An analog audio connection intended for connecting interconnecting audio equipment, and without the amplification required to connect to speakers.
Professional devices use dBu as the unit for signal level.
0 dBu = 0.775 Volts
The levels of professional devices are usually calibrated as +4 dBu.
+4 dBU = 1.228 Volts
The situation is slightly different for semi-professional and home devices. In this type of devices, dBV is used as the unit for signal height.
0 dBV = 1 Volt
Although it is not a rule, -10 dBV is generally used as reference level in semi-professional and home appliances.
-10 dBV = 0.316 Volts
Accordingly, there is a difference of 11.79 dB between the reference levels of professional and semi-professional/home devices. When these two different types of devices are connected to each other, there are inconsistencies in the levels due to the voltage differences between the reference levels.