Just bought the ak240.
A very short listening impressions comparing the ak120 on my own opinion.
Using the uber 1plus2,listening some 16/44 wav and flac files.
For sonics, ak240 is quite similar to ak120, but with a more powerful and full sound with a bit more detailed. I can say that 240 is more 'clear' than 120. But I think the sound signiture of 240 is more 'classic' while 120 is 'pop'.
For treble, ak240 is smoother with less hissing.
For bass, ak240 is more clear and a bit more bouncy.
For vocals. ak240 is a bit backward than 120.
The background of 240 is darker than 120.
Ak240 obviously has a more powerful amp section than 120.
As it is just a very short review and the 240 is not fully run-in, maybe my feelings will change after listening to the ak240 longer.
Also, I not expereinced in hi-fi, so my opinion is not professional.
Lastly, I have to say sorry to my bad English as I am just a Chinese kid..