SPDIF

This is the digital out of the soundcard.

More about SPDIF

Speaker setup

Configure is disabled here as the audio is send straight to the DAC.

Not to be mistaken for unaltered.

Properties

General

Not much to configure here.

The Properties button gives information about the driver.

I use the standard Windows HD drivers.

Formats

Check the sample rates supported by your DAC.

If you play audio with a sample rate not supported by your DAC, the Windows audio engine will do the sample rate conversion.
If you have an upsampling DAC you can use this settings to compare the SRC by Windows and your DAC. Assuming Redbook audio (44.1,) uncheck all but 44.1 and the DAC will do the upsampling.
Uncheck all but the highest input of the DAC and Windows will do the upsampling.

Level

In general it is recommended to set both volume and balance to 100 to avoid any impact of the digital volume control.

Enhancements

I belong to those silly purist who think the greatest enhancement is to disable them all.

Advanced

 

The Default Format is the one used by Windows in shared mode.

The audio engine will mix and resample all the streams to the rate set in this panel.

24 bits: my DAC is 24 bit.

Playing 16 bit using this setting won’t do any harm  as simply 8 zeroes are padded.

I set the sample rate to CD quality as almost all of my audio is 44.1 kHz.

 

Allow applications to take exclusive control should be checked if you plan to use WASAPI.
Give exclusive mode applications priority might save you a couple of dropouts.

WASAPI

WASAPI is Microsoft’s own ASIO, it talks straight to the soundcard if set to exclusive mode.

As it is exclusive mode, no other application can use the sound card.
No more system sounds at full blast over the stereo!

 

As WASAPI in exclusive mode talks straight to the driver of the audio device, the stream send to this device must match the capabilities of this device in terms of bit depth, sample rate, number of channels and audio format (PCM most of the time) otherwise it is silence.

The program using WASAPI can do this by configuring the audio device to match the source.
In this case we have bit perfect playback.
This allows for automatic sample rate switching as well.

 

The developer can also choose to adept the source to the capabilities of the audio device.
If the source is mono and the audio device 2 channel, the developer might decide to send the same signal to both channels.
If the sample rate of the source is not supported by the hardware e.g. 192 kHz source with a 96 kHz audio device, the program using WASAPI has to do the SRC (Sample Rate Conversion).
Check if the SRC implemented by this program is an improvement compared with the SRC provided by Windows because writing a good SRC is not trivial.

 

Obvious using WASAPI in exclusive mode doesn’t guarantee bit perfect playback.
It is up to the developer of the media player using WASAPI to see to it that the playback is bit perfect.
Bit perfect playback is impossible by design if de properties of the audio file e.g. sample rate are not supported by the hardware.

More...