Background

Nowadays, more music enthusiasts and HiFi aficionados hope to have a better listening experience on mobile devices. However, in reality, mobile phones only have Type-C/Lighting ports, lack headphone jacks, and do not have built-in Hi-Res chips; the device storage space/network bandwidth is limited, and it is not possible to store/online play many high bitrate HD audio; traditional HiFi decoders are large in size, not convenient to carry outside, and ordinary portable decoders cannot meet the requirements of HiFi enthusiasts.

Using the MQA Portable DAC/AMP can perfectly solve the above problems. PAWPAW's MQA tail solution implements USB UAC2.0 protocol asynchronous transmission of HD bitrate audio, supports up to 384 kHz PCM, DSD256, and full MQA decoding, ensuring timely, bit-perfect audio parsing. The MQA_HPM_CS131 also enhances the portability of the device while meeting the needs of HiFi audio consumers for high-fidelity lossless playback devices, making it an excellent solution for meeting user needs for Hi-Res audio on mobile devices.

Project Overview

The MQA Portable DAC/AMP solution is an excellent choice for portable high-performance HiFi play sound card solutions, perfectly combining XMOS's proprietary XCORE architecture, high inversions and flexible I/O, high precision clock synchronization and high fidelity digital audio transmission, and MQA's high-performance algorithm, which includes:

• Achieving MQA full decoding, MQA audio files take up less storage space and, through algorithms, can unfold to deliver the highest possible sound quality, catering to users' need for high-bit-rate, high-quality audio on mobile devices.
• By utilizing the standard UAC2.0 (USB Audio Class 2.0) protocol and asynchronous transfer method, it ensures that USB transfers high-definition audio data with high bandwidth while maintaining broad compatibility with major operating systems like Windows, Android, Linux, etc.
• With highly versatile and flexible I/O, it easily enables high-rate I2S (PCM/DSD/DoP/MQA) audio interfaces, meeting the multi-channel needs of portable devices.

In the USB MQA Portable DAC/AMP solution, it's required to use a high-quality external audio clock source (Oscillator/Clock) in the peripheral circuit to ensure low jitter. This solution adopts the asynchronous clock mode from the USB 2.0 protocol. The synchronized audio clock source between the host and the playback device is a local low-jitter active clock on the device, thereby ensuring clock precision and bit-perfect audio data transmission.

The solution requires designers to use an external high-end DAC chip. The DAC should feature high SNR, high THD, high channel separation, and low power consumption. Ensure users can achieve high sampling rates and comply with the power requirements of smartphones. Designers are given maximum flexibility in power design, audio tone preference design, and op-amp selection. Under the bit-perfect premise of the XMOS HiFi USB audio solution, designers can fully leverage analog audio design to meet HiFi audio demands.

Features

USB Protocol

• USB 2.0 (Full-speed and High-speed)
• USB Audio Class 1.0
• USB Audio Class 2.0
• USB Firmware Upgrade (DFU)
• UAC 2.0 protocol, supports ASIO, and is compatible with various operating systems like Windows, Linux, Android, MAC OS, and iOS.

Audio Interface

• I2S

  • Direct Stream Digital (DSD)
  • DSD over PCM (DoP)
  • Pulse-code modulation (PCM)
  • Master Quality Authenticated (MQA)

Audio Sampling Rates

• PCM: 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, 192kHz, 352.8kHz, 384kHz
• DSD: DSD64, DSD128, DSD256
• DoP: DoP64

Solution Diagram

We recommend using the latest XU316-1024-QF60B-PP24 XMOS chip platform as the main control chip for the XMOS USB MQA dongle solution. Since such products have high power consumption and computational demands, it's not advisable to use older XMOS platform chips. This XMOS chip platform can perfectly implement the UAC protocol (UAC1.0 & 2.0) and audio interfaces, and it performs exceptionally well in terms of low jitter clock and bit-perfect quality control, making it an excellent bridge for USB to I2S conversion. Leveraging the low power consumption and high performance of the XU316-1024-QF60B-PP24 chip, MuGu Electronics integrates the full MQA decoding algorithm into the solution, expanding the audio spectrum through the algorithm to provide the highest possible sound quality.

In this solution, we recommend using the CS43131 as the DAC. It supports 384kHz and DSD256 at low power consumption and provides a considerable driving force.

Here are the requirements:

• The XU316-1024-QF60B-PP24 needs 3.3V, 1.8V, and 0.9V power supplies.
• Optionally, you can use an external clock (Oscillator) to provide the MCLK for the DAC via I2S.
• It requires a 16Mbit QSPI Flash externally to store the firmware for the XU316.
• An external DAC is needed (CS43131 is recommended).

Software Framework

The XMOS USB MQA dongle solution is built on XMOS's unique XCORE multi-core architecture. Using the XU316-1024-QF60B-PP24 as an example, this section explains the implementation principles of this solution. We also recommend users refer to the provided documents to deepen their understanding of this architecture.

• XMOS USB Audio Whitepaper

• Software Development Guide

It's worth mentioning that the XU316-1024-QF60B-PP24 has 16 logical cores. The MQA full decoding algorithm takes up a lot of XMOS resource cores, with the pre-allocated resources shown in the above diagram. Additionally, the MQA Decoder Lib and XMOS cross-tile transfers will use an extra 4 logical cores, totaling 12 logical cores in use.

If you need to add more features, you'll have to consider the remaining core allocation. Common additional functions include:

• HID control (play/pause)
• DAC volume control
• Screen display

MQA Full Decoding

• Recording: In the studio, MQA can be fully approved and certified. With the MQA studio toolset, you can preview all playback scenarios.

• Folding: After capturing the recording, MQA folds the file to make the audio file small enough for streaming. MQA calls this "music origami".

• MQA File: "Music origami" has a positive impact on the environment, reducing the carbon footprint of streaming studio-quality sound by at least 80%.

• Decoding: MQA can be played on any device (Android/Windows/iOS), providing audio quality above CD (48kHz). When paired with an MQA decoder (XMOS), MQA files use algorithms to restore the original recording.

• Full MQA Decode: The XU316 can carry the complete MQA decoder to provide the highest possible sound quality when unfolding the file. At this level of decoding playback, users can hear what the artist created in the studio, with precise file matching and specific platform DAC compensation and management.

MQA Certification

The MQA_HPM_CS131 decoder board made by PAWPAW Technology, based on the MQA USB dongle solution, has been certified by MQA UK. You can contact us for reference designs and inquire about MQA-related licensing information.