The dredded BUZZ has infected my system

Kevin. W · 10-08-2003, 09:04 AM

My old setup:
Paradigm Mini Monitors
Paradigm CC-350
Paradigm PS-1000
Rotel RMB-1066

New Setup:

Paradigm Studio 40v3
Paradigm Studio 20v3
Paradigm Studio CC470
Paradigm PW-2100
Rotel RMB-1095

Equipment remaining same:

Panasonic RP82
Marantz AV560U pre/pro
AR surge protector

Problem:

WIth my old setup everything was fine. Not a peep out of the speakers as far as background noise or the 60hz buzz. When I added my 1095 I started to get a background buzz which was minimized by replacing my coax cable(AR Master series) with an optical from DVD to Pre/pro. Bring in the Studios and its the same, but now that I've added the new PW-2100 sub this buzz is LOUD. I've tried running my amp off a different socket via extension cord to upstairs and still the same. I have noticed if I disconnect my AR MAster Series MS230 audio cables from pre to amp there is no buzz when amp and sub are on. Does this mean a cable problem? Time for replacement? why would it work for one setup and not the other?

Kevin

Tom_Link · 10-08-2003, 08:25 PM

I don't know if this will help but my first check would be to make sure the outlets are wired properly. The larger of the two slots in the outlet should be neutral and the smaller should be 115VAC. Sometimes these get reversed. If you don't have a meter, you could get a "cheater plug" and try plugging in your preamp and check for a hum. If you still have a hum, give the plug a 180 flip and test again. Also, you might check all of your grounds to make sure they're properly connected.

Mike Boniferro · 10-08-2003, 09:03 PM

Are you a cable or satellite user? I found that I had to break the gound on my cable coming into my wall to get rid of my hum after an upgrade.

PeterSM · 10-10-2003, 02:44 AM

The buzz / hum is probably caused by a ground loop. Here is a good web page on ground loops and how to correct them.

"epanorama.net/documents/groundloop"

Sorry, the forum won't let me post a real URL. I get this:

In an effort to cut down on the number of members that just post a thread to post a URL to another site you are not allowed to post URLs to other sites until you're have at least posted 15 times.

To keep the message that you just posted use the back arrow on your browser and then remove the URL from your post. This will keep your original message intact and you won't lose its contents.

Bah!

Anyway, in short, it is caused by two or more separate paths to ground, where the ground connections have slightly different potential. The loop consists of two grounded components connected by audio interconnects or an antenna cable. This causes small AC currents to flow through the ground wires and through the components. It's a very common problem when equipment is plugged into different outlets or when antennas / cables are grounded. Cheater plugs and antenna isolation are common and acceptable methods. Think star configuration and one path to ground.

Kevin. W · 10-10-2003, 07:16 AM

Whats weird about the whole thing is the hum/buzz never happened with my old setup which had a sub. But with my new setup adding the sub wether a PS-1000v4 or the PW-2100 cause a LOUD buzz that can be heard upstairs.

Maybe some type of isolation bar(Panamax, Monster Brickwall is needed?)

Kevin

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MikeRP · 10-10-2003, 08:43 AM

Kevin:

Your problem sound exactly like the one I found using an ADCOM 545 amp in conjunction with my Pioneer 45TX.

I have all the interconnects connected to a Monster Power 12 outlet strip.

Well, I checked everything and when I used a cheater plug sparks jumped form the wall when I plugged it in.

So, I gave up....for the last 6 months.

Last night my electrician was installing my whole house surge protector and found my cable ws completely un grounded. So, I don't know if this was the cause but I'll be trying it next week in a second room setup with a Pioneer 41TX. So, I'll let you know.

This is really a pain in the you know where...........

So,Peter what's your take on my situation?

Mike

PeterSM · 10-10-2003, 11:03 AM

Mike,

As for the spark, it seems to me that lack of grounding by itself should not cause a spark. Maybe an outlet has reversed polarity. That could do it. Grounding is needed only for safety should a voltage appear on the chassis through a wiring fault of that component or appliance. What does your electrician have to say about grounding vs. spark?

Quote:

I have all the interconnects connected to a Monster Power 12 outlet strip.

