# O2 AMP + ODAC



## NimbleTurtle

As I was searching for a good amp/ dac, I decided to save myself the trouble of picking between numerous options and get an O2 amp/ dac. 
   
  Now I have to choose between JDS Lab variant and the EHP variant. I can only see the rear view of the former (http://www.jdslabs.com/item.php?fetchitem=39) and the latter seems smaller than I thought (http://epiphany-acoustics.co.uk/wp-content/uploads/2012/04/Epiphany-Acoustics-EHP-O2-Reflection2.jpg). Why is it that the EHP variant is187 dollars and the JDS LAB variant is 285 dollars? 
   
  P.S. Do I need an AC adapter for both? 
   
  I would appreciate it if you guys can help me choose.


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## KmhK

Convert to dollars, it's 18X pounds.
 I believe you need an adapter.


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## alphaphoenix

No.  Assuming the ODAC and O2 are separate, only the O2 amp needs the adapter.  The ODAC gets its source via the mini USB and the 1/8 or RCA to 1/8 on the ODAC feeds to the O2 amp.  If you have the O2/ODAC combo, you only need the one adapter to power the O2.


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## NimbleTurtle

Quote: 





kmhk said:


> Convert to dollars, it's 18X pounds.
> I believe you need an adapter.


 
  Ah damn I see... thanks!


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## NimbleTurtle

Quote: 





alphaphoenix said:


> No.  Assuming the ODAC and O2 are separate, only the O2 amp needs the adapter.  The ODAC gets its source via the mini USB and the 1/8 or RCA to 1/8 on the ODAC feeds to the O2 amp.  If you have the O2/ODAC combo, you only need the one adapter to power the O2.


 
  I'm planning to get a O2 / ODAC combo. Have any of you guys purchased the O2 / ODAC? If so, which variant did you go with?


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## alphaphoenix

If you're getting the O2/ODAC combo (ODAC installed inside the O2), there shouldn't be any difference between the two manufacturers except for distinct aesthetics.  Go for the all inclusive cheaper price.
   
  If you're asking "should I go for the O2/ODAC integrated combo or separate combo" that depends on your setup.  I prefer a separate combo.  You may not care much for the O2, like me, but really fancy the ODAC that gives you much more flexibility.  All-in-one configurations has its advantages.  Again, it's all personal preference.


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## NimbleTurtle

Quote: 





alphaphoenix said:


> If you're getting the O2/ODAC combo (ODAC installed inside the O2), there shouldn't be any difference between the two manufacturers except for distinct aesthetics.  Go for the all inclusive cheaper price.
> 
> If you're asking "should I go for the O2/ODAC integrated combo or separate combo" that depends on your setup.  I prefer a separate combo.  You may not care much for the O2, like me, but really fancy the ODAC that gives you much more flexibility.  All-in-one configurations has its advantages.  Again, it's all personal preference.


 
  Thanks!


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## rudi0504

JDS Lab ODAC usb DAC + JDS Lab O 2 head amp full modification with Black Gate Capasitors


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## lorriman

rudi0504 said:


> JDS Lab ODAC usb DAC + JDS Lab O 2 head amp full modification with Black Gate Capasitors




Nice: did you have to do anything to the O2 electronics for that battery config?

Without the ODAC (which I've managed to slip in under the O2 board) do you think there would be enough room in a B03 enclosure?


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## Zophiel

I'm currently saving up for the O2 and the ODAC as separate entites from JDS.  I want them separate so that i can take the O2 with me to work/ other portability reasons, and when i come home i have a decent Desktop configuration.  The only question i have is, when i own just the O2, before i can afford the ODAC, what benefits will i see from taking the O2's input from my soundcard's output?  Just output impedance and max power?


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## lorriman

zophiel said:


> I'm currently saving up for the O2 and the ODAC as separate entites from JDS.  I want them separate so that i can take the O2 with me to work/ other portability reasons, and when i come home i have a decent Desktop configuration.  The only question i have is, when i own just the O2, before i can afford the ODAC, what benefits will i see from taking the O2's input from my soundcard's output?  Just output impedance and max power?




There are two other improvements depending on your setup.

1)In Win XP digital volume adjustment meant getting less than 16bits of info other than at max volume. The audio quality can audibly degrade at less than max volume. The O2 lets you set max volume at the laptop and use the O2 to turn the volume down. (The ODAC gives you back digital volume control so long as you set it to 24bit as there are enough bits to endure bit stripping.). It;s been said that Vista corrected this XP flaw. 

2)Noise: some kinds of source noise do not increase with increased source volume. If this is the case then by whacking the laptop up to max volume you can get the audio so far away from that background noise that it is inaudible.

One issue with the above is that if you are feeding sensitive phones then even at 2.5x gain you can't get the pot higher than 9pm on the O2 which is in pot channel-imbalance territory (which happens at the lower end) especially if you are a quiet listener. As a loud listener using armatures I am often at 9pm and I believe I may have experienced this issue. It's one reason a lot of O2 users change the 2.5x gain to 1x (ie. no gain).I'm not sure what the situation is with max volume on the source but in some cases it is bound to be too much even for 6pm on the pot.

Possible 3rd: I'm lead to believe that an amp straining to produce current for a low impedance, high-current device can start distorting. I;m not sure that this is true. If so then that extra power will not just give more volume but also avoid distortion in some cases. Perhaps someone can correct that.


Keep in mind also that the Odac requires an amp. So if you haven't already then the O2 is a stunningly good value amp that you'll be needing.

Having said that: the Behringer UCA202 measures well, as done by guess who, and at half the price there's really there's no absolute need for an Odac unless you want the ultimate.(I wanted the ultimate.) It also has the advantage of not (technically) needing an amp. But it does have a very high output impedance so you'll be needing that amp anyway.


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## NimbleTurtle

Quote: 





lorriman said:


> There are two other improvements depending on your setup.
> 1)In Win XP digital volume adjustment meant getting less than 16bits of info other than at max volume. The audio quality can audibly degrade at less than max volume. The O2 lets you set max volume at the laptop and use the O2 to turn the volume down. (The ODAC gives you back digital volume control so long as you set it to 24bit as there are enough bits to endure bit stripping.). It;s been said that Vista corrected this XP flaw.
> 2)Noise: some kinds of source noise do not increase with increased source volume. If this is the case then by whacking the laptop up to max volume you can get the audio so far away from that background noise that it is inaudible.
> One issue with the above is that if you are feeding sensitive phones then even at 2.5x gain you can't get the pot higher than 9pm on the O2 which is in pot channel-imbalance territory (which happens at the lower end) especially if you are a quiet listener. As a loud listener using armatures I am often at 9pm and I believe I may have experienced this issue. It's one reason a lot of O2 users change the 2.5x gain to 1x (ie. no gain).I'm not sure what the situation is with max volume on the source but in some cases it is bound to be too much even for 6pm on the pot.
> ...


 
  What gain should I be using if I'm using a headphone of impendence 50 ohms? 2.5x gain or no gain? 
   
  Btw I noticed that the Epiphany O2/ ODAC combo are encased in one compact form. Is the JDS Lab's combo of the O2/ ODAC also the same compact form as well? I did not see a picture from their website.


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## lorriman

At 50 Ohms I think you'll be fine at 2.5x. However, I'm only going on other people's conversations on diyaudio: I can't do the maths. 

Even for sensitive phones: at 9pm it's not so bad; I;m not really bothered by it. But let's say that the phones had a similar channel imbalance of their own as the pot on the O2, then that could be bothersome and the only solution would be to reverse the phones, L-R and viceversa to cancel them out, which may be annoying for some things (like films).


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## Zophiel

Quote: 





nimbleturtle said:


> What gain should I be using if I'm using a headphone of impendence 50 ohms? 2.5x gain or no gain?
> 
> Btw I noticed that the Epiphany O2/ ODAC combo are encased in one compact form. Is the JDS Lab's combo of the O2/ ODAC also the same compact form as well? I did not see a picture from their website.


 
   You are more interested in the interplay between impedance and sensitivity of the headphone rather than just the Ohms WRT Gain.  Just FYI the O2 is designed to be able to produce appropriate mW accross a LARGE (16-600) range of impedances.  what gain you want to use is your preference.  Once the music is playing at acceptable (your taste) levels, then you want to use the lowest gain you can do achieve this.  the O2 comes default with a 2.5X and 6.5X gain modes, but can be easily customized to 1X/2.5X/6.5X (pick any two).  Youre not going to really need 6.5X except for voltage HUNGRY headphones like HD 650 or the higher end Beyers.


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## lorriman

nimbleturtle said:


> I'm planning to get a O2 / ODAC combo. Have any of you guys purchased the O2 / ODAC? If so, which variant did you go with?





nimbleturtle said:


> I'm planning to get a O2 / ODAC combo. Have any of you guys purchased the O2 / ODAC? If so, which variant did you go with?




Probably you are aware, but just in case: keep in mind that the combo means NO BATTERIES and so no portability. If you want this to do everything for you then it should be separates.


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## NimbleTurtle

Quote: 





lorriman said:


> Probably you are aware, but just in case: keep in mind that the combo means NO BATTERIES and so no portability. If you want this to do everything for you then it should be separates.


 
  I actually did not know that. But either way, I decided to wait for the ODA to come out, and hopefully a combo of ODA and ODAC. The sound coming out of the bigger jack is better than the 3.5 mm one right?


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## mikeaj

Quote: 





nimbleturtle said:


> I actually did not know that. But either way, I decided to wait for the ODA to come out, and hopefully a combo of ODA and ODAC. The sound coming out of the bigger jack is better than the 3.5 mm one right?


 
   
  No.
   
  Well, after plugging / unplugging a 3.5mm jack a lot of times, it may start to go loose and fail on you. The larger jack may take longer to start failing. As long as there's a reasonably secure connection, it's the same. Er...okay, a larger jack may also have a smaller impedance (note that the ground connection is shared between L and R channels), so you would get lower crosstalk with the larger jack. With the 3.5mm jack and 15 ohms headphones, a worst-case scenario, crosstalk is -65 dB with the O2. For 600 ohms headphones, it's -95 dB. I don't think many people would consider that a real concern.


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## lorriman

nimbleturtle said:


> I actually did not know that. But either way, I decided to wait for the ODA to come out, and hopefully a combo of ODA and ODAC. The sound coming out of the bigger jack is better than the 3.5 mm one right?




As Mikeaj says, it really makes no difference (the O2 designer has even said that there is a - very slight - sonic advantage to a 3.5mm jack on the ODAC, interestingly) but the life span of the jack is a factor. The 3.5mm is rated to 2,000 inserts. Not very many really; enough to confidently cover a 1 year warranty but I want mine to last 15 years. I use a short extension purely to avoid using the O2's jack itself. Since I'm already using the Odac I don't bother with an extension lead for the 'in' jack. 

Also, it's worth knowing that the ODA will have almost identical electronics to the O2. Effectively it's an O2 in a bigger case including internal power supply....at extra cost and no batteries?!?!?! hmmm, that makes no sense for me. The one convenience that might have made it an option is more switcheable gain options, ie three rather than the O2's two. A 1x, 4x and 12x would have everything covered, for example. But that's not on the ODA spec: just two switcheable gain options as with the O2.

As it is the O2 is effectively a desktop amp already (ignoring the external PSU). The only (non-stats) headphones it can't power are obscure and probably provide no real increase on modern headphones anyway. That's one powerful amp. It's also quite big for a 'portable' amp. If you get one in a B03 case (adds some height over the standard B02) then it has a desktop presence about it and has room for 1/4" jacks as you can see in some pics where people have done this. 

If you really don't need batteries then the o2 in a B03 case may make you happy for slightly less money than the ODA which doesn't exist yet and of which the designer says it may be late summer or later before the design is released. You could be looking at Christmas before you get one. Even my O2 in a B02 box has small rubberised feet that make it behave like a mini-desktop amp on my desk.

There is one other option worth a mention but you would have to get a 'special build' of an O2: slipping the ODAC underneath the O2 circuit board. The designer didn't realise this possibility. This is how I have it (it's a self-build). There is actually room there. So I have it all in one box: O2, Odac and batteries!!! Yum.


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## hekeli

Quote: 





zophiel said:


> You are more interested in the interplay between impedance and sensitivity of the headphone rather than just the Ohms WRT Gain.  Just FYI the O2 is designed to be able to produce appropriate mW accross a LARGE (16-600) range of impedances.  what gain you want to use is your preference.  Once the music is playing at acceptable (your taste) levels, then you want to use the lowest gain you can do achieve this.  the O2 comes default with a 2.5X and 6.5X gain modes, but can be easily customized to 1X/2.5X/6.5X (pick any two).  Youre not going to really need 6.5X except for voltage HUNGRY headphones like HD 650 or the higher end Beyers.


 
   
  Impedance, sensitivity, hungriness or your tastes have nothing to do with O2 gain structure. Once again here are the key figures for the resulting kindergarden math.
   
  Only thing you need to know is your *source/dac maximum output voltage*. Usually portable daps >0.5V, Fiio E10 1.6V, standard desktop stuff 2V (hello ODAC), some even more. Read the specs.
   
  O2 on AC usage, simply divide *7 / V = max gain*. With batteries it's lower, *4.5 / V*. Anything over this can and will cause *distortion*. Hungry headphones or not, do not go over this limit, there is no need. 1V source with 6.5x gain is the same as 2V source with 3.25x gain. This is the maximum output O2 can do and it's enough for pretty much anything out there.
   
  I use LCD-2 with 1x gain 95% of the time. My DacMagic has pretty high 2.3V output, so theoretical max gain is *7 / 2.3 = ~3x*. If you already have O2 with default 2.5x / 6.5x gains, you can easily convert either to 1x by simply removing the resistor with small pliers (I guess this needs a bit more detailed documentation..). I have done it to get 1x / 2.5x. It's pretty perfect. For the lowest theoretical noise you want to choose the lowest gain that satisfies your volume. But you need to know the gain limit.


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## Zophiel

Quote: 





lorriman said:


> Probably you are aware, but just in case: keep in mind that the combo means NO BATTERIES and so no portability. If you want this to do everything for you then it should be separates.


 
   You can, of course, buy the ODAC and O2 separately and retain the "mobile" advantage of the O2, and like others have said, it is a competant desktop amp on AC Power anyway.


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## Zophiel

Quote: 





hekeli said:


> Impedance, sensitivity, hungriness or your tastes have nothing to do with O2 gain structure. Once again here are the key figures for the resulting kindergarden math.
> 
> Only thing you need to know is your *source/dac maximum output voltage*. Usually portable daps >0.5V, Fiio E10 1.6V, standard desktop stuff 2V (hello ODAC), some even more. Read the specs.


 
  It was taken as an asumption that he was going to use either the typical .5V - 1.0V portable or the more standard 2V soundcard out.  In which case understanding how your headpones react to a given voltage at a given impedance (or a given power) is the only element left.  We have both stated that the majority of headphones fall well within the boundries of the typical source+O2 output combinations.  
   
  The tastes has to do with how loud he likes it.  If he likes it quiet, he may be able to get away with 2.5X on all headphones (as i imagine most would any way)  otherwise he may want 6.5X if he doesnt appreciate his hearing!   It doesnt affect the mechanics of gain, but may affect the  "minimum gain to get it done".


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## OJNeg

Quote: 





lorriman said:


> As Mikeaj says, it really makes no difference (the O2 designer has even said that there is a - very slight - sonic advantage to a 3.5mm jack on the ODAC, interestingly) but the life span of the jack is a factor. The 3.5mm is rated to 2,000 inserts. Not very many really; enough to confidently cover a 1 year warranty but I want mine to last 15 years. I use a short extension purely to avoid using the O2's jack itself. Since I'm already using the Odac I don't bother with an extension lead for the 'in' jack.
> *Also, it's worth knowing that the ODA will have almost identical electronics to the O2. Effectively it's an O2 in a bigger case including internal power supply....at extra cost and no batteries?!?!?! hmmm, that makes no sense for me. *The one convenience that might have made it an option is more switcheable gain options, ie three rather than the O2's two. A 1x, 4x and 12x would have everything covered, for example. But that's not on the ODA spec: just two switcheable gain options as with the O2.
> As it is the O2 is effectively a desktop amp already (ignoring the external PSU). The only (non-stats) headphones it can't power are obscure and probably provide no real increase on modern headphones anyway. That's one powerful amp. It's also quite big for a 'portable' amp. If you get one in a B03 case (adds some height over the standard B02) then it has a desktop presence about it and has room for 1/4" jacks as you can see in some pics where people have done this.
> If you really don't need batteries then the o2 in a B03 case may make you happy for slightly less money than the ODA which doesn't exist yet and of which the designer says it may be late summer or later before the design is released. You could be looking at Christmas before you get one. Even my O2 in a B02 box has small rubberised feet that make it behave like a mini-desktop amp on my desk.
> There is one other option worth a mention but you would have to get a 'special build' of an O2: slipping the ODAC underneath the O2 circuit board. The designer didn't realise this possibility. This is how I have it (it's a self-build). There is actually room there. So I have it all in one box: O2, Odac and batteries!!! Yum.


 
   
  The O2 obviously can be used as a desktop amp, but I'd prefer to use an amp with it's own power supply. I don't like running a nasty power brick of questionable quality around my already cluttered desktop. An internal power supply is a key feature that makes a desktop amp IMO.
   
  My big question is, can he keep the cost down with the ODA? $150 is a pretty sweet price point for a portable amp, but there's no way it'll stay that low if he's adding a step down transformer _and _all the components for a regulated power board _and _a larger case _and _the necessary case components. Do you think he can keep the assembled price under $300? $400? It'd be great if he could release a kit. If not, I'll make the beta22 my next build instead of the ODA.


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## hekeli

Quote: 





zophiel said:


> It was taken as an asumption that he was going to use either the typical .5V - 1.0V portable or the more standard 2V soundcard out.  In which case understanding how your headpones react to a given voltage at a given impedance (or a given power) is the only element left.  We have both stated that the majority of headphones fall well within the boundries of the typical source+O2 output combinations.
> 
> The tastes has to do with how loud he likes it.  If he likes it quiet, he may be able to get away with 2.5X on all headphones (as i imagine most would any way)  otherwise he may want 6.5X if he doesnt appreciate his hearing!   It doesnt affect the mechanics of gain, but may affect the  "minimum gain to get it done".


 
   
  I'm not sure I can follow you. 2V x 6.5 would distort. 1V x 6.5 would not. If you want hearing damage, you don't need to spend money on O2 just to distort it.
   
  (Or perhaps you meant "not the more standard 2V soundcard out"?)
   
   
  Quote: 





ojneg said:


> The O2 obviously can be used as a desktop amp, but I'd prefer to use an amp with it's own power supply. I don't like running a nasty power brick of questionable quality around my already cluttered desktop. An internal power supply is a key feature that makes a desktop amp IMO.


 
   
  Do you usually keep your "power bricks", extension cords etc on your desktop? I certainly don't, they are well hidden. I want as little stuff on my desktop as possible, smaller the better.


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## Zophiel

Quote: 





hekeli said:


> I'm not sure I can follow you. 2V x 6.5 would distort. 1V x 6.5 would not. If you want hearing damage, you don't need to spend money on O2 just to distort it.
> 
> (Or perhaps you meant "not the more standard 2V soundcard out"?)


 
  No sorry, I meant only to use that as a boundry case to say that, in almost any situation (sources from .5 to 2.0V) the O2 provides adequate output voltage (or power) to power just almost any phone.  It is up to you to dial in the correct gain, taking into account your headphones sensitivity, your taste in volume and the O2's output at the impedance of your particular headphone.  Of that large range of output powers, only a small subsection will be suitable for your particular headphone.  I wasn't stating anything novel, just reafirming that the O2 has more than ample output power for just about any phone, and that if you wanted to confirm that, you would have to do math beyond "will the O2 work with my 50 ohm phones".   Given his 7.7 Volt max output (IIRC) I agree that any source and gain combination that would lead to a peak voltage higher than this would just distort, but that was not the point of my statement.


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## NimbleTurtle

Quote: 





lorriman said:


> As Mikeaj says, it really makes no difference (the O2 designer has even said that there is a - very slight - sonic advantage to a 3.5mm jack on the ODAC, interestingly) but the life span of the jack is a factor. The 3.5mm is rated to 2,000 inserts. Not very many really; enough to confidently cover a 1 year warranty but I want mine to last 15 years. I use a short extension purely to avoid using the O2's jack itself. Since I'm already using the Odac I don't bother with an extension lead for the 'in' jack.
> Also, it's worth knowing that the ODA will have almost identical electronics to the O2. Effectively it's an O2 in a bigger case including internal power supply....at extra cost and no batteries?!?!?! hmmm, that makes no sense for me. The one convenience that might have made it an option is more switcheable gain options, ie three rather than the O2's two. A 1x, 4x and 12x would have everything covered, for example. But that's not on the ODA spec: just two switcheable gain options as with the O2.
> As it is the O2 is effectively a desktop amp already (ignoring the external PSU). The only (non-stats) headphones it can't power are obscure and probably provide no real increase on modern headphones anyway. That's one powerful amp. It's also quite big for a 'portable' amp. If you get one in a B03 case (adds some height over the standard B02) then it has a desktop presence about it and has room for 1/4" jacks as you can see in some pics where people have done this.
> If you really don't need batteries then the o2 in a B03 case may make you happy for slightly less money than the ODA which doesn't exist yet and of which the designer says it may be late summer or later before the design is released. You could be looking at Christmas before you get one. Even my O2 in a B02 box has small rubberised feet that make it behave like a mini-desktop amp on my desk.
> There is one other option worth a mention but you would have to get a 'special build' of an O2: slipping the ODAC underneath the O2 circuit board. The designer didn't realise this possibility. This is how I have it (it's a self-build). There is actually room there. So I have it all in one box: O2, Odac and batteries!!! Yum.


 
  Would I be plugging in my headphone jack thru the ODAC or the O2? I'm a bit lost on how they're setup ifI get two of these separately. And are the "BO3" and "BO2" cases options available options on websites that provide the ODAC/ O2? 
   
  Quote: 





mikeaj said:


> No.
> 
> Well, after plugging / unplugging a 3.5mm jack a lot of times, it may start to go loose and fail on you. The larger jack may take longer to start failing. As long as there's a reasonably secure connection, it's the same. Er...okay, a larger jack may also have a smaller impedance (note that the ground connection is shared between L and R channels), so you would get lower crosstalk with the larger jack. With the 3.5mm jack and 15 ohms headphones, a worst-case scenario, crosstalk is -65 dB with the O2. For 600 ohms headphones, it's -95 dB. I don't think many people would consider that a real concern.


 
  Thanks for the info!


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## NimbleTurtle

Quote: 





zophiel said:


> No sorry, I meant only to use that as a boundry case to say that, in almost any situation (sources from .5 to 2.0V) the O2 provides adequate output voltage (or power) to power just almost any phone.  It is up to you to dial in the correct gain, taking into account your headphones sensitivity, your taste in volume and the O2's output at the impedance of your particular headphone.  Of that large range of output powers, only a small subsection will be suitable for your particular headphone.  I wasn't stating anything novel, just reafirming that the O2 has more than ample output power for just about any phone, and that if you wanted to confirm that, you would have to do math beyond "will the O2 work with my 50 ohm phones".   Given his 7.7 Volt max output (IIRC) I agree that any source and gain combination that would lead to a peak voltage higher than this would just distort, but that was not the point of my statement.


 
  Ah makes sense. Thanks. I listen at a pretty medium volume so I think I will go with the 1x and 2.5 x gain. 
   
  Thanks for all the wise words from the very knowledgeable technicians on this board! Much appreciated.


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## NimbleTurtle

BTW I know this has been answered many times before but I feel the need to reconfirm this. 
   
  What exactly does an amp do? Other than providing the potential to drive cans at larger volumes? And is there a way to scientifically prove these effects? 
   
  And oh shoot I have one more question: does impedance affect how "much" it improves the headphones? Is there, for instance, a direct correlation between the improvements of an amp powering a 15 ohm headphone, as opposed to a 600 ohm headphone (other than perhaps, being able to sufficiently listen at preferred volume).


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## Zophiel

In short, amps provide additional power to headphones that may require it.   Go to NwAvGuy's website and read up on some of the more technical details behind impedance and other electrical phenomena.   Chances are, if you don't know explicitly that you need an amp, you probably don't.  Most headphones will benefit some from an amp with a lower output impedance (a cahracteristic of the amp itself) just due to the headphones damping mechanism, but this, as well, is subjective as to whether this change in sound is an improvement or not.  The vast majority of introductory headphones that can be had for $100 and less, likely dont need an amp; the output voltage from the player (be it a computer/laptop or Digital Audio Player {iPod, etc}) is sufficient to drive it to reasonable listening levels.  Some of the more advanced headphones require an amp for one of many reasons.  As the headphone's impedance increases, the voltage produced by the source provides less power, which depending on the sensitivity of the headphone, can lead to reduced or less dynamic listening volume. 
   
  I wont go any further than that, and end with : Educate yourself on the topic, the basics are easy to understand and don't require much math.   If you have a high impedance or a low sensitivity hphone (Beyerdynamics and HiFiMan headphones respectivly as examples) then an amp will likely help, or even be rquired. 
   
   
  The DAC  is another issue altogether, but basically bypasses what may be inferior components in your source with higher quality components.   The DAC/AMP combo is one way to ensure the electronics chain between your digital music files and the music you hear is as high quality and controlled as possible.  Its expensive, but if you are serious about htis hobby, it is a necessary step in acheiving the best possible sound.


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## OJNeg

Quote: 





hekeli said:


> Do you usually keep your "power bricks", extension cords etc on your desktop? I certainly don't, they are well hidden. I want as little stuff on my desktop as possible, smaller the better.


 
   
  It's not space on my desktop that I lack, it's space below it. I have all my cables very neatly networked to be out of sight. I could live with running an external power supply but it's an annoyance.
   
  And moreover, I've had bad experiences with poor external power supplies when used with audio components. Some cheapies don't deliver anything close to the rated wattage. Power supplies are important to keeping line noise out and it's best to have a quality, reliable PS feeding your amp board. Might as well build it into the device and be able to run it off the mains.


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## lorriman

nimbleturtle said:


> BTW I know this has been answered many times before but I feel the need to reconfirm this.
> 
> What exactly does an amp do? Other than providing the potential to drive cans at larger volumes? And is there a way to scientifically prove these effects?
> 
> And oh shoot I have one more question: does impedance affect how "much" it improves the headphones? Is there, for instance, a direct correlation between the improvements of an amp powering a 15 ohm headphone, as opposed to a 600 ohm headphone (other than perhaps, being able to sufficiently listen at preferred volume).




There's quite a lot of info, properly backed up, on this topic at nwavgy's "More Power?" page. Google for the two terms: I can't post a link.

There's a lot of talk of amps 'improving' the sonic quality, but really that shouldn't be happening: they should only be increasing volume. Unless there's a problem....

High output impedance of an older source, ie older ipods/iphones (or not so old Galaxy SII) is perhaps the most common. A decent amp can correct that.

In some high end, low-impedance, high-current headphones the source can distort as its basic amp is overloaded. An amp with adequate power can avoid that.

But really, perfect hifi amping has been a settled technology for more than 20 years and is not expensive. Expensive amps are more marketing than reality. Solid State changed the world. It's even got to the stage where talk of class A or class AB is absurd: a properly made, modern class D amp is much cheaper and genuinely hifi (and cheap on electricity). No one needs class A amps.

So why, then, are amp reviews so often 'expansive' beyond what the above can explain? It's as if the reviewer is saying that the amp adds to the audio, or improves it. Apart from the above issues, that shouldn't happening. Unless there's a problem...

Very few know that amp tech is settled and cheap. Magazines certainly won't tell you. Some premium amp manufacturers build in a bit of distortion increasing with cheapness of the model. Can you imagine why? It's sometimes justified with "2nd order harmonic distortion improves audio", which playing with a multi-order distortion plugin on my laptop: I can tell you it does not. 

No wonder then, that old fashioned tube amps don't sound so bad, even though they also distort: the competition is worse. Some even have issues that give a 3D effect (which the reviewer will experience as a 'bigger soundstage'). In the headphone amp world there is another factor: consumer amps based on popular but flawed DIY designs (Mini3 being an example of one of those designs). These are very common, as are dodgy DIY amps sold on ebay.

People moving from one of these amps to another are going to experience different sonic qualities, sometimes improvements. In the highly subjective world of audio all this passes for normality. And all this chaos is further obscured because there are legitimate sonic improvements due to the common issue of sources having high output impedance. 

The O2 was an attempt to address this by showing that you can build a perfect ('wire-with-gain), powerful, portable amp for $70 in parts. It's been an anti-climax because there is nothing for the reviewers to say beyond: it just increases the volume. Which is exactly all that it should do.

To summarise: source output impedance aside, not many headphones actually need amping. You can tell if they do simply because you can't get the volume. 

I wish it was as simple as that, but with those rarer low-impedance, high current phones (ie. LCD2s, HE-500 etc) potentially causing distortion: how do you measure that as an end user? You'll be trying to guess whether your audio might have distortion that might be fixed by amping.


----------



## lorriman

I forgot to add some critical info: so how do you know an amp is any good?

There are two camps: subjectivists and objectivists. The first listen with their ears and the latter make measurements. 

Any scientifically minded person is liable to lean towards the objectivist camp. The O2 was designed by measurement. Essentially you know an amp should be good if the published specs say so *and* are adequate (some specs leave out essential details). After that you need a decent hifi mag or 3rd party to test and measure the amp. Then you really know.

There is a problem, however. Has every sonic characteristic been measured? Are all these measurements enough? Perhaps 70 years ago some one them were not measured. Perhaps there are unknown qualities to audio yet to be discovered. This plays straight in to the subjectivist camp and is unanswerable.


----------



## Satellite_6

The answer is yes. The doubt is only raised to support a BS argument with no facts behind it.


----------



## lorriman

satellite_6 said:


> The answer is yes. The doubt is only raised to support a BS argument with no facts behind it.




Logically there is no answer. It's rather like trying to prove there isn't a god. It's not logically possible: even if there isn't a shred of evidence of a god as some claim that still doesn't prove the matter. [Edit: a no one has come up with a logical argument that hasn't a flaw against the existence of a god; usually attempts are made with free will but they never hold up].

You may think you have every quality of audio nailed, but only a divine being can tell you that for sure. 

Anyway, I myself am firmly in the objectivist camp but the above is a genuine weakness. Having said that: double blind testing is enough to satisfy me that objectivist equipment is not bested by subjectively designed equipment and that is as good as it gets for now.


----------



## lorriman

I also forgot to add that the FIIO5 amp measures well and is very cheap (other FII0s don't). Quite a few headphones that need the extra power will be just fine with a FIIO5. It also corrects output impedance. All for $15. If you want a DAC that measures well for your laptop then Behringer's UCA202 is cheap. (The ODAC measures wonderfully but strictly speaking it's overkill.) The Behringer has very high output impedance so you will need an amp unless you have very high impedance phones. That FIIO will do but keep in mind it doesn't work when charging so it's not the ideal desktop/laptop solution.


----------



## mikeaj

Quote: 





ojneg said:


> It's not space on my desktop that I lack, it's space below it. I have all my cables very neatly networked to be out of sight. I could live with running an external power supply but it's an annoyance.
> 
> And moreover, I've had bad experiences with poor external power supplies when used with audio components. Some cheapies don't deliver anything close to the rated wattage. Power supplies are important to keeping line noise out and it's best to have a quality, reliable PS feeding your amp board. Might as well build it into the device and be able to run it off the mains.


 
   
  It's not really an external power supply that the O2 uses.  The external unit the O2 uses is just a transformer, to step down the voltage from the wall to something like 13.5-20V AC.  Hence you'd need a different transformer in a country with 115V power as opposed to 230V power.  I think for size and weight concerns, maybe regulatory too (?), the transformer wasn't put inside the chassis.  You can get an upgraded transformer if you really want though; in fact, it's recommended for bench testing or running the planar magnetics run at a loud volume.  Difference in price is only like $5.
WAU12-200
WAU16-400
   
  The power filtering is on the PCB inside the amp.  There are some filter caps and 7812 / 7912 linear regulators.  Power consumption of the O2 is in general pretty low—it's not class A, it only runs off of +- 12V rails, etc.—if it were a power hog, batteries would go out really fast, so it's not.  If the power supply were inadequate, then you think that there would be performance issues under high load, right, or maybe some noise?  I don't think there's evidence of that.  So I think that concerns over power supply quality are not really that well founded.  
   
  I can understand the reservations about having another fat plug-in thing to deal with though.


----------



## NimbleTurtle

Quote: 





lorriman said:


> I also forgot to add that the FIIO5 amp measures well and is very cheap (other FII0s don't). Quite a few headphones that need the extra power will be just fine with a FIIO5. It also corrects output impedance. All for $15. If you want a DAC that measures well for your laptop then Behringer's UCA202 is cheap. The ODAC measures wonderfully but strictly speaking it's overkill. It has very high output impedance so you will need an amp unless you have very high impedance phones. That FIIO will do but keep in mind it doesn't work when charging so it's not the ideal desktop/laptop solution.


 
  I know Nwavguy wrote a pretty favorable review of the FIIO E5. I'll look into that. Though can I take his word for it? And I thought the ODAC was designed so it could be used with headphones of any impedance? Or was that just the O2...


----------



## NimbleTurtle

I have done numerous research on this new hobby of mind, including reading all of Nwavguy's articles, Headfonia's review of the O2/ ODAC (lolz), double-blind tests, etc. 
   
  So am I to take it that everything that people praise about amps is simply a myth? Not necessarily being skeptical here considering how easily the mind fools itself when sound is involved. The reasons why I wanted an amp before are: improved soundstage, greater damping factor (tighter bass), greater extension, more clarity, wider dynamic range, etc. Or at least, that's what the reviewers always seem to rave about. 
  Quote: 





lorriman said:


> There's quite a lot of info, properly backed up, on this topic at nwavgy's "More Power?" page. Google for the two terms: I can't post a link.
> There's a lot of talk of amps 'improving' the sonic quality, but really that shouldn't be happening: they should only be increasing volume. Unless there's a problem....
> High output impedance of an older source, ie older ipods/iphones (or not so old Galaxy SII) is perhaps the most common. A decent amp can correct that.
> In some high end, low-impedance, high-current headphones the source can distort as its basic amp is overloaded. An amp with adequate power can avoid that.
> ...


----------



## muad

I wouldn't call it myth. They believe what they're hearing and sometimes what they're hearing really is there. An amp can be designed to sound more analogue (distortion/noise) or have an emphasis in certain parts of the the frequency response curve. It may "jive" better with the sound signature of their headphones or just appeal to their subjective tastes. I am holding out for the ODA/ODAC. I feel it's the cheapest guarantee of getting an unmolested signal to my headphones or speakers. With other similarly priced gear I won't know if I am missing something... as in you don't know what you don't know!
   
  edit: ...and as a side note, I keep reading the high gain on the O2 is for higher impedence phones. On other amps this is the case, but on the O2 the low gain is for all phones from IEMs to the HD650. The gain switch is only for low output sources like an ipod etc. With the ODAC the output is 2V and the it will clip if the O2 is set to high gain.


----------



## lorriman

nimbleturtle said:


> I have done numerous research on this new hobby of mind, including reading all of Nwavguy's articles, Headfonia's review of the O2/ ODAC (lolz), double-blind tests, etc.
> 
> So am I to take it that everything that people praise about amps is simply a myth? Not necessarily being skeptical here considering how easily the mind fools itself when sound is involved. The reasons why I wanted an amp before are: improved soundstage, greater damping factor (tighter bass), greater extension, more clarity, wider dynamic range, etc. Or at least, that's what the reviewers always seem to rave about.




Well, NwAvGuys mention of double-blind testing busting the cable myth (ie. it turns out that cheap cables do the job just as well as expensive ones) is telling. However, even with that the fact is that I have some defective cables that sound completely awful. Even NwAvGuy mentions poor quality connectors potentially causing issues. I remember at school soldering a new plug on to my cheap headphones only for the audio quality to be catastrophic; I threw them away. (The reason was probably that I didn't know how to solder properly; doing the same job now I have no issues). So it's quite possible that there are sonic improvements under certain conditions: but that shouldn't be happening but for a flaw.

But my own argument leans more towards the fact of non-ideal amps masquerading as hifi mixed in to the fact that music/audio is such a subjective experience; even more so than photos/pictures. People are hearing real differences but not for the right reasons. For example, another factor I didn't mention is people not listening to the same tunes when auditioning equipment. I have tracks that are mastered with quite a bit of 3D DSP work. Others lack it. I can get the same effect by using the 'stereo width' setting in rockbox (set 'channel configuration' to 'custom' to enable that). I prefer it; I personally dislike in-the-audience recordings and prefer to be immersed in the middle of the band. Phase issues can do that with amps: give a 3D effect. The reviewer will be exulting the soundstage. Another reviwer will prefer in-the-audience, in which case poor channel separation will be an advantage. A proper amp should have no effect on soundstage. Impedance interactions can also 'improve' audio by their negative effect: for example a bass weak headhone gets a boomy lift at about 100Hz; some will like that since tastes/genetics vary so much. Some phones will have their characteristics helpfully moderated, but only by virtue of two flaws improving on one another is this happening (a hot treble being attenuated by high output impedace, for example, or vice versa, I can't remember; as well as the taming of an overly bassy headphone). 

It's a heady cocktail of factors and a constant moving target. Magazines and profit motives don't help to dispel it. 

Let's go through your list:


 improved soundstage: phase issues faking 3D
 tighter bass: corrected high output impedance 
 greater extension: on the lows, again corrected output impedance
 more clarity: phase issues, as 3D is sometimes experienced as greater clarity (thinking of recent review I read here)
 more clarity: higher treble due to high out-put impedance
 wider dynamic range: noisy source corrected by whacking up the volume to max (in the quite common case where the noise itself doesn't increase with increased volume)
 Greater detail: as with 6, Windows XP bit stripping for volume control; where only max volume gives you all 16 bits. An amp helps here: max vol on XP, vol control on the amp
 (and one I am adding: sweeter audio: correction of subtle distortion when using weak amp with high current phones)
 (more bass: boomy 100Hz bass boost from high output impedance)
 (less bass: high output impedance attenuating an overly bassy phone)
 (in-the-audience effect, that some prefer, on tracks mastered with strong spatialisation: poor channel separation) 

These are all real effects. Some caused by poor amps, some caused by decent amps helping to correct source flaws (ie. older ipods/iphones and galaxy sII high output impedance). Some caused by poor amps attenuating or boosting exagerrated or inadequate phones.

A good amp with a good source should be adding nothing but volume. Ie. clip+ and FIIO 5. 

Here's how deep the rabbit hole goes: when I connected my ODAC to my laptop I had expected to be able to use digital volume control on the laptop as since it has 24bit it is immune to XP's bit stripping issue. However, I discovered some time later that Windows selected 16bit/44Khz by default!!!!!! Obviously I changed the setting immediately. Had a reviewer had max volume when testing one DAC and much less volume on testing the ODAC: the ODAC would have been objectively producing poorer audio, ***!!!!!!!!


----------



## lorriman

nimbleturtle said:


> I know Nwavguy wrote a pretty favorable review of the FIIO E5. I'll look into that. Though can I take his word for it? And I thought the ODAC was designed so it could be used with headphones of any impedance? Or was that just the O2...




The ODAC only has a line-out which is not headphone compatible. It has to be plugged in to an amp to work.



> Though can I take his word for it?




His open sourcing of the O2 and no-payment for the ODAC pretty much guarantees that his motives are not split. And why would he give such a good review to such a cheap item. It he were trying to make money then he wouldn't have but rather binned the review and reviewed an expensive amp instead. 

Taken as a whole: NWAvGuys materials prove in themselves that he can be trusted. But in any case reviews of his stuff would appear to confirm his claims as does the deference given to him now on diyaudio (which I've inhabited due to my self-build of the O2).

It's a pretty amazing feat, but the critical factor is that he is not making money out of this.


----------



## lorriman

Oh, and I forgot to mention one other thing: quiet listeners vs loud listeners.

Quiet listeners often do not dislike spikes in the audio spectrum: a spike at around 800Hz for example, is a 'forward mid'. But for a loud listener it is a shouty honk. A spike in the treble is a 'shimmer' or a 'sparkle', but for loud listeners it is a painful jab in the ears. A track mastered with vocals given boosted volume, for understandable though mistaken reasons, is hard for loud listeners and must go some way to explain the loudness wars, as strong compression/limiting can remove this problem. Spotify uses limiting most judiciously and to our advantage generally. So personal tastes/genetics really screw up the whole business of reviewing-equipment/music-production.


I discovered some of the above when I started sine wave sweeps to equalize my headphones.. Equalized, the cheap Denon AHC260s sound like my etymotics. Rockbox has the parametric equalizer one needs for this justifying a clip+ purchase even more.

[if anyone is interested: AHC260 equalisation is : -4 db 3220Hz q=3, -2.5db 6450Hz q=4.6, treble set to -10]


----------



## Zophiel

Quote: 





lorriman said:


> 6.    wider dynamic range: noisy source corrected by whacking up the volume to max (in the quite common case where the noise itself doesn't increase with increased volume)


 
   I would just like to add that if you are listening to your headphones near the limit of your source (current or voltage), the source may not have the appropriate power for some of the peak notes, and this will come off as a reduced dynamic range. An amp will correct this by not clipping on these notes.  For what its worth, I think lorriman is spot on and I agree with im 1:1.


----------



## NimbleTurtle

So the ODAC is not as versatile as I thought if it has to be paired with an amp. But then again, I presume this is due to its high voltage? 
   
  So is soundstage and imaging (for headphones) simply an "unnatural" manipulation of the mechanics? People say my HD 598 has great soundstage, and I certainly agree it gives that perception of space. Sorry for asking so many questions but what I really want to improve with my HD 598 is the bass extension. I'm using this straight out of the laptop. Do laptops have an "output impedance" like amps do? I just want the bass to be extended as far as possible. 
   
  P.S. I thoroughly enjoyed your analysis of 'improvements' involving amps. 
   
  Is there really any proof that genetics have an influence on musical "taste"? I don't even like that word... "taste". I prefer the term "priority". I think people differ from each other in their priorities - what they want out of music - and these things are easily changeable, not fixed like it's some sort of genetic quality. 
  Quote: 





lorriman said:


> Well, NwAvGuys mention of double-blind testing busting the cable myth (ie. it turns out that cheap cables do the job just as well as expensive ones) is telling. However, even with that the fact is that I have some defective cables that sound completely awful. Even NwAvGuy mentions poor quality connectors potentially causing issues. I remember at school soldering a new plug on to my cheap headphones only for the audio quality to be catastrophic; I threw them away. (The reason was probably that I didn't know how to solder properly; doing the same job now I have no issues). So it's quite possible that there are sonic improvements under certain conditions: but that shouldn't be happening but for a flaw.
> But my own argument leans more towards the fact of non-ideal amps masquerading as hifi mixed in to the fact that music/audio is such a subjective experience; even more so than photos/pictures. People are hearing real differences but not for the right reasons. For example, another factor I didn't mention is people not listening to the same tunes when auditioning equipment. I have tracks that are mastered with quite a bit of 3D DSP work. Others lack it. I can get the same effect by using the 'stereo width' setting in rockbox (set 'channel configuration' to 'custom' to enable that). I prefer it; I personally dislike in-the-audience recordings and prefer to be immersed in the middle of the band. Phase issues can do that with amps: give a 3D effect. The reviewer will be exulting the soundstage. Another reviwer will prefer in-the-audience, in which case poor channel separation will be an advantage. A proper amp should have no effect on soundstage. Impedance interactions can also 'improve' audio by their negative effect: for example a bass weak headhone gets a boomy lift at about 100Hz; some will like that since tastes/genetics vary so much. Some phones will have their characteristics helpfully moderated, but only by virtue of two flaws improving on one another is this happening (a hot treble being attenuated by high output impedace, for example, or vice versa, I can't remember; as well as the taming of an overly bassy headphone).
> It's a heady cocktail of factors and a constant moving target. Magazines and profit motives don't help to dispel it.
> Let's go through your list:
> ...


----------



## Zophiel

Quote: 





nimbleturtle said:


> So the ODAC is not as versatile as I thought if it has to be paired with an amp. But then again, I presume this is due to its high voltage?
> 
> So is soundstage and imaging (for headphones) simply an "unnatural" manipulation of the mechanics? People say my HD 598 has great soundstage, and I certainly agree it gives that perception of space. Sorry for asking so many questions but what I really want to improve with my HD 598 is the bass extension. I'm using this straight out of the laptop. Do laptops have an "output impedance" like amps do? I just want the bass to be extended as far as possible.
> 
> ...


 
   The ODAC needs an amp for reasons i don't honestly know, but it isnt for high voltage. IIRC it outputs the redbook standard of 2 VRMS.  Which makes me wonder why exactly it NEEDS an amp, since that kind of voltage could run many a headphone.  If anything requires in amp, it is generally because the voltage it outputs is too low, so perhaps im incorrect in the 2 VRMS statement.   Perhaps lorri can ehnlighten us. 
   
   
  Regarding genetics and taste.  Taste is a preferance, and like any preferance from food to clothing, it varies greatly from person to person; saying the cause is genetics is just a simpler way of stating this.  How you percieve sound is an impossibly complicated function of mechanical and psycological factors, starting with such things as the shape of your pene and ear canal and going on to such intangible idea's like childhood trauma (i knew a girl who couldn't listen to one song as it was the song she whitnessed her sister commiting suicide to, thusly adjusting her future musical preferances). So in the end, the golden rule of the "audiophile" hobby is: "If you like the sound of it, its good!"


----------



## mikeaj

Quote: 





zophiel said:


> The ODAC needs an amp for reasons i don't honestly know, but it isnt for high voltage. IIRC it outputs the redbook standard of 2 VRMS.  Which makes me wonder why exactly it NEEDS an amp, since that kind of voltage could run many a headphone.  If anything requires in amp, it is generally because the voltage it outputs is too low, so perhaps im incorrect in the 2 VRMS statement.   Perhaps lorri can ehnlighten us.


 
   
  Like all (audio) DACs with no headphone output, it doesn't have the electronics to handle high current.  It just has a line output, which is intended to be connected to a line input of another device, which is usually several thousand ohms or more (put simply, current is voltage divided by impedance, so high impedance means not much current is required).  You need a specialized design or at least some kind of headphone output / buffer to be able to provide enough current for headphones.  There are some other issues too, but it's mostly about the current.  You might have a nice clean 2V, but when you connect that to some headphones, it won't be nice and clean, and probably not even really 2V anymore.
   
  Some line outputs can do okay driving headphones, but that's pretty much operating them way outside of specification.


----------



## Zophiel

Quote: 





mikeaj said:


> Like all (audio) DACs with no headphone output, it doesn't have the electronics to handle high current.  It just has a line output, which is intended to be connected to a line input of another device, which is usually several thousand ohms or more (put simply, current is voltage divided by impedance, so high impedance means not much current is required).  You need a specialized design or at least some kind of headphone output / buffer to be able to provide enough current for headphones.  There are some other issues too, but it's mostly about the current.  You might have a nice clean 2V, but when you connect that to some headphones, it won't be nice and clean, and probably not even really 2V anymore.
> 
> Some line outputs can do okay driving headphones, but that's pretty much operating them way outside of specification.


 
   Ah, makes sense.  After I posted that conclusion came to me as well.


----------



## lorriman

nimbleturtle said:


> So the ODAC is not as versatile as I thought if it has to be paired with an amp. But then again, I presume this is due to its high voltage?




I'm not expert enough to answer that.




> So is soundstage and imaging (for headphones) simply an "unnatural" manipulation of the mechanics? People say my HD 598 has great soundstage, and I certainly agree it gives that perception of space. Sorry for asking so many questions but what I really want to improve with my HD 598 is the bass extension. I'm using this straight out of the laptop. Do laptops have an "output impedance" like amps do? I just want the bass to be extended as far as possible.




I really don't know about headphone soundstage or what its provenance is. There is a notion that open headphones have more soundstage as the audio is making its way around the head to the other ear, but some sealed multi-armatures have plenty also?!?!?!

For bass extension: 

If the HD598s are at 300 ohms then you almost certainly won't be having serious output impedance issues (but you may be having volume issues). At a shocking 50 ohms output impedance, the Galaxy SII would be starting to affect the frequency curve but not by much. At a pinch, if the phones are in the vicinity of 80 ohms then also you probably won't be having laptop output impedance issues since it does seem that most high output impedance sources don't go above 10 ohms, and the rule is multiply by 8 for the impedance of the phones to be a healthy match.

However if the phones are more like 30 Ohms then it's worth testing the laptops output impedance, which they have like everything else. You'll need a DMM (about $5), a 33ohm resistor and a 3.5mm diy jack. Details on NWavguy's site (the resistor goes in parallel, which isn't clear from his instructions). It's not just a loss of extension but that the bass becomes 'flabby'.

The easy option (and cheapish) is just to get a fiio5. It measures well and will correct the output impedance whatever it is. If you find you really can't hear a difference then maybe the output impedance was low all along. My dell D430 (from 5 years ago) has a surprisingly healthy .5 ohms output impedance, and I'm having trouble distinguishing it from my ODAC (apart from low-level noise)!! 



> P.S. I thoroughly enjoyed your analysis of 'improvements' involving amps.




I'm re-writing my will as we speak. 




> Is there really any proof that genetics have an influence on musical "taste"? I don't even like that word... "taste". I prefer the term "priority". I think people differ from each other in their priorities - what they want out of music - and these things are easily changeable, not fixed like it's some sort of genetic quality.




Well, I go with nature and nurture. However some things are just genetics, which is evolutionarily helpful, for example if a wipe-out plague breaks out that kills everyone except those who can't stand Brussel Sprouts. I reckon the division between loud and quiet listeners is likely genetics. I've moved from mainstream to alternative to progressive. I think that's taste/learning/priorities. Taste is a nice general word that covers a lot of possibilities.


----------



## Zophiel

Some one mentioned earlier that the Fiio E5 cannot be used while charging.  This is untrue, the E11 cannot me used while charging, but the E5 can be.


----------



## lorriman

zophiel said:


> Some one mentioned earlier that the Fiio E5 cannot be used while charging.  This is untrue, the E11 cannot me used while charging, but the E5 can be.




Very good to know that. I was mislead. I don't have the FIIO5.

In that case the Behringer UCA202 DAC + FIIO5 is a viable desktop/laptop solution. All for $45. Bargain!


----------



## adydula

I have had a JDS Labs version of the O2 amp for a few days now. Ordered the ODAC its on backorder, 1-2 weeks out...so far with a HRT MSii+ USB Dac this amp has surpassed anything I have heard to date.
   
  For the $144 assembled its the deal of the century to me.
   
  Add the $99 assembled ODAC...gee for $250 you have a really outstanding setup...$250 is CHEAP for what this does compared to lots of other stuff.
   
  When I get the ODAC in I will post my findings...
   
  My poor old LYR is just sitting there, when I A/B' it with several tubes it sounded muddy to me ...before the O2 arrived i enjoyed it very much.
   
  I am listening with LCD2's and it drives them to painfully high levels more than enough to cause ear damage...beware....I hear no difference with the AC adapter plugged in or out while listening...
   
  I also have a set of Grado 325i's....which before this amp were ok, bright etc....the match between the grados and the O2 amp makes me want to listen to them instead of the LCD2's at times!! go figure..the Grados with the amp are very, very clear and crisp....wonderful soundstage, you hear the decay of a drun beat into the background etc...absolutely allows these cans to show what they really 'can' do...
   
  The LCD 2's have a larger soundstage but its not as clear as the Grados and I paid a bunch of dollars for the LCD2's...the bass is better with the LCD2s for sure...the grados are lacking in that...somewhat...
   
  Aint technology great!!
   
  Alex


----------



## chouck

ODAC + O2 combo portable mod  As currently there are plenty of mobile phones/tablets
http://forum.xda-developers.com/showpost.php?p=27631058&postcount=10 and Apple devices supporting external DAC output it makes sense to issue a version of ODAC + O2 portable combo that can work from 9-8.4V batteries as original O2 design. I just did this mod using JDS Labs combo. The only additional effort is drilling one hole in O2 PCB (on unused spot) and moving USB hole on the back plate. Please see attachments. I think it will be useful for current and future ODAC + O2 combo users as well opens combo to new use cases.
http://www.pbase.com/objective3/inbox


----------



## lorriman

adydula said:


> Add the $99 assembled ODAC...gee for $250 you have a really outstanding setup...$250 is CHEAP for what this does compared to lots of other stuff.




No question. Pure hifi for not much at all. 



> When I get the ODAC in I will post my findings...




looking forward to that.


----------



## goforthepod

Hi, I am a noob here... but where can I buy an O2+ODAC box with external power (no need for batteries) and 6.5mm headphone jack?  Do I have to make one myself (which I am really not confident in doing)?  Please help me out here....
   
  I just realized that it is exactly the ODA (Objective Desktop Amp) that is yet to be released ...


----------



## K_19

What you are looking for is going to be in the O2 desktop amp/DAC combo, which I believe is still a while away from being released.
  
  At this moment, if you want the 6.5mm headphone jack, you'll likely have to do it yourself, although it probably wouldn't hurt to ask one of the builders if it is possible to install it instead of the 3.5mm. I doubt it however as all the mass produced O2 enclosures out there have the 3.5mm.


----------



## lorriman

There is room in the standard B02 for both ODAC and 6.5mm jack if you are willing to give up the batteries. I expect that one of the manufacturers could wire up a 6.5mm jack and leave it within the case waiting for you or a friend to drill a hole. It's mostly plastic and a touch of electrical tape would avoid any possibility of a short in the meantime. An aluminium drill bit costs $3 off ebay. An auto punch costs a little more but you may not need the precision.


----------



## adydula

You can wait or buy the O2 Amp and ODAC the way it is and wire it together OR you can buy the O2 and ODAC combo at:
http://www.jdslabs.com/item.php?fetchitem=48
   
  Its on backorder due the ODAC.
   
  You can use 6.5mm normal headphones as I do with a simple 3.5 to normal size adpater...
   
  I didnt want to wait for the desktop version, theres not going to be any technical performance differences per say.
   
  The batteries in the O2 amp your remove to install the ODAC board, a few wires and some nylon screwe to mount the board and you will have the same thing that the desktop is less the RCA's and larger headphone jack...
   
  OR
  
  you can buy the assembled board and the ODAC and get your own cased etc and make your own.
   
  OR...
   
  Wait for the desktop version when it comes out.....
   
  Alex


----------



## 4nradio

This is my method of combining the O2 and ODAC in the O2's case, with the addition of RCA line outputs (direct from the ODAC). The front and rear panels are my own design, produced by Front Panel Express in Seattle (as recommended by NwAVGuy). As a few others have done, the ODAC  board is mounted upside down beneath the O2's PCB, which retains use of the batteries. This flipped over board is why the USB jack is so close to the bottom of the enclosure.


----------



## lorriman

Interesting. How did you get the RCAs to fit? The BOM's RCAs are too large to my eyes.


----------



## adydula

4nRadio!
   
  Nice Job!!
   
  Alex


----------



## lorriman

bel201smi said:


> O2 AMP + ODAC is the oldest version i think the sound quality is not so very good i think express music is more batter then it...




If I understand you right, you prefer some other device's sound quality to the ODAC+O2. This means either you have a faulty ODAC/O2 or the other device is an imperfect DAC/AMP and you prefer your music with the 'adjustment' it makes to your music.


----------



## GL1TCH3D

Has anyone paired the O2+ODAC with the HD800?
If so, how was it?
I'm thinking of getting the O2+ODAC as a temporary low budget system to run the HD800s.


----------



## adydula

I dont see any issue with the O2 and the HD800. The HD800 is well within the O2's capability.
  What I have personally seen is this combo will allow you to hear what your cans really sound like.
   
  Try many different CD's etc.....you will  be amazed at how revealing and accurate music will be good or bad...
   
  For the price you cant go wrong and as you spend mega-bucks on your future systems it will be fun to compare back this LOW dollar setup!
   
  Alex


----------



## adydula

The ODAC arrived yesterday, had to solder a 3.5 audio out jack to the board and listened for 2 hrs with LCD2's and Grado 325is....will report back later with details....will put the ODAC in a seperate X Box enclosure with both mini and RCA jacks functional.
   
  All this stuff for approx $250 from JDALabs.....great service and always answered my email and phone calls promptly and courteously....


----------



## NimbleTurtle

That looks very nice Adydula!


----------



## adydula

And it really sounds...well like no sound...its the source and the cans.....a very nice inexpensive setup that will allow u to hear your source and cans....as objectively as it gets in this hobby or pastime etc...
   
  Alex


----------



## GL1TCH3D

adydula said:


> I dont see any issue with the O2 and the HD800. The HD800 is well within the O2's capability.
> What I have personally seen is this combo will allow you to hear what your cans really sound like.
> 
> Try many different CD's etc.....you will  be amazed at how revealing and accurate music will be good or bad...
> ...



Aha, thanks.
I received my O2 amp and ODAC and have been enjoying my HD800 through them. Not as warm sounding as the E17 but I noticed the E17 was a bit colored. 
Yes, it does reveal a lot in the songs xD

How do you think it will fare with the LCD2 r1 though?


----------



## adydula

Its a very neutral amp and it will drive the LCD2's R1 or R2 very, very well...the power needed to drive these cans are pretty much the same the impedance is a bit different but nothing this amp cant drive loud enough to cause hearing loss if your not careful.
   
  Alex


----------



## placebo-fi

Quote: 





lorriman said:


> If I understand you right, you prefer some other device's sound quality to the ODAC+O2. This means either you have a faulty ODAC/O2 or the other device is an imperfect DAC/AMP and you prefer your music with the 'adjustment' it makes to your music.


 
   
  Do you mind elaborating the purpose of this post? I find this incredibly unhelpful and borderline religious (not to mention misguided, subjective bias anyone?).


----------



## GL1TCH3D

placebo-fi said:


> Do you mind elaborating the purpose of this post? I find this incredibly unhelpful and borderline religious (not to mention misguided, subjective bias anyone?).




I think he's trying to say that since the O2+ODAC are incredibly neutral and don't color the sound, that you must prefer an amp that colors the sound or that you have a defective O2+ODAC that isn't giving you the top notch quality that it's supposed to.




			
				adydula said:
			
		

> Its a very neutral amp and it will drive the LCD2's R1 or R2 very, very well...the power needed to drive these cans are pretty much the same the impedance is a bit different but nothing this amp cant drive loud enough to cause hearing loss if your not careful.
> 
> 
> 
> Alex




Aha, thanks.
And I'm always trying to be careful with my volume levels whether it be with earbuds on the go where I sometimes might have the urge to increase the volume to drown out more sound or at home when I want to immerse myself even more.


----------



## lorriman

placebo-fi said:


> Do you mind elaborating the purpose of this post? I find this incredibly unhelpful and borderline religious (not to mention misguided, subjective bias anyone?).




The whole point of the O2/Odac combo is that it is a perfect hifi source/amp: the music is being reproduced exactly as produced. So to say that you prefer another combo over the O2 means that either the O2/ODAC is defective or that you prefer the audio flaws of the other amp. But to call the other amp 'better' is really a nonsense.


----------



## writereviews

I wonder if the O2 could power LCD-3s.


----------



## paradoxper

Quote: 





lorriman said:


> The whole point of the O2/Odac combo is that it is a perfect hifi source/amp: the music is being reproduced exactly as produced. So to say that you prefer another combo over the O2 means that either the O2/ODAC is defective or that you prefer the audio flaws of the other amp. But to call the other amp 'better' is really a nonsense.


 
  Fanboyism taken too far.


----------



## paradoxper

Quote: 





writereviews said:


> I wonder if the O2 could power LCD-3s.


 
  O2 drives LCD-3 fine.


----------



## lorriman

paradoxper said:


> Fanboyism taken too far.




Not really. The O2 has been publicly verified :

http://www.innerfidelity.com/content/innerfidelity-headphone-amp-measurement-program-update-july-2012

In consideration of that, neither is there reason to doubt the designer's ODAC measurements. 

The only thing that might be an issue is if one has extremely power-hungry headphones where distortion might occur but more likely just be quiet. But there are precious few of those. The HE6 is thought to need more power than the O2 can provide. 

Sonically reviewing the O2 and declaring another amp 'better' is only to reveal a lack of understanding of what the O2 is all about (other than in the power department, of course). It's not just an amp: it's a demonstration that hifi can be had for not much money and that people are being ripped off. 

If the other amp is also a perfect hifi source, which any properly designed amp should be, then neither would be better.

One of the marvels of the clip+, for example, is that it is almost hifi. It has a tiny bit of almost inaudible noise but that's about it. A clip+ with O2, or the O2/DOAC combo for a PC/MAC gets you hifi everywhere.


----------



## paradoxper

Quote: 





lorriman said:


> Not really. The O2 has been publicly verified :
> http://www.innerfidelity.com/content/innerfidelity-headphone-amp-measurement-program-update-july-2012
> In consideration of that, neither is there reason to doubt the designer's ODAC measurements.
> The only thing that might be an issue is if one has extremely power-hungry headphones where distortion might occur but more likely just be quiet. But there are precious few of those. The HE6 is thought to need more power than the O2 can provide.
> ...


 
  No one has ever said that it doesn't measure nicely. Proves nothing.
   
  You are one of those believers of no amp does or should sound any different and if it does it's flawed or wrong.
  Yet, I'm going to presume you haven't listened to much gear, therefore, you don't trust your ears.
   
  I don't subscribe to measurements yet, they do have their rightful place in the scheme of things. 
   
  The O2 is a great value ODAC as well, However I've heard plenty amps that are better, of course, IMO. But you'll just chalk it up to my love for distortion.


----------



## lorriman

paradoxper said:


> No one has ever said that it doesn't measure nicely. Proves nothing.




Well, it does prove that it is perfectly reproducing the music. Doesn't seem to me that you can go much further than that. 



> You are one of those believers of no amp does or should sound any different and if it does it's flawed or wrong.
> Yet, I'm going to presume you haven't listened to much gear, therefore, you don't trust your ears.




Double blind testing has demonstrated that ears aren't to be trusted. Seems to be true of noses as well: the case of wine pricing fooling the experts in to favouring cheaper wines thinking they had cost more.



> I don't subscribe to measurements yet, they do have their rightful place in the scheme of things.
> 
> The O2 is a great value ODAC as well, However I've heard plenty amps that are better, of course, IMO. But you'll just chalk it up to my love for distortion.




Well, yes. 

But then again, I've a harmonic distortion filter and have found that even the 'euphonic' even-order distortions are unpleasant the more you ramp it up. There's also phase issues that can give a 3D effect (ie. affect the perception of soundstage) though dsp is better for that purpose. And let's not forget output impedance issues. On top of all that are matters of taste. I prefer to be 'in the orchestra' rather than in the audience, so those 3D phase effects might make me think an amp is 'better'. But strictly it's not.

My own theory is that some people are also just more suggestible than others, as is true of hypnotism. An amp's price, weight and largeness of capacitors could be a good vector of suggestion. Mix that in to the heady mix above and you can imagine the problems with reviewing amps sonically.


----------



## PelPix

Quote: 





gl1tch3d said:


> Has anyone paired the O2+ODAC with the HD800?
> If so, how was it?
> I'm thinking of getting the O2+ODAC as a temporary low budget system to run the HD800s.


 
   
  It sounds good, but be warned that it's very bright.  The HD800 is a _really_ bright can and the neutrality of the O2 does nothing to hide that.


----------



## paradoxper

Quote: 





lorriman said:


> Well, it does prove that it is perfectly reproducing the music. Doesn't seem to me that you can go much further than that.
> 
> 
> 
> ...


 
  Yea, I am just gonna go ahead and disagree....Ok? We hear differently, fair?
  It might measure perfectly, however it sounds flawed,imperfect,harsh,clinical,not musical,schitty,meh,different? It's just not distorted enough for my liking. 
	

	
	
		
		

		
		
	


	



   
  You never did answer my question. Have you been to a meet to test the waters? Just wanna know if you've tried anything from
  the TOTL amp pool or even DACs?


----------



## adydula

If an amp measures well, in this case the O2 measures VERY well and I have several other amps....that now sound relatively good but are definitlely colored and or influencing the source for sure....the O2 being as neutral as it is allows you to hear the source and hear what cans really sound like or can sound like.
   
  Measurements if taken properly, dont lie....our brains, our moods, the time of day, our musical tastes all influnece how we hear.....our expectations.
   
  Having some really great stuff their are days when nothing sounds good or pleases me...and I shut it off and go watch the sunset.....etc
   
  Are there amps that are better than the O2, possibly, cost more, for sure...define better...weigh more, have more knobs, looks cool, is larger in size. etc...
   
  But for the price and the invisibility of this amp ie beyond human hearing for $144....duh!!!
   
  Amps that cost thousands more cant be more inaudible. They can have more stuff, more things, more lights, glowing mega buck NOS tubes etc....
   
  The O2 is and will be a standard ie classic for years to come.
   
  Alex


----------



## NimbleTurtle

Quote: 





paradoxper said:


> No one has ever said that it doesn't measure nicely. Proves nothing.
> 
> You are one of those believers of no amp does or should sound any different and if it does it's flawed or wrong.
> Yet, I'm going to presume you haven't listened to much gear, therefore, you don't trust your ears.
> ...


 
  How do you know you're not underestimating the effect of placebo and subjective bias? Did you do a ABX test? It might not even be because you love distortion - it may simply be pure psychological bias that everyone is subject to. I know an audiophile who tested several thousand dollar amps through a blind test. He claimed the O2 and ODAC outdid almost every amp/ DAC except one (I forgot which one). 
   
  O2 & ODAC are basically about $50 dollars each in terms of material cost. The whole purpose of the design behind the two was to prove that inexpensive amps/ DAC can GET THE JOB DONE. Even if there are super expensive amps/ DAC that measure better than the O2/ ODAC, I doubt it will be a significant audible difference (unless it's colored). It certainly isn't worth the money. An amp's job is to amplify. A dac's job is to convert digital to analog. If people have some cash to blow, then that's completely fine. It's certainly none of our business (though I understand some objectivists take it too personally). But sometimes subjectivists harm the wallet of others, claiming crap about synergy and how you need at least a $200 dollar amp to drive a specific can. A load of BS.


----------



## paradoxper

Quote: 





nimbleturtle said:


> How do you know you're not underestimating the effect of placebo and subjective bias? Did you do a ABX test? It might not even be because you love distortion - it may simply be pure psychological bias that everyone is subject to. I know an audiophile who tested several thousand dollar amps through a blind test. He claimed the O2 and ODAC outdid almost every amp/ DAC except one (I forgot which one).
> 
> O2 & ODAC are basically about $50 dollars each in terms of material cost. The whole purpose of the design behind the two was to prove that inexpensive amps/ DAC can GET THE JOB DONE. Even if there are super expensive amps/ DAC that measure better than the O2/ ODAC, I doubt it will be a significant audible difference (unless it's colored). It certainly isn't worth the money. An amp's job is to amplify. A dac's job is to convert digital to analog. If people have some cash to blow, then that's completely fine. It's certainly none of our business (though I understand some objectivists take it too personally). But sometimes subjectivists harm the wallet of others, claiming crap about synergy and how you need at least a $200 dollar amp to drive a specific can. A load of BS.


 
  Ok, I am gonna buy the all black O2/ODAC and call it a day.


----------



## placebo-fi

Subjective bias is a part of our brain's working and should not be ignored. At the end of the day, no one will be listening to music blind. Claiming ODAC+O2's supremacy, that it's equal to everything else out there, is blissfully ignoring/disregarding your own (flawed as they may be) ears and brains, in the same vein that extreme subjectivists blissfully ignore/disregard measurements.
   
  In my opinion, both measurements and subjective perception have a part to play. Look for better measured gears, audition them, compare them volume-matched with your current gear. If you enjoy your music significantly better with the latter gears, and if you have enough disposable income, why not? Should you really be ignoring your own inherent flaws? It's all about enjoyment at the end of the day.
   
  tl;dr be open-minded

 Btw I'm currently using O2 + ODAC as well, certainly won't stop me from auditioning great gears from the likes of Anedio, Violectric, Benchmark, Lavry, HeadAmp etc. Also, O2 is not perfect either http://scientistsaudio.blogspot.jp


----------



## NimbleTurtle

Quote: 





placebo-fi said:


> Subjective bias is a part of our brain's working and should not be ignored. At the end of the day, no one will be listening to music blind. Claiming ODAC+O2's supremacy, that it's equal to everything else out there, is blissfully ignoring/disregarding your own (flawed as they may be) ears and brains, in the same vein that extreme subjectivists blissfully ignore/disregard measurements.
> 
> In my opinion, both measurements and subjective perception have a part to play. Look for better measured gears, audition them, compare them volume-matched with your current gear. If you enjoy your music significantly better with the latter gears, and if you have enough disposable income, why not? Should you really be ignoring your own inherent flaws? It's all about enjoyment at the end of the day.
> 
> ...


 
  Agreed. I think both sides are exaggerating and sometimes taking things out of proportion. Without a doubt the O2/ ODAC are extremely good performers for the price. That was the whole point of their design after all. But it's totally understandable that if a person has enough "goods" with him, he can pay for something far more expensive, for various reasons, including portability, aesthetics, preferred coloration, etc.


----------



## rhythmdevils

Yay, more inexperienced people overconfident about things they have no knowledge or understanding of.  So nice to see.  I'd love to see what the world would look like if it was run by Nwavguy's minions.  Maybe a 5 year old would be president.


----------



## NimbleTurtle

Quote: 





rhythmdevils said:


> Yay, more inexperienced people overconfident about things they have no knowledge or understanding of.  So nice to see.  I'd love to see what the world would look like if it was run by Nwavguy's minions.  Maybe a 5 year old would be president.


 
  I don't claim to be an expert with amp / dacs but I have been learning a lot these past few weeks. Hopefully, I'll be able to actually understand every aspect of measurement data. Not quite there yet though. But I know some people just blindly state opinions with no experience to back them up. It makes the world more confusing to live in.


----------



## purrin

Quote: 





rhythmdevils said:


> Yay, more inexperienced people overconfident about things they have no knowledge or understanding of.  So nice to see.  I'd love to see what the world would look like if it was run by Nwavguy's minions.  Maybe a 5 year old would be president.


 
   
  And everyone would be forced to use an OBJ2/ODAC. And wave little red books with the sayings of the great one. Those who refused would be subject to wearing a dunce cap and placards around their necks stating "audiophool", "decadent stupid rich", or "distortion lover", etc. It will be like an audio Cultural Revolution!


----------



## Anaxilus

Quote: 





lorriman said:


> My own theory is that some people are also just more suggestible than others


 
    
  QFT.  Especially those that cite poor, flawed or misleading studies like those involving wine which in fact do measure differently.  As if throwing the baby out w/ the bathwater invalidates millions of years of aural and neural evolution.  Afterall, more people die from driving their own cars than from mass transportation.  Anyone not taking the bus, train or subway is obviously ignorant and operating under some undue psychological influence.
   
  Quote:


nimbleturtle said:


> I don't claim to be an expert with amp / dacs but I have been learning a lot these past few weeks. Hopefully, I'll be able to actually understand every aspect of measurement data. Not quite there yet though.


 
   
  Careful.  People w/ better test gear and education than some have been doing this for decades and are more aware of what they still do not know than what they do.  A few part time hobbyists seem to be more certain of their knowledge after reading a blog than those that work and study these same issues for decades.  There often seems to be an epistemological problem with those that have a little bit of knowledge knowing everything versus those with a lot of knowledge who are more aware of what they do not know.  Tools and studies are useful but rarely definitive and universally comprehensive.  When you see someone making wild universal and absolute claims like some above, that should be a red flag to the critical mind.  So please educate yourself but do not presume to ever have it all figured out.


----------



## rhythmdevils

Good to have you back Mike.


----------



## Draygonn

[VIDEO]http://www.youtube.com/watch?v=Ym-k5viJ7tA[/VIDEO]

for S&G


----------



## Anaxilus

Quote: 





rhythmdevils said:


> Good to have you back Mike.


 
   
  Thx, good to be back.  Are we in SS yet?


----------



## oyster

In this court everyone's a lawyer & a judge. I don't see the point.
  Listen to your stuff -> express yourself ,why argue when there are no medals awaiting.


----------



## placebo-fi

Typical O2/ODAC thread.

 The only exception was the one started by maverickronin. The absence of minions/agendas, and how helpful the thread was, were almost magical.


----------



## mikeaj

Quote: 





anaxilus said:


> Afterall, more people die from driving their own cars than from mass transportation.  Anyone not taking the bus, train or subway is obviously ignorant and operating under some undue psychological influence.


 
   
  This is pretty much completely OT, but it's interesting you bring transportation up, since it's one of the more well-researched areas where psychological biases prevail, people behave irrationally, the accuracy of self-evaluation is low, and so on.  e.g. percentage of drivers that think they're above average (golden...hands+feet? lol)
   
  But maybe it is on topic.  Some people ignore reasons other than performance defined in certain ways (and in this example, safety?  survival rate?) to own certain things or exhibit certain behaviors.


----------



## PelPix

Guys. Don't turn a product discussion thread into a subjective vs objective debate. We should keep to ourselves and they should keep to themselves and we should join hands and enjoy this budget amp masterpiece.

P.S welcome back mike.


----------



## NimbleTurtle

Yeah I have to say this whole topic was very productive as a whole. Thanks for all the audiophiles' intake on the O2/ ODAC.


----------



## adydula

Your welcome....keep the topic on the topic and stop selling each others religion etc...
   
  The O2 amp and Odac objectively measure very well, seems to sound great. Its relatively cheap and allows many folks without DEEP pockets to have world class sound thats affordable and they dont come with a little red book..
   
  If you want to spend more dollars thats great, thems your dollars go for it....
   
  I just hate spending all those dollars and then find out you really didnt have to ....to get performance as good as or better that the higher priced stuff.
   
  Gosh knows I have spent money on the higher priced stuff with case made out of billet aluminum, that weigh alot, that even perform very very well...but not better than this el cheopo setup...
   
  A lot of us really think the Vioelectric amp (the 200) is a really great amp...I do as well, and the person that designed the O2 (cant say the name here) also thinks its a great amp. Having a $150 amp that compares sonically to a $1000 amp...well wouldnt that be great....or does greatness still come with cost?
   
  I have spent the last three days comparing the O2 to my Lyr and the ODAC to my HRT MSii+...and they all sound good. I have gone back and forth so many times my hand is tired of selecting playback devices in Win7...
   
  The one thing I have noticed it the Lyr and the 02 sound very different....The O2 is 'clear and precise' and I found having a friend swapping them out I could reliably tell the difference and pick the O2 out....not so with the dacs...I cant tell any difference at all.....which for the price tells you another story.
   
  All the best..
   
  Alex


----------



## Anaxilus

Quote: 





adydula said:


> Having a $150 amp that compares sonically to a $1000 amp...well wouldnt that be great....or does greatness still come with cost?


 
   
  It would be great if the $1000 amp in question were great and not merely good or okay.  A good deal is not the same as great ToTL sound.


----------



## muad

What happened to the odac impressions thread? I wad busy yesterday... went to check it today... and its gone! poof... doesn't exist. Did poop hit the fan?


----------



## adydula

There's one here http://www.head-fi.org/t/611778/brief-odac-impressions#post_8418923
   
  This link for me is broken...get a you dont have permission to access this area.
   
  ???????
   
  Alex


----------



## rhythmdevils

Quote: 





muad said:


> What happened to the odac impressions thread? I wad busy yesterday... went to check it today... and its gone! poof... doesn't exist. Did poop hit the fan?


 
   
  I think it got what it deserved.


----------



## adydula

What do you exactly mean by that?? fair and balanced????


----------



## rhythmdevils

Im not sure the universe can handle that much BS. It just imploded.


----------



## adydula

I wish i could have read the thread to make that decision for myself....seems for some reason when this amp and its associated dac gets mentioned it really makes some people go off the handle.....
   
  I have both, I try to objectivley compare and listen to the stuff by buying it and making my own judgement calls before stating one item is better than another etc...
   
  I am an engineer and am very analytical and measurements to mean are a baseline to look at if take properly and presented honestly....too many people are hiding stuff now-a-days...
   
  An honest product for an honest dollar....
   
  Alex


----------



## muad

Quote: 





adydula said:


> I wish i could have read the thread to make that decision for myself....seems for some reason when this amp and its associated dac gets mentioned it really makes some people go off the handle.....
> 
> I have both, I try to objectivley compare and listen to the stuff by buying it and making my own judgement calls before stating one item is better than another etc...
> 
> ...


 
   
  Agreed! I feel there is an abundance of ignorance and deception on both sides of the argument. For someone like myself who simply loves music and wants to find something that plays true to the source at the expense of synergy, it makes difficult to separate truth from misinformation. It really is sad, I would prefer if the conversations stayed away from analyzing V's motives and focused more on the odac/o2 itself.


----------



## rhythmdevils

Most people agree the Odac is good for the price. 
   
  The arguments all start with the wild, inexperienced, often quite ignorant claims his minions make, which are fueled by V's motives and methods.  So clearly we start talking about that.  If his minions would stick to topics both subjective experience and objective knowledge they really had experience with and understood, these threads would stay much more rational and honestly quite positive, because everyone I know with good ears, experience with a lot of gear, and great understanding of measurements etc, think the Odac is good _for the price._


----------



## adydula

There are "minions' on both sides.....so lets stop with that and try to be positive on the devices and share what your experiencing with this stuff...
  Just using that word is enough to beat the drums loud on both sides...
   
  So far I have not had a bad experience with this amp or dac.
   
  The one thing I really like about it is to be able to take AC totally out of the picture....pure DC.....with so many of us wanting to get rid of any and all AC 'worts; this is a good thing to me.
   
  My grados with this amp is totally wild...the bass is really , really tight and defined not as "dee[" as the LCD2's but OMG nice for what the Grados are...I put the Grados on the Lyr I have and the high end softens up alot. That said I believe the o2 is more accurate depiction  of what is really going on.
   
  I never knew what the Grados could sound like until I plugged them into the O2. This was without the ODAC in the picture at all.
   
  I just got a O2 amp pc board from JDS and will put one together so I can have one my main listening room and take one to work!
   
  All the best
  Alexu


----------



## Anaxilus

Well the amp is not nearly as transparent as the ODAC which is why I'm not as big a fan of it yet it's exhaulted as sonic perfection simply out of lack of a better reference by most.


----------



## rhythmdevils

Quote: 





adydula said:


> There are "minions' on both sides.....so lets stop with that and try to be positive on the devices and share what your experiencing with this stuff...
> Just using that word is enough to beat the drums loud on both sides...
> 
> So far I have not had a bad experience with this amp or dac.
> ...


 
   
  Here's a link to the wikipedia page on the word "minion" for clarity http://en.wikipedia.org/wiki/Minion
   
  I think you should re-read my post.  And making claims about "accuracy" using Grados is a bit ridiculous since Grados are about the most inaccurate headphone on the market.  You really can't have any idea what is a more realistic depiction of what is going on if you're using Grados because the whole picture is completely unrealistic.  Fine if you prefer the O2 with your Grados that's awesome, but that doesn't mean it's accurate.


----------



## Vizknox

I found a third variant from Mayflower electronics (http://www.mayflowerelectronics.com/products.html) at a lower price than I've seen anywhere else, however I can't find any feedback from other headfiers on mayflower. I'm interested in getting just the O2 amp for as cheap as possible, and I'd like to buy from mayflower but I'll probably hold off until I hear from someone else that they have had a good transaction with the site. Has anyone bought anything from mayflower?


----------



## purrin

Quote: 





rhythmdevils said:


> Here's a link to the wikipedia page on the word "minion" for clarity http://en.wikipedia.org/wiki/Minion
> 
> I think you should re-read my post.  And making claims about "accuracy" using Grados is a bit ridiculous since Grados are about the most inaccurate headphone on the market.  You really can't have any idea what is a more realistic depiction of what is going on if you're using Grados because the whole picture is completely unrealistic.  Fine if you prefer the O2 with your Grados that's awesome, but that doesn't mean it's accurate.


 
   
  Why do we bother with the "perfectly" measuring ODAC/O2 if we want to hear such a large amount of linear and non-linear distortion from the transducer and the enclosure in the first place? The answer is simple: we don't want our massively distorted headphones to be polluted by any more distortion, even if such distortion is a magnitude or more lower than the headphone. I hope that makes perfect sense to you.


----------



## rhythmdevils

It doesn't.  
	

	
	
		
		

		
		
	


	




  It's like trying to judge the taste of an orange with a mouth full of toothpaste.


----------



## mikeaj

Quote: 





anaxilus said:


> Well the amp is not nearly as transparent as the ODAC which is why I'm not as big a fan of it yet it's exhaulted as sonic perfection simply out of lack of a better reference by most.


 
   
  It's not just you saying this, but addressing the idea that the ODAC is the better value:
   
  If you ignore everything about the sound and look only at the measurements and those of competing products, it seems to me that the O2 would be considered a better value for the money.  Granted, there aren't extensive measurements available for every single competing product.  What's the cheapest amp with similar output power levels (for those who don't remember, above 600 mW across many loads but limited by 7V rms), similar noise levels (about -115 dBV, A-wtd), and lowish output impedance?  That's not to mention the ability to use on battery, which some people actually utilize, despite the size and weight.
   
  I would suspect that a lot of sound cards and pro interfaces at around that cost or not too much higher, not to mention other audiophile DACs, can put up similar or even better figures than the ODAC can.  Or do they not?
   
  Take that as you will.  (I don't mean to restart a traditional audio benchmarks vs. listening experience debate, just saying that this situation has come up again.  Either that, or somebody can tell me that I'm wrong in my assessment of the market.)


----------



## adydula

ok....
   
  thanks for the minion definiton...all warm, and fuzzy now...there are minions on both sides...or you will find that many owners of stuff turn into minions trying to convince themselves
  and others that their purchase is the best and others are el crapo.
   
A *minion* is a follower devoted to serve his/her master relentlessly...still has an overall negative feel to it....minions dont usually allow for any other views other than their masters...
   
  the point i was trying to make is that until i used the grados with the o2 they sounded less than stellar...with the 02 amp they really 
  sound very clean, clear and precise vs they way they sounded to me with other amps.
   
  Never said they were accurate....they subjectively to me sound good.
   
  The LCD'2 have a nice flat FR curve and are more accurate than the grados for sure but they sound very much different...
   
  Having an amp that measures well is good to me....if the measurements are taken properly, accurately then thats one less thing that gets in the way in my analysis...then its on to the listening and the proof of the pudding.
   
  If i listen to a the LCD2's with this amp compared to others that cost more...and can not really hear any differences then why pay the higher price??? 
   
  I would like to see all amps etc have the same set of measurements for all the world to see.....then at least we all start out on the same baseline...and again let the listening begin...
   
  I am not an O2 fanboy, but when i see world class stuff...at this low price, well it is what it is.....and it again allows lots of us without DEEP pockets to enjoy all kinds of cans to be played as about as good as it gets depending on your source material and your subjective brain mood at any one time..
   
  Building stuff with the least amount of parts, at the lowest cost that competes with stuff an order of magnitude says it all..
   
  All the best
  Alex


----------



## frenchbat

That thread almost reached a Godwin point, so I guess it was moderated to death.
  Quote: 





adydula said:


> There's one here http://www.head-fi.org/t/611778/brief-odac-impressions#post_8418923
> 
> This link for me is broken...get a you dont have permission to access this area.
> 
> ...


----------



## qusp

Quote: 





rhythmdevils said:


> Most people agree the Odac is good for the price.
> 
> The arguments all start with the wild, inexperienced, often quite ignorant claims his minions make, which are fueled by V's motives and methods.  So clearly we start talking about that.  If his minions would stick to topics both subjective experience and objective knowledge they really had experience with and understood, these threads would stay much more rational and honestly quite positive, because everyone I know with good ears, experience with a lot of gear, and great understanding of measurements etc, think the Odac is good _for the price._


 
   
  of course it is, the price is based on a false economy, all of the costs to bring it to market, prototype, support etc are void. now there will be a raft of people who believe thats what products should cost. its ridiculous and is not positive for the industry. no question the industry needed a bit of a shake up, but this wasnt the way to do it. the high end is completely un-phased; but some good people wanting to release good products at reasonable prices have been so far undercut that theyve been selling the parts they bought and thrown in the towel.
   
  the end game would be completely homogenous, sounds great hey guys?
   
  adydula: are you sure you understand the word minion? I dont think you do.


----------



## Draygonn

qusp said:


> now there will be a raft of people who believe thats what products should cost.


Recently there was a group buy attempt on Reddit. I don't think they appreciate how cheap these products already are.


----------



## qusp

Quote: 





draygonn said:


> Recently there was a group buy attempt on Reddit. I don't think they appreciate how cheap these products already are.


 

 agreed, if the real costs were factored into the design in a sustainable manner, it would be operating at a loss.


----------



## muad

Quote: 





qusp said:


> some good people wanting to release good products at reasonable prices have been so far undercut that theyve been selling the parts they bought and thrown in the towel.


 
  who?


----------



## qusp

and why would I post that? add insult to injury and betray a confidence. why does it matter to you anyway?


----------



## adydula

Its too bad this thread has degenerated away from the O2 amp and ODAC.....
   
  I am out of here....
   
  Alex


----------



## ishmael

Quote: 





rhythmdevils said:


> It doesn't.
> 
> 
> 
> ...


 

  
   
  What do you mean, that sounds like it would be delicious.


----------



## Radio_head

Quote: 





adydula said:


> Its too bad this thread has degenerated away from the O2 amp and ODAC.....
> 
> I am out of here....
> 
> Alex


----------



## lorriman

rhythmdevils said:


> Most people agree the Odac is good for the price.




This is cunning negative spin. The whole point is that it has been independently verified to be true hifi, reproducing the music exactly as produced and at high power. That's really not "good for the price". 

And 'Most' people? Who are these people? Where are the concrete numbers? At least do a poll.



> The arguments all start with the wild, inexperienced, often quite ignorant claims his minions make, which are fueled by V's motives and methods.  So clearly we start talking about that.  If his minions would stick to topics both subjective experience and objective knowledge they really had experience with and understood, these threads would stay much more rational and honestly quite positive, because everyone I know with good ears, experience with a lot of gear, and great understanding of measurements etc, think the Odac is good _for the price._




The statements you have made there are moving targets. How do you know they have good ears? And what do you mean by "great understanding of measurements"? Where are the measurements/stats, blind-testing that proves these statements? What blind tests exist show that ears cannot be relied upon. So called 'Golden ears' reliably fail double-blind testing.

In the meantime, instead of offering unverified and moving target statements and anecdotes, the designer has fully documented his approach and never had an argument on any of the forums in which he has been caught out. And let's not forget that independent verification.


----------



## lorriman

anaxilus said:


> Well the amp is not nearly as transparent as the ODAC which is why I'm not as big a fan of it yet it's exhaulted as sonic perfection simply out of lack of a better reference by most.




'Not nearly'? Where does that come from? The measurements have the ODAC as better, yes, but the O2's issues are inaudible. They are both, with a human listener, transparent fro practical use.


----------



## purrin

Actually, I'm more impressed by the O2 than the ODAC. The ODAC sounds different depending upon what it's plugged into. The O2s main issues with me are treble stridency and some weakness in the bass. Both can be remedied with an op-amp swap to the LM4592 which I have done myself. The O2 excels is how clean and controlled it sounds. However, the O2 does sound flat in terms of both micro and macro dynamics, and does not extract detail anywhere as well as better amps, e.g UHA-6S, Schiit Mjolnir, etc. Heck, even a slightly colored tube hybrid amp such as the Melos SHA-1 is does dynamics and resolution better. This is of course dependent upon source and transducer quality: DAC, recording, and headphones.
   
  Of course YMMV. The fact that I would be hard pressed to find anything better for less than ~$279 speaks volumes about the O2.


----------



## rhythmdevils

Quote: 





lorriman said:


> This is cunning negative spin. The whole point is that it has been independently verified to be true hifi, reproducing the music exactly as produced and at high power. That's really not "good for the price".
> And 'Most' people? Who are these people? Where are the concrete numbers? At least do a poll.
> The statements you have made there are moving targets. How do you know they have good ears? And what do you mean by "great understanding of measurements"? Where are the measurements/stats, blind-testing that proves these statements? What blind tests exist show that ears cannot be relied upon. So called 'Golden ears' reliably fail double-blind testing.
> In the meantime, instead of offering unverified and moving target statements and anecdotes, the designer has fully documented his approach and never had an argument on any of the forums in which he has been caught out. And let's not forget that independent verification.


 
   
  How many amps and dacs have you heard?


----------



## Jimmy24

I'm using an O2 with HD 650s. How much gain are you guys using for normal listening? I usually have mine about 2 bars. If I want to really hear everything in the mix I set it up to a little less than half way.


----------



## juantendo8

Quote: 





jimbo24 said:


> I'm using an O2 with HD 650s. How much gain are you guys using for normal listening? I usually have mine about 2 bars. If I want to really hear everything in the mix I set it up to a little less than half way.


 
   
  I think that low gain (2.5X) should be just fine for the 650s. They're really not that hard to drive.


----------



## mikeaj

Quote: 





jimbo24 said:


> I'm using an O2 with HD 650s. How much gain are you guys using for normal listening? I usually have mine about 2 bars. If I want to really hear everything in the mix I set it up to a little less than half way.


 
   
  Hm, how much gain?  Clearly that depends on the output level of the source you're amplifying, the headphones too.
   
  None of my headphones need incredible amounts of voltage, so with a 1V rms source I just have 1x and 3.1x gains.  It's on 1x except for some classical music recordings with the relatively insensitive headphones.  With HD 650s I'd be using 1x for myself, most of the time.


----------



## gnarlsagan

purrin said:


> Actually, I'm more impressed by the O2 than the ODAC. The ODAC sounds different depending upon what it's plugged into. The O2s main issues with me are treble stridency and some weakness in the bass. Both can be remedied with an op-amp swap to the LM4592 which I have done myself. The O2 excels is how clean and controlled it sounds. However, the O2 does sound flat in terms of both micro and macro dynamics, and does not extract detail anywhere as well as better amps, e.g UHA-6S, Schiit Mjolnir, etc. Heck, even a slightly colored tube hybrid amp such as the Melos SHA-1 is does dynamics and resolution better. This is of course dependent upon source and transducer quality: DAC, recording, and headphones.
> 
> Of course YMMV. The fact that I would be hard pressed to find anything better for less than ~$279 speaks volumes about the O2.




That's interesting! I might try that swap at some point. I'm not questioning your findings but I'm hoping you could be more specific about detail extraction differences between the O2 and the other amps you mentioned. Maybe a specific sound or section in a specific track? I just never know what to look for when people mention these kinds of things.


----------



## mikeaj

Quote: 





gnarlsagan said:


> That's interesting! I might try that swap at some point. I'm not questioning your findings but I'm hoping you could be more specific about detail extraction differences between the O2 and the other amps you mentioned. Maybe a specific sound or section in a specific track? I just never know what to look for when people mention these kinds of things.


 
   
  Just a couple heads-up:
   
  I think purrin's got a typo there.  You probably want an LM4562 (not LM4592, which doesn't exist?  or at least isn't common).  Hopefully this saves somebody some grief in looking up the part number.  
	

	
	
		
		

		
		
	


	



   
  Secondly, there are some uncharacteristically brief THD and noise measurements of LM4562 in O2 circuit at _that place_ (August), just for reference, to compare to whatever you hear.


----------



## cyberalpha11

Will O2 improve the bass in AKG K550 by making sound much heavier, tighter, deeper and punchier bass?


----------



## mikeaj

Quote: 





cyberalpha11 said:


> Will O2 improve the bass in AKG K550 by making sound much heavier, tighter, deeper and punchier bass?


 
   
  Compared to... what?


----------



## NimbleTurtle

Quote: 





cyberalpha11 said:


> Will O2 improve the bass in AKG K550 by making sound much heavier, tighter, deeper and punchier bass?


 
  From my limited knowledge of amps, it will have tighter bass that extends better but it won't get heavier unless you EQ it.


----------



## cyberalpha11

mikeaj said:


> Compared to... what?



Comparison "with" and "without"O2 when listening to K550.


----------



## mikeaj

Quote: 





cyberalpha11 said:


> Comparison "with" and "without"O2 when listening to K550.


 
   
  I don't mean any offense at all, but right now I seriously can't figure out whether to blame myself or you for wasting both of our times, even if it's just a couple minutes.  
	

	
	
		
		

		
			




   
  Without the amp, you would be plugging the headphones into what?  An amp isn't like an effects processor, EQ, or something like that.  To get sound out of headphones, you're running them out of some type of device.  To gauge the performance of another amp (here, the O2) relative to that, you need to know the characteristics of the original device, how good or bad it is (and in what ways) it is for driving headphones like that.


----------



## placebo-fi

K550 has pretty awful distortion in the bass so not sure if anything can fix that? Google "K550 measurements". I do not have any experience with these cans by the way, just talking from observation.


----------



## cyberalpha11

mikeaj said:


> I don't mean any offense at all, but right now I seriously can't figure out whether to blame myself or you for wasting both of our times, even if it's just a couple minutes.  :mad:
> 
> Without the amp, you would be plugging the headphones into what?  An amp isn't like an effects processor, EQ, or something like that.  To get sound out of headphones, you're running them out of some type of device.  To gauge the performance of another amp (here, the O2) relative to that, you need to know the characteristics of the original device, how good or bad it is (and in what ways) it is for driving headphones like that.




Sorry for not putting my statement clear. Basically the comparison is as below:

CASE 1: ipod classic + k550 (no amp, no ext. DAC)
CASE 2: ipod classic + k550 + O2 (no ext. DAC)

Even though k550 is easy to drive headphone, but I found the bass is a bit soft.
By adding this O2 in the equation, will it further enhanxe the sound quality especially the bass.
This is what I would like to find out.


----------



## adydula

the audio out that u plug your cans in the apple device has been converted from digital and amp in it.
   
  Adding another external amp like the O2 etc may make things worse depending on the quality of the audio out of the device.
  This is like amplifying the stuff twice...
   
  Most of us take the digital bits out to a external dac, then amp for the best possible conversion and amplification.
   
  Alex


----------



## stv014

Amplifying the headphone output of an iPod (and many other devices) with the O2 can easily improve the overall performance, as the O2 itself degrades the audio signal only by a small (normally not even audible) amount, and it can drive headphones better than the iPod. Basically, what you gain by the iPod having to drive only the input of the O2 (which is an easy load compared to a headphone) is greater than what you lose by having the O2 in the signal path. However, using the O2 on an already very good headphone output might not make any useful difference.


----------



## adydula

It wont improve the overall performance, it will just amplify the signal....if thats what you mean about improving "overall" perfromance then i agree....but overall usually implies more that just amplification.
   
  If the source is a stellar signal, then it comes out amplified wonderfully....with no audible additions or subtractions...if the souce is less than stellar, the sound out will be just than that...less than stellar...
   
  I am starting my third 02 DIY....this is a great little device.
   
  Alex


----------



## mikeaj

Read again what stv014 wrote.
   
  The key point is that the signal the iPod "sends" depends on what it's sending to (even with all the same settings, configuration; this is a matter of hardware performance).  If it's connected to one headphone, the signal will be different than if it is connected to a different headphone, which will be different than if it is connected to an amp—the amount of imperfections manifested depends on the load.  When connected to an amp, the imperfections will be smaller.
   
  This isn't so much true for an iPod, but many devices (those not intended for headphones) will sound terrible with headphones but will sound just fine connected to an amp.


----------



## adydula

combine that with double amplicaction and it can make things even worse....
   
  Alex


----------



## mikeaj

Quote: 





adydula said:


> combine that with double amplicaction and it can make things even worse....
> 
> Alex


 
   
  Double amping was already considered.  And for what it's worth, there really shouldn't be too much distinction between having a preamp and power amp (double amping?), multiple stages in one amp (which almost all do unless you're talking about a CMoy), multiple amps strung together, and so on.
   
  As a quick and dirty example, RMAA IMD test results:
   

   
  Test is 60 Hz tone and 7000 Hz tone together, so everything else is bad (higher is worse, aside from at 60 Hz and 7000 Hz).  White line is single amped.  Green line is double amped, where the second amp is better than the first amp.


----------



## sling5s

O2 with dacport or O2 with Odac for Lcd-2 and grado magnums?


----------



## sling5s

How would the Dacport as amp/dac combo compare to O2+ODAC


----------



## mikeaj

Quote: 





sling5s said:


> How would the Dacport as amp/dac combo compare to O2+ODAC


 
   
  O2 is more powerful, which is a statement about output power levels and not any impression about sound quality.  Aside from that, different people are going to have different opinions.  Personally, I'd rather have something all in one and not as clunky as O2+ODAC.
   
  If you listen to very quietly-mastered classical / jazz recordings at a loud listening volume, DACPort is not quite going to be powerful enough for the LCD-2 (maybe; if it's the Rev2, at least according to Tyll's measurements at InnerFidelity, are a little quieter).  i.e. it will not get loud enough.  Sound should still be fine.  Leckerton Audio UHA-6S-MKII, if you have a S/PDIF source or just go with 16/48 max, has similar output levels—actually, a little less into lower impedances and a little more into higher impedances.  I mean, there's a certain power limitation if you're running off of USB.


----------



## adydula

I have one ODAC in a seperate enclosure that I can insert into my high end 2 ch setup so I can compare the dac with other dacs....works well.
   
  I have an integrated O2amp and ODAC in one enclosure for just cans listening that I can move around easlily....to one of my five desktop pcs, notebooks, tablets etc...
   
  The integrated solution is still less than $300....just in this solution no batteries....but this can be done in a larger case...
   
  Alex


----------



## themoddingden

wood aww man .
  do you make them?


----------



## sling5s

Placed order for O2+ODAC combo.  With so much hype on both I'm kind of excited but I fear I will be underwhelmed.
  Why? Well I'm kind of on the "warm, musical, and colored" camp.  That's just my preference.  Can't help it. 
  But I'm hoping I'm pleasantly surprised.


----------



## adydula

sling... dont know what you have or have listened to but the o2 amp just makes things louder and doesnt add or take anything away from your source material or dac output.
   
  if you play crappy tunes into it they will come out crappy tunes.
   
  so make sure you get some reall great recordings to really see what this amp does NOT do.
   
  All the best
  Alex


----------



## sling5s

I just got the O2+ODAC. I could not resist the price and hype. First, I was expecting something bigger. It's so small. Yet, it has a big sound. It really sounds like a desktop amp. Second, I was expecting bright and lean. But it's smooth, clean and not lean at all. Nice bass. Not something you get for something that resembles a portable amp. Really pleasantly surprised. I tried my JH13pro. Wow. Nice and smooth. Not edgy or hot like I expected. The bass finally came alive, something that only happens with a good desktop amp on these. I tried the Grado Magnums. It of course did not warm it up but it did not accentuate it either. It sounded smooth. I tried last my LCD-2 r.1. It no longer sounded warm and creamy. It sounded very neutral for the first time. At least to me. But overall. I am very pleasantly happy. I could not ask for more for such a low price and size. Very powerful transportable, amp/dac combo that more than satisfies.
   
  edit: I still the LCD-2 needs more power.  This little thing is really powerful but I think the LCD-2 needs more to sound full and alive.


----------



## imackler

Quote: 





sling5s said:


> I just got the O2+ODAC. I could not resist the price and hype. First, I was expecting something bigger. It's so small. Yet, it has a big sound. It really sounds like a desktop amp. Second, I was expecting bright and lean. But it's smooth, clean and not lean at all. Nice bass. Not something you get for something that resembles a portable amp. Really pleasantly surprised. I tried my JH13pro. Wow. Nice and smooth. Not edgy or hot like I expected. The bass finally came alive, something that only happens with a good desktop amp on these. I tried the Grado Magnums. It of course did not warm it up but it did it accentuate it. It sounded smooth. I tried last my LCD-2 r.1. It no longer sounded warm and creamy. It sounded very neutral for the first time. At least to me. But overall. I am very pleasantly happy. I could not ask for more for such a low price and size. Very powerful transportable, amp/dac combo that more than satisfies.


 
   
  How does it compare to your Centrance Dacport?


----------



## sling5s

It's so different.  The Dacport sounds like a Class A....which is hard to describe really.  Dacport has similarity with the Asgard which is a Class A amp.
  The Dacport is really airy and the instrument separation is really great.  But what the Dacport lacks is fullness and body that comes with having some bass presence.
   
  The O2 while neutral really has a sense of fullness, body and authority (bass presence).
   
  The Dacport sounds like a good portable amp while the O2+ODAC sounds like a good desktop amp.
   
  So I guess it is honestly like comparing a portable with a desktop amp.  Which is not a fair comparison.


----------



## LouisLoh

Quote: 





sling5s said:


> I just got the O2+ODAC. I could not resist the price and hype. First, I was expecting something bigger. It's so small. Yet, it has a big sound. It really sounds like a desktop amp. Second, I was expecting bright and lean. But it's smooth, clean and not lean at all. Nice bass. Not something you get for something that resembles a portable amp. Really pleasantly surprised. I tried my JH13pro. Wow. Nice and smooth. Not edgy or hot like I expected. The bass finally came alive, something that only happens with a good desktop amp on these. I tried the Grado Magnums. It of course did not warm it up but it did it accentuate it. It sounded smooth. I tried last my LCD-2 r.1. It no longer sounded warm and creamy. It sounded very neutral for the first time. At least to me. But overall. I am very pleasantly happy. I could not ask for more for such a low price and size. Very powerful transportable, amp/dac combo that more than satisfies.


 
   
  Hope you can shed more light on JH13's treble and mids performance when paired with O2/ODAC.


----------



## GL1TCH3D

Has anyone used the O2 with an HE-6?

I like the ODAC+O2 with my HD800 and LCD2 but I wanted to add a pair of headphones that sounded more alive. (Maybe an amp change...)


----------



## alphaphoenix

O2+HE6?  I'm dying to know if anybody has paired the two, but something tells if someone has, the results won't be a surprise.


----------



## K_19

I believe even nwavguy himself would admit that HE6 is one of those rare headphones that O2 just simply won't power well enough.


----------



## GL1TCH3D

alphaphoenix said:


> O2+HE6?  I'm dying to know if anybody has paired the two, but something tells if someone has, the results won't be a surprise.




Yea, I wasn't expecting much. Might have to upgrade to the beta22 at some point >.<


----------



## JRoyen

Sorry if this question has been asked/answered already.... has anyone modded their o2+odac to accept 9v batteries? If so, is it working well? I'll probably house the batteries outside of the case.


----------



## stv014

Quote: 





jroyen said:


> Sorry if this question has been asked/answered already.... has anyone modded their o2+odac to accept 9v batteries? If so, is it working well? I'll probably house the batteries outside of the case.


 
   
  If I recall correctly, some people did it by placing the ODAC board under the O2 PCB where the batteries are, so the batteries could be kept.


----------



## adydula

Its been done several ways, under the board, and in larger cases....dont remember anyone doing it via external....
  Alex


----------



## PanamaHat

Does the ac power need to stay plugged in in order for this to work or is it usb powered? It seems kind of awkward to have the power adapter cable sticking out of the front.


----------



## stv014

Quote: 





panamahat said:


> Does the ac power need to stay plugged in in order for this to work or is it usb powered? It seems kind of awkward to have the power adapter cable sticking out of the front.


 
   
  The O2 and ODAC are powered independently, regardless of whether they are in separate enclosures or not. The latter by USB, and the former by the AC adapter or batteries.


----------



## HamilcarBarca

Quote: 





stv014 said:


> The O2 and ODAC are powered independently, regardless of whether they are in separate enclosures or not. The latter by USB, and the former by the AC adapter or batteries.


 
   
  The standard, all-in-one O2+ODAC requires A/C power, doesn't it?


----------



## adydula

The standard, all-in-one O2+ODAC requires A/C power, doesn't it?
   
  The JDS Labs integrated version has the batteries removed and this is the place where the ODAC resides.
   
  Alex


----------



## Lord Voldemort

Quote: 





k_19 said:


> I believe even nwavguy himself would admit that HE6 is one of those rare headphones that O2 just simply won't power well enough.


 
  I don't see why it wouldn't have enough current for the HE-6.


----------



## BleaK

Looking forward to hearing the ODAC+O2 combo!


----------



## stv014

Quote: 





hamilcarbarca said:


> The standard, all-in-one O2+ODAC requires A/C power, doesn't it?


 
   
  Yes, that is correct, only some custom builds keep the batteries.


----------



## stv014

Quote: 





k_19 said:


> I believe even nwavguy himself would admit that HE6 is one of those rare headphones that O2 just simply won't power well enough.


 
   
  Read his "More Power?" (September 2011) and "O2 Headphone Amp" (July 2011) articles, and the HE-6 measurements at InnerFidelity. From these, it can be estimated that the O2 on AC power would be capable of about 105 dB maximum SPL driving the HE-6 with correctly set gain. Therefore, his opinion would likely be that the O2 is sufficient for those who listen only to music with limited dynamic range (pop etc.), and/or not at high volume, but clearly not for everyone.


----------



## GL1TCH3D

stv014 said:


> Read his "More Power?" (September 2011) and "O2 Headphone Amp" (July 2011) articles, and the HE-6 measurements at InnerFidelity. From these, it can be estimated that the O2 on AC power would be capable of about 105 dB maximum SPL driving the HE-6 with correctly set gain. Therefore, his opinion would likely be that the O2 is sufficient for those who listen only to music with limited dynamic range (pop etc.), and/or not at high volume, but clearly not for everyone.




105dB is more than enough for me o.o
I usually listen around 80dB...


----------



## stv014

It is 105 dB peaks, though. If you measured the 80 dB with an SPL meter, then it is probably an averaged value, and possibly A-weighted as well.


----------



## Battou62

Quote: BleaK 





> Looking forward to hearing the ODAC+O2 combo!


 
   
  Me too! He hasn't updated his blog in 4-5 months and I am starting to get antsy.


----------



## adydula

Thats why I decided to integrate my own and now with several o2's i have several cans in each to compare.
   
  Alex


----------



## stv014

Quote: 





battou62 said:


> Me too! He hasn't updated his blog in 4-5 months and I am starting to get antsy.


 
   
  Recently it even takes weeks for comments to get approved, so it does not look like the ODA will be available soon.


----------



## adydula

But even if the ODA never comes out, you still can get the world class performance at this price point "now"....I wanted to wait as well for the 1/4 phone jack and RCA connectors etc....
   
  But its such a low cost for what it does....why wait...I modified my ODAC's to fit my systems and arrangements...added RCA's etc...
   
  Its not that hard and you can find people to do this for you...
   
  The ODA specs etc will be great I am sure....but I dont think it will be even close to an order of magnitude....
   
  Enjoy now....
   
  Alex


----------



## PanamaHat

This or the new Alo Audio Pan Am. I'm not convinced that the pan am or any other amp worth $300 or up necessarily has better sonic quality. Then again I've never heard a $300 or up amp, only my Fiio e17


----------



## HamilcarBarca

Quote: 





panamahat said:


> This or the new Alo Audio Pan Am. I'm not convinced that the pan am or any other amp worth $300 or up necessarily has better sonic quality. Then again I've never heard a $300 or up amp, only my Fiio e17


 
   
  Price is not necessarily a good predictor of headphone amplifier quality. You don't "get what you pay for" if the phrase means "it costs more, so it's better."
   
  My Matrix M-Stage doesn't produce better-sounding audio than my FIIO E5. The E5 is much smaller and runs from USB power. The M-Stage has more gain and more power. That makes each of them better than the other.


----------



## sling5s

This just can't be my imagination but the USB cable that comes with the O2+ODAC has a ferrite and I believe the ferrite filters the high frequencies. When I changed the USB (ferrite-less) cable, the high frequency came back. At least to my ears. The treble is much better, not recessed as before and the bass has more snap, punch, do to the restoration of the treble balance. Is it just me?


----------



## HamilcarBarca

Quote: 





sling5s said:


> This just can't be my imagination but the USB cable that comes with the O2+ODAC has a ferrite and I believe the ferrite filters the high frequencies. When I changed the USB (ferrite-less) cable, the high frequency came back. At least to my ears. The treble is much better, not recessed as before and the bass has more snap, punch, do to the restoration of the treble balance. Is it just me?


 
   
  The phenomenon you're describing is an analog phenomenon; that's not how we detect problem with digital-audio output. If USB communication to the ODAC is marginal or failing, the result won't be enhanced or attenuated frequencies: We'll probably hear _noise_ (e.g, clicking and popping.)


----------



## adydula

Does anyone know why the ferrite bead might be on a USB cable.
   
  This might help explain or understand what is happening or not happening here?
   
  Alex


----------



## Prava

Quote: 





sling5s said:


> This just can't be my imagination but the USB cable that comes with the O2+ODAC has a ferrite and I believe the ferrite filters the high frequencies. When I changed the USB (ferrite-less) cable, the high frequency came back. At least to my ears. The treble is much better, not recessed as before and the bass has more snap, punch, do to the restoration of the treble balance. Is it just me?


 
   
  There is no way you can filter frequencies from a USB cable because all the data that is travelling through it is purely digital, aka there is no way to modify only a part of it without having something "else" in between.
   
  So, its your head.


----------



## adydula

Prava....
   
  Do you think that there might be any other 'stuff' riding this cable into the DAC???
   
  Alex


----------



## HamilcarBarca

Quote: 





adydula said:


> Prava....
> 
> Do you think that there might be any other 'stuff' riding this cable into the DAC???


 
   
  The ferrite bead (choke, core, etc.) is there to filter out high-frequency noise that might interfere with USB communication.
   
  It's exactly as Prava says: It has zero effect on high-frequency audio signals.


----------



## adydula

and where might this high frequency noise be coming from?
   
  What is the difference between high frequency noise and high frequency audio signals?
   
  Ale


----------



## lukeahale

adydula said:


> What is the difference between high frequency noise and high frequency audio signals?
> 
> Ale




The difference is the high frequency audio signals aren't really frequencies at all during the USB part of this process. They are 1s and 0s (sort of...rather an electrical representation of 1s and 0s). It's not until it gets to the DAC that it actually gets converted into high/low/mid frequencies.


----------



## adydula

So any possible noise from inside the PC that could be inserted or induced into the cable is twarted by the ferrite core on the end of the
  cable that plugs into the dac....
   
  Do you know what actually happens to the unwanted noise or errant sgnals??
   
  Alex


----------



## HamilcarBarca

Quote: 





adydula said:


> So any possible noise from inside the PC that could be inserted or induced into the cable is twarted by the ferrite core on the end of the
> cable that plugs into the dac....
> 
> Do you know what actually happens to the unwanted noise or errant sgnals??
> ...


 
   
  See Ferrite bead.


----------



## adydula

Simply magic....
   
  A.


----------



## sling5s

Anyone use the O2+ODAC as a preamp (with headphone jack as line out)?  To two channel speaker stereo system or desktop amp?  I know it's double amping but many have done it with pico amp/dac and dacport.


----------



## antberg

Quote: 





adydula said:


> Simply magic....
> 
> A.


 
   
  Quote: 





hamilcarbarca said:


> See Ferrite bead.


 
   
  Subscribed ,
  for further question about ferrite which i may encounter soon,thought i already did read the whole thread.
  I ordered an "affordable" O2+Odac combo for my new rig (+HD650) about a month ago (it takes loong time to delivery here in South America),anxious to hear some improvement!


----------



## adydula

antberg..
   
  Congrats on your 02 and ODAC combo, it will be worth the wait and I hope you enjoy it like many of us have......for the price its a very, very clear, open and transparent
  setup...
   
  Alex


----------



## Crispy808

What would it take to move the input power jack to the rear of the unit?  Is the enclosure the limiting factor?  Can you just bridge the connections with wires?  I'm planning on building one as a first DIY, but I don't like having all the inputs/outputs on the front.
   
  The wooden enclosure on the first page is sweet.  Makes me want to test my woodworking skills. 
   
  First time to this site.  I'm fascinated.


----------



## antberg

Welcome to Head-Fi Crispy,and if you are a labour class citizen,"Sorry for your wallet!"  
	

	
	
		
		

		
		
	


	



  Although i don't have remarkable soldering or PCB assembling skill,i think that by DIY it will be possible to change the power or audio input for your device,which by the way is the only thing at the moment i would like to have it modified ,because the ODac is not transportable anyway so a back USB port would be more useful,nothing to worry too much,thought.
   
  Thanks Adydula.
  As i recently brought a practically new pair of HD650 from a Head-fier here at the same time i did order the amp+dac combo,my decision to choose the same combo from JDS came from the impression of most Sennheiser users who say that the HD650 is balanced but nonetheless with a touch of warm and quite recessed highs,so i though a clear ,more transparent setup would be ideal ,an i don't have too much money at the moment neither .Even thought there are many out there who did not like this combo too.Anyway if i don't like the O2+ODac combo (which i am almost sure i will approve) i can sell them easily with almost no loss.


----------



## mikeaj

Quote: 





crispy808 said:


> What would it take to move the input power jack to the rear of the unit?  Is the enclosure the limiting factor?  Can you just bridge the connections with wires?  I'm planning on building one as a first DIY, but I don't like having all the inputs/outputs on the front.
> 
> The wooden enclosure on the first page is sweet.  Makes me want to test my woodworking skills.
> 
> First time to this site.  I'm fascinated.


 
   
   
  The strategy most take is to face the PCB backwards in a larger enclosure.  This puts everything on the back side, like the power jack, input jack, etc.  Then just mount the headphone jack and volume potentiometer to the front side (maybe the LED too) and wire them back to the PCB.


----------



## antberg

Guys,about the ferrite question\problem.
  As i wrote above i did ordered an Odac literally one month ago;does it came already with the "ferrite" change or i have to find out IF i have the same problem of some of us and then send back the unit the them modify my ODac?I though here i would get a quicker response,and i think i have already bore Mr.John Seaber with a lot of questions
	

	
	
		
		

		
			




  Grateful


----------



## lukeahale

If you ordered it from JDSLabs it should include a USB cable with a ferrite bead.


----------



## HamilcarBarca

Quote: 





antberg said:


> As i wrote above i did ordered an Odac literally one month ago;does it came already with the "ferrite" change or i have to find out IF i have the same problem of some of us and then send back the unit the them modify my ODac?I though here i would get a quicker response,and i think i have already bore Mr.John Seaber with a lot of questions
> 
> 
> 
> ...


 
   
  I think the '"ferrite" change" you're describing is an internal change in JDS Labs' C421 amplifier.
   
  The ODAC has an external ferrite on its stock USB cable.


----------



## lorriman

adydula said:


> antberg..
> 
> Congrats on your 02 and ODAC combo, it will be worth the wait and I hope you enjoy it like many of us have......for the price its a very, very clear, open and transparent
> setup...
> ...




This kind of misrepresentation is really quite irritating. It's not 'good for the price': the whole point of the O2/ODAC is a demonstration that perfect audio reproduction is not very expensive. It's not good for the price: it's both cheap and priceless.


----------



## antberg

Quote: 





hamilcarbarca said:


> I think the '"ferrite" change" you're describing is an internal change in JDS Labs' C421 amplifier.
> 
> The ODAC has an external ferrite on its stock USB cable.


 
   
  Quote: 





lukeahale said:


> If you ordered it from JDSLabs it should include a USB cable with a ferrite bead.


 
  Thanks folks,i can see now,in the case of the ODac is the cable with that kind of cylindrical piece plastic covered in some place between both end of it.Just simple as that....


----------



## lorriman

antberg said:


> Thanks folks,i can see now,in the case of the ODac is the cable with that kind of cylindrical piece plastic covered in some place between both end of it.Just simple as that....




As it happens there is a ferrite on the ODAC itself. There was a note by the designer that the production ODACs had a larger one than the final proof version though functionality was the same. In all likelihood you don't need a ferrite on the US cable.


----------



## cel4145

Hey guys. This is a question just about the O2. Hope you don't mind. 
   
  I've got a Xonar Essence STX. Not ready to upgrade to a different DAC yet, but my main phones are all fairly low ohm: SR225i (32 ohm), A900x (40 ohm), HFI-780 (35 ohm). Do you think I would benefit from using the O2 with the STX? The STX is only rated down to 10 ohms. Since my desktop rig has an HK 3390 stereo receiver plugged up to the l/r line out on the Xonar (for my passive bookshelf speakers), I would either connect the O2 to the headphone out on the STX or the tape out on the 3390. 
   
  Now I've tried hooking my E17 up to the headphone out on the STX, and I feel like I can hear a positive difference with the Grados, but I'm not sure. So thought it best to check whether or not an O2 kind of upgrade would be an audible improvement. 
   
  Thanks for any thoughts.


----------



## mikeaj

Quote: 





cel4145 said:


> Hey guys. This is a question just about the O2. Hope you don't mind.
> 
> I've got a Xonar Essence STX. Not ready to upgrade to a different DAC yet, but my main phones are all fairly low ohm: SR225i (32 ohm), A900x (40 ohm), HFI-780 (35 ohm). Do you think I would benefit from using the O2 with the STX? The STX is only rated down to 10 ohms. Since my desktop rig has an HK 3390 stereo receiver plugged up to the l/r line out on the Xonar (for my passive bookshelf speakers), I would either connect the O2 to the headphone out on the STX or the tape out on the 3390.
> 
> ...


 
   
  I think there's some misunderstanding for what the Essence STX is rated for, or what the 10 number comes from.  Actually, who cares what it's rated for?  It has some kind of electronics that can be used to power headphones—let's look at how that does.
   
  By all indications, the Essence STX has some kind of competent TPA6120-based headphone amplifier circuit (also used in FiiO E9 and some others, but the STX has lower noise I think), so that can power pretty much any typical headphone very loud with minimal distortion and problems, except for one thing.  It has around 10 ohms output impedance.  Effectively, you can think of it as there being 10 ohms between its output and any headphones you connect to it, which is a bad thing for some headphones and is generally more of a problem the _lower_ the impedance of the headphones (imagine:  10 ohms is significant compared to 30 ohms but not really so significant when compared to 600 ohms).
   
  So there are some headphones where the O2 should be a little better than the STX, in a non-trivial way.  For these, the O2 should probably sound more like the E17 does, since the O2 and E17 have lower output impedance.  For others (most everything? especially among full-size headphones), it should be pretty much the same, or at most just marginally different.
   
  For those headphones, I'd consider just using the E17.  That said, those headphones have low impedance but mostly constant impedance across frequency, so it probably doesn't matter much.  If you end up with some high-impedance, lower-sensitivity headphones that are too quiet for the E17, run them from the Essence STX.  It should do a great job with those.
   
  Given what you have, don't bother with the O2 unless you just want a shiny new box.


----------



## cel4145

Quote: 





mikeaj said:


> I think there's some misunderstanding for what the Essence STX is rated for, or what the 10 number comes from.  Actually, who cares what it's rated for?  It has some kind of electronics that can be used to power headphones—let's look at how that does.
> 
> By all indications, the Essence STX has some kind of competent TPA6120-based headphone amplifier circuit (also used in FiiO E9 and some others, but the STX has lower noise I think), so that can power pretty much any typical headphone very loud with minimal distortion and problems, except for one thing.  It has around 10 ohms output impedance.  Effectively, you can think of it as there being 10 ohms between its output and any headphones you connect to it, which is a bad thing for some headphones and is generally more of a problem the _lower_ the impedance of the headphones (imagine:  10 ohms is significant compared to 30 ohms but not really so significant when compared to 600 ohms).
> 
> ...


 
   
  Thanks. Yeah. I dont' keep the E17 with my home office setup with the STX where I do most of my serious listening. It's normally in my workplace office with headphones I keep there to use with my laptop, which definitely needs the E17 more 
	

	
	
		
		

		
		
	


	



   
  So I guess maybe the O2 would be some help, then?


----------



## mikeaj

Quote: 





cel4145 said:


> Thanks. Yeah. I dont' keep the E17 with my home office setup with the STX where I do most of my serious listening. It's normally in my workplace office with headphones I keep there to use with my laptop, which definitely needs the E17 more
> 
> 
> 
> ...


 
   
  It could  help some small amount, sure.  I would still recommend saving the money, to either pocket, save for new headphones, or whatever else.
   
  If you got certain IEMs or Sennheiser HD 5x8 series, or some other certain headphones, I would think there should be a little more difference—actually, a really big difference for some IEMs.  As it is, I wouldn't chase the small (miniscule?) stuff, but you're free to do if you want.


----------



## cel4145

Quote: 





mikeaj said:


> It could  help some small amount, sure.  I would still recommend saving the money, to either pocket, save for new headphones, or whatever else.
> 
> If you got certain IEMs or Sennheiser HD 5x8 series, or some other certain headphones, I would think there should be a little more difference—actually, a really big difference for some IEMs.  As it is, I wouldn't chase the small (miniscule?) stuff, but you're free to do if you want.


 
   
  I've got some 16 ohm IEMs, but I don't use them with my desktop setup. 
   
  At this point, I won't be buying any new headphones for awhile. So that's why I was looking to improve the response of the ones I have. Although if it's that minuscule a difference, does seem better not to spend the money.


----------



## BleaK

Just got the O2/ODAC, it sound really transparent and powerfull for such a small box!


----------



## Bojamijams

Has anyone tried the O2 (with which gain, 6.5x or something else?) with any 600ohm headphones? Specifically the DT-880?
   
  I'm interested in using it but would like to know if it has the voltage swing to drive it properly


----------



## HamilcarBarca

Quote: 





bojamijams said:


> Has anyone tried the O2 (with which gain, 6.5x or something else?) with any 600ohm headphones? Specifically the DT-880?
> 
> I'm interested in using it but would like to know if it has the voltage swing to drive it properly


 
   
  I have a 32-Ohm Beyer, so I haven't tried this myself. From the designer's blog.
   
_The DT880-600 needs over 5 Vrms to play reasonably loudly with all types of music. That's 14 volts peak-to-peak a _[sic] _most popular portable amps, and even many home sources, cannot manage that much output.

The O2 and ODA, however, both output over 5 Vrms and work fine with the DT880-600. How much gain you need comes down to the source you're using._


----------



## Bojamijams

Promising! Thank you for that info.


----------



## adydula

7.3 volts at 600 Ohms....
   
  Should do just fine..
   
  Alex


----------



## Bojamijams

Quote: 





adydula said:


> 7.3 volts at 600 Ohms....
> 
> Should do just fine..
> 
> Alex


 
   
  Do you mind explaining how you got to that number? I'd love to be able to figure it out for myself in the future. Thanks


----------



## stv014

Quote: 





bojamijams said:


> Do you mind explaining how you got to that number? I'd love to be able to figure it out for myself in the future. Thanks


 
   
  It is in the "O2 Headphone Amp" blog article of the designer, which is not allowed to be linked here. Check the "THD+N vs OUTPUT & MAX POWER ON AC" graph. Note however, that the 7.3 Vrms level is measured at 1% THD, it is at slightly less than 7 V where the distortion starts to rise due to clipping. Also, to get that high voltage out of the amplifier, you need to either set the gain accurately (using custom resistor values), or use high gain and control the volume at the source. In any case, the 5 Vrms output from a standard 2 V source and 2.5x default low gain should be enough for most people. It is also about the maximum you can get on battery power.


----------



## Bojamijams

I would be getting the amp with a 1x/6.5x gain switch (so that it can drive my JH|13's as well as the DT-800/600)
   
  The source would be the TC 750 preamp (boosting a TT phono signal). Not sure on its output voltage.
   
  I'll order the AC cord from JDS as well just in case the battery can't get there (but I think it probably would be able to)


----------



## stv014

Quote: 





> Originally Posted by *Bojamijams* /img/forum/go_quote.gif
> 
> The source would be the TC 750 preamp (boosting a TT phono signal). Not sure on its output voltage.


 
   
  It has a gain of 40 dB, and a nominal output voltage of 300 mV, but it depends on the input voltage received from the source.


----------



## Bojamijams

Interesting, thank you for looking that up! 
   
  I think I'll get the O2 with a 1.0/6.5x (max low/high basically) and that should give me the power to get the DT880 to proper volume.


----------



## safer

just want to know how good is the Dac compared with more expensive, full size ones.


----------



## hallom

hey guys, anyone here using e-mu 0404 usb? i was wondering how it compares to the odac-o2 combo, as dac+preamp? i'm planning to switch from my emu, so i'm collecting some info.


----------



## adydula

safer,
   
  You can find the designers site easily on the net...and read about his and in the comments / blog there are several comments on dac comparisons.
   
  I have compared with several, HRT MSii+ USB , ESS Sabre Dacs in a high end source, there is no real detectable differences to my ears with cans or speakers IMO.
   
  This is a great dac and compares very well with many others priced much higher....
   
  I am sure others will chime in..
   
  Alex


----------



## safer

thanks for the help. I will try to get one from the forum.


----------



## BleaK

adydula said:


> safer,
> 
> You can find the designers site easily on the net...and read about his and in the comments / blog there are several comments on dac comparisons.
> 
> ...


 I'll second that.


----------



## K_19

Using the combo of JDS ODAC and a DIY Desktop style version of O2 (with RCA's, 1/4 plug)... man... the HD800's sound excellent through them!


----------



## jerg

What's the output power of O2? I'm thinking of getting it to replace the trusty E17 in driving my HE400s.


----------



## mikeaj

Quote: 





jerg said:


> What's the output power of O2? I'm thinking of getting it to replace the trusty E17 in driving my HE400s.


 
   
  On battery, something like 534mW (4.2V) into 33 ohms, 338mW (5.2V) into 80 ohms.  So for ~50 ohms HE-400, maybe something around 500mW (5V), definitely not shy of 350mW.  That's the advantage of packing two 9V batteries.
   
  But to reach that level without clipping the input, you need to be careful about getting the correct gain, given whatever source you're using.  Then again, you _really_ don't want to be pumping 500mW into HE-400 and having that placed on somebody's head.


----------



## jerg

Quote: 





mikeaj said:


> On battery, something like 534mW (4.2V) into 33 ohms, 338mW (5.2V) into 80 ohms.  So for ~50 ohms HE-400, maybe something around 500mW (5V), definitely not shy of 350mW.  That's the advantage of packing two 9V batteries.
> 
> But to reach that level without clipping the input, you need to be careful about getting the correct gain, given whatever source you're using.  Then again, you _really_ don't want to be pumping 500mW into HE-400 and having that placed on somebody's head.


 
   
  I'm thinking of the O2D combo that's built into the O2 casing. The ongoing zeitgeist with planar magnetic cans seems to be that they shine with oodles of high quality power fed into them, and I just wonder if O2 would be up for that or if I should look farther.


----------



## stv014

The HE-400 is one of the more efficient and relatively easy to drive planar magnetic headphones, the O2 should be plenty enough.


----------



## richierich

I'm currently testing the O2 amp from JDS Labs and it indeed is plenty of power for the HE-400s.


----------



## audiocool

i've been seriously considering getting o2+odac for my hd650.  any impressions about this pairing?


----------



## safer

How does the Odac compared with the Bifrost, which seems another DAC with superior value.


----------



## MrMateoHead

Quote: 





mikeaj said:


> It's not really an external power supply that the O2 uses.  The external unit the O2 uses is just a transformer, to step down the voltage from the wall to something like 13.5-20V AC.  Hence you'd need a different transformer in a country with 115V power as opposed to 230V power.  I think for size and weight concerns, maybe regulatory too (?), the transformer wasn't put inside the chassis.  You can get an upgraded transformer if you really want though; in fact, it's recommended for bench testing or running the planar magnetics run at a loud volume.  Difference in price is only like $5.
> WAU12-200
> WAU16-400
> 
> ...


 

 Why would sticking a bigger AC/AC adapter do anything to boost amplifier output? Isn't the "power supply" of the O2 basically 2 9V batteries (so, 18V)? The O2 definitely measures more peak power on AC than battery power, but its hard to imagine a 20 V adapter is going to somehow turn the thing into a beast. Maybe a battery charging beast.


----------



## mikeaj

Quote: 





mrmateohead said:


> Why would sticking a bigger AC/AC adapter do anything to boost amplifier output? Isn't the "power supply" of the O2 basically 2 9V batteries (so, 18V)? The O2 definitely measures more peak power on AC than battery power, but its hard to imagine a 20 V adapter is going to somehow turn the thing into a beast. Maybe a battery charging beast.


 
   
  First off, as I mentioned, there are +-12V regulators on board.  The output of all of that is what is connected to the op amps (so they are running off of +-12V).  That's also what charges the batteries.  12V is higher than 9V or so, so you can charge the battery off of that supply.  On battery operation, there is no 12V to charge the 9V battery, so the op amps are getting voltage from the batteries and thus see +-9V or so (actually a little less as the batteries discharge).  That difference in supply voltage is why the max output is higher on AC power.
   
  No matter the AC input, as long it's high enough, the regulators should work and you'll have +-12V rails.  20V AC input, 14V AC input—who cares**... the supply filtering capacitors and regulators will turn that into +-12V DC (with a small ripple remaining).  The speed at which the batteries charge depends on the current they get; if the rails are +-12V no matter the transformer, then the current will be the same and the charge rate will not depend on the transformer.
   
  **actually, if the input voltage is higher, more energy is wasted as heat in the regulators, so they will heat up a little more.  They can certainly withstand higher temperatures, but over the long long run, elevated temperatures are not good for the nearby electrolytic filtering capacitors.
   
  In practice, if you are really stressing the amp and using a transformer with too low a voltage and/or current rating, the voltage that the regulators see will be too low for them to operate properly and deliver clean +-12V DC outputs.  The power to the op amps will be out of whack and you may have performance issues.  That said, the PSRR of the parts are pretty good, so it may not be that huge of a deal anyway.
   
  It's not so much sticking in a "bigger" AC/AC adapter that boosts the output, but if the one you use is not sufficient, the max output will be less.  In fact, the "standard" adapter that is recommended is kind of marginal in the sense that if you actually stress the amp to its limits, the AC/AC adapter will actually be a liability.  In practice, most people are not bench testing their amps or listening at max volume the amp is capable of with low-impedance headphones (with high impedance headphones, power delivered is less, so even if you max the amp out, that is not drawing as much power), so they won't draw enough power to make that an issue.


----------



## MrMateoHead

Quote: 





mikeaj said:


> First off, as I mentioned, there are +-12V regulators on board.  The output of all of that is what is connected to the op amps (so they are running off of +-12V).  That's also what charges the batteries.  12V is higher than 9V or so, so you can charge the battery off of that supply.  On battery operation, there is no 12V to charge the 9V battery, so the op amps are getting voltage from the batteries and thus see +-9V or so (actually a little less as the batteries discharge).  That difference in supply voltage is why the max output is higher on AC power.


 
   
  Thanks for your response. I wish I had recognized the +-12V limitation sooner, but I didn't because I am slow. Basically then, the O2 is either limited to 9V or 12V. I was paranoid that the 12VAC adapter I am getting with mine may have been a bad choice in terms of achieving maximum output. I will most likely NOT rely on battery power most of the time, so I will slowly trickle charge my batteries to death with the O2's "dumb" onboard battery charger.
   

  I made the following chart from data published on the O2, but note that @50 Ohms, output is estimated. All other impedance points are actual measures. All mW points are also "peak" power, or max before distortion. If everything holds true, the O2 makes a lot more power plugged in than on battery. The mW reduction should be taken carefully though, since the impedance scale is distorted (it is not linear but jumps from impedance to impedance so the power curve is probably longer and flatter). This is to be expected, given the additional voltage available, but I thought it would be cool to see. It would appear that on AC power, the O2 can make well over a half a watt between 33 to maybe 100 Ohms or higher.
   
  This works well for me because I am looking for .5-1 W max for my HE-400s, which are not as efficient as other headphones. Hopefully, this thing will have enough juice for HDR recordings, as my current power output lacks in that area. It is pretty amazing the different that a few volts makes in terms of providing for additional output - though this is helped by the amps low output impedance.


----------



## mikeaj

The difference between 700mW and 450mW is 10*log(700/450) = 1.92 dB.  It's probably a stretch of the imagination to call a 2 dB difference in SPL a big deal; just open up a player with volume control denoted in dB (e.g. foobar) and turn down that slider 2 dB and see for yourself.  Log scale on power may be more appropriate.
   
  If you really want, you can change the two big resistors to a higher value, so the current going to the batteries when charging is smaller.  That increases the charge time but decreases the perpetual trickle charge amount when the batteries are maxed out.


----------



## stv014

Quote: 





mikeaj said:


> The difference between 700mW and 450mW is 10*log(700/450) = 1.92 dB.  It's probably a stretch of the imagination to call a 2 dB difference in SPL a big deal; just open up a player with volume control denoted in dB (e.g. foobar) and turn down that slider 2 dB and see for yourself.  Log scale on power may be more appropriate.


 
   
  450 mW is also enough for more than 120 dB SPL peaks with the HE400 (90 dB @ 0.33 mW), so it is hardly underpowered even allowing for a few dB of random manufacturing variation.


----------



## BleaK

I'm using the ODAC/O2 with HE-500 without any problems. The pairing sounds amazing.


----------



## MrMateoHead

Good input guys. I know that 2 dB is slight, but its real. No props for the pretty chart? What's up guys? 
	

	
	
		
		

		
			




   
  I am not sure the extent to which having 2.5x to 6.5x gain offers in terms of the "120 dB" goal, but I can say that, having heard the pairing now myself, I think 400-500 mWs is still at the lower end of power required to ensure high volume no matter the source material. I can say that, at 6.5x gain, even my cell phone can kill my ears off this thing. Its a great performer.


----------



## HamilcarBarca

Those JDS Labs guys are crazy!
   
  I ordered their O2+ODAC combo this afternoon. Fifty-four (54) minutes later, I received the shipping confirmation. I'll have another new toy before the weekend!
   
  Good work, guys.


----------



## Bojamijams

Is the ODAC+O2 combo able to be powered solely by the USB input?


----------



## kozmo

Quote: 





bojamijams said:


> Is the ODAC+O2 combo able to be powered solely by the USB input?


 

 As a combo, No.
   
  The ODAC can run off the USB on it's own but the O2 requires either the power adapter our battery power. If built in a common chassis, the ODAC board sits where the batteries would normally go, leaving you only able to use the power adapter.


----------



## MrMateoHead

Considering the minor cost differential, I would rather have the ODAC+RCA separately, and the O2 amp w/batteries. The thing runs forever on battery power - 2x longer than my crappy laptop battery. Pretty good amount of coin for what your getting though.
   
  Who knows what the best $300 dollar desktop type amp/DAC is?


----------



## HamilcarBarca

Quote: 





mrmateohead said:


> Considering the minor cost differential, I would rather have the ODAC+RCA separately, and the O2 amp w/batteries. The thing runs forever on battery power - 2x longer than my crappy laptop battery. Pretty good amount of coin for what your getting though.
> 
> Who knows what the best $300 dollar desktop type amp/DAC is?


 
   
  O2+ODAC!


----------



## PanamaHat

When is the ODA coming out?


----------



## HamilcarBarca

Quote: 





panamahat said:


> When is the ODA coming out?


 
   
  Nobody knows. Or, at least, whose who know aren't saying.


----------



## PanamaHat

Wow. Well are the specs really supposed to surpass the o2 or is it just an o2 with a 1/4 inch jack?


----------



## BleaK

Quote: 





panamahat said:


> ...just an o2 with a 1/4 inch jack?


 

 Basicly this.


----------



## MrMateoHead

Quote: 





panamahat said:


> Wow. Well are the specs really supposed to surpass the o2 or is it just an o2 with a 1/4 inch jack?


 

 I am interested in it too, realizing that the O2 is quite awesome for what it is.
   
  There are many avenues that could be taken. High end amps sometimes use batteries, sometimes don't. I think the amp should just be a beast with 3.5mm, RCA jacks in the rear (input/output) and switchable 1/4 - 1/8 jacks and a variable gain switch (0X-10X). 1-3 watts. $200 bucks. Sold.


----------



## mikeaj

Details about the ODA were supposed to have been available by this time, based on previous declarations.
   
  The designer's been "missing" from the internet since September.  Nobody else knows if or when it's coming out.
   
  Hints were that the core design was supposed to pretty much just be a copy of the O2, so you wouldn't suspect any significantly different performance or power output.  There were supposed to be usability tweaks like 1/4" jacks, a back panel with jacks instead of everything on the front, a different power supply, possibly a relay or some other mechanism to suppress turn on/off transients further, and so on.  Not anything to be too excited about.
   
  As it is, you can just put an O2 in a larger box, wire up jacks yourself, and have a desktop version not too different than what the ODA would be.


----------



## Battou62

Yeah I have been getting really frustrated waiting for the desktop version ODA. He hasn't updated his blog since May, and I a getting very tired of waiting. You would think he could at least update everyone on the situation.


----------



## imackler

Just curious. Why some much anticipation? Is it because of the versatility of the O2, able to handle both high sensitivity and more difficult to drive over ear? From using the O2 and ODAC w/ the HD650, I found the bass distortion with the included wall wart on high gain less than ideal. I thought something was broken until JDSLabs said it was normal unless you upgraded the wall wart.  Maybe if your desk space was very limited, but the footpring of my Yulong A800 and ODAC is very small, too.


----------



## stv014

Quote: 





imackler said:


> From using the O2 and ODAC w/ the HD650, I found the bass distortion with the included wall wart on high gain less than ideal.


 
   
  Do not use the O2 with the ODAC at high (6.5x) gain, unless you want to control the volume at the PC. The full scale output voltage of the ODAC will definitely cause clipping in the input stage of the O2 at high gain, regardless of the what wall wart you use. The default 2.5x low gain should be enough, and will not clip.


----------



## imackler

Quote: 





stv014 said:


> Do not use the O2 with the ODAC at high (6.5x) gain, unless you want to control the volume at the PC. The full scale output voltage of the ODAC will definitely cause clipping in the input stage of the O2 at high gain, regardless of the what wall wart you use. The default 2.5x low gain should be enough, and will not clip.


 
  I found that the dynamics were lacking at low gain... I liked the O2 much more with the HD600. One of the really stellar things about the O2 is the versatility. Very nice to run a HD650 and  a sensitive balanced armature iem from the same amp! 
   
  I wish I had known what you said though when I purchased it. I was nervous what was wrong!


----------



## Smoke Signals

Does anyone have experience with the O2+ODAC combo and a pair of HE-500s?


----------



## purrin

Yes.


----------



## stv014

Quote: 





imackler said:


> I found that the dynamics were lacking at low gain...


 
   
  Low gain should not reduce the sound quality, you probably only perceived it as being worse because of the lower volume. Increased loudness gives the impression of better sound. However, if you increase the volume sufficiently to compensate for the lower gain, the sound quality should be fine.


----------



## purrin

Low gain = more global feedback = less involving sounding. YMMV and depends on the implementation. Very noticeable on certain amps.


----------



## imackler

Quote: 





purrin said:


> Low gain = more global feedback = less involving sounding. YMMV and depends on the implementation. Very noticeable on certain amps.


 
   
  What do you mean by "more global feedback"? I'm intrigued. I definitely have found the "less involving sound" part to be true!


----------



## stv014

Quote: 





purrin said:


> Low gain = more global feedback = less involving sounding. YMMV and depends on the implementation. Very noticeable on certain amps.


 
   
  I find the volume mismatch explanation more likely, especially since people have reported the same effect on the perceived sound quality with digital gain. Does the sound improve if you put a 390 Ω resistor between the inverting and non-inverting input of the gain stage op amp (less feedback, but still only 2.5x gain) ?


----------



## purrin

Quote: 





imackler said:


> What do you mean by "more global feedback"? I'm intrigued. I definitely have found the "less involving sound" part to be true!


 
   
  Starting building some amps! http://www.tangentsoft.com/audio/
   
  I stand corrected. I believe the feedback on the O2 is only local. Still likely to have an effect.


----------



## purrin

stv014 said:


> Does the sound improve if you put a 390 Ω resistor between the inverting and non-inverting input of the gain stage op amp (less feedback, but still only 2.5x gain) ?


 

   
  Hmmm. It's worth a shot. The noise floor may rise from -232db to -228db though.


----------



## MrMateoHead

Quote: 





purrin said:


> Low gain = *more global feedback* = less involving sounding. YMMV and depends on the implementation. Very noticeable on certain amps.


 
  What the heck is "global feedback"???
   
  What is "YMMV"?
   
  Opps, someone beat me to the question. What is "Local Feedback"?


----------



## purrin

WARNING. THIS IS IN DIRECT OPPOSITION TO THE PHILOSOPHY OF NWAGUY AND HIS MASTER DOUG SELF 
   
http://www.passdiy.com/pdf/distortion_feedback.pdf


----------



## agdr

Quote: 





mrmateohead said:


> What the heck is "global feedback"???
> 
> What is "YMMV"?
> 
> Opps, someone beat me to the question. What is "Local Feedback"?


 
   
  Global feedback means feedback from the final output terminals of an amplifier back to the input, no matter how many amplifier stages (op amps or transistors or tube gain stages) are in the middle.  For example, in the schematic of AMB's b22 amplifier, R4 is a global feedback resistor.
   
  YMMV = Your Mileage May Vary 
	

	
	
		
		

		
			




   
  Local feedback means feedback from the output back to the input of just one single stage in an amplifier.  For example, if an amplifier has 3 op amps in a row, each one setup for a voltage gain of 2 times (so 2 x 2 x 2 = 8 times voltage gain total from end-to-end), feedback from the output of the 1st op amp stage back to it's input is local feedback just for that 1st stage. Feedback from the output of the 3rd op amp stage back to the input of the 1st would be global feedback in this case.


----------



## BleaK

Quote: 





smoke signals said:


> Does anyone have experience with the O2+ODAC combo and a pair of HE-500s?


 
   
  This is my main rig at the moment. With O2 in low gain. This is personally the best combo I have heard with the HE-500.
   
   
  Again, personally I don't get the craze about having alot of power to drive orthoes. I have owned the NFB-10SE which puts out 6W at 50ohm, and I still thought the ODAC/O2 combo sounded better.
   
  This my preference of course, and someone or many will surely don't agree with it, which is of course totally ok


----------



## HamilcarBarca

Quote: 





purrin said:


> WARNING. THIS IS IN DIRECT OPPOSITION TO THE PHILOSOPHY OF NWAGUY AND HIS MASTER DOUG SELF
> 
> http://www.passdiy.com/pdf/distortion_feedback.pdf


 
   
  Thanks for the warning. It's clear it simply marketing material to help sell Pass Labs equipment. It invents audiophile "extremes", and then uses the resulting strawmen to justify his $60,000+ equipment.
   
  Does his equipment sound good? Perhaps.
   
  Are his white papers any any more valid than AudioQuest's justification for its pure unobtainium wire? Not on its surface.


----------



## purrin

Actually the PassDIY stuff is his DIY stuff where you can get his schematics for free and build his designs. Lots of people on diyaudio.com have built his designs (or even tried to figure out the schematics of his new ones.) The Pass Labs is his commercial stuff which surprisingly isn't that expensive. No doubt he's very good at tooting his own horn. He's very well known after all. (I'm not endorsing his nor I do own any of his stuff.)
   
  No matter who writes what, one still needs to think for themselves, and its best is to experiment to validate various claims. The negative feedback arguments have been around since the dawn of audio reproduction. Here is another article, this time from Stereophile (I know - not exactly the best source) http://www.stereophile.com/reference/70/index.html. My own experiences with building some simple amps and messing around with circuits of tube amps mirrored that of the Stereophile writers' experience, although I feel I'm more in the middle ground and not in the ZERO feedback camp.
   
  Ultimately, I think you can take little bits from Doug Self and a little bits from Nelson Pass to use them for your one's own projects if one is so inclined to get his feet wet.


----------



## HamilcarBarca

Quote: 





purrin said:


> Actually the PassDIY stuff is his DIY stuff where you can get his schematics for free and build his designs. Lots of people on diyaudio.com have built his designs (or even tried to figure out the schematics of his new ones.)


 
   
  I missed that reference.
   
  While I'm not an EE, I find the technical discussions quite interesting. Thanks.


----------



## MrMateoHead

Quote: 





hamilcarbarca said:


> Thanks for the warning. It's clear it simply marketing material to help sell Pass Labs equipment. It invents audiophile "extremes", and then uses the resulting strawmen to justify his $60,000+ equipment.
> 
> Does his equipment sound good? Perhaps.
> 
> Are his white papers any any more valid than AudioQuest's justification for its pure unobtainium wire? Not on its surface.


 
  I looked at the paper. I got no idea why they are selling a 1-3 watt amp with upwards of 10% distortion and calling it clean.
   
  Likewise, it doesn't seem rational that you could "add distortion" to an amp to achieve insane signal to noise levels.
   
  I am no engineer but .. . . .


----------



## stv014

The error in that PDF file is that the "complex signals" are not normalized to a +/-1 Volt range, and they use a 3rd order polynomial for the distortion that gives increasing amount of distortion at higher input signal levels, so with nearly 5 Volts of peak voltage for the 7 tone signal (as opposed to just 1 Volt for the single sine wave), there is no surprise that the amount of distortion would be huge. Especially with the polynomial being applied four times in a row. For more realistic results the input signals should always have had a range of +/-1 Volt, and the distortion polynomial should have been scaled so that its output is also within the same range.
   
  To illustrate the above point, here are a few graphs:
   
  100 Hz sine wave with 1% 2nd order and 1% 3rd order distortion (y = (0.97*x + 0.02*x^2 + 0.04*x^3 - 0.01) / 1.02), the distortion is applied four times to simulate 4 amplifier stages (left channel is the input signal, right channel is the distortion residual):
    
  101, 173, 307, 523, 919, 1607, and 2801 Hz sine waves, each at 1 / 6.0142 amplitude (peaks within +/- 1), the distortion is the same as above:
    
  The same mix of sine waves, but with 1 / 2.5 amplitude for each tone (peak level = ~2.4):
    
   
  With an out of range signal, like in the PDF, the distortion increases by orders of magnitude. However, once the peak level is normalized, the distortion peaks are not higher than with the simple sine wave input. Of course, that is to be expected, since the distortion is frequency independent, and can be described with a simple polynomial with no "memory" of any previous input. So, the article in the PDF file is somewhat misleading.
   
  It is possible to test if an amplifier that uses negative feedback has unexpected high distortion when fed with a complex signal using null testing, and also double-blind listening tests. However, as far as I know, if the distortion+noise is low with _any_ sine wave input (at any level and frequency within the range the amplifier is intended to be able to handle, and with a wide bandwidth measurement), then it is expected to be low also with music.
   
  By the way, I recommend reading this article by Bruno Putzeys on negative feedback, if you have not already done so. It explains well the origin of some feedback myths, and also why they are wrong.


----------



## BleaK

Great post and article, thank you! 
  
  I am learning new things everyday. The more I read, the more I feel "drawn" to the objective camp.
   
  There are so many things that can influence psychoacoustics, but your gear shouldn't be one of them.


----------



## BleaK

On another note, looks like the O2 measure quite well against more expensive amps: http://www.innerfidelity.com/images/121105_blog_update_FirstAmpTests.pdf


----------



## adydula

I sold all my other amps, and have 2 O2's.
   
  One I built and one from JDS Labs.
   
  Went thru all the things being mentioned here and its a good discussion, but I am so glad that I discovered this little gem of an a amp and that it
  performs so well.
   
  I have gone back to the 'music' and playing around with different cans and recordings....
   
  Its a really amazing thing to have such a great performer run off of two 9v batteries for hours...no AC issues or problems.....gone.
   
  It works very, very well with 90+ percent of cans out there....
   
  Now back to the music!
   
  Alex


----------



## Bojamijams

JDS needs to do that Upside down ODAC+O2 with batteries... that would be the bomb AND allow it to be used as a mobile rig with Android devices feeding the ODAC


----------



## Cla55clown

Interesting read through the thread. One question albeit a little off topic: What happened to the OP; the turtle guy? I feel like I'm missing something.
   
  So the consensus is that this is a good amp/dac combo and well worth the money? Currently using a FiiO E10 with my PC and looking to upgrade to a full size desktop.


----------



## stv014

Quote: 





cla55clown said:


> What happened to the OP; the turtle guy?


 
   
  Changed name to "Lord Voldemort". More importantly, though, no one knows what happened to the designer of the O2 and ODAC.


----------



## purrin

Quote: 





bleak said:


> On another note, looks like the O2 measure quite well against more expensive amps: http://www.innerfidelity.com/images/121105_blog_update_FirstAmpTests.pdf


 
   
  I've taken a few measurements of the O2 and ODAC myself. The O2 does not simply measure "quite well". The O2 _destroys_ everything in terms measurements (distortion, noise, etc. as long as its not being pushed past its power capabilities). And will especially destroy anything of discrete design in terms of measurements.
   
  The only thing that might come close is a META42 or well built CMOY (the CMOY will have much less power obviously.)


----------



## BleaK

Quote: 





purrin said:


> I've taken a few measurements of the O2 and ODAC myself. The O2 does not simply measure "quite well". The O2 destroys everything in terms measurements (distortion, noise, etc. as long as its not being pushed past its power capabilities). And will especially destroy anything of discrete design in terms of measurements.


 

 That's really great to hear! Did you post or publish those measurements somewhere, I would love to see more amp measurement!
   
  Also, how did the ODAC measure compared to other DACs? If you did a comparison there as well?


----------



## purrin

I think I may have published a few on my site. Not sure. I know I did publish a few ODAC jitter and distortion measurements (probably buried in a thread somewhere). I do not have instrumentation quality gear (higher noise floor), bit the measurements did corroborate those on nwavguy's site.


----------



## imackler

Quote: 





purrin said:


> I've taken a few measurements of the O2 and ODAC myself. The O2 does not simply measure "quite well". The O2 _destroys_ everything in terms measurements (distortion, noise, etc. as long as its not being pushed past its power capabilities). And will especially destroy anything of discrete design in terms of measurements.


 
   
  This makes me want another one! 
   
  Can anyone confirm that with a higher power wall wart the O2 can operate on high gain without distortion with the HD650/HD600? I didn't experience it on every song but it was quite bad on a few and I don't listen at high volumes...


----------



## purrin

Quote: 





imackler said:


> This makes me want another one!
> 
> Can anyone confirm that with a higher power wall wart the O2 can operate on high gain without distortion with the HD650/HD600? I didn't experience it on every song but it was quite bad on a few and I don't listen at high volumes...


 
   
  Honestly, I wish nwavguy didn't put the pot in between the gain and current buffer stages, just for the sake of lowering the noise floor a few db.
   
  In theory, a higher voltage wall wart should help prevent clipping at the gain stage. What are you running as a DAC or source? Do you know how hot the outputs are? At what gain are you using the O2? Reducing the output of the source (if possible) and turning up the volume on the O2 should help. It definitely not a power issue. The O2 should have enough power to make you deaf or at least give you serious hearing damage with the HD600/HD650s.


----------



## stv014

Quote:  





> Can anyone confirm that with a higher power wall wart the O2 can operate on high gain without distortion with the HD650/HD600? I didn't experience it on every song but it was quite bad on a few and I don't listen at high volumes...


 
   
  The O2 has a regulated power supply, so even if you use a higher power wall wart, it will still be limited to about +/- 11.8 V. The gain stage can only handle peaks of about 10 V before it starts to clip (the op amp used does make a small difference here), and it is before the volume control. Since the ODAC can output ~2.8 V peaks (2 Vrms) at a full scale digital input, applying a gain of 6.5 would require the gain stage to be able to handle about 18 V peaks, and that is well above the limit. Since the volume control is after the gain stage, reducing the volume on the O2 does not fix the clipping. You have to either reduce the volume on the PC, or just use low gain.


----------



## imackler

Quote: 





purrin said:


> Honestly, I wish nwavguy didn't put the pot in between the gain and current buffer stages, just for the sake of lowering the noise floor a few db.
> 
> In theory, a higher voltage wall wart should help prevent clipping at the gain stage. What are you running as a DAC or source? Do you know how hot the outputs are? Reducing the output of the source (if possible) and turning up the volume on the O2 should help. It definitely not a power issue. The O2 should have enough power to make you deaf or at least give you serious hearing damage with the HD600/HD650s.


 
   
  Thanks for the response! 
   
  I was using the ODAC when I had the problems but never noticed when I used the line out from an ipod classic. Should the ipod classic be fine? When I used to use an ipod classic line out and O2 w/ HD600, I was happy with low gain and didn't have any distortion. I didn't have problems unless I put it into high gain. The dynamics with the HD650 seemed better on high gain but the distortion was pretty much a disaster. I guess I should have left it in low gain.


----------



## purrin

stv014 said:


> The O2 has a regulated power supply, so even if you use a higher power wall wart, it will still be limited to about +/- 11.8 V. The gain stage can only handle peaks of about 10 V before it starts to clip (the op amp used does make a small difference here), and it is before the volume control. Since the ODAC can output ~2.8 V peaks (2 Vrms) at a full scale digital input, applying a gain of 6.5 would require the gain stage to be able to handle about 18 V peaks, and that is well above the limit. Since the volume control is after the gain stage, reducing the volume on the O2 does not fix the clipping. You have to either reduce the volume on the PC, or just use low gain.


 

   
  Ah I forgot the regulation. Do you what the +/- PS rails are after the regulator? I forgot what the stock op-amp is in the O2. What do the spec-sheets say the op-amp can actually swing with the actual voltage on the rails?


----------



## Porter1

Quote: 





imackler said:


> This makes me want another one!
> 
> Can anyone confirm that with a higher power wall wart the O2 can operate on high gain without distortion with the HD650/HD600? I didn't experience it on every song but it was quite bad on a few and I don't listen at high volumes...


 

 i see you've gotten several answers above (this forum moves fast!), but this post by hekeli seems to explain why you were seeing distortion: http://www.head-fi.org/t/616331/o2-amp-odac/15#post_8523470
   
  i don't claim to fully understand the principles behind it, but seems like using the ODAC and the 6.5x gain on the O2 puts you over the limit for distortion.  also explains why you didn't see it with your ipod.


----------



## stv014

Quote: 





bleak said:


> Also, how did the ODAC measure compared to other DACs? If you did a comparison there as well?


 
   
stereophile.com has some measurements of various DACs (including currently popular ones like the AudioQuest DragonFly) made with an Audio Precision SYS2722 analyzer. They are not as detailed as those you can find at the ODAC designer's blog, but are worth having a look at.
  I have a relatively detailed set of measurements of the Xonar D1 sound card, which is fairly cheap, and the results are comparable to the ODAC. I did not use a professional audio analyzer, though, so do not expect great accuracy, but I did make efforts to avoid/minimize the hardware and software limitations and flaws of the typical RMAA tests you can find.
goldenears.net has DAC reviews and measurements, too, but they only use RMAA. They do have a table of output impedances for the headphone outputs of various devices, though.


----------



## sling5s

Quote: 





imackler said:


> Thanks for the response!
> 
> I was using the ODAC when I had the problems but never noticed when I used the line out from an ipod classic. Should the ipod classic be fine? When I used to use an ipod classic line out and O2 w/ HD600, I was happy with low gain and didn't have any distortion. I didn't have problems unless I put it into high gain. The dynamics with the HD650 seemed better on high gain but the distortion was pretty much a disaster. I guess I should have left it in low gain.


 
  To fix distortion, lower the pre-amp volume on your computer or source.  Just by a tad.  It works for me when I'm using high gain.  I don't know if it's just my imagination but I too think the LCD-2 sounds better with high gain.


----------



## stv014

Quote: 





purrin said:


> Ah I forgot the regulation. Do you what the +/- PS rails are after the regulator? I forgot what the stock op-amp is in the O2. What do the spec-sheets say the op-amp can actually swing with the actual voltage on the rails?


 
   
  I took the +/- 11.8 V figure from the "O2 Details" (listed under "Popular Posts") page of the designer. The O2 uses 12 V regulators, but the voltage is reduced slightly by the diodes that isolate the two sources of power supply (these are special low voltage diodes that drop less than the typical ~0.6 V), and the MOSFETs in the under-voltage protection circuit. The "Op Amp Measurements" page from August 2011 includes graphs that shows the THD+N vs. voltage performance of the gain stage with a few op amps (the stock one is NJM2068), both on battery and AC power, and at 2.5x and 7x gain. These can be used to find out what the exact clipping level is. Of course, the supply voltage will have a small amount of random variation.


----------



## purrin

OK. I'm measuring 23.3V peak-to-peak (consistent with +/- 11.65) at the power rails at the chip. (Just thinking out loud now - for my own sake and understanding - correct me if I've made any mistakes.) Lets be very conservative and say the op-amp can output 18V peak-to-peak with those rails. 2.0 Vrms = 2.82 peaks = 5.64 peak-to-peak.
   
  5.64 peak-to-peak * 6.5 gain = 36.66 p-p. (> 18 p-p) Oh boy. Not good.
  5.64 peak-to-peak * 2.5 gain = 14.1 p-p. (< 18 p-p) OK. No problem.
   
  Just curious. That explains lot and why I had several friends tell me why their O2s were clipping.


----------



## jcx

the outputs don't swing full current near the rails - the datasheet shows that they drop ~ 2V from each rail at 150 Ohms load +/-12 Vsupply (the O2 paralleled out could drive ~1/2 the Z but you also have to add the current sharing R drop)
   
  but it isn't unusual to have some more amp gain than that which just reaches the max output V at the fullscale source V but lots more gain does constitute poor system gain structure and you can be wasting potential dynamic range
   
  optimal use of DAC + fixed gain amp requires willingness to use software digital volume control, and knowledge of the target headphone V sensitivity


----------



## purrin

Wouldn't the load on the NJM2048 be negligible? The input Z for 4556 op-amps in the next stage should be in the k or M Ohm range? At least this was my assumption.
   
  Still, the pot in the middle arrangement is dumb - mainly because the amp's lack of portability has resulted with some people using it as a "desktop amp" fed directly from their PC line outs or desktop CD players - and the 6.5 gain won't work with, among all things, the ODAC (at least without digital volume control). And 2.5/6.5 gain is just barely enough for some headphones, especially since the O2 seems to have plenty of power / current capability to spare.


----------



## purrin

Quote: 





sling5s said:


> To fix distortion, lower the pre-amp volume on your computer or source.  Just by a tad.  It works for me when I'm using high gain.  I don't know if it's just my imagination but I too think the LCD-2 sounds better with high gain.


 
   
  What kind of voodoo is this? We all know subjective impressions are not reliable.


----------



## sling5s

Quote: 





purrin said:


> What kind of voodoo is this? We all know subjective impressions are not reliable.


 
  Yeah...I have very little knowledge when it comes to the science of music.  Sometimes I speak out of ignorance.  Please excuse. 
  But I do love the subjective experience of music


----------



## jcx

my numbers were for the output
   
  the NJM2068 looks like it is limited in negative output swing to just past -10 V with +/-12 Vsupply even with negligible load


----------



## mikeaj

Quote: 





purrin said:


> OK. I'm measuring 23.3V peak-to-peak (consistent with +/- 11.65) at the power rails at the chip. (Just thinking out loud now - for my own sake and understanding - correct me if I've made any mistakes.) Lets be very conservative and say the op-amp can output 18V peak-to-peak with those rails. 2.0 Vrms = 2.82 peaks = 5.64 peak-to-peak.
> 
> 5.64 peak-to-peak * 6.5 gain = 36.66 p-p. (> 18 p-p) Oh boy. Not good.
> 5.64 peak-to-peak * 2.5 gain = 14.1 p-p. (< 18 p-p) OK. No problem.
> ...


 

  (for NJM2048)
   
  so looks like the negative side clips first, won't get more than -10V there, so +10V on the top gives you 20V peak-to-peak, around 7.07V rms (sine wave).  Any more, and the gain stage will clip.  18V peak-to-peak was a pretty decent estimate, conservative as you said.  edit: whoops jcx just a couple minutes before I responded
   
  I wonder what's the percentage of users feeding roughly RedBook 2V rms sources, as opposed to portable devices or something that could actually use the 6.5X gain without clipping.  That said, Epiphany configured it as 1X / 2.5X by default, and hopefully any DIY builder knows what's up... it's still a hassle though.
   
   



sling5s said:


> Yeah...I have very little knowledge when it comes to the science of music.  Sometimes I speak out of ignorance.  Please excuse.
> But I do love the subjective experience of music


 

   
  Just a friendly reminder, but sometimes you may need to reboot the sarcasm detector.


----------



## purrin

Quote: 





sling5s said:


> Yeah...I have very little knowledge when it comes to the science of music.  Sometimes I speak out of ignorance.  Please excuse.
> But I do love the subjective experience of music


 
   
  I was being sarcastic. Long story if you don't know where the sarcasm comes from.
   
   


mikeaj said:


> That said, Epiphany configured it as 1X / 2.5X by default, and hopefully any DIY builder knows what's up... it's still a hassle though.


 

   
  You would have figured they all came configured like that or similarly. I just noticed the JDS labs version comes in 2.5x/6.5x by default.


----------



## USAudio

.


----------



## agdr

Quote: 





mikeaj said:


> I wonder what's the percentage of users feeding roughly RedBook 2V rms sources, as opposed to portable devices or something that could actually use the 6.5X gain without clipping.  That said, Epiphany configured it as 1X / 2.5X by default, and hopefully any DIY builder knows what's up... it's still a hassle though.


 
   
  Keep in mind that you can always attenuate (make smaller) the input signal if 1x gain is even too much to prevent the first O2 stage from clipping.  Just make R3 and R7 bigger so they form voltage dividers with R20 and R14, respectively, such as 5K resistors.  Has the side benefit of increasing the O2 input impedance.
   
  I tried to talk "Voldemort" into including a first-stage clipping indicator circuit last year with no luck (plus no PCB space left on the O2 to add circuitry in the B2-080 sized box).  Without that a person really has no way of knowing when clipping on either rail is occurring, at least until the clipping gets bad enough to be clearly audible.   A lot of faith is put into the user's ability to know exactly what their source voltage level is, then be able to do the math with the O2 first stage gain settings to not exceed the 7V (rms) maximum swing.


----------



## Smoke Signals

Quote: 





bleak said:


> This is my main rig at the moment. With O2 in low gain. This is personally the best combo I have heard with the HE-500.
> 
> 
> Again, personally I don't get the craze about having alot of power to drive orthoes. I have owned the NFB-10SE which puts out 6W at 50ohm, and I still thought the ODAC/O2 combo sounded better.
> ...


 
   
  What is your low gain setting? 2.5x or 3.0x etc.
   
  Also, how far do you have to turn the volume knob to get it to be too loud?
   
  Thanks.


----------



## BleaK

Quote: 





smoke signals said:


> What is your low gain setting? 2.5x or 3.0x etc.
> 
> Also, how far do you have to turn the volume knob to get it to be too loud?
> 
> Thanks.


 

 I have the standard 2.5x.
   
  At two/three O'clock my ears can't take it anymore. My normal listenig volume is around 10/11. This is with every volume (windows and foobar) on max.


----------



## Smoke Signals

Great, it seems like the O2 on the standard low gain easily handles them then.  Thanks for the valuable info, probably going to pick up a pair soon now.


----------



## Lobe

I hope you guys (who seem a lot more knowledgable than me) could give some advice. I purchased an odac and o2 (separate units) from JDS labs, however between when I ordered and it arrived, I impulse bought an awesome Woo Audio 6 tube amp. So now I am using the odac and wa6 and the o2 is doing nothing, so I want to get a new dac to pair with the o2 for my desktop pc. If I were to get a dac other than the odac, what are some of the best options around the same price range? what about the same performance range?

 The odac seems fantastic from my use so far, but I don't want to buy another one unless it is by far the best option as I would like to try new hardware out.


----------



## Dragunov-21

Question - I've got the integrated O2/ODAC combo.  Is there any way to use it as a pure DAC?  I tried the headphone out while the player was turned off and got nothing, but I'd have thought they'd include the option if it were physically possible (and there's no reason they couldn't include a line out, right?
   
  If not, it wouldn't be too hard to install a line-out socket, would it?


----------



## stv014

Quote: 





dragunov-21 said:


> Question - I've got the integrated O2/ODAC combo.  Is there any way to use it as a pure DAC?  I tried the headphone out while the player was turned off and got nothing, but I'd have thought they'd include the option if it were physically possible (and there's no reason they couldn't include a line out, right?
> 
> If not, it wouldn't be too hard to install a line-out socket, would it?


 
   
  Unless you have some special custom version, there is no line output. It is possible to add one, or modify how the line input jack is wired so that it becomes a line output instead; check a DIY forum (here, or even better at diyaudio.com) for help if needed. If you are not too worried about "double amping", and you have a 1x gain setting (if not, then it can be created by clipping two resistors), you could also just use the headphone output at maximum volume; the quality difference is minor, and probably inaudible.


----------



## purrin

Quote: 





lobe said:


> I hope you guys (who seem a lot more knowledgable than me) could give some advice. I purchased an odac and o2 (separate units) from JDS labs, however between when I ordered and it arrived, I impulse bought an awesome Woo Audio 6 tube amp. So now I am using the odac and wa6 and the o2 is doing nothing, so I want to get a new dac to pair with the o2 for my desktop pc. If I were to get a dac other than the odac, what are some of the best options around the same price range? what about the same performance range?
> 
> The odac seems fantastic from my use so far, but I don't want to buy another one unless it is by far the best option as I would like to try new hardware out.


 
   
  The ODAC is hard to beat at the price. < $500 (or even a little more) is kind of a no-man's land in terms of DACs. Lots DACs in that price range sound muffled, strange, suffer from extreme digititus, or have some kind of flaw which makes them unlistenable. The only one I could think of is maybe the AMB Gamma2. It's not as resolving as the ODAC, but more impactful and dynamic. Unfortunately, it's cheap only if you can DIY. And even if you can DIY, it's a serious pain to build because of the surface mount chips with tiny pins.


----------



## adydula

purrin,
   
  How come you can get away with stating that the ODAC is hard to beat at the price??
   
  Which I whole heartedly agree....
   
  When I state this the hate mail comes in and I get creamed for stating this....
   
  Must be your cat pix....lol
   
  Alex


----------



## HamilcarBarca

Quote: 





adydula said:


> purrin,
> 
> How come you can get away with stating that the ODAC is hard to beat at the price??
> 
> ...


 
   
  Never mind the ODAC! Let's see more cat pix!!


----------



## MrMateoHead

Quote: 





smoke signals said:


> What is your low gain setting? 2.5x or 3.0x etc.
> 
> Also, how far do you have to turn the volume knob to get it to be too loud?
> 
> Thanks.


 

 Feel like I should chime in here -
   
  I can't speak for those relying on a standard 2V output source (like the ODAC or some fancy CD player), but on a "lower quality" source like a cell phone, computer, or Mp3 player, not only is the 2.5X gain good, but the 6.5x is even better.
   
  I can't clip mine off a laptop @6.5X on a music DVD or a movie, so I assume I would need more source voltage to do so. Also, under those circumstances the extra volume is much appreciated.
   
  I would prefer to have a 1X, 2.5X, and 6.5X if possible. Better yet, a variable gain.
   
  On music, crazy time is 12 O'clock with my HE-400s. With my Senns, a bit lower. I am usually listening at what would look like about 7-9 O'clock, which is probably a 1/4th to a 1/3rd.


----------



## Lobe

Quote: 





purrin said:


> The ODAC is hard to beat at the price. < $500 (or even a little more) is kind of a no-man's land in terms of DACs. Lots DACs in that price range sound muffled, strange, suffer from extreme digititus, or have some kind of flaw which makes them unlistenable. The only one I could think of is maybe the AMB Gamma2. It's not as resolving as the ODAC, but more impactful and dynamic. Unfortunately, it's cheap only if you can DIY. And even if you can DIY, it's a serious pain to build because of the surface mount chips with tiny pins.


 
  OK, thanks for this. I had a look at the Gamma1 and Gamma2 a bit before you posted this, and was considering taking it on as a project, but by the sounds of things I'd be best to start my foray into DIY territory with an easier project. With what you have said, it seems like the ODAC is the other option, as I'm not ready to pay close to $1000 for a serious dac yet. That's not a bad thing, I am really pleased with mine.


----------



## HamilcarBarca

Quote:  





> The ODAC is hard to beat at the price. < $500 (or even a little more) is kind of a no-man's land in terms of DACs. Lots DACs in that price range sound muffled, strange, suffer from extreme digititus, or have some kind of flaw which makes them unlistenable. The only one I could think of is maybe the AMB Gamma2. It's not as resolving as the ODAC, but more impactful and dynamic. Unfortunately, it's cheap only if you can DIY. And even if you can DIY, it's a serious pain to build because of the surface mount chips with tiny pins.


 
   
  The ODAC, unlike the O2, isn't available as a kit, only as a finished circuit board.
   
  Quoting the designer of the ODAC and O2 [emphasis in original]: 





> *[size=12.800000190734863px]CAN I BUILD MY OWN ODAC?[/size]*[size=12.800000190734863px] Unfortunately no. The ODAC will be offered only as an assembled board.[/size]
> 
> *[size=12.800000190734863px]WHERE IS THE SCHEMATIC & PARTS LIST?[/size]*[size=12.800000190734863px] ... [T]here are no DIY-friendly 24 bit USB audio chips that meet the design criteria. So we’re forced to use components licensed for OEM use that are not available through normal distribution[/size]


----------



## purrin

Quote: 





adydula said:


> purrin,
> 
> How come you can get away with stating that the ODAC is hard to beat at the price??
> 
> ...


 
   
  LOL. I've been creamed in the past for saying the ODAC or O2 don't sound as good as some select pieces of more expensive equipment, even while acknowledging they (O2/ODAC) are hard to beat, and pointing out diminishing returns of the more expensive equipment.
   
  I think another reason is that the more dogmatic ***-hats have been banned from HF.


----------



## proton007

Quote: 





purrin said:


> LOL. I've been creamed in the past for saying the ODAC or O2 don't sound as good as some select pieces of more expensive equipment, even while acknowledging they (O2/ODAC) are hard to beat, and pointing out diminishing returns of the more expensive equipment.
> 
> I think another reason is that the more dogmatic ***-hats have been banned from HF.


 

 I also think its a matter of point of view. For those who don't have an open budget, it always makes sense to drop that extra 50 on a headphone rather than a DAC.


----------



## Agavehound

I ordered the 02/ODAC combo last Thursday and it shipped the same day. That was five days ago and it was delivered today. All I can say is WHOA! Is that what I've been missing all these years?
   
  My setup before the arrival of the 02/ODAC was a simple desktop setup with a Creative Titanium HD feeding my Sen 598s. I thought it sounded pretty good but it wasn't as good as I hoped it would be. And listening to music straight out of my laptop left a LOT to be desired. So I started to read for possible upgrades and just about everything I read said the 598s don't need amplification and the Titanium HD was pretty decent in the music department. So I started to think that perhaps I needed to spend some big bucks to make an upgrade that was worth the money. The one component I could start with that would have immediate returns was a DAC or DAC/AMP combo for use with my laptop and work pc. I originally thought that an E17 would be the way to go, but somehow it didn't seem like much of an upgrade, especially if I later decided to upgrade the cans. Then I started to read about the 02/ODAC and it seemed like a decent upgrade plus it would be usable when I decided to upgrade my headphones. So I ordered the combo unit and I'm glad I did.
   
  The difference in sound with the 02/ODAC feeding my 598s is a huge improvement over the Titanium HD. My first thought when I fired the 02combo up was that there was more emphasis on the highs. Then I fired up Bohemian Rhapsody. I am hearing a definition and clarity that wasn't there before with the Titanium HD and it's not just the mids/highs but across the entire spectrum. Not only that but everything seems, um, sharper I guess. The sound doesn't sound muddy or blended together and what I'm hearing now are clear notes that are distinct from each other and not overpowering in any way. Very balanced. Now I'm listening to AC/DC Squealer and loving every second of the guitar riffs.
   
  I don't know what made the bigger difference, the DAC or the AMP, but whatever it is, it is totally worth it.  I may even hold off on upgrading my cans now, maybe not...


----------



## mikeaj

Normally I think people make too big a deal of output impedance, but I wonder how much can be attributed to output impedance and damping factor this time around...
   
  Out of all headphones (not IEMs), modern Senn HD 5xx series seems like it is one of the most sensitive to these things.  They say about 50 ohms nominal, but it rises to over 250 ohms.  The ~36 ohms output impedance of the Titanium HD (according to goldenears) causes a ~3.3 dB boost to around 100 Hz with these headphones, quickly sloping off in higher and lower frequencies.  I mean, 3.3 dB is not a lot, but it's not a little either.  Damping factor around 1.5?  Maybe an issue actually?
   
  So I'm not sure how much I'd attribute to O2/ODAC.  Maybe something else would've worked too.  But enjoy what you have, anyway.


----------



## Currawong

Quote: 





purrin said:


> Quote:
> 
> 
> 
> ...


 
   
  I agree with what you guys say. I pinched a friend's ODAC while we were in Tokyo for a while so I could give it a run. On sonic merit alone (ignoring everything else) the ODAC + O2 combo is great. The closest I've come across would be the Dragonfly or Audio-gd NFB-16 (not currently available) which are, respectively, a little flatter and a little-less-clear-but-more-musical sounding.
   
  Some observations:
   
  The ODAC isn't the first to use the output straight from the DA chip. The Metrum Octave does the same trick. The downside of this is that it depends on the amp used having a good input stage. Likewise, the ODAC sounds better with better power feeding it. The slight harshness in the sound disappears if I plug it into my Vaunix USB hub (designed for their lab-use signal generators). If I then feed the output into my Phoenix, which makes most DACs sound excellent, I could just about fool myself into thinking I'm listening to my main DAC + digital accessories.  Other amps I've tried don't fare as well. The ODAC and O2 were designed for each other, so, not surprisingly, work perfectly together.
   
  The O2 doesn't seem to deliver the dynamics of music as well as much more expensive amps, so the overall O2/ODAC combination sounds a little flat in comparison but does a lot better than quite a few more expensive amps. I'd rather listen with the combo than a lot of other gear I've had pass through here that didn't impress as much, but cost a lot more.


----------



## mikeaj

I don't know, is "output straight from the DA chip" kind of misleading?  Or more relevantly, I'm not so sure about dependence on the amp input stage.
   
  Specs on ES9023 are not publicly available, but the literature that's out there calls it a "24-bit stereo audio DAC with integrated 2Vrms op-amp driver."  If there's a trick involved, it's Sabre putting op amps in the DAC IC package.  Do you really consider it to be different than a DAC with an op amp line driver in a separate package?  Lots of ICs these days have many integrated components and functionality though.  That's the name of the game now.


----------



## stv014

Quote:  





> I don't know what made the bigger difference, the DAC or the AMP, but whatever it is, it is totally worth it.


 
   
  I do not think it is the DAC, unless it is poorly implemented on the Titanium HD (the parts used by themselves would allow for excellent performance), but I doubt that is the case. As already explained by mikeaj, the O2 likely made a difference, headphone support is not something sound card manufacturers usually pay much attention to. Also, check that there is no unwanted DSP (EQ, reverb, etc.) enabled on the Sound Blaster, and that you listen to both devices at matched volume (this can actually only be guaranteed with measurements), for a fair comparison.
   
  Quote:  





> I may even hold off on upgrading my cans now, maybe not...


 
   
  Headphones make the most difference to the sound, but it is not easy to find the best ones for your personal preferences.


----------



## Stratok

Hey I have SigDJs and I'd like to get a good dac + amp combo. Could someone tell me if its a good match? I'm not sure what I should check except amp output impedance which seems to be fine if I'm not completely lost


----------



## HamilcarBarca

Quote: 





stratok said:


> Hey I have SigDJs and I'd like to get a good dac + amp combo. Could someone tell me if its a good match? I'm not sure what I should check except amp output impedance which seems to be fine if I'm not completely lost


 
   
  What's a SigDJ?
   
  Unless there's something very unusual about them, the ODAC+O2 combo will work just fine.


----------



## Stratok

Quote: 





hamilcarbarca said:


> What's a SigDJ?
> 
> Unless there's something very unusual about them, the ODAC+O2 combo will work just fine.


 

 Ultrasone Signature DJ sorry.


----------



## cubusmybro

Don't want to start a new thread so I thought I will post here. I bought an O2+ODAC yesterday and I am looking to buy some headphones to use with it. Originally I was thinking of buying the ATH-M50 for $109, but I heard amping it wouldn't do much and if I get something more expensive I could really unlock the full potential of the amp.
If I get something under $300 I will be able to buy the headphones by Christmas. If I wait I can get something up to $400 but not over. I have seen a lot of talk about the HE-400 and it looks pretty sweet. The only thing is that is was designed to not need an amp.
With a nice amp and DAC I think I could drive quite a few sensitive headphones quite easily.

$300 or less would be great but waiting after Christmas for the HE-400 makes a substantial difference I will wait.

If anyone could weigh in it would be great.


----------



## sling5s

Quote: 





currawong said:


> I agree with what you guys say. I pinched a friend's ODAC while we were in Tokyo for a while so I could give it a run. On sonic merit alone (ignoring everything else) the ODAC + O2 combo is great. The closest I've come across would be the Dragonfly or Audio-gd NFB-16 (not currently available) which are, respectively, a little flatter and a little-less-clear-but-more-musical sounding.
> 
> Some observations:
> 
> ...


 
  Really agree. In the category of transparent and flat, it performs way beyond it's price point.     But I wish the O2 was a little more dynamic and musical.  Sometimes it's just little too flat and sterile with my headphones.


----------



## Dragunov-21

Quote: 





cubusmybro said:


> Don't want to start a new thread so I thought I will post here. I bought an O2+ODAC yesterday and I am looking to buy some headphones to use with it. Originally I was thinking of buying the ATH-M50 for $109, but I heard amping it wouldn't do much and if I get something more expensive I could really unlock the full potential of the amp.
> If I get something under $300 I will be able to buy the headphones by Christmas. If I wait I can get something up to $400 but not over. I have seen a lot of talk about the HE-400 and it looks pretty sweet. The only thing is that is was designed to not need an amp.
> With a nice amp and DAC I think I could drive quite a few sensitive headphones quite easily.
> $300 or less would be great but waiting after Christmas for the HE-400 makes a substantial difference I will wait.
> If anyone could weigh in it would be great.


 
   
  What?  You bought an amp and want to buy _'phones_ to match _it_?  Why?
   
  A bit like saying you have a tank full of hi-octane fuel and now you're looking to buy a highly-tuned car to unlock its potential...
   
  As an aside, sensitive phones generally benefit _less_ from amping.  Having an amp will allow you to drive higher-impedance phones, as a rule.  What sort of sound signature do you like, anyway?  You'll also want to make sure you're using decent source material (FLAC, IMO, or at the very least 320kb/s MP3)


----------



## Smoke Signals

Does anyone know how many watts the O2 can push at around 32 ohms?


----------



## mikeaj

Quote: 





smoke signals said:


> Does anyone know how many watts the O2 can push at around 32 ohms?


 
   
  Approximately up to 0.6W on AC power, 0.5W on batteries (half-full charge), per channel.  Listed measurement is 613 mW into 33 ohms on AC and 534 mW into 33 ohms on batteries at 1% THD—with a sharp knee, so under 0.01% until just before that point.


----------



## cubusmybro

Yea I know. I work a little backwards 
I have 1000GB of FLAC so source is not an issue. Most of my music is 70's rock and roll but I played in a jazz band so I enjoy and listen to a lot of 40-70 music too. 
I want to have good imaging with a substantial amount of bass, but I am not a basshead. After some reading I have heard these opinions:

AKG K701: Very detailed but too little bass. Good imaging.
AKG Q701: Detailed with slightly more bass than the previous.
HE-400: Very good sounding and bass, but forward. Sounds fun but not as "realistic".
DT 770 PRO: Good price for value. High and mids are good. A lot of bass, maybe even too much.
HD650: Out of my price range.


----------



## Smoke Signals

Quote: 





mikeaj said:


> Approximately up to 0.6W on AC power, 0.5W on batteries (half-full charge), per channel.


 
  Hmm, so it falls very short in delivering 1 W per channel, man I'm getting a lot of mixed message about the O2 + HE-500.  Some are saying the O2 won't power it and it gives poor dynamics and others are saying it works fine and delivers plenty of power.  This is pretty frustrating.


----------



## sling5s

Quote: 





smoke signals said:


> Hmm, so it falls very short in delivering 1 W per channel, man I'm getting a lot of mixed message about the O2 + HE-500.  Some are saying the O2 won't power it and it gives poor dynamics and others are saying it works fine and delivers plenty of power.  This is pretty frustrating.


 
  I think the mixed message comes from that: the O2 has enough power to give it all the volume you need.  But it does not have the power to give it the headroom and dynamics.


----------



## MHOE

Quote: 





sling5s said:


> I think the mixed message comes from that: the O2 has enough power to give it all the volume you need.  But it does not have the power to give it the headroom and dynamics.


 
   
  Go to his blog, find "O2 summary" article and search for "LCD-2" or "Hifiman"...
   
  O2 is powerful enough to drive LCD-2, HE-500 and even HE-6 (according to nwavguy). Especially if you use SIPs that allow you to change gain resistors to fit your needs better. Of course DO NOT USE BATTERIES FOR POWERING HERE...


----------



## Steelbarrage

HE 400 is definitely worth the extra cash.
  HE 400 does need to be amped no matter what people say.
  I am listening to my pair right now on a Fiio E7 and it doesn't really cut it.
  I am looking to get an O2/ODAC over Christmas unless someone special rises from the grave and mentions the ODA.
  If you can wait and spare the cash I would definitely jump on the HE 400 bandwagon.


----------



## MrMateoHead

Quote: 





cubusmybro said:


> With a nice amp and DAC I think I could drive quite a few sensitive headphones quite easily.
> $300 or less would be great but waiting after Christmas for the HE-400 makes a substantial difference I will wait.
> If anyone could weigh in it would be great.


 
  Dude -
   
  Get the HE-400s + Velour pads and don't look back. They are truly awesome.
   
  I use mine with an O2. It is true they don't "need" an amp, but I promise they will love you for having one. The O2 will drive them loud and hard.
   
  In terms of SPL / Volume, I got my O2 with the stock 2.5X gain and 6.5X gain. More than enough for my music, and plenty for movies / music DVDs and the like. Because the O2 can do a solid half-watt (and I estimated 700 mWs plugged in @ 50 Ohms), you would need a full watt for the next 3 dB in SPL, 2 watts for 3 more, etc. In short, you won't find more (clean) power for that sort of price. Major diminishing returns after that first half-a-watt.
   
  If you decide to get some highly efficient headphones, you may be pissed you got the amp (if gain settings aren't like, 1X and 2.5X). You can barely twist the knob before threatening to blow up some phones.


----------



## cubusmybro

I think that's what I'll do but I just saw another set of headphones, the *Beyerdynamic DT 880 Premium 600 OHM *and with the O2+ODAC it looks like these will really shine. Do you still think the HE-400 will be the best bet?
[size=1.7em]  [/size]


----------



## MrMateoHead

Quote: 





smoke signals said:


> Hmm, so it falls very short in delivering 1 W per channel, man I'm getting a lot of mixed message about the O2 + HE-500.  Some are saying the O2 won't power it and it gives poor dynamics and others are saying it works fine and delivers plenty of power.  This is pretty frustrating.


 

 See my other post. Lets pretend you have headphone which can do 90 dB @ 1 mW. You have to double the power each time to gain another 3 dBs. By the time you apply a half a watt (500 mWs), you are theoretically hitting 117 dB. You should be in pain at that point, or otherwise unwilling to listen very long. At that point, 1 W is only taking you to 120 dB. 2Ws to 123 dB, and so on.
   
  So, "falling very short of 1 W" is NOT a problem, unless your source is utterly "quiet" or has ridiculously high dynamic range. In that case, you will need a lot of power just to supply the peak bursts of sound that are there.
   
  That said, even listening to Chopin, I don't need more than half a dial to experience the raging crescendos and baby-to-sleep key strokes. Trust me, I sweated the numbers myself. Then I got over it. The O2 provides a ton of power compared to the USB devices, you will have to spend a lot more to get to 1W and beyond.


----------



## Smoke Signals

Quote: 





mhoe said:


> Go to his blog, find "O2 summary" article and search for "LCD-2" or "Hifiman"...
> 
> O2 is powerful enough to drive LCD-2, HE-500 and even HE-6 (according to nwavguy). Especially if you use SIPs that allow you to change gain resistors to fit your needs better. Of course DO NOT USE BATTERIES FOR POWERING HERE...


 

 In his article he only says "Hifiman planars", so I can't be certain he is including HE-500s in that.
   
  Edit: Ok thanks Mrmateohead, that's some good info.


----------



## HamilcarBarca

Quote: 





sling5s said:


> Quote:
> 
> 
> 
> ...


 
   
  Of course it does. The mixed message is due to misunderstandings of how amplifiers work.  It delivers clean power, headroom, dynamics, soundstage, you name it.


----------



## proton007

If you're using the ODAC its better because the ODAC itself provides 2V RMS. 
  I use the combo with my HD650, and I don't even need to use the gain.


----------



## miceblue

Quote: 





proton007 said:


> If you're using the ODAC its better because the ODAC itself provides 2V RMS.
> I use the combo with my HD650, and I don't even need to use the gain.


 

 Speaking of gain, new ODAC/O2 user here, what gain settings do people have?
  Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.


----------



## proton007

Quote: 





miceblue said:


> Speaking of gain, new ODAC/O2 user here, what gain settings do people have?
> Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.


 
   
  I made mine myself, I think I have the 1.0x and 10x. I used the sockets in order to change the resistors, but haven't really used the gain.


----------



## MHOE

Quote: 





miceblue said:


> Speaking of gain, new ODAC/O2 user here, what gain settings do people have?
> Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.


 
   
  Use SIPs, you can have whatever gain you want up to 12x... Enough for powering pretty much everything. You can change gain resistors anytime this way to let the amp work for you the best. But I would get WAU 16-400 transformer instead of WAU12-200 that is normally supplied by JDS Labs, especially for Hifimans, Audeze and other low impedance phones etc.
   
If you want more info about how to find out the most suitable gain, read author's blog... There are hints as well as mathematic formulas. If you do not want to calculate anything, I suggest "*THE GAIN RESISTORS" section of O2 details article and/or All about gain article ("A rough guideline" section).*


----------



## HamilcarBarca

Quote: 





miceblue said:


> Quote:
> 
> 
> 
> ...


 
   
  I have the standard 2.5/6.5 dB gain. If I bought another, I'd get the 1.0/2.5 dB option. I tend to listen at low volumes and 6.5 dB gain is WAY more than I need.


----------



## MrMateoHead

Quote: 





miceblue said:


> Speaking of gain, new ODAC/O2 user here, what gain settings do people have?
> Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.


 

 I think those settings would work well. I am at 2.5x and 6.5x, but my understanding is that the amp shouldn't clip unless you feed it 2Vrms and crank it @ 6.5X gain. Can anyone confirm?
   
  With more efficient headphones, 1X should be ideal. For less efficient phones like mine (94dB) the 2.5X is working great, though I could probably get by on 1X. I've only used 6.5X so far on a movie screening test, and in that case it was useful. Chances are, 1X - 2.5X is going to cover a very wide range of phones'. 10X sounds too high to me for practical purposes, but 6.5X is about right to cover all my "non music" needs.


----------



## MHOE

Quote: 





mrmateohead said:


> I think those settings would work well. I am at 2.5x and 6.5x, but my understanding is that the amp shouldn't clip unless you feed it 2Vrms and crank it @ 6.5X gain. Can anyone confirm?
> 
> With more efficient headphones, 1X should be ideal. For less efficient phones like mine (94dB) the 2.5X is working great, though I could probably get by on 1X. I've only used 6.5X so far on a movie screening test, and in that case it was useful. Chances are, 1X - 2.5X is going to cover a very wide range of phones'. 10X sounds too high to me for practical purposes, but 6.5X is about right to cover all my "non music" needs.


 
   
  It can possibly clip when using the amp on battery power under certain conditions... Not skilled enough technically to answer though. I think the best source for answering your question is the blog


----------



## proton007

Quote: 





mrmateohead said:


> I think those settings would work well. I am at 2.5x and 6.5x, but my understanding is that the amp shouldn't clip unless you feed it 2Vrms and crank it @ 6.5X gain. Can anyone confirm?
> 
> With more efficient headphones, 1X should be ideal. For less efficient phones like mine (94dB) the 2.5X is working great, though I could probably get by on 1X. I've only used 6.5X so far on a movie screening test, and in that case it was useful. Chances are, 1X - 2.5X is going to cover a very wide range of phones'. 10X sounds too high to me for practical purposes, but 6.5X is about right to cover all my "non music" needs.


 
   
  With 2V RMS I haven't felt the need to use the gain at all. I don't even max out the 1x. I think I'd kept 10x for sources that don't have a line out. Then I felt I should change it, but now I don't really use it anyways.


----------



## miceblue

Ah, mmk thanks for the feedback guys.  I'm still new to the whole O2/ODAC objective stuff.
  With the 2.5/1.0 gain option, I do notice a background hiss, or some high frequency noise with the 2.5 gain (while using an AC adaptor). Is this normal, because I recall seeing many people say that this amp has a very "black background" sort to speak?


----------



## proton007

Quote: 





miceblue said:


> Ah, mmk thanks for the feedback guys.  I'm still new to the whole O2/ODAC objective stuff.
> With the 2.5/1.0 gain option, I do notice a background hiss, or some high frequency noise with the 2.5 gain (while using an AC adaptor). Is this normal, because I recall seeing many people say that this amp has a very "black background" sort to speak?


 

 There shouldn't be any noise.
  Is it present without the audio signal as well?


----------



## miceblue

Quote: 





proton007 said:


> There shouldn't be any noise.
> Is it present without the audio signal as well?


 
  Yeah that's what I thought. Yes I hear it even with no audio signal.
  On 1.0x gain, I hear nothing, which is what I expect. On the 2.5x gain, I get that kind of background hiss that one would hear with a portable media player and IEM's. It's subtle, but I can definitely tell the difference between the 1.0x and the 2.5x gains.
   
  I don't think it was my desoldering job...the circuit looked pretty clean when I took out the resistors.
   
   
  This happens on multiple computers. And actually, with the O2/ODAC, I discovered that one of my USB ports on my MacBook is dying because the audio produced from that particular port is all distorted like one would find in a horror movie. Switching USB ports fixes this issue. XD


----------



## Currawong

Quote: 





mikeaj said:


> I don't know, is "output straight from the DA chip" kind of misleading?  Or more relevantly, I'm not so sure about dependence on the amp input stage.
> 
> Specs on ES9023 are not publicly available, but the literature that's out there calls it a "24-bit stereo audio DAC with integrated 2Vrms op-amp driver."  If there's a trick involved, it's Sabre putting op amps in the DAC IC package.  Do you really consider it to be different than a DAC with an op amp line driver in a separate package?  Lots of ICs these days have many integrated components and functionality though.  That's the name of the game now.


 
   
  Ahh, thanks for that. I hadn't read the info for that particular chip. Makes a lot of sense now.


----------



## MHOE

Quote: 





miceblue said:


> Yeah that's what I thought. Yes I hear it even with no audio signal.
> On 1.0x gain, I hear nothing, which is what I expect. On the 2.5x gain, I get that kind of background hiss that one would hear with a portable media player and IEM's. It's subtle, but I can definitely tell the difference between the 1.0x and the 2.5x gains.
> 
> I don't think it was my desoldering job...the circuit looked pretty clean when I took out the resistors.
> ...


 
   
  When using 1.0x, you are not amplifying anything... That's the reason you do not hear any sort of unwanted artifacts.
  I have tried to experiment and also noticed a very low level hiss when using too strong gain with sensitive phones. Like 2.5x with headphones that needs 1x in reality... You should use the lowest gain needed from several reasons mentioned on the author's blog, one being audible distortion with non-ideal gain.


----------



## HamilcarBarca

Quote: 





miceblue said:


> Ah, mmk thanks for the feedback guys.  I'm still new to the whole O2/ODAC objective stuff.
> With the 2.5/1.0 gain option, I do notice a background hiss, or some high frequency noise with the 2.5 gain (while using an AC adaptor). Is this normal, because I recall seeing many people say that this amp has a very "black background" sort to speak?


 
   
  No, a hissing noise means there's definitely something wrong with the setup.


----------



## MHOE

Quote: 





hamilcarbarca said:


> No, a hissing noise means there's definitely something wrong with the setup.


 
   
  Yes, this is possible as well... But I don't hear any hiss if using *suitable gain* even though I push the volume knob near to the max. Unfortunately every setup is going to behave a bit differently...


----------



## adydula

I use several DAC's one has a 2.25 volt output and am using the standard gain settings from JDS Labs. the 2.5 and the 6.5. I never really use the 6.5 setting. No Need with the dacs and source I use...PC USB to DAC to the Amp.
   
  Both of the O2's I have, one i built and the other pre-built are dead silent on both gains settings with no input and volume all the way up.
   
  As far as the dynamics and not having enough power.....well the designer did state the O2 amp will drive 98% of all the cans out there....maybe we should list those in that 2%?
   
  I had several can amps and one was a 6 watt and I sold it after listening to the O2's...no real issue with dynamics here with LCD2's, AKG's and Grados...
   
  Best little amp money can buy!
   
  Alex


----------



## HamilcarBarca

Quote: 





mhoe said:


> Quote:
> 
> 
> 
> ...


 
   
  It's broken if there's hiss at any gain.


----------



## MHOE

Quote: 





hamilcarbarca said:


> It's broken if there's hiss at any gain.


 
   
  No, it's not necessarily true... Hiss can always be transferred from your computer via USB cable (less probably but still I would suggest to use Fidelizer to improve the computer's environment + check if the usb cable is working properly and is connected to the amp tightly) and/or there could be problems with a power supply (more probably).
   
  Also, you can possibly catch noises from the outside if using SIPs as I do... I have heard it's not possible to use 1X gain ( = no gain resistors in sockets) for someone because of this. You can spot these problems even though you don't use SIPs when applying 1x (cutting one pair of resistors) I suspect. But I am lucky enough here...
   
  To be even more realistic, all the noises from the outside (open vs. closed doesn't matter unless you use some noise-cancelling phones) are very possibly of much more dB than any low level hiss from the amp... I don't hear any hiss from my amp but I do hear noises from the outside (computer, kitchen, cars if my window is open etc.)


----------



## miceblue

Quote: 





hamilcarbarca said:


> It's broken if there's hiss at any gain.


 
  Then I wonder what's wrong with my circuit... :/
   
  Because it might be relevant, I've mostly been using the new V-MODA Crossfade M-100's with the O2 at home while running on the AC charger.
  If it means anything, I grabbed these measurements from Innerfidelity:
  Volts RMS required to reach 90dB SPL: 0.031 Vrms
  Impedance @ 1kHz: 36 Ohms
  Power Needed for 90d BSPL: 0.03 mW


----------



## HamilcarBarca

Quote: 





mhoe said:


> Quote:
> 
> 
> 
> ...


 
   
  I don't necessarily agree with you on the details, but my blanket statement was at best an over-generalization. An amp is defective, in my opinion, only if it's the source of the noise.
   
  It is possible for external noise to be injected into an amplifier or the analog stages of a DAC. How well this is rejected is a matter for the designer ... and for the purchaser to decide just how much money to spend on this type of feature.


----------



## MHOE

Quote: 





miceblue said:


> Then I wonder what's wrong with my circuit... :/
> 
> Because it might be relevant, I've mostly been using the new V-MODA Crossfade M-100's with the O2 at home while running on the AC charger.
> If it means anything, I grabbed these measurements from Innerfidelity:
> ...


 
   
  You have some very high sensitive phones, I am not surprised you are able to spot some hiss with them... You can even find a note at the author's blog that the complete "dead silent" thing is not necessarily true with high sensitive phones (just discovered this today when reading though some sections there).
   
  Just checked the amp with my IEMs and I can spot a very low hiss level when using higher gain than I should (1x). As I use step-down converter right now (with WAU 16-400), I am going to purchase suitable transformer tomorrow and will test if there is any difference. It's cheap and I wanted to purchase it anyway... So now is the time to do it!
   
  You should use 1x with your phones at best... What exact transformer do you use?


----------



## miceblue

Quote: 





mhoe said:


> You have some very high sensitive phones, I am not surprised you are able to spot some hiss with them... You can even find a note at the author's blog that the complete "dead silent" thing is not necessarily true with high sensitive phones (just discovered this today when reading though some sections there).
> 
> Just checked the amp with my IEMs and I can spot a very low hiss level when using higher gain than I should (1x). As I use step-down converter right now (with WAU 16-400), I am going to purchase suitable transformer tomorrow and will test if there is any difference. It's cheap and I wanted to purchase it anyway... So now is the time to do it!
> 
> You should use 1x with your phones at best... What exact transformer do you use?


 
  Erm, I'm not completely sure. I'm using whatever parts come from the JDS Labs O2.
   
  And OK, I read somewhere on that blog about sensitive headphones/earphones being able to detect a small amount of background hiss.
  While on the topic of sensitive 'phones though, is there a place that I can check out regarding the sensitivity rating? I only know that more sensitive headphones can pick up background hiss more, and they're usually pretty loud in volume/can be "easily driven" by portable media players...I'm not too familiar with the technical explanation. XD


----------



## mikeaj

Lower-spec (lower voltage output, power rating) transformer should not make much (any?) difference for noise performance, but you can try if you want.  Consider all of the power supply filtering inside the amp, the relatively low power draw (especially when not playing at low output power level for IEMs, high PSRR of chips involved.  Thermal noise of some key resistors is a bigger contributor to noise.
   
  Also, maybe this goes without saying, but confirm that it's not noise in the recording you are playing or noise from the source that's feeding the amp.  It's not like the amp won't amplify any audio-range signal that it's receiving on its input, be it music or noise.  Input some noise, and you get the noise out.  It just generates very low noise on its own.


----------



## MHOE

Quote: 





mikeaj said:


> Lower-spec (lower voltage output, power rating) transformer should not make much (any?) difference for noise performance, but you can try if you want.  Consider all of the power supply filtering inside the amp, the relatively low power draw (especially when not playing at low output power level for IEMs, high PSRR of chips involved.  Thermal noise of some key resistors is a bigger contributor to noise.
> 
> Also, maybe this goes without saying, but confirm that it's not noise in the recording you are playing or noise from the source that's feeding the amp.  It's not like the amp won't amplify any audio-range signal that it's receiving on its input, be it music or noise.  Input some noise, and you get the noise out.  It just generates very low noise on its own.


 
   
  To be honest, I am not even trying to listen to music with the amp using IEMs or other very sensitive phones... Also, I can change my gain configuration anytime I want so I am just using the most suitable gain and have no audible hiss even with sensitive phones like Denon D7000. But I am curious about this and do not want to use stepdown converter anymore so I am going to try it. Not talking about the transformer here but rather about the power supply section (stepdown converter, wall sockets etc.). Also, I have ODAC included inside with USB input from my computer...


----------



## MHOE

Quote: 





miceblue said:


> Erm, I'm not completely sure. I'm using whatever parts come from the JDS Labs O2.
> 
> And OK, I read somewhere on that blog about sensitive headphones/earphones being able to detect a small amount of background hiss.
> While on the topic of sensitive 'phones though, is there a place that I can check out regarding the sensitivity rating? I only know that more sensitive headphones can pick up background hiss more, and they're usually pretty loud in volume/can be "easily driven" by portable media players...I'm not too familiar with the technical explanation. XD


 
   
  Yes, you can use sources like innerfidelity or just read specs of your phones... I have googled that yours are very "good" at spotting a hiss.
   
  In general, I would recommend to use O2 with not very high sensitive phones as there is no real reason to do so... You are simply only adding distortion to your sound if you do not use 1x gain configuration with your phones. =/
   
  Transformer from JDS Labs is WAU 12-200... It's good but not ideal especially for low impedance phones that often need more current. But it should not influence hissing or so... I can even test it, I have both transformers right here (12-200, ideal 16-400).


----------



## MrMateoHead

I can get a little hiss through my amp, and I can also hear my cell phone getting into the signal at times. Could be coming through the headphone cable or amp, I am not sure.
   
  I however, am pretty darn sure its my source. I have heard hiss before with IEM and 16 Ohm phones. I am using the "line out" jack which has 100 Ohms resistance. Figured that would be "quieter" than the headphone jack-as-line-out. I haven't tried trimming from max volume to 50% to cut the THD a little though.


----------



## HamilcarBarca

Quote: 





> Originally Posted by *MHOE* /img/forum/go_quote.gif
> 
> Transformer from JDS Labs is WAU 12-200... It's good but not ideal especially for low impedance phones that often need more current. But it should not influence hissing or so... I can even test it, I have both transformers right here (12-200, ideal 16-400).


 
   
  I think a lack of power is likely to affect the DAC first and very audibly.


----------



## MHOE

Quote: 





hamilcarbarca said:


> I think a lack of power is likely to affect the DAC first and very audibly.


 
   
  The DAC is powered via USB, isn't it?


----------



## adydula

Yes it is....powered from the USB voltage in the PC attached to.
   
  Alex


----------



## HamilcarBarca

Quote: 





mhoe said:


> Quote:
> 
> 
> 
> ...


 
   
  Oops. Lack of power may affect the DAC first. But as everyone has noted, the A/C transformer isn't supplying its power.


----------



## adydula

I have actually cut up a usb cable and inserted a ammeter and the current draw both statically and during playback was approx 50 milliamps....not even close to the USB 2.0 spec......
   
  If you PC is built to the USB 2.0 spec power should not be an issue.
   
  Unless you have 99 other things plugged into the other USB ports drawing over 500ma.
   
  Alex


----------



## TunneLVisioN42

I currently have an assembled O2 from JDS labs, I was going to order the ODAC and slip it into the O2 case and just run a 3.5mm from the output to the input of the O2, but then I noticed it does not come with a output 3.5mm on the assembled ODAC board.

 I'm kinda stumped on what to do now, my only previous soldering experience was replacing a cable on my ATH-M50's that a rabit had chewed through, It was a learning experience but I eventually got it, It was quite frustrating having no previous experience and only learning from a tutorial.

 So now I do not know what I should do, I would like to have them both in the same case for the sake of convenience and saving clutter, but I am not sure if I know I would be able to reliably count on my soldering skills again, I don't know how difficult connecting the ODAC internally would be (It LOOKS simple enough but I thought that about my headphones aswell), or how hard soldering a 3.5mm jack to the ODAC would be.

 so with a cheap little radio shack pencil style soldering iron would either of these idea's be good? also does the ODAC just slide into the O2 case and fit snugly?

 Thanks!


----------



## purrin

Get a better soldering iron with rudimentary temp control and practice. And practice more on random stuff you have lying around. I do good enough with one of these: http://www.amazon.com/Weller-WLC100-40-Watt-Soldering-Station/dp/B000AS28UC, although there are much nicer ones available.
   
  You can do OK with a Rat-Shack soldering iron, but I don't recommend it. They were either too cold or too hot (melting stuff). I've learned a lot since those days.


----------



## TunneLVisioN42

My friend has a weller that his father uses and would probably let me borrow it, my main issue with the ATH-M50 was it was hard to get in to the spot I needed to, so that is mostly what frustrated me, but soldering on a 3.5mm for the ODAC would not be that hard right? you have an open working area etc. I have also soldered airsoft guns and such maybe ill just go for it 
	

	
	
		
		

		
			





 I really dont want to buy it stand alone.


----------



## MrMateoHead

Quote: 





tunnelvision42 said:


> My friend has a weller that his father uses and would probably let me borrow it, my main issue with the ATH-M50 was it was hard to get in to the spot I needed to, so that is mostly what frustrated me, but soldering on a 3.5mm for the ODAC would not be that hard right? you have an open working area etc. I have also soldered airsoft guns and such maybe ill just go for it
> 
> 
> 
> ...


 

 Personally, I would send the card back and just buy one assembled. DIY is cool and all, but the hassle isn't always worth the savings.
   
  Otherwise, the process is fairly straightforward, and the DAC should fit right in with some plastic spacers and stuff you can order. But you do give up battery power.


----------



## fenderf4i

purrin said:


> Get a better soldering iron with rudimentary temp control and practice. And practice more on random stuff you have lying around. I do good enough with one of these: http://www.amazon.com/Weller-WLC100-40-Watt-Soldering-Station/dp/B000AS28UC
> 
> 
> 
> ...




I built 4 O2's and an ODAC with the WLC100 iron. It works very well for the price.


----------



## TunneLVisioN42

Quote: 





mrmateohead said:


> Personally, I would send the card back and just buy one assembled. DIY is cool and all, but the hassle isn't always worth the savings.
> 
> Otherwise, the process is fairly straightforward, and the DAC should fit right in with some plastic spacers and stuff you can order. But you do give up battery power.


 
  I have not ordered the ODAC yet, but it's what I want so one way or another I am gonna get this figured out =P I agree that sometimes DIY is not always worth it unless you enjoy what you are doing and have the skills to be absolutely sure you can get it done, if this is the case I LOVE DIY the feeling of creating and pouring effort into something to show fruit is a good one, but quite often I get overambitious and it ends up biting me in the ass and making me frustrated, I have asked JDSlabs if it is possible to send me a ODAC with a 3.5mm already soldered but if this is not an option ill just order the ODAC and 3.5mm jack and try my hand at it. (They confirmed in an email they will do this for me)

 Not worried about the battery space I do not use batteries in my O2 It is only used as a desktop amp (where are you ODA?!) so that is not a problem.
 Thanks for your replies!

 Edit: One more question, I ended up buying just the assembled board of the O2 as I thought i was going to make my own wood enclosure, well that never happened so I just ended up buying the aluminum box enclosure and stuffed it in there, just to make sure the O2 does not use a physical ground correct? I was looking at the "Retrofitting an ODAC to an O2" guide that explains how to directly connect the boards, one of the first directions is "Remove front panel and O2 board from enclosure. Avoid damaging ground wire" so I am curious.


----------



## adydula

When u install the O2 amp in the aluminum case there is a ground wire which is soldered from the board to one of the screws holding the front cover plate.
   
  Take a look at the O2 details section of the blog.
   
  Sorry we arent allowed to link to the site.
   
*B2-080 Enclosure Ground – *_To reduce hum and noise it’s important to ground the enclosure to Pin 1 of the input Jack J2_. That’s the center pin closest to the front panel. You can either use a short piece of lead wire from one of the small resistors (you want the thinnest wire possible) and make a loop where the screw hole is for the lower right corner of the front panel. Or, if you prefer, use fine gauge wire (like AWG30 wire wrap wire) from J2’s ground pin to the lower screw hole on the back panel behind the batteries. Run the wire under the board keeping it to the far right of the enclosure (under the batteries). Don’t forget about the wire if you try to slide the board out later. If you have some contact preservative or similar to help keep the aluminum from oxidizing you can apply a tiny bit to the connection but the front panel should keep it in solid contact. Click the picture for a larger version.
  
  A.


----------



## TunneLVisioN42

Well that answers all my pesky questions thanks a ton guys!


----------



## Agavehound

Got a problem now. I hooked up my 02/ODAC to my work pc per usual, but there is no power. Everything is hooked up properly and switched on, but the power light is not illuminated.  I suspect it's the power supply but not sure. Is there a quick and easy way to see if the PS is bad? If it is bad, where can I find a replacement that won't go out after a freaking week?


----------



## proton007

Quote: 





agavehound said:


> Got a problem now. I hooked up my 02/ODAC to my work pc per usual, but there is no power. Everything is hooked up properly and switched on, but the power light is not illuminated.  I suspect it's the power supply but not sure. Is there a quick and easy way to see if the PS is bad? If it is bad, where can I find a replacement that won't go out after a freaking week?


 
   
  Easiest and quickest way would be to measure using a multimeter.
   
  Also, is the O2 slightly warm to the touch? If yes, that would mean the power regulators are working, which means the problem is somewhere else.


----------



## HamilcarBarca

Quote: 





agavehound said:


> Got a problem now. I hooked up my 02/ODAC to my work pc per usual, but there is no power. Everything is hooked up properly and switched on, but the power light is not illuminated.  I suspect it's the power supply but not sure. Is there a quick and easy way to see if the PS is bad? If it is bad, where can I find a replacement that won't go out after a freaking week?


 
   
  You've checked to see the amp works (and it's not just the LED)? Sorry for the obvious!


----------



## Agavehound

lol, yes of course. I'm at work in multiple meetings today so I'm unable to check it more thoroughly at the moment. A buddy check the PS for output and found nothing. Now, where to get a replacement...asap. I don't want to be without it for long.


----------



## HamilcarBarca

Quote: 





agavehound said:


> lol, yes of course. I'm at work in multiple meetings today so I'm unable to check it more thoroughly at the moment. A buddy check the PS for output and found nothing. Now, where to get a replacement...asap. I don't want to be without it for long.


 
   
  Just in case! A friend of mine, working on a big, expensive equipment-support contract, once drove 2[size=11.0pt]½[/size] hours into the mountains on a service call. When he arrived, he just plugged the transmitter into the electrical outlet, wrote up a invoice for 5 hours' service, and returned to the big city. It's the kind of mistake I would make (but haven't yet.)
   
  Near the bottom of Objective2+ObjectiveDAC Combo Operating Instructions, there is a list of power supplies recommended by the designer. They were available from Mouser a week or so ago, and some are (or were) carried by MarkerTek; DigiKey is another major supplier. You may have local electronic supply shops.


----------



## Agavehound

Quote: 





hamilcarbarca said:


> Just in case! A friend of mine, working on a big, expensive equipment-support contract, once drove 2[size=11.0pt]½[/size] hours into the mountains on a service call. When he arrived, he just plugged the transmitter into the electrical outlet, wrote up a invoice for 5 hours' service, and returned to the big city. It's the kind of mistake I would make (but haven't yet.)
> 
> Near the bottom of Objective2+ObjectiveDAC Combo Operating Instructions, there is a list of power supplies recommended by the designer. They were available from Mouser a week or so ago, and some are (or were) carried by MarkerTek; DigiKey is another major supplier. You may have local electronic supply shops.


 

 Ah, Thanks for the link. Didn't know that was there! Appreciate the response.
   
  Edit: It's been plugged in for 30 minutes and as cold as a brass doorknob. I'm going to try and find one locally so I don't have to go without over the loooong holiday weekend.


----------



## Agavehound

Hey gang, I've located an AC adapter locally, but I don't know if the mA rating is too high. Ouput is variable @9-13VAC and 800mA. Is that too high and will it damage the 02/ODAC unit?


----------



## lowboy

Quote: 





agavehound said:


> Hey gang, I've located an AC adapter locally, but I don't know if the mA rating is too high. Ouput is variable @9-13VAC and 800mA. Is that too high and will it damage the 02/ODAC unit?


 
   
  That will work just fine - a current rating that's too _low_ for a device is what can cause problems.
   
  The current rating (mA) means that the adapter is able to supply _up to_ 800mA of current, but it's the device you plug in that determines how much current is drawn. The O2 instructions (http://www.jdslabs.com/pdf/Instructions_O2.pdf) specify a minimum of 200mA, meaning that the O2 shouldn't draw more than that from a power adapter.
   
  Also, AC adapters that just do one output voltage are usually cheaper, AFAIK.


----------



## Agavehound

Quote: 





lowboy said:


> That will work just fine - a current rating that's too _low_ for a device is what can cause problems.
> 
> The current rating (mA) means that the adapter is able to supply _up to_ 800mA of current, but it's the device you plug in that determines how much current is drawn. The O2 instructions (http://www.jdslabs.com/pdf/Instructions_O2.pdf) specify a minimum of 200mA, meaning that the O2 shouldn't draw more than that from a power adapter.
> 
> Also, AC adapters that just do one output voltage are usually cheaper, AFAIK.


 

 Excellent! I got the variable adapter since it was the only one I could find locally and easily. Hopefully it will last at least 2x as long. (since it was 2x the price. lol)


----------



## mikeaj

13V is a little low, may have problems.
   
  In reality, it depends on how low your home line voltage is, the kind of load you put on the amp (max volume or bench testing into lower-impedance loads requires more power draw).  Voltage you get out is more-or-less just a fixed fraction of the voltage from the wall, so if the line voltage is lower, then the output voltage will be lower too.  Anyway, if it's rated to be 13V at that setting, it might be sitting higher than that at the loads you'd run, considering that you won't pull anywhere close to the 900 mA it's rated for.
   
  It's probably okay, but it's probably best to check the voltage with a multimeter before using.
   
  Actual recommended input to amp is 14-20V AC.  Default transformer in NA yields more like 13.5V unloaded despite being rated at 12V, so that's mostly okay.  If it were actually 12V AC, that would be an issue.


----------



## MHOE

Quote: 





mikeaj said:


> 13V is a little low, may have problems.
> 
> In reality, it depends on how low your home line voltage is, the kind of load you put on the amp (max volume or bench testing into lower-impedance loads requires more power draw).  Voltage you get out is more-or-less just a fixed fraction of the voltage from the wall, so if the line voltage is lower, then the output voltage will be lower too.  Anyway, if it's rated to be 13V at that setting, it might be sitting higher than that at the loads you'd run, considering that you won't pull anywhere close to the 900 mA it's rated for.
> 
> ...


 
   
  I believe the COMPLETELY ideal output should be about 14/15V AC and more than 480mA to be absolutely safe. But generally, it's like above.


----------



## Agavehound

Quote: 





mhoe said:


> I believe the COMPLETELY ideal output should be about 14/15V AC and more than 480mA to be absolutely safe. But generally, it's like above.


 
  If that's true, then why are they recommending the 12VAC 200mA supply. That's the one I got and it lasted all of 8 days


----------



## MHOE

Quote: 





agavehound said:


> If that's true, then why are they recommending the 12VAC 200mA supply. That's the one I got and it lasted all of 8 days


 
   
  Because it's the cheapest and it's going to work with the majority of headphones... But if you read carefully through the entire blog, you will find several notes about ideal transformer and why.
   
  You want 14-20V and more than 400 (or even 500) mA to be absolutely sure. I have 15V + 650 mA to be totally absolutely sure that I meet everything mentioned on the blog.


----------



## HamilcarBarca

Quote:  





> If that's true, then why are they recommending the 12VAC 200mA supply. That's the one I got and it lasted all of 8 days


 
   
  The designer has recommended more than one A/C transformer. Of the ones named on their instruction sheet, JDS Labs ships the one with the lowest current (200mA), output voltage (12VAC), and Mouser price ($5.55).
   
  It's not clear that their choice of models is responsible for an early failure. After all, these are inexpensive, mass-produced parts. I could be wrong about that one but there haven't been many reports of failures.


----------



## MHOE

Quote: 





hamilcarbarca said:


> The designer has recommended more than one A/C transformer. Of the ones named on their instruction sheet, JDS Labs ships the one with the lowest current (200mA), output voltage (12VAC), and Mouser price ($5.55).
> 
> It's not clear that their choice of models is responsible for an early failure. After all, these are inexpensive, mass-produced parts. I could be wrong about that one but there haven't been many reports of failures.


 
   
  I have both WAU 12-200 and 16-400, without any troubles... Purchased 15-650 with europlug for about 5-6 dollars but still it works very nice. No troubles at all.


----------



## agdr

agavehound said:


> If that's true, then why are they recommending the 12VAC 200mA supply. That's the one I got and it lasted all of 8 days




Unfortunately in those few instances when "Voldemort" made a mistake he tended to go into defensive mode rather than fix the problem it seemed.  That WAU12-200 transformer choice was something else I tried to talk him out of at one point last year after he first posted the O2 design. One problem with current capability of the transformer secondary is shown in the simulation below. This is done for a 16VAC transformer but the problem is the same. A half wave rectifier, like the two in the O2, charge up the filter capacitors with a very short high(er) current spike after the rectifier turns on each cycle, as opposed to a lower current spike with full wave or bridge rectifiers. That is a design trade-off in using a half wave rectifier. Note in that LT Spice simulation a 200mA (rms) continuous load produces a 800mA charging spike in each 470uF filter capacitor, and hence through the transformer secondary. 

The chips in the O2 pull about 22mA just as they sit (quiescent current consumed by the chips) and the batteries pull about 22mA of charging current during the maximum part of the charge curve if they are completely dead (7Vdc each where the PM circuit cuts off) so a headphone load of more than only 3mA or so would produce a charging spike of more than 200mA in the transformer. 

If the transformer secondary is rated less than the amount of the charging current spike the core will saturate. That can cause heating and also some noise generation. In the case of heating, the Triad wall adapters may contain thermal fuses (can't find any reference to that, but pretty good guess to be UL certified) which may eventually open up if the transformer gets hot enough. My suggestion to "Voldemort" was to specify the 1 Amp WAU16-1000s (Mouser #553-WAU16-1000), for the case when the O2 was fully loaded with 200mA per channel, or the 400mA WAU16-400 (Mouser #553-WAU16-400) for more normal loads that would probably be the case 95% of the time. He eventually added those two under the "optional" column on his BOM. The 400mA transformer would increase the maximum permissible headphone current load before transformer core saturation from 3mA to 56mA.

To summarize, if your headphone load is less than only about 3mA or so, or up to around 25mA if you are not using batteries (so are not charging anything) you would probably be OK with the 200mA transformer secondary rating. The 12Vac transformer secondary voltage rating is another issue. That is 12Vac if your line voltage is at least 110VAC or so. If your line voltage sags less than that the transformer output will drop lower and the voltage regulators won't have the 3.5Vdc or so across them they like for maximum ripple and noise rejection from the datasheet. At one point some folks had found "12Vac" transformers made for LED lighting, in reality outputting 11Vac, causing the O2 regulators to actually go into dropout. 14 or 16Vac would provide more headroom against line voltage fluctuations. 

If the incoming line voltage from the wall socket is on the high(er) end, 120Vac - 130Vac in the USA, and is known to be fairly stable over the course of the day, then the "12Vac" transformer will be producing closer to 13Vac - 13.5Vac loaded (14.5Vac+ unloaded) and would be OK from a voltage standpoint.

For more tech details, see the second picture down on the left on this rectifier application note for Hammond transformers, the half wave capacitive input situation [can't post the link, just do a Google search on "Hammond rectifier" and it is the first result]. Hammond recommends de-rating the rms secondary current by a factor of 0.28 in the case of half wave rectifiers. So in the case of the 200mA WAU12-200 transformer, that secondary is only good for (200mA)(0.28) = 56mA (rms) continuous, in the case of capacitor input half wave rectification, to prevent transformer core saturation.

EDIT 1 11/22/2012: In fairness to "Voldemort", since he seems to be AWOL these days for some reason, his defense of the first issue a year ago was that the amount of excess heating and/or noise generation in the transformer from small amounts of transformer core saturation would be within specifications. His defense of the second issue was that if low line voltage results in smaller voltage drops across the regulators, or even if they drop out of regulation completely, the power supply rejection ratio of the amplifier op amps is good enough to not matter even if voltage ripple winds up on the power supply rails. True to some extent (many tech details involved), but my view remains why create those marginal operating conditions in the first place when for $1-$2 more USD, the way transformers are priced, you can buy a 14Vac - 16Vac 400mA - 800mA unit and avoid the issues entirely.

EDIT 2 11/25/2012. Added some more information and cleaned up some grammar. Another issue that probably figured into "Voldemort" leaving that WAU12-200 transformer as the primary BOM specification was cost. I can say from some email exchange a year ago that for some reason he was very adamant about keeping the basic parts cost at $30. He considered raising the parts cost even a couple of dollars a big deal. I think his view was along the lines of keeping the O2 very affordable for DIYers.

[ATTACHMENT=267]Capture.PNG (31k. PNG file)[/ATTACHMENT]


----------



## proton007

IDK, in one of my conversations with him, he recommended a 16V power adapter.


----------



## HamilcarBarca

Quote: 





agdr said:


> Quote:
> 
> 
> 
> ...


 
   
  Thank you for the analysis. I'm not an EE, but I'll read it and do my best to understand.


----------



## cubusmybro

I am trying to remove the volume knob so I can put a faceplate on my O2. If anyone could help I would greatly appreciate it because I have no idea.  Thanks


----------



## proton007

cubusmybro said:


> I am trying to remove the volume knob so I can put a faceplate on my O2. If anyone could help I would greatly appreciate it because I have no idea.  Thanks




afaik you should be able to pull it out.


----------



## DairyProduce

Quote: 





cubusmybro said:


> I am trying to remove the volume knob so I can put a faceplate on my O2. If anyone could help I would greatly appreciate it because I have no idea.
> 
> 
> 
> ...


 
   
  Hey!
   
  I just got my O2 amp two weeks ago. Is there any reason you want to remove the volume knob? (replacing a broken one?) Or is it just for cosmetic purposes?


----------



## HamilcarBarca

Quote: 





dairyproduce said:


> Quote:
> 
> 
> 
> ...


 
   
  The knob must be removed to add or remove the faceplate.
   
  I'm not the OP, but I'd like to replace my brushed aluminum faceplate with the black one from Mayflower Electronics. Would you check yours to see if the knob is held in place with a tiny set screw? Mine's at work.


----------



## mikeaj

Seems like it's to be able to "put a faceplate on".  You can't remove or insert a faceplate unless the knob is removed.  If you're worrying about the part breaking, underneath the knob is a high-quality ALPS potentiometer of metal construction.  It's not a tank, but it's not some cheap junk volume control that's going to break (or have mediocre channel balance)
   
  As mentioned earlier, the knob should just slide off with a strong tug.  There's no screw.  Easiest way to remove may be just to unscrew the faceplate and pull on that, which should pop it off.


----------



## DairyProduce

Quote: 





hamilcarbarca said:


> The knob must be removed to add or remove the faceplate.
> 
> I'm not the OP, but I'd like to replace my brushed aluminum faceplate with the black one from Mayflower Electronics. Would you check yours to see if the knob is held in place with a tiny set screw? Mine's at work.


 
   
  Sorry, I don't have any screwdrivers near me (had to borrow my friend's last time to open it). 
  Maybe you can check some photos from jdslabs?


----------



## miceblue

Quote: 





cubusmybro said:


> I am trying to remove the volume knob so I can put a faceplate on my O2. If anyone could help I would greatly appreciate it because I have no idea.
> 
> 
> 
> ...


 

 You need a hex/Allen key to loosen the hex screw on the volume knob. Once you get that loosened, you can just pull the knob off without a problem.
   
  Yes there is a screw. It's pretty standard for all potentiometer volume knobs or else it wouldn't securely stay in place.

   

   

   
   
   
  And yes you need to remove the volume knob to take the faceplate off.


----------



## HamilcarBarca

Quote: 





mikeaj said:


> As mentioned earlier, the knob should just slide off with a strong tug.  There's no screw.  Easiest way to remove may be just to unscrew the faceplate and pull on that, which should pop it off.


 
   


> Originally Posted by *miceblue* /img/forum/go_quote.gif
> 
> You need a hex/Allen key to loosen the hex screw on the volume knob. Once you get that loosened, you can just pull the knob off without a problem.
> 
> ...


 
   
  Thank you both for the replies. While looking at the closeup, I realized that the volume knob on an Objective2 amp is chosen by the manufacturer (distributor.) Mine is from JDS Labs and matches the picture above.
   
   


> Originally Posted by *miceblue* /img/forum/go_quote.gif
> 
> And yes you need to remove the volume knob to take the faceplate off.


 
   
  At least I got one thing right!


----------



## agdr

hamilcarbarca said:


> Thank you for the analysis. I'm not an EE, but I'll read it and do my best to understand.




What it all boils down to is a 14Vac - 16Vac transformer with a 400mA or greater secondary rating (like the WAU16-400) means not having to know any tech details about the whole thing. It will just work, with the one exception of using a low impedance headphone that is also low sensitivity, that might pull more than 56mA per channel. Then use a 14Vac - 16Vac 1000mA unit, like the WAU16-1000 which is only $0.25 USD more anyway at Mouser ($11.50 USD vs. $11.75). Might as well just get the 1000mA unit if there is plug space - it is about 25% larger physically.

To make a 12Vac secondary work with lower line voltage, and/or with only a 200mA current rating, one would need to know the pile of details I posted to be sure it would work for the specific situation. I just updated my post to note that if a person is sure they have high(er) line voltage, like 120Vac - 130Vac in the USA, and is known to be stable plus or minus a few volts over the course of the day, then a "12Vac" secondary will work since it will really be running at 13Vac or more under load. "Voldemort" may have been figuring that into the original specification since much of the line voltage in the US is around 120Vac these days (mine is 121Vac at the moment and is usually +/-1Vac). 

So in that case just "fixing" the secondary current problem (increasing it) is all that is needed, say with a 12Vac 1000mA WAU12-1000 unit (Mouser part #553-WAU12-1000). The voltage regulators in the O2 will run cooler with the 12Vac 1000mA unit than with 14Vac or 16Vac, so if someone is certain they will always have higher AC line voltage that would be a good way to go.

Proton007: Interesting that "Voldemort" suggested the 16Vac! I may have had an effect, lol. :normal_smile :


----------



## Dutchi MerenGue

Quote: 





agdr said:


> What it all boils down to is a 14Vac - 16Vac transformer with a 400mA or greater secondary rating (like the WAU16-400) means not having to know any tech details about the whole thing. It will just work, with the one exception of using a low impedance headphone that is also low sensitivity, that might pull more than 56mA per channel. Then use a 14Vac - 16Vac 1000mA unit, like the WAU16-1000 which is only $0.25 USD more anyway at Mouser ($11.50 USD vs. $11.75). Might as well just get the 1000mA unit if there is plug space - it is about 25% larger physically.
> To make a 12Vac secondary work with lower line voltage, and/or with only a 200mA current rating, one would need to know the pile of details I posted to be sure it would work for the specific situation. I just updated my post to note that if a person is sure they have high(er) line voltage, like 120Vac - 130Vac in the USA, and is known to be stable plus or minus a few volts over the course of the day, then a "12Vac" secondary will work since it will really be running at 13Vac or more under load. "Voldemort" may have been figuring that into the original specification since much of the line voltage in the US is around 120Vac these days (mine is 121Vac at the moment and is usually +/-1Vac).
> So in that case just "fixing" the secondary current problem (increasing it) is all that is needed, say with a 12Vac 1000mA WAU12-1000 unit (Mouser part #553-WAU12-1000). The voltage regulators in the O2 will run cooler with the 12Vac 1000mA unit than with 14Vac or 16Vac, so if someone is certain they will always have higher AC line voltage that would be a good way to go.
> Proton007: Interesting that "Voldemort" suggested the 16Vac! I may have had an effect, lol.


 
   
  lol my head hurts reading that, can you just tell me which one would optimally power my o2 when it arrives without burning out or better still, not burning down my house?


----------



## mikeaj

Quote: 





dutchi merengue said:


> lol my head hurts reading that, can you just tell me which one would optimally power my o2 when it arrives without burning out or better still, not burning down my house?


 
   
  Try rereading the first sentence, unless that was actually too complicated, or...?
   
  For most people and usage, WAU12-200 is probably okay.  There can be problems, particularly if you're using the batteries, and some other factors.
   
  If you don't want to figure anything out, pay $5.45 more and get the WAU16-1000:
here


----------



## Dutchi MerenGue

Quote: 





mikeaj said:


> Try rereading the first sentence, unless that was actually too complicated, or...?
> 
> For most people and usage, WAU12-200 is probably okay.  There can be problems, particularly if you're using the batteries, and some other factors.
> 
> ...


 
  lol my bad, i had just finished overeating kfc and was lying back struggling to read your post while at the same time fighting off drowsiness, thanks for the link tho


----------



## HamilcarBarca

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
   
  More good stuff which I've finally gotten around to reading. Thanks.
   
  If I can impose on you again, I have three questions. Both the Late, Lamented Lord and you mentioned low-impedance, low-sensitivity headphones. AKG rates their K701 at 62Ohms (and 105dB which seems efficient to me.) HiFiMan rates their HE-500 at 38Ohms (and 89dB.) 
   

 Do these represent limiting cases for the O2's design?
 Does the Beyerdynamic DT 990 Premium, rated at 32 Ohms (and 96dB), qualify as inefficient?
 Is the risk of using an inadequate but "approved" transformer on a non-battery-powered O2 setup confined to failure of the transformer itself?
   
  The conclusion, in any case, was easy for me. I work in an office which for years has had insufficient power; in Wintertime; we've been known to trip the breakers without knowing why.
   
  The WAU16-1000 is currently $11 from Mouser. I ordered one this evening and paid $7 for USPS Priority Mail postage.


----------



## Uberbob102000

hamilcarbarca said:


> If I can impose on you again, I have three questions. Both the Late, Lamented Lord and you mentioned low-impedance, low-sensitivity headphones. AKG rates their K701 at 62Ohms (and 105dB which seems efficient to me.) HiFiMan rates their HE-500 at 38Ohms (and 89dB.)




If I recall correctly the AKG rating you listed is dB SPL/ V while the HE-500 rating is 89 dB/mW. The AKG is ~ 94 dB/mW but I'd double check that as it's off the top of my head.


----------



## Bojamijams

Just ordered one from JDS with 1x / 6.5x setup. Going to try it with my turntable and as a dac+amp from laptop. With JH|13's and DT880 600ohm.  pretty diverse. looking forward to it.


----------



## adydula

701's can and are in my case, very well even with batteries only.....not all small portable amps can do this well at all.
   
  The O2 and 701/2's is not an issue.
   
  I have three transformers of all sizes and have switched back and forth and compared to just batteries and there is no audible difference to
  me at all.
   
  I ususally listen to just batteries until they need charging and charge overnight and start the process all over again.
   
  Alex


----------



## HamilcarBarca

Quote: 





uberbob102000 said:


> Quote:
> 
> 
> 
> ...


 
   
  I recall now, after looking at specs for six or so headphones, that some were rated in using dB SPL/V and some with dB SPL/mW. It didn't register with me at the time.


----------



## Uberbob102000

Yea, it got me at first too. 

There's a formula to convert the two, but I don't have it on this computer and after being up for 32 hours of airports and planes I'm not sure I'll even copy pasta the right formula.

EDIT: Since I'm in the market for a DAC/amp again, how does the O2 drive the HD650? I know it drives the two Hifiman headphones I have/want but I haven't found a solid answer on the HD650.


----------



## HamilcarBarca

Quote: 





uberbob102000 said:


> There's a formula to convert the two, but I don't have it on this computer and after being up for 32 hours of airports and planes I'm not sure I'll even copy pasta the right formula.


 
   
  V = IR & P = I²Z if I remember correctly. My question was academic, not interesting enough for me to compute even a few data points.
   


uberbob102000 said:


> EDIT: Since I'm in the market for a DAC/amp again, how does the O2 drive the HD650? I know it drives the two Hifiman headphones I have/want but I haven't found a solid answer on the HD650.


   


  It's the best setup I've heard yet. Assuming the HD-650 is to your liking, I recommend the setup highly.
  Currently, my ODAC+O2 is at work and the HD-650's are at home. They were paired for a couple of weeks, and they made beautiful music together <3. Unfortunately, they didn't give me any kittens.
   
  Tomorrow, the Beyer T70's, which I've now had for almost thirty minutes, goes to work where my ODAC+O2 lives.


----------



## TunneLVisioN42

Got my ODAC, Wondering what kind of 3.5mm cables you guys are using for Output/Input? Looking for something 8 to 12 inches?


----------



## proton007

Quote: 





tunnelvision42 said:


> Got my ODAC, Wondering what kind of 3.5mm cables you guys are using for Output/Input? Looking for something 8 to 12 inches?


 

 I just got a standard cable, nothing fancy. You can get the monoprice cables with gold plated jacks.


----------



## TunneLVisioN42

Yeah I was looking at the monoprice 1.5FT gold plated cable but its a bit long, the FiiO L2 is a bit short.

 Also ODAC sounds great but I often use Teamspeak and my USB Microphone absolutely refuses to work along side my ODAC, I have had this issue before with another USB DAC, it only happens when I try to use USB devices for both MIC and Output so its a software issue.

 Anyone know why this is?

 Edit: Seems its not limited to Teamspeak but windows is causing it.

 2: Yeah If the ODAC is in use, and I enter the recording panel in the sound options the control panel will freeze, If the ODAC is not in use but still selected as default playback and I enter the recording section once more it shows it is working fine and picking up my voice.

 Quite frustrating


----------



## proton007

Quote: 





tunnelvision42 said:


> Yeah I was looking at the monoprice 1.5FT gold plated cable but its a bit long, the FiiO L2 is a bit short.
> 
> Also ODAC sounds great but I often use Teamspeak and my USB Microphone absolutely refuses to work along side my ODAC, I have had this issue before with another USB DAC, it only happens when I try to use USB devices for both MIC and Output so its a software issue.
> 
> ...


 
   
  I'm not completely sure, but does this occur on your computer, or have you duplicated it on some other system? It may be a power issue.


----------



## HamilcarBarca

Quote: 





tunnelvision42 said:


> Got my ODAC, Wondering what kind of 3.5mm cables you guys are using for Output/Input? Looking for something 8 to 12 inches?


 
   
  I just received, from Amazon, a 1.5' extension cable made by Cables to Go (~$4.)
   
  We have a local mom-n-pop shop which sells no-name Chinese cables and some Monoprice cables. The tech will assemble custom cables even with customer-supplied parts.


----------



## TunneLVisioN42

I've had this same issue with 2 other USB based DAC's, my friend has never had this issue, I don't know if its power though what would the issue be stemming from? USB power output? I guess that could be it I will try to replicate it on another computer and share the results

 Edit: Cannot replicate results on another computer, I suspected it was my computer anyways not the actual devices, I have scoured google and have only found 1 person that had the same issue and  the poor guy did not get a reply, anyone have an idea of how to start troubleshooting this? I have not had any issues with non audio USB devices.


----------



## proton007

Quote: 





tunnelvision42 said:


> I've had this same issue with 2 other USB based DAC's, my friend has never had this issue, I don't know if its power though what would the issue be stemming from? USB power output? I guess that could be it I will try to replicate it on another computer and share the results


 

 Yeah, possibly your USB ports cannot power two of these devices at once.


----------



## Uberbob102000

proton007 said:


> Yeah, possibly your USB ports cannot power two of these devices at once.




Good way for him/her to test that would be to get a powered USB hub and see what happens.


----------



## TunneLVisioN42

Here is my motherboard http://www.asrock.com/mb/Intel/P55%20Extreme/ It lists a "Powered eSATA2/Usb Port" I was wondering if this was powered separate from the other USB ports on my motherboard? By the way I also have an older but competent 600w PSU with 40amps on the 12V.

 Is there anything anyone can suggest in the meantime before I purchase a powered USB Hub?


----------



## DairyProduce

Having a O2/ODAC combo, I was wondering. What would be considered an upgrade for this combo?


----------



## proton007

dairyproduce said:


> Having a O2/ODAC combo, I was wondering. What would be considered an upgrade for this combo?




Depends on what kind of upgrade you're looking for. I feel an inbuilt power supply would be good for start.


----------



## DairyProduce

Quote: 





proton007 said:


> Depends on what kind of upgrade you're looking for. I feel an inbuilt power supply would be good for start.


 
  What exactly would that do to the sound?


----------



## HamilcarBarca

Quote: 





dairyproduce said:


> Quote:
> 
> 
> 
> ...


 
   
  Probably nothing but I, too, like to have an integrated transformer. And the connections on the back and output connections on the front.


----------



## Uberbob102000

dairyproduce said:


> Having a O2/ODAC combo, I was wondering. What would be considered an upgrade for this combo?




Well the O2/ODAC could certainly use some usability modifications (like everyone said, possibly inbuilt power supply, input connections on back) but actual upgrade wise you're going to be making a rather large jump in price before you get anywhere.


----------



## DairyProduce

Quote: 





uberbob102000 said:


> Well the O2/ODAC could certainly use some usability modifications (like everyone said, possibly inbuilt power supply, input connections on back) but actual upgrade wise you're going to be making a rather large jump in price before you get anywhere.


 
   
  Any examples on what these actual upgrades are? And around what price?
   
  Thanks!


----------



## adydula

Remember the what the O2 was designed to be....low cost, fewest parts, best performance..and portable...
   
  You start putting stuff in the box, it gets big, and can add problems, like a transformer in the box with all its worts....
   
  Not saying it cant be done, or having a larger enclosure is a bad thing...
   
  Would be nice to see what the ODA really was or hopefully is going to be....
   
  I personally like to have a larger phone jack and rca's...but these can be added easily....
   
  Alex


----------



## DairyProduce

Yeah I'm curious about the ODA as well. But the maker seems to be busy these days(?)


----------



## adydula

Here are some neat pix of someones O2 Black cube...really neat...
   
   

   

   

   

   
  Just might be my next project..
   
  Alex


----------



## HamilcarBarca

Quote: 





adydula said:


> Remember the what the O2 was designed to be....low cost, fewest parts, best performance..and portable...
> 
> You start putting stuff in the box, it gets big, and can add problems, like a transformer in the box with all its worts....
> 
> ...


 
   
  Excellent points.
   
  The upgrades I wanted to have aren't actually to the Objective2 amplifier, they're to the package in which it's usually distributed. But, I knew what I was getting when I bought mine and it still sounds great (and even better with my Black-Friday T70's!)


----------



## adydula

I still am amazed at what this "tiny" device can do....for the cost and how well it drives 98% of the cans out there....
   
  I listen to my friends getting super large power supplies, filtering etc....and I just tell them i run off of pure "dc" when i show
  them the 2 -  9 volt batteries they are flabber-gasted.....lol.
   
  Total transparency for approx $100 in parts, some soldering, a few hours and voila...world class head amp, pure DC.
   
  Alex


----------



## HamilcarBarca

Quote: 





adydula said:


> I listen to my friends getting super large power supplies, filtering etc....and I just tell them i run off of pure "dc" when i show
> them the 2 -  9 volt batteries they are flabber-gasted.....lol.


 
   
  Uh, oh. I just bought me a megapower supply: 16V at 1,000mA. It increased the ODAC+O2's bundled price by $11!


----------



## TunneLVisioN42

Okay well a powered USB Hub is allowing both of my devices to work so you were right proton007. It is really quite weird but my power supply is 5 years old and I am running a GTX 670 so maybe its time to retire the poor fellow for an eternal rest. I don't prefer using a powered USB hub so I guess its time to go power supply shopping (I was planning on getting a dedicated Physx card anyways)

 Sorry to get a little off topic.

 Thanks again guys.


----------



## Uberbob102000

tunnelvision42 said:


> Okay well a powered USB Hub is allowing both of my devices to work so you were right proton007. It is really quite weird but my power supply is 5 years old and I am running a GTX 670 so maybe its time to retire the poor fellow for an eternal rest. I don't prefer using a powered USB hub so I guess its time to go power supply shopping (I was planning on getting a dedicated Physx card anyways)
> 
> 
> Sorry to get a little off topic.
> ...




It may not be your PSU, it could just be due to how your mobo is designed. I haven't had that particular problem with my RIVE, but I've seen similar problems before in regards to USB powered devices.


----------



## Pojosama

I was thinking about getting the 02 + ODAC to upgrade my Creative USB Sound Blaster HD for my HD650s. The question I have is will having to use an adapter to go from the 6.5 mm jack to 3.5 mm to fit in the O2 hurt the sound quality?
   
  I really wish he'd release the ODA. I also have my BX5a monitors connected to the Sound Blaster via RCA cables. Unfortunately, I won't be able to do that either with the O2.


----------



## HamilcarBarca

Quote: 





pojosama said:


> I was thinking about getting the 02 + ODAC to upgrade my Creative USB Sound Blaster HD for my HD650s. The question I have is will having to use an adapter to go from the 6.5 mm jack to 3.5 mm to fit in the O2 hurt the sound quality?
> 
> I really wish he'd release the ODA. I also have my BX5a monitors connected to the Sound Blaster via RCA cables. Unfortunately, I won't be able to do that either with the O2.


 
   
  No, it won't hurt the sound quality. Along with the HD-650, I've connected Beyerdynamic's DT 990 Premium and T70. Sennheiser and Beyerdynamic ship 6.3-3.5mm adapters with these models and they all sound fantabulous with the ODAC+O2 combo.
   
  You could leave the BX5a's connected to the SB even if it's not ideal. That's what I do for my Audioengine A5's. I'd rather have two, switchable outputs but not enough to swap a great combo for something else. I'm an ODAC+O2 fanboy.
   
  If the ODA has two outputs and especially if it has two inputs, my Matrix M-Stage is history.


----------



## adydula

I use a short cable that remains in the 3.5 mm mini connector in the O2 amp and plug the cans 1/4 " into the other end of the cable....this
  way I am not inserting the cans directly into the amp...the 3.5 mm connector in the build is not that robust of  a mechanical connector....
  and i dont want to have to eventually remove it and replace it. I think the duty cycle is 1000 insertions etc...so maybe its not an issue but by using this short
  pigtal  its not an issue...
   
  Alex


----------



## HamilcarBarca

Quote: 





adydula said:


> I use a short cable that remains in the 3.5 mm mini connector in the O2 amp and plug the cans 1/4 " into the other end of the cable....this way I am not inserting the cans directly into the amp...the 3.5 mm connector in the build is not that robust of  a mechanical connector....and i dont want to have to eventually remove it and replace it. I think the duty cycle is 1000 insertions etc...so maybe its not an issue but by using this short pigtal  its not an issue...


 
   
  I used to use a ($3.50) 3.5-3.5mm extension, now replaced with a ($3.99) 3.5-6.3mm extension, for exactly that reason.


----------



## K_19

Quote: 





adydula said:


> Here are some neat pix of someones O2 Black cube...really neat...
> 
> 
> 
> ...


 
   
  Gotta say that's a very nice Desktop version of the O2!


----------



## adydula

yes it it...over at the DIY site...
   
  Alex


----------



## Pojosama

Yeah, the O2 has always interested me, but I decided to wait for the ODA. Since that doesn't look like it's happening, I'm just going to go with this.
   
  Thanks!


----------



## MHOE

Quote: 





pojosama said:


> Yeah, the O2 has always interested me, but I decided to wait for the ODA. Since that doesn't look like it's happening, I'm just going to go with this.
> 
> Thanks!


 
   
  I would not wait for ODA... O2 w/ ODAC instead of batteries along with suitable transformer (14-16VAC, +500 mah) is going to give you the complete desktop experience!


----------



## TunneLVisioN42

Quote: 





uberbob102000 said:


> It may not be your PSU, it could just be due to how your mobo is designed. I haven't had that particular problem with my RIVE, but I've seen similar problems before in regards to USB powered devices.


 
  Yeah I am working on troubleshooting this with folks over at overclock.net, looking at everything I should be able to handle powering both just fine, still trying to figure it out, hoping to get it figured out before my HE-400's get here haha


----------



## Draygonn

mhoe said:


> I would not wait for ODA... O2 w/ ODAC instead of batteries along with suitable transformer (14-16VAC, +500 mah) is going to give you the complete desktop experience!


With the delay/disappearance of the ODA I'm surprised JDSLabs aren't offering a more desktop oriented version. O2/ODAC in a B80-03 enclosure with a nice transformer, 1/4" jack, and rear inputs should satisfy those sick of waiting.


----------



## purrin

Just recase the O2 into a bigger case. Voila, desktop version. I mean, what exactly was going to change in it in the first place? I guess the only thing would to be parallel more 4556 chips in the output and beef up the PS.


----------



## lorriman

dairyproduce said:


> Any examples on what these actual upgrades are? And around what price?
> 
> Thanks!




Violectric (Lake People) has devices that the designer of the O2 has mentioned as being at least as good. They can do 100% of headphones (vs O2 at 98%), have large sockets (RCA etc). An HE6 user might prefer them as the amp. As for the ODAC: it;s as good as you probably ever going to find. The Benchmark DAC1, for example, might be technically better (I might be wrong about that) but the improvement is inaudible.

Both Violetric and DAC1 are very expensive.

The O2 in its original form has 3.5mm sockets which are rated to 2000 insertions. That's not much if you are thinking to use it for 15 years (and estimate form the O2 designer of its possible life-span). A typical external power supply lasts 3 to 5 years. So there is reason to favour a Violectric or the ODA both for practical as well as longevity reasons but for a big price increase.


----------



## adydula

Here is what I gleaned from the blogs...
   
  The ODA was to take the same objective design principles and apply them to an amp optimized for desktop use only, ie no batteries.
   
  It was indicate that it would meet or exceed the same requirements.
   
  With the following :
   
  Higher quality audio inputs and outputs.
   
  Rear Panel Connections
   
  Wider Source Compatibility:
   
  Higher Quality Power Supply
   
  Headphone Protection Relay
   
  Possible Preamp/line out
   
  The ODA was definitely not going to be a portable amp....hence no batteries
   
  I dont want to post whats on the blog, this is not allowed but you can easily find this stuff on it.
   
  Alex


----------



## ostewart

Just got my Black Edition O2 amp from JDS Labs


----------



## USAudio

Quote: 





lorriman said:


> Violectric (Lake People) has devices that the designer of the O2 has mentioned as being at least as good. They can do 100% of headphones (vs O2 at 98%)


 
  I may have misread the article but I was under the impression when he said 98% of headphones he was referring to the other 2% as being other types such as electrostatics, which obviously aren't driven by the Violectric amps either.


----------



## thrand1

Thinking of buying the O2 Amp only from JDSLabs. Current headphones are Shure SRH940 (~40ohms), but have a friend/roommate that would also be using this with Shure SE535 (36 ohms). Is there any reason to order the O2 with a different gain configuration, or is the default 2.5/6.5 going to function fine with both headphones? I don't ever see myself needing/using the 6.5x gain unless I moved to some much more difficult to drive headphones, but I am open to suggestions/advice from those more knowledgeable on this subject  JDSLabs also offers 1.0x/6.5x and 2.5x/1.0x so I wasn't sure if either of those would be better suited for my application.
   
  From reading the "All About Gain" article, am I correct in thinking 1.0x is basically no gain at all, so does that mean the input signal is not boosted as much as you turn the volume knob on the amp? What benefit is there/would there be to the 1.0x gain setting in my application?
   
  Thanks for answering my questions and for your suggestion on what gain config I should use!


----------



## MHOE

Quote: 





thrand1 said:


> Thinking of buying the O2 Amp only from JDSLabs. Current headphones are Shure SRH940 (~40ohms), but have a friend/roommate that would also be using this with Shure SE535 (36 ohms). Is there any reason to order the O2 with a different gain configuration, or is the default 2.5/6.5 going to function fine with both headphones? I don't ever see myself needing/using the 6.5x gain unless I moved to some much more difficult to drive headphones, but I am open to suggestions/advice from those more knowledgeable on this subject  JDSLabs also offers 1.0x/6.5x and 2.5x/1.0x so I wasn't sure if either of those would be better suited for my application.
> 
> From reading the "All About Gain" article, am I correct in thinking 1.0x is basically no gain at all, so does that mean the input signal is not boosted as much as you turn the volume knob on the amp? What benefit is there/would there be to the 1.0x gain setting in my application?
> 
> Thanks for answering my questions and for your suggestion on what gain config I should use!


 
   
  There is definitely a reason to not go for 2.5/6.5... I would much rather go for 1x and 2x/2.5x. Or, at best, use SIPs that allow you to use whatever gain you want. The guy from Mayflower electronics customised me my O2/ODAC combo to perfection (see my signature). I have also seen very good options on Headnhifi.
   
  I personally use only 1x gain as you are not amplifying anything = no distortion, you only use it as a volume knob (but you are not amplifying, only "modifying" the output loudness) and lowering output impedance.


----------



## orangecr

(yet another) newbie question...
   
  I want the O2/ODAC combo from JDS Labs, but I only have around $175 at the moment. Should I get the O2 and use it with the laptop headphone jack for now?  or would it be better if I get something like the Fiio E17, or E10, that has a built in DAC/amp?
   
  Thanks


----------



## kiteki

orangecr said:


> (yet another) newbie question...
> 
> I want the O2/ODAC combo from JDS Labs, but I only have around $175 at the moment. Should I get the O2 and use it with the laptop headphone jack for now?  or would it be better if I get something like the Fiio E17, or E10, that has a built in DAC/amp?
> 
> Thanks


 
   
  If you only have $175, you should definitely get this one instead --> http://hifimediy.com/index.php?route=product/product&path=62&product_id=83
   
  No one, and I really mean no one, will hear any difference, with any kind of speaker.  They are basically identical in every single way.
   
   
  Edit:  Sorry, the Hifimediy has optical-out, that's the difference.


----------



## proton007

Quote: 





orangecr said:


> (yet another) newbie question...
> 
> I want the O2/ODAC combo from JDS Labs, but I only have around $175 at the moment. Should I get the O2 and use it with the laptop headphone jack for now?  or would it be better if I get something like the Fiio E17, or E10, that has a built in DAC/amp?
> 
> Thanks


 

 If you use a laptop as your main source, and have a good headphone, I'm not sure an amp will make a lot of difference, unless you're using something with a wild impedance curve (like some sennsheisers). 
  Better to go for a DAC+Amp combo.


----------



## Uberbob102000

orangecr said:


> (yet another) newbie question...
> 
> I want the O2/ODAC combo from JDS Labs, but I only have around $175 at the moment. Should I get the O2 and use it with the laptop headphone jack for now?  or would it be better if I get something like the Fiio E17, or E10, that has a built in DAC/amp?
> 
> Thanks




You could get the O2 and then use that $42 DAC that was linked. The chips (TE7022 + ES9023) are the same ones used in the ODAC, though not as good of an implementation I'd wager.


----------



## agdr

Quote:  





> Edit:  Sorry, the Hifimediy has optical-out, that's the difference.


 
   
  Actually it does both!  Pretty cool.  It uses a 3.5mm jack that will accept a standard 3.5mm plug, OR it can accept a mini-toslink optical plug.
   
  The headphone jack on my Sony VPCF112FX laptop is the same way.  They just build a led into the 3.5mm jack.  Turns out the mini-toslink plug and 3.5mm jack are the same size and both fit right in.  I can plug my headphones or my mini-toslink-to-standard-toslink optical cable going to an external amp into that laptop jack and it works just great.  All I have to do is switch the default sound device in windows from headphone to digital out and vise versa.
   
  I have this HiFiMeDIY DAC (his ealier version w/o the fancy 3.5mm/toslink jack) and it works great. 
	

	
	
		
		

		
			





   In Windows 7 it causes a Sabre driver (for the chip) to load automatically when plugged in the first time.  I'm sure the ODAC would post better numbers on a dScope or Audio Precision analyzer, by my ancient ears are not likely to hear a difference (I don't have an ODAC).
   
  However the one hiccup is the Sony also has a built-in 24/44 and 24/96 DAC.  When I switch the internal audio settings over from 16/44 to 24/44 I really can't hear any significant difference between the headphone out on the laptop going into an amp vs. the HiFiMeDIY through the USB port even with the volume slider 2/3 down (loss of software bits).  But that is not saying anything bad about the HiFiMeDIY, but rather something good about the internal DAC in the Sony.  I guess the thing here is check your computer, if that is your source, and see if it happens to be 24/44 or 24/96 capable just the way it sits.


----------



## kiteki

> You could get the O2 and then use that $42 DAC that was linked. The chips (TE7022 + ES9023) are the same ones used in the ODAC, though not as good of an implementation I'd wager.


 
   
  Yup it's $42 versus $99 / $149 for pretty much the _exact same DAC,_ and then he has $57 - 107 extra to spend on the amplifier!!
   
  Here are some RMAA results, all very far beyond audible limits if you want to ask the odac designer - http://alkasar.online.fr/mesures/HifiMeDIY%20SABRE%2024-96%20DAC%20v1.htm


----------



## lorriman

usaudio said:


> I may have misread the article but I was under the impression when he said 98% of headphones he was referring to the other 2% as being other types such as electrostatics, which obviously aren't driven by the Violectric amps either.




He does mention at least one very old normal headphone (non-electrostatic) that the O2 hasn't enough power for. Also, I've understood that the HE-6 is not going to hit the transients.


----------



## USAudio

kiteki said:


> Yup it's $42 versus $99 / $149 for pretty much the _exact same DAC,_ and then he has $57 - 107 extra to spend on the amplifier!!
> 
> Here are some RMAA results, all very far beyond audible limits if you want to ask the odac designer - http://alkasar.online.fr/mesures/HifiMeDIY%20SABRE%2024-96%20DAC%20v1.htm



Hmmm, they may use similar chips but the implementations look quite different, so I don't know if we can say they are exactly the same. Also, the price difference is likely due to the fact the ODAC is designed and made in the USA. The HifiMeDIY is likely made in China.


----------



## ostewart

Check out the Stoner Acoustics UD100 DAC, $50 and ClieOS has compared it to the ODAC and its nearly as good.


----------



## orangecr

Wow, thanks a lot. That's a lot of information. 
Love this community, an the mobile site is working great too (first time I see it)


----------



## ostewart

Also someone raved about this DAC recently, for $20 im really interested in getting one.
   
  http://www.ebay.com/itm/ELE-EL-D01-MINI-HIFI-USB-DAC-PCM2704-DAC-BOARD-ELNA-Capacitor-Black-/251075511946?ssPageName=ADME:X:AAQ:US:1123


----------



## adydula

orangecr...
   
  The O2 amp is a totally transparent amp.
   
  Its not supposed to add or take away anything from the source.
   
  So if your source is not that great then your going to amplify its worts...good or bad...
   
  This is what is so great about it...it lets pay more attention to other pieces of the reproduction chain,,,,,
   
  Alex


----------



## glunteer

HiFiMeDiy Sabre or ODAC give a better result than my asus xonar dx? they get along with my fiio e11?


----------



## MHOE

Quote: 





glunteer said:


> HiFiMeDiy Sabre or ODAC give a better result than my asus xonar dx? they get along with my fiio e11?


 
   
  I have Xonar essence ST and ODAC... I would say both have very very good DAC section but the amount of detail is even better with ODAC.
   
  E11 is a *very very good* but a bit coloured amp... It depends on what you want from an amp. O2 is totally uncoloured and more transparent.


----------



## glunteer

Quote: 





mhoe said:


> I have Xonar essence ST and ODAC... I would say both have very very good DAC section but the amount of detail is even better with ODAC.
> 
> E11 is a *very very good* but a bit coloured amp... It depends on what you want from an amp. O2 is totally uncoloured and more transparent.


 
  mhoe but ... you can not use the ODAC and asus xonar simultaneously right? or you use one or the other ...


----------



## MHOE

Quote: 





glunteer said:


> mhoe but ... you can not use the ODAC and asus xonar simultaneously right? or you use one or the other ...


 
   
  Of course you cannot... I just compared DAC sections of ODAC and Xonar essence ST, that's all  I think that Xonar cards are of very good value and the difference is not big but ODAC is for sure better *if you realise its low price*.


----------



## stv014

Quote: 





glunteer said:


> mhoe but ... you can not use the ODAC and asus xonar simultaneously right? or you use one or the other ...


 
   
  If you mean using the ODAC as a DAC to the Xonar (to have access to its surround sound features), then you cannot. But it is of course possible to play separate audio streams on both at the same time.


----------



## stv014

Quote: 





glunteer said:


> HiFiMeDiy Sabre or ODAC give a better result than my asus xonar dx? they get along with my fiio e11?


 
   
  I am not entirely sure about the Xonar DX, but the Xonar D1 (which in theory is the same card as the DX, but with a PCI interface instead of PCIe, and a slightly different PCB layout), according to my tests, is comparable to the ODAC, and should be transparent in theory if it works without problems (no ground loop, no significant EMI, no bad power supply, etc.). It is also better - although it might not be an audible difference - than the RMAA results posted for the HiFiMeDiy DAC, but I do not know how accurate those are, because there are many things people can get wrong with loopback tests, and RMAA does not test the devices very extensively anyway (for example, it would fail to detect the clipping problems of the NuForce uDAC2). Considering its low price, it would be interesting to see more detailed and reliable tests of the HiFiMeDiy Sabre DAC.
  In short, if you do not have interference issues, "upgrading" to the ODAC is probably not worth the money in my opinion. Of course, subjectively the ODAC may still sound better, especially if you expect it to be an improvement.


----------



## autoteleology

I have a Fiio E9 + E7... Would it be a good idea to just buy the ODAC instead of getting the O2 as well?

 In other words, how does the E9 compare as an amp with the O2?


----------



## ostewart

E9 had very high output impedance, which could be problematic with low impedance headphones. O2 suffers from no such problems


----------



## autoteleology

What kind of problems does that cause? Is it worth $150 to fix in your opinion?


----------



## MHOE

Quote: 





tus-chan said:


> I have a Fiio E9 + E7... Would it be a good idea to just buy the ODAC instead of getting the O2 as well?
> 
> In other words, how does the E9 compare as an amp with the O2?


 
   
  I have had both amps... E9 is still neutral but is worse from the technical perspective. I do not find the E9 to be transparent enough. Also, the output impedance of 10 ohms is not very ideal for headphones with impedance up to 80 ohms.
   
  It very depends on what you are looking for with an amp... If you want neutrality, transparency, power and versatility (you can use SIPs with your unit in order to use whatever gain you want to get the cleanest amplification), O2 is what you want. If you just need an amp, E9 is good enough.
   
  But I have bought O2 w/ ODAC installed inside with my desired look and SIPs for changing gain resistors and cannot be happier... I am not planning to purchase anything else regardless the phone I am going to use  It's just perfect...


----------



## kiteki

usaudio said:


> kiteki said:
> 
> 
> > Yup it's $42 versus $99 / $149 for pretty much the _exact same DAC,_ and then he has $57 - 107 extra to spend on the amplifier!!
> ...


 
   
  Hifimediy is a team of Europeans and Chinese selling various DIY audio components, the $42 ES9023 is their only non-diy, finished product.  It's made in and ships from Zurich, Switzerland, I think.
   
  Since I trust my hearing a lot more than measurements (especially RMAA), it's not fair I say they are exactly the same, no.  I think a dScope analysis and several accounts of listening tests would be nice.
   
   


ostewart said:


> Check out the Stoner Acoustics UD100 DAC, $50 and ClieOS has compared it to the ODAC and its nearly as good.


 
   
  There is that one too, yeah.
   
   


> glunteer said:
> 
> 
> > HiFiMeDiy Sabre or ODAC give a better result than my asus xonar dx? they get along with my fiio e11?


 
   
  I'd vote the Hifimediy.  Then later you can use it's optical out, and put the $100 you saved towards a Yamaha reciver with optical in and 5.1.



 Yamaha RX-V371BL 5.1-Channel A/V Receiver by Yamaha 
 $179.95 
 Order in the next 22 hours and get it by Monday, Dec 3.


----------



## kiteki

ostewart said:


> E9 had very high output impedance, which could be problematic with low impedance headphones. O2 suffers from no such problems


 
   


tus-chan said:


> What kind of problems does that cause? Is it worth $150 to fix in your opinion?


 
   
  The 6.5mm jack on your E9 has 10 ohm output impedance which is fine and very common.  The 3.5mm jack has 43 ohm output impedance which can cause issues in for example 16 ohm products, you can try both jacks and hear the difference for yourself.


----------



## autoteleology

By testing through a rapid switch with my Q701 (adapter plugged into 6.3 unscrewed), I'm surprised at how much of a difference there is. It's weird. The 3.5 is not anywhere near as loud, and it sounds a bit different, though I can't put my finger on why.


----------



## glunteer

Thanks for everyone's help ... on second thought, I'll still stick with my xonar dx + FiiO e11 ... 'll save money and buy a better headphone ... thank you!


----------



## kiteki

Ah, well there may be more differences in the 6.5mm versus 3.5mm jacks than output impedance alone, idk.  If you already have the Fiio E9 + E7 I don't think you desperately need to invest in the ODAC or the O2.
   
  The ODAC / O2 project revolves around dScope measurements, accuracy, and concepts of what we can / can't hear.  There are other EE's using the exact same dScope with very different ideas on what we can hear, so take the project with some salt when it comes to how much you need to invest for self-titled "perfect sound".


----------



## autoteleology

Well, if anything, I want to get a better DAC than an E7. I've got no use for a large portable amp (I'm of the opinion that, in real portable use in noisy environments, you're not going to notice a difference for it to be worth the inconvenience), and I'm fine with the E9 (I really love the form factor).
   
  I mean, my Sansa Clip+ probably has a better DAC than the E7.
   
  (not really, but I've just never really been very impressed with the E7 as a standalone or an amp.)


----------



## kiteki

I've never heard the E7, but my favorite sounding DAC's were using a Cirrus Logic CS4398 or AKM AK4396 as the core chip.  I've seen their popularity on diyaudio.com as well, so there is most likely something to it.
   
  Yaya, I know, it's not the baseball players skill / efficiency which counts, it's how you implement the team, lol.
   
  I know, massive portable amplifiers are the suck-ness, and the really slim ones I'm yet to hear any 'real' kind of ampliifer sound from them.


----------



## MHOE

Quote: 





tus-chan said:


> Well, if anything, I want to get a better DAC than an E7. I've got no use for a large portable amp (I'm of the opinion that, in real portable use in noisy environments, you're not going to notice a difference for it to be worth the inconvenience), and I'm fine with the E9 (I really love the form factor).
> 
> I mean, my Sansa Clip+ probably has a better DAC than the E7.
> 
> (not really, but I've just never really been very impressed with the E7 as a standalone or an amp.)


 
   
  From what I've read about E7 not offering complete 16bit depth in reality and their measurements not being very impressive, I would also at least upgrade on E17...


----------



## miceblue

Quote: 





mhoe said:


> From what I've read about E7 not offering complete 16bit depth in reality and their measurements not being very impressive, I would also at least upgrade on E17...


 
  If I recall correctly, "Voldemort" really liked the E7 considering its price. I'm guessing the E17 will only be better considering it has the same DAC but with more options. I own an E7 and find it to be a good companion with my laptop for mobile use.
   
  This isn't totally related to the O2/ODAC itself, but is there a place other than eBay where I could purchase a short 3.5mm male-male cable for cheap? I lost the one that came with the E7 so I can't hook up my Clip Zip to the O2.
  All of the cables I've seen are ~$10. Seriously, $10 for a 3-4 inch cable?


----------



## glunteer

Quote: 





miceblue said:


> If I recall correctly, "Voldemort" really liked the E7 considering its price. I'm guessing the E17 will only be better considering it has the same DAC but with more options. I own an E7 and find it to be a good companion with my laptop for mobile use.
> 
> This isn't totally related to the O2/ODAC itself, but is there a place other than eBay where I could purchase a short 3.5mm male-male cable for cheap? I lost the one that came with the E7 so I can't hook up my Clip Zip to the O2.
> All of the cables I've seen are ~$10. Seriously, $10 for a 3-4 inch cable?


 

 this ?
   
  http://dx.com/p/fiio-l2-standard-3-5mm-male-to-3-5mm-male-cable-10cm-length-65664


----------



## miceblue

Quote: 





glunteer said:


> this ?
> 
> http://dx.com/p/fiio-l2-standard-3-5mm-male-to-3-5mm-male-cable-10cm-length-65664


 
  Yeah one of those. I just checked Amazon for one of those and it's $3. XD
  Thanks for the suggestion!


----------



## stv014

Quote: 





tus-chan said:


> By testing through a rapid switch with my Q701 (adapter plugged into 6.3 unscrewed), I'm surprised at how much of a difference there is. It's weird. The 3.5 is not anywhere near as loud, and it sounds a bit different, though I can't put my finger on why.


 
   
  The E9 has much higher output impedance on the 1/8" jack, and that causes the voltage on the low impedance Q701 to drop by about 3 dB more.


----------



## ayres

hi, i have a question about the power supply for the o2...
   
  is a 13v, 800mA wall wort sufficient for charging the o2?  i know the jds site and the designer's site say, '14-20v'... but i was wanting to double check with other head-fi'ers.  
   
  cheers


----------



## Bojamijams

13v  is not enough


----------



## stv014

JDS Labs actually ships the O2 with a 12 V/200 mA adapter by default. A 13 V/800 mA one is probably enough if you do not use headphones that need a lot of current, and it actually outputs 13 Vrms with a 800 mA load.


----------



## MrMateoHead

Quote: 





ayres said:


> hi, i have a question about the power supply for the o2...
> 
> is a 13v, 800mA wall wort sufficient for charging the o2?  i know the jds site and the designer's site say, '14-20v'... but i was wanting to double check with other head-fi'ers.
> 
> cheers


 

 The 12 VAC adapter sold for the O2 _outputs_ 13.9V @200mA, which meets spec.
   
  Check the actual output rating on that adapter. The 800 mA is more than enough, but you may or may not be below the 14-20V spec.


----------



## stv014

So, how much voltage does that "13 V" adapter output ? If it is 13 Vrms with a 800 mA load (and thus more than 13 unloaded), then it would be OK.


----------



## HamilcarBarca

Quote: 





stv014 said:


> So, how much voltage does that "13 V" adapter output ? If it is 13 Vrms with a 800 mA load (and thus more than 13 unloaded), then it would be OK.


 
   
  It's a step-down transformer, so the output voltage depends on the input voltage.
   
  Is it rated at 13V for a 120V input? What is your line voltage?


----------



## stv014

It is not my transformer, so I do not know the details. Maybe *ayres* can provide the information (it would be best to simply measure the voltage with a DMM if the adapter has already been bought).


----------



## HamilcarBarca

Quote: 





stv014 said:


> It is not my transformer, so I do not know the details. Maybe *ayres* can provide the information (it would be best to simply measure the voltage with a DMM if the adapter has already been bought).


 
   
  Oops, quoted the responder and not the OP. Sorry.


----------



## olsenn

The power circuit of the O2 requires an AC input that exceeds 12V plus any junction drop of the linear regulator IC's. Generally, I'd say anything over 13 volts will likely be okay. Of course you'll also need to make sure it outputs enough current (200mA should suffice, but it wouldn't hurt to get a 400mA+ one, just in case)


----------



## ayres

thanks for the responses... here's a pick of the stats:


if the image doesn't embed, I'll have to try again later.


----------



## stv014

Quote: 





olsenn said:


> The power circuit of the O2 requires an AC input that exceeds 12V plus any junction drop of the linear regulator IC's.


 
   
  That is not entirely accurate, here is a simplified simulation of the power supply (the diodes are not the same as those used in the O2, but the simulator does not have the 1N4002, so I replaced it with whatever I could find with similar specs):
   

   
  The voltage of the AC/AC adapter is specified as RMS voltage, but rectifying that results in DC voltage that is square root of 2 (~1.4142) times higher, minus the 0.6-0.7 V drop on the diodes. Of course, under load it drops further because the capacitors discharge, and the transformer has non-zero resistance as well. The 18 V peak voltage shown on the circuit translates to 12.73 Vrms, and the Rser=1 decreases that by an additional few tenths of a Volt (the green trace on the graph is the output of the transformer, and it has about 17.5 V peaks). The regulator ICs have a voltage dropout of about 2 V, but it may vary with the exact model used; the +/- 14 V minimum voltage (red and blue traces) is just enough to prevent the power supply from falling out of regulation. The 2*100 Ω resistors simulate a DC load of 140+ mA, that is probably enough for not too demanding headphones and the rest of the amplifier. So, I think if the transformer can output at least 13 Vrms even under worst case conditions, then that will work if the headphones do not need a lot of current.


----------



## ayres

pardon the ignorance, but my assumption is that the rating of the transformer will determine the rate at which the batteries recharge - not which headphones the o2 can and cannot drive. but I imagine that if listening while recharging, an insufficient psu could result in a slow battery drain. if an insufficient transformer just means that it takes a little longer to recharge, then the concern is less of a concern, but if the batteries/circuitry could be damaged over time, then there is a concern.

I'm using the o2 with 32 & 300 ohm cans.


----------



## mikeaj

ayres said:


> pardon the ignorance, but my assumption is that the rating of the transformer will determine the rate at which the batteries recharge - not which headphones the o2 can and cannot drive. but I imagine that if listening while recharging, an insufficient psu could result in a slow battery drain. if an insufficient transformer just means that it takes a little longer to recharge, then the concern is less of a concern, but if the batteries/circuitry could be damaged over time, then there is a concern.
> I'm using the o2 with 32 & 300 ohm cans.




Check the circuit (click for legible size, please excuse the quality):


Each battery is charged by the output of the respective regulator (7812 for positive and 7912 for negative), through a diode and the 220 ohms resistor. The regulator output would have to be really really low (+12V regulator outputting less than the battery voltage, almost, i.e. waaaaaay out of regulation), for the battery to actually be powering the amp.

Rate of charging just depends on the regulator output (should be about +12V, -12V) and current battery level. It pretty much just charges as according to what you see in the circuit and Ohm's Law: (Regulator output voltage - diode drop voltage - current battery voltage) / 220 ohms is the trickle charging current. That's not related to the AC adapter rating, except unless it's far below the point where the regulator output voltage is significantly affected.

As for the voltage the regulators receive (needs to be a certain point like 2V above +12V or so, or however much the drop is), that depends on the AC line voltage, transformer, how much the capacitor discharges between cycles on the AC input. Capacitor discharge between cycles depends on current drawn by the amp, thus the discussion about how much power is being used, which in turn depends on what headphones you're using and how loud you're listening and whether or not you're charging the battery, etc.


----------



## adydula

The WAU16-400 is the best transformer for any headphone with the O2.
   
  Alex


----------



## MrMateoHead

Quote: 





adydula said:


> The WAU16-400 is the best transformer for any headphone with the O2.
> 
> Alex


 

 K - Why?
   
  The O2, from what I understand, is either railed to +-9V on battery, or +-12V plugged in. How does the extra current and power help anything?


----------



## HamilcarBarca

Quote: 





mrmateohead said:


> Quote:
> 
> 
> 
> ...


 
   
  See Post #375 and Post #390 in this thread for an analysis of transformer requirements.
   
  Here's the conclusion.
   
_What it all boils down to is a 14Vac - 16Vac transformer with a 400mA or greater secondary rating (like the *WAU16-400*) means not having to know any tech details about the whole thing. It will just work, with the one exception of using a low impedance headphone that is also low sensitivity, that might pull more than 56mA per channel. Then use a 14Vac - 16Vac 1000mA unit, like the *WAU16-1000* which is only $0.25 USD more anyway at Mouser ($11.50 USD vs. $11.75). Might as well just get the 1000mA unit if there is plug space - it is about 25% larger physically._
  [emphasis added]


----------



## adydula

We cant link directly to where this is posted but you can easlily find if if you search.
   
  That said the AC transformer is a critical component. The O2's power supply needs at least 13.5 volts AC.
  The ideal AC transformer would be rated at 13-16 VAC and 400 ma or higher.
   
  The Mouser Triad WAU-12-200 is rated at 12 volts but is really about 13.5 VAC with NO LOAD and with a 120VAC line voltage works just fine for anything but FULL power sine wave testing OR driving LOW impedance power hungry cans. I have actually measured the no load AC voltage and its 13+ volts but varies with the line voltage flucuations.
   
  If you line voltage is actually below 117 VAC and/or you plan to drive difficult low impedance cans (likek HiDiMan planars) ...a 14+ VAC transformer at 400+ ma is suggested. The covers the worse case both for line voltage and low impedance cans....
   
  The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI. But those are more expensive than the WAU12-200.
   
