Android Tablet Sound Quality Evaluation--Rainbow CT971-Muse

CT971-Muse is a newly launched tablet computer from COLORFLY. Its biggest feature is the audio processing technology that combines the colorful C4 player. It is mainly called HIFI sound and has the name of “HIFI Pad”. We even believe that Rainbow has made a breakthrough from the traditional PC hardware accessories brand with high-quality audio player products, and it is a good attempt and idea to enter portable digital devices, even smart digital devices. This is one of our recommendations in the C4 Pro evaluation article. Speculation. However, it is a pity that after more than two years, the COLORFLY Rainbow Digital team, which is positioned in the development of high-quality players, does not seem to show us the determination of Rainbow to enter the digital products, but still stays in the experimental stage. The introduction of a tablet with the core technology of the C4 player may be just another attempt.

COLORFLY Colorful CT971-Muse Tablet PC - Packaging

COLORFLY Colorful CT971-Muse Tablet

Colorful C4 Pro, CK4, and even C3 players are very distinctive in terms of sound. If you don't consider the price or some obvious lack of control, their sound performance and function design have many desirable in portable audio players. Where and what. The CT971 tablet, of course, hopes to extend this advantage to the current hot Android tablet products. However, it is more difficult to fully migrate the C4 Pro technology. Let's take a look at the difference between the main hardware architecture of the CT971 tablet and the core architecture of the previous C4 Pro or CK4.

COLORFLY Colorful CT971-Muse Tablet

COLORFLY Colorful CT971-Muse Tablet-Interface [contains a headphone output connector and a Line Out connector]

COLORFLY Colorful CT971-Muse Tablet PC - Motherboard

COLORFLY Colorful CT971-Muse Tablet PC - Motherboard [with shield]

First of all, the CT971 tablet is a standard 9.7-inch tablet using the Android 4.0 operating system. It has a capacitive touch screen, a camera that is common to most tablets, and is of course compatible with most applications under the Android operating system. So in C4 Pro and CK4, the mysterious C4 Master master chip can't be used. The CT971 tablet, after several R&D experiments, finally decided to use the A10 processor from Quanzhi. Regarding the application of the processor and the Android part, we will talk about it in a future article, and today's article only evaluates and explains the audio subsystem.

COLORFLY Colorful CT971-Muse Tablet - Allwinner All-A10 Processor

COLORFLY Colorful CT971-Muse Tablet - Cirrus Logic CS4270 CODEC [24bit/192kHz]

COLORFLY Colorful CT971-Muse Tablet PC - C4R Headphone Amplifier Chip

In addition to the main control chip, the audio subsystem architecture of the CT971 tablet comes from Rainbow's own design. It uses the external Cirrus Logic CS4270 CODEC chip, and in the C4 Pro and CK4, the CS4398 DAC plays a similar role. It may be that the tablet still needs voice input, so the CS4270 Codec chip is selected. The official indicator of this chip is also very good, more than enough for portable players, but unfortunately, the current Rainbow team did not solve the problem of 44.1kHz and 48kHz sampling rate switching under Android, and Android does not support 24bit sampling accuracy. The file is played. Therefore, Codec will not become an obvious bottleneck.

Although the audio decoding specification has been limited by the Android operating system and software development, in addition to DAC or Codec, another core technology of the C4 player is its amp chip. In the disassembly, we saw that the CT971 tablet uses a C4-R amp chip. This chip is used in the colorful CK4 [low version], while in the high version of the C4 Pro and CK4, the amp chip is C4. The two amp chips can be compared on the two versions of the CK4 player, but since the parameters of the two chips are not public, the difference between the two versions of the player cannot be fully confirmed. It must come entirely from the amp chip. But it can be confirmed that the C4R amp chip is also good in the CK4 low version.

From the point of view of dismantling, Colorful has provided two PCB versions for taking pictures. What is the reason? Mainly because we want to carry out a recoverable disassembly, and the shield of the Rainbow motherboard has been completely welded. According to the colorful technicians, due to the use of external Codec and relatively high-power headphone amplification output, designing this CT971 is far more difficult than the player, WiFi signal interference, system board shielding and so on consume a lot of energy, and we see The stainless steel shield is also much thicker than the common shield and the connection becomes more difficult. So how does the CT971 sound perform?

Objective test:

E-MU 1616M PCIe Digital Audio System

The colorful CT971 tablet provides two 3.5mm interfaces for audio output, one for the Lineout without the amp output and the other for the headphone amplifier output. In accordance with established practice, we conduct a set of objective tests on the two sets of outputs. The test is still in the form of professional-grade sound card entry, combined with common analysis methods to provide intuitive measurement results. The test uses a WAV test file.

