REFERENCE SERIES ™ ™ ™ POWER AMPLIFIERS REFERENCE MANUAL ©2000 Alesis Corporation
Alesis RA150-500 Reference Manual © Copyright 2000, Alesis Studio Electronics, Inc. All rights reserved. Reproduction in whole or in part is prohibited. “RA150/300/500” and “Reference Series” are trademarks of Alesis Studio Electronics, Inc. ALESIS CONTACT INFORMATION Alesis Studio Electronics, Inc. 1633 26th Street Santa Monica, CA 90404 USA Do not use this address for repair service. Telephone: E-Mail: Website: 800-5-ALESIS (800-525-3747) support@alesis.com http://www.alesis.
CONTENTS Introduction ...................................................... 2 How to Use This Manual........................... 2 IMPORTANT SAFETY INSTRUCTIONS .... 3 Instructions de Sécurité Importantes (French) ...... 4 Beim Benutzen dieses Produktes beachten Sie bitte die folgenden Sicherheitshinweise: (German) .......................................................... 5 CE Declaration of Conformity............................. 6 ABOUT THE RA150/300/500............. 7 Principal Features ..............
Introduction/Safety Instructions INTRODUCTION Thank you for purchasing this Alesis RA150, RA300, or RA500™ Reference Series power amplifier. To take full advantage of this amplifier’s functions, and to enjoy long and trouble-free use, please read this user’s manual carefully. HOW TO USE THIS MANUAL This manual is divided into the following sections describing the various functions and applications for the RA series amplifier.
Introduction/Safety Instructions IMPORTANT SAFETY INSTRUCTIONS SAFETY SYMBOLS USED IN THIS PRODUCT This symbol alerts the user that there are important operating and maintenance instructions in the literature accompanying this unit. This symbol warns the user of uninsulated voltage within the unit that can cause dangerous electric shocks. This symbol warns the user that output connectors contain voltages that can cause dangerous electrical shock.
Introduction/Safety Instructions INSTRUCTIONS DE SÉCURITÉ IMPORTANTES (FRENCH) SYMBOLES UTILISÉS DANS CE PRODUIT Ce symbole alèrte l’utilisateur qu’il existe des instructions de fonctionnement et de maintenance dans la documentation jointe avec ce produit. Ce symbole avertit l’utilisateur de la présence d’une tension non isolée à l’intérieur de l’appareil pouvant engendrer des chocs électriques.
Introduction/Safety Instructions BEIM BENUTZEN DIESES PRODUKTES BEACHTEN SIE BITTE DIE FOLGENDEN SICHERHEITSHINWEISE: (GERMAN) 1. Lesen Sie die Hinweise. 2. Halten Sie sich an die Anleitung. 3. Beachten Sie alle Warnungen. 4. Beachten Sie alle Hinweise. 5. Bringen Sie das Gerät nie mit Wasser in Berührung. 6. Verwenden Sie zur Reinigung nur ein weiches Tuch. Verwenden Sie keine flüssigen Reinigungsmittel. Dies kann gefährliche Folgen haben. 7.
Introduction/Safety Instructions CE DECLARATION OF CONFORMITY Manufacturer’s Name: Alesis Corporation Manufacturer’s Address: 1633 26th Street Santa Monica, CA 90404 USA declares, that the product: Product Name: RA150/300/500 Model Type: Audio amplifier conforms to the following Standards: Safety: EN60065 EMC: EN55103:1997 Class B (all tests were performed with fully- shielded cabling.) European Contact: Sound Technology 17 Letchworth Point, Letchworth, Hertfordshire, SG6 1ND, England.
Chapter 1: Introduction CHAPTER 1 ABOUT THE RA150/300/500 PRINCIPAL FEATURES Please remember that a power amplifier is a high-current, high-power device and should be treated with respect and care. Even if you are an audio veteran, we urge you to read the entire manual to make the best use of the RA150/300/500. Thank you for purchasing an Alesis Reference Series power amplifier, one of the most advanced and highest value amplifiers available.
Introduction: Chapter 1 Reference Series Features- 8 • DC coupled, fully complementary discrete amplifier topology • Actively biased, dual differential input stages • Wide bandwidth, low distortion design • Fully protected from all fault conditions • LED output level metering (RA 300, RA 500) • Front panel level controls • Overload/Fault indicators • Bridged mono operation • Balanced 1/4” & RCA single-ended input connectors • XLR input connectors (RA 300, RA 500) • Heavy-duty, dual b
Chapter 2: Connections CHAPTER 2 CONNECTIONS UNPACKING AND INSPECTION Your Alesis RA150/300/500 was carefully packed at the factory, and the shipping carton was designed to protect the unit during shipping. Do not discard the packing materials; they may be helpful in the unlikely event that you need to return your RA150/300/500 for servicing, or for transporting the amplifier when it is not mounted in a rack or other enclosure.
