The Objective2 (O2) Headphone Amp DIY Project

[RocketScientist]

Originally Posted by T2T

RocketScientist,

I can't thank you enough for coming up with such a beautiful portable amp -- and sharing the fabulous design. <snip>

At this point, I want to set my sights on some good, quality portable sources. I know from readings, the Walkman NWZ can be quite good, yet the versions that were manufactured for other parts of the world, cost a bit more and have a higher build quality. I also have a LOD cable for my Sansa player and try that too. After all, with amps, it's basically the same as with computers: "Garbage it, Garbage out."

Thanks again !!

You're very welcome! In my testing, if you want to play native FLAC files, it's hard to beat the original Sansa Fuze with the LOD if that's what you have? The Sony players I've tested have all had one or more serious problems (like rolled off bass) as did the Cowon i7 I tested. The tiny Sansa Clip+ outperforms the Cowon and Sonys using its headphone jack.

In terms of pure audio performance the iPod Touch 3G and 4G still rule supreme of everything I've tested but they won't play FLAC to my knowledge (unless the clever guys at Rockbox have figured out a way to jailbreak them...).

You could transcode FLAC to ALAC and there might even be a way to seamlessly do that on the fly (just drag-and-drop FLAC tracks to the iTouch) in MediaMonkey. I know MediaMonkey will do ultra-high quality LAME MP3 transcoding on the fly from FLAC to an iTouch as I do it all the time.

Not to start a debate, but you can use Foobar's blind ABX add-on and compare the highest quality LAME MP3 settings to the original FLAC files and I bet you won't be able to tell them apart. And with MP3 you can fit much more music on the iPod.

That said, the iPod Touch 4G is getting a bit "old" by Apple standards and I suspect the 5G can't be that far away. It might be worth waiting for to see if it has Apple's rumored 24 bit support.

And, if you don't have an iPhone or iPod Touch, they're good for lots of other things including acting as a wireless smart remote for a lot of audio gear--or playing Angry Birds

[T2T]

That's all good to hear. I do have the Sansa Fuze with an appropriate LOD cable as well as the regular mini to mini cable if the headphone out is desired. I don't have their clip model. The Fuze attracted me because of the use of the mini SD memory cards that could be added on.

My daughter has the 4G iPod which I could test with. However, her genres of music are about 180 degrees different from mine and I'm not sure if she'd appreciate me importing some of my music through her iTunes conduit. Still worth a try though, even if I had to listen to some Black Eye Peas on her player.

[HaroldHill]

My headphones started "clicking" while I was using the O2 on battery power. (My source was running but no music was playing, just the clicking). I shut down, swapped in some cheap headphones and the clicking was still there. When I plugged the adapter in, the clicking was gone, so I assume I had low batteries. Reading through the documentation, I don't think this is expected behaviour when the battery is low. Is there anything I can do about it? Is it an significant problem/risk if I intend to use it plugged into the AC adapter almost all of the time?
Thanks!

[RocketScientist]

@HaroldHill, yes, that's been discussed a dozen or two pages back and I also updated the O2 Details article in several places last month. It only seems to happen with certain brands of batteries and not others (including any of mine). The amp is shutting off as it should, the battery voltage rises up (from the lack of the amp drawing power) more than expected, and it turns itself right back on. The cycle apparently can repeat fairly rapidly.

Lowering R25 to around 1.5M ohm and lowering R9 to around 33K should help solve the problem but nobody has reported back conclusively one way or the other yet. Most do not seem to be concerned enough to make the change. Either way the amp is reminding you to shut it off and charge the batteries.

[HaroldHill]

Thanks, RocketScientist. I found it, as you said, on the details page.

[210]

Good luck with your O2amp, RocketScientist! I've read some negative comments from Dunning-Krugers who don't understand much about it. Regards,

[ilijatg]

Can somebody during the assembly make photos of it. Something along a step by step tutorial, this would be one of my first projects this big, and it would be ressuring to have such a tutorial.
I think timpert wanted to do something like that? Remember the more the marrier and make it simple
thx

[wuffer]

i got mine playing but problem when i use battery only
It wont play :-( only when the power jack is plugged in. when its not plugged in and i turn it on the right battery meassure 0 voltage.
I have tryed with other battery but still the same

Problem solved. The resistor at the power jack input touched the jack input
Now its working great

[T2T]

Originally Posted by 210

Good luck with your O2amp, RocketScientist! I've read some negative comments from Dunning-Krugers who don't understand much about it. Regards,

There will always be some sort of opposition to every product that's on the market, even if it is a do-it-yourself product or item. Unfortunately, one just has to question such motives - or, as I like to say "follow the money trail" and you'll see the source of negativity.

Others can say what they want, do what they do, hate all they want. All that I have to say is that it's very infrequent in my searches and travels that I come across a product where I can say that I've finally found what I've been looking for or my ears were desiring to hear. To me, that's been an expensive process of buying, then selling off what I didn't like.

[RocketScientist]

@illijatg, you can click on most of my blog photos (the O2 Summary article has the most) for larger versions. I don't have any of the group buy PCBs and most of my prototypes have some differences. The photo below is the latest revision I have and is nearly identical to the boards that have been sold.

@wuffer, glad you found the problem. That's a good argument for using cheap batteries for testing.

@210 & T2T, Indeed something like the O2 will always have at least a few detractors. Indeed, some have attempted to spread damaging misinformation.

I have no problems with valid opinions. If someone says the O2 is too large for their pocket or they prefer the distortion other amps inflict on the listener, that's fine. But when they claim the O2 is a badly flawed design, overheats, or doesn't sound as good as other amps that measure well, it's useful to challenge their claims. Depending on where they live, for example, it may be entirely possible to arrange a blind listening test against a much more expensive and well respected amp.

Hopefully as more people build or purchase O2s, and like what they hear, the positive word will spread. Now that Epiphany is a Head-Fi sponsor and advertising their assembled O2, perhaps some of the heavy bias against the O2 by the admins and moderators there will change.