I bought the device from Amazon. It is called a Trifield EMI line meter. It measures dirty electrical noise or EMI noise in millevolts peak to peak. It even lets you hear the electrical noise and if the noise I heard is added to the audio stream I hear, I have to assume it is contaminating the purity of the sound. .What type of device were you using? What are these units? Unless you know about the spectra of noise these measurements tell very little and can be misleading to find a solution. Considering the price of many power devices IMHO we should have a proper analysis carried before going in such expenses - or simply listen to find what you prefer, probably much more reliable than many hand held devices.