Dedicated Audio Power Circuit

[Speedskater]

Middle Atlantic has a most excellent paper on AC power wiring.

"Integrating Electronic Equipment and Power into Rack Enclosures"
'Optimized Power Distribution and Grounding for Audio, Video and Electronic Systems'

http://www.middleatlantic.com/resources/white-papers.aspx

 

[scooter]

The answer to #1 confirms that you have a power circuit related ground loop.

Without knowing the answers to A and B below there is no sense in suggesting any solutions.

REF #A: Electrical panels come with the ground buss and neutral buss bonded. The electrician needs to break the bond when used as a sub-panel. The neutral grounds should only be connected to a safety ground or buss at the main panel.

REF #B: Be sure that the ground wire in each outlet box is NOT touching or connected to the metal box. If it is this establishes different paths to ground and potential differences.

REF #D: This could be a problem. The sub-panel chassis and its metal conduit lines have no continuity to the main electrical panel since it was run through PVC. You say that the sub-panel has its "own" ground. What exactly does that mean? Where does the ground wire go? It should be connected to the ground wire that comes from the main electrical panel not connected to another ground rod or to a metal water pipe for instance.

Assuming A and B are good:

#A: The bonds are broken. He says its not code to have them together.

#B: They are not.

#D: What I meant was that the metal conduit had to be grounded as well in order to meet code. However, its ground does not tie into the subpanel but ties into the main panel.

 

[scooter]

Hopefully you planned the location of the sub-panel in a central location so that most of the wire length was from the main-panel to the sub-panel. Thus reducing the wire length from outlet box to outlet box

Code here doesn't really allow for a sub-panel to be inside of the living space. I would have had to build a special closet of decent size to put the sub-panel inside the house. There are also limits on how far the sub-panel can be from the main panel and how many turns you can make. I basically had no choice but to put it in the garage next to the main panel.

 

[CGabriel]

#A: The bonds are broken. He says its not code to have them together.

#B: They are not.

#D: What I meant was that the metal conduit had to be grounded as well in order to meet code. However, its ground does not tie into the subpanel but ties into the main panel.

Ok, that's all good.

One last test to rest assured that your electrical system is installed correctly. Do you or the electrician have a clamp-on amp meter? Test the safety grounds at the sub-panel to ensure that there is no ground current flowing through the grounds. If this passes, move on to the other tests that I mentioned.

You didn't say what type of power distribution you are using?

 

[scooter]

Ok, that's all good.

One last test to rest assured that your electrical system is installed correctly. Do you or the electrician have a clamp-on amp meter? Test the safety grounds at the sub-panel to ensure that there is no ground current flowing through the grounds. If this passes, move on to the other tests that I mentioned.

You didn't say what type of power distribution you are using?

I will have to reach out to the electrician to see if he has the meter you are suggesting.

I forgot that I had one of those doo-dads that checks for properly wired outlets. I plugged it in to each of the outlets and they are all wired correctly. There aren't any crossed wires either as another poster had suggested.

I tried the extension cord bit. All of the outlets yield the same results and still have the buzzing.

My voltmeter is dead so I will need to buy one online. It will be a few days before I can check voltage across outlets.

I use one of the big APC battery units for the electronics and plug the amps straight into the wall. I tried it without the APC and still get a buzz. However, if I unplug the APC and let it run on battery, the buzz goes away

The tubes definitely buzz more than the SS.

If I was able to run balanced (which I cannot as much of my gear is single-ended), would this problem go away?

 

[CGabriel]

I will have to reach out to the electrician to see if he has the meter you are suggesting.

I forgot that I had one of those doo-dads that checks for properly wired outlets. I plugged it in to each of the outlets and they are all wired correctly. There aren't any crossed wires either as another poster had suggested.

I tried the extension cord bit. All of the outlets yield the same results and still have the buzzing.

My voltmeter is dead so I will need to buy one online. It will be a few days before I can check voltage across outlets.

I use one of the big APC battery units for the electronics and plug the amps straight into the wall. I tried it without the APC and still get a buzz. However, if I unplug the APC and let it run on battery, the buzz goes away

The tubes definitely buzz more than the SS.

If I was able to run balanced (which I cannot as much of my gear is single-ended), would this problem go away?

Unfortunately, ground loop problems can be very vexing. The installation of dedicatedly lines can be a performance advantage but more often than not you end up with unresolvable ground loops. At this point you need to read Bill Whitlock's white paper on grounds and noise.

http://www.jensen-transformers.com/an/generic%20seminar.pdf

Ultimately, you are going to have to make some hard choices, none of them ideal. One solution is to remove the safety ground to the amps. However this is a violation of electrical code and could be a potential shock hazard (although not likely).

Another solution is to only use only a single dedicated circuit. With bi-amping you probably need the added current capability of the extra circuits. I would try to use just two dedicated circuits and get them to work. The more circuits that you have in a system, the less likely you are going to eliminate ground loops.

Single-ended connections are the most sensitive to ground loops and long runs of RCA cables makes the problem worse. Some interconnects perform better than others. An interconnect with a large gauge ground conductor may improve the situation but it won't make it go away entirely. Balanced connections have the potential to solve the problem but that would involve some very pricy equipment changes. FYI, even balanced connections can suffer from ground loop issues but much less likely than with single-ended. When consulting with people that intend to use mono blocks and dedicated lines and long interconnects, I always recommend balanced connections. However this is not always possible as is the case when you want to use a low power tube amp that only has RCA inputs.

Whitlock recommends a ground interrupter which is essentially an audio transformer. It goes between your preamp and amp and requires another set of interconnects for connection. However, it will degrade the audio quality compared to a direct connection. But that is preferable to a humming buzzing audio system. It definitely rubs my audiophile sensibilities the wrong way and would prefer not to use one. We spend all this money on exotic equipment only to insert an audio transformer that are commonly used in PA systems.

You might try a power regenerator that puts out balanced power on the source equipment. Just make sure you can try before you buy.

I have a system in my home that has two power circuits one for the amps and one for the source equipment. These are not dedicated lines so there is a ground potential difference. This caused a ground loop hum/buzz. I was able to reduce it to an almost inaudible level by making a ground connection from the preamp to the amps. So, you can hear it if you stick your ear up to the speaker but it is not audible at the seating position or when playing music. I used a ground braid and connected the chassis of pre and the amps together. BTW, grounding chassis together was a very common practice in the old days of audio.

It is possible to install multiple dedicated lines and use long interconnects of the single-ended variety. However, it requires a meticulous installation. Our reference room system has 6 dedicated lines from a dedicated sub-panel. But it was installed by my sister who is a master electrician. All the lines are in conduit and are relatively short and exactly the same length with identical wire.

 

[DonH50]

A local ground connection might help, using heavy-gauge wire to connect the chassis' of the various components. If they are not in close proximity this probably won't work... I have had that work, using a star ground connection from each component (all) to one of the safety ground terminals in the system.