Hi All,

I have a query about an amplifier I have just acquired, a second hand Roland Cube X20 . It’s in really good condition and all it’s features work fine but when I plug in the jack, before it’s connected to the guitar, I get a distinct hum. This almost disappears when I hold the the other end of the lead - except if I touch the jack tip – then it really screams.

The hum also almost disappears if I touch any metal part of the amp.

When it’s connected to the guitar the hum is still there but not so obvious when it’s being played.

I don’t know much about amps or electronics but I feel that the amp may have an earthing issue. Then again, it might be quite normal. This is my first experience with an amp so I really wouldn’t know.

Any help/suggestions would be greatly appreciated


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Last time I had a similar problem like this, I went through all the grounds first. Meaning, the first ground was the output jack on the guitar. That fixed one situation. The next problem was the cord, I resoldered both plug heads on the cord I was using. And then the third problem was actually a wall Sounder joint on one of the points. If your shop has a chip in it, the chip might be bad. But going over all the grounds is the first step I have found, in most cases if the problem. It takes time to find to weak connection. Good luck

Easy steps first .  You may get alot of suggestions here ,  some involving taking the amp apart etc .. before you  try any of this , try plugging it into a different location in the house .(or extension cord to another outlet) many things can effect the amp . including  lighting and other outside influence .  a simple relocation may  be all it needs . 

Yes pick, all amps made in the last 30yrs are specifically made to not have grounding issues. with that said, check the obvious: Guitar wiring-pickups,switches,pots&output jack. Also check your cable, this is why people spend too much on cables-less money- problems, more money-less problems, cheap or failing cables make lots of noise! unscrew the ends & see if the wire has breaks- this is usually the cause? Check the outlet you are using- it may have a ground problem, this is why I always use a quality power strip & never straight in the outlet (pro tip) Lighting ballasts also make noise. Good luck, it doesn’t sound like you’ll need to take that amp apart, that’s a bad idea if you don’t know what you’re doing & could end up costing you to get it fixed? 

Since it's making a good bit of racket before the guitar is plugged in, I think your problem is the cord or amp jack being loose or bad ground connection at the jack. It's not uncommon to get a little noise in tube amps, but solid state shouldn't have that problem. So if the amp's jack is tight, try another cord before doing anything else.

Many thanks to all for their suggestions.   Yes, it was the cord.   A quick solder job and all is fine.


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