EMI Shield Demo

This is a passive noise canceling circuit. There are no op-amps or active circuitry. The EMI (electromagnetic interference) is a chronic problem on active basses and guitars. This first generation circuit is tuned to 60Hz and is intended for basses only. I am working on another version for guitars. By changing out 2 capacitors, this circuit can be tuned to work with 50Hz. This box MUST be the very first thing that the bass is plugged into or the circuit will not function.

This circuit is fully adjustable. The amount of hum caused by the EMI can be dialed out from a little to a lot. However, the more that is dialed out will start canceling the frequencies of the bass because this is a noise canceling circuit. The circuit is designed so that the signal of the bass will not be completely canceled.

The circuit and design are not patentable. The engineering used in this circuit can be found in the Radio Designer’s Handbook 4th edition. This is simply an application for use with a bass and not DC power filtering. This circuit does phase shift the signal 180 degrees and blends it back into the original signal. This circuit also uses a double tuned circuit to selective cancel out the hum more than all the other frequencies. There is a -3dB to -6dB insertion loss when the EMI Shield is activated. Simply bump up the volume of your amp one

Original Work, Copyright 2017 James D. Whiteside, II all rights reserved, For consideration only, no reproduction without prior permission.