JBL GTS100 owner manual

ment is more likely to pick up such noise than conventional equipment because it has wide frequency band- width and high gain (amplification) cir- cuits. The GTS100 has built-in power supply filters to help prevent noise prob- lems. If noise occurs it is probably the result of improper installation. The following suggestions will help you eliminate most noise problems.

Source Noise – Often noise in a system is picked up by the signal source. Before attempting to eliminate noise from the “amp” be sure it is not being picked up by the signal source and then passed on to the amp. To do this, con- nect the signal source output to an external amplifier which has no other connection to the vehicle except for the audio signal leads. A battery-powered portable with line-inputs works well for this. Listen to see if the noise is present in the signal from the source unit. If so, consult the manufacturer of the source unit, or your JBL dealer, for help in elim- inating this noise. If there is no noise in this signal, it can be eliminated as the source of the noise in your system.

Ground Loops – The vast majority of noise problems in car audio systems are caused by inadequate or improper grounding. The head unit, the amplifier and any other components must be grounded to a major metal member of the vehicle’s frame. Make sure to choose a solid metal ground point. In many new vehicles some structural ele- ments are made of plastic.

Although not usually necessary, practi- cal experience shows that often the noise level in the system will be lower if

the amplifiers and signal processors are all grounded to the same point on the chassis. Usually the head unit does not need to be grounded to the same point as the rest of the system, but in some instances grounding the head unit to the same point will also help. If this does not adequately reduce the noise level, try another ground point on the car frame. Some ground points may work better than others. In some in- stances with plastic-bodied vehicles, grounding the source unit and/or amplifier directly to the battery will provide the best results, although, usually, this provides the worst results with most cars.

In complex systems involving compo- nents from different manufacturers, it helps to know the type of power sup- plies used in each component. For low-level signal processors such as equalizers or electronic crossovers, a manufacturer may either use a power supply which is isolated through a DC- to-DC converter, or a simple regulated supply from the +12V vehicle battery. Components using the latter type of supply can be identified by a direct con- nection from power ground to the shield of the RCA jacks (measured with no other connections present). For these components, the best ground connec- tion may be one where the power ground wire is not connected at all! The RCA cables will provide the ground connection to the source unit. Please note that this is only appropriate for units which draw less than 500mA of current. Higher power units of this type are best connected with their ground

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