A logarithmic voltage reference point equal to 0.775 Vrms
The voltage relative 0 dBu. 0 dBu is defined as 0.775V, (e.g. 4 dBu = 1.228 V). /p /p
a means of expressing voltage, referenced so that 0 dBu equals 0.775 volts, regardless of impedance. 1 mW of power is dissipated if 0.775 volts is applied to a 600-ohm load, so when the load impedance is 600 ohms, 0 dBu = 0 dBm.
Decibel referenced to a microwatt.
dB unterminated. 0 dBu is a voltage reference point equal to 0.775Vrms. [This reference originally was labeled dBv (lower case) but was too often confused with dBV (upper case), so it was changed to dBu (for unterminated).] +4 dBu is a standard pro audio voltage reference level equal to 1.23Vrms. XLR and captive screw audio connectors are commonly used in this equipment.