Let's start with the physical stuff:
1. The form factor is good. It doesn't take up too much space on my desk and it isn't too tall so it doesn't get in the way when doing something else. (See my comments later on the LEDs)
2. The top of the Atom is black while the sides and bottom are white. This looks a bit off on a black mixing desk. I would have preferred it to be all black.
3. The pads, knobs, and buttons feel really nice. If you want an Akai MPD pad tactile feel, these aren't the pads for you. I do wish the knob had a "push" function like the X-Touch Mini. I'm used to using that for parameter selection in plugins.
4. While technically not physical, here's as good a place as any to talk about the LEDs. They are super bright and distracting. Yes, you can dim them in advanced setup, but even then they are still pretty bright. Also, if you unplug and re-plug the Atom, the LEDs return to full brightness. I've resorted to leaving it plugged in and putting a small, flat cardboard box over it when I'm not using it. The green/blue Presonus logo at the very top is easy to cover with Gaffer's tape. BTW, It's blue when connected to SO4 otherwise it's green.
Now for the MIDI stuff:
1. The pads send pre-defined MIDI notes and CANNOT BE EDITED. Even though there are eight banks to chose from, each bank is just a sequential group of MIDI notes. You'll have to use Midi note re-mapping as described here:
https://youtu.be/ceTWomSAMeE to record notes appropriate for a General MIDI Drum Kit.
2. Pads send MIDI Aftertouch which CANNOT be turned off. Search for "reaper midi filter" and you'll find a couple of options to "fix" this.
3. The knobs work as expected, sending a stream of CC's with values of 00-127. I like the fact that these are not continuous meaning they stop at "00" or "127" no matter how many times you turn them. You can also hold down the shift key and get a second set of values for a different CC. Granularity is nice with three full rotations from 00-127. I found them very smooth and linear.
4. The Buttons, starting in the lower left is the SHIFT button. This is an internal button and doesn't send any MIDI messages. It's used as a modifier for other controls.
5. The MODE Buttons are a little strange. They send MIDI CC messages but they also control local behavior at the same time. For example, Note Repeat is a latching button. Pressing it send CC24 with a value of 127. It also puts the Atom into note repeat mode where you can set the repeat rate for rolls. Pressing Note Repeat again sends a CC24 with a value of 0. Full Level does something similar by sending a CC25 and then all pads send full velocity until Full Level is pressed again at which point it sends CC25 with a value of 0. I have to question what the usefulness is in sending the CC messages for the Mode buttons? I'd like to understand that a bit more.
6. For the INST Buttons, the Bank button is similar to the MODE buttons, in that it sends a CC and then controls an internal Atom function, and then sends a CC when released. The Bank button is a momentary so you have to press and hold it to select one of eight pre-defined pad banks. One cool thing the Bank button does is sends a Note Off for all of the notes in the current bank so it could be used as a quick panic for stuck notes. Preset +/- is latching and in addition to sending a CC message it also causes the pads to change what notes they send. Releasing it returns the pads to their normal bank assignment. Show/Hide just sends a MIDI CC and doesn't appear to change anything locally on the Atom.
7. The Song and Event Buttons appear to just send MIDI CC messages and don't appear to have any local functionality. All four are latching.
I'll continue with the buttons on the right after a short break. I plan to continue to update/edit/refine this as I learn more.
One additional thing that just annoys the heck out of me and that is the fact that the PDF manual for the Atom doesn't take you to the page that's referenced in the Table of Contents. Sure, I can jump straight to the page using a "go to page" option but that shouldn't be necessary. OH yeah, I forgot this one. They didn't take into account the title page and table of contents in the page numbering so If the Table of Contents says "34" and you go to "34" you end up on page 32. Annoying.
Feel free to ask any and all questions. I'm happy to take "can you try this?" requests since it helps me learn more about the controller.
Stay tuned,
Ken