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High pitched hum coming from amp... HELP!!! :)


binky_bass
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Hey guys,

I've just recently aquired a mighty Orange AD200 MK3 rig with matching Orange 4x10 and 1x15 from one of our brothers here on BC :)

The rig works 100% fine, its a real beaut, but when I hook up my pedal board I get a slight High pitched hum, the more I increase the gain or volume, the louder it gets, and as soon as I switch on the limiter pedal, or the distortion pedal, the hum is amplified 10 fold, making it impossible to play at any volume.

I would REALLY appreciate some advise on how to get rid of this noise, so I'm just left with a noiseless signal flow.

Here's how its set up, just incase I've done something stupid... (possible!)

The head has 2 4ohm outs which are running to each of the cabs, the power cable is plugged into a 4 point extension lead. The "active" input on the amp goes to a limiter pedal, then a DD-20, then a power brick (quite a chepa one) then a polytune, then an Ibanez Phat head, then a SouceAudio flanger, then a cyborg reverb, then a Boss SYB-5, then a roland expression pedal, then an Ernie Ball jr volume pedal and finally a Morley Bass Wah II (the morley is the only thing powered by a seperate powerbrick)

Both power bricks plug into a 2 point extention cable, attached to the board, so that I can the power EVERYTHING with just one plug. That plug is then plugged into the same 4 point extension as the amp itself.

The board does have a solid a good signal flow with reasonable patch cables that I've used before with no hum. I have coiled up both the power brick leads and the expression pedal lead to save space and prevent tangles, which I've heard... MAY produce feedback?

If anyone knows there stuff and is local (Wickford, Essex) then they would be very welcome to help me out with this issue, I can provide all the tea you want complete with bourbons and you'd be very welcome to try you hand at any of my basses. (see signature!)

I'm hoping one of you tech geniuses can help me deal with this as all the gear is amazing to play with but this hum just spoils it! :(

Thanks, Russ.

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Hey, thanks for your responses! Yes the cab has a tweeter, could that be effected by some issue on the board?

OBBM: cheers, I'll try and see if I can single out the problem by running the chain one by one until the issue occurs, if that fails, I'll message back in here! :)

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You could try powering the pedals from batteries temporarily to see if the power brick is causing the problem.

If you don't get the noise when using batteries then that narrows down the issue. If you still get the noise on batteries then you can rule out the power brick as the source of the noise.

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I've got half a day off tomoz (birthday :) ) so before celebrate I'll be pulling apart the board.

I have a suspicion that the problem may lie within the patch cables or power supply...

If I find the problem, I'll post the solution!

Russ.

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It could be an earth problem or a rf (radio frequency where some of your gear is picking up radio frequency noise and another part is rectifying it and turning it into audio) problem. Just about every electrical device emits small amounts of rf noise and we are surrounded by a sea of (usually) invisible radio noise.

Without hearing it, and sometimes even then, it can be difficult to diagnose. Since you have changed the amp it may just be that, your fx may have been picking up or radiating rf before but this amp picks it up and the previous one didn't. It may even be that the rf source is nothing to do with your rig but the new rig is receiving those frequencies and the old one didn't. Do you still get the same noise in other rooms/buildings?

Work logically. Run everything off batteries if the noise goes then it will be the power supplies. It could be an earth problem or one of them radiating rf.

Try using only one fx at a time. You may find the culprit that way but it could be an interaction between a combination of two or three of them. If that doesn't find the problem then connect them all up and remove one at a time. Reconnect each and remove the next link in the fx chain. If you find the fault then don't forget it might be the box but it could be a connection in the lead to that box.

If it only occurs when everything is plugged in then it might be one fx is causing another to go unstable and oscillate. You do have a lot of fx. chaining them in a different order sometimes cures the problem.

Remember it may not be the new amp. Just because you bought an amp it doesn't necessarily mean your other stuff didn't break that night. The amp may just be more sensitive to noise or it may be radiating rf which is being picked up by one of the fx.

Good Luck.

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Right...

After well over am hour of trying different combinations of different pedals and power supplies I have found the problem....

I have a US made Rocktron Cyborg reverb, and on it's own itsnot at fault, but whenever I power it with a power brick and any other pedal is also plugged into the same power brick, I get the high pitched hum... The more pedals I run along side the reverb in the same power brick, the louder the noise.

So, I am now about to try and arrange my board withthe reverb powered alone and not with any other pedal...

Fingers crossed.

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Trouble shooting this issue was easier with your help guys, so thanks! Everything is quite as a mouse now :) indeed, a decent supply is in order, though currently I'm far to poor for such things, though for the future, which is the best power supply? I have 10 pedals to power...

Russ.

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[quote name='binky_bass' timestamp='1332950593' post='1595419']
Trouble shooting this issue was easier with your help guys, so thanks! Everything is quite as a mouse now :) indeed, a decent supply is in order, though currently I'm far to poor for such things, though for the future, which is the best power supply? I have 10 pedals to power...

Russ.
[/quote]

Check all the pedals for their power draw, in some sort of subdivision of amps, digital ones need much more power than simple analogue ones. Total it up, and ad some headroom, and that tells you how much of a power supply you will need.

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[quote name='binky_bass' timestamp='1332950593' post='1595419']
Trouble shooting this issue was easier with your help guys, so thanks! Everything is quite as a mouse now :) indeed, a decent supply is in order, though currently I'm far to poor for such things, though for the future, which is the best power supply? I have 10 pedals to power...

Russ.
[/quote]

Just upgrading the power supply won't necessarily sort that, that particular needs an isolated supply. Personally I'd just buy the Diago Isolator cable or Gigrig virtual battery so it can still be daisy chained.

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