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Alesis POWER AMPLIFIER RA150, Reference Manual

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Alesis POWER AMPLIFIER RA150 Reference Manual Download Page 10

Introduction:  Chapter 1

8

RA150/300/500 Reference Manual

Reference Series Features-

•

 

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 binding post output
connectors

•

 

Relay-controlled turn on/off

•

 

Silent, convection-cooled design

•

 

Heavy-duty steel chassis

A

BOUT THIS MANUAL

In most respects, the three different amplifiers
covered by this manual are similar except for their
power ratings.  Operational differences will be
noted individually.

Summary of Contents for POWER AMPLIFIER RA150

Page 1: ...REFERENCE SERIES POWER AMPLIFIERS REFERENCE MANUAL 2000 Alesis Corporation ...

Page 2: ...t 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 800 5 ALESIS 800 525 3747 E Mail support alesis com Website http www alesis com ...

Page 3: ...rference 12 Inputs 13 Input Jack Characteristics 13 Cables 15 Cable Wiring Tips 15 Balanced or Unbalanced 16 Outputs 18 What s the Load Impedance 18 Connectors 18 Speaker Cables 18 Connecting Speaker Cables to Binding Posts 19 The Importance of Speaker Polarity 20 Output Connections for Bridged Operation 20 OPERATION 21 Front Panel Controls 21 Volume Controls 21 On Off Switch 21 Mute Switch 21 Pro...

Page 4: ...wledge about amplifiers should use the table of contents to look up specific functions Chapter 1 Introduction If you want to start using the RA150 300 500 right away here s a one page guide to hooking it up and trying it out Chapter 2 Connections This chapter gives detailed instructions for connecting the RA150 300 500 to a variety of typical sound systems Chapter 3 Operation This section explains...

Page 5: ...g periods of time 12 Do not defeat the safety purpose of the polarized or grounding type plug A polarized plug has two blades with one wider than the other A grounding type plug has two blades and a third grounding prong The wide blade or the third prong are provided for your safety When the provided plug does not fit into your outlet consult an electrician for replacement of the obsolete outlet 1...

Page 6: ...rdon secteur ne rentre pas dans la prise de courant demandez à un électricien qualifié de remplacer la prise 10 Evitez de marcher sur le cordon secteur ou de le pincer en particulier au niveau de la prise et aux endroits où il sor de l appareil 11 N utilisez que des accessoires spécifiés par le constructeur 12 N utilisez qu avec un stand ou table conçus pour l utilisation d audio professionnel ou ...

Page 7: ...daß die jeweiligen Geräte sicher installiert sind um Schäden und Verletzungen zu vermeiden Wenn Sie einen Rollwagen benutzen achten Sie darauf das dieser nicht umkippt um Verletzungen auszuschließen 12 Ziehen Sie während eines Gewitters oder wenn Sie das Gerät über einen längeren Zeitraum nicht benutzen den Netzstecher aus der Steckdose 13 Die Wartung sollte nur durch qualifiziertes Fachpersonal e...

Page 8: ...ta 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 Phone 44 1462 480000 Fax 44 1462 480800 October 2000 ...

Page 9: ...ch can accept large diameter wire or 3 4 19 mm spaced dual banana plugs A recessed rear panel switch allows easy selection of stereo or bridged monaural operating modes AC power entry is via a detachable grounded IEC connector cable AMPLIFIER TOPOLOGY The amplifier sections of the Reference Series utilize a direct coupled fully complementary circuit topology The input stages are a dual differentia...

Page 10: ...ing 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 binding post output connectors Relay controlled turn on off Silent convection cooled design Heavy duty steel chassis ABOUT THIS MANUAL In most respects the three different amplifiers covered by this manual ar...

Page 11: ... from your dealer contact the dealer as soon as possible for assistance POWER CONSIDERATIONS THE AC CORD AND GROUNDING The RA150 300 500 s IEC spec AC cord do not substitute any other type of AC cord is designed to connect to an outlet that includes three pins with the third round pin connected to ground earth The ground connection is an important safety feature designed to keep the chassis of ele...

Page 12: ...y not be able to deliver its full rated output both steady state and peak with the result that the sound character can dramatically suffer In short any amplifier will only sound good when connected to adequate AC power The maximum audio output rating of each amp 200 watts bridged for the RA150 to 1000 watts bridged for the RA500 does not represent the total AC power consumption by the unit The fol...

