L-Acoustics LA 24 Owner'S Manual Download Page 1 | Manualshive

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Version 2.2

September 1999

LA 24

OWNERS MANUAL

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Summary of Contents for LA 24

Page 1: ...Version 2 2 September 1999 LA 24 OWNERS MANUAL ...

Page 2: ...ed mono 12 Stereo reverse 13 OPERATION 14 Operating precautions 14 Powering up Soft start 14 Input attenuators 14 Gain 14 Indicators 15 PROTECTION FEATURES 16 Clip limiter 16 Thermal protection 16 VHF protection 16 Short circuit protection 17 AC mains voltage protection 17 DC protection 17 DESIGN FEATURES 18 Cooling 18 Light weight 18 Switch mode power supply SMPS 18 MLS switches 19 SAFETY APPROVA...

Page 3: ...nd packing material even if the amplifier is undamaged Should you ever need to ship the amplifier always use the original packing WARNINGS Read this before operating your amplifier Do not use the amplifier if the power cord is broken or frayed Always operate the unit with the chassis ground wire connected to the electrical safety earth Do not parallel or series connect an amplifier output with any...

Page 4: ...atibility EMC directive These limits are designed to provide reasonable protection against harmful interference between electrical equipment This product uses radio frequency energy and if not used or installed in accordance with the operating instructions may cause interference to other equipment such as radio receivers There is no guarantee against interference even though the amplifier is EMC a...

Page 5: ...ier will mute the input signal When the cooling fans have returned the output heat sinks to the normal operating temperature the input signal is unmuted 4 VHF protect indicator This indicator lights when high level high frequency signals above 12 kHz at full power are present at the output terminals When this happens the input signal is muted and the process cycles until the VHF signal is no longe...

Page 6: ...tch for channel B For reversing the input signal phase of channel B or used in conjunction with the Link Switch to allow bridged operation see page 12 7 Link switch Allows a single input to drive both channels simultaneously or used in conjunction with the Phase Reverse Switch to allow bridged operation see page 12 8 AC line cord OUTPUT CH B MLS Swit ch 0 2 4 5 dB C l i p Limi ter 230 VAC 40 440Hz...

Page 7: ...tput channels until it cools down to a safe operating temperature Make sure that there is an adequate air supply in front of the amplifier and that the rear of the amplifier has sufficient space to allow the exhaust to escape If the amplifier is rack mounted do not use covers or doors on the front or rear of the rack For fixed installations with a central cooling system usually found in fixed inst...

Page 8: ...d via the signal ground Use the balanced input to avoid hum and interference Power consumption There are three ways to determine the power current consumption of the amplifier First the peak current draw at full output power Under this condition the power will trip the wall breaker within 30 seconds and the amplifier will operate for less than 2 minutes before thermally limiting During this time t...

Page 9: ...tion and to upgrade service to meet 1 3 power requirements for heavy duty demands like discos etc The heat power can be calculated according to the following example Consider a headroom of at least 9 dB and a 4 ohm load on an amplifier producing 1400 watts per channel The 1 8 power per channel is then 1400 8 175 watts total output 2 x 175 350 watts The power consumption according to Table 1 is 900...

Page 10: ...neously for mixing or for other purposes Figure 6 Balanced line To connect an unbalanced source tie pin 3 ring on TRS jack to the shield of the connector If you leave one pin disconnected you will lose 6 dB in gain Figure 7 Unbalanced line connection A more optimal method for handling unbalanced sources is shown in Figure 8 This is similar to the connection for balanced lines except pin 3 is tied ...

Page 11: ...wires as short as possible and use good quality stranded speaker cable Do not use shielded wire such as microphone or guitar cable Remember that the speaker cable robs the power of the amplifiers by increasing the load impedance and introducing resistive power losses so called I2 R losses Load matching MLS switches Minimum Load Select MLS switches are located on the rear panel The MLS switches pro...

Page 12: ...on rear panel MLSTM positions can be set differently for each channel and a variety of combinations can be selected to suit different applications see Table 3 Channel Impedance MLS Power Comments A 8 2 dB 650W Power B 8 2 dB 650W reduction A 4 0 dB 1400W High peak B 4 0 dB 1400W power A 8 0 dB 1000W Power B 2 4 dB 1200W matching A 8 2 dB 650W Power B 4 0 dB 1400W sharing Table 3 The way to find th...

