[LAU] Hum pickup in DI boxes

Brandon Hale bthaleproductions at gmail.com
Tue Jun 8 14:21:20 CEST 2021


Have you tried plugging in the laptop without the DI in between? I think 
laptop outputs are balanced, low-impedance, so you shouldn't need the DI 
in between. Even if this is not true, it's at least worth a shot.

Brandon Hale

On 6/8/21 7:43 AM, Bill Purvis wrote:
> 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

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