Ok so I bought 2 cheap little Art Media Tube Pre's for about 30 bucks a piece. I had read some suprising reviews about how they were actually pretty good expecially for the price. So a little curious I bought 2. I actually use mine to warm up my vocals at my live show and the sound is actually very nice and warm. The problem is that on of the pre's has a pretty loud hum. Will changing to a higher quality tube remove the hum?