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Topic: Hummmmmmmmm is what I hear. |
Tommy R. Butler
From:
Nashville, Tennessee
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Posted 29 Aug 2007 5:06 pm |
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Alright I thought i'd go back to some rack gear... Main reason is a tuner and a rack delay / reverb unit. Tired of tryn to bend over and adjust an rv-3. Sooo
I got a tuner, not the cause of the hummmm
I got a power conditioner, Not the cause of the hummm
I got a patch bay, Not the cause of the hummmm
I got a Lexicon MPX100... Definately the cause of the hummmm
I tried isolation tabs and it cut alot of the hummmmm out but not all. I got a pretty good practice room and I am sure that if hummmms a lil here it will hummmm alot everywhere else..
I am pretty sure the cause is the lexicon. It doesnt have a ground in the plug to ground...(made that way)
When I put the unit in line turn the amp on... it hummmms. When I use the ground isolation tabs on the screws it dont hummmmm as bad.. When I take the unit out it dont hummmm at all...
What can I do with this thing ???? |
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Paddy Long
From:
Christchurch, New Zealand
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Posted 29 Aug 2007 5:47 pm
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Tommy what sort of cables are you using in your rack set up. I found George L's eliminated all the hum in my rack.....you can also get hum from wall-wart type power supplies as well.
I also use George L cables from my rack output - either to the speakers, amp, or direct to the desk - poor quality cables here will cause hum as well. |
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Ken Crisp
From:
North Carolina
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Posted 29 Aug 2007 5:50 pm Re: Hummmmmmmmm is what I hear.
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| Tommy R. Butler wrote: |
Sooo When I take the unit out it dont hummmm at all...
What can I do with this thing ???? |
Tommy, when you say take the unit out, I'm assuming remove from the rack mount and not out of the loop.
You could try [for testing purposes] alligator clipping from a non-coated part of the Lexicon [screw, plate or cover] to the other devices. If that works, you can employ a permanent solution. Some of those efx processors are difficult. The processors themselves are saddled with inductors and other components that pick up errant fields and frequencies.
Another idea [not the most popular one], if the lexicon has an EQ, you can try adjusting the hum to a minimum. If its a low hum, try adjusting the low hertz parameters, 100hz, 1khz etc. This however may contour your sound.
Good Luck.
_________________
Sho-Bud D10 Super Pro 8/6. Peavey Session 500 Black Widowed |
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Tommy R. Butler
From:
Nashville, Tennessee
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Posted 29 Aug 2007 6:00 pm
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George L cables is what I am using.
Already tried the alligator clips
No EQ on the reverb unit Lexicon MPX100 |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 29 Aug 2007 6:25 pm
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| I used to have an MPX-100 in a rack and found that the power supply (wall wart) would cause some hum if it was near the unit in the rack. You might try unplugging the Lex from the power conditioner and plugging it in somewhere else and see if the hum goes away. |
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Jerry Roller
From:
Van Buren, Arkansas USA
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Posted 29 Aug 2007 6:40 pm
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Tommy, are you using one combo amp or two or is it a stereo power amp?
Jerry |
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Tommy R. Butler
From:
Nashville, Tennessee
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Posted 29 Aug 2007 7:47 pm
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| Nashville 112's Jerry |
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Tommy R. Butler
From:
Nashville, Tennessee
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Posted 29 Aug 2007 7:48 pm
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| I think you may be right Lee. I wanted to get all this in the rack and power it but I may need to take the wart out away from everything. I'll give it a try and advise... |
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Tommy R. Butler
From:
Nashville, Tennessee
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Posted 29 Aug 2007 8:05 pm
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Alrite Grrrreat just what I didnt want,,, took the Lexicon PS out of the box and plugger it away from the rack power and guess what ??? No hummmmm
I should have remembered that from the last go around... LOL
OK who has the same setup w/o hummm and what reverb/ delay unit r u using so I can get this thing out and get something I can power in the rack??? |
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Larry Clark
From:
Herndon, VA.
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Posted 30 Aug 2007 2:21 am
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| If you want to stay with a Lexicon unit I believe the MX 300 is the least expensive unit that doesn't use a wall wart. They run about $240-$300. |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 30 Aug 2007 4:30 am
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| In my rack, I just moved the power strip around a bit so that I could get the wall wart just a little further away from the Lex. It didn't take much. Perhaps reconfiguring your rack will do the trick. |
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Ken Fox
From:
Nashville GA USA
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Posted 30 Aug 2007 5:28 am
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How many things are grounded to the AC wall outlet? If more than one you have ground loop hum. With just two Nashville 112 amps you can get hum (as both are grounded and that causes a ground loop). It gets worse as you add more grounded devices.
http://www.ebtechaudio.com/humxdes.html |
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Tommy R. Butler
From:
Nashville, Tennessee
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Posted 30 Aug 2007 3:06 pm
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| I took the power supply and ran it out of the rack and plugged it into the same wall plug as the nashville 112's... No hummmmmmm. I could take the rack over near the wall wart and it would start hummmmming. I moved it away from the wall wart and the hummmmm went away...??? |
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Paddy Long
From:
Christchurch, New Zealand
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Posted 30 Aug 2007 4:03 pm
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Tommy - glad you found the problem, I had the same problem when I was using a Profex II with the wal-wart.
I now use a TC m300 which has a dedicate power supply and it is dead quiet. |
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Ken Fox
From:
Nashville GA USA
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Posted 30 Aug 2007 5:08 pm
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I have never really found a problem with a wall wart device. The problem with the Profex 2 and 2 amps is that it tied the two amps grounds together via the left and right output jacks. Now with both amps ground you have created a ground loop. Not the fault of the Profex 2 or any other wall wart device!
The problem is multiple ground paths, that is a ground loop. In the case above you could use a Hum-X on one amp only and solve the problem.
Same occurs with a rack device with a grounded plug and on one amp with a grounded outlet! The racj device will ground itself to the amp via the 1/4" jack!! Now you have another ground loop. A Tubefex or Transtubefex with a grounded AC cord and a Nashville 400 amp is a typical setup that will get you ground loop hum everytime.
Again, use a Hum-X on teh amp or at the Tubefex. Either way it will eliminate the hum.
A quick and dirty solution is to use a two wire ac adapter (ground lift) on the amp or the effects unit. That will allow the amp only to ground in one direction, via the instrument cable connecting it to the other device (not the safest scenario). This is just for testing only! Do no t break ground paths at AC cords!!! That is what a Hum-X was made for. It eliminates the Hum and keeps your amp or device safely grounded. |
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Lee Baucum
From:
McAllen, Texas (Extreme South) The Final Frontier
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Posted 30 Aug 2007 5:10 pm
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| Ken, I don't know that it's really a ground loop. The hum goes away as long as the wall wart isn't near the Lex unit. As I said above, I was able to reconfigure my rack and get the wall wart a little further way from the Lex and the hum went away. |
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Ken Fox
From:
Nashville GA USA
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Posted 30 Aug 2007 5:31 pm
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I see! The transformer can induce hum. There is always a electro magnetic field around the transformer that can induce hum into some equipment and signal lines.
Even the cable can induce hum off of the wall wart. If manufacturers would just use a twisted pair on AC wall warts there would be a lot less of a problem with that. A twisted pair will break up the field that is normally around a pair of parallel conductors used to feed the transformers secondary voltage to the device. |
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