VFE Blues King

The VFE Blues King is a low-gain overdrive pedal from VFE Pedals, a small family business that built its pedals by hand in Pennsylvania¹. VFE describes it as a tool for sculpting low-to-mid gain tones and pushing an amp into its sweet spot, with an EQ curve designed to avoid the tone-masking flaws of many overdrive pedals². Delicious Audio's reviewer called it a "low-gain" distortion pedal that "actually has plenty on tap"¹.

What it does to your sound

The Blues King runs two gain stages, and the DRIVE knob sets the gain of both the pre-gain and main gain stages at once, with a taper aimed at fine-tuning low-gain drive tones². The pre-gain stage's bass response is set by the BASS knob, which is actually a bass cut: turning it clockwise cuts bass to keep the bottom end tight and punchy through the clipping stages². A passive treble cut follows, smoothing grit from the two drive sections².

What sets the Blues King apart from most low-gain overdrives is its adjustable clipping. The SOFT and HARD knobs use what VFE calls variable HCC circuitry to tailor the character and compression of the drive, moving between symmetrical and asymmetrical clipping and blending the characteristics of silicon and germanium diodes²¹.

The controls

The SOFT knob's positions each have a distinct character. Asymmetrical yields the most compression, distortion and even harmonics; symmetrical gives dynamic clipping; and at 12:00 the diode lift removes all clipping components, turning the stage into a clean boost². The HARD knob moves from smooth germanium drive clockwise to biting silicon clipping counterclockwise, with 12:00 again removing the compression². The w20kC pot for SOFT is a 20k pot with a center detent, included with the board².

Clean boost setup

To use the pedal as a full-range clean boost, set TONE clockwise and BASS counterclockwise, with HARD and SOFT both at 12:00².

Power and the internal circuit

The Blues King starts with a simple unity-gain buffer whose input impedance is set by the internal IMPED trimpot². Higher input impedance gives more top end sparkle when the pedal is tied directly to a guitar with passive pickups².

The circuit uses a single-rail power supply rather than split-rail, so no charge pump is needed on the switching board². It can run at up to 18V, and the build documentation reports a measured 9.42V DC on a One-Spot supply². The clipping diodes are BA282 (4) or MA856, 1n914 (2) and 1n34a (3); the MA856 is hard to find, and the suggested substitute is the BA282². In the second gain stage, R12 and R13 are two 470k resistors in parallel, approximating an odd-ball value of 235k².

DIY notes

The PCBs are the actual boards used to build the discontinued VFE line, provided for DIY use². The project is for DIY use only and may not be used commercially, including the sale of completed pedals or kits².

A few points from the build documentation worth knowing:

• Use the component values listed on the image, not the values on the PCB's silk-screen; some values changed over the VFE product cycles².
• The 500kA pot is recommended for the bass control; the PCB image shows 100kA, which the document's author believes is an error².
• The original w1MC pot is no longer available; a 1MB pot works instead, differing only in lacking a center detent and having a different taper around center, with the same range of tones available².
• Put a jumper in the "JUMP" component and leave the "9V" component empty².
• Either wired or PCB-mounted jacks can be used².
• The shopping list covers the audio board only; the v.2 Switching Board document covers the switching parts².

What reviewers said

Delicious Audio reviewed the Blues King in 2012, noting its symmetrical and asymmetrical soft clipping and the ability to blend the distortion characteristics of silicon and germanium diodes¹. The reviewer's honest caveat on all that flexibility:

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