Tone controls get (an undeserved) bad reputation in a lot of DIY hifi circles. They are very difficult to get close to technically perfect (eg exactly Xdb boost at all frequencies above Xhz) and they’re math heavy, so you don’t often see them fully detailed in audio DIY. And in principal all the equipment we’re building is supposed to be perfectly flat and transparent, right? Well that’s what the engineers say, but others might say that transparent is the enemy of fun. I would say that you don’t see tone controls because that’s just not how hifi “is done.” No, that’s not a good reason. And maybe the world needs a simple preamp design with bass & treble…
Here’s some good reading from Baxandall, the papy of modern tone control:
Here’s a good article from John Broskie on his Tilt Control board/kit:
That Tilt Control is a different take on tone controls, but I think it’s pretty elegant. Broskie’s boards and kits are top notch too (not affiliated, I just have a engineering crush on him):
Ideally you’d sandwich this kind of tone control between two cathode followers (or one low gain stage and one follower).