Improving my Bluesound Node 2i

In my BlueOS app settings I have Digital Passthrough enabled, which should be pretty foolproof towards using the Node 2i strictly as a "transport". When you enable that setting, all other settings which could affect your output gain/level are fixed (greyed-out) to their appropriate values. E.g. Output level is locked to "fixed" instead of "variable", Replay-gain is disabled, etc. Even if you have Digital Passthrough already enabled, you might try toggling it off/on again, as software engineers like me LOVE writing bugs like that lol.

Beyond that, there’s a much higher variance in album-to-album digital file/media levels, versus vinyl. I HATE this; it’s one of my main complaints about digital - as I’m constantly re-seeking that "golden" level. Meanwhile I can keep volume pretty much constant though a whole long-ass session of viny. This is what the Replay-gain setting is intended to address, btw. 

Once you’ve verified that setting, it’s unlikely to be a problem with your Node 2i. Maybe Spotify settings? I don’t use that app/streamer. And I’d start looking at the Audio gd DAC (and the rest of your downstream) - for example, that gain switch - is it a little toggle? Or little DIP switches - I REALLY hate those. I’ve had those switches fail in the past. It’s good to have another DAC (or whatever component) on hand or on loan to verify in these scenarios. 

Is there a way to verify that you are truly getting a lossless stream from Spotify? If it has changed for whatever reason to a lossy stream it might explain the lack of sparkle. 

Also, a bit of a long shot and tough to verify, but looking up the Onix, it appears it might be on the older side. Any chance the caps might be getting a little tired? 

Try shutting everything down and unplugging everything including all interconnects then put it all back together and see if that helps.  Especially with DACs and streamers this can sometimes do the trick, and cleaning your connections is a good idea too as oxidation/dirt can affect performance over time.  Hey, it’s free and easy and may help and good to at least rule out if nothing else.  Best of luck.

Spotify "Lossless" is still compressed by about 50%

I stream Qobuz in my main listening room but I also use Spotify since my kids are in that ecosystem.  When A/B ing between Spot and QB the increase in SQ from QB is meaningful, esp. in bass response.  

I often make a playlist on QB and use an app called SongShift (free) to convert the playlist from QB to Spot which I then share with my kids.

Since your beloved playlists can be converted I would recommend giving QB or Tidal a try.

As far as getting more SQ out of your current system, I would recommend trying an external linear power supply for your Node.  I got a notable upgrade with more control and clarity in the bass after the upgrade.  Good Luck and Cheers

When I had my Node2, I installed the LHY power board and used their outboard LPS.  I thought it made a huge difference.

https://www.beatechnik.com/product-page/lhy-bluesound-psu-kit

Very easy to install and really did lift the performance of the Node2 several levels.

Well worth the small investment.