
-10
Channel 2
-
Sig.Clip
-20
Stereo
Headphones
SRA-120
SRA-120
Power
Channel 2
Protect
ASHLY AUDIO INC.
847 Holt Road Webster, NY 14580-9103 Phone: (716) 872-0010
Toll-Free: (800) 828-6308 Fax: (716) 872-0739 Internet: http://www.ashly.com/
Operating Manual - SRA-120 Power Amplifier
Table Of Contents
1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 UNPACKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 AC POWER REQUIREMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1 AC Voltage Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Current Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3 AC Grounding Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4 CABLE REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1 Input Cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2 Output Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5 RACK-MOUNTING REQUIREMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1 Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2 Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3 Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.4 Security Cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6 FRONT PANEL FEATURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1 Power Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.2 Level Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.3 Signal Present Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.4 Clipping Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.5 Protect Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.6 Headphone Jack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7 REAR PANEL FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1 Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.2 Input Sensitivity Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.3 Normal/Bridging Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.4 Stereo/Mono Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.5 Speaker Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8 TYPICAL APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1 Stereo Sound Reinforcement System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.2 Stereo Playback Monitoring System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.3 Mono Operation in High Level Bi-Amped System . . . . . . . . . . . . . . . . . . . . . 9
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Operating Manual - SRA-120 Power Amplifier
9 DESIGN THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10 TROUBLESHOOTING TIPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1 No Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.2 Distorted Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.3 Excessive Hiss Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.4 Excessive Hum Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
11 DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
12 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
13 WARRANTY POLICY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
14 SCHEMATICS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
- WARNING -
THIS APPARATUS MUST BE EARTHED
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Operating Manual - SRA-120 Power Amplifier
1. INTRODUCTION
Congratulations on your purchase of the Ashly
SRA-120 professional stereo power amplifier. This single
rack-space (1 3/4" height) amplifier delivers a substantial amount of power with exceptional audio quality and
many features typically found only in larger power amplifiers,
Both channels of the SRA-120 can easily drive 4
ohm loads, delivering a total of 120 watts of undistorted,
average sinewave power.
The amplifier has an automatic output turn-on
delay and instantaneous output turn-off to protect speakers from transients. Each output will also turn off if it
"sees" a load of 2 ohms down to a short circuit. The outputs are also independently protected from overheat conditions. Each channel will automatically reset itself from
any of these protection modes independent of the other
channel's operation.
The SRA-120 provides front panel level controls,
a stereo headphone jack, and six status LED's for ease of
control and monitoring. The back panel provides both
balanced 1/4" jacks and balanced screw terminal inputs.
Three push-button switches allow selection of stereo,
mono, bridged mode, and input sensitivity, allowing the
amplifier to be applied in any configuration. The
amplifier's signal ground can also be lifted from chassis
ground via a barrier strip jumper.
2. UNPACKING
As a part of our system of quality control, every
Ashly product is carefully inspected before leaving the
factory to ensure flawless appearance. After unpacking,
please inspect for any physical damage. Save the shipping carton and all packing materials, as they were carefully designed to reduce to minimum the possibility of
transportation damage should the unit again require packing and shipping. In the event that damage has occurred,
immediately notify your dealer so that a written claim to
cover the damages can be initiated.
The right to any claim against a public carrier
can be forfeited if the carrier is not notified promptly and
if the shipping carton and packing materials are not available for inspection by the carrier. Save all packing materials until the claim has been settled.
3. AC POWER REQUIREMENTS
3.1 Voltage Requirements
Your SRA-120 amplifier is supplied with a three
conductor grounded AC power cord, and should be
plugged into a standard 3-wire grounded electrical outlet
which supplies 120VAC 50-60 Hz (some export models
are wired for 100 or 240 volts and are labeled as such).
In the event of line voltage sag, or “brown-out”, SRA120 amplifiers will continue to operate normally, albeit
with less power.
