OWNERS MANUAL
Contents
1. 17 Figure 13 LAI 7a Front Panel Detail a 18 LIST OF TABLES Table Output Power Ratings and MLS Switch Settings for the 17 222 2 8 Table 2 MLS Switch Setting 9 Table 3 LAI 7a Current Draw 4 12 Table 4 LAI 7a Maximum Output Power versus Mains Input Power 12 Table 5 LAI 7a Output Power and Input Sensitivity versus MLS Switch Setting 32 dB gain 13 Table 6 Maximum Recommended Length for Damping Factor gt 20 16 L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 2 APPROVALS amended by 92 31 EEC and 93 68 EEC and the requirements of the Low Voltage This equipment conforms to the requirements of the EMC directive 89 336 EEC Directive 73 23 EEC amended by 93 68 EEC Standard Applied EMC Emission EN55103 1 EMC Immunity EN55 103 2 with S N below 1 at normal operation level Electrical Safety EN60065 Class 2 WARNINGS 2 1 EXPLANATION OF GRAPHICAL SYMBOLS 4 _ The lightning symbol within a triangle is MN The exclamation point within a triangle is intende2. Bridged connection Channel A output connector pins 2 to loudspeaker Channel A and B connected via two Channel A and B connected via one separate Speakons Speakon for bi amp applications L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 15 In order to preserve high damping factor essential to the sonic qualities of your loudspeaker system and to prevent overshoot of cone displacement which can result in mechanical damage it is desirable to keep loudspeaker cables as short as possible and with a gauge offering low resistance per unit length Do not use shielded wire such as microphone or guitar cable and remember that the speaker cable robs the power of the amplifier by increasing the load impedance and introducing resistive power losses so called losses The following table provides information regarding the minimum wire cross section versus length Table 6 Maximum Recommended Length for Damping Factor gt 20 Cross Section Gauge 8 ohms 4 ohms Metric mm2 Imperial Metric Imperial Metric Imperial 2 5 13 30 100 ft 15 45 ft 4 50 150 ft 25 75 ft 6 8 75 225 ft 37 110 ft 10 6 120 m 360 ft 60 m 180 ft 7 OPERATION 7 1 OPERATION MODES 7 1 1 STEREO MODE In this mode both channels operate independently of each other and the level attenuators on the front panel cont
3. 4 2 eA oat SHINSTALLATION Mounting 5 3 Operating reai E A R E 5 32 Sali 5 3 2 2 2 5 9 Power Consumption 5 6 5 7 Gain 6 neh eh ioe 6 1 1 Balanced 6 1 2 ete a e 6 2 Connecting Speakers eid eden ie Tol Operation
4. 20 9 1 Troubleshooting sian hain 20 5 tie 21 Assistance and 21 LIST OF FIGURES Figure Front Panel E 6 2 7a Rear Panel hoe abuse apria isa edb ai eb sda 7 Figure 3 LAI 7a Rear Panel MLS 8 Figure 4 XLR Input Connector Wiring 14 Figure 5 Balanced 14 Fig re 6 ites 14 Figure 7 LAI 7a Rear Panel 14 Figure 8 Unbalanced Line Connection 15 Figure 9 Balanced Line with Unbalanced 22 0 11 100000 15 Figure 10 Loudspeaker Connection 5 15 Figure 11 Reverse polarity operation for Channel 16 Figure 12 Bridged mono
5. haus steady ie lends ath 721 1 5 ets casos tab Pe na AA eset 7 1 2 113 Bridged ee al ee 7 1 4 Bridged Mono Mode 7 2 Operating Precautions sisinio tae neea ee eei aE E aE EE E iE Ee Ea a iia e 7 3 Powering Up 5 5 tat E A EE E e E E R TA Input Attenuators aes Std nas ess PS 8 PROTECTION FEATURES ate estas 8 l Clip Eimite e 8 2 Thermal Protection seiiet A aei Eiai 83 VAF Protection E A nls A E A iat 8 4 Short Circuit Protection 8 5 AC Mains Voltage 8 6 Bee ests ta Sete E L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 9 MAINTENANCE
6. Manual V1 0 27 01 2003 MLS positions can be different for each channel and a variety of combinations can be selected as seen in Table 2 There is no risk for amplifier damage since the LAI 7a is very well protected even down to 0 3 ohms However if uncertain or where time does not allow use the default position MLS 0 dB Table 2 MLS Switch Setting Applications Channel Impedance MLS Power Comments 8 3dB Power 8 3dB reduction 840W High peak 840W power 8 Power 8 3dB matching 3dB 220W Power 840W sharing 4 2 CLIP LIMITER The LAI7a Channel A B clip limiters prevent dangerous clipped signals from reaching the loudspeaker and causing damage When an amplifier is severely overdriven the output waveform is clipped and peaks become squared off causing a reduction in crest factor In extreme 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 LAI7a 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 the limiter reduces the input signal proportionally Once the amplifier comes out of a protect condition the output level has a slow rise time the effect is like turning the gain up slowl
