This fine Harmonic Percolator derivative leaves you wondering why the circuit remains a relative secret.
Recorded with Fender Stratocaster and '68 silverface Bassman.
HP-2 volume at noon. Gain control variously at full, noon, and 3 o'clock. Bridge and neck pickups used at various guitar volume levels.
In an age when absolutely nothing is a secret, it’s really weird that a circuit like the old InterFax Harmonic Percolator remains as under the radar as it does. It doesn’t dwell in total anonymity, of course. It is a favorite among deep-diving circuit heads and we’ve seen excellent clones that deliver the essence of the original. Maybe it’s the fact that the Percolator’s greatest champion is Steve Albini—whose often acerbic, confrontational guitar sounds aren’t exactly David Gilmour’s mellifluous cello fuzz tones.
Land Devices HP-2, which uses the Harmonic Percolator circuit as its foundation, might compound confusion about the original’s underappreciated status. It’s a superb distortion device on all fronts. It veers from complex and rich to searing. It’s sensitive and responsive to picking dynamics and volume attenuation. It’s unique sounding. It’s everything a player that’s seen and heard everything could want—or at least wants to experience—in a distortion or fuzz. Maybe the Land Devices HP-2 is the Harmonic Percolator that, at last, reaches the many. It’s certainly got the sonic goods it takes to break through in a big way.
Circuits to the Unknown
Some of the mystery around Harmonic Percolator-derived circuits is attributable to the fact that folks can’t even agree on what it sounds like. Some call its even-order distortion—derived in part from pairing PNP germanium transistors and NPN silicon transistors—tube-amp-like. But it is much too fizzy and fractured around the edges of its complex overtone spectrum to be that. Some call it harsh, but the smooth grunt in its fundamental distortion tones definitely possesses a pleasing luxuriousness. The HP-2 very authentically, and remarkably, retains all of those qualities. And it all comes from a simple circuit that fits on a hand-wired rectangular circuit board about the size of four postage stamps arranged laterally. The hand-wired circuit isn’t the tidiest I’ve seen—at least as far as the soldering is concerned. But there’s no evidence that the solders are anything other than robust. (I’ve seen glorious sounding vintage fuzzes that look much uglier.) And in general, the pedal’s insides are carefully and thoughtfully laid out, with neat, well-ordered wire runs and enclosure-mounted jacks and pots. The simple control set is mysteriously labeled, but the functions are easy to discern through trial and error. The “circle” knob is essentially an input level control. The “triangle” knob is the master output. The orange rocker switch moves between germanium diode clipping and the no-diode “lift” mode.
Because the circuit board is flipped, it’s impossible to tell exactly what components make up the HP-2’s circuit. Some Percolator aficionados insist that original 2N404a and 2N3565 transistors are essential to a complete Percolator experience. I’m with my colleague Joe Gore on this topic: Different transistor types may impart small differences, but a well chosen equivalent set will still deliver the essence of a pedal. As we’ll hear, the HP-2 definitely delivers the sonic qualities you would expect from an original. And while the flipped circuit board makes it impossible to discern specific transistor and diode types, they sure look a lot like a compliment of germanium and silicon transistors and diodes.
HP Sauce (Sonically Speaking)
The HP-2’s tones often dwell in a mystery zone between richness, complexity, and hairiness. And I can understand why otherwise sane and civilized players would argue whether it sounds smooth and amp-like or harsh. I hear aspects of both qualities. It sustains beautifully. But it also fractures and fizzes in nebulous high-harmonic zones as it sings. It’s complex, to say the least. And the near ideal balance between these worlds at many settings makes the HP-2 feel special, unique, expressive, and rewarding and satisfying to interact with.
In tribute to the Harmonic Percolator’s most famous advocate, I played the HP-2 though my Fender Bassman (the backbone for many of Albini’s classic tones). And while I got Albini-worthy ear-fry with a single-coil or a hot bridge humbucker and amp treble at advanced levels, the tone recipes I liked—no, loved, most—were on the more rotund end of the spectrum: a Jazzmaster neck pickup, Fender Wide Range pickups with a little tone attenuation, a Rickenbacker with a two-pickup blend favoring the neck setting. All these round, bass- and low-mid heavy tones were a perfect fit for the HP-2s unique mix of density, definition, and sizzle at the harmonic fringes. The dynamism that comes through careful guitar volume manipulation is magnified via these recipes. Roll things back just a bit and the HP-2’s delicious, almost silky, even-order overdrive characteristics become apparent. Open the guitar volume wide and a layer of grinding overtones and compression kicks in. Love the dark-star-collapsing-on-itself gravity of Neil Young’s tones on the Eldorado EP? An HP-2 and a Fender amp might be the fix you need.
Bear in mind that most of the testing reported here has been about tones generated without the HP-2’s diode lift switch—a mechanism that justifiably gives the unit its “doomsday device” handle. The diode lift switch is a seismic-scale kick in the pants. And if you have a 4x12, a big amp, and a desire to level whole city blocks, the diode lift setting is an able partner in destruction. I liked the greater complexity and overtones of the quieter (a relative term here) diode-clipped setting. But the diode lift setting is not without character and charms. It just may leave you deaf if you dare explore it without ear protection.
If you’re a pedal obsessive that feels like you’ve exhausted the possibilities of the distortion and fuzz standard bearers, the edgy, rowdy, but still complex and creamy distortion from the HP-2 is a wonderland to explore. Is the HP-2 the Harmonic Percolator derivative that spreads the gospel to the masses? No matter what its destiny, it deserves to be heard.