Engineer Electronic Production Story: DIY Design of Classical Power Amplifier Chip

Ever since being fascinated by vinyl and the original version, CD products have been dismissed. Could the advanced digital equipment brought by the progress of the times be inferior to the outdated analog equipment? Although the old analog audio source has its advantages, after all, it is difficult to meet the demand from the durability and the diversity of content. Today, the digital audio source is the only choice. If you use the LP effect standard to require CD, there is no difficulty in theory, and there are few products that can meet this requirement in practical applications. What is the reason? So I also want to know some related answers through practice. The D / A chip troika TDA1541, AD1865, and PCM63 are said to be very popular among the three classics handed down. There have been many different versions of products. Among them, the taste is difficult to express in text language, and there are imported factory machines. There are also DIY products, and the good ones are borrowed from friends, and the machines they own are not very satisfactory, huh, huh.

Let's start with these classic chips first, make according to your own ideas, touch the stones and cross the river to see what level of DIY works you can make, and whether they can reach the production level of the heroes, I personally don't have much confidence Because digital circuits usually have little understanding, they had to temporarily hold up their knowledge and learn the experience of netizens. Zhang Guanli Dai Lalang tried to combine various chips with different purposes into a circuit.

Success requires effort, and after a lot of tossing and tuning, the following two things are completed first.

1: First produced is the hottest and well-known TDA1541 in the forum. It is said that it is not difficult to make this DAC. I also bought several different versions of the finished PCB to assemble myself. The final effect is not to say, there are good Bad, I think the most difficult thing about this D / A is the sense of space or the depth of the sound field and the noise floor. These DIY work done, some versions of sound card test indicators are done very well, but helpless listening is not ideal, remember more than once to see Ming Daxia and other netizens mentioned the wiring skills, they have After reading some relevant theories, I feel that this is indeed a good premise, and these experiences need to be learned.

Power quality is the cornerstone of sound quality. This seems to be the consensus of the majority of diyer, but various circuit forms are dazzling. LM317 and 337 voltage regulators are currently used by most designers, but they have a little experience. : The sound of the final expression of the voltage stabilizing effect of the 78 series I prefer (personal point of view, please do not shoot bricks). The other reason is that there are so many parts on hand that I wasted. IV / LPF is said to be an important part of the DAC. It determines the final sound style of the product. It also takes some brains to choose which form of LPF. The forum has op amps and Marantz HDMA. In order to omit the trouble of debugging, I chose the op amp. Combination (see picture below),

This output circuit looks like a one-armed old man. After careful analysis of the circuit, it seems that the designer intentionally drew a lower arm resistor, otherwise the output midpoint cannot be 0 potential, but the current of the output tube can be adjusted by adjusting the 1.5k resistor. It is also the reason for choosing this circuit. The midpoint output is not at zero potential, but it is not necessarily a bad thing when there is a coupling capacitor. I have seen some foreign players intentionally add a certain bias to the capacitor in the battery when making the speaker crossover. The advantage is that the phase distortion of the capacitor can be reduced (I do n’t know if it is true or false), so the midpoint of the circuit here is not at 0 potential, which may be the original intention of the designer.

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