Enclosure not stated · 3 knobs

Mad Professor Little Green Wonder

Based on the Mad Professor Little Green Wonder· 4 other boards clone it

Category: Overdrive
Controls: Drive · Body · Volume
Price: see vendor

Read the post at Revolution Deux Schematic image PCB layout PCB layout (copper)

From the vendor

Bjorn Juhl's (BJF) overdrive for Mad Professor, conceived as his take on a Tube Screamer-style pedal with more headroom, less bass and low-mid cut, and treble filtering that suits humbuckers and P-90s. A 2SK170 JFET input buffer feeds a TLC272 op amp whose first half clips through two green LEDs in its feedback loop; the second half is a gain stage, and the unusual Body control is a dual 20k pot working in both stages.

The first LGWs used an LF353 op amp for more headroom; later ones use the TLC272, which works at lower voltages and distorts more easily.

Schematic

The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.

Parts list 38 rows

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Fixes to the schematic, from the post

The input buffer JFET's 1M gate resistor (to the bias supply) was missing from the original schematic, as Bjorn pointed out; the author added it to the drawing shown.

Ref	Value	Normalized	Type	Notes
Resistors 18
R1	1M	1M		input pulldown; read from the schematic by eye
R2	5.6K	5.6k		read from the schematic by eye
R3	1M	1M		gate to bias; added by the author, missing from the original drawing; read from the schematic by eye
R4	10K	10k		source; read from the schematic by eye
R5	5.6K	5.6k		read from the schematic by eye
R6	27K	27k		pin 3 to bias; read from the schematic by eye
R7	5.6K	5.6k		in series with Drive; read from the schematic by eye
R8	2K	2k		read from the schematic by eye
R9	1K	1k		read from the schematic by eye
R10	2K	2k		read from the schematic by eye
R11	27K	27k		pin 5 to bias; read from the schematic by eye
R12	2K	2k		IC1B feedback; read from the schematic by eye
R13	470	470		read from the schematic by eye
R14	5.6K	5.6k		read from the schematic by eye
R15	47	47		read from the schematic by eye
R16	27K	27k		bias divider; read from the schematic by eye
R17	27K	27k		bias divider; read from the schematic by eye
R18	1K	1k		LED resistor; read from the schematic by eye
Capacitors 10
C1	47n	47n		read from the schematic by eye
C2	1u	1u		electrolytic, 50V; read from the schematic by eye
C3	100p	100p		IC1A feedback; read from the schematic by eye
C4	220n	220n		read from the schematic by eye
C5	1u	1u		electrolytic, 50V; read from the schematic by eye
C6	100n	100n		read from the schematic by eye
C7	47n	47n		read from the schematic by eye
C8	1u	1u		electrolytic, 50V; read from the schematic by eye
C9	100u	100u		electrolytic, 35V; read from the schematic by eye
C10	100u	100u		electrolytic, 35V; read from the schematic by eye
Diodes 2
D3	1N4007	1N4007		read from the schematic by eye
D4	BZX55C 5V1	BZX55C 5V1		zener, in the LED string; read from the schematic by eye
Transistors 1
Q1	2SK170	2SK170		read from the schematic by eye
ICs 1
IC1	TLC272	TLC272		earlier versions used an LF353; read from the schematic by eye
Potentiometers 3
Drive	B500K	B500k	Potentiometer	read from the schematic by eye
Body	B20K	B20k	Potentiometer, dual	one gang in each stage; read from the schematic by eye
Volume	B50K	B50k	Potentiometer	read from the schematic by eye
LEDs 3
D1	LED	LED		3mm green, clipping; read from the schematic by eye
D2	LED	LED		3mm green, clipping; read from the schematic by eye
LED1	LED	LED		5mm red; read from the schematic by eye

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