Most musical instrument sound pickups, for example those in electric guitars, are comprised of high impedance circuits driven mainly by voltage with very little electrical current flow. That is why handling noise (microphonics) can be a problem for guitar cables. Microphonic noise is caused by the minute voltage generated when a cable is flexed, stepped on, etc. Guitar cables must be designed to prevent this, so a conductive PVC layer is placed under the shield conductor to drain away this voltage. Note: This conductive layer must be stripped back when wiring, or a partial short will result.
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