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The following page was printed from RemoteCentral.com:
Topic: | Help with ground hum/loops in home theater This thread has 26 replies. Displaying posts 16 through 27. |
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Post 16 made on Monday June 28, 2004 at 01:44 |
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Post 17 made on Monday June 28, 2004 at 01:46 |
On 06/27/04 16:51, Michael Clarke said...
We are never affected by 60 hz hum, induced or otherwise.
Power here is 110v, 50hz
The drinks are on me. LOL,, really. must be nice to have exactly 110Volts, what's you secret
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Post 18 made on Monday June 28, 2004 at 18:09 |
Larry Fine Loyal Member |
Joined: Posts: | August 2001 5,002 |
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It must be the metric system. You know how 2.2 pounds = 1 kilogram? Apparently 2.2 Hz = 1 volt, so 2.2 x 50 = 110.
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Post 19 made on Wednesday June 30, 2004 at 22:08 |
Ted Wetzel Founding Member |
Joined: Posts: | November 2001 879 |
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On 06/27/04 17:50, Daniel Tonks said...
I took the CEDIA course on grounding/ground loops, and even still everything is mostly mystery. the CEDIA course was far too short (as many of them are) to be effective. I don't believe Bill Whitlock is still teaching that course for this very reason. NSCA is the place to take it. | Then I added a fancy new DVD player, which very oddly came with a grounded cord. This introduced a HORRIBLE ground loop through the amp's DVD input - even with just a digital coaxial line connecting the DVD to the amp, I had a hum - on the digital input! The only solution I could devise was putting a cheater on the DVD.
I still feel this particular solution is safe because 1) Why in the world does a DVD player need to be grounded, and 2) The system and DVD player are still grounded through the amp. Your loop is probably on the video cables. You have removed the safety ground from the device. It is possible that the unit could short internally, putting 120Volts on the chassis without tripping the breaker. The ground is not there for the performance of the equipment but the safety of the user. In your case you are taking a calculated risk. For an installer to leave it that way in a customers home is a different story.
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Post 20 made on Wednesday June 30, 2004 at 22:15 |
Ted Wetzel Founding Member |
Joined: Posts: | November 2001 879 |
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On 06/27/04 13:55, teknobeam1 said...
Induced 60 cycle hum is completely different
All the shielded cable in the world won't get rid of an induced source of noise in an unbalnced circuit, by virtue of the fact that the shield is actually on of the signal carrying conductors depends on the signal and the wire. I haven't had 60 hz hum induced onto the wire in a long time. fingers crossed. I use Belden 1266 mic line for all of my line level runs. It comes in every color in the rainbow. I use what's commonly called the "telescope" wiring. red to center, black to ground & shield tied to ground at the send end. your shield is NOT part of the signal path this way. I don't do a lot of pro work but I have never had to just leave pin one lifted. the shield should be routed outside of the xlr and tied directly to the chassis. lifting pin one doesn't work if you need phantom power.
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Post 21 made on Thursday July 1, 2004 at 02:17 |
I agree with what you have said. I should have been more specific. When I lift pin one on an XLR connector, it's in a situation where I'm going from balanced +4 to unblance -10. In some situations. this solves a problem. a properly balanced system ussually deals with induction, even in LZ signals. However, a mic. line can still allow a 60Hz induction if it is strong enough, or close enough for a long enough distance. This is why in any venue, the audio spec. is very clear on proximity of signal carrying conducters to AC voltage lines. PVC tubing will of course not stop this problem, neither will copper or aluminum conduit. Steel conduit is the only pipe that will be effective . If the noise is being generated by the electrical system, a high quality ac transformer might be required. They are expensive, but clean up the power. And no, they don't afect the audio quality, in fact, if anything, it will be improved by virtue of the absence of the hum.
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Post 22 made on Thursday July 1, 2004 at 06:21 |
Daniel Tonks Wrangler of Remotes |
Joined: Posts: | October 1998 28,781 |
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On 06/30/04 22:08, Ted Wetzel said...
Your loop is probably on the video cables. Hmm... maybe. I have a rather complicated set of video connections from the DVD, involving component, S-Video *and* composite. Still, having multiple grounds in a system is a good way to promote loops.
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Post 23 made on Saturday July 3, 2004 at 19:32 |
Tom Ciaramitaro Loyal Member |
Joined: Posts: | May 2002 7,967 |
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Larry, I used to think I had a weight problem until I became friendly with the metric system.
Hmm, as I type this, do I recall that the metric system has gotten you back into shape as well?
I'm in shape. Round is a shape, isn't it??
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There is no truth anymore. Only assertions. The internet world has no interest in truth, only vindication for preconceived assumptions. |
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Post 24 made on Saturday July 3, 2004 at 19:41 |
Michael Clarke Long Time Member |
Joined: Posts: | September 2003 169 |
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50hz has its unique set of problems.We use NTSC here so any kind of ground loop, leakage etc. causes a heavy 10 hz (60-50) flicker. 10 hz flickers have been known to trigger epilepsy attacks.
Also, CCTV monitors end up with 10hz flicker if lighting in the monitored area is flourescent.
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Ever notice when you are driving that everybody going slower than you is an idiot and everyone going faster than you is a maniac. |
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Post 25 made on Sunday July 4, 2004 at 00:16 |
Larry Fine Loyal Member |
Joined: Posts: | August 2001 5,002 |
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On 07/03/04 19:32, Tom Ciaramitaro said...
I'm in shape. Round is a shape, isn't it?? "D-oh!"
"Nuts!"
"Mmmmmmmm, donuts!"
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Post 26 made on Sunday July 4, 2004 at 05:16 |
HDTVJunkie Long Time Member |
Joined: Posts: | March 2004 467 |
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On 07/03/04 19:32, Tom Ciaramitaro said...
Larry, I used to think I had a weight problem until I became friendly with the metric system. I used to think gas was expensive until I saw it for 56 cents per liter. Imagine that! Only $.56
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Post 27 made on Sunday July 4, 2004 at 16:38 |
Larry Fine Loyal Member |
Joined: Posts: | August 2001 5,002 |
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On 07/04/04 05:16, HDTVJunkie said...
I used to think gas was expensive until I saw it for 56 cents per liter. Imagine that! Only $.56 I remember back (way back) when I was a kid (well, physically). It was a Sunday afternoon, and the family was headed to the community pool. As we rounded the corner, my dad looked at the sign at the gas station, and said, "I can't believe it! Gas has hit 30 cents a gallon!" Now I see it's "dropped" below $1.70/gal and think what a great price it is. Sheesh!
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