MBP16 Hissing/Static when MagSafe + TB3 Power

[fakestrawberryflavor]

When my MBP16 is connected to both MagSafe and TB3 power at the same time, I get hissing/cracking out of the left side of the machine. Its faint, but I can notice it because the machine is dead silent otherwise. I have 2 LG5K TB3 monitors which provide power naturally (85w) and when 160w MagSafe is connected it sounds like there is a power feedback issue. If I disconnect MagSafe, the sound goes away. If I disconnect both TB3 connections and leave just MagSafe, the sound goes away.

I assumed I needed the MagSafe to provide the appropriate power, since the LG5Ks only provide 85w of power, but the machine seems to be charging and remaining charged just fine with them as the sole power source.

Anyone else having this issue, thoughts or comments?

Edit: both fans remain off regardless, using TG Pro to validate

 

[Sanpete]

Have you tried it with the TB3 cables connected but with the monitors unplugged so no power is delivered? One way to test whether it's a power thing for them or something else.

Only one port at a time is supposed to accept power.

 

[fakestrawberryflavor]

Wanted to update on this

Was the CalDigit TB3 Dock's power supply. Buzzes/crackles or makes a weird sound only when other power sources connected to the MBP. I own two of these docks and two power supplies, and both exhibit the same behavior.

This behavior does not exist when the docks are connected to my Razer Blade 15 2021, fwiw.

 

[wilberforce]

You might try using a ferrite core (bead).

"Ferrite beads are passive electronic components that can suppress high frequency signals on a power supply line. They are normally placed around a power/ground line pair that is incoming to a particular device, such as the power cord for your laptop."

Ferrite Core 1/2 Cord Noise Suppressor (2 Pack)

Black plastic enclosed ferrite core for 1/2" AC power cords. Easy to install, simply snap around cord. Helps reduce EMI on AC power lines. Cable core filter will provide common-mode filtering for multi-strand cables and differential mode filtering for single conductors. Dimensions: 1-5/16" L x 1-...

www.amazon.com

May need to wind with multiple loops