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Overdrives| December, 2006
All distortion and overdrive pedals work on the same basic principle: The pedal’s output is a “clipped” version of the input signal. Imagine a sine wave, the most basic audio signal. The waveform looks like a steady series of gently sloped peaks and valleys equidistant from a central axis. Humans hear sine waves as a pure tone, devoid of character. Now imagine a circuit that electronically chops off the wave’s tops and bottoms, making the waveform appear more like a series of flat-topped mesas and flat-bottomed valleys. The resulting sound is immediately more interesting to the ear because it includes harmonic artifacts that weren’t previously there. Now, say we electronically amplified the signal before the clipping took place, changing the sloping portions of the wave from gentle to extreme. The resulting waveform becomes increasingly square, audible as a buzzy sound. In a sense, distortions are low-fidelity compressors; they force a signal to stay within a limited range, and they mess with the signal within this range. A bass’s signal, however, isn’t a sine wave. When a bass string vibrates, the resulting signal contains rich harmonic content: a fundamental frequency equal to the pitch of the note being played, plus a series of frequencies that are multiples of the fundamental. This assortment of related frequencies, called the overtone series, is part of what gives each instrument its distinctive sound, or timbre. A distortion pedal performs its clipping function on a signal already filled with harmonic information, adding additional frequencies to the signal’s overtone personality and reshaping its audio waveform. This is usually achieved with a circuit containing a small, high-gain, solid-state amplifier called an op amp (operational amplifier), along with one or more diodes, an electrical component which, in this usage, clips audio signals. The diode(s) are usually wired to the op-amp in a way that governs the circuit’s gain, thus limiting the signal to a range determined by the user. Opamps can clip audio, too, although the resulting sound seems less desirable to the ear. Other components are sometimes used for distortion, particularly field-effect transistors (FETs), which—when used as clipping devices—are thought to have a more tube-like sound than diodes. The type and number of diodes used, and their arrangement within the circuit, gives each distortion pedal its unique sound. For example, germanium diodes are said to move more smoothly into clipping than silicon diodes. Also, there are circuits that affect the signal’s two halves (the positive side of the axis and the negative side) in exactly the same way, as well as those that manipulate the signal asymmetrically. This, too, has an impact on tone. Last, since all of this is dependent on the bass signal’s frequency content, placing EQ and other tone-shaping circuits earlier in the signal chain can have an enormous impact on a distortion pedal’s sound. Ashdown Drive PlusThe Drive Plus is Ashdown’s first overdrive stompbox, and it shares the same eye-catching design as Ashdown’s other pedals: five knobs evenly spaced across a rugged steel chassis with a foot-protected VU meter for checking input level. The construction was excellent, but one of the knobs fell off during testing. The VU meter isn’t a gimmick, it’s a functional element that helps establish the right gain for a well-saturated bass signal. Popping it into the red with the input control is the only means of determining the quantity of distortion, much like with a tube amp. There are separate clipping circuits for low and high frequencies and the balance knob blends between each to tilt the tone toward either end of the frequency spectrum. I found this system a little too wonky for quickly dialing in a tone, as getting an intended sound is a three-knob process. The Drive Plus’s distorted tone is a relatively warm, but generic, fur sound, but it’s respectably sensitive to input dynamics and your instrument’s frequency response. List $135 Boss ODB-3 Bass OverdriveThe venerable Boss Bass Overdrive benefits from the standard stompbox-style construction of the other Boss pedals. It’s a clever design that’s been around for a long time, and for good reason. The ODB-3’s simple controls are limited, but potent in their efficacy. The EQ is more powerful than the typical circuit, offering a great deal of boost and influencing the distortion character significantly. The distortion doesn’t offer the run-away wackiness of some more extreme fuzz tones. The balance knob blends the distorted and clean sounds—getting it set right was a big ingredient in an ideal ODB-3 tone recipe. For industrial metal tones and throaty low-gain overdrive sounds, the Boss is an excellent choice. List $129 Bixonic Expandora Exp-2000RThe cool little tuna-can-shaped EXP-2000R is a reissue of a highly lauded distortion pedal originally designed for guitar. The updated Expandora moves the original’s clipping-circuit dip switches to the front panel and offers a bass-guitar setting for low-end frequency response. The pedal felt extremely durable, and the knobs, switch, and jacks were of a high quality. Despite the minimal tone circuitry (the tone knob is a simple high-end rolloff), the Expandora is fairly versatile thanks to the two switches, which govern the distortion circuit’s clipping behavior. A wide range of intensity is available, and each sound