Problem with new 20-amp dedicated circuits using PS Audio Power Port Premier Receptacles

@F1nut,

Thanks, Jesse.

In the end, I'll probably have to have him come back, but I thought I'd try some simple diagnostics before he returns.

As good as most electricians are, few of them in my experience have dealt with the peculiarities of audio set-ups.

This electrician typically deals with commercial sites -- e.g., medical and dental facilities -- which often use hospital grade receptacles and isolated-ground receptacles for sensitive equipment. I hope he can figure it out.

Thanks, guys, for your interest and advice.

Let me start with Jesse's questions:

F1nut wrote: »

Bud, your comment is out of place. It doesn't matter if he uses a PS Audio, Shunyata or generic hospital grade receptacle as the technology is exactly the same, they all have isolated grounds.

I used the same electrician and a PS Audio Power Port Premier receptacle in installing the dedicated circuit to my main system, and it has functioned perfectly. I don't think it's the PS Audio product per se. I suspect it is something about this particular configuration/installation.

F1nut wrote: »

What gauge and type of wire did he run? Are the two new lines grounded on the same leg or opposite legs in the breaker box?

The wire is the same wire used in the dedicated circuit to my main rig -- that is, 12 AWG Romex with four conductors, hot, neutral, and two insulated ground wires. It is manufactured by Southwick Wire.

The two new circuits are wired to my main service panel which is only a few feet from the receptacles themselves.

These two new circuits are wired to the same leg of the breaker box, as are the three additional dedicated circuits in the exercise area of the basement, where my rig is located.

These other three dedicated circuits provide power to:

1. A surge protector into which the stereo equipment (not the amp) are plugged, along with the TV, cable box, and DVD player. The stereo equipment includes a preamp, PS Audio PW DAC MKII, a Wadia iPod dock connected to the DAC via coax, and a Cambridge Audio Azur 840C CD player that I use only as a CD transport to feed the DAC via optical connection. Yes this is a mess! And, it will be easy to eliminate potential sources of the problem from this mess.
2. A power source for a Cybex Arc Trainer, that is plugged into the receptacle only while the machine is in use. The hum is present when the machine is not plugged in. This was supposed to be a fully dedicated circuit, but the installer of a stand-by generator tapped into it for the trickle charger for the battery in the generator because it happened to be located right next to the main panel.
3. A power source for a Trotter treadmill, which like the Arc Trainer, is unplugged when not in use. The hum is present when the treadmill is not plugged in.

My main panel brings in 200 A service, which it distributes not only to various specific appliances/equipment (A/C compressors, air handlers, condensation pumps; water softening equipment, kitchen circuits, etc.) but also to three subpanels (garage, attic air handler, laundry room).

I think the main panel has 40 slots for breakers, some of which are coupled to allow for breakers for heavy-duty equipment (e.g., A/C compressors) and some of which have been set up with "slim" breakers so that one slot in the panel can accommodate two circuits. Each of the dedicated circuits falls into this last category -- that is, each is wired into the main panel using one of these "slim" breakers that allow two circuits into one slot.

Midnite Mick wrote: »

Just curious......why the GFCI's?

In New Hampshire, GFCI receptacles are required by code in any installation below grade, like my basement, unless the receptacle is a specialized circuit -- e.g., like an isolated ground circuit for sensitive equipment. {This is the explanation of my electrician.)

mantis wrote: »

It sounds like your on a circuit with other motors possibly. That would cause the hum.
Another thing that causes hum's is poor grounded Cable systems. Depending not eh circuit again which they live on.
What is strange is the fact that you said they are dedicated circuits. Dedicated circuits usually don't cause any hum unless possibly the breaker is faulty or a poor ground at the panel for that or those circuits.

There are several "motors" wired into this panel (see above). If one or more of these are the source of the hum, I've got bigger problems. I can probably shut down their breakers to see whether they are the source, but I'll do that after I check out sources that will have less draconian consequences for my wallet.

