ART SLA-4 Four Channel Studio Linear Amplifier

Introduction

Thank you for purchasing the ART SLA-4 Four Channel Studio Linear Amplifier. This unit offers a superb level of sound quality, combining clean and powerful linear circuitry with a straightforward user interface. The SLA-4 delivers the power needed for a wide variety of project and professional studio environments, broadcast, and installation applications.

Features:

• Extremely Low Noise, Discrete Linear Design
• 4 x 100 Watts/Channel @ 8 Ohms, 140 Watts/Channel @ 4 Ohms
• 2 x 200 Watts/Channel @ 16 Ohms, 280 Watts/Channel @ 8 Ohms (bridged)
• 2 x 100 Watts/Channel @ 8 Ohms & 1 x 280 Watts @ 8 Ohms (bridged)
• Toroidal Transformer
• 10 Hz to 40 kHz Frequency Response
• 1/4" TRS, and Euroblock Balanced Inputs
• Detente Gain Knobs
• Multi-way Binding Post Outputs
• Low Profile 1U Rack-Mountable Design
• Thermal dependent Cooling System
• Ideal for Pro and Project Studios, Broadcast, and Installation applications

Important Safety Instructions – Read First

CAUTION ⚠️ RISK OF ELECTRIC SHOCK – DO NOT OPEN

ATTENTION: RISK OF ELECTRIC SHOCK – DO NOT OPEN

The symbol ⚠️ indicates the presence of uninsulated dangerous voltage inside the enclosure, which may be sufficient to constitute a risk of shock.

The symbol ℹ️ alerts you to important operating and maintenance instructions in the accompanying literature. Please read the manual.

• Read instructions: Retain these safety and operating instructions for future reference. Heed all warnings printed here and on the equipment. Follow operating instructions printed in this user guide.
• Do not open: There are no user serviceable parts inside. Refer any service work to qualified technical personnel only.
• Power sources: Only connect the unit to mains power of the type marked on the rear panel. The power source must provide a good ground connection.
• Power cord: Use the power cord with a sealed mains plug appropriate for your local mains supply as provided with the equipment. If the provided plug does not fit your outlet, consult your service agent. Route the power cord so it is not likely to be walked on, stretched, or pinched by items placed upon or against it.
• Grounding: Do not defeat the grounding and polarization means of the power cord plug. Do not remove or tamper with the ground connection on the power cord.
• Ventilation: Do not obstruct the ventilation slots or position the unit where the air required for ventilation is impeded. If the unit is to be operated in a rack, case, or other furniture, ensure it is constructed to allow adequate ventilation.
• Moisture: To reduce the risk of fire or electrical shock, do not expose the unit to rain, moisture, or use in damp or wet conditions. Do not place a container of liquid on it, which may spill into any openings.
• Heat: Do not locate the unit in a place close to excessive heat or direct sunlight, as this could be a fire hazard. Locate the unit away from any equipment that produces heat, such as power supplies, power amplifiers, and heaters.
• Environment: Protect from excessive dirt, dust, heat, and vibration when operating and storing. Avoid tobacco ash, drink spillage, and smoke, especially that associated with smoke machines.
• Handling: To prevent damage to the controls and cosmetics, avoid rough handling and excessive vibration. Protect the controls from damage during transit. Use adequate padding if you need to ship the unit. To avoid injury to yourself or damage to the equipment, take care when lifting, moving, or carrying the unit.
• Servicing: Switch off the equipment and unplug the power cord immediately if it is exposed to moisture, spilled liquid, objects fallen into openings, the power cord or plug becomes damaged during a lightning storm, or if smoke odor or noise is noted. Refer servicing to qualified technical personnel only.
• Installation: Install the unit in accordance with the instructions printed in the user guide.

Installation

The SLA-4 can be used in a wide variety of applications, from project or professional studio environments to commercial sound installations. Self-contained in a steel and aluminum enclosure, the unit is designed for many years of use. For greater reliability, it is recommended not to place the unit directly under or on top of other sources of heat. It is important that any rack-mountable unit is properly ventilated, and the SLA-4 is no exception.

AC Power Hookup

The SLA-4 has an internal power supply designed to operate at 120 VAC @ 50 to 60 Hz. Units manufactured for use outside of North America have been modified to comply with the required electrical specifications.

Audio Input Connections

Audio connections to the SLA-4 are balanced or unbalanced 1/4" [Tip = Hot (+), Ring = Cold (-), Sleeve = (Ground)].

Euroblock connections can be wired balanced or unbalanced. Refer to the diagram on page 8 for details.

Speaker Load Safety Precautions

Warning: For optimum performance and reliability, do not operate the amplifier with a speaker load of less than 4 Ohms per channel, or any combination of speakers that together are less than 4 Ohms.

• Using one speaker per channel, it must be rated at 4 Ohms or greater.
• When using two speakers per channel, in parallel, they must each be rated at 8 Ohms, or greater.
• When in bridge mode, the speaker load should be 8 Ohms, or greater.

