Hello Ralf, and welcome to the Tascam Forums. There is a lot going on in that post, and unfortunately I cannot address those other issues (because I don't own a '12). But the answer is no, there is no such thing as "zero latency". However, it doesn't really matter because of latency compensation. With a console as a front end to a DAW, it's really easy to do a loopback test (at least it's easy with Reaper) and add latency compensation. That is one of the strengths of using the Tascam Model series. When recording, Reaper adds a specific amount of delay to the playback of the other tracks so that when you play along with those tracks, you are recording in time with them. It works perfectly, and in practice the latency isn't enough to make a difference when performing. There are also tweaks that can be (must be) made to your setup to reduce latency, and one of those tweaks is changing the buffer size. My personal studio setup is rather complicated (I have a Dante audio network instead of USB, but the issues are the same) but I made adjustments to by DAW settings until I reduced the latency as far as I could go and maintain a reliable connection. Then, I added the compensation using a loopback test.
I really need to do a video on doing a loopback test with Reaper because all of the videos I've seen involve the potentially dangerous practice of plugging a cable from a USB interface output back to it's input. But with a console it's even easier. With Reaper (sorry, that's the only DAW I'm familiar with) you use the ReaInsert plugin that is part of Reaper. All you do is select (in the plugin) a channel that outputs Reaper into your console. It doesn't matter what channel, but make sure it's "zeroed", that is, no FX, EQ, compression, etc.. Assign that channel to the Main Bus and raise the fader to nominal. Then select the input to the plugin from the console, and that would be either the Left or Right output from the Main bus. Raise the Main Bus fader to nominal. Then press the button on the plugin to ping the console and it returns a number. You use that number (it represents the delay by the number of audio packets) and add that to the input compensation in Reaper. It works so well that you will be surprised. I can play back 30 full tracks of audio and record the last 2 tracks in a stereo pair and the whole thing will be in perfect time, providing I am able to play the part correctly, lol.
But take note that I had to tweak everything else first. Your ASIO latency reporting will be a big help in letting you know if what you are doing is working. You have to start with the latency down to a reasonable level before you do the loopback test and add the final delay compensation. When I'm playing guitar, it feels totally "real time" so there there is no discernable delay and it acts as if I'm recording to analog tape. I wrote a 2 part article on setting up the Dante network in my studio but I haven't documented the loopback test so I don't think the articles will be of any use to you since your interface is USB. But no matter what DAW you are using, there are definitely some adjustments you can make to the settings that will help you get that latency down as far as possible. Personally, I find that kind of engineering to be quite interesting.
Be sure and let us know how you make out with it, Ralf.
