PIEZO MAG MIXER

All our products, although supplied with a single 9V battery clip, are designed to work 9V or 18V out of the box. Just add the additional battery, or connect to an 18V battery box, no other changes are necessary.

• Either add another battery snap, as below pic.
• Or snip the single snap and connect to an 18V battery box, Red to Red, Black to Black.

Battery life depends on the battery type, quality, and spec. There’s not a one size fits all answer.

The J-Tone requires just over 2mA of current. So a battery with a capacity rating of 500mA should last ~250 hours.

If battery voltage is measured, that should always be done whilst under load, especially if a battery has had some use. Once battery voltage reads below 6V under load, it should be replaced.

• Distortion will set in according to the battery voltage and signal level coming through the preamp.
• So it’s hard to specify the exact voltage where distortion will set in.
  It depends on the output of the pickup(s), how high the volume is set, and how much low-end EQ you have dialled in.
• If you had low output pickups, the voltage could go lower before distortion set in, for example.

The chips are spec’d to work down to 6V, but they will often work to a much lower voltage. See below about measuring the battery voltage.

DON’T DO THIS:
Don’t disconnect and take the battery out of an instrument to measure the battery. It will often be a false reading if the battery has been used to any extent.

IMPORTANT – Measuring The Battery with an East Preamp:

• The battery should be connected to the preamp with a jack inserted into the instrument so that the preamp is turned on. In other words, the preamp is loading the battery.
• Then probe each terminal with your meter while the battery is powering the preamp.

(The reason for having the battery connected, is that a weak battery can still show what appears to be a decent voltage without the preamp)

We have good number of preamps out there with EMG Actives, and they work well, with happy customers who say they are a good combination.

About Passive Tone Pots

Many of our units have Passive Tones. Our tone pots have the same capacitors as EMG but the tone variation will occur more towards the end of the rotation due to our pots. The maximum effect will be the same as the EMG tone pots. In other words, the passive tone won’t be as smooth as the EMG pots.

+ J-Retro is fine. 

+ J-Deluxe will work fine except the our passive tone is 250K whereas the EMG is 25K. 

* We use the same capacitors as EMG but since our pot is set for passive pickups, although it will still work, all the action will be towards the backed off setting, ie the darkest tone. It won’t be as smooth as the EMG pot, in terms of rotation versus effect. 

+ UNI-PREs have a passive path that isn’t useful with EMG Actives, since the pickups aren’t just a ‘passive’ coil. 

* passive is more is effectively EQ bypass. 

If I connect the red wire (+) to the battery, can the uni-pre 5 handle the EMG impedance? 

+ Connecting EMG Red Wires to the UNI-PRE + Red Wire is fine. 

+ No issue the Pots in the UNI-PRE, each PU has an Input Buffer stage that feeds the Vol &  Blend circuit. 

+ The UNI-PRE Passive Tone is a higher value than the EMG, but it will still work. 

* The Tone Mellow Factor will be the same, but the effect will be more towards to end of the Pot Rotation. 

The MMSR, like the original Pre EB units, doesn’t have any amplification or gain when the knobs are set at their Mid Points to increase levels beyond the output of the pickup.

The MMSR preamp has the same input stage and treble control as the Pre EB to allow for the same interaction between the treble control settings and the pickup.

As for the Stingray sound, it’s not the preamp alone which makes it, it’s the complete combination of all that the instrument consists of.

Single-coil pickups are prone to buzz, especially when used with preamps that amplify the signal. Shielding the pickup cavities with copper foil and grounding it to the bridge ground wire can help mitigate this issue.

How to diagnose noise issues?

    To check if the noise originates from the preamp, disconnect the pickups and attach short wires to the hot and cold screw terminals, bypassing the pickups. If noise persists, the preamp might be faulty.

How to ensure proper grounding?

   Proper grounding helps minimize noise. Make sure that:    
       
• All pots are grounded to the plate or control cavity using adhesive copper foil.
       
