that iron is made in Chicago by Marvel. it's a quality piece. I've used that exact model with no problems. nice and quiet.
the only time I've had really excessive PSU noise there was a problem with the amp dumping current and the transformer was growling because it was angry about that. i once had a Crown DC300-type amp that snarled so badly that it would walk across the bench at power-on. it turned out that someone else had driven a chassis screw into one of the big psu caps. fixing that problem made everything behave normally. you might want to check current and compare the transformers regulation specs to your in-circuit measurements. sometimes you can get hum when a tranny is underloaded or overloaded.