To make this project more affordable, I dismantle old PC sound-card and take out the mini jack connector. It has a good and reliable connector that very suit with this project.
Due to the size of the components required, this project idea is also changed so many times. At the first time, I attempt to built a desktop amplifier. With my giant components on my bin, I was planned to insert sockets for the op-amp IC and input capacitors. Those components can be change easily for my testing purpose.
Then it change again once I have this battery box. This is a nice plastic box for battery that will turn this headphone amplifier project into the tiny amplifier that I've ever build.
I am now measuring the board to fit in this box. Then what components will be chosen is based on the fitment in it.
The bottom surface need to be cut and cleaned in order to have more space. I cut it easily with a hand cutter.
Do you know what is this?
I have an SOIC op-amp IC and need a converter to DIP package. This tiny board do the job very well.
Now you can see how it looks like compare to DIP Ic. I am using AD823 dual op-amp from Analog Device. It's a nice dual channel op-amp Ic that can be operate with low voltage batteries.
First glance of the board. Spotted the Elna Silmic for input capacitor is quite big in this tiny board.
How about this? No difference? Do I only adding the IC? Actually, It's already a full working amplifier with the resistor and capacitor underneath the board.
They are all SMD resistor using in this project.
And they also connect in point-to-point wiring. This project is now become very interesting.
See how complicated the board now. They are all tiny components.
Testing the amplifier for the first time and it's working very well.
Back to the box, the board is glued for more stiffness.
The battery connector is messy. It is still on evaluation test with this tiny box.
Once it is done, the look of the amplifier look very beautiful isn't it?
Update 20 May 2015
I found that using only 2 x 1.5 volt battery is not applicable for many earphone. The non-sensitive earphone will start distortion at medium volume level. I am sure the IC drain so much voltage from the battery and cause this sound distorted. Then now I am using small lithium battery rated 150 mAh 3.7 volt and it working very well without any distortion.
How does it sound?
Simply, the resolution is better than using the normal output from my iPod. Every instrument is now noticeably have better layering. The bass response is tight, the high frequency is smooth and the vocal is more laid back. They are improve but not dominate the overall music presentation. I clearly notice the improvement when listening to Diana Krall album. Song Live in Paris, track 11 - A Case Of You. I notice there is people walking around the stage and a girl cough several time before she start singing. Wow, I am surprise about this micro detail! Overall I am satisfy with the result and this AD823 is playing the major role of this improvement. Part 2 final can be find here
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