Page 13: ...onnect either output terminal to ground or in parallel Bridged mono To bridge the amplifier depress the Link Switch 7 and Phase Reverse Switch 6 Both channels are then driven by a single signal which can be applied at either input A or B You can use any remaining input connectors for linking etc Do not use the remaining XLR and TRS as input jacks simultaneously for mixing or other purposes Connect...

Page 14: ...advantage for signals below 100 Hz such as sub bass etc For stereo reverse operation depress the Phase reverse switch so that Channel B is phase reversed To compensate connect pin 1 on the Channel B Speakon to the speaker s negative terminal and pin 1 on Channel B to the speaker s positive terminal Alternatively connect pin 2 on the channel A Speakon to the negative speaker terminal and pin 2 on C...

Page 15: ...l level at the input 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 start or slow start sequence the fans blow at high speed before going into idle then the two bottom green LED s come on to show that the output circuits are receiving the correct rail voltage Input attenuators The two input level attenuators on the fron...

Page 16: ...rs The rest of the green LEDs form a bar for output levels from 20 dB to 5 dB The CLIP indicator shows when the amplifier output is clipping or limiting Clip indicator LED dynamics under clipping conditions depend on whether the clip limiter is engaged When the clip limiter is engaged the clip indicator flickers briefly limiting When the clip limiter is not engaged the clip indicator lights for a ...

Page 17: ...limit switch 2 Clip Limiter ON switch depressed IN position Clip Limiter OFF switch not depressed OUT position L ACOUSTICS recommends leaving the clip limiters switched on button depressed at all times Thermal protection When the amplifier is driven very hard into low impedances the cooling fans go into high speed If the conditions that cause this continue the TEMP indicator s will light as an ind...

Page 18: ...lf down When the mains voltage is above the minimum start voltage and below its maximum operating voltage the amplifier will restart again It takes a couple of seconds for the amplifier to check its circuits this is known as the soft start or slow start sequence then the gain will slowly and gradually be raised back to normal and the fans then blow at high speed before going into idle The two gree...

Page 19: ... chassis also contribute greatly making rear rack supports unnecessary in many applications Switch mode power supply SMPS Switch mode power supplies are the modern solution to the problems of size and weight However early examples of SMPS used for power amplification in audio applications were less than impressive and literally adopted the type of supply found in many computers today The L ACOUSTI...

Page 20: ...itions where their output impedance rises This produces uncontrollable speaker cone movement and under these conditions clip states are more audible for the case of conventional PSUs By comparison the L ACOUSTICS SMPS produces its rated power output at all frequencies regardless of speaker demands and AC line conditions MLS switches Thanks to the regulated SMPS the maximum power available from the...

Page 21: ...Transients and bursts up to 1 kV conducted through the cables to the unit Electromagnetic fields up to 3 V m radiated on the unit and cables in the frequency range of 27 500 MHz We have extended the tests in two cases and chosen a standard used for heavy industrial situations First we have tested conducted disturbances in the frequency range 150 kHz 80 MHz by injecting 3V amplitude modulated 80 si...

Page 22: ... 230 volt operation only 4 If the four electrolytic capacitors close to the front are rated 2200uF 200VDC the amplifier has the 115 230 volt option 5 Locate the jumper s on the solder side of the circuit board close to the mains switch 6 To select the desired mains voltage install the jumpers as shown in Figure 15 7 For 230 volt operation use a T 15A fuse slow blow for 115 volt change to a T 30 A ...

Page 23: ...red Speakon Check that the 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 your loudspeaker does not have a short circuit in its windings this can occur when the speaker s voice coil gets hot Fault The amplifier goes into protect with power indicators of...

Page 24: ...null and void if the product is subjected to 1 Repair work or alteration by persons other than those authorised by L ACOUSTICS or its agents 2 Shipping accidents war civil insurrection misuse abuse operation with incorrect AC voltage operation with faulty associated equipment and normal wear and tear Units on which the serial number has been removed or defaced will not be eligible for warranty ser...

Page 25: ...tory service you should contact the L ACOUSTICS service department for return instructions and a Return Authorisation number Please note on product return 1 Use the original packing 2 Include a copy of the sales receipt your name return address phone number fax number and defect description 3 Mark the Return Authorisation number on the outside of the packing 4 Ship the product prepaid to L Acousti...

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