Page 13: ...not absolute limits but Alesis cannot guarantee that the RA150 300 500 will meet its published specs if operated outside of these ranges If necessary use a fan to blow air over the RA150 300 500 and promote cooler operation Prevent the side heat sink fins from becoming obstructed There should be enough airspace around the amplifier for it to breathe Always allow adequate ventilation behind the RA1...

Page 14: ... step insures that no small amounts of oil or other substances will inhibit proper adhesion of the feet 3 When the surface has dried attach the feet Please observe the comments on thermal considerations given under Temperature Considerations in Rack Mounting no matter where or how the amp is mounted AVOIDING ELECTROMAGNETIC INTERFERENCE Because the RA150 300 500 contains a large power transformer ...

Page 15: ...red according to IEC standards as shown in the table below These are compatible with the low impedance unbalanced or balanced line level outputs typically emanating from equipment such as mixers synthesizers samplers direct boxes crossovers etc Electric guitars microphones and other low level high impedance output devices require a preamp Connection XLR Phone Jack RCA phono jack Audio Ground Pin 1...

Page 16: ...nbalanced source with an Alesis amplifier Connect the High signal wire as shown in Table 1 and connect the shield wire to both the Low and Audio Ground input connections See Figures 4 and 6 If a two wire tip and sleeve only phone plug is used for an unbalanced input the sleeve of the plug will automatically connect the Low and Audio Ground connections together inside the amplifier Long input cable...

Page 17: ...ay contact cleaner on a clean lint free cloth and vigorously rub the plug until the oxidation is removed Although Alesis does not endorse any specific product chemicals such as Tweek and Cramolin when applied to electrical connectors are claimed to improve the electrical contact between connectors NEVER PLUG OR UNPLUG INPUT CABLES UNLESS THE RA150 300 500 IS TURNED OFF UNPLUGGED FROM THE AC LINE O...

Page 18: ... XLR to XLR cable A slightly more expensive balanced connector is the XLR type most commonly sold as a microphone cable The main advantage of this is that the connector locks in place making it more resistant to accidental disconnection If your mixing console has XLR outputs and you have the RA300 or RA500 amplifier you may connect it with an XLR female to XLR male cable The mixer will have an XLR...

Page 19: ...r direction Advantages Good frequency response specs no inherent hum pickup less expensive than transformers Disadvantages Requires power generates some noise To feed the same source to several different amplifiers The input impedance of the Alesis amplifiers is 20 kΩ in balanced and 10 kΩ in unbalanced configuration Thus the inputs of several amplifiers may be connected in parallel if desired The...

Page 20: ...eakers are very important Speaker cables must deliver large amounts of peak current to a speaker To complicate matters further a speaker represents an inductive load and is more difficult to drive than a purely resistive load Speakers are also very low impedance devices Any resistance between the amp output and speakers will degrade the damping factor efficiency and ultimately the sound quality Al...

Page 21: ...posts and check that the wires can t be pulled out Tip It may be easier to attach the speaker wires before the amplifier is mounted into a rack Using a banana plug Standard dual banana plugs such as Pomona type MDP should be used if the speaker cable will be removed from the amplifier often for example when used in a portable PA system In this case simply 1 Loosen the setscrews in the shaft of the...

Page 22: ...l amplifier it is possible to use it as a mono amplifier with twice the power This uses both sides of the amplifier in a push pull configuration so the speaker must be wired to the amp differently However note that the minimum load impedance is 8 ohms instead of the 4 ohms in stereo operation To connect a speaker in bridged mono mode Following the instructions on the previous page for binding post...

Page 23: ...ly visible When powering a system on or off it is usually advisable to turn on the power amplifiers last and to turn them off first so that any turn on or turn off transient signals generated by other equipment in the system are not amplified and sent to the loudspeakers However the RA150 300 500 s output protection relays have a 4 5 second turn on delay which keeps the loudspeakers disconnected w...

Page 24: ...mal protection circuitry is activated because the amplifier is overheating Thermal protection will stop automatically when the amplifier cools down BACK PANEL CONTROLS AC VOLTAGE SWITCH Located near the power inlet is a recessed switch that allows voltage conversion from 120 volt to 230 volt operation Use a small tool or pen to change the setting of this switch only if it is set to the wrong value...

Page 25: ...ing during a session CHOOSING THE CORRECT SPEAKERS Near field monitoring through reference speakers has become the preferred way to monitor and mix music With near field monitoring small speakers are placed so that they are a few feet from the engineer s ears As a result room acoustics become less important since the primary acoustic interaction involves direct sound from the speakers rather than ...