  Having a AC transformer that provides a 13.5 VAC no load is right on the edge of letting some ripple through under the worst case conditions.....so if your O2 is used with low line voltage, for serious sine wave testing, continous tones, or using lower impedance power hungy cans having a higher voltage AC supply is highly recommended.
   
  I have the 12-200 and the 18-500 and do not hear any real world difference in listening with AKG 701/2's, LCD2's, Grado 325i's.
   
  Again there is more technical details on the other site...do a search and do some reading...
   
  Alex


----------



## muad

adydula said:


> Having a AC transformer that provides a 13.5 VAC no load is right on the edge of letting some ripple through under the worst case conditions.....so if your O2 is used with low line voltage, for serious sine wave testing, continous tones, or using lower impedance power hungy cans




So is the stock JDSlabs wallwart good enough for the HD650?

edit: I just noticed its fine according to nwavguy, supposedly a larger voltage ac adapter is if you want to run hifiman cans etc., otherwise it just makes the regulators run hotter...


----------



## HamilcarBarca

Quote:  





> So is the stock JDSlabs wallwart good enough for the HD650?
> 
> edit: I just noticed its fine according to nwavguy, supposedly a larger voltage ac adapter is if you want to run hifiman cans etc., otherwise it just makes the regulators run hotter...


 
   
  The WAU12-200 was always good enough for my HD-650, Fosxtex T50RP, and Beyerdynamic DT 990 and T70. One last problem is when the line voltage is 'low'. At work, occasionally our voltages dip quite low. Our Plant Manager. says sometimes they measure 105VAC at a few outlets. I've heard no audible effects from whatever's happening in the building, but I bought a Big Boy just in case.
   
  When the input voltage to the O2 is raised, say from ~12V to ~16V, more heat is generated. There's no supposition about this. Personally, I may just be reducing the useful life of the O2, but hopefully it isn't by much. I haven't lost any sleep yet.


----------



## ayres

thanks for the responses... @ hamilcarbarca, i saw those older posts in the upper half of the 300s, and very insightful regarding my psu question.
   
  b/c the o2 is diy conceived, we are, in a way, left to preference - both objectively and subjectively.
   
  i do have a lingering questions, though.  if battery charging is happening when the amp is NOT in use, then does it really matter which transformer is used as long as the batteries are receiving a full charge?


----------



## ayres

additionally, are there sonic differences between the o2 when plugged in to a transformer vs running off the batteries?
   
  cheers


----------



## adydula

ayres...
   
  I cant hear any differences between any of the transformers I have and just running off of batteries.....none, zip, zero, nada....
   
  The reason I got the 18 volt AC transformer was I wanted to hear for myself if there were any real differences using a higher than 13.5 VAC transformer.
   
  If I had to do it again the 16 vac version is what I would buy and use...
   
  Alex


----------



## autoteleology

So, I received my custom O2 a few days ago and it's awesome. Far better than my E9 IMO.

 I went 47/0 with nothing but a Desert Eagle on MW3 using the O2 and a Q701.


----------



## adydula

I have a set of Q701's that I really like, the most comfortable cans ever to me!
  Alex


----------



## Eisenhower

Quote: 





rudi0504 said:


> JDS Lab ODAC usb DAC + JDS Lab O 2 head amp full modification with Black Gate Capasitors


 
   
  that looks nice and all, but you really want it enclosed in metal to reduce noise


----------



## adydula

Unless its a really noisy environment and next to electrical stuff he will most likely be ok..I ran one of my O2's and ODACs 'naked' and didnt have any interference or noise issues that I could discern...this is when i was doing current load measurments to see what the actual current draw was from the USB PC power..
   
  Alex


----------



## wolfetan44

Quote: 





tus-chan said:


> So, I received my custom O2 a few days ago and it's awesome. Far better than my E9 IMO.
> 
> I went 47/0 with nothing but a Desert Eagle on MW3 using the O2 and a Q701.


 
  Wow, are you naturally really good at video games? Or would you give a lot of credit to your Q701's?


----------



## autoteleology

Quote: 





wolfetan44 said:


> Wow, are you naturally really good at video games? Or would you give a lot of credit to your Q701's?


 
   
  Well, I can answer that with just my K/D on the three most recent Call of Duty games.

 My Black Ops K/D is 1.22. This was when I used an XB500 for gaming, and the fact that Black Ops 1 has awful sound for tactical purposes.

 My MW3 FFA (my main game mode) K/D is 2.67. This is when I got my HD598 and my Q701, and the fact that noises on MW3 are super loud. SitRep Pro is almost a game-breaker if you're good at tracking footsteps.

 My Black Ops K/D is 1.33. The sound on this game is terrible. It's so bad that I refuse to play it and I just sold it over eBay yesterday. This is despite having even better equipment than when I played MW3.


----------



## wolfetan44

Quote: 





tus-chan said:


> Well, I can answer that with just my K/D on the three most recent Call of Duty games.
> 
> My Black Ops K/D is 1.22. This was when I used an XB500 for gaming, and the fact that Black Ops 1 has awful sound for tactical purposes.
> 
> ...


 
  Wow, those help a lot


----------



## uguz420

Hello,
   
  I'm using ODAC + O2, but the gain is waaay too much for my 650's if I keep the volume in the OS at maximum.
   
  I'd like to switch to x1 gain instead of x2.5, which I heard wasn't too complicated to do. Is there a guide somewhere? Google has not come up with anything straightforward.
   
  Thanks


----------



## Porter1

yeah the 2.5x is more than enough for the HD650's.  i usually have my volume knob at 9 o'clock for music listening with windows volume at 80%. a 1x/2.5x gain switch would be better.


----------



## mikeaj

uguz420 said:


> Hello,
> 
> I'm using ODAC + O2, but the gain is waaay too much for my 650's if I keep the volume in the OS at maximum.
> 
> ...




With ODAC the gains should be no more than 3.5x anyway, so take the 6.5x option down to 1x. I wouldn't recommend changing the 2.5x to 1x as that would leave the 6.5x option, which is mostly useless (at full volume, it will cause clipping no matter what you set the volume knob to).



Clip one end (or both) of the resistors marked R19 and R23. The idea is to effectively remove them from the circuit, so it's an open circuit there instead of the resistor. The leads are thin, so you can clip them with about anything. You see that they're right next to the volume control knob. That reduces the gain to 1x.

If you really wanted to modify the 2.5x down to 1x instead, clip R27 and R21 (and not R19 / R23).


----------



## xXShakeXx

I do not know if I understand right, sometimes I see people put option on O2 1x instead of 6.5x but what's the point of using an amplifier with gain 1x (which there is no gain),. This is not a waste of money?


----------



## uguz420

double post! (sorry)


----------



## uguz420

Quote: 





mikeaj said:


> With ODAC the gains should be no more than 3.5x anyway, so take the 6.5x option down to 1x. I wouldn't recommend changing the 2.5x to 1x as that would leave the 6.5x option, which is mostly useless (at full volume, it will cause clipping no matter what you set the volume knob to).
> 
> Clip one end (or both) of the resistors marked R19 and R23. The idea is to effectively remove them from the circuit, so it's an open circuit there instead of the resistor. The leads are thin, so you can clip them with about anything. You see that they're right next to the volume control knob. That reduces the gain to 1x.
> If you really wanted to modify the 2.5x down to 1x instead, clip R27 and R21 (and not R19 / R23).


 
   
  Thanks for the advice.
   
  By clipping, do you mean cutting their connection to the board? Are there any risks? Excuse the paranoia, I'm very unfamiliar with these kinds of things, so I'd rather check twice before committing to destruction. I'm not equipped at all to solder something back on if I mess up!
   
   
  Quote: 





xxshakexx said:


> I do not know if I understand right, sometimes I see people put option on O2 1x instead of 6.5x but what's the point of using an amplifier with gain 1x (which there is no gain),. This is not a waste of money?


 
   
  I need the amp because I use the DAC. (to get the sound quality I'm used to when switching between different computers, bypassing their ****ty soundcards)


----------



## HamilcarBarca

Quote:  





> Thanks. Are there any risks or me breaking stuff? I'm very unfamiliar with these kinds of things.


 
   

 Be sure it's disconnected from everything.
 Check carefully to make sure you're cutting the right lead.
 Don't cut or scrape the circuit board.
 Don't touch any other circuit element.
 Check again to make sure you're cutting the right lead.
   

 To be extra safe, use an anti-static wrist band. (This may be overkill.)
   
  You just cutting a small, stiff wire.


----------



## uguz420

Quote: 





hamilcarbarca said:


> Be sure it's disconnected from everything.
> Check carefully to make sure you're cutting the right lead.
> Don't cut or scrape the circuit board.
> Don't touch any other circuit element.
> ...


 
   
   
  Thank you. One question though, how can _removing_ resistors from the board can lead to lower gain?


----------



## mikeaj

xxshakexx said:


> I do not know if I understand right, sometimes I see people put option on O2 1x instead of 6.5x but what's the point of using an amplifier with gain 1x (which there is no gain),. This is not a waste of money?



Current gain. Unity gain buffers are used in many applications.

Such an amp can provide a lot more current than the device behind it, with lower distortion and lower output impedance. 





uguz420 said:


> Thank you. One question though, how can _removing_ resistors from the board can lead to lower gain?




The resistor there is in the feedback loop of the non-inverting amp. It corresponds to R1 in the diagram on the wikipedia page here. You're changing two resistors: one for left channel and the corresponding one for the right channel. With no resistor, the resistance there becomes infinite (okay, not really, just a lot).


----------



## miceblue

Quote: 





xxshakexx said:


> I do not know if I understand right, sometimes I see people put option on O2 1x instead of 6.5x but what's the point of using an amplifier with gain 1x (which there is no gain),. This is not a waste of money?


 
  Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  ^ this
   
  Even with a 1x gain, my headphones do benefit from the O2. The sensitive V-MODA Crossfade M-100 can detect background noise with a 2.5x gain so I avoid that option.


----------



## earphiler

So excited for my odac+o2 combo to drive my newly acquired hd650s. Getting a bamboo front 2.5/6.5 gain stock from mayflower and a jds odac. 

...Now to sell off my hd595, udac2-hp, and the (ra1 altoid tincan clone that's on the way, was gomna be a temporary fix until I got this combo) to feel a bit better !


----------



## Dragunov-21

I haven't tried any other decent amps, but I love my hd 650s, you won't be disappointed pairing them with the O2


----------



## wolfetan44

Quote: 





dragunov-21 said:


> I haven't tried any other decent amps, but I love my hd 650s, you won't be disappointed pairing them with the O2


 
  You like them with the O2?


----------



## miceblue

I went to a local Head-Fi meet and tried the K 702 and Q 701 with an O2/ODAC, Schiit Bifrost/Lyr, and NuForce Icon iDo. The O2/ODAC combo was by far the best-sounding setup. I am SO glad I got the O2/ODAC over the Bifrost/Lyr setup.


----------



## wolfetan44

Quote: 





miceblue said:


> I went to a local Head-Fi meet and tried the K 702 and Q 701 with an O2/ODAC, Schiit Bifrost/Lyr, and NuForce Icon iDo. The O2/ODAC combo was by far the best-sounding setup. I am SO glad I got the O2/ODAC over the Bifrost/Lyr setup.


 
  Really
	

	
	
		
		

		
			





 Then the O2/ODAC is better than the Magni/Modi you think?


----------



## Porter1

Quote: 





dragunov-21 said:


> I haven't tried any other decent amps, but I love my hd 650s, you won't be disappointed pairing them with the O2


 
   
  i second this, absolutely love my O2 and HD650's


----------



## muad

well that's good news for my hd650s... my o2/odac is coming tomorrow


----------



## miceblue

Quote: 





wolfetan44 said:


> Quote:
> 
> 
> 
> ...


 
  I have no idea but I'm curious to know the difference between the O2/ODAC and Magni/Modi as well. I'm looking forward to people's comparisons in the Magni thread.


----------



## adydula

I "had" a Schiit Asgard and a Schiit Lyr.....they have been sold, after I got my first O2 amp.
   
  The O2 amp and ODAC are well designed and implemented.
   
  Yes there are some mechanical things with connectors, size or whether on the front panel or back..but sonically the pairing are transparent and dont get in the way of the music....
   
  So even if the new stuff Schiit comes out with or any vendor or DIY it doesnt take away how well the O2 amp and ODAC perform.
   
  Its easy to get caught up in the bandwagon for new stuff!! Me included....I would wait for nor 'objective' reviews and testing to see how well this new stuff really performs apart from all the emotion!
   
  That said the Schiit stuff does look well built and hope it performs as well!
   
  All the best
  Alex


----------



## yashau

Hi, hope I'm in the right place for this. 
   
  I'm a new owner of the O2 and ODAC, both separate units not the combo build. Maybe this is a stupid question but, since the O2 works fine off the 9V *DC* battery, why is an AC power adapter specifically required for it to function? I'm not complaining just a bit curious. I know next to nothing about electronics.


----------



## Battou62

Quote: 





wolfetan44 said:


> Really
> 
> 
> 
> ...


 
  I am fairly certain the Modi/Magni will not measure near as well as the O2/Odac does. People are already reporting floor noise when the volume is turned up. This is an indication of distortion. The Modi/Magni doesn't have to measure as well as the O2/Odac. As long as it can maintain reasonable transparency and be cheaper than the O2 combo, it will be a hit. Some Schiit products have already been proven to measure poorly, but it doesn't matter because some people like the sound of distortion.


----------



## adydula

yashau,
   
  You can learn a lot about the o2 and the odac at the designers site, which we are prohibited to show the link here...you should easily find it
  by a quick search on the web. Just look for nwavguy.
   
  The AC adapter is used to charge the batteries and if connected it will power the amp and run off the ac adapter supplied power via the O2's ac to dc power circuitry.
   
  If the unit has the batteries removed it can run off the ac adapter.
   
  When its plugged in with batteries its running off the ac adapter and charging your batteries.
   
  If you unplug the ac adapter it runs of the pure DC power from the batteries...
   
  Alex


----------



## miceblue

Quote: 





adydula said:


> I "had" a Schiit Asgard and a Schiit Lyr.....they have been sold, after I got my first O2 amp.
> 
> The O2 amp and ODAC are well designed and implemented.
> 
> ...


 
  That's my only complaint with the O2/ODAC, the placement of ports. The Magni and Modi have much better placement but I'm more concerned about the audio quality than the usability.


----------



## adydula

The I/O ports can be fairly easily moved to the back or front if your a handy person or a good DIY'er...
   
  I have an standalone ODAC with RCA connectors and the  mini-USB and mini-jacks....not hard to do..
   
  The O2 amp can have the larger phone jack etc but it does require some plumbing..and lost of folks don't want to deal
  with that.
   
  I sure do wish nwavguy would re-surface and come out with the desktop version many of us are still hoping will surface someday....
   
  Who knows...
   
  But like you the audio quality is paramount ...
   
  Alex


----------



## Battou62

Quote: 





adydula said:


> I sure do wish nwavguy would re-surface and come out with the desktop version many of us are still hoping will surface someday....
> 
> Alex


 
   
  I know man. Looking back at some of the blogs made me realize I have been waiting on the ODA for over a year now. I wish he would at least give us an update on the project, or simply stop by to say "hey".


----------



## adydula

I have read some on the diy forum and another site but no one really knows where he has disappeared to ...but there is nothing really that the desktop version would bring to the table sonically...
   
  I posted a list of the possible upgrades somewhere in the topics on this site.
   
  Alex


----------



## Bojamijams

Quote: 





battou62 said:


> I know man. Looking back at some of the blogs made me realize I have been waiting on the ODA for over a year now. I wish he would at least give us an update on the project, or simply stop by to say "hey".


 
   
  i thought he was banned from this site? I don't remember why.
   
  But I got my ODAC+O2 combo from JDS and oh MAN do I love this thing!

 Using it with my JH|13's and my 600ohm DT-880 (1x / 6.5x setup) ... this is the best ~300 I've ever spent.  keeping this until it dies.


----------



## adydula

Yes he was banned...but please lets not go down that path.
   
  Lets stick with the actual product etc...design....performance etc.
   
  I did notice that Schiit has a new $99 amp and a new $99 dac which at the price point has caused a lot of attention and can be read about on several other
  threads and at the Schiit site.
   
  I mention this because there are and will continue to be many comparions to these new products to the O2/ODAC products.
   
  From what little real experience some have indicated that these low level entry devices are not as good as the more expensive Schiit ASGARD or LYR of which I owned both for a year or so.
   
  They may good, solid stuff, its just when I heard the O2 and compared well....to me there was no need to have all these amps and I sold the Schiit stuff.
   
  The O2 and ODAC to me is about as good as it gets at this end of the spectrum cost wise, but its a very, very good example of a great well thought out design...that many of
  us really enjoy....
   
  Alex


----------



## MrMateoHead

I just ordered the ODAC, but expect some buyers remorse as my current setup is already very good. I don't think that the ODAC will make a night / day difference in sound in other words. I already own the O2 so I am skipping this Schiit! 
   
  That said, I have to say that the $200-220 dollar Schiit stack is really competitive with the $320 dollar O2 stack (separate components / cabling). If I could have a do-over, I probably would have picked up the $285 dollar O2/ODAC combo unit or just modded myself.
   
  Considering just how perfectly awesome the O2 is, I can't wait to see some measured performance / comparisons between the units. Then I may end up hating myself for blowing so much on headphone components (almost as much as the phones' themself - Doh!). But I know the O2, if it lasts, is going to be a great amp for all future phones' as well.


----------



## Dragunov-21

Quote: 





mrmateohead said:


> That said, I have to say that the $200-220 dollar Schiit stack is really competitive


 
   
  Every time some-one says this, all I can think of is Reggie Watts... erm, very much NSFW:


----------



## Dragunov-21

Quote: 





wolfetan44 said:


> You like them with the O2?


 
   
  Makes me fill the cup every time.


----------



## wolfetan44

Quote: 





dragunov-21 said:


> Quote:
> 
> 
> 
> ...


 
  I'll probably still end up investing in a Crack when I do get a HD650. Or HD700/800. One can only wish.


----------



## proton007

Quote: 





wolfetan44 said:


> I'll probably still end up investing in a Crack when I do get a HD650. Or HD700/800. One can only wish.


 

 I've been keeping my eye on the Crack, but I only have one high impedance headphone.


----------



## moshen

Quote: 





adydula said:


> Yes he was banned...but please lets not go down that path.
> 
> Lets stick with the actual product etc...design....performance etc.
> 
> ...


 
   
   
  That's really interesting to hear. I'm running my O2 with my HE-500 which are a bit power hungry but they sound great. On low gain I don't even hit 9 o'clock for normal listening volume. I'd be really interested to hear the HE-500 on a more powerful setup but it sounds like I might not be missing much if anything. The O2 was a huge step up in sound vs. the Total Bithead which I also have on my HE-500 but I think that's expected since the O2 is much more powerful as well.
   
  How did your LCD2 compare to your Lyr in terms of sound? I really love my ODAC+O2 all in one. I'm tempted to also pick up the O2 and ODAC alone as separate units as well. I wish there was a way to thank NWAvGuy for this design.


----------



## Dragunov-21

Quote: 





proton007 said:


> I've been keeping my eye on the Crack, but I only have one high impedance headphone.


 
  Saw the crack a while back and loved the look of it, but the price has increased substantially and now you've got other stuff to compare it to...  haven't looked too closely because I'm on a buying hiatus, but it used to be a ~$200 amp; now it's a ~$300 amp, and even if that's a fallacy with it only jumping sixty bucks, it's certainly enough to make me think twice about grabbing it when I have a capable budget amp in the O2.


----------



## ostewart

HD700 sound great from the O2, a lot better than the HD650, The HE-6 sounded excellent out of a icon audio HP-8 tube amp, but the O2 still drove them fine


----------



## ostewart

HD700 sound great from the O2, a lot better than the HD650, The HE-6 sounded excellent out of a icon audio HP-8 tube amp, but the O2 still drove them fine


----------



## Battou62

Quote: 





moshen said:


> That's really interesting to hear. I'm running my O2 with my HE-500 which are a bit power hungry but they sound great. On low gain I don't even hit 9 o'clock for normal listening volume. I'd be really interested to hear the HE-500 on a more powerful setup but it sounds like I might not be missing much if anything. The O2 was a huge step up in sound vs. the Total Bithead which I also have on my HE-500 but I think that's expected since the O2 is much more powerful as well.
> 
> How did your LCD2 compare to your Lyr in terms of sound? I really love my ODAC+O2 all in one. I'm tempted to also pick up the O2 and ODAC alone as separate units as well. I wish there was a way to thank NWAvGuy for this design.


 
  Send him an email on his blog. Google nwavguy.


----------



## autoteleology

I'm curious as to why NwAvGuy chose to set all of the inputs and outputs on the front panel.


----------



## purrin

cheaper. only need to machine the front panel.


----------



## adydula

moshen...
   
  I dont want to badmouth Schiit or its products, I have owned several and enjoyed them for what they are.
   
  The Lyr with 6 watts was very inticing to me and thats the main reason I had one....and I went thru several sets
  of tubes etc....monye, time and well.....always confusing and not very objective results...
   
  When I discovered the O2 and its design points etc.....and finally heard the LCD2's with it ....I sold the Lyr with no hesitations....for an
  amp that is 1/3 the cost....
   
  The Lyr basically to me was too 'colored' or just added that subjective warmth sound to the source....not that that is bad for some music and
  recordings....
   
  I wanted a totally transparent amp...so i could judge the source and the transducers.....so the O2 was a perfect choice for me...
   
  Lots of good electrical engineering design, layout, componenet selection based on facts and real data....
   
  All the best
  Alex


----------



## Battou62

Quote: 





adydula said:


> snip


 
  I love to listen to people's descriptions of sound when they do headphone reviews. They use words like "color", "sparkle" , "veil" , "muddy" , and "upfront". There isn't anything wrong with this. My engineering mind simply sees this as "distortion", "distortion", "distortion","distortion". I understand that headphones will always affect sound, but IMO the DAC and AMP should never alter the sound of the source.


----------



## JakeJack_2008

Quote: 





battou62 said:


> I love to listen to people's descriptions of sound when they do headphone reviews. They use words like "color", "sparkle" , "veil" , "muddy" , and "upfront". There isn't anything wrong with this. My engineering mind simply sees this as "distortion", "distortion", "distortion","distortion". I understand that headphones will always affect sound, but IMO the DAC and *AMP should never alter the sound of the source*.


 
   
  So what would you say about the C421 - *Black *edition with a _bass boost_?
   
  Anyway, I am extremely interested in the ODAC and O2.
  I think I'll buy them as separates because the ODAC/O2 combo does _not _have a LINE-LEVEL OUT (unless you mod it yourself).
  (I'd prefer them in one case but with a LINE-LEVEL OUT, if it's possible. Just like the iBasso D12, etc,...).
   
  Also, I'd like the 1/4" headphone jack which is more robust than the 1/8" one. I hope that JDS Labs can provide the 1/4" headphone jack/output.
   
   
  Finally, should I go for RCA outputs? What portable/*trasportable * headphone amps or DAC/amp combos _under $300 _require or accept _RCA inputs?_


----------



## Crispy808

Quote: 





jakejack_2008 said:


> So what would you say about the C421 - *Black *edition with a _bass boost_?
> 
> Anyway, I am extremely interested in the ODAC and O2.
> I think I'll buy them as separates because the ODAC/O2 combo does _not _have a LINE-LEVEL OUT (unless you mod it yourself).
> ...


 

 http://www.head-fi.org/t/640929/diy-desktop-objective2-amplifier


----------



## Dragunov-21

Quote: 





jakejack_2008 said:


> So what would you say about the C421 - *Black *edition with a _bass boost_?


 
   
  That's intentional, engineered EQ.  Not the same thing at all.


----------



## adydula

I bought the 02 not the 421....I dont want any EQ, none, zip, zeto, nada....but I can understand people wanting this and liking it....just not as accurate on the low end as I like....there are many ways with software that you can eq etc...
   
  If asked which one I would buy it would be the 02 each and every time.....unless someone says hey I want a little bass boost etc..I would probably have a discussion about accuracy and bit perfect etc....
   
  On all the AVR's I had in the past all the treble and bass controls to me were worthless and stayed in the center or neutral posiion...always wanted and still do the most transparent and shortest path from the source to the transducer.
   
  I even had a cd deck that drove a PS Audion 200C amp directly, no preamp etc...one less set of cables, on less piece on interconnects etc....
   
  The less stuff to get in the way the better...this is why I stayed away from PC and audio for years and years until the lossless formats came on the scene and bitperfect playback became do-able....
   
  So there ya go...
   
  All the best
  Alex


----------



## miceblue

So I have a question, it's probably a newbish question to ask, but what exactly is transparency and how does one know if X is transparent?
  I see this term used a lot with the O2/ODAC so I'm curious to know about it. For instance, compared to my FiiO E7, instruments within a song just sound much crisper and well-defined. Is this transparency?


----------



## wolfetan44

miceblue said:


> So I have a question, it's probably a newbish question to ask, but what exactly is transparency and how does one know if X is transparent?
> I see this term used a lot with the O2/ODAC so I'm curious to know about it. For instance, compared to my FiiO E7, instruments within a song just sound much crisper and well-defined. Is this transparency?


I'm going to take a stab, I think it means that the O2/ODAC doesn't change or color the sound. It improves on what the headphone does. Like what you said about the sound sounding much crisper and well defined.


----------



## miceblue

Quote: 





wolfetan44 said:


> Quote:
> 
> 
> 
> ...


 
  That could be it. Thanks!
   
  On a different note, does anyone have a 4-ring 3.5mm cable (TRRS connector)? With the V-MODA M-100, I the connection to the O2 is very finicky: if I push it in or rotate the jack a little, the music turns mono. For this reason, I pull out the plug a bit.


----------



## shadow419

Quote: 





miceblue said:


> That could be it. Thanks!
> 
> On a different note, does anyone have a 4-ring 3.5mm cable (TRRS connector)? With the V-MODA M-100, I the connection to the O2 is very finicky: if I push it in or rotate the jack a little, the music turns mono. For this reason, I pull out the plug a bit.


 
  If it's really troubling you, your best bet might be to just use a different male/male 3.5mm cable.  You could also use a female trrs to male trs adapter.


----------



## adydula

miceblue...
   
  In the design stages of the O2 amp the designer went thru a process of identifying several specifications that he thinks can affect the signal being amplified etc...that could add or subtract from the original source.
   
  In the design he went to great pain to design the amp to meet or exceed these specifications.
   
  The specs are discussed in his blog.
   
  These specs according to him if met or exceeded make the amp totally transparent to our hearing etc...
   
  In other words what you put into the amp should come out the same way just amplified somewhat based on the gain etc...
   
  There should be no bass boost, or treble attenuation etc....
   
  So garbage in will be garbage out.
   
  Great stuff in will be great stuff out...
   
  It allows your to see what your cans really sound like or are capable of when using really good source material....
   
  There are countless discussions all over this site and other about how "this amp" or "this dac" works with these cans etc....
   
  With a totally transparent amp and dac...you have a good baseline to compare the other "moving" targets...
   
  The O2 amp and ODAC allow you to do this....
   
  Alex


----------



## JakeJack_2008

Quote: 





sling5s said:


> I think the mixed message comes from that: the O2 has enough power to give it all the volume you need.  But it does not have the power to give it the headroom and dynamics.


 
  This interest me very much: ''the _headroom _and *dynamics'.  *I hope that the ODAC & O2 (as separates) will satisfy my _DT 880 _(*250 Ohm*) in this department.
   
   
  Let me ask this:
  - is the ODAC *musical*? (and you use your _musical _amp)
  - is the O2 set *musical*? (and you use your _musical _DAC)
  - are the DAC & O2 (as combo or separates) *musical*?
   
  Obviously, the _synergy _between the ODAC & O2 and one's heaphones plays a key role here.


----------



## adydula

jack...
   
  the amp and odac are not musical.
   
  They are neutral...whether you hear audio in your cans sounds "musical" depends on how well your source was recorded and how well you cans or speakers reproduce them...
   
  You need to spend some time over at the designers blog and read the instructional articles on needing more power and understand what this amp can provide to drive your cans to their fullest capability...
   
  I believe the power capability available from this amp will exceed what the DT880 require.
   
  Its all there in his blog...go to the O2 Headphone section, search on "880" and you will see the response etc..
   
  Good Luck!
   
  Alex


----------



## JakeJack_2008

Alex,  thanks a lot.


----------



## Battou62

"Musical", "headroom", "dynamics".
   
http://imgur.com/1riWm


----------



## miceblue

Quote: 





adydula said:


> miceblue...
> 
> In the design stages of the O2 amp the designer went thru a process of identifying several specifications that he thinks can affect the signal being amplified etc...that could add or subtract from the original source.
> 
> ...


 
  Ah, that makes sense now. Thank you for clarifying that!


----------



## adydula

When you read about this amp or that amp with this setup or that setup or with these tubes etc sound so good or different its because those amps are most likely adding to or taking away somthing to the source signal etc..acting as a filter or eq'ing the source...
   
  There are other amps that are very very good as well, that ususal cost a lot more etc....than the O2 amp...
   
  With the O2 you can achieve a totally transparent bitperfect flow for a relatively low cost....a great solution.
   
  I would rather have a low cost transparent solution and play with cans and source material than chasing amps that make my stuff sound good or diffferent...
   
  Many will agree and many will not...
   
  Alex


----------



## gnarlsagan

Quote: 





battou62 said:


> "Musical", "headroom", "dynamics".
> 
> http://imgur.com/1riWm


 
   
  +1


----------



## Battou62

I know there is no good convention for describing how something sounds. Sound will always be subjective to a point. What really bothers me is that some people say they don't like the way the O2 / Odac sounds. I think to myself " What. The O2 / Odac is audibly transparent. It shouldn't sound like anything."


----------



## adydula

battou62...
   
  yup agree with you there.....
   
  we are stuck with the source material.....
   
  we listen to music that is recorded and mastered and we make subjective judgements on how it sounds to each of us...
   
  We often compare one song against another, songs from old recordings that have been remastered good and bad.
   
  So its good to have the amp and dac at least be the least 'troublesome' with all the other variables we have to deal with.
   
  The O2 amp and ODAC sure do help mitagate the variables...
   
  On another site, I started a thread on "outstanding demo cd's" It has several hundred suggestions / selections that many people think are really well recorded and mastered....some of the stuff is not to my liking musically...but I do appreciate the quality of the recordings and mastering...
   
  All the best
  Alex


----------



## JakeJack_2008

Quote: 





adydula said:


> When you read about this amp or that amp with this setup or that setup or with these tubes etc sound so good or different its because those amps are most likely adding to or taking away somthing to the source signal etc..acting as a filter or eq'ing the source...
> 
> There are other amps that are very very good as well, that ususal cost a lot more etc....than the O2 amp...
> 
> ...


 
  Yes,
   
   
  Quote: 





> With the O2 you can achieve a totally transparent bitperfect flow for a relatively low cost....a great solution


 
   
  but I've read on this site that a much more difficult  is to make a headphone amp _dead quiet  (_*at this price range*_)  ..a_nd - that person continued - the O2 is a real _ achievement_!
  ... and, if I remember correctly,  _transparency _is _not _diffilcult to achieve_._


----------



## adydula

Well, until the O2 came on the scene many vendors weren't so transparent in posting all there specifications.
   
  The fact that many, many people indicate that one amp with the same set of cans sound different makes you wonder how transparent they really are.
   
  Achieving all the specs down to points beyond audibility seems to be the mark of what transparency is....you don't hear anything but the source that you inject into it....it comes out the same just amplified etc...
   
  We can debate what the tests or specs are until the next Mayan end of the world but for the most part the designer has published what he has determined to be important that influence the transparency of the amp.
   
  Good news here is another headphone site has taken a look at these and has or is incorporating some if not all of the nwavguys specs etc in an attempt to provide some more technical guidance in differentiating the differences in cans via such specs...whether you buy into them or not.
   
  As far at the noise etc.....it does take some experimenting with component selection and layout as is discussed in hi blog....
   
  Good discussion.
   
  Alex


----------



## stv014

Quote: 





> Originally Posted by *JakeJack_2008* /img/forum/go_quote.gif
> 
> but I've read on this site that a much more difficult  is to make a headphone amp _dead quiet  (_*at this price range*_)  ..a_nd - that person continued - is a really _ achievement_!
> ... and, if I remember correctly,  _transparency _is _not _diffilcult to achieve_._


 
   
  If a device has audible background noise, then it is not transparent.


----------



## TheGame21x

I keep wondering whether or not I should upgrade from my Fiio E9-E10 combo to get the O2+ODAC.
   
  Anyone compared the two?


----------



## Uberbob102000

Quote: 





thegame21x said:


> I keep wondering whether or not I should upgrade from my Fiio E9-E10 combo to get the O2+ODAC.
> 
> Anyone compared the two?


 
   
  I've got a FiiO E17 and I'm looking to make the upgrade to the ODAC/O2, so if anyone has those impressions I'd love to hear them. It's either this or the Magni/Modi combo.


----------



## miceblue

Quote: 





battou62 said:


> I know there is no good convention for describing how something sounds. Sound will always be subjective to a point. What really bothers me is that some people say they don't like the way the O2 / Odac sounds. I think to myself " What. The O2 / Odac is audibly transparent. It shouldn't sound like anything."


 
  I try to stick to Stereophile's audio glossary when possible.
http://www.stereophile.com/reference/50/index.html
   
   
   
  Quote: 





adydula said:


> battou62...
> 
> yup agree with you there.....
> 
> ...


 
  Ooh, are you allowed to post the link here? I'm always interested in new kinds of music.


----------



## adydula

http://www.audiocircle.com/index.php?topic=63936.0
   
  Enjoy...lots of great stuff here......
   
  Alex


----------



## lbbef

I'm thinking of getting a o2+odac combo for my ES10...
  Can someone comfirm if they can really fit the odac under the o2 then add in batteries?
  TIA =D


----------



## wolfetan44

What do I need to get to use the O2 portably?


----------



## adydula

There is a picture of a person that mounted an ODAC under the o2 board in the standard enclosure with batteries on the topside as normal. It was very tight and I think they had to do some insulating to prevent shorting etc...I looked for the pix but cant find it at the moment....it may be on the DIY site? If I find it I will post. Its relatively easy to do if you get a larger case and buy a completed board from JDS or build one yourself..
   
  Portable? Buy one with the batteries....JDS labs etc...
   
  Alex


----------



## despine

I have a dumb question, Someone please help me.
   
  I just got the o2/odac, and I'm trying to test it out but I'm not getting any sound.
   
  So far I connected the o2/odac combo to my computer via mini usb, and plugged my headphone jack into the headphone jack in front panel,
   
  but no sound???
   
  Please help~


----------



## wolfetan44

Quote: 





despine said:


> I have a dumb question, Someone please help me.
> 
> I just got the o2/odac, and I'm trying to test it out but I'm not getting any sound.
> 
> ...


 
  Did you get the wall plug for the O2?
http://www.jdslabs.com/item.php?fetchitem=38


----------



## despine

Quote: 





wolfetan44 said:


> Did you get the wall plug for the O2?
> http://www.jdslabs.com/item.php?fetchitem=38


 
  Sorry I forgot to mention that I'm using an a/c adapter from my router, so the amp is turned on with red light
   
  and from my desktop, I see Odac in volume control area, but no sound~
   
  Help me~~~~
   
  Edit:  A/c adapter from the router is 12v and 1amp. I'm not getting any sound from the amp, is it because the adapter isn't putting out enough power?
   
  edit: I'm guessing that I'm not getting any sound because the adapter is probably ac to dc output? arg...
   
Edit: Problem was with the adapter


----------



## wolfetan44

Quote: 





despine said:


> Quote:
> 
> 
> 
> ...


 
  Thats what I was thinking..
  _______________________________________________
   
  How do I use the O2 portably?


----------



## adydula

You need an AC to AC adapter!!
   
  They are very different..
   
  Alex


----------



## miceblue

Quote: 





wolfetan44 said:


> How do I use the O2 portably?


 
  If you bought the O2 as a separate unit and it has batteries installed...you just use it normally. 
	

	
	
		
		

		
			




   
  Source -> 3.5mm O2 source jack
  Headphones -> 3.5mm O2 headphone jack
  Turn-on source, set volume, play music
  Turn volume knob on O2 to low volume, set gain switch to low, turn-on the O2, adjust volume knob accordingly
   
  JDS Labs O2's battery lasts about 8-ish hours at 1.0x gain, max volume knob level, source volume set at public transit bus-listening levels, 32-ohm headphone.


----------



## autoteleology

I've had my O2 for a while, and I've found it to be superb.

 I just got my ODAC, and I'll tell you guys how I feel about it... as soon as I find my fragglesnaggin Q701 cable.
   
  Seriously, where has it walked off to?


----------



## Crispy808

I'm adding a 1/4" Neutrik headphone jack to my O2, but I'm not sure how to wire to P2.
   
  Per the designer's site, "_for P2 the two pads closest to the edge of the board are ground._"  Which of the other two pads correspond to the right and left channels?


----------



## lorriman

lbbef said:


> I'm thinking of getting a o2+odac combo for my ES10...
> Can someone comfirm if they can really fit the odac under the o2 then add in batteries?
> TIA =D




Yes, I did this with my own O2. The ODAC fits perfectly underneath the O2 circuitboard. Quite a marvellous coincidence; I don't think the designer did this deliberately. As someone else mentioned: you need to tape up the bottom of the ODAC with electrical insulating tape since the circuit board traces would otherwise be in direct contact with the aluminium of the case. 

There are also two methods of doing this. If the ODAC is placed upside down, then the aluminium case needs filing down. 

Pics here: http://www.diyaudio.com/forums/headphone-systems/193977-objective2-o2-headphone-amp-diy-project-251.html


----------



## adydula

lorriman...
   
  thanks for posting the link !!
   
  Alex


----------



## k186

At risk of stating the obvious, it should be R17 that needs to be clipped, not R27 (looks like a typo, plus there is no R27).  If this was already addressed in a later post, apologies in advance.

 Edited!  Thanks, stv014! duh, I dunno what I was thinking (late-night post).
  Quote: 





mikeaj said:


> With ODAC the gains should be no more than 3.5x anyway, so take the 6.5x option down to 1x. I wouldn't recommend changing the 2.5x to 1x as that would leave the 6.5x option, which is mostly useless (at full volume, it will cause clipping no matter what you set the volume knob to).
> 
> Clip one end (or both) of the resistors marked R19 and R23. The idea is to effectively remove them from the circuit, so it's an open circuit there instead of the resistor. The leads are thin, so you can clip them with about anything. You see that they're right next to the volume control knob. That reduces the gain to 1x.
> If you really wanted to modify the 2.5x down to 1x instead, clip R27 and R21 (and not R19 / R23).


----------



## stv014

Quote: 





k186 said:


> At risk of stating the obvious, it should be R17 that needs to be clipped, not R27 (looks like a typo, plus there is no R27).  And I think clipping / removing either one of R17 or R21 should suffice for dropping the low gain to 1x.  If this was already addressed in a later post, apologies in advance.


 
   
  Clipping only one of the resistors will drop the gain on only one channel.


----------



## Stratok

Just ordered mine cant wait


----------



## muad

After using some cheap tube amps and audio-gd fun this combo is a breath of fresh air. I believe the o2/odac with my iems and hd650 are as far as I need to go with headphones. If only I could use it as a preamp to a nice power amp in the future...


----------



## miceblue

Quote: 





uguz420 said:


> Hello,
> 
> I'm using ODAC + O2, but the gain is waaay too much for my 650's if I keep the volume in the OS at maximum.
> 
> ...


 
  I can't read circuit diagrams very well, so maybe this can help someone in the future.


----------



## k186

Quote: 





miceblue said:


> I can't read circuit diagrams very well, so maybe this can help someone in the future.


 

 It's right.  F--- me.  That's 2 mistakes.  I'm gonna stop posting altogether.  Wow.  I completely misread your picture miceblue, you're right.


----------



## miceblue

Quote: 





k186 said:


> Quote:
> 
> 
> 
> ...


 
  I dunno. I bought my O2 from JDS Labs and John sent me that photo. I clipped the rightmost resistors since the default 2.5x/6.0x gain was too much for me and now I have 2.5x/1.0x.


----------



## moshen

Quote: 





miceblue said:


> I dunno. I bought my O2 from JDS Labs and John sent me that photo. I clipped the rightmost resistors since the default 2.5x/6.0x gain was too much for me and now I have 2.5x/1.0x.


 
  Yea, I can confirm that photo is correct.


----------



## wolfetan44

Heres the O2 black guys!


----------



## miceblue

Quote: 





wolfetan44 said:


> Heres the O2 black guys!


 
  Nice! It looks pretty sleek. I was going to order my O2 with a black front plate as well, but I wanted it to match the silver front plate of the ODAC so I ended up getting the standard silver one.
  I must admit though, I'm not a fan of all of the O2's inputs being in the front...


----------



## wolfetan44

Quote: 





miceblue said:


> Quote:
> 
> 
> 
> ...


 
  Seeing it in person I think it looks a lot better.


----------



## mac336

hey guys, wondering where they currently stand with regards to releasing an objective desktop amp or if I can purchase an ODAC/o2 amp in the same chasis


----------



## wolfetan44

Quote: 





mac336 said:


> hey guys, wondering where they currently stand with regards to releasing an objective desktop amp or if I can purchase an ODAC/o2 amp in the same chasis


 
  Its on JDSlabs.com go to DAC's and the O2/ODAC amp will be there. I'm not sure I'm allowed to link the website.


----------



## mac336

thanks.  do you know where he currently stands with designs for an objective desktop amp?


----------



## audionewbi

does anyone know how many opamp the headphone out section needs? I wanted to try MUSES01 on this for the fun of it, I just dont know how many I need to buy.
   
  Thanks


----------



## stv014

Quote: 





audionewbi said:


> does anyone know how many opamp the headphone out section needs? I wanted to try MUSES01 on this for the fun of it, I just dont know how many I need to buy.


 
   
  There is one NJM2068 in the gain stage, and two parallel NJM4556's in the headphone buffer. However, it is not recommended to "roll" the headphone driver ICs (which were chosen for being the best for this specific application from many possible options tested) unless you really know what you are doing. It could easily make the amplifier perform worse, or even result in oscillation or other problems. It is safer to "roll" the gain stage op amp (preferably using one of the chips tested by the designer, which are known to work without problems), there is just not much point doing it.


----------



## audionewbi

Quote: 





stv014 said:


> There is one NJM2068 in the gain stage, and two parallel NJM4556's in the headphone buffer. However, it is not recommended to "roll" the headphone driver ICs (which were chosen for being the best for this specific application from many possible options tested) unless you really know what you are doing. It could easily make the amplifier perform worse, or even result in oscillation or other problems. It is safer to "roll" the gain stage op amp (preferably using one of the chips tested by the designer, which are known to work without problems), there is just not much point doing it.


 
  fair enough, I will opt out of it if that is the case, thank you.


----------



## despine

anyone else thinks using 6.5x gain sounds so much better than using 2.5x?
   
   
  I noticed much sharper sounds, more soundstage, more separtion of instruments, harder bass,
   
  and that's me using eph-100 iem, with 128 kbps radio streaming from winamp shoutcast
   
  Since I had gotten the o2/odac, I was using only 2.5x gain and I was completely content, until I tried 6.5x just out of curiosity and immediately noticed difference in sound.
   
  Things just sounded like it occupied much more space and filled more air space and much more fuller, and overal sounded more airy with more pronunciation of harder to hear instruments. 
   
   
   
  At first I thought it was my ear playing tricks, but the songs that I had heard many times sounded, just alot better.
   
  So I proceeded with experimenting with differnt songs, specifically ones with many instruments and of different volume levels.
   
  For obvious reasons I didn't listen to skillrex or some dubsteps, because everything would sound so mushed in to start with.
   
  I listened to some korean ballad, rnb, pop musics, even some classicals,  and  instruments like violin or cello that sounded like it was playing 10 ft away in 2.5x mode sounded like it was playing from 30ft away in
   
  6.5x mode but still managed to sound louder, clearer, and fuller.
   
   
  I lowered the computer side volume to about 30% so I have more room to fine tune the volume on the o2 side.


----------



## miceblue

Quote: 





despine said:


> anyone else thinks using 6.5x gain sounds so much better than using 2.5x?
> 
> 
> I noticed much sharper sounds, more soundstage, more separtion of instruments, harder bass,
> ...


 
  Nope. I read somewhere recently that the 6.5x gain actually starts clipping sound on the O2. 6.5x gain just adds excess background noise for my headphones when I used it so I just took out those resistors.
  Yeah right here. I'm not 100% sure if it's true or not though:


> dano91 said:
> 
> 
> > imackler said:
> ...


----------



## despine

miceblue said:


> Nope. I read somewhere recently that the 6.5x gain actually starts clipping sound on the O2. 6.5x gain just adds excess background noise for my headphones when I used it so I just took out those resistors.
> Yeah right here. I'm not 100% sure if it's true or not though:


 
  
   
   
  ya I remember reading several replies on that issue, that's why I was only using 2.5x, but to me things are on a completely different level at 6.5.
   
  Do you have the o2/odac combo or do you have them separately? I think  I read somewhere that may be the cause


----------



## miceblue

Quote: 





despine said:


> miceblue said:
> 
> 
> > Nope. I read somewhere recently that the 6.5x gain actually starts clipping sound on the O2. 6.5x gain just adds excess background noise for my headphones when I used it so I just took out those resistors.
> ...


 
  I have them as separate units.


----------



## mikeaj

The volume knob on the O2 is after the gain stage, so if the input is high and the gain is high, then it can exceed the amount the amp can handle. You get clipping, no matter what you set the volume to. On most audiophile amps, the volume control operates before the gain. That solution has worse SNR but avoids clipping if the source output is high and amp gain is also high.
   
  If used with ODAC, which outputs standard Redbook ~2V, default gains really ought to be like something between 3-3.5x for high and lower than that for the low (I'd say 1x). If you use ODAC with O2 set at gain above 3.5x, any max-volume signal (or if gain is higher, than some things below that as well) will be clipped at the peaks. That is, with all software volume controls turned to max, if there's a peak in the track that reaches the max, the ODAC will output a signal that will be clipped by the O2 set at gain above 3.5x. In most music releases these days, it reaches near the max all the time. Frequently, on most every beat. If software volume control is turned down, then you'll be cutting everything down to a level below the max the ODAC can output, and you can avoid clipping even on 6.5x gain or whatever.
   
  When the designer decided upon the default gains, it was envisioned (maybe in some sort of distorted fantasy land?) that most people using the O2 would be DIYers making one for themselves and thus setting the gains for themselves, and/or people were going to use this thick large palm-sized amp as a portable / transportable and primarily use portable sources like iPods and phones with weaker outputs that need more gain to reach the same levels. On the other hand, you could call it some kind of modesty (har har?) in not expecting the O2 to be as big a success as it is now among non-DIY users.


----------



## ostewart

O2 review is up:

http://www.head-fi.org/t/643435/review-jds-labs-o2-black-edition

Hopefully getting the ODAC next month too.


----------



## stv014

Quote: 





despine said:


> ya I remember reading several replies on that issue, that's why I was only using 2.5x, but to me things are on a completely different level at 6.5.


 
   
  A louder sound gives the subjective impression of better quality.


----------



## despine

Quote: 





stv014 said:


> A louder sound gives the subjective impression of better quality.


 
  I turned down the volume knob when going to 6.5x to have similar volume levels as when I was listening to it using 2.5x.
   
   
   
  Anyways, after some trials using he-400 at 6.5x gain, sound signature just got way too bright, even at lower volumes, making it unbearable to listen to it. So I guess I'm going to stick with 2.5x so I don't damage my hearings.
   
  and you guys were right about the clipping issue with 6.5x gain, I heard it when using he-400


----------



## stv014

Quote: 





despine said:


> I turned down the volume knob when going to 6.5x to have similar volume levels as when I was listening to it using 2.5x.


 
   
  Volume matching by ear is not good enough, you most likely only get within a few dB of accurate matching (and it is unintentionally biased in the direction of matching the position of the volume knob, rather than the actual SPL), and that is plenty enough for the psycho-acoustic effects of loudness to make the difference in perceived sound quality.


----------



## MrMateoHead

Quote: 





despine said:


> I turned down the volume knob when going to 6.5x to have similar volume levels as when I was listening to it using 2.5x.
> 
> 
> 
> ...


 

 If you are listening loud enough to clip at 6.5X, either you have a really strong input source, or you are listening way, way too loud.
   
  On AC power, the O2 can handle a little more that 2V @ 2.5x gain, so it shouldn't clip until your ears are bleeding.
   
  Seriously though - listen for a lifetime, turn it down. If you can't get enough volume, take them off for about 5 minutes. I gaurantee you will be able to turn the volume down and it will be loud enough.


----------



## stv014

Quote: 





mrmateohead said:


> If you are listening loud enough to clip at 6.5X, either you have a really strong input source, or you are listening way, way too loud.


 
   
  Clipping in the input stage does not depend on the volume setting of the O2, only on the input voltage, gain, and power supply voltage (i.e. clipping is more likely on battery power).


----------



## Jimmy24

Can anyone here compare how O2 differs from a Crack on an HD650? I'm thinking of upgrading to a crack but I'm not sure if I will hear a major difference in sound.


----------



## autoteleology

Custom O2 / ODAC + cable management = not bad


----------



## HeatFan12

Quote: 





tus-chan said:


> Custom O2 / ODAC + cable management = not bad
> 
> 
> 
> ...


----------



## adydula

nice!!
   
  Alex


----------



## wolfetan44

Do I have to unplug my headphone before I turn off my amp?


----------



## autoteleology

No.


----------



## wolfetan44

Quote: 





tus-chan said:


> No.


 
  But don't I have to do that for other amps?


----------



## autoteleology

For very, very expensive amps, I believe so, because of the specific way they power up.

 For consumer gear like the O2, it's not an issue.


----------



## wolfetan44

Quote: 





tus-chan said:


> For very, very expensive amps, I believe so, because of the specific way they power up.
> 
> For consumer gear like the O2, it's not an issue.


 
  Thanks!


----------



## miceblue

Quote: 





tus-chan said:


> Custom O2 / ODAC + cable management = not bad


 
  Woah, that acrylic front...is freaking KILLER! Love it!


----------



## htxmade

Would the O2 + ODAC combo work well with the DT990 600 ohm headphones?
   
  Which AC/AC adapter are you guys using?


----------



## Headzone

Just when I ordered my O2, headnhifi got more case colors back in stock.. I think those look pretty rad.


----------



## proton007

Quote: 





headzone said:


> Just when I ordered my O2, headnhifi got more case colors back in stock.. I think those look pretty rad.


 

 Yeah, especially the matching front plate and the casing.
   
  I soldered mine myself, so I only got the front/back plates. The casing I bought externally, and I think you can buy it in different colors, its just anodized aluminium. A copper colored one would be nice.


----------



## autoteleology

> Yeah, especially the matching front plate and the casing.


 
   
  It doesn't appear that they actually match. The front plate looks brushed, while the casing looks like it has a powder coat.
   
  I like their colors a lot, though.


----------



## adydula

and...the sound is now so 'colored' as well......lol
   
  Alex


----------



## ostewart

Bit of a war going on in my review thread over the O2, just 1 guy saying bad things about the O2 because he doesn't like it with his HD650... each to his own


----------



## adydula

funny how that goes......even when the designer choose the hd650 as his personal favorite...the more i read on these forums the more I see there are lots of people that are really lost when it comes to this stuff...
   
  many folks looking for this or that in sound to make them happy....or what works good with this or that....
   
  do you want accuracy in reproduction or stuff that changes the source to make you happy??
   
  Just know that the 02 and ODAC are transparent and about as good as it gets......maybe this person just doesnt like what he is 'accustomed' to with his 650's...
   
  oh well...the beat goes on....
   
  lol
   
  Alex


----------



## ostewart

Very well put, I will keep enjoying my O2, and hope for a ODA in the future, whenever that comes out....

And am looking forward to getting an ODAC soon too.


----------



## adydula

Dont hold your breath on the ODA....I hope it finally appears but no one seems to know what he is up to.....
   
  You can build an ODA like amp easliy and have 99% of what he stated it could possibly be...
   
  But sonically its pretty much a wash to what we already have...
   
  The one thing I cant state enough is the O2's battery capability......it takes away all those arguments from all those "pure" AC power addicts.....
   
  The O2 runs on pure DC......no ripple, no noise.....and its easy to add the AC adapter and see if you can hear any difference between a half wave rectifier, very unsophisticated and pure DC....boy that one really makes me SMILE!! lol.
   
  All the best
   
  Alex


----------



## proton007

No updates on the ODA.
  But its weird there's no ODA combination being sold by JDS or other makers out there.


----------



## muad

Quote: 





proton007 said:


> No updates on the ODA.
> But its weird there's no ODA combination being sold by JDS or other makers out there.


 
   
  I think part of the whole free/open source design, means anyone can make them but I believe there was a stipulation againgst modifying the design in anyway, at least commerically. I believe the reason for this is if someone messed with the his design it may no longer meet the specs and would tarnish the object of the design.
   
  I eventually gave up waiting for the ODA and picked up and o2/odac combo (<--amazing). I don't believe that the ODA will be done anytime soon if ever. It was a little concerning how he simply dropped off the face of the planet without any explanation. Whatever his reason... I'm grateful for all the work he did, music never sounded so good


----------



## ostewart

Review thread is open again 

Also the pro photographer happens to be my best friend, I moved away when I was younger, but I'm back in england on holiday so I got him to do the photos with his nikon D7000


----------



## proton007

Quote: 





muad said:


> I think part of the whole free/open source design, means anyone can make them but I believe there was a stipulation againgst modifying the design in anyway, at least commerically. I believe the reason for this is if someone messed with the his design it may no longer meet the specs and would tarnish the object of the design.
> 
> I eventually gave up waiting for the ODA and picked up and o2/odac combo (<--amazing). I don't believe that the ODA will be done anytime soon if ever. It was a little concerning how he simply dropped off the face of the planet without any explanation. Whatever his reason... I'm grateful for all the work he did, music never sounded so good


 

 Yeah, I'm also using the O2 + ODAC separately, and see no issues. Maybe he's just busy with other things, and creating the ODAC might've opened up some commercial avenues for him I guess.


----------



## Headzone

Just got my O2 in the house. Doing some comparison now with my Pioneer A-223 integrated amp.
   
  I think the O2 is more articulate sounding, plus it's totally silent at any volumes. Also somehow the O2 bass sounds tighter and more natural. I am actually surprised that there's quite noticeable difference between these amps.. (headphone HD-600 tested)


----------



## hekeli

Quote: 





adydula said:


> even when the designer choose the hd650 as his personal favorite


 
   
  Well he seemed to have very little experience with more expensive (or any) phones anyway, it doesn't mean anything..


----------



## HamilcarBarca

Quote: 





hekeli said:


> Quote:
> 
> 
> 
> ...


 
   
  You mean other than the HD-650, K701, and HE-500?


----------



## adydula

Why does expensive seem to mean good most of the time....?
   
  Alex


----------



## ostewart

True, expensive does not equal quality


----------



## adydula

Headfonia's Erik picked the O2/ODAC combination as his choice for personal Product of the Year 2012.....
   
  Well done nwavguy....
   
  Alex


----------



## MrMateoHead

^^^^ Amen


----------



## Shazb0t

If anyone can help with my question, it would be appreciated.  Thanks.
   
  http://www.head-fi.org/t/644307/q701-with-o2-question


----------



## Artemka

Hey,
   
  Has someone from Canada ordered the O2 from JDSlabs (i'm sure somebody did)?
   
  Were there any extras taxes/duties that you had to pay? I emailed the Jdslabs and they responded nobody complained about the extra fees from Canada? Is that true? Thanks.


----------



## autoteleology

If you're in Canada, just get one of the much nicer Audio Poutine versions (based in Canada) and don't worry about it. It's virtually the same price anyways.


----------



## miceblue

OK, seriously, no joke here.
   
  I have the O2/ODAC plugged-in to my Retina MacBook Pro, only Finder, Activity Monitor, Skype (text chat, no video chat), and Firefox with 1 tab (Head-fi) are open and I can hear the radio. Seriously this is really scaring me. I turned on the O2's gain switch to make sure I wasn't hearing things. It's playing the 106.9 radio station (I know the radio station pretty well). They just finished playing a Nickelback song and now they're playing Jason Mraz's "I'm Yours".
   
   
  I am genuinely confused and scared at the same time. What in the heck is going on? D:
   
  The radio music is louder when I put the ODAC on top of the O2. Retina MacBook Pro -> ODAC (via provided JDS Labs USB cable) -> O2 (via RCA connectors) -> any headphone I use -> my head and I hear the radio station
  *this isn't the first time this has happened either; the first time it happened I just ignored it*
   
   
  What the hay? If I unplug the O2's DC power source, I no longer hear the radio station.
   




   
   
  And "popping" with the O2/ODAC might be due to the computer. I plugged the combo in to a Dell desktop computer at my school and had no "popping" issues. I get the "popping" sound when I plug in/out the combo when I use my Retina MacBook Pro though.


----------



## Bojamijams

Quote: 





artemka said:


> Hey,
> 
> Has someone from Canada ordered the O2 from JDSlabs (i'm sure somebody did)?
> 
> Were there any extras taxes/duties that you had to pay? I emailed the Jdslabs and they responded nobody complained about the extra fees from Canada? Is that true? Thanks.


 
   
  I got it from JDS. No extra fees. Great service.


----------



## adydula

mice....if u run on batteries in the O2 AC unplugged your not hearing this radio station? correct?
   
  Alex


----------



## miceblue

Quote: 





adydula said:


> mice....if u run on batteries in the O2 AC unplugged your not hearing this radio station? correct?
> 
> Alex


 
  Correct. When I'm charging the O2, it seems that I can hear the radio station.


----------



## TheGame21x

First Impressions of the O2+ODAC have been posted over at my site, Musical Musings!


----------



## adydula

mice,
   
  it sounds like the radio station is getting induced into the ac adapter line.....guessing here....try wrapping the ac adapters power line/cord into a small ball...or a small loop etc...see if this attenuates the radio interference....
   
  Alex


----------



## Battou62

Quote: 





thegame21x said:


> First Impressions of the O2+ODAC have been posted over at my site, Musical Musings!


 
  You're not helping me  I want of these combos so bad. I wonder if we will ever hear from "him" again about the ODA.


----------



## miceblue

Quote: 





thegame21x said:


> First Impressions of the O2+ODAC have been posted over at my site, Musical Musings!


 
  Your Magni died? 
  I guess Schiit products will be Schiit. *generalising of course, I have no direct experience with Schiit's customer service and I haven't been too impressed with their products*


----------



## TheGame21x

Quote: 





miceblue said:


> Your Magni died?
> I guess Schiit products will be Schiit. *generalising of course, I have no direct experience with Schiit's customer service and I haven't been too impressed with their products*


 
   
  Yeah. I switched my Magni off before I went to bed the night I got it, woke up the following morning, flipped the switch, nothing happened. Checked the wall wart, nothing was wrong with it but the Schiit was dead. Seeing as this is the first Schiit product I've ever bought, the Magni was not the greatest of first impressions.
   
  Currently waffling back and forth on whether or not I should simply return the things and take a $60 hit (due to shipping and restocking fees) or try to exchange the Magni and sell the M/M combo (the Modi still works, after all) to someone on Head-Fi. Decisions, decisions.
   
  In the meantime, at least I have the O2+ODAC to keep me company!


----------



## adydula

Gosh sounds like a quality control issue there?
   
  All of the Schiit stuff I have had, Asgard, Lyr worked flawlessly regardless of its sonic qualities....and Jason has always been top notch in contacting me with any questions...
   
  Alex


----------



## muad

In Canada the most they can charge you is sales tax on electronics. There are no duties on electronics for personal use.


----------



## miceblue

Quote: 





thegame21x said:


> Quote:
> 
> 
> 
> ...


 
  Holy mackerel this is depressing.
   
  So before I left the house for lunch/grocery shopping, I was doing some headphone testing between my earphones (Sennheiser CX 300 and MEElectronics M9). I come back home 2 hours later and my O2 is dead. To make sure it's my O2, I plugged it into my Clip Zip and I get no sound. Gain on or off, battery-powered or not, headphones or earphones, my O2 doesn't make any sound.
   
  My ODAC works just fine. At the moment I have my earphones plugged-in to that even though it's just a DAC.
   
  What to do?


----------



## TheGame21x

Quote: 





battou62 said:


> You're not helping me  I want of these combos so bad. I wonder if we will ever hear from "him" again about the ODA.


 

 I'm sure "he" will post an update sometime or another. He's gotta be almost finished with the ODA schematics by now. Or not.


----------



## wolfetan44

Quote: 





thegame21x said:


> Quote:
> 
> 
> 
> ...


 
  Why not tell Jason about it?


----------



## miceblue

Quote: 





miceblue said:


> Quote:
> 
> 
> 
> ...


 
  Well then, apparently my AC adaptor is dead. John suggested swapping out the batteries and the O2 seems to be working again.


----------



## lorriman

miceblue said:


> Well then, apparently my AC adaptor is dead. John suggested swapping out the batteries and the O2 seems to be working again.




That wouldn't be so surprising. there aren't many AC-AC adaptors out there and the ones there are do seem to be on the cheaper side. I have both a custom german one commissioned in one of the diyaudio groupbuys (it was expensive), and an ebay one at a quarter the price. The ebay adaptor is, what shall we say, rather too eastern oriental?  

The german one is built like a panzer!!!! I'll never sell it. Respect for our German brothers.  I don't think I'll be needing that ODA power.

The O2 I built myself with leaded eutectic solder, which means it is more reliable, less breakable (from dropping) and probably won't develop a solder fault in future, unlike new unleaded solder. The ODAC is US made, as we all know, so at least it has that going for it: quality build and parts albeit unleaded solder. I'm nicely set up. I regret not building with the B003 case + 1/4 socket and RCAs. It turns out that the 1/8 (3.5mm) sockets are rated for 2000 insertions.  

So now I am using a short belkin 3.5mm lead to avoid those insertions.


----------



## Porter1

Quote: 





thegame21x said:


> First Impressions of the O2+ODAC have been posted over at my site, Musical Musings!


 
   
  bookmarked.  your writing style seems honest and straightforward and i dig that.


----------



## miceblue

Quote: 





lorriman said:


> Quote:
> 
> 
> 
> ...


 
  I've used unleaded solder for electrical lab classes, and yes it's not very good. XD
  I'm not 100% sure if JDS Labs uses unleaded solder on the other hand. As an audio company, I would think they would know better than to use unleaded. At home I have some 62/36/2 solder.


----------



## lorriman

miceblue said:


> I've used unleaded solder for electrical lab classes, and yes it's not very good. XD
> I'm not 100% sure if JDS Labs uses unleaded solder on the other hand. As an audio company, I would think they would know better than to use unleaded. At home I have some 62/36/2 solder.




Well, I'm not sure of the US situation but any commercial electronics sold in to the EU has to use unleaded. Much of US produced goods are already made with unleaded. JDS likely uses leaded but the power supply is probably unleaded.


----------



## Currawong

Quote: 





battou62 said:


> You're not helping me  I want of these combos so bad. I wonder if we will ever hear from "him" again about the ODA.


 
   
  I can't help wondering why people always ask this. Build one in a larger case with a 1/4" socket and RCA inputs and you have an ODA.


----------



## LaRzZa

Quote: 





currawong said:


> I can't help wondering why people always ask this. Build one in a larger case with a 1/4" socket and RCA inputs and you have an ODA.


 
   
  Here are some of the advantages with ODA, not only RCA inputs and 1/4" socket. 
   
  (*CTRL+C* & *CTRL+V* from Guy site)
   
*Real Ground* – The ODA will not have third channel masquerading as a virtual ground to mess up the performance. It uses a proper bipolar power supply referenced to true ground and direct coupled outputs.
   
*Higher Quality Power Supply* – The half-wave power supply in the O2 is something of a compromise for size, cost, and battery charging reasons. The ODA power supply improves on the O2’s in several ways.
   
*Wider Source Compatibility* – The ODA should work with anything from an iPod Line Out Dock (LOD) to high output home DACs with a wide range of headphones. It has more flexible gain options compared to the O2.
   
*Headphone Protection Relay* – The O2, like many amps, produces a “click” in the headphones when you turn it on and a soft “thump” when you turn it off. The ODA uses a headphone relay to eliminate these noises and provide added protection for expensive headphones.
   
*Other Possible Upgrades* – Depending on how the details sort out, the ODA may have some other upgrades as well such as a possible preamp/line output
   
  Happy listening!


----------



## adydula

The ODA as mentioned in the post above is a little different thab the O2, no batteries was one of the design points etc...so no portability. Thats ok with me.
   
  Sonically it seems that it should not be any better or any worse than the existing O2.
   
  Alex


----------



## MrMateoHead

The ODA's relay circuit would be a welcome addition however. So would a triple gain or variable gain switch, clearly marked to simplify adjustments based on source (i.e. 2V position would be 2V source, and so on).
   
  How about bass and treble adjustments? Would that be wrong?
   
  Should accept, at minimum, 3.5mm input, RCA, USB, and a digital in.
   
  Also, I'd like to see it do a solid power upgrade - 1-2 watt max.
   
  I'd pay about $100-$200.


----------



## adydula

Bass and treble would be wrong to me IMO....
   
  This is a purist design..to be flat, transparent, simple straight wire with gain design...etc all specs that matter are well beyond what the human ear can discern...
   
  Adding bass boost, or tone controls would very foreign to this amp....not that it couldnt be done etc....
   
  You can always muck with a software EQ in most players if you like, DSP etc...but not for me.
   
  All the best
  Alex


----------



## chesebert

Is this the latest ultra low-end head amp? How does it compare with Glite?


----------



## miceblue

Quote: 





chesebert said:


> Is this the latest ultra low-end head amp? How does it compare with Glite?


 
  I'm not sure about the Glite, but the $150 O2 sounds very similar to the new $100 Schiit Audio Magni headphone amplifier from what I've read.


----------



## adydula

This amp has been around now for several months.....do a search and you will find the designers site.....
   
  Alex


----------



## mikeaj

Gilmore Lite is quite a different design.
   
  Not sure how to parse "ultra low-end".  Ultra performance at low-end cost?  Or ultra low-end... what?  Grammatically I think it's the latter, but I'm not sure what would be considered low-end here.  It doesn't have the best performance, certainly not the lowest, and it's not the cheapest or most expensive.
   
  At $150 the cost is not that low.  It's just about ~$23 for parts (based on single-unit quantities) on the PCB other than the battery before shipping.  i.e. does not include PCB (I suppose $4-10), enclosure / panels ($25 ish?), rechargeable batteries ($10), AC/AC wallwart ($5-10).  The $23-30 figure would be pretty low.  Silicon costs are very minimal here.
   
  Also check out The Wire on diyaudio, for what you get if you use higher-end ICs.


----------



## Currawong

Ok, I've finally found the bookmark I've been looking for: Measurements of the O2 under real loads, ie: with multiple driver IEMs plugged in.  This is why you pay your money for good amps: Linearity when playing music with headphones plugged in, not just a scope or a computer/ADC which has a flat impedance curve.
   
http://scientistsaudio.blogspot.jp/2012/06/leckerton-uha-6smkii-part-2.html
   
  Before anyone complains to me about posting this, I have two O2s here I built for evaluating headphones, as well the Leckerton.


----------



## mikeaj

Quote: 





currawong said:


> Ok, I've finally found the bookmark I've been looking for: Measurements of the O2 under real loads, ie: with multiple driver IEMs plugged in.  This is why you pay your money for good amps: Linearity when playing music with headphones plugged in, not just a scope or a computer/ADC which has a flat impedance curve.
> 
> http://scientistsaudio.blogspot.jp/2012/06/leckerton-uha-6smkii-part-2.html
> 
> Before anyone complains to me about posting this, I have two O2s here I built for evaluating headphones, as well the Leckerton.


 
   
  Thanks for digging up the link.  It was my request, after all.
   
   
  I can't remember precisely what the context was or which thread it was, but paraphrasing from weeks back, I think it was roughly:
  (1) Me — any evidence that shows that an amp with good performance into all sorts of test tones / loads will do poorly or significantly less well with headphones + music?
  (2) Currawong — yeah, but I hesitate to post because it's an anonymous source; also forgot what the link was so would need to find it
  (3) Me — please post anyway if you ever remember, thanks
   
  Unfortunately for me, I'd seen that before and that's not what I'm talking about.
   
  What is exposed there is how the O2 / other amp output impedance will interact with an IEM with crazy impedance variations, a very well-known and boring result.  Also, we're looking at resulting FR variations of less than 1 dB from max to min:  perhaps audible and a valid point of contention, but largely not much of a big deal at all.  Or is somebody going to suggest that mostly flat EQs with a max 0.7 dB variation ruin the sound quality?
   
  So still no measurement-based evidence, or at least I haven't seen it yet.  Which of course doesn't necessarily prove anything in of itself.


----------



## wolfetan44

Quote: 





currawong said:


> Ok, I've finally found the bookmark I've been looking for: Measurements of the O2 under real loads, ie: with multiple driver IEMs plugged in.  This is why you pay your money for good amps: Linearity when playing music with headphones plugged in, not just a scope or a computer/ADC which has a flat impedance curve.
> 
> http://scientistsaudio.blogspot.jp/2012/06/leckerton-uha-6smkii-part-2.html
> 
> Before anyone complains to me about posting this, I have two O2s here I built for evaluating headphones, as well the Leckerton.


 
  I don't get it. How do I read these graphs? Can someone explain for me!


----------



## miceblue

Quote: 





currawong said:


> Ok, I've finally found the bookmark I've been looking for: Measurements of the O2 under real loads, ie: with multiple driver IEMs plugged in.  This is why you pay your money for good amps: Linearity when playing music with headphones plugged in, not just a scope or a computer/ADC which has a flat impedance curve.
> 
> http://scientistsaudio.blogspot.jp/2012/06/leckerton-uha-6smkii-part-2.html
> 
> Before anyone complains to me about posting this, I have two O2s here I built for evaluating headphones, as well the Leckerton.


 
  From that website, for those particular loads:
  Quote: 





> Not as good as from the Leckerton, but as we are well in 1 dB the result is still very good.


 
  So really it's not a big problem for the O2? Is a 1 dB difference really going to make an amp purchase a make-it/break-it decision?
   
  I'm still fairly new to DACs and amps, so I'm not quite understanding what you're trying to say. Are you saying that with higher impedance headphones the O2 might not give a linear output and have an output that's outside of the 1 dB tolerance?
   
   
   
  Also, since there are now 2 active O2 threads, I think you may have confused this thread from the other one:
  Quote: 





currawong said:


> Quote:
> 
> 
> 
> ...


----------



## mikeaj

Quote: 





wolfetan44 said:


> I don't get it. How do I read these graphs? Can someone explain for me!


 
   
  Those are frequency response graphs, for what is seen across the load (the IEMs / headphones).  Thus any changes here from the amp is going to affect the balance of what you hear.  O2 and Leckerton UHA-6S MKII are tested with three different IEMs.
   
  More or less for these purposes, one can consider that the amp is an ideal voltage source, and it is driving its own output impedance in series with the headphones.  Thus you have a simple voltage divider:
  http://en.wikipedia.org/wiki/Voltage_divider
   
  Note that if the impedance of the load (Z2) varies widely by frequency and the amp output impedance (Z1) is relatively large compared to Z2, then the voltage the load sees (Vout) will be altered compared to the voltage the amp is trying to send (Vin).  The ratio of Vout/Vin is shown in those frequency response graphs.  To see what is what, check the first diagram in the above link.  Note that it's a function of frequency because the load impedance can vary with frequency—output impedance can also vary, but here it's mostly resistive and flat across the audio frequency range.  What you see here is that even though the O2 has a flat FR (less than 0.04 dB variation from 20 Hz to 20 kHz), the response of the output into some IEMs will be a little less flat because the O2's output impedance is somewhere around 0.5 ohms and not 0 ohms.
   
   
  Again, < 1dB is pretty small.  Also, for most headphones, impedance is fairly flat with frequency or generally a lot greater than for some of those IEMs, so the lines will look more like the green one in most cases.  Many amps have much higher output impedance than the O2, so you'll see much more wild swings for the few IEMs like the Westone 4 and UERM listed.


----------



## wolfetan44

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Gotcha! Thanks a bunch!


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Thanks for the explanation.
  I noticed that the K 701 has a rising impedance for frequencies 2 kHz and above (Innerfidelity's measurements seem to go from ~67 ohms at 2 kHz to ~110 ohms at 20 kHz). Could this be a reason why the K 701 is known to be picky with amps?


----------



## mikeaj

Quote: 





miceblue said:


> Thanks for the explanation.
> I noticed that the K 701 has a rising impedance for frequencies 2 kHz and above (Innerfidelity's measurements seem to go from ~67 ohms at 2 kHz to ~110 ohms at 20 kHz). Could this be a reason why the K 701 is known to be picky with amps?


 
   
  Not really.  That rise is fairly smooth and mostly in the upper octave anyway.  The ~60 ohms baseline level is already reasonably high relative to most amps' output impedance.  With an amp with a very high 100 ohms output impedance, that's just a 2.32 dB difference between the level at 2 kHz and 20 kHz then.  People aren't sensitive to small changes in 10 kHz+.  With a 0.5 ohms output impedance, that's a 0.025 dB difference.
   
   
  My guess would be more like

 Relatively low impedance
 Relatively low sensitivity
 Reputation for being good for jazz and classical; most jazz and classical recordings actually have wide dynamic range so listeners will use larger peak volume
 All of the above mean relatively large current required, particularly if listening loudly
 Some amps misbehaving when being asked for large currents (e.g. many popular OTL tube amps)
 Word of mouth and confirmation bias giving an issue more mindshare than it should otherwise have


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Hm you do have a point there.
  I know this is probably going to sound stupid, but with all of the posts of how picky the K 701 is with amps, I was honestly expecting a night and day difference with a good amp. People are always like "oh without a good amp the K 701's sound like garbage" or things of the sort. I hardly find that to be the case. Straight out of an iPhone 4S yes the bass seems leaner than with a good amp and yes the treble is a bit grainy and fatiguing, but amping doesn't make a HUGE difference in sound quality like what I was expecting from people's posts.
   
  That being said, I do really like how the K 701 sounds with the O2.


----------



## mikeaj

Forgot to add a

 Audio forums propensity for hyperbole
   
  Got to filter what you read and adjust expectations accordingly.


----------



## proton007

Quote: 





mikeaj said:


> Forgot to add a
> 
> Audio forums propensity for hyperbole
> 
> Got to filter what you read and adjust expectations accordingly.


 

 That reminds me. How come no one's reviewing the Schiit stack (Magni/Modi) with measurements?


----------



## miceblue

Quote: 





proton007 said:


> Quote:
> 
> 
> 
> ...


 
*purrin* did. Conclusion was that there were _some_ differences despite measuring nearly identical. Another Head-Fier in this thread said they're too close in sound that the Schiit Stack would be a better buy for your money (if you want a desktop setup).


----------



## proton007

Quote: 





miceblue said:


> *purrin* did. Conclusion was that there were _some_ differences despite measuring nearly identical. Another Head-Fier in this thread said they're too close in sound that the Schiit Stack would be a better buy for your money (if you want a desktop setup).


 

 I've read those, I'm referring to the comprehensive O2 style review, with technical measurements.


----------



## proton007

I'd like to see something like this atleast:
   
  Frequency Response 
 THD 1 Khz 150 Ohms 
 THD 1 Khz 15 Ohms 
 THD 20 hz 15 Ohms 
 THD 20 Khz 15 Ohms 
 IMD CCIF 15 Ohms 
 IMD SMPTE 0.002% 
 Noise (ref 400 mV)
 Max Output 15 Ohms 
 Max Output 33 Ohms 
 Max Output 150 Ohms 
 Output Impedance
 Crosstalk 15 Ohms 
 Channel Balance


----------



## stv014

Quote: 





> Originally Posted by *mikeaj* /img/forum/go_quote.gif
> 
> Those are acoustic measurements via HE-500 headphones.  All differences are more-or-less masked by the headphones and maybe the microphone.


 
   
  I suspect the microphone. Especially at higher frequencies, a cheap electret microphone can have higher distortion than a headphone, particularly an expensive planar magnetic one. It appears that *purrin*'s acoustic THD measurements tend to have a fairly constant 2nd order distortion of a couple tenths of a percent at least, which may come from the microphone.
   
  Quote:  





> but couldn't you see any undue amp / headphone interactions by measuring the signal that's across the headphone terminals, thus avoiding all the inaccuracies with most acoustic measurement setups?


 
   
  There are people who believe that the exact same signal across the headphone terminals does not guarantee the same sound.
   
  Quote:  





> Also note that I don't think his gear is good enough for electrical measurements of higher-end amps, particularly with easier loads.


 
   
  It does not take expensive gear to achieve measurement quality that is good enough that if it becomes a bottleneck, then the parameter measured is clearly below any reasonable threshold of audibility anyway. However, one must really pay attention to avoid mistakes in the measurement and analysis that cause large errors, like testing amplifiers without a load, ground loops (very common), incorrect measurement of AC voltage with poor DMMs, using the ADC under conditions it does not perform well or even acceptably (like too low or too high input voltage), buggy/limited software (e.g. RMAA), and more. It is also important to know and understand the specifications and performance of the test gear itself, and how it can make the results inaccurate (sometimes it is possible to compensate "bad" measurements with that knowledge). From my experience doing PC based measurements, it takes quite some work to overcome all those issues, including writing software myself, and building various DIY circuits that work around the limitations of the sound card line input (voltage dividers, pre-amplifiers, differential amplifiers, etc.).


----------



## adydula

If you read the designers blog you can see that this person spent many, many hours designing and engineering the layout of the amp and the dac.....implementation plays a very, very important role, parts selection although important seems less relevant than how the part is used and layed out physically on a pc board etc...
   
  Alex


----------



## proton007

Quote: 





mrmateohead said:


> Or is there some extremely good reason why consumers are supposed to shell out money blindly?


 
   
  Hmmm... trust their ears??


----------



## adydula

Thats why the design points and specs that the O2 has caused such a stir about are very important baselines...with so many opinions, glittering generalities and glowing adjectives the specs provide a baseline to base all of our other opionions on....
   
  Alex


----------



## adydula

I was reading about the simple half wave rectifier power supply in the O2.......its amazing that a simple, not complex power supply...not even a full wave bridge circuit.
   
  The proof is 131 dB of S/N and 0.0009% THD on battery or AC power.
   
  Absolutely amazing.....
   
  Alex


----------



## antberg

Hi folks,i am in quite a problem with my early arrived O2-Odac combo,and so early i thing i almost screw** up my unit.I did paste the question from another O2 related thread.
  ___________________________________________________
  I hope you technical guys can tell me some positive thoughts..
   
  I did received Friday my very first O2-Odac combo.I did ordered them on September ,but then my first package has been lost,then before to JDS send me another unit i had to wait for some complaining form to USPS and then another month to the new package to arrive here.well i did learn something more about patience ,hehe.
   
  So,when i received my combo i've gone to Capital city to find an adapter for the amp,but the first night i have been home with the combo i let the adapter on the 110V switch whereas my home town support 220V.Well for the first days i thought the batteries or the plug where not having a good connection because the O2 were able to work for a couple of minutes before stopping working.
   
  But then,i realize my stupidest misuse:The wrong switch on the voltage input.
  Now,i did call the manufacturer of the adapter and they told me that possibly the adapter would blew just after 30 minutes on the wrong switch input (well it has been all night plugged in ,and the amp turned on).
  My first worries were about the adapter but now i am afraid more about the amp,because they told me too that if the output voltage in my case is wrong the amp could receive more or less for about  28 volts,which i know is very high for the amp,so i hope i did not damaged my beloved and so long awaited amp.
  If this could help you,as i sad before,the amp just work for a few minutes before stopping working,due i suppose to the low charge of the batteries inside.
  I hope i have been clear as English is not my native language.
  Thank you very much guys


----------



## antberg

What upset me right now is that i have been looking for a new Head-Rig ,but at the moment i am being very busy i just can have listening session sometimes on Sundays....And i already messed up.


----------



## wolfetan44

Why not order the adapter on JDSLab's website?


----------



## adydula

I think its because his normal voltage is 220vac, the ac adapater on JDS site are 110VAC.
   
  There are several European 220vac ac adapters you can find that will meet the ac voltage req's...check the DIY Audio site..
   
  Alex


----------



## mikeaj

28 VAC input?
   
  The power supply regulators and capacitors are rated for 35V max, checking the datasheets of the default parts.  28VAC gets 39.6V from 0 to peak, with a slight drop well under 1V from the diode.  So yeah, the filter caps wouldn't be happy seeing that 39V.  Not sure how long it takes to cook these parts.


----------



## proton007

Quote: 





adydula said:


> I think its because his normal voltage is 220vac, the ac adapater on JDS site are 110VAC.
> 
> There are several European 220vac ac adapters you can find that will meet the ac voltage req's...check the DIY Audio site..
> 
> Alex


 

 The voltage at my place is also 220V.
  If you'll take a look at the O2 component list, the 220V adapter links are listed for UK/Australia.
   
  For other countries, you can go to  RS Components, Farnell, or Mouser and order there. Anything from 14-20V , >400mA will do.


----------



## antberg

Well guys ,before hand thank you for some clues.From what i know it seems that it has been receiving 28V for a whole night,but strangely and luckily for me the amp is now working perfectly,as i have been to the electric shop before work ,so i did purchase a pair of normal batteries to see if the amp were working and not damaged,and good for me the amp were working very well with normal batteries.Plus they were kind to let me change the adapter,which now does have a perfect plug size to fit with the amp.Maybe the first adapter ,although difficult to insert into the amp were not having connection with it to be able to recharge the batteries and so neither overfeeding the amp with those 28v.
  Anyway i am glad the amp is working,i have been waiting my combo since September....
  Best regards
  Antonio


----------



## adydula

Great!!!
   
  Alex


----------



## daniel521

I purchased the O2 and it will arrive in a couple of days, I will be using it with an HRT MusicStreamer II? Will I need an addition cable or accessory, or does the O2 come with everything that's necessary to use it with the HRT MusicStreamer II, headphone, and computer?


----------



## Satellite_6

Quote: 





daniel521 said:


> I purchased the O2 and it will arrive in a couple of days, I will be using it with an HRT MusicStreamer II? Will I need an addition cable or accessory, or does the O2 come with everything that's necessary to use it with the HRT MusicStreamer II, headphone, and computer?


 
  You will need:
   
http://www.monoprice.com/products/product.asp?c_id=103&cp_id=10303&cs_id=1030301&p_id=5436&seq=1&format=1#largeimage
   
  and 
   
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021815&p_id=5596&seq=1&format=2
   
  or longer versions.


----------



## daniel521

satellite_6 said:


> You will need:
> 
> http://www.monoprice.com/products/product.asp?c_id=103&cp_id=10303&cs_id=1030301&p_id=5436&seq=1&format=1#largeimage
> 
> ...




Thanks


----------



## HamilcarBarca

Quote: 





satellite_6 said:


> Quote:
> 
> 
> 
> ...


 
   
  Satellite, have you tested those RCA connectors for fit? I know this is an ODAC+O2 thread, but the barrels on that cable are too big for a Matrix M-Stage. It's still a nice cable.


----------



## kskwerl

I just got off the phone with someone from JDS Labs to see when my order would be shipping because it was backordered, he said they will be working through the night to get all the orders out


----------



## Satellite_6

Quote: 





hamilcarbarca said:


> Satellite, have you tested those RCA connectors for fit? I know this is an ODAC+O2 thread, but the barrels on that cable are too big for a Matrix M-Stage. It's still a nice cable.


 
  wat. I have a similar RCA -> RCA cable I used MSII -> M-stage and it worked fine so I have no idea what you are talking about.


----------



## HamilcarBarca

Quote: 





satellite_6 said:


> Quote:
> 
> 
> 
> ...


 
   
  I have that exact cable. The RCA connectors on the M-Stage are a little too close together to fit the plastic-and-rubber barrel around the plug at the end of the cable. (This is probably nothing more than an M-Stage problem, but still ...)


----------



## Satellite_6

Quote: 





hamilcarbarca said:


> I have that exact cable. The RCA connectors on the M-Stage are a little too close together to fit the plastic-and-rubber barrel around the plug at the end of the cable. (This is probably nothing more than an M-Stage problem, but still ...)


 
  And yet, they are not.


----------



## HamilcarBarca

Quote: 





satellite_6 said:


> Quote:
> 
> 
> 
> ...


 
   
  Maybe they vary in size depending on the length or batch or something. Mine are a tight fit on my DAC and an impossible fit on the M-Stage. I was a little disappointed because it was the only inexpensive, short cable I could find.
   
  In any case, you answered my question. You tested it and reported your results. Thanks for the input.


----------



## Crispy808

My O2/ODAC build as I was unsatisfied with the original layout.


----------



## proton007

Quote: 





crispy808 said:


> My O2/ODAC build as I was unsatisfied with the original layout.


 

 Nice!!
  Did you use the original PCB?


----------



## adydula

Nice!!
   
  Alex


----------



## Stratok

That looks sick. If I get too drunk I might find myself trying to build one too.


----------



## Crispy808

Quote: 





proton007 said:


> Nice!!
> Did you use the original PCB?


 
   
  Yes, I did.  I have more pictures in the Post Pics of Your Build thread in the DIY section.


----------



## chrislangley4253

Very nice!


----------



## BleaK

That looks awsome!


----------



## cel4145

Got my ODAC last week, and love it. So I ordered the O2 yesterday 

Anyone found a good solution for strapping the ODAC on to the O2? I don't want to use stick on velcro. Was thinking someone must have come up with some ingenious solutions by now.


----------



## kskwerl

Quote: 





cel4145 said:


> Got my ODAC last week, and love it. So I ordered the O2 yesterday
> 
> 
> 
> ...


 
  I'm going to be looking for the same exact solutions so we'll help each other out on this. I haven't thought of anything yet thought lol


----------



## chrislangley4253

http://www.scotchbrand.com/wps/portal/3M/en_US/ScotchBrand/Scotch/Products/Catalog/~/Scotch-Mounting-Squares?N=6603920&rt=rud


----------



## kskwerl

Quote: 





chrislangley4253 said:


> http://www.scotchbrand.com/wps/portal/3M/en_US/ScotchBrand/Scotch/Products/Catalog/~/Scotch-Mounting-Squares?N=6603920&rt=rud


 
  Thanks, what about like velcro or something that would stick to the amp?


----------



## chrislangley4253

that would probably work too


----------



## cel4145

I don't want anything that I have to stick to the amp and ODAC. Trying to think of something to use as bands or wrap, but maybe I'm deluding myself that it's possible.


----------



## kskwerl

Quote: 





cel4145 said:


> I don't want anything that I have to stick to the amp and ODAC. Trying to think of something to use as bands or wrap, but maybe I'm deluding myself that it's possible.


 
  Yea I don't really want that either but I can't really think of anything else


----------



## cel4145

I'm thinking of trying some of the Velcro strap solutions such as one of these two: 

http://www.amazon.com/Velcro-Velstrap-Straps-Inches-90107/dp/B000TGX0HK/
http://www.amazon.com/Velcro-Wrap-Strap-2-Inches-Pack/dp/B0057564NK/

Just trim off the excess if they are too long. I've had good luck using some of their strap products before. The trick might be to put a thin layer of some kind of foam between the ODAC and O2, so the ODAC doesn't slide around even with the straps.


----------



## kskwerl

Quote: 





cel4145 said:


> I'm thinking of trying some of the Velcro strap solutions such as one of these two:
> 
> http://www.amazon.com/Velcro-Velstrap-Straps-Inches-90107/dp/B000TGX0HK/
> http://www.amazon.com/Velcro-Wrap-Strap-2-Inches-Pack/dp/B0057564NK/
> ...


 
  Like a piece of kitchen drawer mat or something that wouldn't make it slide. Dammit! I just wish I had bigger bands


----------



## HamilcarBarca

Quote: 





cel4145 said:


> I don't want anything that I have to stick to the amp and ODAC. Trying to think of something to use as bands or wrap, but maybe I'm deluding myself that it's possible.


 
   
  Some DAP -- I don't have one and don't even remember the brand -- comes with good-looking silicon bands to attach it to a portable amp. I'm still trying to find something like it to attach a USB drive to my ODAC+O2. No luck yet.


----------



## jkxs

Quote: 





crispy808 said:


> My O2/ODAC build as I was unsatisfied with the original layout.


 
  Nice!


----------



## cel4145

hamilcarbarca said:


> Some DAP -- I don't have one and don't even remember the brand -- comes with good-looking silicon bands to attach it to a portable amp. I'm still trying to find something like it to attach a USB drive to my ODAC+O2. No luck yet.




My E17 came with some, but I don't think they'll be big enough.

There's gotta be a rubber or silicone band that will work. For example, I was looking at this one that is probably be a little too big

http://www.amazon.com/Alliance-Sterling-Ergonomically-Correct-25075/dp/B0017LR7CU/

I'd rather have black or something that's not natural rubber band color. Obviously that one is strong enough, though. From the user comments:

"I use these bands for making traditional style, mostly tree-fork, slingshots. . . They will drive a .38 cal lead ball all the way through a steel soup can at 10 yards."

LMAO


----------



## HamilcarBarca

Oops.


----------



## miceblue

I really wish there was a better input/output layout for the O2 and ODAC (pre-made, I'm not a DIY-er...).
  Getting to the volume knob requires me to reach my hand around the USB and mini-jack cables; this is not convenient since my ODAC ends up getting shifted around. I don't want to use adhesive on them either.


----------



## cel4145

miceblue said:


> I really wish there was a better input/output layout for the O2 and ODAC (pre-made, I'm not a DIY-er...).
> Getting to the volume knob requires me to reach my hand around the USB and mini-jack cables; this is not convenient since my ODAC ends up getting shifted around. I don't want to use adhesive on them either.




I know it won't look as nice since it seems you have the longer version of the ODAC, but turn the ODAC around if you aren't using the RCAs. That should allow you to run the wires so that they are not in the way.


----------



## kskwerl

is there any disadvantage to using something like adhesive velco? If there no danger of the adhesive melting or some kind of velcro sonic phenomenon then I'd be comfortable just using some heavy duty velcro with adhesive on the bottom.


----------



## chrislangley4253

mice.. I don't like how that looks at all. Particularly that 1/4 to 1/8 adapter you are using, that cannot be good for the jack man, you need a sennheiser or grado pigtail adapter

 http://www.bhphotovideo.com/c/product/601983-REG/Sennheiser_092595_3_5mm_Plug_to_6_3mm.html

 You also need to either set the odac behind the o2 or turn it 90 or 180 degrees. I would move it off the top and set it right behind the O2 given the wires you are using.
   
   
  Quote: 





kskwerl said:


> is there any disadvantage to using something like adhesive velco? If there no danger of the adhesive melting or some kind of velcro sonic phenomenon then I'd be comfortable just using some heavy duty velcro with adhesive on the bottom.


 
   
  You should be fine 

 The o2 and odac stay very cool.


----------



## kskwerl

Quote: 





chrislangley4253 said:


> mice.. I don't like how that looks at all. Particularly that 1/4 to 1/8 adapter you are using, that cannot be good for the jack man, you need a sennheiser or grado pigtail adapter
> 
> http://www.bhphotovideo.com/c/product/601983-REG/Sennheiser_092595_3_5mm_Plug_to_6_3mm.html
> 
> ...


 
  Nice, then I guess this is solved for me but I also just wanted to mention I was at work today (I work in a datacenter) and I was thinking about using velco cable ties for ethernet cables. Seems like a good idea but idk how it would be in actual application. I'll bring some home just to try it before I put adhesive velco on mine and I'll report back.


----------



## miceblue

Quote: 





chrislangley4253 said:


> mice.. I don't like how that looks at all. Particularly that 1/4 to 1/8 adapter you are using, that cannot be good for the jack man, you need a sennheiser or grado pigtail adapter
> 
> http://www.bhphotovideo.com/c/product/601983-REG/Sennheiser_092595_3_5mm_Plug_to_6_3mm.html
> 
> ...


 
  Thanks for the suggestions. I was kind of worried about that 1/4" adaptor myself. It would make sense to use that kind of adaptor for a larger, most sturdy/heavy amplifier. Should I just get a mini-jack extender, or do you think the 1/4" to minijack adaptor would be OK? I do use the O2 as a transportable amp so I plug/unplug headphones on a regular basis.


----------



## kskwerl

Quote: 





miceblue said:


> Thanks for the suggestions. I was kind of worried about that 1/4" adaptor myself. It would make sense to use that kind of adaptor for a larger, most sturdy/heavy amplifier. Should I just get a mini-jack extender, or do you think the 1/4" to minijack adaptor would be OK? I do use the O2 as a transportable amp so I plug/unplug headphones on a regular basis.


 
  What was it I remember reading about the lifetime on the jack on the O2? 2000 inserts and outserts?


----------



## chrislangley4253

Quote: 





miceblue said:


> Thanks for the suggestions. I was kind of worried about that 1/4" adaptor myself. It would make sense to use that kind of adaptor for a larger, most sturdy/heavy amplifier. Should I just get a mini-jack extender, or do you think the 1/4" to minijack adaptor would be OK? I do use the O2 as a transportable amp so I plug/unplug headphones on a regular basis.


 

 I think either a mini jack extender or the adapter would work.. I'd use the adapter, myself. You shouldn't have to worry about plugging and unplugging, it would be far more risky to leave a cable plugged in while transporting the amp than it will be to unplug and replug 
  Quote: 





kskwerl said:


> What was it I remember reading about the lifetime on the jack on the O2? 2000 inserts and outserts?


 
  Should be more than that, I think. Most jacks are rated around 5000


----------



## HamilcarBarca

Quote: 





> Originally Posted by *kskwerl* /img/forum/go_quote.gif
> 
> 
> > What was it I remember reading about the lifetime on the jack on the O2? 2000 inserts and outserts?
> ...


 
   
  I read the 2,000 figure in an early post in this thread by lorriman; I don't know him personally, but I find his posts informative and reliable.
   
  Personally, I use a 3.5mm to 6.3mm pig-tail adapter and haven't disconnected it for several weeks.


----------



## kskwerl

Quote: 





hamilcarbarca said:


> I read the 2,000 figure in an early post in this thread by lorriman; I don't know him personally, but I find his posts informative and reliable.
> 
> Personally, I use a 3.5mm to 6.3mm pig-tail adapter and haven't disconnected it for several weeks.


 
  2000 is quite a lot tho don't you think? By that time it'll be years old prob.


----------



## HamilcarBarca

Quote: 





kskwerl said:


> Quote:
> 
> 
> 
> ...


 
   
  No doubt you're right. Even so, an adapter cable is inexpensive insurance. And it's reusable!


----------



## lorriman

hamilcarbarca said:


> I read the 2,000 figure in an early post in this thread by lorriman; I don't know him personally, but I find his posts informative and reliable.





I've just double-checked the product pdf and it says 5,000. And yes I did write 2000 (supposedly from the same document) so I'm not sure what went wrong there. 

So, just to clarify: it has a 5,000 inserts lifespan, not 2,000.

Here's the pdf:

http://www.mouser.com/ds/2/222/STX-3120-5B-284C-184284.pdf


----------



## adydula

13.69 years at once a day...
   
    6.84 years for twice a day.
   
  with extension cable almost forever....
   
  listening to music with the o2...priceless!!!
   
  lol
   
  Alex


----------



## lorriman

adydula said:


> 13.69 years at once a day...
> 
> 6.84 years for twice a day.
> 
> with extension cable almost forever....




Exactly, I use my O2 everyday, and change headphones and configs quite a bit. If I want it to last the 15 years I intend then I must use a short extension cable.

I've also had the unpleasant experience of desoldering one of these and it's a pig. I damaged the circuit board and had to solder in a patch wire which can only increase noise.


----------



## adamlr

sorry for the off topic(ish), but id like to take this chance to ask a question, if i may.
   
  why would you disconnect your headphones at all? iv heard that the "buzz" you get when turning amps on/off can damage your cans, is this an established fact or another controversial topic with mixed opinions all over the place? or is there some other reason? my cmoy (soon to be replaced by O2 that shipped on thursday =]) is allways plugged into my computer, and my headphones are allways connected to the cmoy. is there any reason to disconnect them?


----------



## adydula

lorriman,
   
  yes if you want a 1/4 jack u definitely want to wire that up when DIY'ing and not use the 3.5 jack at all on the board. You could wire after and mechanically file down the front of the 3.5 mm plastic jack part...but thats kind of kludgy...at best
   
  Alex


----------



## mikeaj

Quote: 





adamlr said:


> sorry for the off topic(ish), but id like to take this chance to ask a question, if i may.
> 
> why would you disconnect your headphones at all? iv heard that the "buzz" you get when turning amps on/off can damage your cans, is this an established fact or another controversial topic with mixed opinions all over the place? or is there some other reason? my cmoy (soon to be replaced by O2 that shipped on thursday =]) is allways plugged into my computer, and my headphones are allways connected to the cmoy. is there any reason to disconnect them?


 
   
  People disconnect headphones all the time to be able to plug in different ones. but people also traditionally do so to avoid having  the headphones plugged in while the amp is turning on and off, as you say.  For some amps, that is a safer practice, but for others it shouldn't matter.
   
  As for leaving them in when powering the amp on and off, it depends on the structure of the amp, how it's designed.  More or less, as internal power supply rails are moving from 0 to the operational value (or vice versa, on shut off), this can induce some nonzero output in some parts of the circuit.  Ultimately, this means that an unwanted junk transient signal can be generated between the output and ground, so that's what your headphones would receive this they're plugged in.  That causes the buzz you hear.  In terms of the danger to the headphones, it's the same as any other kind of sound or music you put through the amp.  The magnitude, duration, nature of this junk signal, and the headphone properties determine whether or not it is dangerous.  
   
  Often if there's a signal large enough to cause a problem, you would hear an extremely loud sound out of the headphones as a result.  However, in some cases, the signal is mostly a very low frequency that you can't hear, so that could be damaging without being audible.  Some amps have some relay to disconnect the headphone output on power up / down to avoid this problem; many don't generate a large enough signal to be an issue in the first place.  If properly assembled and working, an O2 is in the latter category and doesn't make a large enough signal to damage any IEMs or headphones. Actually, if it does make a loud sound, that's an indication that something is wrong with the power management circuit.
   
  No reason you can't leave it in all the time.  For that matter, power draw is so low that there's not even really a reason to turn it off, either.


----------



## MrMateoHead

The loudest thump I usually hear is when the batteries are discharged and the O2 shuts itself off. While I don't like popping and buzzing, nothing the O2 does scares me since it is all way too quiet to be bad.


----------



## adamlr

Quote: 





mikeaj said:


> People disconnect headphones all the time to be able to plug in different ones. but people also traditionally do so to avoid having  the headphones plugged in while the amp is turning on and off, as you say.  For some amps, that is a safer practice, but for others it shouldn't matter.
> 
> As for leaving them in when powering the amp on and off, it depends on the structure of the amp, how it's designed.  More or less, as internal power supply rails are moving from 0 to the operational value (or vice versa, on shut off), this can induce some nonzero output in some parts of the circuit.  Ultimately, this means that an unwanted junk transient signal can be generated between the output and ground, so that's what your headphones would receive this they're plugged in.  That causes the buzz you hear.  In terms of the danger to the headphones, it's the same as any other kind of sound or music you put through the amp.  The magnitude, duration, nature of this junk signal, and the headphone properties determine whether or not it is dangerous.
> 
> ...


 

 thanks a bunch =]
   
  so if i understand correctly, while going from "off" mode to "on" mode (or the other way around), some sort of grey area is crossed, which may release unwanted electrical/audio output that can only damage your headphones if they're loud enough?
   
  and you say that a properly assembled O2 (like say, jds) can be left plugged in, and headphones in turn, can be left plugged into the O2, at all times, including turning off/on, and everything should be fine, so long as i keep things on the sensible side of the volume control. right?
   
  i plan on leaving my O2 plugged in to the wall, and disconnect the batteries. im guessing this wont make any difference, since you say it "doesn't make a large enough signal", and that "power draw is so low"?
   
  cheers!


----------



## kskwerl

Is there suppose to be a sold of something rolling around inside the O2? it sounds like a ball on a track or something like that.
   
  Also I thought I was getting a power adapter for this now I'm kinda out of luck


----------



## kskwerl

What kind of power adapter can I use, I'm from USA and I would look on JDSLabs website but I can't get to it


----------



## HamilcarBarca

Quote:


kskwerl said:


> What kind of power adapter can I use, I'm from USA and I would look on JDSLabs website but I can't get to it


 
   
  There is a list of adapters recommended by the designer near the bottom of the instruction page which comes with the O2. I'd post a link to a PDF version ... but JDS' web server isn't responding at the moment. The list is also available on the designer's blog ... but I can't post a link to it here. Trying a Google search for 'objective2 power supply'.
   
  Quote: 





kskwerl said:


> Is there suppose to be a sold of something rolling around inside the O2? it sounds like a ball on a track or something like that.
> 
> Also I thought I was getting a power adapter for this now I'm kinda out of luck


 
   
  No, there isn't supposed to be anything loose. The power adapter isn't included in JDS Labs' base price for the O2 (or ODAC+O2 combo).


----------



## kskwerl

Quote: 





hamilcarbarca said:


> There is a list of adapters recommended by the designer near the bottom of the instruction page which comes with the O2. I'd post a link to a PDF version ... but JDS' web server isn't responding at the moment. The list is also available on the designer's blog ... but I can't post a link to it here. Trying a Google search for 'objective2 power supply'.
> 
> 
> No, there isn't supposed to be anything loose. The power adapter isn't included in JDS Labs' base price for the O2 (or ODAC+O2 combo).


 
  ok I just ordered the power adapter recommend on the list that came with the O2, I'm gonna open it up now and see What this noise is.


----------



## kskwerl

Ok looks like it was just the faceplate that was jiggling around a little cause it wasn't tight enough.
   
  I got some velco circles and they are freaking awesome fit for attaching the ODAC to the O2. Take a look


----------



## chrislangley4253

Perfect, I would suggest rotating the odac 90 degrees and possibly flipping it upside down too, to get the usb cable out of your way.


----------



## kskwerl

Quote: 





chrislangley4253 said:


> Perfect, I would suggest rotating the odac 90 degrees and possibly flipping it upside down too, to get the usb cable out of your way.


 
  oh wow I never thought of that, the flipping it upside down thing. thanks for the tip


----------



## kskwerl

Can anyone comment on the O2 and 600ohm beyers?


----------



## HamilcarBarca

Quote: 





kskwerl said:


> Can anyone comment on the O2 and 600ohm beyers?


 
   
  I'm sure searching this thread will give you the answer you want. This question has been asked and answered numerous times here.


----------



## kskwerl

hamilcarbarca said:


> I'm sure searching this thread will give you the answer you want. This question has been asked and answered numerous times here.




Not to be confrontational but if you know the answer why wouldn't you just quote me and post the answer instead of telling me to search the thread? lol?


----------



## chrislangley4253

Quote: 





kskwerl said:


> Not to be confrontational but if you know the answer why wouldn't you just quote me and post the answer instead of telling me to search the thread? lol?


 
   
  He probably cannot speak from direct experience on the pairing or remember exactly what was said, but he knows someone has spoken on the pairing and that it can be found with some searching.


----------



## cel4145

chrislangley4253 said:


> He probably cannot speak from direct experience on the pairing or remember exactly what was said, but he knows someone has spoken on the pairing and that it can be found with some searching.




+1

And at other times, people only have a quick moment to respond. Or they are on their phone, sometimes making it more difficult to write a longer response or go find the information. 

Personally, I don't understand the need to complain. It's great for me when someone can just point me in the right direction where to find it for myself


----------



## adydula

Do a search its all over the place.....
   
  Alex


----------



## kskwerl

Well it looks like I might have took his suggestion the wrong way lol


----------



## lorriman

kskwerl said:


> Well it looks like I might have took his suggestion the wrong way lol




Understandable. How could you know that it was a popular question. It's not the title of the thread, after all. I think the guy who responded to you probably doesn't remember the answer but at a guess: almost certainly it can be handled with ease.


----------



## kskwerl

lorriman said:


> Understandable. How could you know that it was a popular question. It's not the title of the thread, after all. I think the guy who responded to you probably doesn't remember the answer but at a guess: almost certainly it can be handled with ease.




True. So I ordered a power adapter from mouser and it says estimated shipping date 2/4/13 lmao


----------



## chrislangley4253

Quote: 





kskwerl said:


> True. So I ordered a power adapter from mouser and it says estimated shipping date 2/4/13 lmao


 
  that sounds.. right.


----------



## kskwerl

chrislangley4253 said:


> that sounds.. right.




That's beat what am I gunna do for a month use batteries I guess right?


----------



## kskwerl

kskwerl said:


> That's beat what am I gunna do for a month use batteries I guess right?




Wow I'm dumb lol


----------



## HeatFan12

Did u get the wau16-1000?


Sent from my iPhone using Tapatalk


----------



## SunshineReggae

Quote: 





lorriman said:


> I've just double-checked the product pdf and it says 5,000. And yes I did write 2000 (supposedly from the same document) so I'm not sure what went wrong there.
> 
> So, just to clarify: it has a 5,000 inserts lifespan, not 2,000.
> 
> ...


 

 Also, the way that kind of rating works if I am not mistaken, is that such rating means that xx (usually very high) percentage of all tested are guaranteed to last [in this case] 5000 mating cycles without any issue.
   
  So the odds of it being as such that on the 5001th time of plugging it in it all of a sudden totally stops working, are pretty much zero. If there are to be any assumptions at all, a relatively safe one is probably that somewhere between 5000 and 7000 uses, there's a good chance there will be some technical indication of the jacking having been exposed to usage.


----------



## HamilcarBarca

Quote: 





lorriman said:


> Quote:
> 
> 
> 
> ...


 
   
  Thanks. I won't repeat the 2,000 insertion figure again.


----------



## kskwerl

Quote: 





heatfan12 said:


> Did u get the wau16-1000?
> 
> 
> Sent from my iPhone using Tapatalk


 
553-WAU16-400
WAU16-400
120 to 16VAC 0.4A


----------



## miceblue

A random note, what are the "rails"? It's mentioned in the c421 description as well as being controlled with Arduino software for the upcoming c5.
  From the c421 description:
  Quote: 





> synchronous voltage boosted +/-7V rails with low ripple


----------



## mikeaj

Power supply voltage outputs (which the op amps and so on receive) are commonly called rails. e.g. the +7V rail


----------



## adydula

If you look at schematics, often you see the circuit diagram drawn in between a upper or top voltage bar or 'rail.
   
  On the bottom of the chart you ususally see the ground level or rail....
   
  To make schematic diagrams easier to understand if the distance to the upper voltage reference, source or rail sometimes you will see abbreviated shorter voltage and gnd connections, like with ops amps etc..
   
  When bread-boarding the V+ is usually strung out of the top on the board and the V- or gnd reference is laid out along the bottom....so you have an upper rail and a lower ground rail...like railroad tracks....
   
  Alex


----------



## miceblue

Quote: 





adydula said:


> If you look at schematics, often you see the circuit diagram drawn in between a upper or top voltage bar or 'rail.
> 
> On the bottom of the chart you ususally see the ground level or rail....
> 
> ...


 
   
  Quote: 





mikeaj said:


> Power supply voltage outputs (which the op amps and so on receive) are commonly called rails. e.g. the +7V rail


 
  Ah thank you for the explanations. That makes sense now.


----------



## Bee inthe Attic

How is the O2 with the Senn HD 600 ?
   
  I ask because I'm currently powering my 600's with a Fiio E9, to which many write is the bare minimum of an amp one should use to power 600's. However, after reading the power specs, the O2 and E9 both have similar output into these 300 ohm cans.
   
  Is the O2 not especially good with higher impedance cans like the 600's? Thanks.


----------



## Satellite_6

Quote: 





bee inthe attic said:


> How is the O2 with the Senn HD 600 ?
> 
> I ask because I'm currently powering my 600's with a Fiio E9, to which many write is the bare minimum of an amp one should use to power 600's. However, after reading the power specs, the O2 and E9 both have similar output into these 300 ohm cans.
> 
> Is the O2 not especially good with higher impedance cans like the 600's? Thanks.


 
  Very good. 
   
  No, I assume both amps have ample power and someone told you some BS about the HD 600's being extremely hard to drive.


----------



## TheGame21x

Quote: 





bee inthe attic said:


> How is the O2 with the Senn HD 600 ?
> 
> I ask because I'm currently powering my 600's with a Fiio E9, to which many write is the bare minimum of an amp one should use to power 600's. However, after reading the power specs, the O2 and E9 both have similar output into these 300 ohm cans.
> 
> Is the O2 not especially good with higher impedance cans like the 600's? Thanks.


 

 The O2 is excellent with the HD 600 in my opinion.


----------



## mikeaj

There are two issues:  (1) outputting enough power to make the headphones sound sufficiently loud and (2) sound quality.
   
  The amount of power delivered determines the volume.  Both the O2 and E9 can drive the HD 600 way louder than what a normal person would listen to.  That said, if you're trying to listen to some classical recording with wide dynamic range (thus low average volume), at a very high volume, you need more power output than most portable sources and integrated amps can provide.  E9 was the cheapest desktop form-factor headphone amp with enough power to blow peoples' socks off for the HD 600 for a while (until the recent Schiit Magni).  Anyway, if you're not maxing out the E9, you wouldn't be maxing out the O2.
   
  Different people have different opinions on sound quality, but if you look at what's going on electrically and acoustically, the differences between amplifiers really aren't that great.  (read: that was a big understatement)  Furthermore, HD 600 has high impedance, which makes it relatively easy to drive accurately, so differences between amplifiers are lower for this kind of easier load.
   
  A lot of people tend to confuse power specs with sound quality or performance, even though in reality, they're not using but a small fraction of the power levels their big honking amps are capable of.  Or surely one needs a desktop amp for desktop headphones, right?  (actually no)
   
  The E9 is not especially good with some lower-impedance cans—actually, more like some IEMs.  O2 and E9 both may not be powerful enough for the quietest, least sensitive headphones, if you want to listen at a loud volume.  Other than that, not much to say.


----------



## miceblue

Quote: 





mikeaj said:


> There are two issues:  (1) outputting enough power to make the headphones sound sufficiently loud and (2) sound quality.
> 
> The amount of power delivered determines the volume.  Both the O2 and E9 can drive the HD 600 way louder than what a normal person would listen to.  That said, if you're trying to listen to some classical recording with wide dynamic range (thus low average volume), at a very high volume, you need more power output than most portable sources and integrated amps can provide.  E9 was the cheapest desktop form-factor headphone amp with enough power to blow peoples' socks off for the HD 600 for a while (until the recent Schiit Magni).  Anyway, if you're not maxing out the E9, you wouldn't be maxing out the O2.
> 
> ...


 
  While on the topic of high impedance headphones, though not really related to the O2, why do such headphones exist? I mean the DT880 comes in a whopping 600-ohm version....what benefits do higher impedance headphones offer other than having an amp's output impedance being negligible for the "magic" Z_load/Z_source value being greater or equal to 8?


----------



## Bee inthe Attic

Quote: 





mikeaj said:


> There are two issues:  (1) outputting enough power to make the headphones sound sufficiently loud and (2) sound quality.
> 
> The amount of power delivered determines the volume.  Both the O2 and E9 can drive the HD 600 way louder than what a normal person would listen to.  That said, if you're trying to listen to some classical recording with wide dynamic range (thus low average volume), at a very high volume, you need more power output than most portable sources and integrated amps can provide.  E9 was the cheapest desktop form-factor headphone amp with enough power to blow peoples' socks off for the HD 600 for a while (until the recent Schiit Magni).  Anyway, if you're not maxing out the E9, you wouldn't be maxing out the O2.
> 
> ...


 
   
  The E9 is terrible with most lower impedance cans I've tried it with.... renders the bass far to boomy (due to the 10 ohm headphone jack output).
  But with higher impedance cans like the HD 600, I'm wondering if there is much difference between the E9 & O2. Is there a noticeable sound quality difference to justify dropping $150?
   
  I want to get the most out of my 600's, and I often read on here that they don't _sing_ with the E9. Do they _sing_ with the O2?


----------



## MrMateoHead

They will sing with the O2. The O2 is a good amp.
   
  Don't forget - other than power, output impedance, and flat response, amps like the O2 have a handy gain switch. In a High Dynamic Range recording (like with Gershwin Rhapsody in Blue), you'd be turning the volume knob way more than normal. Without enough power, this recording might not be loud enough for you. But with gain switched to 6.5X, you get more "volume" sooner from the amp. Gain is not really a substitute for power, but it comes in handy with a weak source, or sometimes really High Dynamic Range Recordings.
   
  With the O2/ODAC, the nice part is that noise levels are still surpressed, as in, totally black. The only risk is with clipping. But with a good recording, this hasn't been an issue. And clipping would mean I was blowing my eardrums anyway.


----------



## Satellite_6

You can't use the high gain with a desktop source, however you will *never* need to with the HD 600.


----------



## cel4145

kskwerl said:


> 553-WAU16-400
> 
> 
> WAU16-400
> ...




If it makes you feel any better having to wait on your power source, my O2 came yesterday from JDS Labs, and the power source didn't work. Stuck in Duracell land for a couple of days


----------



## Bananaheadlin

I got the WAU16-400 too, it seemed like the preferred alternative (upgrade).


----------



## kskwerl

Quote: 





bananaheadlin said:


> I got the WAU16-400 too, it seemed like the preferred alternative (upgrade).


 
  Glad to here it


----------



## adydula

the hd600's will "sing" with the O2.....
   
  gosh....
   
  Alex


----------



## MrMateoHead

Quote: 





adydula said:


> the hd600's will "sing" with the O2.....
> 
> gosh....
> 
> Alex


 

 You love it. What was I supposed to say anyhow, they will sound "cold, analytic, and brutally anti-music?" Isn't that what some people say to justify their more expensive purchases? Lol.


----------



## kskwerl

Quote: 





satellite_6 said:


> You can't use the high gain with a desktop source, however you will *never* need to with the HD 600.


 
  What does this even mean?


----------



## chrislangley4253

Quote: 





kskwerl said:


> What does this even mean?


 
  It means the hd600 are very sensitive headphones, and that you'd never need the higher 6.5x gain to drive them. It would be ridiculously loud, at least with a desktop ~2Vrms source..



 What gain do you guys use with your cans? I have my o2 set up with 1x/2.5x. Off the ODAC and grados/t50rp and sennheiser I pretty much exclusively use 1x.. With really quiet recordings I will use 2.5x.. and every once in a blue moon I might find 2.5 lacking, usually when I'm using my clip as a source, I don't think I've ever had the problem off the odac.

 I think 1x/3.5x would be the ideal set up for someone with my sources, meaning the ODAC and Clip+. I might try to bump up the 2.5 to 3.5, anybody know if this should be doable?


----------



## HeatFan12

Well, my Ultrasones are 'singin' with the O2...
	

	
	
		
		

		
			




   
  Just received my good ol' extension cable from Monoprice so my unplug cycles will surely decrease now.  I don't mess with the source as much anymore (like it where it's at) and the WAU16-1000 is always plugged in so minimal unplugging for me on the O2..


----------



## RustA

Finally got it, desktop version of O2/ODAC combo with RCA outputs! My LCD-2 rev2 seem very happy now... So my ears are!


----------



## scuttle

Quote: 





miceblue said:


> While on the topic of high impedance headphones, though not really related to the O2, why do such headphones exist? I mean the DT880 comes in a whopping 600-ohm version....what benefits do higher impedance headphones offer other than having an amp's output impedance being negligible for the "magic" Z_load/Z_source value being greater or equal to 8?


 
   
  They keep down the amount of current needed to supply a given power level. This comes in useful in studios where you have lots of headphones plugged into the same piece of equipment.


----------



## kskwerl

Quote: 





chrislangley4253 said:


> It means the hd600 are very sensitive headphones, and that you'd never need the higher 6.5x gain to drive them. It would be ridiculously loud, at least with a desktop ~2Vrms source..
> 
> 
> 
> ...


 
  ah I see, well I know that but just didn't think that was what he was saying. I have the 2.5x/6.5x, with the HD600s I use the 2.5x but I haven't really even gotten to enjoy the O2 yet as I'm waiting for my power adapter from mouser.com


----------



## Bee inthe Attic

Quote: 





adydula said:


> the hd600's will "sing" with the O2.....
> 
> gosh....
> 
> Alex


 

 lol
   
  I was making light of how often I read that a certain amp makes a certain headphone _sing._
  Because the power specs of the O2 and E9 are similar, I was wondering why many say the O2 would make the HD600's _sing_, but not the E9.


----------



## HamilcarBarca

Quote: 





> Originally Posted by *chrislangley4253* /img/forum/go_quote.gif
> 
> What gain do you guys use with your cans? I have my o2 set up with 1x/2.5x. Off the ODAC and grados/t50rp and sennheiser I pretty much exclusively use 1x.. With really quiet recordings I will use 2.5x.. and every once in a blue moon I might find 2.5 lacking, usually when I'm using my clip as a source, I don't think I've ever had the problem off the odac.


 
   
  I have the Beyerdynamic DT 990 and T 70, Sennheiser HD-650, and Grado 325is. For my listening, the 2.5x setting is too much gain for any of them.


----------



## chrislangley4253

Quote: 





hamilcarbarca said:


> I have the Beyerdynamic DT 990 and T 70, Sennheiser HD-650, and Grado 325is. For my listening, the 2.5x setting is too much gain for any of them.


 
  Yeah! I couldn't stand 2.5 as the low gain!

 I think if the O2 had followed the ODAC he might have dropped the gain options a bit.


----------



## adydula

The O2 will sing because the E9 has some issues......
   
  The main problem is an output impedance of 10 ohms on the 1/4” jack and 43 ohms on the 3.5 mm mini jack. Using the small jack will almost certainly affect frequency response and/or bass performance with many headphones—especially balanced armature IEMs (Shure, Etymotic Ultimate Ears, etc.). While using the bigger jack should work reasonably well for full size higher impedance headphones—80 ohms or higher.
   
  Alex


----------



## Bee inthe Attic

Quote: 





adydula said:


> The O2 will sing because the E9 has some issues......
> 
> The main problem is an output impedance of 10 ohms on the 1/4” jack and 43 ohms on the 3.5 mm mini jack. Using the small jack will almost certainly affect frequency response and/or bass performance with many headphones—especially balanced armature IEMs (Shure, Etymotic Ultimate Ears, etc.). While using the bigger jack should work reasonably well for full size higher impedance headphones—80 ohms or higher.
> 
> Alex


 
   
  my original post referred to the O2 vs E9 with the HD600's (300 ohms), so the high output impedance of the E9 doesn't really effect the synergy between the E9 and 600's.
  I'm not in love with the E9, just wondering why many feel the O2 is leaps and bounds ahead of it with high impedance cans. (I've never heard the O2, and am debating getting one - just trying to decide if spending $150 is worthwhile in my case, considering that I already own the E9)


----------



## chrislangley4253

So... For the third time now I am experiencing noise in the right channel of my o2 while I move the pot during a bass test..

 My first o2 I replaced the pot on and it fixed the problem for a while.. When it came back I bought a completely different o2 from jds thinking maybe the problem was my particular o2.. Nope, seems like it's just a problem these pots have. And not a huge problem at that.. It can just be annoying while I'm running sine sweeps.

 http://www.youtube.com/watch?v=PMd9eYXT0mM

 Please, for the love of all that is headphones. Could a few of you listen to this track and move your volume pot around and tell me if you get any scratching in the right channel?


----------



## miceblue

Quote: 





chrislangley4253 said:


> So... For the third time now I am experiencing noise in the right channel of my o2 while I move the pot during a bass test..
> 
> My first o2 I replaced the pot on and it fixed the problem for a while.. When it came back I bought a completely different o2 from jds thinking maybe the problem was my particular o2.. Nope, seems like it's just a problem these pots have. And not a huge problem at that.. It can just be annoying while I'm running sine sweeps.
> 
> ...


 
  Nothing unusual pops up for me while listening to that track with an AKG K 701 on the ODAC and O2 units I have. Adjusting the potentiometer yielded nothing unusual either, unless the cymbal sounds are what you're referring to as "scratching sounds".


----------



## chrislangley4253

Quote: 





miceblue said:


> Nothing unusual pops up for me while listening to that track with an AKG K 701 on the ODAC and O2 units I have. Adjusting the potentiometer yielded nothing unusual either, unless the cymbal sounds are what you're referring to as "scratching sounds".


 
  Nooope. It'd hit you like a sack of bricks if yours had the same problem that mine keep getting. It's not terrible, but its quite noticeable. I just used this track because it's pretty bassy.


----------



## miceblue

Quote: 





chrislangley4253 said:


> Quote:
> 
> 
> 
> ...


 
  Yup I don't get anything with my sensitive V-MODA M-100's either. That's kind of odd that it happened to you 3 times now though.


----------



## MrMateoHead

Quote: 





bee inthe attic said:


> my original post referred to the O2 vs E9 with the HD600's (300 ohms), so the high output impedance of the E9 doesn't really effect the synergy between the E9 and 600's.
> I'm not in love with the E9, just wondering why many feel the O2 is leaps and bounds ahead of it with high impedance cans. (I've never heard the O2, and am debating getting one - just trying to decide if spending $150 is worthwhile in my case, considering that I already own the E9)


 

 The O2 is superior to the E9 in every way for starters. It is technically portable, it supports a wider range of headphone impedence (16 ohm - whatever), and makes similar if not more power (not sure haven't memorized specs). The thing puts out no noise whatsoever, and the gain switch is handy for using weaker sources like phones and Mp3 players.
   
  That said, if you like the E9 and it is working for you, keep it and save your money. I wouldn't have got an amp period if my laptop had enough juice to run my current phones (it didn't).


----------



## MrMateoHead

Quote: 





chrislangley4253 said:


> So... For the third time now I am experiencing noise in the right channel of my o2 while I move the pot during a bass test..
> 
> My first o2 I replaced the pot on and it fixed the problem for a while.. When it came back I bought a completely different o2 from jds thinking maybe the problem was my particular o2.. Nope, seems like it's just a problem these pots have. And not a huge problem at that.. It can just be annoying while I'm running sine sweeps.
> 
> ...


 

 +1 to getting "scratching" when moving volume knob around in right channel. Weird.
   
  Stops when the volume knob stops. This does not occur with anything else I have ever listened to so far, so I am not sure why that uncomfortably bassy music would do it.
   
  I once lost the Left channel completely one day. Had to unplug the amp completely, and plug everything back in. Seemed to be a possible problem at the headphone jack.


----------



## RustA

Quote: 





mrmateohead said:


> +1 to getting "scratching" when moving volume knob around in right channel. Weird.
> 
> Stops when the volume knob stops. This does not occur with anything else I have ever listened to so far, so I am not sure why that uncomfortably bassy music would do it.
> 
> I once lost the Left channel completely one day. Had to unplug the amp completely, and plug everything back in. Seemed to be a possible problem at the headphone jack.


 
   
  I don't think it's weird since I experienced that with several amps (rarely but yes)... It does not affect the sound at all, you know (only if you are going to slowly manipulate with the knob over longer period of time, you would possibly keep listening to that "scratching" ,-) ).
   
  I would personally check the potentiometer, if it "fits and sits" exactly where it should be and how it should be... Unscrew the panel and the knob and have a look, then get it together again and try to manipulate with it again.


----------



## lorriman

chrislangley4253 said:


> So... For the third time now I am experiencing noise in the right channel of my o2 while I move the pot during a bass test..
> 
> 
> http://www.youtube.com/watch?v=PMd9eYXT0mM




I have this problem and posted a message about it on diyaudio. There was no resolution.


----------



## MrMateoHead

It may be worth adding that, I only pick up the scratch on that youtube video - not on any of my other music.
   
  And with that, there is the variable of the audio signal going through windows -> my DAC -> my amp -> my headphones.


----------



## chrislangley4253

Quote: 





mrmateohead said:


> It may be worth adding that, I only pick up the scratch on that youtube video - not on any of my other music.
> 
> And with that, there is the variable of the audio signal going through windows -> my DAC -> my amp -> my headphones.


 
  it's not the video. Play anything else bassy and you will hear it.


----------



## lorriman

I've just tested this with silence and with a 60Hz sine tone. It doesn't do it with a silence track. If I lower the volume of the source (my laptop) to 6 (Vista) then I only hear it at the end of the O2's volume control on 2.5x gain, whereas otherwise it's prominent already at 11 o'clock. This is true both of O2 stand-alone and O2/ODAC.


----------



## JakeJack_2008

Quote: 





mrmateohead said:


> +1 to getting "scratching" when moving volume knob around in right channel. Weird.
> 
> *Stops when the volume knob stops*. This does not occur with anything else I have ever listened to so far, so I am not sure why that uncomfortably bassy music would do it.
> 
> I once lost the Left channel completely one day. Had to unplug the amp completely, and plug everything back in. Seemed to be a possible problem at the headphone jack.


 
   
  Hold on, not so fast, please.  Right now I'm _sratching _my forehead and debating whether I should forget about the O2 or not.
  But rereading Your post and highlighting the key sentence in red I see that the weird _sratching _occurs only _while _you're playing with the volume  knob.
  So perhaps this is nothing serious, I hope. Also, what model of the O2 (the pot, headphone jack, ...)  are we talking  here about:  from JDS Labs, ..., DIY-made?


----------



## chrislangley4253

Quote: 





jakejack_2008 said:


> Hold on, not so fast, please.  Right now I'm _sratching _my forehead and debating whether I should forget about the O2 or not.
> But rereading Your post and highlighting the key sentence in red I see that the weird _sratching _occurs only _while _you're playing with the volume  knob.
> So perhaps this is nothing serious, I hope. Also, what model of the O2 (the pot, headphone jack, ...)  are we talking  here about:  from JDS Labs, ..., DIY-made?


 
  I don't think it's anything serious. Just an issue that the pots sometimes develop. I have had it happen twice on a DIY O2 and once now on my JDS Labs. It's really non-intrusive, I wouldn't let it keep you from getting the amp. I still recommend it, anyways.


----------



## mikeaj

I've never had an issue with the pot on the one I built.  I wiggled it nonstop for a minute listening to that track and heard nothing like that.
   
  Is it the right channel for everybody, if it happens?


----------



## chrislangley4253

Quote: 





mikeaj said:


> I've never had an issue with the pot on the one I built.  I wiggled it nonstop for a minute listening to that track and heard nothing like that.
> 
> Is it the right channel for everybody, if it happens?


 
   
  Well, I've only had it in the right channel three times. That might just be coincidence though.


----------



## stv014

Probably the pot simply has a minor contact problem while it is being adjusted, and the signal gets amplitude modulated by noise as a result. When there is no signal, it does not result in audible noise; that is also why DC on pots should be avoided, as noted by the designer of the O2, too. It is most noticeable with loud bass because that (and DC) is what can produce the highest level of modulation noise without masking it. The problem could affect the right channel more often because of the way that particular model of pot is built.


----------



## adydula

Chris, what kind of WIERD stuff is that anyway!!
   
  OMG..
   
  No issues here with it?
   
  Alex
   
  oh...what the doctor told me .."dont do that"...


----------



## Draygonn

chrislangley4253 said:


> Please, for the love of all that is headphones. Could a few of you listen to this track and move your volume pot around and tell me if you get any scratching in the right channel?


Mine has the annoying scratching noise issue. It was fine for the first 6 months or so. 



mikeaj said:


> Is it the right channel for everybody, if it happens?


My right channel is affected.


----------



## Dano91

I also have that scratching issue and only in right channel. Started after some 2 months maybe? Bought from Head'n'HiFi. But since it happens only when turning the knob, it keeps me calm.


----------



## agdr

Quote: 





stv014 said:


> The problem could affect the right channel more often because of the way that particular model of pot is built.


 
   
  It could very well be!  Sounds like a lot of folks are having that same issue. If anyone wants to test that theory, the Bourns Pro Audio PTD902-2015F-A103 works as a substitute for the Alps 097 pot in the O2 amp.  It is also a 10K audio taper, 9mm body, 15mm shaft, all same as the Alps and fits right into the O2 PCB holes.  I've built O2s with both the Bourns and Alps pots.  Mouser #652-PTD902-2015FA103, onlinecomponents.com #PTD902-2015F-A103.
   
  The pot comes right out with a vacuum desoldering gun like the Hakko 808, but it would probably be next to impossible to get out with solder wick or a hand solder sucker bulb without destroying the PCB.


----------



## MisterCAG

I was thinking of getting this amp, but I was wondering if there will be any more noticeable changes with my ATH-M50s than say my motherboards integrated sound? I will purchasing the V moda M100s soon as well and I just wanted my audio to be more refined and having a better sound stage, etc.


----------



## RustA

Quote: 





mistercag said:


> I was thinking of getting this amp, but I was wondering if there will be any more noticeable changes with my ATH-M50s than say my motherboards integrated sound? I will purchasing the V moda M100s soon as well and I just wanted my audio to be more refined and having a better sound stage, etc.


 
   
  Yes... SIGNIFICANTLY higher level of clarity, better soundstage, more detail... Noticable even with low-end headphones.


----------



## lorriman

mistercag said:


> I was thinking of getting this amp, but I was wondering if there will be any more noticeable changes with my ATH-M50s than say my motherboards integrated sound? I will purchasing the V moda M100s soon as well and I just wanted my audio to be more refined and having a better sound stage, etc.




There's a discussion about this elsewhere. Standard, cheap, audio chipsets are so well implemented these days that there is a good possibility that you are already getting hifi out of it and the ODAC won't make any difference. It depends on the manufacturer. My 5 year old laptop has an output impedance of .5 and for the life of me I can't tell the difference between it and the O2/ODAC. A friends computer is the same. Both are Dells. 

Perversely, Macs usually have high output impedance which means that while the chipset may be hifi, it will interact with low impedance headphones in negative ways. Older Ipods also have this issue, and the Iphone 5 (but the 3gs and 4 are fine).

I also suspect that where manufacturers have gone for high end chipsets (like Wolfson) then they become hostage to implementation issues and so you get worse audio. A good example of that would be the dire Samsung Galaxy II and III (and maybe I). It's purely about marketing because standard, off-the-shelf chipsets are likely already hifi.


----------



## Satellite_6

The standard Realtek soundcards I have had in pretty much every computer I have owned are always noticeably noisy. 
   
  I never use them for music, rather the ODAC or Music Streamer II which both sound great.


----------



## lorriman

I have a realtek and it's pretty near dead silent on my highly sensitive etymotics. The only way I can tell that there is noise is by plugging and unplugging, and the slightest, tiniest bit of shh disappears.

For an off-the-shelf chipset, already implemented, noise is probably the only thing that could be a problem if the manufacturer doesn't pay attention, but apart from that it should be hifi (perfect square waves, no audible distortion, flat frequency response etc).


----------



## BleaK

Quote: 





rusta said:


> Finally got it, desktop version of O2/ODAC combo with RCA outputs! My LCD-2 rev2 seem very happy now... So my ears are!


 
   
  That is awsome! Is that DIY or special order from JDS?


----------



## cel4145

lorriman said:


> I have a realtek and it's pretty near dead silent on my highly sensitive etymotics. The only way I can tell that there is noise is by plugging and unplugging, and the slightest, tiniest bit of shh disappears.
> 
> For an off-the-shelf chipset, already implemented, noise is probably the only thing that could be a problem if the manufacturer doesn't pay attention, but apart from that it should be hifi (perfect square waves, no audible distortion, flat frequency response etc).




It's problematic to make claims about Realtek like this. Realtek is a company who makes a variety of chipsets. One cannot generalize to all Realtek chipsets, especially given that implementation is a factor. It's not much better than trying to claim that all Geforce cards can play Crysis at 1080p on high frame rates.


----------



## RustA

Quote: 





bleak said:


> That is awsome! Is that DIY or special order from JDS?


 
   
  Have a look at my profile, I have a bit more images there... For example:
   

   
  It's from Mayflower Electronics (but they cooperate with JDS)... It has 1/4 headphone out, RCA out (but you can choose RCA in instead I think), 1/8 in and SIP adapters (in order to be able to use different gain resistors, you have to do a request for this). This particular one also has different volume knob, rubber feet and few internal tweaks (like better capacitors etc.). You can order O2 desktop amp alone, or have ODAC installed inside (as I have).


----------



## lorriman

cel4145 said:


> It's problematic to make claims about Realtek like this. Realtek is a company who makes a variety of chipsets. One cannot generalize to all Realtek chipsets, especially given that implementation is a factor. It's not much better than trying to claim that all Geforce cards can play Crysis at 1080p on high frame rates.




An off-the-shelf implementation is already implemented. So I think you can generalise. 

Sure, if there is no such thing as an off-the-shelf implementation, then you can't. In the meantime I have tested both realteks and sigmatels and I cannot tell any difference between them and my ODAC except for a tiny bit of noise.


----------



## Satellite_6

Quote: 





rusta said:


> Have a look at my profile, I have a bit more images there... For example:
> 
> 
> 
> It's from Mayflower Electronics (but they cooperate with JDS)... It has 1/4 headphone out, RCA out (but you can choose RCA in instead I think), 1/8 in and SIP adapters (in order to be able to use different gain resistors, you have to do a request for this). This particular one also has different volume knob, rubber feet and few internal tweaks (like better capacitors etc.). You can order O2 desktop amp alone, or have ODAC installed inside (as I have).


 
  That is pretty darn cool. I kind of wanted a version like that but I have the standard JDS lab version. From the website it looks like you cannot buy it with an ODAC tho. . .


----------



## RustA

Quote: 





satellite_6 said:


> That is pretty darn cool. I kind of wanted a version like that but I have the standard JDS lab version. From the website it looks like you cannot buy it with an ODAC tho. . .


 
   
  You can from Mayflower, scroll to the bottom... http://www.mayflowerelectronics.com/products.html
   
  Not sure about JDS Labs, maybe you could ask them if they can do it for you... However, as I said, Mayflower cooperates with them, they are even supplied with ODAC boards from them as far as I know. The good thing on Mayflower is that you can get a lot of upgrades if you ask for them. That's what I like.


----------



## MrMateoHead

Quote: 





chrislangley4253 said:


> it's not the video. Play anything else bassy and you will hear it.


 

 Nope. Tried some bass heavy music with Foobar. No issue.


----------



## RustA

Quote: 





mrmateohead said:


> Nope. Tried some bass heavy music with Foobar. No issue.


 
   
  I also do not hear it... It's not that all the O2 amps are faulty or anything like that. As I suggested, check the pot... Or leave it as it is since there are no practical impacts.


----------



## HeatFan12

Looking good RustA. Cheers!

I also purchased my O2 from Tyler (Mayflower). He's listed on JDS as a US distributor. That's how I found Mayflower. Great service.




Sent from my iPhone using Tapatalk


----------



## miceblue

lorriman said:


> mistercag said:
> 
> 
> > I was thinking of getting this amp, but I was wondering if there will be any more noticeable changes with my ATH-M50s than say my motherboards integrated sound? I will purchasing the V moda M100s soon as well and I just wanted my audio to be more refined and having a better sound stage, etc.
> ...




Yeah about the Macs thing. My 6-year old Dell Vostro sounds cleaner than my 4-year old MacBook. Odd.


----------



## chrislangley4253

Quote: 





mistercag said:


> I was thinking of getting this amp, but I was wondering if there will be any more noticeable changes with my ATH-M50s than say my motherboards integrated sound? I will purchasing the V moda M100s soon as well and I just wanted my audio to be more refined and having a better sound stage, etc.


 
   
  It will only improve if there is something inherently wrong with your mobo's sound. Is it noisey? Does it feel like it's lacking anything? If not, It's prolly just fine. The only thing I gained moving off of my mobo was a drop in noise and I feel like I gained a little imaging or soundstage somehow, maybe my mobo rolls  the highs a tad.
   
  Quote: 





rusta said:


> I also do not hear it... It's not that all the O2 amps are faulty or anything like that. As I suggested, check the pot... Or leave it as it is since there are no practical impacts.


 
   
  It is certainly the pot, I just came her to try to get the problem recognized. I've had the pots do this to me 3 times now. It's a little annoying, I don't have the hot air equipment to replace it myself, or I certainly would.. And with something not made by alps, for sure.


----------



## Satellite_6

Quote: 





rusta said:


> You can from Mayflower, scroll to the bottom... http://www.mayflowerelectronics.com/products.html
> 
> Not sure about JDS Labs, maybe you could ask them if they can do it for you... However, as I said, Mayflower cooperates with them, they are even supplied with ODAC boards from them as far as I know. The good thing on Mayflower is that you can get a lot of upgrades if you ask for them. That's what I like.


 
  Ah that's pretty sweet then. I wish I knew about it before but oh well.


----------



## cel4145

lorriman said:


> An off-the-shelf implementation is already implemented. So I think you can generalise.
> 
> Sure, if there is no such thing as an off-the-shelf implementation, then you can't. In the meantime I have tested both realteks and sigmatels and I cannot tell any difference between them and my ODAC except for a tiny bit of noise.




You think. But you do not know. 

I don't doubt the possibility that some implementations of Realtek audio work very well--depending, too, on the rest of the hardware in the laptop. But that's a belief of mine, not a fact. And I would be careful to state it as such. The problem is your faulty logic that, based on anecdotal evidence, you can generalize that Realtek is great across the board. Your listening bias could make them sound the same to you, even though not, just as much as someone else's listening bias could make them feel it's different, when they are sonically the same. Then, have you done a representative sample of laptops currently in production?


----------



## autoteleology

I'm thinking about maybe having a trade for my custom O2 / ODAC for a Magni and a Modi (with cables and a bit of cash).
   
  I'm looking for more power and a more convenient package, and I don't mind terribly a slight (but only slight) drop in SQ.
   
  Would it be worth it to trade?


----------



## RustA

Quote: 





tus-chan said:


> I'm thinking about maybe having a trade for my custom O2 / ODAC for a Magni and a Modi (with cables and a bit of cash).
> 
> I'm looking for more power and a more convenient package, and I don't mind terribly a slight (but only slight) drop in SQ.
> 
> Would it be worth it to trade?


 
   
  I say "why not"? You could always switch back then since it's all relatively cheap, you know...
   
  You could have a look at the new Asgard 2 as well.


----------



## autoteleology

> I say "why not"? You could always switch back then since it's all relatively cheap, you know...


 
   
  Well, not quite. While I had my ODAC custom-built by Audio Poutine, my O2 is one of a kind, as far as I know.
   

   
  If I don't like the M&M, it's almost impossible for me to switch back, and if I could, it would at the very least be very time consuming.


----------



## RustA

Quote: 





tus-chan said:


> Well, not quite. While I had my ODAC custom-built by Audio Poutine, my O2 is one of a kind, as far as I know.


 
   
  Then buy Magni+Modi, compare and see for yourself... But, to be honest, I would rather keep ODAC and search for more suitable amplifier only (to provide you with desirable influence on sound). ODAC is pretty good (there is far more work behind it than using a certain chip as some people here tends to think). You are not going to experience better performance with neither Modi, nor Bifrost. I've even read an opinion that ODAC is very similar in performance to Gungnir as well (outcome of a listening test).
   
  O2 is equally great but I understand that some want the sound to be a bit influenced by amplifier. What exactly do you want to achieve, by the way? "More power" is a very general statement...


----------



## chrislangley4253

What's special about your O2?


----------



## MrMateoHead

Quote: 





chrislangley4253 said:


> It will only improve if there is something inherently wrong with your mobo's sound. Is it noisey? Does it feel like it's lacking anything? If not, It's prolly just fine. *The only thing I gained moving off of my mobo was a drop in noise* and I feel like I gained a little imaging or soundstage somehow, maybe my mobo rolls  the highs a tad.
> 
> 
> It is certainly the pot, I just came her to try to get the problem recognized. *I've had the pots do this to me 3 times now.* It's a little annoying, I don't have the hot air equipment to replace it myself, or I certainly would.. And with something not made by alps, for sure.


 
  Moving off MB sound definitely took me from "noisy - sometimes" to "black, totally black". Makes for a more spacious sound to my ears. The trade-off has been, I also hear any and all artifacts / imperfections / compression in my albums. Some intentional, some as a result of bad recording practices.
   
  As for the noise issue, I feel bad for you. Do you do a lot of sine sweeps or something? Because other than the Youtube link, the problem was not replicated by me.


----------



## chrislangley4253

Quote: 





mrmateohead said:


> Moving off MB sound definitely took me from "noisy - sometimes" to "black, totally black". Makes for a more spacious sound to my ears. The trade-off has been, I also hear any and all artifacts / imperfections / compression in my albums. Some intentional, some as a result of bad recording practices.
> 
> As for the noise issue, I feel bad for you. Do you do a lot of sine sweeps or something? Because other than the Youtube link, the problem was not replicated by me.


 
  Yeah man, I use sine sweeps to tune headphones I'm modding.


----------



## lorriman

cel4145 said:


> You think. But you do not know.




Sure, which is why I mentioned that.



> I don't doubt the possibility that some implementations of Realtek audio work very well--depending, too, on the rest of the hardware in the laptop. But that's a belief of mine, not a fact. And I would be careful to state it as such. The problem is your faulty logic that, based on anecdotal evidence, you can generalize that Realtek is great across the board. Your listening bias could make them sound the same to you, even though not, just as much as someone else's listening bias could make them feel it's different, when they are sonically the same. Then, have you done a representative sample of laptops currently in production?




Despite my not hearing any (significant) difference between my ODAC and my mobo's sound, I would still purchase the ODAC (and even despite _not_ being after accurate audio reproduction), but I'll get to that in a moment. Firstly...

I didn't say I was generalising 'across the board'. I also mentioned that an off-the-shelf implementation is still not a guarantee; noise issues for example, and perhaps also crosstalk, come to think of it, so a reduction in stereo, both of which would be due to a poor 'implantation implementation' -  - of what is otherwise already implemented. 

My own experience is anecdotal which is why I was careful not to make strong assertions. Nevertheless, sighted bias is generally quoted in terms of expectation bias causing people to hear differences that don't manifest when tested by DBT (double-blind testing), rather than people who are surprised to hear no difference despite expectation bias. So while my experience is anecdotal, it is worth a pinch more than the usual sighted testing that hears vast improvements that almost certainly don't exist at all. Indeed I was disappointed. Not only should I have been subject to expectation bias (and be 'confirming' the improvement over mobo sound) but I wanted to hear a difference.

In any case, if there are such things as off-the-shelf implementations then it's most certainly logical that cheap chipsets may be giving people hifi already, in well made mobos. To my mind, I would be very surprised if there were not such implementations considering the cost savings (assuming that the ODAC designer is right in saying that perfect hifi is already reacheable on the cheap). And in my care to be accurate, I also mentioned that I do not know if there is such a thing as an off-the-shelf implementation.

I think I have been careful enough to qualify my statements and not make over-generalisations. Enough to at least motivate the impartial reader to try before they buy.

For my part, I want the guarantee that the ODAC/O2 gives me of reaching audio perfection, and that any old random mobo chipset cannot give without comprehensive and independently verified specs. For this purpose I also purchased etymotics balanced armatures. So I would still buy the O2/ODAC combo. By doing this I can hear a base-line of purist hifi audio (as in high fidelity, rather than 'extremely expensive esoteric audio technology') and therefore can avoid some part of the the endless chasing after something better/purer that appears to afflict so many, and which is unnecessary if your believe, as I do, that true, objectively measured, hifi has been reached since some time ago and is not expensive. (A reason I would avoid Class-A amps in favour of cheap but well implemented and properly specced Class D amps). 

For me, the biggest improvement I have experienced in my journey has been a DSP combo of 'headphone equalisation' using parametric equalizers (see the head-fi thread on that), and the rockbox 'stereo width' feature at 180%. Wow, does a lot of music come alive with that latter. (If anyone tries this, just be sure to enable stereo-width with another setting 'channel-balance -> 'custom'). I think DSP has a serious future in consumer audio. I should perhaps also mention the realisation that as a loud listener, many of the head-fi reviews by ljokerl can result in disappointment as his quiet listener reviews are not a good match. As a rule of thumb, loud listeners require flat headphones to remove honks and spikes that don't trouble quiet listeners. (Worth mentioning that deaf or 2000-4000Hz deficient listeners need mid centric, voice-forward, phones).

Unhappily, in speaker and headphone tech, while etymotics can give audio perfection/nirvana, they don't reach audio paradise in my opinion. And I don't mean the weak bass (which can be equalised in without penalty due to low distortion). My modded Fostex T50rp give a stunning 'texture' to the audio that is highly sensual and very pleasing. I've not found this present in other phones. Indeed, despite the rep of the Senheiser HD-800, I would wish to verify the presence or absence of this attribute before purchase.

Any way, nice to get all that off my chest.


----------



## cel4145

lorriman said:


> Sure, which is why I mentioned that.
> Despite my not hearing any (significant) difference between my ODAC and my mobo's sound, I would still purchase the ODAC (and even despite _not_ being after accurate audio reproduction), but I'll get to that in a moment. Firstly...
> 
> I didn't say I was generalising 'across the board'. I also mentioned that an off-the-shelf implementation is still not a guarantee; noise issues for example, and perhaps also crosstalk, come to think of it, so a reduction in stereo, both of which would be due to a poor 'implantation implementation' -  - of what is otherwise already implemented.
> ...




You had made this declarative statement, 



> Standard, cheap, audio chipsets are so well implemented these days that there is a good possibility that you are already getting hifi out of it and the ODAC won't make any difference. It depends on the manufacturer. My 5 year old laptop has an output impedance of .5 and for the life of me I can't tell the difference between it and the O2/ODAC. A friends computer is the same. Both are Dells.




Is there a "good possibility?" Realtek has six different chipset implementation for 2 channel HD audio alone: http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PNid=24&PFid=27&Level=5&Conn=4

Then there is the problem with believing that hearing things to be the same is somehow more valid than hearing differences. Listener bias is both a result of expectation and poor audio memory. So last fall when I had a chance to demo the Fire Phoenix DAC-02 and compare it with the output of my Xonar STX, I believed them to be roughly the same in SQ. But I did not try to claim that they sounded the same because of the listener bias and because I am not able to level match the two through a set of headphones. Without level matching, they MUST necessarily sound different. So you say that there was no difference, but in all likelihood there was a difference there because the odds are against level matching correctly by ear (I'm assuming you don't have sophisticated equipment to test this). 

But it seems like we do agree on one thing. If someone wants to make sure that they have a hifi audio experience, the ODAC/O2 seems a good way to guarantee that.


----------



## lorriman

> "Is there a "good possibility?"




Sure, and that's not an assertion of a fact. As I wrote, I was careful to qualifty myself.



> "Then there is the problem with believing that hearing things to be the same is somehow more valid than hearing differences."




Hmmm, not sure my argument was that exactly; rather that my expectation bias was to hear a difference, and I didn't. Logically, that removes expectation bias from the picture, thus increasing the validity of the observation ("a pinch more valid"). Whether that actually produces an objective test is of course not the case, as I think we both agree of DBT. And that's why I qualified my observation. (However, I'm not ideologically against the implicit principal in your argument that no subjective options whould be expressed in the forums, but I'm not ideologically for that either).



> "Listener bias is both a result of expectation and poor audio memory.




Sure, and I was careful to qualify my observation.



> "Without level matching, they MUST necessarily sound different. So you say that there was no difference, but in all likelihood there was a difference there because the odds are against level matching correctly by ear (I'm assuming you don't have sophisticated equipment to test this)."




Without perfect level matching, the difference in levels may yet be very slight. Since they didn't sound different then there are three possibilities:

1)I level matched successfully
2)my audio memory failed me
3)even if my audio memory failed me: there was no significant difference that I could detect using this coarse method of comparison and that the level difference was slight. (I think all of us are familiar with huge differences in audio, heavy distortion etc).

As it happens I did attempt level matching by increasing volume of a test tone to the point of discomfort. 

so while hearing a difference can be accounted for merely by expectation bias, I don't think that is the case with hearing no difference against one's expectation bias.

In anycase, I am not attempting to put an objective fact in front of anyone. My observation/test is justified as a healthy and equal counter to those who said that there will definitely be a marked improvement to an external DAC (see earlier in the thread): some of us are not hearing that marked difference even with an ODAC against a sigmatel.

In addition to which: it sows doubt as to that need, and so motivates the individual to determine an objective fact before making such an expensive purchase. Ideally, that would be to see independently verified measurements of a mobo sound card.


----------



## cel4145

lorriman said:


> Sure, and that's not an assertion of a fact. As I wrote, I was careful to qualifty myself.




There's no basis for that claim given that Realtek has a variety of chipsets. Having sampled just a few implementations,some of them could have been the same chipset. So I still think it's a problem to generalize as even a personal opinion to all laptops that there is a "high probability" unless you have sampled like 100 laptops. LOL



lorriman said:


> Without perfect level matching, the difference in levels may yet be very slight. Since they didn't sound different then there are three possibilities:
> 
> 1)I level matched successfully
> 2)my audio memory failed me
> 3)even if my audio memory failed me: there was no significant difference that I could detect using this coarse method of comparison and that the level difference was slight. (I think all of us are familiar with huge differences in audio, heavy distortion etc).




And yet, a difference of more than .1db in level matching has been shown to affect listener response. The odds of you level matching each of your test cases by ear within .1db are highly likely, and your original assertion was that they were the "same"

http://www.head-fi.org/t/616331/o2-amp-odac/825#post_9144635

Now I think it's reasonable to say that they have similar SQ, since SQ is itself always a subjective assessment. 



lorriman said:


> In anycase, I am not attempting to put an objective fact in front of anyone. My observation/test is justified as a healthy and equal counter to those who said that there will definitely be a marked improvement to an external DAC (see earlier in the thread): some of us are not hearing that marked difference even with an ODAC against a sigmatel.




I agree. All our tests are subjective. All of the listening test comparisons we try to make on head-fi should have an implied YMMV.


----------



## chimmycham

I am very interested in this combo.
  What would be my best bet to get it for decently cheap?


----------



## adydula

If you want it cheap....build one yourself.
   
  or
   
  look for a used one in the for sale area.
   
  Alex


----------



## MrMateoHead

Quote: 





chrislangley4253 said:


> Yeah man, I use sine sweeps to tune headphones I'm modding.


 
  Can you create the problem on a different source - such as an MP3 Player or cell phone?
 Or maybe a stereo with a volume knob and headphone jack?


----------



## miceblue

How are so many people having potentiometer problems? Is it due to quality control issues? o.0


----------



## chrislangley4253

Quote: 





mrmateohead said:


> Can you create the problem on a different source - such as an MP3 Player or cell phone?
> Or maybe a stereo with a volume knob and headphone jack?


 
   
  Nope, It's definitely the pot on the O2.
   
  Quote: 





adydula said:


> If you want it cheap....build one yourself.
> 
> or
> 
> ...


 
   
  +1 to the sale/trade forums here


----------



## MrMateoHead

Quote: 





chrislangley4253 said:


> Nope, *It's definitely the pot *on the O2.
> 
> 
> +1 to the sale/trade forums here


 
  I believe you, but, does it happen whether on Battery / AC Adapter?
   
  The major thing is, doing lots of bassy sine sweeps could be an issue for other amplifiers too. Is it really a deal breaker that you can't fiddle with the volume constantly while listening in?


----------



## RustA

Quote: 





mrmateohead said:


> I believe you, but, does it happen whether on Battery / AC Adapter?
> 
> The major thing is, doing lots of bassy sine sweeps could be an issue for other amplifiers too. Is it really a deal breaker that you can't fiddle with the volume constantly while listening in?


 
   
  In my experience with several amps (when this occured, but not with O2 so far), it's not a deal breaker at all... It's just that you sometimes experience a partial distortion when manipulating with a volume knob. Unless you are going to manipulate with it ALL THE TIME, it's not an issue and you could perfectly consider it as "a feature", if you know what I mean...


----------



## autoteleology

I've had a different problem - rare but it has happened. Sometimes I get noticeable noise from the power insert.


----------



## adydula

I get loud metallic sound when i lift up on the front bottom and release it, only when it hits the pc its sitting on.
  Solved by using soft pads underneath with glue.
   
  Doesnt seem to affect the high end treble at all..
   
  Alex


----------



## RustA

Quote: 





tus-chan said:


> I've had a different problem - rare but it has happened. Sometimes I get noticeable noise from the power insert.


 
   
  What do you mean... Like when you're playing music (randomly) or when pressing the power button? It's strange, never happened to me and I already owned 2 different units...


----------



## RustA

Quote: 





adydula said:


> I get loud metallic sound when i lift up on the front bottom and release it, only when it hits the pc its sitting on.
> Solved by using soft pads underneath with glue.
> 
> Doesnt seem to affect the high end treble at all..
> ...


 
   
  Do you have rubber feet on your amp?


----------



## chrislangley4253

Quote: 





mrmateohead said:


> I believe you, but, does it happen whether on Battery / AC Adapter?
> 
> The major thing is, doing lots of bassy sine sweeps could be an issue for other amplifiers too. Is it really a deal breaker that you can't fiddle with the volume constantly while listening in?


 
  Let me try the batteries.
   
  *edit*.. Well, I don't have any scratching at all anymore. Bizarre, I'm sure it will eventually come back. I might update when/if it does on whether the power source affects it (I assume not).
   
  It's not a deal breaker. Just something I noticed... I expect it to get louder until it does bug me enough to change the pot again. This time I'll go with something not made by ALPS.


----------



## MrMateoHead

Quote: 





chrislangley4253 said:


> *Let me try the batteries.*
> 
> **edit*.. Well, I don't have any scratching at all anymore.* Bizarre, I'm sure it will eventually come back. I might update when/if it does on whether the power source affects it (I assume not).
> 
> It's not a deal breaker. Just something I noticed... I expect it to get louder until it does bug me enough to change the pot again. This time I'll go with something not made by ALPS.


 
  OK now we are getting somewhere then.
 Are you using the stock Triad part - the WAU12-200?
   
  Because if you consistently get the scratching when running AC Power, I wonder if the combination of high current demand and 13.5V 200 mA AC adapter is coming up short providing stable power. OR, maybe you have a "dirty outlet". Since I can replicate the issue when plugged in, I should try it again on battery only. 
   
  Makes me wonder if upgrading to one of the ballsier AC adapters might correct the issue, or if the "solution", is to run your sine sweeps and bass dense stuff on the batteries instead.


----------



## Draygonn

mrmateohead said:


> Makes me wonder if upgrading to one of the ballsier AC adapters might correct the issue, or if the "solution", is to run your sine sweeps and bass dense stuff on the batteries instead.


I'm running the WAU16-400 and it scratches.


----------



## MrMateoHead

Quote: 





draygonn said:


> I'm running the WAU16-400 and it scratches.


 

 It sounded like I still got a slight scratch on battery via the YouTube link. Not particularly consistent. Plugged the adapter back in - no worse, no better.
   
  I can't believe people actually listen to that stuff! Its almost painful.
   
  I've got some Royksopp going in Foobar (the alcoholic) and I don't get any scratching at all. I still wonder if there is a noise issue that might be a part of the windows drivers -> browser -> youtube link.  If Sines are scratching in Foobar WASAPI for him I suppose there is little left to blame but the pot.


----------



## Draygonn

Has anyone tried hitting the pot with compressed air? I might give that a try tomorrow.


----------



## chrislangley4253

Alright, my youtube link sucks.. for testing this problem. Try a sine wave around 50 hz

 http://www.realmofexcursion.com/downloads.htm - just click on em.
  Quote: 





mrmateohead said:


> OK now we are getting somewhere then.
> Are you using the stock Triad part - the WAU12-200?
> 
> Because if you consistently get the scratching when running AC Power, I wonder if the combination of high current demand and 13.5V 200 mA AC adapter is coming up short providing stable power. OR, maybe you have a "dirty outlet". Since I can replicate the issue when plugged in, I should try it again on battery only.
> ...


 
   
  You misunderstood me. I couldn't hear it on either ac or battery.. I actually can't hear it at all on the youtube video, it turns out. But I hear it with my sine gen and other places. It's real hard to pick out on music right now.. at other times it sticks out so much that it's very obvious even with music. 
   
  Again, it has nothing to do with the power.
  Quote: 





mrmateohead said:


> It sounded like I still got a slight scratch on battery via the YouTube link. Not particularly consistent. Plugged the adapter back in - no worse, no better.
> 
> I can't believe people actually listen to that stuff! Its almost painful.
> 
> I've got some Royksopp going in Foobar (the alcoholic) and I don't get any scratching at all. I still wonder if there is a noise issue that might be a part of the windows drivers -> browser -> youtube link.  If Sines are scratching in Foobar WASAPI for him I suppose there is little left to blame but the pot.


 
  Try my new link, my youtube video wasn't ideal.
   
  Also, I actually get a little distortion in the left channel too, just not as much as the right.


----------



## Battou62

I am now a proud member of the O2 / Odac club !!! Got my O2 combo last night. Feels good man.


----------



## adamlr

Quote: 





battou62 said:


> I am now a proud member of the O2 / Odac club !!! Got my O2 combo last night. Feels good man.


 

 yes it does!
   
  just plugged in my odac and o2 for the first time myself and im loving it!
  i did have some clicking noises, but i switched to a different usb outlet and it seems to have done the trick. 
   
  now, i have a question, based on what i read here on head-fi, analog volume control has channel issues, where one should have the volume pot at a "9 o'clock position" or higher, in order to avoid said issues. right now thats now problem, but in the not so distant future i plan on getting new headphones and these will be very sensitive, very efficient ones and i suspect the "9 o'clock position" will be too much for them and will force me to reduce the volume and enter into channel imbalance land. 
  my question is this: if i reduce volume via electriq on foobar, would this be the same as digitally lowering volume through my computer (which i understand can degrade sq, although i admit i have my doubts...)? 
   
   
  edit: rather handsome i must say =]


----------



## shadow419

You have two options really.  You can use software volume control, or you can use unity (X1) gain for one of the gain positions on the gain switch.


----------



## adamlr

Quote: 





shadow419 said:


> You have two options really.  You can use software volume control, or you can use unity (X1) gain for one of the gain positions on the gain switch.


 

 i have the standard gain settings: X2.5 and X6.5. so no X1 for me im afraid. unless one can adjust this simply from the inside? im no diyer...


----------



## HamilcarBarca

Quote: 





adamlr said:


> now, i have a question, based on what i read here on head-fi, analog volume control has channel issues, where one should have the volume pot at a "9 o'clock position" or higher, in order to avoid said issues.
> [...]


 
   
  Channel imbalance is a common problem with inexpensive pots. Even so, my O2 doesn't have any (audible) imbalance and I almost always set my O2's volume below 9:00.
   
  Quote: 





adamlr said:


> i have the standard gain settings: X2.5 and X6.5. so no X1 for me im afraid. unless one can adjust this simply from the inside? im no diyer...


 
   
  Change from 2.5x/6.5x to 1.0x/2.5x requires cutting 4 leads to remove two resistors from the circuit.
   
Edit: Spelling correction


----------



## adamlr

Quote: 





hamilcarbarca said:


> 1)Channel imbalance is a common problem with inexpensive pots. Even so, my O2 doesn't have any (audible) imbalance and I almost walys set my O2's volume below 9:00.
> 
> 
> 2)Change from 2.5x/6.5x to 1.0x/2.5x requires cutting 4 leads to remove two resistors from the circuit.


 
  1) thats good to know, thank you.
  2) sounds very D.I.Yish to me, i dont think ill mess about with things like that.
   
  right now i have the volume pot at just about 10 o'clock, so its all good. i guess ill wait and see what happens when i get my next headphones. hopefully ill discover, like you, that no channel imbalance is audible. worst comes the worst ill look for a guide on how to cut those leads the way you suggested. thank you very much


----------



## shadow419

A little diy'ish, but extremely simple to do if you indeed go that route.  I soldered little sockets to "plug" in the gain resistors.  This way I can adjust the gain whenever I need to without having to resolder anything.


----------



## lorriman

If the ODAC is running at 24bit then the computer's volume control won't degrade audio. The ODAC defaulted to 16bit on my Vista laptop. Ideally it should be 24bit 44Khz. Higher sample rates can cause audio degradation, and in any case will cause upsampling, which defeats the purpose.

If foobar is bypassing the standard drivers then you'll need to make sure some other way that it's not running at 16bits.

And yes, reducing volume would solve your problem. I would advise using the system volume since otherwise your sensitive earphones might suddenly find themselves pumping 120db of audio in to your ears curtosy of a web advert or accidental video. I don't beleive there is any need to bypass the system drivers. Bit Perfect and all that is just Bit Nonsense in my view. You won't get any discernible increase in audio quality. 

Alternatively get one of these :

http://www.head-fi.org/t/627755/short-positive-review-iluv-headphone-2-way-splitter-with-dual-independent-volume-controls

They are quite useful.


----------



## lorriman

adamlr said:


> 1) thats good to know, thank you.
> 2) sounds very D.I.Yish to me, i dont think ill mess about with things like that.
> 
> right now i have the volume pot at just about 10 o'clock, so its all good. i guess ill wait and see what happens when i get my next headphones. hopefully ill discover, like you, that no channel imbalance is audible. worst comes the worst ill look for a guide on how to cut those leads the way you suggested. thank you very much




If you want to run your O2 off a low power dap (like an ipod or clip+ etc) then it;s probably best to go for 1x/6.5x. 2.5x can be too little for less sensitive or high ohm headphones when running off a low voltage source, especially if you are EQing in bass (which can lower the source's overall volume to accomodate the bass bump without distortion).

I would also advise against 'the snip' if you don't really know what you are doing. It's very easy to get wrong.


----------



## adamlr

Quote: 





lorriman said:


> If you want to run your O2 off a low power dap (like an ipod or clip+ etc) then it;s probably best to go for 1x/6.5x. 2.5x can be too little for less sensitive or high ohm headphones when running off a low voltage source, especially if you are EQing in bass (which can lower the source's overall volume to accomodate the bass bump without distortion).
> 
> I would also advise against 'the snip' if you don't really know what you are doing. It's very easy to get wrong.


 

 "the snip" just made me literally laugh out loud =]
   
  i did set the sample rate to 24/44khz. though i noticed i can go as high as 24/96. either way, all my files are 320kbps mp3s anyway...
  i never eq the bass up, only eq everything else down. no distortion - ever.
   
  i noticed there are options for eq on the odac menu. bass boost for example. why would i want do eq with my dac??
   
   
  thank you everyone for your help. is ther anyone else that noticed/didnt notice channel imbalance when using the O2? especially if paring with a sensitive headphone and setting the volume knob to under "9 o'clock"? this is really what im asking i think. and if someone did have some issues - what did you do?


----------



## lorriman

He he. 

I always use the bass boost because most of my headphones lose bass under 80Hz, so I bass boost about 6-9 db according to the headphones at 50Hz. Also I use flat headpdhones, partly for the accuracy but also because they have superb distortion handling, so I can EQ without fear to get that bass that I want while having the benefit of flatness elsewhere. I would prefer to bass boost at 30Hz, 12db, but no such option.

This solves the problem that Windows Media Player and so many others distort horribly in the EQs, whereas the Bass Boost doesn't and also provides the bass boost system wide, handy for spotify.

If you consider loudness curves then it;s very handy to be able to bass boost, especially if you listen less loudly. I'm a loud listener, but since I gave up caffiene I've suddenly found myself turning the volume right down. I suspect I;m getting a more accurate treble presentation from my etymotics also, which are otherwise known for their rather strong treble.


----------



## autoteleology

> If you consider loudness curves then it's very handy to be able to bass boost, especially if you listen less loudly.


 
   
  True dat. Add in a bit more bass boost for commuting, because headphones only isolate from mids and highs in most cases.


----------



## adamlr

Quote: 





lorriman said:


> He he.
> 
> I always use the bass boost because most of my headphones lose bass under 80Hz, so I bass boost about 6-9 db according to the headphones at 50Hz. Also I use flat headpdhones, partly for the accuracy but also because they have superb distortion handling, so I can EQ without fear to get that bass that I want while having the benefit of flatness elsewhere. I would prefer to bass boost at 30Hz, 12db, but no such option.
> 
> ...


 

 i allways bass boost, and i dont use neutral cans at all. im a basshead. but i dont understand why one would use his dac for that, whats wrong with just using an equalizer?


----------



## RustA

Quote: 





shadow419 said:


> You have two options really.  You can use software volume control, or you can use unity (X1) gain for one of the gain positions on the gain switch.


 
   
  O2 measures the best with unity gain... So I do only use unity gain.


----------



## Bananaheadlin

adamlr said:


> edit: rather handsome i must say =]




Handsome indeed! May I ask what black knob that is on the volume control?


----------



## lorriman

rusta said:


> O2 measures the best with unity gain... So I do only use unity gain.




Purists eh? Tsk tsk. 

Here's to 12x gain !!!!!!!!! Yeeehaaaarrrr!!! 

:basshead:


----------



## Stratok

When I  ordered my O2 + odac I didnt have an option to choose the gain settings so it comes with the standard 2.5x / 6.5x. I have signature DJ which are 32 Ohm HPs so am I fine with the standard settings or should I try some sorcery and make it 1.0x / 2.5x for example? I also have DT770pro tho they are not getting much head time


----------



## adamlr

Quote: 





bananaheadlin said:


> Handsome indeed! May I ask what black knob that is on the volume control?


 
   
  thats just the standard knob for the black O2 =]
   
  Quote: 





stratok said:


> When I  ordered my O2 + odac I didnt have an option to choose the gain settings so it comes with the standard 2.5x / 6.5x. I have signature DJ which are 32 Ohm HPs so am I fine with the standard settings or should I try some sorcery and make it 1.0x / 2.5x for example? I also have DT770pro tho they are not getting much head time


 
  really? and at what "time" do you have the volume knob? if im not mistaken, the sig dj and the m-100 have the same impedance. but the m-100 are alot more sensitive. as far as i can find on cnet, the sig djs sensitivity is 98db while the m-100 are 103.


----------



## Stratok

Quote: 





adamlr said:


> really? and at what "time" do you have the volume knob? if im not mistaken, the sig dj and the m-100 have the same impedance. but the m-100 are alot more sensitive. as far as i can find on cnet, the sig djs sensitivity is 98db while the m-100 are 103.


 

 I have not yet received it I thought to dig up some info beforehand. Sig DJ has 115db sensitivity i think.


----------



## adamlr

Quote: 





stratok said:


> I have not yet received it I thought to dig up some info beforehand. Sig DJ has 115db sensitivity i think.


 

 98db is the sensitivety of the signature pro. i was wrong.
   
  i cant seem to find the sesitivity of the the signature djs... on the ultrasone site, part of the specs say "SPL: 115 dB", is that sensitivity? sensitivity rating is usually given together with "@ 1kHz 1mW" or something of the sort...
   
  either way, ill be glad to hear how they fair with *2.5 gain, especially if their sensitivity is 115db, which would make them even more sensitive than the m-100.
   
   
   
  anyone here with ~32ohm impedance and ~103db sensitivity cans? if so, is *2.5 gain too much for them, are do you still get manageable volume control without channel imbalance?


----------



## autoteleology

What is the difference between the knob and the pot?


----------



## adamlr

im pretty sure thats just a different name for the same thing: the bit you turn in order to control the volume...


----------



## HamilcarBarca

Quote: 





tus-chan said:


> What is the difference between the knob and the pot?


 
   
  A potentiometer ("pot") is a variable-resistance electrical device.
   
  A knob is a mechanical attachment to allow adjustments.


----------



## ben_r_

And the knob attaches to the shaft of the pot.


----------



## chrislangley4253

Quote: 





lorriman said:


> I would also advise against 'the snip' if you don't really know what you are doing. It's very easy to get wrong.


 
   
  The resistors are labeled... Just clip r19 and r23 to drop the gain to 1x/2.5x, very easy.. If you can work a pair of small scissors.
   
  Quote: 





adamlr said:


> thank you everyone for your help. is ther anyone else that noticed/didnt notice channel imbalance when using the O2? especially if paring with a sensitive headphone and setting the volume knob to under "9 o'clock"? this is really what im asking i think. and if someone did have some issues - what did you do?


 
   
  i notice some very slight channel balance at the _very _beginning of the pot. I choose to drop my gain to 1x/2.5x using the "snip" method, 2.5 is usually too high off the odac with grados/fostex t50rp. At least, it is for my ears.
   
  Quote: 





stratok said:


> When I  ordered my O2 + odac I didnt have an option to choose the gain settings so it comes with the standard 2.5x / 6.5x. I have signature DJ which are 32 Ohm HPs so am I fine with the standard settings or should I try some sorcery and make it 1.0x / 2.5x for example? I also have DT770pro tho they are not getting much head time


 
   
  The aforementioned "snip" mod.. Just clip resistors r19 and r23.


----------



## MrEleventy

I notice some imbalance under 9 here too on my m80s and hd25-1 iis. I'm thinking about doing some mods to my o2, like moving the source and power jack to the back. might do the 1/2.5x gain snip but after I get a he-400. don't want to snip if 2.5x isn't enough to run them. hehe


----------



## Ren19

I just recieved my O2+Odac combo and i'm wondering if its normal that the computer volume control affect the volume of my amp.
   
  If it's normal, should i turn the volume of my computer as low as i can and let my O2 do the amplification?
   
  Thanks.


----------



## MrEleventy

you'd want to set the volume in Windows @100.


----------



## HamilcarBarca

Quote: 





ren19 said:


> I just recieved my O2+Odac combo and i'm wondering if its normal that the computer volume control affect the volume of my amp.


 
   
  That's the way it works for me. Windows modifies the source audio data to reduce the volume and transmits the result, digitally, over USB to the ODAC. (It may be possible to override this behavior but I've never tried.)


----------



## Ren19

Thanks for the replies,
   
  I have noticed something else:  when there is no sound playing trough the O2/Odac i can put the volume to the maximum with the low 2.5x gain and i wont hear a single noise coming out of my headphones. But when i open a music program or when my computer sees that a sound is about to be played i can hear noise. (I believe the noise is still there when the song is playing)
   
  Is there any fix for that?
   
  Also it is major when i put the 6x gain on it, it sounds like i'm in the middle of a rain forest...
   
  Thanks.


----------



## chrislangley4253

Quote: 





ren19 said:


> Thanks for the replies,
> 
> I have noticed something else:  when there is no sound playing trough the O2/Odac i can put the volume to the maximum with the low 2.5x gain and i wont hear a single noise coming out of my headphones. But when i open a music program or when my computer sees that a sound is about to be played i can hear noise. (I believe the noise is still there when the song is playing)
> 
> ...


 
  Interesting... You definitely have something going on here. Try unplugging the o2, and anything else you can think of moving around, maybe moving the odac to a different usb port. The o2 and odac are dead silent, you shouldn't be hearing a noise like that. Someone else will probably chime in with better troubleshooting advice.


----------



## Ren19

I played music on Mac and the noise problem dissapeared. I looked at what could be the problem on Windows and i think it could be because my version of windows is "Not Genuine". On startup, there is a pop-up saying that "Windows Update" and other things may not work because my version is not genuine anymore. So i suspect that this could be the cause even though windows seemed to have installed all the required drivers on first usb plugging.
   
  Could this be caused by something else?


----------



## chrislangley4253

Quote: 





ren19 said:


> I played music on Mac and the noise problem dissapeared. I looked at what could be the problem on Windows and i think it could be because my version of windows is "Not Genuine". On startup, there is a pop-up saying that "Windows Update" and other things may not work because my version is not genuine anymore. So i suspect that this could be the cause even though windows seemed to have installed all the required drivers on first usb plugging.
> 
> Could this be caused by something else?


 
  I don't think that is your problem.. Also, I'll send you a few links to help you fix that authentication problem of yours.


----------



## stv014

Maybe the Windows audio output format is set to 16 bits ?


----------



## Dano91

Quote: 





stv014 said:


> Maybe the Windows audio output format is set to 16 bits ?


 

 There's no reason why it should behave like that even if set to 16bit..


----------



## Ren19

Quote: 





stv014 said:


> Maybe the Windows audio output format is set to 16 bits ?


 
   
  My problem is fixed and this was exactly the cause.
   
  Thanks everyone.


----------



## miceblue

Quote: 





adamlr said:


> Quote:
> 
> 
> 
> ...


 
  Does the M-100 count? You mentioned it earlier. 2.5x gain is too much (I have the 2.5x/1.0x installed).
   
  With my K 701 I have the volume on my computer set to ~60% and the O2 at ~8 o'clock at 1.0x gain.
   
  Speaking of all of this, can anyone explain the source vs amp volume control thing? I used to have the source at low volume, O2 on max until I read otherwise. It doesn't make much sense to me. If I need to adjust the volume, wouldn't it be easier to have amp set at max volume, source at a comfortable loud volume, then just reduce the amp volume from there? That way you don't have to worry about any channel imbalance problems, nor having the amp constantly at a "low" volume and adjusting everything again for different headphones (M-100 for example). Not to mention having the Windows boot-up sound blast at full volume every time you boot because you leave the volume on the source (computer) at max. With the other way I used to have it, I would just swap headphones, lower amp volume accordingly, not worry about channel imbalance at all. Can't get much simpler than that.


----------



## adamlr

Quote: 





miceblue said:


> Does the M-100 count? You mentioned it earlier. 2.5x gain is too much (I have the 2.5x/1.0x installed).
> 
> With my K 701 I have the volume on my computer set to ~60% and the O2 at ~8 o'clock at 1.0x gain.
> 
> Speaking of all of this, can anyone explain the source vs amp volume control thing? I used to have the source at low volume, O2 on max until I read otherwise. It doesn't make much sense to me. If I need to adjust the volume, wouldn't it be easier to have amp set at max volume, source at a comfortable loud volume, then just reduce the amp volume from there? That way you don't have to worry about any channel imbalance problems, nor having the amp constantly at a "low" volume and adjusting everything again for different headphones (M-100 for example). Not to mention having the Windows boot-up sound blast at full volume every time you boot because you leave the volume on the source (computer) at max. With the other way I used to have it, I would just swap headphones, lower amp volume accordingly, not worry about channel imbalance at all. Can't get much simpler than that.


 

 yes it counts! thats the one im talking about! maybe i will "go for the snip"... ill wait and see if i do go for the m-100 first, if i do, ill see how they fair with the *2.5 gain. worst comes the worst, ill send an email to john and ask for some guidance... 
  while were on the subject, how do i take the volume knob off? i want to open up the O2 and take the batteries out and i cant seem to figure out how to take the knob off, which i assume is necessary.
   
   
  and as for the second part of your post, im given to understand that for maximum fidelity, you want to control volume with your amp, not your source. having your source on 100% will deliver the maximum quality, and if its on less, you could be delivering like, 12 bits of digital audio to your amp, as opposed to 16 bits, if the volume was at 100%. granted, i have no idea if this is true, even if it is, i dont know how audible the difference will be and ofcourse, im in no way an authority on these issues.


----------



## MrEleventy

Quote: 





adamlr said:


> while were on the subject, how do i take the volume knob off? i want to open up the O2 and take the batteries out and i cant seem to figure out how to take the knob off, which i assume is necessary.


 
   
   
  Just take the front plate off and the whole board should slide out easily (If your O2 build is like the JDS Labs one). No need to remove the knob.
   


> and as for the second part of your post, im given to understand that for maximum fidelity, you want to control volume with your amp, not your source. having your source on 100% will deliver the maximum quality, and if its on less, you could be delivering like, 12 bits of digital audio to your amp, as opposed to 16 bits, if the volume was at 100%. granted, i have no idea if this is true, even if it is, i dont know how audible the difference will be and ofcourse, im in no way an authority on these issues.


 
   
  That's the same impression that I got from reading other posts about this subject. If you have a 16 bit dac and your files are 16bit, lowering the volume in windows lower your dynamic range / quality of the output. You want to control the volume via the amp. The other bit that I gleemed from this is that if you set the dac to 24 bit and your audio files are 16 bit, you can lower the volume in windows up to a point w/o effecting dynamic range since the dac will take the 16 bit file and upconvert it to 24 and fill in the missing 8bit with just 0s so you can change the volume in windows and all you're losing is 8bits worth of 0s.


----------



## shadow419

Quote: 





adamlr said:


> yes it counts! thats the one im talking about! maybe i will "go for the snip"... ill wait and see if i do go for the m-100 first, if i do, ill see how they fair with the *2.5 gain. worst comes the worst, ill send an email to john and ask for some guidance...
> while were on the subject, how do i take the volume knob off? i want to open up the O2 and take the batteries out and i cant seem to figure out how to take the knob off, which i assume is necessary.
> 
> 
> and as for the second part of your post, im given to understand that for maximum fidelity, you want to control volume with your amp, not your source. having your source on 100% will deliver the maximum quality, and if its on less, you could be delivering like, 12 bits of digital audio to your amp, as opposed to 16 bits, if the volume was at 100%. granted, i have no idea if this is true, even if it is, i dont know how audible the difference will be and ofcourse, im in no way an authority on these issues.


 
  Not sure if JDS uses a set screw or just a press fit knob, but either way should be simple enough.  If it's a press fit just pull it off, if a set screw loosen the screw and it'll fall off.


----------



## HamilcarBarca

Quote: 





adamlr said:


> while were on the subject, how do i take the volume knob off? i want to open up the O2 and take the batteries out and i cant seem to figure out how to take the knob off, which i assume is necessary.


 
   
  There's a set screw on the volume knob. IIRC, all you need is a tiny allen wrench.


----------



## adamlr

Quote: 





mreleventy said:


> Just take the front plate off and the whole board should slide out easily (If your O2 build is like the JDS Labs one). No need to remove the knob.


 
  couldnt seem to take the front panel off together with the knob, im pretty sure i need to remove it first
  Quote: 





shadow419 said:


> Not sure if JDS uses a set screw or just a press fit knob, but either way should be simple enough.  If it's a press fit just pull it off, if a set screw loosen the screw and it'll fall off.


 
   
  Quote: 





hamilcarbarca said:


> There's a set screw on the volume knob. IIRC, all you need is a tiny allen wrench.


 

 yep, looks like an allen key is what i need. thank you very much


----------



## cel4145

adamlr said:


> couldnt seem to take the front panel off together with the knob, im pretty sure i need to remove it first
> 
> yep, looks like an allen key is what i need. thank you very much




You don't have to take the knob off to get to the battery. The faceplate will just come off with the board as you slide it out.


----------



## adamlr

Quote: 





cel4145 said:


> You don't have to take the knob off to get to the battery. The faceplate will just come off with the board as you slide it out.


 

 your not the first to tell me this, but i tried removing the front panel, and it wouldnt budge. i tried removing the back panel aswell but one of the screws wouldnt give...
   
  is there something i should be doing? is there more to it than just unscrewing the screws?


----------



## cel4145

Then maybe you should take off the knob since you are having problems (you need a small non-metric hex key). That way you don't accidentally yank the knob and its connection to the board when you pull the cover off. I changed out my front plate, and there was a touch of hot glue holding it to the board. With the plate glued to the board, it has to pull straight out, not at an angle or off kilter in someway.


----------



## miceblue

Quote: 





mreleventy said:


> > and as for the second part of your post, im given to understand that for maximum fidelity, you want to control volume with your amp, not your source. having your source on 100% will deliver the maximum quality, and if its on less, you could be delivering like, 12 bits of digital audio to your amp, as opposed to 16 bits, if the volume was at 100%. granted, i have no idea if this is true, even if it is, i dont know how audible the difference will be and ofcourse, im in no way an authority on these issues.
> 
> 
> 
> ...


 
  Hm I see. Thanks for the clarification.
   
  I still don't really like that that happens though. With my Retina MacBook Pro on max volume, the O2 set to as low of volume as possible at 1.0x gain, they are super loud for me with the K 701....which basically renders the O2 useless for the M-100 if the O2's potentiometer is at the 7:30 position (yes there's channel imbalance) for the K 701 even at 1.0x gain. With this kind of listening, I can't physically lower the volume with the amp any more or else I will get a really noticeable channel imbalance. All of this seems unreasonable to me.
   
  The creator of the O2 did point out "guilty free" source volume control with the ODAC's 24-bit USB interface and gave a brief sentence or two about the loss of resolution and whatnot. The question is, can you guys actually hear it? I notice no significant increase in sound quality, if any, with the source on max volume, super-limited volume control with the amp versus low volume on source, very diverse volume control with the amp.


----------



## adamlr

Quote: 





cel4145 said:


> Then maybe you should take off the knob since you are having problems (you need a small non-metric hex key). That way you don't accidentally yank the knob and its connection to the board when you pull the cover off. I changed out my front plate, and there was a touch of hot glue holding it to the board. With the plate glued to the board, it has to pull straight out, not at an angle or off kilter in someway.


 

 actually, the plate came loose pretty easily, it felt like it was entirely loose, and the only thing that was holding it back was the volume knob. unfortunately, i dont have an allen key thats small enough, which is really ironic, as i ordered a full set of them off ebay a couple of months ago on a whim, and just yesterday i sent the guy an email, cause they haven't arrived yet >_<
   
  looks like the batteries will remain inside for the time being. i just want to take them out so as to make the O2 a "desktop amp" and use the mains to power it, without any batteries to worry about. supposedly you can leave it plugged in for decades and it wont damage the batteries at all, but im skeptical, and want to remove them just in case anyway.


----------



## adamlr

Quote: 





miceblue said:


> Hm I see. Thanks for the clarification.
> 
> I still don't really like that that happens though. With my Retina MacBook Pro on max volume, the O2 set to as low of volume as possible at 1.0x gain, they are super loud for me with the K 701....which basically renders the O2 useless for the M-100 if the O2's potentiometer is at the 7:30 position (yes there's channel imbalance) for the K 701 even at 1.0x gain. With this kind of listening, I can't physically lower the volume with the amp any more or else I will get a really noticeable channel imbalance. All of this seems unreasonable to me.
> 
> The creator of the O2 did point out "guilty free" source volume control with the ODAC's 24-bit USB interface and gave a brief sentence or two about the loss of resolution and whatnot. The question is, can you guys actually hear it? I notice no significant increase in sound quality, if any, with the source on max volume, super-limited volume control with the amp versus low volume on source, very diverse volume control with the amp.


 

 hmmm, thats bad news i guess... but no, i doubt many people can really hear a difference. infact, if you look on youtube, you can find a video by ethan winer that shows you cant really hear any effect on quality untill you get as low as 8-10 bits, so i guess it really isnt such a big issue using digital volume control. i would greatly appreciate it if you pm me a link to the forbidden blog with that brief sentence, or atleast tell me which article it was in, id really like to read it. 
   
  then again, if even *1 is too much for the m-100, perhaps theres no use snipping my O2, as ill likely have to use digital volume control anyway...
   
  by the way, pardon my newbe question, but how is *1 gain even possible? wouldnt *1 give you the same value you were multiplying in first place? i think ive got something very wrong...
   
  edit: forgot to add that i have no idea what im talking about, everything i have written is in my very humble opinion, if anyone can hear a difference between 24bit audio and otherwise then i wish him the best of luck with it, and in no way am i trying to pick a fight with anyone, or question their believes or anything of the sort.


----------



## MrEleventy

Quote: 





miceblue said:


> Hm I see. Thanks for the clarification.
> 
> I still don't really like that that happens though. With my Retina MacBook Pro on max volume, the O2 set to as low of volume as possible at 1.0x gain, they are super loud for me with the K 701....which basically renders the O2 useless for the M-100 if the O2's potentiometer is at the 7:30 position (yes there's channel imbalance) for the K 701 even at 1.0x gain. With this kind of listening, I can't physically lower the volume with the amp any more or else I will get a really noticeable channel imbalance. All of this seems unreasonable to me.
> 
> The creator of the O2 did point out "guilty free" source volume control with the ODAC's 24-bit USB interface and gave a brief sentence or two about the loss of resolution and whatnot. The question is, can you guys actually hear it? I notice no significant increase in sound quality, if any, with the source on max volume, super-limited volume control with the amp versus low volume on source, very diverse volume control with the amp.


 
   
  My current setup is E17 LO > O2 > M80s, looking at the specs, it's not too far off from the M-100s (28.5 ohms vs 32 ohms, 105db vs 103db), what I do, since all 99% of my files are 16 bit anyways, I set my E17 to run at 24bit and lower the volume by about 25% and that gives me more wiggle room on the O2. I don't know the exact math but doing my own fuzzy math, I figure since 16 to 24 is about 66.7%, I can throw away 33% before losing "quality". I actually don't notice a difference at 50% but my OCD goes off and I crank it back up. 
	

	
	
		
		

		
			




   
  P.S. My O2 is still on the defaulted 2.5x/6.5x, FWIW.


----------



## adamlr

Quote: 





mreleventy said:


> My current setup is E17 LO > O2 > M80s, looking at the specs, it's not too far off from the M-100s (28.5 ohms vs 32 ohms, 105db vs 103db), what I do, since all 99% of my files are 16 bit anyways, I set my E17 to run at 24bit and lower the volume by about 25% and that gives me more wiggle room on the O2. I don't know the exact math but doing my own fuzzy math, I figure since 16 to 24 is about 66.7%, I can throw away 33% before losing "quality". I actually don't notice a difference at 50% but my OCD goes off and I crank it back up.
> 
> 
> 
> ...


 

 this sounds good to me, as im probably going to get the m-100s and im hoping not to have to mess around with the insides of my O2. what i dont undestand is this: my setup is laptop>odac>O2>headphones. so infact, no matter what bit depth i set my odac to, the original files are still being sent through my laptop, so if i lower the volume on my computer, less than the full quality is being sent to the odac, which i assume will compensate by a higher amount of "fake" bits, and not actually solving the volume control issue, no?
   
  and in the hopes of getting an answer, ill quote myself:
  by the way, pardon my newbe question, but how is *1 gain even possible? wouldnt *1 give you the same value you were multiplying in first place? i think ive got something very wrong...


----------



## cel4145

adamlr said:


> looks like the batteries will remain inside for the time being. i just want to take them out so as to make the O2 a "desktop amp" and use the mains to power it, without any batteries to worry about. supposedly you can leave it plugged in for decades and it wont damage the batteries at all, but im skeptical, and want to remove them just in case anyway.




These are the same ones. $9 to replace if you wear them out.


----------



## shadow419

*1 is unity gain. It's also called a buffer at this point since your not increasing the voltage, but you can still provide more power through increased current capability


----------



## adamlr

Quote: 





cel4145 said:


> These are the same ones. $9 to replace if you wear them out.


 
   
  thank you, but im not worried about wearing them out, im worried that with time, constantly being plugged in and charging, theyll die and damage the amp, not necessarily the most reasonable fear, but id still rather just take them out, leave the amp plugged in, and forget about it.
   
  Quote: 





shadow419 said:


> *1 is unity gain. It's also called a buffer at this point since your not increasing the voltage, but you can still provide more power through increased current capability


 
  thank you, so i was half right? *1 does infact mean that your left with the same voltage, i guess thats why its called "unity gain"? so, *1 gain means that you only add current? and this still sounds the same? doesnt it react differently to your headphones specs as opposed to "regular" gain?


----------



## miceblue

Quote: 





mreleventy said:


> Quote:
> 
> 
> 
> ...


 
  Ah okay, 75% volume sounds reasonable. With the 2.5x gain I can hear the background hiss of the O2 though (I posted this in a previous post here), so that's why I keep to the 1.0x; that plus John of JDS Labs recommended the 2.5x/1.0x for low-volume listening.


----------



## lorriman

miceblue said:


> Hm I see. Thanks for the clarification.
> 
> I still don't really like that that happens though. With my Retina MacBook Pro on max volume, the O2 set to as low of volume as possible at 1.0x gain, they are super loud for me with the K 701....which basically renders the O2 useless for the M-100 if the O2's potentiometer is at the 7:30 position (yes there's channel imbalance) for the K 701 even at 1.0x gain. With this kind of listening, I can't physically lower the volume with the amp any more or else I will get a really noticeable channel imbalance. All of this seems unreasonable to me.
> 
> The creator of the O2 did point out "guilty free" source volume control with the ODAC's 24-bit USB interface and gave a brief sentence or two about the loss of resolution and whatnot. The question is, can you guys actually hear it? I notice no significant increase in sound quality, if any, with the source on max volume, super-limited volume control with the amp versus low volume on source, very diverse volume control with the amp.




There's a further complication in that there may be a difference between XP and Vista/7. the suggestion I'e seen is that XP is affected by the 16bit volume issue (necessitating max source volume) but Vista/7 aren't. Apparently XP had an infamous sound system that would do this bit-stripping, as I've seen it called, but Vista/7 aren't affected. It would be good to get a clarification of that. Perhaps it's because Vista/7 default to 24 bit, or perhaps they talk to the amp circuit directly somehow. However, the ODAC horrifyingly defaults to 16bit on my Vista computer which I didn't know for some time, so perhaps not the former. Of course, this could be entirely bogus: in that all 3 OS's are affected equally.

In any case, I tried XP at 16bit mode and reduced source volume to a minimum using my O2 to amplify: I didn't hear much difference. But I would have to repeat that test to be sure of my claim there which I can't do at the moment.

The main things is that most modern sound cards can be easily switched to 24bit mode on Windows which means you can turn the source way down, with all the advantages that brings (and one disadvantage). I would be surprised if there were not some way of verifying that on your MAC, or changing it. (The disadvantage is that some forms of noise can be made inaudible by turning the volume to max on the source and turned down on the amp/O2. )


----------



## MrEleventy

Quote: 





adamlr said:


> this sounds good to me, as im probably going to get the m-100s and im hoping not to have to mess around with the insides of my O2. what i dont undestand is this: my setup is laptop>odac>O2>headphones. so infact, no matter what bit depth i set my odac to, the original files are still being sent through my laptop, so if i lower the volume on my computer, less than the full quality is being sent to the odac, which i assume will compensate by a higher amount of "fake" bits, and not actually solving the volume control issue, no?


 
    
  Volume adjustment is post conversion. It gets adjusted right before going out the 3.5mm jack.
   
  Quote:


miceblue said:


> Ah okay, 75% volume sounds reasonable. With the 2.5x gain I can hear the background hiss of the O2 though (I posted this in a previous post here), so that's why I keep to the 1.0x; that plus John of JDS Labs recommended the 2.5x/1.0x for low-volume listening.


 
   
  That's weird. I don't get a hiss with either gain on mine. My O2 isn't a JDS Labs though. Built by a Head-Fier.


----------



## adamlr

Quote: 





mreleventy said:


> Volume adjustment is post conversion. It gets adjusted right before going out the 3.5mm jack.


 
  i still dont get it, if you adjust the volume on the computer, then youv degraded the sound BEFORE it even reaches your dac. unless the digital volume control is somehow controlling your dacs volume?? i went on "the blog that must not be named" and read up on the odac. he says you can control volume digitaly without loosing fidelity, but he doesnt explain why its possible, just gives the same explanations as given here...


----------



## lorriman

adamlr said:


> i still dont get it, if you adjust the volume on the computer, then youv degraded the sound BEFORE it even reaches your dac. unless the digital volume control is somehow controlling your dacs volume?? i went on "the blog that must not be named" and read up on the odac. he says you can control volume digitaly without loosing fidelity, but he doesnt explain why its possible, just gives the same explanations as given here...




He does somewhere: by changing to 24bit mode.


----------



## adamlr

Quote: 





lorriman said:


> He does somewhere: by changing to 24bit mode.


 

 well, i couldnt find it... ugh, nevermind, i guess ill have to take his/your word for it. perhaps ill get an answer one day... thank you though


----------



## autoteleology

How exactly does one change to 24bit mode in Windows 7?


----------



## MrEleventy

off the top of my head, r click volume, click playback devices, r click your dac and go to properties. last tab, you can set the output.


----------



## MrEleventy

adamlr said:


> i still dont get it, if you adjust the volume on the computer, then youv degraded the sound BEFORE it even reaches your dac. unless the digital volume control is somehow controlling your dacs volume?? i went on "the blog that must not be named" and read up on the odac. he says you can control volume digitaly without loosing fidelity, but he doesnt explain why its possible, just gives the same explanations as given here...




volume control in Windows control the playback device, not Windows output. the dac will get the full bit info and then scaled down from there. post conversion


----------



## cel4145

mreleventy said:


> off the top of my head, r click volume, click playback devices, r click your dac and go to properties. last tab, you can set the output.




Yep. Go into Control Panel->Hardware and Sound->Sound. Select "Properties" for the ODAC and go to Advanced.


----------



## JakeJack_2008

Quote: 





cel4145 said:


> Yep. Go into Control Panel->Hardware and Sound->Sound. Select "Properties" for the ODAC and go to Advanced.


 
   
  I like it. _24-bit _sound with the O2 and ODAC.


----------



## kskwerl

Quote: 





jakejack_2008 said:


> I like it. _24-bit _sound with the O2 and ODAC.


----------



## lorriman

adamlr said:


> i still dont get it, if you adjust the volume on the computer, then youv degraded the sound BEFORE it even reaches your dac. unless the digital volume control is somehow controlling your dacs volume?? i went on "the blog that must not be named" and read up on the odac. he says you can control volume digitaly without loosing fidelity, but he doesnt explain why its possible, just gives the same explanations as given here...







adamlr said:


> well, i couldnt find it... ugh, nevermind, i guess ill have to take his/your word for it. perhaps ill get an answer one day... thank you though




It took ages but I finally tracked it down. This google link will take you to it "Why 24 bits can matter" :

https://www.google.co.uk/search?q=nwavguy+%22WHY+24+BITS+CAN+MATTER%22&oq=nwavguy+%22WHY+24+BITS+CAN+MATTER

I'll just add my ha'penny to clarify the O2 volume control:aAs I've understood it, the O2 works rather differently to many amps (he says not having actually any clue about amps or electronics). Instead of lowering the volume before the audio is pumped in to the amplifying electronics, the voltage is lowered AFTER the amp circuit using a 'voltage divider'. I've no idea what all that means, really, nor the implications as I'm not a genuine electronics person. Perhaps someone can tell us.


----------



## adamlr

Quote: 





mreleventy said:


> volume control in Windows control the playback device, not Windows output. the dac will get the full bit info and then scaled down from there. post conversion


 
   
  well that explains it, thank you very much! so i guess digital volume control really is "guilt free" now, so long as i keep it reasonable.
   
  Quote: 





lorriman said:


> It took ages but I finally tracked it down. This google link will take you to it "Why 24 bits can matter" :
> 
> 
> I'll just add my ha'penny to clarify the O2 volume control:aAs I've understood it, the O2 works rather differently to many amps (he says not having actually any clue about amps or electronics). Instead of lowering the volume before the audio is pumped in to the amplifying electronics, the voltage is lowered AFTER the amp circuit using a 'voltage divider'. I've no idea what all that means, really, nor the implications as I'm not a genuine electronics person. Perhaps someone can tell us.


 

 lol, you may want to edit that link out, it may not be a direct link, but its still kinda cheeky i think 
	

	
	
		
		

		
		
	


	



   
  anyhow, i already read all that, what i was trying to figure out is what MrEleventy was kind enough to explain to me. and id like to point out again that in my personal experience, i personally couldnt tell a difference between 24 bit, and 12 bit depth. i could only notice the differences at around 8-10 bits, and even then, it was mostly just background noise. ill recommend again that you search youtube for ethan winers link where he demonstrates this with a program that "strips" away one bit at a time. i think he even provides a download link so that you can try it for yourself.
   
  not an electronics guy either, so i cant help you there im afriad. thank you for your comments, much obliged =]


----------



## kskwerl

Just put my brand new 1 week old JDS stand alone O2 and ODAC up for sale on the forums if anyone is interested


----------



## mikeaj

Hopefully nobody yells at me for responding to old posts.
   
  Quote: 





mreleventy said:


> My current setup is E17 LO > O2 > M80s, looking at the specs, it's not too far off from the M-100s (28.5 ohms vs 32 ohms, 105db vs 103db), what I do, since all 99% of my files are 16 bit anyways, I set my E17 to run at 24bit and lower the volume by about 25% and that gives me more wiggle room on the O2. I don't know the exact math but doing my own fuzzy math, I figure since 16 to 24 is about 66.7%, I can throw away 33% before losing "quality". I actually don't notice a difference at 50% but my OCD goes off and I crank it back up.
> 
> 
> 
> ...


 
   
  16 bits to 24 bits is a difference of having 2^16 = 65536 possible values vs. 2^24 = 16777216 possible values, or a factor of 2^8 = 256 difference.  So around 20 * log10(256) = 48 dB.  Theoretically you could throw away 99.6% of the signal.  Note that 66% in some software volume control setting may not actually correspond to 66% of the signal.  The scaling often doesn't work that way.
   
  If you're playing a 16-bit file with 24-bit output at 100% volume control, let's say those 24 bits for a particular sample are the ones below, as a simplistic example, ignoring a couple small details.  (The order is from most to least important starting from left.)  Notice the rightmost eight values are 0 because you only have 16 bits of information.:
  01010110 00100111 0000000
   
  If you reduce the volume some digitally, the output will be essentially shifted to the right:
  00010101 10001001 1100000
   
  With a 16-bit output device, the two things would look like
  01010110 00100111
  and
  00010101 10001001  (whoops where'd the last couple bits go?)
   
   
  In practice, no 24-bit output device can achieve 24-bit resolution because internal noise (the output and process is analog, after all) is significantly higher than any amplitude change attempted by any shift in the last few bits.  ODAC effectively "only" has 19.3 bits of resolution because of this, so don't expect to reduce volume by 40 dB in software and not be effectively losing resolution under the noise floor.  Many other 24-bit output devices are worse than that, but some but definitely not all more expensive ones are better. 
   
  Note that in practice, most recordings have noise from the recording studio / mics / etc. that are above the 16 bits, and 16 bits may be overkill also depending on listening volume, room ambient noise level, etc.  As mentioned by somebody, check the YouTube video and link of files for Ethan Winer's audio myths workshop.  There's a demo there of reduced resolution.  Mostly you just get a bit of noise, which may not be noticeable until well past 16 bits, depending.
   
  Quote: 





adamlr said:


> thank you, but im not worried about wearing them out, im worried that with time, constantly being plugged in and charging, theyll die and damage the amp, not necessarily the most reasonable fear, but id still rather just take them out, leave the amp plugged in, and forget about it.
> 
> thank you, so i was half right? *1 does infact mean that your left with the same voltage, i guess thats why its called "unity gain"? so, *1 gain means that you only add current? and this still sounds the same? doesnt it react differently to your headphones specs as opposed to "regular" gain?


 
   
  1x gain is not so much adding current as adding the ability to deliver more current if necessary.  The current actually being delivered depends on the output volume level and the load impedance.  The electronics and structure are different for one amp as compared to another—there may be a difference in noise levels, output impedance, frequency response, nonlinear distortion at different loads / output levels / frequencies and so on.  This may or may not translate into some reliably-perceptible difference in sound quality.
   
  Actually, with 1x gain, you are amplifying any noise from the input by a lesser amount, so that is slightly better, possibly, along with more negative feedback for the gain-stage op amp (which is not the limiting factor; the output stage op amp is).  Probably not any difference in practice.
   
   
   
  Quote: 





lorriman said:


> There's a further complication in that there may be a difference between XP and Vista/7. the suggestion I'e seen is that XP is affected by the 16bit volume issue (necessitating max source volume) but Vista/7 aren't. Apparently XP had an infamous sound system that would do this bit-stripping, as I've seen it called, but Vista/7 aren't affected. It would be good to get a clarification of that. Perhaps it's because Vista/7 default to 24 bit, or perhaps they talk to the amp circuit directly somehow. However, the ODAC horrifyingly defaults to 16bit on my Vista computer which I didn't know for some time, so perhaps not the former. Of course, this could be entirely bogus: in that all 3 OS's are affected equally.
> 
> In any case, I tried XP at 16bit mode and reduced source volume to a minimum using my O2 to amplify: I didn't hear much difference. But I would have to repeat that test to be sure of my claim there which I can't do at the moment.
> 
> The main things is that most modern sound cards can be easily switched to 24bit mode on Windows which means you can turn the source way down, with all the advantages that brings (and one disadvantage). I would be surprised if there were not some way of verifying that on your MAC, or changing it. (The disadvantage is that some forms of noise can be made inaudible by turning the volume to max on the source and turned down on the amp/O2. )


 
   
  There really shouldn't be a difference between OSes in how the volume is handled.  Barring some kind of digitally-controlled analog volume control or some trickeration on the DAC side, volume should be reduced digitally by shifting the bits over so the effective output value is smaller, thus squashing the range down (and throwing away the least-significant bits, more or less).
   
   
  Quote: 





lorriman said:


> I'll just add my ha'penny to clarify the O2 volume control:aAs I've understood it, the O2 works rather differently to many amps (he says not having actually any clue about amps or electronics). Instead of lowering the volume before the audio is pumped in to the amplifying electronics, the voltage is lowered AFTER the amp circuit using a 'voltage divider'. I've no idea what all that means, really, nor the implications as I'm not a genuine electronics person. Perhaps someone can tell us.


 
   
  Right, many audiophile amplifiers use a potentiometer (variable resistor), which is controlled by that volume control knob, to divide down the signal level prior to any gain being applied.  A voltage divider is just a fancy name for usually a couple of resistors in series; the total voltage across the combination of the two is divided between the two resistors—e.g. if one has 100 ohms and the other has 200 ohms, the one with 100 ohms gets 100 / (100 + 200) = 1/3 of the signal, while the one with 200 ohms gets 200 / (100 + 200) = 2/3 of the signal.  O2 potentiometer is after the gain, which is apparently more of a pro-audio style configuration.  It leads to problems of the gain stage clipping if the input level and gain are too high, because the signal level essentially becomes too high for the gain stage to handle.  If the volume control attenuates the input, then you can set the level to be low enough such that it's not clipping the gain stage.
   
  Depending on the main contributors of noise in the system, doing the volume control after the gain could improve the SNR.  More or less it's keeping the signal level high so it is higher relative to the noise level.  The volume control divides down both the signal and the noise (mostly).  Suppose for example that the gain stage contributes some X amount of noise on its output.  If you reduce the signal level prior to the gain stage, the output signal of the gain stage will be lower relative to X, so you'll get a lower SNR.  If you keep the volume control after the gain, the output of the gain stage is large compared to X, and both the output and the noise get reduced by the volume control (somewhat), so the higher SNR is maintained.
   
  Some people say the O2 has way overkill low noise levels, and it would be better to just have the volume control like how most other audiophile amps are, so people wouldn't have that clipping issue with a dumb setting.


----------



## Stratok

**** yeah I just received my o2 and odac 
	

	
	
		
		

		
		
	


	




 SigDJ + odac + O2!


----------



## miceblue

Does anyone here have experience with the Leckerton UHA-6S? I'm curious as to how it compares to the O2 as a more portable option.


----------



## mikeaj

Quote: 





miceblue said:


> Does anyone here have experience with the Leckerton UHA-6S? I'm curious as to how it compares to the O2 as a more portable option.


 
   
  Not me, but I seem to recall that some of the pirate crew (purrin, Anax, maybe others) had heard both and preferred the Leckerton.  Of course, these are the guys who think NwAv's getting money under the table for the O2 / ODAC.
   
   
  Seems like Mr. Leckerton quite knows what's up, is an application engineer at Cirrus.  UHA-6S MKII uses a high-end Cirrus Logic DAC.  There are some measurements of the older version published on the site, not completely comprehensive, but let's assume the rest checks out too.  According to the objectivist camp and so on, there probably shouldn't be a discernible difference in sound between the two devices, operating at levels before clipping.
   
  So at least by the specs, the limitations compared to O2 / ODAC are:

 limited to 16/48 over USB (but there is an S/PDIF input)
 lower output power levels — 30 mW @ 16 ohms, 55 mW @ 32 ohms, 110 mW @ 100 ohms, 55 mW @ 300 ohms (presumably with stock output op amp)
    O2 gets 353 mW @ 15 ohms, 534 mW @ 33 ohms, (interpolated by me) 272 mW or so @ 100 ohms, 94 mW or so @ 300 ohms, on a mid-high charge on battery
   
  So the O2 is better for some planar magnetics, maybe AKG Q701 if you listen really loud.  Otherwise, no lower-impedance sets actually need that kind of power.  O2 is also a little louder for high-impedance sets.
   
  Supposedly the older UHA-6S has higher noise than the MKII, and even though there's no noise level listed, you can look at the spectrum on a THD+N spectrum graph for the original UHA-6S and see most of it around -145 dBV or so, whereas the O2 is around 5 dB quieter across the band.  So at least the amp portion is really really quiet, good if you use some super-sensitive IEMs.
   
  Listed battery life is better than that of the standard O2.


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Ah, thanks for the information. I read somewhere that the Leckerton was preferred over the O2. I also read that the Leckerton offers better detail retrieval over the O2.
  Kind of related to the O2, John of JDS Labs said their new portable amp, the C5, should sound as transparent as the O2. I pre-ordered one, so I guess I'll make a comparison between the two if I can hear any differences.
   
  And I just realised I said the UHA-6S in my previous post when I meant to say UHA-4, the portable amp. XD


----------



## HamilcarBarca

Quote: 





> Originally Posted by *miceblue* /img/forum/go_quote.gif
> 
> Ah, thanks for the information. I read somewhere that the Leckerton was preferred over the O2. I also read that the Leckerton offers better detail retrieval over the O2.


 
   
  The Leckerton doesn't provide better detail retrieval over the O2 because it's not possible: The O2 is transparent. It's easy to believe, although I have no personal experience with the Leckerton, that its performance is every bit as good as the O2.
   
  Is there an actual difference in sound between the two? If there is, a listener might choose either one based on his or her preferences. It's important to differentiate between subjective preferences and claims which are unjustified.


----------



## miceblue

Quote: 





hamilcarbarca said:


> Quote:
> 
> 
> 
> ...


 
  Yeah I know, I'm just restating what I read. I would like to do a [insert sound science term only] test if I ever get the chance.
   
  This probably should be asked in the sound science section, but so many things about the O2/ODAC overlap with it anyway that I'll just ask it here. What measurements account for detail retrieval and soundstage? I can't make any objective reasons for it other than maybe distortion, but I own the FiiO E7 as well and the O2/ODAC and compared next to each other the O2/ODAC has superior detail retrieval, instrument separation, and a much more open-sounding soundstage (yes yes I know these are all subjective observations). The designer of the O2 certainly made positive remarks about the E7 for its price.


----------



## kskwerl

Quote: 





hamilcarbarca said:


> The Leckerton doesn't provide better detail retrieval over the O2 because it's not possible: The O2 is transparent. It's easy to believe, although I have no personal experience with the Leckerton, that its performance is every bit as good as the O2.
> 
> Is there an actual difference in sound between the two? If there is, a listener might choose either one based on his or her preferences. It's important to differentiate between subjective preferences and claims which are unjustified.


 
  IMO the O2 is more neutral than the Leckerton, not that the Leckerton isn't neutral....the O2 is just more neutral. That's the only way I can describe it.


----------



## miceblue

Quote: 





kskwerl said:


> Quote:
> 
> 
> 
> ...


 
  "All animals are equal, but some animals are more equal than others" - George Orwell
   
  Sorry, I couldn't help. XD


----------



## MrEleventy

Quote: 





mikeaj said:


> Hopefully nobody yells at me for responding to old posts.
> 
> 
> 16 bits to 24 bits is a difference of having 2^16 = 65536 possible values vs. 2^24 = 16777216 possible values, or a factor of 2^8 = 256 difference.  So around 20 * log10(256) = 48 dB.  Theoretically you could throw away 99.6% of the signal.  Note that 66% in some software volume control setting may not actually correspond to 66% of the signal.  The scaling often doesn't work that way.
> ...


 
   
  Awesome, great post. I saw the topic being mentioned by others like Defiant in the Modi discussion threads but I never found the math behind it. Thanks for clearing that up with actual math instead of my fuzzy logic.


----------



## miceblue

Quote: 





mreleventy said:


> Quote:
> 
> 
> 
> ...


 
  Wait, so it is OK to have the source at a low-ish volume level without losing information with a 24-bit output?


----------



## mikeaj

Quote: 





miceblue said:


> Wait, so it is OK to have the source at a low-ish volume level without losing information with a 24-bit output?


 
   
  OK?  I don't think anybody's going to label you a sick deviant, no matter how you adjust your volume.  
	

	
	
		
		

		
		
	


	



   
  When representing a 16-bit word on a 24-bit system, you could reduce the level a lot without losing information.  As noted earlier, that's because the 24-bit representation just pads the last 8 bits with zeros.  There's a buffer there.  This is related to the reason why when mixing / mastering in the studio, they use 24 bits (or higher, or floating point).  They need to do all kinds of processing, and boosting and cutting multiple times.  The extra bits provide some good margin to work with.
   
  For outputting 16-bit material on a 24-bit DAC, that's different because the hardware's noise level is a factor.  For example, if you were to play back a signal at a very very low 24-bit level (say all zeros except in the last few digits, meaning something much quieter than can even be represented with 16 bits), that would get lost under the noise.  For a 24-bit DAC with say 19 bits of effective resolution, if you play back 16-bit material, the 16-bit quantization noise (difference between the "true" signal and the 16-bit representation on the disc, from sample to sample) is higher than any noise from the DAC, so the noise from the DAC makes practically zero difference.  Reduce the volume enough, and the quantization noise may be lower than the DAC's own noise, because the music samples have been divided down to a low enough level.  Then it's going to be the DAC that's the limiting factor.
   
  Like I said, there is noise in recordings, noise in listening environments, and very importantly—effects of auditory masking when music is playing (the louder stuff makes certain smaller details and things harder, if not impossible, to discern).  For any of the above to matter, you'd need the considerations in the previous sentence to somehow not matter, plus a whole lot of amplification after the DAC or some very sensitive IEMs, so any small amount of noise becomes actually audible.
   
  Keep in mind that ~100 dB is a whole lot.  If you can hear the 16-bit quantization noise, you are listening way too ****ing loud.  Let's make up somewhat-realistic numbers.  Let's say you reduce the volume in software by 35 dB, such that the signal level out of the DAC is low enough that the effective SNR is 70 dB.  (Oh noes, 70 dB is not hi-fi.  You just used software volume control past the "okay" point and violated everything I said above.  Actually, ODAC and some better DACs should get better performance than that.)  Let's say you have the amp and headphones set such that when volume is on full blast, the peaks reach a deafening 115 dB SPL.  This means with the volume turned down 35 dB, peaks are at 80 dB SPL, for a comfortable level.  So the noise from the DAC is at 10 dB SPL.  You know what kind of room you need to hear noise at 10 dB SPL?  And then instantly when there is any sound from the system, you wouldn't hear the noise anymore.
   
  It's effectively really not a big deal.  Use whatever is convenient for you.


----------



## adamlr

Quote: 





> Originally Posted by *mikeaj* /img/forum/go_quote.gif
> 
> 1x gain is not so much adding current as adding the ability to deliver more current if necessary.  The current actually being delivered depends on the output volume level and the load impedance.  The electronics and structure are different for one amp as compared to another—there may be a difference in noise levels, output impedance, frequency response, nonlinear distortion at different loads / output levels / frequencies and so on.  This may or may not translate into some reliably-perceptible difference in sound quality.
> 
> Actually, with 1x gain, you are amplifying any noise from the input by a lesser amount, so that is slightly better, possibly, along with more negative feedback for the gain-stage op amp (which is not the limiting factor; the output stage op amp is).  Probably not any difference in practice.


 
   
  i really am sorry, and if what i ask is impossible to do, please just tell me, and i promise i wont bug anymore.
  if *1 isnt "adding" anything, then how does it work? if all im doing is "adding ability", then how come the signal gets louder? if im multiplying by 1, why would anything change? is there a way of explaining in layman terms what actually changes when i move the volume control while using *1 gain?
   
  Quote: 





mikeaj said:


> OK?  I don't think anybody's going to label you a sick deviant, no matter how you adjust your volume.
> 
> 
> 
> ...


 

 im afraid iv gotten confused with the explanation of the 000's moving to the left...
  i got that the answer to "if i use the 24 bit option for 16 bit audio does that mean i can use digital volume control without loosing fidelity?" was basically a yes, but heres another question.
   
  i got the original notion from watching ethen winers video on youtube (i was the one who recommended it here). now, in that video, he demonstrated that actual, audible degradation only occurs at around 8-10 bits (ymmv and all that OF COURSE). but i noticed that even that, was mostly just added noise (or was it that the dynamic range shrunk, raising the noise floor?). is that all there is to it? is that how loss of fidelity manifests itself when degrading bit depth - noise? because if so, auditory masking aside, one can quite easily HEAR when hes gone to far with the digital volume control, without any speculations.
  or is there more to it, such as loss of micro detail, or bass texture, or something else?
   
  and thank you for your time explaining all this, cheers


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Wow, thank you for taking the time to write all of that out! 
  I'll have to read it more carefully when I get the chance.


----------



## mikeaj

Quote:


adamlr said:


> if *1 isnt "adding" anything, then how does it work? if all im doing is "adding ability", then how come the signal gets louder? if im multiplying by 1, why would anything change? is there a way of explaining in layman terms what actually changes when i move the volume control while using *1 gain?


 

   
  So if I understand you correctly, you plug headphones into one thing, get a certain volume.  Plug that thing into O2 with 1x gain and volume control turned all the way to the right, plug headphones into O2, and get a louder sound?  If there's a difference in volume there and the original is not heaviliy distorted, then the difference in volume is a consequence of the O2 having a lower output impedance.
   
  What headphones are you using?  For (more or less) any amplifier in this context or audio source, the signal output of the device is split between the source (meaning whatever is connected to the headphones) output impedance and the headphone impedance.  It's a voltage divider.  The source output impedance is a technical modeling term that describes one aspect of how the electric circuit is configured and operates.  The headphones get a percentage share of the signal based on its impedance and the source output impedance.  If the source output impedance is smaller, the headphones see a larger percent of the voltage the source is outputting.  There are a few other ramifications here with output impedance, but this much is sufficient to explain changes in volume.
   
  Which volume control are you talking about?  Software volume control is usually (but not always) as I described earlier.  The volume control on the O2 and most amps is a potentiometer.  Regardless of whatever the gain is, by moving the pot's position, you are changing a few resistance values inside the circuit.  This changes how much of the signal from one part of the amp gets transferred to another part.
   
  In the end, the voltage the headphones receive directly determines how much current is sent and how much power is delivered to the headphones.  i.e. if you know the headphone impedance and the voltage, you can calculate the current and power from that.  The greater the voltage, the greater the current and the greater the power delivered.  Power is energy / time.  The more power delivered, the more energy / time is being converted into mechanical motion and thus the greater the change in sound pressure levels that are getting to your ear.  Thus by reducing the signal level (can be achieved through any number of mechanisms), you can reduce pressure of the sound waves and thus how loud it is.
   
   
  Quote: 





adamlr said:


> i got the original notion from watching ethen winers video on youtube (i was the one who recommended it here). now, in that video, he demonstrated that actual, audible degradation only occurs at around 8-10 bits (ymmv and all that OF COURSE). but i noticed that even that, was mostly just added noise (or was it that the dynamic range shrunk, raising the noise floor?). is that all there is to it? is that how loss of fidelity manifests itself when degrading bit depth - noise? because if so, auditory masking aside, one can quite easily HEAR when hes gone to far with the digital volume control, without any speculations.
> or is there more to it, such as loss of micro detail, or bass texture, or something else?


 
   
  First of all, If you think about 10 bits is okay in Ethan Winer's video (12 bits?  some value; anyhow, I agree), then *all this discussion is about things that don't make any practical difference.  In general there are a lot of people freaking out over pretty much nothing.*  I don't mean to blame anybody, but that's how it is.  Maybe that's the audiophile experience.
   
  What's being shown in Ethan Winer's video is pretty much what would happen if you used software volume control to lower the volume on a 16-bit output system, while simultaneously increasing the volume with your amp such that the total level in the end remains constant (and assuming there are no ramifications of boosting the volume with the amp, amp is noiseless, etc.).  By the way, by 10 bits resolution, that is effectively like 36 dB of volume control, so a pretty high amount.  The noise you get here is really more like the difference between the original signal and the quantized representation.  Actually, maybe not exactly, depending on if there is dithering.
   
  Anyway, this is not what we're talking about.  When reducing volume on a 24-bit output system, it's the inherent noise level of the DAC output itself that is the floor, from thermal noise and whatnot, unless there's something I don't get either.  This kind of noise may or may not have the same characteristics as the quantization noise in the myths video.  Whether that kind of noise or difference gets perceived as noise added to the original (that's pretty much what it is, mathematically), loss of micro detail, bass texture, etc. depends on how you hear things.  I don't really know.  I really doubt it would be bass texture, though, as it should affect all frequencies.  Most likely it's mostly similar to whatever you heard in the video.
   
  Keep in mind that if you reduce the volume in software (even 16 bits), you're not increasing the noise or anything.  Actually, reducing the level could reduce the noise a bit too, depending on the device.  You're just bringing the signal level down so it's quieter.  As a consequence, the signal-to-noise ratio is lower because you've reduced the signal.  No big deal.
   
  The problem is only if you reduce the volume way too much in software and then boost the signal a lot to get to a normal listening level (why would you do this?), bringing up the noise level with it.


----------



## adamlr

Quote: 





mikeaj said:


> So if I understand you correctly, you plug headphones into one thing, get a certain volume.  Plug that thing into O2 with 1x gain and volume control turned all the way to the right, plug headphones into O2, and get a louder sound?  If there's a difference in volume there and the original is not heaviliy distorted, then the difference in volume is a consequence of the O2 having a lower output impedance.
> 
> What headphones are you using?  For (more or less) any amplifier in this context or audio source, the signal output of the device is split between the source (meaning whatever is connected to the headphones) output impedance and the headphone impedance.  It's a voltage divider.  The source output impedance is a technical modeling term that describes one aspect of how the electric circuit is configured and operates.  The headphones get a percentage share of the signal based on its impedance and the source output impedance.  If the source output impedance is smaller, the headphones see a larger percent of the voltage the source is outputting.  There are a few other ramifications here with output impedance, but this much is sufficient to explain changes in volume.
> 
> ...


 
   
  to be polite, i will answer your question and say im using dt770 (250 ohm). but let me explain:
  my O2 has the standard gain options (*2.5 and *6.5). then we got to the subject of using *2.5 gain with sensitive headphones (specifically the m-100, 32 ohm, 105 dB sensitivity) and someone mentioned that *1 gain may be more suitable. which made me ask how *1 is even possible, because when you multiply by one, you keep the original value (obviously). thats what im trying to understand, why does *1 gain make a difference? obviously its "adding" something - what is it? how is it different from *2.5 (for arguments sake) gain?
   
  Quote: 





mikeaj said:


> First of all, If you think about 10 bits is okay in Ethan Winer's video (12 bits?  some value; anyhow, I agree), then *all this discussion is about things that don't make any practical difference.  In general there are a lot of people freaking out over pretty much nothing.*  I don't mean to blame anybody, but that's how it is.  Maybe that's the audiophile experience.
> 
> What's being shown in Ethan Winer's video is pretty much what would happen if you used software volume control to lower the volume on a 16-bit output system, while simultaneously increasing the volume with your amp such that the total level in the end remains constant (and assuming there are no ramifications of boosting the volume with the amp, amp is noiseless, etc.).  By the way, by 10 bits resolution, that is effectively like 36 dB of volume control, so a pretty high amount.  The noise you get here is really more like the difference between the original signal and the quantized representation.  Actually, maybe not exactly, depending on if there is dithering.
> 
> ...


 
  oh i definitely agree theres alot of fuss about nothing going around, this discussion (for me) and many others is my way of trying to weed out the truth amongst all the placebos and biases.
  just so as to explain where im coming from (and in no way am i making a declaration of war on those who object: everything hence forth is in my own, very humble and very uninformed opinion), theres no (audible) difference between 16 bit audio and 24 bit audio, but then i got to reading and found out that reducing volume digitally, restricts the bits going through, thus degrading sq. which would explain using 24 bit audio ("fake" or otherwise), because then you can reduce volume digitally in order to restrict the level going into the O2 and allow for use with more sensitive headphones, without opening it up and messing about with its interior and still maintain high quality sound.  
  in the video, the biggest difference i heard was alot of noise, so i wondered if thats the ONLY difference when degrading bit depth or if there was more to it, which is why i asked, and gave bass texture as an example of something else that may perhaps be effected amongst others. you say all frequencies would be effected the same, so, your saying frequency response DOES suffer from bit depth degradation? say i reduce the digital volume by like, 60%. what effect do you think that would have on sound quality? again, if one (or rather, I) wanted to use his O2 with headphones such as the m-100, using *2.5 gain and had to reduce the digital volume, in order to have a functioning gain switch that wasnt too sensitive, would musical fidelity suffer? how so?
   
  i reduced foobars volume and my laptops volume to very low levels and then, using high gain on the O2, brought it up to my regular listening level. why? to test my theory about noise. i could hear no noise. perhaps it is auditory masking, perhaps its not. but actual effect on fidelity will take a long time to determine, and will be hard to test without the ability of proper a/b comparisons, which is why asked here what would be effected by stripping bits.
   
  and thank you again for giving such in depth explanations, much obliged =]


----------



## mikeaj

Quote: 





adamlr said:


> to be polite, i will answer your question and say im using dt770 (250 ohm). but let me explain:
> my O2 has the standard gain options (*2.5 and *6.5). then we got to the subject of using *2.5 gain with sensitive headphones (specifically the m-100, 32 ohm, 105 dB sensitivity) and someone mentioned that *1 gain may be more suitable. which made me ask how *1 is even possible, because when you multiply by one, you keep the original value (obviously). thats what im trying to understand, why does *1 gain make a difference? obviously its "adding" something - what is it? how is it different from *2.5 (for arguments sake) gain?


 
   
  Oh, I totally misread you then.  My first reply is what's relevant then.
   
  In the real world, if you're connecting headphones (speakers) to an amp and asking that amp to drive them, the amp will not do a perfect job.  There will be some deviation from the original (the input to the amp).  The deviation depends on the electronics design of the amp, the headphones, the output level, and the nature of the input.  A so-called high-fidelity amp will make the signal the headphones receives look very much like the input to the amp, no matter what the other factors are.  Other amps may behave differently.  They may try and fail to maintain an output that looks like the input.
   
  Some people spend megabucks to try to get amps that deviate in certain specific ways, hence a different sound.
   
  By using an amp with 1x gain, you are still using that amp's electronics to run the headphones, so it's not pointless.  You need some kind of amp, or else you don't get sound.  Some are just better than others.  If you use some device not designed to drive headphones at all, you could get some terrible garbled junk out.
   
  So internally, there is some step where you are multiplying by 1, but that's not all that's going on.
   
   



adamlr said:


> you say all frequencies would be effected the same, so, your saying frequency response DOES suffer from bit depth degradation? say i reduce the digital volume by like, 60%. what effect do you think that would have on sound quality? again, if one (or rather, I) wanted to use his O2 with headphones such as the m-100, using *2.5 gain and had to reduce the digital volume, in order to have a functioning gain switch that wasnt too sensitive, would musical fidelity suffer? how so?


 

   
  Frequency response is about the relative amplitudes of signals at the output of the device, at different frequencies (technically it probably should include phase as well as amplitude, but...).  That's unrelated.  Be careful if you talk about reducing volume by a certain amount in software.  Reducing by 60% is turning down 8 dB in foobar.  If you set computer volume to 40 / 100, it's probably reducing it by more than 60%.  Those things rarely scale linearly.
   
  Fidelity would suffer in the sense that you might reduce the SNR, but the noise is probably still inaudible.
   
    
   


adamlr said:


> i reduced foobars volume and my laptops volume to very low levels and then, using high gain on the O2, brought it up to my regular listening level. why? to test my theory about noise. i could hear no noise. perhaps it is auditory masking, perhaps its not. but actual effect on fidelity will take a long time to determine, and will be hard to test without the ability of proper a/b comparisons, which is why asked here what would be effected by stripping bits.


 


   
  You might need some more-sensitive headphones or IEMs and reduce the volume even more in software, maybe more than 6.5x gain too.  Also, play some music or test track that doesn't have noise in the recording itself.  Then you might hear the noise from the DAC without totally blasting your ears off when the actual sounds start playing.  DT 770 250 ohms is too insensitive for this stuff to be a big deal.


----------



## autoteleology

The 6.5x gain on my O2 is a joke. It's like an  "add massive amounts of distortion" button. Is this normal?


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## mikeaj

Quote: 





tus-chan said:


> The 6.5x gain on my O2 is a joke. It's like an  "add massive amounts of distortion" button. Is this normal?


 
   
  Yes.  Or at least, it's not unusual.
   
   
  As discussed before, this is a result of putting the volume control after the gain stage.  You can't control the input voltage with the volume control.  If the input multiplied by the gain is too high, then the gain stage op amp cannot handle outputting anything that high and will clip.  Lots of clipping -> massive amounts of distortion.
   
  Barring some trickeration, electronics can't handle inputs greater than their positive supply rails and less than their negative supply rails, with a margin on top of those (and how much there, depends on the design).  Power supply rails are at +12V and -12V for a range of 24V.  The gain stage can handle roughly 7V rms (sine wave), so that's almost 20V peak-to-peak.  Higher than that, and it's too close to the supply rails and it will clip.  
   
  So if an input is greater than 20V / 6.5 = 3.08V peak-to-peak (1.09V rms for a nominal sine wave), it will be clipped with that 6.5x gain.  Or technically, somewhere around greater than 1.5V on the positive side and less than -1.5V or so on the negative side.
   
  Many computer outputs, many DACs have a full-scale output level greater than 1.09V rms.  In fact, Redbook standard is 2V, and the ODAC follows that.  Lots of audiophile gear is even higher, maybe because (1) you can get and claim higher SNR easier if you're allowed to increase the signal level and (2) in an A/B comparison, louder usually sounds better, so it's an arms race to juice it up.  Why 6.5x gain as a default?  Somehow the designer envisioned that people might be using phones, portable media players, etc. as sources, and these often output 1V or less.


----------



## miceblue

On the topic of power:
   
  Quote:


> O2 gets 353 mW @ 15 ohms, 534 mW @ 33 ohms, (interpolated by me) 272 mW or so @ 100 ohms, 94 mW or so @ 300 ohms, on a mid-high charge on battery


 
  What exactly do these numbers mean? I know the creator of the O2 mentions Vrms, and JDS Labs is using that measurement for their C5 (600Ω: 4.146 VRMS), but what do the above measurements measure? Those above measurements are pretty commonly found in amplifiers from what I've seen (all the news of the FiiO E12 pumping 800+ mW @ 32 ohms). On Tyll's measurements from Innerfidelity, there is the "Power Needed for 90d BSPL" measurement, but it's on the order of 0.0X mW, not a few hundred.


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## shadow419

Those power numbers would be max power into a load before distortion gets too high.  Different companies use different thresholds for distortion when reporting max power into a load, but generally somewhere between 1% and 10% distortion.  Tyll's measurements for power needed to reach 90dB SPL let's you extrapolate how much power you'll need to reach a desired SPL.  For every 3dB you increase the SPL you need double the power.  So for example if you need 0.05mW for 90dB spl, 93 dB would need 0.1mW and so on.


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## mikeaj

Those are max possible power levels.  For the O2, they're the point at which if you draw any more power, the total harmonic distortion will exceed 1%.  That's a common reference point for power amp specs.  Commonly, for consistency, this is done using a resistor as a load, with a single-tone sine wave test.  For a sine wave, the root-mean-square voltage is 1/sqrt(2) of the peak voltage.  Power is rms voltage squared, divided by the resistance:  P = V^2 / R.
   
  The power that can be delivered is different depending on the load impedance, hence the multiple figures.
   
   
  InnerFidelity measurements for headphones indicate how much power is required to make the device output a certain sound pressure level (90 dB SPL, a fairly loud level), using a 1 kHz test tone.  There's quite a wide range.  e.g. 0.004 mW for Shure SE535, 19.69 mW for HiFiMAN HE-6.  That's 37 dB difference between the two.
   
  The more power you deliver, the louder they sound.  Deliver 2x the power, and you get 3 dB SPL higher.  Deliver X mW into a headphone quoted at 90 dB SPL / Y mW, and you get [10*log(X / Y) + 90] dB SPL out.  That's base-10 log, not natural log.
   
  For the SE535, deliver say 500 mW into the 36 ohms or so, and that would be [10*log(500 / 0.004) + 90] = 141 dB SPL.  heh j/k, not really—they would burn out / explode well before 500 mW, and distort horribly before that point. But that's how it works up until the point where they're distorting really badly.
   
  The point I usually make still stands that few people are using these astronomically high levels consistently.  Sure, you need some margin for that really loud peak in that one part of a (classical) recording, but most people get nowhere close to the limits of their amps unless they're using some power monster like HE-6 or whatever, or maybe a 600 ohms Beyer, etc. and are listening loudly.
   
   
  edit: whoops shadow419 got it first


----------



## shadow419

I got it first but you broke down the math way better.


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## miceblue

Quote: 





mikeaj said:


> Those are max possible power levels.  For the O2, they're the point at which if you draw any more power, the total harmonic distortion will exceed 1%.  That's a common reference point for power amp specs.  Commonly, for consistency, this is done using a resistor as a load, with a single-tone sine wave test.  For a sine wave, the root-mean-square voltage is 1/sqrt(2) of the peak voltage.  Power is rms voltage squared, divided by the resistance:  P = V^2 / R.
> 
> The power that can be delivered is different depending on the load impedance, hence the multiple figures.
> 
> ...


 
   
  Quote: 





shadow419 said:


> Those power numbers would be max power into a load before distortion gets too high.  Different companies use different thresholds for distortion when reporting max power into a load, but generally somewhere between 1% and 10% distortion.  Tyll's measurements for power needed to reach 90dB SPL let's you extrapolate how much power you'll need to reach a desired SPL.  For every 3dB you increase the SPL you need double the power.  So for example if you need 0.05mW for 90dB spl, 93 dB would need 0.1mW and so on.


 
  Ah, now things make more sense. Thank you for clearing that up! 
  JDS Labs uses the DT880 (they don't list the ohm value) for their benchmarking tests.
   
  A few more questions:

 The SE535 is rated at 119 dB SPL/mW, whereas the K 702 is rated at 105 dB[/mW?]. These numbers correspond to a headphones SPL at 1 mW, so the higher the value the more "sensitive" it is? If this is the case, Sennheiser's website says the HD650 is rated at 103 SPL[/mW?], which is less sensitive than the K 702 yet the K 702 seems to get pinged a lot for being insensitive, not so much for the HD650 from what I read.
 With the O2's gain at 2.5x, I can hear the background hiss through my sensitive headphones/earphones; the designer of the O2 designed the O2 to have a very "black background", so why is it that with a higher gain I can hear the background hiss?


----------



## shadow419

Take sensitivity ratings from some manufacturers with a grain of salt.  Some of them may fudge the numbers a little or maybe it's just they're testing environment.  Some companies also list sensitivity in dB/mV and not dB/mW.  If you want to compare apples to apples, you need to make sure that the same units are being used since you'll have a higher number if the sensitivity is in dB/mV.  
   
  As far as the amp goes, remember that you want to use as little gain as necessary since the amp will also amplify any noise that's already in the signal.  The less gain you use the lower the noise floor will be.  Sometimes hiss can also come from a ground issue.  Try to track down the source off the hiss.  With in ears and no music playing, I start to hear hiss with x3 gain at about 1 o'clock on the pot.  With unity gain hiss doesn't get audible till 3 o'clock, but my ears are begging for mercy at about 1 o'clock on unity.


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## adamlr

deep breath....
  Quote: 





mikeaj said:


> Oh, I totally misread you then.  My first reply is what's relevant then.
> 
> In the real world, if you're connecting headphones (speakers) to an amp and asking that amp to drive them, the amp will not do a perfect job.  There will be some deviation from the original (the input to the amp).  The deviation depends on the electronics design of the amp, the headphones, the output level, and the nature of the input.  A so-called high-fidelity amp will make the signal the headphones receives look very much like the input to the amp, no matter what the other factors are.  Other amps may behave differently.  They may try and fail to maintain an output that looks like the input.
> 
> ...


 
  about unity gain: im starting to feel like the village idiot, repeatedly asking a question, getting answers, but still not grasping them. in my knowledge, when turning the volume knob, your adding power, which in turn makes for higher volume. if the added power is multiplied by 1, whats going on?
  nevermind. im sure that in time, through my own research (based mostly around ethen winers book) i'll find the answer myself. its just that with my day job, social life, and listening time, my own "research" is moving at a very low pace, so i sometimes ask in the forums. it looks like i asked a question too complex to understand with the small amount of knowledge i have, so im mostly just confusing myself further, and wasting your time. thank you for your patience =]
   
  about the 250 ohm impedance, could this be the advantage to having high impedance headphones that no one seems to know? does insensitivity translate into insensitivity to noise?
  most of this conversation (atleast the bits i contributed) was started in order too asses whether or not using the O2 with sensitive headphones was a good idea or not, as im soon going to get new headphones and am currently trying to decide between the m-100 and the ws 99, both of which are rather sensitive.
  Quote: 





tus-chan said:


> The 6.5x gain on my O2 is a joke. It's like an  "add massive amounts of distortion" button. Is this normal?


 
  what source are you using? if your using the odac, note that the following: playback devices > odac. is not enough. you must also set: volume control options > odac. atleast thats what i did, cause i got alot of noise even at *2.5 gain.
  Quote: 





shadow419 said:


> Those power numbers would be max power into a load before distortion gets too high.  Different companies use different thresholds for distortion when reporting max power into a load, but generally somewhere between 1% and 10% distortion.  Tyll's measurements for power needed to reach 90dB SPL let's you extrapolate how much power you'll need to reach a desired SPL.  For every 3dB you increase the SPL you need double the power.  So for example if you need 0.05mW for 90dB spl, 93 dB would need 0.1mW and so on.


 
  that sounds pretty high actually... i think i may have misunderstood something, but doesn't 10% translate into -20 dBu, and 1% = -40 dBu? i imagine this would be quite audible no? the O2 for example has the following listed in the jds labs spec: "THD 1 Khz 150 Ohms: 0.0016%" which translates (very roughly) into -80 dBu, which i think would be virtually impossible to hear.
  any chance you know what happens to these numbers when the impedance rating is higher/lower? id be very interested to know =]
  Quote: 





mikeaj said:


> Those are max possible power levels.  For the O2, they're the point at which if you draw any more power, the total harmonic distortion will exceed 1%.  That's a common reference point for power amp specs.  Commonly, for consistency, this is done using a resistor as a load, with a single-tone sine wave test.  For a sine wave, the root-mean-square voltage is 1/sqrt(2) of the peak voltage.  Power is rms voltage squared, divided by the resistance:  P = V^2 / R.
> 
> The power that can be delivered is different depending on the load impedance, hence the multiple figures.
> 
> ...


 
  but as i said before, 1% is quite a loud bit of noise no? (honest question) shouldnt the standard be set at say 0.1% (-60 dBu) to be certain you wont hear any noise?


----------



## shadow419

Quote: 





adamlr said:


> deep breath....
> about unity gain: im starting to feel like the village idiot, repeatedly asking a question, getting answers, but still not grasping them. in my knowledge, when turning the volume knob, your adding power, which in turn makes for higher volume. if the added power is multiplied by 1, whats going on?
> nevermind. im sure that in time, through my own research (based mostly around ethen winers book) i'll find the answer myself. its just that with my day job, social life, and listening time, my own "research" is moving at a very low pace, so i sometimes ask in the forums. it looks like i asked a question too complex to understand with the small amount of knowledge i have, so im mostly just confusing myself further, and wasting your time. thank you for your patience =]
> 
> ...


 
  Most companies use the 1%(or even lower) distortion for max power rating.  Some companies will use a higher distortion point to inflate the usable power number.  Not really an issue with most reputable companies.
   
  Think of the amplifier as having two power increasing sections.  The gain stage increases the voltage, and the output stage increasing the current available.  The volume pot on the O2 sits between the two stages and controls how much output from the gain stage is fed into the output stage.  On most amps the volume pot sits before the gain stage and controls how much input is fed into the gain stage.  It's more of a volume attenuator.  Even if the gain stage isn't increasing the signal, turning the volume increases the amount of signal being passed to the output stage of the amp.


----------



## adamlr

Quote: 





shadow419 said:


> Most companies use the 1%(or even lower) distortion for max power rating.  Some companies will use a higher distortion point to inflate the usable power number.  Not really an issue with most reputable companies.
> 
> Think of the amplifier as having two power increasing sections.  The gain stage increases the voltage, and the output stage increasing the current available.  The volume pot on the O2 sits between the two stages and controls how much output from the gain stage is fed into the output stage.  On most amps the volume pot sits before the gain stage and controls how much input is fed into the gain stage.  It's more of a volume attenuator.  Even if the gain stage isn't increasing the signal, turning the volume increases the amount of signal being passed to the output stage of the amp.


 
  so lets see if i understand:
  most amps: signal coming from the source recieves voltage at the gain stage, and current at the output stage with the volume pot controlling how much of the signal from the source comes through.
   
  O2 with unity gain: signal coming from the source recives no added value, but recieves more current before the output stage, with the volume pot controlling how much of the signal from the gain stage reaches the output stage.
   
  is that right?


----------



## shadow419

The output stage op-amps provide the extra current, but yes think you have the gist.


----------



## adamlr

Quote: 





shadow419 said:


> The output stage op-amps provide the extra current, but yes think you have the gist.


 

 thank you so much =]


----------



## JakeJack_2008

Many interesting posts.   - For me, this thread is like a _24-bit Encyclopedia_. Ha, ha, ...
  I'm glad that I found it.
   
   
  Anyway, why the ODAC doesn't handle 88.2 kHz files? I've read that it _cleanly _downsamples 88.2 kHz files to 44.1 kHz files?
  At the same time, the Dragonfly  handles 88.2 kHz files correctly.
  (It does _not _downsample 88.2 kHz files to 44.1 kHz files). - Any comments?


----------



## mikeaj

Quote: 





jakejack_2008 said:


> Many interesting posts.   - For me, this thread is like a _24-bit Encyclopedia_. Ha, ha, ...
> I'm glad that I found it.
> 
> 
> ...


 
   
   
  Either the USB receiver chip (TE7022) or the DAC (ES9023) doesn't support 88.2 kHz.  I forget which.  Some other devices do, as you've seen.
   
  The ODAC isn't responsible for sample rate conversion.  That's in whatever software you're using.  Usually, at least with a reasonable algorithm, sample rate conversion shouldn't really be an issue.


----------



## JakeJack_2008

Quote: 





mikeaj said:


> Either the USB receiver chip (TE7022) or the DAC (ES9023) doesn't support 88.2 kHz.  I forget which.  Some other devices do, as you've seen.
> 
> The ODAC isn't responsible for sample rate conversion.  That's in whatever software you're using.  Usually, at least with a reasonable algorithm, sample rate conversion shouldn't really be an issue.


 
   
  Yeah, You're right, I vaguely remember reading  that it's the receiver.
   
  Nevertheles, there are many   88.2 kHz tracks (on HDTracks.com) by _The Rolling Stones_.
  So, the ODAC will deprive me of listening to The Rollings Stones on 88.2 kHz tracks.
  It will _downgrade - _ha, ha, .. -_  _The Rolling Stones to the Red Book 44.1 Khz_._


----------



## HamilcarBarca

Quote: 





jakejack_2008 said:


> Anyway, why the ODAC doesn't handle 88.2 kHz files? I've read that it _cleanly _downsamples 88.2 kHz files to 44.1 kHz files?
> At the same time, the Dragonfly  handles 88.2 kHz files correctly.
> (It does _not _downsample 88.2 kHz files to 44.1 kHz files). - Any comments?


 
   
  Not many people can hear frequencies as high as 22,050 Hz which is the theoretical limit -- vaguely speaking -- of a 44.1kHz signal. Increasing the sampling rate to 88.2kHz means, again in theory, the DAC can reproduce frequences up to 44.1kHz. However, humans can't hear those frequencies. There's essentially no benefit to the listener.
   
  Why might another manufacturer support 88.1kHz or even 192kHz (which has zero benefit to humans)? Ask them why. Don't forget to mention Nyquist rates. I predict the response, if any, will be "science doesn't apply to our products."


----------



## JakeJack_2008

Quote: 





hamilcarbarca said:


> Not many people can hear frequencies as high as 22,050 Hz which is the theoretical limit -- vaguely speaking -- of a 44.1kHz signal. Increasing the sampling rate to 88.2kHz means, again in theory, the DAC can reproduce frequences up to 44.1kHz. However, humans can't hear those frequencies. There's essentially no benefit to the listener.
> 
> Why might another manufacturer support 88.1kHz or even 192kHz (which has zero benefit to humans)? Ask them why. Don't forget to mention Nyquist rates. I predict the response, if any, will be "science doesn't apply to our products."


 
   
  Yes, I was about to add to my last post that I might _not notice _the difference between 44.1kHz and 88.2kHz (or 96 kHz) sampling rates.
   
  This topic has  been all over this site and the Internet.
  But, I still do _not _understand why do  HDTracks.com and others *sell *176.4 KHz and 196 kHz tracks? The only reason seems to be  that they want to make more money,
  because albums in _very _high resolution (176.4 KHz and 196 kHz) cost more,
_usually _$30 vs. $20 (96 kHz, 88.2 kHz or 48 Khz).
  So, that's a *50%* *rip-off*!


----------



## adydula

Claims both published and anecdotal are regularly made for audibly superior sound quality for two-channel audio encoded with longer word lengths and/or at higher sampling rates than the 16-bit/44.1-kHz CD standard. The authors report on a series of double-blind tests comparing the analog output of high-resolution players playing high-resolution recordings with the same signal passed through a 16-bit/44.1-kHz “bottleneck.” The tests were conducted for over a year using different systems and a variety of subjects. The systems included expensive professional monitors and one high-end system with electrostatic loudspeakers and expensive components and cables. The subjects included professional recording engineers, students in a university recording program, and dedicated audiophiles. The test results show that the CD-quality A/D/A loop was undetectable at normal-to-loud listening levels, by any of the subjects, on any of the playback systems. The noise of the CD-quality loop was audible only at very elevated levels.
   
  From: http://www.aes.org/e-lib/browse.cfm?elib=14195
   
  Alex


----------



## adydula

The ODAC doesn’t support 24/88, it does support the audibly identical 24/44. It’s trivial to re-sample 24/88 audio to 24/44 with no artifacts as it’s a simple divide-by-two operation (and one the operating system will perform for you automatically). I know many audiophiles probably think they’re losing something, but nobody has proven they are. Meyer & Moran demonstrated in a very in-depth study that even 16/44 audio sounded identical to SACD. Another good read is 24/192 Music Downloads. You can try resampling some 24/88 audio to 24/44 and compare them yourself with Foobar and the ABX add-on. It’s been done at HydrogenAudio and elsewhere always with the same result: Unless you mess up the resampling somehow, or change the levels, _you can’t tell them apart_.
   
  But there will always be this debate over normal 44.1 khz 16 bit stuff  vs higher sampling rates and bitdepths...
   
  I have done many ab's here and cant tell the difference...
   
  Alex


----------



## dfferent

I have a possible power supply issue, hoping someone can shed some light on it.
   
  I bought and built a DIY 02 amp, I hadn't done all the tests listed on the blog but it did work ok on battery power.
  Battery power ran down and I plugged in the power supply only to find it was dead.
  Told the supplier who was very quick to refund the cost of the power supply.
   
  Bought a new power supply which also then failed on me at some point, not sure exactly when.
  I don't think either power supply ever charged the batteries.
   
  I now have a 3rd power supply 16vac 1.25A and I have now bought a new amp from JDS, run all the tests suggested on the blog, as a practice run. The new power supply and pre built 02 amp are working fine on battery and power.
   
  I want to run all the tests on the DIY amp, but a little reluctant to lose another power supply as they are expensive here ($25).
   
  Any thoughts on what the problem might be so i can check before powering up the DIY amp for testing.


----------



## RustA

Quote: 





adydula said:


> The ODAC doesn’t support 24/88, it does support the audibly identical 24/44. It’s trivial to re-sample 24/88 audio to 24/44 with no artifacts as it’s a simple divide-by-two operation (and one the operating system will perform for you automatically). I know many audiophiles probably think they’re losing something, but nobody has proven they are. Meyer & Moran demonstrated in a very in-depth study that even 16/44 audio sounded identical to SACD. Another good read is 24/192 Music Downloads. You can try resampling some 24/88 audio to 24/44 and compare them yourself with Foobar and the ABX add-on. It’s been done at HydrogenAudio and elsewhere always with the same result: Unless you mess up the resampling somehow, or change the levels, _you can’t tell them apart_.
> 
> But there will always be this debate over normal 44.1 khz 16 bit stuff  vs higher sampling rates and bitdepths...
> 
> ...


 
   
  I've been able to hear difference only if I purchased hdtracks' version of some favourite album which I previously had only as a cd-rip... I think that the lack of bad cd mastering and overcompression does the trick here.
   
  However, I cannot hear any difference among two different versions of the same hdtracks' album - like 24/96 and 24/192 Green day - American Idiot.


----------



## miceblue

Quote: 





rusta said:


> Quote:
> 
> 
> 
> ...


 
  I've made a thread about this, and apparently HD tracks go through a different mastering process so by nature they sound different from their CD counterparts. With Foobar I scored Total: 26/27 (0.0%) between an HD Tracks song and the same one ripped from a CD.
   
  I have yet to hear a difference between downsampled music though (from HD to CD quality), so the lack of 88 kHz sampling rate really doesn't matter to me.


----------



## JakeJack_2008

Quote: 





adydula said:


> The ODAC doesn’t support 24/88, it does support the audibly identical 24/44. It’s trivial to re-sample 24/88 audio to 24/44 with no artifacts as it’s a simple divide-by-two operation (and one the operating system will perform for you automatically). I know many audiophiles probably think they’re losing something, but nobody has proven they are. Meyer & Moran demonstrated in a very in-depth study that even 16/44 audio sounded identical to SACD. Another good read is 24/192 Music Downloads. You can try resampling some 24/88 audio to 24/44 and compare them yourself with Foobar and the ABX add-on. It’s been done at HydrogenAudio and elsewhere always with the same result: Unless you mess up the resampling somehow, or change the levels, _you can’t tell them apart_.
> 
> But there will always be this debate over normal 44.1 khz 16 bit stuff  vs higher sampling rates and bitdepths...
> 
> ...


 
  Thanx to Alex and others who discussed the high-res audio tracks here.
  I think that it's good to have this mini-discussion here in one place, when we discuss the ODAC & O2.
   
  Well,  the competition, e.g.  the Dragonfly,  can process (without any resampling, etc.) 88.2 kHz files.
  But as it was pointed out in this thread (and on this site and on the Internet) this is of no practical importance at all.
  (The same applies to 96 Khz/24-bit files which are handled via the _USB interface _by the ODAC.)
  I guess that  96 Khz files could be _cleanly _downsapled to 48 kHz files,
  just as 88.2 kHz  files are _cleanly _downsapled to 44.1 kHz files.
  I think that in both cases, _every second _sample is processed,
  or alternatively, _every second _sample is skipped.
  (I don't think that there is any division-by-two done  here.)
   
   
  Finally, how about the lowest hig-resolution handled by the ODAC, namely *48* kHz/*24*-bit.
  (I guess, that the lowest high-res is *48* kHz/*20*-bit, or perhaps even *48* kHz/*16*-bit, which is rarely, if at all used.)
   
   
  Has anyone compared  *48* kHz/*24*-bit vs. *44.1* kHz/*16*-bit? Have you heard any _audible difference_?
  By the way, the difference in the sampling rates is relatively little, namely *48* kHz - *44.1* kHz = _3.9_ kHz.
  But the difference in bit depths is huge: 24 bit - 16 bit = 8 bit. That's 50% over the 16-bit depth.
   
   
   
  Any comments?


----------



## mikeaj

dfferent said:


> I have a possible power supply issue, hoping someone can shed some light on it.
> 
> I bought and built a DIY 02 amp, I hadn't done all the tests listed on the blog but it did work ok on battery power.
> Battery power ran down and I plugged in the power supply only to find it was dead.
> ...


 
   
  I'm not sure, sounds weird to me.
   
  What were the specs of the first two adapters?  What's your wall voltage?  There were some comments about charging batteries while using the O2 with an underspec adapter, but I don't think that would actually kill the transformer.
   
  Check the schematic (click me).  There really isn't much between the battery and the AC power input, so if everything is okay after the battery... what could it be?  I mean, if the regulators somehow failed as short circuits between input and ground, that could be bad, but they're pretty robust.  I don't know if you could really test that without taking them out and using a different test circuit, but that's really not too likely anyway.
   
  Maybe ask at diyaudio or ask the diy subforum if you can't get a good response here.
   

   
   
  Quote: 





jakejack_2008 said:


> Has anyone compared  *48* kHz/*24*-bit vs. *44.1* kHz/*16*-bit? Have you heard any _audible difference_?
> By the way, the difference in the sampling rates is relatively little, namely *48* kHz - *44.1* kHz = _3.9_ kHz.
> But the difference in bit depths is huge: 24 bit - 16 bit = 8 bit. That's 50% over the 16-bit depth.
> 
> Any comments?


 
   
  50% more bit depth is kind of a weird way of putting it, because properly you could say it's 12800% more resolution (smallest possible difference between distinct samples... though I could be butchering the terminology as I'm not a DSP guy), though less in practice if you look at effective number of bits of actual hardware.  50% more bits per sample.
   
   
  Sound science subforum here ran a recent blind test that included 24/96 vs. a file that was converted  24/96 -> 16/44.1 -> 24/96, and people couldn't reliably (and blinded) distinguish the two.  I've tried these kinds of things and not heard the differences, but some people are better at catching small things than I am.
   
   
   
  By the way, some technical minutiae:
   



jakejack_2008 said:


> I guess that  96 Khz files could be _cleanly _downsapled to 48 kHz files,
> just as 88.2 kHz  files are _cleanly _downsapled to 44.1 kHz files.
> I think that in both cases, _every second _sample is processed,
> or alternatively, _every second _sample is skipped.
> (I don't think that there is any division-by-two done  here.)


 

  That is not correct.  To do sample rate conversion down by a factor of two (properly), you need to lowpass filter the original.  Then you throw away every other sample (technically this throwing away every other sample is known as downsampling; abuse of terminology is rampant, and I'm an offender too).
   
  If you don't lowpass filter first, then you can end up content in the original 88.2 kHz file above 22.05 kHz getting aliased down into the 0-22.05 kHz range of the 44.1 kHz file, because the 44.1 kHz file cannot properly represent info above the Nyquist 1/2 frequency of 22.05 kHz.
   
  I guess you can do sample rate conversion in many different ways, including skipping the filtering (or say, doing a linear interpolation or whatever else), but these are not by-the-books correct and may introduce aliasing or whatnot.


----------



## adydula

dfferent...
   
  ok so your diy amp you built has issues. the one you bought assembled works ok.
   
  I would take a very slow and careful look at your DIY amp, check all the  parts you placed on the board for correct insertion and value.
  Especially the diodes and capacitors.
   
  Check all the solder joints, top and bottom.
   
  I would take the board out of the case and see if it works ok outside of the case to make sure there are no shorts to the case.
   
  Also check to make sure all the correct value components are in the correct place on the board.
   
  Also on the designers website there is a troubleshooting section if you havent done this  run thru these checks, if you have do it again.
   
  The power supply is not the thing you plug into the wall thats a AC to AC adpater that provides AC power to the half wave rectifier in the O2.
   
  The amp should not be able to "hurt" the AC to AC adapter which is nothing more than a step down transformer...
   
  Good Luck
   
  Alex


----------



## miceblue

Quote: 





mikeaj said:


> O2 gets 353 mW @ 15 ohms, 534 mW @ 33 ohms, (interpolated by me) 272 mW or so @ 100 ohms, 94 mW or so @ 300 ohms, on a mid-high charge on battery
> 
> So the O2 is better for some planar magnetics, maybe AKG Q701 if you listen really loud.  Otherwise, no lower-impedance sets actually need that kind of power.  O2 is also a little louder for high-impedance sets.


 
  Sorry to bring this up again, I'm trying to scale the O2 against some other amps since I might get an HE-500 in the distant future. You mention the O2 will work with some planar magnetic headphones. The LCD-2 is reported to sound quite good with the O2, and its 0.66 mW to reach 90 db SPL seems logical. It looks that an O2 might even work for an HE-6 (19.69 mW to reach 90 db SPL), maybe?
   
  I often read that the Schiit Audio Lyr is a good "pair" with the HE-500 and according to their website, the output voltage is:
  Quote: 





> Maximum Output: 40V P-P into 32


 
  What is P-P? If it's the Vrms value, then by the previous discussion's calculations, it outputs a whopping 50 W.


----------



## shadow419

40V P-P means peak to peak.  It would be 14 Vrms, and I believe the Lyr is rated at 6W into 32Ω
   
  Edit: I'm an idiot and really have no idea why I wrote 20 Vrms. Im going to blame a long day at work.


----------



## miceblue

Quote: 





shadow419 said:


> 40V P-P means peak to peak.  It would be 20Vrms, and I believe the Lyr is rated at 6W into 32Ω


 
  Oh I see.
  P = (Vrms^2)/R
P = 12.5 W from the calculation. Hm...
  Vrms ~ (1/3) V P-P = ~ 13.33 V
  P = 5.56 W, there we go
   
*MalVeauX* seems to like the Lyr with the HE-500's too. I keep reading that the minimum power for the HE-500 is 1 W, in which the O2 can't deliver enough power.


----------



## miceblue

Quote: 





mreleventy said:


> Quote:
> 
> 
> 
> ...


 
  I just did some subjective tests using Daft Punk's "Voyager" song (16/44.1 EAC CD-ripped) with the M-100's.
   
  1.0x gain:

 source volume ~ 50% of max
 O2 potentiometer ~ 8:45 position
 volume is louder than I would normally listen to music at
 no background hiss
   
  2.5x gain:

 O2 potentiometer left at ~ 8:45 position
 source volume left at ~ 50% of max
 no background hiss (strange, I could have sworn I heard the background hiss earlier.....stopping the music and turning the potentiometer, I can start hearing the background hiss at around the 12:15 position [I did this after doing finishing the testing session])
 volume is much louder than I would normally listen to music at, so I adjusted the source volume until the volume at 2.5x gain is about the same as 1.0x gain (rough estimate): now source is ~31.25% of max (yeah yeah this isn't objective having the by-ear volume guessing)
 I don't notice any degradation of the signal with the lower source volume
   
  So with the 2.5x gain at a lower source volume, I might be losing bits, but I can't hear it, at least not with the M-100. Having the potentiometer at the 8:45 position is pretty much the bare minimal "angle" before the channel imbalance kicks in for me. So even with the ~50% source volume at 1.0x gain, I have practically no wiggle room for volume adjustment using the O2.


----------



## mikeaj

For a sine wave, it's a factor of 2 * sqrt(2) = about 2.83 between peak-to-peak and rms voltages.  The 2 comes from there being a positive and negative component, and the sqrt(2) comes from the shape of the sine wave.  
   
  Power required for any headphones depends on how loud you want to listen.  Power delivered corresponds to the volume setting.  Most people aren't using anywhere close to the maximum capabilities of their amps.  Some amps will distort badly as you try to crank up the power, with lower-impedance headphones; that depends on the design.  1W into HE-500 would be really really loud:  about 117 dB SPL according to InnerFidelity.  1W is just some kind of nice round number people can quote.  It's also a way for HiFiMAN to set expectations and pass the buck.
   
  At an equivalent setting, LCD-2 should only be a few dB louder than HE-500, so it's not in a totally different class.  
   
  Plugged into the wall, extrapolating between known values, O2 on AC power can deliver probably something above 700 mW into 50 ohms.  Anyhow, even being really conservative, you're losing out on less than 2 dB compared to something that can output 1W.  You know how much different 2 dB sounds, right?


----------



## miceblue

Quote: 





mikeaj said:


> For a sine wave, it's a factor of 2 * sqrt(2) = about 2.83 between peak-to-peak and rms voltages.  The 2 comes from there being a positive and negative component, and the sqrt(2) comes from the shape of the sine wave.
> 
> Power required for any headphones depends on how loud you want to listen.  Power delivered corresponds to the volume setting.  Most people aren't using anywhere close to the maximum capabilities of their amps.  Some amps will distort badly as you try to crank up the power, with lower-impedance headphones; that depends on the design.  1W into HE-500 would be really really loud:  about 117 dB SPL according to InnerFidelity.  1W is just some kind of nice round number people can quote.  It's also a way for HiFiMAN to set expectations and pass the buck.
> 
> ...


 
  I don't know too much about how loud something sounds in correspondence to the decibel system. Isn't a +3 dB difference doubling the perceived volume?


----------



## autoteleology

> I don't know too much about how loud something sounds in correspondence to the decibel system. Isn't a +3 dB difference doubling the perceived volume?


 
   
  I believe it's +10dB.
   
  +3dB is how much it takes for the required voltage to double.


----------



## shadow419

10dBspl is a perceived doubling of volume.


----------



## dfferent

@mikeaj
  Thanks for info and suggestions.
  Looking at schematic, i see what you mean about ac direct to battery, so overall any short circuits around power supply would be there even with battery.
   
  @adydula
  Thanks for suggestions, have done all the visual checks a few times, halfway competent at DIY stuff so was confident it would work first time which it did and still does with batteries.
  Will probably plug it into wall wart and do all testing suggested on blog, there's nothing specific in troubleshooting unfortunately that refers to this type of issue.
  Good to know that the amp shouldn't be able to kill the power supply, this was my thoughts too hence the confusion as to why and how it's happened.
   
  At this stage I am chalking it up to bad luck and possibility of bad electrical supply in this room.
   
  PS The 02 and ODAC are outstanding. (full stop. no buts, no 'within this range' etc)


----------



## miceblue

Ah okay. Thanks for the quick replies! So then you're saying the O2 should sound fine with an HE-500 after all?


----------



## shadow419

Quote: 





dfferent said:


> @mikeaj
> Thanks for info and suggestions.
> Looking at schematic, i see what you mean about ac direct to battery, so overall any short circuits around power supply would be there even with battery.
> 
> ...


 
  It's possible you just got a couple of duds the first couple of times on the ac-ac adapters.  Just make sure that the ac adpter is measuring correctly.


----------



## mikeaj

Quote: 





miceblue said:


> Ah okay. Thanks for the quick replies! So then you're saying the O2 should sound fine with an HE-500 after all?


 
   
  Pretty much.  Or at least it will have enough power, unless you listen to ridiculous volumes.  O2 power levels were designed around getting every (non-electrostatic) current-production headphone other than the HE-6 to 110 dB SPL, which is a lot, and then exceeding the target by a little bit.  That's not to necessarily say that it has some magical optimal level, but many amps are around this powerful or more and really shouldn't be considered underpowered in general.
   
  Now, for whatever reasons (no comment on reason why or validity here), some people may or may not like the sound or the pairing.  That's up to you.


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Sweet, that's reassuring. Thank you for taking the time to answer my questions. 
	

	
	
		
		

		
			




   
  I'm still wondering as to how so many people say the HE-500's need 1 W of power to "sound good". I often read the HE-6 needs a lot of power, and yes it does relative to the HE-500, but I don't see it unreasonable for a decent amp to be able to deliver enough power to it. I always see these bizarre amp pairings for the HE-6 that cost over $600..... :/
   
  Tylls commented:
  Quote: 





> The HE-6 (my post on Head-Fi about the HE-6 is here) has been a difficult headphone for many people to get their arms around, and I believe the primary reason for that is their very demanding nature---they require far more amplifier power to sound good than just about any other modern-day headphone made.
> ...
> The EF-6 outputs 5 watts per channel into the 50 ohm impedance of the HE-6, which in my opinion is about the minimum amount acceptable for truly unfettered performance from this juice-sucking can.


 
   
  Skylab commented:
  Quote: 





> If you can afford the HE-6, I would rush to hear them any way you can IF:
> ...
> 2. You have a high-quality speaker amp you can dedicate for use with the HE-6, or a headphone amp with much, much more power than is typical


 
   
   
  Maybe I'm missing something important because these are all consistent findings and thus making the O2 not suitable for such a headphone.


----------



## mikeaj

First of all, maybe IF's measurements of one headphone are not indicative of all samples of that headphone in the wild.  With some of these smaller operations, maybe there is more manufacturing variance?  Or they're changing the design or manufacturing from one batch to another?  But I'd hope not, not at the prices they're asking.  Anyhow, a few dB difference between some samples wouldn't be unusual.  All these calculations are just based on the sample that Tyll measured.
   
  As mentioned before and as you say, HE-6 takes way more power for equivalent volume than most sets, so it's the odd one out.  O2 can only get that a little above 105 dB SPL.  If you want even more than 110 dB SPL (say 114 dB SPL), then 5W sounds right.  But it's not like many orders of magnitude different from other headphones.
   
  Don't listen that loud, or listen to music with a pretty small dynamic range?  O2 and many other "lesser" amps may be enough.
   
   
  Anyhow, there is just an expectation and some kind of intuition that you need to pair expensive headphones with expensive electronics.  It's maybe more a psychological thing than anything else.  People can't really visualize electronics that well, so they probably don't have a good intuition on their operation and requirements.  The hi-fi press doesn't help either, and neither does the sense of needing to keep up with the Joneses and so on.  Also, a lot of audiophile options, like a lot of the cheaper tube amps, would really have trouble with the kinds of high power levels we're talking about, so people could legitimately be using multiple amps that don't really work that well before settling on something overkill.


----------



## shadow419

Quote: 





mikeaj said:


> Pretty much.  Or at least it will have enough power, unless you listen to ridiculous volumes.  O2 power levels were designed around getting every (non-electrostatic) current-production headphone *other than the HE-6* to 110 dB SPL, which is a lot, and then exceeding the target by a little bit.  That's not to necessarily say that it has some magical optimal level, but many amps are around this powerful or more and really shouldn't be considered underpowered in general.
> 
> Now, for whatever reasons (no comment on reason why or validity here), some people may or may not like the sound or the pairing.  That's up to you.


 
   
  Quote: 





miceblue said:


> Sweet, that's reassuring. Thank you for taking the time to answer my questions.
> 
> 
> 
> ...


 
   
  Will the HE-500 get pretty loud with an O2, sure.  May or may not be the ideal pairing, but personally I'd go for a more powerful amp. The math shows that an O2 should get it loud enough for most music, but your ears should be the final say. The HE-6 is a whole different beast.  It's sensitivity is really low for a headphone driver.


----------



## thoughtcriminal

So the he6 aside (and not counting 'stats of course), will the o2 drive pretty much anything you can throw at it? I come from the school that an amplifier should amplify and by that nature any change in sound besides said amplification is undesirable. I understand that on power hungry cans proper amping can tighten everything up, reduce distortion, etc. But I don't want to hear the amp itself. This makes the build philosophy of the o2 very appealing.


----------



## RustA

Quote: 





thoughtcriminal said:


> So the he6 aside (and not counting 'stats of course), will the o2 drive pretty much anything you can throw at it? I come from the school that an amplifier should amplify and by that nature any change in sound besides said amplification is undesirable. I understand that on power hungry cans proper amping can tighten everything up, reduce distortion, etc. But I don't want to hear the amp itself. This makes the build philosophy of the o2 very appealing.


 
   
  O2 with ODAC have plenty of power to drive high-end phones like HD800 or LCD-2 even on unity gain... Even if I apply replaygain, I am still able to use unity gain to properly power both.


----------



## MrMateoHead

Quote: 





mikeaj said:


> Plugged into the wall, extrapolating between known values, O2 on AC power can deliver probably something above 700 mW into 50 ohms.  Anyhow, even being really conservative, you're losing out on less than 2 dB compared to something that can output 1W.  You know how much different 2 dB sounds, right?


 
   
  I think that you are correct about 700 mWs or so into 50 Ohms. BTW people - the HE-400 have been measured by different sources at about 50, not 32 Ohms. Power output of the O2 is regulated however, so while you can reach approximately 700 mWs, you only get there by twisting the knob far, far to the right. You won't be able to, because your ears will hurt.
   
  Also Mikeaj, you are correct - the difference between 700 mWs and 1,000 mWs is completely moot. What matters more or should matter more is the dynamic range of the recordings you are trying to play. It is not without irony that I would suggest classical listeners seek more power than rock/pop/techno listeners.
   
  Quote: 





tus-chan said:


> I believe it's +10dB.
> 
> +3dB is how much it takes for the required voltage to double.


 
  Another way to say it is, you must approximately double your power for each 3 dB gain in volume. To get "twice as loud", you need 10 times the power.
   
  Even with a headphone as relatively "inefficient" as the HE-400, I once estimated needing something like a half a watt or so in order to have the headroom for most all listening conditions. For the most part, that has proven to be a big overestimate!


----------



## JakeJack_2008

Quote: 





mikeaj said:


> ...
> 
> 
> 
> ...


 
   
  Thanx a lot. Some things you said are above my head because I am not an engineer or a DIY-er.
  So, the downsampling is a more complex process than I had thought.
   
  I'll take a look at the thread that discusses 'test: 24/96 vs. a file that was converted  24/96 -> 16/44.1 -> 24/96'


----------



## Dano91

Quote: 





mikeaj said:


> First of all, maybe IF's measurements of one headphone are not indicative of all samples of that headphone in the wild.  With some of these smaller operations, maybe there is more manufacturing variance?  Or they're changing the design or manufacturing from one batch to another?  But I'd hope not, not at the prices they're asking.  Anyhow, a few dB difference between some samples wouldn't be unusual.  All these calculations are just based on the sample that Tyll measured.
> 
> As mentioned before and as you say, HE-6 takes way more power for equivalent volume than most sets, so it's the odd one out.  O2 can only get that a little above 105 dB SPL.  If you want even more than 110 dB SPL (say 114 dB SPL), then 5W sounds right.  But it's not like many orders of magnitude different from other headphones.
> 
> ...


 

 Maybe I'm wrong with my calculations, but - on Hifiman site HE-6 sensitivity is rated 83.5 dB/mW and 50 ohm impedance. That should translates to 96.5 dB/V (mW + 30 - 10 x log impedance). With 83.5 dB/mW and 96.5dB/V you need 447mW and 4.73V to reach 110 dBSPL.
  O2 amp on AC can deliver 4.5V / 613mW at 33 ohm and 7.15V / 639mW at 80 ohms. HE-6 with it's 50 ohms lays pretty much inbetween. 
  So to put it simply, I think O2 amp should have enought power for HE-6 to run them on 110dBSPL.


----------



## RustA

Quote: 





dano91 said:


> Maybe I'm wrong with my calculations, but - on Hifiman site HE-6 sensitivity is rated 83.5 dB/mW and 50 ohm impedance. That should translates to 96.5 dB/V (mW + 30 - 10 x log impedance). With 83.5 dB/mW and 96.5dB/V you need 447mW and 4.73V to reach 110 dBSPL.
> O2 amp on AC can deliver 4.5V / 613mW at 33 ohm and 7.15V / 639mW at 80 ohms. HE-6 with it's 50 ohms lays pretty much inbetween.
> So to put it simply, I think O2 amp should have enought power for HE-6 to run them on 110dBSPL.


 
   
  Yes... the author himself stated that O2 "should be able to power even the hard-to-drive headphones like hifimans - with not much headroom to spare" (something like that, not exactly in these words).
   
_" I suspect with some worst case headphones (like some of the planars from HIFiMan) the O2 will merely get genuinely loud at full output. But for more typical headphones, the O2 will be well under its full output."_


----------



## Dano91

Quote: 





adamlr said:


> about the 250 ohm impedance, could this be the advantage to having high impedance headphones that no one seems to know? does insensitivity translate into insensitivity to noise?


 
  The easiest way to explain "why high impedance headphones" will be quoting Beyerdynamic FAQ page:
   
   
  Quote: 





> "But why high impedance headphones?
> 
> The impedance is determined by the voice coil (dynamic headphones), which is a winded copper wire (coated to avoid a short-circuit). This copper wire is available in nearly every length, but not in every gauge (thickness) and a thicker wire has less resistance than a thin wire ("less fits through"). The magnetic field of the voice coil depends on the number of windings of the coil, causing a low impedance system to use a thicker (also heavier) wire and since the membrane foil can't be infinitely light-weight, the moving mass (voice coil and diaphragm) is relatively high. It's pretty clear that a higher mass can't move as easily (following an audio signal) as a lower mass. This low mass can easily be accomplished with thinner (lower weight) wire, but the thinner wire has a higher impedance. This means that the DT 770 PRO with 250 ohms sound more natural, but plays (depending on the used headphone amplifier) not as loud as the 80 ohms version."


----------



## mikeaj

Quote: 





dano91 said:


> Maybe I'm wrong with my calculations, but - on Hifiman site HE-6 sensitivity is rated 83.5 dB/mW and 50 ohm impedance. That should translates to 96.5 dB/V (mW + 30 - 10 x log impedance). With 83.5 dB/mW and 96.5dB/V you need 447mW and 4.73V to reach 110 dBSPL.
> O2 amp on AC can deliver 4.5V / 613mW at 33 ohm and 7.15V / 639mW at 80 ohms. HE-6 with it's 50 ohms lays pretty much inbetween.
> So to put it simply, I think O2 amp should have enought power for HE-6 to run them on 110dBSPL.


 
   
  No, that's fair enough.
   
   
  Whenever possible I use Tyll's measurements at InnerFidelity rather than manufacturer's spec.  That way it's consistent across brands and there is no temptation to fudge numbers a certain way.  IF measurement is 19.69 mW for 90 dB SPL, so around 77 dB SPL / 1 mW, 6 dB quieter than what HiFiMAN says.
   
  As I mentioned before, maybe Tyll's sample is not indicative of products as a whole, but that's what it is.
   
   
  edit:  re advantage of high-impedance headphones
   
  Aside from weight of the wiring driver coil, yes, higher impedance means that a certain noise level will transfer less power to the headphones.  Likewise, if the sensitivity is lower, a given power level will create lower sound pressure levels to the ear.  Often times, increasing volume does not scale up the noise as much as it does the signal.  So for higher-impedance and less-sensitive headphones, if you're compensating for lower volume by boosting the signal levels (to listen at equivalent volume as another headphone), there will likely be less noise than for normal listening with another headphone.  You get higher SNR.
   
  This is why you could say that sensitive IEMs have some of the most exacting requirements for audio systems.  They'll pick up very low noise levels.  This is one of the reasons why relatively-noisy tube amps are not disasters with high-impedance fullsize headphones—in fact, many people like the combination.
   
  In practice, unless you go to the extremes, like sensitive IEMs, noise is probably not an issue.


----------



## ostewart

I listened to HE-6 through O2 and it sounded pretty darn good


----------



## adydula

Yup they do sound good with the O2....remember this amp was designed to work with 98% of the cans out there....yet we go back and want to have 100%.
   
