FX50B Overdrive Plus

Three FX50Bs, each with a different DOD logo/marque plate:
from left to right, original-series (1986), "transition" (1988), and second series (final version, 1997)

DOD introduced the FX50B in early 1986; featuring a Tone control, it all but completely replaced the FX50 Overdrive Preamp in DOD's lineup. (With the introduction of the FX50B, the two-knob FX50 was no longer featured in advertisements or catalogs, although we have seen a legitimate example of a FX50 from late 1988.) Its circuit was very similar to the FX55B Supra Distortion, but with less distortion and gain. Although the FX50B was a descendent of DOD's highly-regarded Overdrive Preamp/250, sound-wise its competition (the JRC4558-loaded Boss SD-1 and Ibanez TS9) sound better to our ears. In about 1987, the FX50B's circuit was revised such that maxing out the Drive knob also provided a boost in the output signal. The FX50B was discontinued by 1998, with the then-new FX102 Mystic Blues Overdrive (and the December 1997 re-issue of the 250) apparently replacing it in DOD's lineup.

• Controls: Level, Tone, Drive ("Boost" at end of Drive from 1987-on)
  
  
• From the manual (1987, shared with the FX55B): "The FX50B [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 FX50B's DRIVE control is relatively clean in its lower range and becomes a mild distortion in its upper range. This pedal is especially useful to simulate the sound of a tube type overdrive sound."
  
  
• List price (1992): $59.95
  
  
• Technical info:
  
  
  • Specifications (1986-87): Input impedance = 500k Ohms, Output impedance = 1 k Ohms; Max. Gain = 200 V/V; Maximum Output Level = 1.2 V P-P; Bandwidth = 40 Hz to 16 kHz
    
    
  • Notable IC chips: LM1458N op-amps (first versions); LF353-type and 1458-type op-amps (later versions)
    
    
  • Component-side circuitboard images: April 1986 August 1988 November 1997
    
    
  • Related circuits: FX52, FX53, FX55B
  
  
• FX heritage: FX50 FX50B
  
  
• External links:
  • @ ftp.dod.com - instruction manual, .pdf format
  • @ discofreq's FX site
  • @ harmony-central.com
  • @ noiseguide.com
  
  

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