Thanks Mike,
that's pointed me in the right direction! In the plugin the levels are spot on right off the bat with the input and output gains at unity. In the standalone version I need to push the input gain by around 6 - 9 dB from unity to get a decent signal. Without doing that the sounds are really dull and lifeless. On the output side I needed to cut a full 18 dB! It was clipping here before, and between these two adjustments it's sounding a lot better now! Having said all that it still is a bit "grainier" and not as natural sounding to my ears. I agree that I can't hear a difference with most other instruments comparing these sampling rates, but with distorted guitar it is definitely noticeable, especially on high gain amp models. I only came to realize this after reading about it and trying it for myself on my other amp sims.
My UX1 is definitely limited to 48kHz, but I would be surprised if the standalone software would be limited on other devices capable of running higher sampling rates, since Podfarm runs quite happily at 96kHz as a plugin.
AmpliTube was doing the same thing as Podfarm, until I figured out that I had to start a new "Song" and then set the sample rate to 96k in "Project Settings". Unfortunately I can't find that option in Podfarm. I can select File / New, but when I then click on File / Preferences / Hardware / "Asio Settings" nothing happens (no window opens up). I can only open the Audient software manually and change the settings from there, but then the audio drops as described above. Either I'm missing something or you are right!
Thanks again for your help!
Cheers,
Treb