Controls & Indicators – Front Panel

The front panel features controls and indicators for managing the amplifier's operation.

Front Panel Description: The front panel displays four channel level controls, a power switch, and indicator LEDs for signal presence and clipping for each channel.

Power Switch

The Power Switch is located in the center of the unit. During initial installation, ensure all channel level controls are set to a low volume level before applying power.

Channel Level Controls

The dials for the four channel level controls are located to the left and right of the Power Switch. When set to zero (fully clockwise), the level is at maximum. The level is reduced as you turn the control counterclockwise. Full attenuation is at – infinity. The level controls are detented and calibrated in dB.

Signal Indicator LED

This LED indicates that a signal is present. The LED glows when the amplifier's output signal is within approximately 30dB of full scale.

Clip Indicator LED

This LED indicates that the power amp is near or at clipping. This LED illuminates when the output signal from the amplifier begins to distort. If significant clipping occurs, lower the input levels to reduce distortion and the risk of damage to speakers/monitors.

Protect Indicator LED

This LED glows when either or both channels enter protect mode. In protect mode, the output signal to the speakers is muted (channel specific). If a fault condition occurs at the speaker outputs (due to a severe load or short), the LED will light until the fault is removed. Channels One and Two share a Protect LED, as do channels Three and Four. The Protect LEDs also illuminate during power up and down to indicate that the signal is muted.

Rear Panel Connections

The rear panel houses all input and output connections, facilitating easy interfacing with various audio equipment. Standard 1/4" and Euroblock inputs, along with multi-way binding post outputs, simplify patching.

Inputs

The SLA-4 offers two styles of input connections: 1/4" TRS and Euroblock. These are used to connect the output signal from a mixer, preamplifier, crossover, or EQ to the amplifier. Balanced connections are recommended for cable runs longer than 20 feet. For cable runs under 20 feet, unbalanced connections can be used.

The two different input connection types can also be used to link a parallel connection to another amplifier. For example, connect a 1/4" cable to the input of channel one, and then connect from the Euroblock connections to another amplifier channel input.

1/4" Input Jacks

The 1/4" Input jacks are wired as follows: Tip is positive, Ring is negative, and Sleeve is ground. This connection supports both balanced and unbalanced connections.

Euroblock Barrier Strips

Insert wires into the barrier strip and secure them with the setscrew. Each barrier strip can be removed for quick service without disconnecting individual wires.

Stereo / Bridge Amp Mode Switches

The SLA-4 Amp Mode Switches allow selection between Stereo and Bridged Mono Modes. Two separate switches enable bridging of channels 1 and 2, or channels 3 and 4, or both channel pairs. This provides flexibility for optimal utilization in 2, 3, or 4 channel applications. Ensure the power is off and speakers are wired appropriately before changing mode switches.

Output Binding Post

The SLA-4 Outputs are multi-connection jacks compatible with banana jacks, spade connectors, or bare wire.

• Bare Wire Connections: Loosen the red and black caps on the binding posts (do not remove completely). Strip back the wire insulation approximately 1/2 inch, then insert the bare wire into the hole on the side of the plastic assembly. Once inserted, screw the binding post cap down onto the wire. Ensure the wire connected to one post does NOT come into contact with that of another post.
• Spade Connector: Loosen the red and black caps on the binding posts (do not remove completely). Insert the spade connector into the binding post and tighten the caps down on the spade connector. Ensure the connection to one post does NOT come into contact with another post.
• Banana Plug: Insert the banana plugs into the caps of the binding posts. Ensure the red and black caps on the binding posts are tightened down completely and securely connected to avoid the possibility of the banana plugs popping out.

Cooling Fan

The SLA-4 features a cooling fan with thermal-dependent fan-assisted convection cooling. The fan speed is dependent on the internal ambient temperature of the unit and operates at two different levels. Do not block the fan or constrict air circulation, as this may cause the amplifier to overheat and/or shut down.

Rear Panel Diagram Description

The rear panel features:

• Balanced Inputs: Labeled for CH 3, CH 4, CH 1, CH 2. Each input has associated polarity markings (+/-).
• Output Binding Posts: Arranged for CH 3/4 and CH 1/2. Each pair of binding posts is marked with polarity (+/-) and impedance ratings: 8 Ohms Minimum for Bridge Mode, 4 Ohms Minimum for Stereo Mode.
• Stereo/Bridge Switches: Located near the CH 1/2 and CH 3/4 output groups, allowing selection of operating modes.
• Safety Warnings: "TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK DO NOT EXPOSE TO RAIN OR MOISTURE" is prominently displayed.
• Power Input: Standard IEC power connector.
• Fuse Holder: Accessible for fuse replacement.
• Certifications: CE marking.
• Manufacturer Information: "Designed and developed in the USA", "Manufactured in Taiwan".

