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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to sci.electronics,sci.electronics.equipment,sci.electronics.repair
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60 hertz hum
I'm running the output of my computer to my stereo aamplifier.
I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis |
#2
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60 hertz hum
Dennis wrote:
I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis Make sure, that both your computer and your stereo are connected to ground. The netfilter in your computer will otherwise dump a filtercurrent along your audio path ground. |
#3
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60 hertz hum
"Sjouke Burry" wrote in message
... Make sure, that both your computer and your stereo are connected to ground. The netfilter in your computer will otherwise dump a filtercurrent along your audio path ground. More precisely, make sure that your stereo amplifier and your computer are connected to the same ground. Even a few millivolts of AC difference in ground potentials can cause lots of 60 Hz hum. -- James T. White |
#4
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60 hertz hum
"James T. White" wrote in message ... "Sjouke Burry" wrote in message ... Make sure, that both your computer and your stereo are connected to ground. The netfilter in your computer will otherwise dump a filtercurrent along your audio path ground. More precisely, make sure that your stereo amplifier and your computer are connected to the same ground. Even a few millivolts of AC difference in ground potentials can cause lots of 60 Hz hum. But only if you live in the US of A, if you live in other parts of the world, it will be 50 hertz. Alan -- James T. White |
#5
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60 hertz hum
R you sure of that statement ?
"Alan Holmes" wrote in message ... But only if you live in the US of A, if you live in other parts of the world, it will be 50 hertz. Alan -- James T. White |
#6
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60 hertz hum
"kip" wrote in message .. . R you sure of that statement ? Not 100%, no! Alan "Alan Holmes" wrote in message ... But only if you live in the US of A, if you live in other parts of the world, it will be 50 hertz. Alan -- James T. White |
#7
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60 hertz hum
Alan:
Gee.... what about Canada, Japan.... and other countries beside the USA that run 60 Hz power??? -- Best Regards, Daniel Sofie Electronics Supply & Repair - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Alan Holmes" wrote in message ... "James T. White" wrote in message ... "Sjouke Burry" wrote in message ... Make sure, that both your computer and your stereo are connected to ground. The netfilter in your computer will otherwise dump a filtercurrent along your audio path ground. More precisely, make sure that your stereo amplifier and your computer are connected to the same ground. Even a few millivolts of AC difference in ground potentials can cause lots of 60 Hz hum. But only if you live in the US of A, if you live in other parts of the world, it will be 50 hertz. Alan -- James T. White |
#8
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60 hertz hum
"sofie" wrote in message ... Alan: Gee.... what about Canada, Japan.... and other countries beside the USA that run 60 Hz power??? Only backward countries use 60 Hz!(:-) Alan -- Best Regards, Daniel Sofie Electronics Supply & Repair - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Alan Holmes" wrote in message ... "James T. White" wrote in message ... "Sjouke Burry" wrote in message ... Make sure, that both your computer and your stereo are connected to ground. The netfilter in your computer will otherwise dump a filtercurrent along your audio path ground. More precisely, make sure that your stereo amplifier and your computer are connected to the same ground. Even a few millivolts of AC difference in ground potentials can cause lots of 60 Hz hum. But only if you live in the US of A, if you live in other parts of the world, it will be 50 hertz. Alan -- James T. White |
#9
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60 hertz hum
In article ,
Alan Holmes wrote: More precisely, make sure that your stereo amplifier and your computer are connected to the same ground. Even a few millivolts of AC difference in ground potentials can cause lots of 60 Hz hum. But only if you live in the US of A, if you live in other parts of the world, it will be 50 hertz. Neither. The hum you hear in the UK is actually 100 Hz. -- *I believe five out of four people have trouble with fractions. * Dave Plowman London SW To e-mail, change noise into sound. |
#10
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60 hertz hum
"Dave Plowman (News)" wrote in message ... In article , Alan Holmes wrote: More precisely, make sure that your stereo amplifier and your computer are connected to the same ground. Even a few millivolts of AC difference in ground potentials can cause lots of 60 Hz hum. But only if you live in the US of A, if you live in other parts of the world, it will be 50 hertz. Neither. The hum you hear in the UK is actually 100 Hz. How do you work that out? Alan -- *I believe five out of four people have trouble with fractions. * Dave Plowman London SW To e-mail, change noise into sound. |
#11
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60 hertz hum
Sounds like ground loop hum. Try plugging your stereo into the same outlet
or power bar as your computer and see if it goes away. "Dennis" wrote in message ... I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis |
#12
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60 hertz hum
Dennis wrote:
I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis If you have cable TV in any way connected to either your stereo or computer (e.g. via a cable modem), disconnect it and see whether the hum stops. If it does, you know the culprit. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#13
