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Preamps for home hi-fi and
musical instruments

3 -

Schematics and Bill of
Materials for audio
preamplifiers projects

Preamplifiers for musical instruments and home hi-fi

Schematics and Bill of materials for instrument preamplifiers
Schematic and BOM of cheap microphone preamp
1

4

+15V a1

47uF 60V

Q2

Q1

R2
12K

C6 100nF

C7
10uF

10uF

BC548C

C9

100nF
C8

C4

R3

BC560C 12K

47uF 60V

-15V a1

8
R8

6.8K
R9

REF
RG_1

8

C13
47uF 60V

GND

J1

7
4

C17
10uF

C15

Input Jack 6.3

R15
100K

10uF

Output

H4

C

1

GND

Bal In 1 GND

Header 6X2A

Bal In 2

C16
100nF

Q4

R17

Q3

12K

BC560C

BC548C

2

47uF 60V
C21

H5
GND

C23
47nF

Title

GND

Schematic and BOM of cheap microphone preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stereo jFET guitar (instrument, effect) preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stereo dual OpAmp instrument or audio preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stereo circuit with 2 single OpAmp, instrument and audio preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stereo low noise 2 single OpAmp instrument preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Schematic and BOM of power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3
4
5
6
7
8

Printed Circuit Boards for instrument preamps project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Top and bottom PCBs and overlay of INA217 microphone preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Top and bottom PCBs and overlay of stereo jFET preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Top and bottom PCBs and overlay of simple dual OpAmp preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Top and bottom PCBs and overlay of power filters (ver.3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Top and bottom PCBs and overlay of power filters (ver.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Top and bottom PCBs and overlay of power filters (ver.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Two single OpAmp - stereo universal preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Two single OpAmp - stereo low noise universal preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Switch module for preamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The PCB of power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10
12
13
14
15
16
17
18
19
20

Images and Picasa galleries about the prototype of preamps . . . . . . . . . . . . . . . . . . . . . . . . 22
The selectable prototype of jFEt and OpAmp projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Audio mixer with jFET and OpAmp preamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Microphone preamp with INA217 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Date:
File:
2

Mic and instrument preamp with
assimatrical/simmetrical inputs
Number

D
Revision

A3

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

1

P3

1

Size

Schematics and Bill of Materials for audio preamplifiers projects . . . . . . . . . . . . . . . . . . . . . . 2

B

10uF

2

GND

C19
10uF

GND

P2
47kB

U3
OPA137
2

C22
47nF

D

R11
100K

GND

3

C18
100nF

R16
12K

2
C10
3

6

C11 10uF

R10
1M

+15V a2

-15V a2

C20

6

C14
100nF

6

U2
OPA137

470

R12
470

GND

47uF 60V

R5
1K

V_IN-

R14
2.2K

C

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

V_OUT

V_IN+

2

C12
47uF 60V

INA217 AIP

RG_2

3

R13
2.2K

R4
1K

GND
R7

1

P1
1.6kA

6.8K

U1

5

12
11
10
9
8
7

R6

B

D2
1N4148

D4
1N4148

V-

D1
1N4148

7

D3
1N4148

4

GND

6
5
4
3
2
1

GND

7

C3

GND

4

-15V

C5
47uF 60V

C2 47nF

+15V

R1
47K

0
1
2
3
4
5

+48V

V+

This project made for testing and building the best simple solutions for instrument and
audio preamplifiers for home users. Microphone preamp with cheap instrument amplifier INA217, noiseless solution with jFET for guitarists, and very simple but hi-gained
audio circuits with OpAmps for audio solutions for home hi-fi. The next project is to make
audio mixer with these preamplifier circuits.
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:

6

A
C1 47nF

GND

5

3

2

1

3

2

1

3

2

1

3

H1

H2

H3
A

2

3

4

10/17/2011
Sheet of
D:\!Works\..\INA217-MicPreamp.SchDocDrawn By:
5

6

The Picasa album about prototype testing
Description

Comment

Value

Capacitor

Cap

47nF

Polarized Capacitor (Radial)

