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Topic: searching for earth |
Randy Reeves
From:
LaCrosse, Wisconsin, USA
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Posted 30 May 2007 3:44 am |
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I am building a hollow body lap steel. it will have a pickup and two control pots.
in my earlier lapsteel makes I had a metal bridge and screws.
this new lp has a bone saddle, wooden brdige. the only metal are the electronics themselves.
question: I am searching for earth.
what would be a suitable ground?
would the back of the pots be sufficient?
is there a risk for hum without a shielded body?
any thoughts are appreciated. |
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Jim Sliff
From:
Lawndale California, USA
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Posted 30 May 2007 5:29 am
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| Quote: |
would the back of the pots be sufficient?
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Yes, that would be the normal way of doing it. Acoustic guitars with magnetic pickups normally don't have the strings connected to ground; many don't even have controls, with the pickup's wiring being the only ground.
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| is there a risk for hum without a shielded body? |
It depends. You don't mention the type of pickup. A single-coil will ionherently have nore hum than a humbucking design. But the steel body of the guitar should be a pretty good shield itself.
I'd probably add a ground wire that somehow connects to the strings; maybe a small metal plate under or inside the bridge (depending on the bridge design) that contacts the strings with a wire running to the back of one of the grounded pots. That would pretty much connect things like a standard design with a metal bridge.
_________________
No chops, but great tone
1930's/40's Rickenbacher/Rickenbacker 6&8 string lap steels
1921 Weissenborn Style 2; Hilo&Schireson hollownecks
Appalachian, Regal & Dobro squarenecks
1959 Fender 400 9+2 B6;1960's Fender 800 3+3+2; 1948 Fender Dual-8 Professional |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 30 May 2007 5:42 am
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What you refer to as earth, is called a common ground point. The backs of metal pots works fine...run wire to all of them so they are electrically linked. All your ground wires should then be connected to this common ground arrangement. Run a ground wire to the end plate where the strings terminate so they're grounded also.
Hum can be caused by a lot of things, but in your case, a humbucker pickup should give you a decently quiet signal. If you still have hum problems, you might build a lightweight, sheetmetal enclosure for the controls...ground it also.
Edit: Ha, ha! Jim is up and at 'em...beat me to the punch.  But I'm still on my first cup o'java.
_________________
Best regards,
Mike |
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Randy Reeves
From:
LaCrosse, Wisconsin, USA
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Posted 30 May 2007 6:19 am
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my third cup of coffee.
I am using a Seymour Duncan Antiquity single coil.
the whole guitar is wood. the only metal are the control pots and pup.
I could add metal under the bridge and the ball ends of the strings could come in contact with that.
the bridge assembly is essentially like an acoustic. holes and pegs for strings, bone saddle in a slot. |
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Robert Leaman
From:
Murphy, North Carolina, USA
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Posted 30 May 2007 6:00 pm Earth & Common
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It is usual to confuse earth ground with voltage common. Voltage common may be connected to an earth ground or it may be isolated from earth ground. When voltage common is connected earth ground, it must be connected at one and only one point if ground loops are to be avoided. If the voltage common is isolated from earth ground, common-mode noise rejection is enhanced. When voltage common is connected to earth ground, noise voltages appear as differential and are difficult to eliminate.
I spent many years as an industrial electrical control engineer and as many years chasing noise and hum in closed loop control systems. The chase can be very challenging. |
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Randy Reeves
From:
LaCrosse, Wisconsin, USA
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Posted 31 May 2007 3:38 am
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| Robert. I searched for a definition of voltage common and came up with zilch. I understand ground and how circuits need to have a ground. |
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Robert Leaman
From:
Murphy, North Carolina, USA
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Posted 31 May 2007 3:59 am Voltage Common
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Voltage common is defined as the zero voltage point in a system. For example, many designs use a bi-polar supply such as +15V and -15V. This permits easy interface with alternating voltages (for example, audio signals). There is a value between the positive supply and the negative supply that is zero, the equation (+15) + (-15) = 0. This is the common zero voltage point for the system and every voltage in this system is referred to this point, therefore this is a common point.
Voltage measurements are meaningless unless they are referred to a particular point since voltage is defined as a potential difference (EE 101). |
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Robert Leaman
From:
Murphy, North Carolina, USA
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Posted 31 May 2007 4:00 am Voltage Common
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Randy Reeves
From:
LaCrosse, Wisconsin, USA
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Posted 31 May 2007 5:22 am
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| thanks for the brief 101. |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 31 May 2007 6:45 pm
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"Searching for Earth"
Sounds like an episode from "Lost In Space". |
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Randy Reeves
From:
LaCrosse, Wisconsin, USA
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Posted 1 Jun 2007 3:37 am
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| yea, it sounded better than Ground at My Feet, which has a romance novel feel. |
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