I have a slight hearing imbalance that is a little frequency dependent. For example, centering male vocals vs female vocals can have a slightly different balance setting. I usually just adjust things in software/at the source, but having a knob would make that a lot easier. However, it seems like most headphone amps don't have balance controls. I've found a few that do, but they are in the $2k+ range (Violectric HPA V281, Bryston BHA-1).
Does anyone know of any other less expensive headphone amps that do have a built-in balance knob? I'd prefer solid state.
Alternatively, does anyone know if there are amp makers (either commercial or DIY) who could do a custom job such as this?