Ground Loop: Difference between revisions
== Safety Note == |
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== Safety Note | <noinclude> | ||
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[[Image:Cheaterplug.png|right|cheater plug]] | |||
'''Safety Note''' | |||
NEVER use a cheater plug | NEVER use a cheater plug or cut the ground plug off an ac power cord. | ||
or cut the ground plug off an ac power cord. | From the Owners Manual | ||
: Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding-type plug has two blades and a third grounding prong. The wider blade or third prong is provided for your safety. If the provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet. | |||
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[[Image:Cheaterplug.png|right|cheater plug]] | |||
'''Safety Note''' | |||
NEVER use a cheater plug or cut the ground plug off an ac power cord. | |||
From the Owners Manual | From the Owners Manual | ||
: Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding-type plug has two blades and a third grounding prong. The wider blade or third prong is provided for your safety. If the provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet. | : Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding-type plug has two blades and a third grounding prong. The wider blade or third prong is provided for your safety. If the provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet. | ||
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== Diagnosing / Troubleshooting == | |||
System Owner DT recently posted the following:<ref>DT talks about ground loops in [http://bose.infopop.cc/eve/forums/a/tpc/f/3976055944/m/1381066164?r=8511007164#8511007164 Major BUZZ problem]</ref> | |||
To troubleshoot ground loops problems, listen to the audio signal at the mixer with headphones. If the buzz exists at the mixer then do the following: | |||
One by one, disconnect the inputs and outputs to and from the mixer and note if the buzz decreases. If the buzz slowly diminishes with each input or output that is disconnected including those connected directly to microphones and devices not powered from an AC wall plug, then the buzz may be caused by the snake running too close to a noisy AC power line. If the hum reduces dramatically only when inputs or outputs are disconnected which are connected to devices that are AC powered, then it is likely caused by a ground loop. | |||
If the hum is not present in the mixer headphones but only audible from the L1™s, try adding direct boxes between the mixer and the L1™s. | |||
Usually if all equipment powered from AC power is plugged into the same AC wall plug, there will be little or no problem with ground loops. Because the mixer is usually at the back but other equipment powered by AC is at the front, it is impractical to use the same AC wall plug (long extension cords do not qualify as the same wall plug). Try using a direct box with ground lift and connect between the mixer or other audio devices which are AC powered that seem to be responsible for the ground loop. AC devices with 3-prong plugs are most suspect but 2-prong AC powered devices can also cause ground loops. Do NOT modify or isolate the ground pin of devices that have 3-prong AC power cords. | |||
I helped two churches with L1™s reduce hum to acceptable levels by using direct boxes at the audio output of the electric organ and at the audio input to the L1™s . We used a Radial PRODI for the electric organ. I recommend a balanced line-level to balanced line-level direct box for the L1™ inputs. The Radial Twin ISO is a two channel line to line direct box. If the two channels are used on two separate L1™s put the two channel direct box close to the mixer. Alternately, have your local pro audio store help you select single channel line to line or line to mic direct box to be used with each L1™. Be sure that the ground lift switch is in the "lift" position. | |||
The direct boxes can be expensive, check to see if you can return them if they don't solve your problem or if you find that you don't all of them. | |||
In some cases ground loops or buzz in the presence of certain light dimmers can be difficult to completely solve and some residual hum may be audible. There are some types of light dimmers that produce less electrical noise. One technology is known as "zero crossing" switching which generate less electrical interference. | |||
==Ground Loops== | Hopefully some of this info is relevant and helpful. | ||
Dave | |||
Dave also recommended reading [https://web.archive.org/web/20111228084345/http://www.radialeng.com/di-prodi-prod2-development.htm Ground Loops] at Radial Engineering. | |||
== Ground Loops (article excerpt) == | |||
This is an excerpt of an article www.rane.com [http://www.rane.com/note110.html Sound System Interconnection] <ref>Excerpt of Article at www.rane.com [http://www.rane.com/note110.html Sound System Interconnection]</ref> | This is an excerpt of an article www.rane.com [http://www.rane.com/note110.html Sound System Interconnection] <ref>Excerpt of Article at www.rane.com [http://www.rane.com/note110.html Sound System Interconnection]</ref> | ||
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=== Related Discussions === | === Related Discussions === | ||
* [ | * [https://www.bosepro.community/g/portable/topic/two-prong-cheater-plugs-for-ac-power Two Prong Cheater Plub for AC Power] | ||
* [ | * [https://www.bosepro.community/g/portable/topic/grounded-plug Grounded Plug] | ||
* [ | * [https://web.archive.org/web/20111228084345/http://www.radialeng.com/di-prodi-prod2-development.htm Ground Loops] at Radial Engineering. | ||
* [https://www.bosepro.community/g/portable/topic/laptop-playback-noises#6741094332 Laptop Playback Noises]. | |||
* [https://www.bosepro.community/g/portable/topic/magnetic-pick-up-noise Magnetic Pick-up Noise] | |||
Download: [[Media:Sound System Interconnection.pdf|Sound System Interconnection.pdf]] | |||
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