Pre-Owned Seymour Duncan SFX-04 Twin Tube Mayhem


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Pre-Owned Seymour Duncan Twin Tube Mayhem Overdrive/Distortion Pedal

The SFX-04 Twin Tube Mayhem is a distortion pedal with a high-quality guitar preamp that includes a built-in boost. Using a duo of premium, mil-spec, subminiature, USA-made Phillips-Sylvania 62051 pentode tubes, the Seymour Duncan Mayhem is a great effect pedal for old-school metal, nu metal, thrash, death, and doom. The Twin Tube Mayhem pedal has a high-plate voltage and 100% vacuum tube signal path that allow the tubes to operate at their full potential and provide maximum dynamic range.

The SFX-04 Mayhem pedal achieves additional gain with a high-voltage, low-noise, and discrete Class A input stage. The solid state input stage increases the resistance of the Mayhem stompbox to microphonic feedback, resulting in maximum dynamic range, the most gain, and the heavy tone you'd expect from a great tube preamp voiced for metal. The Seymour Duncan Twin Tube Mayhem distortion pedal also features user-selectable 4dB or 8dB boost for pre-setting rhythm and lead levels. The Mayhem distortion pedal uses true bypass switching and has a fully encapsulated toroidal transformer for quiet operation. Its rugged, heavy-duty steel chassis provides exceptional durability.

  • Gain: Before Level Compensation - 97 dB, After Level Compensation - 71 dB
  • Nominal Output Level - 0.25 Vrms (-10dBu)
  • Max. output level before clipping - 5 Vrms (16dBu)
  • Input Impedance: 100KOhm
  • THD @ 100mV RMS output - .5%
  • Noise @ Output - 4mV (< 3dB hum content)
  • Boost Footswitch Gain
  • Two selectable boosts, 4dB and 8dB. No effect on tone, just increased level.
  • Active Equalization Section: Bass Control: 126 Hz, Q = 1.5, Gain = +/-12dB; Midrange Control: 596 Hz / 1389 Hz, Q = 1.5; Gain = +/-12dB; Treble Control: 2.93 KHz, Q = 1.4, Gain = +/-12dB
  • Power Consumption - 11W

This pedal works as described and is in good condition, exhibiting only light wear and some adhesive applied to the back. 

This item is at Five Star Guitars on consignment, as a result all sales are final.


Seymour Duncan


SFX-04 Twin Tube Mayhem




1 x 1/4"


1 x 1/4"


16V (Included)




7.5" x 6.62" x 1.96"




Power Supply

Type: Effects