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Zmode Switch

M136 Bass By Matt Schmill

Pro Z Module Preamp - Overview

The Pro-Z is a small, fully wired highly configurable module preamp.

The preamp below has volume, balance, and 4 bands of EQ control with 3 sets of stacked knobs.
Pro Z Module Wired

All models include the unique Z-Mode control switch and LED battery monitor.
For EQ control, select from 2, 3, 3 + Mid Frequency Switch, or 4 EQ Bands.

The configurations shown below are the most frequently ordered although the preamp can be Custom Configured if what you need is not listed in the tables.

Pricing is simple:
Modules with 2 bands $179
Modules with 3 bands $189
Modules with 4 bands or 3 bands plus a mid-frequency switch are $199
Optional knobs are $5 per single pot, $10 per stacked pot, and come in chrome, black, gold.

Hole counts: The Z-Mode switch always requires 1 hole in addition to the control hole count. For example, the hole count is 1 (for the Z-mode)+2 holes for controls, so 1+2 is 3 holes total. A Z-Mode switch hole is often added to a bass but the switch will fit in most smaller pot holes (we provide spacers which helps). The LED for the battery meter also requires a small hole which is commonly added on the back side to the cavity cover but can be added to the front of the bass.

Configuration Abbreviations
vol = volume bal = balance b = bass m = mid on 3 band t = treble
vn = volume neck     mfsw = mid frequency switch  
vb = volume bridge     lm = low mid on 4 band  
      hm = high mid on 4 band  

Most Popular Configurations for 2 pickups, volume and balance controls
Hole count is 1 for Z-mode switch + # for Controls
  1+2 holes 1+3 holes 1+4 holes 1+5 holes 1+6 holes
2 band vol/bal, t/b vol, bal, t/b vol, bal, t, b    
3 band   vol, m/bal, t/b vol, bal, m, t/b vol, bal, t, m, b  
3 + Mid Freq Switch     mfsw, vol, m/bal, t/b mfsw, vol, bal, m, t/b mfsw, vol, bal, t, m, b
4 band   vol/bal, hm/lm, t/b vol, bal, hm/lm, t/b vol, bal, hm, lm, t/b vol, bal, t, hm, lm, b


Most Popular Configurations for 2 pickups, volume and volume controls
Hole count is 1 for Z-mode switch + # for Controls
  1+2 holes 1+3 holes 1+4 holes 1+5 holes 1+6 holes
2 band vn/vb, t/b vol, vol, t/b vol, vol, t, b    
3 band   vn, vb/m, t/b vol, vol, m, t/b vol, vol, t, m, b  
3 + Mid Freq switch     mfsw, vn, vb/m, t/b mfsw, vol, vol, m, t/b mfsw, vol, vol, t, m, b
4 band   vn/vb, hm/lm, t/b vol, vol, hm/lm, t/b vol, vol, hm, lm, t/b vol, vol, t, hm, lm, b


Most Popular Configurations for 1 pickup
Hole count is 1 for Z-mode switch + # for Controls
  1+2 holes 1+3 holes 1+4 holes 1+5 holes
2 band vol, t/b vol, t, b    
3 band vol/m, t/b vol, m, t/b vol, t, m, b  
3 + Mid Freq switch   mfsw, vol/m, t/b mfsw, vol, m, t/b mfsw, vol, t, m, b
4 band   vol, hm/lm, t/b vol, hm, lm, t/b vol, t, hm, lm, b


Addition Information:

Our Pro Z Preamps feature our unique Z-Mode control which delivers 3 organic bass voices with clarity and definition.


The number one question players ask us is what does a Z-Mode switch do?
You have probably played a passive guitar where the pots where changed to a higher resistance to brighten up the sound and make the guitar feel more lively.
For example, if you remove 220K ohm Fender pots and change them to 500K ohm pots the sound will clearly change.
When you change the pots to a higher resistance the response will start to peak somewhere in the 1 to 5 KHz range (depending on the pickup).
After peaking, the high end will drop off faster but listeners are more sensitive to the peaked frequency than to the fall off in the very high frequencies so the guitar sounds brighter and more open.

So you are probably thinking why doesn't Fender change their stock pots to 500K ohms - the brighter sound is like a food spice sometimes you want it but at other times you do not.
If you have 2 guitars on stage then all is good you can choose what you need when you need it.

