Quloos QU02 USB Bridge

USB Digital Audio Interface to SPDIF AES/EBU I2S

● For QU02, It is a digital audio converter for USB convert to coaxial, optical, AES/EBU, I2S (IIS) digital audio output.

● Briefly speaking, USB Bridge can also be deemed as an external high-quality digital sound card that can connect to mobile phones, computers and tablets.

● The purpose of USB Bridge is to improve the sound quality of DAC, so that the sound quality of DAC connected to computers, mobile phones and tablets can reach or even exceed that of many digital players.

It’s simple. QU02 can be connected to computers, mobile phones and tablets (mobile phones and tablets need an OTG converter to convert to USB-A port) through USB cable, and then output connect to DAC, active speakers with digital audio input, power amplifiers with digital audio input, and DSP of car audio through digital audio cable. The methods of connecting backend devices include coaxial, optical, AES and I2S.

● [Replaceable sound quality/exceeding many digital players] Whether we are designing the QA661, or the designing the a better sound quality QA662, we reached a conclusion that as long as the USB Bridge was excellent enough, the sound quality was replaceable or even exceeded many digital players.

● [Playing online streaming music easily] There is a certain threshold for using online players, which increased user’s difficulty on using them, especially if they wanted to use them well. However, there is almost zero threshold when using USB Bridge to listen online streaming music. No matter is mobile phones, tablets or computers, it’s easy to play online streaming music.

● [The best choice to improve the sound quality] For most DAC, or HiFi devices with DAC, the simplest and most effective way to improve the sound quality is to add an excellent USB Bridge in front of it, with small investment, but realizing a significantly improved sound quality.

When both ends of the isolation are powered by the local pure power supply, we can hear the sound that is smoother, with cleaner background and more details.

● To effectively eliminate the ground loop noise introduced from the computer, the standard USB Bridge are equipped with complete ground isolation, such as INT204, Hydra Z+, Alpha, A.B.C, as well as some excellent USB Bridge in China. It’s obvious that a lot of efforts have been accumulated in this aspect.

● The isolation design of QU02 is also unique. The CPU part of the USB Bridge, the audio output processing part and the clock part are completely isolated. The purpose is to isolate the interference caused by the computer, so that the sound is more pure and accurate.

● However, for almost all similar designs that adopted complete isolation, partial power supply of CPU of USB Bridge is by 5V power supply from USB inputted, so the sound will be greatly influenced by 5V power supply from USB inputted.

● How about QU02? It directly abandoned 5V power supply from USB inputted and uses local pure power supply at both ends of isolation.
    Because both ends are designed with complete isolation, we made the isolation up to 3000 V DC voltage before and after isolation, through Murata isolation power module.
    Through isolating the power supply, we realized the couplings, which not only realizes the complete isolation, but also ensures that both ends are supplied with pure power supply with low internal resistance.

● QU02 selects wurth’s high-precision crystal oscillator for partial CPU of USB, because a poor CPU clock will bring a large EMI interference to power supply and surrounding space. The stability of Wurth crystal oscillator and low jitter will make the position of sound image more accurate, more three-dimensional effect, and more open sound scene.

● The audio of QU02 uses two AS338 crystal oscillators (Accusalicon specifically launched for Hi-End audio applications). This crystal oscillator, with selling price more than US $50/pc, is a more high-end model of popular AS318B in Hi-Fi applications, whose phase noise and jitter performance are leading the similar products.

● The jitter of AS338 is as low as 38fs, much lower than the 88fs of AS318B. The 10Hz phase noise, which has a great influence on hearing, is lower than the popular crystal oscillator CCHD-957 by about 10dB.

The above jitter test diagram is for QU02 engineering machine. About test screenshot under APX555 instrument, our parameters are marked as 80ps, because there will be some deviations on parameters of each machine.

Through applying low noise and pure power supply to power AS338 crystal oscillator, excellent digital signal processing circuit and excellent CPLD frequency division design, we successfully realized the incredible low jitter audio output.There is only 80ps with coaxial output jitter, which is only 40% of jitter 200ps of many single digital audio processing chips.

● The biggest cost gap between different devices generally lies in power circuit. For example, in terms of price, many Linear power chips are 10-20 times than that of general power chips.

● In addition, for most machine designed, there only needs a few power chips. However, we will use over 10 or even dozens of power supply chips, which caused a huge cost gap. We will divide the power supply into several groups according to the major categories (including high-frequency and low-frequency, audio and non-audio). Then, during the second stage, we will divide into several groups according to different current sizes and different interference levels. Finally, during the third stage, we will supply power to each specific electric circuit independently. The advantage is that we realized countless independent power supply effects inside a machine, ensuring the independence of each other, isolating their influences, and ensuring the purity, refinement and accuracy of sound.