7. 27 01 2003 5 3 INTRODUCTION Thank you for purchasing the L ACOUSTICS LAI 7a power amplifier This manual contains important information on operating your power amplifier correctly and safely Please take time to read this manual in order to familiarize yourself with the many advanced features of this amplifier 3 1 UNPACKING Carefully open the shipping carton and check for any noticeable damage Every L ACOUSTICS amplifier is tested and inspected before leaving the factory and should arrive in perfect condition If found to be damaged notify the shipping company immediately Only the consignee may institute a claim with the carrier for damage incurred during shipping Be sure to save the carton and packing materials for the carrier s inspection It is also advisable to save the carton and packing material even if the amplifier is undamaged Should you ever need to ship the amplifier always use the original packing 3 2 FRONT PANEL 6 4 5 6 O vacouszics Power Amplifier LA 17a Figure 1 LAI 7a Front Panel Carry Protection Handle Both handles can be used to 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 Lev
8. This warranty shall be 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 exposure to inclement weather conditions and normal wear and tear Units on which the serial number has been removed or defaced will not be eligible for warranty service L ACOUSTICS shall not be responsible for any incidental or consequential damages with respect to the products warranted L ACOUSTICS reserves the right to make changes or improvements in design or 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 for this information as rights and disclaimers may vary from country to country 11 TECHNICAL ASSISTANCE AND SERVICE International If your L ACOUSTICS product needs repair contact your L ACOUSTICS dealer or distributor or contact L ACOUSTICS by fax or email to obtain the location of the nearest authorized service center Factory Service In the event that your L ACOUSTICS product needs factory service you should contact L ACOUSTICS service department for return instructions and a Return Authori
9. the power supply is operating properly 8 6 DC PROTECTION There are two types of DC protection 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
10. this is NOT a parallel output mode Never connect either output terminal to ground or in parallel 7 1 3 BRIDGED MONO MODE Figure 2 Bridged mono cabling Bridged mono mode is used to deliver both channels power to a single load The nominal impedance of the load must be more gt than 4 ohms input signal is applied to Channel and then linked the Channel B input by physically connecting from the Ch A LINK connector male XLR to the Ch B INPUT connector Neutrik Combo jack Both Channel A and B level attenuators must be at the same position and it is recommended that they are operated in the O dB full position Connect the loudspeaker as shown and always use the Channel A output connector 7 1 4 BRIDGED MONO MODE FEATURES Bridged mono mode combines the power of both 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 zero voltage at the center of the voice coil winding This is because the coil is driven with positive voltage at one pole and an equivalent negative voltage at the other pole So if an 8 ohm load is connected in bridged mode one channel shares one 4 ohm part of the load and the other channel shares the other 4 ohm part The power into
11. to turn down the gain controls during power up to prevent speaker damage in case a high signal is present at the input Remember the old saying amps on last 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 two input level attenuators on the front panel adjust the signal level for their respective amplifier channel in all modes Input level attenuators are calibrated in dB to assist in setting up active loudspeaker systems or cutting down unwanted noise from the input signal In bridged mode both controls must be in the same position so that the speaker load will be shared equally between the channels 7 5 INDICATORS FA PROTECT D 5 10 15 CH A 20 CH B 25 12 LZ ON en 7 271 5 TX 5 VIX YI 20 3 20 5 A 40 K l 4 en 0 can 2 Figure 13 LAI 7a Front Panel Detail The two bottom green LED s indicate that the output circuits are receiving the correct rail voltage The 25 dB LED s illuminate if the output signal is greater than 25dB with 0
12. 4 ohms from an LAI7a MLS at 0 dB is 840 W Therefore the total bridged power into the 8 ohm load will be 2 x 840 1680 W 7 2 OPERATING PRECAUTIONS Never connect either Channel A or B output terminals to ground or to some other output or input terminal see also warnings in Section 2 4 For normal two channel operation connect each speaker load across the output channel s positive and negative terminals Pay attention to speaker polarity loudspeakers connected out of polarity degrade sound quality and may be damaged as a consequence WARNING To prevent electrical shock do not operate the amplifier with any of the conductor portion of the loudspeaker cable exposed L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 17 e Refer to Sections 5 1 5 2 concerning amplifier mounting and cooling considerations e sure that AC mains voltage is correct and the same as the one printed the rear panel of the amplifier See Sections 5 3 5 7 concerning operating voltage grounding and power consumption for more details e Make sure that the power switch is set to off before making any input or output connections or operating the switches on rear panel e Make sure that the switches on the rear panel for clip limiters and the MLS switches are in the correct position See Section 7 concerning operation modes Section 8 1 about clip limiters and Section 4 1 concerning the MLS switches e It is always a good idea
