Audiotroy 10-14-2017
Your sub hookup questions should be addressed directly to Sumiko. As the ground for the speakers on a Rel is not like a nomral ground in an electrical sense. the Rel subs read the signal from the amp like an rca cable.
Hi Dave,
Before I submitted my previous posts about this I had looked at
the manual for the Sumiko sub. As can be seen on page 15 the recommended connection of the black wire in the Speakon cable to a "bridged (differential input) amplifier" (which obviously would also apply to a fully balanced amplifier) is to a chassis screw. That is the same as what is recommended by REL for their subs, and will work ok in most cases as I mentioned, although depending on the amp design hum may result in some cases. But connecting it to the ground shell of an RCA input connector, as I suggested, is a better approach that will certainly work well with this amp, given the mention in the amp’s manual that the RCA ground shell corresponds to signal ground. Which would be the case with almost all other amplifier designs as well, aside perhaps for some that have transformer coupled inputs.
Fsmithjack, two more points on that subject, the first of which you'll be especially glad to hear:
1)The risk to the resistors that I mentioned, if the black wire were connected to the amp’s negative output terminal, would be much greater with the Magicos than with the Rethms, since the much lower efficiency of the Magicos would result in more voltage being applied across the resistors for a given listening volume.
2)If the subs were connected in that manner the risk to the resistors would arise even if the subs were turned off, since it is the ground path through them that is involved.
Regards, and continued good luck!
-- Al
