There is no absolute truth because the basic requirements are always different (hearing ability, premises, equipment, daily form). For many, the truth is that they can't tell any difference in sound. But that doesn't mean that there aren't any.

There are also technical differencies between products. ADI-2 DAC/Pro have switchable D/A filters with certain properties, different latencies, other devices do not, a recording interface also needs fast converters, among other things.

Marketing will always emphasize the special capabilities and features inherent in the devices.

KaiS has already reported why he prefers the D/A filter slow and I also could hear differncies between D/A conversion of ADI-2 Pro and Accuphase some years ago. There I found a setup which made it possible to switch between both quickly. The differences were small but recognizeable. Accuphase's DAC converter board sounded like NOS on the ADI-2 Pro.

That means there are some differences, but they are only really relevant for a few or are even critical for business.

I wouldn't start "putting words on the gold scales" now, everyone sees it from their own perspective.

But what is the reason for your posting? How can I help you?

If you are unsure whether the ADI-2 DAC/Pro in your setup will enrich your sound, then you should try it out at home in your premises.

Quite apart from the sound, I think you could enjoy many of the special features of the ADI-2 DAC/Pro, e.g. auto reflevel, dynamic loudness, slow ramp-up of volume if you plug phones or switch channels, sample rate converter, .. . I personalyl enjoy these and other features every day.

If you are recording and need a digital mixer to route audio my recommendation will always go into the direction to start with a recording interface with TotalMix FX. If you have on top of that some additional bucks left .. then go and enhance your monitoring with the ADI-2 DAC/Pro. Whether it really enhances the sound for your in your premises and with your equipment I can't promise you. But you can be sure its of finest quality and you will get a lot of very useful features.

Additionally you get more safety, that accidently pulling a fader to 0dB in TM FX will not harm your ears and equipment.
Especially useful, if your active monitors have no or only limited volume control.

If you connect the ADI-2 Pro to a digital port of your recording interface, then you can keep all faders at 0dB and then use the volume control of the ADI-2 Pro. It acts there like a monitoring contoller or a "big knob" controlling your final volume.

For some people that definitively need a recording interface with TM FX it might make more sense to get a BBF Pro and then to get better monitors / phones, if sound enhancement is the only priority, because there you have much more headroom for improvements compared to converter differences.

I hope my answer gives you inspirations into what direction to go or to perform tests of your own to exactly know what you will get.
[ EDIT: thanks KaiS for jumping in here how to test properly, see next posting ]

Thank you for your wonderful analysis, so it is not certain that the marketing from RME about crystal clear and transparent sound signature from ADI-2, makes a significant difference from Babyface Pro FS.

The reason for asking was that I have bought the ADI-2 Pro FS R still in the unopened box, but I found an external phono stage for digitizing my records with a high-end moving coil cartridge, and that one only has enough gain for a 20 millivolt microphone signal. I looked at impedance matching for the microphone gain stages available from Thomann, but the Babyface Pro FS seems like the best way to do this if there is practically no difference in its sound quality compared to ADI-2.

Suggestions about what you would do in this situation are greatly appreciated.

I looked at buying the Ortofon MCA-76 that shows up rather often on the second-hand market. It's called a moving coil amplifier, and has good impedance matching for a modern Ortofon MC Quintet cartridge.

The output from the cartridge is something really low like 0.5 millivolt and then, the phono stage has 34 dB. I used an online calculator to get roughly 25 millivolt, so I think that is right.

Isn't it bad to add RIAA in software, because I read dynamic range is lost from the signal source? Maybe, someone knows. On closer inspection of seller descriptions of MCA-76, it is not certain that there is RIAA built in.

Another, bit crazy idea that might turn out to work nicely:

Connect the Ortofon directly to the mic input of BabyFace, prefereably fully balanced, to avoid hum.

Calculating from the spec’s you might end up with about 65 dB or better S/N ratio, BEFORE (software) RIAA EQ.
Software based RIAA EQ further improves that in the treble range, where noise is most annoying.

