How to Build the Business Card Boost Pedal
Your Drunk Beaver business card is a real boost pedal. Here's the full build guide — components, soldering steps, and troubleshooting tips.
You've seen it in the box. Maybe you turned it over a couple of times wondering what those traces on the back are. Maybe someone already told you. Either way — that business card we ship with every Drunk Beaver order is a fully functional boost pedal circuit. Not a decoration, not a gimmick. A real PCB that you can solder components onto and use to push your amp.
I've been shipping these for a while now, and the number one question I get is: "How do I actually build this thing?" Fair enough — I should have written this a long time ago. So here it is. Everything you need to turn a business card into a working guitar pedal.
The circuit is a simple clean boost — just a handful of components. If you've ever soldered anything before, you can do this. If you haven't… well, this guide won't teach you soldering from scratch, but the card is a great first project once you've picked up the basics.
The full KiCad project is on GitHub. You'll find the schematic, board layout, and an Interactive HTML BOM that lets you click through each component and see exactly where it goes on the board. I use interactive BOMs like this myself when assembling Drunk Beaver pedals — it's the fastest way to go from a schematic to a populated board without second-guessing component placement.
The Circuit
It's a single-transistor inverting amplifier — one of the oldest and most fundamental topologies in guitar electronics. If the name doesn't ring a bell, the most famous version probably will: the Electro-Harmonix LPB-1. Same basic architecture. One transistor, a few resistors and caps, and that's it.
The values on this business card PCB aren't random — they come directly from the boost section of our discontinued Fluff pedal. So this isn't a generic example circuit. It's a real design that lived inside a real production pedal.
One thing I love about this card: the PCB layout mirrors the schematic almost 1:1. That's intentional. When you're looking at the board, you're basically looking at the circuit diagram laid out in copper. Makes it a great learning resource — if you can follow the schematic, you can trace every signal path on the actual board.
With different component values, this same topology becomes an LPB-1 clone, a treble booster variant, or a dozen other classic circuits. We'll get to that in the "Experiment" section at the end.
Simulated Frequency Response
Before we solder anything, let's look at what this circuit is supposed to do — in simulation.
I ran the design through CircuitLab with the exact component values from the business card. Here's the frequency response.
You can see the gain curve — how much boost you get across the frequency spectrum. Notice the roll-off on the low end around 56Hz (set by the input coupling cap) and how the high end stays open.
Keep this plot in mind — after the build, we'll measure the real circuit and compare.
Simulated Time Domain
Now the time domain view — feed in a sine wave, see a bigger sine wave come out, inverted (that's the "inverting amplifier" part). Clean, no clipping at low input levels. Push the input harder and you'll start to see asymmetric clipping as the transistor runs out of headroom.
Same story as the frequency response — we'll capture this on the real circuit after the build and compare.
Soldering safety: You'll be working with a hot iron and molten solder. Work in a ventilated space or use a fume extractor — rosin flux fumes aren't good for your lungs. Keep the iron in its stand when you're not using it. Burns happen when you forget where you put it. If you're using leaded solder, wash your hands when you're done. Basic stuff, but worth saying.
This guide assumes you can solder a through-hole joint. If you're completely new to soldering, spend 20 minutes with a beginner tutorial first — YouTube has dozens of great ones. I'm not going to teach soldering technique here, but the business card is an excellent first real project once you know the basics.
Full components list with values and quantities is in the Interactive HTML BOM. Keep it open alongside this guide — it lists every component on the board, and when you hover over one it highlights the exact placement on the PCB image. There are also checkboxes to track which parts you've sourced and which you've placed, so you can work through the build without losing your spot.
What You'll Need
Tools:
- Soldering iron (temperature-controlled preferred)
- Solder (60/40 leaded is easier to work with, especially for beginners — lead-free if you prefer the eco-friendly / RoHS-compliant route)
- Flush cutters for trimming leads
- Silicone soldering mat or anti-static mat to protect your work surface (a sheet of paper works in a pinch)
- Multimeter (for testing)
Components overview:
- Resistors — identified by color bands on the body. Some resistors print the value directly instead of using bands. If you're not sure how to read color codes, search for a resistor color band calculator online, or just measure with a multimeter. Go with 1% metal film resistors — there's no real cost reason to use 5% carbon ones anymore, and tighter tolerance means more predictable circuit behavior.
