Musical Instrument Repairs and Electronics in Oswestry and the Marches


Activator 2 - A DIY onboard JFET preamp kit for guitars and basses

Now Only £29.99 including Worldwide P&P!

Click to see all the contents of the Activator JFET Preamp kit. Click this button to purchase online on a secure server

Give your guitar tone an upgrade!


The Activator has now been upgraded to allow use on higher voltage supplies - this means that two 9v batteries can be used to give a total voltage of 18v. This will allow much more "headroom", essential for use with high output bass guitar pickups!

The Activator is a complete kit containing all necessary parts and materials to convert virtually any electric guitar or bass to an "active" system. A typical installation requires just six soldered connections to complete. All the electronic circuitry is contained in a single compact (30mm x 20mm x 15mm) module. A replacement pre-wired jack socket is provided, together with all that you will need to install the kit, even including solder!

Click the image above to see all the contents of the kit.

The heart of the system - The Activator Module A Naked Activator before encapsulation

Please note that this kit does require a few basic tools, and some degree of basic DIY skills - before you purchase an Activator 2 kit, please take a few moments to download and read through the installation instructions - this is an Adobe Acrobat file and requires the Acrobat Reader which (if you do not already have it) can be downloaded here.

To purchase an Activator 2 kit for just £29.99 including P&P, just click the "Buy Now" button on the right.

The system is based on a hybrid circuit using a JFET input stage to give a smooth "tube-like" sound and to provide a high impedance to buffer the instruments pickups, increasing sustain and high frequencies. This is combined with a BJT output buffer to provide a low impedance output, enabling the module to drive long cables, pedal boards etc without the "tone-sucking" effect that usually results.


Supply Voltage: 9 - 18v
Reverse Polarity Protection: yes
Freq Response: 20Hz - 20kHz
Input Impedance: 1M
Voltage Gain: 5dB
Max undistorted output: 5v pp

The module provides 5dB of clean boost - enough to give a healthy overdrive when needed, but not so much that a clean sound is unobtainable. The circuit uses a symmetrical bias, so that plenty of input headroom is available to accommodate high output pickups without clipping - when the input does overdrive, the JFET gives a "musical" soft clipping, similar to that of a traditional valve (tube) stage. The maximum undistorted output is approximately 5v pp. High quality, low noise components are used throughout to ensure the best possible audio quality. Each module is individually tested both before and after encapsulation and is warranted for 12 months.

The Activator 2 is ideal for musicians who have home recording setups - there are plenty of great sounding amp simulator plugins available in VST or DX format, however unless you have a good (expensive!) preamp, the basic guitar sound is usually muddy and lacking in sustain. An active instrument can be simply plugged into a line input with no loss of tone. Have a listen to the sound clip below to hear the proof of this!

Click to see how an Activator 2 kit can be squeezed into a really tight space!

The instructions detail the installation of the Activator 2 system on a Strat type instrument, however the system can be used on almost all electric guitars and basses - I have even fitted one to my electric mandolin! The illustration here shows the system fitted to a Hohner headless bass, this was quite a tight squeeze, but it did fit in, and made a drastic improvement to the sound of the instrument. Click on the image to view an enlargement.


View Schematic

For the hardcore DIY fanatics, here is a complete schematic, with all component values, of the Activator preamp. This can be built on vero or perfboard - I leave the layout to your imagination!

Sound Clip

Listen to the clip

This is just a short clip of me noodling away to a slow blues - the recording setup was:

Guitar - Strat (1HB, 2SC) Neck Pickup (Select single coil), plugged into the line input of a Tascam US-122 USB interface, no amp simulation or EQ was used, just a small amount of software compression (Using the excellent freeware Kjaerhus Classic Compressor), and some software reverb.

Bass - Hohner headless bass, Neck Pickup (Humbucker), plugged into the line input of a Tascam US-122 USB interface, no amp simulation or EQ was used, again just a small amount of software compression, once again courtesy of the Kjaerhus Classic Compressor.

All recordings were made using Mackie's Tracktion 2 DAW - I would normally use some form of effects and Amp simulation, either using Amplitube, or my Boss GT-6, however the object of this exercise was to record the "raw" sound of the instruments with the Activator 2 fitted.

To purchase an Activator 2 kit for just £29.99 including P&P, just click the "Buy Now" button on the right.

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