Here we have a custom amp from a client that wanted an OTL headphone amp, but with larger output tubes and passive biasing. It uses a 6SN7 for the input and EL34 tubes for the outputs
It's a pretty nice sounding amp, very natural and mellow sounding with fat bass. There is no NFB loops or anything and I built it inside the chassis of a Makoyi amp.
The circuit is dc coupled between stages and capacitor coupled on the output. Output impedance is about 80 ohms or so and is best suited to headphones 300 ohms or higher. It also has a ladder attenuator made with Takman resistors for the volume control.
If anyone else had any cool ideas or wanted something unique made, feel free to message me or post here about it!