I used to use a Behringer, which was great for a bare-minimum, super cheap interface, but my current setup is a Scarlett. I use two channels for a GameBoy stereo out that’s unprocessed and then a mic into SC and back for effects processing.
I often use a LPF on the master out from SuperCollider just for warmth, but mainly for sound design and not usually for music. I’m not saying you shouldn’t, I’m just saying I personally don’t.
UA is really good for sure but from my tests i came to the conclusion that RME does a better job in providing a flat response to the sound output… but i might be wrong
That wouldn’t surprise me. UA as a company does not seem particularly preoccupied with flat frequency responses - all their other gear add a fair amount of coloration to the sound from OP amps and other factors. I really like the preamps of the UA as well as the ability to run UA plugs with super lo latency in the console, but then again I already owned a fair amount of UA plugs when I got the solo. I also like the fact that it is bus powered. But again, other interfaces offers similiar specs (except the UA plugs) and more routing possibilities for less than the Apollo Solo, I just really like this unit. Noise floor seems a non-factor to me almost regardless of which interface you buy, maybe except for the very, very cheapest (haven’t tried those) - all modern interfaces are super quiet compare to any vintage gear I own.
Most interfaces sound pretty great these days. What you pay for is durability. Buy nice or buy twice (thrice?). My 2012 RME UCX is still going strong twelve years later with no issues. High price to start, but then you are done.
I compared a Scarlett with a Fireface a couple years ago and was surprised by the difference. Of course the preamps were different, but even the DAC was noticeably more detailed, better spatial clarity etc. Scarlett felt a bit “smudgy” by comparison. So if I have a choice, I will use the RME, especially for recording / mixing. But on the other hand the price difference is huge and for live performance probably only a concern if the rest of your sound system is top notch.
Also second what sam says, RME lasts forever, I connect to an old UFX with USBC - thunderbolt - FW800 - FW400 and no problems
When I output stereo I started to simply use the headphone out of my MacBook instead of a dedicated DAC. Even on big and loud PAs with a high dynamic range this is sufficient w/ a DI box.
Only scary thing is accidentally plugging out/wiggling the cable… Hasn’t happened yet though.
On multi-channel I use a PreSonus 1824c, but nowadays I’d go for a MOTU Ultralite mk5 b/c you can easily fit it into a backpack and it has plenty of I/O. Although RMEs TotalMix is the gold standard in regards to routing and can save you some headache and time when setting up a performance…
In general: Only difference seems to be software and pre-amps nowadays - latter can be ignored if you don’t use microphones.
Things I found most relevant when evaluating DACs:
Take a look at the oldest product that the company still supports, this will give you a hint how long you can use a new interface
Backpack-compatibility
Support for DC offset (allows to control modular synths if this is of any interest to you)
Linux support / class-compliance - even if you currently don’t use Linux, you could give the interface “a second life” by using it as an audio interface on a raspberry
Proper routing matrix in software (IMO RME TotalMix is really good, Motu is also ok)
A common I/O socket format (e.g. RME often uses the headphone output as a dedicated output, so you need a stereo->mono splitter cable if you need all channels of your interface which would be bad if the cable you brought has a defect…)
ADAT support in case you need more I/O
Soundwise I think I couldn’t tell apart a cheap DAC (e.g. Behringer) from e.g. an UA. If this is your concern you should spend more time regarding speaker/room/volume configuration and your digital sound output (e.g. put a good VST EQ at the end of your chain). This will impact/change/improve(?) your sound much more than any DAC.