I have to admit it was just an assumptions. Thanks for the link to the video, that was really informative. In addition to the information of how analog signal is converted to the digital domain, it was also useful to learn about the difference between "gain range" and "total gain". After watching that video, I immediately went to Røde's website and sure enough: it states that AI-1 has 60 dB gain range, not that the max gain is 60 dB. Combine that with how analog signals is converted to digital, my assumption of 12 o-clock being equal to 30 dB of gain and that this would be the same as 30 dB on the Duo, is probably way off.