LOAD MATCHER

Most audio circuits transfer their maximum power at minimum distortion only when the output impedance is matched to the load impedance. But it is often necessary to connect equipment of differing impedances. For example, how do you correct an amplifier with a 600 ohm output into an amplifier with a 50 ohm input? Usually, if the 50 ohm input is connected across the amplifier with a 600 ohm output, the excessive loading caused by 50 ohms will sharply reduce the output of the 600 ohm amplifier, and will generally increase the distortion sharply.

A minimum loss pad is the device used to match a high impedance to a low impedance. Though there is always a signal level loss through a pad, the circuit shown provides the absolute minimum loss that can be obtained while providing a precise match. If the resistance values work out to odd values, such as 134 ohms, use the closest standard value. Though 5 percent tolerance resistors are suggested, almost as good performance will be obtained with 10 percent resistors.