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Discussion Starter · #1 ·
I have two dedicated circuits ran for my system. Both in phase. One goes to my amplifiers for my mains, the other to my audio rack. With nothing plugged into the main amps inputs, there is absolutely NO sound coming out of the main speakers. When I connect the pre-amp up though, there's all kind of buzzing, and occaional popping sounds. This is both with and without other components connected to the pre-amp. To experiment, I connected both the pre-amp and amps on the same outlet and the buzzing is vertually illiminated. I then ran an extension cord back to the other outlet from the pre-amp, and the buzzing returns.


Will an isolation transformer on the pre-amp circuit solve this problem?
 

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Discussion Starter · #3 ·
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Originally Posted by speco2003
This may be obvious so sorry if it is, but have you but a voltmeter on it and checked them?
On the wall outlets? No. I was going to double check all of that when I get home tonight (polarity, ground, etc.).


The thing is, I had an electrician run these two dedicated lines last night. But the symptoms I described were there before, on totally different lines. Which is one of the reason's I had the dedicated lines ran. I was hoping the dedicated lines would have solved the problem, but not. Which is why I was wondering about isolation transformers.
 

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Discussion Starter · #5 ·
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Originally Posted by TrojanHorse
Plug something into your preamps like a CD player, then try it.
Hi TrojanHorse, do you mean plug something like a CD player directly in the amps? I've had several things plugged and unplugged into the preamp itself, and the buzzing is there either way.
 

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It sounds like you have your amps located near your speakers and your preamp and other sources located some distance away in the rack. How long are your runs from the preamp to the amps? What kind of cable are you using? Are the amps and preamp all 3 wire power plugs? If so before popping for an isolation transformer you may want to run some tests with a ground isolating plug. Not recommended for long term use because of fault hazards but should be no problem to run a few tests to see if the buzzing stops. It is possible that you have a ground loop issue with the plugs carrying their ground back to the panel and your signal ground being carried by your preamp to amp cables.


..Doyle
 

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Quote:
Originally Posted by Rutgar
Hi TrojanHorse, do you mean plug something like a CD player directly in the amps? I've had several things plugged and unplugged into the preamp itself, and the buzzing is there either way.
No, I just mean don't test unterminated sources. Terminate them with a source. You haven't said what equipment you're using, but most people plug their source equpment into the preamp, not the amp.


If you still have the problem, that obviously wasn't it. :)
 

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Discussion Starter · #8 ·
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Originally Posted by DoyleS
It sounds like you have your amps located near your speakers and your preamp and other sources located some distance away in the rack. How long are your runs from the preamp to the amps? What kind of cable are you using? Are the amps and preamp all 3 wire power plugs? If so before popping for an isolation transformer you may want to run some tests with a ground isolating plug. Not recommended for long term use because of fault hazards but should be no problem to run a few tests to see if the buzzing stops. It is possible that you have a ground loop issue with the plugs carrying their ground back to the panel and your signal ground being carried by your preamp to amp cables.


..Doyle
Hi Doyle, Yes you're correct that the amps (up by the speakers) are in a separate location from the the rest of the audio rack. All amps and pre-amps are wired with 3-wired plugs. I have two dedicated lines. One goes to the main amps (2-monoblocks), the other goes to the audio rack with all the rest of the gear. Regardless of whether or not I have any other components plugged into the pre-amp, there is a loud buzz that comes through the speakers when I use both plugs (one plug for the amps, the other plug for the audio rack). Without changing anything else, if I plug both the amps, and preamp together into either outlet via a long extension cord, the buzz quiets down to a tolerable level. I tried a "cheater" plug on the preamp with no difference. The amps have built-in ground lifts that I can switch in or out, and there is a slight difference. But not enough to use that as a solution.


Wow! This is far more complicated to explain than it really is! ;)
 

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Discussion Starter · #9 ·
Quote:
Originally Posted by TrojanHorse
No, I just mean don't test unterminated sources. Terminate them with a source. You haven't said what equipment you're using, but most people plug their source equpment into the preamp, not the amp.


If you still have the problem, that obviously wasn't it. :)
Okay, I got you now. Yes, I've had source equipment connected, and unconnected (to the preamp :) ). It doesn't make any difference.


I just don't understand why I get this loud buzz when I use both outlets, but not when I use just one, when they're both on the same phase in the panel, and both totally dedicated lines.
 

