Flagship Server

The Flagship AA Music Server gives high-performance digital audio playback without the need to break the bank account. It uses the beautiful Streacom FC-10 fanless case available in silver and black colors, with or without optical drive slot.

Computer-based system

ASRock J5040-ITX motherboard based on Intel Pentium Silver SoC (Intel’s code name = Gemini Lake Refresh) gives the required performance in audio playback without compromise to dynamics, hence negate the needs for expensive and high-current linear power supply unit (LPSU).

Inside view with SSD tray lifted

The use of standard motherboard allows future upgrade when better low-powered CPUs and motherboards are available in the future.

LPSU Details

Custom-made toroidal transformer by Toroidy based in Poland is used for stepping down AC line voltage. It is low-noise, audio-grade transformer with primary/secondary static screen, outside magnetic screen, and center potted with epoxy.

Toroidy transformer

6-rail LPSU Main Board

The AC to DC rectification, smoothing, and first-stage voltage regulation for the 6 rails are done on the main PCB.

6-rail LPSU main board

The motherboard is fed by the following independent 4 rails. These 4 rails have the second-stage voltage regulation on the main PCB as well.

  • 5V Standby
  • 5V ATX
  • 12V ATX
  • 3.3V ATX

Voltage regulators are from Texas Instruments used with ripple rejection enhancement circuit.

TI voltage regulators

Good quality components are used in the LPSU board, including Nichicon UKG smoothing aluminum capacitors, Nichicon UFG voltage regulator ripple rejection capacitors, the very expensive KEMET 22uF tantalum voltage regulator output capacitors, and WIMA bypass capacitors.

Voltage regulator input and output capacitors

Separate second-stage voltage regulation board for storage and USB Audio

A dedicated dual-stage regulated 5V rail can support up to 4.5A total current, supporting up to 3 devices in total. For example, it can be 3 SSDs or 2 SSDs plus an optical slim drive for ripping audio CDs. Nichicon UFG used as output and ripple rejection capacitors with WIMA bypass capacitors.

Second-stage voltage regulator board for SSD and USB Audio

A dedicated triple-stage regulated 5V rail with floating ground is available to support either user-selected USB regen cards or USB2 isolator card developed by AA Audio. Vishay MKP bypass capacitors are used only for this rail, replacing the WIMA bypass capacitors used elsewhere. Please note that the third-stage voltage regulator for USB Audio use is Analog Device’s LT1963A which costs a lot more than TI’s LM108x series.

USB2 Isolator

Even with a good LPSU, when the CPU is running, the CPU and supporting chips generate noise, which when bypassed, goes to the common DC ground. To ensure these noises do not get transmitted to USB DAC, we designed our own USB2 Isolator. The sound quality improvement is significant, even for DAC which already has USB ground galvanic isolation.

AA USB2 Isolator working prototype
AA USB2 Isolator installed inside FC10
AA USB2 Isolator with all components and cables are in place
Isolated USB Audio output
Inside picture with the SSD tray installed

Operating System and Playback Software

We experimented with Linux initially and tried various free and paid audio playback software. After we tried the regular Windows 10 and compare with Linux, we discovered that the sound quality is much better with Windows 10 and JPLAY FEMTO. Eventually we settled with Windows 10 IoT Enterprise LTSC custom-built with the unnecessary components removed or disabled (custom Windows installation ISO created). There is no need to use third-party software like AudiophileOptimizer or Fidelizer to optimize Windows further.

The music server works as a headless PC. If any connection to the server is required, for example installing drivers or performing Windows Updates, it can be done remotely from a tablet (RD Client) or from another PC. Some Windows 10 literacy is required to operate this music server. Online remote assist have been tested successfully as well.

For music playback control, BubbleUPnP (Android) or mConnect (IOS, Android) can be used. An example of use case given below.

After the music server AC rocker switch is turned on, the front white LED turns on briefly and then turns off (POST – motherboard’s power on self test). Press the front left button once to start / boot the music server – the white LED stays lit. If DAC is already connected, Windows startup sound can be heard form the hi-fi system. It takes about 30 seconds or more for Windows to stabilize and UPnP server visible within the home network. Launch BubbleUPnP or mConnect from tablet or phone, then select JPLAY FEMTOserver as Folder and JPLAY FEMTO as Renderer. Now ready for music playback control from tablet or phone.

To shutdown, stop music playback from tablet or phone. Press the front left power button twice. This initiates Windows 10 shutdown process. After about 5-10 seconds, the white LED turns off. The rear AC rocker switch can then be switched off.