Disenchantment Feiao K11 R2R Experience Sharing

after uncovering the mystery, it's actually no big deal

we live in a modern society, modernization, in a sense, is to look at the original things from a more scientific perspective, unveil the mysterious veil layer by layer, and restore the essence of things. The progress of science has also driven the progress of engineering, allowing many technologies that were originally out of reach to enter the lives of ordinary people. Remarkable examples, such as the ballpoint pens and sunscreen that were originally used in the aerospace field and are now ubiquitous, although they make our lives less metaphysical and magical, they also make us embrace reality more.

R2R is a technology that has been used for a long time, and it is also used by many HIEND manufacturers. The price has been high, and there are many legends. One thing makes people feel mysterious, either because there is not enough information or the price is relatively high. If there is less contact, it will naturally become mysterious. Through the experience of Feiao K11 R2R, I also think that R2R technology should be disenchanted.

Long-standing Digital-to-Analog Conversion Technology

dates back to the 1980 s. After experiencing vinyl record players and tape players, the emergence of CD marked the spread of music moving towards digitalization. At this time, digital-to-analog conversion became a necessity, that is, digital signals were restored back to analog signals for playback. This leads to two different ideas, one focusing on the use of physical mechanisms for conversion and the other on the use of algorithms for conversion. The derivative of the former is the resistor array decoding, which developed today's R2R decoding; the latter is derived from the delta sigma modulator, which developed the current 1bit decoding technology.

today focused on R2R technology development. At the earliest time, this kind of decoding using physical devices was called switch tree decoding, that is, one resistor corresponds to one voltage, and 16-bit bit depth can sample 65536 points, which means that the same number of equivalent resistors are needed to form a switch array. This is obviously too complicated, and the error of resistor accuracy makes it impossible to realize. Later, engineers optimized it. The second-generation product was called a weighted resistor circuit, which assigned weights to the resistors in the circuit. R was the most significant bit (MSB) and then distributed the resistance value in a power of 2. This circuit could not solve the problem of high resistance value (for example, if this circuit was used to do a 16bit decoding. The last 16-bit resistance value is 32768 times the initial resistance value R, which is almost insulated and power consumption is unimaginable), resulting in high-bit decoding.

through the progress of mathematics and engineering, engineers have designed three generations of products, R2R circuit (also called inverted T-circuit). This circuit does not need to control the current through resistance value like the previous generation of weighted resistor circuit. The whole circuit construction process only needs two resistance values, resistance R resistor and double resistance 2R, which greatly reduces the required number of resistors and the difficulty of engineering implementation. Today, R2R this decoding method is still widely used in high-end instruments and other fields. The implementation in the engineering field can of course further control costs and improve performance by using software, further reduce the required number of resistors by using shift registers, and further optimize sound performance by pre-oversampling algorithms.

, through the above introduction, I hope you can remove several misunderstandings: 1.R2R is equivalent to a resistor array switch, but in fact it is not; 2.R2R needs a lot of resistors, but the number is not as large as expected. 3.R2R costs very high, compared with the current flagship decoding chip price and supply status, it is acceptable to design R2R decoding array by yourself. 4.R2R is the most primitive decoding method, but delta sigma decoding is not too late.

want to say is that the high-priced decoding chips currently on the market are more gimmicks, and good performance still requires designers to design and tune. In fact, TDA1541 is a hybrid decoding, not a complete R2R decoding. The flagship 1704K promotion is 24bit, but the actual accuracy is only 20bit. At present, ADI's R2R chip AD5790 is not used in audio at the beginning of its design, but is a high-end precision instrument. Since there is no development of the finished chip, there will be more freedom in its own development, and the design scheme will blossom from the low end to the high end. However, in terms of optimization, the focus is on digital DSP algorithm, filtering algorithm and resistance precision solution. In high-end models, R2R may only be a simple part of digital-to-analog conversion, while the front digital processing and back-end analog output are more important. This can also see the direction of R2R development: stronger digital processing capabilities and stronger output capabilities.

small appearance connotation

the appearance of Feiao K11 R2R is the same as K11. Because of the decoding appearance of my own home machine, I have great favorable impression on the appearance of Feiao K11. This simple appearance and a scroll wheel can carry out all operations, very modern design. The design of the variable lamp is less heavy in my opinion, but it may still be a plus for desktop equipment. The input has coaxial optical fiber and USB. What makes me not very suitable is that the USB interface is C port instead of the traditional B port. However, as a modern desktop device, it is understandable. After all, the essence is greater than the form.

inside the simple appearance is a very sophisticated circuit board. Yes, even a thousand-yuan entry-level product that is considered by the old burner may be the culmination of ordinary people's experience and deserves to be taken very seriously. K11 R2R as a whole follows part of the K11 circuit, through the modular design to effectively reduce the cost, so that in the implementation of the project, with a better cost-effective. The power supply circuit uses 17 LDO to accurately stabilize multiple voltage values to ensure good power supply quality of the circuit. MCU uses Zhaoyi GD32F303RE, which is a 32-bit 120Mhz processor and is responsible for the processing of the whole machine. To be honest, I think there is a little performance overflow. The USB interface uses Sheng Wei's SA9312L, which is a high-performance audio control chip that supports 32bit/384hz and DSD256. The volume control chip is NJW1195A, a four-channel high-precision volume control chip. The amp chip is a familiar Shengbang micro SGM8262-2. At present, an amp chip is often used in various small tails. I 'd like to share a cold knowledge with you about this chip. The power supply range of this chip is DC 4.5 V-36V or AC ± 2.25V-± 18V. The output power of the chip is also very different depending on the power supply voltage. This is also the reason why K13 using the same chip has 550mw while K11 R2R has 1300mw. Incidentally, the ear discharge power supply of K11 R2R is 9V.

