Obsidian Drive

"Two channels of tube-y overdrive.  Uh how, how, how, how...."




The Obsidian Drive overdrive rack effect module compares to the Blackstone Appliances Blackstone MOSFET Overdrive pedal.  One of Billy Gibbons’ favored pedals, it provides two independent channels of tube-y overdrive driven by a MOSFET buffer and CMOS inverter chip.  The original pedal shares a mid-scoop tone stack between the channels, but ours provides separate mid-scoop tone stacks.



The Blackstone MOSFET Overdrive isn’t a pedal you hear much about.  It’s a bit of an undiscovered pedal, but well worth trying out, in our opinion.  But you don’t have to believe us.  Billy Gibbons has apparently been using them for some time.  The circuit uses a MOSFET input buffer (switchable) but relies on a CMOS inverter chip for its tube-y overdrive tones.  You may have heard CMOS inverter drive tones in an Emma ReezaFRATzitz, Way Huge Red Llama, or Craig Anderton Tube Sound Fuzz derivative.

The circuit has two channels selectable by footswitch, which we call Orange and Red.  They both have Volume, Gain, and Tone controls, which unlike the original pedal, are completely independent.  For both channels, the Volume can provide a slight boost, more if the Gain is also cranked up.  Also, on both channels the Tone is a mid-scoop control.  At one extreme is flat mids, with varying levels of scoop dialed in from there.  But the Gain control behaves differently on the two channels.  On the Orange channel, Gain behaves like you would expect, and goes from clean-ish to raunchy crunch.  On the Red channel, the Gain is lowest and clean-ish in the middle.  Turning the Gain one way from the middle gives you more gain very much like the Orange channel.  Turning the Gain the other direction from the middle gives you more gain, but with a bass cut.  This may be handy if you have a dark setup or humbuckers and you don’t want to get mushy when you add the dirt.  Both directions will get you into raunchy crunch.

The other standard control is an input buffer switch.  You can decide which way you like it, which may vary with your signal chain. 

With footswitchable overdrive channels, it is definitely a “twofer” module that gives you different tone options on tap.  Note that the Channel Select footswitch has an Override Switch, just like all of our other footswitches.  In the normal setting, the override lets you select channels with a footswitch.  If you don’t need to use up a second footswitch for the module to select channels, then on the other setting, it overrides the footswitch input and selects the Red channel, which is the more versatile of the two channels.

Note that we planned to call the two channels Blue and Red for weird technical reasons that didn't work out.  We now call them Orange and Red, even though our old picture shows the Blue and Red labels on the front.



  • Obsidian Drive - Compares to the Blackstone Appliances Blackstone MOSFET Overdrive



 Input buffer (switchable)



  • Buffer Status LED - By default, there is no status LED to show the buffer status.  Either the switch is set to On or Off.  We can add an LED if you want it.
  • Non-Switchable Buffer - If you don't want the switchable buffer, we can hardwire it to be always on or leave it off.
  • External Hi/Lo Controls - There are two internal trim pots that control the gain at different frequency bands.  Normally these are not adjusted, but if you love to tweak, we can put them on the front panel.  If you select this option, it will make the module 3" wide unless you leave off the Buffer switch.


Front Panel

  • Orange Gain
  • Orange Tone
  • Orange Level
  • Red Gain
  • Red Tone
  • Red Level
  • Buffer On/Off switch (default, but optional)
  • Hi (optional)
  • Lo (optional)


Rear Panel

  • Audio In
  • Audio Out
  • On/Off Footswitch
  • On/Off Override
  • Channel Footswitch
  • Channel Override (Red)
  • DC Power
  • DC Power LED


Module Width

  • 2" standard, 3" with options
  • wing modules not currently available 


Power Consumption (aprox)

25 - 35mA


Base Configurations

Part # Description List Price
MOD-OBSIDIAN Obsidian Drive module $229



Part # Description List Price
MOPT-OBSIDIAN-BUFON Buffer Always On, No Switch -$10
MOPT-OBSIDIAN-BUFOFF Buffer Always Off, No Switch -$19
MOPT-OBSIDIAN-HILO External Hi/Lo Controls $29



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