Flip-flops can take an incoming audio signal within a particular voltage range and output a binary signal with a predictable and controllable frequency ratio to the input. In an octave-pedal circuit, a series of flip-flops takes a bass’s fundamental frequency and divides it in half. The resulting signal, which is a “square” wave because of the flip-flops’ on-or-off characteristic, is then mixed back in with some portion of the bass’s unaffected signal. Since square waves have a buzzy sound, a post-flip-flop filtering circuit is often included to smooth out the octave sound. Octave pedals depend on a strong fundamental frequency to function, so they’re monophonic (only able to double one note at a time) and highly sensitive to the quality of the input signal. Also, due to the flip-flop’s inherent limitations, it’s difficult to design a circuit that’s effective over the bass’s entire range.

The other type of octave pedal, here represented by the Electro-Harmonix POG and Boss OC-3 in “poly” mode, uses an analog-to-digital-to-analog (A/D/A) converter to convert an instrument’s analog signal into a digital one. Then, using more sophisticated digital processes than a simple flip-flop, the circuit processes the digital signal, transposes it down an octave, and converts it back into analog. This system allows for much greater sonic manipulation and polyphony (doubling of multiple notes), although the resulting tones can sound less organically connected to the input signal than with the traditional flip-flop-based circuit.

Ashdown Bass Sub-Octave Plus

The Ashdown certainly looks cool, with its VU meter and rack-style bash guard/handle, and it feels rugged enough to last on the road. The snazzy-looking stompbox was frustrating to tweak, though, since the shiny silver knob settings were hard to read. The Sub-Octave Plus didn’t track lower notes very well, forcing me to stay high on the fingerboard, and I was disappointed that I couldn’t turn down my dry signal relative to the octave effect to get a dubby synth sound. The octave effect itself had a timid character. The Sub-Octave Plus’s distortion circuit—its own octave effect independent of the clean octave—gave notes a touch of grit, but it was a fairly subtle effect that left me wanting more.

List $135
Street $100
Power 9V batt. or AC adapter
True bypass Yes
Weight 2 lbs, 10 oz
Warranty One year limited
Made in China
Contact (718) 937-8300; www.ashdownmusic.com

Boss OC-3 Super Octave

Chances are you’re familiar with Boss’s trademark pedal design. There’s a reason: These pedals are built to last. True to its name, the Super Octave is more than your basic octaver. Its drive mode spit out acrid distorted tones that helped my riffs cut through just about anything—even the pedal’s clean octave settings had an aggressive edge. The pedal’s coolest feature is its ability to track polyphonically. While most octave pedals are monophonic—able to process only one note at a time—the OC-3 has a polyphonic mode that ably handles chords and double-stops. The unit tracks well in all modes. Boss recommends using the poly mode as a default setting, but I preferred oct 2 mode (with the two-octaves-below effect turned down); while poly produced a fatter sound, it also introduced a smidge of latency and some “out”-sounding harmonics. Still, I loved the synth-y thwump I got when I rolled off my dry signal in poly mode and cranked the octave 1 knob. Juicy.

List $185
Street $120
Power 9V batt. or AC adapter
True bypass No
Weight 15 oz
Warranty Five years parts, 90 days labor
Made in Taiwan
Contact (323) 890-3700; www.bossus.com

Danelectro DJ-12 Chili Dog Octave

A tasty and cheap offering on Danelectro’s menu of diner-themed effect units, the Chili Dog is a basic octave pedal that produces tones one and two octaves below your input signal. (Unless you’re playing way up the neck, the Chili Dog’s double-octave effect is more of a guitar-oriented feature.) It’s clear Danelectro did some cost-cutting in the construction department: The knobs on the test unit were flimsy and hard to read, and the footswitch didn’t always switch properly. A detachable plastic knob guard made it hard to turn the knobs (that’s kind of the point)—but it’s a tradeoff that seemed worth it, since it certainly upped the pedal’s durability factor. Sonically, the Chili Dog satisfies: It tracks well, and there’s a certain beauty to its simplicity. The octave effect sounded fat and full—exactly what you get from eating too many chili dogs.

List $49
Street $35
Power 9V batt. or AC adapter
True bypass No
Weight 12 oz
Warranty One year limited
Made in China
Contact (805) 389-4605; www.danelectro.com

EBS OctaBass

Let’s hear it for Sweden: It’s given us relaxing massages and scrumptious little meatballs, and now it’s followed up with some of the coolest stompboxes to hit the market. I loved the OctaBass’s compact size and elegant design, though I was annoyed that changing the battery required removing the entire base. The pedal’s two knobs are easy to read and feel solid to the touch. The OctaBass’s 3-position mini-switch selects among high, mid, and low EQ filters, each of which gives the basic octave effect a unique tonal footprint: The smooth-sounding mid setting is ostensibly “flat,” high yields a crisper attack, and low bolsters the signal with creamy low end. The pedal tracked well, though like most other octavers, it had difficulty tracking the lower notes on a standard 4-string. In all, great construction (despite its battery placement), and solid octave heft.

List $199
Street $160
Power 9V batt. or AC adapter
True bypass No
Weight 1 lb
Warranty Two years limited=
Made in Sweden
Contact Dist. in the U.S. by Brooklyn Gear: (718) 858-4900; www.ebssweden.com

Electro-Harmonix Polyphonic Octave Generator (POG)

Looking for something out of the ordinary? Check out Electro-Harmonix. The company’s POG, or Polyphonic Octave Generator, is unlike any other pedal out there. It’s quirky, no doubt, but it’s also just dang cool. Similar to its E-H brother the Bass Micro Synth and its cousin the Harmonic Octave Generator (HOG), the POG has individual sliders for control of its effect parameters. Despite its industrial looks, this pedal is not built to take much abuse, especially with its exposed plastic sliders. Unlike most octavers, the POG tracked perfectly across the entire range of the bass (including open strings), and it handled chords with nary a warble, though its digital conversion yielded a slightly cold, clinical tone. Additionally, the POG has a lowpass filter that acts like an EQ rolling off high frequencies. If detuned upper-octave effects aren’t your cup of tea, you may want a pedal with a little less going on—but if you’re looking for a solid basic octave effect with a lot of crazy new sounds, the POG might be a good choice.

List $419
Street $315
Power 18-volt AC adapter
True bypass Yes
Weight 1 lb
Warranty One year limited
Made in U.S.A.
Contact (718) 937-8300; www.ehx.com