Cap Pol1

47uF 60V

Capacitor

Cap

100nF

Polarized Capacitor (Radial)
High Conductance Fast
Diode

Cap Pol1

10uF

1N4148

1N4148

Quanti
ty

Designator

4 C1, C2, C22, C23
C3, C4, C5, C12, C13,
7 C20, C21

Footprint
RAD-0.3
Elco 12 mm, 2
mil pins

5 C6, C8, C14, C16, C18 RAD-0.3
Capacitor; 2 Leads
C7, C9, C10, C11, C15,
7 C17, C19
Cap, Tantal, 1mil
Diode, Axial; Body 3.8 x 1.9 mm (LxDia. max), Lead
4 D1, D2, D3, D4
DO-35
Dia. 0.53 mm (max)
Panel Connector
3 H1, H2, H3
3 input Small
Panel Connector
2 H4, H5
2 input Small

Connector, 3 pin, 2 mil

Connector

Connector, 2 pin, 2 mil

Connector
Input Jack
6.3

Resistor

Pot Mono 1.6kA

1 P1

Resistor

Pot Mono 47kB
Header
6X2A

1 P2

Jack input 6.3
Pot Mono
MetalCase
Pot Mono
MetalCase

1 P3

HDR2X6_CEN

BC548C

2 Q1, Q4

29-04

BC560C

2 Q2, Q3

Header, 6-Pin, Dual row
Amplifier Transistor NPN
Silicon
Low Noise Transistor PNP
Silicon

Model:Footprint
Capacitor; 2 Leads

1 J1

3 pin mono metal case pot, 2 mil
3 pin mono metal case pot, 2 mil

29-04

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

Res2

47K

1 R1

AXIAL-0.4

Resistor; 2 Leads

Resistor

Res2

12K

4 R2, R3, R16, R17

AXIAL-0.4

Resistor

Res2

1K

2 R4, R5

AXIAL-0.4

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

Resistor

Res2

6.8K

2 R6, R9

AXIAL-0.4

Resistor

Res2

470

2 R7, R12

AXIAL-0.4

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

Resistor

Res2

8

1 R8

AXIAL-0.4

Resistor; 2 Leads

Resistor

Res2

1M

1 R10

AXIAL-0.4

Resistor

Res2

100K

2 R11, R15

AXIAL-0.4

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

Resistor

Res2
2.2K
INA217AI
P
INA217 AIP

2 R13, R14

AXIAL-0.4

Resistor; 2 Leads

1 U1

DIP-8

OPA137

1 U2

006E

DIP, 8-Pin, Row Spacing 7.62 mm, Pitch 2.54 mm
DIP; 8 Leads; Row Spacing 7.62 mm; Pitch 2.54
mm

1 U3

006E

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

Instrument Amp
General Purpose FET-Input
Operational Amplifiers

OPA137
FET-Input Operational Amplifiers

OPA137

Notes

This circuit made for mono
microphone inputs only.
The input is mono, jack inserted directly to the board
with asymmetrical/symmetrical converter, and 3
inputs header inserted for
symmetrical phones with
XLR output. Switch module
required to select between
two inputs (asymmetrical
jack or symmetrical XLR).
The amplifier of this circuit
is INA217. This instrument
amp is very cheap, and
noiseless. Volume and gain
potentiometers included.

Document last modified and saved: 19 October 2011 7:39 PM

- 4

Preamplifiers for musical instruments and home hi-fi

5 -

Schematics and Bill of materials for instrument preamplifiers
Stereo jFET guitar (instrument, effect) preamp

Schematics and Bill of materials for instrument preamplifiers
Stereo dual OpAmp instrument or audio preamplifier
1

1

2

3

4

5

2

A

1
2
3
4
5
6

A

R1
5.1K

Out 2

J1

Q1A
2N3958

A

J1

0
1
2
3
4
5

C3

10uF

R2
10M

R3
51K

R5
220

GND

10uF

GND

R4
51K

GND

B

C4 10uF

GND

2
1
Header 2

GND

R7
22K

H2

Q1B
2N3958

7
R8
10M

2
+15V Stage

1
2

C5

C6
10uF

1

100nF

H3

D

BC548C
Q2
R10

12K

47nF
C8

+15V Input

8

Pot stereo
5kA

C

-15V

Stereo Dual jFET preamp

Size

H2

Number

Revision

D

3

4

5

6

Description

Comment

Value

Footprint

Designator

Polarized Capacitor (Radial)

