Headphones and the Devialet

[thumb5]

Assuming you're using Roon on your Nucleus to play music, this is what's happening in the two different cases:

With the 200 in the path:

• the Nucleus sends the music in digital form (I think over USB in your system?) to the 200
  
• the 200 extracts the digital audio samples from the USB input, and converts them to its native internal format
  
• the 200 does some Digital Signal Processing (DSP) on the digital audio samples - I guess this includes volume and tone control, for example (but I'm ready to be corrected), and possibly other things depending on your 200's configuration and settings
  
• the 200 converts the digital audio samples to analog using an internal DAC, and presents the analog output on the stereo pre-amp outputs you've configured
  
• in your system, the 200's analog stereo pre-amp outputs go to your Taurus where they're amplified in the analog domain to drive your headphones
  

The main things the 200 is doing in this set-up are (I think) volume and tone control, and digital-to-analog conversion using the pre-amp output DAC.

If you had multiple input sources, possibly a mixture of digital and analog, the 200 would also allow you to switch between them so that you could choose which source you listen to on headphones.  You can think of it as being "the pre-amp" for your headphone amp.

This is only part of the job the 200 is doing when you listen via your speakers.  In that case, the internal digital signal in the 200 might be processed further (for example if you have SAM enabled) and is then fed to the ADH output section that drives the speakers.  This is where a lot of Devialet's "magic" lives, and what allows them to produce an amp that combines the sound quality of a class A amp with the power delivery of a class D amp, while fitting it into such a small case.

Without the 200 in the path, if you're still using your Nucleus, you'd need a headphone amp with a digital input.  This is how it would work:

• the Nucleus sends music in digital form (over USB, Ethernet, wi-fi, ... depending on what digital inputs your headphone amp supports) to the headphone amp
  
• the headphone amp converts the digital samples to analog using an internal DAC and amplifies the analog signal to drive the headphones
  
• the headphone amp looks after volume control, of course (maybe in the analog or digital domain)
  

For me, if I were only considering listening to a single, digital source (Roon/Nucleus), I'd say the 200 is not bringing a lot of "value" to that from an audio quality point of view.  However if your headphone amp doesn't have a digital input, the 200 is doing the essential job of converting the digital stream from the Nucleus into analog.  Just my 2p-worth, of course.