I have suspected that the cable TV set up may be a source of the problem, and I'll check that out today. This is an easy one to eliminate.

We've never had a grounding problem in the 18 years we've lived in this house, but I'm beginning to really push the capacity of the circuitry by adding more circuits and more equipment. However, the electrician told me that, although I keep adding "stuff," I'm still not getting close to the maximum capacity of the 200 A service we have.

One question: Would it help to have a small subpanel installed, into which these fie dedicated circuits could be wired? Would that help isolate them from the heavy equipment wired into the main panel?

Again, thank you all for your help and advice. You've certainly given me food for thought and some actions I can take.

I'll do some homework that I can handle on my own, then I'm sure I'm going to have the electrician return, probably to do some reconfiguration of the wiring in the main panel, if possible.

F1nut wrote: »

These two new circuits are wired to the same leg of the breaker box

I'm not 100% on this, but I would have run the two new lines on opposite legs.

Perhaps, I should have watched the electrician while he was doing the installation to ensure he did wire the two on opposite legs.

Inspired by your previous comments, however, I went down to the exercise area and went through a series of unplugging steps to try to identify whether a piece of equipment on my rack was the cause.

Bingo!

After having progressed through unplugging the cable box, cable connection, TV, DVD player, and CD player, when I unplugged the PS Audio PerfectWave DAC MKII, the hum disappeared.

The DAC had been plugged into the surge protector that was plugged into the GFCI receptacle that pre-existed all these changes. Before these changes, the amp had also been plugged into this receptacle, albeit not through the surge protector. I had never had a hum.

So, I left the amp plugged into one of the two new dedicated circuits with the PS Audio receptacles and then plugged the DAC into the other new dedicated circuit with a PS Audio receptacle.

No hum.

Then, I plugged the amp into the same receptacle as the DAC.

No hum.

Then, I plugged the DAC sequentially into each of the other GFCI receptacles.

The hum reappeared in each instance.

So, I have reached the end of what I can do.

If I can plug the DAC into one of the two receptacles into which I shall eventually plug one of the mono blocks, and I don't get a hum (and based on the above "experiments," I don't expect to get a hum), then I can live with the status quo.

But if this would be risky for either the DAC or the mono block with which the DAC shares a receptacle, or if this compromises sound quality, then I still have to do something about the configuration of the GFCI receptacles in relation to the two new dedicated "audio" circuits. Or, perhaps, I can just have another dedicated circuit installed for the DAC.

Again, thanks Jesse, Blue Fox, Midnite Mick, and Mantis for your interest.

Any additional comments about this will be greatly appreciated.

@Midnite Mick,

Thank you.

Wouldn't it be nice if they were all that easy to find?

Cheers!

@Speedskater,

Thank you for that explanation of the way an isolated-ground receptacle should be wired to the bus bar in the main circuit box and other aspects of the use of isolated-ground receptacles.

One question:

At the receptacle end of the circuit, one of the two insulated ground wires goes to the green terminal screw on the receptacle and the other goes to the green screw in the receptacle box.

Then, however, unlike the wiring for a standard receptacle, the grounding screw in the receptacle box is not connected with a pig-tail to the receptacle itself.

Is that correct?

@Speedskater,

Thank you.

I think code requires connecting the second ground wire to the metal box the into which the receptacle fits.

No, not that I recall. It only has the green grounding screw, and the yoke is insulated from the receptacle, I understand the way an isolated ground receptacle is built.

Speedskater wrote: »

Yes the 'yoke' is "brass mounting strap".
The silver clip under the top mounting screw is the grounding contact.

@Speedskater,

That's what I thought. The diagram below shows that the "yoke" in an isolated ground receptacle is insulated from the body of the receptacle ("insulated barrier construction" in the first diagram). I'm not sure what the "grounding contact" on an isolated ground receptacle actually does.