REL G1 Subwoofer Problems

Looking for some help.  I'm at a loss here.  Tried almost everything, but still having a problem.

My G1 is hooked up via REL supplied Speakon to the back speaker terminals of my Krell KAV 2250 in a two-channel stereo system.  High Level connection, per instructions.  I double and triple checked connection, and I have it right.  Red to Left (+) terminal, Yellow to Right (+) Terminal, Black to either (-) terminal.  Also tried reversing Red and Yellow.  

Gain set to 25, crossover at 35Hz.  Called REL USA, and they think I have it right, but they encourage me to go up in gain to 27 or 28.  Problem is, any gain set higher than 10 or 12, or lower if I increase crossover above 35Hz, I start to get a sporadic gargling or "fart" sounds.  Not consistent, but often.  Some orchestral passages with heavy crescendos are no problem.  Bass drums, at high volume, no problem.  Yet, when the sub is in less demanding load, comes the "fart". 

REL USA told me to take out the black wire and float it, i.e. take it out of the negative terminal.  Could be the Krell because is a fully balanced amp and negative terminal may try to drive REL's amp.  did that, No change. Fart. 

Have NOT tried changing Speakon cable.  Have one on order.  May also try Low Level connection via RCA to Pre Amp.  Don't have cables at hand, but will try to get some.  I'll do this to test, but not happy if I have to go this route, as REL highly recommends High Level connection.   

Of course issue goes away if gain set to 10 or 12, or lower, or conversely if crossover set below, say, 28.  At this gain and crossover, the sub is nearly silent.  No bass, no slam.  REL USA agrees that I should have no problem with gain of 25 or 27 and crossover at 35. 

Anyone ever experience this?  If I am overworking the REL, then I should be getting booming bass and not a very good balance with my speakers (Sonus Faber AE II).  Instead I get a "fart" or gargling. 

Have a simple receiver in the house you can drive the sub with via speaker level?  Would answer your question of balanced vs. common ground.  I think you are correct about the balanced amp not liking the Speakon connection.  I was afraid to connect my mono tube amps via Speakon and I just went RCA.   Sounds great.    I almost suggested trying it in a friends system and that would be fine if it wasn't such a beast .  Good luck
 Cut down on the chilli 
I have banned my REL to eat chilies and any other bean products.  Still...

Oddiofyl, thanks.  I am increasingly convinced that my REL and Krell simply don’t get along.  I may forced the low level input route.