Guitar Boost Pedal

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Simple Boost guitar pedal.


Using the guitar pedal prototyping board in previous post, I'm going to make a simple Boost guitar pedal. It is a great first build for guitar pedals.

We are going to use a tl072cp op-amp to create this boost

I’ll give you the parts/values and circuit diagrams for this simple boost pedal.

Parts

  • IC: TL072CP

  • Diode: 1× 1N5817 (reverse protection)

  • Resistors: 100 k (×2), 1 M (×1), 10 k (×1), 100–220 Ω (×1), 2.2 k (LED)

  • Pots: B100k GAIN, B100k VOLUME

  • Caps: 100 nF (×2), 10 µF (×2), 4.7–10 µF (×1), 10–33 pF (×1, ceramic/NPO)

  • Hardware: Previous guitar prototype board that we built.

(Electrolytics: “+” toward the TL072/output side as noted below.)

Circuit Diagram



Wiring (non-inverting TL072 boost)

1) Power & decoupling

  • +9V_RAW → 1N5817 → +9V
    (diode anode to +9V_RAW, cathode to +9V)

  • Pin 8 → +9V, Pin 4 → GND

  • 100 µF from +9V to GND

  • 100 nF directly between Pin 8 ↔ Pin 4 (close to IC)

2) Virtual ground (VREF, buffered by the spare op-amp)

  • +9V → 100 k → (VREF_DIV node) → 100 k → GND

  • 10 µF from VREF_DIV → GND

  • Buffer it with op-amp B:

    • Pin 5 (+IN B) → VREF_DIV

    • Pin 6 (−IN B) ← Pin 7 (OUT B) (tie together)

    • Pin 7 (OUT B) = VREF (use this buffered VREF everywhere below)


3) Input

  • IN_TIP → C_IN 100 nF → Pin 3 (+IN A)

  • Pin 3 → 1 M → VREF



  • IN_SLEEVE → GND

4) Gain network (op-amp A)

  • Pin 1 (OUT A) → R_FB 10 k → Pin 2 (−IN A)

  • Pin 2 (−IN A) ↔ GAIN pot (as variable resistor to VREF):

    • GAIN_L1 → Pin 2 (−IN A)

    • GAIN_L2 & GAIN_L3 tied together → VREF

  • C_FB 10–33 pF across R_FB (from Pin 1 to Pin 2) for stability/ultrasonic roll-off

  • Gain ≈ 1 + (10 k / R_gain) → ~1× to ~11× (~0–20 dB)




5) Output & volume (with TL072 isolator)

  • Pin 1 (OUT A) → R_OUT 100–220 Ω → C_OUT 4.7–10 µF

    • Electrolytic + toward R_OUT/TL072, − toward the pot

  • C_OUT → VOL3

  • VOL1 → GND

  • VOL2 (wiper) → OUT_TIP

  • OUT_SLEEVE → GND



6) Now test

Plug your leads into the guitar and your amp, then hear the clean boost pedal circuit you have created.

Single-glance connection table

Some help for troubleshooting all the connections
NodeConnects to
+9V_RAWDC jack + or battery +
+9VAfter 1N5817 cathode; TL072 Pin 8; power caps
GNDTL072 Pin 4; jack sleeves; VOL1; star ground
VREF_DIVBetween 100 k/100 k divider; 10 µF to GND; to Pin 5
VREF (buffered)TL072 Pin 7; goes to Pin 3 (via 1 M), GAIN_L2/L3, other bias refs
IN_TIP3PDT Column A Top
C_IN node3PDT Column A Middle → 100 nF → Pin 3
Pin 3 (+IN A)To 1 M → VREF
Pin 2 (−IN A)To 10 k from Pin 1; to GAIN_L1
GAIN_L2 & L3Tied; to VREF
Pin 1 (OUT A)To 10 k (to Pin 2); to R_OUT (→ C_OUT)
R_OUT (100–220 Ω)Between Pin 1 and C_OUT
C_OUT (4.7–10 µF)+ to R_OUT side; − to VOL3
VOL3From C_OUT
VOL2 (wiper)3PDT Column B Middle
VOL1GND
OUT_TIP3PDT Column B Top
LED++9V through 2.2 k
LED−3PDT Column C Middle
Column C TopGND

Quick power-on checks (no signal)

Other issues that may occur and where to test: -

  • +9V ≈ 8.6–9.0 V (after diode drop)

  • VREF_DIV ≈ 4.3–4.6 V

  • VREF (Pin 7) ≈ same as VREF_DIV (within a few mV)

  • Pin 1 at idle ≈ VREF (audio rides around it)

  • If you hear hiss/oscillation at high gain: confirm C_FB 10–33 pF is fitted and R_OUT 100–220 Ω is in place; keep input/output leads short.

Tone tweaks (optional)

Things you can do to change the sound characteristics outputted: -

  • More bass: increase C_IN to 220 nF.

  • Tighter top end: increase C_FB toward 33 pF.

  • More/less output swing: adjust VOLUME after C_OUT (leave GAIN to set preamp drive).


Conclusion

You have now have a working boost pedal, a first edition to your home built guitar pedals. This is a great first choice as it is simple and leads to creating other future pedals. 
I hope you have enjoyed making this, I certainly have and I hope to show you more of these pedals along with other things in future.
Thanks
Matty

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