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

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.

Well this thread just gave me a sick feeling.

For years I have had my Hypex based Marantz Ruby integrated connected to my HSU subs using both the positive and negative speaker terminals for many years.  Same with REL subs.

How in the world did this not damage my amp??

Addendum:  I may have found my answer.  AI initially stated the Ruby had a floating ground.  Re-asking the question based on output topology, it said the Ruby uses a single ended hypex module which is tied to a common ground.

Whew!!!!!!!!!

I am confused. Please explain more.

My amps have 2 sets of speaker outputs. But they are probably connected together internally. I use one set for my main speakers, the other for my subs.

Since my JL subs do not have a direct high Impedance input, I am using a Jensen ISO-Max to convert the speaker output (high impedance) to a balanced output for the sub.

So, am I missing something?

ozzy

The KEF KC92 can accept either speaker-level input or line-level input.  It could not care less whether one speaker input wire is connected to ground elsewhere.

Whether an amplifier is internally fully balanced, or not, has no impact on what comes out at the speaker terminals (except possibly sound quality).

You can feed duplicate speaker cables into your subs, no worries.