Hum in My Speakers

I listened to a movie today at quite a nice volume because the kids were not at home. But now I hear a buzzing sound coming out of my tweeters. They are vifa tweeters and I am wondering what's going on. the center and surrounds are not making any sound. The LSI15's are bi-amped. Thoughts?

I think that the first thing I'd try is to "un-biamp" the speakers, and run them on the other amp since apparently the rest of the drivers aren't buzzing. That, or swap the amps and run the tweeters only on the second amp. If the buzzing goes away using the other amp I'd look for a ground fault with the tweeter amp.. If the buzzing doesn't go away, it's most likely the tweeters themselves are possibly "blown", or maybe even some kind of mechanical problem, i.e. a grill or mount buzzing.. How low or high a frequency (relatively speaking!) is the noise?
Best of luck!

I made a mistake. the center is humming in the tweeter too and all the fronts run off of the 7500.

I have the same problem except all my speakers have a slight hum to them and its been that way since day one I just assumed it had something to do with my wire management. Apparently it hasn't bothered me that much because I still haven't taken the time to narrow it down, havn't had the time. When I was just running a Denon receiver to the speakers I never had any noise in my speakers. When I ordered the 990/7700 combo I even made sure to purchase balanced cables so I didn't have any noise and low and behold, I do. The hum is way more noticable when using analog interconnects. I read somewhere on this forum that there was a slight chance the 990 could have a bad chip in it which was really rare but I just don't want to go any length of time without my 990. Maybe this weekend I'll be able to narrow down the problem. Oh yeah, I'm also using dedicated 20 amp receptables.

Guys: I'd definitely start looking for a ground fault in your system & cabling. Google "ground fault" and you'll come up with all sorts of info about causes and fixes.
My system recently had the problem when I hooked in a DTV HD box- The coax feed from the dish is apparently a fairly common source for that type of problem- Check all of your (metallic-) connections, make sure that any 2-prong power plugs all have the phase correct (old gear with the plugs that go in the wall either way have a stripe and/or raised ridge molded on the "ground/neutral" side- they all need to be on the left side of the outlet). While you're at it check the outlets tehmselves to be certain that they're wire correctly. Good luck!

well the common theme between grimster and knownalien is they are both running the 990, and one of the Outlaw Audio amps..

maybe the amp needs a better grounding? Maybe it needs it's own wall plug in? Or a cheater plug.

I have the same 990, but not any Outlaw Audio amps.. and no buzz. I just throwing this out as a similarity between those two people, with very similar problems.

do either of you have differnt amps? DOesn't matter if it's a 2 channel or not. try bypassing the Outlaw Audio amp and see what the results are.

Yeah, but there are too many other 990/Outlaw amp pairings around without a hum to make an interaction the most likely scenario (although it can't be ruled out without finding some other source of the hum that is the real culprit).

the hum is one in which you have to really get up to hear it with your ear right in front of the driver. I should switch and have the 2200's hoocked up to see if there is a hum still.

A hum that low can easily be picked up by cables too close to power cords - that appeared to be the source of it in my system when I had a similar problem a couple years back, and a little judicious cable management resolved it. It's one possibility, at least...

and the amp is just making it louder.. because that's what amps do.. amplify. but worth checking out all possibilities.

i do have the cables close to a power source and i also have the 7500 running on its OWN 20 AMP line.

remember, the 7500 was biamping the LSi15's (fronts). I decided to switch the upper drivers on one of them to be driven by the 2200 which had been driving the rears. Everything is on a component rack and I use the holes in the back to snake the cables through. When I made the switch, the hum was gone from that particular speaker's tweeter and replaced with a slightly more acceptable his. At this point the only thing left to test would be the brand new AudioQuest Type II speaker cables but I doubt there is any problem there. My fear is that something is slightly amiss with the 7500. I am also going to try routing the 7500's power cable away from the interconnects with which it share a hole.

well, with the help of tech support, i was able to narrow it down to the cable box. Now I am really in a pickle. disconnect the coaxial cable and the hum is gone as just a nice peaceful very soft hiss is present.

Ah, the joys of a ground loop from your cable service. Classic problem. Fortunately, there are good ground loop isolators out there that can fix the problem without requiring you to try to convince your cable service to fix their grounding. I've heard that the Jensen isolator is the most effective out there (isolates without killing signal strength), although it's pricier than other alternatives available from places like Parts Express.

Can ground loop problems also become present if you are using a satellite? I have both cable and sat. in my house but only satellite going to my H/T room.

