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Modular EQ project with gyrators

3 -

Schematics and Bill of
Materials for simple EQ
circuits with gyrator filters

Simple gyrator and permanent Q active filter EQ project

Schematics and Bill of Materials for gyrator EQ project
Schematic and BOM of simple “5 band EQ”
1

2

3

5

6

+15V filt1
GND

12
11
10
9
8
7

6
5
4
3
2
1

P1
Header 6X2A
R1
3.3k

-15V filt1
4

A
GND

R3

C

10

10k

R4

U1B
TL074J
7

6
R2

B

5

2
A

3

U1A
TL074J C1
1

A

10u

3.3k

11

10u

1M

12

U1D
TL074J
14

3

R5
1.2k

R10
18k

GND
B

2

C4

C5

330n

330n

R11
18k

A

U2A
TL074J
1

6
5

R6
1.2k

C3

B

GND

U2B
TL074J
7

100n

9

GND

C7

C8

33n

33n

C

10

R7
1.2k

R12
18k

C6
100n

D

11

13

4

GND
U2C
TL074J
8

13
R8
1.2k

R13
18k

GND

C9

C10

10n

10n

D

12

U2D
TL074J
14
R9
1.2k

R14
18k

GND

C11

C12

3.3n

3.3n
B

H1
3
2
1

P2

P4

GND

3
2

-15V

50k

C13
100n

C15
330n

P3

P5
50k

50k

+15V

H3

Read details, updates, advices on the page of schematics and notes. PCB-s and more
notes, pictures, advices about this project are available on the author’s blog and websites:

U1C
TL074J
8

9

C2

This project made to create and try simple and noiseless EQ with circuit called “gyrator”. This method is very simple, easy to assemble, and good quality for home hi-fi
systems. You can find very simple 5 band EQ with this method, and modular EQ with
sub-circuits and mainboard for 10 and 5 band equalizer.

1

P6
50k

3

GND

C14
10n

C16
33n

2

50k
C17
3.3n

H2

1

English blog and PCB order: http://custompcb.blogspot.com/
Hungarian blog and PCB order: http://diyguitarpa.blogspot.com/
The Youtube Channel • Picasa gallery • Email: gitarfogas@gmail.com

3
2

U3B

GND

Schematics and Bill of Materials for simple EQ circuits with gyrator filters . . . . . . . . . . . . . . . 2

B

The power supply for all gyrator EQ projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Schematic and BOM of power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
The power supply PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Math expressions, articles for gyrator EQ designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Articles and images about gyrator EQ projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Math expressions for gyrator design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
The frequency response of 10 channel modular EQ project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Previous PCBs and images for simple 5 band and permanent Q 10 band EQ . . . . . . . . . . . 26
The previous version of simple 5 band EQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
The previous version of RANE based permanent Q project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9

1

A

R16
1.2k

C21

C18

330n

100n

GND

10

U3C

13

8

C

R22 TL074J
18k

R17
1.2k

GND

2

14

D

12

U4A

3

R18
1.2k

R23 TL074J
18k

C19
33n

U3D

A

R24 TL074J
18k

C22
10n

GND

GND

C

1
R19
1.2k
C20
3.3n

R25
3.3k
4

13
R27
10k

10u

D

12
R28

D

U4D
TL074J
14

9
R26

C

10

U4C
TL074J
8

6
5

B

U4B
TL074J C23
7
10u

3.3k
D

11

C24

GND

6
5
4
3
2
1

Top and bottom PCBs and overlay of simple 5 band EQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Top and bottom PCBs and overlay of stereo gyrator module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Top and bottom PCBs and overlay of 2 mono gyrator module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Top and bottom PCBs and overlay of power filters (ver.3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Top and bottom PCBs and overlay of power filters (ver.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Top and bottom PCBs and overlay of power filters (ver.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
The mainboard of 10 band EQ for gyrators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

R21
18k

U3A
TL074J

+15V filt2

1M

P7
Header 6X2A

Title

12
11
10
9
8
7

Printed Circuit Boards for gyrator EQ project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3

R15
1.2k

R20 TL074J
18k

GND

3
4
5
6

2

7

11

6

C

4

1
H4

5

Schematic and BOM of simple “5 band EQ” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
One stereo gyrator filter module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The power filter module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 channel gyrator EQ mainboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

GND
-15V filt2

http://custompcb.blogspot.com/
http://diyguitarpa.blogspot.com/

GND
1

2

Description

Value

5 band stereo gyrator EQ

Size

Footprint

3

Quantit
y

Designator

Date:
File:

