The ζ1 Audio Widget asynchronous USB-I²S module

Quick glance

This page contains the following content:

Installing the board interface pin headers and receptacles

The ζ1 module does not include the female receptacle strips needed to mate the ζ1 module to the main board. Please see the
Parts list section for part numbers and ordering information.

The convention is to install the female receptacle strips on the bottom of the ζ1 module, and the matching male pin headers on the main board.

As mentioned in the parts list section, the 31P and 30P interface connector segments are each to be joined by 2 pieces of female receptacles strips to make up the correct number of positions. In order for the strips to fit, you must remove a small amount of material (0.25mm) off the ends of the strips' plastic housing where they will join together. You can use a sandpaper or a flat file to do this. Test fit the female receptacle strips on the male pin headers.

To ensure proper fit and connectivity, you should mate the male pin headers and female receptacles together first, then insert the solder tails on these to their respective holes on both the main board and ζ1, then solder them. Do one pin first and check that the connector is perpendicular to the boards, reflow and adjust if necessary. Only when everything is aligned perfectly do you solder the remainder of the pins.

After you have finished soldering the receptacles, clean up the flux residue with isopropyl alcohol or special electronics flux remover.

USB connector, cable and plug handling

The ζ1 has a 5-pin Mini-B USB receptacle. You should use the appropriate cable to connect your computer or mobile device to the ζ1. Most computers have USB-A connectors, so you need a USB-A to Mini-B cable. For mobile and tablet devices see the appropriate sections below.

WARNING: Be careful when plugging/unplugging the USB cable, and handle the cable and plug gently. They could exert a large force on ζ1's USB receptacle and cause it to tear off the circuit board.

Using the ζ1 with a computer

The minimum operating system versions supported by ζ1 are as follows:
  • Linux kernel version 2.6.37 or later
  • MacOSX 10.6.4 or later
  • Windows 7 or later
Using ζ1's USB audio functionality is the same as any other outboard USB DAC. You simply connect a USB cable between ζ1 and the computer, and the computer should recognize it as "AMB zeta1 USB-I2S Audio-Widget". Then, you configure your media player software to use the ζ1 as its output device.

Special notes about using ζ1 on Windows

Using the ζ1 with a smartphone or tablet

Not all host devices support streaming digital audio to a asynchronous USB DAC, and not all of them support UAC2. The following are some tips for using ζ1 on iOS and Android platforms. The minimum platform versions are:
  • iOS 7 or later
  • Android 4.1.1 or later, with support for USB OTG and host mode
Android support of USB DACs is a mixed bag, and varies with device manufacturer and model. If the you cannot get the ζ1 to work with your Android device, try
USB Audio Player Pro.

ζ1 could operate in either self-powered or bus-powered mode, and is typically hard-wired to one of these by the main board.

ζ1 in self-powered mode

The γ3 high resolution DAC belongs to this category. You should be able to connect the smartphone or tablet directly to the ζ1 using an appropriate cable. If this doesn't work, then try the bus-powered instructions below.

iOS (Apple iPhone, iPad and iPod Touch)

What you need:
  • One of the following USB camera adapters appropriate for your Apple device. †
    • MD821AM/A - Lightning to USB Camera Adapter (new version)
    • MD821ZM/A - Lightning to USB Camera Adapter (old version)
    • MK0W2AM/A - Lightning to USB3 Camera Adapter (with extra Lightning port for DC power)
    • MC531ZM/A - 30-pin to USB Camera Adapter (for older Apple devices with a 30-pin interface connector)
  • USB cable (USB-A plug to Mini-B plug)
  • iOS 7 or later (iOS 9.3 or later if using the MK0W2AM/A Lightning to USB3 Adapter).

How to connect:
  1. Plug the USB camera adapter into your Apple device.
  2. Connect the USB-A to Mini-B cable between the USB camera adapter and the ζ1.
  3. If you're using the Apple MK0W2AM/A USB3 Camera Adapter, you can optionally connect a power source to its Lightning port to charge your Apple device's battery, but it is not required for the ζ1 to work.
  4. Your Apple device should now play audio through the ζ1. This works with the ζ1 in UAC1 or UAC2 mode. UAC2 is required for sample rates higher than 48KHz.

Android

What you need:
  • Android 4.1.1 or later, with support for USB OTG and host mode
  • USB OTG cable (USB-A socket to Micro USB plug) ††
  • USB cable (USB-A plug to Mini-B plug)

How to connect:
  1. Plug the USB OTG cable to your Android device.
  2. Connect the USB-A to Mini-B cable between the USB OTG cable and the ζ1.
  3. Your Android device should now play audio through the ζ1. This works with the ζ1 in UAC1 mode. UAC2 is required for sample rates higher than 48KHz, but may or may not work on your particular device.

ζ1 in bus-powered mode

The γ1.5 miniature DAC + headphone amplifier belongs to this category.

Most smartphones and tablets cannot supply sufficient current to power the ζ1 and its mated device. Even for those that could, there would be a large drain on the device's battery, leading to very short run-time.

To work around this problem, a powered USB 2.0 hub (having its own DC power adapter) can be used. The hub would supply power to the ζ1 and its connected device while drawing negligible current from the host.

Not all powered USB hubs will work well on all hosts. You should choose a hub that reports low current draw to the host, otherwise the host may refuse to recognize it (and any devices attached to the hub).

