I ordered a BX500 a few weeks ago based on the specs and price, and on positive reviews I'd read. After receiving it, I was pleased with the small size and big power. However, I noticed an odd mosquito-like buzzing coming from both the speaker and headphone outputs. The sound did not vary based on inputs or on volume settings. It wasn't loud enough to really interfere with my practicing, and I doubt it would be heard on a gig, but it was odd and didn't seem right. I did a Google search and came up with the threads here, as well as others. So I called Carvin and asked for Emeric. He happened to be out that day, but Danny got on the line and after I explained the situation he said he thought there had been a fix, and he was surprised I got a non-fixed unit. He set up a UPS pickup for my unit, and before I had a chance to actually pack it up and bring it in to work for shipping, I got an email saying a package was on its way to me from Carvin. Since it would be arriving in a couple of days, I figured I'd just wait until it arrived before shipping back the old one, just to make sure the new one was actually better than the old one. I got the new one and noticed right away it had a higher serial number than the old one (1800 series vs. 1700 series) and upon checking it out, also noticed it had printed "DTEC - POWER" stenciled under the EQ, while my old one didn't. Most importantly, the new one had NO BUZZ. No mosquito sound, no buzzing, nothing. Nice and quiet and works great. So I'm glad I called and went to the trouble to get a corrected unit. Happy I stuck with Carvin and have this nice, light powerful amp. And thanks to Danny for getting my new unit out so fast!