Model:Footprint

10u

Cap, Tantal, 1mil

4 C1, C2, C23, C24

Capacitor

100n

RAD-0.3

4 C3, C6, C13, C18

Radial Cap, Thru-Hole; 2 Leads; 0.3 in Pin Spacing

Capacitor

330n

RAD-0.3

4 C4, C5, C15, C21

Radial Cap, Thru-Hole; 2 Leads; 0.3 in Pin Spacing

Capacitor

33n

CAP, WIMA, 2MIL

4 C7, C8, C16, C19

Capacitor

10n

CAP, WIMA, 2MIL

4 C9, C10, C14, C22

Capacitor

3.3n

CAP, WIMA, 2MIL
Panel Connector
3 input Small

4 C11, C12, C17, C20

2 P1, P7

4 H1, H2, H3, H4

Resistor

50k

HDR2X6_CEN
Pots Plastic
Stereo

Resistor

3.3k

AXIAL-0.4

4 R1, R2, R25, R26

Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin Spacing

Resistor

10k

AXIAL-0.4

2 R3, R27

Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin Spacing

Resistor

1M

AXIAL-0.4

Resistor

1.2k

AXIAL-0.4

Resistor

18k

AXIAL-0.4

Low-Noise JFET-Input Operational Amplifier

J014

Connector; Header; 6x2 Position

5 P2, P3, P4, P5, P6

2 R4, R28
R5, R6, R7, R8, R9,
R15, R16, R17, R18,
10 R19
R10, R11, R12, R13,
R14, R20, R21, R22,
10 R23, R24
4 U1, U2, U3, U4

Revision

10/17/2011
D:\!Works\..\5 band gyrator EQ.SchDoc

4

Polarized Capacitor (Radial)

Header, 6-Pin, Dual row

Number

A

5

Sheet of
Drawn By:
6

Notes
This the simplest schematic
of 5 band stereo gyrator EQ.
The PCB is small, potentiometers inserted to the board.
Cheap, low noise, good
quality for home hi-fi applications.

Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin Spacing

Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin Spacing

Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin Spacing
DIP; 14 Leads; Row Spacing 7.62 mm; Pitch 2.54 mm

The band frequencies of this
board: 100Hz - 300Hz - 1kHz - 3kHz
- 10kHz.

Document last modified and saved: 23 October 2011 6:15 PM

- 4

Simple gyrator and permanent Q active filter EQ project

5 -

Schematics and Bill of Materials for gyrator EQ project
One stereo gyrator filter module

Simple gyrator and permanent Q active filter EQ project

Schematics and Bill of Materials for gyrator EQ project
The power filter module

Notes
This is the part of modular EQ project. This is the most important schematic: the gyrator. The gyrator is the
main filter for the equalizer. The band frequency depend on the value of capacitors “C(a)” on the schematic.
Because this is module only, another modules and mainboard required to complete the multiband EQ. Two
version of PCB-s available for this one module: one of them have stereo potentiometers to adjust both left
and right channel at one time. Another PCB separated to two mono channel with two mono potentiometers to adjust left and right channels independently. The first version is good for home hi-fi users, the second
is better for instrument amplifications. With the EQ mainboard, you can build this module for any frequencies,
set the Q and the boost/cut of the band. Look at the math expressions of this module to count the values of the
resistors and capacitors.

1

2

3

4

A

P1
1
2
3
4
5
6

B

GND

C1
47uF 60V

7
8
9
10
11
12

R1

BC560C
Q1

3

4

5

6

12K

C8
47nF

GND
GND

This schematic contains only one gyrator filter circuit. For this circuit required mainboard to complete 10 channel EQ. For the EQ
bands, C(a) capacitors have to be changed to several values. Visit the authors website for details.
A

http://custompcb.blogspot.com/
http://diyguitarpa.blogspot.com/







8

+15V
2
A

3

4

R2
18k

B

U1A
TL072P
1



R1
1.2k

C1

B

C2
C(a)

C(a)

GND

P1 L

6
C

5

B

P2

U1B
TL072P
7

C3

P1
1
2
3
4
5
6

P1 U
50k
P2 U

C(a)

R3
1.2k

R4
18k

P2 L

7
8
9
10
11
12

Header 6X2A

C4

C

GND

C(a)

GND

-15V
Title

Number

Revision

D

A
Date:
File:
1

2

Comment
Cap

3

Value
C(a)

Header 6X2A

10/17/2011
D:\!Works\..\1 stereo gyrator.SchDoc

Quantity

4

C3

C4

R3

R4

31

6.8µ

100n

470�

100k

63

3.3µ

47n

390�

100k

125

1.5µ

33n

390�

100k

250

680n

22n

330�

82k

500

330n

10n

330�

100k

1K

150n

4.7n

330�

100k

2K

100n

2.2n

330�

82k

4K

56n

1n

390�

82k

8K

22n

470p

390�

82k

16K

10n

220p

390�

100k

Sheet of
Drawn By:
5

Description
4 Capacitor

Hz

The values of R3 is same as R1, the
R2 is same as R4. Also look the math
expressions for another examples.

