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Hum/buzz with XLS 202b


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#1 fsrenduro

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Posted 05 December 2005 - 01:25 PM

I have an XLS-202b in a home theater hookup.  It is powering two 4-ohm towers and sounds very good.  I have a Hosa RCA to XLR cable running from my receiver (Pioneer 815 k) to the amp.  With the volume on the receiver all the way down I can hear a slight hum/buzz type sound coming from the speakers.  

If I unhook the RCA end from my receiver the sound goes away.  If I touch the end of the RCA cable with my finger while it is unhooked the hum is louder.  Since I also have an Onkyo amp hooked up to the receiver with NO hum I'm wondering how to get rid of the hum in the Crown.

I'm guessing it is some kind of grounding issue but what do I ground.  Nothing else that is hooked to my receiver hums (subwoofer, other amp).  If it were the Hosa cable wouldn't it hum even when not hooked to the receiver?

Any ideas?

#2 DGlass

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Posted 05 December 2005 - 04:07 PM

I have removed your duplicate posting in the “Amplifiers-General Discussion” section of this forum. Please only Post once and if it needed we can move it to a more appropriate section. Thanks smile.gif

You are more than likely correct that it is a grounding issue. Not all electronic gear is grounded internally the same especially with the single ended (unbalanced) audio connections used in home Consumer electronics. When combining unbalanced connections with balanced connections, with just a cable, the possibility exists for slight variations of AC on the ground to be transferred into the signal path. Not only this but there is the difference in levels used by Consumer and Pro-Audio as well as Impedances.

There are companies that make devices that match the impedances, boosts the signal level (to +4db pro levels) and provide electrical isolation either with the use of a transformer or an active circuit. Two of these devices I am familiar with are the ART “CleanBox” and the Rolls “MB-15 ProMatch. You might also try Whirlwind and Genelec. smile.gif

#3 fsrenduro

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Posted 15 December 2005 - 11:06 AM

QUOTE(DGlass @ Dec 5 2005, 04:07 PM)
You are more than likely correct that it is a grounding issue. Not all electronic gear is grounded internally the same especially with the single ended (unbalanced) audio connections used in home Consumer electronics. When combining unbalanced connections with balanced connections, with just a cable, the possibility exists for slight variations of AC on the ground to be transferred into the signal path. Not only this but there is the difference in levels used by Consumer and Pro-Audio as well as Impedances.

There are companies that make devices that match the impedances, boosts the signal level (to +4db pro levels) and provide electrical isolation either with the use of a transformer or an active circuit. Two of these devices I am familiar with are the ART “CleanBox” and the Rolls “MB-15 ProMatch. You might also try Whirlwind and Genelec. smile.gif
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I tried an ART Cleanbox and it did nothing for the hum/buzz I'm getting.  It did however raise the noise floor quite a bit so even if it had removed the hum it wouldn't have been the answer.  Just by adding the Cleanbox to the equation and having it potted all the way down the noise floor was easily audible.

Any other ideas.  I'm going to try a Rolls Buzz Off next.  I was hoping this amp hook up would be dead silent like the home theater amp I had before.  Am I wrong in thinking that is possible with pro amps?

#4 fsrenduro

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Posted 19 December 2005 - 12:21 PM

The Rolls Buzz Off did not work either.  Does anyone have any other ideas.  It seems as though the products I've tried are for hooking fixed output units (CD players, etc) to mixers.  Since my pre-outs on my receiver are variable (volume controlled) maybe this messes stuff up.  Although raising the volume does NOT raise the hum.

I saw an amp from Gemsound that has an input sensitivity switch (1, 1.5, 7 volts).  Would that be something that might help.  My guess now is that it is the differences in sensitivity between pro & consumer level.

QUOTE(fsrenduro @ Dec 15 2005, 11:06 AM)
QUOTE(DGlass @ Dec 5 2005, 04:07 PM)
You are more than likely correct that it is a grounding issue. Not all electronic gear is grounded internally the same especially with the single ended (unbalanced) audio connections used in home Consumer electronics. When combining unbalanced connections with balanced connections, with just a cable, the possibility exists for slight variations of AC on the ground to be transferred into the signal path. Not only this but there is the difference in levels used by Consumer and Pro-Audio as well as Impedances.

