Engineer production: complete solution of the headphone amplifier production process

Friends who pay attention to HiFi audio can see the internal structure if they have seen the amplifiers made by famous manufacturers or masters, watched the mirror-like smooth case and spiritually overflowing bile ducts, and then listened to the soft and mellow sounds. If you open the case, you see that there is no expected circuit board inside, but a few thick copper wires are criss-crossed to form a mesh frame, and each component is neatly welded on this frame, and then connected with various colored wires , Will inevitably be surprised. Experts will say that this technique is called scaffolding welding, or lap welding for short, which is both the most traditional and the most vocal and artistic technique. Maybe friends will think: Can I own such a work of art?

A lot of the content below involves DIY. If you want to operate, please pay special attention to safety and carry out under the guidance of experienced friends. Because there are many variables in the actual circuit, only by following the necessary steps carefully and patiently and meticulously adjusting will you get the best possible sound quality. The specific circumstances are different and cannot be fully considered, so please analyze the specific problems. The author only tries to ensure the truth and appropriateness of the statement, and is not responsible for the consequences of imitating the operation.

Seek a solution

As we all know, since it was actually applied to computers, the development of audio technology has continuously created surprises for us, from 8bit to 44.1KHz / 16bit to 96KHz / 24bit, from mono to stereo to multi-channel, from MIDI to MP3 to APE and FLAC, all stimulate our desire for hearing and the pursuit of sound quality. It should be said that with the "fever-grade" sound card innovation AWE64GOLD and Dimeng MX200 have emerged, a group of enthusiastic computer audio enthusiasts began to form, and the computer has become a music appreciation center for many friends.

For many friends who are passionate about music, the greatest joy that audio technology brings to them is when the APE format is widely used-from the quite satisfactory 44.1KHz, 16bit, stereo and lossless compression (96KHz, 24bit Although the high index like multi-channel is more attractive to people, the music we can enjoy only comes from record companies, and the high prices of SACD and DVD-Audio cannot be easily afforded by us; in fact, the masters also said, (When the sound of the CD is played back better, it can also give us a very wonderful enjoyment). From this time on, we can only enjoy the original sound of the CD on the computer. The MP3 and CD Walkman "Electronic Shockproof" compression that had to endure before can finally be thrown out of Jiuxiaoyun.

With the upgrading of hard drive capacity, we can store a large number of high-quality music files for listening at any time. Stimulated by the ensuing demand, the major sound card and speaker manufacturers began to set off a climax of developing products for high-quality audio playback, and even some manufacturers that were only lingering in the traditional HiFi field before also joined in. For a while, Philips 70x, Black Gold II, Black Gold Cannon, Envy24 series, DMXFire1024, RME9624 and Rambler R1900â…¡, Hivi M200, Generation V500, Chaolu, Fayou E Star / Black Diamond, etc. were eye-catching, and even the original did not belong HiFi headphones in the field of computer audio have gradually become the new favorite of more and more friends. For a time, the situation of computer audio seemed to be very good.

But, but, when we listened to the music carefully on the computer audio system that we carefully matched, we found that there are some problems with the sound: the high frequency is not so smooth and delicate, and some are blunt and dry; the middle frequency is not so transparent and soft, and some Dyeing muffled sound; low frequencies are not so compact and strong, and some are loose and turbid. As an experiment, listen to "TemptaTIon" by Diana Krall, "A lover in Berlin" by Kari Bremnes, or "Make me a kite" by Amanda McBroom. Deduction and recording are almost impeccable.

What's the problem? Maybe friends have found out that, at the same price, the sound performance of headphones is better than multimedia speakers. The reason for this is that, on the one hand, the same cost of the headphone unit can be better than the speaker unit; on the other hand, it is due to the amplifier, because the speaker usually requires much more power than the headset. It is difficult to make a satisfactory amplifier under the double constraints of cost and volume (need to be put into the speaker cabinet). So many friends also use headphones as an option. But after buying more high-end headphones to match a good sound card, many friends also found that the problem has not been completely solved, which is also largely due to the lack of the amplifier circuit on the sound card: the amplifier circuit on most sound cards It's just an integrated operational amplifier. From the perspective of indicators alone, the quiescent current of many integrated operational amplifiers is less than 10mA. As a result, when the headphones are directly driven, the integrated operational amplifiers on many sound cards are in a low voltage and Class A and B working state. This is in the computer audio system. Among the many unfavorable factors of sound quality is a considerable problem.

Now that we have found a big problem, we should take the right medicine. On the Internet, there are many finished products, solutions and circuits for headphone amplifiers. Friends can consider DIY one with the author and feel the taste; even if you do not plan to do it yourself, I believe it will be beneficial to open the book.

Perhaps in the face of such a vast DIY project, friends could not help but feel a bit dazed. But do n’t worry, let ’s start with a specific example and introduce step by step how to DIY a headphone amplifier from scratch, from the technical foundation to the purchase of components to the assembly method will be involved. If you follow these necessary steps, believe Victory will be in sight.

DIY a headphone amplifier from scratch (long)

overall appearance

Initial test plan

In the author ’s previous listening experience, Tianlong ’s advanced CD player connected to the McGinto amplifier and pushed the B & W N801 speaker to play the jazz music “This song should only be available in the sky”. I have deeply imprinted the transformer output amplifier in my mind, so this time I also chose the tube scheme.

In fact, we are not very new to electronic tubes. Dear friends, you should remember the famous Aopen motherboards that used electron tubes in the analog audio amplification part. The electron tube used is Sovtec's 6922, which is a kind of bipolar transistor commonly used in low noise high frequency voltage amplification occasions; and Some time ago, the USB tube sound card introduced by the expert of the University of Electronic Science and Technology used the military grade 6N11 of the Beijing factory. This is actually a relationship with the previous E88CC. It is a model of mutual replacement; there are several multimedia speakers of Dajidian. More specific examples will not be listed, in short, everyone can eliminate some strangeness.

DIY a headphone amplifier from scratch (long)

Early graphite screen 6N11 of Beijing factory

Considering that many friends do not have enough knowledge about electron tubes and analog circuits, in order to deal with practical problems correctly, please pay attention to the following absolutely necessary basic knowledge, or you can start reading from the next section, you need to understand the basic knowledge and then turn Take a look. If a friend is interested in technical details, please refer to the relevant information. If this is already in place, you can skip to the next section.

868mhz Antenna Description

The Gold-plated elbow rod antenna is 868/915mhz wireless digital/special meter reading communication system design of the antenna.The antenna standing wave ratio performance is good, small dimension, structure, easy installation, stable performance, has the very good anti vibration and aging.

Specification:

Center Frequency: 868~915MHz

Polarization: Vertical Polarization

Gain: 3.0dBi

V.S.W.R: <=1.5

Impedance: 50Ω

Maximum power: 10W

Connector: SMA-JW

Radome Material: ABS

Connector Material: Copper

Length: 100mm

Weight: 8.3g

Operation Temperature: -40℃~+85℃

Relative Humidity: Up to 95%




868mhz antenna






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