Hi there,
I've been testing my new Studio 1824 off my Fast Track C400. I recorded the demo from my Yahama TG33 module (an early 1990s synth). I found it was surprisingly difficult to get the volumes on both audio interfaces exactly the same, but I think they're close enough. I'll refrain from giving my view. I'm interested what others think.
Thanks
C400:
https://soundcloud.com/user-511601773/c400-tg33-demo
1824:
https://soundcloud.com/user-511601773/1824-tg33-demo