  For the price of admission you could buy an O2 board for $99 from JDS...try it and sell it if you dont like what you hear!
   
  Try that with a $1000 amp.
   
  You havent got a lot to loose...
   
  Alex


----------



## miceblue

Quote: 





adydula said:


> Yup they do sound good with the O2....remember this amp was designed to work with 98% of the cans out there....yet we go back and want to have 100%.
> 
> For the price of admission you could buy an O2 board for $99 from JDS...try it and sell it if you dont like what you hear!
> 
> ...


 
  Yeah I agree that the O2 is an AWESOME amp for the price. I'm just trying to figure out the reasoning behind more expensive amps....usually it just amounts to a fancier-looking case, tubes, more output power (as discussed here power might not even be that as big of an issue as it seems), or more output jack option. I think I'll be set with the O2 for a long while.
   
  I don't even know how one would compare the O2 with other amps since most amps nowadays seem to be built with colouration. If one were to try to compare how an HE-6 sounds with the O2's output power versus a, say Schiit Lyr, you can't really compare the two since they inherently have different sound signatures, no?


----------



## Tyll Hertsens

Quote: 





miceblue said:


> I'm still wondering as to how so many people say the HE-500's need 1 W of power to "sound good". I often read the HE-6 needs a lot of power, and yes it does relative to the HE-500, but I don't see it unreasonable for a decent amp to be able to deliver enough power to it. I always see these bizarre amp pairings for the HE-6 that cost over $600..... :/
> 
> Tylls commented:
> 
> ...


 
   
  Just wanted to point out that those are all Skylab comments, not mine.
   
  I'm not sure I buy the generally held idea that the HE-6 needs as much power as many claim.


----------



## RustA

Quote: 





tyll hertsens said:


> Just wanted to point out that those are all Skylab comments, not mine.
> 
> I'm not sure I buy the generally held idea that the HE-6 needs as much power as many claim.


 
   
  You mean those opinions that several W per channel magically transforms HE-6 into "god mode"? LOL, yeah...


----------



## miceblue

Quote: 





tyll hertsens said:


> Quote:
> 
> 
> 
> ...


 
  Dooh you're right about that. My bad. I always forget to read who the author is on the InnerFidelity posts.
   
   
  Regarding source volume, from this article it looks like the source volume doesn't really matter if you're using Windows Vista or 7. I'm not sure how the audio is regulated with the volume options in Mac OS X (which is what I use):
http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/


----------



## adydula

If I thought I was missing something I would not have sold my Asgard, or my Lyr or my SOHOii, and after listening to a lot of others....I am not missing anything with the O2.
   
  That said there is nothing wrong with wanting a amp that costs more, has billet aluminum casings, wrap around victorian moldings, gold plated contacts, NOS tubes, and on and on and on....its your bucks...
   
  Some folks like the coolness factor and must have their amp in red, or blue or yellow....LOL...
   
  You put a O2 next to a Burson or a Vioelectric amp and the O2 looks like the skinny kid at the beach...but in this case the sand doenst get kicked against the O2, it holds its own.
   
  To me its the absence of colorations, straight wire with gain...
   
  Alex


----------



## RustA

Quote: 





adydula said:


> If I thought I was missing something I would not have sold my Asgard, or my Lyr or my SOHOii, and after listening to a lot of others....I am not missing anything with the O2.
> 
> That said there is nothing wrong with wanting a amp that costs more, has billet aluminum casings, wrap around victorian moldings, gold plated contacts, NOS tubes, and on and on and on....its your bucks...
> 
> ...


 
   
  In my opinion, the only real upgrade (if you prefer neutrality over colouring the music) over O2/ODAC could possibly be DAC2 HGC... People reported even more detail. Whether it's worth the price, that's another question.


----------



## HamilcarBarca

Quote: 





rusta said:


> In my opinion, the only real upgrade (if you prefer neutrality over colouring the music) over O2/ODAC could possibly be DAC2 HGC... People reported even more detail. Whether it's worth the price, that's another question.


 
   
  By no means are the ODAC or O2 perfect; perfection is impossible in electronics.
   
  While some equipment (e.g., Benchmark DAC1) has measurably better performance, the differences aren't audible. The DAC2 HGC might be another DAC which measures better, but it doesn't provide more detail or any other audible improvement over any other transparent equipment.


----------



## RustA

Quote: 





hamilcarbarca said:


> By no means are the ODAC or O2 perfect; perfection is impossible in electronics.
> 
> While some equipment (e.g., Benchmark DAC1) has measurably better performance, the differences aren't audible. The DAC2 HGC might be another DAC which measures better, but it doesn't provide more detail or any other audible improvement over any other transparent equipment.


 
   
  Honestly, I don't believe that O2 and ODAC are as detailed and transparent as it ever gets (with deadly-neutral frequency response)... *I do want to believe it* and I have no scientific explanation on why it shouldn't be true but I just don't believe that we reached the end of this road.


----------



## adydula

The real end of the road lies at a live concert and a good cold beer....
   
  lol
   
  Alex


----------



## miceblue

Quote: 





adydula said:


> The real end of the road lies at a live concert and a good cold beer....
> 
> lol
> 
> Alex


 
  Can't you switch out some of the op-amps to get some performance gains in some areas?
  Project-H seems to be using an op-amp modified O2: http://www.head-fi.org/t/586040/official-asian-anime-manga-and-music-lounge#post_7982781


----------



## RustA

Quote: 





miceblue said:


> Can't you switch out some of the op-amps to get some performance gains in some areas?
> Project-H seems to be using an op-amp modified O2: http://www.head-fi.org/t/586040/official-asian-anime-manga-and-music-lounge#post_7982781


 
   
  You can do several things in order to improve measurements... I've seen a DIY thread somewhere with people posting their findings.
   
  I have several upgrades done on my unit as well and it sounds a little bit better than common O2/ODAC unit (that I have at home as well). However, it's most probably primarily connected to the fact I do not need to use headphone adaptors anymore.


----------



## mikeaj

It's my first time hearing of project h.
   
  Looks like just a standard O2 PCB inside.  They changed the NJM2068 gain stage op amp for the popular and more-expensive FET-input OPA2134.  OPA2134 has several dB higher (i.e. worse) noise.  Even if the distortion performance were better at the gain used (seems not), the output stage is the "bottleneck" anyway.  Several options for the gain stage were measured by the designer for use in the O2.  Check the blog.
   
  I don't see any other changes to the O2 electronics, but I didn't look that hard.
   
  You can always change things, not necessarily for the better.  And if you do change for the better, it very well might not sound perceptibly better.


----------



## HamilcarBarca

Quote: 





miceblue said:


>





> Can't you switch out some of the op-amps to get some performance gains in some areas?


 
   
  It might measure better "in some areas." Nothing is more transparent than transparent.


----------



## JakeJack_2008

Quote: 





adydula said:


> The real end of the road lies at a live concert and a good cold beer....
> 
> lol
> 
> Alex


 
   
Alex, this must be _ the best post ever _on this site!!!
   
I _wholeheartedly _second it.


----------



## adamlr

Quote: 





miceblue said:


> I just did some subjective tests using Daft Punk's "Voyager" song (16/44.1 EAC CD-ripped) with the M-100's.
> 
> 1.0x gain:
> 
> ...


 
   
  i thank you ever so kindly =]
   
  Quote: 





dano91 said:


> The easiest way to explain "why high impedance headphones" will be quoting Beyerdynamic FAQ page:


 
   
  Quote: 





mikeaj said:


> edit:  re advantage of high-impedance headphones
> 
> Aside from weight of the wiring driver coil, yes, higher impedance means that a certain noise level will transfer less power to the headphones.  Likewise, if the sensitivity is lower, a given power level will create lower sound pressure levels to the ear.  Often times, increasing volume does not scale up the noise as much as it does the signal.  So for higher-impedance and less-sensitive headphones, if you're compensating for lower volume by boosting the signal levels (to listen at equivalent volume as another headphone), there will likely be less noise than for normal listening with another headphone.  You get higher SNR.
> 
> ...


 
   
  thank you both very much
   
  Quote: 





adydula said:


> The real end of the road lies at a live concert and a good cold beer....
> 
> lol
> 
> Alex


 





  you inspired me to get up and fetch a beer 
                                                                                                                       
   
  as for the O2 being the end of the road, excluding electrostatics, i can easily believe it (and i say "believe" rather than "agree" because im not nearly informed enough to make such a claim). "wire with gain" is exactly what im looking for, and in this thread, i imagine everyone else is aswell. however, other things are to be considered when choosing an amp, such as channel imbalance, which is in my very humble opinion, the only issue with the O2, though im confident that once iv changed my gain options, and start using unity gain, this will no longer be an issue at all (due to the more-to-the-right position that unity gain will require).
  HOWEVER, marketing schemes and such are pretty powerful, and for the life of me, i cant imagine staying with the O2 when i eventually have enough money for real TOTL gear, and im sure that ill get atleast an asgard, knowing full well that i dont actually need it. kinda ashamed of admitting it, but i never lie.
   
   
  unrelated question: why cant i power headphones with the odac? i can control its volume digitally, why not use it for sensitive, efficient headphones? ive never tried it due to the massive warning jds labs has printed on the instruction manual that comes with the odac (yes i read it, for me its part of the fun of getting new stuff - being geeky about it 
	

	
	
		
		

		
		
	


	




). will it "underpower" the headphones? will it damage them? will it damage the odac?


----------



## mikeaj

Quote: 





adamlr said:


> unrelated question: why cant i power headphones with the odac? i can control its volume digitally, why not use it for sensitive, efficient headphones? ive never tried it due to the massive warning jds labs has printed on the instruction manual that comes with the odac (yes i read it, for me its part of the fun of getting new stuff - being geeky about it
> 
> 
> 
> ...


 
   
  More or less, you can, but not recommended.
   
  ODAC doesn't have electronics dedicated to driving headphones.  The electronics are built to just be a line driver and feed an amplifier's line input (which is in the thousands of ohms and thus doesn't require much current, unlike headphones).  Actually, the line driver is integrated inside the DAC chip for the ODAC, and specs are not publicly available.
   
  It's possible that with low-enough levels and the right headphones, the sound could be okay when directly driving headphones.  Depends on what it's really like internally.  Practically, if you plugged in some low-impedance headphones and cranked the volume, it would probably start to distort badly early.  Sometimes for the right building, you can use a hammer as a wrecking ball, but that doesn't mean you should...
   
  It won't damage the headphones and it probably shouldn't damage the ODAC.


----------



## adamlr

Quote: 





mikeaj said:


> More or less, you can, but not recommended.
> 
> ODAC doesn't have electronics dedicated to driving headphones.  The electronics are built to just be a line driver and feed an amplifier's line input (which is in the thousands of ohms and thus doesn't require much current, unlike headphones).  Actually, the line driver is integrated inside the DAC chip for the ODAC, and specs are not publicly available.
> 
> ...


 
  cheers!


----------



## MrMateoHead

Quote: 





adydula said:


> If I thought I was missing something I would not have sold my Asgard, or my Lyr or my SOHOii, and after listening to a lot of others....I am not missing anything with the O2.
> 
> That said there is nothing wrong with wanting a amp that costs more, has billet aluminum casings, wrap around victorian moldings, gold plated contacts, NOS tubes, and on and on and on....its your bucks...
> 
> ...


 

 You have to remember that after the first watt, even a 6 watt lyr offers *only* 6-9 dB of additional headroom over a 1 watt amp. I consider the O2 a Half-Watt amp, so 9-12 dB gain from say, a lyr, only makes it to "twice as loud" as the O2, while the power output may put my phones at risk.
   
  While I am at it, why don't headphone manufacturers supply information about RMS and Max Power inputs into headphones?
   
  Of someone *really* needed to go so crazy loud, I would start looking at the efficiency of the phones' themselves! Hell, the other day I was thinking about how nice it would be to have a 100 watt version of my amp rather than the 50 watt version. Then I remembered that other than a tiny bit more headroom, I am ultimately not taking much of a step up.


----------



## ProTofik

Hi.
  I am currently enjoying my ODAC + O2 with HD600 but I have a small problem.
  With ODAC set to 50% in windows, O2's gain 2.5X and volume knob at about 9-10am it's still too loud for my liking.
   
  I want to change my O2 gain settings. Now I have 2.5X (gain switch out) and 6.5X (gain switch in). I would like it to be 1X (Gain switch off) and 2.5X (Gain swtich in).
  Which resistors I need to swap / remove to achieve it? 
  Thanks.


----------



## shadow419

R17 and R21 correspond to gain switch in the out position.  For 1x(unity gain) you can leave these empty.
  R19 and R23 is for gain switch in position.  For 2.5x you want 1K OHM resistors in those spots.
   
  You could go the easy route and just clip the resistors in R19 and R23.  That will give you 2.5x with the switch out and 1x with the switch in.


----------



## ProTofik

Thanks. I am going to try it right now. 
   
  Edit: Works exactly as I wanted. Thanks.


----------



## shadow419

Quote: 





protofik said:


> Thanks. I am going to try it right now.
> 
> Edit: Works exactly as I wanted. Thanks.


 
  Glad it worked out for you.  You're welcome and enjoy!


----------



## Stratok

Is there something wrong if I have foobar set to 100% (0.00dB) volume, windows set to 100% volume and O2 with 2,5x gain 9 o'clock and it sounds comfortable? 10-11 o'clock is a bit too loud for my liking. I'm using 32ohm signature DJ.


----------



## mikeaj

Quote: 





stratok said:


> Is there something wrong if I have foobar set to 100% (0.00dB) volume, windows set to 100% volume and O2 with 2,5x gain 9 o'clock and it sounds comfortable? 10-11 o'clock is a bit too loud for my liking. I'm using 32ohm signature DJ.


 
   
  Depends on the source output level, but that seems very typical.  Are you thinking that the amp is too loud?  If you want, you can change the other setting to 1x by clipping resistors, and just mentioned previously in the thread.
   
  Most people don't actually need (> 1) gain unless they listen louder, have inefficient headphones, and/or have higher-impedance headphones.


----------



## Stratok

Quote: 





mikeaj said:


> Depends on the source output level, but that seems very typical.  Are you thinking that the amp is too loud?  If you want, you can change the other setting to 1x by clipping resistors, and just mentioned previously in the thread.
> 
> Most people don't actually need (> 1) gain unless they listen louder, have inefficient headphones, and/or have higher-impedance headphones.


 

 ok thanks  I was just worried if I've missed something. Feels good so I think I'll pass playing with DIY stuff for now.


----------



## lorriman

mikeaj said:


> Depends on the source output level, but that seems very typical.  Are you thinking that the amp is too loud?  If you want, you can change the other setting to 1x by clipping resistors, and just mentioned previously in the thread.
> 
> Most people don't actually need (> 1) gain unless they listen louder, have inefficient headphones, and/or have higher-impedance headphones.




...or are using ipods or clip+ as a source, in which case 6.5x is a good idea. I'm quite bemused at the advice for clipping the 6.5x to leave only 1x and 2.5x. Unless you really know that you will never use an ipod or clip+ or similar then you likely need the 6.5x.


----------



## RustA

Sorry for spamming today, guys, but I feel this could be a great purchase for someone interested in full experience with the great O2/ODAC:
   
  http://www.head-fi.org/t/653996/fs-unique-o2-odac-combo-w-upgrades-read-inside


----------



## shadow419

Quote: 





lorriman said:


> ...or are using ipods or clip+ as a source, in which case 6.5x is a good idea. I'm quite bemused at the advice for clipping the 6.5x to leave only 1x and 2.5x. Unless you really know that you will never use an ipod or clip+ or similar then you likely need the 6.5x.


 
  They reason I recommend clipping the 6.5x if you need a unity gain setting is simple.  If you're using a portable music player/smartphone as a source you're likely out of the home and are using a more portable headphone.  2.5x gain should be enough for most transportable setups.  If home and have a standard dac output, 2.5x gain will be enough for most everything, and unity will cover any sensitive and iem you may use.  6.5x gain is really only necessary if you're using a phone/ipod as a source and have a high Z headphone that needs the higher voltage swing.


----------



## Gumy

Hi people! new around this side of the forum. Got some concern not sure if you guys can help me out on this.
   
  I have my Epiphany O2 for about a month now. Under normal use it sounded great! well.. neutral.
   
  However, when I was playing around with it, when I put the volume on as low as I could and still audible, I notice that my left channel sounds normal, but my right channel is pretty much completely gone. Remember I'm talking about when the volume is VERY low, a level that I wouldn't use it normally.
   
  First I can assure you all there's nothing to do with my ear. I did a test with my IEM, when I get the volume down very low to the point that I can still hear a little on left channel, and NOTHING on the right channel, I switch my left side of IEM to my right ear then I could audit it, while the left channel of the IEM is still pretty much dead silence.
   
   
  My concern is that if this is normal? and if it is something that I should be concern about for future sakes.


----------



## deadlylover

> Originally Posted by *Gumy* /img/forum/go_quote.gif
> 
> My concern is that if this is normal? and if it is something that I should be concern about for future sakes.


 
   
  That's normal, most pots have poor tracking at low volume levels, so one side is usually slightly louder than the other.


----------



## Gumy

Quote: 





deadlylover said:


> That's normal, most pots have poor tracking at low volume levels, so one side is usually slightly louder than the other.


 

 hehe thank you very much XD


----------



## adamlr

Quote: 





gumy said:


> Hi people! new around this side of the forum. Got some concern not sure if you guys can help me out on this.
> 
> I have my Epiphany O2 for about a month now. Under normal use it sounded great! well.. neutral.
> 
> ...


 
  as mentioned, this is normal, and this is i think the bigest fault of the O2. this is also a good example for why one might want to use unity gain and "clip" the 6.5x gain, to allow for low level listening - but still keeping the volume pot on a relatively high position and avoid the channel imbalance area. when i get my m-100s (sensitive headphones), i imagine ill have to "clip" my O2 aswell.


----------



## lorriman

shadow419 said:


> They reason I recommend clipping the 6.5x if you need a unity gain setting is simple.  If you're using a portable music player/smartphone as a source you're likely out of the home and are using a more portable headphone.  2.5x gain should be enough for most transportable setups.  If home and have a standard dac output, 2.5x gain will be enough for most everything, and unity will cover any sensitive and iem you may use.  6.5x gain is really only necessary if you're using a phone/ipod as a source and have a high Z headphone that needs the higher voltage swing.




This may be true for quiet listeners who never use a portable source with their home phones, but for the rest (and I reckon the majority) losing the 6.5x option is liable to be a problem one day. 

Even using the ODAC can be an issue. I used bass adjustment (sound driver setting) for 6db more bass and needed to use 6.5x. And that's not 600ohm headphones but 32ohm. 6.5x isn't as much as one might think. 

In any case, many are going to be using their portables as home sources. Apart from the tiniest bit of noise with sensitive iems, the clip+/Fuze is a hifi source. Ipods are a problem in their own right since they can output so little voltage and have distortion issues at their max volume.


----------



## RustA

Quote: 





adamlr said:


> as mentioned, this is normal, and this is i think the bigest fault of the O2. this is also a good example for why one might want to use unity gain and "clip" the 6.5x gain, to allow for low level listening - but still keeping the volume pot on a relatively high position and avoid the channel imbalance area. when i get my m-100s (sensitive headphones), i imagine ill have to "clip" my O2 aswell.


 
   
  I strongly advise to use 1x gain... I have two different O2/ODAC units and both without any problems with low-level listening, scratching sound or low-level hissing. With ODAC included (with 2v output), you get enough power to amplify most of the headphones even on 1x gain. 1x gain also gives the cleanest possible signal.


----------



## adamlr

Quote: 





rusta said:


> I strongly advise to use 1x gain... I have two different O2/ODAC units and both without any problems with low-level listening, scratching sound or low-level hissing. With ODAC included (with 2v output), you get enough power to amplify most of the headphones even on 1x gain. 1x gain also gives the cleanest possible signal.


 
  yea well at the moment im using 250 ohm beyers and i eq rather heavily, so i need the headroom. im using 2.5x gain, and an odac as my source and its rather optimal tbh. but in a month or so when i have the m-100 i imagine i will have to adjust the gain settings.


----------



## JakeJack_2008

Quote: 





rusta said:


> I strongly advise to use 1x gain... I have two different O2/ODAC units and both without any problems with low-level listening, scratching sound or low-level hissing. With ODAC included (with 2v output), you get enough power to amplify most of the headphones even on 1x gain. 1x gain also gives the cleanest possible signal.


 
  I bought the  _standalone _ODAC and  _standalone _O2  from JDS Labs last week.
  After experimenting a little I am using only the *1x gain. *The volume is at _9 o'clock _and it's quite loud for me.
  I don't need to use the higher gain with the DT 880 *250* Ohm at all. - The O2 is a very powerful headphone amp.
  Besides, the higher gain does _not _seem to sound as clean as the 1x gain.
   
   
  Here's my setup:
   
   


> laptop --> ODAC --> O2 --> Beyerdynamic DT 880 (*250* Ohm).


 
   
   
   
   
   
   
  By the way, following the the JDS Labs instructions, I set the volume to max level on my Windows 7 laptop.
  Also, I don't use any foobar, etc as of yet.
  I am running the O2 either off batteries or an AC adapter (from JDS Labs).
   
   
  The ODAC with the O2 sound _fantastic _to my ears: the resolution, soundstage, airness, cleanness ... of the sound.
   
  I am very happy with the ODAC and O2.
   
   
   
   
  P.S.
  There's no hiss, whining, scratching, buzzing, any distortion of any kind, etc.


----------



## jkxs

Hey guys! I've been trying to sell off a standalone O2 + ODAC combo in the for sale forums, but haven't had any luck in over a month and over 800 page views. Maybe one of you guys will be interested? 
   
http://www.head-fi.org/t/649212/objective2-o2-headphone-amp-odac#post_9163849


----------



## JakeJack_2008

Quote: 





jkxs said:


> Hey guys! I've been trying to sell off a standalone O2 + ODAC combo in the for sale forums, but haven't had any luck in over a month and over 800 page views. Maybe one of you guys will be interested?
> 
> http://www.head-fi.org/t/649212/objective2-o2-headphone-amp-odac#post_9163849


 
   
  No, I am not buying the combo. Last week I bought the ODAC and O2 as two separates from the _well known _
  and with *excellent reputation *JDS Labs. 
  There's _no feedback _about your selling efforts on this site and that's why you're having hard times to sell the combo.
   
  Good luck.


----------



## kskwerl

^ lol wut? I don't think he was directing the sale to you, I just think it was just in general


----------



## RustA

Quote: 





jakejack_2008 said:


> No, I am not buying the combo. Last week I bought the ODAC and O2 as two separates from the _well known _
> and with *excellent reputation *JDS Labs.
> There's _no feedback _about your selling efforts on this site and that's why you're having hard times to sell the combo.
> 
> Good luck.


 
   
  Someone has to be first in order to make any feedback happen.
   
  Btw, I personally have nothing against JDS Labs but they should offer much more info about what gain is suitable with and without ODAC (and stop offer 6.5x configuration when you order an amp with ODAC installed inside), offer more than 1x/2.5x/6.5x settings to choose from, they should also offer WAU16-400 or 16-1000 instead of not completely ideal WAU 12-200 and I would also prefer to have more options to choose from in terms of appearance, pricing is also quite high... Plenty things to improve.


----------



## jkxs

Quote: 





jakejack_2008 said:


> No, I am not buying the combo. Last week I bought the ODAC and O2 as two separates from the _well known _
> and with *excellent reputation *JDS Labs.
> There's _no feedback _about your selling efforts on this site and that's why you're having hard times to sell the combo.
> 
> Good luck.


 
   

 The first thing on the for sale thread is the album link and then a link to my eBay feedback. But then again, I could ask you a few questions also:
  Did I ask about JDSLab's reputation? Why would you bring up trader feedback when you don't have any yourself?
   
  I'm okay with feedback, but I don't see the need for you to put down my listing.


----------



## mikeaj

Maybe you should emphasize that you have the upgraded adapters recommended (by the designer) for power-hungry headphones (that others such as JDSLabs do not provide).
   
  Or consider selling them separately, if that would help?  Probably not, if you want to get rid of both.  Possibly also just take a larger price hit and reduce the price, as most people prefer options from other sources unless there is a significant discount to be had via sale/trade forums.  Do threads usually get that many views without any action?  I think it's the price, really.  For example, Mayflower Electronics offers O2 + ODAC combo in one box for $250 shipped.  
   
  You might as well list what the gains are, as the build doesn't look standard (different faceplate than some are used to).  Maybe offer to change them if you have different resistors handy.
   
  Good luck selling them.


----------



## lorriman

rusta said:


> Btw, I personally have nothing against JDS Labs but they should offer much more info about what gain is suitable with and without ODAC (and stop offer 6.5x configuration when you order an amp with ODAC installed inside), offer more than 1x/2.5x/6.5x settings to choose from, they should also offer WAU16-400 or 16-1000 instead of not completely ideal WAU 12-200 and I would also prefer to have more options to choose from in terms of appearance, pricing is also quite high... Plenty things to improve.




The pricing is low. A proper business costing would not have resulted in such low-cost, hand-built amps (excecpt maybe from China). The designers intent was a for a cheap self-build, but from a business perspective the prices offered by the sellers is a bargain. 

To repeat for the hundredth time, and before anyone else gets stung by your advice: 6.5x is needed if anyone (and especially loud listeners) has any intention of using a portable player as a source, or uses significant EQ. The presence of the ODAC is irrelevent to this unless you really intend to never, ever use an external source; but why lose that flexibility. Even then, I have used the ODAC on a win7 computer that for whatever reason had very low max system volume; I needed 6.5x gain. 

I strongly advise users to avoid 1x 2.5x O2's (or clipping the 6.5x resistors to get the same).


----------



## RustA

Quote: 





lorriman said:


> The pricing is low. A proper business costing would not have resulted in such low-cost, hand-built amps (excecpt maybe from China). The designers intent was a for a cheap self-build, but from a business perspective the prices offered by the sellers is a bargain.
> 
> To repeat for the hundredth time, and before anyone else gets stung by your advice: 6.5x is needed if anyone (and especially loud listeners) has any intention of using a portable player as a source, or uses significant EQ. The presence of the ODAC is irrelevent to this unless you really intend to never, ever use an external source; but why lose that flexibility. Even then, I have used the ODAC on a win7 computer that for whatever reason had very low max system volume; I needed 6.5x gain.
> 
> I strongly advise users to avoid 1x 2.5x O2's (or clipping the 6.5x resistors to get the same).


 
   
  1) Have a look at Mayflower electronics - US company cooperating with JDS Labs with significantly lower prices and as well significantly more customising options.
   
  2) 6.5x is useless, I know it myself, I own a unit with SIP adapters and can choose my gain configuration to whatever value I want anytime.
   
  a) With ODAC - Even if you use replaygain along with EQing, you won't be using anything above 2.5x unless the very extreme cases. I've tried several headphones, flagships or cheaper...
   
  b) Without ODAC - Here it actually is possible to use higher gain in unusual conditions. But 6.5x? Use 1x and 4x or something like that. The rough guideline on the author's website is actually inaccurate.
   
  You will get the very best performance from your amp only in 1x gain mode, its possible to find clues on DIY forums... I've carefully compared different gains and yes, with higher gain than ideal, you get subtle distortion and lost the ultimate transparency + you can get low-level hissing and other problems that some people experience. I see no reason why not go for the best.


----------



## lorriman

rusta said:


> 1) Have a look at Mayflower electronics - US company cooperating with JDS Labs with significantly lower prices and as well significantly more customising options.




Then they may be doing it merely for the joy of it. Once you've totted up manual labour, posting and admin costs, the JDS O2 is well under-priced.



> 2) 6.5x is useless, I know it myself, I own a unit with SIP adapters and can choose my gain configuration to whatever value I want anytime.




It's useless_ to you_. And I'm not seeing an argument here, merely an assertion. I've already justified myself fully and you haven't sought to address what I wrote but just repeat your own listening requirements.



> b) Without ODAC - Here it actually is possible to use higher gain in unusual conditions. But 6.5x? Use 1x and 4x or something like that. The rough guideline on the author's website is actually inaccurate.




What unusual conditions? Using a portable player, with EQ and/or a high ohm headphone is not unusual. The designers recommendation was carefully thought through as is everything he does. 



> You will get the very best performance from your amp only in 1x gain mode, its possible to find clues on DIY forums... I've carefully compared different gains and yes, with higher gain than ideal, you get subtle distortion and lost the ultimate transparency + you can get low-level hissing and other problems that some people experience. I see no reason why not go for the best.




The distortion at high gain shouldn't be possible to hear unless you have poor headphones generating their own distortion. As for noise, that will most likely be your source or an inappropriate volume level for a very sensitive headphone. The 'best performance at 1x' is academic. The real reason for 1x is to get the volume pot past 9 and safely out of the way of channel imbalance (where your source is 16bit an must be run at max digital volume). As it happens, for loud listeners 9 can be just fine with etymotics (EQ'd for more bass) and already past audible channel imbalance. So even that's often not needed. For most, setting the source's volume lower (assuming 24bit) is just fine to avoid the need for 'the snip' to get 1x.

A 1x/6.5x O2 is a fine compromise (and ipod users are more likely than most to need 6.5x). 1x/2.5x is unnecessarily limiting your options.


----------



## MrMateoHead

Gain is Gain - Its about matching an input signal to the output signal.
   
  With 2v RMS, I rarely hit more than 12 O'Clock on the O2.
  With 1V RMS, I easily make it to the right of 12. With some High Dynamic Range recordings, I have reached max volume. At 6.5X, this would not be possible.
   
  With Cell Phones, Mp3 players, and other bad sources, I need 6.5X and a good twist of the dial.
   
  No distortion, no noise. The O2 is good to the point where, when I do hear noise, I know it is within the recording. The flexibility is well worth it.
   
  I have a car radio which does 4V max from pre-outs. As-tested, the "fronts" actually clip after about 3V, while the Subwoofer channel can reach 4V. Both channels clip way before the volume dial is maxed (a 'feature' I despise) - though I swear ambient temp and other factors give and take away my headroom. So, for the first time ever, I have an amp running at almost maximum gain. Meanwhile, source volume of the Radio, CD, USB, and AUX IN are all different. Without a question, very high gain is the cost of trying to ensure that the amp is stressed out before the pre-outs are in that system. It is not ideal in terms of maximizing 'signal to noise', but with good equipment (and I have good equipment), there is no audible penalty for running higher gain.


----------



## cel4145

rusta said:


> 1) Have a look at Mayflower electronics - US company cooperating with JDS Labs with significantly lower prices and as well significantly more customising options.




That description is kind of a stretch. Mayflower is more of a DIYer Ebay seller who has his own website and sells from there, too, an electrical engineering student who says he is borrowing his college's equipment to test his products. He's obviously buying the DIY kits and components from JDS Labs, as anyone else can do. 

Not trying to cast doubts on his ability to put together customized ODAC/O2 builds. But Mayflower is a obviously a one man operation who will work for very cheap. A little bit different from JDS Labs, which is a company that not not only has parts manufactured to build the ODAC/O2, but also designs it's own headphone amps. 



rusta said:


> 2) 6.5x is useless, I know it myself, I own a unit with SIP adapters and can choose my gain configuration to whatever value I want anytime.




The O2 amplifier design is available under a Creative Commons Attribution-NoDerivs 3.0 Unported License. So this discussion is moot. It would be illegal and unethical for a company like JDS Labs that designs their products, too, to violate the IP rights of another designer.


----------



## RustA

Quoteosted by *lorriman* /img/forum/go_quote.gif


> The distortion at high gain shouldn't be possible to hear unless you have poor headphones generating their own distortion. As for noise, that will most likely be your source or an inappropriate volume level for a very sensitive headphone.


 
   
  There are several people who reported problems with low-level hiss... Even the author himself speaks about it on the website. O2 is not dead silent unless you use 1x gain, or low sensitivity headphones, in my experience with two different amps.
   
  I hope you won't call HD800, D7000 or LCD-2 "poor" headphones. And still I have heard subtle distortion on higher gain configurations - very subtle but if you want the highest level of transparency, you cannot ignore it. As I said, the cleanest signal with dead-silent background with all headphones (including IEMs) is most probably only possible to achieve with unity gain.
   
  There are other problems with higher gain - low-level channel imbalance, scratchy sound when manipulating with the volume knob... I am not the one who reported this here, other people experienced it and I know what they are talking about since this is not only a case of O2 or DIY stuff. ,-)
   
  But it's up to you, boys, whatever floats your boat... I have my own highly customised unit and I am very happy with the performance. It's still the same neutral FR but with higher level of transparency + other useful features.
   
  Maybe someone will find my contribution useful... But for now, unsubbed.


----------



## lorriman

rusta said:


> There are several people who reported problems with low-level hiss... Even the author himself speaks about it on the website. O2 is not dead silent unless you use 1x gain, or low sensitivity headphones, in my experience with two different amps.




Well, yes you can get hiss, but at absurd volume levels with ultra-sensitive iems. If windows suddenly pinged you, you would end up with no eardrums and possibly no head.



> I hope you won't call HD800, D7000 or LCD-2 "poor" headphones. And still I have heard subtle distortion on higher gain configurations - very subtle but if you want the highest level of transparency, you cannot ignore it. As I said, the cleanest signal with dead-silent background with all headphones (including IEMs) is most probably only possible to achieve with unity gain.




I don't mean to sound arrogant, but you are almost certainly not hearing anything. As you say "very subtle", which is just a side-step from 'expectation bias'. The numbers just don't show any distortion that anyone is going to hear even at max volume before clipping even with the HD800. Unless I'm reading the charts wrong. The designer did a top job, and his choice of default max gain doesn't compromise the audio in any meaningful way. Or perhaps you have a faulty O2. In any case an ABX/DBT is called for to genuinely verify this.



> There are other problems with higher gain - low-level channel imbalance, scratchy sound when manipulating with the volume knob... I am not the one who reported this here, other people experienced it and I know what they are talking about since this is not only a case of O2 or DIY stuff. ,-)




These aren't high gain issues. I have them myself, and they don't affect the actual audio.


----------



## mayflower1

Quote: 





cel4145 said:


> That description is kind of a stretch. Mayflower is more of a DIYer Ebay seller who has his own website and sells from there, too, an electrical engineering student who says he is borrowing his college's equipment to test his products. He's obviously buying the DIY kits and components from JDS Labs, as anyone else can do.
> 
> Not trying to cast doubts on his ability to put together customized ODAC/O2 builds. But Mayflower is a obviously a one man operation who will work for very cheap. A little bit different from JDS Labs, which is a company that not not only has parts manufactured to build the ODAC/O2, but also designs it's own headphone amps.
> The O2 amplifier design is available under a Creative Commons Attribution-NoDerivs 3.0 Unported License. So this discussion is moot. It would be illegal and unethical for a company like JDS Labs that designs their products, too, to violate the IP rights of another designer.


 
   
  This is Tyler, From Mayflower Electronics. I have tried to not have an account on here for a long time, but I must respond to this.
   
  I am not "obviously" a one man operation who will work for cheap. I have employee's on and off depending on the work needed at the time.
   
  I am NOT by any means buying any "kits" from anyone. I buy my components myself from mouser.com. The only thing I buy from JDS is his boards because buying them myself would costs thousands of dollars. I am not "barrowing" anything from my college. When I have a board that needs advanced troubleshooting, I use the scope at my test-bench at school. Please don't assume anything.


----------



## cel4145

mayflower1 said:


> This is Tyler, From Mayflower Electronics. I have tried to not have an account on here for a long time, but I must respond to this.
> 
> I am not "obviously" a one man operation who will work for cheap. I have employee's on and off depending on the work needed at the time.
> 
> I am NOT by any means buying any "kits" from anyone. I buy my components myself from mouser.com. The only thing I buy from JDS is his boards because buying them myself would costs thousands of dollars. I am not "barrowing" anything from my college. When I have a board that needs advanced troubleshooting, I use the scope at my test-bench at school. Please don't assume anything.




My apologies for assuming you were buying equipment from JDS Labs other than the faceplates and boards.

But you do say on your website that you are a college student, that you are the one doing the building, and that you are using your school's equipment, with the implication that you are testing every amp to make sure that it works properly:



> It is really that good! I am a electrical engineering student with access to our lab which has $20k+ worth of equipment which I can use for test and maintaining the quality of each and every amp that I build. I will be building each one by hand and testing them thoroughly.




http://www.mayflowerelectronics.com/products.html

Sounds awfully like a one man operation, and you would be "borrowing" the use of their equipment based on what you have said. You might should also consult your institution's equipment use policies. Typically, they tend to exclude using college resources to support one's private enterprises, but of course your institution could be different. 

So you might want to update your website so that no one assumes the wrong thing :rolleyes:


----------



## mikeaj

It's a very minor and unimportant point, but I don't know why anybody would think that any of the builders are getting kits from JDSLabs or somewhere else.  It'd be cheaper to get the parts from one of the usual sources like Mouser, Digikey, etc.  It's about the same price if buying single-unit quantities, so of course if buying many more than that, you wouldn't be buying kits from somebody else.
   
  I don't really see why the size of the operation is worth noting, either.  Regardless of who's stuffing boards, it's just one guy that designed the thing.  Support can be gotten here or any number of places.  Who cares?
   
   
  That said, getting the boards from a 3rd party indicates that a builder's not making thousands of amps (or judges that the time, upfront investment, etc. are not worth it).  If you got a thousand boards made or so, it could be cheaper than buying them $6 each from JDSLabs.  To a smaller operation, a couple dollars saved per board is maybe not a huge deal when selling amps for $100+.
   
  Now, some of the faceplate options with others' branding on them really do look amateurish.  Actually, the writing style and grammar on the website don't exactly help either.
   
   
  Given the prices, I think more people should be buying from Mayflower.  It's just that JDSLabs already has name recognition and has a first-mover advantage.  They've got to be making around $100 per O2 sold (cost over materials, so not taking into account some maybe ~30 min build time, operational costs, etc.).  In any case, they seem to have secured enough funds to buy Voldemort's personal weapon of choice, a high-end dScope III audio analyzer (pricing something like $10k), according to the JDSLabs blog.  Good for them.


----------



## cel4145

mikeaj said:


> Now, some of the faceplate options with others' branding on them really do look amateurish.  Actually, the writing style and grammar on the website don't exactly help either.
> 
> Given the prices, I think more people should be buying from Mayflower.  It's just that JDSLabs already has name recognition and has a first-mover advantage.  They've got to be making around $100 per O2 sold (cost over materials, so not taking into account some maybe ~30 min build time, operational costs, etc.).  In any case, they seem to have secured enough funds to buy Voldemort's personal weapon of choice, a high-end dScope III audio analyzer (pricing something like $10k), according to the JDSLabs blog.  Good for them.




I will say that I did contact both Mayflower and JDS Labs with questions before buying the ODAC and O2. I was very impressed with the professionalism of JDS Labs' response and how informative it was, and I went with their products. 

I got the JDS Labs ODAC first through Sonic Electronix because JDS Labs was out of stock on their website. When I ordered the O2 directly from JDS Labs, mine didn't work right. I was very happy with how JDS Labs handled the situation. My O2 would only function properly on 9 volt Alkaline batteries. So JDS Labs immediately sent me a new power supply. When that didn't work, they immediately sent me a new O2, with prepaid return shipping label for RMA, no cost to me. And they didn't even charge for the 2nd O2 for crossshipping, as many places will do. Email support was fast (a few hours even at night) and extremely good. They bent over backwards, and I didn't have to ask them for anything. They just did it. 

Some of the best service I've ever had for an online vendor.


----------



## lorriman

mikeaj said:


> It's a very minor and unimportant point, but I don't know why anybody would think that any of the builders are getting kits from JDSLabs or somewhere else.  It'd be cheaper to get the parts from one of the usual sources like Mouser, Digikey, etc.  It's about the same price if buying single-unit quantities, so of course if buying many more than that, you wouldn't be buying kits from somebody else.
> 
> I don't really see why the size of the operation is worth noting, either.  Regardless of who's stuffing boards, it's just one guy that designed the thing.  Support can be gotten here or any number of places.  Who cares?




The posting was in reference to an unrelated issue. It wasn't making a big deal of a small operation or where the parts came from; as far as I could see the poster was merely speculating.


----------



## TheDuke990

Today I got my O2 + ODAC combo and with the low gain setting I'm very impressed but not with the high gain setting.
  The music sounds a litte bit scratchy and distorted while using the high gain settings compared to the low gain setting by listening to the same volume level.
   
  Low gain and maximum level (potentiometer at max level) -> no distortion
  High gain and half level (potentiometer at half level) -> little bit of distortion
   
  Do you picked up the same experiences by comparing the low and high gain settings ?
   
  Headphone was my Beyer 880 (600 Ohm) and the O2 was driven by a power supply.


----------



## RustA

Quote: 





theduke990 said:


> Today I got my O2 + ODAC combo and with the low gain setting I'm very impressed but not with the high gain setting.
> The music sounds a litte bit scratchy and distorted while using the high gain settings compared to the low gain setting by listening to the same volume level.
> 
> Low gain and maximum level (potentiometer at max level) -> no distortion
> ...


 
   
  Yes. With two different combos, definitely... The lower, the better. IMHO


----------



## lorriman

theduke990 said:


> Today I got my O2 + ODAC combo and with the low gain setting I'm very impressed but not with the high gain setting.
> The music sounds a litte bit scratchy and distorted while using the high gain settings compared to the low gain setting by listening to the same volume level.
> 
> Low gain and maximum level (potentiometer at max level) -> no distortion
> ...




The ODAC's lineout is too high for the high gain setting (which is really for low-voltage sources such as ipods) and will clip, which is probably what you're hearing.the ODACi s pumping out plenty of voltage, so you shouldn't need the O2 on anything more than 2.5x unless you bypass the ODAC to play off your ipod.


----------



## adydula

I never use the 6.5x gain with LCD2's, Grados, Audio Technica, AKG's etc and the ODAC...more than enough power to fully drive these cans and or make you loose your hearing over time...
   
  Alex


----------



## cel4145

lorriman said:


> The posting was in reference to an unrelated issue. It wasn't making a big deal of a small operation or where the parts came from; as far as I could see the poster was merely speculating.




Yep. My fault for speculating on that. I was responding to RustA's assertion that Mayflower is a "US company _cooperating_ with JDS Labs."


----------



## TheDuke990

Thanks 
  And yes the low gain setting deliver more than enough power. It was only question whether my O2 is defect or not.


----------



## mikeaj

Quote: 





theduke990 said:


> Thanks
> And yes the low gain setting deliver more than enough power. It was only question whether my O2 is defect or not.


 
   
  The behavior you describe is how the design works.  Some people might call the design defective (I would say: misconfigured), but your particular sample seems to be working to spec, as it should.
   
  With the default gain levels set on the O2 (configurable by swapping a resistor for each of the  L and R channels), the high gain will clip any input of greater than roughly 7V / 6.5 = 1.08V (rms sine wave), where 6.5 is the default high gain, *no matter what the O2's volume knob is set to*.  ODAC line output is around 2V.  If you set full volume in software, you could well surpass 1.08V all the time with the right music.  Solution is to reduce the output level of the DAC or reduce the gain on the O2.
   
  If low gain is good enough for you, then you can just keep using that and ignore the other setting.


----------



## adydula

yup, agree with that one Mike..
   





   
  Alex


----------



## TheDuke990

Thanks again for all the explanations.


----------



## JakeJack_2008

Quote: 





theduke990 said:


> Today I got my O2 + ODAC combo and with the low gain setting I'm very impressed but not with the high gain setting.
> The music sounds a litte bit scratchy and distorted while using the high gain settings compared to the low gain setting by listening to the same volume level.
> 
> Low gain and maximum level (potentiometer at max level) -> no distortion
> ...


 
   
  Yep, the same over here.
  As I mentioned above in this thread, I am using the _unity gain_ (*1x*) on the ODAC 
  with the Beyerdynamic Beyer 880 (*250 Ohm*; 2005 Edition).
  (Last week the standalone ODAC and standalone O2 arrrived from JDS Labs.)
  If it's quiet around me, the volume on the O2 is set at 9 o'clock.
  If my surrondings are not very quiet  I set the volume  at 10 o'clock.
  There's no need for higher gain in  my situation. - In my opinion the O2 is a very powerful amp indeed.
  I've tried higher gain but the sound was not in the same league as when using the _unity _gain.
   
  Also, I am lucky and happy that my new laptop does not cause any USB-related problems. - 
  I am _knocking on wood _and _touching wood _ right now!
  There's no _whining_, etc as some of you _whined _(ha, ha, ...) about.
  So, I don't need a _powered hub, _but I am gonna get it
  just _for  sake of  experimentation/comparison._


----------



## JakeJack_2008

Quote: 





mikeaj said:


> The behavior you describe is how the design works.  Some people might call the design defective (I would say: misconfigured), but your particular sample seems to be working to spec, as it should.
> 
> With the default gain levels set on the O2 (configurable by swapping a resistor for each of the  L and R channels), the high gain will clip any input of greater than roughly 7V / 6.5 = 1.08V (rms sine wave), where 6.5 is the default high gain, *no matter what the O2's volume knob is set to*.  ODAC line output is around 2V.  If you set full volume in software, you could well surpass 1.08V all the time with the right music.  Solution is to reduce the output level of the DAC or reduce the gain on the O2.
> 
> If low gain is good enough for you, then you can just keep using that and ignore the other setting.


 
  This is an uncharted but very interesting territory for me.
   
  Just out of curiosity, how can one
   
   
  Quote: 





> _reduce the output level of the DAC?_


 
   
  I guess that one needs  to be a DIYer or an engineer who knows how to open the ODAC and _to swap some resistors_?
   
  Obviously, in my case I am applying the second solution, namely using the O2's _unity _(1x) gain and it works fabulously.


----------



## mayflower1

Now, some of the faceplate options with others' branding on them really do look amateurish.  Actually, the writing style and grammar on the website don't exactly help either.
   
  - The cost of having my own plates machined, milled and engraved is astronomical, and requires huge bulk orders. Currently, I have my own engraved acrylic front panels that come as stock with my units. I created that entire website, by myself, with the limited tools at hand, I am not a software engineer. Please point out any grammar imperfections on my website.
   
   
   
   
  Quote:


mikeaj said:


> It's a very minor and unimportant point, but I don't know why anybody would think that any of the builders are getting kits from JDSLabs or somewhere else.  It'd be cheaper to get the parts from one of the usual sources like Mouser, Digikey, etc.  It's about the same price if buying single-unit quantities, so of course if buying many more than that, you wouldn't be buying kits from somebody else.
> 
> I don't really see why the size of the operation is worth noting, either.  Regardless of who's stuffing boards, it's just one guy that designed the thing.  Support can be gotten here or any number of places.  Who cares?
> 
> ...


----------



## mikeaj

Quote: 





jakejack_2008 said:


> This is an uncharted but very interesting territory for me.
> 
> Just out of curiosity, how can one
> 
> ...


 
   
  No, that's my bad.  I worded that poorly and confusingly.  I meant to limit the level output from the DAC, which is generally achieved by turning the volume down in software.  In other words, if all sound information is scaled down prior to being sent to the DAC, you'll never reach 0 dBFS (DAC full-scale output), so the output is effectively limited to a smaller range that won't cause clipping later in the signal chain.
   
  I mentioned resistor swapping for the O2, not the ODAC.  You just need to replace two resistors with two others, by desoldering the ones in place and then soldering in the replacements.
   
  Actually though, ODAC output level is configurable, so one could in theory do some resistor swaps for that as well.  The ES9023 DAC chip includes the line driver, and publicly-available information (I think to get more info, you need to be a designer who's using the chip) seems to indicate that the output level can be set with an external resistor value.  That said, changing surface-mount parts like the ODAC has is a whole lot more troublesome than through-hole components like the O2; documentation and calculations for everything are available for the O2, but not at all for the ODAC.  They're much smaller so more difficult to manipulate physically by hand.
   
   
   
   
   


mayflower1 said:


> Now, some of the faceplate options with others' branding on them really do look amateurish.  Actually, the writing style and grammar on the website don't exactly help either.
> 
> - The cost of having my own plates machined, milled and engraved is astronomical, and requires huge bulk orders. Currently, I have my own engraved acrylic front panels that come as stock with my units. I created that entire website, by myself, with the limited tools at hand, I am not a software engineer. Please point out any grammar imperfections on my website.


 
   
   
  Yeah, doing faceplates would be expensive in any kind of smaller quantities.  I didn't suggest that you're doing anything that doesn't make sense.
   
  I'm also more of a technical guy with spotty grammar, but seeing as you asked, I'll try to find a few issues.  I get the feeling like I'm probably making mistakes and putting a huge foot in my own mouth by doing so, but so be it.
   
   
   
  Front page:


> Whatever you are looking for in a hi-fi system; solid state amps to DAC's,  we have it.  ​If you have a question, special request, or would like to get something personalized, head over to the contact page and shoot us a message.​


 
  Shouldn't that be a colon or maybe em dash instead of the semicolon?  The slashes below are obviously intended and okay in that kind of writing.  Apostrophe after an abbreviation like DAC is a style issue gray area, so that's okay.  The second sentence has some bad parallelism, but this is also common in informal writing and speech.
   
  Several pages mention the o2.  NwAvGuy always abbreviates it as O2, so that's what I would use.
   
   
   


> This design was made by nwavguy. It is the most clean and powerful headphone amp you can buy for under $300. If you google the amp or look in the DIY forum, you will find people raving about this headphone amp. It is really that good! I will be building each one by hand and testing them thoroughly. I use DD version op amps and all name brand components which are longer lasting and clean up the signal a bit.


 
   
  >> no caps for nwavguy
  >> no caps for google
  >> what is "the DIY forum" and why are you talking about it?  DIY forums in general?
  >> name brand is a compound adjective, should be name-brand
  >> most styles have a comma before the which, I would think
   
  Again, it's mostly style and not actual mistakes.  It's also mostly just my opinion.


----------



## miceblue

Question for you guys. This is for a personal project outside of audio but it relates to the O2's potentiometer.
   
  From the designer's part list for the O2, it uses an Alps RK09712200MC 10k potentiometer. The project I'm working on uses a regular 'ol 10k trimmer potentiometer, but I would like to put the finished product in a nice JDS Labs aluminum case. Would using the Alps pot instead of the trimmer work as a replacement?
   
  Right now I'm just using one of these really cheap trimmer pots:


----------



## mikeaj

Quote: 





miceblue said:


> Question for you guys. This is for a personal project outside of audio but it relates to the O2's potentiometer.
> 
> From the designer's part list for the O2, it uses an Alps RK09712200MC 10k potentiometer. The project I'm working on uses a regular 'ol 10k trimmer potentiometer, but I would like to put the finished product in a nice JDS Labs aluminum case. Would using the Alps pot instead of the trimmer work as a replacement?
> 
> ...


 
   
  I'm not an experienced DIYer or really work with these things (read: I could well be way wrong), but on first glance there are some apparent differences:
   
  1.  The 3006P there only has a single channel, whereas the RK097 has essentially two potentiometers controlled by a single knob.
  2.  The 3006P has different pin layout and physical knob.
  3.  Just in case you were being very specific with that image, that 202 at the end signifies 2 kohm resistance and you talked about 10 kohm (would be code 103).
  4.  Unless I missed something, 3006P has a linear taper (resistance linear with respect to rotational distance); default O2 option uses a 15A taper for audio that is nonlinear.


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Yeah that's what I found out from the "post pics of your build" thread. I guess I won't use a volume knob-like potentiometer since they're also pretty pricey (for the linear pots).
  Thanks for the info though!


----------



## adydula

This am I was looking for something to do in between cup of Joe 1 and cup of Joe 2 and hanging pictures for my wife and I said " Hey lets clip thos resistors and play with the unity gain setting"...
   
  Voila...
   
  I am listening to the LCD2's and going back anfd forth with unity and 2.5.gain.
   
  With the LCD2's and 2.5x gain the volume control is set to around 11 o'clock and they are getting loud and coming alive...rather nicely.
   
  With unity gain, the volume control is set to around 2-3pm top match the loudness.....
   
  Even with unity gain this amp can drive LCD2's with authority....but I already knew that....
   
  Al Stewarts ...Year of the Cat Album, "One Stage Before...absolutely 3D, liquidy and transparent.....running unity gain off of "pure DC" (that batteries for you in Rio Linda....lol)...
   
  Gosh its really good...
   
  Alex


----------



## RustA

Quote: 





adydula said:


> This am I was looking for something to do in between cup of Joe 1 and cup of Joe 2 and hanging pictures for my wife and I said " Hey lets clip thos resistors and play with the unity gain setting"...
> 
> Voila...
> 
> ...


 
   
  So do you have any preference between 1x and 2.5x gain? I personally prefer 1x gain for the transparency. Higher gain could possible feel more "powerful" but unity gain delivers pure clarity. To my ears, of course.


----------



## shadow419

I can't speak for others, but unity and 3x gain (what I have mine set to) sound the same. The only difference is how far I have to turn the pot to reach desired volume. As long as you're not clipping the input it sounds great. Of course there's some hiss with iems on 3x gain, but I have to have the pot at 2 o'clock+ and that would seriously hurt my ears


----------



## adydula

My ears and my head are telling me the unity gain setting is sooo much better....but I know thats not totally accurate.
   
  I do notice that with unity gain you have to crank the volume knob much farther to get things to liven up so shall we say...
   
  I dont think there is any reason for me to used anything but unity gain with my setup...
   
  I run from a destop pc, usb to the ODAC etc....mostly listen with batteries until I have to charge them up,
   
  I would say that a pair of LCD2's and the O2 and ODAC is pretty much up there with the best....it would be hard for me to imagine anything being an orde of magnitude better than this setup...
   
  And this is not even considering the cost....which we all know it this case is the deal of the century for head amps and dacs....
   
  Alex


----------



## miceblue

Pardon my ignorance, but I've heard it being used here for a while. What is unity gain?


----------



## RustA

Quote: 





miceblue said:


> Pardon my ignorance, but I've heard it being used here for a while. What is unity gain?


 
   
  1x gain.


----------



## RustA

Quote: 





adydula said:


> *My ears and my head are telling me the unity gain setting is sooo much better*....but I know thats not totally accurate.
> 
> I do notice that with unity gain you have to crank the volume knob much farther to get things to liven up so shall we say...
> 
> ...


 
   
  I wouldn't say _sooo much better_... But after testing two different units and different gain configurations, I must say the difference is noticable if you listen carefully. It's really subtle, not something that all the people have to care about but it's there. IMHO.


----------



## tomb

Quote: 





theduke990 said:


> Today I got my O2 + ODAC combo and with the low gain setting I'm very impressed but not with the high gain setting.
> The music sounds a litte bit scratchy and distorted while using the high gain settings compared to the low gain setting by listening to the same volume level.
> 
> Low gain and maximum level (potentiometer at max level) -> no distortion
> ...


 
   
  The Beyer at 600 ohm would cause any inherent gain issues with the O2 to manifest themselves most easily.  From what little I know about it, the design took a departure from accepted headphone amplifier design and placed the volume pot inbetween the gain stage and output buffer.  That means that any input signal beyond a certain voltage will be clipped.  A high-impedance load such as the 600 ohm Beyers will require much more gain than other headphones.  When that gain is dialed-in, if the source is not below a certain voltage, the O2 will clip.
   
  AMB made these same arguments to the designer.  It reduces the applicability of the design in the real world, perhaps in favor of better testing results.  The volume pot after the gain stage may be less noisy than otherwise.  Plus, 600 ohm headphones are not everyday, run-of-the-mill headphones.  So it may have been a design risk worth taking.
   
  Personally, I find it interesting that some are commenting that lower gain settings are in favor of better sound, but this is exactly what one might expect with that kind of design decision (locating the volume pot in-between amplifier stages).  Clipping is not an immediate, "OMG - it sounds bad!" result in every case. Instead, you may have peaks and highs that somehow seem stilted, reduced, distorted, per se, or a sense that something is not quite right with the settings.
  Quote: 





lorriman said:


> The ODAC's lineout is too high for the high gain setting (which is really for low-voltage sources such as ipods) and will clip, which is probably what you're hearing.the ODACi s pumping out plenty of voltage, so you shouldn't need the O2 on anything more than 2.5x unless you bypass the ODAC to play off your ipod.


 
   
  There's no reason an amp can't handle a strong source, unless the attenuation was placed after the gain stage.  Just my personal opinion again, but it seems somewhat ironic to find that a source from a designer may exceed an amp's gain capability that comes from the same designer.
  Quote: 





theduke990 said:


> Thanks
> And yes the low gain setting deliver more than enough power. It was only question whether my O2 is defect or not.


 
   
  Power is not the question.  This is often misunderstood when looking at gain.  A high-gain setting on an amp, or a strong source may seem like there's a lot of power present - simply because things get loud at very low volume-knob-travel settings.  It doesn't mean there's a lot of power at all - things may start clipping at just a little bit further up on the volume knob.  You could easily have ear-splitting volumes at 9 o'clock, but clipping could occur at 9:30 or 10.
  Quote: 





mikeaj said:


> The behavior you describe is how the design works.  Some people might call the design defective (I would say: misconfigured), but your particular sample seems to be working to spec, as it should.
> 
> With the default gain levels set on the O2 (configurable by swapping a resistor for each of the  L and R channels), the high gain will clip any input of greater than roughly 7V / 6.5 = 1.08V (rms sine wave), where 6.5 is the default high gain, *no matter what the O2's volume knob is set to*.  ODAC line output is around 2V.  If you set full volume in software, you could well surpass 1.08V all the time with the right music.  Solution is to reduce the output level of the DAC or reduce the gain on the O2.
> 
> If low gain is good enough for you, then you can just keep using that and ignore the other setting.


 
   
  I wouldn't call the design "defective," either.
	

	
	
		
		

		
		
	


	




  The volume pot was designed to be put in the place in the circuit where it resides.  It was a conscious decision, perhaps interesting in its deviation from accepted practice.  However, there are consequences for that decision.  An advantage is that there is generally less noise when placing the volume in the interstage instead of at the signal input.  The disadvantage has already been mentioned.  One can design to meet measurements to the exclusion of all else, or one can design a product for the best usability. The two goals may not have the same results.  In this case, if a source is a bit stronger or a pair of headphones needs higher gain, the O2 may have trouble without attenuating the signal at some point in the circuit other than the volume pot.
   
  Quote: 





jakejack_2008 said:


> Yep, the same over here.
> As I mentioned above in this thread, I am using the _unity gain_ (*1x*) on the ODAC
> with the Beyerdynamic Beyer 880 (*250 Ohm*; 2005 Edition).
> (Last week the standalone ODAC and standalone O2 arrrived from JDS Labs.)
> ...


 
   
  Again, gain does not mean power.  Just because 10 o'clock on the volume knob is ear-splitting, doesn't mean the amp is not clipping at 10:30 - or even somewhat clipping at 10 o'clock.  You may simply not notice the increased distortion.  Your acknowledgement that unity gain is superior in sound quality may be a confirmation of this.
   
  As for the USB related connections with the ODAC, I was surprised to see the schematic when it was finally released.  There is no power capacitor anywhere on the PCB.  A typical DIY DAC might have 1000uf to 1500uf onboard the PCB somewhere.  There is only a single SMD 22uf capacitor on the 5V USB buss in the ODAC.  It's no wonder it's super-sensitive to USB power fluctuations, laptops, etc., and that a powered-USB hub works wonders.  Yes, I would consider this _a design-flaw._
   
  Quote: 





jakejack_2008 said:


> This is an uncharted but very interesting territory for me.
> 
> Just out of curiosity, how can one
> 
> ...


 
  Same-same as above.  The lower gain perhaps sounds better because of the minute distortions occurring from clipping at higher gain settings.
   
  Just some guesses and observations - I'm not claiming to be an absolute expert.  It just seemed as if you guys needed some possible explanations or elaborations.


----------



## mikeaj

Quote: 





tomb said:


> As for the USB related connections with the ODAC, I was surprised to see the schematic when it was finally released.  There is no power capacitor anywhere on the PCB.  A typical DIY DAC might have 1000uf to 1500uf onboard the PCB somewhere.  There is only a single SMD 22uf capacitor on the 5V USB buss in the ODAC.  It's no wonder it's super-sensitive to USB power fluctuations, laptops, etc., and that a powered-USB hub works wonders.  Yes, I would consider this _a design-flaw._


 
   
  To me this is an interesting point as well.  The designer claims to have tried the ODAC on all sorts of USB sources and had no issues on all of them, yet in the field there are a lot of people who talk about the issues they've had.  Maybe the designer's laptop and other USB sources are too high quality compared to what's out there?  Is that really the explanation we're going with?
   
  As you say, most DIY audio DACs have some significantly larger bulk capacitor somewhere, but the ODAC does not.  Maybe my ignorance in analog electronics is showing, but my interpretation is that the circuit was reasonably optimized.  I mean, a larger cap is worse in some respects than a smaller one (and not just cost and size).  It should be noted the ODAC's a non-DIY design intended to be only SMT, but it's not like it couldn't have larger capacitance somewhere if it were desired or warranted.  There's plenty of spare PCB space, after all.  The power consumption is pretty low, anyhow.  There probably weren't four PCB revisions and supposedly "more than 100 variations of components" tested for no reason, and the 111 dB dynamic range (on at least some USB port...?) using a chip capable of 112 dB didn't happen by accident.  
   
  Has anybody been able to eek out worse than claimed performance out of the ODAC (say by using noisy USB power) and confirmed it?  I'm curious what difference would show up if somebody could capture that on an audio analyzer or scope.


----------



## lorriman

> There's no reason an amp can't handle a strong source, unless the attenuation was placed after the gain stage.  Just my personal opinion again, but it seems somewhat ironic to find that a source from a designer may exceed an amp's gain capability that comes from the same designer.




I think we have to keep in mind that it isn't a commercial design, but rather aimed at the diyaudio crowd who are electronics people. 

In any case, all that anyone needs to know is that one should use low gain to avoid clipping issues unless the volume doesn't go high enough. In neither case will clipping occur. It's such a simple rule that it would justify doing this for a commercial design.


----------



## adydula

Remember this was an experiment in a low cost amp and DAC to prove a point.
   
  It was an objective experiment.
   
  The design goals and their arguments have been posted and discussed in great detail on the designers site and other DIY sites etc...
   
  It was not designed to work with 100% of the cans out there. (the amp part that is)..
   
   
  It is not perfect, but for what it is, it met the design goals and is a very good amp and dac solution that just happens to compete with much pricier
  amps and dacs.
   
  Many of us have used the amp and dac with little or no issues.
   
  I have been in the PC industry in development since PC1 days.
   
  My 2 ODACS have been used with laptops, desktops, DIY systems, etc...I mean a lot of different brands and designs.
   
  Never once have I had any USB issues with enumeration, setup, whining noises, static, yada, yada, yada...it just works.
   
  The ODAC cant control the power fed to it.
   
  If your pc's USB implementation is crap...or you have a zillion things plugged in to the ports, or have it near sources of interference well...
   
  I for one use my stuff in a clean environment, I dont place my stuff next to the microwave oven, or have it near AC line cords...etc
   
  Remember with a little common sense for $99 for a ODAC, and $99 for an amp...you can have world class performance, totally transparent....
   
  and the designer has stated its 'not perfect'....but for me its very, very close....for 98% of the cans out there...
   
  and now back to the music...
   
  All the best Alex
   
  (Note...one of you exerimenters.....tack a cap to the odac and see it it 'fixes' any of your issues with USB?"
  Let us know the results?)..


----------



## RustA

Quote: 





adydula said:


> Remember this was an experiment in a low cost amp and DAC to prove a point.
> 
> It was an objective experiment.
> 
> ...


 
   
  I have an Acer laptop, nothing spectacular in audiophile terms... Haven't experienced any problems with powering ODAC and audible degradation of sound. I guess playbacking in hibernate mode helps (Jplay Mini player) a bit.
   
  However, as I need to purchase an USB hub, I'll get one with dedicated power supply, switch on/off button for each USB port, overload protection etc. I will try to compare whether the performance of ODAC is better or not with the hub. I'll post my opinion here.


----------



## JakeJack_2008

Quote: 





adydula said:


> This am I was looking for something to do in between cup of Joe 1 and cup of Joe 2 and hanging pictures for my wife and I said " Hey lets clip thos resistors and play with the unity gain setting"...
> 
> Voila...
> 
> ...


 
   
  In the above quotation the followig caught my eagle eye:
   
   
  Quote: 





> Even with unity gain this amp can drive LCD2's with *authority*....but I already knew that....


 
   
   
  For comparison, please see this http://www.head-fi.org/t/603728/o2-vs-totl#post_8272835   
  (One can search the 'O2 vs. TOTL' thread for the '_authority_' word.)
   
  Not being an audio _authority _at all, what does  _'authority' _mean in the audio context?
   
  JJ


----------



## adydula

Thanks for the link to this other thread....
   
  Authority to me in the context of the O2 and the stuff I source from and listen to ......means that there isnt anything that I cant hear or experience well with my cans connected to the o2amp and ODAC combo....
   
  The headphones I use to listen with are easily driven to volumes that are very uncomfortable to listen to and would most likely cause hearing loss / damage etc....
   
  Any amp that can drive cans to ear-splitting levels mean that to me...with authority in terms of enough power to excite them well.
   
  But not all amps can do this "well"....ie transparent, noiseless etc..
   
  Alex


----------



## RustA

So I tried to compare quality of playback using my new* USB hub* (50USD) *with a power supply, having only one of 4 USB ports switched on and having two HQ usb cables with ferrite for connections*:
   
*1)* Laptop --- USB ferrite cable --- ODAC
*2)* Laptop --- USB ferrite cable ---- USB hub ---- USB ferrite cable --- ODAC
   
  At first, I compared both setups using *Kmplayer* and two differents songs... I don't use Kmplayer to play music at all, it was just for fun. There was absolutely no difference. The only thing I realised is how much worse music sounds with Kmplayer in comparison to Jplay Mini in hibernate mode - really really bad quality.
   
  After that, I compared both setups using *Jplay Mini in hibernate mode*. With the first song, I couldn't hear any difference. With the second one, I felt that both setups sound virtually the same but I very slightly prefered the first setup (laptop - cable - ODAC). It could very well be placebo but I thought the second song sounded a little bit more distorted. But the difference was extremely small - like 0.05% (subjectively, of course).
   
OUTCOME (IMHO):
   - don't bother with special audiophile USB hubs unless you have some super noisy environment around you
   - get USB ferrite cables (they are very cheap) instead if you want to feel "safe"
   - digital cables do not matter at all unless you have some really bad ones or use very long connections
   - the more direct connection, the better (try to avoid everything redundant in your audio chain, on both software and hardware side)
   
  The end of story.


----------



## tomb

Quote: 





mikeaj said:


> To me this is an interesting point as well.  The designer claims to have tried the ODAC on all sorts of USB sources and had no issues on all of them, yet in the field there are a lot of people who talk about the issues they've had.  Maybe the designer's laptop and other USB sources are too high quality compared to what's out there?  Is that really the explanation we're going with?
> 
> As you say, most DIY audio DACs have some significantly larger bulk capacitor somewhere, but the ODAC does not.  Maybe my ignorance in analog electronics is showing, but my interpretation is that the circuit was reasonably optimized.  I mean, a larger cap is worse in some respects than a smaller one (and not just cost and size).  It should be noted the ODAC's a non-DIY design intended to be only SMT, but it's not like it couldn't have larger capacitance somewhere if it were desired or warranted.  There's plenty of spare PCB space, after all.  The power consumption is pretty low, anyhow.  There probably weren't four PCB revisions and supposedly "more than 100 variations of components" tested for no reason, and the 111 dB dynamic range (on at least some USB port...?) using a chip capable of 112 dB didn't happen by accident.
> 
> Has anybody been able to eek out worse than claimed performance out of the ODAC (say by using noisy USB power) and confirmed it?  I'm curious what difference would show up if somebody could capture that on an audio analyzer or scope.


 
  You ask good questions and I'm not sure I have the answers.  About the only reason the design wouldn't have a power cap is if the current draw was already high.  Then there might be some concern with the inrush current needed to charge the cap.  That could conceivably cause the DAC to get knocked off, too.  From what you say in terms of power consumption, this is not the case, though.
   
  IMHO, a good-sized power cap is cheap insurance for any power problems that could occur on a USB-powered DAC.  The USB-powered DACs that have them are too numerous to mention.  It should be no different than if there were much larger caps than normal in the PC's power supply - or in a separate USB hub.  AFAIK, it would have no effect whatsoever on the DAC's audio performance, but rather increase the usability factor by minimizing power issues. 
   
  As for the SN/dynamic range, that's probably a function of the board layout and judicious selection of parts - particularly with regard to the smaller SMD sizes that result in much smaller trace lengths and less interference.


----------



## dudebrah

Could someone point me to where I could find a good, short M-M 3.5mm cable to connect my separate O2 and ODAC units? Would really appreciate it!!


----------



## adydula

http://www.jdslabs.com/item.php?fetchitem=L2
   
  I have a few of these and they work well
   
  Alex
   
  also: http://www.amazon.com/3-5mm-Stereo-Reinforced-Premium-Quality/dp/B004LGNB0A/ref=sr_1_3?ie=UTF8&qid=1363043982&sr=8-3&keywords=3.5mm+6inch


----------



## adydula

I know of nobody that has actual proof of how detrimental a poor, bad, crappy, dirty, USB power source affects the capabilities of the ODAC.
   
  There are lots of IMHO comments...
   
  Here are the published specs:
   

 Frequency Response: +/- 0.1 dB (10 hz - 19 Khz 24/44)
 THD+N 100 hz 0 dBFS: 0.0029%
 THD+N 20 hz -1 dBFS: 0.003%
 THD+N 10 Khz -1 dBFS: 0.003%
 IMD CCIF 19/20 Khz -3 dBFS: 0.0011%
 IMD SMPTE -1 dBFS: 0.0004%
 Noise A-Weighted dBu 24/44: --102.8 dBu
 Dynamic Range: > 111 dB A-Weighted
 Linearity Error -90 dBFS 24/44: 0.0 dB
 Crosstalk 0 dBFS Line Out 100K: --93.5 dB
 USB Jitter 11025 hz J-test 24/44: Excellent
 Maximum Output Line Out 100K: 2.0 Vrms
 Distortion: < 0.005%
 PCB Dimensions: 49.0 x 58.0 mm
   
  I wish I could post links to the actual discussions about the O2 and ODAC but we cant here.
   
  There is a lot of very good discussion on why and how the ODAC was designed and why certain parts were used and why not others etc...take a good slow read on the March 1 ODAC blog updates on the ODAC. It will hopefully enlighten a lot of us. It did me.
   
  Alex


----------



## dudebrah

Quote: 





adydula said:


> http://www.jdslabs.com/item.php?fetchitem=L2
> 
> I have a few of these and they work well
> 
> ...


 
   
  Thanks! Also http://www.amazon.com/FiiO-L2-3-5mm-Stereo-Cable/dp/B003UCC78I has the FiiO L2 cable for a couple bucks cheaper + free shipping w/Prime.


----------



## chrislangley4253

Quote: 





dudebrah said:


> Could someone point me to where I could find a good, short M-M 3.5mm cable to connect my separate O2 and ODAC units? Would really appreciate it!!


 
  The Fiio L2's and L8's are popular. I have been using a 1ft monoprice premium lately, the fiio's are a bit too flimsy for my liking, doesn't help that one of my L8's was DOA.


----------



## adydula

Testing.....
   

   
   

   
  Always makes me smile...
   
  Alex


----------



## autoteleology

RustA, if you like KMPlayer, try using PotPlayer instead. It's basically just as powerful with a much cleaner and organized interface.
  
   
  Would it be possible on the O2 to, say, swap out the resistors to set different gains, or the opamps for a higher quality piece that can handle higher loads?


----------



## mikeaj

Quote: 





> Originally Posted by *Tus-Chan* /img/forum/go_quote.gif
> 
> [...]
> Would it be possible on the O2 to, say, swap out the resistors to set different gains, or the opamps for a higher quality piece that can handle higher loads?


 
   
  As for swapping resistors for gain, yes, it's described on the designer's blog.  It's just an elementary textbook non-inverting amplifier setup with an op amp, where you're adjusting what's R1 there in the diagram.  Gain is pretty much (1 + R2 / R1).  Remove R1 and it becomes pretty much infinity, so you get 1x gain.  
   
  R2 in the diagram is 1.5 kohm in the O2.
   
  R1 in the diagram corresponds to:
  R17 -> low gain (switch out), L channel
  R19 -> high gain (switch in), L channel
   
  R21 -> low gain (switch out), R channel
  R23 -> high gain (switch in), R channel
   
  They're on the PCB close to the gain switch.  Swap all you please.  Actually, you could install holders that allow you to insert and change resistors without resoldering.  It's kind of a disappointment that the major builders don't offer this by default and send you extra resistors, which would cost under $1.
   
   
   
  You can change the gain-stage op amp, but the fundamental limitation is not being able to handle voltages past some physical (electrical) limit.  They can't output anything past what the power supply voltage is, and then an additional margin due to the workings of the internal electronics, some junction forward voltage drops.  With a different op amp that can swing closer to the rails, you'd be able to handle slightly higher inputs, but not by a lot.  Definitely not near or past 8.5V rms, where the default limit is around 7V rms.
   
  You could raise the power supply rails from say +/- 12V to +/- 15V, which would make a more significant difference, but again, it's not going to be a lot.  And that would cause higher power consumption and heat—default O2 runs pretty cold though.


----------



## autoteleology

What do you think is the highest gain that the O2 can theoretically handle without clipping?


----------



## mikeaj

Quote: 





tus-chan said:


> What do you think is the highest gain that the O2 can theoretically handle without clipping?


 
   
  It's not really theoretical, as it's been tested and confirmed.  Again, check the blog or ask around.
   
  With a little wiggle room depending on exactly what you define as the clipping point, it's about 7 / X, where X is the output level of whatever source you're using, in volts rms (assuming sine wave as usual).  Or roughly 19.8 / Y, where Y is the peak-to-peak output voltage, if you please.  That's on AC power.  On battery, depends on the battery charge level and battery, but expect more like 4.5 / X.
   
  Pretty much the input level multiplied by the gain can't be larger than 7V on AC, 4.5V or so on battery.
   
   
  All the above is what causes the gain stage to clip.  If the output level is very high (this is controlled by the volume control and not related to the gain issue), then output stage could also clip.  Clipping point depends on the headphones impedance.  Unless you listen really really loud, you're probably not going to drive the amp output into clipping for any traditional dynamic transducer headphone and even most of the planar magnetics.


----------



## JakeJack_2008

Quote: 





adydula said:


> My ears and my head are telling me the unity gain setting is sooo much better....but I know thats not totally accurate.
> 
> I do notice that with unity gain you have to crank the volume knob much farther to get things to liven up so shall we say...
> 
> ...


 
   
  Thanx, Alex and others.
   
  I would call it the _steal _of of the century. Just for under $300 the awe-inspiring sound​* *of the​​ODAC and O2.


----------



## autoteleology

> It's not really theoretical, as it's been tested and confirmed.  Again, check the blog or ask around.


 
   
  I'm not saying your advice is theoretical, as you _clearly_ know what you're talking about. I'm confused by more than the basics myself when it comes to electrical engineering. I'm not questioning your knowledge in the slightest. 
	

	
	
		
		

		
			




   
  I was simply asking what the maximum gain I could shoot for was if I decided to do some tweaking of the board.

 Speaking of, I may or may not be selling my custom O2 and ODAC combo, so be sure to check out my listing, especially if you'd like a version that could be proudly displayed on a desk.
   
  http://www.head-fi.org/t/655211/custom-built-o2-odac-combo-fiio-cable-extendable-usb-cable-and-triad-wall-wart-included


----------



## mikeaj

Quote: 





tus-chan said:


> I'm not saying your advice is theoretical, as you _clearly_ know what you're talking about. I'm confused by more than the basics myself when it comes to electrical engineering. I'm not questioning your knowledge in the slightest.


 
   
  Oh np I didn't interpret it like that (though you'd be surprised how much people like me don't really know).  I was just making a distinction between the kinds of information or statements people throw out there.  Sometimes people are just speculating based on theory.  Sometimes people do calculations or run simulations based on certain models and assumptions.  You could call statements or conclusions from these things "theoretical" I guess, with the implication that maybe it's not certain or known for sure.  When you're talking about a system that's been built and tested and measured to perform as expected and that agrees with well-established and textbook theory, then "theoretical" maybe has the wrong connotation.
   
   
  So with ODAC as source, ~3.5x gain max (use standard resistor value of ~620 ohms), probably, assuming you're making full use of its output.  Good luck on the sale.


----------



## RustA

Maybe someone could be interested in purchasing great DESKTOP O2/ODAC combo (1/4 headphone out, RCA outputs etc.)... 
	

	
	
		
		

		
		
	


	



   
  http://www.head-fi.org/t/656371/unique-o2-odac-desktop-combo-for-sale


----------



## miceblue

Quote: 





rusta said:


> Maybe someone could be interested in purchasing great DESKTOP O2/ODAC combo (1/4 headphone out, RCA outputs etc.)...
> 
> 
> 
> ...


 
  This has been kind of bugging me for a while (not just to pick on you, but in general):
  Quote: 





> As for the sound, this unit sounds a bit more transparent


 
   
  How does one define what transparent "sounds like"? The O2 was designed to "sound transparent", so how can one justify something "sounds more transparent" and how can one actually actually confirm this? The designer of the O2 says it's transparent, but how does he know? I have heard multiple people say a Leckerton amp sounds more detailed than the O2; does this mean it's more coloured than the O2?


----------



## SunshineReggae

Quote: 





miceblue said:


> This has been kind of bugging me for a while (not just to pick on you, but in general):
> 
> How does one define what transparent "sounds like"? The O2 was designed to "sound transparent", so how can one justify something "sounds more transparent" and how can one actually actually confirm this? The designer of the O2 says it's transparent, but how does he know? I have heard multiple people say a Leckerton amp sounds more detailed than the O2; does this mean it's more coloured than the O2?


 

 The last part means nothing, unless it can be demonstrated in double blind tests. Even then, it has yet to be ascertained whether it's actually an increase of detail you'd be talking about, or just more treble (or whatever).
   
  The reason amps can be 'transparent' (which is not the same as 'transparent sounding', which is total nonsense because nobody knows what that even means) is because amping a signal is a science. If an amp measures well, it will perform accordingly. If it measures worse, it will sound different. The problem is that some people may feel that it sounds 'better' when it technically performs worse. At that point all bets are off and even the most badly designed amp can be conceivably sold. Another problem with audio is that impressions can hardly be verified, so even the most objective listener will be exposed to his own subjective preferences when evaluating gear.
   
  All of that does not take anything away from the fact that amping is a science and that scientifically and technically, you can build an amp that objectively performs as well as possible when it comes to sound quality. Contrary to popular belief on headfi, an amp is not able to do anything magical that goes beyond measurements. It can not magically alter the amount of detail that is heard beyond what measurements account for. It can not be made to sound warmer or colder beyond making adjustments to frequency response (which is undesirable and I don't personally know any amps that shoot for strange deviations but I'm sure they're out there) or accounting for impedance mismatches. Likewise for soundstage, etc. The mistake that is often made is that people seem to think an amp is a way to beautify the sound, while in fact all it's supposed to do is to carry out the technical task of amping the signal. It's not even able to 'improve' the sound; all it can do is deviate from good to great measurements negatively and have people experience that as an improvement. It's comparable to brushing your teeth: You can do it with a super expensive brush or with a wooden one, but at the end of the day the ultimate performance would be to get rid of all the plaque. If the wooden one can do it as well as the super expensive one, they're both equal when it comes to the end result. Such is the case with amping as well, except that it just so happens to be that amping has been figured out and can be had for cheap. That is to say, the super expensive high tech brush can be bought for about a hundred bucks in the shape of a fiio e9k.
  What remains are bad amps, exoticly designed amps and super expensive amps, that have you believe some magic is going inside that somehow manages to re-invent the wheel of amping. Newsflash: if there really was some kind of added functionality that improves sound quality that you can find in a kilobuck tube audio product, it would be the number one thing to sell the product with. Just the fact that that doesn't happen, should tell you plenty.
   
  The belief is also that anything that's proven to measure well "only cares about measurements but not about sounding good" and "is analytical and cold sounding". Just in the last month I have seen amps/DACs such as the Benchmark and O2 been accused of such multiple times, ofcourse without so much as a word on double blind testing.
   
  TLDR amping can be transparent because there are scientific goals set for it. When the amp achieves those goals - which is a very, very realistic possiblity - the amp can be considered transparent because it does nothing besides carrying out the scientific task of amplification, with errors only beyond human hearing (which is part of its technical purpose).


----------



## miceblue

Quote: 





sunshinereggae said:


> Quote:
> 
> 
> 
> ...


 
  Hm thanks for the insight. That seems to make sense for the most part.
  I asked because a lot of gear measures quite well (the newest iDevices for example), yet they all sound a little different.
   
  The new JDS Labs C5 amp definitely has a smaller, more closed-in-sounding soundstage compared next to the O2 with some rough volume-matching, yet they both have the same THD+N measurements.


----------



## autoteleology

Headphone measurements are, as of today's methods and technology, a very inaccurate science due to the massive amount of variables that need to be taken into account including head size, headphone positioning, various volumes, integration of equal loudness contours, etc. etc. (but very precise as long as you stay within the boundaries of one site). Amp/DAC measurements, however, should theoretically be an exact science because all you need to do is measure the output with a wire and a dummy load on the component.


----------



## Deni5

Quote: 





miceblue said:


> This has been kind of bugging me for a while (not just to pick on you, but in general):
> 
> How does one define what transparent "sounds like"? The O2 was designed to "sound transparent", so how can one justify something "sounds more transparent" and how can one actually actually confirm this? The designer of the O2 says it's transparent, but how does he know? I have heard multiple people say a Leckerton amp sounds more detailed than the O2; does this mean it's more coloured than the O2?


 
   
  The reference for O2 supposedly was the headphone output of the Benchmark DAC1 and since many highly regarded audio newspapers and so on consider Benchmark DAC1 very transparent if you could not tell apart the O2 from the DAC1 in a blind test then you could say it is "as" transparent.
   
  Imo I hear more differences from different DAC than differences from different amps. Ok, if something is badly designed so it has high distortion in an amp you should be able to hear that as some difference (warmer, less detail), but if something measures good then it's really hard to tell apart (maybe studio professionals can - you have to know what to look for and have a reference).
   
  The term "detailed" is a little vague. I think most relate detail to treble, but I mean even bass can be detailed (but maybe it's a little harder to tell) - so for the Leckerton being more detailed I don't know. I have UHA-6S mkii and I like it very much. Yes it is detailed but more detailed than my O2, I don't know. To me they sound alike and both are very good.
   
  Regarding amp coloration: I think it's there. I can hear that a Fiio E11 sounds a little warmer and is not as detailed in bass, treble and so on. Tube amps is a whole different story to me. I enjoy its sound a lot but it's a sound that is tampered with in different ways - like changing tubes sounds like changing different EQ's to me. Still it's fun to find a match that suits you, because everyone has a different taste in sound signature.
   
  After awhile when I got the O2 I found that SS amps are the way to go for me. I like the whole picture better than the refined picture. Of course there are advantages and disadvantages depending mostly on what type of music you listen to. I find that SS amps suits me better as I like many different music genres.
   
  I know people talk about dry sound, lush sound, liquid sound and so on. I'm having a little trouble to relate to these terms - I'm starting to know what it's about. I think it shows more in the higher price chain. I'm getting a Vioelectric HPA V100 in the near future so it will be interesting to hear what that has to offer in comparison.


----------



## autoteleology

> IMO I hear more differences from different DAC than differences from different amps.


 
   
  There's a huge difference between a low-fi and mid-fi DAC, for sure; however, I remain unconvinced that there is very much, if any, difference between a mid-fi and a hi-fi DAC. I was unable to tell the difference between the PerfectWave DAC II ($4,000) and the ODAC ($150) under meet conditions with a switch time of half a second.


----------



## miceblue

Quote: 





tus-chan said:


> > IMO I hear more differences from different DAC than differences from different amps.
> 
> 
> 
> ...


 
  I've tried the Asgard/Lyr combo at a meet and I actually thought it sounded worse than the O2/ODAC combo with my own audio CD. Instruments seemed a bit more blurry/less defined, bass seemed more present, details from the treble(?) weren't as apparent...
   
  Yet that Schiit combo is quite popular here.
   
  Clarification: I'm not to say the Schiit combo sound bad, I was just stating my own brief personal experiences with the K 701 at a local meet


----------



## mikeaj

With respect to amps, it's conceptually not that complicated.  There's an input signal and and output signal.  If there's no difference between the input and output (impossible, as there's always some noise, distortion, etc.), the amplifier hasn't changed anything—other than scaling everything up or down, which just changes the volume—and it's is delivering that exact input signal to the headphones.  Some people would call that transparent, whatever that means.
   
  So nothing's perfect, but how about really close (defined and measured in what ways)?  After all, human aural acuity is not infinite.  If you get close enough, that might be called transparent too.  At a certain point, there might be nobody in the world that could reliably distinguish two things that are similar enough, be it sounds or images or whatever else.  Based on the reading of previous psychoacoustics research, the O2 designer came up with some measurable design parameters that an amp should exceed, in order to be close enough, that it should sound transparent, and then built something to meet those criteria.  That's the kind of process that many audio designers take, though not many others.  On the other hand, some people claim that there are issues with the psychoacoustics research and boundaries, or they claim that certain proper measurements were not taken or considered, or they argue that A and B and C and D are each insignificant on their own but potentially audible when combined, or they claim that amps have properties that can't be measured at all.
   
  It depends on the headphones you're using, but there are plenty of ways that amplifiers might change the sound a little.  Quoted measurements can be very incomplete.  Just because THD+N is similar with 150 ohms at a certain output level doesn't mean it's similar driving 32 ohms, for example.  Or that the noise level is similar (it's not), as the HD part is dominating the N part of the measurement.  A slight difference in output impedance could make certain particular IEMs sound a bit different.  There might be a different amount of channel imbalance at different rotations of the volume pot.  And so on.
   
   
  The big issue is that everybody's perception of sound is filtered by the brain.  What you perceive depends on a whole lot other than just the sound coming into your ear, such as the way you're listening, your mood, and preconceptions and expectations, etc.  It's unavoidable, no matter what the listener tries to do.  That's not to even mention any very slight differences between how headphones are positioned on the head between one listen and another, and other such environmental factors—which often seem to have a greater impact on frequency response and other measurables, than the differences between certain amps.
   
  Some people perceive differences in the sound between different devices (of course, between listening to device X and device Y, as alluded to above, that is not the only variable that's changed), so that's they way they describe it.  But it's always possible that the differences are due to these other factors and not actually the sound produced, so other people claim it's not real, just in their heads.


----------



## miceblue

Quote: 





mikeaj said:


> With respect to amps, it's conceptually not that complicated.  There's an input signal and and output signal.  If there's no difference between the input and output (impossible, as there's always some noise, distortion, etc.), the amplifier hasn't changed anything—other than scaling everything up or down, which just changes the volume—and it's is delivering that exact input signal to the headphones.  Some people would call that transparent, whatever that means.
> 
> So nothing's perfect, but how about really close (defined and measured in what ways)?  After all, human aural acuity is not infinite.  If you get close enough, that might be called transparent too.  At a certain point, there might be nobody in the world that could reliably distinguish two things that are similar enough, be it sounds or images or whatever else.  Based on the reading of previous psychoacoustics research, the O2 designer came up with some measurable design parameters that an amp should exceed, in order to be close enough, that it should sound transparent, and then built something to meet those criteria.  That's the kind of process that many audio designers take, though not many others.  On the other hand, some people claim that there are issues with the psychoacoustics research and boundaries, or they claim that certain proper measurements were not taken or considered, or they argue that A and B and C and D are each insignificant on their own but potentially audible when combined, or they claim that amps have properties that can't be measured at all.
> 
> ...


 
  You bring up some very good points there; thank you for the explanation.
   
  You mention measurements often being incomplete, I think the same can be said for the O2 and ODAC as well. The designer of the Objective gear only did so many tests too.
  I brought up Leckerton in a previous post because I think it was Currawong(?) who said that the O2 may sound good, but it may have a non-linear response in certain cases....I can't completely remember what was said. I recently came upon this website with different measurements between a Leckerton amp and the O2 and from those specific measurements, the Leckerton performed better objectively than the O2. Would this non-linearity be a reason why some people say the Leckerton sounds "more detailed" than the O2?


----------



## Deni5

Quote: 





tus-chan said:


> There's a huge difference between a low-fi and mid-fi DAC, for sure; however, I remain unconvinced that there is very much, if any, difference between a mid-fi and a hi-fi DAC. I was unable to tell the difference between the PerfectWave DAC II ($4,000) and the ODAC ($150) under meet conditions with a switch time of half a second.


 
   
  I find it a little strange that people are changing amps more often than changing dac's (or so it can sometime seem when reading). Most of the times the dacs in computers and mobilephones aren't a optimal solution (to cut down total cost some parts have to be cheaper).
   
  Anyway I find the ODAC really good. I find differences comparing to my Dacport LX and Meridian Explorer. But I would say not better differences.


----------



## miceblue

Quote: 





deni5 said:


> Quote:
> 
> 
> 
> ...


 
  I read Tyll's article on Innerfidelity about the Meridian Explorer. Do you have the first version, with the high output impedance?


----------



## Deni5

Quote: 





miceblue said:


> I read Tyll's article on Innerfidelity about the Meridian Explorer. Do you have the first version, with the high output impedance?


 
   
  Yes, I do. But I'm not using the headphone out at all. I use the line out to an external amp (O2 or UHA-6S mkii) so no issues at all in that configuration.


----------



## autoteleology

There is one thing about amp/DAC comparisons that annoys me whenever it is mentioned: soundstage. An amplifier or a DAC should not_* *_change soundstage because soundstage, as far as I know, is defined by two things:
  

 size/distance/direction of drivers
 stereo mixing channel imbalance (cymbal is 75% louder in right than in left ear = soundstaged towards right)
   
  If you're driving your headphones correctly and you've got the volume matched, there shouldn't be any difference.


----------



## miceblue

Quote: 





tus-chan said:


> There is one thing about amp/DAC comparisons that annoys me whenever it is mentioned: soundstage. An amplifier or a DAC should not_* *_change soundstage because soundstage, as far as I know, is defined by two things:
> 
> 
> size/distance/direction of drivers
> ...


 
  It's possible. Perhaps our definition of soundstage is different?
  From Stereophile:
  Quote: 





> _soundstaging, soundstage presentation_ The accuracy with which a reproducing system conveys audible information about the size, shape, and acoustical characteristics of the original recording space and the placement of the performers within it.


 
  Of course accuracy is pretty irrelevant, at least from my understanding, unless you know exactly how the recording was put together or the way the instruments were arranged.
   
  I've tried using a 1 kHz file produced from Audacity to volume match 2 amps by-ear (I know it's not the most accurate way to do it, but it's the best I have access to at home)
  I've played the same loop of music through my setups: MacBook Pro -> Audirvana Plus -> ODAC -> amp -> headphone
  I've used the same interconnect cable to switch from amp to amp
  I've used the same headphone in the same position on my head from amp to amp
  Switching times were less than a second
   
  From my testings, I could hear a pretty evident difference in the way the instruments are spread-out in my head between the JDS Labs C5 and the O2. The two points you mention are irrelevant with the setup. I could try a more scientific method of volume matching with a pretty beefy multimeter at school, but from the many tests I've done, I think my observations would remain the same.
   
  Apart from my own personal testing, wouldn't different amounts of distortion, or measurement differences in general, affect how the output sounds anyway?
  And I bring this up again, what measurement accounts for the soundstage? I find the O2 to have a pretty wide soundstage compared to other amps I've tried in my rather limited list.


----------



## autoteleology

Describe the differences you heard.


----------



## mikeaj

Quote: 





miceblue said:


> You bring up some very good points there; thank you for the explanation.
> 
> You mention measurements often being incomplete, I think the same can be said for the O2 and ODAC as well. The designer of the Objective gear only did so many tests too.
> I brought up Leckerton in a previous post because I think it was Currawong(?) who said that the O2 may sound good, but it may have a non-linear response in certain cases....I can't completely remember what was said. I recently came upon this website with different measurements between a Leckerton amp and the O2 and from those specific measurements, the Leckerton performed better objectively than the O2. Would this non-linearity be a reason why some people say the Leckerton sounds "more detailed" than the O2?


 
   
  For a perfectly ideal linear system (and time invariant) one perfect measurement is sufficient.  For everything in the real world, you need more if you want a better characterization.  So yeah, we've seen a lot on the O2 from the designer and others but not everything (can't get everything), and we've seen just some on the ODAC.  However, the more well-behaved something is and closer to ideal, the closer the output would be to a completely known and predictable response, so I wouldn't expect huge surprises lurking if you were to somehow test some different signal or some other reasonable audio input and setup.
   
  An unevenness in frequency response is not a nonlinearity, by the technical meaning of the word, by the way, but I see what you mean.
   
  Note that the difference in frequency response as measured for that test is pretty much entirely a direct consequence of the slightly higher output impedance.  With pretty much anything other than a certain IEM with a really wild impedance curve, it would be much much flatter (and even considering extreme cases like these, do fraction of a dB differences really have much impact on the sound?  Discernible and shouldn't be trivialized, but put it in perspective.).  Many or most people talking about the different amps probably aren't using those exact IEMs; you'd see something else with some other IEMs or headphones.
   
  Even if you were to assume that everybody comparing were using an IEM like that, an FR difference like that is unlikely to make people think one device is more detailed than another.
   
   
   
  As I mentioned before, you can find differences with some bench measurements, but do they really correspond to what people say they hear?


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Hm, that's true....:thinking-smile:
   
  Quote: 





tus-chan said:


> Describe the differences you heard.


 
  From the tests I just did, the instruments sound a little more spread apart in my head on the O2 compared to the C5 and they have better definition. I find that the C5's imaging is a bit more towards the center, which would be better "synergy" for the K 701 since I find the K 701's center imaging a bit left out (subjective stuff yeah). The difference isn't huge, but it's noticeable to me with the K 701 and might be a reason why I tend to use the C5 at home with the K 701 over the O2 (not to say the O2 sounds bad, but just a personal preference).
  I might try this test at school with multimeter volume-matching for a more accurate test.
   
   
  Is there a relatively inexpensive way to get more accurate in-person testing results? I feel like there's a better way to do these tests without having to constantly switch cables, pause/play music, etc. *this part should probably be in the Sound Science threads, but we're kind of on the topic anyway*


----------



## autoteleology

Are you sure it's just not a stronger amplification? The K/Q701 is pretty notoriously annoying to drive for a low impedance dynamic, and I know this because I used to own it.

 As for being able to switch between the amplifiers with little delay, find a cable or device that lets you connect the outputs of both amps to one input to the headphones, without summing to mono.


----------



## miceblue

Quote: 





tus-chan said:


> Are you sure it's just not a stronger amplification? The K/Q701 is pretty notoriously annoying to drive for a low impedance dynamic, and I know this because I used to own it.
> 
> As for being able to switch between the amplifiers with little delay, find a cable or device that lets you connect the outputs of both amps to one input to the headphones, without summing to mono.


 
  I could try it with the M-100 at a later time [probably tomorrow].
   
  Likewise, I could try it with the V-MODA SharePlay cable, maybe?


----------



## cheuh

Hey guys, I'm using a pair of Beyerdynamic DT880 600 ohms with a custom made O2 that I purchased. My source is an Asus Xonar DX sound card and computer volume at 100%. My problem is I can only get normal volume listening levels on low gain(I usually listen to them at 3  o'clock on the volume knob... but I can easily turn it to max and it's not ear deafening levels at all). I would like some extra headroom on the volume pot. On high gain, I notice there is a lot of distortion/crackling noises (it's really noticeable in deep sub bass frequencies)... is this what you call clipping? So my question is can I get these DT880's to play a lot louder without getting any distortions in high gain?


----------



## mikeaj

Quote: 





cheuh said:


> Hey guys, I'm using a pair of Beyerdynamic DT880 600 ohms with a custom made O2 that I purchased. My source is a Xonar DX sound card and computer volume is at 100%. My problem is I can only get normal volume listening levels on low gain(I usually listen to them at 3  o'clock on the volume knob... but I can easily turn it to max and it's not ear deafening levels at all). I would like some extra headroom on the volume pot. On high gain, I notice there is a lot of distortion/crackling noises... is this what you call clipping? So my question is can I get these DT880's to play a lot louder without getting any distortions in high gain?


 
   
  Full-scale output is supposedly 2V rms on the DX, so ideally you'd want a gain of 3.5x.  Actually, default low gain is 2.5x; the amp really isn't capable of all that much more than the max of what you get on low gain, with a source at around Redbook 2V level.  In that case, yeah, high gain would cause clipping.
   
  I guess it's a matter of perspective, what you consider normal, etc.  Some people say they get about normal levels out of an iPod, with 600 ohms Beyers (but not loud levels).
   
  So by either changing the gain by swapping resistors internally, or setting high gain + turning volume down in software to the point where you don't get clipping, you could get say 2.9 dB more than what you're getting at low gain, if the DX really goes to 2V.  You could confirm with say a multimeter and a quick measurement.
   
   
  You know, if low gain is default 2.5x and DX outputs 2V and you're reaching that (no volume turned down somewhere in software), you're getting 5V rms out max on low gain.  You might need to go to a different price tier to find amps that can output a lot more than that.  O2, FiiO E9, some others top out at around 7V, which is 2.9 dB more.  Schiit Magni supposedly does say 8.8V at most, or 4.9 dB over your current setup with O2 on low gain.
   
  I mean, around 10 dB extra is considered perceptually around twice as loud.  To get 10 dB more, you'd be looking at a pretty powerful amp, looking for about 16V rms output, or a huge 416 mW into 600 ohms.  On the other hand, this is already really really loud, at least for most people, and relative to levels that cause hearing damage.  Actually, those kinds of levels can damage the headphones too.  They're rated for 100 mW nominal.
   
   
  So, actually, because this is so loud, maybe you should double-check the output levels you're getting.


----------



## cheuh

Quote: 





mikeaj said:


> Full-scale output is supposedly 2V rms on the DX, so ideally you'd want a gain of 3.5x.  Actually, default low gain is 2.5x; the amp really isn't capable of all that much more than the max of what you get on low gain, with a source at around Redbook 2V level.  In that case, yeah, high gain would cause clipping.
> 
> I guess it's a matter of perspective, what you consider normal, etc.  Some people say they get about normal levels out of an iPod, with 600 ohms Beyers (but not loud levels).
> 
> ...


 
   
  Thanks for that info. I might have to lower the software volume then. Would lowering the Windows volume cause signal degradation? I've read somewhere that it should be kept at 100%?


----------



## miceblue

Quote: 





tus-chan said:


> Are you sure it's just not a stronger amplification? The K/Q701 is pretty notoriously annoying to drive for a low impedance dynamic, and I know this because I used to own it.
> 
> As for being able to switch between the amplifiers with little delay, find a cable or device that lets you connect the outputs of both amps to one input to the headphones, without summing to mono.


 
  Quote: 





miceblue said:


> Quote:
> 
> 
> 
> ...


 
   
  I said I would try it tomorrow, but I just couldn't wait because I'm curious myself to know if it's due to the headphones, hahaha.
  Anyhow, stereo and binaural tracks, 1 kHz rough volume-matching, V-MODA M-100, manual cable switching (SharePlay cable splitter didn't work too well).
   
  I can still perceive similar things with the M-100 as the K 701. C5's L/R placement of instruments in my head seem closer towards the center than the O2. Maybe closer isn't the right word and it's confusing to you guys. C5 seems more diagonally placed from my head (narrower), where as the O2 seems more horizontally placed from my head (wider). O2 has better "synergy" with the M-100 in this sense, opposite of the K 701, since the M-100's soundstage always seemed fairly cramped in width.
   
  Since I usually don't listen to the M-100's at home, I kind of forgot how it sounds for home use. Eh....totally different from the 701's. XD
   
*Tus-Chan*, you mention that the amp shouldn't affect the soundstage. Do you think what I'm perceiving as the soundstage is really different colourations of the frequency response somehow (even though the C5 measures flat according to JDS Lab's measurements)?


----------



## miceblue

Quote: 





cheuh said:


> Quote:
> 
> 
> 
> ...


 
  If you're using Vista (maybe it's 7) and above, the software shouldn't degrade the signal from what I recall.
http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/
  Quote: 





> The Vista/Win7 audio engine automatically* feeds your sound card with the highest-quality output stream that it can handle*, which is usually 24 bits per sample. Perhaps you’re wondering why you should care, given that most music uses only 16 bits per sample. Suppose you’re playing a 16-bit song with a digital volume control set to 10%. This corresponds to dividing each sample by 10. Now let’s assume the song contains the following two adjacent samples: 41 and 48. In an ideal world, after the volume control we would get 4.1 and 4.8. However, if the output stream has a 16-bit depth just like the input stream, then both output samples will have to be truncated to 4. There is now no difference between the two samples, which means we have lost some resolution. But if we can have an output stream with 24 bits per sample, for each 16-bit level we get 28 = 256 additional (“fractional”) levels, so we can still preserve the difference between the two attenuated samples. In fact, we can have ≈4.1016 and ≈4.8008, which is within 0.04% of the “ideal” samples of 4.1 and 4.8.


----------



## adamlr

Quote: 





mikeaj said:


> Full-scale output is supposedly 2V rms on the DX, so ideally you'd want a gain of 3.5x.  Actually, default low gain is 2.5x; the amp really isn't capable of all that much more than the max of what you get on low gain, with a source at around Redbook 2V level.  In that case, yeah, high gain would cause clipping.
> 
> I guess it's a matter of perspective, what you consider normal, etc.  Some people say they get about normal levels out of an iPod, with 600 ohms Beyers (but not loud levels).
> 
> ...


 
   
  one day ill be able to make such calculation too 
	

	
	
		
		

		
			




   
   
  Quote: 





cheuh said:


> Would lowering the Windows volume cause signal degradation? I've read somewhere that it should be kept at 100%?


 

 if you scroll back a few pages on the thread, youll see a whole discussion on this. to sum it up quickly:
  - as miceblue said:
   
  Quote: 





miceblue said:


> If you're using Vista (maybe it's 7) and above, the software shouldn't degrade the signal from what I recall.
> http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/


 
  - if you set your dac to output 24 bits, while playing 16 bit audio, you're "adding fake bits" which will be lost in the digital volume lowering, minimizing degradation to the signal.
  - this is probably irrelevant, as you (or atleast i, and a few others) wont notice any degradation unless you reach about 9 bits, which is unlikely unless your lowering alot of digital volume.
  - ofcourse, ymmv and it all depends on your setup. everything is specific to your gear.


----------



## SunshineReggae

Quote: 





miceblue said:


> *Tus-Chan*, you mention that the amp shouldn't affect the soundstage. Do you think what I'm perceiving as the soundstage is really different colourations of the frequency response somehow (even though the C5 measures flat according to JDS Lab's measurements)?


 
   
  An amp shouldn't negatively impact the soundstage, but it could; it processes the entire audio signal so theoretically it could do almost anything to it. What isn't possible however is for an amp to improve the soundstage beyond what a headphone is capable of. It's safe to say that any amp that measures well, will allow for the full soundstage as brought forth by the transducer. The idea for instance that tube amps create a bigger soundstage than solid state amps because they are tube amps, makes no sense. Likewise, if some person says they felt the soundstage increasing when they were tube rolling, is no evidence of anything other than the problems of tube amps and the caveats of human perception.
   
  Ofcourse, perceived soundstage is different; there's a huge amount of uncertainty and unpredictability involved there. The trick being ofcourse that even an amp that theoretically does not alter soundstage, might still be perceived to offer a smaller soundstage than an amp that actually diminishes it; when human perception enters the picture, things go unreliable and uncertain fast.


----------



## Lord Voldemort

Haven't been on head-fi for a while... 960 posts since I left this thread. Time to get out my reading glasses.


----------



## mikeaj

Quote: 





miceblue said:


> If you're using Vista (maybe it's 7) and above, the software shouldn't degrade the signal from what I recall.
> http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/


 
   
  The software audio stack wouldn't be mangling your audio, but we're all still using real-world hardware aren't noiseless, aren't perfect.  Reduce the output levels, and if the noise levels aren't reduced by the same factor, then you've effectively reduced the SNR.  (depending, quite possibly not by an _audible_ amount or by any difference worth caring about, but still)


----------



## lorriman

mikeaj said:


> As I mentioned before, you can find differences with some bench measurements, but do they really correspond to what people say they hear?




I noticed a significant difference between my clip+ and O2/ODAC soundstage: the clip+ almost as if it had crossfeed in comparison. I was really quite surprised. The difference in the measurements was 65db crosstalk vs 50db. That 15db is audible to me. Certianly, if I were buying a new DAC or recommending one, I would be careful tomake sure it were -65db on crosstalk.

It so happens that even prior to this that I would switch on the rockbox "stereo width" feature to get better soundstage whereas I rarely come across music that needs it when I play CDs off my laptop through the O2/ODAC (which I often do as it happens, since I am working my way through my flatmate's 1000 CD alternative collection; it's better than spotify, I'm so fortunate).

It's surprising to me that miceblue can hear a narrower soundstage on his C5 when it measures about the same as the O2.


----------



## lorriman

miceblue said:


> Hm, that's true....:thinking-smile:
> I might try this test at school with multimeter volume-matching for a more accurate test.
> 
> 
> Is there a relatively inexpensive way to get more accurate in-person testing results? I feel like there's a better way to do these tests without having to constantly switch cables, pause/play music, etc. *this part should probably be in the Sound Science threads, but we're kind of on the topic anyway*




Make sure to play a 60Hz sound file as multmeters don't work well with anything other than that (according to the O2 designer on how to test for output impedance).

I believe there is some gadget for doing blind testing using two devices and the same headphone. Maybe someone can tell us more.


----------



## lorriman

cheuh said:


> Thanks for that info. I might have to lower the software volume then. Would lowering the Windows volume cause signal degradation? I've read somewhere that it should be kept at 100%?





miceblue said:


> If you're using Vista (maybe it's 7) and above, the software shouldn't degrade the signal from what I recall.
> http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/




Quoting the others'



> The Vista/Win7 audio engine automatically feeds your sound card with the highest-quality output stream that it can handle, which is usually 24 bits per sample.


​
I found that my Vista computer automatically set the ODAC as 16bit?!?! I didn't discover this for a while. I've also understood that the Vista/win7+ audio engine processes everything internally at 32bit, so even 16 bit may not be affected for volume control purposes, but which XP definitely is. However, that quoted text does suggest to me that there could still be an undesirable degradation at 16bit output even if Vista is processing at 32bit, so to be on the safe side set the card to 24bit. Don't be tempted to set it to 96Khz, though. If you do then play a 60Hz test tone at high volume: you will likely hear high frequency artifacts. I can hear them with the ODAC. 24bit/44 for music, and 48 for DVD is best (although downsampling may be good enough these days).


----------



## mikeaj

That's cheap multimeters.  Certainly people test signals outside of mains frequencies, when using multimeters in a lab or something more serious.  But if in doubt of your multimeter's capabilities, use 60 Hz if you can, because even the cheapest ones should be fine with that.  It's the most basic expectation and usage for a user.
   
  If you're referencing O2 and Clip+ crosstalk measurements, note the load impedance, as it can well be different for different loads.  The crosstalk also may vary with frequency.  For that matter, -50 dB is undesirable but not a lot at all (would be considered super way overkill for most speakers playback, for sure), particularly if most of the sounds in a recording are amplitude panned so most sounds bleed L/R much much more than -50 dB and the extra amount from the hardware would be trivial.  Again, be careful of quoting certain specific measurements as the explanation of perceived differences.
   
  You can make an ABX box if you really want.  There could be some that are sold out there too.


----------



## miceblue

Quote: 





mikeaj said:


> That's cheap multimeters.  Certainly people test signals outside of mains frequencies, when using multimeters in a lab or something more serious.  But if in doubt of your multimeter's capabilities, use 60 Hz if you can, because even the cheapest ones should be fine with that.  It's the most basic expectation and usage for a user.
> 
> If you're referencing O2 and Clip+ crosstalk measurements, note the load impedance, as it can well be different for different loads.  The crosstalk also may vary with frequency.  For that matter, -50 dB is undesirable but not a lot at all (would be considered super way overkill for most speakers playback, for sure), particularly if most of the sounds in a recording are amplitude panned so most sounds bleed L/R much much more than -50 dB and the extra amount from the hardware would be trivial.  Again, be careful of quoting certain specific measurements as the explanation of perceived differences.
> 
> You can make an ABX box if you really want.  There could be some that are sold out there too.


 
  I've asked this in another thread but the original poster hasn't had time to answer it. How does one read and interpret crosstalk graphs and measurements?
  The C5 for example: Crosstalk @ 150 Ω -67 dB
  ^ I have no idea what that actually means, and various RMAA measurements have a graph to go with this measurement.


----------



## mikeaj

Quote: 





miceblue said:


> I've asked this in another thread but the original poster hasn't had time to answer it. How does one read and interpret crosstalk graphs and measurements?
> The C5 for example: Crosstalk @ 150 Ω -67 dB
> ^ I have no idea what that actually means, and various RMAA measurements have a graph to go with this measurement.


 
   
  More or less, play a tone into one channel, measure the output into that channel (A) and then also into the other one (B).  B is undesired; ideally it would be 0.  Check out the ratio of B/A.  20*log10(B/A) is the quoted result in dB, if A and B were voltage measurements.  It's negative because B is a lot less than A.  
   
  A graph might show values for different frequencies.  Or I guess x axis could be something else.  If somebody gives a single value and doesn't specify frequency, it's probably 1 kHz because in audio land, that's what most people do by convention.  Just like THD measurements—usually at 1 kHz just because that's common practice, not that it particularly means anything special.
   
  Result will depend on frequency tested, load impedance, and potentially even some other factors like position of volume control.  You have to think about the ways in which signals could be mixed or coupled inside an amp.
   
  When driving 150 ohms, O2 gets -91 dB supposedly.  It's -65 dB for 15 ohms, -72 dB for 33 ohms, -91 dB for 150 ohms, -95 dB for 600 ohms.  Even if you hook up the leads correctly, RMAA gives some weird results for crosstalk sometimes.  I don't really know what's up.  The software is pretty buggy, or it also could be a hardware grounding issue or something else that causes the weird results.  I wouldn't take RMAA figures too seriously, anyway.
   
  For that matter, practically I don't really think -91 dB is an improvement over -67 dB when you're listening to anything, particularly if it's not all just supposed to be in one ear.  Actual music in each ear masks any of these effects, even if you could actually discern a difference when testing with a tone in one channel and silence in the other.
   
   
  So what I described at the top is the mechanism by which the measurement is taken (at least conceptually; I don't know the actual procedure for sure but that would produce the desired result... they could do sweeps or something else maybe).  The result should apply for any signal, including music.


----------



## miceblue

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
  Well there goes that theory for the perceived soundstage difference I hear between the O2 and the C5. >_<
   
  Anywho, thanks for explaining that. I still don't quite understand what the number physically means though. -91 dB meaning...the crosstalk is pretty much inaudible? What is considered a "bad" crosstalk value? Likewise for the signal-to-noise ratio measurement. 110 dB meaning.....the signal power is much larger than the noise power? What is considered a "bad" SNR value?
   
   
   
  Quote: 





lord voldemort said:


> Haven't been on head-fi for a while... 960 posts since I left this thread. Time to get out my reading glasses.


 
  If Voldemort is mentioned in a post, it's most likely referring to the designer of the O2 (AKA He-Who-Must-Not-Be-Named), not you.


----------



## mikeaj

There's bad relative to what you can hear and bad relative to other devices.  It's going to depend on a number of things, same for SNR.
   
  Also, when looking at SNR, keep in mind that most recordings have noise from the recording process, already in them.  There's also already acoustic noise in your listening environment.  So past a certain point it doesn't make much sense to obsess about noise from the electronics, if other noise is at a significantly higher level.
   
  If you want, I can post a few tracks with slightly mixed L and R channels to simulate different levels of crosstalk (say, not today but maybe tomorrow; my upload speeds at home leave a lot to be desired).
   
   
  Anyway, this is kind of OT, but I think important.  Don't get too caught up in reading numbers without a frame of reference for them, pretty much.


----------



## miceblue

Quote: 





mikeaj said:


> There's bad relative to what you can hear and bad relative to other devices.  It's going to depend on a number of things, same for SNR.
> 
> Also, when looking at SNR, keep in mind that most recordings have noise from the recording process, already in them.  There's also already acoustic noise in your listening environment.  So past a certain point it doesn't make much sense to obsess about noise from the electronics, if other noise is at a significantly higher level.
> 
> ...


 
  That is definitely a good point. I didn't even think about that!
   
  I don't think it's completely off-topic. A whole lot of thought and numbers went into the design of the O2. It's only natural to wonder if these numbers are actually meaningful for someone without an electrical background, and how it affects the end sound we hear, at least it is to me.


----------



## lorriman

mikeaj said:


> If you're referencing O2 and Clip+ crosstalk measurements, note the load impedance, as it can well be different for different loads.  The crosstalk also may vary with frequency.  For that matter, -50 dB is undesirable but not a lot at all (would be considered super way overkill for most speakers playback, for sure), particularly if most of the sounds in a recording are amplitude panned so most sounds bleed L/R much much more than -50 dB and the extra amount from the hardware would be trivial.  Again, be careful of quoting certain specific measurements as the explanation of perceived differences.




Yes, sir!

In anycase, it's the only measurement that explains the significant difference in stereo that I'm hearing. I'm not saying that the clip+ has little stereo, so while -65db versus -50db difference may not be big, it may still explain the audible loss of stereo I'm experiencing.


----------



## Lord Voldemort

Quote: 





miceblue said:


> If Voldemort is mentioned in a post, it's most likely referring to the designer of the O2 (AKA He-Who-Must-Not-Be-Named), not you.


 
  Oh yeah definitely. The way I got this name in the first place was because the Nwavguy had a reputation for this name. I thought it'd be fun to take it and heck, it was available. I'm a big Harry Potter fan as well. And I did start this thread about a year ago and it's interesting what people have been discussing here. I've learned quite a bit.


----------



## mikeaj

re: crosstalk
   
   
  I created a new thread with a few audio files with different levels of simulated crosstalk.  For best effect, I guess you should use an amp with very low crosstalk of its own.  Details in the link:
   
  http://www.head-fi.org/t/657280/simulated-crosstalk-listening-example-audio-files-inside


----------



## JakeJack_2008

I am very happy with the ODAC and O2 (as two separates).
   
  Should I buy a better quality AUDIOQUEST - FOREST *USB MINI CABLE ($29)*
   
   
  or this [size=small][size=small]http://www.walmart.com/ip/Monster-Digital-Life-High-Speed-Mini-USB-Cable-0.5/17490789[/size][/size]  ???


----------



## wolfetan44

Forest.


----------



## HamilcarBarca

Quote: 





jakejack_2008 said:


> I am very happy with the ODAC and O2 (as two separates).
> 
> Should I buy a better quality AUDIOQUEST - FOREST *USB MINI CABLE ($29)*
> 
> ...


 
   
  Unless one cable or the other is defective, there will be zero audible difference. If one is defective, you'll hear genuine noise when using it.


----------



## thoughtcriminal

hamilcarbarca said:


> Unless one cable or the other is defective, there will be zero audible difference. If one is defective, you'll hear genuine noise when using it.



This man speaks the truth. I'll give you analog cables, but with digital, you won't get any upgrade from the $5 Walmartspecial unless you are trying to run more than 15-20 ft


----------



## adydula

Dont waste your money.....what they said....the Walmart cable will do just fine unless its defective.....
   
  Alex


----------



## JakeJack_2008

Thanx to all of You. So, no Forest, Monster, ... USB cables.
   
  However, I've a little problem. The USB cable which came with the ODAC -
  it's also posted among _cables _on the JDS Labs site - is _way too long_.
  So, this fact triggered my search for _shorter _(and perhaps better quality)
  USB cables. Now, in Staples there's a Monster USB Mini and Micro cable of which length
  is only 6 _inches (_and costs $20_)._
  This is _the same _Monster cable which  I posted above (1.5 feet=45 cm long for $25).
   
  Can you recommend any _shorter (_and cheaper) USB cables than the 6" Monster cable ($20) for the ODAC to connect to my laptop.
  Also, is a *6"* USB cable a good idea? While using the *6"* cable, the ODAC and also the O2 (as two separates) must be very close to my laptop's EMI/RFI?  Does it matter?


----------



## thoughtcriminal

Monoprice.com
Best place to get cheap cables and the quality is pretty good on everything I've purchased from them


----------



## adamlr

while were on the subject of cables. the usb cable that came with the odac from jds labs has a plastic "bottle" for lack of a better word near the micro usb end. is that important? can i use the shorter (with no plastic bottle) micro usb cable that came with my e11 for arguments sake?


----------



## MrEleventy

Quote: 





adamlr said:


> while were on the subject of cables. the usb cable that came with the odac from jds labs has a plastic "bottle" for lack of a better word near the micro usb end. is that important? can i use the shorter (with no plastic bottle) micro usb cable that came with my e11 for arguments sake?


 
   
  I believe you're referring to a ferrite bead. It's used to prevent interference from the devices. I have no experience with the odac so I don't know if it's prone to interference but I know most of the time, USB ports on computers are pretty noisy themselves. MIght be safer to grab one with a bead.
   
  E: Just about any micro cable will work, just use the one that sounds clean to you.


----------



## mikeaj

There are a lot of claims and conjecture out there with little to no supporting evidence of high credence.  It's hard to say what really counts without some stringent testing, but you should be able to make some good guesses otherwise.
   
  The "plastic 'bottle'" thing near the end would be a ferrite bead, which mainly filters out some high-frequency noise.  Seeing as the DAC is powered from USB, this is a good thing; you could possibly even think of it as part of the power supply.  That said, there is filtering on board and I don't think it should really make much of a difference to not have one.  If there's any difference, it would manifest itself in background noise levels (mostly; you probably wouldn't get anything else significant without any increase in noise), so if you don't hear any hiss then you're good to go.
   
  So it's almost certainly not important in the sense of working or in terms of using it and performance, but it probably helps benchmark results in some small but measurable way.  Depends on the source computer.


----------



## miceblue

jakejack_2008 said:


> Thanx to all of You. So, no Forest, Monster, ... USB cables.
> 
> However, I've a little problem. The USB cable which came with the ODAC -
> it's also posted among _cables_ on the JDS Labs site - is _way too long_.
> ...




I can't get the exact size for the cable I have at the moment, but I got one from Monoprice.com that's shorter than the 1.5 ft. one from JDS Labs for < $5.


----------



## autoteleology

> Can you recommend any _shorter (_and cheaper) USB cables than the 6" Monster cable ($20) for the ODAC to connect to my laptop.


 
   
  Get one of these. I have a bunch and they rock.

 http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Dmobile&field-keywords=mini+usb+retractable&rh=n%3A2335752011%2Ck%3Amini+usb+retractable


----------



## JakeJack_2008

Thanx to both of You. I'll check the Monoprice.com and those retractable Mini USB cables on the amazon.com as well.
  As we know, the ODAC uses the _Mini _USB connection and not the _Micro _USB connection.
  So, yes on Mini and Micro.


----------



## JakeJack_2008

Well, aren't You all wrong, because of this:
   
   
  Quote: 





> Borrowed a very expensive *USB cable *this past week to try in my big rig at home.  Source is a Mac Mini > Pure Music (Integer mode) > Ayre QB9.  I had been using the cable that came with the QB9.  As much as I hate to admit *it was a huge step up in performance *- much *greater transparency that allowed much more musical nuance to come through*.  Using the expensive cable, playing Emmylou Harris's Boulder to Birmingham (Producer's Cut 24/96), her emotion comes thru in the music and hits hard.  And the QB9 runs asynchronous transfer mode, so you wouldn't think USB cables should change the presentation.
> 
> Of course all good things must come to an end - cable has to be returned tomorrow.  Took it out the system and put in the old.  Decided to play Boulder to Birmingham one more time.  All that sense of emotion was gone....
> 
> ...


 
   
  Post #525 in the thread: "*USB cable *and *Sound Quality*" - Page 35
http://www.head-fi.org/t/617026/usb-cable-and-sound-quality
   
  Here's a reply (post #528) to the above post:
   
   
  Quote: 





> Don't you think that the fact that the emotional response changed might have something to do with your own emotions?
> 
> *Interesting that your wife noticed a difference, especially since she was in another room **in a separate floor in the house*.
> Did you ask her if something changed or did she just say it out of the blue


 
   
  P.S.
  The above mentioned thread is a very interesting one.


----------



## HamilcarBarca

Quote: 





jakejack_2008 said:


> Well, aren't You all wrong, because of this:
> [...]


 
   
  What he claims is simply impossible with digital communication (including USB.)


----------



## HamilcarBarca

Quote: 





mikeaj said:


> [...]
> The "plastic 'bottle'" thing near the end would be a ferrite bead, which mainly filters out some high-frequency noise.  Seeing as the DAC is powered from USB, this is a good thing; you could possibly even think of it as part of the power supply.  That said, there is filtering on board and I don't think it should really make much of a difference to not have one.  If there's any difference, it would manifest itself in background noise levels (mostly; you probably wouldn't get anything else significant without any increase in noise), so if you don't hear any hiss then you're good to go.
> [...]


 
   
  Would the background noise be analogous to the video "sparklies" produced with a marginal HDMI cable?


----------



## JakeJack_2008

Well, I don't know, to make sure I need to find a wife .... buy very expensive USB cables...
  ..  and see whether she'd notice the difference in sound quality.


----------



## Currawong

Quote: 





hamilcarbarca said:


> Quote:
> 
> 
> 
> ...


 
   
  From someone with both the qualifications and decades of actual experience:
   
   
   


> dan lavry said:
> 
> 
> > Quote:
> ...


----------



## JakeJack_2008

From the above post (#1170):
   
   
  Quote: 





> Keep in mind that with a separate USB to SPDIF, there is still *a cable issue*, leading to the DA. *With the cable, one gets more jitter introduced by electromagnetic interference, termination tolerance, separate grounds for the chassis *(thus ground currents) *and much more (there are at least 5 more factors that come to my mind). *Putting the circuits INSIDE the DA, with a proper layout, yields much better jitter outcome.


 
   
  Very interesting!


----------



## mikeaj

Quote: 





hamilcarbarca said:


> Would the background noise be analogous to the video "sparklies" produced with a marginal HDMI cable?


 
   
  Not really.  Issues with HDMI picture quality at the fringe of not working are due to bit errors, an issue with the digital communications.  Not all the correct 1s and 0s get received.
   
  Power supply filtering on the USB cable (via ferrite bead, so to speak I guess) is about cleaning up the power supply, thus making the analog output marginally less noisy.  This is with all the 1s and 0s properly received, with or without the ferrite bead.  
   
   
   


jakejack_2008 said:


> Well, I don't know, to make sure I need to find a wife .... buy very expensive USB cables...
> ..  and see whether she'd notice the difference in sound quality.


 

   
  Be careful reading anecdotes, examples.  In general, maybe something happened, maybe it didn't.  Trace all the implied cause and effect relationships and make sure they all check up.  Is there any repeatability of results?  Statistically significant repeatability?
   
  Often times people do informal experiments and say they're comparing A vs. B (say, audio components).  However, in reality, when swapping, they also could be changing listening position, the way they listen, expectations, etc., and many other factors that also have an impact.  Sometimes it's just different volume levels.  And they also retain the memory of the previous experience while going through the new one.  If a trial is supposedly (usually single-) blinded, are there any possible clues that might give away the answer?  See Clever Hans, for example, for the horse that could do arithmetic (not really).  When self-reporting and thinking about things, there is a tendency to remember the unusual events but not the common ones.  etc.  When C seems to be correlated with D, is that because C causes D, D causes C, E causes both C and D, there's actually no correlation but actually you have an insufficient sample size, or what?
   
  Anyway, my advice is to leave the thinking cap on and search for different potential explanations.
   



jakejack_2008 said:


> From the above post (#1170):
> 
> Very interesting!


 

   
  With respect to Lavry's response that Currawong posted, a couple considerations:
   
  (1) If you're working hard on a problem, if you want to make the ultimate audio device for max peace of mind, and if you're selling a product, you're going to frame issues in a way that highlights your expertise and the importance of the things you're doing and the problems you're considering.
  (2) The kinds of differences, changes being referenced may or may not have a big impact, may or may not even be audible.  Keep things in perspective.
   
  As for jitter and S/PDIF, Lavry makes an important point, one that's too often overlooked:  it's mostly about how the DAC is handling things, what's actually happening for the D/A.
   
   
   



hamilcarbarca said:


> What he claims is simply impossible with digital communication (including USB.)


 

   
  In general, lots of things are possible with digital communications.  With the right links, right conditions, you can definitely get bit errors, and thus unintended results (depending on how the errors are handled).  Different systems have different levels and types of error detection and/or correction.  Some have none.
   
  But with USB, the actual sonic effect most probably should not be anything like what was implied.  By the way, USB bit error rates are supposed to be better than 10^-12 or so to meet spec.
   
   
  Currawong's example of S/PDIF (digital communications) being a possible issue is another case where you're really talking about the peculiarities of an analog signal affecting an analog process somewhere down the line.  Even supposing that the S/PDIF link sends all the bits properly and they're all received (happens all the time -- success for the digital communications), if the D/A process (which is analog) uses or is affected by the timing and jitter of the S/PDIF input signal (an analog waveform, which represents digital data), the audio performance (analog) of the D/A process could be impacted.
   
  Again, may or may not be impacted audibly (most usually _not_), but it's something that's real.  As mentioned before, it depends heavily on the D/A design and what that's doing.


----------



## HamilcarBarca

Quote: 





mikeaj said:


> Quote:
> 
> 
> 
> ...


 
   
  From 1986 through 2001, I was a programmer working (almost) solely on digital communications, so it's often trivially easy to recognize silly claims about cables, etc. OTOH, 100% of this work was with cables with didn't include a separate power conductor. I had considered only the recovery of the digital signal in my claim.
   
  Thanks. It's good to learn something new.


----------



## mikeaj

Quote: 





hamilcarbarca said:


> From 1986 through 2001, I was a programmer working (almost) solely on digital communications, so it's often trivially easy to recognize silly claims about cables, etc. OTOH, 100% of this work was with cables with didn't include a separate power conductor. I had considered only the recovery of the digital signal in my claim.
> 
> Thanks. It's good to learn something new.


 
   
  I see, a good background and perspective then.  Well, I hope spelling out some of the concepts and writing the extra words weren't wasted, as there are other readers too.
   
   
  But in this kind of situation, do we really call it the digital communications that's making the difference?  It really isn't.  It's the analog considerations of the cable (maybe also taking a loose definition of a "cable" possibly including passive circuit elements like ferrite beads) used for the digital communications.
   
  Usually when we think about digital communications, we're just interested in digitized data getting from point A to point B, maybe in a timely fashion or with some reliability, etc.


----------



## Currawong

I suspect mikeaj is right in this. My own impressions of the effects of different equipment along with asking questions of people who design digital audio gear suggest that a lot more is going on. With something like an ODAC (which everyone should be talking about rather than derailing the thread) it has very little in the way of power circuitry and has a much higher noise floor than many more expensive DACs so I don't think it wouldn't be a surprise if the cable, power or whatever had some effect on the shape of that noise. It was designed to be cheap, however, so it's rather the wrong place to talk about it.


----------



## mikeaj

That's not really what I said, but anyway...
   
  Noise levels should be an aspect that almost everybody can agree on as something that's cleanly measurable, directly can be mapped to some measurement—unlike some facets of sound quality and audio perception.
   
  Anybody recall seeing any noise measurements of ODAC?  Even some "guy" out there never got around to posting those explicitly, though noise floors can be found on some of the other graphs.  Maybe somebody can ask Tyll to do it eventually, though he's a busy guy.  Or we could maybe ask John Seaber of JDSLabs, since they're selling ODACs and also now have lab-grade audio benchmark gear.  For all that's been said on the subject, I want to see the magnitude of changes evidenced by say a powered USB hub vs. a noisy computer USB port, ferrite bead vs. no ferrite bead, etc.
   
  If the differences are as great as some subjective descriptions have been, then they should be readily measurable without much trouble.  If they're not so much (that would be my guess), then that result might fall out as well.  Either way, it would be interesting to see.


----------



## adamlr

Quote: 





mreleventy said:


> I believe you're referring to a ferrite bead. It's used to prevent interference from the devices. I have no experience with the odac so I don't know if it's prone to interference but I know most of the time, USB ports on computers are pretty noisy themselves. MIght be safer to grab one with a bead.
> 
> E: Just about any micro cable will work, just use the one that sounds clean to you.


 
   
  Quote:                                                                                                                                  


mikeaj said:


> There are a lot of claims and conjecture out there with little to no supporting evidence of high credence.  It's hard to say what really counts without some stringent testing, but you should be able to make some good guesses otherwise.
> 
> The "plastic 'bottle'" thing near the end would be a ferrite bead, which mainly filters out some high-frequency noise.  Seeing as the DAC is powered from USB, this is a good thing; you could possibly even think of it as part of the power supply.  That said, there is filtering on board and I don't think it should really make much of a difference to not have one.  If there's any difference, it would manifest itself in background noise levels (mostly; you probably wouldn't get anything else significant without any increase in noise), so if you don't hear any hiss then you're good to go.
> 
> So it's almost certainly not important in the sense of working or in terms of using it and performance, but it probably helps benchmark results in some small but measurable way.  Depends on the source computer.


                                                                                                                                                  
   
  thank you both very much. i guess ill have to try it out myself and see


----------



## adydula

There is a lot of noise data and measurements on the ODAC on the designers blog.
  The first version of the ODAC, despite following the reference design, only had about 98 dB DNR.
  On the fourth version this went down to over 111dB.
   
  There are many obvious advantages to USB power but it often degrades performance due to noise. To get around this, the ODAC uses split digital and analog power supplies each with their own filtering and regulator. The analog supply has additional filtering and the critical reference voltages, and negative supply for the DAC chip, are further optimized.
   
  Also his transpanecy guidelines states that all noise components should be below -110db and the total sum should be below -100dBFS.
   
  Also read where the lab guys state that anything below 100DNR in the real world relates to being transparent...and anything beyond this is well....
  Anything beyond -110dB is well past the point of diminishing returns...
  But for us spec guys ...great.
   
  Take some time over there..lots of good info in his blogs under the ODAC, updates and details..
   
  Alex


----------



## autoteleology

> The "plastic 'bottle'" thing near the end would be a ferrite bead


 
   
  Ha! I always wondered what those things were.


----------



## JakeJack_2008

Quote: 





adydula said:


> There is a lot of noise data and measurements on the ODAC on the designers blog.
> The first version of the ODAC, despite following the reference design, only had about 98 dB DNR.
> On the fourth version this went down to over 111dB.
> 
> ...


 
   
  Very interesting, thanks. Thanx to mikeaj and Currawong as well.
   
  ***************************************
  The following sounds so convincing to a non-expert like me.
   
  AUDIOQUEST - FOREST USB MINI CABLE
  Price: *$29.00*
   
   
  [size=medium]*Surprising Performance, Affordable Price*[/size]
   
  [size=small]*Chuck Those Generic USB Cables and Step Up To Forest USB!*[/size]
  Priced only a few dollars more than generic USB cables, *Audioquest Forest *is a substantial improvement. *Forest *offers a far smoother & richer tonal balance, much greater resolution and a clearer sonic picture. The secret is in *Audioquest*'s unyielding commitment to quality; every aspect of *Forest*'s construction from the type of connectors used to the direction of the conductors has been scrutinized, auditioned, revised and perfected to create a cable that offers outstanding performance for a fraction of the cost of most audiophile designs.
   
_*"The AudioQuest Forest is very affordable by standalone cable standards, and it offers all-round improvements over bundled cables.*_
_*Detail levels are markedly improved, there's greater precision and punch, and a general upgrade in musical expressiveness."*_
 -- _What HiFi?_
   
*Metallurgy*
*Forest* uses *high-quality Long Grain Copper *solid-core conductors. Long Grain Copper has far fewer imperfections than OFC copper for lower distortion and greater conductivity. *LGC* copper conductors are used in many Audioquest analog cables, providing a far smoother, richer and more dynamic sound than the terrible materials used in generic USB cables. LGC's lower distortion characteristics allow *Forest *to deliver greater resolution and musical energy with a noticeably lower noise floor.
*Forest *is a *directional cable*, AQ listens to every primary signal conductor used *in Forest **to determine proper conductor orientation,*
*this simple test yields a surprising improvement to sonic performance.*
   
*Digital Audio over USB*
 There are significant, audible differences between USB cables. We're not sure how this is possible, since USB is purported to be a purely digital interface, however, the sonic differences are repeatable and consistent from system to system. A better USB cable makes a better digital audio cable, period.
   
*Termination*
 All *Audioquest Indulgence *series USB Cables are terminated by *Wave Solder*, a very high-precision soldering method originally developed for surface-mount applications in the computer industry. *Wave Soldering *is fast, efficient and has no human interaction, *eliminating all conventional solder problems*, creating a strong, reliable and electrically consistent connection. *Wave Soldering *is just one feature that makes Indulgence Series USB cables a far better choice than conventional USB Cables
   
   
  From http://www.musicdirect.com/p-58290-audioquest-forest-usb-mini-cable.aspx
   
  *********************
   
  So, what do you think about the *Forest *  *directional cable*s???
   
  Should I follow their advice and  _chuck 
	

	
	
		
		

		
			





 _the USB cable (with a bottle neck) which came with the *ODAC *from the JDS Labs???
   
   
  *********************************************************************************************
   
*P.S.*
  Edited to add this:
   
  AudioQuest - Forest - Mini USB Cable  ($29)
   
  Listed in _The Absolute Sound 2012 High-End Audio Buyer's Guide_
   
 High-Performance Entry-Level USB Cable  Forest is the high-performance entry level cable in AudioQuest's 'Indulgence Series' of USB cables. Boasting solid Long-Grain Copper (LGC) conductors, Forest delivers low jitter, low distortion audio for superior performance. Enjoy Forest USB cables with PCs, DACs, and other digital gear, and experience how good digital music can sound.


  AudioQuest Forest USB cable was honored by being included in _The Absolute Sound 2012 High-End Audio Buyer's Guide_. According to the magazine, "For those on a tight budget, Forest is a large upgrade over a generic USB cable that was never designed for audio. Compared to standard USB cables, *Forest offers a larger and more dimensional soundstage, more liquid and lifelike timbres, and greater transparency*."
   
  ....
  ...
   
  The Next Evolution of USB Cable Performance
  ...
*There are huge differences in the sound of USB cables*. As part of AudioQuest's re-examination of USB cable design, specific attention was paid to maximizing the sonic performance of USB. AQ's Indulgence USB series pushes USB sonic performance to new levels. While test equipment is excellent at tracking control errors or ensuring data pass through, no computer can compete with the human ear when it comes to perceiving the subtle but crucial audio errors and distortion that can reduce the enjoyment of your music and video files via USB.
   
 The Engineering and Construction Edge   
  AudioQuest begins with Long-Grain Copper (LGC) and adds increasing amounts of silver-plate culminating in Diamond USB, whose conductors are made using solid Perfect-Surface Silver (PSS). Solid Polyethylene insulation ensures stable conductor geometry while minimizing insulation induced phase distortion. On the two top USB cables, Coffee and Diamond, AudioQuest's patented Dielectric-Bias System (DBS) polarizes the insulation, *providing a drop in the perceived noise floor and an increase in dynamic contrast.*
   
  From http://www.audioadvisor.com/prodinfo.asp?number=AQMUSBFOR%20.75


----------



## HamilcarBarca

Quote: 





jakejack_2008 said:


> *Forest *is a *directional cable*, AQ listens to every primary signal conductor used *in Forest **to determine proper conductor orientation,*
> *this simple test yields a surprising improvement to sonic performance.*


 
   
  There's no such thing as a "directional [USB] cable" or "conductor orientation" for electrical cables. I guess they couldn't find any other way to justify charging $30 for a $1 cable.


----------



## mikeaj

I mean, it's your money and you can try it if you're curious, but a lot of the claims are dubious at best and so you're not going to find that many positive responses here.  Let's even forget that we're talking about a digital data (well also supply lines) cable.  Lots of previous audio system measurements of "directional" analog audio cables shows pretty much 0 difference no matter which way they're hooked up.  And here you're talking about hooking up something that is steps removed from any analog process.
   
  Something like those HDMI cables with Redmere tech in them are directional, but that's because they're cables with chips (active electronics) in them that actually do things.


----------



## adydula

OMG....
   
  Well if you have the money, buy both and test and let us know!
   
  But if I were you I would 'RUN"...
   
  Alex


----------



## tomb

Quote: 





adydula said:


> There is a lot of noise data and measurements on the ODAC on the designers blog.
> The first version of the ODAC, despite following the reference design, only had about 98 dB DNR.
> On the fourth version this went down to over 111dB.
> 
> ...


 
  OK - I have issues with much of this thread, including the above. 
	

	
	
		
		

		
		
	


	



   
  Quote: 





jakejack_2008 said:


> Very interesting, thanks. Thanx to mikeaj and Currawong as well.
> 
> ***************************************
> The following sounds so convincing to a non-expert like me.
> ...


 
  However, this is just pure bunk ...
   
  Having sold USB-powered DACs for several years, I have told everyone that it's important to ensure that you have a shielded USB cable - not all of them are (mouse, keyboard USB cables), but other than that - it's all 0's and 1's, period.  There may be some incremental differences/improvements to be had if power is an issue (USB-powered DACs), but even then, it doesn't mean squat compared to a good DAC design with onboard regulation (LDO's, capacitors) or good quality USB power (hubs, quality PC power supplies, etc.).  Just MHO ...


----------



## adamlr

just "clipped" my O2. i used my swiss army knife to cut the resistors and it all went very smoothly. my m-100 is still delayed in the mail unfortunately, but i have found the unity gain is quite enough to drive my dt 770s, even with heavy eqing. i cant say ive noticed any improvement of sound quality though, but i was never a "golden ears" type. 
  a note for anyone planning on doing the same with their O2: jds labs apparently glue the board to both the front, and back plate. i had to remove both in order to get the board out.
   
  just wanted to thank everyone in this post for helping me understand what i have to do. big ups


----------



## lorriman

adamlr said:


> just "clipped" my O2. i used my swiss army knife to cut the resistors and it all went very smoothly. my m-100 is still delayed in the mail unfortunately, but i have found the unity gain is quite enough to drive my dt 770s, even with heavy eqing. i cant say ive noticed any improvement of sound quality though, but i was never a "golden ears" type.
> a note for anyone planning on doing the same with their O2: jds labs apparently glue the board to both the front, and back plate. i had to remove both in order to get the board out.




Unity gain gets people past 9 o'clock on the volume control/pot, which is desirable since just before 9 o'clock the volume control has channel imbalance. Other than that there shouldn't be any audible improvement since even with 6.5x gain distortion etc is under audible levels. It's popular to clip the 6.5x gain leaving 1x and 2.5x but 6.5x is needed for connecting low-voltage mp3 players and other low-voltage sources. Unless one is certain that one is never going to do that then it's better to clip the 2.5x. Many high fidelity types wouldn't even dream of using a DAP/mp3-player as a source, but since the clip+ effectively measures as hifi (other than for super-sensitive iems), there is reason even for them to use a DAP; even the IPOD is just about hifi.


----------



## adamlr

Quote: 





lorriman said:


> Unity gain gets people past 9 o'clock on the volume control/pot, which is desirable since just before 9 o'clock the volume control has channel imbalance. Other than that there shouldn't be any audible improvement since even with 6.5x gain distortion etc is under audible levels. It's popular to clip the 6.5x gain leaving 1x and 2.5x but 6.5x is needed for connecting low-voltage mp3 players and other low-voltage sources. Unless one is certain that one is never going to do that then it's better to clip the 2.5x. Many high fidelity types wouldn't even dream of using a DAP/mp3-player as a source, but since the clip+ effectively measures as hifi (other than for super-sensitive iems), there is reason even for them to use a DAP; even the IPOD is just about hifi.


 
   
  yes your right, thats why i "clipped" it in the first place, because the m-100 are sensitive and 2.5x would definitely be too much for them, so unity gain it is.
 and im using the O2 as a desktop amp. theres no way ill ever take it with me portably, so no 6x gain for me. infact, looks like 2.5x is more then i need too...
  btw, while hifi is a somewhat... questionable term, i agree that different sources, atleast to my ears, dont make as big of a difference as their sometimes made out to.


----------



## lorriman

adamlr said:


> yes your right, thats why i "clipped" it in the first place, because the m-100 are sensitive and 2.5x would definitely be too much for them, so unity gain it is.
> 
> and im using the O2 as a desktop amp. theres no way ill ever take it with me portably, so no 6x gain for me. infact, looks like 2.5x is more then i need too...
> btw, while hifi is a somewhat... questionable term, i agree that different sources, atleast to my ears, dont make as big of a difference as their sometimes made out to.




That doesn't make much sense. I use my O2 as a desktop amp also. Clipping the 2.5x would have given me unity gain for my ultra-sensitives and left me the option of playing from my mp3 player or HD650s (serious desktop headphones). 

I've never seen a justification for clipping that 6.5x that adds up. 

For some reason people have got this idea of clipping the 6.5x in to their heads (justified by the higher distortion at 6.5x) and encouraged others to do so too, but all it does is limit your options. That higher distortion isn't audible and is irrelevant.


----------



## shadow419

Quote: 





lorriman said:


> That doesn't make much sense. I use my O2 as a desktop amp also. Clipping the 2.5x would have given me unity gain for my ultra-sensitives and left me the option of playing from my mp3 player or HD650s (serious desktop headphones).
> 
> *I've never seen a justification for clipping that 6.5x that adds up.*
> 
> For some reason people have got this idea of clipping the 6.5x in to their heads (justified by the higher distortion at 6.5x) and encouraged others to do so too, but all it does is limit your options. That higher distortion isn't audible and is irrelevant.


 
   
  Justification for clipping 6.5x gain that adds up:
   
  1. You do not intend to use low voltage sources (<=1V) since your dac/soundcard outputs 2V+
  2. You don't need gain for sensitive headphones, but enough voltage swing for higher z headphones
   
  If you remove the 2.5X option you limit your voltage swing or risk clipping the input.


----------



## thecansmancan

hey all, quick question in regards to the O2. So i know the typical one is bought at JDS or some other such similar retailer. But while on eBay i stumbbled aross this. At $127 its a fair deal cheaper than its JDS counter part. I was curious, do you think there is any real SQ difference or build difference between the two? Anyone have any experience with this one? Thanks so much.


----------



## shadow419

Quote: 





thecansmancan said:


> hey all, quick question in regards to the O2. So i know the typical one is bought at JDS or some other such similar retailer. But while on eBay i stumbbled aross this. At $127 its a fair deal cheaper than its JDS counter part. I was curious, do you think there is any real SQ difference or build difference between the two? Anyone have any experience with this one? Thanks so much.


 
  He's a much smaller builder, but there are members here that use Mayflower Electronics O2's.  Do a search for Mayflower and I'm sure you'll find threads mentioning him.


----------



## adamlr

Quote: 





lorriman said:


> That doesn't make much sense. I use my O2 as a desktop amp also. Clipping the 2.5x would have given me unity gain for my ultra-sensitives and left me the option of playing from my mp3 player or HD650s (serious desktop headphones).
> 
> I've never seen a justification for clipping that 6.5x that adds up.
> 
> For some reason people have got this idea of clipping the 6.5x in to their heads (justified by the higher distortion at 6.5x) and encouraged others to do so too, but all it does is limit your options. That higher distortion isn't audible and is irrelevant.


 
   
  Quote: 





shadow419 said:


> 1. You do not intend to use low voltage sources (<=1V) since your dac/soundcard outputs 2V+


 

 i use an odac which outputs ~2V (dont remember exactly) and have no use for 6.5x gain. distortion doesnt enter into it. as i mentioned earlier, im not the golden ears type. my reason for wanting unity gain is not for sensitive iems, but for sensitive headphones (m-100: 32 ohm, sensitivity of 103 dB @ 1kHz 1mW).
   
  my reasoning behind keeping 2.5x gain? im currently using dt 770s, 250 ohms. i eq rather heavily, dropping frequencies beyond 80hz by 8dB, and dropping frequencies beyond 250 hz by an additional 4 dB, sometimes i eq even more. with this configuration, together with dropping 3 dB of digital volume on foobar (because of a slight increase at ~80 hz that goes above the 0 line - just to be sure theres no clipping. perhaps unnecessary, but im not an expert, and this is my way of taking precautions), i was at ~11-12 oclock on the volume. 
  i wasnt sure if unity gain would still be sufficient for the dt 770s, so i wanted to keep the option for having 2.5x, just in case, in order to still be able to use the 770s when i wanted to. now that i see unity gain is enough for them, this point is moot, but i had no way of knowing at the time.
   
  when portable, i use iems streight from my phone. the O2, together with the Odac stay at home. i have no need for 6.5x gain at the moment, and as im starting college in june, i doubt very much ill be purchasing any new headphones in the next 4 years, and even if i do, it will probably be mad dogs, who dont need THAT much amplification, so i think im safe.
  in fact, seeing as an odac is my source, i doubt ill need more than 2.5x gain for any future headphone, as i dont intend on getting any planar magnetics (except perhaps the mad dogs), or any "hard to drive" cans. 
   
  edit: i wasnt encouraging anyone to do anything, i was simply thanking the participants of this thread that helped me understand which resistors to "clip" and assured me i wouldnt kill the amp while doing it.


----------



## mikeaj

Quote: 





thecansmancan said:


> hey all, quick question in regards to the O2. So i know the typical one is bought at JDS or some other such similar retailer. But while on eBay i stumbbled aross this. At $127 its a fair deal cheaper than its JDS counter part. I was curious, do you think there is any real SQ difference or build difference between the two? Anyone have any experience with this one? Thanks so much.


 
   
  All the versions use the same PCB and same (or equivalent) parts.  The electric circuit is more or less almost identical, so you get almost identical performance.  The same enclosure is being used too, and it's fairly thick aluminum, though maybe not like you see on the expensive hi-fi gear.  All O2s are assembled and soldered by hand, no matter where they came from; there's always a chance of somebody making a sloppy joint or two, but that's not really a real concern to have.  As for the knobs and look of the front panel and so on, that's a matter of personal taste.
   
  As mentioned earlier, Mayflower's just another builder out there, a good option if you want to save a bit of money.  On their website they have an even cheaper version that's missing the batteries—supply your own rechargeables, or just never use them as they're unnecessary if you keep the amp plugged in all the time.


----------



## shadow419

Clipping the input on the O2 isn't just about little more distortion using higher gain.  It sounds bad, really bad.  Having the volume pot in between the gain and output stage, instead of before the gain stage, is a design choice( or mistake depending on your view) the designer made.  When you don't have your gain set properly for your source voltage, and clip the input it sounds absolutely terrible.


----------



## JakeJack_2008

Thanx to all of You who advised me _not _to buy those fancy USB cables.
   
  I've got the following question.
  What should be a _minimal _distance between the ODAC & O2 and my laptop to avoid the _USB-related  EMI/RFI_?
  (The USB cable - with the bottleneck  - which came from JDS Labs is 3 feet long.)
  For instance, is it _safe _to use a _6-inch _USB cable?


----------



## mikeaj

USB-related EMI?  If it's conducted in, then the length probably doesn't matter much.  If it's radiated in, I guess the ferrite bead could help?  The PCBs and internal electronics of the O2 and ODAC don't seem less prone to EMI issues than some others, supposedly.  I'm really not versed in boards, EMC, analog electronics, etc.  Maybe somebody else knows better.
   
  Anyway, it's probably nothing to worry or even think about.  Try it and see.  If there were problems, you'd get something like hiss, hum, weird background sounds, etc., and not anything subtle like slightly skewing the balance or most aspects of sound quality.  So if you don't hear a problem, you probably don't need to think about it.  I think most people are better off using whatever works comfortably and dropping all the small audiophile misgivings and OCD tweakery concerns (not saying you're in that category, but I just don't think it's worth the energy in general, especially without any definitive testing to settle things once and for all).


----------



## autoteleology

I would say to just not worry about it unless it ends up being clearly audible and present. Worrying about tiny technical details that virtually never come into play is only going to interfere with your music enjoyment, probably even more so than the actual problems discussed could if they occurred.


----------



## adydula

One thing that keeps amazing me with the O2 is all the times I have adjusted the volume pot I never have once every heard an noise, clicks, pops or ticks...totally silent.
   
  The background in silent....its the simple things...
   
  Tom....lots of things bug me as well on these forums, lots of just plain silly'ness....but I don't get to hung up over it anymore...just not worth it.
   
  I agree about its all 1's and 0's...and the use of a shielded cable...
   
  I have used unshielded interconnects and a person I really respect told me I was asking for trouble.....I still have them but don't use them.
   
   
  Alex


----------



## thecansmancan

Quote: 





adydula said:


> One thing that keeps amazing me with the O2 is all the times I have adjusted the volume pot I never have once every heard an noise, clicks, pops or ticks...totally silent.
> 
> The background in silent....its the simple things...
> 
> ...


 
  Agreed, there is a lot of headphone jargon you have to wade through on here. Don't let it weight you down. Let us not forget, its all about the music and unless something is preventing you from enjoying it well then its and old case of "if it ain't broke, don't fix it."


----------



## Shazb0t

I'm looking for a short 3.5mm male to 3.5mm female cable that I can use so I don't have to keep unplugging and plugging in different headphones into the port on the o2.  I couldn't find one at some local stores or on monoprice, only long extension cables.  Is there a place that sells something short for this purpose?


----------



## ProTofik

Maybe you can get these to, or something similar:
   
Link 1
Link 2
   
  I don't think you will find short 3.5mm to 3.5mm cable.


----------



## mikeaj

You could make one I guess, but you wouldn't be asking if you had the materials and desire to do that.

The really short stuff is usually M/M, intended for plugging in source to amp. There are quite a few options. e.g. FiiO L2 and L8, cheaper ones too

You could add a M/F 3.5mm adapter to that, which would be another inch and a half, or however long those are.


----------



## Currawong

You could simply buy a headphone double-adaptor.


----------



## Shazb0t

I just want to save the socket on the o2. Sometimes the headphone cable gets stuck in the jack caught on the pin.


----------



## HeatFan12

Quote: 





shazb0t said:


> I just want to save the socket on the o2. Sometimes the headphone cable gets stuck in the jack caught on the pin.


 
   
   
  The headphone out is tight indeed.  Get yourself an extension cable.  They work great and no messing around unplugging anymore.  I don't know where you are located but Monoprice has them for under $2 for the 6ft..
   
  And no, they don't degrade the sound in any way.


----------



## HamilcarBarca

Quote: 





shazb0t said:


> I just want to save the socket on the o2. Sometimes the headphone cable gets stuck in the jack caught on the pin.


 
   
  Amazon may carry a cable you find suitable. Although availability seems to vary, the definitely carried 1' cables in January or February (the last time I looked.) Monoprice, who doesn't offer the same array of lengths, is likely to be cheaper.


----------



## RustA

Quote: 





heatfan12 said:


> The headphone out is tight indeed.  Get yourself an extension cable.  They work great and no messing around unplugging anymore.  I don't know where you are located but Monoprice has them for under $2 for the 6ft..
> 
> And no, they don't degrade the sound in any way.


 
   
  An extension cable can certainly degrade sound quality... I guess you haven't heard a crappy cable for 1 dollar or so? Try it out ,-)
   
  That said, with quality DIY or reasonable priced adapter/cable (around 5-10USD and up, very rough estimate of course!), the only thing that could vary is frequency response (very slightly). Actual quality should be completely the same.
   
http://en.goldenears.net/1414
http://en.goldenears.net/KB_Columns/1921


----------



## mikeaj

Were the links supposed to be given in support of what you wrote or an unrelated issue?

That kind of impedance is pretty rare for a cheap cable, particularly if we're talking about short lengths. And even then, you might need a multi-BA IEM with a crossover to actually get non-trivial frequency response deviations (which are not the only possible changes, but probably the most significant ones). That's the only issue covered by the articles.


----------



## adydula

I have several of these i use...work well...
   
http://www.amazon.com/Hosa-MHE100-5-Headphone-Adapter-Extension/dp/B000068O6B/ref=sr_1_1?s=electronics&ie=UTF8&qid=1364993387&sr=1-1&keywords=hosa+3.5mm+to+1+4


----------



## RustA

Quote: 





mikeaj said:


> Were the links supposed to be given in support of what you wrote or an unrelated issue?
> 
> That kind of impedance is pretty rare for a cheap cable, particularly if we're talking about short lengths. And even then, you might need a multi-BA IEM with a crossover to actually get non-trivial frequency response deviations (which are not the only possible changes, but probably the most significant ones). That's the only issue covered by the articles.


 
   
  It was an example... I've had several adapters (seven at least) and cables (five at least) and yes - some were so crappy that they even couldn't deliver all the signal (the cheapest ones). The majority of them were just fine but slight variation in FR was present (side-by-side testing).
   
  That said, the level of detail or noise level was most probably the same.
   
  My rule: The less, the better (on both software and hardware level). Therefore avoiding any redundant part of my audio chain, including cables and adapters...


----------



## HeatFan12

Quote: 





rusta said:


> An extension cable can certainly degrade sound quality... I guess you haven't heard a crappy cable for 1 dollar or so? Try it out ,-)


 
   
  Quote: 





rusta said:


> My rule: The less, the better (on both software and hardware level). Therefore avoiding any redundant part of my audio chain, including cables and adapters...


 
   
   
  Of course they can degrade sound quality but the one I stated does not.  I have three from Monoprice and connected them all to different amps and went around testing headphones using the adapter and no adapter and there was no difference.  I used eight different headphones.  I am not going to spend money on gear and then have an adapter that's going to bottleneck the chain.  So, you are correct in saying maybe the lesser quality ones do and no I have not listened to all the extension cables out there but also own the Grado 1/4" to mini as well as the 15ft. and various ones from Hosa.
   
  And your rule is a great one and I relate to it because I don't always use the adapters but there are instances when they are necessary and it's good to know when I use them, I don't lose anything.


----------



## autior

Hi guys, two simple question:

 Can I use the O2+ODAC (I'm talking about the "single" solution, not the separated one) only as DAC? (es. source->O2+ODAC(only used as DAC)->AMP->Headphones).
 Can I use the O2+ODAC only as Amp? (es. source->DAC->O2+ODAC(only used as AMP)->Headphones).
   
  I think I read somewhere that the first case is possible, but I don't know about the second one.
   
  Thanks.


----------



## RustA

Quote: 





autior said:


> Hi guys, two simple question:
> 
> Can I use the O2+ODAC (I'm talking about the "single" solution, not the separated one) only as DAC? (es. source->O2+ODAC(only used as DAC)->AMP->Headphones).
> Can I use the O2+ODAC only as Amp? (es. source->DAC->O2+ODAC(only used as AMP)->Headphones).
> ...


 
   
  Both is possible. Buy an O2/ODAC desktop combo from Mayflower Electronics and want RCAs to work as outputs - that way, you have 2x RCA output from ODAC (you bypass the amp) and 1/8 input to the amp (you bypass the DAC).
   
  With ordinary combo unit, you only get 1/8 input to O2...


----------



## autior

Quote: 





rusta said:


> Both is possible. Buy an O2/ODAC desktop combo from Mayflower Electronics and want RCAs to work as outputs - that way, you have 2x RCA output from ODAC (you bypass the amp) and 1/8 input to the amp (you bypass the DAC).
> 
> With ordinary combo unit, you only get 1/8 input to O2...


 
   
  Is there an EU store that sell an O2/ODAC combo with the same mod? (I don't want to pay extra-taxes, I live in Italy)


----------



## ProTofik

autior said:


> Is there an EU store that sell an O2/ODAC combo with the same mod? (I don't want to pay extra-taxes, I live in Italy)




http://www.headnhifi.com/

That's the only EU store I know and use.


----------



## RustA

Quote: 





autior said:


> Is there an EU store that sell an O2/ODAC combo with the same mod? (I don't want to pay extra-taxes, I live in Italy)


 
   
  I was selling this combo one week ago... Nevermind.
   
  I don't think you could get this anywhere in EU. That said, Tyler is able to ship the unit and claim the price to be as high as you want. He shipped several things to me and I haven't paid anything extra until now.


----------



## RustA

Quote: 





protofik said:


> http://www.headnhifi.com/
> 
> That's the only EU store I know and use.


 
   
  He wants a version with outputs from ODAC... headnhifi only offers an ordinary version as far as I know.


----------



## HumanSaurusRex

Does O2+ODAC+2xRCA+1/4"Out fit into the stock case? Or do I need a different case like the B3-080 from www.boxenclosures.com?


----------



## RustA

Quote: 





humansaurusrex said:


> Does O2+ODAC+2xRCA+1/4"Out fit into the stock case? Or do I need a different case like the B3-080 from www.boxenclosures.com?


 
   
  You definitely need B3-080, at least...


----------



## HumanSaurusRex

Any other suggestions? Is it possible to build a O2+ODAC with an additional speaker amp like the 41hz AMP6 in one case with just one power supply?
  Whats the best way to cut out the shape for the USB-input?
   
  Really like this case: http://i5.photobucket.com/albums/y196/Boombastix/jani/20110412/522adc67_P1030012.jpg


----------



## RustA

Quote: 





humansaurusrex said:


> Any other suggestions? Is it possible to build a O2+ODAC with an additional speaker amp like the 41hz AMP6 in one case with just one power supply?
> Whats the best way to cut out the shape for the USB-input?
> 
> Really like this case: http://i5.photobucket.com/albums/y196/Boombastix/jani/20110412/522adc67_P1030012.jpg


 
   
  No idea, really... That said, to get a prepared casing, contact Tyler from Mayflower Electronics, or JDS Labs directly. Both should be able to provide you with laser-cut panels and include that bigger case you need to built a fully-desktop version.


----------



## Hardan

I just got my JDS O2 amp, and in the first song I played I found a new baseline going. I don't know if I haven't paid attention to it before but the amp brought it forward that I really noticed it being there. 
   
  Overvall super happy with my ampflier so far. Next in line is the ODAC for me. 
   
  Questions about the amplifier what gain should I use? Is it depending on genre?


----------



## chrislangley4253

Quote: 





hardan said:


> I just got my JDS O2 amp, and in the first song I played I found a new baseline going. I don't know if I haven't paid attention to it before but the amp brought it forward that I really noticed it being there.
> 
> Overvall super happy with my ampflier so far. Next in line is the ODAC for me.
> 
> Questions about the amplifier what gain should I use? Is it depending on genre?


 
  The lowest gain that gets you to where you need to be volume-wise is a generally the best.


----------



## JakeJack_2008

Quote: 





hardan said:


> I just got my JDS O2 amp, and in the first song I played I found a new baseline going. I don't know if I haven't paid attention to it before but the amp brought it forward that I really noticed it being there.
> 
> Overvall super happy with my ampflier so far. Next in line is the ODAC for me.
> 
> Questions about the amplifier what gain should I use? Is it depending on genre?


 
  Yeah, go for the ODAC. Please don't change your mind.
  You can't 
	

	
	
		
		

		
			





 go wrong with _both _of them


----------



## adydula

Least amount of gain......
  I am using unity gain with several cans just fine.....LCD2's, Q701's and Grado 325'is.
   
  Alex


----------



## Shazb0t

Quote: 





adydula said:


> I have several of these i use...work well...
> 
> http://www.amazon.com/Hosa-MHE100-5-Headphone-Adapter-Extension/dp/B000068O6B/ref=sr_1_1?s=electronics&ie=UTF8&qid=1364993387&sr=1-1&keywords=hosa+3.5mm+to+1+4


 
   
  Picked one up, thanks for the suggestion.


----------



## Dano91

Quote: 





hardan said:


> I just got my JDS O2 amp, and in the first song I played I found a new baseline going. I don't know if I haven't paid attention to it before but the amp brought it forward that I really noticed it being there.
> 
> Overvall super happy with my ampflier so far. Next in line is the ODAC for me.
> 
> Questions about the amplifier what gain should I use? Is it depending on genre?


 
  Use lower gain, higher can cause distortion if used with desktop sources. Higher was made for lower voltage sources, like mobiles/daps..


----------



## autoteleology

Am I the only person who finds the ODA to be extremely ugly?


----------



## shadow419

Quote: 





tus-chan said:


> Am I the only person who finds the ODA to be extremely ugly?


 
  Maybe not super stylish, but ugly?


----------



## adydula

Ugly???
   
  Beauty is in the eye of the beholder?
   
  So go buy a gold case and install a O2 board in it....and be happy!
   
  Alex


----------



## miceblue

tus-chan said:


> Am I the only person who finds the ODA to be extremely ugly?




Who makes the ODA?


----------



## adydula

now thats a good question....
   
  lol
   
  Alex


----------



## adamlr

speaking of which.... dont suppose theres any news on the ODA? i pretty much gave up hope on it to be very honest... last word about it from _"the creator"_ was when? 2012? 2011? i think we can stop waiting for it by now no?


----------



## adamlr

Quote: 





miceblue said:


> Who makes the ODA?


 

 i didnt understand if this was cynical or a real question. if its the latter - then no one. no official ODA design exists yet. he who must not be named made a post on his blog a long time ago, explaining the goals behind this new desktop design and then he basically disappeared. jds labs wrote in their blog that they have no clue whats going on with him, or the ODA... some sellers, like mayflower for example, offer customized O2 designs that turn the O2 into a desktop amp with things such as a 1/4" jack, but nothing official has been created yet.


----------



## miceblue

adamlr said:


> miceblue said:
> 
> 
> > Who makes the ODA?
> ...




Yeah it was a real question. XD

I know that Voldemort has been missing in action and totally absent from contact, which is unfortunate to some extent... :/


----------



## RustA

Quote: 





adamlr said:


> speaking of which.... dont suppose theres any news on the ODA? i pretty much gave up hope on it to be very honest... last word about it from _"the creator"_ was when? 2012? 2011? i think we can stop waiting for it by now no?


 
   
  I also gave up... If anybody wants, there is a fully-desktop version available at least from Mayflower Electronics which feature pretty much all I ever wanted from ODA (RCA outputs and 1/4 headphone out).

 Original ODA project died long time ago. That said, if anybody releases amp/DAC combo called ODA with DSD support, SS nature with some sort of "tube-stage enabler", crossfeed circuit and impedance switch up to 1000USD, I will gladly go for it ,-)


----------



## shadow419

Adgr over on diy has been working on a "ODA" desktop amp in the spirit of the O2 design. Might want to check it out


----------



## RustA

Quote: 





shadow419 said:


> Adgr over on diy has been working on a "ODA" desktop amp in the spirit of the O2 design. Might want to check it out


 
   
  Is it just an ordinary solid-state amp + DAC with better measurements? Or...?


----------



## shadow419

I didn't say anything about a DAC. It's a work in progress, and whether it's ordinary or not is for you to decide. Don't believe anything has been measured


----------



## RustA

Quote: 





shadow419 said:


> I didn't say anything about a DAC. It's a work in progress, and whether it's ordinary or not is for you to decide. Don't believe anything has been measured


 
   
  Ordinary = just normal amplifier/DAC with no additional features... That's all I was asking. ODA was supposed to have ODAC inside, that's why I talked about DAC as well.


----------



## shadow419

Nothing revolutionary it's just a se amp. A few more features than the O2 with much larger voltage rails and current output. 3 position gain switch. Check it out if you're interested


----------



## adamlr

Quote: 





shadow419 said:


> Adgr over on diy has been working on a "ODA" desktop amp in the spirit of the O2 design. Might want to check it out


 

 diy? never heard of them... do you mind posting a link?


----------



## RustA

Quote: 





shadow419 said:


> Nothing revolutionary it's just a se amp. A few more features than the O2 with much larger voltage rails and current output. 3 position gain switch. Check it out if you're interested


 

 Thanks very much for informing us


----------



## adydula

diyaudio
   
  Alex


----------



## adamlr

Quote: 





adydula said:


> diyaudio
> 
> Alex


 

 lol... the fact their called "diy" should have made it obvious that they would sell kits and parts and not pre made stuff, silly me...


----------



## Alchemist007

Would the O2+ODAC combo be a good upgrade from a udac2? I skimmed some of nwavguy's comments on the latter and I have to wonder if it's worth it since he's probably a biased source of information. I'm using Audio Technica A700x headphones.


----------



## chrislangley4253

Quote: 





alchemist007 said:


> Would the O2+ODAC combo be a good upgrade from a udac2? I skimmed some of nwavguy's comments on the latter and I have to wonder if it's worth it since he's probably a biased source of information. I'm using Audio Technica A700x headphones.


 
  It should be a good upgrade. But, I haven't personally heard a udac2. Do you hear any _problems_ with it? If so, the odac and o2 will almost certainly fix it. 

 They definitely measure a lot better. It's just up to your ears and headphones and your source material whether you will hear much of an upgrade. There are too many factors to make sure. My advice? Pick up a used o2 and odac.. or a new one. If it's not worth it, just list it up here. You won't lose much money and it will satisfy your curiosity.

 Happy Listening,
  
  Chris


----------



## Alchemist007

Well I could pass the udac2 to my bro and upgrade but I suppose it would most helpful to hear from anyone who's heard from both of them. Really the udac2 is my first dac/amp purchase so I don't have anything to compare it to besides my computer's sound card.


----------



## HamilcarBarca

Quote: 





alchemist007 said:


> Well I could pass the udac2 to my bro and upgrade but I suppose it would most helpful to hear from anyone who's heard from both of them. Really the udac2 is my first dac/amp purchase so I don't have anything to compare it to besides my computer's sound card.


 
   
  What are your reasons for replacing your uDAC?


----------



## Alchemist007

Well I want to know if it's worth stepping up (if this would be a good step up). I listen to mostly pop/rock and sometimes the flac rips are noticeably better and sometimes not (vs 320kbps mp3), just to give an idea of what I'm listening to. I wouldn't put my budget much higher than $300 but I'm open to other options.


----------



## HamilcarBarca

Quote: 





alchemist007 said:


> Well I want to know if it's worth stepping up (if this would be a good step up). I listen to mostly pop/rock and sometimes the flac rips are noticeably better and sometimes not (vs 320kbps mp3), just to give an idea of what I'm listening to. I wouldn't put my budget much higher than $300 but I'm open to other options.


 
   
  I haven't heard the uDAC.
   
  I have the ODAC+O2 combo (~US$300) and listen to everything from 128kbps MP3's (which are usually acceptable) to 320kbps MP3 files (which are fine) and FLAC (also fine.) Both the ODAC and the O2 are audibly neutral. Would you find this a step up?
   
  On the potential downside, the ODAC is limited to USB input and the ODAC+O2 combo mutes the ODAC when an analog source is attached to the O2's analog input. I'd much rather have switchable inputs. Even so, I'd almost certainly buy another if I was in the market for a DAC+amp.


----------



## Alchemist007

Well, only comparing the udac2 to onboard audio, I'd say it's got punchier bass and brings out some instruments I couldn't hear before (greater soundstage?). What I'd hope for is an even greater soundstage, cleaner highs, and bass that's less 'muddy' as I'd put it. It's not bad by an means but what else would you have in mind if you had this amount of money to spend?
   
  I'm not too concerned about inputs, I listen exclusively on my desktop. I mean 5.1 support would be fantastic for my surround sound speakers but I think that would cost a lot more (so I've kept my music listening to headphones for now).


----------



## SunshineReggae

When NWavGuy says the Udac measures bad, it's not him being biased. It's an objective approach where it's fair to say that compared to amps that measure well, and as far as measurements go, the Udac fares badly compared to certain other products.
  Now the question is whether that means you'll get the change you're looking for with something else. Practically, better measurements equal better performance but there are numerous caveats. I'm not even sure NWavGuy mentioned what he thought about the Udac's sound.
  To find out you're going to have to spend money if you have no other options. It's my experience that when you need to spend money to find out something (rather than just buying something because you definitely want it period), it's best to spend as little as possible. 
  A used O2 combination is a good choice. The fiio e9 measures well as an amp and so does that 30 bucks behringer dac that he mentions in the article. Also the Xonar Essence is a device with pretty good measurements.
   
  Keep in mind though that ultimately, those differences are all rather minor. I never went from one amp to another and noticed a huge improvement in clearity or god forbid soundstage, unless I take my worn out 20 year old entry level mitsubishi integrated with insanely bloated bass and no treble as reference.
   
  For example, my little dot (which was supposedly voiced with certain headphones in mind, which makes alarm bells go off because it smacks of a 'design by ear' approach), of which the measurements are unknown, sounds pretty much similar to my e9 and only a little different than my marantz integrated. And those are varying topologies.


----------



## ProTofik

Hi.
  Some time ago I changed my o2's gain setting to 1x to make it more quiet. I hoped that it would suit me but when connected with odac it's still a bit too loud for my liking. I'm usually listening with volume knob about 8-9am which cause channel inbalance.
   
  I was wondering if there is any other way to make o2 more quiet. I was thinking of replacing the pot with 20k one but I have no idea if that would work.


----------



## adamlr

Quote: 





protofik said:


> Hi.
> Some time ago I changed my o2's gain setting to 1x to make it more quiet. I hoped that it would suit me but when connected with odac it's still a bit too loud for my liking. I'm usually listening with volume knob about 8-9am which cause channel inbalance.
> 
> I was wondering if there is any other way to make o2 more quiet. I was thinking of replacing the pot with 20k one but I have no idea if that would work.


 

 lower your computers digital volume. if your concerned about bit degradation you can set your odac to output 24 bit audio. this way you can "over sample" and add "fake bits" which will be the ones lost in the lowering of digital volume. although, as discussed here a couple of times, the difference isnt exactly noticeable...
   
  right now i have my computers volume at 50%, and the O2s pot at just over 9 oclock. works just fine for me =]


----------



## ProTofik

I always had my ODAC set to 24/44.1KHz. I feel like any volume level below 100% has a bit less punchy bass.
  It might be just a placebo effect but my friend felt the same.


----------



## adamlr

Quote: 





protofik said:


> I always had my ODAC set to 24/44.1KHz. I feel like any volume level below 100% has a bit less punchy bass.
> It might be just a placebo effect but my friend felt the same.


 

 placebo effect? yes and no. yes - because when you lower the volume, the volume of the bass is reduced aswell (ofcourse).
  no - because (in my personal experience blah blah) bit degradation only becomes noticeable at a very low bit depth. around 9 bit (in my experience). 
   
  so even if you were using 16 bit output, lowering digital volume is unlikely to have an audible effect. for further information on bit depth i highly recommend you read at least the op of this thread:
  http://www.head-fi.org/t/415361/24bit-vs-16bit-the-myth-exploded
   
  furthermore, with equalization you can keep the volume low and still maintain a high bass volume. this is what i do myself.


----------



## ProTofik

Thanks. I will have a read later.
   
  I'm not a big fan or eq nor heavy bass.
  I think I will just try to do some proper blind test between 80% and 100%. Hope I was wrong.


----------



## adamlr

Quote: 





protofik said:


> Thanks. I will have a read later.
> 
> I'm not a big fan or eq nor heavy bass.
> I think I will just try to do some proper blind test between 80% and 100%. Hope I was wrong.


 

 good luck


----------



## JakeJack_2008

Quote: 





adamlr said:


> lower your computers digital volume. if your concerned about bit degradation you can set your odac to output 24 bit audio. this way you can "over sample" and add "fake bits" which will be the ones lost in the lowering of digital volume. although, as discussed here a couple of times, the difference isnt exactly noticeable...
> 
> right now i have my computers volume at 50%, and the O2s pot at just over 9 oclock. works just fine for me =]


 
   
  According to the JDS Labs instructions I always set my ODAC to 24-bit/96kHz.
  I only play the Red Book CDs.
  I also rip CDs to WAV files (16-bit/44.1kHz) and then play the WAV files.
  (I don't have any 24-bit/96kHz files yet.)
   
  Any suggestions or comments?


----------



## adamlr

Quote: 





jakejack_2008 said:


> According to the JDS Labs instructions I always set my ODAC to 24-bit/96kHz.
> I only play the Red Book CDs.
> I also rip CDs to WAV files (16-bit/44.1kHz) and then play the WAV files.
> (I don't have any 24-bit/96kHz files yet.)
> ...


 
  good. your "over sampling" 16 but audio into 24 bits. any bit degradation will probably be stripping "fake" bits and no loss of quality should be noticed when lowering digital volume. though as i have already said, even if you didnt over sample, and remained with 16 bits, the difference, though measurable, would most likely not be audible. this is arguable ofcourse, but thats my take on the issue.
   
  what are red book cds?


----------



## ThePeacemaker10

Hey everyone, just a quick question about the ODAC and the O2. I'm looking to purchase some Audioengine A5+'s and Sennheiser HD 598's along with the ODAC and O2 as separate devices. If what I've gathered is correct then I should be fine and dandy connecting things like so:
   
  Computer -> ODAC -> Speakers
   
  Computer -> ODAC -> O2 -> Headphones
   
  Just would like to make sure this setup is good to go before making my purchases.


----------



## adamlr

Quote: 





thepeacemaker10 said:


> Hey everyone, just a quick question about the ODAC and the O2. I'm looking to purchase some Audioengine A5+'s and Sennheiser HD 598's along with the ODAC and O2 as separate devices. If what I've gathered is correct then I should be fine and dandy connecting things like so:
> 
> Computer -> ODAC -> Speakers
> 
> ...


 

 thats how my setup works =]
   
  the a5+ are self powered speakers. i.e, they have an internal amp built into one of them. provide the line out signal from the odac, and you should be fine


----------



## ThePeacemaker10

Quote: 





adamlr said:


> thats how my setup works =]
> 
> the a5+ are self powered speakers. i.e, they have an internal amp built into one of them. provide the line out signal from the odac, and you should be fine


 
   
  Yeah that's what I figured but I wanted some other input about it. Thanks.


----------



## gkanai

Quote: 





thepeacemaker10 said:


> Hey everyone, just a quick question about the ODAC and the O2. I'm looking to purchase some Audioengine A5+'s and Sennheiser HD 598's along with the ODAC and O2 as separate devices. If what I've gathered is correct then I should be fine and dandy connecting things like so:
> 
> Computer -> ODAC -> Speakers
> 
> ...


 
   
  That's about right.
   
  Depending on how hard it is to drive your headphones, you may or may not require a headphone amp. Most headphones do benefit from an amp however, so take that into consideration. If you're going to drive power-hungry headphones like planar-magnetics, then you'll want the O2. If you're more about IEMs, you may want the JDS Labs C5 amp, which is great for IEMs and most headphones, but not the really power-hungry ones.


----------



## Jerrey S

Hey O2+Odac users, have you kept the builtin battery of O2 or removed it? I think the battery is completely useless and wonder if it will degrade fast.


----------



## mikeaj

Quote: 





jerrey s said:


> Hey O2+Odac users, have you kept the builtin battery of O2 or removed it? I think the battery is completely useless and wonder if it will degrade fast.


 
   
  I took out the batteries.  Yeah, it's not good for them to be sitting in there charging for months on end.
   
  Well, you could increase a couple resistor values to slow down the trickle charge, but you may as well just take them out if you never use them.


----------



## Jerrey S

Quote: 





mikeaj said:


> I took out the batteries.  Yeah, it's not good for them to be sitting in there charging for months on end.
> 
> Well, you could increase a couple resistor values to slow down the trickle charge, but you may as well just take them out if you never use them.


 
   
  Thanks. I'll try to do it.


----------



## MrEleventy

I pulled mine as well but I just got a new tube amp, might put them back in and use it as a portable.


----------



## Jerrey S

Another question, anyone feel the O2 is too powerful for HD650? For me the maximum tolerated volume is at 9 o'clock of the button. Consider that HD650 is 300 ohms, I wonder any other headphone can utilize O2's full capacity.


----------



## ProTofik

Ohms doesn't have much do to with the volume level . You may want to change your gain settings to 1x as I did for my hd600.


----------



## adydula

I leave the batteries in.
   
  I unplug the AC adapter and run them down and then re attach the AC and charge them up.....
   
  This keeps the batteries cycled.
   
  If you don't ever intend to use them as intended then remove them.
   
  Alex


----------



## HamilcarBarca

Quote: 





jerrey s said:


> Another question, anyone feel the O2 is too powerful for HD650? For me the maximum tolerated volume is at 9 o'clock of the button. Consider that HD650 is 300 ohms, I wonder any other headphone can utilize O2's full capacity.


 
   
  Read the discussions in this thread about the O2's 1x/2.5x/6x gains.
   
  At the lowest stock gain, 2.5x, I usually can't turn the volume above 10:00 for any headphone I own.


----------



## Shazb0t

I tried to remove the front panel to take the batteries out of my JDS Labs o2.  I couldn't budge the screws with the small screw driver I had.  It appears that they use thread locker.  Anyone else notice this?  Did you just muscle them off?


----------



## miceblue

shazb0t said:


> I tried to remove the front panel to take the batteries out of my JDS Labs o2.  I couldn't budge the screws with the small screw driver I had.  It appears that they use thread locker.  Anyone else notice this?  Did you just muscle them off?




Just try to power it through, or make it easier by using a larger screwdriver. The screws were tight for me too. You can make them looser by screwing the screw part way, unscrew it, screw it, unscrew it, re-screw it. I bought one of their aluminum cases for a school project and I had to self-tap it like this to get a smooth screwing experience.


----------



## adydula

Use a screwdriver that is large enough to do the job....too small you will bugger them up and then will have lots of fun!!
   
  Push really hard to keep the screwdriver from slipping....
   
  Alex


----------



## Shazb0t

I know how to use a screwdriver.  Whatever they did, it's not just a screw in a tapped hole.


----------



## adamlr

Quote: 





shazb0t said:


> I tried to remove the front panel to take the batteries out of my JDS Labs o2.  I couldn't budge the screws with the small screw driver I had.  It appears that they use thread locker.  Anyone else notice this?  Did you just muscle them off?


 
   
  Quote: 





adydula said:


> Use a screwdriver that is large enough to do the job....too small you will bugger them up and then will have lots of fun!!
> 
> Push really hard to keep the screwdriver from slipping....
> 
> Alex


 

 ^this.
   
  my hand hurt like hell after unscrewing those damned screws the first time...


----------



## adydula

Sorry did not mean to educate you on using a screwdriver....call JDS Labs and talk to John if you cant get it open.
  He may be able to suggest something to help...
   
  Alex


----------



## adamlr

oh btw, did you try opening the back panel screws? if the front panel wont open, perhaps try removing the volume knob (1/16" allan wrench unless im very much mistaken) and sliding the board out from the back?


----------



## ThePeacemaker10

Do you guys really recommend taking the batteries out? Nothing's gonna happen if I leave 'em in right?


----------



## shadow419

If you're only going to always run it on AC, I'd take the batteries out.  If you don't want to take them out, I'd run the batteries down like once a week


----------



## HumanSaurusRex

Is it possible to add a optical input to my O2+ODAC combo in a b3-080 case?


----------



## mikeaj

Quote: 





humansaurusrex said:


> Is it possible to add a optical input to my O2+ODAC combo in a b3-080 case?


 
   
  Not without adding in additional electronics, like an optical input DAC.  Or you could always add the input to the case, not hook it up to anything, and thus get no sound.


----------



## trons

Hey guys, so I need to add the O2 amp into my current setup. Currently I have PC>optical toslink>Dacmagic(original)>unbalanced RCA>NAD-320BEE>Wharfedale 9.1.
   
  Can I use an XLR to 3.5mm from the output of the dacmagic to the O2?


----------



## HamilcarBarca

Quote: 





trons said:


> Hey guys, so I need to add the O2 amp into my current setup. Currently I have PC>optical toslink>Dacmagic(original)>unbalanced RCA>NAD-320BEE>Wharfedale 9.1.
> 
> Can I use an XLR to 3.5mm from the output of the dacmagic to the O2?


 
   
  Why not? The O2 accepts a 3.5mm TRS input.


----------



## trons

I just wasn't sure if there was any problem with a balanced output terminating with an unbalanced input. Would I notice a difference inq uality if I used XLR>RCA for my speakers?


----------



## autoteleology

Well, you're not going to get the noise reduction benefits of using a balanced connection, but there likely isn't going to be any _problem_ in terms of output, as long as your cable isn't really long.


----------



## Greenleaf7

HI guys, I am planning to purchase the ODAC + O2 combo. I'm wondering if the dac works if i connect it directly to an iDevice using the Apple camera connector kit.


----------



## Limniscate

Does the O2 start making a thumping sound or pulsating sound through the headphones when the battery is low?


----------



## Shazb0t

limniscate said:


> Does the O2 start making a thumping sound or pulsating sound through the headphones when the battery is low?


 
   
  Yes.


----------



## JakeJack_2008

Quote: 





shadow419 said:


> If you're only going to always run it on AC, I'd take the batteries out.  If you don't want to take them out, I'd run the batteries down like once a week


 
  Good advice. Thanx.


----------



## JakeJack_2008

Quote: 





limniscate said:


> Does the O2 start making a thumping sound or pulsating sound through the headphones when the battery is low?


 
  Good to know it. I haven't expereineced this so far. I'll try soon.
  Thanx.


----------



## Dano91

Quote: 





protofik said:


> Ohms doesn't have much do to with the volume level . You may want to change your gain settings to 1x as I did for my hd600.


 

 I'm not sure if that's a good idea. According to NwAvGuy, peaks in audio at standard listening volumes can be as high as 110 dB for which you will need ~2.5V from amp with HD 600 or 650. But O2 set to 1x gain with ODAC would be able to deliver only 2V.
  I think it's just easier to lower volume in PC.. very probably you won't here any difference in terms of audio quality (Once I made a test with ODAC set to 5% at 16 bit and O2 at full volume, and I couldn't tell the difference with HD 600 vs ODAC at 100% volume @24 bit)


----------



## HamilcarBarca

Quote: 





dano91 said:


> Quote:
> 
> 
> 
> ...


 
   
  I don't quite understand this. The ODAC is supposed to deliver up to 2V RMS; it's not an amplifier. It doesn't have any user settings (like "5%").


----------



## mikeaj

OS volume control, probably.
   
  Whatever 5% there maps to (probably neither 0.1 V nor 0.447 V), that is.


----------



## MrEleventy

hamilcarbarca said:


> I don't quite understand this. The ODAC is supposed to deliver up to 2V RMS; it's not an amplifier. It doesn't have any user settings (like "5%").


 You can set it to 5% via computer volume slider.


----------



## agdr

Quote: 





limniscate said:


> Does the O2 start making a thumping sound or pulsating sound through the headphones when the battery is low?


 
   
  Here is a circuit that fixes the low-battery thumping problem, for anyone into some DIY circuit building work.  
   
  The circuit "latches" the O2 power management circuit when the batteries get low, so that "off" really means "off" rather than the thumping.  To reset this circuit the O2 has to be powered off for about 45 seconds to let the capacitor discharge.  Of course at that point the battery needs charging too since that is what tripped the O2 power management circuit in the first place, otherwise it will just re-latch if the battery is still low (or plug into AC). 
   
  The circuit could just be built up on some cheap perfboard or home etched as shown, then soldered into the points indicated on the O2.  Just wrap a piece of electrical tape around the board to insulate it, with 4 small gauge wires running from the latch board to the O2 PC board.  Since it hooks onto resistors on the top side of the O2 PC board it is easiest to attach when building an O2 up from scratch. Otherwise just a dab of solder on the end of each resistor end to attach the wire.  I've tested the circuit on an O2 and it works well.
   
  R1 and C1 form a time delay circuit to lock out the latch circuit for the first 20 seconds when the O2 is powered on since the O2 mosfets cycle for the turn-on thump prevention.  After that, when the power management mosfets cycle when the battery is low, Q1 turns on while Q2 is already on.  That then shorts out R9 on the O2 PCB, latching the power management circuit "off" as long as the power is still on.  When the O2 power is turned off for about 45 seconds C1 discharges through the power rails, resetting the latch circuit.
   
  Have fun!
  -agdr


----------



## HamilcarBarca

Quote: 





mreleventy said:


> Quote:
> 
> 
> 
> ...


 
   
  My point was there's nothing to set on the ODAC, from computer or otherwise. I replied to a rather confused post.


----------



## Dano91

Quote: 





hamilcarbarca said:


> My point was there's nothing to set on the ODAC, from computer or otherwise. I replied to a rather confused post.


 

 Of course you are right, you can't set anything on ODAC.
  By "5% volume" I meant setting PC volume slider (labeled as odac) to 5%.
   
  The point is, you get 2V RMS only when this slider is set to 100%. 
  And by previous post I wanted to say, that with O2 amp with 1x gain, you get 2V RMS at best, which can be with some headphones (e.g. HD600, 650..) insufficient in terms of audio quality even when they seem to be loud enough.


----------



## adamlr

im having some problems with my odac. sometimes i get crazy, massive, very noticeable distortion and i have to unplug the usb cable from my computer, and then plug it back in again. ive tried different usb outlets but it doesnt help, and im unplugging and replugging my odac almost every day now... on the info sheet provided by jds labs it says the cause is likely weak usb power or bad usb cable. as the cable came from jds labs, im assuming its the former. the solution suggested by jds is to use a powered usb hub, which i can see go for ~30$ on amazon. could anyone explain a little more about this please? is there any other way? my desk is cluttered enough as it is, i dont need another box connected to the mains sitting on it...(edit: or do they run on battery power?). is there a way to fix this through my computers settings or something?


----------



## MrEleventy

it sounds like Windows is powering down the usb ports. try a different power setting in control panel.


----------



## adamlr

Quote: 





mreleventy said:


> it sounds like Windows is powering down the usb ports. try a different power setting in control panel.


 

 thanks. im not very computer savvy im afraid, could you be more specific? im using a laptop on what it calls "high performance" option. the only other power options are all about battery saving and what not ("balanced", "energy saver" etc.). i tried looking around the "devices" section and all - i found no configurations about usb power control


----------



## JakeJack_2008

Very Scary  Moments with the ODAC connected to the O2
   
  Well, I've read in this thread that some of you experienced some buzzing, whining, etc with your O2 & ODAC.
  I thought it would never happen to me, but unfortunately  it did happen, the _buzzing _that is. 
  The buzzing was coming back and going away and coming back and so on every few minutes.
  When there was  no buzzing I _touched _the volume knob on the O2 and the buzzing resumed.
  I _touched _the top of the O2 and the buzzing resumed. I _touched _the ODAC and the buzzing came back.
  The buzzing was on and off in the course of a few hours.
   
  Does anyone  know why did the buzzing occur?
   
  laptop -->  ODAC --> ODAC --> headphones
   
  P.S.
  In my next post (tomorrow?) I'll tell you what really happened.


----------



## adamlr

Quote: 





mreleventy said:


> it sounds like Windows is powering down the usb ports. try a different power setting in control panel.


 

 theres a setting called usb selective suspend setting - its enabled. is it this? should i disable it?
   
  edit: some further google investigation indicates that this may be the solution. though im not 100% sure. oh well, fingers crossed.
  thank you very very much for pointing me in the right direction, theres no way i would have thought of this by myself.


----------



## HamilcarBarca

Quote: 





> Originally Posted by *Dano91* /img/forum/go_quote.gif
> 
> Of course you are right, you can't set anything on ODAC.
> By "5% volume" I meant setting PC volume slider (labeled as odac) to 5%.


 
   
  That should have been obvious, so I must have been having a bad moment. Thanks.
   



> Originally Posted by *Dano91* /img/forum/go_quote.gif
> 
> And by previous post I wanted to say, that with O2 amp with 1x gain, you get 2V RMS at best, which can be with some headphones (e.g. HD600, 650..) insufficient in terms of audio quality even when they seem to be loud enough.


 

   
  No. If the ODAC's output is "loud enough", it's also neutral. There's no insufficiency.


----------



## MrEleventy

adamlr said:


> theres a setting called usb selective suspend setting - its enabled. is it this? should i disable it?
> 
> edit: some further google investigation indicates that this may be the solution. though im not 100% sure. oh well, fingers crossed.
> thank you very very much for pointing me in the right direction, theres no way i would have thought of this by myself.


 Yeah, that should at least knock a variable out if it continues to act up. I think it should be fixed. let's hope.


----------



## chrislangley4253

Quote: 





adamlr said:


> im having some problems with my odac. sometimes i get crazy, massive, very noticeable distortion and i have to unplug the usb cable from my computer, and then plug it back in again. ive tried different usb outlets but it doesnt help, and im unplugging and replugging my odac almost every day now... on the info sheet provided by jds labs it says the cause is likely weak usb power or bad usb cable. as the cable came from jds labs, im assuming its the former. the solution suggested by jds is to use a powered usb hub, which i can see go for ~30$ on amazon. could anyone explain a little more about this please? is there any other way? my desk is cluttered enough as it is, i dont need another box connected to the mains sitting on it...(edit: or do they run on battery power?). is there a way to fix this through my computers settings or something?


 
  I have this problem with my laptop, never could fix it.

 I think it has to do with the windows usb drivers or the drivers that install when you plug in the dac. Try moving it to a different port or deleting the drivers and letting windows install them anew.


----------



## adamlr

Quote: 





mreleventy said:


> Yeah, that should at least knock a variable out if it continues to act up. I think it should be fixed. let's hope.


 
   
  thanks again =]
   
  Quote: 





chrislangley4253 said:


> I have this problem with my laptop, never could fix it.
> 
> I think it has to do with the windows usb drivers or the drivers that install when you plug in the dac. Try moving it to a different port or deleting the drivers and letting windows install them anew.


 
  ill let you know if changing the settings works, if not, ill try deleting the drivers aswell. moving to a different port didnt help. thank you too


----------



## ProTofik

I had similar problem with buzzing Odac. It won't go until disconnected and plugged back in. The solution was to update my Intel chipset and USB drivers.
problem solved.


----------



## adamlr

Quote: 





protofik said:


> The solution was to update my Intel chipset and USB drivers.


 
  i admit i have no idea what that means


----------



## MrEleventy

find the make and model of your computer and head to their website. they'll have drivers that you can download and update with.


----------



## adamlr

Quote: 





mreleventy said:


> find the make and model of your computer and head to their website. they'll have drivers that you can download and update with.


 

 awesome. thanks again!


----------



## JakeJack_2008

Quote: 





protofik said:


> I had similar problem with *buzzing *Odac. It won't go until disconnected and plugged back in. The solution was to update my Intel chipset and USB drivers.
> problem solved.


 
   
  Well, as I mentioned above (post #1302) I had had a similar buzzing problem with my ODAC as well. I switched to the battery power and it didn't help either....
   
  After about 3 hours I noticed that I did _not fully insert _the FiiO line-out cable into the ODAC. - So the solution was a trivial one.
  Simply, due to my negligence I did experinece some on-and-off buzzing from the ODAC.
   
  Well, apart from those three scary hours I have not experienced any buzzing, whining, noise, etc. from my ODAC and O2. They sound fantastic.


----------



## adamlr

Quote: 





jakejack_2008 said:


> Well, as I mentioned above (post #1302) I had had a similar buzzing problem with my ODAC as well. I switched to the battery power and it didn't help either....
> 
> After about 3 hours I noticed that I did _not fully insert _the FiiO line-out cable into the ODAC. - So the solution was a trivial one.
> Simply, due to my negligence I did experinece some on-and-off buzzing from the ODAC.
> ...


 

 glad to hear it. disabling "selective suspend" didnt solve my problem. guess ill have to update my drivers after all...


----------



## JakeJack_2008

Quote: 





adamlr said:


> glad to hear it. disabling "selective suspend" didnt solve my problem. guess ill have to update my drivers after all...


 
  Thanx. I am learning a lot in this thread, e.g. 'selective suspend', etc.
   
  I will be afraid to buy a new laptop or desktop in the future because I might get some buzzing, whining, noise, ... Ha, ha, ...
   
  Also, this USB-business is crazy. So many problems.
   
  By the way, I've read on _this _site and on the Internet that _quality _of USB cables matters. Very interesting. Yeah, it's zeroes and ones, but it matters the way ....
  Anyway, an experienced guy said something like this:
  "I was ignorant about  the impact of the quality of USB cables on sound .... I thought it was just zeroes and ones ..."
   
  Unfortunately, I am afraid 
	

	
	
		
		

		
		
	


	




 to post it here.


----------



## snakeeater692

Do the O2 sound fuller then connected to a direct source or line out compared to headphone out (from Sansa Fuze and my computer's headphone out)? I notice when I connect form my blu ray player line out the sound is more full. Is the thin sound a result or double amping?


----------



## MrEleventy

The O2 is supposed to be transparent so any fuller or thinner sound that you hear should be from the source itself.


----------



## gswilder

O2 Amp & DAC are unbelievably good. Honestly, their size doesn't convey how good these sound. Music is full and rich. Good soundstage. I have tried the Beyerdynamic A1 (which is great with a Beyer HF, but not so much with other brands. A Schiit Lyr (which is my current go to amp). Burson Soloist XL, which is fantastic (and I like it over the non SL version). And a few others. Got a Woo WA6 on the way,
   
  The O2+ODAC com is very very good. One of the better under $300 DAC/AMP combo's out there. Sounds good on my Senn HD800, HD598, HE500's.
   
  Don't let the small size lull you into thinking it is a cheap or toy amp. Highly recommended.


----------



## MrMateoHead

Quote: 





snakeeater692 said:


> Do the O2 sound fuller then connected to a direct source or line out compared to headphone out (from Sansa Fuze and my computer's headphone out)? I notice when I connect form my blu ray player line out the sound is more full. Is the thin sound a result or double amping?


 

 On my laptop, I didn't notice a big difference between line-out and headphone out. The former's higher output impedance should provide lower distortion however.
   
  Your Blu-Ray player likely sounds better because it uses a better DAC than the fuze. The Blu-Ray plater has to support a 24 bit/192 khz multi-channel standard while the Fuze doesn't, and is otherwise designed for a different purpose (which is sourced from a 16-bit 44.1Khz medium). The signal to noise, frequency range, etc. may be superior on the Blu-Ray player.
   
  The O2 is amping whatever output it is being given, so the overall sound quality of your sources at home will be more apparent than you are used to. But no, line-out/headphone out alone is not necessarily a reason why the sound quality is better or worse.


----------



## JakeJack_2008

Quote:


gswilder said:


> O2 Amp & DAC are unbelievably good. Honestly, their size doesn't convey how good these sound. Music is full and rich. Good soundstage. I have tried the Beyerdynamic A1 (which is great with a Beyer HF, but not so much with other brands. A Schiit Lyr (which is my current go to amp). Burson Soloist XL, which is fantastic (and I like it over the non SL version). And a few others. Got a Woo WA6 on the way,
> 
> The O2+ODAC com is very very good. One of the better under $300 DAC/AMP combo's out there. Sounds good on my Senn HD800, HD598, HE500's.
> 
> Don't let the small size lull you into thinking it is a cheap or toy amp. Highly recommended.


 
   
  No,


> the small size *did not *
> 
> 
> 
> ...


 
   
   
   ... and that's why I bought _them._
   
   
   


> One of the better under $300 DAC/AMP combo's out there


 
   
  .... or 
	

	
	
		
		

		
		
	


	




 _the best_???


----------



## miceblue

Quote: 





mreleventy said:


> The O2 is supposed to be transparent so any fuller or thinner sound that you hear should be from the source itself.


 
  What defines transparency for an amp? The O2 was tested against the DAC1 and the designer of the O2 claims test subjects couldn't distinguish a difference between them (he doesn't provide any links to the tests though). Is the DAC1 considered the audiophile standard for transparency? If the DAC1 isn't transparent, then neither is the O2, right?


----------



## autoteleology

Just popping in to tell a discovery I made; seems that my O2 / ODAC stack is susceptible to radio interference from my Wi-Fi antenna. Jury's still out on whether it's the stack itself or just the shielded wires connecting them.


----------



## miceblue

Quote: 





tus-chan said:


> Just popping in to tell a discovery I made; seems that my O2 / ODAC stack is susceptible to radio interference from my Wi-Fi antenna. Jury's still out on whether it's the stack itself or just the shielded wires connecting them.


 
  Happened to me too. At one point I was able to hear a specific radio channel's music.....holy mackerel that was weird.


----------



## shadow419

Quote: 





tus-chan said:


> Just popping in to tell a discovery I made; seems that my O2 / ODAC stack is susceptible to radio interference from my Wi-Fi antenna. Jury's still out on whether it's the stack itself or just the shielded wires connecting them.


 
  Tough luck I guess.  The rca from my dac to amp is literally draped over my wireless adapter, and I've never heard a peep.  Not even my cell phone has caused interference.  Hope you can track down a solution.


----------



## HamilcarBarca

Quote: 





tus-chan said:


> Just popping in to tell a discovery I made; seems that my O2 / ODAC stack is susceptible to radio interference from my Wi-Fi antenna. Jury's still out on whether it's the stack itself or just the shielded wires connecting them.


 
   
  Are you using a USB cable with a "ferrite bead" (such as the one shipped by JDS Labs?)


----------



## autoteleology

hurr durr double post


----------



## autoteleology

> Happened to me too. At one point I was able to hear a specific radio channel's music.....holy mackerel that was weird.


 
   
  I can actually top that... I once had a cheap radio/alarm clock, and I discovered one night that when I touched the antenna on the radio, my body served as some sort of an antenna for a Spanish mariachi station that I couldn't pick up anywhere on the dial normally. 
	

	
	
		
		

		
			




   


> Are you using a USB cable with a "ferrite bead" (such as the one shipped by JDS Labs?)


 
   
  No, I'll have to look into getting one. It's a huge problem and it's extremely annoying.


----------



## mikeyb48

Hi,

I have an Objective O2 + ODAC,and wondered how I can use the USB input for the DAC from a portable player (ipod or whatever ) on it rather then just using the 3.5mm analog input. I bought this without knowing anything about headphone amps lol.

I currently use a 3rd Gen iPod Touch and Fiio L10 (30 pin to 3.5mm) lead to connect it to the O2 but would prefer to use the ODAC rather than the iPods DAC to feed the amp, is it possible and if so how? I suspect a powered USB hub might be required ( which I already own for powering my Rasberry PI ), but I am unsure how to set this up for use with my ODAC as it draws too much power to work directly with the iPod. Or will the iPod work this way as I have also read somewhere that you can't get digital out from iPods/iPads?

The O2 + ODAC sounds great via PC USB 

I tend to have the amp bedside for listening before sleep as I have an Electric-Avenues PA2V2 for portable listening.

Using Sennheiser HD650's.

Any help/info greatly appreciated.

Thanks,

Mike.

PS: apologies if this is in the wrong Forum/Section.


----------



## adydula

Transparency in an amp is basically the signal going in comes out unaltered except for the amplitude.
   
  The old amp definition of a straight wire with gain analogy.
   
  It doesn't filter out or add to the signal input.
   
  The O2 does this very, very well.
   
  Alex


----------



## JakeJack_2008

Quote: 





adydula said:


> Transparency in an amp is basically the signal going in comes out unaltered except for the amplitude.
> 
> The old amp definition of a straight wire with gain analogy.
> 
> ...


 
  I guess that the term 'transparency' also  applies  to DACs? And if so, the ODAC  is transparent as well.
  Moreover, the ODAC and O2 as a combo or as _two separates _are transparent.


----------



## adydula

The amp should do nothing to the signal but amplify it to a level to drive a transducer like a speaker.
   
  So this is a rather simple device.....but amps can influence many unwanted things to the signal.....depending on its design etc...
   
  A Dac takes bits and coverts them to an analog signal, way more complex, and if not designed correctly can attribute to unwanted things in different ways.
   
  Compairing an analog signal in an amp is a lot less complex.
   
  Its hard to say a dac is transparent based on the above definition because your not comparing apples to apples...it bits to an analog signal....no real way to make this comparison. A Dac does a transformation...while an amp 'should not' just amplification...
   
  Alex


----------



## adamlr

Quote: 





mikeyb48 said:


> Hi,
> 
> I have an Objective O2 + ODAC,and wondered how I can use the USB input for the DAC from a portable player (ipod or whatever ) on it rather then just using the 3.5mm analog input. I bought this without knowing anything about headphone amps lol.
> 
> ...


 
  im pretty sure you cant stream digital data from an ipod. galaxy s3 and iphone 4 can if im not mistaken...


----------



## mikeyb48

adamlr said:


> im pretty sure you cant stream digital data from an ipod. galaxy s3 and iphone 4 can if im not mistaken...



Hi,

I thought so, thanks for the info. Anyone help with Digital/USB setup for another DAP on my O2 + ODAC ?

Thanks,

Mike.


----------



## adamlr

Quote: 





mikeyb48 said:


> Hi,
> 
> I thought so, thanks for the info. Anyone help with Digital/USB setup for another DAP on my O2 + ODAC ?
> 
> ...


 

 its not a very common feature i dont think... good luck


----------



## lorriman

adydula said:


> Transparency in an amp is basically the signal going in comes out unaltered except for the amplitude.
> 
> The old amp definition of a straight wire with gain analogy.
> 
> ...




The O2 is claimed to do this perfectly...within the parameters of what is humanly audible. Distortions and noise etc are below audible levels. 

So it really doesn't do it 'really really well' if the O2 is working as claimed. Nor is it 'good for the price', a previous adydula tricksey statement. 

It's perfect at any price, if it does what it is claimed it does (and independent tests at Innerfidelity.com appear to confirm); to perfectly reproduce audio. Defacto hifi.

The O2 is the significant evidence that high end hifi amps/dacs above $300 are arguably a waste of money. Demonstrating that was the whole point of its design, if you read the website. It would appear that the the limitations of the human auditory system were reached in the 90s; and now audio tech is cheap (excepting speakers/headphones which have mechanical limitations).

There is a strong motivation to undermine the O2/ODAC, and on many levels it is attacked. Some of those levels may include 'praisers' who damn with feint praise. Aduyla is even more subtle, if deliberate.

They are winning that battle. But as Thatcher almost said, they cannot win the war.

I do hope that adyula is a person who has simply chosen his words poorly and is accidentally undermining the O2/ODAC, but I have previously criticised his 'positive' evaluations, and am surprised to see a new version of the same.


----------



## adydula

lorriman,
   
  why cant we just be friends!!
   
  let me be very, very blunt.....I am an O2 advocate, because it works and works very very well. period.
   
  I believe regardless of the price that it doenst get any better than this....but the low cost even makes it better....
   
  I have 2 of them now, and 2 Odacs....and I use them all the time.
   
  You can spend more but really you don't have to ....to have great sound with a good pair of cans....
   
  over and out....
   
  the lambic tonight is superb!
   
  Alex
   
  Gee....subtle....I am so proud!!


----------



## HamilcarBarca

Quote: 





> Originally Posted by *JakeJack_2008* /img/forum/go_quote.gif
> 
> I guess that the term 'transparency' also  applies  to DACs? And if so, the ODAC  is transparent as well.
> Moreover, the ODAC and O2 as a combo or as _two separates _are transparent.


 
   
  I think so -- as an analogy to optics. A transparent lens reduces or enlarges but doesn't distort the image.


----------



## Currawong

Quote: 





lorriman said:


> The O2 is the significant evidence that high end hifi amps/dacs above $300 are arguably a waste of money* for me*.


 
   
  FTFY.


----------



## lorriman

currawong said:


> FTFY.




Guffaw!! 

I don't think so. If the O2 claims are true then logically it proves that above $300 is a waste for *everyone*.


----------



## lorriman

adydula said:


> lorriman,
> 
> why cant we just be friends!!
> 
> ...




That's nice, but later it'll be back to "fantastic for the price" or "very very good" etc etc influencing our weaker brethren or casual visitor to pay more for something they think will be better still (the implication of those words). 

I would like to be friends, but the problem is that it's impossible to know whether you are good or evil; the evidence isn't conclusive. Are you a Gandalf or a Saruman? Both have grey beards and white vestments. 

But as the saying, keep your friends close and your enemies closer. However I'm not quite ready for a cuddle just yet. 



> Gee....subtle....I am so proud!!




Yes, but that's only if you are deliberately undermining the O2. In which case I am in admiration of a marvellously executed campaign.


----------



## Currawong

Quote: 





lorriman said:


> Quote:
> 
> 
> 
> ...


 
   
  Enjoyment isn't logical.


----------



## MrEleventy

currawong said:


> Enjoyment isn't logical.



+1 from me
-100 from my wallet. ;D


----------



## HamilcarBarca

Quote: 





lorriman said:


> Quote:
> 
> 
> 
> ...


 
   
  Except in cases where a listener is seeking some particular feature (e.g., switchable inputs, different inputs, or a different case) or some particular form of distortion (e.g., the second-order harmonic distortion commonly associated with vacuum tubes) spending more gets the buyer nothing more than a more-expensive product. It's analogous to spending tens (or hundreds or thousands) of dollars per foot of copper(!) wire.


----------



## lorriman

hamilcarbarca said:


> Except in cases where a listener is seeking some particular feature (e.g., switchable inputs, different inputs, or a different case) or some particular form of distortion (e.g., the second-order harmonic distortion commonly associated with vacuum tubes) spending more gets the buyer nothing more than a more-expensive product. It's analogous to spending tens (or hundreds or thousands) of dollars per foot of copper(!) wire.




Well, yes, but I think that goes under the "all things being equal" clause.


----------



## Poladise

I'm thinking about running my Little Dot Mk iii into a O2, hoping it will have a good hybrid sound. I could raise the O2 volume pot and control the level with the LD, but does anyone know if bypassing the volume section and using the O2 like a power amp would be doable?


----------



## JakeJack_2008

Quote: 





hamilcarbarca said:


> I think so -- as an analogy to optics. A transparent lens reduces or enlarges but doesn't distort the image.


 
  Thanx.
   
  Many times I've read that certain DAC *chips  - *obviously taking into account their *implementations - *sound warm, analog-like, analytical, cold, musical, clinical, sterile, etc.
  Additionally, what I've read on this site and on the Internet, some  modern *DAC*s have _op-amps _built-in and these can surely _color _the sound.
  If I remember correctly, I've read that the HiFiMan Hm601 (or Hm 602, ...?) has a _classic _Philips DAC *chip *which sounds warm and analog-like!
   
  Any comments how does this relate to the ODAC? To me, it sounds  very _transparent_, courtesy of the transparent O2. (I mean that the O2 amp does not 'spoil' the ODAC's trasparency.)
   
   
  P.S.
  It's a shame that Stereophile have never reviewed the O2/ODAC system.


----------



## HamilcarBarca

Quote: 





poladise said:


> I'm thinking about running my Little Dot Mk iii into a O2, hoping it will have a good hybrid sound. I could raise the O2 volume pot and control the level with the LD, but does anyone know if bypassing the volume section and using the O2 like a power amp would be doable?


 
   
  The O2 is a (standard) amplifier which expects a line-level, up to 2V RMS. The MKIII web page says: "Pre-Amplifier Voltage: 10V RMS", so it's not a (standard) pre-amplifier. If you use it for a "pre-amp", you'll have to keep its volume quite low to avoid overloading the input stage of the O2.


----------



## adamlr

hmmmm. im enjoying the conversation going on here. im afraid i dont have enough technical knowledge or audiophile experience to contribute much, but i would like to add something nonetheless.
  the creator of the O2 did say that the amp could compete with any amp under 500$. so, continuing the discussion on whether or not you can have a "better" amp for more money, going on the description of the creator, would you say that >500$ amps exist that do sound "more transparent"? excluding features, looks, build quality and things like that, just sound.


----------



## adydula

oh great now there are degrees of transparency.....
   
  lorri - Buddy ole pal...
   
  ""That's nice, but later it'll be back to "fantastic for the price" or "very very good" etc etc influencing our weaker brethren or casual visitor to pay more for something they think will be better still (the implication of those words).""
   
  But the O2 *is* fantastic for the price and its very very good etc....how the heck is that crapping on the O2?
   
  Maybe I should say the O2 is very, very, very, very. very , good for the price...heck nope i think I will state that in my humble opinion
  that (for currowang) the O2  is just well:
   
PERFECT!!
   
Convinced yet??
   
Alex
  
  Can other amps be as good, yes...they can....but few if any at the cost of the O2.
  Note: I do like LOTR as well!!


----------



## DuckSoup

Recently I found 1 small problem with my O2 (it is from Epiphany Acoustics). Sometimes when I turn the volume pot while something is playing I can hear some cracking in right channel, is not extremly loud, but easly audible. Strange thing for me is that it happens only sometimes. Anyone run into simililar issue? What's the most common cause of such behaviour (broken volume pot)?

Amp is ofc feed by ODAC. Any help is appriciated.


----------



## RustA

Quote: 





ducksoup said:


> Recently I found 1 small problem with my O2 (it is from Epiphany Acoustics). Sometimes when I turn the volume pot while something is playing I can hear some cracking in right channel, is not extremly loud, but easly audible. Strange thing for me is that it happens only sometimes. Anyone run into simililar issue? What's the most common cause of such behaviour (broken volume pot)?
> 
> Amp is ofc feed by ODAC. Any help is appriciated.


 
   
  This can occur with other amplifiers as well, it's connected to the pot... You can have a look at it, or leave it as it is, it's not a problem at all unless you find that behavior annoying.
   
  And yes, it usually occurs randomly... That's normal as well.


----------



## Mahdi8

I've got a jdslabs o2 for two weeks now. Since I plan to use it as a desktop amp fully I've removed the battery a couple days ago. Because of it I start to notice that the amp switch of when I move it because of there is movement in the power adaptor jack so i need to adjust the plug a bit. Is this normal? I always feel the power plug is as solid as the 3.5mm plug but never worry about it until now


----------



## MrEleventy

It shouldn't be. If you bought it from JDS, I would contact them about it. Sounds like a loose solder joint.


----------



## Mahdi8

I bought it used. But it's only one month old. Thanks for the tip. Guess I'll try to open it and see if the jack has loose solder


----------



## DuckSoup

rusta said:


> This can occur with other amplifiers as well, it's connected to the pot... You can have a look at it, or leave it as it is, it's not a problem at all unless you find that behavior annoying.
> 
> And yes, it usually occurs randomly... That's normal as well.



Thanks for the answer. I think I should remove batteries, as my amp is used mainly as desktop, so when I disasemble O2, I will take a look at the pot at the same time.


----------



## mikeyb48

ducksoup said:


> Recently I found 1 small problem with my O2 (it is from Epiphany Acoustics). Sometimes when I turn the volume pot while something is playing I can hear some cracking in right channel, is not extremly loud, but easly audible. Strange thing for me is that it happens only sometimes. Anyone run into simililar issue? What's the most common cause of such behaviour (broken volume pot)?
> 
> Amp is ofc feed by ODAC. Any help is appriciated.


Hi,

I am sure I read this same problem somewhere else on a different amp and it was suggested to ease the volume knob back off the spindle a tiny bit to save it rubbing against the housing, no idea if help but worth a try, just be careful and not pull too hard or far.

Mike.


----------



## Mahdi8

Quote: 





mreleventy said:


> It shouldn't be. If you bought it from JDS, I would contact them about it. Sounds like a loose solder joint.


 
  Just opened it definitely no movement in the solder joint. But looking more to it looks like the Australian adaptor plug that I've got from JDS has a slightly smaller dimension than the power adaptor hole. Might need to rewire the power adaptor with a new plug. I guess it's saver option than unsoldering the board to replace the adaptor connection


----------



## DuckSoup

mikeyb48 said:


> Hi,
> 
> I am sure I read this same problem somewhere else on a different amp and it was suggested to ease the volume knob back off the spindle a tiny bit to save it rubbing against the housing, no idea if help but worth a try, just be careful and not pull too hard or far.
> 
> Mike.



Thanks for the suggestion, I will try it this evening.


----------



## mikeyb48

Quote: 





ducksoup said:


> Thanks for the suggestion, I will try it this evening.


 
  Hi,
   
  hope it helps, I think I read similar problem on PA2v2 portable amp and it cured it, not sure if same issue as yours but might be worth a try anyway.
   
  Mike.


----------



## adydula

I have seen more issues with the plugs that are inserted into the O2....I had one that was 'scratchy', lubricated with Deoxit and its fine now..connectors and the O2 are the weakest link....
   
  Alex


----------



## DuckSoup

mikeyb48 said:


> Hi,
> 
> hope it helps, I think I read similar problem on PA2v2 portable amp and it cured it, not sure if same issue as yours but might be worth a try anyway.
> 
> Mike.



I tried it few minutes ago and despite adjusting volume like crazy I don't hear any cracks anymore, might be just lucky or it is solved


----------



## lcooksl

Am about to get an O2 and have the possibility to choose which two gain settings to get. Still don't find it being clear to me which will be optimal after reading the numerous posts in here. Thinking 1x gain for the first but dunno what second setting to get.
   
  Use case will be either macbook air > EDac (Epiphany Acoustics) > O2 or iPhone5 > LOD via Lightning to 30 pin adapter > O2
   
  It will mainly be used with Heir Audio Tzar 350 iems (350ohm) 
   
  If someone could clarify what second gain setting is optimal to get considering the use case but with least hit to flexibility on which head phone/iems to use. Was thinking 3x but don't know enough about electronics to make a educated decision. Any help appreciated.


----------



## mikeaj

If you always use ODAC as source and never turn the volume down in software, 1x and 3.5x.  With max ODAC output, 3.5x is the max the O2 can handle anyway.
   
  Otherwise, higher values could be appropriate.  Especially if you're focused on IEMs, 1x and 3.5x may still be reasonable choices regardless.


----------



## Sat1re

Why is it shipped 6.5x if 3.5x is the max?


----------



## mikeaj

They just want to follow the "default" values for the O2, for whatever reason.  Those are 2.5x and 6.5x.  It really doesn't make sense for those to be the defaults for the O2 / ODAC combo unless you think that people are using software volume control to reduce the level out of the DAC.
   
  Default values for the O2 were decided by some guy who imagined that a lot of people would use the amp with sources like say an iPod or some portable device (some computers and laptops too) that has a lower output level than standard ~2V Redbook level that the ODAC follows.  For those kinds of devices, more than 3.5x can be handled, and furthermore it could be necessary some people with some headphones, to reach a loud enough volume level.
   
  The smaller the signal out of the source, the more gain you need to reach an equivalent output level.


----------



## RustA

Quote: 





mikeaj said:


> They just want to follow the "default" values for the O2, for whatever reason.  Those are 2.5x and 6.5x.  It really doesn't make sense for those to be the defaults for the O2 / ODAC combo unless you think that people are using software volume control to reduce the level out of the DAC.
> 
> Default values for the O2 were decided by some guy who imagined that a lot of people would use the amp with sources like say an iPod or some portable device (some computers and laptops too) that has a lower output level than standard ~2V Redbook level that the ODAC follows.  For those kinds of devices, more than 3.5x can be handled, and furthermore it could be necessary some people with some headphones, to reach a loud enough volume level.
> 
> The smaller the signal out of the source, the more gain you need to reach an equivalent output level.


 
   
  And is it only about an output level (loud enough = 100% quality)? Or does it help to use higher gain with high impedance headphones (regardless of their sensitivity)?


----------



## mikeaj

Quote: 





rusta said:


> And is it only about an output level (loud enough = 100% quality)?


 
   
  Not really.  All amps have imperfections (e.g. there is nonzero noise, nonzero distortion, for starters), so you never get perfect fidelity.  Also, some people ostensibly prefer a sound with lower fidelity in a certain way and might (confusingly?) define quality in some way that doesn't really relate to fidelity.
   
   


rusta said:


> Or does it help to use higher gain with high impedance headphones (regardless of their sensitivity)?


 

   
  Higher gain usually means worse performance, but it really depends on the device you're talking about.  Certainly for the O2 you could demonstrate some worse performance on a test bench.  You're free to try whatever, but by the textbook you shouldn't intentionally set out to use more gain than is necessary.  Usually it shouldn't make too much practical difference other than the difference in volume and the ramifications of that, like having to use a different position on the volume control.  I wouldn't really overthink it.
   
  All that is regardless of the impedance of the headphones.  Higher impedance just means you need a higher signal (voltage) level to transfer an equivalent amount of power to the headphones.  Thus you need to boost the level by a higher amount, i.e. higher gain.  There's nothing much there about sound quality or anything special to take into consideration.
   
   
   
  The above discussion regarding gain settings was just about avoiding input clipping, which is a different concern than you need to have for many other amps and situations.


----------



## lorriman

adamlr said:


> hmmmm. im enjoying the conversation going on here. im afraid i dont have enough technical knowledge or audiophile experience to contribute much, but i would like to add something nonetheless.
> the creator of the O2 did say that the amp could compete with any amp under 500$. so, continuing the discussion on whether or not you can have a "better" amp for more money, going on the description of the creator, would you say that >500$ amps exist that do sound "more transparent"? excluding features, looks, build quality and things like that, just sound.




No because while there are >$500 amps that have either more power (which one or two bizzare headphones benefit by) or even lower noise/distortion performance, the latter is effectively irrelevant because the O2/ODAC performance in those terms is already at inaudible levels and will make no difference to experience let alone pleasure. So while >$500 amps and dacs might have better performance, it's academic really. The O2 has this even at high gain; so clipping the resistors to configure the minimum gain to 1x shouldn't be done for the sake of audio performance but rather because at the default 2.5x it is already too much gain for many headphones (since the volume knob has left-right audio imbalance when turned down too much) unless you turn down the source. 

And logically, as you've probably guessed, it's impossible to be more transparent. I suppose one could say nearly transparent and even more nearly transparent, but since the O2 is said to be (and independent tests confirm it) actually transparent, then you can't go anywhere from there even if you do spend >$500.

So unless you need some kind of fancy feature that the O2 doesn't have, or have the HE-6 or AKG100, then the O2/ODAC is all you really need. Having said that, the magni/modi offering from Schiit is a designed-by-measurements transparent combo, and cheaper and smaller (and prettier). Being portable and having less power, there may be more headphones that combo can't power, but for many they are worth considering. If you just need an portable amp then another transparent by-measurements design is the JDS C5, which looks good indeed.


----------



## autoteleology

> Also, some people ostensibly prefer a sound with lower fidelity in a certain way and might (confusingly?) define quality in some way that doesn't really relate to fidelity.


 
   
  I've been trying to put this concept into words for ages.


----------



## miceblue

ODAC+O2+LCD-2 = heaven. Oh my gosh that was the most beautiful sound I have heard from an LCD-2. Tube amps don't do the LCD-2 justice from my experience.


----------



## adydula

miceblue I had the same setup, and the LCD2's were superb....unfortunately the LCD2's are now sold. 
	

	
	
		
		

		
			




   
  Only have my Q701's and Grados...
   
  Alex


----------



## adamlr

Quote: 





lorriman said:


> No because while there are >$500 amps that have either more power (which one or two bizzare headphones benefit by) or even lower noise/distortion performance, the latter is effectively irrelevant because the O2/ODAC performance in those terms is already at inaudible levels and will make no difference to experience let alone pleasure. So while >$500 amps and dacs might have better performance, it's academic really. The O2 has this even at high gain; so clipping the resistors to configure the minimum gain to 1x shouldn't be done for the sake of audio performance but rather because at the default 2.5x it is already too much gain for many headphones (since the volume knob has left-right audio imbalance when turned down too much) unless you turn down the source.
> 
> And logically, as you've probably guessed, it's impossible to be more transparent. I suppose one could say nearly transparent and even more nearly transparent, but since the O2 is said to be (and independent tests confirm it) actually transparent, then you can't go anywhere from there even if you do spend >$500.
> 
> So unless you need some kind of fancy feature that the O2 doesn't have, or have the HE-6 or AKG100, then the O2/ODAC is all you really need. Having said that, the magni/modi offering from Schiit is a designed-by-measurements transparent combo, and cheaper and smaller (and prettier). Being portable and having less power, there may be more headphones that combo can't power, but for many they are worth considering. If you just need an portable amp then another transparent by-measurements design is the JDS C5, which looks good indeed.


 

 oh im already and O2 + Odac owner. i was just thinking out loud. thank you for your response. are you saying that ruler flat frequency responses were measured with the O2 at a reasonable, consistent volume? colour me impressed =]
   
  interesting you should mention the C5, because people have reported hearing differences between the O2 and the C5, even though they are both "transparent by-measurements designs". so would they fail a blind test? or is one "closer to neutral" than the other?


----------



## HamilcarBarca

Quote: 





> Originally Posted by *adamlr* /img/forum/go_quote.gif
> 
> oh im already and O2 + Odac owner. i was just thinking out loud. thank you for your response. are you saying that ruler flat frequency responses were measured with the O2 at a reasonable, consistent volume? colour me impressed =]


 
   
  In all electronic equipment, deviations from "ruler flat frequency response" are present and measurable. The deviations of O2 and ODAC were measured to be well below the level of audibility.
   


> Originally Posted by *adamlr* /img/forum/go_quote.gif
> 
> interesting you should mention the C5, because people have reported hearing differences between the O2 and the C5, even though they are both "transparent by-measurements designs". so would they fail a blind test? or is one "closer to neutral" than the other?


 

   
   
  If two amplifiers (e.g., the O2 and C5) are both neutral, then a blind test would show them to be (statistically) indistinguishable, regardless of any anecdotal observations to the contrary.


----------



## adamlr

alright. i can accept that. but what about soundstage for instance? you cant really measure things like that can you? again, im a very happy O2+Odac owner. im not questioning the gear or trying to fault it. but still, and perhaps i have fallen victim to hype and industry propaganda, do you mean to tell me that for like, 95% of all headphones, for ~300$ you get a top notch setup, unmatched by any other as far as measurements and neutrality go? that so long as youre not using power hungry monsters, the objective pair is as good as it gets, excluding things like looks and features? 
  edit: im just saying i find it hard to believe is all. alot of people would consider the asgard (gasps) for arguments sake to be an upgrade. what about things like the Grace M903, or benchmark stuff?


----------



## RustA

Quote: 





adamlr said:


> alright. i can accept that. but what about soundstage for instance? you cant really measure things like that can you? again, im a very happy O2+Odac owner. im not questioning the gear or trying to fault it. but still, and perhaps i have fallen victim to hype and industry propaganda, do you mean to tell me that for like, 95% of all headphones, for ~300$ you get a top notch setup, unmatched by any other as far as measurements and neutrality go? that so long as youre not using power hungry monsters, the objective pair is as good as it gets, excluding things like looks and features?
> edit: im just saying i find it hard to believe is all. alot of people would consider the asgard (gasps) for arguments sake to be an upgrade. what about things like the Grace M903, or benchmark stuff?


 
   
  O2 and ODAC are definitely not the last word... Don't believe it. O2 is brilliant on unity gain as it is completely dead silent and offers great soundstage for the price. But it doesn't work great with high impedance headphones, at least from my experience. ODAC is no less great for the price but even my StageDAC has more detail... And if I take its crossfeed and all the different filters in consideration, Meier's DAC is in another league \(or even several leagues above) in terms of transparency.
   
  Don't get me wrong, I love this Objective stuff and have owned them several times, even had more units at the same time...


----------



## mikeaj

Quote: 





adamlr said:


> alright. i can accept that. but what about soundstage for instance? you cant really measure things like that can you? again, im a very happy O2+Odac owner. im not questioning the gear or trying to fault it. but still, and perhaps i have fallen victim to hype and industry propaganda, do you mean to tell me that for like, 95% of all headphones, for ~300$ you get a top notch setup, unmatched by any other as far as measurements and neutrality go? that so long as youre not using power hungry monsters, the objective pair is as good as it gets, excluding things like looks and features?
> edit: im just saying i find it hard to believe is all. alot of people would consider the asgard (gasps) for arguments sake to be an upgrade. what about things like the Grace M903, or benchmark stuff?


 
   
  Soundstage is mostly a creation of the recording process, mix, mastering.  But for playback of any given recording, it should primarily depend on the transducers and their positioning (for a headphone, having them right next to your ears is way way way wrong, if you're listening to material mastered on and intended for playback on speakers).  Perhaps a combination of other factors: distortion, frequency and phase response, other things, also influence sound stage.  It's something that different people perceive differently, so it's hard to say.  Now, as for what people perceive, that heavily depends on what they're listening for, the state of their mind, and so on—many factors other than just the sound produced.
   
  Other devices may have different features and so on, plugs, aesthetics, etc.  Some have higher power output.  How do you define an upgrade?
   
   


Spoiler: Bonus%20discussion



 
  So let's suppose you're just interested in the signals produced by audio devices, as that's what influences the actual sounds being presented to you.  You could make a case that sound quality is about an entire experience and more than just the sound waves themselves, but that's a topic for another day.
   
   
  So overall, O2 and ODAC both produce very good test benchmark results (except O2 channel balance, possibly).  In most categories, they are well beyond what many people (in the industry) would consider is good enough, individually, for many different measurable parameters like frequency response, noise, harmonic distortion, etc.  Some previous psychoacoustics research has been done to determine these limits.  Some people question the validity of those results.  In fact, many other audio products should exceed those levels as well.
   
  As a result of that (in general), and after some people have listened for themselves, they claim that something like the O2 / ODAC are indistinguishable from ideal parts.  In general, one would expect that very small deviations are indistinguishable from the original.  The point of contention is how close is necessary, and in which ways.
   
  When doing comparisons between audio devices, people often don't very carefully match volume levels; differences in volume are often mistaken for differences in sound quality, so many comparisons cannot be directly taken at face value.  Many others, even run blinded (mostly single blind), do not properly control all the nuisance variables.  There's a real lack of very good data, because it's hard to do.  As a result, people argue over this stuff incessantly, without going anywhere.
   
  I don't think there's any very well-controlled demonstrations that people are sensitive to really small deviations from ideal, like the O2 and ODAC mostly accomplish.  On the other hand, there aren't many demonstrations of much in the first place.  There are many many examples of audiophiles and others who think they can tell stuff apart, not being able to when conditions are better controlled.  There are some anecdotes of people being able to, but then some guys question their methodology (with good reason? decide for yourself).


----------



## adamlr

Quote: 





mikeaj said:


> Soundstage is mostly a creation of the recording process, mix, mastering.  But for playback of any given recording, it should primarily depend on the transducers and their positioning (for a headphone, having them right next to your ears is way way way wrong, if you're listening to material mastered on and intended for playback on speakers).  Perhaps a combination of other factors: distortion, frequency and phase response, other things, also influence sound stage.  It's something that different people perceive differently, so it's hard to say.  Now, as for what people perceive, that heavily depends on what they're listening for, the state of their mind, and so on—many factors other than just the sound produced.
> 
> Other devices may have different features and so on, plugs, aesthetics, etc.  Some have higher power output.  How do you define an upgrade?
> 
> ...


 

 wow. urm, alright. considering all you have written, including the spoiler, i would consider an upgrade like this: noticeably audibly "more transparent" than the objective set and still being able to drive 95% of all headphones just like the O2. excluding build quality, looks, features, exotic\prestigious components. just soundwise, presenting a flat, linear response and having enough power to drive allmost all headphones, but doing so better than the O2.
  in all honesty, i wasnt really considering getting any other amp anyway. but could it be that getting another amp (for the same purpose as the O2, i.e - not more portable or whatever) would simply be redundant? looks like i made the right choice of amps... somehow i still dont buy it though. maybe im too brainwashed


----------



## miceblue

Speaking of comparing the ODAC/O2 to more expensive rigs...


----------



## SunshineReggae

Quote: 





rusta said:


> O2 and ODAC are definitely not the last word... Don't believe it. O2 is brilliant on unity gain as it is completely dead silent and offers great soundstage for the price. But it doesn't work great with high impedance headphones, at least from my experience. ODAC is no less great for the price but even my StageDAC has more detail... And if I take its crossfeed and all the different filters in consideration, Meier's DAC is in another league \(or even several leagues above) in terms of transparency.
> 
> Don't get me wrong, I love this Objective stuff and have owned them several times, even had more units at the same time...


 

 This is the kind of stuff that I don't believe. I especially like the note on detail, which reeks of sighted testing. I also like where you say the Meier's DAC is superior in transparancy - while you introduce forms of distortion such as crossfeed and tweak filters.
   
  Don't get me wrong, I love reading about all the devices that don't actually improve sound quality, but ultimately it's audiophile nonsense.


----------



## SunshineReggae

Quote: 





adamlr said:


> alright. i can accept that. but what about soundstage for instance? you cant really measure things like that can you? again, im a very happy O2+Odac owner. im not questioning the gear or trying to fault it. but still, and perhaps i have fallen victim to hype and industry propaganda, do you mean to tell me that for like, 95% of all headphones, for ~300$ you get a top notch setup, unmatched by any other as far as measurements and neutrality go? that so long as youre not using power hungry monsters, the objective pair is as good as it gets, excluding things like looks and features?
> edit: im just saying i find it hard to believe is all. alot of people would consider the asgard (gasps) for arguments sake to be an upgrade. what about things like the Grace M903, or benchmark stuff?


 

 Have you ever wondered *why* you believe amping should be expensive?
   
  Anyway, yes if you have an amp like a fiio e9 or an O2, its really about as good as it's going to get. For some reason people still want to believe amps can "improve soundstage", make the sound "sweet", or "liquid", and all that nonsense. It's just stupid to be honest. There's really no other word for it.


----------



## miceblue

Quote: 





sunshinereggae said:


> Quote:
> 
> 
> 
> ...


 
  From experience, tube amps tend to be more expensive than solid state. That plus the art of designing them due to heat transfer and whatnot (I don't know how tube amps work yet). Something like the Bottlhead Crack is fairly inexpensive for a tube amp, and it's all analogue, which might be a buying decision for some. My dad really likes the whole analogue experience since he was born in that kind of era for example.
   
  For solid state amps, it seems that most solid states that are more expensive have more inputs and outputs; the O2 only has 1 input, 1 output. I have to wonder how much work went into the SPL Phonitor for example since there are so many things that can be adjusted as for per headphone usage, something the O2 can't. Were the O2 a "one solution for all" thing, wouldn't professionals be using them and all that jazz?
   
  As for soundstage, I, and others, have heard the JDS Labs C5 and its soundstage is smaller than that of the O2. It's one of the main reasons why I use it with the K 701 because with the O2 the K 701's [to me] wonky-sounding soundstage is somewhat alleviated with a smaller soundstage amp. Believe what you want, but I'm just posting my impressions and what I'm hearing. I'm not going to lie and say they sound exactly the same, because they don't, no matter what the numbers say, I hear a difference.


----------



## JakeJack_2008

I'd like to buy a new pair of _preferably open back _headphones: $190 - $299 and use them (only) with the *ODAC *and *O2*.
  As I mentioned in this thread (and in the ODAC thread) I am using my DT 880 (250 Ohm; 2005 Edition) or  sometimes my Sennheiser HD 595 with the JDS Labs ODAC and O2 as two _standalone _units.
  I am super happy. No complaints. .....but I would like to _explore _more.
   
  I thought about buying the UHA-6S MKII, or iBasso D12, or the Dragonfly, or the latest Merridian Explorer, or the DacPort LX, etc.
  but after reading all those discussions in _this _thread and in the relevant threads about the ODAC, UHA-6S MKII,    ,... DacPort LX, etc
  I came to the conclusion that I do _not need _another dac or amp since the ODAC and O2 are _excellent_.
  Furthermore since  headphones have the _biggest impact _on the sound  therefore I should focus on buying a _better _than the DT 880 pair of headphones instead of buying another DAC and headpnone amp. (At least for now.)
  I'd like to buy something like AKG K701/702 or Q701, AT ATH-*AD*900*X, S*ony MA-900, also _closed _back AKG K 550, etc.
   
  My music: rock/hard rock, mainstream metal and obviously some pop.
  I do _not  _listen to rap/hip-hop, electronic, extreme metal, etc.
  (For classical music I can use my Sennhesier HD 595.)
  I am not aiming at headphones that, say, reproduce female vocals better than my DT 880s and  I don't care about this at all.
  Also, I do not need bass-heavy headphones. Obviously some bass is needed for rock/metal.
   
  I know that at least three factors are important in matching a headphone amp with a pair of headphones:
*-* *impedance *
*- max input power *
*- sensitivity*
   
  I would prefer _higher impedance _headphones because of the channel imbalance at low volume levels of the O2. (I haven't tested my O2 for the channel imbalance yet.)
   
   
  Recently*,* I read on this site that the *sensitivity *factor is _more important _for
  higher-*impedance-*headphones than the *impedance *itself.
   
  Since this is the thread about *ODAC & O2 - *although there many  _philosophical _discussions going on here - this is the best place to ask for an advice regarding matching the O2 with very good headphones (under $300) with the proper _impedance_, _max input power _and  above all _sensitivity_.
   
  Thanx in advance.


----------



## mikeaj

Quote: 





adamlr said:


> wow. urm, alright. considering all you have written, including the spoiler, i would consider an upgrade like this: noticeably audibly "more transparent" than the objective set and still being able to drive 95% of all headphones just like the O2. excluding build quality, looks, features, exotic\prestigious components. just soundwise, presenting a flat, linear response and having enough power to drive allmost all headphones, but doing so better than the O2.
> in all honesty, i wasnt really considering getting any other amp anyway. but could it be that getting another amp (for the same purpose as the O2, i.e - not more portable or whatever) would simply be redundant? looks like i made the right choice of amps... somehow i still dont buy it though. maybe im too brainwashed


 
   
  Personally, and it is just my opinion based on my reading of what's out there, I would stockpile different headphones rather than different amps, if I wanted something new (though some amps make no attempt at transparency and so on, definitely sound different, etc.).
   
  Also, a very important point to make is that many many amps and DACs, not just the O2 and ODAC—and for many situations and headphones, plenty of options cheaper than the two as well—have pretty excellent measurements in the areas that people test and ostensibly care about, that matter.  O2 and ODAC aren't particularly special, just two more specimens that do a pretty decent job.  Take that as you will.
   
   
   



> Originally Posted by *JakeJack_2008* /img/forum/go_quote.gif
> 
> [...saving space]
> 
> ...


 

   
  Based on the output power, the noise, distortion, and so on... Almost everything should be okay.  O2 should handle most headphones in a similar manner.  Electrostatics: no.  K1000: no.  HE-6 and maybe some vintage K240 and some others: no if you listen loudly.
   
  Many people will tell you otherwise, or say they don't like certain pairings (as for the reasons, they vary).  That's fine.  They're just talking about what they perceive when listening for themselves, for what that's worth.  Is there some phenomenon that people haven't discovered yet, that the O2 lacks or does differently than something else?  Or a different way to test things?  I think not; other people think it's out there.
   
  Rather than have channel imbalance, you can turn down the volume in software if you're looking at really sensitive IEMs.  For fullsize headphones, O2 channel balance should mostly be in the "okay" or better range (yes, you can do better).  Typical 1 dB off at -55 dB, increasingly better at the higher rotations.  Many headphones are matched worse than that.  Anyway, it doesn't look like you're looking at sensitive IEMs.
   
  This is more a question about headphones than amps or anything else, so maybe a different forum is more appropriate.


----------



## HamilcarBarca

Quote: 





> Originally Posted by *RustA* /img/forum/go_quote.gif
> 
> O2 and ODAC are definitely not the last word... Don't believe it. O2 is brilliant on unity gain as it is completely dead silent and offers great soundstage for the price. But it doesn't work great with high impedance headphones, at least from my experience. ODAC is no less great for the price but even my StageDAC has more detail... And if I take its crossfeed and all the different filters in consideration, Meier's DAC is in another league \(or even several leagues above) in terms of transparency.


 
   
  Are the ODAC and O2 the last word? No, but they're audible neutral and thus price, small or large, is immaterial. Some or many or most listeners find other products more pleasing to the ear; but an added filter, including crossfeed, is either inaudible or it makes the product non-neutral.
   
  Personally, I'm not interested in filters, but that's nothing more than my preference. Others obviously have different preferences which are no less valid than mine.


----------



## adamlr

thanks everyone for your detailed replies. this thread is always educational =]


----------



## gikigill

I have been lurking the thread and it has been great. Learned a lot and got the ODAC on loan.
 Looking forward to hearing and seeing the difference.


----------



## MrMateoHead

Quote: 





rusta said:


> O2 and ODAC are definitely not the last word... Don't believe it. O2 is brilliant on unity gain as it is completely dead silent and offers great soundstage for the price. *But it doesn't work great with high impedance headphones, at least from my experience*. ODAC is no less great for the price but even my StageDAC has more detail... And if I take its crossfeed and all the different filters in consideration, Meier's DAC is in another league \(or even several leagues above) in terms of transparency.
> 
> Don't get me wrong, I love this Objective stuff and have owned them several times, even had more units at the same time...


 
  Can you share which high impedance headphones it "didn't work great with"? I am curious to know their impedance and power requirements.


----------



## MrMateoHead

I really don't get the soundstaging comparisons between amps. Staging, as has been mentioned, is all about the positioning of loudspeakers to the listener. The rest is up to the recording.
   
  I've sat in about a dozen different cars with aftermarket and OEM stereos, and swapped amps in my own car several times. About the only things that ever matter in the amps are power and distortion. The former should err on 'too much', the latter on 'too little'. Where staging was good in a car it was usually a combination of speaker placement and dedicated electronics like time alignment. In my own car I 'pull' my center stage slightly to the left, but treat myself as if I am not centered in front of the stage. Even with that, some recordings are feeding stuff so much into the left or right channels only that the 'illusion' is destroyed.
   
  Headphone staging, to me, is something that can only be done best with electronics and good recordings. Amps just aren't, not matter what people say, a major determining factor of sound reproduction.


----------



## Fearless1

Quote: 





mrmateohead said:


> . Amps just aren't, not matter what people say, a major determining factor of sound reproduction.


 
   I disagree. In accordance to your theory the following factors would play no part in sound reproduction?
   

 *Input Sensitivity : *The signal level required to obtain full power at the amplifier's output. This is determined by the gain and power rating of the amp. 
 *Total Harmonic Distortion (THD) * :* This is a measure of the amount of distortion (modification) of the input signal, which adds additional signal frequencies to the output that are not present in the input signal. THD is commonly measured as a percentage
 *Transient Intermodulation Distortion (TIM) * :* Also sometimes called slew induced distortion, this is a form of distortion said to occur when the input signal changes so fast that the output cannot keep up with it. When this happens, feedback ceases to be effective, since the output signal is delayed too long.
 *Frequency Response * :* The amount of frequency versus amplitude distortion in an amplifier. A perfect amplifier will amplify all signals equally, regardless of frequency. .
 *Phase Response :* This indicates the amount of time that the input signal is delayed before reaching the output, based on the signal frequency.
 *Output Power :* This is most commonly measured into a non-inductive resistive load. This is not done to improve the figures or disguise any possible shortcomings, but to ensure that measurements are accurate and repeatable.
 *Output Current # :* Not often measured, but sometimes quoted by manufacturers, this represents the maximum current the amplifier can supply into any load.
 *Power Bandwidth :* This is usually taken as the maximum frequency at which the amplifier can produce 1/2 of its rated output power
 *Slew Rate # :* Closely related to power bandwidth, the slew rate is the maximum rate of change (measured in Volts per microsecond) of the amplifier output. 
 *Output Impedance * :* This is the actual output impedance of the amplifier, and has no bearing on the amount of current that can be supplied by the output stage.
   
  These all play a part in how our brain perceives factors such as sound stage, bass treble response and etc.


----------



## mikeaj

emphasis added:
  Quote: 





mrmateohead said:


> Headphone staging, to me, is something that can only be done best with electronics and good recordings. Amps just* aren't*, not matter what people say, a *major *determining factor of sound reproduction.


 


fearless1 said:


> I disagree. In accordance to your theory the following factors would play *no part* in sound reproduction?


 

   
  Come on, now...
   
  I don't think you're that much in disagreement.  As for the factors in the list, they're almost all related to power and distortion (which were mentioned): nonlinear and linear.  Though I guess usually people don't lump all that much, including frequency response variations (linear distortion), into the "distortion" umbrella.
   
  But anyhow, the majority of amps are pretty good at all of the things in the list.  You can make ones that aren't, but the baseline for comparison is an environment where most do their jobs, with respect to those parameters and more.  I mean, for example how often is slew rate a limiting factor these days, even more so if you're talking typical headphones-level voltages?


----------



## adydula

That output impedance one is one of the ones that is very important.....and with the advent of the O2 many vendors are now finally stating what their amps output impedance is and has fixed some to be "better''...or become low enough so this doesnt affect the source in any way.
   
  Alex


----------



## JakeJack_2008

Quote: 





adydula said:


> That output impedance one is one of the ones that is very important.....and with the advent of the O2 many vendors are now *finally stating what their amps output impedance is *and has fixed some to be "better''...or become low enough so this doesnt affect the source in any way.
> 
> Alex


 
  There has been _whole lotta scandal _regarding the Meridian Explorer's _output impedance _which measured about *fifty, *yes *50  *Ohm*.*
  When the Meridian released the Explorer (DAC/amp) they were *hiding *the output impedance of their Explorer. ...
  and you know why,  because it was _embarassingly  _high.
  I think the the first guy who revealed  his measurements was purrin and shortly after Tyll from the InnerFidelity did confirm that
  the Explorer's output impedance was about 50 Ohm (48.7?). After this '50 Ohm-revelation' the Meridian, in the next batch/version, 
  considerably lowered the output impedance.
  All those who had bought their 50 Ohm-Explorers earlier demanded a newer version with much lower impedance.
  To find more go to the thread about the Meridian Explorer.
   
  The bottom line is: scandal & shame!
   
  EDIT
  Here's the relevant threads:
http://www.head-fi.org/t/652910/meridian-explorer-dac-amp-stream-of-consciousness-review-warning-not-good/90
  and
http://www.head-fi.org/t/650680/news-meridian-releases-the-explorer-pocket-sized-usb-dac
   
  The _output impedance_  of the current model of the Explorer is (about) 5 Ohm.


----------



## HamilcarBarca

Quote: 





fearless1 said:


> Quote:
> 
> 
> 
> ...


 
   
  Would you elaborate on how each of these affects sound stage, bass treble response and etc.? Thanks.


----------



## Greenleaf7

Quote: 





jakejack_2008 said:


> There has been _whole lotta scandal _regarding the Meridian Explorer's _output impedance _which measured about *fifty, *yes *50  *Ohm*.*
> When the Meridian released the Explorer (DAC/amp) they were *hiding *the output impedance of their Explorer. ...
> and you know why,  because it was _embarassingly  _high.
> I think the the first guy who revealed  his measurements was purrin and shortly after Tyll from the InnerFidelity did confirm that
> ...


 
  Sounds to me like a 'design by ear' product gone terribly wrong


----------



## MagR

Hi
   
  I've got an ODAC+O2 and need some advice. The gains are 2.5x low and 5x high. I'm looking at buying the Beyerdynamic DT880 to add to my HD650's and K701's. At low gain does anyone have any experience of this set up with the 600 ohm version? Low gain should give 5V output. The 250 ohm looks fine for the low gain setting. Does anybody have any experience of how the 250 ohm sounds relative to the 600 ohm version with this set up?
   
  I've also got a technical query. Does this combination of ODAC+O2 work at the higher gain setting or is this higher gain solely for low voltage line level sources? I read on NwAvGuy's blog about overloading input stages and was left confused. The high gain multiplied by the ODAC's output of 2V gives a notional 10V which is greater than the max 7V output of the amp. Does this mean the amp will simply distort when the volume pot asks for more than the 7V available as it runs out of power. Or more worryingly does this mean the input stage is always overloaded at any volume setting so the 5x gain (and any gain over 3.5x for that matter) is unusable with the ODAC supplying it?
   
  I'm leaning towards getting the 250 ohm version as I will never have to worry about accessing a voltage over 5V which might be an issue with the 600 ohm version.
   
  Thanks in advance
   
  Mag


----------



## autior

Hi guys, a quick question by a total newbie: I just got an O2/ODAC combo and I'll use it with my HD598 (I'll switch to HD600 in the future). To use the amp/DAC I have to set something in my PC, like drivers or some audio settings? I'm on Windows 7 x64, my player is Foobar2k, the O2/ODAC is the one from Epiphany.
   
  Thanks.


----------



## JakeJack_2008

Quote: 





magr said:


> Hi
> 
> I've got an ODAC+O2 and need some advice. The gains are 2.5x low and 5x high. I'm looking at buying the Beyerdynamic DT880 to add to my HD650's and K701's. At low gain does anyone have any experience of this set up with the 600 ohm version? Low gain should give 5V output. The 250 ohm looks fine for the low gain setting. Does anybody have any experience of how the 250 ohm sounds relative to the 600 ohm version with this set up?
> 
> ...


 
  I am using:
   
  laptop ---> ODAC ---> O2 ---> Beyerdynamic* DT  880 *(*250 Ohm*; 2005 Edition)
   
  The sound is _superb_. 
	

	
	
		
		

		
		
	


	




  Although, I believe that purists would find some something here and something there, etc.
   
  I've never heard the DT 880 *600 *Ohm.
   
   
   
   
  By the way, there's a very interesting  _guide _to  Sonic Differences Between DT770-DT990 Models with various *impedance*s: 32 ohm, *250 *Ohm and *600 *Ohm.
 [GUIDE] Sonic Differences Between DT770-DT990 Models & More http://www.head-fi.org/t/513393/guide-sonic-differences-between-dt770-dt990-models-more


----------



## ProTofik

I had a chance to listen to t1 (600ohm) from my Odac + o2. As far as I remember with 2.5x gain and volume control at 12 they were quite loud. I was listening to them in loud environment so for everyday use I would probably keep to 1x.


----------



## JakeJack_2008

Quote: 





mikeaj said:


> Personally, and it is just my opinion based on my reading of what's out there, I would stockpile different headphones rather than different amps, if I wanted something new (though some amps make no attempt at transparency and so on, definitely sound different, etc.).
> 
> Also, a very important point to make is that many many amps and DACs, not just the O2 and ODAC—and for many situations and headphones, plenty of options cheaper than the two as well—have pretty excellent measurements in the areas that people test and ostensibly care about, that matter.  O2 and ODAC aren't particularly special, just two more specimens that do a pretty decent job.  Take that as you will.
> 
> ...


 
  Thanx a lot.
   
  JJ


----------



## MrEleventy

Don't have an ODAC but I do have Objective2 and DT880 600ohms. Using the Aune T1 as a DAC. The O2 did a good job powering them. They do get plenty loud. I ran it at around 12-1. Higher depending on music.


----------



## tintin220

Quote: 





rusta said:


> An extension cable can certainly degrade sound quality... I guess you haven't heard a crappy cable for 1 dollar or so? Try it out ,-)
> 
> That said, with quality DIY or reasonable priced adapter/cable (around 5-10USD and up, very rough estimate of course!), the only thing that could vary is frequency response (very slightly). Actual quality should be completely the same.
> 
> ...


 
   
  Any sound degradation that may happen is almost entirely due to shielding. You often see a lot of DIY cable that are honestly probably worse than a Monoprice cable (which are very well made actually), as they consist of nothing but two unshielded wires that are barely twisted. 
   
  EDIT: Sigh... I cannot navigate a forum apparently. Thought this was the most recent page for some reason.


----------



## MagR

Quote: 





jakejack_2008 said:


> I am using:
> 
> laptop ---> ODAC ---> O2 ---> Beyerdynamic* DT  880 *(*250 Ohm*; 2005 Edition)
> 
> ...


 
  Thanks very much for your reply. This is very reassuring. I read the post you link to but it seems to me the writer was using tube amps with high output impedances where things get a little complicated and its difficult to judge just the headphone rather than the headphone plus interaction with the amp.
   
  Regards
   
  Mag


----------



## MagR

Quote: 





protofik said:


> I had a chance to listen to t1 (600ohm) from my Odac + o2. As far as I remember with 2.5x gain and volume control at 12 they were quite loud. I was listening to them in loud environment so for everyday use I would probably keep to 1x.


 
  Thanks for your reply. I checked the specs of the T1 on Beyer's website and unfortunately their sensitivity is 102dB/mW whereas the Dt880 is only 96 dB/mW so need a lot more power to get the same volume.
   
  Regards
   
  Mag


----------



## jellofund

Quote: 





autior said:


> Hi guys, a quick question by a total newbie: I just got an O2/ODAC combo and I'll use it with my HD598 (I'll switch to HD600 in the future). To use the amp/DAC I have to set something in my PC, like drivers or some audio settings? I'm on Windows 7 x64, my player is Foobar2k, the O2/ODAC is the one from Epiphany.
> 
> Thanks.


 
   
  Set up is really very simple - it's plug & play so no drivers to install and all that's required is a couple of minor tweaks to your PC's audio settings.
   
  Epiphany will include an instruction sheet* with your O2/ODAC combo but in the meantime here's a link to the set up guide for JDS Labs (standalone) ODAC which should give you a good idea of what's required:
   
  http://www.jdslabs.com/pdf/Instructions_O2_Standalone.pdf
   
   
  (*if the instructions aren't inside the box check the plastic pouch taped to the outside)


----------



## MagR

Quote: 





mreleventy said:


> Don't have an ODAC but I do have Objective2 and DT880 600ohms. Using the Aune T1 as a DAC. The O2 did a good job powering them. They do get plenty loud. I ran it at around 12-1. Higher depending on music.


 
  Thanks for your reply. I did some research and as far as I can determine the Aune T1 has a line output voltage of 2Vrms the same redbook figure as the ODAC so your results should be comparable. However can I just clarify the gain setting you were using? I want to use my low gain which is set at 2.5x. Are your observations also based on a gain setting of 2.5x?
   
  Regards
   
  Mag


----------



## MrEleventy

magr said:


> Thanks for your reply. I did some research and as far as I can determine the Aune T1 has a line output voltage of 2Vrms the same redbook figure as the ODAC so your results should be comparable. However can I just clarify the gain setting you were using? I want to use my low gain which is set at 2.5x. Are your observations also based on a gain setting of 2.5x?
> 
> Regards
> 
> Mag




Oh, oops. Sorry, forgot to mention that part. Yeah, 2.5x gain. My O2 is a DIY build, not back by a company for full disclosure. At home, I run E17 LO'd into the O2. Ran a variety of HPs through it but mainly DT880 600ohm, DT990 600ohm, DT770s Pro 80ohm, and Technical Pro HPT-990. I should bring my Senn HD600 home and give them a try. Thinking about selling them since DT880s get all attention.


----------



## autior

Quote: 





jellofund said:


> Set up is really very simple - it's plug & play so no drivers to install and all that's required is a couple of minor tweaks to your PC's audio settings.
> 
> Epiphany will include an instruction sheet* with your O2/ODAC combo but in the meantime here's a link to the set up guide for JDS Labs (standalone) ODAC which should give you a good idea of what's required:
> 
> ...


 
   
  Thanks, taken by the enthusiasm I completely forgot to check the plastic pouch content!


----------



## MagR

Quote: 





mreleventy said:


> Oh, oops. Sorry, forgot to mention that part. Yeah, 2.5x gain. My O2 is a DIY build, not back by a company for full disclosure. At home, I run E17 LO'd into the O2. Ran a variety of HPs through it but mainly DT880 600ohm, DT990 600ohm, DT770s Pro 80ohm, and Technical Pro HPT-990. I should bring my Senn HD600 home and give them a try. Thinking about selling them since DT880s get all attention.


 
  Thanks for the clarification. It seems I could run either the 250ohm or 600ohm versions through this amp. The 250 ohm will go louder but have you any experience how the sound of the two differs with the O2? If they will sound virtually the same I may as well get the 250 ohm for simplicity.
   
  Regards
   
  Mag


----------



## jellofund

Quote: 





autior said:


> Thanks, taken by the enthusiasm I completely forgot to check the plastic pouch content!


 

 No worries - I was the same. Think it took me a day or so before I checked the pouch 
	

	
	
		
		

		
		
	


	



   
  Enjoy!


----------



## MrEleventy

magr said:


> Thanks for the clarification. It seems I could run either the 250ohm or 600ohm versions through this amp. The 250 ohm will go louder but have you any experience how the sound of the two differs with the O2? If they will sound virtually the same I may as well get the 250 ohm for simplicity.
> 
> Regards
> 
> Mag


I can't help you there on that. I've only heard the 600 ohms. even amongst people who have heard all three, the consensus is out. some find the 250s better, some think the 600 is better, and then there's some who think they're the same. it's up to your own ears to be really sure. The only thing that everyone seems to agree on Is that the 250 & 600 are better than the 32.


----------



## JakeJack_2008

Quote: 





mreleventy said:


> I can't help you there on that. I've only heard the 600 ohms. even amongst people who have heard all three, the consensus is out. some find the 250s better, some think the 600 is better, and then there's some who think they're the same. it's up to your own ears to be really sure. The only thing that everyone seems to agree on Is that the 250 & 600 are better than the 32.


 
  I am very happy 
	

	
	
		
		

		
		
	


	




 because I'm using the DT 880 (*250 *Ohm) with the O2 and ODAC.


----------



## HamilcarBarca

Quote: 





jakejack_2008 said:


> I am very happy
> 
> 
> 
> ...


 
   
  The 250-Ohm T 70 also sounds great with the ODAC+O2.


----------



## MagR

Quote: 





jakejack_2008 said:


> I am very happy
> 
> 
> 
> ...


 

 Thanks for that. Judging by what you and Mr Eleventy say it seems the differences are marginal. With a 250 ohm impedance you will still get a massive damping factor with the O2's low output impedance. I read one review on HTShack where the reviewer thought the 600 ohm might be intended more for tube amps to counter their high output impedance which isn't an issue with the O2. If I go for the 250 ohm now need to decide between the Pro and Premium (or "Edition" as it is described on Beyer's website). Can you confirm which one you have if you say it sounds great with the ODAC/O2. Is it the Pro with the curly cord or Premium with the straight cable?
   
  Regards
   
  Mag


----------



## HiFiRobot

Quote: 





autior said:


> Hi guys, a quick question by a total newbie: I just got an O2/ODAC combo and I'll use it with my HD598 (I'll switch to HD600 in the future). To use the amp/DAC I have to set something in my PC, like drivers or some audio settings? I'm on Windows 7 x64, my player is Foobar2k, the O2/ODAC is the one from Epiphany.
> 
> Thanks.


 
   
  My advice would be to activate playback through WASAPI or ASIO. There are multiple guides available online on how to do this. I mostly use JRiver with WASAPI playback myself.
   
  Try this guide from page 36 and forward. http://www.dcsltd.co.uk/assets/dCS_Guide_to_Computer_Audio.pdf
  Page 41: Disable all enhancements and put your ODAC in exclusive mode.
  Page 55: Foobar config with WASAPI or ASIO
   
  Also USB DACs should be on their own USB-bus. I use USBview from the HRT website to determine if my DAC is alone on the USB bus.
http://highresolutiontechnologies.com/support/


----------



## autior

Quote: 





hifirobot said:


> My advice would be to activate playback through WASAPI or ASIO. There are multiple guides available online on how to do this. I mostly use JRiver with WASAPI playback myself.
> 
> Try this guide from page 36 and forward. http://www.dcsltd.co.uk/assets/dCS_Guide_to_Computer_Audio.pdf
> Page 41: Disable all enhancements and put your ODAC in exclusive mode.
> ...


 
  The guide is really intersting, I'm reading it. About the DAC, I have it directly connected to the rear of the moterboard by USB cable, I'm not using an hub or a front panel port.
   
  By the way, having the O2/ODAC on 18h per day can lead to problems?


----------



## HiFiRobot

Quote: 





autior said:


> The guide is really intersting, I'm reading it. About the DAC, I have it directly connected to the rear of the moterboard by USB cable, I'm not using an hub or a front panel port.
> 
> By the way, having the O2/ODAC on 18h per day can lead to problems?


 
  It's common that front and back ports share the same USB bus. The idea is to have the DAC alone on a separate USB controller. Easiest way to do this is to have mouse, keyboard on USB 2.0 ports and DAC on USB 3.0 port. Or vice versa. Otherwise use USBview to check.
   
  Sorry, don't know about the 18h a day.


----------



## tintin220

You can leave it on 24/7 forever and it won't contribute meaningfully to the life of the device. Solid state will be just fine.


----------



## autior

Quote: 





hifirobot said:


> It's common that front and back ports share the same USB bus. The idea is to have the DAC alone on a separate USB controller. Easiest way to do this is to have mouse, keyboard on USB 2.0 ports and DAC on USB 3.0 port. Or vice versa. Otherwise use USBview to check.
> 
> Sorry, don't know about the 18h a day.


 

   
  The one selected is the DAC, the other 2 are mouse and printer (by the way I don't have all these USB ports). Unfortunately I only have USB 2.0 ports, there is another way?
  Quote: 





tintin220 said:


> You can leave it on 24/7 forever and it won't contribute meaningfully to the life of the device. Solid state will be just fine.


 
  Good to hear.


----------



## JakeJack_2008

Quote: 





magr said:


> Thanks for that. Judging by what you and Mr Eleventy say it seems the differences are marginal. With a 250 ohm impedance you will still get a massive damping factor with the O2's low output impedance. I read one review on HTShack where the reviewer thought the 600 ohm might be intended more for tube amps to counter their high output impedance which isn't an issue with the O2. If I go for the 250 ohm now need to decide between the Pro and Premium (or "Edition" as it is described on Beyer's website). Can you confirm which one you have if you say it sounds great with the ODAC/O2. Is it the Pro with the curly cord or Premium with the straight cable?
> 
> Regards
> 
> Mag


 
  What I've _read on this site_ the DT 880 *Pro *is _not  _for pleasure listening.
  It's for _analyzing _music/sound/instruments during recording, mixing, etc.
  It's for _professionals working in the studio _and not for us who just want to _enjoy _
  our favorite music and not to _dissect _it, _analyze _it, etc. and therefore 'kill' it.
  In other words, the DT 880 *Pro  *are too analytical and too revealing, etc. 
  and you'd pick up the _details _and not to the music as a whole.
  You'll see the trees and not the whole forest.
   
  Again, this is what I've _read_.


----------



## MrEleventy

nonsense, I love my dt880s *w/ O2* for pure musical enjoyment. heck, I like them better than my hd600s *w/ O2*. the thing is that the sound signature is neutral w/ treble emphasis and it's not for everyone but if you do, it's great.

E: Fixed.


----------



## adydula

Isnt this thread about the O2 amp and ODAC...not on how good or bad you think headphones are.....take that to the DT880 appreciation thread etc...
  Talk about the DT880 with the O2/ODAC fine.
   
  Alex


----------



## tintin220

^ Relax, buddy. Minorly tangential conversation is normal and fine. It's not like anyone is trolling or in a flame war.


----------



## brainbucket

Hey guys, I built an O2 amp yesterday using components from the official BOM (or mouser suggested replacements that were newer and the same spec). The problem is I'm not really impressed about half the time I'm listening. Certain tracks sound really muddy and distorted in the bass on my HD600's and sometimes on my TF10's. Any idea what that is? Is it normal? My source is a schiit bifrost and I'm not double amping or anything. My tralucent t1 which has been compared to the O2 sounds leaps better and does not have this issue with the seeming distortion. It almost sounds like a cheap pair of ear buds that have the volume turned too high and the sound is gargled. Some other tracks sound fairly good though, so it's isolated to certain recordings, but I doubt this is how the recordings actually sound and my other amps have been "coloring" them to sound better.


----------



## tintin220

Quote: 





brainbucket said:


> Hey guys, I built an O2 amp yesterday using components from the official BOM (or mouser suggested replacements that were newer and the same spec). The problem is I'm not really impressed about half the time I'm listening. Certain tracks sound really muddy and distorted in the bass on my HD600's and sometimes on my TF10's. Any idea what that is? Is it normal? My source is a schiit bifrost and I'm not double amping or anything. My tralucent t1 which has been compared to the O2 sounds leaps better and does not have this issue with the seeming distortion. It almost sounds like a cheap pair of ear buds that have the volume turned too high and the sound is gargled. Some other tracks sound fairly good though, so it's isolated to certain recordings, but I doubt this is how the recordings actually sound and my other amps have been "coloring" them to sound better.


 
   
  Well, that's definitely not right, because there are lots of things you can accuse the O2 of being, but muddy/distorted are not among them. Did you troubleshoot it by testing it with a multimeter? If not, step #1 is to go buy one for $5-10 on Amazon and see what you might have soldered incorrectly.


----------



## HiFiRobot

Quote: 





autior said:


> The one selected is the DAC, the other 2 are mouse and printer (by the way I don't have all these USB ports). Unfortunately I only have USB 2.0 ports, there is another way?
> Good to hear.


 
   
  Your motherboard seems to have two USB-buses. Try to move around your USB devices between ports and separate the DAC like in the picture below.
  Which motherboard is it?


----------



## bada bing

Quote: 





brainbucket said:


> Hey guys, I built an O2 amp yesterday using components from the official BOM (or mouser suggested replacements that were newer and the same spec). The problem is I'm not really impressed about half the time I'm listening. Certain tracks sound really muddy and distorted in the bass on my HD600's and sometimes on my TF10's. Any idea what that is? Is it normal? My source is a schiit bifrost and I'm not double amping or anything. My tralucent t1 which has been compared to the O2 sounds leaps better and does not have this issue with the seeming distortion. It almost sounds like a cheap pair of ear buds that have the volume turned too high and the sound is gargled. Some other tracks sound fairly good though, so it's isolated to certain recordings, but I doubt this is how the recordings actually sound and my other amps have been "coloring" them to sound better.


 
   
  What gain are you set on ? It could be that you are right on the verge of clipping and songs that are recorded a bit "hot" break over into clipping.
  One concept that seems to need repeating at regular intervals is that the O2 is a bit different in how it gets to a clipping level. Unlike about every
  other amp out there, the volume control on the O2 does not influence clipping levels, but the gain setting for input level does.


----------



## tintin220

Quote: 





bada bing said:


> What gain are you set on ? It could be that you are right on the verge of clipping and songs that are recorded a bit "hot" break over into clipping.
> One concept that seems to need repeating at regular intervals is that the O2 is a bit different in how it gets to a clipping level. Unlike about every
> other amp out there, the volume control on the O2 does not influence clipping levels, but the gain setting for input level does.


 
   
  Good observation, but he said he's using a Bifrost as a source, and even at the highest gain, there should not be clipping at the amount he's describing. It's not like he has it plugged into his computer's 3.5mm out and is playing at 10% OS volume.


----------



## bada bing

Quote: 





brainbucket said:


> Hey guys, I built an O2 amp yesterday using components from the official BOM


 
  Quote: 





tintin220 said:


> Good observation, but he said he's using a Bifrost as a source, and even at the highest gain, there should not be clipping at the amount he's describing. It's not like he has it plugged into his computer's 3.5mm out and is playing at 10% OS volume.


 
   I am not familar with the output specs of the bifrost. I assume it is somewhere close to standard 2vrms. The "official" BOM for the O2 sets the gain 2.5 and 6.5. So yes, if it is built with the "official BOM", then high gain setting will clip horribly.
   
  I'm guessing that you misspoke, or don't understand what clipping is and how it is generated in the O2. Clipping comes from driving the gainstage op-amp output above about 7vrms.  (2vrms input) * (6.5 gain) = very bad clipping.  There are various scenarios that could result in brainbucket's amp being on the verge of clipping. It depends on the gain setting of the O2, the output level of the DAC and the setting of the OS software volume control. The result could very easily be exactly what brainbucket posted. The important point is that the O2 is vunerable to clipping with an overly hot source  for the gain used and to fix it could be as easy as lowering the software volume control, if clipping is indeed the problem.


----------



## tintin220

Quote: 





bada bing said:


> I am not familar with the output specs of the bifrost. I assume it is somewhere close to standard 2vrms. The "official" BOM for the O2 sets the gain 2.5 and 6.5. So yes, if it is built with the "official BOM", then high gain setting will clip horribly.
> 
> I'm guessing that you misspoke, or don't understand what clipping is and how it is generated in the O2. Clipping comes from driving the gainstage op-amp output above about 7vrms.  (2vrms input) * (6.5 gain) = very bad clipping.  There are various scenarios that could result in brainbucket's amp being on the verge of clipping. It depends on the gain setting of the O2, the output level of the DAC and the setting of the OS software volume control. The result could very easily be exactly what brainbucket posted. The important point is that the O2 is vunerable to clipping with an overly hot source  for the gain used and to fix it could be as easy as lowering the software volume control, if clipping is indeed the problem.


 
   
  No need to be a jerk about it, I didn't know the default gains were 2.5 and 6.5, thought they were 1x and 2.5x.
   
  That said, this would be an easy way to test if this is the issue, use the lower gain setting and see if your problem is resolved. If it isn't, bust out the multimeter. The reason I recommended that is I suspect that an incorrect resistor might have been added to the gain resistors, which could of course result in what bada described.


----------



## Sat1re

How is he a jerk about it?


----------



## mikeaj

Bifrost product page says 2.0 V rms out.
   
   
  Anyway, before running around or jumping to conclusions, it might be worth checking which resistors were actually installed, and so on.  I mean, who cares about speculating about what might be there and the default (though docs give values for 2.5x and 6.5x, sure enough), when what really matters is what's installed, and that can be easily checked?  While you're at it, you could check the build (there are some troubleshooting instructions and voltages to check out that are diagrammed on the designer's blog).  Actually, if you hear obvious distortion, you could give it a quick whirl through say RMAA or whatever else for a quick sanity check, so long as you have some kind of audio input to run it through.


----------



## adydula

Some folks should spend more time on Nwavguy's blog to learn about gain and clipping etc.....
   
  Oh my...
   
  Alex


----------



## HamilcarBarca

Quote: 





adydula said:


> Some folks should spend more time on Nwavguy's blog to learn about gain and clipping etc.....
> 
> Oh my...
> 
> Alex


 
   
  Why should people let a few facts interfere with their presuppositions?.All that hard work learning to speak Audiophilian would be wasted.


----------



## miceblue

Quote: 





adydula said:


> Some folks should spend more time on Nwavguy's blog to learn about gain and clipping etc.....
> 
> Oh my...
> 
> Alex


 
  Honestly, his blog is a big jumble of words. Most people aren't going to go through the many, what would be pages in MSWord, of text he writes and you would get a far more direct answer right here.


----------



## brainbucket

Hey guys, didn't expect so many replies. I did not check the resistances or voltages because I forgot to grab a multimeter from my work. I will when I get a chance, but until then I've played around with it some. If I use the lower gain with the volume maxed out it is a reasonable level and I didn't hear any noticeable clipping. It still does it at the higher gain, but if I lower the the source voltage (using my AK100 right now which should be ~2v at max volume from what I read) it sounds a lot better and gets loud. So I just need to use the software to lower the volume when I use my bifrost I assume?


----------



## HamilcarBarca

Quote: 





miceblue said:


>





> Honestly, his blog is a big jumble of words. Most people aren't going to go through the many, what would be pages in MSWord, of text he writes and you would get a far more direct answer right here.


 
   
  The direct answers you get here are often buried among messages with flowery phrases such as "factors such as sound stage, bass treble response and etc" and other attempts to appear knowledgeable.
   
  Overall, the most complete background discussion is from the designer's blog. We also have a few excellent, and knowledgeable, posters here who aren't fooled by audophile-speak. They know who they are. I'd like to thank them.


----------



## tintin220

Quote: 





hamilcarbarca said:


> The direct answers you get here are often buried among messages with flowery phrases such as "factors such as sound stage, bass treble response and etc" and other attempts to appear knowledgeable.
> 
> Overall, the most complete background discussion is from the designer's blog. We also have a few excellent, and knowledgeable, posters here who aren't fooled by audophile-speak. They know who they are. I'd like to thank them.


 
   
  I think our numbers are more numerous than they appear. Many just don't post often, myself included, because our comments tend to draw a crowd of angry cable loving, blind test hating "audiophiles". A quick look at my post history will show you how some of my recent conversations here have gone...


----------



## grandpatzer

If I get a O2 ODAC is it possible to disable the DAC and just use the O2 AMP with PC soundcard as DAC?


----------



## adamlr

Quote: 





grandpatzer said:


> If I get a O2 ODAC is it possible to disable the DAC and just use the O2 AMP with PC soundcard as DAC?


 

 first of all, you can get a standalone O2. however, if you do get a combo then yes, you can use the 3.5mm input and use your pc soundcard. question is whether or not your pc can give a line out? if you want to send the signal through the headphone jack to the O2 youll be "double amping", and depending on your pcs amp, youll probably get a not so good result...


----------



## grandpatzer

Quote: 





adamlr said:


> first of all, you can get a standalone O2. however, if you do get a combo then yes, you can use the 3.5mm input and use your pc soundcard. question is whether or not your pc can give a line out? if you want to send the signal through the headphone jack to the O2 youll be "double amping", and depending on your pcs amp, youll probably get a not so good result...


 
   
  My PC has a Xonar DX soundcard, I think it has no OR weak amp, so this can be a problem if DX has built in amp because of "double amping"?
  I might invest on a Creative Titanium HD or Z because those are more recommended for competitive gaming.
   
  So basicaly I would connect Xonar DX to O2 ODAC then headphones to O2 ODAC?
So because the O2 ODAC Usb is not connected it is disabled?!


----------



## adamlr

Quote: 





grandpatzer said:


> My PC has a Xonar DX soundcard, I think it has no OR weak amp, so this can be a problem if DX has built in amp because of "double amping"?
> I might invest on a Creative Titanium HD or Z because those are more recommended for competitive gaming.
> 
> So basicaly I would connect Xonar DX to O2 ODAC then headphones to O2 ODAC?
> So because the O2 ODAC Usb is not connected it is disabled?!


 

 errrrr pretty much yea. im almost certain you can use the analog in of the combo and not use the odac if you wish... as for the soundcards i really have no comment. im unfamiliar with pc soundcards. just know that if your using a headphone jack, that means that the signal has already been amped and whatever noise or degradation that the soundcards amp _may_ have added to the signal will also be amplified by the O2.


----------



## mikeaj

Quote: 





brainbucket said:


> Hey guys, didn't expect so many replies. I did not check the resistances or voltages because I forgot to grab a multimeter from my work. I will when I get a chance, but until then I've played around with it some. If I use the lower gain with the volume maxed out it is a reasonable level and I didn't hear any noticeable clipping. It still does it at the higher gain, but if I lower the the source voltage (using my AK100 right now which should be ~2v at max volume from what I read) it sounds a lot better and gets loud. So I just need to use the software to lower the volume when I use my bifrost I assume?


 
   
  You don't need to check voltages or bother troubleshooting, if that's the case.  If you used defaults, that's the gain stage clipping on high gain (if fed a signal higher than a 1.08 V rms sine wave), as mentioned previously.  That's how it works.
   
  You could either just use low gain all the time, lower the source voltage, or lower the gain.  O2 can handle about 7 V.  With low gain of 2.5x and source voltage of 2 V, meaning up to 5 V max, there's not much room to go higher than that.  If you plan on keeping source volume at max, you could just move the values to 1x (remove resistor) and 3.5x or so (no less than 600 ohms; 1000 ohms brings you down to the 2.5x you have now).  Resistors to change are R17 and R21 for low (switch out), R19 and R23 for high (switch in).
   
