DOD FX25 Envelope Filter

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Original series FX25 (1982) with the rare foam treadle (from my personal collection) featuring the earliest known serial number (100743) of an FX-series pedal making this the 743rd FX-series pedal ever made.

Two later original series cosmetic variants of the FX25. Shown is a "3 screw" treadle from 1984 (left) and "2 screw" treadle (right) from late 1987

The FX25 Envelope Filter was derived from DOD's well-received 440 Envelope Filter. Like the 440, the FX25 uses a bandpass filter circuit where the peak frequency is determined by the input signal level, for a touch-controlled wah or auto-wah effect. The FX25 was one of the original ten DOD FX-series pedals that debuted in 1982, and remained in production until it was replaced by the FX25B in 1998.

• Controls: Range, Sensitivity
  
  
• List price (Jan. 1983): $69.95
  
  
• Technical info:
  
  
  • Specifications (circa 1984): Input impedance = 500 k Ohms, Output impedance = 1 k Ohms; Filter frequency range = 50 Hz to 2.5 kHz; Filter Q (Range) = variable 1-100; Gain = O dB
    
    
  • Notable IC chip: two RCA CA3094E high-current OTAs and one TL022CP op amp (1984); one LM13600N dual OTA and one MC1458CP op amp (1987)
    
    
  • Component-side circuitboard images: January 1984 Dec. 1987
  
  
• FX heritage: FX25 FX25B
  
  
• Notable artists using the FX25:
  
  
  • During early ZPZ tours (2006-07?), Dweezil Zappa used a FX25 (among other pedals). It was auctioned on eBay in September 2008 after he reconfigured his pedal drawer.
    
    
  • During Nine Inch Nail's 2009 tour (and possibly earlier tours), guitarist Robin Finck used a FX25 (among other pedals). It was auctioned on eBay in December 2009.
  
  
• External links:
  
  
  • The DOD FX25 Envelope Filter at Effects Database
  • The DOD FX25 Envelope Filter on vintage Harmony Central forums
  • The DOD FX25 Envelope Filter at Noise Guide
  
  

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