Battery drain is often caused by incorrect jack wiring or a short around the battery switching terminal.

The black battery wire must be connected to the jack ring terminal on its own. No ground wires, shielding foil or other conductors should touch that terminal.

With no jack inserted, the battery should be disconnected. With a mono jack inserted, the battery negative should connect to ground and switch the preamp on.

No — our preamp is designed to use a standard mono (TS) jack plug. The preamp’s battery is switched on via the ring-to-sleeve contact in the jack socket. A stereo (TRS) plug routes the ring contact differently, which can prevent the battery circuit from closing. This can cause the preamp to remain off or behave unpredictably. For correct battery sensing and reliable operation, always use a mono plug.

The most common cause is a depleted or unreliable battery.

Replace the battery
Please replace the battery with a known, brand-new battery straight from a sealed packet.
Avoid using one you think is good — even slightly used batteries can cause faults. ✅ We recommend using a reliable brand such as Duracell or Energizer.

Check all wiring connections
Carefully check that all wires are securely clamped into their screw terminals.
Give each wire a gentle tug to confirm it’s firmly in place and hasn’t come loose.

If you’ve completed both steps and the problem persists, please contact us for further support.

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. 

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. 

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. 

• 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.

There is so much electrical interference now with sharp buzzy waveforms of innumerable frequencies, whereas in the earlier days of electric basses and guitars, it was the transformers in the amplifiers and other equipment, and little else, causing just low-frequency hum radiation. Now virtually all power supplies for every type of electrical and electronic apparatus are what is called switch-mode, which radiate very ‘dirty’ high-frequency, often high energy waveforms. And now we’re surrounded by countless pieces of electrical and electronic devices, all contributing to the wash of electrical interference. If there’s any interference noise, many aren’t aware that it’s important to screen PU cavities as the highest priority, even with “noiseless” PUs. Noise can be reduced with humbuckers and dual coil designs, but very few pickups are totally noiseless in my experience.

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