Intro: Headphone Amp (Chu Moy)
I Wanted to make one of these for a while now, not because my mp3 player lacked the power to drive my ashamedly poor headphone or that my headphones had a high impedance but because... it looks good and well, maybe in the future i may buy some good headphones and when that day comes. I shall be ready.
I also loved the look of the penguin mints Bought from Thinkgeek, this only aided my decision to make this amp.
So when i decided it was time to stop dreaming and start injuring myself with the soldering iron, i checked instructables first and was amazed to see no one had posted an instructable for this immensely popular diy amp. So i set about making my own, and this is how it went...
Note: for high res images layout images please visit my photobucket, as they are compressed here.
Step 1: Tools
The tools you need for this build are nothing special. All you need is:
A soldering iron
Some wire strippers (or in my case a leatherman squirt)
Pictured below my tools. The soldering station is an xytronics lf-2000 that i got about 3 weeks ago. any soldering iron will do, but i got this particular station because it was cheaper than the weller equivalents and parts are readily are available in the UK, and its performance amazes me. Highly recommend xytronics if you are after a good soldering station.
Step 2: The Components
The only thing i had real trouble with getting for this build was the protoboard. Being a radioshack model i found it hard to get in the uk, however after a little digging i found a great website that stocks many radioshack components in the uk at good prices. www.t2retail.co.uk
however if you live in the us, all you need to do is go to your local radioshack and pick up most of the components you need.
Also for uk Builders i highly recommend digikey, they are us based which made me think the delivery would take along time however, i ordered Thursday night and they were here by Saturday morning.
ok so here is the raw list:
220 µF/35 V electrolytic capacitor, radial leads (X2) Radioshack (272-1029) Digikey(P5552)
0.1 µF metallized polyester cap (X2) Radioshack(272-1069) Digikey(E1104)
1/4 W metal film resistor assortment Radioshack(271-0309)
Protoboard Radioshack(276-0150) T2Retail(2760150)
Stereo mini jack (3.5mm) Radioshack(274-0246) Digikey(CP-3513)
DIP-8 IC sockets, gold contacts Digikey(AE7313)
9 v battery clip available from any electrical supplier
volume knob (any will do really) Digikey(226-1033)
and for the volume control you can use either of two options, the alps rk097 pot (with internal switch so when the volume is put at its lowest the switch is off, this means no external toggle switch is needed and makes the overall look neater)
or the Panasonic 10K pot (smoother than alps but without the internal switch)
Volume control, Panasonic 10K, horizontal mount Digikey(P2U4103)
Alps rk097 pot can be bought from http://tangentsoft.net/shop/ or http://www.amb.org/shop/
also optional is an led to tell you when the amp is on, no special led needed just a 3mm.
you will also need an enclosure (altoids tin or penguin mints tin, well any tin really)
i used a penguin mints tin purchased from www.thinkgeek.com
For more information on parts and optional components visit
Step 3: The Protoboard
To start you will need to understand the board, as you will see from the images below there are two sides. One side played in copper and the other with white markings to show where the copper beneath is.
the components are laid out on the white side and soldered underneath onto the copper pads.
in the diagrams that will come in later steps it is important to note that they are shown on the topside and take not of what side is what (left or right).
Step 4: Adding Jumpers
The jumpers are made from spare resistor legs (or capacitor/led legs) that are then bent and placed into the holes before being soldered on the other side.
the images below show how i did this.
using my leatherman (or similar tool) i cut the resistor legs off of some spare 550 ohm resistors i had laying around. i found that one leg makes two jumpers.
holding the leg in the middle using the pliers i then pushed either side down to prom a 90 degree angle.
putting the jumpers in one at a time saved me the hassle of loads falling out at once as i flipped the board, after the legs are soldered on, clip the excess of with diagonal cutters (i used my leatherman, oh how i live this tool!)
IMPORTANT!!!!! note that the two sides (left and right) are not symmetrical ! always check the jumper (and components later on) are in the correct place before soldering.
once all the jumpers are in place and the excess clipped we can start adding our first components.
