Enclosure not stated · 5 knobs
Dean Markley Overlord Tube Overdrive
Based on the Dean Markley Overlord Tube Overdrive
- Category
- Overdrive
- Price
- see vendor
From the vendor
A 12AX7 tube overdrive with an internal mains transformer, a close relative of the B K Butler Tube Driver: a 4558 input buffer and drive stage feed the two triodes, followed by a passive Hi/Bass/Mid tone stack. The author owns one and plans to mod it toward the reissue Tube Driver (true bypass, the Bias control replacing Mid, an external 16VAC supply with regulation, Tube Driver values).
The author's planned mods: true bypass; replace the Mid control with the Tube Driver's Bias control; remove the internal transformer and run from a 16VAC adapter with a regulated supply like the Baja Real Tube Overdrive; change the stock values to match the reissue B K Butler Tube Driver; shielded wire for off-board signal runs.
Schematic
The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.
Parts list 61 rows
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Check before you build · 5 values the reader of this schematic was not sure of
- R4 is unreadable on the scan (looks like 2K or 1K).
- Q2 reads 2N4383; probably a 2N4393 JFET.
- R14 and R20 are drawn circled; their role is not clear from the scan.
- VR3 (Mid) reads 10K with an unclear taper letter; VR1 is labeled H1/HI.
- Part of the IC2 output area is blacked out on the scan.
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 24 | ||||
| R1 | 1M | 1M | read from the schematic by eye | |
| R2 | 10K | 10k | read from the schematic by eye | |
| R3 | 2.2K | 2.2k | read from the schematic by eye | |
| R4 | ? | ? | unreadable; read from the schematic by eye | |
| R13 | 10K | 10k | read from the schematic by eye | |
| R14 | 10K | 10k | drawn circled; read from the schematic by eye | |
| R5 | 220K | 220k | read from the schematic by eye | |
| R6 | 1.5M | 1.5M | read from the schematic by eye | |
| R7 | 220K | 220k | read from the schematic by eye | |
| R8 | 8.2K | 8.2k | read from the schematic by eye | |
| R9 | 1M | 1M | read from the schematic by eye | |
| R10 | 2.2K | 2.2k | read from the schematic by eye | |
| R11 | 1K | 1k | read from the schematic by eye | |
| R12 | 10K | 10k | read from the schematic by eye | |
| R20 | 10K | 10k | drawn circled; read from the schematic by eye | |
| R19 | 10K | 10k | read from the schematic by eye | |
| R21 | 68K | 68k | read from the schematic by eye | |
| R18 | 2.2K | 2.2k | read from the schematic by eye | |
| R17 | 68K | 68k | read from the schematic by eye | |
| R15 | 22K | 22k | read from the schematic by eye | |
| R16 | 22K | 22k | read from the schematic by eye | |
| R22 | 1K | 1k | read from the schematic by eye | |
| R23 | 1K | 1k | read from the schematic by eye | |
| R24 | 1.2K | 1.2k | read from the schematic by eye | |
| Capacitors 18 | ||||
| C1 | 47n | 47n | read from the schematic by eye | |
| C2 | 47p | 47p | read from the schematic by eye | |
| C3 | 4.7u | 4.7u | electrolytic, 25V; read from the schematic by eye | |
| C4 | 2.2u | 2.2u | electrolytic, 25V; read from the schematic by eye | |
| C5 | 120p | 120p | read from the schematic by eye | |
| C6 | 47n | 47n | read from the schematic by eye | |
| C8 | 47n | 47n | read from the schematic by eye | |
| C7 | 22u | 22u | electrolytic, 25V; read from the schematic by eye | |
| C14 | 47n | 47n | read from the schematic by eye | |
| C13 | 22u | 22u | electrolytic, 25V; read from the schematic by eye | |
| C9 | 330p | 330p | read from the schematic by eye | |
| C10 | 100n | 100n | read from the schematic by eye | |
| C11 | 47n | 47n | read from the schematic by eye | |
| C12 | 47n | 47n | read from the schematic by eye | |
| C15 | 220u | 220u | electrolytic, 25V; read from the schematic by eye | |
| C16 | 470u | 470u | electrolytic, 25V; read from the schematic by eye | |
| C17 | 220u | 220u | electrolytic, 25V; read from the schematic by eye | |
| C18 | 470u | 470u | electrolytic, 25V; read from the schematic by eye | |
| Diodes 8 | ||||
| D1 | 1N4148 | 1N4148 | read from the schematic by eye | |
| D2 | 1N4148 | 1N4148 | read from the schematic by eye | |
| D3 | 1N4148 | 1N4148 | read from the schematic by eye | |
| D10 | 1N4148 | 1N4148 | read from the schematic by eye | |
| D6 | 1N4148 | 1N4148 | read from the schematic by eye | |
| D7 | 1N4148 | 1N4148 | read from the schematic by eye | |
| D8 | 1N4004 | 1N4004 | read from the schematic by eye | |
| D9 | 1N4004 | 1N4004 | read from the schematic by eye | |
| Transistors 2 | ||||
| Q1 | 2SK30A | 2SK30A | switching JFET; read from the schematic by eye | |
| Q2 | 2N4393 | 2N4393 | drawn 2N4383?; read from the schematic by eye | |
| ICs 2 | ||||
| IC1 | 4558 | 4558 | read from the schematic by eye | |
| IC2 | 4558 | 4558 | read from the schematic by eye | |
| Potentiometers 5 | ||||
| Drive | A500K | A500k | Potentiometer | VR4; read from the schematic by eye |
| Volume | A100K | A100k | Potentiometer | VR2; read from the schematic by eye |
| Hi | A500K | A500k | Potentiometer | VR1; read from the schematic by eye |
| Bass | A100K | A100k | Potentiometer | VR5; read from the schematic by eye |
| Mid | 10K | 10k | Potentiometer | VR3; read from the schematic by eye |
| Switches 1 | ||||
| SW2 | SPST | SPST | in series with R8; read from the schematic by eye | |
| Other 1 | ||||
| V1 | 12AX7A | 12AX7A | tube; read from the schematic by eye | |