First of all I would like to thank Firestone Audio for sending me these products to review.
Here are the pictures:
The USB isolator is a product I wasn’t expecting to change a great amount of audible sound, especially in a setup at my desk, which consists of my modded Denon AH-D2000, the DigiZoid ZO2 and an EHP-O2D. I was trying so hard, for such a long time to hear a difference, whilst using the EHP-O2D in DAC mode. No matter what I did, I couldn’t hear any difference whatsoever in sound. I tried different USB ports, both at the front and back of the PC and 2.0 and even 3.0 ports. I was just about to give up and say: “this product makes no difference”, until I turned on my DigiZoid ZO2 and decided to hook it up to the PC and charge it at the same time, whilst it was in operation. This is where I discovered a difference in sound with and without the GreenKey.