FX87 Psycho Acoustic Processor / Edge

Two 'original series' cosmetic variants of the FX87 from 1988, labeled as the Psycho Acoustic Processor (left) and Edge

The FX87 debuted in late 1987-early 1988 as the "Psycho Acoustic Processor", an enhancer-type pedal not unlike the BBE Sonic Maximizer/Aphex Xciter/Boss EH-2. "Psychoacoustics" refers to how humans perceive sound, and like other enhancers the FX87 was designed to not be noticed when it was on, but would be noticable when turned off. Despite the simplicity of only one control knob (to control the amount of signal enhancement processing) and a LED meter (to indicate the amount of signal processing, and indicate an overload if the red LED is lit), the name of the pedal must have been confusing to potential buyers, because it was re-marketed as the FX87 "Edge" by mid-1988. Operation of the FX87 Edge must have still confused potential buyers, as it was discontinued in 1989.

• Control: Process; Level (LED meter) display
  
  
• From the manual: "The DOD FX87 EDGE pedal is a signal processor that adds a slight edge to the sound after other signal processing has dulled it. This gives the sound new prescence, clarity, and transparency using a unique signal conditioning process that has been re-engineered to fit in DOD's FX pedal chassis. The EDGE process uses 180^o phase chancellation, narrow band delays, and indirect frequency pre-emphasis to create a side chain interference signal. When the FX87 side-chain is mixed back against the original signal, it cancels the specific frequencies where distortion and overload occur, without affecting adjacent frequencies. The EDGE process uses critically spaced (in octaves) tight-time delays to fill the holes left by the 180^o phase notching. Indirect frequency accents are used to return the natural presence to the original signal."
  
  
• Historical context: DOD's previous "enhancer" pedals, the FX85 and 510-A (Performer series, for bass) basically provided an extra tone control instead of true BBE Sonic Maximizer-type signal enhancement. The FX87 replaced the FX85 in DOD's FX-series, but owed more to the concept of the BBE Sonic Maximizer and related processors than the FX85. While DOD seemed to follow Boss' lead more often than not in the 1980s, the FX87 actually pre-dated the Boss EH-2 Enhancer by almost three years (and ironically had been discontinued by the time the EH-2 was introduced in 1990).
  
  
• Catalog description: 1988
  
  
• Ad copy: Sharpen your axe.
  
  
• Technical info:
  
  
  • Specifications: Input impedance = 500 k Ohms; Output impedance = 1 k Ohms; Band Width = 40 Hz to 16 kHz; Signal to noise ratio > 90 dB; Gain = Unity
    
    
  • Notable IC chips: one TLO62CP low-power JFET op-amp; one LM324N low-power quad op amp; two 1458-type dual op amps
    
    
  • Component-side circuitboard images: Feb. 1988 ("Psycho Acoustic Processor") March 1988 ("Edge", but the circuit board is probably a few months older than the rest of this pedal)
  
  
• FX heritage: FX85 FX87
  
  
• External links:
  • @ ftp.dod.com - instruction manual (1988), .pdf format
  • @ discofreq's FX site
  • @ harmony-central.com
  • @ noiseguide.com ("Psycho Acoustic Processor")
  • @ noiseguide.com ("Edge")
  
  

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