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Bass Preamps: The Definitive Guide To Choosing an On-Board Replacement

In this article, we want to help you:

1. Gain an understanding of the considerations to keep in mind when shopping for a preamp.
2. Get the tone you are seeking by adding a preamp to your bass or replacing your current preamp.

Often players start the search for a new preamp by comparing brands, looking for reviews, watching videos, etc.

Of course, these are all good steps in your research, but there are a number of “nuts and bolts” factors which need to be considered first. Before you get to the “subjective” points of a preamp, such as tone, it is important to consider some “objective” factors.

Let’s get to it ->

The Goal Of Adding (Or Changing) A Preamp To Your Bass.

What are you looking to do by putting in a new preamp?

Generally, there are two main reasons why you may find yourself wanting to put in a new preamp.

  1. Seeking Your Dream Tone. You are not lovin’ the current sound of your bass. The current preamp or electronics is affecting the sound in a negative way or you want to add specific parts of the frequency spectrum (more bass, less mid, etc…). Bottom line - you want to gain more control of your bass’s tone, and your current electronics do not offer all of the tonal shaping possibilities (like adding/subtracting treble, mid, or bass) that you want to get your dream tone.
  2. Your Current Electronics are on the Fritz. Something is not working correctly in the control cavity. It could be that the preamp has begun to malfunction or it’s simply that a potentiometer needs to be replaced. Many players find the silver lining in this situation and see it as an opportunity to try a new preamp that has the functionality or tone that they see as lacking in their current setup.

Going from Passive to Active - Why use an Active Preamp?

What does one gain specifically by having an active preamp?

For years, the majority of basses sold in music stores didn’t have active preamps. These basses typically had a simple passive treble roll off circuit. This setup gives some amount of tonal control, but is definitely minimal.

Active circuits (preamps) that have the ability to boost/cut certain parts of the frequency spectrum can open up a lot of tones. Manufacturers have designed their active control circuits in the most musical way that they believe will benefit the tone of a bass.

Consider your EQ on your bass amp, car stereo, home system. Often you need to dial in a bit more bass, back off on the mid, etc..

That extra tone control is what is gained with an on board preamp.  And the control is right at the bass.  Easy to tweak even while playing.

The change is often dramatic....making the bass sound like a completely different instrument.


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So, let’s take a look first at the objective criteria to keep in mind when you’re looking for a new bass preamp…


1. Cavity Space: What room is currently available in the electronics cavity?

If your bass currently has a preamp, chances are you have the space needed to fit in a different preamp. However, if your bass has 3 or less control potentiometers and no preamp, the situation may be different….but let’s not get ahead of ourselves.

We are really considering the size/shape of the electronics cavity here. Some manufacturers route the bass’s cavities spaciously, leaving plenty of open space for additional controls…., On the other hand, some manufacturers create a channel that barely fits the pots that they intend to put into the bass.

As a player, you need to decide if you want to maintain the current layout of knobs and switches or if you are willing to add new holes. Most preamp configurations have multiple potentiometers (Quick definition - potentiometers are the controls that reside inside your bass and are controlled by your knobs) to control the EQ of the preamp as well as control the blending of pickups and master volume, for basses which have two pickups. When thinking about purchasing a preamp that has more controls (potentiometers or switches) than the number of holes currently in the bass, keep in mind that you will need to drill additional hole(s) or use a stacked potentiometer. Adding additional holes is not a difficult task if you are handy with tools or have a tech that can drill the hole for you. Many players will have a tech do the full installation of a preamp, and in that case, you can have them drill the extra holes needed for the new preamp.

When considering a new preamp, you need to be sure that all of the following components can fit in your electronics cavity:
  • Preamp Modules (Not all module are created equal...some are bigger than others)
  • Battery(s)
  • Potentiometers
  • Switches (if needed)
  • Wires


Sometimes a bass’s electronics cavity is surprisingly small. In these tight situations, here are a couple tricks to help a preamp to fit.

