Absolute top tier DAC for standard res Redbook CD

See here for a test of that Behringer DAC: http://nwavguy.blogspot.nl/2011/02/behringer-uca202-review.html
It is in fact remarkably good, and a masive improvement on for example inbuilt laptop DACs. I do enjoy having a few for less demanding applications.
It is not perfect, that is true. However, it is also not true that it should cost an arm and a leg to produce a top quality DAC. Moreover, these days standard Red Book CD resolution is no longer a challenge for any DAC chip set. See here for an example: https://www.jdslabs.com/products/39/odac-objectivedac/ Perfection has been achieved, and for a small outlay

Perfection is easily defined in theory, and pretty easily in practice. It is the quality level above human hearing acuity. The good news is that with DACs that level is reached quite easily, and for fairly modest outlays. Quality wise, DACs are the most accurate part of the audio chain, so they deserve least attention.
Next down the quality pecking order are amplifiers, and then, much further down, loudspeakers (and cartridges).

The uca 220 is technically the same as the uca 202. The only difference is the colour of the case and some software.
Anyone who wants to do a listening test should realize that the uca 202 has a quite low ouput of 1.2V, compared to many DACs that comply with the cd red book standard of 2.0V (or more). A low output level is not a bad idea, given the high input sensitivity of many amplifiers, but in a direct comparison it will not be as loud. Since the brain interprets louder as better, the differential should be compensated (and very precisely) for the comparison to be meaningful.
I do want to repeat that I would never claim that this modest unit is as good as e.g. a Benchmark. It is, however, remarkably good for the price, much better than any laptop sound card, and excellent to upgrade a secundary system composed of  legacy gear.

As for the billions using their smartphone's DAC, some may not be too far wrong: http://www.kenrockwell.com/apple/iphone-6s-plus-audio-quality.htm
I am not an iphone fan, but one has to admit that the audio from many other phones is not nearly as good.

Some sobering thoughts and measurements:
http://archimago.blogspot.nl/2018/01/audiophile-myth-260-detestable-digital.html
http://archimago.blogspot.nl/2017/09/musings-evidence-of-digital-player.html
http://archimago.blogspot.nl/2017/05/measurements-raspberry-pi-3-touch-music.html
http://archimago.blogspot.nl/2017/04/measurements-windows-10-creators-update.html
http://archimago.blogspot.nl/2017/03/musings-computer-audio-part-i.html

I remain to be convinced that there is still meaningful progress to be made in DACs for 16/44. However, some may find the following link on filters interesting: http://archimago.blogspot.nl/2018/01/audiophile-myth-260-detestable-digital.html

Sorry for a potential source of confusion. I did not mean to suggest that the link to Archimago’s page on filters was support for my scepticism. The basis for that scepticism is on the one hand the excellent measured results of all modern DACs when reproducing 16/44, and my own inability to hear obvious differences even with revealing speakers such as my Quad 2805 electrostats. I admit the listening tests were not very rigourous, but they put me off getting into this much deeper. The next upgrade will probably see a better DAC, however (my preamp with phono input is getting long in the tooth but I need to keep it until I have digitized all my last lp records). I am just not sure whether it should be the one in the Oppo 205, the new DSpeaker X4 DAC/preamp/room eq, or something else again.

Shadorne I agree this is an issue to be sorted out. From what I understand it mainly applies to popular recordings mostly recently mastered up to the very margin, so it would not occur with the kind of music I mostly listen to (classical and jazz). Am I right about that?
Am I also right that reducing the output of the digital source somewhat at source (ie. in the Chromecast app or in the Equalizer Apo audio player on my computer) cures the problem as well in the same way Roon does?