From https://singularsound.com/product/beatbuddy : " What kind of power supply can I use with the BeatBuddy?
The BeatBuddy and the MINI 2 are compatible with any adapter that meets these specs: 9 volt, center negative, and a minimum of 300 mA. Do NOT use an adapter with higher voltage, otherwise you will fry your BeatBuddy and the warranty does not cover that!
I might be wrong but I always thought this sort of noise issue was common when sharing power supply between pedals, especially when a digital pedal is in the mix
Avoiding Digital Noise
If you’re powering pedals with a non-isolated power supply, noise can creep into your signal. You can experience digital noise in your audio if you are using digital pedals that are being powered along with other pedals by a power supply that does not have isolated outputs to power each pedal.
I am just using a power supply Strymon Zuma. My BB is plugged in there, but then it goes with 2 jack cables plugged into the Left Right outputs to the mixer so it sounds stereo. This parasitic noise occurs when the BB changes from one song to another, even when it already has the new song charged continues to do so for a moment.