- Capacitors — the circuit uses both film/ceramic (small, non-polarized) and electrolytic (cylindrical, polarized — has a stripe marking negative). For film caps, look for 5mm lead pitch to match the PCB footprint. They're usually rated 50–63V max, which is way more than enough for a 9V pedal. Don't go higher on the voltage rating — film caps rated for 100V+ are physically bigger and probably won't fit the board. For electrolytics, use at least 16V rated caps. For larger values like 100µF, stick to 25–35V max — anything higher and the can gets too big for the board. Check the BOM for exact values.
- Transistor — a standard NPN transistor in a TO-92 package. The default is a BC-series (e.g. BC549, BC550), but you can experiment — more on that in the "Experiment" section. Optionally, grab a 2.54mm pitch 3-pin socket so you can socket the transistor instead of soldering it directly. These usually come in longer strips (8, 20, 40 pins) — just cut off three. Socketing is optional but recommended for two reasons: it avoids overheating the semiconductor during soldering, and it lets you swap transistors easily when you want to experiment with different gain and voicing.
Hardware:
- Enclosure — a standard 1590B or 125B aluminum enclosure to house the build.
- DC jack — 5.5/2.1mm barrel type (standard guitar pedal power jack).
- Audio jacks — two 1/4″ mono jacks (input and output).
- Footswitch — 3PDT (3-pole, double-throw) for true bypass switching.
- Wire — hookup wire for connecting jacks, switch, and power to the board.
- JST XH 2.54mm connectors (optional) — 2-pin for power and 4-pin for FX I/O. These are the same connectors we use in Drunk Beaver production builds. They make wiring cleaner and connections removable, but plain soldered wires work just as well.
Source everything from any electronics store or your local market. Nothing exotic. Total cost for components and hardware — roughly $20–30.
Step 1: Populate the Polarity Protection Diode
Start with the polarity protection diode — it protects the circuit if someone accidentally connects power backwards. The diode is polarized: match the band on the diode body to the line on the PCB silkscreen. Push it through the pads, flip the board, solder, and trim the leads.
It's a small part, easy to solder, and a sensible first component — if you accidentally reverse your power supply later, this little diode saves everything else on the board.
Step 2: Populate the Resistors
Next: resistors. Lowest-profile components go first — that way the bent leads hold them in place when you flip the board to solder on the other side.
Bend each lead at a 90° angle right at the body, push them through the corresponding pads from the component side (check the IBOM for placement), and flip the board over. The bent legs keep the resistors seated while you solder on the back. Solder one lead, make sure the resistor sits flat, then solder the second. Trim the excess leads flush with your cutters.
Resistors aren't polarized, so orientation doesn't matter. One less thing to worry about.
Step 3: Optional — Sockets & Connectors
This step is optional but recommended — especially if you plan to experiment later.
Transistor socket: Solder a DIP socket (or a 3-pin SIP socket) into the transistor footprint instead of soldering the transistor directly. This lets you swap transistors without desoldering — try different gains, different types, hear the difference. Worth it. I'll use similar SIP-3 sockets for the diodes as well — same idea, easy swaps for experimenting. The diode pads on the PCB are 5.04mm apart, so just cut the middle pin off the SIP-3 socket and it fits perfectly.
JST XH 2.54mm connectors:
- 2-pin for the power pads — makes it easy to connect/disconnect a battery or power wiring.
- 4-pin for the FX I/O pads (input, ground, 9V, output) — clean connection to your jacks.
The pads on the PCB are labeled: "−" for ground, "+" for 9V power, "FX Input", and "FX Output" — so you can't mix them up. All Drunk Beaver pedals except the XR series use this same modular JST setup internally.
These connectors are convenient but absolutely not required. Plain wires soldered directly to the pads work fine. If you're going for a quick and simple build, skip the JST connectors — they're more useful if you want a modular setup.
Step 4: Solder Film Capacitors
Film capacitors are not polarized — they go in either orientation. Same technique as the resistors: insert, flip, solder, trim.
For this boost circuit, all the caps in this step are 100nF — and at that value there's no reason to use ceramics. Film caps are better quality, more stable, and readily available in 100nF. These are the coupling caps (input and output) and any filtering caps in the circuit. Their values directly affect the frequency response — the input cap sets how much bass gets through to the gain stage. We'll talk about swapping values in the "Experiment" section.