Stereo gyrator EQ module

Size

D

Polarized Capacitor (Radial)

Change all of the 50K adjustable resistors to 25K

6

Designator
C1, C2, C3, C4

Footprint

LibRef

CAP, 2 and 3 MIL

Cap

1 Header, 6-Pin, Dual row P1

HDR2X6_CEN

Header 6X2A

Pot stereo

50k

1 Resistor

P2

Pots Plastic Stereo

Pot stereo

Res2

1.2k

2 Resistor

R1, R3

AXIAL-0.4

Res2

Res2

18k

2 Resistor

R2, R4

AXIAL-0.4

Res2

dip-8

TL072P

TL072P

1 Low-Noise JFET-Input Operational
U1
Amplifier

Size

C7

B

GND

2

Value
47uF 60V

Date:
File:

3

Footprint
Elco 6mm, 1 mil
pins

Power filter module
Number

Revision

A

This schematic is the partof preamps and EQ projects. This module filtering the symmatrical (+-) power for
circuits. PCB and another modules, mainboards are available.

Description

For 10 band EQ:

12K

C6
47nF

47uF 60V

C

1

100Hz - 330n
300Hz - 100n
1kHz - 33n
3kHz - 10n
10kHz - 3.3n

BC550C
Q2
R2

Header 6X2A

For 5 band EQ:

A

GND

C2
100nF

C

D

Examples of C(a):

C4
10uF C5
10uF

C3
100nF

http://custompcb.blogspot.com/
http://diyguitarpa.blogspot.com/
2

6

A

Title

1

5

10/11/2011
D:\!Works\..\PowerFilter.SchDoc
4

Quantit
y

Sheet of
Drawn By:
5

Designator

6

Model:Footprint

2 C1, C7

Capacitor

100nF

RAD-0.3

2 C2, C3

Polarized Capacitor (Radial)

10uF

Cap, Tantal, 1mil

2 C4, C5

Capacitor

47nF

RAD-0.3

2 C6, C8

Capacitor; 2 Leads

HDR2X6_CEN

1 P1

Header, 6-Pin, Dual row

D

Capacitor; 2 Leads

Transistor PNP Silicon

BC560C

29-04

1 Q1

Transistor NPN Silicon

BC550C

29-04

1 Q2

Connector; Header; 6x2 Position
TO, Flat Index; 3 In-Line, Axial Leads; Body Dia.
4.8mm; Leads 0.48 x 0.5 mm (max)
TO, Flat Index; 3 In-Line, Axial Leads; Body Dia.
4.8mm; Leads 0.48 x 0.5 mm (max)

Resistor

12K

AXIAL-0.4

2 R1, R2

Resistor; 2 Leads

Notes

This module required for the EQ mainboard is the power filter circuit. I like to use this simple circuit
to filter the problems of power. These circuits have to be connected to the headers of mainboard.
These modules required for better power and less noise, but if you think this is not important, you
can wire pin 8 to pin 11 and pin 7 to pin 12 to ignore these circuits and boards.
We have three versions of power filter PCB. No difference between schematics, the one of them is
landscape, the another two is portrait orientation on PCB.

Document last modified and saved: 23 October 2011 6:15 PM

- 6

Simple gyrator and permanent Q active filter EQ project

7 -

Simple gyrator and permanent Q active filter EQ project

Schematics and Bill of Materials for gyrator EQ project
10 channel gyrator EQ mainboard
1

2

3

4

5

6

+15V Filt3
GND
6
5
4
3
2
1

P1
Header 6X2A

+15V Filt1

12
11
10
9
8
7

A

2
3

+15V
3

1

1
B

H3

8

A

3

U1A
TL072JG C1
1

1

10u

1
2
3
4
5
6

1
2
3
4
5
6

Header 6X2A

P5
7
8
9
10
11
12

7
8
9
10
11
12

Header 6X2A

GND

-15V Filt G

12
11
10
9
8
7

GND

+15V Filt2

GND

GND

1
2
3
4
5
6

1
2
3
4
5
6

Header 6X2A

7
8
9
10
11
12

1
2
3
4
5
6

Header 6X2A

P10

P11

GND

GND

1
2
3
4
5
6

1
2
3
4
5
6

Header 6X2A

R6

2
R5

3

A

U3A
TL072JG
1

6
5

B

1
2
3
4
5
6

10u

1M

Stereo gyrator EQ mainboard

Size
GND

10u

3

Quanti
ty

4

Comment

D

Number

Revision

A
Date:
File:

2

Value

GND

P14
Header 6X2A
Title

GND

1

C

7
8
9
10
11
12

Header 6X2A

GND

3.3k

GND

-15V Filt2

GND

12
11
10
9
8
7

3

B

U3B
TL072JG
7

4

5

10u

Description
Polarized Capacitor
(Radial)

GND

10/17/2011
Sheet of
D:\!Works\..\Gyrator EQ mainboard.SchDoc Drawn By:

