I purchased a used SD pickup booster to help my low output Fender Vintage noisless PUPS in my strat. The first thing I noticed was that when on and set to Res at 0, the pedal picked up a lound poping sound as the volume is rolled between 9 & 10? when I switch to Resonance 1 ( very nominal difference in sound) it disappears. Is the booster at 0 picking up a probem in my volume pot that I don't hear without it ( I can put it clean through an amp cranked to 10 and nothing), and then why does it not happen at resonance 1 and how much differnce in tone shoud I be hearing between 0 & 1?