I've done a lot of reading on the forum and tried a bunch of stuff with this issue with no success.

I am having trouble with a lot of hiss when interfacing a TC2290 and a Bludotone Loopalator (Dumbleator-style tube buffered FX loop) in my rig. My Ceriatone HRM Bluesmaster is connected to the Loopalator via 1/4" cables. I am then running the 2290 in the loop of the Loopalator with 1/4" cables as well. (tried XLR to 1/4" with the same result). The loopalator has a Drive knob which is the send level to the 2290 and then an Output knob which controls how much volume goes back to the amp. Regardless of where I have the amp's master, the 2290's input, or the Loopalator's Drive level set at, I am getting a lot of hiss when I turn up the Output of the Loopalator. If I click the Delay off on the 2290, no hiss, so it doesn't look to be a ground loop. When I run the delay level on the 2290 at around 50, the hiss is pretty much gone, when the delay level is high at 95, it is terrible. As well, when I plug the loopalator or the 2290 by themselves into the FX loop of the amp, they sound quiet and fine. Ground loop, noise floor issues, rfi problem? Thanks for any help!!!

Thanks for the idea. No success unfortunately if I run the TC input low or high, or the Loopalator low or high. If I run the delay volume around 50 on the TC, the hiss is hardly noticeable. For some presets this is fine, but others I need to have the mix high, in the 90's where it is noisy right now.

 +1

  I can also hear an audible difference in signal/noise even with my T.C. M300 , I've A/B 'd it several times and I can tell that the T.C. makes some noise in series. I'm definitely in the market for a Exotic X-blend ( Has a tonestack + Series/Parellel switch) or a Suhr Minimix II for Parallel use with my D-lator.