I have been enjoying my WTX-500; my MTD Heir sounds great through it with an Eden 1X12 speaker. I tried playing my plywood URB through it using a Tech21 Bass Driver into the FX return input. This also sounded good, but I found out that 1)this cuts off the input from the EB if it is plugged into the regular input and 2) the manual says: "This (input) is at line level; do not use instrument-level effects in this loop, as they tend to overloaded by the higher signal level, which can cause distortion." I'm presuming that since I'm not using the Send FX output, this doesn't apply, but I would be grateful for some expert advice on this. I'm not hearing distortion, but I don't want to damage anything.