Krell S300i Volume Control Popping Noise

Recently purchased from a dealer, adjusting the volume control up or down makes a popping noise through the tweeter, which I can hear even with music playing. The dealer swapped for a different unit, which still pops, but not all the time. The old unit popped all the time. Not only is the pop annoying, it's a borderline concern for tweeter safety. I called Krell, long story short, was told that, yes, it pops. Speakers are JMlab Electra 915.1, and other equipment includes Musical Fidelity A308cr pre, power, and CD player, and Oppo BDP-83. Interconnects are Cardas, speaker wire is homemade, but also subbed in Monster Cable to no avail. In addition, I get more tweeter hiss with the Krell than through the Musical Fidelity gear. These quirks are not commensurate with my idea of a high-end product. I previously owned a Krell KAV 300iL, and do not recall having this issue. Thanks in advance.