QSC Audio 1200 manual

1 Owner’ s Manual ® A U D I O Rev. C Model 1 100 Model 1200 Model 1400 Model 1700 ▲ ▲ ▲ ▲ Series One *TD-000027-00*[...]

2 EXPLANATION OF GRAPHICAL SYMBOLS The lightning flash with arrowhead symbol, within an equilateral triangle, is intended to alert the user to the presence of uninsulated “ dangerous voltage ” within the product ’ s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to humans. The exclamation point within an [...]

3 I. INTRODUCTION 1.1 WELCOME Thank you for selecting a QSC Series One power amplifier for your audio system. Our goal is to ensure your complete satisfaction with your amplifier purchase. Please do not hesitate to call your QSC Dealer or QSC Audio Products if you have any service problems or questions not answered in this manual. Your QSC Series O[...]

4 automatically as soon as safe operation is assured. An equally important muting circuit protects the loudspeakers from unexpected damage, by muting the amp during turn-on and turn-off and by blocking DC faults, whether caused by the amplifier or preceding components. The front panel presents essential user information and is recessed to prevent d[...]

5 AMPLIFIER PROTECTION Full Short Circuit, Open Circuit, Over-Temp, Ultrasonic and RF Protection. Stable into reactive or mismatched loads. SPEAKER PROTECTION DC Load Fault Protection 3 Second Turn-on, Instant-off Muting COMPLEMENTARY OUTPUT DEVICES 4 8 16 32 POWER SUPPLY Single Transformer with Independent Isolated Secondary Windings, Fault Fuses,[...]

6 2.27 High voltages can be present on the speaker terminals. Always connect speaker terminals with the power off, and use heavy gauge cable with no frayed strands or damaged insulation. 2.28 Please be aware that power amplifiers have high power circuitry inside with potential for fire and shock hazard; never plug in a damaged amplifier until the c[...]

7 2.39 Operation and Indicators Note that the Gain controls are calibrated in dB. As you turn the Gain down, it takes more input signal to reach full power, so the Gain should be kept in the upper 12 dB of its range for full power output from normal signal sources. The “ 0 dB ” reference indicates that the amplifier gain is at 26 dB when the kn[...]

8 III: OPERA TION 3.1 COOLING 3.11 The Model 1100 uses side-mounted, convection-cooled heat sinks for power transistor cooling. When rack mounted, temperature rise should not be excessive for eight-ohm loads at normal listening levels, but operation into lower impedances at high powers may cause heat build-up unless good access to cool air is provi[...]

9 3.12 The Model 1200 uses an internal heat radiator, top ventilation slots, and the faceplate for cooling. The faceplate will get quite warm in severe usage, but this heatsink system will serve adequately when the amp is used in the open air. If the amps are mounted in tightly confined racks, we recommend that a fan be located so that it blows air[...]

10 mismatches will result in slight loss of common-mode rejection, but will still have much greater noise rejection than unbalanced inputs. 3.34 Balanced Inputs For proper balanced-line operation, the cable shield should be connected at the power amplifier end only and kept separate from both signal conductors. The cable shield should be connected [...]

11 3.36 Unbalanced Inputs and Polarity Unbalanced operation raises an interesting question regarding the trade-offs between maintaining standard system polarity and optimal stability. Normally, an amplifier is expected to reproduce input signals in the same polarity, which is called the non-inverting mode, so that a drum beat, for instance, pushes [...]

12 3.38 Good Quality Connections A tight and corrosion-free contact at all connections is essential for good sound and to avoid erratic noises or unstable performance. 1/4-inch connectors are suitable for low-cost portable systems, but must be removed and replaced frequently to avoid corrosion build-up. 1/4-inch plugs are not recommended for long, [...]

13 Connect the amplifier input to Ch. 1 only, and use only the Ch. 1 Gain control, which now controls the entire amplifier. Do not feed another input into Channel 2. The Ch. 2 Gain control should be kept off for safety. An 8 or 16 ohm speaker load should be connected across the two red speaker terminals, using the red terminal of Ch. 1 as the “ +[...]

14 loss of 10% is barely audible, the resultant low damping factor will prevent the amplifier from fully controlling the peaks and dips in frequency response caused by speaker impedance variations. This will result in greater coloration and muddiness. Cable Wire Cable Power Loss, Power Loss, Damping Damping Length Gauge Resistance 8 Ω Load 4 Ω [...]

15 3.7 25 AND 70 VOLT SYSTEMS 3.71 Introduction Commercial sound systems commonly use dozens or even hundreds of speakers for sound distribution. Special methods for connecting and controlling many separate speakers have been worked out by commercial sound contractors. 3.72 25 Volt lines 25 volt distribution systems are popular in small to medium s[...]

16 3.83 Thermal Protection In case of blocked ventilation, improper loading or prolonged short-circuit operation, the temperature of the power transistors can rise to excessive levels. If the temperature of the heat sink rises to 85C, a thermostat will remove power to that channel. Power will be automatically restored when the channel has been allo[...]

17 then the fault is somewhere in the bad channel. Check the input program switches, octal accessory (if any) or jacks. See Section 3.5 for correct switch settings. Inspect the binding posts for damage, and try a different input jack or the parallel channel switches before giving up on the channel. 3.93 Weak But Clear Sound This usually indicates l[...]

18 that stage. Assuming that the hiss has not always been there, this indicates defective electronics. Certain special- effects units are rather noisy, so compare with other users. Crackles — defined as a “ popcorn ” noise. If the crackle persists during pauses in the program material, this indicates defective electronics and must be traced d[...]

19 You may have some problems finding the larger value capacitors in the preferred film-type construction. If necessary, several can be paralleled; simply add the individual capacitances together to get the total rating. You will probably have to locate non-polar electrolytics for values greater than 10-20uf. 4.4 POWER CAPACITY All speakers have a [...]

20 V : MAINTENANCE AND SER VICE 5.1 CLEANING The faceplate and chassis can be cleaned with a soft cloth and mild non-abrasive cleaning solution, such as Windex. Avoid cleaning powders or scrubbing pads, as these will scratch and dull the paint. Be sure to unplug the unit prior to cleaning. Do not apply liquid directly to the surface. Dampen the clo[...]

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22 ® A U D I O “ QSC ” is a registered trademark of QSC Audio Products, Inc. 1675 MacArthur Blvd. Costa Mesa, CA 92626 (714) 754-6175 FAX (714) 754-6174[...]