[ctviggen]

I have an NHT X2 crossover hooked up to a QSC amp to drive two subwoofers.  I used to split the signal from my preamp using balanced cables designed with one input and two outputs.  One of the outputs went to the NHT and one went to my amp, which drove my main speakers full range.  At the time, I do not believe that humming existed.  I've since bought different balanced ICs, which run from my preamp to my amp, still running my main speakers full range.  I then use the unbalanced outputs of my preamp to run to the NHT.  Now, I get low level humming on the subs.  If I disconnect the input from the NHT to the QSC amp, I hear no humming.  Once I reconnect the NHT to the QSC, I get humming.

Could switching from balanced to unbalanced ICs cause this?  If not, what else could cause it?  (I have all my components plugged into a set of outlets run off a dedicated circuit; other than my third sub, that is, but I did not change the sub's connections.)

[John Ashman]

Ground loop, probably.  You'll have to life a ground ot two.  Subs are always causing ground loops if they're powered.

[ted_b]

I have the same issue with my X2.  I tried to find it last night.  This demon was around a couple years ago and I killed it.  I've lifted grounds all over the place, but since the X2 its back, although not all the time.  I've lifted ground on both my subs.  The X2 itself has only a two-prong plug, not a three (so I assume it doesn't need lifting?).  I just put some stuff on I had on last night to try and recreate the hum; it's very low level (subs humming, basically).

Ted

[John Ashman]

Sometimes you can lift one or two grounds, sometimes you have to lift all of them, it just depends.

[ctviggen]

I'm not sure about that, John.  The only difference between the way I have it (my system) hooked up now and the way I had it hooked up before is balanced to unbalanced connection between the NHT and my preamp.  Well, that's not exactly correct now that I think about it.  I had my three amps on a dedicated circuit and a Monster Power Center on the same circuit as my third sub.  I couldn't put everything on one circuit because I kept tripping the breaker when two of my amps turned on at the same time.  I was able to stagger all three amp's turn on times to prevent this from happening.  I then put the Monster Power Center on the same circuit as everything but the third sub.

I'll unhook my third sub (the only thing that's on another circuit, mainly because it's all the way on the other side of the room) and see what happens.  However, I don't think this is cause of it, as it already is not grounded (it has a two-prong plug).

[John Casler]

I have the x-2 also (of course) but "no hum".

Do either of you have your HT LFE output connected to the LFE input of the X-2?

That would be the first place I would look for hum, since the LFE out will likely be connected (at some point) to a cable or dish that is notorius for creating hum.

I would also use the "gain switch setting" on the back of the unit in the low gain position and high gain position to see if that has some effect.

I have mine set up like Bob's with XLR outs from Preamp to Main AMP directly and then RCA outs to X-2 and no problemo.

2nd thing I would do is switch all cables (one at a time) to make sure it wasn't the ground plug or a short in one of the cables.

I also have mine plugged into a BP3.5 Signature which might help.

[ted_b]

Yes, my LFE out is connected into the X2.  I'm gonna have to go through the regular process I guess.  Because mine isn't present all the time I am gonna guess shorted ic somewhere.  I'll report back.

Ted

[JonPugmire]

I had a problem with my X-2 and it turned out that the power supply (which is in the middle of the power cord) was too close to some interconnects.

You might want to check that.