Originally Posted by Omphalopsychite
Yeah, but apparently you haven't listened to both of them and can't describe why the 627 is better. And, yeah, you haven't cited sources for your contention that not everyone thinks the X is better...
This is what Cesar told me in an email:
"Hi Jason, they do have a different sound signature and this mainly from the use of a different potentiometer. The 627X is using a TDK 2CP-601. This is a higher end potentiometer than the one used in the 627 which uses a high quality Alps potentiometer. Some people who have heard both amplifiers have preferred the 627X but others have preferred the 627. Other than this change, and the use of a larger battery, the entire amplifier sections are identical. Unfortunately, there isn't enough people out there yet with both amplifiers to offer much feedback on the differences. Thanks again and let me know if you have any other questions. I will look forward to hearing back from you."
This is what Mike from Headfonia told me in their Q&A page:
"The original 627 has a mid centric sound with a beautiful tubey midrange and an extremely spacious soundstage. The 627X has a more flat sound with better low bass reproduction. The sound of both are quite different from the HM901 I listened to in Tokyo and I still prefer the original 627 for driving the HE-500 and HE-6."
And when I clarified if he preferred the 627 or the 627X, he said:
"I still like the 627 original better."
Hope this helps! Regardless, going by Mike's comments I'd prefer spacious soundstage and tubey midrange to flat + better low bass.