Cap Pol1

10uF

5 Cap, Tantal, 1mil C1, C2, C3, C4, C6

Capacitor

Cap

100nF

C5

Polarized Capacitor (Radial)

Cap Pol1

47uF 60V

1 RAD-0.3
Elco 6mm, 1 mil
1 pins

Capacitor

Cap

47nF

1 RAD-0.3

C8

Panel Connector
2 2 input Small
H2, H3

Connector
Input Jack
6.3

Resistor

Pot stereo
Pot stereo

47kB
5kA

Capacitor; 2 Leads

C7

Panel Connector
1 3 input Small
H1

Connector

Model:Footprint

1 Jack input 6.3
Pots Plastic
1 Stereo
Pots Plastic
1 Stereo

J1

1 HDR1X2

P3

Capacitor; 2 Leads

3 pin, 2 mil connector

2 pin, 2 mil connector

P1
P2

Header, 2-Pin
Header 2
N-Channel Dual JFET (General
Purpose)
2N3958

Resistor

Res2

5.1K

2 AXIAL-0.4

R1, R6

Resistor

Res2

10M

2 AXIAL-0.4

R2, R8

Resistor

Res2

51K

2 AXIAL-0.4

R3, R4

Resistor

Res2

220

2 AXIAL-0.4

R5, R9

Resistor

Res2

22K

1 AXIAL-0.4

R7

Connector; Header; 2 Position
Can; 7 Leads (1 Absent); Pin Circle Dia. 2.54 mm;
Lead Dia. 0.48 mm (max)
TO, Flat Index; 3 In-Line, Axial Leads; Body Dia.
4.8mm; Leads 0.48 x 0.5 mm (max)
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
Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin
Spacing
Axial Device, Thru-Hole; 2 Leads; 0.4 in Pin
Spacing

1 TO-71

Q1

Amplifier Transistor NPN Silicon BC548C

1 29-04

Q2

Resistor

Res2

12K

1 AXIAL-0.4

R10

Resistor; 2 Leads

This very simple, small, cheap
and noiseless preamp made
for musical instruments with stereo (or mono) input. The main
part of this circuit is 2N3958
dual jFET. Ideal for stereo or
mono guitar effects,
keyboards, or to connect another
devices with stereo outputs like
audio mixers. Stereo jack, gain
and volume adjustable resistors
are inserted to the PCB. Very
cheap and very good quality
for guitars. The possible gain
is not too high of this circuit, but
enough for guitars and guitar effects with very warm sound.

Q2

R8

47uF 60V

12K

C11100nF

10uF

BC548C

C14

C12
10uF

100nF
C13

BC560C

R9

C10

12K

47uF 60V

GND

1
Title

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

1

Dual stereo OpAmp w. power filter

Size

2

Number

D
Revision

A
Date:
File:

3

Notes
Quanti
ty

C8 47nF

Q1

C9

2
H3

10/17/2011
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Drawn By:

1
3

A
Date:
File:
2

C7 47nF

+15V

2

Title
GND

C

-15V Clean

3

47uF 60V
C7

P3
Pot stereo
100kA

7

GND

GND

R9
220

R6
4.7k

TL072ACN

GND

The Picasa album about jFET amplifier

Resistor

B

R7
1M

C

GND

GND
1

10uF

R5
4.7k

4

6

GND

GND

5

Header 2

10uF

U1B

6

C4

H1

B

100k

5

C

GND

C6

68p
R4
+15V Clean

2
1

2
3

C5

R3
22K

GND

1

1

GND

P2

R6
5.1K

P2
Pot stereo
47kB

TL072ACN

R2
1M

P1

GND

A

3

Input Jack 6.3
B

U1A

2

Input Jack 6.3
P3

10uF

68p
R1

C3
10uF

0
1
2
3
4
5

Pot stereo
47kB

1

3
C2

6

100k

2

GND

5

C2

C1

P1

C1 10uF

1

B

7
8
9
10
11
12

Header 6X2A

Out 1

H1

4

P4

A

2

3

6
http://custompcb.blogspot.com/
http://diyguitarpa.blogspot.com/

3

Preamplifiers for musical instruments and home hi-fi

10/17/2011
Sheet of
D:\!Works\..\OPAMP-Preamp-Stereo.SchDocDrawn By:
4

5

6

The Picasa album about OpAmp amplifier
Description

Comment

Capacitor

Cap

Value
68p

Quanti
ty

Footprint

Capacitor; 2 Leads

C7, C8

Capacitor; 2 Leads

C11, C13

Polarized Capacitor (Radial)