The Z-Mode system is like changing all your pots out on the fly in the same guitar to give you the flexibility you would get by having 3 guitars with you on stage.
The switch connects to an advanced electronics system which reconfigures the preamp to change the loading applied to the pickups.

  • Mid Z-Mode (center position) - is the sound of your passive bass. You will not lose your passive sound but you will gain more touch responsiveness and better pickup mixing. Typically players spend the majority of their time in this mode.
  • High Z-Mode (toward the bridge) - is a bright aggressive sound like changing all your pots to a higher resistance. This mode is often used for slap playing.
  • Low Z-Mode (toward the neck) - is a deeper fuller sound response. The unique aspect of this mode is it features very good note timing location and is never muddy. Lots of bass players have been looking for this sound and attempt to get it with tone controls on other preamps without success.

Z-Mode responses in an early 70s Vintage Fender Pickup

Z-Modes Early 70s Fender

Note: the Low Z-Mode is adjusted for a Bridge pickup where you have less bass signal generated by the pickup placement - for a Neck pickup the Low Z-Mode gain pot would be set 2 to 4 dB lower.


In summary, the Z-Mode switch gives you 3 organic starting points from which you can adjust pickup balance and add tone control to make getting the sound you want easier..

The Z-Mode switch makes the Audere preamps not only the best sounding preamps but also provides the most versatile tone range in the preamp market.

The Pro Z module preamp sounds great as programmed at the factory. But for those who like to experiment, you can reprogram the Pro Z module to change the Z-Mode loading on the Neck and Bridge pickups. This offers a very unique range of sounds.

The Factory settings for the Z-Mode switch are shown below.

Pro Z module Z-Mode Factory Settings
Position Setting Neck Z-Mode Bridge Z-Mode
Toward Switch dot
3rd position







You can reprogram each of the 3 way switch positions to any of the settings in the table below.

Pro Z Adjustments

Steps to reprogram the Z-Mode switch:
1) Put the Z-Mode switch in any position and depress the push button on the module once. The current mode is indicated by the LED with the number of LED flashes equaling the setting number.
2) If you want to change the setting for this switch position, depress the switch N times (N being the number in the setting column). The system will store this setting for future use.
3) Play the bass and decide if you like this setting or repeat the process to select a different Z-Mode setting.

Pro Z module Z-Mode Table
Setting Neck Z-Mode Bridge Z-Mode













Low' Z-Mode has less high frequency content then Low Z-Mode.
High' Z-Mode removes the capacitance load in the socket from the High Z-Mode and is often brighter.

A typical use for the re-programmable Z-Mode feature is when you have two differ pickup types.
For example - in a P J setup, the J will respond to all of the Z-Modes but most P pickups sound close to the same in High Z-Mode as they do in Mid Z-Mode.
In this scenario you can reprogram the Z-Mode switch to keep the P in Low or Mid Z-Modes while the J is usable in all the modes.

One possible selection of Z-Mode settings for P-J Pickups
Setting Neck Z-Mode Bridge Z-Mode







The re-programmable feature is also particularly useful when working with pickups which are constructed with a small number of windings. This style of pickup construction will not yield a large difference in response between High Z-Mode and Mid Z-Mode but the difference between the Low Z-Mode and Mid Z-Mode responses will get correspondingly larger. If you have pickups with a small number of windings you can reprogram your Z-Mode switch to favor the lower numbered settings in the table above which will to maximize your sound options.

In summary, the re-programmable Z-Mode feature offers more versatility if you need it.

Pro Z Adjustments

Each module has 4 adjustments to optimize the preamp for your personal sound.

1) High Z-Mode Capacitance for the Bridge Pickup
2) Low Z-Mode Gain for the Bridge Pickup
Skip over the Z-Mode setup switch
3) Low Z-Mode Gain for the Neck Pickup
4) High Z-Mode Capacitance for the Neck Pickup

Low Z Mode adjustment: Different types of pickups have very different output levels in the Low Z-Mode so we provide a Low Z Gain adjustment.
There are two pots, one for each pickup. A simple turn is all you need to do to change the Low Z gain level.
The goal of this adjustment is to balance the Low Z-Mode output level with the Mid Z-Mode level.
We adjust the Low Z-Mode to be slightly louder than the Mid Z-Mode level so you hear the low and high frequencies clarity in this mode.

