I've owned my VMS4 for about 6 months. I run a Shure SM58 wireless rig and had major mic distortion problems from the first time I used it. I contacted American Audio and their customer service was great. They sent the adapter out immediately and it helped a lot. Another problem, however, was the adapter is pretty long and coupled with the XLR connector the darn thing stuck out a mile from the back of my VMS4. I've read people frustrated with this issue so I thought I'd let you know how I fixed the problem. Instead of plugging the adaptor into the back of the VMS4 I installed it inline at the wireless receiver. I had to buy an XLR-female 1/4" adaptor but because all of it sits inside my road case it didn't matter.
I also noticed that the new Denon MC-6000 is rack-mountable. Is there any plans to make future models rack-mountable? I was able to do some creative work with Velcro to attach my VMS4 to the slant rack on my case, and all is well.
Thanks to American Audio for a controller that for the most part has delivered a product that works great.