Op-amp headphone amplifier

$C:\upld\cmoy18.jpg$

This is a headphone amplifier similiar to the one designed by Chu Moy. For reference, the original Chu Moy article is here while a great tutorial on building it is here. I have used a different dual operational amplifier, the RC4560, manufactured by Texas Instruments, in the TSSOP package, and chip resistors in order to make an extremely small printed circuit board assembly.

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Step 1: The op Amp

$C:\upld\cmoy01.jpg$

The active device is the RC4560, which Texas Instruments claim to be suitable for, among others, Headphone amplifiers. It can work down to +/- 2 volts, and has low noise and a wide enough bandwidth.

It is available in a TSSOP (Thin Shrink Small Outline Package) which means it is small indeed, small enough for me to demonstrate my one-off microprototyping skills.

sconner1 says: Jul 3, 2012. 12:54 PM

Change the 220 uF caps to 470uF for better bass response and more powerful drums. You'll be hooked and have to re-listen to your whole music collection to hear what you have been missing.
And get some over the ear headphones.
The beauty of headphone amps is lost on "buds".

sconner1 says: Jul 3, 2012. 12:30 PM

1% resistors are usually metal film.
Bonus points for recycling/frugality.

gulshan20 says: Jan 12, 2011. 11:40 AM

sorry for this stupid question,but why do you use capacitors at the inputs?
is the voltage IN always constant?if not,then why did u put it in there?
sorry,i am a college student.
thanks for the reply.
btw,very good project:)

sconner1 in reply to gulshan20Jul 3, 2012. 12:27 PM

They filter out any DC offset in the input signal by blocking DC and allowing AC (audio) to pass.
Otherwise you risk burning out your headphones with amplified DC output.

Unclegummers in reply to gulshan20May 6, 2011. 2:06 PM

He's using the caps to filter the input signal and get rid of any DC component, to not mess with the bias of the amp. Caps are not just for transients, they are used for a lot more.

gjvg says: Jul 5, 2011. 2:43 AM

in the top left schematic i see a ground sign... where do i connect it to?
And is it a problem if i use a 47 ohm resistor instead of a 50 ohm resistor?

sconner1 in reply to gjvgJul 3, 2012. 12:20 PM

That is input signal ground.
Also called shield ground in the signal cable context.

soaringchicken says: Jun 6, 2011. 11:53 PM

This is really quite awesome and amazing.

So I have a pair of OLD headphones with huge speakers. My plan is to replace the old speakers with new 2.5" powerful speakers and to somehow throw a powered amp in there to basically make headphones that when safely removed from the head, could blow my friends away with sound. I figured I could cram at least 1000Ah of power source and can easily fit 80+ watt speakers in there. I'm a novice electrical hobbiest.

Any ideas?

Thanks a ton.

Eng.A.S.M says: Jun 28, 2010. 2:59 PM

(removed by author or community request)

neelandan (author) in reply to Eng.A.S.MJun 28, 2010. 9:55 PM

The sweetest things in this world are made by hand.

Sandisk1duo says: Jun 23, 2008. 8:59 PM

do you think i can make this without any resistors?

bobbyderf123 in reply to Sandisk1duoNov 21, 2009. 6:39 PM

y would u want to make it without resistors anyway?

neelandan (author) in reply to Sandisk1duoJun 23, 2008. 10:02 PM

No.

Sandisk1duo in reply to neelandanJun 24, 2008. 9:42 AM

how about the capacitors on the inputs? inL inR

neelandan (author) in reply to Sandisk1duoJun 24, 2008. 10:29 PM

They may be omitted in most cases. They are needed only when the input signal has a direct voltage component (ie, direct coupled single ended transistor stage without an output capacitor). You can try building one without the input capacitors, and then put them in if the output seems to clip. The low frequency response will be better without them in circuit.

LiporXT says: Oct 2, 2009. 1:37 AM

hello Neelandan I find your instructables really small and cute, congratulations. I have a question: can operate the amplifier with an integrated 3414th jrc? if so, how? thank.. Ps:sorry for the bad english I'm italian..

Re-design says: Sep 24, 2009. 6:57 AM

Hey, I'd build one of these but it's just too darn big. I need something really small and this one's big as a horse. Not really! Great job. I've built my own boards but never a surface mount! Hope you never drop it on the floor you might not be able to find it.

Meigus says: Jan 24, 2009. 11:02 AM

Doesn't your circuit only have the capacity for one channel? If I'm not mistaken, this would be a mono headphone amplifier.

neelandan (author) in reply to MeigusJan 31, 2009. 12:42 AM

The chip I used has two op amps in one package, which shares the supply pins. Therefore this is a stereo amp.

geterkikzkid says: Oct 15, 2008. 4:00 PM

Man, I woulda used a 386 IC That's my favorite chip for the matter.

geterkikzkid in reply to geterkikzkidOct 15, 2008. 4:02 PM

386 OP AMP
http://www.flashicon.net/archives/LM386Pinout.jpg
BTW add heatshrink tubing for stability.

friendspore says: Jan 5, 2008. 11:13 PM

Another site that teach step by step for building cmoy for beginner
http://williamneo.blogspot.com/2008/01/diy-cmoy-headphone-amplifier-for.html
happy building!

Nirjuana says: Nov 27, 2007. 11:39 AM

You done some nice modification in to the original Cmoy circuit but I recommend to use some different kind of power source cos' capacitor-voltage divider has one problem, it gets very easily unbalanced and that means that the positive and negative voltage goes uneven and the virtual ground starts to swing around which can causes problems when battery voltage is dropping. I suggest to use a "virtual ground generator" like TLE 2426. You can find more information about different power sources to Cmoy from here

annex666 says: Sep 29, 2007. 8:17 AM

I'm not sure shorting the power supply counts as reverse polarity protection - I would suggest a series protection diode instead (preferably schottky as you don't have much voltage to waste). ;-) I'm planning to knock up a headphone amp myself if I get time. I'm perfectly happy with the output from my Zen, but I want to implement some LF crossfeed to simulate head diffraction.

yourtvlies says: Sep 11, 2007. 7:01 PM

This is really cool! I dig the compact design. I've attempted a CMoy build before with mixed results. I've got a pair of Grado SR-80s that I'd love to drive with an amp, maybe I'll give it another go.