One for Steve the electrician...

G’day, Steve,

I have a weird problem with one of my audio monitors, when we turn on our reverse cycle air conditioner one of my Mackie monitors goes nuts, sounds like bacon frying, crackling and popping at a 100db! The noise doesn’t affect the volume level, it’s sort of superimposed on top the normal sound output.

When the air conditioner is off the monitor works fine…

Could that be due to perhaps lower than normal voltage supply, the aircon has a 7 horsepower motor which may be reducing the voltage in the house? Maybe a component in the monitor is supersensitive to voltage fluctuations because the other monitor does’nt have this problem?

Thanks for any advice mate (or anyone else),


You don’t want air-conditioners, beer coolers, elevator motors or similar heavy equipment that draws a lot of current on the same circuit as your audio gear. You should run a separate AC line, on an isolated circuit (not shared with any audio gear) on it’s own circuit-breaker, to service the air-conditioner. That’s probably the simplest and least costly fix (as long as the run isn’t too long and it’s accessible to string the cabling).

I wonder if he plugged into a line conditioner it would solve the issue? They can be had pretty cheaply on eBay (Furman makes good ones)

Negative. A line-regulator might solve it. Furman makes those too (I use a Furman AR-15 in the gig-rig, but that model is discontinued) … and line-regulators are VERY expensive.

Thanks for the advice guys (a lot of it… :wink: ), a couple of things I didn’t mention in the original post,
if when the monitor starts to snap crackle and pop I unplug the power cord for maybe 15mins then reconnect, the monitor usually comes good after a couple of tries. That is with the AC on, off, no worries.
I’ve tried different power sources with the same result.

The noise also happens (fades in actually) with no input whatsoever to the monitor, it is the monitor making the noise fer sure.

The mofo AC, ducted to six points, was professionally installed and I believe it has it’s own line.

What sort of a surge protection device would I need to be looking at, if I went that route?

Those line regulators sound scarily expensive but I’ll take a look.



I’d physically trace it. The breaker SHOULD be marked correctly. I’d invest $5 in an outlet tester to insure all were wired correctly re: ground, neutral and hot. Could be the AC motor is ready to take a dirt nap.

Thanks for your efforts Steve, and the other guys.

Yeah, you’re probably right about getting ‘electronics’ help. Everything electrical in our household works perfectly bar the troublesome monitor.
I have a friend who resolders electronic devices when he is faced with ‘vague’ issues, mine may just be one of those.
I’ll ask him to take a look when I see him next.
Until then, I’ll just have to wear it, seeing as the monitor is not actually unusable.

Thanks again,


Also try swapping the power leads round, to eliminate a dodgy one!

Sounds like some kind of electromagnetic interference to me. If it’s newly occurring then first question is - has anything changed? If nothing, then perhaps it’s some sort of component failure/earthing issue in the affected monitor… one that would normally filer out any external electrical noise induced in the cabling by the presence of nearby electrical equipment e.g. the air conditioner. Swap the monitors - left to right, does the problem follow the monitor?

You can use isolation transformers too. They pop up used a lot on the bay.


I’ve tried swapping the power leads around, no joy there.

When I got the monitors about 18 months ago they worked just fine, and the problem is definitely isolated to the one which makes the noise.

The AC has now been off for a couple of days and the monitor works fine, it sure looks like there is something that is ‘triggered’ in the troublesome monitor by the use of the AC.

I’d better have someone take a look at the monitor, me thinks…

BTW, there was a guy on the Mackie forum who had a slightly different problem which ended up being a faulty component that was sensitive to ‘normal’ voltage fluctuations in his environment. Could be the case here, maybe?

Thanks for trying to help everyone,


In audio gear such as monitors, there are usually conditioning elements (components) built into the power regulation circuits. When such devices are operated in electrically noisy environments and continually subjected to spikes etc. this is a strain on these components which could cause them to eventually fail. E.g. varistors are often used to shunt voltage spikes on the input, and over time, or given a hefty spike will fail, i.e. can no longer recover - this is just an example, there are other components such as failing condensors and diodes which could also be causing your problem.

I’d suggest you have the monitor in question serviced - specifically describing the problem you’re having.

For the long-time however, I’d suggest you get a qualified electrician come and measure your power circuits, and see if you can have the noisy equipment transfered to another phase or otherwise isolate your branch for your gear. Furthermore, see about having your studio power circuits rewired with a common central ground (star-grounding).

Send it in for repair before it blows up.

You could have a bad power supply in the unit ( which is what is sounds like)

If a psu filter capacitor goes bad, it will hum and since it only happens when the ac is on, I am leaning toward that even though is it a sizzle which typically is not a sign of a cap going bad. Transistors will sizzle…

The import thing is have it repaired before it is unrepairable.

When you run a heavy load like your ac, the voltage will fluctuate but it is not always seen with a meter because you need a fast meter to catch it. Scopes are better for this and you can see harmonics and distortion in the AC sines. Motor loads also will create noise too in the house electric. There usually are capacitors on motors too that store energy to help them start spinning and they help maintain steady voltage to prolong motor life. Depending on the age of your HVAC system, if the cap is failing on the motor, the brushes in the motor are old,… this can all add certain conditions to the entire house’s electrical system.

Or, you may just have a bad component in your speaker’s amp.