REL Subwoofers, Class D Amps and Neutrik Cables.

I don't know what "caps on the black wire" may refer to in this case. But an approach that should work fine is to obtain a simple RCA plug, perhaps at Radio Shack, solder the black wire to the ground sleeve connection point of the plug, while leaving the center pin unconnected, and inserting that plug into an unused RCA connector on the integrated amp. That would establish a circuit ground connection between the amp and the sub. Don't connect to one of the galvanically isolated digital inputs on the amp, though. And connecting to an analog output jack might be slightly preferable to connecting to an analog input jack.

Another approach that might work ok, depending on the internal grounding configuration of the amp, would be to simply connect the black wire to a chassis screw on the amp.

Good luck. Regards,
-- Al

My experience is with IcePower based amps, specifically ones using the ASP series Ice modules. These modules have 40 VDC on their speaker output terminals in relation to amplifier ground....

I was not aware of that. If that is the case with your Peachtree Grand then, yes, as the person you quoted stated you would need to have capacitors in series with the red and yellow wires. Assuming, that is, that the sub itself does not have capacitors in series with its high level inputs. (When you said that "Rel's new subs do not have the issue," I'm not sure how they could be immune to 40 VDC at their inputs unless their inputs were AC-coupled, presumably with capacitors).

Have you asked Peachtree if the Grand Integrated has a significant DC voltage such as 40V on its outputs? FWIW, its manual does not have any cautionary statements regarding the presence of DC on its outputs. Also, they would be the ones, not Sumiko or REL, who presumably could best advise as to the suitability of using an RCA shell for the ground connection.

Also, you could use a multimeter to measure whatever DC may be present. With no signal going into the amp, you would measure between each of the output terminals and the shell of an analog RCA connector.

And if you have or can obtain a multimeter, by measuring for continuity or resistance you could use it to determine if on the cable your dealer supplied the ground connection of the Neutrik connector is connected to the ground sleeve of the RCA plug, and that the center pin of the RCA plug is connected to nothing.

Good luck. Regards,
-- Al

Kijanki, thanks. Your expertise on Class D is always valuable.

Rick, as a point of information REL usually recommends that if a single sub is being connected to monoblock amps it is usually best to connect the black wire to a ground point on the preamp. Ideally, IMO, to a circuit ground point such as an RCA shell, but preamp chassis might work just as well, depending on the specific design.

Also, since your Simaudio's are Class AB, the DC offset issue that has been discussed isn't a concern in your case.

Regards,
-- Al