gonk, I ordered the MIC SPLITTER/COMBINER from partsExpress along with a 15' and two 3' XRL cables. I just can't isolate my ground hum and when I run just one sub with the Velo XLR LFE output, it's silent. As soon as I use the unbalanced outs on the SMS, I get the ground loop again.

The MIC SPLITTER/COMBINER looks like the best option for my situation, giving me all balanced connections from the pre to the SMS, to the MIC SPLITTER/COMBINER and to the subs. I like the fact that the MIC SPLITTER/COMBINER also offers a ground lift switch on the box itself. I'm confident this will solve my problem.

rmassey,

When you have the hum, does disconnecting the yellow video cable cause it to go away?

I use s-video, but I can try to disconnect it and let you know.

--- I just checked, no affect.

The only thing I notice, is when I unplug the unbalanced line from the sub or the SMS, the hum stops. I even tried to lift the ground on the sub and then on the SMS, no affect. I unplugged all the obvious Coax (Sat & ant) from the system, still no affect.

The mic/combiner spliter gizmo arrives on Thrusday, I hope it does the trick.

rmassey,

Not to belabor the point (just trying to help), are the two subs plugged into different circuits? As I understand it, ground loop arises from a differential between two different ground potentials. Thus, plugging two devices into one phase on one circuit avoids that risk, but two different phases or circuits introduces the risk. I sure hope the problem is not that use of one balanced and one unbalanced input introduces that risk because that is precisely what I had planned to do. Let us know how the splitter works out.

no problem Chessman, I'm happy to discuss/try different things to cure this. thanks for your interest and comments.

I have both subs plugged into a panamax 5300 via a good quality 3 prong grounded extension cord, along with the SMS and all my other gear.

The subs are about 11 feet from my rack, hence the need for an ext. cord.

Also, sorry about the use of my rmassey99 ID above.... I had a bit of a password problem last week and created this temp ID to contact the mod. I mistakenly posted replies with this ID, meaning to only use my rmassey ID.

Sorry for the confusion.

The results are in..... not good.

The PE mic combiner/splitter is crap. It did not get rid of the hum at all, in fact it made it a bit worse over using 1 XLR and 1 RCA output on the SMS.

Not only that, but it totally jacked my previously flat curve introducing some kind of mega noise into the signal.

This thing is going back to PE.

gonk, no worries on the recommendation, I had to give it a try. I was hopeful, but I guess you cannot use a $25 part on a $600 audiophile unit and expect positive results.

I wonder if a splitter cable would give better results (less in the signal path)?

I wonder if a RCA to XLR single cable would work out. I'd use the RCA out on the SMS to XLR in on the sub, eliminating the use of RCA in on the sub.

I have some cables here and will give this a try today.

Problem solved.... I picked up an XLR Y splitter from Guitar Center for $15 (similar to the Sweetwater link above). Both subs are all quiet and flatness has been acheived

OK, now I can get more into the SMS and dial it in without distraction.