5

Designator

Footprint

4 Cap Pol1

C1, C2, C3, C4

Cap, Tantal, 1mil

4 Connector

H1, H2, H3, H4
P1, P2, P3, P4, P5, P6, P7, P8,
P9, P10, P11, P12, P13, P14

Panel Connector 3 input Small

Model:Footprint

Resistor

3.3k

4 Res2

R1, R2, R4, R5

AXIAL-0.4

Resistor

1M

2 Res2

R3, R6

AXIAL-0.4

U1, U2, U3

dip-8

DIP; 8 Leads; Row Spacing 7.62 mm; Pitch 2.54 mm

14 Header 6X2A

Low-Noise JFET-Input Operational Amplifier 3 TL072JG

HDR2X6_CEN

Boards for gyrator

6

Connector; Header;
6x2 Position
Axial Device, ThruHole; 2 Leads; 0.4 in
Pin Spacing
Axial Device, ThruHole; 2 Leads; 0.4 in
Pin Spacing

Header, 6-Pin, Dual row

Printed Circuit

P13

U2B
TL072JG C3
7

6
5
4
3
2
1

8

6

C4

H4

B

7
8
9
10
11
12

Header 6X2A

R4

GND

1

7
8
9
10
11
12

Header 6X2A

7
8
9
10
11
12

Header 6X2A

3.3k

2

http://custompcb.blogspot.com/
http://diyguitarpa.blogspot.com/

P6
1
2
3
4
5
6

P12
Header 6X2A

12
11
10
9
8
7

6
5
4
3
2
1

GND

P9

7
8
9
10
11
12

GND

D

GND

+15V Filt G
P8

C

Header 6X2A

3

P4

7
8
9
10
11
12

GND

2

This is the schematic of the mainboard of
modular gyrator-EQ project. For this mainboard
required the gyrator circuit (10 board) and
power filter module. Visit the website for details,
PCB, and schematics.

7
8
9
10
11
12

H1

P3

P7
Header 6X2A

2

GND

-15V Filt1 GND

6
5
4
3
2
1

B

-15V Filt3

GND

-15V

5

3.3k

1M

GND

H2

2

R3

10u

2

A

U1B
TL072JG
7

6
R2

4

C2
3

U2A
TL072JG
1

1
2
3
4
5
6

4

8

GND

A

P2

R1
3.3k

EQ project

Notes
This is the mainboard for modular gyrator EQ. The mainboard contains required circuits and headers to
connect gyrator modules, potentiometers, and power filters. The finalized EQ can works with several frequencies and Q-s, and you can choose two versions of gyrator modules, one for stereo solutions with only
one stereo adjustable resistors, the second is two separated mono resistors for all bands for instrument
amplifications. Look at the difference on the PCB section.

Document last modified and saved: 23 October 2011 6:15 PM

9 -

C17

P6

C20
C10 C11

P5

R7 C6

C3

C18

C9
R18

R23R22

P4

C17

P6

C20
C10 C11
R12

C18

R8

R18

R17
C16

U3
R23R22

C14 C22

P4

H3

H4

C19

P1

P2

R16

C21 R21C13

C9

C7
C8

P5

R7 C6

C3

12
6

R20

P7

R15C15

R26

R4 R3 R19U4

R28 R27

H1

7
1

12
6

BOTTOM LAYER

7
1

TOP OVERLAY ON TOP LAYER

C24

R6

P3

U2

C4

R5
R25

C5

C23
C2

H2

U1

C1

R10

R1

C12R9 R11R13R14R24

R2

This the simplest ”all in one”
5 band EQ PCB. Very simple,
low noise circuit for home hi-fi
users. If you want more band,
check the modular version of
this project to insert any type
of gyrator modules to the
mainboard.

H3

H4

Notes

C14 C22

U3

C19

P1

12
6

R17
C16

P2

R16

12
6

R20

R15C15

C21 R21C13

R8

C7
C8

R4 R3 R19U4

R26
R28 R27

7
1

P7

R12

R6

P3

U2

C4

R5
R25

C24

H1

7
1

PCB TOP OVERLAY

TOP LAYER

C5

C23
C2

H2

U1

C1

R10

Simple gyrator and permanent Q active filter EQ project

C12R9 R11R13R14R24

R2

PCB for the simple EQ project
Top and bottom PCBs and overlay of simple 5 band EQ

R1

- 8

Simple gyrator and permanent Q active filter EQ project

Document last modified and saved: 23 October 2011 6:15 PM

- 10

PCB for the modular EQ project
Top and bottom PCBs and overlay of stereo gyrator module

Simple gyrator and permanent Q active filter EQ project

PCB for the modular EQ project
Top and bottom PCBs and overlay of 2 mono gyrator module
Notes

Stereo gyrator module
with one stereo potentiometer to adjust left and right
channel at once. This solution recommended for home
hi-fi users. This module most
be connected to the project’s mainboard.

Dupble-Mono gyrator module with two single potentiometers to adjust left and right
channel separately. This solution recommended for instrument amplifications. This module most be connected to the
project’s mainboard.

