I play a Warwick Thumb Bolt-on. These are know to have a distinctive "growl". It really sounds sweet when I practice at home. However, that growl turns into a "bbrrrraaapp" (nice description) when I have to play louder in band rehearsals. I'm not really pumping too much volume, just enough to get over the drummer who's not a real banger. I practice through a Hartke Kick-back 12. I don't schlepp my Ampeg with me for rehearsing. I'm thinking the amp just can't handle it though it's only turned up about 1/3 on the master vol (I keep the volume on my bass all the way up). On the amp I cut the mids totally for the most part and the low and hi are about 1/2-way up. It's also got a parametric eq (shape control) that I have set to cut the mids too. I tried cutting back on the volume on the bass and pushing the master up a bit, but there really wasn't the tones I get at low volumes. I was worried that it might be the bass. The only thing to do I guess is bring the Ampeg.