The Huminator

Do you have a hum or other noise in your pedal(s)? A very likely cause is noise coming through your AC adaptors. Many cheap adaptors lack even basic power supply filtering, so any noise in your AC mains ends up coming through to your pedal.But don’t despair. Here’s a useful and simple project: build a box that will eliminate hum in your pedal caused by crappy cheap power supplies. And all the parts are easy to find at your local Radio Shack.

The Schematic

Power enters through J1. D1 is a diode the protects against reverse-polarity, i.e. hooking up the wrong polarity adaptor. R2 limits the current the LED which expects 3 volts and would quickly burn out if directly connected to the 9 volt source. R1, C1 and C2 form the filter that reduces hum.

The Parts List

Parts Substitution

If you can’t find the exact parts listed above, you can substitute the following values/types:

LED: any kind of visible LED
3.3K ohm 1/2W 5% Carbon Film Resistor: any resistor of ½ watt or higher, values anywhere from 1k to 4k ohms.
100 ohm 1/2W 5% Carbon Film Resistor: any 100 ohm resistor of ½ watt or higher.
1N4001 Micro 1A diode: Could use just about any 1N400X value
0.047µF 50V 10% PC-Mount Capacitor: any 0.047µF film cap rated for 18 volts or more

Let's Wire it up!

I’ve arranged the wiring so it closely matches the schematic. That way it is easier to translate the schematic into actual wiring. The orange lines indicate the positive voltage and the yellow lines indicate the negative voltage, also known as ground. You can do the wiring by soldering components directly to wires, or use a small bit of perfboard/circuit board.

To ensure this thing actually works for you, be sure to check the connections on the DC power jacks before you solder them. Remember that the standard for pedal powering is tip-negative.

I decided to build mine by using two wires that acted as positive and negative connections. Then I soldered parts between the wires to match the schematic.

After testing all the connections, screw the top on, and make up a quick label with my Brother PTouch label maker!

Make a Patch Cable

To make a power patch cable to go from the output of the Huminator to your pedal, get two 2.1mm DC plugs, and a length of two-conductor wire. Solder the two-conductor wire to each of the plugs and you’re ready to go.

Hooking it Up

Plug your 9 volt AC/DC adaptor into the input. Then plug a 2.11mm DC to DC patch cord into the output of the Huminator and then into your pedal. No more hum!