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6L6 31st July 2012 03:14 AM

Building the O2 Headphone Amp
How to build an Objective2 Headphone amplifier.

This is such an awesome project that I hope that someone might see this and 'get off the fence' and build one. It's a great first project, but it has such fantastic performance that even the most diehard DIYer will be extremely pleased with it.

If you are not familiar with the O2, here is some more information -

NwAvGuy: O2 Headphone Amp

And this link has all the really good information in it for the DIY constructor -

NwAvGuy: O2 Details

One of the reasons that this project is so good, other than it's very good design, is that it is documented better than just about any other DIY project ever. Just about all your questions are answered by the designer himself. It is wonderfully beneficial to read the above all the way through before starting construction.

This is my visual build log for the O2.
This is the board in it's empty state.
The Box Enclosures box and the faceplate, purchased from JDS labs. See this page -- JDS Labs - Store - DIY Parts
Here is a good photo for scale, 2 normal 9v batteries.
And this is the small AC wall-wart for charging or playing. With the amp playing on either the AC supply or the internal DC batteries, it sounds the same.
Some (but not all) of the various components to go on the board.
That is everything sans enclosure and batteries.
It is absolutely imperative that you check and double check the locations of the items as you stuff the board, and measure everything that you have the capability to measure before installing it.
Most of the specified resistors are these cute tiny 1/8 watt items, shown with a 'normal' 1/4 watt Dale for comparison. Also look at the PCB and see one installed. You don't want to remove one of these if you don't have to.
I made one error when ordering, where I entered a quantity of one when I needed two. So I replaced both with a bigger (1/4w) resistor, seen here mounted 'soldier style.'

If you have bunch of 1/4w resistors on hand I see no reason why you couldn't use them mounted as such in all the locations where a 1/8w would go. There is plenty of room.
I ordered my parts from Mouser, merely copy and pasting from the published BOM into the order page on Mouser's site. When you order, there is a place for you to enter a 'customer part number' which is a great time to label the parts to match the board.

The 2 circles are my pattern to cut down on stuffing errors - the top circle is to match the part description against the BOM. The bottom circle is to verify the value printed matches what I measure it to be. It doesn't take much time, and cuts errors way down. :) :) :)
It's always a good idea to leave a bit of room between the board and PSU filter resistors. They get hotter than the other resistors.
Diodes match the board, put the striped end (of the diode) on the striped end.(of the board)
I forgot to take a photo with just the resistors and nothing else. Oh well… The ceramic caps (the yellowish ones) are next. As always, we will stuff the board smallest items first, then the next bigger, and so on.
The next components are the blue film caps and the DIP sockets. (for the opamps)
The regulator pieces are next, they are also polarized, the heavy white line of the board shows the back (tall and or flat) side of the power devices.
And there is the proper orientation of the device.
The can capacitors have the potential to blow up if installed improperly. They are polarized, and even marked twice -- the long lead is the positive, and the stripe with the " - " sign is the negative.
The pads for the caps are also well marked, the + is clearly visible, and also you can see the bit of heavier line on the circle, to mark the negative. That's a very nice touch.
Again, where you have a can cap, you will see those markings.

By this time you should have the bulk of the board stuffed minus the edge with all the jacks.
The AC plug supplied didn't quite fit the holes in the board. The supplier probably made a change recently without telling anybody. Oh well. You can see where I filed the connection down, to let it fit smoothly on the PCB.
It seemed the most logical to stuff the components on the edge from the bottom to the top. It worked well, and nothing interfered with anything else. Easy!
In every photo of the PCB on NwAvGuy's site, the watermark completely obscures the battery terminals! Anyway, it is supposed to look like this. :)

At this point you are ready to do some testing. Go to this page - NwAvGuy: O2 Details Scroll down to the photo of the Multimeter and start the testing procedure!

As mentioned in the build guide, if the solder pins are not cleanly trimmed it will snag on the case. However don't remove the center front pin because…
You need to attach a wire to it to attach to a bare parch of the case via a panel screw. A thin wire or a trimmed component lead will do nicely here.
Here is the O2 playing music for the very first time. It looks great! Interestingly, my phone was playing the music and taking the photo… Cool.

The O2 is completely silent and sounds fantastic! :D :D :D :D :D


Here is my amp with a Stainless Steel faceplate from member 'Yangoran'

It looks great!!

everlong 31st July 2012 10:19 AM


Originally Posted by 6L6 (
As mentioned in the build guide, if the solder pins are not cleanly trimmed it will snag on the case. However don't remove the center front pin because…
You need to attach a wire to it to attach to a bare parch of the case via a panel screw. A thin wire or a trimmed component lead will do nicely here.

Nice post:)

That wire(for ground?), is that important? Can't remember that I put a wire there when I made my o2.

6L6 31st July 2012 11:52 AM

The wire is there to get the case to the same potential as the ground of the circuit, which should make it quieter.

ChicaneBT 1st August 2012 12:29 PM

Thanks for this presentation. It made me more enthusiastic about DIY'ing this product al tough I have zero experience in soldering. I have watched the online video's of the Tangent Tutorials about soldering (Tangent Tutorials). Maybe it's wise for me to start out with a cheap cmoy amp (not a JDS labs cmoy which is probably as expensive as the O2) but on the other hand this amp is way way better. And as far as I can see these components are the same size as a cmoy amp, not something they call SMD soldering on Tangent where the parts are really miniaturized and so has to be your soldering.

haejuk 1st August 2012 09:05 PM

This is a really good post about this project and fills in a few gaps that nwavguy's blog left out about DIYing this amp for first timers. This was my first project and I found it very very helpful to go through and match all the parts in the BOM to where they should go on the board before I ever started soldering. Other than that there is enough information out there to easily build this amp for any first timer. It isn't the easiest first project, but if you read enough about it you will build it without any problems!

The original AC power jack was discontinued and replaced by another a few months back. I had a difficult time finding a replacement before the one you used came out, but JDS Labs sold an original one to me for the same price as they sell the cMoy power jack.

Rullknufs 1st August 2012 09:20 PM

Thank you very much for this. I haven't built an O2 amp yet but I'm really considering doing it in the future.

skunark 7th September 2012 04:37 AM

Another killer tutorial!


Rullknufs 7th September 2012 06:08 AM

Yes indeed. Though I'd recommend soldering the diodes before R1 and R2 due to the difference in size. And maybe take the ESD sensitive components last to reduce the risks of frying something.

merlin2069er 10th September 2012 06:48 PM

Great build. I didn't ground my case. :o

rajinisiv 8th December 2012 05:03 PM

I have build my amp. I already have JdLab Cmoy2.3BB. But Cmoy sounds life like ... but O2 seems to loose details.. really pissed off... is it my fault .. or anything..

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