Audio Level Converter

0.7746 volts RMS is the voltage that delivers exactly 1 milliwatt of power into a 600-ohm load, which was the standard telephone-line impedance audio equipment was originally designed to match. The unit predates modern high-impedance line-level gear by decades, but the reference voltage stuck as the professional audio standard even though most modern equipment no longer actually uses 600-ohm loads.

The crossover happens at about +2.218 dBu, which is the fixed offset between the two scales -- below that level, a signal reads as a negative number of dBV, and above it, the dBV figure turns positive. This offset exists because dBu and dBV reference two different voltages (0.7746V and 1V respectively), so the two scales never fully agree except at that single crossing point.

dBu and dBV are both analog units tied to a real, fixed voltage, so a given dBu or dBV reading means the same physical signal strength everywhere. dBFS measures a digital signal's level relative to the loudest value a digital system can represent without clipping, and that ceiling has no fixed real-world voltage behind it -- the mapping between an analog dBu level and a digital dBFS level depends entirely on the analog-to-digital converter's own alignment, which is why this calculator's dBFS output assumes one common but not universal convention.

Consumer line level is commonly -10 dBV, roughly equivalent to about 0.316 volts RMS, while professional line level at +4 dBu works out to roughly 1.228 volts RMS -- nearly four times the voltage. That gap is why connecting consumer and professional gear directly, without a level-matching pad or preamp, typically produces either a weak, noisy signal or an overloaded, distorted one.