Micro Booster MK4 Onboard Guitar Preamp with Push-Push Switch-Pot

You can order this product in the USA from Gear Hero HQ.

The Micro Booster MK4 Onboard Guitar Preamp takes the magnetic pickup’s signal and delivers a controllable boost that can push a guitar amplifier into solo mode on the fly. An integrated two-bands EQ performs soft tonal correction if needed and allows you to use it either as a Clean Flat Boost, Mid Boost, Treble Boost, Boosted V-Cut, etc. depending on your preference or practical application.

 Wiring Examples & FAQ
 Demo Video | More
 9V battery not included.

SKU: uBST4 Category:

The Boost Knob

From buffer level up to +16dB of clean boost with gentle Baxandall EQ and Push-Push True Bypass.

The BECOS Micro Booster MK4 Onboard Guitar Preamp can be installed in any guitar or bass to boost the signal from passive magnetic pickups. It can be powered with one 9V standard alkaline battery or two batteries connected in series for 18V increased headroom. The booster is powered when the instrument cable TS mono plug is inserted into the instrument output. With very low power consumption, the booster can run for months. To conserve energy it is advisable to remove the instrument cable when it is not used.

Built with monolithic amplifiers employing innovative high-performance concepts for pristine audio, the Micro Booster MK4 has an exceptional frequency response and extremely low noise & distortion. This is a replica of the input preamp designed for our CompIQ TWAIN dual-band compressor, with added correction functionality.

The Micro Booster integrates a Baxandall correction stack which adds flexibility for independent tonal tweaking of Lows and Highs – frequency pivot centered around 720Hz. With mild adjustability of +/-6dB at 70Hz and 3.5KHz  and zero to +16dB variable general Gain, it can be configured as a Clean Flat Boost or Mid Boost, Treble Boost, Lows Boost, Boosted V-Cut, etc. without going into extremes. With tone knobs centered, the boost is completely flat. When the gain is set to zero, it acts as a silent high-performance buffer.

The Micro Booster MK4 can be optionally configured with a linear B500K switch-pot (used with humbuckers) or with a linear B250K switch-pot (used with single coils) which can be soldered directly on the circuit board. The potentiometer side of the switch-pot is not part of the booster’s circuit. It only replaces a potentiometer in your instrument (volume or tone) while adding the convenience of a signal routing switch on top of it. The mechanical PUSH-PUSH switch side of the switch-pot routes the signal through the booster (switch UP) or sends it True Bypassed straight to the output (switch DOWN). A board-only version is available if you wish to add the Micro Booster MK4 alone, without replacing a potentiometer in your instrument. A separate DPDT switch (not included) needs to be wired for signal routing in such installations.

An iron-made shielding can cover the entire active circuitry to protect it against radiant electromagnetic interference.

The basic interconnecting wires, battery holder, battery clip, and a new TRS output connector are supplied along with the uBST4 board and the optional Push-Push switch-pot.

Several shortcut points are added on the circuit board to eliminate the usage of some wires when reconnecting the replaced potentiometer. Insertion points are also available for a neat transfer of the guitar Tone Capacitor directly on the booster’s board, if the booster is to be placed on top of a tone potentiometer.

The Micro Booster MK4 is pin-compatible with MK3.

More info

 Wiring Examples & FAQ
 Demo Video | More
 9V battery not included.

⚠️ Note! The installation should be performed by a skilled technician who understands guitar electronics, wiring diagrams, signal flow, and can perform modifications if needed or desired. We cannot and we will not make custom wiring drawings. We can only provide the most common wiring examples from which you may derive a particular configuration. We strongly advise you to draw and archive the original instrument wiring for future reference. Plan your custom installation on paper, and use that as your guidance. Hand working and solderings are required. Woodwork may be necessary. Proper mechanical, electric, and testing tools are needed.
Weight 0,25 kg
Dimensions 4,9 × 3,2 × 2,8 cm

250K Switch-Pot (push-push), 500K Switch-Pot (push-push), No Switch-Potentiometer

Technical Specifications

Input impedance: >1MΩ
Output Impedance: ~100Ω
Power Voltage: 9V-18VDC
Recommended Battery: 9V Alkaline (not included)
Power-On Switch: The circuit is powered when the instrument cable's plug is inserted (take it off the instrument to preserve battery life)
Current Consumption: 1.7mAh @ 9VDC; 2mAh @ 18VDC
Frequency Response: 10Hz – 30KHz (flat)
Tone Stack: Center frequency 720Hz, Lows +/-6dB @ 70Hz, Highs +/-6dB @ 3.5KHz
THD: 0.02% 1.0 kHz, 0Bu in / +15dBu out, 600Ω Load, 18VDC power
Max Input Level: +15dBu
Max Output Level: +15dBu
PCB Circuit & Switch-Pot body, without trimmer knobs: 49.3mm (length), 31.6mm (depth), 27.7mm (height);
Push-Push Switch/Pot (the potentiometer is not part of booster's circuit)
Parts Supplied: 1 x Micro Booster MK4 board, 1 x 8-Wire Set 20 cm long, 1 x 10-Pin Header (unsoldered), 1 x Battery Holder, 1 x Battery Clip, 1 x TRS Output Connector, 1 x Push-Push Switch-Pot (optional; B500K linear pot for humbuckers or B250K linear pot for single coils)
Product Weight (without battery): 54 gr.
Packed Weight: 160 gr.

