I am in dire need of some help. I have a wicked hum in my system that is driving me absolutely crazy. It all started earlier this month when I added a Sherbourn 5/1500 5 x 200 watt amp to my DSP-A1, which I am now using as a pre/pro and as a power amp for my center rear channel and the Yamaha front effects speakers. (In addition to the Sherbourn, I also added a Smart Devices CS-3X, Jr.). Now, I have to say that for the most part I have been thrilled with the performance of both new components. The center back channel adds much more than I thought it would to movies, both those that are specifically encoded for it and those that aren't, and the Sherbourn is so much more powerful and dynamic than the Yamaha, yet more detailed too. I could only be happier if I got rid of this hum.
Prior to buying the Sherbourn I had read about other people having problems with hum, so it was something I was aware could be a problem. A post I read just before ordering the amp led me to believe that at least one problem reported in one of the A/V magazines was due to some minor damage in shipping. I was, as you might imagine, a little worried when my amp arrived in a damaged box with the power cord missing (I honestly believed somebody dug down through the double boxing to steal the cord), but after a few phone calls I had the amp up and running with a replacement cord.
I noticed the hum the first night I got things set up, and figured I'd spend the next day going over connections. But when I got up the next day the hum was gone. I soon realized what was going on when I turned the TV on. At that point the buzz returned. After mentioning the problem on one of the forums I was told I had a ground loop problem and that I need to get a Xantech Ground Breaker, and for about $4, I figured it was worth a try. I wasn't really sure where it was supposed to go in the system, but the way I tried it made no difference. I then got a Monster Power HTS 2000 PowerCenter. Again, no dice. In fact, things sounded worse, but I chalked that up to the fact that I had caused such a mess with the wires.
This hum is really starting to drive me bonkers. I've become so "tuned" to it that I can now hear it over the sound of music or a soundtrack. That wasn't the case for the first couple of weeks, but now I think I focus on it so much that I hear it all the time. I'm even starting to hear it when I have everything turned off, and only after paying careful attention do I figure out that I'm just imagining it. The worst part is it seems that this hum has now infected my Definitive Technology PowerField 1500 subwoofer.
I'm hoping that after I give a good, detailed description of my system and the problem that I'm having that somebody out there will be able to lead me to a solution. I'm pretty comfortable with my equipment, but I don't know beans about electrical circuits and such, so treat me like an idiot and be very descriptive.
Like I said, I'm using the DSP-A1 as a pre/pro and power amp for the center back and front effects speakers. The left, right, and center pre-outs from the DSP-A1 are connected directly to the Sherbourn with Radio Shack RCA interconnects, I believe the Gold variety, and if I remember correctly the box claimed that they were shielded. Each cable is 12 feet long. The surround pre-outs are connected to the CS-3X, Jr. with the same type of Radio Shack connectors, only they are only 6-feet long. The left and right surround outputs from the CS-3X, Jr. are connected to the Sherbourn with another pair of the 12-foot long Radio Shack cables. Finally, the center back channel from the CS-3X, Jr. is connected to the DSP-A1's main left channel input with another of the 6-foot long Radio Shack cables.
My speakers are connected to the Sherbourn with Home Depot 12-gauge speaker wire with RCA brand single banana plugs on each end. My Definitive Technology BP 10 fronts and my CLR 1000 are connected to the Sherbourn with 15-foot long speaker cables, while my BP 8 surrounds are connected with 50-foot runs of the wire. My C1 center back channel is connected to the DSP-A1 with a 50-foot flat Monster Cable that I believe is 14-gauge, but I have two more 50-foot runs of the Home Depot 12-gauge wire waiting in the wings. The center back channel uses the same banana plugs I'm using everywhere else. The subwoofer is connected to the DSP-A1's subwoofer output with about a 20 foot long Monster Cable.
The following components are connected to the DSP-A1. I have a Pioneer Elite DVL-91 DVD/LD combi player connected to the DSP-A1 via analog audio, composite video, s-video, and coaxial digital (DVD DD/DTS/PCM). I also have a coaxial output from the AC-3 RF output connected to a Sony demodulator, which is in turn connected to the DSP-A1 by an optical digital cable. I have a Pioneer CLD-D703 LD player that is connected by its analog audio outs, composite video, s-video, and optical digital (PCM). I have had an AC-3 RF output added by MSB, and it is connected to the DSP-A1's AC 3 RF input via coaxial digital cable. I have two JVC S-VHS ET vcrs, which are both connected to the DSP-A1 via analog audio, composite video, and s-video cables. The interconnects I am using are mainly of the variety you can by at Wal-Mart under the RCA, Magnavox, and Phillips brands.
