mark1101 Posted January 7, 2004 Share Posted January 7, 2004 I changed where I plug my system into when I took down the x-mas tree. Actually, I put everything back the way it used to be. However now, I get a power supply hum in my EQ. It is a brand new DBX-1215. It didn't hum where it was plugged in last week. I get no hum through the speakers, the sound is fine. However, you can just stand near it and hear a med/high pitch hum when it is turned on. The other components are just a CD player, and Scott 299. Both are fine. I checked all connections, reversed AC plugs where not 3-prong. Had no effect on hum. I am suspicious of the CATV outlet. The system was not near it when it sounded fine. Now it is right near the CATV outlet and cable runs behind the audio system. I checked those connections and they seem fine. OK, besides telling me to lose the EQ, what could be the source of this hum? Thanks Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 7, 2004 Share Posted January 7, 2004 Might be something else plugged into that circuit causing the issue. Got any battery chargers, flourescent lights, other known offenders near there? Quote Link to comment Share on other sites More sharing options...
mark1101 Posted January 7, 2004 Author Share Posted January 7, 2004 No. I am actually even plugged into the same power surge protector that I was before I moved the system. I have moved the system from one side of the TV to the other. The only difference I can see is being near the cable TV outlet and the short run of cable to the TV, if that has anything to do with it. Can it be the surge protector? It is supposedly a good one. I paid about $40.00 for it, and the TV and HT are also plugged into it. By the way, I'm a sniper now. Thanks Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 7, 2004 Share Posted January 7, 2004 Try it without the power strip/surge protector. If that doesn't work, take the Eq into another room completely. Or, put everything back like it was before, see if the problem goes away. If it doesn't, the water is getting deep. Tom Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 7, 2004 Share Posted January 7, 2004 I bought a Audio Control Richter Scale Bass EQ/crossover years ago at Goodwill for twenty bucks. The PS transformer hummed, I thought it was defective. I emailed Audio Control, and asked if I could get a price on a replacement. It was still under the five-year warranty, so they said send it in. They also said replacement of the PS transformer probably won't get rid of the hum either. So I spent ten bucks on shipping, and they did change out the PS transformer free of charge. And guess what?! It still hums! They said it was a cheap unregulated supply, they didn't lie. It doesn't hum through speakers, just the PS tranny. Power switch on or not, it stills hums. I just turn off the power strip when not in use. Quote Link to comment Share on other sites More sharing options...
neo33 Posted January 8, 2004 Share Posted January 8, 2004 "Can it be the surge protector? It is supposedly a good one. I paid about $40.00 for it, and the TV and HT are also plugged into it." I paid $500 for my audio surge protector . Damn it, I must stop myself from being suckered into paying that outrageous price again! Quote Link to comment Share on other sites More sharing options...
mark1101 Posted January 8, 2004 Author Share Posted January 8, 2004 Mark, I think you are on to it. The way you describe it, that's what I am experiencing. I said it didn't make the sound originally. However, now I am wondering becasue when I first got the unit I can not remember powering it by itself with no music and hearing the hum. It is possible it did this right out of the box. But it makes such an audible hum/whine that I can't imagine missing it when I first plugged it in. All right, now what? Is the power supply defective. I see Mike mentioned his was replaced and still did the same thing. Is the DBX-1215 a piece of crap? It sure works pretty well if you use it correctly. Quote Link to comment Share on other sites More sharing options...
mark1101 Posted January 8, 2004 Author Share Posted January 8, 2004 Mark, I have the CD player sitting right on top of the DBX right now. For X-mas, I took my audio rack down to the basement system to make more room upstairs for the tree. The DBX, and CD player are sitting right on top of a cornwall right now, and the Scott is on the top of the stack. I know I should be shot for such a setup, but I have a new cabinet coming and it is only temporary. There is definitely some vibration as well (so I may need to tighten the PS). Sometimes a heavy bass note skips CDs. It makes sense that separating the equipment might help. I already tried running ground wires touching all the chassis together, no change. Reversed plugs, isolated plugs, all while in the stack configuration, no change. I will take the DBX out of the system into and plug it in in another room all by itself and see what I get before I take it apart. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
mark1101 Posted January 8, 2004 Author Share Posted January 8, 2004 Mark, If the problem is a noisy or defective power supply (not an unfastened one), does that mean that the life expectancy is any less? Should I send this unit back? It is brand new. How do you think a manufacturer would respond to a complaint of this sort? The unit works fine, it just makes noise. The noise does not affect the performance as far as I can tell. Can a unit develop this problem? Or is it generally there from day 1? Sorry for so many questions. Thanks Quote Link to comment Share on other sites More sharing options...
mark1101 Posted January 9, 2004 Author Share Posted January 9, 2004 Mark, Last night I took the DBX apart. It hummed no matter where I plugged it in all by itself disconnected from the audio system. There are 2 power supplys wrapped in a thin sheet metal shield curved over them. Both were physically loose although they were fastened with nuts, bolts and star washers. I tightened everything up and they still hum a small amount. They look to me like pretty cheap power supplys. If you push down on them with your finger you can quiet them some, as the shields seem to be resonating the sound. The unit functions fine. I would bet it was like this out of the box and I never noticed it. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
mark1101 Posted January 9, 2004 Author Share Posted January 9, 2004 Mark, I could tell by your response, you might be a little disgusted with the idea of having a new unit humming in the rack (or probably having an EQ at all). So, I got to thinking and called DBX. They verified that it was a batch issue and will replace both the transformers for free. They said that there were misaligned plates and too little enamel causing this issue on various units. Since I had this unit apart last night, I can tell it will be a simple repair as they each mount with 2 bolts, and simply plug into the circuit boards. DBX said the unit should not hum and recommended I immediately send it in for a free test and repair. Actually, good customer service. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 10, 2004 Share Posted January 10, 2004 I think Mark is hot on the tail of this thing, but if you look inside with the hood open, do one other thing first! Unplug it! And if there are large storage/filter capacitors in the power supply, wait some hours (or even a couple of days)to let them discharge a bit on their own before sticking your hands inside to touch ANYTHING. We don't know if there's a high voltage bleeder circuit in place, so it would probably not be unwise to unplug and wait for a bit, first. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 10, 2004 Share Posted January 10, 2004 Oh! You've already got the thing fixed (hopefully) by sending it back to DBX. Glad they are willing to help, and not say something like "Sorry, our boxes have never been known to hum! Tough luck!" I just wanted to prevent the zzzzzzzzzzzzzAP I once got awhile back because I forgot to unplug the power cord. Lessons like that teach very quickly and effectively! Quote Link to comment Share on other sites More sharing options...
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