● There are two main reasons that explains why Linear’s power chip is expensive. On the one hand, the parameters are excellent, rare low noise, and fast enough transient response. On the other hand, the actual performance of the sound is good. The sound of the linear power supply chip is exquisite and has many sound details. Compared with the conventional power supply chips, it is significantly improved.

● How excellent are the parameters of Linear power chip? Let's just take a brief look at the noise index. The noise of LT3042 is 0.8uV, which is only 8% of the 9uV noise of the commonly used low-noise power supply chip ADP151, and only 1% of the 75uV noise of the regulator chip LM7805.

● The Linear power chip used by QU02 includes multiple LT3042, LT1963 and LT3693.

● To achieve excellent sound quality and actual hearing sense, QU02 uses not only complex power circuit design and expensive power chips, and also uses the Philips axial electrolytic capacitor, Philips 135 electrolytic capacitor, Philips 030 axial electrolytic capacitor, Murata power source isolation module, Murata common mode inductance, WIMA film capacitor, ERO film capacitor, Panasonic SMD film capacitor.

● For most of the independent USB Bridge on sale now, the power supply used in the circuit before isolation is the 5V power supply from USB inputted, which determines that the sound will inevitably be influenced by the quality of USB inputted power supply. When connected to a computer with a better power supply, the sound will be better. However, when connected to a computer or mobile phone with a bad power supply, the sound will be worse, which is manifested in that the sound tends to become hazy, thin, weaken details, unclean and lacking in three-dimensional sense.

● Some user will try to add USB noise purifier to solve this problem. However, although most USB noise purifiers can bring a clean sound, but they also cause the loss of sound details or make the sound thin, which makes the original goal became impossible.

● Because QU02 used Murata power isolation module and completely abandoned 5V power supply from USB inputted, realizing that the sound is completely free from the influence of power supply from USB inputted. The advantage is that when the mobile phone is used as the sound source, it will have better sound quality performance than similar products. The difference between the sound computer inputted and mobile phone inputted has been narrowed. Adopting mobile phone as the sound source can realize HiFi sound.

● An OTG conversion cable to USB-A port is needed, If the QU02 is connected to Android or iPhone and tablets, so as to realize a convenient online streaming music playing and wonderful enjoyment of a high quality of sound.

● When we conduct the actual test with 75ohm Canare coaxial cable in a length of 10m, there is almost no influence to sound quality. When the length of coaxial line is increased from 1.5m to 10m, the Jitter is only increased from 72ps to 74ps, so that such a slight difference can be ignored.

● If needing a longer distance, it is recommended to use AES for connection. In theory, AES can support a long distance transmission of 100m.

● Therefore, your computer and audio can be free from each other.

● When using QU02, we find that not only the coaxial cable can be a length of 10 meters, but also the USB cable can be a length of 10 meters through our actual measurement, which is very friendly to car audio users.

● No matter you plan to install QU02 in trunk of the car and use a long USB cable to connect the phone and tablet to the dashboard, or you plan to install QU02 under the seat and use a long coaxial cable to connect to DSP input of car audio in rear boot, both are achievable, which is more convenient and can experience better sound quality of Hi-Fi on car audio.

● QU02 uses external 12V power input. Since the maximum power supply of car can reach 14V, it cannot be used directly. Therefore, we provide two vehicle power supplies for car audio users to choose (need to purchase separately). These two power supplies are equipped with noise filtering function, and the voltage will be stabilized to a fixed 11.5V to ensure stable use and sound performance. One of the two vehicle power supplies is the interface of the vehicle cigarette lighter, which can be directly plugged into the vehicle cigarette lighter. The other type of power input is connected by terminal blocks, and ACC is provided as the control input for power startup. (When purchasing the vehicle power supply, please find it directly in the store or kindly consult us)

QU02 has I2S, AES, Optical, 2 Coaxial digital audio signal output.

Four groups of switches can adjust four conventional I2S cable sequences, so as to realize the compatibility with DAC of different brands

Note: Cannot connect with HDMI of computer, TV and set-top box

Statement: The above internal pictures and PCB plate pictures are for reference only. To continuously improve the sound quality and performance of product, materials or circuits are subject to change without notice.

● Input power: DC12V 2A (range: 11-13V, >500mA), 5.5 x 2.1mm, positive inside and negative outside
● Power consumption of whole machine: <5W
● Systems supported: Windows (ASIO driver), Mac, Android, iOS, Linux (drive-free)
● Size of host: 197 x 197 x 45mm (Not including exposed sockets and foot mats)
● Weight of host: 1.29kg
● Size of package: 330 x 260 x 75mm
● Weight of package: 1.72kg
● Package list: QU02 host, USB Cable(USB-A to B, L=1.5M), Instruction Manual, DC12V 2A Power Supply (Input AC110~240V)

Price: QU02 USB Bridge US $389.99 (Not included shipping)