TH Custom Effects Build Documentation · V1.3 · 2013

All-in-One

Universal Recording & Practice Tool — V1.3

A multi-input mixer, FX-loop, tone shaper, speaker emulator and DI box on one PCB. Built around three TL07x op-amps, it combines guitar input gain, send/return loop, aux mixing, single-knob tone, soft-clipping speaker saturation, two cascaded 24 dB Sallen-Key low-pass voicings, and a balanced XLR line output.

Guitar + Aux + FX-loop 2× Sallen-Key 4th-order LP Ge/Si soft clipping Balanced XLR DI 9 V DC 1590E enclosure 3× DIP-IC build
01

Overview & Features

All-in-One block diagram showing signal flow from guitar/aux/FX-loop through gain, mix, tone, saturation and filter stages to AMP-OUT and balanced XLR line-out

Block diagram — signal paths from inputs through gain, mixer, tone, saturation, filter and dual outputs.

The All-in-One is the Swiss-army knife of the TH Custom Effects line-up: a single PCB that brings together everything you need for recording, home practice and small-stage use. Despite the high parts count it is an easy build — board-mounted pots and switches mean almost no off-board wiring.

Depending on which sections you populate, the All-in-One can act as all of the following — together or in any subset:

Input gain stage

Buffered guitar input with 1 MΩ-lin GAIN pot. Sets the level feeding the FX-loop and downstream mixer.

FX-loop send/return

True buffered send and return — drop any external pedal chain into the loop without impedance mismatch.

Wet/Dry blender

25 kΩ-lin pot blends FX-return signal with the dry guitar — full panner, 100 % wet to 100 % dry.

Aux mixer

Stereo-summed AUX input with its own log volume pot. Plug in a phone or backing-track player.

Tone control

Single-knob wide-range tone — passive Baxandall-style tilt around an active op-amp stage.

Speaker saturation

Soft-clipping stage with germanium and silicon diodes plus a 30 Hz high-pass — emulates a driven cab.

Dual cascaded LP filter

Two switchable 12 dB Sallen-Key low-passes in series — 4.8 kHz then 3.98 kHz, totalling 24 dB/octave.

Balanced XLR line-out

TL082 differential driver feeds an XLR socket — true balanced DI with two complementary phases.

Three independent outputs

AMP-OUT (full mix, post-tone), MIC/LINE A & B (post-filter), and LINE-OUT — feed amp, recording chain and PA from one box.

Modular by design: the prototype was built with the All-in-One main board plus optional external modules (Valv-e-tizer tube preamp, Headphone Amp + Stereo-Sim, 10 W power amp). Build only the sections you actually need — most stages can be left unpopulated and bypassed with a wire link.
02

Circuit Theory

All-in-One V1.3 full schematic

Schematic — all stages on a single sheet. Power section bottom-left, signal flow runs roughly left-to-right and top-to-bottom.

Active devices

Three op-amp packages handle every signal stage:

IC1 (TL074, quad) — Tone control (A), speaker-saturation high-pass & clipping driver (B), low-pass stage 1 (C), low-pass stage 2 (D).
IC2 (TL074, quad) — Input gain buffer (A), FX-loop return / Wet-Dry mixer feedback (B), Wet/Dry mixer summing (C), main mix bus driver into the AMP-OUT chain (D).
IC3 (TL082, dual) — Balanced XLR driver — non-inverting and inverting halves produce the two complementary phases for pin 2 (XLR-2) and pin 3 (XLR-3).

Power and bias

D9 (1N4001) provides reverse-polarity protection on the +9 V input, followed by bulk decoupling C21 (220 µF) and the local rail bypass C23 (100 n). The bias network is split into two virtual references: VR (the standard half-supply mid-rail set by R30 / R31 = 22 k each, bypassed by C18 22 µF) and VC (a second mid-rail, decoupled by R39 22 k and C27 22 µF, used by stages that need an isolated quiet reference). Splitting VR and VC keeps switching transients on the AMP-OUT path out of the sensitive XLR driver.

Signal path

Stage 1 — Input gain (IC2A). Guitar enters via C9 (10 µF coupling) into a 1 M pull-down (R42) and a non-inverting op-amp gain stage. R16 (100 k) and the GAIN pot (1 M-lin) in the feedback path set the gain from unity (pot at min) up to ×11. Output at C13 (10 µF) feeds both the FX-SEND pad and the wet/dry mixer.

