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Yuzu Audio 87 FET Mic Kit Manual

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Yuzu Audio
DIY Audio Electronics
Made Easy
Build Guide v1.0

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Summary of Contents for Yuzu Audio 87 FET Mic Kit

  • Page 1 Yuzu Audio DIY Audio Electronics Made Easy Build Guide v1.0...

  • Page 2: Table Of Contents

    Table of Contents Introduction ....3 Chapter 1: Getting Started ..4 Chapter 2: PCB Assembly ..5 Ground Pins .

  • Page 3: Introduction

    Thank you for purchasing the Yuzu 87 FET Microphone Kit from Yuzu Audio. We hope you are excited to build our faithful recreation of the classic German large-diaphragm condenser microphone from the late 1960s. Arguably the most famous microphone in the recording industry after the SM57, the U87 has been a staple in studios across the world since its inception, capturing vocal and instrument performances on countless hit records.

  • Page 4: Chapter 1: Getting Started

    Getting Started Required tools to complete this build: Recommended tools for a smoother build: Soldering Iron: Desoldering Wick or Pump: A good-quality soldering iron with temperature control You may find it useful to have a wick or pump in case is necessary to get clean solder joints on this build.

  • Page 5: Chapter 2: Pcb Assembly

    PCB Assembly ~ Components List ~ Ground Pins PCB A PCB B Ground Pin Ground Pin First, let's start the PCB assembly by soldering each component one by one: Insert the isolation turrets into insertion point GG on PCB A and G on PCB B. Trim some of the excess from the back of the PCB while still mainting some room to solder a wire later on.

  • Page 6: Zener Diode

    PCB Assembly ~ Components List ~ Zener Diode PCB A PCB B Zener Diode R7 1G Next, we can focus on diodes and resistors: Solder the zener diode onto PCB A. Solder resistor R7 onto PCB B by lifting one of the resistor legs towards ground pin G.

  • Page 7: Resistors & Inductors

    PCB Assembly ~ Components List ~ PCB A PCB B Resistors & Inductors L1/L2 47uH 330k 300k 150k 6.8k R15/R16 150k R3/R6 560r R4/R5 68M/60M R18/R19 2.2k In this step, we finish soldering the resistors along with the inductors: Solder all the remaining resistors to their corresponding locations.
  • Page 8 Pro Tip! You may find that some circuits require resistors to be Wheatstone Bridge matched to a high degree of precision. In fact, the U87 circuit falls into that category where R18 and R19 must be matched to less than 0.4% of each other. Most ohmmeters are not up to the task and this is where the wheatstone bridge comes into play.

  • Page 9: Tantalum Capacitors

    PCB Assembly ~ Components List ~ Tantalum Capacitors PCB A 22uF 4.7uF Next, we will start working on the capacitors, starting with the tantalum kind: Solder all the tantalum capacitors onto PCB A. Trim any excess with wire cutters after soldering.

  • Page 10: Film Capacitors

    PCB Assembly ~ Components List ~ Film Capacitors PCB A PCB B 0.033uF C2 0.01uF 0.47uF 0.01uF C16/C17 330pF It's time for the film capacitors in this step: Solder all the film capacitors except for the Styroflex which will be soldered later on. Trim any excess with wire cutters after soldering.

  • Page 11: Electrolytic Capacitors

    PCB Assembly ~ Components List ~ Electrolytic Capacitors PCB A C11/C13 2.2uF 10uF In this step, we take care of the electrolytic capacitors: Solder all the electrolytic capacitors onto PCB A. Trim any excess with wire cutters after soldering. ~ Build Notes ~ Double-check the orientation of the capacitors against the PCB marking.

  • Page 12: Jfet Transistor

    PCB Assembly ~ Components List ~ JFET Transistor PCB A 25k Trimmer JFET Transistor Let's focus on the JFET transistor and the trimmer resistor for now: Solder the JFET transistor onto PCB A with its middle pin (the gate terminal) lifted towards ground pin GG.

  • Page 13: Styroflex Capacitors

    PCB Assembly ~ Components List ~ Styroflex Capacitors PCB A PCB B C6 220pF C1/C4 470pF Almost done with the capacitors! Before finishing up 10pF with the Styroflex capacitors, let's clean the PCBs 560pF first: Clean off any flux or solder residue using isopropyl alcohol and a toothbrush.

  • Page 14: Toggle Switches

    PCB Assembly ~ Components List ~ Toggle Switches PCB C 2 x Switch 2-way 1 x Switch 3-way This step completes the PCB assembly with the toggle switches: Solder the 3-way toggle switch onto the PAT slot on PCB C and the remaining 2-way toggle switches onto the LC and PAD slots.

