> Anybody used an hum eliminator device like an Ebtech and does it have an effect on the sound at all? <
Yes, the Ebtech unit does affect the sound a little, and it has poor headroom so it breaks up at higher levels. I have an eight channel model I'm not using anymore if you'd like to buy it.
All such devices are based on audio isolation transformers. Good audio transformers are expensive because it's tough to make transformers with a good frequency response and low distortion. I've used Jensen transformers and they're excellent, but they are not cheap. Much better is to track down the problem at the source. For example, if your gear offers balanced connections, use them instead of regular unbalanced cords. Or if you have noisy solid state light dimmers (which an audio isolation transformer won't help anyway), replace them with variable power transformers.