There are companies that make devices that match the impedances, boosts the signal level (to +4db pro levels) and provide electrical isolation either with the use of a transformer or an active circuit. Two of these devices I am familiar with are the ART “CleanBox” and the Rolls “MB-15 ProMatch. You might also try Whirlwind and Genelec. smile.gif
View Post


I tried an ART Cleanbox and it did nothing for the hum/buzz I'm getting.  It did however raise the noise floor quite a bit so even if it had removed the hum it wouldn't have been the answer.  Just by adding the Cleanbox to the equation and having it potted all the way down the noise floor was easily audible.

Any other ideas.  I'm going to try a Rolls Buzz Off next.  I was hoping this amp hook up would be dead silent like the home theater amp I had before.  Am I wrong in thinking that is possible with pro amps?
View Post


#5 Bud Bolf

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Posted 19 December 2005 - 01:33 PM

Hi,
You know, David was really on the right track.
If you look at the Plug on your Consumer equipment I bet you
will see that it is just a 2 prong plug with no Ground at all.
My Sony Reciever, VCR's, DVD players, etc...  ALL have just
a 2 prong ungrounded Plug.
The only equipment that I find works well when plugged into my Mixer
is of course pro audio and my CD player that has a DC Transformer.
When I try my 5 disc Sony CD Player, you guessed it, Hum.

I have not done it yet, but I was going to try and run a Ground wire from
my wall plug outlet to a ground location (Screw, possibly) on a piece of equipment that I would like to use with my PA and see if the Hum dissapears.
If it does, then daisy chain to each other piece of equipment that I want to plug in, so everything has a Common Ground.
I think that this will work, but like I said I have not tried it.

Another option I thought of, especially if the above works, is to purchase some 3 wire grounded plug cords, (you can buy 3', or 6 foot cords with a plug on one end and three bare wires at the other end) and install them into my equipment in place of the non grounded plug.

That's my thought on it, so if anyone tries it let me know if it works.

  Bud

#6 DGlass

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Posted 19 December 2005 - 01:52 PM

QUOTE(fsrenduro @ Dec 19 2005, 12:21 PM)
The Rolls Buzz Off did not work either.  Does anyone have any other ideas.  It seems as though the products I've tried are for hooking fixed output units (CD players, etc) to mixers.  Since my pre-outs on my receiver are variable (volume controlled) maybe this messes stuff up.  Although raising the volume does NOT raise the hum.

I saw an amp from Gemsound that has an input sensitivity switch (1, 1.5, 7 volts).  Would that be something that might help.  My guess now is that it is the differences in sensitivity between pro & consumer level.


The input sensitivity will have nothing to do with a hum/buzz only the amount of drive level needed to get to full output. There still has to be something going on with the system itself that is causing the noise.  Most Consumer audio equipment will only have a two conductor AC cable while most Pro Audio gear has a three conductor AC Plug. Due to this Consumer electronic gear is not grounded internally the same especially and with the single ended (unbalanced) audio connections AC noise can be induced into the audio path.
Sometimes in tracking down this type of issue you can spend a lot of time. Since the hum/buzz goes away when you disconnect the amplifier inputs the amplifier is amplifying what it is getting or it's a grounding related issue.

Do you have light level controllers in the house (or Rack) that could be on the same circuit? These could be generating hash onto the AC that is getting into the Consumer electronic gear and passed onto the amplifier.

The only solution might be to install a Balanced Power supply/conditioner like the Equi=Tech "Model Q series" ( http://www.equitech.com/products/products.html ), the b-p-t power centers ( http://www.b-p-t.com/products.shtml ), the Furman "RI-1210 ( http://www.furmansou...d/balanced1.php) or "IT series"(http://www.hometheat...-12-2000.html  ) There are many others that make these Balanced Power Centers these are just a few.

Here are a couple of articles on Balanced AC Power you might be interested in.
http://www.equitech.com/articles/bpng.html
http://www.epanorama.net/documents/groundl...nced_power.html

#7 DGlass

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Posted 19 December 2005 - 02:20 PM

A couple other things that have occurred to me.

Do you have a Cable TV System and is the system plugged into the audio system? If you do try disconnecting it as you may be getting a ground problem from the Cable.

