So since I haven't been able to go through a full project with the FF800 due to some driver issues I have been testing my gain going in and out through my API 2500 so hopefully when this is all resolved I'll at least have my equipment calibrated.  Things have been appearing awfully weird on the meters.  It seemed I was having to push levels really hot into the API.  There were times when I was having to mash down on the threshold almost full on just to get 3-4dB of reduction which seemed odd to me considering RME is supposedly -15dBFS = +4dB = 0VU.

So I am running a -15dBFS 1 kHz test tone through to see what's up.  With the RME Ins and Outs set to +4dBu (which I thought was pretty much the standard) the API VU meter In and Out is showing -6VU.  I was under the impression this should be reading 0VU. given that RME is -15dBFS = +4dB = 0VU. 

So just for shits since the RME has 3 options for I/O (-10dBV, +4dBu, and HI GAIN) I tried the high gain setting.  Now the -15 test tone is reading on the API meters as 0VU.

So what does this mean?  Is something screwed up on my system/interface.  Again the issue is that I though with typical line level +4 ins and outs I should be getting to 0VU at -15dBFS whereas using the +4 option gets me a reading of -6VU not 0VU and the "HIGH GAIN" setting is what actually gets me to 0VU.

Any clarification would be awesome.  Thanks guys.