Burson Audio low level noise

I have a 160D has any one else experienced a low level hum/electronic hash noise? I can hear it about a foot or two away from the speaker. Is it normal in general to not have perfect silence?
Gentlemen, the cause for the hum is in the unit itself.
I will not publish it here due to legal restrictions, but it
can be changed by a repairman. Please send me an
email if you want a hum-free preamp.
sold it back to Burson and they gave me credit towards a Conductor. Its a way better unit.
It was an issue with the 160DS units. I bought one new when they released and within a year it had developed this noise. Hash is the right word for it, wasn't a ground hum. Bothered me enough to sell it onward. With any luck its been addressed in recent product revisions, the 160D/DS date back quite a few years now. I think they were Burson's first entry into this market.