  • Page 15: Chapter 3: Pcb Wiring

    PCB Wiring Now that the PCBs are assembled, we can link them together by using silver teflon wires: Cut and strip four pieces of wires to appropriate lengths. Wires should run from the back of each PCB. Wire point G of PCB B to GG of PCB A from the back of each isolated turret.

  • Page 16: Chapter 4: Switch Wiring

    Switch Wiring Now let's do the same for the switch PCB by wiring the pattern, low-cut and pad selectors: Cut and strip seven pieces of wires to appropriate lengths. Wires should run from the front of PCB B to the back of PCB C.
  • Page 17 Did You Know ? Polar Patterns Multiple polar patterns on a microphone can be obtained in various different ways including mechanical and electrical methods. Mechanical methods make use of air vents in the microphone body to allow or prevent sound to penetrate from the back of the capsule in order to achieve different diaphragm pressures.

  • Page 18: Chapter 5: Transformer Wiring

    Transformer Wiring Let's tackle the transformer wiring now before securing it into its designated slot on the PCB: Wire the black wires to points p+ and p-. Wire the yellow wires to points s+ and s-. Secure the transformer onto the PCB by using the provided zip ties through the PCB holes.
  • Page 19 Pro Tip! Transformer Windings You may stumble upon a scenario where you are unsure as to which wires belong to the primaries or secondaries of your transformer. Some may even be wired incorrectly from the factory! Therefore, checking the resistance on the windings can be a useful method for determining the correct wiring.

  • Page 20: Chapter 6: Xlr Wiring

    XLR Wiring Finally, let's wrap up the main microphone assembly before calibration by wiring up the XLR connector: Wire Pin 1 of the XLR to 1 of PCB A, Pin 2 to 2 and Pin 3 to 3. Secure PCB C onto the top of the microphone body by using three M2 x 6mm standoffs and three M2 x 12mm screws.
  • Page 21 Did You Know ? Circuit Designations The original U87 was designed with the traditional German tuchel connector in mind and therefore, this is the circuit U87i designation without any affixed letters. Later on, the circuit was adapted to accommodate the American switchcraft connector also known today as XLR and was named the U87i.

  • Page 22: Chapter 7: Calibration

    Calibration Drain Voltage Measurement Now let's calibrate the JFET transistor by measuring its drain voltage: Connect the positive probe of your multimeter to the drain terminal of the transistor. Connect the negative probe of your multimeter to the common ground. Set the multimeter to the 20V DC range.

  • Page 23: Thd Measurement

    Calibration Alternatively, if you have access to an oscilloscope or a THD Measurement measurement software that can display THD levels, you can follow the following steps for a more accurate calibration procedure: Connect a mic preamp of your choice to the microphone with an XLR cable.
  • Page 24 Pro Tip! JFET IDSS Measurement One of the most crucial steps to a great-sounding U87 microphone is the calibration of the bias signal that feeds the JFET. The reason behind this is that the quality of JFETs can vary considerably and therefore every circuit must be calibrated to each transistor in order to provide the best THD response.

  • Page 25: Chapter 8: Capsule Wiring

    Let's finish the last step of the build by wiring the capsule: Capsule Wiring Secure the capsule onto the saddle with two 0-80 x 3/16" screws. Attach one of the backplate wires to the side of the capsule with a 0-80 x 1/8" screw and the other one through one of the saddle screws.
  • Page 26 Did You Know ? Capsule Backplates The original K87 capsule on the U87 was manufactured with electrically-isolated backplates and since the capsule was a dual-diaphragm design, it came with 4 terminals. When the circuit design was changed to the U87a version in 1986, the capsule was switched to the K67 as used in the famous U67 tube microphone manufactured prior to the U87.

  • Page 27: Chapter 9: Troubleshooting

    Troubleshooting Congratuations on finishing up the Yuzu 87 FET ~ Q & A ~ microphone build! Q: I hear a loud pop when flicking the switches. If for some reason your microphone is not behaving as intended, you can follow these basic steps for A: This is unfortunately normal behavior due to the troubleshooting: nature of toggle switches used in this kit.

  • Page 28: Acknowledgements

    Acknowledgements Dany Bouchard (poctop) at vintagemicrophonepcbkit.com Pei-Chung Ting (chunger) at store.studio939.com AMI/TAB Funkenwerk at tab-funkenwerk.com Heiserman Audio at heisermanaudio.com ShuaiYin Electronics at shuaiy.com...

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