ground loop hum solution

[colinlewissmith]

This might help with some of you looking for solutions to ground loop hum issues.

I created a ground loop in my system through introduction of a Behringer Feedback Destroyer (used as a parametric equalizer). The simple product linked to below solved the problem. I only used one channel (i.e one of the 2 left/right channels), and inserted it between my AV reveiver and the Behringer unit. I.E. AV receiver --->ground loop isolator--->behringer--->sub

The device breaks the ground loop at the signal level, without compromising electrical safety.

Works perfectly.

Xitel Ground Loops isolator:

http://www.xitel.com/product_gli.htm

Available in Canada at: http://www.minidisc-canada.com/shopexd.asp?id=51

[colinlewissmith]

I have attached a pic of the device, and a diagram of where it is inserted in my system.

regards Colin

[Stan]

This might help with some of you looking for solutions to ground loop hum issues. I created a ground loop in my system through introduction of a Behringer Feedback Destroyer (used as a parametric equalizer). The simple product linked to below solved the problem. I only used one channel (i.e one of the 2 left/right channels), and inserted it between my AV reveiver and the Behringer unit. I.E. AV receiver --->ground loop isolator--->behringer--->sub The device breaks the ground loop at the signal level, without compromising electrical safety.
Works perfectly. Xitel Ground Loops isolator:
http://www.xitel.com/product_gli.htm
Available in Canada at: http://www.minidisc-canada.com/shopexd.asp?id=51

Yes such devices can address ground loop hum.

BUT.

Some introduce audible distortion of their own. The ones that use transformers can do this for example. Such as the old Radio Shack version, which adds harmonic distortion which is audible and easily measured. I'd want to know that the device did not alter the signal in that or any other manner before using one. Ideally, solve the ground loops at the root cause.

This is an example of a unit to avoid...I've measured a few percent harmonic distortion from it in a test (the test was done due to some harshness found after inserting the unit into a system):

http://rsk.imageg.net/graphics/product_images/pRS1C-2160121w345.jpg

Maybe the transformers saturate above some signal strength or something, I did not test further after finding the issue.


Stan / sjmarcy

[majorloser]

Jensen Transformers
http://www.jensen-transformers.com/iso_vid.html

You also need to address satellite an cable TV coax since groundloop hum can be introduces through those devices.

[lradden]

colinlewissmith & majorloser thanks for taking the time to research these devices. One of these should help with the minor ground loop I have in my system.

Once again thank you both very much.

[Stan]

Here is an example of the distortion issue I raised. This is a graph from a well made device by Jensen. As you can see, unlike an interconnect, there is a clear limit to the strength of the signal that can be passed in the realm of audio signals sent to a sub. The product is speced out at a -10dB level corresponding to just over 0.3 volts.

http://www.pbase.com/sjmarcy/image/74910132/original.jpg

So when you use such a device, make sure that you do so within the signal strengths it can handle well. The Radio Shack unit must have a low signal strength limit or something.

This also brings up the possibility of setting up your system accordingly. As in setting the sub signal from your AVR or PREPRO on the lowish side and then turning up the gain at the sub a hair. But I'd want to measure actual voltages against the specs in that case anyway.

Stan / sjmarcy

[Ddavidson]

colinlewissmith & majorloser thanks for taking the time to research these devices. One of these should help with the minor ground loop I have in my system.

Once again thank you both very much.

Good information on the available plug and play options colinlewissmith & majorloser. Forum members suffering from these issues would find this info of great value.

Ddavidson

[cschang]

Good information on the available plug and play options colinlewissmith & majorloser. Forum members suffering from these issues would find this info of great value.

Ddavidson
Agreed...maybe it should be some kind of sticky.

[lradden]

I'll 3rd the recommendations from Ddavidson & cschang. Nice work colinlewissmith & majorloser, many of us suffer from these hums and this could be a great help.

[Stan]

I'd suggest that if stickying is desired, that overall hum reduction strategies be reviewed. There are quite a few. Many may wish to eliminate any hum issues that arise, without changing the audio signal in doing so.

Also as far as any specific remedy devices go, it might make sense to test them out first. For example the Xitel audio signal device has a frequency response rating of 20-20K +/- 3 dB. http://www.xitel.com/customerdata_pdfs/GLI.pdf Any issues at 20 Khz don't matter here, but the low end would matter. I would want to be sure that 20 Hz was not 3 or 6 db down for example, for a subwoofer application. Not to mention the signal strength issue some transformer devices exhibit with signals of normal strength. Note that the LFE channel has an extra 10 dB of oompth compared to the normal channels.

