Build a Classic JFET Buffer Pedal 🚀
- JC - Linear Systems
- 4 days ago
- 2 min read

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
Stompville’s guide and schematic: great step-by-step build article (stompville.co.uk, pedalpcb.com, effectpedalkits.com, diyeffectspedals.com, circuitdiagram.co, effectpedalkits.com, muzique.com, forum.pedalpcb.com).
EffectPedalKits overview with J113-based variant and theory (effectpedalkits.com).
dpFX Pedals shows a clean hand-drawn version using 2N5458 (dpeffects.com).
Simple JFET Buffer board from PedalPCB if you're looking for convenience (pedalpcb.com).
🔗 References
Stompville – JFET Guitar/Instrument Buffer (schematic image above) (stompville.co.uk)
EffectPedalKits – JFET Buffer tutorial (effectpedalkits.com)
dpFX – JFET Buffer/preamp schematic (dpeffects.com)
PedalPCB – Simple JFET Buffer module (pedalpcb.com)
✅ 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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