The noise of the resistor is often ignored, but it is very important to the audio equipment. The resistance noise is generally only audible to the millivolt amplifier. Therefore, many people advocate the use of metal film resistors in many audio equipments, mainly in terms of noise, stability and accuracy. Because the stability of carbon film resistors is not as good as metal film resistors, it is less used in audio equipment. , that sound resistor selection we usually need to pay attention to the following points.

1. Preamplifiers and frequency equalization circuits, especially small-signal amplifiers such as phono amplifiers, microphone amplifiers, etc., should use metal film resistors to avoid affecting signal-to-noise ratio and stability. Among them, the gain setting resistor should use an error of less than 1% to ensure the gain between the channels is consistent.
2. The power output stage resistor should use the nominal power as the actual loss power more than 2 times, and select the high stability non-inductive wirewound resistor or the non-inductive carbon-doped resistor. The resistors used in the rest of the circuit, the nominal power generally has no special requirements, you can choose 1/4W. Do not use 1/8W or 1/16W resistors as much as possible, because the noise figure and stability of the noise figure of the resistor are related to volume. 
3. The input stage of the post-amplifier with AC amplification program and its negative feedback circuit should use metal film resistor with error less than 1% to ensure the stability and balance of the circuit. The remaining circuits can be used with metal with error less than 2%. Membrane resistance.
4, the resistance used by the tube amplifier, the withstand voltage should not be less than its working voltage, otherwise it may break down burnout, or arcing phenomenon, the nominal power is generally not less than twice the actual power consumption.

Due to the improvement of the process, the carbon film resistance performance is not low today, the noise figure of the small carbon film resistor has reached 3-5μV/V (1MΩ), and the resistance value is smaller. Many mid-range audio equipment are generally considered to be carbon film resistors in consideration of price factors. In fact, the noise source of audio equipment is often dominated by power supply or induced current AC. Therefore, in the future, carbon film resistors may be used in high-end audio equipment as well as metal film resistors.