REL subs with Rowland Amplifiers

@ricred1   So, REL are suggesting that you run a ic from your LFE on the sub to your preamp? I guess that would ground the sub, but I wonder if you also wouldn't potentially create a ground loop? 
As I stated before, the ground connection that Jeff added for me on the back of my amp is the way I would think is the most effective way to get this accomplished. 

I just received a call from REL. They said I could ground the sub/amp by going from the REL’s LFE to my Rowland Corus preamp while leaving the black lead floating.

Not sure that the REL person is realizing that the inputs of your amp are transformer coupled, and the amp’s descriptions at the JRDG website and in the manual state that "transformer coupled input circuitry provides universal component compatibility and virtually eliminates ground loop noise..."

So it seems to me that due to the isolation the input transformers presumably provide it is likely that connecting the sub’s ground to the preamp’s ground, via the LFE or whatever, will not result in an effective connection between the sub’s ground and the amp’s ground, which is what matters. On the other hand, though, I suppose it is possible that an adequate ground path between the sub and the amp could be formed via that connection in conjunction with the AC safety ground wires in the power cords of the preamp and the amp, which ultimately connect the chassis of the preamp and the amp together.

In any event, given that none of us have much familiarity with how grounds are handled internally in these designs it’s worth a try. And I don’t think it could do any harm to give it a try; just be alert to the possibility of a loud hum. IOW keep the sub’s level control at a low setting when you begin the experiment.

Best regards,
-- Al

I should have mentioned at the beginning the most frustrating thing about this situation is my dealer is a REL and Rowland dealer. He has the ability to connect the REL to the exact amp and preamp that I have, but he won't. When I told him about my situation, he said that he would connect the REL to the Rowland 625 S2, but to date he hasn't.

The other frustrating thing is trying to find out the truth regarding the sound quality difference between the high-level and low-level input.  During a telephone conversation two days ago a REL representative told me there wasn't a difference in sound quality between the two inputs, but the high-level input helps facilitate a better blend between the sub and speakers. Yesterday, a different REL representative sent me this via email... Low level input is about 80% of the high level input. If both inputs offered the same sound quality I wouldn't worry about the high-level input anymore. 

 @ricred1  I think the blend is where it’s all at. The fact that the subs take their signal directly from the amp in the high level set up is what has distinguished REL’s for me over the years. REL used to claim that this was allowing the sub to more carefully track the signal at the amp end, not sure if they still claim that anymore. 
Your dealer is possibly wondering how to connect the sub ground wire to the amp chassis...as unlike many other amp manufacturers, Jeff chooses not to include a separate ground connector on his chassis. If you look at Lamm, Pass and others they do include this. Nonetheless, as I said before, Jeff is willing to add this necessity ( which I believe it really is) to your chassis.

I have been corresponding with Justin Magana who is REL’s Chief Engineer. Based on his advice I twisted the red and yellow wires together and connected my REL via the high-level input. The black wire is floated. It worked! I have plenty of output from the sub and absolutely zero hum.