Introduction: How to Make a Pocket Headphone Amp!
In this instructable, I will be showing you how to make a headphone amp. If you have some big headphones such as Sennheiser, beats by dre or some other big headphones (in my case, some sony MDR-XD100) an or an MP3 player isn't enough, especially if they have a high impedance. This circuit was originally developed by a man by the name of and it has been extremely popular. There is only one difference with mine (and most others) and that is the fact that he used two single op-amps and we will be using a dual op amp.
So lets get started!
Please don't be too critical, I'm only 14!
Step 1: Parts
Here are the parts you will need:
OPA2134PA op-amp. There are alternatives but I have had most success with this one. The only other one that I would recommend is OPA2132
1x IC socket
2X 470uf or higher 10V capacitors
2x stereo audio jacks
2x 0.2uf MKT or pollyester capacitors
2X Pannel mount LEDs
1X NPN transistor
1 or 2 9V battery clips
male header pins
1X stereo 10k potentiometer
10k, 100k, 1k, 4.7k, 47ohm resistors (I got packs of 8)
2x SPDT micro switches
3v button cell and holder
A PROJECT ENCLOSURE! Be creative!
Step 2: The POWER Section
Follow the schematic for the power section if you can.
1. mark a line with a width of 2 holes right down the PCB board. This will be the ground.
2. Solder in the male header pins for + and -
3. Now solder in the Two 4.7k resistors.
4. Solder in the 470uf capacitors
5. Look at the diagram (pic 5) and look closely at the "stray" resistor. this is 1k and it's for the power LED
6. try and solder it so it's as compact as possible
In the diagram, the green lines represent the under-board connections. They are usually made with jumpers or solder. In the last picture, I have an example of the under-board connections or "green lines"
Don't worry about the other parts in the last picture, they are for later.
Step 3: The IC Section
Now we are getting into the IC section! this is where the amplification happens.
First we solder in the IC socket for the OPA2134PA. DON't INSERT THE IC YET!
Next we solder two 100k resistors from the ground strip the pins 5 and 3 of the IC socket.
Then we solder in the 1k resistors from the ground strip to pins 2 and 6 of the IC socket
Picture 2 is a pinnout diagram for the pins.
Now solder in the 0.2uf capacitors. Solder one pin of the capacitors to the 100K resistors (pins 5 and 2)
Solder the 10k resistors, like the capacitors to the 100k resistors, to the end of the 1k resistors.
Now solder the 47Ohm resistors to pins 1 and 7.
Now connect the ends of the 47ohm and the 10k resistors
Now at header pins to the connected ends of the 10k and 47ohm resistors and the other end of the capacitor.
Now it should look like picture 8
The last step for this section would have to be to connect the power supply to the op-amp. The + connection will go to pin 8 and the - voltage connection will go to pin 4
All done on the circuit!
Step 4: The LED Flasher Circuit
This is the LED flasher end of the circuit. Follow the circuit diagram and if you want more details on the circuit, look at my ultimate LED guide. This is almost self explanatory as I have explained this in the Guide. How you integrate it is totally up to you. If you do it on PCB, use header pins for the outputs to the LED.
Step 5: Wiring Everything Up
I've included two pictures to help you wire the potentiometers for volume control. Wire up the power LED and the light flasher LED once they have been mounted in the case.. The positive output from the LED flasher circuit will go into one of the switches and from the output of the switch to the LED. I also have a picture on the pinnout of the 3.5mm stereo jack. Now wire up power, all ground connections together and all signal wiring. Here is a signal diagram:
Jack L+R ⇒⇒ Potentiometer L+R ⇒⇒Audio in L+R ⇒⇒ Audio out L+R ⇒⇒ Jack L+R
Make sure all solder connections are good
Step 6: Close Up the Case
Finnish everything up and test to make sure it's ok. If it's all good, close up the case
Step 7: Finished!
All done!. Enjoy your headphone amp!
If you find this instructable insufficient to build a headphone amp, LET ME KNOW so I can improve it.
If you have and problems, head over to here to troubleshoot.