# dBV and dBu

Discussion in 'Wiki' started by mbenonis, Aug 31, 2008.

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dBV is a type of decibel measurement, referenced to one Volt (V). dBu is also a type of decibel measurement, referenced to 0.775V. Measurements in dBV and dBu can be converted to and from Volts and each other, but not power or current without knowledge of the load impedance (see Ohm's Law).

To convert a value x, in Volts, to a value, y, in dBV:
y = 20 * log_10(x / 1)

To convert a value y, in dBV, to a value x, in Volts:
x = 10^(y / 20)

To convert a value x, in Volts, to a value, y, in dBu:
y = 20 * log_10(x / 0.775)

To convert a value y, in dBu, to a value x, in Volts:
x = 0.775 * 10^(y / 20)

To convert a value x, in dBu, to a value, y, in dBV:
v = 0.775 * 10^(y / 20) [Convert dBu to Volts]
y = 20 * log_10(v / 1) [Convert Volts to dBV]

To convert a value y, in dBV, to a value x, in dBu:
v = 10^(y / 20) [Convert dBV to Volts]
y = 20 * log_10(v / 0.775) [Convert Volts to dBu]

Common Values:
-10 dBV is 0.316V, or 316 mV.
+4 dBu is 1.228V.
The difference, in dB, between +4 dBu and -10 dBv is -11.78 dB, or about -12 dB.
These values can be derived with the equations above.