COLORFLY Colorful CT971-Muse Tablet - Frequency Response Curve

COLORFLY Colorful CT971-Muse Tablet - Noise Distribution

COLORFLY Colorful CT971-Muse Tablet - Dynamic Test

COLORFLY Colorful CT971-Muse Tablet - Total Harmonic Distortion

COLORFLY Colorful CT971-Muse Tablet - Intermodulation Distortion

COLORFLY Colorful CT971-Muse Tablet - Resolution Curve

Test items LineOUT HPOut
Noise level, dB (A): -96.5 -96.2
Dynamic range, dB (A): 96.3 96.1
Total harmonic distortion, %: 0.0047 0.0049
Intermodulation distortion, %: 0.034 0.035
Stereo resolution, dB: -72.2 -71.9

COLORFLY Colorful CT971-Muse Tablet - Frequency Response Scan

COLORFLY Colorful CT971-Muse Tablet - Resolution Test

COLORFLY Colorful CT971-Muse Tablet - Resolution Frequency Analysis

COLORFLY Colorful CT971-Muse Tablet - Frequency Response Scan

COLORFLY Colorful CT971-Muse Tablet - Resolution Test

COLORFLY Colorful CT971-Muse Tablet - Resolution Frequency Analysis

From the spectrogram analysis of RMAA and frequency response scanning, although the signal-to-noise ratio and dynamic items scored higher in the RMAA test, careful analysis of the frequency distribution map revealed that some details were obscured. With the frequency response scan, we found that in the amp output test, there is a continuous noise floor in the low frequency, and the sound in the high frequency part is not clean enough. Relatively speaking, the linear output noise performs better, but the sound is still not clean enough. From the RMAA test results, in the intermodulation distortion project of 60Hz and 7kHz for the test signal, the output of CT971 also showed very obvious intermodulation distortion. In terms of resolution, it is not ideal. From these test data, it performs better than some mobile phones and tablets [intermodulation distortion is not good enough], but it is worse than CK4, C4 Pro and even C3 players.

Subjective sense of hearing

COLORFLY Colorful CK4 Portable Audio Player [Low Edition]

AKG K701 Headphones

AKG K240 MKII Headphones

Edifier Edifier H850 Headphones

Wisconsin VSONIC GR07 in-ear headphones - retrofit wire bracket

In the subjective sense, we still use the headset system as the main monitoring device, we use AKG K701, K240MKII, Philips SHP9000, Edifier H850, Vsonic GR07, Aurvana Air and other headphones as a reference. Our main contrast player is the iPad3 and the colorful CK4 player [low version], and the CK4 low version player also uses the colorful C4R amp chip.

The driving force of the colorful CT971 flat-panel amp is indeed much better than that of the iPad3 or similar devices such as tablets and mobile phones. Although the C4R amp chip is also used, the output of the CT971 amp is also significantly better than the CK4 low-profile version, especially It is quite obvious when paired with large-size headphones, but the CK4 and CT971 are similar in sound style.

In terms of high frequency, the performance of CT971 is relatively poor, its high frequency is not detailed enough, and it can be obviously slightly dry on the small earplug with high sensitivity, and even some distortion of the broken sound. We carefully analyzed that this may be affected by some operations of the operating system, and some distortions do not seem to be too regular. But if you want to compare the Lineout of the CT971, you will find that the amp chip may still amplify this part of the high frequency distortion. After all, the CT971's amp output power is still very good. Compared with the iPad3, the high frequency of the CT971 naturally has better dynamics and better density, but its performance is not detailed enough, and some details appear rough. Compared with CK4, its high frequency style is similar, but the quality of CK4 is better.

The CT971 headphone output has obvious advantages in the intermediate frequency. Although its sound is still slightly rougher than CK4, the whole dynamic is better, the vocal performance is more full, and it does not appear to be blunt, on K701, 240MKII or even SHP9000. The vocal performance is much better than the iPad or mobile phone. The whole voice is full and three-dimensional. Compared to CK4, the dynamics and sound thickness are better. Of course, used to match the rambler H850 or Aurvana Live! Such headphones, CT971 IF performance is also significantly better. In terms of low frequency, CT971 also has better driving force and dynamics, and its performance is better than CK4, iPad and so on.

Summary: From the sound performance point of view, the high-frequency part of the CT971 is not good enough. In some transient details and resolution, it is even weaker than the iPad. Of course, it is weaker than CK4. Some operations in the system may be random. Bring some obvious high frequency distortion. Overall, its high frequency is rough. However, due to the large enough driving force of the amp, its sound density and dynamics are obvious when paired with large-sized headphones. In the mid-range and low-frequency parts, its style is very similar to that of the CK4, and its driving force is better, which brings better dynamics, especially in the mid-range performance, with headphones, available in similar products. Obviously fuller, three-dimensional, with a tensioning sound.

Although, in this article, we did not talk about the CT971 as an Android tablet, the most fundamental tablet application experience, but here we want to specifically remind everyone, from our simple use, the CT971 firmware is far from mature. Touch screen operation sensitivity, system stability, and even interference between the player and the function operation are more obvious. Although we have been conducting "sound quality evaluation", we never recommend that you buy a mobile phone or tablet with good sound quality. In the case of obvious homogenization of smart devices, multimedia applications and sound quality are one of the most closely related applications to user experience. However, as a smart device, the most basic control still needs to be guaranteed. At present, CT971 does not have such a level. . Regardless of system stability or sound quality, Rainbow said it will introduce software and even hardware modifications. This version of CT971 may be considered an engineering version. We look forward to the new version of CT971 tablet brought by Colorful. .  

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