Clean Boost

The LPB-1 on nine strips with no cuts · One transistor, about 18 dB · By Onion Madder · Mess O' Pedals

The Electro-Harmonix LPB-1 is the most-copied one-transistor booster there is, and this is it on a nine-by-thirteen scrap of stripboard with no cuts and no links: every part stands across strips in its own column. One 2N3904, five resistors, two capacitors, and it turns whatever you feed it into about eight times as much of the same thing, from a low impedance that will drive anything after it. Two things the original does not have: a Schottky in the supply so a backwards battery does nothing, and a 1M on the input so the board is quiet about being switched. Built, and it works.

The Clean Boost layout drawn as a stripboard diagram, titled Clean Boost, 13 by 9 stripboard. Nine orange copper strips lettered a to i run left to right with thirteen columns numbered above them, and no strip is cut. Standing across the strips in their own columns are the Schottky diode D1 at the top left, the resistors R1 and R3 near it, the transistor Q1 in the middle with its legs marked C, B and E on three strips, the resistors R2 and R4 below, the film capacitors C1 and C2 as green boxes, and the resistor R5 near the right. Beside the board its panel parts are drawn with a wire to each hole: a 9 V battery snap and a toggle switch on the left, two 1/4 inch jacks on the right. Holes carrying wires off the board are labeled in the margins: plus 9V and IN on the left, OUT and GND on the right. Below it the same board is drawn a second time from the solder side, mirrored, with the column numbers running right to left and every solder point as a dark dot. A parts list runs underneath and a credit line reads Made with Copper Bottom. — The board as the layout file draws it, with the panel parts beside it: the battery, the power toggle in its positive lead, and the two jacks. The file itself is below. The lower drawing is the solder side, mirrored - the side you actually work on.

The Clean Boost built on a small piece of stripboard, lying on a dark bench with its parts standing up and wires trailing off it: a 9 V battery standing behind it, a potentiometer and a small blue toggle switch on flying leads, and a 1/4 inch jack with a blue right-angle plug in it. At the top right another jack and the ring modulator board with its two yellow transformers are wired to it. — Built and working, on the bench in September 2026. The board, a 9V battery, a small toggle in the battery lead as the power switch, the jacks on flying leads, and the ring modulator board wired in at the top right, which is how the result below was found. The pot in the photo is the LPB-1's volume pot, tried and not kept.

What you'll need

tap to expand / collapse

1× 2N3904 NPN transistor (Q1) - spot it: the small black half-round body with the type printed on the flat face. With the flat face toward you and the legs down, the legs are E, B, C left to right. On this board it sits in one column with its three legs across three strips, and the drawing labels each leg
1× 1N5817 Schottky (D1) - spot it: small black body, band at the cathode end. Reverse-polarity protection; it stands up, band toward the clean rail
1× 430K (yellow-orange-yellow, R1) - from the rail to the base
1× 43K (yellow-orange-orange, R2) - from the base to ground. Do not swap these two. 430K up and 43K down puts the base near a volt, which is where the transistor amplifies. The other way round pins the base near the rail and it does nothing but pass DC
1× 3K3 (orange-orange-red, R3) - the collector load. Stands up
1× 390R (orange-white-brown, R4) - the emitter resistor. The gain is very nearly R3 divided by R4
1× 1M (brown-black-green, R5) - the input pull-down. Stands up. It gives the input cap somewhere to sit, so a bypass switch, if you add one, does not pop
2× 100n film (104, C1 and C2) - in and out coupling. Ceramic discs work; film is quieter
1× stripboard, 9 strips × 13 holes or larger. No cuts, no links: every part stands across strips in its own column

Off the board

1× SPST toggle, the power switch, in the battery's positive lead
2× 1/4 in jack, in and out
1× 9V battery snap, or a DC jack. The board draws about half a milliamp, so a battery lasts about as long as its shelf life
No pot. The LPB-1 puts a 100k volume pot on the output. Mine had one on the bench and it did nothing worth a hole in the box, so it is not on the drawing. If you want it: lug 3 to OUT, lug 1 to ground, wiper to the output jack

The transistor, from the front

 2N3904, TO-92, flat face toward you, legs down
        _____
       (     )
       |_____|
        | | |
        E B C      emitter  base  collector

The three legs land on three different strips in one column: emitter on the strip that feeds R4, base on the strip R1, R2 and C1 share, collector on the strip R3 and C2 share. The drawing labels each leg where it lands. A transistor in backwards is the classic way a one-transistor booster does nothing, so check the letters against the netlist before you power it.