High Z Mode adjustment: Different types of pickups have a unique High Z-Mode resonant peak frequency.
A hand wound pickup will have normally have a lower resonant frequency to it's peak than machine wound pickups.
By adding capacitance to these sockets you can lower the peak frequency location to make a machine wound pickup closer to the hand wound custom pickup.
The two capacitors, one for each pickup, are socketed so that you have the option of optimizing the resonate peak frequency in High Z Mode.
FYI -most players never change their High Z-Mode caps since they like our default selections which are 680 pf on the Neck and 330 pf on the Bridge.
We offer a kit of different cap values; In the graph below you can see the effect each cap has on a Fender Squier Vintage Modified Duncan Designed pickup.

High Z-Mode Cap Kit

To change the caps you simply pull them up out of the sockets and push the new ones back into the sockets.
When you order a Jazz you can add a cap kit to your order for $12 (normally $15 without a preamp order).

We have pre-wired the electronic assembly to make installation as simple as possible.

You will need to select a spot for the Module, LED Battery Meter, install the controls into the Bass body, and connect the pickup wires and ground wire.

The module will be custom wired for your selections:
• Volume control selection - single, volume & balance, volume and volume, master volume, volume and volume
• The EQ circuit based on 2, 3, 3 with a Mid Frequency switch, or 4 Band Active EQ.
• Emergency back up Active/Passive switch (not recommended)
• 9 or 18 volts of battery power.

The only soldering required is wire to wire joints for your pickups and ground connections.

The controls are on high quality flexible wires to facilitate an easy installation.
Most controls can be single or stacked knobs to allow for a configuration that corresponds to your available holes.

After we have wired your assembly together it is connected to a bass pickup and then driven by a wide band magnetic field. All of the controls are tested and a frequency scan is completed for all 3 of the Z-Modes.

For more information see the PDF of the Pro Z Installation

The Pro Z preamp module is just about the size of a 9V battery: 2.00"L x 1.05"W x 0.30"H.

The switches are mini toggle switches with bushings of 1/4" diameter, 9.0mm length; the finish is chrome and each switch comes with additional decorative washer and nut sets; in both Black Nickel and Gold for versatile finishing.

The preamp is mounted with Double sided tape patches that are included

The true sound of your passive bass is available using Mid Z-Mode with Tone controls in the center detent.

Players often think they need an active/passive switch to get a passive sound which is correct for many other types of preamps but not with Audere preamps.

There are a variety of reasons given for installing an A/P switch but the top 3 are:
1) Most preamps do not sound like a passive bass due to distortion - our advanced design eliminates this distortion.
2) Many preamps do not sound like a passive bass due to tone control curves - our tone controls are flat in the center detent.
3) Players worry about the battery dying - our modules include an intuitive LED battery meter.

In the Pro Z module we offer an active/passive switch but we do not recommend it - the control is only useful for emergency operation.

In a volume and balance configuration - the balance is an active control so the only function you will have in passive mode is the volume with both pickups mixed together at 100% levels.

In a volume and volume configuration - you need to add a master volume which is the only volume control function you will have in passive mode with both pickups mixed together at 100% levels.

As described in the Passive Tone Control section on this page, this traditional control is available and works in both passive and active modes.

The active mixing design provides a broader range of usable sounds as you adjust the pickup mix.

Our front end is a stereo design so the pickup signals are electrically separated from each other.
After buffering, the signals are mixed together by the balance control or the dual volume controls depending on the preamp's control configuration.
This design is especially useful if you have 2 different types of pickups; for example in a PJ configuration, the P retains its classic P sound and the J retains its classic J sound.

Our balance (also known as a blend) control gets slightly louder as you move toward soloing either the Neck or Bridge pickup.
This type of response curve makes soloing a pickup easier on stage as you do not need the sound guy's help to keep your volume level reasonable.

The single pickup module removes the balance or 2nd volume control, as you would expect.

The Z-Mode table changes to

Pro Z module single pickup Z-Mode Table
Setting Z-Mode








Low' Z-Mode has less high frequency content then Low Z-Mode.
High' Z-Mode removes the capacitance load in the socket from the High Z-Mode and is often brighter.