3.2 Current Requirements
The actual AC current consumption by the amplifier depends greatly on the audio signal and the load
impedance. For typical audio program material with the
SRA-120 driving both channels just peaking at the clipping level, the following AC line current is drawn and
should be used for system design purposes:
Idle 0.1A
8Ω loads 0.6 Amps
4Ω loads 1.0 Amps
Table 3.1: Estimated Maximum RMS AC Line Current
Draw
3.3 AC Grounding Requirements
To reduce the risk of ground loop hum, all system ground references should originate at the same point
in your AC power distribution. Never remove the
amplifier’s ground pin as it is both unlawful and dangerous, creating a potential shock hazard.
4. CABLE REQUIREMENTS
4.1 Input Cables
Be sure to use shielded cable whether balanced
or unbalanced. Shielding which is properly grounded will
protect the signal from outside electrical interference such
as RF, fluorescent lighting, even computer noise. As a
general rule, unbalanced or single-ended (tip-sleeve) lines
of less than 10 feet are satisfactory, but greater distances
may require a balanced signal. Avoid running input lines
in close proximity or parallel to long speaker lines, AC
power cables, or power transformers, as this may generate hum or oscillation.
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Operating Manual - SRA-120 Power Amplifier
4.2 Output Cables
The wire gauge used for speaker cables is important, in that inadequate wire gauge adds significant resistance to the speaker’s own impedance, reducing the
power which is actually delivered to the speaker. It also
results in a decrease in the damping factor and possible
fire hazard.
Since power at the speaker load is a primary concern in system design, we have included a table to best
determine appropriate wire gauge for your application.
Table 4.1 lists the percentage of the speaker load power
which would be lost in an arbitrary 100 ft. run of 2-conductor cable. This table expresses the power loss as a
percentage of the load’s power rather than the total amplifier output power, so that you can use this table to accurately determine power loss to the load at other cable
lengths. For example, if you plan to deliver 100 watts to
an 8Ω load through 50 ft of 14 ga. cable, the power loss
in the cable would be 3.2% ÷ 2 = 1.6% of 100 watts or
1.6 watts lost in the cable. Table 4.1 also gives the resistance per 100 feet of common copper wire gauges.
Wire Gauge Ω/100ft 8Ω load 4Ω load 2Ω load
5. RACK-MOUNTING REQUIREMENTS
5.1 Mechanical
All Ashly amps are designed to fit in standard
19-inch racks. Avoid placing the amp immediately next
to devices which are sensitive to heat or magnetic fields
(high-gain preamps, magnetic data storage, etc.)
5.2 Cooling
The SRA-120 will cool more efficiently with
space above and below the chassis, although most applications will not require this.
The following chart indicates maximum BTU per
hour under varying load conditions, so that accurate assessment of room ventilation needs can be made. Thermal output is approximated by subtracting audio output
power from the total power consumption of the amplifier. All values assume the amplifier is driving both channels and just peaking at the clipping level.
Idle 40 BTU
8Ω loads 200 BTU
#8 .0605Ω 0.8% 1.5% 3.0%
#10 .1018Ω 1.3% 2.5% 5.1%
#12 .1619Ω 2.0% 4.0% 8.1%
#14 .2575Ω 3.2% 6.4% 12.9%
#16 .4094Ω 5.1% 10.2% 20.5%
#18 .6510Ω 8.1% 16.3% 32.6%
Table 4.1: Percentage of speaker load power lost in 100
foot run of 2-conductor cable.
4Ω loads 320 BTU
T able 5.2: Maximum BTU per hour (both channels driven)
5.3 Grounding
In some installations where a sound system is
sensitive to RF noise or system-induced oscillation, it may
be necessary to ground the amplifier's chassis to the rack
enclosure. This is accomplished using star type
lockwashers on the four rack mounting screws. These
star washers will penetrate through the amplifier's paint
to adequately ground the chassis to the rack.
5.4 Security Covers
For installations where it is desirable to protect
the front panel level controls from tampering or accidental misadjustment, use an Ashly security cover. Installation is simple and does not require removal of the equipment from your rack. See your Ashly dealer for details.
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Operating Manual - SRA-120 Power Amplifier
p
-3
SRA-120
Stereo
Power Amplifier
-6
Protect
6. FRONT PANEL FEATURES
6.1 Power Switch
When the unit is switched on there is a 2 second
delay, during which time the PROTECT circuit will activate. The load is disconnected during this power-up sequence . When turning off the amplifier, the load is removed instantly, and the protect LED will briefly turn on
as the power supply discharges.
