Difference in sound between the RME ADI-2 DAC and the RME ADI-2 Pro DAC

I would say there is no difference in sound quality.  The "pro" version just adds analog audio inputs which allow you to record sounds into a computer.

You're better off getting the non-Pro version and then adding a really good external linear power supply.

Yes additional analog inputs and also headphone outs as well. I have the FS version and added the Teddy Pardo power supply and absolutely love it. Don’t think there’s any difference in sound as it uses the identical chip set.

It used to use the same chip until a fire at AKM limited availability. . The DAC is using an ESS chip and though they make it sound  extraordinary with their other components, it's an  ES9028Q2M. Check out its specs.

I first t he DAC first bought and the day I received it went on sale for $999- $300 off. The Pro went down from $1999 to $1699. After a couple of weeks, the Pro returned $2K and the DAC remained on sale everywhere. I picked up the Pro on sale.

Both are a great buy- incredible versatility with Bass, Treble, and a 5 band Parametric Eq. If you listen to the pro in balanced mode the volume jumps significantly in low power mode. I don't have measurement tools but it may double.

Both units are easy to love and recommend.

Agree with others above. Have the FS with Teddy Pardo PS. The Teddy Pardo made a nice improvement across the board, plus a lot more options for power cables.

Maybe this experience of forum member VySer with Teddy Pardo will be an eye-opener...