Audioengine A5 buzzing

I have exactly the same issue :( So following this thread with interest..

edit: found this topic, getting the idea it is normal for all a5's: http://www.head-fi.org/forum/thread/385161/audioengine-a5-humming-hissing-popping-cracking

Is it a hum or a hiss?  Where is your volume set on the dial? There should be a slight hiss (white noise) coming from these speakers when you put your ear up to them but that is it. The only other two common concerns are the speaker balance goes out when the volume is set very low and after 10min there will be light/heavy popping sound when the internal amp shuts off.

I own the A5's and experienced some humming when i first had them set up, i wrote audioengine about this problem and they suggested i swap out their headphone jack adapter for a different, more sturdy one. After performing this i no longer have that digital hum noise, but a common thing for all AE5's is after about 10 to 15 minutes there is a kind of startling POP that is turning off the internal amp and is just upstream noise from that but is slightly annoying, nothing to turn a buyer away though.

A hum isn't normal, is it still present when you unplug the source from the back of the speakers? If it's still there it's probably a defective set of speakers....

Get a line conditioner or plug them into a different wall socket. UPS will also work.

I've written audioengine and they clarified that little white noise from those speakers is normal. 

I have a set of Mackie MR8's and I experience the exact same issue as you are having. Sometimes, when I have them plugged into my macbook (through the headphone jack), I hear a low buzzing sound, and it definitely comes from both speakers. It's prominent enough to hear over softer parts of some of my music. The problem goes away when I plug them into my ipod, however, and it is intermittent, so I've not bothered to spend too much time trying to figure out what the deal is. I suspect it has something to do with my macbook's headphone jack, and I'm hoping to solve it once I get a DAC. 

Just figured I'd let you know that it probably isn't an issue with your speakers. 

I found that my Audioengine A5s (which I received last Tuesday, I think) have a brittle stuttering hum whenever they're powered on. Part of it is that I have pretty good hearing. I was just a few moments ago listening to a podcast through some Alessandro 1s (whatever the cheapest model is) in a silent room and I could make out the hum. It was very annoying. I switched on some music (a Tortoise album) and when the music is louder, I can't really make out the hum. But when the music is quiet (drum fills and you know--it's Tortoise, it's always kind of quiet [dynamic might be the best word]) I can definitely make out the hum. I have them plugged into an extension cord that's plugged into a power strip with a million other things plugged into it (other extension cords, a lamp, a guitar amp, a computer, the router, the modem, maybe some other stuff?), but that is my only option. I'm not really sure what to do about it. I emailed support, and they gave me back several things to test (move them to another room, try a different source, etc.), which I have not had time to do yet. I'm at a loss. The speakers sound amazing, but this clipped, brittle hum is driving my crazy.

Just caught this thread.

I had the same problem months ago until I figured it out.  I had two DACs plugged into the speaker inputs (rear and top).  When I unplugged one of them, the noise went away.  They have been very silent ever since. 

Yuck. I've tried plugging a source into both (either) inputs and the terrible (relatively) stuttering sound continues. It happens even with no source plugged in. If I power on the speakers, activate them by playing some sort of sound, and then unplug everything but the power cord and the cable connecting the speakers, I still hear it. I think I need to send them back. I'm really bummed.

They're going to send me a new pair and also a return shipping label. I'll let you know how the next set turns out. The customer service at Audioengine is ridiculously grand, though.

UGH. I received a replacement set of speakers today, and they are slightly better than the first ones I received. I might look into buying a power conditioner, but I really don't want to spend another hundred bucks on anything related to my music setup. I found, honestly, the best solution was to stop angling the speakers toward myself and suffer a more limited soundstage. Now I don't notice the hum at low volumes.