6.2 Level Controls
Front panel level controls allow precise independent input level attenuation to the power amp sections.
When in mono or bridged mode, channel 1 controls both
power amp channels. We recommend setting these controls full CW and controlling system gain at the mixer or
preamp instead.
Level (dB) Level (dB)
0
-1
-10
Channel 1
-
-20
Sig.Clip
-6
0
-1
-3
-10
Channel 2
-
-20
Sig.Clip
Stereo
Headphones
(Mono)
6.5 Protect Indicators
Protect mode in the SRA-120 is automatically
activated during extreme fault conditions, as well as during power-up and power-down. When in protect mode, as
indicated by the red LED, the speaker output terminals
are internally disconnected. Conditions causing the amplifier to switch into protect mode include the following:
Turn-on delay/Instant turn off
Output short circuit
Load impedance below 2 ohms
DC at output (below 8Hz)
Ultrasonic signal (above 20KHz)
6.3 Signal Present Indicators
Green signal present LED's indicate the presence
(about 30dB below maximum output) of signals into the
power amp circuitry.
6.4 Clipping Indicators
Clipping occurs when the signal peak levels extend beyond the available power supply rails, essentially
“cutting off” the crest portion of the waveform. This produces signal distortion and can potentially damage drivers, as the signal begins to look like a square wave. The
red CLIP LED's illuminate at the onset of clipping, and
accurately track both the output load and the AC line voltage.
SRA-120
Made In USA
TO RED U CE T HE RISK OF ELECTR I C SHOCK DO N OT REMO VE
COVER. NO USER SERVICEABLE PARTS INSIDE. REFER
SERVICING TO QUALIFIED SERVICE PERSONNEL. TO REDUCE
THE RISK OF FIRE REPLACE ONLY WITH SAME TYPE FUSE.
TO REDUCE THE RISK OF FIR E OR ELECTRIC SHOCK DO NOT
EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE.
AVIS:
NE PAS OUVRIR.
Amplifier overheating
Each channel automatically resets itself within
one second of removal of the fault condition. In the event
of overheating, it may take several minutes for the amplifier to reset. If thermal shutdown occurs, check to see
if the cooling fins have access to fresh air.
6.6 Headphone Jack
The Stereo headphone output jack will drive any
impedance stereo headphones. Channel 1 is connected
to the 1/4" jack tip contact and channel 2 is connected to
the ring.
MDA 3A
RISQUE DE CHOC ELECTRIQUE -
120VAC
50-60Hz
350W
Ch.2 Out
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Operating Manual - SRA-120 Power Amplifier
SRA-120
Power
Channel 2
Protect
7. REAR PANEL FEATURES
7.1 Inputs
The input of the SRA-120 amplifier is equipped
with balanced 1/4" tip-ring-sleeve (TRS) phone jacks and
balanced screw-terminal inputs. Each channel's connectors are internally wired in parallel and may be used with
balanced or unbalanced connections. The nominal input
impedance (balanced) is 20KΩ and the maximum input
level is +22dBu.
Balanced Inputs
It is recommended that balanced input connections be used whenever possible to reduce ground-loop
and environment-induced hum and noise. The (+) signal
is on the tip of the phone jack, the (-) signal is on the ring,
and the shield is on the sleeve.
Unbalanced Inputs
If an unbalanced input connection is used, then
the (-) connection should be connected to ground. Use of
a mono (tip-sleeve) plug will automatically tie the (-)
connection to ground. Never float (leave unconnected)
pin 2 or pin 3 when using an unbalanced signal.
Input Ground
The CHASSIS GROUND terminal is internally
connected to the chassis, the AC earth ground, and the
power amplifier’s signal ground. The INPUT GROUND
terminal is tied to the 1/4" jack's sleeve. It is recommended that the input and chassis ground terminals remain connected with the factory-supplied jumper strap.
