[Sykes22]

I’m looking for a headphone amp with tone controls, and preferably with valves.
Does anyone know if there is such a thing?

[vonnie123]

https://www.usaudiomart.com/details/650218119-luxman-sq38fd-rare-115v-us/images/5682346/

This is an integrated, but you could adapt it to make it work. 

You might want to check with Schiit Audio and see if they have something that can be adapted to a standard tubed HA.