Ashly MFA-6000, MFA-8000 manual Cable Requirements, RACK-MOUNTING Requirements

Operating Manual - MFA-8000 and MFA-6000 Power Amplifier

peaking at the clipping level, the following AC line cur- rent capacities are recommended for system design pur- poses:

Load	MFA-6000	MFA-8000
Idle	1 Amp	1.2 Amps
8Ω × 2	7.5 Amps	10 Amps
4Ω × 2	10 Amps	15 Amps
2Ω × 2	15 Amps	20 Amps

Table 3.1: Recommended AC line current capacity

Both MFA amplifiers consume less than 12 amps when operating at 1/8 power into 2Ω loads. This condi- tion satisfies the UL, CSA and building electrical code requirements for a piece of audio equipment not to con- sume more than 80% of the current available when plugged into a grounded 15 amp outlet and operated at 1/8 of maxi- mum power.

3.3AC Grounding Requirements

To reduce the risk of ground loop hum, all system ground references should originate at the same point in your AC power distribution. Never remove the amplifier’s ground pin as it is both unlawful and dangerous, creating a potential shock hazard.

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, even computer noise. As a general rule, unbalanced or single-ended (tip-sleeve) lines of less than 10 feet are satisfactory, but greater distances may 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 gener- ate hum or oscillation.

4.2Output Cables

The MFA amplifiers are capable of delivering high levels of output current, therefore the wire gauge used for speaker cables is particularly important. Inadequate wire gauge adds significant resistance to the speaker’s own impedance, reducing the power which is actually deliv- ered to the speaker. It will also result in a decrease in the damping factor and possible fire hazard.

Since power at the speaker load is a primary con- cern in system design, we have included a table to best determine appropriate wire gauge for your application. Table 4.1 lists the percentage of the speaker load power which would be lost in an arbitrary 100 ft run of 2-con- ductor cable. This table expresses the power loss as a per- centage of the load’s power rather than the total amplifier output power, so that you can use this table to accurately determine power loss at other cable lengths. For example, if you plan to deliver 100 watts to an 8Ω load through 50 ft of 14 ga. cable, the power loss in the cable would be 3.2% ÷ 2 = 1.6% of 100 watts or 1.6 watts lost in the cable.

Wire Gauge	Ω/100ft	8Ω load	4Ω load	2Ω load
	.0605Ω
8		0.8%	1.5%	3.0%
10	.1018Ω	1.3%	2.5%	5.1%
12	.1619Ω	2.0%	4.0%	8.1%
14	.2575Ω	3.2%	6.4%	12.9%
16	.4094Ω	5.1%	10.2%	20.5%
18	.6510Ω	8.1%	16.3%	32.6%

Table 4.1: Percentage of speaker load power lost in 100 foot run of 2-conductor cable.

5.RACK-MOUNTING REQUIREMENTS

5.1Mechanical

All Ashly amps are designed to fit in standard 19- inch racks. The front panel rack-mount ears are suffi- ciently strong for most applications. If you desire further integrity for mobile racks, we recommend using the four additional holes in the back of the chassis for supplemen- tal rear-mounting (see dimensional drawings).

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 the amplifier for cooling purposes. Ther- mal output of the amp is measured in max BTU/hour for typical audio program material when both channels are just peaking at the clipping level.

Load	MFA-6000	MFA-8000
Idle	420	500
8Ω	1900	2420
4Ω	2300	3450
2Ω	4140	4830

Table 5.1: Maximum BTU/hour

5