User manual ALESIS RA300

[. . . ] REFERENCE SERIES TM TM TM POWER AMPLIFIERS REFERENCE MANUAL ©2000 Alesis Corporation Alesis RA150-500 Reference Manual © Copyright 2000, Alesis Studio Electronics, Inc. Reproduction in whole or in part is prohibited. "RA150/300/500" and "Reference Series" are trademarks of Alesis Studio Electronics, Inc. ALESIS CONTACT INFORMATION Alesis Studio Electronics, Inc. 1633 26th Street Santa Monica, CA 90404 USA Do not use this address for repair service. [. . . ] Since there is no difference between these signals, the differential amplifier or transformer will reject the interference to a great degree. This tendency to ignore interference is called Common Mode Rejection. If you have the RA150, which doesn't have an XLR input, you may use an XLR-F to TRS-M cable or adapter. The 1/4" input jack of the RA150 is balanced. (See Figure 5 on page 17. ) To connect an unbalanced source to the amplifier input: Unbalanced cable Simply use a standard, shielded 1/4" patch cord. Or, if the source has an RCA/phono output, use a shielded phono-to-phono cable. Unbalanced-to-balanced cable with telescoping shield In some installations, you may be able to eliminate a ground loop even though the source is unbalanced by wiring a cable or adapter that has the shield connected at only the unbalanced end, using the inner conductor wires to carry the "hot" signal to pin 2 and the ground to pin 3 of the RA150/300/500. This may keep any ground potential difference between the source and the amplifier out of the signal path. The following diagram shows an adapter that assumes pin 2 of the XLR connector is "hot"; note that the shield of the phone jack is NOT connected to pin 1 (the ground of the amplifier), but is left floating (disconnected). To connect a balanced line output to feed the RA150/300/500: You have two options: TRS-to-TRS cable Most modern mixing consoles, such as the Alesis Studio 32, feature balanced outputs on 1/4" TRS jacks. This is the same balancing connector used by the RA150/300/500. Get a 3-conductor cable with a 1/4" male TRS connector at each end. Male XLR Connector 2 (hot) 1 (float) 3 (cold) 1/4 " phone jack XLR-to-XLR cable A slightly more expensive balanced connector is the XLR type, most commonly sold as a "microphone cable". The main advantage of this is that the connector locks in place, making it more resistant to accidental disconnection. If your mixing console has XLR outputs, and you have the RA300 or RA500 amplifier, you may connect it with an XLR female to XLR male cable. (The mixer will have an XLR male jack, the amp has an XLR female jack. ) If you have an RA150 without an XLR input, then make a 1/4" mono to 1/4" TRS adapter. Wire the "hot" of the input signal to the tip, the shield/ground to the ring, and leave the sleeve disconnected at the RA150. 16 RA150/300/500 Reference Manual Chapter 2: Connections Isolation transformer or direct box If your mixer or other sound source doesn't have a balanced output, you may turn it into a balanced signal with an external device, either active (electronic, powered) or passive (a transformer). These commonly available audio accessories have a balanced line output, usually in the form of an XLR connector, and an unbalanced line input, usually in the form of a 1/4" phone jack. A line transformer can also convert balanced signals to unbalanced signals. Advantage of a transformer: High signal carrying capacity, no power required, generates no hiss. Disadvantages: Inexpensive transformers may color the sound due to frequency response irregularities and can pick up hum due to inductive nature of transformers. Very high-fidelity models are expensive. Active direct boxes use an active electronic circuit to drive a balanced line, but does not work in the other direction. Advantages: Good frequency response specs, no inherent hum pickup, less expensive than transformers. Disadvantages: Requires power, generates some noise. To feed the same source to several different amplifiers: The input impedance of the Alesis amplifiers is 20 k in balanced and 10 k in unbalanced configuration. Thus, the inputs of several amplifiers may be connected in parallel if desired. [. . . ] See Bridged Mono noise, 25 Output Relays, 26 Outputs, 18 phase. See polarity phone plug inputs, 14 polarity, 20 how to test, 22 power output, 30 Power cable, 3 power loss in speaker cable, 18 protection, 7 Rack Mounting, 11 RCA/phono input jacks. See Repair Service, 29 Safety, 3, 24 shield telescoping, 24 sound level meter, 25 Specifications, 30 thermal protect mode, 27 transformer input, 17 transformers power, 7, 33 TRS jacks, 14, 16 turn-on delay, 21 unbalanced input, 14, 16 Unbalanced-to-balanced cable, 16 ungrounded outlets, 9 volume controls, 21 XLR input, 16 XLR input jacks, 13 34 RA150/300/500 Reference Manual ALESIS LIMITED WARRANTY ALESIS ("ALESIS") warrants this product to be free of defects in material and workmanship for a period of one (1) year for parts and for a period of one (1) year for labor from the date of original retail purchase. This warranty is enforceable only by the original retail purchaser and cannot be transferred or assigned. [. . . ]