Audio Signals

[gaz7224]

Hi,

I'm not clear in my mind about the different signal levels and the part 'ohms' play.

Is it right that unbalanced line level signals are -10db, and balanced line level signals are +4db?  I think this is because balanced lines contain two signals.

Microphone level is something like -60db to -30db I think?

How does impedance effect signal level?  Mic level lines from condenser mics can travel long distances because they're low impedance, is that right?  But what about balanced line level signals? Are they still low impedance, even though they're +4db?  Or is the length of balanced line level leads reduced because they're +4db?  This is the bit I'm confused about.   If the fact that mic signals are low (-60db) allow them to be sent over long distances, then does that mean that balanced line level signals, which are higher (+4), can't be sent over such long distances? Or doesn't it matter - any balanced signal can be sent over long distances, regardless of how loud the signal is due to the noise cancelling effects of balanced audio lines?

Thanks,
Gaz

[stainless]

here's a somewhat technical answer I found on the web 

Z is impedence, or in other words the electrical resistance property of the amplifier inputs/outputs. Impedence, restricts the flow of the electrical current. Z = V/I. Whereby V = voltage and I = current.. A high Z will give you a high voltage and a low current.
Hi Z means high impedence. It is used mainly as inputs. Lo Z means low impedence.
If you connect a low impedence output to a high impedence input, you would get a lower voltage at your output end.
Vout = Zout/Zin x Vin.
If Zout = low, and Zin = high, you would get a lower ratio of voltage.
This are the basic ohms law.
To get the least noise and best efficient power on your amplifier, impedence matching is a must. It avoids, the reflective waves (Electro magnetic wave) which reduces the so called ringing effect seen on the electrical voltage which induces noises.
I hope that helps.

balanced lines consist of a +, -, and shield/ground, whereas an unbalanced line is just  2 conductors a + and a -. unbalanced are typically hi-Z and the signal deteriorates with long cable runs... and they can be potentially noisy.  Low Z can have long runs before signal degradation becomes an issue (hence stage 'snakes' are commonly 100')

unless it's not an option, use low-Z balanced cables whenever you can. Most 'modern audio gear excluding  guitar and bass amps have balanced inputs/outputs,