There’s a very strong argument for top-end bass builders to choose John East’s Uni-Pre as standard equipment for potentially all of their offerings. Bold statement? Allow me to rationalize it. I’ve come to think of the Uni-Pre preamp as a sort of Tolkien-esque “One Pre”; a single preamp to rule them all. One for nearly all uses, all instrument types, and all tonal goals. However, as the overworked saying goes, “With great power, comes great responsibility,” and the reason I opened by saying builders may want to outfit their creations with a pre-configured iteration of this super-achiever pre rather than everyone, is that there is always a danger of overcomplication and subsequent disuse or disinterest for the less technically-inclined end-user thumper. The Uni-Pre can be ordered in variations consisting of 3 to 5 knobs and switches; I chose a 4-knob configuration of the Uni-Pre for my installation.

What It Is

East UK’s current onboard flagship, the modular, class-A FET-equipped Uni-Pre system comprises an impressive list of features. Let’s begin with perhaps the most unique and technically exciting aspect of the way audio passes into and through the preamp. The Uni-Pre actually employs two completely separate audio paths with dedicated potentiometer segments, specialized for passive and active modes of use. This is achieved by using custom spec’d, multi-segmented stacked concentric pots, controlled by a single shaft. In other words, it’s akin to having two blends and two volume controls at your fingertips, each betrothed to its isolated active or passive audio paths, with proper pot values for each.

East UK Uni-Pre Onboard Preamp

But before the signal is routed to either path, it first passes through a full-time, passive, stereo tone control that keeps each pickup isolated from the other until after the buffer stage in active mode or the blend stage in passive operation. That means you get the benefits and sonic hallmarks of a passive tone control no matter which mode you select. This is important, because my feeling is that a lot of what people think they enjoy or even prefer about a passive system comes down to capacitance and the way in which a passive tone control interacts with the pickup coils and colors tone. The way this system is laid out, one can achieve the passive instrument style response and tone, while still reaping the benefits of a buffered system, low-impedance output, and additional EQ beyond the tone control, if desired. As a good modular system promises, the passive tone may be omitted as well, and its function defeated via a jumper on the main board.

Further along the active path, an adjustable-gain (0 to +12dB), stereo input buffer is met by the post-passive tone signal and can mix many types of pickups with differing output levels, regardless of type. The stereo functionality allows you to set the gain variation for each pickup independently. Moving further along the active path into the EQ section, we find a treble control that can be variably adjusted between 1kHz and 7.5kHz via an internally mounted trimpot thumbwheel, with push/pull functionality for a 10kHz shelving boost. This is stacked atop a bass control that’s adjustable in a similar way, but actually allows for specification of BOTH the bottom AND top end of the control’s envelope, from 20-80Hz on the low end and 40-200Hz at the higher end. Finally, we encounter a stacked, semi-parametric midrange control that gives you boost and cut capability from 100Hz on the low end to 2.5kHz up top. Whew!

East UK Uni-Pre Onboard Preamp

That’s quite an impressive list of capabilities, and perhaps now it’s becoming clearer how a practiced user might coax just about any passive or active tone or timbral footprint out of the Uni-Pre. You get true, passive tone operation while in either passive or active mode, which I find useful for essentially “tuning” the top end of the pickups’ response and potentially adding a little resonant peak at the cutoff point, and then three very customizable and flexible EQ controls after that point. In active mode, you get the additional perk of a very well-designed and usable active blend, which allows for many more shades of variance between 0 and 100% of each pickup’s output relative to the other. If you choose to stay in passive mode or want a real, honest, true passive path with value-correct pots and all, you get that, as well (the passive blend and volume segments of the stacked blend/volume control are a fairly standard 250k). Of note, because it’s so unusual and therefore super cool to a gearhead, the stacked blend/volume control comprises five completely separate analog potentiometer segments! One for active blend, one for active volume, one for passive volume, and the traditional dual ganged element for passive blend. You switch between active and passive modes by pulling up on the tone control to enter full passive operation with the 4 and 5-knob variants, or via a toggle switch with the 3-knob version.

Quick Start Guide

I installed the Uni-Pre in one of my MTD 635 basses, which come equipped with underwound, naturally very bright Bartolini pickups. I really enjoy that crispy, modern tone … most of the time. But when I don’t, it’s necessary to use the treble control to essentially tune the ultra-high end response and cutoff of the pickups to create the overall frequency spectrum I want, often capping out around 8-10kHz – which then disallows the possibility of adding a little lower treble grit around 2.5kHz or setting more of a modern tone by goosing 5kHz, or so.

