Black Frog

What's the +4/-10 button do on some gear? That "+4 -10" button changes the nominal operating level between the two standards. This nominal level is what is referenced to "0dB" on the meters. Since 0dB is an arbitrary point, there needs to be a reference as to what zero actually will be for further measurements or metering. The -10dBV level is often classified as "consumer gear", and the higher level of +4dBu is usually pro gear. +4 dBu audio voltage reference level is equal to 1.23 Vrms. -10 dBV is a standard voltage reference level for consumer and some pro audio use, equal to 0.316 Vrms. RCA connectors are a good indicator of units operating at -10 dBV levels.