Enclosure not stated · 2 knobs
Bajaman LA2A Style Optical Limiter rev2
Based on the BAJA Optical Limiter· 2 other boards clone it
- Category
- Compressor
- Controls
- Limit · Level
- Price
- see vendor
- Tags
- freestompboxes.org trace
From the vendor
Bajaman's own LA-2A style optical limiter built around the Compulator idea: a 2SK117 JFET input buffer, an LDR attenuator before an LF353 gain stage, and a side chain taken before the attenuator (feed-forward), so it only clamps peaks rather than adding sustain. The optocoupler is a homemade yellow LED and LDR in a sealed black tube.
The LDR should read about 90 ohms in sunlight; a type reading 350 ohms or more is wrong for this project.
Schematic
The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.
Parts list 41 rows
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| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 24 | ||||
| R1 | 100 | 100 | supply; read from the schematic by eye | |
| R2 | 47K | 47k | read from the schematic by eye | |
| R3 | 47K | 47k | read from the schematic by eye | |
| R18 | 10K | 10k | input; read from the schematic by eye | |
| R19 | 1M | 1M | read from the schematic by eye | |
| R20 | 68K | 68k | source; read from the schematic by eye | |
| R21 | 68K | 68k | read from the schematic by eye | |
| R22 | 100K | 100k | read from the schematic by eye | |
| R23 | 560 | 560 | bypass output; read from the schematic by eye | |
| R4 | 2.7K | 2.7k | read from the schematic by eye | |
| R6 | 560 | 560 | read from the schematic by eye | |
| R7 | 4.7K | 4.7k | read from the schematic by eye | |
| R8 | 560 | 560 | read from the schematic by eye | |
| R13 | 1K | 1k | read from the schematic by eye | |
| R14 | 100K | 100k | read from the schematic by eye | |
| R15 | 10K | 10k | read from the schematic by eye | |
| R16 | 1.5K | 1.5k | read from the schematic by eye | |
| R17 | 1K | 1k | read from the schematic by eye | |
| R24 | 560 | 560 | Limit wiper to IC2; read from the schematic by eye | |
| R12 | 4.7K | 4.7k | read from the schematic by eye | |
| R11 | 10K | 10k | read from the schematic by eye | |
| R9 | 10K | 10k | read from the schematic by eye | |
| R10 | 1.5K | 1.5k | read from the schematic by eye | |
| R5 | 560 | 560 | LED resistor; read from the schematic by eye | |
| Capacitors 7 | ||||
| C1 | 220u | 220u | electrolytic; read from the schematic by eye | |
| C2 | 10u | 10u | electrolytic; read from the schematic by eye | |
| C3 | 10u | 10u | electrolytic; read from the schematic by eye | |
| C5 | 10n | 10n | input; read from the schematic by eye | |
| C6 | 100n | 100n | read from the schematic by eye | |
| C7 | 1u | 1u | non-polar, bypass output; read from the schematic by eye | |
| C4 | 1u | 1u | non-polar; read from the schematic by eye | |
| Diodes 2 | ||||
| D1 | 1N4148 | 1N4148 | read from the schematic by eye | |
| D2 | 1N4148 | 1N4148 | read from the schematic by eye | |
| Transistors 1 | ||||
| Q1 | 2SK117 | 2SK117 | JFET buffer; read from the schematic by eye | |
| ICs 2 | ||||
| IC1 | LF353N | LF353N | read from the schematic by eye | |
| IC2 | LF353N | LF353N | read from the schematic by eye | |
| Potentiometers 2 | ||||
| Limit | B10K | B10k | Potentiometer | 10k lin; read from the schematic by eye |
| Level | B10K | B10k | Potentiometer | 10k lin; read from the schematic by eye |
| LEDs 2 | ||||
| LED1 | LED | LED | yellow 5mm, indicator; read from the schematic by eye | |
| LED2 | LED | LED | yellow 5mm, optocoupler; read from the schematic by eye | |
| Other 1 | ||||
| LDR1 | LDR | LDR | about 90 ohms lit; with the yellow LED in a black tube; read from the schematic by eye | |
Other boards based on the BAJA Optical Limiter
- Baja Optical Limiter Effects Layouts (blog)
- Madbean Holy Roller / Baja Optical Limiter Tagboard Effects