This headphone amplifier circuit is different to conventional modern construction techniques in that it is air Wired,P2P (peer to peer) or free form wiring just like in the good old Valve days before the intervention of  PCB's and the transistor.

Rather than a traditional enclosure, the hole circuit is encapsulated in polyester resin to enhance the internals.

If your reading this and thinking why do you need an amplifier for headphones then click here

Although allot of cMoy headphone amplifiers are designed to be portable this one is designed for the desktop although a battery pack could be made also.

This is a pretty long instructable so "make a brew" as we say in Yorkshire and get comfy .

On the upside there is plenty of pictures :)

Step 1: The Schematic

Here is the EaglePCB schematic of headphone amplifier it follows the cMoy design

The component list is as follows

Power supply section

1x DC Power Jack
1x 5mm LED
R1LED      : 1x 1k  to 10k 0.6 watt metal film resistor   (For the Power LED, Anywhere from 1k to 10k will be good it all depends on the input voltage and how bright you like your LED.)
CP1/2        : 2x 470uf 35 or 50v  Power Capacitors 
RP1/2        : 2x 4.7k 0.6 watt metal film resistors   (For the power supply Voltage divider)

Amplifier section

IC1       : 1x  OPA2107 Dual Operational Amplifier
C1L/R  :  2x Wima MKS 0.68uf 63v  Capacitors (for the audio signal input)
C2/3     :  2x 0.1uf Polyester Box capacitors (To stabilise the OP-AMP)
R1LED :  1x 1k      0.6 watt metal film resistor (1/2 Watt)
R2L/R  :  2x 100k  0.6 watt metal film resistors (1/2 Watt)
R3L/R  :  2x 1k       0.6 watt metal film resistors  (1/2 Watt)
R4L/R  :  2x 10k     0.6 watt metal film resistors   (1/2 Watt)
R5L/R  : JUMPERED (optional,)
2x 3.5mm Stereo Jack Sockets

