Valv-e-tizer

The Valv-e-tizer allows you to build a real tube pedal for your pedalboard. Based on the tube and part values chosen it can range from ultra-clean to heavy distortion. The circuit was inspired by Juansolo’s BoobTube design; credit for the original topology goes to him. Board V1.5 adds extra mounting holes to support the tube socket during tube insertion and removal.

The intention is a board that can be used to try out most basic tube-amp circuits without the lethal hazard of working on real high-voltage amplifiers. Tube heaters can run on 12 V or 6 V; the 6 V option is used here to allow standard 9 V pedalboard operation.

Finished Valv-e-tizer V1.5 — 12AU7 tube with LED glow indicator in a 1590BB enclosure.

Valv-e-tizer V1.5 schematic — © 2013 TH Custom Effects.

Voltage Multiplier & Heater Supply

The 9 V rail feeds a Cockcroft-Walton voltage multiplier built from one gate of the CD40106 hex Schmitt-trigger inverter IC (IC1A) and seven stages of diode-capacitor doublers (D1–D7, C1–C6, C8 — all 47 n at 80–100 V rating). IC1A is configured as a self-oscillating square-wave generator with R1 (2k7) and C7 (1 n), running at approximately 309 kHz. Each doubler stage adds roughly one supply voltage; seven stages from a 9 V source yield approximately 50–80 V DC for the tube anode supply. The remaining five gates of IC1 (B–F) are not used for oscillation — their inputs and outputs are chained together to minimise switching noise.

The tube heater is powered through a uA7806 / 78M06 6 V linear regulator (IC2), with C9 (220 µ) as the main supply filter and C10 (47 n) as a high-frequency bypass cap. The 6 V heater runs both triode sections of the selected 9-pin Noval tube simultaneously.

Triode Gain Stage V1A

The guitar signal enters via the IN pad, passes through the C11 (22 n) input coupling cap, then reaches the grid of V1A (the first triode section) with R4 (1 M) providing a grid-leak resistor to ground. The anode load resistor R5 (150 k) connects the plate to the high-voltage rail. The cathode of V1A connects to BIAS1 (5k/10k trimpot) which sets the quiescent operating point; C15 (150 n) bypasses the cathode to ground above ≈ 1.3 kHz, increasing AC gain in the mid and high band. C12 (47 n) is a grid-stopper cap at the output of the anode. The GAIN pot (50k-lin) attenuates the signal between the two triode stages — at minimum gain the signal passes through R5 directly; at maximum the full anode swing is forwarded.

Triode Stage V1B — Two Topologies

The output of the GAIN pot feeds through C16 (47 n) coupling cap into the grid of V1B (second triode section). R7 (100 k) provides grid leak. How V1B is wired depends on the voicing chosen:

Clean & Distortion voicings — Common-Cathode Amplifier. R6 (150 k or 180 k) acts as the anode load resistor; the output is taken from the anode via C14 (1 µ) coupling cap. The cathode connects to R3 (820 R or 0 R jumper) and BIAS2. C17 (150 n) bypasses the V1B cathode above ≈ 1.3 kHz when R3 = 820 R (full bypass when R3 = 0 R jumper). This gives a second voltage-gain stage, so the signal passes through two common-cathode amplifiers in series.

Ultra-Clean voicing — Cathode Follower. R6 is replaced by a wire jumper (0 R), connecting the anode directly to the high-voltage rail. The output is taken from the cathode via C18 (1 µ) coupling cap — not from the anode. This is a cathode-follower (common-anode) stage: it has unity voltage gain (≈ 1×) but very low output impedance, making it excellent for driving cables and downstream effects without loss. C14 is not fitted in this voicing. In the ultra-clean build V1A (common-cathode) provides the voltage gain; V1B (cathode follower) provides impedance buffering.

Tone & Output

The plate of V1B connects through C14 (1 µ) coupling cap into a simple passive high-cut (treble-cut) tone control: the TONE pot (100k-log) shunts C13 (47 n) to ground from the signal line, rolling off high frequencies progressively as the pot is turned counter-clockwise. The output then goes to the VOL pot (100k-log) which controls output level. R2 (100 k, optional) provides a grid-stopper for V1B in certain voicings. R3 (820 R or 0 R jumper) in the V1B cathode path determines the amount of cathode degeneration — 820 R gives a smoother sound; 0 R maximises gain and tends toward harder breakup.

LED Indicator

The on-board status LED is mounted from the PCB underside through a hole in the Noval socket so it glows from inside the tube. R8 (2k2) is the series current-limiting resistor; the LED can be made switchable by lifting R8’s output leg and wiring it to a switch that closes to ground.

