I am trying to design an OTL that will drive ANY impedance cans. My main phones are Audeze LCD-2 CB which are 70 ohms. I also have 32 ohm ohm HE-4xx and 300 ohm HD-650s. I have built four HP amps using Aikido topology, which sound fantastic with 300-600 ohm HP, but not enough oomph for low impedance. I do have 600 ohm OPT but the secondary is only 8 ohms (I was saving them for a 6C33C project). The schematic is attached (preliminary), PS schematic to follow.