In the Pro Z Module preamps you can select either a 2, 3, 3 with mid range frequency switch, or 4 band tone control.


The active tone control pots contain a center detent where the response is flat, giving you the uncolored sound.

Our tone controls are different than most preamps in the following ways:
1) The boost/cut amount changes slowly at first off the center detent and then the action speeds up as the knob is rotated farther from the detent.
2) Mid-range controls use wide bandwidths - the issue with narrow bandwidths is the phase shift changes too fast vs. frequency and they sound artificial while our wide frequency mid-range controls is more musical.
3) The Bass and Treble controls are shelving which extends to lower and higher frequencies than other preamps. The shelving control makes our specs look very different than most preamps. Our spec is at the 1/2 boost or cut frequencies. You can think of our specs as all the frequencies below 180 Hz or above 3.2KHz (for a 4 band example) have a significant level of boost or cut range.

The frequency response points:

  4 Band 3 Band 2 Band

Bass shelving Hz - dB

180 +/- 16 dB 200 +/- 16 dB 200 +/- 18 dB
1st Mid Peak Hz - dB 250 +/- 10 dB 500 +/- 10 dB  
2nd Mid Peak Hz - dB 750 +/- 10 dB    
Treble shelving Hz - dB 3.2K +/- 18 dB 2.5K +/- 16 dB 2.0K +/- 17.5 dB

The 3 band mid range frequency switch moves the frequency of the Mid range control to 250, 500 or 850 Hz.


In summary, we design very musical tone controls that are easy to use and give you lots of control of your sound.

The LED battery meter is very intuitive and will give you plenty of warning that you need to replace your battery.


When you first insert your cable the preamp will power up and show you the battery strength by modulating the intensity of the Blue LED for 2 seconds.

Battery LED Sequence

When your battery needs to be replaced the LED will flash a notably faster sequence for 5 seconds. At this point you still have 10+ hours of playing life so it will not die on you at a gig. But you must change it before your next gig.


Important Note when your battery is brand new you may have a high enough voltage that the center flash will not dim and will stay bright the 2 seconds then it will dim as it ages.


In summary, the LED Battery Meter allows you quit worrying about the battery's status.

The Pro Z module preamps will run about 250 hours on a premium 9 volt battery.
If you are running 18 volts then the battery life will be longer.


Since we sometimes get asked:
1) Rechargeable batteries. Not recommended - their voltages tend to be different and they self-discharge faster than normal batteries and when they die you get no warning.
2) Lithium batteries. Not recommend - they cost a lot more and do not work any better plus they have safety issues.

The Audere preamps sounds the same when running on 9 or 18 volts in most cases.

Since our preamps do not add a lot of gain to the signal path in most cases they work exactly the same with either voltage.
The output level does not increase with an 18 volt system unlike several common preamps.
We recommend you save some weight and space and only use 1 battery unless you already have an 18 volt battery box.

You will get more head room on 18 volts but the preamps are designed with parts which are fully qualified to run at the lower voltages so unless you use your tone controls maxed out and play really hard, you will not be needing the extra voltage.

You can always change the battery supply later and the preamps will automatically adjust in between 9 and 18 volts.

The output level when the tone controls are flat (in center detent) is the same as your passive bass.
Always connect a bass with an Audere preamp into the passive input on your amplifier.


We do not include excess gain, there are several reasons why:
1) This allows the preamp to run on a single 9 volt battery without distortion. Lots of other preamps have added so much gain to the output that they are still clipping with 18 volts of power which is why they never sound like a passive bass.
2) All bass heads work well with a passive jazz bass input levels since this is the most common bass. When you plug into an active input on most bass amps they simply divide down the input level (tossing away the extra gain) and then proceed through the amplifier like you plugged into the passive input without the extra gain.
3) We make your bass to actually sound better as opposed to tricking your ear by making it louder. If you turn up your bass sound intensity any where in the signal path it sounds better due to how the human ear works as demonstrated by the Fletcher Munson curves.
Fletcher-Munson Curves
You hear the bass (especially) and the treble better when the sound level is louder as shown in the graph.
A lot of preamp companies use this effect to trick players into thinking the quality of their active sound is better by simply increasing the sound level but if you back it down to an equal volume level you might not be very impressed.
Our design captures all the fine detail of your playing style and brings it out so it really sounds better instead of just louder.
4) Most effects are designed to work with the passive bass pickup levels and our preamp gives them the unamplified signal level they expect.