Stage 2 — FX-loop return (IC2B). FX-RETURN comes back via R28 (27 k) and R29 (14 k) — these set the return level with a small attenuation, then C15 (100 n) couples into IC2B configured as a non-inverting buffer with R23 (82 k) / R2 (56 k) gain ratio. C17 (100 p) is a feedback HF roll-off keeping the loop stable. R3 (100 k) provides input bias.

Stage 3 — Wet/Dry mixer (IC2C). The dry signal (R17, R13 = 33 k each) and wet signal (R18, R14 = 33 k) feed the WET/DRY 25 k-lin pot wired as a panner. The pot wiper goes to IC2C's +IN; R10 (10 k) and R9 (100 k) set the inverting gain, and R7-style summing keeps the mix bus low-impedance. Output appears at C4 (10 µF).

Stage 4 — Aux mixer. AUX-IN passes through C1 (10 µF) to the AUX-IN-VOL 100 k-log pot, which feeds the same summing junction as the wet/dry output via R10 (10 k). This is a passive mix into IC2C's feedback summing junction — no separate aux op-amp.

Stage 5 — Tone control (IC1A). A wide-range single-knob tilt-style active Baxandall, built around the TONE 100 k-lin pot. R24 / R27 (47 k) set the bass and treble pivot levels; R25 / R26 (15 k) define the slope; C14 / C16 / C19 (10 n each) define the corner frequency. The R41 1 M sets DC feedback; R40 1 M provides input bias from VR. Output at C30 / C29 (100 n) feeds the next stage.

Stage 6 — Speaker-saturation emulation (IC1B + diode network). A 2nd-order Sallen-Key high-pass (R20 33 k, R22 150 k, C10 / C12 47 n each) followed by a soft-clipping stage. The SATURATION 10 k-lin pot drives the signal into a six-diode clipping network: two 1N4148 silicon diodes (D2, D4) set a hard cap at ±0.6 V, and six AA112 germanium diodes (D1, D3, D5, D6, D7, D8) in series-parallel arrangement provide soft asymmetric clipping with a lower threshold (~0.3 V each). The high-pass before the clippers removes sub-bass that would otherwise pump the diode network. R1 (1 k) is a series build-out resistor at the output of the clipping bus. The HP-BYPASS switch lets you skip the whole stage.

Stage 7 — Cascaded LP filters (IC1C + IC1D). Two 2nd-order Sallen-Key low-passes wired in series. IC1C uses R12 / R7 (22 k each), C8 (2n2) and C6 (1 n) for a 4.8 kHz corner. IC1D uses R5 / R11 (22 k each), C11 (3n3) and C5 (1 n) for a 3.98 kHz corner. R6 / R15 are 0 R jumpers between the stages. The LP-BYPASS / LP-BYPASS1 switches allow individual or full bypass of the filter chain. See section 03 for the full analysis.

Stage 8 — Output volumes & AMP-OUT (IC2D). The MIX-VOL 100 k-log pot feeds IC2D wired as a unity-gain inverting buffer (10 k / 10 k). The FX/MIX SPDT switch lets you select pre- or post-saturation source for AMP-OUT. C20 (10 µF) couples to the AMP-OUT pad. Separately, the VOLUME 10 k-log pot feeds the LINE-OUT pad through R8 (470 R) and R3 (470 R) build-out resistors that set the recording-level output impedance.

Stage 9 — Balanced XLR driver (IC3A + IC3B). C26 (220 n) couples the line-level signal through R36 (330 k) bias resistor to the IC3A non-inverting input, followed by R32 / R37 / R38 (1 k / 10 k / 10 k) gain network and C24 (10 µF) coupling to XLR-2. IC3B is the inverted phase: R34 / R35 (10 k / 10 k) at unity-gain inverting, C25 (10 µF) coupling to XLR-3, with R33 (1 k) build-out and R38 (10 k) feedback. The two XLR pins carry the same signal in opposite phase — true balanced output, common-mode-noise-rejecting.

