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Power supplies and hum - 2 supplies now humming


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Hi all,
I've been a lurker on here and TB for years, and have enjoyed learning from the collective wisdom (despite my GAS being encouraged!)

I have a pedal board that is now giving mains hum when listening through headphones (in ears in church, and for testing I've been using my earwig headphone amp).

On diagnosing the fault I seem to have had 2 supplies both start humming - one for a DHA VT1 drive pedal (12V, 1250 mA), and the other from effectspowersupply for running tuner (ST200) and chorus (CE-2B). I also have a Carl Martin comp/limiter which runs off AC, and a an old silver Qtron+ which runs off its own 24V supply, both of which are still noise free. All supplies have been plugged into a 4 way extension at the top of the board.

I'm not aware of any power fluctuations, drinks spollages or problems that could have caused this, so wondered if anyone wiser than me could think of a possible reason? All pedals run hum free when tested individually with a Uniross regulated supply. I've separated signal and power lines.

I'm seriously having to consider dropping the VT1 and chorus at the moment just to get noise free. Chorus I can live without, but the VT1 is really nice for some subtle valve breakup.

If anyone has any thoughts or things to try I'd be most grateful, particularly if they don't involve spending 100s in new power options!

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[quote name='tayste_2000' timestamp='1332867233' post='1594202']
Check your instrument leads and patch leads, work it 1 cable at a time.

Thanks for the help. I've tried this. Hum only exists when PSUs mentioned above are applied to the pedal.

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[quote name='phil.i.stein' timestamp='1332871146' post='1594268']
quick experiment : if possible, plug the two into seperate sockets (i.e. try not running them off the same 4-way). any difference ?
Good idea. Alas, no difference. Swapping out either of the PSUs for an old Uniross one makes the hum go away. Time to spend some money on new power options methinks.

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