Is it worth upgrading my audio interface

Danny1969

@Ramirez ;
Some valid points taken from real world recording  experience and I respect that. I do feel I can hear a difference though. The gain bunching you mention is something I know about. I've designed quite a few mic pre amps and getting a pot with the right kind of log law to prevent that effect means generally a custom job. Log lin and Audio won't get near, Log X will kind of be OK until the last quarter then it will generally all come at once. Resistor ladder switching is more controllable but more complex and dearer to implement so most designers including myself who have to use off the shelf components make do. 

What I think I hear when plug'ed into a nice pre is a rounder fatter more focussed sound ..especially on kick and snare but also on loud vocals. Other stuff like overheads and guitar mics though I'm not so fussed. From an electronics point of view I think there's a pleasing harmonic content added with transformer coupled pre amps and a more focussed sound from the class A biased transistors rather than the use of op amps like you get in cheap pre amps . 

WiresDreamDisasters

Worth bearing in mind, some preamps sound totally shite when overdriven. Like the Focusrite ISA220 and 430. They're both great preamps and have nice built in EQ and compression, but they sound terrible when you try to get some saturation out of them. The Presonus ADL600 sounds a lot nicer for that. I don't know if it's valve versus solid-state or what.... but this was my experience.

The SSL X-Logic Alpha is another one that I had to be careful with the gain with - sounded crap when it was driven slightly.