13. 5 3 RADIO INTERFERENCE A sample of this product has been tested and complies with the limits for the European Electro Magnetic Compatibility EMC directive These limits are designed to provide reasonable protection against harmful interference from electrical equipment This product uses radio frequency energy and if not used or installed in accordance with these operating instructions may cause interference to other equipment such as radio receivers However there is no guarantee that interference will not occur in a particular installation L ACOUSTICS LAI 7 Manual V1 0 27 01 2003 4 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 on a circuit different from that to which the receiver is connected Check if the affected unit complies with the EMC limits for immunity CE labelled If not address the problem with the manufacturer or supplier of the affected unit All electrical products sold in the EC must be approved for immunity against electromagnetic fields high voltage flashes and radio interference Consult the dealer or an experienced radio TV technician for further assistance L ACOUSTICS LAI 7 Manual V1 0
14. H Once the AC connector is connected to a suitable AC supply the amplifier can be started with the power switch When you power up the amplifier it takes a couple of seconds to check its circuits this is known as the soft or slow start sequence the fans then blow at high speed before going into idle and the two bottom green LED s come on to indicate that the output circuits are receiving the correct rail voltage 5 3 1 DENMARK National deviation concerning installation of the LAI 7a Danish safety regulations stipulate the use of 8 A mains fuse Since the LAI 7a uses an internal primary mains fuse of 15 the LAI 7a must be equipped with an industrial mains connector rated for 16 Aor alternatively be installed to a fixed 16 circuit 5 3 2 SWITZERLAND National deviation concerning installation of the LAI 7a Swiss safety regulations stipulate that a type 23 mains connector must be used 5 4 GROUNDING There is no ground lift switch or terminal on this amplifier The signal ground is always floating via a resistor to chassis and the grounding system is automatic If a potential above 0 6 V presents itself between signal ground and chassis ground a short circuit is introduced between the two thereby enabling electrical 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
15. In the interest of safety never disconnect the earth pin on the AC power cord For all units that are CE approved radio interference there is an AC mains filter This filter needs the chassis ground for reference otherwise a current loop is formed via the signal ground Use the balanced inputs to avoid hum and interference 5 5 POWER CONSUMPTION There are three ways to define the power current consumption of a power amplifier First the peak current draw at full output power Under this condition the power amplifier will trip the mains breaker within 30 seconds and the amplifier will operate for less than 2 minutes before thermally limiting It is therefore meaningless to state the input power at full power since the heat power at full power will be limited by the protection circuits In practice there are no audio program materials which produce sustained full output power only sine wave signals for test purposes It is more useful to state the current draw for different loads and output power levels The current draw is stated in Amperes rms and this figure corresponds to the value of the mains fuse required L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 Table 3 LAI 7a Current Draw 4 ohms Operating Condition Current Draw in Amperes rms Idle state no load A rms 1 8 of full power 9 dB 6 A rms 1 3 of full power 5 dB 9 A rms Full power 0 dB at kHz 1 THD 16 A rms S