East UK Uni-Pre Onboard Preamp

The passive tone control of the Uni-Pre has worked really well for me to approximate the general type or vibe of pickup I want to go for in terms of resonant peak and high-end roll-off, which kind of sets the overall soundstage for what I want to achieve at a certain time, which can then be modified with the uber flexible 3-band EQ without burning one of those valuable bands just to get the initial voicing desired. And the Uni-Pre makes that much more feasible due to the highly adjustable treble peak, mid center, and even the width and breadth of the bass control.

Want more aggressive spank and growl from a bass with single coils? Turn the tone down to taste, set the treble for 3kHz and boost slightly, adjust the bass to offer just enough depth, and then determine whether you want a midrange cut or boost according to your specific instrument’s construction and pickups (or leave it flat). And that last item is greatly facilitated by the sweepable mid frequency, conveniently located on a stacked pot shaft with the mid cut/boost, rather than being mounted inside the control cavity as a fourth thumbwheel. I’ve found the easiest thing to do is to boost all the way, then sweep that mid center frequency from one extreme to the other to very clearly hear what you might want more or less of – then adjust the boost or cut at the frequency until ultimate satisfaction is achieved (the desired effect).

East UK Uni-Pre Onboard Preamp

Want a gospel-ready, modern, hi-fi tone? Pull up on that treble control to realize the fixed 10kHz bright boost, turn your mid control’s frequency to about 1kHz and cut, set the bass window narrow and low, and boost ‘til the holy spirit moves you.

How about a solid classic rock tone? Set treble around 3kHz but leave flat, boost mids around 800Hz, make the bass 25 or 6 to 4 (or simply flat to start), then use the passive tone to give you the right amount of roundness and warmth. Boost that treble for a little added grit and presence.

East UK Uni-Pre Onboard Preamp

Have it Your Way

So for someone who understands all this technical jargon and equalization parameters – someone who has at least a burgeoning awareness of the effect of different points along the audible audio spectrum – the East UK Uni-Pre is an almost unmatched tool for sculpting nearly any kind of tone that’s possible with EQ and high-end filtering. Knowing that EQ can’t transform the timbre of one type of pickup into another – i.e. a single-coil into a parallel-wired, dual-coil humbucker – is an important understanding and expectation to have. But the Uni-Pre will most definitely offer the entire range of famously recorded tones from the same type of instrument, from, say, the dark and muted Chromatic Fantasy Jaco J-Bass tone to the hyper high-end hoisted, mid-scooped and modern Marcus Miller Power or Detroit vibe. It even goes so far as to be able to simulate the use of nickel or steel roundwounds, and potentially even flats, from any other starting point. But, it’s a preamp that begs to be customized and suited to a specific instrument and its pickups, so some time spent getting familiar with the various EQ centers possible for each control is highly advisable.

East UK Uni-Pre Onboard Preamp

A skilled builder could definitely develop a set of characteristics and settings they feel would offer the most value to a specific model they manufacture, without needing to switch between different preamp products for different basses; different “presets” if you will for tonally varying axes. And a player who has taken the time to develop strong opinions about what s/he likes in a preamp will be supremely satisfied. However, the Uni-Pre might offer too dizzying an array of possibilities for the more casual user. Of course, with its extremely high-quality components, feature set, and price point, it’s certainly not aimed at the first-time preamp modder anyway. It should also be noted that John East offers a number of other top-tier preamp options, many of which are more “plug-and-play” friendly and very easy to comprehend. I hope you find value in the companion videos in demonstrating just a small sampling of the various settings and possibilities the Uni-Pre offers.

East UK Uni-Pre Onboard Preamp



Manufacturer: East UK, Bumble Clumps Northampton Road Weston on the Green OX25 3TJ UK
++44 (0) 1869 343112.
Configuration:Units available from 3 to 5-knob installations, with and without separate switches.
Controls:Passive tone with push/pull for passive output, stacked treble and bass with push/pull Bright function on treble, stacked mid and mid frequency sweep, stacked volume and blend.
Input Topology:Class-A, FET.
Pre-Shape:Gentle lift at the lower and higher frequencies, shelving +4dB at 40Hz & 10kHz.
Pickup Gain:Internal trimmers 0-12dB for each pickup in active mode.
Bass Control: +/- 18dB with internally adjustable ‘bass window.’
Bass Window: Lower frequency filter 20-80Hz & higher frequency filter 40–200Hz.
Mid Control: +/- 18dB with frequency sweep 100Hz – 2.5kHz.
Treble Control: +/- 18dB with internally adjusted shelf frequency 1kHz – 7.5kHz; pull for Bright peaking at 10kHz.
Warranty: 1 Year, material defects and workmanship.
Price: 204.43 - $279.75, depending on configuration and hardware color.