To use our Z-Mode technology, you must have PASSIVE PICKUPS, meaning that the pickup does NOT have a semiconductor component in the pickup.
The concept of changing the loading on an active pickup does not make sense - in theory an active pickup would ignore the loading applied.


There is a lot of confusion among players and technicians about active pickups - most pickups are passive but they are sometimes called active when they are connected to a preamp. The connection to a preamp does not make the pickup active - it only makes the system active and these pickups will work with our preamps.


The vast majority of basses have passive pickups. EMGs are the most common active pickups.
If you are uncertain about your pickups, Google them (fastest), check with the manufacturer, or send Sales at Audere an email.
About 99% of the time you can also look at the red wire off the battery and see if it goes to the pickup to supply power in which case it is an active pickup.

Pickup coil configuration switches work well with the Z-Mode system.

If you have a pickup coil configuration switch then the Z-Mode loading will effect each coil configuration differently, giving you more options for your sound.
Our favored modes are series connections for hum-bucking and single coil modes.
Parallel connections are sometimes used for a passive bass as this configuration can drive a cable to slightly higher frequencies but our preamp drives the cable so this is not a consideration and the sound is often less interesting depending on your pickup's design.

The coil configuration switch comes before the preamp and the only restriction is do not connect the pickup common to ground in any of the configurations.
If you see a connection to ground off an existing coil configuration switch then disconnect that node of the switch from ground and connect it to the green/white (pickup common) wire off the Pro Z module.

Note using a separate coil configuration switch for each pickup is a nice option.

In addition to active tone controls we offer a passive tone control option which is a traditional variable high frequency roll off control. This control is like a tone in the 3rd position of a passive jazz bass and players either love them or could care less about having this option.

In theory this type of control changes the frequency above which the frequency response is reduced, or starts to roll off. In practice, the frequency response curve is more complex (see the curves below). This style of tone control can only reduce the signal level.

Passive tone control works in active and passive modes if you have a preamp active/passive bypass switch.

A typical Tone Control response is shown below.

High Frequency Response - TONE in Passive Mode
P mode frequency response passive tone control

Treble roll off position: Black - 100%, Red 66%, Green 33%, Blue 0%
These curves were acquired using a Nordstrand NJ5 pickup connected with a 10' low loss cable into an Avalon U5 preamp.

The change in frequency response at the top end depends on the pickup in passive mode. The cable and bass power amplifier loading in both active and passive modes since the tone comes after the preamp in all modes.

How long do I have to wait to get it?
How much is shipping?
Has my Custom Configuration been tested?
The most common installation problems.
What makes Z-Mode fundamentally different?
Why a 3 Position Toggle Z-Mode Switch?
What are Internal Z-Modes?
How hard is it to install?
How big is the module?
Pickup wires 1 to 5
Why is the pickup ground separated from the jack ground?
How do I ground the pots?
Why remove the cable when not in use?
Why does it pop when I plug in the cable into the bass with the amp power on?
Why is there no sound for the first few seconds after power up?
How is the module mounted?
What if I don't know anything about bass guitar wiring?
What type of wire is used?
Why so many wires?
What types of switches are used?
What types of pots are used?
What type of solder is used?
What passive EQ controls do you offer?
Too many knobs - I ALWAYS set my X control to the same position!
Do you provide knobs?
What colors of hardware can I get?
Do I hear more static noise in the High-Z setting?
What are the 2 adjustment pots on the module?
Does the active/passive switch bypass the electronic circuit to make it a passive preamp?
What can't I get my peak frequency response higher in High Z-Mode?
Why does High Z-Mode sound exactly like Mid Z-Mode?
My bass has only 3 holes for controls - can I use this preamp?
What if I don't want to drill a hole for the Battery indicator LED?
What is heat shrink and why would you include any with my preamp?
What if my bass control holes are 0.4" diameter?

