I have uploaded a zip file - out.dng is the output of validate dng.
https://dl.dropboxusercontent.com/u/9906333/dngs.zip
Look at the edges of the white chair - you will see classic jpeg compression artifacts.
Note that this is the default lossless jpeg conversion only.
I used the program as
dng_validate -dng out.dng <input>
I confirmed this with a build in Visual Studio using qDNGUseLibjpg=0
I would appreciate the admins looking at the provided examples.