The description says that the DAC can be used for I2S or S/PDIF signals and that switching can be done with jumper J3. Since I wanted to connect both types of input, I connected J3 with a toggle switch on the front of my Amp. S/PDIF signal from my CD drive and I2S from a Raspberry Pi and a HifiBerry Digi-Pro hat. Roon installed on the RPI. CD playing, with J3 closed worked well. As soon as an I2S signal is also send to the DAC, it switches to I2S, regardless of the position of J3. Also after switching off the I2S signal, it remains locked on I2S. Service desk of Audiophonics waved me away, saying basically that this is the way this DAC works. To me this is a design flaw that needed a resolution, which I have found. When switching to S/PDIF (closing J3), the I2S / BCK connection between the RPi/HifiBerry to the DAC needs to be interrupted. I use a dual toggle switch to do that, works well now. So first 5 stars with just CD, then to 1 star for not working as expected and finally to 3 because of the design flaw. For the money though a good sounding DAC with the option to upgrade the OPA to a better one. Greetings.