Cap Pol1

10uF

Cap

47nF

Polarized Capacitor (Radial)

Cap Pol1

47uF 60V

2 RAD-0.3
Elco 12 mm, 2
2 mil pins

Capacitor

Cap

100nF

2 RAD-0.3

C9, C10

Panel Connector
3 3 input Small
H1, H2, H3

Connector
Input Jack
6.3
Header, 2-Pin

Header 2

Resistor

Pot stereo

47kB

Resistor

Pot stereo
Header
6X2A

100kA

Model:Footprint

C1, C5
C2, C3, C4, C6, C12,
6 Cap, Tantal, 1mil C14

Capacitor

Header, 6-Pin, Dual row

Designator

2 RAD-0.3

1 Jack input 6.3

J1

1 HDR1X2
Pots Plastic
1 Stereo
Pots Plastic
1 Stereo

P1

1 HDR2X6_CEN

P4

1 29-04

Q1

1 29-04

Q2

Capacitor; 2 Leads

3 pin, 2 mil connector

Connector; Header; 2 Position

P2
P3

Resistor

Res2

100k

2 AXIAL-0.4

R1, R4

Resistor

Res2

1M

2 AXIAL-0.4

R2, R7

Resistor

Res2

22K

1 AXIAL-0.4

R3

Resistor

Res2

4.7k

2 AXIAL-0.4

R5, R6

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

Resistor

Res2

12K

2 AXIAL-0.4

R8, R9

Resistor; 2 Leads

1 dip-8

U1

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

Amplifier Transistor NPN Silicon BC548C
Low Noise Transistor PNP
Silicon
BC560C

Low-Noise J-FET Dual Operational
TL072ACN
Amplifier

Notes

This is another really simple,
good quality and cheap
preamplifier with stereo
jack input for guitar effects
or keyboards. The possible
gain is much higher than
jFET circuit, and the sound
is better for keyboards or
mixers than the guitars or
guitar effects. The dual
OpAmp must be compatible with TL072. Gain and
volume pots has inserted to
the PCB board.

Document last modified and saved: 19 October 2011 7:39 PM

Preamplifiers for musical instruments and home hi-fi

- 6

7 -

Schematics and Bill of materials for instrument preamplifiers
Stereo circuit with 2 single OpAmp, instrument and audio preamplifier
1

2

3

4

5

6

Preamplifiers for musical instruments and home hi-fi

Schematics and Bill of materials for instrument preamplifiers
Stereo low noise 2 single OpAmp instrument preamplifier
1

Notes

2

3

4

5

6

Notes

P4

Header 6X2A

P2
Pot stereo
47kB

C1

1
2
3

C2

68p

J1

0
1
2
3
4
5

C3

10uF

C4

10uF

2

Input Jack 6.3

GND

P1
2
1
Header 2

1

GND

GND

B

5
LF356D

C6

C5

10uF

68p
R4

R3
22K

100k
7

+15V Clean

U4

2

8

R6
4.7k
P3
Pot stereo
100kA

5
4

1

R7
1M

R5
4.7k

6

3
C

H1

U3 8

3
R2
1M

GND

GND

6

4

B

10uF

100k

7

R1

C

LF356D

This circuit looks like the
previous version of TL072
compatible OpAmp preamplifier, but for this, two
single OpAmp device
required, instead of one
dual. The reason of this solution is the better quality, if
you want to use for example really noiseless single
LF or LT serial integrated
circuits instead of relative
noisy one dual TL072.

