02
Schematic
Re-Verb V4 full schematic. IC1 = TL074 quad op-amp; IC2 = BTDR-2 reverb brick; REG = 78L05. VB = virtual ground rail (≈ +4.5 V).
Spring reverb pedal with Accutronics/Belton BTDR-2 brick, variable tone shaping, feedback loop, and DEEP boost switch. Fits a standard 1590B enclosure.
If you wish to add reverb to your pedalboard or use it in your amp because it does not have one — you are at the right place. The Re-Verb uses the Accutronics® BTDR-2 digital reverb brick for two reasons: it is easy to use and good sounding.
There are three brick variants: Short (BTDR-2S), Medium (BTDR-2M), and Long (BTDR-2L). The Short version is commonly preferred, but all three have useful reverb times in the 1.5–2.9 second range and each sounds good in practice.
What makes this reverb special is its unique tone control. You can shape the colour of the reverb signal and boost the lower or higher end. When dry and wet signals are mixed, this produces a distinctive character. An additional DEEP boost switch is available for immediate cathedral-like sounds — the tone control still functions in this mode, though with a reduced range.
Rev 4.0 features an optimised layout and adds a feedback loop with a dedicated pot, allowing the reverb tail to self-oscillate for ambient and experimental textures.
Re-Verb V4 full schematic. IC1 = TL074 quad op-amp; IC2 = BTDR-2 reverb brick; REG = 78L05. VB = virtual ground rail (≈ +4.5 V).
The guitar signal arrives at the IN pad and passes through a 100 nF coupling cap (C4) and a 1 MΩ pull-down resistor (R4) to the non-inverting input (+IN) of IC1B. IC1B is wired as a unity-gain voltage follower (OUT tied directly to –IN), presenting a high input impedance to the source. A 2.2 MΩ resistor (R3) to ground sets the DC bias at the input.
The output of IC1B feeds the tone control network (TONE pot, R5, R6, R14, R15, R16, R17, C6, C7) and the IC1C drive stage. The DEPTH switch routes the signal to select Normal or Deep mode (see Section 06).
The TONE pot (100 kΩ linear) is wired between two signal paths. On the CCW side (pin 1), R14 (47 kΩ) connects to the IC1B output bus; C6 (47 nF) to ground forms a mild HF roll-off shelf. On the CW side (pin 3), R15 (47 kΩ) connects to the IC1C output rail; R16 (15 kΩ) with C7 (47 nF) forms the complementary passive network. R17 (15 kΩ) couples the tone pot wiper back to IC1C's inverting input. R5 (240 kΩ) and R6 (47 kΩ) set the baseline gain of IC1C.
IC1C is an inverting amplifier whose output drives BTDR-2 input pin 3. The 78L05 regulator supplies a clean +5 V to the brick's power pin (VA), decoupled by C3 (47 µF). The two brick outputs (OUT1 = pin 6, OUT2 = pin 5) are summed through R7 and R13 (both 5.1 kΩ) to form the wet reverb signal.
IC1D is the output inverting amplifier. R9 (10 kΩ) feeds the summed wet signal to –IN; R10 (33 kΩ) from VB sets the operating point; R11 (12 kΩ) is the feedback resistor. The REVERB pot (25 kΩ linear) attenuates the wet signal before IC1D. C8 (4.7 nF) in parallel with R11 rolls off high-frequency content above ≈ 2.8 kHz.
The FEEDBK pot (10 kΩ linear) taps IC1D's output and returns it through C11 (100 nF) and R19 (33 kΩ) into IC1C's inverting input. The OSC switch optionally routes this through R20 (68 kΩ) to modify the self-oscillation threshold. C12 (100 nF) decouples IC1D's output at the feedback wiper. After IC1D, the signal passes through C9 (1 µF) and R12 (33 kΩ) to the OUT pad.
IC1A has +IN tied to ground and OUT tied to –IN — standard practice to keep the unused op-amp gate stable and low-noise.
