Enclosure not stated · 3 knobs
Maxon OD-820 Overdrive Pro
Based on the Maxon OD-820· 6 other boards clone it
- Category
- Overdrive
- Price
- see vendor
From the vendor
Maxon's 'Klon killer': a 2SK246 JFET input buffer feeds a dual-gang Drive pot that both sets the gain of a 4558 clipping stage (diodes in its feedback loop) and blends between that and a clean path, followed by a mixing stage, a Tube Screamer-style tone control and a volume buffer. A MAX1044 charge pump gives the op-amps +/-9V for extra headroom. The post finds it more transparent than the Klon Centaur, without its mid-range texture.
The parts list gives no part numbers for the clipping diodes; the post suggests 1N914/1N4148 as in most Maxon overdrives, though other diodes work.
Schematic
The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.
Parts list 55 rows
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Check before you build · 3 values the reader of this schematic was not sure of
- The parts list (image 4) uses PCB numbering that does not match the schematic designators; rows follow the schematic. Two values disagree: the schematic's R13 reads 62k while the list's matching value is 52K, and the list has a 3K2 that does not appear on the schematic.
- D3 is drawn as a 4.7V zener ('4.7Z') in the LED circuit; the reading is not certain.
- D1, D2, D5 and D7 are marked only 'SiDi' (silicon diode); D6 has no marking.
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 22 | ||||
| R9 | 10K | 10k | read from the schematic by eye | |
| R15 | 1M | 1M | read from the schematic by eye | |
| R16 | 10K | 10k | source; read from the schematic by eye | |
| R10 | 560 | 560 | read from the schematic by eye | |
| R13 | 62K | 62k | parts list has 52K; read from the schematic by eye | |
| R1 | 2.2K | 2.2k | read from the schematic by eye | |
| R6 | 1K | 1k | read from the schematic by eye | |
| R7 | 56K | 56k | read from the schematic by eye | |
| R17 | 7.5K | 7.5k | read from the schematic by eye | |
| R20 | 100K | 100k | read from the schematic by eye | |
| R18 | 20K | 20k | read from the schematic by eye | |
| R3 | 56K | 56k | read from the schematic by eye | |
| R11 | 1K | 1k | read from the schematic by eye | |
| R14 | 220 | 220 | read from the schematic by eye | |
| R4 | 1K | 1k | read from the schematic by eye | |
| R8 | 47K | 47k | read from the schematic by eye | |
| R2 | 100K | 100k | read from the schematic by eye | |
| R5 | 1K | 1k | read from the schematic by eye | |
| R12 | 100K | 100k | read from the schematic by eye | |
| R19 | 3.9K | 3.9k | LED resistor; read from the schematic by eye | |
| R21 | 10K | 10k | bias divider; read from the schematic by eye | |
| R22 | 10K | 10k | bias divider; read from the schematic by eye | |
| Capacitors 19 | ||||
| C7 | 100n | 100n | input; read from the schematic by eye | |
| C9 | 1u | 1u | electrolytic; read from the schematic by eye | |
| C1 | 100n | 100n | read from the schematic by eye | |
| C3 | 100p | 100p | read from the schematic by eye | |
| C8 | 220n | 220n | read from the schematic by eye | |
| C11 | 220n | 220n | read from the schematic by eye | |
| C12 | 10n | 10n | read from the schematic by eye | |
| C4 | 10p | 10p | read from the schematic by eye | |
| C10 | 220n | 220n | read from the schematic by eye | |
| C6 | 10u | 10u | electrolytic; read from the schematic by eye | |
| C2 | 20p | 20p | read from the schematic by eye | |
| C5 | 1u | 1u | electrolytic; read from the schematic by eye | |
| C13 | 100u | 100u | electrolytic; read from the schematic by eye | |
| C16 | 10u | 10u | electrolytic; read from the schematic by eye | |
| C15 | 100u | 100u | electrolytic; read from the schematic by eye | |
| C14 | 10u | 10u | electrolytic; read from the schematic by eye | |
| C17 | 10u | 10u | electrolytic; read from the schematic by eye | |
| C18 | 220u | 220u | electrolytic; read from the schematic by eye | |
| C19 | 220u | 220u | electrolytic; read from the schematic by eye | |
| Diodes 6 | ||||
| D1 | ? | ? | silicon clipping diode; read from the schematic by eye | |
| D2 | ? | ? | silicon clipping diode; read from the schematic by eye | |
| D3 | 4.7V | 4V7 | zener, reading uncertain; read from the schematic by eye | |
| D6 | ? | ? | supply protection; read from the schematic by eye | |
| D5 | ? | ? | silicon diode; read from the schematic by eye | |
| D7 | ? | ? | silicon diode; read from the schematic by eye | |
| Transistors 1 | ||||
| Q1 | 2SK246 | 2SK246 | JFET buffer; read from the schematic by eye | |
| ICs 3 | ||||
| U1 | 4558 | 4558 | JRC4558; read from the schematic by eye | |
| U2 | 4558 | 4558 | JRC4558; read from the schematic by eye | |
| IC1 | MAX1044 | MAX1044 | charge pump; read from the schematic by eye | |
| Potentiometers 3 | ||||
| Drive | 250K | 250k | Potentiometer | VR4a/VR4b, dual gang; read from the schematic by eye |
| Tone | 20K | 20k | Potentiometer | VR2; read from the schematic by eye |
| Volume | 100K | 100k | Potentiometer | VR3; read from the schematic by eye |
| LEDs 1 | ||||
| D4 | LED | LED | read from the schematic by eye | |
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