-15V Clean

-15V

C7 47nF

C8 47nF

3
+15V

1

Q1

C9
47uF 60V

2
D

H3

Q2

R8

3

12K

C11100nF
BC548C

C12
10uF

10uF
C14

100nF
C13

BC560C

R9

C10

12K

47uF 60V

GND

1
D
Title
GND

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

1

2

C2

68p
R1

Value

Stereo single OpAmp preamp w. power filter
Number

Revision

A
Date:
File:

3

Quanti
ty
Comment

Capacitor

68p

2 Cap

Polarized Capacitor (Radial)

10uF

6 Cap Pol1

Capacitor

47nF

2 Cap

10/17/2011
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D:\!Works\..\LF356-Preamp-Stereo.SchDoc Drawn By:

4

Footprint

5

Designator

RAD-0.3

6

Capacitor; 2 Leads

C7, C8

Capacitor; 2 Leads

C11, C13

Polarized Capacitor (Radial)

47uF 60V

2 Cap Pol1

Capacitor

100nF

2 Cap

RAD-0.3

C9, C10

Panel Connector
3 Connector 3 input Small
H1, H2, H3
Input Jack
1 6.3
Jack input 6.3
J1
1 Header 2

Resistor

47kB

1 Pot stereo

Resistor

100kA

1 Pot stereo
Header
1 6X2A

Header, 6-Pin, Dual row

Model:Footprint

C1, C5
C2, C3, C4, C6, C12,
Cap, Tantal, 1mil C14
RAD-0.3
Elco 12 mm, 2
mil pins

Header, 2-Pin

J1
B

C4
10uF

Input Jack 6.3
2
1
Header 2

GND

HDR1X2
Pots Plastic
Stereo
Pots Plastic
Stereo

P1

HDR2X6_CEN

P5

Capacitor; 2 Leads

3 pin, 2 mil connector

Connector; Header; 2 Position

P2
P3

10uF

100k

+15V Clean
3

3
2

C
H3

GND

1

P3
Pot stereo
100kA

1

8

R7
1M

R6
4.7k

6

3

1

R5
4.7k

U2
5

2

2
H2

B

C6

68p
R4

C

-15V Clean

C7 47nF

This solution is really cheap,
against the noise one powerfilter circuit included (for
both OpAmps). Stereo
jack input, stereo/mono
and bypass switch, gain
and volume potentiometers
inserted to the board.

+15V

C10

C8 47nF

47uF 60V

Because the circuit noise,
distortion (and the gain)
depending on the included
single OpAmp, the solution
recommended for all nonguitar instrument, and audio amplifiers for home hi-fi
solutions.

Q1

C15 47nF

100nF
BC548C

C16

C18
47uF 60V

Q3

R10
12K

100nF

10uF

BC548C

C22

C20
10uF

100nF
C21

1

Capacitor

2

C19

12K

47uF 60V

Title

R9

C11

12K

47uF 60V

GND

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

D

Stereo preamp w. 2 single OpAmp and 2 power filters

Size

Number

Revision

Value
68p

Quanti
ty
Comment
2 Cap

10/17/2011
Sheet of
D:\!Works\..\LT1115-Preamp-Stereo.SchDocDrawn By:

4

Footprint

5

Designator

RAD-0.3

6

Model:Footprint

Polarized Capacitor (Radial)

10uF

8 Cap Pol1

C1, C5
C2, C3, C4, C6, C12,
Cap, Tantal, 1mil C14, C20, C22

Capacitor

47nF

4 Cap

RAD-0.3

C7, C8, C15, C16

Capacitor; 2 Leads

Capacitor

100nF

4 Cap

C9, C13, C17, C21

Capacitor; 2 Leads

Polarized Capacitor (Radial)

47uF 60V

4 Cap Pol1

RAD-0.3
Elco 12 mm, 2
mil pins

Header, 2-Pin

1 Header 2

Resistor

47kB

1 Pot stereo

Resistor

100kA

1 Pot stereo
Header
1 6X2A

Header, 6-Pin, Dual row

HDR1X2
Pots Plastic
Stereo
Pots Plastic
Stereo

Capacitor; 2 Leads

C10, C11, C18, C19

Panel Connector
3 Connector 3 input Small
H1, H2, H3
Input Jack
1 6.3
Jack input 6.3
J1
P1

