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Topic: Noise in my amp |
Jimmie Martin
From:
Ohio, USA
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Posted 27 Apr 2009 1:10 pm |
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My amp makes a humming noise when i turn it on but if i turn off my mpa lexicon 110 it stops. What am i doing wrong. Thanks in advance. Jimmie  |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 27 Apr 2009 1:15 pm
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Do you have the Lex unit sitting on top of or near the amp? That will cause the amp to hum.
Lee |
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Michael Douchette
From:
Gallatin, TN (deceased)
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Jimmie Martin
From:
Ohio, USA
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Posted 27 Apr 2009 5:03 pm amp
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| The lex. is in a rack case but it is about 8'from it. |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 27 Apr 2009 5:35 pm
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| If it's 8 feet away, that shouldn't be the problem. What else is in the rack? Does the Lex have an external power supply (wall wart)? I used to use an MPX100 and I had to move things around in the rack, to make sure the wall wart wasn't too close to the Lex, or it would cause lots of humming. If there is a wall wart, is it plugged in on the inside of the rack case? |
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Jack Stoner
From:
Kansas City, MO
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Posted 28 Apr 2009 2:19 am
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It's a "ground loop hum". Typical when many units that are both AC powered are connected. Technically a ground loop is a difference of "potential" on the ground of two different devices.
You can prove this by isolating the Lex from the AC ground with a ground lifter, or, as previously mentioned, if you have other equipment in the rack, one of those could be causing the ground hum problem.
You could also get an "Ebtec hum eliminator" and put it in the line between the Lex and the amplifier. |
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Jimmie Martin
From:
Ohio, USA
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Posted 28 Apr 2009 2:26 am hum
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The only other thing in the rack is a Korg 2000 tuner and it isn't hooked up. It does have a wall wart. Where do you get a hum eliminator at? I thought about turning the rack around and then the tuner would be in between the lex. and the amp. Thanks for your imput guys. Its very helpfull. Micheal i don't have a lyric sheet.  |
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Michael Douchette
From:
Gallatin, TN (deceased)
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Posted 28 Apr 2009 3:25 am
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Jimmie, it does sound like ground hum, from your description. Jack gave some great advice above. You initially said,
| Quote: |
| My amp makes a humming noise when i turn it on but if i turn off my mpa lexicon 110 it stops. |
Have you tried just going straight to the amp with nothing else in line at all? Is the hum there? It may be, but at a lower level. The lex may be boosting the signal output to where it's more audible. Try the ground lift thing, and see if that helps.
I had the strangest hum one day at the house doing overdubs. The first day, all was fine, clear and clean. Next day, after setting up again, the hum was unbelievable. I tried lifting, switching, everything I could think of. Then, I moved the mic away from the amp face about an inch more than it was, and it stopped. Go figure...
_________________
Mikey D... H.S.P.
Music hath the charm to soothe a savage beast, but I'd try a 10mm first.
http://www.steelharp.com
http://www.thesessionplayers.com/douchette.html
(other things you can ask about here)
http://s117.photobucket.com/albums/o54/Steelharp/ |
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Ken Metcalf
From:
San Antonio Texas USA
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Posted 28 Apr 2009 4:17 am
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When I first got my lexicon it had a hum and I was told by the lexicon folks that it should be in an effects loop, I have heard this complaint a lot from guitar players and such using it in line like a stomp box. After I messed around adjusting the levels I got the hum to basically go away and it worked fine.
Now I run it in the effects loop of a Walker SS Preamp.
My laptop had a wicked hum and I put a HUM-X on the power plug going into the 110volt, that solved that problem also, with no effect on the sound.
_________________
MSA 12 String E9th/B6th Universal.
Little Walter PF-89.
Bunch of stomp boxes |
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Jack Stoner
From:
Kansas City, MO
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Posted 28 Apr 2009 4:25 am
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The Lexicon's are "line level" units, not low level instrument level devices. If they are used in low level situations there will be a low signal to noise ratio (more noise). In a Peavey amp such as the Nashville 1000 or Nashville 112 they can be used in the Post EQ loop as it is a higher level loop. The Pre-Eq loop is a low level and should not be used. On a Nashville 400 it can be used between the Preamp Out and the Power Amp in as that is "line level".
The same way it should not be used between a guitar and amp since that is a low level situation.
This shouldn't affect the ground loop hum, but it will affect signal and noise.
Back to the rack units. If another rack unit is plugged in, even though it's not powered on and/or connected via a guitar cord, it can cause ground loop hum through the rack rails in the case. Isolating the rack rails can fix this situation. They even sell nylon isolation tabs, called "humfrees" (Musician Friend has these). |
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Jimmie Martin
From:
Ohio, USA
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Posted 28 Apr 2009 5:35 am amps
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| There is a lot more to this than i thought. When the lex. is not plugged in to the wall there is no hum at all. Right now the lex. and amp are both hooked up in fx send and fx return. Do you think the hum frees will do it? Thanks guys you are a blessing. Jimmie |
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Jimmie Martin
From:
Ohio, USA
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Posted 28 Apr 2009 12:19 pm hum
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| I fixed it. All that i did was turn my rack around and put the tuner in between the lexicon and amp and the humming quit. Thanks guys. |
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