BOTTOM LAYER

Notes

TOP OVERLAY ON TOP LAYER

TOP LAYER

TOP LAYER
PCB TOP OVERLAY

11 -

PCB TOP OVERLAY

BOTTOM LAYER

Simple gyrator and permanent Q active filter EQ project

TOP OVERLAY ON TOP LAYER

Document last modified and saved: 23 October 2011 6:15 PM

- 12

Simple gyrator and permanent Q active filter EQ project

13 -

PCB for the modular EQ project
Top and bottom PCBs and overlay of power filters (ver.3)

Simple gyrator and permanent Q active filter EQ project

PCB for the modular EQ project
Top and bottom PCBs and overlay of power filters (ver.2)

BOTTOM LAYER

TOP LAYER

TOP LAYER

We have 3 versions of power filter
PCB. No difference between schematics, the one of them is landscape,
the another 2 is portrait.

BOTTOM LAYER

Notes

OVERLAY ON TOP LAYER

C3

C2

C3
7
P11

3
1
C2

R2

R2

C1

Q2
C7

C4

C1

C2

C6

C2

C6

C3

C8

C3

C8

7
1

R1

P1

P1
12
6

3
1

C4

C4
3
1

OVERLAY ON TOP LAYER

3
1

C8

C8

Q1

3
1

C6

R1
C1

Q2
C7

R1

We have 3 versions of
power filter PCB. No
difference between
schematics, the one of
them is landscape, the
another 2 is portrait.

C5

C7

Notes

3
1

Q2 R2

C6

12
6

C5

7
P11

R1
C1

Q1

Q1
3
1

C7

3
1

Q2 R2

PCB OVERLAY

Q1

C5

C5

C4

PCB OVERLAY

12
6

7
1

12
6

Document last modified and saved: 23 October 2011 6:15 PM

Simple gyrator and permanent Q active filter EQ project

- 14

PCB for the module of Parametric EQ project
Top and bottom PCBs and overlay of power filters (ver.1)

TOP LAYER

Notes
We have 3 versions of power filter PCB. No difference between schematics, the one of them is
landscape, the another 2 is portrait.

R2

C6 C2

Q1
C1

R1

3
1

C5

C7
Q2

C4

3
1

BOTTOM LAYER

C3 C8

P1
12
6

PCB OVERLAY

R2

C6 C2

Q1
C1

R1

3
1

C5

C7
Q2

C4

3
1

7
1

C3 C8

P1
7
1

12
6

OVERLAY ON TOP LAYER

Simple gyrator and permanent Q active filter EQ project

- 15

16 -

Simple gyrator and permanent Q active filter EQ project

PCB for the modular EQ project
The mainboard of 10 band EQ for gyrators

For 5 band EQ:






PCB OVERLAY

100Hz - 330n
300Hz - 100n
1kHz - 33n
3kHz - 10n
10kHz - 3.3n

For 10 band EQ:


TOP LAYER

Notes
This is the mainboard for 10 band gyrator EQ. Gyrator modules and power filter modules required. The frequency, Q and cut/
boost values depended on the parts of gyrator modules only. Look at the table on the gyrator’s schematic page, and read the
page about the math expressions.

Change all of the 50K adjustable resistors to 25K

Hz

C3

C4

R3

R4

31

6.8µ

100n

470�

100k

63

3.3µ

47n

390�

100k

125

1.5µ

33n

390�

100k

250

680n

22n

330�

82k

500

330n

10n

330�

100k

1K

150n

4.7n

330�

100k

2K

100n

2.2n

330�

82k

4K

56n

1n

390�

82k

8K

22n

470p

390�

82k

16K

10n

220p

390�

100k

The values of R3 is same as R1, the R2 is same as R4. Also look the
math expressions for another examples.

BOTTOM LAYER

OVERLAY ON TOP LAYER

Document last modified and saved: 23 October 2011 6:15 PM

- 17

Simple gyrator and permanent Q active filter EQ project

18 -

Simple gyrator and permanent Q active filter EQ project

PCB for the modular EQ project
The mainboard of 5 band EQ for gyrators
Notes

TOP LAYER
For 5 band EQ:
100Hz - 330n
300Hz - 100n
1kHz - 33n
3kHz - 10n
10kHz - 3.3n

For 10 band EQ:


Change all of the 50K adjustable resistors to 25K

Hz

C3

C4

R3

R4

31

6.8µ

100n

470�

100k

63

3.3µ

47n

390�

100k

125

1.5µ

33n

390�

100k

250

680n

22n

330�

82k

500

330n

10n

330�

100k

1K

150n

4.7n

330�

100k

2K

100n

2.2n

330�

82k

4K

56n

1n

390�

82k

8K

22n

470p

390�

82k

16K

10n

220p

390�

100k

PCB OVERLAY







This is the mainboard for modular gyrator EQ. The mainboard contains required
circuits and headers to connect gyrator
modules, potentiometers, and power
filters. The finalized EQ can works with
several frequencies and Q-s, and you
can choose two versions of gyrator
modules, one for stereo solutions with
only one stereo adjustable resistors,
the second is two separated mono resistors for all bands for instrument amplifications. Look at the difference on the
PCB section.

The values of R3 is same as R1, the R2 is same as R4. Also look the
math expressions for another examples.

