Build a SansAmp GT2 Clone

The SansAmp is a solid-state device designed to emulate the tone of a vacuum tube guitar amplifier, and allow for patching directly into a studio mixer or stage PA. It was developed by B. Andrew Barta, the founder of the company Tech 21, to meet his need as a performing musician.

Barta used his expertise from repairing, modifying and customizing guitar amplifiers, plus ten years of research, to develop the SansAmp circuitry. Barta's intention was not to become a manufacturer, but rather he sought to license his technology to others. However this was before the direct recording movement and the manufacturers of the day couldn't see the product's potential. So Barta set off on his own, with the support of musicians, notably Mick Jones of the rock band Foreigner, who helped get the word out.

This SansAmp was the first device to enable musicians to dial in monster tones and patch them directly to a studio mixer or stage PA. It is built with 100% analog circuitry and incorporates mic and speaker simulation with pre- and power-amp distortion characteristics. The result is a pedal that is prized for achieving monster tone without lugging amps, speaker cabinets and microphones to find the elusive "sweet spot."

The original SansAmp product is now sold by Tech 21 as the "Classic" model. The GT2 model is a refinement of the original that allows for easy selection of amplifier type, modification and speaker cabinet/mic placement configurations. The main difference between the two is versatility. While the GT2 offers Fender-, Marshall- and Boogie-style amp emulations, the Classic will also emulate Ampeg-, Hiwatt- and Vox-types. The Classic model is made for "fiddling" and gives more subtle nuances in the "clean-to-just-on-the-verge-of-breakup" range.

The GT2, on the other hand, gets up and running with a minimum of tweaking. Another major difference is that the Classic has no EQ of its own, since it was primarily intended to plug right into a mixing console with its own EQ. The GT2 has active EQ on-board, so it can switch between the amp's own tone (when the GT2 is in bypass), or the emulated tone (when the pedal is engaged). There is also a cost difference between the two. The SansAmp Classic list price is $345 while the GT2 list price is $195.

The GT2 controls include:

• Mic - has three microphone positioning options: Classic is distant miking without ambiance; Center is close miking at the center of the speaker cone; Off-Axis is close miking at the edge of the speaker cone.
  
  
• Mod - emulates three setup options: Clean is a stock tube amp setup; Hi Gain adds an extra gain stage, as if an extra 12AX7 preamplifier stage is added; Hot Wired is a scooped-out midrange for what SansAmp describes as a "sizzling, over the edge" quality.
  
  
• Amp - selects from three classic amp types: Tweed emulates Fender-style amps; British emulates Marshall-style amps; California emulates Mesa-Boogie-style amps.
  
  
• Drive - adjusts the overall amount of gain and overdrive.
  
  
• Level - adjusts the output level, without altering any tonal characteristics.
  
  
• Hi/Lo - the Hi and Lo pots are on-board active tone controls to compensate for the limited range of guitar speaker cabinets and combos.

Take a look at this video demonstrating the different tones achieved with the SansAmp GT2:

BUILDING A SANSAMP GT2 CLONE

The folks at TonePad.com have published a schematic and printed circuit board design, with parts list, available here. Here's a video demonstration of the TonePad version:

The active components in the GT2 are four TL072 operational amplifiers and 2N5088 transistor. The TL072 is a low-noise JFET-input op amp with low noise and low total harmonic distortion (.003%). TonePad rates the construction of this project to be bit more difficult than the average pedal due to the number of off-board connections (four potentiometers, three switches). Visit the project home page for the details on building the project including sound samples, build reports and other information. A printed circuit board can be purchased from TonePad for $14.00.