  • Try putting the battery on the back of a single potentiometer. Use foam around the battery to keep it from bouncing around
  • Try putting the preamp on the back of a single potentiometer. Double stick tape can keep it in place. Be careful to not crimp wires
  • If the jack is currently on the face of the bass, try moving it to the side, and in order to free up an extra hole on the face of your bass

2. Number of Knobs & Switches and using Stacked Pots/Controls 

The easiest installs are those that don't require drilling holes in the bass for new controls. Generally, when we are asked for recommendations, we try to suggest a solution that doesn't require adding new holes. On a brand new bass build, the sky can be the limit, but when retrofitting, we do have some ways to avoid drilling new holes in some situations. Stacked pots are a great solution for a lot of basses.

Stacked controls use a single potentiometer for two independent functions. Think Treble/Bass or Volume/Volume. For us bass players, this is a space saving feature that is pretty great.

Let’s say your current (2 pickup) bass has 4 knobs (Volume, Blend, Tone1, Tone2) and you want to install a 3 band preamp.

A 3 band preamp for a 2 pickup bass will have five controls, (one possible configuration could be Volume, Blend, Treble, Mid and Bass). Most likely you’ll want to use two of your four holes for your Volume and Blend controls, leaving you two spots (holes) left. For your remaining controls (Treble, Mid, Bass), You can either drill another hole to get a total of 5 holes for the potentiometers, or you can use a stacked potentiometer.

The stacked potentiometer will have two separate controls on it. In the case of 2 and 3 band preamps, this stacked control will usually be the treble and bass. Each work independently of each other, but the controls are wired to the same physical potentiometer.


3. Battery Voltage: Should I use 9 or 18 Volts in my circuit?

The standard battery that is found with nearly all preamps is a 9 volt battery. A few circuits require two 9 Volt batteries (making 18V), but on the whole, most preamps work with either a single 9 volt or two 9 volts, (making it an 18 volt circuit).

So… which is better?

Is there an advantage of an 18 volts powered preamp?

Does the old adage “More is Better” apply here?

In the case of bass preamps, the answer is YES, but only marginally so.

With 18 volts, the preamp has a better signal to noise ratio. Essentially, there will be less distortion (noise) when boosting the signal of your treble, mid and/or bass knobs. That being said, most players will not hear the difference. Certainly, if a manufacturer specifies 18 volts, then use 18 volts…but if they specify that 9 or 18 volts can be used, you are probably fine using a single 9 volt.

If you’re facing a space crunch in your electronics cavity, you have two choices: Use a single 9 volt battery or add route a hole for a battery compartment. By and large, just using the space available and installing a single 9 volt will serve you well. The “more is better” approach may not necessarily be worth the extra effort of adding a hole for a battery box.

4. Active-Passive Control - What is Active/Passive switching, and do I need it?

Some preamps come preconfigured with an independent switch or a push/pull potentiometer (usually found on the volume) that will route the signal through the preamp or bypass the preamp. This is called the Active/Passive switch.

As a way to illustrate this idea, consider a common signal path in a bass with a preamp:
Pickups -> Blend Pot -> Volume Pot -> Preamp - > Jack

The bypassed (or passive) signal path would look like this:
Pickups -> Blend Pot -> Volume Pot - > Jack

Essentially, a player would be able to control the blend of their pickups (if a multi pickup bass) and the volume, but have no tone controls.

So, you may be asking…

Why would anyone go to the expense of installing a preamp if they were going to use it in passive mode?

A couple situations come to mind. I have experienced both of them and I’m sure many players can relate.

1 - Inconvenient battery death: Picture yourself on a gig or in a rehearsal. You are playing with a band, and notice tone distortion or a lowering of volume. Your battery could be dying. If you have the ability to bypass the preamp, you can engage that bypass and then keep playing until your next break when you can change the battery, or just leave your bass in passive mode until the gig is over. Many players preemptively change their preamp’s battery on a weekly or bi-weekly basis…depending on how often they play. If this doesn’t sounds like you, or you just want another backup plan, you may want to have the Active/Passive switch in your preamp.

2 - Engineer’s preference: More than once, when in the studio, I have been asked to play my bass flat, with no preamp or tone alteration. Many engineers prefer a flat signal, so that they can adjust it in their mixing process later. It may not be the tone that you are accustomed to hearing live, but, the engineer will dial it in later.