   
   



grandpatzer said:


> My PC has a Xonar DX soundcard, I think it has no OR weak amp, so this can be a problem if DX has built in amp because of "double amping"?
> I might invest on a Creative Titanium HD or Z because those are more recommended for competitive gaming.
> 
> So basicaly I would connect Xonar DX to O2 ODAC then headphones to O2 ODAC?
> So because the O2 ODAC Usb is not connected it is disabled?!


 

   
  Nah, actually the O2's input jack itself is the switch.  If you plug something in, it disconnects from the ODAC.
   
  Or at least, that's how it's supposed to be.  I didn't verify myself.
   
  Unless you're using CMSS-3D or whatever processing Creative offers these days, or especially EAX (rare for current titles, if I'm hearing things correctly), I wouldn't think there's much substance to claims about gaming audio.  The way you get significant changes is to change the bits that get sent to the DACs.  If you're not doing software processing that changes those bits, it's just about DAC performance, and that's a small blip in the grand scheme of things.
   
   
   


adamlr said:


> errrrr pretty much yea. im almost certain you can use the analog in of the combo and not use the odac if you wish... as for the soundcards i really have no comment. im unfamiliar with pc soundcards. just know that if your using a headphone jack, that means that the signal has already been amped and whatever noise or degradation that the soundcards amp _may_ have added to the signal will also be amplified by the O2.


 
   
  A lot of times, double amping is really no big deal.  I mean, it's a lot easier for an amp to drive a line input (thousands of ohms impedance, thus low current and so on) than it is for that amp to drive some actual headphones.
   
  And DX I think is like D1, which has ~100 ohms output impedance.  It's supposed to be a normal line output that's driven by some high-quality audio op amp that's not particularly some high-current output part.  It's not really much of an amp in the sense that most people are talking about.


----------



## adamlr

Quote: 





mikeaj said:


> A lot of times, double amping is really no big deal.  I mean, it's a lot easier for an amp to drive a line input (thousands of ohms impedance, thus low current and so on) than it is for that amp to drive some actual headphones.
> 
> And DX I think is like D1, which has ~100 ohms output impedance.  It's supposed to be a normal line output that's driven by some high-quality audio op amp that's not particularly some high-current output part.  It's not really much of an amp in the sense that most people are talking about.


 

 i did state that i didnt know anything about pc soundcards, and i also said that noise may be added, not that it definitely would. its just the my laptops headphone jack is really really hissy, which was one of the reasons i got an external dac/amp in the first place. so if i were to send a signal through it and into my O2 id get sound thats just as bad. this is what i was talking about.
   
  entirely unrelated edit: my mouses scroll wheel stopped working about a week ago and i was all upset about getting a new one because i really like my mouse... then my roomate walked in and asked to use my printer. i obliged and when getting up to fetch a glass of water i accidentally dropped the mouse on the floor. now its working fine again! im so pleased!


----------



## grandpatzer

When you write it disconnects ODAC, this meanst the O2 Amp is still active?
  So basicaly Xonar DX is DAC and O2 is only AMP?  (sorry still audio beginner)
   
  Quote:


> Nah, actually the O2's input jack itself is the switch.  If you plug something in, it disconnects from the ODAC.
> 
> Or at least, that's how it's supposed to be.  I didn't verify myself.
> 
> Unless you're using CMSS-3D or whatever processing Creative offers these days, or especially EAX (rare for current titles, if I'm hearing things correctly), I wouldn't think there's much substance to claims about gaming audio.  The way you get significant changes is to change the bits that get sent to the DACs.  If you're not doing software processing that changes those bits, it's just about DAC performance, and that's a small blip in the grand scheme of things.


 
   
  Well I might buy Creative soundcard, so I guess I would be using CMSS-3D then.
   
  I play alot Counter Strike: GO, so I guess IF there is a difference between ODAC and CMSS-3D it definitively will be picked up by a competitive fps game like Counter Strike: GO
   
  Maybe I'll just get the O2 ODAC and see how the position is compared to the Xonar DX, if no difference gaming then sell DX.
  Maybe I also try out the Creative Titanium HD and if there is no difference with the ODAC I sell the Titaniu HD aswell


----------



## autior

Quote: 





hifirobot said:


> Your motherboard seems to have two USB-buses. Try to move around your USB devices between ports and separate the DAC like in the picture below.
> Which motherboard is it?


 

 The motherboard is an AsRock Z68 Extreme 4 Gen 3, I got 2 USB 3.0 ports but they never worked (maybe because I have a Sandy Bridge processor? I don't know). Anyway I did as you said (I connected everything but the O2/ODAC on the rear of the motherboard, and the amp/dac on the front USB 2.0 port), now the O2/ODAC has his own bus. 
	

	
	
		
		

		
		
	


	



   
  One more question: I'm using the USB input with the PC (for music listening) and the 3.5 input with the monitor (for gaming, because my PS3 is connected to the monitor by HDMI cable). Can this configuration ruin the output sound quality? (I obviously use only a source at once, but each of them is connected 24/7).


----------



## mikeaj

Quote: 





adamlr said:


> i did state that i didnt know anything about pc soundcards, and i also said that noise may be added, not that it definitely would. its just the my laptops headphone jack is really really hissy, which was one of the reasons i got an external dac/amp in the first place. so if i were to send a signal through it and into my O2 id get sound thats just as bad. this is what i was talking about.


 
   
  I don't mean to hound any point, but that's more of the source being noisy than anything to do with double amping.  (and depending on what you call an amp, there is way more than double amping going on for music production as well as playback)
   
  One point to make is that some mid-high level discrete sound card like a DX is in a totally different league than some laptops' hissy onboard sound.  It gets better performance than a lot of megabucks audiophile gear.
   
  Also, did you ever try the laptop with the O2?  A lot of times, the noise doesn't scale up as you turn the volume up, so if you send max volume to an external amp and turn the volume down on the amp, you can effectively turn down the noise (as compared to the source by itself)... assuming you weren't already maxing out the volume.  You can think of it as increasing the signal level more so than the noise level, so the resulting SNR is higher.
   
   
  Quote: 





grandpatzer said:


> When you write it disconnects ODAC, this meanst the O2 Amp is still active?
> So basicaly Xonar DX is DAC and O2 is only AMP?  (sorry still audio beginner)


 
   
  Right, I mean that if you plug in X to the O2's input, the O2 will switch to using X.  It disconnects itself from the ODAC, so it no longer gets a signal from there.  Yes, this means Xonar DX would be DAC and O2 would be the amp.  No ODAC involved.
   
   
  Quote: 





autior said:


> One more question: I'm using the USB input with the PC (for music listening) and the 3.5 input with the monitor (for gaming, because my PS3 is connected to the monitor by HDMI cable). Can this configuration ruin the output sound quality? (I obviously use only a source at once, but each of them is connected 24/7).


 
   
  If I understand you correctly, you have PS3 ---HDMI--->  monitor ---stereo 3.5mm---> O2/ODAC combo to headphones?
   
  In general, look for which connections are digital and which are analog.  This means the monitor is responsible for taking the digital audio info and doing the digital-to-analog conversion for sounds coming from the PS3.  It probably has some cheap hardware in there to do that, probably doing a worse job than the PS3 itself would, and worse than the ODAC.  This means you're relying on the monitor for D/A but using the O2 as an amp.  ODAC is bypassed.
   
  But I don't think that's likely to "ruin" the sound quality.


----------



## adamlr

Quote: 





mikeaj said:


> I don't mean to hound any point, but that's more of the source being noisy than anything to do with double amping.  (and depending on what you call an amp, there is way more than double amping going on for music production as well as playback)
> 
> One point to make is that some mid-high level discrete sound card like a DX is in a totally different league than some laptops' hissy onboard sound.  It gets better performance than a lot of megabucks audiophile gear.
> 
> Also, did you ever try the laptop with the O2?  A lot of times, the noise doesn't scale up as you turn the volume up, so if you send max volume to an external amp and turn the volume down on the amp, you can effectively turn down the noise (as compared to the source by itself)... assuming you weren't already maxing out the volume.  You can think of it as increasing the signal level more so than the noise level, so the resulting SNR is higher.


 

 perhaps it is the source and not the amp, tbh i dont care anymore, the Odac+O2 combo is more than satisfactory as far as im concerned =]
   
  i didnt actually try the laptop with the O2, but the hiss was more or less the same on all volumes if i remember correctly... does that make sense?


----------



## autior

Quote: 





mikeaj said:


> If I understand you correctly, you have PS3 ---HDMI--->  monitor ---stereo 3.5mm---> O2/ODAC combo to headphones?
> 
> In general, look for which connections are digital and which are analog.  This means the monitor is responsible for taking the digital audio info and doing the digital-to-analog conversion for sounds coming from the PS3.  It probably has some cheap hardware in there to do that, probably doing a worse job than the PS3 itself would, and worse than the ODAC.  This means you're relying on the monitor for D/A but using the O2 as an amp.  ODAC is bypassed.
> 
> But I don't think that's likely to "ruin" the sound quality.


 
  Yes, that's the chain that I'm talking about. The main problem of the monitor is that it has a very poor amplifier, that's why I'm using it with the O2, and I know that the monitor DAC is probably poor but I think it's ok for gaming. What I'm asking is if having each of the input connected (but NOT using them at the same time) can generate interferences or any kind of problem while listening music with the PC (I don't think, but you never know).
   
  The audio chains are: PC--USB-->ODAC--O2-->HD598 and PS3--HDMI-->Monitor--3.5mm-->O2-->HD598. My question was a little tricky, sorry.


----------



## mikeaj

Quote: 





adamlr said:


> perhaps it is the source and not the amp, tbh i dont care anymore, the Odac+O2 combo is more than satisfactory as far as im concerned =]
> 
> i didnt actually try the laptop with the O2, but the hiss was more or less the same on all volumes if i remember correctly... does that make sense?


 
   
  Okay, that's what I expected.  I don't mean to hound a point, but in case anybody was curious, let's say the noise didn't scale at all and you had the source turned down say 25 dB in software compared to max.  Then if you instead use an external amp, you could turn the source to max (25 dB more) and then turn the volume down on the amp to compensate.  If the amp practically doesn't add any more noise of its own, which is what the O2 would do (it has some but very little), then if you're running through the amp, that means you can get 25 dB higher SNR with that setup.
    
   
  Quote:


autior said:


> Yes, that's the chain that I'm talking about. The main problem of the monitor is that it has a very poor amplifier, that's why I'm using it with the O2, and I know that the monitor DAC is probably poor but I think it's ok for gaming. What I'm asking is if having each of the input connected (but NOT using them at the same time) can generate interferences or any kind of problem while listening music with the PC (I don't think, but you never know).
> 
> The audio chains are: PC--USB-->ODAC--O2-->HD598 and PS3--HDMI-->Monitor--3.5mm-->O2-->HD598. My question was a little tricky, sorry.


 
   
  What I remembered must have been wrong then.  I thought that plugging something into the O2's jack would disconnect the amp from the ODAC.  That's the way I thought it was described on the blog... though really, it depends on how the jack is wired up to the components.  (I think a couple of traces need to be cut on the PCB for that behavior, or... maybe I should just look it up.)  e.g. referenced here:
http://www.jdslabs.com/pdf/Instructions_ODAC_DIY.pdf
   
  If both the ODAC and the monitor are hooked up to the O2 simultaneously, that could be a problem, depending on the electronics.  If a device is turned off yet is still physically connected, that can present a weird load to the other device; that's not ideal.  Depends.  If you wanted, you could benchmark the different configurations.  If there's something wrong, it should show up pretty easily (and should be audible, I would think).
   
  But if it sounds fine, I wouldn't worry about it.


----------



## grandpatzer

Quote: 





autior said:


> Yes, that's the chain that I'm talking about. The main problem of the monitor is that it has a very poor amplifier, that's why I'm using it with the O2, and I know that the monitor DAC is probably poor but I think it's ok for gaming. What I'm asking is if having each of the input connected (but NOT using them at the same time) can generate interferences or any kind of problem while listening music with the PC (I don't think, but you never know).
> 
> The audio chains are: PC--USB-->ODAC--O2-->HD598 and PS3--HDMI-->Monitor--3.5mm-->O2-->HD598. My question was a little tricky, sorry.


 
   
  Quote: 





mikeaj said:


> Okay, that's what I expected.  I don't mean to hound a point, but in case anybody was curious, let's say the noise didn't scale at all and you had the source turned down say 25 dB in software compared to max.  Then if you instead use an external amp, you could turn the source to max (25 dB more) and then turn the volume down on the amp to compensate.  If the amp practically doesn't add any more noise of its own, which is what the O2 would do (it has some but very little), then if you're running through the amp, that means you can get 25 dB higher SNR with that setup.
> 
> What I remembered must have been wrong then.  I thought that plugging something into the O2's jack would disconnect the amp from the ODAC.  That's the way I thought it was described on the blog... though really, it depends on how the jack is wired up to the components.  (I think a couple of traces need to be cut on the PCB for that behavior, or... maybe I should just look it up.)  e.g. referenced here:
> http://www.jdslabs.com/pdf/Instructions_ODAC_DIY.pdf
> ...


 
   
  My impression was that PC--soundcard-->--3.5mm-->O2-->HD598
Is perfectly fine, basicaly the ODAC would be disabled and the O2 amp active.
   
That is however what I have been told, have not studied any documents regarding the subject.
   
So if wanting to use ODAC then: PC -- USB -- O2 AMP/ODAC -- HD598


----------



## MrMateoHead

Quote: 





mikeaj said:


> A lot of times, double amping is really no big deal.  I mean, it's a lot easier for an amp to drive a line input (thousands of ohms impedance, thus low current and so on) than it is for that amp to drive some actual headphones.
> 
> And DX I think is like D1, which has ~100 ohms output impedance.  It's supposed to be a normal line output that's driven by some high-quality audio op amp that's not particularly some high-current output part.  It's not really much of an amp in the sense that most people are talking about.


 
  This is correct. In some cases, soundcards have 2 'headphone jacks' - the first is a high impedance out (~100 ohms), the other is a dedicated headphone jack (~10 ohms or less).
   
  The most current Xonar DX card has 2V out, and dedicated headphone amplification through the front out / Headphone out jack. My guess is that output impedance is probably 10 ohms, given that many good computer cards use TI chips. That is also probably about twice the output voltage typical in a computer. I could not find exact specs online.
   
  In either case, the lowest possible distortion is the goal when using a headphone amp as a line out. That said, my line out (100 ohms), and headphone jack sounded exactly the same to me through the O2. If you wanted to, you could use any of the other outputs to listen for an 'audible' difference in outputs. So long as the amplifier is delivering a flat, full-range frequency response, I don't see how 'double amping' can hurt.


----------



## adamlr

Quote: 





mikeaj said:


> Okay, that's what I expected.  I don't mean to hound a point, but in case anybody was curious, let's say the noise didn't scale at all and you had the source turned down say 25 dB in software compared to max.  Then if you instead use an external amp, you could turn the source to max (25 dB more) and then turn the volume down on the amp to compensate.  If the amp practically doesn't add any more noise of its own, which is what the O2 would do (it has some but very little), then if you're running through the amp, that means you can get 25 dB higher SNR with that setup.


 

 hound away =] im sorry but i cant seem to remember where this discussion started... its possible i was mistaken about something, that does tend to happen =\
   
  any which way you choose to see it, no noise, is better than some noise. my headphone out on the laptop is very hissy. according to what you wrote i could scale it down using just the O2, but fact of the matter is, using and odac+o2 eliminates the hiss completely, which is important to people like me who listen a relatively low levels, and listen to downtempo\ambient electronica, which has alot of quiet passages.
  if your saying that i could have eliminated the noise completely without and external dac (i dont know if 25dB would have done the trick, perhaps they would have) then its already too late - i already got an external dac. i still dont regret it


----------



## JakeJack_2008

Quote: 





adamlr said:


> perhaps it is the source and not the amp, tbh i dont care anymore, the Odac+O2 combo is more than satisfactory as far as im concerned =]
> 
> *i didnt actually try the laptop with the O2*, but the hiss was more or less the same on all volumes if i remember correctly... does that make sense?


 
   
   
  Good point. It has not accured to me yet. I'm gonna try:
  laptop --> headphone jack ---> O2 --> DT 880 (250 Ohm)
  I'll be double-amping, but we shal see.


----------



## autior

Quote: 





mikeaj said:


> What I remembered must have been wrong then.  I thought that plugging something into the O2's jack would disconnect the amp from the ODAC.  That's the way I thought it was described on the blog... though really, it depends on how the jack is wired up to the components.  (I think a couple of traces need to be cut on the PCB for that behavior, or... maybe I should just look it up.)  e.g. referenced here:  http://www.jdslabs.com/pdf/Instructions_ODAC_DIY.pdf
> 
> If both the ODAC and the monitor are hooked up to the O2 simultaneously, that could be a problem, depending on the electronics.  If a device is turned off yet is still physically connected, that can present a weird load to the other device; that's not ideal.  Depends.  If you wanted, you could benchmark the different configurations.  If there's something wrong, it should show up pretty easily (and should be audible, I would think).
> 
> But if it sounds fine, I wouldn't worry about it.


 
  I'll do some tests then, thanks for the answers.


----------



## Bojamijams

Has anyone tried to build an ODAC+O2 combo that can run off of a battery?
   
  I know someone mentioned it here, oh tens and tens of pages ago, that they managed to it by flipping the PCB upside down.
   
  If it can do that with a rechargable battery, and be able to play and charge at the same time, I would be SOOOOO happy.


----------



## tintin220

Quote: 





bojamijams said:


> Has anyone tried to build an ODAC+O2 combo that can run off of a battery?
> 
> I know someone mentioned it here, oh tens and tens of pages ago, that they managed to it by flipping the PCB upside down.
> 
> If it can do that with a rechargable battery, and be able to play and charge at the same time, I would be SOOOOO happy.


 
   
  I have built several for friends/family, but used larger cases (such as Box Enclosure B3 / B4, a Hammond, and a Context Eng). I figured that in 99% of scenarios where a device needs a USB DAC, said device would be a computer, not a smartphone, so the amp just had to be transportable, not pocket portable. The DAC is bus powered so it doesnt have anything to do with the batteries, except take up too much space in the B2 case. In theory, it could be done with a smaller case but you'd have to (1) cover the ODAC in electrical tape to prevent shorts and (2) solder your battery terminals straight and very low. With the batteries touching the O2 board, you *might* have just barely enough clearance to fit the ODAC board, but again, it'd be touching the top case so you'd have to cover it thoroughly. I honestly wouldn't recommend this as the tight fit could damage that board. The batteries just take up too much space in a B2. In most cases, your terminals won't be soldered that neatly; in my current O2 that I built, the batteries themselves touch the top case and were a tight fit to slide the O2 board in, that's how tight the clearances are.
   
  My recommendation? Get a B3-080 case. It's only a dollar or so more expensive from Allied Elec.


----------



## mikeaj

Quote:


bojamijams said:


> Has anyone tried to build an ODAC+O2 combo that can run off of a battery?
> 
> I know someone mentioned it here, oh tens and tens of pages ago, that they managed to it by flipping the PCB upside down.
> 
> If it can do that with a rechargable battery, and be able to play and charge at the same time, I would be SOOOOO happy.


 

   
   
  You don't mean where the O2 is also powered off of USB, right?  
   
  As mentioned above, just fitting the ODAC in is a matter of space.  No reason you can't have both the 9V batteries and the ODAC in the same enclosure, especially if the enclosure is larger than the default one.  It's just that most builders just usually put the ODAC in the space where the batteries would have been, out of convenience, when putting both ODAC and O2 in the same case.


----------



## Ganda

"Giant Killer"  That is all I have with these AMP-DAC combo. I'd buy then for saving money and getting better sound quality.


----------



## miceblue

I have a few 24/192 files; how does that get translated through the ODAC's output? Does it get converted to 24/96?
  ^ relating to this, how does a DAC down-sample something? e.g. if I tried to play a 24/96 ALAC file on an iPhone
   
  Relating to this, but slightly off-topic, this website sells up-converted "HD" albums. Is there any benefit to this, or should I not even bother and just buy the regular 16/44 album?
http://www.hifitrack.com/en/node/21496


----------



## HamilcarBarca

Quote: 





miceblue said:


> I have a few 24/192 files; how does that get translated through the ODAC's output? Does it get converted to 24/96?
> ^ relating to this, how does a DAC down-sample something? e.g. if I tried to play a 24/96 ALAC file on an iPhone


 
   
  The ODAC doesn't accept 24/192 input. If you're playing 24/192 files, or any other format not accepted by the ODAC, they must be converted to a supported format (e.g., 24/96) before being sent to the ODAC. IOW, your question relates to your player not the ODAC.
   



miceblue said:


> Relating to this, but slightly off-topic, this website sells up-converted "HD" albums. Is there any benefit to this, or should I not even bother and just buy the regular 16/44 album?
> http://www.hifitrack.com/en/node/21496


 

   
  There's zero benefit unless they're remastering. If they are, you may or may not find the result superior.  If they're simply "up-converting", the best you can hope for is they don't add audible artifacts.
   
  Buy the CD instead.


----------



## miceblue

Quote: 





hamilcarbarca said:


> Quote:
> 
> 
> 
> ...


 
  So if I hear stuff through my headphones with 24/192 tracks , and the ODAC doesn't support 24/192, then what does the ODAC do?
   
  I figured as much for the up-converting files. I would buy the CDs but I have to pay import fees.


----------



## HamilcarBarca

Quote: 





miceblue said:


> So if I hear stuff through my headphones with 24/192 tracks , and the ODAC doesn't support 24/192, then what does the ODAC do?


 
   
  The ODAC converts audio encoded in digital form (1's and 0's, a/k/a discrete) into analog form (waves, a/k/a continuous). It's these electrical waves which tell the drivers in headphones how to move back and forth, thus producing the sound we can hear. The 'DAC' in ODAC describes its purpose: It's a Digital-to-Analog Converter.
   
  Your player software (or hardware) "down-converts" the 24/192 digital representation of the audio into a format the ODAC will accept (e.g., 24/96). Only then is the ODAC able to convert the "digital  audio" into "analog audio".


----------



## OICWUTUDIDTHAR

Thoughts on using an ODAC+WA2 Combo? I only need USB input and it seems the ODAC is still basically a benchmark dac?


----------



## miceblue

Quote: 





hamilcarbarca said:


> Quote:
> 
> 
> 
> ...


 
  Oh okay that makes sense now. Thanks!


----------



## autoteleology

I did a blind A/B of the ODAC/O2 v. the Magni/Modi at a meet and the results were really disappointing. The difference between the two was minute to my ears, if it exists at all.


----------



## Bojamijams

Sorry I should've specified more.
   
  My idea was to get an ODAC+O2 combo in one case with rechargable batteries.   Likewise, add a Line-Out option on it.
   
  The DAC can then be powered by USB alone and give a line-out.  This would be VERY useful for driving it through a smartphone to get a line out for your car.  But obviously other applications too
   
  Thus the ability to drive the WHOLE thing (DAC+AMP) without needing an external power source (hence the batteries), would be the ultimate "on-the-go" setup. 
   
  I realize the original request for ability to charge the batteries WHILE playing would be pretty hard so that can be removed, but the ability for the batteries to be charged through USB would be phenomenal (especially if they can take 1A-2A charge)
   
  Quote: 





tintin220 said:


> I have built several for friends/family, but used larger cases (such as Box Enclosure B3 / B4, a Hammond, and a Context Eng). I figured that in 99% of scenarios where a device needs a USB DAC, said device would be a computer, not a smartphone, so the amp just had to be transportable, not pocket portable. The DAC is bus powered so it doesnt have anything to do with the batteries, except take up too much space in the B2 case. In theory, it could be done with a smaller case but you'd have to (1) cover the ODAC in electrical tape to prevent shorts and (2) solder your battery terminals straight and very low. With the batteries touching the O2 board, you *might* have just barely enough clearance to fit the ODAC board, but again, it'd be touching the top case so you'd have to cover it thoroughly. I honestly wouldn't recommend this as the tight fit could damage that board. The batteries just take up too much space in a B2. In most cases, your terminals won't be soldered that neatly; in my current O2 that I built, the batteries themselves touch the top case and were a tight fit to slide the O2 board in, that's how tight the clearances are.
> 
> My recommendation? Get a B3-080 case. It's only a dollar or so more expensive from Allied Elec.


 
   
  Quote: 





mikeaj said:


> You don't mean where the O2 is also powered off of USB, right?
> 
> As mentioned above, just fitting the ODAC in is a matter of space.  No reason you can't have both the 9V batteries and the ODAC in the same enclosure, especially if the enclosure is larger than the default one.  It's just that most builders just usually put the ODAC in the space where the batteries would have been, out of convenience, when putting both ODAC and O2 in the same case.


----------



## stv014

Quote: 





> Originally Posted by *MrMateoHead* /img/forum/go_quote.gif
> 
> The most current Xonar DX card has 2V out, and dedicated headphone amplification through the front out / Headphone out jack. My guess is that output impedance is probably 10 ohms, given that many good computer cards use TI chips. That is also probably about twice the output voltage typical in a computer. I could not find exact specs online.


 
   
  My Xonar D1 (the PCI version of the DX) which I have tested extensively is from 2011, and I doubt that a major hardware revision (such as adding a TI headphone amplifier) has been made since then without renaming the card. I assume your claim of dedicated headphone amplification is based on this part of the manual: _"The Front Out jack has a built-in high-quality amplifier to drive headphones. Connect your stereo headphones directly to this jack."_ - but it is there in the manual of every Xonar card, and the specifications say nothing about a headphone amplifier. I assume if there was one, ASUS would make it more obvious to potential customers. The "front out" jack on my card (which looks the same as any picture I have seen of this model) is driven by an NJM5532 op amp, and it definitely has 100 Ω output impedance.


----------



## chrislangley4253

Quote: 





tus-chan said:


> I did a blind A/B of the ODAC/O2 v. the Magni/Modi at a meet and the results were really disappointing. The difference between the two was minute to my ears, if it exists at all.


 
  I can almost guarantee that any minute difference that you heard was most likely due to slightly different volumes, unless you had them volume matched.

 A/B'ing _good_ gear is always a bit disappointing.


----------



## autoteleology

I've read that volume matching needs to be done to approximately 0.2dB in order to remove loudness bias... there is no way my by-ear approximation got anywhere close, and I still heard no difference whatsoever.


----------



## miceblue

Quote: 





tus-chan said:


> I did a blind A/B of the ODAC/O2 v. the Magni/Modi at a meet and the results were really disappointing. The difference between the two was minute to my ears, if it exists at all.


 
  Were you expecting a large difference or something? These comparisons had been made before and the same results occurred.


----------



## Greenleaf7

Has anyone experienced the  O2 + ODAC with the following headphones? 
   
  HD 650
  HD 800
  LCD 2
  Hifiman He 500
   
  I have a budget of $1000+ and plan on using the headphones for mainstream (billboard top 100) music and movies. I've been told that headphones play the biggest part in influencing sound quality,  thus I'm inclined to allocate more of my budget towards headphones. Also, i might or might not have the luxury of auditioning the above headphones with the O2 and ODAC before purchase. I'm open to suggestions for other headphones as well. Looking forward to hearing from those who have heard those phones with the O2!


----------



## tintin220

Quote: 





greenleaf7 said:


> Has anyone experienced the  O2 + ODAC with the following headphones?
> 
> HD 650
> HD 800
> ...


 
   
  Honestly, the O2 works well with everything just about, except those rare cans that require absurd gain. If you want power and literally the most neutral, audibly perfect sound, get the O2. Other amps are for if you want coloration, which you might very well prefer (I know I do), but facts are facts, and the O2's design, performance, and clarity is well-documented.


----------



## miceblue

Quote: 





greenleaf7 said:


> Has anyone experienced the  O2 + ODAC with the following headphones?
> 
> HD 650
> HD 800
> ...


 
  LCD-2.2 sounds amazing with the O2!
   
  HE-500 sounds okay but the 9 kHz peak annoyed me. Tube amps help mask that flaw...


----------



## Greenleaf7

Quote: 





miceblue said:


> LCD-2.2 sounds amazing with the O2!
> 
> HE-500 sounds okay but the 9 kHz peak annoyed me. Tube amps help mask that flaw...


 
  That's great to hear. Since you've heard both the LCD2 and HE 500 with the O2, which of those do you feel are more suited for mainstream music?
  Also, I see that you own a K701, mind telling me how it sounds through the O2? Thanks!
   
   
  Quote: 





tintin220 said:


> Honestly, the O2 works well with everything just about, except those rare cans that require absurd gain. If you want power and literally the most neutral, audibly perfect sound, get the O2. Other amps are for if you want coloration, which you might very well prefer (I know I do), but facts are facts, and the O2's design, performance, and clarity is well-documented.


 
  I second that. I don't fancy coloration, I like my music to sound as intended. Currently favoring the O2 and ODAC since it boasts an excellent price to performance ratio, is technically excellent and measures well on top of everything. What headphones do you use with your O2?


----------



## ProTofik

I heard every headphones you named on Odac and o2 and they all do very well.
For mainstreamam music i think I will recommend hd650 for you. Lcd2 are also a great choice of you can spend more money. 
I don't think you will like hd800.
About he500... I just don't like these headphones...

Remember that more expensive headphones doesn't equal better sound. I heard most of top tier headphones and I still love my hd600 . I don't think I will change them any soon.


----------



## Greenleaf7

Quote: 





protofik said:


> I heard every headphones you named on Odac and o2 and they all do very well.
> For mainstreamam music i think I will recommend hd650 for you. Lcd2 are also a great choice of you can spend more money.
> I don't think you will like hd800.
> About he500... I just don't like these headphones...
> ...


 
  The HD 650 holds its own very well and is great value IMO. I won't be getting the HD 800 unless i can get a used one for a good price so it's my least likely choice for now. 
  Why doesn't the HE 500 appeal to you? Most who have heard both claim that the LCD 2 offers better base and the HE 500 offers better balance for all music genres, though admittedly i yet to hear either myself.


----------



## MrMateoHead

Quote: 





tus-chan said:


> I did a blind A/B of the ODAC/O2 v. the Magni/Modi at a meet and the results were really disappointing. The difference between the two was minute to my ears, if it exists at all.


 
  It is good to think that a less expensive amp produces such good results.
   
  The other differences that matter are aesthetics (Jacks in the front of O2 is a little messy), and the fact that the O2 has a gain switch (1X, 2.5X, or 6.5X) while the Magni is fixed at 5X (which is quite high, if not too high for an amp with that much power).


----------



## miceblue

Quote: 





greenleaf7 said:


> Quote:
> 
> 
> 
> ...


 
  For mainstream music? It depends on what kind of sound you're looking for since the two have different sound signatures. I gravitate towards the HE-500 over the LCD-2 for mainstream music because of its airiness and spacious soundstage, but the LCD-2 has much better texture and a more realistic timbre to my ears.
   
  With the K 702, I like the sound out of the O2/ODAC combo. I don't know how it compares to the widely recommended Matrix M-Stage amp though. I actually prefer the JDS Labs C5 with the K 701 since the 701's imaging sounds a bit unnatural to my ears with the O2.


----------



## MrMateoHead

Quote: 





stv014 said:


> My Xonar D1 (the PCI version of the DX) which I have tested extensively is from 2011, and I doubt that a major hardware revision (such as adding a TI headphone amplifier) has been made since then without renaming the card. I assume your claim of dedicated headphone amplification is based on this part of the manual: _"The Front Out jack has a built-in high-quality amplifier to drive headphones. Connect your stereo headphones directly to this jack."_ - but it is there in the manual of every Xonar card, and the specifications say nothing about a headphone amplifier. I assume if there was one, ASUS would make it more obvious to potential customers. The "front out" jack on my card (which looks the same as any picture I have seen of this model) is driven by an NJM5532 op amp, and it definitely has 100 Ω output impedance.


 
  Interesting review page! It is nice to see such detailed analysis of component performance. Clearly, low-impedance loads (like headphones), will have a serious bass roll-off with that card, suggesting to me that is in not actually using a 'dedicated' amplifier. The STX uses a TI Chip, which is probably what I was thinking about.
   
  Did you ever bother to try other loads - like 32, 50, 300, and 600? Those impedance's seem to be fairly common.


----------



## lcooksl

Listening to music just now with the chain Macbook Air > MF VLink II > Heed Obelisk DA > O2 > Heir Tzar 350. Sounds surprisingly well....actually awesome at 1x gain and with 15V psu.


----------



## MrEleventy

lcooksl said:


> Listening to music just now with the chain Macbook Air > MF VLink II > Heed Obelisk DA > O2 > Heir Tzar 350. Sounds surprisingly well....actually awesome at 1x gain and with 15V psu.
> 
> 
> 
> ...


Nice custom O2.


----------



## MrMateoHead

Your amp is sick looking


----------



## tintin220

Quote: 





mrmateohead said:


> It is good to think that a less expensive amp produces such good results.
> 
> The other differences that matter are aesthetics (Jacks in the front of O2 is a little messy), and the fact that the O2 has a gain switch (1X, 2.5X, or 6.5X) while the Magni is fixed at 5X (which is quite high, if not too high for an amp with that much power).


 
   
  In some ways, NwAvGuy has succeeded in that not only has the O2 proven to be indistinguishable from many solid state amps priced several times higher, but I would say the Modi/Magni release is a direct response to the popularity of the ODAC/O2, itself an amp that many cannot distinguish from the O2, Asgard, etc. Though still vilified by many, this point has been proven pretty resoundingly. Ironically enough, I am a tube guy, but I know that the tubey sound signature I love is a result of distortion (beautiful, beautiful distortion 
	

	
	
		
		

		
		
	


	




) and that tube amps are generally not "high fidelity" in the historical sense of the term, which refers to exact reproduction of the source.


----------



## autoteleology

Given my very limited experience with tube amps, I really like the sound that they provide (and I love the idea of tube rolling and modding). However, I'm not sure I would ever use a tube amp for mixing/mastering/etc, because I feel like the same distortion that makes the sound euphonic would also be a) coloring the output and b) covering up errors that I would need to be fixing (clipping comes to mind). Are my suspicions grounded in reality?


----------



## MrEleventy

tus-chan said:


> Given my very limited experience with tube amps, I really like the sound that they provide (and I love the idea of tube rolling and modding). However, I'm not sure I would ever use a tube amp for mixing/mastering/etc, because I feel like the same distortion that makes the sound euphonic would also be a) coloring the output and b) covering up errors that I would need to be fixing (clipping comes to mind). Are my suspicions grounded in reality?




I think they are. You want neutral if you're mixing/mastering. In theory, SS would be the best way to go since even the sound of tubes can vary depending on their lifespan. Tubes are more for the experience.


----------



## tintin220

Speaking of the Magni, I do also believe the Magni's 5x gain is very high. I personally listen to my O2 at 1x (unity) gain since I only have low-impedance cans right now. It's being driven by a γ2, which is only 1.4 Vrms, though truthfully, I also can't tell it apart from the ODAC (or really any well-designed DAC). 
   
  Regarding aesthetics though, it's a great match for the O2, right down to the convenient front 3.5mm DAC output. I prefer its versatility as far as inputs and outputs, including two analog outs. For those up for the challenge, it's a bit pricier than an ODAC to build. (For those wondering, the silver B3-080 houses a σ25 PSU; I plan to get a matching black case and install matching screws on the O2). 
   
  I actually much prefer the look of the O2 to the Modi/Magni. Granted, I am a research scientist, but I am really partial to the O2's blue-collar, scientific instrument-like, DIY aesthetic. Don't get me wrong, I am also a fan of the Apple-esque cleanliness that defines Schiit's product line, but the Magni unfortunately feels and cheap in comparison to its larger cousins (which, in all fairness, it is cheap in comparison). The M&M stack (to me at least) comes off as trying too hard and has that knockoff feel to it. As for the O2, it can be made to look a lot cleaner if you custom make your own front panel instead of getting a pre-printed one.
   
  ==


----------



## autoteleology

That setup isn't going to look so clean after you add a headphone cable, a power cable to the O2 (unless you've got a battery or are using some kind of custom back entry we can't see), and a data cable to the DAC.

 I like the utilitarian look of the O2 (especially *my* O2) more than the Apple-esque look of the M&M (mainly because it looks better than everything else on your desk and matches virtually nothing), but thanks to NwAvGuy showing an incredible lack of foresight by putting all of the inputs and outputs on the front, it is virtually impossible to not create a jungle of tangled wires coming and going around the Objective stack. This irritates me to no end.


----------



## tintin220

Quote: 





tus-chan said:


> That setup isn't going to look so clean after you add a headphone cable, a power cable to the O2 (unless you've got a battery or are using some kind of custom back entry we can't see), and a data cable to the DAC.


 
   

   

   
  ==
   
  It does help that the y2's (USB) inputs are on the back and you can use a single small mini-to-mini to connect the two. All those ports you see on the front are actually outputs, not inputs. The DAC is actually currently USB-powered since the PSU is off. Like I said, the y2 is extremely versatile.
   
  Utilitarian is a great word to describe the aesthetic. It's exactly how I feel about it, and why I think it looks better than the M&M.


----------



## miceblue

Quote: 





tus-chan said:


> Given my very limited experience with tube amps, I really like the sound that they provide (and I love the idea of tube rolling and modding). However, I'm not sure I would ever use a tube amp for mixing/mastering/etc, because I feel like the same distortion that makes the sound euphonic would also be a) coloring the output and b) covering up errors that I would need to be fixing (clipping comes to mind). Are my suspicions grounded in reality?


 
  Cover-up errors and coloured output are why I think people like tube amps. It makes the sound sound more "round" and "soft" from my experience. An example would be with the HE-500. The O2 reveals the 9 kHz treble peak really easily. Put it with a Woo Audio WA7 and that peak is reduced and is much less annoying; however, at the cost of losing the same airiness that the O2 provides and the soundstage is more cramped-sounding.


----------



## tintin220

Quote: 





miceblue said:


> Cover-up errors and coloured output are why I think people like tube amps. It makes the sound sound more "round" and "soft" from my experience. An example would be with the HE-500. The O2 reveals the 9 kHz treble peak really easily. Put it with a Woo Audio WA7 and that peak is reduced and is much less annoying; however, at the cost of losing the same airiness that the O2 provides and the soundstage is more cramped-sounding.


 
   
  That's why I like it. But, as I mentioned earlier, that's not "high fidelity" in the truest and original sense of the term.
   
  It's kind of funny (sad?) that when the O2 reveals deficiencies in a headphone's performance, oftentimes, people will then attribute these flaws to the O2, when really, it's the headphones that are problematic, and proclaim that the O2 is xyz-deficient.


----------



## Greenleaf7

Quote: 





tus-chan said:


> That setup isn't going to look so clean after you add a headphone cable, a power cable to the O2 (unless you've got a battery or are using some kind of custom back entry we can't see), and a data cable to the DAC.
> 
> I like the utilitarian look of the O2 (especially *my* O2) more than the Apple-esque look of the M&M (mainly because it looks better than everything else on your desk and matches virtually nothing), but thanks to NwAvGuy showing an incredible lack of foresight by putting all of the inputs and outputs on the front, it is virtually impossible to not create a jungle of tangled wires coming and going around the Objective stack. This irritates me to no end.


 
  That's a cool red stack you have. I've seen desktop O2s that are aesthetically better than the regular O2s. The one made by audio poutine has a 1/4 jack, all the switches and outputs moved to the back of the amp, and even comes with RCA outputs like a regular desktop,  which gives it a more elegant look. They do cost a bit more of cost but i think its well worth the upgrade if aesthetics and functionality are your concern. If i'm not mistaken, head n hifi and one other seller are developing a desktop version as well. I'm planning on getting a desktop o2 for myself and I'm hoping they will be available soon.


----------



## Greenleaf7

Quote: 





miceblue said:


> For mainstream music? It depends on what kind of sound you're looking for since the two have different sound signatures. I gravitate towards the HE-500 over the LCD-2 for mainstream music because of its airiness and spacious soundstage, but the LCD-2 has much better texture and a more realistic timbre to my ears.
> 
> With the K 702, I like the sound out of the O2/ODAC combo. I don't know how it compares to the widely recommended Matrix M-Stage amp though. I actually prefer the JDS Labs C5 with the K 701 since the 701's imaging sounds a bit unnatural to my ears with the O2.


 
  Appreciate your feedback. It seems like pretty close race between the LCD 2 and HE 500. Many reviews in other treads like the LCD2 vs HE 500 claim that there is no clear winner, being that both tend to shine in different areas and ultimately the choice comes down to personal sounds preference. And on top of that the HE 500 costing $300 less makes for a real bargain.


----------



## HamilcarBarca

Quote: 





greenleaf7 said:


> Quote:
> 
> 
> 
> ...


 
   
  I'd be wary. The O2 doesn't have or supply or create imaging. It's simply neutral.
   
  If there is any audible difference between it and the C5, it the C5 which is unnatural. However, from its reviews and specs, I don't think that's true either. It appears to be neutral as well.


----------



## miceblue

Quote: 





hamilcarbarca said:


> Quote:
> 
> 
> 
> ...


 
  I do hear a difference between the O2 and C5. The C5 sounds more closed-in and the mids are ever-so-slightly more forward to my ears. They are close in sound though.


----------



## fihidelity

Has anyone had any experience with the O2 and the HD700, 650 or 600? I'm thinking of getting one of these pairs and I need an amp to pair with it.


----------



## chrislangley4253

Quote: 





fihidelity said:


> Has anyone had any experience with the O2 and the HD700, 650 or 600? I'm thinking of getting one of these pairs and I need an amp to pair with it.


 
  It works fantastically with the 580/600/650. I have not tried the 700 or 800.


----------



## HamilcarBarca

Quote: 





chrislangley4253 said:


> Quote:
> 
> 
> 
> ...


 
   
  I'd agree that it works fantastically with the 650. I haven't tried the 580, 600, 700, or 800.
   
  To the OP: It'll work the exactly same with just about anything short of a power-hungry orthodynamic or electrostatic set.


----------



## Modulus

Does anyone own both the 02/odac and the new Audinst HUD-MX2? I am interested in hearing how the MX2 compares to the clarity of the O2. It doesn't seem as though anyone has done any measurements of the MX2 yet.
   
  Any insights would be very much appreciated.


----------



## fihidelity

Quote: 





chrislangley4253 said:


> It works fantastically with the 580/600/650. I have not tried the 700 or 800.


 
   
  Quote: 





hamilcarbarca said:


> I'd agree that it works fantastically with the 650. I haven't tried the 580, 600, 700, or 800.
> 
> To the OP: It'll work the exactly same with just about anything short of a power-hungry orthodynamic or electrostatic set.


 
  Thanks chaps, I already have a Magni and whilst it's supposed to sound good with the Hd600 and 650, I hear it's a bit bright with the 700s. I'm going to try any get an O2 or an iFi iCAN to try with them and see how they pair.


----------



## ProTofik

Quote: 





fihidelity said:


> Has anyone had any experience with the O2 and the HD700, 650 or 600? I'm thinking of getting one of these pairs and I need an amp to pair with it.


 
   
   
  I use ODAC/O2 combo everyday with my HD600 and I haven't heard anything better for these headphones yet. My friend use the same combo with HD650 and it also sounds great.
  At first try it sounded a bit too bright for my liking but once I got used to it (after 2-3f hours?) I absolutely love it.


----------



## chrislangley4253

Quote: 





modulus said:


> Does anyone own both the 02/odac and the new Audinst HUD-MX2? I am interested in hearing how the MX2 compares to the clarity of the O2. It doesn't seem as though anyone has done any measurements of the MX2 yet.
> 
> Any insights would be very much appreciated.


 
   
  FWIW, the designer of the amp was not a fan of Audinst, in general. Just throwing that out there.
   
  Quote: 





fihidelity said:


> Thanks chaps, I already have a Magni and whilst it's supposed to sound good with the Hd600 and 650, I hear it's a bit bright with the 700s. I'm going to try any get an O2 or an iFi iCAN to try with them and see how they pair.


 
   
  I do not expect the O2 to take care of any brightness problems with the 700. I do not expect the O2 to sound much different from the magni at all, but best of luck.


----------



## Modulus

Quote: 





chrislangley4253 said:


> FWIW, the designer of the amp was not a fan of Audinst, in general. Just throwing that out there.


 
   
  That's interesting. Has this been a recent comment, or from when he was active around 2011? At that time the MX1 was the Audinst flagship, the MX2 is a very recent release and benefits from a significant redesign. I would be interested to hear what he has to say about the new design. I'm sure the manufacturers must have been aware of the O2, at its price point it certainly seems like a response to the O2.
   
  If the O2 design is as accomplished as it appears, why are other manufacturers not simply copying it? It is open source after all.


----------



## RustA

Quote: 





fihidelity said:


> Thanks chaps, I already have a Magni and whilst it's supposed to sound good with the Hd600 and 650, I hear it's a bit bright with the 700s. I'm going to try any get an O2 or an iFi iCAN to try with them and see how they pair.


 
   
  I would not pair HD700 and iFi iCAN at all... I was myself doing a research and iFi iCAN is suitable rather for HD600 or HD650, especially if considering to use iCAN's crossfeed.
   
  HD700 exhibit serious ringing and peaks and its treble response is therefore problematic (a lot more than what some people find problematic about HD800), therefore I would most probably only pair HD700 with a tube amp... Well, I would never purchase HD700 to be honest, it's an overpriced headphone for sure. Get HD600, or go straight for HD800.


----------



## RustA

Quote: 





modulus said:


> That's interesting. Has this been a recent comment, or from when he was active around 2011? At that time the MX1 was the Audinst flagship, the MX2 is a very recent release and benefits from a significant redesign. I would be interested to hear what he has to say about the new design. I'm sure the manufacturers must have been aware of the O2, at its price point it certainly seems like a response to the O2.
> 
> If the O2 design is as accomplished as it appears, why are other manufacturers not simply copying it? It is open source after all.


 
   
  It's not open source... You cannot modify it or use it for commercial purposes (like using the design as a basis for your commercial product). You can only use it as it is = be a commercial builder.
   
  Of course, you could do whatever you want with the circuit for your DIY purposes... But not commercially.


----------



## mikeaj

Quote: 





modulus said:


> That's interesting. Has this been a recent comment, or from when he was active around 2011? At that time the MX1 was the Audinst flagship, the MX2 is a very recent release and benefits from a significant redesign. I would be interested to hear what he has to say about the new design. I'm sure the manufacturers must have been aware of the O2, at its price point it certainly seems like a response to the O2.
> 
> If the O2 design is as accomplished as it appears, why are other manufacturers not simply copying it? It is open source after all.


 
   
  re: Audinst... that's from a while back.  Also, the guy is known to have opinions (educated guesses? call them whatever you will) about stuff, even that he's not tested.
   
  As for copying the O2, depends what you mean.  If you're talking about building O2s, that's what people like Epiphany, JDSLabs, and Mayflower do, and commercially so.
   
   
   


rusta said:


> It's not open source... You cannot modify it or use it for commercial purposes (like using the design as a basis for your commercial product). You can only use it as it is = be a commercial builder.
> 
> Of course, you could do whatever you want with the circuit for your DIY purposes... But not commercially.


 

   
  It's open source but not completely unrestricted.
   
  See this:
http://creativecommons.org/licenses/by-nd/3.0/
   
  So a company copying it, modifying it, and selling an improvement (marketing it as such) isn't really permissible.
   
   
  Now, the bigger deal is that a design like the O2, at least on a macro level, could be done by anybody.  Pretty much every DIY designer's done something more complicated.  O2 is the simplest possible two-stage amp topology out there.  Only thing simpler is a one-op amp design, a CMoy.  It's not like the idea broke any new ground or wasn't something that people could have done before.  The circuit's just a bit more optimized than what most DIY designers could do without a bit of hard work, a decent audio analyzer, and a few board revisions.  That just means that the performance has been improved from "most likely good enough" to "even more likely good enough" for most purposes, according to some.  But any reasonable audio company could have designed the same with a bit of work.
   
  O2's biggest innovation or contribution was the power / protection / battery run-down circuit... which ended up not working as intended for a lot of people, who used different batteries.  Whoops.  But that's a challenge of a DIY design where you're not as in control of which exact parts are used.
   
  It's not like other companies have anything really novel to copy there, that they could use as an advantage.  It didn't tell them something they didn't already know before.  Well, if they weren't paying attention to certain other previous designs, then maybe they might not have thought about paralleling JRC4556s as a cheap way to implement a decently-high-current output.  But there are plenty of buffers and other topologies you can use instead, that also work.
   
  Saving an audiophile company a few bucks per unit on chip costs isn't going to make or break them.


----------



## HiFiRobot

Quote: 





autior said:


> The motherboard is an AsRock Z68 Extreme 4 Gen 3, I got 2 USB 3.0 ports but they never worked (maybe because I have a Sandy Bridge processor? I don't know). Anyway I did as you said (I connected everything but the O2/ODAC on the rear of the motherboard, and the amp/dac on the front USB 2.0 port), now the O2/ODAC has his own bus.
> 
> 
> 
> ...


 
   
  Regarding the USB 3.0 ports, I believe you have to install the USB 3.0 drivers to get them working http://www.asrock.com/mb/Intel/Z68%20Extreme4/?cat=Download
  I have the Z77 Extreme 4 and that was the case for me on Win7 64-bit.
   
  I do not think your HDMI monitor setup will affect your DAC sound.


----------



## Airstripone

Just bear this in mind, when you buy O2+ODAC combo from JDS Labs you will get a non-battery version of O2.


----------



## Greenleaf7

Does anyone know where i can get a desktop version of the O2? Ie. with 1/4 jack and outputs located behind the amp. (besides audio poutine and mayflower electronics)


----------



## earphiler

just came here to say i've been a happy customer with o2+odac (separate boxes odac from jds labs and o2 from mayflower) paired with my hifiman he-400.


----------



## JakeJack_2008

Quote: 





earphiler said:


> just came here to say i've been a happy customer with o2+odac (separate boxes odac from jds labs and o2 from mayflower) paired with my hifiman he-400.


 
   
  Welcome to the club. Let me tell you this.
  You are only one 
	

	
	
		
		

		
		
	


	




 of  many _super happy _users of the O2 and ODAC.


----------



## Ultimate Mango

Is there any O2+ODAC combo which can also serve up a preamp output? I would love to upgrade my Audioengine D1 but use both the RCA output and the headphone amp...
The Burson Conductor is awfully tempting and ten times the price. 

There has to be such an ODAC flavor, right?


----------



## autoteleology

I've used the O2 as a preamp for actual concerts with full-range speakers and it's done a great job.


----------



## TunneLVisioN42

Speaking of using it as a pre amp I gotta question, I recently got a Wii U for me/family/friends to play occasionally for a bit of fun here and there, If I split the HDMI out into audio/video is there anyway I could send that to the O2/Odac combo? which I then use as a preamp


----------



## leadbythemelody

Getting mine two days later! I got the RCA ODAC and I plan on connecting it to my macbook with an O2 amp. Sorry for being a newb, but what does the RCA output do when connected to a computer with a 3.5mm plug?


----------



## HamilcarBarca

Quote: 





leadbythemelody said:


> Getting mine two days later! I got the RCA ODAC and I plan on connecting it to my macbook with an O2 amp. Sorry for being a newb, but what does the RCA output do when connected to a computer with a 3.5mm plug?


 
   
  To connect an ODAC with RCA output to a "standalone" O2, you'll need an RCA-to-3.5mm adapter. Is that what you're asking?


----------



## Greenleaf7

leadbythemelody said:


> Getting mine two days later! I got the RCA ODAC and I plan on connecting it to my macbook with an O2 amp. Sorry for being a newb, but what does the RCA output do when connected to a computer with a 3.5mm plug?




First connect the odac to your computer using the supplied USB cable. Since you got the RCA odac, you have the option of using either a RCA to mini or mini to mini cable to connect the odac to the o2 amp.


----------



## leadbythemelody

I already have a RCA to 3.5mm adapter but what's the difference of connecting the ODAC to the O2 with a mini-to-mini cable versus an RCA-to-mini cable? Sorry for the confusing post haha.


----------



## Greenleaf7

Quote: 





leadbythemelody said:


> I already have a RCA to 3.5mm adapter but what's the difference of connecting the ODAC to the O2 with a mini-to-mini cable versus an RCA-to-mini cable? Sorry for the confusing post haha.


 
   
  The original ODAC design only incorporated a 3.5mm output to lower cost. The designer felt that there would be no audible benefit in using a RCA output over the 3.5mm out. The RCA outputs on the ODAC like the one you have were later added by ODAC manufacturers. You can read up more on the design process by googling 'ODAC realsead'.


----------



## HamilcarBarca

Quote: 





leadbythemelody said:


> I already have a RCA to 3.5mm adapter but what's the difference of connecting the ODAC to the O2 with a mini-to-mini cable versus an RCA-to-mini cable? Sorry for the confusing post haha.


 
   
  No apology is necessary. I misunderstood your question.
   
  It shouldn't make any difference. Choose the one that's more convenient for you.


----------



## leadbythemelody

Okay thanks guys!


----------



## leadbythemelody

My HD650's distort on high gain when connected to the O2, but it's fine on low gain? Why is that?


----------



## gikigill

The O2 is pretty powerful and ifyour high ga in is 6.5x, it's too much for the headphones to handle. Stock settings for gain are 1x and 6.5x.


----------



## MrEleventy

It's 2.5x and 6.5x actually. I don't think it's the headphones. on high gain, the o2 is probably clipping. The high gain was meant for low lowered sources like cell phones or other headphone output and not the odac.


----------



## Greenleaf7

leadbythemelody said:


> My HD650's distort on high gain when connected to the O2, but it's fine on low gain? Why is that?


 you should post this question in sound science. There are some very knowledgeable people who are more than willing to help


----------



## adydula

HD650 are 300ohm cans.
   
  If i remember correctly these cans were highly favored by NWAVGUY and has a lot of information on them in his blog.
   
  He stated that these cans needed 2 volts RMS to drive the HD650's to realistic levels.
   
  This is 5.7 volts peak to peak.
   
  The power graphs show the voltage at 150 ohms and 600 ohms being almost the same at 7.3 volts....so the amp is clipping etc.
   
  I found this out as well with other cans.
   
  I run at unity gain and 2.5 sometimes...
   
  Alex


----------



## Greenleaf7

I recommend you read the article titled 'more power'. He explains very comprehensively how much power is necessary, along with formulas and calculations if you're keen on the technical stuff.


----------



## TunneLVisioN42

Off topic a bit, just posting here to say I am looking to sell my O2/Odac in favor of trying something different, PM me for details, I will be creating a classified tomorrow!


----------



## leadbythemelody

Okay thank you for the help/info guys!


----------



## Leliana

I'm trying to get my JDS o2/odac combo to connect to my laptop and pc, but neither of them detect that anything has been plugged in. My audio gd 5 connected with no trouble when I got it. Cant seem to see it in device manager or playback devices.
   
  If I can't get it to connect I'm going to have to sell it to someone who can get it to work (In Melbourne). It arrived here only a day ago, it didn't come with a usb cable either, so I have to use one I've been using for my tablet.
   
  Any ideas on what to do?


----------



## adydula

What is your OS? Win7 ? Win8?
   
  Make sure your USB port is on....try a different port?
   
  Do any other USB devices work in that port?
   
  Try the device on a different PC ?
   
  Alex


----------



## Greenleaf7

Quote: 





leliana said:


> I'm trying to get my JDS o2/odac combo to connect to my laptop and pc, but neither of them detect that anything has been plugged in. My audio gd 5 connected with no trouble when I got it. Cant seem to see it in device manager or playback devices.
> 
> If I can't get it to connect I'm going to have to sell it to someone who can get it to work (In Melbourne). It arrived here only a day ago, it didn't come with a usb cable either, so I have to use one I've been using for my tablet.
> 
> Any ideas on what to do?


 
  I might be a good idea to forward your problems to JDS labs themselves. Odds are that you're not the first who has encountered those problems. Hopefully they'll be able to provide you with a solution.


----------



## Leliana

It is working now, after about 3-4 restarts it has finally been picked up in the back port of my pc, btw I'm running windows 7.


----------



## Greenleaf7

Glad you've got it up and running. Enjoy your music!


----------



## eimis

I've got some O2 PCBs for sale if anyone's interested.


----------



## leadbythemelody

Question...can you use the O2 amp while it's charging?


----------



## gikigill

Yes.


----------



## leadbythemelody

kk, thank you


----------



## autior

Hi, I have an O2/ODAC by Epiphany, and I use it daily with my PC (via the USB 3.0) and with a console (with the 3.5mm input, only for amplification purposes). When I use it with my console I have no problems, but with the PC the drivers crash (like once a day at least) while watching films, video on youtube or something like that, and when that happen I just have to reboot my PC to listen audio again.
  
  How can I solve this? I can't use the O2/ODAC as a normal audio card?


----------



## autoteleology

If I had to take a guess I'd say your Windows audio drivers might be corrupt, or the ODAC might be malfunctioning.


----------



## autoteleology

If anyone is looking to buy the O2 and ODAC, I'm selling mine here on the forums.

http://www.head-fi.org/t/670297/custom-o2-odac-combo-plus-bonus-accessories-free-shipping-no-fees


----------



## kskwerl

^ best signature lol


----------



## autoteleology

If you're referring to the fact I have the exact same ad three times in my signature, then yeah. I really want to sell these as fast as possible so I can fund a new purchase, so I'm trying really hard to get them sold.


----------



## kskwerl

tus-chan said:


> If you're referring to the fact I have the exact same ad three times in my signature, then yeah. I really want to sell these as fast as possible so I can fund a new purchase, so I'm trying really hard to get them sold.




That's awesome! Lol you should make the picture of it your avatar too


----------



## Meremoth

I'm looking to purchase a prebuilt desktop version of the O2/ODAC combo, but there are quite a few different companies to buy from:  JDS Labs, Mayflower, Audio Poutine, Epiphany, and Head 'n' HiFi to name a few.

 Are any of these versions different from each other and/or offer more custom options?  Is there a preferred seller?  
   
  Also, has anyone used the LCD-3's with the O2/ODAC?  If so, any issues?  
   
  Thanks.


----------



## adydula

I used the odac o2 combo for many months with LCD2's..absolutley no issues driving them to riduclous level..
   
  A.


----------



## kskwerl

meremoth said:


> I'm looking to purchase a prebuilt desktop version of the O2/ODAC combo, but there are quite a few different companies to buy from:  JDS Labs, Mayflower, Audio Poutine, Epiphany, and Head 'n' HiFi to name a few.
> 
> 
> Are any of these versions different from each other and/or offer more custom options?  Is there a preferred seller?
> ...




mayflower is selling an O2 with the power adapter on the back panel. which is very nice compared to having it on the front (which looks horrible IMO). its the same amp with no sonic difference just the ac power on the back label. His desktop variants of the O2 are nice as well.


----------



## orangecr

Quote: 





kskwerl said:


> mayflower is selling an O2 with the power adapter on the back panel. which is very nice compared to having it on the front (which looks horrible IMO).


 
  I just got one from JDS Labs. I would have gotten the Mayflower just because of that apparently insignificant detail.


----------



## kskwerl

Quote: 





orangecr said:


> I just got one from JDS Labs. I would have gotten the Mayflower just because of that apparently insignificant detail.


 
  hahaha I've had the JDS Labs one, it just never made sense from the beginning. Why would you ever put the ac adapter in the front, it must have made the design easier.
   
  EDIT: Also LMAO @ "uglyjoe" in this FS thread  http://www.head-fi.org/t/666964/spc-occ-cooper-hybrid-cable-made-by-chris-himself-headphone-lounge


----------



## BenF

Quote: 





kskwerl said:


> mayflower is selling an O2 with the power adapter on the back panel. which is very nice compared to having it on the front (which looks horrible IMO). its the same amp with no sonic difference just the ac power on the back label. His desktop variants of the O2 are nice as well.


 

 The pictures on their webpage show the power adapter in the front:
http://www.mayflowerelectronics.com/black-objecective2---mayflower-edition.html


----------



## Meremoth

Quote: 





benf said:


> The pictures on their webpage show the power adapter in the front:
> http://www.mayflowerelectronics.com/black-objecective2---mayflower-edition.html


 
   
http://www.mayflowerelectronics.com/objective2-with-rear-power.html


----------



## Ultimate Mango

Is Mayflower the only game in town doing an O2+ODAC that has a pre-out from the ODAC using RCA on the back? 
   
  I am looking for that exactly, but don't understand why Mayflower charges such the premium compared to the JDSLabs build....


----------



## MrEleventy

ultimate mango said:


> Is Mayflower the only game in town doing an O2+ODAC that has a pre-out from the ODAC using RCA on the back?
> 
> I am looking for that exactly, but don't understand why Mayflower charges such the premium compared to the JDSLabs build....


 mayflower is a smaller operation/ company


----------



## Meremoth

It looks like Mayflower's O2/ODAC combo is actually $30 cheaper than JDS Labs, unless I'm missing something?  

 Their "desktop" version is more expensive, though.  
   
  I think JDS Labs can do a "desktop" version for $25 more, but the only difference is a bigger case with a 1/4" output jack.  I think the Mayflower desktop version has that plus RCA inputs.  
   
  Maybe someone else can verify all that.


----------



## leadbythemelody

Hey pplz I'm selling my O2 amp and ODAC w/RCA output.
   
  http://www.head-fi.org/t/671641/obejctive-2-amplifier-and-odac-with-rca-output-by-jds-labs


----------



## miceblue

Speaking RCA cables, does it provide any audible advantage over a regular 3.5 mm cable? I plan to use the ODAC and hook it up to an amplifier that only has RCA inputs. My ODAC has the RCA output option but I don't have a RCA-RCA cable. I was planning to use a 3.5 mm miniplug to RCA though, which I do have, and I was wondering if this is OK to use.


----------



## autoteleology

Probably "technically better" (inaudibly so) channel isolation, but other than that, no.


----------



## ohmicide

anyone know if these are good with production software? I've looked everything but haven't found much info on this. I need something for both Mac and PC with quality at least as good or better than my current Apogee ONE.


----------



## DonJunker

I've bought the O2/ODAC combo from Epiphany Acoustics. It comes with a 230/12V AC transfomer. I am a little confused that the designer is so worried about the 12V AC transformers, and recommends at least 14V AC for the transformer, for the 7812 and 7912 regulators to have headroom for regulation in case of ripple on the DC voltage. The 12V AC is a RMS value mening that rectified though a full-wave rectifier the DC level will be approx. 17V DC leaving plenty of room for regulation. Is it me misunderstanding something here?  (I guess so...the designer seems very capable )


----------



## stv014

Quote: 





donjunker said:


> I've bought the O2/ODAC combo from Epiphany Acoustics. It comes with a 230/12V AC transfomer. I am a little confused that the designer is so worried about the 12V AC transformers, and recommends at least 14V AC for the transformer, for the 7812 and 7912 regulators to have headroom for regulation in case of ripple on the DC voltage. The 12V AC is a RMS value mening that rectified though a full-wave rectifier the DC level will be approx. 17V DC leaving plenty of room for regulation. Is it me misunderstanding something here?  (I guess so...the designer seems very capable )


 
   
  It is slightly less than 17 V because there is a 0.6-0.8 V voltage on the rectifier diodes. Also, the voltage drops under load, especially since only a half-wave rectifier is used with 2*470 uF capacitors on each rail. Finally, the AC voltage is not guaranteed to be accurate either.
  The 12 V/200 mA power supply is enough for headphones that do not need a lot of current, but it may not be enough under heavy load (when using inefficient low impedance headphones).


----------



## DonJunker

stv014 said:


> It is slightly less than 17 V because there is a 0.6-0.8 V voltage on the rectifier diodes. Also, the voltage drops under load, especially since only a half-wave rectifier is used with 2*470 uF capacitors on each rail. Finally, the AC voltage is not guaranteed to be accurate either.
> The 12 V/200 mA power supply is enough for headphones that do not need a lot of current, but it may not be enough under heavy load (when using inefficient low impedance headphones).



 
 Thank you for the clarification. It's true it's only a dual polarity half wave rectifier. There may be room for some improvement on the PSU part (and perhaps better decoupling on supply of the DACs, as close a possible), even though the designer states that it won't matter and may cause the sound to worsen to e.g. improve the capacitor bank size with low ESR/ESL capacitors  I have ordered a 15V AC 1A adapter..just to be sure  I use Denon d2000 which is low-impedance


----------



## JakeJack_2008

Quote: 





stv014 said:


> It is slightly less than 17 V because there is a 0.6-0.8 V voltage on the rectifier diodes. Also, the voltage drops under load, especially since only a half-wave rectifier is used with 2*470 uF capacitors on each rail. Finally, the AC voltage is not guaranteed to be accurate either.
> The 12 V/200 mA power supply is enough for headphones that do not need a lot of current, but it may not be enough under heavy load (when using inefficient low impedance headphones).


 
  I don't understand any of the technical discussion here,
  but this is what I wanted to know:
   
   
  Quote: 





> The *12 V/200 mA *power supply is enough for headphones that _do not need a lot of current_,
> but _it may not be enough under heavy load _(when using *inefficient low impedance *headphones).


 
  Thanx for the _last  
	

	
	
		
		

		
			





 _sentence.


----------



## kskwerl

I just received the Mayflower O2 with power adapter on the rear panel. sonically its obviously the same and I'm very happy with it. the front panel looks much cleaner without the power adapter.


----------



## eimis

If i had my way i'd also put input to the back and use RCAs.


----------



## kskwerl

Quote: 





eimis said:


> If i had my way i'd also put input to the back and use RCAs.


 

 same. the power is in the back but still no RCA's. He does however have the "desktop" version of the O2 with RCA's but on that version the power is still in the front.


----------



## JakeJack_2008

Quote: 





donjunker said:


> Thank you for the clarification. It's true it's only a dual polarity half wave rectifier. There may be room for some improvement on the PSU part (and perhaps better decoupling on supply of the DACs, as close a possible), even though the designer states that it won't matter and may cause the sound to worsen to e.g. improve the capacitor bank size with low ESR/ESL capacitors I have ordered a 15V AC 1A adapter..just to be sure  I use Denon d2000 which is low-impedance


 
  Everything is Chinese for me except for the last sentence:
   
   
  Quote: 





> I have ordered a 15V AC *1A* adapter..just to be sure  I use Denon d2000 which is *low-impedance*


 
  Well, *1A* is way above  *200mA* which is needed for, say, my DT 880 (*250 Ohm*).
   
  By the way, are there any *low-impedance* headphones which really  _require _*1A*-current?
   
  What would happen if I used the 15V AC *1A* adapter with the O2 and my DT 800 (250 Ohm)?
  Would it _affect negatively _the sound in _this _case because of too much current (that is *1A)*?


----------



## DonJunker

Quote: 





jakejack_2008 said:


> Everything is Chinese for me except for the last sentence:
> 
> 
> Well, *1A* is way above  *200mA* which is needed for, say, my DT 880 (*250 Ohm*).
> ...


 

 Actually I didn't mean the DAC's but the output stage of the O2 (+ gain amplifier). Basically I just mean that there maybe is room for improvement with a better voltage supply for the OPAMPs. E.g. like bypassing each OPAMP's +/- supply with e.g.  10uF+0.1uF (SMD ceramic X7R) to ground, with the smallest capacitor soldered directly on the pin and the larger one as close as possible (I think The Wire amp uses something like that too).
  I'm not sure it will have a significant effect on the sound, as the designer seems to have thought of alot of aspects and has spent alot of time implementing the components. But I'll try it anyway as I have the capacitors. It sure won't degrade the performance.
   
  Quote from designers home page:
Question:
  1. The main cans I'll be using are a pair of Beyerdynamic DT990Pro's, 250Ohms. I may also use my Koss portapro's occasionally. On the Beyer's: am I correct in assuming that the O2 would be sufficiently powerful to drive these?

 2. On Power Supplies: would I be better served by the xicon 412-218054, or the WAU16-1000? In other words, would I be better off with more voltage headroom or more current headroom? I'm more concerned with getting the best match for the Beyers than the portapro's; in either case, the price difference over the WAU16-200 is inconsequential to me.
   
Answer from designer:
  1 - Yes, with power to spare. Just get the gain correctly.

 2 - Go with the WAU16-400 (400mA) or WAU16-1000 (1A) (or other 14 - 16 VAC wall transformer).
   

   
  I just ordered the 1A since it did cost the same as the 500mA variant   My headphones are 25 Ohm.
   
  The current value of 1A just means it will be *able* to supply 1A. The O2 just draws the current from the adapter that your headphone+volume requires..as long as it is below 1A it's no problem


----------



## kskwerl

http://www.mayflowerelectronics.com/custom-products.html

I spoke and bought too soon


----------



## miceblue

I know this is the wrong thread and this may not necessarily apply for the O2, but when shopping for a wall wart, do you guys have any preferred brands and/or vendor?

I'm asking because I purchased a new STAX rig from Japan and I live in North America where the outlet voltage is 120 V instead of 100 V in Japan. I'm looking for a >= 4 W, 12 V DC, linear (not switchmode), positive barrel wall wart and I'm having a hard time finding one.

But while we are on the topic of wall warts, and this does apply to the O2, how does a different wall wart affect the O2's performance? e.g. I think I read that a different wall wart may be preferable for driving the he-500.


----------



## kskwerl

^LOL at that avatar


----------



## doof-ed

I'd like to build one of theses and have built a cmoy and I know I can make it fine. I would like to use it portably I know its large but it would be in a bag. I have a fiio e11 and I enjoy it but would like to build my own amp in the next level up. 
I've been reading and reading and reading but I just need to ask: 

1) coupled with a iPod 5.5g and lod what is the bass like? I have Hd 25 1-ii and do enjoy my hip hop and bass. I've been reading about bass mods and seems ok.

2) any idea where I can read about the different op amps, I have no idea what the differences are


----------



## tuna47

Anyone compare odac to the bifrost looking to see if its worth the money to change


----------



## boombobby289

I'm newbie to a portable DAC.
  Besides O2, does JDSLabs' Standalone ODAC works with other portable amps like Fiio E12?
   
  If my below setup works:
   
  iPad 2 + CCK (camera Connection kit) + OADC [DAC] + Fiio E12 [AMP]


----------



## autoteleology

All DACs work with all external amps as long as one side doesn't come bundled with both (like an ODAC + O2 combo in one box) and provided you can actually connect the two together with the same interconnects or with adapters.


----------



## BenF

Quote: 





boombobby289 said:


> I'm newbie to a portable DAC.
> Besides O2, does JDSLabs' Standalone ODAC works with other portable amps like Fiio E12?
> 
> If my below setup works:
> ...


 

 I have ODAC and E12, they sound great together.


----------



## boombobby289

Quote: 





benf said:


> I have ODAC and E12, they sound great together.


 
  How is your setup for ODAC and E12?
 Do you play them with iDevices like iPad?


----------



## miceblue

Quote: 





boombobby289 said:


> Quote:
> 
> 
> 
> ...


 
  Only the iPad is able to use an external DAC at will with the Camera Connection Kit. Other iDevices require a special "Apple certified" DAC....and those are mighty expensive.
   
  You can use an external amp with any iDevice as long as you:

 Have a non-jailbroken iDevice
 Use a "Line-Out Dock" connector such as the FiiO L9


----------



## boombobby289

Quote: 





miceblue said:


> Only the iPad is able to use an external DAC at will with the Camera Connection Kit. Other iDevices require a special "Apple certified" DAC....and those are mighty expensive.
> 
> You can use an external amp with any iDevice as long as you:
> 
> ...


 
  Is there any other cheaper way to bypass the internal DAC of iDevices yet to have portability ?
 I don't mind to use power bank or battery pack.


----------



## glunteer

I bought a o2 ... that will be good?

 My setup looks like this: asus xonar dx> o2> dt 770 80 ohm
   
  thx


----------



## Porter1

Quote: 





glunteer said:


> I bought a o2 ... that will be good?
> 
> My setup looks like this: asus xonar dx> o2> dt 770 80 ohm
> 
> thx


 
   
  great setup.  i've ran Titanium HD > O2 > DT 770 80ohm and it sounds fantastic.


----------



## BenF

Quote: 





boombobby289 said:


> How is your setup for ODAC and E12?
> Do you play them with iDevices like iPad?


 
   
  I use them with Foobar on Windows 7.


----------



## glunteer

Quote: 





porter1 said:


> great setup.  i've ran Titanium HD > O2 > DT 770 80ohm and it sounds fantastic.


 

 I'm glad to see that
   
   
*EDIT:*
   
*would be nice to buy an ODAC combo? and sell my asus xonar dx?

 I have the DT 770 (as I said), and I use a m-audio AV40*


----------



## Currawong

Quote: 





boombobby289 said:


> Quote:
> 
> 
> 
> ...


 
   
  No, for a number of reasons. First is that they have to get permission from Apple, to ensure they aren't making rubbish which causes iDevices to crash or otherwise malfunction. Secondly, the reason companies do that is because they wish to make a DAC that is better than the quality of what is in an iDevice (which is already pretty good, all things considered), and that isn't cheap.


----------



## bhazard

Quote: 





currawong said:


> No, for a number of reasons. First is that they have to get permission from Apple, to ensure they aren't making rubbish which causes iDevices to crash or otherwise malfunction. Secondly, the reason companies do that is because they wish to make a DAC that is better than the quality of what is in an iDevice (which is already pretty good, all things considered), and that isn't cheap.


 
   
  Or three, because the only true reason, is most likely that Apple wants companies to pay a licensing fee, so they lock it down. It's always about the $$$.


----------



## miceblue

#3 makes the most sense to me.
   
  You can still bypass the iPad's DAC with the Camera Connection Kit and the ODAC is compatible.


----------



## bhazard

Quote: 





miceblue said:


> #3 makes the most sense to me.
> 
> You can still bypass the iPad's DAC with the Camera Connection Kit and the ODAC is compatible.


 
  But not the iphone 5 with the camera kit? That's strange.


----------



## tuna47

Odac only works with iPad camera kit into a power USB hub


----------



## Currawong

Quote: 





bhazard said:


> Quote:
> 
> 
> 
> ...


 
   
  It is not just the licence, as companies have to implement it _perfectly_ or Apple will say "no". Companies like Centrance and Cypher Labs have to go to a HUGE amount of trouble to get something working that Apple will approve. Apple makes the dollars because they design reliable products. To maintain that reliability they are strict. In their (and my) experience, customers will blame Apple for problems, even if their product isn't obviously the cause. Warranties and service eat up huge amounts of profit.  So you are right, but not quite for the reason you think. 
	

	
	
		
		

		
			




   
*boombobby289*: Here's what I reckon though: Use the O2 with your iPhone or iPod. Be happy. Sometime, if you have the chance, see if you can't compare it to a Centrance M8 at a meet with very good headphones and your own music. Maybe you'll want to upgrade, maybe not.


----------



## bhazard

Quote: 





currawong said:


> It is not just the licence, as companies have to implement it _perfectly_ or Apple will say "no". Companies like Centrance and Cypher Labs have to go to a HUGE amount of trouble to get something working that Apple will approve. Apple makes the dollars because they design reliable products. To maintain that reliability they are strict. In their (and my) experience, customers will blame Apple for problems, even if their product isn't obviously the cause. Warranties and service eat up huge amounts of profit.  So you are right, but not quite for the reason you think.
> 
> 
> 
> ...


 
  It would be nice to think that way, but it is simply not true. The same could be said for the $30 lightning adapters and cables. Is it truly $30 worth of adapter? Once it was cracked, they were easily found for $5-9 in 3 packs. If the DAC bypass was cracked, they would have no say in it either. 
   
  They make the $ because they have people like yourself fooled that their products are any more reliable than their competition. Allowing us to plug into the DAC we wanted would give most of us an even better experience than the "Apple certified" ones.


----------



## conheo

Can i use the headphone out of O2 (as gain 1x) as a preamp ? Cause the output of ODAC feed my other headphone amplifier is too loud for my sensitive headphone (like AD v.v...). So im willing to use it as preamp but not sure if it will ok ?


----------



## stv014

Yes, you can use it for that purpose without problems. Or just drive the headphones with the O2 (which works well with sensitive/low impedance headphones and IEMs) if the other amplifier has a high gain. Another solution is to reduce the volume on the PC, with 24-bit volume control, you can attenuate by 10 dB and still have better than 100 dB dynamic range on the ODAC.


----------



## HaVoC-28

Quote: 





stv014 said:


> Yes, you can use it for that purpose without problems. Or just drive the headphones with the O2 (which works well with sensitive/low impedance headphones and IEMs) if the other amplifier has a high gain. Another solution is to reduce the volume on the PC, with 24-bit volume control, you can attenuate by 10 dB and still have better than 100 dB dynamic range on the ODAC.


 
   
  Only by 10 dB ? 
	

	
	
		
		

		
		
	


	




 (with music from CD i think that we have more headroom than just 10 dB on 24 bits output) .


----------



## stv014

Quote: 





havoc-28 said:


> Only by 10 dB ?
> 
> 
> 
> ...


 
   
  The ODAC is not capable of the theoretical dynamic range allowed by 24 bit samples, so it is 111 (from measurements) - 10 = 101 dB. In practice, more attenuation would likely still not produce audible noise, but 10 dB should be a "safe" amount even with high quality recordings.


----------



## tuna47

How does the odac stand up to the bifrost any hear both


----------



## burritoboy9984

Just finished up my first O2/Odac combo and thought I would share. I'll post pics with the Odac tomorrow when I have a chance. I'm going to be dimming the led soon, that is for sure, lol.


----------



## mikeaj

Looks like... a blue LED?
   
  In case you missed it, the voltage drop across the LED on the O2 part is used as a reference for the power management circuit. If you swap the color and thus get something with a different forward voltage drop, funny things could happen like things not turning on. But if it works, no problem.


----------



## deejay220989

Hi Guys,
   
  I'm getting a Beyer DT770 250 ohm soon, and planning to get JDS Labs O2 amp for it. But I'm wondering if its worthy to get the ODAC too.
   
  I've never used a DAC before, and I'm not sure if the ODAC will make much difference to what I'll be listening.
   
  I usually listen to FLAC from my laptop or my portable player (iRiver H320)
   
  Please advise.
   
  Thanks!


----------



## stv014

Quote: 





> Originally Posted by *deejay220989* /img/forum/go_quote.gif
> 
> I've never used a DAC before, and I'm not sure if the ODAC will make much difference to what I'll be listening.
> 
> I usually listen to FLAC from my laptop or my portable player (iRiver H320)


 
   
  That unfortunately does not really tell much, laptops and portable players have quite variable sound quality, about which often little to no reliable information is available. In terms of measured performance, the ODAC is very likely to be an improvement, but if you are lucky with the laptop/DAP, it might still sound good enough (that is, not noticeably different from the ODAC, other than volume) anyway. But it could also be audibly noisy, or have some other problems.


----------



## burritoboy9984

mikeaj said:


> Looks like... a blue LED?
> 
> In case you missed it, the voltage drop across the LED on the O2 part is used as a reference for the power management circuit. If you swap the color and thus get something with a different forward voltage drop, funny things could happen like things not turning on. But if it works, no problem.




It is actually a white led. I changed the stock led out for a 1.8v diode, then hooked into the 12v rail for the white led with a resistor inline. I'll probably change the resistor today or tomorrow so you can see the white a little better, lol.

-Erik


----------



## chrislangley4253

Quote: 





conheo said:


> Can i use the headphone out of O2 (as gain 1x) as a preamp ? Cause the output of ODAC feed my other headphone amplifier is too loud for my sensitive headphone (like AD v.v...). So im willing to use it as preamp but not sure if it will ok ?


 
   
  Yup! I use it as a preamp for my speaker amp all the time, because the output of the ODAC is too high for it too. However, why not just plug your headphones into the O2?


----------



## Rikuo

Figure this is probably the best place to ask this.



So I got an Odac in the mail today, Already owned the O2amp. 

Threw them all in the same case / etc. Hooked it up to my PC and everything works great, Sound is amazing.

But whenever i try to change the Bit depth to 24bit, It just doesnt work.

If i hit "Test" on windows, it says "Failed to play test tone"
If i hit apply on 24bit, I get absolutely no sound.


I've tried different Usb slots, Different usb cables, Restarting


No clue why 24bit will not work.


Any idea guys?


----------



## deejay220989

So, I just got to know about Schiit's Magni/Modi. Anyone tried them with DT770?

 Magni/Modi or O2/ODAC?


----------



## MrMateoHead

Quote: 





rikuo said:


> Figure this is probably the best place to ask this.
> 
> 
> 
> ...


 

 Sampling Rate - what is that set to? The max for the ODAC would be 96 khz. Also, make sure that you have the ODAC selected when making the adjustment.


----------



## Nowhere

amidst the chaos of purchasing the amp/dac i made the rookie mistake of not being sure of the connections, i just assumed the o2 had rca connections on it as it seemed most amps did and so i got the odac with rca to connect but upon receiving both i come to find out the o2 doesn't have rca.
   
  doh!
   
  now i have to wait to ship out a proper cable so i can start listening, what type of cable would be better to go with? thanks in advance
   
  there's a "fiio l2 3.5 to 3.5 cable" or there's a "mediabridge 3.5 to rca cable" around the same price.
   
  would there be any difference in going straight from 3.5-->3.5 vs 3.5--->rca ??
   
  oh and would i be able to plug headphones directly into the odac plugged into the computer through usb and listen to music while waiting for my new cable? or is that a big no go, do not enter area.


----------



## RAZRr1275

There have been a lot of questions around here about the o2 vs magni so here are my impressions of the two. Excuse the awkward transition into the article as it was written for my blog which can be found here http://musicandlistening.wordpress.com/
   
  So apparently I was lying a while back when on an audio subreddit, I said that I wouldn’t do a blind abx test. To provide a bit of context, a friend of mine purchased a Schiit Magni, so we decided to compare it to the o2 since one of the things that we’ve seen around some audio sites a lot is the idea that all “transparent” gear should sound the same or at least in a blind abx test. The results were interesting.
   
  As far as our method goes, we decided to make all parts of the setup identical (same set of Denon D2000 headphones, cables, and ODAC) except the Magni and O2. Then we started abx testing in two methods. For both methods, we took 30 seconds of listening in which we knew which amp we were listening to based on verbal confirmation (before this we had only spent about 15 minutes on each other’s amps). After that, we started blind testing and left the song playing pulling out the headphone cable between each declaration of an answer until 10 answers were recorded. For the first test, after each pull out of the cable at which either a change or no change could occur, we had to name which was the Magni and which was the O2 based on the 30 second preview that we had. Both of us got between 4 and 6 correct in each of our 3 sets of 10 trials. For the second method (fourth set of 10 trials), we simply had to declare if the amplifier switched. I scored a 9 out of 10 correct and my friend scored a 4 out of 10 correct.
   
  I’m sure you’re saying at this point that because the results of the blind abx were inconclusive, that there is no sonic difference. That’s not the case though. During most of the trials, we both had moments in which we knew (and usually exclaimed it out loud in the form of expletives) that we had screwed up which was which and the data showed it in that once the switch got made in our mind, we guessed correctly that there was a change, but got confused on which was the O2 and which was the Magni. The other thing that we noticed was what exactly we were listening for was different — after we finished abxing we debriefed as far as what in the tracks we were listening to for the giveaways of which was which. For a certain track, one of us would say vocals and the other bass kick or one of us guitars and the other piano. Upon re-listening to the track without commenting on which differences we heard, we were able to understand where we had gone wrong. On some tracks there was no difference between the vocal presentation, but there was in the bass and vice-versa. The other problem that we noticed with abxing is the mental pressure aspect. The idea that there could be no change (and the subsequent desire to not look like an idiot by getting it wrong) created a scenario in which the test was not necessarily about what was being heard — it was about the game being played. I had many times in the test where I detected a change or no change — and then the second guessing started. Would he really put a no change there? Would he really switch? Once the doubt in what you heard becomes apparent, the awfulness of auditory memory shows up and you begin to invent differences all in the name of not of the inherent desire to not want to look as if your ears are inferior in terms of detecting differences. It’s equivalent to taking a scantron test and noticing that every single correct answer is A except you aren’t detecting differences on something reliable like knowing a fact. We found that with sighted listening, since the mental game was out of the equation, we were better able to focus on differences in general sound signature and individual details at the same time instead of attempting to focus on mind games and sound at the same time.
   
  So without further hesitation, here’s what we heard during our abx trials and sighted listening. Keep in mind that these are generic impressions based on listening to both amps on the same track set of tracks and that these impressions might not apply for every single track that one listens to.
   
  1) The O2 has a much cleaner presentation as far as detail retrieval
   
  2) On certain songs, the Magni suffered as far as sub bass. It was almost non-existent on some tracks and on others it appeared as a fuzzy fwump noise while the O2 delivered a precise thump
   
  3) The Magni’s vocals almost have a veiled warm and thick quality while the O2s were somewhat brighter
   
  4) The O2 has more sparkle on instruments such as guitars and piano
   
  5) The O2 has a better soundstage as far as width and better placement of things within the soundstage


----------



## Dano91

Quote: 





nowhere said:


> amidst the chaos of purchasing the amp/dac i made the rookie mistake of not being sure of the connections, i just assumed the o2 had rca connections on it as it seemed most amps did and so i got the odac with rca to connect but upon receiving both i come to find out the o2 doesn't have rca.
> 
> doh!
> 
> ...


 
  There shouldn't be any audible difference between 3.5->3.5mm vs 3.5->rca, but i prefer rca simply because it seems to be more robust.. I'm using BJC MSA-1 and I can only highly recommend it.
  And yes, you can use your headphones directly from odac.. true, it's far from being ideal, as odac has way too high output impedance, but you won't damage anything.. only audio quality may suffer a bit.
  Hope this helps


----------



## Nowhere

Quote: 





dano91 said:


> There shouldn't be any audible difference between 3.5->3.5mm vs 3.5->rca, but i prefer rca simply because it seems to be more robust.. I'm using BJC MSA-1 and I can only highly recommend it.
> And yes, you can use your headphones directly from odac.. true, it's far from being ideal, as odac has way too high output impedance, but you won't damage anything.. only audio quality may suffer a bit.
> Hope this helps


 

 thanks!
   
  i might have to go with the mediabridge, that bjc is out of my price range. $34.50 for a 4 foot cable before shipping... the mediabridge has 900+ ratings on amazon and overall good rating... should be good enough for me.


----------



## aleksa

Finally I've finished my o2 amplifier. This was my fist DIY audio project and I've learned a lot. 
  It took me some time to put everything in place, but I am very happy with sound and how it looks 
	

	
	
		
		

		
			




  I really enjoyed building o2 amp and hopefully my next project will be a tube amp.
  Hope you like it


----------



## BenF

That is one gorgeous amp!


----------



## BenF

This may be old news, but JDS O2 is down to 129$, probably thanks to competition.
  Even though I have NFB-11.32 and E12, I am tempted.


----------



## autoteleology

That is by far the best O2 I've ever seen. Great job on the amp!


----------



## aleksa

Quote: 





benf said:


> That is one gorgeous amp!


 
   
  Thank you Ben 
	

	
	
		
		

		
			




   
   
  Quote: 





tus-chan said:


> That is by far the best O2 I've ever seen. Great job on the amp!


 
   
  Thank you Tus-Chan. I appreciate it


----------



## K_19

Quote: 





aleksa said:


> Finally I've finished my o2 amplifier. This was my fist DIY audio project and I've learned a lot.
> It took me some time to put everything in place, but I am very happy with sound and how it looks
> 
> 
> ...


 
   
  Looks awesome! Kind of WA7-esque.


----------



## glunteer

guys ... need to take a course ... using this ODAC with RCA and 3.5mm output I could use the RCA to my m-audio AV40 and 3.5mm for my beyer dt 770?

 if so, how would I do to change the sound of each other?


----------



## BenF

Quote: 





glunteer said:


> guys ... need to take a course ... using this ODAC with RCA and 3.5mm output I could use the RCA to my m-audio AV40 and 3.5mm for my beyer dt 770?
> 
> if so, how would I do to change the sound of each other?


 
   
  You sure could use them together.
  What do you mean by "how would I do to change the sound of each other" ?


----------



## aleksa

Quote: 





k_19 said:


> Looks awesome! Kind of WA7-esque.


 
  Thank you K-19 
	

	
	
		
		

		
		
	


	



  Yeah, now I see that it is similar 
	

	
	
		
		

		
		
	


	



  However, I didn't have WA7 in mind while I was building my amp.
   
  I am really enjoying the sound of o2 amp. 
Right now it is playing Ali Farka Toure "Talking Timbuktu". Highly recommended album


----------



## glunteer

Quote: 





benf said:


> You sure could use them together.
> What do you mean by "how would I do to change the sound of each other" ?


 

 because I made an audio switcher (diy) that has two 3.5mm outputs - one for speaker and one for the headphone, I choose where to play the sound.

 was wondering if the sound would ODAC simultaneously on the speaker and the headphone or would choose?
   
  could explain? My English is very bad ... I try to learn but is difficult ^^


----------



## BenF

Quote: 





glunteer said:


> because I made an audio switcher (diy) that has two 3.5mm outputs - one for speaker and one for the headphone, I choose where to play the sound.
> 
> was wondering if the sound would ODAC simultaneously on the speaker and the headphone or would choose?
> 
> could explain? My English is very bad ... I try to learn but is difficult ^^


 
   
  Does your switcher allow both outputs to be active simultaneously? That's not recommended.
  If only one output can be active at a time, that's OK, as long as your headphones are easy to drive - otherwise you'll need a headphone amplifier too.


----------



## glunteer

Quote: 





benf said:


> Does your switcher allow both outputs to be active simultaneously? That's not recommended.
> If only one output can be active at a time, that's OK, as long as your headphones are easy to drive - otherwise you'll need a headphone amplifier too.


 
  no no... my diy has no output simultaneously, or sound out the headphone or speaker...
   
  I already have the o2 as an amplifier...
   
   
  then I'll buy that the ODAC output with RCA and 3.5mm, because I will not need more to use my switcher 

 thanks for the help Benf


----------



## tuna47

Anyone compare odac to the bifrost


----------



## chrislangley4253

Quote: 





tuna47 said:


> Anyone compare odac to the bifrost


 
  All over the place. Try a little harder


----------



## lac29

So I'm unsure if my power on/off LED is broken but can someone tell me if their computer detects the O2/ODAC (like when you check foobar's output page under preferences or if you check your windows sound settings) by simply plugging in your O2/ODAC to your computer and plugging in the power wart (not actually turning it on)?


----------



## burritoboy9984

Quote: 





lac29 said:


> So I'm unsure if my power on/off LED is broken but can someone tell me if their computer detects the O2/ODAC (like when you check foobar's output page under preferences or if you check your windows sound settings) by simply plugging in your O2/ODAC to your computer and plugging in the power wart (not actually turning it on)?


 
   
  The odac is powered solely from the usb connection. Your computer should detect it when you plug in the usb cable.
   
  -Erik


----------



## lac29

Thanks a ton!  So it looks like my ODAC is working ok but do you know how I can troubleshoot the problem if right now my LED isn't turning on/red when the wall wart and everything else is hooked up?  It was working fine yesterday but for some reason isn't working today.


----------



## adydula

Is your O2 amp home built or did u buy it from completley built?
   
  Alex


----------



## lac29

Completely built JDSLabs.   It's been working fine for the past 7 months until suddenly today.  I did bring it to work in a plastic ziplock bag in the heavy rain.  But I'm pretty darn sure I kept it dry.  I also let a coworker use it but he says it was working fine (with the LED red light working) and I kind of trust him.  I plan on bringing it home to look more into it.  Any help would be greatly appreciated!


----------



## adydula

I dont know how technical you are, I have built several and could tell you to check voltages etc, remove the led, replace etc..but I would just give JDS Labs a call....
   
  John is really pretty good at helping his customers.
   
  Alex


----------



## burritoboy9984

adydula said:


> I dont know how technical you are, I have built several and could tell you to check voltages etc, remove the led, replace etc..but I would just give JDS Labs a call....
> 
> John is really pretty good at helping his customers.
> 
> Alex




+1, I purchased just the o2 board from him and he went above and beyond to help me with a minor issue I had.

-Erik


----------



## lac29

Thanks ... I'm just getting into the DIY stuff and got some soldering equipment but I'm too green to really be of any help to myself at this point.  I plan on just contacting JDS and seeing if they can help out or if needbe have me send it back for repair.


----------



## santhoshr

I would like to buy o2 odac combo, I have couple of questions, will I be able to disable DAC functionality and use only amp function ? Since sometimes I just need amp function like listening through my PC d2x sound card. Next among available pre built DAC/amp combo which company do you guys recommend (jds, epiphany, etc) ?


----------



## BenF

Quote: 





santhoshr said:


> I would like to buy o2 odac combo, I have couple of questions, will I be able to disable DAC functionality and use only amp function ? Since sometimes I just need amp function like listening through my PC d2x sound card. Next among available pre built DAC/amp combo which company do you guys recommend (jds, epiphany, etc) ?


 

 The JDS combo has a 3.5mm input, so you can use it as just an amp and bypass the DAC.


----------



## santhoshr

^ thanks BenF


----------



## miceblue

This might be a stupid question, but under the ODAC settings on Windows 8 (I just upgraded to it yesterday), it gives me the option to output audio at 32-bit, 192 kHz. What exactly happens if I select this instead of the ODAC's native 24/96 resolution?

   
  Actually I just read that. What is "shared mode?"


----------



## HaVoC-28

Quote: 





miceblue said:


> This might be a stupid question, but under the ODAC settings on Windows 8 (I just upgraded to it yesterday), it gives me the option to output audio at 32-bit, 192 kHz. What exactly happens if I select this instead of the ODAC's native 24/96 resolution?
> 
> 
> Actually I just read that. What is "shared mode?"


 
   
  No sound , an error message or something totaly distorded . And 24/96 is just one of the supported samples rates of ODAC (16/24bits   44/48/96 khz) .
   
  Shared mode , should refer to the shared mode of WASAPI . Where everything you play is converted to the bitdepth / sample rate set in the windows mixer .


----------



## miceblue

Hm that's weird. I had the 32/192 option selected and audio plays just fine. No matter which option I choose though, the "test" button never works.


----------



## stv014

Quote: 





miceblue said:


> Hm that's weird. I had the 32/192 option selected and audio plays just fine. No matter which option I choose though, the "test" button never works.


 
   
  It is probably downsampled by Windows.


----------



## miceblue

Huh that's weird. It must have been a Windows update or something because now the only options it gives are the ones the ODAC supports. XD


----------



## Modulus

Hey guys.
   
  DIY related question. How difficult, if at all possible, would it be to increase the current of the amplifier circuitry, ie. to increase the wattage. Is this feasible?
   
  All of O2's competitors have greater output power in terms of watts per channel. I'd be interested in a DIY fix to better drive orthos.
   
  Cheers!


----------



## proid

Quote: 





modulus said:


> Hey guys.
> 
> DIY related question. How difficult, if at all possible, would it be to increase the current of the amplifier circuitry, ie. to increase the wattage. Is this feasible?
> 
> ...


 
  Very easy, just double the 4556 at the output stage and you get double current output.


----------



## Modulus

Quote: 





proid said:


> Very easy, just double the 4556 at the output stage and you get double current output.


 
   
  How much does that component cost? And why isn't that standard practice? Have you heard this configuration?
   
  Thanks for your response.


----------



## proid

Quote: 





modulus said:


> How much does that component cost? And why isn't that standard practice? Have you heard this configuration?
> 
> Thanks for your response.


 
   
  For double current ouput, the added component will cost about 5$. But if you using this configuration, battery can only last half time as before and original O2 is able to drive almost any headphone so it's not necessary.


----------



## Modulus

Quote: 





proid said:


> For double current ouput, the added component will cost about 5$. But if you using this configuration, battery can only last half time as before and original O2 is able to drive almost any headphone so it's not necessary.


 
   
  There seems to be growing consensus that orthos benefit from higher current, so I thought it could be an interesting modification for these kind of phones. There's been lots of talk of people strapping their cans to speaker tabs and the like. What would happen if you added even another 4556? Would there be degradation of sound?
   
  On a related note, what are the copyright restrictions on the O2 design? In terms of modifying and rebranding the design?


----------



## MrEleventy

It's open source so you'll have to follow open source licensing. You can modify and rebrand as well as sell but you can't do anything to limit people from doing the same to your product.


----------



## stv014

You can of course freely modify it for your own personal usage, but the license (Creative Commons Attribution No-Derivs 3.0) actually does not allow for the distribution of modified versions without the designer's permission.
   
  Adding more 4556's might not require major changes to the schematics, but you would need to modify the PCB layout, which has been carefully optimized for the best performance, and does not have much space for additional parts. As a quick hack solution, you could just solder the additional chips in parallel onto the existing ones, with the exception of the output and inverting input pins, which for each amplifier should be soldered together and connected through 1 Ω resistors to the headphone output. Note that this modification will increase the DC offset on the output somewhat (because of the doubled input bias current from the 4556 chips), and the power supply section may possibly also need some changes for the doubled current output.


----------



## agdr

Quote: 





modulus said:


> DIY related question. How difficult, if at all possible, would it be to increase the current of the amplifier circuitry, ie. to increase the wattage. Is this feasible?
> 
> All of O2's competitors have greater output power in terms of watts per channel. I'd be interested in a DIY fix to better drive orthos.


 
   
  If you are thinking desktop and not portable, take a look at this one that I came up with:
   
https://drive.google.com/folderview?id=0B67cJELZW-i8VmhVNk5PODNtZnc&usp=sharing   80mm x 160mm PCB -> latest date
   
  All DIY that uses 3 of the NJM4556AL (SIP inline version of the NJM45556 instead of the DIP version, but same internals) in parallel on each channel for a total of 320mA usable (after quiescent chip draw) output per channel.  Has +/-16Vdc rails (in one position, +/-7Vdc in the other switch position) for a 14.5Vdc maximum swing vs. the O2's 10Vdc max (10.5V rms vs. 7V rms with the O2).  So it will drive cans that need more voltage swing and/or a lot more current.  4 gain positions vs. 2, 3.5mm and 1/4" out, RCA and 3.5mm input, pre-amp output, clipping indicator, 0.5R balancing resistors instead of 1R, 2 sets of voltage regulators (pre and final low noise LDO), output relay to prevent thumps, 1K pot for low Johnson noise and some other goodies.  
	

	
	
		
		

		
			




   
  I'm not selling anything.  It is all DIY.  The PC board can be made by sending the Gerber file in the link off to a board house like Seeed Studio (4 layer, 160mm x 80mm).  The build involves some surface mount parts, 1206 sized resistors and caps along with the through hole, so a little more involved - and twice as many parts - as the O2.  But similar design with the pot and coupling caps in the middle and gain stage in front.  So far the consensus has been (big discussion in another forum) that it is different enough to be a separate design, not a O2 derivative.  No batteries, no power management circuit, not portable.
   
  It uses the larger (than the O2) B4-080BL case, or can use 2 boards end-to-end in a longer B4-160BL case, which then easily holds an ODAC on the back board.  The back board just has the PSU section populated in the 2 board option, while the front board has everything but the PSU populated.  In one of the folders in the link there are CAD files for the front and back panels which can be sent off to outfits like Proto Panel (the one I used) or Front Panel Express.  The panel hole measurements are all also in a spreadsheet there to self-drill the panels that come with the case.  The BOM lists all the Mouser numbers and some cross references to Digikey, Farnell, Allied, and others.


----------



## Modulus

@stv014
  Thank you for the very useful information.
   
  @agdr
  Wow. You've done an incredible amount of work on that, it's very impressive. Definitely adds some good features to the minimal O2 design. I've always felt the O2 is somehow just 'not quite right'. It seems conflicted whether to be a portable or desktop rig. I have no interest in portable audiophilia beyond good buds, and I'm sure most people are using the O2 as a desktop solution.
   
  In my opinion the front AC plug, the unnecessary battery circuit and the lack of current (to preserve battery, as mentioned by another member) are problems. I am interested in building an amp that deals with these as efficiently as possible. But circuitry diagrams are scary 
	

	
	
		
		

		
		
	


	




.


----------



## miceblue

Quote: 





agdr said:


> Quote:
> 
> 
> 
> ...


 
  Woah....that's freakin awesome! Very nice job with that!


----------



## tdockweiler

Do you think it's possible for a powered USB hub (attached to a massive surge protector) to degrade the sound of a DAC?
   
  I had this weird problem with the V-Moda M80 today where when used with the O2 it had very bloated bass and the low mids were too forward and fatiguing. When I switched it to another amp it was perfect (no bass roll-off on the amp).
  I took the powered USB hub out and the M80 now seems fine on the O2. It was like whatever was screwing up the O2 wasn't getting through on the other amp. Bizarre.
   
  I'm trying to figure out what caused this because it shouldn't be the O2s fault but something else weird going on.
   
  Nothing else on that powered hub attached. Maybe it's just a bad hub (it's a Belkin). I'm using very short high quality cables too ($10 ones).
   
  I should point out that the differences are barely noticeable on my Q701 and HD-650. Mostly it's on headphones that are closed and with a little bass emphasis.


----------



## MrEleventy

tdockweiler said:


> Do you think it's possible for a powered USB hub (attached to a massive surge protector) to degrade the sound of a DAC?
> 
> I had this weird problem with the V-Moda M80 today where when used with the O2 it had very bloated bass and the low mids were too forward and fatiguing. When I switched it to another amp it was perfect (no bass roll-off on the amp).
> I took the powered USB hub out and the M80 now seems fine on the O2. It was like whatever was screwing up the O2 wasn't getting through on the other amp. Bizarre.
> ...



... How are you powering the O2 via a USB hub? Isn't it wallwart or batteries only? 

That aside, the M80s don't really gain anything from amping. I've ran them from a multitude of amps and never noticed a change vs just from the source itself. Just enjoy them as is.


----------



## tdockweiler

Quote: 





mreleventy said:


> ... How are you powering the O2 via a USB hub? Isn't it wallwart or batteries only?
> 
> 
> 
> ...


 

 I'm using a wall wart for the O2. No surge protector.
   
  I actually just got the M80 today and my only good setup right now is on my PC. I haven't used a portable player in months really. I have a Clip+ and two Ipods I'll test them with later.


----------



## MrEleventy

Ooooooohhhhhhh. Ok, I think I understand now. You're saying that plugging and unplugging the hub from your computer is effecting the O2. It kinda sounds like something isn't grounded and getting into the O2. If the hub uses a seperate usb cord, try to find one with a ferrite bead and see if that does anything.


----------



## BenF

Quote: 





tdockweiler said:


> Do you think it's possible for a powered USB hub (attached to a massive surge protector) to degrade the sound of a DAC?
> 
> I had this weird problem with the V-Moda M80 today where when used with the O2 it had very bloated bass and the low mids were too forward and fatiguing. When I switched it to another amp it was perfect (no bass roll-off on the amp).
> I took the powered USB hub out and the M80 now seems fine on the O2. It was like whatever was screwing up the O2 wasn't getting through on the other amp. Bizarre.
> ...


 

 Powered hub can definitely affect the sound, if it doesn't provide the correct voltage/current - 5v/500ma


----------



## tomb

Quote: 





benf said:


> Powered hub can definitely affect the sound, if it doesn't provide the correct voltage/current - 5v/500ma


 
  It depends on the power supply quality of the hub, the power demands of the DAC, and the voltage regulation capability of the DAC.  These things are all variable.  If the DAC is limited on its own capability of regulating voltage, then a powered hub may make things worse, because the powered hub's voltage supply may be from a cheap, switching supply.  If the powered hub is from a high-quality power supply, then it will make things better.  On the other hand, if the power demands of the DAC are high, but onboard voltage regulation is great, then a sufficiently powered hub may make a lot of positive difference - especially if a laptop is in the equation (never enough power).  An in-between DAC (low-power, but poor voltage regulation) may be at the complete mercy of the power supply - either PC or powered hub.  Even the cable may have effects when it comes to the power supply.


----------



## glunteer

So... which would correct voltage and current for the ODAC?


----------



## BenF

Quote: 





glunteer said:


> So... which would correct voltage and current for the ODAC?


 

 USB standard - 5v and 500mA. But it's also important that the power will be noise-free.


----------



## glunteer

Quote: 





benf said:


> USB standard - 5v and 500mA. But it's also important that the power will be noise-free.


 

 but the computer does not supply 500mA, right?


----------



## BenF

Quote: 





glunteer said:


> but the computer does not supply 500mA, right?


 

 USB 2.0 port does provide 500mA, USB 3.0 port can give 1000mA.


----------



## glunteer

benf said:


> USB 2.0 port does provide 500mA, USB 3.0 port can give 1000mA.




Thanks benf


----------



## tdockweiler

Thanks for the help on the USB hub issue. It's really always impressive to me how with the right headphone and amp (O2) I can detect issue with my setup when things are "off".
  My idea is that I had my powered USB hub attached to a massive MOV-based home theater surge protector. Maybe some type of garbage/interference was getting through and messing with things. I never heard this issue with my Micro Amp or the old Magni at all. Maybe the O2+Modi is that super duper revealing? 
	

	
	
		
		

		
			





 I did have TONS of stuff attached to the surge protector.
   
  Strangely I only heard this with my Vmoda M80 and DJ100. Basically inaudible with my HD-650 and Q701. It seems it's only noticeable with closed bassy headphones that have forward low mids and are portable. 
   
  I also don't use USB cables with ferrite beads. Guess i'll try some again. I don't think it's really noise, but something weird about my surge protector. It could be a poor quality wall wart on the USB hub. 
   
  I'm sure when I connect it straight to the wall it's OK.
   
  Strangely i've always had weird/random issue with every DAC i've owned when attaching it to my desktop USB ports. Lots of static/popping etc. It's especially bad on my laptop. Mostly occurs when scrolling in Windows and it was gone with a powered USB hub. 
   
  Just kind of confusing why it only happens on the O2.
   
  I think I might buy a USB 3.0 hub and some short USB cables with ferrite beads.
   
  BTW O2 now sounds good with everything I have now. It reminds me of my Headroom Micro really. I no longer have the ODAC, but Modi.


----------



## adydula

Sometimes the simplest chain is the best.
   
  I have heard or experienced popping and ticking while listening to music via a pc and a music player..ie software.
   
  In most cases its the pc and or sound driver interaction with the OS etc. Ususally it can be fixed by having a more powerful pc, better drivers, and adjusting the buffers on the system usually in the software player.
   
  I hate to say this but i have expereinced differences in audio playback quality on the same pc but different USB ports,
   
  Once you get it right its pretty good...
   
  Alex


----------



## chrislangley4253

Quote: 





adydula said:


> I hate to say this but i have expereinced differences in audio playback quality on the same pc but different USB ports,
> 
> Once you get it right its pretty good...
> 
> Alex


 
  I have experienced very noticeable differences between one particular computer's usb 3.0 and usb 2.0 ports. Undoubtedly there was some problem with the 3.0 drivers, but it sounded horrid.


----------



## adydula

I think that my objectivity is getting cross pollinated over time with my subjectivity!
  A.


----------



## tdockweiler

Quote: 





adydula said:


> Sometimes the simplest chain is the best.


 
   
  Totally agree. I also try to make sure my USB cables are as short as possible. It can't hurt really.
  I replaced my USB cables with ferrite core version (probably not needed).
   
  I switched the USB hubs wall wart to a power strip with no surge protection but that didn't help at all. Not sure why. I guess maybe the fault is the powered hub or having it use two USB cables.
   
  I get an almost identical sounding problem when I connect my amps to a surge protector (mov based).
   
  Right now I have my DACs connected right to my PC and it seems fine. Weird.
   
  Whenever I use a MOV based surge protector it sounds like I'm getting extra distortion. It's barely audible but that's what it sounds like. It makes my HD-650 sound even more muffled.
   
  It sounds similar to double amping two portable devices. Like Clip+ to E11 or something, but almost worse. It would actually sound OK on some headphones but horrible on others.


----------



## kingofzero

agdr said:


> If you are thinking desktop and not portable, take a look at this one that I came up with:
> 
> https://drive.google.com/folderview?id=0B67cJELZW-i8VmhVNk5PODNtZnc&usp=sharing   80mm x 160mm PCB -> latest date
> 
> ...


 
  
 I would buy a complete unit w/ integrated ODAC in an instant if it was available, I don't trust my soldering skills heh. How long have you been testing it?
  
 Does this version increase the requirements for lower end headphones?


----------



## adydula

I was actually thinking of building this but the pc boards have a minumum order and it gets pricey...unless u can get a bunch of people to help finance etc..
  
 Alex


----------



## Ashade

You can buy the PCB's from JDS Labs for $6. The ODAC + O2 can be built for has low as $180 (even less...) If you pay your cards properly. I finished building one last month (and it's even possible to keep the batteries....).


----------



## exquisite

Anybody around owns the Epiphany Acoustics UK version of this combo? (DAC+AMP) in the same box ? 
  I have bought one a month ago and can´t figure out which are the *low/high* gain settings without opening it .
 The manufacturer told me they use *1X/5X *as default, but another user here told me his unit was *2.5X/6.5X *so 
 I´m a little confused .
 Thanks.


----------



## Ashade

2 .5x/6.5x is the stock design for the O2, but the guy provided instructions to do other configurations. If they say it is 1x/5x... they are the builders you know? I can tell you that I don't pass of 10 or 11 o´clock (35% to 45% of the max volumen) with the Q701 and 2.5x gain selected.


----------



## adydula

I have one set for unity gain and 2.5x the other is 2.5/6.5 etc....with all my cans the unity gain drives them very very loud...
  
 LCD2, Q701, Grado 325is, Beyer 1350, Beyer T90 etc
  
 A.


----------



## exquisite

Thanks for the answers. The question was specifically related to the EHP-O2 unit - this one : 
  
  http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2d-miniature-desktop-headphone-amplifier-with-usb-dac/
  
  So far I have 2 users(owners) saying it´s 2,5X/6,5X and the manufacturer (backed up by another user) saying it´s 1X/5X . 
  
 PS: never asked about loudness levels, just about manufacturing specs. It´s a shame this is not listed on vendor´s page.


----------



## Ashade

I understand that. I was giving you a reference for you to get an idea and being able to try to identify your gain. The other option you have is open it and have a look to the actual resistances. That way you can get the gain values.


----------



## adydula

Send them a note and ask them?
  
 The gain is really an easy thing to change etc...done this on an amp..simple cut and end of two resistors etc...
  
 A.


----------



## MrEleventy

The original designer of the O2 has it set at default, 2.5x/6.5x. Since it's a DIY kit, you can change it to whatever you wish. If Epiphany built it to exactly as NW intended, then it's 2.5/6.5. If they say they changed it, it's whatever they changed it to. If the site says 1/5, then it's 1 and 5.


----------



## Ashade

Which is something I'm considering for my next build because I never use 6.5x. 2.5x is already excessively loud.

I'm considering either 1x/2.5x or 1x/5x


----------



## adydula

Again, this is really not an issue...very easy to adjust etc...
  
 A.


----------



## agdr

kingofzero said:


> I would buy a complete unit w/ integrated ODAC in an instant if it was available, I don't trust my soldering skills heh. How long have you been testing it?
> 
> Does this version increase the requirements for lower end headphones?


 
  
 I've had one playing continuously 24/7 for at least a month now.  The amp will power the same range of headphones that the O2 amp will, plus hard-to-drive phones that require a lot more current and/or more voltage.  320mA per channel vs. about 120mA per channel for the O2, and 10.5Vdc (rms) output swing with +/-16Vdc supplies vs. 7Vdc (rms) with the +/-12Vdc supplies in the O2.
  
 A few folks out there are in the process of building the amps (past PC board run).  Maybe someone will eventually put a finished one up for sale. 
	

	
	
		
		

		
			




  
  


adydula said:


> I was actually thinking of building this but the pc boards have a minumum order and it gets pricey...unless u can get a bunch of people to help finance etc..
> 
> Alex


 
  

 Alex - I am probably going to do another at-cost board run in a few weeks.  I'll send you a PM. I'll find out where the appropriate place to post about that is over here, probably in the DIY section.  Yeah, that 5 board minimum for the 4-layer PC board fab at Seeed Studio is a big hurdle for the DIY effort.  Folks only need 1 board, or 2 if built up in the B4-160 case with the power supply and ODAC on the back board.


----------



## adydula

agdr,
  
 Thanks for this information, I sent you a PM.
  
 Your one of the few people that I respect when it comes to an honest enginering design discussion about the O2.
  
 I will sign up for one board and a hardware kit....but you have me thinking of the all in one amp with the ODAC inside...just one more board...
  
 hmmm
  
 Alex


----------



## agdr

adydula said:


> I will sign up for one board and a hardware kit....but you have me thinking of the all in one amp with the ODAC inside...just one more board...


 
  
 That two board option really is an interesting way to go.  The B4-160 case, which is twice as long, is just $5 more at Allied Electronics or Newark with about the same shipping cost.  Same parts, the power supply parts just go on the back board along with an ODAC.  An ODAC would still mount in the single board B4-080 option, bolted upside down onto a blank board slid into the upper slot of the case.
  
 I should say that I've decided to work on a version 2.0 with a few additions.  I'll need to build it and test it again so the boards for that likely won't be out for several months, maybe even next year.  In the meantime the current version at the google link works fine.
  


modulus said:


> @agdr
> Wow. You've done an incredible amount of work on that, it's very impressive. Definitely adds some good features to the minimal O2 design. I've always felt the O2 is somehow just 'not quite right'. It seems conflicted whether to be a portable or desktop rig. I have no interest in portable audiophilia beyond good buds, and I'm sure most people are using the O2 as a desktop solution.
> 
> In my opinion the front AC plug, the unnecessary battery circuit and the lack of current (to preserve battery, as mentioned by another member) are problems. I am interested in building an amp that deals with these as efficiently as possible. But circuitry diagrams are scary
> ...


 
  
 Hey thanks.  Sorry about the delayed reply, I hadn't circled back yet after posting. 
  
 I'm a fan of the O2 and have posted several modifications to it elsewhere over the last couple of years since the O2 was released.  That size issue was kind of the one big hiccup right out of the gate though, IMHO.  The O2 was a little too large to be in the truely "portable" DIY headamp category, like AMB's mini^3 which I'm pretty sure was one of the things NwAvGuy intended it to compete against, but too small to include desktop things like RCA and 1/4" jacks, at least not in the B2 case.  That stuff can fit in the B3 case of course, and I know that several of the O2 builders out there offer that mod.
  
 I was eager to ditch the O2's power management circuit for an actual anti-thump time-delay relay in the desktop amp.


----------



## Currawong

agdr said:


> Alex - I am probably going to do another at-cost board run in a few weeks.  I'll send you a PM. I'll find out where the appropriate place to post about that is over here, probably in the DIY section.  Yeah, that 5 board minimum for the 4-layer PC board fab at Seeed Studio is a big hurdle for the DIY effort.  Folks only need 1 board, or 2 if built up in the B4-160 case with the power supply and ODAC on the back board.


 
  
 I remember the DIY Audio board run for O2s was huge. If you can PM me (or another mod) prior to posting in the DIY forum about it, I'd appreciate it. Due to issues in the past, group buys are restricted to DIY items, with permission.
  
 Just an FYI for everyone: If anyone plans on building for the purpose of selling them, then that person (or people) if they are members here, have to PM Jude or myself to register as a Member of the Trade (which means you get a tag under your name). That is explained in the rules. One O2 builder refused to abide by the rules and was banned, so I really want to make sure people are aware of this in advance so that doesn't become a problem again.


----------



## bada bing

I jumped the gun on a ODA PCB group buy and made an order for 10 ( in white 
	

	
	
		
		

		
		
	


	




 ).
 It isn't a cheap amp to build, with all options, my total parts were ~$250 for 1.
 It appears to go a long ways towards eliminating the weaknesses of the original
 O2 for desktop use IMO.
  
 The PSU section on the PCB is useful. I'm thinking of using the PSU section
 of one of the boards to power a populated dynalo board I have sitting unused.
 I like the idea of a one box amp build with the transformer located at the wall.
 Should make for a nice compact desktop footprint with the benefit of the isolation
 from the transformer.
  
 Thank you very much *adgr* for publishing the exceptional documentation on the
 project. It is appreciated. I'll definitely ask for a couple boards of your next revision
 when the time comes.


----------



## dclaz

The O2/ODAC all in 1 combo isn't suited for outputting to amplified speakers right? I may have to grab the ODAC now and the O2 down the road when I buy some nice headphones.
  
 Is it reasonable to say the O2 will drive any set of cans you throw at it? HD800's LCD2's etc?


----------



## Ashade

That's what the designer states. I'm pretty sure it can, it is a pretty powerful amp.


----------



## ProTofik

Hd800 are driven by o2 without a problem. Not sure about the lcd2 through


----------



## hekeli

When I had O2 and LCD-2, no problem.. I did some skull crushing tests with War of the Worlds audio track..  No dynamics missing there pfffft...


----------



## adydula

It was designed to work very well with 98% of the cans out there....
  
 take a look at the blog its all there...
  
 Alex


----------



## Uchiya

I haven't been able to find a post if the O2 can or has been used with the Energizer XP8000 or XP18000 battery packs?


----------



## Ashade

Correct me if I am wrong but I don´t think it will work on the outside power input as it requires an AC 20V input, and that battery would only provide DC. You might make it work internally through the battery inputs though.
  
 What´s the idea exactly?


----------



## Uchiya

The Energizer battery packs provide ac power up to 20v.


----------



## Ashade

In that case it would work, but that is not what the official specs say:
  
 Energizer XP8000 
  

*Battery Cell:* Lithium Polymer
*Power Capacity:* 8000 mAh
*Rated Input:* DC 19V, Max 3500 mA
*Rated Output:* 
 DC 5V, 1000 mA
 DC 12V, 3000mA
 DC 19V, 2000mA
  
 XP18000 battery packs:
  

*Battery Cell:* Lithium Polymer
*Power Capacity:* 18000 mAh
*Rated Input:* DC 19V, Max 3500 mA
*Rated Output: *
DC 5V, 1000 mA
DC 10.5V, 2000mA
DC 19V, 3500mA
  
 Source: 
 http://www.energizerpowerpacks.com/il/products/xp8000/
 http://www.energizerpowerpacks.com/th/products/xp18000/


----------



## Uchiya

Damn.


----------



## Ashade

Is it for a ODAC + O2 combo?


----------



## Uchiya

Yeah, I don't mind lugging the O2 amp around if it could have used the energizer pack.


----------



## Ashade

It is possible to build the combo with built in batteries (you can even include rca outputs on the back if you want, although I didn,t). I don´t think I have any pictures of the inside right now...
  

  

  
 EDIT: I found one half assembled:


----------



## Uchiya

Ah nvm, I guess I could replace the screws in the back with thumb screws and carry a bunch of 9v nimhs.


----------



## Ashade

Ok... This is the thing...
  
 You are supposed to use lithium batteries rated at 9.5V, that if I remember properly are those of 7cells. Initially, as far as I know, only the 250mAh ones are rated at that voltage. The real problem is not that: I am currently using 500mAh ones rated at 8.4V and they work fine BUT, the power circuit cuts the feeding under a certain voltage, and I think it is somewhere between 7.5 and 7.7V, therefore you are not using the full capacity of the batteries... the above mentioned ones are for that reason lasting more.
  
 Now, I found some very expensive 9V batteries rated at 500mAh on ebay coming from Japan. The other option is to actually modify the power circuitry to reduce that cut off voltage, but I have not seen anybody doing that yet, although I think it is as easy as making some calculations and replace the value of two or three resistors.
  
 The funny stuff is that that cutoff voltage don´t allow you to turn on the device, but there is no problem on listening under that voltage if it was already on, so lets see you turn it on during the morning, and leave it on all day. You could be listening to it, and it would probably last more than 7-8hr, though I didn´t try it yet.


----------



## Uchiya

Oivey, that's a shame.  I wish I could live with the hp out from my Samsung Note.


----------



## Ashade

Well, I mean, it´s not that bad, but it is not an E17... You can wait for the E18, I think it´s gonna be awesome. I´ll get one for sure.
  
 I am going to try it probably tomorrow on my way, so might report back about it. By the way, the ODAC works flawlessly both in my Mote II and my Nexus 10.


----------



## dclaz

The O2/ODAC all in 1 combo isn't suited for outputting to amplified speakers right? Or you can use the headphone out as a line out in to powered speakers?
  
 I'm just wondering what my ideal solution is if I plan to use both speakers and headphones with my PC. I want to be able to swap between them with minimal fuss/cable swapping.


----------



## BenF

dclaz said:


> The O2/ODAC all in 1 combo isn't suited for outputting to amplified speakers right? Or you can use the headphone out as a line out in to powered speakers?
> 
> I'm just wondering what my ideal solution is if I plan to use both speakers and headphones with my PC. I want to be able to swap between them with minimal fuss/cable swapping.


 
  
 You would be much better off with separate ODAC and O2. Having  2 amplifiers one after another is not a good idea.


----------



## chrislangley4253

benf said:


> You would be much better off with separate ODAC and O2. Having  2 amplifiers one after another is not a good idea.


 
  

 Uhhhm, pretty sure the designer said that double amping makes no difference so long as both amps are properly designed.

 I double amp my O2 and Emotiva Mini-X into my Polk floorstanders all the time. I have not used powered speakers, however.


----------



## BenF

chrislangley4253 said:


> Uhhhm, pretty sure the designer said that double amping makes no difference so long as both amps are properly designed.
> 
> I double amp my O2 and Emotiva Mini-X into my Polk floorstanders all the time. I have not used powered speakers, however.


 
  
  
 When you double amp, the worst specifications of each amp combine - if one amp has hiss problem, the resulting "double-amp" will have hiss problem, even if the second amp doesn't have this issue. If one amp cuts bass below 50 Hz, the resulting "double-amp" will have no bass under 50Hz.
 Also, even if each amp has normal amount of noise (X), then the resulting "double-amp" will have twice as much (2X).
 Since there are no perfect amps, double amping always leads to worse results.


----------



## Ashade

All of this is true but it's not as bad as you are painting it. For a Mid-Fi set up is more than reasonable. If you are searching for Hi-Fi, I suppose you are not looking at this combo (although I don't consider it a bad combo either). Either way, it's a perfect valid temporary solution if it's the only option you can set up at the moment.



dclaz said:


> The O2/ODAC all in 1 combo isn't suited for outputting to amplified speakers right? Or you can use the headphone out as a line out in to powered speakers?
> 
> I'm just wondering what my ideal solution is if I plan to use both speakers and headphones with my PC. I want to be able to swap between them with minimal fuss/cable swapping.




I just don't like the separated solution, to be honest. The other option you have is to get a line out of the DAC itself and build it in the back off the combo, specially if you consider building it yourself.


----------



## mcandmar

2nd that, adding RCA outputs is an easy solution however its not advised to have two devices connected to the output of the ODAC at the same time so i would wire a switch to toggle the output between the RCA jacks or the O2 board.
  
 If you do want to double amp i would setup one of the gain positions for 1x or unity, basically remove two resistors for that position to minimize the amplification as the ODAC already outputs 2.3v line out level.  If you amplify beyond that level and feed it into the line in of the external speakers it will clip/distort and sound really bad.
  
 If your not aiming for a portable solution i would suggest building both of them in separate enclosures with RCA jacks, thats how i have mine setup so i can mix/match with other dacs and amps.


----------



## SunshineReggae

ashade said:


> All of this is true but it's not as bad as you are painting it. For a Mid-Fi set up is more than reasonable. If you are searching for Hi-Fi, I suppose you are not looking at this combo (although I don't consider it a bad combo either). Either way, it's a perfect valid temporary solution if it's the only option you can set up at the moment.
> I just don't like the separated solution, to be honest. The other option you have is to get a line out of the DAC itself and build it in the back off the combo, specially if you consider building it yourself.


 
  
 By what standards are the O2 amp and dac _not _hifi?


----------



## Ashade

Reread the post and please tell me where I'm mentioning anything about that.

Did you read the conversation or are you just looking for controversy?


----------



## SunshineReggae

ashade said:


> Reread the post and please tell me where I'm mentioning anything about that.
> 
> Did you read the conversation or are you just looking for controversy?


 
  
 You called the O2 "mid fi". Whatever that means, it implies there's a league of amps and dacs above it. It would make sense to expect you to call that hifi. According to what you wrote anyway.


----------



## Ashade

What I said is that double amping was a mid-fi combo solution. And in any case, the O2 has several flaws that can make you consider it mid-fi under several circumstances, which doesn´t diminishes the fact that is probably the best amp under $500.

You can read the posts and interpret them whatever you want, as they weren't very specific but, as we say here: To the good listener (reader in this case), not many words are needed.


----------



## stv014

benf said:


> When you double amp, the worst specifications of each amp combine - if one amp has hiss problem, the resulting "double-amp" will have hiss problem, even if the second amp doesn't have this issue. If one amp cuts bass below 50 Hz, the resulting "double-amp" will have no bass under 50Hz.
> Also, even if each amp has normal amount of noise (X), then the resulting "double-amp" will have twice as much (2X).
> Since there are no perfect amps, double amping always leads to worse results.


 
  
 The O2 does not cut bass below 50 Hz (it has less than 0.1 dB attenuation at 20 Hz), and should not have even nearly audible hiss at a sane listening volume. When used at unity gain at maximum volume with the ODAC and a speaker amplifier, most of the noise will probably come from the speaker amp, and a few dB more from the ODAC than the O2. Almost all frequency response error will be from the speakers themselves (combined with the room acoustics), and they will be responsible for most of the non-linear distortion as well, especially in the bass range.


----------



## stv014

ashade said:


> What I said is that double amping was a mid-fi combo solution. And in any case, the O2 has several flaws that can make you consider it mid-fi under several circumstances


 
  
 What are those flaws exactly (I listed a few limitations here, but none of them apply to the case of "double amping" the ODAC with the O2 at 1x gain), and what is your definition of "mid-fi" ?


----------



## Ashade

stv014 said:


> What are those flaws exactly (I listed a few limitations here, but none of them apply to the case of "double amping" the ODAC with the O2 at 1x gain), and what is your definition of "mid-fi" ?






 


As I said, "under certain circumstances". I never said they applied to double amping. In any case, double amping is not the optimal solution, specially when 1x is not an option provided by JDS labs, and not everybody has the skills required for DIY. Anyway, I'm not gonna keep on with the longings for controversy from some individuals in this forum.


----------



## stv014

ashade said:


> As I said, "under certain circumstances". I never said they applied to double amping


 
  
 Well, you did say "double amping" is a mid-fi solution. But how do you define "mid-fi" exactly, and what is it about "double amping" that specifically guarantees mid-fi status at best ? After all, one setup with "double amping" can very well be better than another without it, and devices may internally contain multiple stages and thus be technically double (or triple, or whatever) amped. The O2 itself is arguably "double amped" compared to a simple CMoy. But in reality what matters is the overall performance of the entire chain, regardless of how many components it has.


----------



## Ashade

stv014 said:


> After all, one setup with "double amping" can very well be better than another without it, and devices may internally contain multiple stages and thus be technically double (or triple, or whatever) amped.




You are absolutely right (was this what you wanted to hear? There you have it).



stv014 said:


> The O2 itself is arguably "double amped" compared to a simple CMoy.




I don't know what you are talking about. The guy was asking if he could double amp their active monitors, but I suppose you started your own personal crusade here.

Anyway, I'm learning a lot, so you can go on with your lectures, definitions and clarifications.


----------



## adydula

What flaws sonically does the O2 amp have????
  
 I dont know ANY????
  
 Really...remember this was designed as a low cost, excellent design....portable amp.
  
 There are no sonic flaws that i am aware of.
  
 The only real world flaws would be not so transportable, not so efficient cabling and connector locations, but sonically its pretty close to perfect.
  
 It adds nothing and takes away nothing.
  
 Another non sonic flaw would also be not having enough power for the "other" 2% of the headphones out there....
  
 A.


----------



## miceblue

Well for one it's way too loud for sensitive headphones when the potentiometer is past the channel imbalance region.


----------



## adydula

What sensitive headphones??
  
 And how does that equate to a detrimental listening experience?
  
 A.


----------



## miceblue

Pretty much any earphone, some portable headphones like the V-MODA M-100, and even with the K 701 it's too loud for me on 1.0x gain. I have to lower the digital volume when I use the O2 and want to listen to music at a low volume level.

I can't really enjoy listening to music if it's too loud for me.


----------



## mcandmar

miceblue said:


> Well for one it's way too loud for sensitive headphones when the potentiometer is past the channel imbalance region.


 
  
 Please explain the channel imbalance region?   Curious to know as i remember reading something about 12 o'clock being the optimum position.
  
 And does 1x gain no satisfy the needs for sensitive headphones (what i use for Grados), or are you talking about IEM's?


----------



## miceblue

mcandmar said:


> miceblue said:
> 
> 
> > Well for one it's way too loud for sensitive headphones when the potentiometer is past the channel imbalance region.
> ...


 
 The channel imbalance region is the part of the volume potentiometer that produces audio, but the left and right channels are at different volume levels (i.e. the left channel is louder than the right channel). At around the 9 o'clock position, the channel imbalance disappears. I don't actually know if this happens to all potentiometers, but it seems to be common in audio products for some reason.
  
 1.0x gain should be plenty for sensitive headphones in general. Even with the fairly insensitive Mad Dog headphones I never had to go past the 12 o'clock position to get a sufficiently loud volume level at 1.0x gain.


----------



## mcandmar

Interesting, thanks for that.  Good to know as i only ever use the 9,10,11 o'clock position with 1x gain and Grados, and the same three positions with 2.5x gain for the Sennheisers.


----------



## MrEleventy

miceblue said:


> The channel imbalance region is the part of the volume potentiometer that produces audio, but the left and right channels are at different volume levels (i.e. the left channel is louder than the right channel). At around the 9 o'clock position, the channel imbalance disappears. I don't actually know if this happens to all potentiometers, but it seems to be common in audio products for some reason.
> 
> 1.0x gain should be plenty for sensitive headphones in general. Even with the fairly insensitive Mad Dog headphones I never had to go past the 12 o'clock position to get a sufficiently loud volume level at 1.0x gain.


Not all. It's not an issue with digital pots but all analog pots do, it just varies in how bad it can get depending on quality of said pot.


----------



## adydula

For 99% of us this is not a real issue at all.
  
 None of the headphones I use are listened to at less than a nine o'clock position....below nine o'clock would be low fi to me....lol.
  
  
 So what are the real audio deficiencies with the O2 amp???
  
 Alex


----------



## MrEleventy

adydula said:


> For 99% of us this is not a real issue at all.
> 
> None of the headphones I use are listened to at less than a nine o'clock position....below nine o'clock would be low fi to me....lol.
> 
> ...


How does pot position equate to being low/mid/hi-fi?  That just means that's how sensitive they are. IEMs are typically the ones with channel imbalance issues since they're in your canal and doesn't take a lot to drive them...


----------



## miceblue

The less pot you have, the less high-fi it is.


----------



## adydula

Dont use iem's they to me are really a compromise compared to normal headphones....
  
 With headphones I never listen to anything below 9 oclock on the O2.
 Ususally between 9 pm and Midnight....lol
  
 Listening at very low levels with headphones the volume is so low the sound is just not very realistic to me....just not enjoyable at all....so this to me is low-fi.
  
 When I listen i do so with enough amplitude to make the experience enjoyable to me without hurting my hearing/ears...
  
 If I used IEM's I might be concerned about ch imbalance....but to me its not an issue at all.
  
 I played tones and listened at very low levels and dont really hear any imbalance with both of my O2's..
  
 I still find the overall capabilites of the O2 to far outweigh any possible ch imbalance issue.
  
 Alex


----------



## miceblue

adydula said:


> Dont use iem's they to me are really a compromise compared to normal headphones....
> 
> I played tones and listened at very low levels and dont really hear any imbalance with both of my O2's..
> 
> Alex


 
 Well I'm guessing they're called In-Ear Monitors for a reason. I don't use them because they're uncomfortable for me. XD
  
 And the channel imbalance seems to happen to pretty much all analogue potentiometers in audio gear. JDS Labs measured the channel imbalance for the O2. The lack of channel imbalance in their C5 amp is why I tend to use that over the O2 since I can comfortably listen to music at a sufficiently low volume.


----------



## CantScareMe

I've had this piece of gear for a long time and really like it. Wrote a review on this thread for anyone interested:
  
http://www.head-fi.org/t/684861/audinst-hud-mx2-vs-odac-o2-vs-graham-slee-bitzie-a-few-portable-dac-amps


----------



## Gilly87

Hey O2/ODAC owners!
  
 I am a big fan of the HRT Microstreamer, which I own, and have heard some people say that it can rival full-size amp/dac combos. Personally I am very curious about this, but I don't have anything to compare it to. I do know that it sounds great, much better than any of my mobile sources or the cheaper DACs I've tried (ELE DAC, Hifimediy Saber), so I am willing to bet it could hold its ground.
  
 So, I'm curious if any ODAC/O2 owners in LA would be interested in meeting up at a coffee shop or the like to compare and see if the little HRT can match up to the O2/ODAC combo. I have the HD650 and a Beyer DT770 LE 32 ohm for use in the comparo. I have a Schiit Asgard too; if anyone is interested in comparing it to the O2 I would gladly bring it along 
  
 The gauntlet has been thrown down!


----------



## adydula

Wish you were on the east coast, be happy to play and compare.
  
 I do have a HRT MSii+ Asynchronous USB DAC and the ODAC and it are very close, hard to tell any real world difference.
  
 Alex


----------



## Gilly87

Too bad...
  
 I've heard a few people say the MSii+ is better than the uS, but I've also heard some say it's better than the ODAC too, which is part of what makes me curious to see how close these two really are...if the uS could rival the O2/ODAC in a portable package, I wonder how many units they'd sell overnight XD
  
 Quote:


adydula said:


> Wish you were on the east coast, be happy to play and compare.
> 
> I do have a HRT MSii+ Asynchronous USB DAC and the ODAC and it are very close, hard to tell any real world difference.
> 
> Alex


----------



## tdockweiler

adydula said:


> Wish you were on the east coast, be happy to play and compare.
> 
> I do have a HRT MSii+ Asynchronous USB DAC and the ODAC and it are very close, hard to tell any real world difference.
> 
> Alex


 
  
 Have you ever heard the MSII? I bet the MSII+ must be like a 10% improvement over the MSII and even more transparent.
 I wonder if there are any more DACs under $300 that get close to the ODAC sound.
  
 So far i've only heard two..


----------



## TwoPointNine

LinusTechTips has just done an unboxing and review for the O2 AMP+ODAC:
  
http://www.youtube.com/watch?v=i33wY_RQGII


----------



## adydula

tdock...
  
 I had both the MSii and MSii+....
  
 Alex


----------



## Edgard Varese

New O2 owner here... arrived just a couple of hours ago.


----------



## eimis

Have anyone compared BCL (lehmann black cube linear) to O2 for HD650?


----------



## MrMateoHead

edgard varese said:


> New O2 owner here... arrived just a couple of hours ago.


 

 Welcome to the club! It is a great amp, so I am sure you will love it.


----------



## Edgard Varese

mrmateohead said:


> Welcome to the club! It is a great amp, so I am sure you will love it.


 
 I'm really pleased with it thus far. In addition to taming the bass bloat on low impedance cans it also reels in the sibilance a bit.  This is really an excellent product.


----------



## adydula

Congrats on your new amp....yes it is an excellent amp for headphones....
  
 Enjoy
  
 Alex


----------



## cocolinho

New user of O2 as well. I was looking for a transportable amp to drive my HD600 and Mad dogs. Hope I will enjoy it!


----------



## MrMateoHead

Make sure you newbs come back with your impressions. I like to hear how people adjust to their new equipment.


----------



## mcandmar

Since i built my O2 i have also built a CMoy clone, Grado RA-1 clone, and a JLH Clone and although they all have their own distinct character and pros and cons the O2 is the one that has become my reference point that i judge all others against.  And to be honest none of them even come close to its level of transparency and detail.
  
 Same story with trying out different headphones or cables, i can never really say what their strength or weakness is without running them off he O2.
  
 I often wonder what will happen if i build a high end solid state amp, will the O2 remain the reference point, or will the better amplifier become the new reference point?


----------



## adydula

mcandmar....
  
 I found the O2 competes with and bests many amps costing a lot more ......
  
 While there are really some great amps out there they cost more, but also have a better build quality, in that they are built to last forever, like the vioelectric
 amps, better switches and jacks... also better or nicer ergonomics.
  
 That said the O2 as it stands is right in there as far as audio specs, and transparency...etc
  
 I think you will be pleasantly surprised in your journey...
  
 Alex


----------



## tdockweiler

adydula said:


> mcandmar....
> 
> *I found the O2 competes with and bests many amps costing a lot more ......*
> 
> ...


 
  
 I've found this the case too, but I haven't really tried anything over $500 yet.
  
 I'm surprised it held up so well to my Headroom Micro Amp + Astrodyne PS. I mean that amp was originally $350 and another $60 or so for the power supply.
  
 The O2 is the closest i've come to it's sound. They basically sound the same or extremely close. I actually think the Micro Amp sounds more transparent but maybe we're talking 99% vs 95% 
	

	
	
		
		

		
			




  
 I actually prefer the O2 to even the E9, Asgard 1/2 and Magni, but not the Micro Amp.
  
 Sometime I'd like to compare the O2 to the Leckerton UHA-6S MKII. That thing is $280 though and not $120.
  
 If I had anything to complain about with the O2, there is not much. I wish it's treble was a bit smoother with the Q701. It's still good and much better than the Magni's treble though.
  
 My Micro Amp sounds like a more refinement O2 with all the rough edges taken off. No need to pair it with specific headphones and it's perfectly with even the brightest headphones.
  
 I sold the O2 to fund an Asgard 2 purchase (which I hated). No clue why I did that..in the end I just ended up with a new DAC 
	

	
	
		
		

		
		
	


	




. Should have just kept the O2 since it was for my bedroom setup.
 I was stupid and wanted slightly smoother treble. We're talking like a 3-5% improvement for long listening sessions! Can you say nit-picking?
  
 What I like in an amp is for it to work well with them ALL and not be only good for specific headphones. The O2 is basically that. Well as long as it's not like super power hungry like an HE-6 or whatever.


----------



## mcandmar

Funny you should mention the treble, i know exacltly where your coming from as i've actually had two, the first was bought ready built, the second i sourced the components and built myself looking for that last bit of refinement.  I basically followed the alternative kit list in the BOM with better Panasonic electrolytics, Wima film caps, Dale mil spec resistors, DD opamps, gold plated dip sockets, gain resistor sockets, red/gold pcb, and a few other tweaks like rear mounted RCA inputs and power connector.  The 2nd one ended up being that little bit smoother, and with a little less harshness in the high frequency's.  The difference is subtle, but enough to be noticeable.  Worth the effort if your considering getting another one.


----------



## MrMateoHead

tdockweiler said:
			
		

> *I sold the O2 to fund an Asgard 2 purchase (which I hated). No clue why I did that..in the end I just ended up with a new DAC
> 
> 
> 
> ...


 
 Well, the JDS Labs O2 is only $130 now, a little cheaper than when I first bought it.


----------



## adydula

Gosh...for $130, to me this is the buy of the century for GREAT perfomance.
  
 Alex


----------



## MrMateoHead

^^^^^ What you said. Even though I paid something like $320 for an O2 and an ODAC, I would do it again in a heartbeat. That you can get both right now for $280 is just awesome. Though, honestly, I am not 100% sure the ODAC was a must


----------



## Edgard Varese

mrmateohead said:


> ^^^^^ What you said. Even though I paid something like $320 for an O2 and an ODAC, I would do it again in a heartbeat. That you can get both right now for $280 is just awesome. Though, honestly, I am not 100% sure the ODAC was a must


 
  
 I'm going to end up getting the ODAC because I'm about at the end of my rope with my current DAC (an eMu 0202, which requires drivers and doesn't play too nicely with the computer anymore).


----------



## Ethereal Sound

Does anyone know how the ODAC compares to the built in DAC of the asus xonar essence STX? I'm considering getting the ODAC stand alone to hook up to my emotiva x a100 because my STX is producing too much hiss from my computer.


----------



## MrMateoHead

ethereal sound said:


> Does anyone know how the ODAC compares to the built in DAC of the asus xonar essence STX? I'm considering getting the ODAC stand alone to hook up to my emotiva x a100 because my STX is producing too much hiss from my computer.


 

 The ODAC will give you 0 Hiss. It is totally black. That is the best feature, and at first, the strangest thing in the world (I guess I was used to SOME level of noise from all my devices).
  
 That said, the STX is a very good DAC. Near all the computer sound cards I have heard in recent years are very, very good. Overall sound quality I doubt there is much difference between ODAC and STX. BUT the noise levels are certainly a change.
  
 In terms of features, however, you are giving up a lot. The ODAC only reproduces up to 24-bit 92khz, so it will downsample Blu-Rays. There are no DSP features and only a single 3.5mm output. I do use mine as a soundcard, essentially, and in that role I have found no faults. It is plug n play via USB, but you will need a permanent USB connection for it which may not be as 'clean' an install as an internal card.


----------



## stv014

The STX DAC has about the same SNR on the line output as the ODAC at 44.1 kHz, and is better than the ODAC at 48 and 96 kHz.
  
 Audible noise with speakers or anything driven by an external amplifier is most likely caused by a ground loop. So, if you do get the ODAC, you may want to invest in a USB isolator as well.


----------



## Ethereal Sound

Interesting....sigh, why must finding a DAC prove to be so difficult! 
	

	
	
		
		

		
		
	


	




 
 Is the ODAC comparable to the Audioengine D1?


----------



## BenF

ethereal sound said:


> Interesting....sigh, why must finding a DAC prove to be so difficult!
> 
> 
> 
> ...


 

 D1 is more versatile - it has an optical input, RCA outputs, volume control and supports up to 192Khz.
 ODAC has (IMHO) a better DAC chip.
  
 If you have an optical out, go with D1 - optical usually results in better SQ than USB.
 Anyway, you will be happy with either one - no wrong choice here really.


----------



## MrMateoHead

benf said:


> D1 is more versatile - it has an optical input, RCA outputs, volume control and supports up to 192Khz.
> ODAC has (IMHO) a better DAC chip.
> 
> *If you have an optical out, go with D1 - optical usually results in better SQ than USB.*
> Anyway, you will be happy with either one - no wrong choice here really.


 
 Can you substantiate that claim with anything other than assumption? Not to pick on you, but I am not sure what difference there is between optical and USB other than different connectors.
  
 What are the specifications of each? USB is known to handle 24-bit, 92 khz. I don't think optical is actually THAT good in comparison. A quick Google search shows that toslink is lower voltage, and 20-bit 48khz max. It doesn't do multi-channel HD audio unless it is compressed.


----------



## proton007

mrmateohead said:


> Can you substantiate that claim with anything other than assumption? Not to pick on you, but I am not sure what difference there is between optical and USB other than different connectors.
> 
> What are the specifications of each? USB is known to handle 24-bit, 92 khz. I don't think optical is actually THAT good in comparison. A quick Google search shows that toslink is lower voltage, and 20-bit 48khz max. It doesn't do multi-channel HD audio unless it is compressed.




Vinyl is better than cd.
2 channel is better than 5.1
Tubes are better than solid state.

See where I'm going with this?


----------



## adydula

disagree totally....
  
 sorry
 Alex


----------



## MrMateoHead

proton007 said:


> Vinyl is better than cd.
> 2 channel is better than 5.1
> Tubes are better than solid state.
> 
> See where I'm going with this?


 
 I am laughing out loud. I guess this is yet another time to be quiet.


----------



## BenF

mrmateohead said:


> Can you substantiate that claim with anything other than assumption? Not to pick on you, but I am not sure what difference there is between optical and USB other than different connectors.
> 
> What are the specifications of each? USB is known to handle 24-bit, 92 khz. I don't think optical is actually THAT good in comparison. A quick Google search shows that toslink is lower voltage, and 20-bit 48khz max. It doesn't do multi-channel HD audio unless it is compressed.


 

 Just my personal experience, especially with NFB-11.32.
 Using a good USB to Optical/Coax converter improved the sound compared to USB.
 There are others in the NFB-11.32 thread that reported similar experience.


----------



## Ashade

proton007 said:


> Vinyl is better than cd.
> 2 channel is better than 5.1
> Tubes are better than solid state.
> 
> See where I'm going with this?




I suppose he's being ironic... maybe not.


----------



## proton007

adydula said:


> disagree totally....
> 
> sorry
> Alex


 
  
 Damn you people! 
	

	
	
		
		

		
			




  
 There's nothing pure left in this world.


----------



## adamlr

proton007 said:


> Damn you people!
> 
> 
> 
> ...


 

 i may be totally wrong here, but i have the feeling he was being just as sarcastic as you were, and it was you who misunderstood him... either way, good times...


----------



## adydula

when vinyl was THE only choice except for AM radio, reel to reel, and 8 track tape.....I spent so many freaking hours and dollars trying to get rid of the hiss, static, pops and ticks it wasnt funny.
  
 Anti static mats, anti tracking pressure, phase linear 3000 secret electronics hiss removal circuits, watching my snow plow shure stylus plow thru the analog cuts on a record...watching large pieces of vinyl being worn out...having the source deteriorate from the first play....
  
 but ah...it sounded so good, so pure....so esoteric...
  
 Yeah right....
  
 LOL
  
 A.
  
 oh yeah remember discwasher.....and record duster brushes....oh my...


----------



## eimis

^ Yeah... all of this is not for me, I learned the hard way. Couldn't get rid of IGD. Tried different cartridges. Just too fussy...so I sold my sl-1210mk2, preamp...
  
  
  
 Still got all my vinyls though.


----------



## adydula

vinyls are great at yardsales!!!
  
 LOL..
  
 Alex


----------



## mannkind246

Can anyone share the comparing in term of  sound signature between O2 and Tralucent T1?
 Which one has more clarity, more detail, more depth, wider sound stage?


----------



## proton007

adamlr said:


> i may be totally wrong here, but i have the feeling he was being just as sarcastic as you were, and it was you who misunderstood him... either way, good times...


 
  
 Yes, you were totally wrong.


----------



## conheo

mrmateohead said:


> ^^^^^ What you said. Even though I paid something like $320 for an O2 and an ODAC, I would do it again in a heartbeat. That you can get both right now for $280 is just awesome. Though, honestly, I am not 100% sure the ODAC was a must


 
 and I bought odac+o2 like new for 150aud ....and i did in a hearbeat :">


----------



## SunshineReggae

mannkind246 said:


> Can anyone share the comparing in term of  sound signature between O2 and Tralucent T1?
> Which one has more clarity, more detail, more depth, wider sound stage?


 

 The point of the O2 is it doesn't _have _a sound signature. Whatever "sound" the T1 has is caused by distortion, whether it's a high output impedance or something else.
  
 An amp can't magically improve sound stage, either. It can probably mess up the sound stage by being a severely bad product, or it can do DSP stuff such as emulating 3D, (like the ICan) but it can't "improve" soundstage just by being an amp.


----------



## Uchiya

Combo is okay.  Nothing special.  It gets me by.  Saving up for Bifrost/Lyr again.


----------



## miceblue

Can the ODAC play DSD files? I was interested in a binaural DSD album but I don't even think I can properly play it with the ODAC.


----------



## Ashade

uchiya said:


> Combo is okay.  Nothing special.  It gets me by.  Saving up for Bifrost/Lyr again.


 
  
 I didn't get anything you said here...


----------



## Uchiya

ashade said:


> I didn't get anything you said here...


 

 The O2 + Odac combo, it is okay.  Not as special as everyone made out to be.  I bought it thinking it was a great value but for $300 new w/shipping but it leaves me wanting. I 'd rather save up and go all out for a nice combo, Uber-Bifrost/Lyr from Schiit, which I use to have but sold to experiment.  Now that is about $1k with nice tubes but a better investment, imo.


----------



## Ashade

uchiya said:


> The O2 + Odac combo, it is okay.  Not as special as everyone made out to be.  I bought it thinking it was a great value but for $300 new w/shipping but it leaves me wanting. I 'd rather save up and go all out for a nice combo, Uber-Bifrost/Lyr from Schiit, which I use to have but sold to experiment.  Now that is about $1k with nice tubes but a better investment, imo.


 
  
 Good to know. Let me know about your impressions of that final combo when you get it and how it compares with the O2 + ODAC.


----------



## MrMateoHead

uchiya said:


> The O2 + Odac combo, it is okay.  Not as special as everyone made out to be.  I bought it thinking it was a great value but for *$300 new w/shipping but it leaves me wanting*. I 'd rather save up and go all out for a nice combo, Uber-Bifrost/Lyr from Schiit, which I use to have but sold to experiment.  Now that is about $1k with nice tubes but a better investment, imo.


 
 Wanting for what I wonder? I know it isn't as aesthetically pleasing as all the Schiit gear buttt....


----------



## Uchiya

Lyr/UberFrost is far more engaging, UberFrost/Meier Classic as well.  Individual sounds can hang in their own space.  The o2/odac is a little soft, a little blurry, the distinction is never night and day but it's enough.  Kind of like the difference between a hot girl showing cleavage and no cleavage.  I prefer the cleavage.
  
 But for sheer transportability if I can't live without my music; o2/odac is the bees knees!


----------



## Ashade

uchiya said:


> Lyr/UberFrost is far more engaging, UberFrost/Meier Classic as well.  Individual sounds can hang in their own space.  The o2/odac is a little soft, a little blurry, the distinction is never night and day but it's enough.  Kind of like the difference between a hot girl showing cleavage and no cleavage.  I prefer the cleavage.
> 
> But for sheer transportability if I can't live without my music; o2/odac is the bees knees!


 
  
 What headphones are you using as reference? Just to get an idea of the total combo.


----------



## Uchiya

K712pros


----------



## Ashade

uchiya said:


> K712pros


 
  
 Nice. Looking forward to get an opportunity to listen to that combo.


----------



## zowki

Is anyone else dissatisfied with the O2 volume knob? It feels a little stiff and harder to twist in comparison to my Leckerton UHA-6S.MKII. Is there a smoother potentiometer I could buy to replace it?


----------



## mcandmar

Hard to improve on the alps pot for that size, it does loosen up with a bit of use though..


----------



## adamlr

proton007 said:


> Yes, you were totally wrong.


 

 yes i was


----------



## miceblue

Does the ODAC support DSD playback?


----------



## Ashade

miceblue said:


> Does the ODAC support DSD playback?


 
  
 I don't know but I can try to check it today during the evening.


----------



## Ashade

miceblue said:


> Does the ODAC support DSD playback?


 
  
 It does. Tried with JRiver on an iMac.


----------



## miceblue

ashade said:


> miceblue said:
> 
> 
> > Does the ODAC support DSD playback?
> ...



Nice! That's good considering the original designer didn't even mention it once in his blog posts. XD

Thanks for the confirmation!


----------



## Ashade

No problem, just to be exact, I tried DSF, but supposedly is basically the same thing. It played nice on the iMac via ODAC.


----------



## Radioking59

ashade said:


> It does. Tried with JRiver on an iMac.




Are you sure JRiver isn't converting DSD to PCM? It says "By default, DSD will be converted to PCM for playback" here:

http://wiki.jriver.com/index.php/DSD_Format


----------



## miceblue

Oh dang it. That's a good point.

Audirvana Plus does something similar:


> DSD to PCM high quality conversion using best in class iZotope 64-bit SRC for the downsampling conversion


----------



## Ashade

radioking59 said:


> Are you sure JRiver isn't converting DSD to PCM? It says "By default, DSD will be converted to PCM for playback" here:
> 
> http://wiki.jriver.com/index.php/DSD_Format




What would be proper way to try it? I thought something similar but I didn't come with other solution. Let me know and I'll try what I can.


----------



## Radioking59

ashade said:


> What would be proper way to try it? I thought something similar but I didn't come with other solution. Let me know and I'll try what I can.




Follow the directions in that link for bitstreaming, but I'm guessing it's just going to be a waste of time.


----------



## Ashade

radioking59 said:


> Follow the directions in that link for bitstreaming, but I'm guessing it's just going to be a waste of time.


 
  
 Thank you! It will probably be, but I will try it just for the shake of curiosity.


----------



## zowki

Purchased this volume knob for my O2/ODAC:
 http://www.jaycar.com.au/productView.asp?ID=HK7009
  
 The knob improved grip and the slightly bigger size increased precision.
 However, the volume potentiometer is poorly lubricated and still feels stiff. I'm considering lubing it up with some Deoxit contact cleaner.
  
 Edit: There wasn't any opening in the potentiometer to spray the contact cleaner inside so I just sprayed it all around it in hopes that some would seep in. It didn't do anything. The volume knob still feels as stiff as before.


----------



## adydula

Take the frontplate off...if you have not when u tried to lubricate the pot.
  
 Put the knob back on, it is still hard to turn?
  
 Wondering if the shaft might have been hitting the front plate hole and causing resistance.
  
 Both of my 02's have the pots and are not that hard o adjust?
  
 Alex


----------



## zowki

adydula said:


> Take the frontplate off...if you have not when u tried to lubricate the pot.
> 
> Put the knob back on, it is still hard to turn?
> 
> ...


 

 I did take the frontplate off. I took the whole board out of the chassis to lubricate the pot. The pot itself didn't have any openings in it.


----------



## adydula

The good news is although the pot might be a bit stiff to turn, the pot is a pretty good potentiometer.
  
 I have small rubber feet on my amps and have no issue turning the volume and the amp stays put.
  
 If you buld an 02 you can install it in larger case that weighs more and it should help the feel etc...
  
 Alex


----------



## miceblue

Hm, I might try this right now with the ODAC, providing it isn't going to be downsampled.
http://www.audiostream.com/content/how-play-dsd-file-using-foobar2000

http://www.2l.no/hires/index.html
^ [legally] free DSD and high-resolution music files


I'll get there eventually...36 KB/second download speeds, yay.


----------



## stv014

It is very unlikely (about 0% chance) that the ODAC natively supports DSD. Not many DACs do at a low cost. The ODAC does not even support PCM at 88.2 kHz sample rate, which is what DSD is commonly converted to.


----------



## miceblue

Yup, no sound is coming out of my rig while playing the DSD file in Foobar. I can't even properly setup Foobar to play DSD files though since there aren't any drivers for the ODAC in the ASIO settings. Bummer...


Oh derp. Audirvana Plus on Mac tells you if it can play DSD files or not.


----------



## adydula

The ESS DAC chip in the ODAC does PCM only.
  
 Alex


----------



## stv014

adydula said:


> The ESS DAC chip in the ODAC does PCM only.


 
  
 And even if it did support DSD, the TE7022L does not. While good DAC chips with DSD support are available at a reasonably low cost (like the CS4398), if it is not supported by the USB/PCI interface chip and drivers, it will still not work.


----------



## adydula

yup...what he said..


----------



## a_recording

Has anyone in this thread with a Mac with USB 3 ports or Mavericks encountered any problems with their ODAC? I recently got a new iMac and have been experiencing glitches and pops on the oDAC (which works fine when plugged into a Win 8 computer). I exchanged the iMac for a new one hoping it was a hardware issue, but the new one gets glitches as well. :/


----------



## miceblue

a_recording said:


> Has anyone in this thread with a Mac with USB 3 ports or Mavericks encountered any problems with their ODAC? I recently got a new iMac and have been experiencing glitches and pops on the oDAC (which works fine when plugged into a Win 8 computer). I exchanged the iMac for a new one hoping it was a hardware issue, but the new one gets glitches as well. :/



I have a MacBook Pro Retina Display running Mountain Lion and USB 3.0 ports are just fine on my end with a Monoprice USB cable connected to the ODAC. I haven't upgraded to Mavericks yet due to people saying it actually slows down their laptops.

I don't know if it makes a difference, but have you tried adjusting the configurations in the Audio MIDI Setup app in the Utilities folder of the Applications folder?


----------



## adydula

FYI...
  
 I have had several USB dacs, both asynchronous and synchronous...I use a music player called JRIVER Media Center.
  
 I have had to adjust the player software buffering setting from a default 100ms to 50 ms to get rid of pops and clicks.
  
 Depending on what youc pc is, memory, speed , cache you will possibly experience these very noticeable and annoying pops/clicks.
  
 The Jriver interact forum has many posts about these types of issues with computer dacs and how to adjust to elimante.
  
 Good Luck..
  
 Alex


----------



## miceblue

a_recording said:


> Has anyone in this thread with a Mac with USB 3 ports or Mavericks encountered any problems with their ODAC? I recently got a new iMac and have been experiencing glitches and pops on the oDAC (which works fine when plugged into a Win 8 computer). I exchanged the iMac for a new one hoping it was a hardware issue, but the new one gets glitches as well. :/



It's probably a problem with Mavericks actually.


mrspeakers said:


> Mavericks has really trashed my audio IO. Just getting things stable again...




Yet another reason to not upgrade. XD


----------



## Ashade

miceblue said:


> Yet another reason to not upgrade. XD


 
  
 LOL. Nice to know, I will be holding the upgrade for a while.


----------



## austonia

+1 joining this club with a Mayflower O2+ODAC combo (rear power jack, low gain option)
  
 not the newest or shiniest model but it'll do for a transportable unit i can take to work. replacing a Soundblaster MP3+


----------



## adydula

You can read about why an AC to AC adapter is used on the designers website under the O2 Design Process area. We cant provide u the direct link here.
  
 Basically there are several choices, but take a look over there and if you still dont understand why you can PM me.
  
 Thanks
 A.


----------



## austonia

adydula said:


> You can read about why an AC to AC adapter is used on the designers website under the O2 Design Process area. We cant provide u the direct link here.
> 
> Basically there are several choices, but take a look over there and if you still dont understand why you can PM me.
> 
> ...


 
  
 Appreciate your offer. I looked at design process but it's over my head. What I understand is, it's best for this design, and there's good science behind that. Good enough for me.


----------



## adydula

Many of the AC to DC adapters have noise issues and one way to get rid of that is to go with a AC to AC adapter, and do the AC to DC conversion yourself.
  
 Many people think that AC power is "dirty or bad" and go thru some fairly expensive "solutions" to clean up or minimize their perceived beliefs that AC power is an issue etc....long debates....LOL.
  
 The neat thing with that is all you have to do is run the O2 amp on batteries alone, NO AC, no ripple, no possibility of noise from the power source...just PURE DC, exactly what the doctor ordered.
  
 With a simple unplug of the AC adapter you can see for yourself if there is any impact on running with the AC adapter or just with batteries (Pure DC).
  
 The designer has measurements with AC power on his site...and they are exceptional.
  
 Another reason why this little amp is such a marvel....
  
 All the best
 Alex


----------



## stv014

The main reason why the O2 uses an AC-AC adapter instead of an AC-DC one (which are more common) is that it needs a dual +/- 12 V power supply, and that is not possible with most AC-DC adapters without using a rail splitter/active ground that the designer wanted to avoid. With AC power input, it is easy to create a dual DC power supply using two simple half-wave rectifiers.


----------



## MrMateoHead

All I want now is for someone to do a Full-On O2 Desktop Amp. Seems this product is definitely dead in the water for whatever reason.
  
 1/4 and 1/8 jacks x 4 (yes, let it run at least 2-pairs for you and a friend)
  
 1-3 watts max output
  
 Keep the battery power for power outages? Lol. If there is a battery(ies) some kind of 'low charge' warning.
  
 Variable Gain
  
 1/8 in / RCA in
  
 Better cable management
  
 $200 or so (preferable less).
  
 Done, I'll take three.


----------



## mcandmar

Add to that the approach of integrating the AC-AC transformer inside the enclosure would have created issues of shielding the noise from the sensitive electronics inside the case.  Not to mention the can of worms of various safety type approvals in order to sell the product in various markets, an external AC transformer was the easy cost effective solution.
  
 I actually went a step further and created my own little power supply box with a small toroid to feed mine, total overkill but hey why not..


----------



## adydula

mateohead...if you haven't already check out the DIYaudio site under headphone amps...lots of discussion and updates to the O2 good or bad depending on your view...
  
 AGDR is a person that is leading the way over there now for this amp...
  
 FYI
  
 Alex


----------



## austonia

.


----------



## adydula

Yup.....u can get the ODAC and the batteries in a case, but the small original case makes this a challenge...but it can be done.
  
 or get a larger case...
  
 or be happy with what you have got!!
  
 Its pretty darn good!
  
 Alex


----------



## austonia

.


----------



## evilsync

What are peoples thoughts on using o2+odac combo to drive Beyer T90's and EarSonic SM64's?
  
 I've been doing some googling and haven't quite found an answer - but wasn't there meant to be a ODA (desktop amp), whatever happened to this concept?
  
 Cheers fellas.


----------



## adydula

I use the O2 and ODAC with T90's all day long....
  
 one word "EXCELLENT"...
  
 Alex


----------



## evilsync

adydula said:


> I use the O2 and ODAC with T90's all day long....
> 
> one word "EXCELLENT"...
> 
> Alex


 
  
 Thanks, that's reassuring.  Did you look at any other alternatives for the T90's?


----------



## miceblue

I prefer the Woo Audio WA7 Fireflies for the T90 since the T90 has a pretty prominent treble response and I didn't like it out of the O2/ODAC combo too much.

* Not my rig, but I listened to it at a local Head-Fi meet


----------



## agdr

evilsync said:


> I've been doing some googling and haven't quite found an answer - but wasn't there meant to be a ODA (desktop amp), whatever happened to this concept?
> .


 
  
 The designer of the O2 headphone amp never did post his ODA before he dissapeared last year.  Earlier this year I whipped up a DIY version of an ODA, based on the original O2 design.   Same overall design as the O2 just with each section upgraded to take advantage of the additional space and power supply in a desktop design.   See this post:
  
http://www.head-fi.org/t/616331/o2-amp-odac/1635#post_9748634
  
 Hey my appologies to Currawong!  I hadn't followed up on this thread in awhile and never saw his post #1677 until now, when I went back to find the post number of my old post.  I'll follow up with him to find out the best way to post the files here.  I haven't tried posting those yet because I want to do a couple of small updates (then fab and test the boards), but got sidetracked on another O2-related DIY project, an O2 output upgrade PCB.  This one slides right into the top slot on O2's standard B2-080 case, above the O2 PC board, and plugs in place of the two O2 NJM4556A chips.
  
 The O2 booster and upgrade board does a few things.  It replaces the O2's two NJM4556A output chips by a lower distortion (by datasheet numbers, NOT dScope tested) and lower output DC offset OPA140+LME49600 pair.  I have measured the DC output offset.  20uv vs. 3mV (3000uV) for a standard O2 with the NJM4556A chips, a 93% reduction.  The O2's designer noted in his posts that the output distortion of the NJM4556A output chips swamp that of the NJM2068 gain chip, making it pointless to replace the NJM2068 with something even lower distortion.  The upgrade board solves that problem. The board also includes a few optional O2 modifications I've posted elsewhere over the years including: output anti-thump resistors; power manageement latch circuit to prevent that oscillation noise when the batts get low; and an optional 1/4" Neutrik jack that fits upside down (but the 1/4" jack does require the taller B3-080 case). 
  
 The OPA140 is a DC precision op amp with good AC datasheet parameters (around 8x better than the O2 designer's posted dScope measured numbers with the NJM4556A) while the LME49600 is the well known 250mA audio output buffer.   Note the O2's power supply in the O2 won't allow continuous (sine wave) output past around 200mA but it certainly can burst up there in a "music power" sense where peaks in music are 3x to 4x the average.  The OPA140 has extremely low current draw, just 2mA, and the LME49600 is run in low bandwidth mode (still 110mHz which is way above what is needed for audio).  So the upgrade chips pull only slightly more current than the original NJM4556A, making it still battery friendly.  The OPA140 can be replaced with the OPA827, OPA627, OPA1641, LME49710, LME49990 but all with differing effects on DC output offset and current draw.   See the build instructions. 
  
 Both boards are 100% DIY.  The files contain Gerber files you can send out to Seeed Studio or other 4-layer fab house and make your own boards.  If Currawong will allow I may make single PC boards available at cost if anyone is interested if there is some way to do that and stay within forum rules.  The fab house has a 5 board minimum which is a bit of a DIY hurdle.  The ODA board has a lot of surface mount parts and has parts on both sides of the board, although I kept the minimum part size on either board 1206 SMD (larger size) to make them as DIY friendly as possible.  The O2 upgrade board is all surface mount but on just one side.  So both are  essentially solder skills V2.0 vs. the O2.
	

	
	
		
		

		
			




  
 Best to wait a little bit on the ODA since I am doing a few small updates on the design and want to fab/test it first.  I'm slowly tinkering around a whatever a V2.0 might be, but that wouldn't be until later next year if at all.
  
 (image missing)


----------



## adydula

Hello,
  
 Ever since the designer disappeared there has been a lot of activity on other sites on the Objective 2 amp.
  
 If your into DIY you can put a desktop version of the O2 together.
  
 AGDR is one of the most knowledgeable people on the O2 that I know other than the designer himself.
  
 He has done and shared many, many updates to the O2.
  
 Even though to me, the O2 is pretty close to sonic perfection and a stellar deal when it comes to price and how it performs against other headphone amps, there are always areas and ways to make things "better" in many respects.
  
 Less noise, more power, useability, etc..
  
 AGDR has and is doing a "stellar' job working on the base O2 amp and making it even better in that context.
  
 I cant wait to get the boards and start building another derivative of this marvelous design.
  
 Alex


----------



## Battou62

It should be noted also that the designer of "The Wire" is releasing some new amp versions and possibly a dac on the DIY audio site.


----------



## lokesen

I just made a custom O2 amp + ODAC, but I didn't like the front panel with the power plug in the front. So I designed one myself with a laser engraved silver front and 2 mm acrylics on top of that. I made 4 spare ones. The front panel is 1mm larger around the edge, than the original and I really think that make it look much better than the original. The panel is anodised aluminium, rather than the shiny brushed original ones (they look very bad my opinion).
  
 I couldn't get the camera to capture the nice silvery finish though, hope you like it anyway.


----------



## adydula

Very nice!!
  
 Alex


----------



## idlelabor

Hi guys, recently decided to try IEMs and bought the VSONIC GR07 Bass Editions. Having a hard time trying to decide whether or not to get this combo or the Schiit Magni and Modi stack. Just wondering if these will bring about any positive difference towards the sound of IEMs in general?


----------



## miceblue

idlelabor said:


> Hi guys, recently decided to try IEMs and bought the VSONIC GR07 Bass Editions. Having a hard time trying to decide whether or not to get this combo or the Schiit Magni and Modi stack. Just wondering if these will bring about any positive difference towards the sound of IEMs in general?



For sensitive earphones, you'd probably be better off with the O2 due to its lower gain and lower power output, meaning you'll likely hear less background hiss and be able to listen to music at a quieter listening level.


----------



## adydula

Agree....


----------



## austonia

.


----------



## Peti

I was wondering if anyone have a first-hand experience with the O2+Odac & HD800? The nominal impedance of the HD-800 ,as we all know, is 300 Ohms. BUT, based on the innerfidelity's impedance graph (http://www.innerfidelity.com/images/SennheiserHD800.pdf) for lower frequencies, the HD800 requires ~640 ohms! Would the O2 be able to properly drive the HD800 to bring out the best from the HD800 when it comes to bass?
  
 I'm having hard time to find an expert answer for this question...


----------



## GigArt

I would not recommend using ODAC\O2 (which has brighter sound signature) with HD800 (bright too). Russian headfiers spend thousands and thousands of bucks to make HD800 sing perfectly


----------



## James-uk

I own the O2 and HD800. The only reason I now use the HDVD800 instead is because it had more inputs, looks pretty and has a higher output impedance so it adds a touch of warmth which suits my taste.(although this could be placebo) If I had to do a blind test between the 2 I would probably fail. The only thing I find with O2 is that on some quiet recordings I had to have the volume pot high and I'm a moderate volume listener. Any louder though and it would be into dangerous territory . It's a transparent amp and won't sound any different from any other transparent amp regardless of cost.


----------



## James-uk

In response to GigArts comment. O2/odac is transparent therefore neutral. HD800s are also neutral therefore transparent. The resulting sound is neutral. They might sound bright compared to lesser phones on flawed amps. Now my subjective taste means I like a touch more warmth than neutral which is partly why I chose the HDvD800. I've done some sighted a/b comparisons and I think I would probably fail a blind test. It Made me realise that the O2 is all anyone needs for sq.


----------



## GigArt

Neutral ODAC\O2 + neutral HD800... Does this dead neutral type of sound bring pleasure? For me - definitely not. It's a matter of taste and musical preferences though.


----------



## James-uk

For some it doesn't i completely agree. I like neutral so the music does the work. That said I sometimes reach for my Hd650s to add a bit of warmth to some of the colder sounding albums I own. I blame the producer/sound engineer for this problem though not the HP.


----------



## adydula

The O2 can drive the HD800s just wonderfully....
  
 A.


----------



## Peti

I think the whole point of the HD-800 is to present everything the way the producer and artist intended to sound. The reason I'd like to pair'em with the O2+Odac is that this amp-dac combo is well-known for its neutrality and my aim is to listen the music exactly the way it meant to be...no coloartion whatsoever.
  
 I fail to understand the logic behind having 1200-1550$ spent on the neutral HD800 and combine it with an amp which colors its sound. I think, and please take issue with me if i'm not correct - if the O2 can properly drive the HD800 in the bass territory (~640 Ohms!) then the infamous treble issue" of these headphones will vanish, or at least significantly reduced.
  
 To be correct, I have never tried this combination, so it is only specualtion from my side. However, I strongly contemplate this combination for the future for myself as the "ultimate rig". So all opinions are welcome.


----------



## ostewart

I personally dont like the HD800 for its unforgiving nature.

I much prefer the HE-6 or T1 for their more musical yet detailed sound. The T1 sounds fantastic with the O2, it can't quite power the HE-6 though.

I have come to learn that total neutrality does not mean listening pleasure. I enjoy a more neutral sound, but the HD800 is just too clinical, I want to enjoy my music, not analise every bit of it.


----------



## Peti

I'm sure its unforgiving nature comes handy when you have quality lossless audio material with high dynamic range to pair with!


----------



## James-uk

I want to hear every last bit of music as the artist intended. That's why I love the HD800 paired with a transparent amp such as the O2. This pairing does exactly that . I can see how this is transparency isn't for everyone though, we all have a flavour when it comes to the sound we like, when I buy a new album from a favourite band or artist I always hope that is been recorded /mastered to my taste but ultimately The goal of high fidelity sound is transparency .


----------



## James-uk

Yes dynamic range is very important , I used to think lossless also but I've since discovered that to my ears well done compression , like mastered for I tunes, is as good as lossless to my ears. But that's for another thread!


----------



## ostewart

Its such a subjective hobby.

I prefer my german maestro GMP 400 with my tube amp, but my final audio design piano forte X-G with the O2 or iCan+iTube rig.

Personal preferences. Valve amps colour the sound, but the colouring helps the GMP but not the PF X-G.


----------



## James-uk

Yes it is. A mate of mine has some ie8s and whenever he sticks the 800s or 650s on he takes them off and says 'not enough bass' . Funny enough his 'favourite albums for the ie8s ' are always what I would consider bass light albums. The bass heavy ie8s make up for the mastering shortcomings. Makes sense.


----------



## Peti

You're talking sense here. According to my experiences though, modern pop music (hard rock and metal included) are way too compressed thus they are no-no for the HD800  + O2 combo I'm afraid. Naturally, there are exceptions, but the vast majority of the pop music since the early 90's are not meant to be listened via hi-end, neutral gears like the HD800 & O2.
  
 That's a lesson I've learned through my Ultrsone Pro750.


----------



## tomb

peti said:


> You're talking sense here. According to my experiences though, modern pop music (hard rock and metal included) are way too compressed thus they are no-no for the HD800  + O2 combo I'm afraid. Naturally, there are exceptions, but the vast majority of the pop music since the early 90's are not meant to be listened via hi-end, neutral gears like the HD800 & O2.
> 
> That's a lesson I've learned through my Ultrsone Pro750.


 

 O2 is high-end?


----------



## James-uk

If hi-end means the highest possible fidelity then yes.


----------



## tomb

james-uk said:


> If hi-end means the highest possible fidelity then yes.


 

 No


----------



## miceblue

james-uk said:


> I want to hear every last bit of music as the artist intended. That's why I love the HD800 paired with a transparent amp such as the O2. This pairing does exactly that . I can see how this is transparency isn't for everyone though, we all have a flavour when it comes to the sound we like, when I buy a new album from a favourite band or artist I always hope that is been recorded /mastered to my taste but ultimately The goal of high fidelity sound is transparency .



Technically that's impossible unless you use the exact same equipment the artist used to create the album in the first place. 

For all you know, the artist could have made the album using a Beats Studio headphone and your HD800 makes the album sound unusually bass-light from what the artist intended it to sound like.

Objectively, the HD800 isn't neutral either.
http://www.innerfidelity.com/images/SennheiserHD800.pdf
Bass roll-off at 70 Hz and the brightness at 4-8 kHz are pretty noticeable to many people, myself included.

I tend to find the Objective 2 to be a great headphone amplifier overall, but synergy with certain headphones makes it a not-so-good choice. Brighter headphones like the AKG K 701 and HD800 don't sound too nice with the O2 in my experience.


----------



## James-uk

We cannot control what happens in the studio but we can expect most producers/engineers to be working with neutral set ups. And this shows given that most modern recordings sound perfect on the HD800s to me using the O2 . And as for the inner fidelity graph. That is a headphone response , headphone frequency responses are not suppose to be flat because their FR should represent speakers in a room. By the time the sound reaches our ears from flat speakers in a treated room then it looks more like that curved frequency response therefore being perceived as flat by our ears and brains. Therefore it is like listening to flat speakers , so it sounds neutral. If you had a perfectly flat FR on them inner fidelity graphs the actual perceived sound wouldn't be realistic .


----------



## Peti

After all that said, I still haven't found a reliable answer for my initial question which was:
  
 "based on the innerfidelity's impedance graph (http://www.innerfidelity.com/images/SennheiserHD800.pdf) for lower frequencies, the HD800 requires ~640 ohms! Would the O2 be able to properly drive the HD800 to bring out the best from the HD800 when it comes to bass?"


----------



## James-uk

Yes the O2 can handle that impedance curve.


----------



## James-uk

THD+N vs OUTPUT & MAX POWER ON AC: At 1 Khz with both channels driven here’s the distortion versus output on AC power into 15, 33, 80, 150 and 600 ohms. At 150 & 600 Ohms the output voltage was essentially the same at about 7.3 volts RMS. And even at about 200 mW of output into any of the loads the distortion is still below about 0.0025%! Maximum power is about 640 mW at 80 ohms. The power limits shown below exceed the power requirements established for the assumed worst case headphones (HiFiMan planars and 600 ohm version of the Beyer DT880):


----------



## TheDuke990

miceblue said:


> Objectively, the HD800 isn't neutral either.
> http://www.innerfidelity.com/images/SennheiserHD800.pdf
> Bass roll-off at 70 Hz and the brightness at 4-8 kHz are pretty noticeable to many people, myself included.


 
  
 Roll-off be roughly 1db (70Hz) sorry but this not worth mentioning.
  


james-uk said:


> I want to hear every last bit of music as the artist intended. That's why I love the HD800 paired with a transparent amp such as the O2. This pairing does exactly that . I can see how this is transparency isn't for everyone though, we all have a flavour when it comes to the sound we like, when I buy a new album from a favourite band or artist I always hope that is been recorded /mastered to my taste but ultimately The goal of high fidelity sound is transparency .


 
  
 I'm on your side. I found my combo HD800 + O2 amazing. Simply neutral and that is perfect for most of my records.


----------



## nabwong

So I'm interested in getting an o2. I'm currently using the modi-vali. I'm beginning to realize that it can't drive all my headphones. Maybe only 2 of them. Is the odac necessary for me since I have the modi? Is the performance similar? I can save some money just getting the o2 amp. Any pros and cons I haven't thought of? I would have just gotten the magni but the gain seems too high that 5x. I set my PC volume at 100. Should I get the low gain mod on the o2 or just regular? I'm driving grados HF-1 and HF-2.


----------



## Peti

james-uk said:


> THD+N vs OUTPUT & MAX POWER ON AC: At 1 Khz with both channels driven here’s the distortion versus output on AC power into 15, 33, 80, 150 and 600 ohms. At 150 & 600 Ohms the output voltage was essentially the same at about 7.3 volts RMS. And even at about 200 mW of output into any of the loads the distortion is still below about 0.0025%! Maximum power is about 640 mW at 80 ohms. The power limits shown below exceed the power requirements established for the assumed worst case headphones (HiFiMan planars and 600 ohm version of the Beyer DT880):


 

 Thanks for your answer!


----------



## adydula

O2 is a high end amp when it comes to providing a very, very affordable heaphone amp that delivers a very high end audiophile experience.
  
 Straight wire with gain.
  
 It doesn't come in a 20 pound 1/4 thick walled aluminum chassis.
  
 It doesn't come with a 40 pound external power supply.
  
 It doesn't come with all the bells and whistles that are associated with "high end" or "high cost'.
  
 It just does what it does very, very well.
  
 You may wear out the power on/off switch after 1000 or 2000 cycles or so...not a high end component.
  
 But for around $100  or so its indeed an exceptional audio device that compares very well with the so called "high end" devices out there from an audio perspective..
  
 Alex


----------



## miceblue

theduke990 said:


> miceblue said:
> 
> 
> > Objectively, the HD800 isn't neutral either.
> ...



http://en.wikipedia.org/wiki/Just-noticeable_difference
1 dB is noticeable.



james-uk said:


> We cannot control what happens in the studio but we can expect most producers/engineers to be working with neutral set ups. And this shows given that most modern recordings sound perfect on the HD800s to me using the O2 . And as for the inner fidelity graph. That is a headphone response , headphone frequency responses are not suppose to be flat because their FR should represent speakers in a room. By the time the sound reaches our ears from flat speakers in a treated room then it looks more like that curved frequency response therefore being perceived as flat by our ears and brains. Therefore it is like listening to flat speakers , so it sounds neutral. If you had a perfectly flat FR on them inner fidelity graphs the actual perceived sound wouldn't be realistic .



I didn't say it was supposed to be flat, and the roll-off at 70 dB isn't neutral by any definition.
http://www.headphone.com/learning-center/about-headphone-measurements.php


----------



## TheDuke990

And in mids and treble we have more than 5 to 10db differences from the "zero line". Sorry but for me 1db is not worth to mention at all.


----------



## AsianBatman

nabwong said:


> So I'm interested in getting an o2. I'm currently using the modi-vali. I'm beginning to realize that it can't drive all my headphones. Maybe only 2 of them. Is the odac necessary for me since I have the modi? Is the performance similar? I can save some money just getting the o2 amp. Any pros and cons I haven't thought of? I would have just gotten the magni but the gain seems too high that 5x. I set my PC volume at 100. Should I get the low gain mod on the o2 or just regular? I'm driving grados HF-1 and HF-2.


 
  
 If you already own a dac, I do not see the point in buying the odac. The o2 comes with the 2.5x and 6.5x gain. I personally use 1x and 2.5x after removing the resistor myself.


----------



## MrMateoHead

asianbatman said:


> If you already own a dac, I do not see the point in buying the odac. The o2 comes with the 2.5x and 6.5x gain. I personally use 1x and 2.5x after removing the resistor myself.


 

 If you want a completely black background, than the ODAC is a good way to get it! I used the O2 with my computer's realtek chipset for awhile and while the noise levels were typically below what I could detect, the ODAC eliminated any background hiss.


----------



## nabwong

asianbatman said:


> If you already own a dac, I do not see the point in buying the odac. The o2 comes with the 2.5x and 6.5x gain. I personally use 1x and 2.5x after removing the resistor myself.




Thanks. I just got a o2+odac from a friend and will do a modi-vali comparison. Can't wait for it to arrive.


----------



## cocolinho

adydula said:


> O2 is a high end amp when it comes to providing a very, very affordable heaphone amp that delivers a very high end audiophile experience.
> 
> It doesn't come with all the bells and whistles that are associated with "high end" or "high cost'
> 
> ...


 
 +1, I fully agree with you, don't need to spend much more to get the same results


----------



## adydula




----------



## tdockweiler

nabwong said:


> So I'm interested in getting an o2. I'm currently using the modi-vali. I'm beginning to realize that it can't drive all my headphones. Maybe only 2 of them. Is the odac necessary for me since I have the modi? Is the performance similar? I can save some money just getting the o2 amp. Any pros and cons I haven't thought of? I would have just gotten the magni but the gain seems too high that 5x. I set my PC volume at 100. Should I get the low gain mod on the o2 or just regular? I'm driving grados HF-1 and HF-2.


 
  
 If you have a Modi, there is no point in getting the ODAC. They're both basically transparent to me and I had a hard time telling them apart.
 I could probably do it with a T90 or some more expensive headphones, but not with an HD-650 or Q701.
  
 O2 is definitely a better all-around than the Vali. I use mine in my bedroom with my Xbox 360 and it does perfectly for that.
  
 Magni is also OK, but a tad brighter/thinner than the O2 with some headphones.


----------



## nabwong

tdockweiler said:


> If you have a Modi, there is no point in getting the ODAC. They're both basically transparent to me and I had a hard time telling them apart.
> I could probably do it with a T90 or some more expensive headphones, but not with an HD-650 or Q701.
> 
> O2 is definitely a better all-around than the Vali. I use mine in my bedroom with my Xbox 360 and it does perfectly for that.
> ...


 
  
 Thanks for your impresssions. I'm waiting to get the o2+odac this thursday or friday and then i'll be able to do a comparison. I love my he400 with the vali. It sounds really smooth but not bloated. It would be interesting to see how it sounds with the o2. My problem is that none of my other headphones (grado, AT, senns) seem to pair well with the Vali, just my opinion of course. They sound too congested. 
  
 I was gonna go magni but the 5x gain is too high I think. Vali is 4x and it's already too much, maybe. So i'm looking forward to the 2.5x or even 1x gain. We'll see. I can't wait to get it.


----------



## tdockweiler

nabwong said:


> Thanks for your impresssions. I'm waiting to get the o2+odac this thursday or friday and then i'll be able to do a comparison. I love my he400 with the vali. It sounds really smooth but not bloated. It would be interesting to see how it sounds with the o2. My problem is that none of my other headphones (grado, AT, senns) seem to pair well with the Vali, just my opinion of course. They sound too congested.
> 
> I was gonna go magni but the 5x gain is too high I think. Vali is 4x and it's already too much, maybe. So i'm looking forward to the 2.5x or even 1x gain. We'll see. I can't wait to get it.


 
  
 I had that problem too with the Vali. Sounded amazing and dead neutral with the Q701 but terrible with the HD-650. It made the mids so thick that the sound was all congested. Bass was very sloppy. I thought maybe it was due to not having enough power for the HD-650, but my 38ohm DJ100 gave me similar results.
  
 Don't ask me how, but Q701 sounded better from the Vali than the O2 (slightly), but O2 is a better all-rounder by far.
  
 Since the Vali only worked well with 2/5 of my headphones I swapped it for an O2!
  
 So far i've only heard two other amps that are at about the same level as the O2. That's the iFi iCAN and Headroom Micro Amp. Both of those are $220-$279 though!
 iCAN is great, but a tad warmer than the O2 and has a more closed in soundstage. It was good, but not great with the HD-650.
  
 I use my HD-650 with the O2 almost every day in my bedroom for gaming. Perfect for that.


----------



## Ashade

Not finished yet but you can get an idea. I chose some warmer colors this time. The power input will be moved to the back and in it's place there will be a 1/4 input (if I get it to fit). ODAC will be added later while holding the batteries (as last time).


----------



## tdockweiler

Think I want to try an OPA2134 in my O2. Doubt the difference will be audible. Heck, I don't even currently know what parts to swap out. Doesn't it have 3 op-amps inside?
  
 It'd be funny if after replacing those op-amps it'd sound 99.9% identical to my Micro Amp. That's what inside my Micro, but it has 6 of them soldered to the board.
  
 Right now it's already about 95-97% identical in sound


----------



## proid

tdockweiler said:


> Think I want to try an OPA2134 in my O2. Doubt the difference will be audible. Heck, I don't even currently know what parts to swap out. Doesn't it have 3 op-amps inside?
> 
> It'd be funny if after replacing those op-amps it'd sound 99.9% identical to my Micro Amp. That's what inside my Micro, but it has 6 of them soldered to the board.
> 
> Right now it's already about 95-97% identical in sound


 
  
 I think there will be a very big different between opa2134 and stock NJM2068. Opa2134 has thick, warm, smooth sound, and not very detail, NJM2068 is totally opposite: extremely clean, clear, big sound stage, extremely detail, even swap between ne5532( 2nd stock recommend for O2) and NJM2068 i can hear the different quite clearly.


----------



## nabwong

I just received my o2+odac. Quick question, is it just me or is there a sound difference between 2.5x and 6.5x gain. I find the 6.5x to be more congested and bloated than the 2.5x. Also more sibilance. Yes, I reduced the volume when I went higher gain. My laptop volume is 100%.


----------



## proid

nabwong said:


> I just received my o2+odac. Quick question, is it just me or is there a sound difference between 2.5x and 6.5x gain. I find the 6.5x to be more congested and bloated than the 2.5x. Also more sibilance. Yes, I reduced the volume when I went higher gain. My laptop volume is 100%.


 
  
 Yes, that's true. O2 sound better with less gain.


----------



## nabwong

proid said:


> Yes, that's true. O2 sound better with less gain.


 
 Thanks. Then I'm probably gonna change it to 1x/2.5x. I just got it like 30mins ago and i'm surprised it's so amazing. It's crazy for the amount of money I paid for it. Maybe will do a comparison with modi/vali.


----------



## AsianBatman

nabwong said:


> Thanks. Then I'm probably gonna change it to 1x/2.5x. I just got it like 30mins ago and i'm surprised it's so amazing. It's crazy for the amount of money I paid for it. Maybe will do a comparison with modi/vali.


 
  
 Which headphones are you using? It would probably sound less congested with 250+ ohm headphones. I find 1x is good enough for all my headphones. a900x, he-300, ahd2k, dt880 (250 ohm) and k550.


----------



## nabwong

asianbatman said:


> Which headphones are you using? It would probably sound less congested with 250+ ohm headphones. I find 1x is good enough for all my headphones. a900x, he-300, ahd2k, dt880 (250 ohm) and k550.




He400 - main pair. 

Hf1, hf2, hd595, w10vtg - all of them responded the same way. Lower gain is much better. Looking forward to changing the gain. I don't foresee using the 6.5x at all.


----------



## mcandmar

6.5x was intended for low power sources, i.e. battery powered portable gear.  With a full voltage redbook level input it will distort pretty bad.
  
 I found 1x was perfect for 32ohm cans, and 2.5x was about right for my 300ohm HD650's.


----------



## AsianBatman

nabwong said:


> He400 - main pair.
> 
> Hf1, hf2, hd595, w10vtg - all of them responded the same way. Lower gain is much better. Looking forward to changing the gain. I don't foresee using the 6.5x at all.


 
  
 All those are relatively low ohm headphones. I never use 6.5x before I changed it. I used it once for my dt770 80ohm and it made the bass really bloated and sloppy.


----------



## MrMateoHead

Don't go clipping your O2 right away because you think high gain = bad sound.
  
 The 6.5x gain is still useful for HDR recordings and weak sources (i.e., virtually any common device you probably would use as a source aside from the ODAC).
  
 Spend some more time listening and playing around before you do it. Better yet, plug an Mp3 player or cell phone into it with some classical to see what I mean.


----------



## AsianBatman

mrmateohead said:


> Don't go clipping your O2 right away because you think high gain = bad sound.
> 
> The 6.5x gain is still useful for HDR recordings and weak sources (i.e., virtually any common device you probably would use as a source aside from the ODAC).
> 
> Spend some more time listening and playing around before you do it. Better yet, plug an Mp3 player or cell phone into it with some classical to see what I mean.


 
  
 I did try that with my TV, ipod and S3. Unfortunately that yield the same result.


----------



## MrMateoHead

Asian Batman, in your previous post you said you used the 6.5x gain "once" before you changed it, and it made the bass all sloppy on your DT770s. That is not proof that SQ is 'always' better at low gain. Now you are telling me that you plugged in and used high gain with multiple sources. Which was it?
  
 Either way, gain is not about SQ - it is about source matching and while it can affect SQ, it is not really the first place to go when summarizing an amps performance!


----------



## AsianBatman

mrmateohead said:


> Asian Batman, in your previous post you said you used the 6.5x gain "once" before you changed it, and it made the bass all sloppy on your DT770s. That is not proof that SQ is 'always' better at low gain. Now you are telling me that you plugged in and used high gain with multiple sources. Which was it?
> 
> Either way, gain is not about SQ - it is about source matching and while it can affect SQ, it is not really the first place to go when summarizing an amps performance!


 
  
 Thanks for pointing that out. I only had my DT770 at the time I got my O2/Odac, so using it once with 6.5x with multiple sources in a day. I count that as once upon a time, but sorry for the confusion. Hope that clears that up. I never said anything about SQ or anything about it being better at low gain. I just said that I find 1x to be sufficient for the headphones I do have.


----------



## MrMateoHead

Oh OK. I thought that you were equating gain levels with sloppy bass, which would have been strange.


----------



## AsianBatman

mrmateohead said:


> Oh OK. I thought that you were equating gain levels with sloppy bass, which would have been strange.


 
  
 I can understand the confusion cause in a way I was stating that the DT770 had a bad bass response with the high gain level with the sources I tried it with. For bass heavy songs, the bass sounds like someone is holding their hands on a subwoofer as the bass hits. I was not trying to generalize 6.5x = sloppy bass.


----------



## nabwong

mrmateohead said:


> Don't go clipping your O2 right away because you think high gain = bad sound.
> 
> The 6.5x gain is still useful for HDR recordings and weak sources (i.e., virtually any common device you probably would use as a source aside from the ODAC).
> 
> Spend some more time listening and playing around before you do it. Better yet, plug an Mp3 player or cell phone into it with some classical to see what I mean.


 
  
 You know what, you're absolutely right about needing the 6.5x gain for classical. Just turned on some Ravel Piano Concerto in G with Thibaudet. That 2nd movement especially is super quiet. I'm glad I've not changed the gain. The irony is I'm a classical trumpet player and it took me this long to turn on some classical music.


----------



## MrMateoHead

nabwong said:


> You know what, you're absolutely right about needing the 6.5x gain for classical. Just turned on some Ravel Piano Concerto in G with Thibaudet. That 2nd movement especially is super quiet. I'm glad I've not changed the gain. The irony is I'm a classical trumpet player and it took me this long to turn on some classical music.


 
 No one ever just says I'm right! Glad to help.
  
 High Dynamic Range soaks up power big time - and makes setting gain and volume levels tricky. Certainly what is about right for classical will brutalize your ears with pop. Try a Blu-Ray or DVD at some point also - much the same. That is why I would rather have a little too much gain than not enough - particularly with an amp like the O2 which is so perfectly silent!


----------



## Dano91

nabwong said:


> I just received my o2+odac. Quick question, is it just me or is there a sound difference between 2.5x and 6.5x gain. I find the 6.5x to be more congested and bloated than the 2.5x. Also more sibilance. Yes, I reduced the volume when I went higher gain. My laptop volume is 100%.


 
  
 That's strange, cause I didn't hear any difference between 2.5x vs 6.5x with HD600 or HD800.
 You just have to be sure to lower the volume *in* *pc* if you wanna use 6.5x, so the output from odac is 1V max, if using AC adapter. In case of batteries it's even lower (cca 0.7V). According to my measurements 1V is around 67-68% on windows volume slider, 0.7V is cca 55%


----------



## Nec3

Does anyone know the maximum operating temperatures on this amp/dac? I put it on top of my PC that runs about 30-40 degrees celcius (chassis temps) when on max load. Then the heat transfers to my DAC that gets quite warm.

 Edit: I use an infrared thermometer, the bottom of the ODAC is 33 degrees celcius.


----------



## MrMateoHead

dano91 said:


> That's strange, cause I didn't hear any difference between 2.5x vs 6.5x with HD600 or HD800.
> You just have to be sure to lower the volume *in* *pc* if you wanna use 6.5x, so the output from odac is 1V max, if using AC adapter. In case of batteries it's even lower (cca 0.7V). According to my measurements 1V is around 67-68% in windows volume slider, 0.7V is cca 55%


 

 What were you measuring? Output from the ODAC at those system volume levels? It would seem that this is a useful thing to know.


----------



## Dano91

mrmateohead said:


> What were you measuring? Output from the ODAC at those system volume levels? It would seem that this is a useful thing to know.


 
  
 Yes, I used simple DMM at 50Hz sine wave @ 0 dBFS.


----------



## mcandmar

dano91 said:


> Yes, I used simple DMM at 50Hz sine wave @ 0 dBFS.


 
  
 Something wrong there, with a 0db sine wave you should have measured ~2.8v or ~2v RMS.   Specs for the ODAC are, quote "*Line Output: *Approximately 2 Vrms into 5K ohms or higher"


----------



## Dano91

mcandmar said:


> Something wrong there, with a 0db sine wave you should have measured ~2.8v or ~2v RMS.   Specs for the ODAC are, quote "*Line Output: *Approximately 2 Vrms into 5K ohms or higher"


 
 That's correct - with volume slider at 100% I measured 1.999V, 
 at 90% - 1.588V
 80% - 1.336V
 70% - 1.060V and so on
  
*EDIT*: I did full plot from 100% to 0% on volume slider in Win at 5% steps if anyone is interested:


Spoiler: Warning: Spoiler!



50 Hz, sine wave, 0 dBFS  
 100% 1.999 V
  95    1.774 
  90    1.588
  85    1.490
  80    1.336
  75    1.182
  70    1.060
  65    0.941
  60    0.838
  55    0.707
  50    0.561
  45    0.501
  40    0.398
  35    0.315
  30    0.250
  25    0.198
  20    0.141
  15    0.089
  10    0.050
   5     0.020


----------



## adydula

I never ever use 6.5....not needed at all.
  
 Alex


----------



## MrMateoHead

I use 6.5X all the time. Even in my car, the gain is cranked (yikes!). Necasary in the day of having CD, USB, Aux Inputs and Radio etc. Its impossible to set amps properly for each source and still guarantee yourself ample headroom to push someone's crappy Mp3 player mix with justice. 
	

	
	
		
		

		
		
	


	



  
 Thanks Dano 91 - Its geek gratification to know what my pre-outs are doing at a given volume on the Windows slider 
	

	
	
		
		

		
		
	


	



  
 I am actually a little surprised that its clearly non-linear volume adjustment - but pretty close.


----------



## jring

nabwong said:


> I just received my o2+odac. Quick question, is it just me or is there a sound difference between 2.5x and 6.5x gain. I find the 6.5x to be more congested and bloated than the 2.5x. Also more sibilance. Yes, I reduced the volume when I went higher gain. My laptop volume is 100%.


 
 Hi,
  
  
 as has been said before, ODAC is rated to deliver 2V RMS at 0dB and this is too much for O2 at 6.5x gain, regardless of power option and O2 volume pot setting. This means that the O2 input stage will clip when driven by ODAC at 100% software volume and music going up to 0dB. 
  
 So either turn down the volume in software (not so bad if you run ODAC at 24 bit) or change one of the gain modes to 3.5x which happens to be the max gain with ODAC and mains power - on battery it's 2.5x btw...
  
 Joachim


----------



## ShenaRingo326

Is it a good idea to keep the output of odac at 1.0V for 1.0x or 2.5x gain on the O2?


Thanks!


----------



## mcandmar

No, optimum is to keep the ODAC at 100% volume = 2v, and then adjust gain and volume on the O2 accordingly.
  
 As i said previously, for low impedance cans like 32ohm Grados 1x gain is fine, for 300ohm cans like HD650's 2.5x is about right.  I dont see any reason to use any higher gain unless your source is low power and you need to make up for it.


----------



## nabwong

mcandmar said:


> No, optimum is to keep the ODAC at 100% volume = 2v, and then adjust gain and volume on the O2 accordingly.
> 
> As i said previously, for low impedance cans like 32ohm Grados 1x gain is fine, for 300ohm cans like HD650's 2.5x is about right.  I dont see any reason to use any higher gain unless your source is low power and you need to make up for it.




I thought I didn't need 6.5x but classical music, especially slow movements of piano concertos are really quiet.


----------



## BenF

nabwong said:


> I thought I didn't need 6.5x but classical music, especially slow movements of piano concertos are really quiet.


 

 What about congestion, bloat and sibilance you reported before?


----------



## mcandmar

nabwong said:


> I thought I didn't need 6.5x but classical music, especially slow movements of piano concertos are really quiet.


 
  
  
 You don't, you just need to turn the volume knob a bit more..


----------



## nabwong

benf said:


> What about congestion, bloat and sibilance you reported before?




I'm not sure why but this is less of a problem when the volume is between the 10-2 o clock position than when it is below the 9 o clock position on 6.5x gain. Another observation is this bloating issue is more prevalent on pop, rock, commercial music. I don't hear the bloat too much if at all on classical recordings. Maybe the soundstage? Recording space? Mix? I don't know. I'm not an engineer so I don't know the physics or math. Just my observation.


----------



## jring

nabwong said:


> I'm not sure why but this is less of a problem when the volume is between the 10-2 o clock position than when it is below the 9 o clock position on 6.5x gain. Another observation is this bloating issue is more prevalent on pop, rock, commercial music. I don't hear the bloat too much if at all on classical recordings. Maybe the soundstage? Recording space? Mix? I don't know. I'm not an engineer so I don't know the physics or math. Just my observation.


 
  
 Volume @ 10-2 o'clock at 6.5x... with an ODAC...
  
 8-O
  
 What cans are you using? I guess the only thing I'd notice in that circumstances with any of my phones would be the popping sensation when my eardrums split...
  
 Joachim


----------



## miceblue

Maybe it's the HE-6? XD


----------



## nabwong

jring said:


> Volume @ 10-2 o'clock at 6.5x... with an ODAC...
> 
> 8-O
> 
> ...




Classical music. Slow movement of a piano concerto. 2nd movement of Ravel piano concerto in G with Thibaudet is really really quiet.


----------



## jring

nabwong said:


> Classical music. Slow movement of a piano concerto. 2nd movement of Ravel piano concerto in G with Thibaudet is really really quiet.


 

 Listening to it atm... spotify only unfortunately but still nice. ODAC at 100%, O2 on 2.5x. Highest I can bear with my K240 Sextett, which is not really efficient either although no comparision to an HE-6, is around 12 o'clock (and actually too loud for an adagio and way too loud for my ears around 6:30).
  
 And now I was in for a painful surprise when spotify gave me a loudness war commercial - luckily I had already turned it down a bit to 10 o'clock but it still hurt...
  
 So the question stands - what cans need 6.5x and up 2 o'clock even with Ravel's piano concert in G - 2. adagio assai with Thibaudet 
  
 Joachim


----------



## nabwong

jring said:


> Listening to it atm... spotify only unfortunately but still nice. ODAC at 100%, O2 on 2.5x. Highest I can bear with my K240 Sextett, which is not really efficient either although no comparision to an HE-6, is around 12 o'clock (and actually too loud for an adagio and way too loud for my ears around 6:30).
> 
> And now I was in for a painful surprise when spotify gave me a loudness war commercial - luckily I had already turned it down a bit to 10 o'clock but it still hurt...
> 
> ...


 
  
 Spotify (using premium) is way louder than my CD ripped to itunes. On spotify, I have it up till 9.30 oclock max on 6.5x and 11.30 on 2.5x BUT on my itunes I need it to be 2 oclock on 6.5x. So you don't need the 6.5x gain there.


----------



## ILoveGrado

Besides recharging the battery, the AC adaptor will allow you to accept true line out (2V) without fear of clipping the input stage. It is recommended to use AC adaptor  when you are going to use it with ODAC or any desktop source. I think the battery mode will only accept 1.5-1.7 V of input before clipping. In other words, you can accept louder source and therefore get it louder at output stage using the AC Adaptor.


----------



## tupi3

mcandmar said:


> No, optimum is to keep the ODAC at 100% volume = 2v, and then adjust gain and volume on the O2 accordingly.
> 
> As i said previously, for low impedance cans like 32ohm Grados 1x gain is fine, for 300ohm cans like HD650's 2.5x is about right.  I dont see any reason to use any higher gain unless your source is low power and you need to make up for it.


I have an O2/ODAC combo and back when I bought it I had no idea what the gain setting was so I got one with the default 2.5x and 6.5x gain. I'm using low impedance headphones (Grados). Am I ruining the sound quality by using higher gain settings?


----------



## adydula

Its real simple, start with the lowest gain setting, use the volume control to set the music to what you like for reasonable listening so you wont KILL your hearing over time,
  
 If that works there is NO need for higher gain.
  
 I run my T90's at unity gain and can blast my head off!!
  
 Alex


----------



## conheo

nabwong said:


> I thought I didn't need 6.5x but classical music, especially slow movements of piano concertos are really quiet.


 
  
 could you please provide the link to this masterpiece...


----------



## nabwong

conheo said:


> could you please provide the link to this masterpiece...




Here you go

http://www.amazon.com/Ravel-Piano-Concertos-etc-Thibaudet/dp/B0000042EU/ref=sr_1_2?ie=UTF8&qid=1390406694&sr=8-2&keywords=thibaudet+ravel

YouTube

http://m.youtube.com/watch?v=3vEKOCQPhQM


----------



## glunteer

I was reading this thread and saw many people saying that using a powered usb hub greatly enhances the sound of the ODAC.
  
 could you recommend any usb hub powered up to $ 30.00 for use with ODAC?
  
 Thanks


----------



## BenF

glunteer said:


> I was reading this thread and saw many people saying that using a powered usb hub greatly enhances the sound of the ODAC.
> 
> could you recommend any usb hub powered up to $ 30.00 for use with ODAC?
> 
> Thanks


 

 Whaaaaat? Who was saying that?


----------



## glunteer

benf said:


> Whaaaaat? Who was saying that?


 
  
     


  

    
 I saw some people here in the topic saying


----------



## BenF

glunteer said:


> I saw some people here in the topic saying


 

 Can you find this?


----------



## glunteer

benf said:


> Can you find this?


 
     


  

    
 I searched the smartphone yesterday ... I can not find here on my pc ...

 You do not believe that will improve the sound?


----------



## BenF

glunteer said:


> I searched the smartphone yesterday ... I can not find here on my pc ...
> 
> You do not believe that will improve the sound?


 

 No reason why it would.
 I used to connect my DACs through a USB Hub (non-powered), it caused a lot of noise.


----------



## glunteer

benf said:


> No reason why it would.
> I used to connect my DACs through a USB Hub (non-powered), it caused a lot of noise.


 
 I may be wrong then ... however thanks for the help


----------



## manbear

I'm not sure about powered hubs, but some people find that if you have DAC that's powered entirely by USB, you can improve the sound by using a battery power supply and a cable splitter. For example, Anker batteries are batteries with USB ports used for charging phones. If you get a USB Y-splitter and block the pin that carries power on the plug that goes into your laptop, all the power to the DAC comes from the battery and not from the laptop. I do this with my USB DAC. It doesn't make much difference, really, but it depends on the particular DAC model as well as on the laptop.


----------



## mcandmar

Isolating the computer as a power source and substituting a decent low noise power supply, or battery, can improve the ODAC.   As not all computers are built equal your results may vary.


----------



## AsianBatman

glunteer said:


> I may be wrong then ... however thanks for the help


 
 Only way I can see the ODAC improving from a powered usb hub is if the usb port you are using on your computer/laptop does not provide sufficient power. I can't hear the difference between my laptop or pc or office pc (powered usb hub). Sorta like the whole cable debate. Your ears hear what you want it to hear imo. Just my two cents.


----------



## Battou62

mcandmar said:


> Isolating the computer as a power source and substituting a decent low noise power supply, or battery, can improve the ODAC.   As not all computers are built equal your results may vary.


 
 TBH a well built power supply should be the cornerstone of any pc build.


----------



## mcandmar

I agree, but a decent PC power supply makes an awful supply for a DAC.  For example in the below image the top trace is a 5v linear regulator supply, the bottom is the power coming out of the USB port on my PC, which happens to have a Corsair AX850 power supply feeding an Asus Sabertooth x79 motherboard.  The real problem is the many sources of noise at various frequencies operating inside the computer.


----------



## AsianBatman

Question: Are there measurements of sound output of the ODAC via different power sources to see the affects of usb power on dither and such?


----------



## adydula

Spend some time on the designers website and look at the design docs, spec and his plots.....
  
 Alex


----------



## AsianBatman

adydula said:


> Spend some time on the designers website and look at the design docs, spec and his plots.....
> 
> Alex


 
 I did.... but I don't think I saw output measurements of the ODAC with different power sources. I might have overlooked it. Please P.M. me if you find it yourself. Thanks!


----------



## glunteer

Thank you so much for helping me 

 I have another question, I use the cable AUDIOQUEST Forest here, it does not come with ferrite, someone already did a test and feel the difference using ferrite?


----------



## AsianBatman

glunteer said:


> Thank you so much for helping me
> 
> I have another question, I use the cable AUDIOQUEST Forest here, it does not come with ferrite, someone already did a test and feel the difference using ferrite?


 


tdockweiler said:


> It's possible there is no audible difference with some headphones and the included cables 1 foot length. Not sure.
> 
> A good test would be to try to use a longer length (like 5 feet) and try many different headphones. A closed and very revealing headphone is best.
> 
> ...


 
  
 I didn't see any benefit of adding a ferrite bead usb to my setup.


----------



## glunteer

asianbatman said:


> I didn't see any benefit of adding a ferrite bead usb to my setup.


 
 I do not feel much difference when I switch cables. I think with ferrite would be even less
  
  
    
 I asked out of curiosity


----------



## adydula

I don't think there are measurements comparing different USB or other power sources.
  
 What you should be thinking about is how the ODAC was designed and does it meet the design criteria that that the designer was aiming for and that is a genuinely transparent DAC.
  
 The O2 amplifier was created as a simple, low cost, minimalist design delivering 100% transparent performance into nearly any headphone. The ODAC takes the same minimalist approach to transparency.
  
 One of the "several" areas that many people think that are necessary for high end DAC performance and or audio nirvana is the use of a elaborate and/or High Current Power Supply.
  
 The ODAC disappears from your audio chain while using a PCs USB power supply.
  
 Even if the PC's USB power is not 100% clean the ODAC circuitry is designed to handle that. Yes dirty USB power can degrade performance. The ODAC uses split digital and analog power supplies each with their own filtering and regulator. The analog supply has additional filtering and the critical reference voltages, and negative supply for the DAC chip, are further optimized.
  
 I have tried several pcs of all kinds and brands and have used an o'scope to see the trash coming from the pc riding on the DC USB power...but the end result is it doesn't matter as long as the DAC can handle this junk and the ODAC does this nicely.
  
 I have used powered USB hubs as well and I can not hear any detectable audio differences.
  
 I would not sweat this at all...unless you have some real audible distortion or noise its not going to get any better or worse with most well designed USB pc power sources...
  
 enjoy!
  
 Alex


----------



## glunteer

adydula said:


> I don't think there are measurements comparing different USB or other power sources.
> 
> What you should be thinking about is how the ODAC was designed and does it meet the design criteria that that the designer was aiming for and that is a genuinely transparent DAC.
> 
> ...


 
     


  

    
 Very good your comment !


----------



## conheo

nabwong said:


> Here you go
> 
> http://www.amazon.com/Ravel-Piano-Concertos-etc-Thibaudet/dp/B0000042EU/ref=sr_1_2?ie=UTF8&qid=1390406694&sr=8-2&keywords=thibaudet+ravel
> 
> ...


 

 Base on the youtube link...I try with HD650 / K601 / HD800 out from ODAC/O2, 2.5x gain, computer vol max, my room is very quiet and has a relax atmosphere  . The music is playing nice with the volume knob around 9h30-11, at 11 is really loud for me. Let's just say i don't have any hearing problem as i go to doctor not long before. 
  
 maybe you use tooooo difficult headphone to drive......like vintage AKG or HE6 ? That why you need too much gain like this.


----------



## nabwong

conheo said:


> Base on the youtube link...I try with HD650 / K601 / HD800 out from ODAC/O2, 2.5x gain, computer vol max, my room is very quiet and has a relax atmosphere  . The music is playing nice with the volume knob around 9h30-11, at 11 is really loud for me. Let's just say i don't have any hearing problem as i go to doctor not long before.
> 
> maybe you use tooooo difficult headphone to drive......like vintage AKG or HE6 ? That why you need too much gain like this.




Without sounding like an A-hole, I explained before that the cd and the ripped cd is the one that has the low volume. 

The YouTube link is fine. The spotify is fine. The cup-string-cup-headphone out is fine. I am not hearing impaired. I'm 35 with perfect hearing except when the wife is talking. Then all bets are off.


----------



## conheo

that is clear now anyway. that why i ask for providing the link....bad luck it is the "loud version"


----------



## nabwong

conheo said:


> that is clear now anyway. that why i ask for providing the link....bad luck it is the "loud version"




Haha no worries. Just joking. I wish the cd is louder anyway.


----------



## jring

nabwong said:


> Without sounding like an A-hole, I explained before that the cd and the ripped cd is the one that has the low volume.
> 
> 
> 
> ...


 
  
 Can't help with the selective hearing in regard to your significant other which seems to be a common problem 
 But for the interestingly mastered CD - why don't you rip it to wav or flac and normalize it in audacity?
  
 Joachim


----------



## nabwong

jring said:


> Can't help with the selective hearing in regard to your significant other which seems to be a common problem
> But for the interestingly mastered CD - why don't you rip it to wav or flac and normalize it in audacity?
> 
> Joachim




Good idea. I'm fine with it. Makes the 6.5x seem useful. Haha.


----------



## Spidermeng

hi,

 May i know STANDALONE ODAC can directly play with ipad air > cck > STANDALONE odac > amp ? (without any usb hub)


----------



## AsianBatman

spidermeng said:


> hi,
> 
> May i know STANDALONE ODAC can directly play with ipad air > cck > STANDALONE odac > amp ? (without any usb hub)


 
  
 The only connection the ODAC has is via usb.


----------



## miceblue

spidermeng said:


> hi,
> 
> 
> May i know STANDALONE ODAC can directly play with ipad air > cck > STANDALONE odac > amp ? (without any usb hub)



I've read that the ODAC works with the iPad, but I haven't heard anything about the iPad air. At least with my iPhone 4S, the power draw from the ODAC is too much and it doesn't work without a USB hub.


----------



## ILoveGrado

It should work, but you gonna need linear usb power supply to power the ODAC


----------



## locksbury

Hi
  
 I'm thinking of DIYing my own O2+DAC combo in order to give a audio standard across all my PCs. Being in the UK, it appears Headnhifi have the best prices for the kits, but I was wondering if anyone has ordered stuff from them for delivery in the UK and whether that attracted any extra taxes?
  
 It'd be nice not to have a sting in the tail after saving a good amount of building the combo myself.


----------



## ProTofik

locksbury said:


> Hi
> 
> I'm thinking of DIYing my own O2+DAC combo in order to give a audio standard across all my PCs. Being in the UK, it appears Headnhifi have the best prices for the kits, but I was wondering if anyone has ordered stuff from them for delivery in the UK and whether that attracted any extra taxes?
> 
> It'd be nice not to have a sting in the tail after saving a good amount of building the combo myself.


 
 I did order from them 3 or 4 times and got taxed only once. The only way to avoid taxes is to get lucky.


----------



## rikaldrey

You pay extra taxes from item from Switzerland? I thought they are with EEA something? He has a new design this year. Clean front plates, and some extra rca i/o at the back.


----------



## ProTofik

rikaldrey said:


> You pay extra taxes from item from Switzerland?


 
 Yes. I don't understand it myself but it can't be helped.
 I don't mind paying taxes but £8 royalmail fee is way too much, especially when the tax itself is £3.


----------



## hekeli

Switzerland is not EU so taxes apply. But if you choose "*Weekly Priority Mail*" as delivery option, it's sent from Germany every Wednesday, so no taxes. I guess this is a bit obscured info so many people don't realize it.


----------



## rikaldrey

hekeli said:


> Switzerland is not EU so taxes apply. But if you choose "*Weekly Priority Mail*" as delivery option, it's sent from Germany every Wednesday, so no taxes. I guess this is a bit obscured info so many people don't realize it.


 
 Thanks for this info.
  


protofik said:


> Yes. I don't understand it myself but it can't be helped.
> I don't mind paying taxes but £8 royalmail fee is way too much, especially when the tax itself is £3.


 

 I don't mind paying the extra fee to Royal Mail as they are doing this service. What is absurd is this service is the default, and they don't give information to people that there is a way around this. I am not from the UK but lived there for just 5 years, I get so irritated every time I hear this Royal Mail fee. Now, the way around this is to tell the sender to label the parcel with "Goods to be declared/cleared by the recipient" or something like that and your Customs will contact you directly and you would have to complete some forms and pay them directly. It's not worth 8GBP for 1 item.
  
 Back to topic, even with the extra fees it is still cheaper than buying locally. I think the only advantage of buying locally is if you value your country's economy. ;P


----------



## locksbury

Quote:


hekeli said:


> Switzerland is not EU so taxes apply. But if you choose "*Weekly Priority Mail*" as delivery option, it's sent from Germany every Wednesday, so no taxes. I guess this is a bit obscured info so many people don't realize it.


 
 I did spot this option and read about it on Headnhifis website, but just wanted to check.


protofik said:


> I did order from them 3 or 4 times and got taxed only once. The only way to avoid taxes is to get lucky.


 

 Just as I thought; I'll have to take my chances then.


----------



## jring

locksbury said:


> Quote:
> I did spot this option and read about it on Headnhifis website, but just wanted to check.
> 
> Just as I thought; I'll have to take my chances then.


 
  
 Well, if you use the EU shipping option there should be no duties or taxes for you since it's inside EU. At least that's what it was for me...
  
 Joachim


----------



## locksbury

jring said:


> Well, if you use the EU shipping option there should be no duties or taxes for you since it's inside EU. At least that's what it was for me...
> 
> Joachim


 

 Yeah, if the chap is popping over the border to Germany to post things, then no extra tax.


----------



## muscleking

my o2, odac have been running for 300+ hours with a DT1350. all i can say it's amazing. didn't sound good first later it gets better and better. not sure why. maybe some breakin and some mental break in. i really like this set up then xonar stx and ma900, however it's different with a open headphone.
  
 one question. when i put the miles davis trumpet on the o2 and odac it sounded like, completely wrong. why is that? anybody tried this? on the stx is ok. the sound is like muffled and like when you halfway plug an earphone sometimes in a player you hear partial sounds.


----------



## nabwong

muscleking said:


> my o2, odac have been running for 300+ hours with a DT1350. all i can say it's amazing. didn't sound good first later it gets better and better. not sure why. maybe some breakin and some mental break in. i really like this set up then xonar stx and ma900, however it's different with a open headphone.
> 
> one question. when i put the miles davis trumpet on the o2 and odac it sounded like, completely wrong. why is that? anybody tried this? on the stx is ok. the sound is like muffled and like when you halfway plug an earphone sometimes in a player you hear partial sounds.




Maybe cos miles never had a good sound?


----------



## adydula

muscle.....what cd / track exhibits this sound?
  
 I find that the o2 and odac follows the old adage "garbage in ..garbage out"...many songs I like have
 been recorded really crappy....etc...
  
 I look for the music I like that is well recorded and mastered....there is so much mediocre stuff out there...
  
 Alex


----------



## locksbury

Muhahahah, just got paid! Now to order that O2+ODAC kit in blue. The X3 can wait.


----------



## realityhas

I just bought the new O2 (the one with no battery and with RCA/ power/ input on the back) from headnhifi.com in Switzerland, because I live here.
*i can make some photos if you want, but you can find them here *http://www.headnhifi.com/O2-desktop-amplifier

 I'm quite happy, this is my first headphone amp and I was skeptical: turns out the difference is quite noticeable. But onestly, I'm more surprised by how good it looks than its sound 
	

	
	
		
		

		
		
	


	




. Anyway, now my chain is complete and I'm happy of its sound.
 I use it with the HE400 from hifiman.

 I'm just curious of 2 things, I'm sure you can answer me.

 1) Should i leave the jack in when I turn on the amp ? And when I turn it off? Should the volume be down to zero?

 2) The Odac light is always on, even when my pc is off, will this ruin it? How do you turn it off?



 And, just as a curiosity, for those of you that have the he400 with this amp, is 9'o clock a safe listening volume (with low gain). At what volume do you listen? I already have tinnitus on cold months (every year), I don't want to damage my earing  
  
  
 thank you


----------



## locksbury

realityhas said:


> I just bought the new O2 (the one with no battery and with RCA/ power/ input on the back) from headnhifi.com in Switzerland, because I live here.
> *i can make some photos if you want, but you can find them here *http://www.headnhifi.com/O2-desktop-amplifier
> 
> I'm quite happy, this is my first headphone amp and I was skeptical: turns out the difference is quite noticeable. But onestly, I'm more surprised by how good it looks than its sound
> ...


 

 1) As with any audio amplifier, to save any thump in your speakers/headphones and to save your own ears, especially if you accidentally left music playing and the volume is at full when you turn it on; you should always turn the control to minimum when turning it on or off. (Always was a good idea when I was doing stage crew at university!)
 2) As it appears you bought the mains powered version of the amp/dac combo, I think the LED on the front is the power indicator for the O2 amp section only and the ODAC board inside is powered from the USB on your PC. So you should be fine.
  
 HTH


----------



## realityhas

locksbury said:


> 1) As with any audio amplifier, to save any thump in your speakers/headphones and to save your own ears, especially if you accidentally left music playing and the volume is at full when you turn it on; you should always turn the control to minimum when turning it on or off. (Always was a good idea when I was doing stage crew at university!)
> 2) As it appears you bought the mains powered version of the amp/dac combo, I think the LED on the front is the power indicator for the O2 amp section only and the ODAC board inside is powered from the USB on your PC. So you should be fine.
> 
> HTH


 
 Thank you for your fast response 

 1) So, as long as i turn the volume down, I can leave the headphone jack inserted even when I turn it off ?

 2) I bough the O2 amp separate from the Odac. The O2 amp light is on ONLY when i turn it on with the front button. But the ODAC led is on all the time, even when the PC is off. The ODAC is connected only via usb, and it has no buttons so i cant turn it off


----------



## AsianBatman

realityhas said:


> Thank you for your fast response
> 
> 1) So, as long as i turn the volume down, I can leave the headphone jack inserted even when I turn it off ?
> 
> 2) I bough the O2 amp separate from the Odac. The O2 amp light is on ONLY when i turn it on with the front button. But the ODAC led is on all the time, even when the PC is off. The ODAC is connected only via usb, and it has no buttons so i cant turn it off


 
  
 It's fine to leave your headphone jack in, the O2 is pretty good at not making that pop noise that ruin headphones like some tube amps. I got my ODAC from mayflower electronics and does not have a led on it. I'm assuming your PC is fairly new and most motherboards have "charging" future that allows phones and such to be charged while the PC is off. It is safe and I don't believe there is a way to turn it off. My Audio-gd light stays on when I turn my PC off also.


----------



## realityhas

asianbatman said:


> It's fine to leave your headphone jack in, the O2 is pretty good at not making that pop noise that ruin headphones like some tube amps. I got my ODAC from mayflower electronics and does not have a led on it. I'm assuming your PC is fairly new and most motherboards have "charging" future that allows phones and such to be charged while the PC is off. It is safe and I don't believe there is a way to turn it off. My Audio-gd light stays on when I turn my PC off also.


 
  Yeah, I bought it this summer and it charges my phone too...

 Thank you both very much


----------



## adydula

Some PCs allow for thu USB port to be available even when powered down. for charging devices etc like was said here in earlier posts.
 If you want and have more USB ports you can try one that is not powered on.
  
 Some laptops etc have both powered and unpowered USB ports and some can be changed in the BIOS. Check with your PC manufacturer of website/manual etc.
  
 I don't think the ODAC being plugged in all the time and the light one really would hurt anything.
  
 Good practice is to always turn down the volume when inserting or removing the headphone plug.
  
 On my two O2 amps I usually turn down the volume, remove the plug and then turn it off. No thumps.
  
 Even with the O2 amp volume all the way down there is still a small thump to be heard.....I have several sets of cans,
 LCD2's, M50's, Grado 325is, AKG 701/702, Beyer DT 1350, Beyer T90's....none of them are harmed by this thump.
  
 Here is something to think about as well: Someone asked: Is keeping the power supply on 24/7 and switching (on or off) the DC supply to the amps at board level will minimize the thumps.
  
 The answer is yes and here are the cases to think about:
 (This is from another post on another forum fyi...)
 PM me if you want the link etc).
  
 Case I:
 You keep PS AC adapter ON 24/7 & use FP switch to turn amp ON/OFF-minimal thump.
  
 Case II:
 You turn AC adapter ON & use FP switch to turn amp ON/OFF-minimal thump (same as above).
  
 Case III:
 FP switch is in ON position & you turn ON AC adapter- Loud thump, worst case is AC half cycle.Even if you plan to keep AC power supply ON 24/7 there may be situation of momentarily supply failure (lasting just under a second) or brown outs resulting in large thumps. The batteries in O2 also act like "online UPS" to eliminate Case III type situation.C1(1uF) is also useful in reducing power ON thumps The "minimal thump" will still be more than O2 using standard BOM. BTW High impedance, low sensitivity h/p are more immune to power ON/OFF transients than low impedance, high sensitivity h/p e.g. IEMs.Other well designed desktop amps usually employ some sort of relay mechanism to connect h/p after the PS has stabilized & disconnect the h/p in case of supply failure/turn OFF/ DC at o/p type situation.
  
 A.


----------



## r010159

On another note, I am having a bit of apparent trouble with my JDSLabs O2/ODAC combo. I have left the unit on for days. Recently, I have noticed that when music is played, I sometimes get some distortion , in particular with vocals reaching high frequencies. Now I think this may not be the O2/ODAC. But I am not sure. The distortion sounds like rapid krincking of the cellophane wrapper on a pack of cigarettes. So this is happening in the analog part of the signal chain. This means its either the O2 part, the headphones, or possibly some connection that is loose or incomplete between the headphones and the O2, like the headphone jack. The jack on the headphones is a little dhort and may not be making a good connection I am just guessing here. What is interesting is that this problem can disappear, even at higher volumes. But I had turned the unit off for some time. So this may be temperature related.

Also, music can be intermittent. Part of the reason is the audio file. Another cause is when my poor Intel Duo is apparently being overtaxed when I am doing something else on the computer. There alao was a previous problem with iTunes doing this. So I need to look into this problem further.


----------



## MrMateoHead

r010159 said:


> On another note, I am having a bit of apparent trouble with my JDSLabs O2/ODAC combo. I have left the unit on for days. Recently, I have noticed that when music is played, I sometimes get some distortion , in particular with vocals reaching high frequencies. Now I think this may not be the O2/ODAC. But I am not sure. The distortion sounds like rapid krincking of the cellophane wrapper on a pack of cigarettes. So this is happening in the analog part of the signal chain. This means its either the O2 part, the headphones, or possibly some connection that is loose or incomplete between the headphones and the O2, like the headphone jack. The jack on the headphones is a little dhort and may not be making a good connection I am just guessing here. What is interesting is that this problem can disappear, even at higher volumes. But I had turned the unit off for some time. So this may be temperature related.
> 
> Also, music can be intermittent. Part of the reason is the audio file. Another cause is when my poor Intel Duo is apparently being overtaxed when I am doing something else on the computer. There alao was a previous problem with iTunes doing this. So I need to look into this problem further.


 

 Check your "buffer" settings on your audio player. I had stuttering with Foobar until I set a pretty high buffer (like a full 1 second).
  
 Surest solution for the static problem:
 1) Download Audacity
 2) Drag and drop audio file with static into audacity window
 3) Select View > Show Clipping
 4) Notice the presence or lack of the color red
  
 What you are hearing is the O2/ODAC playing back the Clipped audio present in the recording itself. The resolution of the thing is so damn high, it can actually do this. I thought my headphones were going bad when I started noticing it. Generally speaking however, it has more to do with the overly "Hot" (compressed) recordings that have been put out over and over again into the world. I am sorry to say that there is no real cure for it. Sometimes you can get lucky and there is another version of the recording to check out. But, generally, the clipping is at the recording level so it is beyond control.
  
 Interestingly, I usually see clipped vocals if the artist is a female. Clipped music is usually in the rock / metal recordings as they assume that no dynamic range is awesomer than some dynamic range. Pop recordings are usually well done because I think there is more money to spend getting it right. Garage bands seem to try to save a few bucks and boy, it can really ruin an otherwise great album.


----------



## r010159

I thank you for you reply. This sounds like the problem The specific instance I remember is with female vocals. Next time I hear it, I will put it through Audacity. The O2/ODAC combo is turning out to be a real good purchase of mine!


EDIT:

PS: What is the difference between the headphone input and the line input? Also, is the higher gain setting really a bass boost?


----------



## jring

r010159 said:


> I thank you for you reply. This sounds like the problem The specific instance I remember is with female vocals. Next time I hear it, I will put it through Audacity. The O2/ODAC combo is turning out to be a real good purchase of mine!
> 
> 
> EDIT:
> ...


 
  
 Hi,
  
 the O2 should have a Line-In and a Headphone-Out. The ODAC just has a Line-Out, sometimes not even that if it is integrated in the same enclosure as the amp.
  
 The gain switch does not boost the bass but switches the amp to a different and usually higher voltage gain. This is for sources with a low input voltage like a cellphone and with the default 6.5x with pressed gain switch and an ODAC as a source, the amp will clip regardless of the volume pot setting if the digital volume is at 100%.
  
 Joachim


----------



## ShenaRingo326

jring said:


> Hi,
> 
> the O2 should have a Line-In and a Headphone-Out. The ODAC just has a Line-Out, sometimes not even that if it is integrated in the same enclosure as the amp.
> 
> ...




Actually if you have the JDS labs o2+odac combo, when the o2 amp power is off, the line in jack functions as the line out of the odac, so you can connect it to another amp.

When the o2 power is on, the line in jack functions as the line in for the o2 amp, and you can actually send signals to the o2 at the same time from both odac and line in.


----------



## locksbury

Now that my O2+ODAC DIY parts are on order from headnhifi.com, I can't wait to see what new detail in my music I discover with my Grado SR-60s. 
	

	
	
		
		

		
		
	


	



  
 In the meantime I have questions:
  
 a) Most of my music collection is sampled at 16/44.1, but I understand DVDs are at 16/48 and I recently got some 24/96 tracks (only cause they were free), so would it be best to set the ODAC to rates to 24/96 and let the OS do any re-sampling as required?
  
 b) I'm going to use the amp/dac combo across all my PCs (win7 gaming rig, mac mini and linux laptop). Has anyone used the ODAC with linux?


----------



## Dano91

r010159 said:


> I thank you for you reply. This sounds like the problem The specific instance I remember is with female vocals. Next time I hear it, I will put it through Audacity. The O2/ODAC combo is turning out to be a real good purchase of mine!
> 
> 
> EDIT:
> ...


 
 It's not a bass boost and you really shouldn't be using higher gain with ODAC (only in special circumstances), because it can make distortions / clipping. The problems you described earlier sounds just like that to me.
 Higher gain is meant to be used with low power devices like mobiles etc..


----------



## jring

locksbury said:


> Now that my O2+ODAC DIY parts are on order from headnhifi.com, I can't wait to see what new detail in my music I discover with my Grado SR-60s.
> 
> 
> 
> ...


 
  
 I'm listening to it atm on my laptop with ubuntu 12.04 lts. Works out of the box as with all other linux systems with usb audio drivers... I also have it at my goflex nas with debian sometimes...
  
 About bit depth and sample rate, people are bound to disagree... after all resampling and multiplying is not exactly bit-perfect... that being said I'm lazy and use it on 24bit default (and whatever sample rate the file has) so I can use soft-volume without loosing resolution.
  
 Joachim


----------



## jring

shenaringo326 said:


> Actually if you have the JDS labs o2+odac combo, when the o2 amp power is off, the line in jack functions as the line out of the odac, so you can connect it to another amp.
> 
> When the o2 power is on, the line in jack functions as the line in for the o2 amp, and you can actually send signals to the o2 at the same time from both odac and line in.


 
  
 Ouch, two sources working against each other sounds - not such a good idea... mine is self built from a head'n'hifi kit and I used the switched input jack to connect ODAC to O2 only when no plug is in.
  
 I'll probably put on the 3.5mm smt jack on the pads on the ODAC board and drill a hole in the backplate as line-out but then one would have to put a blank jack inside the line-in in order to open the connection to O2 when using ODAC alone (especially with the amp off one would not like its inputs in the circuit). Or I need to find a 3.5mm switched stereo jack in SMT and a similar pad layout as the one used in ODAC... I actually found one some time ago after long googling but available in quantities only 
  
 Joachim


----------



## r010159

It looks like I damaged my unit. I went to get up and walk away from the desk, still within reach of the line to my headphones. I did not know it, but the chord was wrapped around my foot. This ended up yanking the unit off the desk and disconnecting the USB cable. This twisted the socket of the microUSB and broke it off to roll around inside of the unit. 

I contacted JDSLabs and they quickly replied, like within an hour. I need to ship the unit in for repair. If the unit cannot be repaired, they will sell me a discounted DAC board. I hope this will not take long.

Bob Graham

EDIT:

I will keep everyone informed how JDSLabs handles this problem.


----------



## adydula

JDS is very good at customer service.
  
 I am sure they will repair if possible or sell you a new ODAC discounted as you indicate they said.
  
 However...remember you had this accident, not them.....its not a JDS issue there at all....
  
 We all have done stupid things like this....ME included.
  
 Be careful!!
  
 A.


----------



## jhao19

I was just wondering if the O2 would be able to drive desktop speakers?  The Klipsch 2.1 ProMedia to be exact.  I'm guessing yes, as the speakers themselves are also self powered, right?


----------



## gikigill

Get the ODAC to power the speakers. The speakers have the amp so you just need a DAC.


----------



## jhao19

gikigill said:


> Get the ODAC to power the speakers. The speakers have the amp so you just need a DAC.


 
 I actually have a Xonar DX to act as my DAC in my computer


----------



## jhao19

Would it be bad to have the audio go from
  
 Xonar DX -> O2 -> Speakers?


----------



## gikigill

Then you don't need the ODAC.


----------



## ILoveGrado

jhao, you can do that, but there is no point in doing that and you also are running the risk of clipping the O 2 input stage and damaging your speakers


----------



## AsianBatman

@jhao19 There really is no point in doing that. You will just amplify whatever distortion your Xonar is outputting.


----------



## jhao19

ilovegrado said:


> jhao, you can do that, but there is no point in doing that and you also are running the risk of clipping the O 2 input stage and damaging your speakers


 
 It's mostly for simplicity reasons, as I have a port switcher attached to the output of the O2, and this way I can easily switch between headphones and speakers.  As long as I don't turn on the gain setting for my O2, I don't think I hear any clipping.  Will my speakers be safe as long as I don't blast my volume?
  


asianbatman said:


> @jhao19 There really is no point in doing that. You will just amplify whatever distortion your Xonar is outputting.


 
 But then I wouldn't have a DAC, and my motherboard audio isn't the best =\.  Is it really bad?  I don't think I hear any distortion (at least no buzzing/hissing or anything)


----------



## gikigill

The Asus has a built in DAC.
  
 You,re only amplifying the signal twice which amplifies the noise twice too.


----------



## AsianBatman

jhao19 said:


> It's mostly for simplicity reasons, as I have a port switcher attached to the output of the O2, and this way I can easily switch between headphones and speakers.  As long as I don't turn on the gain setting for my O2, I don't think I hear any clipping.  Will my speakers be safe as long as I don't blast my volume?
> 
> But then I wouldn't have a DAC, and my motherboard audio isn't the best =\.  Is it really bad?  I don't think I hear any distortion (at least no buzzing/hissing or anything)


 
 I'm really confused. Do you have the O2/Odac combo or separate components? Xonar (Dac) --> O2 --> speakers. If you don't hear anything then I guess it doesn't hurt if that is the setup you are going with.


----------



## r010159

adydula said:


> JDS is very good at customer service.
> 
> I am sure they will repair if possible or sell you a new ODAC discounted as you indicate they said.
> 
> ...




Well, I am impressed. I am not easily impressed. I shipped my unit in Monday. JDS Labs received it Wednesday. They repaired it and shipped it back the same day, using second day air. I will be receiving it this Friday, tomorrow.

Bob Graham

EDIT: Also, they are not charging me anything, even for the 2nd day shipping back to me.


----------



## jhao19

asianbatman said:


> I'm really confused. Do you have the O2/Odac combo or separate components? Xonar (Dac) --> O2 --> speakers. If you don't hear anything then I guess it doesn't hurt if that is the setup you are going with.


 
 No ODAC, just the O2.  I don't own an ODAC.  And cool, maybe I just don't have a trained enough ear to pick up all the doubly amplified noise or something?  I just wanted to make sure all my components were safe


----------



## ILoveGrado

jhao if you are careful with the volume , you should be okay.


----------



## ILoveGrado

in that case, it is not the O2 that drives your speakers...what your speakers "see" is just the output of its internal amp..no matter what you put before the internal amp...unless you remove the internal amp, it will become unecessary for you to put O2 in the signal chain. in which case I dont think o2 is capable of driving a desktop speaker. I recommend removing the O2 and use it for something better


----------



## jhao19

ilovegrado said:


> in that case, it is not the O2 that drives your speakers...what your speakers "see" is just the output of its internal amp..no matter what you put before the internal amp...unless you remove the internal amp, it will become unecessary for you to put O2 in the signal chain. in which case I dont think o2 is capable of driving a desktop speaker. I recommend removing the O2 and use it for something better


 
 Haha, yeah, the O2 is only there for convenience sake, as my headphones are connected to a signal mux.  So what's actually going on is this.
                                                                                                
                                                                                                                                -> Desktop Speakers
 Xonar DX -> O2 -> audio switcher (makes it so I can pick which device my audio goes into) -<
                                                                                                                                -> K702's
  
 This way I can switch back and forth with a simple twist of a dial!


----------



## locksbury

In a similar (but digital) vein to jhao19's switchable setup...
  
 I have two PCs at my desk, one is a Mac Mini (on top of the desk itself) and my Windows PC (where I've got the USB hub in my monitor cabled to one of the root USB sockets on the motherboard) and I'm aiming to use an O2+ODAC as a common sound platform for both.
  
 So, whilst I can try swapping the ODAC USB input lead between my monitor or windows pc directly and Mac Mini to essentially 'swtich' the input; I was wondering if anyone has run their ODAC through a USB routing switch?


----------



## adydula

The O2 amp was not designed to drive speakers...that would be like using a Porsche to pull a load designed for a MAC truck....not a good idea at all.
  
 Its a headphone amp....and even then there are headphones that the O2 doesn't handle really well as 98% of the other cans out there.
  
 Take a search on DIYAUDIO and read all about it etc...
  
 A.


----------



## AsianBatman

adydula said:


> The O2 amp was not designed to drive speakers...that would be like using a Porsche to pull a load designed for a MAC truck....not a good idea at all.
> 
> Its a headphone amp....and even then there are headphones that the O2 doesn't handle really well as 98% of the other cans out there.
> 
> ...


 
  
 An Amp is essential a wire with gain. For his intended purpose, it is fine. He isn't powering passive speakers, but active ones.


----------



## glunteer

jhao19 said:


> Haha, yeah, the O2 is only there for convenience sake, as my headphones are connected to a signal mux.  So what's actually going on is this.
> 
> -> Desktop Speakers
> Xonar DX -> O2 -> audio switcher (makes it so I can pick which device my audio goes into) -<
> ...


 
  
 Should use so:
  
                                                                                                -> Desktop Speakers
 Xonar DX -> *audio switcher (makes it so I can pick which device my audio goes into)* -> O2 -< K702's


----------



## adydula

An amp is theoretically a straight wire with gain when its built correctly etc....but when you attach a load on the output of the amp it affects the amp and its circuitry.....
  
 Taking a look on DIYAudio isn't necessary but for those that want to just may be know a little more or learn something it can be a very interesting journey....but hey lots of us a happy just being appliance operators...
  
 All the best
 Alex


----------



## AsianBatman

adydula said:


> An amp is theoretically a straight wire with gain when its built correctly etc....but when you attach a load on the output of the amp it affects the amp and its circuitry.....
> 
> Taking a look on DIYAudio isn't necessary but for those that want to just may be know a little more or learn something it can be a very interesting journey....but hey lots of us a happy just being appliance operators...
> 
> ...


 
  
 Thanks.....


----------



## r010159

I just received me O2D back from repair. This works was well as it did before that unfortunate event of it jumping off of my desk and damaging itself.  One day turnaround time at JDS Labs and return by the end of the same week, not bad!
  
 ...detailed punchy bass, nice crisp treble, well-defined midrange...it pays to have a capable amp for my DT880s. IMO this is a good pairing.
  
 Bob Graham


----------



## adydula

Glad your back online Bob!!
  
 I have several Beyers and the O2 and ODAC are absolutely superb with them IMO.
  
 Listening with DT1350's right now...gosh these are great little cans...
  
 All the best
 Alex


----------



## James-uk

I've just notice that in mac audio midi the output to odac is locked at 16 bit. I can't change it to 24 bit? Any ideas?


----------



## r010159

I do not think you will find a difference in SQ from a 16-bit source. However, I recently started to use a player on my Mac that bypasses the limitations of Core Audio and runs the O2D at 24-bit 96K. Good audio software must do the same in the form of special device drivers. I think the most benefit to be had is by bypassing Core Audio of the Mac.

Bob Graham


----------



## James-uk

r010159 said:


> I do not think you will find a difference in SQ from a 16-bit source. However, I recently started to use a player on my Mac that bypasses the limitations of Core Audio and runs the O2D at 24-bit 96K. Good audio software must do the same in the form of special device drivers. I think the most benefit to be had is by bypassing Core Audio of the Mac.
> 
> Bob Graham



Thanks for the reply, I only prefer 24bit so I can use software volume with headroom to spare. What's the name of the software you are using?


----------



## r010159

It is Audirvana Plus. AP compared with its rival is more inexpensive at $70. Even though it is complete with the audio performance settings, its UI functionality is lacking. You can use iTunes to manage your audio library, but there are glitches when using it as an player integrated with iTunes. I use it in standalone mode.
  
 Bob Graham
  
 EDIT: There is an emphasis on some higher freqs with Audirvana, one IMO being at about the 5K point.


----------



## adydula

With my music player I can drop the bits down from 16, one bit at a time, I have done this several times and I do not hear any audible differences until I get down to 8-10 bits....amazing.
  
 Alex


----------



## r010159

adydula said:


> With my music player I can drop the bits down from 16, one bit at a time, I have done this several times and I do not hear any audible differences until I get down to 8-10 bits....amazing.
> 
> Alex




Must be very good dithering software with the player.

EDIT: It looks like the O2D supports integer mode.

Bob Graham


----------



## r010159

I hope all is doing well! I have a question. I am looking at a second pair of headphones for my mother. She does appreciate good headphones. I am deciding between the HD600s and the HE-4s. Do any of these two work well with the O2D? Anyone know the difference between the two?
  
 Bob Graham


----------



## skeptic

r010159 said:


> I hope all is doing well! I have a question. I am looking at a second pair of headphones for my mother. She does appreciate good headphones. I am deciding between the HD600s and the HE-4s. Do any of these two work well with the O2D? Anyone know the difference between the two?
> 
> Bob Graham


 
  
 Difference boils down to one being a high ohm dynamic and the other a low ohm ortho.  While I like my bedside odac->o2 quite well with my alpha dogs, westone 4's and, to a lesser extent, my dt880's, I don't care much at all for the combo with my hd650's or hd800's.  The Senns just sound much better from my bottlehead amps.  hd600's are fairly similar to hd650's, so I wouldn't recommend either to be paired with the O2D.


----------



## PTom

Anyone tried the O2 with the beyerdynamic T1? Any good?


----------



## headwhacker

ptom said:


> Anyone tried the O2 with the beyerdynamic T1? Any good?




O2 can properly drive T1. I use DX50 as source and the 2.5X gain provides loud enough but noise/distortion free sound. O2 is quite flat and neutral. T1 will let you hear what the source feeds it thru O2.


----------



## PTom

The epiphany acoustics O2 is battery powered so I am wondering if it will have as much power as say the FiiO E9, matrix mstage, schiit magni etc.


----------



## Dano91

r010159 said:


> I hope all is doing well! I have a question. I am looking at a second pair of headphones for my mother. She does appreciate good headphones. I am deciding between the HD600s and the HE-4s. Do any of these two work well with the O2D? Anyone know the difference between the two?
> 
> Bob Graham


 
 I'm using HD 600 with O2+odac and I simply love that combination. Difference between those two is that hd 600 are more neutral/linear, easier to drive and more comfortable for long listening, HE-4 has better bass.


----------



## Dano91

ptom said:


> The epiphany acoustics O2 is battery powered so I am wondering if it will have as much power as say the FiiO E9, matrix mstage, schiit magni etc.


 
 I don't know about matrix, but E9 and magni has more power, but the real question is, if you really need that more power? Simple answer is no, you don't, because O2 can drive 99% of all headphones to crazy  volumes.. (That can be calculated with quite simple math)


----------



## PTom

Thanks for the reply Dano91. My main concern is that the T1 has a really high impedance i.e. close to 1400 ohm at mid bass frequencies (http://www.innerfidelity.com/images/BeyerdynamicT1.pdf) so I'm guessing they would require rather large voltages to drive properly?


----------



## chococya96

It seems like O2+ODAC combo is not self-powered via AC instead, uses USB as power source (it only powers the amp).
  
 I always had a impression that it was self-powered but... Oh stupid me.


----------



## jring

chococya96 said:


> It seems like O2+ODAC combo is not self-powered via AC instead, uses USB as power source (it only powers the amp).
> 
> I always had a impression that it was self-powered but... Oh stupid me.


 
  
 In the O2+ODAC combo the battery space is usually taken up by the ODAC board (although other solutions exist either with a larger box or creative packaging). The O2 part is then powered by the wall wart (or batteries if these are still present) and the ODAC is always USB powered.
  
 Joachim


----------



## Dano91

ptom said:


> Thanks for the reply Dano91. My main concern is that the T1 has a really high impedance i.e. close to 1400 ohm at mid bass frequencies (http://www.innerfidelity.com/images/BeyerdynamicT1.pdf) so I'm guessing they would require rather large voltages to drive properly?


 
 Not really, in fact voltage requirement is depended only on headphone's sensitivity which doesn't necessarily correlates with hp's impedance curve. Look here: http://doctorhead.ru/upload/iblock/efd/fr.png
 At 500 Hz it has higher sensitivity than on 1 kHz despite being higher impedance on 500 Hz.
  
 In worst case they measured sensitivity of 96 dB/V and at best 109.9 dB/V. Which means that for playing 110 dB you would need 5.01 V in worst case and 1.01 V in best case and in average it's 3.13 V. O2 amp max output is 7.15 V, but exact number depends on used source and gain.
 Feel free to ask more if you are interested 
  
 P.S: Beyers T1 has a relatively hot treble which when used with O2 can make some not very pleasing sound.


----------



## Xenophon

I own the Epiphany acoustics DAC/Amp implementation of the O2 and while it's extremely good for its price, it's not the end-all in terms of quality amplification.  You'll be able to drive most headphones loud, yes.  But loudness is only part of the equation, as are voltage swing and current considered independently.
  
 I owned the DT-880's in 600 ohm, sold them since as I upgraded my headphones and after auditioning I came to the conclusion that the BD 'house sound signature' was not my cup of tea (just a matter of taste, no reflection on quality).  
  
 They worked well with the O2-stack but occasionally it just ran out of steam.  You don't just need gain (voltage), the power source needs to be able to *supply* sufficient *power* to meet demand and with high impedance cans or low sensitivity ones, especially listening to music with a large dynamic range (classical) the O2 just isn't enough, distortion will start popping up and hitting the gain button only makes that worse, what you need is power on tap and that simply doesn't come in small packages with small power supplies, sorry.  Take a look at the distortion graphs on the designer's site.
  
 Having said this, I still use this little dac/amp daily in my office and it's a sight better in terms of SQ compared to the FiiO combo imho.


----------



## PTom

From the last two posts it seems that it would be better to go for another amp for my T1. Any suggestions in the under £200 ($300) range?


----------



## Xenophon

Sub 200 GBP will be tough for something half decent, I'm assuming you only need the amp, not the DAC.  
  
 I'd advise the classifieds here or ebay, what you could also do is pick up a used stereo receiver or small low-power speaker amp and run the T1 from the speaker taps but I can't recommend anything in particular as I don't own the T1 so can't say anything about good pairings.  
  
*Caution:  if you go the speaker amp way you can save lots of cash and get great sound BUT research it well and be sure to understand all aspects of it before proceeding as this has the potential to blow up your eardrums, the headphone and/or the amp.*


----------



## Dano91

Regarding O2 power capabilities I have one question - according to designer's site, O2 is able to produce 7.15V when powered from AC. In a same time designer states that max input voltage before clipping is 7.15 / GainValue.
 Does this mean that when used with ODAC, which has 2V output and standard O2 gain options (2.5x and 6.5x) you can produce 5V on output at 2.5x gain? This will also mean if we want to reach that 7.15V limit with 2.5x gain, we have to use some other source capable of outputting cca 2.8V ?


----------



## headwhacker

dano91 said:


> Regarding O2 power capabilities I have one question - according to designer's site, O2 is able to produce 7.15V when powered from AC. In a same time designer states that max input voltage before clipping is 7.15 / GainValue.
> 
> 
> Does this mean that when used with ODAC, which has 2V output and standard O2 gain options (2.5x and 6.5x) you can produce 5V on output at 2.5x gain? This will also mean if we want to reach that 7.15V limit with 2.5x gain, we have to use some other source capable of outputting cca 2.8V ?



 


Gain is a logarithmic value. The formula if I remember it right is 20(Log X)

X is the gain value. 

To put that into O2 + ODAC perspective. If O2 is powered from an AC adapter It can supply as high as 7V to a load and if powered by battery can only go as high 4.5V.

7V(O2) / 2V (ODAC) = 3.5X

Means O2 can amplify ODACs sgnal at max 3.5X gain without clipping.

20 (Log 3.5 ) = 10.88 dB

I used this online tool to get the gain in V (http://www.sengpielaudio.com/calculator-gainloss.htm)

= 3.5V


----------



## Dano91

headwhacker said:


> dano91 said:
> 
> 
> > Regarding O2 power capabilities I have one question - according to designer's site, O2 is able to produce 7.15V when powered from AC. In a same time designer states that max input voltage before clipping is 7.15 / GainValue.
> ...


 
 I think voltage gain is measured either in dB or as a ratio (eg. 3.5x), not in V directly, since gain is Vout/Vin, but maybe I'm wrong with this, nevertheless lets assume that I have only odac+o2 and some "voltage hungry" hp which will need 7V.
 So I will have these two options - change the O2 gain internally to 3.5x so I get 2V (odac) * 3.5x (gain in o2) = 7V on output OR 2nd option to use higher default gain in o2 (6.5x) but lower the output from odac to 7/6.5 = 1.08V lets say by lowering the volume in PC?
 Is this assumption correct?


----------



## r010159

What is difference in SQ between the O2 + ODAC and the C5D?  I am thinking of purchasing JDS Labs portable amp and pair it with either the HD600 or HE-4.
  
 Bob Graham


----------



## Xenophon

On a very quick view I think that specs wise they're comparable.  (As I said, a very quick look, do your homework).  
  
 The HE-4 has a 86 dB sensitivity, that's less than the HE-500 which I own and the HE-500 can't be driven to its potential on the O2 so for sure this will not be the perfect combo, you'll need something morte powerful.
  
 From the Headdphonics review:
  
 "Be under no illusion though that just because its 50% less magnets and has a $450 price tag this headphone is not necessarily much easier to drive and that this level of musicality can be easily obtained under regular amping conditions. The HE4 still requires a good amp to maximize it’s potential. Tested out of a Go Vibe Vulcan+ and and headphone out of the Maverick D1 Dac/Amp it didn’t do it justice instead giving it a very thinned out experience even when tuned to the max."
  
This corresponds with what I think so I wouldn't advise you to do this.


----------



## r010159

xenophon said:


> On a very quick view I think that specs wise they're comparable.  (As I said, a very quick look, do your homework).
> 
> The HE-4 has a 86 dB sensitivity, that's less than the HE-500 which I own and the HE-500 can't be driven to its potential on the O2 so for sure this will not be the perfect combo, you'll need something morte powerful.
> 
> ...




OK. I guess it is the HD600. The F**o that I have broke today. Battery refuses to charge which is a common problem with products from this maker. So I will need to order the C5D today. Now, what source do you recommend? Something small at least transportable, and hopefully does not cost over $100?

EDIT: I just ordered the C5D!

Bob Graham


----------



## miceblue

r010159 said:


> What is difference in SQ between the O2 + ODAC and the C5D?  I am thinking of purchasing JDS Labs portable amp and pair it with either the HD600 or HE-4.
> 
> Bob Graham



The O2/ODAC combo sounds more transparent to me compared to the C5D; mostly a larger soundstage, better instrument separation. The overall sound signatures are about the same though, the C5D sounding a tad bit warmer and the midrange a bit more forward. If you're looking for a portable O2/ODAC unit, the C5D is great in that regards.

As for the HD600, I'm not too sure, but both the C5D and the O2/ODAC pair well with the HD650, as I just tried out yesterday. I tried the HE-4 with the O2/ODAC at a mini-meet recently, and they seem lacking in bass. I think the bass boost of the C5D can come in handy in that case.


----------



## miceblue

xenophon said:


> On a very quick view I think that specs wise they're comparable.  (As I said, a very quick look, do your homework).
> 
> The HE-4 has a 86 dB sensitivity, that's less than the HE-500 which I own and the HE-500 can't be driven to its potential on the O2 so for sure this will not be the perfect combo, *you'll need something morte powerful.*
> 
> ...



Can you explain this? One of my friends has an Emotiva amp and although it sounds great with the HE-4, I really need to turn down the source's digital volume to get the HE-4 to sound quiet enough for my listening sessions (otherwise my ear drums would blow out).

Planar magnetics needing a speaker amp to sound their best is a myth to me. I just tried the Emotiva with the the V-MODA Crossfade M-100. The M-100 has a dynamic driver and is not a difficult load on the amp at all. The same effects I heard from the HE-4 from the O2 to the Emotiva can be heard with the M-100; so headphones don't require a powerful amp at all. Heck, the O2 gives me plenty of head-room to play with even at 1.0x gain: I was running it with the volume knob at around 12 o'clock with most of my music.


----------



## r010159

miceblue said:


> The O2/ODAC combo sounds more transparent to me compared to the C5D; mostly a larger soundstage, better instrument separation. The overall sound signatures are about the same though, the C5D sounding a tad bit warmer and the midrange a bit more forward. If you're looking for a portable O2/ODAC unit, the C5D is great in that regards.
> 
> As for the HD600, I'm not too sure, but both the C5D and the O2/ODAC pair well with the HD650, as I just tried out yesterday. I tried the HE-4 with the O2/ODAC at a mini-meet recently, and they seem lacking in bass. I think the bass boost of the C5D can come in handy in that case.




I am looking for a portable unit for a couple of reasons. Otherwise, I would get the O2/ODAC unit. For that matter, the particular user of the C5D is not that discriminating. It is good that the HD650 pairs well with this DAC/amp.

Thanks for your reply!

Bob Graham


----------



## r010159

miceblue said:


> Can you explain this? One of my friends has an Emotiva amp and although it sounds great with the HE-4, I really need to turn down the source's digital volume to get the HE-4 to sound quiet enough for my listening sessions (otherwise my ear drums would blow out).
> 
> Planar magnetics needing a speaker amp to sound their best is a myth to me. I just tried the Emotiva with the the V-MODA Crossfade M-100. The M-100 has a dynamic driver and is not a difficult load on the amp at all. The same effects I heard from the HE-4 from the O2 to the Emotiva can be heard with the M-100; so headphones don't require a powerful amp at all. Heck, the O2 gives me plenty of head-room to play with even at 1.0x gain: I was running it with the volume knob at around 12 o'clock with most of my music.




I think even though headphones can sound good without a more powerful amp, with some phones there is a better transient response, particularly with the bass. But this is just my impression. FWIW I also find the 12-o'clock volume position to be plenty loud to me at the low gain setting.

Bob Graham


----------



## r010159

miceblue said:


> The O2/ODAC combo sounds more transparent to me compared to the C5D; mostly a larger soundstage, better instrument separation. The overall sound signatures are about the same though, the C5D sounding a tad bit warmer and the midrange a bit more forward. If you're looking for a portable O2/ODAC unit, the C5D is great in that regards.
> 
> As for the HD600, I'm not too sure, but both the C5D and the O2/ODAC pair well with the HD650, as I just tried out yesterday. I tried the HE-4 with the O2/ODAC at a mini-meet recently, and they seem lacking in bass. I think the bass boost of the C5D can come in handy in that case.




This is good to know. Right now the ODAC/O2 with some music had me looking around the room when there were spoken words in the recording. I also reached for my phone when I heard a sound that seemed to be coming from my cell phone. Yes, the O2 is transparent. 

Bob Graham


----------



## Xenophon

miceblue said:


> Can you explain this? One of my friends has an Emotiva amp and although it sounds great with the HE-4, I really need to turn down the source's digital volume to get the HE-4 to sound quiet enough for my listening sessions (otherwise my ear drums would blow out).
> 
> Planar magnetics needing a speaker amp to sound their best is a myth to me. I just tried the Emotiva with the the V-MODA Crossfade M-100. The M-100 has a dynamic driver and is not a difficult load on the amp at all. The same effects I heard from the HE-4 from the O2 to the Emotiva can be heard with the M-100; so headphones don't require a powerful amp at all. Heck, the O2 gives me plenty of head-room to play with even at 1.0x gain: I was running it with the volume knob at around 12 o'clock with most of my music.


 
 To get the full explanation you'd have to get the input of an amp builder, which I'm not.  But I'll try paraphrasing what some people here on Head-Fi who are no fools explained and what a personal friend of mine who's a conductor and owns audiophile equipment worth a rather big house + an engineer have explained me.  But first two points in the interest of full disclosure:
  
 1. I currently drive my HE-6 with the Violectric V-200 fed via XLR from my V800 DAC.  The V200 delivers 2750 mW into the HE-6's 50 Ohm.  Until recently I was of exactly the same opinion as you are,(headphones don't require a speaker amp) just check some previous posts of mine.  If you go by the numbers and do the math, that's a very reasonable conclusion, the Vio should drive the HE-6 without any problem at all and with headroom to spare.  Hell, even the O2 looks (marginally) doable on paper.  I've since talked to many people who presented imo good arguments to the contrary suspended judgment and ordered a FirstWatt F3 amplifier.  It's designed to drive high efficiency speakers.  It outputs 15W into 8 Ohm.  Do the calculations and you'll say that at 50 Ohm it will certainly not do better than the Vio.  Yet, people who own even less powerful FirstWatt amps and who have owned the Vio swear to me that they get superior results.  A fellow Head-Fier drives them from an F1-J model of the same brand with a 10W output in 8 Ohm.  Note:  The firstWatt amps are not your typical speaker amps, if you want to know more about the design, check www.firstwatt.com
  
 2. I've heard the HE-6 with a couple of conventional (high powered) speaker amps and some of them sounded like crap, high noise floor, distortion...but in all likelihood that's because they had a lot of gain (as the HE-6 and HE-4 are planar magnetic designs we can largely discount impedance mismatch, certainly if we're not talking tube amplifiers).  Headphones don't require massive gain, nor do they require huge current.  What they require is sufficient *power* to drive them well and sufficient *power reserve on tap at all times.*  With designs like the 6 and to a slightly lesser extent the 4 I believe that the problem lies there:  not enough power 'on tap' to deal with dynamic range.  On modern pop records that's mostly not such an issue but with classical music for instance it is (you'll have to take my word for it or do some digging).  If you take a look at most headphone amp measurements (for the rare brands who don't outright fudge the numbers or present them in a very selective way) then you'll see that what they post as performance is typically a static picture (power output into a specific load with distortion measured at a certain frequency etc).  But they don't take dynamics and fluctuation into account.  Simple observation, look for yourself.  If you run efficient cans from a decent headphone amp then typically you won't run into a problem but with extreme cases and dynamic music, despite the static measurement data showing all's well, the amp will simply not be able to timely deliver sufficient power (the 'power reservoir' so to speak being too small).  That's where the advantage of speaker amps lies imo. 
  
 Again, I'll let you know once I received my FirstWatt and I've gained some experience + the 'new toy' syndrome has blown over.  It's an experiment but the explanations I've heard (and which I probably didn't accurately reproduce above) sound plausible to me.  Plausible enough to sink about 3000 USD into this little experiment anyway.
  
 In short:  I'm not claiming that a speaker amp may be required let alone the best for any and all headphones, I'm not claiming that just hooking up any 100 WPC amp is a shortcut to nirvana, I'm not saying that all headphone amps are crap (I own several and with the right cans they're very good).  But I do think that it's plausible that with insensitive designs such as the HE-6, HE-4, HE-5...speaker amps can bring something to the table that most headphone amplifiers cannot due to their form factor if for nothing else:  massive power on tap and instantly available.  It's not about driving them 'loud', that's gain and comparatively easy to accomplish, it's about driving them to their max potential and getting the very best out of them.
  
 I hope the above makes some sense but if you want the full technical explanation I'll gladly hook you up with some guys who have a more solid theoretical basis.


----------



## headwhacker

^ Quite a long post. But by the gist of it, I think I can sum it on one word -- "Snake oil".
  
 People can always believe what they want to believe. I agree with amp headroom and stuff but you have to draw the line between sense and just myth.
  
 Sure speaker amps should be fine and can be used to drive headphones, but if anyone is telling me that I need a speaker amp to drive a headphone then something is wrong. Either the headphone design is inefficient or people just buy in to the idea of bigger/powerful is better.
  
 An O2 in itself is more than enough to drive almost all headphones. I even needed to limit my O2 to 2.5x gain so I don't run into an accident of driving my T1 to very loud volumes.


----------



## Xenophon

headwhacker said:


> ^ Quite a long post. But by the gist of it, I think I can sum it on one word -- "Snake oil".
> 
> People can always believe what they want to believe. I agree with amp headroom and stuff but you have to draw the line between sense and just myth.
> 
> ...


 
 I'm not trying to convince you nor anyone else but let me remark that your reaction is low on one parameter which contradicts your professed aversion to 'snake oil' and love of rationality:  I do not read a single solid argument.  I'm not proselytising, just going to give it a try and we'll see.  Believe what you want (and hone those reading skills because nowhere did I say that 'a' speaker amp is 'required' to drive 'a' headphone, I honestly couldn't care less.


----------



## r010159

Lets take an extreme example of an audiophile looking for the best transient response from their amplifier. He happens to be an engineer at JPL. He wanted the best guarateed transient response, among other things, from his amp. So he purchased this big turkey of an amp. When turned on, it actually dimmed the lights in his house, until the internal capacitors charged up. 8-O I have seen him actually turn the unit off and it still powered his speakers for up to a half an hour later. 8-O This tells you how much an emphasis he placed on this parameter of an amplifier. It is not only to have significant power available, but also how quickly that power can be delivered. I do believe this amp of his to be overkill to the extreme. I think a fraction of an amplifier compared to his wil still be a very good amplifier. And we are not trying to power a setup of power hungry speakers, just a pair of headphones, 

I thought all of you would find this a little amusing. 

Bob Graham


----------



## tomb

What all of you guys are trying to describe is slew rate: how quickly an amplifier can rack up the voltage.  An example of a top-flite headphone amplifier is AMB's B22 - it has a slew rate of 198V per micro-second.  For comparison, one of the faster opamps available - the AD8397 - has a slew rate of 53V per micro-second.  The classic OPA2134 (used in the CMoy) has a slew rate of 20V per micro-second.  Those specs for opamps are "laboratory conditions," though.  There's an awful lot of extra amplifier circuitry necessary if they are to provide that to a meaningful load.  The B22, on the other hand, meets that 198V per micro-second level while providing 49V point-to-point.
  
 Slew rate can be shown graphically (somewhat) by square wave response, too.  Interestingly, the O2 has a slew rate of only 3.5V per micro-second.  Not surprisingly, the designer dismisses the slew rate specification by referring to an "industry rule of thumb" and by stating, "There can be ugly side effects associated with excess slew rate."  Well, yeah - if the amplifier or opamp has a ringing issue, but that would be shown in the square wave response, too.
  
 Anyway, orthos are supposed to be very transient-responsive, somewhat similar to an electrostatic.  That means you need peak voltage and it needs to be fast.  Sometimes speaker amps can do that easier than many headphone amps.  However, I think if you look at the B22 as a headphone amp example, it's quite possible to achieve that with a headphone amp, too.


----------



## r010159

tomb said:


> What all of you guys are trying to describe is slew rate: how quickly an amplifier can rack up the voltage.  An example of a top-flite headphone amplifier is AMB's B22 - it has a slew rate of 198V per micro-second.  For comparison, one of the faster opamps available - the AD8397 - has a slew rate of 53V per micro-second.  The classic OPA2134 (used in the CMoy) has a slew rate of 20V per micro-second.  Those specs for opamps are "laboratory conditions," though.  There's an awful lot of extra amplifier circuitry necessary if they are to provide that to a meaningful load.  The B22, on the other hand, meets that 198V per micro-second level while providing 49V point-to-point.
> 
> [snip]




Very interesting read! I also did not realize slew rate can vary so widely between amps. I wonder how fast a slew rate increase would stop making an audible difference? I am surprised the O2 is so slow. It is a good sounding amp. But with the right amp and headphones, I am sure I would notice a difference. What do you think?

Bob Graham


----------



## miceblue

tomb said:


> What all of you guys are trying to describe is slew rate: how quickly an amplifier can rack up the voltage.  An example of a top-flite headphone amplifier is AMB's B22 - it has a slew rate of 198V per micro-second.  For comparison, one of the faster opamps available - the AD8397 - has a slew rate of 53V per micro-second.  The classic OPA2134 (used in the CMoy) has a slew rate of 20V per micro-second.  Those specs for opamps are "laboratory conditions," though.  There's an awful lot of extra amplifier circuitry necessary if they are to provide that to a meaningful load.  The B22, on the other hand, meets that 198V per micro-second level while providing 49V point-to-point.
> 
> Slew rate can be shown graphically (somewhat) by square wave response, too.  Interestingly, the O2 has a slew rate of only 3.5V per micro-second.  Not surprisingly, the designer dismisses the slew rate specification by referring to an "industry rule of thumb" and by stating, "There can be ugly side effects associated with excess slew rate."  Well, yeah - if the amplifier or opamp has a ringing issue, but that would be shown in the square wave response, too.
> 
> Anyway, orthos are supposed to be very transient-responsive, somewhat similar to an electrostatic.  That means you need peak voltage and it needs to be fast.  Sometimes speaker amps can do that easier than many headphone amps.  However, I think if you look at the B22 as a headphone amp example, it's quite possible to achieve that with a headphone amp, too.



Interesting to know. I was unaware of what the "slew rate" is despite seeing it in some op-amp specification sheets.

As mentioned, I found the speaker amp to have a similar effect on planar magnetic headphones as dynamic driver types, so the extra oomph is ruled out in that case and the difference in sound quality was characteristic of the amp, not as a result of the extra headroom or "reserve power." Whenever people talk about speaker amps and planar magnetic headphones, they never do a test with other types of headphones and they tend to come to the conclusion that the extra oomph from the speaker amp magically causes the headphones to transform in sound quality.

The amp itself sounded great compared to regular headphone amplifiers I've tried!


----------



## James-uk

Basically the O2s slew rate exceeds any possible scenario that could be thrown at it so nothing extra would make an audible difference. The O2 is transparent and will not get in the way of the recording. You will hear exactly what your HP are capable of and how they should sound. If you don't like what you hear from the O2 use eq or buy new headphones.


----------



## r010159

james-uk said:


> Basically the O2s slew rate exceeds any possible scenario that could be thrown at it so nothing extra would make an audible difference. The O2 is transparent and will not get in the way of the recording. You will hear exactly what your HP are capable of and how they should sound. If you don't like what you hear from the O2 use eq or buy new headphones.


 
  
 My listening to the O2 tells me it is definitely a transparent amplifier. But what exactly would I get with a better quality amplifier. I do know that more power does not necessarily equate to higher fidelity. What are we talking about here? Features? Balanced line out? A better designed power supply? Better noise rejection? I am just making this stuff up trying to figure out the differences. Still, I am quite happy with the O2D.
  
 Bob Graham


----------



## r010159

miceblue said:


> Interesting to know. I was unaware of what the "slew rate" is despite seeing it in some op-amp specification sheets.
> 
> As mentioned, I found the speaker amp to have a similar effect on planar magnetic headphones as dynamic driver types, so the extra oomph is ruled out in that case and the difference in sound quality was characteristic of the amp, not as a result of the extra headroom or "reserve power." Whenever people talk about speaker amps and planar magnetic headphones, they never do a test with other types of headphones and they tend to come to the conclusion that the extra oomph from the speaker amp magically causes the headphones to transform in sound quality.
> 
> The amp itself sounded great compared to regular headphone amplifiers I've tried!


 
  
 I did notice a significant difference, including the bass response, going from an iPad headphone jack to the O2. This noticeable difference in the responsiveness of the bass I attributed to power and slew rate. Maybe it was in my specific case? I do not know.
  
 Bob Graham


----------



## James-uk

r010159 said:


> My listening to the O2 tells me it is definitely a transparent amplifier. But what exactly would I get with a better quality amplifier. I do know that more power does not necessarily equate to higher fidelity. What are we talking about here? Features? Balanced line out? A better designed power supply? Better noise rejection? I am just making this stuff up trying to figure out the differences. Still, I am quite happy with the O2D.
> 
> Bob Graham



Better features and coloration is all you can get. The better features (plus it looks really nice) is the reason I brought the Sennheiser HDVD800 , I have my ps4 on optical ( I'm a sad 32 year old gamer!) plus my mac on USB . It's been designed with a 47 ohm output impedance so should add a touch of warmth the the HD800 because of its impedance curve but to be honest I think I would fail a blind test between it and the O2/odac. It cost me 6X more than the O2D so I've paid all that for optical connection and looks ( oh and I can have 4 headphones connected at once) so I have the HD650 and 800s always plugged in. Oh and they are both connected with balanced cables and that makes no difference to sound quality .


----------



## James-uk

By the way I spent an afternoon doing sighted A/B comparisons between O2 and HDVD800 (using balanced connection) with some of my favourite records . Obviously being sighted it was flawed but both sounded identical to my ears . I'm confident in saying I would fail a double blind test. It confirms to me that solid state amps / dacs really do all sound the same if certain criteria is met and exceeded.


----------



## r010159

james-uk said:


> Better features and coloration is all you can get. The better features (plus it looks really nice) is the reason I brought the Sennheiser HDVD800 , I have my ps4 on optical ( I'm a sad 32 year old gamer!) plus my mac on USB . It's been designed with a 47 ohm output impedance so should add a touch of warmth the the HD800 because of its impedance curve but to be honest I think I would fail a blind test between it and the O2/odac. It cost me 6X more than the O2D so I've paid all that for optical connection and looks ( oh and I can have 4 headphones connected at once) so I have the HD650 and 800s always plugged in*. Oh and they are both connected with balanced cables and that makes no difference to sound quality .*


 
  
 I agree. The balanced outputs provide for noise isolation in a noisy environment, which has nothing to do with the quality of the amplifier. For instance, I think mics have balanced inputs because of the noisy environment that they can operate in. Still, the better amps tend to have balanced outs, probably as a marketing decision than any real difference it makes in quality.
  
 Bob Graham


----------



## James-uk

r010159 said:


> I did notice a significant difference, including the bass response, going from an iPad headphone jack to the O2. This noticeable difference in the responsiveness of the bass I attributed to power and slew rate. Maybe it was in my specific case? I do not know.
> 
> Bob Graham



I pads only output 1volt so not enough power for something like a 300ohm senn which needs about 6 volts to be able to reproduce the full dynamic range of a recording. Now if you connect a sensitive , low impedance iem to an I pad it would sound identical to it connected to the O2 .


----------



## Xenophon

james-uk said:


> Basically the O2s slew rate exceeds any possible scenario that could be thrown at it so nothing extra would make an audible difference. The O2 is transparent and will not get in the way of the recording. You will hear exactly what your HP are capable of and how they should sound. If you don't like what you hear from the O2 use eq or buy new headphones.


 
 There's such a thing as the right tool for a job.  Overall and considering the price the O2 and its clones are great, hell, I'm listening to it now (mainly because I live in 2 locations and it's a damn sight easier to move than my 30 kg tube amp).  If you use it with cans and under conditions that do not exceed its technical limitations then you'll indeed be hard pressed to hear a difference -apart from colouring which is a subjective quality- with other amplifiers and arguably it makes no sense in spending more, strictly going by objective criteria.
  
 This entire discussion evolved out of a members' question if the O2 would be a good pairing to drive a HE-4.  And for those headphones and listening to certain types of music at a certain loudness level, it is NOT the right instrument and while I agree that I might not be able to hear a difference between ss amp A and B, when driven within their limits, with for instance my HE-6 I can assure you that at *any* loudness level I could easily tell apart my Vio and the O2 even if one were able to eliminate sound colouring.  That doesn't make the O2 bad, it's just not the right tool for the job with those cans.
  
 My other hobby is riding motorcycles.  Here in India I ride an Enfield bullet and given local road and traffic conditions it's just perfect (19 HP, max speed 70 mph on a good day, old school carburettor, price about 1300 GBP).  I Europe I ride an Agusta Brutale 1090RR (160 HP, max speed limited to 180 mph, 18000 GBP).  What works here wouldn't work there and vice versa.
  
 As a -speaker but that's irrelevant now- amp builder said:
  
 "There is no such thing as a _perfect_ amplifier. Every audiophile and his associated equipment has specific needs, but in each case there is such a thing as a _best_ amplifier - the one that makes you happy."


----------



## headwhacker

james-uk said:


> Better features and coloration is all you can get. The better features (plus it looks really nice) is the reason I brought the Sennheiser HDVD800 , I have my ps4 on optical ( I'm a sad 32 year old gamer!) plus my mac on USB . It's been designed with a 47 ohm output impedance so should add a touch of warmth the the HD800 because of its impedance curve but to be honest I think I would fail a blind test between it and the O2/odac. It cost me 6X more than the O2D so I've paid all that for optical connection and looks ( oh and I can have 4 headphones connected at once) so I have the HD650 and 800s always plugged in. Oh and they are both connected with balanced cables and that makes no difference to sound quality .


 
 I agree, better amp than O2 only translate to additional features, connection and more power. But if you are looking for SQ improvement, it's better to look for a better headphone or better source.


