Buzz Drive

"Several overdrive configurations using CMOS inverter chips"




The GT Buzz Drive overdrive rack effect module is available in several configurations that compare to some well-known pedals including Way Huge Red Llama, Mad Professor Stone Grey Distortion, and Way Huge Fat Sandwich



There are several technical ways to create overdrive, distortion, and fuzz tones.  Most of them use tubes, transistors, or op amps, perhaps with some clipping diodes.  One of the less common ways to do it is to use a CMOS inverter chip as an op amp substitute.  This has been done in the DIY pedal community for decades, as well as in a few commercial pedals.  The Emma ReezaFRATzitz, Way Huge Red Llama, Way Huge Fat Sandwich, and Mad Professor Stone Grey Distortion are some of the better-known effects built around inverter chips. 

Nearly all of those circuits have two gain stages built with inverters, along with some method of controlling the gain and volume.  Most also contain some form of tone controls, from very simple to moderately complex.  Perhaps some buffering.  But the core tone comes from those inverter stages.  The drive can go from moderate fattening, through overdrive, and into distortion and singing, sustaining fuzz-like high gain.  The sound is a bit unlike most other overdrive, distortion, and fuzz circuits.  It can provide great clarity for notes and chords, even with considerable bass content in those drop tunings.  It can also work well for bass.

Our Buzz Drive circuit allows us to build several different inverter circuits that compare to several of the commercial and DIY inverter drive effects.  All of these configs go from clean-ish to heavy overdrive, with lots of harmonic content.  Some will get you into distortion, or possibly even some fuzz, but that may be a bit misleading.  All of them have lots of volume on tap.  While most top out in the heavy overdrive range at the max setting on the Drive control, the extra volume can kick your amp or whatever else is downstream into a "heightened state of awareness", resulting in heavy overdrive stacked into yet more drive downstream, resulting in more drive range than you get out of the Drive controls alone on these configurations. 



  • CraigTone - Compares to the Craig Anderton Tube Sound Fuzz - an early DIY design.  Very simple circuit.  Used as the core of the other configurations.  This is the later version of the circuit without the op amp input stage.  
  • CraigTone (Early) - Compares to an early version of the Craig Anderton Tube Sound Fuzz.  The early version included an op amp input stage, much like the Rising Sun circuit.
  • Moose Steak - Compares to Charlie Barth's Moosapotamus Tube Steak Fuzz.  Nearly identical to the later CraigTone, but utilizing groups of inverters in parallel.
  • Rising Sun - This configuration is based on a circuit published in an electronics magazine back in the 70's, possibly pre-dating the Tube Sound Fuzz.  The early Tube Sound Fuzz is very similar, but lacking some controls.  It's an odd config.  Drive is controlled by an op amp ahead of the inverter stages, which are fixed gain.  The Bias control lets you cut back that op amp output before it goes into the inverters.  The Amplitude controls a side chain which impacts both gain and tone together.  This is a very pleasant overdrive, a configuration that has been growing on us since we first began building it.  Maybe someone could convince us to make the gain in one of the inverter stages to also be adjustable...  
  • Alpaca - Compares to the Way Huge Red Llama.  Nearly identical to the later Tube Sound Fuzz and Tube Steak Fuzz designs.

  • BuzzStone - Compares to the Mad Professor Stone Grey Distortion.  Adds an op amp input stage with FET clipping and a simple Tone control after the inverter gain stages

  • BLT - Compares to the Way Huge Fat Sandwich.  Still a Tube Sound Fuzz variant at heart, but surrounded by complex tone shaping controls, transistor input stages, multiple gain controls, and hard and soft clipping.  Sort of a tweaker's paradise for a very simple circuit

The default controls for each configuration are:

CraigTone - Gain, Volume (optional tone stacks)

CraigTone (Early) - Drive, Volume (optional tone stacks)

Moose Steak - Gain, Volume (optional tone stacks)

Rising Sun - Amplitude, Drive, Bias, Volume (optional tone stacks)

Alpaca - Gain, Volume (optional tone stacks)

BuzzStone - Gain, Volume, Tone

BLT - Gain, Resonance, Presence, Tone, Volume.  Three internal trimmers for Curve, Highs, and second Gain can be made external controls.






  • Active Tone Stack - For any config except BLT.  Gives you Hi/Lo active Baxandall tone controls
  • Extra Noise Caps - Trim a little high-frequency noise (along with a smidge of high-frequency signal) out in the inverter stages
  • Simple Tone Control - Adds a simple hi-cut Tone control (not for BLT, BuzzStone already has it) with a focus on highs and presence.  Helps with noise if you have some when the Volume or Gain is cranked up.
  • HP/LP Switch - Switches the range of the Simple Tone control to give you a different range of control.  This is very similar to the HP/LP switch on our Neurotic Drive.  Requires Simple Tone Control option.
  • Inverter Gain - Adds a Gain control in the Inverter stage of the Rising Sun or Early CraigTone configurations.
  • Parallel Inverters - The main technical difference between the Moose Steak and the CraigTone or Alpaca is how the inverters are configured.  In most of these configs, there are two inverter stages, comprised of one inverter in each stage.  That leaves 4 inverters in the CMOS chip unused.  The Moose Steak uses those extra inverters by putting three inverters in parallel in each of the two inverter stages.  This is also done in the BLT.  If you choose this option for any of the other configurations, we will use the extra inverters in parallel.  There isn't a big difference, maybe a slight fattening of tone.


Front Panel

See the information about controls for each configuration above.  The optional controls include Hi and Lo tone controls with the Active Tone Stack, a single Tone control for the Simple Tone stack, and the HP/LP switch for the Simple Tone Stack


Rear Panel

  • Audio In
  • Audio Out
  • On/Off Footswitch
  • On/Off Override
  • DC Power
  • DC Power LED


Module Width

  • 1.5" or 2" module width, depending on configuration and options
  • left or right wing module configuration may be available, depending on options


Power Consumption (aprox)

Most configurations will use about 20 - 30mA.  The BLT uses about 55 - 65mA.


Base Configurations

Part # Description List Price
MOD-BUZZ-CRAIG BuzzDrive Module, CraigTone Configuration $169
MOD-BUZZ-EARLYCRAIG BuzzDrive Module, Early CraigTone Configuration $169
MOD-BUZZ-SUN BuzzDrive Module, Rising Sun Configuration $189
MOD-BUZZ-MOOSE BuzzDrive Module, Moose Steak Configuration $169
MOD-BUZZ-ALPACA BuzzDrive Module, Alpaca Configuration $169
MOD-BUZZ-STONE BuzzDrive Module, BuzzStone Configuration $189
MOD-BUZZ-BLT BuzzDrive Module, BLT Configuration $199



Part # Description List Price
MOPT-BUZZ-BAX Active Tone Stack $39
MOPT-BUZZ-NOISE Extra Noise Caps $0
MOPT-BUZZ-TONE Simple Tone Control $19
MOPT-BUZZ-GAIN Inverter Gain $19
MOPT-BUZZ-PARALLEL Parallel Inverters $0



Part # Description List Price
MPT-BUZZ-CA Replacement pot, switch, jack, LED cable assembly $19
MPT-BUZZ-KNB Replacement control knob $2
MPT-BUZZ-PB Replacement power board $29
MPT-BUZZ-SB Replacement switching board $29