Ground Loops - Eliminating System Hum and Buzz

highfigh

highfigh

Audioholic Overlord
'josh' the DC part of your post is totally incorrect. Planet Earth works the same way with DC as with AC. In the past, we didn't see much high voltage DC in contact with Earth. But now some electric cars have high voltage batteries and in an accident, the safety worker have to be careful not to electrocuted.
With electric cars and even electric tools, I'm more concerned about the Lithium batteries going off like a small rocket. The local SnapOn guy was charging a Ryobi battery in his former garage, near his former SnapOn truck filled with former tools, his former pickup truck, his former Camaro and the Alpha Romeo he inherited from his dad. The new garage isn't quite done.
 
J

joshk03

Audioholic
Speedskater & TLS Guy, perhaps you could update your last posts? The mistake has been corrected.
 
S

Speedskater

Audioholic Chief
Speedskater & TLS Guy,
....................................
Speedskater, they work the same, but should never be connected together.
In a hi-fi component, the AC Safety Ground is connected to the chassis and the DC supply common (aka ground) is also connected to the chassis.
 
NorseMythology

NorseMythology

Junior Audioholic
I get a nasty POP when I turn my bathroom exhaust fan off, I get some feedback when I turn the lights on and off in the bathroom but not like the exhaust fan. Any ideas?
 
S

Speedskater

Audioholic Chief
There are suppressor circuits for that type of POP. But the parts are tricky to purchase and install.

Use a long extension cord to power your hi-fi from different circuits in your home. (as a test)
 
highfigh

highfigh

Audioholic Overlord
In a hi-fi component, the AC Safety Ground is connected to the chassis and the DC supply common (aka ground) is also connected to the chassis.
Sometimes. There's plenty of gear that uses a two prong AC plug. In that case, the ground only meets the AC neutral inside of the breaker panel although this can be different in various countries.
 
fabiocz

fabiocz

Audioholic
How much volts is considered less/more dangerous in ground loop ?
Example:
3v = low ?
20v = high ?
 
B

bikdav

Senior Audioholic
What can be done about computers? My BUZZ noise comes from the desktop PC. Actually, I have 2 desktop PCs. I tried both of them on my system and they both emit that same BUZZ. I even tried another amplifier. That didn't solve anything.
 
K

kenwstr

Audioholic Intern
What can be done about computers? My BUZZ noise comes from the desktop PC. Actually, I have 2 desktop PCs. I tried both of them on my system and they both emit that same BUZZ. I even tried another amplifier. That didn't solve anything.
I recently installed a new AV specked PC in a PA system that I maintain. So, I did a lot of R&D for the spec and how best to connect it into the PA system. Turns out that while PC audio has definitely come a very long way over the last decade or so, it is still not comparable to a good CD player unless you spend an insane sum on filtering and isolation etc. Part of the problem is the USB power. However, you can still get a good result on a budget of a few hundred by paying simple attention to basic filtering and electrical isolation.

As far as my research revealed, best practice is to use an external DAC rather than the computing devices sound card and headphone jack. While there are some very good shielded internal DACs available, this is still not best practice. An external DAC gets this process out of the PC case and away from interference effects and power noise that PC's are generally riddled with. Oddly enough USB is still considered very highly for PC audio despite it being very old tech. I used a Trip-Lite U023 USB cable because of the high shielding and ferrite chokes that suppress a degree of noise from the PC. The DAC itself is a Radial USB-Pro. This incorporates further noise filters, capacity to accept high res audio, audio transformer and ground isolation (eliminates potential ground loop hum). I am using a standard lossless uncompressed bit stream (less than the DAC's capacity). The DAC's balanced output is from it's internal audio transformer which allows PC/DAC ground shield to be isolated from the PA ground shield (ground lift). This is a relatively inexpensive pro audio DAC but up there in quality and durability. It was a convenient option to connect with the mixing desk's balanced XLR inputs and provide electrical isolation at the same time. I have listened to music from this DAC directly into my HD650 phones and it is equivalent to anything I have heard from any digital source and I am eminently pleased with the result for the money.

You could probably find a similar device with single ended audio outputs or use a balanced to unbalanced (single ended) converter.

At home, I use an Essence HDACC to connect all my digital sources into an analogue stereo system. This does not in itself provide ground loop isolation though but I am not using it to connect computers to the stereo. For that, I would have to use and audio transformer between the HDACC and the analogue Stereo system. So basically, the options are either a DAC with an output & ground shield isolation or use a separated audio transformer if ground loop hum exists.

Both perform very nicely IMO however, to get the same kind of filtering and isolation as I have with the PA, but in an unbalanced or single ended solution, in a high end HiFi solution would generally take separate components (filters, isolator, USB power conditioner....) and add up to a premium price. Which is why many people are ditching computer audio in favor of audio specific devices to serve digital music into high end DACs. Perhaps something like a music server or smart player connected to a network drive or simply a streaming service. The only advantage I can see offered by a computer is the convenience of playlists. Where I am, that's about $2500 AUD to setup a full HD AV PC and external DAC with appropriate filtering and electrical isolation. That's a big investment for that playlist function alone.
 
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highfigh

highfigh

Audioholic Overlord
What can be done about computers? My BUZZ noise comes from the desktop PC. Actually, I have 2 desktop PCs. I tried both of them on my system and they both emit that same BUZZ. I even tried another amplifier. That didn't solve anything.
It's possible that the buzz may be from the display or a power supply. Is the computer close to the amplifier, or in another room? If the latter, run an extension cord from the outlet powering the audio system to the computer and if the noise stops, you have a ground loop. If possible, it may be necessary to use a separate ground wire to connect them.
 

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