Sadowsky BP4K Onboard Bass Preamp Installation Manual

Introduction

Thank you for purchasing your Sadowsky® Onboard Bass Preamp 4-Knob system! This kit includes the renowned Sadowsky preamp featuring volume and balance controls, a passive Vintage Tone Control (VTC), and a tandem potentiometer for active EQ with bass and treble boost. The VTC's push/pull function allows switching between active and passive modes, with VTC functionality present in both. Designed for most J-style basses with a 4-hole metal control plate. Newer active J-style basses with side jacks and battery compartments may require minimal modification. The system comes pre-wired with pots mounted on a control plate, including the output jack and battery clip. Soldering is typically not required for installation. Pickup wires and bridge ground connect to screw terminals on the balance pot.

For passive vintage J-style basses with control plates, relocating the jack to the side and routing a cavity for the battery and circuit board might be necessary. If you lack experience with routing or drilling, or are unsure about the process, professional installation by a guitar technician is strongly recommended.

Note: This preamp is designed for two passive pickups only. It is not compatible with active pickups requiring volume or balance pots other than 250K or 500K. The included output jack has METRIC threads and will not fit Imperial threaded jack plates.

Tools Required

• Screwdriver to remove the old control panel
• Small screwdriver for the terminal screws on the balance pot
• Possibly a soldering iron for unsoldering pickups and bridge ground from old components

Control Functions

• Volume control: Fully right equals maximum volume.
• Balance control: Switches between the two pickups in end positions. In intermediate positions, it mixes the signal from both pickups; the middle position provides a 50/50 mix.
• Bass / Treble: These controls offer boost only. Fully left is the neutral position (no boost). Fully right provides an 18 dB boost at 40 Hz (Bass) and 4 kHz (Treble).
• Vintage Tone Control (VTC): A passive treble cut that functions in both passive and active modes. Fully right means no treble cut.
• Push/Pull switch on VTC control: Switches between passive mode (preamp bypass) and active mode. Note: Switching to passive mode does not turn off the battery. The battery is activated whenever a cable is plugged into the output jack. Remove the cable during extended breaks or when the bass is not in use.

Specifications

*Note: The battery drains as soon as a cable is plugged into the output jack. Switching to bypass does not extend battery life. With normal use, expect approximately six months of battery life.

Installation

1. Remove the old control plate and output jack from your instrument. If you need to retain the original output jack, it must be a stereo jack with three contacts (TRS), as the ring contact is used to close the battery circuit.
2. Identify and mark the "hot" and ground wires from the pickups and the bridge ground wire. When unsoldering wires from old components, ensure a stripped and tinned piece of bare wire remains at the end for insertion into the screw terminals on the balance pot.
3. Verify there is sufficient space in the electronics compartment for the new preamplifier electronics and a 9 V block battery. If space is insufficient for the battery, a technician may need to install a separate battery compartment.
4. If the compartment is not already shielded, shielding it now (using shielding paint or copper foil) is recommended.
5. Find a suitable position for the circuit board within the electronics compartment. The PCB has double-sided tape attached to its back. Plug in the connectors and secure the PCB in place with the tape.
6. Install the pre-wired output jack from the kit in the position of the old jack.
7. Connect the pickup cables to the balance control's screw terminals. Connect ground wires to the black terminals and hot wires to the green terminals. Note: Swapping wires in the green terminals can reverse the balance control's working direction.
8. The bridge ground cable can also be connected to one of the screw terminals for the ground contacts (black terminals), as these are sufficiently large for two wires.
9. Connect a 9 V battery to the battery clip and insert the battery into the compartment.
10. Attach the new control plate to your bass using the original screws.
11. Plug an instrument cable into the output jack, connect an amplifier, and test the new electronics.

Connection Diagram Overview

This diagram illustrates the physical layout of key components. It shows the positions for the Neck Pickup, Bridge Pickup, and Bridge Ground connection. A note indicates that swapping the input connections to the balance control can reverse the pan direction.

Schematic Diagram Description

This schematic diagram details the internal wiring of the Sadowsky BP4K Onboard Bass Preamp system.

Components and Connections:

• Pickups: The Neck Pickup and Bridge Pickup each provide a "Hot Output" wire. The Bridge Ground provides a ground wire.
• Volume Pot (A 500K): Connected to terminals 9 (common ground), 10, and 11.
• Balance Pot (R1=0.5A250K): Connected to terminals 9 (common ground), 12, and 13. Terminals 12 and 13 receive the hot output wires from the Neck and Bridge pickups. A note specifies that swapping connections to terminals 12 and 13 will reverse the pan direction.
• VTC (Vintage Tone Control) Pot (A 250K P/P): Features a push/pull switch. It is connected to terminals 5, 6, and 9 (common ground). Terminals 5 and 6 are part of the VTC circuit. The push/pull function toggles between passive (bypass) and active modes.
• Treble / Bass Pot (R1:A25K / R2:A25K): A tandem potentiometer for active EQ boost. It connects to terminals 3, 4, and 9 (common ground). Terminals 3 and 4 are for the Treble/Bass EQ circuit.
• Output Jack (M 50112 C): A stereo jack with Tip, Ring, and Sleeve connections. Terminal 0 (Tip) is the hot output. Terminal 2 (Sleeve) is the ground connection. Terminal 1 (Ring) is used for the battery connection, closing the circuit when a cable is inserted.
• PCB (S-S PCB STD): The main circuit board, with numbered connection points corresponding to the wiring.

Wire Color Coding from PCB:

• Black (0): Ground
• Brown (1): Output Jack Ring (Battery connection)
• Red (2): Output Jack Sleeve (Ground)
• Orange (3): Connected to Treble/Bass pot
• Yellow (4): Connected to Treble/Bass pot
• Green (5): Connected to VTC pot
• Blue (6): Connected to VTC pot
• Purple (7): Connected to Balance pot (pickup hot)
• Grey (8): Connected to Balance pot (pickup hot)
• White (9): Common connection point for Volume, Balance, VTC, Treble/Bass pots, and Bridge Ground.

Pickup and Ground Connections:

• The hot output wire from the Neck Pickup connects to either terminal 7 or 8 on the Balance pot.
• The hot output wire from the Bridge Pickup connects to the remaining terminal (8 or 7) on the Balance pot.
• The Bridge Ground wire connects to the common ground terminal 9.

Warranty Note: The document includes a disclaimer stating that defects or damage caused by improper installation or the use of unsuitable tools, including cutting cables and soldering within the kit, are excluded from the warranty.

Manufactured by Warwick GmbH & Co Music Equipment KG, Gewerbepark 46, D-08258 Markneukirchen. Visit www.sadowskybass.de or info@sadowskybass.de for more information.