Parasound A 51 manual Technically Speaking

14TECHNICALLY SPEAKING continued

hum (or 50 Hz hum in regions with 50 Hz AC). The harmonics of these frequencies (120 Hz, 240 Hz, 480 Hz or 100 Hz, 200 Hz, 400 Hz) may add buzz in addi- tion to the hum.

The ideal of zero voltage ground for all the compo- nents in a system is practically impossible, because some resistance between the ground points of differ- ent components is inevitable. By keeping components close together with their power cords plugged into a common AC outlet or power strip, you’ll avoid the problems created by resistance in the house’s wiring.

Hum and buzz is also caused when unwanted voltage flows through multiple component ground points called ground loops. Here are three tips to avoid ground loops:

1.Use balanced input lines with your Parasound A 51. (See Balanced and Unbalanced Lines in this section).

2.When rack mounting, always use the insulated

“shoulder” washers. These break the ground loops caused by metal-to-metal contact between the rack, the components, and their rack-mount bolts. Extra washers are available from rack manufacturer Middle Atlantic Products, www.middleatlantic.com.

3.Use the Ground switch on the A 51 to eliminate most ground loops. This separates the A 51’s signal input ground from its chassis ground to isolate unwanted voltage in the ground shield of the unbalanced (RCA) input cable. Be sure your system installation is finished before you try moving the Ground switch from its Normal to its Lift position.

A51 Amplifier

Parasound Products, Inc. San Francisco, CA USA

L U C A S F I L M

Manufactured under license from Lucasfilm Ltd. Lucasfilm and THX are registered Trademarks of Lucasfilm Ltd.

WARNING

To Prevent Fire Or Shock

Hazard, Do Not Expose This

Unit To Rain Or Moisture.

CAUTION

To Prevent Electric Shock,

Do Not Remove Cover. No

User-Serviceable Parts Inside,

Refer Servicing To Qualified

Service Personnel.

	Input Select
Balanced		Unbalanced
		Ch 1
		Ch 2
		Ch 3
		Ch 4
				Fuse
		Ch 5		T15A/250V1-115V Area
				T8A/250V-230V Area
				AC 115V	60Hz
				AC 230V	50Hz
	Audio		Lift
Man
	12 V	50 mV 250	Normal	Power Consumption: 1800W
Input		Sensitivity	Ground
	Auto Turn On

Ground Switch, set to up position