I was playing around on my fretless yesterday without plugging it in to the amp, and I realised that the 'mwah' is much more pronounced on its own, unplugged. When I plug it into my practice amp, the mwah doesn't come through as clearly. What's the deal? I'm sure the setup is fine because I can hear the mwah very clearly when it's unplugged. I've got the strings set up with as low action as it can get before it starts to buzz. Or is this a pickup problem?