Original Post said:
Yes, that is pretty much exactly correct. That is: "the switch's labels refer to the level of the incoming signal." And, as well, it is the case thatl "moving the switch to the -10dBV position adjusts the gain to a setting that is more compatible with softer sound sources." At least once I edited the original post to change that little "u" to a big "V," which is the right symbol.
In particular, moving it to the -10dBV setting probably inserts (or increases the gain at) an amplification stage that affects the input before it goes on. If you look at the block diagram in your manual (I'd expect there is one for this type of gear), it should be reasonably clear what's going on.
Later Post said:
Anyways, which setting would I use?
The easy answer: use the one that works.
It sounds, from your description of what's happening, like the bluetube - whatever claims it may make - is incapable of amplifying the signal from your mic sufficiently to output a +4dBu signal without creating more noise than you like. This does seem a bit surprising: while it depends on the mic, most large diaphragm condensors have a relatively high output level. Whether it means the bluetube isn't usable depends on what use you're trying to put it to, I suppose.
Anyway, the main thing to keep in mind about -10dBV and +4dBu is that they're just levels. One's louder/hotter/higher than the other, that's all. There's no magical characteristic that's different between them. It's just that the +4dBu signal is about 12dB higher than the -10dBV.*
Quick comparison of two ways you could hook stuff up (for the purpose of explanation, using somewhat arbitrary dB figures for gain, though they're probably in the ballpark, and assuming I was right that the switch on the Digi input inserts a gain stage):
1) Crank up the bluetube, set the Digi input at +4: the mic signal comes into the bluetube, gets amplified by 50 dB (say), then goes into the Digi input and on to the Digi's circuitry, converted to digital, etc.
2) Turn down the bluetube a bit, set the Digi input at -10: the mic signal comes into the bluetube, gets amplified by 38 dB, then goes into the Digi input, gets amplified by another 12 dB, and goes on the Digi's circuitry, gets converted to digital, etc.
Basically, what you've done is partially substituted the amp on the Digi's line input for the bluetube's amp, by having the Digi input amp provide 12 dB of gain, and reducing the gain the bluetube is supplying by the same amount. If that produces a quieter signal, it's presumably because the Digi's amp is quieter, at least in this particular application.
The highjacker said:
Is it OK to lie to Miss Mia
Well, you're not actually lying. When you turned down the Focusrite preamp, you reduced the level of the output until it
was at (or in the vicinity of) -10dBV.
And anyway, if you were lying, I think Mia would find it refereshing, as she is probably more accustomed to having people lie by telling her what's entering her is bigger than it really is.
____
I know. You'd think it was 14 dB, but it's not ... because one has a "V" at the end and the other a "u." Anyway, that's a level of detail that's not important here.
