I'm using the Upton RS II on my upright bass. I run it through a Phil Jones Bass Buddy to the mixer. I get a little boomy sound sometimes and the sound is very uneven across the register. I can hear what I play on the E, A, D strings and an open G, but as I move up the G string, the sound disappears more and more, and I'm not able to hear what I play in my in-ear monitor or through a PA-system. My bass is very even across the register, and if the acoustic sound would be reproduced when amplified, this shouldn't be a problem. What could be wrong? I'm not very good with technical stuff, eq etc. Thanks in advance for any help!