03

Filter Analysis

The filter section is the heart of the All-in-One's voicing. It contains three Sallen-Key 2nd-order stages: one high-pass that defines the bottom edge of the speaker-saturation chain, and two low-passes that cascade to a 24 dB/octave 4th-order brick-wall in the recording path.

Speaker-saturation high-pass (IC1B)

A 2nd-order Sallen-Key high-pass sits in front of the diode clipping network. Its job is to remove sub-audio content that would otherwise modulate the clippers and produce muddy, pumping artefacts. The labelled "30 Hz" in the schematic is the design-intent corner; the calculated value with the populated parts is closer to 48 Hz. The Q is well below Butterworth, giving a gentle skirt that does not boost low-mid.

Speaker-Sat HP — IC1B

2nd-order Sallen-Key high-pass · 12 dB/oct
R20
33 kΩ
R22
150 kΩ
C10
47 n
C12
47 n
f₀
48
Hz
Q
0.38
overdamped
slope
12
dB/oct
f₀ = 1 / (2π × √(R20 × R22 × C10 × C12))
Below the corner, response rolls off at 12 dB/oct so 60 Hz hum and stage-floor rumble are heavily attenuated before they reach the clipping diodes.

Cascaded low-pass — IC1C → IC1D

Two Sallen-Key low-passes wired in series. Each individual stage is 12 dB/oct (2nd-order); cascaded they form a 4th-order, 24 dB/oct brick-wall low-pass. The two corners are intentionally staggered — IC1C at 4.8 kHz, IC1D at 3.98 kHz — so the combined response begins rolling off softly above 4 kHz and reaches its full 24 dB/oct slope by 5 kHz. Either stage can be bypassed individually with the LP-BYPASS switches to soften the cut.

LP Stage 1 — IC1C

2nd-order Sallen-Key · 12 dB/oct
R12
22 kΩ
R7
22 kΩ
C8
2n2
C6
1 n
f₀
4877
Hz
Q
0.74
~Butterworth
slope
12
dB/oct
Higher Q (≈ 0.74) gives a slight peak just below corner — adds a small "edge" to the upper-mid response that helps cut through a mix.

LP Stage 2 — IC1D

2nd-order Sallen-Key · 12 dB/oct
R5
22 kΩ
R11
22 kΩ
C11
3n3
C5
1 n
f₀
3982
Hz
Q
0.91
resonant
slope
12
dB/oct
Higher Q (≈ 0.91) places a noticeable resonance just below 4 kHz — a useful "speaker presence" peak that emulates the upper-mid bump of a typical 12" guitar speaker.
f₀ = 1 / (2π × √(R1 × R2 × C1 × C2)) | Q (LP) = √(R1·R2·C1·C2) / (C2 × (R1 + R2))

Customising the LP corners

The filter values define the speaker emulation voicing. If the stock 4.8 / 3.98 kHz pair sounds too dark, raise the corners by reducing C8 and C11. Keep C5 and C6 unchanged — they set the Q of each stage.

ChangeFromToNew cornerVoicing
C82n21 n≈ 7.2 kHzBrighter, more open top end on stage 1
C8 + C62n2 / 1n1 n / 560 p≈ 9.6 kHzFully open — minimal speaker emulation, line-style
C113n32n2≈ 4.9 kHzStage 2 matched to stage 1 — flatter combined response
C113n34n7≈ 3.3 kHzDarker — emulates older or smaller speaker

Feel free to substitute your own values. For different topologies entirely, Texas Instruments' free Filter Pro software can design a custom 4th-order Sallen-Key low-pass with any chosen corner and Q — just keep the resistors in the 1–22 kΩ range to fit the PCB footprint.

Speaker-saturation clipping

Six-diode soft-clip network — D1, D3, D5, D6, D7, D8 (AA112 Ge) + D2, D4 (1N4148 Si): the germanium diodes start conducting at ~0.3 V each; the silicon pair sets a hard ceiling at ±0.6 V. The combination produces a soft, slightly asymmetric clipping curve with rich even-order harmonics — the characteristic warm "speaker-on-the-edge" feel rather than the harsh edge of pure silicon clipping. The SATURATION pot sets the drive into the diode network, not the level out — turn it up for more compression and harmonics, not more volume.
04

Bill of Materials

Resistors are 1 % metal film ¼ W. Capacitors marked "box film" should be 5 mm or 7.5 mm pitch polyester or polypropylene boxes. Electrolytics should be at least 16 V; the schematic-marked 22 µF / 22 V parts (C18, C27) tolerate 25 V types as direct substitutes.

