[DJ The Rocket]

My LCD-XC (2014 version) sounds very fine with the O2.

According to Innerfidelity, one XC they measured needed almost exactly half as much power as their Alpha Prime, and a different XC needed about a third as much. That strongly suggests the o2 just isn't powerful enough for the Alpha Ps, and their driver principle probably doesn't matter, thanks!

 

[raoultrifan]

I don't have the Prime, but I own K701 and T50RP MK3 and these headphones could be easily driven by the Objective2 headamp with a gain between 2.5-3.5X, depending on the dynamic of the songs listening to. Comparing these headphones with Prime, seems that:
- AKG K701 needs 0.320 Vrms to get a SPL of 90dB
- FOSTEX T50RP MK3 will need 0.206 Vrms to get to 90dB
- Alpha Prime needs 0.174 Vrms for getting to 90dB

Actually, Objective2 can push up to 7.3 Vrms on high impedance loads (>150 ohms) and about 6 Vrms on 50 ohms headphones which means about 0.7W per channel. If I'm not mistaking (Tyll's measurements and also http://www.digizoid.com/power.php helped me here too), for the Alpha Prime that means peaks getting to about 120dB of loudness (please be aware of http://www.sengpielaudio.com/TableOfSoundPressureLevels.htm), quite fair I'd say if using normal-to-high compressed music (blues, jazz, classics and similar) but kinda loud is using highly compressed music (feel free to check https://en.wikipedia.org/wiki/Loudness_war). AFAIK the average SPL on normal music listening should be some where around 85dB, but actual peaks could get up to 110-120dB, depending on the dynamic of the recorded music.

Hence Alpha Prime is the easiest headset to drive from all of the above, I would really not worry about pairing it with the O2, especially that my FOSTEX T50RP MK3 is using similar drivers with the Alpha Prime and I have no issues with my FOSTEX headphones pairing with the O2.

I'm also able to pair the O2 with Beyerdinamic DT880 600-ohms version (about 85mW@7.3V RMS which is >110dB) and unless using low-dB recorded music I'm having no issues listening to these Beyers on a good level, though their maximum power is available to about 8V RMS where they could get about 100mW of power.

There are probably amps out there able to pair even better with planar headphones, especially in respect with output intensity (mA), as we all know that planars could make a better pair with valve or transistors output stage buffers.

 

[MrMateoHead]

I've noticed that the O2 sounds amazing with dynamic drivers, it will lift a dynamic to it's theoretical maximum capability (/exaggeration but not really). It plays great with any dynamic from 16 to 600 ohms. But the o2 doesn't do very well at all with planar magnetic drivers. It seems particularly ill-suited for my 45ohm Alpha Primes, which sound terribly ordinary on it. I realize that the o2 is pretty marginal power-wise, but it's no better at low volumes.

Has anyone else with planar magnetics thought the same? Can anyone explain why this would be? I didn't think their power requirements were really that different. Am I wrong and they are different, or is this some compromise in the o2 design, making it optimized for one and not the other?

It doesn't make a ton of sense that the O2 would be better at powering dynamic, as opposed to planar drivers. I own both. They both sound great. The HE-400s are much improved on the O2, since they are the least efficient cans I've played with on it. I think planars might be a little harder to drive, since they will have lower average impedance (e.g. a flat curve), but easier in the sense that they don't have a lot, if any, phase shifting. The O2 can do more than a half watt at 50 ohms so it can drive the HE-400s to levels I can't sustain.

 

[Architeuthis]

The diy O2 I bought several years ago no longer charges. What batteries does it need, and are they easy to install?

 

[DJ The Rocket]

The diy O2 I bought several years ago no longer charges. What batteries does it need, and are they easy to install?

Sounds like you got excellent life from them, replacing batteries once a year is common.

You need two 9v Nimh batteries. I ordered a pair of Tenergy 250 maH from walmart a couple weeks ago for less than $10, the low discharge ones were $15ish I think. Replacing them is easy: unscrew the four front panel screws (not the rear panel, you'll see why), slide the board out, and you should be able to take it from there.

