I have not heard the F3, but the J2 has the finest rendering of inner detail, micro dynamic finesse of any amplifier I've ever heard.
The Atma-sphere S-30 has a smoother top end and is faster. They're comparable quality amplifiers and neither will be absolutely better than the other.
The Atma-sphere S-30 has a smoother top end and is faster. They're comparable quality amplifiers and neither will be absolutely better than the other.