Is it damaging? Balanced amps & high-level sub input

@jbuddha882, is it possible that what you read related to not connecting at subwoofer high level connection to both the positive and negative speaker binding posts of the amp?

I am always reluctant to make sweeping pronouncements when it comes to anything electrical, as I am woefully ignorant of how the gear that i love actually works, but I will pass on the net result of a series of emails i exchanged with a REL Regional Sales Manager and with the chief engineer (and a co-founder) of Gato Audio, a fine Danish firm.  The latter cautioned that as a matter of film policy they recommend against high-level connections for both their AB amps (which are not balanced) and their Class D amps (which are, like, i think most or all Class Ds) full differential) mainly because they don’t want to have any responsibility if a subwoofer is not actually designed to handle the high-level voltage and current nor, in the case of the Class D models, if the user connects the subwoofer to both the positive and negative speaker out posts.

The REL sales manager was willing to repeat what REL has always said in their manuals: if at all possible, use the high-level connection method *BUT* if the amp is Class D or fully balanced Class A or AB, never, never, connect both the negative and positive posts, because on those amps the negative is connected to the amp’s common ground.  In those cases, connect to the positive post and ground the black wire. And when in doubt, just assume it’s balanced and ground the black wire.

In the case of my Gato PWR-222 monoblocks, the Gato fellow kindly confirmed for me that “the negative speaker pole is indeed connected to common grounding of the amplifier.” So, on those, my RELs are high-level connected with the black wire connected to the amps’ negative speaker post.  On my JRDG 625 S2, which is Class AB fully balanced, the black wire is floated and i ground the pre-amp from an unused output to the airship transmitter for the Carbon Special with a spare interconnect cable.

@kirkwallace great info and thanks for sharing your experience sir. I just received an email from one of the village elders at TMR, he said to connect both the positive posts, to both positive high level inputs, not one of each +/- , for say the left side. I’m assuming for the same logic, that the negative is tied to common ground, and imperative for signal in balanced topology. 

@jbuddha882 i’m not following your last sentence, but it is probably my fault not yours. I would follow what the TMR person said. 

My last sentence was an almost exact quote, or exert from your original post, so I’m not sure what you don’t get? Like the REL rep stated, the negative binding posts are connected to the amps common ground. So ie leave those, untapped. 

Sorry, but that it not at all what the REL sales manager said. If your amp is balanced or Class D, the negative speaker posts are not connected to ground. In my case, the guy who designed the amp confirmed that the negative post was connected to ground, and in that case you connect the black wire to it, but that is not a general rule.