All of a sudden, I am getting a 60Hz constant tone from my Harmon/karden multimedia speakers connected to my Mac mini via the wired headphone outlet. The tone persists even with the audio connector unplugged. Nor does the volume control change the tone. Power input to the speakers is via a wall-wart, 15V AC, 1.1 amp, the power supply that came with the speakers. I would guess a rectifier or other component failure in side the speaker case. There are actually two speakers, the power going to the right one, with the left speaker getting audio only via an RCA cable from the right speaker. Both speakers are emitting the tone, but the volume on the left one is perhaps 10% of the volume on the right one.

Before yesterday, the speakers worked as expected on the same and another computer.

What is going on here other than the obvious (that the audio circuit is picking up the 60Hz tone from the AC power)? The suddenness of the change implies component failure, perhaps a filter or rectifier. Is this something that can be fixed by simple component replacement? The unit is old enough that it is probably regular PCB with discreet non-exotic components, with the only SMDs resistors, etc.

Computer speakers on Amazon range from about $15 to over $300, is it likely that simply buying a new set would be the most effective route? If so, is there a tighter cost range in which I'm more likely to find decent quality?

Important selection factors (in order of importance):

• decent/OK sound quality (I'm no audiophile, don't need big booms in games)
  
• reputable manufacturer (mostly because this implies longevity, or a reasonable warranty/customer service)
  
• appearance/size (will easily fit on my crowded desktop, or be mountable on wall, or small shelf)
  
• minimal components (don't need or want a separate woofer)
  
• minimal cabling (USB-powered is OK, as is AC powered, but not eager to deal with another battery-powered device)
  
• not made in China
  
• cost

Suggestions/recommendations appreciated. TIA.

Just a stab in the dark. Maybe the Ferrite ring has degraded over time and is not blocking the 60 hz frequency on the power line. they have clip on noise filters filter ferrite chokes on Amazon for $9 for 10 pieces.

quote:

Originally posted by Rey HRH:
Just a stab in the dark. Maybe the Ferrite ring has degraded over time and is not blocking the 60 hz frequency on the power line. they have clip on noise filters filter ferrite chokes on Amazon for $9 for 10 pieces.

Those clip on ferrites do nothing in the 60 Hz range, and they barely do anything in the kHz range since they are made for higher frequencies.

That said, this is where I'd get my Tektronix oscilloscope with a high impedance probe out and start probing around. Without that we're guessing, but my first guess based on experience would be old capacitors that have degraded. I had this happen to a power supply that I own, and I bought some new 12,000 uF caps from Digikey and I was good to go again. But it took an oscilloscope to ensure I was not merely guessing. YMMV.

I think the cause is a ground loop or bad power supply.

Ground loops can be caused by different pieces of audio equipment having slightly different connections to AC return or earth ground. Disconnect everything possible from you audio system, fully unplug them from the wall and start adding things back one at a time to see what is to blame.

I also agree with the other person that said that ferrites are for much much higher frequencies. They will do nothing for 60 or 120Hz.

If you like the HK's sound there are a bunch for sale on Ebay for 20-30 buck range. Take your pick. It will cost a lot more to have them repaired or to buy a new pair. I just entered "Harmon/karden multimedia speakers" in the Ebay search function.

Thanks for the comments, after looking around a little, replacing is going to be more economical than repair, but I'm the kind o guy who likes to tinker, and hate the idea of throwing somehting out when I can fix it with my own hands. Perhaps that's why I have dozens of old appliances, etc. taking up storage room for "when I have the time to get to them."

I agree, the 60Hz signal has to be coming from somewhere, bleed-through from the power line is the most logical place, so it probably is the power supply. Easy fix, just replace the PS. Unfortunately, 120V AC -> 15V AC appears to be unobtainable, output 15V DC is common, Digikey/Mouser have 18 V AC, but not 15V. Isn't Digikey required by law to stock every electrical component known to man?

quote:

Originally posted by architect:
Thanks for the comments, after looking around a little, replacing is going to be more economical than repair, but I'm the kind o guy who likes to tinker, and hate the idea of throwing something out when I can fix it with my own hands. Perhaps that's why I have dozens of old appliances, etc. taking up storage room for "when I have the time to get to them."

^^^ I know the feeling.

I was going to say stay with HK, my HK Soundsticks speakers sound really great but seems they are kind of expensive now.
As I recall my Gen 1's were non BT, only wired and somewhere around $150.
So these may be way out of what you were considering.
Now seems the new ones are much more but all are also BT.
They look slick and do sound amazing and I am pretty critical of speakers.
As for finding something not Chico > good luck.
I have seen some Bose 2.1 offerings that were quite good, had them prior to the HK's.

HK Soundsticks 4

Why not use a process of elimination and try replacing the audio cable? Then the power supply?

So just out of curiosity to see what the low-cost options might be like, I picked up one of these. Cheap, but one day free delivery, take a chance. Short review: they suck, tinny and nasal, zero bass, not much better than the in-video-monitor speakers I've been using as a stop gap. Makes even Tom Waits sound like like a high-pitch Chinaman.

Yes, I shouldn't have expected much for $23, but audio pricing ramps up so quickly from near zero to unbelievable for marginal increases in listen-ability, even though bang for the buck is a whole lot better than it used to be in the descrete component days. Where the sweet spot for my limited requirements might be, I have yet to determine. Those H-k speakers posted by Schulzy look pretty sweet, but need way too much real estate as well as hard to explain to my budget management staff (she usually indulges me, but gets a little tweaked when spending seems unjustified). Not to mention that we have somewhat different tastes in music.

Anybody want to help me restore a factory-wired Marantz 70W RMS tube amp (maybe a model 2, but it is too deep in the closet to tell) from the early 70's? Blows fuse immediately upon power up, I think the problem is in the complicated rectifier/filter sub-unit smack in the center of the circuit board. Of course, factory parts are no longer available, but discrete components should be available. I still remember how magnificent this amp sounded.

Thanks for the suggestion PASig, but I get the dynamo hum even with the audio cable disconnected. That pretty much puts it on the power side (as does 60Hz in the first place). Could be something internal, but I wouldn't bet that way.