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

 

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.

 

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.

 

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.

 

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

 

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.

 

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

 

R you sure of that statement ?

 

Neither. The hum you hear in the UK is actually 100 Hz.

 

Alan:
Gee.... what about Canada, Japan.... and other countries beside the USA that
run 60 Hz power???
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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Only backward countries use 60 Hz!-)

Alan

 

Not 100%, no!

Alan

 

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.

 

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In other words, you recognize what a bad idea this is.

is completely

 

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
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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.

 

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"crikey"

exclamation UK OLD-FASHIONED INFORMAL
an expression of surprise

 

YIKES!

 

Ken:
I have traveled the world over..... been to the UK many times on business
trips, personal vacations, etc.... but I had never heard the work "crikey"
until today.
How about up in Canada ?? Have you?