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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

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.

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anonymous Sun, 07/04/2004 - 19:28

Consumer/professional are just tags really. Those are different scales too and you should be aware of that, +4 is a little higher level, but not much. Remember db scale is all about reference. In +4 dbu gear the optimal operating level corresponds to 1.x volts or so (sorry I don't remember exactly), while in -10dbV, the optimal level is less. Very old gear used to be all -10dbV, but then +4dbu emerged as a standard. It doesn't really have to do much with being pro or con really. Good +4dbu gear sometimes has more headroom though, but that is also related to its design. Also, +4dbu gear has balanced connections, while -10dbV gear has unbalanced, though this is not a rule per se.
When you set your interface or whatever to -10dbV, you're just "optimizing" it for operation with other -10dbV gear. That is all.

The sine thing is just about callibration. As all things audio, a system needs to be calibrated (or referenced to some standard) for optimal operation. Optimal operation meaning getting the best out of a system, taking in consideration the noise floor of the system, and also the hottest signal it can handle (aka dynamic range). So this means for ex, if you're using a digital system, you have to reference 0 VU to something, for ex, -18 dbfs, -20 dbfs, or so.
Hope this helps.