Hi fi and AV systems typically comprise of a number of individual, interconnected components, and as such, any problems arising must be carefully and systematically diagnosed to ensure that the cause of the fault is accurately located.

As a guide, a typical faultfinding procedure is detailed below. No matter how complex you hi fi or AV system is the same faultfinding procedures can be applied.

In the event that your system requires service, we strongly recommend that this be undertaken by an authorized service technician.

Hum is a particularly annoying form of noise in any high fidelity system and at some time has been experienced by many of us.

Hum may result from a number of different situations and to make matters worse maybe caused by a seemingly illogical combination of circumstances.

One or more of three specific causes creates hum in the system.

Induced Hum
Hum can be induced into the system from one or more sources and is generally associated with the radiation of noise from one system into another.

Hum and noise can be radiated from any object or system involving AC voltage and current such as power supplies in amplifiers, motors, switching equipment etc. All of these may be found in your hi fi system or within your own home.

Hum may be induced into any part of the system, so there are no specific instructions that can be given which will offer a guaranteed cure. A good practice to adopt is to keep low-level signal equipment such as phono systems, tuners etc. well away from high-level signal equipment such as power amplifiers. Alternatively, careful designs must be employed to negate these effects on

low-level signal equipment. Another good practice to adopt is to keep all signal leads away from power leads.

The practice of neatly tying excess leads together for a tidy looking installation should be resisted, as this could be the cause of induced hum in the system.

Earth Loops
Earth loops are a particularly annoying cause of hum in the system. Earth loops are created by mains frequency current flowing in the screen of signal leads and becomes apparent with the lack of adequate earthing between the various pieces of equipment making up the hi fi system. This is further compounded by the fact that the equipment earthing considerations vary between different manufacturers and countries.

Perreaux products used with equipment manufactured by other manufacturers may cause an earth loop situation, but Perreaux products used with other Perreaux products will not cause an earth loop situation provided the following precautions are observed:

• The entire hi fi/AV system must be connected to the same mains/line power outlet. This will ensure that each piece of the system shares the same earth or ground. This rule applies to all installations of all brands of equipment. A preamplifier or power amplifier may be operated from an extension cord plugged into the same mains/line outlet.

• When a piece of equipment is supplied with a three pin mains/line supply lead all three pins must be connected in the correct fashion - see your dealer if in doubt.
• Check all interconnecting signal leads for good connections, both internal connections and firm contact with the sockets. While the centre pin may make firm contact, it is very important that the outer contact is also firm.

Never remove the earth/ground wire from the mains/line supply of any piece of equipment. This could be hazardous.

Broken Earth Connections
This is a common cause of hum and noise in the system. In many instances, the only way to eliminate the possibility of hum problems arising through a broken earth connection somewhere in the system is to physically check every connection.

When experiencing a problem, such as one channel not working, or a noise in one channel, it is good practice to adopt a method of isolating the problem to a specific item or area. This practice will assist in diagnosing, curing, or at least advising your technician of the problem and result in a saving of time, money and perhaps frustration.

A logical approach to isolating the probable cause of the problem is to start at the loudspeakers and work back to the music source, eliminating each piece of equipment in turn.

Check that the entire system is connected in the proper manner and that the mains/line supply is connected and switched on.

For clarity during this section, we have labeled one loudspeaker "A" and the other loudspeaker "B". In this example, loudspeaker "A" appears faulty.

Step 1 - Initial System Connections
LoudspeakerChange the loudspeaker leads from one loudspeaker to the other. If the fault remains in loudspeaker "A", then loudspeaker "A" is at fault, go no further.
If the fault now appears in loudspeaker "B" then the problem lies further up the line. Move on to step 2.

Step 2 - Loudspeaker Leads
Change the loudspeaker leads completely from left channel to right and from right channel to left by now swapping them at the amplifier output. If the fault now appears in loudspeaker "B", then that loudspeaker lead is at fault, go no further.

If the fault appears in loudspeaker "A" then loudspeaker leads are OK. Move on to step 3.

Step 3a - Input Sources (Channels)
Change the input plugs on the rear of your amplifier, as follows: Change each input source in turn by swapping the plugs left to right and right to left. If the fault changes to loudspeaker "B" on any one of the selected inputs, then that particular input source is possibly at fault. Move on to step 3b.

If the fault stays in loudspeaker "A", then it is probable that the fault may exist within the amplifier.

Step 3b - Input Sources (Interconnects)
Change the interconnect leads completely from left channel to right and from right channel to left by now swapping them at the source component"s output. If the fault stays in loudspeaker "B", then the interconnect lead is at fault, go no further.

If the fault appears in loudspeaker "A", then the interconnect lead is OK.

Should the fault prove to be in the amplifier it will be necessary to determine where the fault actually lies. Most of this has been done, for instance, you now know what input/s and what channel is affected. This information will assist your Perreaux dealer or service person when or if any service is required.

If the apparent fault is noise in one or both channels and has been localised to the amplifier, it will be necessary to determine whether or not the noise increases with the volume control; whether or not the noise exists when no input at all is connected to the amplifier; and what type of sound the noise is. For example, low frequency humming noise or high frequency hissing noise. This information will also assist your service person in making repairs or adjustments.