The Sadowsky Onboard Bass Preamp (4-Knob System) is a completely prewired system offering the same controls and the same legendary active preamp as all Sadowsky basses. This preamp is designed for installation on most J-style basses with a metal control plate. What is a VTC (Vintage Tone Control)?: “It works just like a standard Fender tone control. It is a passive control in which 10 is flat and as you roll it down it knocks off a broad swath of high end to give you a warmer tone. Although the control is passive, it functions with the bass in either active or passive mode. A little rolled off knocks off a lot of string noise. All the way rolled off, it gives you a lot of that "motown/flatwound" sound.” — Roger Sadowsky