Stan / sjmarcy

[Ddavidson]

Agreed...maybe it should be some kind of sticky.
Even if only as a general service note in the FAQs (that such devices exist). Needless to say Hsu would need to be careful as to not promote any brand/model it didn't want to.

Ddavidson

[wid]

I could see Dr. Hsu making his own brand and selling it on the Hsu site. I bet it wouldn't be to difficult to do, for him at least.

[Ddavidson]

I could see Dr. Hsu making his own brand and selling it on the Hsu site. I bet it wouldn't be to difficult to do, for him at least.Would you like it TurboCharged or SuperCharged http://forum.hsuresearch.com/images/icons/icon10.gifhttp://forum.hsuresearch.com/images/icons/icon10.gif
http://forum.hsuresearch.com/images/icons/icon10.gif


Ddavidson

[wid]

:D :D

[lradden]

DDavidson & Wid let's sticky this bad boy and when the Dr. makes his own it can be SuperTurbocharged.:D For now we just have to settle for the plain old hum eliminator.

[majorloser]

Here's a good link to learn about ground loops:

http://www.audioholics.com/techtips/setup/avhardware/groundloopcableTV.php
http://www.audioholics.com/techtips/audioprinciples/interconnects/GroundLoopPrimer.php


(Sorry Peter for the link to another forum :o )

[lradden]

Major I'm sure Peter won't mind the links. Thanks again for all the valuable information.

[Stan]

Here's a good link to learn about ground loops:
http://www.audioholics.com/techtips/setup/avhardware/groundloopcableTV.phphttp://www.audioholics.com/techtips/audioprinciples/interconnects/GroundLoopPrimer.php
(Sorry Peter for the link to another forum :o )

I'm a bit leery of that site, some of you may know why, LOL.

The first URL suggests a cable transformer and ignores by the books fixes such as properly grounding your cable in the first place. Most (maybe all) Cable TV companies will do that for free. They do around here. Or even the old try using the same power outlet strategy which can help if that is possible for you. Many HT style surge protectors have a cable in and out area which does the same thing

The second URL is written by the Business Development guy from the company that sells the products the article suggests! Again, I noticed that some basic things are not mentioned. The host site is known for such articles and reviews.

I will see if I can find a few URLs that present more of an overview of the matter, as well as various fixes besides instantly installing more devices from their advertisers.

Stan / sjmarcy

[Lwang]

Good information on the available plug and play options colinlewissmith & majorloser. Forum members suffering from these issues would find this info of great value.

DdavidsonThis should be made into a sticky, even if not for the specific product recommendation, it could be used as a first step into the understanding of what could be the likely cause of the hum instead of having someone say "this sub won't stop humming".

Thanks for the info colinlewissmith & majorloser.

[monomer]

Stan... just so you don't think everyone's ignoring your cautions... I understand and agree with all you've said. Why audibly degrade your signal when there might be another (possibly easier) fix at the source? Gaining knowledge can be more work than simply buying and installing a product but it might ultimately lead one to a better solution to eliminating hum. Any additional links you can provide would be great. Thanks...

[majorloser]

For me the fix was quite simple. I connected a wire between all of my amp chassis and my pre/pro. I just used a screw on the back of each component to attach the wire. This grounded them all together.

[tdekany]

colinlewissmith & majorloser

Thanks guys!

I printed out your info for future reference. Will be moving at some point and I'll need all the help (just in case.)

[Stan]

Stan... just so you don't think everyone's ignoring your cautions... I understand and agree with all you've said. Why audibly degrade your signal when there might be another (possibly easier) fix at the source? Gaining knowledge can be more work than simply buying and installing a product but it might ultimately lead one to a better solution to eliminating hum. Any additional links you can provide would be great. Thanks...

Thanks, Monomer. In the end, truth tends to come out.

Stan / sjmarcy

[lradden]

Thanks to colinlewissmith & majorloser researching these eliminators, it now sounds like we're all in agreement about these being good devices. I'll contact Peter and see if we can get a sticky.

[Stan]

Thanks to colinlewissmith & majorloser researching these eliminators, it now sounds like we're all in agreement about these being good devices. I'll contact Peter and see if we can get a sticky.

Well that may be the case for some, but I'd refer you to my posts above. The noted products may or may not alter the audio signal. And may or may not be the ideal solution to any hum issues which may arise. Most of the time (60-70% by one survey and 80% from another) the trouble is the difference between the power and cable TV grounds. That is trivial to fix via either local grounding of your cable TV cable or via a filter on your cable (which won't affect audio). It is easier to filter the video signal than the audio signal without harm. Some of the ideas here involve altering the audio signal to a degree, and as the first course of action. It is my opinion that the use of such a inline audio signal device be done only after various other strategies have been implemented. But other opinions are certainly welcomed and respected.

