The Objective2 (O2) Headphone Amp DIY Project

Ok, I went thru the list and the bom had $8 cutters in it, solder wick and solder.

I've got it down to $54. Why are the gain resistors in there twice? should I remove the second set? (are they higher quality?)

Oh, and it looks like there is a set set of op amps.

You should have four gain resistors: two for high gain (1 per channel) and two for low gain. There should also be a pair only of the NJM4556A opamps.

For importing to Mouser, I found that I had to change the columns so that the MFR part number was column 1 and QTY was column 2. For some reason the Mouser part number was useless when importing.
 
If anyone wants a copy of my Mouser Project file, updated to the latest BOM, with all the gain resistors and sockets, and tweaked to get rid of back orders, PM me with your email address and I will share it with you. Since I am on the Canadian Mouser site, you will have to copy it to your profile before ordering I think.
 
thanks.. since the search function is a bit overwhelming for a thread this big, let me just try it this way. If anyone in the U.S. is willing to sell an O2 wood case for $50 or less please PM me. :-D

thanks.

my jds labs O2 outta be here in 2 weeks give or take. along with my Cavalli audio stacker II tube hybrid which most frequently draws comparisons to their Liquid fire amp (which retails for roughly $3300). Its going to be very interesting comparing the sounds of these two amps.. especially given the unwanted bias i will surely insert due to the fact that one costed me $145, and the other costed me about $1100 ;-D

good times!
 
It's going to be very interesting comparing the sounds of these two amps.. especially given the unwanted bias i will surely insert due to the fact that one costed me $145, and the other costed me about $1100 ;-D

good times!

Not to mention the fact that tubes distort in ways that people often prefer. While you're at it, swap out your fancy time corrected cable on only one channel with a piece of crap cable (play with inline caps and resistors while you're at it) and be amazed at how much more spacious and 3D everything becomes. Yeah... some distortion is really liked, especially when it's not measured because it's a time domain thing. As long as everything else is ruler flat and quiet, then it's worth charging a bunch for.

Too bad the O2 doesn't distort worth crap. If we could build in something hard to measure but not as hard to hear which still sounded cool, then we could charge >$450 a unit.

Sorry. I'm not trying to hate... just being real, if a bit cynical. I wouldn't mind having a go with some tubes. It's been a long time (15+ years) since I've heard anything from tubes... that I know of.
 
I just wanted to post a quick success story. I picked up parts for a pair of O2s, one for me and one for a friend for whom this was his first soldering project ever (I've been doing this a long time. :) We spent the weekend assembling and testing them, and they both work great on the first try. This is his first head amp and he LOVES the sound with his Sennheiser HD-595s (64ohm).

I'm listening right now and love it. 'course, I also love my PIMETAv2 and my 12AU7/IRF510 Hybrid tube amp too, so apparently I'm pretty easy to please. :)

RS: Quick design question, if this is the appropriate forum for it. I'm working on a design for a head-amp with a simple mixer on the front-end for use at my office so I don't have to keep switching inputs between my iPhone, Desktop, Laptop, and desk phone. But I need an inverting amp for the mixer. Rather than add Yet Another OpAmp to the signal path, would U1 work in inverting mode? Obviously, I'm talking about a different board layout not trying to modify the current boards. Thoughts?

Thanks for the wonderful write up and making everything so easy. :)
 
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My first DIY for anything electronics-related

Hello All,

I've been in the market for headphone amp for a while and its taking me a lot longer to find one that's the best for me and my budget. Frankly all these electronics ohms, watts, and what not are beyond my understanding (although I do understand the basics and science was my strong point, no electronics education whatsoever). I am liking the whole objective, being-able-to-measure mentality instead of getting duped into buying some $500 headphone amp that doesn't even match up to the O2.


1) I'm looking for a cheap amp in terms of price. I'm on a tight budget. 2) I'm looking to learn. I love learning new things. Also looking for a new project or hobby as I have some free time on my hands.


Question.... How hard is this project? From 1 to 10. 1 being so easy that anyone that has never soldered a single thing and has no electronics knowledge whatsoever can do by simply following detailed how-to tutorials. 10 being you need special equipment and skills and measurements, math, etc.

I know I can buy a fully assembled one but I want to learn a little something and also make it myself. Have some fun while I'm at it. However, I do NOT want to do that if I'm going to end up messing it up or ending up with a defective product because that will turn my hobby into a frustrating and angry nightmare, and the money saving aspect of doing it myself will be completely moot and I'll be out a good amount of money.



I never took electronics. But I'm always learning and smart. The best way for me to learn is to just jump in and do it while reading a few steps ahead so I don't make a huge error. I have never soldered a thing in my life. Is this project doable for me? How long would something like this take?

I ordered a solder (for something else) and am not sure if I'm going to need any other equipment, such as a multimeter?

Any input appreciated.
 
If you haven't checked this out, do it. You won't be doing super small parts like on the videos, but it teaches you everything you need to know.

Out of 10, it'll be a 3 or 4 if you don't have experience but are smart and follow the instructions. A multimeter is suggested! It doesn't have to be more than most flea market cheap units, or whatever your neighbor will let you borrow.

The solder flux should be for electronics and not plumber flux.
 
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Joined 2004
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Hello All,


I'm looking for a cheap amp in terms of price.

I do NOT want to do that if I'm going to end up messing it up

Is this project doable for me? How long would something like this take?

Any input appreciated.

Cheap is subjective, but you will not find a less expensive, better performing headphone amp than this. if you are willing to build a nice wooden enclosure for it it could cost you less than $40.

No one can guarantee that you are not going to "mess up", other then yourself. But this project is quite easy to solder. So, if you can follow directions I think you can do it.

After getting all the parts together it should take no more than two hours to solder and screw all together. But some old geezer could not walk a mile in two days. Only you know if you are an electronic " geezer"

Just do it!!,
 
Sweet, I might give this a shot! I have a multimeter back when I was testing my motorcycle battery's alternator. Gotta dig it out of the garage somewhere.


I read through RocketScientist's articles and the Resource page but he doesn't go too much into detail. It's written for people who know what a schematic translates to on the PCB board lol. All I know so far is put wire through board, solder the back. Do it where the holes are. Nothing else.

I'm willing to give it a shot at least and if it doesn't work out or I get stuck, I'm sure I can post some pics and get some help.

Thanks for the feedback.
 
Finally finished building my stock version of the O2 (everything BOM except the coupling caps which are mouser MKT181's). I also used the B3 case so I could put the AC jack and the RCA inputs in the back, everything else is in the front on the board.

One thing I noticed is that should C11/R14 or C12/R20 lose contact to ground either by a bad solder or to hot an iron (these traces are more SMD size than typical P2P PCBs folks are used to), a serious faulure mode presents itself. High DC offset to both the headphones and the DAC.

I suppose it is only an issue for startup/debug, but the failure is transperant to the power management and the Q1/Q2 mofsets stay on.

My advice when working with this PCB is don't consider it a typical P2P PCB, keep your iron low and go slow. And when doing final testing check the DC offset on both the output and input.

Double check that C11/12 R14/R20 are grounded solid after flexing the board into the case and running power for a while, this connection is critical to the health of your dac.