DO NOT use lithium batteries! That will result in a very bad day. I'd advise against being the first to try the Chinese 600 maH Nimh batteries until someone confirms the Nimh part. A brand like Tenergy is fully trustworthy though

 

[Architeuthis]

Sounds like you got excellent life from them, replacing batteries once a year is common.

You need two 9v Nimh batteries. I ordered a pair of Tenergy 250 maH from walmart a couple weeks ago for less than $10, the low discharge ones were $15ish I think. Replacing them is easy: unscrew the four front panel screws (not the rear panel, you'll see why), slide the board out, and you should be able to take it from there.

DO NOT use lithium batteries! That will result in a very bad day. I'd advise against being the first to try the Chinese 600 maH Nimh batteries until someone confirms the Nimh part. A brand like Tenergy is fully trustworthy though

Thank you, I appreciate it.. Very helpful.

 

[Nitreb]

Thank you, I appreciate it.. Very helpful.

Take also care to unscrew the ground wire from the casing before sliding the board out:

 

[Heitosj]

For the love of god someone help me. I've been with this O2 dac amp combo for about 2 years. Some point in time, audio would only come from one side of the hd 650, with a little tap on the o2 usually solving it. Until it didn't. Months of rage and misery, finally got to replace the p2 jack on the amplified output (notice that english is not my main language and this kind of mechanical repair is often hard where i live, and the dac "not amplified" output its working), and for about 3 weeks, I was happy. Suddenly total, it stars again. I swear for my life that it took all the happiness I had ever feel in my life for me not to throw and smash this thing on the wall. Is there any thing I can do by now to resolve this? Right now I have the same symptoms as when this problem started, first the audio cut would be rare, only when the combo makes some movement on the table, then would happen as I changed volume, then in the end it would come any time spontaneously.

 

[DJ The Rocket]

@Heitosj I know how you feel, nothing is more frustrating than getting your groove disrupted by your equipment!

If replacing the jack fixed it for a little while, I'd bet that's still the issue. How sure are you that you soldered the new jack onto the board securely? How sure are you that you didn't jostle adjacent parts, like the volume pot?

Maybe you should consider a panel mounted jack instead. Those will last a lot longer and take far more force than PCB mounted jacks.

 

[MrMateoHead]

For the love of god someone help me. I've been with this O2 dac amp combo for about 2 years. Some point in time, audio would only come from one side of the hd 650, with a little tap on the o2 usually solving it. Until it didn't. Months of rage and misery, finally got to replace the p2 jack on the amplified output (notice that english is not my main language and this kind of mechanical repair is often hard where i live, and the dac "not amplified" output its working), and for about 3 weeks, I was happy. Suddenly total, it stars again. I swear for my life that it took all the happiness I had ever feel in my life for me not to throw and smash this thing on the wall. Is there any thing I can do by now to resolve this? Right now I have the same symptoms as when this problem started, first the audio cut would be rare, only when the combo makes some movement on the table, then would happen as I changed volume, then in the end it would come any time spontaneously.

Sounds to me like you might actually have a dying / dead ODAC. I don't think that the first revision of the ODAC was super-reliable, mine died after a couple of years and had the same L-channel cut out, then a tap might bring it back etc. I'd wager that the amp itself is fine, but the ODAC is toast. I'd get it repaired and consider replacing the ODAC with the ODAC revision B, which hopefully is solid. FYI I went through two or three ODACs before getting a new one that worked fine. But I doubt it will last! So at some point I will have to get another USB DAC.

 

[DJ The Rocket]

@MrMateoHead that's extremely unusual to go through multiple ODACs. What kept happening to them? Are you one of the 0.5% of the population with a USB drive that makes the revA go unstable then?

