on a rockboxed iriver unity gain is at 0dB gain for l+r channel IMHO.
I taped 2 shows with 0db gain with my high-sens 4060s, great result

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on my R09 gain was set to 13 when I first started a recording after unwrapping it from the box.
maybe 13 is the unity gain, am sure guysonic or others may contribute here.