Seymour Duncan SFX-04 Twin Tube Mayhem

Seymour Duncan SFX-04 Twin Tube Mayhem

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SFX-04 Twin Tube Mayhem, Tube Guitar Preamp from Seymour Duncan in the SFX series.

2 user reviews
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Seymour Duncan SFX-04 Twin Tube Mayhem tech. sheet

  • Manufacturer: Seymour Duncan
  • Model: SFX-04 Twin Tube Mayhem
  • Series: SFX
  • Category: Tube Guitar Preamps
  • Added in our database on: 11/04/2007

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Seymour Duncan SFX-04 Twin Tube Mayhem user reviews

Average Score:4.0( 4/5 based on 2 reviews )
 1 user review50 %
 1 user review50 %

tjon901's review"Seymour Duncans take on a metal pedal"

Seymour Duncan SFX-04 Twin Tube Mayhem
The Twin Tube Mayhem is one of the pedals in Seymour Duncans twin tube line of pedals. This pedal is designed to get a high gain metal tone. It is not really a pedal as much as it is a preamp. It has a couple of tubes in it to add warmth to the sound so you dont have to use it with your amps preamp. It has a true bypass switch so it does not color your sound when you dont want it to. It has 5 knobs on its face. The knobs are a Volume Knob, Bass, Mid, Treble and gain. It has a low and high frequency switch and too foot switches. The first foot switch controls the on and off operation of the pedal and the 2nd is a built in boost.


The pedal is solidly built. It has an all steel chassis and the tubes in it are super durable. The knobs are big enough to be adjusted on the fly but the switches are pretty small. The knobs have a little bump in the middle of the sweep so you can feel when they are at noon. This is a nice feature to let you know where you are at if you cannot see the pedal. The writing on the pedal can be hard to read because of the script it is in. The pedal comes with an ac adapter and it will only work with the included adapter.


The high and low freqency switch makes or breaks the pedal for me. In the middle of the pedal there is a switch that adjusts the midrange. The midrange is the most important part of a metal tone. The mid control on the pedal lets you sweep the midrange from 600Hz to a crazy 1.4kHZ. This pedal sounds pretty thin over all. The bass knob does not help much. It kinda sounds more like a treble cut then a bass knob. The boost knob is a clean boost that you can switch from 4 to 8db. I wish you could use the boost knob without having the overdrive on but you cant. The boost only works if you have the gain from the pedal switched on.


I did not like this pedal much. Since it is advertised as a preamp pedal you are supposed to be able to use it on its own without having to be in front of another amp. The sound the pedal puts out on its own is too thin. The sound relies on you having a thick power section to go with it. It can not hang on its own. I would recommend a solid amp over this pedal.

greatsessions's review (This content has been automatically translated from French)

Seymour Duncan SFX-04 Twin Tube Mayhem
Pedal / preamp tube (pentode 2). This pedal has the trunk, power will be done by the amp (combo or head) or a power amp (I would advise the VHT 90 I tried with the pedal)
the adjustment level: a gain, very powerful, a volume that has an effect on the sound, plus ca c sends more high wholesale.
a medium bass equalizer very reactive to acute d (get a lot of distortion, saturation and overdrive.
an actuation switch (bypass), a booster switch for 4 or 8 dB, a filter for the midrange to dig their way or have extreme metal rock mediums way.
a guitar input, an output to the amp.

SOUND: mesa boogie oriented, a grain powerful, precise and thick. you will find tests of the pedal on youtube with good quality sound to get an idea.

This pedal turns any amp apartment in total killing, and its mark with a hot iron in an amp head / body.

I love her for the mesa. on the other hand I do not use more because I invest in a high-end head so it will be redundant.

the power is 16V with a transformer supplied by Seymour Duncan

roughly c dla baaaaalle


Config ultra simple, no need for manual, it says qq settings are explained for novices big sound


As I said above, the mesa-type, ideal for rock, big large rock, heavy metal and heavy metal (black, death, grind, no problem)
little special affection for his personal death metal but c


I have been using a little amp Line 6 Flextone III XL and studio on a Valvestate 100W stack.
it is very very strong, can jump in with both feet
very good value for money, turns any amp basically any amp lamp for 300 euros!
I would do choice except to buy a head amp premium in which case the pedal has less interest.
basically if you want the mesa for less than the mesa but with the quality inherent in seymour duncan, then go ahead, you gonna take off the wallpaper the walls!

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  • Seymour Duncan SFX-04 Twin Tube Mayhem
  • Seymour Duncan SFX-04 Twin Tube Mayhem

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Other names: sfx 04 twin tube mayhem, sfx04twintubemayhem, sfx04 twintubemayhem, sfx 04 twintubemayhem, sfx04 twin tube mayhem, sfx 04twin tube mayhem

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