Note! The product name, design, circuit, components, description, pictures, technical specifications, functionality, etc. may change anytime and without prior notice (Terms and Conditions). We advise you to check the manual (only available as a downloadable PDF above in this page) for details on the product's current features and functionality. If you spot errors, inconsistencies, or if you need more information or assistance, please contact us.

Frequently Asked Questions

The booster comes latest in the signal path, after the pickup's switch, so, yes, it works for all pickups in the instrument. The booster comes with its own output connector, and the whole ensemble simply replaces the existent output connector in your instrument. The potentiometer side of the switch-pot is not part of the booster circuit. It just replaces a pot in your guitar (volume or tone). As a result, that pot/knob also becomes a push-push switch. The booster board is just neatly attached neatly to the new switch-pot. The switch side of the switch-pot permanently routes the signal through the booster (switch UP) or is bypassed directly to the output of the instrument (switch DOWN). Please download and read the manual for relevant information and consult the wiring diagram examples available.

The potentiometer side of the switch-pot is NOT part of booster's circuit, and is meant to replace volume or tone potentiometer in your instrument for the convenience of having a switch and a potentiometer into one single physical device. So the potentiometer has to be rewired just as it used to be - passive. If it is the tone control that is put in place of, the tone capacitor has to be moved to the new pot as well. If it is the volume control that is to be replaced, you just have to rewire the new pot as it used to be. Booster's PCB is just attached to the switch-pot to pack everything in place. The switch side of the component routes signal through booster or true by-pass.

Here's what can help to contain the noise:

  • A proper shielding of the electronics cavity.
  • Connect all ground wires in a single point that makes contact with the shielding.
  • Reduce the length of every wire in the electronic cavity before the booster, because every wire is an antenna.
  • Stay away from the guitar amplifier and other electromagnetic sources such fluorescent lights or tv or power lines - they all radiate noise which is picked up by the pickups and the wires in the guitar, which amplified, will start to be heard. Also change the position of the guitar in relation to these sources, to hear the influence on noise. More noise will be heard when you don't touch the strings.
  • Single coils are notorious for being a bit noisier than humbuckers.

The booster is powered only when the instrument cable is inserted. Power consumption is very low, and a good alkaline battery can last for months. Most likely, the battery will have enough power for at least 300 hours of continuous usage, maybe more. The optimum battery voltage is above 7V. The booster can be powered with up to 18VDC by using two 9V batteries connected in series. When the battery voltage drops low enough the booster is likely to distort.

Yes. Installing it in a Gibson original or a Gibson-like guitar is the easiest installation because there is plenty of room in the electronic compartment. The Push-Push switch pot's shaft precise dimensions (9.8mm) allow for the easiest installation in place of bridge pickup controls (tone or volume), because they are placed on the edge side of the guitar, where the top wood is thinner. We did install it in place of neck pickup tone control though, where the body wood is a bit thicker (around 8 mm) and we had to remove some wood. Of course, every guitar is a bit different and the wood may be thicker or thinner from one instrument to another. We have a video installation of the Micro Booster MK3 in an original Gibson Standard Traditional guitar on our You Tube channel which you can check-up.

Probably not, if the switch-pot is soldered on the board, or with difficulties due to the MK4's bigger size. The Telecaster electronics compartment is very narrow and the bottom between the potentiometer and the pickup switch may have to be routed so that the 9V battery can also be fitted inside. Some wood trimming might be needed as well just near the tone or volume control to make room for the booster's circuit. If needed, the booster knobs can be taken out through the metal plate of the controls, but because they are off-axis with the switch-pot, the holes will not be in line with the other holes in the plate. However, the booster can be added as board only and a separate DPDT mini switch could be wired to the board for by-pass function. Obviously, it can also be installed as an always on preamp.

Most likely, yes. There is usually enough room underneath the pickguard for the battery and booster's circuit. If needed, the booster knobs can be taken out through the plastic pickguard. Some wood trimming may be needed in some bodies if the booster is to be installed on the bridge/center tone pot. Please watch a video of the Micro Booster MK3 installation in a Fender guitar on our You Tube channel.

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