Preamp FAQ

Q: What is a Preamp?

A: A preamp is just as it sounds, a pre-amplifier. It is an electronic amplifier that prepares an electronic signal for further amplification through your basses amplifier or signal processing chain through say a pedal board,mixing board, before hitting the end of the signal such as your amp or USB interface for recording. The idea of a preamp started with the need to amplify a low level signal, most likely from high impedance pickups, to line level. Preamps are used in many transducers in audio applications such as pickups and microphones. Equalization and tone control are used in many preamps found in the music industry.

A preamp can be onboard an instrument, outboard through use of a pedal, or incorporated into the housing of the amplifier. Depending on size and fitment for onboard use, some require an outboard preamp due to lack of fitment of modules, controls, and batteries onboard the instrument. If you feel you may be in a situation where fitment is a concern for an onboard preamp please contact us:

Phone: 1-877-839-3531
Hours: Monday - Friday, 10am - 7pm EST

Q: What preamp fits my bass?

A: This varies with each instrument. Fitment and size restriction is always something to consider when purchasing an onboard preamp. If the instrument is equipped with a rear route, battery compartment, and has a control cavity depth greater than 1.25", many if not all of the preamps we carry will fit just fine. We ask if there are any concerns for fitment that you contact us and we can work through the options on a case to case basis.

For situations like a Jazz bass or P-bass where the controls are top routed and mounted to either a control plate (Jazz Bass), or pickguard(P-bass) fitment can be slightly more difficult and we recommend consulting us for assistance on preamps outside those listed as retrofit for these style of basses.

Q: Can my preamp run on 9v or 18v and is it necessary to run one or the other?

A: This is dependent on the preamp. The option to run additional DC voltage to supply more power to the preamp is there to increase the headroom of the preamp since there would be less of a chance of the signal getting clipped due to lower or inconsistent voltages. This is not necessary for everyone and is a preference on a user to user basis. Some feel that running 18v for the additional headroom is worth the additional routing for a battery box, and some do not.

Below are the preamps that we carry currently and the power requirments and options for each listed:

  • *Bartolini - Can run either 9v or 18v. An extra battery clip is included with the Bartolini preamps to make them 18v operable if an 18v battery box is equipped.

  • *Aguilar -Can run either 9v or 18v. These our pre-wired in house by one of our technicians and can be accommodated for either power supply option.Additional 6dB headroom with use of 18v power.

  • *East/ACG - All East and ACG preamps can run 9v or 18v power. Additional battery clip not supplied. Modification is required to install battery clip.

  • *Glockenklang -9v required.

  • *Delano -Can run either 9v or 18v. Additional battery clip not supplied.

  • *Nordstrand (with the exception of the 2B-MM Musicman Preamp) - Can run 9v or 18v power. Additional battery extends battery life and provides additional headroom. Additional battery clip included

  • *EMG - Can be run 9v or 18v power. EMG kits are supplied with only 1 battery clip for 9v. Additional clip will have to be soldered in as there is not a modular solution available and soldering the wiring is recommended.

  • *Duncan -9v required. Some can use 18v for additional headroom. Consult us.

  • *Mike Pope - 9v or 18v. Active pickups such as EMG requires 18v.

Q: What is meant by the terms ‘active bass’?

A: Generally speaking, the term means that there is a battery in the bass. Most commonly, the battery is being used to power a preamp. The preamp uses a battery and thus the instrument is powered (active). Occasionally, the pickups are active; a bass with active pickups would, of course, also be considered active.

Most pickups (even in ‘active basses’) are actually passive. A bass can have an active preamp with passive pickups: This is the most common scenario.

EMG, MEC and some others have models that are active and require a battery. Sometimes these pickups are used with preamps as well, but not necessarily.

Many preamp manufacturers are designing their control harnesses with passive pickups in mind, as they are more common both as retrofit parts and for OEM use

Q: What is meant by the term active/passive switching?

A: Some instruments have a switch which changes the signal from active to passive.This switch is not changing the pickups, or how they function: the switch is not making a pickup active or passive. It is changing the signal path for the controls.

More precisely, an active passive switch is a bypass switch. When in 'passive' mode, the signal bypasses the active part of the preamp (which is typically the EQ section).

Q: Do I need Active pickups to work with a preamp

A: No. Most aftermarket (not originally installed in the bass) preamps are designed with passive pickups in mind.

Q: Does my preamp come supplied with knobs?

A: This varies with preamp. See below for more details:

  • *Bartolini - Included is only one knob for the concentric (stacked) pots. These are black plastic knobs. We stock knobs to match the included knob. They are available on our knob page

  • *Aguilar - No.

  • *East - Yes.

  • *ACG - No. Although they previously came included before.

  • *Glockenklang -No.

  • *Nordstrand -No.

  • *Delano - No.

  • *Seymour Duncan - Yes. Black plastic knobs are supplied.

  • *EMG - Yes. Fluted black plastic knobs are supplied.

