SRA 1222 SRA 2422 SRA 3622 Studio Reference Amplifier User Manual *TD-000107-00* TD-000107-00 rev.
IMPORTANT SAFETY INSTRUCTIONS & EXPLANATION OF SYMBOLS 1- Read these instructions. 2- Keep these instructions. 3- Heed all warnings. 4- Follow all instructions. 5- Do not use this apparatus near water. 6- Clean only with a dry cloth. 7- Do not block any ventilation openings. Install in accordance with QSC Audio Product’s instructions. 8- Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat.
TABLE OF CONTENTS INTRODUCTION General Overview..........................................................................................4 Illustrations.............................................................................5 UNPACKING Unpacking and Inspection..................................................................................6 What is Included.............................................................................................6 SETUP Stand-alone Mounting..........................
INTRODUCTION- General Overview QSC’s SRA Series Amplifier Congratulations on your purchase of the SRA (Studio Reference Amplifier)Series power amplifier. To help you obtain the best results from your purchase, we encourage you to carefully review this manual. With information including connections, configuration and operation, it offers many useful guidelines.
INTRODUCTION- Illustrations Front Panel (gain control security cover removed) 1- Power switch 4- Channel 1 signal and clip indicators 2- Channel 1 gain control 5- Channel 2 gain control 3- Power “on” indicator 6- Channel 2 signal and clip indicators Note! Amplifiers are shipped with the gain controls set at maximum gain (+29 dB) and with gain control security cover installed. See page 10 for security cover removal and installation information.
UNPACKING AND INSPECTION The SRA amplifier is highly durable and carefully packaged. We recommend you inspect the unit carefully after removing it from the packaging, as occasionally there may be damage due to some unfortunate incident during shipment. Report any damage to the shipping carrier. We recommend saving the carton and packing material in case the unit must be shipped back to your dealer, distributor, or service center.
SETUP- Stand-alone mounting (cont’d.) Dimensions shown are useful for non-rack mount installations. Rack Mounting Rack mounting the amplifier Rack mounting is optional. The amplifier fits a 483 mm (19”) width equipment rack. To rack mount the amplifier: 1- Install the rack mount ears (see below and the following page for details). 2- Position the amplifier in the equipment rack and secure all four corners of the front panel using machine screws and washers.
SETUP- Rack Mounting Continued, from previous page..... Attaching the rack mount ears: 1- Remove the two screws holding the front panel end cap in place. Use a #2 cross point screwdriver (Phillips). 2- Place the rack mount ear as shown, aligning it so the screws will go back into their original locations. 3- Insert the screws and tighten being sure to keep the rack mount ear properly aligned. 4- Repeat procedure for the other side When installing equipment into a rack, distribute the units evenly.
SETUP- Supporting the rear of the amplifier Supporting the rear of the amplifier If transporting the amplifier in a loaded equipment rack, support the rear of the amplifier using rear rack ears. They are optional and not included with the amplifier. QSC’s Technical Services Group has the rear rack ear kits for sale. The rear ear kit mounts two ways (shown below): - using machine screws to secure the amplifier to the rear ears - using a post and the notch to support the rear.
SETUP- Removing the Gain Control Security Cover Gain Control Security Cover The amplifier is shipped with its gain controls at their maximum setting of +29 dB and a security cover installed to prevent tampering. To adjust gain settings, remove the cover. Reinstall the cover to prevent unintentional changes. Cover retaining tab detail (left) and corresponding chassis retaining slot (right). Removing the Security Cover 1- Using a 5/64” (or 2 mm) hex key, remove the cover’s retaining screw and set it aside.
SETUP- Installing the Gain Control Security Cover 4- Gain controls exposed for adjustment. Installing the Gain Control Security Cover 1- Slide the cover into the front panel recess. Push it fully to the right and against the front panel. You should feel the cover’s retaining tabs drop into the slot in the front panel.
