![]() ![]() When painting, pay particular attention to the area that contacts the jack, the pots and the switch. To correct these issues, the control cavity should be repainted with shielding paint or lined with copper foil. Loss of contact on these components leads to noise when you touch the knobs. It is important that the pots and switch on the preamp also remain well connected to the shielding. A shield cavity that is ungrounded will add noise to the circuit. ![]() This results in a shielding cavity that is no longer grounded. If the jack has worked loose or has been changed many times, it is possible for the paint in this area to become worn away. When the jack is tightened against the inside of the painted cavity, the shielding paint is effectively grounded. This connection is made through the jack. As the shielding ages/wears the connection to the preamp becomes degraded and interference (electrical, radio, microwave noise) is allowed in. To prevent interference, the control cavity (including the cover plate) is lined with shielding paint or shielding tape thereby creating a capsule around the preamp. Active electronics are highly sensitive to outside interference which affects it as noise.
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