Why is the D400 "better" than the D200

[Confused]

From the marketing texts of the D400: 

(I'm afraid something got lost here in translation e.g. 'Current return from the total mass')

Finally, a dual-mono solution at an affordable price! The Devialet 400 is the most comprehensive and high-performance dual-mono model. Extreme power (400 W), an inexhaustible wealth of adjustable parameters and unsurpassed performances (THD + N 0.00025%), the Devialet 400 finally enables you to make the transition to a  system comprised of two power blocks.

In this configuration, the Devialet 400 offers you unequalled musical resolution and beats every record. Devialet's technology is magnified through its operation in mono-block mode via a dedicated power supply and an ADH core for each channel.

• the power supply and balanced converter dedicated to each speaker offer you more power and greater dynamics, most notably by way of SAM technology
  
  
• the use of the Devialet 400 in mono-block mode enables the elimination of the current return from the total mass and the further improvement of the performance of the DAC "Magic Wire" and  analogue inputs (THD + N 0,00025%). The dual-mode also reduces signal jitter for all digital inputs.
  

I think it boils down to separated power supplies and ADH cores (less crosstalk/noise/ground contamination, more power per channel) and the use of 2 DAC IC's (I think the DACs run in parallel in order to sum the outputs and average the difference) vs. 1 per channel (less distortion and jitter).

I get your point.
But how comes a D250 shows similar sound characteristic improvements (Compared to a D200 being a half D400) as a D400 without the concept of dual mono. Only by raising the voltage in the power supply as they say? Other than that their hardware is completely the same (you know I had both on my workbench). That's not conclusive to me thus some kind of processing might be envolved ?!

gui

I recall discussing this with Devialet's Mathieu Pernot, maybe about three years ago.  He stated that the hardware is indeed identical.  The difference is in the control of the power supply.  I cannot claim to fully understand this myself, or it's absolute significance in terms of sound quality, but the difference is in the control of the power supply, that is the 200's power supply does have some limitations imposed versus the D250, the reason being that if you did not, the 200 would overheat.  One thing I am clear about, Mathieu Pernot said absolutely nothing about any differences in processing, although could you consider some kind of electronic control over the power supply as 'processing'? I think this could certainly give that impression.