Noise coming from tweeter when amp get turned on

Have you tried disconnecting the preamp from the power amp. Leaving the power amp on & only the power amp, do you still get this low level hiss?

I once asked this question from, Bob Cordell of Cordell Audio at www.cordellaudio.com.

Here is his answer.

"The hiss you hear is the natural noise of the power amplifier. All electronic cicuits make noise, some more than others. When you put your ear to the tweeter, that is a very sensitive test for noise, especially if your speakers are sensitive speakers. It does not mean that there is anything wrong with your amplifier, especially if you hear about the same amount of noise coming from both the left and right speakers"

I hear the same "white noise" with my setup (Bryston B60R, Triangle Heliade ES). I can also hear it through the midrange, although at a lower level. I have noticed the same sort of hiss with previous audio systems, and it is only apparent when I put my ear next to the speaker, so I don't worry too much about it.

That said, you might try separating your cables from your power cords to be sure your not picking up emf noise.

The hiss is normal and ought be identical from both tweeters. It is one indication that the tweeters are working. It may not be a good idea to advance the volume beyond normal listening levels to perform the test.