HI there,
I have a Ring Pro V2 hardwired direct to the transformer (no existing doorbell & Pro power kit v3 installed) and a plug in chime. There is a constant buzz from the transformer. Is there a solution to this because it’s untenable to live with.
Thank you very much
Matt
Curious, why did you install the pro power kit v3 if you don’t have an existing doorbell? Ring Pro V2, while it is made for an existing doorbell system, if you don’t have the doorbell, you don’t need to install the power kit. The power kit is basically to keep the Ring Pro V2 running while the doorbell energizes the solenoid for the physical chimes based on the test I did. I’m going to hazard a guess that the hum is from the extra voltage level you have created because the solenoid it is meant for isn’t in circuit. Also you might want to make sure that under device settings for the Ring Pro V2 that you have the In-Home Chime setting turned off so it doesn’t try to send a signal to an non-existing device. Which may possibly cause a power issue with the Ring Pro itself (IE could burn it out way too soon).
Hi @user54914. When you say Pro V2, are you referring to a Video Doorbell Pro 2? If so, @Skull_One is correct on not needing to install the Pro Power Kit and should be removed when the Pro 2 is hardwired directly to a transformer.
Thank you both. Yes, I am referring to the Video doorbell Pro 2, apologies. I have removed the pro power kit and it’s wired directly to the transformer and yet it still buzzes unfortunately. Do you think it could be a faulty transformer? Trying to get this sorted before my wife calls an electrician, my ego won’t be able to cope! 
@user54914. Knowing if the transformer is defective because of its buzzing is out of my scope of support, but personally, I would replace it just in case before having to call an electrician. If the new transformer is buzzing just as loud, then I would have to recommend consulting a qualified electrician for further assistance.