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Фрагмент инструкции
• Prevent the side heat sink fins from becoming obstructed. There should be enough airspace around the amplifier for it to “breathe.” • Always allow adequate ventilation behind the RA150/300/500. Do not seal any enclosure that holds the RA150/300/500. • Never throw a coat or other flexible fabric or covering over the top of the amp when it’s in use. • You may wish to leave an empty rack space above or below the amp to promote good air flow. If multiple amplifiers are mounted in the same rack, there should be at least one rack space left between them; solid blank panels may be used to fill the spaces, but perforated grilles used as fillers will help exhaust the hot air from within the rack. OTHER RACK MOUNTING TIPS • Due to the RA150/300/500’s weight (from 15 to 28.5 lbs.), it’s a good idea to mount it in the bottom of the rack frame. Support of the back of the unit may be necessary for portable or road use. • Alesis Reference amplifiers are well shielded; however, mounting low-level electronics some distance away from power amplifiers is common practice to reduce the possibility of electromagnetic interference into the low level units, which may sometimes be unusually susceptible to picking up such radiation. When wiring a rack, it is good installation practice to route all AC wiring along one side of the rack and all audio wiring along the other side to avoid coupling AC-borne interference into the audio. RA150/300/500 Reference Manual Connections: Chapter 2 MOUNTING ON A SHELF OR IN A NON-RACK ENCLOSURE To mount the amplifier on a shelf or other flat surface, Alesis recommends using the enclosed stick-on feet to avoid scratching the shelf’s surface with the amplifier bottom. To properly mount the stick-on feet: 1 Place the amplifier upside down on a clean cloth or piece of cardboard so the amp top does not scratch your work surface. 2 Clean the bottom of the amp where you plan to stick the feet. Isopropyl alcohol is recommended as a cleaning agent. This step insures that no small amounts of oil or other substances will inhibit proper adhesion of the feet. 3 When the surface has dried, attach the feet. Please observe the comments on thermal considerations given under “Temperature Considerations in Rack Mounting” no matter where or how the amp is mounted. AVOIDING ELECTROMAGNETIC INTERFERENCE Because the RA150/300/500 contains a large power transformer, we recommend that you do not: • Place the RA150/300/500 next to an unshielded video monitor, as the magnetic fields may distort the image. • Place tapes, disks, or other magnetic media close to the RA150/300/500. • Play guitar, bass, or any other instrument with magnetic pickups near the RA150/300/500. No damage will occur but AC fields may enter the pickups, causing hum. RA150/300/500 Reference Manual Chapter 2: Connections RA150/300/500 Reference Manual 13 INPUTS INPUT JACK CHARACTERISTICS The RA150/300/500 include two balanced, 1/4" TRS (tip-ring-sleeve, 3-conductor) phone jack inputs, and unbalanced RCA/phono inputs. The RA300 and RA500 feature combination XLR input jacks as well. The inputs are wired according to IEC standards, as shown in the table below. These are compatible with the low-impedance, unbalanced or balanced, line-level outputs typically emanating from equipment such as mixers, synthesizers, samplers, direct boxes, crossovers, etc. Electric guitars, microphones, and other lowlevel/ high-impedance output devices require a preamp. Connection XLR Phone Jack RCA/phono jack Audio Ground Pin 1 Sleeve Shell High (+) Pin 2 Tip Pin Low (–) Pin 3 Ring -- RA150 Back Panel RA300 Back Panel RA500 Back Panel Connections: Chapter 2 Warning: Be sure that the AC power is off prior to connecting or disconnecting any signal wiring. The input circuits of the Alesis amplifiers are electronically balanced. They may be fed from either symmetrical (“balanced”) or unbalanced sources. On the RA300 and RA 500, there are two combination XLR/1/4” (6.3 mm) jacks provided, one for each channel. Figure 3. Balanced wiring of an XLR input connector. Figure 4. Unbalanced wiring of an XLR input connector. Figure 5. Balanced wiring of a 1/4” (6.3 mm) three- wire phone plug. Figure 6. Unbalanced wiring of a 1/4” (6.3 mm) three-wire phone plug All input wiring should be done with shielded cable. To use an unbalanced source with an Alesis amplifier: Connect the High (+) signal wire as shown in Table 1 and connect the shield wire to both the Low (–) and Audio Ground input connections. See Figures 4 and 6. If a two-wire (tip and sleeve only) phone plug is used for an unbalanced input, the sleeve of the plug will automatically connect the Low and Audio Ground connections together inside the amplifier. Long input cable runs, particularly in areas with high electrical interference, should be done with symmetrical (“balanced”) configuration, if possible, to lessen the possibility of interference being picked up by the cables. Only one input jack of a channel should be used at a time:...
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