SETUP- Cooling Requirements Cooling Air Inlet and Exhaust Vents The amplifier has a rear-mounted variable-speed fan. Speed is determined by the temperature of the amplifier’s internal heat sink assembly. Cooling air enters the rear of the amplifier and exhausts from the front vents. If mounting in an enclosure, be certain not to restrict airflow. Warm air exhausts through the front panel vents. Cool air is pulled into the rear of the amplifier.
SETUP- AC Power Requirements AC Power Verify operating voltage before plugging amplifier into AC mains. Make sure the AC mains voltage is the same as specified on the serial number plate. Do not use a smaller gauge cord than supplied with the amplifier! 120 Volt models are supplied with a #14 AWG cordset. 220 Volt models are supplied with 1.0 mm2 cordset. The serial number plate is affixed to the rear panel, bottom right corner, adjacent the AC cord entry.
SETUP- Operating Mode Selection Mode Switches The mode switches are located on the rear panel. The switches are recessed to prevent accidental changes. It is best to set the switches as required before mounting the amplifier in an equipment rack as they may become difficult to access. Change switch positions by sliding the switch left or right. Operate the switches with a small, flat-tip screwdriver or similar tool. Do not use a pencil or other item that could break and fall into the amplifier.
SETUP- Operating Mode Selection: Stereo Stereo Mode Notes: •To operate in stereo mode, set switches 4, 5, 6, and 7 to the left position. •Input connections: connect one input to CH1 and the other to CH2. Use the XLR or RCA connectors. •Output connections: using the binding posts or the Speakon connectors, connect CH1 and CH2 outputs to their respective speakers. Stereo Mode: mode switches 4, 5, 6, and 7 to the left. Biamp Notes: • Switch settings are the same as for stereo mode (see top of page).
SETUP- Operating Mode Selection: Parallel Parallel Mode In parallel mode, channel 1 and channel 2 XLR inputs are connected in parallel. Applying an input signal to either XLR input will drive both channels. SRA amplifier CH1 XLR Input CH1 Output Each channel still has independent gain control, clip limiting, and output connection, just like stereo mode. Do not use the RCA inputs if operating in parallel mode.
SETUP- Operating Mode Selection: Bridge Bridge Mode SRA amplifier In bridge mode, both output channels are interconnected into one, higher power output. The result is one output with about 4 times the peak power and about 3 times the sustained power of a single channel. Use CH1’s gain control, clip limiter, and LF filter. Use channel 1’s XLR or RCA input. CH1 Input XLR or RCA CH1+ Output Mode switches set for bridge Do not useCH2 input! CH2 input is internally bridged with CH1.
SETUP- Clip Limiter Clip Limiters The SRA has separate clip limiters for each channel which respond only to actual amplifier clipping. Amplifier clipping generates internal error signals which cause the clip limiter to quickly reduce amp gain and minimize the overdrive. To preserve as much of the program dynamics as possible, limiting occurs only during actual clipping. Each channel has its own clip limiter switch that can be operated independently.
SETUP- Low Frequency Filter Low Frequency Filters Unless you already have filtering in the signal path preceding the amplifier, use the low frequency filter to protect your speakers from cone overexcursion caused by frequencies below the speaker’s limits. The speaker’s documentation will specify the low frequency limit. Generally, match the frequency selection to your speaker’s low frequency capability.
CONNECTIONS- Inputs, General Information Audio Input Connections Input connections to the SRA can be made with balanced XLR connectors for all operating modes, or unbalanced RCA connectors for Stereo and Bridge mode. We recommend using the balanced XLR connectors whenever possible. Unbalanced connections are prone to noise and interference pickup as well as ground-loop induced hum. The XLR connectors are precision balanced (0.
CONNECTIONS- Inputs: XLR and RCA Connector Pinouts XLR Connector Pinout Jumper Balanced Unbalanced pin 2 pin 3 pin 2 pin 1 pins 1 and 3 RCA (phono plug) Connector Pinout Signal (+) Ground Daisy Chain Example (parallel mode only) All amplifiers being daisy chained must be in parallel mode.
