Evaluating Equipment-induced EMI noise in one’s audio system

Audiophiles have long recognized power line noise as the bane towards enjoying one’s audio system since at least the 1970’s (if not earlier). Folks appreciate their rigs often when the power grid has lower traffic during off-peak hours, such as late into the evening. More recently, perhaps beginning in the mid-1980’s or so (please don’t hold me to dates here, as I’ll stipulate I might be off on time), audiophiles have employed numerous devices such as power conditioners, power line filters, power regenerative devices, even battery-driven gear as a way to reduce power line noise getting into one’s system. And many of these devices actually work as claimed. But in this thread. I want to explore the extent to which the audio equipment, itself, whether a power line noise treatment device or an essential or auxiliary piece of audio electronics component introduces EMI or RFI noise into one’s system. I’ll describe a simple, inexpensive tool and method to evaluate any component’s inherent line noise. And whether one should use that as a guide to accept or reject a given audio component in one’s system. I will present my findings for two well known components familiar to most folks here in the forum. One will be a power conditioner that regenerates a corrected AC power signal. The second component will be a Class D amplifier and external power supply. Buckle up and let’s have some fun!