dBV

dBV is a unit of electric voltage level expressed in decibels with reference to 1 volt. It is commonly used in audio and electronics to describe the amplitude of voltages in signal paths, particularly for line-level signals and gain stages.

The formal definition is dBV = 20 log10(V_RMS / 1 V), where V_RMS is the root-mean-square voltage in volts. The inverse relationship is V_RMS = 10^(dBV / 20) volts. Because the reference is 1 V, every 20 dB step corresponds to a tenfold change in voltage.

Examples illustrate the scale: 0 dBV equals 1.0 V RMS; -10 dBV is about 0.316 V RMS; -20 dBV is about 0.1 V RMS; +4 dBV is about 1.585 V RMS. These values reflect a voltage-only scale and do not directly convey loudness, which depends on frequency response and impedance as well as the device.

dBV is often contrasted with dBu, another common audio reference. dBu uses a reference of 0.775 V RMS, so 0 dBV is roughly +2.2 dBu. As a result, equipment ratings expressed in dBV may differ numerically from those in dBu even when representing similar signal levels.

In practice, dBV is used to specify and compare signal voltages in analog audio gear, from mixers and preamps to amplifiers. Measurements assume RMS voltage; converting from peak values requires division by the square root of two.