[LAU] Hum pickup in DI boxes

Bill Purvis bill at billp.org
Tue Jun 8 13:43:27 CEST 2021

Not strictly a Linux problem, but I hope for advice.

We're using a Behringer X32-Rack mixer for our church PA system. One of 
the inputs that we need is
for people to plug in laptops - usually via the headphone socket into a 
Stagg dual DI box. We seem
to get a lot of hum pickup on that, which I think is down to the 
proximity to the laptops. We have
another identical DI box at the other end of the room which takes 
keyboard and bass and I've had no
problems with that. Is there an alternative method we can try? We do 
raise the ground lift switch on
the DI box, which reduces the hum somewhat but still get enough hum to 
be noticeable when nothing
else is playing. I wondered if the matching transformers in the DI box 
are acting as pickups for the
RF noise generated by the laptops. The mixer on EQ display with RTA 
shows noise across the audible
spectrum, but most of the audible sound is mains hum.


| Bill Purvis                            |
| email: bill at billp.org                  |

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