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.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 !!
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
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. 
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. 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!
Thanks!
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@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.
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.
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
I think timpert wanted to do something like that? Remember the more the marrier and make it simple
thx
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
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
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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.
@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.
@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.
Hi all, I received an assembled O2 board.It looked very good. It came with the batteries charged. I plugged in a source and my headphones and it sounded very good. No noise at all from the volume control wiper. Dead silence with no input and volume control all the way up and gain switch in either position. I received my wall wart the next day and plugged it in overnight to charge the batteries. Last night while watching a movie, the amp started a rapid clicking sound. I turned it off and plugged my old XM5 in its place, no clicking, so not my source.
I thought maybe that was the batteries were discharged low enough for the protection circuit to cut in. So I plugged in the wall wart and turned on the O2 again. It sounded fine again but within seconds, the clicking started again. So, not the batteries, I thought, and not the protection circuit since I had AC power applied. Time to troubleshoot. Checking heat and the regulators were too hot to touch for more than an instant.
Looking at the circuit board I saw no obvious problems. Getting out the pcb layout and the schematic and the layout, I found that pins 2 & 3 of U5 were shorted together. It wasn't a whisker style short but it looked like it was designed that way. Got out the soldering iron and ran the tip between the two pins and the pins just cleared right up.
So there was a dead short on the output of the positive regulator. Before the positive supply battery discharged enough to cause the protection circuit to cut in, the O2 sounded pretty good even when AC was supplied and the unit had AC powered negative supply and battery powered positive supply (positive supply from regulator shorted to ground).
Before I started the movie, I had (I thought) charged the batteries overnight by plugging in the wall wart. So over a period of a couple of days, I had been discharging the positive supply battery without recharging while the negative supply battery was recharged.
Anyway, after removing the short, the O2 worked fine and apparently suffered no damage to the circuit. My phones seem to have suffered not at all through the imbalance of running off positive battery and negative wall power supplies. My phones are HD600's.
So is there anything that I should be concerned about from 3-4 hours of running so imbalanced a supply situation before fixing the short?
I thought maybe that was the batteries were discharged low enough for the protection circuit to cut in. So I plugged in the wall wart and turned on the O2 again. It sounded fine again but within seconds, the clicking started again. So, not the batteries, I thought, and not the protection circuit since I had AC power applied. Time to troubleshoot. Checking heat and the regulators were too hot to touch for more than an instant.
Looking at the circuit board I saw no obvious problems. Getting out the pcb layout and the schematic and the layout, I found that pins 2 & 3 of U5 were shorted together. It wasn't a whisker style short but it looked like it was designed that way. Got out the soldering iron and ran the tip between the two pins and the pins just cleared right up.
So there was a dead short on the output of the positive regulator. Before the positive supply battery discharged enough to cause the protection circuit to cut in, the O2 sounded pretty good even when AC was supplied and the unit had AC powered negative supply and battery powered positive supply (positive supply from regulator shorted to ground).
Before I started the movie, I had (I thought) charged the batteries overnight by plugging in the wall wart. So over a period of a couple of days, I had been discharging the positive supply battery without recharging while the negative supply battery was recharged.
Anyway, after removing the short, the O2 worked fine and apparently suffered no damage to the circuit. My phones seem to have suffered not at all through the imbalance of running off positive battery and negative wall power supplies. My phones are HD600's.
So is there anything that I should be concerned about from 3-4 hours of running so imbalanced a supply situation before fixing the short?
Are C13 and C14 decoupling capacitors?
And kind of off-topic question, but I'd really love to hear the explanation of the design decision. Why choose specifically this cap type for C13/14 and not just use the same small ones as others? I thought all types of caps are pretty much the same at sound frequency. I mean, I know there are "audiophile" caps at 10 dollars per 0.1 uF, but I thought that's rubbish. Am I deriously wrong?
P.S. And why 50V, why so big a margin?
P. P. S. For the sake of testing, while I don't have a proper power supply, can I use 12V DC supply?
And kind of off-topic question, but I'd really love to hear the explanation of the design decision. Why choose specifically this cap type for C13/14 and not just use the same small ones as others? I thought all types of caps are pretty much the same at sound frequency. I mean, I know there are "audiophile" caps at 10 dollars per 0.1 uF, but I thought that's rubbish. Am I deriously wrong?
P.S. And why 50V, why so big a margin?
P. P. S. For the sake of testing, while I don't have a proper power supply, can I use 12V DC supply?
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RocketScientist will give the best answer but I just happened to be logged in and spotted the post.
The metal film are much more linear than electrolytics and so are better to use in the signal path (than electros). The 2.2uF (or higher) value is needed to keep the low end gain roll off (below 30Hz or so) acceptable. Something like the 0.22uF would have a much greater low end roll off (would start at a higher frequency like 80 Hz or more). There are 2.2uF MLCC ceramics but they are likely more expensive which is probably why RocketScientist went with the metal film. The voltage rating was probably just by default - that is kind of the mimimum as I recall for 2.2uFs.Hope this helps!
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no, i would say he didnt use a ceramic in the signal path, well, because although they are good enough, they still arent of the quality of film, which is also much less microphonic, which in a portable...who knows it wouldnt be the first time a cap has audibly rang. the npos are getting there, but 2.2uf? nah, you can get a much better film cap
Thanks for quick reply! It all makes sense now, though I'm very sure I saw 2.2 uF non-polarized caps of much smaller size.
Size considerations aside, can a human actually hear a difference?
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I tend to agree here that the iPod touch is a great player, especially connected to O2 via LOD. I have seen 2 apps that will allow you to play FLAC on the iPod touch, FLAC Player and Golden Ears.
I have not tried them but I am thinking of giving FLAC Player a go.
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
I don't think a step-by-step tutorial is really necessary, even for a novice.
You start by figuring out what all the components are, which include deciding the values of the resistors (I use a DMM as I find the colour coding scheme absolutely beyond sense). Then you start stuffing the board following the BOM and the references on the PCB (270kΩ 1/8W to R4, R5, R8 and R24 f.ex.), starting with the smallest components, and working yourself from the middle of the board outwards.
I took a photo with only the smaller components in place: The diodes, resistors and ceramic capacitors, and sockets for the gain resistors. It might help as a reference.
http://i.imgur.com/zbLgf.jpg
.
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