Enclosure not stated · 4 knobs
Benson PreampVerified
Based on the Benson Preamp· 7 other boards clone it
From the post
This one just traced over on FSB. It's essentially a modified Wampler Plexidrive with an added bass control. Unless you're really sure any through-hole J201s you have on hand are in spec/authentic, I'd suggest using MMBFJ201s, which are the SMD version which are still in production and much easier to get in spec than the discontinued through-hole version. SMD to through-hole conversion boards here.
Update August 19, 2019:
Corrected a few values that have now been confirmed by Benson. The traces haven't changed however.
Schematic
This is a board layout, a drawing of where each part goes, and the post may link the schematic it was drawn from. Open the layout at Effects Layouts (blog). No KiCad fragment has been drawn for this circuit yet.
Parts list 26 rows
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Check before you build · 1 value the reader of this layout was not sure of
- 33nF film cap at top right (column 18, rows D-F): the populated board prints 33nF but the wiring diagram prints 22nF for the same part; entered as on the populated board
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 9 | ||||
| ×3 | 1K | 1k | read from the layout by eye | |
| ×1 | 3.9K | 3.9k | read from the layout by eye | |
| ×2 | 10K | 10k | read from the layout by eye | |
| ×1 | 12K | 12k | read from the layout by eye | |
| ×1 | 47K | 47k | read from the layout by eye | |
| ×1 | 100K | 100k | read from the layout by eye | |
| ×1 | 220K | 220k | read from the layout by eye | |
| ×2 | 470K | 470k | read from the layout by eye | |
| ×2 | 1M | 1M | read from the layout by eye | |
| Capacitors 8 | ||||
| ×1 | 250pF | 250p | read from the layout by eye | |
| ×1 | 470pF | 470p | read from the layout by eye | |
| ×1 | 2.2nF | 2.2n | read from the layout by eye | |
| ×3 | 22nF | 22n | read from the layout by eye | |
| ×1 | 33nF | 33n | wiring diagram prints 22nF; read from the layout by eye | |
| ×2 | 100nF | 100n | read from the layout by eye | |
| ×1 | 10uF | 10u | electrolytic; read from the layout by eye | |
| ×1 | 100uF | 100u | electrolytic; read from the layout by eye | |
| Diodes 1 | ||||
| ×1 | 1N4001 | 1N4001 | read from the layout by eye | |
| Transistors 3 | ||||
| Q1 | J201 | J201 | JFET; SMD works best; read from the layout by eye | |
| Q2 | J201 | J201 | JFET; SMD works best; read from the layout by eye | |
| Q3 | J201 | J201 | JFET; SMD works best; read from the layout by eye | |
| Potentiometers 4 | ||||
| Bass | B2M | B2M | Potentiometer | read from the layout by eye |
| Treble | A250K | A250k | Potentiometer | read from the layout by eye |
| Gain | A1M | A1M | Potentiometer | read from the layout by eye |
| Master | A100K | A100k | Potentiometer | read from the layout by eye |
| Trimmers 1 | ||||
| ×2 | 50K | 50k | read from the layout by eye | |
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