Step 5: Adding the Power Supply
The diagram shows the layout and polarity of the capacitors in this section.
i did not put the led in this step as i still need the enclosure for the tin to arrive, however that should be self explanatory, short leg towards negative (black).
i also left the two wires for the battery until last, to prevent the wires getting in the way of soldering.
r1=4.7 KΩ 1/4 W metal film resistor
c1= 220 ΩF/35 V electrolytic capacitor, radial leads
when the components are placed into there holes bend the legs to help hold them in place until soldered, then clip the excess of the legs.
Step 6: Soldering the IC Socket
The purpose of this socket is to allow you to change op-amps without the need to solder, it also prevents the amp from getting hot and damaged during soldering by eliminating the need to solder it on the board
NOTE: the orientation of the ic socket, notch towards the bottom.
the images below show where the legs should sit, however we will not solder the other components till the next step.
Step 7: The Amp Circuit
R2 = 100 K 1/4 W metal film resistor
R3 = 1 KΩ 1/4 W metal film resistor (this gives a huge gain of 11, we will change this later but for now put in the 1k.
R4 = 10 KΩ 1/4 W metal film resistor
C2= 0.1 µF metallized polyester cap (X2) Radioshack(272-1069) Digikey(E1104)
NOTE! in the diagram it show r5 being a resistor, in most cases a resistor isn't needed and another jumper is used, a resistor is only needed if there is distortion ir a hiss when no audio source is connected. so for now solder a jumper in place of r5 as i have.
As you will see i have bent the resistor legs to make it look neither, i suggest you do the same.
Also 2 lengths of wire need to be soldered, the diagram shows these on top however as show in the image below i soldered them beneath also for neatness.
also to note is that the amp is not put in place until last to save it being stressed from the heat of the board as you solder.
I recommend you use a continuity tester (in a multimeter) to test from solder bridges and shorts, remembering where the jumpers are.
however this can be skipped.
Now onto adding the external parts
Step 8: Adding the Jacks and Volume Control
First step is to solder wire to all the pins of the headphone jacks, about 2 inches long. once this is done we can solder up the potentiometer (these are not connected to the amp till later so you dont need to worry about layout, just solder a length of wire to each of the jack pins and for the pot, see the image below)
your jacks layout may differ, however it usually goes from top (closes to the hole) to the bottom
Ground right left .
Note: i means input. so il ir and ig mean Input left input right and input ground, these abbreviations match that of the final layout diagram on the next page
Step 9: Completing the Build
As you will see from the image below, all the connections for the jacks and pot are listed, take a few minutes to understand it all.
the images really do all the talking in this part
Once this is all hooked up correctly, solder your power source (9v battery) and turn it on.
before you plug anything in have a feel around all the components checking for any heat, if it does get hot, take out the battery and check the underside for solder bridges and shorts, also make sure everything matches the diagrams.
Next plug in only your headphones and put the gain up full and listen for any static, if all is good then plug in your mp3 player and take it for a test drive. once again if anything isn't working check the circuit as above
now you may have noticed you cant get much further than half way without suffering from distortion, this is due to the high gain, we will now replace R3 with resistors that will lower the gain now we know the circuit is stable.
2.0 KΩ gain 6
2.5 KΩ gain 5
3.3 KΩ gain 4
4.7 KΩ gain 3
10 KΩ gain 2
I replaced mine with a 2.2kΩstor for a gain of around 6 and this worked well for me.
once you are happy with the gain, you can get to putting it in the tin
Note: The images of the finished amp used in this instructable show another cmoy i have where a Panasonic pot was used and a toggle switch was used in series with the power supply.
Step 10: Enclose It!
I didn't get any images of this as it is pretty straight forward, drill a hole big enough for the part to put through and well, put it through the hole.
REMEMBER: to insulate the bottom of the tin using insulating tape, foam or a cut rubber mat. This will stop shorting.
once its done, enjoy!
If you liked this instructable please comment, rate and show to others.
I also entered this for the thinkgeek competition as not only did i buy the tin from thinkgeek but they also offer a mint tin cmoy, this shows you how to make that famous thinkgeek product.