----------



## tomb

james-uk said:


> Basically the O2s slew rate exceeds any possible scenario that could be thrown at it so nothing extra would make an audible difference. The O2 is transparent and will not get in the way of the recording. You will hear exactly what your HP are capable of and how they should sound. If you don't like what you hear from the O2 use eq or buy new headphones.


 

 Sorry, I don't mean to be critical, but this is simply an unsubstantiated rationalization in order to justify the small investment in an O2.
  
 I am not at all saying that the O2 is bad - far from it.  However, when people take that ~$129 investment (a good buy, no doubt) and try to convince everyone that it's as good as it can get ... that's where rationality has left the discussion.


----------



## r010159

About an amplifier's slew rate: http://forums.audioholics.com/forums/amps-pre-pros-receivers/7278-de-mystifying-slew-rate-amplifiers.html
  
 And an interesting article about an amplifier's damping factor: http://www.crownaudio.com/media/pdf/amps/damping_factor.pdf
  
 It looks like current technology does make these and other parameters easily met. But then what is the actual difference between an well-designed $300 amp/DAC and a much more costly $1000 amp/DAC? Is the $1000 implementation addressing limitations of the $300 implementation? If so, what are they? Or is the difference that of features and a pleasantly colored sound? And the rest of the difference being expectation bias?
  
 Bob Graham


----------



## Xenophon

r010159 said:


> About an amplifier's slew rate: http://forums.audioholics.com/forums/amps-pre-pros-receivers/7278-de-mystifying-slew-rate-amplifiers.html
> 
> And an interesting article about an amplifier's damping factor: http://www.crownaudio.com/media/pdf/amps/damping_factor.pdf
> 
> ...


 
 All of the above and then some.  Get a good book on amplifiers or hire a consultant; I'm sure that for a couple of thousand he/she could explain in detail what it's all about and then you'll have a good basis to decide wether or not to spend more than 300 USD.  The previous remark is only half made in joking. 
  
 On the one hand you have technology which comes at a cost and it's a general law in economics that beyond a certain point there's no linear relationship anymore between performance increase and cost, cost rises exponentially if you want to achieve those last couple of %.  Wether that's worth it or not depends on a) your finances and b) what you want to achieve.  Everyone has his own point of diminishing returns beyond which they stop.
  
 Then there's intangibles such as personal preference, brand reputation etc which are worth more for one person vs another.  And convenience.  Example:  the amp I purchased last week costs, all said and done and delivered to me, about 3000 USD.  The builder actually published the detailed plans, and provides free advice about construction.  Depending on the material you use, it's possible to build it for around 800 to 1200 USD (the case is actually the biggest cost).  Add about 350 for shipping everything.  That would equal 1500 USD or half of what I'm paying.  Am I irrational for paying double?  No because in my own appreciation, the time, frustration and effort it would take me to build it myself carries a larger cost than the difference.
  
 I fully agree that there's lots of vapourware and hype in audio (imo about cables etc) but be under no illusion:  there's no free lunch when all is said and done (cfr. my first remark about technology).  In fine the only person who can decide is yourself.


----------



## r010159

xenophon said:


> All of the above and then some.  Get a good book on amplifiers or hire a consultant; I'm sure that for a couple of thousand he/she could explain in detail what it's all about and then you'll have a good basis to decide wether or not to spend more than 300 USD.  The previous remark is only half made in joking.
> 
> [snip]
> 
> I fully agree that there's lots of vapourware and hype in audio (imo about cables etc) but be under no illusion:  there's no free lunch when all is said and done (cfr. my first remark about technology).  In fine the only person who can decide is yourself.


 
  
 I agree that the $300 DAC/amp is not what some would term as the  "endgame".  You are definitely getting more value out of your expensive amplifier. And there is that law of diminishing returns that one has to justify when paying up for the amp. But I like to know in practical "everyday life" terms what are the differences. I remember in the past there was very little being written on the subject. At this point, I think the difference between what one would term as a "good" amp, and one that is "excellent" is altogether not anywhere near as much as the price difference would imply. One of these days I would like to attempt to hear the difference myself.
  
 Bob Graham


----------



## r010159

For craps and giggles I decided to hook my iPad up to the DAC part of the O2 + ODAC. I have never heard my iPad this good! I am looking forward to the C5D that I have just ordered. I will be quite a sight with the Denny's restaurant crowd whom I visit every morning, with full-sized headgear and all.
  
 Bob Graham


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## JacobLee89

I'm currently waiting for the output booster mod kit for the 02, by AGDR. The thread is in the modding section of the forum ((under the thread name:_ __O2 headamp output booster & modification PCB_)) . As far as I know, the mod eliminates the turn off thump entirely, alongside lowering distortion and a whole list of changes that would be easier explained by just directing you to the document.
  
 Currently I am using my O2 + ODAC with my HD650s, which has the general consensus that it (the headphones) works better with tube amps. Some have claimed that with the O2 mod by agdr, the amp sounds much less "digital". This may or may not be beneficial to the HD650's "less than neutral" sound signature. Unfortunately, the mod requires some direct tampering with the original PCB meaning I may not be able to directly compare the O2 with the modded variation, unless of course I get another one.
  
 For others with the HD650's and this objective stack, I'll be sure to comment back on this thread to say how well this combination works with the (still awaiting) mod.


----------



## Xenophon

Looks like an interesting mod for sure and at least theoretically it should improve some aspects of the design.  Only, I don't feel it's still a good deal if you have to first get the original, then purchase the kit and install it.  We're then reaching a price point then where I believe better overall quality to be available.
  
 But I'm curious to hear your impressions (BTW:  coupling a HD-650 to a tube amp...only for serious warmth lovers imho).


----------



## agdr

The booster board will also increase the O2's slew rate. 
	

	
	
		
		

		
			





   I added some information about that to the build instructions at the Google Drive link yesterday after the good discussion in this thread made me realize that was another benefit of the board I had forgotten about.
  
 The O2's orginal NJM4556A's have a slew rate of 3V/uS while the NJM2068 gain chip is 6V/uS from the datasheets.  The NIM4556A would be the limiting factor end-to-end in the O2 amp then, giving an O2 amp slew rate of around the 3V/uS.
  
 The OPA140 on the booster board has a slew rate of 20V/uS, while the optional OPA827 slews at 28V/uS.  They loop around LME49600s that has a slew of 2000V/uS, but in that circuit arrangement the op amp is the limiting factor. 
  
 So with the default OPA140s the booster board slews at around 20V/uS, replacing the 3V/uS NJM4556As, which in turn lets that NIM2068 chip's 6V/uS become the new limiting factor.  Long story short the end-to-end slew rate of the O2 amp should double from around 3V/uS to 6V/uS with the booster board.
  
 To go a step further the O2's NJM2068 gain chip can be replaced with an LME49720 which has similar low noise specs, slightly better distortion specs, and slew rate of 20V/uS.  The O2 designer has a rather favorable writeup about the chip (vs. the NJM2068) in the "op amp measurements" section of his blog.  So then you get 20V/uS slew end-to-end with the LME49720 slewing at 20V/uS, as does the OPA140+KME49600 combination on the booster board.
  
 The O2's designer had a good point about slew rate in his blog.  He notes real world audio sources don't slew much faster than 0.6V/uS and the signal processing chain at the studios has similar limitations.  So he doubled that to around 1.2V/uS just to be safe, if I'm remembering correctly, then noted the NJM4556A's 3V/uS is still about twice that making it more than adequate in his view.  He also noted the only downside to more slew is the potential for oscillations from a badly designed circuit.  I've measured the booster out to 200mHz so that isn't a problem here.
  
 On the other hand there is that link to a good writeup on slew that was posted a few posts ago.  That author makes similar remarks to the O2 designer about real world source slew limitations, but then goes on to say something like "that is for 20kHz but well designed amplifiers are usually designed to be flat out to 100kHz, requiring a slew of 10V/uS" (paraphrased) and goes into some supporting detail. So there are certainly other interesting opinions about how much slew is needed and why.


----------



## r010159

agdr said:


> The booster board will also increase the O2's slew rate.
> 
> 
> 
> ...


 
  
 Can you give me a link to the O2 designers blog, where he discusses his design decisions and the reasons behind them? I am sure I will find this interesting to read.
  
 Thanks!
  
 Bob Graham


----------



## miceblue

Nope. It's illegal to post links to websites of previously banned members of Head-Fi.

You can just Google "nwavguy o2" though and it should be within the first two listed websites. XD


----------



## r010159

OK. Sorry. I was not thinking.
  
 Bob Graham


----------



## Xenophon

r010159 said:


> Can you give me a link to the O2 designers blog, where he discusses his design decisions and the reasons behind them? I am sure I will find this interesting to read.
> 
> Thanks!
> 
> Bob Graham


 
 You'll have found it by now.  It actually IS an interesting read and he undoubtably knows what he's talking about but be aware that it only presents his viewpoint of course.


----------



## agdr

Yep, he managed to get himself banned. If you find it do a search for "slew" and "slew rate" in the topics around July and August of 2011.  There is more than one chunk of stuff.


----------



## Xenophon

For a really good explanation on slew rate, check this out (math challenged persons should take a deep breath before clicking though)  http://www.onmyphd.com/?p=slew.rate


----------



## r010159

That article on slew rate reminds me too much of the electrical engineering classes I took in a previous lifetime.  Still, an interesting read on the basics. The article demonstrates to me how much I have forgotten.
  
 Looking for past articles on slew rate by the designer of the O2 (the one whose name cannot be spoken), I found a treasure-trove of information spanning several threads. Much of the discussions involve the technical aspects of amps. I can see a long night ahead of me.
  
 Bob Graham


----------



## JacobLee89

"_ To put this into laymans terms and by my attempt to steer this into basic audio talk, is the slew rate useful for lowering distortion throughout the frequency range or does it lower distortion in the extremes of the frequency ranges? Of course I am referring to the frequency ranges that is audible to the human ear."_
  
 Was what I was wondering until I read somewhere that Slew Rate is associated with the "speed" of the amplifier and affects transients in music such as a hard hitting drum beat. But I shall leave that question there in case it has any validity.
  
 Much thanks in advance.


----------



## Xenophon

I don't know if I understand you correctly but slew rate requirements for a component to deliver distortion free output at a fixed, maximum voltage are indeed frequency dependent is the short answer.  
  
 If you want to calculate it and for a more complete explanation, see here:  http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/a741p3.html
  
 If you want the background for the formula used, check the link I posted previously, it's all there.


----------



## JacobLee89

xenophon said:


> I don't know if I understand you correctly but slew rate requirements for a component to deliver distortion free output at a fixed, maximum voltage are indeed frequency dependent is the short answer.
> 
> If you want to calculate it and for a more complete explanation, see here:  http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/a741p3.html
> 
> If you want the background for the formula used, check the link I posted previously, it's all there.


 
 Thanks for the clarification!
  
 It does seem that the improved slew rate is beyond the margin of my hearing ability, but that of course is only part of the many improvements.


----------



## RAZRr1275

Are there any pretty cheap solutions for the ODACs power supply issues?


----------



## BenF

razrr1275 said:


> Are there any pretty cheap solutions for the ODACs power supply issues?


 

 What are they (issues)?


----------



## RAZRr1275

benf said:


> What are they (issues)?


 
 From what I've read, the fact that it uses USB power instead of a cleaner power supply method means that it's not using the fantastic Sabre chip to its full potential


----------



## BenF

razrr1275 said:


> From what I've read, the fact that it uses USB power instead of a cleaner power supply method means that it's not using the fantastic Sabre chip to its full potential


 
  
 Try a USB Isolator:
http://hifimediy.com/index.php?route=product/product&path=60&product_id=122


----------



## RAZRr1275

benf said:


> Try a USB Isolator:
> http://hifimediy.com/index.php?route=product/product&path=60&product_id=122


 
 Hm - does that essentially turn the computers usb power output into a powered USB hub?


----------



## BenF

razrr1275 said:


> Hm - does that essentially turn the computers usb power output into a powered USB hub?


 

 It's not a hub and it doesn't take any external power.


----------



## RAZRr1275

benf said:


> It's not a hub and it doesn't take any external power.


 
 I meant that in the sense of does it clean up the power that the computer gives to the ODAC?


----------



## BenF

razrr1275 said:


> I meant that in the sense of does it clean up the power that the computer gives to the ODAC?


 

 Supposedly.
 I didn't hear any difference, but maybe my laptop's USB power is clean enough as it is.


----------



## JacobLee89

benf said:


> Supposedly.
> I didn't hear any difference, but maybe my laptop's USB power is clean enough as it is.


 
 As far as I know /have read, the ODAC has it's own power regulator but is not as efficient as people would want it.
  
 If you're interested on a DIY alternative there's a project over in the DIY section called doodlebug, which is designed to not only isolate signal and power, but also include its own "externally-powered, linear-regulated" power supply.
  
 This essentially means I intend to use DIY, AND DIY modding to improve my Objective stack 
	

	
	
		
		

		
			





.
  
 Once again, when I get my hands on a doodlebug PCB and get it working, I'll let you guys know.


----------



## RAZRr1275

jacoblee89 said:


> As far as I know /have read, the ODAC has it's own power regulator but is not as efficient as people would want it.
> 
> If you're interested on a DIY alternative there's a project over in the DIY section called doodlebug, which is designed to not only isolate signal and power, but also include its own "externally-powered, linear-regulated" power supply.
> 
> ...


 
 Well if you find sonic benefits let me know as I might want you to do it to my ODAC. I'm not diy savvy myself


----------



## skeptic

Just wanted to say thanks to tomb and agdr for the interesting discussion of slew rates.  
  
 Out of curiosity, does anyone know what the slew rate is on the wire?  Is Robaroni's post referencing 22V/us for the stock build correct (http://www.diyaudio.com/forums/headphone-systems/208709-using-ha-5002-instead-lme49600-wire-2.html )?


----------



## adydula

For you guys that think that the O2 will "work better or sound better???" on el crapo PC usb 5 volts I have used the ODAC on over 20 pcs of all types and flavors. I also used and external very high dollar DC power supply and I could not hear any real audible differences.
  
 All the measurements that the designer took and are published on the other site meet or exceed anything that might cause the loss of transparency etc or the ability of it to do what it was intended to that is to be a excellent digital to analog convertor.
  
 The ODAC like the O2 was and still is an experiment to prove to the world that great audio can be had at less than astronomical prices....
  
 Unless you really have a really poor PC USB implementation and violate the USB specs there should be no real world difference in what the ODAC does.
  
 You can easily splice pure DC to power the ODAC to see what "pure DC" will do.....simple DC batteries have no AC ripple or warts...even mega buck AC to DC power supplies have issues....
  
 All the best
 A.


----------



## mcandmar

I tested a simple regulated power source with an ODAC and found the complete opposite. A good clean source made a noticeable difference, so much so i built an dedicated power supply / isolator for it. A good power supply is key to any good piece of audio hardware.


----------



## r010159

mcandmar said:


> I tested a simple regulated power source with an ODAC and found the complete opposite. A good clean source made a noticeable difference, so much so i built an dedicated power supply / isolator for it. A good power supply is key to any good piece of audio hardware.


 
  
 I understand that the power supply is critical in a design of an audio amplifier. For instance, I think having a separate power circuit, including a separate ground, for the analog and digital parts of the system, is a good feature to have. And having a each power rail separately regulated is another important feature.  There must be other tricks involved with providing a clean power source. I am trying to remember things from over 30 years ago.
  
 What are other features of a good, clean power source?
  
 Bob Graham


----------



## r010159

adydula said:


> For you guys that think that the O2 will "work better or sound better???" on el crapo PC usb 5 volts I have used the ODAC on over 20 pcs of all types and flavors. I also used and external very high dollar DC power supply and I could not hear any real audible differences.
> 
> [snip]
> 
> ...


 
  
 I believe you. But perhaps the power being provided to the power circuit of the ODAC is relatively clean? For that matter, back in time, I remember coming across some poor PC power supplies. I came across a few power supplies on PCs that were not up to spec or even failed.  This was not that uncommon. But maybe that is not the case anymore, particularly with the better makes of computers?
  
 Bob Graham


----------



## lokesen

Objective2 Amplifier + ODAC Illustrated Write-up
  
http://diy.koenigs.dk/2014/02/21/o2odac-amplifier-and-dac/


----------



## JacobLee89

adydula said:


> For you guys that think that the O2 will "work better or sound better???" on el crapo PC usb 5 volts I have used the ODAC on over 20 pcs of all types and flavors. I also used and external very high dollar DC power supply and I could not hear any real audible differences.
> 
> All the measurements that the designer took and are published on the other site meet or exceed anything that might cause the loss of transparency etc or the ability of it to do what it was intended to that is to be a excellent digital to analog convertor.
> 
> ...


 
  
 The main reason why I'm interested on the doodlebug is primarily because I have other DAC's that cannot have the same regulated power implementation as the ODAC (i.e: ELE DAC EL-D01 that goes for $15 max). If I truly cannot hear a difference on the ODAC, then I am free to use it somewhere else. I'm sure my USB microphones may benefit from a cleaner power.


----------



## adydula

USB power in PCS do present potential issues:
  
 Audio Out voltage: The voltage can be as low as 4.5 volts. Add potential losses from power filtering and other DAC and op amp circuitry. So your lucky to get 4 volts peak to peak output swing without clipping. Do the math this is 1.4vrms which is short of the redbook standard for output of 2 vrms. This turns out to be 3db less than the redbook 2vrms standard. That's a potential loss of 3db of dynamic range compared to other redbook standard devices like a cd player and most DIY dacs have this shortcoming.
  
 Possible Greater Noise:
  
 Yes USB power is potentially dirtier than a dedicated regulated DC power supply.So this means the design of the DAC for 16 bit performance needs some attention. Extra filtering and good design. There are dacs that tout 24 bit performance but in reality do not deliver this performance.
  
 Jitter related to Power and or ground "noise"...this can be influenced by a crappy USB power source. The noise can affect by modulating the digital bit stream creating jitter.
  
 The ODAC was designed with all the above plus more in mind. The designer's careful design and by using the right components has overcome the issues from a crappy USB power supply. Remember that most USB power sources in modern day PCs can almost always source 500ma. There are some exceptions...go read about these on a different site.
  
 Also remember even if you do use an external mega buck regulated DC supply the USB Dac still has to be connected to the PC and noise can still come into the DAC and cause issues if its not properly designed or filtered. The ODAC has different power supply filtering for the digital and analog sides. Also capacitor selection and the use of inductor filtering helps to reduce the USB issues so they are essentially non-issues.
  
  As I have discovered an independent power supply doesnt really do anything or make much difference. Also the ODAC delivers the 2vrms redbook standard! Which is that 3db dynamic range issue. Some USB dacs are deficient in this area.
  
 The ODAC also was optimized for the lowest jitter related to the power source. Both the best noise reduction and distortion reduction and the lowest jitter. This was found in not only the design, but the physical layout of components. Lots of electronic stuff really look "pretty" but the ODAC doesnt win awards for how it looks, but how it performs. The ODAC is very quiet...with a -60dBFS signal, it had an impressive 112dB of dynamic range, and that was with the prototypes! The $1600 Benchmark DAC1 was measured at 111dB.
  
 Modern day CDs have 96dB of dynamic range. I could go on and on and on..... but go read for yourself. For $99 this is the DAC deal of all times. Enjoy.. A.


----------



## locksbury

Hi guys
  
 Just a bit of a quick update, I put my O2 kit together last week for some tests and it's sounding promising on the Grados! Personally I had no 'ZOMG' moments, but the little extra bass on stuff like AC/DC and Muse is welcome, I can't wait to see how things change as my brain adapts. Now just to fit the ODAC in the same case so I can use the batteries!


----------



## adydula

Hey Jacob....
  
 Yes there are other USB devices that if not designed well might be impacted by "polluted" USB power....
  
 A.


----------



## adydula

locksbury...
  
 post some pix of your project and let us see how you fitted the ODAC in the O2 assembly...
  
 Alex


----------



## r010159

locksbury said:


> Hi guys
> 
> Just a bit of a quick update, I put my O2 kit together last week for some tests and it's sounding promising on the Grados! Personally I had no 'ZOMG' moments, but the little extra bass on stuff like AC/DC and Muse is welcome, *I can't wait to see how things change as my brain adapts*. Now just to fit the ODAC in the same case so I can use the batteries!


 
  
 I think this is the case for many music setups. I think quick A/Bing provides only part of the answer.
  
 Bob Graham


----------



## MrMateoHead

Toms Harwardware set up an blind test of the DAC2, O2/ODAC, Asus Xonar, Realtek 889:
  
http://www.tomshardware.com/reviews/high-end-pc-audio,3733.html
  
 Conclusion? Any more than $2, and you are buying "features" - not distinguishable performance. Wonder how that would sit with some of the other forums lol. The weak spot was that there were just 2 listeners that had good equipment themselves, but not necessarily any formal training.
  
 I am currently using the ODAC with a desktop amp / 2.1 setup and couldn't be more pleased. Sounds awesome - luckily, the amp has no noise or problems I can detect. Needed a break from headphones. I enjoyed my own realtek chipset long enough, but wouldn't give up the O2/ODAC, its too good.


----------



## adydula

Its a simple design, but the wonder is what the designer went thru and did to make it as good as it is....."is the rest of the story".
  
 Taking the time to do layouts, over and over and over just to get the measurements as best possible....
  
 Trying to match reference circuit measurements or best them...this is wonderful engineering...and we all benefit!!
  
 Ah....such a great time to be in audio!!
  
 A.


----------



## mcandmar

You really need to stop drinking the koolaid, i mean seriously dude its getting a little obsessive.


----------



## Xenophon

mcandmar said:


> You really need to stop drinking the koolaid, i mean seriously dude its getting a little obsessive.


 
 No, it's the O2 and this is typical for threads dealing with it 
	

	
	
		
		

		
		
	


	




....fierce defenders and seriously critical opinion, usually ends in shouting matches.  I take the middle ground:  respect for what the designer did but it's not the last word in amplification by a long shot.  And scr*w kool-aid, have a beer


----------



## JacobLee89

xenophon said:


> No, it's the O2 and this is typical for threads dealing with it
> 
> 
> 
> ...


 
 My view is a bit simpler:
  
 If you found Heaven in your audio setup: Feel free to defend it, but I may or may not care.
 If you still haven't found it in your setup : Feel free to defend it anyhow, it's your hard earned cash.
 If you're defending something that is poorly designed: Please see me ignoring you as a compliment.
  
 Not saying that the O2 or ODAC is poorly designed in any way shape or form, the "open hardware" part of it just seems so ignored, even more so on the ODAC which seems baffling not to be DIY/mod friendly.


----------



## sonic2911

Can anyone compare the o2/odac with magni/modi?


----------



## miceblue

I was going to respond, but then I saw Magni/Modi. I can chime in about the Vali vs O2 though. XD


----------



## sonic2911

the vali has ringing problem now. many people can't stay with it.


----------



## miceblue

sonic2911 said:


> the vali has ringing problem now. many people can't stay with it.




I...don't even understand why that's there. That's a fundamental problem that shouldn't exist in any amplifier. That's just plain stupid.

For anyone wondering, when you plug in a headphone, any headphone, into the Vali's headphone out port, a ~2 kHz or so signal gets played through your headphones at a set volume level and you can't do anything about it other than wait it out for a few minutes.


----------



## Xenophon

sonic2911 said:


> the vali has ringing problem now. many people can't stay with it.


 
 Never heard the Vali but if this is true then it's simply an atrocious design error and I'd never purchase anything  from that manufacturer.


----------



## adydula

Never had a vali, had a Lyr, never had any hum, well built performed well but not anywhere near transparent etc...that said lots of people love it.
  
 Ah the wonderful world of tubes, hot, glowing, humming, lots of distortion but very nostalgic!
  
 Wonder what exactly you would like to DIY or Mod to the ODAC to make it "better"??
  
 A.


----------



## Xenophon

adydula said:


> Never had a vali, had a Lyr, never had any hum, well built performed well but not anywhere near transparent etc...that said lots of people love it.
> 
> Ah the wonderful world of tubes, hot, glowing, humming, lots of distortion but very nostalgic!
> 
> ...


 
  
 Don't know if that part was directed at me or someone else but if at me:  I wouldn't do a thing.  The design is what it is and if I'd want to upgrade the wiser course would imo simply be to purchase another amp rather than sinking a proportionately high amount into the O2.  
  
 BTW, I also like tubes.  As you say, they come with their warts but the subjective experience also counts.  Last time I put in a new driver tube I was stuck with horrible micro phonics...2 days of suffering before the person quietened down.


----------



## lokesen

lokesen said:


> Objective2 Amplifier + ODAC Illustrated Write-up
> 
> http://diy.koenigs.dk/2014/02/21/o2odac-amplifier-and-dac/


 
 Added a few sections to the write-up. Cheers.


----------



## MrMateoHead

adydula said:


> Its a simple design, but the wonder is what the designer went thru and did to make it as good as it is....."is the rest of the story".
> 
> Taking the time to do layouts, over and over and over just to get the measurements as best possible....
> 
> ...


 

 Any company (or in this case, person) worth their salt would spend the time to "develop" a design until it meets or exceeds its design criteria. It is not all signal to noise, either. A good amp should have power! Lots of it. It sets up the ability to drive anything, and provide ample headroom for HDR recordings (like classical which I am increasingly getting more into).
  
 Maybe the O2 is what happens when engineers, instead of marketers, are 'driving' product development.
  
 A big piece of the story missing over at Toms was a measure of the power output! Specifically, we have no idea how strong the amps were other than given an ability (or not), to drive a high-impedance load. The headphones they used were quite efficient. But for what it is worth, apparently the listeners could not reliably detect what should have been dismal output impedance / sloppy bass of the 889. More discernible was the -1.4dB response at 100 hz.


----------



## r010159

mrmateohead said:


> Any company (or in this case, person) worth their salt would spend the time to "develop" a design until it meets or exceeds its design criteria. It is not all signal to noise, either. A good amp should have power! Lots of it. It sets up the ability to drive anything, and provide ample headroom for HDR recordings (like classical which I am increasingly getting more into).
> 
> Maybe the O2 is what happens when engineers, instead of marketers, are 'driving' product development.
> 
> A big piece of the story missing over at Toms was a measure of the power output! Specifically, we have no idea how strong the amps were other than given an ability (or not), to drive a high-impedance load. The headphones they used were quite efficient. But for what it is worth, apparently the listeners could not reliably detect what should have been dismal output impedance / sloppy bass of the 889. More discernible was the -1.4dB response at 100 hz.


 
  
 I do believe you are correct. The focus of the O2 project was what can be accomplished by the design of the product, not marketing concerns, or sloppy engineering. As far as Toms goes, I do see the listeners as being experienced. But there is a difference between an experienced ear and a well-trained and experienced ear. So to me, as a measured interpretation of the results, this means the discerning* average *listener will not be able to reliably tell the difference. But an experienced audiophile probably can.
  
 Bob Graham


----------



## headwhacker

the O2 was designed with considerations and compromises so that it can drive 90+ % of headphone out there. From highly sensitive iems to full size cans.
  
 Looking pretty, and unnecessary features are very low to non-existent in the list of design goals.


----------



## MrMateoHead

r010159 said:


> I do believe you are correct. The focus of the O2 project was what can be accomplished by the design of the product, not marketing concerns, or sloppy engineering. As far as Toms goes, I do see the listeners as being experienced. But there is a difference between an experienced ear and a well-trained and experienced ear. So to me, as a measured interpretation of the results, this means the discerning* average *listener will not be able to reliably tell the difference. But an experienced audiophile probably can.
> 
> Bob Graham


 
 What is an average listener? What is an Audiophile?
  
 One listener in the test used $3K worth of gear - including Senn 800s and an Asus Xonar that were the same as in the test. The other person used 86K (Euro, so about $129,000) worth of gear! The rich person also used Senn 800s. Both were at an advantage, in the sense that they were familiar with some of the test gear.
  
 I highly doubt the former or latter would identify as "average" listeners. As audiophiles, they failed to reliably detect the amps through Senn 800s which are nothing if not unforgiving. So, essentially, the test, if you believe its results, rules out the possibility that anyone could tell a difference in a blind test. I doubt that will change their audio budgets, but certainly it rules out amplifiers as a major differentiating factor (at least among HQ properly designed amps that aren't _trying_ to have a sonic signature).
  
 Now, I use ~$700 worth of gear on headphones, and ~$450 for the 2.1 setup. I've got maybe $600 in my car. Or in other words, I have no listening setup that I currently listen to that I've spent more than $1,000 on. I think I get a very high quality listening experience and can hear "crap" much more easily than most. But I could not, through any speaker you gave me, tell the difference between source-matched and volume-matched amplifiers that I rely on.
  
 Of course, given performance and features that I might want (bridgeability, high power, etc), I wouldn't stick with a realtek chipset when an O2 is available for a mere 50X more!


----------



## r010159

mrmateohead said:


> What is an average listener? What is an Audiophile?
> 
> One listener in the test used $3K worth of gear - including Senn 800s and an Asus Xonar that were the same as in the test. The other person used 86K (Euro, so about $129,000) worth of gear! The rich person also used Senn 800s. Both were at an advantage, in the sense that they were familiar with some of the test gear.
> 
> [snip]


 
  
 I missed that. They are definitely not your average listener, more like audiophiles to have purchased that expensive equipment. What I meant by audiophile is a well-trained ear that comes with experience.
  
 Bob Graham


----------



## JacobLee89

Quote:


razrr1275 said:


> Well if you find sonic benefits let me know as I might want you to do it to my ODAC. I'm not diy savvy myself


 
 I have definitely misread that. The doodlebug is not a direct modification of the ODAC, but is a standalone USB isolator which includes its own power regulator.
  
 On other news, I have finally acquired and built my own booster board for the O2 amp.
 Because I haven't quite grasped the terminology in describing sound I'll try to keep this as simple as possible:
  
 With my HD650s (currently only headphones), the change was definitely noticeable: small details I previously had to concentrate on became sharper, bass gained a bit more "thump", and I am sure I had some "out of headphone" experiences with some of my tracks (i.e: Sileypud from Ultrasone's 2006 Test Demo CD).
  
 I wouldn't say it changed the sound signature at all, but rather widened its dynamics "on top of" O2s neutral sound.
  
 Definitely worth the money and effort. Thumbs up to adgr!


----------



## mcandmar

> Originally Posted by *JacobLee89* /img/forum/go_quote.gif
> 
> With my HD650s (currently only headphones), the change was definitely noticeable: small details I previously had to concentrate on became sharper, bass gained a bit more "thump", and I am sure I had some "out of headphone" experiences with some of my tracks (i.e: Sileypud from Ultrasone's 2006 Test Demo CD).
> 
> ...


 
  
 I can 2nd that, its pretty much what i experienced too. I built mine using the optional OPA827 opamps. Overall i found better clarity and detail, and as above more energy in the mid / low end. It puts a bit of life back into the music basically.
  
 I've attached a pic for those who are wondering what were talking about. Highly recommended.


----------



## AsianBatman

Is that an ODAC PCB on top?


----------



## JacobLee89

asianbatman said:


> Is that an ODAC PCB on top?


 
 The T shaped Blue PCB is the Booster board modification.


----------



## Xenophon

jacoblee89 said:


> I have definitely misread that. The doodlebug is not a direct modification of the ODAC, but is a standalone USB isolator which includes its own power regulator.
> 
> On other news, I have finally acquired and built my own booster board for the O2 amp.
> Because I haven't quite grasped the terminology in describing sound I'll try to keep this as simple as possible:
> ...


 
 Thanks!  Although I personally won't upgrade mine -for reasons already mentioned- that's good to know and I salute adgr for his engineering, the effort he put into this and for the results!


----------



## JacobLee89

xenophon said:


> Thanks!  Although I personally won't upgrade mine -for reasons already mentioned- that's good to know and I salute adgr for his engineering, the effort he put into this and for the results!


 
  
 The only way to make it a huge hit for a decent price, would be to DIY the O2 as well, which can squeeze the budget into under $190 for the entire setup, of course that doesn't include the wall wart and soldering gear.
  
 My real reasoning is that I'd wanted an upgrade that didn't require me to spend a non existant $700, which of course would be the BH Crack with various options chosen. Though right now with the booster board I feel ample satisfied for now.


----------



## skeptic

Thanks for the write up on the booster board!  I've been sufficiently tempted and am adding it to my diy list to take on after I finish my wire se-se.


----------



## agdr

Hey thanks to all the builders for the O2 booster board listening reports!


----------



## JacobLee89

Did not want to drill holes for the two booster board LED's
 Spent 5x longer making an acrylic panel.
  

  
  
 On hindsight I wish I had access to a laser printer.


----------



## Claritas

I came across a recent article about the designer that might interest some other owners: http://spectrum.ieee.org/geek-life/profiles/nwavguy-the-audio-genius-who-vanished.


----------



## mcandmar

He raises an interesting point about the domain name, www.nwavguy.com its due to expire on the 9th..


----------



## Claritas

Tyll just put up a poll about him: http://www.innerfidelity.com/content/nwavguytroll-or-hero-1.


----------



## PTom

Has anyone considered creating a NWAvGuy appreciation thread? I wonder how the mods will react 
  
 Even though he was banned a while ago, his products are so influential on head-fi and he seems to be one of the most talked about person on these forums which is incredible considering the fact that not only was he banned a fair while ago, he's also vanished completely.


----------



## PTom

He seems to be turning into a legendary figure of sorts....


----------



## JacobLee89

ptom said:


> He seems to be turning into a legendary figure of sorts....


 
  
 He is the engineer head-fi deserves, but not the one it needs right now


----------



## gikigill

He is the engineer who held a mirror to audiophilias dirty underbelly and it didn't like what it saw.

His presentation was wrong but his arguments were right.


----------



## headwhacker

Audiophilia I think at some point has become a religion that no matter how you bring forth an argument that falsify a long standing belief will always be met with harsh retribution.


----------



## r010159

headwhacker said:


> Audiophilia I think at some point has become a religion that no matter how you bring forth an argument that falsify a long standing belief will always be met with harsh retribution.


 
  
 This is a very wise comment.
  
 I think the guy had the right intentions, and the tech "know how", and experience to back it up. But his approach was that of a singular quest. This showed in how he came across at times. But there is allot to be learned from a person like this. So people like him are worth accepting for who they are. It is not like a person could not reason with him. He was just a bit too aggressive at times. However, his contributions more than outweighed how his aggressive approach came across at times. His absence from the Internet community is a big loss.
  
 I used to be like this on Silicon Investor, during its heyday. No, I am not an expert on the stock market, But I have  an accurate BS detector in such matters. I have learned since then to be more diplomatic and relaxed about things.
  
 I hope he is well.
  
 BG


----------



## tomb

1. He played the Pied-Piper's music of "it's cheap and it's as good as you can get."
  
 That's unfortunate in that the proper context was never honestly portrayed.  There are good people selling the O2.  It's not trash at all, but when people try to make out that it's the best you can get, no matter the cost, well ...
  
 2. David Schneider is wise.  I have suspected the same thing:

The DScope is prohibitively expensive.
Either he was fabulously wealthy in his own right, or it was supplied to him by an employer with tremendous resources.
Employers with those kind of resources often have a well-developed and mature bureaucracy  Such an environment is going to have significant conflict-of-interest standards, including those pertaining to outside work using company equipment: meaning _absolutely forbidden_.
The IEEE article is a proof in and of itself: his blog's popularity rose to the point that it was noticed outside of the sub-culture that we inhabit.
  
 JMHO ...


----------



## headwhacker

Well, he is an engineer first and enthusiast second. I sure did learn a lot from his blog which re-ignited my passion for DIY. I used to stay up all night designing circuit boards for digital circuits back in college. Skills which are almost forgotten until I went out doing research on audio stuff.
  
 I for one could not get the idea how an amplifier could cost several thousands of dollars just to do one particular function. Not to mention the ludicrous prices are for some some cables.


----------



## tomb

headwhacker said:


> Well, he is an engineer first and enthusiast second. I sure did learn a lot from his blog which re-ignited my passion for DIY. I used to stay up all night designing circuit boards for digital circuits back in college. Skills which are almost forgotten until I went out doing research on audio stuff.
> 
> I for one could not get the idea how an amplifier could cost several thousands of dollars just to do one particular function. Not to mention the ludicrous prices are for some some cables.


 
  
 No one ever said that there weren't excesses in our culture.  Those exist almost anywhere that there's money to be made.  By the same token, excesses exist on the bottom end, too - by claiming that something cheap is just as good.
  
 "Engineer" is an abused term, also.  I know nothing for fact, but the idea that you'd sit a truly qualified - or even further, registered - "Engineer" down in front of a DScope every day is a stretch.  A typical registered engineer's _monthly_ salary (certainly two months) may exceed the total investment in the DScope.  More typically, a truly qualified "Engineer" is paid to operate and/or design equipment that is worth significantly more than an _annual_ salary.
  
 Again, JMHO ... 
  
 P.S. It's my fault more than anyone's probably, but this is a serious digression from the thread.  I apologize.


----------



## Xenophon

+1 with the above. Some gear is ridiculouslyl overpriced for what it is/does, there's no denying that. I applaud the O2's designer for exposing this and showing that it can be done differently. But there's a huge difference between doing that and becoming/attracting zealots who think the O2 is somehow the sum of all amplifiers. It's not. Cheap and it can compete with seriously more expensive gear but it's also limited, denying that does a disservice to the project imo. And last but not least, objectivism and musical enjoyment will always remain an uneasy marriage, not everything can be reduced to a graph.


----------



## proton007

tomb said:


> No one ever said that there weren't excesses in our culture.  Those exist almost anywhere that there's money to be made.  By the same token, excesses exist on the bottom end, too - by claiming that something cheap is just as good.




"Good" is a vague term. Of course there are specs that can be bettered, whether or not they matter is the question that Nwavguy answered. Reading through his blog also raised the confidence of many engineering oriented audio enthusiasts, it became easier to distinguish the boundaries between science and aesthetics and pure b.s. because suddenly everyone was willing to talk about these things.

Him being present or absent doesn't really matter IMO. His voice was heard and the O2 became an icon for his line of thinking.
That's all that matters.


----------



## bpower

I found the reaction to his "attitude" quite telling. He a professional engineer, and a lot of the people he was criticising quite frankly were not. Sure they engineered things for a living but they never worked in a professional enviroment with engineers before. When an engineer sees a design with a fault in it he must call it out, he'd be grossly negligent if he didn't. The feelings or the "good standing" of the original designer don't come into it. Likewise when an engineer, or any scientist, sees someone misusing math or misunderstanding some principle of their discipline they call them out. The vali thread was a great example of this. He behaved like a conscientious engineer while others thoroughly exposed their own ignorance (and worse) for all to see.


----------



## JacobLee89

bpower said:


> I found the reaction to his "attitude" quite telling. He a professional engineer, and a lot of the people he was criticising quite frankly were not. Sure they engineered things for a living but they never worked in a professional enviroment with engineers before. When an engineer sees a design with a fault in it he must call it out, he'd be grossly negligent if he didn't. The feelings or the "good standing" of the original designer don't come into it. Likewise when an engineer, or any scientist, sees someone misusing math or misunderstanding some principle of their discipline they call them out. The vali thread was a great example of this. He behaved like a conscientious engineer while others thoroughly exposed their own ignorance (and worse) for all to see.


 
  
 One could also say that the culture between the O2 designer's methodology clashed with the audiophile community. In some fields of professionalism, negative and constructive criticism must be taken both during and after the design has been developed. The mindset is of one that focuses on improving the design by any means possible, regardless of who put the most effort in *or how someone feels about it*.
  
 The mentioned culture however, is one only developed once you work in such an environment. For those whom are unfamiliar with said culture, they can see people coming off as brash, aggressive, and highly opinionated.


----------



## tomb

bpower said:


> I found the reaction to his "attitude" quite telling. He a professional engineer, and a lot of the people he was criticising quite frankly were not. Sure they engineered things for a living but they never worked in a professional enviroment with engineers before. When an engineer sees a design with a fault in it he must call it out, he'd be grossly negligent if he didn't. The feelings or the "good standing" of the original designer don't come into it. Likewise when an engineer, or any scientist, sees someone misusing math or misunderstanding some principle of their discipline they call them out. The vali thread was a great example of this. He behaved like a conscientious engineer while others thoroughly exposed their own ignorance (and worse) for all to see.


 

 Just an FYI, but IMHO, this violates our Professional Engineering Code of Ethics.
  
 "Call them out?'  On a public forum/blog?  The only way that would be justified is in case of life-safety.  Even then, you better be d*mn sure and prepared to take it through to its conclusion.  The _first step, _is to give the original designer the benefit of doubt (at least in public, no matter what you personally think).  If you are contemplating going public with a design error, you contact him/her, find out the goals involved in the design, the decisions made, and the context with which any performance claims might have been made.  If something like an error-of-omission was made, then you allow the original designer to make good on it, first.
  
 You also should not _insult_ a Professional Engineer by equating one with, "or any scientist."


----------



## bpower

tomb said:


> Just an FYI, but IMHO, this violates our Professional Engineering Code of Ethics.
> 
> "Call them out?'  On a public forum/blog?  The only way that would be justified is in case of life-safety.  Even then, you better be d*mn sure and prepared to take it through to its conclusion.  The _first step, _is to give the original designer the benefit of doubt (at least in public, no matter what you personally think).  If you are contemplating going public with a design error, you contact him/her, find out the goals involved in the design, the decisions made, and the context with which any performance claims might have been made.  If something like an error-of-omission was made, then you allow the original designer to make good on it, first.
> 
> You also should not _insult_ a Professional Engineer by equating one with, "or any scientist."


 
 Well if you want to stick to the Professional Engineering Code of Ethics you should also mention that he broke an even more fundamental rule of design criticism. Full disclosure! Who are you? Where do you live? How many X's have you designed? Whats your agenda? Everyone has an agenda, good-faith criticism of design is one of those audiophile myths you hear about. Are you using a Cloak of Anonymity? Remember the Grand Order of Professional Engineers has explicitly banned such cloaks.
  
 Whether or not we may criticise "from the bushes" is left to the discretion of the Engineer, but it is frowned upon.


----------



## Claritas

bpower said:


> Well if you want to stick to the Professional Engineering Code of Ethics you should also mention that he broke an even more fundamental rule of design criticism. Full disclosure! Who are you? Where do you live? How many X's have you designed? Whats your agenda? Everyone has an agenda, good-faith criticism of design is one of those audiophile myths you hear about. Are you using a Cloak of Anonymity? Remember the Grand Order of Professional Engineers has explicitly banned such cloaks.
> 
> Whether or not we may criticise "from the bushes" is left to the discretion of the Engineer, but it is frowned upon.


 
  
 I don't see why it matters who he is, except as a matter of curiosity and gossip. Maybe he's an alien who returned to his home planet like the founders of all the other religions. 
	

	
	
		
		

		
		
	


	




 Whether he was right or wrong doesn't depend on that.


----------



## miceblue

I'm sure this applied to NwAvGuy too, but my favourite quote from JDS Labs is:
http://blog.jdslabs.com/?p=722


> It makes perfect sense from a marketing standpoint to enable the latest features on a new device. Fortunately, we’re engineers and not marketers.


----------



## proton007

miceblue said:


> I'm sure this applied to NwAvGuy too, but my favourite quote from JDS Labs is:
> http://blog.jdslabs.com/?p=722




From a marketing standpoint it makes perfect sense to take people's money without actually giving them anything in return 

Fortunately we have engineers willing to call something b.s. when they see it.


----------



## headwhacker

But in the real-world a good Business must have a good balance of Engineers and Marketers. Of course you can tell which group have the strongest influence over how the company operates.
  
 A business consists only of Engineers can create awesome stuff but unable to sell enough to make money; thus collapse.
  
 A business consist only of Marketers will only be good at spreading hype on products but will never deliver.
  
 I just notice the conversation is getting off-topic. No? (Or not, O2 and ODAC is NwAvGuy) lol


----------



## tomb




----------



## proton007

headwhacker said:


> But in the real-world a good Business must have a good balance of Engineers and Marketers. Of course you can tell which group have the strongest influence over how the company operates.
> 
> A business consists only of Engineers can create awesome stuff but unable to sell enough to make money; thus collapse.
> 
> A business consist only of Marketers will only be good at spreading hype on products but will never deliver.




Marketers usually have the habit of over-committing. Unrealistic schedules, features that don't really make sense but somehow the "customer wants them!" (Guess who convinced the customer in the first place).

But, as you said, the Engineer can't sell. They're more like "take it or leave it."
But hey, if your market is majority enthusiasts, you don't need a lot of marketing to convince them.

Back to the topic.

WHO IS NWAVGUY? A vigilante? A crusader who fights all audiophile injustice? 
Where does he live?
What does he eat for breakfast? 
Who is he sleeping with?


----------



## miceblue

Well NwAvGuy did get zero money from the ODAC and O2. XD


----------



## headwhacker

proton007 said:


> But hey, if your market is majority enthusiasts, you don't need a lot of marketing to convince them.


 
  
 Then you only limit your business to "niche". When economy collapse, niche business are the first to go away. As people will limit expenses to "essentials".  But then if you don't rely on your business as your only source of income, I guess it's fine. Altmann is the best example I can think of.


----------



## proton007

headwhacker said:


> Then you only limit your business to "niche". When economy collapse, niche business are the first to go away. As people will limit expenses to "essentials".  But then if you don't rely on your business as your only source of income, I guess it's fine. Altmann is the best example I can think of.




Better stock up then!


----------



## adydula

Hey guys the thread starter in post one :
  
 ""As I was searching for a good amp/ dac, I decided to save myself the trouble of picking between numerous options and get an O2 amp/ dac. Now I have to choose between JDS Lab variant and the EHP variant. I can only see the rear view of the former (http://www.jdslabs.com/item.php?fetchitem=39) and the latter seems smaller than I thought (http://epiphany-acoustics.co.uk/wp-content/uploads/2012/04/Epiphany-Acoustics-EHP-O2-Reflection2.jpg). Why is it that the EHP variant is187 dollars and the JDS LAB variant is 285 dollars? P.S. Do I need an AC adapter for both? I would appreciate it if you guys can help me choose.""
  
 Lets get back to the thread.....
  
 Thanks
 Alex


----------



## jring

adydula said:


> Hey guys the thread starter in post one :
> 
> ""As I was searching for a good amp/ dac, I decided to save myself the trouble of picking between numerous options and get an O2 amp/ dac. Now I have to choose between JDS Lab variant and the EHP variant. I can only see the rear view of the former (http://www.jdslabs.com/item.php?fetchitem=39) and the latter seems smaller than I thought (http://epiphany-acoustics.co.uk/wp-content/uploads/2012/04/Epiphany-Acoustics-EHP-O2-Reflection2.jpg). Why is it that the EHP variant is187 dollars and the JDS LAB variant is 285 dollars? P.S. Do I need an AC adapter for both? I would appreciate it if you guys can help me choose.""
> 
> ...


 
  
 You might want to check the EHP price again - it's 187 UK pounds for the O2+ODAC combo, not dollars. Although right now it's on discount at 167 pounds.
 The EHP offer includes the AC adapter and you can choose UK, EU or US versions. With the JDS offer the adapter is not included.
  
 Joachim


----------



## JacobLee89

jring said:


> You might want to check the EHP price again - it's 187 UK pounds for the O2+ODAC combo, not dollars. Although right now it's on discount at 167 pounds.
> The EHP offer includes the AC adapter and you can choose UK, EU or US versions. With the JDS offer the adapter is not included.
> 
> Joachim


 
  
 £167 works out to be around $280 (rounded up, at time of writing)  And with the adapter the JDS variation is $300 (rounded up, at time of writing).
  
 Without postage costs, this works out well. But with postage, this is far more of a deal for people in the UK than for anyone else.
  
 Add the O2 output booster board upgrade and a USB isolator, and you have a clear contender for for a dac+amp end game set-up fit for a starving student's budget.


----------



## James-uk

jacoblee89 said:


> £167 works out to be around $280 (rounded up, at time of writing)  And with the adapter the JDS variation is $300 (rounded up, at time of writing).
> 
> Without postage costs, this works out well. But with postage, this is far more of a deal for people in the UK than for anyone else.
> 
> Add the O2 output booster board upgrade and a USB isolator, and you have a clear contender for for a dac+amp end game set-up fit for a starving student's budget.



Are JDS or epiphany going to manufacture the booster board O2 or are they not allowed?


----------



## JacobLee89

james-uk said:


> Are JDS or epiphany going to manufacture the booster board O2 or are they not allowed?


 
  
 The O2 output booster PCB is a DIY project by AGDR that's is on its 3rd revision. I found out about it in the DIY section of this forum:
  
http://www.head-fi.org/t/693300/o2-headamp-output-booster-modification-pcb
  
 With it installed, I have noticed better clarity on certain instruments, and that transients (i.e: a drum being hit / staccato notes) became sharper and more "thumpier". Imagine it as a O2 which had a good meal and a hot shower.
  
 The only downside is that the DIY project requires SMD soldering, requiring an additional flux pen/dispenser and at least tweezers of some sort. The good news is that everything is documented, and following the build instructions (read through everything once though) step by step has made the process easier. (This was also my first SMD project)
  
 It'll be best to contact AGDR about obtaining the PCB, or the kit. I am however unsure when the next batch of PCB's will be available.
  
 *edit*
  
 I guess them (JDS / epiphany) "building" the PCB's may just be up to AGDR's decision. The design leaves much possibility for several tweaks (even a complete PCB overhaul), and the constant design changes could just discourage JDS or epiphany from including such a mod. 
  
 Wouldn't hurt contacting them to raise their awareness of such a gem though.


----------



## rikaldrey

jacoblee89 said:


> £167 works out to be around $280 (rounded up, at time of writing)  And with the adapter the JDS variation is $300 (rounded up, at time of writing).
> 
> Without postage costs, this works out well. But with postage, this is far more of a deal for people in the UK than for anyone else.
> 
> Add the O2 output booster board upgrade and a USB isolator, and you have a clear contender for for a dac+amp end game set-up fit for a starving student's budget.


 

 Don't forget about HeadnHifi if in Europe. With just a few more, you can get the new revision which has the AC input and RCA output at the back with a 1/4" Headphone out in the front. Very clean-looking. If you want to save even more you can get the DIY kit. Keep in mind he is based in Switzerland, so you'll have to check the Germany(He ships it from Germany) shipping option to prevent paying the Royal Mail(If in the UK) pigs or your respective local post offices the extra fee and tax.


----------



## locksbury

rikaldrey said:


> Don't forget about HeadnHifi if in Europe. With just a few more, you can get the new revision which has the AC input and RCA output at the back with a 1/4" Headphone out in the front. Very clean-looking. If you want to save even more you can get the DIY kit. Keep in mind he is based in Switzerland, so you'll have to check the Germany(He ships it from Germany) shipping option to prevent paying the Royal Mail(If in the UK) pigs or your respective local post offices the extra fee and tax.


 

 Yeah, that's what I did; got the DIY kit shipped from Germany and incurred no further charges. 
	

	
	
		
		

		
			





 Hopefully this coming week I can get the ODAC wired up and finally try the whole thing!


----------



## agdr

jacoblee89 said:


> I guess them (JDS / epiphany) "building" the PCB's may just be up to AGDR's decision. The design leaves much possibility for several tweaks (even a complete PCB overhaul), and the constant design changes could just discourage JDS or epiphany from including such a mod.
> 
> Wouldn't hurt contacting them to raise their awareness of such a gem though.


 
  
 Hey good question!  I have not copyrighted the O2 booster board in the spirit of the O2 designer's goals with the O2 amp.  The Gerber files to make PC boards are posted at the Google Drive link in that DIY thread (use the V3.0 which includes the headphone relay).  Anybody can make boards, including companies.  I know that the forum here keeps close watch over the commercial end of things.  Any company planning on selling the boards, either bare or assembled, better not make any mention of it here in the forum unless they are properly set up with Head-Fi as a commercial vendor.  But as far as license goes there isn't any, and I get no royalties the same as the O2's designer didn't for the O2.  Anybody can make the O2 booster board. 
	

	
	
		
		

		
		
	


	



  
 As for DIY, the mods here will let me sell the stuff at-cost to help out with the minimum board order quantities at the PCB fabrication outfits. I have one board left from the existing batch and a parts kit (only for those overseas, in the US you have to use Mouser or Digikey direct) as per the DIY booster board thread.  Send me a PM if anyone is interested. I'll probably do another board run in the near future too.
  
 EDIT: the last board from the current run just found a home.  I'll post in the DIY section thread when I do another board run.


----------



## tomb

jacoblee89 said:


> james-uk said:
> 
> 
> > Are JDS or epiphany going to manufacture the booster board O2 or are they not allowed?
> ...


 
  
 Someone has developed an O2 booster board?  And you notice "better clarity," "transients ... became sharper," and now things "are more thumpier?"
  
 Just curious, but was that a _subjective_ or _objective_ conclusion?
  
  
 P.S. I am _certain _that agdr has come up with something worthwhile.  In no way am I attempting to state that it's not an improvement.  If I had an O2, I'd build his booster board, too.


----------



## adydula

The booster  board has a long and well worth reading thread on the diyaudio site.
 I have heard no real world audio improvements that my ears can detect.
  
 The booster board does reduce the dc offset voltage from 3mv to 10uv a 98% reduction in this voltage.
 It also replaces the two NJM4556A output chips with a OP140 and LME49990 pair on each channel.
  
 The booster board also allows for higher voltages for higher impedance and low-sensitivity headphones.
 The O2 runs 12 volt rails. The booster board allows for this voltage to run at 15 vdc.
  
 There is also a 18vdc modification if desired.
  
 Another neat thing is the board reduces turn off thumps.
  
 There are several other neat modifications, like being able to add a 1/4" Neutrik jack!
  
 Enjoy
 Alex
 and Thanks to AGDR!


----------



## JacobLee89

tomb said:


> Someone has developed an O2 booster board?  And you notice "better clarity," "transients ... became sharper," and now things "are more thumpier?"
> 
> Just curious, but was that a _subjective_ or _objective_ conclusion?
> 
> ...


 
  
 We can quite comfortably say that it's subjective. I sadly do not have any measuring equipment, and do not have another O2 to do any A/B testing with. Only my very likely biased memory of how it used to sound, and my ears. I may have been subjected to some mental voodoo magic in this case. I now have 2 additional green LED's I can oogle at though....
  
 I'm not going to defend the O2, or the booster board though it did "feel" like it has some sort of improvement on my HD650s after the mod, and by no means (from what I've read so far) that the O2 can get any close to a BH Crack in terms of pairing with the HD650. Which of course will be my next acquisition to save up for.
  
 I'm quite midway in this sort of topic: I find the subjective viewpoint as important as the objective. I could use analogies, but we are all of different backgrounds, perspectives, ear sizes, and appetite.


----------



## mcandmar

tomb said:


> Someone has developed an O2 booster board?  And you notice "better clarity," "transients ... became sharper," and now things "are more thumpier?"


 
  
 Obviously subjective, but i found exactly the same after building and testing one for myself. Regardless of measurements or semantics, it just sounds better.   ......IMO
  
 Also i do have two O2's so i was able to do some side by side comparisons to satisfy my own curiosity.


----------



## r010159

jacoblee89 said:


> We can quite comfortably say that it's subjective. I sadly do not have any measuring equipment, and do not have another O2 to do any A/B testing with. Only my very likely biased memory of how it used to sound, and my ears. I may have been subjected to some mental voodoo magic in this case. I now have 2 additional green LED's I can oogle at though....
> 
> I'm not going to defend the O2, or the booster board though it did "feel" like it has some sort of improvement on my HD650s after the mod, and by no means (from what I've read so far) that *the O2 can get any close to a BH Crack in terms of pairing with the HD650*. Which of course will be my next acquisition to save up for.
> 
> I'm quite midway in this sort of topic: I find the subjective viewpoint as important as the objective. I could use analogies, but we are all of different backgrounds, perspectives, ear sizes, and appetite.


 
  
 I think on a future upgrade my money may be spent on the BH Crack amp instead of the booster board. How does it compare to the O2? What is the cost involved with parts?
  
 BG


----------



## agdr

adydula said:


> The booster  board has a long and well worth reading thread on the diyaudio site.
> I have heard no real world audio improvements that my ears can detect.


 
  
 Hi Alex!  This is good news, since you know what they say about medical doctors - "first do no harm". 
	

	
	
		
		

		
		
	


	




   Alex and the other builders know I've stayed away from making any comments on how I think the booster board sounds or making any sound claims.  That is all your guy's jobs! 
	

	
	
		
		

		
		
	


	




   There are a lot of folks here on the foum with critical listening ears much better than mine.  I'm just the engineer. 
  
 If the booster does make any headphones or IEMs sound better it is probably due to some combination of the stuff that is objective (measureable) with the booster board:
  
 * Like Alex says that 93% or so reduction in output DC offset from 3mV for the standard O2 to 30uV or so with the booster means that the transducers in headphones or IEMs stay much closer to their natural mechanical "zero" resting point.  If this makes a difference at all in the sound it is more likely to be with sensitive IEMs than headphone.  In fact, for my fairly sensitive AKG-K550s, I wrote their tech support once about the issue.  The answer that came back was 3mV being no problem at all since the standard volume level is around 40mV and maximum around 130mV.  3mV just put the transducer diaphram slightly to one side.  But I've read posts where people with some IEMs swear it makes a huge difference to have the transducer resting in the middle.  So... you tell me from the listening! 
	

	
	
		
		

		
		
	


	



  
 * The latest version 3.0 with the relay completely eliminates all O2 turn-on and turn-off thumps with the one wire addition going from the booster to the O2 board.  This won't change listening sound any, but at least the thumps are gone.  One anoyance nailed.
  
 * Double the slew rate as mentioned in posts above from the O2 amp's 3V/uS to the 6V/uS limit of the O2's input NJM2068 gain chip.  As per the discussions above the digital 16/44 signal processing chain limits slew such that the O2's 3V/uS *should* be adequate, but there are certainly many other opinions here.  Again, you guys tell me from the listening if there is a difference.
  
 * +/-15Vdc upgrade capability for folks with high impedance and low sensitivity phones that can't get enough volume from the O2.  This would be a fairly small subset of users.
  
 * Those mezmerizing green LEDs! 
	

	
	
		
		

		
		
	


	




   They perform a couple of useful diagnositic functions.  The LEDs are hooked in after the O2's power management mosfets vs. the O2's red which is before the mosfets.  So when the green LEDs come on you know your mosfets have turned on and the O2 amp circutis are getting juice.  And since one LED is on each power rail, if only one LED ever comes on you know you have lost on power rail, and even know which one based on which LED went dark.  When the O2's batteries run down and the O2's power management circuit shuts it down, you finally have a way to know what has happened.  The O2 red LED will still be on but both green LEDs will go off.
  
 * Should be slightly lower noise and distortion from the datasheet numbers, but this is yet to be fully measured.  I've recently bought one of the QA400 analyzers (essentially a USB soundcard in a box set up for distortion measurements) and ran some initial tests on both the standard O2 and one with the booster.  To the limit of the QA400, which is 10 or 20dB  noiser than a dScope or AP analyzer, the two looked essentially identical within the margin of error.  The booster was just a tad better in THD+N, but again figuring in the margin of error it is a wash.  But most likely both units are bumping up again that higher noise floor in the QA400.  I'm in the process right now of stuffing a notch filter PCB I built to try to take those noise THD+N numbers down further.  But again, the good news here is that the booster board did not appear to make the O2's THD+N any worse.  Even if the THD+N numbers eventually do measure better than the stock O2 there is a good argument to be made as to whether that would even be audible or not.  You tell me with the listening!
  
 * Higher current drive capability for folks with low impedance low sensitivity headphones.  Again this is likely to be a small subset of headphones or IEMS out there.
  
 * Zero output impedance capability.  The folks who have built booster boards should keep in mind they can short the four O2 1-ohm resistors straight across, as shown in the diagrams here, to get true zero ohms out.  The stock O2 needs those resistors to balance up the two paralleled sections of the NJM4556A output chips.  To make the booster board plug and play I designed it to use those 4 resistors as they sit when you plug in the board, so you still wind up with the O2's 0.5 ohm output resistance.  But the booster chips don't need any resistor.  You can just short those right across underneath the O2.  Whether having zero ohms out vs. 0.5 ohms makes any difference in the sound, well... you tell me with your listening!


----------



## JacobLee89

agdr said:


> * Zero output impedance capability.  The folks who have built booster boards should keep in mind they can short the four O2 1-ohm resistors straight across, as shown in the diagrams here, to get true zero ohms out.  The stock O2 needs those resistors to balance up the two paralleled sections of the NJM4556A output chips.  To make the booster board plug and play I designed it to use those 4 resistors as they sit when you plug in the board, so you still wind up with the O2's 0.5 ohm output resistance.  But the booster chips don't need any resistor.  You can just short those right across underneath the O2.  Whether having zero ohms out vs. 0.5 ohms makes any difference in the sound, well... you tell me with your listening!


 
  
 The Zero output impedance mod does seem to me like something that requires more fiddling than it's worth, therefore I've left the output impedance at 0.5. The booster board still (either subjectively or objectively) sounds like an improvement over the stock O2.
  
 However I am now curious as to how an amplifier's output impedance would affect headphones. Currently reading up on Benchmark Media's article on it, which is convincing me to try it out.
  
 *edit**
 Done the mod and cannot hear any noticeable change. Might be noticeable with lower impedance headphones / IEMS


----------



## tomb

jacoblee89 said:


> tomb said:
> 
> 
> > Someone has developed an O2 booster board?  And you notice "better clarity," "transients ... became sharper," and now things "are more thumpier?"
> ...


 

 Sorry, I couldn't resist.  Thank you for your thoughtful and considerate reply, despite my smart-alecky irony.


----------



## agdr

jacoblee89 said:


> However I am now curious as to how an amplifier's output impedance would affect headphones. Currently reading up on Benchmark Media's article on it, which is convincing me to try it out.


 
  
 You might want to try actually going in the other direction and *adding* some series resistance and then see how that sounds.  I'm not entirely convinced that near-zero ohms output impedance yeilds the best results for some heapdhones, even though I know the O2's designer cited this paper from Benchmark showing that was the case:
  
http://test.benchmarkmedia.com/discuss/sites/default/files/Headphone-Amplifier-Performance-Part-2.pdf  (opens PDF)
  
 I asked that question too about headphone amp output impedance to the Harmon/AKG tech support foks about the AKG-K550s.  The surprising answer that came back was an amp output impedance within +/-20 ohms of the headphone impedance (which is 32 ohms) is what they recommend.  That equates to an amp output imipedance of 12 ohms - 52 ohms.  Adding series resistance effectly changes a headamp's damping factor.  
  
 An easy way to try that out with the O2 is get a "bare" 3.5mm plug and 3.5mm jack.  Then just solder resistors between the L and R channels on the plug and jack, but run the ground straight across of course.  Then plug that into the amp output and your headphones into that adaptor.  That way you don't have to mess with anything inside the O2 to try it out.
  
 On my O2 Desktop Amp board (also DIY, not commercial) I've left a provision for adding a series resistor on the output of each channel. Those holes can also be wired to an external 5 position front panel switch with resistors set for something like 1R, 10R, 20R, 80R, and the ubiquitous 120R to give 5 different damping factors.  I see this HA-501 headamp by Teac has that fetaure:
  
http://www.teac.com/product/ha-501/


----------



## miceblue

agdr said:


> adydula said:
> 
> 
> > The booster  board has a long and well worth reading thread on the diyaudio site.
> ...



Hm, this sounds very interesting. Maybe you can work with JDS Labs to get some things measured. After all, they do have the same PrismSound dScope Series III analyser that NwAvGuy used for his measurements. It would be interesting to see if a group could do blind tests too in lieu of what NwAvGuy did with the O2 vs DAC1PRE (I believe it was).

I would be interested in one of these.


Also, the higher current could be beneficial for planar magnetic headphones, which are current-dependent from what I understand.


----------



## agdr

I wanted to follow-up on what I posted earlier in the slew rate discussion about possibly being able to fit a LME49990 dual-SMD to DIP adaptor in place of the O2's NJM2068 gain chip to raise the end-to-end slew rate all the way up to 20V/uS.  Well turns out the adaptor does fit and work just fine, photos below.  I'm listening to an O2 + booster board with the dual LME49990 chips in place of the O2's NJM2068 chip as I write this.
  
 That dual LME49990 op amp "roll" beats the NJM2068 in datasheet parameters in all areas, unlike the LME49720 which is more of a straight across wash.  The O2 designer noted in his blog that the LME49720 was similar to the NJM2068, with the major downside just being it was more expensive.  He never did evaluate the LME49990, probably beause it only comes in surface mount and at the time was quite a bit more expensive.  Back then one cost around $8 as I recall, but now they are down to $2.50 or so.  The LME49990 is also the chip that opc uses in his "Wire" DIY headphone amp, wrapped around the LME49600.  I used the OPA140 instead in the booster board since it is a DC precision chip, along with having good AC parameteres, and getting the O2's output DC offset down was a big design goal.
  
 I see that folks on eBay are selling these dual LME49990 adaptors with the two chips already soldred on for around $15.  Not bad, assuming the chips are real which is always a concern on eBay.  If you buy one make sure you get the adaptor for DUAL chips to DIP.  Folks are also selling just a single LME49990 to DIP adaptor.
  
 Using a LME49990 dual SMD adaptor in a standard O2 that has the original NJM4556A output chips probably won't buy much in terms of either slew rate or THD+N improvement.  Even though the LME49990 slews at 20V/uS the overall slew rate would still be limited by those output chips which are just 3V/uS.  Same with the THD+N, even the O2's designer noted in his blog the THD+N of the output chips are the O2's limiting factor, being higher than the THD+N of the NJM2068 gain chip.  But the O2 booster board also slews at 20V/uS.  With the booster the whole thing is 20V/uS slew rate end to end.
  
 The first two photos show both sides of the adaptor (both LME49990 chips) vs. the size of the O2's original NJM2068 chip.  The next photo shows good clearance around the adaptor in the O2.  The final shows plenty of clearance to the top of the booster board.


----------



## agdr

miceblue said:


> Hm, this sounds very interesting. Maybe you can work with JDS Labs to get some things measured. After all, they do have the same PrismSound dScope Series III analyser that NwAvGuy used for his measurements.


 
  
 Good thoughts!  I've actually already had that discussion with John (JDS) in another forum regarding my version of an O2 Desktop Amplifier DIY project.  His position at that time was that he feels blocked in performing a test by the O2 designer's license terms of "no derivitives", which is certainly a valid point   A bunch of PM correspondence proceeded to head my way from various folks about the issue. The net result I've run with is the belief that the ODA is different enough not to be considered a derivitive.  Then there is that nagging problem of the O2 designer having dissapeared and being out of contact for a license release.
  
 As for the booster board, by making it a separate board I'm trying to do an end-run around the O2 designer's terms.  But viewed a certain way - probably John's - it would still be considered a modification of the O2 since it plugs in and replaces the O2's output chips.
  
 So that is why I'm messing around with using a QA400 + notch filter for THD+N measurements.  Eventually I may just rent an Audio Precision system 2 and make some measurements.


----------



## r010159

Some very talented EEs here! I wonder how much the booster board with components would cost me? Also, how difficult would it be to install the booster board? Would any O2 board traces have to be cut? I know some holes would have to be drilled and some soldering would be involved. Now that there is a way to increase slew rate, besides having better output chips, all of you now have my interest in this project.
  
 BG


----------



## JacobLee89

agdr said:


> That dual LME49990 op amp "roll" beats the NJM2068 in datasheet parameters in all areas, unlike the LME49720 which is more of a straight across wash.  The O2 designer noted in his blog that the LME49720 was similar to the NJM2068, with the major downside just being it was more expensive.  He never did evaluate the LME49990, probably beause it only comes in surface mount and at the time was quite a bit more expensive.  Back then one cost around $8 as I recall, but now they are down to $2.50 or so.  The LME49990 is also the chip that opc uses in his "Wire" DIY headphone amp, wrapped around the LME49600.  I used the OPA140 instead in the booster board since it is a DC precision chip, along with having good AC parameteres, and getting the O2's output DC offset down was a big design goal.


 
  
 For the UK guys, there's an ebay seller that does these in the UK. The problem is that the width of the adapter seems to too wide to fit in the space the O2 board has:
  

  
 I would probably sand it down, but since I am in no rush and the price including postage varies little, I shall play the safe game and buy one from the US seller.


agdr said:


> I asked that question too about headphone amp output impedance to the Harmon/AKG tech support foks about the AKG-K550s.  The surprising answer that came back was an amp output impedance within +/-20 ohms of the headphone impedance (which is 32 ohms) is what they recommend.  That equates to an amp output imipedance of 12 ohms - 52 ohms.  Adding series resistance effectly changes a headamp's damping factor.
> 
> http://www.teac.com/product/ha-501/


 
  
 It seems like playing about with the output impedance is more of an experimental procedure, than of one that yields much rewards in terms of audio improvement. Since I've already done the mod I guess I can play about with the resisters, without the need to calculate that 0.5 ohms.


----------



## locksbury

adydula said:


> locksbury...
> 
> post some pix of your project and let us see how you fitted the ODAC in the O2 assembly...
> 
> Alex


 

 Finally got it complete today! Sounds good on the Mac! Will try running it under Windows 7 later and I suspect I'll have to a little digging to get it to work in Linux.
  
 Otherwise, I couldn't be happier! 
	

	
	
		
		

		
		
	


	




 Pics attach as promised! To fix the ODAC in, I had to resort to bolting it to the bottom of the case (taped over the connections that went to the wires) and no I'm not taking it apart again.


----------



## chuck8403

Just received my O2+ODAC from JDS Labs. Unfortunately, the wall wart I ordered didn't work. I use a wall wart from a previous order and it worked fine. Contacted JDS Labs and they responded immediately. They had a solution already in place within 30 minute of my contacting them. I can't recommend them enough. Great customer service. Great products also. Currently listening to music through the O2 and HD650s. Sounding great.


----------



## PTom

Has anyone directly compared the O2 made by JDS Labs to the Epiphany Acoustics version. Any difference in sound?


----------



## James-uk

ptom said:


> Has anyone directly compared the O2 made by JDS Labs to the Epiphany Acoustics version. Any difference in sound?



I own both, they sound identical .


----------



## skeptic

jacoblee89 said:


> I would probably sand it down, but since I am in no rush and the price including postage varies little, I shall play the safe game and buy one from the US seller.
> 
> .....


 
  
 Thanks for pointing this out!  For whatever reason, when I searched yesterday, the US seller didn't even come up.  Just ordered 1 to go along with my agdr board.  
  
 My alpha dogs and ML Mikros 90's both sound great with the stock O2.  Can't wait to give them a listen with the booster and 49990's in place


----------



## agdr

r010159 said:


> Some very talented EEs here! I wonder how much the booster board with components would cost me? Also, how difficult would it be to install the booster board? Would any O2 board traces have to be cut? I know some holes would have to be drilled and some soldering would be involved. Now that there is a way to increase slew rate, besides having better output chips, all of you now have my interest in this project.
> 
> BG


 
  
 The bill of materials for the O2 booster boards adds up to around $56 at Mouser, including the LEDs, but minus shipping costs.  The at-cost price on the PCB was $8 on this last run ( I had 10 made and was charged $80 at Seeed Studio, including shipping).  I will probably do another board run in the next month or so.  I'll post in the board's thread in the DIY forum here when those are back.
  
 The booster board just plugs right into the O2 amp  in place of the two NJM4556A chips (the ones next to the battery in the middle).  You unplug those two chips then plug in the booster board.  It slides into the top slot in the standard O2 B2-080 case.  There are 3 wires that go from the booster board to the O2 PCB that have to be soldered on.  Two are grounds, one going to either middle battery terminal and the other in front going to a resistor.  The 3rd one is for the no-thump relay circuit and goes from the booster board to another resistor in the power management section of the O2.   Pictures of exactly where those 3 wires attach are posted at the google drive link.  After all the surface mount soldering one does in soldering up the booster board those 3 wires will be a piece of cake! 
	

	
	
		
		

		
		
	


	



  
 No holes have to be drilled anywhere except for two small ones in the front panel if you want to be able to see the LEDs on the booster board. I have the measurements of where those holes need to be posted in the build instructions.
  
 Good questions!


----------



## JacobLee89

agdr said:


> No holes have to be drilled anywhere except for two small ones in the front panel if you want to be able to see the LEDs on the booster board. I have the measurements of where those holes need to be posted in the build instructions.


 
  
 Or you can waste even more time and manually shape out a panel out of clear plastic. Just to avoid drilling two extra holes (which makes no sense because I had to drill and expand 11 holes regardless)
  
 I also realised that we of the O2 Output Booster board thread, have began hijacking this thread. Unsure whether I should feel sorry or not.


----------



## pearljam50000

How does it compare to Meridian Explorer, and in general is there any other dac+amp for 300$ that is better than this? thanks.


----------



## r010159

jacoblee89 said:


> Or you can waste even more time and manually shape out a panel out of clear plastic. Just to avoid drilling two extra holes (which makes no sense because I had to drill and expand 11 holes regardless)
> 
> I also realised that we of the O2 Output Booster board thread, have began hijacking this thread. Unsure whether I should feel sorry or not.


 
  
 It is still O2 related and also IMO a nice break from the regular discussion. 
	

	
	
		
		

		
			




  


agdr said:


> [good info deleted]
> 
> The booster board just plugs right into the O2 amp  in place of the two NJM4556A chips (the ones next to the battery in the middle).  You unplug those two chips then plug in the booster board.  It slides into the top slot in the standard O2 B2-080 case.  There are 3 wires that go from the booster board to the O2 PCB that have to be soldered on.  Two are grounds, one going to either middle battery terminal and the other in front going to a resistor.  The 3rd one is for the no-thump relay circuit and goes from the booster board to another resistor in the power management section of the O2.   Pictures of exactly where those 3 wires attach are posted at the google drive link.  After all the surface mount soldering one does in soldering up the booster board those 3 wires will be a piece of cake!
> 
> ...


 
  
 Surface mount chips? I do not know how to reliably solder them. I understand there is soldering paste for this. But I will pose my further fabrication questions on the separate O2 booster board thread. Other than that, I think this project would be a "no brainer" decision for me. It will turn my O2 + ODAC into the desktop amp it aspires to be! Oh yes, now that I mentioned it, will this also work for my setup (O2 + ODAC)?
  
 BG


----------



## agdr

jacoblee89 said:


> Or you can waste even more time and manually shape out a panel out of clear plastic. Just to avoid drilling two extra holes (which makes no sense because I had to drill and expand 11 holes regardless)
> 
> I also realised that we of the O2 Output Booster board thread, have began hijacking this thread. Unsure whether I should feel sorry or not.


 
  
 Lol!  Hey I like how your panel turned out. 
	

	
	
		
		

		
		
	


	




   This thread had kind of died off it seems, so a kick in the pants probably hasn't hurt.  Since the last booster board from this run went out the door though I am going to essentially shut up in this thread and post any new stuff in the DIY forum thread for the project.  Feel free to PM me with questions too.  Thanks again to the mods for even allowing discussion of an O2-related project in the first place!


----------



## JacobLee89

r010159 said:


> Other than that, I think this project would be a "no brainer" decision for me. It will turn my O2 + ODAC into the desktop amp it aspires to be! Oh yes, now that I mentioned it, will this also work for my setup (O2 + ODAC)?
> 
> BG


 
  
 It works, and to a point it's giving me enough of an improvement to keep me happy with my HD650s.
  
 Waiting patiently on the updates on the USB isolator over in the DIY threads so I can squeeze out some extra performance out of my ODAC.


----------



## Twolf

Has any of you guys tried the O2 amp with AKG K501 headphones, or something else from that era (K400/K401/K500)?


----------



## bar1

Yes, O2 + K501 sounds great.


----------



## anthk

I have a odac+o2 combo. There are different posts on the internet saying how you could use just one of the component for various functions. I am hoping that other owners could verify the facts for me please.
 1. Power on the combo. Use the line-in pot then the combo becomes an amp.
 2. Power OFF the combo. The line-in pot somehow becomes a line out of the ODAC.
 3. If I want to connect a speaker to the combo, should I
  a)  power on the combo and use the headphone out as usual , or
 b) power  off the combo and treat the line-in as line out from the dac?
  
  
  
 Thanks.


----------



## Veetastic

anthk said:


> I have a odac+o2 combo. There are different posts on the internet saying how you could use just one of the component for various functions. I am hoping that other owners could verify the facts for me please.
> 1. Power on the combo. Use the line-in pot then the combo becomes an amp.
> 2. Power OFF the combo. The line-in pot somehow becomes a line out of the ODAC.
> 3. If I want to connect a speaker to the combo, should I
> ...


 
 I also own an O2 + ODAC combo from mayflower and these are some of my observations.
  
 I can't verify anything. I am not really sure if the audio that I am getting from the line-in is actually from the ODAC or not. However, there is in fact audio that is coming from the line-in once the O2 amp is turned off. Whatever indication this is I do not know. Even when the power is on the line-in still acts as an output for what I believe to be the ODAC. The volume knob does not affect the actual output of the line-in. I think that while the combo is still connected to the computer via usb, the line-in will continue to act as an output for the ODAC. 
  
 I suppose this would be useful if you had another amp and wanted to use the ODAC as the D/A converter or you simply wanted to test different D/A converters. As far as speakers go, you will need an amp for them and I do not think directly connecting them to the ODAC which has no power output is ideal. Of course, this depends on what type of speakers you run too. 
  
 There seems to be a lot of flexibility with the combo as far as I know and you can personally try out what you think works the best for you since you already have the unit with you. Good luck.


----------



## anthk

veetastic said:


> I also own an O2 + ODAC combo and these are some of my observations.
> 
> I can't verify anything. I am not really sure if the audio that I am getting from the line-in is actually from the ODAC or not. However, there is in fact audio that is coming from the line-in once the O2 amp is turned off. Whatever indication this is I do not know. Even when the power is on the line-in still acts as an output for what I believe to be the ODAC. The volume knob does not affect the actual output of the line-in. I think that while the combo is still connected to the computer via usb, the line-in will continue to act as an output for the ODAC.
> 
> ...


 

http://www.techpowerup.com/reviews/JDSLabs/O2_ODAC/1.html

 Look at the last sentence of the "spec " . Seems like the combo has more functions than it is advertised


----------



## r010159

Reading a review of the O2 + ODAC at http://www.techpowerup.com/reviews/JDSLabs/O2_ODAC/4.html
  
 The specs there list the Op Amps as swappable. Is this true. Considering the talk about the O2 booster board, I am not so sure.
  
 BG


----------



## Poladise

Scary behaviour from my O2. Extremely loud buzz came through the headphones. Like a 60Hz square wave at what seemed like the amps maximum output. Pulled the headphones off after about 1 second and I powered off the amp another 2 seconds later just praying it hadn't damaged my LCD-2s. I'm guessing the battery was empty, which usually shuts it off with a thud, but this time I can only guess it was stuck between the ON/OFF state causing it to power up & down rapidly.
  
 Plugged in some cheap headphones and powered on again, buzz still there. Plugged on the mains and the amp worked normally (LCDs were OK too). I'm never using this on battery again and it's made me reluctant to even use it on mains tbh. Mine is the Epiphany Acoustics EHP-O2. Has anyone else experienced this?


----------



## James neutron

I experienced occasional buzzing or popping noise in my ODAC as well. Troubleshooting the issues I found either one of the batteries to be slightly dislodged and did not make a perfect connection anymore or it drained faster than the other and the amp failed to power off correctly. Measuring the voltage of your batteries might give you some insight into this.
 After a full recharge things should go back to normal. If they don't, contacting the manufacturer is recommended.
 For me personally battery use with the O2 is iffy and chose to power it by mains only.


----------



## wewewho77

poladise said:


> Scary behaviour from my O2. Extremely loud buzz came through the headphones. Like a 60Hz square wave at what seemed like the amps maximum output. Pulled the headphones off after about 1 second and I powered off the amp another 2 seconds later just praying it hadn't damaged my LCD-2s. I'm guessing the battery was empty, which usually shuts it off with a thud, but this time I can only guess it was stuck between the ON/OFF state causing it to power up & down rapidly.
> 
> Plugged in some cheap headphones and powered on again, buzz still there. Plugged on the mains and the amp worked normally (LCDs were OK too). I'm never using this on battery again and it's made me reluctant to even use it on mains tbh. Mine is the Epiphany Acoustics EHP-O2. Has anyone else experienced this?




Mine also behave like those of yours
Are there more Epiphany Acoustics that shows this kind of behaviour?
Makes me plug cheap HP first before plugging my HE500


----------



## A1Dan

poladise said:


> Scary behaviour from my O2. Extremely loud buzz came through the headphones. Like a 60Hz square wave at what seemed like the amps maximum output. Pulled the headphones off after about 1 second and I powered off the amp another 2 seconds later just praying it hadn't damaged my LCD-2s. I'm guessing the battery was empty, which usually shuts it off with a thud, but this time I can only guess it was stuck between the ON/OFF state causing it to power up & down rapidly.
> 
> Plugged in some cheap headphones and powered on again, buzz still there. Plugged on the mains and the amp worked normally (LCDs were OK too). I'm never using this on battery again and it's made me reluctant to even use it on mains tbh. Mine is the Epiphany Acoustics EHP-O2. Has anyone else experienced this?



Same thing happened with my JDS Labs O2 a couple of days ago. Turns out I hadn't plugged the power adapter in fully and the battery had completely drained.


----------



## chuck8403

a1dan said:


> Same thing happened with my JDS Labs O2 a couple of days ago. Turns out I hadn't plugged the power adapter in fully and the battery had completely drained.


 
 I have had a few of the Triad power supplies shipped to me bad. Did not realize they were bad until I bought a O2+ODAC from JDS Labs with a bad power supply and the LED did not light up. I tried another that I had and it lit up. That may be the reason your batteries discharged.


----------



## agdr

poladise said:


> Scary behaviour from my O2. Extremely loud buzz came through the headphones. Like a 60Hz square wave at what seemed like the amps maximum output. Pulled the headphones off after about 1 second and I powered off the amp another 2 seconds later just praying it hadn't damaged my LCD-2s. I'm guessing the battery was empty, which usually shuts it off with a thud, but this time I can only guess it was stuck between the ON/OFF state causing it to power up & down rapidly.
> 
> Plugged in some cheap headphones and powered on again, buzz still there. Plugged on the mains and the amp worked normally (LCDs were OK too). I'm never using this on battery again and it's made me reluctant to even use it on mains tbh. Mine is the Epiphany Acoustics EHP-O2. Has anyone else experienced this?


 
  
 The problem is a bit of a design hiccup with the O2.  The batteries tend to rise up in voltage a little bit once the load is cut off (when the battery is low and the O2's mosfets turn off).   If they rise up too much in voltage the O2's power management circuit thinks the batteries are charged up again and turns the mosfets back on.  That load causes the battery voltage to drop again, the O2 mosfets cut off again, and the whole thing repeats at that 60Hz-or-so rate.
  
 The best quick solution is to try changing your batteries to a newer (fresher) pair or a different brand.  The problem shouldn't show up at all with the O2 running on AC.
  
 Here is a permanent fix, below in the red circle, but it involves whipping up a little circuit board. It is a modification I posted a year or two ago on another forum.  The resistor, capacitor, and two additional transistors form a latch circuit that keeps the O2's power management circuit off permanently, until the next on/off switch toggle, once the batteries are low and toggle the O2's power management circuit mosfets.  The parts to the right of the red circle are just the O2's power management circuit. The modification doesn't affect the sound in any way since it is just wired into the O2's power management circuit that decides when to cut off the O2 batteries. 
  
 The 2.2uF capacitor needs to be ceramic or film, not electrolytic (too much leakage). The two transistors can be common 2N7000's if they are a version that have +/-30V maximum gates rather than the more common +/-20V gates.


----------



## anthk

veetastic said:


> I also own an O2 + ODAC combo and these are some of my observations.
> 
> I can't verify anything. I am not really sure if the audio that I am getting from the line-in is actually from the ODAC or not. However, there is in fact audio that is coming from the line-in once the O2 amp is turned off. Whatever indication this is I do not know. Even when the power is on the line-in still acts as an output for what I believe to be the ODAC. The volume knob does not affect the actual output of the line-in. I think that while the combo is still connected to the computer via usb, the line-in will continue to act as an output for the ODAC.
> 
> ...


 

 My only concern is would any of these connections overload the circuit/headphone/speaker and cause damages?


----------



## Poladise

Thanks for the info agdr


----------



## agdr

Here is some potential good news for folks with the low battery problem.   The O2 booster board is a T shape, but the PC board fabrication house does 5cm by 10cm of area whether it is used or not.  Looks like I can fit a couple of those O2 latch circuit boards in the unused space around the booster board. 
  
 The way it would work is just unplug the U2 chip on the O2 board (the NJM2903D) and plug in this little board instead.  What looks like a DIP socket on the little boards is two more sets of connection pins, like on the booster board, that plug into the O2's U2 socket.  Plus one wire has to go from the latch board and solder on to the end of a resistor on the O2 PCB.  Just like that no more low-battery "motorboating".   The O2 stays off until the O2 power switch is turned off then on to reset the latch circuit.  This board could also be used with the O2 booster board, but most likely the booster board solves the problem all by itself since the headphone relay has an 5 second turn-on delay.  The relay (and headphones) would just stay off while the O2's PM circuit is oscillating.
  
 All DIY (and surface mount parts and soldering).  The LM2903 surface mount comparator chip on the latch PC board just replaces the NJM2903 that was in the O2's U2 socket (exact same specifications for both), plus adds the extra O2 power management latch circuit.
  
 I don't want to sidetrack this thread with my DIY stuff, so check in the DIY forum here in the booster board thread for follow-ups.  It will probably be a few weeks before I do a board run.  All at-cost of course (non-commerical).  I'll post the Gerbers again so anyone who wants to can fabricate boards too.


----------



## locksbury

Hi
  
 I had success yesterday listening to my O2+ODAC combo on my Windows box and again very please with the sound. 
	

	
	
		
		

		
			




  
 However, when I tried it on my Linux laptop (fresh Slackware 14.1 install), there was no sound... 
	

	
	
		
		

		
		
	


	



  
 I've done the usual searches on this forum and elsewhere, but not found any useful info and so I thought I'd pick your brains here.
  
 So far:
  
 - ODAC works with Mac and Windows, so the hardware is good.
 - Confirmed the laptop is outputting sound from it's own speakers.
 - When plugged in, the ODAC is shown as detected in ALSAmixer.
 - I checked I'd unmuted the channel and turn the volume up to 100%.
  
 Any ideas or suggestions from other who've had this issue?


----------



## pearljam50000

Can anyone compare to Meridian Explorer?


----------



## James neutron

What would you like to know? And in what context (e.g. which headphones will you use) ?


----------



## pearljam50000

SQ wise only.
I'm not sure about the headphones as of yet.


----------



## James neutron

I think the choice between the two is largely dependent on the headphones you will be using.  The sound quality is very similar between the two and I think it's ultimately up to personal taste/preference in choosing one over the other.
 The o2-Odac has the ability to drive better more demanding headphones, while the Explorer is more limited and won't reach nearly the same loudness with less sensitive headphones.
 Meridian also had issues with the first few batches due to the high output impedance, which affected it's performance with low impedance, high sensitivity, headphones like IEMs.
 But from what I understand that issue has been addressed and the output impedance was lowered to 5 ohm (compared to the original 50 ohm).
 I had the first version, but didn't notice any impedance related issues with it driving either my high impedance AKGs or the portable Martin Logan, rated at a low 26 ohm.
 Ultimately the Meridian will be more limited in terms of output power. So if you plan to buy a headphone with a relatively low sensitivity and high impedance you might prefer a bit more headroom. Otherwise it should be fine.


----------



## jring

No idea why Slackware doesn't work (I assume you know http://linuxcritic.wordpress.com/2009/08/18/how-to-set-up-sound-in-slackware/) but I can confirm that ODAC works fine with linux in general (tried various ubuntu and debian systems).
  
 Joachim


----------



## locksbury

jring said:


> No idea why Slackware doesn't work (I assume you know http://linuxcritic.wordpress.com/2009/08/18/how-to-set-up-sound-in-slackware/) but I can confirm that ODAC works fine with linux in general (tried various ubuntu and debian systems).
> 
> Joachim


 
 Hi Joachim
  
 As per sods law I managed to get some sound a bit later; well at least playing through Xmms. 
	

	
	
		
		

		
		
	


	



  
 I'll have to look at that guide you linked and similar ones later to get all sound via the ODAC.
  
 Locksbury


----------



## CADCAM

Is there a way to run an ODAC from the optical or digital coax output of a disc player? Or is it strickly USB?
 I have a O2 (and love it) and would like to bypass the internal DAC on my cd player and use the ODAC as an external DAC.


----------



## BenF

cadcam said:


> Is there a way to run an ODAC from the optical or digital coax output of a disc player? Or is it strickly USB?
> I have a O2 (and love it) and would like to bypass the internal DAC on my cd player and use the ODAC as an external DAC.


 

 ODAC is strictly USB


----------



## CADCAM

I purchased a DAC that has optical, digital coax and BNC inputs. Can I run all three of my optical drives to it? All my drives have optical out as well as digital coax. I was going to purchase a BNC to RCA (75 ohm) cable for the third drive. Sorry if this question is off topic.


----------



## locksbury

locksbury said:


> Hi Joachim
> 
> As per sods law I managed to get some sound a bit later; well at least playing through Xmms.
> 
> ...


 
  


jring said:


> No idea why Slackware doesn't work (I assume you know http://linuxcritic.wordpress.com/2009/08/18/how-to-set-up-sound-in-slackware/) but I can confirm that ODAC works fine with linux in general (tried various ubuntu and debian systems).
> 
> Joachim


 
  
 I took a look at that guide and a few others, but still can't get the ODAC to be set as the main sound card in Linux. Will have to do some more digging. Oh well, at least I can use xmms to listen to my music collection.


----------



## jring

http://alexpb.com/notes/articles/2009/04/20/howto-change-default-sound-card-slackware-linux/


----------



## bpower

Hi Guys,
  
 I recently bought the EHP-02 from Epiphany. When listening to some tracks with a lot of dynamic range Im getting a lot of distortion (clipping?) at the load bits. I get the distortion at high volumes . but not crazy high, I could turn it up another couple of notches and still listen comfortably. A In the track below on Spotify at around 6:30 it gets really bad, like listening to a speaker phone up too loud. I get similar results with my hd 600s and M50. I get much less distortion on iems but the sound gets a bit mushed together and seems to struggle generally.
  
Alexei Sultanov – Rachmaninov : Piano Concerto No.2 in C minor Op.18 : II Adagio sostenuto
  
  
 Am I just asking too much of the amp to power the cans comfortably at high volumes? At gain x6 I never goes past 11 oclock, so I thought it would have plenty of power in reserve.


----------



## SilverEars

I have the HD-650 and pressed the gain button, and the music distorted like a mutha.  I have it on unity gain now and it's much tighter.  If you raise the gain, does it drastically raise the output impedance?


----------



## skeptic

Gain doesn't affect output impedance. What you are hearing is likely clipping - a known issue with the o2 if you have a high output source and try to run the o2 at high gain. Just run it in the low gain setting, or by clipping one resistor, you can set it to 1x/2.5x as the two positions.


----------



## skeptic

On an unrelated note, I was all excited to try my agdr booster board for the first time today. Had everything fully populated and looking pretty good, and then, like a total genius I soldered ic1 in backwards and ripped a leg off trying to reverse it. A torrent of invective followed... 

The most frustrating part is that I am leaving on a family trip Friday and there is no chance mouser or digikey will ship a replacement in time. Guess I'll have something to anticipate upon returning. Otherwise I think I did okay for a newbie at surface mount.


----------



## bpower

Yes, the low gain improved things. Its not clipping now, but it still fells like its struggling. Instrument separation, soundstage and detail suffer badly. 
  
  Im feeding it with usb, I have dac/amp combo, so thats my source.


----------



## SilverEars

Anybody know of a portable DAC/Amp that is on the same level or can better the ODAC/O2 combo?  So far, I haven't found anything that can top it.  I listen to iems though.  I have tested with really high end iems such as the 334 and the 846.


----------



## James-uk

For them easy to drive HP the I phone 5s will sound identical .


----------



## James-uk

bpower said:


> Yes, the low gain improved things. Its not clipping now, but it still fells like its struggling. Instrument separation, soundstage and detail suffer badly.
> 
> Im feeding it with usb, I have dac/amp combo, so thats my source.



The only way the O2 will struggle is with power into inefficient headphones on dynamic / quiet records. This will only show itself as the volume pot not getting any louder after a certain point. For example I had a 'high res' copy of muse and I pumped it really loud one day , after turning it up to ear splitting levels at 12 o clock on the volume pot I turned it even more ( stupid I know!) but it didn't get louder , I continued to turn it and nothing happened. Basically the O2 ran out if steam but the sq was the same. It didn't matter because A , it was already too loud, and B, I just downloaded a different master with 'normal' mastering and it would louder while having the same dynamic range ( but why would I want to go louder !)


----------



## JacobLee89

skeptic said:


> On an unrelated note, I was all excited to try my agdr booster board for the first time today. Had everything fully populated and looking pretty good, and then, like a total genius I soldered ic1 in backwards and ripped a leg off trying to reverse it. A torrent of invective followed...
> 
> The most frustrating part is that I am leaving on a family trip Friday and there is no chance mouser or digikey will ship a replacement in time. Guess I'll have something to anticipate upon returning. Otherwise I think I did okay for a newbie at surface mount.


 
  
 Your surface mount soldering looks cleaner than mine!
  
 I also did the same mistake: soldering an IC backwards.. I fixed it by using a heatgun, and ensuring I did not apply more heat than necessary, and stopping once the IC showed signs of moving.


----------



## headwhacker

silverears said:


> Anybody know of a portable DAC/Amp that is on the same level or can better the ODAC/O2 combo?  So far, I haven't found anything that can top it.  I listen to iems though.  I have tested with really high end iems such as the 334 and the 846.


 
  
 Amp-wise, the Leckerton UHA-6SMKII can match, if not exceed, O2 in transparency and clean background. As for the DAC, it's no contest. ODAC is better. But if you consider the size and if you are going to use it mainly as a portable the Leckerton paired with a DAP with a very capable DAC is the way to go.


----------



## SilverEars

headwhacker said:


> Amp-wise, the Leckerton UHA-6SMKII can match, if not exceed, O2 in transparency and clean background. As for the DAC, it's no contest. ODAC is better. But if you consider the size and if you are going to use it mainly as a portable the Leckerton paired with a DAP with a very capable DAC is the way to go.


 
 Thanks for the response I may try it out.  What about the UHA760?  Is it better SQ wise?  Why is it twice the value?


----------



## headwhacker

silverears said:


> Thanks for the response I may try it out.  What about the UHA760?  Is it better SQ wise?  Why is it twice the value?


 
  
  
 The 760 adds minor improvements on the amp section, digital volume control, 3-step gain switch and crossfeed. But it's the same amp otherwise. However, I think the 760 is a step back with the DACs implementation as you will lose the TOSlink, Coax SPDIF input.
  
 Also the 6SMKII has socketed opamp so you have an option to use different opamps anytime you like. For 760, you have to choose one upon purchase because you can't change it later down the road.
  
 Personally if you will not use the crossfeed function, get the 6S-MKII and ask Nick to modify the gain steps from the default 0dB/18dB (low/high) to -12dB/12dB.
  
 If you have a sensitive iems, the default low gain (0dB) is too much and does not allow wider range on the volume pot.


----------



## SilverEars

headwhacker said:


> ask Nick to modify the gain steps from the default 0dB/18dB (low/high) to -12dB/12dB.
> 
> If you have a sensitive iems, the default low gain (0dB) is too much and does not allow wider range on the volume pot.


 
  
 You have Roxanne and I know it's very sensitive and IEMs I will be using will be sensitive like Roxanne.  Is yours set from -12dB/12dB?  Is it like the Alps Pot?  If you get lucky with a good pot you're golden? 
	

	
	
		
		

		
			





​
  
 I'm guessing you have tried the ODAC/O2 combo and compared with the Leckerton.


----------



## headwhacker

silverears said:


> You have Roxanne and I know it's very sensitive and IEMs I will be using will be sensitive like Roxanne.  Is yours set from -12dB/12dB?  Is it like the Alps Pot?  If you get lucky with a good pot you're golden?
> 
> 
> 
> ...


 
  
 I only have the O2 not the ODAC and I use the amp section of the leckerton since I don't like it's CL DAC compared to the Wolfson on DX50. I used bring the O2/DX50 on the go. While the SQ is top notch, the size and awkward placement of jacks and switches on the O2 is a hassle sometimes. The leckerton is much compact and a better fit with my DX50. 
  
 I compared a number of portable amps against O2 (C5D, UHA-4, PHA-1), none of them can match it's transparency and clear background except for UHA-6SMKII with the ADA4627-1 opamp.
  
 I use my O2 now as a desktop amp.


----------



## SilverEars

I have the C5D right not and I personally feel that it's not up to snuff.  It sound artificial.  
  
 The thing is I've tried feeding other DACs to the O2, and I could notice the suttle differences, and favor the ODAC.   The thing is I need a good DAC/Amp combo, and from what it sounds, you think it's the amp that makes the sound transparent.  I put lots of weight on the ODAC also.  Without both, it's not transparent to me.  I guess I will try the Leckerton and find out if it can match the ODAC/O2 combo.


----------



## headwhacker

silverears said:


> I have the C5D right not and I personally feel that it's not up to snuff.  It sound artificial.
> 
> The thing is I've tried feeding other DACs to the O2, and I could notice the suttle differences, and favor the ODAC.   The thing is I need a good DAC/Amp combo, and from what it sounds, you think it's the amp that makes the sound transparent.  I put lots of weight on the ODAC also.  Without both, it's not transparent to me.  I guess I will try the Leckerton and find out if it can match the ODAC/O2 combo.


 
  
 I will get an ODAC in the future and make further comparison. My DX50 with Rockbox sounds the most transparent to me.
  
 I agree the C5D sounds artificial. I was hoping it to be closer to O2 since JDS Labs is making both O2 and ODAC. It would have been the perfect portable amp since it's thinner and narrower albeit longer than the leckerton but matches most DAPs in dimension.
  
 It actually stacks perfectly with DX50 and is friendly inside my pocket. (loose pocket, not the tight ones  )


----------



## miceblue

headwhacker said:


> silverears said:
> 
> 
> > I have the C5D right not and I personally feel that it's not up to snuff.  It sound artificial.
> ...



JDS Labs makes the C5D, they only assemble the O2 and ODAC. The latter were made by NwAvGuy ≠ JDS Labs.


----------



## headwhacker

miceblue said:


> JDS Labs makes the C5D, they only assemble the O2 and ODAC. The latter were made by NwAvGuy ≠ JDS Labs.


 
  
 I know that. Geez just saying since they are assembling O2 and ODAC, I'm assuming they could have cook up something similar SQ-wise on a smaller package.


----------



## Xenophon

If you're in Singapore and have to import anyway, take a look at the Epiphany acoustics version of the ODAC/O2.  But check about the voltage offerings.  On the JDS the normal high gain setting is x6.5 I believe.  That's simply too much, distortion starts kicking in with a vengeance and it'll be driven into clipping with some cans/music/volume combos.  If JDS offer an option to lower the standard gain settings I'd take it if I were you.


----------



## skeptic

jacoblee89 said:


> Your surface mount soldering looks cleaner than mine!
> 
> I also did the same mistake: soldering an IC backwards.. I fixed it by using a heatgun, and ensuring I did not apply more heat than necessary, and stopping once the IC showed signs of moving.




Thanks for the kind words and for sharing your heatgun approach! I'll definitely have to give that a try the next time I have to remove a multipin component.


----------



## headwhacker

xenophon said:


> If you're in Singapore and have to import anyway, take a look at the Epiphany acoustics version of the ODAC/O2.  But check about the voltage offerings.  On the JDS the normal high gain setting is x6.5 I believe.  That's simply too much, distortion starts kicking in with a vengeance and it'll be driven into clipping with some cans/music/volume combos.  If JDS offer an option to lower the standard gain settings I'd take it if I were you.


 
  
 I already have an O2 and it's available locally which was from JDS Labs. The gain setting is easy to change by just clipping the resistor on the 6.5x. Now my O2 has 1x and 2.5x gain.


----------



## Dook0

Has someone got the limited edition of the combo O2+DAC ?


----------



## anthk

xenophon said:


> If you're in Singapore and have to import anyway, take a look at the Epiphany acoustics version of the ODAC/O2.  But check about the voltage offerings.  On the JDS the normal high gain setting is x6.5 I believe.  That's simply too much, distortion starts kicking in with a vengeance and it'll be driven into clipping with some cans/music/volume combos.  If JDS offer an option to lower the standard gain settings I'd take it if I were you.


 

 jds manuals says you need a higher rating ac converter.


----------



## Xenophon

I can't say anything about JDS as I don't own their version but I did try that with the Epiphany Acoustics one which I still own:  did't make a difference to me.  But once again, can't say about the JDS product.


----------



## anthk

xenophon said:


> I can't say anything about JDS as I don't own their version but I did try that with the Epiphany Acoustics one which I still own:  did't make a difference to me.  But once again, can't say about the JDS product.


 

 Should be the same thing really...
 I guess we can use the low gain only then


----------



## YoYo JoKeR

Guys,
  
 What is your opinion on M stage VS O2 amp?
  
 There are very less comparisons between these two. Any light upon this topic would be really helpful.
  
 Purely based upon SQ, ignoring all other factors like price and portability.


----------



## Solrighal

I need help. No, really. I was just about to order the O2+ODAC when I noticed the limited edition.

All my music is accessed via my Mac mini right now. I want to output via USB to the O2+ODAC then to my headphones. If I could also output from the ODAC via RCA (L+R) to my Marantz stereo amp which powers my loudspeakers that would be perfect. 

In the specs for the limited edition it states that it has both RCA analogue input *and* RCA DAC line output. When I look at the photo though I only see one pair (L+R) of RCA sockets. Do these sockets act as either input or output depending on what they are connected to? Is that even possible? What am I missing? I have no use for an RCA input and can't think why anyone would.


----------



## JacobLee89

solrighal said:


> I need help. No, really. I was just about to order the O2+ODAC when I noticed the limited edition.
> 
> All my music is accessed via my Mac mini right now. I want to output via USB to the O2+ODAC then to my headphones. If I could also output from the ODAC via RCA (L+R) to my Marantz stereo amp which powers my loudspeakers that would be perfect.
> 
> In the specs for the limited edition it states that it has both RCA analogue input *and* RCA DAC line output. When I look at the photo though I only see one pair (L+R) of RCA sockets. Do these sockets act as either input or output depending on what they are connected to? Is that even possible? What am I missing? I have no use for an RCA input and can't think why anyone would.


 
  
 It looks like it can either output from RCA as a standalone DAC, or act as an amp from being connected to a DAC via RCA.
  
 I'd send an email to JDS to clarify this.


----------



## hekeli

@Zorrofox
  
 Especially since you are from Europe, you would be cheaper and much better off with the Head'N'Hifi desktop version which _also works as a preamp_. Add ODAC normal or XL version as you like (you should also choose 1x / 3x custom gains for O2). Having everything in one case is pointless unless you really need small footprint for serious mobile use etc (but he does also have the combo version). Choose Weekly shipping option so it comes from Germany (no customs).


----------



## Solrighal

jacoblee89 said:


> It looks like it can either output from RCA as a standalone DAC, or act as an amp from being connected to a DAC via RCA.
> 
> I'd send an email to JDS to clarify this.




Yeah, I've emailed them about this. They could make it a bit clearer I think. It makes sense an output bypassing the amp section (with power off) but I can't work out why anyone would need an RCA analogue input.

Thanks for the advice.


----------



## JacobLee89

solrighal said:


> Yeah, I've emailed them about this. They could make it a bit clearer I think. It makes sense an output bypassing the amp section (with power off) but I can't work out why anyone would need an RCA analogue input.
> 
> Thanks for the advice.


 
  
 It would be more convenient with a 3.5mm analogue input. However there's a good collection of amps which do use RCA analogue input, such as the BH Crack. The perceived benefit could be that each (left/right) signal has their own ground.
  
 Though for an ODAC there is little to gain sonically from choosing between the RCA and the 3.5mm version.


----------



## anthk

All of our O2+ODACs are wired so that the right 3.5mm jack serves as analog input to the O2, as well as DAC line-output.
  
 So, you may use this jack to access the ODAC's line output. There's no need to turn the O2 off. The line output will function while O2 is powered on or off.
  
 Let me know if you have any other questions.
  
 Best regards,

      John Seaber
JDS Labs, Inc. | Tel: (314) 252-0936

 This is the email response I got from JDS. I assume this is the same for mayflower, epiphany etc


----------



## Solrighal

anthk said:


> All of our O2+ODACs are wired so that the right 3.5mm jack serves as analog input to the O2, as well as DAC line-output.
> 
> So, you may use this jack to access the ODAC's line output. There's no need to turn the O2 off. The line output will function while O2 is powered on or off.
> 
> ...




Hopefully John will read this... 

Dear John,

Many thanks for answering my email earlier today re. the rear RCA's on your limited edition model. 

I'm no expert when it comes to anything really but might it not be a good idea to elaborate on these details on your website? It seems as though you rely too heavily on the site visitor having prior inside-knowledge of the products you sell. That seems like a somewhat flawed business plan, if you don't mind me saying. I like to think I am reasonably savvy when it comes to consumer electronics but I've been pretty much in the dark for the best part of 48hrs as to what your products are actually capable of. My money could easily have gone elsewhere in that time. That may well happen anyway but you can thank the UK government's ludicrous import tariffs for that. 

Please don't take offence at my comments. Your products are great. Your personal service is clearly excellent. I just feel your website, though attractive, could be more informative.

A fan.


----------



## r010159

solrighal said:


> Hopefully John will read this...
> 
> Dear John,
> 
> ...





> [some of post deleted]





> Please don't take offence at my comments. Your products are great. Your personal service is clearly excellent. I just feel your website, though attractive, could be more informative.
> 
> A fan.


 
  
 I think John is relying on the information already available for the O2 + ODAC, for instance, from the designer himself in his blogs. But I agree that the technical discussion of NwAvGuy should also be, at the very least, linked to by his site.
  
 BG


----------



## Solrighal

r010159 said:


> I think John is relying on the information already available for the O2 + ODAC, for instance, from the designer himself in his blogs. But I agree that the technical discussion of NwAvGuy should also be, at the very least, linked to by his site.
> 
> BG




You're probably right but it wouldn't take much to fill in the gaps. I'm only mentioning because I do like to support the smaller companies. I'm gonna take a punt and suggest we're unlikely to see Mr Sony or Mr Panasonic posting on these forums, but John does. That attention makes such a difference for the end-user. I kinda wish I hadn't said anything now.


----------



## hekeli

I kind of agree with the vague descriptions.
  
 Even Walter who I love could be a smidgen more descriptive. For example O2 desktops RCA output - is it volume controllable (preamp) is common question - yes it is!
  
 (And these have nothing to do with NwAvGuy, all the mods and tweaks are done by the seller!)
  
 Also the gain stuff should be clearly explained since it's a common source of gripe (why am I hearing distortion??). 1x / 3x should be suggested default when bundling with ODAC.


----------



## Solrighal

hekeli said:


> I kind of agree with the vague descriptions.
> 
> Even Walter who I love could be a smidgen more descriptive. For example O2 desktops RCA output - is it volume controllable (preamp) is common question - yes it is!
> 
> ...




This is true. My frustration is amplified (geddit?) by the fact that my internet speed where I live is ridiculous which means that, particularly the JDS Labs site which does look beautiful, takes an eternity to load. This is nobody's fault but my stupid country. The UK is a joke. Still, even that's changing as Scotland is about to vote for independence. Then the world is our oyster. The future is bright.


----------



## r010159

solrighal said:


> You're probably right but it wouldn't take much to fill in the gaps. I'm only mentioning because I do like to support the smaller companies. I'm gonna take a punt and suggest we're unlikely to see Mr Sony or Mr Panasonic posting on these forums, but John does. That attention makes such a difference for the end-user. I kinda wish I hadn't said anything now.


 
  
 I hope I did not come across aggressive. I think you mentioning this will actually help John gauge what he can do on his end to make a difference in future purchases.


----------



## Solrighal

r010159 said:


> I hope I did not come across aggressive. I think you mentioning this will actually help John gauge what he can do on his end to make a difference in future purchases.




Not at all my friend, no problem. It's intended to be constructive criticism but sometimes I get taken the wrong way or I'm maybe not quite as polite as some think I should be. If I genuinely didn't care about these smaller companies (not small but not Sony either) I wouldn't have said anything at all. Web design kinda is my field, though only as a hobby. One that's not got a lot of attention of late since I keep buying damned expensive gadgets


----------



## MrMateoHead

hekeli said:


> I kind of agree with the vague descriptions.
> 
> Even Walter who I love could be a smidgen more descriptive. For example O2 desktops RCA output - is it volume controllable (preamp) is common question - yes it is!
> 
> ...


 
 I know JDS would be willing to provide you with either 1X / 2.5X or 2.5X / 6.5X if you requested it - the old website used to tell you you could choose.
  
 But, by default, the 2.5X / 6.5X gain levels are ideal for matching the O2 to a 2V source (2.5X reaches full power), or a typical 1V source (6.5X is perfect for Mp3 player, tablet, computer, etc.). 6.5X also comes in handy for HDR recordings as sometimes I struggle at 2.5X to reach the volume I want. I've also, btw, never been able to clip the O2 - I've only ever heard my recordings clip.
  
 Then again, the O2 is very powerful, so many persons using very efficient cans with it should, IMHO, use the windows or whatever source volume control to reduce signal strength so they can twist the knob as much as they want to. That is a lot better than eliminating rid of useful gain headroom - especially when the O2 is black no matter the gain/volume level.


----------



## Solrighal

mrmateohead said:


> Then again, the O2 is very powerful, so many persons using very efficient cans with it should, IMHO, use the windows or whatever source volume control to reduce signal strength so they can twist the knob as much as they want to. That is a lot better than eliminating rid of useful gain headroom - especially when the O2 is black no matter the gain/volume level.




You raise a point I've always been confused about. Does it really make no difference to sound quality what level is sent out to the DAC? I realise the volume level would be reduced but would the quality not be reduced too?


----------



## headwhacker

mrmateohead said:


> I know JDS would be willing to provide you with either 1X / 2.5X or 2.5X / 6.5X if you requested it - the old website used to tell you you could choose.
> 
> But, by default, the 2.5X / 6.5X gain levels are ideal for matching the O2 to a 2V source (2.5X reaches full power), or a typical 1V source (6.5X is perfect for Mp3 player, tablet, computer, etc.). 6.5X also comes in handy for HDR recordings as sometimes I struggle at 2.5X to reach the volume I want. I've also, btw, never been able to clip the O2 - I've only ever heard my recordings clip.
> 
> Then again, the O2 is very powerful, so many persons using very efficient cans with it should, IMHO, use the windows or whatever source volume control to reduce signal strength so they can twist the knob as much as they want to. That is a lot better than eliminating rid of useful gain headroom - especially when the O2 is black no matter the gain/volume level.




If you use the O2 with sensitive iems, then the default 2.5x / 6.5x is way too much regardles whether your source is a 1V mp3 player or the 2V ODAC.

Fortunately, this is easy to address. Just clip the resistor on the 6.5x bridge and you instantly have a 1x /2.5x gain option.

You can reduce the gain further to 0.5x or 0.25x for those uber sensitive iems. Just need to find the right resistor value.


----------



## SilverEars

headwhacker said:


> You can reduce the gain further to 0.5x or 0.25x for those uber sensitive iems. Just need to find the right resistor value.


 
 How is that possible?  The gain equation is 1+R1/R2 or something like that.  if you clip R2 for example, it's infinate resistance.  Which means gain=1.  Therefore, it can never be lower than one I would think.
  
 Taken from the designer's website regarding gain:
  
*RESISTOR VALUES:* Some amplifiers let you set the gain by changing resistor values. The diagram to the right shows a typical non-inverting amplifier stage. The gain is given by 1 + 1000/500 = 3. For all the math, see Wikipedia Gain andWikipedia Amplifiers. Some amplifiers may have multiple gain stages, in which case you have to multiply the gain of each stage together. So an amp with a 2X and 3X stage has a total gain of 6X.


----------



## headwhacker

silverears said:


> How is that possible?  The gain equation is 1+R1/R2 or something like that.  if you clip R2 for example, it's infinate resistance.  Which means gain=1.  Therefore, it can never be lower than one I would think.
> 
> Taken from the designer's website regarding gain:
> 
> *RESISTOR VALUES:* Some amplifiers let you set the gain by changing resistor values. The diagram to the right shows a typical non-inverting amplifier stage. The gain is given by 1 + 1000/500 = 3. For all the math, see Wikipedia Gain andWikipedia Amplifiers. Some amplifiers may have multiple gain stages, in which case you have to multiply the gain of each stage together. So an amp with a 2X and 3X stage has a total gain of 6X.



 


Ah, you are right, 1x is the smallest gain possible. I completely mixed it up with the UHA-6S which can be modified up to -12dB (0.25x)


----------



## hekeli

mrmateohead said:


> But, by default, the 2.5X / 6.5X gain levels are ideal for matching the O2 to a 2V source (2.5X reaches full power), or a typical 1V source (6.5X is perfect for Mp3 player, tablet, computer, etc.). 6.5X also comes in handy for HDR recordings as sometimes I struggle at 2.5X to reach the volume I want. I've also, btw, never been able to clip the O2 - I've only ever heard my recordings clip.


 
  
 While I have a very hard time understanding why anyone would care to use O2 with some tablet etc, even ignoring that, why isn't all of this info on the sellers pages so everyone understands what they are getting into.. but yeah sure you can always clip a resistor..
  
 Anyways, I've rarely need more than unity gain with any of my headphones. Atleast it's better quality in theory, isn't that why we use O2 anyway..


----------



## forsberg

I've been reading nwavguy's blog and I agree with his scientific approach to sound quality, and the impression is that the O2 amp/dac is "perfect" in the sense that it doesn't change anything from the original signal other than conversion to analog then amplify.

But, how do things like soundstage get measured?


----------



## headwhacker

forsberg said:


> I've been reading nwavguy's blog and I agree with his scientific approach to sound quality, and the impression is that the O2 amp/dac is "perfect" in the sense that it doesn't change anything from the original signal other than conversion to analog then amplify.
> 
> 
> 
> But, how do things like soundstage get measured?



 


soundstage is a subjective term and I don't think it can be measured.


----------



## forsberg

headwhacker said:


> forsberg said:
> 
> 
> > I've been reading nwavguy's blog and I agree with his scientific approach to sound quality, and the impression is that the O2 amp/dac is "perfect" in the sense that it doesn't change anything from the original signal other than conversion to analog then amplify.
> ...




That's what I want to find out, is how soundstage translates to measurements. It is impossible for two identical waves to enter your ears but have narrow vs wide soundstage. There has to be some differences.


----------



## Solrighal

hekeli said:


> While I have a very hard time understanding why anyone would care to use O2 with some tablet etc, even ignoring that, why isn't all of this info on the sellers pages so everyone understands what they are getting into.. but yeah sure you can always clip a resistor..
> 
> Anyways, I've rarely need more than unity gain with any of my headphones. Atleast it's better quality in theory, isn't that why we use O2 anyway..




This is exactly how I see it. There's another manufacturer in Europe who's making pretty much the same thing (with some useful variables thrown in) and when you visit his site he does explain why someone would choose different gains and for a small fee allows you to select your choice. Information is power. And I also agree that, since the whole point of the O2 is it's inherent transparency, it surely makes sense that using as little gain as possible would be the best way to maintain the 'Straight Wire' ethos.




forsberg said:


> That's what I want to find out, is how soundstage translates to measurements. It is impossible for two identical waves to enter your ears but have narrow vs wide soundstage. There has to be some differences.




I'm definitely no expert on technical matters like this but isn't it the case that the actual headphone used determines the soundstage? I mean, when I switch between my Q701's and my M-100 all aspects of the sound change but in particular it's the soundstage which is markedly increased. I haven't changed any other hardware or software. It's just the way the cans are designed. Feel free to shoot me down.


----------



## MrMateoHead

hekeli said:


> *While I have a very hard time understanding why anyone would care to use O2 with some tablet etc, even ignoring that, why isn't all of this info on the sellers pages so everyone understands what they are getting into.. but yeah sure you can always clip a resistor..*
> 
> Anyways, I've rarely need more than unity gain with any of my headphones. Atleast it's better quality in theory, isn't that why we use O2 anyway..


 

 Well, I can tell you that both my $100 dollar throwaway Nokia phone and Nexus Tablet both sound excellent with the help of the O2; not quite ODAC awesome but hardly "bad" (no hiss, lots of detail, smooth). They have Internet radio apps and Pandora and what not, so can act as quite the jukebox when I am in the mood. Come to think of it, I don't know the last time I really heard a "bad" DAC, mostly issues I have are with background noise and lack of power. As an owner of IEMs, however, I get that the added sensitivity and isolation can be a curse - but to that I wonder why people buy super-powerful amps like the O2 to drive them, from which they only need 1/1000 to 1/100 of the power it produces. Sort of a mis-match.
  
 Anyway signal "gain" is just another spec that is almost never provided in the audio world (or it is in the place of power, to make things more confusing). I bought a cheap amp to drive some speakers a month ago, in part because it specified, clearly, that it needed about 1V to reach its rated RMS power of 50 wpc. Good to know, since it is designed for multiple-zone audio applications, and the length of the cable run could be long enough to degrade the 2V signal I would be feeding it. Knowledge is power . . .


----------



## gjc10212

solrighal said:


> This is exactly how I see it. *There's another manufacturer in Europe who's making pretty much the same thing (with some useful variables thrown in)* and when you visit his site he does explain why someone would choose different gains and for a small fee allows you to select your choice. Information is power. And I also agree that, since the whole point of the O2 is it's inherent transparency, it surely makes sense that using as little gain as possible would be the best way to maintain the 'Straight Wire' ethos.
> I'm definitely no expert on technical matters like this but isn't it the case that the actual headphone used determines the soundstage? I mean, when I switch between my Q701's and my M-100 all aspects of the sound change but in particular it's the soundstage which is markedly increased. I haven't changed any other hardware or software. It's just the way the cans are designed. Feel free to shoot me down.


 
 Who?


----------



## r010159

solrighal said:


> [part of post deleted]
> 
> I'm definitely no expert on technical matters like this but isn't it the case that the actual headphone used determines the soundstage? I mean, when I switch between my Q701's and my M-100 all aspects of the sound change but in particular it's the soundstage which is markedly increased. I haven't changed any other hardware or software. It's just the way the cans are designed. Feel free to shoot me down.


 
  
 This is an excellent observation! I agree. I think it is the headphones that determine soundstage.
  
 BG


----------



## Solrighal

gjc10212 said:


> Who?




http://www.headnhifi.com/index.php?route=common/home

I apologise for the slip there, I thought I was in the JDS Labs thread and didn't want to advertise a competitor. Walter isn't technically in Europe but not too far off. I'd give his website 10/10 and Walter had to deal with me making a small mistake in my order but he dealt with it very well. Of course, I've yet to receive the goods so a final verdict will have to wait but I'm hopeful.




r010159 said:


> This is an excellent observation! I agree. I think it is the headphones that determine soundstage.
> 
> BG




Nobody ever says that, do they? Seems obvious to me and doesn't need abx double blind testing to work out.


----------



## miceblue

r010159 said:


> solrighal said:
> 
> 
> > [part of post deleted]
> ...



Listen to something like the FiiO X5 or E12. Both are infamous for having a small soundstage. Then compare it to the O2, which is known to have a large soundstage.


----------



## Solrighal

miceblue said:


> Listen to something like the FiiO X5 or E12. Both are infamous for having a small soundstage. Then compare it to the O2, which is known to have a large soundstage.




I won't thanks but I take the point. To be fair though you're not really comparing like for like are you? What's the relative power outputs of all those amps?


----------



## hekeli

mrmateohead said:


> Well, I can tell you that both my $100 dollar throwaway Nokia phone and Nexus Tablet both sound excellent with the help of the O2; not quite ODAC awesome but hardly "bad" (no hiss, lots of detail, smooth). They have Internet radio apps and Pandora and what not, so can act as quite the jukebox when I am in the mood.


 
  
 That's just silly to me and not very realistic usage scenario atleast for "desktop O2". Are you also using batteries? I'd never bother to carry O2 and something like HD800 around my house, then again I'm not the most extreme audiophile type anyway.. and who's to say ~3 volts wouldn't be enough for most headphones. I'm not saying 1/3x should be default, I think the main point was just describing these scenarios better for the consumer..


----------



## miceblue

solrighal said:


> miceblue said:
> 
> 
> > Listen to something like the FiiO X5 or E12. Both are infamous for having a small soundstage. Then compare it to the O2, which is known to have a large soundstage.
> ...



I don't think power is really a factor for something sensitive like the M-100. Even if they all had the same power output, what would that mean?

O2:


> Max Output 15 Ohms 337 mW Excellent
> Max Output 33 Ohms
> Max Output 150 Ohms
> 7 Volts RMS (19.802 Vp-p)
> 200+ mA peak current




X5:


> Output Power 1 > 460 mW@16Ω THD<1%
> Output Power 2 > 255 mW@32Ω
> Output Power 3 > 28 mW@300Ω
> MAX output voltage > 8 Vp-p
> MAX output current > 150 mA




E12:


> Output Power >880mW@32Ω
> MAX output voltage 15.5 Vp-p
> MAX output current 170 mA


----------



## PTom

I'm noticing some distortion on high gain running my Beyerdynamic T1, is this normal? If so is there a fix for this?


----------



## MrMateoHead

hekeli said:


> That's just silly to me and not very realistic usage scenario atleast for "desktop O2". Are you also using batteries? I'd never bother to carry O2 and something like HD800 around my house, then again I'm not the most extreme audiophile type anyway.. and who's to say ~3 volts wouldn't be enough for most headphones. I'm not saying 1/3x should be default, I think the main point was just describing these scenarios better for the consumer..


 
 Mine is the battery-powered version. You must be imagining me dragging my amp around with headphones and a phone/tablet stuffed in my oversized pocket walking around the house. That is not the case. What is the case is that I actually use different sources with my amp, so I do in fact benefit from a high / low gain switch. Most "desktop" setups can be "set it and forget it", but I still like some flexibility. I did in fact value the portability of the thing, even if its not AS portable as other devices / amps.
  
 Anyway, to each their own. There is a lot of documentation on the O2 and even if a consumer ignorantly bought an O2 without knowing what gain settings they really needed/wanted, I really doubt the stock settings would be THAT awful. Then again I wouldn't be one to buy a near 1-watt amp with a pair of IEMs in the first place, but that's just me. I bought some inefficient planars and ran them off (gasp!) my laptop first to see how far I could get with a lowly Realtek chip.


----------



## chuck8403

ptom said:


> I'm noticing some distortion on high gain running my Beyerdynamic T1, is this normal? If so is there a fix for this?




From O2 blog:

THE GAIN RESISTORS: Before you solder in the four gain resistors by the gain switch, you might want to consider different gains than the approximately 2.5X and 6.5X default values. You want just enough gain so typical music plays loudly enough with your headphones and source and not much more. Extra gain means using less of the volume control’s range, more noise, more distortion, and makes accidental headphone damage more likely.


----------



## anthk

miceblue said:


> Listen to something like the FiiO X5 or E12. Both are infamous for having a small soundstage. Then compare it to the O2, which is known to have a large soundstage.


 

 This is just a random guess.
 I think this has to do with the resolving power of your dac and mostly headphone/speakers

 I suppose soundstage is basically sound localization. A small difference in amplitude and L/R balance are sonic cues for our brains to understand where sound comes from. So, if your dac/headphone can't resolve those details , then the info would be lost.

 It would be nice if someone could find a journal on this. I haven't got a science journal DB since I graduated


----------



## Solrighal

The initial comparison I made was between my headphones. My Q's have a bigger soundstage than the M's because the Q's are open cans whereas the M's are closed. My M's have more bass because they are closed whereas my Q's are open. I am not a scientist. Luckily, to appreciate good sound I don't need to be.


----------



## Solrighal

Or maybe it's because those tiny portable amps have so many twists and turns in their circuitry in order to pack in that power. I mean, a Golf R will go as fast as a Jag. I'll take the Jag. 

Or something like that.


----------



## Solrighal

Just for the sake of curiosity what level should I be looking to set my Mac to? I've went for the 1x/3x option on gains. I'll be driving AKG Q701's.

And another question, why are there so many posts on this thread where the poster has been banned and why are there so many people on the net who seem to have a massive chip on their shoulders about this amp? I can't wait for its delivery.


----------



## miceblue

solrighal said:


> Just for the sake of curiosity what level should I be looking to set my Mac to? I've went for the 1x/3x option on gains. I'll be driving AKG Q701's.



75% and above is recommended to get a bit-perfect signal.


----------



## Solrighal

miceblue said:


> 75% and above is recommended to get a bit-perfect signal.




Isn't that a bit vague? Why not 100%?


----------



## adydula

An awful lot of how a soundstage is perceived is how the source was originally recorded and mic'd. and how the interim devices add and detract from this and finally the actual transducers that "try" to reproduce what was recorded etc.
  
 We all notice how some recordings sound open and spacious even on the not so great cans.
  
 But the same recording sounds even more open and spacious on those cans that reproduce the source very well.
  
 If the dac and amp are really transparent and do not add or detract the original recording and how it was done, and the transducers play the biggest part. If the recording isn't done well, even if the cans are great in this respect the sound will not be that spacious IMO.
  
 From wiki:
 "The term soundstage refers to the depth and richness of an audio recording and usually relates to the playback process. According to audiophiles, the quality of the playback is very much dependent upon how one is able to pick out different instruments, voices, vocal parts, and such exactly where they are located on an imaginary 2-dimensional or 3-dimensional field. The quality of this soundstage can enhance not only the listener's involvement in the recording, but also their overall perception of the stage"
  
 The only measurement that I am aware of is the Off axis response that is often spec's with normal loudspeakers that relates to soundstage somewhat.
  
 A.


----------



## miceblue

solrighal said:


> miceblue said:
> 
> 
> > 75% and above is recommended to get a bit-perfect signal.
> ...



If you have an amp that's too loud, like the O2, for sensitive headphones, then reducing the digital volume is the only way to make things listenable sometimes. You probably won't hear a difference anyway. XD


----------



## Solrighal

Are





miceblue said:


> If you have an amp that's too loud, like the O2, for sensitive headphones, then reducing the digital volume is the only way to make things listenable sometimes. You probably won't hear a difference anyway. XD


 

Are there full-size headphones out there that the O2 would be too loud for? What about if you were using unity gain (1x)?


----------



## kuhchuk

I'm not sure if this has been documented before, but it certainly caught my interest when I discovered it.  I have an O2/ODAC combo unit from Mayflower Electronics, and when I went to plug in my headphones earlier, I accidentally plugged them into the line in without noticing.  I started up some music on my computer, and tried to increase the volume on the O2, but to no avail.  Then it caught my eye that I had plugged it into the wrong port. 
  
 From this, I made the logical conclusion that what I was receiving was the line out from the ODAC.  Since I've been using my O2 as a pre-amp for an extremely awful receiver (it has issues with audio dropping out at low levels), I decided to try plugging my receiver into the Line In port on the O2.  It brought me great joy to find out that it works great, and seems to be just loud enough to avoid most problems that the receiver has at low levels.

 At this point, I plugged my headphones back in, and found that both the speakers and the headphones will play at the same time.  This means that I no longer have to unplug my receiver to use headphones and vice-versa.  It's also providing me with some really neat sound effects since I'm using a pair of open headphones (HE-400).
  
  
 I'm assuming this was an unintentional oversight, but in my book it's a damn great feature to have, and I intend to play around with it a ton.


----------



## adydula

Q701s will be ok with unity gain, I have a set and there is no problem with them.....6.5 is way too much...not necessary at all.
  
 A.


----------



## miceblue

solrighal said:


> Are
> 
> 
> 
> ...


Yeah the K 701 is fine with the unity gain and max digital volume.


----------



## Solrighal

adydula said:


> Q701s will be ok with unity gain, I have a set and there is no problem with them.....6.5 is way too much...not necessary at all.
> 
> A.







miceblue said:


> Yeah the K 701 is fine with the unity gain and max digital volume.




I thought so. I have an excellent advisor.


----------



## jring

solrighal said:


> You raise a point I've always been confused about. Does it really make no difference to sound quality what level is sent out to the DAC? I realise the volume level would be reduced but would the quality not be reduced too?


 
  
 Hi,
  
 reducing output level in software makes a difference when you're running a DAC in 16 bit mode because the dynamic range the human ear can measure is about 16 bit.
  
 That's the reason why running a DAC in 24 bit mode is useful (unlike higher sample rates imho) - you can use software volume with impunity - regardless of the question whether your material is 24 bit or 16 bit upscaled.
  
 Joachim


----------



## jring

solrighal said:


> Isn't that a bit vague? Why not 100%?


 
  
 You're right here - bit-perfect means 100% software volume and running the DAC at the bit width of the files.
  
 Joachim


----------



## Solrighal

Hi, thanks for your input. So 24bit goes lower & higher in the frequency range than 16bit? I did not know that. I just assumed it referred to the amount of detail contained within the file and not the range. 

I'm always learning.


----------



## r010159

jring said:


> Hi,
> 
> reducing output level in software makes a difference when you're running a DAC in 16 bit mode because the dynamic range the human ear can measure is about 16 bit.
> 
> ...


 
  
 Interesting. No offense, but I do not think it works this way. Something tells me this oversimplification has lead to a fallacy.  The volume level is mapped to more bits. But when turned to half volume, you are still dealing with half of the available information.  All the extra bits give you is a more graduated scale between no volume and full volume. This does not mean you just can throw away the bits to no effect, which is what you are implying.  
  
 So there must be something I am not understanding of your explanation. Are you talking about 16-bits being mapped to the lowest order of 24-bits? Is that what is actually happening? This would mean the last part of the range of volume would make no audible difference at all. I do not think this is the case.
  
 Like I said, I may be misunderstanding something here. 
	

	
	
		
		

		
			




  
 BG


----------



## r010159

solrighal said:


> Hi, thanks for your input. So 24bit goes lower & higher in the frequency range than 16bit? I did not know that. I just assumed it referred to the amount of detail contained within the file and not the range.
> 
> I'm always learning.


 
  
 Yes, I agree with your assessment. The 24 bits vs 16 bits represent the level of detail represented by the numbers in the file. But like you, I will wait for an explanation of this.
  
 BG


----------



## James-uk

I simplify bits in my mind as noise floor. The more bits you have the more scope for lower noise floor and therefore greater dynamic range. If you take a 16 bit recording and play it out as 24 bit into a 24 bit dac you have basically added unnecessary headroom and therefore you can turn down software volume (reduce the bits) and it won't matter until you drop it down below 16bits (back to original file) even then you can see examples online of slowly dropping off the bits and It only becomes noisy and audible At about8-10 bits.


----------



## James-uk

This video explains it better

http://m.youtube.com/watch?v=Zvireu2SGZM


----------



## SilverEars

So the 16-24 upscale isn't really scaling?  If it was 16 -> analog -> 24, then it would be scaling.  But since it's 16-24 digital scaling there is no way to scale proportionally digitally since it's in bits.  So that probably means the extra 8 bits on top of 16 are just padded(never listened in directly to the DAC line-out), not actually containing any information.  Therefore, it's safe to have the volume 16/24 = .66 or %67 or greater without performance hit.
  
 Not sure how correct my assumptions are since you turn down the volume on the DAC, the amp output you can hear the volume decrease.  So, not sure if it's safe.


----------



## Solrighal

Well, that's cleared that up then


----------



## BenF

silverears said:


> So the 16-24 upscale isn't really scaling?  If it was 16 -> analog -> 24, then it would be scaling.  But since it's 16-24 digital scaling there is no way to scale proportionally digitally since it's in bits.  So that probably means the extra 8 bits on top of 16 are just padded(never listened in directly to the DAC line-out), not actually containing any information.  Therefore, it's safe to have the volume 16/24 = .66 or %67 or greater without performance hit.
> 
> Not sure how correct my assumptions are since you turn down the volume on the DAC, the amp output you can hear the volume decrease.  So, not sure if it's safe.


 

 Since there are 8 bits of volume, that means you can control volume using 256 values without degrading the quality.


----------



## jring

r010159 said:


> Interesting. No offense, but I do not think it works this way. Something tells me this oversimplification has lead to a fallacy.  The volume level is mapped to more bits. But when turned to half volume, you are still dealing with half of the available information.  All the extra bits give you is a more graduated scale between no volume and full volume. This does not mean you just can throw away the bits to no effect, which is what you are implying.
> 
> So there must be something I am not understanding of your explanation. Are you talking about 16-bits being mapped to the lowest order of 24-bits? Is that what is actually happening? This would mean the last part of the range of volume would make no audible difference at all. I do not think this is the case.
> 
> ...


 
  
 Hi,
  
 when 16 bit audio data is mapped to 24 bit words this means multiplying by 256 or shifting left by 8, which is the same. The missing bits on the right hand side are set to 0.
  
 EDIT: This multiplication is necessary in order to keep the volume equal for 16 bit and 24 bit mode. I one just kept the same numeric value in 24 bit as in 16 bit, the music would be inaudibly quiet. Thanks to user r010159 for pointing out that I was a bit quick here.
  
  
 16 bit word:
  
               1001100110011001
  
 24 bit word - high 16 bits same as before followed by 8 zero bits:
  
 100110011001100100000000
  
 If you're then halving the volume all words are divided by 2 or shifted to the right by 1 - left side is padded with zero bits again:
  
 010011001100110010000000
  
 So what you loose is one of the zero bits on the right hand side which were added by converting 16 to 24 bit.
  
  
 In the case of native 24 bit material the case is a little bit different but not much:
  
 100110011001100110011001
  
 now we half the volume by dividing by 2 or shifting right 1 place - left side is padded with zero bits again:
  
 010011001100110011001100
  
 So we effectively lost the least significant bit on the right hand side which can be ignored since
  
  
 a) the effective resolution of the best 24 bit DACs is only 21 bits and often less - so an error in the least significant bit will not be measurable
  
 b) because human hearing can only resolve 16 bits of dynamic range anyways
  
 EDIT: Please note that this argument is a bit simplified by assuming unsigned integers. In reality we need signed numbers and in 2's complement notation multiplication and left shifts are not equivalent. But in essence it's the same in 2's complement - namely for data scaled from 16 to 24 bits no data is lost by setting software volume to 50% and for 24 bit data the least significant bit is lost.
  
 Joachim


----------



## jring

solrighal said:


> Hi, thanks for your input. So 24bit goes lower & higher in the frequency range than 16bit? I did not know that. I just assumed it referred to the amount of detail contained within the file and not the range.
> 
> I'm always learning.


 
  
 Hi,
  
 no, bit width has nothing to do with frequency range, it means how fine the differences in amplitude can be resolved.
  
 Frequency range is governed by the sample rate via the nyquist frequency - the highest frequency which can be reconstructed from a sampled signal with sampling rate fS.
  
 The nyquist frequency is 0.5 * fS or 22kHz for the usual CD sample rate of 44kHz. Since 22kHz is way above the limit of human hearing around 16kHz sampling rates of more than 44kHz are of dubious value for music meant to be listened to by humans - as opposed to dogs or bats.
  
 Joachim


----------



## r010159

jring said:


> Hi,
> 
> when 16 bit audio data is mapped to 24 bit words this means multiplying by 256 or shifting left by 8, which is the same. The missing bits on the right hand side are set to 0.
> 
> ...




You are placing the 16-bits left justified. The 16-bit number needs to be placed in the rightmost position to preserve the mathematical significance of the original 16-bit number. The volume operates on the number in this fashion. So should your analysis.

>>a) the effective resolution of the best 24 bit DACs is only 21 bits and often less - so an error in the least significant bit will not be measurable

You have just halved the volume. According to your analysis, this should make no audible difference. It does. Try it and see. IMO that is why it is best to keep the volume at the computer to full value. If it really does not make a difference, then why mess with the volume at all? What is the point in changing it from the computer instead of the amp?

BG


----------



## jring

r010159 said:


> You are placing the 16-bits left justified. The 16-bit number needs to be placed in the rightmost position to preserve the mathematical significance of the original 16-bit number. The volume operates on the number in this fashion. So should your analysis.
> 
> BG


 
 You are right if you expect the 24 bit word to have the same numerical value as the 16 bit word. But max electrical amplitude of the DAC stays the same regardless of word width and must be reached at the max value of 16 bit or 24 bit data - so a multiplication must take place. If the 16 bits are put to right of the 24 bit word it is mathematically correct but the music would be inaudibly quiet.
  
 Also it should be said that this example simplifies things a bit by assuming unsigned data - in 2's complement multiplication and shifting left are not equivalent so it cannot be visualized so easily but in essence things stay the same - namely for data scaled from 16 to 24 bits no data is lost by setting software volume to 50% and for 24 bit data the least significant bit is lost.
  
 Joachim


----------



## r010159

jring said:


> You are right if you expect the 24 bit word to have the same numerical value as the 16 bit word. But max electrical amplitude of the DAC stays the same regardless of word width and must be reached at the max value of 16 bit or 24 bit data - so a multiplication must take place. If the 16 bits are put to right of the 24 bit word it is mathematically correct but the music would be inaudibly quiet.
> 
> Also it should be said that this example simplifies things a bit by assuming unsigned data - in 2's complement multiplication and shifting left are not equivalent so it cannot be visualized so easily but in essence things stay the same - namely for data scaled from 16 to 24 bits no data is lost by setting software volume to 50% and for 24 bit data the least significant bit is lost.
> 
> Joachim




I see how you are thinking of this. Thanks for the discussion.


----------



## Solrighal

Guys! Guys! I guess I should be ashamed but this is confusing. I think I'll just set the Mac volume as high as I can get away with whilst still having plenty of leeway on the hardware control. I've opted for 1x/3x and I'm using Q701's. Funny thing with them is that although they're 62Ohm impedance (which isn't particularly high) I read there's something else about them that makes them more demanding than it would appear.


----------



## miceblue

solrighal said:


> Guys! Guys! I guess I should be ashamed but this is confusing. I think I'll just set the Mac volume as high as I can get away with whilst still having plenty of leeway on the hardware control. I've opted for 1x/3x and I'm using Q701's. Funny thing with them is that although they're 62Ohm impedance (which isn't particularly high) I read there's something else about them that makes them more demanding than it would appear.



Probably an amp with a high current output. I've read the same thing and I haven't found that to be the case, so I don't know what people are talking about. XD


----------



## Solrighal

I can't remember what it was that's supposed to be difficult with the AKG's. I'll be able to let you know soon enough


----------



## Solrighal

Does the O2 benefit headphones such as the V-Moda M-100? I wouldn't have thought so myself but what do I know?


----------



## miceblue

solrighal said:


> Does the O2 benefit headphones such as the V-Moda M-100? I wouldn't have thought so myself but what do I know?


Whatever sound the O2 has, it benefits the M-100 from my experience; the soundstage opens up a bit. I don't use the O2 with the M-100 though since it's too loud for me, but if you lower the digital volume it should be fine.


----------



## Solrighal

Nah, I doubt I'll use them much. I just wondered since, although my phone can push the M's loud enough they do benefit from the kick in the backside the E18 gives them. Same volume but more drive and attack and everything just feels bigger.


----------



## SilverEars

what about built in sound card?  You have no choice but to use the software volume control.  Is it software or is it software controlling analog like the Dragonfly?


----------



## agdr

solrighal said:


> I can't remember what it was that's supposed to be difficult with the AKG's. I'll be able to let you know soon enough


 
 It is the sensitivity, which is the other thing along with impedance that figures into how hard a set of headphones is to drive.
  
 The current AKG701's have a sensitivity of 105dB/V from AKG's specification sheet.  That means with 1V(rms) into the headphones you will get a sound pressure level (SPL) of 105dB. 
  
 A rule of thumb for headphone amps is to be able to hit 120dB, which is just as ear-splittingly loud as most folks would ever want to get headphones.  The O2 headamp can muster 7V(rms) of output swing, which would give:
  
 SPL = 105dB(SPL)/V + 20log[7V(rms)] = 121dB, which hits the mark.
  
 BUT... then you have to also check the current draw at that maximum voltage swing and make sure the amp can sink/source that, too. 
  
 At 7V(rms) into 62 ohms we get:
  
 Iout(rms) = 7V(rms) / 62 = 113mA, and that is per channel. 
  
 The output chips in the O2 can sink/source around 120mA per channel maximum, but that is if you have a transformer that is big enough to supply that much current to the output chips in the first place.  As I've posted earlier in this thread the half wave voltage doubler power supply in the O2 results in large current spikes through the transformer when the diodes conduct, such that the transformer secondary needs to be rated at about 3 times as large as the DC (rms) value being supplied.  For the details see the second picture down on the left here, half wave capacitor input power supply.  Idc = Irms = .28 * secondary rating, or use a secondary rated at 1/.28 = 3.5x the Irms value:
  
http://www.hammondmfg.com/pdf/5c007.pdf (opens PDF)
  
 So for 113mA x 2channels, plus 25mA of quiescent current in the O2 chips, plus 25mA more for the O2's internal battery charging, that gives a current draw on AC of:
  
 I(max, rms) = 113mA + 113mA + 25mA + 25mA = 276mA.
  
 Your transformer secondary would then need to be rated at least 3x that, or 3 * 276mA = 828mA, which means round up to the next standard value of 1A.  The Triad WAU16-1000 (Mouser #553-WAU16-1000 for $11) would be perfect.
  
 For a lot of high sensitivity headphones, like my AKG-K550's at 115dB/V, the output voltage level needed is so low [about 60mV(rms) = 0.06V(rms) at nromal listening levels]  that the smaller 400mA-rated transformer secondaries are just fine.  But the 701's are one of those harder-to-drive lower sensitivity, lower impedance, headphones that need the larger voltage swing and the associated higher current drive.
  
 What happens if you use the smaller 400mA transformer secondary with the 701's?  After all, the maximum DC current draw we calculated was 276mA total, which would seem to be within the 400mA rating of the smaller WAU16-400 transformer, at least ignoring that half-wave rectifier current spike behavior for now. Well first off that 113mA per channel was all the way up at 120dB.  For most listening you might only be consuming 70mA or 80mA per channel or so, peak.   Then when you figure in "music power", where the peak levels of music are 3x or so the average, that may drop the average current draw down even further to 40-50mA per channel.
  
 Then what happens if the transformer rating is too small is the iron core saturates, which can create distortion in the voltage and current output, and the transformer heats up more than normal.  Whether that AC power input distortion makes it to the O2 amp output would depend on a lot of factors with the regulator chips and the op amp PSRR.  You might never hear it.  But for $3 more or so between the 400mA WAU16-400 and 1A WAU16-1000, might as well get the 1A secondary if you are ordering that O2 transformer for the first time and have a harder to drive pair like the 701.


----------



## r010159

agdr said:


> It is the sensitivity, which is the other thing along with impedance that figures into how hard a set of headphones is to drive.
> 
> The current AKG701's have a sensitivity of 105dB/V from AKG's specification sheet.  That means with 1V(rms) into the headphones you will get a sound pressure level (SPL) of 105dB.
> 
> ...


 
  
 This reminds me of the test problems in one of my EE courses that I took and forgot eons ago. This is a very nice analysis. I have a question. I purchased my O2/ODAC already preassembled. How difficult would it be to replace the existing transformer with the one that you mentioned? A simple re-soldering job? This may become a nice side project for me to get me out of the doldrums.
  
 EDIT: Let me ask a stupid question. How simply can the amp be redesigned to moderate the current spikes that develop when the diodes start to conduct? I am a little embarrassed to say what I am thinking is the solution.
  
 BG


----------



## Solrighal

I feel like I've stumbled into some kind of alternate reality. I now know exactly why I'm driving a van for a living. This is way over my head guys. I've re-read that twice now and I still don't know if my new amp and headphones are gonna work out.


----------



## r010159

solrighal said:


> I feel like I've stumbled into some kind of alternate reality. I now know exactly why I'm driving a van for a living. This is way over my head guys. I've re-read that twice now and I still don't know if my new amp and headphones are gonna work out.


 
  
 Sorry. Let this commercial break end for the original program to resume. 
	

	
	
		
		

		
		
	


	



  
 If I understand the tech part well enough, the short of it is the O2 should be able to power the AKGs. But the O2 is not in the optimal configuration for those phones. There is room for improvement. I will let the original author elaborate on this.
  
 BG


----------



## jring

r010159 said:


> How difficult would it be to replace the existing transformer with the one that you mentioned? A simple re-soldering job?


 
  
 Literally plug'n'play - you just get the 1A wall wart, plug that and are ready to go.
  
 Joachim


----------



## SilverEars

jring said:


> Hi,
> 
> when 16 bit audio data is mapped to 24 bit words this means multiplying by 256 or shifting left by 8, which is the same. The missing bits on the right hand side are set to 0.
> 
> ...


 
 You sound like you know a bit about digital volume levels.  
	

	
	
		
		

		
		
	


	




  Can you explain how it ties into percentage of the software volume levels on the computer?


----------



## Solrighal

jring said:


> Literally plug'n'play - you just get the 1A wall wart, plug that and are ready to go.
> 
> Joachim




Are you seriously saying that all that ^up there^ boils down to using a different plug?


----------



## Xenophon

FWIW:  I use the Epiphany acoustics O2/DAC to drive my HE-500's in my office setup.  These are lower sensitivity (about 89 dB) 38 Ohm cans.  Not ideal with the O2, it simply lacks oomph for these.  Tried changing the stock wall wart to a higher grade one but to my ears it makes no difference.  I'm ok listening at low/moderate volume to classical but if I dial in gain and crank up the volume quality suffers big time.  I applaud agdr's explanation and design efforts but if I were him and with his obvious technical knowledge:  build something new from the ground up and market it.  I'm not big on incremental development to adjust a design, better in general to start from a white page imo.


----------



## Solrighal

xenophon said:


> FWIW:  I use the Epiphany acoustics O2/DAC to drive my HE-500's in my office setup.  These are lower sensitivity (about 89 dB) 38 Ohm cans.  Not ideal with the O2, it simply lacks oomph for these.  Tried changing the stock wall wart to a higher grade one but to my ears it makes no difference.  I'm ok listening at low/moderate volume to classical but if I dial in gain and crank up the volume quality suffers big time.  I applaud agdr's explanation and design efforts but if I were him and with his obvious technical knowledge:  build something new from the ground up and market it.  I'm not big on incremental development to adjust a design, better in general to start from a white page imo.




I would have the thought the O2 could deal with those easily.


----------



## Xenophon

solrighal said:


> I would have the thought the O2 could deal with those easily.


 
 Depends on how you define 'deal with' I guess.  Don't want to start a long argument but if I compare the sound quality (not 'volume') out of the O2 to what I get connecting them to my 2.7 W into 50 Ohm V200 or my 1.5 WPC tube amp then there's a clear difference.  It's ok at low gain/lowish volume though.  And the comparison is of course not 100% honest from a price point view (V200/V800 setup is >2k USD) and comparing a tube amp to the O2 more or less negates what the O2 stands for.


----------



## jring

silverears said:


> You sound like you know a bit about digital volume levels.
> 
> 
> 
> ...


 
  
 Well, if you're changing the volume using the software volume slider to say 30%, all sample values are multiplied by 0.3. If you do this to to 16 bit data this means you loose between one and two bits of resolution. If the 16 bit data was scaled to 24 bit before, you still loose 1 to 2 bit of the 24 bit data word, but they're the ones which were added when scaling to 24 bit and therefore don't contain any relevant information.
  
 Joachim


----------



## jring

solrighal said:


> Are you seriously saying that all that ^up there^ boils down to using a different plug?


 
  
 Indeed agdr has shown that the 12V 200mA wall wart which tends to be used for O2 can be inadequate in a worst case scenario and a 400mA or even 1000mA rated wall wart might be beneficial in these scenarios (this was btw. also stated by the designer on his pages). My O2 came with a 15V 400mA wall wart by default and has so far been fine with that.
  
 You can just get another wall wart. Just look that it has the correct plug and have 13.5 - 20 Volt and it MUST be of the AC type - which is kinda uncommon. More than 15 or 16 Volts wastes a lot of energy and makes the power regulators get quite warm.
  
 Joachim


----------



## Xenophon

jring said:


> Indeed agdr has shown that the 12V 200mA wall wart which tends to be used for O2 can be inadequate in a worst case scenario and a 400mA or even 1000mA rated wall wart might be beneficial in these scenarios (this was btw. also stated by the designer on his pages). My O2 came with a 400mA wall wart bye default and has so far been fine with that.
> 
> Joachim


 
 What headphones are you using with it?


----------



## Solrighal

jring said:


> Indeed agdr has shown that the 12V 200mA wall wart which tends to be used for O2 can be inadequate in a worst case scenario and a 400mA or even 1000mA rated wall wart might be beneficial in these scenarios (this was btw. also stated by the designer on his pages). My O2 came with a 400mA wall wart bye default and has so far been fine with that.
> 
> Joachim




Is this dependent on the mains voltage? I have 240V here.


----------



## JacobLee89

solrighal said:


> Is this dependent on the mains voltage? I have 240V here.


 
 you only need a mains adapter, which converts whatever you have into 15-20V AC. In this case, just buy an adapter from a local store that has that function and you'll be good to go.
  
 They more or less look like this, but some have interchangeable plugs at the end:
  

  
  
 I can only imagine what 240 would do to a poor O2


----------



## Solrighal

jacoblee89 said:


> you only need a mains adapter, which converts whatever you have into 15-20V AC. In this case, just buy an adapter from a local store that has that function and you'll be good to go.
> 
> They more or less look like this, but some have interchangeable plugs at the end:
> 
> ...




Thanks mate. I actually know that and one is being supplied by the manufacturer of my O2 but "jring" appears to state a couple of posts previously that it might be beneficial to get a more powerful one for the O2 when it is paired with the Q701's. I'm just asking if that advice applies irrespective of what the actual mains voltage is.


----------



## jring

xenophon said:


> What headphones are you using with it?


 
  
 AKG K240 Sextett, K141 Monitor,  Beyer DT990  -  I also jury-rigged it to a Stax Energizer driving my SR-5 and Lambda Pro and it didin't sound bad at all. Common knowledge says those stax energizers want a few watts at least but for my listening levels I haven't heard a difference to using a power amp.
  
 Joachim


----------



## jring

solrighal said:


> Thanks mate. I actually know that and one is being supplied by the manufacturer of my O2 but "jring" appears to state a couple of posts previously that it might be beneficial to get a more powerful one for the O2 when it is paired with the Q701's. I'm just asking if that advice applies irrespective of what the actual mains voltage is.


 
  
 Just look at the wall wart supplied with your O2 - it should have the specifications printed on it. If your mains is 240V it obviously must be 240V primary and should have anything from 12V to 20V secondary (12V flat is frankly not enough but the 12V nominal transformer specified by the designer has actually 13.5V or so) and 200mA or more.
  
 If it says 200mA it might be a bit on the weak side with demanding headphones and high listening volume (although I'd think more like HE6 demanding) and 400mA might be a quick upgrade option. But I'd first test it and listen for bloated bass, which is usually a sign of an amp with not enough current.
  
 Joachim


----------



## hekeli

Well walter supplies 15V 500mA power so shouldn't be a problem..


----------



## Solrighal

jring said:


> Just look at the wall wart supplied with your O2 - it should have the specifications printed on it. If your mains is 240V it obviously must be 240V primary and should have anything from 12V to 20V secondary (12V flat is frankly not enough but the 12V nominal transformer specified by the designer has actually 13.5V or so) and 200mA or more.
> 
> If it says 200mA it might be a bit on the weak side with demanding headphones and high listening volume (although I'd think more like HE6 demanding) and 400mA might be a quick upgrade option. But I'd first test it and listen for bloated bass, which is usually a sign of an amp with not enough current.
> 
> Joachim




That's good info with a simpler explanation. It's not that I'm thick but the last time I had to look at numbers such as those above I was wearing shorts. 




hekeli said:


> Well walter supplies 15V 500mA power so shouldn't be a problem..




Perfect! Thanks.


----------



## JacobLee89

jring said:


> AKG K240 Sextett, K141 Monitor,  Beyer DT990  -  I also jury-rigged it to a Stax Energizer driving my SR-5 and Lambda Pro and it didin't sound bad at all. Common knowledge says those stax energizers want a few watts at least but for my listening levels I haven't heard a difference to using a power amp.
> 
> Joachim


 
  
 The stock O2 has only +/- 12Vdc power rails, I cannot see how a more powerful adapter would do anything different.


----------



## r010159

jacoblee89 said:


> The stock O2 has only +/- 12Vdc power rails, I cannot see how a more powerful adapter would do anything different.


 
  
 The difference is in the current that the power adapter can provide. But in terms of voltage...
  
 BG


----------



## Xenophon

r010159 said:


> The difference is in the current that the power adapter can provide. But in terms of voltage...
> 
> BG


 
 ...there's nothing to be done, regardless of what you try, those 12V are an absolute limit (or you'll drive it into clipping).


----------



## r010159

xenophon said:


> ...there's nothing to be done, regardless of what you try, those 12V are an absolute limit (or you'll drive it into clipping).


 
  
 Makes sense to me.


----------



## Solrighal

So.......


----------



## mcandmar

Get the bigger one as per agdr's post. As hekeli said Headnhifi sells a 240v version with a 15v 500ma output. I dont know off hand where to source a larger one, but worth searching for anyway.


----------



## Solrighal

What about 1200mA? Would that do the job or can I not go over 1000mA?


http://www.maplin.co.uk/p/maplin-20w-switched-mode-acdc-fixed-voltage-15v-worldwide-power-supply-l48bl


----------



## r010159

solrighal said:


> What about 1200mA? Would that do the job or can I not go over 1000mA?
> 
> 
> http://www.maplin.co.uk/p/maplin-20w-switched-mode-acdc-fixed-voltage-15v-worldwide-power-supply-l48bl


 
  
 You cash go over that, it still will work, but there may be no advantage to anything over 1000mA.


----------



## Solrighal

r010159 said:


> You cash go over that, it still will work, but there may be no advantage to anything over 1000mA.




I'm only posting that because the shop is only 12miles away and I can't see a 1000mA version.


----------



## r010159

solrighal said:


> I'm only posting that because the shop is only 12miles away and I can't see a 1000mA version.


 
  
 Go for it!


----------



## Solrighal

This one may be the right one...


http://www.maplin.co.uk/p/maplin-12w-acdc-multi-voltage-power-supply-l82bf


----------



## r010159

solrighal said:


> This one may be the right one...
> 
> 
> http://www.maplin.co.uk/p/maplin-12w-acdc-multi-voltage-power-supply-l82bf


 
  
 Looks good to me.


----------



## Solrighal

r010159 said:


> Looks good to me.




Cool, thanks. I'll wait though and see how I like the sound of the supplied supply first. I may not hear anything wrong.


----------



## mcandmar

Thats a DC supply, you need an AC.


----------



## Solrighal

mcandmar said:


> Thats a DC supply, you need an AC.




Jeez, nothin's ever easy.


----------



## Solrighal

This?

http://www.maplin.co.uk/p/maplin-10w-linear-acac-multi-voltage-power-supply-n58at


----------



## r010159

solrighal said:


> This?
> 
> http://www.maplin.co.uk/p/maplin-10w-linear-acac-multi-voltage-power-supply-n58at




You do not need a variable power supply, but since it can be setup to provide 12V, IMO it should work. The plug needs to be able to fit its receptacle on the amp, but I see it comes with an assortment of plugs.


----------



## Taowolf51

I just installed this on my computer as a dedicated audio device hub:
  
 http://www.amazon.com/gp/product/B005ARQV6U/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
  
 I seem to notice a boost in quality coming from my ODAC in detail and dynamics, I'm not sure why, it could be my brain telling me stupid things again. I was having some issues with the ODAC and my motherboard's USB ports (major distortion after leaving it plugged in for a few hours, fixed by unplugging and replugging) and I think it may have been fixed with this hub, though it hasn't been long enough to confirm).


----------



## r010159

mcandmar said:


> Thats a DC supply, you need an AC.




Oops. I made a mistake. This is the first.time I came across a AC/AC power supply. Sorry!


----------



## mcandmar

solrighal said:


> This?
> 
> http://www.maplin.co.uk/p/maplin-10w-linear-acac-multi-voltage-power-supply-n58at


 
  
 Yes that should work, though the fact they say "linear" in the description doesn't make any sense but that was probably just Maplin.  As long as it is an AC output it will be fine.
  


r010159 said:


> You do not need a variable power supply, but since it can be setup to provide 12V, IMO it should work. The plug needs to be able to fit its receptacle on the amp, but I see it comes with an assortment of plugs.


 
  
  
 12v is too low, you ideally want 14v or higher, in the above unit the 15v output would be ideal.


----------



## mcandmar

taowolf51 said:


> I just installed this on my computer as a dedicated audio device hub:
> 
> http://www.amazon.com/gp/product/B005ARQV6U/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
> 
> I seem to notice a boost in quality coming from my ODAC in detail and dynamics, I'm not sure why, it could be my brain telling me stupid things again. I was having some issues with the ODAC and my motherboard's USB ports (major distortion after leaving it plugged in for a few hours, fixed by unplugging and replugging) and I think it may have been fixed with this hub, though it hasn't been long enough to confirm).


 

 Its possible the small capacitor on each port is helping to stabilize the power supply, also the fact it isn't taking power through the motherboard may be helping. Either way $20 seems a good deal to add USB3 interfaces to a pc..


----------



## r010159

mcandmar said:


> Yes that should work, though the fact they say "linear" in the description doesn't make any sense but that was probably just Maplin.  As long as it is an AC output it will be fine.
> 
> 
> 
> 12v is too low, you ideally want 14v or higher, in the above unit the 15v output would be ideal.




Ah yes, I remember why. Stay around with you guys, and I begin to remember things!


----------



## Solrighal

solrighal said:


> This?
> 
> http://www.maplin.co.uk/p/maplin-10w-linear-acac-multi-voltage-power-supply-n58at







mcandmar said:


> Yes that should work, though the fact they say "linear" in the description doesn't make any sense but that was probably just Maplin.  As long as it is an AC output it will be fine.
> 
> 
> 
> 12v is too low, you ideally want 14v or higher, in the above unit the 15v output would be ideal.




So this is the one then. I don't understand why it states 10V in the header and then goes on to describe it as variable up to 15V. Still, it's cheap enough and I've learned something today. 

Many thanks guys.


----------



## Solrighal

Please, if this question demands a complicated answer then just say good night and I'll put this light out and sleep. 

Why, if it is the case that as Maplin's states, most devices require DC power, the O2 needs AC power?


----------



## jring

solrighal said:


> Please, if this question demands a complicated answer then just say good night and I'll put this light out and sleep.
> 
> Why, if it is the case that as Maplin's states, most devices require DC power, the O2 needs AC power?


 

 Hi,
  
 the amp in the O2 runs on DC too but it has its own circuitry to generate that from AC. And since this circuitry needs to generate +12V and -12V it really needs a 13.5-20V AC supply.
  
 Joachim


----------



## r010159

solrighal said:


> Please, if this question demands a complicated answer then just say good night and I'll put this light out and sleep.
> 
> Why, if it is the case that as Maplin's states, most devices require DC power, the O2 needs AC power?




Certain operations need to be made on the AC to provide DC to the circuit. The is normally provided by the wall-wart. So there is a reason the designer had to do this himself inside of the unit. IMVVHO, he may be providing power to internal circuits that have different DC power requirements. 

Notice the VV in the previous sentence?


----------



## mcandmar

In short, because the AC to DC conversion is done inside the O2.


----------



## Solrighal

Cheers again guys. I get it. I get th "vv" too, lol. I was thinking the same


----------



## Taowolf51

mcandmar said:


> Its possible the small capacitor on each port is helping to stabilize the power supply, also the fact it isn't taking power through the motherboard may be helping. Either way $20 seems a good deal to add USB3 interfaces to a pc..


 
  
 Possibly. The USB situation on my motherboard is a mess, it was one of the earlier USB-3 boards (Gigabyte X58A-UD3R) and has a bunch of different types of USB slots (USB 3, 2, E-Sata USB, and power USB) from 2 or 3 different USB controllers. The difference isn't subtle, which is why I'm so confused.
  
 The hub is pretty nice for $20, though there are some drawbacks. Reportedly, the USB 3 speeds slow down with each extra USB 3 device you plug in beyond one. Plus, if you plug anything USB 2 into it, the whole hub becomes a USB 2 hub. The manufacturer hasn't confirmed this, though. None of this is a problem for me, though, since this is a dedicated audio USB hub, and no audio gear needs USB 3.


----------



## agdr

solrighal said:


> So this is the one then. I don't understand why it states 10V in the header and then goes on to describe it as variable up to 15V. Still, it's cheap enough and I've learned something today.
> 
> Many thanks guys.


 
  
 That one looks like a winner. 
	

	
	
		
		

		
			





   Like macandmar says just set it on 15Vac and away you go.   The 5mm x 2.1mm tip should fit the O2.
  
 The wattage rating is a little odd.  The specs say 9.6 watts which they've rounded up to 10W in the title.  At 1 amp and a power factor of 1 that would give 9.6W / 1A = 9.6Vac, which implies the current rating would drop at 15Vac.  But no problem.  They seem to think the secondary can handle 1 amp and the "wattage" rating is really a heat dissipation thing.  Since the power going into the O2 is in the form of current spikes there is plenty of transformer "cool down" time inbetween current pulses, as opposed to using the transformer for something like outdoor lighting where it would be a constant sinusoidal current waveshape.  Most likely this is just a transformer with a single winding and a variable mechanical tap on the winding, turned by that yellow voltage adjust knob.   So it really would be a 1 amp sized winding, just tapped off at different (voltage) points.
  
 In other words the important thing is at least 14Vac and a secondary rating of at least 1 amp, and you have both here.  
	

	
	
		
		

		
		
	


	




   Good find!


----------



## Solrighal

I haven't even got my O2 yet and I'm already changing parts, lol. I had hoped it might arrive yesterday but no such luck. Now we're into the interminable post-free weekend and looking at Monday with crossed fingers.


----------



## jring

solrighal said:


> I haven't even got my O2 yet and I'm already changing parts, lol. I had hoped it might arrive yesterday but no such luck. Now we're into the interminable post-free weekend and looking at Monday with crossed fingers.


 

 Just wait how it sounds stock - I'm pretty sure it will drive your phones just fine.
  
 Joachim


----------



## Solrighal

jring said:


> Just wait how it sounds stock - I'm pretty sure it will drive your phones just fine.
> 
> Joachim




No worries mate. I have no intention of spending money unless it is absolutely necessary. This is why I've chosen to go with the ODAC and O2 in the first place. It's going to be hooked up to my Mac mini and two external drives so the whole thing will be relatively small and cheap, yet still providing quality sound.

Does the O2 get particularly hot in operation?


----------



## Solrighal

Houston, we have a problem.

I've just read that the ODAC doesn't play well with a USB3 output!

http://www.head-fi.org/t/690214/jds-labs-o2-odac-issue/0_20

Is this true? If so it's gonna be a real problem for me as my Mac only has USB3 outputs. Damn it, nothing's ever easy.


----------



## Solrighal

There is a God and he doesn't like me, or he has a warped sense of irony. Not 10 minutes after my last post I get email confirmation that my amp is out for delivery today!


----------



## Taowolf51

solrighal said:


> Houston, we have a problem.
> 
> I've just read that the ODAC doesn't play well with a USB3 output!
> 
> ...




I'm playing my ODAC through a USB 3 port, sounds fine.


----------



## Solrighal

taowolf51 said:


> I'm playing my ODAC through a USB 3 port, sounds fine.




On a Mac?


----------



## SilverEars

Damn Mac's.  Get a windows PC.  Much cheaper and compatable than the "alumanium" Johnny I'ves keeps raving about.


----------



## Solrighal

silverears said:


> Damn Mac's.  Get a windows PC.  Much cheaper and compatable than the "alumanium" Johnny I'ves keeps raving about.




It doesn't seem to be a Mac-specific issue. There are reports of problems with Windows too. It seems the common factor is the ODAC.


----------



## Taowolf51

solrighal said:


> On a Mac?


 
  
 PC, through a PCI-E hub.
  
 USB 3 is backwards compatible to USB 2, it's possible that they may be having issues with crappy early USB 3 controllers, but it should work fine with the spec itself.


----------



## Solrighal

taowolf51 said:


> PC, through a PCI-E hub.
> 
> USB 3 is backwards compatible to USB 2, it's possible that they may be having issues with crappy early USB 3 controllers, but it should work fine with the spec itself.




I think so too. I've had some encouragement over at Computer Audiophile. I'll just have to wait and see. I hate waiting, lol.


----------



## miceblue

solrighal said:


> taowolf51 said:
> 
> 
> > I'm playing my ODAC through a USB 3 port, sounds fine.
> ...



The ODAC works flawlessly for me with a Retina Display MacBook Pro, which has USB 3.0 ports.


----------



## Xenophon

^^+1, same config.  Never had an issue, it's plug and play here.


----------



## Solrighal

miceblue said:


> The ODAC works flawlessly for me with a Retina Display MacBook Pro, which has USB 3.0 ports.







xenophon said:


> ^^+1, same config.  Never had an issue, it's plug and play here.




Oh this is making me feel good. What is the build year of your MacBooks?


----------



## Xenophon

Built in Q4 of 2013.


----------



## Solrighal

xenophon said:


> Built in Q4 of 2013.




I was expecting that. My Mac is late 2012. If it's a software issue then there's a good chance it's been fixed since I bought my Mac but if it's a hardware problem I could be stuffed.


----------



## miceblue

solrighal said:


> miceblue said:
> 
> 
> > The ODAC works flawlessly for me with a Retina Display MacBook Pro, which has USB 3.0 ports.
> ...



Mine's the 1st generation of the Retina MacBook Pro (from 2012).


----------



## Ali-Pacha

Happy owner of a head'n'hifi O2 amp, paired with my HD600. Natural and relaxing sound.
  
 Ali


----------



## jring

solrighal said:


> Houston, we have a problem.
> 
> I've just read that the ODAC doesn't play well with a USB3 output!
> 
> ...


 
  
 I just plugged my ODAC from a USB2 to a USB3 port to check and as expected it still plays fine. My O2 does not get warm.
  
 Joachim


----------



## Solrighal

That's good to know. I'm still worried but, I'm like that I guess. Thanks for the info all the same.


----------



## Solrighal

ali-pacha said:


> Happy owner of a head'n'hifi O2 amp, paired with my HD600. Natural and relaxing sound.
> 
> Ali




The HD600 may well be my next pair of headphones. I'm glad you're enjoying it.


----------



## Ali-Pacha

solrighal said:


> The HD600 may well be my next pair of headphones. I'm glad you're enjoying it.


 
 Kinda relief after some Stax SR-009 "details overdose" sessions 
	

	
	
		
		

		
			




  
 Ali


----------



## James-uk

ali-pacha said:


> Kinda relief after some Stax SR-009 "details overdose" sessions
> 
> Ali




How do you find the stax? I'm tempted but I do love the 800s and 600s .


----------



## Solrighal

ali-pacha said:


> Kinda relief after some Stax SR-009 "details overdose" sessions
> 
> Ali




Yeah, that must be annoying.


----------



## Ali-Pacha

SR-009 are a kind of "everything / everywhere" tool. Extension, details, dynamics, clarity, bass slam, magnificent decay, speedy gonzales transients, and so on. On the other hand, SR-Lambda and SR-5 are vintage mids cans (and I love them this way).
 With the O2, HD600 have a good level of transparency, they keep this so special low-mids emphasis, and also this 130 hz bump. Maybe a bit veiled, but the O2 gives them enough clarity / neutrality to fight this Sennheiser trend.
 Summary : O2 is the amp to get for stat's head when they go dynamics 
	

	
	
		
		

		
		
	


	



  
 Ali


----------



## James-uk

How would you compare hd800 with sr009? I find the 800s with O2 do all the things you list . Is it next level or just different flavour?


----------



## miceblue

james-uk said:


> How would you compare hd800 with sr009? I find the 800s with O2 do all the things you list . Is it next level or just different flavour?



STAX headphones have a unique sound. They have treble, but it's really smooth and effortless. The HD800 sounds a bit grainy in comparison from what I've listened to.


----------



## James-uk

The hd600 / O2 combo definitely suits my taste more than any other combo for the majority of music , although given the right recordings the hd800 /O2 has the edge.


----------



## James-uk

miceblue said:


> STAX headphones have a unique sound. They have treble, but it's really smooth and effortless. The HD800 sounds a bit grainy in comparison from what I've listened to.




I sometimes find the 800s treble elevated but I don't hear 'grainy' . I think I need to hear stax for reference so I can understand .


----------



## Ali-Pacha

Unfortunately, I've never heard HD800. From what I've read, they are kind of merciless cans, amazing with a good amp, but sometimes cold and edgy compared to stat's smoothness.
 I think stats are fundamentally a different flavour : the music is just there, sometimes with a kind of ethereal presentation, and amazing extension. When you go back to dynamics, the sound has more thickness and impact, but also a kind of laziness / sluggish presentation.
 I do like the O2 amp (don't we forget the thread ! 
	

	
	
		
		

		
		
	


	




) because it brings more air to my HD600...even if it doesn't convert a dynamic into an estat.

 Ali


----------



## James-uk

ali-pacha said:


> Unfortunately, I've never heard HD800. From what I've read, they are kind of merciless cans, amazing with a good amp, but sometimes cold and edgy compared to stat's smoothness.
> I think stats are fundamentally a different flavour : the music is just there, sometimes with a kind of ethereal presentation, and amazing extension. When you go back to dynamics, the sound has more thickness and impact, but also a kind of laziness / sluggish presentation.
> I do like the O2 amp (don't we forget the thread !  ) because it brings more air to my HD600...even if it doesn't convert a dynamic into an estat.
> 
> Ali



Thanks for taking the time to describe the difference. It backs up what I thought . Im very intrigued . My wallet is shaking in fear!


----------



## Solrighal

james-uk said:


> Thanks for taking the time to describe the difference. It backs up what I thought . Im very intrigued . My wallet is shaking in fear!




I would agree but my wallet's been missing since 1998.


----------



## r010159

solrighal said:


> No worries mate. I have no intention of spending money unless it is absolutely necessary. This is why I've chosen to go with the ODAC and O2 in the first place. It's going to be hooked up to my Mac mini and two external drives so the whole thing will be relatively small and cheap, yet still providing quality sound.
> 
> Does the O2 get particularly hot in operation?


 
  
 I have had my O2/ODAC on for about two weeks. No problems here.


----------



## Solrighal

r010159 said:


> I have had my O2/ODAC on for about two weeks. No problems here.




Thanks.


----------



## Solrighal

I received my ODAC XL & O2 this morning. They are tiny! I somehow wasn't prepared for that. Anyway, I hooked it all up via USB 3 to my Mac mini, selected "ODAC" in Sound Preferences and it's working perfectly with no problems at all. Whatever problems others were having previously when connecting via USB 3 seem to have been fixed. Music plays with no stuttering or pops & clicks. I'll be back later with an early assessment of the sound but for now I'm off to listen to some music. Here's what I'll be reviewing...

http://www.headnhifi.com/dac/odac-xl-version

http://www.headnhifi.com/amplifiers/desktop-headphone-amplifiers/O2-desktop-amplifier

Main headphones will be bass-modded AKG Q701's and V-Moda M100 XL's.


----------



## jring

solrighal said:


> I received my ODAC XL & O2 this morning. They are tiny! I somehow wasn't prepared for that. Anyway, I hooked it all up via USB 3 to my Mac mini, selected "ODAC" in Sound Preferences and it's working perfectly with no problems at all. Whatever problems others were having previously when connecting via USB 3 seem to have been fixed. Music plays with no stuttering or pops & clicks. I'll be back later with an early assessment of the sound but for now I'm off to listen to some music. Here's what I'll be reviewing...
> 
> http://www.headnhifi.com/dac/odac-xl-version
> 
> ...


 
  
 Have fun with 'em. Btw, one can put the ODAC board into the O2 enclosure for an even smaller package, which (unless advanced hackery is used) will make the O2 mains only and of course there is no room for RCA plugs...
  
 Joachim


----------



## Taowolf51

If you think the ODAC XL is tiny, you should see the standard one!


----------



## Solrighal

I'll be straight up. This is the best I have *ever* heard music. It's the first time since buying the Q701's that I haven't been looking for an EQ. I must confess to having had a couple of beers today. A proper review will have to wait I'm afraid. I've been reading every thread I could find on this combo before I finally put the money down. Some people thought it was of marginal benefit whilst others had an almost religious experience. I belong in the latter group. I like to think of myself as someone who knows quality when he hears it. I'm not rich but have always loved music. I started my working life with a part-time job in a hi-fi shop. I'm pretty sure I've never heard music reproduced with quite the same clarity as I'm hearing right now. Right now, by the way, is Communique by Dire Straits.

By far the biggest feature, at least initially, is the inky blackness that this combo delivers. There is absolutely no noise. Nada, zilch! I'm listening to the AKG Q701's right now. I have tried my V-Moda M-100's but they sounded like what they are. It's not hi-fi. That was a surprise to be honest. Up to now I've used the Q's and M's interchangeably, depending on whether I wanted to hear bass or not. With the E18 as DAC/amp I could do that but not with the ODAC/O2. There's a gulf between their resolving capabilities. The M's are still great headphones of course. I'll be using them as portables forever I think. Out & about they rock!

One thing I'm noticing that night be slightly counter-intuitive is that with the Q's the soundstage seems to have shrunk. Not a bad thing. Before it was wide but, and I confess I'm only noticing this now, it was imprecise. Now it's absolutely focused. I'm listening to Eddi Reader now and her voice is dead centre but with instruments which seem to swirl around her. It's meant to sound like that. I know Eddi and know this to be how it was mixed. I've never heard that before though. Candyfloss & Medicine is a spectacular album to be honest. It's not very forgiving of crap playback though.

I bought my ODAC XL and O2 (desktop version) from Walter & Stefan at Head'n'Hifi. I opted for 1x/3x gains, recommended to me by Hekeli from these forums. That was an excellent call. I've yet to find anything that Unity (1x) gain can't deal with. The build quality is superb. Really, both units are very nicely assembled. Photos to follow. I went for the XL version of the ODAC because I wanted to be able to use existing cables I have kicking around. Currently I'm using Linn Black RCA interconnects which are obviously far too long but I can't remember ever seeing anything shorter. The Linn's to my ears are pretty neutral cables. I've had them for a while and used them in a few different places in my system and they seem to add very little to anything. Maybe a tad lean but only a wee bit.

This has turned out longer than I intended, lol. It's not definitive by any means. Just my opinion. This is money very well spent. Want to know something? My wife likes this sound. For the first time in thirty years she's actually noticed an improvement!


----------



## Ali-Pacha

My O2 Amp (with some company). From headnhifi, have changed the volume knob with a better one.
  

  
 Low points : battery life (not that terrible for a desktop use), everything's on the front panel (but I'm used to it now), low quality volume knob (but the pot is very solid / smooth)
 High points : power, gain multiplier (excellent for low output sources), very "obvious" sound, withou any blur or mis-eq, rock solid case, great performance for the price.

 Ali


----------



## Solrighal

I'm finished for tonight. My stereo sounds fantastic! It's a cliché we see a lot around here but I heard things tonight I've never heard before. How much did this cost? Crazy.


----------



## r010159

solrighal said:


> I'm finished for tonight. My stereo sounds fantastic! It's a cliché we see a lot around here but I heard things tonight I've never heard before. How much did this cost? Crazy.


 
  
 I feel the same way with my unit. The DT880 headphones with this unit does "sing". I know there are better quality amp/DACs available. But will I be able to hear the difference? How obvious will this difference be? And what is the cost of such a unit? I think this unit hits the sweat spot of performance to cost for a minimalist design. The only thing I see lacking are some optional features, like direct DSD decoding and an optical input, for instance. But nothing important to me right now.
  
 BG


----------



## Xenophon

For the price and if you have headphones that can be driven to the max by it (the majority) the O2 is hard to beat. Yes there are better options available but it quickly becomes a matter of diminishing returns. Is it worth it? Depends on your finances and how much you crave those last %, everybody has his own limit. I heard amp and dac combos ranging from the price of the ODAC/O2 upto 50k USD. My sweet spot for a good combo is about 7-8 k, not willing to go beyond that. But it's certainly true that in hifi a lot of bulls***ware is being peddled at tremendous premiums so caveat emptor always applies, certainly if you spend higher amounts.

Enjoy the music!


----------



## Solrighal

Any thought on interconnects people? I'm using Linn Black RCA's to connect DAC & amp but they're a metre long and I wouldn't mind something neater. Trouble is most quality cables tend to be thick and fairly rigid so a short length wouldn't be flexible enough. With the two units stacked 4 or 5 inches would be perfect. I'll go have a look at Toxic Cables but I just know it's going to cost a fortune. I'm definitely not spending more on the cables than the amp, that's for sure.


----------



## Solrighal

ali-pacha said:


> My O2 Amp (with some company). From headnhifi, have changed the volume knob with a better one.
> 
> 
> 
> ...




Hi mate. What was wrong with the original volume knob and what's so good about your replacement? And where did you get it?


----------



## Ali-Pacha

solrighal said:


> Hi mate. What was wrong with the original volume knob and what's so good about your replacement? And where did you get it?



 

Cheap plastic, which doesn't cover the lockwasher of the potentiometer (raw metal colour).
I've bought a black aluminum potentiometer at Mayflower electronics...my sister (who lives in Seattle) brought it to me the last time she came back to France.

Ali


----------



## Xenophon

solrighal said:


> Any thought on interconnects people? I'm using Linn Black RCA's to connect DAC & amp but they're a metre long and I wouldn't mind something neater. Trouble is most quality cables tend to be thick and fairly rigid so a short length wouldn't be flexible enough. With the two units stacked 4 or 5 inches would be perfect. I'll go have a look at Toxic Cables but I just know it's going to cost a fortune. I'm definitely not spending more on the cables than the amp, that's for sure.


 
 Take a look at some of these, they're not too expensive and well built (i own a set of rya interconnects):  http://epiphany-acoustics.co.uk/products-page/
  
 Warning:  I'm not a cable lore guy, feel that these are the last part in your chain that you should dump money into and as you say, spending more on the cables than the device is madness.


----------



## SilverEars

ali-pacha said:


> solrighal said:
> 
> 
> > Hi mate. What was wrong with the original volume knob and what's so good about your replacement? And where did you get it?
> ...


 
 Was your original Alps?  Does your new one have better balance at low volume rotation?


----------



## Solrighal

ali-pacha said:


> solrighal said:
> 
> 
> > Hi mate. What was wrong with the original volume knob and what's so good about your replacement? And where did you get it?
> ...




That's true. I hadn't actually noticed that washer but you're right enough. I guess a bit of extra weight might help too. I'll look into that. Is it just a standard fitting or is there anything special about it? You can tell I'm not very knowledgeable about such things, lol.


----------



## Solrighal

I 





silverears said:


> Was your original Alps?  Does your new one have better balance at low volume rotation?




I know your question's not aimed at me but FYI my gains are 1x & 3x. On unity gain my volume sits at around 3 o'clock driving the Q701.


----------



## SilverEars

I'm glad you are enjoying the objective combo.  The imbalance is more of concern to me because I use iems that are very sensitive with them.  K701 has low sensitivity so it shouldn't have issues.


----------



## Solrighal

xenophon said:


> Take a look at some of these, they're not too expensive and well built (i own a set of rya interconnects):  http://epiphany-acoustics.co.uk/products-page/
> 
> Warning:  I'm not a cable lore guy, feel that these are the last part in your chain that you should dump money into and as you say, spending more on the cables than the device is madness.




I totally believe cables make a difference and I've got a fair selection here, although they're all too long. It's a bit tricky once you've bought into the whole Objective spiel though because now I'm looking for a cable to specifically do absolutely nothing to the sound. To be as transparent as possible. I've now tried three different interconnects and every one sounds different and every one changes the sound. Hmm...


----------



## r010159

solrighal said:


> I totally believe cables make a difference and I've got a fair selection here, although they're all too long. It's a bit tricky once you've bought into the whole Objective spiel though because now I'm looking for a cable to specifically do absolutely nothing to the sound. To be as transparent as possible. I've now tried three different interconnects and every one sounds different and every one changes the sound. Hmm...


 
  
 You found cables to make a difference? How noticeable is the difference to you? I may have to try this myself.
  
 BG


----------



## Solrighal

They can make a big difference! My Furukawa's sound quite dark but my Linn's are, erm, lighter? Difficult to describe actually. The thing is depending what's used at this early part of the chain kinda determines what's used further along. At least with headphones there's only really two cables to worry about. My speaker cables are Mogami, very warm. I like it like that.


----------



## Xenophon

If you can point me to a single double blind study that was conducted with scientific rigour and shows subjects can differentiate reliably between various cables I'll fly over to Scotland myself, buy you dinner and eat haggis.


----------



## Ali-Pacha

silverears said:


> Was your original Alps?  Does your new one have better balance at low volume rotation?



 

Potentiometer and volume knob are two separate things ! The volume pot is always an Alps RK097.

Ali


----------



## Xanode

miceblue said:


> Nope. It's illegal to post links to websites of previously banned members of Head-Fi.
> 
> You can just Google "nwavguy o2" though and it should be within the first two listed websites. XD


 
 ITS "illegal" is it? Who's gonna arrest me? the headfi police? lol


----------



## Solrighal

xenophon said:


> If you can point me to a single double blind study that was conducted with scientific rigour and shows subjects can differentiate reliably between various cables I'll fly over to Scotland myself, buy you dinner and eat haggis.




That may very well be the case, however I believe I hear a difference.


----------



## Solrighal

I'm using JRiver MC19 and it has an option called integer mode. What is it and should I be using it?


----------



## r010159

solrighal said:


> I'm using JRiver MC19 and it has an option called integer mode. What is it and should I be using it?




It makes the handling of data between computer and your ODAC more efficient. I do not know if it actually makes a difference. I have my reservations about this.


----------



## Solrighal

I've switched it on and off again repeatedly and I can't hear any change in the sound. Perhaps the player needs restarted after a change?


----------



## miceblue

solrighal said:


> I've switched it on and off again repeatedly and I can't hear any change in the sound. Perhaps the player needs restarted after a change?



It probably doesn't make an audible difference, but rather, it optimises the pathway the digital audio is processed.
http://www.amr-audio.co.uk/large_image/MAC%20OSX%20audio%20players%20&%20Integer%20Mode.pdf

I think it's more for peace of mind.


----------



## Solrighal

miceblue said:


> It probably doesn't make an audible difference, but rather, it optimises the pathway the digital audio is processed.
> http://www.amr-audio.co.uk/large_image/MAC%20OSX%20audio%20players%20&%20Integer%20Mode.pdf
> 
> I think it's more for peace of mind.




Aye, it makes zero difference. Or I'm deaf.


----------



## Solrighal

Does anyone know how to setup JRiver for use with the ODAC? Specifically the sample rate selections. I'm kinda lost to tell the truth.


----------



## anthk

solrighal said:


> Aye, it makes zero difference. Or I'm deaf.


 

 i think the one who must not be named said jitter is more obvious/important in recording stage instead of playback stage. i am not surprised that we cant hear a random 1ms delay.


----------



## anthk

xanode said:


> ITS "illegal" is it? Who's gonna arrest me? the headfi police? lol


 

 nah. you just get stoned to death. by headfi police.


----------



## Solrighal

anthk said:


> nah. you just get stoned to death. by headfi police.




Ah, I remember those days with fondness.


----------



## adydula

Those days are still here, posting this persons website or links to it are not allowed.
  
 That said most all of know where it is etc...
  
 On the ODAC with JRiver.
  
 I have 2 ODACS and use JRiver.
  
 Its fairly simple to do. I  use WIN 7 and a pc not a mac.
  
 I would add the JRiver Intereact support forum is loaded with techie info etc.
  
 The way I have mine setup is as follows:
  
 DSP Studio:
 Output Format checked, nothing else
 Sample Rate set to No Change
 Channels set to Source Number of Channels
 No Mixing
 No Subwoofer stuff
  
 Playback Options:
 Audio Output set to WASAPI
 WASAPI Settings: Device Default or ODAC, Check Open Device for Exclusive Access, BitDepth set to Automatic,
 Buffering set to 100ms default. If you have pops or clicks set lower...on one system this is set to 25ms. If you have issues at the default 100ms setting to higher times makes this worse.
  
 All the other stuff on the Options Page is pretty much default.
  
 With windows there are other WIN7 settings that need to be setup correctly as well but I don't know the MAC equivelents.
  
 On a PC when the little ICON in the upper right side of the JRiver  screen turns "Blue" you basically have achieved BITPERFECT with the JRiver player....that is what the source is is the source out....
  
 That said the OS settings may or may not impact these.
  
 Glad you liking the O2 and ODAC....for the bucks you cant beat it....for sure.
  
 All the best
 Alex


----------



## Solrighal

I was actually making a veiled drug reference, lol. Never mind. I love the ODAC XL & O2 combo so much here's a couple of pictures...


----------



## r010159

adydula said:


> [deleted]
> 
> Playback Options:
> Audio Output set to WASAPI
> ...




For the Mac, output is set to ODAC. Let the different bit rates default. Any further question, you can PM me.


----------



## Solrighal

r010159 said:


> For the Mac, output is set to ODAC. Let the different bit rates default. Any further question, you can PM me.




I've got my Mac set to ODAC in Sound Preferences. In Audio Midi Setup I've set output to 2ch/24bit @ 44.1khz. I had intended to set this to 96khz but it won't stick. Is this correct?


----------



## miceblue

solrighal said:


> r010159 said:
> 
> 
> > For the Mac, output is set to ODAC. Let the different bit rates default. Any further question, you can PM me.
> ...



Mine seems to work. I'm still running the latest version of Mountain Lion if it makes any difference. Mavericks still seems to have too many issues for me to upgrade. XD



Speaking of which, this thread might come in handy to some people who use OS X.
http://www.head-fi.org/t/539740/mac-os-x-music-players-alternatives-to-itunes


----------



## headwhacker

I have bit perfect which works on top of iTunes. It automatically sets the matching bit/sample rate of the DAC with the music currently playing in iTunes.


----------



## Solrighal

miceblue said:


> Mine seems to work. I'm still running the latest version of Mountain Lion if it makes any difference. Mavericks still seems to have too many issues for me to upgrade. XD
> 
> 
> 
> ...




My ODAC doesn't look like that in the left pane. I don't have the 64ch option. In the right pane you have it set to 16bit, not 24bit. I can make my screen look like yours when the player is stopped but as soon as I restart it goes back to 44.1khz, irrespective of whether I set it to 2ch-16bit or 2ch-24bit. Hmm...


----------



## Solrighal

I'm on Mavericks btw. You're not using JRiver though are you, Mike?


----------



## miceblue

solrighal said:


> miceblue said:
> 
> 
> > Mine seems to work. I'm still running the latest version of Mountain Lion if it makes any difference. Mavericks still seems to have too many issues for me to upgrade. XD
> ...



Oh whoops. I set it to 2ch-24bit now. Thanks for catching that! 


The 64ch thing is a whole separate program/setting. You should have the 2 USB icons for the ODAC (1 for output, 1 for input).
https://code.google.com/p/soundflower/


Maybe JRiver Media Center has its own DAC options for the sampling rate and bit-depth. Or it may just be a bug with the software. I can't use the demo version of it since I wasted that opportunity back when it was in the beta stage for OS X (version 16 I think).


----------



## Solrighal

I definitely don't have the 64ch option. What would that be used for anyway?


----------



## Solrighal

Is soundflower something you installed yourself? Who made your ODAC?


----------



## headwhacker

solrighal said:


> My ODAC doesn't look like that in the left pane. I don't have the 64ch option. In the right pane you have it set to 16bit, not 24bit. I can make my screen look like yours when the player is stopped but as soon as I restart it goes back to 44.1khz, irrespective of whether I set it to 2ch-16bit or 2ch-24bit. Hmm...



 


I think your Music player is setting the dac to the correcponding bit/sample rate of the currently playing file. That is bit perfect playback (Not to be confused with bitperfect app).


----------



## miceblue

solrighal said:


> Is soundflower something you installed yourself? Who made your ODAC?



I dunno what the 64ch thing is for.

Yes, Soundflower is a separate program I installed myself. I use it to capture audio from the computer to the computer (e.g. play audio in iTunes and record it with Audacity).


JDS Labs made my ODAC. I purchased it a few years ago, so the case was different from yours, but everything else should be the same.


----------



## Solrighal

miceblue said:


> I dunno what the 64ch thing is for.
> 
> Yes, Soundflower is a separate program I installed myself. I use it to capture audio from the computer to the computer (e.g. play audio in iTunes and record it with Audacity).




Phew, you had me worried there. Yeah, the 64ch thing refers to recording channels. Many moons ago I had the same thing in Windows with the drivers for an M-Audio 2496Audiophile sound-card I had installed. I never used them but that's the MIDI default channel spread. 

You're right about the bit perfect thing too. I tried a high-res version of Pink Floyd' "Momentary Lapse of Reason" - total waste of money btw, luckily I nicked it - and the setting persisted then reverted to 44.1khz.

All is well with our world's. As well as they can be anyway.


----------



## ieee754

Is there any quality loss if I connect O2 with another amp? I'd like to use my ODAC but it's in combo with O2 and I don't want to mess with internal electronics.


----------



## AsianBatman

If your amp section is powered off, the amp line out works as a dac only. There should be no quality loss.


----------



## ieee754

asianbatman said:


> If your amp section is powered off, the amp line out works as a dac only. There should be no quality loss.


 
 Does it really work? After turning off amp I don't hear anything from headphones. Shouldn't it play at a very low volume?


----------



## Solrighal

ieee754 said:


> Does it really work? After turning off amp I don't hear anything from headphones. Shouldn't it play at a very low volume?




No. If it does you're about to become a billionaire.


----------



## ieee754

It works! But I had to connect headphones to line-in of the amp, and it plays only at low/moderate level. Why do I need O2 then?


----------



## AsianBatman

ieee754 said:


> It works! But I had to connect headphones to line-in of the amp, and it plays only at low/moderate level. Why do I need O2 then?


 
  
 Well, my stand alone odac also works when I plug in my headphones, but it does not have nearly enough power to actually drive headphones to optimal listening levels. I find that my iems do well with the ODAC alone and adjusting the volume in windows to 100% produces a decent volume. Which amp are you planning to use with your DAC?


----------



## ieee754

asianbatman said:


> Well, my stand alone odac also works when I plug in my headphones, but it does not have nearly enough power to actually drive headphones to optimal listening levels. I find that my iems do well with the ODAC alone and adjusting the volume in windows to 100% produces a decent volume. Which amp are you planning to use with your DAC?


 
 I used Sennheiser Momentums which are pretty efficient and the volume level of ODAC is listenable, but it lacks bass a bit. I'm not sure about new amp, I'm interested in getting Hifiman headphones (now waiting to see reviews and measurements of HE-560) which require a lot of power so I'm asking just in case O2 was not enough. Do you know any O2-like (in terms of transparency) amp that could drive even HE-6?


----------



## AsianBatman

ieee754 said:


> I used Sennheiser Momentums which are pretty efficient and the volume level of ODAC is listenable, but it lacks bass a bit. I'm not sure about new amp, I'm interested in getting Hifiman headphones (now waiting to see reviews and measurements of HE-560) which require a lot of power so I'm asking just in case O2 was not enough. Do you know any O2-like (in terms of transparency) amp that could drive even HE-6?


 
  
 Unfortunately, I do not have any experience with Hifiman products aside from my short lived possession of the HE-300 (sold it). As far as amps go, I only own the O2 and NFB-12.1. Both are efficient to drive HD600 and Denon 2k. Hopefully someone else may point you in the right direction in terms of amps for HE-6.


----------



## Solrighal

asianbatman said:


> Unfortunately, I do not have any experience with Hifiman products aside from my short lived possession of the HE-300 (sold it). As far as amps go, I only own the O2 and NFB-12.1. Both are efficient to drive HD600 and Denon 2k. Hopefully someone else may point you in the right direction in terms of amps for HE-6.




That's interesting that you're O2 was capable of driving the HD600. Do you know what gain setting that was with? I ask because I quite fancy a pair of HD600's in future.


----------



## ieee754

asianbatman said:


> Unfortunately, I do not have any experience with Hifiman products aside from my short lived possession of the HE-300 (sold it). As far as amps go, I only own the O2 and NFB-12.1. Both are efficient to drive HD600 and Denon 2k. Hopefully someone else may point you in the right direction in terms of amps for HE-6.


 
 Ok, thanks anyway, I didn't know that this is possible to use ODAC directly from the combo.
  
 By the way, is there any reason to think that O2 won't be able to drive headphones like HE-500 even at high volume? I did the math and it seems that O2 with 613mW at 33ohms headphone impedance is able to drive any headphone with efficiency above 87.5 dB/mW to peak SPL of 115dB without clipping, here is how I calculated it:
  
 E - headphone efficiency in dB
 P - power from amplifier (for O2 it's 613)
  
 10^((115 - E)/10) = P
 115 - E = 10 * log(P)
 E = 115 - 10 * log(P) = 115 - 10 * log(613) = 115 - 27,87 = 87,13
  
 I was told in another thread that O2 can't drive HE-500 at high volume, but it seems that to reach 115 SPL only 398mW is required, is there some property of O2 that makes it worth getting better amp?


----------



## AsianBatman

solrighal said:


> That's interesting that you're O2 was capable of driving the HD600. Do you know what gain setting that was with? I ask because I quite fancy a pair of HD600's in future.


 
  
 I clipped my O2 myself to 1x/2.5x gain and use 1x gain with my HD600. I am among many that find the O2 sufficient in driving the HD600. Although I do prefer my NFB 12.1 for the HD600 since it adds a little darkness to the sound. 
  


ieee754 said:


> Ok, thanks anyway, I didn't know that this is possible to use ODAC directly from the combo.
> 
> By the way, is there any reason to think that O2 won't be able to drive headphones like HE-500 even at high volume? I did the math and it seems that O2 with 613mW at 33ohms headphone impedance is able to drive any headphone with efficiency above 87.5 dB/mW to peak SPL of 115dB without clipping, here is how I calculated it:
> 
> ...


 
  
 To be honest, that math goes over my head. Been awhile since I've dealt with that kind of stuff, but I'm assuming that ohm swings cause by different frequency output causes a fluctuation in output mW? Best analog I can think of is subwoofer amps for cars. Just cause an amp is rated for 1000 watt doesn't mean it's better than an amp rated for 500 watt, in this case you would want to look at the RMS output an amp has and out steady the wattage is when the sub hits at different volumes. I could be completely wrong. Just from following the Hifiman thread, I don't see many O2s used for HE-500.


----------



## Solrighal

asianbatman said:


> I clipped my O2 myself to 1x/2.5x gain and use 1x gain with my HD600. I am among many that find the O2 sufficient in driving the HD600. Although I do prefer my NFB 12.1 for the HD600 since it adds a little darkness to the sound.




That's good to know. I use 1x/3x gains so I'd get away with it. Thanks for the info.


----------



## miceblue

ieee754 said:


> asianbatman said:
> 
> 
> > Unfortunately, I do not have any experience with Hifiman products aside from my short lived possession of the HE-300 (sold it). As far as amps go, I only own the O2 and NFB-12.1. Both are efficient to drive HD600 and Denon 2k. Hopefully someone else may point you in the right direction in terms of amps for HE-6.
> ...



Reaching the right power is one thing, but having sufficient current going through a low-impedance/efficient headphone is another. I don't know the current limitations for the O2's op-amps, but planar magnetic headphones are current-demanding. You might not have the same bass slam as with an amp of higher current output.


----------



## AsianBatman

solrighal said:


> That's good to know. I use 1x/3x gains so I'd get away with it. Thanks for the info.


 
 Of course the gain depends on your source also. I find that I need higher gain if I use it with my cellphone, and less if I use it with the Odac. How far into the future will this investment be? :]


----------



## Solrighal

asianbatman said:


> Of course the gain depends on your source also. I find that I need higher gain if I use it with my cellphone, and less if I use it with the Odac. How far into the future will this investment be? :]




I'll be using the ODAC as my main source for quite some time yet. I don't know about the Senn's, I'm torn between them and Grado's.


----------



## AsianBatman

solrighal said:


> I'll be using the ODAC as my main source for quite some time yet. I don't know about the Senn's, I'm torn between them and Grado's.


 
  
 I was once torn also. Still want to own a pair of Grado's though and do plan on investing in a pair down line, just to quench my curiosity.  Was hoping for a 325i or something above that.


----------



## Solrighal

asianbatman said:


> I was once torn also. Still want to own a pair of Grado's though and do plan on investing in a pair down line, just to quench my curiosity.  Was hoping for a 325i or something above that.




I was also looking at the 325 bit for me it's a lot of money. £300 here. It would have to sound very good indeed because it's ugly as sin, uncomfortable & poorly built. I suspect the Senn might come first. I don't suppose you're in a position to compare the HD600 with the AKG Q701?


----------



## AsianBatman

solrighal said:


> I was also looking at the 325 bit for me it's a lot of money. £300 here. It would have to sound very good indeed because it's ugly as sin, uncomfortable & poorly built. I suspect the Senn might come first. I don't suppose you're in a position to compare the HD600 with the AKG Q701?


 
  
 Not a solid comparison. Had the chance to audition a friend's Q701s for a night. I preferred the sound and comfort of the HD600. The Q701 was too analytical for my taste and exploited some of my lower quality tracks.


----------



## Solrighal

asianbatman said:


> Not a solid comparison. Had the chance to audition a friend's Q701s for a night. I preferred the sound and comfort of the HD600. The Q701 was too analytical for my taste and exploited some of my lower quality tracks.




I've heard that complaint before. These are my only reference you see. The details are incredible but there are times I'd prefer a bit more warmth. Not often mind, with the ODAC & O2 these are luscious but, as you imply, with the "right" recordings.


----------



## agdr

miceblue said:


> Reaching the right power is one thing, but having sufficient current going through a low-impedance/efficient headphone is another. I don't know the current limitations for the O2's op-amps, but planar magnetic headphones are current-demanding. You might not have the same bass slam as with an amp of higher current output.


 
  
 Yeah that is the problem.  With the O2's 7Vdc peak swing on batteries you would need 7v / 33R = 212mA per channel.  The O2 can only handle around 120mA per channel with the standard NJM4556A chips.
  
 Headphones like that are one of the reasons why I designed the O2 booster board.  The output chips are good for up to 250mA on peaks.


----------



## r010159

agdr said:


> Yeah that is the problem.  With the O2's 7Vdc peak swing on batteries you would need 7v / 33R = 212mA per channel.  The O2 can only handle around 120mA per channel with the standard NJM4556A chips.
> 
> Headphones like that are one of the reasons why I designed the O2 booster board.  The output chips are good for up to 250mA on peaks.




Thanks for this bit of information. Now I understand the real advantage for using the booster board. Not just for a subtle change in fidelity.


----------



## Solrighal

"Booster board". That's twice now. What's this all about?


----------



## adydula

you can get details on the booster boards at diyaudio....
  
 There is also a thread on this site as well....
  
 fyi
  
 Alex


----------



## AsianBatman

Great help...
 Much appreciated...
  
 Thanks....


----------



## Solrighal

adydula said:


> you can get details on the booster boards at diyaudio....
> 
> There is also a thread on this site as well....
> 
> ...




Cheers.


----------



## Solrighal

Following on from the earlier group-think on power supplies and current I've just managed to get my paws on this...

http://www.maplin.co.uk/p/maplin-10w-linear-acac-multi-voltage-power-supply-n58at

Does it make a difference? Hmm...

I feel a lot better though


----------



## adydula

I have used most all of the adapters and none really make any real world discernible difference to me.
  
 I can understand how one might feel a lot better though!!
  
 A.


----------



## Solrighal

adydula said:


> I have used most all of the adapters and none really make any real world discernible difference to me.
> 
> I can understand how one might feel a lot better though!!
> 
> A.




It's just a placebo isn't it? To be honest if you knew the trouble I actually went to to source that supply you'd be seriously impressed. The company I bought it from did avert thing they possibly could, at 3 different stores and on their website, to thwart my attempts to get it.

It turned out there's some new European Directive being enacted which effectively outlaws all AC - AC adapters currently on sale. I have no idea why.


----------



## agdr

r010159 said:


> Thanks for this bit of information. Now I understand the real advantage for using the booster board. Not just for a subtle change in fidelity.


 
  
 Along with double the otuput current, the no-thump headhone relay, and the indicator LEDs the other truely hard-and-fast benefit is the ability to run the O2 at +/-15Vdc for the rare 600 ohm low-sensitivity headphone where the O2's standard +/-12Vdc power supply won't produce enough volume.  The O2's standard output chips could overheat at +/-15Vdc, depending on specifics of the load, due to the small DIP8 package type.
  


solrighal said:


> It's just a placebo isn't it? To be honest if you knew the trouble I actually went to to source that supply you'd be seriously impressed. The company I bought it from did avert thing they possibly could, at 3 different stores and on their website, to thwart my attempts to get it.
> 
> It turned out there's some new European Directive being enacted which effectively outlaws all AC - AC adapters currently on sale. I have no idea why.


 
  
 Hey you definitely get an "A+" on part sourcing!  I had completely forgotten about that EU power efficiency directive.  They want all power supplies to be switchers, that run at 100kHz - 1mHz or so, which are more efficient than transformers.  They also can produce switching noise so audiophiles have typically avoided them.  It can definiltey be done though - JDS Labs C5 headamp has a switcher in there and he's shown me the FFT of the output.  It is completely free of switcher noise.


----------



## Solrighal

The one I bought can be set to a few different voltages, 15V being the max. I went with 15V since the one supplied as stock was 15V. Did I do the right thing?

I've also just ordered another geek improvement which I'm sure is gonna make this sound like the dogs. I have a new machined aluminium volume knob en - route from New Yawk! 

I have to thank ali-pacha for that idea. Shipping is costing me 4 times the value of the knob, lol.

I also finally found a use for those silicon bands that Fiio ships with their units. I'm using two of them to keep the ODACXL/O2 in a neat wee bundle.

There's only one wee tweak I want to perform but one thing about this project of mines has a significant sway over my choices. Namely - the design ethos behind the O2. I've got the models of both that gave stereo RCA sockets. This is great but creates some problems for me...

All my interconnects are 1.0m long and generally pretty stiff. They look ridiculous.

I need a very short stereo RCA interconnect. I can't find any online ready made so I've put the feelers out to Toxic Cables. They can make them short enough and flexible enough to allow them to be tucked in discretely. Toxic Cables are not cheap and this causes me dilemma number one - I'm not prepared to spend more on the cable than the O2 itself cost me.

Even if Toxic can do it cheap enough there's dilemma number two. The ethos behind the O2 and (to a lesser extent) the ODAC is transparency and neutrality. To this end I can hardly use an overtly coloured cable which is what I believe silver brings to the party (Toxic like silver).

Am I mad? Discuss.


----------



## Xenophon

Well, my opinion is worth what you pay for it and I totally respect that you're free to do whatever you like with your money so don't take the following in a negative way because it's not intended so:
  
 I.m.o. what you're trying to do is to turn a donkey into a race horse by investing in extra training, feeding it class A vegetables in stead of hay, putting platinum horse shoes on it and coating it in teflon spray to reduce the drag coefficient.  All very nice tweaks.  But the fact of the matter is that it remains a donkey, not an arab stallion.  Only, by the time you're done you'll have sunk so much into it that you could have purchased a zero frills arab in the first place.
  
 Long story but professionally I see this all the time.  It's the type of thing that typically makes any infrastructure project cost 2.1 times the initial budget.  Safe to say that I'm not an incrementalist I guess.


----------



## mcandmar

solrighal said:


> Even if Toxic can do it cheap enough there's dilemma number two. The ethos behind the O2 and (to a lesser extent) the ODAC is transparency and neutrality. To this end I can hardly use an overtly coloured cable which is what I believe silver brings to the party (Toxic like silver).
> 
> Am I mad? Discuss.


 
  
 Sheez, here goes nothing.  If you can pick up a silver cable for pocket money (i.e. second hand on eBay) go for it as they do make a difference, but dont spend any real money on it.
  
 As for silver bringing coloration to the party, i would argue to the complete opposite, its what your not hearing with cheapy cables that makes them sound smoother. Silver cables dont add anything so if your music sounds harsh and sibilant with them, then the recording is just harsh and sibilant, end of story.
  
 /flame suit on.


----------



## miceblue

Silver is a better conductor than copper. From this, for all we know copper is the one colouring the music, not silver. XD

I'm planning to make my own copper-based cable for a balanced headphone cable.




And from personal experience, the hand-made silver interconnect cable that a local Head-Fier made seemed more transparent than my copper-based FiiO one.


----------



## headwhacker

the 5% difference in conductivity I doubt makes up for a difference between Cu and Ag if there is any at all. Before you beat each others head debating cables I would worry first on the plugs on each ends, the solder joints and the insulating material. Also most plugs are gold plated which are way less conductive than Cu.

the signal has already been degraded before it even travel along the length of the cable. Now give that a thought first.

EDIT: Also just to add, the length and the gauge of the cable has more impact on conductivity/resistance than the chemistry. 1 meter silver 35 gauge vs. 1 inch 22 gauge copper. Place you bets.


----------



## adydula

Don't you think that short, stiff cables that are bent severely to your portable stuff has an adverse effect?
  
 Imagine how the electrons flowing and hitting the 180 degree twist or turn in the cable??
  
 OMG, that bend area must get really warm on high volume loud passages?
  
 Maybe someone can come up with a cable cooler to help reduce the heat....??
  
 Hope you smiling...
  
 A.


----------



## Solrighal

So... 

I knew that was a tricky question. I mean, will I even hear any difference on such a short run? 

Anyway, silver is good then and anything it adds is more likely just something to copper masks. That's interesting. I wish I could find a short cable on eBay but I've never seen anything with RCA plugs that's shorter than 0.5m.

If anyone does come across anything let me now.


----------



## Solrighal

I did some research on my cables and found that the general consensus of the Linn Black interconnects I've been using between the ODAC & O2 are generally considered to be rather bright & edgy. That hasn't been my experience in their previous role (Bluray to amp) but I thought I'd rummage around and find something else to switch with. I chose a pair of pretty old QED Silver Anniversary cables. At least they're shorter at 0.5m as opposed to the Linn's 1.0m.

It's been a very long time since I actually sat down with the specific intention of listening to cables. I reckon they'll sound different but I'm not sure they'll be any better. Definitely better looking though.


----------



## r010159

mcandmar said:


> Sheez, here goes nothing.  If you can pick up a silver cable for pocket money (i.e. second hand on eBay) go for it as they do make a difference, but dont spend any real money on it.
> 
> As for silver bringing coloration to the party, i would argue to the complete opposite, its what your not hearing with cheapy cables that makes them sound smoother. Silver cables dont add anything so if your music sounds harsh and sibilant with them, then the recording is just harsh and sibilant, end of story.
> 
> /flame suit on.


 
  
 Kinda like how the tube amp alters the signal? Definitely not accurate, but in this case pleasant?


----------



## syphen606

adydula said:


> Don't you think that short, stiff cables that are bent severely to your portable stuff has an adverse effect?
> 
> Imagine how the electrons flowing and hitting the 180 degree twist or turn in the cable??
> 
> ...


 
  
 Uhm.... Yes..  darn 180 degree bends slowing down my electrons!


----------



## krismusic

How on earth have cables ended up being discussed on a thread dedicated to the ultimate rationalist amp???


----------



## JacobLee89

krismusic said:


> How on earth have cables ended up being discussed on a thread dedicated to the ultimate rationalist amp???


 
 +1 and seconded. I believe folk tales have creeped in.


----------



## anthk

jacoblee89 said:


> +1 and seconded. I believe folk tales have creeped in.


 

 that's why i use superconductor cables @ 4k, such pure sound.


----------



## krismusic

anthk said:


> that's why i use superconductor cables @ 4k, such pure sound.



Grrrr!


----------



## Solrighal

krismusic said:


> How on earth have cables ended up being discussed on a thread dedicated to the ultimate rationalist amp???




It was me who introduced cables and I think it's valid. As I said earlier, since the ethos of the ODAC/O2 is transparency it would seem essential to use a cable between the two units which added as little colouration as possible. How is that not relevant?


----------



## JacobLee89

solrighal said:


> It was me who introduced cables and I think it's valid. As I said earlier, since the ethos of the ODAC/O2 is transparency it would seem essential to use a cable between the two units which added as little colouration as possible. How is that not relevant?


 
  
 The consensus between cable material/quality bringing out any sonic improvements/transparency is tied, and is questionable at best. Several well documented double blind tests on cables have been inconclusive, and the O2 ethos focuses more on minimising costs through careful design choices.
  
 I'm not saying that cables do not do anything, but for me it's borderline negligible. 
  
 And now I am starting to sound like O2 designer guy. Time to push the play button and ignore words for now.


----------



## headwhacker

solrighal said:


> It was me who introduced cables and I think it's valid. As I said earlier, since the ethos of the ODAC/O2 is transparency it would seem essential to use a cable between the two units which added as little colouration as possible. How is that not relevant?


 

 Cables are important and as valid to get the best setup possible. But not in the context of Cu sounding different than Ag.


----------



## krismusic

Personally I think cables need to be long enough to reach between components and terminated with good quality connectors. The end. They are not going to make equipment you don't like into equipment you do like.


----------



## Solrighal

krismusic said:


> Personally I think cables need to be long enough to reach between components and terminated with good quality connectors. The end. They are not going to make equipment you don't like into equipment you do like.




No, of course not but they can alter the character somewhat so they do matter to some. For instance my main headphones for critical listening are my Q701's. If I was given the choice of a cable which was bright and another on the dark side I'd prefer to go dark with the Q's. Given the cost of cables it's not unreasonable to want to try and get it right. I'd ideally like a cable which is transparent but I don't know if that exists. 

My whole reasoning behind buying the O2 was to have one component in my system which is essentially neutral. Then, if at a later date I change my DAC, I will easily hear any difference there.


----------



## Solrighal

I've been switching phono cables around all day and have just noticed that my AC input socket is very loose (wobbly). I don't remember it being this way when I first installed the O2 and all I've done with it since then is swap the power supply for a beefier 1A version. I did note that the plug supplied with the original (500mA) supply was very tight compared to the new supply. I've tried wiggling it around and there doesn't appear to be any connection problem? Should I just ignore it? I don't intend to be removing it any time soon.


----------



## adydula

Spread the connectors apart abit...
  
 A.


----------



## Solrighal

adydula said:


> Spread the connectors apart abit...
> 
> A.




You mean go inside the case?

Can I just take the back off or do I need to take both off for access?


----------



## adydula

Does the other AC supply still fit snugly?
  
 A.


----------



## Solrighal

adydula said:


> Does the other AC supply still fit snugly?
> 
> A.




I'm scared to try it. It was so tight in the first place I'm worried if I try it again I might do some real damage. At least at the moment the amp is working fine. Anyway, I had a look at the screws and I don't have whatever tool it takes to get those out. They look like Torx heads but I'm not sure. I'd have to get into town to do something about that.

I'd kinda like to attempt some DIY anyway. This booster board piques my interest, as does the 0 Ohm impedance mod (whatever that is).


----------



## Solrighal

OK, I tried the original and it's still tight and the socket is still loose...


----------



## adydula

Well, that tells me something...
  
 My two 02's, one I built and one I bought have the same AC input connector soldered on the board.
  
 All of my AC to AC wall worts fit nice and snug with no real movement.
  
 So one of your adapters must have an slightly different plug on it that it loose or the first one is so tight it mechancally could have opened the onboard connector somewhat and now you have a loose situtatuon.
  
 You could go back to the place you bought the 02 or ac adapter, try another adapter or have the ac connector on board replaced and try the one that is loose now?
  
 Its not hard to do, my units have simple Phillips head self tapping screws that make taking it apart simple.
  
 Do you really hear any very noticeable difference between the two??
  
 I honestly never have...if that's the case I would just use the better fitting one!
  
 All the best
 Alex


----------



## Solrighal

I don't hear any difference at all. Both plugs fit securely, it's just that the original is very tight. If I open it up is it possible to fix the socket myself? Going back to the manufacturer is not an option as he's in Switzerland and I'm in Scotland.


----------



## Solrighal

I'm thinking of buying a pair of Sennheiser HD650's. Will the O2 drive them ok?


----------



## syphen606

solrighal said:


> I'm thinking of buying a pair of Sennheiser HD650's. Will the O2 drive them ok?


 
  
 The O2 will drive them just fine in low gain. High gain will cause distortion.
  
 That said, I do prefer using my Crack compared to my O2 or C421 with the HD650's. They all drive them fine however.


----------



## miceblue

syphen606 said:


> solrighal said:
> 
> 
> > I'm thinking of buying a pair of Sennheiser HD650's. Will the O2 drive them ok?
> ...



I like the Crack in general for its sound. Crack is some good stuff. :rolleyes:


----------



## Solrighal

syphen606 said:


> The O2 will drive them just fine in low gain. High gain will cause distortion.
> 
> That said, I do prefer using my Crack compared to my O2 or C421 with the HD650's. They all drive them fine however.




So unity gain will drive them to decent volumes?




miceblue said:


> I like the Crack in general for its sound. Crack is some good stuff. :rolleyes:




I've heard that


----------



## jring

solrighal said:


> I'm scared to try it. It was so tight in the first place I'm worried if I try it again I might do some real damage. At least at the moment the amp is working fine. Anyway, I had a look at the screws and I don't have whatever tool it takes to get those out. They look like Torx heads but I'm not sure. I'd have to get into town to do something about that.
> 
> I'd kinda like to attempt some DIY anyway. This booster board piques my interest, as does the 0 Ohm impedance mod (whatever that is).


 
  
 The screw heads on a head_n_hifi built amp are torx but I'm not sure about the size since I don't have access to the unit atm. Best take the amp to a hardware store and get a fitting torx bit.
  
 As for the power plug - as long as wiggling the plug does not make it loose contact or short against the case, I would leave it as is. Btw. did you hear a difference between the stock 4-500mA transformer and the 1000mA one - I'd be most surprised...
  
 The O2 has 0.5 ohms output impedance which is good for 4 ohms headphones as per the "1/8 of headphone impedance" rule. Since I don't know any 4 ohms phones... I'm fine with it as is...
  
 Joachim


----------



## Solrighal

There was no difference at all, at least to my ears. It was a learning experience though. Who knows, this AC-AC unit may become a collectors piece in the new Europe. I've re-installed the original power supply and no amount of wiggling causes any problems. I'll get into town hopefully later in the week and get a set of Torx heads. It's actually something I've always meant to buy bit I've never gotten around to. I will now. I'd actually be interested to know if there are any other mods which might improve the sound quality...


----------



## adydula

There aren't any mods that will improve the audible sound quality of the O2.
  
 The design and measurements make it totally transparent...if you don't like to hear what the source material is like then the O2 is not the amp for you.
  
 The comments about the crack and other headphones are valid, maybe your taste but not necessarily accurate or transparent.
 I have several tube amps, sold most of them due to added coloration...but again you might like that type of sound.
  
 There is a booster board that AGDR has designed that helps with power for the other 2% of the cans that the O2 was not designed to drive to their limits.
  
 You could order a ac jack from mouser etc....and get it and try your ac adapters in a dry fit....and see if it makes sense to replace the one
 on the board.
  
 http://www.mouser.com/ProductDetail/Kobiconn/163-7620E-E/?qs=%2fha2pyFaduipJSLWTjADy1%252byZ8QiQUJwx%252biCWTioyxo%3d
  
 Alex


----------



## adydula

Fyi...the HD650 was a favorite of the original designer....he has write up on his blog if u search...
 A.


----------



## Solrighal

That's a fair comment my friend. I don't really know what I was thinking on looking for "better sound" as the transparency and the ethos were the precise reasons I went for the ODAC / XL. I'll have a look for the write-up from the man with no name.


----------



## adydula

Hey np!!
  
 All is good...
  
 There is an ODA type of amp being designed and built by agdr on DIY.
  
 It looks like it will be a really nice desktop type similar to the O2 In ways.
  
 It has a lot of what was thought might be in the designers desktop version before he left the scene.
  
 I will be building one of these....not for any sonic differences but lots of user efficiencies and additions.
  
 Enjoy you O2 its a stellar device for sure!!
  
 All the best
 Alex


----------



## Solrighal

This would explain why agdr knows so much about the O2.


----------



## adydula

Yes,
  
 Agdr has many posts and discussions on the diy blog with the designer.....very interesting.
  
 I think agdr is probably the most knowledgeable engineer that understands the O2 very well inside and out.
  
 We all can learn, but some people just have the engineering (electrical) knowledge or nac that most of us never will.
  
 Its good he is playing around with the ODA from his perspective...I cant wait to build one.
  
 Alex


----------



## nekroseven

I've got HD558 and a Xonar DG.
  
 I'm looking for a desktop amp/dac combo with optical input so I can use Dolby Headphone from the DG. I'm looking to spend $100-150 ideally but I'm willing to shell out if I think it's worth it.
  
 A second option would be to splurge and get the O2/ODAC combo because I may decide later to grab a pair of Q701. Would it be worth it to get the O2/ODAC over just getting an O2 amp alone?


----------



## Solrighal

Yes, but it only accepts USB in, not optical.


----------



## Solrighal

USB cable - worth spending more?


----------



## pearljam50000

Is it a good budget rig for HD800?


----------



## Xenophon

It'll work. Is it good? Imo no, unless you spent all your cash on the headphones and have to live like a pauper for the time being, in which case it becomes a viable option. It's a bit like buying an Audi r8, minus its engine due to lack of cash, then putting in the block of a dodge.


----------



## Eternal Phoenix

xenophon said:


> It'll work. Is it good? Imo no, unless you spent all your cash on the headphones and have to live like a pauper for the time being, in which case it becomes a viable option. It's a bit like buying an Audi r8, minus its engine due to lack of cash, then putting in the block of a dodge.


 
  
 I'll +1 this
  
 Living like a pauper (student...) it works, but saving the pennies for an Invicta..


----------



## headwhacker

xenophon said:


> It'll work. Is it good? Imo no, unless you spent all your cash on the headphones and have to live like a pauper for the time being, in which case it becomes a viable option. It's a bit like buying an Audi r8, minus its engine due to lack of cash, then putting in the block of a dodge.






eternal phoenix said:


> I'll +1 this
> 
> Living like a pauper (student...) it works, but saving the pennies for an Invicta..




How much power do you guys think is needed to power an HD800?


----------



## Xenophon

With the HD-800 imo it's not so much a matter of power, they have a nominal impedance of 300 Ohm but are very efficient, would have to look it up and see what the impedance does over the frequency range but I think power wise it'd work.  But they're very finicky about DAC/AMP combo's, partially also due to their resolving/detailed nature, it's easy to make them sound harsh or lifeless.  To me the combo with O2/ODAC is far from ideal but give it a try and judge for yourself.


----------



## headwhacker

xenophon said:


> With the HD-800 imo it's not so much a matter of power, they have a nominal impedance of 300 Ohm but are very efficient, would have to look it up and see what the impedance does over the frequency range but I think power wise it'd work.  But they're very finicky about DAC/AMP combo's, partially also due to their resolving/detailed nature, it's easy to make them sound harsh or lifeless.  To me the combo with O2/ODAC is far from ideal but give it a try and judge for yourself.



 


Yeah it's very efficient at 102 dB/1Vrms. If I follow the guy's calculation, for HD800 to reach 115dB SPL it would need around 66mW of power. 115 dB is already very loud and could potentially be harmful for long term listening. 

At 300 ohms the O2 can potentially put out around 170mW of power. Of course the load impedance can vary wildly at different frequency response. But still at > 100mW of power is more than enough to drive HD800.

Unless my calculations and understanding is off then I suppose sound preference could be more of the deciding factor for O2 driving HD800 rather than power output?


----------



## Xenophon

Fwiw I think you have it right.  Can't do an A/B now because my O2 combo is in my residence in Delhi and my HD 800 and myself are in Europe now with my other amps but I did try them with it and didn't much care for the sound.  There are a couple of threads about the pairing thing.  To me the 800 sound just right with my Violectric setup as those are not the ultimate in resolving capability and the v200 is voiced slightly warm. They also do very well with a good quality tube amp imo. I tried them with other amp combo's such as the Burson conductor and that was just too harsh for my liking.  Very detailed amp but just too much to take for extended sessions, it took away the pleasure of listening to music and turned it more into a technical exercise.  It's very much a matter of preference so beware of people who categorically and unconditionally state a 'best' combo.


----------



## Solrighal

I have a question (what, another?). I get the ethos of the O2 - a straight wire with gain for as little money as possible - but what about the ODAC? I'm not unhappy with it or anything as I'm currently getting the best sound I've personally ever experienced. However, I'm sitting here awaiting delivery of my latest purchase - Sennheiser's HD650 - and I'm already thinking about the next step. Can the ODAC be improved upon?

I've read that using an optical interface can bring improvements all by itself but how does the DAC used in the ODAC rank? I'm a great believer in the old saying, "garbage in, garbage out". 

I'd be interested in anyone's opinions and, preferably, experiences.


----------



## MaciekN

Zorrofox read some about optical vs coax. When I was researching that subject it turned out that 1) optical connection has lower bandwidth and 2) it supposedly adds jitter (some tough-to-get-rid form). The only benefit of optical over coax is that you always get galvanic isolation, which is nice but not obligatory to get good sound. You can also achieve galvanic isolation with coax but then you have to worry about controlling the impedance of the whole connection (plugs, cables, etc).
  
 Overall both optical and coax interfaces are used to transmit SPDIF signal, which is criticised for mixing clock info with signal info, and although with modern chips it is not much of a problem for quality audio it's just simpler to use straight USB->i2s conversion, rather than USB->SPDIF->i2s. That's what you get with ODAC. So technically speaking ODAC is not garbage, it's a very competent DAC. If I were you I wouldn't worry about it.
  
 Give the combo a listen when your HD650 arrives and if you would still want to upgrade keep in mind that you wouldn't get much improvement, if any, from upgrading the DAC.


----------



## Solrighal

I wasn't implying the ODAC is garbage! I love it. I just want to know what more expensive DAC's bring to the party. Surely they must add something? This is why I pointed out that all the O2 has to be is transparent, ie transparent to the source data. That source data is surely variable depending on the DAC used? 

Let me re-state; I think the ODAC / O2 work wonderfully together and if this truly is the pinnacle then great, I'll go on a better holiday


----------



## James-uk

solrighal said:


> I wasn't implying the ODAC is garbage! I love it. I just want to know what more expensive DAC's bring to the party. Surely they must add something? This is why I pointed out that all the O2 has to be is transparent, ie transparent to the source data. That source data is surely variable depending on the DAC used?
> 
> Let me re-state; I think the ODAC / O2 work wonderfully together and if this truly is the pinnacle then great, I'll go on a better holiday




The odac is transparent , the odac/ O2 combo sounds identical to the benchmark dac1 and dac2. They are 2 of the most advanced / technically perfect dacs ever created. Our ears just can't hear that improvement .


----------



## James-uk

http://www.tomshardware.com/reviews/high-end-pc-audio,3733-19.html


----------



## JacobLee89

solrighal said:


> I wasn't implying the ODAC is garbage! I love it. I just want to know what more expensive DAC's bring to the party. Surely they must add something? This is why I pointed out that all the O2 has to be is transparent, ie transparent to the source data. That source data is surely variable depending on the DAC used?
> 
> Let me re-state; I think the ODAC / O2 work wonderfully together and if this truly is the pinnacle then great, I'll go on a better holiday


 
  
 From as far as I have seen, comparisons say that the bifrost (with uber and gen 2 usb, costing $520) is only slightly more resolving than the ODAC. Some have even said that if all you're using is USB input, then upgrading to the benchmark DAC 1 won't bring anything new.


----------



## Xenophon

It's not the pinnacle by a long shot.  But a lot depends on what you need and what you're willing to spend for incrementally smaller gains.  Extra money will bring you DAC's with more options, ,connectivity, up/resampling options, zero sampling (massively underrated imo if your source quality is good), digital filters that may or may not add anything etc etc.
  
 You need to try them, it's as simple as that, regardless of the objective spiel they're not the same.  Or if cash is no object but time is precious, get an MSB Diamond dac+, the power base and femto upgrade and for a mere 85000 USD + UK VAT you're set.  Never seen an O2 connected to it, though.
  
 About the USB/optical debate:  a lot if not all depends on the implementation.  A blanket statement that one will always outperform the other is not useful imo.


----------



## Solrighal

85 grand? Is that all? Nah, even if I had that kind of money spare I'd be too busy on my jetski. Good info though and nice to know that, even if this isn't the summit, at least I can see it from here.


----------



## jring

solrighal said:


> USB cable - worth spending more?


 
  
 IMHO no, the one with the ferrite pearl delivered by head_n_hifi should be just fine.
  
 Joachim


----------



## Solrighal

james-uk said:


> http://www.tomshardware.com/reviews/high-end-pc-audio,3733-19.html




Wow! I think I'll take my wife out for a meal at the weekend. That's quite an eye-opener and fair puts this hobby in perspective. Thanks.


----------



## Solrighal

jring said:


> IMHO no, the one with the ferrite pearl delivered by head_n_hifi should be just fine.
> 
> Joachim




I suspected this myself. Digital is digital eh? It either works or it doesn't. What's the purpose of the "ferrite pearl"?


----------



## Xenophon

solrighal said:


> 85 grand? Is that all? Nah, even if I had that kind of money spare I'd be too busy on my jetski. Good info though and nice to know that, even if this isn't the summit, at least I can see it from here.


 
 I wouldn't get it either, even if I had the disposable income commensurate with it.  If nothing else, DAC-technology is still evolving at a reasonably fast pace, a top of the line DAC purchased 7 years ago would be less than mid-end now.
  
 My advice/'philosophy':  a) *take your time to get to know what you have* and don't lose yourself in sites like this, there's always 'better' and many wizards promoting things they may not even have heard, far less compared to other gear. The taller the claim, the higher the burden of proof.  b) *Invest in quality music material *after all, that's what this is all about and if that stinks, no expensive gear will fix it. c) *Learn what your sound signature preferences are, once again, this takes time. *d) *Many roads lead to Rome*, what's right for me/my music may not be right for you. e) *Audition gear *there's no substitute for your own ears.  I had to purchase some items unheard due to my situation living in 2 countries and in retrospect, some things I'd have done differently.  
  
 For the rest, personally I like source/amp to be as neutral as possible and adapt the sound to my liking via a judicious choice of headphones.  Just my opinion.  Also, neutrality is not the end all and certainly does not equate euphony in all cases.  
  
 If I were you I'd take a break from tinkering, enjoy the music and then go out and audition something radically different to see how it compares.  Try a tube amp/dac for instance, that'll provide significant contrast.


----------



## Solrighal

xenophon said:


> I wouldn't get it either, even if I had the disposable income commensurate with it.  If nothing else, DAC-technology is still evolving at a reasonably fast pace, a top of the line DAC purchased 7 years ago would be less than mid-end now.
> 
> My advice/'philosophy':  a) *take your time to get to know what you have* and don't lose yourself in sites like this, there's always 'better' and many wizards promoting things they may not even have heard, far less compared to other gear. The taller the claim, the higher the burden of proof.  b) *Invest in quality music material* after all, that's what this is all about and if that stinks, no expensive gear will fix it. c) *Learn what your sound signature preferences are, once again, this takes time. *d) *Many roads lead to Rome*, what's right for me/my music may not be right for you. e) *Audition gear *there's no substitute for your own ears.  I had to purchase some items unheard due to my situation living in 2 countries and in retrospect, some things I'd have done differently.
> 
> ...




I agree with everything you've said. In particular I like to think of having a wide range of headphones with different sound signatures as a very expensive EQ. 

I will be investing in a valve amp, particularly since I read they can work particularly well with the HD650's.


----------



## Solrighal

Well, I managed to fix my wobbly power socket. I needed a T5 bit so I bought a set. The problem turned out to be a loose lock-nut on the back of the socket. I guess it happened in transit between Switzerland Scotland. I also took delivery of my Pyst phone cables. Much better looks but no discernible difference in sound.

I'm now waiting for my HD650's to be delivered and that'll be me set for a while. My wallet (and wife) can't take any more


----------



## krismusic

xenophon said:


> I wouldn't get it either, even if I had the disposable income commensurate with it.  If nothing else, DAC-technology is still evolving at a reasonably fast pace, a top of the line DAC purchased 7 years ago would be less than mid-end now.
> 
> My advice/'philosophy':  a) *take your time to get to know what you have* and don't lose yourself in sites like this, there's always 'better' and many wizards promoting things they may not even have heard, far less compared to other gear. The taller the claim, the higher the burden of proof.  b) *Invest in quality music material* after all, that's what this is all about and if that stinks, no expensive gear will fix it. c) *Learn what your sound signature preferences are, once again, this takes time. *d) *Many roads lead to Rome*, what's right for me/my music may not be right for you. e) *Audition gear *there's no substitute for your own ears.  I had to purchase some items unheard due to my situation living in 2 countries and in retrospect, some things I'd have done differently.
> 
> ...



A damn fine post.


----------



## krismusic

solrighal said:


> Well, I managed to fix my wobbly power socket. I needed a T5 bit so I bought a set. The problem turned out to be a loose lock-nut on the back of the socket. I guess it happened in transit between Switzerland Scotland. I also took delivery of my Pyst phone cables. Much better looks but no discernible difference in sound.
> 
> I'm now waiting for my HD650's to be delivered and that'll be me set for a while. My wallet (and wife) can't take any more



Very pleased to hear that the socket was an easy fix. 
The O2 is a little wonder. I don't know if it beats amps costing hundreds or thousands but it is definitely worth the £80 I paid for it and that is good enough for me. 
One thing though. 
These comparisons to the Benchmark DAC may be a bit disingenuous. 
I have read that the Benchmark is predominantly a DAC. Hence the name I guess!
Apparently it is available without an amp for only £150 less. 
This would indicate that the amp being measured against the O2 only costs £150. 
Or have I got this wrong?
Whatever. The O2 will do me until I have some serious cash to spare.


----------



## hekeli

krismusic said:


> These comparisons to the Benchmark DAC may be a bit disingenuous.
> I have read that the Benchmark is predominantly a DAC. Hence the name I guess!
> Apparently it is available without an amp for only £150 less.
> This would indicate that the amp being measured against the O2 only costs £150.
> Or have I got this wrong?


 
  
 Couldn't be more wrong. DAC2 D version is without *pre*amp (no analog inputs). There's always a world class (measuring) headphone amp (two of them).
  
 Hmph I think my O2 broke or something. Left side has a loud hiss and sounds quieter.. time to open it up I guess.


----------



## hekeli

I don't see anything funny at quick glance..
  
 Exact symptom: No hiss at pot minimum position, hiss starts to get very loud the more I open the pot - but when I get from 95% to 100% full open pot, the hiss disappears completely. Any hints?


----------



## skeptic

solrighal said:


> I wasn't implying the ODAC is garbage! I love it. I just want to know what more expensive DAC's bring to the party. Surely they must add something? This is why I pointed out that all the O2 has to be is transparent, ie transparent to the source data. That source data is surely variable depending on the DAC used?
> 
> Let me re-state; I think the ODAC / O2 work wonderfully together and if this truly is the pinnacle then great, I'll go on a better holiday


 
  
 I think the odac is a great value but as others have noted, it isn't the pinnacle.  This whole hobby boils down to a line drawing exercise and diminishing marginal returns.  Everyone ultimately has to draw that line in the sand relative to their own ears, wallets and priorities.
  
 I like my odac and listen to it frequently, but I also agree with some of the more serious dac reviewers on head-fi that sabre dacs seem to leave just a little something to be desired in terms of treble timbre and bass tonality.  The burrbrown dac chip in my Keces 131 doesn't measure quite as well as a sabre (although my recollection is that the dac on the whole measures slightly better than the odac), but this implementation sounds a little more real to me overall, particularly in the highs and deep bass.  You might give at least the first post of this thread a good read while noting that the authors are not particularly inclined towards sabre dacs.  http://www.head-fi.org/t/693798/ranking-of-21-dacs-and-dac-configurations-and-why-chocolate-ice-cream-must-die  They still rank the odac in a category entitled "recommended for others" and praise its value and incredible sonic similarity to benchmark's products.  But I tend to agree that objectively better sound is still out there, albeit on an exponential pricing curve.


----------



## Solrighal

That's the thing. I'm not science-minded but I understand the rationale and criteria used to measure an amplifier. A DAC on the other hand is something else. DAC's surely come in different flavours?


----------



## MaciekN

These "flavours" are highly discussable, depends on one's approach to the hobby. What do you feel needs clarification about DAC measurements?


----------



## James-uk

I think this is worth a watch. Highlights the kind of thinking some people have on digital. Makes me realise how people can get carried away when talking about dacs in general. 

http://m.youtube.com/watch?v=cIQ9IXSUzuM


----------



## JacobLee89

james-uk said:


> I think this is worth a watch. Highlights the kind of thinking some people have on digital. Makes me realise how people can get carried away when talking about dacs in general.
> 
> http://m.youtube.com/watch?v=cIQ9IXSUzuM


 
  
 Makes me glad that I remained sceptical of DACS to this day - and counting -


----------



## Solrighal

maciekn said:


> These "flavours" are highly discussable, depends on one's approach to the hobby. What do you feel needs clarification about DAC measurements?




Hi. It's not that I doubt the testing of DAC's, I just don't really understand how it works. What is the reference point that DAC's are tested against?

It's as much to do with myself. If I open up my O2 I have an understanding of what I'm looking at. I understand how an amp works and I'm able to identify what I'm looking at. Open up an ODAC and I'm pretty much lost from the get-go. It's an age thing. Also my line of work in the real world takes my nowhere near this kind of subject.


----------



## MaciekN

DACs are supposed to convert digital signal to analog one. Many (not all) signals were first analog, then they were recorded and digitized, that is sinewaves representing amplitude and frequency were saved as ones and zeroes. Looking at it from another perspective: There is this Nyquist-Shannon theorem (you can check it on wikipedia) that states that any bandlimited signal can be reproduced if we have at least 2 points representing the original sinewave. The video posted above explains it nicely. So essentially DAC is supposed to reconstruct the original analog waveform, any deviation (called also artifacts) from the original will be a kind of distortion. There are many kinds of distortion, both in frequency domain (think THD, IMD measurements) and time domain (jitter) and granted that all of them remain low enough, your hearing will not be able to tell the difference between original and reconstructed signal, 100% the same in your perception. On paper ODAC (and many other DACs) achieves this. So any % of distortion in DAC measurements reflect how much it deviates from ideal.
  
 Note that usually headphones have around 100x higher distortion levels than modern day D/A chips.
  
 On the PCB side of things ODAC is very simple. First, you have the Tenor chip that takes 0s and 1s from USB at a rate determined by the PC and decodes it into i2s signal, where (as far as I remember) each channel and clock info run on separate buses (cables) into the ESS DAC chip. There each sample for each channel is taken at a very strict pace (determined by master clock), converted from current to voltage and amplified (all of this integrated into the chip) and then sent straight to the output as a set sinwaves that make up music.
  
 Some designs use SPDIF for digital signal, where 0s and 1s representing samples and clock info are encoded into a single stream passed with controlled impedance coax or optical connection into a receiver chip, where it is broken down into i2s and sent to DAC. Supposedly this last step was a problem for older receiver chips, resulting in jitter (as sample info modulated clock info and vice versa), but modern chips handle it just fine. In ODAC this one step is omitted, so there is nothing to fix after decoding SPDIF.
  
 There is also an inductor that probably filters high frequency noise from USB. All the rest are resistors and capacitors controlling chip functions, modes, and such.


----------



## Solrighal

maciekn said:


> DACs are supposed to convert digital signal to analog one. Many (not all) signals were first analog, then they were recorded and digitized, that is sinewaves representing amplitude and frequency were saved as ones and zeroes. Looking at it from another perspective: There is this Nyquist-Shannon theorem (you can check it on wikipedia) that states that any bandlimited signal can be reproduced if we have at least 2 points representing the original sinewave. The video posted above explains it nicely. So essentially DAC is supposed to reconstruct the original analog waveform, any deviation (called also artifacts) from the original will be a kind of distortion. There are many kinds of distortion, both in frequency domain (think THD, IMD measurements) and time domain (jitter) and granted that all of them remain low enough, your hearing will not be able to tell the difference between original and reconstructed signal, 100% the same in your perception. On paper ODAC (and many other DACs) achieves this. So any % of distortion in DAC measurements reflect how much it deviates from ideal.
> 
> Note that usually headphones have around 100x higher distortion levels than modern day D/A chips.
> 
> ...




Wonderful post! Even more so because I now understand something I didn't this morning. Given those relative distortion figures it's amazing the DAC's relevant at all.

Thanks very much for this, I've pasted it into Evernote


----------



## adydula

DAC chips made by semiconductor companies are spec'd and used in reference circuits.
  
 The ODAC was designed to try to meet or exceed the DAC chip specs....
  
 In the process of the actual physical design and several layouts the designer indicates the issues of actual physical placement
 on his attempts to meet or exceed these types of measurements.
  
 So be carfeful on comparing specs on a DAC chip by itself.
  
 Placing a chip into a circuit design on a physical board and depending on the bells and whistles outside of the chip can dramatically
 affect the overall performance and measurements.
  
 The minimilastic design and careful layout that are documented on the designers blog make the ODAC an exceptional DAC.
  
 All the gory details are over there for all to read...
  
 All the best
 A.


----------



## Solrighal

Excellent post my friend


----------



## BrettMatthews

Just sent the payment for my new Desktop O2/ODAC, should pair well with my HE-400's that are on the way!


----------



## Solrighal

brettmatthews said:


> Just sent the payment for my new Desktop O2/ODAC, should pair well with my HE-400's that are on the way!




Enjoy


----------



## Solrighal

I've been listening to my brand new HD650's for six hours now. My previous best were my Q701's. The Q's don't really compete to my ears, and by quite some margin. Unity gain on the O2 provides ample power to drive these but I really am hearing things I've never heard before. The Senn's have real body to their sound, weight.

I'm thinking it won't get much better than this


----------



## Xenophon

Enjoy them, never heard them myself but from the reviews I gather they sound relaxed and warm with slightly elevated mid bass. Maybe a bit like my HE-500 although those are probably faster. Wait a few months and then try something lighter, more transparent and with bigger soundstage for contrast, if you want to stick with Senn, the HD-800 for instance. Or in my preferred brand, the HE-6 though that will def. Demand much more power than what your present setup can deliver. I know the 'can't get much better' tune (evil grin). If you like the HD 650 sound then I'm pretty sure you'll dig tube amps too.


----------



## AsianBatman

solrighal said:


> I've been listening to my brand new HD650's for six hours now. My previous best were my Q701's. The Q's don't really compete to my ears, and by quite some margin. Unity gain on the O2 provides ample power to drive these but I really am hearing things I've never heard before. The Senn's have real body to their sound, weight.
> 
> I'm thinking it won't get much better than this


 
  
 Money well spent :]


----------



## Solrighal

Thanks guys. Famous Blue Raincoat by Jennifer Warnes sounds better on these than anything I've heard before. I know valves are supposed to work well for the HD650's and I'll definitely be picking one up (maybe Lyr from what I read) but I'm getting new cables first.

I think I'm gonna hit Forza Audio Works because their cables look well made and they're European so no import tax for me. They also only seem to offer copper cables but I think copper meant to be warmer than silver so should be better matched to the warmth I'm hearing. I'd hate to add silver cables and end up losing the very qualities that make me love this sound. Did I mention the sound? Liquid mids.

Something like this should suffice...

http://forzaaudioworks.com/en/product.php?id_product=68

The only thing I don't like about these aftermarket cables is that they look heavy. Can anyone comment on this?


----------



## r010159

solrighal said:


> I've been listening to my brand new HD650's for six hours now. My previous best were my Q701's. The Q's don't really compete to my ears, and by quite some margin. Unity gain on the O2 provides ample power to drive these but I really am hearing things I've never heard before. The Senn's have real body to their sound, weight.
> 
> I'm thinking it won't get much better than this




Tell me more on what you like of the HD650s? I wonder how they compare to my DT880s? I am happy to hear that you are enjoying your new setup. I am right now listening to the Brandenburg Concertos.


----------



## Solrighal

I can only really compare the Senn's to the Q701's as they're the only other audiophile headphones I have experience of.

The Senn's have just as much detail - possibly even more - but it comes out of a darker background. I think the HD650's are better throughout the frequency range with a much better delivery at the extremes. Bass is much fuller and feels more connected to the rest of the music. The treble sounds lesser at first but that seems to be more because treble from the Q's is so far over the top. The treble is sweet and never sharp unless the recording is already.

The mids & vocals are superb! Liquid smooth, like oil. 

The 650's don't have such an expansive soundstage as the Q's but the flip-side is a much more cohesive presentation of small groups/locations. I've heard it said that the Sennheiser's have a "three blob headstage" but I don't hear it that way.

Music seems much more organic to me, both acoustic & electronic. My O2 has gains of 1x/3x and Unity is fine for everything I've played. You'd have to be deaf to require more volume. 

As far as comfort is concerned the HD650's win hands down. I find them to be extremely comfortable, the best I've worn. A complaint I often read is that they have too much clamping force. I don't find this to be the case, ymmv. 

I actually want a new cable but I'm going to need to be careful as, for the first time, I'm looking to not change the sound at all. Actually, if I could find an extension cable which wouldn't degrade the sound that would do me. Perhaps later, once these are fully burned-in, I'll be more able to choose a direction of travel. 

This will sound a bit mad and it's not scientific but the HD650's *feel* as though they could swallow a lot more power. 

I know these are supposed to like a nice valve amplifier and to this end I hope to buy something from Schiit. People seem to rave about the Crack but DIY is not one of my strong points and it's a bit expensive.

One important aspect of the Sennheiser's is sound isolation/leakage, loads of it. I know it & now my wife knows it so the whole shooting match is getting packed up and moved to the guest room. This means I need to find a monitor or attempt running headless via Splash top on my iPad. We'll see.

Either way, I know these are the headphones for me.


----------



## Xenophon

If you get the Forza cable, do share your opinion as they look well constructed to me, thinking of getting one for my hifiman cans. And no crap with duty and vat if I get them shipped to Europe. Sitting at the airport now, listening to Bach (not the Brandenburg concertos but the musical offering), sadly not on my normal cans but with my parrot zik nc bluetooth headphones. Couple of long flights ahead....


----------



## Solrighal

xenophon said:


> If you get the Forza cable, do share your opinion as they look well constructed to me, thinking of getting one for my hifiman cans. And no crap with duty and vat if I get them shipped to Europe. Sitting at the airport now, listening to Bach (not the Brandenburg concertos but the musical offering), sadly not on my normal cans but with my parrot zik nc bluetooth headphones. Couple of long flights ahead....


 

I'll do that if I go for them. I'm concerned that the Forza might be a bulky obtrusive cable because one of the great aspects of th 650's is their comfort. I don't want to compromise that.

Anyone want to buy a well looked after one month old pair of AKG Q701's?


----------



## MaciekN

Zorrofox, just so you know - the long 300 ohm voice coil of your HD650's is made of pure aluminium. I would guess that even 3 meters of aftermarket cable would yield little difference electrically.


----------



## Solrighal

maciekn said:


> Zorrofox, just so you know - the long 300 ohm voice coil of your HD650's is made of pure aluminium. I would guess that even 3 meters of aftermarket cable would yield little difference electrically.




Thank you very much, I'm looking for something pretty right now. Why is aluminium the deciding factor, if you don't mind my asking?


----------



## Solrighal

The postie just delivered my new knob from Mayflower Electronics in New York. 

Happy days  

Sorry Walter


----------



## r010159

I would suggest an EQ for your J River player. There are some pro level ones out there. J River now supports 64-bit plugins. I think you will get more our of this than any change of cables. I am happy that you are getting so much from your setup including your headphones. Music can make life a little more tolerable!


----------



## Solrighal

Life is great right now. End of the month will be a different story... Ye cannae' tak it wi' ye  

Cable wise I'm thinking of buying a 1.5m length of the Noir along with a further 3m as an extension for the other side of the room. Would 4.5m cause any problems do you think?

The Sennheiser HD 650 I'm using right now is the highest hi-fi I've ever heard before. This is uncharted territory for me. There's so much more depth than the AKG Q701. It only does width. I much prefer this denser, more focused delivery. And yet they still manage to relax. Bloody brilliant!


----------



## MaciekN

solrighal said:


> Thank you very much, I'm looking for something pretty right now. Why is aluminium the deciding factor, if you don't mind my asking?


 

 Aluminium has better conductivity to weight ratio, so a 300 Ohm voice coil made out of copper would be considerably heavier, since we are talking about dozens of meters of wire here. Weight translates into higher inertia of the driver, and ideally there should be none (or as low as possible). The only loss with aluminium is in efficiency, the same logic applies to aftermarket cables, it's a controversial topic to say the least (cables making audible difference). But if you simply want to get something pretty then it's a different story of course


----------



## adydula

Before you spend your dollars on tubes....listen to a tube amp and compare before!!
  
 A;


----------



## Solrighal




----------



## Xenophon

solrighal said:


> Life is great right now. End of the month will be a different story... Ye cannae' tak it wi' ye
> 
> 
> 
> ...


 
 Nah, 4.5 meter won't be a problem, don't worry.  The drop is negligible over that distance.  As long as you don't run cable around the block you're good.  BTW, I was curious about this but forgot to ask:  what type(s) of music do you listen to?  HD-650 should be great with jazz/blues I think.
  
 About tube amps:  I agree that you should definitely listen before purchasing, depending on the topology and tubes they can sound very different, from 'lush' and 'laid-back' (maybe not a good combo with the HD-650) to relatively neutral such as my DV 337.  But a good second hand one can be had for relatively little money.  I purchased my DV 337 for a song and it's the best investment of the past year.  Only, if you're prone to upgrade-itis it might not be a good idea, tubes can become expensive even if you stick to something like 6AS7/6SJ7.  Enjoying my HE-500 with O2 now, back in Delhi.  Got 36 CD's with Scarlatti keyboard sonatas to rip.


----------



## Solrighal

That's good to hear about the cable length not being a problem. I'm not buying yet though because last night I noticed my headphones are improving themselves every day. Or my brain is. How bad can the original Sennheiser cable be after all?

Auditioning amps is going to be nigh-on impossible where I live. I've yet to meet a real person who doesn't think that even just upgrading the bundled phone buds is a bout of esoteric madness. That's true by the way. Nah, I'll just need to do a lot of research around here and make sure I'm going in the right direction. Dark Voice is another in the mix I guess. Too much choice!


----------



## Solrighal

Is there an ethical reason why the O2 couldn't do crossfeed? I searched the blog but couldn't find a reference.

It's quiet tonight


----------



## miceblue

solrighal said:


> Is there an ethical reason why the O2 couldn't do crossfeed? I searched the blog but couldn't find a reference.
> 
> It's quiet tonight



I didn't know ethics was a subject discussed in audio. XD


----------



## Solrighal

I'll hold you to that


----------



## Solrighal

I'm loving this combo with my new HD650's. So much detail from the ODAC.


----------



## miceblue

Speaking of the ODAC....
I am much preferring the Audio GD NFB-2 with the K 701 and O2. It sounds far more transparent than the ODAC to me: more spacious-sounding, greater dynamics, deeper-bass, better instrument separation, less grainy treble, and is just overall much more smooth-sounding. I had the same impressions with the HiFiMan HE-4.



*prepares body for crusade of ODAC fanboys


----------



## Solrighal

I could probably switch my ODAC for one of those. I'm sure my wife would never notice 

I'm torn. I've been looking at getting a valve amp for recreational purposes but I do wonder if the money's better spent on a DAC. Hmm...

Sorry, O/T.


----------



## pearljam50000

delete


----------



## miceblue

solrighal said:


> I could probably switch my ODAC for one of those. I'm sure my wife would never notice
> 
> I'm torn. I've been looking at getting a valve amp for recreational purposes but I do wonder if the money's better spent on a DAC. Hmm...
> 
> Sorry, O/T.



That's a good question. I've been really into DAC technologies recently.


----------



## Solrighal

I think DAC's are too often taken for granted. I understand why a linear, transparent amp might be desirable but can you even get transparency from a DAC?


----------



## James-uk

Yes.


----------



## Solrighal

james-uk said:


> Yes.




Is it the ODAC?


----------



## Xenophon

Agree that the Master 7 is in a much higher league but the comparison is hardly fair, price wise. We're talking about a >2k usd device so I'd hope it does things better. For the dac/amp question: tough but if you want to try tubes I'd go for a used tube amp first, the precision of the dac becomes less relevant then, all things considered. And it'd be a hell of a lot cheaper, really going to a significantly better dac will cost a lot more cheddar than improving or changing the amp part. Not to mention that amps depreciate a lot slower than dacs.


----------



## James-uk

I find head fi so frustrating. The only thing that we need to be concerned with now is the transducer . Spend your money on music and headphones not dacs/ amps. If the odac/O2 can give the volume you need then you can move on from the amp/dac conundrum! I put money on the fact that the hd800 will sound the same on the O2 /odac as any transparent TOTL dac/amp in 1000( insert any year) years time. The transducer is the sound!!!!


----------



## Xenophon

You'd lose that bet. Dead certain of it.


----------



## Solrighal

xenophon said:


> You'd lose that bet. Dead certain of it.




I think so too. I don't think the amp can be beaten (certainly not for the same money) but DAC's are developing all the time.


----------



## James-uk

I bet £1000 . See you in 1000 years for my money


----------



## James-uk

Our ears are the bottleneck now . Yes amps and dacs a can be better but we won't hear a Difference.


----------



## Xenophon

I'm willing to do 1000 Gbp right now, HD800, ODAC and my V800, blind test with classical music.


----------



## James-uk

Assuming v800 meets transparency criteria you are on!


----------



## miceblue

xenophon said:


> You'd lose that bet. Dead certain of it.



No doubt. One of my friends has a whole bunch of amps and DACs from his trips over from Japan and Hong Kong, and the O2 and ODAC certainly get overshadowed by some of the larger units. He buys stuff used though, so his things are often 1/3-1/2 the price.


----------



## James-uk

Anecdotes. My mate had this thing once that did this thing that you know did that.


----------



## James-uk

solrighal said:


> I think so too. I don't think the amp can be beaten (certainly not for the same money) but DAC's are developing all the time.



How are dacs developing?


----------



## James-uk

solrighal said:


> Is it the ODAC?



Yes the odac is transparent based on current recording methods


----------



## Solrighal

So in that case all DAC's will sound the same?


----------



## James-uk

solrighal said:


> So in that case all DAC's will sound the same?



Yes all dacs that meet the transparency criteria Will sound the same. Basically most modern dacs sound the same to human ears.


----------



## miceblue

solrighal said:


> So in that case all DAC's will sound the same?




According to pure objectivsts, and those who worship NwAvGuy as a God, yes. According to people who embrace both objective measurements and subjective listening, such as myself, no. I don't think we can measure everything we listen. Just like many biological processes, we can only model and hence measure a small part of what goes on in the human body.

Purrin is a highly respected member and he has his own measurement rigs:
http://www.head-fi.org/t/693798/ranking-of-21-dacs-and-dac-configurations-and-why-chocolate-ice-cream-must-die


----------



## James-uk

The odac is way past the point of transparency. You can either dwell on myths and bull**t or enjoy the music. I know which I am doing!


----------



## James-uk

miceblue said:


> According to pure objectivsts, and those who worship NwAvGuy as a God, yes. According to people who embrace both objective measurements and subjective listening, such as myself, no. I don't think we can measure everything we listen. Just like many biological processes, we can only model and hence measure a small part of what goes on in the human body.
> 
> Purrin is a highly respected member and he has his own measurement rigs:
> http://www.head-fi.org/t/693798/ranking-of-21-dacs-and-dac-configurations-and-why-chocolate-ice-cream-must-die



I read the first paragraph. It's so bias its untrue.


----------



## skeptic

Thanks to some very gracious trouble shooting help from agdr (hint: having a diode in the wrong orientation is a bad plan), I'm pleased to report that I got my O2 booster board (v.3.0) [see http://www.diyaudio.com/forums/headphone-systems/244473-o2-headamp-output-booster-pcb.html ] up and running today and also swapped in the optional dual LME49990 adaptor for the stock gain chip (bringing the amp's slew rate up to a respectable 20V/us).
  
 I'm very happy with the results!  DC offset is now essentially nonexistent per my cheap meter, turn on/off thump is eliminated, and the overall sound does seem to have_ _improved in a couple of respects to my ears.  While acknowledging that this all may be attributable to the delusions of my heat oppressed brain (thanks Shakespeare and Hume!), I could swear that the minor treble glare I occasionally perceived in the O2 has vanished and the deep bass seems just a little bit more present.  For example, I have a great recording of traditional Anglican choral and pipe organ music that was made a few years back in the renowned St. Martin-in-the-Fields Cathedral (on Trafalgar Square) - http://www.amazon.com/Chorales-Preludes-David-W-Bowerman/dp/B008P76WZM/ref=sr_1_1?ie=UTF8&qid=1397345635&sr=8-1&keywords=choral+scholars+of+st+martin .  The organ, in particular, always sounded just the tiniest bit thin on my stock self-built O2 (relative to my mainline and also the live evensong services I made a point of attending at that Cathedral while traveling - the acoustics in which are arguably the best in the world for choral music).  With agdr's booster and the LME49990 adaptor in place, my AD's seem to be singing this music back just a bit closer to the sound of live.  
  
 I think I'm going to have to build up my spare O2 board and related components so I can actually A/B rapidly between the stock and modified amps, but as noted by one or two others in the thread, agdr's board truly does seem to result in subjective as well as objective improvements!


----------



## James-uk

At its best, the ODAC sound expansive, detailed, and precise in imaging. At its worst, the ODAC sounds closed-in, flat, dull, uninteresting, and with wooly bass (Class S). It depends upon the USB connection. Overall the ODAC is not as precise in rendering of sounds. This is where the comparable Modi exceeds its performance. 

^(Quote from said shoot out)

^^^^^This is hilarious . It depends on the USB connection!


----------



## miceblue

Well my older MacBook's USB connection is kind of lame and yeah, I can agree with that observation.


----------



## James-uk

Bring some double blind examples to the table and I'm all ears.


----------



## miceblue

How does one do blind experiments with DACs exactly? And especially in the case where it gets plugged into 2 different connections?


----------



## James-uk

miceblue said:


> How does one do blind experiments with DACs exactly? And especially in the case where it gets plugged into 2 different connections?




Google double blind test.


----------



## r010159

james-uk said:


> At its best, the ODAC sound expansive, detailed, and precise in imaging. At its worst, the ODAC sounds closed-in, flat, dull, uninteresting, and with wooly bass (Class S). It depends upon the USB connection. Overall the ODAC is not as precise in rendering of sounds. This is where the comparable Modi exceeds its performance.
> 
> ^(Quote from said shoot out)
> 
> ^^^^^This is hilarious . It depends on the USB connection!




The one thing that makes his reviews suspect to me is he uses audio descrptions that should only apply to amps or headphones. I think he gets a bit carried away with himself. One distinguishing feature of one DAC he has described as having great vocals. Huh? 

Also I do not think many would agree with the following statement:

_All DACs have a readily identifiable and describable sound. We can listen to something and say "Ah, that's a Bifrost. Or that's a PWD2." _

For what I see are obvious reasons, this is very likely not to be true. And listening tests published on the Internet support this opinion of mine. (I do not remember what periodical on the Internet I got this from. Audiophile?)

Oh yes, that USB comment is a little amusing. I think the author of that comment and others like it has some explaining to do. IMO USB used to be a problem with audio. Other than bandwidth considerations, 
this has no longer been the case. Still, now you have USB 3.0 now to consider for bandwidth.

I do agree that there are some aspects of the sound experience that cannot be accurately measured as such, at least for now. But measurements are a very good place to start. And if you only considered objective measurements, IMO you still would end up with a good piece of gear.


----------



## miceblue

james-uk said:


> miceblue said:
> 
> 
> > How does one do blind experiments with DACs exactly? And especially in the case where it gets plugged into 2 different connections?
> ...



I didn't find anything that tells you how to do the tests though....there's a bunch of results for the results of the tests though. XD



miceblue said:


> This might be a stupid question to ask, but is there a relatively easy way to do A/B comparisons between DACs?





m2man said:


> You can do it with some pro audio gear. Something with spdif in and 6 spdif out. This feeds two DACs. Then you go to one amp with different inputs and can change one the fly. It's too spendy to do cheaply. You just need a crazy pro audio friend. PM me. One of the Seattle meet regulars has this gear. He set up my PWD and his v800 this way.


----------



## Xenophon

james-uk said:


> Assuming v800 meets transparency criteria you are on!


 
 Define transparency in a precise way and take a look at its specs here:  http://www.violectric.de/Pages/en/products/dacv800.php  If I agree to your definition then we'll set it up next time I'm in the UK (june) or if you're in Europe.  For the amp I propose a First Watt F5.  And we both bring the money in cash and put it down before starting.  Fair warning:  I own both as well as a HD-800 and trust me, I can tell the difference.  A similar bet already scored me a bottle of Yquem '89 but I'll be happy to accept your money and enrich my cellar some more.


----------



## anthk

james-uk said:


> Assuming v800 meets transparency criteria you are on!


 

 i saw their specs page. they seems to be doing THD with -1dbfs... that's not very nice is it?


----------



## anthk

james-uk said:


> I find head fi so frustrating. The only thing that we need to be concerned with now is the transducer . Spend your money on music and headphones not dacs/ amps. If the odac/O2 can give the volume you need then you can move on from the amp/dac conundrum! I put money on the fact that the hd800 will sound the same on the O2 /odac as any transparent TOTL dac/amp in 1000( insert any year) years time. The transducer is the sound!!!!


 
  
  
  
 That, and the ear pads. This is purely an anecdote.
 The pads of my old headphone is so worn that it fell off. The effect is immediate. You notice the sound being thin and not musical and all that.
 New pads. Voila. Good as new.

 I thought I could identify the difference between odac and fiio e10 . These two dacs measures well ( odac is better numerically of course, but e10 fits my applications as well) and I am quite confidently say if you do a proper double blind test on me, I would not be able to differentiate the both of them consistently with my current headphone.
 The pads on the other hand though, you have to be deaf to not be able to tell if it is working or not.


----------



## headwhacker

anthk said:


> That, and the ear pads. This is purely an anecdote.
> The pads of my old headphone is so worn that it fell off. The effect is immediate. You notice the sound being thin and not musical and all that.
> New pads. Voila. Good as new.
> 
> ...


 
  
 I agree most of the difference that can be improved or become worse is in the headphones. There is only so much improvement that can be done on amp/source. A crappy headphone remains crappy regardless of source. Although a very good sounding headphone can sound bad if not sufficiently amped. I think this can be easily rectified without costing much.


----------



## ZenocideZ

O2 + odac or teac ud h01? Both usd 250


----------



## Solrighal

zenocidez said:


> O2 + odac or teac ud h01? Both usd 250




To be partnered with what?


----------



## Xenophon

anthk said:


> i saw their specs page. they seems to be doing THD with -1dbfs... that's not very nice is it?


 
 I'm surmising (but will happily stand corrected if someone has other info) that it has some technical (other than pimping the results) reason. The ODAC's designer also lists his THD+N specs at 20Hz and 10kHz at -1 dBFS.  He/she's btw also mentioning Violectric as one of the few manufacturers who provide meaningful measurement data.  About the USB implementation I quote the following, hoping that this is allowed as a direct link is not according to Head-FI TOS:
  
_"There are only a few USB interface chips capable of 24 bit operation. The best option we could find is the Tenor TE7022. It’s used in the Violectric USB 24/96 and several other commercial 24 bit USB DACs. Notably, it does not require proprietary drivers to work with any popular operating system including Windows because, like the Benchmark DAC1, it’s a USB Audio Class 1 interface. It also has respectably low jitter."_
  
 If James-UK is still interested:  best not to clutter the thread with methodology discussion so feel free to pm me on this.


----------



## agdr

ZenocideZ:  For more of an apples-to-apples setup to the ODAC + O2 you would need the UD-H01 dac + HA-501 headamp, which goes for $650.  That brings the Teac stuff up to $900.   The headamp output on the UD-H01 wouldn't have the current drive capability of the O2 or the HA-501 from the way they have described it.
  
http://www.teac.com/product/ha-501/


----------



## ZenocideZ

thank you for the clarification. I might be double up the investment now just go for nad d3020 as my local store bundle a free pair of psb speaker ....


----------



## krismusic

The one aspect of the sound I am getting from my system, iPhone 5S, O2,HD600 that I would like to improve is "presence". Which component would most affect this?


----------



## MrMateoHead

krismusic said:


> The one aspect of the sound I am getting from my system, iPhone 5S, O2,HD600 that I would like to improve is "presence". Which component would most affect this?


 

 A headphone with more treble.


----------



## r010159

Is jitter something to be concerned about with present day USB DACs? I have been told that it is a non-issue as far as audio use is concerned.


----------



## Xenophon

r010159 said:


> Is jitter something to be concerned about with present day USB DACs? I have been told that it is a non-issue as far as audio use is concerned.


 
 The way I understand it is that_ if properly implemented _any jitter differences between modern DACs should be below the threshold of audibility, the gains that ultra-precision DACs bring are mathematical, not audible.  But I guess this is one of those contentious topics that makes DACs such as the Calyx femto sell (no negative reflection on the Calyx btw, it looks built like a very high end tool and has many other features, it's just that I doubt femtosecond precision makes a difference).


----------



## anthk

xenophon said:


> I'm surmising (but will happily stand corrected if someone has other info) that it has some technical (other than pimping the results) reason. The ODAC's designer also lists his THD+N specs at 20Hz and 10kHz at -1 dBFS.  He/she's btw also mentioning Violectric as one of the few manufacturers who provide meaningful measurement data.  About the USB implementation I quote the following, hoping that this is allowed as a direct link is not according to Head-FI TOS:
> 
> _"There are only a few USB interface chips capable of 24 bit operation. The best option we could find is the Tenor TE7022. It’s used in the Violectric USB 24/96 and several other commercial 24 bit USB DACs. Notably, it does not require proprietary drivers to work with any popular operating system including Windows because, like the Benchmark DAC1, it’s a USB Audio Class 1 interface. It also has respectably low jitter."_
> 
> If James-UK is still interested:  best not to clutter the thread with methodology discussion so feel free to pm me on this.


 

 I am also curious about the reason behind using different input for different Hz test signal.
 odac guy used 0 dbfs for 100hz but -1 for 20 and 10k. Is there a reason for such difference?


 In a certain blog post about a crap dac, a certain guy who must not be named used -1 dbfs test signal which gave better results than 0 dbfs , since at 0 dbfs there is a power supply issue with that dac and the distortion is massive.
 Would it be the same case here?


----------



## Solrighal

I'd like to upgrade my USB cable. Not for sound (not possible) but something better built and a bit swisher looking would be nice. What's the purpose of the ferrite bead (?)? I've never seen one on after-market cables so does it matter?


----------



## Whitecitadel

Does anyone have any recommendations on gain settings (1x I expect?) for O2 when paired with some Sennheiser momentums? (18ohm, 110db/v, 200mw max)



solrighal said:


> I'd like to upgrade my USB cable. Not for sound (not possible) but something better built and a bit swisher looking would be nice. What's the purpose of the ferrite bead (?)? I've never seen one on after-market cables so does it matter?




The purpose of the ferrite bead is to prevent RF picked up in the cable shield flowing, often referred to as a choke. PC often a good source of electrical noise and RF emissions, so there to stop any currents induced on the shield reaching the DAC.

If you just want something pretty there is a UK site, think it's called pexon or something like that which is popular with keyboard moderns as they make custom USB cables with para cord sleeves if looks are important. Think he does short audio cables as well made to order but disclaimer never used them and not affiliated in any way! Digital USB is USB, probably be just as ok as original cable, something from maplin or something out of china for few quid from farnell or somewhere!

Found this thread quite informative, can see there is a lot of passion on this forum and not just for music  I just want something half decent for PC to replace digital out to amp and speakers I no longer have space for since downsizing home office so o2&odac seem ideal.


----------



## Solrighal

Thanks for the USB info. I can help you too. I own the O2 with gains of 1x / 3x. It drives every set of phones I own on 1x. From the insensitive Q701 to the 300Ohm HD650. Any genre you like. I don't even know for a fact that 3x gain works, lol. It will drive your Momentums no sweat.


----------



## pearljam50000

I read here somewhere that the SQ of the O2/ODAC depends on the quality of the USB you are using.
 What does that mean? aren't all USB sockets the same quality? and how can you tell if your laptop's USB is any good?
 Thanx.


----------



## r010159

pearljam50000 said:


> I read here somewhere that the SQ of the O2/ODAC depends on the quality of the USB you are using.
> What does that mean? aren't all USB sockets the same quality? and how can you tell if your laptop's USB is any good?
> Thanx.



 
I have been having a conversation with an embedded software engineer (the types that make things like DACs professionally) and some recording engineers. Here is what I learned so far. I will update this as my conversation develops. (The long version is followed by the short version).
 
*The long story:*
 
There is USB class 1 and class 2 implementations. Class 1 requires no special device driver. Class 2 does require its own driver, but it is a more accurate way of transferring information using USB. In other words, there is much less jitter (distortion) with class 2 devices. And custom drivers for this are only available for the Mac and Linux. As a consequence, very few DACs support class 2 designs. The ODAC is class 1 design that uses one of the few chips that support 24-bit data.
 
All PCM/SPDIF/I2S DACs have the most accurate timing by the nature of the chips used in their design. Next are class 2 designs. Next are USB class 1 designs operating in isochronous mode, which is the case with the ODAC. Then finally there are older USB designs which are, according to one engineer, "crap".
 
All DACs that are designed to faithfully reproduce the audio signal will sound the same. But some DACs introduce a type of distortion that makes the music more pleasant to the ear. This is where they can differ in how they sound. Please note that the latter DACs do not reproduce the sound accurately on purpose. For instance, this is the reason why there are those of use who like tube amps. Tube amps generate distortion by introducing the pleasing even harmonics to the sound. I also think this is how DAC manufactures can differentiate their DAC from other DACs.
 
In recording studios, the difference between a budget properly designed DAC (to the numbers like THD, SNR, FR) and high-end DACs (like the Benchmark DAC) is noticeable but not anywhere near as great as the difference between a good budget DAC and a poorly implemented one. We are talking the difference between inches compared to feet here. IMO I think the ODAC fits in the category of a good budget DAC.
 
*The short version: *The difference is in older poorly implemented USB and those of current day USB. For current day USB chip implementations, they are all the same.
 
Am I verbose or what?? 
	

	
	
		
		

		
			





 
 
PS: I will ask about the differences between asynchronous compared to isochronous implementations of USB.

EDIT: Class 2 USB is not *natively* supported in Windows. But this person said it may be in Mac OS and Linux. I just checked and they both do.


----------



## r010159

I have asked John Seaber of JDS Labs the question on the difference between asynch and adaptive implementations of data transfer with USB. I am paraphrasing since I did not receive his permission to quote him. He said that adaptive works better with some operating systems like that which is used for portable devices. Otherwise asych offers no audible difference over adaptive because of how ADC chips are implemented nowadays. The Mac OS happens to work just as well with both transfer methods.
 
This stuff is definitely interesting! Thank goodness for the Internet.

EDIT: The Tenor TE7022L chip that the ODAC uses is known to be a good chip. Internally it reclocks the audio information to reduce jitter, like the other better chips do. So adaptive approaches. (compared with asynchronous) can provide good results depending on how the circuit is implemented. (This information is from another source)


----------



## adydula

For the reference to the SQ being affected with the O2/ODAC....
  
 That's note correct at all.....I don't want to get into a this cable is better than that cable...that should be for a separate thread about USB cables In general.
  
 Any well made USB cable with a ferrite bead will do very very well....with no real discernible difference between them,
  
 Belkin has a nice cable with a ferrite bead and doesn't break the bank.
  
 All the best
 Alex


----------



## Whitecitadel

pearljam50000 said:


> I read here somewhere that the SQ of the O2/ODAC depends on the quality of the USB you are using.
> What does that mean? aren't all USB sockets the same quality? and how can you tell if your laptop's USB is any good?
> Thanx.




Some DAC's rely on he timing from the USB port, and if it's oscillator is prone to wander it could affect your DaC timing. Perhaps that what is meant by bad port as different implementations may or may not have accurate timings on the USB?

No such problem with odac as it has it's own internal oscillator.


----------



## Solrighal

adydula said:
			
		

> . Belkin has a nice cable with a ferrite bead and doesn't break the bank.




Got a link for that by any chance?


----------



## krismusic

Am I verbose or what?? 
	

	
	
		
		

		
		
	


	



Really interesting and clearly explained. Even I understood.


----------



## jring

pearljam50000 said:


> I read here somewhere that the SQ of the O2/ODAC depends on the quality of the USB you are using.
> What does that mean? aren't all USB sockets the same quality? and how can you tell if your laptop's USB is any good?
> Thanx.


 
  
 Hi,
  
 under normal operating conditions and using a USB cord with a ferrite bead I have not seen problems - on a lot of different boxes with different operating systems and hardware.
  
 I have seen problems in highly abnormal conditions like having too many power hungry devices on the same USB hub of my laptop - Vcc was down to 4 dot something Volts and ODAC was misbehaving but I wouldn't blame it. Also when programming Arduino boards on the same USB hub and the arduino does funny things with the USB data and clock pins ODAC started skipping - also I can't blame it.
  
 In both cases plugging the ODAC into another USB port of my laptop fixed the problem - one could of course also just remove the other device acting up but I tend to like to listen to good music while hacking.
  
 Joachim


----------



## Solrighal

So the ferrite bead is an essential component?


----------



## AsianBatman

solrighal said:


> So the ferrite bead is an essential component?


 
  
 I'm using a ferrite bead usb right now, but did not see any difference between one without a ferrite bead. I just happen to have one laying around.


----------



## jring

asianbatman said:


> I'm using a ferrite bead usb right now, but did not see any difference between one without a ferrite bead. I just happen to have one laying around.


 
  
 Once again in normal conditions the ferrite bead will not have any effect. If your USB power is very noisy either because of lots of HF generating components inside your PC or your cell on channel search right beside it, it might prevent you from hearing effects due to the noisy power.
  
