Yeah, the nice distortion comes from the Hotcake (Mark will know why he uses this one...)
It does not cut treble/bass and boost mids like other overdrives, and might seem less creamy for this reason, but in fact it is great to add all kind of subtle distortion as the clean sound is not compromised. And when you turn up the gain, there is a lot of distortion, more than with a typical tube screamer.