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Seymour Duncan Mayhem Metal Overdrive SFX-04

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Seymour Duncan Mayhem Metal Overdrive SFX-04

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Manufacturer Seymour Duncan
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Seymour Duncan Mayhem Metal Overdrive SFX-04

Capitalizing on the success of their previous stompbox offerings, Santa Barbara-based Seymour Duncan released their latest pedal, the SFX-04 Twin Tube Mayhem. The Twin Tube Mayhem is a high gain guitar preamp that uses a duet of subminiature 6205 vacuum tubes and is voiced to evoke the heaviest sounds that define metal. The new-old-stock, USA-made Phillips Sylvania 6205s represent the pinnacle of tube technology. They were designed and manufactured to meet the U.S. Governments MIL-E-1 spec for reliability under conditions of severe shock, vibration, and temperature. They provide extremely long service life and exhibit virtually no tendency toward microphonics.

High-quality vacuum tubes are only part of the key to a great-sounding tube preamp. Too often, inexpensive tube gear runs in starved plate mode, where the tubes function like clipping diodes and do not actually amplify. The Twin Tube Mayhem employs a fully encapsulated, toroidal transformer to achieve the high plate voltage required for true tube amplification and maximum dynamic range. Additional gain is achieved with a high voltage, low noise, discrete Class A input stage. The solid state input stage increases the resistance of the stomp-box to microphonics. The result is maximum dynamic range, the most gain, the smoothest tone, and the low-order harmonics one expects from a great tube preamp.

The Twin Tube Mayhem also features a user-selectable 4dB or 8dB boost. This allows for lead and rhythm levels to be set independently. Voiced for heaviest rock tones, the Mayhem offers raw tube sound, thick distortion, and present low order harmonics. The Twin Tube Mayhem also features true bypass with gold relays, over 90 dB of gain, a silent switching circuit designed to eliminate pops and clicks, and a heavy-duty chassis with a nickel plated chassis and stylish chicken head knobs. A 16-volt AC transformer is also included.


Before Level Compensation 97 dB
After Level Compensation 71 dB
Gain measured at 1 KHz

Nominal Output Level 0.25 Vrms (-10dBu)
Nom. Output level measured with 100mV 1 KHz input signal and all controls set to 12 oclock

Max. output level before clipping 5 Vrms (16dBu)
Max. output measured with gain set at 50% and all other controls set full up and boost footswitch set to 8dB

Input Impedance: 100Kb

THD @ 100mV RMS output  .5% 

Noise @ Output  4mV (< 3dB hum content) 

Boost Footswitch Gail

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  11 W

External Dimensions  7.50 X 6.62 X 1.96 (190mm X 168mm X 50mm)

Weight 3.15 lbs. (1.43KG)

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