Well made,
a bargain,
and it worked for me

none

I have two tube amps used in an active bi-amp system and both of them have (depending on time of day) a mechanical transformer buzzing sound. The fact that the buzz is variable leads me to suspect that DC voltage from the mains could be causing the transformers to rattle. I could measure DC from the wall, but I did not entirely trust what I was reading. In my case, the mechanical buzz (or hum) was also partly induced into the audio signal. This was obvious because of the mechanical noise intensity changed with the buzz through the speakers. In the worst periods, the transformers could be heard several feet away, while the sound through the speakers was only noticeable at 1-3 feet. Although this goes against the normal understanding of mechanical vs. audio signal hum, I believe the vibration caused by the transformers was creating a microphonic effect on the tubes via the chassis. In any case, inserting the Channel Islands Audio XDC•2 greatly reduced both the mechanical and through the speaker hum to the point where it is no longer a concern. As a bonus both the mid / high and bass amplifiers have gained more definition with no loss of dynamics. The XDC is placed between the Shunyata Hydra 4 and the amplifiers.

Customer Service

great phone support