A few further notes:
-what is the standard line out level of a balanced output? +4dBv or -10dBv? or can it be both?
As he said, it can be both. Whether one is standard sort of depends on what you mean by "standard." Balanced +4 dBu is certainly more common than balanced -10 dBV.
(Note the letters after "dB" -- they're different from yours, and that matters. dBV is voltage relative to 1 volt and dBu is voltage relative to .775 volts. Sometimes dBv is used to mean the same thing as dBu, but that's sufficiently confusing that it seems to have fallen into disfavor).
-what is the standard level of an unbalanced output?+4dBv or -10dBv? or can it be both?
Ditto. Unbalanced -10 dBV is more common and might be considered standard, if you have a somewhat loose definition of what "standard" means.
-what is the standard line in level on home stereo equipment?
Consumer line-level, or -10dbV (roughly)...
Yeah, that
is a standard.
-what is the standard line in level on nearfields?
Many nearfields have both -- all will have +4...
Of course a non-powered (passive) nearfield would want something considerably higher than either +4 or -10 (duh).
Passive nearfields ordinarily (maybe even always) have a volume/gain control. I would expect that nearly all of them would not be overloaded by a +4 dBu input in ordinary use, and that the range of gain available would be enough for ordinary use with either level of input. Theoretically, if it's a perfect linear amplifier, when turned up "all the way," you should get approximately 12 dB less SPL if your input is at -10 dBV. But: (i) the amplifier may start distorting unacceptably at about the same volume level either way and (ii) all of this is probably above the level you'd want for ordinary use.
-If I want to plug a dynamic microphone into the card, what type of line in do I need?
Depends on the sound card... you'd plug the mic to a mic pre, then connect the mic pre to the soundcard's line input.... whether that line-in is -10 or +4 depends on the soundcard...
Yes. Also, if the card has a mic preamp in it, you could plug in the mic, which is well below either -10 or +4.
-is it true that balanced connections allow for and increased by 16dB signal to go through, thus giving better signal to noise ratio for recording?
Not really -- given a properly-matched gain structure, there's no difference in headroom... the advantage of the higher gain structure is that the noise floor is significantly farther away from the signal level at +4 than it is at -10.
And given the same reference point, a +4 signal is 12.xx dB higher than a -10 signal.
11.786 dB, to be more precise. That's the difference between the two signal levels. Not 14, and not 16, in any event. Because +4 is referenced to .775 volts, which is 2.214 dB lower than 1 volt.
Signal level and balancing are different issues, and this is a place where people often get them confused.
Note that if you take a true differential balanced input and plug it into an unbalanced input (
i.e. ground one of the legs, or leave it disconnected), you throw away 1/2 of the signal's voltage: rather than receiving a signal equal to the difference between +[signal voltage] and -[signal voltage], the box that's getting the signal receives a signal equal to the difference between +[signal voltage] and ground. Cutting voltage in half is about a 6 dB reduction (6.0206, if you want to be a bit more precise).
Whether any of this has anything to do with signal to noise ratio depends on where the noise we're talking about is coming from.
If we're talking about noise in the signal coming out of the box producing the signal (
e.g. noise in the background, noise from the mic, noise from the mic preamp, noise from an EQ unit ...), the level of the line and whether it's balanced will have approximately no effect on the ratio between the signal and this noise.
If we're talking about noise that's induced into the signal while it's running through the cable, the ratio of the signal to this sort of noise would be improved both by having a higher signal level and by using a balanced line (for different reasons). However, in typical use (well-placed lines under 10 feet (say), and a recording environment that's not underneath a radio transmission tower or something), the noise induced into a line will probably be very slight -- way less than the noise that comes from other places in a typical "home studio" set up.
A higher level in a line will make the ratio of the signal to induced-in-the-cable noise higher, because the signal will be higher and the noise will be the same. A balanced line (if connected to a balanced input with a differential amplifier) will make the ratio of the signal to induced-in-the-cable noise higher, because of "common mode rejection:" noise induced into both legs will cancel out, at least to some degree.
-are balanced connections a real need for "pro-sound" recordings?
No.
-more generally, wich card among those I mentioned before would you go for, considering audio quality, latency and CPU usage, and wiring options?
I have no idea.
