Enclosure not stated · 4 knobs

Mad Professor Snow White Auto Wah

Based on the Mad Professor Snow White AutoWah· 4 other boards clone it

Category: Wah / Envelope
Controls: Sensitivity · Decay · Bias trim · Resonance
Price: see vendor
Also as: Vero layout · from Revolution Deux
Tags: freestompboxes.org trace

Read the post at Revolution Deux Schematic image Alternate schematic freestompboxes.org thread PCB layout by DimebuGG Harald Sabro (vero layout)GuitarPCB.com (mods) Vero layout

From the vendor

Bjorn Juhl's (BJF) envelope filter for Mad Professor. A 2N5457 JFET input buffer feeds an NE5517/LM13700 state-variable filter, while an LM324 gain stage, rectifier and BC550 current source make the envelope follower that sweeps the filter. The post summarizes My7of9's explanation of the circuit blocks from GuitarPCB.

My7of9's mod: a 1N34 germanium diode for D6 and a 1uF electrolytic for C8 make it funkier. Raising R18 to 47K lets the Sensitivity pot sit nearer 12 o'clock (gain is the Sensitivity pot divided by R18); keeping R18 at 20K and using a 47K pot does the same. A side-chain mod lets fuzz or distortion go before the auto wah, with a buffer/splitter and an extra jack.

Schematic

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

Parts list 60 rows

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Check before you build · 2 values the reader of this schematic was not sure of

R26 reads 7k9.
The two OTA halves are drawn as A2:A and A2:B without a part number; the block schematic names the NE5517.

Ref	Value	Normalized	Type	Notes
Resistors 31
R17	10K	10k		read from the schematic by eye
R6	1M	1M		read from the schematic by eye
R4	1M	1M		read from the schematic by eye
R5	10K	10k		read from the schematic by eye
R18	20K	20k		read from the schematic by eye
R10	20K	20k		read from the schematic by eye
R11	20K	20k		read from the schematic by eye
R24	10K	10k		read from the schematic by eye
R23	10K	10k		read from the schematic by eye
R19	4.7M	4.7M		read from the schematic by eye
R9	4.7M	4.7M		read from the schematic by eye
R13	330	330		read from the schematic by eye
R27	4.7K	4.7k		read from the schematic by eye
R31	6.8K	6.8k		read from the schematic by eye
R26	7.9K	7.9k		read from the schematic by eye
R21	47K	47k		read from the schematic by eye
R22	47K	47k		read from the schematic by eye
R1	5.1K	5.1k		read from the schematic by eye
R2	330	330		read from the schematic by eye
R3	330	330		read from the schematic by eye
R7	330	330		read from the schematic by eye
R12	330	330		read from the schematic by eye
R8	6.8K	6.8k		read from the schematic by eye
R16	6.8K	6.8k		read from the schematic by eye
R30	6.8K	6.8k		read from the schematic by eye
R14	4.7K	4.7k		read from the schematic by eye
R15	4.7K	4.7k		read from the schematic by eye
R29	1K	1k		read from the schematic by eye
R28	100K	100k		read from the schematic by eye
R20	47	47		read from the schematic by eye
R25	1K	1k		LED resistor; read from the schematic by eye
Capacitors 12
C1	22n	22n		read from the schematic by eye
C11	1u	1u		read from the schematic by eye
C3	220n	220n		read from the schematic by eye
C2	68n	68n		read from the schematic by eye
C4	8.2n	8.2n		read from the schematic by eye
C8	2.2u	2.2u		read from the schematic by eye
C10	100n	100n		read from the schematic by eye
C6	22n	22n		read from the schematic by eye
C5	22n	22n		read from the schematic by eye
C9	1u	1u		read from the schematic by eye
CF	100n	100n		read from the schematic by eye
C7	100u	100u		electrolytic; read from the schematic by eye
Diodes 6
D1	1N4148	1N4148		read from the schematic by eye
D2	1N4148	1N4148		read from the schematic by eye
D6	1N4148	1N4148		read from the schematic by eye
D5	1N4007	1N4007		read from the schematic by eye
D4	1N4007	1N4007		polarity protection; read from the schematic by eye
D3	5.1V zener	5V1		read from the schematic by eye
Transistors 3
Q3	2N5457	2N5457		read from the schematic by eye
Q2	BC550	BC550		read from the schematic by eye
Q1	BC550	BC550		read from the schematic by eye
ICs 3
A1	LM324	LM324		read from the schematic by eye
A2	NE5517	NE5517		LM13700 equivalent; read from the schematic by eye
U1	7805	7805		regulator; read from the schematic by eye
Potentiometers 4
Sensitivity	B100K	B100k	Potentiometer	P1; read from the schematic by eye
Decay	C1M	C1M	Potentiometer	P3; read from the schematic by eye
Bias trim	B50K	B50k	Potentiometer	P2; read from the schematic by eye
Resonance	B50K	B50k	Potentiometer	P4; read from the schematic by eye
LEDs 1
D7	LED	LED		read from the schematic by eye

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