FX55B Super Distortion / Supra Distortion

From left to right, "Super" Distortion pedals from early 1986 ('tall' knobs) and mid-1986 ('medium' knobs), then
"Supra" Distortion pedals from late 1987 (original series, 'medium skirted' knobs) and mid-1995 (second series, 'small' knobs)

DOD introduced the FX55B in early 1986; featuring a Tone control, it replaced the FX55 Distortion in DOD's lineup. DOD's original name for the FX55B was the "Super" Distortion, but by Fall 1986 it had become the "Supra" Distortion (see below). With a circuit very similar to the FX50B Overdrive Plus, but with a greater distortion effect and (initially) up to five times as much gain, the FX55B subsequently found a niche as DOD's "entry-level" distortion pedal. In 1987, the FX50B and FX55B's circuits were revised such that maxing out the Distortion knob also provided a boost in the output signal. The FX55B was discontinued by 1998, with the introduction of the final-series FX55C.

• Controls: Level, Tone (boosts treble frequencies when turned clockwise, bass frequencies when turned counterclockwise), Distortion (gain "Boost" available from 1987-on)
  
  
• From the manual (1987, shared with the FX50B): "The ... FX55B [is a] very high-gain preamplifier that [is] overdriven to help produce a distorting of the input signal and help sustain the notes longer. These effects help simulate the characteristic distortion of a guitar amplifier turned up so high that it "clips" the signal, distorting it. [T]he FX55B [has] an extra amount of gain boost in [its] upper range for a greater distortion effect. ... The FX55B's distortion is a symmetrical standard distortion sound with a boost of gain in its upper range."
  
  
• "Super" vs. "Supra" Distortion variants: The initial FX55Bs produced were labeled and marketed as the FX55B "Super Distortion". However, DiMarzio had previously trademarked the name "Super Distortion" for a guitar pickup. Just as the name of the Boss DF-2 was changed from "Super Distortion and Feedbacker" to "Super Feedbacker and Distortion", due to pressure from DiMarzio's legal team, DOD Electronics likely re-named the FX55B as the "Supra Distortion" by Fall 1986.
  
  
• List price (1992): $59.95
  
  
• Technical info:
  
  
  • Specifications (1986-87): Input impedance = 500k Ohms, Output impedance = 1 k Ohms; Max. Gain = 1000 V/V; Maximum Output Level = 1.2 V P-P; Bandwidth = 40 Hz to 16 kHz
    
    
  • Official schematic provided with pedal by DOD (dated 1-16-86)
    
    
  • Notable IC chips: LF353-series and LM1458N op-amps
    
    
  • Component-side circuitboard images: December 1985 February 1986 July 1986 December 1987 July 1995
    
    
  • Related circuits: FX50B, FX52, FX53
  
  
• FX heritage: FX55 FX55B FX55C
  
  
• External links:
  • @ ftp.dod.com - instruction manual, .pdf format
  • @ discofreq's FX site
  • @ harmony-central.com
  • @ noiseguide.com
  
  

home FX index America's pedal? field guide serial no. info FX literature
what's new? FX tech info links disclaimer/legal/contact us