Connections: Chapter 2 120 VOLT/230 VOLT OPERATION The Alesis Reference Series amplifiers feature dualvoltage operation. The AC input voltage is selected by a recessed switch on the back panel. The tab is recessed and a tool (small screw driver, pencil, pen, etc.) is required to shift from 120-volt to 230-volt operation. Units sold in areas with 120V power (as in the United States) should come with the switch already set to that position.
Chapter 2: Connections refrigerators, coffee pots, toasters, air conditioning, or stage lighting, plug the RA150/300/500 into a different circuit with a lesser load. • OPERATING ENVIRONMENT TEMPERATURE CONSIDERATIONS IN RACK MOUNTING The RA150/300/500 can be mounted in an equipment rack (taking up 2 rack spaces or 3 spaces for the RA500), placed on a shelf, tucked away in a vocal booth, etc. When you install it, keep in mind that heat is the major enemy of electronic equipment.
Connections: Chapter 2 MOUNTING ON A SHELF OR IN A NON-RACK ENCLOSURE AVOIDING ELECTROMAGNETIC INTERFERENCE To mount the amplifier on a shelf or other flat surface, Alesis recommends using the enclosed stick-on feet to avoid scratching the shelf’s surface with the amplifier bottom.
Chapter 2: Connections INPUTS INPUT JACK CHARACTERISTICS The RA150/300/500 include two balanced, 1/4" TRS (tip-ring-sleeve, 3-conductor) phone jack inputs, and unbalanced RCA/phono inputs. The RA300 and RA500 feature combination XLR input jacks as well. The inputs are wired according to IEC standards, as shown in the table below.
Connections: Chapter 2 Warning: Be sure that the AC power is off prior to connecting or disconnecting any signal wiring. The input circuits of the Alesis amplifiers are electronically balanced. They may be fed from either symmetrical (“balanced”) or unbalanced sources. On the RA300 and RA 500, there are two combination XLR/1/4” (6.3 mm) jacks provided, one for each channel.
Chapter 2: Connections CABLES CABLE W IRING TIPS Use only high quality cables when interfacing equipment with the RA150/300/500. These should be good quality shielded cables with a stranded (not solid) internal conductor. Although quality cables cost more, they do make a difference. Route cables to the RA150/300/500 correctly by observing the following precautions.
Connections: Chapter 2 BALANCED OR UNBALANCED ? With long cable runs (e.g., over 6 meters/20 feet) in noisy electrical environments, the cable itself can act as an “antenna” and pick up RF fields, AC hum, or other types of interference. To avoid these problems, many professional studios and live sound companies use balanced line connections.
Chapter 2: Connections Isolation transformer or direct box If your mixer or other sound source doesn't have a balanced output, you may turn it into a balanced signal with an external device, either active (electronic, powered) or passive (a transformer). These commonly available audio accessories have a balanced line output, usually in the form of an XLR connector, and an unbalanced line input, usually in the form of a 1/4" phone jack.
Connections: Chapter 2 OUTPUTS SPEAKER CABLES Warning: Be sure that the AC power is off prior to connecting or disconnecting any signal wiring. W HAT'S THE LOAD IMPEDANCE? Alesis amplifiers can reliably drive 4 Ω loads in Stereo mode and 8 Ω loads in Bridged Mono mode. However, the impedance of a loudspeaker varies with frequency, and its nominal rated impedance is not necessarily its minimum impedance.
Chapter 2: Connections In recent years, expensive audiophile cables of high current capacity have appeared. These have been somewhat controversial; some feel the extra expense produces an audible improvement in sound quality, while others find no sonic difference between audiophile cables and other heavy-duty wiring. While Alesis does not endorse any particular brand of cable, we suggest that you investigate different cable types for yourself to discover if they improve the sound of your particular setup.
Connections: Chapter 2 THE IMPORTANCE OF SPEAKER POLARITY OUTPUT CONNECTIONS FOR BRIDGED OPERATION The speaker cone’s motion should mimic the instrument it’s reproducing. For example, a kick drum pushes air toward you on the initial transient, so a speaker reproducing a kick drum should have its cone push air toward you. If the polarity is reversed, the cone will suck air away from you.
Chapter 3: Operation CHAPTER 3 OPERATION FRONT PANEL CONTROLS ON-OFF SWITCH The following diagram shows the various front panel controls, as described next. Press the switch to turn the amplifier on, and again to turn the amplifier off. RA150 Upon turning on the amplifier, the power indicator LED will light. Note that in direct sunlight, this light may not be easily visible. RA300 RA500 VOLUME CONTROLS Detented level controls are on the front panel, where they can be easily adjusted if necessary.
Operation: Chapter 3 PROTECT/CLIP INDICATORS Clip lights for each channel indicate the onset of actual clipping. Even if the problem occurs for only a few microseconds, a pulse-stretching circuit will allow the LED to light long enough for you to see that a problem is occurring. Because of the RA150/300/500’s ability to enter and exit clipping with as few audible artifacts as possible, you may not hear any distortion even if the indicator flashes.
