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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
almarg's avatar
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almarg
9,670 posts
 
PM answered.

Best regards,
-- Al

ricred1 OP
1,976 posts
 
Although I'm frustrated with the inability to at least try the high-level input, I ordered a second REL Carbon limited that I should have on Monday. The addition of a single REL has increased my enjoyment of my 2-channel system; so I figure dual subs will be better. I reached out to REL again today in hopes that someone can provide a simple way to use the high-level input without damaging my amplifier or sub. Hopefully someone from REL will contact me tomorrow. 
daveyf's avatar
daveyf
2,835 posts
 
In the past whenever I have contacted REL, i have done so via e.mail. They have always responded fairly quickly to all of my inquiries and questions.

The addition of another REL should give you a nice boost in SQ, albeit with a lot more set up time involved and experimentation in positioning, x-over, and volume settings in order to get the blend to be invisible. It took me almost two months to get it right...and I am still making very minor adjustments even now!! Two subs are more than twice as difficult to dial in than just one...BUT the effort will be worth it.
ricred1 OP
1,976 posts
 
Thanks, I will send them a email.
almarg's avatar
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almarg
9,670 posts
 
As a point of information, for a great many years prior to the introduction of many of their current models, REL manuals recommended that when connecting to amplifiers whose outputs are balanced or bridged that the black wire be connected to a chassis screw.

That should have and apparently did work well in most cases, although not quite all. An exception being a few amplifier designs in which chassis and circuit ground are completely isolated, in which case the result of doing that would probably be a large hum. Another special case involved some long obsolete early class D designs which had very high DC voltages (something like 24 VDC if I recall correctly) on both their plus and minus output terminals, relative to ground, and therefore required blocking capacitors between the amp outputs and the sub.

I don’t know what the reason may have been for REL to abandon that long-standing recommendation of using a chassis screw when connecting to balanced or bridged amplifier outputs, and now recommending that the black wire be floated.

Best regards,
-- Al
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