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MF MD HG PlugPlay guitars ampseffects 05-26-15
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Product 500251

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 pre...Read More

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Make major mayhem with this crunchy pedal voiced for metal.

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.

Stir things up with the Mayhem. Click or call today.


SFX-04 Twin Tube Mayhem Distortion Guitar Effects Pedal

  • 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

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by PowerReviews

(based on 7 reviews)

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Reviewed by 7 customers

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Full METAL distortion pedal


  • 2 Pedal In 1
  • Tube Warmt


    Best Uses

      This is a distortion pedal, and it really can gain up your amp to the moon and back. If you own a cheaper amp that has weak distortion, then this pedal will make it sound like never before. I have used many distortion pedals before, and this is the best by far. Sounds great on a mid gain, range setting, and a high gain range. With the boost Switch, you can get 4 or 8 dbs of power added to the original amount of gain you added on. Sounds great on 4db, a solo setting, and insane sustain and deepness of distortion on the 8db setting. Like I said, you can get any amount of gain you want from this pedal, because it is so versitile. The high plate voltage and 100% vacuum tube signal path allow the tubes to operate at their fullest potential and provide maximum dynamic range. The only bad flaw on this pedal is that you can not use just the gain boost without the other side of the pedal on. On the bright side, it has fully encapsulated toroidal transformer for a quiet no-hum or buzz, for recording and before the concert.

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      Best heavy distortion pedal I have heard!

      By DetroitLP-3H-ZO

      from Detroit

      Hands down best I have heard! LOTS of balls to this sound! Classic warm thick bassy distortion fantastic tone not dark (unless you want it to be) its exactly what I was looking for. EQ gives plenty of tonal variety. +4 or +8dB gain intensifies the tone for an awesome lead sound. Roll back guitar volume smooths the tone nicely. This pedal will push a tube amp to full bore metal and beyond at the cost of muddiness (I didnt buy the pedal to do this anyway). Its noisy at higher gains so get a good gate if you want I run it behind a Decimator G. Built like a tank. Runs fine off a CIOKS AC10 PSU (pedal needs 16V AC 650mA).

      Comment on this review


      The end all metal pedal

      This is simply the best high-gain pedal on the market. Do not hesitate just buy it!

      Comment on this review


      Nice distortion preamp...

      By R8:2 in Fresno

      from Fresno, Ca

      I have a Peavey Valveking 112. The amp has lot's of gain on tap, but the gain is too "scattered" and you can't tighten it up so you have too much fuzzy gain that when it get's to big get's out of control and you lose tone. So I bought the Mayhem Distortion pedal hoping to get a Dual Rectifier sound, but what I managed to pull out of it was a quasi-Marshall sound likened to the JVM410. Lot's of gain on this big box and it's built like a tank and appears to be excellent quality. If you have a 7 or 10 band EQ (I have a Fish & Chips)you can pull a myriad of possible sounds out of this gizmo. It's pretty expensive, but it's the best I've heard so for because it's hot a really nice "tube" distortion when run through a tube amp like the Valveking. So is you're planning on throwing down a couple grand for a Roadster, Raider or a JVM410 combo I would suggest you take a listen to this little puppy first. :)

      Comment on this review


      If you know how to adjust EQ's and use effects

      By SoundofThunder89

      from Seattle, WA

      I have read lots of reviews that people can't get that low Goth metal sound from this pedal. The only thing I can think of is their other equipment is not set up for it. If you are using the right kind of cabinets and speakers this thing will CRUSH! It is super high gain reminds me very much of the Rivera K Tre head I had. What that means is you can go from mild to wild and get great sounds through the whole spectrum. It is too bad that people aren't learning how to use effects these days, because this thing is amazing. I really did not need a high gain head but do need the high gain sound now and again, so this works perfectly.

      Comment on this review


      Mesa Bottle Rocket revisited

      By Sickroy

      from Oceanside, California

      Back in 2004 when I bought my Mesa Recto 50 watt half stack Mesa also sold two pedals. One was more off a preamp pedal(I forgot the name) and the other was a distortion preamp pedal called the Bottle Rocket. Both ran off of two 12AX7 tubes and when it came to delivering distortion both were monsters. Then in 05 Mesa discontinued them. Since then I have been trying to find a pedal that would make practicing as fun as playing through my Recto. Lone and behold, Seymour Duncan comes out with this monster and boom!, practice just became a hell of a lot more interesting. Im not saying this is Recto in a box. But, it is the closest thing to that ficticous decription that I can find. I have been using it in front of a Fender Champion 110 solid state and can dial up just about any lush tube tone gain that I need and at apartment friendly volumes as well. It also works well with my Marshall KKMG10 sig. solid state practice amp. But do not expect great sound with bunk guitars, bunk pickups or bunk amps. Remember, to acheave great tone you need to have all your bases coverd. This pedal will work well with a solid guitar with quality pickups(moderate to high gain passive work the best) and a good clean channel from either a quality solid state or tube amp. The tunning you use will also make a differance(don't expect deep doom distortion tones tuned to standard). For me it works with more variety when I used my 335 with Gibson 57 classic and 57 classic plus pickups than when I use my ESP Travis Miguel signiture viper with active EMG pickups and EMG Afterburner. With the ESP's pickups all ready having a high gain active preamp kinda equals overkill, so I have to tweak the EQ, gain and volume knobs on the Mayham, guitar and amp. But all in all, I love this pedal and I'm not a pedal guy. Best $ I ever spent. Also , with these tubes(new school military spec. micro tubes) I should never have to replace them, according to the owners manual.

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      Buy it if you want to sound different!

      By Anonymous

      from Undisclosed

      When I first played through it I felt little dissapointed, then I put the Fish & Chips EQ with it... and it came alive and gave me that sound I have been looking for! I have to turn the volume down on the pedal so my speakers don't waffle and my cab can handle 400watts you do the math! If you are looking for that tone that will set you apart from other guitar players by this!

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