A Disney Sound Source / Covox Speech Thing / Faster Than Light Sound Adapter replica
Mode can be selected with the DIP switches on the card:
The last options is mostly so that it will be detected as a sound device by Dungeon Master in DOS.
The device includes a switchable bass filter that you may adjust to your liking:
So, this is a Disney Sound Source clone and not just a regular resistor DAC that can be found aplenty around the internet. The difference between a regular DAC (or Covox Speech Thing) is that the DSS has a 16-level output FIFO that makes the sound perhaps a little better. Some games require a DSS and won't work with a Covox device; for example Wolfenstein 3D, for which you can find demo video below.
It also has a built-in headphone amplifier, ESD protection and some filters to make sure the sound does not get distorted by your headphones (a common issue with simpler adapters available elsewhere) or that the sound level is reduced.
The most common feedback I received from beta testers was regarding the type of USB connector to use. Almost everyone preferred USB-C, so that is what is used as the power supply. Please note that it is quite sensitive to the type of charger you use. Some may not be well-filtered and can produce an audible hum from the mains. If that happens, try a different charger. It doesn't seem to matter whether you use a cheap or expensive one; it appears to be completely random.
If you have any questions, please don't hesitate to ask!
David