The DSP board is great, how it works has never been a secret. Think of the DSP board as an analog mixer with channel inserts and two sends, built into the S2400 audio path, and under control of the S2400.
Check out this post, there’s a lot of useful info in the thread in general. It explains the DSP hardware architecture.
If you remember way back when, the initial discussion of FX were that they were going to run on the S2400’s own CPU. If that had been the case, those FX would have been in the digital domain.
Instead the DSP card sits in between the main board and outputs. The built in analog filters aren’t part of the DSP audio, either.
lilbrimstone explained a useful workaround,
“with the current firmware it’s possible to record DSP in a live loop if the live loop input is set to USB. No cables required! I can do pretty much exactly what I’d like to do, it’s just cumbersome like I said. The sequencer has to be running and you only get the length of the pattern to record, then you have to convert to wav and delete / add to track.”
You can also do it if you have a mixer via the live looper.
There are all kinds of options for what you are monitoring and how.
Later in the thread av500 said that resampling with dsp via a menu is in the roadmap