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L-ACOUSTICS LA15a 115V Manual V1.0  27/01/2003   

 

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8.5 AC MAINS VOLTAGE PROTECTION 

If the AC mains voltage is outside the allowed operational voltage (over or under voltage), the power 

supply will automatically shut down. Once the mains voltage is above the minimum start voltage and 
below its maximum operating voltage the amplifier will restart. It takes a few seconds for the amplifier 
to self-check (this is known as the soft or slow start sequence), the gain will slowly and gradually be 

increased back to the previously set level and the fans will blow at high speed before going into idle. The 
two green ”ON” LEDs indicate when the power supply is operating properly.  

8.6 DC PROTECTION 

There are two types of DC protection: 1) Fuses on the supply branches of each channel; 2) DC crowbar 

protection that shorts the output if more than 10 volts DC are detected on the outputs. Both these 
circuits are activated if a DC level is detected on either channel. 

9. MAINTENANCE 

Under normal use your power amplifier should provide years of trouble-free service. The only user 
maintenance required is to vacuum the front grill periodically.  
In some extreme cases it may be necessary for authorized service personnel to clean the inside of the 

amplifier. This is usually necessary after prolonged use in environments where cracked-oil smoke 
machines are present. 
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 
unsecured Speakon connector (at the amplifier output terminals or loudspeaker). 
Check also that VHF protection is not activated. If it is, remove possible high frequency oscillations 

from the relevant input. 

Fault: The amplifier goes into thermal protection when driven at low level. 

Check that nothing causes a short circuit at the amplifier's output, e.g. faulty cabling or a loudspeaker 
component short circuit in the voice coil. 

Fault: The amplifier goes into protection with the power indicators off. 

Check that the AC line voltage is within the amplifier’s operating range: 65-135 V @ 115 V (or 130-
265 V @ 230 V). Over/under-voltage protection may have occurred. If the amplifier is connected by 

mistake to a 3 phase supply, an internal non-resettable fuse or resistor may have blown (return the 
amplifier to your supplier for service). 

Fault: The amplifier does not respond even after checking above items. 

In the unlikely event of a non-user rectifiable fault, return the amplifier to your supplier or an 

approved service centre (see Section 11).  

L-ACOUSTICS cannot be held responsible for damage or injury as a result of the top or 
bottom covers being removed.

 

Содержание LA15a

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

Страница 2: ......

Страница 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 ...

Страница 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...

Страница 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...

Страница 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 ...

Страница 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 ...

Страница 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 ...

Страница 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...

Страница 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 ...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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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