16. LS Minimum Load Select switches located on the rear panel offer power impedance matching allowing the LAI 7a to power 2 ohm loads without increased heat loss Please refer to Table to determine the power delivered into a specific load for various MLS switch settings Note that higher powers can be achieved utilising higher MLS positions when connected to lower speaker impedances and as be seen in Table the LAI 7a can produce output power in excess of 850 watts Essentially the LAI 7a amplifier is a power converter and by selecting MLS positions you are allocating a portion of the available 700 watts power LACOUSTICS CH B LINK CH ALINK INPUT gt JaN GAN Y a 9 9 7 9 MS oA 69 eve LA 17 ia do aB RNa Power Amplifier 45 Figure 3 LAI 7a Rear Panel MLS Switches Table 1 Output Power Ratings and MLS Switch Settings for the LAI7a LAI7a LOAD CONFIGURATION 3 dB 0 dB 16 ohms Stereo 2 channel 110 W 215 W 8 ohms Stereo 2 channel 220 W 430 W 4ohms _ Stereo 2 channel 430 840 W 2ohms Stereo 2 channel 870 W 1200 W 16 ohms Bridged mono 440 W 840 W 8 ohms Bridged mono 870 W 1680 W 4ohms_ Bridged mono 1740 W 2400 W Power watts EIA kHz 1 THD L ACOUSTICS LAI 7
17. Version 1 0 January 2003 LAI 7a TABLE OF CONTENTS LIST OF FIGURES ick ate each athe LIST OF TABLES ea oe 2 2 1 Explanation of Graphical Symbols 2 2 1 0 000 2 2 WARNING Wiha alsa teaver em reas eles 2 3 CAUTION EG EE pastas binds Sasso tae eae ahaa 2 4 Important Safety Instructions 2 5 User Responsible teehee tere eet a hints a a 2 5 Speaker 2 5 2 Speaker Output Hazard essiens aa ie p ai ii 2 5 3 Radio Interterence 2 2 E sales E E E 3 p Unpacking oeer ieee eae eE EEEE e aE EEEa OEE E E E E Era teats 8720 S E NE E E S A E AEEA 3 3 ASEE EA EE ENET E E AE EE EEE asa EE EE 4 REAR PANEL FEATURES eiee eni ia e ra E oi 4 1 Impedance Matching MLS
18. d to alert the user to the intended to alert the user to important presence of un insulated dangerous voltage operating and service instructions in the within the amplifier s enclosure that may be of literature accompanying the product sufficient magnitude to constitute a risk of electric shock to humans 2 2 WARNING 2 3 CAUTION To reduce risk of fire or electric shock do not To reduce the risk of fire or electric shock do expose this apparatus to rain or moisture 4 not remove screws No user serviceable parts inside Refer servicing to qualified service personnel 2 4 IMPORTANT SAFETY INSTRUCTIONS Before using your amplifier be sure to carefully read these operating instructions and follow the safety suggestions outlined below Keep this manual for future reference Heed all warnings 2 3 Follow all instructions 4 Do not use this unit near water Do not spill water or other liquids into or on the unit Do not operate the amplifier while wet or standing in liquid 5 Clean only with a dry cloth 6 Do not block the air intake or exhaust ports Install the unit in accordance with the instructions outlined in this manual 7 not operate the amplifier near heat producing devices such as radiators heat registers stoves or any other apparatus that produces heat 8 Always operate the unit with the chassis ground wire connected to the electrical safety earth Do not defeat
19. dB referenced to full output power These LED s also act as signal present indicators The rest of the green LEDs form a bar display indication of output levels from 20 dB to 5 dB L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 18 The CLIP LED indicates when the amplifier output is clipping or limiting It has two different indication statuses e If the clip limiter is engaged the CLIP LED has a short time constant and illuminates briefly e If the clip limiter is not engaged the CLIP LED has an increased time constant and illuminates for a longer period The remaining TEMP and PROTECT LEDs indicate if any protection circuits are activated Protection features are described in the following section 8 PROTECTION FEATURES Each L ACOUSTICS amplifier has many advanced protection features protecting both the amplifier and the loudspeakers connected to it should a fault condition arise Under normal use these features are inaudible All protection circuits are independent 8 1 CLIP LIMITER The clip limiter prevents dangerous clipped signals from reaching the loudspeaker and causing damaging When an amplifier is severely overdriven the output waveform is clipped peaks are squared off reducing the crest factor In extreme cases the waveform can approach that of a square wave An amplifier is normally capable of producing far more power under these conditions than its normal undistorted rated output power The clip limite
20. econd the maximum expected average current under worst case conditions corresponding to 1 3 full power program material according to the FTC standard At this level the music will be in a state of constant clip and is therefore the highest power level one can obtain without completely obliterating the program material Third the normal operating power as defined by the safety standard IEC 65 ANSI UL 6500 and used by a majority of safety agencies The normal operating power is measured using pink noise with an average output power equal to 1 8 of full power The 1 8 full power specification is as loud as you can play music while making some attempt to avoid obvious clipping and corresponds to 9 dB of headroom which is very low for normal audio program Table 4 LAI7a Maximum Output Power versus Mains Input Power MAXIMUM OUTPUT POWER MAINS INPUT POWER Load of ch Power 1 3 Power 1 8 Power watts see note see note 2 2X 430 730 480 2X 840 1330 840 2X 1200 2200 1400 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 It is recommended that you specify your power distribution service to ensure sufficient current for at least 1 8 power operation to upgrade service to meet 1 3 power requirements for heavy duty demands like discos etc 5 6 HEAT POWER CALCULATION The heat power can be calculated according to the follo
