The J Bass Project (Part 2 - The Bass Preamp)

I'm thrilled with the progress we've made on this Jazz Bass project so far. The new Nordstrand Big J Blade (Warm & Wooly) pickups sound fantastic - big, punchy, and with a healthy dose of growl, which is exactly the tone I was looking for. They've made a noticeable difference in rehearsals and even my drummer commented on how much better the bass sits in the mix, because he can actually hear me now.

But the journey isn't over yet. Next, we're tackling the biggest letdown of this bass when I first bought it: the onboard preamp.

The stock preamp was so bad it felt like an afterthought. It's hard to believe that something this low-quality could be included in a mid-range bass. It was noisy, had weird frequency response, and a useless slap switch. Worst of all, it made the bass feel stiff and unresponsive due to its low headroom.

If you had played it, this preamp would’ve inspired you to stick with a passive setup.

Years ago, I gave up on it and switched to only using the bass in passive mode. Eventually, the preamp died completely, and I replaced it with a Fat Bass Tone passive wiring harness. This was a major improvement, adding a useful tone knob for dialing back the high-end.

The passive setup sounds great with the new pickups, but I'm curious to see what this bass can do with a high-quality preamp. So in this article, we'll explore the world of preamps and find the perfect one to unlock even more potential from this bass.

Choosing a Bass Preamp

These days, we're spoiled for choice when it comes to bass preamps. It can be a bit overwhelming to find the perfect one for your Jazz Bass.

The first step is to figure out how many knobs and switches you have available - as that will guide the inquiry into the available options that will work without drilling new holes. My Jazz Bass has four knobs and one switch, which gives me a lot of choices.

Next, I decided I wanted to go with a three-band bass preamp for more control over the midrange.

Once you know how many knobs and EQ bands you want, the next step is to consider the preamp's "flavor." Some preamps have a distinct personality that colors your sound, like the Darkglass Tone Capsule. Others are very neutral and transparent, like the Nordstrand 3b.

I'm happy with how the Big J Blades sound passively, so I didn't want an overly colored preamp. However, since I'm planning on wiring it with a bypass switch, I also wanted a preamp that adds a bit of its character.

The Contenders

John East Uni-Pre: The Uni-Pre is one of the most flexible preamps in the market, not only due to how much control you get with the carefully chosen frequencies, but also because it can be configured in multiple ways with its internal dip switches to better match with your pickups and how you intend to use it.
Aguilar OBP-3: An industry-standard preamp found in many boutique basses. Many of the people who’ve installed the OBP-3 tend to comment on how “their bass woke up” after installing it. The OBP-3 adds a subtle warmth and punch due to its high headroom.
Trickfish IPA: The IPA is designed by Mike Pope, the man responsible for designing the preamps used on many Fodera Basses, and multiple other bass innovations. As an accomplished bass player himself, Mike Pope and the folks at Trickfish designed a preamp that adds a touch of polish and shine to your tone while making it practical for the gigging musician.

The Winner

After some consideration, I chose the Aguilar OBP-3. I think it will complement the passive tone of the Big J Blades nicely and give me more tonal options.

All of these shortlisted preamps would have been a good choice. They are all of the highest quality, which is one of the reasons you’ll often find them in high-end bass builds.

I ordered the pre-wired OBP-3 with a push-pull bypass switch (on the volume pot) and a mid-frequency switch (800Hz or 400Hz). The pre-wired version saves time and ensures everything is soldered correctly.

Installation

The preamp arrived beautifully wired. The folks at Fat Bass Tone did a much better job than I could have done myself, so ordering the preamp pre-wired was a good idea. Installing the preamp was straightforward with the included diagram.

Remove the old wiring harness
Solder the hot wires to the blend pot
Solder the ground wire to the bridge ground.
Connect the battery

The whole process took about 35 minutes.

The OBP-3 has a lot of wiring, but everything fits without excessive bending of any wires. The 9-volt battery also fits inside the cavity, which I didn’t have to do, since my bass has a dedicated battery compartment.

Aguilar OBP3 Bass Preamp Installed in Fender Jazz Bass Guitar

Having this extra space means that I could experiment with running the preamp at 18 volts, but for now, I'm happy with the standard 9-volt operation.

How Does The OBP3 Bass Preamp Sound?

After making sure everything was connected properly, I eagerly plugged in and tried the new preamp. The first thing I checked was the difference between the preamp bypassed and engaged with all knobs at noon (no addition or decrease in the EQ). I was pleasantly surprised to find very little difference. If anything, there was a slight boost in the low end and the higher frequencies seemed to have been smoothed out a bit. The difference is very subtle, to the point where I think most won’t notice a difference between the bass in passive mode and the preamp engaged with knobs at noon.

