The optional card contains a high spec, low jitter A/D converter and gives the VoiceMaster Pro a 24-bit S/PDIF digital output capable of up to 96KHz sample rate on an RCA phono connector. It has a word clock in the connector for syncing to external devices too. Unless your computer has a S/PDIF input built-in (some cheaper internal sound cards do) it does not allow you to connect the unit directly to your computer for recording into your DAW - you will need an audio interface/sound card with an RCA S/PDIF input for this (check out the Focusrite Saffire as an example).

There are a few reasons why you may want a digital output from the VMPro:

• cable interference is not an issue with digital signals so no noise will be induced as with an analogue connection, thus the recorded signal will have a slightly lower noise floor.
• the VoiceMaster Pro converter is of better quality than that in your audio interface/sound card.
• all analogue inputs on your interface are being used so you only have the option of connecting to it via S/PDIF.

The part is 'MH444 Platinum ADC R2' (some stores may refer to it as just Voicemaster Pro digital card or something similar).