Altec Lansing 4200A, 6125A manual Cable Requirements, RACK-MOUNTING Requirements

Operating Manual 6125A and 4200A Multi-Channel Power Amplifier

4.CABLE REQUIREMENTS

4.1Input Cables

Be sure to use shielded cable whether balanced or unbalanced. Shielding which is properly grounded will protect the signal from outside electrical interference such as RF, fluorescent lighting, and computer/display emis- sions. As a general rule, unbalanced or single-ended (tip- sleeve) lines of less than 10 feet are satisfactory, but greater distances or noisy field environments require a balanced signal. Avoid running input lines in close proximity or parallel to long speaker lines, AC power cables, or power transformers, as this may generate hum or oscillation.

4.2Output Cables

These amplifiers are capable of delivering high levels of output current, therefore the wire gauge used for speaker cables is particularly important. Inadequate wire gauge can add significant resistance to the speaker’s own impedance, especially over long distances, reducing the power which is actually delivered to the speaker. It could also result in a decreased damping factor and possible fire hazard. Since power at the speaker load is of primary con- cern in system design, we have included a table to best determine appropriate wire gauge for your application. The following table lists the resistance per 100 feet of com- mon copper wire gauges, and also gives the percentage of the speaker load power which would be lost in an arbitrary 100 ft run of different gauges of 2-conductor copper speaker wire.

Wire Gauge	Ω /100ft	8Ω load	4Ω load
#8	.0605Ω	0.8%	1.5%
#10	.1018Ω	1.3%	2.5%
#12	.1619Ω	2.0%	4.0%
#14	.2575Ω	3.2%	6.4%
#16	.4094Ω	5.1%	10.2%
#18	.6510Ω	8.1%	16.3%

Table 4.1: Wire gauge resistance/power loss

This table expresses the power loss as a percent- age of the load’s power rather than the total amplifier out- put power in order to accurately determine power loss at other cable lengths. For example, if you plan to deliver 150 watts to an 8Ω load through 50 ft of 14 ga. cable, the power loss in the cable would be half that of a 100 ft run of #14 wire as shown in the table, or 1.6% of 150W, which is an insignificant 2.4 watts. However, if you were to run 200 ft of 18 ga. cable to a 4Ω load, the loss would be twice that of the 100 ft run shown in the table, or 32.6% of 250W, which is 81.5 watts lost as heat. Always be sure to use adequate gauge speaker wire.

5.RACK-MOUNTING REQUIREMENTS

5.1Mechanical

The 6125A and 4200A amplifiers are designed to fit in standard 19-inch equipment racks. The front panel rack-mount ears are sufficiently strong for most applica- tions, however if you desire further integrity for mobile racks, we recommend using the four additional holes in the back of the chassis for supplemental rear-mounting (see dimensional drawing for details).

5.2Cooling

Be certain that both the front and back of the rack have unhindered access to free air flow. Fan direction is from front to back. It is not necessary to leave empty space above or below.

5.3Grounding

In some installations where the sound system is sensitive to RF noise or system-induced oscillation, it may be necessary to ground the amplifier’s chassis to the rack enclosure . This is accomplished using star type lockwashers on the four rack mounting screws. These star washers will penetrate through the amplifier’s paint to ad- equately ground the chassis to the rack.

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