Enclosure not stated · 3 knobs
From the vendor
Jack Orman's Booster 2.5 (with modifications by Dron Nelson): two cascaded JFET mu-amp stages with a Drive pot between them and a passive tone control before the volume. The post shows it because the OKKO Diablo's schematic follows the same cascaded Microbooster formula, also used in the Catalinbread Dirty Little Secret and Formula No. 5.
The drawing notes that the two 100 ohm source resistors can be 1K for a milder overdrive.
Schematic
The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.
Parts list 34 rows
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Check before you build · 1 value the reader of this schematic was not sure of
- The .001uF cap near the Drive pot is drawn without a clear second connection; its exact placement is not certain.
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 13 | ||||
| R1 | 1M | 1M | input pulldown; read from the schematic by eye | |
| R2 | 1M | 1M | read from the schematic by eye | |
| R3 | 33K | 33k | gate stopper; read from the schematic by eye | |
| R4 | 100 | 100 | source; read from the schematic by eye | |
| R5 | 1M | 1M | read from the schematic by eye | |
| R6 | 1M | 1M | read from the schematic by eye | |
| R7 | 470K | 470k | read from the schematic by eye | |
| R8 | 1M | 1M | read from the schematic by eye | |
| R9 | 100 | 100 | source; read from the schematic by eye | |
| R10 | 1M | 1M | read from the schematic by eye | |
| R11 | 1M | 1M | read from the schematic by eye | |
| R12 | 39K | 39k | tone; read from the schematic by eye | |
| R13 | 47K | 47k | tone; read from the schematic by eye | |
| Capacitors 13 | ||||
| C1 | 10u | 10u | electrolytic, supply filter; read from the schematic by eye | |
| C2 | 10n | 10n | input; read from the schematic by eye | |
| C3 | 24p | 24p | read from the schematic by eye | |
| C4 | 22u | 22u | electrolytic, source bypass; read from the schematic by eye | |
| C5 | 100n | 100n | read from the schematic by eye | |
| C6 | 100n | 100n | read from the schematic by eye | |
| C7 | 470p | 470p | read from the schematic by eye | |
| C8 | 1n | 1n | read from the schematic by eye | |
| C9 | 100n | 100n | read from the schematic by eye | |
| C10 | 100n | 100n | read from the schematic by eye | |
| C11 | 100n | 100n | output; read from the schematic by eye | |
| C12 | 10n | 10n | tone; read from the schematic by eye | |
| C13 | 22n | 22n | tone; read from the schematic by eye | |
| Diodes 1 | ||||
| D1 | 1N4148 | 1N4148 | polarity protection; read from the schematic by eye | |
| Transistors 4 | ||||
| Q1 | J201 | J201 | read from the schematic by eye | |
| Q2 | J201 | J201 | read from the schematic by eye | |
| Q3 | J201 | J201 | read from the schematic by eye | |
| Q4 | J201 | J201 | read from the schematic by eye | |
| Potentiometers 3 | ||||
| Drive | 500K | 500k | Potentiometer | read from the schematic by eye |
| Tone | B100K | B100k | Potentiometer | read from the schematic by eye |
| Volume | A100K | A100k | Potentiometer | read from the schematic by eye |