Drive architecture and circuit update
Architecture and production values · November 2026
The current production drive voicing, optional clipping stages and feed-forward compressor configuration, using the November 1 bench brief.
One drive path, four combinations
The always-connected LED-feedback drive feeds an optional zener ladder, then optional CRz transistor fuzz. Clean selects the ladder; CRz selects the fuzz. This gives LED feedback alone, LED plus ladder, LED plus fuzz, or all three in series.
Progressive LED feedback
Six red LEDs per polarity share R53 = 470 Ω, with a soft knee around 9 V and ceiling around 12 V. Ring onset depends on input level: about 50 % Dist with a hot pickup, 80–95 % with a light touch. Rail grind starts above about 1.5 V peak at the input jack.
Production zener ladder
Two-step zener ladder: soft shoulder from ±3.65 V, flat at ±4.55 V. The production soft rung uses 3.0 V zeners and 1N914 diodes through R60 = 270 Ω; the hard rung uses 3.9 V zeners with 1N914 diodes. Re-match Volume when changing modes.
CRz fuzz
MMBT3904 and MMBT5088 transistor stages provide the fuzz, with separate bias, gain and level trims. Successive nonlinear stages reshape each other; their asymmetries and harmonics are not simply additive. Overload recovery with fuzz engaged is about 50 ms, a fuzz-stage figure.
Independent VCA dynamics
Comp independently engages the SSI2162 compressor and gate after Aurora Curtain. The input, filters and all clipping combinations work with Comp off. LED rounding is nonlinear feedback; VCA compression is controlled by the separate sidechain.
Current production values
The November 1 production brief gives the current values below. Earlier October exports and Word references preserve development history, but do not define the production calibration.
| Item | November production specification |
|---|---|
| Drive voicing | R5 150 Ω; C3 and C11 47 µF each; mid leg 390 Ω / C25 680 nF; treble leg 1 kΩ / 39 nF |
| Drive feedback | Maximum effective feedback 23 kΩ; R54 220 kΩ; reference sweep 12.2 kΩ |
| Ring and ladder | R53 470 Ω; R60 270 Ω; production shoulders ±3.65 V and flat clamps ±4.55 V |
| Coupling | R58 1 MΩ gives C30 corner 0.72 Hz; every inter-stage coupling corner below 2 Hz |
| Compressor | R31 and R48 2.2 kΩ; R29/R95 100 kΩ; R33 1 MΩ; R39 100 kΩ; C56 220 nF |
Compressor mode and staging
Shipped configuration: JP1 = A, JP2 = B. The compressor sidechain is feed-forward from Audio_In; the PEAK pad stays unbridged. The gate is keyed from the Wall of Ice output through main-board TO_COMP (J23) into compressor J10.
The gate key is pre-distortion and post-Wall-of-Ice, with about 50–60 dB of dynamic range in the supplied bench results. It follows the input rather than the already clipped waveform.
The detector starts compressing at about 0.4 V peak at TP1. Below that threshold there is no compression; above it, gain reduction grows at about 15 dB per volt until the knee clamp limits it to about 21 dB. Knee1 is inert at polish settings.
ERR1 starts at 12–15 kΩ, C_LVL1 at maximum fully CCW, Knee1 at minimum and BLEND1 at 65–75 % wet. Out_LVL1 unity is around 23 % travel (4.6 kΩ). Use the production setup table for timing, gate settings and the maximum-output check.
The gate follows a clean pre-drive tap
Shipped configuration: JP1 = A, JP2 = B. The compressor sidechain is feed-forward from Audio_In; the PEAK pad stays unbridged. The gate is keyed from the Wall of Ice output through main-board TO_COMP (J23) into compressor J10.
The gate key is pre-distortion and post-Wall-of-Ice, with about 50–60 dB of dynamic range in the supplied bench results. It follows the input rather than the already clipped waveform.
Wall of Ice supplies +6 dB ahead of the drive. Its output keys the gate before the notch blend and clipping. The gate’s close sequence includes about 0.3 s detector hold plus the G_SLOW_REL1 ramp; opening is immediate with C56 = 220 nF.
Coupling and DC handling
The production low-frequency specification with filters open is flat to ±0.1 dB from 20 Hz upward in the low-frequency band. Every inter-stage coupling corner is below 2 Hz; C30 / R58 on the main board is about 0.72 Hz and C2 / R33 on the compressor is about 0.71 Hz.
Voicing legs, deliberate filters and the CRz low cut are separate from coupling corners. The U3A presence shelf and Aurora Curtain determine the upper-band balance. The approximately 50 ms overload-recovery result belongs to the fuzz stage, not the whole pedal.
Compressor audio connector
The main board’s J10 COMP connector is crossed relative to compressor J1: main-board J10 pin 2 carries the Aurora return into compressor J1 pin 1 (SigIn); compressor J1 pin 2 (SigOut) returns to main-board J10 pin 1. The switch then chooses the compressor return or the direct path. Matching pin numbers straight through would not follow these net names.
References
Current production references and data tables:
Drive voicing, response and ladder · Compressor board map and setup · Detector curve and measurement scope · Player’s guide