I have just bought a new NAD C355BEE. I was suprised from the start that there was a slight hum from the transformer - not much, but audiable and annoying. I expected to be dead quiet. Has anybody else some experience with that problem, maybe also with other amplifiers?
Tcch, if there's a hum, they'll swap it out. I assume you mean from the amp, not through the speakers. Just a loose winding which can happen in toroidal transformers. We've seen it with many manufacturers. It's pretty rare on an NAD, but it happens.
Anything with a large transformer is susceptible to mains borne noise in the form of hum. True, some large transformers hum more than others, but in the end, if the mains is bad then the chances are your transformer will hum. This is true of any component irrespective of price.
By all means swap out the NAD, find something else, but this is the way of things.
An update: I tried to swap the amplifier. In the store, the salesman connected it: the hum was even bigger there. Then he connected a new fresh open C355BEE - the same hum there as well. On the other hand, I didn't hear any hum from different equipment in the store - including some other NAD high power product.
So I had to return it. And I am sorry for that, because otherwise I really liked the amp. To bad NAD was not careful enough about this relatively straightforward detail, because I would be more than happy to pay additional money for a higher quality transformer with this package.
Interesting. We haven't had any issues at all with this piece. No noise, no hum, not at the store, not reported by customers. I'll look at it more carefully, but maybe there was a bad batch of transformers? How loud are we talking? From what I understand, physical hums are the result of a winding breaking loose from the epoxy. This seems to be more common with toroids for some reason, but has remained quite rare for us with NAD. When we sold B&K, it was a common and annoying hassle.
How loud are we talking? - Hard question. I was able to hear it from 3m in my quiet room. In the store I was able to hear it when I was close to the amplifier. But more importantly: I did't hear anything from other amplifiers in the store (and some other stores).
I belive NAD can do better, and probably they will do better in the next round of production. I guess I am just unlucky.