First, for recording you should absolutely stay with UCX II.
Every other solution is a downgrade in various ways.

RME’s TotaMix FX offers EQ and other FX that you could try to fit your headphones’ sound.

If you still don’t like the sound of your headphones, get a pair of ones you like.
Trying to fit headphones’ sound by amp changes is a fruitless attempt, amps only offer minor variations of sound changes (EQ and DSP FX excluded).

Once you compare at exact same loudness (and possible FX), the amp differences disappear in the air.

My go to mixing headphones are Drop / Hifiman HE 4XX - the mix results sound great, and being planar magnetics the type of headphone amp is very uncritical.
And it doesn’t cost.

The key word is “subtle”.

That’s my experience too:
not enough difference to significantly change headphones’ or speaker’s sound to correct possible flaws, e.g. add significant amounts of bass to a lacking transducer.

Typical example:
the never ending search for an amp to partner with the famous Sennheiser HD 800S, where 3 dB of well tuned bass EQ would have solved most of the problem, with any amp.

Headphones or speakers for studio monitoring have a different purpose from those made for listening pleasure:

They have to, as easy as possible, lead you to a good sounding mix.
This means they have to show flaws of the recording and mix, but may not sound hyped or lacking anywhere.
E.g. studio monitor has a lot of punch -> resulting mix hasn‘t!

To stay with the example:
I could not do a mix with the Sennheiser HD 800S, EQed or not.

It’s a very personal thing and the resulting mixes are the only judge-able criterion.

Buying a better external headphone amp is a must. Don't listen to people who say the difference is negligible, they probably have never mixed on headphones extensively and don't know what they're talking about.

I'm mixing 95% of the time on headphones since I have annoying neighbours and no treated room anyway (only checking translation from time to time on my speakers) and it only really became possible as I bought a dedicated quality headphone amp. I make electronic & dancefloor oriented music and without this combination you won't be able to push at satisfactory high levels (from time to time, of course) to check that your music at 0db sounds great and loud like your reference tracks. Also I've noticed while mixing that amps allow for much more clarity and details in lows/mids/highs, it opens up and make the most of your headphones.

Where I started out I tried the usual budget devices like Scarlett 2nd/3rd gen, Motu (M4, which I still own, best portable USB-driven interface in this category, but limited in power precisely due to USB), Audiotent ID14 MK1, which all around have headphone output around 113/118dbish. Not good enough. I found out later that only the Audiotent MK2 had loud-ish headphone amp (125.5db) in this price range but even so I'd recommend always getting an external amp.

https://d9w4fhj63j193.cloudfront.net/20 … l%20V1.pdf [ID14 MK2]

The reason for that obviously is the fact that, at this price point, you can't expect a good built headphone amp to be included in the sound interface. Also, having a dedicated external amp will you not only the power you need to drive hungry (or even normal) headphones, but also more dynamics in combination with the soundcard's external output.

I'm not surprised the UCX II is disappointing when it comes to the headphone amp (113-115db only??), because again, I've never come across a good built-in amp unless you pay more than 2/3k for a sound interface.

The only brand that comes to mind with very good built in amp is the UAD series, for example the Apollo Twin X is known for being powerful with output dynamic range of 127DB and headphone output of 124DB (and better converters than the entry-level competitors obviously)

https://media.uaudio.com/support/manual … Manual.pdf [Apollo Twin X]

That said, I hate UAD locked system and love everything about RME, including TotalMix and the way it integrates seamlessly with my setup and workflow, so I'm still gonna go for the UCX II because for me it's the best sound interface still as of 2022 at this price point and for my needs. I don't need anything more expensive with more inputs as I do most of my stuff in the box with plugins anyway, a couple hardware synths maybe max. (I'll probably upgrade with the UCX III in the future, hoping they improve the low dynamic range and headphone amp situation to match UAD's. Or the UFX III if they come up with it before (likely), if I need the extra inputs it provides.

And also, because, and this is key, I'm using an external amp. I have noticed RME products are more quiet vs. the competition in terms of dynamic range (115db only for the UCX II!!), so you absolutely need to be aware of this and pair it with an external amp or the ADI.

https://gearspace.com/board/featured-ar … rface.html

"It’s 115dB dyn range in comparison to my Apogee Sym Desktop’s 129dB DA. The truth is if you’re gain structuring properly, it’s no biggie. I really enjoy the TotalMix software. I have had several mixes where I want to get it louder, but hey, the future looks bright for audio."

As of now I'm using the Lake People G103 S MK2 released in December (much improved and more powerful vs. the MK1), with pre-gain set on the +12db selectable, it's excellent for the price 250 EUR, cheaper than the THX/AAA series you have and best in this 200-400 eur range I believe, with very transparent sound.

https://manuals.plus/m/3c5897f78c5e3d57 … _optim.pdf [Lake People G103 S MK2]

Once I move to the UCX II though, I'll definitely replace the amp as well with the addition of a ADI-2 Pro (dynamic range of 144db) or the upcoming RME ADI-2/4 Pro SE, which I suspect will have least the same db power (if not slightly more).

The regular non-Pro ADI-2 DAC FS you're aiming for is a lot less powerful so I would advise to save up and buy one of the two aforementioned models. Really worth saving if you rely heavily on it daily.

Alternative option and cheaper amp if you want the power without RME - get the Topping A30 Pro (300-350 EUR) or even better quality the A90 Discrete (650 - 700 EUR) which is state of the art and can drive any headphone with great transparent sound. Both come with 145db dynamic range and were released this/last year. Check Audiosciencereview and other places online for full reviews.

Good luck.

"Condensed" is exactly the word I use too, or "compressed", always with most audio interfaces having low headphone output power.

Welcome to the club I've been there, it's a journey to perfect headphone sound quality, loudness, headroom and dynamics Very simple actually:

Step 1, you've found your perfect pair of cans, done, good job. Don't listen to KaiS, it has nothing to do with the headphones, even with 3'000 USD Audeze it will still sound shit with no amp - or another way to put it, it will only render 30 to 50% of the headphones potential. So not 'subtle' at all. 'Subtle' won't cut it when we're talking of improving by a magnitude of 50 to 70%.

Now step 2, get the (premium and transparent) amp or the ADI (Pro) your UCX II deserves. That's it fixed, you're welcome.

Thanks for the context, very interesting analog vs. digital and perceived loudness explanation. It is true but in my opinion it's still one part of the problem, the problem being oftentime poor headphone amp in interfaces causing this issue. I mean how come UAD which seems to be the exception here manages to get 127db (124 db headphone) then?

Yes 30% is probably too harsh lol, but 95 to 100% hmm is too extreme on the other side of the spectrum (in my perception and experience and with different low/mid-level interfaces). But I'm not specifically using the UCX II / ADI-2 Pro so I wanna save my assessment for later when I have them I'll report, I'm sure it's awesome including in headphone mixing context.

That said one day I would like to know why the 2021 released RME UCX II only has 115db output dynamic range versus 127db (124db > headphone output) for the similarly priced Apollo Twin X.

A higher interface output would help me and people like @wommas to be confident enough in the RME interface, and prevent having to stack it up with additional amp and/or the ADI, don't you think?