From first hand: No special transconductance(no idea what that means) amplifiers are necessary, just a wire loop that matches output impedance of usual audio am

From first hand: No special transconductance(no idea what that means) amplifiers are necessary, just a wire loop that matches output impedance of usual audio amplifier, as described in the article. Hearing aid manufacturers and audiologists prefer their proprietary solutions so they push for removal of T-coil.