[BC] Audio levels

[Richard Fry]

> 0 dBu is 0.775 volts, no load reference.
>
> 0 dBv is 1 volt , no load reference.
____________

Presumably "0 dBu" means decibels w.r.t one microvolt.  By definition, a 
voltage of 0 dBu (0 dBµV, really) is one one-millionth of a volt, not 0.775 
volts.

A voltage of 0.775 volts across a 600 ohm load results in 1 milliwatt of 
power dissipation (0 dBmW), but that same voltage across a 50 ohm load 
results in 12 milliwatts of dissipation (~10.8 dBmW).  The load impedance 
at any given point in a circuit must be known to determine the energy level 
there.

One milliwatt of audio is a standard reference level used in the audio and 
broadcast industry, and 600 ohms is a typical impedance used in audio 
signal distribution.

RF