'High Headroom, Low-Noise, 3-ACTIVE BAND ONBOODD EQ PREAMP in Two Configurations Voiced SpecificLly for Fretless Basses with either Active or Passive Pickups. Seymour Duncan Tone Circuits Will Add to Tremendous Amount of On-Board Tonal Versatility to Any Bass with Two Pickups. Our Design Enables Players to Boost or Cut SpecificLly Focused Frequencies in Order to Achieve Signature Tones and to dial in A great sound No Matter What The Situation. The STC-3ASB and STC-3PSB Preamps Provides Bass and Treble Controls, in Midrange Control, a Master Volume, in Blend Control, and Our Special Frequency Contour Switch. These preamps Were Voiced by Steve Bailey To Have Three Bands of Focused EQ, Together with a Switch That Engages A Frequency Contour Optimized to Bring Out Fretless Harmonics AS WELL AS MID-Range Boost. The Frequency Contour Is Engaged by Pulling Up of the Volume Control. The STC-3ASB is designed to be paired with Active Pickups, While The STC-3PSB is designed to be paired with passives.we Included Two Small Trim Pots On The Circuit Board Can be Tweaked to Preset The Frequency Contour EQ Just the Way You Want. The STC-3ASB and STC-3PSM Tone Circuits Will Work In Any Fretless Bass That Is Equipped With Two Pickups and Has Space For 4 Control Knobs (Volume / Freq Switch, Blend, Concentric Bass and Treble, and Midrange Controls) and to Single 9V Battery in The Control Cavity. Two 9V Batteries Can Be Wired Together in Series For Added Headroom. We includes HIGH Hardware Required Mounting-Quality Potentometers on pre-Wired Harness, Battery clip, and Black Anodized, Kurned, Dome-Style Knobs. '