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QSC ISA 280 User Manual

Summary of ISA 280

  • Page 1

    User manual isa audio power amplifiers isa series installed sound amplifiers td-000093-00 rev.C *td-000093-00* n isa 300t n isa 500t n isa 800t n isa 280 n isa 450 n isa 750

  • Page 2: Important Safety Precautions

    Caution: to reduce the risk of electric shock, do not remove the cover. No user- serviceable parts inside. Refer servicing to qualified personnel. Fcc interference statement note: this equipment has been tested and found to comply with the limits for a class b digital device, pursuant to part 15 of ...

  • Page 3: Table of Contents

    Introduction: isa series overview .......................................................................................4 front panel illustration .........................................................................................4 rear panel illustrations .......................................

  • Page 4: Introduction-

    Front panel (all models) thank you for the purchase of your new isa amplifier. To get the most out of your amplifier, review this manual carefully. The installation, connection and operation sections provide useful guidelines to get you up and running quickly and correctly. The qsc shipping box shou...

  • Page 5: Introduction-

    1. Gain controls 2. Terminal block inputs 3. Dataport v2 connector 4. Xlr inputs introduction- rear panel illustrations 9. Serial number label 10. Circuit breaker for ac power 11. Tabs for securing output wires 12. Ac power connector, iec type rear panel isa 280 isa 450 isa 750 5. Mode switches 6. M...

  • Page 6: Features & Setup-

    The front panel of isa series amplifiers is tailored for installed sound. The power switch is the only front panel control; gain controls are located on the rear panel to minimize control tampering. Led indicators are provided for power, input signal and to warn of clipping. If the power led fails t...

  • Page 7: Features & Setup-

    Features & setup- led indicators clip : red led that illuminates when the amplifier clips. Normal indication: illumination briefly at extreme output power peaks. Occasional clipping (once briefly every few seconds) when operation at high power levels is normal. At power-on, the clip leds may briefly...

  • Page 8: Features & Setup-

    Features & setup- gain controls & input jacks gain controls- the gain controls are located on the rear panel to minimize control tampering after installation. When viewing the amplifier from the rear, they are on the left end, top and bottom, as shown in the illustration to the right. The gain contr...

  • Page 9: Features & Setup-

    Dataport v2- what it is- the dataport v2 is used for connection to optional qsc dataport accessories. Dataport accessory devices can provide remote cinema monitoring, dsp, filter and crossover functions. The “v2” dataport connection is a “version-2” of qsc’s original dataport. It has a reduced featu...

  • Page 10: Features & Setup-

    Features & setup- stereo & parallel operating modes parallel: the channel 1 and channel 2 inputs are connected together, applying a single input signal to both channels of the amplifier. A signal into any input jack will drive both channels. Each channel's low frequency filtering, clip limiting, and...

  • Page 11: Features & Setup-

    Features & setup- stereo & parallel mode dip switch settings isa 280, isa 450, isa 750: refer to the switch setting keys for each mode, to the right. These keys are printed on the amplifier’s rear panel for easy reference when you are behind the equipment rack. Setting the dip switches for stereo or...

  • Page 12: Features & Setup-

    Features & setup- bridge operating mode & dip switch settings bridge mode operation- note that speaker connection for bridge mono mode is different than other modes. See section on connections: outputs for proper bridge mode output connections. Setting the dip switches for bridge mode- bridge mode c...

  • Page 13: Features & Setup-

    Features & setup- low frequency filter & dip switch settings setting the filter dip switches- 1- set switch #3 and #8 to the on or off position as desired. 2- select the desired roll-off frequency at switch #2 and #9. 3- if filter off is selected, the frequency selection has no effect. If operating ...

  • Page 14: Features & Setup-

    Features & setup- frequency response curves frequency response curve for: isa 300t isa 500t isa 800t note! There is no “filter off” selection on “t” models. Frequency response curve for: isa 280 isa 450 isa 750 50 hertz selection 75 hertz selection filter on 70 hertz selection filter on 30 hertz sel...