 Joachim


----------



## AsianBatman

jring said:


> Once again in normal conditions the ferrite bead will not have any effect. If your USB power is very noisy either because of lots of HF generating components inside your PC or your cell on channel search right beside it, it might prevent you from hearing effects due to the noisy power.
> 
> Joachim


 
  
 Yes. I completely understand that. I'm just putting in my experience.


----------



## adydula

A cable with a ferrite bead is not essential.
  
 Its a good idea to have a cable with a ferrite bead just for insurance.
  
 It really will not help or improve the quality of sound, but if there is any RFI it will help eliminate this unwanted RF from entering into the DAC from the PC or any
 induced RFI from electrical devices.
  
 The ODAC has additional filtering but the ferrite bead on the cable is a good idea.
  
 Here is a mini USB that is good and again is rather affordable:
  
 http://www.amazon.com/Belkin-Series-5-Pin-Mini-B-Cable/dp/B007XZX8F4/ref=sr_1_12?ie=UTF8&qid=1397613982&sr=8-12&keywords=belkin+mini+usb+cable
  
 Alex


----------



## Whitecitadel

solrighal said:


> So the ferrite bead is an essential component?




I personally consider it a bit of a"seat belt". If you don't have an issue, it's redundant, if you do have an issue it's going to save you.

(Being careful here as I am new!)
If you read some odac articles on "the internet", you can see someone once wrote: 





> There is some measurable improvement from using a USB cable with a ferrite "choke" at the ODAC end of the cable.




I have no opinion either way, just pointing out what I read. The Belkin cable looks a good option. 

Enough about the chokes, more about me  placed order yesterday with Stefan at head'n'hifi so just need to wait for the post pixies them get the soldering iron out... (And I think his cable cones with a choke anyway)

Just need to try and contain my enthusiasm for using a b3-80 larger enclosure to keep the batteries, or trying to squeeze the odac in under the PCB so I can save the batteries as others have done. Need to just get it together first I think before I go too crazy with elaborate plans...


----------



## Solrighal

Thanks guys. My mind is now at ease. I'll buy a set cable and see how it goes. Since I'm using a Mac mini with no audio stuff in the vicinity I don't foresee a problem. 

And yes, Walter's cable does use a ferrite bead.


----------



## MaciekN

Would you guys think that analog crossfeed is a worthy addition to O2? If not, what else you'd wish it had?


----------



## Solrighal

Deja vu?


----------



## Spiral Out

maciekn said:


> Would you guys think that analog crossfeed is a worthy addition to O2? If not, what else you'd wish it had?


 
 I find crossfeed to work well with old recordings from the 60's that have everything panned hard right and left (A lot of Beatles recordings for example).Other than that I have found it has very little effect and can actually change the tone of the headphones. I have yet to find one that doesn't change the tonality, even if it is just very slight. 
  
 I don't think there is anything I would add to the ODAC. For what it is (a fairly inexpensive usb dac) it is perfect. I guess it would be nice to have a spdif or coax digital input, but according to the designer it would have affected the performance and raised the price significantly.


----------



## Solrighal

It could be argued that that change in tone you hear when you use crossfeed is actually the music becoming more accurate. Most music (I think) is produced to sound good primarily through loudspeakers so adding this cross-channel information is *meant to happen*.


----------



## Spiral Out

solrighal said:


> It could be argued that that change in tone you hear when you use crossfeed is actually the music becoming more accurate. Most music (I think) is produced to sound good primarily through loudspeakers so adding this cross-channel information is *meant to happen*.


 
 That is an interesting way to look at it that I had never considered


----------



## adydula

Just got this...
  
 Its the latest in what a desktop version of the O2 might have been:
 (I will start a separate thread on this ODA V2.0 amp from agdr).

  
 You can follow the details here:
  
 http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda.html


----------



## Xenophon

Now THAT is interesting!  Nice to see agdr applying his considerable talents to an own design.  Will read through the thread at diyaudio although the technical details are way over my head.


----------



## pearljam50000

Is the O2 AMP + ODAC the best value for money DAC/AMP on the market today?


----------



## krismusic

pearljam50000 said:


> Is the O2 AMP + ODAC the best value for money DAC/AMP on the market today?



I have the O2 amp only. I have not heard many amps but those that I have heard lead me to believe that the O2 is the best £80 I have spent in audio.


----------



## Xenophon

pearljam50000 said:


> Is the O2 AMP + ODAC the best value for money DAC/AMP on the market today?


 
 Depends on your budget and their ability to suit your purpose.  If you need to drive a Stax or a K-1000 or HE-6 then obviously they're not due to totally unsuitable.  If you're sitting on a 7 figure bank account then the spending of a large amount to get an incrementally smaller performance increase may well represent better value.
  
 On a limited budget and with headphones that play nice with 'em they're hard to beat imo....speaking strictly sound wise and not considering connectivity etc.


----------



## SilverEars

So I recently got an LCD-2, and decided on Beta 22 to drive it.  Beta 22 trumps O2.  I realized that hard to drive headphones arn't O2 thing although iems sounded good.  I learned something from this.  Just because you find this in some blog with the designer claims it can do what more expensive amps can do, don't believe it until you do a comparison even though he shows his measurements(some values are useful but doesn't not tell you the whole story).  I mean every solid state measures well, so what makes some better that the others?  
  
 When you only have the O2, you cannot know if it's really bad sounding amp.  After listening to my Beta 22, and went back to O2, I can hear bloating with O2.
  
 I think the whole time what make the setup great was the ODAC.  I think ODAC truely is a great DAC.


----------



## r010159

The ODAC/O2 appeared to be an outstanding value when it first came out. IMO it still is a good value. This device was made by its design engineer to make a point, that a good USB DAC/amp designed by the numbers can be made without the costly use of more advanced and complex technology, or costly components, bringing the cost well below competing devices. This adheres to the principle of KISS (keep it simple). This is a device that has its design process, implementation, and performance testing approaches fully documented for the world to see. So you know exactly what you are getting, which is not true for the many other devices out in the market. He published everything you need to know how to fabricate the amp part. You can also purchase it fully assembled with the DAC part by manufacturers who remain true to the design engineers wishes.
  
 Given the whole package as outlined above, IMO this is a rather unique product, besides being a good value. But of course there are better more expensive units out there.  Its up to you to determine if the price difference for a more expensive unit is worthwhile. Double the price will only yield an incremental improvement in quality.
  
 Just my two cents.


----------



## Porter1

i've been using the O2 for about 2 years with a generic radio shack 1/8" right angle adapter(http://www.radioshack.com/product/index.jsp?productId=2103788).  it's been placing undue stress on the input adapter, right channel is starting to give out.  bummer.


----------



## krismusic

r010159 said:


> The ODAC/O2 appeared to be an outstanding value when it first came out. IMO it still is a good value. This device was made by its design engineer to make a point, that a good USB DAC/amp designed by the numbers can be made without the costly use of more advanced and complex technology, or costly components, bringing the cost well below competing devices. This adheres to the principle of KISS (keep it simple). This is a device that has its design process, implementation, and performance testing approaches fully documented for the world to see. So you know exactly what you are getting, which is not true for the many other devices out in the market. He published everything you need to know how to fabricate the amp part. You can also purchase it fully assembled with the DAC part by manufacturers who remain true to the design engineers wishes.
> 
> Given the whole package as outlined above, IMO this is a rather unique product, besides being a good value. But of course there are better more expensive units out there.  Its up to you to determine if the price difference for a more expensive unit is worthwhile. Double the price will only yield an incremental improvement in quality.
> 
> Just my two cents.



Good post. Says better than I could what appealed to me about the ethos of the O2. 
It's true that I have not heard many amps but I have heard a couple. 
All I do know is that I enjoy listening to my set up.


----------



## anthk

porter1 said:


> i've been using the O2 for about 2 years with a generic radio shack 1/8" right angle adapter(http://www.radioshack.com/product/index.jsp?productId=2103788).  it's been placing undue stress on the input adapter, right channel is starting to give out.  bummer.


 

 undue stress? I am curious about this since I suppose even with the adapter, there isnt much weight stressing the port, right?


----------



## anthk

silverears said:


> So I recently got an LCD-2, and decided on Beta 22 to drive it.  Beta 22 trumps O2.  I realized that hard to drive headphones arn't O2 thing although iems sounded good.  I learned something from this.  Just because you find this in some blog with the designer claims it can do what more expensive amps can do, don't believe it until you do a comparison even though he shows his measurements(some values are useful but doesn't not tell you the whole story).  I mean every solid state measures well, so what makes some better that the others?
> 
> When you only have the O2, you cannot know if it's really bad sounding amp.  After listening to my Beta 22, and went back to O2, I can hear bloating with O2.
> 
> I think the whole time what make the setup great was the ODAC.  I think ODAC truely is a great DAC.


 
 What is bloating sounding?


----------



## Luminair

adydula said:


> Its the latest in what a desktop version of the O2 might have been:


 
  
 Going on record to say that I've wanted to buy one of these since before nwavguy disappeared and ruined all our lives. All I wanted upgraded over the portable design was simultaneous stereo pass-through on the rear not affected by the volume knob. I never expected it would lead to such a wait. My kingdom for this!!


----------



## Xenophon

luminair said:


> Going on record to say that I've wanted to buy one of these *since before nwavguy disappeared and ruined all our lives*. All I wanted upgraded over the portable design was simultaneous stereo pass-through on the rear not affected by the volume knob. I never expected it would lead to such a wait. *My kingdom for this!!*


 
  
 For lovers of objective stuff some of the posters here sure have a sense of theatrics 
	

	
	
		
		

		
			





.  
  
 When I get back to Europe this summer I'm gonna build myself a ß22 amp, that'll be a nice complement to my HE-6.


----------



## anthk

xenophon said:


> For lovers of objective stuff some of the posters here sure have a sense of theatrics
> 
> 
> 
> ...


 

 Please do make a post on how it works out


----------



## adydula

You know that there are more expensive amps that are not as good as the O2 as well.....
  
 Seems like the O2 is and has been touted as a good value for the money, me included, and any "better" amps are most always tied to more money.
  
 The 02 is very unique when you understand what the designers intent and design goals were.
  
 Totally "transparent", nothing added, nothing taken away, great specs, great performance due to critical design and layout.
  
 And using the parts that don't break the bank.
  
 AGDR's version of the O2 morphed into the ODA improves upon this platform.
  
 All the best
 Alex


----------



## Solrighal

adydula said:


> AGDR's version of the O2 morphed into the ODA improves upon this platform.
> 
> All the best
> Alex




Does this even exist?


----------



## JacobLee89

solrighal said:


> Does this even exist?


 
 There's alot of DIY and soldering required. And the link to that should be a few posts ago.


----------



## Solrighal

jacoblee89 said:


> There's alot of DIY and soldering required. And the link to that should be a few posts ago.




It doesn't really exist then, not for me anyway.


----------



## Xenophon

solrighal said:


> It doesn't really exist then, not for me anyway.


 
 It exists alright but -I only gave it a quick look- doesn't look like a simple build at all with soldering on both sides of the board, lots of small components.  You could wait until someone offers pre-built kits -it really looks interesting- but due to the licensing terms on the original the legal status doesn't appear to be 100% clear and I guess everyone's holding off for the time being.  A pity, really.


----------



## adydula

Its not a beginners DIY project if you don't know how to solder well.
  
 The parts are in the $200 range, ask me how I know...I just totaled them up on mouser.com
  
 A case for another $20.
  
 A larger AC adapter about $30 or so.
  
 And the time and effort in soldering and getting it to work.
  
 Alex


----------



## Xenophon

adydula said:


> Its not a beginners DIY project if you don't know how to solder well.
> 
> The parts are in the $200 range, ask me how I know...I just totaled them up on mouser.com
> 
> ...


 
 Yeah...therein lies the problem.  Stuffing the board is not that hard.  Soldering can be learned.   The problems start if you have to debug things, that requires advanced electronics knowledge, we're not dealing with a simple schematic such as an OTL tube amp here.  But good luck with the build and let us know.  Though I'm not the biggest fan of the original O2 I agree with your remark that there's lots of more expensive but lesser quality stuff on the market.  And agdr's project looks fascinating.


----------



## adydula

agdr's worked on his first try....I hope mine goes as well.
  
 I am a really anal builder, slow and methodical.
  
 I check components before installing and then measure them after placed and soldered as best possible.
  
 But I have a strong background in electronics and troubleshooting...you have to be able to understand basic ac and dc
 circuit theory to some level to understand where to start, whats not working etc..
  
 All that said, this is a really nice step for the base O2.
  
 I don't think it will sound that much different, but its specs are "better" and it adds some end user bells and whistles that to some
 are really desired, like a 1/4 jack.
  
 I am waiting on parts...
  
 Alex


----------



## mcandmar

> Originally Posted by *adydula* /img/forum/go_quote.gif
> 
> The parts are in the $200 range, ask me how I know...I just totaled them up on mouser.com
> 
> A case for another $20.


 
  
 That doesn't sound too bad considering how many more parts are inside that amp.  If you build a regular O2 with equal quality parts it will still cost you ~$80 for a bag of bits from Mouser.  ...ask me how i know


----------



## SilverEars

xenophon said:


> For lovers of objective stuff some of the posters here sure have a sense of theatrics
> 
> 
> 
> ...


 
 I'll be posting impressions of HE-6 with my B22.


----------



## SilverEars

anthk said:


> What is bloating sounding?


 
 It means the sound is not refined or tight.  I guess it would be distorted?


----------



## Xenophon

Let me know, very curious .  It certainly won't lack in the power dept.  How many boards is your build, btw?


----------



## adydula

Please remember this is an 02 ODAC thread not a HE and B22 thread...
  
 thanks!
  
 A.


----------



## adydula

mcandmar,
  
 The parts list is extensive, the WIMA caps are one of the largest expense in the list... $40+ just in these caps and there are lots of others.
  
 A.


----------



## SilverEars

xenophon said:


> Let me know, very curious .  It certainly won't lack in the power dept.  How many boards is your build, btw?


 
 Mine is 2 channel.  It sounds fantastic with my LCD 2.2.  Resolution is unreal, O2 sounds bloated.  I guess you need lots of power for Orthos.


----------



## miceblue

silverears said:


> xenophon said:
> 
> 
> > Let me know, very curious .  It certainly won't lack in the power dept.  How many boards is your build, btw?
> ...



Yeah I find the O2 to lack microdetails and control with the Alpha Dog, LCD-2, LCD-X, or HE-4. One of the Emotiva amps drives the HE-4 far better than the O2. Maybe current is more of a factor than power per se?


----------



## Porter1

anthk said:


> undue stress? I am curious about this since I suppose even with the adapter, there isnt much weight stressing the port, right?


 
  
 when the input cable gets taut (which happens in my setup from time to time) it applies bending moment to the jack, instead of the usual axial tension.  a bit of speculation on my part.  but the audio corrects itself when i push one way or another on the jack.


----------



## adydula

FYI:
  
 ~~HiFiMan HE-4/5 – They’re rated 86 dB SPL at 1 mW and 38 ohms. To drive them to realistic peaks of 110 dB SPL they need a whopping 200 mW (enough to fry some headphones). That’s about 2.8 V RMS and a peak current of 104 mA per channel in 38 ohms.
  
 O2 has :
  
 ~~Max Output (33 Ohms) 613 mW Max Output (150 Ohms) 355 mW Max Output (600 Ohms) 88 mW.
  
 The designer has said many times over that these types of can are some of the hardest to drive.
  
 ~~it seems the 38 ohm planar HiFiMan HE-4/HE-5LE and 50 ohm HE-6 are especially tough cans that need lots of current.
  
 ~~The power limits of the O2 exceed the power requirements established for the assumed worst case headphones (HiFiMan planars and 600 ohm version of the Beyer DT880):
  
 110 SPL is pretty loud.
  
 A.
  
 .


----------



## SilverEars

miceblue said:


> Yeah I find the O2 to lack microdetails and control with the Alpha Dog, LCD-2, LCD-X, or HE-4. One of the Emotiva amps drives the HE-4 far better than the O2. Maybe current is more of a factor than power per se?


 
 When it comes down to it, it's power. 
  
 The loudness it the SPL or dB/mW , which depens on power, and power is multiple of voltage and current.  
  
 Although current depends on impedance, it's not just the current(it's with voltage) since the sound output is dB/mW.  W is power.  There are headphons with less impedance that is not that loud, and there are headphones with high impedance that are loud.
  
 When you raise the volume, it's amplifying the voltage swing until when it distorts where the supply cannot support it any more.  I guess it would be how much Voltage headroom the amp provides.  Current is just the draw.


----------



## Xenophon

adydula said:


> FYI:
> 
> ~~HiFiMan HE-4/5 – They’re rated 86 dB SPL at 1 mW and 38 ohms. To drive them to realistic peaks of 110 dB SPL they need a whopping 200 mW (enough to fry some headphones). That’s about 2.8 V RMS and a peak current of 104 mA per channel in 38 ohms.
> 
> ...


 
 No.  I own a HE-6.  Tried it at the time with O2/ODAC.  It most definitely, empathically *does not * work for them.  I don't care what numbers get pulled out of hats but this I know for sure, it's plain and simple to anyone simply trying it.  Not even a question of volume, it sounds like fried crap.


----------



## SilverEars

My Beta 22 is 40Vpp and O2 amp looks like 10Vpp since it's 7Vrms.  O2 amp is current limited to 200mA for very low impedance phones.  For 35ohms or above, the power is limited to Voltage supply and headphones impedance.


----------



## SilverEars

Just looked at my LCD-2 specs:
  

Impedance:  60 Ohms, purely resistive
Efficiency:  90 dB/1 mW
Maximum power handling:  15 W (for 200 ms)
*Optimal power requirement:  1-4 W*


----------



## adydula

In my post I did mention the he 6's they are even more difficult to drive at 83.5 db/mw and 50 ohm.
 (than the 4 or 5's).
  
 I would not use an O2 to drive HE6's.
  
 My LCD2's are driven my O2's to ear splitting hearing damage levels with aplumb.
  
 The O2 is not the perfect amp but for 98% of whats out there it works as well as most anything else out there.
  
 A.


----------



## skeptic

miceblue said:


> Yeah I find the O2 to lack microdetails and control with the Alpha Dog, LCD-2, LCD-X, or HE-4. One of the Emotiva amps drives the HE-4 far better than the O2. Maybe current is more of a factor than power per se?


 
  
 Insensitive low impedance cans are current hungry as a general rule.  That said, I found my AD's to be quite good with my stock O2 (even at unity gain) and very good with the agdr booster board (3.0) and dual LME49990 adaptor in place.  
  
 AD's aren't ever going to rival hd800's, for example, when it comes to microdetails, but I haven't noticed anything suggesting a lack of control or power.  Any chance you might elaborate on the latter observation?  I'd be interested to see if I could perceive the same if I knew exactly what you were listening to and for?  Theoretically, my understanding has been that part of the beauty of orthos is that damping is pretty much a non-issue due to the flat impedance curves.  (See Steve Eddy's posts at the bottom of page 2: http://www.head-fi.org/t/617902/effects-of-damping-factor-on-planar-magnetics-orthodynamics/15)


----------



## SilverEars

skeptic said:


> Theoretically, my understanding has been that part of the beauty of orthos is that damping is pretty much a non-issue due to the flat impedance curves.  (See Steve Eddy's posts at the bottom of page 2: http://www.head-fi.org/t/617902/effects-of-damping-factor-on-planar-magnetics-orthodynamics/15)


 
 I thought damping factor was a ratio, and 1 is ideal.  ratio of impedances not about flatness.  If the impedance is high everywhere relative to output impedance, it has high damping factor.  It could still be flat but low everywhere.
  
 Even the ones that are not flat can have low damping.


----------



## skeptic

silverears said:


> I thought damping factor was a ratio, and 1 is ideal.  ratio of impedances not about flatness.  If the impedance is high everywhere relative to output impedance, it has high damping factor.  It could still be flat but low everywhere.
> 
> Even the ones that are not flat can have low damping.




The point (per Steve Eddy's post no 28 in the link above) is that damping is simply a moot consideration with orthos if the headphone has no resonances in the audible range. A flat impedance curve means no resonances that need to be controlled.


----------



## SilverEars

skeptic said:


> The point (per Steve Eddy's post no 28 in the link above) is that damping is simply a moot consideration with orthos if the headphone has no resonances in the audible range. A flat impedance curve means no resonances that need to be controlled.


 
 Well if you look at a resonance on an impedance vs frequency graph, it's the point where impedance is the lowest.  If the impedance is low everywhere, the damping is still low at any frequency.  If the there is only resonance dip at certain frequency, that means at certain frequency it is not damped well.  This makes sense to me, I still don't get how orthos explanation logically go with that example.


----------



## MaciekN

Flat impedance line means only as much as no strange FR humps resulting from low damping factor/high amp output imedance. With dynamic headphones that usually have some sorts of impedance peaks you get a boost, or a null if the amp is running out of voltage headroom.  Driver resonance is a whole other matter (by this I mean resonances of the membrane itself, not the suspension).


----------



## MaciekN

silverears said:


> Well if you look at a resonance on an impedance vs frequency graph, it's the point where impedance is the lowest.  If the impedance is low everywhere, the damping is still low at any frequency.  If the there is only resonance dip at certain frequency, that means at certain frequency it is not damped well.  This makes sense to me, I still don't get how orthos explanation logically go with that example.


 

 Resonance frequency is assumed to be the frequency at which impedance is at it's HIGHEST and it does not usually correspond to driver break-up modes which are the peaks in the frequency response (not impedance).
  
 Orthos work in a different way than dynamics, the coil is moving differently relative to magnets, that is why they are seen as a resistive load in contrast to reactive load presented by dynamic headphones. If you take a look at some pictures presenting internals of both types of headphones and read a bit how amp is actually damping the headphone you'll see wherein lies the difference.
  
 Saying that "damping is low when impedance is low" is generally true, but please consider that if you have an output imedance of, say 1 Ohm, then you are fine damping-wise at 8 Ohms and up, and there are no headphones reaching 8 Ohms in their impedance. Thats speakers territory.


----------



## anthk

xenophon said:


> No.  I own a HE-6.  Tried it at the time with O2/ODAC.  It most definitely, empathically *does not * work for them.  I don't care what numbers get pulled out of hats but this I know for sure, it's plain and simple to anyone simply trying it.  Not even a question of volume, it sounds like fried crap.


 
 What is the AC adapter you are using?
 I heard that the 110v ones out there arent enough for high gain mode.


----------



## Xenophon

anthk said:


> What is the AC adapter you are using?
> I heard that the 110v ones out there arent enough for high gain mode.


 
 No, no....been there, tried that.  I'm on 220V and already tried a more powerful than stock adapter.  It's very simple:  while it might work ok with most headphones, the O2 is simply not the tool for cans like the HE-6.  In high gain even with cans like the HE-500 you push it into clipping, btw.  This is one of the issues that adgr's setup addresses.
  
 But it's not an issue to me, I use it in standard gain, low/mid volume in my office setup and am happy enough with it.  Though I have to say I'm more impressed with the DAC than the amp part.


----------



## adydula

If you like agdr booster board's then take a look at his ODA V2 that he just got working at DIY.
  
 More power.
  
 A.


----------



## Solrighal

Just a message to let you guys know that whilst I only understand half of what you speak, nonetheless this is a fascinating thread.

Kudos to the engineers of this world.


----------



## tdockweiler

I replaced the op-amps in the O2 a few days ago with the OPA2227. Expected it to sound mostly the same, but I don't think I like it.
 It actually now sounds too warm, almost muddy sounding with my HD-650 and DJ100. The OPA2134 I seem to love (in my other amps) and I should have went with that.
 Seems impossible. It's actually hard to believe this is an O2.
  
 I will instead try the LM4652 and see how that goes. OPA627 sounded like a fun experiment, but too much trouble and they cost way too much.
  
 I guess there must be a reason why most amps use the OPA2134 instead of the 2227. Don't think it has to do with price..
  
 I don't use the O2 much and kind of wanted to try some things to make it sound very slightly different with my Q701.


----------



## anthk

xenophon said:


> No.  I own a HE-6.  Tried it at the time with O2/ODAC.  It most definitely, empathically *does not * work for them.  I don't care what numbers get pulled out of hats but this I know for sure, it's plain and simple to anyone simply trying it.  Not even a question of volume, it sounds like fried crap.


 

 Not to be challenging you in a hostile way or anything, I am simply curious and I hope someone could shred some light on this problem. You see, theoretically, there should be sufficient power for the headphone. Yet, you find the power lacking.
 What might be the possible reasons behind this discrepancy ?


----------



## GigArt

xenophon said:


> No.  I own a HE-6.  Tried it at the time with O2/ODAC.  It most definitely, empathically *does not * work for them.  I don't care what numbers get pulled out of hats but this I know for sure, it's plain and simple to anyone simply trying it.  Not even a question of volume, it sounds like fried crap.


 
 I agree. I tried ODAC\O2 with Hifiman HE-4... Well, the bass was weak, the sound was lifeless, constrained and harsh in treble region (though super detailed). Actually, even if the amp can drive Hifiman HE-4\HE-6\LCD-2 to high volume levels it doesn't mean the amp drives them well. In case of O2 and most other amps there might be power supply and current limitations. According to russian audiophile community Doctorhead, Beta 22 is a different story - dynamic, smooth in treble, punchy, spacious! It's no surprise - serious power supply does its job well. Beta 22 really helps to get the best out of HE-4\HE-6\LCD-2 and any other HPs. Using speaker amps to drive power-hungry headphones doesn't give the same performance as Beta 22 (speaker amps are designed to work optimally with very low impedance - 4-8 Ohms) but it's still better for orthos than typical HP amps. 
  
 To sum up, O2 is a nice little amp for the price. But using it with orthos - please, no.


----------



## skeptic

Gigart - if you haven't heard it with fostex, ADs etc, you're really not in a position to judge orthos across the board. Recall that the O2 was, for a very long time, LFF's (creator of the paradox etc.) amp of choice for his orthos. He recommended it frequently for fostex drivers and many of us enjoy the combo. 

Audeze and Hifiman are hardly the only game in town. I'd wager fostex has sold 100x as many orthos as the boutique brands combined.


----------



## GigArt

Sure, I forgot about T50RPs - they are significantly easier to drive. But I decided to try Fostex TH600 with my ODAC\O2. O2 is more than enough for TH600. Though LFF Paradox will be my next HP if I won't like TH600.


----------



## skeptic

gigart said:


> Sure, I forgot about T50RPs - they are significantly easier to drive. But I decided to try Fostex TH600 with my ODAC\O2. O2 is more than enough for TH600. Though LFF Paradox will be my next HP if I won't like TH600.


 
   
 Cool.  I'd be curious to read about your take on the combo with the th600's once you have them on hand.  I have yet to hear a paradox, but LFF's ears are pretty darn golden, and I have no doubt they sound great.  Several of his past off the cuff recommendations as to well recorded music have become favorites in my collection.  
  
 Quote:


adydula said:


> If you like agdr booster board's then take a look at his ODA V2 that he just got working at DIY.
> 
> More power.
> 
> A.


 
  
 Definitely on my short list along with trying my hand at a pupdac!  Given how much I like agdr's booster, I can only imagine how good the high powered version might be.  I have to finish my wire se-se off first though and figure out how the hell one actually wires up a case - the only thing building kits and pocket amps simply doesn't prepare you for.  Then building an ODA to compare to the Wire sounds like a lot of fun.


----------



## Xenophon

anthk said:


> Not to be challenging you in a hostile way or anything, I am simply curious and I hope someone could shred some light on this problem. You see, theoretically, there should be sufficient power for the headphone. Yet, you find the power lacking.
> What might be the possible reasons behind this discrepancy ?


 
 You run into voltage/current limitations of the design at the HE-6's impedance, given its 83.5 dB sensitivity.  See the 'more power?' article on the designer's blog which gives a good overview, in particular, take a look at the output graphs listing Vmax and current at 1% THD+N into various impedances.  Simply put:  you'll drive it into clipping at anything approaching normal levels, even when not taking into account headroom or dynamic music etc.  This is assuming that there's no more current limitations at 50 Ohm loads (at 33 Ohm it's limited to 4.5V/613 mW).
  
 Nothing against the O2 (been getting some hate mail from people who seem to think I have something against the design which, for the record, is not the case) but it's not the right tool for the HE-6.


----------



## adydula

The O2 drives the LCD2's with AUTHORITY.
  
 This means with clarity, loud, soft, anywhere in between.
  
 Totally in command.
  
 For anyone that's interested in an ODA check out www.agdraudio.com
  
 You can get one all built and tested.
  
 The parts with a case and AC adapter costs $250+ easily and you do all the work.
  
 A fully assembled one tested will cost a bit more....more than ample power to drive most anything.
  
 A.
  
 oh...NOTE: the O2 was not meant to drive HE6's.....its one of those 2% cans that are well....just hard to drive due to their inefficiency.


----------



## pearljam50000

Too bad it's not good with the HD800 from what i read here, i wanted a budget rig if i ever get the HD800 in the future,it would have been perfect


----------



## gikigill

As an HE-6 and an O2 owner, nothing drives the HE-6 properly except a speaker amp.
  
 The O2 can drive 90% of the cans and for the price, it does a great job. Best enjoyed with IEM,s as they seem to sound better
  
 than headphones for some reason.


----------



## gikigill

adydula said:


> The O2 drives the LCD2's with AUTHORITY.
> 
> This means with clarity, loud, soft, anywhere in between.
> 
> ...


 
  
 Looking at your website mate, great job. Might be getting some stuff off you soon for a Desktop ODA.


----------



## SilverEars

Guys, I just realized where I'm getting my resolution on my LCD-2.  ODAC.  Now I realized why the combo sounded so great with iems, it was the ODAC the whole time.  O2 can be replaced, but not the ODAC, it well made DAC IMO.


----------



## Xenophon

^+1...agree 100%, the DAC implementation is a work of genius, a lot better than the amp imo.


----------



## SilverEars

xenophon said:


> ^+1...agree 100%, the DAC implementation is a work of genius, a lot better than the amp imo.


 
 What the..? We agree on everything.  
	

	
	
		
		

		
			





  Make sense as two Ortho owners, we know what amps are needed.
  
 Anyway, I did A/B test with all my DACs.  I'm a DAC freak.  
	

	
	
		
		

		
		
	


	




  I believe DACs make a huge difference, I can hear the differences to, and ODAC does really well.  I compared with the DACs I have, I wonder what DAC would be next level up?  Since now I believe that DACs can make a difference.
  
 There are reasons why people are getting Beta 22 for their LCDs. I've A/B the O2, and it's bloated.


----------



## SilverEars

xenophon said:


> ^+1...agree 100%, the DAC implementation is a work of genius, a lot better than the amp imo.


 
 What other DACs have you tried?


----------



## Xenophon

silverears said:


> What other DACs have you tried?


 
 Whenever I have the chance I try auditioning stuff, have to compensate for the fact that 2/3rd of the time I live in Delhi (for the job), the equivalent of the sahara for high end audio (for most people here it's high end if it goes LOUD, but granted, if I were the average Joe here then I'd have other priorities than audio gear).  For DACs, the technology and various ways it gets implemented are fascinating.  Problem is that it's not always possible to make that the only variable in the chain as I live in 2 locations.
  
 Let's put it this way, the cheapest external DAC I've heard would be the ODAC, the most refined (and very likely most expensive) one to date the MSB Diamond DAC IV Select which I first got to know while on a trip to Japan of all places.  Apart from ODAC I only own the V800 which I still find very good, despite the USB that's outdated.  Was actually looking to upgrade but after talking to some people here came to the conclusion that it'd cost mucho dollars to make a sizeable difference in quality.  Most fascinating products to me at the moment -at human price levels- are the Auralic Vega and (totally different approach, NOS) the Metrum Acoustics Hex.


----------



## SilverEars

Although I doubt it, but possibly the O2 amp not sounding very good with my LCD-2 could be my 12 VAC Triad wall wart.  Can I get more voltage swing with a higher voltage wall ward?  on the O2 plug it says 14-20VAC.  Should I get a 20VAC?


----------



## Xenophon

All I can say is that I tried a different ww some time back and to my ears it didn't change a thing.  The max voltage swing is determined by the inner electronics and short of redesigning stuff and swapping components there's nothing that can be done.  Even if you'd feed it a signal that had already x dB of gain over normal (rebook) level dialed in, you'd just drive the amp into clipping.


----------



## SilverEars

I've stated that since according to the designer's spec's it's 7Vrms max, it's 10Vpp max.  Correct me if I'm wrong about the specs.
 .  
 If what I said is right, is it peaked at that value because of the regular only output that much?
  
 The 12VAC triad would provide at max RMS of 12VAC which is around 8.5VDCpp, and I would asume DC output is less though.  So, if you provide a higher valued transformer, wouldn't you get the 10Vpp Max?  Which transformer would help hit that voltage is the question.


----------



## anthk

xenophon said:


> All I can say is that I tried a different ww some time back and to my ears it didn't change a thing.  The max voltage swing is determined by the inner electronics and short of redesigning stuff and swapping components there's nothing that can be done.  Even if you'd feed it a signal that had already x dB of gain over normal (rebook) level dialed in, you'd just drive the amp into clipping.


 

 is your v800 much better than the odac?


----------



## anthk

xenophon said:


> You run into voltage/current limitations of the design at the HE-6's impedance, given its 83.5 dB sensitivity.  See the 'more power?' article on the designer's blog which gives a good overview, in particular, take a look at the output graphs listing Vmax and current at 1% THD+N into various impedances.  Simply put:  you'll drive it into clipping at anything approaching normal levels, even when not taking into account headroom or dynamic music etc.  This is assuming that there's no more current limitations at 50 Ohm loads (at 33 Ohm it's limited to 4.5V/613 mW).
> 
> Nothing against the O2 (been getting some hate mail from people who seem to think I have something against the design which, for the record, is not the case) but it's not the right tool for the HE-6.


 

 I am not a fanboy of the O2 amp . I know there are things that o2 wont be able to do obviously. I am just looking into the numbers, sort of as an exercise for me to better understand those spec

 To reach 110 SPL, I calculated that @ 50 ohm, 2.99 V rms is required and 447 mW is the power needed.

 That's without headroom or listening to dynamic stuff that is said to be requiring 115 SPL.

 I read the graphs in that blog. To maintain 0.002% THD+N the power is in general < 300 mW.

 That's why the sound is bloated. Am I correct so far?


----------



## SilverEars

What I come to understand about THD for SS amps is that, the value below 1% is meaningless since it's inaudible according to sciene. Headphones distortion is significant so that's where it matters.  I understand that when SS distort in an audible level, it's basically clipping.  Pretty much the spec and measurement do not tell you much about performance of SS amp since they will typically measure below great performing level.  What is more useful is how the headphones is performing under load of the amps and sources.  What the amp is outputing from each particular DAC.  Do different amp change the output of one DAC if the amps were swapped?
  
 I don't quite understand how tighness of sound and bloating is caused by.  I'm guessing possibly from damping, but O2 dfinately sound less controlled an bloated and my Beta 22 does sound tighter.  I've also noticed with using different DACs to the Beta 22.  I A/B'd and came into conclusion that ODAC is a good DAC, and O2 doesn't have enough power to support my LCD-2, although it is being fed in by ODAC.


----------



## adydula

Wow.....my experience is totally different with LCD2's....not bloated at all....not in the least...crystal clear, tight bass...wonderful transparent sound.
  
 I have a HRT MSii + and I cant tell the difference between it or the ODAC...both superb.
  
 I have several ac adapters and even with the most capable one...its not a issue.
  
 The only thing that can cause distortion in my setup is running on 6.5x gain...I turned my O2s into Unity gain and 2.5 x...I hardly ever use 2.5.
  
 A.


----------



## Xenophon

anthk said:


> is your v800 much better than the odac?


 
 Yes to me it is better but not if you're strictly talking 'sound quality'.  It's better because it offers me stuff I find useful that can't be found on the ODAC such as XLR-output, discreet volume control that's of a good enough quality so it can double as a pre-amp, the possibility to hardware-set pre-gain on a number of levels, hardware control of oversampling between x1,2,3,4, 'best' (depending on input) or to switch it off entirely.
  
 For the DAC:  both use the Tenor USB-implementation , the differences are in the DAC-chipset proper (iirc ES9023 for the ODAC and the  PCM1792 for the V800) but especially in the way the signal is treated post-processing (filtering and conditioning etc).  They do have a slightly different 'signature' and I prefer what the V800 offers but of course you need to keep in mind that that 'signature' is not just created by the DAC-chip (frankly I don't believe there to be much if any difference there, certainly not audible) but mainly by what happens to the signal next, the OPA's used in the DAC's amplification stage etc.


----------



## SilverEars

xenophon said:


> Yes to me it is better but not if you're strictly talking 'sound quality'.  It's better because it offers me stuff I find useful that can't be found on the ODAC such as XLR-output, discreet volume control that's of a good enough quality so it can double as a pre-amp, the possibility to hardware-set pre-gain on a number of levels, hardware control of oversampling between x1,2,3,4, 'best' (depending on input) or to switch it off entirely.
> 
> For the DAC:  both use the Tenor USB-implementation , the differences are in the DAC-chipset proper (iirc ES9023 for the ODAC and the  PCM1792 for the V800) but especially in the way the signal is treated post-processing (filtering and conditioning etc).  They do have a slightly different 'signature' and I prefer what the V800 offers but of course you need to keep in mind that that 'signature' is not just created by the DAC-chip (frankly I don't believe there to be much if any difference there, certainly not audible) but mainly by what happens to the signal next, the OPA's used in the DAC's amplification stage etc.


 
 I would have to agree with this, when I say DAC, I mean the implemention.  Likely it's not the chip, but the implemention of the output stage is what makes the big different.  I believe the DAC chips have schematic inside with amps inside, and that could possibly make crucial changes to the signal also.


----------



## thirddegreee

Hello everyone. First post here and got a question...
  
 I possess the Sennheiser HD650s and I mostly listen to music through my 3 year old laptop (Dell XPS L502x which has the Realtek ALC665 chip) and that seems OK to drive the headphones at a more than reasonable quality and volume. I've got a full-sized CD Player which is 15 years old now, the Sony XA2ES, and plugged the HD650s into the headphone socket on that and switched between that and laptop with the same music (Original CD v FLAC on the Dell) and to me there is no difference in audio quality. The Sony XA2ES has more power to drive the HD650s louder but that isn't that important for me. Of course both the Sony XA2ES and the Dell could have rubbish headphone outputs so maybe I could benefit from new equipment to maximise the HD650s.
  
 I suppose my question would be - has anyone else got my set up (HD650s with the Dell XPS L502x) and found that the O2+ODAC combo been a significant improvement?
  
 Thanks in advance to anyone who reads this and more thanks if you reply!


----------



## cddc

O/O seems quite popular here


----------



## PTom

I find the O2/ODAC combo sometimes sounds a bit harsh with the LCD 2, I'm not sure if this is due to the amp or DAC.


----------



## SilverEars

ptom said:


> I find the O2/ODAC combo sometimes sounds a bit harsh with the LCD 2, I'm not sure if this is due to the amp or DAC.


 
 I have Beta 22 amp and the O2 coming out of ODAC, and compared the two amps.  Beta 22 has more control.  When I went from O2 to Betat 22, O2 sounded very loose or distorted, not as refined.  I don't see anything wrong with ODAC, I will of course try out other DACs in the future to see if I can find a better one.


----------



## r010159

I have had my O2/ODAC turned on for a month now. So far, very good. I thought I was running into trouble with some dropouts and static. But once I changed a setting in my J River media player the problem went away for a week now. I do not think it was the amp/DAC.

PS: The beta22 may be a very good amplifier. But using discrete components? This may be because the designer wanted a DIY design. But other than that reason, using entirely discrete parts with today's tech is unnecessary and IMO actually very silly. I still am going to look into this myself.


----------



## Xenophon

r010159 said:


> I have had my O2/ODAC turned on for a month now. So far, very good. I thought I was running into trouble with some dropouts and static. But once I changed a setting in my J River media player the problem went away for a week now. I do not think it was the amp/DAC.


 
 OT:  Are you happy with this J River player?  I gave it a try on my Mac and while the interface is great and a lot slicker than Amarra, I found it didn't come close to Amarra in sound quality.


----------



## r010159

xenophon said:


> OT:  Are you happy with this J River player?  I gave it a try on my Mac and while the interface is great and a lot slicker than Amarra, I found it didn't come close to Amarra in sound quality.




I found the J River to be better than both the Fidelia and Audirvana+ players. I have not tried Amarra, but I understand that it is supposed to be a very good player. I am finding so far that all bit-perfect sound very close when lossless compressed files are played. Only a better ear than mind could tell the difference.


----------



## Solrighal

I don't understand why a software player would make *any* difference at all. Surely, as long as no EQ is used they should all sound exactly the same? 

If they do indeed sound different then it makes a mockery of any attempt at bit-perfect further down the chain?

I also use JRiver.


----------



## Xenophon

solrighal said:


> I don't understand why a software player would make *any* difference at all. Surely, as long as no EQ is used they should all sound exactly the same?
> 
> If they do indeed sound different then it makes a mockery of any attempt at bit-perfect further down the chain?
> 
> I also use JRiver.


 
 That's rich, coming from a cable-believer 
	

	
	
		
		

		
		
	


	




  
  
 It's as with anything to do with digital I guess: * in theory* there should not be any difference.  Unfortunately implementation comes between theory and practice.  I don't know enough about software players except that for Amarra it provides for buffering, sampling and a number of other gimmicks.  Presumably the others do this as well.  Have to say that when I installed the trial I was extremely sceptical.  But when I heard the result -at that time on my DT-880's- I whipped out my card in a hurry.  This was without eq but at the time on my 2009 MBP which had -I'm being kind- a less than stellar USB-implementation.  2 drawbacks: a) expensive by comparison and b) interface is very much 1990's and their integration with iTunes kills me.
  
 Nowadays I mainly use its eq function with classical pieces, very good parametric equalizer.  Anyway, I read about the J River player and installed it on a whim to give it a spin but wasn't impressed.


----------



## r010159

solrighal said:


> I don't understand why a software player would make *any* difference at all. Surely, as long as no EQ is used they should all sound exactly the same?
> 
> If they do indeed sound different then it makes a mockery of any attempt at bit-perfect further down the chain?
> 
> I also use JRiver.




There will be a difference in two areas. One is the decoding of lossy audio files. The other is when the player is performing a sample rate conversion. The quality of either one will depend on how it is done by the player.

As a side note, when I had players setup where they should be bit-perfect, a trained ear still could hear a small difference. I would not of believed this myself if it were not for the purposely confusing blind testing that I did. I may try this exersize again one of these days.

Bit perfect playback? I am now a bit suspicious.


----------



## Solrighal

I still don't buy it. To my mind any difference has to be down to something being either done wrong or something being added. And cables are not a good comparator. All sorts of physical conditions can alter the signal in a cable. This cannot be the case when comparing software players in the same machine. 

However... 

I use Neutron via OTG USB on my portable rig and Neutron, with all the bells & whistles turned off, is head & shoulders above every other Android player. Go figure.


----------



## James-uk

http://archimago.blogspot.ca/2013/06/measurements-part-i-bit-perfect.html?m=1
Players make no difference in SQ. I only use pure music for convenient auto sample rate switching which my I tunes doesn't do.


----------



## Solrighal

r010159 said:


> Bit perfect playback? I am now a bit suspicious.




We could start a club


----------



## PTom

silverears said:


> I have Beta 22 amp and the O2 coming out of ODAC, and compared the two amps.  Beta 22 has more control.  When I went from O2 to Betat 22, O2 sounded very loose or distorted, not as refined.  I don't see anything wrong with ODAC, I will of course try out other DACs in the future to see if I can find a better one.


 
 I read that Audeze recommend an amp that can output at least a couple of watts into a 60 ohm load and the O2 seems to come up short in this respect at least so maybe this is why they don't work perfectly with the LCD 2?
  
 What are some objectively well performing amps that could output more than 1 watt into a 60 ohm load?


----------



## miceblue

ptom said:


> I find the O2/ODAC combo sometimes sounds a bit harsh with the LCD 2, I'm not sure if this is due to the amp or DAC.



I've found that to be the case too, and I don't like the combo in that regards.


----------



## adydula

I have used all the players mentioned and have removed all but JRiver.
  
 The main issue with players and with JRriver is setting it up correctly for bitperfect playback and the corresponding operating switches.
  
 JRiver will produce bit perfect playback as long as you the operator knows what your doing....LOL.
  
 There is an indicator that turns "blue" with it that indicates what it is getting in is going out....
  
 JRiver has many, many settngs for a wide variety of things, very easy to mess up if your not thinking.
  
 There support site is really good and there is a wealth of technological knowledge on their site.
  
 I find the interface easy to use, and there are usually three different ways to view and set up etc.
  
 A.


----------



## adydula

Audeze LCD-2 revision 2 the specs are:
  
 • Impedance: 60 Ohms, nominal
 • Maximum diaphragm excursion: 2.5mm p-p
 • Efficiency: 91 dB/1mW
 • Maximum output: 133dB, 15W
  
 The O2 not only has lots of voltage, but it also has lots of current for low impedance loads that require it—like AKG K701s, Audeze LCD-2s ec...
  
 There are many happy LCD-2 users using the O2. It has power to spare to drive the LCD-2 to hearing damaging levels and beyond.
  
 The LCD-2 hits 110 dB with about 1 volt of input. Peaks of 110 dB are considered plenty loud by most people (hearing damage starts past 85 dB). 110 dB is standing on a sidewalk next to a jack hammer tearing up concrete. Even if you plan for 115 dB peaks, which is extremely loud, you only need about 1.7 Vrms which is 0.048 watts. The O2 can provide 5+ Vrms which is good for 124 dB SPL with the LCD-2. And that's running from battery power. If you really wanted to push the headphones to 133 dB you would need 14 Vrms which is 3.2 watts.
  
 But, long story short, even at an ear splitting 124 dB SPL that's a peak voltage of 7 volts. Ohms law gives a peak current of 7/60 = 117 mA. The O2 has a peak current capability of 200 mA per channel--nearly twice what's required.
  
 Again LCD2's are driven very, very well with the simple little ole battery powered or AC powered manner.
  
 A.


----------



## Solrighal

adydula said:


> I have used all the players mentioned and have removed all but JRiver.
> 
> The main issue with players and with JRriver is setting it up correctly for bitperfect playback and the corresponding operating switches.
> 
> ...




Is this blue "indicator" on the Mac version? Where should I see it?


----------



## PTom

adydula said:


> Audeze LCD-2 revision 2 the specs are:
> 
> • Impedance: 60 Ohms, nominal
> • Maximum diaphragm excursion: 2.5mm p-p
> ...


 
 Have you personally heard the LCD 2 with the O2 amp? If so, did you find any problems with SQ i.e. like harsh treble?


----------



## adydula

PTom,
  
 In my posts I have indicated that I have LCD2's R2's and have had many hours with them on 2 separate O2 Amps and ODAC's...with very good results.
  
 I also had at the time a Schitt Asgard and a Schitt Lyr (6 watts) and the I sold those and kept the O2's..that should tell you something.
  
 There are so many variables, and personal tastes and opinions.
  
 I wanted people to know that there are many happy LCD2 owners using the O2 amp with great success.
  
 Accuracy and transparency are very important to me....I want an amp to just be an amp...and not add or detract with anything else other than perfect amplification to the incoming signal. The O2 does this marvelously well.
  
 Having an amp like this or a V800 etc...takes this variable out of the picture and you don't have to worry about this part in the chain.
  
 I wonder if people really take the time to make sure the source material, the amp gain settings, player setups are correct to allow bit perfect playback.
  
 Its easy to start mucking with stuff and not understanding what your doing and just trusting your ears, brain and what mood and how much beer you might have had!!! LOL.
  
 All the best
 Alex
  
 NOTE: Garbage in Garbage out......


----------



## adydula

I don't have the Mac version but here is the PC version and where the "blue" indicator lights up when playing in bitperfect mode..
  

 If you hover over this icon you will see no changes being made message when its working correctly.
  
 You can go in and change or modify behaviors depending on bitdepth, number of channels and lots of other stuff.
  
 You can even go in an reduce the bit depth to see what effect if any on SQ.
  
 Alex


----------



## SilverEars

ptom said:


> I read that Audeze recommend an amp that can output at least a couple of watts into a 60 ohm load and the O2 seems to come up short in this respect at least so maybe this is why they don't work perfectly with the LCD 2?
> 
> What are some objectively well performing amps that could output more than 1 watt into a 60 ohm load?


 
 Check out the Beta 22 thread if you want to know where Audeze headphones are most talked about.  My Fiio E17 can drive my LCD-2, does it drive well? No, it does not.  Does the O2 drive it well, no it does not.  Just because it can draw enough power does not mean it will drive it well.   Go to meets and look at what the Audeze headphones are driven by and ask them why they use those amps.  If people are using O2 to drive their LCDs it's because they have not tried more capable amps.  
  
 There are two amps that are recommended in the LCD thread, Beta 22 and Schiit Mjolnir(people don't recommend certain amps for no reason).  You can build Beta 22 in single ended or balanced configuration, and the Mjolnir is balanced.  
  
 Specs are specs, and I know how to read them.  They don't have the whole picture when it comes to what comes out of the headphones.  I would recommend IEMs, but not recommend HD650(sounds terrible) and Audeze phones for the O2.  Having the specs to power them, and how they are driven is another.


----------



## Xenophon

^ +1.


----------



## adydula

Kool I humbly disagree....
  
 Its your bucks enjoy...
  
 A.


----------



## Solrighal

adydula said:


> I don't have the Mac version but here is the PC version and where the "blue" indicator lights up when playing in bitperfect mode..
> 
> 
> 
> ...




Yes, I see that. Sometimes anyway. Other times I use the volume levelling functions.




silverears said:


> Check out the Beta 22 thread if you want to know where Audeze headphones are most talked about.  My Fiio E17 can drive my LCD-2, does it drive well? No, it does not.  Does the O2 drive it well, no it does not.  Just because it can draw enough power does not mean it will drive it well.   Go to meets and look at what the Audeze headphones are driven by and ask them why they use those amps.  If people are using O2 to drive their LCDs it's because they have not tried more capable amps.
> 
> There are two amps that are recommended in the LCD thread, Beta 22 and Schiit Mjolnir(people don't recommend certain amps for no reason).  You can build Beta 22 in single ended or balanced configuration, and the Mjolnir is balanced.
> 
> Specs are specs, and I know how to read them.  They don't have the whole picture when it comes to what comes out of the headphones.  I would recommend IEMs, but not recommend HD650(sounds terrible) and Audeze phones for the O2.  Having the specs to power them, and how they are driven is another.




There's a Crack+Speedball in the FS threads and I'm looking at that as a potential end-game for my 650's. It's a lot of money for me though.


----------



## PTom

silverears said:


> Check out the Beta 22 thread if you want to know where Audeze headphones are most talked about.  My Fiio E17 can drive my LCD-2, does it drive well? No, it does not.  Does the O2 drive it well, no it does not.  Just because it can draw enough power does not mean it will drive it well.   Go to meets and look at what the Audeze headphones are driven by and ask them why they use those amps.  If people are using O2 to drive their LCDs it's because they have not tried more capable amps.
> 
> There are two amps that are recommended in the LCD thread, Beta 22 and Schiit Mjolnir(people don't recommend certain amps for no reason).  You can build Beta 22 in single ended or balanced configuration, and the Mjolnir is balanced.
> 
> Specs are specs, and I know how to read them.  They don't have the whole picture when it comes to what comes out of the headphones.  I would recommend IEMs, but not recommend HD650(sounds terrible) and Audeze phones for the O2.  Having the specs to power them, and how they are driven is another.


 
 Thanks, that's quite interesting, Mjolnir sounds interesting but it's not easily available at a reasonable price this side of the Atlantic. Also heard Burson conductor and Meier Concerto are worth looking at for the LCD 2.


----------



## JacobLee89

silverears said:


> Specs are specs, and I know how to read them.  They don't have the whole picture when it comes to what comes out of the headphones.  I would recommend IEMs, but not recommend HD650(sounds terrible) and Audeze phones for the O2.  Having the specs to power them, and how they are driven is another.


 
  
 I have yet to find a single track I dislike with my HD650 and O2 (booster mod) + ODAC, in fact I enjoyed the combination for a good while before the O2 was modded. The HD650's however do have a history/myth of the pre-2007 Sennheiser veil, so a good amount of HD650 reviews with the Objective stack is a merry mixture of thoughts.


----------



## SilverEars

jacoblee89 said:


> I have yet to find a single track I dislike with my HD650 and O2 (booster mod) + ODAC, in fact I enjoyed the combination for a good while before the O2 was modded. The HD650's however do have a history/myth of the pre-2007 Sennheiser veil, so a good amount of HD650 reviews with the Objective stack is a merry mixture of thoughts.


 
 Sonically speaking, I favored the 650 with Tubes.  Tubes are regarded as having higher distortion and providing 2nd harmonic distortion that people may favor the coloration of the sound.  
  
 At the meet I've heard the LCD-3 with Isabella, a tube amp which sounded fantastic, also Alpha Dogs mr. speakers brought with his top tube amp sounded fantastic.  I believe amps generally do not have the level of distortion as the headphones.
  
 What is this booster mod you speak of? I'm curious to try it.  Thanks.


----------



## PTom

adydula said:


> PTom,
> 
> In my posts I have indicated that I have LCD2's R2's and have had many hours with them on 2 separate O2 Amps and ODAC's...with very good results.
> 
> ...


 
 My setup is O2/ODAC (Epiphany Acoustics) and I use lossless files (FLAC) using Vox (no equalization applied, all settings on default) on a Macbook Pro (Late 2010 version). The lowest amp gain setting is used. The LCD 2 Rev 2 as well as the amp/DAC all use stock cables. I'm not sure which part of the chain I should look into adjusting?
  
 The harshness I observe on certain tracks could be due to the mastering but well known albums like Coldplay/Adele: Greatest Hits sound distractingly harsh with respect to the treble.


----------



## krismusic

You know. You can nit pick all you like but the O2 with the Sennheiser HD600's is phenomenal. I'm sitting here listening to ZZ. Top. All the grunge and distortion that the band intend is all there but it is like the crust on a pie. The O2 lifts the lid so that you get all the lovely juicy bits inside.  and all for under£400! Crazy.


----------



## Xenophon

adydula said:


> Kool I humbly disagree....
> 
> Its your bucks enjoy...
> 
> A.


 
 No problem, it 'd be boring if everyone was in perfect agreement all the time.
  
 About the amping and the powering of headphones, the best non-sound analogy I can think of would be those limited power versions of motorcycles that people who are not yet 24/don't have their license for a sufficiently long time yet can purchase/ride with.  Sure, they run.  But the second you can pull the plugs out and have full power available they're something different.  
  
 I know it's far from a perfect analogy and stipulate that the degree to which this will manifest itself differs but you catch the meaning.
  
 Will take a look at that J River player again tomorrow, indeed a crapload of option menus to wade through


----------



## Solrighal

krismusic said:


> You know. You can nit pick all you like but the O2 with the Sennheiser HD600's is phenomenal. I'm sitting here listening to ZZ. Top. All the grunge and distortion that the band intend is all there but it is like the crust on a pie. The O2 lifts the lid so that you get all the lovely juicy bits inside.  and all for under£400! Crazy.




^this^



xenophon said:


> No problem, it 'd be boring if everyone was in perfect agreement all the time.
> 
> About the amping and the powering of headphones, the best non-sound analogy I can think of would be those limited power versions of motorcycles that people who are not yet 24/don't have their license for a sufficiently long time yet can purchase/ride with.  Sure, they run.  But the second you can pull the plugs out and have full power available they're something different.
> 
> ...




JRiver is good. It's not pretty but it's good. A big plus - for me - is that it allows remote control via various devices.


----------



## r010159

[VIDEO][/VIDEO]





solrighal said:


> ^this^
> JRiver is good. It's not pretty but it's good. A big plus - for me - is that it allows remote control via various devices.




I went through all the settings and turned off all the options. I allowed the rest to be their default values. I found that players that tout bit-perfect playback come out of the box that way where all parameters are set to their default. There was still a small difference between the Audirvana+ and J River players. I would of not thought anything of these small difference if it were not for the test subjects ability to pick out J River. But there will be more significant differences in the area of lossy audio files and sample rate conversion. Both involve mathematical operations where there are trade offs between different approaches.

By the way, I did extensive blind testing with a musician that had a well-trained ear with good FR. I cannot call the results conclusive, but IMO they are highly suggestive.

And I just discovered the remote control aspect of J River. Next is setting it up to stream music across the Internet to my iPad when I am in a sit down bookstore or coffee shop. The C5D which I also own will come in handy here.

Life is sweet! 

PS: the discussion of my blind testing started here: http://www.head-fi.org/t/699832/mac-users-what-audio-player-do-you-guys-use/30


----------



## adydula

Its amazing to compare an O2 amp that can be had for less than $100 to a B22 that fully assembled can easliy cost $1000+. There are folks that have compared these two and cant hear any real world differences.
  
 Its hard for folks not to think that the more a piece of gear costs the better it will sound.
  
 Its also nice to have a world class amp and dac for the low cost the o2 and odac provide many of us that cant afford the higher priced end stuff.
  
 Like I said it your money...enjoy....
  
 Motorcycles!!! If you only knew...
  
 A.


----------



## skeptic

silverears said:


> Sonically speaking, I favored the 650 with Tubes.  Tubes are regarded as having higher distortion and providing 2nd harmonic distortion that people may favor the coloration of the sound.
> 
> At the meet I've heard the LCD-3 with Isabella, a tube amp which sounded fantastic, also Alpha Dogs mr. speakers brought with his top tube amp sounded fantastic.  I believe amps generally do not have the level of distortion as the headphones.
> 
> What is this booster mod you speak of? I'm curious to try it.  Thanks.


 
  
 SilverEars - here's the link to the diyaudio thread on agdr's booster board: http://www.diyaudio.com/forums/headphone-systems/244473-o2-headamp-output-booster-pcb.html
  
 Starting in late-May, agdr has also indicated that he will be selling completed booster boards for those who don't want to take on the surface mount work: http://www.agdraudio.com/Page2.html
  
 I completed mine a week or so back and find that it is a very nice improvement on the stock O2, along with the dual LME49990's you can add to the gain stage to up the slew rate.  Really enjoying the finished result with my AD's as a bedside rig.


----------



## Xenophon

adydula said:


> Its amazing to compare an O2 amp that can be had for less than $100 to a B22 that fully assembled can easliy cost $1000+. There are folks that have compared these two and cant hear any real world differences.
> 
> Its hard for folks not to think that the more a piece of gear costs the better it will sound.
> 
> ...


 
 It are two very different products with different properties, I'm not comparing them, the only thing I'm saying is that -being a HE-6 owner- the B22 is the only viable option for me if I'd have to choose between those 2.  That's a simple fact that even the developer himself wouldn't dispute.  Can't say about LCD-2 as I've never heard them on any amplifier.  
  
 My point is that the O2 isn't the end all in terms of amplification and one shouldn't go overboard in trying to make out like if it were.  Every piece of gear has weaknesses and in the end it's as you say:  if you have the money then it's yours to spend and until further notice nobody can tell you what to spend it on.  Speaking just for myself I know full well that more money doesn't equate automatically to more quality, audio's full of vapourware, nice cases containing badly assembled junk and assorted BS.  
  
 Analogy to motorcycles chosen because I happen to ride an Enfield here in India and an MV Agusta brutale in Europe....talk about the right tool for different circumstances.


----------



## anthk

xenophon said:


> It are two very different products with different properties, I'm not comparing them, the only thing I'm saying is that -being a HE-6 owner- the B22 is the only viable option for me if I'd have to choose between those 2.  That's a simple fact that even the developer himself wouldn't dispute.  Can't say about LCD-2 as I've never heard them on any amplifier.
> 
> My point is that the O2 isn't the end all in terms of amplification and one shouldn't go overboard in trying to make out like if it were.  Every piece of gear has weaknesses and in the end it's as you say:  if you have the money then it's yours to spend and until further notice nobody can tell you what to spend it on.  Speaking just for myself I know full well that more money doesn't equate automatically to more quality, audio's full of vapourware, nice cases containing badly assembled junk and assorted BS.
> 
> Analogy to motorcycles chosen because I happen to ride an Enfield here in India and an MV Agusta brutale in Europe....talk about the right tool for different circumstances.


 

 I agree.
 With He-6 , I have seen the match showing that O2 can't properly drive it.
 LCD-2 though, maybe my math is off


----------



## proid

adydula said:


> Its amazing to compare an O2 amp that can be had for less than $100 to a B22 that fully assembled can easliy cost $1000+. There are folks that have compared these two and cant hear any real world differences.
> 
> Its hard for folks not to think that the more a piece of gear costs the better it will sound.
> 
> ...


 
  
 Don't take that post too seriously, O2 is very good indeed but it has its limit. I think the guy who posted that comparison just doesn't have really good hearing ability. I haven't heard the B22 with my own gear and setup but O2 is still 1 step down compare to my PPAV2 and 2 step down compare to my friend's Dynalo, with me i can hear the different very clearly and the O2 is definitely not up to level of these two so i don't even care to compare it to B22.


----------



## Xenophon

OT but I've been playing some more with this JRiver player (on my MBP).  Too many options and scattered all over the place would be my main criticism for now.  Forget my previous remark about it not sounding good, I screwed up a config option.  I take it that the blue icon meant to indicate bit perfect rendition is the EQ symbol that I marked below.  Will try and run some comparisons with Amarra but in the looks department it's already the hands-down winner.


----------



## r010159

xenophon said:


> OT but I've been playing some more with this JRiver player (on my MBP).  Too many options and scattered all over the place would be my main criticism for now.  Forget my previous remark about it not sounding good, I screwed up a config option.  I take it that the blue icon meant to indicate bit perfect rendition is the EQ symbol that I marked below.  Will try and run some comparisons with Amarra but in the looks department it's already the hands-down winner.




The indicator is only there with the Noire default skin. I turned adaptive volume off which made a noticeable difference in volume where now I do not have to turn up the O2. I have found the last two versions to be problematic with DSP Studio. After I make some changes and then listen to the music, the volume begins to cut in and out. When I leave DSP Studio, this behaviour stops. Once again I do not think this is the O2, because this never happens any other time.

So the lesson of the day Is when the sound cuts in and out, even with static at times, first check your connections. Then check your software, the player in my case. Turning off the playback from memory option solved most of my problems.


----------



## adydula

NP I don't take posts seriously anymore...not worth it....all I know is I have owned LCD2's and the O2 has the capability to blow you ear drums out with it..
  
 There are other amps that would drive the HE6's as well as the B22 but this is an O2 ODAC thread so lets agree to take these issues up in the appropriate thread.
  
 I will say this regardless of what has or will be posted...try your cans with an O2, YOURSELF and see if it meets your standards or not...don't trust me or anyone else.
  
 Recommendations are great but lots of them are biased.
  
 Motorcycles!
  
 I have spent more time in the past 20 years of racetracks at speeds of 180mph+ than I care to remember and have taught high speed race skills on many tracks here in the USA.
  
 We used to say 'Go fast or Go Home!!'
  
 LOL
  
 Alex


----------



## adydula

With the JRiver....many of those options are NOT needed for Bitperfect playback.
  
 Bit Perfect playback is easy to setup.....its when you go in and start changing things and the blue light doesn't light up....and you forgot what u did.
  
 Smiling...
  
 A.


----------



## Solrighal

Playback from memory has it's uses. My Mac mini has 16GB installed so it's no problem for me. As far as I can gather it only pre-loads whatever is in your Now Playing list.


----------



## Solrighal

Would AGDR's Booster Board be of any use to my HD 650's?


----------



## skeptic

As a general matter, I can't wrap my mind around why we are discussing the O2 and HE6 in the same sentence - maybe we should assess its performance with K1000's or maybe a pair of magnepans while we're at it?  The designer was totally candid about the fact that the O2 wasn't intended to drive outlier phones - which _very few _head-fiers own to begin with.  Fostex and, to a lesser extent, Audeze orthos are certainly fair game for discussion.  There is no question that the O2 drives the former very nicely, and we seem to have some divergent opinions as to the latter.  Fair enough.  The amp is also excellent with iem's at unity gain, and I like it with my dt880's but no so much my hd650's for whatever reason (although I should really try them again with the agdr booster in place).  
  
 Quote:


proid said:


> Don't take that post too seriously, O2 is very good indeed but it has its limit. I think the guy who posted that comparison just doesn't have really good hearing ability. I haven't heard the B22 with my own gear and setup but O2 is still 1 step down compare to my PPAV2 and 2 step down compare to my friend's Dynalo, with me i can hear the different very clearly and the O2 is definitely not up to level of these two so i don't even care to compare it to B22.


 
  
 These are valid subjective impressions, but I think it is worth noting that other veteran head-fiers (e.g. as quoted below) have arrived at opposite conclusions on these points.  On the specs, the O2 trumps both of those amps in spite of the fact that the ppav2 measurements were made without a load.  So the interesting question in my mind becomes _why _many of us ultimately prefer other amps (at least with particular phones) that don't meet the same measurements.  I _love _my mainline, for example, and have often hypothesized that a certain amount of even order distortion is making up for the room effects we don't get with headphones, creating (for some of us at least) an illusion of music that sounds more like a live performance in an acoustically pleasing venue.   
  
 I also chuckled a bit at the comparison to the dynalo since just the other day, USG, a head-fi veteran since 2004, posted the following about his GS-1 over in the hd650 thread:
  


> Regarding the O2, the GS-1 can play louder than the O2 but I don't think I'd want to bet on my ability to distinguish between the O2 and the GS-1 at moderate listening levels with my T-1s (dac used was a North Star 192MKII with either a Blue Circle Thingee or a HiFace transport, ... the HiFace having more resolution and a hotter treble than the BCT and the Thingee having less resolution but a better tone ).  Unfortunately, once I discovered no apparent JND between the O2 and GS-1 with the T-1s, I never bothered to compare extensively or further with the 650s, '04/880s, or the 701s I almost never use.


----------



## skeptic

solrighal said:


> Would AGDR's Booster Board be of any use to my HD 650's?


 
  
 I'm inclined to think there would be audible improvements, since I'm increasingly convinced that I like the amp with my AD's quite a bit better following the installation of the booster.  Admittedly, It has been a while since I listened to my 650's with my O2, since I didn't really love the combo stock, but I'll try to remember to bring the 650's home from the office to try them out with the booster.
  
 If you implemented the further mod to raise the voltage on the power rails (which the booster makes possible - see the second asterisk on http://www.agdraudio.com/Page2.html), my guess is that that might further audibly improve performance with high impedance headphones.


----------



## Solrighal

I was getting excited at first but now I'm thinking (from what I've read thus far) that I might not be able to fit the booster board in my case as it has two sets of RCA's on the rear plate.


----------



## Xenophon

skeptic said:


> I'm inclined to think there would be audible improvements, since I'm increasingly convinced that I like the amp with my AD's quite a bit better following the installation of the booster.  Admittedly, It has been a while since I listened to my 650's with my O2, since I didn't really love the combo stock, but I'll try to remember to bring the 650's home from the office to try them out with the booster.
> 
> If you implemented the further mod to raise the voltage on the power rails (which the booster makes possible - see the second asterisk on http://www.agdraudio.com/Page2.html), my guess is that that might further audibly improve performance with high impedance headphones.


 
 Sticking to the objective mantra and playing devils' advocate for a moment:  given the specs/measurements of the HD-650 and the pre booster-board O2, where do you expect to find objective improvements by adding this?  Going by the designer pages, power appears to be ample to drive it and I'll just refer to the qualities that have so vociferously been defended in this thread for the other aspects (neutrality etc).
  
 So, let's have it, where are the auditive improvements?


----------



## skeptic

xenophon said:


> Sticking to the objective mantra and playing devils' advocate for a moment:  given the specs/measurements of the HD-650 and the pre booster-board O2, where do you expect to find objective improvements by adding this?  Going by the designer pages, power appears to be ample to drive it and I'll just refer to the qualities that have so vociferously been defended in this thread for the other aspects (neutrality etc).
> 
> So, let's have it, where are the auditive improvements?


 
  
 A good question indeed.  Even though distortion measurements started off, and then were reduced further, below the what is often considered the threshold of audibility, my understanding is that different "measurement first" designs and topologies are still often (if not usually) perceived as sounding different [for reasons beyond my understanding and pay grade].  For example, I've read a lot of posts here and elsewhere regarding both the O2 and the Wire.  It could be the product of confirmation bias, but I have yet to see a single post here or on diyaudio where someone suggests these two ultra low noise/distortion amps sound indistinguishable.    
  
 My sense is that perceived differences may have a few different sources:
  
 (i) Different active devices (e.g. op amps, to say nothing of tubes) _do_ seem impart subtle differences to sound quality, and I imagine this is further complicated by the fact some of these semi-conductors have fet vs. bipolar inputs.  Think about the fact that certain diy amps (e.g. the dynahi/dynafet and differing fet vs. bjt revisions of the ehh rev. A) were created based on this theory - that these transistor types have different flavors.  So by replacing my output chips with the booster board circuit, and also my gain stage chip with dual LME49990's, I think it is unsurprising that I would hear subtle but discernible differences - although I still do intend to build another stock o2 to compare back to back.  Making matters even more interesting, agdr's bom offers up several different chips that can be used in place of the OPA140's on the booster.  Some are fet inputs, and some are bjt's, and they all have differing impacts on noise, distortion and dc offset.  So there's also the potential to build and compare different versions of the booster circuit and see if we can hear any differences.
  
 (ii) The serious reduction in dc offset on the headphone jack may also play in.  I used to think of dc offset simply in terms of not damaging the headphones, but as tangent and others explain it, minor dc on your jack also reduces dynamic range and possibly causes its own distortion.  The booster is a 150x reduction in dc offset from stock.
  
 (iii) Some argue slew is inaudible above and beyond what the stock O2 can swing.  Others claim to love the 4 channel B22 because of its gargantuan ~170 something V/us slew rate, if memory serves.  Raising slew from the stock 3V/us to 20V/us with the LME49990's can't hurt.
  
 (iv) Doubling current output on peaks compared to the stock O2 can only benefit transient response. 
  
 All in all, to the best of my understanding, the booster is pretty awesome on paper, and my ears seem to like it a lot as well.  That said, if I'm off on any of the above - please jump in and correct me!


----------



## GoldenboyXD

Just a noob question: 
	

	
	
		
		

		
			




  
 Will you be able to use the O2 without the batteries inside and just using the PS adaptor?


----------



## adydula

Yes the O2 can jut run on batteries...inside with the ac adapter unplugged...
  
 Ptom...."Coldplay/Adele: Greatest Hits sound distractingly harsh with respect to the treble"
  
 I humbly suggest that these sources are not even close to being the best in judging what the O2 is capable of doing...there are many other much higher quality choices to show what the O2 and other amps can do.
  
 I really like Adele but the recordings that are out there IMO are not very well done...its sad but it is what it is.
  
 I have many well recorded uncompressed and well mastered recordings that make me smile all the time with the O2 and other good amps....like the V800.
  
 Good amps wont make ho-hum material sound better....and not so good amps or tube amps with distortion can help reduce certain frequency response making some material sound less harsh...but this is not the O2's fault.
  
 Garbage in Garbage out..
  
 When I listen to something that sounds like crap to me I always go back to my gold standards to make sure nothing else has changed.
  
 A.


----------



## GoldenboyXD

How about the other way around? Using only the AC adapter without the batteries? I plan to use this on my PC and i don't want to worry about the batteries inside.


----------



## adydula

Yup that works too.... I run one that way with my PC.
  
 A.


----------



## GoldenboyXD

Thanks! 
	

	
	
		
		

		
		
	


	




 I appreciate it.


----------



## Xenophon

skeptic said:


> A good question indeed.  Even though distortion measurements started off, and then were reduced further, below the what is often considered the threshold of audibility, my understanding is that different "measurement first" designs and topologies are still often (if not usually) perceived as sounding different [for reasons beyond my understanding and pay grade].  For example, I've read a lot of posts here and elsewhere regarding both the O2 and the Wire.  It could be the product of confirmation bias, but I have yet to see a single post here or on diyaudio where someone suggests these two ultra low noise/distortion amps sound indistinguishable.
> 
> My sense is that perceived differences may have a few different sources:
> 
> ...


 
 Thanks for a well considered reply, it made for interesting reading.  Fwiw, I'm no electronics specialist by a long shot but I do agree with your observations about differently sounding OPA's and the complex -and mostly unpredictable- result of many small variances interacting.  Very interesting remarks about the slew rate, a couple of months ago I observed (don't recall if in this or another thread) that the slew rates the O2 could handle were imo marginal and almost got crucified for it 
	

	
	
		
		

		
		
	


	




.
  
 My main point all along has been that perhaps there's more between heaven and earth than what's readily measurable.  I tend to shy away from both the absolute subjectivists -who tend to be good at burning other people's cash- as well as scope wielding objectivists for whom there's only 1 path to follow and where any deviation from the true religion is considered a capital offence.  Fanatics on both sides......
  
 The booster board as well as agdr's overhauled and assembled product look very interesting, I'm sorely tempted to give one of them a try and compare with the ODAC/O2 sitting on my desk and feeding my HE-500 right now.  But don't want to be stuck soldering a bagful of tiny components and at the price of the finished product I'd be about halfway down a B22-build or 2/3 down a F5-clone.  But it sure takes up less desk space and (especially compared to the F5) one can run it without heating up the entire office.


----------



## anthk

xenophon said:


> Thanks for a well considered reply, it made for interesting reading.  Fwiw, I'm no electronics specialist by a long shot but I do agree with your observations about differently sounding OPA's and the complex -and mostly unpredictable- result of many small variances interacting.  Very interesting remarks about the slew rate, a couple of months ago I observed (don't recall if in this or another thread) that the slew rates the O2 could handle were imo marginal and almost got crucified for it
> 
> 
> 
> ...


 

 What does higher slew rate translate into sound? Faster... response?


----------



## Xenophon

Faster tracking and better response in (leading) transients, especially at higher frequencies.  That's what I could make of it at the time anyway.  But it's a complicated story and many factors (power supply, caps..) come into play, perhaps skeptic can provide a better answer as I'm pretty sure he's a lot more proficient in this stuff than I am..
  
 Dug up a link for you:
  
 http://www.onmyphd.com/?p=slew.rate


----------



## anthk

xenophon said:


> Faster tracking and better response in (leading) transients, especially at higher frequencies.  That's what I could make of it at the time anyway.  But it's a complicated story and many factors (power supply, caps..) come into play, perhaps skeptic can provide a better answer as I'm pretty sure he's a lot more proficient in this stuff than I am..
> 
> Dug up a link for you:
> 
> http://www.onmyphd.com/?p=slew.rate


 

 what i gathered from your link is that, if the SR is above a certain value, it doesn't do anything for the signal. Hence the question, what is enough?
 O2 designer quote 0.2 uV/ Vrms, though I have no way of verifying it, nor the knowledge to


----------



## jring

anthk said:


> what i gathered from your link is that, if the SR is above a certain value, it doesn't do anything for the signal. Hence the question, what is enough?
> O2 designer quote 0.2 uV/ Vrms, though I have no way of verifying it, nor the knowledge to


 
  
 Hi,
  
 you might want to google "o2 op amp measurements slew rate", choose the first result and search for slew rate. This is the designers thoughts on this - his results are 0.9V/microsecond for 44kHz material, 1.8V/microsecond for 96kHz and 3.6V/microsecond for 192kHz. He comes to this result by assuming that the amp must be able to deliver +10V at point t0 for one sample and -10V at point t0+T for the next one. So you get Vpp/(1/fSample) or 20V/(1/44kHz)) or 20V/22microseconds = 0.9V/microsecond - rinse and repeat for the other sample rates.
  
 O2 at 3V/microsecond meets all but the last and this is kinda irrelevant because this would mean you were "listening" to signal close to 100kHz at 0dB - not sure what this will do to the rest of your chain including your ears, though.
  
 TLDR: The slew rate of O2 at 3V/microsecond is sufficient for audio at sample rates up to 192kHz.
  
 Joachim


----------



## SilverEars

Just got the HE-6.  This thing is rediculously hard to drive.  I have 2 channel Beta though, I guess 4 channel is warrented with these.  As for O2, I will not even try it.


----------



## adydula

Yup they are very inefficient for sure.....get out your checkbook.....
  
 A.


----------



## Xenophon

silverears said:


> Just got the HE-6.  This thing is rediculously hard to drive.  I have 2 channel Beta though, I guess 4 channel is warrented with these.  As for O2, I will not even try it.


 
 They're exceedingly hard to drive well, which is why I urge anyone considering a purchase to think it over and know what they're getting into in terms of amplification cost / total system cost.  These are not a casual purchase.
  
 That being said, they do sound absolutely glorious once you get it right.  With the right amplification imo nothing except perhaps the really high end electrostats driven by an equally high end amp stage come close.  But then you're looking a a budget the size of a small car.  Your B22 has the juice though, certainly if you run the HE-6 balanced.
  
 Enjoy and keep us posted!


----------



## SilverEars

I know my 2 channel has enough juice since I can have it output at a comfortable volume and also at a level where I can hear the dynamics and the details, but I think it's rediculous how much close to max volume I must rotate, and even at max, it's not blasting loud.  
  
 Reason why I think my Beta 22 drives it to potential is because it is very clear sounding, sound is tight and treble extension is there.  Vocals are rediculous!!!!!!!!!!!!!!
  
 Something interesting I discovered is that, just because it gets loud doesn't mean the dynamics are there.  Sure, on paper it give you a value at certain output level, but is the dynamics there?
  
 What I discovered is that with the hard to drive headphones like the HE-6, It's plenty loud at middle point, but audibly when I turn it up it doesn't get that much louder, but I hear more dynamics.  For example, you guys notice weak amps do not push the bass for bigger cans?  This probably cannot be measured, but has to be experienced, just like difference in sound of the solid-state amps that are flat and have less than audible distortions(how do you tell them apart besides your ears?).  
  
 I have to conclude that just because it provide loud volume, does it mean it has enough juice to bring out the headphones to full potential?  I don't think numbers and the experience are consistant.
  
 Have you guys had that?  As you turn the volume it's linear to a certain point then it decays?


----------



## Xenophon

What I've experienced personally though it appears to fly into the face of conventional engineering and powering specs is that loudness in fact doesn't equate to good performance over the frequency range.
  
 With dynamic headphones of high impedance and in marginal cases (just sufficient power) this is to be expected as typically impedance will fluctuate wildly (look at the T1 figures for instance) and this could cause 'local frequency' under powering so to speak.  However, I've also found this to be the case with the HE-6, which is a planar that presents ruler-flat impedance over the entire band.  You can be in a situation of sufficient volume, yet be faced with week, booming bass and thin, brittle treble.  Yet when coupled to a more powerful amp and at the same volume, these issues go away.
  
 Don't ask me to explain, it's one of those cases where the figures don't match with reality as I perceive it.


----------



## headwhacker

xenophon said:


> What I've experienced personally though it appears to fly into the face of conventional engineering and powering specs is that loudness in fact doesn't equate to good performance over the frequency range.
> 
> 
> 
> ...



 


With Dynamic driver headphones like the T1 which the load impedance swings wildly at different frequencies, it is understandable to think that it requires a powerful amp with lots of reseved power. But a very efficient and easy to drive can at the same time (102 dBSPL/1mW), I think also compensate for the varying load impedance.

I've been using T1 with portable amps UHA-6SMKII including O2 and plugged it in directly into a DAP (DX90) and so far I can't find any track which I can discern any noticeable distortion nor weakness is bass weight and impact. The treble details sounds comparable to my ears as well regardless of the amp I use. (Hifi-M8, O2, DX90). Of course the powerful amp supply the loudest volume. but my point is at similar volume level, the T1 sounded pretty much the same without any hint of distortion or shifting in frequency response.


----------



## PTom

headwhacker said:


> With Dynamic driver headphones like the T1 which the load impedance swings wildly at different frequencies, it is understandable to think that it requires a powerful amp with lots of reseved power. But a very efficient and easy to drive can at the same time (102 dBSPL/1mW), I think also compensate for the varying load impedance.
> 
> I've been using T1 with portable amps UHA-6SMKII including O2 and plugged it in directly into a DAP (DX90) and so far I can't find any track which I can discern any noticeable distortion nor weakness is bass weight and impact. The treble details sounds comparable to my ears as well regardless of the amp I use. (Hifi-M8, O2, DX90). Of course the powerful amp supply the loudest volume. but my point is at similar volume level, the T1 sounded pretty much the same without any hint of distortion or shifting in frequency response.


 
 Do you think the T1 sounds sibilant/piercing with the O2? I use the T1 with the O2/ODAC and I don't like the combination much. I haven't tried the T1 with any other amp but with the O2/ODAC, I found the highs deeply flawed.


----------



## headwhacker

I don't have the ODAC, but O2 with my DX50 as source, I don't find T1 piercing, but yet it's a bit sibilant on some female vocals (Norah Jones) but it's not as bad as the sibilance I hear on my JH16.


----------



## Xenophon

Think it's not so much a question of amps as of the Beyerdynamic sound signature that you either like or don't.  I owned the DT-880's and though they were good value overall, never liked the treble. Not on my ODAC/O2, not on my V800/V200.  Thought it was model-specific but when I auditioned the T1 I found the same thing (of course in general they're a different kettle of fish vs the 880's).  I'm sure they're good headphones, just not to my personal taste.


----------



## PTom

I guess that's what people mean when they talk of synergy. Some headphones are great but flawed in some aspects and need equipment that enhances its strengths and negates its weaknesses to be truly great.


----------



## PTom

In the objective vs subjective debate I'm starting to think that both sides are right. The O2 might well be the 'perfect' amplifier if all you need is amplification, however you might not end up with a 'perfect' sounding system unless it complements your headphones.


----------



## Solrighal

One of the things I like about the O2 is that it offers me a constant, something which allows me to instantly judge a headphones sound signature. Everything else is a variable.


----------



## James-uk

solrighal said:


> One of the things I like about the O2 is that it offers me a constant, something which allows me to instantly judge a headphones sound signature. Everything else is a variable.


 
This.


----------



## PTom

solrighal said:


> One of the things I like about the O2 is that it offers me a constant, something which allows me to instantly judge a headphones sound signature. Everything else is a variable.


 
 Personally I would prefer a system i.e. DAC+amp+headphone that sounds good to me. The *ability *to judge a headphone (i.e. one component of the system) does not give me much pleasure. After all isn't this hobby about enjoying music?


----------



## Solrighal

ptom said:


> Personally I would prefer a system i.e. DAC+amp+headphone that sounds good to me. The *ability* to judge a headphone (i.e. one component of the system) does not give me much pleasure. After all isn't this hobby about enjoying music?




Of course it's about enjoying music but I am not a rich man. Removing one variable simply increases my chance of finding contentment.


----------



## PTom

I know what you mean. Settling on one amp possibly narrows down the list of suitable headphones for your tastes. However that might not necessarily result in the best sound quality or value for money just simplicity (or lack of choice depending on how you want to look at it).
  
 I thought headphones were more important for SQ than amps? If that is the case it might be better to decide on a headphone and then find out from current owners which amps go well with it.
  
 I used to be in awe of the O2 till I actually owned/heard it, now I'm a believer of systems and synergy.


----------



## Solrighal

Even at the level I'm at this is pure indulgence but when I got my ODAC/O2 and plugged them in I was blown away. I've never heard music as beautifully as I'm hearing it now with the HD650's. 

This will not be my last amp however. I intend to buy something with valves to emphasize the smoothness of the Sennheiser's, maybe a Schiit Lyr. I'd really like a Crack+SB but it's kinda out of my reach and I think the Lyr may prove useful to a wider range of headphones. 

I would say headphones are more important for sound signature but "quality" to my mind is not exactly the same thing. Headphones are more about presentation whereas the amp only really has to provide a clean original signal.


----------



## r010159

ptom said:


> In the objective vs subjective debate I'm starting to think that both sides are right. The O2 might well be the 'perfect' amplifier if all you need is amplification, however you might not end up with a 'perfect' sounding system unless it complements your headphones.


 
  
 I agree with this.


----------



## MrMateoHead

***Delete


----------



## SilverEars

LOL.  O2 drives the HE-6 to loud volumes, just like the LCD-2.  There is no question O2 can drive HE-6 to listenable volume and louder.  
  
 I don't know what it is in the Amp design would account for the better sound.  It is obvious that HE-6 sound better on the Beta 22.  Is it the THD, or flat FR, or the SPL or output impedance?  If you look at these numbers, they are well below the value that is audible compared to what is caused by the headphones.  Low quality amp can measure just as well as the best sounding amps.  Measurements are measurements.


----------



## MaciekN

I remember a post from O2 thread at diyaudio where the deisgner of The Wire said he could easily tell his amp apart from O2 with HE-6. The reponse was that O2 was not designed to drive such inefficient and power hungry headphones - that these were simply the 1 or 2% that need a more capable amp.
  
 By the way you may have noticed my General Headphone Amplifier Survey thread but just to be sure I am posting it here as well. I am doing a case study on what poeple expect a good amplifier to have and what are the qualities of amps that poeple here hold most important and I would really appreciate some feedback from those who have the O2.
  
 Survey link: https://www.surveymonkey.com/s/773TTR3


----------



## Solrighal

Survey completed.


----------



## MaciekN

Thank you, much appreciated.


----------



## gikigill

Survey done.


----------



## r010159

Survey done.


----------



## skeptic

xenophon said:


> Thanks for a well considered reply, it made for interesting reading.  Fwiw, I'm no electronics specialist by a long shot but I do agree with your observations about differently sounding OPA's and the complex -and mostly unpredictable- result of many small variances interacting.  Very interesting remarks about the slew rate, a couple of months ago I observed (don't recall if in this or another thread) that the slew rates the O2 could handle were imo marginal and almost got crucified for it
> 
> 
> 
> ...


 
  
 Thanks for the thoughtful response Xenophon.  I love your humorous characterization of the hard core subjectivist vs. objectivist factional dispute!  Also, I tend to agree that the standard array of audio measurements just don't seem to paint a complete picture of everything that we seem able to perceive.  It should be fascinating to see what audio measurements look like 30 years from now.    
  
 Per the thread on diyaudio, I think the earlier discussion of slew rate in this thread was what led agdr to suggest, test and ultimately recommend the substitution of dual LME49990's in the boosted O2 gain stage.  So thanks for your role in that!
  
 As far as pricing goes though, I'm pretty sure I paid well under $100 total for the booster board, all its component parts (including the optional led's, extra zener, etc.) and the dual LME49990 adaptor (populated), from ebay.  That'll barely buy you a cheap imported chassis for a B22 or F5 build!  I'd encourage you to give it a go since it really does make for an excellent compact/bedside rig.  The booster was my first real smd project (aside from the op amps on my mini3), and as agdr commented to me, the 1206 sized smd components used on the booster really are a lot more humane than the ultra-tiny 0805's used on the Wire.  Just wipe a dab of solder onto one pad or the other.  Then pick up the component with your tweasers and set it on the board right up against the edge of the pre-tinned pad.  Then apply a little heat to the pretinned pad while sliding the component into position, effectively soldering that first side.  Then solder the other side just like you would with anything else.  Add a little more solder to the first side if need be.  It really is arguably faster and easier than through-hole once you've done a few.  Seeing the faint lines defining the orientation of the diodes was the hardest part!  I used a little chipquik paste flux for the op amps but found that I didn't really need it for the other components (was using rosincore cardas quad solder).


----------



## Currawong

I was talking to Tyll a while back and one measurement that isn't easily done without horrendously expensive equipment is Transient IMD.


----------



## miceblue

currawong said:


> I was talking to Tyll a while back and one measurement that isn't easily done without horrendously expensive equipment is Transient IMD.



Speaking of Tyll, it was interesting to see that the O2 wasn't listed in his "Wall of Fame" for amplifiers even though it measures quite well and was comparable to the Pico Slim (I think?), which wasn't in the list either.


----------



## Currawong

miceblue said:


> currawong said:
> 
> 
> > I was talking to Tyll a while back and one measurement that isn't easily done without horrendously expensive equipment is Transient IMD.
> ...


 
  
 IIRC the Pico Power measured better (and is under $500, which was nwavguy's challenge, wasn't it?). The Pico Slim has some noise from the volume chip.


----------



## skeptic

currawong said:


> I was talking to Tyll a while back and one measurement that isn't easily done without horrendously expensive equipment is Transient IMD.




Interesting! Thanks for sharing this Currawong! I looked it up and found the following summary explanation: 

"There is also transient intermodulation distortion (TIM) to which modern integrated circuits are susceptible. Such circuits depend upon feedback for their linearity, but time delays in the feedback can cause intermodulation distortion on fast transients in the signal."

So I wonder, if this arises based on time domain issues in feedback amps (all op amps require feedback to operate in a linear mode, for example) - does that mean this type of distortion isn't present at all in nonfeedback SET amps? 

If so, here's hoping that the TIM measurement process and equipment become cheaper and more widespread over time.


----------



## MaciekN

gikigill said:


> Survey done.


 
  
  


r010159 said:


> Survey done.


 

 Thanks!


----------



## James-uk

maciekn said:


> I remember a post from O2 thread at diyaudio where the deisgner of The Wire said he could easily tell his amp apart from O2 with HE-6. The reponse was that O2 was not designed to drive such inefficient and power hungry headphones - that these were simply the 1 or 2% that need a more capable amp.
> 
> By the way you may have noticed my General Headphone Amplifier Survey thread but just to be sure I am posting it here as well. I am doing a case study on what poeple expect a good amplifier to have and what are the qualities of amps that poeple here hold most important and I would really appreciate some feedback from those who have the O2.
> 
> Survey link: https://www.surveymonkey.com/s/773TTR3




Done.


----------



## adydula

Yes,
  
 But all music is not the same, there is a lot of stuff out there that sounds like crap when used with decent transparent electronics...
  
 I find Adele's recording very offensive in that department especially sibiliant to me...terrible high end...
  
 Imagine having separate cans, amps to make your recording sound good to you....
  
 I like the O2 and ODAC for a good rational base that presents all music equally....good stuff sounds good, bad stuff sounds bad...I look
 for good and great recordings...even the same material remastered and be better or worse thatn the originals etc...
  
 If you find a set of cans that work well with good material that is a marriage made in heaven.....
  
 It looks like some of you seem to have this with your HE6's and B22's...that's great but that setup costs apprecialbly more
 than a O2 amp setup.
  
 But like you say its a hobby and your bucks!
  
 Alex


----------



## Xenophon

Alex,
  
 I agree 100% with your philosophy, for me also, to the max extent possible any colouring should come from the headphone (or EQ'ing) with the rest of the chain as transparent/neutral as possible.  That's what I tell my wife when she asks me why on earth 
  own 3 headphones 
	

	
	
		
		

		
			





  Those are words quickly uttered but fact is, many people prefer a coloured rendition, at least in the short run.  With classical music I'm fortunate in the sense that most present day recordings are high-quality.  Been reading up on diyaudio about agdr's new design...fascinating stuff (though I personally think he went a bit overboard with the bass boost thing) but assembly seems anything but simple.  And there's the matter of the AC output wall wart for EU users.... but good luck putting it together.


----------



## Solrighal

I've bought more albums from Amazon since getting the 650's a month ago than I have in the previous year. That should say something.


----------



## Whitecitadel

solrighal said:


> I've bought more albums from Amazon since getting the 650's a month ago than I have in the previous year. That should say something.


 
  
 You have a free Amazon prime trial? 
	

	
	
		
		

		
		
	


	






  
 Actually just wanted to post to share my good news:
 Quote Deutsche Post AG: 





> Die Sendung wurde am 25.04.2014 im internationalen Logistikzentrum Frankfurt zur Weiterbeförderung nach Großbritannien übergeben.


 
 Which even with my rudimentary understanding of German means my o2 kit and odac are in Frankfurt on their way to the UK 
	

	
	
		
		

		
		
	


	



  
 Great service from Stefan at Head'n'HiFi, especially when I wanted to add something to my order at the last minute!


----------



## Solrighal

I bought from Stefan & Walter too. You won't be disappointed.


----------



## Currawong

skeptic said:


> currawong said:
> 
> 
> > I was talking to Tyll a while back and one measurement that isn't easily done without horrendously expensive equipment is Transient IMD.
> ...


 
  
 I think this may be it and why regular measurements may not pick up on some of the distortion we hear during music playback.  For me a SET amp is a trade-off -- a better response in exchange for a bit of harmonic distortion (and in my case, a lot of mucking about with tube rolling). That may be one of the reasons why non-feedback amps, such as SET amps, have a better reputation with listeners, as do Nelson Pass' amps. 
  
 A parallel example for me is what happens with planar headphones and phase distortion. Even if a pair of headphones has a flat phase response (ie: using regular measurements doesn't appear to have phase distortion) in the area between the diaphragm and the ear their can still be a small amount of audible phase cancellation during music playback, which is why Audeze created the Fazer system. Consequently, the audible effect is that instrument position seems more precise with the LCD-X and XC than with their previous models.


----------



## adydula

Xenophon,
  
 I went thru many sets of headphones, bought and sold....finally settled on a few (4) right now!! That suit me just fine.
  
 Been thru the tube amps and rolling.....gosh what a ton on bucks went down that hole....LOL
  
 The ODA bass boost in my build will be left out.
  
 The bass boost that is in it is only a 3db boost on the low end.
  
 I might add it later just to see etc. But I kind of doubt it.
  
 There are a lot of "improvements" that can be used or not depending on what you want in the end.
  
 I have started soldering today and am posting pix on DIYAUDIO's site..
  
 All the best
 Alex


----------



## Solrighal

I've found another benefit of using the O2. Whenever I make EQ changes in JRiver I can be absolutely sure that what my ears are hearing is the *result* of that change, and not some unforeseen interaction between a coloured amp & - by definition - a coloured source.

So for instance I seem to have stumbled upon my headphone Holy Grail, the Sennheiser HD 650. The signature is almost perfect to my ears. Almost. And the only way I know this for sure is because I'm using perfectly transparent amplification. 

Feelin' the love?


----------



## anthk

solrighal said:


> I've found another benefit of using the O2. Whenever I make EQ changes in JRiver I can be absolutely sure that what my ears are hearing is the *result* of that change, and not some unforeseen interaction between a coloured amp & - by definition - a coloured source.
> 
> So for instance I seem to have stumbled upon my headphone Holy Grail, the Sennheiser HD 650. The signature is almost perfect to my ears. Almost. And the only way I know this for sure is because I'm using perfectly transparent amplification.
> 
> Feelin' the love?


 

 I'm  a bit torn between buying a HD600 or HD650. I think I might go after hd600 since I usually listen to metal or similar genres...


----------



## adydula

Zorrofox....agree 100000%.
  
 The hd650's are a very nice set of headphones...I have a set of Beyer 1350's and T90's that are my favorites...
  
 I haven not had the pleasure of listening to hd650's but will someday!!
  
 Alex


----------



## James-uk

anthk said:


> I'm  a bit torn between buying a HD600 or HD650. I think I might go after hd600 since I usually listen to metal or similar genres...



I have both and hd800. For me personally the 600s win out over 650. The 600s have a bigger soundstage and better imaging. They are also more accurate in tone to my ears too. The 650s just have a little to much bass which takes away from the rest of the spectrum and closes in the soundstage to my ears/brain. I currently give 50/50 head time to hd600/800 and the 650s are getting none . I will be selling them soon because they are pretty much in new condition so would be a waste to leave them collecting dust . I love the sound of the 650s btw but I just love the 600s that little bit more. I actually think the hd600s balance is more natural and realistic than the 800s and if I could get some sort of hd800/600 hybrid I would be in heaven and would probably never need another pair of headphones.


----------



## Xenophon

The above just shows that in the end it's all about personal taste.  I started out with a pair of BD DT-880's in 600 Ohm.  Overall very good cans for the price but I just didn't like their treble presentation.  Assumed it was the model but after some listening to other models up to the T1, I concluded it was to a large extent the BD 'house sound' that wasn't for me.  For they time being I found my nirvana between the HE-500, HD-800 and the headphone that for me is the person king of the universe, the HE-6.  But obviously I haven't heard all cans under the sun.  Am curious (but fearful) to try the SR-009 and I suspect that for my music the AKG Q-701 might be worth giving a spin.  Only trouble is that my dear wife insists that one pair of cans coming in = another pair going out.


----------



## Solrighal

adydula said:


> Zorrofox....agree 100000%.
> 
> The hd650's are a very nice set of headphones...I have a set of Beyer 1350's and T90's that are my favorites...
> 
> ...




I can't get enough of them. I've just passed the 200 hour mark with the Senn's, 90% of that with my ODAC/O2 and they sound wonderful! I hear people say the 650's pair very well with certain valve amps but I'll be damned before I feel as though anything's missing right now.


----------



## headwhacker

solrighal said:


> I can't get enough of them. I've just passed the 200 hour mark with the Senn's, 90% of that with my ODAC/O2 and they sound wonderful! I hear people say the 650's pair very well with certain valve amps but I'll be damned before I feel as though anything's missing right now.


 
  
 A lot of people who like valve/tube amps will say the same for most headphones not just the HD650. I for one don't want extra harmonics or "pleasant distortion" added to the original music.


----------



## tralalakuda

Hi guys,
  
 I currently already have a Modi/Magni and planning to offload my Magni so that I can couple my Modi with Asgard 2 with its capability of having RCA pre-amp output for desktop monitoring speaker as one of the feature I like. However I come across this O2/ODAC Limited Edition which says that the RCA jack on the backside of product can also be used as DAC output (presumably the same use as Asgard 2's pre-amp output?). I'm wondering if it's worth to take this O2/ODAC Limited Edition combo better than getting an Asgard 2?
  
 I read a lot of positive reviews about O2/ODAC combo however having use Modi/Magni, I'd say that Schiit really make a good product and I believe that their flagship Asgard 2 will not disappoint me, nevertheless I come across a few review saying that Asgard 2 is definitely good but not good enough (depending on how you phrase that, I saw this quite a few times in a few websites and reviews).
  
 Just for information I'm currently using HD650 as my cans.
  
 Thanks!


----------



## anthk

Got a pair of hd600  to go with the combo today.
 I listen mostly to metal music. Even with their ridiculously compressed albums, the songs benefits from the neutrality around the vocal range of the HP and better instrument separation. (Oh, and bass extension balah blah).
 I have some nicely recorded orchestra music around and the headphone shines with those tracks.
 Shame that the metal tracks arent properly mastered.


----------



## Xenophon

anthk said:


> Got a pair of hd600  to go with the combo today.
> I listen mostly to metal music. Even with their ridiculously compressed albums, the songs benefits from the neutrality around the vocal range of the HP and better instrument separation. (Oh, and bass extension balah blah).
> I have some nicely recorded orchestra music around and the headphone shines with those tracks.
> Shame that the metal tracks arent properly mastered.


 
 Tell you the truth, I wonder why pop/metal etc are in such a dire situation and why it's systematically recorded  so loud and compressed  to the extreme so that dynamic range gets reduced to a fraction of what it could be.  Thank God that nowadays classical music is usually very nicely mastered, at least if you shy away from the compilations.  And of course the really old re-editions, just listened to a '30s recording of the Berliner Philharmoniker....recorded in mono on a 78 rpm record, now available on CD.  Magnificent but not with the HD-800.  Labels such as BIS, Harmonia Mundi....really top quality.  Never heard the HD 600 but it sounds like the 800's little brother, perhaps a bit more benign (not a bad thing).


----------



## anthk

xenophon said:


> Tell you the truth, I wonder why pop/metal etc are in such a dire situation and why it's systematically recorded  so loud and compressed  to the extreme so that dynamic range gets reduced to a fraction of what it could be.  Thank God that nowadays classical music is usually very nicely mastered, at least if you shy away from the compilations.  And of course the really old re-editions, just listened to a '30s recording of the Berliner Philharmoniker....recorded in mono on a 78 rpm record, now available on CD.  Magnificent but not with the HD-800.  Labels such as BIS, Harmonia Mundi....really top quality.  Never heard the HD 600 but it sounds like the 800's little brother, perhaps a bit more benign (not a bad thing).


 

 It is such a shame.
 Might be those punks who put big ass radios on their bikes are to be blamed...(just kidding)


----------



## Solrighal

I've got a question. When I bought my O2 I opted for gains of 1x/3x on the advice of a kind forum member. These gains work superbly with every pair of headphones I've tried. In fact, I've never had to use 3x gain, even with my HD 650's or my Q701's. 

So why are the "standard" gains always 2.5x/6x? It looks like overkill to me. 

If I listen to Rammstein as loud as I can take it (and far louder than I need it) the volume will be around the 4 o'clock position with the HD650's. Using the M -100's I'd be lucky to need to go past 1 o'clock.

So why do they use 2.5x as the low gain standard? I also seem to remember reading years ago that it's better to use more of the volume range (or something, I can't remember).


----------



## headwhacker

To cover as many source voltages out there.


----------



## adydula

Zorrofox your not the only person that has asked this question, even agdr thought it was too much for his use..even with 1x or unity gain.
  
 That said the designer has said:
  
 The O2 has 2 gain settings to help match it to different sources and headphones The default low gain setting for the O2 is ~2.5X (~8 dB) for use with typical headphones and/or high output home sources. And at the high gain setting it’s ~6.5X (~16 dB) for low output sources or high impedance headphones needing lots of voltage.
  
 There are several ways to change the gain in the o2 via resistor swapouts and or removal and voltage divider schemes.
  
 I have two O2's one with 1x and 2.5 the other with 2.5 and 6.5...never ever use the 6.5.
  
 The ODA that agdr has designed has a default gains selection of 1/2x, 1x, 2x and 3x with the default 1K attenuation resistors. It has a gain switch as well. You can also modify the 4 settings to 6 gain setting with and external switch if desired.
  
 It all depends on your cans, what the impedance is etc...low? high? etc
  
 Take a read at the designers site about voltage and again....its very informative..
  
 Alex


----------



## mcandmar

The 6x gain was intended for low power battery sources, things like the iPod Shuffle than outputs less than 1v rms, i.e. half of a normal consumer level device.  1x is fine for a majority of 32ohm cans with reasonable sensitivity from a redbook level source ~2v.  For higher loads like the 300ohm HD650's ~2.5x gain is the optimum.


----------



## Solrighal

I confess I hadn't ever considered connecting a portable (battery) device to the O2. That males sense I guess. I'm not sure if there's too many people using it in this way though.


----------



## hekeli

Well people even carry "portable" tube amps and $2k phones around so... I'm happy with my phone or laptop, I don't think I'm an that "audiophile" by far even though I appreciate good sound at home..


----------



## Solrighal

hekeli said:


> Well people even carry "portable" tube amps and $2k phones around so... I'm happy with my phone or laptop, I don't think I'm an that "audiophile" by far even though I appreciate good sound at home..




And some people eat their toe nails.


----------



## Whitecitadel

adydula said:


> I have started soldering today and am posting pix on DIYAUDIO's site..
> 
> All the best
> Alex


 
 Do you have link to thread? (PM if not allowed on forum?) will be starting mine soon...
  


solrighal said:


> I confess I hadn't ever considered connecting a portable (battery) device to the O2. That males sense I guess. I'm not sure if there's too many people using it in this way though.


 
 Its not just a portable battery power device, its the o2 running on battery as well, my understanding from the designers site is that 6.5x is there for low voltage inputs when running on battery (EDIT: Running o2 on battery I mean). A red book standard device with 2v output like the odac on a desktop PSU is going to be nowhere near needing that kind of gain is my understanding.
  
 Just impulse bought new temperature controlled soldering iron (£30/Maplin in sale, digital version of far east one the designer recommended) as the ones I have are all a bit overkill for delicate PCB work - shame I probably won't have time to assemble before the holiday weekend coming up in the UK.


----------



## Xenophon

whitecitadel said:


> Do you have link to thread? (PM if not allowed on forum?) will be starting mine soon...
> 
> Its not just a portable battery power device, its the o2 running on battery as well, my understanding from the designers site is that 6.5x is there for low voltage inputs when running on battery (EDIT: Running o2 on battery I mean). A red book standard device with 2v output like the odac on a desktop PSU is going to be nowhere near needing that kind of gain is my understanding.
> 
> Just impulse bought new temperature controlled soldering iron (£30/Maplin in sale, digital version of far east one the designer recommended) as the ones I have are all a bit overkill for delicate PCB work - shame I probably won't have time to assemble before the holiday weekend coming up in the UK.


 
 Here ya go, i'm following this one too....
  
 http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda-36.html


----------



## Whitecitadel

Just came back from lunch and building security had my package from Stefan! 
	

	
	
		
		

		
		
	


	



  
 Read the o2 ODA thread - interesting. Did you mean to include a link to your separate build thread Xenophone?


----------



## mcandmar

whitecitadel said:


> Its not just a portable battery power device, its the o2 running on battery as well, my understanding from the designers site is that 6.5x is there for low voltage inputs when running on battery (EDIT: Running o2 on battery I mean). A red book standard device with 2v output like the odac on a desktop PSU is going to be nowhere near needing that kind of gain is my understanding.


 
   
O2 running on batterys has nothing to do with it, it does however create another problem where the max voltage swing on the outputs is reduced which you may run into with power hungry headphones like the HD600 series.  If anything you are forced to use a lower gain setting when running on batterys.


----------



## Xenophon

whitecitadel said:


> Just came back from lunch and building security had my package from Stefan!
> 
> 
> 
> ...


 
 If and when I get around to it, I'll certainly do so.  But not now, don't have the time at present while my job keeps me in India.  I have a vision of me hopping from business hotel to business hotel lugging along a soldering station, cutters, pliers and a bagful of tiny components to keep me occupied at night   Hopefully I'll be able to stay in Europe for a couple of years starting next summer and then some serious electronics tinkering is certainly on the agenda.  For now I relegate myself to reading up on the design -really interesting as you know- and kowtowing to guys like Adyula who are courageous enough to play pioneer and debug things.


----------



## Whitecitadel

mcandmar said:


> O2 running on batterys has nothing to do with it, it does however create another problem where the max voltage swing on the outputs is reduced which you may run into with power hungry headphones like the HD600 series.  If anything you are forced to use a lower gain setting when running on batterys.


 
  
 Thanks for correction - too much late night reading and mixed issues there then.
  
 Considering adding LED to my odac (going in separate B2-080), seen diagrams to use the second signal ground and the pad near the coil - assuming the 10mA or so from the USB 5v rail is inconsequential to the performance of the ODAC? Anyone else using LED on their odac?
  
 Hands up that its partly as it will look smart under the o2, but also useful to indicate its powered up as my desk is a bit busy with stuff and its not always clear if something is not working as expected.


----------



## jseaber

whitecitadel said:


> Thanks for correction - too much late night reading and mixed issues there then.
> 
> Considering adding LED to my odac (going in separate B2-080), seen diagrams to use the second signal ground and the pad near the coil - assuming the 10mA or so from the USB 5v rail is inconsequential to the performance of the ODAC? Anyone else using LED on their odac?
> 
> Hands up that its partly as it will look smart under the o2, but also useful to indicate its powered up as my desk is a bit busy with stuff and its not always clear if something is not working as expected.


 
  
 Use a large resistor (20-30k) and high efficiency LED (5k-10k mcd). This will result in current consumption well below 1mA.


----------



## Whitecitadel

jseaber said:


> Use a large resistor (20-30k) and high efficiency LED (5k-10k mcd). This will result in current consumption well below 1mA.


 
 Thanks for tip!
  
 I had to order some thinner solder earlier (I mainly solder connectors usually, decided to get something a bit more delicate and easier to control for the o2/odac) so I already picked out a 3mm in red with integral resistor rated 8mcd a max If 10mA.
  
 I will test it on 5v PSU with DMM first to see what it pulls if not look for something high efficiency with large resistor as you suggest. I intentionally looked for low mcd LED as I didn't want to light the room with it, didn't think to get high efficiency with large resistor...
  
 By the way, really like the JDS o2 panel design with the symbols not lettering 
	

	
	
		
		

		
		
	


	




 sadly international shipping and UK import made it not a cost effective option for me.


----------



## adydula

My ODA is  coming right along. got most of the 1206 SMD resistors installed, not as bad as it looks but does take awhile and you have to have a steady hand and really know how to solder....
  
 I hope to have my 24 vac 1.8 amp adapter in tomorrow from Mouser and be able to apply power to check stage 1 of the power and relay action....
  
 There is a lot of discussion at DIY audio on options and new stuff that have come into being since the V2.0 of the ODA have come about...if your at all serious about this amp you should go over there and follow the thread...I don't want to post in several sites etc...most of my experience is over there under the headphone area and the ODA thread.
  
 Discussing voltage swings and gain and options...depending on what your cans are etc..
  
 Moving Right Along..
  
 Alex


----------



## Tequilasunriser

Looking forward to your ODA progress.


----------



## jring

solrighal said:


> I've got a question. When I bought my O2 I opted for gains of 1x/3x on the advice of a kind forum member. These gains work superbly with every pair of headphones I've tried. In fact, I've never had to use 3x gain, even with my HD 650's or my Q701's.
> 
> So why are the "standard" gains always 2.5x/6x? It looks like overkill to me.
> 
> ...


 
  
 Hi,
  
 1x/3x is the optimum when using the O2 with the ODAC only. The reason is that the ODACs 2V output as per redbook standard would overload the O2 input stage for higher gains even on AC power. Overloading the input stage results in clipping with terrible sound and a chance to fry your phones.
  
 You can calculate the max permissible gain by dividing the O2s max. output voltage of 7V on AC power or 4.5V on low batteries by the input voltage of your source. In case the O2 on AC power and the ODAC it's 7V / 2V = 3.5. Please note that turning down the O2 volume pot will not prevent it from clipping with excessive gain - only turning down the volume of the source works,but that means using the dreaded software volume for ODAC due to no hardware volume pot, which might or might not result in a loss of resolution depending on bit rate.
  
 Higher gain options are available since not all users use redbook compatible sources, especially mobile stuff tends to have max output voltages of less than half of redbook standard...
  
 Joachim


----------



## icc900

Helpful...Thanks for sharing.


----------



## r010159

Here is something that relates to the DAC. This has to do with integer mode which is the passing of audio information to the DAC. It looks like if integer mode is properly implemented, there should be no audible difference between it being off or on. This has to do with converting audio data from higher resolution format to that of lower resolution using dithering. Since the DAC supports using 24-bits internally, and players like J River are using 64-bit audio information internally, there will be no difference. The conversion should be trivial in this case. Even if DSP effects were being used in the player, the conversions between integer and float data should not lose information.

The only other reason for integer mode would be to address latency issues which involve the timing of audio information to the DAC. This is not a problem with audio players. Even if it was, the data is being buffered at the USB interface to the DAC anyways.

Apparently the push to implement integer mode with the various players is more for marketing purposes than for technical reasons. And if there is actually a difference, the software developer really screwed something up that is meant to be simple.


----------



## Whitecitadel

Well I got all the parts sorted and resistors on last night, took a while to get going with decent flow through to other side as my soldering is a bit rusty! Glad I bought a decent temp controlled iron in a sale recently with a small tip as the pads for the 1/8w resistors are quite small. Checked few online tutorials, think my theory is good need more practice - any tips welcome!
  
 Blog says 3x gain should be 750Ohm resistors as a pair, but head'n'hi-fi supplied 715Ohm as part of their gain resistor bundle (which was comprehensive covering all the blog gain options and more it seems) - these sound about right for 3x gain right?
  
 Calculation: 





> High Gain Ratio = 1 + R16/R19
> = 1 + 1500/715
> = 3.09x
> 
> ...


 
  
 Have left out R17/R21 for 1x gain on low.
  
 Surprised how long its taking to assemble, probably just me checking every component before installation and its properly in before I snip legs and move on. Suspect the caps will be quite fast to do, the IC sockets a bit fiddly, then just need to tackle the ESD sensitive bits - but I have grounded mat and wrist strap in a draw somewhere to take care of that.
  
 Fingers crossed it works on power up!


----------



## PTom

I had a question about the ODAC. How does the ES9023 chip objectively perform compared to the ES9018 chip? I know the latter is much more expensive and is used in high end DACs. Any thoughts?


----------



## Whitecitadel

ptom said:


> I had a question about the ODAC. How does the ES9023 chip objectively perform compared to the ES9018 chip? I know the latter is much more expensive and is used in high end DACs. Any thoughts?


 
  
 I can't say I have heard both, but if it helps the ODAC designer wrote on his blog in the comments for the post "odac-may-update":


> Ultimately, the ES9023 properly implemented, is an audibly transparent DAC. The window glass is completely clean. There are no perceptible flaws. It's not possible to get the glass perceptibly cleaner. While the ES9018 or ES9012 might even better measurements, I honestly don't believe they can improve on the sound quality when listening blind.


 
  
 HTH


----------



## miceblue

Speaking of "transparency," the O2 is supposed to be transparent compared to the DAC1 PRE. People make the claim that it's supposed to follow a "wire with gain" kind of model, but in recent listening tests I haven't found that to be the case.

MacBook Pro (X volume level) -> V-MODA Crossfade M-100
versus
MacBook Pro (X volume level) -> O2 (maximum on the volume knob, unity gain, AC powered) -> V-MODA Crossfade M-100

Were the theory of a "wire with gain" true, I should hear no difference between the above setups, no? I find the MacBook Pro's headphone out to sound much more coherent and transparent than through the double amping. Through the double amping, the bass becomes woolier and more bloated, and the treble subdued a bit. Instrument separation becomes more blurred and it just sounds less transparent to me.


----------



## adydula

Try that with any other amp.
  
 Try that with the vmoda driving the o2.
  
 The setup and conclusions your assuming are not correct at all.
  
  
  
 Whitecitadel...are your sure u need 3x gain? What cans are you going to drive?
  
 Alex


----------



## miceblue

adydula said:


> Try that with any other amp.
> 
> Try that with the vmoda driving the o2.



Well for one, I don't have another amplifier modeled after the "wire with gain" approach. Secondly, I don't have another amp with unity gain. Thus, any other test I do with another amp I have is not going to answer my questions.


----------



## anthk

miceblue said:


> Speaking of "transparency," the O2 is supposed to be transparent compared to the DAC1 PRE. People make the claim that it's supposed to follow a "wire with gain" kind of model, but in recent listening tests I haven't found that to be the case.
> 
> MacBook Pro (X volume level) -> V-MODA Crossfade M-100
> versus
> ...


 

http://apple.stackexchange.com/questions/57186/what-is-the-impedance-of-the-line-headphone-jack-on-macbook-pro-retina

 Impedence mismatch?


----------



## Solrighal

Can I ask a question of the gurus here? 

If I stack the ODAC & O2 does it matter what goes on top? I know there should be no interference but I thought I'd see if there's an accepted wisdom on this.


----------



## adydula

No one in there right mind would do this in the real world.
  
 But....with the volume control cranked up to max what do u think the maximum voltage RMS is ??
  
 What do you think the vmoda's input would be designed to handle?
  
 What happens if the latter amp is over driven or provided with distortion ?
  
 What happens if clipping is occurring?
  
 and yes how about impedance mismatching and all the above.
  
  
 I think I will stick my finger in a hot cup of coffee and see if it affects the taste???
  
 Sorry to be a bit condescending but this type if off the wall testing is probably better off in a thread about how to measure stuff etc....or a thread why not double amp????
  
 Really..
  
 Alex


----------



## adydula

Zorrofox...it shouldn't matter....jus don't stack them in a microwave! LOL.
  
 Alex


----------



## Solrighal

adydula said:


> Zorrofox...it shouldn't matter....jus don't stack them in a microwave! LOL.
> 
> Alex




I just thought I'd ask, lol. I don't do microwaves anyway.


----------



## Xenophon

@miceblue: not a good idea. Google 'gain structuring'. At best you'll amp distortion and cause clipping, at worst something will go snap, crackle and pop.


----------



## mcandmar

> Were the theory of a "wire with gain" true, I should hear no difference between the above setups, no? I find the *MacBook Pro's headphone out* to sound much more coherent and transparent than through the double amping. Through the double amping, the bass becomes woolier and more bloated, and the treble subdued a bit. Instrument separation becomes more blurred and it just sounds less transparent to me.


 
  
 There is your problem right there, headphone outputs and line outputs are not the same thing.  I would totally expect that setup to sound like garbage.


----------



## mcandmar

solrighal said:


> Can I ask a question of the gurus here?
> 
> If I stack the ODAC & O2 does it matter what goes on top? I know there should be no interference but I thought I'd see if there's an accepted wisdom on this.


 
  
 Put the O2 on top or the volume control is more awkward to use. Seriously though it makes no difference whatsoever.


----------



## anthk

mcandmar said:


> There is your problem right there, headphone outputs and line outputs are not the same thing.  I would totally expect that setup to sound like garbage.


 
  
  


adydula said:


> No one in there right mind would do this in the real world.
> 
> But....with the volume control cranked up to max what do u think the maximum voltage RMS is ??
> 
> ...


 

 Just saw that the o2 amp is turned to max vol...
 I think I saw the HP in question is ~100 db/ mW. You shouldn't need that much volume really.


----------



## gikigill

More than the O2, it's your ears which are gonna take a hammering. I have never dared to max the volume on most of my headphones.


----------



## Solrighal

T





mcandmar said:


> Put the O2 on top or the volume control is more awkward to use. Seriously though it makes no difference whatsoever.




Thats the way I have it right now but aye, I wasn't expecting it to matter since these boxes are so well laid out but what do I know


----------



## miceblue

anthk said:


> http://apple.stackexchange.com/questions/57186/what-is-the-impedance-of-the-line-headphone-jack-on-macbook-pro-retina
> Impedence mismatch?





adydula said:


> No one in there right mind would do this in the real world.
> 
> But....with the volume control cranked up to max what do u think the maximum voltage RMS is ??
> 
> ...





xenophon said:


> @miceblue: not a good idea. Google 'gain structuring'. At best you'll amp distortion and cause clipping, at worst something will go snap, crackle and pop.





anthk said:


> mcandmar said:
> 
> 
> > There is your problem right there, headphone outputs and line outputs are not the same thing.  I would totally expect that setup to sound like garbage.
> ...





gikigill said:


> More than the O2, it's your ears which are gonna take a hammering. I have never dared to max the volume on most of my headphones.




I just quoted people and will address all of them in 1 response.

I wasn't using maximum volume from the MacBook to the O2, just volume 1/16 for example, so the VRMS value going into the O2 and the volume going to the headphone shouldn't be a problem at all with the O2 at unity gain.
1/16 volume from MacBook -> 1.0x gain/no gain from O2 at maximum volume = 1/16 volume to ears assuming the O2 is just a "wire with gain"

A mismatch of impedance is probably a more likely thing to occur now that I think about it, but I'll have to look into the gain structure stuff too.


As for someone actually doing this in reality, it's definitely a legitimate situation. I like the sound out of ___ system, but the volume is too quiet and I would like to make it louder. A "wire with gain" would provide exactly this, no? And say it's a computer soundcard (MacBook in this example), you can't actually separate the DAC and amp components.


----------



## jring

Hi miceblue,
  
 the Vmoda is 32 ohms and that's most probably way too low for the macbook. The usual rule of thumb is that the headphone impedance should be 8-10 times or higher than the output impedance of the amp. That would mean the output should have 3-4 ohms or less and apple seems to state less than 24 ohms...
  
 http://apple.stackexchange.com/questions/57186/what-is-the-impedance-of-the-line-headphone-jack-on-macbook-pro-retina
  
 So the sound of the Vmoda is probably a bit colored when directly connected to the macbook and will sound different when when the macbook just drives the O2 with >10k ohms input impedance.
  
 Joachim


----------



## adydula

I cant even belive this is happening......OMG...
  
 This is really well.....you know.....
  
 Have fun....
  
 A.


----------



## miceblue

jring said:


> Hi miceblue,
> 
> the Vmoda is 32 ohms and that's most probably way too low for the macbook. The usual rule of thumb is that the headphone impedance should be 8-10 times or higher than the output impedance of the amp. That would mean the output should have 3-4 ohms or less and apple seems to state less than 24 ohms...
> 
> ...



Yeah that may very well be the case. Is there a way to measure the output impedance with things lying round the house? That stackexchange link didn't give a specific value. I'm inclined to think Apple updated their specs since the Retina Display line since there's a pretty substantial difference in sound between that and my 2008 MacBook.

The O2's output impedance is about 0.5 Ω according to the blog.





adydula said:


> I cant even belive this is happening......OMG...
> 
> This is really well.....you know.....
> 
> ...



Thank you for the constructive feedback and explanations, I feel edified now.


----------



## adydula

If you want some good advice get an amp that will play your tunes at the volumes you desire instead of double amping.....
  
 Save your self time and effort...
  
 But if you persist you can easily measure impedance if you have an oscilloscope or ac voltmeter, a signal generator, a variable resistance load or decade box. You need to understand the difference between DC resistance and impedance....so if you have these items "lying around the house" have at it....
  
 A.


----------



## mcandmar

miceblue said:


> I wasn't using maximum volume from the MacBook to the O2, just volume 1/16 for example, so the VRMS value going into the O2 and the volume going to the headphone shouldn't be a problem at all with the O2 at unity gain.
> 1/16 volume from MacBook -> 1.0x gain/no gain from O2 at maximum volume = 1/16 volume to ears assuming the O2 is just a "wire with gain"


 
   
 The signal itself may be low but the amplification further down the chain will only amplify the noise and raise the noise floor.  Its very dangerous to do that as any noise introduced into the signal after the macbook will play out your headphones unattenuated. For example have you ever heard a pop or rustling sound when plugging/unplugging an interconnect?   Don't ever try that with the O2 on full volume if you care about your hearing or headphones.  I also would'nt trust the macs s/w volume control not to revert to full volume and pop something.
  
 Quote:


miceblue said:


> As for someone actually doing this in reality, it's definitely a legitimate situation. I like the sound out of ___ system, but the volume is too quiet and I would like to make it louder. A "wire with gain" would provide exactly this, no? And say it's a computer soundcard (MacBook in this example), you can't actually separate the DAC and amp components.


 
  
 No easy way around that other than using a DAC with a toslink or USB connection from the Macbook.


----------



## BenF

ptom said:


> I had a question about the ODAC. How does the ES9023 chip objectively perform compared to the ES9018 chip? I know the latter is much more expensive and is used in high end DACs. Any thoughts?


 
 It really depends on the implementation. ODAC sounds as good as NFB11.32 with ES9018.


----------



## Whitecitadel

adydula said:


> Whitecitadel...are your sure u need 3x gain? What cans are you going to drive?
> 
> Alex


 
  
 So I have low=1x, high=3x, I am using Sennheiser Momentums which on paper are super-easy to drive. The 1x is for the Momentums and the odac as the source, the 3x was just some future proofing and for using 0.5v LOD from an iPod etc.
  
 I don't anticipate using 3x really, it was just a decision on what to build it with really...


----------



## Solrighal

whitecitadel said:


> So I have low=1x, high=3x, I am using Sennheiser Momentums which on paper are super-easy to drive. The 1x is for the Momentums and the odac as the source, the 3x was just some future proofing and for using 0.5v LOD from an iPod etc.
> 
> I don't anticipate using 3x really, it was just a decision on what to build it with really...




That's the same spec as I use and 1x is enough to drive my HD650's with most albums.


----------



## mcandmar

whitecitadel said:


> So I have low=1x, high=3x, I am using Sennheiser Momentums which on paper are super-easy to drive. The 1x is for the Momentums and the odac as the source, the 3x was just some future proofing and for using 0.5v LOD from an iPod etc.
> 
> I don't anticipate using 3x really, it was just a decision on what to build it with really...


 
  
 If your building it yourself buy the resistors for the various gains (cheap) and a terminal strip to chop up and use as sockets.


----------



## PTom

>


 



whitecitadel said:


> > *Quote:* "Ultimately, the ES9023 properly implemented, is an audibly transparent DAC. The window glass is completely clean. There are no perceptible flaws. It's not possible to get the glass perceptibly cleaner. While the ES9018 or ES9012 might even better measurements, I honestly don't believe they can improve on the sound quality when listening blind."
> 
> 
> 
> ...


 
 Ok let me get this straight, He Who Must Not be Named  "*believes*" the ES9018 or ES9012 can't improve the sound quality even though they *measure *better! Surely that statement goes against everything I thought he stands for.


----------



## James-uk

ptom said:


> Ok let me get this straight, He Who Must Not be Named  "*believes*" the ES9018 or ES9012 can't improve the sound quality even though they *measure* better! Surely that statement goes against everything I thought he stands for.




Once you get past the point of transparency it could measure a million times better but our ears wouldn't know or care. That's the point. He believed in doing enough to bet the job done .


----------



## Xenophon

Actually it doesn't. We're at a level where the limiting factor is no longer the abstract chip specs but implementation, even when well executed becomes the bottleneck and more relevant than chipset spec differences.


----------



## mcandmar

ptom said:


> Ok let me get this straight, He Who Must Not be Named  "*believes*" the ES9018 or ES9012 can't improve the sound quality even though they *measure *better! Surely that statement goes against everything I thought he stands for.


 
  
 Yeah that's right, the flag ship chip is no better than the bargain basement entry level chip


----------



## Whitecitadel

mcandmar said:


> If your building it yourself buy the resistors for the various gains (cheap) and a terminal strip to chop up and use as sockets.


 
 The head'n'hifi kit comes with all the values and the SIP sockets, decided against the sockets and just soldered in the 3x and left out the others for 1x for now. 
  
 Nice neat job by the way


----------



## mcandmar

whitecitadel said:


> The head'n'hifi kit comes with all the values and the SIP sockets, decided against the sockets and just soldered in the 3x and left out the others for 1x for now.
> 
> Nice neat job by the way


 
  
 Oh didn't know that, i only bought the PCB from them.


----------



## PTom

james-uk said:


> Once you get past the point of transparency it could measure a million times better but our ears wouldn't know or care. That's the point. He believed in doing enough to bet the job done .


 
 Do you know if he or anyone else has conducted blind tests to compare the ES9023 to more expensive chips?


----------



## Whitecitadel

ptom said:


> Ok let me get this straight, He Who Must Not be Named  "*believes*" the ES9018 or ES9012 can't improve the sound quality even though they *measure *better! Surely that statement goes against everything I thought he stands for.


 
  
 According to manual my wife's car is good for about 130MPH and my car 150MPH, this makes my car the "better" car, as it measures with higher performance.
  
 The performance of either in the real world is limited to the traffic flow on the local motorway (freeway) of about 70MPH, so using the one that measures better in day to day use makes no discernable difference from the one that measures in excess of the required performance.
  
 If you were go to a racetrack and measure performance, a bad implementation (aka driver in my  analogy) could make the one with lower specs perform better...


----------



## PTom

Btw, I was trying to sell my LCD 2 recently and a potential buyer came to listen to it at my house. He brought a Hugo Chord DAC/amp which cost north of $1000 and it definitely sounded better with the LCD 2 than the O2/ODAC. I didn't do a blind test but I felt there was a big difference. The O2/ODAC is the most expensive setup I had ever tried till that point and I was quite skeptical about the benefits of expensive setups based on what I've read on the sound science part of town till trying the Hugo Chord.
  
 I honestly don't believe it was expectation bias or anything psychological.


----------



## Whitecitadel

mcandmar said:


> Oh didn't know that, i only bought the PCB from them.


 
  
 I had a go at the mouser import but the head'n'hifi kit was better value - also bear in mind Stefan uses the better B2-080 cases with the countersunk bolts rather than the self tappers that stand proud to the panel. Can't fault the kit, has everything needed including PSU with right country plug (I am in the UK).
  
 Didn't get time last night to carry on, no time tonight either


----------



## James-uk

ptom said:


> Do you know if he or anyone else has conducted blind tests to compare the ES9023 to more expensive chips?




No need. I trust the science , logic and reason behind it. Same way I trust the theory of gravity when I'm walking near the edge of a cliff


----------



## PTom

So was there a particular scientific study on this? I mean for example have the different limits of human hearing  (i.e. in terms of frequency response, resolution of human hearing etc.) been quantified objectively and compared to the performance of the ODAC and DACs with a ES9018 chip. With the results showing that both surpass the said limits?


----------



## Solrighal

james-uk said:


> No need. I trust the science , logic and reason behind it. Same way I trust the theory of gravity when I'm walking near the edge of a cliff




Agreed.


----------



## James-uk

I clearly can't trust my eyes whilst listening to music though because I thought you had asked if I had heard the es9023. That's what the O2 and hd800 do to you. In a world of my own right now! Listening to Damien Rice album 'O' by the way. It's a lovely album and it's recorded superbly. Highly recommended if you haven't heard it.


----------



## Solrighal

'O' is very good eh? It actually sounds very good on almost anything. If you like that, try "Kiss Each Other Clean" by Iron & Wine. Lovely sounds.


----------



## James-uk

solrighal said:


> 'O' is very good eh? It actually sounds very good on almost anything. If you like that, try "Kiss Each Other Clean" by Iron & Wine. Lovely sounds.




Will check that out. Thanks.


----------



## Tequilasunriser

PTom, you're in an O2+ODAC thread. Take the vitriol elsewhere.
  
 None of us care that you felt a $1000+ amp sounded better than our $65 amp. For $65 I think we can all agree it sounds really damn good.


----------



## CADCAM

tequilasunriser said:


> PTom, you're in an O2+ODAC thread. Take the vitriol elsewhere.
> 
> None of us care that you felt a $1000+ amp sounded better than our $65 amp. For $65 I think we can all agree it sounds really damn good.


----------



## James-uk

solrighal said:


> 'O' is very good eh? It actually sounds very good on almost anything. If you like that, try "Kiss Each Other Clean" by Iron & Wine. Lovely sounds.



Only 2 tracks in and It's great ! I didn't realise I already have a single by him called flightless bird, American mouth. The mrs must of downloaded it, I like that song too. Thanks again for recommendation.


----------



## James-uk

All I will say is I obsessed over this for a long time to find out how deep this rabbit hole goes and I'm satisfied by all the information out there to come to the conclusion that the O2/odac is transparent and you won't get 'better ' ie more hifi. I could spend my time finding all the links again but I don't need to . You need to do it for yourself and satisfy your own mind . It's a revelation! My eyes are wide open now and I am the happiest I've been in this hobby. I've stopped chasing the mystical 'end game' that the machine wants us to believe in just to keep taking our money!


----------



## mcandmar

whitecitadel said:


> I had a go at the mouser import but the head'n'hifi kit was better value - also bear in mind Stefan uses the better B2-080 cases with the countersunk bolts rather than the self tappers that stand proud to the panel. Can't fault the kit, has everything needed including PSU with right country plug (I am in the UK).
> 
> Didn't get time last night to carry on, no time tonight either


 
  
 Only reason i did the Mouser route was because i wanted to use better components, but i agree the kit form is better value.
  
 Also agree about the front panels aesthetics, i sourced my odac and o2 enclosure from them for that reason.  The red/gold PCB is just lovely too, all their parts have a quality feel to them.


----------



## Solrighal

I also have one of Walter's creation's and couldn't be happier. The only slight fly in the ointment was the volume knob itself. I felt it kinda cheap and let the side down so I imported a couple of fancy knobs from Mayflower Electronics in New York. Slick!


----------



## James-uk

I got a subscription to gadget magazine for Xmas and I was reading an item this morning about high res DAPs . Apparently the Sony has' awesome precision in the organisation of its spacious soundstage ' and the Astell and Kern ' is dynamic and extraordinarily fluid, making for a direct and organic performance . Timing could do with a little tightening up , but there's a relaxed presentation that some will love.' This grinds my gears! Someone is getting paid to write this absolute rubbish.


----------



## Solrighal

That's precisely why I gave up with Hifi magazines years ago. All they do is keep themselves in a job.


----------



## PTom

tequilasunriser said:


> PTom, you're in an O2+ODAC thread. Take the vitriol elsewhere.
> 
> None of us care that you felt a $1000+ amp sounded better than our $65 amp. For $65 I think we can all agree it sounds really damn good.


 
 Calm down, no need to be rude. I think you need to put things in perspective, it's just an opinion about a headphone amp, not something important enough to take personally, lol...


----------



## anthk

ptom said:


> Btw, I was trying to sell my LCD 2 recently and a potential buyer came to listen to it at my house. He brought a Hugo Chord DAC/amp which cost north of $1000 and it definitely sounded better with the LCD 2 than the O2/ODAC. I didn't do a blind test but I felt there was a big difference. The O2/ODAC is the most expensive setup I had ever tried till that point and I was quite skeptical about the benefits of expensive setups based on what I've read on the sound science part of town till trying the Hugo Chord.
> 
> I honestly don't believe it was expectation bias or anything psychological.


 
 What were the differences that you heard?


----------



## Whitecitadel

mcandmar said:


> Only reason i did the Mouser route was because i wanted to use better components, but i agree the kit form is better value.
> 
> Also agree about the front panels aesthetics, i sourced my odac and o2 enclosure from them for that reason.  The red/gold PCB is just lovely too, all their parts have a quality feel to them.


 
 Whilst I was paying the shipping I got a second PCB in case I want to build a second o2 later (in a B3-80 with the ODAC as batteries), agree very high quality as far as I can tell.
  
 I like what you did with the separate ODAC, also what I am planning, what LED did you use in the ODAC the same as the o2? I notice the panel is nicely printed, where did you get it can I ask?


----------



## adydula

The whole idea behind the O2 was to build an amp that was as perfect and transparent with the least amount of parts and cost and work with 98% of the headphones out there. It has opened many eyes, pissed off some, and helped keep the business lean towards the open and honest side.....
  
 Some of the items mentioned that might measure better may not have been available when the designer went thru the process.
  
 If your transducers in your head cant be improved, that's your EARS, then using parts that spec better wont really matter a hill of beans, but there isn't anything wrong in using them etc... it cant hurt, but may cost more.
  
 Having a car be able to go faster isn't a real great comparison to the finite capabilities of the human ear.....but I like fast cars but would rather have one that had a great suspension etc..
  
 The O2 for the cost (some folks hate that comment) performs very well and competes with many other higher cost alternatives.
  
 Its not fancy and its not really the most durable construction.....if you want billet aluminum knobs and a chassis that weighs a few pounds then this isn't the item for you....but I guess you could put an O2 in a BIG aluminum case with a few bricks and if you don't tell anyone I wonder if they would know....
  
 All the best
 Alex


----------



## mcandmar

whitecitadel said:


> Whilst I was paying the shipping I got a second PCB in case I want to build a second o2 later (in a B3-80 with the ODAC as batteries), agree very high quality as far as I can tell.
> 
> I like what you did with the separate ODAC, also what I am planning, what LED did you use in the ODAC the same as the o2? I notice the panel is nicely printed, where did you get it can I ask?


 
  
 You can squeeze an ODAC and batteries into a regular B2 case, but the B3 will give you a bit more spare to add RCA's and a 6.5mm headphone socket if you wanted to.
  
 LED is the same one as used in the O2, and now that i think about it the O2 front panel i used on that one may have come from Mayflower electronics. Its all so long ago i cant really remember, i just liked the clean look without any vendor markings on it.


----------



## anthk

adydula said:


> The whole idea behind the O2 was to build an amp that was as perfect and transparent with the least amount of parts and cost and work with 98% of the headphones out there. It has opened many eyes, pissed off some, and helped keep the business lean towards the open and honest side.....
> 
> Some of the items mentioned that might measure better may not have been available when the designer went thru the process.
> 
> ...


 

 As an owner, I do wonder if the combo would break down soon.


----------



## Xenophon

As regular readers know, I think the ODAC and especially the O2 have their limitations and are not the end-all.  However, for the price (there, I said it) they do perform very well.  
  
 I own the Epiphany Acoustics build.  It's small, it looks flimsy.
  
 And it's been sitting on my desk in New Delhi for the past 2.5 years, being used at least 10 hours/day and exposed to temperatures (summertime, like right now) of >40 centigrade during the day to an average in-use ambient temperature of I'd guess 34 centigrade with the ac on.  During monsoon, add >90% humidity.  And dust the entire year, currently on my 2nd cinema display due to fine dust getting in.  
  
 Haven't had a problem with it yet and though I'm only a single owner I believe it can safely be said that though it's not built like a tank, it won't fall apart after one month either.


----------



## mcandmar

Its so simple there isn't really anything to go wrong.  The parts that will fail first are either the cheap filter capacitors that are only rated for 2000 hours, or the volume pot will go noisy.  Either will only cost a few $ to replace.   High ambient heat will drastically reduce the capacitor lifetime, and dust wont do the volume pot any favors, but lifes too short to worry about it.


----------



## jring

mcandmar said:


> Its so simple there isn't really anything to go wrong.  The parts that will fail first are either the cheap filter capacitors that are only rated for 2000 hours, or the volume pot will go noisy.  Either will only cost a few $ to replace.   High ambient heat will drastically reduce the capacitor lifetime, and dust wont do the volume pot any favors, but lifes too short to worry about it.


 
  
 Well, electrolytics certainly do age, but I'd say we're safe with the O2 for quite some time. First of all, the stuff from the BOM ist rated for 3000h and also this is a worst case value at the maximum allowable temperature which is 85 degrees centigrade or higher and with maximum voltage and ripple. The rule of thumb is to double the rated lifetime for every 10 degrees centigrade below that. Since we tend to have 20 degrees room temp over here most of the time and the caps do not really get warm, I'd say the caps have 35 degrees maximum so I'd start thinking about the caps after 96k hours or some 11 years of permanent runtime. So for india it's maybe half of that but stil a lot of listening time.
  
 Joachim


----------



## Nec3

mcandmar said:


> Its so simple there isn't really anything to go wrong.  The parts that will fail first are either the cheap filter capacitors that are only rated for 2000 hours, or the volume pot will go noisy.  Either will only cost a few $ to replace.   High ambient heat will drastically reduce the capacitor lifetime, and dust wont do the volume pot any favors, but lifes too short to worry about it.


 
 2000 hours... Hmm.... Welll..... should I be worried? I think it's ~4000 hours of usage by now...


----------



## adydula

The things I would be most concerned with is the number of insertions in and out of the jacks....the jacks are not the highest quality....but they are rated at something like
 2000 + insertions etc.
  
 There are better mechanical jacks etc...
  
 That said I am not in the least worried about that....I use a 3.5mm to 1/4 phone adapter cable that I leave plugged into the amp and just plug and unplug with the 1/4 side.
  
 Also I am building, nearly complete and ODA both 3.5mm and 1/4 jacks.
  
 Alex


----------



## miceblue

xenophon said:


> As regular readers know, I think the ODAC and especially the O2 have their limitations and are not the end-all.  However, for the price (there, I said it) they do perform very well.



Yup and yup.


----------



## adydula

To be fair that can be said for many other amps and dacs as well........
  
 Spend you money wisely...
  
 yup and yup...
  
 A.


----------



## r010159

I am trying to determine the one difference between the C5 and O2. The thought I have is the O2 is a bit more transparent. Anyone want to take a stab at this?

PS: I needed some warranty work on the C5 which turned our to be a trivial problem. The unit was received, fixed, and shipped the same day. Thanks JDS Labs.


----------



## MrMateoHead

Lets turn from theory and opinion for a moment to a technical issue I am having!
  
 Anyone else get channel cut out with a mere gentle "wiggle" of the 02's input connector? Lately I am needing to give it a little wiggle to correct static / channel cut out issues. I think it also sometimes happens at the headphone out. Is that symptomatic of possible soldering issue inside, or maybe just a "feature" of the low-cost connectors?


----------



## adydula

I never had that issue but had a ac power issue with a connector that if wiggled just right I lost power!!
  
 I used some deoxit and mild bending of contacts and its fine now.
  
 A.


----------



## tomb

mrmateohead said:


> Lets turn from theory and opinion for a moment to a technical issue I am having!
> 
> Anyone else get channel cut out with a mere gentle "wiggle" of the 02's input connector? Lately I am needing to give it a little wiggle to correct static / channel cut out issues. I think it also sometimes happens at the headphone out. Is that symptomatic of possible soldering issue inside, or maybe just a "feature" of the low-cost connectors?


 

 The only question about a 3.5mm jack failure is when, not if.  You might be able to blame it on the "low-cost" selection, but I don't think so.  There is simply a limitation of geometry when it comes to 3.5mm jacks.  The contact area is super small, so any small potential for corrosion has a huge impact on connectivity.  Similarly, the spring strengths in the size of the metal required fatigues rather easily, also causing intermittent contact problems.  It's the nature of the beast in 3.5mm connectors.  You are best to keep things plugged in as continuously as you can. 
  
 Just an FYI, but the physical geometry critical point is well exceeded with 1/4" connectors.  Equipment stored up and un-used for decades often makes perfect electrical contact with 1/4" connectors.


----------



## Xenophon

For my O2/ODAC combo keeping the 3.5 mm jack plugged in all the time is exactly what I do, I use a female 1/4" to male 3.5 mm connector in which I plug my headphones but the connector itself just stays plugged in all the time.  Same with the USB-input, BTW.  In general, the less swapping out, the longer things will last.  Though I have to say that even icd the unit were to fail catastrophically right now, I'd still consider it a good deal after 2.5 years.  And it'd provide me with a good excuse for buying agar's new and improved version, would just need to find a solution for the power supply issue, given EU regulations.  It would be nice to use the electronics in question but provide a high quality pot, luxurious aluminium case, billet Al knob, 1/4" output etc.


----------



## mcandmar

xenophon said:


> For my O2/ODAC combo keeping the 3.5 mm jack plugged in all the time is exactly what I do, I use a female 1/4" to male 3.5 mm connector in which I plug my headphones but the connector itself just stays plugged in all the time.  Same with the USB-input, BTW.  In general, the less swapping out, the longer things will last.  Though I have to say that even icd the unit were to fail catastrophically right now, I'd still consider it a good deal after 2.5 years.  And it'd provide me with a good excuse for buying agar's new and improved version, would just need to find a solution for the power supply issue, given EU regulations.  It would be nice to use the electronics in question but provide a high quality pot, luxurious aluminium case, billet Al knob, 1/4" output etc.


 
  
 Whats the issue with the power supply?


----------



## Xenophon

Wall power adaptors with a transformer are outlawed (energy efficiency) you need a switching power supply.  And none of those will output AC, which the design requires....


----------



## mcandmar

Ahh yes i had forgotten about that.  I'll refrain from ranting about stupid EU laws since your in Belgium 
	

	
	
		
		

		
			




  
 Might i suggest your build your own, buy an encapsulated toroid and put it into a box..


----------



## headwhacker

r010159 said:


> I am trying to determine the one difference between the C5 and O2. The thought I have is the O2 is a bit more transparent. Anyone want to take a stab at this?
> 
> PS: I needed some warranty work on the C5 which turned our to be a trivial problem. The unit was received, fixed, and shipped the same day. Thanks JDS Labs.


 
  
 I had the C5D and yes I can say O2 is more transparent. The only thing you have with C5/D over O2 is portability. Everything else, O2 hands down. Suffice to say I sold the C5D and still enjoying O2.


----------



## SilverEars

headwhacker said:


> I had the C5D and yes I can say O2 is more transparent. The only thing you have with C5/D over O2 is portability. Everything else, O2 hands down. Suffice to say I sold the C5D and still enjoying O2.


 
 I agree with this, but I have ODAC/O2 combo.  I tried the C5D, and it didn't sound as natural as the ODAC/O2 combo.  It sounded too tight and refined to the point where it sounded too artificial, especially the bass.  In other words, it wasn't as transparent and natural sounding as the ODAC/O2.  I don't like to use ODAC/O2 with my high end cans that need lots of voltage as it's obvious to my ears it doesn't sound right(I have orthos), but I do like the ODAC/O2 with iems and ODAC as my source.  I'm looking for a portable that can do just as well or better the ODAC/O2 combo for iems.  
  
 I personally think it's the ODAC that's making the difference.  Which I heard is a simple build using only the required components to implement the DAC.  I believe it's the ESS 9023, not the new popular 9018 which is much more expensive.


----------



## jring

mcandmar said:


> Ahh yes i had forgotten about that.  I'll refrain from ranting about stupid EU laws since your in Belgium
> 
> 
> 
> ...


 
  
 Or try head'n'hifi, they're based in switzerland and couldn't care less about EU regulations... you could also just buy their version with 1/4" out and RCA in...
  
 Joachim


----------



## adydula

Well I am happy to say my ODA is up and functional!!!
  
 This is my board that I sent to AGDR for testing the last minute changes to the reduced AC supply and a few other last minute improvements....you can read all the techie details at diyaudio.com

 The designer, agdr of this ODA had some last minute concerns with the AC supply voltages and heat dissipation etc as well as a few minor "make it even better" items.

 The voltage has ben reduced from 24VAC to 16 VAC. This means that no additional heat sinking will be needed and the unit will not get overly warm, unlike some other headphone amps I have had the you could fry and egg on!

 This version of the ODA has a 1/4 jack and a 3.5mm input jack for headphones. It has RCA inputs and outputs. It has a 4 position gain selection switch, a clipping LED indicator, and two power rail LEDS.

 The DC offset voltages are down to 2 micro volts on one side and 4 micro volts on the other side or channel.
 This is 21 times lower than the original O2 amp.

 So I hope to find some time in the next few days to do some serious listening and report on how it sounds compared to the original O2 with several headphones.

 I still have to drill out the front panel and get it mounted in its nice shiney RED case!!! LOL.
  

  
  

  
 If your at all interested in this ODA version you can contact agdr over at DIYAUDIO.COM.
 He also has a website agdraudio.com as well.
  
 He is one of the most knowledgeable people I have run into that understands circuit design, audio applications etc...very helpful.
  
 Alex


----------



## adydula

In the ODA agdr has used a higher quality jack:
  
 "The 3.5mm jacks are higher quality Switchcraft jacks, with actual springs inside and not just springy metal, another thing a lot of folks have posted about (bad jacks)."
  
 But with the unit having a 1/4 jack I do not think I will be using the 3.5mm one.
  
 Alex
  
 Note: It may be possible to replace the 3.mm jack in the O2 with one of these? Will take a look.


----------



## SilverEars

Hi, great job on the build.  Wasn't there an add-on to increase the power supplied to the amp, instead of a brand new board build?  If there is one, I want to try it out for my O2 and my HE-6


----------



## Whitecitadel

mcandmar said:


> Might i suggest your build your own, buy an encapsulated toroid and put it into a box..


 
  
 +1 on DIY 
  
 Or buy a spare from head'n'hifi I think they sell them seperate.
  


adydula said:


> Note: It may be possible to replace the 3.mm jack in the O2 with one of these? Will take a look.


 
  
 You can use any jack with o2 if you mount it on the panel not the board, any board mounted jack would need compatible leg arrangements however. I also think you need an isolated jack otherwise if its metal surround your grounding the signal to the case in more than one location?
 Neutrik do a nice one from what I have read, and this is what the "pre-built" providors seem to use in their "desktop" versions on the o2.
  
 Without sounding like a head'n'hifi advert  they do sell a kit with panels and a 6mm jack and isolated RCA set to convert your o2 to a desktop version.


----------



## Solrighal

whitecitadel said:


> Without sounding like a head'n'hifi advert  they do sell a kit with panels and a 6mm jack and isolated RCA set to convert your o2 to a desktop version.




I own that version, although I bought mine pre-built. It's an excellent device & a bargain. Particularly if you have the skills to build it yourself.


----------



## adydula

Yes there is a O2 Booster Board :
  
 The final circuit uses the OPA140 op-amp (FET input, DC precision, low THD+N) looped around an LME49600 audio current buffer on each channel to replace the O2 Headphone Amp's original NJM4556A output chips. Many other op amps would also work, such as the OPA827 and OPA627 with varying effects - see the full op amp rolling write-up in the build instructions. The board includes several optional "upgrade" modifications for the O2 headphone amplifier including an "anti turnoff thump" resistor, mosfet "on" indicator LEDs, and a 1/4" jack. The board produces a 93% reduction in the O2 amp's DC output offset voltage to around 20uV from the O2's standard 3mV. Output current capability is increased from 120mA per channel to 200mA for "music power" (playing music rather than sine wave testing). The O2's power supply has limitations that would prevent continuous current draw above 200mA per channel.
  
 There are (3) versions of the pluggable PC board....check  it out at DIY audio....
  
 .http://www.diyaudio.com/forums/headphone-systems/244473-o2-headamp-output-booster-pcb.html
  
 Alex


----------



## adydula

In regards to the headn hi fi desktop kit etc...the agdr version is a lot more than just adding mechanical jacks or better switches. Its a totally new upgrade which involves lots of changes to "improve" on the O2...but cost is not one of them!! It is more expensive to build etc.....
  
 Here are the highlights for the agdr ODA DIY:
  

· *Up tp +/-16Vdc power rails with adjustable regulators for up to a 11Vpeak swing. Useful for high impedance headphones.*
· *Lower noise voltage regulators, LT1963A and LT3015. Probably won’t make any audible difference, though.*
· *Twice the output current capability and power dissipation - 280mA per channel. Useful for low impedance and low sensitivity headphones.*
· *4 NJM4556A chips to handle the current and +/-16Vdc dissipation, two per channel. Uses the SIP 8 pin inline version, NJM4556AL.*
· *NJM2068 replaced with OPA627, which is now in a feedback loop with the NJM4556 chips to null out DC offset and reduce distortion even further. DC output offset voltage should be around 0.3mV = 300uV per channel.*
· *Has input RCA jacks and output ¼” Neutrik jack in addition to better (Switchcraft) 3.5mm jacks.*
· *Bass boost circuit – switchable on/off.*
· *Rotary gain switch with 4 gain settings.*
· *Relay-based no-thump circuit that waits 2 seconds to switch in the headphones and then drops them out quickly on power switch-off.*
· *Should have even lower background noise than the O2 headphone amp at high gain settings. 4 layer PCB with full middle ground plane.*
· *Volume pot is on the input now rather than the middle of the circuit, so it can attenuate “hot” sources as much as needed. Still no pot turning noise.*
· *Coupling cap is on the input, 4x as large to work with the 10k pot vs. 40.2k resistor in the O2, to block all incoming DC from the source. *
  
*It is extremely versatile and there are many options when building that you can add, change or leave out, like gain settings, preamp usesage that is very versatile, bass boost if desired, etc....*
  
*It has leds that show the power rails working, a clipping led, power off switch in the rear....etc*
  
*Alex*


----------



## eimis

Did somebody actually measure it or is it just a theoretical improvement?


----------



## MrMateoHead

tomb said:


> The only question about a 3.5mm jack failure is when, not if.  You might be able to blame it on the "low-cost" selection, but I don't think so.  There is simply a limitation of geometry when it comes to 3.5mm jacks.  The contact area is super small, so any small potential for corrosion has a huge impact on connectivity.  Similarly, the spring strengths in the size of the metal required fatigues rather easily, also causing intermittent contact problems.  It's the nature of the beast in 3.5mm connectors.  You are best to keep things plugged in as continuously as you can.
> 
> Just an FYI, but the physical geometry critical point is well exceeded with 1/4" connectors.  Equipment stored up and un-used for decades often makes perfect electrical contact with 1/4" connectors.


 

 Thanks for the reply. The problem is, I typically leave things hooked up and virtually never disconnect - and yet experience this issue. I've only owned the O2/ODAC for perhaps a year or so. I assume that one day I will jack in and that will be it - one or two channels out, static, etc. I happen to love the amp so it is disappointing to hear that, apparently, this is "the nature" of 3.5mm jacks. Certainly I have many other products that use them without these symptoms.


----------



## Xenophon

Agdr should imo put some distance between his new build and the odac/o2. It might have been inspired by them but at least to me it's clear that his is a much higher specced product sold at a commensurately higher price. Only drawback is that I don't think it is something that just about anyone could build, been following your construction of it on diyaudio and this is most def. Not for novices. When it becomes available in hopefully a couple of weeks I'll seriously consider it for my office but first I'll build a power supply for it.


----------



## adydula

MrMateoHead....
  
 Not to worry, its an easy replacement if it ever comes to that.....
  
 Alex


----------



## adydula

eimis,
  
 take a look at the ODA thread at DIYAudio.
  
 Some stuff has been measured its a 40+ page thread, very informative, you will get a good idea on how it came to become what it is today...
  
 I will have mine here probably late this week or early the next and I intend to do some critical listening etc and report back.
  
 Alex


----------



## SilverEars

Ok, I have a question regarding the sonic difference I am hearing with my smartphone headphone out and ODAC/O2 out with iems.  These are iems and they are very sensitive with low impedance.  
  
 What in hell make them sound punchier, dynamic(and transparent?)  with ODAC/O2?  Is it feeding more current than what my smartphone is feeding it?  Which doesn't make sense, but I thought I throw that out there.
  
 I was going to throw this on the science forum, but since we got the Objective geeks here, I put it here.


----------



## adydula

Do you know what the output impedance of your phone is?
  
 Alex


----------



## r010159

I understand you have made changes to the O2 to come up with this design, correct? Considering this, how faithful are you to the original design of the O2? Or is this a total redesign of the O2? Will any objective measurement be taken to verify performance?


----------



## SilverEars

adydula said:


> Do you know what the output impedance of your phone is?
> 
> Alex


 
 1.2 ohms.


----------



## jring

silverears said:


> 1.2 ohms.


 
  
 What phone is this - the value is amazingly good for a phone if it's true and should be ok for typical IEMs with 16 ohms (headphone impedance divided by 8 or 10 is the usual rue of thumb).
  
 If the output impedance is higher than 1/8 or 1/10 of the headphone impedance the frequency response will usually be quite non-linear. This is because headphones are not a purely resistive load and thus the actual impedanc depends on the frequency of the signal.
  
 Joachim


----------



## Nec3

I have this ODAC/O2 Combo
 http://www.jdslabs.com/products/48/o2-odac-combo/

 The FiiO X3 has a Coaxial Out option (3.5mm male to Coaxial female connector). Is there a way to plug in the Coaxial Out to the Odac?


----------



## BenF

nec3 said:


> I have this ODAC/O2 Combo
> http://www.jdslabs.com/products/48/o2-odac-combo/
> 
> The FiiO X3 has a Coaxial Out option (3.5mm male to Coaxial female connector). Is there a way to plug in the Coaxial Out to the Odac?


 

 No


----------



## adydula

Hello,
  
 On the question pertaining to the ODA and measurements. I chatted with AGDR and he replied with some information:
  
 "I don't have a dScope (what NwAvGuy used) or the equivalent Audio Precision tester. I did get a QA400 distortion analyzer, essentially a sound card set up in a box for measurements, and posted those. To the limit of the QA400 (which is about 10dB noisier than an AP) the O2 and ODA showed the same noise floor and distortion. So, at least via the QA400, it is no worse than the O2, at least in terms of background noise and THD, and likely better from the data sheet measurements. But no, we'll never know for certain until someone out there with a dScope or AP does the tests.

 I do believe the noise floor on the ODA is lower though, since I can hear it myself with the gain turned up on both. With a dScope or AP with that extra 10dB of range, I would expect to see the ODA edging out the O2 on noise floor. And from a circuit standpoint I would expect the same, given the lower noise power supply, lower noise pot and ground return resistor in the middle, and lower noise LME49990 chips in the gain stage. Having more NJM4556ALs in parallel also increases S/N since signal adds linearly while noise adds via RMS.

 Distortion *should* be slightly lower, via the datasheets numbers of the LME49990 vs. the NJM2068 chips. But interesting thought experiment there. If you were to take an O2, add the booster board, and then replace the NJM2068 with a dual LME49990 adapter, that would probably match, or even possibly beat, the ODA in distortion. But not noise due to the O2's 10K pot. No way to get rid of that - can't fit in the pile of 4.7uF coupling caps needed.

 Power though I can defininitely measure. Just a load resistor and scope. But it is really the distortion and other measurements at a high power output that matter.

 The main tangible benefits of the ODA are lower background noise, something I can hear myself between the O2 and ODA on high gain, and the ability to drive higher current loads. Plus the clipping indicator and the pile of additional jacks and input select switch the O2 doesn't have. But even there the O2 can be modified to have more in/out jacks if folks use the taller B3-080 case."
  
 I might add that there are these comments about things that should be better than the O2 and have been measured:
  

· *Twice the output current capability and power dissipation - 280mA per channel. Useful for low impedance and low sensitivity headphones.*
 *       Lower DC offset voltage.*
  
*Alex*


----------



## SilverEars

jring said:


> What phone is this - the value is amazingly good for a phone if it's true and should be ok for typical IEMs with 16 ohms (headphone impedance divided by 8 or 10 is the usual rue of thumb).
> 
> If the output impedance is higher than 1/8 or 1/10 of the headphone impedance the frequency response will usually be quite non-linear. This is because headphones are not a purely resistive load and thus the actual impedanc depends on the frequency of the signal.
> 
> Joachim


 
 Galaxy S4


----------



## HaVoC-28

adydula said:


> · *Twice the output current capability and power dissipation - 280mA per channel. Useful for low impedance and low sensitivity headphones.*
> *       Lower DC offset voltage.*
> 
> *Alex*


 
  
 But it will not improve anything for 99% of the headphones out their 
	

	
	
		
		

		
			





 , bah ortho users will be happy


----------



## jring

silverears said:


> Galaxy S4


 
  
 You know this and have the updated firmware?
  
 http://www.jensign.com/S4Distortion/
  
 Joachim


----------



## adydula

Yup agree there are (2) versions of the ODA...from agdr:
  
 "The "standard" build going forward will have +/-12.5Vdc rails, just slightly more than the O2 headamp's 12.0Vdc rails, but 3x more current capability of course. This build works with any headphone impedance values from 16R to 600R or more. This +/-12.5Vdc build will now use a 1K linear volume pot rather than a log pot, since the linear pot has twice the power dissipation rating as it turns out. The 1K pot will work just fine whether the attentuation resistors are used or not. The transformer will probably change to 16Vac at 2.4A (Mouser WAU16-2400) but that is one of the things I'm still testing. Anything in the 16vac - 20Vac range with adequate current for the headphone load will probably work too, and is being evaluated.

 The second "optional" build is for folks who specifically have 300 ohm or 600 ohm (or higher) headphones that almost have enough volume with the O2 headamp, but not quite. This build has +/-15Vdc power supply rails and uses a 5K volume pot (linear or log taper, either is fine) again for pot power dissipation reasons. The transformer with this +/-15Vdc build remains that same as up until now, 20Vac - 24Vac. This +/-15Vdc build should *only* be used with 300R or higher headphones for output chip power dissipation reasons.

 Note that if you have 300R or 600R headphones that are nowhere near loud enough with the O2 then the +/-15Vdc rail option here isn't likely to help. You need a lot of additional voltage swing to get adequate dynamic range on music peaks, such as AMB's b22 headamp with +/-30Vdc rails or a tube amp.
  
 I have the standard build and will use it with Beyer T90;s. DT1350's, AKG Q701 *until I sell....I don't have any cans that need the higher rail voltages etc..
  
*Best new stuff: *
  

· *Up tp +/-16Vdc power rails with adjustable regulators for up to a 11Vpeak swing. Useful for high impedance headphones.*
· *Lower noise voltage regulators, LT1963A and LT3015. Probably won’t make any audible difference, though.*
· *Twice the output current capability and power dissipation - 280mA per channel. Useful for low impedance and low sensitivity headphones.*
· *4 NJM4556A chips to handle the current and +/-16Vdc dissipation, two per channel. Uses the SIP 8 pin inline version, NJM4556AL.*
· *NJM2068 replaced with OPA627, which is now in a feedback loop with the NJM4556 chips to null out DC offset and reduce distortion even further. DC output offset voltage should be around 0.3mV = 300uV per channel.*
· *Has input RCA jacks and output ¼” Neutrik jack in addition to better (Switchcraft) 3.5mm jacks.*
· *Bass boost circuit – switchable on/off.*
· *Rotary gain switch with 4 gain settings.*
· *Relay-based no-thump circuit that waits 2 seconds to switch in the headphones and then drops them out quickly on power switch-off.*
· *Should have even lower background noise than the O2 headphone amp at high gain settings. 4 layer PCB with full middle ground plane.*
· *Volume pot is on the input now rather than the middle of the circuit, so it can attenuate “hot” sources as much as needed. Still no pot turning noise.*
· *Coupling cap is on the input, 4x as large to work with the 10k pot vs. 40.2k resistor in the O2, to block all incoming DC from the source. *
 FYI
  
 Alex


----------



## adydula

Also note that there is a good chance of this ODA being measured with the same dScope that the O2 was measured with in the near future if and when this happens the results will be posted at DIY.

Alex


----------



## r010159

adydula said:


> Also note that there is a good chance of this ODA being measured with the same dScope that the O2 was measured with in the near future if and when this happens the results will be posted at DIY.
> 
> Alex


 
  
 If this happens and it test well, I will sign up for one. The ODA may test out good. But still I would be surprised if it is actually noticeability better than the O2. If it does, I am a sure customer (once I save up the dinero).


----------



## Xenophon

r010159 said:


> If this happens and it test well, I will sign up for one. The ODA may test out good. *But still I would be surprised if it is actually noticeability better than the O2.* If it does, I am a sure customer (once I save up the dinero).


 
  
 After extensively reading what agdr did, the components and the way he organised things, my guess is that it will test 'better' in the technical sense.  Wether it will be meaningful in the audible domain is something else.  What's certain is that the new device will drive more headphones and drive them better than the basic ODAC/O2.  Besides, in that last combo, it's the ODAC that's hard to beat imo, the O2's a much softer target.


----------



## adydula

Yes it will be interesting, but again the ODA is meant to be what it might have been etc.....
  
 I think AGDR has done a really great job in designing this version of an ODA and sharing with us all what it is and how he came up with his design.
  
 He has listened to may headphone folks and take in several ideas to make it a better operational amp.
  
 I will have mine here on Saturday and I will start listening etc...
  
 There are a few things that I left out and might add or change in the future, ie bass boost etc.
  
 Stay tuned.
  
 Alex


----------



## adydula

Here's is a picture of the front panel ready for my drill press....Its a red panel, its covered with the drilling template agdr provides at DIY.
  

  
 Alex


----------



## XIX47

I have a couple of newbie questions if you do not mind me asking
  
 After turning on the O2 amp, should I delay plugging in the headphone cable until the amp "warms up"?
  
 Also, should the O2 be placed on top of a cover to prevent damage to the wooden desktop it is on? I have heard that amps can damage wooden desktops due to the amount of heat generated.
  
 This is my first headphone amp and I have started using it tonight. So far I have noticed that the sibilance of the DT-990s has been greatly reduced. I like that very much. I wonder if it would be adequate for a pair of AKG k712s or similar models.


----------



## Xenophon

xix47 said:


> I have a couple of newbie questions if you do not mind me asking
> 
> After turning on the O2 amp, should I delay plugging in the headphone cable until the amp "warms up"?
> 
> ...


 
 No and no.  It's not supposed to run hot and it doesn't, not even at (too high) ambient temperatures.  The warnings are usually about tube amps or some very specific *FET designs running in full class A at low efficiency.  On some of those you could bake an egg.  
  
 Enjoy but read up on its capabilities and know that it's not 'the ultimate' in amplification.  No idea about suitability for the K712, don't know them.


----------



## Nec3

xenophon said:


> No and no.  It's not supposed to run hot and it doesn't, not even at (too high) ambient temperatures.  The warnings are usually about tube amps or some very specific *FET designs running in full class A at low efficiency.  On some of those you could bake an egg.
> 
> Enjoy but read up on its capabilities and know that it's not 'the ultimate' in amplification.  No idea about suitability for the K712, don't know them.


 

 I took a temperature scan of the bottom of my odac+o2. It runs at 40 degrees celcius (103 farenheit). I think it's a fairly suitable temperature?
 Of course, I put this on top of my PC near the front port without fans because I have nowhere else to put it.


----------



## XIX47

xenophon said:


> No and no.  It's not supposed to run hot and it doesn't, not even at (too high) ambient temperatures.  The warnings are usually about tube amps or some very specific *FET designs running in full class A at low efficiency.  On some of those you could bake an egg.
> 
> Enjoy but read up on its capabilities and know that it's not 'the ultimate' in amplification.  No idea about suitability for the K712, don't know them.


 

 Alright. Wanted to make sure just in-case.
  
 Yep, it is a budget amp with a neutral sound signature. I do not have a lot of space on my desktop or a bid budget, so it is fitting in nicely with my setup (especially since it is black like the rest of my computer/peripherals). I have no plans to buying very expensive headphones in the future so I should be good with the O2 for a long time?


----------



## Xenophon

nec3 said:


> I took a temperature scan of the bottom of my odac+o2. It runs at 40 degrees celcius (103 farenheit). I think it's a fairly suitable temperature?
> Of course, I put this on top of my PC near the front port without fans because I have nowhere else to put it.


 
 Just for the hell of it I took a reading with my IR-kitchen thermometer.   Device is sitting on my desk, been switched on for 4 hours and the temperature measured at the top of the enclosure is 36.4 centigrade with an ambient temperature in my office of 30 centigrade (not a typo   Fair to say that it doesn't require a massive heatsink although I do believe that the lifespan of some components might be a bit longer at lower temps.  Mine is the epiphany acoustics ODAC/O2 version, btw.  If you want to go wild & crazy:  liquid cooling anyone?


----------



## Xenophon

xix47 said:


> Alright. Wanted to make sure just in-case.
> 
> Yep, it is a budget amp with a neutral sound signature. I do not have a lot of space on my desktop or a bid budget, so it is fitting in nicely with my setup (especially since it is black like the rest of my computer/peripherals). I have no plans to buying very expensive headphones in the future* so I should be good with the O2 for a long time?*


 
 In short, yes though there's no 1-1 relationship between price and ease/quality of driving.  I use the device in my office, have a vastly more expensive setup at home that offers different things but if you don't have really insensitive cans it'll do fine (it drives my HE-500 acceptably and those are not the most sensitive cans around).  The DAC is top-class (for practical purposes), the amp's a bit less imo but still hard to beat at the price.


----------



## Solrighal

xix47 said:


> I have a couple of newbie questions if you do not mind me asking
> 
> After turning on the O2 amp, should I delay plugging in the headphone cable until the amp "warms up"?
> 
> ...




Can I ask you what DAC you're using?


----------



## XIX47

solrighal said:


> Can I ask you what DAC you're using?


 

 Sure, since I am going to do quite a bit of gaming, I have a SB Z as a DAC. The built-in amp of the SB Z is not powerful enough to drive the headphones, hence why I bought the O2 amp. I do have plans to listen to orchestra/acoustic music in the future as well.


----------



## Whitecitadel

Finally got my o2 together this afternoon, sounding good!

Zorrofox does your volume knob sit flush with the panel? I fitted the retaining nut which looks like it should sit under the vol knob but it's proud just wondering what a pre-built looks like (as there from the same place)


----------



## Solrighal

whitecitadel said:


> Finally got my o2 together this afternoon, sounding good!
> 
> Zorrofox does your volume knob sit flush with the panel? I fitted the retaining nut which looks like it should sit under the vol knob but it's proud just wondering what a pre-built looks like (as there from the same place)




The volume knob was the only part of Walters work which jarred with me. I was able to see the assembly underneath the plastic knob.

I ordered two of these and received them within 10 days...


https://www.mayflowerelectronics.com/shop/customization-and-accessories/aluminium-volume-knob/

They do the job beautifully.


----------



## adydula

I have the new "AGDR" ODA Version 2.0 up and running, playing wonderfully here.....I am waiting on a tool to complete the front panel alignment for the holes drilled for all the jacks, switches etc...
  
 Here are some pix:
  

 Fig 1: The venerable O2 on the left the new ODA in the middle and one of my external ODACS on the right.
 The rear RCA jacks allow for a second DAC if you want via RCA jacks and you can easily compare dacs with the press
 of the input selection switch second from the right,.

 Fig 2: Lots of room inside for mounting an internal ODAC if you want as well as other
 options that you can include in your ODA.

 Fig3: Size Differences.

 Fig 4. Simplicity

 Fig 5: Will put feet on the ODA in the near future.

 Fig 6. Preliminary Pilot holes.

 Fig 7. Back Panel, RCA inputs, On/Off Switch and the AC Power input.

 Fig 8. Ready for Case.

 Fig 9.Playing music!!
  
 More to come...
 Alex


----------



## headwhacker

Looking nice, I hope a commercial version appears soon.


----------



## Xenophon

Congrats! Enjoy. How does it sound (strange question in the objective context but you know what I mean)?

I saw the other build pics but am struck again by the high component density on the board. Not a good project for a first build.


----------



## adydula

Hello,
  
 Thanks...this project has been a very good one for me....I was waiting on someone to grab the design and re-invent the amp in a desktop version with a 1/4 jack and RCA plugs etc.
 With this design we get that an much more.
  
 I have listened to it for about 4 hours and have made comparisons to the venerable O2.
  
 Being an analytical person I hate to make verbose generalizations but my gut is telling me its as good as the O2 for sure and maybe better....I am going to find a helper to do some real double blind testing....like the O2 designer would approve of.
  
 We all are biased and that includes me as well.
  
 I was blown away at the first sounds....and the fact that I have to go back a forth with the O2 and "really try to hear differences" is a good thing....
  
 Its not a first time build for sure, but its very well documented now by AGDR at DIY...the build instructions are really good now.
 (the hardest part is the SMD parts and soldering) This does take a steady hand and patience.
  
 There are a lot of options and "customizing" if you desire and how they would fit your particular needs.
  
 To some this may be a bit confusing....but all the explanations are there it takes some time to digest etc..
  
 Not all options have to be done or included, like bass boost, pre-amp out etc..
  
 Its a keeper here, and I will post my objective and subjective impressions soon!
  
 All the best
 Alex


----------



## HaVoC-28

Waiting for the carrefully level matched comparison + ABX / Blind test .


----------



## Whitecitadel

solrighal said:


> The volume knob was the only part of Walters work which jarred with me. I was able to see the assembly underneath the plastic knob.
> 
> I ordered two of these and received them within 10 days...
> 
> ...




Ok so probably as designed, if I turn it one way it's louder, the other quieter, does what I need so far 

Will trawl RS and farnell at some point and see what local options are.


----------



## Solrighal

whitecitadel said:


> Ok so probably as designed, if I turn it one way it's louder, the other quieter, does what I need so far
> 
> Will trawl RS and farnell at some point and see what local options are.




I checked for local options too but found nothing satisfactory. Good luck.


----------



## adydula

I set the levels with a SPL to 85db with a 1Khz tone.
  
 I went back and forth between the O2 and ODA.
  
 Even though this is not blind testing.....which I still intend to do, after I get it in the case and buttoned up..
  
 I was able to come to a conclusion that they both sound pretty much the same.
  
 The ODA will be sent out to be measured objectively soon.
  
 I used Brian Broomberg's "Wood" cd for wonderful bass.....for checking an amps bass tonality this is a great reference.
  
 The bass was as good as the O2's, not any less IMO.
  
 I could go on and on about how great it sounds, but the same that has been said by me about the O2 pertains here as well.
  
 Great stuff sounds great, crap sounds like crap!
  
 Its dead silent at all gain positions (all 4) with the volume cranked up to full roatation.
  
 So far  I am the only person that has one of these ODA's  except for the designer AGDR.
  
 There is another being built in process overseas I believe.
  
 As soon as my reamer arrives I will finish up the front panel holes and get it in the case and do some double blind testing.
  
 Alex


----------



## adydula

Ok here is my first set of results doing a real double blind test with a helper.

 All that had to be done once the level sets were done was to swap the headphone jack from the ODA to the O2 etc or not! (I choose a level that produced 95 db) enough to make the cans really sound "good" or "loud" etc.

 I did a run of 10 samples.
 (I used Eva Cassidy's "Ain't No Sunshine" for the test.)

 I was not able to successfully pick out either amp to any degree of certainty.

 Half the time I was wrong half the time I was correct....but I was never really sure.

 It was very hard to detect which one was playing and any differences....very easy to get confused.

 This tells me that the amps are very very close, and that's a good thing.

 To maintain the same sonic qualities of the O2 is no easy feat to me...to be as transparent and as good as the O2 is awesome.

 I have to give kudos to my wife who ran the switching or not switching!!

 I also spent an hour just listening, really listening to really low level in he background instruments to see if the resolving was nay better on one or the other. Same conclusion, its all there in both of the amps.

 Ok so I am very happy that the ODA to me soncially seems from the same sonic "tree" that the O2 is.

 No for some listening!

 Alex


----------



## Xenophon

Thanks for your impressions and the testing (and thanks to your wife, I know how mine would roll her eyes were I to ask her to run the double blind test  
  
 It'd be interesting to test the new version vs the old with some headphones where I feel the O2 delivers only marginally good performance such as the HE-500 and (the most extreme and in fact unfair case) my HE-6.  I'm tempted to purchase one myself but at 479 USD + the price of the ODAC + import duty and 21% VAT it's no longer in the realm of 'bargain', especially if I have to build a power supply for it (am in the EU) and a bit of a large bet for a blind purchase  because I'm not convinced it'll be able to drive the two cans in question satisfactorily, never mind what their formal specs say.  Of course I could probably sell it on if I didn't like it.
  
 Hmm, gotta sleep on this one for a while.


----------



## adydula

Hey, I understand that....
  
 I don't have any HE's around and don't know of any one near me etc.....but I will ask around.
  
 The "other" version" may be better, but I would pm agdr directly and ask him.
 (other version that being with higher rail voltages etc).
  
 In one of his posts he recommends the Beta for those types of cans...
  
 I have around $250 in this so far, with me doing the labor and having the good fortune of haning it work the first time.
  
 The gain switch was defective but that was replaced.
  
 We have one final small (2) resistor change to reduce the heat on IC11.
  
 That should be it  for awhile!
  
 All the best
 Alex


----------



## adydula

Xenophon,,,,
  
 Agdr posted this:

 *ODA works perfectly with HE500 and HE6 up to 118dB and 113dB*
 So here is your answer about the HE500 and HE6. The ODA will not only power both perfectly with the standard +/-12.5Vdc power rails, they will do so all the way up to 118dB and 113dB, respectively. And those were just the power levels that broke the spreadsheet. Nobody should be listening to headphones at those levels anyway! See the hearing damage chart at the bottom of the fellow's spreadsheet.

 I have created a new folder at the V2.0 ODA Google Drive link called "Headphones vs. the ODA". Here is a direct link to it:

https://drive.google.com/folderview?...28&usp=sharing

 In there I have used a nice power calculation spreadsheet that was posted on Head-Fi back in December. See the README file in that folder. It has a link to that post with the sheet, and links to the specification pages for the HE500 and HE6.

 For more normal levels I have also included sheets for both at 95dB.

 Note that only the 113dB power level with the HE6 is coming near the using the full 7.25V(rms) swing of the ODA with the +/-12.5Vdc rails, at 6.67V(rms). The current is still a no-brainer for the ODA, divided by 6 for the 6 output chips with 70mA available each for powering the load.

 So.. these kind of headphones are exactly what the ODA eats for lunch. 
	

	
	
		
		

		
			





 Also note that the +/-15Vdc power rails should not be used with either headphone. +/-12.5Vdc does the job as per the charts, and the output chips could overheat at the higher voltages. Those are only for 300R and 600R cans.

 --> I'm going to post this PM contents in the thread becasue it is an excellent question and really shows what the ODA is useful for. More good work, Alex! Thanks. 
	

	
	
		
		

		
		
	


	



   
 
agdrView Public ProfileSend a private message to agdrVisit agdr's homepage!Find More Posts by agdrAdd agdr to Your Contacts
 




  ​


----------



## adydula

Just another aside, the cost of the panels in the completed and tested ODA is about $100 more if I got he panels done by Front Panel Express. Seeing how I just retired I am on a fixed income and wanted to keep the costs down as much as possible.
  
 If your handy with mecahanical tools and stuff you could look at maybe buying the board and mount it in a box and drill holes etc...not that hard but again time consuming etc..
  
 Alex


----------



## Xenophon

Thanks a lot Alex!  
  
 I'm not listening at anything near those levels, no problem, don't want a peak in a classical record to wipe out some nerve endings   Hearing still extends to >15kHz at age 41, not too shabby for a guy who listens to music wearing headphones for hours/day.
  
 I'm sorely tempted...only the power supply left to consider but that's a small thing and easily fixed.  If I order it I'll go with the Front Panel enclosure, you're absolutely right that everything could be built from scratch but as you say, it's a tradeoff between money and time...and with all the business trips and time away my wife would appreciate it if I'd pick spending some cash over spending hours in the basement tinkering away.  Hmm, gonna do some re-reading at DIY-audio I guess.  Decisions, decisions....  But it'll take up less desk space than the vintage Pioneer SX-1980 I managed to find (FedEx guy still gives me the fisheye over its 40 kg) 
	

	
	
		
		

		
		
	


	



  
 Next project here will be a self built 45 or 300B tube amp....crunching the numbers.


----------



## adydula

Vintage SX-1980.....oh my.....
  
 Would I like to have that!!!
  
 I am a real "sucker" for the old Pioneers!!!
  
 Reminds me of my youth!!
  
 Alex
  
 (Smiling!!!)


----------



## ieee754

Is it normal that O2 distorts bass very badly at 6.5x gain (even at volumes much lower than I listen on 2.5x, which sound clean)? I have only low impedance headphones (18 and 35 ohm), if that matters.


----------



## headwhacker

ieee754 said:


> Is it normal that O2 distorts bass very badly at 6.5x gain (even at volumes much lower than I listen on 2.5x, which sound clean)? I have only low impedance headphones (18 and 35 ohm), if that matters.




What is the Vrms level of your source? At 6.5x your source voltage must be less than 1Vrms.


----------



## ieee754

headwhacker said:


> What is the Vrms level of your source? At 6.5x your source voltage must be less than 1Vrms.


 
 I have JDSLabs integrated O2/ODAC combo, so it is probably at proper level. I have read somewhere that higher gain equals to lower output power, and since I use current driven headphones maybe it should clip? But I don't have to listen very loudly to get these distortions so I'm not sure.


----------



## jring

ieee754 said:


> I have JDSLabs integrated O2/ODAC combo, so it is probably at proper level. I have read somewhere that higher gain equals to lower output power, and since I use current driven headphones maybe it should clip? But I don't have to listen very loudly to get these distortions so I'm not sure.


 
  
 Yes, with the ODAC the O2 at 6.5x gain will clip regardless of the volume pot setting. This is because the 6.5x gain option is for low output devices like mobile players. The ODAC delivers a 2V redbook compatible signal and thus 3.5x gain is the possible maximum.
  
 Joachim


----------



## ieee754

jring said:


> Yes, with the ODAC the O2 at 6.5x gain will clip regardless of the volume pot setting. This is because the 6.5x gain option is for low output devices like mobile players. The ODAC delivers a 2V redbook compatible signal and thus 3.5x gain is the possible maximum.
> 
> Joachim


 
 You're right, when I set volume in Windows to 80%, the clipping disappears. Now I know that there is nothing wrong with my O2. So 6.5x is only useful for amping external sources, I thought it's for high impedance headphones, which require higher voltage.
  
 Thanks guys!


----------



## adydula

Not very many people really understand what gain is and how it differs to volume etc....The 6.5 gain setting is seldom used.many folks, and your correct with the ODAC its not needed...it will distort.
  
 The ODA has a clipping indictor and it doesn't take much to clip..
  
 A.


----------



## ieee754

adydula said:


> Not very many people really understand what gain is and how it differs to volume etc....The 6.5 gain setting is seldom used.many folks, and your correct with the ODAC its not needed...it will distort.
> 
> The ODA has a clipping indictor and it doesn't take much to clip..
> 
> A.


 
 ODA looks very interesting. Do you think that upgrading from O2 to ODA would make a difference for amping HE-560 (it has about the same efficiency and impedance as HE-500)?


----------



## adydula

Yes I believe it would....or I should say the potential is there...
 What is the sensitivity rating?
 Alex


----------



## adydula

Fyi.. I am taking all ODA questions and topics over to a separate thread:
  
http://www.head-fi.org/t/719611/objective-desktop-amp-a-version-from-agdr#post_10564054
  
 Alex


----------



## r010159

Has anyone noticed the highs are a bit emphasized on many jazz and rock albums. At first I thought it was the O2, but since the O2 has a flat frequency response, I am thinking it is the recordings. This particularly shows up with guitar work.

Bob


----------



## GigArt

I agree. I mostly prefer to listen to extreme metal with agressive drumming. Harshness is obvious with my Fostex TH600 wich tend to be a bit treble-happy.


----------



## jring

r010159 said:


> Has anyone noticed the highs are a bit emphasized on many jazz and rock albums. At first I thought it was the O2" but since the O2 has a flat frequency response, I am thinking it is the recordings. This particularly shows up with guitar work.
> 
> Bob


 
  
 Same here with a DT990 on O2. I think that the O2 with its neutral sound does nothing to soften the emphasized treble (and bass in case of my DT990). With the right music, it's big fun, but I can imagine that some listeners will have problems with that combination.
  
 Joachim


----------



## Solrighal

It's smooth as butter with my HD 650's.


----------



## r010159

jring said:


> Same here with a DT990 on O2. I think that the O2 with its neutral sound does nothing to soften the emphasized treble (and bass in case of my DT990). With the right music, it's big fun, but I can imagine that some listeners will have problems with that combination.
> 
> Joachim


 
  
 Yes, it can be fun. But after listening to these particular albums for weeks, and then when I listen to an amp that colors the sound a bit to be more "analog" like, I find it is a nice break for my ears. I can see why some like tube amps.
  
 Bob


----------



## r010159

I have been comparing the OSAC/O2 to other more expensive ones using Amazon's loaner program. 
	

	
	
		
		

		
			





 A recognized $400  DAC/amp was not as good as the O2. So I purchased what I thought to be a very good DAC/amp, the Duet 2, that is used by some mobile recording artists. This is where I went to the heart of the matter by thinking that this should be a good and accurate DAC/amp. Keep in mind this is a $500 DAC/amp that until recently used to sell for $600
  
 I have noticed some differences. First, the Duet has more depth to its soundstage. Also the upper frequency sounds like from the cymbals come across a bit more clearly. I think this is related to jitter. And the Duet does have a different sound signature probably done on purpose. It give a more analog like sound to the music. And the songs which go into clipping do sound much better.  I can see some of the reasons why there are people that prefer analog gear like tube amps.
  
 [deleted useless information]
  
 So with respect to $300 and even $400 DAC/amps, IMO the ODAC/O2 competes well. We are definitely getting our moneys worth.
  
 FWIW
  
 Bob
  
 O2/ODAC = dry martini
 Duet = martini with more vermouth
  
 A matter of taste.


----------



## r010159

solrighal said:


> It's smooth as butter with my HD 650's.


 
  
 It looks like the particular selection of headphones can make the difference.
  
 Bob


----------



## Xenophon

r010159 said:


> Yes, it can be fun. But after listening to these particular albums for weeks, and then when I listen to an amp that colors the sound a bit to be more "analog" like, I find it is a nice break for my ears. I can see why some like tube amps.
> 
> Bob


 
 I'm glad you guys are broadening your horizons.  Basically I also think that for the money and up to about 300-350 USD the ODAC/O2 (but more the dac than the amp) will hold its own and be hard to beat.  But there IS better/more enjoyable, never doubt it.  In the strictly objective domain I believe agdr's version of the desktop ODA is a fine example.
  
 I'm on the fence between tubes and ss gear.  I like a slightly warm sound but dislike the typical 'lush' 'syrupy' tube sound (which is just an indication of an improperly conceived/built tube amp imo but that aside).  But any colouring I try to do via my headphones.  This probably also explains Zorrofox's impression as what he describes seems to jibe with the HD-650 sound signature.


----------



## Solrighal

Yes, that was the point I was trying to make. The O2 acts like a clear window on the music and/or equipment. I also own a pair of Q701's and they sound very bright and edgy. They sound like that on everything though but even more so via the O2.

I'd also like to try a tube amp but in the back of my mind I suspect that a tube amp is only really adding distortion. With some headphones and/or music this added distortion will make for a better sound but I suspect that won't be the case with every possible combination.

We've all read many times of the special synergy between the Crack and 650's but this surely means that with other headphones this synergy is lost and in fact the Crack possibly makes things worse.


----------



## miceblue

The Crack is an OTL amplifier and works best with high impedance headphones where voltage swing is more important than current delivery. XD


----------



## Solrighal

miceblue said:


> The Crack is an OTL amplifier and works best with high impedance headphones where voltage swing is more important than current delivery. XD




Yes but what does this actually mean in sonic terms? What would I expect to hear change in the sound?


----------



## greenkiwi

solrighal said:


> Yes but what does this actually mean in sonic terms? What would I expect to hear change in the sound?


 
 I think that it's more about the actual needs of headphones.  Some need high voltage swings to generate sound (I believe high impedance 300-600ohm), while others need high current (think orthos).  So if you have the former, the Crack will work well... if you have the latter, you will run into problems because you will be asking the amplifier to provide too much current.  i.e. operate outside of its designed operating state.  (I would guess sonically, you'd have more distortion.  In the same sense that if you have too high an input signal on the O2 and have the wrong gain selected, you get clipping, as you are outside of the design envelope.)


----------



## miceblue

Well its output impedance is some 120 ohms or something too, so that in itself makes the bass more woolly and ill-defined for lower-impedance headphones. That sound happens to sound okay with a K 701 on the other hand.


----------



## Solrighal

Thanks guys, that helps a bit.


----------



## mcandmar

miceblue said:


> Well its output impedance is some 120 ohms or something too, so that in itself makes the bass more woolly and ill-defined for lower-impedance headphones. That sound happens to sound okay with a K 701 on the other hand.


 
  
 That's it exactly.  I know users with T1's and HD800's also report the Crack as pairing very well with them, it seems just about any high impedance headphone sounds great with it. In my opinion the reason why many people rave about the HD600 series with the Crack is they are normally a laid back dark sounding headphone, the Crack give them that bit of dynamic energy they are lacking.


----------



## headwhacker

mcandmar said:


> That's it exactly.  I know users with T1's and HD800's also report the Crack as pairing very well with them, it seems just about any high impedance headphone sounds great with it. In my opinion the reason why many people rave about the HD600 series with the Crack is they are normally a laid back dark sounding headphone, the Crack give them that bit of dynamic energy they are lacking.


 
  
 For T1, it's hard to believe you need high powered amp to drive it to it's best performance. (Talking about > 1W amps) I do believe tube amp makes T1 sound different and people like it but definitely not because tube amps deliver more power than O2 but it's because of everything else tube amp adds to the signal.
  
 O2 in itself has enough voltage swing (through a wall power at 7Vrms) to drive T1 properly to very high volume level. But it's definitely has not enough current for the Orthos. Which is where the ODA comes in.


----------



## CADCAM

Does anyone have the ODAC and run Linux as an OS? I run PCLinuxOS 64 and want to verify that the ODAC works and is recognized with the OS before purchasing.
 thanks for any help


----------



## greenkiwi

I can try tonight. Given that it's a standard class 1 USB audio device any modern Linux system should have support right out of the box.


----------



## Xenophon

Tube amps are great at voltage and hence at higher impedance loads.  For optimal theoretical damping with dynamic headphones you'd need a 7-8 factor difference between the output of the amp and the cans' nominal impedance (which might be < 50% of max impedance at certain frequencies), if it's much less then you  get a typical 'loose' bass due to lack of control over the diaphragm.  Planars are reasonably insensitive to this phenomenon though.  My 38 ohm HE-500 plays very nice with tube amps.


----------



## greenkiwi

xenophon said:


> Tube amps are great at voltage and hence at higher impedance loads.  For optimal theoretical damping with dynamic headphones you'd need a 7-8 factor difference between the output of the amp and the cans' nominal impedance (which might be < 50% of max impedance at certain frequencies), if it's much less then you  get a typical 'loose' bass due to lack of control over the diaphragm.  Planars are reasonably insensitive to this phenomenon though.  My 38 ohm HE-500 plays very nice with tube amps.


 
 Is that because planars end up being a simpler purely resistive load?


----------



## jring

cadcam said:


> Does anyone have the ODAC and run Linux as an OS? I run PCLinuxOS 64 and want to verify that the ODAC works and is recognized with the OS before purchasing.
> thanks for any help


 
  
 Works fine here with different Ubuntu and Debian flavours. As has been said before - it should work with just about anything capable of using a USB audio class 1 device...
  
 Joachim


----------



## CADCAM

I have a Maverick D2 and my system ignores the DAC when I plug it in...
 Do you happen to know if I need to install something from the Package Manger? BTW using Clementine to play tunes but tried Pandora and get the same


----------



## miceblue

james-uk said:


> At its best, the ODAC sound expansive, detailed, and precise in imaging. At its worst, the ODAC sounds closed-in, flat, dull, uninteresting, and with wooly bass (Class S). It depends upon the USB connection. Overall the ODAC is not as precise in rendering of sounds. This is where the comparable Modi exceeds its performance.
> 
> ^(Quote from said shoot out)
> 
> ^^^^^This is hilarious . It depends on the USB connection!





miceblue said:


> Well my older MacBook's USB connection is kind of lame and yeah, I can agree with that observation.





james-uk said:


> Bring some double blind examples to the table and I'm all ears.




Here's an example of a bad USB port. I think even a mostly deaf person can tell it's bad.
Foobar2000 + WASAPI output -> ODAC -> USB audio recorder with line out connection from ODAC to a different computer -> Audacity
https://dl.dropboxusercontent.com/u/2816447/BadUSB.wav


----------



## Xenophon

greenkiwi said:


> Is that because planars end up being a simpler purely resistive load?


 
 There are a couple of issues with high output impedance for the amp and low impedance headphones:
  
 - The higher the output impedance, the higher the voltage drop with a low impedance load--> This can cause insufficient 'drive' of headphones (insufficient volume, distortion...) if your amp is not up to it.
  
 - With dynamic cans, impedance fluctuates across the frequency band, this may or may not exacerbate the previous problem, planars are not subject to this fluctuation as they indeed *behave* like a resistive load even though (long explanation which I'll skip) they're really not.
  
 - Damping:  Also plays with planars, I frankly don't understand all aspects so what follows is speculation:  if a headphone is underdamped it'll start showing signs such as 'loose' bass.  Fact is, none of my planars show this, even though they're low impedance loads connected to a high impedance output sources.  Electrical damping is negligible due to this.  I suspect the all things considered good damping is related to mechanical damping due to the different structure with the membrane and the metal conductive tracers.
  
 The above -especially about damping- is speculation, there are a number of interrelated factors at play and I lack the knowledge to really give a founded opinion.  But in the end, who cares, the sound is good. I did extensive comparisons with my planars connected to a tube amp vs to my (close to zero output resistance) V200 and the bass on the V200 is a bit tighter but not a big deal.   If your tube amp is *sufficiently powerful* and you use planars I don't think you need to worry.  With dynamic cans that have a low impedance it's best to try before you buy.  Imo really low impedance headphones and tubes are a no-no.
  
 Or if you have either the time, knowledge and skills, develop a custom tube amp that ensures a decent impedance match (can be done but tends to become expensive) or lacking those skills but possessing money, the great equalizer, hire someone to do it for you.


----------



## James-uk

xenophon said:


> There are a couple of issues with high output impedance for the amp and low impedance headphones:
> 
> - The higher the output impedance, the higher the voltage drop with a low impedance load--> This can cause insufficient 'drive' of headphones (insufficient volume, distortion...) if your amp is not up to it.
> 
> ...




I have a similar experience with a higher output impedance amp. My HDVD800 amp has a supposed 47 ohm output and therefore using the hd800s with it I expect bass to have a bit more 'bloom' and the upper mids and treble to be slightly quieter due to its impedance curve ( 600ohm across mid bass and less than 300ohm across upper mids into treble ) but when I switch between the hdvd800 and O2 it's very difficult to hear any difference . I would put money on me failing a blind test between them.


----------



## headwhacker

james-uk said:


> I have a similar experience with a higher output impedance amp. My HDVD800 amp has a supposed 47 ohm output and therefore using the hd800s with it I expect bass to have a bit more 'bloom' and the upper mids and treble to be slightly quieter due to its impedance curve ( 600ohm across mid bass and less than 300ohm across upper mids into treble ) but when I switch between the hdvd800 and O2 it's very difficult to hear any difference . I would put money on me failing a blind test between them.




The HD800 may have a nominal impedance of 300Ohms but like other dynamic driver phones it's load impedance can fluctuate wildy at different frequencies, Most of the time the wild flunctuation is at the mid bass. HD800 could easily go up to 600ohms at the mid bass, which could explain why you don't hear much difference against O2.


----------



## James-uk

headwhacker said:


> The HD800 may have a nominal impedance of 300Ohms but like other dynamic driver phones it's load impedance can fluctuate wildy at different frequencies, Most of the time the wild flunctuation is at the mid bass. HD800 could easily go up to 600ohms at the mid bass, which could explain why you don't hear much difference against O2.




That's my point, the fluctuating impedance should mean that with a higher output amp such as the hdvd800 the damping factor means it should effect the sound compared to the O2. If I'm right in thinking a high output impedance amp won't act like the O2 and won't give equal voltage across the fluctuating impedance curve because the damping factor is poor. Basically high output amps would supply more voltage at the highest part of the impedance curve and less at the lowest and therefore alters the headphone frequency response. I don't hear this with the hdvd800 however , it sounds the same as the O2 yet it's damping factor is much worse . Why is that do you think? Maybe the damping factor is still high enough that is not having a noticeable effect?


----------



## pearljam50000

Can anyone compare the 02 and Vali with HD800?


----------



## headwhacker

james-uk said:


> That's my point, the fluctuating impedance should mean that with a higher output amp such as the hdvd800 the damping factor means it should effect the sound compared to the O2. If I'm right in thinking a high output impedance amp won't act like the O2 and won't give equal voltage across the fluctuating impedance curve because the damping factor is poor. Basically high output amps would supply more voltage at the highest part of the impedance curve and less at the lowest and therefore alters the headphone frequency response. I don't hear this with the hdvd800 however , it sounds the same as the O2 yet it's damping factor is much worse . Why is that do you think? Maybe the damping factor is still high enough that is not having a noticeable effect?




Assuming the worst impedance swing at 600 ohms, Damping factor is between 6 - 12. So it's possible HD800 is still adequately damped.


----------



## James-uk

headwhacker said:


> Assuming the worst impedance swing at 600 ohms, Damping factor is between 6 - 12. So it's possible HD800 is still adequately damped.



Good point. I can't help but wonder why the HDvd800 engineers decided on a 47 ohm output. It's a well designed amp otherwise. Granted its expensive and has snake oil balanced connections but I do like running multi headphones from it. The O2 /odac sounds the same at 1/5 the cost though and probably measures better. Gotta love the O2!


----------



## Xenophon

james-uk said:


> Good point. I can't help but wonder why the HDvd800 engineers decided on a 47 ohm output. It's a well designed amp otherwise. Granted its expensive and has snake oil balanced connections but I do like running multi headphones from it. The O2 /odac sounds the same at 1/5 the cost though and probably measures better. Gotta love the O2!


 
 It's extremely pricey for what it is.  But ok, it's Sennheiser so there's the name premium (just take a look at their new cables...)+ the case that must cost a pretty penny to fabricate and the connectivity options.  Beats me too why they settled on the 47 Ohm output impedance (I'd guess some of their measurements were 'helped' by selecting that value although generally lower = better) but let's not forget that the 1996 IEC 61938 standard still specifies an insane 120 Ohm.
  
And admit it, guys, it looks more impressive sitting there than an ODAC/O2.  I'd say the components would be higher specced too but after my last shocking look under the hood of a tube amp that retails for >3 kUSD I'm no longer convinced of the positive correlation between price and quality.


----------



## adydula

FYI....thought I would share the thoughts of AGDR in his ODA designand damping for headphones and amps:
  
*Output damping factor resistors. *This version of an ODA has PC board holes for a series resistor on each channels output (R88 & R89) that changes the damping factor. This resistor can simply be omitted and the PC holes shorted out with a jumper wire to get the lowest output impedance and highest damping factor, about 0.083 ohms. That is the default in the BOM. Some headphones may sound better to the user with a lower damping factor (adding in the series resistors), especially adding more bass. In an email exchange with AKG (Harman International) they said that the recommended amplifier output impedance for my AKG K550 headphones is the same as the phones, 32 ohms, +/-20 ohms in either direction. Not zero ohms. These two R88 & R89 resistor pads have three holes to accommodate different sized resistors. Just run the jumper between the two outer holes, and it doesn’t matter if the (bare) jumper wire touches the middle hole. 
 An external 6 position rotary switch can be mounted on the front panel with wires running to these PCB holes to give more damping factor selections. I’ve included a suitable optional panel mount rotary switch in the BOM. 
 So in most cases the two damping factor resistor positions on the PC board will simply be jumpered across (not used) to obtain the lowest amplifier output impedance of 0.083 ohms per channel. But if you want to experiment with different damping factors the holes are there to insert resistors and give it a try! I would suggest trying the following: 
 • 10 ohms, which is a common resistor value used on many amps that don’t have output short circuit protection like this amp does. The resistor helps limit current spikes in those amps. 
 • A resistor equal to the impedance of your headphones if under 80 ohms or so. In the case of my AKG-K550s, 30 ohms. That will result in a 50/50 voltage divider and cut the maximum output voltage swing to the headphones in half. 
 • 120 ohms. A very old standard for headphone amp output impedance was 120 ohms, but that had more to do with the use of tubes at the time. Some older headphones may have been designed with that standard in mind though! Unless the headphones being used are 300R or 600R, a significant amount of the voltage swing would be dropped across the 120R resistor though. 
  
 Alex


----------



## pearljam50000

Is anyone using the O2 with HD800 as their main amp?


----------



## James-uk

I alternate between the O2 and hdvd800. They sound identical but I use the latter more because it has 2 amps inside so I can run the 800s and 600s simultaneously and swap to suit the album. I often go back to the O2 just to keep things in perspective when I see new gear!


----------



## pearljam50000

Thanks!
I was worried because i read here somewhere that the HD800 has no bass with 02 , because it's not powerful enough.


----------



## James-uk

It's plenty powerful enough. Normal listening I have the pot set to about 10-11 o'clock and occasionally 12 with quiet recordings.


----------



## derbigpr

xenophon said:


> Tube amps are great at voltage and hence at higher impedance loads.  For optimal theoretical damping with dynamic headphones you'd need a 7-8 factor difference between the output of the amp and the cans' nominal impedance (which might be < 50% of max impedance at certain frequencies), if it's much less then you  get a typical 'loose' bass due to lack of control over the diaphragm.  Planars are reasonably insensitive to this phenomenon though.  My 38 ohm HE-500 plays very nice with tube amps.


 
  
  
 Majority of headphones are insensitive to that. I don't hear absolutely any difference between a <1 ohm output impedance 1000 dollar headphone amp and a 400 dollar integrated amplifier headphone output with 220 ohms output impedance when it comes to bass tightness, not even with 32 ohm headphones. Only with in-ears there's an audible difference.  People think too much of the damping factor, nobody even cared about it or talked about it before the whole O2 story started blowing it out of proportion and everyone suddenly started talking about it as if it's the most important spec when it comes to headphone amplifiers, and as if only amps with very low output impedance sound good.


----------



## adydula

Output Impedance is a very important and a critical part of a good headphone amps design....
  
 Many headphones are designed to be used best with near zero output impedance.
  
 There is a lot of data published by vendors and the designer of the O2 as well about this topic and damping etc.
  
 I would much rather have an amp the has a near zero output impedance period.
  
 Things that can go bad with high output impedance is voltage swings to the headphones. As headphone impedance changes with frequency these variations can be very noticeable and huge and thus very audible. 
  
 But to some depending on the headphone and source material could possibly like this "sound".
  
 If someone wants more technical details send me a PM.
 Also: http://www.head-fi.org/t/583798/low-output-impedence-headphone-amps
  
 The great thing about the O2 is its near zero output impedance in a low cost headphone amp.
  
 Also the new 'ODA" takes all this in account and even offers a selectable damping selection if desired. This way you can play with this specification to see for yourself etc...
  
 There are headphones that have designed for higher output impedances than zero...The AKG 550's according to AKG were designed best to be used with a output impedance of 32 ohms +/- 20 ohms. So there are exceptions etc.
  
 All the best
 Alex


----------



## derbigpr

adydula said:


> Output Impedance is a very important and a critical part of a good headphone amps design....
> 
> Many headphones are designed to be used best with near zero output impedance.
> 
> ...


 
  
  
  
 Majority of headphones were designed like that K550.   I guarantee you if you sent emails to each and every manufacturer out there to give you a recommendation on output impedance that's perfect for their headphone models, maybe 2 out of 10 would say close to zero ohms. In my experience only a few headphones (mostly in-ears and small portables with 16 ohms of impedance) were affected and showed any difference in sound when comparing them with low and high output impedance amps. Almost no Beyerdynamics or Sennheisers, and most AKG's definitely don't need low output impedance, and most are tuned to work with higher value, Beyer even makes their own amps with high output impedance, so does Sennheiser, not because they don't know how to make ones with low output impedance, which is really simple, but because they tune their headphones and amps to match together as good as possible and to sound as good as possible. Also to match as much equipment out there as possible, and believe it or not, most people don't use separate headphone amps at all, not even with higher end headphones, they just plug them into their integrated amplifiers in their main hi-fi systems, which all have high output impedance.  None of the professional studio equipment has low output impedance either, even really expensive consoles, interfaces, etc. have over 50 ohms of output impedance.
  
 Yes, with low impedance headphones low impedance output it is better in theory, but doesn't mean it is always better in practice, some headphones can sound better with some of that "loose" bass added, but it ultimately comes down to personal preference. But it's just wrong to imply that headphone amps with low output impedance are better than those with high output impedance, or that they will sound better, are better engineered, etc. Because it's simply not true, there are many factors other than output impedance alone that matter far more. I mean, my Musical Fidelity M1HPAP is better than Beyerdynamic A1 on paper, it has less than 1 ohm output impedance vs. 120 on the A1, yet, the T1's definitely sound better on the A1, so does the DT990, DT880 and even an 80 ohm DT770.


----------



## adydula

Understand what your stating and agree on most of it.
  
 I still would like to have an amp that has close to zero output impedance and start from there. Yes there are headphones that will sound "better" at higher output impedances and these can be accommodated with resistors etc, switches etc.
  
 All you really need to know is most headphones work best when the output impedance is less than 1/8th the headphone impedance. If you want to be assured a source will work well with just about any headphone, simply make sure the output impedance is under 2 ohms.
  
 What is fact is an amp with a very low output impedance impacts the sound in the least manner.
  
 If a headphone is designed to work best with a high output impedance amp there usually us a reason for that...
  
 there are 3 areas that output impedance matters:
  
 1. The greater the output impedance the greater the voltage drop with lower impedance loads. This drop can be large to enough to prevent driving low impedance headphones to sufficiently loud levels.
  
 2. Headphone impedance changes with frequency. If the output impedance is much above zero this means the voltage delivered to the headphones will also change with frequency. _The greater the output impedance, the greater the frequency response deviations_. Different headphones will interact in different, and typically unpredictable, ways with the source. Sometimes these variations can be large and plainly audible.
  
 3. As output impedance increases electrical damping is reduced. The bass performance of the headphones, as designed by the manufacture, may be audibly compromised if there’s insufficient damping. The bass might become more “boomy” and less controlled. The transient response becomes worse and the deep bass performance is compromised (the headphones will roll off sooner at low frequencies). A few, such as those who like a very warm “tube like” sound, might enjoy this sort of under damped bass. But it’s almost always less accurate compared to using a low impedance source.
  
 The 1/8 rule comes into play here to mitigate the "possible" issues in these areas.
  
 If you pick a high dollar amp made by a firm that makes headphones it may be that that amp may very well work better with those cans, but may not work well with others.....
  
 Even the designer of the O2 states some headphones will sound better with a higher output impedance.
  
 Back in the old days stereo receivers and professional gear had high output impedance jacks for sure.There is a lot of history here and the 120 ohm 1996 standard that Stereophile scoffed at....
  
 But even Sennheiser has stated they design their audiophile and portable headphones for zero ohm sources.
  
 With all this rambling output impedance is still very important thing to consider and damping etc...several amps since the advent of the O2 have started to spec this out clearly so consumers are aware. This IMO is a good thing.
  
 Alex


----------



## adydula

Here is a post from another Headfi person sometime back...
  
 "
 It's largely a matter of perspective:  If certain headphones don't pair well with a neutral, low output impedance amp, I think xxxGuy would point out that it's not the amp's fault.  I would agree here, since designing around such an amp is really the only way to get a stable reference point for headphone performance:  The concept of amp neutrality is objectively well-defined, but coloration spans a huge multidimensional spectrum.  Similarly, 0 ohm output impedance is well-defined, whereas banking on pretty much any other output impedance is totally arbitrary.  For the sake of standardization and keeping consumers from going crazy and broke, headphone designers should really be designing around 0 ohm output impedance amps.  If certain headphones are depending on a high output impedance amp to roll off certain frequencies that the headphones go overboard on, I'd personally consider that a design flaw in the headphones.
  
 In a perfect world, all headphones would be designed around neutral, low output impedance amps, but this is the real world...and sometimes maybe they aren't.  Even if they are, headphones are impossible to make perfect with our current technology, so even some headphones technically designed around low output impedance amps might have flaws that some higher output impedance amps could alleviate by happenstance.  (Or maybe you just prefer muddy bass? 
	

	
	
		
		

		
			





)  At that point, you pretty much have to search for a Goldilocks zone...but what if a particular amp DOES compensate perfectly for a headphone's flaws?  In that case, the amp and headphone combination becomes much more than the sum of its parts.  Independently, I'd consider both flawed...but together, they could be a perfectly viable or formidable choice for great audio.
  
 Ultimately, no amp will be the best choice for all headphones.  However, I think a powerful, objectively well-measuring, neutral, low output impedance amp is inherently more versatile than colored amps:  It may not compensate for any sonic flaws in the headphones, but it also won't introduce any of its own that will exacerbate them or otherwise make things worse.  Neutral amps may not sound great with ALL headphones, and saying they do would be an overstatement...but they're a good middle ground between warm and bright, and they're really the only stationary targets for designing headphones around.  The same applies to low output impedance, since the effect of high output impedance is an arbitrary sort of frequency response rolloff, which would count as a source of coloration.
  
 That's a big reason why I went for the O2:  I'll just restrict my headphone purchases to the ones that work well with it, which means "no stats, K1000's, Sextets, or headphones that need extra coloration to sound good."  The last part means I'm sacrificing a few opportunities in favor of simplicity:  No headphones are perfect, and there may be a particular amp that matches a particular pair of headphones better than the O2 will ever match anything.  For instance, the FA-002W High Editions can be really great headphones according to LFF, but they're picky about amps, and the O2 (and presumably any other neutral amp) doesn't make the cut.  Nevertheless, I want the versatility to try (and judge) a bunch of cans without worrying about amp coloration as a variable or trying n*m combinations of headphones and amps, so the O2 is perfect for me.  I'd recommend it (or another inexpensive and neutral amp, such as The Wire) to anyone in the same boat.  If I need to tweak, I'll go for an EQ or DSP.  (It is interesting though that you could add a switched output resistor to it.  That would definitely increase the versatility aspect further.)
  
 However, if you're set on a particular flagship headphone, you may get more mileage finding the perfect amp for that particular headphone model.  If you're a serious headphone hobbyist (deep pockets 
	

	
	
		
		

		
		
	


	




), you may get more mileage just playing with amp options too.
  
 Here is the link to this discussion: http://www.head-fi.org/t/583798/low-output-impedence-headphone-amps/15
  
 Enjoy
 Alex


----------



## adydula

Just for an exercise in getting the truth from the source:
  
 Here is a note to Senn Support:
  
 Message:
 HD800 What is the amplifier output impedance for the best sound from the HD800's? Amps have different output impedances from near zero ohms to several hundred?

 Thanks in Advance
 Alex
  
 Reply, which was very quick:
  
 Good Afternoon Mr Alex

 Thank you for contacting Sennheiser Technical Support. The HD 800 headphones have an impedance of 300 Ohms which means that they need to be connected to an amplifier that is outputting at least 300 Ohms. Anything less than 300 Ohms and the headphones will not be able to reach their full potential. For the HD 800 we would recommend our HDVD 800 amplifier.

 Have a great day.
  
 (name removed).
  
 Now the HDVD 800 amplifier is only $1995 and its output impedance spec is listed as 16 ohms?
  
 Now how is that going to work?
  
 Alex


----------



## Xenophon

adydula said:


> Just for an exercise in getting the truth from the source:
> 
> Here is a note to Senn Support:
> 
> ...


 
 Wonder what that guy was smoking but it sure wasn't a pack of Gauloises....  He's off his rocker about the amp, anyone with eyes can plainly see that those 300R are not exactly constant across the fq spectrum AND iirc the HDVD-800 output Z is about 46 R.......


----------



## adydula




----------



## adydula

To be fair I asked Senn about this discrepancy and got this reply:
  
 Good Afternoon Mr Dydula,

 Thank you for contacting Sennheiser Technical Support. The HDVD 800 is capable of producing a range out output levels going all the way up to 600 Ohms.

 Have a great day.
  
 FYI
  
 Alex


----------



## HaVoC-28

adydula said:


> Just for an exercise in getting the truth from the source:
> 
> Here is a note to Senn Support:
> 
> ...


 
  
 I guess that he wanted to say that you need an amplifier that is rated to drive at least a 300 ohms headphone . (wich allready don't mean anyting : / ) .
  
 1th level support , are from marketing / secretarial departement?


----------



## James-uk

That kind of poor communication and engagement is enough to make me want to sell my HD800s!!! If you make the most advanced headphone ever at least have the confidence to be transparent with your information and employ someone to respond with facts rather than random bull**** and lack of understanding !


----------



## James-uk

I suppose that's why we love the O2 . Totally transparent in every possible way !


----------



## Solrighal

james-uk said:


> I suppose that's why we love the O2 . Totally transparent in every possible way !




Ba-boom!


----------



## HaVoC-28

james-uk said:


> That kind of poor communication and engagement is enough to make me want to sell my HD800s!!! If you make the most advanced headphone ever at least have the confidence to be transparent with your information and employ someone to respond with facts rather than random bull**** and lack of understanding !


 
  
 We could do a similar test with other headphone brands , and i guess that it will not be that different from sennheiser from most .
	

	
	
		
		

		
			




  
 If you reply to them , and point that the informations are incorrect they will pass your email to tech 2 support or something like that where some one with a bit more knowledge on the subject will give you a "decent" response (i hope so) .


----------



## James-uk

https://m.facebook.com/story.php?story_fbid=841752309179115&id=367116489976035

I just spotted this . Another example of why we can't trust our ears.


----------



## adydula

If you pay this much money or were anticipating on spending this much money on headphones I would hope you would get honest and accurate answers up front without having to play 20 questions in the first place!!.
  
 Yes the O2 was very refreshing in that way and it indeed turned out to be a absolutely wonderful amp for 98% of the cans out there...and the ODA as I see it now rounds out the rest pretty much.
  
 Soon we will have measurements and hope they meet and exceed the O2...
  
 Alex


----------



## pearljam50000

Is there going to be another version soon, and if so what would be the price?thanks.


----------



## adydula

As far as the ODA and follow on's there are a few "upgrades or improvement projects"...one is a O2 booster board that can plug into the sockets of an existing O2 amp The latest O2 booster board is 3.1.
  
 Version 3.1 is:
  
 The final circuit uses the OPA140 op-amp (FET input, DC precision, low THD+N) looped around an LME49600 audio current buffer on each channel to replace the O2 Headphone Amp's original NJM4556A output chips. Many other op amps would also work, such as the OPA827 and OPA627 with varying effects - see the full op amp rolling write-up in the build instructions. The board produces a 93% reduction in the O2 amp's DC output offset voltage to around 20uV from the O2's standard 3mV. Output current capability is increased from 120mA per channel to 200mA for "music power" (playing music rather than sine wave testing). The O2's power supply has limitations that would prevent continuous current draw above 200mA per channel.
  
 Details on this can be found at DIYAUDIO.COM.
 Boards and parts lists can be found there as well.
 Link: http://www.diyaudio.com/forums/headphone-systems/244473-o2-headamp-output-booster-pcb.html
  
 A desktop ODA is close to completion in (2) formats one with 12.5  volt rails and a second optional one :
  
  
 The second "optional" build is for folks who specifically have 300 ohm or 600 ohm (or higher) headphones that almost have enough volume with the O2 headamp, but not quite. This build has +/-15Vdc power supply rails and uses a 5K volume pot (linear or log taper, either is fine) again for pot power dissipation reasons. The transformer with this +/-15Vdc build remains that same as up until now, 20Vac - 24Vac. This +/-15Vdc build should *only* be used with 300R or higher headphones for output chip power dissipation reasons.

 Note that if you have 300R or 600R headphones that are nowhere near loud enough with the O2 then the +/-15Vdc rail option here isn't likely to help. You need a lot of additional voltage swing to get adequate dynamic range on music peaks, such as AMB's b22 headamp with +/-30Vdc rails or a tube amp.
  
 The standard version is pretty much done and I have built one and have been using it for over a week and its a wonderful amp, as good as the O2 is and better in other respects.
  
 Soon we will have lab measurements as well to benchmark against the O2 itself.
  
 The booster board is a simple DIY mod that can be used with the current O2 amp and in the same enclosure. The ODA is more of a desktop not portable headphone amp.
  
 The booster board can also be bought assembled and tested from agdraudio.com
  
 All the best
 Alex


----------



## derbigpr

james-uk said:


> That kind of poor communication and engagement is enough to make me want to sell my HD800s!!! If you make the most advanced headphone ever at least have the confidence to be transparent with your information and employ someone to respond with facts rather than random bull**** and lack of understanding !


 

  I've never in my life, never ever, and I've sent quite a few emails for technical support, had a proper answer to my question. Sometimes they don't answer at all (*cough* Musical Fidelity *cough*). It seems that people who answer these email's as a rule are totally clueless about the things you ask them about, and just have a pattern or a list of answers that they can offer you depending on the type of question you ask. They're most definitely not engineers of technically qualified for the job, they're usually people whose working potentials go no further than answering telephone calls or replying to emails.  I mean, if they guy who answered from Sennheiser doesn't even know that HD800's don't have a equal impedance across all frequencies, then how much does he know in general....not much. Probably never even put the HD800's on his head, and is probably not even interested in headphones.
  
 That said, you can be damn sure that Sennheiser engineers know what they're doing, probably better than anyone else in the world when it comes to headphones considering how long they've been in the business and how many different types of headphones they produce,  so you can be sure that there's a good reason why their amps have an output impedance that they have, and that is to work with their high end headphones as good as possible.


----------



## adydula

You would hope....
  
 Wonder why they call it tech support???
  





 A.


----------



## Xenophon

You need to be able to find guys who are passionate about what they do...and generally that means that if a company reaches a certain size you won't be able to reach those.  I contacted and got very detailed replies to questions from people like Fried Reim (Violectric) and Nelson Pass, just to name two who are active in the hifi/audio field.  And this was to questions that were really unrelated to a specific purchase I was contemplating.  Sure, they make a living out of it but that's almost a side effect for most of them.  Personally I couldn't imagine a greater hell than dragging myself to work to do a job I didn't care about.   Doesn't matter if it's about electronics, law, medicine, cultivating orchids, raising cattle or baking pastry, everyone has a talent but sadly, most people don't develop it.
  
 Sitting back in my office in Delhi now, reading up on some stuff and looking worried at my ODAC/O2 that's sitting on my desk in the 37 centigrade heat (read an article on the plane about how every 10 centigrade increase in temp over average spec for certain components shortens their lifetime by half...poor capacitors).  Anyway, going to contact agdr tomorrow and place an order, spent my last hours in Europe yesterday building a power supply for it, damn those EU regulations.  
  
 Off to bed now but first I'll do some more reading about impedance and load matching between tubes/output transformers/my HE-6 for a build I'm working on.  The deeper I delve the more complicated it becomes, reached a level where everything starts to matter if you want the best possible performance.  Gonna cost me 3 times what an off the shelf product would run but hey, that's why it's called a hobby I guess.


----------



## adydula

Xenophon,
  
 Great!! Tell AGDR you know me etc....he is a really great person who has really gone out of his way to help me and others with the O2 Booster board DIY projects and the new ODA.
  
 I am totally elated how the ODA turned out, its really a world class amp to me and it has made listening to my T90s a real pleasure.
  
 Yes even with my listening tests with the O2 the sound is very very similar it has more current capacity and all those nice extras that make it a more functional and efficient unit.
  
 Over at DIY the posted some info on torroidal transformers that can be used to build a ac supply for the ODA etc..
  
 Alex


----------



## adydula

Ok folks AGDR just posted this at DIYAUDIO.COM
  
 "I'm also going to let the cat out of the bag about something. John at JDS labs has agreed to dScope test the O2 booster board too, along with the ODA, and is in-process with that right now as time permits on his end. We will finally have some dScope measurements for the O2 booster board! A huge thanks goes out to John for the testing."
  
 I knew this was in progress and had to wait until AGDR made this public....so hopefully we will have some discrete data soon!
  
 Alex


----------



## 214324

Would be awesome to see JDSLabs include booster boards on their O2s.


----------



## r010159

adydula said:


> Ok folks AGDR just posted this at DIYAUDIO.COM
> 
> "I'm also going to let the cat out of the bag about something. John at JDS labs has agreed to dScope test the O2 booster board too, along with the ODA, and is in-process with that right now as time permits on his end. We will finally have some dScope measurements for the O2 booster board! A huge thanks goes out to John for the testing."
> 
> ...




**Fanboy Alert **

John is one heck of a guy who is outrageously committed to his customers too. There was a time I thought the problems I was having related somehow to the other product of his, the C5D. Boy, was I wrong. My apologies to John on that one.

I am very interested in how these DIY projects test out on the dScope, particularly the ODA. Thanks to AGDR, we have additional options. Options are always a good thing.

Bob

PS: I hope he received his evaluation unit back that he let me borrow.


----------



## Solrighal

I'm sorry about this but I'm going to ask a question that I know has been asked before (possibly by me) but ill be damned if I can find the answer via search.

I came so close to disaster last night when my 18 month old LaCie hard drive failed! I've always had my music backed up but it now exceeds the size of my largest backup disk.

I wasn't able to repair the disk so this morning I had to go to the city and buy another disk to transfer my files to and hopefully be able to reformat the LaCie.

Sorry, I digress. Anyway, because I'm sitting here twidling my thumbs waiting for my backup to complete I thought I'd review all my system settings.

I'm usiang a Mac (latest Mavericks) and as far as I remember I need to go into Audio Devices and choose my ODAC then set input & output to 96000Hz. I'm able to set the output no problem but the input is greyed out.

What am I missing here? And yes, this is most possibly a question for the software section but I find you guys here very reliable & knowledgeable.


----------



## jring

solrighal said:


> I'm usiang a Mac (latest Mavericks) and as far as I remember I need to go into Audio Devices and choose my ODAC then set input & output to 96000Hz. I'm able to set the output no problem but the input is greyed out.


 
  
 Hi,
  
 I don't know a lot about MacOS but I'd assume audio input to refer to ADC functionality (as in sampling music from vinyl etc) which the ODAC does not offer.
  
 Joachim


----------



## Solrighal

jring said:


> Hi,
> 
> I don't know a lot about MacOS but I'd assume audio input to refer to ADC functionality (as in sampling music from vinyl etc) which the ODAC does not offer.
> 
> Joachim




Thanks for the reply. I thought I remembered altering this in the past but I may be mistaken.


----------



## headwhacker

Input will only be accessible for Mics or any other input Device. ODAC is an output device.


----------



## Solrighal

It is as simple as that, isn't it? I am a buffoon. Thank you.


----------



## anthk

r010159 said:


> **Fanboy Alert **
> 
> John is one heck of a guy who is outrageously committed to his customers too. There was a time I thought the problems I was having related somehow to the other product of his, the C5D. Boy, was I wrong. My apologies to John on that one.
> 
> ...


 

 Simply having a slightly more expansive version with say, sturdier jacks, might be worth it


----------



## r010159

anthk said:


> Simply having a slightly more expansive version with say, sturdier jacks, might be worth it




That is my biggest gripe, how 'inexpensive" parts are being used.

Bob


----------



## adydula

AGDR's ODA uses better Swithcraft jacks and will last longer for sure....also it has a sturdy Neutrik  1/4 jack.
  
 Alex


----------



## adydula

98% of my music is 44.1khz 16 bit. I have some 20 bit stuff and HD Track samples.
  
 I have my Win 7 OS playback set to 44.1Khz, 24 bits.
  
 If I play any higher sample rate stuff I change it to that and go back to 44.1/24.
  
 This came from a well know Dac design engineer.
  
 Alex


----------



## Solrighal

So there's no harm in me setting output to 96000Hz?


----------



## James-uk

solrighal said:


> So there's no harm in me setting output to 96000Hz?



The best way is to get it to automatically change the output frequency to match the file being played. Unfortunately I tunes and midi don't work together and do this. For that reason i downloaded channel D 'pure music ' for mac . It's a software player that bolts on to I tunes so you can still use the i tunes interface but pure music does the processing etc so it auto changes the settings on midi. It has lots of other features and you can download it for 1 month free so maybe give it a go and see if you think it's worth the money.


----------



## greenkiwi

BitPerfect also does this really well, and costs $10.
  
 http://bitperfectsound.blogspot.com/


----------



## Solrighal

I'm not trying to be awkward but there are no words to describe how much I detest itunes.

I use JRiver or Cog.


----------



## James-uk

solrighal said:


> I'm not trying to be awkward but there are no words to describe how much I detest itunes.
> 
> I use JRiver or Cog.



Oh, why the hate for I tunes? Its as user friendly as I could want so I don't know what else you would want from a ui?


----------



## Solrighal

It would be useful if it could deal with my 65,000 flac files for starters. I'd also prefer my music player to not also be a shop. Also, I'm old-school.


----------



## miceblue

solrighal said:


> I'd also prefer my music player to not also be a shop.



That's a stupid excuse.


----------



## Solrighal

miceblue said:


> That's a stupid excuse.




It's an irrelevant excuse. What about flac?


----------



## tdockweiler

Nobody uses FLAC. Only 1% of music users listen to that. LHZ/OGG/ASDF formats are much better and more widely supported.
  
 Also, if an mp3 player doesn't support ASDF format it's not worth using!
  
 Oh and in an unrelated note..I HATE the MKV container. I should like it, but just can't.


----------



## HeatFan12

tdockweiler said:


> *Nobody uses FLAC*. Only 1% of music users listen to that. LHZ/OGG/ASDF formats are much better and more widely supported.
> 
> Also, if an mp3 player doesn't support ASDF format it's not worth using!
> 
> Oh and in an unrelated note..I HATE the MKV container. I should like it, but just can't.


 
  
  
 That's pretty funny!  Cheers tdock!!


----------



## greenkiwi

solrighal said:


> It's an irrelevant excuse. What about flac?


 
 I do find it frustrating that it doesn't support FLAC (particularly that you can't even fool it into accepting FLAC or auto converting FLAC to ALAC), but I just accepted it and have everything in ALAC.  Most other players play that too... so I'm all good.


----------



## Xenophon

I guess that makes me one of those fools that do use FLAC. And fwiw I also detest iTunes and so far have not found a simple, easy to use no bs system to organise my music (lots of files, various versions of the same classical piece but brought by various artisrs/recording labels etc. Don't even need a graphical interface, just a db with various query options linked to a player (jriver for the time being).

The HD-track craze is the latest to separate fools from their money, it makes absolutely no sense to pay for extra resolution beyond what's essentially the redbook cd standard. Any benefits there are will be inaudible, this can be demonstrated but there are always people willing to pay up for the hype.


----------



## r010159

I find iTunes integration to be very buggy with all the premium players that I have tried. ITunes simply does not cooperate well with external software.


----------



## Xenophon

Ot but the above is the reason why I'm now typing this from a Samsung tab and not an ipad...the smothering love of Apple. A lovely ecosystem if you go all in but then you better accept that it'll be their way or the highway....all the way, all the time. To their credit, they're not coy about it.


----------



## greenkiwi

xenophon said:


> I guess that makes me one of those fools that do use FLAC. And fwiw I also detest iTunes and so far have not found a simple, easy to use no bs system to organise my music (lots of files, various versions of the same classical piece but brought by various artisrs/recording labels etc. Don't even need a graphical interface, just a db with various query options linked to a player (jriver for the time being).
> 
> The HD-track craze is the latest to separate fools from their money, it makes absolutely no sense to pay for extra resolution beyond what's essentially the redbook cd standard. Any benefits there are will be inaudible, this can be demonstrated but there are always people willing to pay up for the hype.


 
 There's nothing foolish about using FLAC.


----------



## headwhacker

heatfan12 said:


> That's pretty funny!  Cheers tdock!!


 
 +1 Funny indeed ...


----------



## Super MANSKITO

Should I do a subjective review with my T1s and HE-500s? It came in the mail yesterday.  Its an O2/DAC limited edition from JDS labs.


----------



## tdockweiler

Ok, I actually like FLAC but stopped using it so much when I found out I can't really hear much of a difference between 320kbps and FLAC. Let's not go there though. I did that test YEARS ago.
 Sarcasm doesn't usually translate well online, but I could have sworn Apple said they wouldn't support FLAC because they have almost no requests for it. I bet FLAC is really at the 1% usage mark. Makes you sick right?
 Previously I was using WAV because it had better support than FLAC at the time! This didn't make sense though for a 16GB mp3 player.
  
 I really do hate the limited file support on Ipods and Itunes. Heck I don't even know if Xvid or the MKV container is supported on even an Ipad. You'd think so! Xvid is so dang common. I'll be glad when Divx dies!
  
 Right now I use a mix of Foobar and Itunes. I actually prefer the interface of Itunes to Foobar. Foobar actually annoys me even more!
  
 I also have a worthless Ibook G4 I use in my bedroom and the only decent music player for it is Itunes. Linux is not worth using on it since it has a PPC processor.
  
 BTW It kind of stinks having both an Ipod Touch 2G and a Clip+. It's like i'm usually keeping around two different libraries.
  
 Another thing...I have this weird habit of listening to Itunes samples for up to 2 hours. Mostly ambient electronic. The samples are often really long and even sound pretty OK!
  
 If I HAVE to buy mp3 I usually go to Amazon or ugh... Google Play. I think everyone hates Google...
  
 BTW I really love the O2 with the LM4652. I'm using that instead of the OPA2227 and stock op-amps. For JUST the Q701, the OPA2227 would be better, but it's not a perfect match for the HD-650. LM4652 sounds more "neutral" (yes, I know).


----------



## SilverEars

Guyz, I've tried feeding other DACs to O2, and it's not the same as ODAC feeding it.  I just tried feeding it DX90 and X5 line-outs. And, also C5D in the past. It doesn't sound as detailed and clear as when ODAC is feeding it.  Do you think there was something on the ODAC that matches well with O2?  U know who probably knows something we don't about the match up.  I need to read up on it, maybe he talks about it.


----------



## headwhacker

tdockweiler said:


> Ok, I actually like FLAC but stopped using it so much when I found out I can't really hear much of a difference between 320kbps and FLAC. Let's not go there though. I did that test YEARS ago.
> 
> 
> Sarcasm doesn't usually translate well online, but I could have sworn Apple said they wouldn't support FLAC because they have almost no requests for it. I bet FLAC is really at the 1% usage mark. Makes you sick right?
> ...



 


Apple is not supporting FLAC because they have their own lossless compressed format which is ALAC (m4a). Converting between the 2 formats is seamless.

I understand if you don't hear much difference between 320k MP3 and a FLAC. It does make sense depending on the music. But for critical listening lossy format is just like that, lossy. Imagine people are arguing about differences between a 16 bit lossless file against a 24 bit file from the same master.


----------



## headwhacker

silverears said:


> Guyz, I've tried feeding other DACs to O2, and it's not the same as ODAC feeding it.  I just tried feeding it DX90 and X5 line-outs. And, also C5D in the past. It doesn't sound as detailed and clear as when ODAC is feeding it.  Do you think there was something on the ODAC that matches well with O2?  U know who probably knows something we don't about the match up.  I need to read up on it, maybe he talks about it.



 


I'm curious to hear the ODAC as well with O2. DX90 already sounds detailed and clear with O2.


----------



## miceblue

greenkiwi said:


> I do find it frustrating that it doesn't support FLAC (particularly that you can't even fool it into accepting FLAC or auto converting FLAC to ALAC), but I just accepted it and have everything in ALAC.  Most other players play that too... so I'm all good.



Sure it can. That's what Fluke is for.






silverears said:


> Guyz, I've tried feeding other DACs to O2, and it's not the same as ODAC feeding it.  I just tried feeding it DX90 and X5 line-outs. And, also C5D in the past. It doesn't sound as detailed and clear as when ODAC is feeding it.  Do you think there was something on the ODAC that matches well with O2?  U know who probably knows something we don't about the match up.  I need to read up on it, maybe he talks about it.



I haven't tried the DX90, but the X5's DAC sounded coloured to me. Likewise for the C5D, but I vastly prefer the C5D's DAC to that of the X5. I'll be receiving the Geek Out soon, so it'll be interesting to compare that to the ODAC.
http://geek.lhlabs.com/force/geekout/898-geek-out-vs-the-others-3rd-installment


----------



## SilverEars

headwhacker said:


> silverears said:
> 
> 
> > Guyz, I've tried feeding other DACs to O2, and it's not the same as ODAC feeding it.  I just tried feeding it DX90 and X5 line-outs. And, also C5D in the past. It doesn't sound as detailed and clear as when ODAC is feeding it.  Do you think there was something on the ODAC that matches well with O2?  U know who probably knows something we don't about the match up.  I need to read up on it, maybe he talks about it.
> ...


 
 If you can get a hold of an ODAC, you should try it.  You may hear what I'm talking about.
  
  


> I haven't tried the DX90, but the X5's DAC sounded coloured to me. Likewise for the C5D, but I vastly prefer the C5D's DAC to that of the X5. I'll be receiving the Geek Out soon, so it'll be interesting to compare that to the ODAC.
> http://geek.lhlabs.com/force/geekout/898-geek-out-vs-the-others-3rd-installment


 
 I don't find the X5 colored.  I was thinking the opposite, quite neutral.  reason why I think it's neutral is it now forward in any way.  The highs are not forward, there isn't bass quantity like the DX90, and not punchy sounding either.  I had the C5D and it sounded unnatural, the bass was too tight and smooth.  The sound was too smooth to my ears, and lacked detail.  I think it was on the colder side.
  
 It's just that either DX90 and X5 doesn't have a clean LO or O2.  heaphone out of X5 sounds much clearer than feeding X5 LO to O2, it sounds not as clear.
  
 Why do you think X5 is colored?


----------



## greenkiwi

miceblue said:


> Sure it can. That's what Fluke is for.


 
 I didn't think that Fluke worked with iTunes > 10.7, it used to and I'd done it... 
  


> Does BitPerfect support high-res FLAC playback?
> 
> 
> 
> ...


 
  
 If you still can, that's awesome... and I could play them with BP then.


----------



## Solrighal

I've been building my digital music collection for 14 years. When I started out flac was the way to go; lossless & relatively compact. Like most I started out on Windows but when Windows 8 was leaked I jumped ship to Apple. It made sense at the time as we already had an iPad & iPhone in the house. I still have the iPad but the iPhone is long gone (replaced with a Note 3).

Irrespective of what proportion of users choose flac I can't see any commercial sense in Apple not supporting us. 

I also much prefer navigating my music via folder structure. I have never in my life made a Playlist by genre. I know what I want to listen to and I know where to find it. Perhaps this is why I keep Cog installed. 

Anyway, my collection is now sitting at something like 100,000 tracks and the majority are flac. There's no way I'm going to start converting them to alac just so I can use the overblown iTunes interface. In fact, the only reason I bought JRiver is because of the remote apps that are made for it.


----------



## miceblue

silverears said:


> I don't find the X5 colored.  I was thinking the opposite, quite neutral.  reason why I think it's neutral is it now forward in any way.  The highs are not forward, there isn't bass quantity like the DX90, and not punchy sounding either.  I had the C5D and it sounded unnatural, the bass was too tight and smooth.  The sound was too smooth to my ears, and lacked detail.  I think it was on the colder side.
> 
> It's just that either DX90 and X5 doesn't have a clean LO or O2.  heaphone out of X5 sounds much clearer than feeding X5 LO to O2, it sounds not as clear.
> 
> Why do you think X5 is colored?



"Neutral" is so subjective in audio it's not even funny. People say the HD800 is neutral, others say the LCD-2 is neutral; they sound completely different from one another. XD

Yes, the highs are not forward, but they're a bit soft on the details to me and like FiiO's typical house sound, the sense of soundstage is narrow. The bass is not forward either, but it seems a bit bloated and thick (not punchy), which isn't unusual for a FiiO product from my experience. From my experience with FiiO's products, they tend to have a shouty upper-midrange that bothers me, and that was definitely evident to me with the X5 and is one of the reasons why I don't like it.

Objectively, FiiO's own published measurements of the X5 are nearly perfectly identical between the headphone out and the line out.
http://fiio.com.cn/products/index.aspx?ID=100000055517771&MenuID=105026016





greenkiwi said:


> miceblue said:
> 
> 
> > Sure it can. That's what Fluke is for.
> ...



I'm using the latest version of iTunes with OS X 10.8.5. You have to set iTunes to run in 32-bit mode. Granted, Fluke + iTunes is pretty much completely useless since you can only add one music file at a time, but the ability to play FLAC in iTunes is still possible nonetheless.


----------



## headwhacker

true, neutral is very subjective without a reference. DX90 might sound like having a boosted bass but it's possible the X5 rolls off the bass a bit. ( I have not heard the X5 yet).

As for me Rockbox is a good know flat/neutral reference. When I compare DX90 with my rockboxed DX50 I hear just about the same bass quantity except DX90 has slightly more bass extention (a bit more rumble). Especially with the slow roll off filter and driven by O2 using my T1 or DT250.


----------



## adydula

Wow....
  
 I don't use Apple at all.
  
 I use only FLAC, lossless and bitperfect playback.
  
 Simple and it works..
  
 Apples world is all about making money. Which is fine. So is Windows but to me its a much more relatively open OS.
 You have a lot less issues with new stuff etc....and being the majority of the world base out there STILL, usually programs etc will work first time..or better the first time etc.
  
 I just don't like or need the Apple closed world.
  
 JRiver is a great simple to use player and works very well in the Windows world.
  
 With all the talk about getting the most out of your stuff, and worrying about how to set up the correct Bitdepth and sample rate....why would you even consider anything but a lossless file format???  Even 320 bits...OMG.
  
 DBPoweramp works very well with ripping to Flac, Foobar is a good alternative, but not as user friendly as a windows gui program like JRiver.
  
 Each to his own....
  
 Alex


----------



## James-uk

I converted to the dark side a couple of years back from Microsoft to apple and I haven't looked back. Call them what you like, I admit they have me , I'm in their pocket but my 'digital ' life has never been more carefree and easy . I have a mac / iPad/ I phone / Apple TV and Everything works with continuity and without hassle . I want computers and devices to make my life easier and to just enjoy using them. I never enjoyed using windows it was so high maintenance .


----------



## James-uk

greenkiwi said:


> BitPerfect also does this really well, and costs $10.
> 
> http://bitperfectsound.blogspot.com/




Thanks for posting this. I downloaded it (no brainer for the price) and it's fantastic. Gets out the way and just does what it needs to. Can't believe I hadn't discovered this before. Pure music has more features but I don't care for them and it's more intrusive on the I tunes ui.


----------



## mcandmar

tdockweiler said:


> BTW I really love the O2 with the LM4652. I'm using that instead of the OPA2227 and stock op-amps. For JUST the Q701, the OPA2227 would be better, but it's not a perfect match for the HD-650. LM4652 sounds more "neutral" (yes, I know).


 
  
 I was never a fan of those JRCs either, i highly recommend you look into the Booster Board with OPA827's...


----------



## jseaber

hybridcore said:


> Would be awesome to see JDSLabs include booster boards on their O2s.


 
  
 agdr kindly provided us with a boost board in exchange for dScope analysis. I'm impressed with his progress, unfortunately, this modification must remain a DIY project in its current state. This is not agdr's fault, but rather a result of agdr choosing to adhere to the CC BY-ND 3.0 Attrib license on O2.
  
 agdr has posted initial findings to his main thread. We still have more questions to answer. Key results so far:
  

Max output power at 150-600 ohms is identical to a stock O2. The booster can accommodate increased supply rails from +/-12V to +/-15V, but thermal dissipation in O2 is insufficient for smaller loads, so this mod is not production acceptable.
Max output power at 32 ohms is ~35% stronger than a stock O2 in bursts, however, the booster's LME49600's overheat within 60-90 seconds of continuous maximum load. The thermally overloaded chips quickly exceed 60C, causing THD+N to rise dramatically before thermal shutdown. This is obviously not production acceptable.
THD+N is limited by the NJM2068 with booster installed. A stock O2 already performs well here.
Turn on/off relay works perfectly. Nice addition!
  
 In short, the base O2 circuit needs to be abandoned to thermally satisfy LME49600s.


----------



## headwhacker

Thanks for sharing your finding. O2 has already proven that it's as good as it gets from the design target.


----------



## Xenophon

The O2's good but it has its limitations, as was recognised at the outset by the designer.  I salute agdr for the work he did but repeat what I said a couple of 100 posts back in the thread:  with his talent I'd opt for revolution and a new design on my own terms rather than incrementalism and respecting the constraints of the existing product.  My hat off to him, I hope he carries this forward.


----------



## SilverEars

Damn!!! This combo is rediculously transparent!!!  I just got a TOTL CIEM called Hidition NT-6 .  My god, never heard details like this, and the objective combo provides.  I hear everything on Kind of Blue.  Everything!!!


----------



## miceblue

jseaber said:


> but thermal dissipation in O2 is insufficient for smaller loads, so this mod is not production acceptable.
> Max output power at 32 ohms is ~35% stronger than a stock O2 in bursts, however, the booster's LME49600's overheat within 60-90 seconds of continuous maximum load. The thermally overloaded chips quickly exceed 60C, causing THD+N to rise dramatically before thermal shutdown.



So under normal operating conditions, people with the booster board have been listening to their music with a bunch of added THD+N because of the thermal instability?


----------



## Xenophon

miceblue said:


> So under normal operating conditions, people with the booster board have been listening to their music with a bunch of added THD+N because of the thermal instability?


 
 No, you'd only encounter those conditions using low-impedance headphones at very high (unlistenable) sustained volumes.  At loud volume absorbing a peak without extra distortion but while delivering extra power would be possible.  Wether wise for your ears is a different matter.


----------



## schmalgausen

Hi all,

 In all manuals we can see 2 methods to connect O2 and ODAC according to usage of 3.5 input socket: 1) to keep O2 input on it, 2) to change it to ODAC output. 

 However, ODAC has two outputs: four pins in the middle of PCB and 3.5 mm socket. Why nobody uses them both? Pins to connect ODAC with O2 and 3.5mm socket to get direct ODAC output. Does such setup affect the output quality with some negative influence of O2 input?


----------



## headwhacker

xenophon said:


> No, you'd only encounter those conditions using low-impedance headphones at very high (unlistenable) sustained volumes.  At loud volume absorbing a peak without extra distortion but while delivering extra power would be possible.  Wether wise for your ears is a different matter.



 


The booster board is suppose to increase current output which is needed by low impedance low sensitivity planars. The 35% increase in current at 32 Ohm load translate to around 2 - 3 dB SPL. 

For 150+ Ohm load, the booster board has very little to no added benefit. 

I'm pretty sure using an HE-6 will easily hit that maximum load of the booster board. A Stock O2 can drive HE-6 at a little below 110 dB . With the booster board it can reach around 112 dB. Which is loud enough for most people but certainly is not painfully loud. Some people listen at around 115 dB.

Just as John mentioned, this is just not acceptable in HE-6 context. ( Which is supposedly what the booster board is about).


----------



## Xenophon

OK, owning an HE-6 and odac/o2 combo I'm not going to enter into this pointless discussion again, certainly not with people who don't own the 6 but suffice it to say that even with the booster board I wouldn't ever use let alone recommend this.  There's other gear for the 6.


----------



## headwhacker

I'm not trying to argue but rather trying to make sense of the booster board's benefit as add-on for O2.


----------



## gikigill

You need about 50 O2 amps with booster boards to power the HE6 properly.


----------



## adydula

The O2 also handles playing music into all kinds of loads. If testing is done with sine waves the output amps will overheat eventually. This is with sustained high power sine or square wave testing into low impedance loads. This is also true with lots of high power headphone and speaker amps. These are designed to play real world music not test signals.
  
 But testing often involves using signals and sign waves but should be used for long period of times.
  
 So its has to be noted that testing into low impedance loads should be limited to a few seconds with the O2 and the booster board as well. Especially below 150 ohms.Also the xfmr should be 15 vac or greater when doing this.
  
 I haven't heard of any O2 or booster boards having issues playing for long periods of time with lower impedance loads below 150 ohms. I have used several cans with low level impedance for hours and hours...with no heating issues.
  
 If you want HOT just try a Class A amp, one which I had and I don't want to disparage other good amps or companies. The one I had was HOT to handle and to the touch but the chassis was designed to be the heat sink!! It still worked well.
  
 A.


----------



## greenkiwi

I also think it's a question of DIY v production. 

If you are producing a product and putting your name on it, it has to meet different standards and some of those are about consistency and being able to stand up to abuse/non designed use.


----------



## adydula

Yes and no....there are amps both for headphones and speakers that will NOT handle sine waves for very long....there are products in production that will fail in long term 100% duty cycle tests....
  
 You would have to define NON-designed use?? That's a BIG open field......whats the standard for non-designed use or Abuse????
  
 A.


----------



## Mjolnir125

schmalgausen said:


> Hi all,
> 
> In all manuals we can see 2 methods to connect O2 and ODAC according to usage of 3.5 input socket: 1) to keep O2 input on it, 2) to change it to ODAC output.
> 
> However, ODAC has two outputs: four pins in the middle of PCB and 3.5 mm socket. Why nobody uses them both? Pins to connect ODAC with O2 and 3.5mm socket to get direct ODAC output. Does such setup affect the output quality with some negative influence of O2 input?


 

 I have an O2+ODAC from Mayflower Electronics and it seems to have what you are describing. When the ODAC is plugged in through USB, the "line in" jack actually doubles as a line out for the DAC. This works with the unit turned off or without the AC adapter turned on, since the ODAC is 100% usb powered. When the ODAC is disconnected, it functions as a line in for the O2 amp. This isn't a very well advertised feature to be honest, and I only learned about it when watching a video about the unit by the guy who owns Mayflower electronics. I think the JDSlabs models also have this feature, but I don't know for sure.
  
  
 So basically, the O2+ODAC units have the same line out capability as buying the two units separately, but you get them in a much smaller package.


----------



## skeptic

james-uk said:


> I converted to the dark side a couple of years back from Microsoft to apple and I haven't looked back. Call them what you like, I admit they have me , I'm in their pocket but my 'digital ' life has never been more carefree and easy . I have a mac / iPad/ I phone / Apple TV and Everything works with continuity and without hassle . I want computers and devices to make my life easier and to just enjoy using them. I never enjoyed using windows it was so high maintenance .


 
  
 I agree with the goal - if only it worked out that way.  IOS versions of Spotify and Overdrive, my two most used apps, are garbage compared to android.  On the flipside, android phone makers seem incapable of producing a device without audible his when using iem's.  My current combo is a rooted note 2 (which supports airplay), several pc's, an ipad 4, and multiple apple tv's.  The fact that I have to jump through huge hoops to put my existing flac library on my ipad is absurd.  Third party paid apps let me play the files, but there is no supported way of loading them on the device, and folders have to be manually created.  Talk about not making life easier.  Apple is the devil notwithstanding their tasteful asthetics.
  


mcandmar said:


> I was never a fan of those JRCs either, i highly recommend you look into the Booster Board with OPA827's...


 
  
 I haven't been keeping up with the booster board thread like I should have been, did you conclude these sound better in the booster than the stock OPA140's?  The 3.0 sounds awesome to me stock, with the lme49990 adaptor in the 02 gain stage.  Frankly, I'm not skilled enough to try desoldering the 140's anyways, but still curious.
  


jseaber said:


> ....In short, the base O2 circuit needs to be abandoned to thermally satisfy LME49600s.


 
  
 Thanks for sharing the preliminary findings!  So I don't run into issues, I'd be grateful for any further info you can provide as to what sort of load gave rise to the thermal problems.  Was this really just an issue that came up with hifiman and/or audeze's?  I've been running my alpha dogs via my boosted o2 for months with no evident problems (and certainly no shutoffs).  It is an excellent sounding combo and truly remarkable, imo, that a battery driven amp can be engineered to come within a stone's throw of the performance of the wire (at least on paper, pending the results of your testing), and with far less dc offset!
  


headwhacker said:


> I'm not trying to argue but rather trying to make sense of the booster board's benefit as add-on for O2.


 
  
 In a nutshell, by adding the booster board and a dual lme4990 adaptor in the gain stage, you get a drastic improvement in dc offset, as well as improvements in current output for transients, slew rate (up to 20v/us) and presumably distortion over the stock O2, pending jds' lab confirmation.  Eliminating all turn on/off thump is also cool.  Perhaps its just confirmation bias in my head, but I continue to believe that the boosted o2 sounds better and just slightly different from stock.  There was something about my stock build, albeit a diy effort, that sounded slightly thin and piercing on occasion.  With the booster, its the same degree of transparency that we've all come to expect from the o2 but minus what I previously found slightly objectionable.  YMMV as always.


----------



## adydula

I think the testing done was done with a sine wave for a long period of time, more so that the few seconds warned about by the designer.
  
 With real music playing I never had a heating issue.
  
 Alex


----------



## GTan

I just purchased an O2/ODAC Limited Ed from an Australian distributor. I have some technical questions, when I connect the ODAC to my iPad via the CCK and USB Hub,
  
 1. I observed that the volume controls on the iPad is adjustable, this psychologically lead me to believe I'm double amping. But this is not possible right? Given it's a digital out connection to the DAC. This does not happen on my Sony PHA-2 DAC/Amp - I am able to connect directly from the iPad to DAC and the iPad detects this and changes to line-out without volume controls.
  
 2. If the O2/ODAC is powered via the mains, why is the iPad still throwing the device is consuming too much power error? Is the ODAC still drawing power despite it being connected to the mains?


----------



## jseaber

mjolnir125 said:


> This isn't a very well advertised feature to be honest, and I only learned about it when watching a video about the unit by the guy who owns Mayflower electronics. I think the JDSlabs models also have this feature, but I don't know for sure.
> 
> 
> So basically, the O2+ODAC units have the same line out capability as buying the two units separately, but you get them in a much smaller package.


 
  
 Thanks for the feedback. DAC line output is listed in the product "Tech Specs". Additional detail has been added to page 1 of the Instructions:
  
CONNECTIVITY 
Analog Output3.5mm or 6.35mm*​Analog Input3.5mm or shared RCA*​Digital InputMini-USB​DAC Line Output3.5mm or RCA**​Power Input14-20VAC​  ​* _Denotes Limited Edition_ ​** _See Jack Configurations below_
  
  
 There are two ways to wire an O2+ODAC. We use Method 1 by default, which provides DAC line output and is safe to use with any consumer level line-input device. This is the most common request. Method 2 mechanically disconnects ODAC's line output from the 3.5mm jack, so that it's only active while an analog input source is disconnected. This method is preferred when using the 3.5mm jack primarily for analog input (no need to disconnect USB cable).
  
 O2+ODAC can be assembled in over 20 possible combinations aside form our default offerings, while remaining in accordance with the designer's license. We're working on a site update which will soon make all options easier to understand and request.
  


skeptic said:


> Thanks for sharing the preliminary findings!  So I don't run into issues, I'd be grateful for any further info you can provide as to what sort of load gave rise to the thermal problems.  Was this really just an issue that came up with hifiman and/or audeze's?  I've been running my alpha dogs via my boosted o2 for months with no evident problems (and certainly no shutoffs).  It is an excellent sounding combo and truly remarkable, imo, that a battery driven amp can be engineered to come within a stone's throw of the performance of the wire (at least on paper, pending the results of your testing), and with far less dc offset!
> 
> In a nutshell, by adding the booster board and a dual lme4990 adaptor in the gain stage, you get a drastic improvement in dc offset, as well as improvements in current output for transients, slew rate (up to 20v/us) and presumably distortion over the stock O2, pending jds' lab confirmation.  Eliminating all turn on/off thump is also cool.  Perhaps its just confirmation bias in my head, but I continue to believe that the boosted o2 sounds better and just slightly different from stock.  There was something about my stock build, albeit a diy effort, that sounded slightly thin and piercing on occasion.  With the booster, its the same degree of transparency that we've all come to expect from the o2 but minus what I previously found slightly objectionable.  YMMV as always.


 
  
 We've tested default O2+ODACs in the past for over 8 hours under a full power, 1kHz sine wave at @ 150 ohms. I've also duplicated NwAvGuy's basic measurements of O2 and ODAC under a 32 ohm load. While these tests are far from a real world usage scenario, it proves the amp is thermally stable. 
  
 It was my intention to perform equal benchamrks on agdr's O2 booster board using the same tests @ 32 ohms. My usual quick test routines take at least an hour--just for a quick look. It's easy to spend an entire day investigating a device. Anyway, the LME49600s only lasted for a few minutes of testing before the chips overheated and spoiled test results. I'll produce new benchmarks ASAP at reduced power. The point is, the booster board is marginally stable in terms of power dissipation. I doubt it will overheat while listening at reasonable volumes with most dynamic headphones. Give it an inefficient 20-60 ohm headphone playing at high volumes, and there's a strong chance the chips will at least overheat enough to increase THD+N to audibly unacceptable levels, >= 0.5%. agdr has admitted that his enclosure has become warm to the touch under with some listening. By the time my testing configuration was warm to the touch, the chips were either distorting, or seconds from distorting (> 50C). Here are a couple frantic photos taken while testing. Sorry for the shaky angles:
  
 
  
 I've also tested the reference LME49600 board from National Semi. / TI. The reference board has around 10x more copper surface area than agdr's booster board, so the LME49600s can handle more power. Thermal dissipation is an important design consideration. 
  


xenophon said:


> The O2's good but it has its limitations, as was recognised at the outset by the designer.  I salute agdr for the work he did but repeat what I said a couple of 100 posts back in the thread:  with his talent I'd opt for revolution and a new design on my own terms rather than incrementalism and respecting the constraints of the existing product.  My hat off to him, I hope he carries this forward.


 


greenkiwi said:


> I also think it's a question of DIY v production.
> 
> If you are producing a product and putting your name on it, it has to meet different standards and some of those are about consistency and being able to stand up to abuse/non designed use.


 
  
 Both well put. I congratulate agdr's DIY contributions. It takes successes, failures, and passion to build remarkable projects. The successor to O2/ODAC logically most _not _be derived from Objective2, as it's both a legal and engineering dead-end.
  
  


gtan said:


> I just purchased an O2/ODAC Limited Ed from an Australian distributor. I have some technical questions, when I connect the ODAC to my iPad via the CCK and USB Hub,
> 
> 1. I observed that the volume controls on the iPad is adjustable, this psychologically lead me to believe I'm double amping. But this is not possible right? Given it's a digital out connection to the DAC. This does not happen on my Sony PHA-2 DAC/Amp - I am able to connect directly from the iPad to DAC and the iPad detects this and changes to line-out without volume controls.
> 
> 2. If the O2/ODAC is powered via the mains, why is the iPad still throwing the device is consuming too much power error? Is the ODAC still drawing power despite it being connected to the mains?


 
  
 1) This is a feature of iOS7+. Like desktop operating systems, iOS7 allows the user to control volume digitally for audio output device. For iOS6 and older, digital volume was locked to 100% for external DACs (and UAC1 was limited to iPad then). There's little incentive to digitally force 100% volume. It's actually best for a DAC to operate slightly below 100% volume to prevent overfill errors at 0dB peaks. Consider this a functionality improvement in iOS7. 
  
 There's also a hardware flag in some DACs called 'Hardware Volume Control'. The flag is normally enabled to allow an operating system to use its digital volume control as described above. I imagine some DACs have this option disabled, which should prevent iOS7, Windows, etc. from controlling volume. 
  
 Last, your Sony is an MFi certified device and therefore does not present itself as a UAC1 device. UAC1 devices are definitely processing a digital signal regardless of the operating system volume; the device drivers in iOS surely have a different feature set for MFi connections.
  
 2) O2 is powered by AC. ODAC is powered by USB. You can find more information here.


----------



## Fsatsil

> I haven't been keeping up with the booster board thread like I should have been, did you conclude these sound better in the booster than the stock OPA140's? The 3.0 sounds awesome to me stock, with the lme49990 adaptor in the 02 gain stage. Frankly, I'm not skilled enough to try desoldering the 140's anyways, but still curious.




Removing surface mount opamps is a lot easier then you may think. All you need is some good desoldering braid and a pin. Use the braid to remove as much solder as you can from the opamp legs being careful not to overheat the chip then use the pin to VERY GENTLY pry each leg up while you heat it with your soldering iron. It only takes a very slight upward pressure on the opamp legs and as soon as the solder melts you will feel the leg pop up from the board. Wether it's worth the effort is different story. I've tried the opa140, lme49990, Ad8610, and ada4627 and didn't hear much if any difference between them so I stuck with the opa140 for the best battery life.


----------



## James-uk

jseaber said:


> Thanks for the feedback. DAC line output is listed in the product "Tech Specs". Additional detail has been added to page 1 of the Instructions:
> 
> CONNECTIVITY
> 
> ...




Interesting point about dac volume being at 100% . Correct me if I'm wrong but does this mean it's best to turn the digital volume down a few db in bit perfect/ pure music for mac etc for care free listening at best sound quality?


----------



## jseaber

james-uk said:


> Interesting point about dac volume being at 100% . Correct me if I'm wrong but does this mean it's best to turn the digital volume down a few db in bit perfect/ pure music for mac etc for care free listening at best sound quality?


 
  
 Yes, a single single notch below 100% is best. It's rare to hit 0dB in high quality recordings, but if you happen to listen to tracks with significant 0dB content, it's a useful adjustment. I found a great explanatory article last year and will have to dig that up again...


----------



## James-uk

jseaber said:


> Yes, a single single notch below 100% is best. It's rare to hit 0dB in high quality recordings, but if you happen to listen to tracks with significant 0dB content, it's a useful adjustment. I found a great explanatory article last year and will have to dig that up again...




Thank you.


----------



## 214324

jseaber said:


> Yes, a single single notch below 100% is best. It's rare to hit 0dB in high quality recordings, but if you happen to listen to tracks with significant 0dB content, it's a useful adjustment. I found a great explanatory article last year and will have to dig that up again...


 
 Please do so.
  
 Also, how is progress on an ODA? Just curious because I remember asking a couple months ago and was curious how you guys are doing, unless you're not allowed to say which is perfectly fine.


----------



## jring

schmalgausen said:


> In all manuals we can see 2 methods to connect O2 and ODAC according to usage of 3.5 input socket: 1) to keep O2 input on it, 2) to change it to ODAC output.
> 
> However, ODAC has two outputs: four pins in the middle of PCB and 3.5 mm socket. Why nobody uses them both? Pins to connect ODAC with O2 and 3.5mm socket to get direct ODAC output. Does such setup affect the output quality with some negative influence of O2 input?


 
  
 Hi,
  
 it could be problematic to have the ODAC drive two powered on amps - this depends on the amps input impedances - O2 is quite high here (which is desirable) but others might not be so kind...
  
 Also it's not recommended at all to have anything drive the unpowered input stage of any amp as this might result in funny sound at best and sth breaking if you're not lucky.
  
 I plan to solder the 3.5" jack on the ODAC board when I find time and will use an extra 3.5 plug in the O2 line in socket to isolate the O2 from ODAC using the latters line-out - my O2 has the input wired as an input when a plug is in.
  
 Joachim


----------



## adydula

John,
  
 NwAvguy has stated:
  
*SINE WAVE TESTING:* While I’ve abused the O2 in a variety of ways playing real music into assorted worst case loads, and it has survived nicely, it will eventually overheat the output op amps with sustained high power _sine wave_ (or square wave) testing into low impedance loads. This is true of many high power headphone (and loudspeaker) amps that are designed for music not test signals. _It’s important to limit full power sine wave testing to a few seconds_ below about 150 ohms and let the output ICs cool down between tests. _You should also run sine wave tests with at 15 VAC or greater wall transformer_.
  
 To be fair have you measured the booster board at 150 ohms?
  
 Alex


----------



## SilverEars

Hi, something I've noticed is that when I feed O2 LOs other than ODAC, it doesn't output as detailed sound and less definition.  I'm not sure if O2 is transparent.  
  
 What I noticed is ODAC is overly bright in itself, and matches ODAC well, as I believe O2 probably cut's off the sharpness.  The pairt is perfect, the best sounding source I've ever heard for my CIEMs.  Believe me, I've tried all the high end DAPs out there, and nothing can match this pair.  So accurate and realistic.  The pair is amazingly clear and detailed.  I don't if you guys ever heard very dynamic imaging, but it pushes my CIEMs to unbelievable dynamism.  I didn't know CIEMs can do such things.
  
 Now, if I can get a portable to sound exactly like this pair, I'm done searching for portables.  You hear me JDS Labs?


----------



## jseaber

adydula said:


> John,
> 
> NwAvguy has stated:
> 
> ...


 
  
 agdr and I have discussed this and believe NwAvGuy made a mistake here. With a 15VAC transformer, voltage drop across U5 and U6 is higher, resulting in another thermal issue. It's best to use 14VAC with O2 as far as heat is concerned.
  
 Yes, I suspect that even the default NJM4556s would overheat with time while driving since waves at full power. The issue is that I was able to complete testing with O2 at 32 ohms. I was not able to complete the same tests with an O2 booster at 32 ohms. Its output power will need to be limited next time testing is conducted.
  
 The booster board is thermally stable into 150+ ohm loads. See post #3055 for initial test notes. Output power is unchanged with the booster board into these loads, so it brings no audible advantages aside from the relay's pop-free on/off behavior (which is nice).
  


hybridcore said:


> Please do so.
> 
> Also, how is progress on an ODA? Just curious because I remember asking a couple months ago and was curious how you guys are doing, unless you're not allowed to say which is perfectly fine.


 
  
 I've revealed as much as I can in post #3073


----------



## James-uk

jseaber said:


> Yes, a single single notch below 100% is best. It's rare to hit 0dB in high quality recordings, but if you happen to listen to tracks with significant 0dB content, it's a useful adjustment. I found a great explanatory article last year and will have to dig that up again...




Sorry , another question regarding this. Is it the dac volume I should turn down or the digital volume (dither) ? My dac volume is adjustable from the mac master volume and I can also turn down the digital volume using 64 bit dithered volume control. What are your thoughts on dithered volume control ? Sorry for the questions i just like to know I'm getting the best possible playback etc .


----------



## adydula

John,
  
 Thanks for the reply.....sounds like your working on a desktop amp of some kind...and if you have tested a LME49600 board my guess its designed around that!!! LOL??
  
 Anyway...what voltage is your dScope outputting for this testing???
  
 In "his" blog I see a graph of 4.2vrms for 33ohms....so if your running tests above this voltage I would expect this to overheat???
  
 Alex


----------



## jseaber

james-uk said:


> Sorry , another question regarding this. Is it the dac volume I should turn down or the digital volume (dither) ? My dac volume is adjustable from the mac master volume and I can also turn down the digital volume using 64 bit dithered volume control. What are your thoughts on dithered volume control ? Sorry for the questions i just like to know I'm getting the best possible playback etc .


 
  
 Either volume control will satisfy the end goal of avoiding a 0dB condition as observed at the DAC. Sorry, I'm not familiar with the specific controls in your system.


----------



## James-uk

jseaber said:


> Either volume control will satisfy the end goal of avoiding a 0dB condition as observed at the DAC. Sorry, I'm not familiar with the specific controls in your system.



I thought as much but just checking. Thanks.


----------



## Solrighal

james-uk said:


> I thought as much but just checking. Thanks.




I'm not sure I'm understanding this. I use JRiver. I've set the volume control to change the internal volume but how much should I cut it in dB? 10dB? 20dB? 

Sorry for being obtuse.


----------



## adydula

zorofox...
  
 take a look here:
  
http://www.audioholics.com/audio-technologies/the-case-for-not-going-above-0-dbfs-for-digital-playback-systems
  
 I also found this:
  
 "Unless you ask Jriver to perform any manipulation of the data it will output exactly what the source bits are and there should be no need to activate additional clipping protection. The default is bit transparent to the sound driver.

 Then it depends on the sound driver whether you have any manipulation. ASIO, Kernel streaming, and both WASAPI modes are bit transparent. Jriver's volume control only attenuates."
  
 AND THIS:
  
 So with just about _any_ DAC, you should be avoiding playback at 0dB on the computer, regardless of whether or not they're clipping this test signal.
 JRiver's Volume Leveling feature takes this inter-sample clipping into account, but I don't know of any other players which do. (and JRiver won't prevent inter-sample clipping without Volume Leveling or Peak Level Normalization enabled)
 I would suggest reducing the volume by at least 4dB and probably 6dB to be safe, if you are using player which does not account for this.
  
 Hope this helps
 Alex


----------



## Xenophon

The way I understand it is that intersample clipping is basically the result of an unholy alliance between music that's being recorded at 0 dBFS, the absolute highest 'legal' state possible and digital processing in the sound card or DAC that's not properly implemented and under certain conditions (very quickly changing output that's either mounting or descending close to 0) can cause 'overshoots' due to the processing not using the actual 'real' level but a projection based on the 'curve slope'.
  
 Most quality DACS/sound cards are actually designed to'permit' a small overshoot of 1-2 dB without clipping the signal.  Don't ask me how as imo it flies in the face of the very definition of 0 dBFS but anyway.
  
 Sloppy recording in the loudness wars and too much and badly implemented digital wizardry will get you any time.  I stick to classical, better dynamic range, no such issues, oversampling and filters 'off' on my DAC and everything into my tubes where the distortion at least sounds nice (kidding, I do listen to ss too).


----------



## Solrighal

Thanks for the input guys. I've dropped the max volume by 6dB just in case. To be honest I rarely listen to the kind of recordings likely to cause problems but I guess it's better to err on the side of caution.


----------



## Cyune

Hi. I'm new to this forum, and I'm thinking about purchasing a desktop O2/ODAC combo (1/4'' jack, RCA connectors) with a modified gain of 1x/2.5x.
  
 Quote:


> Originally Posted by *jseaber*
> 
> agdr and I have discussed this and believe NwAvGuy made a mistake here. With a 15VAC transformer, voltage drop across U5 and U6 is higher, resulting in another thermal issue. It's best to use 14VAC with O2 as far as heat is concerned.


 
  
 Do O2/ODAC manufacturers stock ~14V >400mA power supplies (instead of the standard 12V 200mA power supply)? Or will it be cheaper to purchase separately?
  
 The LEDs on the unit look extremely bright. Would this be easy to switch out for a dim orange/red LED? Or can I order it with this variant?
  
 Are there any other options/modifications you can suggest before pulling the trigger?


----------



## jseaber

cyune said:


> Do O2/ODAC manufacturers stock ~14V >400mA power supplies (instead of the standard 12V 200mA power supply)? Or will it be cheaper to purchase separately?
> 
> The LEDs on the unit look extremely bright. Would this be easy to switch out for a dim orange/red LED? Or can I order it with this variant?
> 
> Are there any other options/modifications you can suggest before pulling the trigger?


 
  
 The default Triad WAU12-200 and WAU12-1000 power adapters we stock for North American customers generate 13.50-13.95VAC depending on the specific line voltage of your home/building. A 14VAC adapter is non-standard since transformers must be produced at integer multiples of line voltage. For example:
  
 120V:12V = 10:1
 120V:15V = 8:1
  
 Manufacturers tend to assume input line voltage of 115VAC. If you assume 115VAC, required ratio for 14VAC output is 8.2143....or for 120VAC input, 8.57143...
  
 More importantly, O2 is internally limited to 12VAC. Its regulators require at least a 1.5V drop for normal performance. Extra voltage drop across a regulator is ideal _as long as heat __dissipation __is acceptable!_ This is one of NwAvGuys minor oversights. Heat output at regulators U5 and U6 increase proportionally to supply voltage. Input of 14-15VAC is fine for most loads. With 16VAC+ input and a small load impedance (32 ohms) driven to high levels, it's possible to drive U5/U6 to dangerous IC temperatures.
  
*tl;dr -- Stick with the supplies we recommend. Operating voltage is within expectations. When you increase voltage, it's wasted as heat.*
  
 The LEDs are high efficiency, low brightness. Changing the LED is discouraged since it's part of the power management circuit. If you wish to install a different LED, make sure to select a part with the same voltage drop as the standard part.


----------



## Cyune

Thank you for the thorough feedback!


----------



## schmalgausen

Is it necessary to omit R1, R2, D2 and D6 in full desktop setup? Some instructions prescribe such action.


----------



## jring

schmalgausen said:


> Is it necessary to omit R1, R2, D2 and D6 in full desktop setup? Some instructions prescribe such action.


 
  
 The designer himself stated that those plus the battery terminals can be left out in the comments to the details article on his blog (which must not be named here), so it's probably safe. OTOH having them in doesn't hurt either.
  
 Joachim


----------



## miceblue

What....I think my O2 died on me. The power light is on, the DAC works, but upon plugging in headphones to the O2, I hear absolutely nothing, not even the "pop" upon turning it on/off. It was working earlier today. :/


Got it. It was running on batteries.


----------



## adydula

Wow!!
  
 That's funny.....
  
  Batteries!!
  
 A.


----------



## jseaber

Head-Fi user RealMode took the following image of his O2+ODAC with a FLIR thermal camera. He says he's too new to post the picture himself:


----------



## adydula

what were the parameters when this image was taken?
  
 Alex


----------



## RealMode

Ambient temp was around 21C.
 Unit was on for a few hours of mild use then I turned it off, removed the case and powered it up on a piece of plastic and ran random tracks at 50% knob volume on the 2.5x setting for 5 min with a old pair of Sony MDR-V500DJ's and then took the shot from 5-7cm above.
  
 I have a better lens on order that should make the shots much clearer. I plan on re-doing the test with a more extended burn when it shows up.


----------



## James-uk

http://archimago.blogspot.ca/2014/06/24-bit-vs-16-bit-audio-test-part-ii.html?m=1

Another result in for the objective crowd . No surprises here.


----------



## SilverEars

Guyz, ODAC + O2, is the best ever with iems.  It beats everything I compare with.  The must transparent and detailed.  That ES9023 is cheap and well performing.  
  
 Also, is there anyway to up my performance of the ODAC?  Noise isolation or stable PS?  I notice the ODAC degrades if I feed it my smartphone's OTG.  My guess is it lacks juice.  This makes me think that ODAC needs better power supply.   Any good suggestions? 
  
 Thanks,
 SE


----------



## Solrighal

You say the ODAC "degrades" but what are you comparing it with?


----------



## jring

silverears said:


> Guyz, ODAC + O2, is the best ever with iems.  It beats everything I compare with.  The must transparent and detailed.  That ES9023 is cheap and well performing.
> 
> Also, is there anyway to up my performance of the ODAC?  Noise isolation or stable PS?  I notice the ODAC degrades if I feed it my smartphone's OTG.  My guess is it lacks juice.  This makes me think that ODAC needs better power supply.   Any good suggestions?
> 
> ...


 
  
 Hi,
  
 ODAC uses about 1 watt or 200mA at 5V USB power. If your smartphone cannot supply this, the voltage might get too low and this might create audible artifacts. Things you could try are the following:
  
 - try to run ODAC at your smartphone OTG plug while the smartphone is being charged (if it's not the same plug) and see if ODAC performs as expected.
  
 - plug a powered USB hub between you smartphone OTG and the ODAC and see if ODAC performs as expected.
  
 Not sure what to do while on the go...
  
 Joachim


----------



## adydula

I inserted an ammeter in a USB cable and and never saw more than 50ma or so of current draw...
  
 Alex


----------



## Solrighal

Hey folks. Check out this statement...

http://www.head-fi.org/t/197776/sennheiser-hd650-impressions-thread/18120_40#post_10677481


----------



## mcandmar

Sorry but he is right.


----------



## miceblue

mcandmar said:


> Sorry but he is right.



I concur. HD650 on the Bottlehead Crack is probably one of the most enjoyable setups I've heard.


----------



## Solrighal

Yeah but he wasn't talking about the BH Crack and his suggestions were way more expensive than the shortlist provided by the op. 

I need Crack.


----------



## jring

adydula said:


> I inserted an ammeter in a USB cable and and never saw more than 50ma or so of current draw...
> 
> Alex


 
  
 I haven't but I found a quote by the designer stating 1W. Although I have seen experienced weird behaviour of my ODAC in low voltage situations (lots of hungry arduino stuff on a neighbouring usb port of my laptop).
  
 Joachim


----------



## adydula

I saw that as well, but I cut up a perfectly good USB cable and inserted a ammeter in series with the +5 vdc line... and had to see this for myself.
  
 I was surprised... there is not that much circuitry in the ODAC SMD PC card....
  
 Alex


----------



## mcandmar

Just checked my notes, i measured mine at 57ma playing a 0db sine wave into a 100k load.  I too was surprised at how low it was, and due to the lack of power supply filter caps there didn't seem to be any noticeable startup peak.


----------



## BenF

mcandmar said:


> Just checked my notes, i measured mine at 57ma playing a 0db sine wave into a 100k load.  I too was surprised at how low it was, and due to the lack of power supply filter caps there didn't seem to be any noticeable startup peak.


 
 57mA into 100k load is 5.7V peak-to-peak - which is 2Vrms, ODACs output.
 Lower load would result in higher current.


----------



## jring

benf said:


> 57mA into 100k load is 5.7V peak-to-peak - which is 2Vrms, ODACs output.
> Lower load would result in higher current.


 
  
 Indeed although really low ohm loads are not really feasible (or will sound horrible w/o an amp), as might higher sample rates...
  
 Joachim


----------



## liamstrain

I have the 600/Crack as my current favorite set up at home. But I have an 02/0dac combo unit coming, I'll be curious to listen to the differences. 
  
 I got the O2 mostly to power the LCD 2's I have on the way... until I build out either an M3 or Dynahi.


----------



## Solrighal

liamstrain said:


> I have the 600/Crack as my current favorite set up at home. But I have an 02/0dac combo unit coming, I'll be curious to listen to the differences.
> 
> I got the O2 mostly to power the LCD 2's I have on the way... until I build out either an M3 or Dynahi.




I'm looking forward to your appraisal.


----------



## ericr

+1


----------



## r010159

solrighal said:


> Yeah but he wasn't talking about the BH Crack and his suggestions were way more expensive than the shortlist provided by the op.
> 
> I need Crack.




Crack sounds like it would be a pleasurable experience.


----------



## liamstrain

solrighal said:


> I'm looking forward to your appraisal.


