I recently purchased a brand new Boss Katana 100 watt head which includes a 5 in. speaker in the front for practice purposes. I have not been using it with a cab since I cannot fit one (nor do I need one) in my dorm room. I only use a cab at rehearsals with my band.

I have noticed that the 5 in. speaker included in the amp head is making a very prominent and annoying buzzing sound which becomes louder as notes decay. I  have ruled out the noise being caused by my guitar or any pedals. My whole rig sounds fine when used with a different amp.

I was wondering if anyone else has experienced this. Since the Katana line is still relatively new, there is not much information out there about troubleshooting the amps. 
winter994 I have the boss katana 50 and I'm having the same problem that you describe. I always use the amp at 5 watt and the problem begin after I played some backing tracks through the aux input.
I would contact Roland directly, describing in full detail what you're setup is and how you're using it. Explain the conditions when the buzzing does occur and the conditions when it doesn't occur. Giving the conditions for when it doesn't occur will help greatly with isolating the cause of the fault.
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