I am happy to test any such products which come my way. If anyone would like to have them professionally measured. I'll share the results, if any.

Stan / sjmarcy

[tdekany]

Thanks to colinlewissmith & majorloser researching these eliminators, it now sounds like we're all in agreement about these being good devices. I'll contact Peter and see if we can get a sticky.

Yes, see if he can get it up there as a sticky.

[majorloser]

The real problem with ground loop hum is how difficult they can be to narrow down the offending source. Every situation is different. In my case I still have a slight hum but it's not huge. By grounding all of the components in my closet the hum was reduced by about 90%. I have four different 20A electrical services in this component closet so ground hum was inevitable. I have also added a filter and surge suppression on the satelite coax and the telephone line since these were other possible points.

My suggestion would be to do what I did:

Disconnect all components and subwoofers from your receiver (or pre/pro) except your speakers (and amps if you have separates).
Power up and check for hum.
If you have a pre/pro, is there a hum on just one channel?
If the problem is just with that one channel then check the interconnect cable.
No hum, power down and connect only one component.
Power up again and check for hum
No hum, power down to disconnect the first device and connect a different device.
Power up again and check for hum
Repeat steps 5 and 6 until HOPEFULLY you'll find the offending device.
Once you find the offending device you have the option of grounding that device to your receiver (pre/pro) or using some sort of isolation transformer.Subwoofers can sometimes be a problem mainly because they can be on a different electrical circuit (outlet) in the room since they can't always be next to the component rack.

In my case I never really found the offending device. I think it's because I'm using seven Behringer A500 with an un-balanced pre/pro (B&K Ref 31). The A500 realy should be used with balanced connections. I know I should just buy a "un-balanced to balanced" transformer for all seven channels but they ain't cheap. Besides, I got almost 90% of the hum with with just a few cents of wire grounding all of the chassis in the closet. And I still never addressed isolation for the subwoofers and the projector since they are also on two different circuits.

It takes some time, but working with each device separately to determine where the problem lies (for the most part) will pay off. I would also suggest you read up on the subject. There are a lot of good sources out there and many good audio forums that have addressed this common problem. But like everything in life, take everything you read "with a grain of salt". Some sources have a motive behind their suggestions or just an axe to grind.

[Stan]

The real problem with ground loop hum is how difficult they can be to narrow down the offending source. Every situation is different. In my case I still have a slight hum but it's not huge. By grounding all of the components in my closet the hum was reduced by about 90%. I have four different 20A electrical services in this component closet so ground hum was inevitable. I have also added a filter and surge suppression on the satelite coax and the telephone line since these were other possible points. My suggestion would be to do what I did:
Disconnect all components and subwoofers from your receiver (or pre/pro) except your speakers (and amps if you have separates).
Power up and check for hum. If you have a pre/pro, is there a hum on just one channel? If the problem is just with that one channel then check the interconnect cable. No hum, power down and connect only one component. Power up again and check for hum No hum, power down to disconnect the first device and connect a different device.
Power up again and check for hum Repeat steps 5 and 6 until HOPEFULLY you'll find the offending device. Once you find the offending device you have the option of grounding that device to your receiver (pre/pro) or using some sort of isolation transformer.Subwoofers can sometimes be a problem mainly because they can be on a different electrical circuit (outlet) in the room since they can't always be next to the component rack. In my case I never really found the offending device. I think it's because I'm using seven Behringer A500 with an un-balanced pre/pro (B&K Ref 31). The A500 realy should be used with balanced connections. I know I should just buy a "un-balanced to balanced" transformer for all seven channels but they ain't cheap. Besides, I got almost 90% of the hum with with just a few cents of wire grounding all of the chassis in the closet. And I still never addressed isolation for the subwoofers and the projector since they are also on two different circuits. It takes some time, but working with each device separately to determine where the problem lies (for the most part) will pay off. I would also suggest you read up on the subject. There are a lot of good sources out there and many good audio forums that have addressed this common problem. But like everything in life, take everything you read "with a grain of salt". Some sources have a motive behind their suggestions or just an axe to grind.

Oh you have many amplifiers too? I have (lessee...) thirteen or fourteen in my system. That complicates things!

There are many good URLs on ground loop issues. I have not found any perfect ones, but this one is pretty comprehensive if you click and read a bunch to get a sense of the situation.

http://www.axiomaudio.com/tips_eliminate_hum.html

DON'T do what Axiom Audio suggests...they recommend the very Radio Shack device that I have measured and heard. I know for a fact you don't want it within 49 1/2 feet of your rig. Sure the hum will go away. But harsh distortion is added on stronger signals, especially low notes.

http://www.axiomaudio.com/tips_eliminate_hum.html

Stan

[majorloser]

Oh you have many amplifiers too? I have (lessee...) thirteen or fourteen in my system. That complicates things!