Tip (+)
Ring (-)
Sleeve (Ground)
Stereo Phone Plug
used for balanced
Pins are
numbered
in the
connector
insert.
2 = (+)
3 = (-)
1 = (gnd)
Input Output
(-) (+) (-) (+)
Chassis Ground Signal Ground
Balanced Audio Connecto rs
XLR Male
Terminal Strip
Figure 7.1: Balanced Input Connections (recommended)
Tip (+)
Sleeve (Ground)
Mono Phone Plug
used for unbalanced
Pins are
numbered
in the
connector
insert.
2 = (+)
3 = (gnd)
1 = (gnd)
Input Output
(gnd) (+) (+)
Chassis Ground Signal Ground
(gnd)
Unbalanced Audio Connectors
XLR Male
Terminal S trip
Figure 7.1a: Unbalanced Input Connections
tput Ch.1
Bridged Mode:
Posts Only. Chan.2 is (+) and
Chan. 1 is (-). Do Not Connect
Either Output to Ground.
Use Red Binding
(+)
(-)
45W/Ch.@ 8
60W/Ch.@ 4
Stereo
Mono
Norm
Bridged
0dB
-10dB
Input
Sensitivity
Channel 2
Input
Input is active balanced.
If unbalanced connection is used,
be sure to ground unused path.
(+)
(+)(-)
Input
Ground
(-)
Channel 1 (Mono)
Inpu t
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Operating Manual - SRA-120 Power Amplifier
In situations where the power amp and its signal
source are separated by great distances, a ground voltage
difference may exist between the amp’s chassis ground
and the input cable’s ground. Connection of these two
grounds through the jumper strap may cause large ground
currents to flow (which is known as a ground loop), causing a hum noise in the amp’s output. Unless you have
such a situation with a hum problem that cannot be solved
by using balanced input connections, the ground jumper
strap should remain in place.
7.2 Input Sensitivity Switch
This switch selects between a 0 dBu input sensi-
tivity in the "out" position for use with professional audio sources, and -10 dBu input sensitivity in the "in" position for use with low line-level sources such as tape
decks, CD players, DAT machines, etc.
7.3 Normal/Bridging Switch
This switch selects between NORMAL mode in
the “out” position where both outputs are in-phase with
their respective inputs, and BRIDGED mode in the “in”
position where channel 1 output is switched out of phase
with it's input. In BRIDGED mode, the channel 2 red binding post becomes the (+) in-phase speaker output terminal
and the channel 1 red binding post becomes the (-) out-ofphase speaker terminal. To properly operate in bridged
mono mode, the Mono switch must also be selected.
7.4 Stereo/Mono Switch
This switch selects between stereo mode in the
"out" position and mono mode in the "in" position. In
mono mode, channel 1 input is sent to both amplifier channels, and is controlled through the channel 1 level control.
7.5 Speaker Outputs - Binding Posts
A pair of dual banana binding posts provide the
stereo speaker outputs. The minimum load impedance is
4 ohms per channel in normal mode, and 8 ohms in bridged
mode. In BRIDGING mode, the channel 2 red binding
post is the (+) in-phase speaker output terminal and the
channel 1 red binding post becomes the (-) out-of-phase
speaker terminal.
CAUTION! NEVER CONNECT THE TWO RED
BINDING POSTS TOGETHER OR CONNECT
EITHER RED BINDING POST TO A BLACK
BINDING POST!
8. TYPICAL APPLICATIONS
8.1 Stereo Sound Reinforcement System
In this situation, the audio source feeding the SRA-120 is a professional level (0dBu) stereo mixer. All three
mode switches should be in the "out" position.
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Operating Manual - SRA-120 Power Amplifier
8.2 Stereo Playback Monitoring System
Here the SRA-120 is fed from a low line-level (-10dBu) stereo tape machine or CD player. Only the sensitiv-
ity switch should be depressed.