Page 26: ...s since massive amplification of even a couple millivolts of noise can give an audible signal Most ground loop problems can be solved by plugging all equipment into the same grounded AC source However it is important to make sure that the AC source is not overloaded and is properly rated to handle the gear plugged into it For really tough cases you may need to break the connection that causes the ...

Page 27: ...n controls are left all the way up while the mixer s output is turned down This can lead to blown speakers if the mixer is accidentally turned up but more importantly it amplifies the noise floor of the mixer output stage or wiring unnecessarily Keeping the source level as high as possible and lowering the amplifier input gain will keep the noise level at a minimum The input sensitivity of the RA1...

Page 28: ...urrent output protection relays which disconnect the output in the event of overheating DC offset audio signals below 5 Hz on the output terminals or excessively low line voltage When this happens in the RA300 500 the PROTECT indicators of both channels will glow Additional protection circuitry keeps RFI out of the audio circuits assuring clean stable operation in difficult environmental condition...

Page 29: ... may be in thermal protect mode PROTECT LEDs on Normal operation will resume when its internal temperature has dropped to reliable levels Power is not connected Time for a coffee break Low output power Line voltage set improperly Set the switch on the back panel to the 120 V position Bass disappears speakers sound out of phase Amplifier accidentally set to Bridge Mono mode when wired for stereo Se...

Page 30: ...dspeakers Check crossover and connections Check speaker connections Thin or Muffled Sound Balanced connector with one side disconnected or no ground with an unbalanced input Make sure input cables are connected to ground as required CARE AND MAINTENANCE CLEANING Disconnect the AC cord then use a damp cloth to clean the RA150 300 500 s metal and plastic surfaces For heavy dirt use a non abrasive ho...

Page 31: ...t covered by the Alesis warranty Tape a note to the top of the unit describing the problem include your name and a phone number where Alesis can contact you if necessary as well as instructions on where you want the product returned Alesis will pay for standard one way shipping back to you on any repair covered under the terms of this warranty Next day service is available for a surcharge Field re...

Page 32: ... Maximum input level 26 dBu Input impedance 20k Ω balanced 10 kΩ unbalanced Crosstalk 85dB 1kHz Output offset 50 mV Servo controlled Reference 300 Size 18 9 W x 3 9 H x 10 63 D 480mm x 99 mm x 270 mm Rack units 2RU height Weight 19lbs 8 6Kg Rated output per channel 4 ohms 1kHz 02 THD N 150 watts RMS per channel 8 ohms 1kHz 05 THD N 90 watts RMS per channel 8 ohms bridged mono mode 300 watts RMS Si...

Page 33: ...to Noise Ratio 105dB 22Hz 22kHz bandwidth referenced to rated output Frequency Response 10Hz 70kHz 0 3dB Damping Factor 200 Slew Rate 60 V µs two channel 120 V µs bridged mono Input Sensitivity 4dBu 1 23 V for rated output with input control at maximum Maximum input level 26 dBu Input impedance 20k Ω balanced 10 kΩ unbalanced Crosstalk 85dB 1kHz All measurements done over a 20Hz 22 000Hz range wit...

Page 34: ...Specifications 32 RA150 300 500 Reference Manual RA500 RA300 ...

Page 35: ... circuitry will activate the output relay and disconnect the loudspeaker load This circuitry will also mute the amplifier during power on off transitions The power supplies of the amplifier shall utilize heavy duty stacked steel EI laminated transformers for maximum performance and reliability with high current bridge rectifiers massive secondary capacitors and current in rush limiters An external...

Page 36: ...r 18 input clipping 26 Inputs 13 magnetic fields 12 Maintenance 28 Meters 22 Mono See Bridged Mono noise 25 Output Relays 26 Outputs 18 phase See polarity phone plug inputs 14 polarity 20 how to test 22 power output 30 Power cable 3 power loss in speaker cable 18 protection 7 Rack Mounting 11 RCA phono input jacks See Repair Service 29 Safety 3 24 shield telescoping 24 sound level meter 25 Specifi...

Page 37: ...arising during normal use that are due to defects in material or workmanship in the product THE ABOVE WARRANTIES ARE IN LIEU OF ANY OTHER WARRANTIES OR REPRESENTATIONS WHETHER EXPRESS OR IMPLIED OR OTHERWISE WITH RESPECT TO THE PRODUCT AND SPECIFICALLY EXCLUDE ANY IMPLIED WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY OR OTHER IMPLIED WARRANTIES Some states do not allow limitati...

Page 38: ...Warranty 36 RA150 300 500 Reference Manual ...

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