You might also try a Ground Loop Isolator like the Radio Shack 270-054 between the Receiver and the amplifier.

#8 fsrenduro

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Posted 19 December 2005 - 03:07 PM

I have tried unplugging my cable from my system and nothing changed.  I do also have light dimmers that I think are on the same circuit.  I've checked the system with these lights off and it doesn't seem to change anything.

In terms of three prong vs. two prong… I had a 7 channel home theater amp (400 wpc into 4 ohm) that was three prong hooked into this exact same system and it was dead silent.  At almost $3k it was too much for me to justify the cost so that's why I thought I'd try pro amps.  If this amp didn't buzz or hum it doesn't seem like I'd need several hundred dollars more of a product to clean my power (although I could be wrong).  

I'm gonna give the Radio Shack thing a try.  The grounding of my two pronged receiver seems like a good idea but I'm not gonna mess with plugging bare wires into any outlets.

Thanks for the suggestions so far.

QUOTE(DGlass @ Dec 19 2005, 02:20 PM)
A couple other things that have occurred to me.

Do you have a Cable TV System and is the system plugged into the audio system? If you do try disconnecting it as you may be getting a ground problem from the Cable.

You might also try a Ground Loop Isolator like the Radio Shack 270-054 between the Receiver and the amplifier.
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#9 Bud Bolf

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Posted 20 December 2005 - 08:23 AM

Hi again,
  I was just going to connect a Ground wire to the Coverplate Screw and then connect the wire to a screw on my equipment Chassis.
It's only about 3 feet from the plug.
The same thing you do if you use the grey adaptor when plugging a 3 blade grounded plug into an old non grounded 2 blade plug, they have a short green wire with a Crimp connector for attaching it to the Coverplate screw.
Not as good of a ground as attaching to the actual ground wire, but something to try.
Just thoughts here.
I need to try a few things, before spending lots of money at the problem.
I first noticed this myself when trying to play a DVD and route the Audio into my Mixer, HHHuuuuuuummmmm.

Later,
    Bud

#10 DGlass

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Posted 20 December 2005 - 10:52 AM

Bud

Adding a ground wire or a 3-wire AC cord may or may not work depending on the grounding scheme that the consumer gear uses. As a matter of fact it may make things worse. What could be happening is that the ground in a 2-wire AC system is shared by the negative side of the RCA connector so any noise on the grounds of the Single-ended connector goes to the audio path of the Balanced input and gets amplified. The best solution for this is audio connection isolation or Balanced AC Power depending on the situation.
Adding a 3-wire AC cable for a safety ground may not fix it either in that the chassis of the 2-wire AC equipment may not be grounded anyway as the ground is commonly shared by coupling with the audio signal. blink.gif

Here are a few articles on the issues involved with audio system grounding issues:

http://www.epanorama.net/documents/groundloop/
http://www.equitech.com/articles/rep1.html
http://www.trinitysoundcompany.com/grounding.html
http://www.findarticles.com/p/articles/mi_..._21/ai_97745360
http://www.dself.dsl.pipex.com/ampins/balanced/balanced.htm
http://www.rane.com/note151.html
http://www.passlabs.com/downloads/articles/ground-loops.pdf


As you can see this quite an involved issue that many people have spent a lot of time trying to resolve over the years and it could be caused by several issues.

Happy Reading………… biggrin.gif

#11 DGlass

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Posted 20 December 2005 - 11:17 AM

Did the other amp have single ended (RCA) inputs? If so than that would explain the no noise issue with the other amplifier. Going from single ended Unbalanced Consumer Equipment to Balanced Pro Audio can be the situation were the ground loop is introduced.


QUOTE(fsrenduro @ Dec 19 2005, 03:07 PM)
I have tried unplugging my cable from my system and nothing changed.  I do also have light dimmers that I think are on the same circuit.  I've checked the system with these lights off and it doesn't seem to change anything.

In terms of three prong vs. two prong… I had a 7 channel home theater amp (400 wpc into 4 ohm) that was three prong hooked into this exact same system and it was dead silent.  At almost $3k it was too much for me to justify the cost so that's why I thought I'd try pro amps.  If this amp didn't buzz or hum it doesn't seem like I'd need several hundred dollars more of a product to clean my power (although I could be wrong). 