Yes, I have heard of grounding problems with satellite connections. I haven't ever had satellite, though, so my experience is nil.

where can I look to get these devices Gonk, and how will I know they will work with my Comcast cable box?

Here's one source for the Jensen I\'ve heard folks say good things about . There's also one from Parts Express and one Xantech unit from Home Tech . Any of them should help with problems in a cable service (which box being used shouldn't matter since it's related to the signal itself), although I don't know if any of these are supposed to be used with satellite service.

Most splitters have a screw on the side where you can run a bare piece of copper wire from to your house electrical ground, (ground rod, copper pipe suppling your water). This should clear up most ground loop problems, and it's cheaper too!. Jim

i did that and nothing happened. The weird thing is that there is NO hum or hiss in the surrounds which are also connected to the system. I am not blaming the 7500 (the 2200's power the surrounds) but you would think that the ground loop problem would be heard in the surrounds as well. As for the outlets and what is connected to what I have a BIG Monster Surge Protector and line conditioner. That is plugged into a regular 15 amp outlet. These are connected to this Monster powerstrip: LCD TV, cable box, DVD player, both 2200's (using the two "high current" plugs on the power surge protector). Also the SVS sub is NOT connected to the surge protector but it share the same circuit with it. The 7500 amp runs on its own 20 amp outlet that I installed (yes, I did a good job with the right guage wire) but the computer's PSU is also run off of this 20 amp outlet (even with the computer off the hiss is present). It may be important to note that from the 20 amp to the component rack, it has quite a ways to travel . . . on a cable unfortunately designed for 15 amps. I will try to provide a picture later.

Having the 7500 on a different breaker circuit is almost certainly your problem - there's apparently a difference between the ground potentials on the two circuits. Since the one circuit is 20A, I'd suggest plugging everything into it, if possible. That's the easy and cheap solution.

but I am pretty sure I have tried that too . . . plugging the 7500 into the Monster Surge Protector/power strip with the same results. That WAS, however, before I found the defective coaxial cord.

Did anyone ever solve the hum problem? I have a hum slightly different from what's been mentioned. I have a very subtle hum coming from my sub...no other speakers. My system could really use some wire management, but is this truly the fix? Although subtle, I know its there and it bothers me. Help.

Outlaw 990 Preamp
Outlaw 7700 7-Chnl Amp
Pioneer Elite DV-79AVi
Martin Logan Aeon i Front
Martin Logan Cinema Center
Martin Logain Descent Sub
Monitor Audio Bronze Surr
Panasonic AE900U Projector
Panamax 5400 Conditioner

i have found that sometimes amps in subwoofer cause a hum.. this MAY be normal. I'd call or write to ML and find out.

Wire management really can help. If it's only the sub, I'd check both the route of the sub interconnect and try plugging the sub into a different outlet - it could be on a different circuit from the rest of your system, with a somewhat different ground, and the ground difference could be the cause.

Skyblazer/Gonk - thanks. I'll try both recommendations.

New issue, I just purchased the MX-3000 remote, called some A/V dudes who quoted me $400 big ones to program it. Is this normal or are they trying rip me off? Luckily the software came with it however, after two days of NO progress, I'm tempted to call someone. The shameful part is, I'm a computer systems architect and by no means is this a simple task. So is it worth me calling someone who knows what the heck they're doing or should I tough it out?

The MX-3000 is targetted to the market of folks who pay to have it programmed - the programming is often bundled in with the remote. $400 is probably not an uncommon quote for that service. Having some experience already with URC's software, I'd probably tough it out, but after that much hassle I'd be tempted to recruit some help too. How much gear are you trying to operate?

atleast the following:

Outlaw 990 Preamp
Pioneer Elite DV-79AVi
Panasonic AE900U Projector
DIRECTV® HD Receiver
...and maybe the lights

That's not too bad. Are you retaining the default button style and layout structure, or are you trying to do a completely custom "skin" to the remote?

Wow.. $400 to program a remote.. seems pretty steep to me. I'm not familiar with that remote.. but sometimes the instructions are tough to figure out.

I'd look around if your local area or on here if there is someone who could come program it for you. for a lot less.

I just checked the specs.. wow.. pricey.. looks very sweet. It would be to advanced for me to use though.

SOrry i can't be of more help.
good luck.

Gonk - - applying the custom skins is the one thing I did figure out. It would be nice if I could suck the functions right out of the component remotes then customize them as I go. As my system evolves, I'm sure other devices will join the fun.

Skyblazer - - I actually purchased the remote from a direct distributor so I guess you can say I got a deal @ $650.

gonk, I purchased the Jensen. I will let you know at the end of the week if it worked.