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It may be related to the length of your cables running from preamp to amp and what they are running near. Possibly running parallel to some power lines or other high current lines. They may be picking up some amount of interference. If it is ground loop related then possibly the long lines between the power grounds of the amps and preamps vs the ground that is carried by the preamp signal wires may be where the issue is. Cheater plugs often help to isolate a problem and may be worth a try even though the amps have ground lift switches. Sometimes the ground lift is implemented differently on gear and there may be some coupling with capacitors that you are unaware of. I don't imagine that you have the ability to run a balanced line to your amps but if you do, that might be worth a try. You have pretty well eliminated the Amp and preamp as the sources of the problems by putting them on the same plug and having no problems. That then says the problem is either in cabling or grounding between the units. You might want to verify in your power panel that indeed these outlets are on the same phase. Typically that would mean that they are either both on odd number or both on even numbers. There should be small schematic in your power panel that tells which ones are on which phase.


..Doyle
 

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Discussion Starter · #11 ·
Quote:
Originally Posted by DoyleS
It may be related to the length of your cables running from preamp to amp and what they are running near. Possibly running parallel to some power lines or other high current lines. They may be picking up some amount of interference. If it is ground loop related then possibly the long lines between the power grounds of the amps and preamps vs the ground that is carried by the preamp signal wires may be where the issue is. Cheater plugs often help to isolate a problem and may be worth a try even though the amps have ground lift switches. Sometimes the ground lift is implemented differently on gear and there may be some coupling with capacitors that you are unaware of. I don't imagine that you have the ability to run a balanced line to your amps but if you do, that might be worth a try. You have pretty well eliminated the Amp and preamp as the sources of the problems by putting them on the same plug and having no problems. That then says the problem is either in cabling or grounding between the units. You might want to verify in your power panel that indeed these outlets are on the same phase. Typically that would mean that they are either both on odd number or both on even numbers. There should be small schematic in your power panel that tells which ones are on which phase.


..Doyle
Wow! Thanks Doyle! I tried the ground lift directly on the amp power cord and it's like a black hole it's so quiet! So much for the "built-in" ground lifts on those amps.


Whew! I feel much better now. :)


Now I need to plug all the other stuff back in, and see if it stays that way.
 

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Quiet is Good! :)


I think I would double check to see if your electrician actually got those two plugs on the same Phase in your power panel.


..Doyle
 

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Discussion Starter · #13 ·
Quote:
Originally Posted by DoyleS
Quiet is Good! :)


I think I would double check to see if your electrician actually got those two plugs on the same Phase in your power panel.


..Doyle
I will double check that tomorrow. Thanks.
 

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Ground lifts on the amp are typically to lift the ground on the interconnects, not the power cable. When you say ground lift on the power cable, I presume you just used a cheater plug?


Go to Home Depot or the like and get a circuit tester (they are yellow and have three lights, you plug them in and they light up to tell if something is wired wrong on the circuit). They look like the plug end of an extension cord.
 

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Discussion Starter · #15 ·
Quote:
Originally Posted by TrojanHorse
Ground lifts on the amp are typically to lift the ground on the interconnects, not the power cable. When you say ground lift on the power cable, I presume you just used a cheater plug?


Go to Home Depot or the like and get a circuit tester (they are yellow and have three lights, you plug them in and they light up to tell if something is wired wrong on the circuit). They look like the plug end of an extension cord.
Yes, I simply used a cheater plug. I already have a circuit tester, and it shows everything is okay.
 

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Quote:
Originally Posted by Rutgar
Yes, I simply used a cheater plug. I already have a circuit tester, and it shows everything is okay.
Everything is not Ok, you used a AC Ground Lift NOT A GOOD IDEA. You need to find the cause of the issue, something else is on the circuit causing this or your whole house is not grounded properly. You can injure or kill yourself or someone else with the use of an AC Lift, this is not what they are designed for.
 

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Discussion Starter · #17 ·
Quote:
Originally Posted by speco2003
Everything is not Ok, you used a AC Ground Lift NOT A GOOD IDEA. You need to find the cause of the issue, something else is on the circuit causing this or your whole house is not grounded properly. You can injure or kill yourself or someone else with the use of an AC Lift, this is not what they are designed for.
Nonsense. I've lifted grounds on amplifiers for years to get rid of ground faults. Not once have I ever "injured or killed" someone or myself. Most audio equipment doesn't even have grounds, and many High-End Power Cords have a removeable ground pin for also eliminating ground faults. Unless you can come up with what you consider a "safe" way to remove the buzz, then my gound pin is going to remain lifted.
 

