VFE Pale Horse

The VFE Pale Horse is an overdrive pedal that now exists as a DIY project: a set of printed circuit boards for builders to assemble themselves. The PCBs are the actual boards used to build the recently discontinued line of VFE pedals, provided for DIY use only¹. VFE describes the result as a "unique and wide-ranging overdrive that can cover a lot of bases!"¹

Each VFE project, the Pale Horse included, has two PCBs: an audio board and a switching board, wired together to form the complete circuit². The audio PCB measures 2.17" x 2.025"¹.

The controls and internal trimmers

The Pale Horse carries external pots for drive, tone and level, plus a LOW control and a COMP control, and hides two trimmers inside for tweaking the input impedance and the frequency center of the tone pot².

The COMP control is the unusual one. Instead of a simple gain knob, it moves between two clipping characters, with a center detent that gives a clean boost. The pot itself is a 1M pot with a W taper and center detent¹.

A few component details matter to builders:

• The DRIVE pot is a 1MA pot with 10% tolerance instead of the usual 20%¹.
• The 10kA level pot labeled on the PCB is actually 50kA¹.
• The 2n5484 or J113 transistor must be used for proper operation¹.
• The build calls for a 10uF bi-polar electrolytic capacitor².

One builder documented that a J112 substitution, even though very close in spec to the J113, caused a sputtered output from the gain stage and did not work correctly in this circuit².

Optional socketed mod resistors

The PCB includes two optional socketed resistor positions. The *100k sets the lowest input impedance value of the OPA2134 when the IMPEDANCE trimmer is turned all the way down; 100k was found to be a good overall value. The *1M sets a high impedance input on the tone section and/or rolls off some subs, but the author found it was not needed on their build¹.

Power: split rail, plus and minus 9V

The Pale Horse uses a split rail, +9V and -9V, for operation². The VFE documentation describes the same thing as a split-rail supply¹. This is not the single 9V supply most pedals run on: the circuit generates both a positive and a negative rail from the input.

Before inserting the IC, the build guide's author confirms ground continuity between the two boards, -9V on pin 4 and +9 on pin 8 of the IC². In one documented build powered by a 9.42V One Spot, the measured readings were:

All readings were taken with the pedal powered by a 9.42V One Spot supply¹.

Building the Pale Horse from the DIY PCBs

The madbeanpedals build guide shows most of the process of building one of the VFE projects³. The build uses 16mm pots mounted on the enclosure and then soldered to the PCB; 9mm pots can be substituted but should be checked for clearance with the drill holes². The trimmers are Bourns 3362p, which the guide's author used in all their builds².

A few assembly notes from the build guide:

• The 2n5484 transistor can be socketed rather than soldered directly².
• The LED indicator is left unsoldered until final assembly: load it loose into the PCB, assemble the pedal with all the pots and jacks screwed down, then solder it directly to the board².
• The author used two 4u7 BP caps in parallel in place of the 10uF BP¹².

On the LOW control and bass response, the build guide notes that with only a 4u7 cap, when the Fat control is turned all the way up, the corner frequency of the added bass would be around 68Hz².

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