Need a few more pieces of the puzzle from you.
1.) Are you listening with IEM's?
2.) Are you using a power cord extension? Are you using an adapter for your headphones?
3.) Can you run a cable from one of the screws on the Burson Fun to your source ( DAC or PC in most cases?)
4.) If you wait 2-5 minutes with it on does the buzz go away?
5.) Try shielding RCA cables like these:
https://www.amazon.com/FosPower-Ste...d=1580942894&s=audio-video-accessories&sr=1-7
6.) Turn it off wait 20s, turn it on wait 2 minutes. Do this 3 times. Does the noise go away?
7.) With it on and buzzing gently rotate / spin the barrel of the power supply connector that goes into the Fun. Does the noise go away?
8.) There is a pretty good chance your filter caps for the mains hum have lifted off the PCB and thus no longer have contact. Can you power off the unit, wait 30s, and unplug it. Remove the PCB and take a side-profile picture of the caps. Much like in this thread:
https://www.head-fi.org/threads/burson-audio-fun-2w-pc-class-a-headphone-amp.881515/page-11
Here is the pic I'm talking about. See how the caps have pulled up? That may be your issue as well.
From another thread:
"When I asked Burson about the noise issue they said it was an effect of the Max Current Power Supply. It has a hum around 60hz when powered on that gets pushed up to 170khz as it warms up making the noise go away. Its interesting that some people dont have the hum at all, perhaps it depends on the electrical setup in your home rather you get it or not. I didnt have the hum with the Play when I had it, only the Fun had it."
Another thread response and fix:
"
raoultrifan said:
I wonder if with no inputs connected and volume to the min. the same noise is still present. If not, try increasing the volume (no input source connected) and see if noise appears.
If still noise, perhaps a new PSU might help? Maybe a computer desktop +12V to try out?
It's odd because I have absolutely no noise with FUN nor with BANG. Fan tested with 100dB sensitive 18 Ohms IEMs, BANG tested with 90dB/mw/1m speakers.
I've received replacement PCB from Burson and now my FUN works as it should.
Old PCB definitely had some contact/ground issues as the AMP was working well if you were lucky enough to eliminate the noise with switching it off and on in addition to PSU barrell roll."