Fuse and AC Power Input

Fuse

The SLA-4 utilizes a (T10A 250v 20mm) 10 Amp fuse. Replace blown fuses only with a fuse of equal rating.

AC Power Input

The SLA-4 features an internal power supply. Plug the detachable cable into a standard wall outlet. Ensure the supplied voltage matches the required voltage labeled on your amplifier. Never plug the amplifier into an outlet that does not match the required voltage, as serious damage could result.

Operation

Connect source audio material directly into each input channel and set the channel level controls to provide an appropriate level to each channel's speakers.

Normal Operation

For a typical four-channel setup, connect the source (mixer, EQ, etc.) outputs into channels one through four of the amplifier. Connect your speakers to the outputs on the rear of the amplifier. Ensure your front level controls are turned down to their lowest level (full counter-clockwise). Turn the amplifier on, and then slowly turn the input level up. Use the front level controls to regulate the output volume. Avoid raising the volume past the clip level; however, an intermittent clip signal is acceptable.

Mono Bridge Operation

Ensure the amplifier is shut off. Press the appropriate Stereo/Bridge switch (on the back) to the "in" position. Connect an input signal to channel 1 (when bridging channels 1 and 2) or channel 3 (when bridging channels 3 and 4). Connect your speaker across the two appropriate red output-binding posts on the rear of the amplifier. Turn your equipment on; the amplifier should be the last piece of equipment turned on (ensure its volume is turned down). Apply an input signal to your amplifier. Use channel 1 or channel 3 level controls to adjust your amplifier's output level.

Protection

The SLA-4's output circuitry is fully protected from short circuits. An ultrasonic network decouples RF from the output, helping to keep the amplifier stable with reactive loads.

The SLA-4's external heatsinks dissipate heat during normal operation. A rear-mounted variable-speed fan provides additional cooling for the amplifier's internal circuitry as needed. Typically, at low to moderate signal levels, the fan runs at a low idle speed. If the internal temperature rises above a set level, the fan switches to a higher speed to remove more heat. If the heatsinks reach 194 degrees Fahrenheit, the amplifier will mute until it cools down sufficiently for safe operation. Ensure adequate ventilation around the heatsinks if rack-mounting the SLA-4 in an enclosed space.

The SLA-4 is fully protected against shorts, opens, over-current, and over-voltage. A relay disconnects the outputs under any of these fault conditions and automatically returns to normal operation once the fault is removed.

The amplifier is stable into loads as low as 2 ohms (stereo mode) and 4 ohms (bridged mode) for fixed or permanent installations. However, for continuous operation of all channels at mid to high signal levels, the amplifier should be operated with a minimum load of 4 ohms per channel in stereo mode and 8 ohms per channel in bridged mode. Otherwise, the overload and thermal protection circuitry may cycle the amplifier on and off as it protects itself.

Warranty Information

Limited Warranty

Applied Research and Technology will provide warranty and service for this unit in accordance with the following terms:

Applied Research and Technology (ART) warrants to the original purchaser that this product and its components will be free from defects in workmanship and materials for a period of three years from the date of purchase. ART will, without charge, repair or replace, at its option, defective products or component parts upon prepaid delivery to the factory service department or an authorized service center, accompanied by proof of purchase date in the form of a valid sales receipt.

Exclusions

This warranty does not apply in the event of misuse or abuse of the product, or as a result of unauthorized alterations or repairs. This warranty is void if the serial number is altered, defaced, or removed.

ART reserves the right to make changes in design or additions or improvements to this product without obligation to install the same on products previously manufactured.

ART shall not be liable for any consequential damages, including without limitation, damages resulting from loss of use. Some states do not allow limitations of incidental or consequential damages, so the above limitation or exclusion may not apply to you. This warranty gives you specific rights, and you may have other rights that vary from state to state.

For units purchased outside the United States, an authorized distributor of Applied Research and Technology will provide service.

Service

The following information is provided in the unlikely event that your unit requires service:

1. Be sure that the unit is the cause of the problem. Check that the unit has proper power supplied, all cables are connected correctly, and the cables themselves are in working condition. You may want to consult with your dealer for assistance in troubleshooting or testing your particular configuration.
2. Contact the Customer Service department via the website at: http://www.artproaudio.com. Navigate to the "Resources" page and fill out the "Return Authorization Request" form. Your report will be submitted to the department for immediate evaluation.
3. If returning the unit for service, pack the unit in its original carton or a reasonable substitute. The original packaging may not be suitable as a shipping carton, so consider placing the packaged unit in another box for shipping. Print the RA number clearly on the outside of the shipping box.
4. Include, with your unit, a note with the RA number and your contact information, including a daytime phone number, preferably attached to the top of the unit.

Fill in the following information for your reference:

Date of purchase: _________________________

Serial Number: _________________________

SLA-4 Specifications

ART maintains a policy of constant product improvement. ART reserves the right to make changes in design or make additions to or improvements upon this product without any obligation to install the same on products previously manufactured. Therefore, specifications are subject to change without notice.