Four levels of analog signals

Analog signal levels may be classified into the following four levels.

1.Mic Level
2. Professional Line Level
3. Instrument Level
4. Consumer Line Level

1. Mic Level

Low impedance (Lo-Z), no reference voltage
In general, signals received by microphones are very small (about -30dbu) and have no standard, and are vulnerable to noise due to low impedance because clean sound must be recorded. In order to operate the signal transmitted to the microphone in professional audio equipment, it must be converted to a pro-line level around +4dbu, which is an internationally promised criterion.
The mic pre-amplifier is changing the mic level signal to the pro-line level signal.
The microphone pre-amplifier not only amplifies the microphone's weak signal but also changes the sound to a characteristic color scheme according to the configured parts.
The most important thing when recording a microphone is 1) which microphone to use and 2) which microphone preamplifier to use. A balanced cable using an XLR connector is used for the microphone.

2. Professional Line Level

It is a signal used in professional audio equipment. It is also called the line level for short.
The amplification of the signal is done through a line amplifier. The internationally promised criterion is +4dbu. In order to obtain clean and high-quality signals, a balanced cable using connectors such as XLR and TRS is used.
In general, studio consoles, mixers, and outboard equipment use professional line levels.

3. Instrument Level

High impedance (Hi-Z), no reference voltage
Small sounds from musical instruments such as electric guitar and bass are amplified through pickup and use high impedance to reduce increasing noise.
At the instrument level, unbalanced cables using connectors such as TS and RCA are used.
If these instrumental levels are desired to be operated by professional audio equipment such as consoles, mixers, and PA systems, equipment such as DI-BOX (Direct Injection Box), which changes the unbalanced signal to the balanced signal, Mic-level, and provides impedance matching, should be used.

4. Consumer Line Level

As a signal used in home audio equipment or instruments used by a typical consumer, the internationally promised criterion is -10dbV (-7.8dbu).

If you want to operate the consumer line level in professional audio equipment, you can properly operate it at +4dbu, the standard for professional line level, if amplified by +11.2dbu through a line amplifier.
Unbalanced cables using connectors such as RCA, TS, 3.5mm TS, etc. are used.

-Ted Kim