REL subs with Rowland Amplifiers

Interesting Richard. I got the exact same advice from REL and then on a subsequent call was told that the LFE.1 channel takes precedence ( same as the low level connection). If it is connected via an RCA cable. The second adviser told me that i should just run a wire from the preamp to the REL chassis to establish just a ground and not an RCA cable...i did neither. No question that attaching the RCA CABLE TO THE PREAMP AND TO THE REL CREATES A GROUND.

I've already sent Rowland an email requesting the cost of adding an external ground screw. Hopefully they will respond tomorrow and I will ship my amplifier to them before the end of the week.

Al do you have any idea as to why my balanced JR model 8T has no issues when connected in the manner that i suggested? ( which also was the way that REL had suggested to me to do the hook up when I first acquired my sub).

First, it's noteworthy that while in the case of stereo amps having outputs that are not differential (i.e., that are not balanced or bridged) the many REL manuals I've had occasion to look at over the years recommend connections exactly as you have described (red to right positive, yellow to left positive, and the black to either negative connector), but not a single one of those manuals makes that recommendation in the case of amps having differential (balanced or bridged) outputs.

Second, while as I had mentioned that approach **might** work with amps having balanced or bridged outputs, depending on the internal grounding configurations of the sub and the amp, and in fact over the years I've seen a number of members here report doing exactly that with no apparent issues, at best connecting a full-amplitude amplifier output to the circuit ground of a sub is poor practice from a design standpoint, and at worst it could have the various adverse effects I described earlier. 

Just to cite one potential example:  I know that many Audio Research balanced amps connect circuit ground to chassis ground/AC safety ground with a 10 ohm resistor.  **If** the sub does likewise it would mean that a full amplitude output of the amp would be applied across a total of 20 ohms.  And if the two 10 ohm resistors have not been chosen to have particularly high power handling capability one or both of them could burn out, eventually if not sooner.  Resulting in hum and/or degraded sonics.

Is there a logical reason why when both subs are connected through the high-level input with the REL supplied speakon cable no hum is audible, but when I use the Signal speakon cables the hum is clearly audible? This is with no RCA cable connected to the RELs LFE inputs and into my preamps outputs.

I don't know.  But if you have a multimeter it might be worthwhile to verify that both cables are wired identically, and that no shorts exist between the yellow, red, and black wires of the Signal Cables.  Also, I see that the Signal Cable is described as being unshielded.  I don't know if the stock REL cables are shielded or not, but if they are perhaps the Signal Cable is picking up EMI from something nearby while the REL cable is not.  

Best regards,
-- Al

Al, unless I’m mistaken, Richard had Signal make him dual cables for dual subs...as such, I think that Signal ties the red and yellow cables together per cable. That is what they did for my dual sub arrangement for my dual cables. Therefore, each cable has a Speakon end at the sub and a red/yellow connector and a black connector ( at the amp end).

Al,
I’m assuming if the Signal Cable is picking up EMI from something nearby to cause the hum, adding an external ground screw on my amplifier won’t eliminate the hum?
Silly me the hum is being caused from the REL not being grounded. When I connect an RCA cabke from the REL's LFE to my preamp the hum isn't there. Unfortunately I don't like the way it sounds when connected like that, because all of the dynamics are missing.