RefQtyValueColour codeNotes
Resistors — Metal film 1 % ¼ W
R1, R32, R3331 kΩ
BrownBlackBlackBrownBrown
Brown · Black · Black  |  Brown · Brown
Metal film ¼ W
R2156 kΩ
GreenBlueBlackRedBrown
Green · Blue · Black  |  Red · Brown
Metal film ¼ W. Schematic shows 58 k — 56 k is the standard E12 value used on the PCB.
R3, R82470 Ω
YellowVioletBlackBlackBrown
Yellow · Violet · Black  |  Black · Brown
Metal film ¼ W. LINE-OUT build-out resistors
R411k8
BrownGreyBlackBrownBrown
Brown · Grey · Black  |  Brown · Brown
Metal film ¼ W
R5, R7, R11, R12, R30, R31, R39722 kΩ
RedRedBlackRedBrown
Red · Red · Black  |  Red · Brown
Metal film ¼ W. Filter R's (R5/R7/R11/R12) and bias dividers (R30/R31/R39)
R6, R1520 R
jumper / wire link
Wire link — bridge between LP filter stages
R9, R16, R19, R214100 kΩ
BrownBlackBlackOrangeBrown
Brown · Black · Black  |  Orange · Brown
Metal film ¼ W. (Doc table erroneously shows qty 1 — schematic confirms 4)
R10, R34, R35, R37, R38510 kΩ
BrownBlackBlackRedBrown
Brown · Black · Black  |  Red · Brown
Metal film ¼ W. (Doc table erroneously shows qty 4 — schematic confirms 5)
R13, R14, R17, R18, R20533 kΩ
OrangeOrangeBlackRedBrown
Orange · Orange · Black  |  Red · Brown
Metal film ¼ W
R221150 kΩ
BrownGreenBlackOrangeBrown
Brown · Green · Black  |  Orange · Brown
Metal film ¼ W. Speaker-sat HP filter R
R23182 kΩ
GreyRedBlackRedBrown
Grey · Red · Black  |  Red · Brown
Metal film ¼ W
R24, R27247 kΩ
YellowVioletBlackRedBrown
Yellow · Violet · Black  |  Red · Brown
Metal film ¼ W. Tone control bass/treble pivot R's
R25, R26215 kΩ
BrownGreenBlackRedBrown
Brown · Green · Black  |  Red · Brown
Metal film ¼ W. Tone control slope R's
R28127 kΩ
RedVioletBlackRedBrown
Red · Violet · Black  |  Red · Brown
Metal film ¼ W. FX-return level
R29114 kΩ
BrownYellowBlackRedBrown
Brown · Yellow · Black  |  Red · Brown
Metal film ¼ W. FX-return level
R361330 kΩ
OrangeOrangeBlackOrangeBrown
Orange · Orange · Black  |  Orange · Brown
Metal film ¼ W. XLR driver input bias
R40, R41, R4231 MΩ
BrownBlackBlackYellowBrown
Brown · Black · Black  |  Yellow · Brown
Metal film ¼ W. Pull-down / DC-feedback resistors
Capacitors — Film box (non-polarised)
C5, C621 nBox film. LP filter shunt caps tuning — see §03 for alternatives
C812n2Box film. LP stage 1 feedback cap tuning
C1113n3Box film. LP stage 2 feedback cap tuning
C10, C12247 nBox film. Speaker-sat HP filter caps
C14, C16, C19310 nBox film. Tone control corner caps
C7, C15, C23, C29, C305100 nBox film. AC-coupling and supply decoupling
C171100 pCeramic. FX-return op-amp HF roll-off
C261220 nBox film. XLR driver input coupling
Capacitors — Electrolytic (polarised)
C1, C2, C3, C4, C9, C13, C20, C22, C24, C25, C281110 µFPolarised electrolytic ≥ 16 V — observe polarity
C18, C27222 µFPolarised electrolytic ≥ 25 V. VR / VC bypass
C211220 µFPolarised electrolytic ≥ 16 V. Main supply bulk
Semiconductors
IC1, IC22TL074PQuad op-amp, DIP-14. Pin-compatible alternatives: TL084 TL064 RC4136 — TL074 is the standard low-noise JFET-input choice
IC31TL082PDual op-amp, DIP-8. Pin-compatible alternatives: TL072 NE5532 OPA2134 — NE5532 or OPA2134 give lower noise on the XLR output
D1, D3, D5, D6, D7, D86AA112Germanium signal diode, VF ≈ 0.3 V. Substitutes: 1N34A 1N270 OA90 — any small-signal Ge diode with VF ≈ 0.3 V works. Bend the leads gently — the glass body breaks easily.
D2, D421N4148Silicon signal diode. 1N914 works identically
D911N4001Reverse-polarity protection. Any 1N400x family or 1N5817 Schottky for lower drop
Pots — 16 mm right-angle PCB-mount
GAIN11 MΩ B (linear)16 mm right-angle PCB. B taper = linear (Alpha/Bourns convention)
WET/DRY125 kΩ B (linear)16 mm right-angle PCB. Wet/dry panner — linear is correct for blend
TONE1100 kΩ B (linear)16 mm right-angle PCB. Tilt tone — linear preserves symmetric boost/cut
SATURATION110 kΩ B (linear)16 mm right-angle PCB. Drive into diode clip network
MIX-VOL, AUX-IN-VOL2100 kΩ A (log)16 mm right-angle PCB. A taper = audio log — correct for level controls
VOLUME (LINE-VOL)110 kΩ A (log)16 mm right-angle PCB. Recording-level output
Switches
FX/MIX, LP-BYPASS2DPDT on-on-onMouser 633-M202403. Three-position toggle for source / two filter stages
HP-BYPASS1SPDT on-onStandard miniature toggle. Bypass for speaker-saturation high-pass + clip stage
Connectors & Hardware
IN, FX-SEND, FX-RETURN, AMP-OUT, LINE-OUT, MIC/LINE A, MIC/LINE B, AUX-INSolder padsWire to panel-mount jacks of your choice. 6.35 mm mono / TRS for guitar, 3.5 mm for AUX, panel switching jacks for MIC/LINE A and B
XLR-2, XLR-31XLR connectorImportant: wire XLR-2 to pin 2 (hot, IC3A output), XLR-3 to pin 3 (cold, IC3B output). Do NOT connect ground to XLR pin 1 from this PCB — see §06 for the correct grounding scheme
+9 VBAT12.1 mm DC jack or battery snapCentre-negative is the standard pedal convention. Battery snap can be wired in parallel — D9 prevents reverse current either way
IC sockets314-pin × 2, 8-pin × 1DIP sockets recommended — IC swap is the easiest way to taste-test op-amp options
05

