Balanced Version= With 2.5mm Balanced out Interface and still have 3.5mm interface Standard Version= Only have 3.5mm interface WARNING! F1 is designed to drive high-impedance earphones, essentially set to what is high-gain mode on other amps. This leads to distortion (when using 3.5mm se out)...

I believe these IEMs deserve their own thread as they are great! https://www.pioneerelectronics.com/PUSA/Headphones/Premium/SE-CH9T Feel free to share (or copy across from other threads) your impressions here. I plan to review them soon.