Hi guys,
I also tried once the Fender Mustang IV which sounds really good. However, I got one that came with that buzzy digital sound during the phase when the tone is dying. This was very annoying and I sent it back. Later I have seen in the internet that many people talk about this buzz/hum issue. It is obviously specific for Mustang III and IV and may come from the power amp. I have no clue what the real reason is. Do you have this problem with your Mustang III?
Cheers
Sacapuntas