Build Guide

The board is dense but logically grouped. Following a strict bottom-up build order — flat parts first, tall parts last — keeps everything sittable on a flat surface during soldering and avoids reflow on previously-fitted parts.

All-in-One V1.3 PCB silk-screen layout showing component reference designators

PCB layout (silk-screen). Top edge carries the pots; left edge carries the LINE-OUT and MIC/LINE pads.

All-in-One V1.3 PCB populated with components

Reference photo — populated PCB before pots are mounted.

Diodes — populate first

Start with D9 (1N4001) at the power input, then D2 / D4 (1N4148), and finally the six AA112 germanium diodes (D1, D3, D5, D6, D7, D8). Bend the AA112 leads slowly with two pliers — the glass body breaks if you stress the leg-to-body junction. Observe polarity (band end = cathode).

Resistors

All 47 resistors next. Sort by value first; check the colour bands against §04 before insertion. R6 and R15 are 0 R wire links — use a clipped resistor lead.

IC sockets

Two 14-pin sockets (IC1, IC2) and one 8-pin (IC3). Notch on the socket should match the silk-screen. Do not insert the ICs yet.

Ceramic and film capacitors

C17 (100 p ceramic) first, then all box-film caps in ascending value: 1 n (C5, C6), 2n2 (C8), 3n3 (C11), 10 n (C14, C16, C19), 47 n (C10, C12), 100 n (C7, C15, C23, C29, C30), 220 n (C26). Non-polarised — orientation does not matter.