21. el 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 systems Input attenuation can also be used to reduce unwanted noise from the input signal See Section 7 4 for further details 3 Over Temperature Protect Indicator This indicator illuminates if the amplifier tries to operate above its maximum operating temperature 90 C The indicator first comes on as a warning to either turn down the input level or check amplifier ventilation Beyond the maximum temperature the amplifier will mute the input signal When cooling fans have returned the output heat sinks back to normal operating temperature the input signal is un muted 4 Protect Indicator VHF and short circuit This indicator illuminates when signals above 2 kHz are continuously present at full power at the output terminals If this occurs the input signal is muted and the process cycles until the VHF signal is no longer present L ACOUSTICS LAI 7 Manual V1 0 27 01 2003 6 5 Clip Limit Indicator This indicator signals when the amplifier output is clipping or limiting There are two different indication states depending on whether the rear panel clip limiter is engaged see Sections 4 2 8 1 e If the clip limiter is engaged the Clip Limit Indicator has a short time constant and illuminates briefly e If the clip limiter is not engaged the Clip Limit Indicator has an inc
22. hes a temperature above 90 C 8 3 VHF PROTECTION If a signal above 12 kHz is detected at the amplifier outputs for more than five seconds at full output power VHF protection mutes the input signal This is indicated on the front panel LED indicator labeled PROTECT After five seconds the outputs will un mute and return to normal operation unless the output signal has remained unchanged in which case the VHF protection will re initiate 8 4 SHORT CIRCUIT PROTECTION All L ACOUSTICS amplifiers are completely short circuit protected Short circuit protection circuitry permits very high peak currents but still holds the output devices within the safe operation area If a short circuit condition is maintained the affected channel will eventually go into thermal protect cycle until the short circuit has been removed L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 19 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 LEDs indicate when
23. ill depend on the specific MLS switch setting Input sensitivity is summarized below in Table 5 Table 5 LAI 7a Output Power and Input Sensitivity versus MLS Switch Setting 32 dB gain LAI7a LOAD CONFIGURATION 3 dB 0 16 ohms Stereo 2 channel 110W 215 W 2 7 dBu 5 6 dBu 8 ohms Stereo 2 channel 220 W 430 W 2 7 dBu 5 6 dBu 4ohms Stereo 2 channel 430 W 840 W 2 6 dBu 5 5 dBu 2ohms Stereo 2 channel 870 W 1200 W 2 6 dBu 4 0 dBu 16 ohms Bridged mono 440 W 840 W 2 7 dBu 5 5 dBu 8 ohms Bridged mono 870 W 1680 W 2 6 dBu 5 5 dBu 4 5 Bridged mono 1740 W 2400 W 2 6 dBu 4 0 dBu Power in watts EIA I kHz 1 THD Sensitivity in dBu L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 13 6 CONNECTIONS 6 1 INPUT CONNECTIONS 6 1 1 BALANCED INPUTS XLR Input connectors are active balanced and wired according to IEC 268 i e pin 2 hot in the following way PIN GROUND SHIELD PIN 2 HOT PIN 3 COLD Gnd Figure 4 XLR Input Connector Wiring Figure 5 Balanced XLR wiring The Neutrik Combojack includes 4 6 3 mm phone jack which is wired in parallel with the in the following manner TIP HOT RING COLD SLEEVE SHIELD GROUND J Figure 6 4 TRS plug The input impedance is high enough 20 kOhms balanced to allow daisy chaining multiple parallel input connections The headroom of the input circuits is al
24. l 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 unit was dropped or the enclosure is damaged 17 Do not remove top or bottom covers Removal of the cover will expose hazardous voltages There are no serviceable parts inside and removal may void the warranty 18 An experienced user shall always supervise the use of professional audio equipment especially if inexperienced adults or minors are using the equipment 2 5 USER RESPONSIBILITY 2 5 1 SPEAKER DAMAGE Your amplifier is very powerful and can be potentially dangerous to both loudspeakers and humans alike Loudspeakers can be damaged or destroyed by overpowering especially with the high power available from a bridged amplifier Always check the loudspeaker s continuous and peak power handling capabilities Note even when using the amplifier s front panel attenuator to reduce the gain it is still possible to reach full output power if the input signal level is high enough 2 5 2 SPEAKER OUTPUT HAZARD Power amplifiers are capable of producing hazardous output voltages To avoid electrical shock do not touch any exposed speaker wiring while the amplifier is operating Refer to Section 6 2 concerning proper connection of loudspeakers 2
