Mesa/Boogie packed a lot of controls into the Subway D-350, including a four-band (Bass, Low Mid, High Mid, Treble) Baxandall EQ, separate Gain and Master Volume controls, Active/Passive and Input Mute switches. They even included a Bright switch that can add some top-end glitter to your sound.
The amp also includes a fixed high-pass filter and a Variable Voicing control, which shifts the amp’s response from a flatter to a more vintage-voiced curve.