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| RamjetR:
--- Quote from: dave197878 on April 23, 2012, 05:52:12 pm ---The amp and PC is running off the PC atx power supply (12V Yellow and black wires). I plugged in head phones to the audio jack to test and theirs no noise. So at this point i figured it was the amp creating the noise but as mentioned above with the same power supply and plunging an mp3 into it as the source it works fine.. So the ground loop only appears when both the amp are plunged into the power supply and pc audio jack. Only when one of these factors is removed the issue seems to go away. So yes its a ground loop issue.. I have a ground loop isolator 3.5mm in my car for my sirius radio I use it to remove the alternater sound so I gave it a try on the PC out and it worked... Anyone see an issue with this fix.. it is a bandaid fix but it does work. Should I worry about the ground loop causing any other havoc? Can it effect the crt or do any damage? TY for the help every one. --- End quote --- Headphones aren't connected to another earth, thats why you wouldn't hear it. Are both the PC and AMP running on the same ATX supply from the PC? or a separate power supply and the PC still has it's own? Reason I ask is this: If it's on the same ATX power supply as the PC is running on, then is there enough current on the available on the 12V rails to run your PC and the AMP? You'd be suprised to know how much current the amp may need. But on the plus side, it wouldn't be an earth issue. But you may be seeing voltage regulation fluctuations appearing as audio hum. If they are on different powersupplies, then just run a link wire connecting the case of the powersupplies to each other. That should be all you need. The noise isolator from your car, is that an 3.5mm line level audio filter? If it's truely an isolator then it's probably separated the earths properly, but the issue is just going to arise again when you connect stuff from one powersupply to the PC which is on the other one. Ramjet |
| GregD:
Sorry to hijack the thread but you guys seem to know what you are talking about. My setup has separate power supplies for the pc and the amp, both plugged into the same smart strip. I tried plugging the amp into a different outlet but I got the same noise. Do I just have a bad power supply for the amp? |
| dave197878:
I am using one power supply for both Amp and PC. The Amp is small 20 W @ 12V =1.6 amps Does not seem like allot for a 12v rail... --- Quote from: RamjetR on April 24, 2012, 05:27:37 am --- Headphones aren't connected to another earth, thats why you wouldn't hear it. Are both the PC and AMP running on the same ATX supply from the PC? or a separate power supply and the PC still has it's own? Reason I ask is this: If it's on the same ATX power supply as the PC is running on, then is there enough current on the available on the 12V rails to run your PC and the AMP? You'd be suprised to know how much current the amp may need. But on the plus side, it wouldn't be an earth issue. But you may be seeing voltage regulation fluctuations appearing as audio hum. If they are on different powersupplies, then just run a link wire connecting the case of the powersupplies to each other. That should be all you need. The noise isolator from your car, is that an 3.5mm line level audio filter? If it's truely an isolator then it's probably separated the earths properly, but the issue is just going to arise again when you connect stuff from one powersupply to the PC which is on the other one. Ramjet --- End quote --- |
| RamjetR:
Dave, Well, without actually doing an Ohm test on your grounds between your Amp and PC ground, I can't think of anything else to tell you. It shouldn't be an earth problem if your using the power from a standard 4 pin utilux connector that you would plug into a DVD/burner drive. Obviously the earths would be tied together nicely. The mouse noise is interesting though. I'm suprised that you'd hear that if it weren't being induced somewhere. I've had that issue years ago with an old wireless mouse which generated noise on my long 3.5mm audio lead to my stereo. I just changed it to a smaller cable and it went away. Unless your mouse is on another USB hub with it's own powersupply maybe? Do you have any other USB hubs with external power? maybe HDD's too? Unplug everything except the necessary stuff to run and slowely plug them back in till the noise comes back? It's a long shot but it's possible something else is doing it? Otherwise, I'm pretty much out of advice without actually being there to check with a Multimeter. GregD:- Need more info mate, A sketch is the best way to show us what your setup is. Keep it block diagram if detailed electronic schematic symbols aren't a strong suit. Two separate power supplies though, try tieing a wire between the case of the powersupply in one and the other one. See if that helps. But from experience, I've found that unless your going audiophile quality amplifiers... you never truely get a quiet amp on a PC. But I'm assuming your problems are noticeably louder than background white noise. |
| eds1275:
A dimmer switch on the same circuit would also potentially add noise. If you've got one on your marquee try turning it all the way up to see if it gets better, and then around 50% to see if it gets worse. |
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