5. Mix and Match - Do I need a specific preamp for specific pickups?

Normally, no. You can use a set of Nordstrand pickups with a Bartolini preamp, Aguilar pickups with a John East preamp, etc…. The one caveat to this is using EMG active pickups. We recommend using an EMG Bass preamp with EMG pickups. They are built for each other in a way that the other pickups and preamps are not. It is possible to use EMG pickups with other preamps, but there are some other considerations. Drop us a line if you need to do that.


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Of course, finding the tone is not all about practical, objective factors. There are a number of subjective factors at play as well. Let's go through a few to give you something to think about.


1. More Volume - Should I expect an increase in volume/output with a preamp?

Some players look to get a preamp simply to increase the output of their bass. This usually is possible, but shouldn’t be the main goal of changing or adding a preamp (to a passive bass).

Most preamps, with their EQ controls set flat, will have little to no effect on the tone of the instrument, including the volume. Of course, there are always exceptions - see below *. When the EQ pots are turned up and boosting, then you’ll get increased volume. This is happening, however, with a boost of the signal within the frequency range that is being boosted. Boosting bass frequencies will have the biggest effect, then mid, then treble (in most cases).

*Some preamps (Nordstrand, Bartolini, others) have a trim pot for the overall output. These preamps can raise the overall output. In that case, a preamp with it’s EQ pots set flat can have more or less output than the bass would otherwise have even though the EQ controls are set flat.


2. 2 Band VS 3 Band?

Aside from spatial considerations, the 2 vs 3 band question is largely one of deciding whether you want the ability to adjust the mid range frequencies. Two band preamps have the ability to adjust treble and bass, whereas 3 band preamps have treble, mid and bass adjustable frequency ranges.

Personally, I like to add just a touch of mid to most basses when playing with a band. I find that it helps the bass sit a little closer to the front of the mix. In general, the price difference between a 2 and 3 band preamp is not that much, and for me it is worth it.

It really depends on whether you need the mid adjustment or not.

Consider the settings on your amplifier that you are already using and use that to help guide your decision.

3. Boost Only, or Boost & Cut?

There are a few preamps available with EQ controls that are boost only...Aguilar’s OBP1, Sadowsky’s On Board Preamp, Nordstrand’s 2B+ are a few of the leading examples. Most other preamps, both 2 band and 3 band have both boost & cut.

Opinions (on both sides) are fairly strong as to whether it is better to have both boost & cut or boost only.

By in large, players tend to boost more than cut. That being said, most of us have probably played basses where it is nice to roll off the treble or mid control a bit, depending on the bass itself, the amp or the room in which we are playing. For that reason, I prefer to use a preamp that has both boost & cut control. Boost & Cut preamps account for the vast majority or preamps sold.

For the players who have a strong leaning towards a boost only preamp, they are able to get the sound they like, without needing to cut frequency at the bass. Some may simply like the boost-handling (frequencies or frequency curves) of a particular preamp and they don’t see the sacrifice of the ability to cut as a detriment.


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 Thoughts on Installation

Now that you’ve got an arsenal of information to aid you in your search for a preamp to give your bass the tone you have in your head, there are a few parting thoughts we wanted to leave you with. Of course, not every bass player has the skills of a tech....So what do you do when the preamp arrives in your mailbox?

1. Shielding

Quite honestly, shielding could be a separate article on its own. That being said, if you are changing your bass’s electronics, it is a good time to evaluate the shielding and install it if necessary. For that reason, let’s discuss it here - as installing shielding tape is quickly done if the electronics are already out (or coming out) of the bass.

Shielding a bass electronics cavity


In most higher end instruments, you will find shielding tape, rather than a painted cavity. In general, shielding tape simply works better. The paint is probably better than nothing, but it is the “go to” of mass manufacturing operations because it is quick. In our years of working with basses, we have usually solved RF interference issues in a bass by installing shielding tape over shielding paint.

If your bass doesn’t have shielding tape in the cavity, consider putting some in when you install a new preamp. It is not expensive, takes 10-20 minutes, and well worth the effort.