 

[Heitosj]

Sounds to me like you might actually have a dying / dead ODAC. I don't think that the first revision of the ODAC was super-reliable, mine died after a couple of years and had the same L-channel cut out, then a tap might bring it back etc. I'd wager that the amp itself is fine, but the ODAC is toast. I'd get it repaired and consider replacing the ODAC with the ODAC revision B, which hopefully is solid. FYI I went through two or three ODACs before getting a new one that worked fine. But I doubt it will last! So at some point I will have to get another USB DAC.

It seems that this is the case. A few hours ago I emailed JDS Labs and, I crap you not, I didnt have the order number, any receipt or anything like that to prove my purchase, and in a few minutes with a pic taken they send my an adress for free repair, even with the product out of warranty period, that would take a 3 days maximum AND they would ship it back to me (international adress, I'm from Brazil) for free. Damn, that was unexpected. They said it was a 2011 version in which this issue was very common. Great company fellows.

 

[MrMateoHead]

@MrMateoHead that's extremely unusual to go through multiple ODACs. What kept happening to them? Are you one of the 0.5% of the population with a USB drive that makes the revA go unstable then?

Where are you getting the data for this interesting fact: "0.5% of the population with a USB drive that makes the revA go unstable?" Please let me know what the size of the population is, or how you in anyway know this and aren't making it up for the sake of questioning my diagnosis. No, I don't think there is anything special about my USB jacks - I used my original ODAC with USB 2.0 / 3.0 jacks on two different computers with motherboards made by major vendors. When mine had issues the very first thing I did was find other USB jacks on different computers / USB hubs.

What happened is that mine slowly died - but after playing with headphones, the amp, and the ODAC (my O2 is not the integrated version), I realized it was the ODAC that failed. So, I sent it to JDS labs, who attempted to repair it / replace it. I believe it was the third try (and a new Rev A ODAC) that finally worked. So that was two fails and one success. So to be clear I probably only went through one ODAC, but then again I don't remember if JDS was trying to fix it, or sending me new ODACs each time. I think what happened was an attempted fix, twice, which failed, and then a new unit, which worked. BTW I'd mention that John at JDS was 100% helpful and probably could have told me to go screw. He didn't, he kept at it until I was back in business. So for that, I highly recommend JDS Labs - apart from the O2 they have a lot of cool products out these days.

To be clear it was John that made me aware that there is a reason that there is a Rev B ODAC. The Rev A was not a perfect design or 100% reliable. Probably they do have a low failure rate, but they do fail. Sorry. And this is coming from someone that loves his ODAC.

To get back to the point, IF Heitosj has an integrated unit with the Rev A ODAC, his issue sounds just like the issue I was having. But because the ODAC is soldered in, It will be hard to be 100% certain which part is the culprit.

 

[MrMateoHead]

It seems that this is the case. A few hours ago I emailed JDS Labs and, I **** you not, I didnt have the order number, any receipt or anything like that to prove my purchase, and in a few minutes with a pic taken they send my an adress for free repair, even with the product out of warranty period, that would take a 3 days maximum AND they would ship it back to me (international adress, I'm from Brazil) for free. Damn, that was unexpected. They said it was a 2011 version in which this issue was very common. Great company fellows.

So I stand by what I said! It seems to be a known issue to them, and they are willing to deal with it.

I'm glad JDS Labs is helping you fuss-free. This is why they rock!

 

[Heitosj]

To get back to the point, IF Heitosj has an integrated unit with the Rev A ODAC, his issue sounds just like the issue I was having. But because the ODAC is soldered in, It will be hard to be 100% certain which part is the culprit.

Boy oh boy, wish I didnt have read that. Thing is, i will send this to them, wait for at least 2 months + possible taxes (because thats how the tax system rolls in brazil lol) and at least 2 more months for someone to bring'em to me in argentina (to make it simple, its impossible to me to receive this in argentina, taxes would be way too expensive!), so at least 5 months for me to hears this baby again, and to discover then that I have the possibility to need to go through 2 more ships until I get a "working" sample makes me quite... anxious