That's good to hear, because I'm still looking for a dac/amp with variable line out Here is the ebay ad that I responded to:
http://www.ebay.com/itm/FIRE-PHOENIX-DAC-05-OPA2604-CS3310-CS4398-192K-24BIT-USB-DAC-Headphone-Amplifier-/380468008371
I asked the seller if 1) it was compatible with a USB 3.0 port on a late 2012 iMac, 2) if the volume knob controls the line out volume level and 3) the differences between the DAC-02 and DAC 05.
The response was that "1. the DAC are only USB 2.0 port", "2. DAC volume control is in earphone", and 3. the two DACs have different chips. I quoted a couple of passages from the reply because I thought I might be misunderstanding them. In any case, what I took away from the reply was that the DAC won''t work with my iMac's USB3 ports and the volume knob does not affect the volume of the line-out. Is that incorrect? Did you purchase from a different seller? I'd love for this unit to work on my iMac, because it's under my budget and the reviews sound great.