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Powered by a single AAA cell,this amplifier is scarcely thicker than the audio cable and fits between the line out socket of your PC sound card and yo...
The circuit has to be assembled on a circuit board. I find that a piece broken off a larger board will be sufficient. It has green solder mask on, in ...
It will need something to hold the circuit board, a battery and the headphone socket. I shall use a AAA cell to power it, and use the metal cladding f...
The board has been cut and filed to make it about as wide as a AAA cell.
The figure shows the circuit, which has been unashamedly copied from the datasheet published by MAXIM for their chip. In addition to the chip and batt...
A small (jewellers') screwdriver was sharpened into a chisel and a recess dug out of the component side of the circuit board. This board is made of pa...
I shall be looking at the underside of the chip, so a scheme of connections is prepared looking at the chip that way. The data sheets show the connec...
The other side of the board shows the holes, the solder resist scraped away for the wires that connect to ground, and the copper bevelled away for tho...
Two wires that connect to ground have been soldered in this picture.
It needs a steady hand, a fine tip on the soldering iron, and good lighting in order to place the wires and solder exactly where they have to go. The...
Two capacitors from old hard disk drives have been liberated to be used in this circuit. I have drilled a few more holes, and cut a few channels for ...
The capacitors have been soldered in position in this picture.
The capacitor for decoupling the power supply has been connnected up, this time it is on the same side as the chip.
I have doubts whether everything will fit in the small volume, so it is time for a size check with the input capacitors and the headphone socket. The...
The circuit board is complete, with the input coupling capacitors placed on either side of the board. It is still smaller than a AAA cell.
This is one shell of a AA cell. Two such shells were soldered together.
The two AA shells soldered together is ready for cutting and bending to form the AAA cell holder.
The two wires carry the signal to the headphone socket at one end from the amplifier chip at the other, past the AAA cell held securely in between.
The socket for the headphones is to be made of parts from an old one to fit in the diameter of the AAA cell.
The spring connector contacting the tip of the jack has been fitted.
The tip contact was modified, and the contact for the ring on the jack has been fitted.
The jack inserted into the completed socket. It seems to be okay. It has to be inserted with a bit of Tender Loving Care or the thing might come apart...
The AAA cell and socket inside the metal cabinet. The cell looks mangled because I used it as a template to bend the sheet metal.
The spring contact for the battery negative is next soldered in. The picture shows the earphones I am using to test this with.
The positive contact for the battery is a piece of double sided copper clad board. The side which contacts the battery has clearance cut along the edg...
The headphone amplifier is complete, and it works. The chip I used has a gain of 2 so it needs line levels (around a volt rms) in order to work. Wit...
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