I have a mono XLR PA system that works well with Shure dynamic mics. I'm needing to swap one out with a mic with greater pickup. When plugging this mic into the system, there is a buzz, and it gets louder when the mic is touched. I'm trying to understand why one dynamic mic would work with no buzz, but another has a loud buzz? Are microphones grounded internally in different ways? Should I be looking for a specific mic that would work with this system?
The phenomenom that is happening sounds indeed like a grounding issue and yes, some microphones are internally grounded differently than others.
One way to check if the microphone is properly grounded is to use an ohm multimeter and measure between the body of the microphone and pin 1 of the XLR connector. If it shows more than 0 ohms, then it might be a grounding issue. You can also troubleshoot using a different preamp or cable.
But there are even more other possibilites of interference like some wireless transmission, etc.
Does your PA System have a list of compatible mics? Are there mics that are known to be for sure compatible?
AKG has a chat customer support. If nothing helps I propose you can also ask them https://www.akg.com/support-contact.html