Electrolytic capacitors — observe polarity

Long leg = positive. Eleven 10 µF (C1, C2, C3, C4, C9, C13, C20, C22, C24, C25, C28), then C18 / C27 (22 µF), and finally C21 (220 µF). The PCB silk-screen shows the + or stripe marking — do not skip this check.

Off-board pads — wire later

Solder header pins or use direct flying leads at the I/O pads (IN, FX-SEND, FX-RETURN, AUX-IN, AMP-OUT, LINE-OUT, MIC/LINE A, MIC/LINE B, XLR-2, XLR-3, +9 V battery, GND). Wire the panel jacks/switches/XLR last during enclosure assembly.

Bypass switches — HP-BYPASS, FX/MIX, LP-BYPASS, LP-BYPASS1

The two DPDT on-on-on (FX/MIX and one of the LP-BYPASS) and the SPDT (HP-BYPASS) are panel-mount; the second LP-BYPASS1 also panel-mount. Wire short, twisted pairs of solid hookup wire from the PCB pads to the switch lugs.

Pots — mount on the back side of the PCB

The seven 16 mm pots (GAIN, WET/DRY, TONE, SATURATION, MIX-VOL, AUX-IN-VOL, VOLUME) all mount on the opposite side of the PCB so their shafts protrude through the enclosure. Apply double-sided tape to the pot bodies first to make sure the metal cases cannot short any pin protruding through the PCB. Tack the centre lug, push the pot snug to the board, let the solder set, then solder the remaining lugs — this aligns the pots cleanly horizontal.

Trim the pot anti-rotation tabs

Each 16 mm pot has a small bracket / lug on its body that prevents it from rotating in a chassis hole. Clip these off before mounting — they will otherwise prevent the PCB from sitting flush against the enclosure top.

Insert the ICs — last step before power-up

Pin 1 alignment matters — the dot or notch goes to the silk-screen marker. Insert IC1, IC2 (TL074) and IC3 (TL082) only after all soldering is complete.

Detail of 16 mm pot mounted on back side of PCB

Pot mounting detail — note the use of insulating tape between pot body and PCB to prevent shorts.

06

Switching & Wiring

Bypass switches — what each one does

SwitchTypeAction
HP-BYPASSSPDT on-onBypasses the speaker-saturation high-pass + diode clipping stage (IC1B). Off = clean signal, On = saturation engaged.
FX/MIXDPDT on-on-onSelects the AMP-OUT source: FX (post-FX-loop only), MIX (post wet/dry mixer, no tone), TONE (post tone control). Centre position is MIX.
LP-BYPASSDPDT on-on-onThree-way LP filter selector: Pure (both LPs bypassed), 4.8 kHz (only IC1C engaged, 12 dB/oct), 3.98 kHz (both stages engaged, 24 dB/oct cumulative).
LP-BYPASS1SPDT on-onOptional second-stage isolator. Combined with LP-BYPASS, gives finer control over which filter is active. See "Configuration notes" §08.

Output wiring

The All-in-One has four independent outputs, each suited to a different destination:

OutputSourceTypical use
AMP-OUTPost FX/MIX selector, full mix busGuitar amp input — full-range signal with optional tone shaping. No filter on this output
MIC/LINE APost-LP filter, post-volumeHeadphone amp / IEM feed
MIC/LINE BPost-LP filter, post-volumePower amp input / second monitor feed
LINE-OUTPost-LP filter, post-VOLUME pot, single-endedStage mixer / recording interface line input
XLR-2 + XLR-3IC3 balanced driver, post-LP, post-VOLUMEBalanced DI to mixing console / studio interface
XLR pin 1 — do NOT connect to the PCB ground: the All-in-One's signal ground reaches the XLR through the chassis ground only. Wiring XLR pin 1 directly to the PCB GND creates a ground loop with the receiving mixer's phantom-power return path. Use a separate short wire from the chassis to XLR pin 1 only.