BOTTOM LAYER

This is the mainboard for 5 band gyrator EQ. Gyrator
modules and power filter modules required. The frequency, Q and cut/boost values depended on the parts of
gyrator modules only. Look at the table on the gyrator’s
schematic page, and read the page about the math expressions.

OVERLAY ON TOP LAYER

Notes

Document last modified and saved: 23 October 2011 6:15 PM

Simple gyrator and permanent Q active filter EQ project

- 19

20 -

Simple gyrator and permanent Q active filter EQ project

Schematics and Bill of Materials for all EQ project
Schematic and BOM of power supply

The power supply for

1

2

3

4

A

R1
KBL04

C6
47n

3

B

D1

10 1W

IN

OUT
ADJ

A

2
+15V Out

+15V In
C2
2200u

C4
100n

D2
16V Zener

C3
47u

C5
100n

C7
47n

1

2

B

2

1

GND
15V AC - 2

H1

C8
47n

C9
47n

3

GND
2200u
C11

C10
2200u

R2

D3
16V Zener

100n
C13

-15V In

10 1W

C12
47u

H2
C14
100n
-15V Out

1

all gyrator EQ projects

15V AC - 1

C1
2200u

LM317BT
U1

6

1

3

5

C

2

ADJ
IN
OUT

C

3

U2
LM337BT

Title

Power supply

Size
D
http://custompcb.blogspot.com/
http://diyguitarpa.blogspot.com/

1

Description

2

D

Date:
File:

3

Quanti
ty

Value

Revision

10/17/2011
D:\!Works\..\Power supply.SchDoc
4

Designator

Sheet of
Drawn By:

5

6

Polarized Capacitor (Radial)

Cap Pol1

4 2200u

Polarized Capacitor (Radial)

Cap Pol1

2 47u

Footprint
ELCO 22 MM 4
MIL
Elco 12 mm, 2
mil pins

Capacitor

Cap

4 100n

RAD-0.3

Capacitor

Cap

4 47n

RAD-0.3

C6, C7, C8, C9

Full Wave Diode Bridge

KBL04

1

Bridge hor.

D1

Zener Diode

16V Zener

2

Connector

2

DIODE-0.7
D2, D3
panel connector
3 input big
H1, H2

Res2

2 10 1W

AXIAL-0.4

R1, R2

LM317BT

1

221A-04

U1

3 pin, 3 mil connector
Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin
Spacing
TO, Thru-Hole, Vertical, Heatsink Mounted; 3 InLine Leads; Pitch 2.54 mm

3-Terminal Adjustable Negative Voltage
LM337BT
Regulator 1

221A-04

U2

TO, Thru-Hole, Vertical, Heatsink Mounted; 3 In-Line Leads; Pi

Resistor
3-Terminal Adjustable Positive
Voltage Regulator

Comment

Number

A

C1, C2, C10, C11

C4, C5, C13, C14

Model:Footprint

C3, C12
Radial Cap, Thru-Hole; 2 Leads; 0.3 in Pin
Spacing
Radial Cap, Thru-Hole; 2 Leads; 0.3 in Pin
Spacing
Diode, Thru-Hole; 2 Leads; 0.7 in Pin Spacing

Document last modified and saved: 23 October 2011 6:15 PM

Simple gyrator and permanent Q active filter EQ project

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22 -

Simple gyrator and permanent Q active filter EQ project

PCB for all EQ project
The power supply PCB

TOP LAYER

PCB OVERLAY
H1

D1

U1

R1

1 2 3
C5

C9
C1

C8

C2

C6

U2
1 2 3
C14

D2
C12

R2
C7

C4

D3

C10

C11
C3

H2

C13

OVERLAY ON TOP LAYER
BOTTOM LAYER
H1

D1

U1

R1

1 2 3
C5

C9
C1

C8

C2

C6

1 2 3
C14

D2
C12

R2
C4

U2

C7

C10

D3
C11
C3

H2

C13

Document last modified and saved: 23 October 2011 6:15 PM

Simple gyrator and permanent Q active filter EQ project

- 23

24 -

Simple gyrator and permanent Q active filter EQ project

Help for gyrator EQ designs
Articles and images about gyrator EQ projects
With this project, very important to inform about the adjustable EQ designs. Because the modules can be set to
several adjustable values, maybe you need expressions to get the value of resistors or capacitors. Here is the page
to help.
Useful links and articles:

About Operator Adjustable Equalizers:

Math expressions,
articles for gyrator EQ
designs










Equalizer History
Industry Choices
Terminology & Definitions
Active & Passive
Graphics & Parametrics
Constant-Q & Proportional-Q
Interpolating & Combining
Phase Shift Examples

Design aspects of equalizers with lots of expressions.
The Evolution of an EQ Design
Software for EQ filter design

Images about this project:






The Piacsa album of projects
Prototype of 5 band and 10 band EQs
The new PCBs of modular gyrator EQ
PCBs and schematics of modular UREI clone parametric EQ project
RSS channel of my Picasa gallery

Document last modified and saved: 23 October 2011 6:15 PM

mined, and one will be chosen for this filter’s EQ sections.