How long do I have to wait to get it?
All the module preamps require we take a pre-tested module and wire it to your configuration, test it, pot it into a case, and test it again.
This process can take up to 1 week be most often we are faster.
Shipping is normally by USPS priority mail which is 2-4 days.
How much is shipping?
Add a preamp to your cart - the system will calculate the shipping cost to you by different speed options.
Note in the US we recommend Priority shipping as Express shipping is expensive will normally only saves you a maximum of 1 day - sometimes it takes longer.
When shipping overseas Express is only a little more in many cases and can make a big difference in speed.
Has my Custom Configuration been tested?
We test every preamp after construction and before potting.
Then after potting before shipping it.
We connect each preamp up to a real pickup and do a magnetic scan for both channels in all Z-Modes and verify each control work correctly.
The most common installation problems
1) Connecting the pickup common to the ground (scratchy controls, causes distortion, may shut down the preamp - especially if you turn up the bass, and drains battery).
2) Not getting a good pickup connection (causes low volume and possibly distortion).
3) Not connecting the ground wire to the bridge (causes increased hum while playing).
4) Incorrectly wiring an output jack if you must move the wires to an existing jack.
What makes Z-mode preamps fundamentally different?
The Z-Mode system changes the sound by changing the loading on the pickup.
This changes how the pickup interacts with the string and changes the sound of the bass.
Players have long understood this effect and sometimes will change the pots in a bass from 220K ohm pots to 500K pot to brighten up the tone.
The Z-Mode system uses the same concept but the range we can cover is much larger than you can get by just changing out passive pots.
For more info on Z-Mode see the Z-Mode & String Vibrations page.
Why a 3 Position Toggle Z-Mode Switch?
Three different Z-Modes offers a good trade-off between distinctive sounds and complexity of controls.
What are Internal Z-Modes?
With the new programmable Z-Mode design (the Pro series) you have access to an expanded set of Z-Modes than we traditionally offered.
In a single pickup configuration you now have access to 5 Z-Modes per pickup which are an extension of the Low, Mid and High Z-Modes and for more on impedance control see the Technical Details page.
The Low' is similar to the Low Z-Mode depending on your pickup but has less high frequency content in the signal.
The High' is just like High Z-Mode without a cap in the sockets of the preamp.
In a dual pickup system you now have access to 9 different Z-Modes which include different Z-Modes on the separate pickups.
For example, one internal setting applies Low' on the neck pickup and High on the bridge pickup so the neck pickup is extremely deep sound and the bridge pickup is brighter with lots of sound control by simply moving your hand locations.
The 9 internal combinations of Z-Modes were selected as a trade-off between what is reasonable to support in the hardware design and complexity of setup.
How hard is it to install?
We have an example of an installation under Support/Documents or follow the Install link.
We recommend that you have experience with a soldering iron and installing simple electronics. A Luthier or repair shop can do it for you if you are uncertain.
The Install example shows how you can play test the unit early in the installation.
How big is the module?
The preamp is 2.00" by 1.05" by 0.30". This is the same x by y size of a common 9 volt battery with a connector snapped onto the top. The thickness is thinner than a battery.
Pickup wires 1 to 5
Pickups can have 2, 3, 4 or even 5 wires but most jazz pickups have 2.
• Every pickup has at least 2 wires, Hot and Common must be connected to our board at the screw connector as shown in the installation instructions.
• If you have think you have only 1 wire, it's probably a coax (center is insulated from the outer braid) - the center is hot and the braid is common.
• If you really have only 1 wire (very rare), this wire is the hot and you must pull up the pickup and find the wire connection to ground - disconnect it and run a longer wire back to the pickup common.
• If you have a 3rd wire and it is a braided shield that wraps around the pair of wires, this is a Ground wire and can be connected to the Cavity Ground.
• If you have a 3rd wire and it is red and goes to the battery - Stop - you have active pickups and this type of pickup is not compatible with the preamp..
• If you have a 4 wires you have a dual coil pickup - see the manufacturer's site for how to wire for series mode.
• If you have a 5th wire and it is a braided shield that wraps around the 2 pair of wires, this is a Ground wire and can be connected to the Cavity Ground and see the 4 wire note above.
Why is the pickup ground separated from the jack ground?
We create a split power supply so we can DC couple the pickup signal to the input of the amplifier.
This allows us to move the capacitive coupling to the output signal, which has a low impedance drive source, instead of having it coupled at the pickup side which is a high impedance signal.
This provides a cleaner signal path and is required for Low Z-Mode operation.
Some pickups like Nordstrands have the pickup common connected to a shield ground by default - simply undo this connection.
The pickup's ground goes to Grey/White and the pickup's common is wired to green/white.
How do I ground the pots?
The barrel of the pot is metal and is normally grounded by pressing against the shielded cavity.
Put the copper shielding down before the pot and connect a wire from the shielding to ground.