Power enters through a 1N4001 reverse-polarity diode (D1). C1 (100 µF) decouples the 9 V rail; R1 and R2 (10 kΩ each) form the virtual ground divider, setting VB ≈ 4.5 V; C2 (47 µF) decouples VB. The 78L05 provides the clean +5 V required by the BTDR-2 digital module, decoupled by C3 (47 µF).
C8 (4.7 nF) in parallel with feedback resistor R11 (12 kΩ) creates a first-order low-pass in the feedback path, reducing closed-loop gain above:
Above ~2.8 kHz the feedback gain decreases, softening high-frequency content in the reverb tail.
| Reference | Qty | Value | Colour Code | Notes |
|---|---|---|---|---|
| Resistors | ||||
| R1 | 1 | 10K | Brown · Black · Black | Red · Brown | Metal film ¼ W |
| R2 | 1 | 10K | Brown · Black · Black | Red · Brown | Metal film ¼ W |
| R3 | 1 | 2M2 | Red · Red · Black | Yellow · Brown | Metal film ¼ W — input pull-down |
| R4 | 1 | 1M | Brown · Black · Black | Yellow · Brown | Metal film ¼ W |
| R5 | 1 | 240K | Red · Yellow · Black | Orange · Brown | Metal film ¼ W |
| R6 | 1 | 47K | Yellow · Violet · Black | Red · Brown | Metal film ¼ W |
| R7 | 1 | 5K1 | Green · Brown · Black | Brown · Brown | Metal film ¼ W — reverb brick OUT1 summing |
| R8 | 1 | 10K | Brown · Black · Black | Red · Brown | Metal film ¼ W |
| R9 | 1 | 10K | Brown · Black · Black | Red · Brown | Metal film ¼ W |
| R10 | 1 | 33K | Orange · Orange · Black | Red · Brown | Metal film ¼ W |
| R11 | 1 | 12K | Brown · Red · Black | Red · Brown | Metal film ¼ W — IC1D feedback |
| R12 | 1 | 33K | Orange · Orange · Black | Red · Brown | Metal film ¼ W — output protection |
| R13 | 1 | 5K1 | Green · Brown · Black | Brown · Brown | Metal film ¼ W — reverb brick OUT2 summing |
| R14 | 1 | 47K | Yellow · Violet · Black | Red · Brown | Metal film ¼ W |
| R15 | 1 | 47K | Yellow · Violet · Black | Red · Brown | Metal film ¼ W |
| R16 | 1 | 15K | Brown · Green · Black | Red · Brown | Metal film ¼ W — tone network |
| R17 | 1 | 15K | Brown · Green · Black | Red · Brown | Metal film ¼ W — tone network |
| R19 | 1 | 33K | Orange · Orange · Black | Red · Brown | Metal film ¼ W |
| R20 | 1 | 68K | Blue · Grey · Black | Red · Brown | Metal film ¼ W — optional, OSC path only |
| Capacitors | ||||
| C1 | 1 | 100 µF | Electrolytic polarised — 9 V rail decoupling | |
| C2 | 1 | 47 µF | Electrolytic polarised — VB virtual ground decoupling | |
| C3 | 1 | 47 µF | Electrolytic polarised — VA (+5 V) decoupling | |
| C4 | 1 | 100 nF | Box film — input coupling cap | |
| C5 | 1 | 100 nF | Box film — decoupling | |
| C6 | 1 | 47 nF | Box film — tone network alt: 10 nF | |
| C7 | 1 | 47 nF | Box film — tone network alt: 10 nF | |
| C8 | 1 | 4.7 nF | Box film — HF shelf on IC1D feedback | |
| C9 | 1 | 1 µF | Box film — output coupling cap | |
| C11 | 1 | 100 nF | Box film — feedback loop coupling | |
| C12 | 1 | 100 nF | Box film — IC1D output decoupling | |
| Semiconductors | ||||
| D1 | 1 | 1N4001 | Rectifier diode — reverse polarity protection on +9 V rail | |
| IC1 | 1 | TL074 | Quad JFET op-amp, DIP-14 alt: TL064 alt: TL084 | |
| IC2 | 1 | BTDR-2L | Accutronics/Belton Digi-Log reverb brick alt: BTDR-2S alt: BTDR-2M | |
| REG | 1 | 78L05 | +5 V voltage regulator, TO-92 | |
| Potentiometers | ||||
| REVERB | 1 | B25K | 25 kΩ linear, 16 mm right-angle PCB mount | |
| TONE | 1 | 100k-lin | 100 kΩ linear, 16 mm right-angle PCB mount | |
| FEEDBK | 1 | 10k-lin | 10 kΩ linear, 16 mm right-angle PCB mount | |
| Hardware | ||||
| DEPTH | 1 | SPDT | Mini toggle switch — DEEP / Normal mode selector | |
| OSC | 1 | SPDT | Mini toggle switch — feedback routing optional | |
The DEPTH SPDT switch changes how the IC1B output is routed into IC1C, altering gain and tone-stack interaction to produce the characteristic cathedral bloom.
