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Topic: Ground lifts |
Bill Fall
From:
Richmond, NH, USA
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Posted 14 Apr 2008 2:01 am |
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| I'm setting up a rack case using a multi-plug Furman Power Conditioner as the common power source for 2 amps & effects. Do I need to use ground lifts for one of the amps? For the effects units as well? |
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Jack Stoner
From:
Kansas City, MO
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Posted 14 Apr 2008 2:27 am
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You don't need to do anything unless you do run into a ground loop problem. I had a rack with a Rocktron preamp, T.C. Electronic G-Major effects processor and either a MosValve 500 power amp or a Peavey DPC1000 power amp and didn't have any problems.
Rather than lift the ground, get some "Humfrees", which are nylon straps that isolate the equipment from the rack rails as that will stop hum many times. I know Musicians Friend has them and a lot of other music stores have them. |
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Bill Fall
From:
Richmond, NH, USA
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Posted 14 Apr 2008 2:41 am
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| Thanks Jack. And good mornging! |
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Jim Sliff
From:
Lawndale California, USA
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Posted 14 Apr 2008 5:04 am
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What Jack said.
A ground lift is the last-resort used when a tech can't locate the real problem. They are also quite dangerous (I've been knocked across the stage by a tech's ground lift...one I wasn't warned about). Don't use them. Isolate and fix the problem if there is one, or use equipment specifically designed to safely deal with it.
_________________
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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Don Poland
From:
Hanover, PA.
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Posted 14 Apr 2008 5:58 am
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Wouldn't a simple non-conductive(nylon, rubber, plastic...etc) washer work just as well? I am not being argumentative here, but for the cost of the Humfree's you could buy a whole bunch of washers. Am I missing something here? Inquiring minds want to learn 
p.s. Now that I think about it, I guess you would need plastic or nylon screws too, or you would be "conductive" in the threaded area also. This is a good topic....HOW do you properly isolate your rack gear??? |
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Jack Stoner
From:
Kansas City, MO
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Posted 14 Apr 2008 7:59 am
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Dan, there are other ways other than the "humfrees". I had a Korg DTR-2000 rack tuner and it came with a mounting "isolation" kit.
But, if you have a rack ground loop problem the first step is to isolate which item is causing the problem. Is it a bad guitar/patch cord, or is it actually a ground loop problem. If it is a ground loop problem and only one device is causing the hum you don't have to isolate everything - just the one device. |
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Jerry Overstreet
From:
Louisville Ky
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Posted 14 Apr 2008 1:40 pm
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If you connect 2 combo amps such as 2 NV400's, 112's, etc. into an fx unit as in a stereo config to a single instrument, I can almost promise you there will be hum from the ground loop. I hear there are devices on the market that deal with this problem, but I've never tried them. I've always just lifted the ground on one of the amps by means of a 3/2 power cord adaptor. Works for me. YMMV.
This is a different condition than what is caused by
adjacent gear in a rack config.
My suggestion is to wire it all up first and see what happens, then search the forum archives on the subject and make your own intelligent decision on how to deal with it if it becomes a problem.
Best of Luck with your new rig, BTW. |
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Pit Lenz
From:
Cologne, Germany
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Posted 14 Apr 2008 3:20 pm
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Don,
You think right. Plastic washers only isolate the bottom surface of the screw´s head.
But plastic screws are too weak to hold yor equipment securely.
You could isolate the threaded area of the screw that goes through the frontplate with a short piece of heatshrink tube.
Don´t forget to put washers on the frontplate´s backside, too.
Cheaper, but more work ( as always...) |
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