Traditionally in guitar electronics people soldered directly to the back of pots. This was a poor idea for several reasons.
1) You need to use a very aggressive flux in the solder (acid core was traditional). If the flux is not thoroughly cleaned off it will reactivate when it gets humid and can corrode the metal and cause the pot to fail.
2) You have to heat the heck out of the part. This often shifts the resistance and permanently increases the noise of the resistance element. Many pots have internal plastic parts that can be damaged by this much heat.
Why remove the cable when not in use?
Most preamps use a stereo jack where one side of the battery is connected to the ring terminal.
When a MONO cable is inserted into the jack the ring is shorted to the body and the preamp powers up.
So you should remove the cable when not playing which removes the power from the preamp or you will soon have a dead battery.
Why does it pop when I plug in the cable into the bass with the amp power on?
Due to the standard power switching used for the battery connection the battery is connected to the input of the guitar cable during the time the cable is sliding into the jack.
Most players develop a habit of partially pulling out the other end of the cable before inserting the connector into the bass jack
Some players use a guitar cable with an integrated disconnect switch.
Planet Waves and others have cables with this feature. Neutrik has a "Silent Plug" (NP2C) out that we haven't tried but it looks interesting.
Why is there no sound for the few seconds when the unit first powers up?
We mute the sound during the battery test time.
The hardware is initializing the power supply level and checking the switch positions to set the Z- mode etc.
The muted output is much better then listening to the uncontrolled hardware startup.
How is the module mounted?
We provide durable double-sided sticky pads to go under the module, secure but still removable.
What if I don't know anything about wiring an electric bass guitar?
Installation is simple if you have experience with installing music electronics.
However, typical hand tools for soldering wire connections and assembly are required.
If you are uncertain about the installation we recommend you have a guitar setup or repair technician or a Luthier install it for you.
The module and controls are all pre-wired to make it easy to install; you will need to:
1) connect the pickup wires
2) install copper shielding in front of the switches and pots
3) put the switches and pots into the body mounting holes
4) install the LED battery indicator
5) connect shielding and bridge grounding to the jack.
What type of wire is used?
The wire is a Mil-grade thin Teflon jacket over 24 AWG with 19 sub-strands for high flexibility.
Most of the wires have a base color and a 2nd colored strip.
The advantage of using Teflon is the insulation can be very thin and will not burn back from high heat during soldering.
The disadvantage is it is harder to strip unless you use a very sharp stripping tool.
Why so many wires?
18 base configurations, not including all the control options. The good news is we'll pre-wired it for you.
What types of switches are used?
We use SPDT (on/off/on) for the Z-mode switch and 3 band Mid Frequency switch. A QPDT (on/none/on) for the preamp override switch.
What types of pots are used?
The pots we use are high end audio grade with low noise metal film resistance elements (often called industrial controls).
The pots are small 9mm units which provide you with more vertical space to stack the electronic module and battery.
Our pots are all 100K ohms with the volume pots having an audio taper and active tone controls having a linear taper.
What type of solder is used?
We use lead free environmentally friendly solder for SMT processing and hand soldering.
The technical classification is SAC 305 which is 96.5% Tin, 3% Silver, 0.5% Copper - flux type is no clean
What passive EQ controls do you offer?
We do offer a tone type control which is the traditional variable frequency roll off where the start of the roll off is changed as the control is rotated.
In theory the Mid range frequencies are not affected by this control but in practice the mid range is actually significantly changed during operation.
Too many knobs - I ALWAYS set my X control to the same position!
If you want a quasi-fixed position control, for example, if you always add/delete a little mid range, then we can wire up your unit with a trimmer which is a small plastic part which stays hidden in the control cavity. These controls are multi turn adjustments so you have a very accurate set point.
The size of the adjuster is roughly 3/8" square by < 1/4" deep.
This allows you to setup the bass as desired then forget about that control.
If you change your mind later, then you can move the adjustment to a new setting.