  • *Mike Pope -No.

** Knobs are available on our knob page in various styles and finishes.


Q: Do Preamps come prewired?

A: Depends on the manufacturer of the preamp. See below for more details:

  • *Aguilar - Yes. These are wired in house by one of our technicians.

  • *Bartolini - Yes. These are wired by Bartolini and come mounted on a PC board(as pictured). The controls are removed from the PC board for installation. The preamps can be modified with potentiometers that we have in house. This type of modification is recommended to be performed by a qualified technician.

  • *East - Yes. These are wired by East. The J-Retro's (which include the J-Retro 01,J-Retro Deluxe, and DJ-Retro) come mounted to a control plate as do the BTB MMSR and Marcus Retro 01(with the exception of the 5-string Marcus Miller Retro)

  • *ACG -Yes. These are wired by East/ACG and are connected via cabling to the main PC board.

  • *Glockenklang - Yes. These are wired by Glockenklang.

  • *Delano - Yes. These are wired by Delano. There are limited configurations for these preamps, but we do carry the potentiometers to make the necessary changes to a control configuration of interest.

  • *Nordstrand - Yes. These are wired by Nordstrand. We also carry pots necessary for some modification.

  • *EMG - Technically yes. These are solderless by design and include cabling to connect the modules together (EMG's solderless/modular design) These are intended for active pickups, though passive options do exist. The Modular designs are intended to be used with EMG pickups as all newer EMG pickups are using modular connections on the pickups themselves.

  • *Seymour Duncan - Yes. These are wired by Seymour Duncan and are in a set configuration with no modifications available.

  • *Mike Pope Flexcore - Yes. These are prewired in house by one of our technicians. These are a solderless/modular design that use cabling to connect the modules together. Screw terminals connect the pickup wiring as well.

** Potentiomers for additional configuration and customization can be found on our potentiometers page.


Q: I do not see a configuration that matches the control configuration I would like. Can I change controls?

A: This depends on what preamp that is being used. We have potentiometers to make many changes to preamps that do not have control configurations to suit your needs. They can be found on our on potentiometers page Potentiometers. If you have questions of what will complete your install feel free to contact us

Phone: 1-877-839-3531
Hours: Monday - Friday, 10am - 7pm EST

Q: What are the sizes of the preamp modules

A: This varies with each preamp manufacturer. See below for more information:

  • *Bartolini - For the Three band:One of the modules is roughly 0.625"(15.8mm) x 1.19"(30.2mm) x 1.75"(44.45mm). Second module is 0.625"(15.8mm) x 1" x 1.25".
    For the Two Band:There is just one module and it is roughly 0.625" x 1.19"(30.2mm) x 1.75"(44.45mm).

  • *Aguilar - For OBP-2 & OBP-3 0.98"(24.8mm)W x 0.98"(24.8mm)L x 0.59"(14.9mm)D
    For OBP-1: 1" x 1" x 0.625"
  • *Nordstrand - For 2B Module: Dimensions are 1.06"(26.9mm) x 1.375"(34.9mm) x 0.50"(12.7mm)

  • *Delano - 0.78"(20mm) x 1.19"(30.2mm) x 0.625"(16mm)

Q: What capacitors are used with the Nordstrand Mid Pot?Can they be changed?

A: Mid: +/-12 dB@1K (mid freq selector toggles between 1kHz and 400Hz)

The 1kHz is with no external capacitors selected. The 400Hz uses a 33nF to the outside lugs of the pot or 120nF to the grey leads on the board.

We do not stock capacitors to make changes, but they can be purchased from various online retailers such as Small Bear Electronics or DigiKey.

Q: What preamps have gain control on the units?

A: This depends on the preamp. See below for those that include and do not:

  • *Bartolini - Gain adjustment is available on unit.

  • *Aguilar - No gain adjustment available.

  • *East/ACG - Gain adjustment available on unit.

  • *Glockenklang - No gain adjustment available.
  • *Delano - No gain adjustment available.
  • *Nordstrand -Gain adjustment available on unit.
  • *EMG - No gain adjustment available.

Q: What does VPP,MPP,T/B and all of these other acronyms stand for?

A: The nomenclature is a form of short hand to describe the control configurations on preamps.See the key below:

  • V A/P or VPP:This stands for Volume Active/Passive and is a single Master Volume Control intended with a DPDT switch on the body of the pot to allow switching from Active to Passive or vice versa and serves as the main preamp bypass.

  • V/V:This stands for Volume/Volume and is a stacked Volume of Volume control to be used to control two different pickups volume from a single potentiometer.

  • MPP:This stands for Mid Push-Pull and is also a Potentiometer equipped with a DPDT siwtch to allow switching of the center selected mid frequencies.

  • T/B:This stands for Treble/Bass Stack and is a dual stacked EQ potentiometer that controls modulation of both the treble and bass frequencies.
  • BL:This stands for Blend control and is used to control the mix of two pickups.