Wei Liang Yap Posted June 30 Share Posted June 30 If my active DI box picks up a humming noise when I put my hand near/on it, and also seems to function like a microphone (it sends a noise when I knock it),... is it time to bin it? I had a look inside - the capacitors look ok, and measure correctly (with a capacitance meter). (I was wondering whether to replace the caps). Thanks in advance Link to comment Share on other sites More sharing options...
John Vere Posted July 1 Share Posted July 1 It would be useful to know the brand and model. I’m assuming that it runs on Phantom power. If it has a battery option try that. I’ll also assume you tried a few different cables. Link to comment Share on other sites More sharing options...
Wei Liang Yap Posted July 1 Author Share Posted July 1 Thanks. It is a Behringer Ultra DI. Same problem regardless of phantom power or battery. However after I cleaned the contacts in the jack inputs (the input and the link out) - the problem seemed to improve a lot. I don't understand why though. Link to comment Share on other sites More sharing options...
Glenn Stanton Posted July 2 Share Posted July 2 loose contacts. solder joints inside which may have deteriorated over time. Link to comment Share on other sites More sharing options...
mettelus Posted July 2 Share Posted July 2 (edited) On 6/30/2024 at 10:06 AM, Wei Liang Yap said: DI box picks up a humming noise when I put my hand near/on it Are you working in a carpeted or dry environment? People actually generate voltage on their own which leads to a phenomenon called electro-static discharge (ESD)... the same thing as getting zapped on a door knob in winter when walking across carpets. Definitely check contacts and solder joints, but a quick test would be to ground yourself to your computer chassis (or anything metal in the same circuit) and see if that hum goes away. If it does, a grounding strap for yourself may mitigate that greatly... they are a pain in some ways, but you can also put them on your ankle (rather than wrist) to be effective... they just need to touch skin to work. If you can make it hum getting near it, ESD would be my first concern; but since you can also get a thump kicking it, that leans very heavily toward a bad contact or cold solder joint... can you see any cracks on the solder joints in the unit (including the wires to the jacks)? Edited July 2 by mettelus Link to comment Share on other sites More sharing options...
Glenn Stanton Posted July 2 Share Posted July 2 completely safe as well... Link to comment Share on other sites More sharing options...
Wei Liang Yap Posted July 3 Author Share Posted July 3 Thank you everyone. On this occasion the solution was cleaning the contacts on the jack inputs (the unbalanced side of the DI box). On stage, swapping to a different DI box resolved the problem at the time - so I do not think it was static. Prior to fixing it, the problem was reproducible in a different environment (my house). Link to comment Share on other sites More sharing options...
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