Ashly SRA-120 User Manual
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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