Hiss at addition in system LAMM L2


Hiss (noise) from speakers at addition in system LAMM L2.

Three weeks ago, I have bought preliminary amplifier L2 reference
Improvement in sounding all system was huge!!!! The overall dynamics and scale of the music!!!
Illusion of a presence(finding) in a concert hall has appeared.

But I am disturbed with the following:
At addition in system L2 strong enough noise (hiss) has appeared from
speakers. At inclusion of toggle-switch MUTE hissing disappears, at deenergizing
Toggle-switch MUTE all room is filled with noise (hiss).
Even at listening music on silent passes or piano music
Such noise level it is normal or L2 demands repair?
anton9005
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Prior to acquiring my L2 Ref I also auditioned the LL2 Deluxe and loved it. It bettered my Hovland HP-100 and did everything well. Funny enough it was as quiet as the Hovland and both were dead quiet as compared to the L2-Ref! The only reason I jumped on the L2-Ref was I thought (and maybe foolishly) it would be that much better than the LL2 deluxe which in my case it was not. Based on typical used prices IMHO the LL2 Deluxe is the darling of the Lamm line-up...
how could u possibly deal with a piece of equipment that introduces a hiss to your system? i dont care how good the soundstage is. i would junk it or sell it. it would be a good idea to let the poor potential buyer know about the issue.
Tvad , I am thinking about lowering the gain on my LL2 Deluxe
If you recall,how much gain in db did you reduce.
Many thanks
ed