Crystal cMoy Free Form Headphone Amplifier

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

Comments

[szechuan53]

this is gorgeous! i immediately began building a guitar booster pedal, i just need the epoxy and some sealed jacks. this is simply the best way i have ever seen electronics presented, kudos to you!

[mrlunna13]

Absolutely beautifully done! So pleasant to the eyes! It looks like it belongs in a display with a "DO NOT TOUCH" sign next to it.
Great ible by the way!!

[TJParmenter]

This thing looks so sweet

[Technoshaman]

A Burr-Brown amp beautifully free-formed in clear resin... engineering, machinery, and art, each at their best!

[Marker1024]

This is soo cool! I love the idea of casting in resin. The amp is truly beautiful you should be proud. I hope to make one of these some day. Please post a video of it in action?

[tamasic1]

Instead of using wire to suspend the electronics for casting, attach tiny diameter acrylic tubes to the vent holes on the capacitors using a little resin to hold them in place. Have them point straight down, like the wire suspenders. Two birds with one stone. Suspension of electronics and vent tubes without drilling, Possibly invisible after casting.

[bugsy_malone 666]

I really like this, the finish is superb! I was wondering how much power it will handle and if there is a way to add volume control? I have some little 1.5-2" speakers I got from an iMac which I'd like to make resin shells for but they also need driving, this would be perfect!

[Dream Dragon]

That is SO AWESOME it is OFF THE SCALE!

Now your headphones can go up to 11 TOO!

[salmansheikh]

One beautiful project.

[gweeds]

Awesome!

[jeffeb3]

This is so freaking cool. I am going to have to make something in resin very soon. Very creative using the LED power, and the wire sculpture as part of the schematic. I need to think of a good analog electronics project, so I can use a bunch of big capacitors or inductors. Maybe I need a new power supply for something :)

What kind of planning did you do for parts placement? Did you do that in a CAD program (eagle, KiCAD, or something else)?

[koogar]

Hi Jeff

I pretty much laid it out as in the eagle schematic.I then bent the power and ground bus within the maximum dimensions I wanted.
Jeff ,I dont think i would advise encapsulate a power demanding PSU or anyting that generates heat.
This particular project generates no heat.

[emdarcher]

one of the most beautiful electronics projects that I have seen.

[Carlos Marmo]

Dear Friend.

How you avoided the crushing of components, or fractures of the "block", due to shrinkage of the resin, after catalyzation?
Forgive-me for my bad english.

Thanks.

[koogar]

mix the catalyst at 1% to slow the curing and stop excessive heat.

[tpod]

I can't find .6w resistors. The lowest wattage I can find is 1/8 watt. Is it because I'm in the US? I realize this might be a stupid question. Electronics are not my strong suit.

[koogar]

1/2 watt would be better you should be able to find those or 1/4

1/8 will work but borderline

in the UK 1/2 watt have been basically phased out for 0.6watt

[Pesoen]

"I can't find .6w resistors. The lowest wattage I can find is 1/8 watt"

1/8 = 0.125

[kormsbee]

Too bad it's a one off. I'd buy one. Its fantastic

[nsievers]

Well done and original. As someone who has built several Chu Moy amplifiers in more traditional ways, I can really appreciate this project.

[EET1982]

Hi how are you? I was wondering if it would be possible to put a pot to adjust the volume. This is a great instructable. Thank you for sharing :)

[honda53rider]

Hey grate build! Im not big into electronics but im starting to and your instructable is grate! But where can i buy all the parts? I looked around on some internet sites like mouser but i don't know enough to make shore im ordering the right parts. I also feel that if i walk down to radio shack and ask for help the people there will have no idea that half these thing even are.

Any help would be grate!
Thanks honda53rider!

[dean14111]

hey, how did you elavate the electronics from the bottom of the mold? if you did. becuase im building i differnt project and i dont want the electronics to touch the bottom of the mold. please reply.
thanks

[Tspherix]

Step 14 showed 'Elevating the circuits'- Great idea!

[koogar]

To elevate the circuit within the casting I soldered a couple of wire risers on the virtual ground running down the middle of the amplifier.

http://runawaybrainz.blogspot.co.uk/2012/04/audio-crystal-cmoy-freeform-headphone.html

[JSquadra6869]

Is there any way that you can add a potentiometer in somewhere for volume control? If so, where would that go?

[kivanović]

Can I use this (http://www.ti.com/lit/ds/symlink/opa2604.pdf) chip instead of OPA2107 amplifier?

[koogar]

yes that will be fine Kivanovi

[kivanović]

Thank You for your answer!

[Husham Samir]

excellent work!!!

[undinstructable]

Excellent job! Bravo!
Very nice look!

[lstellaus]

Very nicely done!

[tudgeanator]

Truly beautiful work. On your schematic the current limiting resistor for the LED is 10k, whereas in your writing you say it is 1k a couple of times, jsuk :P.

[koogar]

Thanks
Anywhere from 1k to 10k will be good it all depends on the input voltage and how bright you like your LED.

I think at some point down the line I did change it for that very reason :)

[XLR8R22]

Wow! Great looking build! I built a similar headphone amp but used a tube/mosfet hybrid design, but I just stuffed it all in a cheap plastic box. This gives me some great ideas, thanks for sharing!

[cazcharles]

Absolutely Fantastic, i'm going to have a go at something similar, could you tell me the values of the turquoise resistors and what voltage LED did you use

[Arx]

What do you think would happen if you powered it with the wrong polarity of adaptor?

I'd be a bit concerned with covering the capacitor's vents. It might make for a pretty big bang.

[koogar]

I don't see a reason that the polarity could be reversed if your using a manufactured power supply with a jack.

I suppose you could using a battery pack or pick up a power supply with negative centre jack by mistake, but they are pretty rare I haven't seen one in years and believe me I have boxes full of wall warts and power bricks.

And yes it would be a nice bang.

Plenty of commercial products go bang when the polarity is reversed also :)

[sconner1]

One could (with a few more parts) make it polarity proof by adding a bridge rectifier on the power input. That way it won't matter which polarity is used.
Heck, throw in a filter capacitor and use an AC wall wart.
This basically moves most of the power supply inside the resin and makes it more resilient/flexible. Use any wall wart up to 30VAC depending on the opamp and cap voltages you use.

ooh OOH, and a slide pot on top for volume control.
Oh the possibilities!

[Arx]

Yeah, that's what I was thinking. All except for the 30VAC part. Most common opamps want max +/- 18V.

Rectified 30VAC will give you 42V, and that's not accounting for the fact that under such a light load the transformer will probably give you way more than its rated voltage.

A 20VAC tranformer would probably be about the limit without adding regulation. I would probably not go higher than 15, just for safety.

If you just used a diode instead of a bridge, the 30VAC would work, but you would get a lot more ripple, and would probably not be able to use lower voltage 9VAC etc, which are way more common.