The cost of this option is the same as a regular pot but you need to put a note with the order to get it wired up this way, and include an email address in case we have questions.
If you do not want one of the tone controls and you do not have room to store the control in the body of the bass, you can remove the control pot by cutting off the pot and insulating the wires.
That tone control section will default to a flat response.
Do you provide knobs?
We can supply knobs with the preamp but they are an optional item.
If you select a standard configuration in the tables on the main page then we will offer a knob set to you when you put the preamp into the cart.
You can also knobs direction from the purchase menu under knobs.
You can also use your own knobs.
Single controls have a 6 mm shaft size.
Stacked controls have both a 6 mm and 8 mm shaft.
All knobs need a set screw to hold onto the shaft.
What colors of hardware can I get?
The switches are chrome and we provide a chrome, a black and a gold washer/nut set so you can coordinate the look with your other hardware.
We also sell knob sets and individually in these colors.
Do I hear more static noise in the High-Z setting?
Yes and this is true for any comparable preamp.
The pickups with this loading will pick up more noise from various sources in the environment.
Increased shielding of the pickup cavities can help reduce the noise in this and all Z-Modes.
What are the 2 adjustment pots on the module?
On the lower edge of the module, away from the wires, are the Low Z-mode gain adjustment. This adjusts the loudness of the pickups in this mode, more information is on the Low Z page.
Does the Active/Passive switch bypass the electronic circuit to make it a passive preamp?
Yes - in passive mode you could remove the battery and still play, that is the ultimate test of whether a preamp is passive.
But the passive mode is only designed for emergency backup.
What can't I get my peak frequency response higher in High Z-Mode?
Many players prefer the resonant frequency in the 2k to 5k range which is the mid to upper range of a female vocal.
The factors that determine the location of the peak frequency are explained in more detail in the High Z feature section.
The peak frequency location varies due to the pickup's design and if your pickup is of the very low turn variety, then there is a limit to what adjustments can be made external to the pickup.
The adjustment range provided by the preamp loads the pickup from a small Capacitance, lower than any guitar cable / amp combination, to a Capacitance larger than most 50' cables
If you can not get the resonant peak location high enough (this would be a rare type of pickup or unusually high peak location request) then you can change out the pickup to one with a higher resonance location. In general - look for a pickup with a ceramic magnetic or neodymium magnet as these will have fewer turns of wire due to the strong magnets.
Why does High Z-Mode sound exactly like Mid Z-Mode?
If your pickup is a non-traditional design with a low amount of coil inductance and a low amount of capacitance, then the High Z-Mode resonant frequency could be located at a frequency too high for your speaker system to response too. Add more capacitance using the sockets on the preamp. This will bring the resonant frequency into a range where you can hear it.
My bass has only 3 holes for controls - can I use this preamp?
There are lots of options for what to do with your 3 holes. One of the possible configurations is: 1st hole for a volume/volume; 2nd hole for the Z-Mode switch; and the 3rd hole for a Treble/Bass tone control.
What if I don't want to drill a hole for the Battery Indicator LED?
The LED comes standard on all units. It is really nice to know your battery level is good before you step onto the stage. I would recommend you allow us to wire it up and if you decide you do not want it then cut off the LED and insulate the wires with the enclosed heat shrink pieces. But it's your preference and if you add a note to the order saying delete the LED then we will.
What is heat shrink and why would you include any with my preamp?
Heat shrink tubing is a plastic tube which is used to insulate wiring.
The tubing shrinks or reduces its diameter when you heat it. It comes in various types of plastic, sizes and shrinking ratios.
You can shrink it with a hot air source (a match can be used with care). Just be careful you do not apply too much heat to the tube or other parts on you bass. We supply you with a few pieces so you can insulate your wiring if you need to.
What if my bass control holes are 0.4" in diameter?
We supply rubber rings to fit over the switches and single pots to expand the diameter. This works well for most applications. If you require a special sized spacer ring then most Luthiers could help you out.

Read the small print in our Satisfaction Guarantee but the basic concept is you get 10 days from when you receive the preamp to try it out and make sure it works in your bass for your playing style.