Looking for advice on my chain of OG DT -> ST -> DNII -> DTII.
Specifically, what to do with levels and the three compressors that are available so that all four boxes are audible. Don’t have a mixer yet, and when OB arrives for the DNII this can be handled inside Ableton. However, I would like to at least consider performing live and anyway would like the sound to be as good as possible.
Am very ignorant of what “gain staging” actually means - happy to be pointed to existing topics.
In a nutshell, gain staging refers to the balancing act which happens when you are seeking the optimal level where your signal has the least line noise but produces good levels and then how much gain (volume) the mixer of the device you’re feeding audio into is set to receive.
With older gear where, just for example, the signal might degrade over a certain level due to older op amp designs, but your device with a mixer that you’re feeding audio into may have an audible noise floor when you start turning up the gain, so while it can be used to describe other similar situations, in this situation I’m describing you would want the optimal balance between output volume (where unless you intend to capture the self-noise) you have an output level which does not have a lot of self-noise which can be detected, and an input volume on the mixer that does not create audible line noise from the mixing device but still gives sufficient volume to the audio source.
That, in a nutshell, is gain staging.
For you, these are all modern devices and Elektron specifically uses a volume knob which is an attenuator from 0 up to line level, and line level is typically the “optimal” output level for recording (although in practice that may vary).
So that essentially means when the volume knobs are on 10, your elektron devices should all be putting out roughly the same volume level, and I don’t feel like pulling up the manual but it’s whatever the db spec stated by the manual is.
So you could pretty much turn the output volume up all the way and then on the input device’s mixer, start low and move up to a volume that you feel is reasonable, and then you’ll need to check that mix across the 4 devices with some audio playing in order to make sure you’re happy with the final output levels. As long as it’s not clipping then it’s probably fine and can always be adjusted further.
I believe @Tchu says he sets his elektron devices to about 30 on the input of the mixer, maybe he can confirm.
Unfortunately, I don’t have a lot of advice on what to do with 3 compressors, but you could probably get creative if you’re up to it.
Simple to describe but worth a visualization.
“Gain staging” is finding your ideal balance of volume levels within each patch, within each device, between all devices.
Not even getting into the concept of “headroom”, you are looking to make sure you understand how much gain you need while understanding when you are distorting or clipping (analog much more pleasant than digital, but occasionally cleverly handled in the latter.) It will change based on volume, timbre, how much of the dynamics and frequency spectrum a bass patch or pad may take up. As well, you will be trying to not use too much gain for a quiet signal if you can.
Ultimately it is a workflow not an end state, finding your ideal time-energy in tweaking levels and occasionally tweaking but being able to move on. It’s much easier for simpler mixes, so keep that in mind and let that guide as much of your programming as possible so you’re not worrying too much to get everything playing nicely.
Instead of worrying about perfect levels which will certainly change from source to source and device to device… listening and practicing mixing will tell you what sounds good so much more than trying to guess.
Next you get to learn eq-ing track to track and decide to decide 
I suspect OP just isn’t very familiar with the hardware side of audio routing/staging, I’d assume concepts like headroom and eq are already present in their daw workflow but I don’t know for certain, it just sounded like for this person gain staging never really came up outside of being a phrase people use to describe what they know they’d now like to do.
Although if you have other questions about what’s been said, OP, I’m sure we’ll do our best to clarify.
Yep yep, some overlap with your post, and I figured I would also give another perspective on the concepts being referred to and their application, what people are looking to avoid and why it’s good to develop your ears and figure out what’s actually worth worrying about.
Less a hard numbers game as abstract goals you’re seeking to achieve without tweaking back and forth forever.
Regarding the compressors in your signal chain — I would recommend leaving them off or using them in extremely subtle ways as you get started. Compression is an awesome audio tool, but it can really mess up your mix if it’s not dialed in the right way.
I think if you have four Digi boxes running together, your first goal should be to just get the levels balanced across you tracks and make sure you can hear everything clearly. Use the Base-Width filter to carve out low end on anything that isn’t kick/bass, make use of panning, try modulating volume or velocity to get some dynamics going. Basically try to find ways to carve out space and make room in your mix — if you’re listening to your song and you wish the kick was louder, for instance, try to think about what elements you can turn down before you reach to turn the kick volume up.
Maybe I’m just projecting my own advice to myself but, for me, it’s pretty easy to get a “full” mix from even one Digi box, let alone four. But “full” isn’t really the goal — a much more interesting goal is how you keep things balanced, create a sense of foreground/background, create a sense of space and ambience, all that good stuff. Strive for clarity and fullness will follow.
Thanks all for the observations.
Wise words!
One trick i saw from similar post, is to press Samples button and set recording to Main LR src. Then you can use kick and bass f.e. and see on meter where do you hit your levels. That can be your base for other instruments