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TorbenGB
2006-11-20, 03:37
One of my SB3's is connected to a set of Wharfedale amplified speakers via mini-jack. I have noticed that the speakers are humming when the power is turned on - even if no player is attached. This humming is annoying because it is rather loud -- well, not loud as in loud but as in not-quiet.

I must fix this humming because it is annoying!
What tips can you give me to get rid of this humming?

I suspected the cable between speaker and player to be the culprit, because the mini-jack was not original but had some poor-looking soldering. The cable itself seemed fine, but rather than soldering on a mini-jack, I decided it would be better to use a factory-made Sennheiser cable with mini-jack already attached, which I then soldered onto the board inside the powered speaker. But it still hums just as loud as before, so this was not the problem in the first place. Who knew.

What else can I do, apart from throwing away rather good(?) speakers and buying new ones?

CCRDude
2006-11-20, 10:04
Ever heard about energy conservation? If you don't use it, don't use standby, but an extension lead with a switch for example ;)

It sounds like other speakers won't solve the problem anyway; I've got the same experience with two SB3s - when they're finished playing, it still hear some humming. Good to remind me to choose the next CD or turn it off ;)

edit: sorry, overread that in your case it's even without a player attached; reminds me of a typical audio problem: if both devices are on different fuses, the level of the ground wires may not exactly be the same, resulting in static humming. Happens most often with computers attached to HiFi equipment, since those are often some way apart (chance to be on different fuses is higher).

TorbenGB
2006-11-20, 10:51
Update: as discussed in this newsgroup thread (http://groups-beta.google.com/group/sci.electronics.repair/browse_thread/thread/d4bff7917fcd9deb/9c95c976c4fff337), it's common for speakers to hum when they're not plugged into anything, but plugging them into a proper system should make it stop. I plugged the speakers into my cheapo MP3 player and it was perfectly quiet!

Seems to me that there might be an electronic fault in the SB3 itself that is causing this. Is this generally poor SlimDevices manufacturing quality, or is my specific unit faulty?

michel
2006-11-20, 11:01
The Squeezebox is absolutely quiet when not playing back a signal. What you experience is most likely a not so perfect amplifier humming.

alex.sh
2006-11-27, 17:11
Still humming? Actually, the humming is often caused by feedback through the ground (the third prong on the power cord) from the amp or other components when they are all connected to the same circuit (one or more power outlets that are routed through a same line to your home's main power supply).

First just use a three-prong to two-prong adapter on the amp, then other components until the humming disappears. I had the same problem and I just broke off the ground on the amp and pre-amp power cords and it disappeared.

richidoo
2006-11-27, 18:29
Try turning off the flourescent display on SB using the brightness button on the remote. The display causes a harsh buzzing in the right channel, normal for all SB3s. You can set the display to come on only for changes, then shut off after a few seconds delay. Choose the smallest font too, although this has less efect than the dimming.
Good luck
Rich

TorbenGB
2006-11-28, 01:56
First: the humming is gone. How? By wiggling the minijack plug a little, then it stopped. Apparently the minijack socket in the SB3 is not as eminent quality as the rest of the unit.

the humming is often caused by feedback through the ground
- I'm in Austria, Europe. We do have ground in the sockets, but the plugs don't. So grounding is not a problem -- it isn't there.

use a three-prong to two-prong adapter on the amp, then other components until the humming disappears
- I don't have an amp, only directly attached amplified speakers. It all runs off the same power strip.


Try turning off the flourescent display on SB using the brightness button on the remote. The display causes a harsh buzzing in the right channel, normal for all SB3s.
- None of my 3 SB3's create any interference like this -- and I should hope this is not "normal"! Are you serious? Might there be a problem with the one(s) you have?

richidoo
2006-11-28, 06:24
Try turning off the flourescent display on SB using the brightness button on the remote. The display causes a harsh buzzing in the right channel, normal for all SB3s.
- None of my 3 SB3's create any interference like this -- and I should hope this is not "normal"! Are you serious? Might there be a problem with the one(s) you have?

Yup, they all have it, but if you can't hear it, don't worry about it! It is subtle, audible with poweramps which are always at full gain, on sensitive speakers, using no external volume attenuation, more audible when SB volume is turned down. If you mute your SB, and turn up your speakers all the way to max, with the display lit full bright, you might hear it in the right speaker. Sounds like your hum was much more pronounced than that! Glad you figured it out.
Rich

mudlark
2006-11-30, 04:42
The other alternative is to use an external dac. if you use the optical connection there cannot be an electrical loop.
M.