USB Audio¶

About USB Audio¶

The miniDSP Flex HT accepts multichannel (8-channel) PCM audio over USB at sample rates up to 96 kHz. The same USB connector is used for playing USB Audio as well as for configuration and Dirac Live calibration.

To play USB Audio from a computer, use the supplied cable to connect the USB 2.0 (Type B) port of the Flex HT to a free USB port on your computer.

Alternatively, connect a network streamer to the USB port. For examples using the Raspberry Pi, see these application notes on our website:

Note

While some miniDSP processors provide the processed outputs to the computer over USB, the Flex HT does not.

USB Audio channel mapping¶

The channel mapping of USB Audio differs from HDMI. They are shown in the table below:

Channel	HDMI Audio	USB Audio
1	Left Front	Left Front
2	Right Front.	Right Front
3	LFE	Center
4	Center	LFE
5	Left Surround	Left Back
6	Right Surround	Right Back
7	Left Back	Left Surround
8	Right Back	Right Surround

In the Flex HT, we have chosen to use the HDMI channel mapping as the default. Some additional configuration may be required for USB Audio:

macOS. The channel mapping can be changed directly in macOS. See macOS channel mapping below. Alternately, the configuration described in Configuration for USB Audio below can be used.
Windows. The channel mapping can not be changed in Windows. Use the configuration described in Configuration for USB Audio below.

macOS¶

The miniDSP Flex HT is USB Audio compliant, so no drivers need to be installed to play audio on macOS. Open Audio MIDI Setup (in Applications->Utilities) and click on its name in the list on the left-hand side.

Set sample rate¶

Click on the selector next to Format to bring up the sample rate and bit depth selector. Sample rates up to 96 kHz can be selected:

Default audio device¶

To set the Flex HT as the default audio output device, right-click and select "Use this device for sound output":

Set miniDSP Flex HT as default macOS output device

Note that individual audio playback apps may allow the Flex HT to be selected for audio output independently of the system default. They may also control sample rate automatically.

macOS channel mapping¶

To change the channel mapping to match HDMI, click on the Configure Speakers... button. On the dialog that pops up:

Select "7.1 Rear Surround" from the drop-down selector near the top.
Swap the channel assignment for Center and Subwoofer.

This is highlighted in the screenshot below.

Configure USB channel mapping for Flex HT in macOS

Windows 11¶

Note: to play USB audio from Windows, the miniDSP UAC2 driver package must be installed first.

Default audio device¶

To set the miniDSP Flex HT as the default audio output device, open the Settings app and navigate to the System → Sound page. Select the Flex HT with the radio button:

Set miniDSP Flex HT as default Windows 11 output device

Set sample rate¶

To change the bit depth and sample rate, click on the rightward angle symbol >. Click the selector next to Format to pop up the sample rate menu. Sample rates up to 96 kHz can be selected:

Set miniDSP Flex HT sample rate in Windows 11

ASIO¶

If your audio application supports ASIO® audio drivers, we recommend selecting the miniDSP ASIO Driver in its settings. This typically allows the application to automatically change sample rate. For example, in JRiver Media Center:

miniDSP UAC2 control panel¶

The current settings of the miniDSP Flex HT can be viewed by opening the miniDSP UAC2 Control Panel from the Windows Start menu (under the miniDSP Ltd folder). This control panel allows you to view current settings. In addition, it can be used to set buffer size, although we recommend that you leave this setting at the default. If you are having an issue with inadequate output volume over USB playback, check the Volume tab.

To see the installed version of the UAC2 driver, use the About tab:

Configuration for USB Audio¶

The difference in channel mapping for USB Audio and HDMI can be confusing. However, it is not too difficult to adapt by using some changes in labeling and channel routing. There are two steps:

Change the input channel labels on the Input Channels tab, as shown in this screenshot:
Change the routing on the Channel routing tab as shown in this screenshot:

With this done, the output channel labelling and Mixer tab examples in the rest of this manual are correct.

Tip

If you use both the HDMI and USB inputs for multichannel audio, create a separate preset for each. When switching inputs, switch presets as well.