L-Acoustics LA15a Owner'S Manual Download Page 2 | Manualshive

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Summary of Contents for LA15a

Page 1: ...Version 1 0 January 2003 LA15a 115V Version OWNERS MANUAL ...

Page 2: ......

Page 3: ...2 Cooling 10 5 3 Operating Voltage 10 5 4 Grounding 11 5 5 Power Consumption 11 5 6 Heat Power Calculation 12 5 7 Gain and Sensitivity 13 6 CONNECTIONS 14 6 1 Input Connections 14 6 1 1 Balanced Inputs 14 6 1 2 Unbalanced Inputs 15 6 2 Connecting Speakers 15 7 OPERATION 16 7 1 Operation Modes 16 7 1 1 QUAD Mode 16 7 1 2 Tandem Mode 17 7 1 3 Bridged Mono Mode 17 7 1 4 Bridged Mono Mode Features 17 ...

Page 4: ...Balanced Line with Unbalanced Equipment 15 Figure 10 Loudspeaker Connection Details 15 Figure 11 Reverse polarity operation for Channels B and D 16 Figure 12 Bridged mono cabling 17 Figure 13 LA15a Front Panel Detail 18 LIST OF TABLES Table 1 Output Power Ratings and MLS Switch Settings for the LA15a 8 Table 2 MLS Switch Setting Applications 9 Table 3 LA15a Current Draw 4 ohms 11 Table 4 LA15a Max...

Page 5: ...ated dangerous voltage within the amplifier s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to humans The exclamation point within a triangle is intended to alert the user to important operating and service instructions in the literature accompanying the product 2 2 WARNING To reduce risk of fire or electric shock do not expose this apparatus to rain or moist...

Page 6: ... Do not run the output of any amplifier back into another channel s input 16 Refer all servicing to qualified service personnel Servicing is required when the apparatus has been damaged in any way such as Power supply cord or plug is damaged Liquid has been spilled into the unit An object has fallen into the unit The unit has been exposed to rain or moisture The unit does not operate normally The ...

Page 7: ...cur in a particular installation If this equipment does appear to cause harmful interference to radio or television reception verify by turning the equipment on and off The user is then encouraged to try to correct the interference by one or more of the following measures Reorient or relocate the antenna Increase the separation between the equipment and receiver Connect the equipment to an outlet ...

Page 8: ... carry the amplifier and the handles also provide protection for the front panel For fixed installation or when rack front covers are too shallow the handles may be removed by unscrewing the retaining bolts behind the front panel 2 Input Level Attenuators These controls are used to alter the signal level entering the amplifier They are calibrated in dB to assist in the setup of active loudspeaker ...

Page 9: ...llowing for convenient cleaning of the filters Foam filters should be used at all times 7 Power Switch Turns the mains power on or off 3 3 REAR PANEL Figure 2 LA15a Rear Panel 1 Output Speaker Connector The Neutrik Speakon connector may be unfamiliar to some users See Section 6 2 for details 2 Minimum Load Selector MLS Switch These switches are used to select the maximum output power See Section 4...

Page 10: ...pedances and as can be seen in Table 1 the LA15a can produce output power in excess of 380 watts Essentially the LA15a amplifier is a power converter and by selecting MLS positions you are allocating a portion of the available 1200 watts power Figure 3 LA15a Rear Panel MLS Switches Table 1 Output Power Ratings and MLS Switch Settings for the LA15a LA15a LOAD CONFIGURATION 3 dB 0 dB 16 ohms Quad 4 ...

Page 11: ...cases the waveform can approach that of a square wave Normally an amplifier is capable of producing far more power under these conditions than its normal undistorted rated output power The LA15a clip limiter works by monitoring the output and comparing the distortion produced between the input and output of the amplifier If the distortion exceeds 1 THD for any reason voltage or current clipping th...

Page 12: ...fiers can be removed from the rack by simply removing the 4 button head screws APSUP is suitable for use with all LA amplifiers 5 2 COOLING Your amplifier uses a forced air cooling system to maintain a low and even operating temperature All fan cooled L ACOUSTICS amplifiers have front to rear airflow There are several reasons for this one being that there is usually cooler air outside the rack tha...