As I stated before, "But like everything in life, take everything you read with a grain of salt. Some sources have a motive behind their suggestions or just an axe to grind."

Which one might you be?

[Stan]

>>>Originally Posted by Stan
Oh you have many amplifiers too? I have (lessee...) thirteen or fourteen in my system. That complicates things!<<< As I stated before, "But like everything in life, take everything you read with a grain of salt. Some sources have a motive behind their suggestions or just an axe to grind." Which one might you be?

I'm just an enthusiast like (I presume) you.

This is my amp setup for 5.1:

5 for the 5 tweeters, active XO
5 for the 5 mids/upper woof, active XO
1 for the deep sub, active XO
1 for the mid bass module active XO
1 for the Buttkickers, active XO, set very deep
(2 for the extra two speakers, passive XO and 1 for the rear center, passive XO...but they are not yet installed and so not counted)

So it looks like 13 amplifiers right now. No ground loop hum at all. No audio frequency transformers in the path, very little speaker wire. The bass is covered in three main ranges: triamped. BTW I just measured the buttkickers which are mounted to the floor in such a way as to use it as a diapragm. They hit 106 dB down very deep all by themselves. On some program material you can feel wind from the floor. I need to make sure that their phase is set properly RE the other bass units as that is more than I expected from these tactile devices.

Stan / sjmarcy

[lradden]

My suggestion would be to do what I did:

Disconnect all components and subwoofers from your receiver (or pre/pro) except your speakers (and amps if you have separates).
Power up and check for hum.
If you have a pre/pro, is there a hum on just one channel?
If the problem is just with that one channel then check the interconnect cable.
No hum, power down and connect only one component.
Power up again and check for hum
No hum, power down to disconnect the first device and connect a different device.
Power up again and check for hum
Repeat steps 5 and 6 until HOPEFULLY you'll find the offending device.
Once you find the offending device you have the option of grounding that device to your receiver (pre/pro) or using some sort of isolation transformer.Thanks majorloser you've been a great help throughout this thread. I already have some of my gear linked as you describe, but the BFD was always a problem. Hopefully the eliminator will solve this last peice of the puzzle.

Keep the suggestions coming you're a big help to us all and we appreciate all you're doing.:cool:

[wongmb]

Once you find the offending device you have the option of grounding that device to your receiver (pre/pro) or using some sort of isolation transformer.

I find out its my new cd player thats giving me the hum. Can you elaborate what you mean by "grounding it to the pre/pro" ? My pre-pro's design is double insulated (i.e two prongs only) while my cd player is 3 prongs.

[majorloser]

I find out its my new cd player thats giving me the hum. Can you elaborate what you mean by "grounding it to the pre/pro" ? My pre-pro's design is double insulated (i.e two prongs only) while my cd player is 3 prongs.

If your pre/pro has a phono input then it will have a ground screw in the back. If not, the first thing you need to check (if you have access to a multi-meter) is if the chassis on the pre/pro shares the ground on the RCA connections. With the power off and the pre/pro unplugged check the resistance between the chassis case (any rear screw) of the pre/pro and the outside conductor of the RCA jack your CD player uses. If they are connected then just run a wire from case to case using an exterior screw on each device.

[RHui_BC]

So, im wondering if this solution will work for car audio? I have this horrible buzz coming from my speakers.

[majorloser]

So, im wondering if this solution will work for car audio? I have this horrible buzz coming from my speakers.

With cars it's usually coming from the ignition system. Does the noise go away with the engine "OFF" and the key in accessory position?

[Hiccups]

For home audio systems with ground loop problems, there's another option: the EB Tech Hum-X http://www.ebtechaudio.com/humxdes.html. If a ground loop hum is coming from the AC ground connection on one of your components, the Hum-X gets rid of it without putting anything into the audio path. I use one quite successfully between a DAC and an integrated amp.

A simple test to see if the Hum-X would solve a ground loop problem is to try a 3-prong to 2-prong "cheater" plug. If the hum goes away with a cheater plug, the Hum-X will do the trick without the loss of the ground safety connection.

NEVER USE THE 2-PRONG CHEATER PLUG FOR PERMANENT INSTALLATION ON A DEVICE DESIGNED FOR A 3-PRONG PLUG. ONLY USE IT TO TEMPORARILY TEST IF IT ELIMINATES THE HUM.

[Rbar]

I get a hum when I touch the subwoofer jack to the outside of the input jack. Once the inside is connected, the hum goes away and I get no sound out of the subwoofer -- it "auto" shuts itself off.
Any suggestions?
Rbar