AIO Product Manual
17
USB Audio
The AIO is a USB Audio 2.0 Class compliant device and operates according to the USB
specification.
macOS (CoreAudio)
Support for USB audio is part of macOS and its audio component, CoreAudio. The AIO
is automatically detected whenever it is powered on and connected to a Mac USB port.
Programs send audio to and from the AIO the same as any other audio device, such as
the internal speaker and microphone.
Windows (ASIO)
Windows has no built-in support for USB Audio 2.0 and requires a driver to be installed
to support the AIO. Echo supplies a driver that supports the ASIO (Audio Stream
Input/Output) protocol as well as other audio APIs. Most professional audio and test
applications support ASIO, which Echo recommends for use with the AIO.
Multi-AIO Synchronization
Every AIO has its own internal crystal for generating the audio clocks with a tolerance
of ± 50ppm. When set for a nominal sample rate of 48,000 sample/sec, the actual
sample rates can vary up to 4.8 samples/sec between two AIOs. This causes problems
if multiple AIOs need to be used together for more channels than a single AIO can
provide. Output audio and recordings will drift between them and be out of sync.
To overcome this, the AIO may be programmed to slave its audio clock to the 8kHz
USB Start-of-Frame signal instead of using its internal clock. Multiple AIOs connected
to the same computer and running off of the USB clock will have their audio clocks
synchronized, running at precisely the same sample rate.