3 pin, 2 mil connector

Connector; Header; 2 Position

P2

Resistor

100k

2 Res2

AXIAL-0.4

R1, R4

Resistor

1M

2 Res2

AXIAL-0.4

R2, R7

Resistor

22K

1 Res2

AXIAL-0.4

R3

Resistor

4.7k

2 Res2

AXIAL-0.4

R5, R6

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

HDR2X6_CEN

P4

29-04

Q1, Q3

2 BC560C

29-04

Q2, Q4

Resistor

12K

4 Res2

AXIAL-0.4

R8, R9, R10, R11

Resistor; 2 Leads

U1, U2

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

AXIAL-0.4

R2, R7

Resistor

22K

1 Res2

AXIAL-0.4

R3

Resistor

4.7k

2 Res2

AXIAL-0.4

R5, R6

Resistor

12K

2 Res2

AXIAL-0.4

R8, R9

Resistor; 2 Leads
DIP; 8 Leads; Row Spacing 7.62 mm; Pitch 2.54 mm

Ultra Low Noise Precision High-Speed Operational Amplifier
2 LT1028CN8 dip-8

Amplifier Transistor NPN Silicon
Low Noise Transistor PNP
Silicon

The difference between
this and the previous
version of board, here
we have two power
filter, one filter for one
OpAmp for the best result of really low noise
and distortion. The circuit recommended for
home hi-fi and instruments, included instrument effects.
Gain and volume potentiometers,
bypass
and
stereo/mono
switches included to the
board with stereo jack
input.

P3

2 BC548C

2 Res2

U3, U4

R11

3

1M

dip-8

BC560C

A

Resistor

Q2

GND

Date:
File:

R1, R4

29-04

100nF
C13

47nF

BC560C

AXIAL-0.4

1 BC560C

C14

Q4

C17

2 Res2

Q1

C12
10uF

10uF

-15V Clean 1
D

100k

29-04

Q2

C9

R8
12K

This is the last version of
OpAmp preamplifiers.
This have best quality.
This is the reason why
two single OpAmp
included instead of
one dual. LT1115 or
LT1028 recommended
for best result, maybe
one of LF or NE serial
OpAmps.

LT1028CN8

GND

GND

Resistor

1 BC548C

Wide-Bandwidth Single J-FET Operational Amplifier2 LF356D

LT1028CN8

C5

R3
22K

GND

H1

1

8

GND

P1

GND

6

3
R2
1M

2
3

GND

5

2

C3
10uF

0
1
2
3
4
5

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

Amplifier Transistor NPN Silicon
Low Noise Transistor PNP
Silicon

U1

1

10uF

100k

+15V Clean 1

Description
Description

P2
Pot stereo
47kB

C1

GND

GND

2

A

Header 6X2A

-15V

H2

7
8
9
10
11
12

7

A

1
2
3
4
5
6

A

4

A

7
8
9
10
11
12

7

1
2
3
4
5
6

4

P5

Document last modified and saved: 19 October 2011 7:39 PM

- 8

Preamplifiers for musical instruments and home hi-fi

9 -

Preamplifiers for musical instruments and home hi-fi

Schematics and Bill of materials for instrument preamplifiers
Schematic and BOM of power supply
1

2

3

4

A

R1

15V AC - 1

KBL04

C6
47n

3

B

D1

C1
2200u

10 1W

LM317BT
U1
IN

OUT
ADJ

6

A

2
+15V Out

1

3

5

+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

C14
100n
-15V Out

1

10 1W

C12
47u

H2

C

2

ADJ
IN
OUT

C

3

U2
LM337BT

Title

Power supply

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

1

2

Number

Revision
D

A
Date:
File:

3

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

Sheet of
Drawn By:

5

6

Notes

This is the power supply. Very simple and good quality low power circuit. Two adjustable regulators
can be fixed to the heatsink. The adjustable regulator with Zener diode have cleaner output than simple
7815 and 7915 regulators.