  • Page 15: Features & Setup-

    Features & setup- clip limiter & dip switch settings caution: clip limiting reduces extreme overdrive peaks, allowing a higher average signal level without audible distortion. However, increasing the gain with the clip limiter engaged, until clipping is again audible, can double the average output p...

  • Page 16: Installation:

    Installation: rack mounting and mounting dimensions securing the front ears to the rack rails use four screws and washers when mounting the isa amplifier to the front rails. Support the weight of the amplifier while securing it to the rails to avoid bending or distorting the front rack mount ears. I...

  • Page 17: Installation:

    Installation: cooling requirements & ac mains fan cooling- keep the front and rear vents clear to allow full air flow. Make sure that plenty of cool air can enter the rack, especially if there are other units which exhaust hot air into it. Connecting to the wrong line voltage is dangerous and may da...

  • Page 18: Connections:

    Unbalanced inputs: connect the conductors to the connector as shown. Make sure that the unused side of the balanced input is connected to ground, as shown. Xlr: unbalanced connection terminal block: unbalanced connections xlr : balanced connection terminal block: balanced connections connections: in...

  • Page 19: Connections:

    Connections: inputs- dataport v2 the isa series of amplifiers come with a dataport v2 connector that may be used for connecting to accessory qsc dataport devices. The v2 (or version 2) dataport does not have the full capability of the standard dataport. The dataport v2 must be connected to a qsc dat...

  • Page 20: Connections:

    Connections: outputs- using the screw terminal connections general- the screw terminal output connections are protected by a hinged plastic cover. To make connections to the screw terminals, you will need to swing the cover door open. Gently pry the cover with your finger tips on the side that has t...

  • Page 21: Connections:

    Connections: outputs- direct low impedance (lo-z) bridge mode precautions: do not use 2 ohm loads in bridge mono mode! 4 ohms is the minimum impedance for bridge mono operation! This mode puts a high demand on the amplifier and speaker. Excessive clipping may cause protective muting or speaker damag...

  • Page 22: Connections:

    Connections: outputs- distributed high impedance (hi-z) , stereo & parallel stereo and parallel amplifier mode distributed output connections- use these terminals for 25, 70 or 100 volt distributed loads when the amplifier is in stereo or parallel mode. The isa 300t, isa 500t and isa 800t amplifiers...

  • Page 23: Connections:

    Connections: outputs- distributed high impedance (hi-z) , bridge mode output terminal safety warning! Do not touch output terminals while amplifier power is on. Make all connections with amplifier turned off. Risk of hazardous energy! Bridge mode operation combines the output power of both channels ...

  • Page 24: Connections:

    Connections: power sharing between high & low impedance outputs the isa 300t, isa 500t and isa 800t models are equipped with autotransformer-coupled, high impedance (high-z) outputs. They are also equipped with low impedance (low- z) “direct” outputs. The high impedance outputs are not isolated. The...

  • Page 25: Connections:

    Connections: securing output wiring to chassis part of any quality sound system installation is ensuring that your connections remain tight and reliable over time. Making high quality terminations to the screw terminals is one part of that reliability equation. Keeping those terminations from moving...

  • Page 26: Operation:

    Operation: ac power switch, led indicators, gain controls normal operating levels the amplifier’s protective muting system guards against excessive internal temperatures. With normal ventilation and 4 to 8 ohm loads, the amplifier will handle any signal level, including overdrive. Lower load impedan...

  • Page 27: Applications:

    Applications: general application information the isa 280, isa 450 and isa 750 amplifiers are optimized for directly driving low impedance loads. Low impedance (lo-z) loads are those loads between 2 and 16 ohms. These models are not suitable for driving “constant voltage” 70v lines. These low impeda...

