On a 1-5 star rating:

5 stars for the DAC/Preamp (considering its price point)
4 stars for the Controller App. (works well with a few annoyances)
3 stars for the documentation.
2 stars for no WiFi.
1 star for its native file handling capability BUT with a freeware software solution it becomes 5 stars (see below).

This review is more focused on providing a review of the functionality of the DAC of those things that may not be obvious from the documentation. To keep this as brief as possible I am intentionally not restating what can be found in the product documentation since you can read this for yourself.

While I am calling this a review, I am purposely not saying much regarding sound quality which is so subjective and system / room dependent. But I will say I am very happy with the sound quality of this DAC. I upgraded from a Bluesound Node 2 and realized significant and noticeable improvement in sound quality plus higher resolution and DSD.

The controller app itself is pretty good but a lot of its functionality is not documented so you also have to figure it out on your own. Once you do you will realize it’s pretty good. It just takes some time to get used to. There are a few functional annoyances but that may just be because I am used to using the BluOS app.

STREAMING SERVICES work very well. I tried it with both Tidal HiFi and QoBuz HiRez. The MQA decoding of Tidal sounded excellent, so good I am not renewing my QoBuz.

REQUIRES A HARD WIRED ETHERNET CONNECTION because the controller app will not work unless the DAC is directly connected to your router via Ethernet. You should not purchase the NT-505 unless you have a hard wired Ethernet connection available. The DAC does have both coax and Toslink inputs so one could use an external streamer connected to the digital input on the DAC but then you would have to use the streamer’s controller app and none of the other functions of the NT-505. That really wouldn’t make sense.

MUSIC FILES ON A SERVER OR NAS: The native file handling capabilities of the NT-505 are awful if you have a large number of music files. It is slow to load and every time you turn on the DAC or your controller app it seems to take forever to re-load. I was ready to return this DAC until I noticed a single line in the documentations were TEAC recommends third party free ware called MinimServer to access and manage music files instead of their own software. You MUST use MinimServer if you have any significant amount of music files in your library.   MinimServer is very fast to load large amount of music files and more importantly maintains the index of music files in the server’s memory even when the DAC is off so it doesn’t have to rebuild the index every time you turn on the DAC. MinimServer performs very well with 1T of music files that I have stored on a remote PC. If you have a NAS compatible with MinimServer you can install MinimServer on the NAS and then use another free software called MinimWatch on your PC to configure and control MinimServer. MinimServer and MinimWatch are both very well documented and a Google search will get you all you need to know.

MUSIC FILES ON LOCAL USB DRIVE: The local USB port on the front of the DAC is intended for USB thumb drives but with this configuration you can’t use MinimServer and are limited to using the DAC’s native file management with the limitation described above. But with a smaller number of files this isn’t that much of an issue. I tested it with a connected HD with about 200 GB of music files and it did ok but when I tried loading more the DAC choked and froze.

PLAYING MUSIC FROM A COMPUTER: There is a USB type A-B connection on the rear to connect a computer directly to the DAC but I have not tested it since this DAC can play all high rez and DSD files from the a remote server or NAS.

I am not going to plug any source for purchases except to say that I bought the DAC from a large online seller that offers a 60 day return for any reason with full refund or credit for something else. That is more than enough time to fully evaluate this DAC.

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   Node 2i as well and likely any other standalone streamer if a buyer wanted to use the NT-505 somewhere without a hard Ethernet connection.

Now since you had the node2 hanging around, that is one thing, but at $550 it is just about the most expensive solution to needing a wired connection that I can think of.  Since you will definitely need to install this thing near an electrical outlet or six (depending on related equipment), one of those units that uses your home's AC wires as an ethernet cable should work just fine.  They usually have at least one ethernet port as well as wifi.   Some even have pass-thru AC so they don't actually use up a receptacle.  $50 or less.  Note:  Even the most hi-res recordings do not require huge bandwidth, so you don't need the fastest unit out there if its mission in life is to connect to your streamer.
I'm using Serviio as my music server.  My NT-505 had no problem finding and indexing all the music on my shared drive on my network.  Serviio is free.
That is a good suggestion. I Googled Ethernet over home AC line and saw a number of low priced options out there. One reason I prefer my Node2 as a streamer is I actually like the BlueOS app interface more than the Lumin app. I am also now subscribing to Amazon Music HD and have not found a way to stream AM HD using the Lumin app. The BlueOS app streams AM HD fine.
I also have the NT-505 and love the unit although I had the rear Network plug/connection fail and had to send the unit back for warranty repair work. The TEAC was fixed, no cost to me, and now works as good as new. I did not have the patience for the TEAC app, also thought it was a real pain having to reload / look for all my music files each time I started the TEAC up. I have over 4TB of various types of files from the lowly mp3 to FLAK to native DSD files. The TEAC app was also slow to page through all my files so my solution was Roon. Roon works amazingly well with the TEAC and through Roon I access Tidal, which also works flawlessly and sounds great. One reason I chose Tidal was for the MQA experience, which the TEAC unfolds. I have mixed feeling about MQA, but since the TEAC will unfold this type of file and many do sound amazing, why not subscribe to a streaming app that has it available and therefore have one more file type I can listen to. For the price, which falls under $2K it is a steal. I think it does have its own voicing and that is one that makes digital a little bit smoother. Maybe it rolls the top frequencies a little or filters off some of the digital glare, but what ever it does it makes the music so enjoyable. I use the TEAC with a tube preamplifier and tube amplifiers and this in my opinion is a great match up, however I believe it would sound fantastic in a solid state system also. With solid state it might not be as "smooth" sounding I don't know haven't tried, but I do recommend the TEAC as a great Streamer/DAC/Preamplifier/Headphone Amp.
what tube preamplifier are you using with the NT505?