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REL subs with Rowland Amplifiers

I'm having issues connecting my REL Carbon limited subwoofer to my Jeff Rowland 625 S2 amplifier via the high-level input. I connected my sub according to REL's instructions...yellow lead to positive on one channel, red lead to positive on the other channel, and floating the black wire(ground). I get minimum output when connected according to the instructions. When I use the low level input, the output is sufficient and the sub sounds great. Per my conversation with Jeff Rowland I need to ground the black wire by loosening a screw on the amplifier and connecting the black wire, but if it isn't properly grounded I may damage my amplifier. Is there anyone that owns a REL with Jeff Rowland 625 S2 amplifier or other balanced differential amplifier? If so, how do you connect your REL via the high-level input. Is there an easier way to ground the wire than unscrewing the screw on my amplifier. I just don't want to unscrew the screw and prefer another method of grounding the sub.   
ricred1
ricred1 OP
2,019 posts
 
Al,

Do you think grounding the black wire to the chassis of my 625 S2 will result with proper output of the subwoofer?
almarg's avatar
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almarg
9,670 posts
 
Yes, I would think that to be highly likely.  Given what Jeff has told you, given that REL's recommendation has up until recently been to do that, and given my technical understanding of the situation.

Best regards,
-- Al

ricred1 OP
2,019 posts
 
I just received a call from REL. They said I could ground the sub/amp by going from the REL's LFE to my Rowland Corus preamp while leaving the black lead floating.
daveyf's avatar
daveyf
2,871 posts
 
@ricred1   So, REL are suggesting that you run a ic from your LFE on the sub to your preamp? I guess that would ground the sub, but I wonder if you also wouldn't potentially create a ground loop? 
As I stated before, the ground connection that Jeff added for me on the back of my amp is the way I would think is the most effective way to get this accomplished. 
almarg's avatar
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almarg
9,670 posts
 
I just received a call from REL. They said I could ground the sub/amp by going from the REL’s LFE to my Rowland Corus preamp while leaving the black lead floating.

Not sure that the REL person is realizing that the inputs of your amp are transformer coupled, and the amp’s descriptions at the JRDG website and in the manual state that "transformer coupled input circuitry provides universal component compatibility and virtually eliminates ground loop noise..."

So it seems to me that due to the isolation the input transformers presumably provide it is likely that connecting the sub’s ground to the preamp’s ground, via the LFE or whatever, will not result in an effective connection between the sub’s ground and the amp’s ground, which is what matters. On the other hand, though, I suppose it is possible that an adequate ground path between the sub and the amp could be formed via that connection in conjunction with the AC safety ground wires in the power cords of the preamp and the amp, which ultimately connect the chassis of the preamp and the amp together.

In any event, given that none of us have much familiarity with how grounds are handled internally in these designs it’s worth a try. And I don’t think it could do any harm to give it a try; just be alert to the possibility of a loud hum. IOW keep the sub’s level control at a low setting when you begin the experiment.

Best regards,
-- Al


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