stax adapter + elekit 8200 tube amp

was weighing my options for a new electrostatic headphone. rather than get a dedicated amp i was looking into using my existing elekit 8200 with an adapter (uses speaker input ->electrostatic headphone output) but i read that amps with a transformer (eg elekit 8200) dont like to power another transformer which is what a stax adapter is (transformer to power electrostatic headphones). can anyone clarify or explain why?