Question: How does the Stereo 50 achieve 25W+25W?
The short answer is that the Stereo 50 is measured using a music signal into real speakers (the LS3.5 to be precise) as opposed to a sine wave test into a resistor.
This has been outlined in the technical specifications area of the Retro Stereo 50 webpage: http://ifi-audio.com/portfolio-view/retro-stereo-50/
As this uses a music signal, this we feel is relevant in the real world and differences tend to be large.
For the technical reason behind this, please read here: http://ifi-audio.com/wp-content/uploads/data/RetroStereo50WattsandWatts.pdf