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60 hertz hum
On 2006-01-03, Dennis wrote:
I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, what about with the computer turned off (but plugged in)? if it's still there the noise is comiing from the cabling (called a gound loop) one thing that helps sometimes is to ensure that the sterio and all the devices that are connected to it and (subwoofer, DVD player) and any devices that are connected to them... are all connected to the same electrical outlet (and to the same filter if any) if that helps there's a relatively inexpensive device called a audio isolating transformer that'll probably kill the hum and let you return the power cabling to its original configuration. another option would be to go with a non-conductive connection (like fibre optic if your sterio and sound card support it) Bye. Jasen |
#14
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60 hertz hum
In article ,
Dennis wrote: I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Sounds like you've got a ground loop. You could try removing the screen connection on the interconnect. Or buy a transformer designed to prevent ground loops from a car audio place. -- *Modulation in all things * Dave Plowman London SW To e-mail, change noise into sound. |
#15
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60 hertz hum
Something you might try (although you didn't hear it from me) is completely
disconnecting the ground pin on your computer. You didn't mention what kind of computer you're using, but if it's a laptop, grounding isn't too essential. (In fact, having a permanently lifted [broken off, actually] ground pin on mine has several times saved my laptop from almost certain major damage when connected to equipment with a ground fault - a common problem in my line of work.) In my case, I'm also using a laptop for a home music recording studio (I know, not the best choice, but it was sitting around...). All of the audio I/O is via an external high-quality device, but ground loop hum was killing me, *even though everything was plugged into the same outlet strip*. Breaking off the computer's power supply ground pin completely solved the problem. -- Mark "I prefer heaven for climate, hell for company." "Dennis" wrote in message ... I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis |
#16
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60 hertz hum
Mark Moulding wrote:
Something you might try (although you didn't hear it from me) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In other words, you recognize what a bad idea this is. is completely disconnecting the ground pin on your computer. You didn't mention what kind of computer you're using, but if it's a laptop, grounding isn't too essential. (In fact, having a permanently lifted [broken off, actually] ground pin on mine has several times saved my laptop from almost certain major damage when connected to equipment with a ground fault - a common problem in my line of work.) In my case, I'm also using a laptop for a home music recording studio (I know, not the best choice, but it was sitting around...). All of the audio I/O is via an external high-quality device, but ground loop hum was killing me, *even though everything was plugged into the same outlet strip*. Breaking off the computer's power supply ground pin completely solved the problem. -- Mark "I prefer heaven for climate, hell for company." "Dennis" wrote in message ... I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#17
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60 hertz hum
CJT:
Some years ago when I was in the pro-audio installation business for an on the road entertainment company, us installation techs would always carried about a dozen "u-ground" 3 wire to 2 wire ground adapters in our tool boxes so the ground could be temporarily "lifted" on various pieces of gear to eliminate ground loops and the subsequent hum problems. (don't cut off ground pins on the plugs of equipment) Usually the problem would originate because remote equipment was on a different circuit from the breaker box and was located some distance from the main head-end gear. -- Best Regards, Daniel Sofie Electronics Supply & Repair - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "CJT" wrote in message ... Mark Moulding wrote: Something you might try (although you didn't hear it from me) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In other words, you recognize what a bad idea this is. is completely disconnecting the ground pin on your computer. You didn't mention what kind of computer you're using, but if it's a laptop, grounding isn't too essential. (In fact, having a permanently lifted [broken off, actually] ground pin on mine has several times saved my laptop from almost certain major damage when connected to equipment with a ground fault - a common problem in my line of work.) In my case, I'm also using a laptop for a home music recording studio (I know, not the best choice, but it was sitting around...). All of the audio I/O is via an external high-quality device, but ground loop hum was killing me, *even though everything was plugged into the same outlet strip*. Breaking off the computer's power supply ground pin completely solved the problem. -- Mark "I prefer heaven for climate, hell for company." "Dennis" wrote in message ... I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#18
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60 hertz hum
In article ,