CONNECTIONS- Outputs: Selecting Speaker Cable, Connecting to Loudspeakers Connecting the Outputs to the Loudspeakers There are two basic speaker connection configurations for the SRA amplifier. Stereo and parallel modes use two separate output connections (two loudspeaker loads). Bridge mode uses one output connection (one loudspeaker load). Use either the binding post or the Speakon output connectors. Each connector type is detailed in the following sections.
CONNECTIONS- Outputs: Binding Posts Using the Binding Posts The binding posts support several connection methods; banana plugs, spade lugs, or direct wire connection. European models do not support the use of banana plugs. If using banana plugs, plug into the binding post directly. If using spade lugs, refer to the diagram, below, for acceptable dimensions of lug. If connecting the cable directly, strip about 1/2-inch of insulation from the ends and neatly twist any loose strands.
CONNECTIONS- Outputs: Binding Posts Stereo and Parallel Mode output connections using binding posts Connect each set of binding post outputs to its respective loudspeaker. Z= 2 ohms minimum Maintain proper polarity when hooking up loudspeakers. Connect each red binding post (+, or positive) to the red (or +, positive) terminal of each loudspeaker. Connect each black binding post (-, or negative) to the black (or -, negative) terminal of each loudspeaker.
CONNECTIONS- Outputs: Speakon connectors Speakon Outputs The Speakon connectors offer quick, reliable connection and disconnection of the speakers. Although more expensive than banana or spade-lug style speaker cable termination, the speed, convenience, and reliability make Speakon use popular with portable and live sound setups.
CONNECTIONS- Outputs: Speakon connectors Stereo or Parallel Modes Stereo and Parallel modes use one cable for each channel. Each cable connects to its respective output connector and speaker. 2 wire Speakon cables CH1’s Speakon can be used with a four conductor cable for carrying both outputs. The required signal splitting would take place at the speaker-end of the cable. Speakon cable wiring Bridge Mode Bridge Mode Speakon connection uses CH1’s Speakon only.
CONNECTIONS- Outputs: Speakon Biamp Application Biamp Operation In biamp, one channel is used for lows, while the other channel is used for highs. It requires the use of signal processing equipment between the source material and the amplifier. Always test the system at the lowest practical power level for proper operation. Biamp-ready loudspeakers have no crossover and connect to the amplifier using the four-conductor Speakon.
CONNECTIONS- Remote on/off (remote trigger) Remote Trigger Remote turn-on and turn-off capability is provided by the remote trigger jacks on the rear panel. Remote trigger can be operated by two methods, 12 Volt DC or contact closure (switch, relay). The IN and OUT jacks can be used interchangeably as they are wired in parallel. The amplifier’s front panel power switch must remain in the ON position when using the remote trigger feature.
CONNECTIONS- Remote on/off (remote trigger) 12 VDC Type 12 VDC Remote Trigger Output. Connect to SRA amplifiers using mono mini plug (tip positive, +). 12 Volt DC Remote Trigger For 12 Volt DC remote trigger operation, use a mono (2 terminal) 3.5 mm mini-plug. Do not use a stereo (3 terminal) plug. Processor (or other “master” turn-on device) with 12 VDC remote trigger output. Connect a suitable twoconductor cable to the plug.
CONNECTIONS- Remote on/off (remote trigger) Contact Closure Type Contact closure remote trigger output. Connect to SRA amplifiers using stereo mini plug (ring and sleeve). 12 Volt DC Remote Trigger For contact closure remote trigger operation, use stereo (3 terminal) 3.5 mm mini-plug. Do not use a mono (2 terminal) plug. Processor (or other “master” turn-on device) with contact closure remote trigger output. Connect a suitable twoconductor cable to the plug.