Three voicings are listed below. The clean and distortion versions use the same layout but different component values; the ultra-clean version adds a few optional parts. Populate only the values for your chosen voicing.

The BOM lists three different-sounding voicings. The clean and distortion versions are built identically — only the component values differ. The ultra-clean version adds a few optional components. Populate only the values for your chosen voicing; refer to the voicing table in section 06.

PCB top side — populated example.

Side view showing component heights.

PCB assembly diagram — component placement reference.

Small Diodes

Start with D1–D7 (1N4148). These are low-profile and go first. Check polarity carefully — the cathode band must face the direction marked on the PCB silkscreen. All seven multiplier diodes are oriented in the same direction along the chain.

Resistors

Fit R1–R8. Use the colour band SVGs in the BOM to verify each value before insertion. For R3: if building the clean or distortion voicing with 0 R, install a short wire link rather than a resistor. For R2: only fit for the ultra-clean voicing.

IC Socket (DIP-14)

Fit the DIP-14 socket for IC1. Do not insert the CD40106N IC yet. Align pin 1 notch with the PCB marking. Tack two opposite corners before soldering all pins to avoid shifting.

Voltage Regulator IC2

Fit the uA7806 / 78M06 regulator. Check the package orientation — the flat face of the TO-92 or TO-220 package must match the PCB marking. The heater draws significant current; ensure the regulator makes good thermal contact if using a TO-220 package.

Film Capacitors

Fit C7 (1 n), then C11, C12, C13, C15, C16, C17 (signal path). Then fit C1–C6, C8, C10 (multiplier chain). Multiplier caps C1–C6, C8, C10, C16 must be rated 80–100 V minimum. Film caps are non-polarised — orientation does not matter.

Electrolytic Capacitors

Fit C9 (220 µ), C14 (1 µ), and optionally C18 (1 µ, ultra-clean only). Electrolytics are polarised — the long leg (positive) must go into the + pad. C9 is the main supply filter; its + terminal faces the positive supply rail.

LED (underside mounting)

The 3 mm LED is mounted from the underside of the PCB so it shines upward through the hole in the Noval socket and into the tube. Carefully check LED polarity (long leg = anode = +) before soldering. Make sure the LED is centred under the socket hole. Do not solder the Noval socket yet.

Noval Socket

Mount the 9-pin Noval print socket last among through-hole components. Leave a small gap (2–3 mm) between the bottom of the socket and the PCB surface to allow airflow and reduce heat transfer to the board. If your socket has a centre hole, verify the LED sits correctly below it before soldering all socket pins.

Socket mounting height and port detail.

Trimpots & Potentiometers

Fit BIAS1 and BIAS2 (6 mm trimmer pots). Then fit the three 16 mm PCB-mount pots: GAIN (50k-lin), TONE (100k-log), VOL (100k-log). Insert all pots into the PCB before soldering any of them to ensure co-planar seating against the panel.

PCB detail showing BIAS trimpots and main capacitors.

Insert ICs & Tube

After all soldering is complete and inspected, insert the CD40106N into its DIP-14 socket (pin 1 orientation). Do not insert the tube until the pedal is mounted in the enclosure and all wiring is complete. When inserting or removing the tube, hold the socket firmly against the PCB — the V1.5 board has additional mounting holes for a support bracket for this purpose.

Tube insertion. Insert the tube carefully, aligning the pins with the socket holes. A missing or partially inserted pin will result in a dead channel or unexpected behaviour. The V1.5 PCB mounting holes allow a printed or machined bracket to support the socket during tube handling.

Making the LED Switchable (optional)

To make the LED on/off switchable: do not pass the right (output) leg of R8 through its PCB hole. Instead, bend the leg upward and wire it via a SPST switch to ground. When the switch is open, the LED is off; when closed, it lights.

LED switchable wiring — R8 right leg wired to switch, switch to ground.

Three voicings are supported by the PCB. Use the table below to select component values for each voicing. Components not listed are identical across all three builds.

All measurements in millimetres. Print the template at 100% scale (no scaling / fit-to-page) and verify the outer dimensions match before drilling.

1590BB drilling template — verify 95 mm height before drilling.

Single-sided artwork (71 mm × 56 mm). Note: C18 does not appear in the PCB layout — it is an optional through-hole add-on position.

Copper layer (mirrored for toner-transfer / photo-resist).

Component placement layout.

Full PCB assembly overview.

PCBs purchased from TH Custom Effects are intended for DIY and non-commercial use only. Redistribution of PCBs and artwork from this document is not permitted. You may use these instructions and PCBs to build and sell your own product based on PCBs ordered from TH Custom Effects.

© TH Custom Effects 2013–2026. Build documentation V1.0.