The layout file is the guide

Like every layout on this shelf, the build document for this one is the file itself: ↓ Download Clean_Boost.json - import it into Copper Bottom and the editor gives you the board picture, the placement walkthrough, the electrical checks and a printable build sheet, all from the same file. No coordinates are written out on this page on purpose: the editor is the viewer, and a number typed twice is a number that can drift.

The netlist

Quoted verbatim from the layout file. It was written from the board, so checking the board against it can only pass - what it is for is carrying the circuit somewhere else, and telling you what each strip is supposed to be doing while you stare at it.

# Clean Boost - LPB-1 values, one transistor, no cuts # 9 strips of 13 holes, 9 parts, 0 chips, 0 cuts # # Every strip is one node. Parts stand across strips, each in its own column. # Diode band points at its second hole (the rail). RAW: @+9V D1.A RAIL: D1.B R1.A R3.A COL: R3.B Q1.C C2.A BASE: R1.B R2.A Q1.B C1.B EMIT: Q1.E R4.A IN: @IN C1.A R5.A OUT: C2.B @OUT GND: R2.B R4.B R5.B @GND

The off-board wiring

Four pads leave the board, and none of them needs explaining.

Pad	Goes to
+9V	The battery snap's red lead through the power toggle, or a DC jack's center pin. It reaches nothing but the Schottky, so a backwards plug does nothing at all
GND	Ground: the battery's black lead and both jack sleeves
IN	The input jack's tip
OUT	The output jack's tip

Built, and heard

Built on the bench in September 2026, straight off the file above, and it works great as a booster. The power switch is a plain toggle in the battery's positive lead; the LPB-1's volume pot was on the bench too and came off, because it did not do anything worth keeping.

It was drawn for the ring modulator, and that part did not work out. The ring hears my synths, barely hears a bent toy and does not hear a guitar, and the theory was that a passive diode ring just needed more signal from a lower impedance in front of it. This board is exactly that, it went in front of the program input, and it did nothing for the ring at all. So the ring mod's problem is not level, and this became a booster in its own right, which is a better outcome than the one I was after.

How it works, in one breath

It is a single common-emitter stage, the oldest amplifier there is. R1 and R2 divide the supply down to about 0.8 V on the base, which puts about 0.2 V on the emitter and half a milliamp through the transistor, and leaves the collector resting near 7.5 V with room to swing. The signal comes in through C1 onto the base, and whatever it does to the base voltage, the collector does about 3K3 ÷ 390R, roughly eight times, upside down. That is about 18 dB. C2 takes the DC off the collector and hands the signal to the jack. Those are the circuit's numbers; the board works, but nobody has put a meter on it yet.

Things to try

The volume pot back. A100K, lug 3 to OUT, lug 1 to ground, wiper to the output jack. It is on the LPB-1 and not on this one; your ears may differ from mine
Less gain. A bigger R4 lowers it: 1K in place of the 390R is about three times instead of eight, closer to a buffer than a boost. Untested
A true bypass. A DPDT with the jacks on its commons, one throw pair jumpered straight through, the other pair to IN and OUT. R5 is already on the board so the switch does not pop. Untested
In front of something quiet. A bent toy, a contact mic, a passive pickup into a pedal that wants line level. That is what a clean boost is for

Circuit values from the Electro-Harmonix LPB-1, the one-transistor booster half the pedal world has copied since 1968. The Schottky on the supply, the pull-down on the input and the layout are Onion Madder's, drawn in Copper Bottom. No drill template yet; it is not boxed.