Much more noise. The sort of noises that tells you where the recording was made and who stood where. The good kind of noise.
I added a fourth PS Audio Noise Harvester.
For years I thought no matter what I did to the system and the room I would always ultimately hear the vague outlines of my room imposing itself on the recording. With these in place, my room consistently dispappears and the venue comes forth. Amazing! I've heard numerous AC products and these are IMO special.
These were added to two PS Audio Duets - one for the front end and one for the monoblocks - with the NH's making a more substantial improvement for the dollar spent than did the Duets on sale.
The dynamics of my tube amps remained if not improved and the Duets are mandatory gear down here in Tornado Alley.
I would highly recommend the current PS Audio line of AC products. Not an ad, just a recommendation for something I tried and feel strongly about. In this case the fourth NH is plugged into an outlet in a room adjacent to the music system. The benefit to the system surprised me more than I thought it might.
I can think of few instances where I would not expect the NH's to be obviously beneficial.
You can find three for under $200 most anywhere.
Bang for the buck: 5+