1590BB

3-band parametriq EQ (full control)

Category: EQ / Filter
Price: €10.70in stock

Buy the PCB at TH Custom Effects Build document

From the vendor

This is the full-control implementation of the 3-Band Parametric EQ. Each band provides independent adjustment of centre frequency, bandwidth (Q) and cut/boost level via three dedicated pots. V2.0 introduced a revised layout with greater spacing between pots for easier panel mounting and operation. The circuit uses op-amp gyrators to simulate inductors, forming bandpass resonators. An on-board bridge rectifier (polarity protection) and ICL 7660S charge pump provide symmetric ±9 V from a standard 9 V DC supply. 3-Band Parametric EQ V2.1 full schematic. Three gyrator bandpass stages (LOW / MID / HIGH) share common ±9 V rails generated on-board. Signal enters through a 1 μF film coupling cap (C

Schematic

The schematic is in the vendor's build document. Open the build document. No KiCad fragment has been drawn for this circuit yet.

Parts list 39 rows

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Ref	Value	Normalized	Notes
Resistors 15
R1	1M	1M	Input pull-down to VR
R2	100k	100k	VR bias divider
R3	10k	10k	Input buffer feedback
R6	250k	250k	Low band frequency resistor
R8	470R	470	Low band Q series resistor
R11	120k	120k	Mid band frequency resistor
R13	470R	470	Mid band Q series resistor
R16	47k	47k	High band frequency resistor
R17	10k	10k	Virtual ground divider
R19	10k	10k	Virtual ground divider
R20	470R	470	High band Q series resistor
R21	10k	10k	Summing amp feedback
R22	10k	10k	Summing amp input
R23	33k	33k	IC4B feedback
R24	33k	33k	IC4B input
Capacitors 14
C1	1 μF	1u	Film box — input coupling
C3	100 pF	100p	MLCC — VR HF decoupling
C4	220 nF	220n	Film box — Low band gyrator cap
C5	47 nF	47n	Film box — Low band resonator cap
C8	86 nF	86n	Film box — Mid band gyrator cap
C9	33 nF	33n	Film box — Mid band resonator cap
C10	100 nF	100n	Film box — +18 V supply decoupling
C11	33 nF	33n	Film box — High band gyrator cap 33n not 47n
C12	4n7	4.7n	Film box — High band resonator cap
C13	100 pF	100p	MLCC — VR HF decoupling
C14	1 μF	1u	MLCC — output coupling
C2	100 μF	100u	Electrolytic — +9 V filter, observe polarity
C6	10 μF	10u	Electrolytic — charge pump output, observe polarity
C7	100 μF	100u	Electrolytic — +18 V filter, observe polarity
Diodes 2
D1	1N5817	1N5817	Schottky — charge pump diode, observe polarity
D2	1N5817	1N5817	Schottky — charge pump diode, observe polarity
ICs 4
IC1	TL072	TL072	Dual op-amp — input buffer (A) + summing amp (B)
IC2	ICL 7660S	ICL 7660S	Charge pump — negative rail MAX1044
IC3	TL072	TL072	Dual op-amp — Low band (A) + Mid band (B) gyrators
IC4	TL072	TL072	Dual op-amp — High band gyrator (A) + output stage (B)
Crystals 2
X1	Pad	PAD	+9 V power pads
X2	Pad	PAD	+9 V power pads
Other 2
B1	Bridge rectifier	BRIDGE RECTIFIER	Polarity protection — can be omitted if supply polarity is guaranteed
AC1	DC connector	DC CONNECTOR	9 V DC supply input