JBL GTS100 owner manual

wires connected directly to the chassis of the head unit. The trickiest grounding task is created when some components of this type are mixed with other compo- nents using isolated supplies. For this type of system, the following grounding scheme will usually work:

1.Connect the head unit chassis to a solid vehicle ground using a short, heavy gauge wire (>AWG10). Do not connect this to the vehicle’s wiring harness, but go directly to a metal part of the vehicle.

2.Connect all non-isolated signal- processor grounds directly to the head unit chassis at the same point. Run each wire individually. Due to wire resistance connecting multiple wires to a single wire, then running the single wire to the head unit, is not the same!

3.Connect all amplifier and isolated signal processor grounds directly to the vehicle chassis at the same point as each other, but not necessarily to the same point as the head unit.

Power-line Noise – The built-in power supply filter of the amplifier makes external filters unnecessary. In some cases, power supply noise can enter the system through the head unit power supply or the supply of an equalizer or other signal processor. Putting a filter on the head unit or signal processor power supply input may then be helpful.

Power wires carrying high currents may induce noise in nearby signal wires. Make sure that power wires and signal wires do not run together for long dis- tances. When power and signal leads

must cross, they should cross at right angles. If you suspect that power line noise is being induced in the signal leads, you can repeat the test for source noise described previously, but perform the test at the amplifier end of the signal cables.

Other Noise Sources – Common noise problems will be solved by proper grounding and power supply connec- tions. However, there are many noise suppression devices (such as spark plug and coil lead suppressers and rotor and coil bypass capacitors) avail- able at auto parts or car stereo stores. There are also noise suppressers that can be connected directly to the alter- nator that are effective in some situa- tions. The use of any such suppressors should be discussed with a JBL autho- rized installation specialist. Certain vehicles are particularly “noisy,” espe- cially models that have solid state igni- tion systems or that have non-metal bodies. Such vehicles may require elec- trical noise suppression devices which are not normally needed.

Antenna – A common noise problem is generated by a “ground loop” produced by the antenna shielded cable being grounded at both the antenna mounting point and at the head unit input. In this instance, insulate the antenna ground from the chassis of the vehicle at the antenna mounting point so the antenna shield is grounded only at the radio’s antenna input. Commercial antenna ground-loop isolators are also available.

Switching Noise – The GTS100 has a highly developed switching power sup- ply which generates some RF interfer-

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