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Query re, Buzzing noise from a power lead


johnnyfingers

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I bought a second hand Hammond XB1 keyboard and plugged it in to my PA which also powers a couple of other keyboards. A loud buzz noise occurs when I turn on the PA (but strangely the Hammond is still turned off at the machine end)and at this point I am worried I have bought a dud machine. I change the actual plug on the power cord, insert a new fuse, and the buzz still occurs. I then try the power cord from my Mixer but the buzz still occurs. HOWEVER, I then try the power cord from my Korg M1 and ......magic........the buzz disappears and the Hammond plays fine. Anyone have an idea what's going on here? Two power cords buzz, one is fine, and they all look the same. The odd thing is that the buzz generated from the Hammond's power cord occurs even before I turn the macahine on.
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I'm a little confused as to which power cord you are referring to. The power cord to the Hammond is causing the buzz?

 

Maybe you are using (or were given) the wrong power supply. An improper power supply can cause all sorts of strange things (including buzz). I can't be more specific than that because I do not exactly understand what you are describing.

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The Korg M1 uses a standard grounded (3-prong) AC cable (see image below); I'll assume the same is true for the Hammond XB-1, and the unnamed mixer.

 

http://www.oselectronics.com/Images/pg_116/55782.gif

 

A logical guess would be a disconnected or intermittent ground on the first two cables. A quick check with a multimeter will confirm this.

 

Advice: throw out the two 'buzzy' cables, go to your local computer or electronics supplier, and buy two new ones.

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Your buzz sounds like a ground loop.

 

I had a similar problem with my first XB-2. I wound up having to lift the ground on the XB-2 to get rid of an apparent ground loop. Perhaps the third cord has a bad ground, which got rid of the loop.

 

What was strange about my ground loop is the XB-2 was not connected to my mixer at all. It went directly into a 147 Leslie with foot preamp, which was not grounded.

"In the beginning, Adam had the blues, 'cause he was lonesome.

So God helped him and created woman.

 

Now everybody's got the blues."

 

Willie Dixon

 

 

 

 

 

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  • 2 weeks later...

Try a three-prong adapter on the cord (and the others too for that matter) to see if the ground is the problem. WARNING! Do not use an adapter with the ground pin lifted as a permanent solution unless you don't mind seeing someone get electrocuted on one of your gigs! (thanks Bobsk8)

http://www.adorama.com/images/Product/ZZAC32.JPG

The one below will supposedly eliminate the ground hum while maintaining a safe electrical ground

http://www.zzounds.com/media/feed/large/EBTHUMX.jpg

"Oh yeah, I've got two hands here." (Viv Savage)

"Mr. Blu... Mr. Blutarsky: Zero POINT zero." (Dean Vernon Wormer)

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I have had problems over the years caused simply by either having the power supply from one piece of equipment too close to either another piece of equipment or too close to audio cables. Simply moving the cables or the piece of equipment solved the problem.

No guitarists were harmed during the making of this message.

 

In general, harmonic complexity is inversely proportional to the ratio between chording and non-chording instruments.

 

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Originally posted by Ed Coury:

Try a three-prong adapter on the cord (and the others too for that matter) to see if the ground is the problem.

http://www.adorama.com/images/Product/ZZAC32.JPG

The one below will supposedly eliminate the ground hum while maintaining a safe electrical ground

http://www.zzounds.com/media/feed/large/EBTHUMX.jpg

A ground loop should only occur if the ground of both devices is not grounded to the same exact voltage ground point. Then the ground of your audio cable ( shield) between the devices has a small AC voltage drop across it which is the difference in the 2 ground potentials and this voltage induces a signal input on the amp and the result is 60 hz hum. This usually occurs when you are using 2 AC outlets that have a slight difference in their ground potential due to ( for instance) that one AC line has a much longer path back to the electrical box. This should not occur if everything is plugged into the same AC outlet ( via power strips).

 

If all this is OK, then you possibly have a problem in the power supply on the problematic keyboard. If youi have a good voltmeter, you can connect one end of the lead with it set to read AC volts, to the ground pin of your AC input strip and touch the ground of your audio out cable and the center conducter coming out of the keyboard. You should read zero AC volts on the most sensitive AC volt setting. If you don't, you have a problem in the keyboards power supply.

 

Do not use an adapter with the ground pin lifted as a permanent solution unless you don't mind seeing someone get electrocuted on one of your gigs..... ( I have seen that once and it is not pretty)

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You might try a direct box with a line lift to your PA. It could be that will break the 60 cycle hum.

Jimmy

 

Those are my principles, and if you don't like them... well, I have others. Groucho

NEW BAND CHECK THEM OUT

www.steveowensandsummertime.com

www.jimmyweaver.com

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no JF a Direct Dox will have 1@ 1/4" in and 1@ 1/4" out and 1@ XLR out. Plug the 1/4" cord from the keyboard out to the 1/4" IN on the direct box. Then run an XLR to the PA board. I find when I do this instead of long lines to the board I get less hum.

 

Check out your favorite online music store and do a seach. or check out below and do a search.

 

www.americanmusical.com

Jimmy

 

Those are my principles, and if you don't like them... well, I have others. Groucho

NEW BAND CHECK THEM OUT

www.steveowensandsummertime.com

www.jimmyweaver.com

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