25. possible LI 6 LAB GRUPPEN HH uz LAB GRUPPEN AMPLIFIER H D Figure 6 Line Connection Figure 9 Balanced Line with Unbalanced Equipment 6 2 CONNECTING SPEAKERS Speaker connections are made via the two Neutrik NL4FC Speakon connectors The Speakon connector is designed for high power speaker connections and assures correct polarity locks securely in place and prevents from shock hazard The LAI 7a power amplifier Speakon connectors are wired in the following manner Channel A Channel B Pin 1 Channel A Channel B Pin Channel A Channel B Pin 2 Channel B Pin 2 Channel B For normal two channel operation connect each speaker load across the Channel A B output terminals positive and ground Since the Channel A Speakon is bi wired it is possible to access both channels on a single connector For bi amped operation be careful whether Channel A or B outputs are assigned to the LF or HF component of your active loudspeaker system As standard L ACOUSTICS active 2 way loudspeakers are cabled as follows LF 1 1 Ch HF 2 2 Ch Also pay attention to speaker polarity loudspeakers connected out of phase degrade sound quality and may be damaged as a consequence Figure 10 Loudspeaker Connection Details
26. r 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 the limiter reduces the input signal proportionally Once the amplifier comes out of a protect condition the output level has a slow rise time the effect is like turning the gain up slowly Note if the signal is distorted 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 LACOUSTICS recommends leaving the clip limiters switched ON at all times Channel A B rear panel clip limiter buttons depressed in the IN position 8 2 THERMAL PROTECTION If the amplifier is driven hard into a low impedance load the cooling fans will run at high speed If this condition persists the Temperature indicator s will illuminate indicating that the amplifier is about to go into thermal shutdown After five seconds the amplifier will go into thermal protection by muting the input signal After 15 20 seconds the amplifier will have cooled down enough for the amplifier to come out of shutdown and operate as normal If the load conditions remain unchanged the thermal protection will be reinitiated Thermal protection starts when the Intercooler heat sink reac
27. reased time constant and illuminates for a longer period 6 Fan Grill Filters Two grilles with foam filters are located on the front panel in order to prevent dust from entering the amplifier The grilles are removed by simply pulling them off allowing 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 3 4 5 5 4 gt mae Clip Liiter A 5 5 INPUT LINK CHA UNK INPUT Figure 2 LAI7a Rear Panel 3 1 Output Speaker Connector The Neutrik Speakon connector may be unfamiliar to some users A full description is found in Section 6 2 2 Minimum Load Selector MLS Switch These switches are used to select the maximum output power See Section 4 1 3 Clip Limiter Switch Turns the clip limiter on switch IN position or off switch OUT position See Sections 4 2 8 1 4 Input Signal Connector The Neutrik Combojack features XLR and TRS phone jacks Pin 2 hot see Section 6 1 1 5 Link Output XLR male connector 5 connected in parallel to the female connector 4 for linking the channel to another input 6 AC Power Cable L ACOUSTICS LAI 7 Manual V1 0 27 01 2003 7 4 REAR PANEL FEATURES 4 1 IMPEDANCE MATCHING MLS SWITCH The M
28. rol the respective channel levels Never connect either Channel A or B output Speakon terminals to ground or in parallel The recommended minimum nominal impedance for stereo operation is 2 ohms per channel Note Concerning Bench Test Procedures Channel B is always polarity reversed at the input but this polarity reversal is internally compensated for by feeding the minus pin on the Channel B output with the positive output voltage Channel A is operated with normal polarity With channel A and B operating in opposite or reverse polarity the energy storage in the power supply is more efficient This is significant for signals below 100 Hz sub bass etc and improves the power bandwidth Note Formerly this was referred to as reverse stereo operation for the LAI 7 For this reason be sure to use balanced inputs on all measurement equipment also oscilloscope probes if you are bench testing INPUT BUFFERS POWER AMP SPEAKER Figure 11 Reverse polarity operation for Channel L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 16 7 1 2 TANDEM MODE In tandem mode both Channel A and B inputs are linked and receive the same signal Channel B to A linking is performed by physically connecting from the Ch A LINK connector male XLR to the Ch B INPUT connector Neutrik Combo jack Both Channel A and B level attenuators are active allowing you to set different levels for each channel Note only the inputs are connected in parallel and
