I have dedicated lines, but why is this happening?

When my central air kicks on, I hear a pop through each speaker.

Now the odd part is, I just started hearing this recently. I never remember hearing it for the first several months after I had the dedicated lines installed.

I have made several changes to my system recently that has taken the transparency of my system to a level I didn't think was possible, but I don't think that could explain why I am just now hearing the pops. Or could it?

But the primary question remains. Why is the air conditioning popping through my speakers when I have dedicated lines.

Could this be coming back through the main bus bar ground in my panel?

What would fix it?

I obviously know crap about this stuff.
Ah,you may have a grounding problem.Recheck the outlet ground and more importantly the ground connection at source.
If you have a basement you can drill a hole in the floor and drive a new ground rod.Run a separate ground wire from your outlet to this new ground rod.If you have an outlet like from PS Audio which has an isolated ground this is perfect because your outlet box and stuff is grounded normally and the isolated ground is all that is connected to our new ground rod.They may be i dunno $100 or something but the best improvment period in reducing noise and of course less noise means more music.Hope this helps.
I had this exact problem. For me, it was a bad tube in the right side of my phono stage, plus a different tonearm cable. It was all phono related for me. Not sure if that applies in your case.
ground your dedicated line to the box (fuse panel) instead of the buse bar. kurt
Why bother with dedicated lines if you don't isolate the grounds? As to the air conditioning popping: don't have a clue, but maybe it's related. peace, warren
It may be time to look at the A/C unit as the source of the popping. Areas I would look at include making sure all the electrical connections are tight and corrosion free. Obviously do this with A/C breaker off. Don't overlook the exterior disconnect box as those contacts may be showing signs of corrosion/oxiditation. Also you may want to see if the A/C is low on refrigerant as this can cause increased load during start up.

As far as Peterd's suggestions, I've never been a fan of floating grounds (ie a ground bar that is not tied to system ground) and they are specifically prohibited by the US National Electric Code due to shock hazard potential. For what it's worth ground rods work better in moist soil and the recommendation is to locate them outside at least 1 foot beyond the spill line of the roof so as to take advantage of natural rainfall.
I also agree that perhaps the AC is the culprit. Perhaps it's now drawing more current at startup.

But I would seriously doubt grounding is the issue.

Dedicated does not mean isolated. Your dedicated lines are tied together with everything else at the power panel so it is very easy for noise generated by something like the AC unit to find it's way into your gear.
When an air conditioner cycles, there are relay contacts that are actuated. These relays commonly arc when they are actuating, whether opening or closing. The older they get, the more they arc. This arc throws wideband hash into the air and onto the power line. It is similar to a small arc-weld. This is very likely to be the culprit. You probably need better RFI/EMI protection/filtering in your system.
Two things you can check:

The central ac unit may have a problem such as a faulty compressor (overheats?), pull-in contacts, loose wiring on the motor, loose wiring in the circuit (wire nuts, j-boxes, etc), loose fan belt on the blower, or a bad low-voltage transformer. I would bet on the contacts that pull in the blower line voltage.

The work done by the electrician. Each circuit have its own neutral home-run? Sometimes they'll cheat by grabbing the nearest white wire. Big no-no.

All motors cause transients and surges in your house power system. The above can make it worse, in terms of hearing the noise in your gear. If everything checks out ok (including your gear), then you may look into getting a whole-house surge suppressor (TVSS) installed in your main panel. I also agree it ain't a grounding issue and that dedicated circuits are not the cure-all for power problems.
TWL's answer makes the most sense. I sometimes get a pop from the microwave. It's RF and it somehow gets in my system. Maybe shielding the RF source will work.
I resolved this problem at the source of noise in my home. I filter the AC blower, AC compressor, microwave oven, all three computers, the refrigerator and every other device that causes me misery.

Expensive you say? Not at all. You can buy good filters for each of the above items for less than one audiophile device.

More importantly these don’t degrade the performance of your sound system. Stopping the noise from entering your stereo is much easier than trying to remove it once it’s already there.

Here is the company I bought my suppressors from:
Some very good points here and one that was overlooked.

As Herman stated, dedicated lines do not mean isolated or filtered lines. Everything in your house ties back into the breaker box, so it would not be unusual for noise to find its' way from one circuit into another. This is not to mention that dedicated lines do nothing to keep out "sludge" that was already present on the lines feeding your house.

As Gs stated, many electricians will "share" the neutral wire with other circuits and this is not a good thing. Since AC is traveling on both the "hot" and the "neutral", having "half" the circuit dedicated with the other half "shared" doesn't make much sense.

Albert stated that filtering other devices in the house will cut down on the amount of "crosstalk" between noisy devices feeding from outside circuits without detriment to you dedicated lines. This too is a very valid valid approach to noise reduction.

