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Help - Scratch/Hum from Alesis Keys amp


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Hello all.


Ok, so I've had this alesis sumo 300 amp for about 7 or 8 months now. I got back from a gig last night & hooked up the rig here. Now, whenever I play above a certain level (this also happens if I hold the sus pedal down for a while) the sound rapidly gets scratchier and scratchier until it deteriorates into just total staticy hiss, at which the amp emits a deep hum. I'm at a total loss to explain why it's doing this, but it's only when I use headphones. Unfortunately, I have to use headphones exclusively out of respect for my parents, and cause of the fact that I usually play more at night. Does anyone know what can cause this? I REALLY don't want to have to replace my whole amp. Any suggestions? Thanks.

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How long is the warranty? You may be better off just replacing it than dealing with the downtime of waiting to get it repaired. If you bought it at a reputable dealer, they may even just swap it out for a new one.

Stephen Fortner

Principal, Fortner Media

Former Editor in Chief, Keyboard Magazine

Digital Piano Consultant, Piano Buyer Magazine


Industry affiliations: Antares, Arturia, Giles Communications, MS Media, Polyverse



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This might be a dumb remark (and I've been known to make them from time to time), are you 100 percent certain the problem is with the amp and not with the keyboard or even the mixer?


I say that because I had a problem years ago and I sent a piece of equipment to the US and I learned the problem was elsewhere. Boy did I feel dumb.


If the problem is in fact with the amp, it should be under warranty and as Stephen Fortner remarked, the store might even swap one with you. They also might give you a loaner until yours come back from the shop. Repairs from major companies are very fast. I dropped off (here in Holland) my QSC for repairs (outside of warranty) and had it back within two weeks or so.


Report back after all of this has been resolved. I always like to hear how things turn out.

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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There's a cat caught in the back. ;)


Are you sure its the amp and not your board or youor headphones? If you connect the headphones to the board does it go away.


I would start by trying another pair of headphones, then I would try those headphones on the headphone out from your board.


Also, substitute the cables between your board and the amp and, if there is any other gear between your board and the amp, remove it.


I am guessing that at the moment you have never tried the amp without headphones when the problem is occuring and that it would be incovenient to do that so subbing headphones is the next option. If I understand correctly, you don't actually know at the moment that the problem only occurs with headphones.


If my guess of what is wrong is correct ( a bad power cap), you should get the same problem without headphones (unless the headphone amp has its own Vcc, which is unlikely on an economy amp.)

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