29. sation number Please note for product return 1 Use the original packing 2 Include a copy of the sales receipt your name return address phone and fax number email address and a description of the defect 3 Mark the Return Authorisation number on the outside of the packing 4 Ship the product prepaid to L ACOUSTICS Attention After Sales Service SAV Parc de la Fontaine de Jouvence 91462 Marcoussis cedex France Telephone 33 169 63 69 69 Email info I acoustics com Fax 33 169 63 69 64 website www l acoustics com L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 21
30. so high enough to accept the maximum output level from virtually any low level signal source Balanced signals are less sensitive to AC hum and radio interference The source impedance should be less than in order to avoid high frequency loss long cables To daisy chain amplifiers use the XLR male connector labeled Link provided on each channel This connector is wired in parallel with the Neutrik Combo jack on each input LACOUSTICS CH B INPUT CH B LINK CH A LINK INPUT AN T _ a ee i A 2 J J 32 gt 4 ERA A XLR 1 4 gt Pin 5 Sleeve 2 Pos 3 Neg 7 230 240 50 60Hz Power Amplifier Must be grounded Current consumption 9 7A Figure 7 LAI 7a Rear Panel Detail L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 14 6 1 2 UNBALANCED INPUTS To connect an unbalanced source tie pin 3 ring on TRS jack to the shield of the connector Note if you leave pin 3 disconnected you will lose 6 dB A better method for using unbalanced sources is shown in Figure 8 This is similar to the connection for balanced lines but pin 3 is connected to the shield at the source The hum and noise rejection for the cable is equivalent to that for a balanced line To minimize hum use balanced inputs whenever
31. table applications without rear support are not covered under warranty For all portable applications the amplifier should be fixed in the back with a rear support kit L ACOUSTICS part code APSUP The amplifier support kit APSUP is a universal rear support kit for any 19 rack since it is adjustable to accommodate varying rack depths Two rear support brackets two amplifier support brackets four M4 hex button head screws and four washers are included in each APSUP kit The kit integrates the amplifier support bracket with the amplifier and the rack support bracket with the rack Depth is adjustable and amplifiers 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 than inside and therefore the amplifiers can run at higher continuous power levels without thermal problems Never try to reverse the airflow since the Intercooler needs a pressure chamber between the fans and heat sink and this only works in one direction of the airflow Should a heat sink get too hot its sensing circuit will mute the overheated channel If the power supply overheats another sensing circuit will mute all output channels un
32. 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 130 265 V 230 or 65 135 115 Over under voltage protection may have occurred If the amplifier is connected 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 L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 20 10 WARRANTY This product is manufactured by L ACOUSTICS and is warranted to be free from defects components and factory workmanship under normal use and service for a period of one year from the date of original purchase During the warranty period L ACOUSTICS or its nominated agents will undertake to repair or at their option replace this product at no charge to its owner if the unit fails to perform as specified provided the unit is returned undamaged and shipping is pre paid to the factory or an authorised service facility