Page 13: ...al protection If a unit in the system is faulty its mains fuse will blow due to this automatic ground system If you wish to tie the signal ground to chassis connect the XLR connector s shell lug to pin 1 In the interest of safety never disconnect the earth pin on the AC power cord For all units that are FCC approved radio interference there is an AC mains filter This filter needs the chassis groun...

Page 14: ...er 1 3 Power 1 8 Power Idle watts see note 1 see note 2 8 ohms 4X 370 1140 820 175 4 ohms 4X 380 1325 840 175 2 ohms 4X 500 2125 1440 175 note 1 Mean power with music as program source amplifier driven to clip level note 2 Normal music power with 9 dB headroom IEC standard power rating MLS switch set at 3 dB It is recommended that you specify your power distribution service to ensure sufficient cu...

Page 15: ...e 4 ohms is generally taken as the reference For the LA15a peak output power into 4 ohms is 600 W MLS switch 0 dB and standard gain is 32 dB This corresponds to an input sensitivity of 1 22 Vrms or 4 4 dBu For the LA15a the input sensitivity will depend on the specific MLS switch setting Input sensitivity is summarized below in Table 5 Table 5 LA15a Output Power and Input Sensitivity versus MLS Sw...

Page 16: ...which is wired in parallel with the XLR in the following manner TIP HOT RING COLD SLEEVE SHIELD GROUND Figure 6 TRS plug The input impedance is high enough 20 kOhms balanced to allow daisy chaining or multiple parallel input connections The headroom of the input circuits is also high enough to accept the maximum output level from virtually any low level signal source Balanced signals are less sens...

Page 17: ...peakon connectors are wired in the following manner Channel A B Channel C D Pin 1 Channel A Channel C Pin 1 Channel A Channel C Pin 2 Channel B Channel D Pin 2 Channel B Channel D Since the Channel A B Speakon is bi wired it is possible to access channels A and B on a single connector similarly the Channel C D Speakon provides access to channels C and D This is useful for bridged or bi amped opera...

Page 18: ... the respective channel levels All link switches i e Link A B Link B C Link C D are in the OUT position This is used for stereo amplification of 2 way active enclosures or 4 channel amplification of passive enclosures Please refer to Section 6 2 for details concerning Speakon pin assignments Never connect either Channel A B or C D output Speakon terminals to ground or in parallel The recommended m...

Page 19: ...B full position Connect the loudspeaker as shown in Figure 12 7 1 4 BRIDGED MONO MODE FEATURES Bridged mono mode combines the power of two channels into one speaker This results in twice the voltage swing four times the peak power and just less than three times the full power of a single channel One way to understand the load and power from the amplifier s perspective in bridged mode is that it is...

Page 20: ...t amps off first 7 3 POWERING UP SOFT START When you power up the amplifier it takes a few seconds to check its circuits this is known as the soft or slow start sequence The fans blow at high speed before going into idle and the two bottom green LEDs illuminate to show the amplifier is operational 7 4 INPUT ATTENUATORS The four input level attenuators on the front panel adjust the signal level for...

Page 21: ...orted or clipped before it reaches the amplifier the clip limiter cannot detect it and will not be activated Under normal operation clip limiting is inaudible The limiter can be turned On or Off by depressing or pressing the relevant rear panel clip limit switch L ACOUSTICS recommends leaving the clip limiters switched ON at all times Channel A B rear panel clip limiter buttons depressed in the IN...

Page 22: ...esent If you are using your amplifier for heavy duty use e g concert touring it is recommended that you have your amplifier serviced every 3 years purely as a preventative measure 9 1 TROUBLESHOOTING These are typical things to check if you think your amplifier is faulty Fault No output If the output bar graph is functioning there is nothing wrong with the amplifier The likely cause is an unsecure...

Page 23: ...r manufacturing without assuming any obligation to change or improve products previously manufactured This warranty is exclusive and no other warranty is expressed or implied This warranty does not affect your statutory rights International Please contact your supplier since rights and disclaimers may vary from country to country 11 TECHNICAL ASSISTANCE AND SERVICE International If your L ACOUSTIC...

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