Chapter 3: Operation USING THE RA150 AS A HEADPHONE AMPLIFIER The RA150 is particularly suited for use driving high-impedance headphones in studio applications. However, the power is considerably greater than that provided by most "headphone amplifiers", which are often rated at 1 watt or below. Due to the high efficiency of headphones and the power of the amplifier, serious hearing damage may result from misuse of this product. Exercise caution regarding sound levels.
Operation: Chapter 3 ABOUT GROUND LOOPS A hum or buzz may be introduced into some audio systems by a phenomenon known as a ground loop. This can occur if a piece of equipment “sees” two or more different paths to ground, as shown below. shielded cable Device B Device A path 1 path 2 To AC power service One path goes from device A to ground via the ground terminal of the three-conductor AC power cord, but A also sees a path to ground through the shielded cable and AC ground of device B.
Chapter 3: Operation SYSTEM SETUP AND TESTING Before applying power for the first time, double check the wiring to insure that everything is firmly connected and that the proper signals are being fed to the proper places. If a low frequency signal in a multi-amplified system is applied to a high frequency transducer, the transducer can be damaged, and a loose connection can cause noise which can damage any transducer.
Operation: Chapter 3 Amplifier input clipping On the other hand, the maximum level at the amplifier’s input terminals is +26 dBu, regardless of the setting of the channel input level controls. It is possible that the output signal from the source may be too high and, thus, distorted before it reaches the amplifier gain control, either because the source device is clipping or the amplifier input stage is overloaded.
Chapter 4: Troubleshooting CHAPTER 4 TROUBLESHOOTING TROUBLESHOOTING INDEX Once all gain adjustments are made and proper operation is confirmed, no special considerations are required for Alesis Reference Series amplifiers. Aside from the front panel gain controls, there are no user adjustments or routine maintenance operations necessary (or available).
Troubleshooting: Chapter 4 Symptom Audio cuts in and out Unit shuts down, all lamps are off Thin or Muffled Sound Cause Intermittent amplifier input signal If the sound cuts out for a minute or two and then returns, the amplifier may be overheating and cycling through thermal protect mode Dirty volume pot Blown fuse Internal thermal fuse activated Defective loudspeaker drivers In a multi-amplified system with a low level crossover network, bad outputs from the network, or improperly connected loudspeake
Chapter 4: Troubleshooting OBTAINING REPAIR SERVICE Before contacting Alesis, check over all your connections, and make sure you’ve read the manual. Customers in the USA and Canada: If the problem persists, contact Alesis USA at www.alesis.com & find the Product Support web page. Make sure you have the unit’s serial number with you. If necessary contact one of our technicians; if appropriate, you will be given a return order (RO) number and instructions on how to return the unit.
Specifications SPECIFICATIONS Reference 150 Size Rack units Weight Rated output, per channel 4 ohms @ 1kHz, .02% THD+N 8 ohms @ 1kHz, .05% THD+N 8 ohms, bridged mono mode Signal to Noise Ratio Frequency Response Damping Factor Slew Rate Input Sensitivity Maximum input level Input impedance Crosstalk Output offset 18.9" W x 3.9" H x 10.25" D (480mm x 99 mm x 260 mm) 2RU height 15lbs = 6.
Specifications Reference 500 Size Rack units Weight Rated output, per channel 4 ohms @ 1kHz, .02% THD+N 8 ohms @ 1kHz, .05% THD+N 8 ohms, bridged mono mode Signal to Noise Ratio Frequency Response Damping Factor Slew Rate Input Sensitivity Maximum input level Input impedance Crosstalk 18.9" W x 5.63" H x 10.71" D (480mm x 143 mm x 272 mm) 3 RU height 28.5lbs = 13.
Specifications RA300 RA500 32 RA150/300/500 Reference Manual
Specifications Architect's and Engineer's Specifications The power amplifier shall be a two-channel unit capable of being switched to single-channel bridged mode operation. All components shall be of high quality and mechanical construction and optimized for high reliability under adverse physical and electrical conditions. Cooling shall be convection-type only, with no fan mounted inside the amplifier.
Index INDEX 120-volt to 230-volt conversion, 10, 22 AC cord, 9 AC power, 10 balanced inputs, 14 balanced lines, 16 banana plugs, 19 Bridged Mono mode, 17, 20 cables shielded input, 15 speaker, 18 class AB, 7, 33 cooling, 7, 11 direct box, 17 Fuse, 10 gain setting, 25 ground audio, 9, 14 ground lifter, 24 ground loop, 24 grounding, 3 headphone amplifiers, 23 heat sink, 11 high-temperature operation, 11 impedance input, 17 speaker, 18 input clipping, 26 Inputs, 13 magnetic fields, 12 Maintenance, 28 Meters,
ALESIS LIMITED WARRANTY ALESIS ("ALESIS") warrants this product to be free of defects in material and workmanship for a period of one (1) year for parts and for a period of one (1) year for labor from the date of original retail purchase. This warranty is enforceable only by the original retail purchaser and cannot be transferred or assigned. The purchaser should register thier product online @ www.alesis.com within 14 days of purchase.
Warranty 36 RA150/300/500 Reference Manual
