ear-01 MINI headphone amplifier of the report  by: mingtau

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This sample PCB is a headphone amplifier. Ive heard the performance personally, so that I am highly interested in it. Ben wants to keep the op amp of this kit as a secret, and the op amps pin definition is not as usual as common op amp such as: opa2134, tl072Ketc. So be sure not to change this IC.

 

Here are the parts listed below:

EAR-01

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Specification

Quantity

Reference

1

PCB EAR-01 67*96.5mm

1

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2

IC EAR-01

1

U2

3

IC socket 8pin (15u) GOLD

1

U2

4

lm317 (motorola) 

1

U1

5

BOURNS SVR 2K

1

VR1

6

ON MUR460 fast rectifier

2

D1,D3

7

Vishay General Diode 1n4004

1

D5

8

Philips 180[ 0.6W 1%

1

R1

9

Philips 10[ 0.6W 1%

2

R6,R7

10

Philips 3K[ 0.6W 1%

2

R4,R5

11

WIMA MKP2 0.1uF/100V 5%

1

C2

12

WIMA BlackBox 0.15uF/63V 5%

1

C5

13

UCC mkp2000 0.22uF/100V

2

C12,C13

14

Alps VR 50K

1

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15

Screw M3P0.5*6mm

1

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16

High Quality 3PIN terminal blocks

3

L2,L3,L4

17

Nichicon MUSE ES 100uF/50V

2

C8,C9

18

Nichicon MUSE ES 470uF/35V

2

C10,C11

19

Nichicon MUSE FW 10uF/63V

1

C3

20

Nichicon MUSE KZ 330uF/50V

1

C4

21

Nichicon MUSE KZ 1000uF/50V

1

C1

22

Heat sink c

1

U1

Ive changed the value of R1, cause the formula of lm317s output voltage is Vout = 1.25*(SVR/R1 + 1). I used a 2K bourns svr. The 180ohm R1 can make sure the output voltage lower than 15.14v, and will be easier to adjust the output voltage when we adjust the svr.

 

    Besides, I use 2 MUR460 to make a full wave rectification. And the pin of MUR460 is too thick to fit in the PCBs pad. I have to solder them on the pad by soldering tin.

Here is the picture of all the components of the kit:

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Lets solder the components from low to high. The resistors first then the reverse current  protection diode, and then the 8-pin ic socket.

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Next we place we place the Wima MKP2 0.1uf/100V capacitor, Nichicon FW 10uf/63V aluminum capacitor, and Bourns 2K SVR.(Please ignore the MUR460, I placed them in the solder side of the PCB in the end)

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Wima black box 0.15uf/63V

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Then the 0.22uf capacitors and the 3-pin gold plated terminal blocks. (The 0.22uf capacitors will do no effect to sounds, but only prevent the oscillation of high frequency. You can use whatever you like but aluminum capacitors here.)

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In normal situation, we must short spot A, lets take a look at the figure below from realaudio.

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But we have alternative solution here. We can use a copper wire to short the R2 and R3.

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We can use less soldering tin here.(LOL)

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Next lets place the Nichicon KZ and ES aluminum capacitors. Its almost finished!

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Lets get the ALPS SVR and LM317 soldered, and then we can connect the kit to the power and spot the voltage. Here is the method: we test the 8-pin ic socket in pin2(V+) and pin4(ground). We screw the Bourns SVR till the voltmeter to 12.0V. Finally we can cut off the power and put the op amp on to listen to some music.

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