Several others mentioned loose connections at the breaker box, ground system, the central air unit itself, etc... These too should all be checked out. It is good practice to clean the connection at the ground rod every once in a while and this may be your perfect opportunity to do so. Personally, i would kill the mains of the house before attempting to do this though. You might be surprised how many electronic components "leak" voltage from the device to ground, even when not turned on. You don't want your body acting as the conductor bridging the electrical gap between the ground wire and the ground rod as you separate the two.

The part that was overlooked ( from what i can tell ) is that it's quite possible that one of the components that you recently "upgraded" to may not have proper filtering in the power supply. Can you think back to when you first noticed the compressor / fan problem and if you had just swapped some components or cabling in the system ? It's possible that there's nothing wrong with your central air unit and that the problem itself is a poorly designed component.

The reason that i bring this up is that i went through something similar quite a while back. At the time, i was using several different PLC's in various systems. I swapped a PLC ( Brand A ) into a system where i was previously using a different ( Brand M ) PLC. After doing so, i noticed that i was now hearing the noise generated by the arc of a lightswitch coming through this system whereas i had never heard or noticed it before. Re-installing the Brand M PLC into the system solved the problem. Obviously, not all PLC's are as effective as we would like to think. As such, it would only be logical that some components aren't as well designed / filtered as others too. Does this make sense and is the appearance of the noise and the replacement of a piece of gear more than a coincidence ? Sean
Maybe the AC's relay contacts are fried, and it's easily replaceable? Nothing like really dirty contact sparking to mess up your minigrid, eh?
Thanks for all of your replies.

The dedicated lines do not share neutral lines. I helped the electrician pull and install the lines.

I don't believe the problem could be a result of corroded or loose wiring as we just built the house a year ago so everything is new. But then again, it would be worth checking.

Albertporter, I will definitely check out your suggestion. It certainly makes more sense to keep something out rather than trying to get rid of it later.

Sean, the only changes I have made in recent months were to change the caps in my amp as you know and I then added interstage transformers to my Audio Note DAC. Nothing else other than isolation platforms and DH cones. So I don't think a component change is the problem. But I do think the suggestion to clean the grounding rod is a good idea. I hadn't thought of that and that could help.

I have also been considering installing balanced power transformers on my dedicated lines ala Jon Risch. Would this eliminate the problem?


One more question regarding Warrenh's post about a dedicated ground.

Sean, I searched your posts on isolated grounds here and I am still not sure I understand it.

When we installed my dedicated lines we used 12ga. Romex and 20 amp breakers. We ran each leg in conduit with the conduit tied to the breaker box, but with the conduit stopping short of the outlet boxes (plastic). The ground in the Romex is connected from the Acme outlets to the panel.

The only thing plugged into the outlets are my audio equipment since they are located under the house. I had a hole cut in the hardwood floor behind my equipment rack and ran all power cords out of sight through the floor to the outlets beneath.

How do I change this to make it an isolated ground?
An additional suggestion: try measuring the AC voltage at the receptacle before and during the moment the A/C system is energized. Buy a plug-in AC voltage meter from Radio Shack. At the instant the A/C system activates, the high starting current of the compressor may momentarily drop the AC voltage at your stereo to 100 VAC or even less. If your gear already draws significant current, or your entire neighborhood is blasting their A/C systems, or you have the whole house lit up, the voltage may already be dipped. If the additional voltage dip is low enough, one or all of the pieces in your system may be generating the pop noise.
Thanks for the suggestion, Bigdope. I will try it and see what kind of drop I get.
Bigdope, I measured the drop and the drop was 119.4 v to 118.8. Not much.

But it does seem this symptom started with the onset of much warmer weather when summer started. Things will begin to cool off on Maui by the end of the month. We'll see what happens as things get cooler into November and December.
Fiddler: Did you try cleaning the ground connections / ground rod yet ? I'm curious as to whether this did anything or not.

Other than that, it's possible that the fan motor has some type of capacitor or "condensor" that is going bad. These typically help to reduce or absorb the turn on "transient" or "spike" that motors or generators produce on start-up. Don't know if your system has one of these or not, but it might be worth checking into. Sean

PS... Does this happen if you have everything disconnected from the amp with just the amp powered up and connected to the speakers ? You might try tracking down which component(s) it is coming in through.
Sean, I haven't checked my ground connection yet. I need to either try to find it myself or call the electrical sub that did our house.

I have not tried your suggestion with just the amp plugged in, but I will try that and then each component until I see if there is one offender. I don't guess there is any harm in the pop, but I think it is symtematic of another problem, i.e. the ground.

I will report back after trying the ideas.

Thanks all for your suggestions.