 
  
 I need to dig out some of my testing equipment to better volume match, as well as remove the dac from the evalution - however initial impressions are that the O2 (via the ODAC) with the HD600s is very clean sounding. Maintains all the excellent character of the headphone. I do find myself reaching for the high-gain button - which is not surprising. I still think the 600 + Crack is a more _musical_ combination - adding the slight harmonic distortion and "tubey" sound which warms up the 600 a bit. So that is my preference currently for general listening - but I do not think that in any way represents a more accurate sound - the 02 definitely takes the cake there. 
  
 I did find the 02 to be slightly better (more apparent detail) than headphone out from the D100, which is surprising, as it has tested pretty well. And it could be that not perfectly level matching is at work there as well. 
  
 All in all, the 02 is very competent as an amplifier, and at its price range, I wouldn't hesitate to recommend it. Ample power and control for the phones I have tested so far (Fostex T50RP, Beyer 880/600, Senn 600, Grado 225i, AKG Sextetts, Denon D2000, Beyer 1350) and dead quiet even with my TripleFi10s and Etymotic ER4. 

 I will be curious to see how it handles the LCD 2s.
  
 I'll also update my impressions (again, once I sort level matching) with the Lovely Cube. And, either the M3 or Dynahi - once I decide on which I'll be getting (if either).


----------



## tdockweiler

I seriously don't understand why there is not more love for the O2 + HD-650/600. Makes no sense. To me it's a perfect match.
 I guess it doesn't add anything to how it's normally going to sound. My HD-650 manages to sound great with most neutral amps.
 The HD-650 actually sounds much better with the O2 than my Q701. I'll someday figure out why the Q701 is only so-so with the O2.
 Wouldn't imagine it's a lack of power and it's not because I prefer more coloration.
  
 I installed the OPA2277 in the O2 and the Q701 did improve somewhat.


----------



## JacobLee89

tdockweiler said:


> I seriously don't understand why there is not more love for the O2 + HD-650/600. Makes no sense. To me it's a perfect match.
> I guess it doesn't add anything to how it's normally going to sound. My HD-650 manages to sound great with most neutral amps.
> The HD-650 actually sounds much better with the O2 than my Q701. I'll someday figure out why the Q701 is only so-so with the O2.
> Wouldn't imagine it's a lack of power and it's not because I prefer more coloration.
> ...


 
  
 I chose HD650's for the closest thing you can have for a comfortable all-rounder open headphone.
 I chose the O2 (now modded with booster board) + ODAC for it's balance between performance, availability, price, and flexibility. In fact it was a place-holder for the BH Crack when I get the funds.
  
 Never did I thought I'd be content with just sticking to this combination. The more I listen, the less I feel inclined to upgrade to the Crack.


----------



## Solrighal

jacoblee89 said:


> I chose HD650's for the closest thing you can have for a comfortable all-rounder open headphone.
> I chose the O2 (now modded with booster board) + ODAC for it's balance between performance, availability, price, and flexibility. In fact it was a place-holder for the BH Crack when I get the funds.
> 
> Never did I thought I'd be content with just sticking to this combination. The more I listen, the less I feel inclined to upgrade to the Crack.




^ this ^

Whilst I'd really like to hear a valve-amp with the 650's I can't honestly say there's anything particularly missing from the sound I have now.


----------



## adydula

I don't think your missing with the O2 but what you will get with other amps, tube amps in particular is more attenuation to the signal and or source that you will either like or dislike depending on the source and your ears.
  
 Been there done that...l.but this is the subjective part of the hobby that makes it really interesting and many people rich...lol
  
 Alex


----------



## liamstrain

LCD 2.2 arrived this afternoon. Initial impressions with the O2/ODAC:

 "oh. my. god."


----------



## Solrighal

liamstrain said:


> LCD 2.2 arrived this afternoon. Initial impressions with the O2/ODAC:
> 
> 
> "oh. my. god."




Lousy eh?


----------



## liamstrain

Hah! No, quite good. They are still a bit underpowered, but not much. For a transportable computer audio rig, and especially for anywhere near the price, this is hard to beat. 

If I can create a rechargeable battery pack, I'll be all set.


----------



## Xenophon

adydula said:


> I don't think your missing with the O2 but what you will get with other amps, tube amps in particular is more attenuation to the signal and or source that you will either like or dislike depending on the source and your ears.
> 
> Been there done that...l.but this is the subjective part of the hobby that makes it really interesting and many people rich...lol
> 
> Alex


 
 +1.  I started out with ss gear but now listen mostly to tubes (and waste my time building tube amps but that's another matter) and tend to prefer the way tubes sound.  But let's be clear:  it's totally subjective and what I actually prefer is the sound of some second harmonic distortion that gets thrown in.  If you want accuracy above all, stay away from tubes, simple as that.  
  
 Considering a tube amp:  hold on to your wallet and know that a) there's *a lot *of 'high end' totally overpriced but badly built crap being sold b) many of those 'lush' sounding tube amps  don't run the tubes under recommended specs (worst of all, I think some of the builders live in blissful ignorance) and c) don't pay crazy prices for 'exotic' tubes, differences in amp topology and operating point  will have a far greater influence.  I see people waxing lyrical about one brand of 6AS7 vs another one but -after hearing MANY tubes- any differences between different brands of one type will be at best extremely small imo, provided they're run according to specs.


----------



## adydula

My O2 drove my LCD 2 R2's to ear splitting levels.... worked wonderfully.
  
 Alex


----------



## HaVoC-28

tdockweiler said:


> I seriously don't understand why there is not more love for the O2 + HD-650/600. Makes no sense. To me it's a perfect match.
> I guess it doesn't add anything to how it's normally going to sound. My HD-650 manages to sound great with most neutral amps.
> The HD-650 actually sounds much better with the O2 than my Q701. I'll someday figure out why the Q701 is only so-so with the O2.
> Wouldn't imagine it's a lack of power and it's not because I prefer more coloration.
> ...


 
  
 I both love HD600 and K702 ANV on o²  (well any headphones that i pluged with O² sounded good so 
	

	
	
		
		

		
			





)


----------



## JacobLee89

It's almost safe to say that you can't go (too) wrong with the O2 + ODAC combo as your first setup.


----------



## pearljam50000

Too bad they suck with HD800( from what i read here)


----------



## Solrighal

pearljam50000 said:


> Too bad they suck with HD800( from what i read here)




Since I can buy a car for the price of the 800's I'm not overly concerned.


----------



## HaVoC-28

pearljam50000 said:


> Too bad they suck with HD800( from what i read here)


 
  
 HD800 needs a 1k headphone amp at least to sound decently it's an well known fact here 
	

	
	
		
		

		
		
	


	



  
 I gess that if i try a HD800 on O² it will sound good as the others 
	

	
	
		
		

		
		
	


	



  
 But i can perfectly understand that some don't like the combo ^^ .


----------



## liamstrain

HD800 are very highly resolving and bright to my ears. The 02 isn't going to change that - many other amps will roll off the highs a bit. So it comes down to the subjective again. The 02 can drive them just fine, but it might not be a good match for many peoples preferences (who might prefer a more forgiving, relaxed sound - though, I'd argue if they want that - they should not buy the HD800).


----------



## adydula

The O2 allows you to hear what the HD800's really sound like..... other amps will add to or color the sound.
  
 Transparent is well "transparent"......
  
 Its not an amp to tune with....
  
 A.


----------



## Solrighal

adydula said:


> The O2 allows you to hear what the HD800's really sound like..... other amps will add to or color the sound.
> 
> Transparent is well "transparent"......
> 
> ...




This is very true. Also, what the O2 is very good at is providing a very clear window through which the attributes of any given headphone can be appraised. A true reference, if you like.

Then, when you find your preferred signature, you can flavour with valves and money no object cases.

At least, that's my take on headphone amps.


----------



## adydula

Well....so you use the O2 to find a set of cans u like then go get a tube amp to make them sound different???
  
 This doenst work well at all across the wide myriad of cd's and sources...
  
 I use the O2 as a reference amp, and look for well recorded and mastered marterial..I long gave up on having an amp, or set of tubes to make things sound good to me....there is too much stuff out there to have sonic perfection all the time with all music.
  
 Lousy material is not going to be made better with tube amps and tube swapping....its essentially like using hardware to act as an equalizer. That's very costly...IMO.
  
 A.


----------



## Solrighal

That's not what I said and no *I* don't. Read it again because I can't explain that any clearer.

I use my O2 as my only amp. It truly is my reference.


----------



## adydula

Cool didn't mean to offend!
  
 I understand what you said...
  
 Lots of other folks do not...
  
 All the best
  
 A.


----------



## Solrighal

All is well my friend. Go Messi!


----------



## JoeDoe

If anyone is interested, I'm selling a Mayflower O2/ODAC Combo (desktop version). Hate to let it go because it's such a bargain, but it's not going to overthrow the Asgard 2/Bifrost stack.
  
 PM me if interested.


----------



## Solrighal

joedoe said:


> If anyone is interested, I'm selling a Mayflower O2/ODAC Combo (desktop version). Hate to let it go because it's such a bargain, but it's not going to overthrow the Asgard 2/Bifrost stack.
> 
> PM me if interested.




I'd be interested to hear your comparison of these.


----------



## TheGame21x

solrighal said:


> I'd be interested to hear your comparison of these.


 
 Seconded.


----------



## ericr

+1 (cause I don't think "thirded" is a word)


----------



## JoeDoe

solrighal said:


> I'd be interested to hear your comparison of these.


 
  


thegame21x said:


> Seconded.


 
  


ericr said:


> +1 (cause I don't think "thirded" is a word)


 
 I'll get on it.


----------



## mstrmind5

I'm sorry if this has been asked before, but would the O2+ODAC properly drive the DT880 600 ohm variant. If so, what gain settings do you suggest. It will be exclusively used with a desktop PC. Anyone with experience Epiphany's offering, as I'm in the UK and it seems the logical choice.


----------



## liamstrain

Yes. It powers it just fine. The standard gain settings work great, though I do often turn the high-gain button on with the 880/600s.


----------



## mstrmind5

Thanks for the quick anwser. Would that be 2.5x/6.5x gain. Would want the two settings to allow for use with anything up to 600 ohms (too unreasonable!).
  
 I've read/heard elsewhere that having the volume dial too low can lead to channel imbalance and too high can lead to noise or even clipping. The suggestions, and those offered by JDS Labs for example, are 1.0x/3.5x or sometimes 1.0x/2.5x.


----------



## headwhacker

mstrmind5 said:


> Thanks for the quick anwser. Would that be 2.5x/6.5x gain. Would want the two settings to allow for use with anything up to 600 ohms (too unreasonable!).
> 
> I've read/heard elsewhere that having the volume dial too low can lead to channel imbalance and too high can lead to noise or even clipping. The suggestions, and those offered by JDS Labs for example, are 1.0x/3.5x or sometimes 1.0x/2.5x.


 
  
 If you are not planning to use other DAC than ODAC with O2, 1X/3.5X gain is the best combination. You can push O2+ODAC to it's maximum power output for hard to drive cans and not worry about clipping (@ 3.5X) and still use sensitive headphones and not worry about channel imbalance (@1x)


----------



## liamstrain

Mine is the JDS "standard" gain or 2.5-6.5 - no issues powering anything I have.


----------



## mstrmind5

headwhacker said:


> If you are not planning to use other DAC than ODAC with O2, 1X/3.5X gain is the best combination. You can push O2+ODAC to it's maximum power output for hard to drive cans and not worry about clipping (@ 3.5X) and still use sensitive headphones and not worry about channel imbalance (@1x)


 

 Planning on using only the ODAC+O2 combo with a PC, so good to know. 1.0-3.5 gain does seem to offer the best flexibility for the spectrum of headphones, so that will be the option I will chose. Thanks.
  


liamstrain said:


> Mine is the JDS "standard" gain or 2.5-6.5 - no issues powering anything I have.


 

 Thanks for the feedback. How do the 880's sound with the O2 combo?
  
  
 Open question to anyone.
  
 As I'm in the UK, are Epiphany's version the best choice          
 http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/
 or maybe Head 'n' Hifi                                             
 http://www.headnhifi.com/amplifiers/O2-ODAC-fully-modded
  
 Aesthetically I prefer the Head 'n' Hifi offering, but price, possible custom fees and warranty dealings find me leaning to Epiphany instead. I can't really consider JDS Labs for the same reasons as Head 'n' Hifi.
  
 Thanks all.


----------



## liamstrain

mstrmind5 said:


> Thanks for the feedback. How do the 880's sound with the O2 combo?


 
  
 Sounds like the 880. Detailed, with spectacular mids and highs, and well extended bass. A well mannered and very neutral sound signature - with all the detail you could ever lust for - just like you would expect of the 880/600.


----------



## mstrmind5

liamstrain said:


> Sounds like the 880. Detailed, with spectacular mids and highs, and well extended bass. A well mannered and very neutral sound signature - with all the detail you could ever lust for - just like you would expect of the 880/600.


 

 That's what I was looking for, a neutral and clean sounding amp/dac.
  
 Just hope someone with experience/dealings with Epipihany and Head 'n' Hifi could shed light on their offerings before I buy.


----------



## Eternal Phoenix

mstrmind5 said:


> That's what I was looking for, a neutral and clean sounding amp/dac.
> 
> Just hope someone with experience/dealings with Epipihany and Head 'n' Hifi could shed light on their offerings before I buy.


 
  
  
 Hi, 
  
 I've had the original Epiphany EHPO2D for almost exactly two years now, it has proved faultless so far, despite a fair bit of lugging it around.

 Mine was setup with 1x/2.5x gain as I use it with extremely sensitive CIEMs and there you do get some channel imbalance in the last mm or so of volume pot, I've placed a small mark on mine so I know where that is and don't go below it.
  
 ^Yes it does put too much power out for supersensitive CIEMs but there is not one trace of background hiss, which was the entire reason I bought it in the first place.
  
 They're now offering their new EHPO2Di for less than I got my unit so...
  
 Also, I use my HD800 on 1x gain as well, gets nowhere near the end of the pot.
  
  
 Ok, that's me done. (Any more Q's?)


----------



## mstrmind5

eternal phoenix said:


> Hi,
> 
> I've had the original Epiphany EHPO2D for almost exactly two years now, it has proved faultless so far, despite a fair bit of lugging it around.
> 
> ...


 

 Hi there,
  
 I've also seen the EHP-O2Di, looks like a good upgrade from the previous version. I will get gain of 1.0x, but I see/hear suggestions for the 2nd gain value of 2.5x or 3.5x. Considering I'm driving the 600 ohm DT880, would your suggestion for the 2nd gain value of 3.5x tally with headwhacker
 http://www.head-fi.org/t/616331/o2-amp-odac/3135#post_10703732
  
 Epiphany's site lists gain at 1.0x/5.0x. Can I request a change from Oliver to have the 5 changed to 3.5 gain (does it cost extra)?


----------



## pearljam50000

Can anyone compare to GeekOut as DAC/amp?


----------



## miceblue

pearljam50000 said:


> Can anyone compare to GeekOut as DAC/amp?



It sounds pretty similar to the ODAC/O2, but I think the Geek Out edges out in terms of sound quality overall.
More details:
http://geek.lhlabs.com/force/kickstartergeekout/866-who-received-the-geek-out.html?start=850#25991




My unit might be defective though so you can ignore the part about the background hiss.


----------



## Solrighal

I'm in the UK and I went for Head'n'Hifi. There will be NO import tax, there wasn't for me. Build quality is superb and I went for gains of 1x/3x. This works great for all my headphones but particularly well with my HD650's.


----------



## mstrmind5

solrighal said:


> I'm in the UK and I went for Head'n'Hifi. There will be NO import tax, there wasn't for me. Build quality is superb and I went for gains of 1x/3x. This works great for all my headphones but particularly well with my HD650's.


 

 How long have you had yours and what are they like to deal with? No import tax is only true if it's shipped from Germany owing to Swiss EU status iirc.
  
 I do prefer the look of Head'n'Hifi over Epiphany, but it's about £20 more and I'm concerned about the warranty and shipping back to them. I also can't seem to find the warranty length on their website. If that issue could be resolved I would probably consider it.
  
**1 year warranty opposed to **2 years with Epiphany*


----------



## Xenophon

mstrmind5 said:


> That's what I was looking for, a neutral and clean sounding amp/dac.
> 
> Just hope someone with experience/dealings with Epipihany and Head 'n' Hifi could shed light on their offerings before I buy.


 
 I have the Epiphany EHP-O2.  Also own a HD-800 but never use it with this combo (cfr infra).  Happy with the Epiphany product but be aware that if you use the gain setting it'll start distorting at high volume with inefficient or high impedance cans.  Only niggle I have with the Epiphany product is the fron power supply, it's been performing very well in the heat of my Delhi office for the past 2 years.
  
 As I said before, I'm VERY impressed with the DAC portion, the amp is just average imo.  
  
 Head 'n hifi can ship from France or Germany, that 'avoids' customs fees from Switzerland to the EU.  No experience with them.  
  
 For the price the ODAC/O2 combo is unbeatable, especially the ODAC.  In retrospect I'd probably purchase the DAC, a version with RCA connects, and then plug it into my own amp.
  
 Many people talk about neutral sound reproduction but few are those who understand what they're talking about and even less people like the result.  First off, the ODAC/O2 combo is pretty transparent provided you don't touch that gain button.  The HD-800 is extremely detailed but I wouldn't call it a perfectly neutral (whatever that may mean) headphone, it's a bit too strident in the highs for that.  Detailed and neutral are different things.  If you go for the combo with the ODAC/O2, make sure that you can take it, it may be too much.  I guarantee fatigue or annoyance if your recording is of less than pristine quality.  One of the reasons why many people like the HD-800 with a good tube amp (apart from the impedance which typically plays well with tubes) is that the tube amp takes down the detail and stridency (I hope that's a correct English word) a bit.
  
 As always, everything 'IMO' and 'YMMV'.


----------



## Solrighal

It does get shipped from Germany. I've had my O2 and ODAC for around 5 months now. Warranty work would be a hassle but there's not very much to go wrong and I hope I could work out any problem myself, possibly with the help of some of the many clever people in this very thread.


----------



## mstrmind5

Quote:


xenophon said:


> I have the Epiphany EHP-O2.  Also own a HD-800 but never use it with this combo (cfr infra).  Happy with the Epiphany product but be aware that if you use the gain setting it'll start distorting at high volume with inefficient or high impedance cans.  Only niggle I have with the Epiphany product is the fron power supply, it's been performing very well in the heat of my Delhi office for the past 2 years.
> 
> As I said before, I'm VERY impressed with the DAC portion, the amp is just average imo.
> 
> ...


 
 (cfr infra)?!
  
 I've read about the gain distortion at higher volumes, that's why I'm looking at setting gain values of 1.0x/3.5x to mitigate that as best as possible (what gain values do you have?).
  
 The newer version of the EHP-O2D (the EHP-O2Di) have copied Head'n'Hifi and relocated the power input to the back with RCA sockets that double as both line input for the amp and line output for the dac which should be an improvement.
 http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/
  
 I do like the look of Head'n'Hifi, but Epiphany is cheaper and a 2 year warranty opposed to 1 year.
  
 This would be my first amp/dac setup, looking to drive my newly acquired dt880 600 ohm and anything below that impedance-wise I may get in future. Spending about £200 on both the dac and amp combined. Have looked at tubes (LD MKIII) and know the advantages for driving higher impedances and complimenting the dt880 sound signature, but prefer SS as a first step because of it's transparency, although I may in a few months get a tube amp if as you say the O2/ODAC might not be to my liking.
  
 What about the O2 amp don't you like?


----------



## mstrmind5

solrighal said:


> It does get shipped from Germany. I've had my O2 and ODAC for around 5 months now. Warranty work would be a hassle but there's not very much to go wrong and I hope I could work out any problem myself, possibly with the help of some of the many clever people in this very thread.


 
 Thanks for that.
  
 Do you ever use the higher gain setting? If so, how high do you turn the volume pot to and do you ever hear any distortion with your HD650?


----------



## Solrighal

I never hear distortion and unity gain generally offers more than enough volume for me. The only time I use 3x gain is with some older recordings or when I'm using my Q701's. 

I'd probably go for that Epiphany version, particularly given the longer warranty period. Head'n'Hifi do a great job though and I've no complaints.


----------



## mstrmind5

I guess with a dt880 600 ohm I would expect to use higher gain a little more often.
  
 Epiphany seems the most logical choice for me.
  
 Thanks.


----------



## adydula

FYI...
  
 A sample ODA amp has been shipped to a person that will do measurements via a dScope to compare with the O2 amps measurements.
  
 As soon as I have them I will post here or prove a link etch...\
  
 So far my ODA is performing flawlessly with my Beyer...
  
 Alex


----------



## JacobLee89

I had practically zero distortion problems with the 6x gain after I did the booster board upgrade. Though I hardly ever use such gain, and decided to just chop it off for a practical (to me) 1x and 2.5x gain selection.
  
 Though the modification was on a second hand O2, and does require knowledge on SMD techniques (or a lot of patience). AGDR has a post highlighting the many benefits of installing the booster board, as well as additional mods you can make to increase the output (i.e more volume, though I had little use for that mod).
  
http://www.head-fi.org/t/693300/o2-headamp-output-booster-modification-pcb
  
  


adydula said:


> FYI...
> 
> A sample ODA amp has been shipped to a person that will do measurements via a dScope to compare with the O2 amps measurements.
> 
> ...


 
  
 I'd be interested to see how it performs compared to the booster boarded O2, and whether the differences are worth the investment. By that I mean just getting the parts, equipment wise I am all set.


----------



## adydula

Hey,
  
 The ODA is definitely an eye test and takes a lot patience to build. The SMD IC's have very close pin spacing and was a challenge.
  
 That said if your a patient person and pays attention to details its not that bad.
  
 The differences between the O2 and ODA are far more than measurements.
  
 I did blind testing and can't tell the difference between the two, even though I thought I would be able to.
  
 It has more current capacity and just a smidgen greater voltage than the O2.
  
 The mechanics is what it sets it apart from the O2.
  
 The ability to attach two external docs ands switch between them.
  
 RCA Pre-amp outputs.
  
 RCA rear input jacks.
  
 Clipping LED indicator light, that tell you if your clipping via too high gain etc.
  
 Dual Power rail leds.
  
 No-thump turn off and turn on.
  
 4 selectable gain settings.
  
 1/4" and 3.5mm phone jacks.
  
 Optional Bass Boost. (3 db)
  
 Tailor-able attenuation resistors.
  
 Multiple Pre-Amp wiring setup.
  
 To me its the perfect objective desktop headphone amp.
  
 AGDR has a version 2.1 in the works and has the boards on order, and a wish list for a possible version 3.0 board.
  
 Alex


----------



## willmax

Hi everyone, can someone tell me if there is a workable bass boost mod for the O2?
 I'm not a bass head but sometimes it is nice having the option of a bass boost switch like most amps from JD Labs do.
 If someone could point me in the right direction it would be appreciated. Thanks


----------



## Poimandres

I will be joining the club as I ordered a custom o2 with odac from JDS Labs. Is there any advantages to using the battery (which mine won't come with) as opposed to the wal-wart? Other than portability that is?


----------



## liamstrain

willmax said:


> Hi everyone, can someone tell me if there is a workable bass boost mod for the O2?
> I'm not a bass head but sometimes it is nice having the option of a bass boost switch like most amps from JD Labs do.
> If someone could point me in the right direction it would be appreciated. Thanks


 
  
 I'd just use a good EQ from your source. I have yet to find a good "bass boost" that didn't introduce a lot of distortion in the process.


----------



## SilverEars

I'm looking to improve the ODAC, and I suspect with better USB power supplied, it could perform better.  I've seen threads online of people connecting it to regulated power supply, and curious how much the DAC would benefit from it.  I'm actually considering buying a powered usb hub and connecting it to that to make sure the usb is supplying enough power to the DAC.  I have experienced lack of power to the ODAC causing certain frequencies to sound hollow, and I suspect it was from the USB not outputting enough amps to it.


----------



## miceblue

silverears said:


> I'm looking to improve the ODAC, and I suspect with better USB power supplied, it could perform better.  I've seen threads online of people connecting it to regulated power supply, and curious how much the DAC would benefit from it.  I'm actually considering buying a powered usb hub and connecting it to that to make sure the usb is supplying enough power to the DAC.  I have experienced lack of power to the ODAC causing certain frequencies to sound hollow, and I suspect it was from the USB not outputting enough amps to it.



Maybe the new Schiit Wyrd USB Decrapifier?
http://schiit.com/products/wyrd-usb-decrapifier

I hate that gawd-awful name...


Or the iFi iPurifier if you can get a male USB B to female mini-USB cable.


----------



## Solrighal

I also hate that name. It's an interesting theory though but I can't say that I hear any problems with my USB output. I'm using a 2012 Mac mini running the latest Mavericks.


----------



## adydula

Here we go again....I find this topic very funny... its been discussed many times....
  
 I was one of the guys that spent a lot of time testing and running the ODAC off of pure DC, that's batteries,  Lab grade highly regulated LAMBDA DC power supply, and over a dozen different PC's, laptops etc with and without powered USB hubs.
  
 In all our testing we never could tell any real world difference in the actual sonic quality, period.
  
 I can understand the desire to make things better, but this is not an area that will really bring you audio nirvana.
  
 There are real issues with timing, stuttering, pops and clicks with various dacs, but that's usually to to other issues that can be improved etch.
  
 IMO your wasting your money but hey if you think it makes your audio experience better well have at it,
  
 I am saving my $$$ for another set of headphones!!
  
 Alex


----------



## Poimandres

Good to know that batteries didn't help in that regard. Thanks.


----------



## SilverEars

adydula said:


> Here we go again....I find this topic very funny... its been discussed many times....
> 
> I was one of the guys that spent a lot of time testing and running the ODAC off of pure DC, that's batteries,  Lab grade highly regulated LAMBDA DC power supply, and over a dozen different PC's, laptops etc with and without powered USB hubs.
> 
> ...


 
 Is it in this thread? If you can post me the measurements and information on your results, I would appreciate it very much.  Also, what headphones were you using?
  
 Thanks,
 SE


----------



## Poimandres

Do you have the o2 silverears? How does it stack up to the pure ii?


----------



## Xenophon

miceblue said:


> Maybe the new Schiit Wyrd USB Decrapifier?
> http://schiit.com/products/wyrd-usb-decrapifier
> 
> I hate that gawd-awful name...
> ...


 
 Or how to sell a box with little circuitry except some LED's on the front panel for 99 USD.  To their credit, they state themselves that they don't think it'll have an effect on sound.  To those who believe it does, drop me a mail, I've got a great deal on some cables......


----------



## miceblue

xenophon said:


> miceblue said:
> 
> 
> > Maybe the new Schiit Wyrd USB Decrapifier?
> ...



Isn't it just a linear power supply? Or something like that at least.


----------



## SilverEars

miceblue said:


> Isn't it just a linear power supply? Or something like that at least.


 
 This is really important to read that Schiit included:
  
Are you saying I need to get this thing if I have a USB DAC?

Nope, not at all. *Most USB DACs work just fine when running on computer power, without any hitches, glitches, or strange noises.* However, if you have USB power problems, this is a great way to eliminate them. Especially if it’s a USB-powered DAC
 
 Well, I could just buy a $20 powered hub if I’m having USB port power management problems, right? 
 
*Yep you can, and yep, that would solve that problem. *
 
Isn’t this just a way to get another $99 out of us? 
 
*Not unless you buy it…and keep it.*
 
This is the most honest marketing I've ever run into.  






  I think they mean try it and see if it helps.


----------



## miceblue

silverears said:


> miceblue said:
> 
> 
> > Isn't it just a linear power supply? Or something like that at least.
> ...



But that didn't answer my question though. XD


----------



## SilverEars

miceblue said:


> But that didn't answer my question though. XD


 
 The specs say linear.  
	

	
	
		
		

		
		
	


	




  It's a regulator in a box, it keeps voltage stable(just like the PC's regulator keeps the 5V stable), and since it's not connected to the PC's supply, it has lower noise than if the power was supply from a noisy PC usb connector.  It's probably more informative to measure your USB noise.
  
 The name is funny also.  It's make by *Schiit *and it's called, "Wyro USB De*crap*ifier"  It de-poopoos your usb.  
	

	
	
		
		

		
		
	


	




 
  
 Schiit has a sense of humor.


----------



## adydula

I like their sense of humor and stories, I have bought several Schitt amps in the past years and they have always worked fairly well. I never liked the "hot" Asgard just because it was hot, sounded ok. The Lyr allowed me to try a six watt amp on headphones that normally only get milliwatts of power from most of the "portable" amps available etc. What I admire is what they have come from and their stuff is made in the USA by US citizens....
  
 That said, this is a $99 product that I do not need and I agree it will most likely NOT change your sonic experience from the mundane to the surreal....lol
  
 Anyway, of you have an extra $99 try one and let us know what exactly changed for you...
  
 Alex


----------



## Poimandres

I received my O2+Odac last night and although I haven't had the time to listen to it I will say that I expected it to be bigger. It is really quite small. Is it recommended to use the ferrite USB cable? I have an ultraviolet that I was thinking about using.


----------



## Solrighal

I was also expecting something bigger, lol. It punches well above its weight though, don't worry. And yes, use the supplied cable with the ferrite bead. A fancy USB cable does nothing but look fancy.


----------



## XIX47

I have a question: is it possible for the O2 amp to blow out the drivers of a pair of headphones with the volume control know at near or at the maximum (9-12 o'clock?). While learning to use foobar2000 and it options playing FLAC soundtracks, I have noticed that I have to lower the FB2000's db settings to greatly reduce crackling noises during tracks (and having to crank the volume with my O2 amp). I am using a pair of K712's, so I am very hesitant of using the O2 amp at such high volumes long turn. During gaming, I only have set at 5-6 clock usually.


----------



## pearljam50000

Does the ODAC really sound like Benchmark DAC1?


----------



## James-uk

pearljam50000 said:


> Does the ODAC really sound like Benchmark DAC1?




Yes.


----------



## liamstrain

xix47 said:


> I have a question: is it possible for the O2 amp to blow out the drivers of a pair of headphones with the volume control know at near or at the maximum (9-12 o'clock?). While learning to use foobar2000 and it options playing FLAC soundtracks, I have noticed that I have to lower the FB2000's db settings to greatly reduce crackling noises during tracks (and having to crank the volume with my O2 amp). I am using a pair of K712's, so I am very hesitant of using the O2 amp at such high volumes long turn. During gaming, I only have set at 5-6 clock usually.


 
  
 I'm not quite sure what you are running into. If you have Foobar up high, and the 02 down low, you get crackling, but Foobar low and 02 high, you don't? 
  
 DB is DB - if the overall volume is reasonable, the 02 isn't putting more energy into the headphone than when the situation is reversed.


----------



## JoeDoe

solrighal said:


> I'd be interested to hear your comparison of these.


 
  


thegame21x said:


> Seconded.


 
  


ericr said:


> +1 (cause I don't think "thirded" is a word)


 
  
  
 Gentlemen, I've been A/Bing the two for most of the week (probably around 20 hours) and well frankly, the O2/ODAC wins. 
  
 The two sound _very_ similarly - both are quite transparent, no noticeable issues in any of the frequency ranges, soundstage and separation are right on par with each other. To make a long story short, the only discernible difference I can hear is a _barely _blacker background on the O2/ODAC. It's noticeable in songs where the instrumentation or vocals are sparse, but noticeable nonetheless (think the countoff of _Back in Black_ or the organ in _Turn Me On_)
  
 Needless to say, I'll be keeping this little wonder and selling the $700 stack instead.


----------



## pearljam50000

Can anyone confirm that the HD800 has no bass with the O2?


----------



## liamstrain

pearljam50000 said:


> Can anyone confirm that the HD800 has no bass with the O2?


 
  
 That would be negative. The HD800's bass sounds like it always does - unless you are comparing it against a system which intentionally bloats it.


----------



## pearljam50000

Thanks.
Sounds like a good budget rig for HD800 ^_^
I read here somewhere that the GeekOut sounds similar, or slightly better than O2/ODAC, what do you guys think?


----------



## pearljam50000

Sorry,one more question:
Will there ever will be an ODAC with 24/192 and DSD support?


----------



## BenF

pearljam50000 said:


> Sorry,one more question:
> Will there ever will be an ODAC with 24/192 and DSD support?


 
  
 ODAC can't be changed.
 Also, ES9023 doesn't support DSD.
 192Khz is posswible over I2S - http://www.ebay.com/itm/SABRE-HI-END-DAC-24bit-192khz-with-ES9023-WM8804-and-i2s-input-diy-DAC-/271259596887


----------



## Poimandres

joedoe said:


> Gentlemen, I've been A/Bing the two for most of the week (probably around 20 hours) and well frankly, the O2/ODAC wins.
> 
> The two sound _very_ similarly - both are quite transparent, no noticeable issues in any of the frequency ranges, soundstage and separation are right on par with each other. To make a long story short, the only discernible difference I can hear is a _barely _blacker background on the O2/ODAC. It's noticeable in songs where the instrumentation or vocals are sparse, but noticeable nonetheless (think the countoff of _Back in Black_ or the organ in _Turn Me On_)
> 
> Needless to say, I'll be keeping this little wonder and selling the $700 stack instead.




I am glad to hear that you prefer the o2/odac to the schiit. Makes me glad that I ordered it.


----------



## Poimandres

BTW. What are your thoughts on the Stoner Acoustics DAC that I sold you?


----------



## Solrighal

joedoe said:


> Gentlemen, I've been A/Bing the two for most of the week (probably around 20 hours) and well frankly, the O2/ODAC wins.
> 
> The two sound _very_ similarly - both are quite transparent, no noticeable issues in any of the frequency ranges, soundstage and separation are right on par with each other. To make a long story short, the only discernible difference I can hear is a _barely _blacker background on the O2/ODAC. It's noticeable in songs where the instrumentation or vocals are sparse, but noticeable nonetheless (think the countoff of _Back in Black_ or the organ in _Turn Me On_)
> 
> Needless to say, I'll be keeping this little wonder and selling the $700 stack instead.




Myself & my wallet are eternally grateful to you my friend. 




pearljam50000 said:


> Can anyone confirm that the HD800 has no bass with the O2?




The whole point of the O2 is that it is transparent. It neither adds nor subtracts from the sonic signature of the headphones it drives. If the headphone sounds lean then it's supposed to sound lean. If the user doesn't like that then fair enough, there are two options - persevere with the headphone and buy an amp which will add or remove whatever sonic trait you choose. Or buy another headphone.


----------



## TheGame21x

joedoe said:


> Gentlemen, I've been A/Bing the two for most of the week (probably around 20 hours) and well frankly, the O2/ODAC wins.
> 
> The two sound _very_ similarly - both are quite transparent, no noticeable issues in any of the frequency ranges, soundstage and separation are right on par with each other. To make a long story short, the only discernible difference I can hear is a _barely _blacker background on the O2/ODAC. It's noticeable in songs where the instrumentation or vocals are sparse, but noticeable nonetheless (think the countoff of _Back in Black_ or the organ in _Turn Me On_)
> 
> Needless to say, I'll be keeping this little wonder and selling the $700 stack instead.


 
  
 Oh snap, plot twist!
  
 Thanks for the comparison!


----------



## XIX47

liamstrain said:


> I'm not quite sure what you are running into. If you have Foobar up high, and the 02 down low, you get crackling, but Foobar low and 02 high, you don't?
> 
> DB is DB - if the overall volume is reasonable, the 02 isn't putting more energy into the headphone than when the situation is reversed.


 
 I did not type my question clearly, sorry. The Db on Foobar2000 has to be lowered by -7.5 to -10 db with the db slider on top of the Foobar window, and the volume knob on the O2 has to be turned further to the right to increase the volume. That way most of the crackling has been eliminated or faded from my tracks.
  
 So I am good to go then even though I am using more power from the O2 amp to increase the volume? I like to find another solution to the crackling but this seems to be the best option for me now.


----------



## jseaber

xix47 said:


> I did not type my question clearly, sorry. The Db on Foobar2000 has to be lowered by -7.5 to -10 db with the db slider on top of the Foobar window, and the volume knob on the O2 has to be turned further to the right to increase the volume. That way most of the crackling has been eliminated or faded from my tracks.
> 
> So I am good to go then even though I am using more power from the O2 amp to increase the volume? I like to find another solution to the crackling but this seems to be the best option for me now.


 
  
 To avoid clipping with tracks stronger than -10dB, O2+ODAC needs to be assembled with a maximum gain of 3.5x.
  
 Have you tried low gain?


----------



## XIX47

jseaber said:


> To avoid clipping with tracks stronger than -10dB, O2+ODAC needs to be assembled with a maximum gain of 3.5x.
> 
> Have you tried low gain?


 

   I only have the O2 amp, and for my headphones it needs to be set on maximum gain or the sound quality is reduced (especially during explosions in movies & games).


----------



## liamstrain

xix47 said:


> I did not type my question clearly, sorry. The Db on Foobar2000 has to be lowered by -7.5 to -10 db with the db slider on top of the Foobar window, and the volume knob on the O2 has to be turned further to the right to increase the volume. That way most of the crackling has been eliminated or faded from my tracks.
> 
> So I am good to go then even though I am using more power from the O2 amp to increase the volume? I like to find another solution to the crackling but this seems to be the best option for me now.


 
  
 It sounds like the problem is your soundcard - not the 02. (Fwiw, I've NEVER heard gain clipping from the O2 with any headphones, even with high-gain on). 
  
 You should be just fine - the total energy to the headphone is what matters (in your case, the sum total of your source input + the 02), not whether the 02 is turned up to compensate for a lower source input.


----------



## JoeDoe

xix47 said:


> I only have the O2 amp, and for my headphones it needs to be set on maximum gain or the sound quality is reduced (especially during explosions in movies & games).




Whatcha rockin? HE-6s?!?!


----------



## XIX47

joedoe said:


> Whatcha rockin? HE-6s?!?!


 
  
  
   AKG K-712s.
  


liamstrain said:


> It sounds like the problem is your soundcard - not the 02. (Fwiw, I've NEVER heard gain clipping from the O2 with any headphones, even with high-gain on).
> 
> You should be just fine - the total energy to the headphone is what matters (in your case, the sum total of your source input + the 02), not whether the 02 is turned up to compensate for a lower source input.


 
   Hmm, with every other possibility eliminated, you must be correct. I have not really played around with the settings of the SB Z. Is this something that can be fixed via tweaking of the options in the SB Z control panel?


----------



## liamstrain

I'm going to be of zero help to you on that question. I just don't know a damn thing about that card, or windows audio these days. Sorry man. 
  
 But for others who may be able to help - are you using a line out? or the headphone out, to feed the 02?


----------



## XIX47

liamstrain said:


> I'm going to be of zero help to you on that question. I just don't know a damn thing about that card, or windows audio these days. Sorry man.
> 
> But for others who may be able to help - are you using a line out? or the headphone out, to feed the 02?


 
 No problem, I may have to ask this question in the SB Z thread if it is indeed causing my issues.
  
 The Headphone out to feed the O2. Wait a minute, could it be the double-amping that creates some of these crackling issues?


----------



## liamstrain

It's possible, but shouldn't be that big a deal. I was just asking to minimize unknowns. You might try a line out, if it has one. Just out of curiosity. I don't know what it's line level is though - you might be right back to square one.


----------



## XIX47

Yeah, I am going to ask for advice in the SB Z thread later today/tonight since it is going off-topic in this thread. Thanks for you help guys.


----------



## Poimandres

Hmmm anyone here using mediamonkey and the o2/odac?  Using wassapi I am unable to play in 16bit 44.1 through mediamonkey.  I need to change it above in order for it to play.  Since I set the ODAC to 24bit 96k per JDS Labs instructions I also set MM to that and it plays, it also seems to play fine at other samples just not 16 44.1.  I tried changing the odac to that and then MM still no go.  Any thoughts?


----------



## ohcrapgorillas

I'm a recent O2 convert from Asgard 2. I got a great deal on the classifieds here and am stunned with this little guy. I can't really tell any difference between it and Asgard with the HD650, even after several days of back and forth. I love the battery-powered aspect of the whole thing too, I can take it into the living room and listen to records or just lie on my bed or etc.
  
 A few questions: Does having it plugged in recharge the batteries? Does high gain or high volume drain the batteries faster? and I was wondering if anyone wanted to trade faceplates? I have a silver JDS O2 faceplate and would really like a black one instead to complement the Gamma2 DAC.


----------



## JoeDoe

ohcrapgorillas said:


> I'm a recent O2 convert from Asgard 2. I got a great deal on the classifieds here and am stunned with this little guy. I can't really tell any difference between it and Asgard with the HD650, even after several days of back and forth. I love the battery-powered aspect of the whole thing too, I can take it into the living room and listen to records or just lie on my bed or etc.




Right there with ya man, Asgard and Bifrost are out, O2/ODAC are in.


----------



## jseaber

ohcrapgorillas said:


> I'm a recent O2 convert from Asgard 2. I got a great deal on the classifieds here and am stunned with this little guy. I can't really tell any difference between it and Asgard with the HD650, even after several days of back and forth. I love the battery-powered aspect of the whole thing too, I can take it into the living room and listen to records or just lie on my bed or etc.
> 
> A few questions: Does having it plugged in recharge the batteries? Does high gain or high volume drain the batteries faster? and I was wondering if anyone wanted to trade faceplates? I have a silver JDS O2 faceplate and would really like a black one instead to complement the Gamma2 DAC.


 
  
 Batteries trickle charge while the AC adapter is connected (no risk of overcharging).
  
 Run time is dictated by output power, not gain. In other words, louder listening volumes will drain the batteries faster.


----------



## TheGame21x

So, had a learning experience regarding the O2 + ODAC last night.
  
 For the longest time, I've been thinking of buying another ODAC to drive other headphone amplifiers because I bought the combo with the ODAC built in, thinking there was no way to output to another amplifier.
  
 Come to find out last night after reading up on the combo at the JDS Labs website that the front line in jack performs double duty and works as a line in from an external source or a line out for the ODAC. For a second, I thought that feature was limited to new runs of the O2 + ODAC combo but, just for curiosity's sake, I went ahead and tried it and (of course) it worked.
  
 So, while I might want to get another combo just for the heck of it down the road (sure would be nice to have at my desk at work), I'm glad I don't have to rush out and get one now.


----------



## goober-george

thegame21x said:


> So, had a learning experience regarding the O2 + ODAC last night.
> 
> For the longest time, I've been thinking of buying another ODAC to drive other headphone amplifiers because I bought the combo with the ODAC built in, thinking there was no way to output to another amplifier.
> 
> ...


 

 So are you saying there is no purpose to buying the ODAC buy itself then? Unless for some reason you wanted another box.


----------



## TheGame21x

goober-george said:


> So are you saying there is no purpose to buying the ODAC buy itself then? Unless for some reason you wanted another box.


 
 If you already have the combo and don't need RCA output or want it in a more convenient spot or something along those lines, I would imagine not.
  
 I'm glad I found that out though. Just saved myself some money.


----------



## pearljam50000

Can anyone confirm that the GeekOut sounds similar to 02+ODAC?


----------



## shak85

I've ordered and got o2 from epiphany acoustics . I was wondering since i have only ordered the o2 and not the odac , is there much of difference when using a cheap dac with my o2 , like the ele el-d01 ? Does the o2 work well without the odac ?


----------



## liamstrain

shak85 said:


> I've ordered and got o2 from epiphany acoustics . I was wondering since i have only ordered the o2 and not the odac , is there much of difference when using a cheap dac with my o2 , like the ele el-d01 ? Does the o2 work well without the odac ?


 
  
 You should be fine. The 02 is happy with most input sources.


----------



## goober-george

I just received the O2 AMP + ODAC combo made by Mayflower Electronics and it just took my Mad Dogs to a whole new level. I really don't even know if I need to spend anymore on new headphones, dacs or amps. It's that good.


----------



## adydula

There ya go..... enjoy George!
  
 Alex


----------



## skeptic

goober-george said:


> I just received the O2 AMP + ODAC combo made by Mayflower Electronics and it just took my Mad Dogs to a whole new level. I really don't even know if I need to spend anymore on new headphones, dacs or amps. It's that good.


 
  
 Glad to hear you're enjoying this combo - +1 for the o2/odac with fostex t50rp variants!  Sounds awesome with alpha dogs too!  I think the sound gets a little better still with the agdr booster board and lme49990's in the gain stage, but confirmation bias and my pride in completing a smd project may be playing some role in that opinion


----------



## Poimandres

glad to hear you are enjoying it. I decided to go with jds labs variant even though mayflower is literally 1/2 hour from me.


----------



## goober-george

skeptic said:


> Glad to hear you're enjoying this combo - +1 for the o2/odac with fostex t50rp variants!  Sounds awesome with alpha dogs too!  I think the sound gets a little better still with the agdr booster board and lme49990's in the gain stage, but confirmation bias and my pride in completing a smd project may be playing some role in that opinion


 
  
 I will say one thing though, at times the O2 is bit bright in the treble area(actually it's probably my Mad Dogs), but with some songs it's just so crisp and lush at the same time it's amazing. I also will have to take back my statement about spending more, because now I just want to upgrade to Alpha Dogs and I just ordered Sennheiser HD-600s.
 Oops.


----------



## adydula

I love the O2 and the ODAC, its a marvelous pairing for most cans except ones like HE6's etch...
  
 I built the desktop O2 called the ODA from an engineer over at DIY Audio, it has measurements similar and in some cases better than the O2.
  
 Designed in the same spirit it has evolved to version 2.1 and may evolve even further.
  
 It has 3 times the current capability of the O2 and can drive even HE6's with authority.
  
 Check it out if your a DIY person, you can't buy this one .....maybe someday.
  
 Alex


----------



## TheGame21x

...I want one.
  
 Ugh. I wish I was more handy with electrical engineering.


----------



## Poimandres

Not necessarily EE but you should definitely have soldering skills.


----------



## JacobLee89

thegame21x said:


> ...I want one.
> 
> Ugh. I wish I was more handy with electrical engineering.


 
  
 EE would help troubleshoot mistakes and faults. Soldering skills however can be seen as a completely separate skill, though both seem to compliment each other very well.
  
 I for one am a hobbyist whom picked up soldering but know next to nothing about electronics. Luckily I am as thorough as I am patient when following assembly instructions.
  
 I still can't find a good reason yet to try out the ODA, since my O2 already has the mod board. Perhaps I'll give the ODA a shot once it reaches the next few revisions and when I find myself with "real" disposable income.


----------



## adydula

I would recommend you to build at least an O2 like the 'kit' type from Jds labs. Its not really a kit, but the pc board and all the parts to populate an O2. You will need a case and the AC adapter.
  
 You will have to read the designers blog for instructions on how best to populate it and test it etch..
  
 But before I would build this I would practice soldering, with a pert board from radio shack, buy some cheap resistors etch and practice soldering point to point and adding wires etc.
  
 Soldering is no hard but it takes some learning and practicing to understand how it works, to know if a joint is done properly or not and how to re-work etc.
  
 The other thing with DIY is having some understanding what the parts are, How to tell a resistor from a capacitor etc.
 Some parts are directional and some have polarity. If installed incorrectly a capacitor will burst of explode making a mess.
  
 The ODA uses really very small parts in several areas and there are choices to make on how to set up certain things, kind of like options. It helps to understand how to make the choices for you particular situation.
  
 I have seen people trying to get a basic O2 up and running and having all kinds on issues, mainly due to lack of knowledge and understanding.... and crappy soldering.
  
 The parts for an ODA cost me close to $300.
  
 It is well structured and very compartmentalized when it comes to testing etch... very well thought out.
  
 You can get lots of web help from the folks at DIY audio.
  
 ODA pc boards for version 2.1 are in test. If your interested send AGDR at diyaudio a pm.
  
 All the best
 Alex


----------



## HaVoC-28

thegame21x said:


> ...I want one.
> 
> Ugh. I wish I was more handy with electrical engineering.


 
  
 Your current cans will not improve with an ODA , so you don't need one unless your planing in buying some HE-6 
	

	
	
		
		

		
			





 


adydula said:


> The parts for an ODA cost me close to $300.
> 
> Alex


 
  
 300$ ? hum same budget as an allready made G103-S from lake People : / . But kuddos for AGR on his work on ODA .


----------



## Xenophon

thegame21x said:


> ...I want one.
> 
> Ugh. I wish I was more handy with electrical engineering.


 
 The ODA is definitely not a starter project, certainly if you've never soldered before.  Parts are very small and if you don't know what you're doing and have no equipment, debugging will be virtually impossible. There are many other projects out there that will give you a good dac/amp with power to spare and are easier builds due to less parts and larger components/spacious boards.  Take a look on diyaudio.


----------



## shak85

I got my o2 amp today and it says on the top to charge it for 8-12 hours before first use. Is it ok if i use while charging ?


----------



## Solrighal

I'm unsure what the booster board is for. Would it benefit my HD 650's?


----------



## Xenophon

solrighal said:


> I'm unsure what the booster board is for. Would it benefit my HD 650's?


 
 I.m.o. no.  It's an add-on module for an existing O2 that basically provides some extra oomph but with the 650 I don't think it'll result in an audible difference.


----------



## shak85

shak85 said:


> I got my o2 amp today and it says on the top to charge it for 8-12 hours before first use. Is it ok if i use while charging ?


 
  And how do i know if it charging or not ? Is there a led indicator ?


----------



## Solrighal

shak85 said:


> I got my o2 amp today and it says on the top to charge it for 8-12 hours before first use. Is it ok if i use while charging ?







shak85 said:


> And how do i know if it charging or not ? Is there a led indicator ?




I'm pretty sure it's OK to use whilst charging but there's no charging indicator I'm afraid.


----------



## JacobLee89

xenophon said:


> I.m.o. no.  It's an add-on module for an existing O2 that basically provides some extra oomph but with the 650 I don't think it'll result in an audible difference.


 
  
 It has for me. But it's difficult to tell if it's subjectivity speaking since I haven't got a spare O2 at hand.
  
 The booster board essentially replaces both MOSFETs with ones much better across the board. Other mods were mentioned outside of the booster board mod, including 0 output resistance and mods for higher voltage swing. Both by the looks of it, do require the booster board mod to be installed first.
  
 I got the O2 booster board mainly because I am more than happy to stick with this little amp. The booster board just allows it that slightly increased versatility with other headphones should I have the itch to expand from the HD650.


----------



## HaVoC-28

jacoblee89 said:


> It has for me. But it's difficult to tell if it's subjectivity speaking since I haven't got a spare O2 at hand.


 
  
 Then get an O² without booster board to exactly know if it had something or if it's just old plain placebo .
  
 It's an O²/ODAC thread , we have to be a minimum objective 
	

	
	
		
		

		
		
	


	



  
 (just kidding)


----------



## JacobLee89

havoc-28 said:


> Then get an O² without booster board to exactly know if it had something or if it's just old plain placebo .
> 
> It's an O²/ODAC thread , we have to be a minimum objective
> 
> ...


 
 I have to say: "This is where the fun starts" , though I'd like to think that I am Objective 2! (I'm not ashamed of this one)


----------



## TheGame21x

jacoblee89 said:


> EE would help troubleshoot mistakes and faults. Soldering skills however can be seen as a completely separate skill, though both seem to compliment each other very well.
> 
> I for one am a hobbyist whom picked up soldering but know next to nothing about electronics. Luckily I am as thorough as I am patient when following assembly instructions.
> 
> I still can't find a good reason yet to try out the ODA, since my O2 already has the mod board. Perhaps I'll give the ODA a shot once it reaches the next few revisions and when I find myself with "real" disposable income.


 
  
 Soldering is what worries me. Every time I've picked up a hot soldering iron, I keep worrying i'm going to burn myself. I'm thinking of trying to assemble my own O2 at some point, after a little practice. Maybe on a CMoy or something like that.
  
 And, mod board?


xenophon said:


> The ODA is definitely not a starter project, certainly if you've never soldered before.  Parts are very small and if you don't know what you're doing and have no equipment, debugging will be virtually impossible. There are many other projects out there that will give you a good dac/amp with power to spare and are easier builds due to less parts and larger components/spacious boards.  Take a look on diyaudio.


 
  
 Oh I can tell. Just looking at the O2 is worrying enough given my newbie status as it pertains to soldering.
  


havoc-28 said:


> Your current cans will not improve with an ODA , so you don't need one unless your planing in buying some HE-6


 
  
 Oh I know I don't need one but the variable gain settings and bass boost circuit (what can I say? I'm a basshead) by themselves are enough to pique my interest. And who knows? I've been bitten by the planar bug with the HE-400 so someday I might end up getting an HE-6, if only just to see what the fuss is about.


----------



## adydula

The ODA has more advantages over the O2 than just more current capacity for HE6 type cans.....
  
 You can have 2 sets of cans attached at the same time due to this increased current capacity... and quickly listen to one then another.
  
 You can have 2 dads connected at the same time and switch between them to make dad "testing" or "listening" more efficient....
  
 There are 4 selectable gains.
  
 The power switch is on the back as many desired.
  
 The AC power jack is on the back as many desired.
  
 There is a pre-amp option that can be wired up in several ways if needed.
  
 There is a clipping led indicator to actually tell you if your clipping at various gain settings.
  
 There are (2) Power rail leds to indicate power is on and available for the +/- supplies.
  
 I have my ODA connected to my Onkyo AVR to drive a set of speakers for gaming.
  
 Anytime I can turn this off and pick up my connected cans and listen to music via JRiver...
  
 Not only does the ODA have similar and in some cases better specs its much more versatile to me in my usage scenario.
  
 Yes is will not make your headphones sound any better relatively but its current capacity is a plus and you might need that one day if you go the HE6 route.
  
 The ODA doesn't make the O2 bad it just takes it to the desktop level.
  
 But if u can't solder get someone to build you one.
  
 Alex


----------



## TheGame21x

Do you have any pictures of what a completed ODA would look like?


----------



## JacobLee89

thegame21x said:


> Soldering is what worries me. Every time I've picked up a hot soldering iron, I keep worrying i'm going to burn myself. I'm thinking of trying to assemble my own O2 at some point, after a little practice. Maybe on a CMoy or something like that.
> 
> And, mod board?


 
  
 With soldering getting precision tweezers and the "helping hands" tool will help keep things in place, and out of burning range for your fingers. Solder flux is almost a must for anyone learning to surface mount.
  
 As for how to's, youtube has plenty of good videos. The how to's with the most views are generally very good as far as I've seen. That's where I've learnt to surface mount.
  
 As for the "mod board", I was referring to the output booster board by ADGR. The mod itself may or may not improve the already decent performance of the O2, but it is certainly much easier to do than the ODA by the looks of it.


adydula said:


> The ODA doesn't make the O2 bad it just takes it to the desktop level.


 
  
 Ever since I've modded the O2, it's almost constantly connected thanks to the increased power drain. The ODA is getting increasingly tempting. Tinker fingers are getting excited over the thought.


----------



## adydula

Pictures... take a look here.....I started this ODA thread some time back.... scroll down etch and there are lots of pix from my DIY build experience.
  
http://www.head-fi.org/t/719611/objective-desktop-amp-a-version-from-agdr
  
 Also look over at DIYAUDIO.COM under headphone systems and the ODA thread, its 50+ pages long now.
  
 The ODA is now moving to version 2.1, its been built by AGDR and is under burn in testing at the moment.
  
 Several people have PC boards reserved for this build level.
  
 Alex


----------



## Xenophon

I'm not comfortable with recommending ANY setup as good for the HE-6 as long as I haven't tried it myself. I know the power/spl numbers the ODA should be able to reach with it but suffice it to say that I've heard the 6 from amps that could provide the same or better and it sounded like crap. And let's not forget the heating issue that might pop up. I agree that it's a great effort but it has issues that make it unsuitable for mass production.


----------



## adydula

I am afraid your confused...there is no heating issue with the ODA.
  
 The booster board was looked at by JDS awhile back this may be what your thinking about.
  
 I have thermocoupled measured the ODA for several days, if you want HOT try a Schitt Asgard.....that's HOT.
  
 Alex


----------



## vertical

poimandres said:


> glad to hear you are enjoying it. I decided to go with jds labs variant even though mayflower is literally 1/2 hour from me.




Hi Poimandres. 

If you don't mind me asking...why didn't you go with Mayflower?

Thx


----------



## Poimandres

I really wanted to go with a local vendor however I did not want to pay NYS taxes, I also ended up returning the O2/ODAC and decided to keep the Fiio X5.


----------



## Solrighal

poimandres said:


> I really wanted to go with a local vendor however I did not want to pay NYS taxes, I also ended up returning the O2/ODAC and decided to keep the Fiio X5.




Just curious, is there a way to go with a local vendor *without* paying local taxes?


----------



## Poimandres

Unfortunately not.  Also I wasn't sure if I was going to keep it so I went with JDS.


----------



## Solrighal

poimandres said:


> Unfortunately not.  Also I wasn't sure if I was going to keep it so I went with JDS.




Bizarre. Do these local taxes apply to everything you buy locally?


----------



## vertical

OK, I get the sales tax part...that's your choice. 
  
 I think that their return policies are the same.
  
 Since my parents live near Mayflower I will consider them and maybe look to see if sales tax and shipping balance out if I pick up an item...
  
 Thx


----------



## Poimandres

solrighal said:


> Bizarre. Do these local taxes apply to everything you buy locally?


 

 How does that even apply?  What is bizarre is your interest in this and your candor, it would be nice if you would stop trolling.  However as taxed as our country is it is certainly not as taxed as you brits or the rest of Europe.


----------



## Solrighal

poimandres said:


> How does that even apply?  What is bizarre is your interest in this and your candor, it would be nice if you would stop trolling.  However as taxed as our country is it is certainly not as taxed as you brits or the rest of Europe.




There's no need to be defensive mate. I was merely interested that given where you live you'd not prefer to pay a local tax as opposed to whatever tax is applicable where JDS operates. I clearly don't understand the tax system in your country. 

Anyway, I'll say no more & apologise for offending you.


----------



## jseaber

solrighal said:


> There's no need to be defensive mate. I was merely interested that given where you live you'd not prefer to pay a local tax as opposed to whatever tax is applicable where JDS operates. I clearly don't understand the tax system in your country.
> 
> Anyway, I'll say no more & apologise for offending you.


 
  
 Sales tax in the United States is collected only from customers who reside in a state in which a vendor operates. Our facility is located in Illinois, USA. Therefore, only Illinois residents pay sales tax.


----------



## Solrighal

Thank you John. I can't say as I understand the logic there to be honest. I could go on about that one for ages, but not here. I'm sorry for de-railing the thread.


----------



## jseaber

solrighal said:


> Thank you John. I can't say as I understand the logic there to be honest. I could go on about that one for ages, but not here. I'm sorry for de-railing the thread.


 
  
 Hehe, agreed. The logic of US state sales tax made more sense before the Internet age. It's a topic of ongoing debate...


----------



## adydula

This is from a engineer in Colorado that has been measuring the new ODA amp... its really quite amazing!!
  
https://www.youtube.com/watch?v=VTbWVEKzVpY
  
  
 FYI
 Alex


----------



## Poimandres

jseaber said:


> Sales tax in the United States is collected only from customers who reside in a state in which a vendor operates. Our facility is located in Illinois, USA. Therefore, only Illinois residents pay sales tax.


 

 Sorry Zorrofox I actually believed you were trolling.  In this case the only state in the US that has to pay taxes (assuming the purchase is made online) on a JDS Labs product is Illinois, since they are based there.  The one main exception to this is Amazon, it seems everyone gets charged their local taxes no matter where that person resides in the US.


----------



## Solrighal

That's OK my friend, no worries. I was right though, that is bizarre.


----------



## TheGame21x

jacoblee89 said:


> With soldering getting precision tweezers and the "helping hands" tool will help keep things in place, and out of burning range for your fingers. Solder flux is almost a must for anyone learning to surface mount.
> 
> As for how to's, youtube has plenty of good videos. The how to's with the most views are generally very good as far as I've seen. That's where I've learnt to surface mount.
> 
> ...


 

 I'm considering getting a soldering kit (IE the soldering iron itself, helping hands, some solder) and thinking about buying a cheap DIY kit. Something basic like a CMoy board that won't put me out too much money if I end up screwing it up.


----------



## adydula

The cmoy is a good starting project..... good luck and enjoy.... take your time etch..
  
 Alex


----------



## Dark_wizzie

jseaber said:


> Hehe, agreed. The logic of US state sales tax made more sense before the Internet age. It's a topic of ongoing debate...


 
 Hey,
  
 I believe JDSLabs has its own dac/amp solution. I'm guessing it is not related to the Objective. What is the purpose of this product? Do you think it is superior to the Objective in some ways or was it just a shot at trying to make something nice yourself? I believe the JDSLabs offering is rechargeable by USB, so maybe that's the difference?


----------



## jseaber

dark_wizzie said:


> Hey,
> 
> I believe JDSLabs has its own dac/amp solution. I'm guessing it is not related to the Objective. What is the purpose of this product? Do you think it is superior to the Objective in some ways or was it just a shot at trying to make something nice yourself? I believe the JDSLabs offering is rechargeable by USB, so maybe that's the difference?


 
  
 JDS Labs launched in 2007 with the cMoyBB, long before O2 and ODAC came about (2011-2012). At its peak, the cMoyBB sold around 10 units/day, and still remains well reviewed for an entry-level amp. cMoyBB represents JDS Labs's origin, so we keep it around for fun.
  
 Customers requested more features over the years, which lead to development of the JDS Labs c421 amplifier in 2010 (pardon the old site). I resigned from my full-time engineering job in 2011 and hired Nick to keep up with JDS Labs's growth. c421 was intended to replace the cMoyBB. The design landed about 50% over-budget, and if there was a production issue to be had, we encountered it. Initial circuit board yield was around 80% (99.5%+ is normal); nearly all enclosures were off-spec; production ran months late. In other words, c421 taught us how _not_ to manufacture a product.
  
 We were as surprised as everyone else when NwAvGuy's O2 appeared later that same year. NwAvGuy had designed O2 to dominate the headphone amplifier market, and it still delivers today. I feared that NwAvGuy would review our c421 like he had other manufacturers' products, and a poor review from NwAvGuy might have destroyed JDS Labs in 2011. We were still a small DIY shop, so existing customers began asking us to build and supply O2 boards. I agreed to build a few, and we listed blank PCBs in the store.
  
 Objective2 took off and has since spawned several DIY companies. This happens with any worthwhile opensource project, as some see an opportunity and jump towards quick profit. I still remember the first time I tried an O2 in my home office. It pushed my Sennheisers to levels I'd never hard before--a killer design. Since 2011, we've grown JDS Labs not around O2 specifically, but around the idea of excellent objective and subjective performance. c421's failures enabled us to become the leading O2/ODAC manufacturer.
  
 So, you're asking about C5 and C5D. Neither is related to NwAvGuy's work and that's thoroughly explained in the C5 release article. It took about a year to stabilize c421 production after initial release. Meanwhile, JDS Labs grew from two guys in a basement to a multi-department organization covering 7500 sq.ft, and shipping over 15,000 items annually. C5 is the logical successor to c421. To summarize its release article, C5 is a portable amp best paired with IEMs and moderately efficient dynamic headphones. C5D is the same amplifier with a high performance DAC. Objective2 and O2+ODAC are more powerful designs in a desktop form factor.
  
 Every project has unique design goals, so if you want to skip the above story:
  

*C5/C5D*
*​*Developed by JDS Labs from 2012-2013; predecessor developed 2010-2011
Portable form factor
Perfect channel balance
USB rechargeable
Output power limited to ~88mW max (for IEMs, moderate efficiency dynamics)

*O2/ODAC*
Developed by NwAvGuy from 2011-2012
Desktop form factor; O2 is arguably portable
Amp+DAC limited to AC power
High output power, up to 650mW (for virtually all dynamic headphones)

  
 Sorry for the long post. Hope that answers the question.


----------



## goober-george

My O2 AMP/ODAC suddenly stopped working (it won't turn on anymore), at the same time my friend's external hdd failed to recognize his thumb print after being plugged into my laptop. It was working a moment before and now both our devices are no longer working. What could of gone wrong?
 My O2 AMP/ODAC is still being recognized by usb just not turning on.


----------



## jseaber

goober-george said:


> My O2 AMP/ODAC suddenly stopped working (it won't turn on anymore), at the same time my friend's external hdd failed to recognize his thumb print after being plugged into my laptop. It was working a moment before and now both our devices are no longer working. What could of gone wrong?
> My O2 AMP/ODAC is still being recognized by usb just not turning on.


 
  
 When ODAC connects and O2 will not turn on, the AC adapter is either unplugged, damaged, or otherwise unable to provide power to the amp.


----------



## goober-george

Tried another adapter and now it turns on but still does not play any sound. I will show pics of the internals soon, to see if you guys can spot anything wrong. Another thing, while we were listening to the amp we were going through a storm and our power did go out. That may have had something to do with it.


----------



## goober-george




----------



## liamstrain

goober-george said:


> Tried another adapter and now it turns on but still does not play any sound. I will show pics of the internals soon, to see if you guys can spot anything wrong. Another thing, while we were listening to the amp we were going through a storm and our power did go out. That may have had something to do with it.


 
  
 You had another AC/AC adapter of the correct rating, sitting around? Most are AC/DC adapters, and won't work properly.


----------



## goober-george

liamstrain said:


> You had another AC/AC adapter of the correct rating, sitting around? Most are AC/DC adapters, and won't work properly.


 

 Honestly my friend took the amp and tried another adapter that lit up the amp (supposed to be same output), like it was working but still didn't provide sound.  So, I'm not 100% sure if my amp/dac is fried or if I just need a new adapter.


----------



## shak85

Can anyone suggest a good case for the O2 amp and its accessories ?


----------



## Dark_wizzie

jseaber said:


> JDS Labs launched in 2007 with the cMoyBB, long before O2 and ODAC came about (2011-2012). At its peak, the cMoyBB sold around 10 units/day, and still remains well reviewed for an entry-level amp. cMoyBB represents JDS Labs's origin, so we keep it around for fun.
> 
> Customers requested more features over the years, which lead to development of the JDS Labs c421 amplifier in 2010 (pardon the old site). I resigned from my full-time engineering job in 2011 and hired Nick to keep up with JDS Labs's growth. c421 was intended to replace the cMoyBB. The design landed about 50% over-budget, and if there was a production issue to be had, we encountered it. Initial circuit board yield was around 80% (99.5%+ is normal); nearly all enclosures were off-spec; production ran months late. In other words, c421 taught us how _not_ to manufacture a product.
> 
> ...


 
 Cool, that explains a lot. Thanks.


----------



## vertical

Agreed. Excellent info..especially the product positioning bits.

Thx!


----------



## Netforce

Custom o2 from jds labs came in today


----------



## vertical

Nice!


----------



## miceblue

netforce said:


> Custom o2 from jds labs came in today



Is that Reimu from the Touhou series? : D


----------



## Netforce

miceblue said:


> Is that Reimu from the Touhou series? : D


 
 Yup!


----------



## FiJAAS

I have a few questions, I have an iMac and I would like to know how can I connect Logitech X-530 5.1 Speaker System to the O2 Amp + ODAC Combo?

Also, which one is better? The O2 Amp + ODAC Combo or Sound Blaster Omni Surround 5.1 ?


----------



## liamstrain

the ODAC/O2 is 2 channel, not 5.1, so you are already going to be a bit more limited from that standpoint. To connect them to the O2, connect the green plug from the audio input cable to the “line out” jack on your O2 (if you got a version with RCA plugs for the DAC out, then use an RCA to 3.5mm female converter - you should be able to find one on monoprice). Do not use the black or orange plugs. Your rear speakers will not have sound. 
  
 If you want 5.1 sound (surround + subwoofer), then you will need to get a 5.1 soundcard (or something like the Sound Blaster Omni Surround 5.1). 
  
 As for which is "better" - with the Logitec speakers, it doesn't matter. You will not be able to hear a difference between any DAC/Amp that isn't seriously flawed.


----------



## FiJAAS

liamstrain said:


> the ODAC/O2 is 2 channel, not 5.1, so you are already going to be a bit more limited from that standpoint. To connect them to the O2, connect the green plug from the audio input cable to the “line out” jack on your O2 (if you got a version with RCA plugs for the DAC out, then use an RCA to 3.5mm female converter - you should be able to find one on monoprice). Do not use the black or orange plugs. Your rear speakers will not have sound.
> 
> If you want 5.1 sound (surround + subwoofer), then you will need to get a 5.1 soundcard (or something like the Sound Blaster Omni Surround 5.1).
> 
> As for which is "better" - with the Logitec speakers, it doesn't matter. You will not be able to hear a difference between any DAC/Amp that isn't seriously flawed.




Thanks for the help, I'll stick with the omni.


----------



## Dark_wizzie

netforce said:


> Custom o2 from jds labs came in today


 
 I didn't know JDS did custom engravings, that is cool!


----------



## Medaud

Hey guys, I'm thinking of pulling the trigger on the Epiphany Acoustics EHP-O2Di, but I'm wondering about the gain. It comes with 1x/5x, but I've read people suggestion 1x/2.5x instead. Do you think 1x/5x would be fine? I'm using ATH-A900x.
  
 Also that JDS custom engraving is awesome, how did you get them to do it?


----------



## HiFiRobot

medaud said:


> Hey guys, I'm thinking of pulling the trigger on the Epiphany Acoustics EHP-O2Di, but I'm wondering about the gain. It comes with 1x/5x, but I've read people suggestion 1x/2.5x instead. Do you think 1x/5x would be fine? I'm using ATH-A900x.
> 
> Also that JDS custom engraving is awesome, how did you get them to do it?




With 42ohm and 100db headphones the 5x won't be usable. Go for 2 or 2.5x. I have 1x/5x and only use 5x when I am using smartphone headphone out as source, otherwise 1x for all my headphones. I you are using ODAC then skip 5x. But if you are planning to buy high impedance low sensitivity headphones maybe keep 5x or change to 3-4x.


----------



## Xenophon

^+1
  
 Don't go for 5x gain, it's unusable with those cans you'd want to use it with (distortion will kick in with a vengeance).


----------



## Medaud

Thanks a lot guys. I'm sure the 1x setting is fine for my ath a900x, I just want my second gain to be as flexible and future proof as possible. I might upgrade to some Sennheiser 300 ohm headphones in the future or something else, I'm not sure. In short I'm worried that 5x is overkill and i should change it to 2.5-3.


----------



## Solrighal

I have gains of 1x/3x and 3x is more than enough for my 300 Ohm 650's.


----------



## jseaber

medaud said:


> Hey guys, I'm thinking of pulling the trigger on the Epiphany Acoustics EHP-O2Di, but I'm wondering about the gain. It comes with 1x/5x, but I've read people suggestion 1x/2.5x instead. Do you think 1x/5x would be fine? I'm using ATH-A900x.
> 
> Also that JDS custom engraving is awesome, how did you get them to do it?


 
  
*Engraving*: Click the Engrave button in the shopping cart. You can find more in this article: Custom Engraving Examples


----------



## gauchotodd

I just wanted to add my great experience with the O2+ODAC that I got from JDS. A couple weeks ago I ordered a custom unit with the power and RCA ports in the rear and a 1/4" port in front. 59 minutes after placing the order I received a shipment notification with a tracking number, and almost exactly 48 hours later it made its way from IL to my desk in Honolulu. Super impressed!
  
 I have my HE-500s plugged into them, and although they're still burning in I'm really happy (after changing the stock pads) with how clean and neutral the sound is through the O2+ODAC. About a week after I got the unit I picked up a pair of KRK Rokit5s and plugged them into the ODAC and had an awful static/hum from the speakers which hadn't been present in the previous owner's setup (I confirmed firsthand before purchasing). Naturally, I contacted JDS and received an immediate and personalized response, which was far more pleasant and informative than I expected or can even recall experiencing from pretty much any customer service in any industry.
  
 After a bit of troubleshooting it was pretty clear that it was an issue with ground loop noise which apparently isn't uncommon with the Rokits. With both the RCA and USB cables plugged in simultaneously the hum was present, but would go away with either one disconnected. JDS recommended a ground loop isolator which I just received yesterday, and it perfectly solved the issue.
  
 Really can't recommend them enough, it was well worth the little extra bit to customize the O2+ODAC how I wanted, and I have total peace of mind that they'll take care of me if any issues come up. They even offered to send me another ODAC to test out to see if by some chance mine was faulty. These guys clearly know how to take care of their customers, and I hope they're successful enough to see them around for a long time!


----------



## vertical

That IS good service...
  
 Thx for taking the time to type out the whole story for the rest of us


----------



## Medaud

I've read that the 3.5mm socket is only rated for 2000 insertions. I think I'll buy a short extension cable to prolong its life, would a cheap extension cable such as this be fine, audio quality wise?


----------



## adydula

yes


----------



## Medaud

Thank you good sir.


----------



## adydula

I use them all the time..... on two O2's.
  
 Alex


----------



## Medaud

The extension cables? EDIT: The reason I ask is that there are a lot of people talking about expensive cables and the difference they make. You can get some pretty expensive 3.5mm extensions on amazon. Makes you a bit worried about the dirt cheap chinese ones on ebay...but then again other people say it doesn't make any audible difference.


----------



## adydula

Cables have been debated over and over and over and over.... lots of emotion etch.
  
 You won't have any degradation with most cables that are well made.
  
 That said id you buy exoensive cable they will work well too, but IMO not really make any real world difference in this case with a small 6" dongle etc.
  
 I have several 3.5 mm dongle from various vendors, some are well made some are not, mechanically, but sonically they work.
  
 You can buy one from amazon etch for a low cost and test yourself.
  
 All the best
 Alex


----------



## JacobLee89

As far as I am concerned, buying a replacement 3.5mm jack and replacing the old one via soldering is an option that many seem to ignore.


----------



## mcandmar

Exactly, its a $1 problem. http://ie.mouser.com/Search/Refine.aspx?Keyword=STX-3120-5B
  
 Its rated for 5000 mating cycles, so if you unplug it every day it will last ~13 years, and come to think of it anytime i have had to replace headphone sockets the amp was at least 10 years old.


----------



## jring

poimandres said:


> How does that even apply?  What is bizarre is your interest in this and your candor, it would be nice if you would stop trolling.  However as taxed as our country is it is certainly not as taxed as you brits or the rest of Europe.


 
  
 The bizarre part from a non-US point of view is that you don't pay sales tax by ordering out-of-state (although it seems that in most cases you should declare every item bought out-of-state in your home state and pay a so-called use tax).
  
 In most other countries sales tax or equivalent are levied by the federal government and thus are the same everywhere and can't be avoided unless buying sth. internationally and then you pay duties plus tax at customs.
  
 Joachim


----------



## Xenophon

jring said:


> The bizarre part from a non-US point of view is that you don't pay sales tax by ordering out-of-state (although it seems that in most cases you should declare every item bought out-of-state in your home state and pay a so-called use tax).
> 
> In most other countries sales tax or equivalent are levied by the federal government and thus are the same everywhere and can't be avoided unless buying sth. internationally and then you pay duties plus tax at customs.
> 
> Joachim


 
 I do believe that in most US states you're _supposed_ to self-declare and pay the use tax.  But rates are relatively low, I recall something like 7% when I was living in TX years ago.  Compare that with rates (for essentials like bread) of average 6% in the EU and about 21% for anything else, there are small variation between countries though but the bounds are set on an EU level.  And it's levied automatically by the seller if you're a private person purchasing, the entire system is coordinated between member states of the EU.  
  
 Don't even get me started on income tax...in Belgium the highest slab (quite easy to fall under it, btw) is currently 50% and that's AFTER the deductions for social security.  But then we get back a lot via almost free healthcare and university education.


----------



## Solrighal

Check this out... 

http://www.head-fi.org/t/730167/do-i-need-an-amp-well-im-glad-you-asked/0_40#post_10787299


----------



## adydula

Several updates on the ODA amp from AGDR at DIYAUDIO.COM....

 He has sent the ODA  to Mike G and Mike has done measurements that are posted here and at DIY Audio. Mike also hooked up the ODA and played his 15" Alec's with the ODA....amazing etc.

 AGDR is working on some THD measurements and has received the ODA back from Mike G and has modified it and will be sending it back for round two... of testing.

 Mike has possibly discovered a THD issue with the original O2 with the volume pot being at mid way etc..AGDR has been analyzing this and thinks he knows what the issue might be. Its still below audible hearing etch.

 You can read the techie stuff again over at DIY Audio.

 That said none of this affects the sonic equality at all but AGDR being a perfectionist has continued to make improvements to the ODA. None of them really would be audible but makes the ODA better, safer from line input transients and more easy to build. So the latest V2.1 boards are going to be sent out shortly after he gets parts from Mouser. The 2.1 can be seen in this thread above and photos.

 Details on the 2.1 revisions are listed in great detail on agar's Google drive under the 2.1 area.

 I will be updating my 2.0 ODA with a few of the component updates, one being a transport across the AC power inputs to help with any surges, two regulator capacitors from 10uf to 22uf..based on data sheet errata, no sonic issue here, just one of a corner case oscillation possibility.... and a Pico amp fuse in series with one of the ac line inputs.

 Also the big news is that agar asked me to share he will be offering ODA BOARDS with the small hard to solder SMD parts' Here is his post:

 "In other news I have decided to sell ODA boards with just the SMD stuff soldered on for an additional $39 labor fee plus the $32 or so worth of SMD parts. All as time permits, lol, which will probably mean weekends, just doing them as ordered. If you run into anyone in your travels wanting a through-hole only ODA, feel free to point them to the posting:"

 You can send AGDR a pm directly and/or read the post at diyaudio in the vendor area.

 Alex


----------



## James-uk

Good morning. Just thought I would add to the pot of subjective impressions regarding O2 vs more expensive designs. In this case it's vs the benchmark dac1. Ever since getting into hifi I've wanted the Dac1 because it is a well built dac/amp designed around an objective approach to accurate sound. the only problem with this level of engineering was the cost especially here in the uk. Anyway because the dac2 is now out it's been discounted heavily so got a really good price . I knew already it wouldn't sound different to the O2 because I trust the science so I didn't buy it for better SQ , I just wanted the O2 sound with more versatility , especially the optical port for use with my PS4. Anyway I've been listening extensively and it sounds identical to the O2 . No surprises but it is nice to confirm with my own ears. Have a great day everyone. 

James.


----------



## adydula

Cool....there ya go!
  
 Enjoy
  
 Alex


----------



## Solrighal

That's saved me money.


----------



## James-uk

solrighal said:


> That's saved me money.




Indeed. Just highlights yet again what an achievement the O2 /odac are. Like I said I only needed something different because if connectivity but for USB audio odac / O2 are all anyone needs for perfect hifi reproduction.


----------



## Solrighal

I'm honestly of the opinion that 'coloured' amps are simply a con.


----------



## James-uk

Off topic but Are we allowed to link eBay items to head fi? Now I have the dac1 I don't need the hdvd800 anymore .


----------



## liamstrain

solrighal said:


> I'm honestly of the opinion that 'coloured' amps are simply a con.


 
  
 You can, through negligence or intent, force enough problems into an amp to audibly affect the sound. So in that respect, it's not a con. My question is, why would you? And that part may be.


----------



## pearljam50000

Hi, i got the Geek Out, and read that it's similar to the ODAC/02 , my question is how similar, and if there is any point in getting the ODAC/O2?


----------



## Solrighal

liamstrain said:


> You can, through negligence or intent, force enough problems into an amp to audibly affect the sound. So in that respect, it's not a con. My question is, why would you? And that part may be.




Yeah, that's what I think too. Sure, if you feel your headphones are too bright then an option might be to buy an amp which is warm to compensate, but why not get a transparent amp in the first place and then choose headphones with a signature you're happy with? 

Synergy? Bah, humbug.


----------



## liamstrain

Right. I try to get as transparent as I can from a hardware perspective. If I want a "warmer sound" I'll use an EQ. 

With that said, I do like the slight harmonic distortion of some tube amps...


----------



## Solrighal

Yeah, but at least you're conceding it is actually distortion. It's when people use words like 'better' that's annoying.


----------



## hekeli

Well honestly it's pretty easy to jump into inexperienced facts and conclusions. But having had lots of mid- to semi-highend stuff like the HD800 / Benchmark DAC2 / CMA800R combo, any differences I've _personally _found to ODAC/O2 are pretty subtle at best. Sometimes I felt O2 being slightly more "difficult" or "disruptive" to follow, but yeah that's the subjective and sighted stuff for ya.. I keep my CMA800R just in case. 
	

	
	
		
		

		
			





 (But could be my O2 was even gradually going bad since now it's kaputt with hissing pot and imbalance)
  
 I tried the $6500 EAR HP4 today with my HD800's. I'd (again personally) never pay that much for the subtle warming/smoothing I think I heard.. but I did end up going home with HE560's which actually make a different sound... well duh.. 
	

	
	
		
		

		
		
	


	



  
 In addition to the already ditched DAC2, I've comparisons with ODAC and my new HRT HD (using the CMA800R as quick A/B switch). Nothing there really. But uh I still like to keep the HD for XLR and 20 effective bits as measured by stereophile.. didn't pay much for it used either..


----------



## liamstrain

Oh yeah, I hold no delusion that my sometime preference for what is a measurable flaw, constitutes anything like "better."


----------



## Vader2k

Hi all.
  
 Kinda jumping into this thread feet first with a fairly specific question.  Apologies in advanced if this has already been discussed somewhere before.
  
 I have the Fidelio X1s and I use them pretty extensively off the headphone-out of my Marantz AVR (SR6005) with Dolby Headphone.  The X1s are known to have somewhat uncontrolled bass, but I feel it is more pronounced on my AVR.  The Marantz doesn't have a dedicated headphone amp, but rather the signal from the left and right speaker amps is attenuated by a resistor.  I've never been able to find the output impedance of the headphone-out, but I was told the output voltage is 1V @ 16 Ohms, 2V @ 32 Ohms.  I suspect this high voltage, and probably not much damping, is the cause for the bass bloat.
  
 Currently, I just EQ the bass to -2 dB to help take some of the edge off.  However, I've been pondering double-amping the DH processed signal through an O2 amp to hopefully better control the bass and not have to resort to taking some of it away.
  
 I have two questions regarding going this route:

Would I be fine with the stock gain of 2.5x / 6.5x or would I be better served with 1.0x / 3.5x?  I know the X1s are easy to drive and want to make sure I have enough play on the pot.
What would be a recommended volume to set the AVR at?  The headphone-out is of course variable and can go from –80.5 dB to 18 dB.  I normally listen around -28 db.
  
 Thanks!


----------



## goober-george

o2 dac/amp is back to life after ordering a new wall plug! As to the question reguarding the x1s the o2 amp should have no problem driving them. It is a neutral amp with a slightly bright sound and nice flat bass.


----------



## adydula

I would not double amp ....if the amp is the culprit for the bass you don't like adding an amp is not going to filter that out.... especially the 02 which whatever you put into it goes out amplified.
  
 If you get an O2 with an ODAC you will actually hear what your headphones actually "soundlike: without any EQ.
  
 The amp at unity gain and or 2.5 will be more than enough to drive your headphones.
  
 All the best
 Alex


----------



## Solrighal

Just as a point of interest Alex, if I can get the same adequate volume with unity gain as I can with 3x gain is there any other advantage in using unity?


----------



## adydula

Yes technically if you use the lowest gain you will have the lowest distortion levels.
  
 If there is distortion and there is in most things electrical, the higher gain the distortion gets amplified as well and distortion and or noise etc.
  
 I most always use unity gain on the o2 and my ODA.
  
 But depending on your headphones and there sensitivity it may be necessary to step in a little,,,,
  
 Alex


----------



## liamstrain

adydula said:


> Yes technically if you use the lowest gain you will have the lowest distortion levels.


 
  
 With that said, the distortion levels on the o2 are so far below audible, that there is no reason to suggest a benefit from an actual listening standpoint. Merely the theoretical.


----------



## goober-george

liamstrain said:


> With that said, the distortion levels on the o2 are so far below audible, that there is no reason to suggest a benefit from an actual listening standpoint. Merely the theoretical.


 
 Interesting, I feel I don't get enough volume for most of my headphones unless I adjust to the higher gain. Is there an optimal  setup when hooking up the o2 dac/amp? I just try to match the volume until it becomes a comfortable listening experience at 12 o'clock.


----------



## headwhacker

goober-george said:


> Interesting, I feel I don't get enough volume for most of my headphones unless I adjust to the higher gain. Is there an optimal  setup when hooking up the o2 dac/amp? I just try to match the volume until it becomes a comfortable listening experience at 12 o'clock.



 


That exactly is what the gain (or an amplifier in general)is for. To get more volume. The optimal setting is where you get the volume you want.


----------



## Solrighal

Many thanks Alex & everyone. That was actually what I was thinking myself but it's good to have it confirmed. I can generally get by on unity except for some older recordings which need a bit more. I realize I can't actually hear distortion but, well, I'd still rather it wasn't there in the first place. 

I'm loving my O2 by the way. The whole setup never disappoints.


----------



## adydula

No its not theoretical.... yes the THD measurements are inaudible but by using the higher gains with certain
 "hot" recorded material you will cause the O2 to clip and introduce distortion that you can hear. The O2 doesn't have clipping leds or any indicators to let u know this might be happening.
  
 Many people have reported hearing distortion when using higher gain settings.
  
 Me included and u can see these on a scope.
  
 My ODA has clipping less and when playing music with higher -db gain recordings the amp clips readily.
  
 Having your gain setting set so you get a "good" safe volume is a general way to look at this but not very exact.
  
 Alex


----------



## Solrighal

I've never heard it clipping myself but I've certainly read many reports of it doing so. I don't think I listen to "hot" music much. I'm not even sure I've ever listened to those recordings but it would be interesting to try just for reference.


----------



## Vader2k

adydula said:


> I would not double amp ....if the amp is the culprit for the bass you don't like adding an amp is not going to filter that out.... especially the 02 which whatever you put into it goes out amplified.
> 
> If you get an O2 with an ODAC you will actually hear what your headphones actually "soundlike: without any EQ.
> 
> ...


 
  
 I don't feel the Marantz is bad at handling bass, though.  I think it's just not pairing well with the X1s.  When I owned the K702 Anniversarys, they worked really nicely with the Marantz.  I was hoping that a second amp in the chain would be better able to handle the signal coming off the AVR and refine it in a way that is more compatible with the X1s.  Is what I'm trying to achieve possible with any amp?
  
 If I was doing music listening, I'm sure the X1s would sound awesome off the amp/DAC combo, but I primarily game and watch movies and I really like the Dolby Headphone processing effect, so throwing a DAC in the mix would remove that option.


----------



## liamstrain

adydula said:


> No its not theoretical.... yes the THD measurements are inaudible but by using the higher gains with certain
> "hot" recorded material you will cause the O2 to clip and introduce distortion that you can hear. The O2 doesn't have clipping leds or any indicators to let u know this might be happening.
> 
> Many people have reported hearing distortion when using higher gain settings.
> ...


 
  
 Hmm.. well, I have never experienced clipping or distortion with the O2/ODAC combo, despite needing to use high gain to drive my LCD 2's... but then, I don't go for earsplitting. I also usually use software to attenuate recordings that butt up against the redline (bad mastering).
  
 The 02's THD chart stays very low - even the worst performing chip stays under .01, pretty much right up until you get to where is will clip... I don't think audible distortion is the amp at that point, but either the headphones or the recording...


----------



## adydula

Exactly....
  
 The distortion you hear from running at high gain settings with hot dubbed source material comes from the source not the amp per say...I had a set of LCD 2's R2's for awhile and could easily hear distortion when the amp actually clipped at 6.5x....
  
 No reason to run it that high of a gain anyway.
  
 Using JRiver you can see the gain settings applied to the material being played unless u use replay gain to average things out, you can get songs that easily clip at 2--4x gain settings.
  
 How do you enjoy your lcd2s?
  
 Alex


----------



## adydula

If you like your Marantz for the Dolby processing that's fine. The O2 amp being very neutral or transparent should not add or detract from what u put into is within its design.
  
 Most likely the damping factor of the Marantz is helping cause the bass to what it is etch..
  
 You could just try an o2 and odac to see how they compare.
  
 Good Luck
 Alex


----------



## Vader2k

adydula said:


> If you like your Marantz for the Dolby processing that's fine. The O2 amp being very neutral or transparent should not add or detract from what u put into is within its design.
> 
> Most likely the damping factor of the Marantz is helping cause the bass to what it is etch..
> 
> ...


 
  
 Yeah, I suppose hearing the X1s separate from the Marantz for comparison wouldn't be a bad idea, just to be able to hear how much difference there is in the bass in the first place.
  
 Thanks for the help.


----------



## hekeli

liamstrain said:


> Hmm.. well, I have never experienced clipping or distortion with the O2/ODAC combo, despite needing to use high gain to drive my LCD 2's... but then, I don't go for earsplitting. I also usually use software to attenuate recordings that butt up against the redline (bad mastering).
> 
> The 02's THD chart stays very low - even the worst performing chip stays under .01, pretty much right up until you get to where is will clip... I don't think audible distortion is the amp at that point, but either the headphones or the recording...


 
  
 The O2 gain structure has been discussed in numerous posts and threads, yet all the time there's some misunderstanding? Someone should make a clear example FAQ page somewhere for ready quoting... the main point is that distortion happens _before_ the pot. If you "blast" a ~2 volt source like ODAC and use 6.5x gain, you might easily go into distortion (2 x 6.5V = 13V, well over 7V... of course real music is not continuous full blast sinewave but yeah "hot" music might do it). So regardless how "loud" you play, it's still distorted even if listening pot in whisper quiet position. Depending on how experienced one is, light <10% distortion might go easily unnoticed if not paying attention..
  
 The gain should be chosen by the source you intend to use and only that. For ODAC 1x/3.0-3.5x is around optimal, enabling all audio extremes (while never being able to clip). Of course you can have 6.5x if you lower the volume in your player/OS accordingly (someone posted some volt measurements here for ODAC and Windows volume control I think..)... but it would only make sense if you intend to sometimes use poor source like portables outputting just 1 volt and need the full ~7V output. Even playing "quiet classical" is not a sane reason for overdoing it, since the peaks would still clip. If there are no "0dBFS peaks", well obviously your file should be normalized/replaygained louder then..


----------



## Aikanaro

love how this combo just amplifies. no frills, you get your money's worth. difficult to beat at that price range imo


----------



## liamstrain

hekeli said:


> The O2 gain structure has been discussed in numerous posts and threads, yet all the time there's some misunderstanding? Someone should make a clear example FAQ page somewhere for ready quoting... the main point is that distortion happens _before_ the pot. If you "blast" a ~2 volt source like ODAC and use 6.5x gain, you might easily go into distortion (2 x 6.5V = 13V, well over 7V... of course real music is not continuous full blast sinewave but yeah "hot" music might do it). So regardless how "loud" you play, it's still distorted even if listening pot in whisper quiet position. Depending on how experienced one is, light <10% distortion might go easily unnoticed if not paying attention..


 
  
 Thank you for clarifying. Some pots control from the input stage, others are on the output.


----------



## Medaud

If you want to mod the gain, how difficult is it to remove the resistors and solder on some new ones? I haven't soldered since secondary school.


----------



## miceblue

pearljam50000 said:


> Hi, i got the Geek Out, and read that it's similar to the ODAC/02 , my question is how similar, and if there is any point in getting the ODAC/O2?



I find that the Geek Out is a bit better than the ODAC/O2 overall in terms of sound quality, but if you prefer having separate modules like the ODAC and O2, then I would recommend the Objective combo for that. I'll probably still use the ODAC for the RCA and 3.5 mm interconnect outputs, but I've been using the Geek Out more than the Objective combo recently. Having the ability to play high resolution masters natively, as well as DSD, is a plus too.


----------



## adydula

The gain in the o2 can easily be set with by clipping resistors or changing their values, no transistors...
  
 A.


----------



## Medaud

adydula said:


> The gain in the o2 can easily be set with by clipping resistors or changing their values, no transistors...
> 
> A.


 
  
 Sorry, my bad, resistors. To change their values (other than to 1x), you would have to remove them and solder on some new ones, correct?


----------



## adydula

Yes,
  
 The gain resistors are identified in the BOM....for values from 1x to 12x.....
  
  
 R17, R19, R21, R23
  
 Take a look over there.
  
 Alex


----------



## barihunk

hekeli said:


> The O2 gain structure has been discussed in numerous posts and threads, yet all the time there's some misunderstanding? Someone should make a clear example FAQ page somewhere for ready quoting... the main point is that distortion happens _before_ the pot. If you "blast" a ~2 volt source like ODAC and use 6.5x gain, you might easily go into distortion (2 x 6.5V = 13V, well over 7V... of course real music is not continuous full blast sinewave but yeah "hot" music might do it). So regardless how "loud" you play, it's still distorted even if listening pot in whisper quiet position. Depending on how experienced one is, light <10% distortion might go easily unnoticed if not paying attention..
> 
> The gain should be chosen by the source you intend to use and only that. For ODAC 1x/3.0-3.5x is around optimal, enabling all audio extremes (while never being able to clip). Of course you can have 6.5x if you lower the volume in your player/OS accordingly (someone posted some volt measurements here for ODAC and Windows volume control I think..)... but it would only make sense if you intend to sometimes use poor source like portables outputting just 1 volt and need the full ~7V output. Even playing "quiet classical" is not a sane reason for overdoing it, since the peaks would still clip. If there are no "0dBFS peaks", well obviously your file should be normalized/replaygained louder then..


 
  
 +1 - the documentation is still out there, if one bothers to read it. It's dense reading but it's there.
  
 I would venture to say though that if your music is pretty varied though, and *if* you use replaygain, I think 2x/6.5x is still a workable gain. I find it to be quite useful for my replaygain-ed library since rather than "adding" gain what it does is reduce gain (make louder tracks softer) so I rarely if ever hit clipping even at 6.5x gain. (even the 2.0V ODAC may not reach 2.0V at 100% on the computer because of the negative gain applied by replaygain)
  
 The other issue is that most folks with pre-built O2/ODACs have the lower power 12v 200mA AC adaptor, as opposed to the slightly higher end 16v 400mA adapter alternative in the BOM. 
 Kind of wish though that the O2 included some sort of clipping indicator to satisfy my OCD tendencies though.


----------



## wigglepuff

How would the Philips X1  sound on this compared to using a fiio e07k or e17? I'm looking for an amp that will output clear and neutral sound (given the music played isn't bass intensive also) without making the bass bloat or boomy.  I currently only have the e07k and the bass is a little bit better compared to the onboard alc889 which sounded all over the place and made my ears hurt even on low volume.
  
 I could just use the e07k's dac and use the O2 as amp but I can't find an O2 for testing in my area. Do I also need the l7 cable for the 07 and o2amp to work?


----------



## Medaud

barihunk said:


> +1 - the documentation is still out there, if one bothers to read it. It's dense reading but it's there.
> 
> I would venture to say though that if your music is pretty varied though, and *if* you use replaygain, I think 2x/6.5x is still a workable gain. I find it to be quite useful for my replaygain-ed library since rather than "adding" gain what it does is reduce gain (make louder tracks softer) so I rarely if ever hit clipping even at 6.5x gain. (even the 2.0V ODAC may not reach 2.0V at 100% on the computer because of the negative gain applied by replaygain)
> 
> ...


 
  
 Argh, it's so difficult to figure out the best gains when you have to take so many things into consideration. :/ I ordered a 1x/5x config, but reading the last few posts was just about to attempt to change my order to 1x/3x. Then you wrote about replaygain, which I use too. So I guess suddenly 1x/5x would be fine with me? Even more so if I change to a pair of 300ohm headphones in the future?
  
 lol, anyway, I think I'll just wait for my 1x/5x O2/ODAC to arrive and see how it goes. Worst comes to worst I'll change the gain resistors.


----------



## adydula

My ODA has a clipping led.
  
 The gains are 1x, 2x, 4x 6x....I only see clipping on 4x and 6x with hot titles -10 to -14 db or so....I can stop the clipping by lowering the player volume a bit, using replay gain in the player and or use a lower gain setting. I most always use 1x and sometimes 2x....never a need with my Beyer T90s to go to any higher gain settings.
  
 Alex


----------



## Cankin

With ODAC as source and power adaptor, I use only gain of 1x with my HD800. Volume knob at 10 o'clock even with quiet classical recording. 
  


medaud said:


> Argh, it's so difficult to figure out the best gains when you have to take so many things into consideration. :/ I ordered a 1x/5x config, but reading the last few posts was just about to attempt to change my order to 1x/3x. Then you wrote about replaygain, which I use too. So I guess suddenly 1x/5x would be fine with me? Even more so if I change to a pair of 300ohm headphones in the future?
> 
> lol, anyway, I think I'll just wait for my 1x/5x O2/ODAC to arrive and see how it goes. Worst comes to worst I'll change the gain resistors.


----------



## barihunk

medaud said:


> Argh, it's so difficult to figure out the best gains when you have to take so many things into consideration. :/ I ordered a 1x/5x config, but reading the last few posts was just about to attempt to change my order to 1x/3x. Then you wrote about replaygain, which I use too. So I guess suddenly 1x/5x would be fine with me? Even more so if I change to a pair of 300ohm headphones in the future?
> 
> lol, anyway, I think I'll just wait for my 1x/5x O2/ODAC to arrive and see how it goes. Worst comes to worst I'll change the gain resistors.


 
  
 IMHO ordering with 1x gain is not the best choice, for the simple reason that you can just clip whichever resistor pair you want to achieve 1x gain (i.e. removing the gain resistors). Better to order something higher then clip or de-solder the resistors if you don't want the high gain. I have a custom built O2 from when the design first debuted and can easily swap gain resistors, so I've gone anywhere from 2x/6.5x to 1x/4x then now back to 1x/6.5x - 1x works great for sensitive phones, 6.5x works pretty well for my HE-560. 
  

 IIRC a good way to change volume is to just leave the O2 at whatever gain you determine, at max volume, and change the volume in software, where you can change volume in 24/32bits.


----------



## Cankin

Someone recently asked my opinion about O2/Odac and if this combo have no bass.
I guess it depends on that person's preference, it is not hard to see some members would try as hard as they can to color the sound.

On the other hand, there are some of us who prefer their DAC and Amp have no or very little coloration. To my ears, O2 & ODAC achieve my requirement of "colorless".

In fact, I wanted one immediately right after I heard it, regardless of price. It sound just like another DAC I wanted for a long time.

You may ask which is the other DAC? The other DAC is Apogee Symphony, which is not often talked about on Head-Fi.

How do they sound like? Nothing. They are so transparent that they sound like nothing.

I guess you can say my decision is purely based on my subjective experience, nothing objective lol.

In conclusion, I would not recommend O2/ODAC if you are trying to color your sound or cover flaws of your badly mastered recording. But if you want something that let you enjoy how your music and headphone sound, you should get them.


----------



## goober-george

This may be a dumb question but, is there any cable that would allow me to hook up my O2 DAC/AMP to my Mad Ear with no rca inputs and only a micro usb port? Some sort of micro usb to rca input cable?


----------



## Dark_wizzie

adydula said:


> Mike has possibly discovered a THD issue with the original O2 with the volume pot being at mid way etc..AGDR has been analyzing this and thinks he knows what the issue might be. Its still below audible hearing etch.
> 
> You can read the techie stuff again over at DIY Audio.
> 
> ...


 
 THD is total harmonic distortion, yes? I'm not such a techie like them but I don't understand how midway point of the volume knob presents special problems with THD... Only two things I think of in this case is: 1) Volume knob set too low, channel imbalance problem 2) Volume knob too high, hear noise floor, distortion increases (But won't be specially apparent at halfway point).
 Also worth noting... Although the O2 can _probably _drive the HE-6, the ODA can definitely drive the HE-6 IIRC. So is AGDR making a finished product or is he selling parts? Thank you for sharing this news with us.


medaud said:


> Argh, it's so difficult to figure out the best gains when you have to take so many things into consideration. :/ I ordered a 1x/5x config, but reading the last few posts was just about to attempt to change my order to 1x/3x. Then you wrote about replaygain, which I use too. So I guess suddenly 1x/5x would be fine with me? Even more so if I change to a pair of 300ohm headphones in the future?
> 
> lol, anyway, I think I'll just wait for my 1x/5x O2/ODAC to arrive and see how it goes. Worst comes to worst I'll change the gain resistors.


 
 I don't really see how a person needs more than one gain setting for only one pair of headphones. For the majority of people, the defaults are more than enough. They're the defaults for a reason.


----------



## hekeli

Regarding the midway pot... it's funny that something is broken in my O2 in such way that there's a loud hiss on other channel, but only when midway.. 
	

	
	
		
		

		
			





 As soon as I hit max it disappears.. so maybe my fault is revealing the THD problem?


----------



## liamstrain

goober-george said:


> This may be a dumb question but, is there any cable that would allow me to hook up my O2 DAC/AMP to my Mad Ear with no rca inputs and only a micro usb port? Some sort of micro usb to rca input cable?


 
  
 I'm not quite sure what you are trying to do. If you use it as a DAC from your computer, then it is a USB connection, and no RCA would be needed.


----------



## adydula

AGDR is selling ODA boards on eBAY. I posted this in the ODA thread in this site.
  
http://www.ebay.com/itm/Objective2-O2-Desktop-Headphone-Amplifier-ODA-PC-Board-V2-1-/191284729783?ssPageName=ADME:L:LCA:US:1123
  
 FYI
 Alex


----------



## adydula

In regards to the THD at midway volume pot settings AGDR thinks he understands what is happening and is asking an engineer with a dScope to take a look at this with an 02 compared to the ODA.
  
  
 I can share this:
  
 "Apparently many of the op-amps have input impedance non-linearity that produces distortion with increasing source resistance, with the op-amp looking back into the source."
  
 There is a lot of techie stuff about the impedance changing etc I have links to this stuff etc. Doug Self etc.
  
 If this is the case its possible that this is one area the designer missed, There aren't any 1/2 volume THD measurements in his blog that I can find.
  
 When and if the O2 is measured I will be glad to share the THD measurements etc.
  
 FYI.
 Alex


----------



## JacobLee89

goober-george said:


> This may be a dumb question but, is there any cable that would allow me to hook up my O2 DAC/AMP to my Mad Ear with no rca inputs and only a micro usb port? Some sort of micro usb to rca input cable?


 
  
 If it isn't any special DAC/AMP combination you're using. It really should be like so:
  
 PC (usb cable) ---> Objective DAC / Objective 2 (3.5mm jack cable)  -----> Headphones
  
 Though I believe what you're trying to do is connect your MAD EAR amp to the DAC side of your O2/ODAC
  
 In this case you'll need to connect a 3.5mm to RCA cable from the *input *side of the O2/ODAC, and plug it into the MAD Ear.


----------



## Dark_wizzie

adydula said:


> AGDR is selling ODA boards on eBAY. I posted this in the ODA thread in this site.
> 
> http://www.ebay.com/itm/Objective2-O2-Desktop-Headphone-Amplifier-ODA-PC-Board-V2-1-/191284729783?ssPageName=ADME:L:LCA:US:1123
> 
> ...


 
 Ahh... I see. Unfortunately assembling this is way beyond my league. I can only wait until somebody sells a finished product.


----------



## XIX47

Never a good idea while posting half awake.....


----------



## Faemix

Hey folks.
 I will order a O2/Odac combo. I'm actually using a Q701.
 Should I modify gain or stick with default settings ?
 I'm not sure I need 6x...
  
 Is a 1x gain is enough for Q701 ?
  
 Thanks for help !


----------



## adydula

You do not need 6x at all for Q701's...I had them for awhile etch... works well with unity gain or 2.5x.
  
 Alex


----------



## Faemix

adydula said:


> You do not need 6x at all for Q701's...I had them for awhile etch... works well with unity gain or 2.5x.
> 
> Alex


 

 Thanks for reply, Alex.
 If I don't need 6x, should I use another value or just don't care about that ?


----------



## adydula

Faemix,
  
 The stock gain settings from JDS Labs is 2.5 and 6.5 I believe.
  
 You never really will need the 6.5 for your headphones....
  
 You could just leave it like it is and try the 2.5x settings and see how you like that and where the volume control settings are,.
  
 If you think the 2.5x is too much you can snip some resistors and get unity gain where the 6.5 setting was... this is what I did on one of my O2's.
  
 I don't use earbuds etch and only run headphones and have not found any headphones that unity or 2.5 can't drive well.
  
 There are some really inefficient headphones that would be an issue with the O2 but they are far and few between etch.
  
 Give John Seaber a call at JDS Labs and discuss with him....
  
 FYI
 Alex


----------



## Faemix

adydula said:


> Faemix,
> 
> The stock gain settings from JDS Labs is 2.5 and 6.5 I believe.
> 
> ...


 

 Many thanks Alex.
 I will go with unity and 2.5x then and switch transistor to get a 6x if I need this someday.
  
 Thanks again. Really helpful.


----------



## XIX47

adydula said:


> You do not need 6x at all for Q701's...I had them for awhile etch... works well with unity gain or 2.5x.
> 
> Alex


 
  
 Hmm, how loud were the headphones at default gain? I have the k712s which people claim to have nearly identical drivers, and at 2x the sound is quieter/fainter with distorted bass in my experience.


----------



## Solrighal

I have gains of 1x/3x and that's more than enough for my Q's.


----------



## adydula

Hmmm.... never heard distorted bass at unity or 2.5x if played at levels that don't destroy your hearing.
  
 There are so many people that use the 02 amp at 2.5 levels and drive the Q701 and Q702 and Audeze LCD2's to ear splitting levels.....
  
 If you listen to levels cranked past 12 o'clock etch you might be damaging your hearing over time.
  
 Also the quality of the recording your playing has.a profound influence on its sound quality.
  
 If your really hearing distortion with 2.5x gain setting then something is wrong with your setup or source.
  
 A.


----------



## Nec3

My audio is set at 15/100 on the PC, 3 o'clock on the volume dial at 1x gain with the Q701's paired with ODAC/O2.
 Once in a while I double the windows volume to 30/100 if I want to have "fun"


----------



## adydula

Try 100% on your pc and lower your amp volume.


----------



## Solrighal

I have my JRiver max volume set to 98%,a 2dB cut in effect. When it's set to 100% it will occasionally clip.


----------



## adydula

Yup I see that as well at 100% but only with really hot songs.  If you use replay gain in JRiver this can be pretty well eliminated even with the player at 100%.
  
 Alex


----------



## Medaud

adydula said:


> Yup I see that as well at 100% but only with really hot songs.  If you use replay gain in JRiver this can be pretty well eliminated even with the player at 100%.
> 
> 
> 
> ...



 


I wonder if that's the case in foobar as well.


----------



## castleofargh

I clearly advise people who don't have an impossible to drive 600ohm low sensi headphone, to get the 1x 2.5x version. but anyway the difference is a pair of resistors, so it's not really an important choice and it can be reversed easily enough.
  
  
 Quote:


xix47 said:


> adydula said:
> 
> 
> > You do not need 6x at all for Q701's...I had them for awhile etch... works well with unity gain or 2.5x.
> ...


 
 you simply never can make assumptions between gains. in effect you're just changing the resistor in the op amp and the resistor of the volume knob at the same time to get pretty much the exact same thing. mostly the difference will be clipping level and you most likely will only ever get than with the 6.5X.
 people will pretty much always feel like the higher gain on an amp is more dynamic, clearer, with better bass etc. that's because louder sounds better and very different indeed both in precision and in frequency response. but it's only a psycho acoustic trick and the signal is just louder. (or one resistor is badly soldered? you have the distortion in both ears?)
  
 in effect it is always better to use the lower gain if it's loud enough. and that on any amp on the planet. for the O2 specifically, as the only weak spot for this amp is the channel imbalance at low volume, using the lower gain let you turn the knob out of that imbalance zone.
  


nec3 said:


> My audio is set at 15/100 on the PC, 3 o'clock on the volume dial at 1x gain with the Q701's paired with ODAC/O2.
> Once in a while I double the windows volume to 30/100 if I want to have "fun"


 
 as advised, you should get that windozz volume up.
 15% on my computer(win 7) is about -25DB(at least that's what windows is saying ^_^).
 so with that setting, you're crushing(understand removing) the quietest 25DB of your track.
 objectively, if your media player is set to output music in 24bit as advised by nwavguy, it doesn't matter and you can keep doing it as there will be no audible difference. 24bit being effectively maybe 20bit or 19bit so 20*6=120DB or 114DB. worst case scenario 114-25=89DB of music, that is good enough for audible perfection.
 but then don't mess too much with replaygain as it's gonna remove even more DB. same for some EQ, so you can see how it is best to have some room. lower your O2 level a little and rise your windows level, the only limit to that should be widowzzz and your media player at 100%, or audible channel imbalance from the O2.
 I spend most of my time at 9 o'clock and then fine tune with foobar.


----------



## castleofargh

medaud said:


> adydula said:
> 
> 
> > Yup I see that as well at 100% but only with really hot songs.  If you use replay gain in JRiver this can be pretty well eliminated even with the player at 100%.
> ...


 

  so yes it happens but I can't remember if I was using wasapi when that clipping occured on some very very rare songs. I have something like -3DB on the preamp stuff of foobar just for that and since then I never experienced it again.


----------



## Medaud

castleofargh said:


> so yes it happens but I can't remember if I was using wasapi when that clipping occured on some very very rare songs. I have something like -3DB on the preamp stuff of foobar just for that and since then I never experienced it again.



 


Can you link to the article nwavguy wrote about windows volume and setting the output to 24bit? This dB talk is really confusing to me, but my understanding from this thread (http://bit.ly/1tffqzj) was that replaygain didn't audibly degrade sound quality, likewise with foobar's volume control.

EDIT: Btw is anyone else unable to get the BBCode editor to appear? This Rich Text editor is killing me and my posts.


----------



## XIX47

I am going to be testing my setup with the O2 amp at the lower gain setting. I am not sure if it will be lough enough since my foobar2000 settings lower the loudness by -13 Db due to crackling sounds (that is properly from the CD source themselves due to inadequate mastering).
  
 But I do not want to blow out my headphone drivers so I have to test it out on different volume settings.


----------



## castleofargh

medaud said:


> castleofargh said:
> 
> 
> > so yes it happens but I can't remember if I was using wasapi when that clipping occured on some very very rare songs. I have something like -3DB on the preamp stuff of foobar just for that and since then I never experienced it again.
> ...


 

 like I said, individually nothing really matters. all we have to keep in mind is that we have a fixed available dynamic range and a track that need to fit in it. there are a few things that might lower that DR. so if we abuse them all, we can end up with very little left on the digital side. as long as you control what you're doing, there is no reason to be afraid of using anything, be it EQ, replaygain or foobar/windows volume control.
 imagine someone using a powerhouse amp with high gain and sensitive headphones. let's imagine the amp has huge channel imbalance so he can't really use the amp knob. he will remove say 50DB with foobar to get the right sound level for normal listening. if the tracks already have replaygain you can pretty much remove 10db for some files. if he stays on 16bit that's 96DB available, meaning that he will at best hear 96-50-10=36DB of the loudest part of each tracks. not cool if you like classical or jazz.
  
 about using 24bit for the odac, I don't remember where I saw that, but it's a real nobrainer. there are no negative side effect to outputting 16/44 tracks as 24/44(and let the DAC oversample when it needs to). it's just adding some zeros at the end of each sample, the original sample is kept untouched. so then if you digitally lower your volume too much for some reasons, then instead of starting to destroy the quietest sounds of the track, foobar will use those bits to write the music and you'll lose no data from the track(up to a point).
 so if it's needed you have it, if it's not needed it's just a bunch of zeros that the DAC will note use. I would advise everybody to use asio or wasapi and select 24bit as output format. that way you can fine tune your system's loudness on the computer without having to think about it too much.
 I wouldn't pretend anything about sample rate, but bit depth is actually very straightforward.


----------



## Medaud

castleofargh said:


> like I said, individually nothing really matters. all we have to keep in mind is that we have a fixed available dynamic range and a track that need to fit in it. there are a few things that might lower that DR. so if we abuse them all, we can end up with very little left on the digital side. as long as you control what you're doing, there is no reason to be afraid of using anything, be it EQ, replaygain or foobar/windows volume control.
> imagine someone using a powerhouse amp with high gain and sensitive headphones. let's imagine the amp has huge channel imbalance so he can't really use the amp knob. he will remove say 50DB with foobar to get the right sound level for normal listening. if the tracks already have replaygain you can pretty much remove 10db for some files. if he stays on 16bit that's 96DB available, meaning that he will at best hear 96-50-10=36DB of the loudest part of each tracks. not cool if you like classical or jazz.
> 
> about using 24bit for the odac, I don't remember where I saw that, but it's a real nobrainer. there are no negative side effect to outputting 16/44 tracks as 24/44(and let the DAC oversample when it needs to). it's just adding some zeros at the end of each sample, the original sample is kept untouched. so then if you digitally lower your volume too much for some reasons, then instead of starting to destroy the quietest sounds of the track, foobar will use those bits to write the music and you'll lose no data from the track(up to a point).
> so if it's needed you have it, if it's not needed it's just a bunch of zeros that the DAC will note use.




Ah, I see. Makes sense.



castleofargh said:


> I would advise everybody to use asio or wasapi and select 24bit as output format. that way you can fine tune your system's loudness on the computer without having to think about it too much.




I thought ASIO and WASAPI bypassed the system mixer, so it wouldn't matter what output format/loudness you chose?


----------



## castleofargh

medaud said:


> castleofargh said:
> 
> 
> > I would advise everybody to use asio or wasapi and select 24bit as output format. that way you can fine tune your system's loudness on the computer without having to think about it too much.
> ...


 
 I use wasapi(only because It shows each outputs in foobar separatly so I can use shortcut keys to switch between them. no audio quality reason) and it let you pick the output bitdepth so it's your choice and that choice. on asio I seem to remember that it will select the highest possible bitdepth for your DAC/soundcard (showing that at least asio and me are on the same page for audio output bitdepth ^_^).
 asio and wasapi are here to bypass windows mixer and whatever thx surround stuff that may be working in the background of your soundcard, you're perfectly right about that. but your audio player can still do whatever it likes. volume, EQ, replaygain are all working within the audio player effectively ruining the bit perfect concept.


----------



## Medaud

castleofargh said:


> I use wasapi(only because It shows each outputs in foobar separatly so I can use shortcut keys to switch between them. no audio quality reason) and it let you pick the output bitdepth so it's your choice and that choice. on asio I seem to remember that it will select the highest possible bitdepth for your DAC/soundcard (showing that at least asio and me are on the same page for audio output bitdepth ^_^).
> asio and wasapi are here to bypass windows mixer and whatever thx surround stuff that may be working in the background of your soundcard, you're perfectly right about that. but your audio player can still do whatever it likes. volume, EQ, replaygain are all working within the audio player effectively ruining the bit perfect concept.




Would setting the output in windows mixer to 24 bit have the same effect as getting foobar to output 24 bit?


----------



## castleofargh

if you use wasapi or asio then windows setting should be bypassed and only output what is set in your audio player. if not then yes your windows output setting will be what decides of the bitdepth. it's one or the other and they ultimately do the same thing for bit depth at least.


----------



## Medaud

Okay, thanks. I don't use wasapi or asio so I'll just set the windows output as 24 bit then...when I get my O2/ODAC.


----------



## WilliamLeonhart

Hi everyone
 I'm currently a proud owner of the O2/ODAC (combined version). The sound is extremely enjoyable on my Grado's and gives my old sound system a new life (I connect O2 directly to the speaker amp via an 3.5 jack). Will the ODAC RCA gives better sound quality than the 3.5mm version?
 Thanks


----------



## Mjolnir125

My O2/ODAC has no issues driving my K702 with any song I have (even very quiet high DR tracks). I have the Mayflower O2 amp which I believe has 2.5x gain for the low setting and 6.5x or so gain for the high setting. On high gain with max PC volume (using the ODAC) there is a lot of clipping which is to be expected, since the high gain setting is actually only for using the line in, and not the ODAC. The high gain is for quieter sources, not harder to drive headphones.


----------



## WilliamLeonhart

I once tried connecting the Sennheiser HD580 to my O2 and the sound was very narrow and lacked details. My friends often say O2 can't drive the AKG flagship siblings (K701, K702 and Q701) to their fullest (I mean soundstage, details....), but from what I read here I think I should try to get my hands on a real pair as soon as possible to experience them first hand.


----------



## castleofargh

williamleonhart said:


> Hi everyone
> I'm currently a proud owner of the O2/ODAC (combined version). The sound is extremely enjoyable on my Grado's and gives my old sound system a new life (I connect O2 directly to the speaker amp via an 3.5 jack). Will the ODAC RCA gives better sound quality than the 3.5mm version?
> Thanks


 
 I wouldn't put too much hope on that. but maybe using only a dac to feed your speaker amp? it shouldn't change much( if you don't clip the amp with the O2), and maybe nothing at all as the O2 is really clean, but you would avoid double amping for no particular reason.
 but that's just a suggestion, if you're happy with what you hear now, you should keep it that way. we never get enough of what we don't need ^_^.
  


williamleonhart said:


> I once tried connecting the Sennheiser HD580 to my O2 and the sound was very narrow and lacked details. My friends often say O2 can't drive the AKG flagship siblings (K701, K702 and Q701) to their fullest (I mean soundstage, details....), but from what I read here I think I should try to get my hands on a real pair as soon as possible to experience them first hand.


 
 your friends seem to mistake signature and driving capacity. I don't like the k701 flat so with the O2 I would have to EQ it a lot, and most of our feeling of details and soundstage actually come from the signature so that would change too.
 if I was one of those people allergic to EQ because of urban legends from 1960, then I would need a colored amp to compensate instead(that would destroy the signal more than any parametric EQ, but that's how it is for allergic people). in the end it's only because I don't like the signature of the K701 so it would be a mistake to get one for me in the first place.


----------



## WilliamLeonhart

Hi castle, what amp would you recommend for K701 at the price range below $300?


----------



## HaVoC-28

What , O² can't drive K7XX/Q701 ? and HD580 lacking details and narrow soudstage , really ?


----------



## WilliamLeonhart

I can say that the HD580 lacks details & the soundstage really really sucks on my O2/ODAC with Celine Dion and the likes. Experienced it first hand. The AKGs are from what I heard, have not verified it though.
  
 My O2/ODAC was assembled from DIY boards. Did fantastic jobs on Grados (325, MS Pro and even the low-priced iGrado) and HD598. But I was really disappointed when I plugged the HD580s into these.
  
 @castle: thank you for your advice on the O2. Yes I do try to avoid double amping, thanks to my experiences back in 2012 I used to plug my O2 into the iBasso D2 (amp+dac). The O2 did not improved the sound of the D2 at all - the only thing O2 did on D2 was to... amplify the volume. No better soundstage or clearer sound as it did on DACs without amp built in. Now since my Denon amplifier can drive the loudspeaker just fine even when plugged directly into the ODAC, I see no point in using the O2 in this case.


----------



## Solrighal

The O2 is transparent. Any defects felt are merely a description of the basic sound signature of any given pair of headphones. Change the headphones for something you actually like.


----------



## James-uk

I still don't get why people blame their amps for sound quality. Especially the O2 and unless they are using a massive fail of an amp. I've plugged my headphones into lots of modern amps / dacs/ using various bit rates and the only thing that makes any noticeable difference to soundstage yadda yadda is the headphone itself . I'm getting to old and intolerable to listen to people taking nonsense about amps/dacs/ cables . It's the headphones or the amp you are used to is massively coloured ( high output impedance or distortion / maybe both) the O2 is transparent it's a fact. It's well documented. Don't blame the O2 blame yourself for being an idiot.


----------



## bikutoru

Currently testing a device from a well respected company against my O2/ODAC with AKG K702. I just got that stupid itch that something might be better. The device in question can do DSD, hight PCM rates, etc, etc. The sound might be a little better or just of a different flavor because a DAC chip inside is from a different manufacture, but on the negative side there are clicks, white noise which people mistake for analog sounding, when you layer it with music, and some other minor issues. All of it at twice the price! O2/ODAC might not be as sexy and portable, but I think it cost should be weighted in gold! I only wish NwAvGuy would come back and did something else, I'd say anything, to create something like O2/ODAC that holds so well against all these other much more expensive solutions, it is a real talent. When I buy a more expensive solution I think that all these low level distraction that I use to have in the pure analog domain are gone, but it seems that the industry is still battling them, while I'm in my hole with 02/ODAC and a pair of headphones enjoying the music!
  
 During the last two years with O2/ODAC and K702 I tried a few others, but always went back to O2/ODAC, it is dead silent, it has more then enough power to drive K702 it is transparent and music/sound, if you use good recording in lossless, is sublime!


----------



## barihunk

james-uk said:


> I still don't get why people blame their amps for sound quality. Especially the O2 and unless they are using a massive fail of an amp. I've plugged my headphones into lots of modern amps / dacs/ using various bit rates and the only thing that makes any noticeable difference to soundstage yadda yadda is the headphone itself . I'm getting to old and intolerable to listen to people taking nonsense about amps/dacs/ cables . It's the headphones or the amp you are used to is massively coloured ( high output impedance or distortion / maybe both) the O2 is transparent it's a fact. It's well documented. Don't blame the O2 blame yourself for being an idiot.


 
  
 Amen. IMHO the only role any amp should play is to faithfully *amplify* the signal given to it. And in this respect specifications and measurements are critical.


----------



## WilliamLeonhart

It may very well be the pair of HD580, after all they're quite old and discontinued long ago. I did not hear any distortion on the HD580, though. As I have said above, I have not tried the AKGs with O2 myself, so I was asking for your guys' clarification on this. Where I live, the price of K702 via official distributors is nearly $500, so almost no one buys them and it is not easy to audition a pair.
 And to clear things up I have not mentioned colored or transparent at all. I think the O2 may help the DAC gives a better soundstage and better details since when I do a/b on ODAC and O2+ODAC on low-impedance IEM (e.g. the Grado iGi, 24ohm), the sound that comes directly from ODAC is more congested than when amped.
 And yes both the amp and the DAC is extremely great for their prices - that's why I've been keeping them for so long. Yet I've been given the impression that most things about headphones are based on personal preferences, so I think it is quite understandable that some people may like the, say, K702s, amped with O2 and  others do not. And I honestly do not expect the O2 to be able to drive all the phones to their best (or maybe to someone's particular liking).
 Obviously I'm the newbie here, so I can't be "right" or "smart" on everything. I've been following discussions on head-fi for >3 years (didn't register and post since I'm not a native speaker of English), and I really appreciate it that head-fi helps me understand my hobby better. Just hope that we are not too hasty in dealing out judgements of stupidity


----------



## Solrighal

You're almost there my friend. The 02 neither adds nor subtracts anything to/from the signal. Buy headphones that you know gave a sound you will love and the O2 will allow them to go there. It really is that simple.


----------



## Solrighal

I have an O2 built by Head'n'Hifi and it's the model with stereo RCA outputs. Can I connect this to a stereo I terraced amplifier? Will it pass through the signal without needing to be switched on?


----------



## liamstrain

Is it an Odac/O2 or just an O2? On the combo, typically the RCA outputs are line level outs from the DAC - not amped, or modified by the volume pot - so you can connect them to your stereo like any other input. 
  
 I don't know the implementation that Head'n'Hifi uses though.


----------



## Solrighal

That's how I figured it worked with the combo but I've got separate amp & DAC units. The DAC is connected to the O2 with RCA's and then there's the RCA output on the amp. I suspect it's only useful for active speakers or power amps and not for integrated amps.


----------



## liamstrain

solrighal said:


> That's how I figured it worked with the combo but I've got separate amp & DAC units. The DAC is connected to the O2 with RCA's and then there's the RCA output on the amp. I suspect it's only useful for active speakers or power amps and not for integrated amps.


 
 I'd just get an RCA splitter from the DAC.


----------



## Solrighal

liamstrain said:


> I'd just get an RCA splitter from the DAC.




Aye, that's a good idea. I'll look into it.


----------



## greenkiwi

O2 + ODAC question - is the O2 supposed to select between analog and ODAC when a 1/8" input is put into the front input connector?


----------



## oryan_dunn

greenkiwi said:


> O2 + ODAC question - is the O2 supposed to select between analog and ODAC when a 1/8" input is put into the front input connector?


 
 It uses the DAC if USB is plugged in.  In that case, the 1/8" input is now an 1/8" line out from the DAC.
  
 I wish there were a switch to toggle instead, so you wouldn't have to pull the USB cable to use an analog source.


----------



## jring

oryan_dunn said:


> It uses the DAC if USB is plugged in.  In that case, the 1/8" input is now an 1/8" line out from the DAC.
> 
> I wish there were a switch to toggle instead, so you wouldn't have to pull the USB cable to use an analog source.


 
  
 Actually the original O2 & ODAC instructions wired the input jack exactly as you described - when you put sth in there, it overrides the ODAC as input. Some suppliers did change this though...
 If you can solder, it shouldn't be too difficult to hook it up according to the original instructions on the designer's blog.
  
 Joachim


----------



## castleofargh

oryan_dunn said:


> greenkiwi said:
> 
> 
> > O2 + ODAC question - is the O2 supposed to select between analog and ODAC when a 1/8" input is put into the front input connector?
> ...


 

 that's how mine (JDS lab) works. and I became aware of it maybe 6months after I had the odac/o2 ^_^. I think I even complained somewhere that I wished I could use the odac alone and should have bought it in 2 boxes 
	

	
	
		
		

		
			





.
 silly detail, but the odac being usb powered, we don't have to turn the O2 ON to use it as a standalone DAC. I also realized that very late so I mention it for others .


----------



## muad

Hey guys, I was thinking of making a custom o2/ odac. I was thinking of placing it in a larger enclosure and making it rear powered. I wanted to internally run the headphone out to a 2 way switch, one side going to a 1/4 headphone jack and the other going to a set of rca jacks in the rear. I figure this would allow me to easily switch between dac/preamp to my speakers (with unity gain) and headphone amp.
  
 What do you guys think? Would this work? Also, would I experience a loss of performance/measurements?


----------



## liamstrain

Yes it will work. I do not see how it could affect performance in any way.


----------



## WilliamLeonhart

castleofargh said:


> that's how mine (JDS lab) works. and I became aware of it maybe 6months after I had the odac/o2 ^_^. I think I even complained somewhere that I wished I could use the odac alone and should have bought it in 2 boxes
> 
> 
> 
> ...


 
 The friend who assembled my diy O2+ODAC mentioned it to me when he gave me my current setup. I still think this design is fine, since I can use the O2 as a standalone amp and the ODAC as a standalone dac without a power adapter. I don't use these at the office or anywhere else at all, so I think this is as mobile as I'll ever gonna need.


----------



## Cankin

muad said:


> Hey guys, I was thinking of making a custom o2/ odac. I was thinking of placing it in a larger enclosure and making it rear powered. I wanted to internally run the headphone out to a 2 way switch, one side going to a 1/4 headphone jack and the other going to a set of rca jacks in the rear. I figure this would allow me to easily switch between dac/preamp to my speakers (with unity gain) and headphone amp.
> 
> What do you guys think? Would this work? Also, would I experience a loss of performance/measurements?


 
  
 I got my O2/ODAC from JDS Labs with all those features you mentioned including 1/4 headphone jack, rear power input, rear RCA and custom gain.


----------



## maidos

regarding the standalone dac, would it be better to get a regular version or the tad bit expensive one with the rca outputs?


----------



## muad

Yeah but the dac out doesnt have native preamp functionality. I was looking for a variable line out.


----------



## greenkiwi

Thanks, I'll post a few pictures.  I believe that I have it wired so that it is supposed to cut the signal out when an input is plugged in, but it doesn't seem to be working.
  
 Btw, is it a mechanical switch?  i.e. the presence of a plug in the jack should cut out the ODAC signal?


----------



## jring

greenkiwi said:


> Thanks, I'll post a few pictures.  I believe that I have it wired so that it is supposed to cut the signal out when an input is plugged in, but it doesn't seem to be working.
> 
> Btw, is it a mechanical switch?  i.e. the presence of a plug in the jack should cut out the ODAC signal?


 
  
 Yes, the input jack from the O2 parts list has a switch and will either ground the input of the O2 when no plug is in (for O2 standalone) or connect ODAC to the input w/o plug (ODAC/O2 combo). You can get the instructions for this if you google for odac may update - we aren't allowed to post the links here due to some unfortunate events of the past.
  
 Joachim


----------



## TheGame21x

castleofargh said:


> that's how mine (JDS lab) works. and I became aware of it maybe 6months after I had the odac/o2 ^_^. I think I even complained somewhere that I wished I could use the odac alone and should have bought it in 2 boxes
> 
> 
> 
> ...


 
  
 Same here, except for me it was more like over a year until I figured out the front input of the O2+ODAC functions as a line out for the ODAC too.
  
 I was considering buying a standalone ODAC for the longest time until i figured that out.


----------



## Nec3

O2 left channel died, bye guys have fun with your hifi endeavors!

I'll be using the ODAC with the Dared MP5 if the dealer confirms the deal


----------



## muscleking

does your guys o2 amp when you turn the volume knob, hear some like static noise on the right channel? only when turning the volume dial up and down.
  
 I am thinking about getting an amp from woo audio. does it blow the o2 out of water or into the water?


----------



## Nec3

muscleking said:


> does your guys o2 amp when you turn the volume knob, hear some like static noise on the right channel? only when turning the volume dial up and down.
> 
> I am thinking about getting an amp from woo audio. does it blow the o2 out of water or into the water?


 


 If you're talking about the Woo Audio 7, then yes it's better than the O2.

 I don't hear any static when turning the volume knob with the O2.


----------



## HaVoC-28

"Better" or more to your liking ? Because beside output power , in technical aspect the O² will have the upper hand .
  
 Prices don't mean anything in audio ...


----------



## castleofargh

muscleking said:


> does your guys o2 amp when you turn the volume knob, hear some like static noise on the right channel? only when turning the volume dial up and down.
> 
> I am thinking about getting an amp from woo audio. does it blow the o2 out of water or into the water?


 

  do a few min-max-min full range movements with the knob, it's usually enough to move the dust away from the path.


----------



## muscleking

I am thinking about stax 507 with GES. Or get a hd800 with the 7.



nec3 said:


> If you're talking about the Woo Audio 7, then yes it's better than the O2.
> 
> 
> I don't hear any static when turning the volume knob with the O2.


----------



## muscleking

Dust? I am talking about I can hear something in the headphone on right side when adjusting volume. 

But I will try that too. 

I remember there is something about cutting a jumper on the circuit board has to do with the impedance? Right now if I press the boost button I hear distortion at moderate volume on some songs with all my low impedance headphones. Normal?



castleofargh said:


> do a few min-max-min full range movements with the knob, it's usually enough to move the dust away from the path.


----------



## castleofargh

muscleking said:


> Dust? I am talking about I can hear something in the headphone on right side when adjusting volume.
> 
> But I will try that too.
> 
> ...


 

 the knob is just a contact sliding on a surface when you change volume level. so some parts can get dirty and alter the connection, making those noise only when you turn it. if it's only dust it will move away at some point solving the problem. if it's some kind of oxidation or some wear off of the resistive surface you might not be so lucky.
  
  
  
 about the gain(unrealated), it can be changed, but do you need the higher gain to listen to your headphones? low gain is better unless you need to go louder obviously.


----------



## vertical

castleofargh said:


> the knob is just a contact sliding on a surface when you change volume level. so some parts can get dirty and alter the connection, making those noise only when you turn it. if it's only dust it will move away at some point solving the problem. if it's some kind of oxidation or some wear off of the resistive surface you might not be so lucky.
> 
> about the gain(unrealated), it can be changed, but do you need the higher gain to listen to your headphones? low gain is better unless you need to go louder obviously.


 
  
 +1. 
  
 Muscleking, check out post #3332 (link pasted below) and those around it...
  
 http://www.head-fi.org/t/616331/o2-amp-odac/3330#post_10794974


----------



## DObleX

O2+ODAC vs Creative Titanium HD sound card + external O2 amp. Which of them will be the best in sound quality?


----------



## Medaud

doblex said:


> O2+ODAC vs Creative Titanium HD sound card + external O2 amp. Which of them will be the best in sound quality?




Sound quality wise I think they would both be excellent. It really depends on what you want. If you want the DSP that Titanium HD provides, then get it. If you don't want the DSP, then get the ODAC. One reason a lot of people get the TItanium HD is the CMSS 3D virtual surround which a lot of people agree is the best out there. However, if you don't play games where CMSS 3D can be used then what's the point? Just remember that the ODAC only provides transparent sound. What you play is what you get. You don't get any DSP whatsoever. So if you're a sucker for Creative's crystallizer and bass boost then don't get the ODAC.

If you want DSP then also take a look at creatives new Z lineup. It's a newer generation, and while it won't give you CMSS 3D, it will give you TruStudio Pro which is almost as good.

EDIT: Just to clarify on any bias I might have: I looked into a lot of options before I got my ODAC/O2. It's funny, I kind of came full circle. I started out watching TekSyndicates youtube rant on soundcards and how useless they are. It sounded logical so initially I thought he was right and I would just get the ODAC/O2. But then I researched further and read refutations of his video on overclock.net. Then I looked into getting a Titanium HD or Creative Z card after watching comparisons between different virtual surround sound DSP on youtube (CMSS 3D sounds the best imo). However, I then read about all the different problems people were having with Creative drivers and faulty products. Also many new games include their own virtual surround in the form of FMOD so you can just use the headphone setting. Also there is Razer surround which works with the ODAC/O2 and doesn't sound bad at all. So anyway I ended up looking into the ODAC/O2 again (lol) and after researching further ended up getting it. I figure for music if I want DSP I can just use the EQ in foobar (I got tired of creative's crystallizer a few months ago). For movies LAV audio filters provide a great surround sound to stereo demuxer which I use. Finally if I want virtual surround in games I can just use Razer surround. I am okay with not getting top of the line CMSS 3D, plus again most newish games are moving to their own sound systems, such as FMOD.

So in a weird way I started out liking teksyndicates video, then hated it, and then in the end I kind of came to the same conclusion as him (on my own), lol. That said his video is still filled with mistakes and flaws, e.g. he completely ignores the DSP that sound cards provide, which is kinda the main reason for getting them at least from a gaming perspective.

EDIT 2: Oh one more very important thing; if you get the Titanium HD or a Creative Z, don't get the O2. The soundcards already have amps built in so you will essentially be double amping. You should decide between ODAC/O2 vs sound card.


----------



## HaVoC-28

medaud said:


> EDIT 2: Oh one more very important thing; if you get the Titanium HD or a Creative Z, don't get the O2. The soundcards already have amps built in so you will essentially be double amping. You should decide between ODAC/O2 vs sound card.


 
  
 Hum no double amping unless he connect to the dedicated headphone out where is the built in headphone amp  , if he use an external amp such as o² he will plug it in their respective line out (RCA for titan HD ans jack 3.5 for Z) .


----------



## DObleX

*Medaud*, thanks for respond. So, I'd like to clarify my post. I have Titanium HD. Sound quality I mean the music only. I have 250Ohm headphones and feel, that sound card cannot fully open them. Amp is necessary. I don't use of any DSP and CMSS 3D. Play games very rare. So, foobar (flac)+creative+O2 vs foobar (flac)+O2/ODAC without any dsp or other. Furthermore, it's possible to replace op apms on Creative.
 Quote:


medaud said:


> EDIT 2: Oh one more very important thing; if you get the Titanium HD or a Creative Z, don't get the O2. The soundcards already have amps built in so you will essentially be double amping. You should decide between ODAC/O2 vs sound card.


 
 Wrong! Built in amp in Titanium HD is crap, trash, useless. I use analog out (that much better!) for headphones.


----------



## HaVoC-28

Then only buy an O² , you don't need an ODAC .


----------



## Medaud

havoc-28 said:


> Hum no double amping unless he connect to the dedicated headphone out where is the built in headphone amp  , if he use an external amp such as o² he will plug it in their respective line out (RCA for titan HD ans jack 3.5 for Z) .






doblex said:


> Wrong! Built in amp in Titanium HD is crap, trash, useless. I use analog out (that much better!) for headphones.




You are right, I forgot the Titan HD has outs without amps.

DObleX I don't think you would get much sound difference if you exchange the Titan HD with an ODAC, unless you're using some DSP with the Titan HD. We all know of tom's Hardware blind test, you won't get better quality.

EDIT: I agree with HaVoC, if you're satisfied with your Titan HD setup, just get the O2.


----------



## DObleX

*HaVoC-28, Medaud, *thanks! But I'd like to hear the owners, who have both and Titanium HD, and ODAC to make a final decision.


----------



## HaVoC-28

At level matched it will sound the same .


----------



## muscleking

fixed the dust problem when turning volume dial distortion sound.
 somehow fixed itself but i just turned it back and forth many times and seems ok now.


----------



## audionewbi

I have a pair of Muses01 opamp and I like to try to put in O2 to see how it sounds. Can someone guide me on which one I need to remove and replace with Muses01? Thanks in advance.


----------



## 50Hz

I haven't seen from many other LCD-X owners with the O2. I've got just the amp running from my Mbox 3. I usually have it on 1 X gain but occasionally if I want to really crank it I'll switch it to 3.5. So clean and loud and punchy. Couldn't want anything more.
  
 I do eq the headphones to closer match the harman target response curve. I can share the Equalizer APO config file if anybody is interested.


----------



## HaVoC-28

50hz said:


> I haven't seen from many other LCD-X owners with the O2. I've got just the amp running from my Mbox 3. I usually have it on 1 X gain but occasionally if I want to really crank it I'll switch it to 3.5. So clean and loud and punchy. Couldn't want anything more.
> 
> I do eq the headphones to closer match the harman target response curve. I can share the Equalizer APO config file if anybody is interested.


 
  
 Well because many says that ortho/planar/isometric drivers needs a lot of mW to work well , also the product page specification from audeze say something like :  "Optimal power 1-4W" .
  
 Is this a kind of hype to have a "hard to drive" headphone , or a way to encourage people in buying expensive stuffs to put Audeze on a good light ? Marketing ?
  
  
 But it's great that you report your liking with LCD-X and O² .


----------



## Dark_wizzie

I had LCD-X with my O2. Worked very well. It's almost as if, running a hard to run headphone somehow validates a person as an ultra-audiophile, so people want to brag about how they are able to run hard-to-drive headphones. 
	

	
	
		
		

		
			





 
  
 BTW JDS, I'm sure you're aware of the ODA. What say you if your competitors start making it for sale?


----------



## Solrighal

50hz said:


> I haven't seen from many other LCD-X owners with the O2. I've got just the amp running from my Mbox 3. I usually have it on 1 X gain but occasionally if I want to really crank it I'll switch it to 3.5. So clean and loud and punchy. Couldn't want anything more.
> 
> I do eq the headphones to closer match the harman target response curve. I can share the Equalizer APO config file if anybody is interested.




I also use EQ but I don't know what the Harman response curve but I'm interested. I use GlissEQ in JRiverMC right now.


----------



## castleofargh

solrighal said:


> 50hz said:
> 
> 
> > I haven't seen from many other LCD-X owners with the O2. I've got just the amp running from my Mbox 3. I usually have it on 1 X gain but occasionally if I want to really crank it I'll switch it to 3.5. So clean and loud and punchy. Couldn't want anything more.
> ...


 

 I think I originally stole this from innerfidelity.

  
 the black one is what people preferred/found neutral for headphones. so if your raw measurement of headphone (the gray lines on tyll's graphs) looks like the black curve here, harman claims from the study that it is what most people will find neutral and prefer.  the main conclusion of the studies at harman showed pretty much that all people of all ages of all races did tend to favor neutral sounding gears, as in with the same FR that from flat speakers in an ideal room once the sound has travelled toward us. so not really neutral anymore as trebles get attenuated with distance.
  
 compared to the usual compensation curves, this one does ask for a bass boost, and does let the trebles go down as they would naturally in the air when coming from speakers. 
 to make it simple, you take the graphs from almost everywhere, and when they show something like a slow regular down slope from bass to trebles, chances are it would be close to flat on harman's target curve.
 think LCD2 as closer to flat for them than ER4 or HD800. something I clearly tend to agree with ^_^.
  
 http://seanolive.blogspot.fr/2014/01/the-perception-and-measurement-of.html   this video is a "short" version of the 2 main papers done on the subject.


----------



## tinyman392

castleofargh said:


> I think I originally stole this from innerfidelity.
> 
> 
> the black one is what people preferred/*found neutral* for headphones. so if your raw measurement of headphone (the gray lines on tyll's graphs) looks like the black curve here, harman claims from the study that it is what most people will find neutral and prefer.  the main conclusion of the studies at harman showed pretty much that all people of all ages of all races did tend to favor neutral sounding gears, as in with the same FR that from flat speakers in an ideal room once the sound has travelled toward us. so not really neutral anymore as trebles get attenuated with distance.
> ...


 
  
 The Olive Welti experiments were designed to find the most preferred sound, with respect to music, regardless of sound signature type (e.g., _any_ sound signature).  They were not designed to find the most neutral sound, it shouldn't be read that way (it wasn't its focus or intent).  They wanted to find out what people's preferred sound signature was, and they determined that it was non-neutral.  I should also note that in terms of speaker response, the preferred also was non-neutral, rather, they also preferred a warm tilt.  With headphones, they preferred slightly more bass, specifically sub-bass.  
  
 Now we have to figure out why they prefer that sound over neutral (which Etymotics are not DF neutral still, they tone down the treble by a few dB to compensate for compression which has gone way up since then).  IMO, I feel that this preference towards a warmer sound is due to compression.  But, that's just speculation.


----------



## miceblue

tinyman392 said:


> castleofargh said:
> 
> 
> > I think I originally stole this from innerfidelity.
> ...



Yup, exactly that.

What defines a preferred sound in headphones? I think the video is saying the preferred sound is more akin to the sound of flat speakers?

And then, what does neutral mean in this case?


----------



## tinyman392

miceblue said:


> Yup, exactly that.
> 
> What defines a preferred sound in headphones? I think the video is saying the preferred sound is more akin to the sound of flat speakers?


 
  
 LOL, I was updating my post while you ninja quoted it   If I'm not mistaken, Tyll did report that users preferred a non-neutral speaker signature as well.  He described the signature as a linear line with a 10 dB bump in the bass and a 0 dB gain in the treble.  
  
 Essentially, they also retested flat speakers vs non-flat.  The surprising thing is that the signatures of the headphones and speakers still didn't match up   The results are interesting, but should also be noted, there was a small sample size.  
  
 It's been a while since I looked at the stuff regarding the paper, please correct me if I'm wrong.


----------



## castleofargh

tinyman392 said:


> The Olive Welti experiments were designed to find the most preferred sound, with respect to music, regardless of sound signature type (e.g., _any_ sound signature).  They were not designed to find the most neutral sound, it shouldn't be read that way (it wasn't its focus or intent).  They wanted to find out what people's preferred sound signature was, and they determined that it was non-neutral.  I should also note that in terms of speaker response, the preferred also was non-neutral, rather, they also preferred a warm tilt.  With headphones, they preferred slightly more bass, specifically sub-bass.
> 
> Now we have to figure out why they prefer that sound over neutral (which Etymotics are not DF neutral still, they tone down the treble by a few dB to compensate for compression which has gone way up since then).  IMO, I feel that this preference towards a warmer sound is due to compression.  But, that's just speculation.


 
 in fact from what they did years ago on speakers they did find that people tended to prefer flat speakers (real flat). what wasn't flat is the response we get where we are sited in the room (room reflection+ high frequencies getting attenuated in the air faster than low frequencies over a distance). so in a way the slightly warmer FR is a perfectly natural phenomenon in real life listening, be it from speakers or a real band, and the farther away we are from a band the warmer they will sound.
  
 and what they tested for headphone too was as you say, what people preferred (they did several trials in several countries, not just the 10 employees or something at the beginning). but they started with the assumption that people would like to have in headphones the sound they prefered from flat speakers, so with the tilt in FR from the start as this time air couldn't do the trick by itself in headphones. and they seemed from the results to be right about that. so the "prefered" headphones end up with the warm tilt to simulate the change that would occur if there was more distance between the drivers and the ears.
  to me etymotic worked to get neutral sound without a care in the world if it was natural or not(and that's why they are so cool as monitoring IEMs), while olive worked to get the sound from neutral speakers in that one cool room at that one distance that is their "ideal" listening room.
 so if the band was playing on my lap and the singer singing into my ear, then I would think that etymotic got it right. but if the band is supposed to be on stage and me 30 or 40meters away, then Olive certainly has the more realistic idea and I would expect the sound to have maybe 2 or 3DB tilt from 20hz to 20khz.
  
 but yeah I should be careful when I write neutral or flat, as it can mean so many things.


----------



## MrMateoHead

castleofargh said:


> I think I originally stole this from innerfidelity.
> 
> 
> the black one is what people preferred/found neutral for headphones. so if your raw measurement of headphone (the gray lines on tyll's graphs) looks like the black curve here, harman claims from the study that it is what most people will find neutral and prefer.  *the main conclusion of the studies at harman showed pretty much that all people of all ages of all races did tend to favor neutral sounding gears, as in with the same FR that from flat speakers in an ideal room once the sound has travelled toward us*. so not really neutral anymore as trebles get attenuated with distance.
> ...


 
 Just a quibble -
  
 Harmon's research, while generating the new curve, did NOT conclude that "all people of all ages / races" expressed a preference for that particular curve. The population administered the listening test was far, far smaller than that, and I don't recall being representative of the general population (as defined by average age, sex, or race, for example, or trained / untrained listening skills). While their approach, and conclusions should be repeatable, that study was not the end-all be-all of sound perception studies.


----------



## miceblue

mrmateohead said:


> castleofargh said:
> 
> 
> > I think I originally stole this from innerfidelity.
> ...



Did you take a look at the video overview?


----------



## castleofargh

mrmateohead said:


> Just a quibble -
> Harmon's research, while generating the new curve, did NOT conclude that "all people of all ages / races" expressed a preference for that particular curve. The population administered the listening test was far, far smaller than that, and I don't recall being representative of the general population (as defined by average age, sex, or race, for example, or trained / untrained listening skills). While their approach, and conclusions should be repeatable, that study was not the end-all be-all of sound perception studies.


 
  
  
  
 the trial about races/countries was one test on it's own. age was another one. and did involve hundreds of people. the conclusions were that on average people tended to like the same thing.  not like it's actually a surprise. the "young people love bass" myth has brothers in every technological fields, kodac made different batches of the same camera films for different countries for no real reason except urban legend and force of habits (Germany more green, USA more red...). surprise we're all humans!!!!
 then other tests showed that the people tested liked the sound of neutral speakers in a room the best.
 then another test showed that trying to use the perceived signature of neutral speakers in a room, on headphones, made the test subject to mostly favor that signature over diffuse field and free field calibration and even over the natural headphones signature.
 other tests made people swap headphones, another simulated different headphone signatures in on particular model, another test just gave an EQ to people and let them play with it. I think that over the last year(maybe a little more), harman has been at it and passed the statistically significant level.
 all those tests have a common idea and all end up being conclusive for that common idea.
 so if we tend to all like pretty much the same thing, and if test subjects preferred that one signature to the usual compensation curve used, or other already existing headphones, am I wrong in saying that the conclusion of the tests is pretty much that people of all age and race tend to favor that curve?
  I wasn't trying to sell anything, I just made some simplified explanation for zorrofox who didn't hear about it. there is I think 2 topics about, at least one of the trials on headfi and a lot of PDFs available on Sean Olive's blog, and on AES.
  
  
 anyway I think I've unintentionally made a long enough out of topic, sorry guys let's odac/o2.


----------



## MrMateoHead

miceblue said:


> Did you take a look at the video overview?


 
 Unless I missed something - the summary says they used 11 trained listeners in the first test. They then also used approximately 200 persons trialed with "virtual" headphones to test preferences of persons from different nationalities / ages and so on. My quibble is that one shouldn't conclude that Harmon decoded "global" preference for headphone frequency response - that conclusion is too broad given the limitations of the study and its focus, and anyway an $8 billion dollar industry could be composed by well over a million people. Their effort to actually do R&D on headphone response curves is great, but even Harmon admits that there are other, measurable factors that weren't being considered (like headphone distortion). Obviously, if "Headphone A" had a perfect, subjectively neutral response curve, but couldn't playback at 70dB without major distortion (while Headphone B could), a sample of the population would probably hate it (the hard of hearing aka older persons, for example). Science is great, but more work is needed, obviously. Furthermore, knowing what might be preferred doesn't mean that a company will actually MAKE the thing - given that target response would be just one factor in product development process (which has to be delivered at a competitive cost).
  
 I don't dispute their findings - but I just wouldn't declare them 'global' either, and that is what the poster seemed to be implying.


----------



## castleofargh

mrmateohead said:


> miceblue said:
> 
> 
> > Did you take a look at the video overview?
> ...


 

 but you're just being picky on words. my sentence was "*the main conclusion of the studies at harman showed pretty much that all people of all ages of all races did tend to favor neutral sounding gears, as in with the same FR that from flat speakers in an ideal room once the sound has traveled toward us*." again I was simplifying to make it short in English when I'm a surrendering frog by birth.
 my sentence uses "pretty much all" instead of all, "tend to favor" instead of "blindly followed the global rule of humanity", and doesn't even talk about that curve. only about a general idea. it's a study, we're humans and yes we're all free to like whatever we want. it doesn't say that more bass can't be fun, or that more trebles can be nice on classical... I didn't think I was a dictator when I wrote that sentence.
 I read "X product is the bestest" all day long on headfi even when it's a placebo product, I didn't think my sentence would be such a problem. diffuse field or slightly modified diffuse field is what is used to show 99% of headphone and IEM measurements nowadays, apply harman's curve (that isn't night and day different) and tell me it doesn't seem more accurate about what flat sounds like. to me(and a great deal of people I talked to) diffuse field compensation makes bright headphones look flat.


----------



## Dark_wizzie

What is the Harman Curve and how is it derived? I recall that the human ear is more sensitive to some frequencies than others, so if we want a perfectly neutral sounding headphone for example, would the FR curve have be closer to an equal-loudness-contour than a flat line on a FR graph?


----------



## castleofargh

dark_wizzie said:


> What is the Harman Curve and how is it derived? I recall that the human ear is more sensitive to some frequencies than others, so if we want a perfectly neutral sounding headphone for example, would the FR curve have be closer to an equal-loudness-contour than a flat line on a FR graph?


 

 I think we should stop hijacking this topic.
 the curve is about the first graph I have posted.
 at the moment what I'm advocating for, is for us to use harman compensation curve for headphone graphs instead of basic diffuse field as it's done right now in most cases. but it's just a way to show the frequency response, the measurements are still the same.
 flat raw measurements are the real deal flat as in "set by science" flat. then we try to find compensation curves for our faulty ears ^_^(that would be related to equal loudness contour and will slightly deviate from one person to another). then we need to compensate depending on the source of sound.
 the problem has been solved years ago for speakers(by harman), but I think it isn't yet solved for headphones, and it isn't for IEMs. and that curve to me shows something closer to what I actually hear compared to diffuse field compensation.


----------



## adydula

Please take this topic to its own thread and lets get back to the O2/ODAC.
  
 Thanks
 Alex


----------



## faisal2003456

So, I'm on the JDS labs site and I'm wondering.... Which gain set-up for the HD600? I figure the lower the gain, the less distortion I'll get. Oh also, I listen to music at relatively high volumes I guess.
  
 I was looking at some Audio-GD and Schiit products, but I'm a college student who moves between home and the dorms A LOT. I need a transportable single-unit device and the O2+Odac fits my size requirements. I saw some Nuforce products for cheap , like the Icon DAC and Icon HD (HDP without the extra inputs); but man.... Nuforce's reputation is trashed. I don't see any reviews of their stuff anymore. I'd rather not take a gamble.


----------



## Solrighal

I use gains of 1x/3x with my HD 650 and I only rarely feel a need to use the higher setting.1x is generally more than enough.


----------



## jring

faisal2003456 said:


> So, I'm on the JDS labs site and I'm wondering.... Which gain set-up for the HD600? I figure the lower the gain, the less distortion I'll get. Oh also, I listen to music at relatively high volumes I guess.
> 
> I was looking at some Audio-GD and Schiit products, but I'm a college student who moves between home and the dorms A LOT. I need a transportable single-unit device and the O2+Odac fits my size requirements. I saw some Nuforce products for cheap , like the Icon DAC and Icon HD (HDP without the extra inputs); but man.... Nuforce's reputation is trashed. I don't see any reviews of their stuff anymore. I'd rather not take a gamble.


 
  
 Hi,
  
 if you plan to use ODAC and O2 always in combination and also on the go, 1x and 2.5x are your best bet. 2.5x is the highest gain which works with a high voltage source like ODAC (2V redbook) on batteries. If you are using it powered and with ODAC, 3.5 is the limit. If you use higher gain than 2.5 on batt or 3.5 powered with ODAC it will distort regardless of the O2 volume setting.
  
 All the higher gain settings are for low output sources only.
  
 On the other hand you can get the default config of 2.5 and 6.5 for maximum flexibilty and see if 2.5 is ok for you. If you see you need a finer volume control with high sensitivity phones, you could clip the high gain resistors to give you 1x for the high setting (slight cosmetic problem here).
  
 I for my part have not been able to get anywhere close to 12 o'clock with ODAC on 2.5x regardless of cans and my sextetts are not really easy to drive...
  
 Joachim


----------



## faisal2003456

Thank you for the replies. I couldn't find a battery powered O2+ODAC (single unit) that was pre-assembled. Where can I find one? I'd prefer a battery, but wall-powered is fine. The brick is pretty small. I was thinking about either:

 The 1.0X and 2.5x or
 The 1.0X and 3.5X
  
 So I was never considering the 6.5x (which is ridiculous).

 If the 2.5x can get the HD600/650 to ear-splitting volumes with no distortion then I'll just get that.
  
 Also, I was thinking about get the model with the RCA outputs on the back to run into a speaker-amp (if I ever get one). Is there some kind of auto-switching in place?

 Cheers!


----------



## jring

faisal2003456 said:


> Thank you for the replies. I couldn't find a battery powered O2+ODAC (single unit) that was pre-assembled. Where can I find one? I'd prefer a battery, but wall-powered is fine. The brick is pretty small. I was thinking about either:
> Also, I was thinking about get the model with the RCA outputs on the back to run into a speaker-amp (if I ever get one). Is there some kind of auto-switching in place?


 
  
 The normal O2 ODAC combos won't have batteries since the ODAC goes where the batteries are. I have see some hack jobs of putting the ODAC under the O2 board...
  
 RCA plugs usually don't have a switch unlike the 1/8" plug...
  
 Joachim


----------



## faisal2003456

jring said:


> RCA plugs usually don't have a switch unlike the 1/8" plug...
> 
> Joachim




Thanks, I meant if you plug headphones in will the RCA outs disengage.


----------



## liamstrain

faisal2003456 said:


> Thanks, I meant if you plug headphones in will the RCA outs disengage.


 
  
 They do not on my JDS build.


----------



## ethan7000

Got a standalone ODAC from JDS up for sale if anyone is looking, thanks.


----------



## glunteer

Guys, 
  
 I tried putting in my hd 600 out of ODAC and for my surprise the sound out loud, is that right?
  
 It was not for the sound is low, because the ODAC has no amplification?
  
 Thanks


----------



## oryan_dunn

glunteer said:


> Guys,
> 
> I tried putting in my hd 600 out of ODAC and for my surprise the sound out loud, is that right?
> 
> ...


 
 Yep, it could be loud on headphones:
http://en.wikipedia.org/wiki/Line_level
  
 Though, others may correct me, I don't think there is much current, so it may not sound very good.
  


> Different make and model headphones have widely varying impedances, from a common low of 32 Ω to a few hundred ohms; the lowest of these will have results similar to a speaker, while the highest may work acceptably if the line out impedance is low enough and the headphones are sensitive enough.


----------



## castleofargh

glunteer said:


> Guys,
> 
> I tried putting in my hd 600 out of ODAC and for my surprise the sound out loud, is that right?
> 
> ...


 

 it's normal that the sound is loud out of any DAC, they usually provide close to 2V for an amp input of a few thousand ohm.
 now why you shouldn't do that:
 -the output of a DAC is usually around 100/150ohm and I have no idea how the ODAC behaves when plugged into a load as low as a headphone.
 -you'll have to reduce the volume with your computer, even if you're using 24bit output in foobar, you might very well end up crushing the least significant bits of your music.


----------



## glunteer

oryan_dunn said:


> Yep, it could be loud on headphones:
> http://en.wikipedia.org/wiki/Line_level
> 
> Though, others may correct me, I don't think there is much current, so it may not sound very good.


 
  
  


castleofargh said:


> it's normal that the sound is loud out of any DAC, they usually provide close to 2V for an amp input of a few thousand ohm.
> now why you shouldn't do that:
> -the output of a DAC is usually around 100/150ohm and I have no idea how the ODAC behaves when plugged into a load as low as a headphone.
> -you'll have to reduce the volume with your computer, even if you're using 24bit output in foobar, you might very well end up crushing the least significant bits of your music.


 
  
  
 Thanks for help oryan and castle 
	

	
	
		
		

		
			




  
 -------------------------------------------------------------------------------------
  
 Excuse me, but I have one more question ...

 When I'm listening to music Birdy - Wings, at the beginning of the song has a distortion (0,00 to 0,27 sec), I do not know if it's my problem O2 or ODAC, or is a badly recorded music.
  
****UPDATE: I'm using this power supply with my O2, this is what is distorting the sound?*
  
*Broadxent AA-1675* (http://www.emtcompany.com/broadxent-aa-1675-ac-power-supply-charger-adapter/101318691.html)


----------



## Dark_wizzie

Question: Regarding the line out of Odac... is that the "input" hole on my Mayflower o2/odac? What is it used for exactly?


----------



## castleofargh

dark_wizzie said:


> Question: Regarding the line out of Odac... is that the "input" hole on my Mayflower o2/odac? What is it used for exactly?


 

 to make it simple, without usb that plug uses only the O2, and with USB it uses only the ODAC.
 no USB it's an input and you plug another DAC into the O2, with USB you must use it as an output and it uses the ODAC to go into another amp. your choice.


----------



## bada bing

glunteer said:


> Thanks for help oryan and castle
> 
> 
> 
> ...


 
  
 That power supply is AC input, 16V DC output. According to the online specs:

Input: 120V AC 60Hz 17W
Output: 16V DC 750mA

 That won't work at all for the O2. It requires an AC output to the O2. ~16VAC give or take.


----------



## glunteer

bada bing said:


> That power supply is AC input, 16V DC output. According to the online specs:
> 
> Input: 120V AC 60Hz 17W
> Output: 16V DC 750mA
> ...


 
     


  

    
 I will buy a new power supply to see if it improves, will give my feedback here on the topic.
  
 Thanks so much


----------



## mstrmind5

Hi all,
  
 Can the o2+odac combo be safely used with a usb hub?


----------



## Dark_wizzie

Sure? I don't get why it'd be unsafe.


----------



## castleofargh

mstrmind5 said:


> Hi all,
> 
> Can the o2+odac combo be safely used with a usb hub?


 

 it might not give the ultimate performance if other USB devices use a lot of power, but there is no guaranty that your computer would yeld better result if the devices are plugged into another USB slot on the computer instead of being linked to the hub. if you're afraid or if you actually hear something "wrong" for some reasons, maybe a powered hub could actually improve things by delivering the right voltage that maybe your computer doesn't really offer. or the power supply of the powered hub could be the faulty one and add noises to the odac...
 if you plan on being paranoid, the possibilities are endless ^_^.


----------



## adydula

It can be used with or without a USB hub.
  
 Alex


----------



## potkettleblack

Hi all,
  
 I'm planning on getting the 02+odac for a future hd650/600 purchase.
  
 I currently own a pair of ps500e's.
  
 Is the impedance of the grado's too low to be used with the 02+odac? Will there be a humming noise?
  
 I'm very new to this sorry.
  
 One more thing, is it best to turn my macbook volume and vlc player all the way down and let the volume on the amp/combo do the rest or vice versa?
  
 Thanks in advance guys.


----------



## Grave

The O2 is basically noiseless.
  
 Max out the digital volume to 100% and then carefully use the volume knob on the O2.


----------



## castleofargh

grave said:


> The O2 is basically noiseless.
> 
> Max out the digital volume to 100% and then carefully use the volume knob on the O2.


 

 that!
 and vlc at 100%, not 200% ^_^
  
 still you won't die if you fine tune your volume with say a 10db margin from your laptop. I find that laziness is more than enough rewarding compared to the potential least significant bit loss of music.


----------



## potkettleblack

Big up yourselves gentleman.
  
 So 100% on both and then take it from there with the 02 volume knob - screw** fabulous


----------



## mstrmind5

Thanks @Dark_wizzie, @castleofargh and @adydula.


----------



## glunteer

glunteer said:


> Thanks for help oryan and castle
> 
> 
> 
> ...


 
 I tested another power supply and got the same thing, it seems that the music is poorly recorded


----------



## Solrighal

I have the internal volume in JRiver set to 98%. This way even very hot recordings don't clip.


----------



## jring

solrighal said:


> I have the internal volume in JRiver set to 98%. This way even very hot recordings don't clip.


 

 With ODAC/O2 100% should be fine with 0dB - and that's maximum digital out... unless you use hi gain on O2 but the 98% won't help...
  
 Joachim


----------



## Solrighal

I use Voxengo's Span VST plug-in (amongst others) & on certain tracks the peaks will go over 0dB which results in clipping. Keeping the internal volume at 98% avoids this.


----------



## mcandmar

How can you go over 0db?


----------



## Poladise

mcandmar said:


> How can you go over 0db?


 

 It wont go above, but it will clip.


----------



## Poladise

Does anyone know if the o2 will run off ac with the batteries removed?


----------



## castleofargh

I use a -2db gain margin in foobar. it's usually not needed, but even when not abusing EQ and DSPs(and I'm usually pretty careful with those not to pass 0db) I still had a very few number of mp3s that clipped if I kept everything at 0db. and it is solved as soon as I lower the volume one way or another, so it's obviously not some hardcoded clipping. 
 don't ask me how it happens, but it does sometimes and the -2db gain seemed to have solved it for me.
 so if Zorro had the same experience, I understand why he would avoid 100% and keep a little margin just in case.
  
 but I have to say, this has nothing to do with the odac/O2.
  
 I've seen this recently (no I won't buy one, I don't need one, I'm strong willed) on bechmark product page. maybe it's related, maybe it's not, maybe it's a problem with mp3gain, maybe what they talk about is nonsense. I really have no idea ^_^.
 


> High Headroom DSP - with 3.5 dB "Excess" Digital Headroom All of the digital processing in the DAC2 HGC is designed to handle signals as high as +3.5 dBFS. Most digital systems clip signals that exceed 0 dBFS. The 0 dBFS limitation seems reasonable, as 0 dBFS is the highest sinusoidal signal level that can be represented in a digital system. However, a detailed investigation of the mathematics of PCM digital systems will reveal that inter-sample peaks may reach levels slightly higher than +3 dBFS while individual samples never exceed 0 dBFS. These inter-sample overs are common in commercial releases, and are of no consequence in a PCM system until they reach an interpolation process. But, for a variety of reasons, virtually all audio D/A converters use an interpolation process. The interpolation process is absolutely necessary to achieve 24-bit state-of-the art conversion performance. Unfortunately, inter-sample overs cause clipping in most interpolators. This clipping produces distortion products that are non-harmonic and non-musical . We believe these broadband distortion products often add a harshness or false high-frequency sparkle to digital reproduction. The DAC2 HGC avoids these problems by maintaining at least 3.5 dB of headroom in the entire conversion system. We believe this added headroom is a groundbreaking improvement.


----------



## Solrighal

That's what I meant by over  I guess it's expressed as under (-2dB) but you all know what I mean. Like Castle above I'd say there are very few times its an issue but I did see it once or twice so it's fixed & can't happen in future  

Truth be told, I'm not sure I can actually hear the clipping, it's maybe more psychosomatic.


----------



## glunteer

Guys,
  
 thanks for the help, the problem was with a RCA splitter I was using, and only a few songs that distorted, so it was hard to find.


----------



## Dark_wizzie

potkettleblack said:


> Hi all,
> 
> I'm planning on getting the 02+odac for a future hd650/600 purchase.
> 
> ...


 
 Should be the other way around... The digital volume should be at 100% for everything: Windows, VLC, Foobar, Youtube. And then you adjust the volume knob on the O2 accordingly. However... the gains here are really just theoretical. And with the O2 and an easy to drive headphone, things get really loud really quickly, so you'll be turning the volume knob pretty low. And too low can cause channel imbalance. (Say, under 8 or 7 oclock position)
  
 The impedance of the O2 is very low, it's not an issue. The humming should be from the noise floor, right? That should be fine too.
  


mstrmind5 said:


> Thanks @Dark_wizzie, @castleofargh and @adydula.


 
 No problem, I'm glad I helped in some way.


----------



## gradofans

I'm looking for a cheap DAC now , maybe it's proper for me to get an ODAC ...
 But I can't find anywhere to try it. ...


----------



## jring

poladise said:


> Does anyone know if the o2 will run off ac with the batteries removed?


 

  just fine.
  
 Joachim


----------



## jring

gradofans said:


> I'm looking for a cheap DAC now , maybe it's proper for me to get an ODAC ...
> But I can't find anywhere to try it. ...


 
  
 It's usually sold only by a few companies and even fewer have a showroom. So your best bet is to go to a meet or find some friendly head-fier with one in your area.
  
 Joachim


----------



## vertical

jring said:


> It's usually sold only by a few companies and even fewer have a showroom. So your best bet is to go to a meet or find some friendly head-fier with one in your area.
> 
> Joachim




I second that. Meets are a great place to hear a lot of equipment, meet great people, and find out about new music


----------



## jasonhanjk

poladise said:


> Does anyone know if the o2 will run off ac with the batteries removed?


 
  
 Nope. The AC are meant to charge the batteries. Removing the batteries and you won't get your ground.
 It will work if you add 2 caps and resistor divider but there would be more noise / voltage unbalance / DC at output.


----------



## mcandmar

jasonhanjk said:


> Nope. The AC are meant to charge the batteries. Removing the batteries and you won't get your ground.
> It will work if you add 2 caps and resistor divider but there would be more noise / voltage unbalance / DC at output.


 

 ^ utter nonsense.


----------



## mikeaj

jasonhanjk said:


> Nope. The AC are meant to charge the batteries. Removing the batteries and you won't get your ground.
> It will work if you add 2 caps and resistor divider but there would be more noise / voltage unbalance / DC at output.


 
  
 No, that's not how it works. Just check the circuit diagram. The AC goes into half-bridge rectifiers into filters and 7812 / 7912 linear regulators to generate +12 V / -12 V rails. It's those +12 V and -12 V rails that charge the batteries and also power the electronics (the three op amps). If the AC is disconnected, the voltage rails drop to the battery voltages instead. The ground is from the AC input. Whether or not the batteries are in doesn't affect the power delivery other than drawing some amount of current from the rails.
  

 Check the top side.
  
 There are many people who have build or gotten an O2 without the batteries. Many O2 / ODAC combos people sell don't come with batteries.


----------



## headwhacker

jasonhanjk said:


> Nope. The AC are meant to charge the batteries. Removing the batteries and you won't get your ground.
> It will work if you add 2 caps and resistor divider but there would be more noise / voltage unbalance / DC at output.


 
 Sure you can. O2 can be powered and operated from AC without the batteries. Otherwise, How do you think the O2/ODAC combos work? The ODAC board occupies the space where the batteies are placed.


----------



## castleofargh

last time I emailed JDS for what was in the end a dumb question(don't ask me I'm ashamed), he answered me as if I was a very interesting person with a good question in less than 40mn. so maybe you should just email the guy where you bought it or plan to buy it. ^_^
 I know the odac/o2 combo can have some very minor changes compared to both bought separately (usually stuff you can undo in 20sec and a soldering iron so I don't expect a radical power supply change in the schematics).


----------



## Solrighal

My O2 has stereo RCA outputs. The lower gain is 1x (unity) can I output the signal from my O2 to my Marantz integrated stereo amp?


----------



## adydula

I have an 02 without batteries and it runs on AC only??
  
 Must be magic?
  
 Alex


----------



## castleofargh

at last something magic about the O2!!!!!
 we have been waiting for a sign for so long, something that measurements wouldn't explain. a subjective reason to want it that wouldn't be some stupid idea of transparency and low noise.
  
 "O2, it runs without batteries or legs!"




  
 what a great day.


----------



## headwhacker

castleofargh said:


> at last something magic about the O2!!!!!
> we have been waiting for a sign for so long, something that measurements wouldn't explain. a subjective reason to want it that wouldn't be some stupid idea of transparency and low noise.
> 
> "O2, it runs without batteries or legs!"
> ...


 
 So does it mean O2/ODAC is now a going audiophile?


----------



## Dark_wizzie

headwhacker said:


> So does it mean O2/ODAC is now a going audiophile?


 
 One factor of an amp/dac being an audiophile item is high price, which the Objective does not deliver.


----------



## adydula

The O2 is not totally perfect, even though I am a ardent user of 2 of them plus an improved ODA of AGDR's design.
  
 Recently a person reported frying a NJM4556A chip using a set of HE400's.
  
 The cans used were 35 ohms and have a sensitivity of 92.5 db/mW. (HE400's).
  
 You can easily go way over the maximum output dissipation for the NJM4556A chips in the upper volume levels of musical peaks. Headphones like that need an ODA type of amp. So it is quite possible to go 100% or more of the maximum allowed package dissipation for certain combinations of low impedance low sensitivity headphones AND higher volume levels AND specific music that has high or sustained peaks.  
  
 The maximum power dissipation for the NJM4556A chip's DIP8 package is listed as 700mW on the datasheet here:

http://www.cn.njr.com/PDF/NJM4556A_E.pdf

 But that is at room temperature and the insides of the O2 will get warm with those output chips dissipating and the voltage regulator heat. So de-rate that to 600mW.

 Then the chip quiescent current is listed as 8mA to 12mA. The higher current end will usually happen at higher output levels. So be conservative and say 11mA, with the O2 on AC power that gives (12 * 2 * 0.011A) = 264mW. Just like that the quiescent current has used up about half the available chip power dissipation just sitting there at idle: 600mW - 264mW = 336mW left for headphones on each NJM4556A chip.

 Using 120dB as the maximum level (musical peaks) in the headphone spreadsheet. But at just 112dB the HE400 needs 1.76Vrms and 50mA. So that is 12V - 1.76V across the chip, or 10.24V. The power dissipation for both chips halves then (in the same NJM455A package) is 10.24V * 0.05A = 512mW, which is 35% over the 336mW maximum chip power dissipation from above. At 115dB the power dissipation is 100% over limit at 660mW. That is more than enough to cause the chip to explode in half like that. 
	

	
	
		
		

		
			





 Working with the numbers the maximum loudness level to hit the 336mW of available package dissipation would be 107.5dB.

 So this person would need to listen to his headphones at lower levels and/or get a higher current amp like the ODA to keep that from happening. 
  
 The O2 is not safe from internal chip damage for any 16 ohm and up headphone.
  
 This recent event occurred with a commercially purchased O2.
  
 FYI
  
 Alex
  
 Note the technical details come from a very highly qualified EE.


----------



## Medaud

adydula said:


> The O2 is not totally perfect, even though I am a ardent user of 2 of them plus an improved ODA of AGDR's design.
> 
> Recently a person reported frying a NJM4556A chip using a set of HE400's.
> 
> ...




Having recently bought an O2/ODAC this is not very comforting...it has handled my 42 ohm ATH-A900x without a problem so far though. The problem with the ODA is that people seem to be taking it in a different direction than what the O2/ODAC was originally all about, e.g. implementing a "bass boost" feature and such.


----------



## MrMateoHead

Anyone that expects at Amp to run at 100% volume sustained for long periods into low impedance loads without frying itself is being a little unreasonable, IMHO. 108 dB is basically hearing damage - totally unnecessary.
  
 I wouldn't be TOO worried that the O2 lacks enough thermal dissipation to provide maximum sustained power without damage.
  
 I guess the common-sense solution would be to choose more efficient headphones that keep the O2 within a safer power range!


----------



## adydula

The ODA has an option for a bass boost, being a purist I did not implement that. The way the ODA is laid out you can easily leave things out or in as you please.
  
 Having three times the current capacity is a plus for me.
  
 That said, Mr Mateohead....I agree with your comments that listening to headphones at reasonable levels makes good sense and protects your hearing..... but knowing eactly your amp and headphones are doing is a plus as well.
  
 The ODA designer has had many conversations with the O2 designer in the past. This was one topic they debated.
  
 Also the ODA designer has tried and has met most of the O2 measurements and capabilities take a good read over at DIYAudio.com.
  
 All the best
 Alex


----------



## potkettleblack

Hi lads,
  
 anyone know how to get the silver odac + o2 with the custom options? it seems it will only let you customise the black one


----------



## jring

adydula said:


> ...But at just 112dB the HE400 needs 1.76Vrms and 50mA. So that is 12V - 1.76V across the chip, or 10.24V. The power dissipation for both chips halves then (in the same NJM455A package) is 10.24V * 0.05A = 512mW, which is 35% over the 336mW maximum chip power dissipation from above...


 
  
 Hi,
  
 care to explain this part, specifically why you subtract the 1.76Vrms from 12V to multiply by 50 mA? I would expect 1.76Vrms times 50mA or 0.09VA (this is apparent power usually expressed in VA instead of W). Probably take this times 2 for stereo.
  
 Also the quiescent current can be taken from the supply current vs temperature diagram in the data sheet and is 9mA at Vcc=+-15V and room temperature and will fall with rising temperature.
  
 Joachim


----------



## jring

solrighal said:


> My O2 has stereo RCA outputs. The lower gain is 1x (unity) can I output the signal from my O2 to my Marantz integrated stereo amp?


 
  
 I do this all the time since I had not drill until lately and so couldn't populate the ODAC 1/8" Line-Out socket yet. Of course you are double amping here but I have not heard a problem.
  
 Joachim


----------



## Solrighal

jring said:


> I do this all the time since I had not drill until lately and so couldn't populate the ODAC 1/8" Line-Out socket yet. Of course you are double amping here but I have not heard a problem.
> 
> Joachim


Thanks for the input Joachim. I have it connected now & it's sounding fantastic. Is it double-amping though. I'm using unity gain with the volume set to max. Surely that's just the same signal my ODAC would be putting out?


----------



## potkettleblack

Thanks mate.
  
 I see you commenting on ALL the hd800 youtube videos


----------



## adydula

Joachim, here is your answer from AGDR:
  
 The 1.6Vrms * 50mA is the power that gets delivered to the load (the headphones) and not the power dissipated by the output chips.   The voltage that winds up across the output chips is the power supply voltage going into the chip minus the headphone voltage at the chip output, 12Vdc - 1.6Vrms.  That is wiith the O2 on AC, things are better on batteries with the lower voltages.

 That is the voltage that winds up across the output transistor in one half of the push-pull output stage in the chip, whichever of the two is "on" at the moment.  The power dissipated by that transistor then is that voltage difference across it, 12Vdc - 1.6Vdc, times the current through the headphones (which has to go through that output transistor to get there from the chip power supply lead), for a total of (12Vdc - 1.6Vrms) * 50mA = 52mW for each amplifier, or 2x that for both halves of the chip 104mW.

 But here is the tricky part.   That is just one output transistor.  Using rms voltages takes care of the other automatically.  rms voltages are always the thing to use in power calculations since it is essentially the "heating" value of a sine wave.  The rms voltage for a pure sine wave is 0.707 times the peak votlage, say just the positive half, and takes the negative wave half into account automatically in the math.  In terms of the chip's internal power dissipation that just means the positive push-pull transistor and the negative alternately get the 50mA going through them to the positive and negative power supply rails, respectively, as the sine wave does its thing.

 He is quite right about the total quiescent current though!  Good find.  I took the 11mA off the table in the datasheet and didn't notice that graph. So the actual quiescent current at the typical O2 inside temp, say 50C maximum, would be around 8.5mA from that graph, 2.5mA less that what I used.  So the new chip power dissipation due to the quiescent current would be slightly less:  (24 * 0.0085A) = 200mW. But at the higher voltage swings (higher volume levels) the output chip(s) would still be nearly 100% over their maximum power dissipation and would pop.

 So to sum it up, the designer's blog and posts leave the impression that any headphone from 16 ohms and up are "safe" with the O2, in terms of not causing internal damage to the chips. But that just isn't the case.  There are combinations of some low-sensitivity low-impedance headphones + higher volume levels + music with higher peaks and/or sustained peaks that will overheat the O2's output chips.  Luckily getting all of those things together at once is relatively rare, which is why you don't see more O2's blowing their output chips.   If anyone does have their output chips pop like that be sure to replace them as a set.  If one cracked open the other was nearly there too and is damaged.
 ***************
  
 Hope this helps...
  
 Alex


----------



## mikeaj

I'm pretty surprised anybody could stand to listen that loudly, to be honest. For HE-6, I'd believe it. For HE-400? That seems nuts to me. Pretty much if some music is pegged at an average level of -10 dBFS or higher, nobody's listening on 110+ dB SPL peaks. At least, I hope. The time when those levels get actually used may be for more brief peaks on music with some 25+ dB dynamic range.
  
 I mean, how many people have even fried their O2s with test signals?
  
 But yeah, using planar magnetics, I'd maybe stick chip heatsinks on just out of principle, even without trying to calculate how much that'd help with thermal dissipation:
 http://www.ebay.com/itm/New-High-Quality-5pcs-11x11x5mm-adhesive-Aluminum-Heat-Sink-For-Memory-Chip-IC-/131014795047
  
  


solrighal said:


> I have it connected now & it's sounding fantastic. Is it double-amping though. I'm using unity gain with the volume set to max. Surely that's just the same signal my ODAC would be putting out?


 

 Yes, double amping, while outputting the same level and behaving practically the same, yes. I'm sure whatever noise level the O2 adds is insignificant compared to everything else.


----------



## Solrighal

As long as it doesn't fry anything it's cool I suppose. I've no idea why the RCA outputs on my O2 are connected to the amp though. Unless it's maybe for active speakers.


----------



## mcandmar

solrighal said:


> Thanks for the input Joachim. I have it connected now & it's sounding fantastic. Is it double-amping though. I'm using unity gain with the volume set to max. Surely that's just the same signal my ODAC would be putting out?


 
  
 Depending on how it is implemented you should be able to tap into the ODAC output using the line in socket on the front of the amp, i.e. bypassing the O2 amplifier.


----------



## Solrighal

I'm thinking about buying a pair of these for the ODAC... 

http://www.futureshop.co.uk/product_info.php?products_id=6183#.VDK4fIFwaBY

What do you guys think? It will avoid Double-amping and keep the front of my O2 tidy.


----------



## jring

adydula said:


> Joachim, here is your answer from AGDR:


 
  
 Thanks for the explanation... I would do the math for a Class B output stage like this... Total power consumption is power supply voltage times current.
  
 Pps = Vps * Ips
  
 assuming a sine wave we get
  
 Pps = Vps * 0.45 * Vrms / Rl
  
 so with Vps=24V (both rails), Vrms=1.76V and Rl=35 ohms we get Pps=540mW
  
 For the power dissipation in the amp we have to subtract the power delivered to the phones from this:
  
 Pdiss = Pps - Pout
  
 Pout = Vrms * Iout = 88mW
  
 Pdiss = 452mW
  
 Now we add quiescent current times supply voltage Vps * Iq =  204mW giving 656mW which is a close call with the 700mW max dissipation and in a cabinet but it should not go up in flames. I first thought we had to multiply Pdiss by two for two amps in the package but since they're switched in parallel they shrare the load and each sees only half of the current.
   
Joachim


----------



## adydula

Take a look at what actually happened here:
  
http://www.head-fi.org/t/736374/jds-o2-blew-an-op-amp-pic-inside-question-regarding-replacement
  
 Alex


----------



## jring

adydula said:


> Take a look at what actually happened here:
> 
> http://www.head-fi.org/t/736374/jds-o2-blew-an-op-amp-pic-inside-question-regarding-replacement
> 
> Alex


 

 Seing is believing... although one must wonder at what levels this guy listens... or he burning in sth?
  
 Joachim


----------



## adydula

I agree there, I was wondering if by accident or oversight the amp was left on and music was playing and the volume control was turned up all the way etc
  
 Sounds not likely, but stranger things do happen.
  
 The good news here is if you take a look at what AGDR has done with his booster board for the O2, ($30-$50) project this can be avoided pretty much.
  
 The booster board details are over at diyaudio as well.
  
 Alex


----------



## JacobLee89

adydula said:


> I agree there, I was wondering if by accident or oversight the amp was left on and music was playing and the volume control was turned up all the way etc
> 
> Sounds not likely, but stranger things do happen.
> 
> ...


 
  
 If memory serves me right. AGDR mentioned that the original opamp, in the BOM for making the O2, starts getting hot once it nears 15V. With that in mind a single voltage spike would have easily done some damage. One of the optional booster board mods did include replacing one of the remaining opamps on the O2 board, so that the full 15V could be used.


----------



## adydula

One voltage spike would not do this IMO, the chip has to get "hot" enough to split open ...it has to happen over a small period time, probably 10-30 min in my best guess.....
  
 Alex


----------



## jring

adydula said:


> One voltage spike would not do this IMO, the chip has to get "hot" enough to split open ...it has to happen over a small period time, probably 10-30 min in my best guess.....
> 
> Alex


 
  
 This or a massive overvoltage... thunderstorm anybody? Although this probably would have fried a lot of other stuff too.
  
 Joachim


----------



## adydula

If it was a massive spike more than this would have been damaged.
Alex


----------



## BiffZiff

Is there any benefit from ordering the OW or the O2+ODAC from any one place compared to another?

 I have heard of Mayflower and JDS so far.  I am in the states. 
  
  
 Also I have a Asus Xonar DX, is the DAC on this any better in terms of sound quality?


----------



## headwhacker

get it from where you can get it cheaper.


----------



## Dark_wizzie

biffziff said:


> Is there any benefit from ordering the OW or the O2+ODAC from any one place compared to another?
> 
> I have heard of Mayflower and JDS so far.  I am in the states.
> 
> ...


 
 Lolno. A sound card will not be better than Odac in sound quality. The question is whether you are capable of hearing a difference. That's a different matter. But at least you'll know it's better.
  
 JDS tends to cost more, but allows for custom engravings. Mayflower is cheaper. The differences between the two vendors aren't really that big. You might just decide to go for whichever version looks cooler to you. (They look pretty different on the enclosure side.)
  
 In terms of sound quality and all that jazz, no, they should be the same. It's based on the same schematics. I've have a good experience with Mayflower's customer service, but I also heard good things about JDS customer support. Mayflower is slowly working on releasing the ODA for sale, but that's not really O2.


----------



## glunteer

biffziff said:


> Is there any benefit from ordering the OW or the O2+ODAC from any one place compared to another?
> 
> I have heard of Mayflower and JDS so far.  I am in the states.
> 
> ...


 
 I had a xonar dx and then bought an ODAC, the difference is small, the ODAC is more neutral than the Xonar DX.


----------



## HaVoC-28

glunteer said:


> I had a xonar dx and then bought an ODAC, the difference is small, the ODAC is more neutral than the Xonar DX.


 
  
 At volume matched and all DSP's option off it sounded the same to me . Also Xonar DX output voltage is slightly lower than ODAC , 1.95V for my former DX and 2.03v on my ODAC (Multimeter) .


----------



## Peti

I am considering to pull the trigger on this combo. I got an issue though: I spend most of my time both sides of the pond (110 volts vs 220 volts) so can I use it in the EU if I buy the 110 V version in the US?
  
 Would it be just enough to get both a 110V and 220V AC transformers?


----------



## Medaud

biffziff said:


> Also I have a Asus Xonar DX, is the DAC on this any better in terms of sound quality?




The SQ is not better, but the main thing with sound cards is that they provide a lot of DSP that DACs don't...


----------



## Dark_wizzie

The sound quality should be better, but probably not audibly better. It measures better as a whole. If not, what the hell is the point of the Odac?


----------



## jseaber

dark_wizzie said:


> The sound quality should be better, but probably not audibly better. It measures better as a whole. If not, what the hell is the point of the Odac?


 
  
 As far as I'm concerned, and I probably shouldn't share this, ODAC gives you peace of mind.
  
 Some people actually need a DAC. You might be experiencing distortion, hum, or other background noise. These are obvious signs that you need a DAC. For situations in which you're not sure if you need a DAC, an amplifier resolves nearly all headphone listening inadequacies (better THD+N, output-Z, output power, even superior SNR for sub-unity listening).
  
 So, if you already have clean audio and a clean amplifier, ODAC ensures your audio signal is optimal. Whether or not you can hear the difference depends entirely on your equipment.


----------



## Dark_wizzie

jseaber said:


> As far as I'm concerned, and I probably shouldn't share this, ODAC gives you peace of mind.
> 
> Some people actually need a DAC. You might be experiencing distortion, hum, or other background noise. These are obvious signs that you need a DAC. For situations in which you're not sure if you need a DAC, an amplifier resolves nearly all headphone listening inadequacies (better THD+N, output-Z, output power, even superior SNR for sub-unity listening).
> 
> So, if you already have clean audio and a clean amplifier, ODAC ensures your audio signal is optimal. Whether or not you can hear the difference depends entirely on your equipment.


 
 I agree with you. But I also bought an Odac because I knew it measured better (instead of only as a peace of mind deal). The improvements, whether audible or not, exist. And that makes me happy. It's not wholly rational but I openly acknowledge that.
  
 Also, in order for the Odac to provide a peace of mind, it ought to have better sound quality than whatever a personally originally had. All of this rests on the measurements of the Odac. We're always back to the performance of the Odac.


----------



## jseaber

dark_wizzie said:


> I agree with you. But I also bought an Odac because I knew it measured better (instead of only as a peace of mind deal). The improvements, whether audible or not, exist. And that makes me happy. It's not wholly rational but I openly acknowledge that.
> 
> Also, in order for the Odac to provide a peace of mind, it ought to have better sound quality than whatever a personally originally had. All of this rests on the measurements of the Odac. We're always back to the performance of the Odac.


 
  
 Well put. I think most ODAC adopters will agree with you!


----------



## jring

peti said:


> I am considering to pull the trigger on this combo. I got an issue though: I spend most of my time both sides of the pond (110 volts vs 220 volts) so can I use it in the EU if I buy the 110 V version in the US?
> 
> Would it be just enough to get both a 110V and 220V AC transformers?


 
  
 The AC power supply for O2 contains an old fashioned transformer and thus is either for 110V or 220V. It has to be like this due to the way the O2 power supply works (two way rectifier) - DC switching power supplies don't care about input voltage but won't work with O2 or even break stuff.
  
 So either get two O2 wall warts or a 220V to 110V transformer - whatever is cheaper and/or lighter.
  
 Joachim


----------



## Peti

jring said:


> The AC power supply for O2 contains an old fashioned transformer and thus is either for 110V or 220V. It has to be like this due to the way the O2 power supply works (two way rectifier) - DC switching power supplies don't care about input voltage but won't work with O2 or even break stuff.
> 
> So either get two O2 wall warts or a 220V to 110V transformer - whatever is cheaper and/or lighter.
> 
> Joachim


 

 Gotcha! Thank You.


----------



## adydula

The ODAC provides a certain level of confidence to me... it measures well, it allows good sound to come forth... and its really inexpensive.
  
 I have done lots of AB blind testing and with several other dacs I have there is no way I can really reliably tell any audible difference.... some of these dacs cost a lot more than the odac.
  
 Alex


----------



## BiffZiff

Thank you all for your answers. I also wanted to ask.  Is it best to buy, The combo amp + odac in one unit or two units seperate and chain them together? The price ios really not that much different.  What are the pro's and cons of each.


----------



## castleofargh

biffziff said:


> Thank you all for your answers. I also wanted to ask.  Is it best to buy, The combo amp + odac in one unit or two units seperate and chain them together? The price ios really not that much different.  What are the pro's and cons of each.


 

 both in one box has no battery. that's pretty much it. so if you see a possible use as portable or lost in the desert go for it in 2 pieces.


----------



## Medaud

dark_wizzie said:


> The sound quality should be better, but probably not audibly better. It measures better as a whole. If not, what the hell is the point of the Odac?




Okay, so it measures better, but audibly you probably won't hear a difference, as Tomshardware already showed. That's why I said, if you like the DSP that a sound card provides, then you might not want to get an odac. The sound card will still sound great plus you will get the DSP.


----------



## adydula

The O2 and follow on ODAC was an experiment to design with low cost components designed very well that could produce world class performance and measurements to prove a point.
  
 They are indeed highly successful.
  
 That's the point... with these you know you will get really great performance with little or no interaction or additions to the source material for a decent cost.
  
 Enjoy
  
 Alex


----------



## Solrighal

I also like the karma effect of using an essentially open-source device.


----------



## r010159

solrighal said:


> I also like the karma effect of using an essentially open-source device.




I agree! I always like going with the open source, both in hardware and software.


----------



## vertical

r010159 said:


> I agree! I always like going with the open source, both in hardware and software.




Interesting to categorize it as open source. The design certainly didn't get kicked off for capitalistic reasons. Hmm, I wonder if the DAC algorithm might be running on top of Linux...jk.


----------



## Solrighal

I don't think genuine value for money happens very often in the tech world, certainly not without poor people in some far off land being shafted by big corporations. The O2 also enables the owner to find exactly the right pair of headphones pretty quickly because that word 'synergy' never really gets used here. I read some of the other amp threads and people tie themselves in knots compensating for bad characteristics with yet more, opposite, traits. Stuff that!


----------



## castleofargh

anybody creating something and giving it away is demi-god to me(the mum giving fresh baked stuff to the neighborhood, included). I love internet for that, you always find a guy ready to waste 20mn of his life to help a noob like me, with zero benefits for his own life. and sometimes, you get a guy creating an amp from scratch simply to demonstrate an idea. because "words are wind" and "you know nothing john snow".
 whatever nwavguy did, he surely deserved a little more love and a little less of the vendetta that went and still goes against him.
  


> The prisoner who now stands before you
> Was caught red-handed showing feelings
> Showing feelings of an almost human nature;
> This will not do.
> Call the schoolmaster!


 
  
  
 also thanks to people like J Seaber and the few others who jumped into the adventure to provide a ready made solution to our solderingly inapt selves.


----------



## adydula

Lets please be careful and not go down the road of the designers reasons and past history... it will shut this thread down. Its not that I am not willing to chat about it but this is not the place.
  
 There are other sites to do this on.
  
 That said, I am glad AGDR has taken up the charge with the ODA.....there are very few people that I have met that really understand electronics design that have taken so much time to try to improve upon what the O2 designer was trying to do.
  
 Alex


----------



## Peti

Maximum respect to the creator of the O2/ODAC! Also, the same goes to Head-Fi letting this thread going on considering the "prelude". Either way I have found a kind of balance by reading both sources. As usual, the truth is always somewhere in the middle. My first experience into hi-end headphones was through this site and I have found so much useful info here I can't tell from headphone reviews to how to customize my foobar.
  
 Not sure if this was discussed before but I'm curious if the O2/ODAC can sufficiently run the HE-600 monster from Hifiman?
  
 Any useful comments/experiences are welcome!


----------



## Dark_wizzie

Wut? HE-600s? Those exist?


----------



## Peti

Yeah, the new flagship of hifiman havent heard of it yet? just kidding, i meant the HE-6


----------



## Dark_wizzie

peti said:


> Yeah, the new flagship of hifiman havent heard of it yet? just kidding, i meant the HE-6


 
 Lol, Headfi profile view shows the posts I need to catch up on, and it cuts off at the latter half, so I was reading the preview of HE600s and going OMG WHAAATTT RLLY??? 
	

	
	
		
		

		
			




 He-6 is very borderline and depends on how loud you listen, what tracks are played, and who's measurements you believe (hifiman vs Inner fidelity). My advice is if you want to power HE-6, get another amp or wait for the ODA which Mayflower is... slowly working on. The ODA will power the HE-6 without problem but also cost more.


----------



## Xenophon

peti said:


> Maximum respect to the creator of the O2/ODAC! Also, the same goes to Head-Fi letting this thread going on considering the "prelude". Either way I have found a kind of balance by reading both sources. As usual, the truth is always somewhere in the middle. My first experience into hi-end headphones was through this site and I have found so much useful info here I can't tell from headphone reviews to how to customize my foobar.
> 
> Not sure if this was discussed before but I'm curious if the O2/ODAC can sufficiently run the HE-600 monster from Hifiman?
> 
> Any useful comments/experiences are welcome!




I own the HE-6 and an ODA. As was remarked, all kinds of numbers are circulating and kt depends on what you choose to believe reading those. I have the luxury of actually being able to try it and compare with my other amps, bypassing the theoretical calculations. Conclusion: no way is the HE-6 pfoperly powered by the ODA. I love the concept but it's not the ultimate amp solution for everything you can throw at it.


----------



## Dark_wizzie

xenophon said:


> I own the HE-6 and an ODA. As was remarked, all kinds of numbers are circulating and kt depends on what you choose to believe reading those. I have the luxury of actually being able to try it and compare with my other amps, bypassing the theoretical calculations. Conclusion: no way is the HE-6 pfoperly powered by the ODA. I love the concept but it's not the ultimate amp solution for everything you can throw at it.


 
 The last time I crunched the numbers, with a worst case scenario, ODA is capable of powering HE-6.


----------



## headwhacker

I always hear people say when they are not satisfied how the headphone sound from a particular amp that it needs more power.

Just recently saw someone argued that grado phone @ 32ohm and 98 dB needs more than 200mW to sound nice


----------



## Xenophon

I know those numbers. My only reply is: hook it up to an ODA, then to some more powerful amps and compare. The difference is not subtle and it's not about sound coloration either. Try it, then come back and report. I'm all in favour of objectivity a d science but if you just trust your ears (or could somehow measure what comes out of the HE-6) then you'll conclude that apparently there's a problem with the model used.


----------



## JacobLee89

Is it possible that we are also ignoring inconsistency with Quality Control during manufacturing of the gear?


----------



## Peti

Thanks for the feedbacks! I guess at the end of the day I gotta give this combo a try one day to hear the results with my own ears..


----------



## adydula

Xenphon,
  
 AGDR read your post on the ODA and your headphones.
  
 He asked me to contact you and said you may need the 15volt rails to power the HE6's.
  
 The lower 12.5 volt rails would drive the cans to 113db the 15 volt rails would drive them to 116db.
  
 AGDR told me he would be glad to convert your unit to 15vdc rails if you would like.
  
 Please let me know or contact him via a PM over at www.diyaudio.com.
  
 NOTE: He is willing to do this at NO COST to you!
  
 FYI
 Alex


----------



## Dark_wizzie

113db is already ridiculous. I don't think Xenphon meant to say "Well I was hitting 113db peaks so my HE-6 didn't sound so well"...


----------



## castleofargh

dark_wizzie said:


> 113db is already ridiculous. I don't think Xenphon meant to say "Well I was hitting 113db peaks so my HE-6 didn't sound so well"...


 

 what they're not mini speakers?


----------



## JacobLee89

castleofargh said:


> what they're not mini speakers?


 
  
 A circular saw averages at 110Db.


----------



## Jakkal

Can someone who has O2/ODAC combo from Headnhifi confirm that, on their unit the imput jack also is line out from the ODAC?
Thanks


----------



## adydula

Understand....
  
 AGDR just wants him to know he is willing to help if its needed to get his ODA to the higher 15 rails which would be better in his situation anyway.... at no cost!!
  
 Alex


----------



## Dark_wizzie

castleofargh said:


> what they're not mini speakers?


 
 I never understood what the emoticon means or what it's actually showing. There's a guy wearing headphones smacking the butt of a dog with a human face wearing earphones and his head inside of a plastic bag? Wut?


----------



## No_One411

dark_wizzie said:


> I never understood what the emoticon means or what it's actually showing. There's a guy wearing headphones smacking the butt of a dog with a human face wearing earphones and his head inside of a plastic bag? Wut?


 
 Beating a dead horse. 
  
 Means the topic has already been discussed to death.


----------



## Jakkal

dark_wizzie said:


> I never understood what the emoticon means or what it's actually showing. There's a guy wearing headphones smacking the butt of a dog with a human face wearing earphones and his head inside of a plastic bag? Wut?




I think that icon was related to the famous Sennheiser veil. Thats why the dead horse has plastic bag on his head.


----------



## No_One411

jakkal said:


> I think that icon was related to the famous Sennheiser veil. Thats why the dead horse has plastic bag on his head.


 
 LOL! 
  
 I suppose that's another way to put it. 
  
 ngl, thought it mean ******** for the longest time.


----------



## adamlr

ive had my O2 for around a year now, and recently its been acting up... whenever i turn the volume pot, a loud hissing sound occurs. once ive finished adjusting the volume the hissing goes away, its only while i turn the knob. any ideas for a solution? i cant really afford sending it off to jds... 
 cheers


----------



## jseaber

adamlr said:


> ive had my O2 for around a year now, and recently its been acting up... whenever i turn the volume pot, a loud hissing sound occurs. once ive finished adjusting the volume the hissing goes away, its only while i turn the knob. any ideas for a solution? i cant really afford sending it off to jds...
> cheers


 
  
 That's a new one. Can you replicate the sound with other audio sources and cables?
  
 If you're unable to find a cause, please email us and I'm sure we can assist at no cost to you. That's what the 2-year warranty is for!


----------



## castleofargh

isn't it the usual dust(also known as Pringles particles) breaking the surface contact inside the knob? do you have this at any volume or only at specific places on the knob?
 try going from min to max and back a few times to see if that changes anything.


----------



## adamlr

castleofargh said:


> isn't it the usual dust(also known as Pringles particles) breaking the surface contact inside the knob? do you have this at any volume or only at specific places on the knob?
> try going from min to max and back a few times to see if that changes anything.


 
  
 i took the knob off and dusted everything, i think ill take it to work tomorrow and go over it with the compressor (not sure thats the word... its an air pressure machine). cheers
  


jseaber said:


> That's a new one. Can you replicate the sound with other audio sources and cables?
> 
> If you're unable to find a cause, please email us and I'm sure we can assist at no cost to you. That's what the 2-year warranty is for!


 
  
 hard to tell, its not persistent - it comes and goes. if the problem keeps happening after ive cleaned it up ill be sure to email you. thanks!


----------



## GoldenboyXD

I also wanted to know if it's okay to put a lube inside the control knob like low viscosity oil or penetrating oils? I also have this problem...


----------



## eimis

I couldn't stand channel imbalance with a carbon pot so I got myself a 10k 23 steps stepper pot from aliexpress. It's fine balance wise, but sometimes it doesn't lock to step properly and I have to wiggle back and forth a few times. Was thinking of using a 255 step stereo i2c pot + attiny avr + a clicky pot. Might be nice to make a kit


----------



## LogicalDisconnect

Can anyone recommend something similar to the O2 / ODAC combo but that has both USB and SPDIF inputs? I basically want a completely transparent DAC and amp but I need USB and optical and ideally both coax and optical inputs. I currently have a Benchmark DAC2 HGC but don't need all the extra features so I'm looking to downgrade while still maintaining transparency. Thanks.


----------



## JacobLee89

logicaldisconnect said:


> Can anyone recommend something similar to the O2 / ODAC combo but that has both USB and SPDIF inputs? I basically want a completely transparent DAC and amp but I need USB and optical and ideally both coax and optical inputs. I currently have a Benchmark DAC2 HGC but don't need all the extra features so I'm looking to downgrade while still maintaining transparency. Thanks.


 
  
 I've read some positive reviews on the audio-gd NFB11.32 , from someone whom did move from the O2 stack. I think only the NFB11 is available now but it seems to be the same model which underwent some revisions. This has both USB and optical for your needs.


----------



## muad

Your best bet would be the benchmark dac1. They can be had new for 800-900 right now.


----------



## LogicalDisconnect

Unfortunately in Aus so at the price of a new DAC1 HDR I may as well keep the DAC2. Was hoping there might have been something cheaper without so many features (eg XLR outputs).


----------



## hekeli

Sold my DAC2 too, I think your best bet is Emotiva DC-1. I would buy it, but Emotiva outsourced international sales to Bongo or such crap, the shipping fees are quite stupid. Rolling on with a used HRT HD I got cheap for now..
  
 Though there's a small sale going on now, $474 is a bit tempting..


----------



## adamlr

castleofargh said:


> isn't it the usual dust(also known as Pringles particles) breaking the surface contact inside the knob? do you have this at any volume or only at specific places on the knob?
> try going from min to max and back a few times to see if that changes anything.


 
  
  


jseaber said:


> That's a new one. Can you replicate the sound with other audio sources and cables?
> 
> If you're unable to find a cause, please email us  looks like a thorough dust and clean did the job


 
  
 looks like a thorough dust and clean did the job 
	

	
	
		
		

		
			




  
 ill be sure to send off an email if it comes back. 
  
 thank you both


----------



## castleofargh

adamlr said:


> castleofargh said:
> 
> 
> > isn't it the usual dust(also known as Pringles particles) breaking the surface contact inside the knob? do you have this at any volume or only at specific places on the knob?
> ...


 

 cool


----------



## saxon48

Recently picked up the non-integrated O2 + ODAC combo for $225 from a user on here to complement my HD600s. I gotta say that while pricey for me, this is certainly one of the best investments I've ever made. The amp powers my 600s so amazingly well, ahh, I can't praise these enough! <3


----------



## JacobLee89

saxon48 said:


> Recently picked up the non-integrated O2 + ODAC combo for $225 from a user on here to complement my HD600s. I gotta say that while pricey for me, this is certainly one of the best investments I've ever made. The amp powers my 600s so amazingly well, ahh, I can't praise these enough! <3


 
  
 It's safe to say that either the O2 or the ODAC themselves are a worthwhile investment.
 Even more so for anyone wanting to begin their dabbling in this headphone hobby.


----------



## Nec3

jacoblee89 said:


> It's safe to say that either the O2 or the ODAC themselves are a worthwhile investment.
> Even more so for anyone wanting to begin their dabbling in this headphone hobby.


 
 +1 to this!

 The O2 + ODAC can be customized in almost every way possible. Heck, JDS Labs will engrave the cases for you if they're purchased from their website. I changed the op amps because one blew, the op amp that came with the ODAC when I first purchased it sounds different from the ones JDS Labs sent to me recently. Heck, it's like tube rolling Solid State


----------



## 214324

Wondering how JDSLabs is doing with an ODA prototype. I've heard Mayflower has one but it might just be AGDR's ODA v2.1 board he sent them instead of their own work.


----------



## EdibleStereos

Does anybody know if the obective2 has been o-scope measured while connected to actual headphones?

 I'm wondering if it can maintain its tight specs while hooked up to the varying load of a headphone and their voicecoil.

 I'm thinking of picking up a kit or board to make a desktop version.


----------



## jring

ediblestereos said:


> Does anybody know if the obective2 has been o-scope measured while connected to actual headphones?
> 
> I'm wondering if it can maintain its tight specs while hooked up to the varying load of a headphone and their voicecoil.
> 
> I'm thinking of picking up a kit or board to make a desktop version.


 
  
 dscope... the audio analyzer brand is called dscope. The measurements published by the designer are mostly just labeled with the load (usually 15 and 150 ohms) and I think this was not actual headphones since some measurements probably would destroy them - THD vs Uout into clipping with your precious custom IEMs - any takers? Although the current limiter might actually save your phones.
  
 Some plots are labeled as taken with Sennheiser CX300 phones connected - so I would assume the others have been taken into test loads.
  
 If you want to take more realistic measurements you could try to measure real world headphones with an LCR Meter as a first step and build a corresponding dummy load with correct impedance, inductivity and capacitance, although this would need more measurements to model the dummy load more closely to the actual headphones.
  
 Joachim


----------



## diamondears

Is it possible to make the O2's headphone output to be a fixed line out (O2 volume control deactivated)?

Reason asking is I want to use my existing pre-amp for volume control as it can be remote controlled.


----------



## schmalgausen

diamondears said:


> Is it possible to make the O2's headphone output to be a fixed line out (O2 volume control deactivated)?
> 
> Reason asking is I want to use my existing pre-amp for volume control as it can be remote controlled.


 
 Normal volume control has zero resistance in MAX position.


----------



## diamondears

schmalgausen said:


> Normal volume control has zero resistance in MAX position.




So I'll just max out the O2 volume control, and I'll get normal volume levels using my pre-amp? This wouldn't damage the O2 nor get the volume on the HP too loud, yeah?


----------



## mcandmar

The input socket on the front of the amp should also give you a line out signal from the DAC, bypassing the O2 amp altogether.


----------



## diamondears

mcandmar said:


> The input socket on the front of the amp should also give you a line out signal from the DAC, bypassing the O2 amp altogether.


I only have O2, no ODAC.

My DAC's line out is connected to my integrated amp/pre-amp's line in, and the pre-out is connected to the O2's line in.


----------



## schmalgausen

Many preamps have direct line-out without voluming. I would use such out with O2 volume, because I believe onboard resistor matches with input imperdance of O2.


----------



## diamondears

schmalgausen said:


> Many preamps have direct line-out without voluming. I would use such out with O2 volume, because I believe onboard resistor matches with input imperdance of O2.


Yes, I know that. I use the Tape Out of the pre-amp. But since I can't use the pre-amp's volume control and remote control anyway, I just connect my DACs line out to the O2, and use O2's volume. 

What I wish I could do is use my pre-amp's volume and REMOTE CONTROL. If I do this, and just max out the O2's volume, this would increase the O2's output impedance? By how much?


----------



## WilliamLeonhart

A question. I have a ODAC board connected directly onto the O2 board (DIY). When I use the line-out of the ODAC (to connect to other amp or to low-impedance IEM), I've found that the sound is considerably worsened. The other amps are pretty ok (Fiio E12K and Little Dot I+ w/ 6CQ6 tubes), and the in-ear that I used were Grado iGi and Sony STH30. 
  
 The strange thing is when I use the line out of the O2, everything is fine. I don't know why this happen. Is it that when I connect 2 boards (O2 and ODAC together), the output signal of the ODAC onto the independent line-out is worsened somehow?


----------



## diamondears

williamleonhart said:


> A question. I have a ODAC board connected directly onto the O2 board (DIY). When I use the line-out of the ODAC (to connect to other amp or to low-impedance IEM), I've found that the sound is considerably worsened. The other amps are pretty ok (Fiio E12K and Little Dot I+ w/ 6CQ6 tubes), and the in-ear that I used were Grado iGi and Sony STH30.
> 
> The strange thing is when I use the line out of the O2, everything is fine. I don't know why this happen. Is it that when I connect 2 boards (O2 and ODAC together), the output signal of the ODAC onto the independent line-out is worsened somehow?


 I think you're just experiencing how good the O2 is. Without the O2, other stuff you do/use just sounds bad...


----------



## castleofargh

a DAC into an IEM is a bad move, plain and simple. the DAC is expecting an easy job going into several Kohm, not feeling like it is short circuiting into an IEM. plus you have to set volume digitally which has limits before you start crushing the music.
  
 for the rest I don't know.


----------



## diamondears

There's a reason why we need amplifiers. A DAC or CD player are never meant and designed to amplify. However, if the line outs are balanced, they can be used as good headphone outs, based on what I've read.


----------



## saxon48

There's no harm in keeping the O2+ODAC plugged into power all the time, right?


----------



## castleofargh

saxon48 said:


> There's no harm in keeping the O2+ODAC plugged into power all the time, right?


 

 I use it mostly at night as I go to bed, put on the headphone, set the computer to turn off at the end of the movie, and often turn myself OFF to sleep long before the computer ^_^. so in effect the O2 is turned ON all night most nights. doing so for more than a year now, nothing exploded yet 
	

	
	
		
		

		
			





.
 so I would guess it's pretty safe.


----------



## zowki

This is a question for people who have had the O2 for more than a year. I could never bear to use an O2 for long because I found the volume knob too stiff. Does using it for a year or more cause the volume knob to loosen and turn more smoothly? In comparison, my Leckerton UHA-6S MKII has a much smoother volume knob.
  
 Edit:
 If it helps, the O2s I've used are made by JDS and Mayflower. Perhaps other manufacturers could improve on this?


----------



## Xenophon

Strange, I own one made by Epiphany Acoustics in the UK, never had a problem with the volume knob, just smooth operation at what I consider a normal (light) level of mechanical resistance. If it hasn't broken in in a year of regular use, it never will. Send them a mail or if the warranty has lapsed, take it apart and check it out to see if you can solve tge issue yourself.


----------



## Peti

Does anyone know what is the default gain settings on the mayflower O2/Odac?


----------



## Dark_wizzie

peti said:


> Does anyone know what is the default gain settings on the mayflower O2/Odac?


 
 According to Mayflowerelectronics' Ebay listing:


> This amp will drive any headphones from 16ohm to 600 ohm headphones via the switchable gain button which comes as standard with 2x and 6.5x gain settings.


 
 Doesn't mean there's no chance to ask for different gain, that's just the default.


----------



## Xenophon

Yes but what they don't say is that with 6.5x gain, distortion increases seriously at higher volume levels.  And I'd change 'will drive *any* headphones from 16 to 600 ohm' into 'will drive *most *headphones'.  Not to detract from the good price/quality ratio but it's not the end-all of amplification.


----------



## Solrighal

This might be useful. Following advice from a serial poster in this thread I've been using my O2 connected to my Marantz PM6004 integrated stereo amp and from there out to my Dali Zensor 1's. The sound is excellent. The O2 volume control is set mid-way and my Marantz volume control roughly the same. It's perhaps worth noting that my O2 has custom gains of 1x/3x (chosen after taking more advice from another poster here). I only use 1x gain.


----------



## Xenophon

I was just about to ask why you're daisy chaining amps but then I realised you were talking about listening to speakers.  I should get myself an ODAC with RCA out, currently listening to my HE-6 on the headphone out of my Pioneer SX-1980 (about 20 WPC into 50 Ohm) but all I've got laying about here to connect it to my PC is a FiiO F17/E09K combo.  Your gain settings on the ODAC are -imo- optimal to drive most cans with good volume control/sound quality.
  
 If you'd like to experiment with speaker emulations via headphones, check out the 'Out of your head' thread here.  It's not perfect but some of the virtualizations REALLY make it sound like I'm sitting in a concert hall.


----------



## diamondears

solrighal said:


> This might be useful. Following advice from a serial poster in this thread I've been using my O2 connected to my Marantz PM6004 integrated stereo amp and from there out to my Dali Zensor 1's. The sound is excellent. The O2 volume control is set mid-way and my Marantz volume control roughly the same. It's perhaps worth noting that my O2 has custom gains of 1x/3x (chosen after taking more advice from another poster here). I only use 1x gain.


 Your O2 has an ODAC in it?


----------



## Solrighal

diamondears said:


> Your O2 has an ODAC in it?


 
  
 No, sorry. I have two separate units, the ODAC is an 'XL' version from Head'n'Hifi & my O2 is the 'Desktop' version. The ODAC has all connections on the rear panel - USB in & RCA out. The O2 also has inputs on the rear panel as well as RCA out. It's a very flexible set-up.


----------



## Rajikaru

This is my Mayflower O2+ODAC. I just put in a couple of hours of listening last night, using it to drive the 90 dB/mW Hifiman HE-560. I was satisfied at the 3-4 o'clock position on the volume knob, and I listen loud. 
  
 For exceptionally quiet tracks, the volume may have to be turned up higher. 
  
 How does it sound? Like the track being played through the sound signature of the headphone. Bass is present and has impact. 
  
 A tip for driving less sensitive headphones (90 dB/mW range): The gain settings have to be optimized.
  
 The common mistake when trying to drive a less sensitive headphone with the O2 is to switch to high gain, and if the source output voltage exceeds a certain amount (see below), and the amp is going to clip and sound harsh or broken. 
  
 To get the most output on AC power (which is the only option for an O2+ODAC anyway), 7 divided by the output of your source is the optimum gain. If the number exceeds 7, it's going to clip (*edit: regardless of volume control). For example:
  
 FiiO X5 - 1.5 V output, the optimum gain on the O2 would be 7/1.5=4.6666 which translates to a practical gain of 4 or 4.5.
 Most DACs output at 2V, so 7/2 = 3.5 optimal gain. 
  
 The default gain settings for 2.5 and 6.5 were made to account for both battery and AC usage with a variety of source input voltages:
 2-2.5V desktop DACs (use 2.5 gain)
 .5-.7V portable sources (use 6.5 gain)
  
 This is to the best of my understanding. Hopefully JDS or Mayflower will let me know if something isn't right. 
  
 Hope this helps!


----------



## headwhacker

That is about right. JDS Labs provide the option for a gain of 1x and 3.5x for O2. Which I think is the best gain combo that will maximize the use of O2 with majority of the source out there including ODAC.


----------



## Dark_wizzie

xenophon said:


> Yes but what they don't say is that with 6.5x gain, distortion increases seriously at higher volume levels.  And I'd change 'will drive *any* headphones from 16 to 600 ohm' into 'will drive *most *headphones'.  Not to detract from the good price/quality ratio but it's not the end-all of amplification.


 
 Ok, if we want to nitpick about HE-6 or the K1000s. There's an ODA for that. Even with HE-6 I'm not fond of damaging my long-term hearing.


----------



## Xenophon

I'm not nitpicking; if you use a qualifier like 'any' in a commercial context then you know what's coming if it's really 'most'.  Also, it's not a simple matter of SPL reached at a given power, that's akin to hooking up a can of compressed air to a trumpet and saying it sounds nice once it reaches x dB when you hit the regulator.  I won't enter -again- into a pointless polemic about driving it, but get yourself a HE-6 and hook it up to various amps, you'll see.


----------



## Dark_wizzie

Ok.


----------



## Peti

So the HE-6 with the O2/ODAC is a no-no combo?


----------



## Xenophon

peti said:


> So the HE-6 with the O2/ODAC is a no-no combo?


 

 Indeed, the ODAC is fine, it's the O2 that can't pull the HE-6.  Simply not enough schwung, even at low volumes it doesn't sound right.  If you're contemplating a HE-6 you need to be aware of what it is you're getting.  I consider it the best headphone I heard to date, besting my HD-800 in all fields except soundstage.  But they're a royal pain in the behind to get the best out of.


----------



## Peti

ehh, can't be harder than the HD800 to bring th best out of it


----------



## Dark_wizzie

HD800 is super easy to power when you place it next to the HE6.


----------



## Solrighal

I think if I ever do buy another pair of expensive headphones it'll be the HD 800. I'm a bit concerned that they'd be overly bright compared to the HD 650. Reports do seem to suggest that to be the case. I also might need to buy another amp which I'd be loathe to do.


----------



## Dark_wizzie

It's kindda funny that a $1000+ headphone can't nail the FR...


----------



## castleofargh

solrighal said:


> I think if I ever do buy another pair of expensive headphones it'll be the HD 800. I'm a bit concerned that they'd be overly bright compared to the HD 650. Reports do seem to suggest that to be the case. I also might need to buy another amp which I'd be loathe to do.


 

 you don't want it. it's er4s meets k701 but worst (but with bass!). on paper it's amazing, in practice every single note is grabbing your brain's attention and you can't ever hope to do anything focused while listening to the hd800. let alone relax. it's to the point where amazing is just too much to handle. and of course if you're ok with the signature of the hd650, then it will definitely be much too bright(think from 5 to 8DB to EQ down depending where you look at).
  
 no I see a much more realistic path for you. like going for something like audeze, and to buy it with the right amp, you'll have to get a shady loan in the back office of a gloomy pub. and then become a hitman for the local boss who bought back your debt. you'll be famous for killing them with headbutts thanks to the strength in the neck you'll acquire from hours with the LCD. 
  
 see! doesn't that seem a lot more reasonable than getting a hd800? 
	

	
	
		
		

		
		
	


	



  
  
 I must go now and send a scenario to luc besson(I'll just had a few Audis and a ninja so he'll feel right home.)


----------



## Xenophon

solrighal said:


> I think if I ever do buy another pair of expensive headphones it'll be the HD 800. I'm a bit concerned that they'd be overly bright compared to the HD 650. Reports do seem to suggest that to be the case. I also might need to buy another amp which I'd be loathe to do.


 

 I'm forever on the fence about selling mine but whenever I feel like I'm going to put them up for sale I give'm one more listen and their soundstage and detail are just so good with large orchestral works that I simply can't.  But I'll gladly stipulate that they're way too expensive vs some competitors (notably my HE-6 but I don't count the cost of amplification).  They get perhaps 10% of the head time my HE-6 get.  
  
 The problem is that some of their strengths, notably the resolution and detail becomes a serious weakness with less than perfect recordings (many old classical recordings) where the artefacts become so in your face that it sucks the enjoyment right out of the music.
  
 They can be a touch heavy in the treble but I don't feel it's really a weakness or a fault.  However, if you have a definite preference for the HD-650 over the 600 then I'd advise caution and yes, you might be happier with something by Audeze (or the Hifiman HE-500, best price/quality around imo).  I only heard the LCD-3 and while it's a very good headphone, it's not neutral at all and -for me at least- not suitable for classical instrumental music.


----------



## Peti

dark_wizzie said:


> HD800 is super easy to power when you place it next to the HE6.


 

 I wasn't talking about powering the HD800 but to find a proper amp (coloration, etc). But I want pure FIDELITY so the O2/ODAC is the perfect choice for me if I ever buy an HD800 again.


----------



## Rajikaru

solrighal said:


> I think if I ever do buy another pair of expensive headphones it'll be the HD 800. I'm a bit concerned that they'd be overly bright compared to the HD 650. Reports do seem to suggest that to be the case. I also might need to buy another amp which I'd be loathe to do.


 
  
 For an amp and DAC released in 2011 and 2012, with the amount of controversy and discussion it is still generating today...
  
 Other amps will come and go, but I'm keeping mine. 
  
 Two decades from now, it is either going to so ubiquitous that practically everyone will have one, or it's going to be a collector's item.


----------



## Mjolnir125

rajikaru said:


> This is my Mayflower O2+ODAC. I just put in a couple of hours of listening last night, using it to drive the 90 dB/mW Hifiman HE-560. I was satisfied at the 3-4 o'clock position on the volume knob, and I listen loud.
> 
> For exceptionally quiet tracks, the volume may have to be turned up higher.
> 
> ...


 
 Yup, the high gain setting is not for low sensitivity headphones, but rather for quiet sources using the line in. Using the high gain with the ODAC will clip if your source is also set to maximum volume and you are listening to a song that is close to the max level. Given that I only need to be at the 3 O'clock position with both my HD600s and K702's I can't imagine what would ever need more than 50% of the ODAC's output (unless you are listening to some incredibly quiet high DR stuff).


----------



## headwhacker

mjolnir125 said:


> Yup, the high gain setting is not for low sensitivity headphones, but rather for quiet sources using the line in. Using the high gain with the ODAC will clip if your source is also set to maximum volume and you are listening to a song that is close to the max level. Given that I only need to be at the 3 O'clock position with both my HD600s and K702's I can't imagine what would ever need more than 50% of the ODAC's output (unless you are listening to some incredibly quiet high DR stuff).


 
  
 The 6.5x gain was there for sources with 1 Vrms (on AC power) or below. 2.5x for anything else up to around 2.5 Vrms. This is to accomodate a wide range of sources. I believe most of the complaint about O2 clipping and not sounding right is due to source/gain mismatch.
  
 I have a DX90 @ 1.7 Vrms and O2 at 2.5x gain drives my T1 very well with the volume knob between 1 to 3 o'clock position.
  
 I have an O2+ODAC coming from JDS Labs with 1x and 3.5x gain. HE-6 is not of my wish list so I got myself covered on the DAC/Amp part for a long time. I hope


----------



## castleofargh

headwhacker said:


> mjolnir125 said:
> 
> 
> > Yup, the high gain setting is not for low sensitivity headphones, but rather for quiet sources using the line in. Using the high gain with the ODAC will clip if your source is also set to maximum volume and you are listening to a song that is close to the max level. Given that I only need to be at the 3 O'clock position with both my HD600s and K702's I can't imagine what would ever need more than 50% of the ODAC's output (unless you are listening to some incredibly quiet high DR stuff).
> ...


 

 not a surprise really. more than half the people I talk to that are already into audio, so more than half of a very precise population target, have no clue about how to use gain settings and go with the usual moaaaarrrrr is better idea that leads to really messed up things. like clipping when it shouldn't, or people crying over the very huge channel imbalance while using sensitive IEMs on high gain or simply the fact that the volume level is harder to set...
 I'm very sure a lot of the dissatisfied users with the O2 were themselves the cause of the problem. that and those who expect an amp to sound "different". those guys will never like anything transparent obviously.
  
 I think that having the X1 gain is a good start for 90% of headphones/IEMs. then 2.5 or 6times the gain should be picked in accordance to our harder to drive headphone.
 that way I see very little reason to be dissatisfied.


----------



## headwhacker

castleofargh said:


> not a surprise really. more than half the people I talk to that are already into audio, so more than half of a very precise population target, have no clue about how to use gain settings and go with the usual moaaaarrrrr is better idea that leads to really messed up things. like clipping when it shouldn't, or people crying over the very huge channel imbalance while using sensitive IEMs on high gain or simply the fact that the volume level is harder to set...
> I'm very sure a lot of the dissatisfied users with the O2 were themselves the cause of the problem. that and those who expect an amp to sound "different". those guys will never like anything transparent obviously.
> 
> I think that having the X1 gain is a good start for 90% of headphones/IEMs. then 2.5 or 6times the gain should be picked in accordance to our harder to drive headphone.
> that way I see very little reason to be dissatisfied.


 
  
 It's a shame really. A lot of people insist that high gain always sound better even for sensitive iems. Then complain if they hear a hiss.


----------



## jseaber

rajikaru said:


> To get the most output on AC power (which is the only option for an O2+ODAC anyway), 7 divided by the output of your source is the optimum gain. If the number exceeds 7, it's going to clip eventually as the volume gets turned up. For example:
> 
> FiiO X5 - 1.5 V output, the optimum gain on the O2 would be 7/1.5=4.6666 which translates to a practical gain of 4 or 4.5.
> Most DACs output at 2V, so 7/2 = 3.5 optimal gain.
> ...


 
  
 Best summary I've seen in a long time.
  
 Default gain of our custom O2+ODACs is 1.0/3.5x, which is optimal as long as the O2+ODAC is driven by its own DAC. It makes sense to increase gain only if you plan to listen from from a weaker external source, or if the majority of your music is recorded well below 0dB.


----------



## adydula

Yup that makes perfect sense...

 Alex


----------



## bada bing

rajikaru said:


> The common mistake when trying to drive a less sensitive headphone with the O2 is to switch to high gain, and if the source output voltage exceeds a certain amount (see below), and the amp is going to clip and sound harsh or broken.
> 
> To get the most output on AC power (which is the only option for an O2+ODAC anyway), 7 divided by the output of your source is the optimum gain. If the number exceeds 7, it's going to clip eventually as the volume gets turned up. For example:
> 
> ...


 
  
  


jseaber said:


> Best summary I've seen in a long time.
> 
> Default gain of our custom O2+ODACs is 1.0/3.5x, which is optimal as long as the O2+ODAC is driven by its own DAC. It makes sense to increase gain only if you plan to listen from from a weaker external source, or if the majority of your music is recorded well below 0dB.


 
  
 Actually, this is a bit confusing. The O2 has very unusual clipping behavior and clips *only* based on the level of the input. The O2's volume control has no effect at all on clipping behavior. The 7v / the output voltage level of the source is a useful rule of thumb, but brings up a consequence of the clipping behavior - the maximum power output is produced without clipping at only one input level. You can not adjust the O2 to maximum power output below clipping by using the O2's volume pot. This is different that just about every other amp on the market. Not important unless the discussion is about "hard to drive" headphones. The O2 has only a moderate output on paper, but in practical real world use it is even less. Recorded material doesn't stick very well to the 0 db standard recording level, which makes it impossible to set the gain at a level that allows the O2 to produce it's maximum rated unclipped output power with a typical random selection of recorded material. A workaround would be to use  digital software volume control in conjunction with the gain settings, but that's somewhat problematic.
  
 All this isn't important until the discussion turns to "hard to drive" headphones, but the discussion seems to go there somewhat often. The O2's design objectives were "numbers first" and as a consequence the full rated power of the amp is less usable in the real world. Understanding the unusual design trade offs that were made to generate the last bit of measurement benefit is necessary for max power usage.


----------



## Rajikaru

jseaber said:


> Best summary I've seen in a long time.
> 
> Default gain of our custom O2+ODACs is 1.0/3.5x, which is optimal as long as the O2+ODAC is driven by its own DAC. It makes sense to increase gain only if you plan to listen from from a weaker external source, or if the majority of your music is recorded well below 0dB.


 
  
 Thanks!
  


bada bing said:


> Actually, this is a bit confusing. The O2 has very unusual clipping behavior and clips *only* based on the level of the input. The O2's volume control has no effect at all on clipping behavior.


 
  
 Understood. Edited my original post.


----------



## HotIce

I wonder if anyone ever tried to replicate the measures posted online in terms of power output.
 One thing which struck me, is how an amp rated for 630+mW on 33 ohms, which would require over 130mA of RMS (assuming power figures in the most noted web sites are RMS) current, would work with the original NJM4556AD current stage opamp, which is rated at 70mA peak.


----------



## jseaber

hotice said:


> I wonder if anyone ever tried to replicate the measures posted online in terms of power output.
> One thing which struck me, is how an amp rated for 630+mW on 33 ohms, which would require over 130mA of RMS (assuming power figures in the most noted web sites are RMS) current, would work with the original NJM4556AD current stage opamp, which is rated at 70mA peak.


 
  
 We've replicated every test and verified each specification by published NwAvGuy on Objective2 and ODAC. All measurements are legitimate, if not slightly conservative.
  
 Objective2 uses two, parallel NJM4556 ICs _per channel_. Available current handling is doubled to 2*70 = 140mA.


----------



## HotIce

jseaber said:


> We've replicated every test and verified each specification by published NwAvGuy on Objective2 and ODAC. All measurements are legitimate, if not slightly conservative.
> 
> Objective2 uses two, parallel NJM4556 ICs _per channel_. Available current handling is doubled to 2*70 = 140mA.


 
  
 I see, thanks. I finally been able to find a schematic which is bigger than 200x200 pixels 
	

	
	
		
		

		
		
	


	



 So it is 630mW peak on 33 ohms, right?


----------



## diamondears

jseaber said:


> We've replicated every test and verified each specification by published NwAvGuy on Objective2 and ODAC. All measurements are legitimate, if not slightly conservative.
> 
> Objective2 uses two, parallel NJM4556 ICs _per channel_. Available current handling is doubled to 2*70 = 140mA.


 

Hello there John. 

Is there a plan to make a much more portable O2? Is that even possible with the license and present design?

Also, is there an existing portable amp out there whose design is based or similar to the O2 and ODAC?

Cheers.


----------



## jseaber

hotice said:


> I see, thanks. I finally been able to find a schematic which is bigger than 200x200 pixels
> 
> 
> 
> ...


 
  
 O2 produces 613mW @ 33 ohms.
  


diamondears said:


> Hello there John.
> 
> Is there a plan to make a much more portable O2? Is that even possible with the license and present design?
> 
> ...


 
  
 Modifying O2 breaks the license. Even disregarding the license, it makes no engineering sense to modify O2. A portable (or desktop) amp should be designed from the ground up with desired features and performance in mind. It's quite possible to design an amp with equal or greater performance than O2. We've done so several times in the past two years (sorry, cannot share R&D!).
  
 Battery capacity is the greatest limitation when designing a portable amp. The market has shifted dramatically since 2011, and I think there's a strange obsession now with max output power. Sure, it's important to adequately power headphones, but most portable users have high sensitivity sets which are easily driven by an amp with much less power than O2:
  

[SPL Chart Data]
  
 We could design a portable amp that blows away O2 in terms of max output power, but I think doing so is unnecessary. Run-time for 1W of output power would be incredibly short, even with a large Li-Ion battery; run time would be fine when driving efficient headphones and/or listening at moderate volumes. Again, portable users typically do not need more so much power. Driving truly demanding headphones necessitates AC power.


----------



## diamondears

jseaber said:


> O2 produces 613mW @ 33 ohms.
> 
> 
> Modifying O2 breaks the license. Even disregarding the license, it makes no engineering sense to modify O2. A portable (or desktop) amp should be designed from the ground up with desired features and performance in mind. It's quite possible to design an amp with equal or greater performance than O2. We've done so several times in the past two years (sorry, cannot share R&D!).
> ...


 I'm with you re not needing too much power. Most portables out there are more than enough even for HPs. 

What I wish is to have an O2 in a truly portable build. O2's present power and battery life is more than enough for me. What I think would be great is to use its excellent transparency into the usual/popular portable build plus its present battery life and power.


----------



## jseaber

diamondears said:


> I'm with you re not needing too much power. Most portables out there are more than enough even for HPs.
> 
> What I wish is to have an O2 in a truly portable build. O2's present power and battery life is more than enough for me. What I think would be great is to use its excellent transparency into the usual/popular portable build plus its present battery life and power.


 
  
 Understood!
  
 O2 is as small as possible with its dual 9V batteries. Fitting into a smaller case would require replacement of its entire power supply circuitry to accommodate a Li-Ion. This would mean a new design that should not carry the Objective name, in my opinion.


----------



## diamondears

jseaber said:


> Understood!
> 
> O2 is as small as possible with its dual 9V batteries. Fitting into a smaller case would require replacement of its entire power supply circuitry to accommodate a Li-Ion. This would mean a new design that should not carry the Objective name, in my opinion.


 Is there something like that already in the works? Or is it out already (C5/C5D)? What's the differences between C5/C5D and O2/ODAC aside from the physical/build?


----------



## HotIce

When I compared the O2 and the FIIO E12, I could not tell them apart, sound wise.
 I ended up with the E12 because of portability, and the ability to power/charge via USB.
 I also like more the E12 design with the diamond buffer within the feedback loop, and the higher P2P voltage swing, but again, this made no practical difference as I could not have told them apart in a blind test.


----------



## Peti

What? The JDSLAbs C5/C5D use the same NWAVGuy stuff as in the O2/ODAC??


----------



## Rajikaru

The original design decision to go with dual 9V batteries have always appealed to me, because lithium ion batteries on competing solutions (such as the mentioned FiiO E12) have a finite lifespan. 

 Unless they are sent back to the manufacturer for battery replacement, which would involve shipping and labor costs, along with cost of the battery, it would also make the lifespan of device itself shorter by inheritance.  

 The O2s dual 9V batteries will of course have to be replaced eventually, but those are available everywhere, affordable, and easily user replaceable.  

 That being said, I'm very interested in the AC powered ODA.
  
 The O2 is currently a conditional recommendation for a 88-90dB/mW headphone such as the HE-560, with the conditions being that the gain settings are optimized to 7/input voltage (AC power only). An ODA with 3x the max continuous output and multiple gain settings would remove that condition.


----------



## HotIce

Shouldn't be that bad on the E12. Remove two screws, slide the circuitry, and replace the battery pack.
 According to FIIO info, the E12 has an 11V pack, charge pumped to create +/-11V rails.


----------



## jseaber

peti said:


> What? The JDSLAbs C5/C5D use the same NWAVGuy stuff as in the O2/ODAC??


 
  
 No, not at all! You'll see from benchmarks that C5D and O2+ODAC both perform extremely well. O2+ODAC has a more powerful amplifier.
  


diamondears said:


> Is there something like that already in the works? Or is it out already (C5/C5D)? What's the differences between C5/C5D and O2/ODAC aside from the physical/build?


 
  
 Sorry, I cannot share our R&D projects. C5D has a completely different design topology than O2+ODAC. The main differences are portability and output power:
  
*C5D*

Single opamp per channel / Peak output of 
63 step digital potentiometer; perfect channel balance
+/-7VDC operating voltage
USB rechargeable Li-Ion Battery
DAC: Self-powered SA9027 + PCM5102A
  
 *O2+ODAC*

3 Opamps per channel
Analog potentiometer
+/- 12VDC operating voltage
AC operation only
DAC: USB powered TE7022L + ES9023


----------



## zealsoijun

Light Harmonic Geek Out 1000 over all.


----------



## castleofargh

they both use volts!!!!  you're caught red handed


----------



## Rajikaru

zealsoijun said:


> Light Harmonic Geek Out 1000 over all.


 
  
  
 Yeah it's cool...
  
 Geek Out 1000: 4.3 Vrms
 Output at 32 Ohms = 4.32/32 = 577 mW
 Output at 50 Ohms 4.32/50 = 369 mW
  
 But it's not exactly a power upgrade either.


----------



## diamondears

jseaber said:


> No, not at all! You'll see from benchmarks that C5D and O2+ODAC both perform extremely well. O2+ODAC has a more powerful amplifier.
> 
> 
> Sorry, I cannot share our R&D projects. C5D has a completely different design topology than O2+ODAC. The main differences are portability and output power:
> ...


 Thanks, John. Very looking forward to what your R&D is working on now. 

Cheers.


----------



## theodoro

Hello guys, 
 I finally got my O2 and i used it for about 5 days. I really like it   So far i used it with my HD600 and DT990 Pros (250omhs) and i can say it made both headphones sound more natural (which i didn't expect with the DT990s)  and more detailed. However i didn't hear a HUGE difference or that the headphones NEED the amplification since i don't believe it's a night/day difference. 
 My DAC is the crappy PC on-board DAC, so my question is: will the Odac improve even more the sound quality or i should expect the same improvement?


----------



## diamondears

theodoro said:


> Hello guys,
> I finally got my O2 and i used it for about 5 days. I really like it   So far i used it with my HD600 and DT990 Pros (250omhs) and i can say it made both headphones sound more natural (which i didn't expect with the DT990s)  and more detailed. However i didn't hear a HUGE difference or that the headphones NEED the amplification since i don't believe it's a night/day difference.
> My DAC is the crappy PC on-board DAC, so my question is: will the Odac improve even more the sound quality or i should expect the same improvement?


 
 I suggest get an excellent DAC. It's where the "tweaking" happens. Suggest also to get a DAC with multiple digital filter options that you can toggle while listening to your music. There are digital-sounding filters, analogue-sounding, and there's somewhere in between...


----------



## theodoro

diamondears said:


> I suggest get an excellent DAC. It's where the "tweaking" happens. Suggest also to get a DAC with multiple digital filter options that you can toggle while listening to your music. There are digital-sounding filters, analogue-sounding, and there's somewhere in between...


 I have no idea what "digital filters" are. I would get an Odac, but if you have an other suggestions at the same money with rcas, I would love to hear them


----------



## castleofargh

diamondears said:


> theodoro said:
> 
> 
> > Hello guys,
> ...


 

 I suggest the opposite ^_^.
 to me most DACs should and will sound about the same and tweaking should happen with the headphone's choice(or some EQ). 
 having several filter choices is like having a choice between good filtering and bad ones. I trust the engineer making the DAC to test and find out what system offers the best result. but of course I'm thinking maximum fidelity when I think DAC. others do believe that DACs have to sound differently just like amps.


----------



## WilliamLeonhart

Get the O2. It all depends on your budget, but I think in term of value, nothing beats the O2 in that price range. I've been without my ODAC for 3 weeks and have to make do with the SteelSeries soundcard. Def. not the stuff for music.


----------



## HotIce

castleofargh said:


> I suggest the opposite ^_^.
> to me most DACs should and will sound about the same and tweaking should happen with the headphone's choice(or some EQ).
> having several filter choices is like having a choice between good filtering and bad ones. I trust the engineer making the DAC to test and find out what system offers the best result. but of course I'm thinking maximum fidelity when I think DAC. others do believe that DACs have to sound differently just like amps.



I do think sound is made where signal converts from mechanical to electric and vice versa.
Sound waves to mic, it's the first step.
Back than, vinyl groves to voltage via turntable head.
Today there's no such step and we go from voltage to sound waves via speakers.
Anything in the middle if decently designed, should have minor effects.
That's the engineer in me talking 

Despite that, even if I cannot tell much differences, I do feel fatigue when listening certain components, which I do not feel with others.
That is pretty repeatable experience.


----------



## diamondears

castleofargh said:


> I suggest the opposite ^_^.
> to me most DACs should and will sound about the same and tweaking should happen with the headphone's choice(or some EQ).
> having several filter choices is like having a choice between good filtering and bad ones. I trust the engineer making the DAC to test and find out what system offers the best result. but of course I'm thinking maximum fidelity when I think DAC. others do believe that DACs have to sound differently just like amps.


 

 Not with my DACs. There are differences between selectable filters in DACs...well, some DACs. Your recording, player and HP has to be up to it though.
  
 Engineer decides which filter is best---shouldn't the decision maker be us who will listen to the music and use the gears that we choose?


----------



## headwhacker

diamondears said:


> Not with my DACs. There are differences between selectable filters in DACs...well, some DACs. Your recording, player and HP has to be up to it though.
> 
> Engineer decides which filter is best---shouldn't the decision maker be us who will listen to the music and use the gears that we choose?


 
  
 I think the point was filtering should be done by EQ or by the specific headphone to get the SQ you desire. DACs and amps should be transparent or unfiltered at all. The idea of O2+ODAC is a wire with gain between the music and the headphone. Coloration should be done on either ends and not in between.


----------



## Rajikaru

diamondears said:


> Engineer decides which filter is best---shouldn't the decision maker be us who will listen to the music and use the gears that we choose?


 
  
 Only if they want to think about it...
  
 Some prefer to roll many variables and turn it into a mad science project:
 Roll DAC * Roll DAC filters * Roll Amp * Roll tubes * Roll opamps * Roll cables * Roll headphone pads...
  
 Some prefer simplicity - "If it isn't broken, don't fix it":
 Transparent DAC + Transparent Amp + Headphone Sound Signature (All Stock)
  
 or something in between.
  
 De gustibus et coloribus non est disputandum 
 "There can be no disputing matters of taste and colors."


----------



## diamondears

rajikaru said:


> Only if they want to think about it...
> 
> Some prefer to roll many variables and turn it into a mad science project:
> Roll DAC * Roll DAC filters * Roll Amp * Roll tubes * Roll opamps * Roll cables * Roll headphone pads...
> ...


 

 Completely agree. I just want to roll DAC filters... One of the filters should be transparent, I agree. But my DAC now, oh wow, there are 5 filters on them that I consider transparent......don't know which one is actually the truly transparent one. With all 5, the sound changes as I change my upstream gear.


----------



## adamlr

theodoro said:


> Hello guys,
> I finally got my O2 and i used it for about 5 days. I really like it   So far i used it with my HD600 and DT990 Pros (250omhs) and i can say it made both headphones sound more natural (which i didn't expect with the DT990s)  and more detailed. However i didn't hear a HUGE difference or that the headphones NEED the amplification since i don't believe it's a night/day difference.
> My DAC is the crappy PC on-board DAC, so my question is: will the Odac improve even more the sound quality or i should expect the same improvement?


 
  
 when you say your dac is an on-board pc dac, im assuming that youre connecting your new O2 to the computer via the headphone jack? if so, your not only using your onboard dac, but are infact using both the onboard dac and the onboard amp - the signal coming out of the headphone jack is already post amplification, and passing that signal through the O2 is infact "double amping".
 hypothetically, if there was a way to change the computers settings that would make the headphone jack a line-out, and the signal came directly from the dac to the output (bypassing the onboard amp), then you could tell the dac and amp apart, because you would use the O2 as a single amp - and maybe youd discover it was actually the onboard amp that was crappy. however, i have no idea if such an option exists.
  
 would the Odac improve the sound quality? well the odac connects to the pc via usb cable, it doesnt receive a signal, it receives data. that data is converted to a signal (Digital to Analog Converter) which is passed clean onto the amp. the idea behind the Objective bunch is that theyre meant to do these things as transparently and accurately as possible. so if your onboard dac or amp are infact as crappy as you say they are, the Odac will definitely give you a more accurate sound. i believe thats what most O2 users would call quality (although ofcourse i may be wrong).
  
 on a personal note, i think the recording/mixing quality, and the file quality are the ones that make the most difference. when i decided on getting an external dac, it was because my headphone jack was hissy and it was driving me mad. other than that hiss, i cant say the difference blew my mind, but it was definitely worth it in my own, very humble opinion. ive been using the O2 and Odac for over a year and have no complaints. 
  
  


castleofargh said:


> to me most DACs should and will sound about the same and tweaking should happen with the headphone's choice(or some EQ).


 
  
 +1


headwhacker said:


> The idea of O2+ODAC is a wire with gain between the music and the headphone. Coloration should be done on either ends and not in between.


 
  
 my thoughts exactly
  


rajikaru said:


> Some prefer to roll many variables and turn it into a mad science project:
> Roll DAC * Roll DAC filters * Roll Amp * Roll tubes * Roll opamps * Roll cables * Roll headphone pads...


 
  
 some would rather have control over the process =]
  
 different approaches, but which is actually more like a science project? which one may be more cost effective? does that matter? or is it all just about having fun? would a new toy make me as happy as some new music? ahh the questions we face


----------



## diamondears

I think many assume that there is a DAC that fits all---100% transparent. No. And the reason is each and all DACs use a digital filter. That digital filter can never be 100% transparent like vinyl gear. This is the main consequence of using digital technology. At any price. 

Therefore, every DAC introduces a tweak on the recording, it's just the gravity that's different with each DAC. That tweak is due to the DAC chip, implementation and the DAC filter used. 

Now, assuming everything else equal, the most influential factor to the sound is the DAC filter. This is why every DAC using the same type of DAC filter has a similar sound quality/characteristic. In fact the most consistent influence in a DAC's sound characteristic is the DAC filter. 

What many considers as the most transparent, objectively, is what's commonly known as the linear phase filter, which is used in our beloved ODAC. 

But as in the case of anything digital, there's a trade-off, and, in the case of linear phase filter, that would be pre-ringing and post-ringing of certain frequencies especially in the uppermost frequencies. So even the linear phase would sound "digitally", though perfect and, in fact, the best, IMHO, in terms of transparency and, as I said, measurements. 

So, if we use another filter that removes those pre-ringing and/or post-ringing, there's nothing wrong with it as in fact we're trying to even improve the close perfect, objectively, linear phase. But as there's trade-off in anything digital, again, 100% transparent isn't possible. 

So using another digital filter to remove/reduce those pre and post ringings is still not 100% transparent, BUT could be closer to your subjective measurements based on the music you listen to and prefer. This preference is different in every person. So different filters, IMHO, should be interchangeable in a DAC. 

Personally, I prefer the minimum phase filter, because it removes the pre-ringing, which IMHO is the main reason for that "digitally" sound. This filter doesn't remove post-ringing, which for me is alright because real live analogue sound has post-ringing as well (think echoes, reverberations, and the like). However, as said, there's a trade-off, and in the case of minimum phase filter, that would be time domain differences/delays and slight-roll-off of the upper frequencies. In my ears, these trade-off doesn't make the sound "digitally", it just makes the sound a tiny bit more "scattered", for lack of better term. On the lower registers/frequencies, this makes the bass bit more/bigger. On the upper frequencies, I can't discern it much, and I think that's because of the un-corrected and existing post-ringing, which offsets the high frequency roll-off. IMHO, this post-ringing gives out a better soundstage. 

So I sincerely suggest a DAC with good DAC chip, good implementation and interchangeable multiple filters that preferably includes linear and minimum phase filters.


----------



## HaVoC-28

adamlr said:


> when you say your dac is an on-board pc dac, im assuming that youre connecting your new O2 to the computer via the headphone jack? if so, your not only using your onboard dac, but are infact using both the onboard dac and the onboard amp - the signal coming out of the headphone jack is already post amplification, and passing that signal through the O2 is infact "double amping".
> hypothetically, if there was a way to change the computers settings that would make the headphone jack a line-out, and the signal came directly from the dac to the output (bypassing the onboard amp), then you could tell the dac and amp apart, because you would use the O2 as a single amp - and maybe youd discover it was actually the onboard amp that was crappy. however, i have no idea if such an option exists.


 
  
  
 Most onboard audiochips don't have an headphone amp , it's only a plain line out , with a limited output power/voltage and a high impedance output (well an line out ) . But now with the ALC 1150 their is more and more , what you can say an headphone amp for the onboard audio chip . He has to check what is the audio chip and if their is an headphone amp .
  


diamondears said:


> Personally, I prefer the minimum phase filter, because it removes the pre-ringing, which IMHO is the main reason for that "digitally" sound. This filter doesn't remove post-ringing, which for me is alright because real live analogue sound has post-ringing as well (think echoes, reverberations, and the like). However, as said, there's a trade-off, and in the case of minimum phase filter, that would be time domain differences/delays and slight-roll-off of the upper frequencies. In my ears, these trade-off doesn't make the sound "digitally", it just makes the sound a tiny bit more "scattered", for lack of better term. On the lower registers/frequencies, this makes the bass bit more/bigger. On the upper frequencies, I can't discern it much, and I think that's because of the un-corrected and existing post-ringing, which offsets the high frequency roll-off. IMHO, this post-ringing gives out a better soundstage.
> 
> So I sincerely suggest a DAC with good DAC chip, good implementation and interchangeable multiple filters that preferably includes linear and minimum phase filters.


 
  
 And you have confirmed your thoughts on the effects of DAC filters with an blinded double ABX ? (well we are on a ODAC/O² thread so ) .


----------



## diamondears

havoc-28 said:


> Most onboard audiochips don't have an headphone amp , it's only a plain line out , with a limited output power/voltage and a high impedance output (well an line out ) . But now with the ALC 1150 their is more and more , what you can say an headphone amp for the onboard audio chip . He has to check what is the audio chip and if their is an headphone amp .
> 
> 
> And you have confirmed your thoughts on the effects of DAC filters with an blinded double ABX ? (well we are on a ODAC/O² thread so ) .


 Yes on the differences between different filters. Different type of DAC filter sounds different to me, and it's substantial. 

Differences in sound of different DAC unit using the SAME filter, which most people A/B or compare or demo, are always the SAME to my ears of other things are equal.


----------



## headwhacker

My new Samurai X themed O2+ODAC from JDS Labs. The free engraving turns out to be great. I didn't expect it would cover the whole area on the top.


----------



## diamondears

headwhacker said:


> My new Samurai X themed O2+ODAC from JDS Labs. The free engraving turns out to be great. I didn't expect it would cover the whole area on the top.


 Nice.


----------



## Solrighal

I'd quite like to remove the screenprinting on my O2 & ODAC. Does anyone know a way to do this without damaging the faceplate? Rubbing alcohol perhaps?


----------



## JacobLee89

solrighal said:


> I'd quite like to remove the screenprinting on my O2 & ODAC. Does anyone know a way to do this without damaging the faceplate? Rubbing alcohol perhaps?


 
 If it's the JDS labs ODAC, I think that's done by laser engraving and you'll have to "remove" the rest of the coating.
  
 Just did a scratch test on the ODAC on a part that was already scratched, and realised that the logo was done by using a colour removal method using laser etching. This is also a method used on some higher end gaming keyboards as well to ensure that the text on the keys don't wear out.
  
 For nay sayers, here's an example of colour removal via laser etching:
  

  
 This means that the only way to remove the visuals, is to either repaint it entirely, or to strip everything down.


----------



## Solrighal

Thanks for the info Jacob. My O2 is from Head'n'Hifi and I'm pretty sure it's just printed on. I'll try and find some rubbing alcohol and give it a bash. There's nothing to lose as I'll never sell my O2 or ODAC, they're far too good to lose.


----------



## Rajikaru

headwhacker said:


> My new Samurai X themed O2+ODAC from JDS Labs. The free engraving turns out to be great. I didn't expect it would cover the whole area on the top.


 
  
 Very cool how the image goes over the top grooves on the casing, and how the grooves work with the symmetry in the image. 
  
 I had one engraved by JDS Labs as well, and it's beautiful.


----------



## jseaber

solrighal said:


> I'd quite like to remove the screenprinting on my O2 & ODAC. Does anyone know a way to do this without damaging the faceplate? Rubbing alcohol perhaps?


 


solrighal said:


> Thanks for the info Jacob. My O2 is from Head'n'Hifi and I'm pretty sure it's just printed on. I'll try and find some rubbing alcohol and give it a bash. There's nothing to lose as I'll never sell my O2 or ODAC, they're far too good to lose.


  

 We have inventory of scratch-and-dent endplates which have not been engraved. Send a picture of the plate you need via email or PM and we'll hook you up (no cost)!


----------



## Solrighal

jseaber said:


> We have inventory of scratch-and-dent endplates which have not been engraved. Send a picture of the plate you need via email or PM and we'll hook you up (no cost)!


 
  
 Colour me blown away! This is a very nice offer John. This is the second time I've written this out because I initially thought my O2 was different in having a 6.3mm output on the front panel. Then I checked your site and I see that you do a 'Custom' version with this same output.
  
 Still, I'm in Scotland and the postage wouldn't be worth your while. The kindness is noted though and I won't hesitate to send any business I can your way. Actually, I do anyway. I've always admired your company philosophy.
  
 Here's a photo of my O2 / ODAC to demonstrate just how unobtrusive they can be in the desktop environment. I'm turning into an evangelist 
  
 Paint tins as monitor stands? Indeed, made of plastic and filled with gravel from the driveway. Simple & free.


----------



## castleofargh

you've fooled us for years zorro, but now I see on the pics that your solid state love was only propaganda.
  you busted yourself, we can all see the big glowing tube at the top of your audio system!


----------



## Solrighal

Lol, according to my wife I'm the big glowing tube


----------



## diamondears

Would it be possible for the O2 to be balanced considering it's design? Is the design inherently SE? Is there a good reason the designer made it SE aside from cost issues?


----------



## adydula

If you read his blogs he mentions that to him there is no real need for a balanced amp in terms of sound quality etc... compared to an SE amp. Also the added cost and parts is basically against what he was trying to do etc..
  
 That said a balanced O2 "type" amp could be made.
  
 Alex


----------



## Ali-Pacha

Until now I had only one HD600 to hook on my O2, but K7xx is coming 
	

	
	
		
		

		
		
	


	



  
 Ali


----------



## diamondears

adydula said:


> If you read his blogs he mentions that to him there is no real need for a balanced amp in terms of sound quality etc... compared to an SE amp. Also the added cost and parts is basically against what he was trying to do etc..
> 
> That said a balanced O2 "type" amp could be made.
> 
> Alex


 

 Thanks.


----------



## doublin

Silly question. Can I unplug the battery from my standalone O2 so that it will only run through the AC adapter I'm using? I'm currently am using the O2 as my desktop amp and not planning to use it for portable use. Sorry if it has been answered before.
  
 EDIT: Used the search button and stumbled upon this: http://www.head-fi.org/t/616331/o2-amp-odac/3480#post_10932475 . So I'm guessing that it CAN be used without batteries, then?


----------



## diamondears

doublin said:


> Silly question. Can I unplug the battery from my standalone O2 so that it will only run through the AC adapter I'm using? I'm currently am using the O2 as my desktop amp and not planning to use it for portable use. Sorry if it has been answered before.
> 
> EDIT: Used the search button and stumbled upon this: http://www.head-fi.org/t/616331/o2-amp-odac/3480#post_10932475 . So I'm guessing that it CAN be used without batteries, then?


 Why do you need to remove the batteries? You'll need it when you used the money for electricity to buy another HP...


----------



## chrislangley4253

doublin said:


> Silly question. Can I unplug the battery from my standalone O2 so that it will only run through the AC adapter I'm using? I'm currently am using the O2 as my desktop amp and not planning to use it for portable use. Sorry if it has been answered before.
> 
> EDIT: Used the search button and stumbled upon this: http://www.head-fi.org/t/616331/o2-amp-odac/3480#post_10932475 . So I'm guessing that it CAN be used without batteries, then?


 
 You can use it without batteries, but I dunno why you would want to remove the portable functionality.


----------



## doublin

chrislangley4253 said:


> You can use it without batteries, but I dunno why you would want to remove the portable functionality.


 
 Might be an incorrect statement, but wouldn't connecting the O2 power adapter even after the battery is full _might _damage the battery? Kinda like leaving a phone charged even after the battery is full. Of course, this is just my assumption.


----------



## chrislangley4253

doublin said:


> Might be an incorrect statement, but wouldn't connecting the O2 power adapter even after the battery is full _might _damage the battery? Kinda like leaving a phone charged even after the battery is full. Of course, this is just my assumption.


 
 Negative, there is a charging circuit in anything that uses rechargable batteries to prevent this from happening. At least, anything that is well designed.. Same thing goes for your phone, except there may be a circuit in the charger as well as the phone in that case. Designers anticipate this problem.


----------



## doublin

chrislangley4253 said:


> Negative, there is a charging circuit in anything that uses rechargable batteries to prevent this from happening. At least, anything that is well designed.. Same thing goes for your phone, except there may be a circuit in the charger as well as the phone in that case. Designers anticipate this problem.


 
 So, it's safe for me to just keep powering the O2 with the AC adapter with the batteries then? That's good to know.


----------



## chrislangley4253

doublin said:


> So, it's safe for me to just keep powering the O2 with the AC adapter with the batteries then? That's good to know.


 
 Yup! I'm sure others will chime in with the same answer, or if I am wrong


----------



## diamondears

chrislangley4253 said:


> Yup! I'm sure others will chime in with the same answer, or if I am wrong


 I think maybe the O2 wouldn't work without the battery in there even if the adaptor is plugged. Maybe the AC current has to pass thru the batteries to get thru? But I'm not sure.


----------



## headwhacker

O2 will work without the batteries and powered only by an AC adaptor. It's better to leave the battery out if you are just going to use O2 as a desktop amp and no intention of using it as a portable.


----------



## adydula

If you leave the batteries in and use AC, once in awhile disconnect the AC power and use the batteries and run them down so they will be recharged. If you don't do this your batteries will most likely have a shorter lifespan.
  
 Alex


----------



## doublin

adydula said:


> If you leave the batteries in and use AC, once in awhile disconnect the AC power and use the batteries and run them down so they will be recharged. If you don't do this your batteries will most likely have a shorter lifespan.
> 
> Alex


 
 I don't quite understand. Does it mean that in order to have a longer battery lifespan, I should leave them on while running on AC?


----------



## Solrighal

Batteries like to go through the charge cycle every so often, it keeps them fresh. However, if you're never likely to use the O2 as a portable then there's no point in them being in there. Other than to add a little mass to counter the tugging of cables.


----------



## jcx

batteries differ by chemistry as to what they want - NiMH don't really like float/trickle charge - more recent formulations may withstand it better than older ones
  
http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride
  
 NiMH is the more common rechargable "9 V" battery today
  
 the O2 charging circuit isn't smart enough to give good battery cycle life - but it usually isn't critical


----------



## adydula

If you don't need the batteries then just take them out.
 Alex


----------



## diamondears

adydula said:


> If you don't need the batteries then just take them out.
> Alex


 Is there anything bad that might happen if you leave them there but permanently plug the AC adaptor? Batteries exploding like mad and destroying my headphones 1 foot farther? What would be the extent of damage? What's the radius of the explosion and after effects? Does this cause radiation? Do I have to wear masks? Is there an antidote?


----------



## WilliamLeonhart

headwhacker said:


> My new Samurai X themed O2+ODAC from JDS Labs. The free engraving turns out to be great. I didn't expect it would cover the whole area on the top.


 
 Look nice.
  
 My O2 and ODAC is DIY from JDS'boards. I'm thinking of wrapping them in giftwrap paper (the ODAC is put inside a plastic box, the O2 a metal one).


----------



## diamondears

adydula said:


> If you leave the batteries in and use AC, once in awhile disconnect the AC power and use the batteries and run them down so they will be recharged. If you don't do this your batteries will most likely have a shorter lifespan.
> 
> Alex





diamondears said:


> Is there anything bad that might happen if you leave them there but permanently plug the AC adaptor? Batteries exploding like mad and destroying my headphones 1 foot farther? What would be the extent of damage? What's the radius of the explosion and after effects? Does this cause radiation? Do I have to wear masks? Is there an antidote?


Seriously, would the battery explode or leak if I permanently plug the AC adaptor like a desktop amp?


----------



## headwhacker

diamondears said:


> Seriously, would the battery explode or leak if I permanently plug the AC adaptor like a desktop amp?


 
  
 I don't think it will explode. It just make the lifespan very short.


----------



## diamondears

headwhacker said:


> I don't think it will explode. It just make the lifespan very short.


 Thanks.


----------



## diamondears

Does any of you have the customized O2 with 6.5mm HP out jack and RCA inputs? Do you find the sound different from the regular 3.5mm out and in? 

I find my customized O2 better at the low frequencies. I'm serious.


----------



## Solrighal

diamondears said:


> Does any of you have the customized O2 with 6.5mm HP out jack and RCA inputs? Do you find the sound different from the regular 3.5mm out and in?
> 
> I find my customized O2 better at the low frequencies. I'm serious.


 
  
 It ahould make no difference at all.


----------



## diamondears

solrighal said:


> It ahould make no difference at all.


 Yeah. I'm thinking it might be the RCA-3.5mm adaptor I'm using before on the regular issue O2. The adaptor prolly reduced the bass signal a bit. The difference is audible to my ears.


----------



## diamondears

diamondears said:


> Yeah. I'm thinking it might be the RCA-3.5mm adaptor I'm using before on the regular issue O2. The adaptor prolly reduced the bass signal a bit. The difference is audible to my ears.



And prolly the 6.5mm-3.5mm HP jack adaptor too.


----------



## diamondears

For those who find the O2 a bit thin, these might be the culprits. So, if possible, don't use adaptors at all. I knew there's a reason for the customization.


----------



## adydula

I have one of my O2 amps with ac plugged in most all of the time and every other month or so I unplug it and let the batteries discharge.
  
 If you leave the ac on all the time it should not hurt the amp just the batteries might degrade in their capability to hold a "full" charge like when they were new.
  
 Batteries like nicads in the O2 don't normally do bad things, but batteries are batteries and there is never a 100% for sure.
  
 Just take them out if you don't need them.
  
 Alex


----------



## diamondears

adydula said:


> I have one of my O2 amps with ac plugged in most all of the time and every other month or so I unplug it and let the batteries discharge.
> 
> If you leave the ac on all the time it should not hurt the amp just the batteries might degrade in their capability to hold a "full" charge like when they were new.
> 
> ...


 Yeah, will just take them out. Thanks.


----------



## diamondears

diamondears said:


> For those who find the O2 a bit thin, these might be the culprits. So, if possible, don't use adaptors at all. I knew there's a reason for the customization.


 

 And may I add...my customized O2 has a unity gain (1x and 3.5x gain settings). So this may be a factor on the more bass that I'm hearing compared to the regular O2, which has 2.5x and 6.5 gain settings. I find that whenever I use the higher gain setting, the sound becomes bit more bright.
  
 Anyone here find this true as well?


----------



## JacobLee89

diamondears said:


> And may I add...my customized O2 has a unity gain (1x and 3.5x gain settings). So this may be a factor on the more bass that I'm hearing compared to the regular O2, which has 2.5x and 6.5 gain settings. I find that whenever I use the higher gain setting, the sound becomes bit more bright.
> 
> Anyone here find this true as well?


 
  
 My gain setting are 1x and 2.5x. Having installed the output booster board mod I don't really hear a change in the highs.
 Then again I am listening through a pair of HD650s.


----------



## doublin

Hey guys, I just received my power adapter today so I can finally use my O2 amp. I did encounter a pretty big problem though. When I connect my headphone through the amp and straight to my laptop, I hear this tearing/breaking sound when the music goes very low or very high(not volume) and I heard this from a lot of my songs. I tried connecting my headphone straight to my laptop and didn't hear the tearing(not sure if this is the correct term), so I'm pretty sure it came from the O2. Did I just bought a somehow faulty O2 amp?
  
 EDIT: I actually clicked the gain setting which somehow became the cause of the tearing. Is it normal? On another note, is it normal for me to need to turn the knob until ~3 o clock for the volume to be loud? I'm using HD600 and Alpha Dog and both kinda have the same volume.


----------



## potkettleblack

That's a problem, and from what I've read a rare thing.
  
 Did you get it from JDS labs? If so I'd contact them straight away, their customer service is exceptional.


----------



## doublin

potkettleblack said:


> That's a problem, and from what I've read a rare thing.
> 
> Did you get it from JDS labs? If so I'd contact them straight away, their customer service is exceptional.


 
 I bought it used from a previous owner who bought it from JDS. I'm not quite sure the age of the amp. I might ask the guy later.
  
 EDIT: The previous owner said that it's still under warranty as he bought it on July. I might need more feedback though before I send it as I don't have an extra amp to drive the headphone if I were to send the amp for repair.


----------



## diamondears

doublin said:


> Hey guys, I just received my power adapter today so I can finally use my O2 amp. I did encounter a pretty big problem though. When I connect my headphone through the amp and straight to my laptop, I hear this tearing/breaking sound when the music goes very low or very high(not volume) and I heard this from a lot of my songs. I tried connecting my headphone straight to my laptop and didn't hear the tearing(not sure if this is the correct term), so I'm pretty sure it came from the O2. Did I just bought a somehow faulty O2 amp?
> 
> EDIT: I actually clicked the gain setting which somehow became the cause of the tearing. Is it normal? On another note, is it normal for me to need to turn the knob until ~3 o clock for the volume to be loud? I'm using HD600 and Alpha Dog and both kinda have the same volume.


 Do you have the O2+ODAC?


----------



## Solrighal

What gains does your O2 have? My O2 has gains of 1x/3x and on the higher setting 3 o'clock on the volume is right at the top end of my personal range. No tearing though. This is with my HD 650.


----------



## JacobLee89

solrighal said:


> What gains does your O2 have? My O2 has gains of 1x/3x and on the higher setting 3 o'clock on the volume is right at the top end of my personal range. No tearing though. This is with my HD 650.


 
  
 For me, I use 100% volume settings on windows, and anything close to 12 O'clock is too much for my ears. Also with the HD650's.


----------



## doublin

diamondears said:


> Do you have the O2+ODAC?


 
 Standalone O2 and a standalone ODAC, both separate.
  


solrighal said:


> What gains does your O2 have? My O2 has gains of 1x/3x and on the higher setting 3 o'clock on the volume is right at the top end of my personal range. No tearing though. This is with my HD 650.


 
 Not sure about the gains but I think it's the standard O2 version so it's the standard gains available. Without using the gains, I need to turn the knob to around 3~4 o clock for it to be loud. The one with tearing is when I use the gains.


----------



## Solrighal

jacoblee89 said:


> For me, I use 100% volume settings on windows, and anything close to 12 O'clock is too much for my ears. Also with the HD650's.


 
  
 I never use 100% in software, always 96% here which is a 2dB cut in practice. It allows a bit of headroom for hot recordings.


----------



## Solrighal

doublin said:


> Standalone O2 and a standalone ODAC, both separate.
> 
> Not sure about the gains but I think it's the standard O2 version so it's the standard gains available. Without using the gains, I need to turn the knob to around 3~4 o clock for it to be loud. The one with tearing is when I use the gains.


 
  
 That's where the volume control should be getting seriously loud. I think you're used to more run-of-the-mill equipment where it's a rare event when the volume control even hits 12 o'clock. Having almost the full range of the pot is a desirable asset, it allows you to fine-tune the volume with a greater degree of accuracy. This is a good thing. Does the tearing sound happen at all volumes on high gain or just when you're seriously pushing the level?


----------



## doublin

solrighal said:


> That's where the volume control should be getting seriously loud. I think you're used to more run-of-the-mill equipment where it's a rare event when the volume control even hits 12 o'clock. Having almost the full range of the pot is a desirable asset, it allows you to fine-tune the volume with a greater degree of accuracy. This is a good thing. Does the tearing sound happen at all volumes on high gain or just when you're seriously pushing the level?


 
 The tearing happen even when the volume is low, so I assume it happen at all volume. As for the volume knob, I notice that I'll turn the knob at around 3 o clock for some music and settled at 12~1 o clock for other music, so I guess that's normal.


----------



## Solrighal

Yeah, some music is recorded very loud and some isn't. I'm not sure why you're getting the noise you are though but you're surely not using high gain much with the HD 600's.


----------



## doublin

solrighal said:


> Yeah, some music is recorded very loud and some isn't. I'm not sure why you're getting the noise you are though but you're surely not using high gain much with the HD 600's.


 
 I don't know, the volume I'm using for my HD600 is actually pretty similar to the Alpha Dog which is at 12 for loud recording and 3~4 for low.


----------



## Solrighal

That's pretty much bang on for me.


----------



## diamondears

solrighal said:


> I never use 100% in software, always 96% here which is a 2dB cut in practice. It allows a bit of headroom for hot recordings.


 Software should always be 100%, otherwise you lose some digital bits. Headroom should be on the amp volume/power.


----------



## diamondears

jacoblee89 said:


> My gain setting are 1x and 2.5x. Having installed the output booster board mod I don't really hear a change in the highs.
> Then again I am listening through a pair of HD650s.



Using the same O2 unit, from 2.5x gain to 6.5x, at same ear volume level, I hear more treble, more sparkle. Same is true if I switch from 1x gain to 3.5x gain, bit more sparkle/treble. I hear it. 

So for those who find the O2 in the bright side of neutral, IMHO you should get a custom O2 with unity/1x gain and with inputs and outputs matching your gears. Just sayin.


----------



## castleofargh

diamondears said:


> solrighal said:
> 
> 
> > I never use 100% in software, always 96% here which is a 2dB cut in practice. It allows a bit of headroom for hot recordings.
> ...


 

 we already talked about this with zorro. we have a few tracks that ends up clipping at 100% and not a little lower. it's rare and not a drama, but it does happen to zorro, me, and others.
 maybe it has to do with replay gain or some weird math trick as suggested by benchmark? maybe it's because of some EQ(I always take my EQ down to 0db but who knows)? all I know is the solution came with the "sacrifice" of 2 or 3db, so we do it.
 the day you can hear the difference from losing those least significant 2db you call me ^_^.
 also as long as you output foobar in 24bit you have all the margin you'll ever need. even with relaygain and -2db (I actually use -3db cause I'm a rebel and just want to see the world burn
	

	
	
		
		

		
			





).
 the margin between idealistic theory and audible change is quite wide for that matter and in any case I prefer crushing a few least significant bits instead of getting some clipping.
 now if you don't ever have any clipping due to max volume, then of course 100% is very much ok and you're not doing anything wrong.


----------



## Solrighal

If you're outputting to a 24 bit DAC you'll never hear the loss of a couple of bits. I read here somewhere that there's a test you can do where the signal is gradually reduced from 24 bits to see where human hearing starts to notice the difference and it's something like 12 bits! Anyway, the extra 8 bits over 16 bits is only padding and simply can't be heard. This is why it's often advised to buy a 24 bit DAC; not because it gives you more information but because it allows some latitude with software volume.


----------



## diamondears

castleofargh said:


> we already talked about this with zorro. we have a few tracks that ends up clipping at 100% and not a little lower. it's rare and not a drama, but it does happen to zorro, me, and others.
> maybe it has to do with replay gain or some weird math trick as suggested by benchmark? maybe it's because of some EQ(I always take my EQ down to 0db but who knows)? all I know is the solution came with the "sacrifice" of 2 or 3db, so we do it.
> the day you can hear the difference from losing those least significant 2db you call me ^_^.
> also as long as you output foobar in 24bit you have all the margin you'll ever need. even with relaygain and -2db (I actually use -3db cause I'm a rebel and just want to see the world burn ).
> ...




I see. Is this related to too much Vrms output on your sources? If you're using ODAC, JDS Labs suggests you use the unity/1x gain, not the 2.5x gain on the regular issue O2.


----------



## Solrighal

I only ever really need unity gain. 3x is for headphones I might never own. I think there's a tendency for people to listen too loud when using headphones. Really, as long as the environment around you is quiet there's no need. Your brain will adjust to a quieter signal and normalize it with time. I also think people use the volume control as a tone control. if you perceive the sound as lacking attack then sure, turning up the volume will give the impression that the attack is increased but unfortunately so is everything else. You end up with tonal compression and a sore head. In reality the problem is that you've bought the wrong headphones for your particular taste.


----------



## castleofargh

diamondears said:


> castleofargh said:
> 
> 
> > we already talked about this with zorro. we have a few tracks that ends up clipping at 100% and not a little lower. it's rare and not a drama, but it does happen to zorro, me, and others.
> ...


 

 doesn't seem so for me, it's really looks like something happening on the digital side(and maybe on the computer and has nothing to do with the odac?). I clipped the O2 only once when I tried measuring it and pushed it to the max with different loads and sources. it was very obvious and nothing like the subtle little thing I'm talking about.
  
 and yeah I'm also at unity gain at all time.


----------



## headwhacker

diamondears said:


> Software should always be 100%, otherwise you lose some digital bits. Headroom should be on the amp volume/power.




Better check this out. It shows that volume control only affects SNR not resolution.

http://youtu.be/JYjHKv2_OqQ

With modern 24-bit DACs it's moot.


----------



## JacobLee89

headwhacker said:


> Better check this out. It shows that volume control only affects SNR not resolution.
> 
> http://youtu.be/JYjHKv2_OqQ
> 
> With modern 24-bit DACs it's moot.


 
  
 I always do 100% digital so it just simplifies whatever I'm doing.
  
 Just being lazy really.


----------



## diamondears

headwhacker said:


> Better check this out. It shows that volume control only affects SNR not resolution.
> 
> http://youtu.be/JYjHKv2_OqQ
> 
> With modern 24-bit DACs it's moot.


 

 I'm talking about digital players.


----------



## headwhacker

diamondears said:


> I'm talking about digital players.


 
  
 How do you think digital players control volume? Unless we are thinking about different things.


----------



## headwhacker

jacoblee89 said:


> I always do 100% digital so it just simplifies whatever I'm doing.
> 
> Just being lazy really.


 
  
 Either way is not really an issue. I also do the same thing for similar reason. But with sensitive phones (i.e. Grados), I don't worry much decreasing the volume on my Mac to get into proper listening level thinking that I'm losing something.


----------



## castleofargh

it's not really hard. CDs with great dynamic will have maybe 65db used(usually a good deal less than that). so that's about 11bit of signal. you add 20 or 30db to ensure a background noise low enough not to ever be audible, and you end up with a reasonable need for 16bit resolution as a nice comfort margin(wow it's as if they had thought about it when they came up with redbook ^_^).
 so when you output your music on the odac in 24bit(as recommended), you get some nice "extra" bits with nothing but zeros that are begging you to be used for volume control on the computer. that's the real pure lazy man way
	

	
	
		
		

		
			





.
  
 let's say that 24bit dacs are really 20bit as a conservative estimation. that's still 4bits available before "attacking" the 16bits of a CD. so about 6*4=24db you can use on you computer, with no real danger of changing anything on the record itself.
 as long as you use proper settings and know what you're doing there is no risk of degrading your music.
  
 on a 16bit DAC (does that even exist anymore?) I wouldn't give you the same speech obviously.


