Jungson JA88D mute function

Does anyone have any experience with the mute function of a Jungson JA88D integrated amp or any other Jungson product.
My Jungson JA88D mute function does not mute the entire signal when engaged. I am getting a very very minimal signal (volume level) through my speakers when I use the Mute function. It is not entirely silent. I have very efficient Altec speakers (100bd) and I am concerned as to whether I have a problem with the amp or if this is normal for the combination I have.
Please let me know?
thanks