FX85 Harmonic Enhancer

Both cosmetic variants of the FX85 Harmonic Enhancer, from early 1986 (left) and 1987

The FX85 Harmonic Enhancer debuted in 1984 as the 11th DOD FX-series pedal to be introduced, and one of the last to sport "bars" graphics. The FX85 was the first DOD pedal to feature a "presence" control (allowing the user to "adjust the amount of harmonic enhancement", according to the manual). This feature was subsequently integrated into the circuit of several later distortion pedals, starting with the FX56 American Metal. Based on its absence in DOD's 1987 pocket catalog (PEDALB.CAT 87A), the FX85 was discontinued by 1987.

• Controls: Level (0-12 dB of gain), Presence
  
  
• Catalog descriptions:1984 1986
  
  
• Manual: 1985
  
  
• Technical info:
  
  
  • Specifications: Input impedance = 220 k Ohms; Output impedance = 1 k Ohms; Gain = 0-12 dB; Enhancement frequency = 1kHz-20 kHz; Signal to noise ratio = 90 dB (manual) or 95 dB (catalog descriptions)
    
    
  • Notable IC chips: one NE570N compander; one TLO62CP low-power JFET op-amp; one TL022CP low-power dual op amp (early versions) or a LM1458N dual op amp (later versions)
    
    
  • Component-side circuitboard images: Jan. 1986 Feb. 1987
  
  
• FX heritage: FX85 FX87
  
  
• External links:
  • @ discofreq's FX site
  • @ harmonycentral.com
  • @ harmony-central.com (via archive.org)
  • @ noiseguide.com
  
  

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