[Irwin]

I just picked up a NAD 3120 integrated amp. 4 to 5 seconds after the amp is turned on there is a tone burst that comes out of my speakers that goes right to left,and is gone in about a second.Other than this glitch the amp works perfectly.Is this a sign of trouble brewing,of should I learn to live with this minor annoyance?

[MaxCast]

I would take it back.

[Tonto Yoder]

Max,
the 3120 would probably be difficult to take back: it was manufactured in 1987 at the latest. Some second-hand dealers might offer 30 day warranties, but I'd guess it was an as-is sale.
http://207.228.230.231/info/NAD_3120.pdf

I'm not technically-minded, so I can't offer a diagnosis of the problem.
My recollection was that these great-sounding NAD's were prone to failure since they were built to a certain price-point and could only include a certain level of parts.