I always had issues when using the RP1000 with my Rivera's effects loop, connected with the 4CM. When I wanted the Rivera's tone I made a preset with the Amp Loop on but never really used it because there was a major volume drop and some tonal issues. Turned the clean sparkle of my clean channel into a muddier clean channel, took away dynamics of the tube amp, etc. Last week I traded my Rivera Chubster 40 1x12 for a Budda Superdrive II 30 2x12. The Budda is a great amp and I'm liking both the clean & ovedrive channels. I hooked up the RP1000 using the 4CM and the same thing happened: volume drops/tone issues, however it's more of an issue with the Budda because I really want to use my Budda's natural tone plus all of the sounds and versatility of the RP1000. I tried turning off all amps & cabs so I could run just the regular distortions, delays, modulation, etc. like a regular pedalboard. Ran into the same issues. In the past I've had my preset levels up pretty high and used the RP's master volume to control the main volume. I reversed this thinking and cranked the master volume to 99 and adjusted the preset levels to taste but the same thing happened. I'm pretty much convinced that my RP1000 has issues when placed in an amp's effects loop. I have to run it that way because the delays do not sound very good in the front of the amp. Other modulation also sounds better in the effects loop. I'm at my wit's end and tempted to sell the RP1000 so I can get a Line 6 M13. I would just use it for regular effects in the front of the amp and in the effects loop. I think the issue I'm having with the RP1000 is something with the various volume adjustments throughout the device. Any thoughts, opinions, help on this? Thanks!