Seymour Duncan SFX-03 Twin Tube Classic

The SFX-03 Twin Tube Classic ($299 retail/ $209 street) is a new take on the dual-channel, tube overdrive pedal. Rather than employing the usual 12AX7s, the Twin Tube derives its muscle from a duet of subminiature 6021 tubes coupled with a high-voltage power supply. The 6021s are built to military specifications, and purportedly last several times longer than typical tubes. This is a good thing, as the tubes have to be replaced by a technician. It is also notable that the tubes drive the SFX-03’s entire signal path, instead of simply functioning as clipping diodes, as is the case with several other “tube” overdrive pedals. Because the unit’s proprietary 16VAC power supply is contained in an external wall wart, the pedal itself measures a relatively small 7.5" x 6.62" x 1.96", and even given its heavy-duty metal enclosure, weighs in at just a little more than three pounds.
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When used with an amplifier, the Twin Tube provides two preset levels of overdrive in addition to the amp’s basic tone. The pedal has individual Volume and Gain controls for its Rhythm and Lead channels, along with a single set of Bass and Treble controls common to both. Rugged metal footswitches for (true) Bypass and Channel Select, and three LEDs (for on/off and active channel status) complete the control panel.

I tested the pedal using a Fender Stratocaster, a PRS Custom-24, and a Gibson Les Paul Custom through a Rivera Chubster 40, a Vox AC30 reissue, and a vintage 50-watt Marshall half-stack. Despite the disparate tonal characteristics of these guitars and amps, the Twin Tube performed beautifully with them all, never masking or otherwise interfering with their individual personalities. In all cases, the sound was full and rich, and no matter how much I cranked up the gain, the tones remained exceptionally smooth and tight with lots of wonderful overtones.

The Twin Tube’s versatile Bass and Treble controls are voiced to provide low-end oomph (40Hz to 200Hz) and high-end sparkle (2kHz to 20kHz), rather than dramatically affect the mids, and cranking the tone knobs also delivers a significant gain boost. Having a separate set of tone controls for each channel would have added some versatility, but, in practice, I didn’t find the single set to be an issue, as I mostly used the EQ to compensate for the tonal differences of the various guitars and amps.

The Rhythm channel’s overdriven sounds ranged from an amp-like raggedness (one of the true tests of an overdrive pedal) to a totally kick-ass crunch. The Lead channel starts where the Rhythm channel leaves off, and gradually moves into supersaturated territory. From snarly harmonic squawks to singing woman tones to crushing, Hiwatt-like distortion, the Twin Tube delivered the goods. And, by turning the Gain down and the Volume up, I was able to get a nice clean tube sound, as well.

Numerous tube-driven preamp pedals have been introduced over the years—most of them being large and costly, or lacking in tonal versatility. The Twin Tube delivers the sorts of sounds typically associated with a good tube amp, and in a small package for a reasonable price. That’s why it merits an Editors’ Pick Award.