has a pleasant midrange quality that is occasionally absent in other fuzz tones. All-around, a really simple and effective little distortion pedal. List $200 Chunk Systems Brown DogThe Australian-made Brown Dog is a unique breed of distortion pedal, incorporating several cool ideas for expanded flexibility and outputting a variety of intense fuzz tones. The steel casing was solid, and the soft-style mechanical footswitch is an interesting alternative to the more conventional clicky type. The drive knob governs the Brown Dog’s fuzz-tone waveform by amplifying the signal before the clipping circuit. When turned all the way up, with the two-position character switch in hard mode, the Dog doles out a buzzsaw square-wave tone. Gate governs the point where the clipping sets in, allowing for very crisp and precise fuzz sound with zero noise between plucking attacks. The Brown Dog does not offer a truly warm, tube-like overdrive sound, but it’s unmatched for synth-like grittiness. One bonus: the Brown Dog is designed for use with Chunk’s 00Funk Mark II envelope filter (see page 52) for truly nasty synth sounds. List $290 Digitech Bass DriverLike the rest of Digitech’s X-Series pedals, the nicely priced Bass Driver achieves its wide-ranging distortion sounds with a proprietary Audio DNA chip. The digital technology has a distinctively different personality than the conventional diode-clipping distortion tones found elsewhere in this roundup. It’s much better behaved and incredibly tight and controlled. The Bass Driver’s morph knob is the pedal’s primary tone control, altering the distortion’s personality from murky and thick to crispy and richly filled with harmonics. Unlike some of the nuttier pedals, chords and double-stops ring true and clear with the Bass Driver. Its construction was solid. List $119 DNA Analogic Bd-1 Bass DraggerWhile you must excuse the manual’s poorly translated Japanese (On the battery location: “Earning the strength of case and limiting the troubles or damages …”), the DNA Analogic was a superb performer. Its aluminum case was thick and substantial and the domed metal knobs are among the most heavy-duty I’ve encountered. Sonically, it’s relatively one-dimensional, providing a mellifluous fur at lower boost settings and gradually folding-in upper-harmonics and soft-handed compression as the knob was turned. The bass and treble controls coax interesting color from the well-behaved clipping circuit, with treble having a particularly potent impact on texture and tone. I also liked the DNA’s just-right note envelope: It’s lies perfectly between squishy softness and brutal immediacy. List $300 EBS ValveDriveThe ValveDrive is a remarkably versatile distortion, and it’s the only tube-equipped pedal in our roundup. While its glowing tube (aided by an amber light) may imply a warm tube-like tone, the ValveDrive is actually best suited to intense, nasty distortion with burly character and thick low end. Its EQ filters aren’t as powerful as I had hoped, only adding subtle shades to the overall tone, but the footswitchable vintage setting adds a significant alternate personality to the vicious Swede, subduing its relentless blitzkrieg. There’s a presence and precision to the EBS that’s uncommon in overdrives. Construction-wise, it’s made from solid stuff, with a heavy-duty tube protector and thoughtfully recessed knobs. Since the single 12AX7 needs some serious voltage, the EBS doesn’t have a battery option. Its big footprint may be a turn-off, but for intense distortion that doesn’t sacrifice precision for vibe, it’s a good bet. List $399 Frantone Electronics BassweetThe Frantone Bassweet is housed in a hardy yet lovely purple case with sweet cream-colored Bakelite knobs and a bright green steel-bezeled LED. While detaching the bottom plate is the most involved of all battery-replacement methods, it’s also the most robust. Frantone put a lot of attention into audio-impacting detail, and the resulting tone—classic bass fuzz with a vivid harmonic signature—is a testament to the excellent design. Smooth-sounding germanium transistors are used for clipping, and the remaining electrical components are high quality, like silver/Teflon wiring and a New-Old-Stock Fairchild transistor driver from the ’70s. Its tone is a beautiful realization of the bass fuzz sound, dripping with soul-stirring personality. Sustain increases the fuzz intensity and tone is a basic high-cutting filter. All together, the Bassweet was simple and extremely effective. List $235 Fulltone Bass-Drive MosfetThe MOSFET-edition Bass-Drive from boutique pedal designer Michael Fuller is one of the baddest overdrives around. It has a heavy-gauge steel chassis, solid footswitches and hardy plastic knobs with setscrew attachment. The design is exceptionally clever and versatile. Three clipping modes offer a trio of killer overdriven tones, ranging from a smooth, subdued midrange tone, to a more aggressive sound featuring asymmetrical clipping for ear-tickling harmonic emphasis. The diode clipping circuit can be swapped for a tube-like MOSFET clipping circuit with the flick of a mini switch. The resulting sound was remarkably warm and woolly, with a bigger bottom than its diode-clipping pedal-mate. The Bass-Drive does not offer hugely buzzy metal sounds, but for warmth, girth, and versatility therein, it’s awesome. It even features a hi-fi clean-boost circuit for hitting the front end of an amp with a clean high-gain signal. List $179 Gallien-Krueger