8.3 Mono Operation in High Level Bi-Amped System
Here the SRA-120 is fed from the high frequency output of a professional two-way crossover. The stereo/
mono and normal/bridged switches are both depressed to obtain the maximum amount of power when amplifying a
mono signal. In this mode, the channel 1 input feeds both sides of the amp, but the phase of channel 1 is inverted so
the voltage difference between the channel 2 and channel 1 red binding posts is twice as great as either would be
relative to the black binding posts. The (+) in-phase speaker connection is then made to the channel 2 red binding post
and the (-) out of phase speaker connection is made to the channel 1 red binding post. (Warning: the output power
available to the horn or loudspeaker is doubled when in bridged/mono mode. Some horn drivers may be damaged by
excessive power.)
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Operating Manual - SRA-120 Power Amplifier
9. DESIGN THEORY
Ashly engineers set out to design a single rack
space stereo power amplifier delivering a minimum of
120 watts total with the sonic excellence, mechanical ruggedness and unsurpassed reliability Ashly amps are known
for. These qualities were upheld while containing other
important parameters such as weight, depth, serviceability and cost.
The result of this design philosophy is a superior
sounding all-discrete bipolar power amp section at the
heart of the amp. The voltage gain stages of the amp are
totally discrete transistors operating "class A" for low
distortion. The output section is a full complementary
bipolar push-pull stage. The active balanced input and
level control stages utilize low-noise op-amps for constant input impedance with accurate, low noise level control. All integrated circuitry was kept outside the feedback loop of the power amp section to maintain excellent
transient response.
A toroidal power supply transformer is used to
minimize induced hum noise and to reduce overall weight.
Epoxy sealed output relays are used to protect speakers
and the amplifier from turn on transients, excessive load
current and overheat conditions. A unique rear-panel sensitivity switch (0dBu or -10 dBu) is provided to interface
the amp with professional line level equipment or directly
with low line level tape machines and CD players.
The SRA-120 is packaged in an extremely rugged one piece welded 14-gauge steel chassis. The power
transformer is located near the front center of the amp to
minimize front panel torsion. Channels 1 and 2 circuitry
are on separate plated-through glass epoxy circuit boards
with plug-in connectors for all wiring to ensure ease of
servicing. Each channel has a large, extruded aluminum
heat sink with vertically oriented fins for maximum convection cooling action.
10. TROUBLESHOOTING TIPS
10.1 No Audio Output
• Power switch is on but not illuminated:
Line fuse on rear panel is blown or power outlet
is dead.
IF LINE FUSE IS BLOWN, REPLACE ONLY
WITH SAME TYPE AND RATING FUSE.
• Power switch is lit but no signal present indicator activity:
There is no input signal applied or input level
controls are turned off. NOTE: In MONO mode,
channel two input is disconnected and channel
one input is sent to both channels.
• Protect LED remains lit:
Amp is in thermal protect mode. Loudspeakers
have been disconnected until the amplifier returns
to a normal temperature. The amplifier relies on
convection air currents to move ver tically through
the side fins to keep cool. If the protect indicators
come on because of overheating, mount the
amplifier with air space above and below to allow
convection cooling action to occur.
Amp is protecting speakers from ultrasonic
signals. Disconnect input cables to see if
ultrasonic signal is coming from audio source.
• Protect LED remains lit and relay clicking is heard:
Output is short circuited or load impedance is
too low. Check speaker cables for shorts,
increase load impedance by disconnecting some
speakers.
A high frequency oscillation in the sound system
is occurring when the relays close. Turn down
the input level contr ols to verify that the amplifier
alone is not causing the problem.
Be sur e to use good quality shielded and balanced
input cable. Do not run input cables alongside
output speaker wires over long lengths
(i.e..through the same conduit).
10.2 Distorted Sound
• Output level meters indicate 0dB level (red CLIP LED on):
Amplifier is being clipped. Reduce the signal
level at the signal source.
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Operating Manual - SRA-120 Power Amplifier
• Signal present indicators active but clip LED is not:
Applied input signal is distorted before it gets to
the amp. Check to see if a piece of equipment in
the signal chain before the amp is clipping.
Normally the amplifier should be operated with
input levels fully CW to maximize headroom in
the signal source. Also check for damaged
speaker drivers that could cause distorted sound.
If distorted sound is still heard, there may be an
internal problem. Call Ashly Audio service department at
1-800-828-6308.