1.1 TheSimple
Gyratorgyrator and permanent Q active filter EQ project
gyrator makes a nice RCL circuit. It gives symmetrical impedance (on a logarithmic
e) around the resonance frequency.

- 25

Help for gyrator EQ designs
symmetrical impedance makes it ideal for an equalizer.
Math expressions for gyrator design

C1
2

=>
C2

L

The Gyrator
The gyrator makes a nice RCL circuit. It
gives symmetrical impedance (on a logarithmic scale) around the resonance
frequency.

Rs

0

0

C1

R1
2

=>

C2
+

L
1

The active inductor is actually just a
Sallen and key HP filter drawn slightly
differently. It too functions as a series
connection between a capacitor and
an inductor. The major difference is
that the inductor has a parallel resistor.
page
11
of 27parallel resistor makes the impedRp
This
ance of the circuit NON-symmetrical
around the resonance frequency, thus
making the circuit less suited for EQ’s.

-

R2

Rs

0

Because of this parallel resistor, the
gyrator is preferred to implement the
inductor in the EQ sections of this filter.

0

Figure 11: The active inductor

L

(

C2 ⋅ R1 ⋅ R2 − R1

)

Rs

R1

2

s +

ωo

⋅s + ωo
Q

2

2

s +
EQnotch ( s)

Rp

2

s +

ωo

⋅s + ωo
Q

ωo

2

⋅s + ωo
Q ⋅ Kn

2

Kp and Kn are the gains of the EQ at their center frequency ωo. Their frequency response can
look like this:
10

The symmetrical impedance makes it
ideal for an equalizer.

he active inductor
inductor is factually just 1a Sallen and
slightly differently. It too
Rs key
R1 HP
+ R2filter
L drawn
C2 ⋅ R1 ⋅ R
res
2

C

C

R

R

s a series connection 1between
2 1 2 a capacitor and an inductor. The major difference
nductor has a parallel resistor. This parallel resistor makes the impedance of the
N-symmetrical around the resonance frequency, thus making the circuit less suited

@delta-audio.com

EQpeak ( s)

Kp ⋅ ωo
2
⋅s + ωo
Q

www.delta-audio.com

Figure 10: The gyrator

C1

2

s +

1

R2

one version 1.0

The EQ is described by a transferfunction as any other second order system. There is
however a minor change to the way that it is written.

R2 − R1

this parallel resistor, the gyrator is preferred to implement the inductor in the EQ
this filter.

( )

dB Kp
5

Gain [dB]

-

R1

www.delta-audio.com

Simple gyrator and permanent Q active filter EQ project

3.3.2 The mathematical EQ

There are at least two ways of making
a capacitor act like an induction. One is
called the gyrator, and one is called the
active inductor. In the following the two
circuits will be examined, and one will
be chosen for this filter’s EQ sections.

C1
+

Active filter one version 1.0

26 -

0

( )

dB Kn

5

10

1

EQ peak
EQ notch
The SUM of the two EQs

10
freq [hz]

100

The two EQs have identical Qs of 2 and fo = 10 Hz. Kp = 2 and Kn = 0.5. The SUM of the two
filters is 0 dB witch means that two EQ sections can cancel each other out, if they share Q
and fo. The gain in dB must be the same for the two (Notch is negative of cause and peak is
positive)
The feature, that the EQs cancel each other when the have the same Q and “opposite”
gains; is called "reciprocal". This is a special type of EQ, since there are also circuits that are
"non-reciprocal".
jrm@delta-audio.com

Document last modified and saved: 23 October 2011 6:15 PM

page 13 of 27

Simple gyrator and permanent Q active filter EQ project

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Simple gyrator and permanent Q active filter EQ project

Help for gyrator EQ designs
The frequency response of 10 channel modular EQ project

Previous PCBs and
images for simple 5
band and permanent Q
10 band EQ

Document last modified and saved: 23 October 2011 6:15 PM

- 29

30 -

Images about first prototype
5 band stereo permantnt Q graphic equalizer
The previous version of RANE Layout
basedsize:
permanent
Q project
1:1
I/O

Images about first prototype
5 band stereo graphic equalizer
The previous version of Layout
simplesize:
5 band
1:1 EQ

Simple gyrator and permanent Q active filter EQ project

I/O channel, connector for
input/output, VCC, VEE, etc...