Diesel DawgRenowned for its venerable line of bi-ampable heads and cabinets, Gallien-Krueger’s first (and only) pedal borrows the high-gain circuit from GK’s flagship 2001RB head. The Diesel Dawg’s aluminum and steel case felt hefty, and I especially dug the slide-out battery drawer with its easy-turning thumbscrew. While the pedal’s girth imparts a sense of heavy-duty ruggedness, the Dawg does seem overly large considering its relatively compact solid-state circuitry. The GK essentially has a gritty fuzz tone with exceptional flexibility afforded by the three-band EQ. It unloads a lot of sustain, and at higher gain settings, it begins to get unruly, adding chirpy harmonics and ringing overtones in an alluringly nutty fashion. List $199 HAO RR-1 Rust Ride Bass DriverThe rugged Rust Ride is exceptionally simple but capable. Its steel case and steel switch and jacks are tough, and the single chicken-head knob is big and easy to see. Tone sculpting is limited to a three-position switch that brings in one of three EQ filters for varying levels of treble-response. The Rust Ride’s distortion was warm and sweet, nothing like the grating violence of a high-output fuzz tone. The dedicated active and passive jacks, each with its own input impedance, are an excellent detail, as are the dual outputs for dry/wet dual-amp tone. Not versatile at all, but for a tube-like overdrive sound, it’s quite realistic. List $200 Homebrew Electronics HematomaThe Homebrew Hematoma is essentially two pedals: The bp switch activates a clean 5dB boost, buffering the signal for further embellishment down the pedal line. Bo engages the Hematoma’s smooth-sounding clipping circuit. The pedal’s construction was excellent, although the purple-on-black lettering was tough to read in dark rooms. In the stanky bo mode, the pre-gain knob adds volume to the sound, but the distortion intensity is more a product of gain and tone. Sounds range from raspy low-gain fur to all-out squashed fuzz, with excellent note-to-note composure and control. I especially dug the eq shift switch, which changes the tone control’s range to thicken and sweeten the sound. List $155 Ibanez Phat-Hed PD7The Ibanez TONE-LOK series pedals feature a sort of mechanical programming design: the handy push-button knobs are retractable for adjustment and lockable for longer-term setting and protection. This feature enhanced the pedal’s durability, but otherwise its construction was average, with a lightweight cast-metal case, easy-popping plastic battery-access button, and too-tiny slide switches for the mode and attack functions. Feature-wise, the PD7 is quite rich. Via the mode switch, it offers a clean boost, a warmer overdrive sound, and buzzier distortion sound. In either setting, the PD7’s distortion is of the furry, restrained variety, but the two attack settings contribute extra high-end overtones that lace the fur with a sizzly top end. It’s an excellent pedal for clacky metal tones, as well as lightly smudged blues sounds. List $83 MXR Bass Blow TorchIt’s called “bass,” but our instrument’s sonic signature is in the midrange, where the right boost means cutting through a loud band. To capitalize on this, MXR designed the Bass Blow Torch, which focuses its distortion on midrange frequencies and has extensive midrange adjustability. Exceptionally dense, with a robust case and high-quality hardware, the Blow Torch uses an 18-volt power supply for maximum headroom and increased EQ range. The distortion is warm and colorful, but engaging the side-mounted torch boosts the clipping gain and dollops fizzy upper-harmonics on the signal. Coupled with distortion, the 3-band active EQ is highly effective. The three-position midrange center-frequency shift moves the distorted tone from burly to brassy as it’s shifted upwards. List $229 Nobels ODR-B Bass OverdriveGermany’s Nobels takes the familiar Boss-like stompbox format and adds a few innovative features, like a topside flip-up battery door and a groovy remote activating jack for triggering the effect with an external switch. Its construction was average; I don’t expect that it would break easily, but its small plastic knobs and plastic jacks aren’t exactly confidence inspiring. Its distortion tone is pretty run-of-the-mill, although the 3-band EQ goes a long way toward massaging intrigue out of the fuzz sounds. Drive works as expected, upping the attack ante and bringing increased color and texture. The low price is an attractant, while the no-frills distorted tones get the job done. List $89 Prescription Electronics Depth ChargeFor a simple all-around fuzz with intuitive features and slammin’ tone, the Depth Charge is a definite go-to. The metal case is of the straightforward home-project variety, but it works. The gold-capped plastic knobs felt rugged and were well spaced, but the labeling was wanting. Metal jacks and a clean-clicking metal switch round out the package, and a lime-green LED handles status reporting. The Depth Charge’s tone was fuzzy and buzzy, but without the self-oscillating freak-out of some more extreme pedals. The blend knob governs the dirt-to-direct ratio, and is an excellent means of preserving low end amidst its crackling mayhem. The tone control is more than a simple high-cut circuit; instead, it’s a set of active filters that substantially alter the Depth Charge’s sonic signature. This pedal has freakiness grounded in robust sonic solidity. List $250
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