User manual QSC AUDIO MODEL 3500

[. . . ] 16 IV: SPEAKER PROTECTION 4. 1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V: MAINTENANCE AND SERVICE 5. 1 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. 4 Obtaining Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EXPLICATION DES SYMBOLES GRAPHIQUES Le symbole èclair avec point de flèche à l'intrérieur d'un triangle équilatéral est utilisé pour alerter l'utilisateur de la présence à l'intérieur du coffret de "voltage dangereux" non isolé d'ampleur suffisante pour constituer un risque d'elétrocution. Le point d'exclamation à l'intérieur d'un triangle équilatéral est employé pour alerter les utilisateurs de la présence d'instructions importantes pour le fonctionnement et l'entretien (service) dans le livret d'instruction accompagnant l'appareil. CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN CAUTION: To reduce the rish of electric shock, do not remove the cover. [. . . ] For permanent wiring harnesses, the barrier strip is the cheapest and best. The signal wiring can be stripped and wrapped around the terminal screws, or spade terminals can be soldered or crimped onto the ends of the signal conductors. When crimping, be sure to use the proper tool with generous pressure, and test the resultant crimp by pulling while closely inspecting. If the wire wiggles inside the crimped terminal, the contact will go bad. The spade lug, or bare wire ends, can then be tightly screwed down to the proper positions on the barrier strip. If high pressure is maintained in the crimp and the screw terminal, a "gas-tight" connection is formed which will exclude corrosion for many years. 3. 4 OCTAL MODULE ACCESSORIES 3. 41 3. 42 Octal Socket Each channel has an octal socket for active and passive plug-in accessories. This is shipped with a protective label to prevent corrosion of the pins. Input Transformer Although the audio benefits of transformerless coupling are well recognized, certain users still prefer the security of a transformer-coupled input in severe environments. In addition to the QSC model T-1 input transformer, the Bauer Communication model RE-11P-QN is available for QSC amplifiers. Active Accessories In a number of special cases, the user needs built-in power limiting, bi-amp capability, etc. In order to serve these needs without adding to the basic cost of the amplifier, the octal socket has been designed with low-level DC power tapped off the internal supply of the amplifier. If the parallel-channel switches (#5, 6, see Section 3. 51) are switched on, the signal into Ch. To prevent this, and still permit patching to additional amps, keep the Gain for Ch. 2 fully off. 3. 6 SPEAKER CONNECTIONS 3. 61 Speaker Terminals Red and Black 5-way binding posts, on standard 3/4-inch centers, are located on the rear of the chassis of all Series One amplifiers. The 1100 features a pair of standard 1/4" headphone jacks on the front panel. They are connected to the speaker outputs of the amplifier through a resistive pad that prevents excessive power levels from damaging the headphones. Always fully turn down the Gain controls before plugging in headphones to prevent accidental exposure to excessive sound levels that can cause permanent hearing damage. 3. 62 3. 63 Terminal Polarity The Red binding post carries the positive or "hot" speaker output. Speaker Cables In order to obtain the full benefit of the high power and high damping factor of the amplifier, the user must avoid cable losses. The best way is to use the heaviest-gauge, finely stranded wiring possible. 12gauge speaker cable is available, and heavier gauge "specialty" cable is sold by audio dealers. Cable Termination A major problem with heavy-gauge cables is that the ends are too large to fit most speaker terminals. [. . . ] You will probably have to locate non-polar electrolytics for values greater than 10-20uf. 4. 4 POWER CAPACITY All speakers have a maximum long-term power limit which is determined by the temperature rise of the voice coil. The speaker can withstand short peaks above this level, since the voice coil takes a little while to overheat. The time lag depends on the size and mass of the voice coil and ranges from a fraction of a second to several seconds. The required speaker rating for a given amplifier power depends on the type of program material. [. . . ]