IC1B output routes through the full tone control network before reaching IC1C. The TONE pot operates over its full range, allowing precise shaping from warm to bright.
A second signal path sums the IC1B output through a different node into IC1C, increasing effective gain into the brick and shifting the tonal character to a fuller, deeper sound. The TONE pot still functions with reduced range.
The FEEDBK pot (10 kΩ linear) controls how much of IC1D's output is returned to the drive stage. At low settings: subtle density and sustain. At high settings: self-oscillation, producing infinite sustain and a pitched drone.
The OSC switch routes the feedback signal. In one position, feedback is limited to the standard path through R19. In the other, R20 (68 kΩ) adds a second injection point, modifying the oscillation threshold and character.
PCB component placement. BTDR-2 brick across the top; three pots on the reverse side.
Fully populated board with BTDR-2H brick installed.
Solder D1 (1N4001) first — cathode band toward +9 V. Then populate all resistors, starting lowest-profile first.
Fit a DIP-14 socket for IC1. Align notch to silkscreen. Solder two opposing corners first, check alignment, then complete all 14 pins. Do not insert the TL074 yet.
Solder REG in its TO-92 footprint. Confirm flat-face orientation from silkscreen.
Populate C4, C5, C6, C7, C8, C9, C11, C12. Film caps are non-polarised — orientation does not matter.
Solder C1 (100 µF), C2 and C3 (47 µF). Longer lead (positive) goes to the pad marked + on the silkscreen.
Press the BTDR-2 into its 6-pin header. Match the pin numbering on the brick label (6–5–4–3–2–1) to the PCB footprint.
Mount the three 16 mm right-angle pots (REVERB, TONE, FEEDBK) on the rear side of the board. Cover the exposed back of each pot with insulating tape before placing down — solder pins are close to component leads. Press firmly and solder all three pins per pot.
Solder DEPTH (and optionally OSC) mini toggle. Solder the middle pin first, position upright while reheating, then complete the two outer pins.
Pre-bend leads slightly inward, seat in the DIP-14 socket with pin 1 matching the notch, press firmly until flush.
Inspect all joints under good light. Check for IC pin bridges, correct electrolytic polarity, and secure brick seating. Verify +9 V and GND connections at the board edge pads.
Assembled board with three right-angle pots and SPDT toggle switch fitted.
The Re-Verb V4 fits a standard 1590B enclosure. The drill template measures 58 mm × 110 mm.
Drill template for the 1590B enclosure — three knobs (REV, TONE, FDBK), DEEP toggle, input/output jacks, 9 V jack.
Three knobs control reverb level (REV), tone character (TONE), and feedback intensity (FDBK). The DEEP toggle is positioned toward the top-right of the face.
Re-Verb V4 in a brushed-aluminium 1590B enclosure with custom face plate.
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