• The bridge and other ground wires are properly connected to the jack’s middle tag.
   

Where to find shielding guides?

   
• Here are some useful resources:
   
       
• YouTube: How to shield a bass guitar in 10 easy steps
           

• Low battery voltage: Batteries with low voltage (below 6V under load) can cause distortion and other issues. Always use fresh batteries and check voltage under load. 

• Battery failure noise: A failing battery can produce a repeating noise as it attempts to power up the preamp and fails. Replace the battery immediately. 

• Battery drain in passive mode: Some East UK preamps draw power from the battery even in passive mode. This is a design feature to avoid loud thumps when switching between modes, but it means the battery will drain regardless of the selected mode. 
• Make sure the black battery lead terminal has only one wire connected.
• Always remove the jack plug from the instrument when not in use, as inserting the jack activates the battery connection.
• Use a new, high-quality battery for best performance.
• Check that the jack socket is not touching any wiring outside of the preamp circuit, as this can cause unnecessary power drain.

• Scratchy pots: The pots used in East UK preamps are sealed, and cleaning them is not recommended. The pots are sealed, and if the cleaner gets in there, the stiction will be lost.  Scratchy pots are usually a sign of an electronic or electrical problem. 

• Loose or sloppy pots: The stacked pots used in East UK preamps, particularly those with pull switches, can feel loose or sloppy due to manufacturing clearances. This is a known issue, and replacement may not solve the problem. Consider returning the preamp for a refund if the slop is unacceptable. 

• Knobs turning each other: This usually indicates a bent middle shaft on the stacked pot, often caused by a knock to the upper knob. Carefully straightening the shaft might fix the issue. 

My stacked knobs are rubbing against each other. What can I do? 

This issue typically arises when the upper knob has been bumped, causing a slight bend in the middle shaft. You can try to carefully straighten the shaft yourself, but proceed with extreme caution as any sharp movement may break it. 

To straighten the shaft: 

• Remove the upper knob. 
• Inspect the lower knob shaft to ensure it is straight. 
• If the lower shaft is fine, remove the lower knob. 
• Identify where the middle shaft contacts the outer shaft (a magnifier may be helpful). 
• Using larger pliers, gently and firmly nudge the middle shaft away from the point of contact. Avoid any sudden movements. 
• If you are uncomfortable performing this adjustment, you can return the unit to East UK for a pot replacement. 

• Distortion in active mode: The J-Retro and Uni Pre models are not designed to be used at maximum volume in active mode, especially with significant EQ boost. Back off the volume to increase headroom and avoid distortion. 

• Balancing active and passive levels: To achieve similar levels in active and passive modes, fully back off the internal gain preset adjusters, set the EQ to neutral, and adjust the volume as needed. 

The MMSR preamp’s compatibility with the 5-string Stingray is complicated by the 3-way pickup selector switch. Workarounds include rewiring the existing switch, installing a separate switch for the East UK preamp, or permanently wiring the pickup in a preferred configuration. 

First, ensure you are using a fresh battery. A low battery can cause distortion, even if it shows sufficient voltage when not under load. 

Next, check if the distortion occurs in passive mode. If so, the issue lies elsewhere in your setup. 

If the distortion only happens in active mode, try lowering the volume knob on your bass. East UK preamps are powerful and can generate high output levels, especially with significant EQ boost. Lowering the volume creates more headroom and avoids clipping. 

Yes, some looseness in the treble push/pull knob is normal, particularly compared to standard single-shaft knobs. This is due to the complex mechanism required for the dual concentric rotation and the up/down motion of the bright switch within a compact 9mm pot. Rest assured, ALPS pots are known for their durability and reliability, and the looseness does not affect their functionality. 

The J-Retro focuses on active functionality. It features a smooth active blend, pickup gain trim for each pickup, a bright switch on the treble control, and a sweepable mid control. The passive signal path is minimal and lacks a passive tone control (except for the J-Retro Deluxe). 

