I have an original Allo supply and have compared the two. The SMPS is grainier and a little peaky in the treble. To me it imposes things on the music. To my ears, the Shanti doesn't do this. The USBridge Sig becomes far more transparent and "disappears" into the system. The result is that you get a much better feel for the original recording quality, for better or worse. The *distinction* between recordings is startlingly better. The same goes for the DigiOne Sig. I have the original DigiOne Pro and it didn't stay in my system--it had that "glassy" sound that I associate with coax. I also have an original USBridge with the Sparky board. It was okay but again it didn't stay in the system, because it wasn't better than a direct USB connection from my Mac Mini.
The USBridge Sig/Shanti combo is clearly superior to a direct USB connection from the Mac Mini or any of the other PCs I have lying around. I haven't heard any of the more expensive renderers, like the ultraRendu or SOtM or Lumin or what have you, so I don't know how much better it gets, but for $400 this is a very big improvement in my system.
This past week I helped a friend on the opposite coast set up a USBridge Sig/Shanti combo with Moode Audio and Kazoo so he can stream hi-res Tidal. Previously he had a Macbook Pro directly connected to his DAC. After we got the Allo/Moode/Kazoo system up and running, he texted me "thank you thank you thank you thank you thank you."