What is the difference between audio gain and volume adjustment?
Volume，usually set in the end of a input channel in the mixer，, Modern mixer adjust volume with a fader. Adjust the volume of a road is to adjust the road signal, the total output noise level . In daily life, adjust the volume, such as MP3, computer speakers or TV, DVD.
Gain, usually appears in the first row of the mixer as a red knob. Gain in a sense can be understood as "volume", but they are different. Adjusting the gain is to adjust the signal of the pre-amplified signal, in other words，adjust the input sensitivity of the input device (such as Line in input and Mic input).
In general, the gain adjust too small that can reduce the signal to noise ratio; the gain adjust too much that will produce whistle. Because impedance of the line input (Line in, 0dB) and the microphone input (Mic, -70dB) is different, if you want to achieve the relative balance of SNR(signal-noise ratio) ,you need to adjust the gain. But adjusting the volume is impossible to do that. Therefore, adjusting the gain is critical.
Somebody will ask: "why not open the volume to achieve effect, since it is to adjust sensitivity of input?" In fact, this question can be answered as follows: If the gain is too small, SNR(signal-noise ratio) will be very low, while increasing the volume at the same time, SNR(signal-noise ratio) is not change. In other words, while increasing the signal volume, the volume of noise is also increasing, so the volume can not adjust the input sensitivity. If the gain is too big, it will cut the part of the sound , resulting in distortion, eventually leading to SNR. At this time even if the volume is reduced, the sound is still distorted.
Therefore, the gain used in adjusting the signal-noise ratio of the input signal to make it balance. While the volume enlarged or reduced adjusted signal-noise ratio ,finally signal will into the busbar. So they are different.