Downloads: EaglePCB .SCH Schematic and PDF below

<p>This is one of my favorite Instructables of all time. I have shared it with many, and am hoping to one day try making it myself.</p>
<p>Glad the readers are still enjoying my Instructable.</p><p>Its great to see the readers builds :)</p>
<p>Its Very Nice !!!!!! </p>
<p>Remake this amp for second time,added two 9V rechargeable battery and edit the schematic after discussion with my dad.Replacing OPA2107 with TL072NC,added a plastic shell casing and a hook(I need portability).Works perfectly with my Alessanddro MS1i.</p>
<p>Hey! how you identify the audio_in 1,2 and 3 pins in socket?</p>
Great instruction ! :D <br>*the diode by the led is just for visual purpose
<p>Hey! how you identify the audio_in 1,2 and 3 pins in socket?</p>
<p>Hey can you please help me with the OPA2107 replacements. i can't find it</p>
<p>Hey, I just wanted to say that this method for prototyping is extremely beautiful. Its very inspiring!</p>
<p>Add a series schottky diode with the positive supply, and that should make any possibility of capacitor failure from reverse polarity very minimal, while not reducing the supply that much from the ideal voltage.</p><p>Keeping the LED after the diode will work as a signal of reversed polarity.</p><p>Also, for a better spread light from the LED to the resin, you could have sanded it lightly so it would get a white finish to it.</p>
<p>Another method used to protect against polarity reversal is to put a diode back-biased across the power input. This way the diode shorts out a reversed power supply. </p><p>The advantage of this method is that it does not introduce any voltage drop. But the diode needs to be hefty to hold the power supply in its current limiting mode without opening.</p>
<p>In series with that back-biased diode, add the coil of a relay. The coil will limit the amount of current passing through the diode. Then, have the relay break the power connection to the rest of the circuit and maybe light-up a red LED to show the fault condition.</p>
<p>I like your idea much better! I don't like the reverse-diode protection because it could potentially damage the power supply, or it could be damaged and impossible to repair (in this particular case). Having the relay there makes a lot of sense, and there's a lot of very small relays in the marked so it wouldn't add much weight or complexity to the project.</p><p>Honestly going to use that in my builds from now on!</p>
<p>I think it might be better, now that I thought about it some more, to either use a SSR instead of a mechanical relay to cut down on the time it takes to shut down power, or to wire a mechanical relay with a blocking diode so it energizes with correct polarity and block power to the amp until the relay has time to trip</p>
<p>hey there, love this instructable, how much did this cost you make and how long did it take ?</p><p>i shopped around for an OPA2107 and some places wanted &pound;12 for a single piece :O..</p><p>but, looks like you put some real time and effort into yours ?</p><p>i wonder what it would look like it it had a frosted with a blue LED in it! :O</p>
Hello,<br>This is an awesome instructables!! And the end product looks awesome<br><br>Just a Q: how would I go about adding a potenciometer?
I have never seen precision and art like soldering like that. You operated like a surgeon! Outstanding!
<p>Dear all. </p><p>I am from Viet Nam.<br>I dont know name of Liquid make resin molding.<br>Where do me can order this liquid? (Amazon, alibaba)<br>Please help me.</p>
<p>Usually you are not supposed to take plastic to a belt sander because it clogs up the sandpaper. Did you have any problem in this regard?</p>
<p>Not if you run it slowly and don't over heat the work.</p><p>Depends very much on the plastics.</p><p>I am willing to sacrifice a &pound;2 belt to get the result.</p>
<p>That's just what I did, sacrificed a belt. </p><p>But in retrospect, after doing my first ever casting, I do realize that if I sanded more slowly this would not have happened. </p><p><a href="http://www.instructables.com/id/Ice-Cube-Clock-3/" rel="nofollow">http://www.instructables.com/id/Ice-Cube-Clock-3/</a></p>
<p>I noticed that you have Top and side views but not bottom. I think a bottom view would be incredibly useful understanding the layout.</p>
<p>Beautiful work.</p>
<p>Very sexy!</p>
<p>Nice <br>nod to some of the craftsmanship of valve days reminds me of Hiwatt amp porn <br>like <a href="http://hiwatt.org/images/70HiwattFacesGuts.jpg" rel="nofollow">http://hiwatt.org/images/70HiwattFacesGuts.jpg</a></p><p>Inspired, <br>beautiful build &ndash; much more &ldquo;3D&rdquo; than I&rsquo;m used to looking at electronics.</p><p>Love <br>the screwdriver lead bending tip for this kind of application too. </p>
<p>A step by step instructable where the &quot;why&quot; was explained just as well as the &quot;how&quot;. I'm going to do this project not just to have a headphone amp for my bose over-ear phones, but to learn more about electronics along the way. Thanks! May be the best instructable I've read.</p>
<p>stunning, never wanted a pre amp untill now.</p>
<p>Beautiful preamp!</p>
<p>Excellent job man!!</p>
Amazing and looks cool. I love it great
<p>Wow! pure genius! </p>
<p>I know it's counterintuitive, but actually pouring a thin stream of resin from a height of 3 feet or so is better for eliminating bubbles than pouring close to the mold.</p>
