One that quickly comes to mind, was a particular add on tone control unit made by Parasound and, was designated model# REQ-150. A small black box that received a good review from the Sensible Sound a while back.
Tone controls? Sorry about the heresy.
I need tone controls! Too much of the music I listen to needs it. A lot of 70's, 80's, 90's, 00's rock. Some acoustic music. Who makes excellent preamps with tone controls OR what other box can I use that won't degrade the sound too much? Currently use a PS Audio 4.5, Adcom GFA-555II, JPW speakers.