Description

Comment

Quanti
ty

Value

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

Designator
C1, C2, C10, C11

C4, C5, C13, C14

Boards for
instrument preamps
project

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

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; Pitch 2.54 mm

Resistor
3-Terminal Adjustable Positive
Voltage Regulator

Printed Circuit

Diode, Thru-Hole; 2 Leads; 0.7 in Pin Spacing

Document last modified and saved: 19 October 2011 7:39 PM

Preamplifiers for musical instruments and home hi-fi

- 10

11 -

Preamplifiers for musical instruments and home hi-fi

PCB for the instrument preamps
Top and bottom PCBs and overlay of INA217 microphone preamp
PCB TOP OVERLAY
C7

R4

C18

U3

D2

C19

C6

R12

C8

D1

R14
R13

C9
R9 R8

C17

C16

C15

C12

R15
C11
D4 D3

R7 R6 R5

P2

R10
R11

P1
Q4

3
1

Q2

U2
C1

R3 R2

C21

C2

R16
Q3
C4

C5

C14
C10

3
1

3
1

TOP LAYER

3
1

C13

U1

Q1

C22

C23

C20

C3

J1

R1

R17
H1

H2

C18

U3

R7 R6 R5

R14
R13

C9
C17

R12

C8

C16

P2

R10
R11

C6

D1

R9 R8

H5

C7

R4
D2

C19

H4

H3

C15

C12

P1

Q2

U2
C1

R3 R2

C13

U1
C21

C2

R16

3
1

Q3

C14
C10

C4

3
1

BOTTOM LAYER

C5

3
1

3
1

Q4

Q1

C22

C23

C20

C3

J1

R1

R17
H2

H1

H3

H4

TOP OVERLAY ON TOP LAYER

R15
C11
D4 D3

H5

Document last modified and saved: 19 October 2011 7:39 PM

- 12

Preamplifiers for musical instruments and home hi-fi

13 -

PCB for the instrument preamps
Top and bottom PCBs and overlay of stereo jFET preamp

Preamplifiers for musical instruments and home hi-fi

PCB for the instrument preamps
Top and bottom PCBs and overlay of simple dual OpAmp preamp

BOTTOM LAYER

TOP LAYER

TOP LAYER

BOTTOM LAYER

TOP OVERLAY ON TOP LAYER

OVERLAY ON TOP LAYER

PCB TOP OVERLAY
H1

P2

P1

Q1
1

7
5

R6

C3

C4

C1

H3

C6

C1

R10R2

C2

C6

R10R2

H2

C12

3
1

C8

R8

Q1

C8
C7

P3

C9

R8

Q1

C8
C7

Q2

C5

R6 R7

C5

R6 R7

R9
C10
C9

R9
C10

C8

P3

P3

C12

Q2

Q2

Q2

R1 R5

U1

C14

J1
J1

H2

C2

C4

C13

3
1

H3

C7

C3

3
1

C5

R9

C3

3
1

R7

C5

R1 R5

U1

C1

C14

R9
C7

C13

C1

3
1

R7

R1

R2

C11

H1

R2

C11

H1

C3

R1

R8
R6

H3

R8

R4

H3

3
1

H1

3

R5

H2

R4

P2

H2

P2

P2

R5

1

R3

5

Q1

7

3

R3
P1

PCB OVERLAY

C6

R4 R3

C4

J1

C6

R4 R3

C4

J1

C2

P1

C2

P3
P1

Document last modified and saved: 19 October 2011 7:39 PM

- 14

15 -

PCB for the instrument preamps
Top and bottom PCBs and overlay of power filters (ver.2)

Notes

Notes

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

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

C3

C2

C3
7
P11

C4

C4

3
1

3
1
C2

R2

C1

R2

3
1

OVERLAY ON TOP LAYER

3
1

C8

C8

R1

C1

C2

C6

C2

C6

C3

C8

C3

C8
P1

P1
12
6

Q2
C7

7
1

R1

3
1

C6

C5

C7

R1
C1

Q2
C7

Q1

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

OVERLAY ON TOP LAYER

C4

TOP LAYER

TOP LAYER

BOTTOM LAYER

PCB for the instrument preamps
Top and bottom PCBs and overlay of power filters (ver.3)

Preamplifiers for musical instruments and home hi-fi

BOTTOM LAYER

Preamplifiers for musical instruments and home hi-fi

12
6

7
1

12
6

Document last modified and saved: 19 October 2011 7:39 PM

Preamplifiers for musical instruments and home hi-fi

- 16

17 -

PCB for the instrument preamps
Top and bottom PCBs and overlay of power filters (ver.1)

Preamplifiers for musical instruments and home hi-fi

PCB for the instrument or hi-fi preamps
Two single OpAmp - stereo universal preamp

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.

TOP LAYER

BOTTOM LAYER

BOTTOM LAYER

OVERLAY ON TOP LAYER

C3 C8

H3
Q1

3
1

Q1

P1
12
6

C7

PCB OVERLAY

C10

C7

C4

C10

P3

Q2

P3

Q2

C4
C14

H1

C14
H1

3
1

R2

P2

R9 R8 R7 C9
H3

7
1

P2

R9 R8 R7 C9

H2

3
1

R1

H2

3
1

C6 C2

3
1

C5

C7
Q2

Q1
C1

C4

3
1

PCB OVERLAY

R6 R5

R6 R5

C12

3
1

C12

R2

C4

R1

3
1

C5

C7
Q2

C6 C2

Q1
C1

C8
C1

C3 C8

C13

P1
7
1

U3

12
6

R2

C8

C11

C1

R2

C11

C2

C2

C13
U4

J1

J1

C3
R1 R4 C5

U4
C3

U3

R1 R4 C5

R3 C6

R3 C6

P1

OVERLAY ON TOP LAYER

P1

Document last modified and saved: 19 October 2011 7:39 PM

- 18

Preamplifiers for musical instruments and home hi-fi

19 -

PCB for the instrument or hi-fi preamps
Two single OpAmp - stereo low noise universal preamp

PCB for the instrument or hi-fi preamps
Switch module for preamps
1

TOP LAYER

BOTTOM LAYER

Preamplifiers for musical instruments and home hi-fi

2

3

4

5

6

A

A

6

5

4

1

A/B Switch

B
2

1

SW1
A/B Switch
3

6

5

4
3

4

2

SW2

P5

12
11
10
9
8
7

6
5
4
3
2
1

2
5

3

A/B Switch
SW3
1

B

6

Header 6X2A

C

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

Title

Switch module

Size

Number

Revision

A

D

Date:
File:
1

10/18/2011
D:\!Works\..\Switches.SchDoc
2

3

D

Sheet of
Drawn By:
4

5

6

TOP LAYER

BOTTOM LAYER

OVERLAY ON TOP LAYER

H2

H3
C22
C20

C22

C18

C21 R10R11 C19

C17 Q4

C20
C15 C16 C14
3
1

C13

R8 R9
P3

C12

3
1
3
1

Q2

Q1

C9

C11

C4

U1

C10

C3
C6

Q2

R2
U2

R7
R1
R3
R4

C5

C7

Q1

R6
C3

C4

U1

C6

C2

R5

C2

R2
C1

R5
C1

P3

C12

R6

3
1

3
1

C5

C7

R8 R9

P1

J1

C8

U2

R7

P1

J1

R1
R3
R4

PCB OVERLAY

C9

C13

3
1

3
1

C11

C8

C15 C16 C14

3
1

Q3

C10

Q3

P2

C17 Q4

P2

H1

7
1

H2

H3

7
1

PCB OVERLAY

H1
C18

C21 R10R11 C19

OVERLAY ON TOP LAYER

Document last modified and saved: 19 October 2011 7:39 PM

Preamplifiers for musical instruments and home hi-fi

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21 -

Preamplifiers for musical instruments and home hi-fi

PCB for the instrument or hi-fi preamps
The PCB of power supply

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: 19 October 2011 7:39 PM

Preamplifiers for musical instruments and home hi-fi

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23 -

Preamplifiers for musical instruments and home hi-fi

Images about the prototypes of this preamp project
The selectable prototype of jFEt and OpAmp projects
The Picasa gallery about this circuit

Images and Picasa
galleries about the
prototype of preamps

Document last modified and saved: 19 October 2011 7:39 PM

Preamplifiers for musical instruments and home hi-fi

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25 -

Preamplifiers for musical instruments and home hi-fi

Images about the prototypes of this preamp project
Audio mixer with jFET and OpAmp preamps

Images about the prototypes of this preamp project
Microphone preamp with INA217

The Picasa gallery about this circuit

The Picasa galleries about this circuit:
• Planning and collecting parts
• Images about the prototype
• Testing the INA217 board

Document last modified and saved: 19 October 2011 7:39 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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