DOD FX15 Swell Pedal

The FX15 Swell Pedal was introduced in late 1984, and was designed to help guitar players approximate backwards guitar sounds (where a note's amplitude swells rather than decays) in real time. DOD's circuit used a minimum of parts and appeared to be utterly unique compared to the Boss SG-1 Slow Gear. As with the Boss SG-1, the FX15's sales were slow (partially due to its somewhat counterintuitive design -- see below), and it appears to have been discontinued by late 1986.

• Controls(with descriptions from the manual):
  • Decay (0.7-2 s) - "controls the time for the signal to return to normal when the switch is released"
  • Attack (20 ms to 1 s) - "controls the time for cut/boost to occur when the switch is pressed"
  • Cut/Boost (-37 dB to +14 dB) - "when the switch is pressed there will be a cut in signal if rotated counter clock wise from center, a boost if clock wise from center"

• Using the DOD FX15: Perhaps because of its relatively steep learning curve, DOD added an additional page to the FX15's user manual. In our opinion, the two most important things to remember are (1) the footswitch is wired as a "momentary" type, meaning you have to hold the treadle down while in use; and (2) the Cut/Boost control should never be at "noon" (at its center position, with unity gain) if you expect the FX15 to do anything when the treadle is held down.
• Technical info:

• Specifications: Input impedance = 500 k Ohms, Output impedance = 1 k Ohms; Decay, Attack, and Cut/Boost as listed above
• Notable IC chips: CLM-50 (LED Photoconductor D.I.P. Optoisolator, a type of VCA?) and a TL022CP op-amp. Alone among DOD's FX series, the FX15's circuitboard does NOT include a MC14007UBCP-type chip, as there is no FET switching circuitry (however, this pedal is NOT true-bypass).

Component-side circuitboard image: August 1984