sofie wrote: Some years ago when I was in the pro-audio installation business for an on the road entertainment company, us installation techs would always carried about a dozen "u-ground" 3 wire to 2 wire ground adapters in our tool boxes so the ground could be temporarily "lifted" on various pieces of gear to eliminate ground loops and the subsequent hum problems. (don't cut off ground pins on the plugs of equipment) Usually the problem would originate because remote equipment was on a different circuit from the breaker box and was located some distance from the main head-end gear. Crikey. You'd have been shot in the UK. ;-) 1:1 repcoils are the correct way with balanced pro audio gear. You *really* shouldn't mess with safety earths. -- *Why is a boxing ring square? Dave Plowman London SW To e-mail, change noise into sound. |
#19
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60 hertz hum
"Dave Plowman (News)" wrote in message Crikey. You'd have been shot in the UK. ;-) 1:1 repcoils are the correct way with balanced pro audio gear. You *really* shouldn't mess with safety earths. *Why is a boxing ring square? Dave Plowman London SW - - - - - - - - - - - - - - - - "crikey" exclamation UK OLD-FASHIONED INFORMAL an expression of surprise |
#20
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60 hertz hum
I knew that would raise some rabble. Yes, of course I recognize the
potential (so to speak) problems with opening the safety ground connection. However, a few interesting points exist in this particular situation: - The device is a laptop, and there is no direct connection from the ground pin through the (double-insulated) AC adapter/charger to the laptop chassis, so it's really not much of a "safety" ground. - There are two small value (10 nF) caps from each side of the power line to the ground terminal inside the adapter, presumably as an RFI suppression measure. - All of the audio equipment involved was plugged into the *same* outlet strip - it seems highly unlikely that there'd be much of ground loop within the 6" or so of 16 gauge wire separating the plugs - Finally (and this is really no excuse), my house is old enough that I'm not convinced that all of the three prong outlets have their ground pin connected to anything at all. It's not so old that it's knob-and-tube, but the outlets were originally two prong, and I think that many were just replaced with three-prong as placebos, without pulling a ground wire. At least the garage (with the concrete floor and the power tools) is wired correctly... -- Mark "I prefer heaven for climate, hell for company." "sofie" wrote in message ... CJT: Some years ago when I was in the pro-audio installation business for an on the road entertainment company, us installation techs would always carried about a dozen "u-ground" 3 wire to 2 wire ground adapters in our tool boxes so the ground could be temporarily "lifted" on various pieces of gear to eliminate ground loops and the subsequent hum problems. (don't cut off ground pins on the plugs of equipment) Usually the problem would originate because remote equipment was on a different circuit from the breaker box and was located some distance from the main head-end gear. -- Best Regards, Daniel Sofie Electronics Supply & Repair - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "CJT" wrote in message ... Mark Moulding wrote: Something you might try (although you didn't hear it from me) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In other words, you recognize what a bad idea this is. is completely disconnecting the ground pin on your computer. You didn't mention what kind of computer you're using, but if it's a laptop, grounding isn't too essential. (In fact, having a permanently lifted [broken off, actually] ground pin on mine has several times saved my laptop from almost certain major damage when connected to equipment with a ground fault - a common problem in my line of work.) In my case, I'm also using a laptop for a home music recording studio (I know, not the best choice, but it was sitting around...). All of the audio I/O is via an external high-quality device, but ground loop hum was killing me, *even though everything was plugged into the same outlet strip*. Breaking off the computer's power supply ground pin completely solved the problem. -- Mark "I prefer heaven for climate, hell for company." "Dennis" wrote in message ... I'm running the output of my computer to my stereo aamplifier. I'm getting an annoying 60Hz hum through both speakers. This occurs with all inputs and outputs muted. If I unplug the plug from the back of the computer the hum stops. Help please, Dennis -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
#21
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60 hertz hum
Mark Moulding wrote: I knew that would raise some rabble. Yes, of course I recognize the potential (so to speak) problems with opening the safety ground connection. However, a few interesting points exist in this particular situation: - The device is a laptop, and there is no direct connection from the ground pin through the (double-insulated) AC adapter/charger to the laptop chassis, so it's really not much of a "safety" ground. - There are two small value (10 nF) caps from each side of the power line to the ground terminal inside the adapter, presumably as an RFI suppression measure. - All of the audio equipment involved was plugged into the *same* outlet strip - it seems highly unlikely that there'd be much of ground loop within the 6" or so of 16 gauge wire separating the plugs - Finally (and this is really no excuse), my house is old enough that I'm not convinced that all of the three prong outlets have their ground pin connected to anything at all. It's not so old that it's knob-and-tube, but the outlets were originally two prong, and I think that many were just replaced with three-prong as placebos, without pulling a ground wire. At least the garage (with the concrete floor and the power tools) is wired correctly... -- Mark Hi... As a side issue, there are testers available for only a couple of dollars that you can plug into your outlets that will (by way of three neon lamps) easily tell you whether or not ground exists, and if hot/neutral are reversed. Just mentioned it wondering if it might not increase your comfort level. Ken |
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