New Trim-1 mono stepped attenuator

The Trim-1 stepped attenuator offers 11 positions and can viewed as high-quality replacement for a potentiometer. In other words, it can be used in non-audio as well as audio applications. Making a linear potentiometer replacement is easy: just divide the require resistance by 11 to get each resistor's value. For example, if a 100k potentiometer replacement is needed, use 9.09k 1% resistors or 9.1k 5% resistors. If ½W resistors are used, then the dissipation limit for the Trim-1 would be 5.5W, as 11 x 0.5W = 5.5W.

For audio use, a log tapper is desired. The amount of attenuation per step depends on the application. For example, if one Trim-1 is used per monobloc power amplifier, as a volume-matching control in a bi-amplifier setup, where the tweeter or midrange is a few dB more efficient than the woofer, then -1dB (or -0.5dB) decrements are suitable. (Many feedback-free tube amplifiers present a slight gain mismatch between channels, as the tubes are not perfectly matched; thus, -0.5dB decrements are useful.) On the other hand, if dual mono volume controls is the intended application, then -6dB decrements are a better choice.

A Trim-1 can be used as a balance control of sorts, by using -1dB steps and using only one in the right channel and using a -5dB two-resistor voltage divider on the left channel. Then turn the Trim-1 to its sixth position (-5dB), so the channels match.

The Trim-1 kit includes the PCB and 11-position rotary switch and user guide. Resistors are optional.