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!
There may be noise but the equipment rectifiers will filter out most of the noise, so the EMI noise may not be the main culprit because it will be filtered out. Another thing to consider about the power conditioner or power regenerator is they lowered the impedance which improve the dynamic of the down stream equipment. It is something you could measure. A lot of power filters which may filter out the noise but it increases the impedance which takes away the dynamic. |
Well I wished I would have searched here first. I just learned this same lesson. i found an EMI tester on ebay and thought it would be a great tool to own. Turns out i got exactly the same kind of results as you. Around 70mv noise directly from my outlet. Then I connected my well known company power conditioner/power supply surge protector yada yada and now it measures 170mv noise. I called the company and asked why and they only told me that Its best to just ignore what the emi meter says and just listen to the music. I feel like if i listen to the music it will be from power directly out of the wall outlet because its not as noisy as the power conditioner. Can I hear it? no. can i measure it? yes. Snakey oil. i would love to know which brand you tested that reduced the noise. |
@venpick said:
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No load connected. Correct? EMI = electromagnetic Interference. Correct? If there is not any load connected to the outlet there will only be an electric field. Correct? No load no current. No current no magnetic field. Correct? No EM field. Add small load, small EM field. Add large load, large EM field. Higher reading... Plug in a table lamp with a regular filament incandescent bulb. What does the meter measure? The incandescent bulb is a pure resistive load. EM field yes. EMI? I don’t think so. Food for thought, without an EM field nothing electrical will work. Light bulb won’t light. Motor shaft won’t turn. Jim
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