Wiring Diagrams | DiMarzio RG Wiring, DiMarzio Neck & Bridge Humbuckers/DiMarzio IBZ Middle Single Coil, IBZ 5-Way Switch, 1 Push-Pull Volume (Dual Sound Neck), 1 Push-Pull Tone (Dual Sound Bridge), 1 DPDT (Add Neck & Bridge); Neck, Neck & Middle, Middle, Bridge & Middle, Bridge Rotork: Limit Switch Boxes Mechanical or proximity switch (Option) or DPDT (Option) Position transmitter (Option) Visit the YT-870 page on the YTC website. YT-875 . Ex D IIC T6; 316 construction; Mechanical or proximity switch (Option) or DPDT (Option) Position transmitter (Option) 5E3 Mods - Rob Robinette Switch is ON-OFF-ON SPDT or DPDT (Single or Dual Post Dual Throw). Feedback signal is tapped from the speaker jack's 'Tip' terminal. Photo by Mark Herrick. Feedback Switch With Speaker Impedance Switch. Speaker Selector Switch on left (3-way slide switch) with 56k feedback resistor connected to the switch's 8 ohm input. Champ Micro - Rob Robinette Champ Micro Amplifier. Development. My recommended power transformer is the Hammond 270AX 240-0-240V for 120V mains (USA) and I recommend the Hammond 369HX for international builders which is 225-0-225V HT Using my Firefly's Hammond 269EX 190-0-190v power transformer I only got a B+1 of 285V and the V1 plates were at 110V which is a little low.