, from the overall perspective of circuit disassembly, we can see that the use of Feiao chip IC is more localized. With the rise of the domestic chip industry, manufacturers can purchase high-performance chips at a lower price and feed back to users at a more affordable price. This is not just a matter of pride.

is the fully differential complementary R2RDAC module designed by Feiao himself. The principle of R2R is briefly described above. In addition, two words need to be said, differential and complementary. Differential refers to the separation of channels. Using the mark of the frame clock in the PCM music file, the signal is divided into two blocks to decode and process the data of the left channel and the right channel respectively. Based on this mechanism, through FPGA processing, the data of a channel is divided into positive and negative while processing and comparing with each other for correction, which is complementary. The use of these two mechanisms can greatly reduce the requirements for resistance accuracy. Feiao's design should be said to have achieved a good balance between cost and final effect. This is also one of the reasons why other manufacturers can generously announce their 0.1% accuracy without boasting about the high accuracy of their own resistors or keeping secrets. Engineering optimization has greatly reduced the implementation requirements.

in this circuit to say what regret, is the absence of high-precision crystal oscillator, R2R although because the processing speed is relatively slow, relatively insensitive to the clock signal, but the actual use of experience down, in fact, it is still very obvious, this for the accuracy is relatively low R2R is especially obvious, this is obviously reflected in the response to the front end. If there are two high-precision crystal oscillator, I believe there will be better performance, which also belongs to the future of this decoding circuit.

has the basic circuit, feiao also attaches great importance to digital processing, writes a filter for K11 R2R, and distinguishes OS (super-sampling) and NOS (non-super-sampling) in sampling, which can better let users experience the style of R2R.

retro sound

should be based on the premise: 1.K11 R2R comes with a 12V switching power supply. If it can be replaced by a linear power supply, there will be a more stable power supply environment and a relatively clean sound background. 2.K11 R2R is also relatively sensitive to the front end due to its own reasons. The results of using mobile phones and M17 are very different. When I use it, I connect the electricity and use the M17 coaxial output with better performance as the sound source, in order to achieve the best performance of this machine.

after I have heard many R2R decoding, I still feel that there are some commonalities. R2R decoding has better performance in low frequency diving due to its filtering advantage, which is actually lower in low frequency frequency. Another thing is that the sound separation is good and the intermediate frequency is high. This native feature is more natural than the effect obtained by DS decoding and filtering. This can be said to be a feature that many people like.

in the K11 R2R sense of hearing, is able to reflect the characteristics of R2R decoding. If in NOS mode, the sound image separation and positioning sense are very good, creating a very good sense of space and atmosphere; The low frequency is very powerful, especially the diving feeling is very obvious. The intermediate frequency is forward as a whole, the sound edge is very smooth, and the difference from the general non-R2R can be easily recognized. The high frequency is bright and smooth, without sharp feeling, and the attenuation will soon have a crisp texture. The sound as a whole shows a warm tonality. The analytic power of sound is relatively not prominent, and it is more about the creation of a sense of taste and atmosphere.

will feel that K11 R2R is an old style restored by modern technology. It has a sound bottom with high separation and heavy bass in modern aesthetics, and has a warm performance that emphasizes overall feeling and hearing resistance in the past. It is the same as the current mainstream R2R decoding idea. Feiao has a high degree of sound completion at a reasonable cost, which is enough to show the stylized listening feeling brought by R2R decoding method.

if R2R decoding wants better quality performance, it needs a larger scale and higher precision resistor array, which is the cost; it also needs more advanced digital and filtering algorithm precipitation, which is time, and this progress is not achieved overnight. I believe that in the future, Feiao will get better and better for the development of R2R technology.

the right location

, no matter how the desktop is arranged, it is possible to put down a K11 R2R. The small size wins a desktop position for yourself. The display or a storage compartment can easily accommodate it. This can have a more flexible space to connect your earplugs or large earphones and provide a convenient and practical experience. There may be no sense of ritual, but it is more arbitrary, making good sounds readily available.

In terms of external expansion, K11 R2R can be equivalent to a center of desktop media, which is the consistent style of Feiao desktop equipment. The rear optical fiber can be connected to PS5,RCA output terminal can be connected to desktop speaker, and it is also very convenient to switch headphones and line output with a button operation, and a desktop audio-visual system can be easily built.

today, consumption is more and more rational and use, and the competition in the industry also makes the decentralization of technology faster and faster. Compared with the lack of innovation and price increase of foreign brands to maintain the status of the industry, the decentralization of domestic brands is more pragmatic and enterprising. With the decentralization of this technology, many legends become within reach, and people's understanding of it will become more and more rational. I think the so-called disenchantment, that is, everyone can contact, after all, no one will have any imagination of braised pork, right?

Author:chen_racon202102-28 10:31

web site:https://weibo.com/ttarticle/p/show?id=2309405138972119531541