I installed my pickup on my upright bass right under the bridge, the pickup is a flat piece of copper tightly pushed on the body. But I get a lot of feed back even when I turn the amp away from my and turn down the gain. Also I get an unsettling buzz on the low notes. I feel it's because the copper is not tight on the body but I've tried to adjust it best I could and it won't work. What can I do?