I installed the Jensen and the hum is still present. Now I am really confused!

knownalien,

Try this:

http://www.ecost.com/ecost/ecplasma/shop/detail.asp?dpno=501009

I already own this though:

Monster HTS 2000 MKII

I just spent the last 2 1/2 hours figuring all this out. Look at my sig. I decided switched the 7500 on the mains with the 2200's. The hum went away. I switched outlets on them but it didn't matter, the 7500 hums but the 2200's don't. The 2200's no power each LSi15 (not bi-amped). While I don't get a hum, I do get a hiss from the tweeter, but nothing from the mid-range drivers.

so, did something go bad in my 7500???

well,

now the 7500 is driving the center and two rears. But get this, the hum exists only in the center (as it always had) and only ONE of the rears.

And one question I just noticed: I own the Outlaw PCA interconnects to wire all of my speakers to their amps. The have arrows that indicate which direction the signal should travel. All of mine are correct, however, some of the cable have red lettering and some have blue. Does this mean anything?

The colored lettering is to differentiate between left an right. Only the arrow makes a difference. Usually only one side of an audio interconnect is grounded!

I am updating because the hum is now in both rears (it always had been) but on different drivers. so on the left speaker it is the upper driver and on the right it is the lower driver. It is in both tweeters. If NOT the 7500, could my speakers be showing blown crossovers? Because the bottom line is that the 2200's are not producing a hum and the fronts now are free of hum. The process of elimination is starting to point in the direction of the 7500.

But I feel like the culprit is REALLY the cable box. If I unplugg its power cord completly, the sound still exists, but it I unplugg the cloaxial the problem DOES go away. This is why #1 I am baffled the Jensen doesn't work and #2 that somehow the 2200's are doing a better job of "shielding" the channels.

If unplugging the coaxial eliminates the problem, I'd put in a call to your cable company and get them to check the ground on your cable service. It's possible that it's too messed up for even the Jensen to fix matters.

I would love to do that but I am pretty sure they will ask if ANYTHING with the picture or internet is affected by my complaint. If I say no, then they will likely tell me that their is no "issue" and the problem must lie with my gear.

But Gonk, the thing that keeps nagging me is why the 2200 seems to handle that hum but the 7500 can't? All other things being equal.

If you tell them that the problem occurs only when the cable is connected to your system and does not happen when you physically remove the cable TV from the system, then they really have to come out and look at it. We're talking about grounding here, and even as crummy as cable TV service can be this is not something they can blow off - after all, if they're doing it wrong, they are technically at risk of creating code violations.

I can't say what might be the difference in the two that has created the greater sensitivity in the 7500, but it's worth keeping in mind that the two amps are significantly different designs.

Knownalien - Let me weigh in this discussion. I have had some experience with ground loops. My hobby is electronics and over the years I have developed a passion for amplifiers. the amplifiers I have connected to my 990 are all hand built and provide some 2000 RMS watts of power all without a detectable hum.

The existance of a ground loop in your system invariably shows up in the input stage and therefore receives the full amplification of your amplifier and a very audible noise from your speakers.

Ground loops are caused by small variations in the resistance of the wires that return the signal to ground. Like the design of any high power amplifier, your system there should only have a single point where everything is grounded. When you connect the 990 to the 7500, the cables set the appropriate ground level for the 7500. Therefore, all cables should be of the same quality and they should all be about the same length. If the cable company has grounded your system, you probably may want to reconsider any other grounds you might have implemented.

Since the 2200 are mono blocks you would only be connecting one cable to them without any possibility of a gound loop (there is only one ground).

Outside of that I would switch some of the cables from the 990 to the 7500 to see if I could get the hum to move arround. You may detect a faulty cable. Failing all of these things, and an unwilling cable company, I would start suspecting the 7500, a loose wire or something.

I once had a small ground loob in my dual subwoofer amplifier. I got all of my test equipment out and started to trace it down, only to find out that it was being caused by a "Y" connector that I had used to split the signal. The one foot "Y" connector had just enough resistance differences to set up the ground loop. After I directly connected both amps to the 990, the hum disappeared.

You may want to google "ground loops" there are some excellent articles on this subject out there.

well, the interconnects I use are all of Outlaws top of the line non-balanced cables. Switching them would seem like a good idea, but for one, Outlaw (since they make both the cables and 990) has made it very hard to remove the cables esp. since they have the ends which require "screwing" in a bit and second, I am pretty sure that this comes down to a cable in the CABLE box because when it is unplugged, the hum goes away.