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Quote:
Originally Posted by Rutgar
Nonsense. I've lifted grounds on amplifiers for years to get rid of ground faults. Not once have I ever "injured or killed" someone or myself. Most audio equipment doesn't even have grounds, and many High-End Power Cords have a removeable ground pin for also eliminating ground faults. Unless you can come up with what you consider a "safe" way to remove the buzz, then my gound pin is going to remain lifted.


WOW you are so ignorant or arrogant I don't know which. You truly think most gear is not grounded? Here is a link explaining 2 prong gear
http://www.newton.dep.anl.gov/askasc...9/eng99158.htm


If he has all balanced gear then he would lift pin one on an end of a cable to safely break a loop. If he is mixing balanced and unbalanced gear, isolating the unbalanced gear so it doesn't touch any metal in a rack or other gear can help.


Read the second to last paragraph in this article
http://svconline.com/mag/avinstall_p...phile_systems/

http://www.prg.com/support/education/glossary/audio/g


Read about ground lifting in the above link

http://www.avsforum.com/avs-vb/showt...35#post5711435
 

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Discussion Starter · #19 ·
Quote:
Originally Posted by speco2003
WOW you are so ignorant or arrogant I don't know which.
Oh yeah, that's persuasive, and furthers your point. :rolleyes: I noticed you didn't address the fact that many high-end power cords have removable ground pins to squelch ground loops. I also notice you didn't offer any real suggestions as to how to remove the buzzing without lifting the ground. The one article that talks about an alternate way refers only to "balanced" interconnects. Something my Classe' SSP-30 MKII does not have. One of the other articles you pointed to talks about "polarized" plugs. Which I agree is VERY DANGEROUS to invert when trying to eliminate buzz. But has nothing to do with lifting ground pins. Again, I've done it for years and I've NEVER seen nor heard of a problem. Is it my first choice? No. If I can find another way of getting rid of the buzz I will. If not, THE GROUND PIN IS GONE BABY!
 

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Quote:
Originally Posted by Rutgar
Oh yeah, that's persuasive, and furthers your point. :rolleyes: I noticed you didn't address the fact that many high-end power cords have removable ground pins to squelch ground loops. I also notice you didn't offer any real suggestions as to how to remove the buzzing without lifting the ground. The one article that talks about an alternate way refers only to "balanced" interconnects. Something my Classe' SSP-30 MKII does not have. One of the other articles you pointed to talks about "polarized" plugs. Which I agree is VERY DANGEROUS to invert when trying to eliminate buzz. But has nothing to do with lifting ground pins. Again, I've done it for years and I've NEVER seen nor heard of a problem. Is it my first choice? No. If I can find another way of getting rid of the buzz I will. If not, THE GROUND PIN IS GONE BABY!
I offered you 2 solutions in my post. Reread it. Check this site from RANE, scroll down til you get to Ground, there you will find many useful links to help you, and another note about how dangerous its is.
http://rane.com/par-g.html



I will say this, I do audio for a living and have done so for the last 15 years, what you are doing is dangerous, there is no ifs ands or buts about it. It is stupid, dumb, idiotic, dangerous and deadly. Continue to do it if you wish, but do not call it nonsense as others may follow your lead and DIE. It is electricity it kills and hurts I have seen it happen.


As for your situation there is something wrong with your house AC ground it seems, if you are not qualified to check it out have someone do it for you that is. I personally have never seen a so called hi end power cord with removable pins, they must exist as you point them out. I would like to see one of these myself.

Your right you could lift the AC on all your gear but one piece and be safe, as long as all your interconnects carried pin 1, BUT if one of those would ever get cut or worn thru then you have a dangerous situation.

There are other reasons and ways to fix this properly. I am not there with you so I cant completely tech your system, but we have given you advice. You will notice Doyle said the AC lift is not a good idea just a way to help tech the problem out.


And did you even see this from the Sound and Video contractor article?"If a short develops in a "ground lifted" piece of equipment, the audio or video cables that interconnect equipment will carry lethal voltages throughout the system and/or start a fire. Never defeat the function of the third prong on any equipment's AC plug. It is both illegal and very dangerous."

Your right its all nonsense.


But hey you do what you want.
 
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