FX-loop wiring

FX-SEND is a buffered output ready to drive any standard 1/4" effects pedal input. FX-RETURN is a high-impedance input expecting line-level return signal. With nothing patched, the loop signal still reaches the wet/dry mixer — but the WET/DRY pot has no audible effect because send and return carry the same signal. Use a short patch cable to bridge SEND to RETURN if you want to disable the loop entirely.

07

Enclosure & Layout

The recommended enclosure is a Hammond 1590E (188 × 119 × 37 mm). The seven board-mounted pots and the panel switches all sit on the top face; the I/O jacks are split between the top edge (FX-SEND / FX-RETURN, headphone, AUX), the back edge (IN, +9 V, line outs) and the side (XLR).

All-in-One V1.3 inside the 1590E enclosure with optional sub-modules

Interior layout of the prototype showing the All-in-One main board (green) plus optional Valv-e-tizer tube preamp (blue), Headphone Amp + Stereo Sim (magenta) and 10 W power amp (yellow).

Optional sub-modules

The All-in-One was designed as the centrepiece of a modular system. Three sister boards extend its capability:

Valv-e-tizer tube preamp

External 12AX7 / ECC83 tube input stage feeds the All-in-One IN pad. Adds tube-style overdrive and harmonic warmth before the gain pot.

Headphone amp + stereo-sim

Driven from MIC/LINE A. Provides headphone-level output with simulated stereo width — practice silently with the speaker emulation.

10 W power amp

Driven from MIC/LINE B. Built-in mini speaker amp for desktop practice — no separate guitar amp needed.

Tube preamp mounting: if you use the Valv-e-tizer with a fixed-bias build (no front-panel pots), you still need to mount the 9-pin tube socket securely. A panel-mount socket is the cleanest solution. Test-fit before drilling — the prototype acrylic cover seen above is structural, not decorative: it holds the tube socket and protects the glass envelope from accidental knocks during transport.

Finished prototype

All-in-One V1.3 prototype in 1590E enclosure with all controls labelled

Prototype top panel — all controls and switches in place, with the optional tube preamp visible top-left.

Front-panel labelling: in the prototype above, the TONE pot is unlabelled, and the two right-hand switches were screen-printed in the wrong order — the FILTER selector should read 4 kHz / 5 kHz / Pure and the saturation switch should read On / Off. Plan your panel artwork carefully and check it twice before you commit to a printed front.
08

Configuration Notes

The All-in-One is intentionally over-specified — most users will not need every section. You can leave parts of the circuit unpopulated and hardwire the bypass switches to skip those sections entirely. Below are the four most common simplifications.

Always-on 5 kHz LP

If you always want the 4.8 kHz LP active before the line-out, hardwire LP-BYPASS to the IC1C side and omit IC1D + R5 + R11 + C5 + C11 entirely.

Save: 4 R, 2 C, ½ IC1

No speaker-saturation

Skip the entire IC1B + diode network if you don't need cab simulation. Hardwire HP-BYPASS to bypass and omit R20, R22, C10, C12, all eight diodes, and the SATURATION pot.

Save: 2 R, 2 C, 8 D, 1 pot, ¼ IC1

No tone control on AMP-OUT

If you always want the mixed signal direct to the amp without the tone control involved, hardwire FX/MIX to the MIX position and skip the routing through IC1A.

Save: jumper FX/MIX

Custom LP corner

Use TI's free Filter Pro software to design a different 4th-order Sallen-Key. Keep R5 / R7 / R11 / R12 in the 1–22 kΩ range to fit the PCB footprint; vary C5 / C6 / C8 / C11 freely.

See: Texas Instruments Filter Pro

Recommended interconnection — full pedalboard configuration

The prototype was wired as follows for live use:

FromTo
Guitar INValv-e-tizer input
Valv-e-tizer outputAll-in-One IN pad
All-in-One MIC/LINE B10 W power amp input
All-in-One MIC/LINE AStereo headphone amp
All-in-One LINE-OUTStage mixer / recording interface
All-in-One AMP-OUTExternal guitar amp (no filter on this path)
All-in-One XLR-2 + XLR-3 + chassis groundFOH desk mic input
You've built a serious tool: recording, practice, stage and DI duties in a single 1590E box. The modular philosophy means you can start with just the All-in-One main board and add the optional sub-modules as your needs evolve.

Disclaimer & Licence

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 V1.3.