In all cases, it's important to connect the ζ1 last, so that when the ζ1 gets power from the USB hub, the smartphone or tablet is available for USB device enumeration.

iOS (Apple iPhone, iPad and iPod Touch)

What you need:
  • One of the following USB camera adapters appropriate for your Apple device. †
    • MD821AM/A - Lightning to USB Camera Adapter (new version)
    • MD821ZM/A - Lightning to USB Camera Adapter (old version)
    • MK0W2AM/A - Lightning to USB3 Camera Adapter (with extra Lightning port for DC power)
    • MC531ZM/A - 30-pin to USB Camera Adapter (for older Apple devices with a 30-pin interface connector)
  • USB cable (USB-A plug to Mini-B plug)
  • A Powered USB hub and a USB hub to host cable (if your hub doesn't include one). One end of this cable should have an USB-A plug for connection to the USB camera adapter, the other end should have the appropriate plug for your hub's host connector (usually USB-B or Mini-B). On some hubs this cable is a "pig tail" (i.e., permanently attached to the hub).
  • If you're using the Apple MK0W2AM/A USB3 Camera Adapter, you can optionally connect a power source to its Lightning port to charge your Apple device's battery, but it does not provide sufficient power for a ζ1 configured for bus-powered operation. The powered USB hub listed above is necessary to remedy this situation.
  • iOS 7 or later (iOS 9.3 or later if using the MK0W2AM/A Lightning to USB3 Adapter).

How to connect:
  1. Connect the USB hub's DC power adapter and plug it into an AC wall outlet.
  2. Connect the USB hub host cable between your USB camera adapter and the hub's host side connector.
  3. Connect the USB-A to Mini-B cable from the hub to the ζ1.
  4. Plug the USB camera adapter into your Apple device.
  5. Your Apple device should now play audio through the ζ1. This works with the ζ1 in UAC1 or UAC2 mode. UAC2 is required for sample rates higher than 48KHz.

Android

What you need:
  • Android 4.1.1 or later, with support for USB OTG and host mode
  • Powered USB 2.0 hub
  • USB OTG cable (USB-A socket to Micro USB plug) ††
  • USB cable (USB-A plug to Mini-B plug)
  • USB hub to host cable (if your hub doesn't include one). One end of this cable should have an USB-A plug for connection to the OTG cable, the other end should have the appropriate plug for your hub's host connector (usually USB-B or Mini-B). On some hubs this cable is a "pig tail" (i.e., permanently attached to the hub).

How to connect:
  1. Connect the USB hub's DC power adapter and plug it into an AC wall outlet.
  2. Connect the USB hub host cable between your Android device and the hub's host side connector.
  3. Connect the USB-A to Mini-B cable from the hub to the ζ1.
  4. Your Android device should now play audio through the ζ1. This works with the ζ1 in UAC1 mode. UAC2 is required for sample rates higher than 48KHz, but may or may not work on your particular device.
   †    Non-Apple generic USB camera adapters probably won't work, even if they have the correct connectors.
   ††   The Micro-USB plug on the USB OTG cable should have its pin 4 (ID) internally connected to pin 5 (GND). This will set the Android device's USB port to run in host mode.

Switching between UAC1 and UAC2 modes

If you only plan to use Linux, MacOSX or ASIO-enabled media player software on Windows, use UAC2. If you want to use generic players on Windows, use UAC1.

The Reset and Prog switches on the ζ1 module are used to toggle between UAC1 and UAC2 modes, as follows:
  1. Press Prog and hold until the external LED changes color and then go dark.
  2. Release Prog.
  3. Press and release Reset.
  4. The ζ1 is now set to the new mode. The external LED will glow red in UAC1 mode, or green in UAC2 mode.
On some main board implementations, such as the
γ1.5 miniature USB DAC + headphone amplifier, the Reset and Prog switches are also replicated on the main board and accessible on the rear panel.

Rather than using the Reset and Prog switches, on the γ3 high resolution DAC, you should use its on-screen Menu Setup to change UAC modes.

The Reset and Prog switches are also used to setup the ζ1 module for firmware flash. See the Firmware section.

Asynchronous rate-feedback indicator

In asynchronous USB mode, the DAC's clock is used to control all data transfer timing from the host, in order to keep the timing as perfect as possible, thereby eliminating jitter.

There are two LEDs on the ζ1 module, one red and one green, that are indicators of asynchronous mode rate-feedback activity. Most of the time both LEDs are off, but one or the other LEDs would blink on momentarily when the computer is telling the computer to speed up or slow down the data transfer.

These LEDs are informational only, perhaps useful for debugging.

Firmware & device driver source code

The Audio Widget firmware and Win-Widget ASIO UAC2 device driver are open source. Both are hosted at Github:
The source code repositories listed above is for your interest and perusal. However, for the ζ1 module, please use the pre-compiled firmware image and Win-Widget installation executable binaries offered for download at this website. They were compiled with the appropriate options to ensure compatibility with the AMB-branded Audio Widget modules. They were also extensively tested to ensure stability.

AMB follows the development of both projects and releases its own binary updates based on the main Github repository, and such updates are announced at the AMB DIY audio forum.

For instructions on how to flash the firmware, see the Firmware section.


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