Can someone please explain these terms to me? From what I understand, these are simply the LEVELs that a particular piece of gear is optimized to perform at (+4 dBu being at a much louder signal level than -10 dBV <- Is this correct?) . The only thing is, I always see something like "+4 dBu is used for PROFESSIONAL gear and -10 dBV is used for CONSUMER gear." I would like to assume that I have professional equipment ($$), but how does one KNOW this. Also, there is sometimes a switch that will allow you to go between these settings. Lets say the switch is set at -10dBVs. Does that mean that this switch modifies the INPUT level AS WELL as the OUTPUT level for -10dBVs, or does this switch just controll the OUTPUT level of the signal. Though I'm not sure if this applies to the above, but I've also heard of putting a pure sinewave (say 1 KHz) into an input to get an optimum level. Any info on this as well would be much appreciative.