2. Tech Requirements - Do I need a Tech to install a preamp?

Obviously, this will depend on your experience and expertise with wiring/soldering in general, as well as your familiarity with circuits for basses/guitars. By no means, do you need to be a professional tech to install a new preamp, but having the ability to solder cleanly is necessary.

A couple preamps, notably EMG Bass Preamps, have a modular system that is a bit “plug and play” oriented. EMG has built in quick connections for the pickups to hook up to EMG preamps. John East J Retro Preamps have a wire terminal on the preamp circuit board that allows for screwing down the pickup wires.

Nearly all other preamps require the pickup wires to be soldered to the preamp’s wiring harness, usually at the blend or volume pot. Depending on your bass, you may also need to wire to an existing battery box and to the jack (if the jack is a barrel or non-standard style jack)

Using a tech will often save you some time and frustration if your soldering and troubleshooting skills are not high. When calling around to techs, ask if they have much experience installing active electronics in basses. Some do not. Often a tech can sort it out on the first go, but like any profession, there are a variety of skill levels in practice.


Some preamps do not come wired into a configuration with the controls/preamp module/battery/jack connected. Aguilar does not wire up their on-board bass preamps at the factory. Aguilar preamps are most commonly sold in this “not pre-wired” condition, however, we do offer an Aguilar bass preamp pre-wire service.


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Which Bass Preamp is The Best?

Making declarative statements about the various brands of preamps is not what this article is about.  Writing a post on the 'Best Preamp Brands' or 'Top 10 On Board Bass Preamps' may get some views, but we'd be breaching boundaries of intellectual honesty with those kinds of articles.

We are all different...our musical styles are different.  Beyond that, even the needs of a particular bass is different.

We have personally installed countless Aguilar, ACG, Audere, Bartolini, East, EMG, Noll, Glockenklang, Delano, Mike Pope, Nordstrand Audio, Seymour Duncan and other preamps. 

These engineers/designers all know what they are doing and create great products.   

But still, what do players love about specific preamps? 

Below are some quick anecdotes that we have gathered over the years. This list covers what we currently carry and will be amended as we add new preamps to our inventory.


Aguilar OBP1 Preamp:

  • Great option if you want boost only 2 band from your preamp
  • "Reminded me of my Sadowsky Preamp"
  • 18Volts is recommended to handle the headroom
  • "I can dial in a LOT of bass with this preamp"
  • Several customers prefer the lower frequency center of the treble control of this preamp (4kHz)


Aguilar OBP2 & Aguilar OBP3 Bass Preamps: 

  • Clean & clear, several control configurations
  • Well loved mid frequency options
  • "Gave my bass some ballz"
  • Often seen as one of the more 'powerful' to dial in a lot more of bass, mid and treble


Bartolini NTBT and NTMB Bass Preamps:

  • Capable of producing great fat, thick and round tones
  • Moderately aggressive (not subtle, not overly aggressive)
  • Players commonly cite this preamp is being quite musical
  • Ability to adjust the overall output of the active signal


EMG BQS, BQC, & BTS System Bass Preamps:

  • Easy install
  • Excellent pairing with EMG pickups 
  • Really cuts through the mix
  • Popular in Spector, Modulus basses
  • More powerful and cleaner than a lot of stock preamps
  • "Brought my bass to life"


John East J Retro:

  • “One of the most profound upgrades to my Jazz Bass®!”
  • Rich deep tone in a small tweak
  • Tonally, this preamp is extremely versatile
  • Easy Install
  • “Has turned my cheapo MIM J Bass® into a killer!”
  • Ability to adjust the input gain of each pickup


Nordstrand Audio Bass Preamps:

  • Transparent
  • “My bass sounds so musical after swapping in this preamp”
  • Boost and cut is not is "just right"
  • Mid boost is in the upper mid-range compared to other preamps (wired for 1kHz and 400Hz switchable)
  • Treble boost is in the lower treble range compared to other preamps (4kHz) making treble boost less "airy"
  • Ability to adjust the overall output of the active signal


• • • • • 


We hope this article has been informative and given you a place to start if you are anticipating installing a preamp.  

Drop us a line with any questions you have.

We'd love to hear your thoughts on various preamps and installation that you have used in your basses over the years.  Please leave your comments below: