Simple two capacitor isolator. This circuit is a simple isolator for TV and Radio antenna connection. This circuit passes radio frequency signals nicely, but does not pass significantly 50 Hz signals, so the ground loop is eliminated. The circuit can be easily built into antenna connector or to a small box.
![Ground Loop Isolator Install Car Ground Loop Isolator Install Car](/uploads/1/2/6/3/126346129/346268269.jpg)
Fort check that you have made the cabling between equipments properly.Proper audio cable connection methods are essential in getting humm freesystem.Rane technical note Sound System Interconnection is a very good source for informationhow the audio wiring between equipments should be connected. This is a wellworth to read article.
Breaking of ground loop can be done in many ways, some which are betterand some are less good.
Dangerous method: break the mains ground connections
Logically you could think, you could eliminate ground loops bydisconnecting the power-cord ground pins on all your gear.Some people might try to break the ground connection by cutting thegrounding pin in the connector, using cheater plug,cutting the ground wire in equipment, taping over the grounding connector etc.
Do not do this.Removing the ground connection isn't right. It is against electrical safety regulationsand potentially very dangerous. Removing ground connectioncan defeat the actions of your noise filter or spike protectors inside the equipments.If the ground connection is cut then a fault in the isulation inside equipment willcause dangerous voltages to the equipment case instead of burning a fuse.Removing the ground connection from the equipments which have itis dangerous, against electronic safety regulations andyou risk damaging your equipment.Running without a power ground will not automatically electrocute you butwill make this much more propable if something goes wrong in your system.
NEVER use a three wire to two wire adapter on ANY piece of audio gearwhere a human can POSSIBLY come into contact with it. You're askingfor a nice 120v 'signal' thru someone's body. Yes it MIGHT eliminatethe hum, but there's a MUCH safer way to do the same thing.
Is a GFCI a substitution for ground conductor ?
![Ground Ground](/uploads/1/2/6/3/126346129/503895960.jpg)
Ground fault interrupterscan be used as replacement forground connections in three prong receptables according NEC.The NEC requires that three prong receptacles without groundthat are protected by GFCI must be labelled as such.
The NEC, section 210-7(d), and CEC, section 26-700(9), are quiteexplicit that GFCIs are a legal substitute for a grounded outletin an existing installation where there is no ground available inthe outlet box. But your local codes may vary.
Because the NEC talks only about existing installations without groundit seems that you can't use GFCI as ground fault problem solver, becauseyour system already have grounding (and GFCI is a substition for groundingin installation where there is no ground conductor).
Transformer isolation of whole studio system
You can isolate your system completely from the power company with aspecial transformer. But if you're going to go to the trouble of doingthis, you might as well consider rewiring your studio with good powersystem which has proper start grounding. The use onlyprofessional equipments with balanced audio input and outputs anddo the wiring correctly. If you stil face problems you can considerusing balanced power system to power your equipments.
Solving the ground loop hum problem using the right ground loopisolator is the safe, effective way to eliminate unwanted hums atan affordable price. Typically ground loop problems can be solvedwith audio isolation transformers connectedto the audio line. There are also commercial audio distributionamplifiers which provide this isolation.
Regardless of what type of ground loop isolation method is used, remember,never remove the ground prong on the power cable.This maywork as a temporary solution, but personal safety should not be compromised.
If you can't find the ground loop and don't want to use isolationtransformer, try tempting the circuit withan even better ground. Heavy-gauge wire has very littleelectrical resistance, so less current is likely to flow through theshield. Get some heavy gauge wire and run lengths of it fromyour computer's chassis to each other chassis. On audioequipment, there's usually a screw marked for this purpose.You should hear the hum go down as soon as you make theconnection. If heavy-duty ground connections don't stop the hum, you'llhave to use suitable isolator in that audio line.
Direct (DI) boxes as ground loop problem solvers
Direct boxes are devices that convert unbalanced instrument-level (or line-level)outputs into balanced, microphone-level inputs.They are used heavily in large, arena-size sound reinforcement systems where the keyboards,etc., are located far away from the mixer. Impedance differences between the keyboard andmixer prohibit one from running cables directly out of the bass amp of keyboard and to themixer.
To use the Direct Box, one takes the guitar amp's output (it usually has one on the back),and, using a 1/4' patch cable, plug the other end into the direct box input.Make sure that the switch(if it has one) labeled 'Speaker/Instrument' is on 'Instrument.'Plug a normal XLR cable into the output end and the other into your cabling which goes tothe mixer.
If the system is grounded at bothe ends and ground potentials start flowing, you'll get aground loop. Ground loops can be identified by a low hum (60Hz in the US and 50 Hz in Europe)through the sound system. First place to check: direct box.Direct box usually has a switch labeled 'Ground Lift' for solving this type of problem.The ground lift switch will lift the ground (safely) and the hum should stop.If the switch isn't there, use a special ground lift cable on the XLR cable.Do not, by any means, disconnect the grounding pin of the AC cord.
How to use noise gate to reduce hum
Noise gate does not let any sound through the gate unless the soundhas a signal level which is higher than the set threshold value.If the problematic hum source is some instrument and the hum is very fainta noise gate can make less annoying. When you set the noise gate thresholdso that the gate does not pass any signal when there is no signal fromthe instrument then the hum is not added to the main mix. When the instrumentis played a very weak humming is quite hard to notice.
Commercial products for audio line ground loop elimination
- ES034 Ground loop isolator - isolation transformer for car audio from Scosche Industries
- FGA-40 Ground Isolator is 1:1 audio isolation transformer with 10 kohm impedance from Monacor (Best.-Nr. 06.4370)
- Ground LP Isolator (270-0054) from Radio Shack, designed for car audio
Equipment to remove hummign already in signal
- N'Hummer 1a AC Line Noise Eliminator from Stro Lion Technologies
- SN-700 Noise/Hum Eliminator - a single-ended, realtime noise eliminator which tries to eliminate huming noise form audio lines, made by Roland.
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