FX22 Vibro Thang Vibrato/Phaser

All three cosmetic variants of the FX22, from 1995 (left), 1997, and 1998

The FX22 Vibro Thang was introduced at the Winter 1996 NAMM meeting. Its circuit was innovative in that it provided both phase shifting and vibrato effects, each tied to the same Speed control, which could then be combined to simulate a rotary speaker effect. While the FX22 was a versatile and musical-sounding effects pedal, initial sales likely suffered due to its name and odd control names, and the abundant typos in its instruction manual probably did not inspire confidence in those who bought it. In 1998, the FX22 was one of the pedals given a cosmetic "facelift" before production moved to China with the VFX series.

• Controls (1996-98): RPMs (speed of the vibrato and phaser), Drop (vibrato depth; vibrato is off when turned ccw), Intensity (amount of phasing; phaser is off when turned ccw), Image (phasing regeneration)
  
  
• Controls (1998-VFX): Speed, Depth, Doppler, Image
  
  
• From the manual: "The FX22 Vibro-Thang is a specially-designed vibrato that has special phasing circuitry. This special phasing circuitry adds dimension and color much like a rotary speaker. The Vibro-Thang, can give you tones from honky-tonk, rock-a-billy, to guitar sound that is produced in Led Zeppelin's "No Quarter". You obviously haven't settled for any old vibrato pedal, so get full use of the FX22 by reading this manual (before operating it). Thank yo'all [sic] and safe pickin."
  
  
• Image of original box and manual
  
  
• Technical info:
  
  
  • Notable IC chips: Two LM13600N dual OTAs (for a 4-stage phaser), one JRC 2904D CMOS analog switch (for the vibrato circuit?)
    
    
  • Component-side circuitboard images: December 1995 December 1997 January 1998
    
    
  • Circuit revisions: The lone example of the 'original' graphics FX22 we have seen did not permit a fast vibrato effect, while both examples of subsequent versions we have examined did. If the difference was intentional, it was not noted on its circuit board ID number ("P/N# 80-1022-A0" for all versions we have examined). However, one of the resistors located between the RPMs/Speed pot and the JRC 2904D chip was changed from 22 kOhms (1995) to 10 kOhms (1997). We haven't traced the circuit or attempted to modify the only original FX22 available to us at this time, but carefully clipping another 22 kOhm resistor in parallel to the existing 22 kOhm resistor (for a net resistance of close to 10 kOhm) might be an easy way to determine whether or not the change in resistance is responsible for the change in vibrato speed.
    
    
  • Second LED: All three of the FX22s we have examined included a second LED (labeled as D6) on its circuit board. This LED is always on (when power is supplied and a 1/4" plug is inserted into the Input jack) and pulsates with the Speed control; as such, it might have been more useful if it was visible from outside the pedal.
    
    
  • Related circuit: FX20C (loosely based)
    
    
• External links:
  • @ ftp.dod.com - instruction manual (1998), .pdf format
  • @ DOD.com
  • @ discofreq's FX site
  • @ harmony-central.com
  • @ jfrankcarr.com
  • @ noiseguide.com
  
  

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