I bought a PT380 used a number of years ago. It has always made a lot of noise (sound). The output is quite stable and much better than the previous RPC I had, so on that front I'm happy.

The unit is loud. Fans are fine, but just idle, it sounds like bacon crackling and it makes a loud high frequency hum. This is annoying. Reading other comments, some have said their units make a noise like this and others have said they hear nothing. Tech support has been very responsive, but I am getting the impression that some units are just loud. "Why not consider selling that and upgrading to a newer unit?" Hmmm. It works properly and the noise isn't worth the $5k or so I would lose in that deal.

Has anyone tried to determine the source of the noise? I can try to poke at it a little closer once my new caps arrive, but I'm considering trying to apply some sound deadening on the non-temperature sensitive parts.

Any experience or other ideas?