Good decision.
And yes, the cassette deck will perfectly work, connected directly to ADI-2 Pro.

No, you have a misconception about what impedance is.
It’s not level.

It will perfectly fit.

The deck has an output impedance of 1 kOhm, ADI-2 Pro has an (unbalanced) input impedance of 10 kOhm.
The resulting signal damping is 0.8 dB.

Nominal deck output is about 580 mV (Dolby Level, depends on how hot you recorded etc.).
ADI-2 has a minimal sensitivity of 1.2 V.
You end up with a healthy headroom of some 6 dB.

You asked, so here we go
My above posting was a quick look approximation.
Now let’s calculate that more precisely than we practically need, just to show how that works, and what it sometimes takes to answer a simple question.

You start with looking at the Technics RS-M10 schematic:
https://elektrotanya.com/technics_rs-m1 … ad.html#dl
You see the used chip for driving the output is the NE646B Dolby B NR codec.

So look at it’s datasheet (ignore the “B”):
http://www.elektronikjk.com/elementy_cz … /NE646.pdf
On page 2 you find:
“All levels referenced to 580 mV rms (0 dB)”
This is where the DD-sign in your deck’s VU-meters should be calibrated to.
Looking at the NE646 pinout you see pin 7 is output.

In the deck’s schematic, follow the signal trace to the RCA output.

• Starting at NE646 Pin 7, you find:
• A series cap C51 25V 4.7 uF
• Switch S1-13 pin 37 - 38 linked for playback position
• A series resistor R81 470 Ohm = 0.47 kOhm
• R91 10 kOhm to ground
• The simple headphones amp around Q7 which can be approximated as R99’s 47 kOhm to ground (might be lower, depends on the unknown transformer T8 ratio and load).
• Series resistor R93 1 kOhm to output connector.
• We connect ADI-2 Pro’s input resistor of 9 kOhm to ground.

Now the Damping is to be calculated on the base of Ohms Law.

(1) ADI 9 kOhm + R93 1 kOhm = 10 kOhm (to ground).
(2) R91 10 kOhm || R99 47 kOhm = 8.25 kOhm (to ground).
(1) || (2) = 4.51 kOhm (to ground).
This is the load R81 0.47 kOhm sees, so we can calculate the 1st voltage divider’s damping (we calculate in kOhm).
0.47 kOhm into 4.51 kOhm = x 0.91 damping.
The 2nd voltage divider is R93 1 kOhm into ADI-2’s 9 kOhm.
1 kOhm into 9 kOhm = x 0.9 damping.

Now the dampings are multiplied: 0.91 x 0.9 = 0.82
We started with Dolby Level 580 mV.
580 mV x 0.82 = 476 mV = -4.2 dBu at Dolby Level on tape.

ADI-2 Pro’s lowest Reference Level is +4 dBu, so 7.8 dB headroom for peaks above tape’s Dolby Level of 200 nWb/m magnetization.
This is enough for FE and CR tapes max. saturation level.
Metal tapes can be a bit hotter, so switching to ADI-2 Pro’s next higher +13 dBu Ref. Level might be necessary if ADI-2 Pro’s analog input’s meter shows “OVR”.

According load impedance:
As you can see, the deck’s internals are already loaded with 8.5 kOhm, so it doesn’t matter if this goes down to 5 kOhm total for the chip.
The cap C51 together with the total load resistance defines the lower cutoff frequency:
4.7 uF into 5 kOhm = 6.8 Hz, no problem.

Remark:
The deck’s spec’s say output level is 420 mV into 22 kOhm.
This probably is meant with an 8 Ohms headphone connected, as the simple headphones amp Q7 - T8 does not fully decouple the load.
A typical fault of the Japanese cassette recorders of that era.
Only relevant if you plug low impedance ‘phones into this really bad sounding amp.