Step 5: Solder Electrolytic Capacitor
Electrolytic capacitors are polarized — they care which way they go in. The longer lead is positive, and there's a stripe on the body marking the negative side. Match the polarity markings on the PCB silkscreen. Check the IBOM overlay if you're unsure.
If you put an electrolytic in backwards, it won't work — and it could eventually pop. Double-check before soldering.
Step 6: Place the Transistor
The transistor is the heart of this circuit — it's what does the actual boosting. Three pins: Collector, Base, Emitter. The footprint on the PCB has each pad labeled right on the silkscreen, so you can confirm the pinout at a glance. The layout is designed for NPN European BC-series transistors (BC549, BC550, etc.) — match the flat side of the package to the outline on the silkscreen and push it through. For this build I'm using a BC546B.
Using a 2N-series transistor (2N3904, 2N5088, etc.)? These have a different pinout — the pins are in reverse order compared to BC-series. You need to place it backwards (facing the opposite way from the silkscreen outline) for the pins to line up correctly. Check the datasheet for your specific transistor if you're unsure — confirm BCE pin order against the board pads.
If you installed a socket in Step 3, just push the transistor into the socket. You can trim the legs a bit shorter first if they're too long for a clean fit. If not using a socket, solder directly — leave a millimeter or two of lead between the body and the board for heat clearance.
Solder all three pins (if no socket). Trim leads.
Transistors are sensitive to heat. When soldering directly (no socket), work quickly — in, solder, out. Don't hold the iron on any transistor pin for more than 2–3 seconds. If a joint isn't flowing, pull away, let it cool, and try again. Overheating can permanently alter the transistor's gain characteristics or damage it outright.
Step 7: Mount Pot & 3PDT in the Enclosure
Before wiring anything, mount the potentiometer and the 3PDT footswitch in the enclosure. These are the mechanical anchor points — everything else connects to them or to the main board.
Once the pot is secured, solder the main PCB directly onto the pot lugs. The pot holds the board in place — no extra mounting hardware needed. The board sits right on the pot, clean and solid.
Make sure the board is level and seated properly before soldering all the connections. Once it's tacked in place, it's not going anywhere.
Step 8: Wire Jacks & DC Socket — Daughter PCBs
Now we need to get signal in and out, and power in.
I'm using our own Drunk Beaver production daughter boards for the jacks and DC socket. They make wiring clean and consistent — plug into the JST connectors (if installed) or solder directly. The photo shows the setup.
If you don't have daughter boards (they're not available for sale yet, but I could send them with any order, just ask), the next block shows how to wire it by hand.
Jacks & DC Socket — Manual Wiring
If you don't have daughter boards, here's how to wire jacks and power by hand:
- Input jack: Tip terminal → wired directly to the 3PDT switch. Sleeve terminal → 3PDT ground.
- Output jack: Tip terminal → wired directly to the 3PDT switch. Sleeve terminal → input jack sleeve terminal (ground).
- DC socket: Center (negative) → board "-" pad or black wire of JST connector, also connect to input jack sleeve terminal. Barrel (positive) → board "+" pad or red wire of the connector. (Standard guitar pedal center-negative convention.)
Step 9: Wire the 3PDT Switch & LED — Daughter Board
The 3PDT (3-pole, double-throw) footswitch gives you true bypass switching — when the pedal is off, your signal passes straight through without touching the circuit. The LED is your status indicator.
I'm using a Drunk Beaver 3PDT daughter board here. It handles all the switching logic and LED current limiting on a single small PCB. Solder the switch and LED to the daughter board, connect to the main board, done.
If you're wiring by hand, the next block has the manual approach.
3PDT & LED — Manual Wiring
If you're wiring by hand, here's the standard true-bypass 3PDT configuration. Looking at the switch from the solder side, the nine pins form a 3×3 grid — three columns (poles), three rows. The center row is the common for each pole; the switch toggles between connecting center to top (effect on) and center to bottom (bypass).
- Pole 1 (left column) — input routing: Pin 1 (top) → to board FX Input pad and → jumper wire to Pin 6. Pin 2 (center) → input jack tip. Pin 3 (bottom) → jumper wire to Pin 9.