I'm gonna give the Radio Shack thing a try.  The grounding of my two pronged receiver seems like a good idea but I'm not gonna mess with plugging bare wires into any outlets.

Thanks for the suggestions so far.

QUOTE(DGlass @ Dec 19 2005, 02:20 PM)
A couple other things that have occurred to me.

Do you have a Cable TV System and is the system plugged into the audio system? If you do try disconnecting it as you may be getting a ground problem from the Cable.

You might also try a Ground Loop Isolator like the Radio Shack 270-054 between the Receiver and the amplifier.
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#12 Bud Bolf

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Posted 20 December 2005 - 10:17 PM

QUOTE(DGlass @ Dec 20 2005, 12:17 PM)
Did the other amp have single ended (RCA) inputs? If so than that would explain the no noise issue with the other amplifier. Going from single ended Unbalanced Consumer Equipment to Balanced Pro Audio can be the situation were the ground loop is introduced.


QUOTE(fsrenduro @ Dec 19 2005, 03:07 PM)
I have tried unplugging my cable from my system and nothing changed.  I do also have light dimmers that I think are on the same circuit.  I've checked the system with these lights off and it doesn't seem to change anything.

In terms of three prong vs. two prong… I had a 7 channel home theater amp (400 wpc into 4 ohm) that was three prong hooked into this exact same system and it was dead silent.  At almost $3k it was too much for me to justify the cost so that's why I thought I'd try pro amps.  If this amp didn't buzz or hum it doesn't seem like I'd need several hundred dollars more of a product to clean my power (although I could be wrong). 

I'm gonna give the Radio Shack thing a try.  The grounding of my two pronged receiver seems like a good idea but I'm not gonna mess with plugging bare wires into any outlets.

Thanks for the suggestions so far.

QUOTE(DGlass @ Dec 19 2005, 02:20 PM)
A couple other things that have occurred to me.

Do you have a Cable TV System and is the system plugged into the audio system? If you do try disconnecting it as you may be getting a ground problem from the Cable.

You might also try a Ground Loop Isolator like the Radio Shack 270-054 between the Receiver and the amplifier.
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Thanks for the Info David.

I hope that you and yours Has a Very Merry Christmas!
Take Care,
Bud

PS. Please help Kickboxer on his problem with connecting two CTS 600 Amps
for Home Audio use. Preamp questions etc..
I started to help him but obviously as you can see from this post,
Home Audio is not my specialty. Thanks

#13 jeenie67

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Posted 03 March 2006 - 08:58 PM

Hello, Hum Of any amount bugs me. With knowledge of home wiring(trained w/ electricians although I wont work as one)the first place you go is to the fusebox/breakerbox. Open it up to expose the internal wiring, put one hand in your pocket, and just LOOK. Is the wiring 12/2, does it have THREE wires? One black to the hot side/breaker switch, white to a bus bar or a long bare copper strip w/ screws, and a bare cooper wire to the panel-then to earth. And by EARTH....is there a big wire going outside to a buried pipe, or to an inside pipe(NOT TOO COOL maybe not code). This is the first step. Get the house grounded properly(see some electrical kind of guy or message me here, I'm only to happy to help....all code, all legal beagle. From there go to the business end of the wire, the outlet. Is the black wire to the BRASS SCREWS?  The white to the SILVER SCREWS, a third bare copper wire to the GREEN GROUNDING SCREW...this is your third ground. If not, fix it before any purchases. Then work you way up the wire of your component to the chassis. Open it up and just look. Then you can report your findings to a schooled technician/engineer. I hope I've shed some light on the subject for you and others. Thank You, Eugene Z.

#14 jeenie67

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Posted 09 March 2006 - 07:04 AM

Here is another possibility, doesn't cost $...doesn't add another box into the system.  Direct all ground wires to ONE POINT with EQUAL legnth cable/wire/..ing. This is accomplished by using a power strip with NO LIGHTS, LED'S, NOTHING ! Just a bare bones power strip. All mains grounds ,all unit auxillary grounds terminate at this point, and ALL EQUAL LEGNTH. This is called a "star" ground point. Will not matter what house wiring you have although an old two wire without the 3rd wire is best. DO NOT DISABLE ANY THIRD GROUND ! There goes your homeowners if anything, even not related happens.   Eugene Z