The J-Tone emphasizes replicating the original passive design while adding bass and treble active EQ. It offers Vol/Vol/Tone or Vol/Blend/Tone configurations for an authentic passive signal. The passive tone control functions in both active and passive modes. It also includes a plug-in tone cap for adjustable passive tone color and frequency wheels for customizing the bass and treble voicing. 

East UK preamps use sealed pots, making it unlikely that dirt is the culprit. The crackling is usually caused by the inner and outer shafts of the stacked knobs momentarily losing contact during rotation. Cleaning the pots is not recommended as it can damage the sealing and potentially worsen the issue. 

First, ensure that your pickup cavities are properly shielded. Use copper foil and connect the shields to the ground wire of your output jack. (see faq How to prevent buzzing… for more detailed info)

Next, check the height of your pickups. They should be adjusted close enough to the strings for a strong signal without causing interference. 

If the noise persists, it could be inherent to single-coil pickups, which are known for their susceptibility to hum. Consider using hum-canceling pickups or explore further noise reduction techniques. 

Battery life varies depending on the type, quality, and capacity of the battery used, as well as the specific preamp model and playing habits. However, with a typical industrial battery and average usage, you can expect around 2 months of battery life for 3-hour gigs every day.

East UK preamps are known for their high-quality components, flexible EQ options, and focus on preserving the natural tone of the instrument. Unlike many other preamps, East UK designs feature a separate amplifier stage for each EQ band, resulting in greater precision and minimal interaction between controls. This allows for a more powerful and focused EQ that helps you dial in your desired sound with accuracy. The company prioritizes performance over cost-cutting measures, ensuring a low noise floor and a pristine signal path. 

Crackling noises when turning knobs are typically not caused by dirty pots in East UK preamps, as the pots are sealed. The issue usually stems from the inner and outer shafts of the stacked knobs making and breaking contact as you rotate them. This is particularly noticeable with the treble knob due to the additional push-pull bright switch mechanism. While the pots are high quality and durable, this slight play in the shafts is a known characteristic. 

To minimize the crackling, try grounding yourself to the plate, jack, or strings with one hand while rotating the upper knob with the other. If this reduces the noise, consider installing a spring between the upper and lower knobs to maintain ground contact. 

If the issue persists or worsens, it could indicate a bent shaft, which might be carefully straightened. However, extreme caution is advised, as any sharp movement could break the shaft. For severe cases, returning the unit to East UK for pot replacement is recommended. 

Distortion in active mode, especially at higher volumes, can occur due to the limited headroom provided by a 9V battery. The J-Retro, with its extensive EQ options, can generate high signal levels that exceed the battery’s capacity, leading to clipping. 

To address this: 

• Check the battery: Ensure you’re using a fresh, high-quality 9V battery. A weak battery can cause voltage drops under load, resulting in distortion. 

• Adjust input gain: Back off the gain trim presets for both pickups fully anti-clockwise. This minimizes the input signal level. 

• Lower the volume: Instead of running the volume at maximum, back it off slightly. This creates more headroom and allows you to utilize the EQ boosts without causing clipping. 

• Consider 18V operation: While not essential, using an 18V power supply doubles the headroom, allowing for higher output levels and reducing the likelihood of distortion with extreme EQ settings. However, this does not change the overall gain or tone of the preamp. 

• Passive mode testing: To isolate the issue, test the bass in passive mode with the volume at max and both pickups selected. If distortion persists, the problem likely lies elsewhere, such as the pickups or the amplifier. 

You can reach East UK via: 

Sales: sales@east-uk.com

Tech Support: tech@east-uk.com

Info: info@east-uk.com

Online contact form

Our preamps were designed first and foremost  to unlock and expand the great sounds within passive pickups. They work with active pickups too.

+ Is the EQ fully working, bass/treble & mid/sweep? 

