Ground Lifts and Hum eliminators

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jaykeMURD

jaykeMURD

I sit on you.
So I've been doing some recording; recording my guitar. Micing it with sm57 and an LDC, like normal. I have started (again) using my DigiTech Metal Master Distortion pedal. I love this pedal. I have been tuning lower, and it gives excellent, meaty distortion. Sounds good and all, HOWEVER once I turn the unit on (in between guitar and amp) lots of him and/or hiss becomes present in the track. It's extremely annoying and yucky. I have read about these "ground lift" plugs that safely do something about the ground and remove a lot of unwanted hiss and hum. There are also numerous hum eliminators. Now, is this a simple fix, or will I actually have to buy something to cut down on the noise. I've used, even owned, a Rocktron HUSH rackmount thing and it seemed to do pretty well. That was a bout a year ago, but my little cousin decided it needed a "cleaning" and sprayed windex all over and into it and shorted it out! I don't know how the HUSH would do...... so whats the plan fellas and lassies!? :confused:
 
jaykeMURD said:
I have started (again) using my DigiTech Metal Master Distortion pedal. I love this pedal. I have been tuning lower, and it gives excellent, meaty distortion. Sounds good and all, HOWEVER once I turn the unit on (in between guitar and amp) lots of him and/or hiss becomes present in the track.
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Could be a ground loop, dirty power (poor power supply in the unit), or a generally poor ground on the whole system that becomes more noticeable when distortion is added by raising the gain.


jaykeMURD said:
I have read about these "ground lift" plugs that safely do something about the ground and remove a lot of unwanted hiss and hum.
Click to expand...

Uh... don't go there. Lifting the ground on a power cord is never the right plan. Shared grounds are desirable, but not at the expense of having ungrounded equipment. Make sure everything is plugged into the same outlet strip and you shouldn't need to do any power cord ground lifting.


jaykeMURD said:
There are also numerous hum eliminators. Now, is this a simple fix, or will I actually have to buy something to cut down on the noise.
Click to expand...

There are two decent ways to eliminate hum caused by ground problems: ground bussing and isolation.

Ground bussing: a lot of noise is introduced when the path of least resistance from one (often ungrounded) device to ground is through the shield of an audio cable. This technique involves picking a "sacrificial" jack on each device (or slipping a spade under an unpainted metal case screw on the device) and connecting them all together with a heavy gauge (e.g. 10 AWG) wire, then connecting that bundle of ground wires to the ground pin on a grounded power plug and plugging it into an electrical outlet.

Isolation: for each cable between the two devices, put a transformer in the line and don't connect the ground across the transformer.

In this case, I'm guessing this pedal has a wall wart power supply (which by its very nature doesn't provide a ground). In that case, I'd tend to recommend finding a groundable case screw and grounding the heck out of it.
 
Cool. If I try the "ground bussing" method...does the wire gauge matter? I only have some really, really thin wire, and lot and lots of thicker guage wire. I understand finding an unpainted screw on the unit and grounding it. But how exactly do I ground it? Run it out side to my car!? :D From what you recommended, could I cut the plug end off an old applieance cord and use it for it's ground into a wall socket?

Whats this Isolation method? Placing a transformer between amp and pedal? Huh, whats a transformer? ;)

Thanks a lot anyway man.
 
jaykeMURD said:
Cool. If I try the "ground bussing" method...does the wire gauge matter? I only have some really, really thin wire, and lot and lots of thicker guage wire.
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The heavier the better. You're trying to make the ground path through your wire be dramatically easier to go through than the cable shield.


jaykeMURD said:
I understand finding an unpainted screw on the unit and grounding it. But how exactly do I ground it? Run it out side to my car!? :D From what you recommended, could I cut the plug end off an old applieance cord and use it for it's ground into a wall socket?
Click to expand...

Or go to Home Depot or some place and buy a power plug with screw terminals. Probably much better than destroying other equipment.


jaykeMURD said:
Whats this Isolation method? Placing a transformer between amp and pedal? Huh, whats a transformer? ;)
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http://www.accessorywarehouse.com/shop/customer/product.php?productid=12100
 
jaykeMURD said:
If I got something like this....how and where does it go? Does it go between amp and wall socket? Between pedal and wall socket? What kind of connections does this little "Ground Loop Isolator" have?

Thanks again!
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In the middle of the audio cable between one device and the next. (Well, you'll need a second audio cable. :D)

Also, note that I'm not necessarily recommending that particular isolation transformer. I don't have any experience with... well... any of them, really. I've never run into a situation that was so bad that I needed to use one. Any transformer will have some effect on the audio quality, so look at reviews and try to find a decent one.
 
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