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Build a Classic JFET Buffer Pedal 🚀


If you're looking to preserve your guitar's tone over long cables or through multiple pedals, a JFET buffer is an ideal first step. It's a simple, low-noise solution that matches the high impedance of your pickups to the rest of your signal chain. Here's how it works and how to build one.


🎛️ How It Works


  • Input coupling and RF filter (R1, C1): These components block DC and filter out unwanted high-frequency noise.

  • Biasing network (R2–R6): Sets the JFET’s operating point around half the supply voltage for optimal performance.

  • JFET source-follower (Q1): Provides near-unity voltage gain, incredibly high input impedance, and low output impedance.

  • Output coupling & load (C3, R4): Removes DC and ensures clean transitions.


The common design uses JFETs like the 2N5457, J201, or MPF102, and operates on a 9 V supply.


🔧 Building Tips from Stompville


  • Use any general-purpose JFET—2N5457, J201, MPF102—with the same pinout (stompville.co.uk, muzique.com).

  • Input impedance is set by R2; values up to 10 MΩ are acceptable.

  • Bias current around 70–200 µA (via R3 and a current source bias) ensures low power draw and transparency.

  • Adjust R1/C1 for your preferred RF cutoff—it defaults around 33 kHz at 4.7 kΩ and 470 pF (stompville.co.uk).


🛠 Parts List (Typical Values)

Component

Value

Description

R1

4.7 kΩ

Input RF filter resistor

C1

470 pF

RF filter capacitor

R2

680 kΩ – 2 MΩ

Bias voltage divider

R3

4.7 kΩ

Sets JFET source-bias current

R4

680 kΩ

Output load

R5, R6

1 MΩ each

Gate-source biasing

C2, C3

10–47 µF

Input, output coupling

Q1

JFET (2N5457 etc.)

Core buffer transistor

📌 Why Use a JFET Buffer?


  • High input impedance protects your pickup tone.

  • Low output impedance drives long runs or pedal chains effectively.

  • Zero gain – no added coloration, just clean signal preservation.

  • Low noise and power consumption—perfect for pedalboard integration.


🧰 Learn More & Build Yours



🔗 References



✅ Ready to Build!


Much of the magic lies in sourcing a good JFET and drilling a couple of biasing resistors to hit ~½ Vcc at the source.

 
 
 

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