Some tests you can do to check if either of the modules appears to attenuate the signal level: 

+ The Orange Wire (Oe for short), which feeds the jack, can be disconnected from the Mid Sweep module. 

• Then you can use as a signal tracer when the bass is connected to a rig. 

+ To check the raw PU signal: 

• Connect Oe in parallel with the Red wire going into the Bass/Treble module. 

• Is the raw PU signal at a reasonable level? 

• So this is the reference signal and level the Bass, Mid, and Treble EQ has to work with. 

• (Remove the Oe wire once the test is complete) 

• Do you have the original PU? 

• Some aftermarket PUs can have lower output than original MM PUs. 

+ To check the Bass/Treble module assuming the raw PU signal is OK: 

• Remove the Yellow Wire from the 3W Screw Terminal. 

• Insert the Oe wire in its place and tighten. (Bypassing the Mid) 

• With Bass & Treble in their centre clicks, is the level about the same as the raw PU? 

• Do the Bass & Treble controls boost to good additional level when turned CW? 

• There is a Red Jumper Link in the middle of the circuit board, swapping the setting (middle and pin by green pot) often improves aftermarket pickups. 

• Findings from the tests above? 

• Return the Yellow Wire to the middle aperture of the 3W Terminal Block. 

+ Assuming the level and operation of the Bass/Treble is satisfactory, to check the Mid: 

• Oe returned to the middle aperture of the Mid 3W Terminal Block. 

• With upper Mid knob in its click, is the signal level the same as the Bass/Treble set in their clicks? 

• Upper knob CW to max boost and sweep the lower knob to sweep through its frequency range. 

+ Like the original Pre-EB MM EQs, the East MMSRs don’t add any gain when the EQ knobs are set to neutral. 

Passive Mode means the system is entirely powered by the energy from the pickups alone, hence no positive gain adjustment. (So passive mode operates without a battery in place, like the old school passive basses) 

The only way to balance active and passive is to make sure that the active gain trims are fully backed off. 

Then, using the vol set at max for passive, in active, compensate for any increased levels dialled in using the EQ, by backing off the volume. 

Yes, since many players find it a plus to have the passive roll-off in active mode as well as passive, the system was designed that way.  

PASSIVE TONE WITH ACTIVE MODE 

+ Players who work with lots of styles in the same gig such as functions and theatre productions, for example: 

* Often set up a brighter sound with the active controls. 

* Then for more mellow pieces, leave the active controls put, and just back off the tone. 

* Fully up again for the brighter sound setting. 

The thought was that it’s more of a bonus overall, and we’ve that many pro players breathe a sigh of relief when they find the passive tone works in active and passive. And comments like – “why doesn’t everyone do it that way?” 

NOISE CANCELLING HUMBUCKERS 

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+ Total noise cancellation is virtually impossible. 

* For it to be perfect, the coils would need to be in exactly the same position, physically exactly the same size and construction, with mirror image coils. 

* To call a pickup noiseless is rarely a truth, buyers are misled. 

SINGLE COILS 

============ 

+ Often based on original vintage designs, they are the easiest to make/replicate and often sound really pleasing. 

* This type is the most prone to interference but grounded copper foil screening in the pickup cavities can help massively, even just the on ‘floor’ of the cavity can make an enormous difference. 

SCREENED HUMBUCKERS 

===================== 

+ A combination of hum-cancelling coils and screening can help to create a virtually silent pickup. 

* It is important that the pole pieces and/or magnets are grounded. 

GROUNDED POLE PIECES 

===================== 

+ Vintage pickups rarely had their magnets or magnetic pole pieces grounded. 

+ Many modern pickups do have grounded pole pieces and magnets, but making an electrical connection with magnets can be an issue. 

+ Where adhesive-backed copper foil is taped across the underside of magnets, it can work for a while but may eventually lose contact. The adhesive needs to be conductive but the conductivity is poor with many lower cost types of foil tape, that state conductive adhesive. 

