The audio interface is the bridge between electrical signals and VA’s numerical processing. Converter quality, analogue circuitry, drivers and the selected Windows audio API all influence latency, stability, supported formats and measurement performance.

MME, WASAPI and ASIO

MME

The historical Windows multimedia interface. It offers broad compatibility and remains useful for legacy devices and VA functions that still depend on the traditional path.

WASAPI

The modern Windows audio API. VA supports event-driven capture and rendering, shared mode for convenient system integration and exclusive mode when direct control of the endpoint format and latency is required.

ASIO

A low-latency professional driver model commonly supplied with audio interfaces. In the current VA release, ASIO support is available only in the 64-bit version.

64-bit requirement for ASIO Select VA64 when an ASIO driver is required. VA32 continues to provide MME and WASAPI operation but does not currently expose the ASIO engine.

Shared and exclusive WASAPI

Shared mode cooperates with the Windows audio engine and can use system format conversion. Exclusive mode gives VA direct access to the endpoint for the selected session, avoiding the shared mixer and allowing stricter control, but the requested format must be accepted by the device.

Choosing an interface

  • Stable drivers
  • True line-level inputs
  • Low and predictable distortion
  • Adequate sample rates and bit depth
  • Independent input and output paths
  • Known gain and calibration behaviour
  • ASIO support when low latency matters
  • Electrical protection for external circuits

Measurement limitations

Most audio interfaces are AC-coupled and therefore cannot measure true DC. Their bandwidth is normally limited to audio frequencies or slightly above. Calibration and correction curves can reduce systematic amplitude errors, but cannot recover information outside the physical bandwidth or dynamic range of the converters.