  • Page 28: Applications:

    Applications: low frequency filtering & distributed outputs the low frequency filtering is another difference in the characteristics of the “non-t” and the “t” amplifiers. Because transformers and other magnetic devices are prone to low frequency “misbehavior” (called saturation) , the autotransform...

  • Page 29: Applications:

    100 volt, two-zone example: the illustration to the right shows a typical two-zone 100 volt system. When using 100 volt speaker loads, make sure that connec- tions to the amplifier are made to the 100 volt output terminals. If using the isa 300t, 300 watts per channel (zone) can be delivered. Make s...

  • Page 30: Applications:

    Applications: multiple low impedance loads in series (all models) series connection is where the same signal current flows through each of the speaker loads. The signal goes into one terminal of the first speaker and out its other terminal; then the signal goes into one terminal of the next load, an...

  • Page 31: Applications:

    Applications: multiple low impedance loads in parallel (all models) if each speaker load is connected across the same signal source (the output of the amplifier), then the loads are in parallel with one another. If one of the speakers fails in a parallel-connected system branch, the remaining speake...

  • Page 32: Applications:

    32 the dsp-3 digital signal processing module provides compressor-limiter, multiple parametric filters, high- and low-pass filters, shelf filters, multiple delays, polarity reversal, muting and attenuation. These features and more come packed into a small module that interfaces with the dataport v2 ...

  • Page 33: Troubleshooting:

    • indication: clip led flashing • if the red clipindicator flashes when signal is applied, the amplifier output may be shorted. Check that the speaker cable connec- tions are tight and reliable at both ends. Check the speaker cables for stray strands or breaks in the insulation. Trim off all loose s...

  • Page 34: Troubleshooting:

    Problem: distorted sound magnetic field from power supplies in equipment can induce hum into cabling that is located in the field. If hum is a problem, try relocating cabling so that is away from power supplies, transformers and other magnetic field producing devices. Troubleshooting: distortion, no...

  • Page 35

    Specifications isa 280 isa 450 isa 750 output power in watts ftc: 8 ohms per channel (20-20k hz., 0.1% thd) 185 260 450 4 ohms per channel (20-20k hz., 0.1% thd) 280 425 650 eia: 16 ohms (1 khz., 0.1% thd, 1 channel driven) 100 140 250 8 ohms (1 khz, 0.1% thd, 1 channel driven) 200 280 475 4 ohms (1...

  • Page 36

    Specifications isa 280 isa 450 isa 750 amplifier protection full short circuit, open circuit, thermal, ultrasonic and rf protection. Stable into reactive or mismatched loads. Cooling continuously variable speed fan; back-to-front air flow. Indicators front panel: power led (green), 2 each signal (gr...

  • Page 37

    Specifications isa 300t isa 500t isa 800t output power in watts low impedance ftc: 8 ohms per channel (20-20k hz., 0.1% thd) 185 260 450 4 ohms per channel (20-20k hz., 0.1% thd) 280 425 650 low impedance eia: 16 ohms (1 khz., 0.1% thd, 1 channel driven) 100 140 250 8 ohms (1 khz, 0.1% thd, 1 channe...

  • Page 38

    Specifications isa 300t isa 500t isa 800t amplifier protection full short circuit, open circuit, thermal, ultrasonic and rf protection. Stable into reactive or mismatched loads. Cooling continuously variable speed fan; back-to-front air flow. Indicators front panel: power led (green), 2 each signal ...

  • Page 39

    Disclaimer qsc audio products, inc. Is not liable for any damage to speakers, amplifiers, or any other equipment that is caused by negligence or improper installation and/or use of the isa amplifier. Product warranty qsc guarantees the isa amplifier to be free from defective material and/or workmans...

  • Page 40

    Qsc audio products, inc. 1675 macarthur boulevard costa mesa, california 92626 usa “qsc” and the qsc logo are registered with the u.S. Patent and trademark office. ©2000 qsc audio products, inc..