- Pole 2 (middle column) — LED & input grounding: Pin 4 (top) → LED cathode (shorter leg). Pin 5 (center) → board "−" ground pad. Pin 6 (bottom) → jumper wire to Pin 1.
- Pole 3 (right column) — output routing: Pin 7 (top) → from board FX Output pad. Pin 8 (center) → output jack tip.
For the LED: connect the board's "+" (9V) pad through a current-limiting resistor to the LED anode. The LED cathode goes to Pin 4. When the effect is engaged, Pin 5 (ground) connects to Pin 4 — the LED cathode gets ground, the circuit completes, and the LED lights up. In bypass, Pin 5 (ground) connects to Pin 6 — the board's FX Input is pulled to ground, preventing noise from the floating input stage. The LED cathode is disconnected from ground, so the LED stays off.
4.7kΩ works well for a typical red LED on 9V — but the right value depends on your LED color and forward voltage. Search for an "LED resistor calculator" online to dial it in for your specific LED.
There are plenty of 3PDT true-bypass wiring diagrams online — pick the layout that matches your enclosure.
Test It
Plug your guitar into the input, output to your amp. Apply power. Stomp the switch.
If all goes well — you'll hear your guitar with a bit more guts behind it. Congratulations, your business card is now a guitar pedal 🎉.
No sound?
- Check that your solder joints are actually connected — reflow any that look cold (dull, blob-ish, not shiny).
- Verify electrolytic capacitor polarity.
- Measure voltage on board "+" and "-" pads.
- Make sure the transistor is oriented correctly (BC-series: flat side matches silkscreen, 2N-series: backwards).
- Check power supply polarity. Try a fresh battery if using one.
Weak signal or oscillation?
- A cold joint on the output capacitor is the usual suspect.
- If it squeals, check that your input and output wires aren't running parallel and close together — separate them.
- Measure voltage at the transistor collector — you should see something between 4V and 7V (roughly half supply). 0V or 9V means a problem in the bias network.
Real-World Bode Plot
Remember the simulated frequency response from earlier? Now let's see how the real thing compares.
Here's the bode plot measured on the actual built circuit — same kind of sweep, real hardware.
As you can see the real circuit -3dB low frequency cut-off is a bit lower around 40Hz, compared to simulated 56Hz. The point isn't that they match perfectly — it's that you can predict circuit behavior in simulation before building, and the real result is close. That's how you design pedals: simulate, build, measure, tweak.
Real-World Time Domain
And here's the time domain capture — same input signal as the simulation, measured on the real circuit with an oscilloscope.
Compare this to the simulated time domain plot from the beginning. Same inverted output, same amplitude behavior. Push the input harder and you'll see the same asymmetric clipping characteristics show up in the real hardware. Input signal is 1kHz 600mV sine wave, something you would expect from average humbucker pickups. The output is asymmetrically clipped 8.4V. The circuit gives about 22dB of gain, simulation was more optimistic with something closer to 27dB.
This tutorial is a miniature version of the same workflow I use for every Drunk Beaver pedal: simulate, build, measure, tweak.
Experiment
The board has pads for experimenting with clipping diodes — try different combinations (silicon, germanium, LED) and hear how they color the sound. When the boost pushes hard enough, the diodes start clipping and add harmonic distortion character. Or leave the diode pads empty for a dirty transistor boost.
Alternative component values: With different resistor and cap values, this same circuit becomes an LPB-1 clone — the most famous single-transistor boost ever made. The IBOM shows the stock Drunk Beaver values; the original LPB-1 values are well-documented online. Try both and compare.
Stack it with your other pedals: A clean boost in front of an overdrive or fuzz does magical things. If you've got a Secret Sauce, try running this boost into it — it pushes the clipping stage harder and fattens up the whole thing. Works with pretty much any OD or fuzz. If you're into germanium treble boosters, check out Hoverla — same single-transistor family, different character.
And here's the story behind the stock values on this card: they're lifted from the boost section of our discontinued Fluff pedal. The Fluff is gone, but its boost circuit lives on — in every box we ship 😎.
One more thing: I've been thinking about offering a kit — the business card PCB plus all the components, connectors, and a simple enclosure, ready to build. Would that be something you'd be interested in? Drop a message, or tag me on Instagram — I want to know if this is worth doing.
Built it? I want to see it. Tag us on social media and show me what you made 🦫🍺.
