Hum Filter

You can purchase a hum eliminator for $70 or for less than a dollar accomplish the same thing using a high-pass filter using a resistor and a capacitor. The EXACT SAME THING! So, I have included oscilloscope shots of the before and after along with recording the hum. I have demonstrated the $1 circuit and modified a guitar cable to install it. I show the circuit, explain the circuit and show you how to build this filter.

It is just absolutely nuts to pay $70 for a box when you can put that same circuit in a cable for next to nothing.

If you have a hum either caused by a loud preamp, ground loop, power supply, etc. then this filter is the first thing to try. Normally, you install this just before the last piece of equipment that is going to the PA. For example: between the amp and the sound board. Or if the amp is the last in the chain, then install this between the pedal board and the amp input.

Update: This filter will attenuate the signal by 10 to 15dB. Nothing is free. The hum will be gone, but you will need to set your volume up higher to get the same signal strength out. Also, if you install this BACKWARDS, it makes the hum LOUDER! The resistor side of the filter goes towards the downstream piece of equipment. For example, if you connect the amp's line out to a mixer, the resistor goes toward the mixer.


Original Work, Copyright 2013 James D. Whiteside, II all rights reserved, For consideration only, no reproduction without prior permission.