http://microprojects.rentahost.net

http://microprojects.rentahost.net

R

R

C
R

C

R

C
C

P

P

C

D

P

C

P

B

+

C

C

C

C

C

C

+

+

R

C C

-

Q

+

C

C

+

Powertransistor or powerfet

Q

-15V

R

C

C

+

Single transistor or JFET

J

Q

C

5 channel stereo graphic EQ by SF
http://microprojects.rentahost.net

Q

U P

P

C

+

Integrated circuit

B

C

B

C

C

R

B

R

C

1

C

+

R
R

-

V+

R

R
C

C

Q

Q
C

C

C

V-

R

C

C

C

R

C

R
R

U

-

R

Left

U P

R

C

R

R
C

C

C

R

C

U P

C

R

C

R

R

R

R

R

R

C
C

R

R

R

R

R

R

C

R

C
C

R

R

B

R

R

C
C

U P

R

R

C
C

R
R

R

R

R

R

C
C

U

C

C
RightB
3
2
1:Cut
R 2:Boost
3:Sig
1 R3 2

R

R

C

R

R

C

C

R

R

R

R

R

R

C
C

R

R

C

-

Right

C
R

R
C

R

R

Left

R

R

R

R

R

+

P

Q

C

R

P

C

B

-

B

C

P

P

P

Right

+

C C+

Integrated circuit

C

R

Integrated circuit

Q

-

Integrated circuit

R

C C

C

C

R

+

Left

R

5 channel stereo permanent Q graphic EQ by SF
R
R
http://microprojects.rentahost.net

+
I/O

C

R

Q

C C+
+

U

R

C
C

C

C

R

+

U

R

C

Integrated circuit
U

R

R

I/O

U

C

U

C

R

U

R

R

R

Integrated circuit
U

R

R
R

R

R
R

R

R

R

B

C

C

R

C
C

2

R

C

C TR

+

U

R

R

Integrated circuit

Integrated circuit

U

R
R

R

C
C

Integrated circuit

C

Q

R
C

1:Cut
2:Boost
3:Sig

R
R

C

R

C
C

R

C

TR

RQ

Right
3

C

V+

3

Left

R

U

R
R

R

U

1

+

U

C

R

Potentiometer

P

J

R

R

TR

U

R

C

R

C

C

R R

R
J

R

C

Resistor

Potentiometer

+
D

R
C

R

R

U

R

1

Trimmer potentiometer

P

R
R

R

R

+

Trimmer potentiometer

R
R

R R

R

P
R

R
S

2

Powertransistor or powerfet
Potentiometer

Resistor

TR

R

R

Trimmer potentiometer
Single transistor or JFET

Q
R

R

J

C+

TR

-

J

U

TR

Resistor
R
Dual transistor or JFET

Q

-

1

S

R

Jumper

+

+

GND
Q

C

S

-

R

C
R

D
C
U
R
R R
RR
R
C
RR
U
R
+
3 2 D
R
C
RR R S C
R
R R
R
RR
R
C
R
VR R
J R
R
R
C
+
R
R
C
R
R
R R
C+

RR

+

I/O

+15V

R R

C+

Diode
Powertransistor or powerfet
Q

R C
C

R

R

C

D

+

R
RR R
R
R
R
R
R

C

Electrolic capacitor
Single transistor or JFET

R

C
C

R R

C+

Dual transistor or JFET

Q

+
D

R

TR

Good
quailty non-electrolic
J
Jumper
C + polarized
capacitor, for example Tantal

A

U

TR
S

R

R

+

P

C

Electrolic capacitor

C+

R

R

+

C

C

Non-polarized capacitor,
C ceramic, or some good quality
D WIMA capactors
like
Diode

D

R

J

3

+

C

C

2

1

+

R

C+

R

+

R

R

R R

TR

R

+

C

R

R

+

R

2

C

R

R

+

R

C

A

+

R

C R

R

C

+

R

TR

R

+

Good quailty non-electrolic
C + polarized capacitor, for example Tantal
S
Relay

D

R

+

+

R

C

R

-

-

Q

+

U

C C

+

R

U

C

C

+

R

D

C+
U

3

1

+

C

In 1

Electrolic capacitor

Dual transistor or JFET

3

I/O

R

I/O

R

I/O

TR

R

U

R

R

In 2

Diode

Q

2

1

R

I/O

U

R

+

+

R

Q

D

D

R
R
C
C
5 band stereo permantnt
Q graphic
equalizer
R
R
C
S
R
R
+
D
R
R
C
Layout size:S 1:1
S
C
R R
R
R
R
R
C
C
http://microprojects.rentahost.net
R R
R
TR
R
R
R

+

C

Good quailty non-electrolic
C + polarized capacitor, for example Tantal

C

R

+

B

TR

I/O

Non-polarized capacitor,
C ceramic, or some good quality
like WIMA capactors

R

GND
GND

R

+

Relay

Relay

I/O channel, connector for
input/output, VCC,
VEE, etc...
Non-polarized
capacitor,
C ceramic, or some good quality
like WIMA capactors

C
C

Out 2
S

C
R

TR

I/O

+
D

I/O

Out 1

S

TR

+

I/O

I/O channel, connector for
input/output, VCC, VEE, etc...

+

S

+

Simple gyrator and permanent Q active filter EQ project

5 channel stereo permanent Q graphic EQ by SF
http://microprojects.rentahost.net

Document last modified and saved: 23 October 2011 6:15 PM

English blog and PCB order: http://custompcb.blogspot.com/
Hungarian blog and PCB order: http://diyguitarpa.blogspot.com/
The Youtube Channel • Picasa gallery • Email: gitarfogas@gmail.com


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