When self-made audio speaker devices, if you want to make the entire system have a good performance, it is important to use fever components, but the reasonable layout, power supply, ground wire processing, and the connection form between levels and other details must not be ignored. Some effective methods are briefly described as follows:
1. It is better to use shielded wires for the input wires of all levels and the input and output wires of the front circuit to greatly reduce the induced noise and improve the signal-to-noise ratio.
2. The volume control level should be set before the final power amplifier level to prevent the front panel noise from being amplified unreservedly, resulting in a decrease in the signal-to-noise ratio of the entire system.
3. The pre-stage should be powered independently. It is best to use the pre-stage servo power supply or the adjustable power supply board. If it is from the final stage power amplifier, resistors must be added for current limiting, three-terminal integrated voltage stabilization and decoupling should be strengthened to prevent the power supply from passing through. The resulting modulation distortion.
4. The principle of "simplicity and fever" should be adhered to, and the pictures should not be fresh at the moment, and some "grandcaption" boards should be added to the system. In addition, the more functional boards are not the better, which may eventually lead to excessive phase shift, reduced signal-to-noise ratio, and increased expenses, which is not worth the gain.
5. When the final stage power amplifier adopts DC servo, current feedback constant current power amplifier, it is necessary to reserve enough margin for loop variable power and power supply rectification and filtering to prevent top-cutting distortion and overload distortion in large dynamics. In addition, because the constant current power amplifier itself requires several times the power reserve, this will lead to a substantial increase in cost. This is also a shortcoming of constant current power amplifiers compared to voltage power amplifiers, and it is also one of the most commercially available commercial power amplifiers that do not use constant current power amplifiers. the reason.
6. When multi-level circuits are connected, pay attention to the handling of the ground wire, and ground it strictly. The reason for this is that grounding is an important means of suppressing noise and interference. However, unreasonable grounding will cause severe hum or self-oscillation of the amplifier. Commonly used grounding methods are: step-by-step series grounding method and parallel one-point grounding method, which should be adopted according to the specific situation or both. In addition, it is advisable to use series grounding between all levels. The output ground and load ground should be connected in parallel with one point grounding and connected to the chassis. This is beneficial to suppress the self-excitation of the amplifier.
7. All levels are placed in the chassis, and reasonable layout should be paid attention to, and the signal flow direction should be as straight as possible. If the signal is twisted and twisted and the input and output circuits cross, it is easy to cause cross-connection and coupling, resulting in oscillation and noise. The small-signal circuit should be far away from the high-current circuit and the power supply, and the high-current connection should be as short and thick as possible. The signal wire should be shielded wire, and refer to "Article 6" to connect the ground wire to the chassis. In addition, heat-generating components such as radiators and ring transformers should be placed as close as possible to the heat dissipation window to facilitate convection heat dissipation. In addition, it should be far away from other components to prevent heat radiation from affecting the electrical performance of other components.
8. The internal resistance of the power supply part (including transformer, rectifier and filter circuit) should be small, and it is better to use toroidal transformer because of its advantages such as low magnetic leakage, low mechanical noise, small size, and high cost performance. For rectification, high-speed bridge rectification should be used. In addition, the pre-stage power supply can also adopt double-bridge rectification to avoid ripple current flowing to the amplifier through the secondary center tap. At the same time, the filter capacitor should use high-quality large-capacity electrolysis and high-frequency small capacitors to store enough energy to meet the power demand of instantaneous large signals and prevent clipping and distortion. The cost of the entire power supply should account for about 3/5 of the cost of the Hi-Fi power amplifier.
9. In order to ensure the full performance of the circuit, the power supply voltage should use the recommended value, and the limit value should not be used to avoid irreversible loss, but it can not be used with derating to avoid degrading the circuit performance or failing to reach the nominal index.
10. When self-made audio circuit, you should strictly control the soldering iron temperature and soldering time. In addition, the tip of the soldering iron should not leak electricity, and the insulation resistance should be >10MΩ, and it is better to use a grounded soldering iron to avoid unnecessary losses. The flux can be rosin, and acidic substances such as solder paste should not be used. When the radiator is in use, apply fine sandpaper to carefully polish the mounting surface so that the power device can be in close contact with it. At the same time, the heat dissipation surface should be cleaned up. Moreover, the radiator should be made of high-quality products with extremely low thermal resistance, and an appropriate amount of thermally conductive insulating silicone grease should be applied between the power element and the mounting surface.