10.3 Excessive Hiss Noise
If an excessive hiss noise is heard relative to the
signal level, then the amplifier may not be getting
a strong enough input signal. Push the r ear panel
sensitivity switch to the out position and increase
the output level of the audio source which feeds
into the amplifier. If excessive hiss noise is still
heard, then a noisy signal is being fed into the
SRA-120. Isolate which piece of equipment in
the audio chain is causing the noise. The audio
source medium itself may contain the noise.
10.4 Excessive Hum Noise
This is usually caused by "ground loops" in the
system wiring. In a complex sound system where
there are many components separated by
significant distances and where several power
outlets are being used, there are many
opportunities for this problem to occur. If
possible, feed every component in the system from
one power source with a single gr ound point. Use
balanced input and output connections between
widely separated components. If a hum noise still
exists, the SRA-120 signal ground can be
disconnected from its chassis gr ound by removing
the jumper strap from the input barrier strip.
If you still need help, get in touch with your Ashly
dealer, or call Ashly direct: (800) 828-6308. In New
York State, dial (716) 872-0010.
11. DIMENSIONS
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Operating Manual - SRA-120 Power Amplifier
12. SPECIFICATIONS
12.1 Output Power:
Maximum Average Power, 0.1% THD, 1KHz
RMS Watts Per Channel, Both Channels Driven
8 ohms: 40W
4 ohms: 60W
Bridged Mono Mode:
8 ohms: 120W
FTC Continuous Power, 0.1% THD, 20Hz-20KHz
RMS Watts Per Channel, Both Channels Driven
8 ohms: 40W
4 ohms: 55W
12.2 Frequency Response:
±0.2dB 20Hz - 20KHz
12.3 Total Harmonic Distortion (35W/ch.):
.01% 1ΚΗz, 8Ω
.05% 20Hz-20KHz 8Ω
12.4 IM Distortion (35W/ch.):
(SMPTE): .01% 8Ω
12.13 Power Requirements:
110-125VAC, 50-60Hz (240V Available)
12.14 Shipping Weight:
20 lbs.
Specification conditions are 120VAC 60Hz at 25°C.
13. WARRANTY POLICY
We thank you for your expression of confidence
in Ashly products. The unit you have just purchased is
protected by a limited five year warranty. To establish
the warranty, you must first complete and mail the warranty card attached to your product.
Fill out the information below for your records.
Model Number _________________________________
Serial Number _________________________________
Dealer ________________________________________
Date of Purchase _______________________________
Dealer’s Address _______________________________
_______________________________________________
12.5 Output Hum And Noise:
(dB below full output 20Hz - 20KHz, unweighted)
>100dB
12.6 Damping Factor:
>200 into 8Ω, <1KHz
12.7 Full Power Input Sensitivity:
switchable .775Vrms/.245Vrms
12.8 Voltage Gain:
switchable 26.0dB/36.0dB
12.9 Input Impedance:
20KW balanced
12.10 Bandwidth:
100KHz
12.11 Slew Rate:
20V/µS
12. 12 Rise Time:
2µS 10%-90%
_______________________________________________
Dealer’s Phone _________________________________
Salesperson ____________________________________
OTHER INFORMATION:
_______________________________________________
_______________________________________________
_______________________________________________
12
Operating Manual - SRA-120 Power Amplifier
14. SCHEMATICS:
Figure 15.1: SRA-120 Block Diagram and Wiring Diagram.
13
14
Operating Manual - SRA-120 Power Amplifier
Figure 15.2: SRA-120 Channel One Schematic Diagram.
Operating Manual - SRA-120 Power Amplifier
15
Figure 15.3: SRA-120 Channel Two Schematic Diagram.
Operating Manual - SRA-120 Power Amplifier
ASHLY AUDIO INC. 847 Holt Road Webster, NY 14580-9103
Phone: (716) 872-0010 Fax: (716) 872-0739
Toll Free (800) 828-6308 Internet: http://www.ashly.com
1997 by Ashly Audio Corporation. All rights reser ved worldwide.
Printed in USA 4/97 SRA Rev 3
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