Enclosure not stated · 2 knobs
Arsenio Novo Tube Sound Overdrive
Based on the Arsenio Novo Tubesound Overdrive· 2 other boards clone it
From the vendor
Arsenio Novo's 1995 newsgroup design: a complementary 2N3904/2N3906 pair with all their terminals overlapped, biased by equal resistors in each leg, with a large cap from the emitter leg to ground. The negative feedback around both base-emitter junctions gives a gradual, square-law, tube-like clipping rich in second harmonic. The post finds it COT-like but more natural, with low-to-medium gain blues tones that clean up with the guitar's volume knob.
Novo: adjust the bias trimmer for symmetrical clipping on a scope, or by ear for the most sensitivity around mid-turn. Novo: drive the input from a low-impedance stage if the guitar has no preamp; do not make the input cap much larger or the circuit cuts out. Novo: the emitter capacitor can range from 0.1u to 1u for different bass characteristics. Author's mod: a B100K pot wired as a variable resistor in series after the input cap smooths the tone and reduces gain and harsh highs (or a fixed 10-15K resistor). Author's mod: raise the input cap to 22n or 33n, depending on how much bass is wanted. Author's mod: a 4.7n cap in parallel with an A500K volume pot tames the top end. Author's mod: replace the emitter bypass cap with 470n and add a 10u cap in series with an A4.7K pot in parallel with it, as a gain / low-end saturation control from treble boost to full-range boost.
Schematic
The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.
Parts list 11 rows
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Check before you build · 1 value the reader of this schematic was not sure of
- The emitter bypass cap C2 is drawn as 22u, while Novo's text gives 0.1u to 1u as its range and the author's mod refers to a 10u bypass cap.
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 4 | ||||
| R1 | 1M | 1M | input pulldown; read from the schematic by eye | |
| R3 | 220K | 220k | read from the schematic by eye | |
| R2 | 10K | 10k | read from the schematic by eye | |
| R4 | 10K | 10k | read from the schematic by eye | |
| Capacitors 3 | ||||
| C1 | 4.7n | 4.7n | input; read from the schematic by eye | |
| C2 | 22u | 22u | electrolytic, emitter bypass; read from the schematic by eye | |
| C3 | 100n | 100n | output; read from the schematic by eye | |
| Transistors 2 | ||||
| Q1 | 2N3906 | 2N3906 | PNP; read from the schematic by eye | |
| Q2 | 2N3904 | 2N3904 | NPN; read from the schematic by eye | |
| Potentiometers 2 | ||||
| Bias trim | 20K | 20k | Potentiometer | VR1, bias balance; read from the schematic by eye |
| Vol | A100K | A100k | Potentiometer | read from the schematic by eye |
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