Do you have any of the following symptoms when your headphones are plugged into professional equipment?

If so, you may need my headphone impedance corrector and attenuator.

The purpose of the headphone impedance corrector and attenuator is to increase the impedance of the load on the headphone amplifier. This reduces the load on the amplifier output, preventing cascading electron noise, preventing excess current through the amp, and keeping this current from increasing the volume and causing distortion.

This is done by inserting a 100-ohm resistor in series with each earpiece. Now, instead of the 8-ohm load commonly used with consumer electronics, the load is closer to the 50 to 600 ohm professional headphones, yet it is not such a high impedance that the headphones fail to work. Two 100-ohm 2-watt resistors are needed.

There are several the resistors can be put in, depending on the kind of setup you have, and what equipment is going to be used with what:

  1. Inside the headphone earpieces. Do this if the headphones are not going to be used with anything else.
  2. If there is room, a miniature switch can be put into the earpiece the stereo cable enters. This is used to insert and remove the resistors.
  3. The resistors can be put on the wires leading to the jack, inside the equipment feeding the headphones. This will work only if the jack is hand-wired in, instead of mounted on a printed circuit board. It is also good only if the equipment will not be used with real 600 ohm phones.
  4. A short adaptor cable containing the resistors can be built. The cable is plugged into the equipment, and then the headphones are plugged into the cable.

In each case, the resistors must be inserted into the two signal lines for the left and right channels, NOT in the common ground line. Here isa diagram of the wiring in the adaptor cable:

Headphone adaptor cable

This adaptor cable has worked with 8-ohm Koss and Radio Shack headphones connected to the following equipment:

Mixing your own music