<p>Beautiful! I absolutely love the look of the guts-within-clear-resin concept.<br><br>I bought this kit (link) to build a digital &quot;ice cube&quot; clock with a blue fluorescent display. <br>https://www.adafruit.com/products/194<br>The kit has that acrylic enclosure, but I would like instead to enclose it in resin. This would make it even more like the ice cube of its moniker. <br><br>One concern is that contraction of the resin during cure would crack the glass fluorescent tube. Any thoughts on that? I can get replacement tubes on eBay for $6, so I might just try it and see what happens. <br><br>Another thought: In order to avoid having to do the sand-and-polish, how 'bout if I put the circuit inside an acrylic box and pour the resin into that? Will the seam between the two clear plastics disappear? Or will the resin dissolve the acrylic? An then there's the heat. I could use polycarbonate instead, which is less susceptible to chemical interaction than acrylic and has a higher service temperature.<br><br>Shifting the topic from the enclosure to the amp: Another reason for me to have a headphone amp is that I have damaged hearing (too many Greatful Dead concerts when I was young). The high frequency in my heaing roughly follows a second-order attenuation starting aaround 300 Hz. With a headphone amp, I can build-in filter circuitry to compensate for this attenuation. </p>
<p>Thats absolutely beautiful :O </p>
excellent job, i think i would have tinted the resin slightly, with a fluorescent pigment and used a uv LED inside, there are so many applications for embedding electronics as art, and this has created eexcitement for the sculpture aspect of electronics
&quot; air Wired,P2P (peer to peer) or free form wiring just like in the good old Valve days before the intervention of PCB's and the transistor.&quot; <br>It's actually called &quot;point to point&quot; wiring and PCB's and Transistors don't &quot;intervene&quot; with anything. I think you mean &quot;invention&quot; or &quot;advent&quot;. It's enough to put me off reading the rest of the article for fear of screaming at my monitor in frustration. <br> <br>VERY nice job though friend! Good to see your fabrication skills far outweigh your language skills :)
I'm curious as to how you found the correct lengths for the large copper wire and how you knew where to bend them. obviously you had an idea of how you wanted this to look but reviewing the pictures I'm still uncertain how I would be able to get the correct length and shape without making it look terrible. you did an absolutely beautiful job and I wish to congratulate you on a functional piece on art. thank you for sharing this amazing project.
Thanks for this Instructable! It motivated me to build one myself! <br>http://flic.kr/s/aHsjNKT5wE
Precioso! Very good looking and... It finally works. Gorgeous! I wish I had the patience and skills to build one. I am impressed.
Hi there!! It is very good instruction. Well done. <br>Ive got a question. I am thinkin to use this resin coating for my project. Is this copper skeleton essential? Thanks in advance
Is it possible to do this with a electronic project with a screen and toggle switches. <br>Do you have any examples of this.
My wife bought the parts for this cMoy amp circuit for my birthday so that I could build a couple of these. Anyhow, we managed to get only quality components, yet everything was still very affordable.<strong><em> I just finished making my first one of these 15 mins ago and it worked perfectly the first time--no kidding! </em></strong>My success on this was due to your generous build documentation. I haven't sealed the circuit yet because I want to see what I can do to add mods I can insert onboard (volume, on/off, bypass...etc), but<strong> the music that gets pumped out of this is a very beautiful thing</strong>. I've tested this amp with all of my Kicker, Philips/o'neil, V-Moda Crossfade, and TurtleBeach headphones. The circuit delivers on every single one. Thanks again for posting this.
I am new to all these Headphone Amplifier thing and was just wondering, how is the quality on such design? compared to commercial amps?
testing the circuit will eliminate any need for diodes..... although it looks pretty cool.... wall sockets? i guess you need diodes since it changes polarity (60hz...well at least in korea)
This is soooo sweet! Now I have to go build one (or two). <br>Many thanks for posting such a great article with clear photos. This is definitely one of my favorites.
wow!it is so coollllllll!!!
stunning , im thinking of making my xbox laptop (battery powered ) incased in such , what would be the weight of 3201cm3 be ? im assuming heavy but how heavy 7 lbs i assume as water weighs that not bad as fiberglass 3/16 of an inch is 8 lbs
I don't know what resin weighs but 3201cc of pure water would weigh about 3.2kg. I'd assume most resins like this ultraclear one would be quite a bit heavier.
I do know that this particular resin weighs around the same as water.But if it was possible to encapsulate an XBOX your about right legless:P

About This Instructable




Bio: Rupert Hirst "If I can't beg,buy,borrow or find something then I guess I will just have to make it!"
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