Seymour Duncan SFX-04 Twin Tube Mayhem Distortion Guitar Effects Pedal  

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The Seymour Duncan 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-Syl... Read More

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The Seymour Duncan 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
  • (Measured at 1 KHz)
  • Nominal Output Level — 0.25 Vrms (-10dBu)
  • (Measured with 100mV 1 KHz input signal and all controls set to 12 o'clock)
  • Max. output level before clipping — 5 Vrms (16dBu)
  • (Measured with gain set at 50% and all other controls set full up and boost footswitch set to 8dB)
  • Input Impedance: 100K ohms
  • 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
One year replacement warranty on all pickups.

  • Customer Reviews

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(based on 2 reviews)

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(24 of 25 customers found this review helpful)


Beast of Brutality!


from Griffin Georgia.

The Twin Tube Mayhem may very well be the Holy Grail of heavy guitar tone. Performance and Sound- The distortion you can get out of this unit is very extreme, but never too much. It is ideal for anthing from moderate rock such as Nickelback to blistering hi-gain metal. Even with the gain maxed, it still has touch dynamics and a very even and clear sound. Chords are clear, and single notes are defined and articulate. Actives, passives, single coils, and humbuckers all have an appropriately different voice, with different amounts and structures to the gain. So if you feel this preamp is weak or fuzzy, it's not the preamp, it's your pickups. A fuzzy or buzzing distortion is the result of adding this much distortion to a low output pickup. I recommend EMG's PA-2 or Afterburner gain booster to solve this problem. Tips and Tricks with Helpful Hints- This preamp is an absolute god-send for the gigging musician, especially in small venues. Since the SFX-04 is a tube driven preamp, all it lacks is a tube power amp and a speaker to be an actual amp! I take advantage of this in smaller venues by leaving my amps at home and running the unit directly into the venues PA System, with a noise-gate and 10band EQ(along with other things). Another option is to run the unit into a stereo power amp(VHT 90/2/90 is my preference), then into your two slant 4x12 cabinets, or two full stacks if bleeding ears are your thing. A marvelous pair with this preamp is Peavy's Vyper tube stack. The Vyper's only tubes drive the power amp. The preamp is solid state. Catch my drift? -I hope this review will help you get the most from this pedal, as I have. Heck, even reaching half of this pedal's potential, it's still an amazing piece of equipment.

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(46 of 51 customers found this review helpful)




from U.S. military overseas

This pedal is sweet! The sound quality is unlike anything else out there. Giving away my BOSS distortion pedals (except gt-8) because they just cant touch this thing for tone. If you like uber tight processed distortion keep your BOSS gear, but if you like tube style distortion that retains note clarity get this unit. Definately tailored toward hard rock, metal, death, and doom. If your looking for light or classic rock with very little distortion dont buy, you will have to crank the unit down so much it would just be a waste of money. But if you want to play some Hendrix style with tons of tube sounding feedback you will be in heaven, as well as playing any kind of metal. No matter how far you crank the lows and cut back on the high end this pedal will not sound "muddy", and my RG gained a ton of sustain using this pedal with the gain up around 3/4. I am playing through a Marshall solid state combo amp plugged into the clean channel and i swear it sounds 1000 times better when i use this pedal. Hands down the best distortion pedal i've ever heard. Cant talk anymore, have to go make some more ears bleed! Buy it!!

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