60Hz hum from speaker with no input - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 11 Old 12-10-2019, 12:51 AM - Thread Starter
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60Hz hum from speaker with no input

this thing has been bugging for for a while now. I have searched so many places, and it keeps talking about "AC ground loop" ... which doesn't seem to be the problem I have. I hear a 60Hz hum on both speakers.

Setup:
AC plug ---> Parasound A21 ---> speaker

The Amp is resting on a glass panel, only electrical wire connected to Amp are (a) AC power and (b) wires to the speaker.

It might be something wrong with the AC connections in this OLd house, but not able to figure out what.

Here are other facts,
- I tried connecting 2-prong power, didn't help
- I tried connecting to different AC outlet in different rooms, same problem
- I tried connecting different speakers, same result
- I have 2 brands of sub-woofer, even they hum with or w/o any input connected
- I have hum coming out of Marantz Sr5012, as well as Denon AVRX3400h


it seems that my house is *** haunted ***, can somebody point me to possible problem and solution ... thanks
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post #2 of 11 Old 12-10-2019, 02:06 AM - Thread Starter
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just to add ...
- A21 is used Amp I bought, not sure how old it is. The loudness goes down with gain, and barely audible at 25% gain.
- I see the same issue with emotiva basx a-100, which is about a year old
- also same issue with NEW outlaw model 7000x that I bought a week ago

so, it doesn't seem like it has anything to do with age of the gear.
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post #3 of 11 Old 12-10-2019, 03:26 AM
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How close is your nearest neighbor?

Run an temporary extension cord from the neighbors house to your set up and check the hum. Also, purchase an outlet tester from the hardware store. It's a small inexpensive plug-in with three colored LED's that can help diagnose mis-wired outlets.
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post #4 of 11 Old 12-10-2019, 10:20 PM - Thread Starter
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Quote:
Originally Posted by NightHawk View Post
How close is your nearest neighbor?

Run an temporary extension cord from the neighbors house to your set up and check the hum. Also, purchase an outlet tester from the hardware store. It's a small inexpensive plug-in with three colored LED's that can help diagnose mis-wired outlets.
Thanks. Not sure about neighbor, but definitely "outlet tester" seem like good idea ... I guess the device you refer to looks like this: https://www.amazon.com/Sperry-Instru.../dp/B000RUL2UU
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post #5 of 11 Old 12-10-2019, 10:44 PM
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Quote:
Originally Posted by Dilip Chhetri View Post
Thanks. Not sure about neighbor, but definitely "outlet tester" seem like good idea ... I guess the device you refer to looks like this: https://www.amazon.com/Sperry-Instru.../dp/B000RUL2UU
Cable tv of any kind coming to the house?
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post #6 of 11 Old 12-10-2019, 11:30 PM - Thread Starter
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Originally Posted by audiofan1 View Post
Cable tv of any kind coming to the house?
there is cable internet, but I already try disconnecting the Cable from outside the house ... and no effect :-(
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post #7 of 11 Old 12-10-2019, 11:34 PM - Thread Starter
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I tested AC voltage at different outlets in the house
- between neutral and hot, it's about 120V [all outlets/rooms]
- room1:
hot and ground: 100V
- room2:
hot and ground: 118V
- room3:
hot and ground: 65V
ground and neutral: 50V <---- totally wierd
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post #8 of 11 Old 12-11-2019, 12:28 AM
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That is very strange and could be the cause - ground and neutral are supposed to be at 0V because they are tied together at the breaker box. To have ground and neutral at such an odd voltage implies a connection problem somewhere, so you might need an electrician to fix it. It could be creating a huge ground loop and thus the hum, and at least a safety issue.

It's entering from the input as it varies with the volume control, so the fact one room has wild voltages could be generating a ton of interference.
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post #9 of 11 Old 12-11-2019, 03:11 AM
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That's the tester I was referring to but based on the voltage readings you posted I agree, it's probably time to consult a qualified electrician. The wiring in older homes can be dangerous to more that your home theater.
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post #10 of 11 Old 12-11-2019, 05:25 AM
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Just connect the amp to an input source, which is how you’ll be using it anyway. Good chance the noise will go away.

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Wayne A. Pflughaupt


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post #11 of 11 Old 12-11-2019, 06:01 AM
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Quote:
Originally Posted by Wayne A. Pflughaupt View Post
Just connect the amp to an input source, which is how you’ll be using it anyway. Good chance the noise will go away.

Regards,
Wayne A. Pflughaupt
Duh, it's a stand-alone power amplifier. I was thinking receiver.

Yep, try giving it an input.

Still, those voltage readings are whacky.
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