33. the safety purpose of the grounding type plug A grounding type plug has two pins and a third grounding prong The third prong is provided for your safety If the provided plug does not fit into your outlet consult an electrician for replacement of the obsolete outlet 9 Connect only to AC power outlets rated 230 240 V 50 60 Hz L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 3 10 Do not use this amplifier if the power cord is broken or frayed Protect the power cord from being walked upon or pinched particularly at the plugs and the point where the power cord exits from the apparatus 11 Only use accessories specified by the manufacturer 12 The unit is intended to be mounted in a 19 rack Follow the mounting instructions outlined in this manual and always rear support the unit when used in portable applications When a rack on wheels is used for portable applications use caution when moving the loaded rack in order to avoid injury from tipping over 13 Unplug this apparatus during lightning storms or when unused for long periods of time 14 Do not connect an amplifier output in parallel or series with any other amplifier s output Do not connect the amplifier output to any other voltage source such as a battery mains source or power supply regardless of whether the amplifier is turned on or off 15 Do not run the output of any amplifier back into another channel s input 16 Refer all servicing to qualified service personne
34. til the power supply 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 installations with a central cooling system usually found in fixed installations with a dedicated rack room it may be necessary to calculate the maximum heat emission Please refer to Sections 5 6 and 5 7 concerning Power Consumption and Heat Power Calculation 5 3 OPERATING VOLTAGE WARNING A label just below the mains cable on the rear of the amplifier indicates the AC mains voltage for which the amplifier is wired Connect the power cable only to the AC source referred to on the label The warranty will not cover damage caused by connecting to the wrong type of AC mains L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 10 L ACOUSTICS switch mode amplifiers use primary switching i e the mains power is rectified directly before the transformer which means that the power supply is insensitive to the mains frequency and will operate from DC to 400 Hz The amplifier is supplied with an approved European AC line connector If this power plug is not appropriate for your country it can be cut off and wired to a suitable connector in the following manner BLACK or BROWN LIVE WHITE or BLUE NEUTRAL GREEN or GREEN YELLOW EART
35. wing example Consider headroom of at least 9 dB 1 8 of full power and a 4 ohm load on an amplifier producing 840 watts per channel The 1 8 power per channel is then 840 8 105 watts and the total output power is 2 105 210 watts The power consumption according to Table 4 is 840 watts Table 4 gives the active power consumption of the amplifier for different loads and power levels The heat power produced is the difference between the power consumption and the output power 840 210 630 watts per amplifier L ACOUSTICS LAI 7a Manual V1 0 27 01 2003 12 5 7 GAIN AND SENSITIVITY As standard the LAI 7a is delivered with 32 dB gain For most professional applications mixing consoles operate at a nominal level of 4 to 6 dBu therefore the 32 dB position provides optimal gain structure with plenty of fader movement In addition all L ACOUSTICS LLC analog controllers and OEM factory presets for approved digital processors are optimized for use with 32 dB gain amplifiers Sensitivity is defined as how many volts rms or dBu referred to 0 775Vrms are required at the amplifier input to obtain full output power Since the output power delivered varies with the load impedance 4 ohms is generally taken as the reference For the LAI 7a full output power into 4 ohms is 840 W MLS switch 0 dB and standard gain is 32 dB This corresponds to an input sensitivity of 1 46 Vrms or 5 5 dBu For the LAI 7a the input sensitivity w
36. y Under normal operation clip limiting circuitry is inaudible Note if the signal is distorted or clipped before it reaches the amplifier the clip limiter cannot detect this and will not be activated Channel A B clip limiters can be turned on or off by depressing or pressing the relevant clip limit switch L ACOUSTICS recommends leaving the clip limiters switched ON button depressed at all times Clip Limiter ON switch depressed IN position Clip Limiter OFF switch not depressed OUT position L ACOUSTICS LAI 7 Manual V1 0 27 01 2003 9 5 INSTALLATION 5 1 MOUNTING The LAI 7a is two rack units high 2U and will mount an ElA standard 19 rack Four mount points are provided on the front panel of the amplifier for rack mounting For permanent installation the amplifier can be mounted using standard 19 rack mount rails and or slides within the amplifier rack using the four front mount points Amplifiers may be stacked directly on top of each other and there is no need for spacing between units If it is the intention to fill a rack with amplifiers we recommend racking is started from the bottom of the rack It is also recommended that rear supports are used for amplifiers mounted in the middle of the rack For touring or portable sound system applications it is essential that all LAI7a amplifiers are rear supported in addition to front panel mounting Any mechanical damage to LAI7A amplifiers used in por
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