The UK left the EU group of countries, at the end of 2020. Since then, the way sales taxes are paid has changed. 

Your sales taxes are now paid in locally instead of the UK. 

Pre Brexit the taxes would be charged by the UK – 20% VAT, so our units were 20% more expensive than now, compared to pre Brexit. 

A REMINDER:  

At the point of payment, our website states EX VAT = no sales tax, so the prices are 20% cheaper than they were before Brexit. 

Since Brexit, when the UK left the EU, all EU countries charge the tax at the point of import. 

So now you pay Italian VAT, the UK does not charge the tax any more, so you will get a request to pay the Italian VAT sales tax once your order arrives in you country. 

The UK is like any other non-EU country, if you buy from the USA or China, you pay the import and sales tax, same for UK, we don’t charge tax, the Italian Government charges the sales tax now. 

We occasionally get this error with PayPal currency exchange, unfortunately. 

Even though PayPal and our shopping cart system, WooCommerce, are both worldwide industry standards, neither company has taken the opportunity to work with the other for a fix. 

EXCHANGE RATES 

As for the pricing difference, when the prices were set last, we made sure the $/GPB were within 5-10% max with the spread of exchange rates, but the local pricing is actually controlled by the dealers and outlets. Over the last 10 years or so, our last price rise was 2009, the UK currency has been eroded dramatically, taxes have changed, brexit making it an even greater differential. Dealers have the option to roll with it or stay where they are if their sales aren’t effected, greatly. 

Our pot threads are the standard 10mm length, same length that most use for rear mount. 

Most bass bodies are 6mm or 1/4″ thick in the cavities. 

Our nuts are ~2mm thick and one washer is 0.4mm

The spring is to keep the upper knob grounded during rotation.

It’s possible to screw the terminal shut leaving a gap beneath the little plate looking pretty much the same as when the terminal is fully open. In other words, the screw terminal has been tightened up and you’re putting the wire in beneath the plate, and it won’t grip the wire. 

See if you can unscrew it and have the little plate go down to the bottom. 

Our products are at the high end, individual with creative edge, focusing foremost on performance and functionality beyond others. Customers give us lots of praise and often buy again, multiple times for their suite of instruments and instrument upgrades. 

Did you try a new battery? 

Is the current battery old or a low cost type? 

If the battery is low, it shouldn’t be less that 6V when under load (ie when the preamp is on). 

Please try a brand new known battery and if things get better, see the description below for what’s probably happening. 

We’ve seen there to be lots of dud and battery copies over the last 10 years or so, even whole boxes of reputably named batteries that have little or no power right out of the box. 

Many chips shut down without any noise with a low battery, but often ours, amongst the higher spec chips, don’t. 

An Industrial Duracell, according to their spec sheet, should just last over 100 hours before it reaches 6V. 

NOTE: It’s very important to measure a battery under load of the circuit it’s being used with or with a proper battery tester. (Just measuring with a meter, which has very little loading effect, can be very misleading since batteries recover off-load to seemingly workable voltages, maybe 7-8V) An Industrial Duracell, according to their spec sheet, should just last over 100 hours before it reaches 6V. 

NOTE: It’s very important to measure a battery under load of the circuit it’s being used with or with a proper battery tester. (Just measuring with a meter, which has very little loading effect, can be very misleading since batteries recover off-load to seemingly workable voltages, maybe 7-8V) 

The UNI-PRE is relatively thirsty compared to other units due to an increased number of chips compared to the more regular units. The extra chips are there to allow for the internal frequency wheel settings as well as other features. 

A UNI-PRE takes ~5mA whereas other units with many fewer features may take 2.5mA or less. I take the view that, although power consumption is important, performance is our highest priority, and fortunately, battery capabilities tend to increase as time goes on. 

Yes, any regular hum-cancelling pickups will be fine.

Please check red jumpers are present as shown in pic https://www.east-uk.com/wp-content/uploads/2026/06/red-jumpers.jpg