Clavinet.Com Presents: Upgrading the D6 Preamp

This information was provided by Jim Williams of Audio Upgrades in Van Nuys, California. Jim has been working for Stevie Wonder for over 25 years, refurbishing the five clavinets that Mr. Wonder owns. Jim is also responsible for the "Hard Hammer" Rhodes sound that "Dyno-My-Piano" copied. This sound was sampled by the "Ballad" patch on the Yamaha DX7 and is still heard today.

This modification that Jim has *generously* provided upgrades the D6 preamp with low noise transistors and premium film caps. According to Jim, this mod opens up the top end details, reduces noise and distortion and adds the "natural air" back in to the sound of the clavinet.

  1. Change the front end transistor BC 413C to a Motorola MPSA18. The pinout is reversed on the replacement transistor.
  2. Replace the .01 uf film caps (black) to Wima MKP-3 .01 uf 1000 volts.
  3. Replace the thin 4.7 nf disc cap between the two indutors (coils) with a Wima MKP-2 4700 pf (.0047 uf) 630 volts.
  4. Change the .22 uf film cap on the output with a Wima MKS-2 polycarbonate film (or mylar) .22 uf 63 volt. Add a Wima MKP-2 .01 uf 1000 volt across it on the back of the pcb.
  5. Replace the .015 uf cap with a Wima MKP-2 .015 uf 400 volt cap.
  6. Replace the 100 uf 16 volt electrolytic cap with a Rubycon ZL or Panasonic FC electrolytic cap. Bypass it with a .1 uf 50 volt mono ceramic cap.
  7. Bypass the 6.8 uf 20 volt green tantalum cap with a Wima MKP-2 .01 uf 250 volt cap

Inside Stevie Wonder's Clavinet


  1. The bypass caps can be soldered on the rear of the PCB.
  2. The Wima caps can be obtained from the Intertechnical Group in Malvern, NY or TAW electronics in Burbank, CA.
  3. Rubycon caps can be ordered through Future/Active Electronics with offices located in large cities.
  4. Panasonic caps can be got from Digi-Key, 1-800-digikey.
  5. The Motorola transistors can be got from Allied, Newark Electronics, etc.

JimWilliams: "I installed a balanced XLR line driver for recording and on stage, it helps interface to pro systems. They also have an "effects" loop installed so the Mutron envelope follower he uses can be routed through before the line driver."