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23 Feb 06 - 07:49 AM (#1676690) Subject: Tech: Stereo hum From: kendall I have a reasonably good sound system the works well on all but one mode. When I turn the phono on, I get a low hum. Even if the turn table is not on, it still hums. Any ideas? (Don't nobody suggest it hums because it doesn't know the lyrics) |
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23 Feb 06 - 07:55 AM (#1676691) Subject: RE: Tech: Stereo hum From: The Fooles Troupe Beat me to it - is it a valve or a transistor, or even a more modern 'Integrated circuit based' type? The gain is highest for the phono input, so any stray electric fields are likely to be magnified the most there. Any faulty signal earth could be responsible. |
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23 Feb 06 - 08:01 AM (#1676700) Subject: RE: Tech: Stereo hum From: Paul Burke Could be an earth loop somewhere- I once cured a friend's system using a nail- clipper- I just cut through one of the screen connections, and the hum disappeared magically. He viewed me as a combination of Einstein and Brunel for quite some time after. |
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23 Feb 06 - 09:39 AM (#1676799) Subject: RE: Tech: Stereo hum From: kendall A screen connection? and that is? I once cured this in an old system by reversing the power plug, but now that they are all polarized you can't do that. Besides, it hums as soon as I turn it on. |
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23 Feb 06 - 10:12 AM (#1676819) Subject: RE: Tech: Stereo hum From: gnomad When you say the TT is not on I'm assuming you mean that it is connected to power, but not in use? If so, is there a third lead from the turntable, in addition to the left & right channels? My own TT has such a lead which connects to a dedicated earth terminal on the amp. On one of my amps disconnection makes no difference, but on the other one disconnecting produces a hum, while a loose connection gives hum + crackle. Of course if there's no 3rd lead, or no earth terminal, this is no help, in which case sorry, no idea! |
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23 Feb 06 - 10:15 AM (#1676824) Subject: RE: Tech: Stereo hum From: Paul Burke Are the leads the concentric type with a single pin in the middle, or do they have separate little pins? |
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23 Feb 06 - 10:21 AM (#1676829) Subject: RE: Tech: Stereo hum From: Stilly River Sage I have exactly the same problem. I set up my sound system with lots of devices going into the amplifier. I finally figured out that the hum has to do with the turntable. SRS |
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23 Feb 06 - 10:43 AM (#1676844) Subject: RE: Tech: Stereo hum From: JohnB Both of my setups have what someone described earlier. You have a ground wire coming from the turntable, which you connect to the a screw marked "ground" on the back of the amplifier (where all the other wires go in and out. JohnB |
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23 Feb 06 - 10:55 AM (#1676854) Subject: RE: Tech: Stereo hum From: Paul Burke Another thought- it could be the positioning of the turntable wrt the other components- the transformers can give out a hefty external 50Hz magnetic field. Trey a bit of sheng phooey on it. |
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23 Feb 06 - 12:25 PM (#1676910) Subject: RE: Tech: Stereo hum From: bobad You may want to try one of these http://www.radioshack.com/sm-see-all-needs-and-wants--pi-2062214.html. If it doesn't work you can always bring it back. |
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23 Feb 06 - 07:06 PM (#1677186) Subject: RE: Tech: Stereo hum From: Stilly River Sage It looks like its battery operated. |
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23 Feb 06 - 07:19 PM (#1677189) Subject: RE: Tech: Stereo hum From: Bert but now that they are all polarized you can't do that... ...replace the plug or file that prong down. Does your stereo have a ground pin on the plug? If so check that you house is grounded correctly. Lots of times ground wires get corroded and nobody cares until the stereo starts acting up. Go to your breaker box and follow the ground lead from there to the actual ground which may be a water pipe or a rod buried in the ground. Check all connections and replace any that are corrioded. Make sure that all equipment that is connected to the stereo is correctly grounded and goes to the one ground. Or you might need to relace the smoothing capacitors in your power supply. |
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24 Feb 06 - 02:17 AM (#1677418) Subject: RE: Tech: Stereo hum From: The Fooles Troupe When I bought my house I had the electrician add some power points. he was concerned cause the earth seemed problematical - it was connected to the water pipe feed from the street. What we didn't realise was that some clever turkey had replace d the feed-line with plastic water pipe - an inch of water pipe is not considered a good ground, so he added a new earth stake along with the ELCB. I refrained from mentioning the smoothing capacitors, as that game is not for inexperienced amateurs. |
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24 Feb 06 - 03:24 AM (#1677437) Subject: RE: Tech: Stereo hum From: Paul Burke That's our advantage here in the UK. Unless you are relly out in the sticks, the earth is taken to ground at the substation, and the earth and neutral are connected where the feed enters the house. I don't see how you can smooth 60Hz AC at 100A with a capacitor. |
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24 Feb 06 - 08:19 AM (#1677585) Subject: RE: Tech: Stereo hum From: kendall Well folks, you are not going to believe this. Having tried everything I could think of, and checking out some of the suggestions from you all, I disconnected the ground wire from the amp and the hum went away. Now, the whole system has no ground, and no hum. Fascinating. |
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24 Feb 06 - 08:28 AM (#1677594) Subject: RE: Tech: Stereo hum From: George Seto - af221@chebucto.ns.ca Kendall, that proves the point. You had two "unconnected" grounds. Assuming the turntable was properly polarized, it means that either the outlet where the turntable was connected to, or the amp was connected to, was at a different potential. What this creates is something called a ground loop. The reason why some of those people mentioned a third wire, is to eliminate that situation. If your turntable had the ground attached directly to the amp, it would have done the same thing. |
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24 Feb 06 - 09:46 AM (#1677669) Subject: RE: Tech: Stereo hum From: kendall It's strange to me that it only hummed when the phono was on. Anyway, thanks to all of you for helping on this. |
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24 Feb 06 - 12:32 PM (#1677822) Subject: RE: Tech: Stereo hum From: open mike yep--sounded like a grounding problem to me.. i recenl.ty had a satellite dish installed and the installer would not put it in unless i had an adequate ground rod..so we proceeded to get a copper rod from the hardware store and pound it 8 feet into the ground..the wire is not strong enough to withstand pounding directly so i had to start the proceedure by taking another heavier rod and making a hole, then shield the rod with a larger diameter pipe until it was nearly level with the ground. Glad you found the solution for your hum.... now go learn the words! |