CONNECTIONS- DataPort What is a DataPort? The DataPort is a QSC-specific connection used for interfacing amplifiers, amplifier monitoring devices and signal processors. QSC Audio produces a line of digital signal processing as well as other accessories that plug directly into the DataPort. The DataPort connection provides all the necessary interconnects between the accessory and the amplifier. For home theater and studio applications, DSP can be very useful for “tuning” the response of the system.
USE- Front Panel Controls and Indicators AC Power Switch On the front panel, left side, is the Power switch. The switch is labeled ON, above it and to the left. To turn the power on: Press in on the upper portion of the rocker switch. The amplifier will go through its power-up cycle; the red-colored Clip LEDs will illuminate briefly, then the greencolored Power LED will remain on. To turn the power off: Press in on the bottom portion of the rocker switch.
APPLICATION EXAMPLE- 7.1 Surround 7.1 Surround Application The block diagram, at right, shows how SRA amplifiers might be connected in a 7.1 home theater application. The connections shown are simplified so as to convey the signal routing scheme. All amplifiers shown are operated in stereo mode. Amplifier inputs can be via the RCA or XLR connectors. Amplifier outputs can be via the binding posts or the Speakon connectors.
TROUBLESHOOTING The amplifier won’t turn on when the Power switch is operated (green Power LED not illuminating)• Verify AC power source is providing required voltage. The simplest test is to plug a known-working lamp into the same outlet and verify it works. Properly functioning AC power is required in order to operate the amplifier. • Check each end of the amplifier’s power cord. The AC plug or IEC-type connector needs to be properly inserted. Inspect the cord for damage.
TROUBLESHOOTING I am using the amp for a subwoofer application and it sounds “rubbery”, what’s up?• Verify that the Clip Limiters are OFF. Why? The Clip Limiter is set to respond as quickly as possible after clipping is detected. On low frequency material, this may be perceived as a “rubbery” effect. It may be preferable to turn Clip Limiting off, and let the amp clip occasionally, especially if the speakers are robust.
SPECIFICATIONS- SRA Series SRA1222 SRA2422 SRA3622 Output Power: (watts per channel, stereo/parallel mode) 8 ohms, 20Hz to 20kHz, 0.03% THD 4 ohms, 20Hz to 20kHz, 0.05% THD 2 ohms, 1kHz, 1.0% THD 200 350 600 425 725 1200 725 1100 1800 Output Power: (watts, bridge mode) 8 ohms, 20Hz to 20kHz, 0.10% THD 4 ohms, 20Hz to 20kHz, 0.10% THD 750 1200 1550 2400 2400 3600 Output circuitry: class AB 2-tier class H 2-tier class H Distortion (SMPTE-IM): <0.01% <0.02% <0.
SPECIFICATIONS- SRA Series ALL MODELS Voltage gain: 28× (29 dB) Controls: FrontRear- AC switch, Recessed Ch. 1 and Ch. 2 gain knobs DIP switch (Ch. 1: clip limiter on/off, LF filter on/off, LF filter freq select—20 or 50 Hz; Ch. 2: clip limiter on/off, LF filter on/off, LF filter freq select—20 or 50 Hz; inputs parallel or stereo; bridge mode) Connectors: InputOutputRemoteDataPort- gold-plated RCA, 3-pin XLR (1 each per channel) Neutrik Speakon (1 per channel) and safety-shrouded binding posts two 3.
WARRANTY INFORMATION & HOW TO CONTACT QSC WARRANTY (USA only; other countries, see your dealer or distributor) Disclaimer QSC Audio Products, Inc. is not liable for any damage to speakers, or any other equipment that is caused by negligence or improper installation and/or use of this amplifier product. QSC Audio Products 3 Year Limited Warranty QSC Audio Products, Inc.
QSC Audio Products, Inc. 1675 MacArthur Boulevard Costa Mesa, California 92626 USA “QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office. ©2002 QSC Audio Products, Inc.