My tv cable enters my living room from the wall opposite my Home Theater setup. My room is a rectangle about 25 X 17 X 8 or 9, and my TV is situated along one of the short walls. The coaxial tv cable comes into the room through the floor along the back wall. I have a long run of tv cable that I have tried to keep next to the walls. It runs to the back left corner of my room, then down the left side wall to the left front corner, where it then turns right and heads to the TV. The subwoofer is situated in that front left corner, and there is mass of tv cable directly behind it coiled like a snake, a big no-no, I know. The tv cable is currently running into the Xantech Ground Breaker, then from there into the HTS 2000's, then from there to a splitter. From the splitter I run into each vcr, one of which is then attached to my 50-inch Hitachi's main input, the other to an aux input. This allows me to tape two different shows at once.
I realize that my electrical outlets will be important. There is one outlet directly behind the tv set, in about the middle of the front wall. Initially I plugged the Sherbourn directly into that outlet. My other gear was plugged into a power strip that was in turn plugged into that same outlet. There is another outlet along the left front wall, over by the subwoofer that is in the corner. The sub is plugged directly into that outlet, as is another power strip that has has my phone and answering machine. After I noticed the hum problem, I plugged the Sherbourn directly into the corner outlet with the subwoofer. It made no difference. When I got the HTS 2000, I plugged all of my components (which are contained in a rack to the right of my TV) and the Sherbourn (which is situated on a TV stand to the left of my TV–hence the need for the 12-foot cables to reach from the DSP-A1 to the amp) into the HTS 2000, and that is how things are currently setup, so only one plug on the outlet behind the TV is being used at this time.
Here's a description of the problem I am having. When I first turn on the Sherbourn and it powers up, I hear a faint hum, much like the hum of any other piece of electrical equipment. I don't believe this hum rises to the level of a buzz. I have heard other amps making this same noise, and after the initial power-up, I have to be very close to hear the hum at all. In fact, my computer, which is in another room, is more audible from my HT listening position than the amp itself. I don't really consider this hum to be a problem.
In addition to the amp hum, I also have a buzz coming out of my speakers, predominantly it seems from the front speaker, but present in all. With the TV off the sound is low, but audible if there is no other sound in the room. It occurs regardless of whether the DSP-A1 is powered up, and the DSP-A1's volume control does not effect it. It stays at a constant level. I've heard people mention a 60 hz hum. Not really knowing what they mean by that, in my mind I could imagine it sounding like this. Just a constant, electrical buzzing from the speaker.
When I turn the TV on, the buzz gets more intense. It reminds me of the sound a car stereo makes when it is getting engine noise, although nothing I do causes the level of the buzz to go up or down. It just intensifies when the TV is turned on. As per suggestions, I have unplugged the tv cable from the TV, and it makes no difference. The buzz is still there.
At times the buzz seems louder to me, but I think it is more a matter of how much I pay attention to it. While it isn't a terribly loud sound, with no sound in the room I can definitely hear it from my seat, especially if the TV is on. With the TV off it is less noticeable but still present.
The subwoofer is beginning to sound like a fish tank, and I think I'm having a problem with the outlet where it is connected. Although the plug fits snugly into the outlet, it seems that it only draws power if it is in a certain position. When it does draw power, it causes that fish tank BUZZ sound, which is much louder than anything coming from the Sherbourn or the speakers. It's a sound like bees or something. Not terribly loud, but you notice it. It's also one of those buzzes that you seem to feel. I've noticed that it appears to be worse when I have something else plugged into the same outlet. In addition, I plugged a surge protector into that outlet and then plugged the subwoofer into the surge protector. The subwoofer BUZZ got much worse, and I've found that it is less obtrusive if I just plug the sub directly into the wall.
This is very long, but I need help. I've tried to provide every piece of information I have on the situation, but if somebody out there needs to know more, please let me know. I'm counting on somebody having an answer for me, or at least some suggestions for a plan of attack to find and eliminate this problem. And yes, I've done a search on this topic, and printed a few things out. But like I said before, I need to be treated like an idiot on this one. I didn't understand a lot of what I read in the other posts, so offer plenty of explanation if you think you can help me. Any response is greatly appreciated.
