Analysis of six terms (DAC, ADC, DSP, codec, op amp, headphone amplifier)

ADC and DAC, DSP

ADC is an analog-to-digital signal encoding chip, such as TLV320ADC, and DAC is a digital-to-analog signal decoding chip, such as ES9028. The former is generally used for recording and the latter is generally used for decoding audio. The intermediate digital signal processing process is handled by the DSP. The analog signal is input from the ADC, encoded into a digital signal, and then handed over to the DSP for calculation and processing, and finally handed over to the DAC to decode the digital signal back into an analog signal for output.

Op amp and headphone amp

Headphone amplifier is the name of a category of products, not a chip type. There may be multiple op amp chips in a headphone amplifier, such as OPA1612 and OPA2604. In addition, op amp chips are also classified. Some only work on external speakers and not on headphones, such as NXP's TFA9890. Some only work on headphones and not on external speakers, such as Maxim's MAX97220. The two op amp chips, OPA1612 and OPA2604, can work on both headphones and external speakers.

Codec and independent DAC

We have always believed that the codec must be integrated into the SoC, while the independent DAC is external to the SoC, so the codec and independent DAC can be well identified by the position arrangement between the chips. In fact, this is a wrong idea.

Codec can also be independent of SoC. For example, the codecs of Samsung and Apple phones are generally independent of SoC, which can be regarded as independent audio chips. In other words, the Qualcomm WCD9335 codec in Samsung S7 (Snapdragon 820 version) is also an independent audio chip, but the decoding effect is not as good as chips such as CS4398. Similarly, vivo Xplay5 has both WCD9335 codec and CS4398 DAC. Why is the codec not as good as the independent DAC?

Codecs integrate ADC, DAC, and other audio-related modules. For example, AK4961 integrates ADC, DAC, and amp functions. It is a complete audio solution. It should be more powerful than an independent DAC that only knows how to decode but cannot be used independently, right? The problem lies in the focus. Codecs integrate more functions, so there are more things to take into account. The amount of calculation will naturally be shared by multiple functional modules, and the decoding efficiency and effect will naturally not be as good as an independent DAC.

In the past few years, the Hi-Fi solution with three independent chips seemed to be more popular, such as the vivo Xshot, TLV320ADC+CS4398+MAX97220. Since the emergence of DACs with highly integrated op amp chips such as SABRE9018Q2C and ES9118, the industry seems to have begun to pay attention to this new Hi-Fi solution. The biggest advantage of doing so is that it saves space inside the phone, while also continuing to satisfy consumers' desire to pile up materials on the Hi-Fi circuit. The integration level is between codec and independent DAC, taking into account both decoding effect and efficiency.

Finally, let’s take a look at the three mainstream Hi-Fi chips on the market: independent DAC, DAC with integrated op amp chip, and codec, as well as the corresponding models.

Independent DAC series:

Horizontal comparison of mainstream independent DACs

ES9018K2M: vivo X3, vivo Xplay3S, vivo X5Max, Xiaomi Note Standard Edition, Meizu MX4 Pro and Meizu PRO 5, Blue Magic MOS1 max, TCL Dongdong Gun 2, Gigaset ME and Gigaset ME pro

SABRE9018C2M: LG V10, Lenovo Lemon X3, Xiaomi Note top version

ES9018AQ2M: Geek Out V2 portable decoder and headphone amplifier, can be used with a smartphone. Generally, it is best to find a mobile phone with a relatively high USB output power. If the power is too low, it will not be able to drive this portable all-in-one. Due to the high power consumption and heat generation, it is not recommended to use it with a mobile phone for a long time, and the sound quality is not as good as when connected to a computer.

ES9028Q2M: vivo X6Plus, vivo Xplay5 flagship version

ES9028C2M: LG G5 B&O Hi-Fi module

AK4490: ZTE Axon 7

AK4375: nubia Z9 Max, nubia Z9 Max Elite Edition and nubia My Prague, vivo X5ProV, vivo Y27, vivo X6 and vivo X6S, Gigaset ME pure

CS4398: vivo X1, vivo Xplay, vivo Xshot, vivo X5, vivo X5F, vivo X5Pro, vivo Xplay5, vivo X6S Plus

Many readers may wonder, for the same ES90xx chip, what do the suffixes such as C2M and Q2M mean? In fact, it represents the different packaging methods of the chip. C2M is the smallest of the three packaging specifications, K2M packaging area is between C2M and Q2M, and Q2M is the largest of the three packaging specifications. Comprehensively comparing the parameters of the above ESS DAC chips, the ES9028C2M used in the LG G5 B&O Hi-Fi module is relatively the best. However, similar to the Geek Out V2, an independent decoder and headphone amplifier, the LG Hi-Fi module also has the problem of high heat and high power consumption.

DAC chip integrated with op amp chip:

Horizontal comparison of DAC integrated with op amp chip

AK4376: Representative models include nubia Z11 and vivo X7

ES9118: No specific model

SABRE9018Q2C: No specific model

Codec series:

Horizontal comparison of mainstream codecs

338S1285: iPhone 6s

338S1201: iPhone 6 Plus

338S1117: iPhone 5

Lucky CS47L91: Samsung S7 (Exynos 8890 version)

CS43L36: Meizu PRO 6

WM5102: Samsung S4, Meizu MX3, Lenovo K860i

WCD9335: Samsung S7 (Snapdragon 820 version)

AK4961: nubia Z7 and nubia Z9

Summary: There are many mobile phones that use these chips, but they are far behind the Walkman in terms of power supply scale and number of op amps, so the sound cannot be compared. To give the simplest example, the ES9018K2M on the mobile phone is actually a scaled-down version of the ES9018, specially customized for mobile devices. The former is dual-channel, and the latter is 8-channel. Whether it is dynamic range or signal-to-noise ratio and other parameters, ES9018 is far superior to ES9018K2M. For example, HIFIMAN 901 uses two ES9018 DACs. At the same time, the professional op amp chip models used in HIFIMAN 901 are also more advanced than those of Hi-Fi mobile phones, and the number is also larger, namely two OPA2107 and two OPA627.

As shown in the figure above, from ES9018K2M to ES9028Q2M/C2M, the gap in key indicators is gradually shortened compared to ES9018S. On the other hand, the new chip ES9038PRO continues to make breakthroughs in key indicators, and DNR and THD+N are raised to new heights.

On the other hand, back to the three mainstream chip solutions for Hi-Fi mobile phones, independent DAC and DAC integrated with op amp chips generally have better sound quality than codec solutions. Among them, DAC integrated with op amp chips, which saves more internal space of the body, will become the mainstream solution in the future and be used in Hi-Fi mobile phones.

Finally, in a short period of time, the Hi-Fi chips with better performance and higher overall level generally perform worse in terms of battery life and heat generation. This is also an unavoidable technical bottleneck, just as when recording and decoding 4K videos, the power consumption and heat generation of mobile phones will also increase. Better sound quality and more outstanding picture quality performance must come at a price.