I assume you mean you have all the power chords connected to a strip. Which plug is sparking? Are components on when you plug it in? That could explain the spark. Plugs are not the best switches.

I use a wall switch (switched outlets) to turn on amps.

A single power strip for all components is a star configuration and should reduce ground loops if there is no other ground such as an antenna or cable. However, the power strip may not provide sufficient power - check its rating. I have also seen ground loops caused by failure to ground a turntable properly. That can be tricky.

A powered subwoofer can be a problem because it is often plugged into a separate outlet from the other amps.

The only thing other I can suggest is to read the article I referenced above in my pseudo URL, try everything in that, and if that doesn't work call an electrician who is experienced in audio. Not all electricians are familiar with audio ground loops. Their main concern is that the polarity of all outlets is the same and to make sure all outlets are wired correctly, to code, to provide "safe" grounded power for each item plugged in. Safe power with multiple ground points is in conflict with the need to eliminate audio ground loops. Each component may be safe, but the problem is very small currents running throughout the unbalanced audio interconnects that connect components together.

Things were much easier, if not safer, when nothing was grounded and there were only two prongs on a power chord.

Wayne A. Pflughaupt · 10-10-2003, 04:14 PM

I’m guessing the new sub has a grounded power cable, where the other one didn’t? Typically a ground loop won’t manifest itself until a component with a grounded plug is introduced to the system.

As others have noted, in almost every instance it is a CATV or satellite feed that is the source of a ground loop.

Regards,
Wayne A. Pflughaupt

MikeTz · 10-10-2003, 09:52 PM

Kevin:

Ground loops can be a real pain. First, make sure all your RCA terminations are plugged all the way in and tight. Same for speaker cables, make sure the connections are tight. Unplug all your source components, still have the buzz? Then put your amps (receiver, amp, powered sub, etc.) on the same outlet, still have a buzz? Then use cheater plugs one at a time until the hum goes away.

If you unplug all the source components and the hum goes away, then plug one component in at a time until you hear the buzz. Then put that component on a cheater.

This process is tedious and a pain in the neck but it usually identifies the source of the ground loop. Cable TV inputs are a prime offender so make sure you disconnect the cable input during the process of disconnecting source components. If your cable TV input is the offender get a CATV ground isolator.

MT

Kevin. W · 10-11-2003, 11:24 PM

If anyone can explain why my solution is working I'd like know. I went throught the process of disconnecting everything and reconnecting one by one. But as soon as I added that first cable from the pre/pro to amp the buzz happened. So I thought to myself what can I do to my pre/pro or amp to maybe ground them better.

Solution:

I ran some tv cable from the hookup on the back of my pre/pro to my surge protector. Buzz still remains. So I ran the tv cable from the wall to a splitter, from the splitter to my TV and surge protector and from the surge out to the pre/pro. And wouldn't you know it worked. Now I'm back to the original 1095 ear up against the speaker buzz. I get to keep my new Paradigm PW-2100 sub.

ht_addict

PeterSM · 10-12-2003, 12:37 AM

I have a theory as to why it worked, but I am not sure.

What happens if all the TV cables are removed completely from the system? No component connected to the wall, and no components connected together throught the TV cable. Do you still have the hum? (I am guessing no.)

Then what happens if you run the TV cable from the wall directly to the pre-pro without a splitter or a surge protector in line? Does it hum then? (I am guessing yes.)

If my guesses are correct, then you can conclude that two independent ground paths, one through the TV cable's shield and the second through pre-pro power cable is the cause of the ground loop.

Once this is established, then it would seem that the most important change you made when reconfiguring your TV cable is to install the splitter in-line with the TV cable. If all the above is true, then evidently the splitter made it go away. The reason for this is probably that the splitter is an RF transformer that also isolates the ground, that is, it removes direct DC connection through the shields. You can test this using an ohm-meter with the splitter, measuring resistance between the shield parts (the threads) on input and output jacks. The circuit is probably open.

The point of the above is that you need to change one thing at a time to see what is causing it and what is fixing it. I may not have it right, but I think that with enough fiddling the cause of the loop and the fix could be found.

Hope that was some help.