Preamp Observations

Before I describe the tones, here are a couple of things I noticed about this preamp:

Big increase in output: This preamp has a lot of gain on tap. Boosting the frequencies significantly increases the output volume. I actually had to use the input pad switch on my amp to keep things under control and keep it from overloading my amp’s preamp.
Sensitive EQ: Moving the pots in any direction makes a big difference in your tone and output. A small adjustment can make a big difference, so be careful when dialing in your sound.
Great choice of frequencies: Each one of the frequencies is tuned just right, unlike the OEM preamp. Turning the bass knob up makes the bass sound bigger and fuller, yet it never gets flabby. The 300hz mid frequency center works great if you want more low-mid thump, and the 800hz is great if you want some of that active bass burpy sound that also cuts through big guitars. The biggest surprise was the treble knob since it gives it some sparkle when boosted without ever getting clanky. Great if you want some more snap when slapping or getting more of the pick attack. And when cutting the treble, it works like a (better) tone knob, in the sense that it doesn’t change the character of the mid range when rolled back like a traditional tone knob.

Two Ways to Use the Preamp

After playing around with the preamp for a couple of hours, I found two main ways to use this preamp for my needs:

Subtle Enhancement: Make small increases to each frequency band for a subtle boost across the entire band. Doing this keeps most of the character of the Big J Blades while adding a bit more output, and more emphasis on the fundamental frequencies of each note, while still keeping the character very organic.
Dramatic Tone Shaping: You can also go more heavy-handed in boosting or cutting each of the three frequencies. When you do this, the character of the preamp takes over and it pretty much sounds like a different bass, in a good kind of way. It’s very interesting how it alters the feel of the bass, it now feels similar to when you are playing your bass through a high-powered bass amp at high volume.

The boosted tone is very different from the subtle setting, with a more prominent fundamental and a very clean character. This cuts through a mix nicely, not because of volume, but because of the reduced harmonic content and the emphasis on the fundamental note.

Even when boosting the preamp significantly, it remains incredibly dynamic and responsive. It has tons of headroom, and I couldn't make it clip or compress, even when playing aggressively. This is with the preamp running at 9 volts, so I'm not sure if the 18-volt mod is necessary.

Favorite Tones

After spending even more time with the preamp, I arrived at some settings that I think can give me a variety of tones that were impossible to get with the passive setup.

Both Pickups Full On: With a slight boost to the bass and mids (300Hz setting) and a tiny cut to the highs, this gives me a natural, organic tone that's slightly bigger and clearer than the passive sound. If I want to add some high-mid sizzle, I can simply flip the switch to the 800Hz setting.
Reggae/Dub Tone: Pushing the bass a bit further, adding a touch of mids at 800Hz, and cutting the highs completely creates a big, dark, and tubby tone perfect for reggae or dub.
Neck Pickup Tone: Boosting the high-mids at 800Hz, adding a bit of treble, and a hint of bass to the neck pickup creates a beautiful, singing tone that combines the best of a Jazz Bass and a P-Bass. This is my favorite tone of them all and sounds great played fingerstyle, and with a pick, and it’s glorious when you add some overdrive.
Aggressive Pick Tone: Favoring the bridge pickup, rolling back the neck pickup a bit, and boosting the mids at 300Hz creates a cutting, aggressive tone perfect for rock. Boosting the mids at 300hz balances out the honk from the bridge pickup and makes it sound somewhere in the neighborhood of what you would expect from an active humbucking style pickup.

Live Use

For gigs, I'll keep the bass and mids slightly boosted and adjust the treble to taste. I'll switch the mid-frequency switch to 300Hz when favoring the bridge pickup and 800Hz when favoring the neck pickup. This should give me a wide range of tones without needing to make major adjustments on the fly.

This will be entirely dependent on what songs I’m playing, but it’s very easy to access each one of those tones without having a drastic change in volume, and they’re simple enough to do on the fly in between songs.

Final thoughts after two upgrades

After upgrading the pickups and the preamp, this bass feels completely transformed. It's like it's leveled up into a whole new tier of instrument. It's still the same familiar bass, but the tone is miles better. The tone is now what I'd expect from a much more expensive instrument.

Adding the preamp was a great move. While the passive tone was already excellent, the preamp brings out even more of what I love about these pickups. Plus, it opens up a whole new world of tonal possibilities, which is great for recording or dialing in specific sounds. So far, I'm incredibly happy with the results.

Compared to the original preamp, the Aguilar OBP-3 is in an entirely different league. I now genuinely believe that the reason why many bass players shy away from onboard preamps is because they tried a low-quality one like the one originally installed in my Fender Jazz Bass Deluxe 24 V. If instead, they would’ve tried one equipped with an OBP-3 (or any other high-quality preamp), they would surely feel differently about them.

The Next Step: Upgrading the Bridge

The next step in this journey is to replace the bridge. The current one is pretty banged up, and after talking to Brian from Fat Bass Tone, he believes a new bridge could make a noticeable difference because Fender basses from the early 2000s were not known for their high-quality hardware. So I'm following Brian's advice and will see what a new bridge can do for this bass.

~ JJ Monzon