yo I'm having trouble trimming samples. I'm confused on how to do it up to the knobs. start and end. idk what to do or how it works

I haven't used my 404sx much but you can edit the beginning and end with the mark button really quick. I do that and truncate the parts I don't need/

With the knobs Ctrl1 and Ctrl2 you can change start/end-points with +/- 30. But you can do it multiple times, and you can do it really fast.

Here's a video of a guy showing that:
https://www.youtube.com/watch?v=N-GztP2f0Js

I start with Mark-buttons and then adjust with the knobs.
DEL, MARK, DEL to truncate your last played pad.

thanx y'all i eventually figured it all out

You can also set the END by holding down MARK and playing a pad. MARK will blink, if you press it again, you set the end of the sample. Pretty quick.

i do it with mark but .. then adjust with CTRL's to trim start point a bit finer

note if you keep your samples on gate mode you dont need to mess trimming the end points too tight .. plus you can gagde how rapid response your sample are when you trigger them 1 1

Like jangle said, rough trim your sample with the mark button then fine tune trim it with the start and end knobs. Also, for cutting off the ends of samples (especially longer ones), I like to use the reverse button to cut off the clip at the end of the waveform. Finally, when using the start and end knobs, you can trim with the knobs, then press the START/END/LEVEL so that it's unlit, then turn it back on and your sample won't be truncated so that you can keep on trimming it without getting rid of parts of the sample you would potentially keep. At least this is how it is on the 404 SX. I hope this makes sense haha.