----------



## jseaber

diamondears said:


> Software should always be 100%, otherwise you lose some digital bits. Headroom should be on the amp volume/power.


 
  
 Every DAC we've measured performs dramatically worse at full-scale, 100% volume. Decrease your software volume slider by -0.1dB (a single notch will do) for optimal THD+N performance.
  
 See Gibbs phenomenon:
 http://en.wikipedia.org/wiki/Gibbs_phenomenon


----------



## Medaud

jseaber said:


> Every DAC we've measured performs dramatically worse at full-scale, 100% volume. Decrease your software volume slider by -0.1dB (a single notch will do) for optimal THD+N performance.
> 
> See Gibbs phenomenon:
> http://en.wikipedia.org/wiki/Gibbs_phenomenon




Are we talking the windows volume slider here or what software exactly?


----------



## jseaber

medaud said:


> Are we talking the windows volume slider here or what software exactly?


 
  
 Use any digital volume slider at your disposal. The key is to avoid a full-scale signal into the DAC.


----------



## blse59

jseaber said:


> Use any digital volume slider at your disposal. The key is to avoid a full-scale signal into the DAC.


 

 Wow, this is the first I've heard this. Practically every article/blog I've read regarding this issue says to keep digital volume at 100%. Thanks.


----------



## Solrighal

In the days of 16 bit DAC's it would be good practise to use software volume at 100% but since the advent of 24 bit DAC's.


----------



## jseaber

blse59 said:


> Wow, this is the first I've heard this. Practically every article/blog I've read regarding this issue says to keep digital volume at 100%. Thanks.


 
  
 It was a surprise when I first noticed the measurements. After checking different units and DAC models, and conferring with other engineers, it was clear that full scale DAC performance is rarely discussed.
  
 THD+N performance is 2-3x better for input just below 0dB. Keep in mind you're rarely going to hit 0dB peaks when listening to music. Even today's heavy handed recordings will only hit 0dB peaks for a few seconds throughout an entire track. And even if you do listen to a track full of 0dB peaks, 100% digital volume may yield THD+N of 0.0070% at peaks through ODAC (worst case), versus ~0.0025% at slightly reduced digital volume. It takes focused, well trained ears to detect this difference. We expect transparency at THD+N below ~0.005%. It's a rather small audible difference, yet objectively/measurably obvious.
  
 We include a short blurb in the_ Listening Tips_ of JDS Labs instruction Guides:
  


> For maximum signal fidelity, keep ODAC digital volume set slightly below 100% at the computer. Only control volume from your headphone amplifier.


 
  
 Zorrofox is correct. Digital volume control is fine to use aggressively as long as the DAC has excellent dynamic range.
  


solrighal said:


> In the days of 16 bit DAC's it would be good practise to use software volume at 100% but since the advent of 24 bit DAC's.


----------



## Medaud

blse59 said:


> Wow, this is the first I've heard this. Practically every article/blog I've read regarding this issue says to keep digital volume at 100%. Thanks.




Also the first I heard of it. I've been running my volume at 100% up til now. Now I turned down the windows volume slider one notch...the OCD in me is acting up but I think I'll survive


----------



## diamondears

First time for me too. Thanks for that, JSeaber. 





jseaber said:


> It was a surprise when I first noticed the measurements. After checking different units and DAC models, and conferring with other engineers, it was clear that full scale DAC performance is rarely discussed.
> 
> THD+N performance is 2-3x better for input just below 0dB. Keep in mind you're rarely going to hit 0dB peaks when listening to music. Even today's heavy handed recordings will only hit 0dB peaks for a few seconds throughout an entire track. And even if you do listen to a track full of 0dB peaks, 100% digital volume may yield THD+N of 0.0070% at peaks through ODAC (worst case), versus ~0.0025% at slightly reduced digital volume. It takes focused, well trained ears to detect this difference. We expect transparency at THD+N below ~0.005%. It's a rather small audible difference, yet objectively/measurably obvious.
> 
> ...




Thanks for that, John. First time for me too. All my DACs automatically disables the digital volume control on the source player, but never experienced anything bad on the O2s (I've got 3).

I think this has got to do with the Vrms coming out of the digital player for which the DAC input isn't designed?


----------



## jseaber

diamondears said:


> First time for me too. Thanks for that, JSeaber.
> Thanks for that, John. First time for me too. All my DACs automatically disables the digital volume control on the source player, but never experienced anything bad on the O2s (I've got 3).
> 
> I think this has got to do with the Vrms coming out of the digital player for which the DAC input isn't designed?


 
  
 Hm, I suppose you could phrase it that way. "VRMS" does not come out of a digital player, as Volts RMS is an analog unit; a digital player generates a digital signal, involving 0's and 1's as I'm sure you know. For example, the maximum signal magnitude a 24-bit digital audio player can generate = 100% volume = 0dB = 111111111111111111111111 binary
  
 No amplifier is involved when measuring DAC line-output, so by definition, full scale output is that of the DAC. In the case of ODAC, its output is 2.0VRMS for input of 0dB. The test condition I've mentioned applies to any signal frequency at exactly 0dB. In other words, this is a general DAC phenomenon. It's impossible to feed a DAC more than 0dB.


----------



## diamondears

jseaber said:


> Hm, I suppose you could phrase it that way. "VRMS" does not come out of a digital player, as Volts RMS is an analog unit; a digital player generates a digital signal, involving 0's and 1's as I'm sure you know. For example, the maximum signal magnitude a 24-bit digital audio player can generate = 100% volume = 0dB = 111111111111111111111111 binary
> 
> No amplifier is involved when measuring DAC line-output, so by definition, full scale output is that of the DAC. In the case of ODAC, its output is 2.0VRMS for input of 0dB. The test condition I've mentioned applies to any signal frequency at exactly 0dB. In other words, this is a general DAC phenomenon. It's impossible to feed a DAC more than 0dB.


 
I see. Thanks for the time, John.


----------



## castleofargh

zorro, at last someone is saying we might not be completely crazy \o/. this is a great day for us, thank jseaber. 
	

	
	
		
		

		
		
	


	



  
 my idea about this was somehow far fetched(as always when you wrongly try to find a cause to your consequence instead of going the other way around)but I'll give it a go anyway I have no shame ^_^:
 with some little jitter variations between 2 samples, it should be possible that the resulting sine would sometimes not really reach 0db when it should, and at other times try to very slightly pass 0db when obviously it shouldn't. making that tiny little part to clip. of course for that we need the signal to be at 0db and the jitter to be fluctuating in value from one sample to the next(constant lag would do nothing).
 that's how I imagined it could happen. as I can't think of a reason why there should be a problem on the digital side, unless we go clip the signal with some EQ or a DSP, but it's another matter and it's easy to control.


----------



## Solrighal

Yeah, it's a good (and rare) feeling to be right, for sure.
  
 I've certainly come across at least a couple of albums that clip naturally but I can't remember what they were & they're clearly not something I listen to regularly or I would definitely remember them. However, here's a fact. I keep my volume control in JRiver 19 at 96% as I've previously stated. This equates to a 2dB cut in real terms. Now, if I introduce EQ in the shape of my iZotope Ozone 6 plug-in, that 2dB gap disappears. The level is maxed and sometimes easily exceeded. I'm not sure it's actually audible in a blind test but when you see it happening graphically it's difficult not to immediately want to do something about it. Someone earlier mentioned OCD - welcome to my world.


----------



## MrMateoHead

jseaber said:


> Use any digital volume slider at your disposal. The key is to avoid a full-scale signal into the DAC.


 

 Not to argue with the facts but, I am quite sure the directions that came with my O2 instructed me to set my windows volume to 100% and 24-bit, 96khz.
  
 Would it be too confusing to tell consumers to set windows volume to 96-98% for optimal performance?


----------



## jseaber

mrmateohead said:


> Not to argue with the facts but, I am quite sure the directions that came with my O2 instructed me to set my windows volume to 100% and 24-bit, 96khz.
> 
> Would it be too confusing to tell consumers to set windows volume to 96-98% for optimal performance?


 
  
 I'm sure it did. The document revision date is printed at the bottom of the guide, and has since been updated.


----------



## Medaud

mrmateohead said:


> Not to argue with the facts but, I am quite sure the directions that came with my O2 instructed me to set my windows volume to 100% and 24-bit, 96khz.
> 
> Would it be too confusing to tell consumers to set windows volume to 96-98% for optimal performance?




I'm 99% certain mine did too. Btw does this count for all DACs? I've got an HTPC hooked up to a Yamaha receiver and have set the volume to 100%. Would it be beneficial to turn this down a notch too, or does this issue only occur with the ODAC?


----------



## MrMateoHead

I have some albums with known clipping problems. I too use the ODAC to feed a Yamaha Receiver for when I am headphoned-out. I've never heard the Yamaha clip (which sounds like static/tearing). But if the clipping is at the recording level, cutting digital volume doesn't really get rid of the staticky noise. Just the same, I would still cut the windows volume a hair, as advised, to maximize performance.
  
 What is nice, however, is that the Yamaha does not "hiss" with the ODAC at all, at any volume I've listened at (and this is an old, cheap base model receiver).


----------



## jseaber

medaud said:


> I'm 99% certain mine did too. Btw does this count for all DACs? I've got an HTPC hooked up to a Yamaha receiver and have set the volume to 100%. Would it be beneficial to turn this down a notch too, or does this issue only occur with the ODAC?


 
  
 Yes, this applies to all DACs I've analyzed. I'll post screenshots next time I have the dScope running. Busy day today, unfortunately...


----------



## castleofargh

mrmateohead said:


> I have some albums with known clipping problems. I too use the ODAC to feed a Yamaha Receiver for when I am headphoned-out. I've never heard the Yamaha clip (which sounds like static/tearing). But if the clipping is at the recording level, cutting digital volume doesn't really get rid of the staticky noise. Just the same, I would still cut the windows volume a hair, as advised, to maximize performance.
> 
> What is nice, however, is that the Yamaha does not "hiss" with the ODAC at all, at any volume I've listened at (and this is an old, cheap base model receiver).


 

 we're obviously not talking about clipping that is already on the record(like almost all rap albums I ever owned). except some clever DSP you can't really solve that.
 what we're talking about is something that ends up clipping a little @ 100% digital volume(so anything digital has to be maxed out), but doesn't when you just lower the digital volume a little. it's a very peculiar kind of problem and certainly doesn't relate to all the other possible reasons for clipping to occur on the record, or at the amp stage.


----------



## diamondears

castleofargh said:


> we're obviously not talking about clipping that is already on the record(like almost all rap albums I ever owned). except some clever DSP you can't really solve that.
> what we're talking about is something that ends up clipping a little @ 100% digital volume(so anything digital has to be maxed out), but doesn't when you just lower the digital volume a little. it's a very peculiar kind of problem and certainly doesn't relate to all the other possible reasons for clipping to occur on the record, or at the amp stage.


 
  
 In what types of DACs does this issue becomes a non-issue? 32-bit DACs? If this issue applies to all DACs, why does many DACs automatically disables the volume control on the digital player? They automatically decrease the volume to less than 100%?


----------



## castleofargh

no idea, I don't even know what causes it. I just got lucky and realized one day that I didn't get the clipping on one song after I lazily used foobar volume control to turn the music down a little instead of the amp knob. that's not a finding, that was just random luck and I don't know why or if it's even related to the DAC.
 could have been some DSP working on my computer pushing stuff +1db and me not knowing? you know like the THX stuff turning ON when using the integrated speakers of a laptop.
  
  
 the guys from benchmark mentioned something with the oversampling process but they don't explain it so that may not even be related.


----------



## Solrighal

DAC's of more than 16-bit resolution just add zero's to the signal. This 'extra' information is inaudible so it's possible to attenuate the signal without losing any information. Or something like that.
  
 This has been discussed in-depth previously and I'm pretty sure it was in this thread somewhere.


----------



## SunTanScanMan

jseaber said:


> Every DAC we've measured performs dramatically worse at full-scale, 100% volume. Decrease your software volume slider by -0.1dB (a single notch will do) for optimal THD+N performance.
> 
> See Gibbs phenomenon:
> http://en.wikipedia.org/wiki/Gibbs_phenomenon


 

 I don't own the O2/ODAC but I do like to peruse this thread from time to time. Glad I did. I was also under the impression that software volume had to be at 100%. Thanks for the information.


----------



## mikek200

james-uk said:


> How do you find the st ax? I'm tempted but I do love the 800s and 600s .


 
 I just joined this thread,Bought the HD600 & a used pair of modded Hd580,and the 02 +ODAC,
 I,vie been waiting for my new Stax amp{KGST} to be built.
  
 I have to tell you ,I extremely impressed with the non-stax sound quality,but sometimes I miss the tremendous detail
 The new/used pair of HD 580,s are fantastic.
  
 Every time my builder tells me,"It,s going to be another 4 week delay"--I answer.."OK,no problem,just buzz me ,when its down"--LOL


----------



## mikek200

solrighal said:


> I totally believe cables make a difference and I've got a fair selection here, although they're all too long. It's a bit tricky once you've bought into the whole Objective spiel though because now I'm looking for a cable to specifically do absolutely nothing to the sound. To be as transparent as possible. I've now tried three different interconnects and every one sounds different and every one changes the sound. Hmm...


 
 Thank God,finally,someone who appreciates good cables.
 After I bought my Stax setup,and dropped $3200.00 on my 009's,I went looking for a good pair of interconnects.as luck has it,I found a pair od the B/S forum,being sold by Currawong,and they were $1000.00,after thinking about it,I e-mailed Currawong and asked him a few tech questions,concerning the IC's,and all he said was,I,m not telling you anything,UNTIL YOU LISTEN TO THEM FOR 24HOURS,so,I bought them.
 My wife has been chasing me around the house ,ever since.
 They are the finest IC, I own,and the SQ,increased about  20-25 %
 They are  the totl Van Den Hul,they run $1500.00,Currawong sold them to me for $1000.00-the deal of the century,besides my HD600 & 02 +ODAC.
  
 Mike


----------



## mikek200

ali-pacha said:


> SR-009 are a kind of "everything / everywhere" tool. Extension, details, dynamics, clarity, bass slam, magnificent decay, speedy gonzales transients, and so on. On the other hand, SR-Lambda and SR-5 are vintage mids cans (and I love them this way).
> With the O2, HD600 have a good level of transparency, they keep this so special low-mids emphasis, and also this 130 hz bump. Maybe a bit veiled, but the O2 gives them enough clarity / neutrality to fight this Sennheiser trend.
> Summary : O2 is the amp to get for stat's head when they go dynamics
> 
> ...


 
 Excellent way of putting it,Ali-Pacha


----------



## mikek200

solrighal said:


> The one I bought can be set to a few different voltages, 15V being the max. I went with 15V since the one supplied as stock was 15V. Did I do the right thing?
> 
> I've also just ordered another geek improvement which I'm sure is gonna make this sound like the dogs. I have a new machined aluminium volume knob en - route from New Yawk!
> 
> ...


 
  
  
  
  
  
 I think Schiit 's IC's are 3" long
 Try them


----------



## Solrighal

The PYST is about 6" long and I use them at the moment. It might be purely psychological but there's a certain logic in having as short a cable run as possible. Whether it actually makes a difference in lengths under 0.5m is debatable.


----------



## Oldandcurious

doublin said:


> Silly question. Can I unplug the battery from my standalone O2 so that it will only run through the AC adapter I'm using? I'm currently am using the O2 as my desktop amp and not planning to use it for portable use. Sorry if it has been answered before.
> 
> EDIT: Used the search button and stumbled upon this: http://www.head-fi.org/t/616331/o2-amp-odac/3480#post_10932475 . So I'm guessing that it CAN be used without batteries, then?




After less than a week, I decided to remove the batteries from my JDSLabs' O2. It has been working without a problem. I never planned using it as a portable, so no I see no need to keep the batteries.


----------



## donaldduck2004

hey guys I was looking for a DAC and a good headphones amplifier. I need the DAC would give another output to give signal to speaker amplifier. So I think I would need a two-RCA-output DAC. What do you think?


----------



## HaVoC-28

donaldduck2004 said:


> hey guys I was looking for a DAC and a good headphones amplifier. I need the DAC would give another output to give signal to speaker amplifier. So I think I would need a two-RCA-output DAC. What do you think?


 
  
 If you don't need to use speackers and headphone at same time a simple switch would do the trick . If you don't want a switch their is versions of  standalone ODAC with 2 outputs , like the XL version from the swiss assembler " head" n" hifi " , one rca output and the second  output is 3.5 mm jack , but shouldn't matter at all , just buy the right cables (but it's advised to don't use both output at same time ) .


----------



## diamondears

havoc-28 said:


> If you don't need to use speackers and headphone at same time a simple switch would do the trick . If you don't want a switch their is versions of  standalone ODAC with 2 outputs , like the XL version from the swiss assembler " head" n" hifi " , one rca output and the second  output is 3.5 mm jack , but shouldn't matter at all , just buy the right cables (but it's advised to don't use both output at same time ) .




What switch? Where can I get that?


----------



## HaVoC-28

diamondears said:


> What switch? Where can I get that?


 
  
 In amazon.com try rca switch or audio selector , something like that .


----------



## donaldduck2004

havoc-28 said:


> In amazon.com try rca switch or audio selector , something like that .


 and will this solve the problem of one output?


----------



## Solrighal

http://www.headnhifi.com/dac/odac-xl-version


----------



## HaVoC-28

donaldduck2004 said:


> and will this solve the problem of one output?


 
  
 http://www.amazon.it/HQ-Commutatore-stereo-3-uscite/dp/B000I8OOS8/ref=sr_1_1?s=electronics&ie=UTF8&qid=1418577559&sr=1-1&keywords=rca+switch
  
 Yeah i use a similar Switch for my ODAC . so i just switch from an output to another depending on the needs .
  
 Or the ODAC XL if you don't want the switch (Zorrofox kindly provided you a direct link) .
   
when i purchased my ODAC the XL version didn't existed yet . Just don't power on at the same time both speacker amp and O² (it will not harm anything but performance may be degraded) .


----------



## donaldduck2004

.





havoc-28 said:


> http://www.amazon.it/HQ-Commutatore-stereo-3-uscite/dp/B000I8OOS8/ref=sr_1_1?s=electronics&ie=UTF8&qid=1418577559&sr=1-1&keywords=rca+switch
> 
> Yeah i use a similar Switch for my ODAC . so i just switch from an output to another depending on the needs .
> 
> ...


 what do you suggest? Switch or odac XL version. What advantage will I have?
I'll buy from Italy. Is it simple to find?




solrighal said:


> http://www.headnhifi.com/dac/odac-xl-version


 oh thanks!


----------



## Rajikaru

donaldduck2004 said:


> .
> what do you suggest? Switch or odac XL version. What advantage will I have?


 
  
  
 If you get the O2+ODAC integrated unit (I have one built by Mayflower Electronics), the ODAC can serve as the DAC for the O2 while also outputting the line-out signal through the front port. This, I believe, should solve your problem.
  
 I'm not sure if all O2+ODAC units work this way, but that's how the unit I have works. If it didn't, then a set-up like this (that's the O2+ODAC in the background), which includes a switch for A/B testing, wouldn't be possible:


----------



## donaldduck2004

Wait wait wait. The odac output is good fit headphones?I don't think so... This is the problem. The best choice I think would be the switch...


----------



## Rajikaru

Yes, I realize this is confusing, because it isn't really well explained in the product's documentation. 
  
 If you look at the image I just posted, the ODAC output is going into another amplifier, not headphones.  
  
 With the integrated O2+ODAC (in one case), the ODAC can simultaneously feed the built-in O2 and output a line-out signal through the front port. 
  
 The ODAC's line-out output, through the front port in the integrated unit, should always go into an amplifier or powered speakers.


----------



## jseaber

rajikaru said:


> If you get the O2+ODAC integrated unit (I have one built by Mayflower Electronics), the ODAC can serve as the DAC for the O2 while also outputting the line-out signal through the front port. This, I believe, should solve your problem.
> 
> I'm not sure if all O2+ODAC units work this way, but that's how the unit I have works. If it didn't, then a set-up like this (that's the O2+ODAC in the background), which includes a switch for A/B testing, wouldn't be possible:


 
  
 ODAC performs best under a single load. To achieve published performance, we strongly discourage paralleled loads to ODAC. Properly customized assemblies allow ODAC to be disconnected from O2 when driving an external line-level device.
  
 You can find connectivity advice in the JDS Labs O2+ODAC instructions.


----------



## HaVoC-28

donaldduck2004 said:


> .
> what do you suggest? Switch or odac XL version. What advantage will I have?
> I'll buy from Italy. Is it simple to find?


 
  
 At my knowledge their no Itlian assembler/distributor of ODAC/O² , in Europe their is :
  
 http://epiphany-acoustics.co.uk/    (U.K.) .
  
 http://www.headnhifi.com/  (Switzerland)   use "weekly priority mail" as shipping to avoid eventual customs .


----------



## Rajikaru

jseaber said:


> ODAC performs best under a single load. To achieve published performance, we strongly discourage paralleled loads to ODAC. Properly customized assemblies allow ODAC to be disconnected from O2 when driving an external line-level device.
> 
> You can find connectivity advice in the JDS Labs O2+ODAC instructions.


 
  
 Thanks for the heads up, John!
  
 I'm not noticing any sonic degradation with the way I have it wired, though.  
  
 Wouldn't putting a switch in front, as I have, effectively qualify as a single load depending on the switch position? Or does this still count as a parallel load?


----------



## donaldduck2004

But give me an information. Odac is a good choice for a DAC for headphones and speakers (of course with a separate amplifier for each)?


----------



## jseaber

rajikaru said:


> Thanks for the heads up, John!
> 
> I'm not noticing any sonic degradation with the way I have it wired, though.
> 
> Wouldn't putting a switch in front, as I have, effectively qualify as a single load depending on the switch position? Or does this still count as a parallel load?


 
  
 Yes, a passive switch is an excellent solution.
  
 There's been a fair amount of confusion about ODAC's load capabilities, which has not been helped by the default O2+ODAC wiring. NwAvGuy claimed the ES9023 would respond acceptably under a 5k load (i.e., two 10k devices in parallel). We've found this is not always true. ODAC measures as expected with a single 10k+ load. Results under paralleled or smaller impedance loads are unpredictable.


----------



## headwhacker

jseaber said:


> Yes, a passive switch is an excellent solution.
> 
> There's been a fair amount of confusion about ODAC's load capabilities, which has not been helped by the default O2+ODAC wiring. NwAvGuy claimed the ES9023 would respond acceptably under a 5k load (i.e., two 10k devices in parallel). We've found this is not always true. ODAC measures as expected with a single 10k+ load. Results under paralleled or smaller impedance loads are unpredictable.


 
  
 Hi John,
  
 I'm planning to get another O2 and stack it with my existing O2+ODAC. Effectively running ODAC with 2 O2 parallel loads. The reason being that I can have 4 different gain settings for better gain matching with different headphone loads and the ability to quickly switch between 2 full-size headphones while music is playing. 
  
 Are you saying when running parallel loads with ODAC you get inconsistent measurements? Could you publish the ODAC's measurements while driving 2 O2s in parallel? Thanks


----------



## jseaber

headwhacker said:


> Hi John,
> 
> I'm planning to get another O2 and stack it with my existing O2+ODAC. Effectively running ODAC with 2 O2 parallel loads. The reason being that I can have 4 different gain settings for better gain matching with different headphone loads and the ability to quickly switch between 2 full-size headphones while music is playing.
> 
> Are you saying when running parallel loads with ODAC you get inconsistent measurements? Could you publish the ODAC's measurements while driving 2 O2s in parallel? Thanks


 
  
 From what I can recall, ODAC performs acceptably with paralleled O2's. It struggles with reduced load impedance, and behaved less ideally with mixed, paralleled devices (i.e., an O2 and a preamp).
  
 Sorry, I have no screenshots saved. Will update next time I have the dScope out.


----------



## diamondears

jseaber said:


> From what I can recall, ODAC performs acceptably with paralleled O2's. It struggles with reduced load impedance, and behaved less ideally with mixed, paralleled devices (i.e., an O2 and a preamp).
> 
> Sorry, I have no screenshots saved. Will update next time I have the dScope out.





John,

On unrelated note, do you see any cons on setting the O2 at max volume pot position to use it as a "power amp", such as clipping, distortion, breakage in parts, etc.? The preamp is either the Audiolab 8200CD or the Roksan Caspian M2's preamp section. 

Cheers.


----------



## blse59

My O2 just shipped today. I can't wait to use it.


----------



## robkez313

Hi,
 i have Sounblaster Z, AD700 and K550 (just bought) headphones. Will i notice any difference if i buy O2 AMP + ODAC?


----------



## chrislangley4253

robkez313 said:


> Hi,
> i have Sounblaster Z, AD700 and K550 (just bought) headphones. Will i notice any difference if i buy O2 AMP + ODAC?


 
 Do you notice any noise or unwanted distortion with your current setup? If so, the o2 and odac would remove this problem.

 Do you feel the need to turn up the headphones to a louder volume? If so, yes the o2 and odac will give you a higher gain and allow you to reach higher volumes.

 Other things that could matter would be impedance and distortion.. The o2 amp undoubtedly has a lower impedance than the soundblaster.. and the ODAC undoubtedly has less distortion..  But, will you hear a difference? Probably not. 


 Look up the impedance of your headphones and the impedance of the soundblaster. If the impedance of the soundblaster is 1/8th or less of the impedance of your headphones you are in very good shape. This rule is generally accepted in the audio community.

 I have not heard a soundblaster, and I have not looked up the impedance values of it, nor your headphones. I will leave this up to you.  The above information should help you decide if you should try the o2 and odac.

 Good luck with your research


----------



## Solrighal

Don't forget the warm glow imparted by the ODAC / O2.


----------



## chrislangley4253

solrighal said:


> Don't forget the warm glow imparted by the ODAC / O2.


 
 Trollololol?


----------



## Solrighal

chrislangley4253 said:


> Trollololol?


 
  
 What are you trying to infer?


----------



## Nec3

robkez313 said:


> Hi,
> i have Sounblaster Z, AD700 and K550 (just bought) headphones. Will i notice any difference if i buy O2 AMP + ODAC?


 


 I can answer for your K550's, but I don't know much about the AD700. I used an Xonar DG 5.1 and K550 beforehand I switched to A900X. Although let's just ignore the A900X.

 The K550's with the ODAC/O2 becomes a bit brighter in lower treble and soundstage becomes a bit larger. You'd have to spend some time with the K550's to notice the difference, or if you've never heard any better headphones; you'll definitely notice the upgrade a little. The AKG K550 likes warmer sources for a bigger bass bump (i.e. a tube amplifier).

 The lower treble in the AKG K550 does get fatiguing and it was smoothed out with just using Xonar DG 5.1 rather than the ODAC/O2. That's why I switched to the ATH-A900X because the K550's prefer portable devices overall.

 In a nutshell, enjoy your Soundblaster Z until you decide to get a headphone that requires heavy amplification. This should give you some time to wait for the ODAC/O2 to go on sale.


----------



## schmalgausen

AD700 pushed me into amplifiers world many years ago as very sensitive to amplification phones. Nobody compared this Xonar with O2, but there is a chance to be appreciable.


----------



## Solrighal

chrislangley4253 said:


> Trollololol?


 
  
  


solrighal said:


> What are you trying to infer?


 
  
 I can only assume you're referring to yourself then.
  
 Happy Christmas.


----------



## chrislangley4253

solrighal said:


> Don't forget the warm glow imparted by the ODAC / O2.


 

  



chrislangley4253 said:


> Trollololol?


 
  
  


solrighal said:


> What are you trying to infer?


 
  
 I thought you were joking.
  
 I've never heard the ODAC+O2 described as having a "warm glow".
  
 It's cool if that's the way you hear it, but I think most people describe it as pretty transparent.


----------



## blse59

What do you think of keeping a cable like this plugged in to preserve the life of the headphone-out jack?
  
http://www.amazon.com/dp/B00GZQWI6C/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=1FCJ214026JGQ&coliid=I3D8OO5EGSGB3W&psc=1
  
 I'd rather have an adapter to keep plugged in rather than deal with a long cable. Any recommendations?


----------



## Solrighal

chrislangley4253 said:


> I thought you were joking.
> 
> I've never heard the ODAC+O2 described as having a "warm glow".
> 
> It's cool if that's the way you hear it, but I think most people describe it as pretty transparent.




Sorry, I was meaning the warm glow you get from not buying the mainstream options out there and going with something actually proven to be transparent.


----------



## chrislangley4253

blse59 said:


> What do you think of keeping a cable like this plugged in to preserve the life of the headphone-out jack?
> 
> http://www.amazon.com/dp/B00GZQWI6C/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=1FCJ214026JGQ&coliid=I3D8OO5EGSGB3W&psc=1
> 
> I'd rather have an adapter to keep plugged in rather than deal with a long cable. Any recommendations?


 
 I do this with a similar cable and or sennheiser 3.5mm to 1/4" pigtail adapter. I secure the cable/adapter to my desk with masking tape. Can't tell you how many times it has probably saved my output jack.
  

  

  
  


solrighal said:


> Sorry, I was meaning the warm glow you get from not buying the mainstream options out there and going with something actually proven to be transparent.


 
 Hah, easy misunderstanding.


----------



## blse59

chrislangley4253 said:


> I do this with a similar cable and or sennheiser 3.5mm to 1/4" pigtail adapter. I secure the cable/adapter to my desk with masking tape. Can't tell you how many times it has probably saved my output jack.


 
  
 Thanks! I think I might go that route.


----------



## castleofargh

I've stuck the o2 to the table (with 2 little straps you use to hang stuff without piecing the wall). and the O2 is facing the direction I take when I go out of the room, so the only result of me being an idiot(and it happened quite a few times already) end up with the headphone unplugged on a straight axis.
 but I can certainly understand the concern.


----------



## schmalgausen

I've built my O2 with the Desktop kit and don't have any troubles with the weak output.


----------



## Solrighal

castleofargh said:


> "and it happened quite a few times already..."


 
  
 Welcome to my world


----------



## Arm3nian

Would 1x/2.5x gain be enough for o2+odac or should I go for 1x/3.5. Using hd650s. Thanks


----------



## headwhacker

arm3nian said:


> Would 1x/2.5x gain be enough for o2+odac or should I go for 1x/3.5. Using hd650s. Thanks


 
  
 Should be enough but I would go with 1x/3.5x. This would make the maximum power output of O2 available when you need it.


----------



## chrislangley4253

arm3nian said:


> Would 1x/2.5x gain be enough for o2+odac or should I go for 1x/3.5. Using hd650s. Thanks


 
 I have mine at 1x/2.5x and I almost always find it enough.. But, I don't think I would mind having 1x/3.5x. 

 I usually stay on 1 unless I'm using a source other than my odac.. such as a sansa clip. At such times, I wish I had more than 2.5x on very quiet recordings.
  
 1x/3.5x sounds pretty choice to me, I wish mine was like that.


----------



## Solrighal

I have gains of 1x / 3x and rarely use the higher gain.


----------



## diamondears

What's the ideal max volume pot position on the O2? If 5 o'clock is the max, is 2, 3 or 4 ideal with still headroom left for dynamic peaks? Been reading Nwavguy's blog site and he didn't mention it (I might have missed it).


----------



## Arm3nian

IIRC the best position is 12 o'clock.

Can anyone find how much power the o2 puts into 300ohms? It would make the gain decision much easier, but taking a guess with 97db/mw the hd650 has you should be able to reach peaks of 120db. Again that is peaks, so if a track is mostly -30 db, then unity gain should be enough. I can see how more gain might be useful in some situations but 3.5x seems ear damaging.


----------



## Xenophon

arm3nian said:


> IIRC the best position is 12 o'clock.
> 
> Can anyone find how much power the o2 puts into 300ohms? It would make the gain decision much easier, but taking a guess with 97db/mw the hd650 has you should be able to reach peaks of 120db. Again that is peaks, so if a track is mostly -30 db, then unity gain should be enough. I can see how more gain might be useful in some situations but 3.5x seems ear damaging.


 

 P=U^2/R assuming a purely resistive load (which is a gross simplification with most headphones).


----------



## Solrighal

I'm a 50 year old male with just slightly less than perfect hearing. On my O2 at unity gain driving my 300 Ohm HD 650's I generally have the volume control somewhere between 12 & 2 o'clock. Sometimes 3 o'clock with the addition of alcohol.


----------



## HaVoC-28

On my HD600 => unity Gain , 10h30  don't touch the volume plot and varying volume in foobar from -18dB to 0 dB . 
 I only turn up the knob for some very quiet classical pieces to 3 o'clock (when i want it loud) .
  
  
 DT-880 600 ohms => same unity gain , but half curse (12 o'lock and crank up in extreme cases ) .
  
 It tend to listen at low/moderate volume most times .
  
 (ODAC as source) .
  
  
 But as some said , 1X/3.5X some the most versatile setting (even if i choose 1X/2.5x , anyway as said i listen at moderate volume so 
	

	
	
		
		

		
			





) .


----------



## diamondears

solrighal said:


> I'm a 50 year old male with just slightly less than perfect hearing. On my O2 at unity gain driving my 300 Ohm HD 650's I generally have the volume control somewhere between 12 & 2 o'clock. Sometimes 3 o'clock with the addition of alcohol.




On my LCD-2 Rev. 2, my volume is normally at 1 o'clock, loudest I could bear continuously is at 3 o'clock. Based on my limited research this is ok, with up to 4-5 o'clock as headroom, but I FEEL (not hear) like the amp is having a difficult time...lol

This is unity gain btw. I have custom 1/3.5x gain settings.


----------



## Solrighal

diamondears said:


> On my LCD-2 Rev. 2, my volume is normally at 1 o'clock, loudest I could bear continuously is at 3 o'clock. Based on my limited research this is ok, with up to 4-5 o'clock as headroom, but I FEEL (not hear) like the amp is having a difficult time...lol
> 
> This is unity gain btw. I have custom 1/3.5x gain settings.


 
  
 That sounds about right to me. I think the optimum mechanical position on a rotary volume pot has to logically be T.D.C.


----------



## diamondears

solrighal said:


> That sounds about right to me. I think the optimum mechanical position on a rotary volume pot has to logically be T.D.C.




T.D.C.?


----------



## castleofargh

I would go with top dead center ^_^ more an engine thing than an audiophile one.
  
 edit: as far as the knob itself is concerned, the best position is maxed out, as this is where less resistance is applied and where channel imbalance has no reason to exist. but as to know how the amp likes it with that architecture, I really wouldn't know.
 too low wouldn't be good for channel imbalance, too high might distort and clip. so middle is a safe bet in most situations I guess.


----------



## vertical

solrighal said:


> That sounds about right to me. I think the optimum mechanical position on a rotary volume pot has to logically be T.D.C.




Lol. Be sure your knock sensors are in proper working order.


----------



## Solrighal

What can I say? I'm old skool.


----------



## diamondears

castleofargh said:


> I would go with top dead center ^_^ more an engine thing than an audiophile one.
> 
> edit: as far as the knob itself is concerned, the best position is maxed out, as this is where less resistance is applied and where channel imbalance has no reason to exist. but as to know how the amp likes it with that architecture, I really wouldn't know.
> too low wouldn't be good for channel imbalance, too high might distort and clip. so middle is a safe bet in most situations I guess.




Based on my not so comprehensive readings of Nwavguy's blogs, clipping at high volume pot positions would be non-existent at unity/no gain, only happens on true gains. So for unity gain, I think way past TDC won't knock the pistons...


----------



## headwhacker

diamondears said:


> Based on my not so comprehensive readings of Nwavguy's blogs, clipping at high volume pot positions would be non-existent at unity/no gain, only happens on true gains. So for unity gain, I think way past TDC won't knock the pistons...


 
  
 Clipping will always depend on the voltage level of the source. O2+ODAC with 1x/3.5x gains. Clipping is non existent.


----------



## Arm3nian

Delete


----------



## ansi

Just got my ODAC+O2 a couple of weeks ago, and been listening extensively with Beyerdynamic T90 and Hifiman HE-400. Great for both. Unfortunately T90 sounds so good with it, now I don't use HE-400 for anything at all. Has also made my Yulong U100 useless. Just can't go back now.
  
 By the way, to those who are looking to buy the JR Audio ODAC+O2 from China: The "2035 MK1" that goes for around 100 dollars is the one you want if you want one that's built according to the original design. The more expensive MK2 ($130) and MK3 ($150) have been modified to sound warmer, and that's the only difference aside from the shinier casing. When I asked JR Audio about it they amusingly said that "MK1 has the sound foreigners tend to like".


----------



## adydula

ANSI..... the O2 and T90s combination is absolutely great......I have several O2's and a ODA.
  
 I sold most of my cans and have mostly the T90s and O2/ODA amps....
  
 No real need to spend more etc..its about as good as technology gets at this time.
  
 Alex


----------



## diamondears

ansi said:


> Just got my ODAC+O2 a couple of weeks ago, and been listening extensively with Beyerdynamic T90 and Hifiman HE-400. Great for both. Unfortunately T90 sounds so good with it, now I don't use HE-400 for anything at all. Has also made my Yulong U100 useless. Just can't go back now.
> 
> By the way, to those who are looking to buy the JR Audio ODAC+O2 from China: The "2035 MK1" that goes for around 100 dollars is the one you want if you want one that's built according to the original design. The more expensive MK2 ($130) and MK3 ($150) have been modified to sound warmer, and that's the only difference aside from the shinier casing. When I asked JR Audio about it they amusingly said that "MK1 has the sound foreigners tend to like".




Foreigners have better cans, they mean?...


----------



## ansi

diamondears said:


> Foreigners have better cans, they mean?...


 
  
 I think he was referring to the perceived tendency of foreigners to gravitate towards neutral and analytical, and that they may actually have some other headphones than Sennheiser HD-650...


----------



## Arm3nian

I got my hd650s a couple of days ago off Amazon for $313, cheapest they've been for years. They only sound slightly better than my hd555s, but I'm using onboard on my $70 motherboard lol. Looking for a big upgrade with o2+odac.


----------



## TeddyK

havoc-28 said:


> But as some said , 1X/*3.5X* some the most versatile setting (even if i choose 1X/*2.5x* , anyway as said i listen at moderate volume so
> 
> 
> 
> ...


 
 2.5X;3.5X : Is there a reason not to choose 3X gain with O2 ?


----------



## jseaber

teddyk said:


> 2.5X;3.5X : Is there a reason not to choose 3X gain with O2 ?


 
  
 Dig into the underlying mathematical requirements of O2+ODAC and you'll find that 3.5x is the optimal high gain position. Gain of 3.0x would waste a few decibels of headroom.


----------



## Arm3nian

teddyk said:


> 2.5X;3.5X : Is there a reason not to choose 3X gain with O2 ?




Potential channel balance problems as the blog mentions. More noise and distortion is always something that comes with more gain. Now if the noise and distortion are actually audible is another story, but theres no point to higher gain if a lower setting does everything you need. The difference is only 3db between 2.5 and 3.5, not that huge of a difference anyway. If headphones don't get loud enough with 2.5x then 3.5x is barely going to help.


----------



## TeddyK

Thanks for your responses.


----------



## diamondears

jseaber said:


> Dig into the underlying mathematical requirements of O2+ODAC and you'll find that 3.5x is the optimal high gain position. Gain of 3.0x would waste a few decibels of headroom.




Hello John. Can you elaborate on this? Is 3.5x gain still the optimal high gain position as compared to unity gain even when the HP can get loud enough at unity gain? Say HP is 91 db /mW and 50 ohms impedance. 

Also, what do you mean by losing/wasting few decibels of headroom if 3.0x gain? You mean unity gain?

Cheers.


----------



## Solrighal

I thought it was a case of the least gain required the better. Or am I wrong?


----------



## headwhacker

diamondears said:


> Hello John. Can you elaborate on this? Is 3.5x gain still the optimal high gain position as compared to unity gain even when the HP can get loud enough at unity gain? Say HP is 91 db /mW and 50 ohms impedance.
> 
> Also, what do you mean by losing/wasting few decibels of headroom if 3.0x gain? You mean unity gain?
> 
> Cheers.


 
  
 By optimal it just mean you have the maximum output of O2 available to use. O2 has a maximum output of around 7Vrms.
  
 If ODAC is your source (2Vrms output), 7 / 2 = 3.5
  
 if O2 is set to 3.5x gain you have as much as 7Vrms of headroom. Above 3.5x O2 will clip. Below that you won't reach 7Vrms. Hence, you are losing a few dBs of headroom.
  
 But if you have a source other than ODAC, which most probably have a different output voltage then the optimal gain value will change. ( 7Vrms / source voltage).
  
 If your HP gets loud enough at 1x gain then it is the optimal gain.


----------



## jseaber

diamondears said:


> Hello John. Can you elaborate on this? Is 3.5x gain still the optimal high gain position as compared to unity gain even when the HP can get loud enough at unity gain? Say HP is 91 db /mW and 50 ohms impedance.
> 
> Also, what do you mean by losing/wasting few decibels of headroom if 3.0x gain? You mean unity gain?
> 
> Cheers.


 
  
 X = Objective2's maximum VRMS input signal before clipping = 7/A
 A = Gain (Vout/Vin)
  
 ODAC output = 2.0VRMS = X
  
 2.0 = 7/A
*A = 7/2 = 3.5*
  
 Setting high gain to 3.5 gives maximum amplification of 2*3.5 = 7.0VRMS. This is slightly below O2's maximum capability of ~7.5VRMS, but ensures no clipping will occur.
  
 Most listening with dynamic headphones is (or rather, should be) conducted at low gain, since the noise floor is superior. Assuming a 1.0/3.5x gain configuration for O2+ODAC, unity gain of 1.0 gives output ranging from 0.0 to 2.0VRMS, and high gain gives a range of 0.0 to 7.0VRMS.
  
 At a proposed high gain of 3.0, output would be limited: 0.0 to 6.0VRMS. This is a loss of 1VRMS compared to 3.5x. Why unnecessarily limit the amplifier?


----------



## diamondears

jseaber said:


> X = Objective2's maximum VRMS input signal before clipping = 7/A
> A = Gain (Vout/Vin)
> 
> ODAC output = 2.0VRMS = X
> ...




Thanks John. Very clear. 

One last question for now: in terms of SQ, and assuming the HP could get loud enough on 1.0x gain, would there be any improvement or advantage in using the 3.5x gain instead?

Cheers.


----------



## blse59

diamondears said:


> Thanks John. Very clear.
> 
> One last question for now: in terms of SQ, and assuming the HP could get loud enough on 1.0x gain, would there be any improvement or advantage in using the 3.5x gain instead?
> 
> Cheers.


 

 Nope, never. Lower gain will always have higher quality SQ in practically every scenario.


----------



## diamondears

blse59 said:


> Nope, never. Lower gain will always have higher quality SQ in practically every scenario.




Yes, that's my current understanding too, but you never know. I always hear the higher gains to have more treble, maybe the additional noise, etc. But I ask re higher gains bec they feel more powerful..


----------



## Arm3nian

jseaber said:


> X = Objective2's maximum VRMS input signal before clipping = 7/A
> A = Gain (Vout/Vin)
> 
> ODAC output = 2.0VRMS = X
> ...


 
 I don't understand this. I thought gain was the last step before sending the signal into the headphones? At 2v the o2 can output 13.3mw into 300ohm headphones, making all of my previous calculations an order of magnitude off. The maximum output power specified then is with 3.5x gain with a 2v input source such as the odac, making it 7VRMS.
  
 So using this to save time for (hd650s 97.8db/mw efficiency and 300ohms impedance): http://www.headphone-amplifier.com/calculator.htm
 unity gain (2000mv) would give me 109db, 2.5x gain (5000mv) would give me 117db, and 3.5x (7000mv) gain would give me 120db. Not that much of a difference between 2.5x and 3.5x, but the 8db gain from 1x to 2.5x might be useful. Question is how much distortion/noise is added with each different setting.


----------



## headwhacker

arm3nian said:


> I don't understand this. I thought gain was the last step before sending the signal into the headphones? At 2v the o2 can output 13.3mw into 300ohm headphones, making all of my previous calculations an order of magnitude off. The maximum output power specified then is with 3.5x gain with a 2v input source such as the odac, making it 7VRMS. So with 3.5x gain the o2 could output 177mw into 300ohm headphones.


 
  
 That is about right. At 3.5x gain and ODAC as source, max power around that value (163mW) for 300ohm load. At unity gain (1x) O2 acts like a buffer and output is 2Vrms for max power of 13mW for 300ohm load.


----------



## jseaber

arm3nian said:


> I don't understand this. I thought gain was the last step before sending the signal into the headphones? At 2v the o2 can output 13.3mw into 300ohm headphones, making all of my previous calculations an order of magnitude off. The maximum output power specified then is with 3.5x gain with a 2v input source such as the odac, making it 7VRMS. So with 3.5x gain the o2 could output 177mw into 300ohm headphones.


 
  
 Voltage gain occurs in any stage of amplification (either as attenuation, unity gain, or amplification). An amplifier can have any number of stages. In O2, voltage gain occurs in the pre-amplification stage, followed by analog attenuation, then a current buffer output stage.
  
 Someone posted a longer mathematical explanation in this thread a few weeks ago, so I will not repeat the exercise.


----------



## Arm3nian

headwhacker said:


> That is about right. At 3.5x gain and ODAC as source, max power around that value (163mW) for 300ohm load. At unity gain (1x) O2 acts like a buffer and output is 2Vrms for max power of 13mW for 300ohm load.


 
  
  


jseaber said:


> Voltage gain occurs in any stage of amplification (either as attenuation, unity gain, or amplification). An amplifier can have any number of stages. In O2, voltage gain occurs in the pre-amplification stage, followed by analog attenuation, then a current buffer output stage.
> 
> Someone posted a longer mathematical explanation in this thread a few weeks ago, so I will not repeat the exercise.


 
 Yeah updated my post. I was picturing a completely different design. Thanks


----------



## Solrighal

So 3.5x is better than 3.0x but not as good as 1.0x?


----------



## headwhacker

solrighal said:


> So 3.5x is better than 3.0x but not as good as 1.0x?


 
 better at what? 3.5x can supply more power than 3x and 1x. But in return noise/distortion is higher than 3x and more so than 1x.
  
 If your headphone is loud enough at 1x then you don't need to raise the gain and is technically better than higher gain. But for harder to drive phones which need more power than 1x can provide then the higher gain is better.


----------



## diamondears

solrighal said:


> So 3.5x is better than 3.0x but not as good as 1.0x?



I think John's point is just that since you have a free choice of a 2nd gain in an O2 (in addition to unity), might as well get the 3.5x to maximize possible gain without any clipping.


----------



## Solrighal

diamondears said:


> I think John's point is just that since you have a free choice of a 2nd gain in an O2 (in addition to unity), might as well get the 3.5x to maximize possible gain without any clipping.


 
  
  


headwhacker said:


> better at what? 3.5x can supply more power than 3x and 1x. But in return noise/distortion is higher than 3x and more so than 1x.
> 
> If your headphone is loud enough at 1x then you don't need to raise the gain and is technically better than higher gain. But for harder to drive phones which need more power than 1x can provide then the higher gain is better.


 
  
 OK, I think I understand. I only listem to HD 650's and unity is fine for me.


----------



## diamondears

I have another question...let's say my HP doesn't sound loud enough to my liking using unity gain on O2 and I'd like to increase volume, which is better, (a) increase Vrms output on the DAC (my DAC can be increased from default 2Vrms up to 2.8Vrms), or (b) use the 3.5x gain on the O2?


----------



## headwhacker

diamondears said:


> I have another question...let's say my HP doesn't sound loud enough to my liking using unity gain on O2 and I'd like to increase volume, which is better, (a) increase Vrms output on the DAC (my DAC can be increased from default 2Vrms up to 2.8Vrms), or (b) use the 3.5x gain on the O2?


 
  
 increase the DAC output and stay at 1x on O2.


----------



## diamondears

headwhacker said:


> increase the DAC output and stay at 1x on O2.




Why? To avoid additional noise? What else?


----------



## Solrighal

Happy new year everyone!


----------



## Peti

+1
  
 Let me wish to all of you an abundant New Year in superb music, headphones and amps. I have ordered my O2/ODAC for Christmas and LOVING it!


----------



## WilliamLeonhart

Guys I have this strange issue on my DIY O2/ODAC (boards made by JDS): sometimes when I click on another song on foobar it gives a small (but clearly audible) crackling sound. It does not happen everytime but sometimes it's louder than the others. I'm a bit worried. This does not happen on my integrated Realtek, and on the O2/ODAC it happens to every cans I own (all of them Grados).
  
 Have you ever had this issue? It happens to me both on low gains and high gains.


----------



## WilliamLeonhart

After further checking I found that foobar often makes a small "tsk" sound when I was switching songs (on both my Realtek and the O2/ODAC), but the crackling sound only happens on the O2/ODAC. Quite audible.


----------



## headwhacker

diamondears said:


> Why? To avoid additional noise? What else?


 
  
 I only realize this while reading through the sound science forum. 
  
 Since the O2's volume control is between the gain and the output stage, O2 will apply the gain first on the signal before it is attenuated by the volume control. This means that if the gain ratio is too high for the input voltage, the signal clips even if the volume knob is far from the it's max level.
  
 I think this make sense but not 100% sure. Can anybody else can confirm this?


----------



## diamondears

headwhacker said:


> I only realize this while reading through the sound science forum.
> 
> Since the O2's volume control is between the gain and the output stage, O2 will apply the gain first on the signal before it is attenuated by the volume control. This means that if the gain ratio is too high for the input voltage, the signal clips even if the volume knob is far from the it's max level.
> 
> I think this make sense but not 100% sure. Can anybody else can confirm this?




2.0Vrms x 3.5 gain won't clip. That's the limit before clipping. Otherwise, I would have not asked the question and just preferred increasing the Vrms out of the DAC. But I think yeah, if gaining rads to clipping, that means something is being done on the SQ?


----------



## Jakkal

headwhacker said:


> I only realize this while reading through the sound science forum.
> 
> Since the O2's volume control is between the gain and the output stage, O2 will apply the gain first on the signal before it is attenuated by the volume control. This means that if the gain ratio is too high for the input voltage, the signal clips even if the volume knob is far from the it's max level.
> 
> I think this make sense but not 100% sure. Can anybody else can confirm this?


 
 That is correct, it was explained earlier in this tread.


----------



## WilliamLeonhart

williamleonhart said:


> Guys I have this strange issue on my DIY O2/ODAC (boards made by JDS): sometimes when I click on another song on foobar it gives a small (but clearly audible) crackling sound. It does not happen everytime but sometimes it's louder than the others. I'm a bit worried. This does not happen on my integrated Realtek, and on the O2/ODAC it happens to every cans I own (all of them Grados).
> 
> Have you ever had this issue? It happens to me both on low gains and high gains.


 
 Hi can anyone please offer me some advice


----------



## diamondears

williamleonhart said:


> Hi can anyone please offer me some advice




What's your computer? I've read somewhere that you would have to close all programs/apps to stop the clicking and pops, especially if you're playing large file formats such as DSD.

I was using iPhone 6 with Onkyo HF Player HD olaying some DSD files and I experienced clicks and pops. They disappeared when I closed all the apps. Maybe they eat too much memory, processing or something.


----------



## castleofargh

williamleonhart said:


> williamleonhart said:
> 
> 
> > Guys I have this strange issue on my DIY O2/ODAC (boards made by JDS): sometimes when I click on another song on foobar it gives a small (but clearly audible) crackling sound. It does not happen everytime but sometimes it's louder than the others. I'm a bit worried. This does not happen on my integrated Realtek, and on the O2/ODAC it happens to every cans I own (all of them Grados).
> ...


 

 play around with the buffer size in foobar maybe.
 are the files of different resolutions?


----------



## MrMateoHead

+1 to checking the buffer in Foobar. The default is probably too low.


----------



## Peti

I got this most unusual issue with my O2/ODAC. I mean it's been working flawlessly but when ordered I have required special gain settings of 1X and 3.5X.
  
 When I got it my HD800 got too loud on low gain when the knob had been set around 11 o'clock. Highly compressed music needs even less juice. My highest DR musics sound loud enough on LOW gain around 4 o'clock. (Brothers in Arms, Dark Side of the Moon SACD, etc.)
  
 Is it normal at 1X gain or they somehow forgot to adjust the gain settings according to my request? Anyone can comment on this who has HD800 and O2/ODAC please?
  
 Contacted the company a few days ago but got no response yet, hence I write here. Don't want to name them b/c the product itself is awesome I'm just puzzled with this gain settings issue and it's maybe just me who got it wrong.
  
  
 Thank You


----------



## blse59

peti said:


> I got this most unusual issue with my O2/ODAC. I mean it's been working flawlessly but when ordered I have required special gain settings of 1X and 3.5X.
> 
> When I got it my HD800 got too loud on low gain when the knob had been set around 11 o'clock. Highly compressed music needs even less juice. My highest DR musics sound loud enough on LOW gain around 4 o'clock. (Brothers in Arms, Dark Side of the Moon SACD, etc.)
> 
> ...


 
  
 That sounds about right. 1x gain is enough to drive most headphones. I looked up the specs and the 800 has about the same impedance and sensitivity as the 650.
  
 Maybe an 800 owner can chime in for reassurance.


----------



## WilliamLeonhart

mrmateohead said:


> +1 to checking the buffer in Foobar. The default is probably too low.


 


castleofargh said:


> play around with the buffer size in foobar maybe.
> are the files of different resolutions?


 


diamondears said:


> What's your computer? I've read somewhere that you would have to close all programs/apps to stop the clicking and pops, especially if you're playing large file formats such as DSD.
> 
> I was using iPhone 6 with Onkyo HF Player HD olaying some DSD files and I experienced clicks and pops. They disappeared when I closed all the apps. Maybe they eat too much memory, processing or something.


 Thanks guys. I will try this when I get home. My laptop is 4yo and I tend to put it into hibernation rather than shutting it down. Also I often open a lot of Chrome tabs (due to my 2nd job as a translator).


----------



## Solrighal

peti said:


> I got this most unusual issue with my O2/ODAC. I mean it's been working flawlessly but when ordered I have required special gain settings of 1X and 3.5X.
> 
> When I got it my HD800 got too loud on low gain when the knob had been set around 11 o'clock. Highly compressed music needs even less juice. My highest DR musics sound loud enough on LOW gain around 4 o'clock. (Brothers in Arms, Dark Side of the Moon SACD, etc.)
> 
> ...


 
  
  


blse59 said:


> That sounds about right. 1x gain is enough to drive most headphones. I looked up the specs and the 800 has about the same impedance and sensitivity as the 650.
> 
> Maybe an 800 owner can chime in for reassurance.


 
  
 Yes, 1x (Unity) gain should be more than enough. That's all I use for my HD 650.


----------



## adydula

Check buffer timings in Foobar....
  
 Alex


----------



## Peti

Thanks for the feedbacks everyone. I forgot to mention that my foobars sound level was turned 100% while the windows volume bar on 96%. So it is considered normal...I am just taken aback that a hp like the HD800 is such "easy" to drive by the O2at unity gain. I thought I would need to use more often the high gain setting with my high DR music.


----------



## castleofargh

peti said:


> Thanks for the feedbacks everyone. I forgot to mention that my foobars sound level was turned 100% while the windows volume bar on 96%. So it is considered normal...I am just taken aback that a hp like the HD800 is such "easy" to drive by the O2at unity gain. I thought I would need to use more often the high gain setting with my high DR music.


 

 well it's understandable. given how people mistake coloration with driving ability when they talk about amping the hd800, and how probably 95% of headfi have the wrong idea about gain switch.


----------



## Peti

At least, it seems, you're among the 5 percent. Enjoy!


----------



## castleofargh

peti said:


> At least, it seems, you're among the 5 percent. Enjoy!


 
  
 it wasn't a critic against you or 95% of headfi members(way to make lot of friends easily ^_^), we can't know what we don't know. I will never blame someone for not knowing something, I wasn't born audiophile.
	

	
	
		
		

		
			




 I'm just stating what I think is the situation. on headfi we're informed but not really taught much.


----------



## Peti

If you could spare some of your most precious time to educate us, clueless headfi'ers, (the 95%) and divulge your take in a nushell on the gain and its use would be most appreciated..


----------



## castleofargh

well if you want to learn gain in detail, you'll have better sources than poor me, like... nwavguy maybe? ^_^ I first learned from his blog so I hope it's reliable intel 
	

	
	
		
		

		
		
	


	




.
 but in short, gain changes the voltage "gain" compared to the value the DAC is sending. volume control also changes voltage(voltage=loudness), so people assume that it's just a glorified volume switch. some think it some kind of magic power booster. some even mistake the very perceptual "louder is better" for sound changes and imagine that high gain has more bass, better dynamic, better soundstage etc...(same BS as with cables) but it has nothing to do with gain changing the sound, and everything to do with us and how biased we are to loudness changes.
  
 anyway the very general rule is that gain is used to match the voltage provided by the DAC. but for a headphone user it's usually more simple than that, you always go with the lower gain and only ever change up when you can't get the headphone loud enough with the volume knob.


----------



## Peti

"but for a headphone user it's usually more simple than that, you always go with the lower gain and only ever change up when you can't get the headphone loud enough with the volume knob."
  
 That's the part I already knew. Thanks for the rest. And before pulled the trigger I made sure to carefully scrutinize the aforementioned guy's webpage, along with the comments. It was eye-opening, to say the least and the conclusion I distilled was the one I quoted you for here. Yet, I'm still amazed how loud my HD800 gets even at low gain, I can't help it.


----------



## WilliamLeonhart

Hi, I see I can change buffer size in foobar, but how do I change buffer timing? Also, shoud I set windows driver to 24bit?


----------



## castleofargh

williamleonhart said:


> Hi, I see I can change buffer size in foobar, but how do I change buffer timing? Also, shoud I set windows driver to 24bit?


 

 buffer length is in ms so it's a timing ^_^. we all suggested the same thing. does that change anything for your noises? (except that the song starts later with a huge buffer obviously)


----------



## WilliamLeonhart

castleofargh said:


> buffer length is in ms so it's a timing ^_^. we all suggested the same thing. does that change anything for your noises? (except that the song starts later with a huge buffer obviously)


 
 Hi, at the moment I find things to be perfectly fine. I increased the buffer and also set fade-in and fade-out to about 300ms. I've been using my phones for more than 1 hours and so far no problem.
  
 Once again thank you guys a whole lot.


----------



## blse59

After one month of ownership, still loving the O2. It's like having a clear window into my dac and headphones.


----------



## WilliamLeonhart

Guys what value should I set for the buffer on foobar? Is it "the more the merrier"? Can the ODAC be overloaded or something?


----------



## ericr

[suited name="lehoang15tuoi" url="/t/616331/o2-amp-odac/3855#post_11257210"]Guys what value should I set for the buffer on foobar? Is it "the more the merrier"? Can the ODAC be overloaded or something?
[/quote]

In my experience, the smaller the buffer the better. With my ODAC I use at work I've set the buffer in Foobar to the smallest size (50ms IIRC) as this eliminates the pops and clicks I was getting previously.

Note: Foobar with wasapi in event mode.


----------



## WilliamLeonhart

I tried that and it worsened immediately  Clicks and pops happen 2 out of 3 times


----------



## blse59

williamleonhart said:


> Guys what value should I set for the buffer on foobar? Is it "the more the merrier"? Can the ODAC be overloaded or something?


 

 I leave it at the default. Everything is fine. Is there a way for you to reset all Foobar settings back to default and try again? I have no idea what may be causing your clicks and pops. Is it just Foobar and not any other player?


----------



## castleofargh

williamleonhart said:


> Guys what value should I set for the buffer on foobar? Is it "the more the merrier"? Can the ODAC be overloaded or something?


 
  it depends on the computer and how many programs are running at the same time. there are no magic value the audiophile can cling onto as the golden number of bettererer sound.
 I have 120ms, but there is a pretty wide range of values that are "popless"^_^ for me when changing songs or after some hours of play. just try something, if it works then it works. or you can go warrior on the problem and follow the idea behind that explanation http://www.head-fi.org/t/539638/how-to-set-perfect-buffer-lengths


----------



## MrMateoHead

Just felt like Congratulating the O2/ODAC today.
  
 I've been listening to the Realtek 892 on a new motherboard for a week or so, finding it to be an excellent source overall. No noise detectable through the 02, which was a first for my experiences with computer audio. It didn't drive the HE-400 headphones nearly as well as the O2, which clearly gave them better bass and "punch". But as a source it works very well.
  
 But going back to the ODAC its amazing at how easily I can detect the added resolution and "bite" in my music. It truly is an excellent 2-channel solution and it really is a cut above even the excellent Realtek chips these days.


----------



## WilliamLeonhart

castleofargh said:


> it depends on the computer and how many programs are running at the same time. there are no magic value the audiophile can cling onto as the golden number of bettererer sound.
> I have 120ms, but there is a pretty wide range of values that are "popless"^_^ for me when changing songs or after some hours of play. just try something, if it works then it works. or you can go warrior on the problem and follow the idea behind that explanation http://www.head-fi.org/t/539638/how-to-set-perfect-buffer-lengths


Thanks for thelink. I really appreciate it. Will try when I get home


----------



## blse59

Leaving the standalone O2 plugged in while it's powered off, how much power does it draw? I assume it occasionally draws power when the battery charge naturally trickles down. Maybe pennies worth a year?


----------



## puzzlerecovery

Is there a point to buying the O2/ODAC combination with a pair of Philips X2s (30 Ohms)? I've been researching an incredible amount but haven't come up with anything significantly definitive.


----------



## blse59

puzzlerecovery said:


> Is there a point to buying the O2/ODAC combination with a pair of Philips X2s (30 Ohms)? I've been researching an incredible amount but haven't come up with anything significantly definitive.


 

 I haven't had any experience with the X2 myself. At the official X2 thread I'm sure there will be people who can answer your question:
  
http://www.head-fi.org/t/723025/philips-fidelio-x2


----------



## adamlr

puzzlerecovery said:


> Is there a point to buying the O2/ODAC combination with a pair of Philips X2s (30 Ohms)? I've been researching an incredible amount but haven't come up with anything significantly definitive.


 
 is there a point? i dont know, what are you trying to achieve? assuming the X2s are "easy to drive" (which i wouldnt know btw) then you wouldnt necessarily NEED the combo if thats what your getting at. what point are you talking about?


----------



## JacobLee89

puzzlerecovery said:


> Is there a point to buying the O2/ODAC combination with a pair of Philips X2s (30 Ohms)? I've been researching an incredible amount but haven't come up with anything significantly definitive.


 
  
 If you're going for your first desktop dac/amp combination, you cannot go wrong with the O2/ODAC at all. it's a huge leap of an improvement over onboard sound. Just bear in mind that the O2/ODAC combo is a relatively neutral sounding set up, so you will just end up with what the Philips X2 has to offer. Some, like me, appreciate this function whereas others prefer to have a more specific colouration to partner up with their headphones.
  
 If you're going for portability, you may want a portable dac/amp instead, something like the fiio e18.


----------



## blse59

jacoblee89 said:


> If you're going for your first desktop dac/amp combination, you cannot go wrong with the O2/ODAC at all. it's a huge leap of an improvement over onboard sound. Just bear in mind that the O2/ODAC combo is a relatively neutral sounding set up, so you will just end up with what the Philips X2 has to offer. Some, like me, appreciate this function whereas others prefer to have a more specific colouration to partner up with their headphones.
> 
> If you're going for portability, you may want a portable dac/amp instead, something like the fiio e18.


 

 Agreed! The best thing about it is it will last you years and works extremely well with almost any headphone you throw at it. Perfect for people who want to stay in the hobby.


----------



## WilliamLeonhart

jacoblee89 said:


> If you're going for your first desktop dac/amp combination, you cannot go wrong with the O2/ODAC at all. it's a huge leap of an improvement over onboard sound. Just bear in mind that the O2/ODAC combo is a relatively neutral sounding set up, so you will just end up with what the Philips X2 has to offer. Some, like me, appreciate this function whereas others prefer to have a more specific colouration to partner up with their headphones.
> 
> If you're going for portability, you may want a portable dac/amp instead, something like the fiio e18.


 
 Or the C5D! Can't go wrong with anything made by JDS Labs!


----------



## JacobLee89

williamleonhart said:


> Or the C5D! Can't go wrong with anything made by JDS Labs!


 
  
 Portable DAC/AMPS is a world I have no idea in ! I did find that the Fiio E18 has a slight channel imbalance. So the C5D is definitely worth a shot!


----------



## puzzlerecovery

Nah, not looking for something portable. I'll probably pick up the O2/ODAC combo after tax return money comes. Thanks guys.


----------



## Condocondor

Teak?


----------



## Solrighal

My turn. Freak?


----------



## castleofargh

solrighal said:


> My turn. Freak?


 

 "my name is Reek it rhymes with freak"
 winter is coming


----------



## Solrighal

castleofargh said:


> "my name is Reek it rhymes with freak"
> winter is coming


 
  
 Haven't you got an argument to be getting on with?


----------



## vertical

solrighal said:


> Haven't you got an argument to be getting on with?



What! Where? Is there drama somewhere nearby that will be entertaining to follow?
Jk


----------



## Solrighal

vertical said:


> What! Where? Is there drama somewhere nearby that will be entertaining to follow?
> Jk


 
  
 I don't know any more, I unsubscribed, lol.


----------



## Kevin.T

Hey guys, new O2 owner here!

 First, let me get this out of the way: I love this little unit. After a lot of back and forth with my Burson Soloist (sighted, not accurately level-matched, etc.), I can say that it drives the LCD-2 just fine. It might not be everyone's cup of tea: it is deadly neutral, no 'euphonic' presentation going on here. However, I can't hear anything that would lead me to believe the LCD-2 is not adequately powered by the O2.
  
 Now for the meaty stuff. This information might be valuable to Peti, who observed something similar 2 pages back. I ordered my O2 with the Medium gain settings, which is 1x and 3.5x. Upon receiving it and trying it with my stable of headphones (LCD-2, SR225i and Momentum), I noticed that they all get really loud with the volume pot under 9 o'clock on low gain (1x). Here's where it gets interesting: using all 3 headphones, for the same volume output, I have to crank the volume knob slightly higher on the Burson than on the O2 (for example, 9 o'clock on the Soloist is roughly equal to 8 o'clock on the O2 in terms of volume output using the LCD-2). The low gain setting on the Burson Soloist is *2x*.

 I'm inclined to think that I (and maybe also Peti, from what he seems to be saying) might have gotten a unit that has the 2.5x/6.5x gain settings by mistake! Unless there's something that I'm missing (I'm no electrical engineer), this seems to be the only logical conclusion I can jump to. :S

 (I'd really like to take a picture of the internals to confirm with you guys, but it seems I don't have the right key to unscrew the volume knob in order to open the unit.)


----------



## jseaber

kevin.t said:


> Hey guys, new O2 owner here!
> 
> First, let me get this out of the way: I love this little unit. After a lot of back and forth with my Burson Soloist (sighted, not accurately level-matched, etc.), I can say that it drives the LCD-2 just fine. It might not be everyone's cup of tea: it is deadly neutral, no 'euphonic' presentation going on here. However, I can't hear anything that would lead me to believe the LCD-2 is not adequately powered by the O2.
> 
> ...


 
  
 Kevin - Here's a quick way to confirm gain. At low gain on a 1.0/3.5x unit, listening volume at 100% should audible match the output strength of your audio source. If the amp is louder, gain must be set higher.


----------



## Kevin.T

jseaber said:


> Kevin - Here's a quick way to confirm gain. At low gain on a 1.0/3.5x unit, listening volume at 100% should audible match the output strength of your audio source. If the amp is louder, gain must be set higher.


 

 Hi,

 Thank you for the very quick and helpful response! I just tried it and you are correct: the volume output is the same with headphones straight out of my Macbook as it is with the O2 placed between the laptop and headphones. Therefore, the low gain is definitely 1x.


----------



## Peti

And thank you Kevin, for bringing up the issue again. Just conducted the test suggested by jseaber and it turned out that my HD800 gets audibly louder when turned back on to the O2! At maximum volume right out of the source I can still listen the music but as soon as I turn it back on the O2 at maximum level it gets wayyyy too loud to be listened to. I think it is obvious now, I got my O2/ODAC with the factory gain settings instead of 1X - 3.5X (


----------



## castleofargh

peti said:


> And thank you Kevin, for bringing up the issue again. Just conducted the test suggested by jseaber and it turned out that my HD800 gets audibly louder when turned back on to the O2! At maximum volume right out of the source I can still listen the music but as soon as I turn it back on the O2 at maximum level it gets wayyyy too loud to be listened to. I think it is obvious now, I got my O2/ODAC with the factory gain settings instead of 1X - 3.5X (


 

 you can just open the box with a screwdriver and look if you have some resistors or not. http://www.techpowerup.com/reviews/JDSLabs/O2_ODAC/images/comp_1.jpg
 if you can see slots on the board next to the knob without 2 of the resistors, then you have 1X. and if you get 4resistors (2 pairs), you can just butcher a pair to turn the O2 into a 1X ^_^.


----------



## Peti

castleofargh said:


> you can just open the box with a screwdriver and look if you have some resistors or not. http://www.techpowerup.com/reviews/JDSLabs/O2_ODAC/images/comp_1.jpg
> if you can see slots on the board next to the knob without 2 of the resistors, then you have 1X. and if you get 4resistors (2 pairs), you can just butcher a pair to turn the O2 into a 1X ^_^.


 

 Loser here: When done with this operation, will it deprive me from the higher gain? Or I will end up having 1X - 6.5X? (I got Mayflower)


----------



## Solrighal

peti said:


> Loser here: When done with this operation, will it deprive me from the higher gain? Or I will end up having 1X - 6.5X? (I got Mayflower)


 
  
 Is sending it back to the manufacturer not an option?


----------



## Peti

solrighal said:


> Is sending it back to the manufacturer not an option?


 

 Will contact them again for sure. The first time I got no response though...


----------



## blse59

peti said:


> And thank you Kevin, for bringing up the issue again. Just conducted the test suggested by jseaber and it turned out that my HD800 gets audibly louder when turned back on to the O2! At maximum volume right out of the source I can still listen the music but as soon as I turn it back on the O2 at maximum level it gets wayyyy too loud to be listened to. I think it is obvious now, I got my O2/ODAC with the factory gain settings instead of 1X - 3.5X (


 

 Not trying to insult your intelligence 
	

	
	
		
		

		
			





 but it doesn't hurt to double check. Is the gain switch on the O2 in the farthest out position? Pushed in is high gain, pushed out is low gain.


----------



## Peti

blse59 said:


> Not trying to insult your intelligence
> 
> 
> 
> ...


 

 Ehh, that was hurt, blse59!!
  
 Of course it was low gain at 100% completely turned as far out as possible.


----------



## blse59

peti said:


> Ehh, that was hurt, blse59!!
> 
> Of course it was low gain at 100% completely turned as far out as possible.


 

 Hehe, ok. You never know. Sometimes with problems it's something stupid that gets overlooked like that.


----------



## Peti

blse59 said:


> Hehe, ok. You never know. Sometimes with problems it's something stupid that gets overlooked like that.


 

 It still hurts though. Anyhow, just contacted Mayflower, I hope they'll get back to me by tomorrow. Other than this issue I'm in complete love with the O2/ODAC!!


----------



## Solrighal

If they don't fix it I'll sell you mines.


----------



## WilliamLeonhart

Never knew the O2 was powerful enough to charge the HD800 to such loud volume!


----------



## headwhacker

williamleonhart said:


> Never knew the O2 was powerful enough to charge the HD800 to such loud volume!


 
  
 Let me guess people from HD800 threads tells people that HD800 requires a speaker amp to sounf nice.


----------



## burritoboy9984

williamleonhart said:


> Never knew the O2 was powerful enough to charge the HD800 to such loud volume!




I took an O2 odac combo to one of the Dallas meets a couple of years ago, and it blew away several people who had $3k+ setups driving their HD800's.

Erik


----------



## headwhacker

Other than HE-6, O2/ODAC is more than enough to drive almost anything out there. Even the HE-560 which is next to HE-6 in power hungry cans sound excellent driven by O2+ODAC.


----------



## Rajikaru

+1 
  
 I have them both, and can confirm that O2+ODAC, on a gain setting of 3.5x, does an excellent job of driving an HE-560.


----------



## WilliamLeonhart

Very nice to hear! I never knew the O2 could be so powerful


----------



## Peti

burritoboy9984 said:


> I took an O2 odac combo to one of the Dallas meets a couple of years ago, and it blew away several people who had $3k+ setups driving their HD800's.
> 
> Erik


 

 It made me feel so good to read this haha!!


----------



## JacobLee89

peti said:


> It made me feel so good to read this haha!!


 
  
 It's like I always say:
  
 Can never go wrong with the O2/ODAC combo.


----------



## adydula

What he said!!
  
 The only other amp I like other than the O2 is the ODA. 3x the current capacity....
  
 Alex


----------



## Solrighal

I've been trialling a Project Ember for the last three weeks.


----------



## adamlr

adydula said:


> What he said!!
> 
> The only other amp I like other than the O2 is the ODA. 3x the current capacity....
> 
> Alex


 
 made quite the double take there... so theres an ODA available for 550$ now hu? or did you get the diy kit? will you share your experience with us?


----------



## adydula

Be Happy too....u can read all about it here:
  
http://www.head-fi.org/t/719611/objective-desktop-amp-a-version-from-agdr
  
 Also I have many post at diyaudio.com under the headphone amp section under ODA.
  
 Mine was a total DIY build, board from AGDR and parts from mouser.com and digikey.
  
 AGDR does sell boards and has a board with all the SMD parts installed and you have to solder in the larger parts.
  
 You can PM him at diyaudio.com and ask him about a built one etc....
  
 Alex


----------



## blse59

solrighal said:


> I've been trialling a Project Ember for the last three weeks.


 

 How much do one of those doohickeys cost?


----------



## Solrighal

blse59 said:


> How much do one of those doohickeys cost?


 
  
 The Ember starts at $325. I'm comparing it to my O2 but as an upgrade rather than as a competitor.


----------



## HaVoC-28

solrighal said:


> The Ember starts at $325. I'm comparing it to my O2 but as an upgrade *Sidegrade / different coloration* rather than as a competitor.


 
  
 Fixed


----------



## Solrighal

havoc-28 said:


> Fixed


 
  
 Sorry, but no. At least, not when driving either the HD 650 or the Q701. The Ember is a world apart I'm afraid. It's been quite an eye-opener for me to be honest. I went into the trial actually rooting for the O2 but it doesn't compete on any level.


----------



## HaVoC-28

solrighal said:


> Sorry, but no. At least, not when driving either the HD 650 or the Q701. The Ember is a world apart I'm afraid. It's been quite an eye-opener for me to be honest. I went into the trial actually rooting for the O2 but it doesn't compete on any level.


 

 If you say so , O² was an eye opener for me but on the opposite way, amps that i liked => sound the same , colored one sound different for X reasons ,i prefer stick to amps that sound the same or very similar => on Blind ABX at level matched = > can't figure wich is wich at least i know that they don't add anything to the sound ^^ (and keep the more convenient/cheapest of the lot => O²) .
  
   But well if you are happy with the ember thing , great for you


----------



## Solrighal

havoc-28 said:


> If you say so , O² was an eye opener for me but on the opposite way, amps that i liked => sound the same , colored one sound different for X reasons ,i prefer stick to amps that sound the same or very similar => on Blind ABX at level matched = > can't figure wich is wich at least i know that they don't add anything to the sound ^^ (and keep the more convenient/cheapest of the lot => O²) .
> 
> But well if you are happy with the ember thing , great for you


 
  
 It's all good and I actually agree with you. I'm a big fan of the O2. I like the way it sounds and I like the philosophy behind it. I'd have liked to have met NwAvGuy, he's an interesting guy.
  
 Still, music is about more than accuracy it seems, at least for me. When I compare the two amps I can't say the Ember adds detail or anything like that because it doesn't. What it does do though is take the details the O2 lays out bare and throws them in the air and plays them where they fall. Some details are now further back in the mix & less prominent whereas others are taking centre-stage where previously they were equal to everything else. It's a coloured sound certainly, but it's tastier to my ears. There's also a far larger sound-stage now. The HD 650's don't have the largest sound-stage out there and it's commented on a lot. It's quite a bit more expansive on the Ember than on the O2. My AKG Q701's actually change character the most through the Ember. They do seem to like power, the more the better. That was also a surprise to me. They still have the 2k spike though so I rarely use them.
  
 The O2 did allow me to listen to a lot of headphones before deciding on my main pair. It is a very good tool for hearing into the the sonic signature of the headphone itself. I'm pretty much stuck now on the HD 650. Nothing else I've heard even gets close. I know there are more expensive options out there and trust me, if I could afford them I'd be trying them out. No-one seems to have stumbled upon an HD-650 type of sound though. Almost everything I've heard has treble that I find frankly awful.
  
 That's all just my opinion though and I can totally see why some might be happy with the O2. And of course, they're not competitors anyway. The O2 had a budget criteria in it's mission statement and given that it's a superb wee amp.
  
 As ever, YMMV.


----------



## HaVoC-28

solrighal said:


> It's all good and I actually agree with you. I'm a big fan of the O2. I like the way it sounds and I like the philosophy behind it. I'd have liked to have met NwAvGuy, he's an interesting guy.
> 
> Still, music is about more than accuracy it seems, at least for me. When I compare the two amps I can't say the Ember adds detail or anything like that because it doesn't. What it does do though is take the details the O2 lays out bare and throws them in the air and plays them where they fall. Some details are now further back in the mix & less prominent whereas others are taking centre-stage where previously they were equal to everything else. It's a coloured sound certainly, but it's tastier to my ears. There's also a far larger sound-stage now. The HD 650's don't have the largest sound-stage out there and it's commented on a lot. It's quite a bit more expansive on the Ember than on the O2. My AKG Q701's actually change character the most through the Ember. They do seem to like power, the more the better. That was also a surprise to me. They still have the 2k spike though so I rarely use them.
> 
> ...


 

  
 The important thing is that ember seams to bring something more to your listening , and it's what matter ^^ . Ember has a different presentation than O² ? Not a problem , some will prefer O² , some the ember , etc
  
 Also an amp has more chances to influence the sound in comparison to DACS ... (IMO) .
  
 At least it's still a interesting comparison beetween O²/Ember and some will be gladfull to have this hints


----------



## Solrighal

havoc-28 said:


> The important thing is that ember seams to bring something more to your listening , and it's what matter ^^ . Ember has a different presentation than O² ? Not a problem , some will prefer O² , some the ember , etc
> 
> Also an amp has more chances to influence the sound in comparison to DACS ... (IMO) .
> 
> At least it's still a interesting comparison beetween O²/Ember and some will be gladfull to have this hints


 
  
 Yeah, that's it. It's all about the music after all. I'm certainly not hinting at anything though, merely attempting to explain my own reasoning for moving on from the O2. I won't be knocking the O2 anytime soon, that's for sure.


----------



## castleofargh

that's always the problem with taste. we tend to assume that we will like real sound and so we think that transparent is what we'll love the most.
when in practice, there is only a minority of people who love transparency.
neutral gears are most likely called boring in reviews, and strangely enough, colored amp are the ones described as natural. I guess euphony is what many people are really looking for, not high resolution nor transparency.
now the simple fact that you(Zorro) notice a clear difference with the ember tells me it is not a transparent amp. still, what matters is to enjoy the sound.


----------



## Solrighal

castleofargh said:


> that's always the problem with taste. we tend to assume that we will like real sound and so we think that transparent is what we'll love the most.
> when in practice, there is only a minority of people who love transparency.
> neutral gears are most likely called boring in reviews, and strangely enough, colored amp are the ones described as natural. I guess euphony is what many people are really looking for, not high resolution nor transparency.
> now the simple fact that you(Zorro) notice a clear difference with the ember tells me it is not a transparent amp. still, what matters is to enjoy the sound.




Yeah, I agree. It would probably be fair to state that the O2 is more transparent but that the Ember is more musical (or euphonic), to my ears. It would seem that I like the concept of transparency but I find the reality to be somewhat bland.

I think the extra power plays it's part too. I'm able to listen at much higher levels than is possible on the O2. I found with the O2 that the sound tended towards edginess as the volume increased. I hadn't noticed that as a problem until I moved to the Ember.


----------



## WilliamLeonhart

+1. It's true that the O2 can lean a bit towards edginess. Listening to the O2 right after using the LD I+ made me realized that. But most of the time I still feel that the O2 (and ODAC) offers a very natural sound.


----------



## diamondears

williamleonhart said:


> +1. It's true that the O2 can lean a bit towards edginess. Listening to the O2 right after using the LD I+ made me realized that. But most of the time I still feel that the O2 (and ODAC) offers a very natural sound.



What do you mean by edginess?


----------



## Xenophon

williamleonhart said:


> +1. It's true that the O2 can lean a bit towards edginess. Listening to the O2 right after using the LD I+ made me realized that. But most of the time I still feel that the O2 (and ODAC) offers a very natural sound.


 

 Given that the LD 1 is a low cost tube amp, it's far more likely that considered from a signal fidelity perspective  the LD  produces  distortion that sounds pleasing to you.  Which is fine.  But read post 3916 above:  many people who profess searching neutrality actually don't like it when it's presented to them.


----------



## WilliamLeonhart

diamondears said:


> What do you mean by edginess?


 
 The trebles were harsher. Upper-freqs were grainy.  On new Grados (not broken in, mind me I believe it's real),  it's too harsh and fatiguing for me. I want bright-but-smooth trebles.


----------



## WilliamLeonhart

xenophon said:


>


 
 Yep. I bought the 6CQ6 version of the LD I+ and currently using Mullards tube. I bought the I+ to complement the O2, and I think it's done a great job. When I first heard the Grado SR325is + O2/ODAC combo, I immediately fell in love with the sound and sold everything else I had at that point to buy these. I have never tried Beyers or other "neutral" cans on the O2, so I can't tell if that "neutrality" is my thing. But 99% it is not, because I did not enjoy the Sony V6 nor the DT880 (on other amps).


----------



## diamondears

williamleonhart said:


> The trebles were harsher. Upper-freqs were grainy.  On new Grados (not broken in, mind me I believe it's real),  it's too harsh and fatiguing for me. I want bright-but-smooth trebles.



For Grados, I suggest you use OCC cables (try Oyaide, very cheap). Use OCC USB cable and OCC interconnects. My O2 sounds amazing wth them (don't have the ODAC though).


----------



## WilliamLeonhart

So I should use OCC to connect the amp and the DAC, as well as for USB? For amp/DAC I see the point, but for USB I can't. I thought it would  just transfer the digital signal?


----------



## diamondears

williamleonhart said:


> So I should use OCC to connect the amp and the DAC, as well as for USB? For amp/DAC I see the point, but for USB I can't. I thought it would  just transfer the digital signal?



I couldn't believe it myself when I swapped USB cables myself. It changed from being "digitally" to "analogue-like". Try it. I bought a Neo Oyaide USB cable for only around US$100. Try Oyaide, very cheap (not Furutech, made a mistake, Furutech is expensive, which you don't need at all).


----------



## diamondears

diamondears said:


> I couldn't believe it myself when I swapped USB cables myself. It changed from being "digitally" to "analogue-like". Try it. I bought a Neo Oyaide USB cable for only around US$100. Try Oyaide, very cheap (not Furutech, made a mistake, Furutech is expensive, which you don't need at all).



Specifically, try Neo by Oyaide dB+ Class S USB cable. Highly recommended.


----------



## WilliamLeonhart

Can the ODAC take optical input? My ODAC is DIY so I can ask a friend to mod it


----------



## HaVoC-28

diamondears said:


> Specifically, try Neo by Oyaide dB+ Class S USB cable. Highly recommended.


----------



## Solrighal

Fancy USB cables are aesthetically pleasing.


----------



## diamondears

solrighal said:


> Fancy USB cables are aesthetically pleasing.



Try that specific brand, then come back here if you don't see any difference.


----------



## diamondears

I'm as anti snake oil as you can get, I have 3 O2s and think pricier amps are it. But that USB cable really sounds analogue to me. Removes the digital harshness or edginess as described by @lehoang15tuoi.


----------



## James-uk

A digital cable sounding analogue . Do you even understand how digital cables work? If you did you would realise how silly that sounds.


----------



## diamondears

james-uk said:


> A digital cable sounding analogue . Do you even understand how digital cables work? If you did you would realise how silly that sounds.



Have you heard it? If you did, you would realize how silly you sounded.


----------



## Peti




----------



## Solrighal

I've never heard any expensive USB cables but logic tells me they either work or they don't. I do want a better quality cable though, even if it's only for the looks. Those Neo cables do look nice but £60 is over the top for me.


----------



## headwhacker

diamondears said:


> I'm as anti snake oil as you can get, I have 3 O2s and think pricier amps are it. But that USB cable really sounds analogue to me. Removes the digital harshness or edginess as described by @lehoang15tuoi.


 
  
 ABX or it's a fulla


----------



## WilliamLeonhart

$100 is even higher than the price I paid for the O2... Also I'd have to mod the O2 for it to take optical. I really really have to think this through... The thought that it will not improve much scares me


----------



## Solrighal

I'm not cynical about everything. I've heard differences in analogue cables for instance, sometimes quite obvious too. Digital doesn't work like that though. 

What's the significance of that cable being class S? I didn't know there were different classes of USB cables.


----------



## Jakkal

williamleonhart said:


> The trebles were harsher. Upper-freqs were grainy.  On new Grados (not broken in, mind me I believe it's real),  it's too harsh and fatiguing for me. I want bright-but-smooth trebles.


 
 For Grados and other treble happy headphones you can check Project Polaris. It has bandwidth adjustments for smoothing out the treble and it has a lot of other features like six gain settings, three settings for output impedance and others.


----------



## diamondears

solrighal said:


> I'm not cynical about everything. I've heard differences in analogue cables for instance, sometimes quite obvious too. Digital doesn't work like that though.
> 
> What's the significance of that cable being class S? I didn't know there were different classes of USB cables.



It's just branding/series. They have Class B and A, which has smaller gauge copper, the other just regular copper (not OCC) or vice-versa, not sure on other classes. 

I A-B'd it with my other USB cables (regular USB cable, Wireworld and Furutech G2).


----------



## bar1

james-uk said:


> A digital cable sounding analogue . Do you even understand how digital cables work? If you did you would realise how silly that sounds.


 

 +1


----------



## vertical




----------



## James-uk

diamondears said:


> Have you heard it? If you did, you would realize how silly you sounded.




Google is your friend. Go and do the research. I know you hear a difference between the cheap usb and expensive one but that doesn't mean the difference exists. Expectation bias makes fools of us all .


----------



## headwhacker

james-uk said:


> Google is your friend. Go and do the research. I know you hear a difference between the cheap usb and expensive one but that doesn't mean the difference exists. Expectation bias makes fools of us all .


 
  
 Anyone who knows how digital data is transmitted will surely feel silly just by the thought of actually undergoing any test. It's purely expectation bias and goes to prove we can't trust what we hear if we see where the sound is coming from no matter how perfect our hearing maybe.


----------



## diamondears

headwhacker said:


> Anyone who knows how digital data is transmitted will surely feel silly just by the thought of actually undergoing any test. It's purely expectation bias and goes to prove we can't trust what we hear if we see where the sound is coming from no matter how perfect our hearing maybe.



Do you really know how digital sound is transmitted?


----------



## WilliamLeonhart

From my very limited knowledge, the computer gives the DAC data (bytes and bits), not analog signal. So I honestly don't know how USB cables can improve the sound.


----------



## diamondears

DP


----------



## diamondears

williamleonhart said:


> From my very limited knowledge, the computer gives the DAC data (bytes and bits), not analog signal. So I honestly don't know how USB cables can improve the sound.



Just try it. Blind test it if you like.


----------



## headwhacker

diamondears said:


> Do you really know how digital sound is transmitted?


 
  
 So now you  hear digital sound? There is no such thing whatever gets transmitted through a USB cable is just a data like any other data. That is why you need a DAC to listen to music.
  
 But then if you listen directly to a digital data then I can't argue with you my brain still can't process/interpret digital data.


----------



## diamondears

headwhacker said:


> So now you  hear digital sound? There is no such thing whatever gets transmitted through a USB cable is just a data like any other data. That is why you need a DAC to listen to music.
> 
> But then if you listen directly to a digital data then I can't argue with you my brain still can't process/interpret digital data.



You're putting words into my mouth. Where did I say I hear a digital signal?

Hey, if you can't hear any difference, that's perfectly ok and have fun. 

But I blind tested it, and I definitely hear differences. The main difference with the Neo by Oyaide dB+ Class S OCC copper USB cable is it brings better bass and the treble isn't harsh. As I said, the resulting sound sounded more analogue-like.


----------



## jseaber

headwhacker said:


> Anyone who knows how digital data is transmitted will surely feel silly just by the thought of actually undergoing any test. It's purely expectation bias and goes to prove we can't trust what we hear if we see where the sound is coming from no matter how perfect our hearing maybe.


 
  
 Not sure if I've shared this already.
  
 While differential, digital data arrives the same via one cable compared to another cable (i.e., jitter is largely a function of the transmitting device and receiving controller), the +5V and GND lines are susceptible to interference. A DAC that relies on the USB's +5V supply is therefore susceptible to interference from the attached USB cable, and not all USB cables perform the same with respect to EMI. Placing a good ferrite on an ordinary USB cable improves dynamic range by up to 10dB on ODAC. NwAvGuy vaguely addressed this difference.
  
 We sure felt silly when we cancelled development of a new DAC last year over cabling performance. The concept DAC plugged directly into a USB port, like a thumb drive. Two prototypes were built: one with a direct USB type A (male) connector, and an otherwise identical version equipped with a mini-USB jack (female). The direct USB prototype eliminated the need for a cable, but ruined performance. Project cancelled! Of course, there are solutions to such interference, but the point is, a USB device which relies on the +5V line may be sensitive to the EMI performance of its USB cable.
  
 So, ferrites matter. Since not all USB cables utilize the same ferrite, it's possible to observe varying jitter and dynamic range performance with a USB driven DAC. A decent ferrite costs about $1. As for those $100 USB cables, well, aesthetics are nice, too. Just make sure there's a ferrite attached!


----------



## headwhacker

EDIT: wrong thread


----------



## WilliamLeonhart

Thanks Seaber. I'm currently using a cable from my old digital cam that has a ferrite bead. 
  
 Too bad you had to cancel the direct usb DAC  Is it possible to include the ferrite in your "DAC thumb?"


----------



## jseaber

williamleonhart said:


> Thanks Seaber. I'm currently using a cable from my old digital cam that has a ferrite bead.
> 
> Too bad you had to cancel the direct usb DAC  Is it possible to include the ferrite in your "DAC thumb?"


 
  
 Nah, that concept design is long gone. There is no direct substitute for a ferrite on a cable. The easiest, non-EMC, solution is to supply power external from the USB cable.
  
 I wasn't entirely convinced the world needed another tiny DAC, so we halted development and moved on to more exciting projects.


----------



## s0ckpupp3t

jseaber said:


> I wasn't entirely convinced the world needed another tiny DAC, so we halted development and moved on to more exciting projects.


 
 Do tell, what "exciting projects"?


----------



## WilliamLeonhart

jseaber said:


> Nah, that concept design is long gone. There is no direct substitute for a ferrite on a cable. The easiest, non-EMC, solution is to supply power external from the USB cable.
> 
> I wasn't entirely convinced the world needed another tiny DAC, so we halted development and moved on to more exciting projects.


 
 I really hope you guys will produce a mobile DAC/amp that's smaller than the C5D. I like the C5D a lot, but as I use 2 smartphones at once, I can't put the C5D into my pocket.


----------



## jseaber

williamleonhart said:


> I really hope you guys will produce a mobile DAC/amp that's smaller than the C5D. I like the C5D a lot, but as I use 2 smartphones at once, I can't put the C5D into my pocket.


 
  
 One day. For now, battery capacity is the limitation for a strong portable amp. Users want longer run time and more power, and that necessitates a larger battery.


s0ckpupp3t said:


> Do tell, what "exciting projects"?


 
  
 I've already said too much.


----------



## snowlune

I couldn't find a thread on the O2 in the DIY section so I'm just going to ask here.

 So, I soldered together my own O2+ODAC a couple of months ago and everything works fine so far. However, there might be few small problems.

 Because this was my first DIY attempt, I didn't honor the "put everything in shortest to tallest" rule too throughly, and the regulators (U5, U6) ended up being too tall, which can potentially short to the case. I've checked, and there is around 1mm of space between the top to the case, but it might touch the case if the amp is held upside down or if I apply pressure to the board.

 I've tried heating up the joints to push the regulators down a bit, but I cannot heat all 3 joints on the regulator at the same time and the top of the regulator gets quite hot during soldering which makes it hard to push down.

 Can any experienced DIYer tell me if this could cause a problem, and if so, how could I fix it?


----------



## headwhacker

jseaber said:


> Not sure if I've shared this already.
> 
> While differential, digital data arrives the same via one cable compared to another cable (i.e., jitter is largely a function of the transmitting device and receiving controller), the +5V and GND lines are susceptible to interference. A DAC that relies on the USB's +5V supply is therefore susceptible to interference from the attached USB cable, and not all USB cables perform the same with respect to EMI. Placing a good ferrite on an ordinary USB cable improves dynamic range by up to 10dB on ODAC. NwAvGuy vaguely addressed this difference.
> 
> ...


 
  
 I saw your comment about USB cable with ferrites before (not sure if it's this thread). The measured difference is huge but was it tested to be audible against quality cable without ferrites? Can't seem to find any comment about it from Nwavguy's blog. Thanks


----------



## HolyCheese

I have a question regarding low volume listening. I almost Always listen at low volums with my x2's. ATM I'm listening to the lowest possible volume possible without channel imbalance at 1x gain.
  
 Is it possible to set the gain at e.g. 0.5x?
 Or would it be a better alternative to buy another volume pot without channel imbalance?


----------



## HolyCheese

snowlune said:


> I couldn't find a thread on the O2 in the DIY section so I'm just going to ask here.
> 
> So, I soldered together my own O2+ODAC a couple of months ago and everything works fine so far. However, there might be few small problems.
> 
> ...


 
  
 Buy something called a solder sucker, or solder wick (goat wick) And make sure to let the IC cool down between attempts. I'm not sure how long you tried but if I recal correctly overly heating the IC's can damadge them.


----------



## Xenophon

You could try it as described above but be aware that there's a possibility that you'll fry the component (or in a worst case scenario the pcb).  I don't know what the component you're trying to insert deeper looks like so maybe the following is totally impossible but you might be able to cut off the leads going into the pcb, then heat the joints, remove the solder with a wick and resolder the shortened component (I had to do that after clumsily soldering a varistor once).  Or if electrical insulation from the top of the case is an issue and you can live with the rest, use goop and/or a piece of keratherm insulting pad between the component and the top of the case.  Not ideal and it won't protect against mechanical stress but you'll have excellent electric insulation and don't risk frying stuff.


----------



## jseaber

holycheese said:


> I have a question regarding low volume listening. I almost Always listen at low volums with my x2's. ATM I'm listening to the lowest possible volume possible without channel imbalance at 1x gain.
> 
> Is it possible to set the gain at e.g. 0.5x?
> Or would it be a better alternative to buy another volume pot without channel imbalance?


 
  
 Minimum gain is 1.0x for most amplifiers, including O2. To de-amplify, you need another volume control. The volume control at your source should get the job done.
  
  


headwhacker said:


> I saw your comment about USB cable with ferrites before (not sure if it's this thread). The measured difference is huge but was it tested to be audible against quality cable without ferrites? Can't seem to find any comment about it from Nwavguy's blog. Thanks


 
  
 Good question. We're talking about the difference between 98dB and 108dB noise floor. I suspect you'd notice the difference with sensitive headphones. I'll have to experiment with the ears.


----------



## Solrighal

It's not easy to find a nice USB cable at a reasonable price with a ferrite bead. I can't find any.


----------



## jseaber

solrighal said:


> It's not easy to find a nice USB cable at a reasonable price with a ferrite bead. I can't find any.


 
  
 Pick any USB without a ferrite, then attach TDK p/n ZCAT2035-0930. This part is available at Amazon, eBay, Mouser, DigiKey, and works well.
  
 For thicker cables, try p/n ZCAT2436-1330.


----------



## snowlune

holycheese said:


> Buy something called a solder sucker, or solder wick (goat wick) And make sure to let the IC cool down between attempts. I'm not sure how long you tried but if I recal correctly overly heating the IC's can damadge them.


 
  
 Thank you for your advice. I've tried using wick (not too skilled with the solder sucker) but to no avail. When I try to desolder it, a bit of solder stubbornly remains inside the hole and the component is still stuck. I'm not sure if I'm just too inexperienced or my equipment is **** but I'm a bit paranoid about overheating and breaking something.
  


xenophon said:


> You could try it as described above but be aware that there's a possibility that you'll fry the component (or in a worst case scenario the pcb).  I don't know what the component you're trying to insert deeper looks like so maybe the following is totally impossible but you might be able to cut off the leads going into the pcb, then heat the joints, remove the solder with a wick and resolder the shortened component (I had to do that after clumsily soldering a varistor once).  Or if electrical insulation from the top of the case is an issue and you can live with the rest, use goop and/or a piece of keratherm insulting pad between the component and the top of the case.  Not ideal and it won't protect against mechanical stress but you'll have excellent electric insulation and don't risk frying stuff.


 
  
 Thank you for the reply. Yeah, it would be pretty sad to fry something and break my O2 which is working right now. About cutting off the leads and resoldering it, the O2's board is pretty clustered and the component at issue here is surrounded by other components that would make it a bit hard to cut. Also, I'm not sure whether the leads would be long enough after cutting to be soldered again.
  
 About insulating the component from the top of the case, that is a good idea. I'm not sure if I can find that where I live. I'll use my multimeter to test some things like household paper and tape and try to find something I can use to insulate the component.


----------



## JacobLee89

snowlune said:


> Thank you for your advice. I've tried using wick (not too skilled with the solder sucker) but to no avail. When I try to desolder it, a bit of solder stubbornly remains inside the hole and the component is still stuck. I'm not sure if I'm just too inexperienced or my equipment is **** but I'm a bit paranoid about overheating and breaking something.


 
  
 Out of curiousity, how did you use the wick?
  
 The only method I know is placing the wick on top of part, and then placing the iron on top of the wick. I've read somewhere that solder likes to flow towards the hottest component.
  
 Sometimes I pull on the wick gently when the solder starts soaking into the braid, and the solder sometimes get wicked along the length of material. I'm not sure if that's a recommended thing to do though.
  
 Using solder flux also helps, but that's where my knowledge of "why" ends.


----------



## HolyCheese

@snowlune
 Yea in this case I'd also suggest to just insulate it. Try using insulation tape. It's pretty thin and should do the trick. I'm not sure how it would be called in you country but the stuff usually comes in red, blue, and brown greenish colour, is rubbery and stretchy.
  
 However i'm not sure what the best way to apply it would be. Since putting the tape all around the metal part might make it too hot?
  
 If you have a hot glue gun (also not sure how you call this in english) you can also try to apply a little of this glue to the top of the IC. Make it some kind of hat. 
  
 Only problem is that with alot of movement the glue gets loose after a while, so just leave it in the case and it should be fine.


----------



## HotIce

Desoldering multi-pin, through hole, ICs, is a PITA, if your plan is to save the IC. Especially for plated through holes, where solder sips in. I never solder through hole ICs directly and use sockets instead.
Given that replacing the OP-amp will not break your bank account, the safest way is to cut the pins, and then pull them one by one. Otherwise overheating might make more damages than the ICs cost. You might end up with detached solder pads/tracks, which is not where you want to be.
If you want to play with OP-amps rolling, I suggest to cut the pins, pull them one by one (at that point is easy - apply heat on bottom, pull pin with tweezers from up), and install sockets in there.


----------



## Solrighal

jseaber said:


> Pick any USB without a ferrite, then attach TDK p/n ZCAT2035-0930. This part is available at Amazon, eBay, Mouser, DigiKey, and works well.
> 
> For thicker cables, try p/n ZCAT2436-1330.




Thanks John, that's most helpful. Is there a reason why the ferrite bead always seems to be at the DAC end of the cable? 

I'm also tempted to ask if you think I might be wasting my money but I suspect I already know the answer to that one. Even if it only looks better that would be enough, as long as the price is right.


----------



## jseaber

solrighal said:


> Thanks John, that's most helpful. Is there a reason why the ferrite bead always seems to be at the DAC end of the cable?
> 
> I'm also tempted to ask if you think I might be wasting my money but I suspect I already know the answer to that one. Even if it only looks better that would be enough, as long as the price is right.


 
  
 There's a set of equations to answer this EMC question.
  
 From my intuition (and emprical results), the ferrite is placed nearest to the receiving end to minimize EMI. Placing the ferrite at the opposite end would expose the majority of the cable length to interference before the signal reaches the receiving device. EMC is not my specialty. PhDs in the field may slap me.


----------



## adydula

The Ferrite bead at the dac end makes sense, it provides the "filtering or prevention" of any possible interference into the dac that "might" cause issues in the DACS functioning....that is tuning the bits into analog. I like to call these "ferrite chokes" instead of beads.....LOL.
  
 I scoped several cables with and without ferrite beads and have not seen any real EMI or interference...I seem to have a clean environment.
  
 Don't place your cell phones, VAC power cords etc near the cable....
  
 Many are under $10
  
http://www.amazon.com/Monoprice-1-5-Feet-Mini-B-Ferrite-105446/dp/B003L18RZU/ref=sr_1_3?ie=UTF8&qid=1424109570&sr=8-3&keywords=usb+cable+with+ferrite
  
 Heres one with ferrite chokes on both ends:
 (now this has to "sound" better than a cable with only one "bead"!)
	

	
	
		
		

		
			




  
http://www.amazon.com/Tripp-Lite-Hi-Speed-Ferrite-U023-003/dp/B008VOPCGY/ref=sr_1_2?ie=UTF8&qid=1424109570&sr=8-2&keywords=usb+cable+with+ferrite
  
 Alex


----------



## snowlune

jacoblee89 said:


> Out of curiousity, how did you use the wick?
> 
> The only method I know is placing the wick on top of part, and then placing the iron on top of the wick. I've read somewhere that solder likes to flow towards the hottest component.
> 
> ...


 
  
 I think normally I do the same thing. Sometimes I put a dab of solder on the iron so the heat transfers faster through the wick.
 I need to buy some solder flux though....
  


holycheese said:


> @snowlune
> Yea in this case I'd also suggest to just insulate it. Try using insulation tape. It's pretty thin and should do the trick. I'm not sure how it would be called in you country but the stuff usually comes in red, blue, and brown greenish colour, is rubbery and stretchy.
> 
> However i'm not sure what the best way to apply it would be. Since putting the tape all around the metal part might make it too hot?
> ...


 
  
 The insulation tape idea is smart. I could tape it to the top of the case. That way, I won't have to worry about the regulator melting the adhesive and creating a mess.
  
 Hmmm, I'm not so sure about the hot glue gun.
 You see, the part I'm having trouble with is not the IC, but the voltage regulators, which get a bit hot after use.
  
 But the insulation tape idea is flawless, and I'll look into that. Thanks tons for the idea!


hotice said:


> Desoldering multi-pin, through hole, ICs, is a PITA, if your plan is to save the IC. Especially for plated through holes, where solder sips in. I never solder through hole ICs directly and use sockets instead.
> Given that replacing the OP-amp will not break your bank account, the safest way is to cut the pins, and then pull them one by one. Otherwise overheating might make more damages than the ICs cost. You might end up with detached solder pads/tracks, which is not where you want to be.
> If you want to play with OP-amps rolling, I suggest to cut the pins, pull them one by one (at that point is easy - apply heat on bottom, pull pin with tweezers from up), and install sockets in there.


 
  
 Hahaha, I guess I'm lucky that I'm not desoldering an IC, but the voltage regulator.
 I could just try to cut them off and buy new ones but shipping to Canada is expensive


----------



## HolyCheese

Voltage regulator is an IC, right? ;p
 Anyway, try the tape on the casing, maybe use some good glue that won't be affected by warmth.
  
  
 Btw anyone still have some idea for the channel imbalance?


----------



## HotIce

Oh, sorry, I lost track and thought you were attacking the OP-amps.
The MC7912/7812 are just about $0.50, and you should be able to find them pretty much everywhere. Also, they are three pins inline,which would eventually make the disoldering operation much simpler.
Chip Quik is another solution, but it will end up costing you much more than the VRs.


----------



## snowlune

holycheese said:


> Voltage regulator is an IC, right? ;p
> Anyway, try the tape on the casing, maybe use some good glue that won't be affected by warmth.
> 
> 
> Btw anyone still have some idea for the channel imbalance?


 
  
 Yeah, that's what I did. Stuck a bit of electrical tape to the inside of the case.
  
 Also, I have the same channel imbalance issue. You could go buy a better pot, but I don't know if it's possible to have negative gain.
 I think Nwavguy mentioned somewhere that you can set the sampling rate to 24/44 so that even if you lower the volume on your computer the extra bits will make up for the loss of bit depth. Of course, this is assuming that your music is 16/44. I just keep the volume at 70%. I doubt that you'd be able to hear the bit depth difference between 100% and 70% in a blind test.


hotice said:


> Oh, sorry, I lost track and thought you were attacking the OP-amps.
> The MC7912/7812 are just about $0.50, and you should be able to find them pretty much everywhere. Also, they are three pins inline,which would eventually make the disoldering operation much simpler.
> Chip Quik is another solution, but it will end up costing you much more than the VRs.


 
 Oh, I've never heard of Chip Quik before. Thanks for the tip, I might get some of that for future projects.


----------



## Vadercellkey

Hello! I really wanna know if somebody knows this:

http://m.aliexpress.com/item/2030141321.html

Any word its better then none...XD


----------



## MrKazador

You can flood the pins with solder and use your iron at an angle. Another option is to use a solder called chip quick.


----------



## mcandmar

vadercellkey said:


> Hello! I really wanna know if somebody knows this:
> 
> http://m.aliexpress.com/item/2030141321.html
> 
> Any word its better then none...XD


 
  
 I guess it had to happen eventually.  At first glance it looks like a carbon copy copy of the PCB's, but as with most stuff made in china the parts used are just nasty, they even left out the filter choke on the ODAC board power supply to save a few cents.   Buy a real one and support a local business...


----------



## jseaber

mcandmar said:


> I guess it had to happen eventually.  At first glance it looks like a carbon copy copy of the PCB's, but as with most stuff made in china the parts used are just nasty, they even left out the filter choke on the ODAC board power supply to save a few cents.   Buy a real one and support a local business...


 
  
 Wow, that's a knockoff! I'd love to see this thing on the dScope.
  
 It's funny they've missed the entire point of the design.


----------



## Solrighal

jseaber said:


> Wow, that's a knockoff! I'd love to see this thing on the dScope.
> 
> It's funny they've missed the entire point of the design.


 
  
 Yeah, but they've fully grasped the point of capitalism. I'm not sure which is worse.


----------



## WilliamLeonhart

Here in VN people make "clones" of famous amp/dac design as well. But (at least for audio gear) our manufacturing capacity has never been that great to justify producing fakes rather than importing and selling stuffs from famous companies.


----------



## diamondears

solrighal said:


> Yeah, but they've fully grasped the point of capitalism. I'm not sure which is worse.



Which to blame, the copiers (they actually just learned the ropes), or the owners who took away money from their own country and poured money (and knowledge) to another country to transfer labor costs to save a lot just for themselves?


----------



## Jony27

Im about to purchase this combo to power my Q701s.
  
 The O2 is the HeadnHifi version which seems to come with 2 sets of RCA plugs at the back?
  
 Also, the ODAC is the EP version which comes with both RCA and jackplug.
  
 My question is, how should I wire everything up?
  
 O2 > ODAC via jackplug or RCA?
  
 I also want to connect my active speakers to the chain, but I dont know to which device.
  
 Do I connect it to the ODAC via jackplug/RCA(depending on which I use above) or do I connect it to the O2's RCA lineout?
  
 So from above it will be either one of these setup:
  
                                                              />RCA>--(Active Speakers)
                                                             /
 (PC)---->USB>---(ODAC)-->RCA>--(O2)-- \
                                                              \>Jackplug>--(Headphones)
  
  
  
                                    />RCA>--(Active Speakers)
                                   /
 (PC)---->USB>---(ODAC)-->JackPlug>--(O2)-->Jackplug>--(Headphones)
  
  
  
                                    />Jackplug>--(Active Speakers)
                                   /
 (PC)---->USB>---(ODAC)-->RCA>--(O2)-->Jackplug>--(Headphones)
  
 Thanks.


----------



## pearljam50000

Has anyone compared the O2/Odac to Geek Out 720(or1000) with HD800?


----------



## HolyCheese

Whats wrong with the china amp? I don't see anything in particular wrong with the amp. Is it just the quality of the components? And where is a choke left out? How do you know/see?


@Jony Maybe consider just buying http://www.headnhifi.com/amplifiers/desktop-headphone-amplifiers/O2-ODAC-fully-modded this. You can connect the speakers to the analog input.
  
 If you want it cheaper and in seperate cases just use your 2nd or 3rd example. Whichever is easiest with the wires.


----------



## Jony27

Actually buying it from someone on here for €170 for the two.
 So works out much cheaper.


----------



## Solrighal

jony27 said:


> Im about to purchase this combo to power my Q701s.
> 
> The O2 is the HeadnHifi version which seems to come with 2 sets of RCA plugs at the back?
> 
> ...


 
  
 If you're going with Head'n'Hifi then you should look to buy the ODAC XL and the O2 Desktop version. Depending on what headphones you're going to drive I'd suggest gains of 1x / 3x. Connect your PC via USB to the input on the rear of the ODAC. Run RCA phono cables from the rear of the ODAC (output) to the rear of the O2 (input). Connect the O2 to your loudspeakers via the RCA outputs on the O2. Use 1x gain when driving your speakers. Job done.
  
 How do I know this? I have exactly this set-up.
  
 I'm selling my ODAC / O2 if you're interested.


----------



## Jony27

Cheers for that.
 But unfortunately it's all been paid for and ready for shipment.
 Its just the regular desktop O2 and the regular ODAC with RCA/jackplug.
 Also, would 1x gain be enough for the Q701?
  
 And out of curiousity, how much would you have wanted for your combo?


----------



## Solrighal

jony27 said:


> Cheers for that.
> But unfortunately it's all been paid for and ready for shipment.
> Its just the regular desktop O2 and the regular ODAC with RCA/jackplug.
> Also, would 1x gain be enough for the Q701?
> ...


 
  
 I'd take £100 for both units as well as a pair of Schiit PYST interconnects.
  
 Walter's a nice reasonable guy. Send him an email saying you'd like different units and, unless he's already posted them, I'm sure he'd accommodate you.
  
 And yes, 1x is enough for decent, but not deafening, volume.


----------



## Jony27

Damn good price.
 Bought it second hand off someone here for €170 which is about £130 
 Literally sent it 30mins before you had replied.
 Ah well, you win some, you lose some.


----------



## Solrighal

No problem mate. Enjoy your purchase.

I might do better if I ever got around to advertising it.


----------



## Jony27

solrighal said:


> No problem mate. Enjoy your purchase.
> 
> I might do better if I ever got around to advertising it.




Are you in a hurry? I do prefer the matching colour of your stack plus cheaper is a bonus. I might try and sell on the one I just bought and get yours. Unless you're in a hurry to sell.


----------



## Vadercellkey

holycheese said:


> Whats wrong with the china amp? I don't see anything in particular wrong with the amp. Is it just the quality of the components? And where is a choke left out? How do you know/see?


 
  
 Yeah... dont know! Apparently they've missed the design too.


----------



## Solrighal

jony27 said:


> Are you in a hurry? I do prefer the matching colour of your stack plus cheaper is a bonus. I might try and sell on the one I just bought and get yours. Unless you're in a hurry to sell.




I'm in no hurry at all. I'm in the UK though if that's a problem.


----------



## Jony27

In the UK too, Belfast, Northern Ireland to be precise 
 Ill see what I can do with it when they arrive.


solrighal said:


> I'm in no hurry at all. I'm in the UK though if that's a problem.


----------



## WilliamLeonhart

Just out of curiosity, how many companies are producing O2 and ODAC? JDS Labs, Mayflower, Headnhifi. Who else?


----------



## Solrighal

williamleonhart said:


> Just out of curiosity, how many companies are producing O2 and ODAC? JDS Labs, Mayflower, Headnhifi. Who else?


 
  
 Epiphany Acoustics in England make & sell them.


----------



## raoultrifan

Check on eBay for "AGDR audio" and you'll be surprised about a new improved version of O2. Feel free to check AGDR's projects on diyaudio or on his own website.
  
 AGDR is more like "successor" of nwavguy's project, in terms of improving and developing the O2 project for headphones with more power demands. So, if you're hungry for more power or you need to drive some planars, check out his website.


----------



## diamondears

raoultrifan said:


> Check on eBay for "AGDR audio" and you'll be surprised about a new improved version of O2. Feel free to check AGDR's projects on diyaudio or on his own website.
> 
> AGDR is more like "successor" of nwavguy's project, in terms of improving and developing the O2 project for headphones with more power demands. So, if you're hungry for more power or you need to drive some planars, check out his website.



What are the tweaks aside from more power?


----------



## WilliamLeonhart

if I want to change maximum/minimum gains on my O2, what part will I have to replace?


----------



## diamondears

williamleonhart said:


> if I want to change maximum/minimum gains on my O2, what part will I have to replace?



Max Vrms that O2 can handle is 7Vrms, more than that and it will clip, IIRC. Is there a HP out there that requires more than 7Vrms???


----------



## headwhacker

diamondears said:


> Max Vrms that O2 can handle is 7Vrms, more than that and it will clip, IIRC. Is there a HP out there that requires more than 7Vrms???


 
  
 Try HE-6


----------



## diamondears

headwhacker said:


> Try HE-6



How much does it need?


----------



## headwhacker

diamondears said:


> How much does it need?


 
  
 Assuming your target maximum volume loudness is 115dB and a 3dB headroom. To drive HE-6 to 118dB requires around 12Vrms


----------



## diamondears

headwhacker said:


> Assuming your target maximum volume loudness is 115dB and a 3dB headroom. To drive HE-6 to 118dB requires around 12Vrms



How about 110dB?


----------



## chimmycham

I've heard from numerous sources that the O2/ODAC is very neurtral and "cold" sounding compared to a combo like the magni2/modi2 or the vali/modi2.
  
 Can anyone attest to this?


----------



## adydula

The ODA offers several benefits over the O2 for desktop use, including:

 * Three times the output current capability at 300mA per channel
 * Super quiet 2 stage power supply with regulators heat sinked to the case
 * Input power CRC filter to remove power line noise
 * Lower noise and THD LME49990 (optional FET LME4988) gain stage chips
 * 1K volume control and 4.99K ground return resistors for lower Johnson noise
 * Lower distortion and higher S/N ratio with 6 paralleled op amps per channel
 * Rear RCA in, from 3.5mm in, input select, 4 position gain switch, front 3.5mm & 1/4" out, front pre-am out, damping factor adjust.

 Also one of the things that the O2 has issues with is those hard to drive headphones like HE500 and HE6.
  
 It has a pre-amp option I use to drive a network Onkyo receiver for listening and gaming.
 Clipping LEDS to see when your clipping at various gains.
  
  
  A fellow in the O2/ODAC thread was asking about the ODA powering the HE500 and notoriously hard-to-drive HE6. Turns out the answer is no problem at all for the ODA. AGDR has added a folder to the V2.0 ODA Google Drive link called "Headphones vs. the ODA" with the spreadsheets and a README with all the details.
https://drive.google.com/folderview?...28&usp=sharing
  
http://www.bing.com/videos/search?q=oda+amp+youtube&FORM=VIRE1#view=detail&mid=90789AE352B2C205664E90789AE352B2C205664E
  
http://www.head-fi.org/t/719611/objective-desktop-amp-a-version-from-agdr
  
 I have an ODA and its very, very good.
 Alex


----------



## headwhacker

diamondears said:


> How about 110dB?


 
  
 Antilog ((110 - 83.5) / 10) = 0.446 W
  
 sqrt (0.446 * 50 ) =  4.7 Vrms


----------



## adydula

From AGDR at Diyaudio:
  
 So here is your answer about the HE500 and HE6. The ODA will not only power both perfectly with the standard +/-12.5Vdc power rails, they will do so all the way up to 118dB and 113dB, respectively. And those were just the power levels that broke the spreadsheet. Nobody should be listening to headphones at those levels anyway! See the hearing damage chart at the bottom of the fellow's spreadsheet. 

 I have created a new folder at the V2.0 ODA Google Drive link called "Headphones vs. the ODA". Here is a direct link to it:

https://drive.google.com/folderview?...28&usp=sharing

 In there I have used a nice power calculation spreadsheet that was posted on Head-Fi back in December. See the README file in that folder. It has a link to that post with the sheet and links to the specification pages for the HE500 and HE6. They are 38 ohm at 89dB/mW sensitivity, and 50 ohm at 83.5dB/mW respectively. Note that per mW is assumed, both by the fellow who created the spreadsheet and by me, since the manufacturer does not say whether per mW or per V. Per mW is the older and more standard measure so its a good bet.

 For more normal levels I have also included sheets for both at 95dB.

 Only the 113dB power level with the HE6 is coming near the using the full 7.25V(rms) swing of the ODA with the +/-12.5Vdc rails, at 6.67V(rms). The current is still a no-brainer for the ODA, divided by 6 for the 6 output chips.

 So.. these kind of headphones are exactly what the ODA eats for lunch. 

 Also please note that the +/-15Vdc power rails should not be used with either headphone. +/-12.5Vdc does the job as per the charts. The output chips could overheat at the higher voltages. Those are only for 300R and 600R cans.  
  
 FYI
 Alex


----------



## MrMateoHead

chimmycham said:


> I've heard from numerous sources that the O2/ODAC is very neurtral and "cold" sounding compared to a combo like the magni2/modi2 or the vali/modi2.
> 
> Can anyone attest to this?


 

 By definition neutral is neutral. It can't be hot or cold. My Odac does run cool however and I hear the Schiit stuff can run pretty hot


----------



## raoultrifan

Thanks adydula for your very fast answer! I've read your posts from audiocircle and diyaudio while ago and I respect your work done there. I've also read all of agdr's posts, since he was talking with nwavguy on how to better design the O2. 
  
 My O2 is modded a little bit by myself: 2 headphone front jacks (1 big and 1 small), back jack and RCA input pugs, back power plug, changed 2 small capacitors on PSU, changed NJM2068 with LM4562 (can be no improvements on audio spectrum...ofc, but at least I might be able to use high gains in the future) etc. I will try myself the 15V mod presented by agdr, also the electrolytic caps mode and maybe some other mods too. All I need is a bit more time for that. 
  
 I strongly recommend the agdr's ODA to anyone trying a decent upgrade from O2, because ODA has the same neutral sound signature like O2, but is more powerful and technically is having less distortions. I am thinking of getting one ODA myself, in case I'll buy some planars or 600 ohms headphones, mostly because now I'm using the O2 at 1x gain for K550 and SR60i, at 2.5X gain for K701 and I don't have a 3-way push button to select a higher gain value like 4X or 5X. So having 2 decent headphones amplifier will better pair with all of my headphones.
  
 Regards!


----------



## headwhacker

adydula said:


> From AGDR at Diyaudio:
> 
> So here is your answer about the HE500 and HE6. The ODA will not only power both perfectly with the standard +/-12.5Vdc power rails, they will do so all the way up to 118dB and 113dB, respectively. And those were just the power levels that broke the spreadsheet. Nobody should be listening to headphones at those levels anyway! See the hearing damage chart at the bottom of the fellow's spreadsheet.
> 
> ...


 
  
 It should be dB/mW as their spec for the newer cans is specified in dB/mW.
  
 That power estimate is conservative imo. I'm pretty sure some will argue you need more headroom if you are listening to some rare wide DR recordings. And granted we want to keep an anolog volume control between 11 to  3 o'clock position. Many wants to see an amp be capable of driving a can at 118 dB to 120dB to be on the safe side.
  
 Nwavguy even recommends a 1 to 3dB headroom at a target SPL. 115 dB being the loudest level that majority of people can tolerate. Thus 118dB should be a good target SPL for an amp on a given load.


----------



## Peti

> My O2 is modded a little bit by myself: 2 headphone front jacks (1 big and 1 small), back jack and RCA input pugs, back power plug, changed 2 small capacitors on PSU, changed NJM2068 with LM4562 (can be no improvements on audio spectrum...ofc, but at least I might be able to use high gains in the future) etc. I will try myself the 15V mod presented by agdr, also the electrolytic caps mode and maybe some other mods too. All I need is a bit more time for that.


 
 Would love to see a pic/pics of your O2!!


----------



## raoultrifan

No time for quality photos...sorry, so please check the photos I just did quickly with my phone right about now.
  
 The back plate is upside down (2mm not aligning on the vertical, upper side), because of my mistake when I did the holes drilling for RCA and power plugs. 
  
 The front plate is still having the power plug, which is still operational, so you can charge the O2 from the front plug or from the backside plug. On the right side you can see that the small jack for input signal is missing and it was replaced by the big Neutrik headphones jack.
  
 Headphones output cables for Neutrik plug and power cables from front to back panel are all shielded, just in case of any possible interferences.
  
 Just hope in the summer to have some time to move on with the 15V mod and put some small radiators onto opamps.


----------



## Peti

Nice job pal! I do like it. Especially the knob, is it home-made as well? Looks bigger than the stock one.


----------



## luiztfc

Hi. Due to unforeseen events, I'll have to settle with a cheaper amp+dac for my LCD 2s. What would be better, Magni Modi combo or O2+Odac?


----------



## raoultrifan

peti said:


> Nice job pal! I do like it. Especially the knob, is it home-made as well? Looks bigger than the stock one.


 
 Thanks man. It's the default knob from Head'n'HiFi online store (Swiss).
  
 @luiztfc, optimal power requirement for LCD2 would be 1 – 4W, so...you might want to try something else maybe. Or at least go for an Asgard or Magni2, but try it out first before buying.


----------



## diamondears

headwhacker said:


> It should be dB/mW as their spec for the newer cans is specified in dB/mW.
> 
> That power estimate is conservative imo. I'm pretty sure some will argue you need more headroom if you are listening to some rare wide DR recordings. And granted we want to keep an anolog volume control between 11 to  3 o'clock position. Many wants to see an amp be capable of driving a can at 118 dB to 120dB to be on the safe side.
> 
> Nwavguy even recommends a 1 to 3dB headroom at a target SPL. 115 dB being the loudest level that majority of people can tolerate. Thus 118dB should be a good target SPL for an amp on a given load.



Why would one want to listen at more than 110dB is beyond me. Even 90dB is irritating already. DSD music format prolly needs more than 110dB though.


----------



## diamondears

luiztfc said:


> Hi. Due to unforeseen events, I'll have to settle with a cheaper amp+dac for my LCD 2s. What would be better, Magni Modi combo or O2+Odac?



You're in an O2-ODAC thread...


----------



## headwhacker

diamondears said:


> Why would one want to listen at more than 110dB is beyond me. Even 90dB is irritating already. DSD music format prolly needs more than 110dB though.


 
  
 Modern pop/rock records goes very loud at around 90dB. The older mastered rock albums you may need more than that. usually > 100dB. But there are a few classical recordings with a DR of around 30 - 35dB (transients/peaks). The assumption is the average listening level is 85dB. Add 30 - 35 dB and that accounts for 115 - 120dB peak. 
  
 If you never listen to those kind of records then 110 dB peak is adequate. But I imagine your volume pot is always near if not close to the maximum position
  
 To put things into perspective, I have a few classical and lots of old rock/rock n roll albums (e.g. nut cracker, beatles, eagles). I find myself turning the volume pot of my O2+ODAC @ 3.5x to 1 o'clock position a few times listening to some of these records using my HE-400i  (93dB/mW). HE-6 requires approximately 8 times the power needed by HE-400i to reach the same level of SPL. O2 obviously don't have enough power for these types of records.


----------



## diamondears

headwhacker said:


> Modern pop/rock records goes very loud at around 90dB. The older mastered rock albums you may need more than that. usually > 100dB. But there are a few classical recordings with a DR of around 30 - 35dB (transients/peaks). The assumption is the average listening level is 85dB. Add 30 - 35 dB and that accounts for 115 - 120dB peak.
> 
> If you never listen to those kind of records then 110 dB peak is adequate. But I imagine your volume pot is always near if not close to the maximum position
> 
> To put things into perspective, I have a few classical and lots of old rock/rock n roll albums (e.g. nut cracker, beatles, eagles). I find myself turning the volume pot of my O2+ODAC @ 3.5x to 1 o'clock position a few times listening to some of these records using my HE-400i  (93dB/mW). HE-6 requires approximately 8 times the power needed by HE-400i to reach the same level of SPL. O2 obviously don't have enough power for these types of records.



Yeah, that's about my experience too. That HE-6 must be one really power hungry HP. 8 times???


----------



## headwhacker

diamondears said:


> Yeah, that's about my experience too. That HE-6 must be one really power hungry HP. 8 times???


 
  
 every 3dB increase requires approximately 2x the power.


----------



## diamondears

headwhacker said:


> every 3dB increase requires approximately 2x the power.



Off topic, but is there any advantage/reason to get the HE-6 SQ-wise? Became interested on the HE-6 because I like the idea of being able to use my speaker amp with it, less gears on the rack, and I have a good extra speaker amp.


----------



## headwhacker

diamondears said:


> Off topic, but is there any advantage/reason to get the HE-6 SQ-wise? Became interested on the HE-6 because I like the idea of being able to use my speaker amp with it, less gears on the rack, and I have a good extra speaker amp.


 
  
 I'm intrigued as well with HE-6. But the power requirements just puts me off. SQ will always be personal preference. You should go and audition the HE-6 with a capable amp. 
  
 I'm actually looking at HE-560. Currently loving the 400i with O2+ODAC. HE-560 will require 2x the power of 400i @ 50ohms which I'm trying to find out if O2 can adequately drive and if there are any spare. 
  
 I can't find any measurement online of how much power O2 can deliver @ 50ohm load. 
  
 But my calculation is that O2 should be able to drive a 50 Ohm load @ 900mW. My assumption is based on the 33 ohm load measurement (613 mW) in which O2 reach maximum current. As the load increase the current required decreases and the voltage increase. 
  
 I was hoping someone with the capability would have done the measurements at 50 ohm load. Violectric includes 50ohms in their amp lineup specs.


----------



## diamondears

headwhacker said:


> I'm intrigued as well with HE-6. But the power requirements just puts me off. SQ will always be personal preference. You should go and audition the HE-6 with a capable amp.
> 
> I'm actually looking at HE-560. Currently loving the 400i with O2+ODAC. HE-560 will require 2x the power of 400i @ 50ohms which I'm trying to find out if O2 can adequately drive and if there are any spare.
> 
> ...



The LCD-2.2 is 50ohms, and 91dB/mW sensitivity. It only needs tiny bit less than 2Vrms at 110dB.


----------



## HotIce

If these 900mW are meant RMS, then you need about 9.5V peak (19V peak to peak) to get that power on 50 Ohm.
If you look at the 4556 output swing charts, on a 150 Ohm load, the IC already drops a couple of Volts per side, WRT the supply rail. And that is going to get worse on 50 Ohm.
So to get a clean 9.5V peak, you will need at least +/-12V supply. Forget about getting that power under battery supply.
But you have another problem. 9.5V peak, on 50 Ohm, is 190mA peak, divided by the two 4556 buffers, its 95mA each, which exceeds the 70mA max ratings.
This on purely resistive loads. When 'i' becomes non trivial (reactive loads), current figures will get worse.


----------



## diamondears

hotice said:


> If these 900mW are meant RMS, then you need about 9.5V peak (19V peak to peak) to get that power on 50 Ohm.
> If you look at the 4556 output swing charts, on a 150 Ohm load, the IC already drops a couple of Volts per side, WRT the supply rail. And that is going to get worse on 50 Ohm.
> So to get a clean 9.5V peak, you will need at least +/-12V supply. Forget about getting that power under battery supply.
> But you have another problem. 9.5V peak, on 50 Ohm, is 190mA peak, divided by the two 4556 buffers, its 95mA each, which exceeds the 70mA max ratings.
> This on purely resistive loads. When 'i' becomes non trivial (reactive loads), current figures will get worse.



Wouldn't sensitivity play a huge part? It is a bigger factor than the impedance of the HP, as a matter of fact.


----------



## HotIce

Absolutely. I was just looking at the 900mW power figure.


----------



## headwhacker

diamondears said:


> The LCD-2.2 is 50ohms, and 91dB/mW sensitivity. It only needs tiny bit less than 2Vrms at 110dB.


 
  
 True but my target is at 118dB to account for all types of music and the peace of mind of making sure clipping would not happen.


----------



## headwhacker

hotice said:


> If these 900mW are meant RMS, then you need about 9.5V peak (19V peak to peak) to get that power on 50 Ohm.
> If you look at the 4556 output swing charts, on a 150 Ohm load, the IC already drops a couple of Volts per side, WRT the supply rail. And that is going to get worse on 50 Ohm.
> So to get a clean 9.5V peak, you will need at least +/-12V supply. Forget about getting that power under battery supply.
> But you have another problem. 9.5V peak, on 50 Ohm, is 190mA peak, divided by the two 4556 buffers, its 95mA each, which exceeds the 70mA max ratings.
> This on purely resistive loads. When 'i' becomes non trivial (reactive loads), current figures will get worse.


 
  
 I was talking about O2 powered by AC wall adaptor of course. So yes +/-12V into O2 is possible. 613mW is the measured and published output @ 33 Ohms. Should be worse than 50 ohms can manage 190mA peak of current.
  
 It's correct the 4556 chip's max current is 70mA. But connected in parallel should double the current available which in theory is 140mA per channel. So 95mA per channel is well within the spec as documented in his blog.
  
 Nwavguy guys blog mentioned that O2's current peak limit is around 200mA.


----------



## HotIce

95mA per 4556, which is 25mA over max rating. And this math is resistive load based. Phase makes things more interesting.


----------



## headwhacker

hotice said:


> 95mA per 4556, which is 25mA over max rating. And this math is resistive load based. Phase makes things more interesting.


 
  
 the 70mA figure is per chip. 2 chips in parallel means each chip only delivers 48mA of current. Planars are resistive load which makes the math more likely to fit here than other types of headphone drivers.


----------



## HotIce

OK, let's get the math back on track 
900mW on 50 Ohm (resistive), is ~9.5V peak, and 190mA peak. The O2 has two 4556 current buffers, so each one gets 95mA. But the 4556 has a 70mA maximum rating.


----------



## headwhacker

hotice said:


> OK, let's get the math back on track
> 
> 
> 
> ...


 
  
 Sorry, I can see where I got myself confused. 
	

	
	
		
		

		
		
	


	




 I'm looking at 4556 data sheet now. Are you sure 70mA current limit is peak and not rms? From the maximum voltage vs output current graph it goes all the way to 200mA.


----------



## HotIce

That's only one rail (the - one) and imagine how THD is when the + side is trimming at 70mA 
If the manufacturer says 70mA maximum, it is better to stay out of there. Not exceed.
Good rule is to design such that maximum operating circuit conditions, never exceeds 90% of the ICs maximum ratings. And this accounts also for the fact that manufacturers themselves keeps a margin.


----------



## headwhacker

hotice said:


> That's only one rail (the - one) and imagine how THD is when the + side is trimming at 70mA
> 
> 
> 
> ...


 
  
 The + rail still able to swing 7V at 100mA. Given that we are shooting for the max output with THD still in acceptable range. 200mA peak limit as nwavguy presented is still plausible. Of course an actual measurement @50 ohms would be very interesting.


----------



## MrMateoHead

headwhacker said:


> I can't find any measurement online of how much power O2 can deliver @ 50ohm load.
> 
> But my calculation is that O2 should be able to drive a 50 Ohm load @ 900mW. My assumption is based on the 33 ohm load measurement (613 mW) in which O2 reach maximum current. As the load increase the current required decreases and the voltage increase.
> 
> I was hoping someone with the capability would have done the measurements at 50 ohm load. Violectric includes 50ohms in their amp lineup specs.


 
 Well, given the measurements that have been done online, the O2 seems to reliably deliver 200 mWs at very low distortion and something like a half a watt at high distortion (unless we're talking about 600 Ohm cans). But it isn't clear to me where the real power "ceilings" are.
  
 I did an estimate once that put the O2 at more like ~700 mWs @ 50 ohms (and probably am wrong). But I do think the power and voltage curve is actually cresting around that impedance. Also that could be a really high distortion level. Even with the most inefficient phones' it is hard to imagine needing more than 1 watt on any type of sustained basis. Unless you want to blow your ear drums. I use the HE-400s with mine and I can attest that anything after about 1 O'Clock @3.5x gain is well into "getting too loud" range. They are spec'd as 92.5dB efficient. The new 560s are spec'd at 90 dB, so, I would expect the O2 to be pushed harder, but still up to providing very loud listening levels.
  
 @33 Ohms NwAvGuy published 613 mW and @80 Ohms 639 mWs.
  
 In any case, purchasing an amp under the assumption that you may want 115 dB out of cans is pretty crazy! It also assumes that the cans can deliver those volumes without distorting like crazy . . .


----------



## headwhacker

mrmateohead said:


> Well, given the measurements that have been done online, the O2 seems to reliably deliver 200 mWs at very low distortion and something like a half a watt at high distortion (unless we're talking about 600 Ohm cans). But it isn't clear to me where the real power "ceilings" are.
> 
> I did an estimate once that put the O2 at more like ~700 mWs @ 50 ohms (and probably am wrong). But I do think the power and voltage curve is actually cresting around that impedance. Also that could be a really high distortion level. Even with the most inefficient phones' it is hard to imagine needing more than 1 watt on any type of sustained basis. Unless you want to blow your ear drums. I use the HE-400s with mine and I can attest that anything after about 1 O'Clock @3.5x gain is well into "getting too loud" range. They are spec'd as 92.5dB efficient. The new 560s are spec'd at 90 dB, so, I would expect the O2 to be pushed harder, but still up to providing very loud listening levels.
> 
> ...


 
  
  
 Where did you find the measurement @ 80ohms?  No doubt 560 will push O2 harder. What I'm trying to find out is, at worst possible condition, if O2 still has enough power to drive 560.


----------



## diamondears

All I can say is, I have yet to find a recording, including classical (I have a Decca series CD of their best recirdings compilation that uses mics quite far from the instruments, some hovered I think), that the O2 cannot handle.

Maybe someone could suggest a recording that needs more than 110dB? I wanna try it.


----------



## MrKazador

The loudest I measured my mrspeakers mad dogs 3.2 was about 110db with the o2. This was a hair before clipping.


----------



## headwhacker

mrkazador said:


> The loudest I measured my mrspeakers mad dogs 3.2 was about 110db with the o2. This was a hair before clipping.


 
  
 What is the output voltage of your source and at what gain is O2 set when you measured 110dB?


----------



## MrKazador

http://www.fiio.net/en/products/7/parameters
  
 I'm using the Fiio D3, it doesn't list the output voltage. o2 is set to 6.5x gain and adjusting the Windows 7 volume so it doesn't clip.


----------



## diamondears

headwhacker said:


> What is the output voltage of your source and at what gain is O2 set when you measured 110dB?



What's the recording (classical?) you determined to have the need for more than what O2 provides to reach 118dB?


----------



## headwhacker

mrkazador said:


> http://www.fiio.net/en/products/7/parameters
> 
> I'm using the Fiio D3, it doesn't list the output voltage. o2 is set to 6.5x gain and adjusting the Windows 7 volume so it doesn't clip.


 
  
 The spec page is useless does not give any clue about the output voltage.
  
 I'm guessing the D3 has fix output level which is greater than 1V. At 6.5x gain, O2 easily clips. That's why you have to turn down the volume control in Windows to avoid O2 from clipping. Not an ideal match to get the maximum power output from O2.
  
 If other Fiio products is any indication I think the output voltage of D3 is 1.5V. Too much for O2 at 6.5X. Did you try it at 2.5X?


----------



## headwhacker

diamondears said:


> What's the recording (classical?) you determined to have the need for more than what O2 provides to reach 118dB?


 
  
 Yes I listen to classical as well.


----------



## diamondears

headwhacker said:


> Yes I listen to classical as well.



What specific song and album? I'll buy it and listen for myself.


----------



## Xenophon

headwhacker said:


> Where did you find the measurement @ 80ohms?  No doubt 560 will push O2 harder. What I'm trying to find out is, at worst possible condition, if O2 still has enough power to drive 560.


 

 Don't own the 560 but I do own the 500 and the ODAC/O2 drives those beautifully so I wouldn't worry.  I listen to classical (hifi dynamic range, medium average volume).  Not the HE-6 though, regardless of what the spreadsheets say.


----------



## headwhacker

diamondears said:


> What specific song and album? I'll buy it and listen for myself.


 
  
 Not the widest DR but try the album Tchaikovsky: The Nutcracker. I think it is the 2011 remaster.
  


xenophon said:


> Don't own the 560 but I do own the 500 and the ODAC/O2 drives those beautifully so I wouldn't worry.  I listen to classical (hifi dynamic range, medium average volume).  Not the HE-6 though, regardless of what the spreadsheets say.


 
 Thanks


----------



## MrMateoHead

headwhacker said:


> Where did you find the measurement @ 80ohms?  No doubt 560 will push O2 harder. What I'm trying to find out is, at worst possible condition, if O2 still has enough power to drive 560.


 
 With a mere 3 dB efficiency difference, however, the 560s only need approximately "twice" the power to hit the same levels. There is plenty of volume left on the dial for that. 
	

	
	
		
		

		
		
	


	



  
 As for the link, I don't think I can provide it. Just Google "O2 Amp More Power" - should be the second link. It takes you to a certain person's blog who published a ton of performance data about the O2.
  
 Wish I had means of measuring my own listening levels / power output. Suffice to say I would be quite shocked to find out I was ever utilizing more than the first mW of the O2 (given that the HE-400 supposedly require only 0.33 mW to reach 90 dB!). If Innerfidelity is correct, the 560's need 2.53 mW to reach 90 dB, and they measure at a lower 43 Ohms. With close to 10X that power available at low distortion, I would think it is up to the task of blowing your miiiiind.


----------



## MrKazador

headwhacker said:


> The spec page is useless does not give any clue about the output voltage.
> 
> I'm guessing the D3 has fix output level which is greater than 1V. At 6.5x gain, O2 easily clips. That's why you have to turn down the volume control in Windows to avoid O2 from clipping. Not an ideal match to get the maximum power output from O2.
> 
> If other Fiio products is any indication I think the output voltage of D3 is 1.5V. Too much for O2 at 6.5X. Did you try it at 2.5X?


 
  
 2.5x doesn't clip at all with full Windows volume which is why I'm using 6.5x to get the most that I can from the amp. I could adjust the gain but I don't really feel like it...


----------



## Jony27

Received my combo today, just wondering which gain is set when the gain button is pressed down?
 For the standard gain which is 2.5x/6.5x, would it be the higher or lower gain?
 Also, whats a good Windows volume for the amp on low and high gain?


----------



## MrKazador

Pushed in is 6.5x. Volume depends on your source output voltage and gain setting (2.5 or 6.5).


----------



## jellofund

jony27 said:


> Received my combo today, just wondering which gain is set when the gain button is pressed down?
> For the standard gain which is 2.5x/6.5x, would it be the higher or lower gain?
> Also, whats a good Windows volume for the amp on low and high gain?


 
  
 This might be useful for setting up the ODAC
  
 http://www.jdslabs.com/pdf/Instructions_ODAC_Standalone.pdf 
  
 In case it's of interest the reasons for setting Windows / digital volume just below 100% are discussed on this page: http://www.head-fi.org/t/616331/o2-amp-odac/3720


----------



## headwhacker

mrkazador said:


> 2.5x doesn't clip at all with full Windows volume which is why I'm using 6.5x to get the most that I can from the amp. I could adjust the gain but I don't really feel like it...


 
  
 I'm afraid 6.5x in your case doesn't get the most out of O2 but rather cripples it. That is why you are only getting 110 dB out of your Mad Dogs. I bet you'll measure greater SPL at 2.5x.
  
 6.5x is only meant for sources that can only deliver 1V of signal or less. It's important to get the proper match between your source and the gain settings in O2 so you have the 7Vrms available to drive headphones and avoiding clipping.


----------



## vertical

Doesn't using the higher gain also increase the noise floor?


----------



## MrKazador

headwhacker said:


> I'm afraid 6.5x in your case doesn't get the most out of O2 but rather cripples it. That is why you are only getting 110 dB out of your Mad Dogs. I bet you'll measure greater SPL at 2.5x.
> 
> 6.5x is only meant for sources that can only deliver 1V of signal or less. It's important to get the proper match between your source and the gain settings in O2 so you have the 7Vrms available to drive headphones and avoiding clipping.


 
 I measured 112db with 6.5x (Windows volume at 38) and 108db with 2.5x (Windows volume maxed) playing Metallica - No Leaf Clover. The volume was maxed out on the o2. Wouldn't adjusting the Windows volume decrease the voltage so it matches perfectly with the 6.5x gain setting?


----------



## jseaber

mrkazador said:


> I measured 112db with 6.5x (Windows volume at 38) and 108db with 2.5x (Windows volume maxed) playing Metallica - No Leaf Clover. The volume was maxed out on the o2. *Wouldn't adjusting the Windows volume decrease the voltage so it matches perfectly with the 6.5x gain setting?*


 
  
 Yes, this is a valid way to achieve peak output power from O2+ODAC a 6.5x gain.


----------



## adydula

and what might lowering the volume to 38 do??? good? bad?
  
 Alex


----------



## JacobLee89

vertical said:


> Doesn't using the higher gain also increase the noise floor?


 
  
 If there's an audible noise floor to begin with, then yes.
  
 If you have a noise floor that is incredibly difficult to locate even at high volumes in a low-gain setting, you'll most likely not notice it in high-gain settings either.


----------



## vertical

Okay. Yeah, makes sense...Thx

So, ideally, one should just use the lowest gain setting that achieves their target volume level.


----------



## raoultrifan

O2 with original opamps clips after 7V, so for 2V sources max. gain would be 3.5X. If you upgrade gain opamp to 5532 or to 4562 you might be able to increase the gain up to 4X at most, but at 4X the max. output should be 8V which is quite too much for the 2x4556 buffers. If you'll increase the voltage to 15V, then max. output might get up to 10V, but on 12V will most likely clips after 7.5-8V, so changing gain opamp will probably give you only 0.5V more (4X instead of 3.5X) if not incrrasing voltage too.


----------



## diamondears

Can someone compute the mW and Vrms requirement of the HE-6 based on its sensitivity of 83.5 dB/mW and impedance of 50 ohms?


----------



## headwhacker

diamondears said:


> Can someone compute the mW and Vrms requirement of the HE-6 based on its sensitivity of 83.5 dB/mW and impedance of 50 ohms?


 
  
 115dB = 1413mW / 8.4Vrms
  
 110dB = 447mW / 4.72Vrms
  
 105dB = 141mW / 2.66Vrms


----------



## jseaber

diamondears said:


> Can someone compute the mW and Vrms requirement of the HE-6 based on its sensitivity of 83.5 dB/mW and impedance of 50 ohms?


 
  
 45 mW --> 100 dB
 141 mW --> 105 dB
 447 mW --> 110 dB
 794 mW --> 112.5 dB
 1413 mW --> 115 dB
  
 P = [(VRMS)^2 / Z]
 VRMS = (P*Z)^0.5
_Where: Z = headphone impedance in ohms, P = output power in mW_
  
  
 See also:
 https://docs.google.com/a/jdslabs.com/spreadsheets/d/1****TwWffXKld7PgHt5wZOP7KnBVO6SyvG9yZEJ-smI/edit#gid=1006269980


----------



## diamondears

jseaber said:


> 45 mW --> 100 dB
> 141 mW --> 105 dB
> 447 mW --> 110 dB
> 794 mW --> 112.5 dB
> ...



So 7Vrms clipping point would come up to how many dB?


----------



## headwhacker

diamondears said:


> So 7Vrms clipping point would come up to how many dB?


 
  
 O2 will start to clip around 6.8 Vrms. Theoretically O2 can only drive HE-6 at 113dB max.


----------



## jseaber

diamondears said:


> So 7Vrms clipping point would come up to how many dB?


 
  
 Clipping should occur close to 110dB listening volume. It's easy to refer to an SPL chart. 
  
 Slightly off topic: Peak output from O2 is 7.55VRMS for 150+ ohm loads. I need to verify how NwAvGuy arrived at the 7.0VRMS limit. It may be a conservative rounding error. Or a real input limit. Poke me if this isn't answered this week!
  
 Edit: Sorry for the repeat posts, headwacker. I'll sign off.


----------



## diamondears

headwhacker said:


> O2 will start to clip around 6.8 Vrms. Theoretically O2 can only drive HE-6 at 113dB max.




113dB is very loud sir! 113dB isn't enough on your classical music you mentioned?



jseaber said:


> Clipping should occur close to 110dB listening volume. It's easy to refer to an SPL chart.
> 
> Peak output from O2 is 7.55VRMS. I need to verify how NwAvGuy arrived at the 7.0VRMS limit. It may be a conservative rounding error. Or a real input limit. Poke me if this isn't answered this week!
> 
> Edit: Sorry for the repeat posts, headwacker. I'll sign off.




110dB is good enough for me! And that's the extreme hungry power HE-6. Don't understand the talk about O2 lacking power.


----------



## headwhacker

jseaber said:


> Clipping should occur close to 110dB listening volume. It's easy to refer to an SPL chart.
> 
> Peak output from O2 is 7.55VRMS. I need to verify how NwAvGuy arrived at the 7.0VRMS limit. It may be a conservative rounding error. Or a real input limit. Poke me if this isn't answered this week!
> 
> Edit: Sorry for the repeat posts, headwacker. I'll sign off.


 
  
 No harm done John. Your post is just as important and informative. I think Nwayguy just use 7Vrms as a conservative limit but O2's measured peak is well beyond 7Vrms. I think it's 7.3Vrms if you extrapolate it from his published measurements at 150 and 600 Ohm load.


----------



## headwhacker

diamondears said:


> 113dB is very loud sir! 113dB isn't enough on your classical music you mentioned?
> 110dB is good enough for me! And that's the extreme hungry power HE-6. Don't understand the talk about O2 lacking power.


 
  
 113dB is an ideal level. Usually you have 1 to 3dB margin of error. So John's estimate of 110dB represents real world usage scenario. That is why I always add 3dB on top of my target SPL when looking for an amp.
  
 Try it first so you can see why. Classical music has lots of peaks and and silent passages. And the difference between the silent and the loudest level is around 20dB to 30 dB. Modern pop/rock songs (highly compressed) would work and enough for HE-6 driven by O2.


----------



## diamondears

headwhacker said:


> Not the widest DR but try the album Tchaikovsky: The Nutcracker. I think it is the 2011 remaster.
> 
> Thanks




What record label?


----------



## Tostitostelli

rudi0504 said:


> JDS Lab ODAC usb DAC + JDS Lab O 2 head amp full modification with Black Gate Capasitors



I has to know where that awesome case comes from! Or has you made it yourself? *k back to normal english*


----------



## HotIce

jseaber said:


> Clipping should occur close to 110dB listening volume. It's easy to refer to an SPL chart.
> 
> Slightly off topic: Peak output from O2 is 7.55VRMS for 150+ ohm loads. I need to verify how NwAvGuy arrived at the 7.0VRMS limit. It may be a conservative rounding error. Or a real input limit. Poke me if this isn't answered this week!
> 
> Edit: Sorry for the repeat posts, headwacker. I'll sign off.



 

7.55V RMS at clip, or with THD under 0.1%?
With 12V Rail, and tossing about 0.35V on the schottky diode (D1/D5), leaves 11.65V to the OP-amp.
7.55V RMS is 10.68V peak, which leave less than 1V to be shared between the Vce of the VAS BJT, and the Vbe of the driver.
Given the Vbe of the driver around/at-least 0.65V, leaves less than 0.35V for the Vce of the VAS BJTs, and BJTs really do not like to work in that area, in the analog space.


----------



## Nec3

Can someone explain a bit how well the ODAC scales up to higher grade DAC's? How much would I have to spend to get a decent upgrade out of the ODAC loop?


----------



## Solrighal

nec3 said:


> Can someone explain a bit how well the ODAC scales up to higher grade DAC's? How much would I have to spend to get a decent upgrade out of the ODAC loop?


 
  
 +1 I'd also like to know where to go next.


----------



## Rajikaru

nec3 said:


> Can someone explain a bit how well the ODAC scales up to higher grade DAC's? How much would I have to spend to get a decent upgrade out of the ODAC loop?


 
  
 First, you need to come up with a  definition for  'higher grade DAC'.
  
 Other than that, the answer depends on the game master of whichever fantasy role play you subscribe to. 
  
 In other words, outside of objective parameters, everything is intangible, unverifiable, and subjective.


----------



## Tostitostelli

nec3 said:


> Can someone explain a bit how well the ODAC scales up to higher grade DAC's? How much would I have to spend to get a decent upgrade out of the ODAC loop?


 
 Well I've read and seen allot of reviews where the ODAC is portrayed as ''punching above its weight''. I personally wouldnt know, but if any DAC can, the ODAC can.


----------



## Nec3

rajikaru said:


> First, you need to come up with a  definition for  'higher grade DAC'.
> 
> Other than that, the answer depends on the game master of whichever fantasy role play you subscribe to.
> 
> In other words, outside of objective parameters, everything is intangible, unverifiable, and subjective.


 
  
 I was going to type out paragraphs, but I'm going to throw that out the window.
  
*If I spent $350 on a DAC* like a Little Dot DAC_I or Schiit Bitfrost, *would I hear an upgraded difference other than coloration?* Such as *more **detail retrieval *and the *"speed of sine waves"* (for lack of a better term), because from what my understanding is; there is a loss of 1's and 0's from a digital signal to an analogue signal.
 I can only assume that paying more money for a DAC means better engineered DAC's that converts the 1's and 0's to just 1's and 0's instead of half a 1 and sometimes no 0.
 Right now I'm going for a Little Dot Mk.3 amp, and I'm wondering if there would be any reason to upgrade from the ODAC.

 Edit: I'm not here to prove a point, I'm just here to ask for opinions on whether or not it's worth to spend the extra money to upgrade from the ODAC. Just purely based on experience. I know how subjective audio can get and I'm not here to start another sound science debate.

 P.S. the headphone I'm using is an AKG Q701.


----------



## diamondears

nec3 said:


> I was going to type out paragraphs, but I'm going to throw that out the window.
> 
> *If I spent $350 on a DAC* like a Little Dot DAC_I or Schiit Bitfrost, *would I hear an upgraded difference other than coloration?* Such as *more **detail retrieval* and the *"speed of sine waves"* (for lack of a better term), because from what my understanding is; there is a loss of 1's and 0's from a digital signal to an analogue signal.
> 
> ...






nec3 said:


> I'm just gonna roll with that and "save" money for my amp.
> 
> Thanks for the share.



I suggest you invest in a DAC and just buy a transparent amp like the O2--as transparent as a wire with gain. 

Problem with people saying "all DACs are the same" is that they're comparing DACs with the SAME digital filter (most common is standard/linear filter). IME, they would all sound the same. So when you look for a DAC, one should look at the digital filter or filters used. 

Some filters have pre-ringing, post-ringing, rolls off the high frequency slower/faster/suddenly/earlier/later, and some has different amounts of timing phase delays. All these affect the SQ. Now if you're told that a certain DAC sounds better and because of it it's much more pricey, but it has a same standard linear filter as that of the ODAC, IME you're being snake oiled. But if the filters arent the same, look at the implementation of the filters as one could have pre-ringing and later rolling off but faster/sudden rolling off, while the other have no pre-ringing and earlier rolling off but slower. These two filters would sound dramatically different, unless the implementation were designed to offset their peculiar characteristics and they eventually ended up sounding the same. 

As usual, my honest advise is invest in a DAC with several digital filters to choose and good implementation. Then just get a transparent amp that would just "transport" the sound from the DAC. 

My honest 2 cents.


----------



## Solrighal

diamondears said:


> I suggest you invest in a DAC and just buy a transparent amp like the O2--as transparent as a wire with gain.
> 
> Problem with people saying "all DACs are the same" is that they're comparing DACs with the SAME digital filter (most common is standard/linear filter). IME, they would all sound the same. So when you look for a DAC, one should look at the digital filter or filters used.
> 
> ...


 
  
 This sounds like good advice. Are there any DAC's you'd specifically recommend?


----------



## castleofargh

diamondears said:


> nec3 said:
> 
> 
> > I was going to type out paragraphs, but I'm going to throw that out the window.
> ...




but to accept your point of view, we first need to believe ultrasounds matter. because we're not talking filters at 5khz here, but stuff starting very high in the trebles even on 16bit NOS dinosaurs, and in ultrasounds for anything modern I guess.
 for OS DAC your post doesn't make much sense to me as there is no need for an aggressive filter anymore, and thus no filter problem.
did I miss something?


----------



## diamondears

castleofargh said:


> but to accept your point of view, we first need to believe ultrasounds matter. because we're not talking filters at 5khz here, but stuff starting very high in the trebles even on 16bit NOS dinosaurs, and in ultrasounds for anything modern I guess.
> for OS DAC your post doesn't make much sense to me as there is no need for an aggressive filter anymore, and thus no filter problem.
> did I miss something?



No, some filters start rolling off early at around 10khz, but slowly. This definitely sounds much less digitally or less fatiguing to me than the standard linear filter which has a brick wall filter at 20khz (vertical or steep or sudden rolling off). 

And this is true as well to ultrasounds from pre-ringing and post-ringing. It definitely causes sound to sound digitally and fatiguing. If you compare a standard filter with ringing vs let's say a slow filter with no ringing at same DAC (hence same implementation and so other factors are exactly the same), you'll see/hear the differences easily. 

It's just too bad that the industry doesn't offer many DACs with multiple filters. I guess it's preferable for them to use the better filter in a higher model. My DAC has 7 filters, and as I've said before this is so fun as its like changing tubes in one amp. It's not cheap but it's not too expensive as well. There's a reason why it has a large following.


----------



## Nec3

diamondears said:


> No, some filters start rolling off early at around 10khz, but slowly. This definitely sounds much less digitally or less fatiguing to me than the standard linear filter which has a brick wall filter at 20khz (vertical or steep or sudden rolling off).
> 
> And this is true as well to ultrasounds from pre-ringing and post-ringing. It definitely causes sound to sound digitally and fatiguing. If you compare a standard filter with ringing vs let's say a slow filter with no ringing at same DAC (hence same implementation and so other factors are exactly the same), you'll see/hear the differences easily.
> 
> It's just too bad that the industry doesn't offer many DACs with multiple filters. I guess it's preferable for them to use the better filter in a higher model. My DAC has 7 filters, and as I've said before this is so fun as its like changing tubes in one amp. It's not cheap but it's not too expensive as well. There's a reason why it has a large following.


 
 I'm going to leave the odac/o2 as it is...I went for a dac/tube amp combo that is completely coloured (20hz-20khz +/-3db)


----------



## diamondears

nec3 said:


> I'm going to leave the odac/o2 as it is...I went for a dac/tube amp combo that is completely coloured (20hz-20khz +/-3db)



Huh????

Just meant that with multiple filter options in one DAC, you can change the sound like changing tubes in one DAC. Actually, it's like changing DACs. It's like having 7 DACs if it has 7 filters.


----------



## diamondears

solrighal said:


> This sounds like good advice. Are there any DAC's you'd specifically recommend?



Audiolab 8200CD. 7 digital filters including the standard one. Not cheap though, but not too expensive either. If you want cheaper, I'd recommend the Cambridge Audio DacMagic Plus. 

Let me also say that when I went into headphones (coming from speakers), I had full appreciation of the multiple digital filters only when I got an O2. With the O2, I can see more the differences in the filters in one DAC. It pays to have a truly transparent amp. If I want to change the sound, I just change filters or HPs.


----------



## Nec3

diamondears said:


> Huh????
> 
> Just meant that with multiple filter options in one DAC, you can change the sound like changing tubes in one DAC. Actually, it's like changing DACs. It's like having 7 DACs if it has 7 filters.




Ah, well I just prefer my dacs unfiltered


----------



## Solrighal

diamondears said:


> Audiolab 8200CD. 7 digital filters including the standard one. Not cheap though, but not too expensive either. If you want cheaper, I'd recommend the Cambridge Audio DacMagic Plus.
> 
> Let me also say that when I went into headphones (coming from speakers), I had full appreciation of the multiple digital filters only when I got an O2. With the O2, I can see more the differences in the filters in one DAC. It pays to have a truly transparent amp. If I want to change the sound, I just change filters or HPs.


 
  
 Thanks very much mate. The Audiolab is way out of my reach unfortunately but the DacMagic is a contender I guess. I have the chance of a Musical Fidelity V-DAC II for much cheapness but I'm not convinced it would be a step-up from the ODAC.
  
 I do agree with your rationale about the O2. I employed the same logic when choosing headphones and that led me to what are probably going to be my end-game cans, the HD 650 from Sennheiser. Using the Senn's has now allowed me to identify my end-game amp, the Project Ember.
  
 Only the DAC to go.


----------



## diamondears

nec3 said:


> Ah, well I just prefer my dacs unfiltered



Nec3, every DAC has a filter. So yours is filtered too.


----------



## diamondears

solrighal said:


> Thanks very much mate. The Audiolab is way out of my reach unfortunately but the DacMagic is a contender I guess. I have the chance of a Musical Fidelity V-DAC II for much cheapness but I'm not convinced it would be a step-up from the ODAC.
> 
> I do agree with your rationale about the O2. I employed the same logic when choosing headphones and that led me to what are probably going to be my end-game cans, the HD 650 from Sennheiser. Using the Senn's has now allowed me to identify my end-game amp, the Project Ember.
> 
> Only the DAC to go.



I have the DacMagic Plus, and it's a great DAC. It's Minimum Phase filter is IMO better than the Audiolab's Minimum Phase filter. Interestingly, they're designed by same person (John Westlake). Audiolab has the most popular Sabre chip, while the DacMagic has the most popular Wolfson chips.


----------



## Solrighal

The trouble with DAC's is that I'm not really sure there's anything wrong with the ODAC in the first place. I'll wait until I get my Ember & get used to that before I make any decisions. Ideally I'd like to borrow a couple to see if I can hear any difference.
  
 Edit - I said O2 where I should have said ODAC. Sorry for any confusion, it was very late at night.


----------



## castleofargh

nec3 said:


> diamondears said:
> 
> 
> > Huh????
> ...



lol, good luck with that.


----------



## diamondears

solrighal said:


> The trouble with DAC's is that I'm not really sure there's anything wrong with the O2 in the first place. I'll wait until I get my Ember & get used to that before I make any decisions. Ideally I'd like to borrow a couple to see if I can hear any difference.



What do you mean you're "not really sure there's anything wrong with the O2"? You mean ODAC?

Haven't heard the ODAC, but if anything, it's just limited by the filter. For those who like that filter, I think there could be none better than the ODAC.


----------



## WilliamLeonhart

Pardon my for my ignorance but how do I change the filters on my ODAC?


----------



## headwhacker

williamleonhart said:


> Pardon my for my ignorance but how do I change the filters on my ODAC?


 
  
 You can't


----------



## headwhacker

solrighal said:


> I do agree with your rationale about the O2. I employed the same logic when choosing headphones and that led me to what are probably going to be my end-game cans, the HD 650 from Sennheiser. Using the Senn's has now allowed me to identify my end-game amp, the Project Ember.


 
  
 It does not quite make sense to me. If O2 helped you find HD650 as your end game phone, then it should be mutually inclusive. O2 should be the same as well. Now that you realize that HD650 -> project ember is you end of game combo. Doesn't it tell you that HD650 isn't quite the headphone you thought it should sound paired with O2?


----------



## Solrighal

diamondears said:


> What do you mean you're "not really sure there's anything wrong with the O2"? You mean ODAC?
> 
> Haven't heard the ODAC, but if anything, it's just limited by the filter. For those who like that filter, I think there could be none better than the ODAC.


 
  
 You're absolutely correct, my mistake. I meant to say ODAC. It was late & I wasn't thinking straight.


----------



## Solrighal

headwhacker said:


> It does not quite make sense to me. If O2 helped you find HD650 as your end game phone, then it should be mutually inclusive. O2 should be the same as well. Now that you realize that HD650 -> project ember is you end of game combo. Doesn't it tell you that HD650 isn't quite the headphone you thought it should sound paired with O2?


 
  
 I see what you mean & I agree, mostly. Being transparent, the O2 allowed me to hear into the sound signatures of various headphones. Of all the ones I bought the 650's were a revelation. I like their non-aggressive nature which, although perhaps laid-back compared to some, still reveal all the detail in the recording. I had no intention of upgrading the O2 - in fact I considered the O2 to be the ultimate amp. I started talking with some people on another forum and was persuaded to give the Project Ember a try. I was going to get it at home for a few weeks and - in my opinion - get the chance to finally prove to myself that valves were just hot air.
  
 I was so wrong! The combination of the Project Ember with the HD 650 is magical. It's not expectation bias because I fully expected (wanted) the O2 to be superior. The Ember beats it in every way. All the detail is there but now there's a much larger sound-stage and a 'weight' to the music that was previously missing. I had to make a serious re-evaluation of my attitude to hi-fi. I was also lucky enough to have a Project Polaris side-by-side with the Ember & the O2 for evaluation. I liked it too but not to the same extent as the Ember. The O2 is undoubtedly transparent & for that it has to be commended. However, perhaps one of the more telling details in the O2's mission statement is that it has to be built for under $100. I feel that's often left out of discussions surrounding it. Are more expensive components better sounding? I have no idea. All I can say is that to my ears the Project Ember delivers a better sound than the O2.
  
 So I'm buying a Project Ember. In an ideal world I would hold on to the O2 and do a similar test with DAC's but no-one's offering me a DAC at home to test over a prolonged period. I've already sold my O2 to part-fund my purchase of the Ember. Once I get my Project Ember I'll have the best sound I've ever heard via headphones. If I never get the chance to hear a different DAC I'll still be happy. But the O2 being beaten was nothing short of a revelation for me and so I can't help wondering if similar gains are to be had by a change of DAC.
  
 None of this is to say the O2 is bad. It's absolutely not. If it's the only amp you ever hear then it's fantastic and maybe for some will always be the end-game. Not to me though. I can only go on what I hear. I didn't do any proper ABX testing or anything like that. I frankly don't believe I'm able to retain an accurate impression of sound characteristics when switching amps & I don't have any friends living locally who would be able to help me out anyway. I have to go on what my brain tells me after 6 weeks of auditioning. I'll tell you this - when I sent the Ember on to it's next tester I was bereft. To the point where I haven't listened to my headphones since.
  
 Now I'm slowly amassing the money to purchase the Ember and when I have it I'll then look into a replacement DAC. If I get to test one and hear no difference then I'll be keeping my O2, saving some money & I'll still be happy.
  
 I want to say this too. In no way am I trying to suggest that the Project Ember is the ultimate amplifier. There is a huge range of options out there & I'm almost certain there will be some that are even better. However the Ember really turned my opinions of amplifiers upside-down and, coupled with the warm feeling I get from the Ember community at DIYAH (without whom I'd have never had the opportunity to hear it) I'm happy that I've made the correct choice.
  
 I hope that goes some way to explaining my reasoning & the decisions I've made.
  
 Gordon.


----------



## JacobLee89

On a slightly differing topic. It seems like some of us O2'ers are slowly migrating to either Project Ember, or Project Polaris. One reason why I am on the reluctant side of making the move of buying one is due to the fact that my O2 has already gone through some mods, which - at least for me - has made some noticeable improvements. I'm unsure if the Polaris would offer much in terms of improvement. The ember is definitely a choice, but I don't feel comfortable with transporting tubes when I myself would be moving places quite often.
  
 Actually, for now I think I will settle with this little bias of mine, just so that I can control my spending for a little longer..
  
 *Edit*
 Also I've seen the Bravo Audio S1 laying around in the void.. Some people say that - with some opamp rolling - they prefer it over the schiit magni. Unfortunately this amp hasn't seen much of the limelight over here, so that's yet another curiosity on my list.


----------



## castleofargh

are people moving to something else because it's an upgrade? or simply because they realized a little late that  transparent wasn't their idea of good sound?
 IMO most people just want the sound of speakers in their headphones. that's what they call "real/good" sound. speakers tend to have some massive mess going on, be it from distortion levels or the impact of the room(plus of course the bass felt by the body). my own experience of tube stuff sometimes can give some kind of similar feelings and I really understand that many people would prefer that to transparent sound.
 to me that's like adding lens flare on 3D rendering. you try to give a feeling of reality by adding the stuff we strive to get rid of IRL. and when we do get rid of those stuff, people call that unnatural ^_^.
  
 for vinyl fans, lot of distortion, bad crosstalk, very rolled off trebles, and you turned that "nasty/cold" perfectly fine CD into the nice nostalgic sound of vinyls. colored amps are doing that in a special way. I do enjoy colored sound, but I would be very sad if I didn't also have the odac/o2 or another transparent amp as a reference.


----------



## headwhacker

castleofargh said:


> are people moving to something else because it's an upgrade? or simply because they realized a little late that  transparent wasn't their idea of good sound?
> IMO most people just want the sound of speakers in their headphones. that's what they call "real/good" sound. speakers tend to have some massive mess going on, be it from distortion levels or the impact of the room(plus of course the bass felt by the body). my own experience of tube stuff sometimes can give some kind of similar feelings and I really understand that many people would prefer that to transparent sound.
> to me that's like adding lens flare on 3D rendering. you try to give a feeling of reality by adding the stuff we strive to get rid of IRL. and when we do get rid of those stuff, people call that unnatural ^_^.
> 
> for vinyl fans, lot of distortion, bad crosstalk, very rolled off trebles, and you turned that "nasty/cold" perfectly fine CD into the nice nostalgic sound of vinyls. colored amps are doing that in a special way. I do enjoy colored sound, but I would be very sad if I didn't also have the odac/o2 or another transparent amp as a reference.


 
  
 It's our nature to get sick of having the same thing repeatedly for a long time then when we experience something new we get a very pleasant feeling which will last as long as you get sick of it as well.
  
 That is what I observe with myself and others in this hobby. Experiencing color or different flavor to the sound is nice once in a while, but I do it by changing headphones and/or eq. The changes are not too hard to detect and imo is easier to predict the than rolling amplifiers to get the desired coloration.


----------



## diamondears

headwhacker said:


> It's our nature to get sick of having the same thing repeatedly for a long time then when we experience something new we get a very pleasant feeling which will last as long as you get sick of it as well.
> 
> That is what I observe with myself and others in this hobby. Experiencing color or different flavor to the sound is nice once in a while, but I do it by changing headphones and/or eq. The changes are not too hard to detect and imo is easier to predict the than rolling amplifiers to get the desired coloration.



Yeah, more options gets us farther from boredom aka upgradetitis. I have avoided upgradetitis on my gears by buying new HPs and playing around with 7 filters on my DAC. It's like having 7 CD players right in front of me. The O2 is perfect for this as its so transparent it just gets the signal from the DAC, passes it thru, and enable it to get accessed by the headphone thru the headphone jack out. In other words, with the O2, you can now see the music 20/20 from the DAC. 

I really couldn't find any justification for buying another amp. I tried, looked for other amps regardless of price. Even when abroad I looked and looked. Couldn't find any.


----------



## Solrighal

castleofargh said:


> are people moving to something else because it's an upgrade? or simply because they realized a little late that  transparent wasn't their idea of good sound?
> IMO most people just want the sound of speakers in their headphones. that's what they call "real/good" sound. speakers tend to have some massive mess going on, be it from distortion levels or the impact of the room(plus of course the bass felt by the body). my own experience of tube stuff sometimes can give some kind of similar feelings and I really understand that many people would prefer that to transparent sound.
> to me that's like adding lens flare on 3D rendering. you try to give a feeling of reality by adding the stuff we strive to get rid of IRL. and when we do get rid of those stuff, people call that unnatural ^_^.
> 
> for vinyl fans, lot of distortion, bad crosstalk, very rolled off trebles, and you turned that "nasty/cold" perfectly fine CD into the nice nostalgic sound of vinyls. colored amps are doing that in a special way. I do enjoy colored sound, but I would be very sad if I didn't also have the odac/o2 or another transparent amp as a reference.


 
  
 This is more or less how I interpret my experience too. I wouldn't necessarily say the valve sound is better but to me it's preferable. I deally I would have held on to the O2 but I needed to raise the money for the Project Ember somehow & selling the O2 is a step in that direction. I can't say I'm happy about it though.


----------



## Medaud

The only problem I have with my O2/ODAC is the channel imbalance at low volumes. I would upgrade if there was another Amp/DAC with the same transparency but without the imbalance.


----------



## Solrighal

medaud said:


> The only problem I have with my O2/ODAC is the channel imbalance at low volumes. I would upgrade if there was another Amp/DAC with the same transparency but without the imbalance.


 
  
 Could this possibly be because your gains are too high for the headphones you are using?


----------



## JacobLee89

medaud said:


> The only problem I have with my O2/ODAC is the channel imbalance at low volumes. I would upgrade if there was another Amp/DAC with the same transparency but without the imbalance.


 
  
 Odd. This would be the first time I've heard of an O2 with a channel imbalance.


----------



## castleofargh

jacoblee89 said:


> medaud said:
> 
> 
> > The only problem I have with my O2/ODAC is the channel imbalance at low volumes. I would upgrade if there was another Amp/DAC with the same transparency but without the imbalance.
> ...


 

 the knob at low volume levels will tend to have some channel imbalance and you can have more or less luck depending on the knob. the very traditional advice is to avoid the first 1/4 or 1/3 of this kind of knobs. step volume and digitally controlled volumes are usually free of that problem.
@Medaud if you're not already at unity gain, look for how to get it(will need to get rid of a pair of resistors). if you're already at unity gain and it's still necessary for you to lower the volume into channel imbalance, then you can lower your computer by... IDK 15 or 20DB without any problem for sound(just select the output to be 24bit in your audio player). that often takes you out of imbalance.
 else, you may want to look for an amp with step volume(each step is a pair of resistors so the imbalance can only be the error margin of the 2 resistors), the trouble with that is that you can't set the loudness in between 2 steps :'(. or else get something with a digitally controlled volume(pretty much the same idea but with a lot more values to set your loudness and maybe a little more noise). as portable amp I use the UHA760 for that very reason with very sensitive IEMs. but it's not a powerful amp like the O2, so it should be limited to portable gears.


----------



## Medaud

solrighal said:


> Could this possibly be because your gains are too high for the headphones you are using?




I'm on 1x unity gain, headphones are ATH-A900x with windows volume slider at 98% and default format in windows set to 24bit 96kHz.



jacoblee89 said:


> Odd. This would be the first time I've heard of an O2 with a channel imbalance.




It's been mentioned quite a few times. Only happens when you turn the volume knob way down.



castleofargh said:


> the knob at low volume levels will tend to have some channel imbalance and you can have more or less luck depending on the knob. the very traditional advice is to avoid the first 1/4 or 1/3 of this kind of knobs. step volume and digitally controlled volumes are usually free of that problem.
> @Medaud
> if you're not already at unity gain, look for how to get it(will need to get rid of a pair of resistors). if you're already at unity gain and it's still necessary for you to lower the volume into channel imbalance, then you can lower your computer by... IDK 15 or 20DB without any problem for sound(just select the output to be 24bit in your audio player). that often takes you out of imbalance.
> else, you may want to look for an amp with step volume(each step is a pair of resistors so the imbalance can only be the error margin of the 2 resistors), the trouble with that is that you can't set the loudness in between 2 steps :'(. or else get something with a digitally controlled volume(pretty much the same idea but with a lot more values to set your loudness and maybe a little more noise). as portable amp I use the UHA760 for that very reason with very sensitive IEMs. but it's not a powerful amp like the O2, so it should be limited to portable gears.




Would it work to just lower the windows volume slider further? How would this affect the quality of sound, would there be any audible difference? Thanks for the advice.


----------



## castleofargh

well you go with the idea that 1bit gives you about 6db, so the problem is to know how many effective bits your DAC has.
 by lowering the volume on the computer you can visualize it as cutting the quietest part of the signal. you really have no need to go all the way down to 24bit for the music signal as albums will usually not go past 65 or 70db of dynamic even for classical. so the question is how low you really need the quantization noise to be?
  
 you can turn the windows value to decibel instead of percentage, that gives a better idea of what you're doing I think(just right click the value into sound properties and it will let you select % or db). I just set the volume in foobar, but I can understand how it's more convenient to set it in windows for utube games etc.
  
 in my situation, I tried to get the lower value on the O2 that had no big obvious channel imbalance(checked with some tones looped into my soudcard) and from that I went to set my computer. I never had to go below -15DB in foobar. to that you add the replaygain I use on all my tracks so the value changes depending on how dynamic the song is, but let's say around -10db/-15db for not dynamic songs. so I end up at about -25db/-30db when I listen quietly to metallica... and above for my usual listening levels and for anything with some actual dynamic in the song.
 6*5=30db so I give away 5 bits max, not really a drama for me, but for somebody with a 16bit DAC it's another story.


----------



## adydula

There's a new build of the ODA over at DIYAUDIO if anyone is interested:
  
 http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda-74.html
  
 You can follow this persons build to see if you think you might want to tackle the project!
  
 Alex


----------



## JacobLee89

adydula said:


> There's a new build of the ODA over at DIYAUDIO if anyone is interested:
> 
> http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda-74.html
> 
> ...


 
  
 I'll need to save up a bit, grab a whole spool of solder wick, and a PCB holder or some sort.
 Then I'll tackle this!


----------



## HotIce

I am not sure if anyone tried this, but it should be possible to replace U5 and U6 with with MC7815 and MC7915 respectively, and change R1 and R2 to 390 Ohm, to have a 6V P2P boost.
The 20V AC supply should be good, or eventually bump it to 22..24V AC.
The NJM4556 can take up to +-18V, so 15V should be safe.
I would not use it in that configuration to feed high demanding low Z HPs (as the Pd for it tops 800mW for the SIP8 version), but for HPs with higher Z and hard to drive, similarly to the "there is no replacement for displacement", there is no replacement for voltage


----------



## adydula

Have u ever looked at AGDR's O2 booster board?
  
 Alex


----------



## HotIce

Reading right now.
What I was proposing is much less involved, and requires $2 of parts and dis-soldering two easy TO-220 ICs, and two resistors.


----------



## mcandmar

Low impedance phones need current not voltage.   The mods you have listed are fairly easy to do but there is a gotcha to do with the current handling limits of the IC's.  I believe this fundamental issue was what started the O2 Booster project in the first place.


----------



## HotIce

Which is exactly what I stated (FWIW, Z == Impedance):

"I would not use it in that configuration to feed high demanding low Z HPs (as the Pd for it tops 800mW for the SIP8 version), but for HPs with higher Z and hard to drive"

Ie, a 600 Ohm HP, at about 13V peak, would ask for about 20mA, or about 10mA per buffer.
A 300 Ohm, about 20mA per buffer, well within the IC specs.


----------



## castleofargh

the list of headphones needing 13V is rather short I would guess. there are already not so many headphones that will need more than a basic O2's voltage to reach some 115 or 120db. and I would guess that those limited by the O2 are mainly so because of an overall power limit like orthos where sensitivity and impedance are both rather low.


----------



## adydula

Hey I took the liberty to talk to the O2 Booster design engineer and here are his comments for your read:
  
 Interesting!  You are right, that exact issue is covered on the 4th to the last page in the O2 Booster Board build instructions here

https://drive.google.com/folderview?id=0B67cJELZW-i8ejFUWGFNLWdIWVU&usp=sharing

 under the "O2 Headphone Amplifier +/-15Vdc Power Supply Upgrade" heading.

  In addition to replacing the regulators there are a couple of more parts that have to change (for voltage rating).  And the big thing - whether he leaves the NJM4556A's in or replaces them with the Booster Board - no less than 600 ohm headphones if using the NJM455As or no less than 300 ohm if using the Booster Board. 

 The issue here is the amount of power dissipated by the output chips, as that poster notes.  Even though both chips (NJM4556A or the LME49600 buffers on the booster board) are rated for +/-15Vdc rails, the math still has to be done tp make sure the chips won't overheat with a given load at that voltage level.   The higher the chip supply voltage the more chip power dissipation for a given ohm load and given output voltage swing.

 Remember that even with the original O2 +/-12Vdc rails there is a problem with the NJM4556A's overheating with the combination of a 16 ohm load, low sensitivity headphones, higher volume levels, and music with high sustained musical peaks.
  
 Fyi... an thanks to AGDR.
  
 Alex


----------



## diamondears

Is NWAVGUY interested in EVEN improving this design? Or its potential maximized already?


----------



## PDVJAM

diamondears said:


> Is NWAVGUY interested in EVEN improving this design? Or its potential maximized already?


 

 Well, no one knows who is he and where he is now


----------



## PDVJAM

I also have a question. I'm planning to buy o2+odac for the following set of headphones: CIEM with 16ohm and sensitivity 111db, hd650, audeze lcd-2 and hifiman he-6. Would it be enough to have gain settings 1x (for CIEM)/3x (for all other) in this case?


----------



## headwhacker

pdvjam said:


> I also have a question. I'm planning to buy o2+odac for the following set of headphones: CIEM with 16ohm and sensitivity 111db, hd650, audeze lcd-2 and hifiman he-6. Would it be enough to have gain settings 1x (for CIEM)/3x (for all other) in this case?


 
  
 HE-6 will be too much for O2 to handle. HE-560 is borderline maximimum O2 can drive. At 1x O2+ODAC may be too load for the CIEM. But you can reduce the volume on your PC to compensate.
  
 HD-650 and LCD-2 should be easy for O2 at 3X. JDS Labs allows an option for 1X/3.5X gain.


----------



## Thad-E-Ginathom

diamondears said:


> Is NWAVGUY interested in EVEN improving this design? Or its potential maximized already?


 
  
 NwAvGuy doesn't "exist" any longer.


----------



## upstateguy

castleofargh said:


> are people moving to something else because it's an upgrade? or simply because they realized a little late that  transparent wasn't their idea of good sound?
> <snip>


 
  
 Agree with you completely.
  
 It's very hard to obtain the level of resolution you get from an O2 with a tube rig.
  
 What you will get with a tube rig is various amounts of coloration, which is why people roll tubes.
  
 Another approach might be to start with the highest resolution you can get, and then if needed, color to taste with EQ.


----------



## adydula

now thats a great idea!
  
 Alex


----------



## WilliamLeonhart

thad-e-ginathom said:


> NwAvGuy doesn't "exist" any longer.


 
 Who keeps that domain online though... Must be an admirer, perhaps. Anw he doesn't exist anymore.


----------



## Thad-E-Ginathom

williamleonhart said:


> Who keeps that domain online though... Must be an admirer, perhaps. Anw he doesn't exist anymore.


 
  
 It's a good question, and the beginning of potentially endless speculation. Is there a _NwAvGuy Disappearance  _thread? I guess we shouldn't take it further here. Actually, I guess there isn't so much active interest these days.


----------



## castleofargh

well he's still the one who created the O2 ^_^. and I know I found more audio answers in his blog than on any other website, so I recognize the hand that didn't try to feed me BS and will always be grateful. and TBH I didn't buy the O2 because I'm a fanboy(even though I clearly am by now), but because it was the only amp with extended measurements available outside of a few DIY projects.


----------



## headwhacker

castleofargh said:


> well he's still the one who created the O2 ^_^. and I know I found more audio answers in his blog than on any other website, so I recognize the hand that didn't try to feed me BS and will always be grateful. and TBH I didn't buy the O2 because I'm a fanboy(even though I clearly am by now), but because it was the only amp with extended measurements available outside of a few DIY projects.


 
  
 I agree his blog has ton of information about amps/dac. It was a fun read and very easy for me to understand all the things I need to know about amplifier.
  
 It made me stop hanging out in the portable amp forums. If I'm not looking to get an HE-6, I would not be looking for any other amp than O2.


----------



## WilliamLeonhart

So far I still think the O2+ODAC is best value for the price. It can't compete with (much) higher ranged amps (like the Aune S16 that I enjoy tremendously), but still, for that price.


----------



## PDVJAM

williamleonhart said:


> So far I still think the O2+ODAC is best value for the price. It can't compete with (much) higher ranged amps (like the Aune S16 that I enjoy tremendously), but still, for that price.


 

 AUNE S16 has 30ohm output impedance. So it is best suited for 240+ ohm headphones. And this is bad.


----------



## upstateguy

williamleonhart said:


> So far I still think the O2+ODAC is best value for the price. *It can't compete *with (much) higher ranged amps (like the Aune S16 that I enjoy tremendously), but still, for that price.


 
  
 I'm not sure I understand what you're saying so I think I'm going to *disagree* with you. 
  
 Are you trying to say that the Aune S 16 *has audibly more resolution or sounds* different than the O2+ODAC?


----------



## adydula

It cant compete is quite a statement, how? In what ways??
  
 Sonically?
 Transparency?
 Freq Response?
 Power Output at what Impedance?
 THD?
 IM?
 Cross Talk?
 Connectability?
 Versatilty?
 Connections?
 Feel Good?
 Cosmetics?
 Size?
 Weight?
  
 Alex


----------



## diamondears

castleofargh said:


> well he's still the one who created the O2 ^_^. and I know I found more audio answers in his blog than on any other website, so I recognize the hand that didn't try to feed me BS and will always be grateful. and TBH I didn't buy the O2 because I'm a fanboy(even though I clearly am by now), but because it was the only amp with extended measurements available outside of a few DIY projects.



+1. Once you read his blog you'd understand completely why it ruffles so many feathers. It just screams lots of lost money...for the snake oils, that is...



williamleonhart said:


> So far I still think the O2+ODAC is best value for the price. It can't compete with (much) higher ranged amps (like the Aune S16 that I enjoy tremendously), but still, for that price.



Gotta disagree. I've tested and compared so many amps, including high-end ones, locally and abroad, and I've found none more transparent. Yeah, NONE. 

Of course, if by "can't compete" you mean in terms of "sound likeability", that's entirely subjective as that's in the realm of non-transparency or coloration... Which of course O2 would be beaten easily... Peace bro...


----------



## upstateguy

diamondears said:


> <snip>





> Of course, if by "can't compete" you mean in terms of "sound likeability", that's entirely subjective as that's in the realm of non-transparency or coloration...
> 
> 
> 
> ...


 

  
 Gotta wonder what you mean by "beaten easily" ?
  
 And I gotta disagree that it would be, "Carver Challenge" style.


----------



## diamondears

upstateguy said:


> Gotta wonder what you mean by "beaten easily" ?
> 
> And I gotta disagree that it would be, "Carver Challenge" style.



O2 would be beaten easily when it comes to who has the better coloration...


----------



## WilliamLeonhart

The thing is, I've never quite understood "transparency", but to me the S16 (as a DAC + amp) gives a more detailed and airy sound than the O2+ODAC that I own. Also, there's a feeling that it suffers from less noise and jitters. That's entirely subjective, of course, I can't prove it. I have never leaned too much on the technical side of things, but what I got told is that the S16 has better USB input (and better other components) than the O2+ODAC. Then again, people can customize their O2, so still there's stuffs for argument.
  
 And don't get me wrong. As I said earlier, the O2+ODAC is still the best valued amp/dac that I've ever seen. Which means that _if _someone tells me to choose between the S16 and the O2+ODAC for free, I'd go with the S16. But is the S16 worth 2 times the price of the O2+ODAC (I can have the S16 for $500), then it's a big no. I also will have to buy an amp for the S16 too.


----------



## PDVJAM

williamleonhart said:


> The thing is, I've never quite understood "transparency", but to me the S16 (as a DAC + amp) gives a more detailed and airy sound than the O2+ODAC that I own. Also, there's a feeling that it suffers from less noise and jitters. That's entirely subjective, of course, I can't prove it. I have never leaned too much on the technical side of things, but what I got told is that the S16 has better USB input (and better other components) than the O2+ODAC. Then again, people can customize their O2, so still there's stuffs for argument.
> 
> And don't get me wrong. As I said earlier, the O2+ODAC is still the best valued amp/dac that I've ever seen. Which means that _if _someone tells me to choose between the S16 and the O2+ODAC for free, I'd go with the S16. But is the S16 worth 2 times the price of the O2+ODAC (I can have the S16 for $500), then it's a big no. I also will have to buy an amp for the S16 too.


 
  
 What headphones you use with S16?


----------



## headwhacker

williamleonhart said:


> The thing is, I've never quite understood "transparency", but to me the S16 (as a DAC + amp) gives a more detailed and airy sound than the O2+ODAC that I own. Also, there's a feeling that it suffers from less noise and jitters. That's entirely subjective, of course, I can't prove it. I have never leaned too much on the technical side of things, but what I got told is that the S16 has better USB input (and better other components) than the O2+ODAC. Then again, people can customize their O2, so still there's stuffs for argument.
> 
> And don't get me wrong. As I said earlier, the O2+ODAC is still the best valued amp/dac that I've ever seen. Which means that _if _someone tells me to choose between the S16 and the O2+ODAC for free, I'd go with the S16. But is the S16 worth 2 times the price of the O2+ODAC (I can have the S16 for $500), then it's a big no. I also will have to buy an amp for the S16 too.


 
  
 Technically transparency means an amp is capable of reproducing the signal fed from it's input with almost exact shape when it comes out of the ouput (mostly with bigger amplitude). transparency usually is synonymous to accuracy.
  
 Most people judge audio gear by ears alone which is definitely the least reliable way (but easily the most satisfying for majority.) Why? because everyone has a different reference of what a good sound is. Old folks who grew up with tubes and vinyl will have those gears as reference for good sound. Younger generations who grew up with MP3s normally would take something that sound louder as better.
  
 Take your case for example, S16 in pure technical perspective is already flawed having a 30 ohm output impedance as mentioned earlier. It's been established that high OI affects the FR response of dynamic-driver based headphones at low load impedance like the grados which I can see you are using. (Look for "electrical damping" or simply damping factor)
  
 I have nothing against you liking the amp for how it sounds like paired with your headphones. But as far as accuracy goes, the S16 definitely is not. 
  
 Personally, having a transparent/accurate amp makes my life simple when choosing headphones because I am assured that what I hear is exactly what the headphone is designed for. Same goes with the source. I can hear exactly how the source was created mastered. It's both a curse and a gift because excellent source sounds equally excellent. Same goes with bad source (masters as well). All I need to know now is if the amp has enough power to drive my headphone well and not how the amp will affect the sound I hear.
  
 If you look at the amp forums, you can see people spend a lot of time trying as many amp as possible. Then try as many headphone combinations. I'm not saying it's a bad thing because as a hobby it could be a very nice experience. Especially for people who has time. But I don't want to spend nor have a lot of time to spend looking for the gears I want.


----------



## diamondears

headwhacker said:


> Technically transparency means an amp is capable of reproducing the signal fed from it's input with almost exact shape when it comes out of the ouput (most with bigger amplitude). transparency usually is synonymous to accuracy.
> 
> Most people judge audio gear by ears alone which is definitely the least reliable way (but easily the most satisfying for majority.) Why? because everyone has a different reference of what a good sound is. Old folks who grew up with tubes and vinyl will have those gears as reference for good sound. Younger generations who grew up with MP3s normally would take something that sound louder as better.
> 
> ...



Exactly.


----------



## diamondears

If you like coloration, EQ is there. If you like different sound signature, there are lots of HPs to choose from. I get why tubes could be fun though.


----------



## WilliamLeonhart

headwhacker said:


>


 
 Thanks for the clarification. I'm as much of a O2+ODAC fan as anyone here, but your post really offer me another insight into my choice of amps. Generally for slower music I prefer my LD I+ to the O2, but from your post I gather that the sound of the O2 is the exact, accurate sound that the _headphone manufaturer_ wants us to hear?


----------



## WilliamLeonhart

diamondears said:


> If you like coloration, EQ is there. If you like different sound signature, there are lots of HPs to choose from. I get why tubes could be fun though.


 
 I'm not quite a fan of digital EQ. It was a long time ago, when I only had a SR60i and a HD448 when I came to the realization that no amount of EQ can replicate the choice of another amp (or another headphones). I could be wrong with something you guys agreed as "absolute accuracy" like the O2+ODAC.


----------



## diamondears

Me I just want to hear the intended recording and intended HP design. I completely want what the experts--recording engineers and HP designers/manufacturers--intended.

IMHO, I think this is the best way to enjoy music. Because the recording is always the best way possible to record a certain song. So I want to hear what that is exactly. That's my 1st preference.

When I tried tubes way back in speakers, I was really disappointed because the music coming out was always different than the intended recording. It always feels "not right" to me. Never was there an instance where I didn't prefer the transparent or accurate version. And I've always found that the non-transparent/accurate version sounds better only as compared to transparent version if the speakers and/or source (CD player) is not accurate or not good quality.


----------



## headwhacker

williamleonhart said:


> Thanks for the clarification. I'm as much of a O2+ODAC fan as anyone here, but your post really offer me another insight into my choice of amps. Generally for slower music I prefer my LD I+ to the O2, but from your post I gather that the sound of the O2 is the exact, accurate sound that the _headphone manufaturer_ wants us to hear?


 
  
 Yes, accurate is a sense you hear exactly how a headphone renders the music playing. It's what most people refer to wire with gain. The amp gets out of the way. 
  
 EQ has been villified by audiophiles and I seldom use it. But I believe it's better to use it than having multiple amps for diiferent flavor or use tube amps and roll tubes. It's not a bad thing to do. But there are a lot of reasons outside of audio why I don't like tubes.


----------



## diamondears

headwhacker said:


> Yes, accurate is a sense you hear exactly how a headphone renders the music playing. It's what most people refer to wire with gain. The amp gets out of the way.
> 
> EQ has been villified by audiophiles and I seldom use it. But I believe it's better to use it than having multiple amps for diiferent flavor or use tube amps and roll tubes. It's not a bad thing to do. But there are a lot of reasons outside of audio why I don't like tubes.



If transparency and accuracy is the preference, upstream gear is more important. So player, then DAC, in that order, are more important.


----------



## thecrow

diamondears said:


> Me I just want to hear the intended recording and intended HP design. I completely want what the experts--recording engineers and HP designers/manufacturers--intended.
> 
> IMHO, I think this is the best way to enjoy music. Because the recording is always the best way possible to record a certain song. So I want to hear what that is exactly. That's my 1st preference




Firstly let me say I totally agree with you and have the same ideology that I base my audio decisions around. These ideology is partly behind me buying a pair of hd800s and currently waiting for my odac (and O2) to arrive. This is why I like thd idea of a neutral sound that i can tweak with an eq as my primary set up. 

Having said that........there is that notion that a recording musician pointed out to me that when the musical product is mastered it is done whilst also considering what this music is going to be passed through before reaching the listeners ears. Hence why some albums are being "mastered for itunes" or why the final product of something produced in one period of time (say the 80s or 70s) would be polished differently if in fact the same song was being produced today -eg the type of speakers consumers if the time are likely to have due to musical trends. 

Unfortunately that makes notion of "that's how the producer" wanted it to hear a little shaky. Just a little - Hence why I am personally not a fan of colouring (at this point, but this is Ll a journey so don't hold me to it) and dont even ask me about (50) shades of grey.


----------



## castleofargh

williamleonhart said:


> The thing is, I've never quite understood "transparency", but to me the S16 (as a DAC + amp) gives a more detailed and airy sound than the O2+ODAC that I own. Also, there's a feeling that it suffers from less noise and jitters. That's entirely subjective, of course, I can't prove it. I have never leaned too much on the technical side of things, but what I got told is that the S16 has better USB input (and better other components) than the O2+ODAC. Then again, people can customize their O2, so still there's stuffs for argument.
> 
> And don't get me wrong. As I said earlier, the O2+ODAC is still the best valued amp/dac that I've ever seen. Which means that _if _someone tells me to choose between the S16 and the O2+ODAC for free, I'd go with the S16. But is the S16 worth 2 times the price of the O2+ODAC (I can have the S16 for $500), then it's a big no. I also will have to buy an amp for the S16 too.


 

 the basic idea behind HIFI is what it says, high fidelity. so we take the album(nothing we can do if they recorded crap on it), and try to use a sound system that will not audibly alter the signal that was on the album. as simple as that.
 it has nothing to do with the sound being nice, or euphonic, or "foot taping". that's supposed to be the job of the band and recording engineer.
 of course the headphone isn't transparent at all, so you can either see it as even more of a need to have everything else transparent to limit the damage done to the albums by the headphone. or you can think "F it!", bad for bad at least I'll go for a sound that's fun.
 both are cool and rational ways of thinking.
 the perpetual struggle comes when one of the fun group comes saying his sound is superior when it most likely is inferior on measurements if it's colored. otherwise there would never ever be a debate in the amp section of the forum apart from "can it drive this?". (how nice that would be...)
  
 anyway there is no reason why the aune s16 would be a bad product, but as mentioned, I for one wouldn't buy it because of it's 30ohm output. that wouldn't give a good enough damping on many of my gears, and would dramatically affect the sound of most of my IEMs. so again you see "it can't compete" is a very relative thing, because in the context of my house, the aune and O2 indeed can't compete ^_^.
 and about more noise and jitter on the o2... please don't let stuff you read getting to your head. did you actually hear noise on the O2? I'm a real bugger when it comes to background noise and I heard noises from crap DACs, noises from crap tablets, but never yet from an average source into the odac/O2 combo.
 also do you have any idea what jitter sounds like? when did you ever hear jitter knowing it was jitter and nothing else? see where I'm going?
  
 all in all, we're not saying that the O2 is the best, in fact we're only saying that it sounds the same as many other audibly transparent amps, even superior ones(on measurements).


----------



## castleofargh

diamondears said:


> If transparency and accuracy is the preference, upstream gear is more important. So player, then DAC, in that order, are more important.


 
 with all parts of the sound system considered equal, I would obviously agree with you. but that's not the case at all IRL.
 a DAC can get perfect signal reproduction down to what? -100 or 110db for several products.
 an amp can get that on specs, but in many situation when we have finished setting our volume to our headphone,the actual noise floor is much higher, crosstalk may drop on low impedance headphones, and distortion may have a hard time staying below -100db.
 and of course headphones: non flat frequency response, 180degree sound sources when the album was mastered on speakers, and distortions usually between -60 and -40db!!!!!
  
 a bad source, just ok amp as far as driving power is concerned, and a great headphone. that will often measure better than the very best DAC and amp into an average headphone. because the damage coming from the headphones/speakers are so huge.
 so unless you already have great headphones and speakers, investing in the source isn't actually a logical choice for me.


----------



## diamondears

castleofargh said:


> the basic idea behind HIFI is what it says, high fidelity. so we take the album(nothing we can do if they recorded crap on it), and try to use a sound system that will not audibly alter the signal that was on the album. as simple as that.
> it has nothing to do with the sound being nice, or euphonic, or "foot taping". that's supposed to be the job of the band and recording engineer.
> of course the headphone isn't transparent at all, so you can either see it as even more of a need to have everything else transparent to limit the damage done to the albums by the headphone. or you can think "F it!", bad for bad at least I'll go for a sound that's fun.
> both are cool and rational ways of thinking.
> ...



The Aune S16 having a 30ohms output impedance is a big deal and real design flaw, unless its intended only for 240 ohms cans or above and they write that down on the packaging. 

I think this is where NWAVGUY has made his biggest contribution on the HP industry, the truth about damping and output impedance. Who among us here have known about output impedance requirements for damping (at least 1/8 of HP impedance) without NWAVGUY?


----------



## diamondears

castleofargh said:


> with all parts of the sound system considered equal, I would obviously agree with you. but that's not the case at all IRL.
> a DAC can get perfect signal reproduction down to what? -100 or 110db for several products.
> an amp can get that on specs, but in many situation when we have finished setting our volume to our headphone,the actual noise floor is much higher, crosstalk may drop on low impedance headphones, and distortion may have a hard time staying below -100db.
> and of course headphones: non flat frequency response, 180degree sound sources when the album was mastered on speakers, and distortions usually between -60 and -40db!!!!!
> ...



You have a point. Maybe I'm talking about one with an already good HP. But I think you're just saying--its easy to get a transparent amp (a bad source is actually reasonably transparent already), so don't **** it up with a bad HP. So transparency at source is still the priority on that one. Maybe there's just lots of bad HPs out there to **** up even the best sources.


----------



## castleofargh

yup that's pretty much it.
 sadly for us, the best headphones are still miles away from the signal fidelity of an average source. we compromise with standards and come up with that weird world where jitter at -115db on a DAC makes people scream in distress, while at the same time we call marvelous a headphone with distortions starting 60db louder and going up... makes me wonder why people are concerned about DACs at all.


----------



## diamondears

castleofargh said:


> yup that's pretty much it.
> sadly for us, the best headphones are still miles away from the signal fidelity of an average source. we compromise with standards and come up with that weird world where jitter at -115db on a DAC makes people scream in distress, while at the same time we call marvelous a headphone with distortions starting 60db louder and going up... makes me wonder why people are concerned about DACs at all.



Hmmm..I'm concerned about DACs. Though what I really want and been suggesting is one with several filters. 

What do you think are the specific HPs that qualifies as a great HP to make an excellent source worth investing?


----------



## HotIce

diamondears said:


> The Aune S16 having a 30ohms output impedance is a big deal and real design flaw, unless its intended only for 240 ohms cans or above and they write that down on the packaging.
> 
> 
> 
> I think this is where NWAVGUY has made his biggest contribution on the HP industry, the truth about damping and output impedance. Who among us here have known about output impedance requirements for damping (at least 1/8 of HP impedance) without NWAVGUY?



 
Really?

https://www.google.com/search?num=100&q=audio+amplifier+output+impedance+damping

A few out of the zillions (yes, they all predates the article you refer to):

http://sound.westhost.com/impedanc.htm
http://www.audioholics.com/audio-amplifier/damping-factor-effects-on-system-response

IOW, like NFB, it is as old as a topic as audio amplification is, with very much controversial opinions on the real (as in really audible, by real people, in A/B tests) effects on the sound.


----------



## castleofargh

diamondears said:


> castleofargh said:
> 
> 
> > yup that's pretty much it.
> ...


 

 well none really. to me first and foremost it needs to have the signature I want, because something with signature that doesn't sound neutral to me is a 100% error on my appreciation graph (as even the loudest sound will be impacted). so I tend to go for the signature I like over anything else. making it hard for me to recommend a product as it's a matter of taste.  the Olive&Welty compensation curve works nicely as to what I feel is neutral. so a little warmer than a diffuse field curve.
 by default I like to go for headphones/IEMs that have slightly too much bass, because EQing down isn't detrimental. when trying to counter a roll off is.
 I'm not young and don't care much for trebles, so I don't mind a phone that rolls off trebles soon if the rest is what I look for. but others might find that to be extremely important. so I guess that's a matter of priorities as you can't get it all good anyway. 
 ideally having a precise left/right balance should mater a great deal, but I don't know who does and who doesn't make extra efforts about finding fitting drivers. etymotic on the er4, senn on the hd800 I think, probably a few others, but I don't really know where to find that information. and measurements on the net are but one set, so there is not much to say if others will also have the same balance.
 still going for something that tends to stay as close to 0.1%(60db below signal)  as possible on innerfidelity's graphs, with a signature close to what you believe to be relatively neutral should yeld the best result.
  
 about the tech, electro/orthos seem to be able to give the best performances overal, but they're too heavy for me to enjoy 
	

	
	
		
		

		
			





(and there you know that I always settle for convenience despite what I claim. but hushhhhh, some still think I'm an objectivist).


----------



## vertical

hotice said:


> diamondears said:
> 
> 
> > The Aune S16 having a 30ohms output impedance is a big deal and real design flaw, unless its intended only for 240 ohms cans or above and they write that down on the packaging.
> ...



Hi Hotice
Thx for the links. 
From my view (watching the drama surrounding NWG) it wasn't that he offered up original concepts but that, due to the huge attention he cornered, NWG brought the concepts to many Head-Fiers that may not have learned about them otherwise.


----------



## diamondears

castleofargh said:


> well none really. to me first and foremost it needs to have the signature I want, because something with signature that doesn't sound neutral to me is a 100% error on my appreciation graph (as even the loudest sound will be impacted). so I tend to go for the signature I like over anything else. making it hard for me to recommend a product as it's a matter of taste.  the Olive&Welty compensation curve works nicely as to what I feel is neutral. so a little warmer than a diffuse field curve.
> by default I like to go for headphones/IEMs that have slightly too much bass, because EQing down isn't detrimental. when trying to counter a roll off is.
> I'm not young and don't care much for trebles, so I don't mind a phone that rolls off trebles soon if the rest is what I look for. but others might find that to be extremely important. so I guess that's a matter of priorities as you can't get it all good anyway.
> ideally having a precise left/right balance should mater a great deal, but I don't know who does and who doesn't make extra efforts about finding fitting drivers. etymotic on the er4, senn on the hd800 I think, probably a few others, but I don't really know where to find that information. and measurements on the net are but one set, so there is not much to say if others will also have the same balance.
> ...



Have you heard the headphone called NAD?


----------



## MrMateoHead

I'm pretty sure a big reason I'd buy an O2 over an Aune or many other amps is because I can get one made in the USA. Maybe the internals are made in China or something, but to me, High Price + Made in China = A great profit margin, not necessarily a great product (though if China can make an iPhone they obviously can make whatever the amp designers want). Some designers want a superior product, some probably fantasize about a superior profit. Only a few can get both.
  
 I think the only way to satisfy the most rabid audiophiles at this point would be to let them mix their own music. That way, using colored headphones, colored amps, and colored DACs, they can finally get the last bit of coloring complete - the recording itself! HA. I am sure it would be hard for them to start EQing and re-setting levels. But that would be A LOT cheaper than hiring the band to come to the recording studio and play the song the way they want, excuse me, the way it was "meant" to be heard.


----------



## HotIce

The S16 costs 3x the price of the O2 (so we are in an all different category), but I would not call it out because of the build quality.
As PCB/layout maniac as I am, IMO the S16 PCB and layout quality beats the O2 fair and square:


----------



## castleofargh

diamondears said:


> Have you heard the headphone called NAD?


 
 well I got to listen to it for the first time like 10 days ago, the specs certainly interested me for some times now so I was curious. TBH I didn't buy one on the spot because I feared the clamp would hurt me on the long run and I'm not sure I can just bend something like I did on the hd650(I've got kind of a big head). else it's clearly a nice bang/$ headphone. it's also clearly not something for fans of the hd800 signature ^_^.


----------



## upstateguy

williamleonhart said:


> <snip>





> Generally for slower music I prefer my LD I+ to the O2,...





> <snip>


 
  
  


williamleonhart said:


> <snip>
> 
> I came to the realization that no amount of EQ can replicate the choice of another amp (or another headphones).
> 
> <snip>


 
  
*I was curious about this.  Are you sure you couldn't replicate or at least come very close to the LD sound  with the O2 using DSP and EQ?*
  


> Originally Posted by *castleofargh* /img/forum/go_quote.gif
> 
> <snip>
> 
> ...


 
  
  
*Do you have a graph of the O&W curve?  I'd like to take a look at it. 
	

	
	
		
		

		
		
	


	


*
  
*EQing down a strong bass rather than boosting a weak treble.....  Something I've done with my 650s from time to time.   *


----------



## castleofargh

http://www.innerfidelity.com/content/headphone-target-response-curve-research-update
 there is a bunch of intel and 2 or 3 PDF on doc olive's blog describing the all process (as there were several papers published from several tests conducted in several countries in the end).
 the main point is that the curve was supposed to be only what people preferred, not a neutral target. but in the end it appears that people favor a sound that is close to listening to neutral speakers in a room. so close to diffuse field target, with a slight tilt into warmth.


----------



## upstateguy

castleofargh said:


> http://www.innerfidelity.com/content/headphone-target-response-curve-research-update
> there is a bunch of intel and 2 or 3 PDF on doc olive's blog describing the all process (as there were several papers published from several tests conducted in several countries in the end).
> the main point is that the curve was supposed to be only what people preferred, not a neutral target. but in the end it appears that people favor a sound that is close to listening to neutral speakers in a room. so close to diffuse field target, with a slight tilt into warmth.


 
  
 I couldn't find any of the EQ curves posted online.  I'd like to see the *"Harman target curve"* for the senn 800s for instance, so I can play with the frequencies myself.


----------



## castleofargh

upstateguy said:


> castleofargh said:
> 
> 
> > http://www.innerfidelity.com/content/headphone-target-response-curve-research-update
> ...


 
 ????
 you have the compensation curve, just take a raw measurement and make it look like the curve.
 Tyll did some examples and probably the hd800 too, but he used a curve he modified for his own taste(can't get why he did that really, it totally defeated the purpose of using harman curve).


----------



## upstateguy

castleofargh said:


> upstateguy said:
> 
> 
> > castleofargh said:
> ...


 
  
 I'm at one of my other locations and all I have here is a 701, (which I never use) and a T-1, but there was no FR for the T-1.
  
 I tried to make a foobar curve for the 701 but I'm not that satisfied or impressed with the results.
  
 What do you think?  Can you  adjust it or somehow fix it?  (I also have the 31 band foobar EQ)


----------



## diamondears

vertical said:


> Hi Hotice
> Thx for the links.
> From my view (watching the drama surrounding NWG) it wasn't that he offered up original concepts but that, due to the huge attention he cornered, NWG brought the concepts to many Head-Fiers that may not have learned about them otherwise.


Yup. My point.


----------



## PDVJAM

BTW, about 1/8 impedance rule. Who knows - for example I have 16Ohm impedance and two AMP's with 2Ohm and 0.5Ohm impedance. Is in this case lower is still better, or they both will drive this IEM's without any its frequency changes?


----------



## diamondears

pdvjam said:


> BTW, about 1/8 impedance rule. Who knows - for example I have 16Ohm impedance and two AMP's with 2Ohm and 0.5Ohm impedance. Is in this case lower is still better, or they both will drive this IEM's without any its frequency changes?



I've read some experts suggest 1/10, so the difference prolly matters.


----------



## castleofargh

upstateguy said:


> castleofargh said:
> 
> 
> > upstateguy said:
> ...


 
 not sure how much success you would get from trying to get the sub bass up, but else the K701 is not very far off (you take the raw reading, so the grey lines on your graph, not the colored ones!!) and EQ thinking of making it look like the harman curve. it's not super fun to do and does take some time, so don't expect me to do it for you on the k701 that I don't own. sorry ^_^
 in fact even for the stuff I own, I went and tried it, but then always finished messing around by ear. so I have no strict harman example to show.
 on the hd800 it's mostly a massive treble roll off job as anybody can suspect. I don't know many people to enjoy the hd800 without EQ and plugged into a transparent source.
  
 also I do urge you to get a parametric EQ of sort. the problem of sliders is that each one of them may induce it's own phase shift/pre-ringing stuff. you could achieve what you have on that EQ with 2, or maybe 3 points on a parametric EQ. not saying you would actually hear the difference, but it will be an improvement.
 or else for this very purpose you might be interested in this cool UI for equalizerAPO that lets you put pictures in the background to ease up on following frequency curves. http://www.head-fi.org/t/691762/10-band-multichannel-parametric-eq-gui-for-windows


pdvjam said:


> BTW, about 1/8 impedance rule. Who knows - for example I have 16Ohm impedance and two AMP's with 2Ohm and 0.5Ohm impedance. Is in this case lower is still better, or they both will drive this IEM's without any its frequency changes?


 
 I'm from the "lower is better" school. but sadly it's not always true. still the theory of impedance bridging is an almost 0ohm source into ... well whatever, it doesn't matter when the source is really close to zero. the 1/8 or 1/10 is a kind of practical compromise, not a value set in stone and have 1/150 is no problem at all if you have the "juice". so in that regard both amps will affect a low impedance IEM with some crossover and change slightly the signature. and obviously the 2ohm amp will change it more than the 0.5ohm amp.
 now as both are still in the 1/8 ratio, you might not actually notice the difference(that's one of the purpose of the 1/8 suggestion). on mono drivers with a stable 16ohm impedance it is 100% sure that you wouldn't hear the difference.
 and the last silly little point to consider is: what did the manufacturer use to tune his IEM? ^_^ did he do it with some uber low impedance amp, or did he use some casual DAP thinking of what the customer would use?
 when it was the ipod's glorious time, many products were made for ipods... so by using a 0.5ohm amp it might actually not have given the intended sound(we're still talking meaningless changes in most cases, but you got the idea).
 that said, your 16ohm IEM may very well be 16ohm at 1khz (that's what the specs write, the impedance at 1khz) but may very well go lower at other frequencies and thus justify the 0.5ohm amp instead.
 again I'm a "lower is better" person when it comes to amps. I don't desperately seek the 0.03ohm, but I wouldn't get anything above 1ohm as an amp if I planned to ever use it with my IEMs(I'm more lenient on DAPs because worst case scenario I add an amp ^_^).


----------



## PDVJAM

> Originally Posted by *castleofargh* /img/forum/go_quote.gif
> 
> and the last silly little point to consider is: what did the manufacturer use to tune his IEM? ^_^ did he do it with some uber low impedance amp, or did he use some casual DAP thinking of what the customer would use?
> when it was the ipod's glorious time, many products were made for ipods... so by using a 0.5ohm amp it might actually not have given the intended sound(we're still talking meaningless changes in most cases, but you got the idea).
> ...


 
  
 Well, according to manufacturer specs they are:
 - Sensitivity (500 Hz): 111 dB/mVt
 - Impedance (500 Hz): 16.5 Ohm
  
 Don't know how it's correlated with 1kHz
  
 And they told me that IEM's were designed for near zero impedance sources.


----------



## castleofargh

pdvjam said:


> Well, according to manufacturer specs they are:
> - Sensitivity (500 Hz): 111 dB/mVt
> - Impedance (500 Hz): 16.5 Ohm
> 
> ...


 
 eheheh
 well I bet 500hz is half of 1khz! 
	

	
	
		
		

		
			





 
 seriously it's a special case, almost all specs are given at 1khz.
 anyway it's simple, is it a multidriver? if it is then you can be pretty sure that the impedance changes somewhere along the frequencies. and if they made it for near zero impedance sources, there you have your answer ^_^.


----------



## adydula

I thought this was an O2 + DAC thread not a how to tune EQ curves etc???
  
 A.


----------



## upstateguy

> Originally Posted by *castleofargh* /img/forum/go_quote.gif
> <snip<
> you might be interested in this cool UI for equalizerAPO that lets you put pictures in the background to ease up on following frequency curves. http://www.head-fi.org/t/691762/10-band-multichannel-parametric-eq-gui-for-windows...
> <snip<


 
  
 Thanks for the tip... I have a few of the Windows parametric equalizers somewhere in my laptop..... 
	

	
	
		
		

		
		
	


	



  
  


adydula said:


> I thought this was an O2 + DAC thread not a how to tune EQ curves etc???
> 
> A.


 
  
 I guess It drifted a little.... but very useful information and something else to play with in this hobby.
  
 Anyway, back on topic, I rolled into my second location late last night and just finished watching a netflix movie with my O2 and 880s.  Gotta love that little transparent amp.


----------



## Jony27

Do you guys use any specific driver for the ODAC?
 As of now I just use generic windows 7 drivers.
 Also using foobar as my player.


----------



## castleofargh

jony27 said:


> Do you guys use any specific driver for the ODAC?
> As of now I just use generic windows 7 drivers.
> Also using foobar as my player.


 

 it's recommended to output 24bit(not that you'll really hear the difference in most cases), so check that it is what you have set on foobar and maybe on windowzzz if you don't go through wasapi or asio? else I don't think the odac really needs anything.


----------



## Medaud

How do you set it in foobar? I've got it set in windows but not foobar afaik.


----------



## raoultrifan

I use generic driver + WASAPI-push. I find it being the best, especially on low-end computers (no glitches or pops anymore).
 I'm also using a decent buffer of at least 10 seconds and high prio.


----------



## castleofargh

medaud said:


> How do you set it in foobar? I've got it set in windows but not foobar afaik.


 
 file->preferences->output
  


raoultrifan said:


> I use generic driver + WASAPI-push. I find it being the best, especially on low-end computers (no glitches or pops anymore).
> I'm also using a decent buffer of at least 10 seconds and high prio.


 
  the purpose from what I understand(maybe I'm wrong?) is that you pre-process the format conversion to PCM and other stuff like EQ, DSPs and visualizations stuff. so that there is no more delays when the samples nee to be sent to the odac. but on computers most likely to be able to process several Ghz of data per second, what kind of work will require a 10seconds advance? even when running a huge rendering in 3DS max, with some viruses on the computer, I still imagine a 10s buffer as an overly cautious value (I know I would kill any computer hanging on me for 5seconds with fire of mass destruction
	

	
	
		
		

		
		
	


	




).
 I don't think your 10s buffer does anything wrong to the music so it's probably very ok, but the delays when using dsps and stuff would probably drive me crazy.


----------



## raoultrifan

Castleofargh, it's not adding any delay at all, it's just a read-ahead and cache it into RAM. It's all about zero-latency and jitter and not at all about working with 3DS Max, it's more about Windows itself here. 
  
 Stuffs like SpeedStep/CPU_governor or even when you're accessing your home network (especially via Wi-Fi) creates sometimes small pops or strange noise on your music. Looks like some audiophiles were able to prove that buffering your entire melody into RAM will help (there are players what does that), along with disabling intermediary CPU steps (CPU to full power everytime) and completely disabling network adapters.
  
 Feel free to check your own computer with something like: http://www.resplendence.com/download/LatencyMon.exe or DPC Latency Checker especially while connected to Wi-Fi from a Windows computer.
 Check also http://www.sweetwater.com/sweetcare/articles/solving-dpc-latency-issues/ and http://www.pcdj.com/dpc-latency-checker-is-your-windows-computer-capable-of-running-dj-software/ for details.
  
 Right now I'm on a Lenovo T440 (i5-4cores/8GBRAM/SSD), connected to Wi-Fi and replying to few emails and browsing 1 or 2 webpages and after 30 secs. of running LatencyMonitor looks like my laptop is unable to deal with "handling real-time audio": *18629 microsecs. max. latency*!, so trust me when I say that, at least for my laptop, running ODAC with WASAPI-push and at least 10 secs. of RAM buffering + high_prio foobar does help a lot.  I had also installed some ASIO drivers, but the quality was not OK for my ears and then I got back to my WASAPI-push setting, most likely because was a ASIO driver used for Terratec soundcard (same USB Tenor chip like ODAC). If anyone was able to make ODAC working perfectly with ASIO, please let me know.
  
 Anyway, I really think we're kind of off-topic right now, but I just hope this will help some people to understand that it's not all about the hardware, but it's about the software too.  Though trying to play bitperfect on a Windows machine is utopic (Linux and OSX rulez on this one).
  
 Regards!
  
 P.S.: Main issue on all of my Windows systems looks like would be ndis.sys.


----------



## castleofargh

18000µs that's 0.018s


----------



## raoultrifan

castleofargh said:


> 18000µs that's 0.018s


 
 Exactly...and that's 18ms, which is quite high latency for an operating system to handle correctly audio stream.


----------



## mahaqmi

Hi guys. I am trying to build the O2 amp myself to save money rather than buying fully assembled (not really experienced, but since i can build my own PC and save cost so why not?).

I have found the website to buy the parts but can someone give me a link to the design (circuit design)? I have searched at the NwAvGuy blog but cant seem to find the circuit design. I apologize for asking a stupid favor (im a noob with this thing). My brother will also help me since he have more experience with doing this type of project


----------



## HotIce




----------



## adydula

Building a PC and building this amp are two very different projects.
  
 At least buy the barebones printed circuit board and use it for your build.
  
 One of the things that make this O2 amp great is the layout, without using this pc board you most likely will not get close to the specs of the original design.
  
 Good luck, I hope you know how to solder and debug circuits.
  
 Alex


----------



## mahaqmi

Oh god.. I hope my brother can understand the circuit well LOL. Sorrry for the noob question but is there 2 circuit in the diagram?


----------



## HotIce

One is the power supply (upper), and other other is the amp proper (lower).


----------



## mahaqmi

Oh i thought the O2 will always need a battery to run. That means i can use the power supply instead of battery? That's nice. Thanks man!!


----------



## MrKazador

Why do you need the schematic? Buy the PCB and case at jdslab. The PCB has a silkscreen of all the components so you just drop the right part in there and solder. I use my o2 as a desktop amp with no batteries, just a wall adapter.


----------



## vertical

mrkazador said:


> Why do you need the schematic? Buy the PCB and case at jdslab. The PCB has a silkscreen of all the components so you just drop the right part in there and solder.



Yeah, that...+1


----------



## adydula

You really need to go over to his site and do some slow reading to understand what your getting into....
  
 Alex


----------



## dazzerfong

mahaqmi said:


> Hi guys. I am trying to build the O2 amp myself to save money rather than buying fully assembled (not really experienced, but since i can build my own PC and save cost so why not?).
> 
> I have found the website to buy the parts but can someone give me a link to the design (circuit design)? I have searched at the NwAvGuy blog but cant seem to find the circuit design. I apologize for asking a stupid favor (im a noob with this thing). My brother will also help me since he have more experience with doing this type of project


 

 No offense mate, but saying you knowing how to build a PC helping you is more or less the same thing as you claiming to know how to shoot because you played a shooter. Nada. If you can't read the blueprint, or even something relatively simple as understanding how the thing is biased to achieve a certain gain, just swallow your pride and buy the whole thing assembled. If you think you'll save money by going this way, if you're inexperienced, you'll just end up wasting more money (from the wrong components. bad solder joints), lack of quality control from lack of testing equipment (ie. no sound or, worse, your amp delivering a dose of DC to your headphones), and most importantly, waste a lot of time which in the end is fruitless because you don't understand it.
  
 If you're still keen, well, I guess go ahead. If I were you, pay heed to the other member's suggestions and grab the kit from JDS Lab or something. At least that stuff _will_ work provided you follow the instructions.


----------



## mahaqmi

Thanks for all of the replies and suggestions. Im still not sure to build it or buy it assembled. I need to wait for it next week and in the mean time i will checkout and read the nwavguy's blog for more info. Anyway, i didnt expect building an amp would be the same like building a pc but im trying to cut cost as i have read the assembled is near double the price. Sorry if i make anyone feels uneasy because of my silly questions towards the o2!


----------



## adydula

ditto...


----------



## headwhacker

Building a PC nowadays is nowhere near the complexity as what it was 20 years ago. Back then you must have at least a basic knowledge of electronics. Not just finding where each part fits. You can easily blow up a card just by setting the wrong jumper or inserted in wrong orientation.
  
 Nonetheless a DIY project gives one a sort of satisfaction. But for the inexperienced, you should start with the kit and should follow the instructions. Plan ahead and read nwavguys blogs and don't be discouraged.


----------



## MrKazador

I never built anything like the o2 but I have done some soldering. It really wasn't that difficult and there is tons of information on how to build and test it. If you're confident in your soldering abilities then I say go for it!


----------



## HotIce

mahaqmi said:


> Thanks for all of the replies and suggestions. Im still not sure to build it or buy it assembled. I need to wait for it next week and in the mean time i will checkout and read the nwavguy's blog for more info. Anyway, i didnt expect building an amp would be the same like building a pc but im trying to cut cost as i have read the assembled is near double the price. Sorry if i make anyone feels uneasy because of my silly questions towards the o2!



 
If you plan to build it yourself, in order to save money only, you are likely better off getting an assembled version.
You are going to save around $50, and this assuming you do not do any mistakes and fry something.
If instead you want to do that because you want to start an electronics DIY hobby, then hack away!


----------



## Thad-E-Ginathom

mahaqmi said:


> Thanks for all of the replies and suggestions. Im still not sure to build it or buy it assembled. I need to wait for it next week and in the mean time i will checkout and read the nwavguy's blog for more info. Anyway, i didnt expect building an amp would be the same like building a pc but im trying to cut cost as i have read the assembled is near double the price. Sorry if i make anyone feels uneasy because of my silly questions towards the o2!


 
  
 Double not-very-much is still not very much! Along with others, I also say that it is a small price to pay to get something that works and avoid the cost of wasting money on something that doesn't.  
  


mrkazador said:


> I never built anything like the o2 but I have done some soldering. It really wasn't that difficult and there is tons of information on how to build and test it. If you're confident in your soldering abilities then I say go for it!


 
  
 I can (or could, 20 years ago) solder as in gold, silver, gas torch, red-heat metal, acid baths, and all that stuff. I could do it well too. I _cannot_ do neat electrical soldering. 
  
 I'm not saying that I couldn't. I hear people who say it only needs practice, just like brazing/hard soldering. 
  
 The last thing I tried was replacing a dead mouse-button switch, It was kill-or-cure on a throw-away item. I made it work, but with problems such as the trace coming away from the board, it was a truly horrible job. Wouldn't like to do that to an amplifier board.
  
 The last thing I didn't try was replacing a broken USB cable on a HiFiMeDIY DAC. I stared and soul-searched, but however I looked at it, those solder points were just too close for my known skill level. It's no good doing number 4 properly when 1-3 are ruined. I found a man to whom it was easy and now my DAC works again.
  
 There are DIY projects suited for beginners. Even projects that don't involve delicate PCB traces, where solder blobs are the order of the day. _One of these days, _I'll get that round tuit and _learn_ electrical soldering. I don't think I'll be _starting_ with an 02, though.


----------



## sanakimpro

Dear all,
Has anyone tried to measure / compare the O2/ODAC with other setups such as Meier Audio's Classic/Daccord, or more expensive ones like SPL Auditor?
I am using the O2/ODAC from Epiphany Audio with the Beyerdynamic T1's and usually use HIGH GAIN at 12pm to 1pm and its already very loud. Sometimes I feel that the bass might be lacking though, but I'm not sure if its the real thing, or its an o2/odac weakness.
Thanks so much!


----------



## sanakimpro

Hi Don,
 Can you please share if there are any differences after you used your 15V AC 1A adapter compared to the original 230V->12V adapter?
 Thanks!
 best wishes,
 Shu


----------



## RepEvox

So I've got a computer and a souncard that I don't use for the 7.1 features because they don't actually work very well with headphones. I bought it to avoid buying a DAC and amp but here I am. I'm thinking of getting the $280 combo or maybe the Schiit Modi/Magni stack, but the question I have is the same.
  
 How the hell do I connect these things if I want to use my soundcard's features? It doesn't have optical or RCA out, only 3.5mm jacks for left/right/center/SPDIF. I read some threads about people who have used a soundcard's optical output to an external dac and amp, then to your headphones, but I just don't see how with the O2 or Schiit stack and my Xonar DX. Should I just accept the fact that the Amp/DAC combo will replace my soundcard and just go for it? I plan to overhaul my audio setup and pair the combo with some Beyerdynamic DT770/990's or alike headphones. I use all types of media like games with surround (motive for buying xonar dx), movies, and music obviously.


----------



## dazzerfong

If you're using an external DAC, use your USB port and hook it to your computer. You don't connect your DAC through optical for the ODAC.


----------



## RepEvox

Really?
  
 Huh. Some people on reddit explained it that way I thought.


----------



## dazzerfong

repevox said:


> Really?
> 
> Huh. Some people on reddit explained it that way I thought.


 

 The ODAC only has a USB-mini port, no optical-in.


----------



## RepEvox

dazzerfong said:


> The ODAC only has a USB-mini port, no optical-in.


 
 Are you talking about the JDS labs or the link to the Modi I posted? It looks like an optical in...they make two models; one with optical in and one with USB. As for the JDS labs, well you would be right I think. Either way, I think I'll just get a dac/amp combo and say screw the soundcard.


----------



## dazzerfong

repevox said:


> Are you talking about the JDS labs or the link to the Modi I posted? It looks like an optical in...they make two models; one with optical in and one with USB. As for the JDS labs, well you would be right I think. Either way, I think I'll just get a dac/amp combo and say screw the soundcard.


 
 I know nothing about the Modi, all of what I'm saying applies to the ODAC.


----------



## HaVoC-28

atoniolin said:


> Dear all,
> Has anyone tried to measure / compare the O2/ODAC with other setups such as Meier Audio's Classic/Daccord, or more expensive ones like SPL Auditor?
> I am using the O2/ODAC from Epiphany Audio with the Beyerdynamic T1's and usually use HIGH GAIN at 12pm to 1pm and its already very loud. Sometimes I feel that the bass might be lacking though, but I'm not sure if its the real thing, or its an o2/odac weakness.
> Thanks so much!


 
  
 Used T1 / SPL Auditor in past , sold auditor and switched to O² , didn't feel any lacking but i am more tolerent to lacking a bit in bass departement than having too much bass ...


----------



## adydula

The O2 is really hard to beat for most headphones!
  
 Been there done that with many other amps.....the only real thing with the O2 IMO is its mechanical build is less than stellar and the switches, buttons and plugs arent industrial strength...but these dont matter sonically.
  
 The ODA I have is much more versatile, sonically about the same but with more current and lots of nice things to have to help in mucking around....clipping led, power leds, RCA jacks etc.
  
 Alex


----------



## MrMateoHead

I dunno - The jacks DO matter sonically when the connection quality is poor.
  
 A little knock or "wiggle" of the cables on the input side often cause me to lose the L channel. I find that a bit irritating at times (but seems to happen more with my 3 inch cable (a little stiff). Same with the headphone in jack - a bit temperamental.


----------



## K_19

Question about the O2/ODAC combo units from various vendors...
  
 With these combo units, especially the desktop units where the ODAC output is at the back (whether by 3.5 or RCA), is there a particular hardware or space limitations that prevent the INPUT from also going into the back as well? I love the looks and functionality of the combo units, but it's just that the inputs remaining in the front which just seems... odd to me from conventional desktop use standpoint (makes sense of course if this is a portable use, which is indeed its original design, and maybe even for studio use where inputs are frequently in the front). I ask as if it is a desktop unit, I would think that it'd make most sense to put _everything_ to the back yet in both JDS/Mayflower units, the inputs always remain in the front... except for standalone O2's where RCA input is actually available. So I'm assuming this is basically due to hardware/space limitation, but was wondering if that is indeed why it is so.


----------



## headwhacker

k_19 said:


> Question about the O2/ODAC combo units from various vendors...
> 
> With these combo units, especially the desktop units where the ODAC output is at the back (whether by 3.5 or RCA), is there a particular hardware or space limitations that prevent the INPUT from also going into the back as well? I love the looks and functionality of the combo units, but it's just that the inputs remaining in the front which just seems... odd to me from conventional desktop use standpoint (makes sense of course if this is a portable use, which is indeed its original design, and maybe even for studio use where inputs are frequently in the front). I ask as if it is a desktop unit, I would think that it'd make most sense to put _everything_ to the back yet in both JDS/Mayflower units, the inputs always remain in the front... except for standalone O2's where RCA input is actually available. So I'm assuming this is basically due to hardware/space limitation, but was wondering if that is indeed why it is so.


 
  
 I think JDSLabs released a Special Edition before for O2/ODAC. The analog IN of the O2 is shared by the analog OUT of the ODAC with a pair of RCA jacks mounted at the back of the panel. Making the front panel clean and uncluttered.


----------



## sanakimpro

I have mine called EHP-O2Di from Epiphany Acoustics in the UK. The setup is as follows, 
 Back:
 RCA: serves as Line In or Line Out
 (when used as Line in, bypass ODAC, only use O2)
 (when used as Line Out, uses the ODAC, takes input from USB, bypass O2)
 USB port input for the ODAC
 Power Supply 
  
 Front:
 Power Switch
 3.5mm jack
 Volume knob
 Gain switch (x1, x2.5)
  
 I find it pretty reasonable for my use.
 However, this design does not have batteries built in, so it is needs mains power all the time.


----------



## K_19

atoniolin said:


> I have mine called EHP-O2Di from Epiphany Acoustics in the UK. The setup is as follows,
> Back:
> RCA: serves as Line In or Line Out
> (when used as Line in, bypass ODAC, only use O2)
> ...


 
  
 Sounds like a great set up, makes the most sense from the desktop use perspective. I guess it's impossible to have two input/outputs in the back, you need to sacrifice one of them in the back (or just leave one of them in the front) if you're going the RCA route?


----------



## sanakimpro

k_19 said:


> Sounds like a great set up, makes the most sense from the desktop use perspective. I guess it's impossible to have two input/outputs in the back, you need to sacrifice one of them in the back (or just leave one of them in the front) if you're going the RCA route?


 
 Usually I use the USB input into my ODAC so that I can use the ODAC and O2. 
 The RCA serves as Line In and Line Out depending on what is connected to them. So far, no issues. 
 If I use a DAP line out into the ODAC's Line In, the output at the front will be the O2 amplified version. 
 Very happy with my O2/ODAC so far.


----------



## adydula

Well.... yeah!!  If the jack is worn out or bad it will affect the connection and the quality of listening due to intermittent connectivity etch, but if a cheap mechanical switch is making good contact there is no real sonic difference.
  
 The O2 parts for jacks are not the best mechanical choices but for a few thousand insertions they are for the most part just fine.
  
 Many of us know that and use pigtails that aren't removed very often to alleviate this or just buy and use a better jack and or switch, like the ODA from AGDR does.
  
 Alex


----------



## sanakimpro

Regarding power adapters, I am a little bothered. My unit came with a 12VAC, 500mA adapter, but I thought I have read somewhere that the minimum voltage was 13.5V (JDS?). They do recommend a 12VAC adapter nevertheless, which makes it even more confusing.
 I bought a 18VAC adapter in the end but couldn't tell the difference in volume when I kept the knob fixed and swapped adapters. Is this right? Or is the 18VAC going to provide better voltage swings, slew rates, etc?
 Thanks!


----------



## headwhacker

atoniolin said:


> Regarding power adapters, I am a little bothered. My unit came with a 12VAC, 500mA adapter, but I thought I have read somewhere that the minimum voltage was 13.5V (JDS?). They do recommend a 12VAC adapter nevertheless, which makes it even more confusing.
> I bought a 18VAC adapter in the end but couldn't tell the difference in volume when I kept the knob fixed and swapped adapters. Is this right? Or is the 18VAC going to provide better voltage swings, slew rates, etc?
> Thanks!


 
 No it will not make any difference, except wasted energy by releasing more heat and sucking more power from the power line than what O2 needs.


----------



## K_19

Hey all,
  
 Had a question about this combo in regards to powering the Q701, K701/2 series of headphones. What is the range of volume that is usable when using those headphones under the 1x gain? So for most modern tracks, what position on the volume knob is everyone at for decent volumes? This would be mainly used only through ODAC USB and rarely (if ever) any other sources, so mainly concerning the volume position it's being used with the usb/full 2v line output from the dac. Most of the tracks used would be mostly just modern recordings, although there are a few classical/lower mastered tracks that may need some more volume than those. Just trying to see which gain settings would be the best as as there is a used unit I'm looking at which has 1x and 5x gain settings... while I'm sure 5x gain would certainly be way too high for these I'm not so sure about the 1x.... 
  
 Thanks in advance.


----------



## headwhacker

k_19 said:


> Hey all,
> 
> Had a question about this combo in regards to powering the Q701, K701/2 series of headphones. What is the range of volume that is usable when using those headphones under the 1x gain? So for most modern tracks, what position on the volume knob is everyone at for decent volumes? This would be mainly used only through ODAC USB and rarely (if ever) any other sources, so mainly concerning the volume position it's being used with the usb/full 2v line output from the dac. Most of the tracks used would be mostly just modern recordings, although there are a few classical/lower mastered tracks that may need some more volume than those. Just trying to see which gain settings would be the best as as there is a used unit I'm looking at which has 1x and 5x gain settings... while I'm sure 5x gain would certainly be way too high for these I'm not so sure about the 1x....
> 
> Thanks in advance.


 
  
 The range of the volume knob will depend on the headphone load impedance and sensitivity. Set the gain to 1x/3.5x if you are using ODAC as the source.


----------



## K_19

headwhacker said:


> The range of the volume knob will depend on the headphone load impedance and sensitivity. Set the gain to 1x/3.5x if you are using ODAC as the source.


 
  
 I'm thinking that'd be the most ideal setting as well, but the used unit I'm looking at (at a very good price) has the gains set at 1x and 5x (It's from Epiphany Acoustics), so just wondering how much range the 1x would have for the K's as I know 5x is impractical with ODAC as source (And I'm not so sure whether it's as straightforward to mod that particular gain setting to something else since it's not the stock 2.5x/6x gain, which is easy as clipping resistors).


----------



## MrKazador

atoniolin said:


> Regarding power adapters, I am a little bothered. My unit came with a 12VAC, 500mA adapter, but I thought I have read somewhere that the minimum voltage was 13.5V (JDS?). They do recommend a 12VAC adapter nevertheless, which makes it even more confusing.
> I bought a 18VAC adapter in the end but couldn't tell the difference in volume when I kept the knob fixed and swapped adapters. Is this right? Or is the 18VAC going to provide better voltage swings, slew rates, etc?
> Thanks!




Taken from the blog

. If your line voltage is below 117 VAC or 235 VAC, and/or you plan to drive difficult low impedance headpones (i.e. HiFiMan planars), I would suggest a 14+ VAC transformer at 400+ mA. The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI. But those are more expensive than the WAU12-200. The WAU20-200 also works for higher impedance headphones.


----------



## sanakimpro

mrkazador said:


> Taken from the blog
> 
> . If your line voltage is below 117 VAC or 235 VAC, and/or you plan to drive difficult low impedance headpones (i.e. HiFiMan planars), I would suggest a 14+ VAC transformer at 400+ mA. The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI. But those are more expensive than the WAU12-200. The WAU20-200 also works for higher impedance headphones.


 
 Thanks! Mine is a Beyerdynamic T1, DT 770/80, DT 880/250 and Custom One Pro. Figure if any of them requires the 14+ VAC?
 Much appreciated!


----------



## castleofargh

are we seriously down to decide what VAC should be used for what headphone?
 hey my laptop uses 20V, maybe I should put 30V to get it go faster, and directly into 220V it would be crazy good
	

	
	
		
		

		
			





. just be happy that the O2 doesn't blow up in your face when not using the recommended products.
  
  
  
  
  
 for those with very little electric knowledge that are concerned about power requirements for headphones vs amps, download the excel stuff(click on the picture at the bottom) http://www.apexhifi.com/specs.html 
 you just enter the values of your headphone and how loud you want to go, and by changing the loudness you can see how it affects the voltage and learn what to expect from different sources.
  
 also useful for gain, find out how voltage variations translate into db("calculator free" method) http://www.sengpielaudio.com/calculator-gainloss.htm


----------



## DIscoYou

With the Epiphany Acoustics O2Di (Amp & DAC) does anyone know how the headphone and DAC outs switch? Is it a case of the RCAs only being live when there are no headphones plugged in?
  
 http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/


----------



## KeithEmo

There are two things you should know....
  
 First, virtually all solid state headphone amps have a gain that is set by the circuitry (and you can vary it with the volume control). Likewise, things like slew rate aren't likely to change much as long as it's operating "within normal limits"). This means that changing the supply voltage a little is _NOT_ going to change the amount of volume you get with a particular setting. In general, the only thing it will alter significantly might be the maximum output level you can get before it clips. (The gain will be exactly the same, but, with the lower supply voltage, it will "run out of steam" at a slightly lower level. If the supply voltage gets too low, you may simply reach a point where the amp can't make any usable output before it starts to distort.)
  
 You should consider the manufacturer's recommendations because, depending on the exact circuitry they used, a voltage that is much too high can make the unit run very hot - or just plain burn it out (most components will just run a little bit hotter as you raise the voltage, but, at some point, many will just plain die), and an amp that clips sooner will sound "rougher and less dynamic".
  
 Second, when you have a device that uses an AC adapter that _PUTS OUT_ AC, that means that most of the power supply - the rectifiers and regulators - is inside the device itself. When an AC voltage is rectified, you end up with a DC voltage more or less proportional to it (and about 1.5x as much). This voltage is them smoothed by filter capacitors, and then usually smoothed more perfectly by a regulator. In the process of smoothing the signal, the regulator loses some voltage - typically 1 or 2 V - so you need more voltage going into the regulator than you're asking it to put out. In fact, most small AC adapters are somewhat "soft" in terms of what voltage they put out - their output varies depending on how much current you draw from them and how heavy the power supply itself is. A typical adapter rated "15VAC @ 500 mA" probably really puts out around 17 VAC @ 0 mA, and maybe as low as 10-12 VAC @ 500 mA. Another, bigger adapter, rated at "12VAC @ 2 Amps" may put out 14 VAC @ 0 mA, 13.5 VAC @ 500 mA, and 12 VAC @ 2 Amps. In this  case, the bigger power supply is actually putting out _MORE_ voltage at 500 mA than the smaller one rated for the higher voltage.
  
 AC power supplies that put out DC voltage are different, and fall into three major groups. Two of them (linear regulated and switch mode regulated) put out pretty much the same voltage regardless of the current you draw until you reach their limit - at which point the voltage drops suddenly or is shut off entirely. The third type (unregulated) acts like I described above, and has a voltage that drops lower as you increase the current you draw (and, again, heavier units can deliver more current with less of a drop in output voltage). 
  
 If you received a unit, and it came with a power supply, then you should assume that the folks you bought it from made sure that the one they included exceeds the required amount of voltage and current required to work properly... and that adding a bigger one or one at a higher voltage is probably unnecessary and not especially beneficial. (When they told you what one to use, they were probably being conservative; that way, as long as you bought one that met those ratings, they were sure it would work properly.)
  
 Quote:


atoniolin said:


> Regarding power adapters, I am a little bothered. My unit came with a 12VAC, 500mA adapter, but I thought I have read somewhere that the minimum voltage was 13.5V (JDS?). They do recommend a 12VAC adapter nevertheless, which makes it even more confusing.
> I bought a 18VAC adapter in the end but couldn't tell the difference in volume when I kept the knob fixed and swapped adapters. Is this right? Or is the 18VAC going to provide better voltage swings, slew rates, etc?
> Thanks!


----------



## adydula

Most wall transformers put out DC but _the O2’s power supply requires at least 13.5 volts *AC*_. The ideal transformer would be rated at 14 - 16 VAC and 400 mA or higher. In North America the Triad WAU12-200 from Mouser is rated at 12 volts but is really about 13.5 VAC with no load, and on normal 120 volt line voltage works fine for anything but full power sine wave testing or driving rare low impedance power hungry cans. _If your line voltage is below 117 VAC  or 235 VAC, and/or you plan to drive difficult low impedance headpones (i.e. HiFiMan planars), *I would suggest a 14+ VAC transformer at 400+ mA.*_*The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI.* But those are more expensive than the WAU12-200. The WAU20-200 also works for higher impedance headphones. At least some European 230 volt input 12 VAC output transformers only measure around 11.5 to 12 volts on normal line voltage and won’t work (especially if designed for halogen lights). You can also change the power jack to a 5.5mm x 2.5mm version if needed to match the plug of different wall transformers.


----------



## lerad

Good Day! i have o2/odac combo from jds labs and planning to get hd650 or he400i, can o2 bring out the best sound on both headphones i mentioned or does it pair well?


----------



## dazzerfong

lerad said:


> Good Day! i have o2/odac combo from jds labs and planning to get hd650 or he400i, can o2 bring out the best sound on both headphones i mentioned or does it pair well?


 
 If by 'best' you mean 'just louder' and, depending on your source, less noise/distortion, yes. If by 'synergy', that depends on your preference of sound.


----------



## diamondears

lerad said:


> Good Day! i have o2/odac combo from jds labs and planning to get hd650 or he400i, can o2 bring out the best sound on both headphones i mentioned or does it pair well?



Yes. It doesn't color or tweak the sound coming from the source nor coming out of the HP though.


----------



## lerad

dazzerfong said:


> If by 'best' you mean 'just louder' and, depending on your source, less noise/distortion, yes. If by 'synergy', that depends on your preference of sound.


 
 Thanks! i listen to all kinds of music genres. if you can recommend me a amp/dac combo price range $200-$300 what would it be? for hd650 or he400i


----------



## lerad

lerad said:


> Thanks! i listen to all kinds of music genres. if you can recommend me a amp/dac combo price range $200-$300 what would it be? for hd650 or he400i


 
  
  


diamondears said:


> Yes. It doesn't color or tweak the sound coming from the source nor coming out of the HP though.


 
 Thanks


----------



## diamondears

lerad said:


> Thanks



Try it first, very cheap anyway. Then go up the price ladder once the "itch" comes. That way you don't gamble on pricier gears, unless of course you were able to critically listen to them and you think you like them before you buy. Even then, still a bit of gamble because there might be better or equal gears much lesser price. You can always sell your current gear once you itch for another gear.


----------



## thecrow

I'd go with the old advice I was given and that is choose your headphone - the one that sings for you. 

Then use the Odac and O2 (with relevant EQing) which you already have which are fair value at their price points and get to know your headphone better. This will also help you decide what different/extra/specific qualities, if anything, you are looking for in your next purchase of an amp and dac to match with your headphone

If you do a little mix and matching with what you already have you may even find that you may just want to change the dac or just the amp. 

I feel that the ODAC and O2 are great starting points before outlaying more. Great reference points. Great way to sus out your headphones better.


----------



## lerad

thecrow said:


> I'd go with the old advice I was given and that is choose your headphone - the one that sings for you.
> 
> Then use the Odac and O2 (with relevant EQing) which you already have which are fair value at their price points and get to know your headphone better. This will also help you decide what different/extra/specific qualities, if anything, you are looking for in your next purchase of an amp and dac to match with your headphone
> 
> ...


 
  


thecrow said:


> I'd go with the old advice I was given and that is choose your headphone - the one that sings for you.
> 
> Then use the Odac and O2 (with relevant EQing) which you already have which are fair value at their price points and get to know your headphone better. This will also help you decide what different/extra/specific qualities, if anything, you are looking for in your next purchase of an amp and dac to match with your headphone
> 
> ...


 
  
  


diamondears said:


> Try it first, very cheap anyway. Then go up the price ladder once the "itch" comes. That way you don't gamble on pricier gears, unless of course you were able to critically listen to them and you think you like them before you buy. Even then, still a bit of gamble because there might be better or equal gears much lesser price. You can always sell your current gear once you itch for another gear.


 
 Thanks for the input guys!


----------



## dazzerfong

lerad said:


> Thanks for the input guys!


 
 One more thing: if you like your headphone as-is, the O2/ODAC is perfect for the job. If you're not, that's when other things like tube amps come rolling in (pun intended). Even then, keeping the O2/ODAC around even if you've got superior gear is decent as it's an excellent reference combo.


----------



## lerad

dazzerfong said:


> One more thing: if you like your headphone as-is, the O2/ODAC is perfect for the job. If you're not, that's when other things like tube amps come rolling in (pun intended). Even then, keeping the O2/ODAC around even if you've got superior gear is decent as it's an excellent reference combo.


 
 yes that was im thinking also. maybe nextweek ill purchase hd650. this hobby isn't cheap
	

	
	
		
		

		
			





. thanks guys! Good day..cheers!


----------



## dazzerfong

lerad said:


> yes that was im thinking also. maybe nextweek ill purchase hd650. this hobby isn't cheap
> 
> 
> 
> ...


 
 It's relatively cheap compared to a lot of hobbies _if you're careful._ If not, well, I hope you're loaded.


----------



## diamondears

dazzerfong said:


> It's relatively cheap compared to a lot of hobbies _if you're careful._ If not, well, I hope you're loaded.



What I learned from experience even when I'm still into speakers (before I got into HPs) is this---get all upstream gears as transparent and neutral as you can...if one of them isn't, meaning it's tweaking or coloring the recording, you'll eventually play a recording that will sound funky or not good, which in turn will make you look for other gears especially the downstream gear---speakers or HPs...and you won't be satisfied because, again, you'll eventually hear a recording that's seem to be bad...and on and on and on...and the itch won't go away...all the while it's the fault of the upstream gear. My honest 2 cents.


----------



## MrMateoHead

Does anyone have a guide to THD / S/N ratio?
  
 In pondering the O2 versus other amps I've owned, I've started to question how much THD is tolerable or what S/N ratio is "ideal". I have a Class D car amp that sounds great, but has audible "hiss" at near-full volume with a silent source. Of course, that could relate to my deck, but lets just say I know that the amp is the main culprit.
  
 My Yamaha Receiver still sounds great after all these years, but at "reference" volume ("O dB" on the dial from -96dB to start), it has audible hiss. Source is ODAC, so I know it is the amp. I am sure paying bigger bucks next time might get me an amp that is black through more of the power range.
  
 Then there is the always black O2.
  
 The "hiss" is never an issue for the first two amps, considering normal playback volumes and listening environments. But the O2 has certainly trained me to desire that added level of blackness, as I swear it adds some benefit to the perceived "transparency" of my speakers. I'd like to upgrade my receiver next year probably and am looking at Sabre DAC models from Pioneer (love the Class D amps would love to try one), and the ever-popular Sony models which are supposedly now awesome again (I owned one once and didn't like the sound much at all).


----------



## KeithEmo

Note that the 0DAC uses a Sabre DAC chip - so has a little of the characteristic Sabre "flavor" - it tends to "illuminate details very brightly" or "sound a tiny bit etched", even though it isn't bright sounding overall. (I tend to think of it as sounding rather like the original DragonFly - although a little bit better.)
  
 That's not at all an indictment of how it sounds - I rather like it - just don't assume you're starting with a dead-neutral sounding source.


----------



## diamondears

keithemo said:


> Note that the 0DAC uses a Sabre DAC chip - so has a little of the characteristic Sabre "flavor" - it tends to "illuminate details very brightly" or "sound a tiny bit etched", even though it isn't bright sounding overall. (I tend to think of it as sounding rather like the original DragonFly - although a little bit better.)
> 
> That's not at all an indictment of how it sounds - I rather like it - just don't assume you're starting with a dead-neutral sounding source.



I don't think Sabre equals not-neutral. The Audiolab is Sabre but ain't bright at all. In fact 3 of its 7 digital filters I find on the warm side.


----------



## JacobLee89

I like to believe that we still don't know what "true neutral" sounds like in this crazy world of audio.
  
 What if humidity and altitude were contributing factors as well? We wouldn't even get to the bottom of this if that were the case!


----------



## castleofargh

jacoblee89 said:


> I like to believe that we still don't know what "true neutral" sounds like in this crazy world of audio.
> 
> What if humidity and altitude were contributing factors as well? We wouldn't even get to the bottom of this if that were the case!


 

 we could record everything at sea levels, and listen to music only at sea level to get a standard. but what about climate change? when the sea will have risen 1m, do we all move up or not? ^_^


----------



## KeithEmo

I have to disagree with you there.
  
 Right now I own a Wyred4Sound DAC2 (Sabre), an Audiolab (Sabre), an Emotiva DC-1 (Analog Devices), and several other smaller Sabre and non-Sabre DACs, and I just sold a Benchmark DAC1 Pre. I have always found that the ones that use the Sabre chip have a distinct sound. It's not that the ones that use the Sabre are technically brighter; the Sabre chip itself is admirably flat, and there are plenty of DACs that use the Sabre chip that are downright dark, but there's still a certain "flavor" that always seems to go with the Sabre chip. (The closest way I can describe it is like the audible equivalent of the unsharp mask sharpening used by Photoshop. It seems to make treble frequencies "stand out" from the rest of the frequency spectrum without actually boosting the high frequencies; it gives the impression of making more detail audible.) Both the Wyred4Sound and the AudioLab have selectable filters, and the effect is there with all the choices (although it's more obvious with some choices than with others). I simply don't imagine anyone saying that any of those filters on the AudioLab, or on the Wyred4Sound, end up sounding like a Benchmark, or an Emo DC-1 (both of which are in fact rather neutral).
   Back when the Sabre DACs were first being introduced, ESS made a major point of stating in their literature that they'd voiced their DACs based on responses from user "listening tests" rather than specifically doing their best to make their DACs simply neutral - and this seems to fit with my experiences.
  
 I would agree, though, that some units that use the Sabre DACs are closer to neutral than others - but I don't think I've heard a Sabre DAc yet that I would characterize as 'totally neutral".
  
 Quote:


diamondears said:


> I don't think Sabre equals not-neutral. The Audiolab is Sabre but ain't bright at all. In fact 3 of its 7 digital filters I find on the warm side.


----------



## MrMateoHead

Indeed every time I switch back from the ODAC to my other sources, I get a sense of "relief" when the Sabre is back on. I think the term "etching" the sound is the most correct statement. The ODAC/Sabre manages to sound a little "brighter" or "harder" than my other DACs, with a sense that depth and detail has been improved. It feels "hi res". I would compare it to turning on what I call the "harshilizer" effect of many stereos I play with - you know, that feature that "restores detail" to your "lossy files". The exception is that with the Sabre you gain the sense that detail and dynamics have improved with the added harshness.
  
 While my Realtek sounds very good and detailed etc., it does usually also seem a little "softer". Could be placebo, could be difference in source voltage, whatever, but it seems there and the ODAC is the most satisfying overall experience for me at the moment.


----------



## AlanU

Am I one of the few here that uses a Grant fidelity B-283 mk2 tube processor/buffer with Black treasure CV181-z /6sn7 tubes??
  
 I'll have to say that the Burson Da160 dac and Tube buffer makes the objective amp an incredible experience.
  
 The note decay and "tube" sound  provides and incredible intimate sound for female vocals while it manipulates the source not the amplification of the 02 amp. I prefer manipulating the source in most cases so that I do not concern myself of "lack of power" due to low wattage tubes.
  
 To put things into perspective I can easily enjoy my 02 amp with tube buffer  equally as much as using my newly acquired Burson Virtuoso with the same tube buffer. I can truthfully question myself why I'd spend so much more for the Burson Virtuoso. 
  
 With my HD 650 or HD800's I think the 02 amp is incredible even if it was repackaged into a larger frame/body and more cosmetically pleasing for $500+ dollars. I would imagine much more expensive amps would be more appealing due to physical presentation (on your desktop). Ownership of a more expensive amp would give the owner a mental "impression" that since it more expensive it will be "substantially better".... probably more of an emotional preference based on validating spending extra beans $$$$
  
 I do find my Burson to be a fine amp but I give equal kudo's for the 02 amp to do a stellar job in clean amplification.


----------



## DIscoYou

discoyou said:


> With the Epiphany Acoustics O2Di (Amp & DAC) does anyone know how the headphone and DAC outs switch? Is it a case of the RCAs only being live when there are no headphones plugged in?
> 
> http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/


 

 Anyone?


----------



## JacobLee89

discoyou said:


> Anyone?


 
  
 It might be better to send them an email about it.
 Also it would be better if they added that on the product description page.


----------



## blacknile

Hi, I asked this question some time ago to Oliver from Epiphany Acoustic, who replied as follows:
  
 "the RCAs on the back will output the line level input direct from the DAC so you would connect that to your pre amp as you say.
  
 The only little thing to mention, which won't affect usability, is that the DAC can only support one output at a time (the internal headphone amp or the RCA line out) and there is no internal switching mechanism.
  
 As such, you simply have to either power off the pre amp if using the headphones or power off the O2Di if using the speaker system. The DAC gets it's power via USB so will always be on regardless of when the red light on the O2Di is on or off."
  
 Hope it helps.


----------



## DIscoYou

blacknile said:


> Hi, I asked this question some time ago to Oliver from Epiphany Acoustic, who replied as follows:
> 
> "the RCAs on the back will output the line level input direct from the DAC so you would connect that to your pre amp as you say.
> 
> ...


 
  
 That's very informative, thanks.
  
 It is interesting that the DAC is USB powered. Isn't the amount of power available to a USB device lower than the amount of power that a line level output can need? (I think it was a Z review where I saw him mention that).


----------



## castleofargh

discoyou said:


> blacknile said:
> 
> 
> > Hi, I asked this question some time ago to Oliver from Epiphany Acoustic, who replied as follows:
> ...


 

 usb is 5V, a DAC is supposed to output something like 2V into several thousand ohm of an amp input, so the current requirement is ludicrously small and so is the power.
 now for stuff with DAC and amp both powered by USB, I might not make the same comment, because an amp may need real power ^_^.


----------



## KeithEmo

castleofargh said:


> usb is 5V, a DAC is supposed to output something like 2V into several thousand ohm of an amp input, so the current requirement is ludicrously small and so is the power.
> now for stuff with DAC and amp both powered by USB, I might not make the same comment, because an amp may need real power ^_^.


 
  
 Correct, and most USB ports can supply up to at least 500 mA (most modern ones can do more). This is a couple of watts, and so is plenty for most "normal power" headphone amps.
  
 The voltage also isn't a limitation per-se; many USB DACs use tiny power switchers that convert the +5V USB power into +/- 5V (or even higher voltages) for driving their audio circuitry. Some of the headphone amplifier chips commonly used by USB DACs even have this capability built right in (so they can deliver an output signal up to almost +/- 5V even when running from a single +5V supply.


----------



## dorino

USB provides more than enough, as has been mentioned. I'd be sure it's alone on the bus, though, or at least nearly.


----------



## chongky

Tip for those who find the ODAC a bit thin in the mids. Don't upsample your ODAC to 24-bit/96Khz on Windows, instead go for 24-bit/44.1Khz if you're listening to CD quality material. Mids gain a hint of warmth and become more liquid, though at the expense of a smaller soundstage. Try it.


----------



## schmalgausen

Wasapi output ignores Windows settings, doesn't it?


----------



## jseaber

chongky said:


> Tip for those who find the ODAC a bit thin in the mids. Don't upsample your ODAC to 24-bit/96Khz on Windows, instead go for 24-bit/44.1Khz if you're listening to CD quality material. Mids gain a hint of warmth and become more liquid, though at the expense of a smaller soundstage. Try it.


 
  
 This tip is applicable to all DACs! Here's a set of measurements of a PCM5102A DAC to back you up. The ES9023 in ODAC performs the same.
  
 Win7 set to 24/96k, streaming a 24/96k sine wave at 10kHz *(no up-sampling):*

  
  
 Win7 set to 24/96k, streaming a 24/44.1k sine wave at 10kHz *(up-sampled):*

  
  
 Check out that noise!


----------



## chongky

schmalgausen said:


> Wasapi output ignores Windows settings, doesn't it?


 
 According to JDS Labs operating instructions, for Windows Vista/7/8:
  
 Right click volume icon in taskbar, click 'Playback devices', set ODAC as default device. Suggested Properties (right click on ODAC "Speakers" icon): Enhancements: Check "Disable all enhancements".
  
 At Advanced, JDS suggests 24-bit, 96000 Hz (Studio quality), and then "Apply". I don't. At the expense of soundstage, the mids gain a fraction more warmth and a touch of liquidity if you choose the 24-bit, 44100 Hz option. I suggest this if you are listening to CD quality music. However, if you have high resolution 96000 Hz files your mileage may differ.
  
 It's a small difference, not night and day, but it does make the mids sound less thin and anaemic.
  
 Hope this works for you.


----------



## schmalgausen

chongky said:


> According to JDS Labs operating instructions, for Windows Vista/7/8:
> 
> Right click volume icon in taskbar, click 'Playback devices', set ODAC as default device. Suggested Properties (right click on ODAC "Speakers" icon): Enhancements: Check "Disable all enhancements".
> 
> ...




But what player with what output settings?


----------



## chongky

schmalgausen said:


> But what player with what output settings?


 
 I use Foobar. Go to File --> Preferences --> Output, set Device to WASAPI (Event): Speaker (ODAC). Then go down and Output format as 24-bit.
  
 It should ensure bit perfect playing using the ODAC.
  
 Also at DSP manager of Foobar under File --> Preferences --> Playback do not resample.
  
 Hope this helps.


----------



## KeithEmo

chongky said:


> According to JDS Labs operating instructions, for Windows Vista/7/8:
> 
> Right click volume icon in taskbar, click 'Playback devices', set ODAC as default device. Suggested Properties (right click on ODAC "Speakers" icon): Enhancements: Check "Disable all enhancements".
> 
> ...


 
  
 I don't ever remember anyone claiming that Windows does a _good_ job of upsampling.
  
 In general, for best sound quality, you should _ALWAYS_ be using a bit-perfect mode (in Windows that would be WASAPI).
  
 I suspect their advice was being offered as "the lesser of two evils". (If you're not willing to set up and use WASAPI, then you have no choice but to pick a single default sample rate. Setting the default to 96k will result in your 44k content being upsampled to 96k, and your 96k content being played at its native sample rate. This is less bad than setting it to 44k, in which case your 44k stuff would play at its native rate, but your 96k stuff would be_ DOWN_sampled to 44k. However, WASAPI is the really good choice.)


----------



## dorino

The set up for foobar is very similar in Jriver, MusicBee and so on.
  
 On Mac, it's similar, but many audio players are bit-perfect by default and don't need any reconfiguring.
  
 On Linux, just turn off ALSA resampling in your player and make sure it's allowed to be exclusive.


----------



## castleofargh

jseaber said:


> chongky said:
> 
> 
> > Tip for those who find the ODAC a bit thin in the mids. Don't upsample your ODAC to 24-bit/96Khz on Windows, instead go for 24-bit/44.1Khz if you're listening to CD quality material. Mids gain a hint of warmth and become more liquid, though at the expense of a smaller soundstage. Try it.
> ...


 

 do you happen to have the same test done with16/44 and then 24/44 as the output setting, but using 16/44 files?
 I was just asked if 24/44 was a "real value". my buddy might no be alone thinking "but it's wrong, the output is 24/44 and the track is 16/44!"
  
 thank you for this one anyway it's good to have.


----------



## dorino

Don't upsample. Just output at whatever the track is.


----------



## jseaber

castleofargh said:


> do you happen to have the same test done with16/44 and then 24/44 as the output setting, but using 16/44 files?
> I was just asked if 24/44 was a "real value". my buddy might no be alone thinking "but it's wrong, the output is 24/44 and the track is 16/44!"
> 
> thank you for this one anyway it's good to have.


 
  
 Bitrate only impacts the noise floor (i.e., background hiss). The signal remains the same in terms of THD, just with more hiss.
  
 Here's a quick test with the OS set to 24/44.1k, playing a 24/44.1k signal:
  

  
  
 Here's the same 24/44.1k OS setting playing a 16/44.1k signal:
  

  
  
 Notice the baseline noise moves upwards.


----------



## castleofargh

thanks a bunch! be it to buy you something or to ask a question, you're impressively quick to react! 
	

	
	
		
		

		
			




  
 yeah I wasn't expecting a difference in distortion, just that it makes for a complete set or measures so people don't have to trust me to see what does what. so really useful in it's own way ^_^.


----------



## dazzerfong

Hate to disturb you folks with something of a technical nature, but I decided to put a standalone ODAC onto my phone (Z1 Compact, Lollipop). Unfortunately, it didn't work: I tried using a powered USB hub, but that didn't do anything either. I'm positive that my phone has USB audio enabled, so any pointers?


----------



## jseaber

dazzerfong said:


> Hate to disturb you folks with something of a technical nature, but I decided to put a standalone ODAC onto my phone (Z1 Compact, Lollipop). Unfortunately, it didn't work: I tried using a powered USB hub, but that didn't do anything either. I'm positive that my phone has USB audio enabled, so any pointers?


 
  
 We've had a few calls from owners of various DACs recently, reporting that an Android Lollipop update in April broke USB audio support. Not just for ODAC, but for all USB DACs. This may not be your particular issue, but what equipment have you tried?


----------



## Medaud

chongky said:


> According to JDS Labs operating instructions, for Windows Vista/7/8:
> 
> Right click volume icon in taskbar, click 'Playback devices', set ODAC as default device. Suggested Properties (right click on ODAC "Speakers" icon): Enhancements: Check "Disable all enhancements".
> 
> ...




But what if you're gaming or watching movies? Some games and movies might have 48000Hz sample rate. So while you might not be upsampling the music you're suddenly downsampling the game's audio?


----------



## James-uk

I know it makes no difference to perceived SQ but nice to see this awesome transparent DAC is even better on paper now. 
http://epiphany-acoustics.co.uk/the-odac-gets-an-update/


----------



## castleofargh

james-uk said:


> I know it makes no difference to perceived SQ but nice to see this awesome transparent DAC is even better on paper now.
> http://epiphany-acoustics.co.uk/the-odac-gets-an-update/


 

 so did someone end up getting in contact with nwavguy(if he's alive) to get the right to modify the boards, or did everybody just decide to do what they wanted since some changes were necessary anyway?
 because I know he gave the stuff to be used for free, but I have kind of a doubt that it includes using the name to make something else (I'm just really guessing here).


----------



## JacobLee89

castleofargh said:


> so did someone end up getting in contact with nwavguy(if he's alive) to get the right to modify the boards, or did everybody just decide to do what they wanted since some changes were necessary anyway?
> because I know he gave the stuff to be used for free, but I have kind of a doubt that it includes using the name to make something else (I'm just really guessing here).


 
  
 Regardless, we could benefit if we bought them whilst they are still available.


----------



## mcandmar

james-uk said:


> I know it makes no difference to perceived SQ but nice to see this awesome transparent DAC is even better on paper now.
> http://epiphany-acoustics.co.uk/the-odac-gets-an-update/


 
  
 Interesting bit of marketing as its got a different USB controller and DAC chip so its got nothing to do with an ODAC at all.  Basically its a completely new DAC, and one that is based on a Ti PCM chip so it gets a big thumbs up from me.


----------



## jseaber

castleofargh said:


> so did someone end up getting in contact with nwavguy(if he's alive) to get the right to modify the boards, or did everybody just decide to do what they wanted since some changes were necessary anyway?
> because I know he gave the stuff to be used for free, but I have kind of a doubt that it includes using the name to make something else (I'm just really guessing here).


 
  
 The official release article and ownership information is available here:
 http://blog.jdslabs.com/?p=1003
  
 I would quote, but the article is rather lengthy. In summary, Yoyodyne Consulting owns ODAC. NwAvGuy owns O2.
  


mcandmar said:


> Interesting bit of marketing as its got a different USB controller and DAC chip so its got nothing to do with an ODAC at all.  Basically its a completely new DAC, and one that is based on a Ti PCM chip so it gets a big thumbs up from me.


 
  
 Indeed, the chipset update is a significant change. The performance criteria and test methodology is the same.


----------



## castleofargh

nice article, it does explain a lot of interesting points.


----------



## Jason8777

I'm asking this question for a friend of mine.  He has O2 amp + ODAC with RCA in the back.  He recently asked me to build him a Bottlehead Crack and he wants to know if he can use the O2 amp + ODAC as a DAC to connect to the bottlehead crack.  Can he do that or Does he need to get another DAC? Thank you.


----------



## dorino

jason8777 said:


> I'm asking this question for a friend of mine.  He has O2 amp + ODAC with RCA in the back.  He recently asked me to build him a Bottlehead Crack and he wants to know if he can use the O2 amp + ODAC as a DAC to connect to the bottlehead crack.  Can he do that or Does he need to get another DAC? Thank you.


 

 I'm pretty sure there's no way to use just the ODAC in the typical combo configuration. He'd need another DAC to avoid double amping.


----------



## K_19

dorino said:


> I'm pretty sure there's no way to use just the ODAC in the typical combo configuration. He'd need another DAC to avoid double amping.


 
  
 Actually, I'm not sure which build the poster's combo unit is (JDS? Mayflower? Epiphany? DIY? etc), but with the most O2/ODAC combo units with the RCA in the back the RCA is for the line out; which means that you can definitely use it as a DAC only to the Crack. There are some units that have the RCAs that act as both inputs and outputs, while I haven't heard of any RCA included units that has the RCA's for line in _only_ (to have another DAC connected to the O2 amp) so I think it's a safe bet that those RCA's in the back does do ODAC line out.


----------



## thecrow

I haven't looked at it for a while but isn't the rcas at the back line outs direct from the dac?


----------



## thecrow

Looks like you just need to plug something in the front 3.5mm jack (if you have that) and then the rcas are dac outs
https://www.jdslabs.com/pdf/Instructions_O2-ODAC.pdf


----------



## Jason8777

thecrow said:


> Looks like you just need to plug something in the front 3.5mm jack (if you have that) and then the rcas are dac outs
> https://www.jdslabs.com/pdf/Instructions_O2-ODAC.pdf


 
 Thank you.  He has the above Amp.


----------



## dorino

k_19 said:


> Actually, I'm not sure which build the poster's combo unit is (JDS? Mayflower? Epiphany? DIY? etc), but with the most O2/ODAC combo units with the RCA in the back the RCA is for the line out; which means that you can definitely use it as a DAC only to the Crack. There are some units that have the RCAs that act as both inputs and outputs, while I haven't heard of any RCA included units that has the RCA's for line in _only_ (to have another DAC connected to the O2 amp) so I think it's a safe bet that those RCA's in the back does do ODAC line out.


 

 Interesting. Neat.


----------



## DIscoYou

jason8777 said:


> I'm asking this question for a friend of mine.  He has O2 amp + ODAC with RCA in the back.  He recently asked me to build him a Bottlehead Crack and he wants to know if he can use the O2 amp + ODAC as a DAC to connect to the bottlehead crack.  Can he do that or Does he need to get another DAC? Thank you.


 
  
 I asked functionally the same question a few pages back, and I received this informative response from blacknile:
  


blacknile said:


> Hi, I asked this question some time ago to Oliver from Epiphany Acoustic, who replied as follows:
> 
> "the RCAs on the back will output the line level input direct from the DAC so you would connect that to your pre amp as you say.
> 
> ...


----------



## diamondears

Hope this is ok to ask here, but any of you know a portable integrated DAC + amp (not transportable like the O2) that has equal or better SQ than the sound coming out of the iFi micro iDSD + O2?


----------



## jring

discoyou said:


> I asked functionally the same question a few pages back, and I received this informative response from blacknile:


 
  
 Hi,
  
 I would recommend to plug something into the input jack of O2 while using the RCA outs - this will break contact between O2 and the ODAC line out on the RCAs. Also I would unplug the RCA out (and the input jack) when using ODAC together with O2.
  
 Having ODAC drive an unpowered input stage along with a powered one is in my opinion even worse than two powered ones. In the latter case you might get too low an input impedance with two input stages in parallel but with an unpowered input some protective measures on the unpowered input will probably make for funny results...
  
 Joachim


----------



## Meremoth

I currently use ATH-AD900X's for everything.  Don't have any other headphones.  I'm going to purchase a O2+ODAC today for my PC.  Questions:
  
 1. Where should I buy it or does it matter?
  
 2.  Was looking at JDS Labs website and there are different customizable options:  

Rear mounted vs Front mounted power jack.  Any difference/benefit?
3.5mm vs. 6.35mm (headphone jack output)  - I need 3.5mm for both AD900X and TH-900, correct?
DAC line-output = Default 3.5mm vs Deadicated read line output 3.5mm vs Dedicated rear RCA line-outputs (I have no idea about any of this)
Gain = Medium (1.0x , 3.5x), Standard (2.5x, 6.5x), (1.0x, 2.5x)   (also have no idea what to choose)
  
 The O2+ODAC will be used for both my AD900X's and TH-900's.  
  

 I have finally decided to pull the trigger and get this amp/dac because I've been listening to my 900X's on my iPad lately and realized how much better they sound on my iPad vs my PC (PC using very old Realtek onboard sound).  
  
 Thanks in advance to anyone who can offer any help/advice/suggestions/informations/recommendation/tips/opinions etc.    It will be very much appreciated.  
  
 Sincerely,
  
 Jeremy (wannabe audiophile)


----------



## thecrow

meremoth said:


> I currently use ATH-AD900X's for everything.  Don't have any other headphones.  I'm going to purchase a O2+ODAC today for my PC.  Questions:
> 
> 1. Where should I buy it or does it matter?
> 
> ...




The placement of power jack does not matter - comes down to hiw you want it on your desk. 

Size of headphone jack selection comes down to the size of your connection at the end of your headphones. You can always get adaptors if there is a difference. I prefer the 6.35mm but that's because my main headphone has a 6.35 connection. 

Dac line out put doesnt matter either. John at jdslabs tells me there are no audible differences between rca or 3.5mm connections. Again if you need something different in the future you can just get a short/cheap adaptor. You can use these outputs if you don't want to use the O2 amp. What it does is it takes the analogue signal (from the odac) before it gets to the O2 so you can say connect it to another amp. Hence its a dac line out. 

John at jdslabs recommends the medium gain settings with the odac. It essentially comes down to what dac/source you are using. Your headphones can sometimes alter the choice if they are hard to drive headphones. 

You can also buy the odac and O2 as two separate units. The two benefits to that is that you can replace or upgrade them individually in the future as they are not in one unit. The O2 by itself also has a battery in it if you want to transport it around. The O2/odac combo does not. 

However that means there are two units on your desk. But the odac is no bigger than a packet of smokes. 

Jdslabs also have a free engraving service. You can have an image engraved on the top. I had a couple of black and white friendly images engraved and they came up fantastic. 

If you email jdslabs their service is fantastic. If you email them your headphone info I'm sure they'll confirm if the medium setting is what you want. 

Hope that helps.


----------



## Meremoth

thecrow said:


> The placement of power jack does not matter - comes down to hiw you want it on your desk.
> 
> Size of headphone jack selection comes down to the size of your connection at the end of your headphones. You can always get adaptors if there is a difference. I prefer the 6.35mm but that's because my main headphone has a 6.35 connection.
> 
> ...


 
  
 Thanks for the reply, thecrow!  

 Awesome advice on getting the units separately!  I think that's what I'll do.  

 I think both the 900X's and TH-900's are suppose to be easy to drive.  

 Free engraving service, you say?   That's pretty sweet!   Another decision for a super indecisive (me) person, haha.  You said black and white?  Do they do the engravings in color?  Out of curiosity, what did you get engraved on yours?  
  
 I just plan on using the O2 and ODAC, my headphones (AD900X & TH900) and my PC, and that's all (for now).  Is there any additional things I need to purchase in order to make this all work (cables, adapters, etc.)?  

 Just found out the TH-900's are 6.35mm, so that's the headphone jack output I'm going to get.  Would a 3.5mm to 6.35mm adapter (for my 900X's), degrade the sound at all?  
  
  
 Thanks again.


----------



## thecrow

meremoth said:


> Thanks for the reply, thecrow!
> 
> 
> Awesome advice on getting the units separately!  I think that's what I'll do.
> ...




The headphone adaptor would be fine. Sound would be fine. 

With the separate odac you also get the choice of rca connections out rather than 3.5mm. I would just leave it with the standard 3.5mm. 

Check with jdslabs re what else you need. You get the usb cable cable for the odac. You'll need to buy the power cord thingy to connect the O2 to the wall - they sell that. And from memory you'll need a cable to go from the odac to the o2. Either a 3.5mm cable or a 3.5mm to rca connections if you choose to get the rca connections on the O2. You would use that if you wanted to connect , say another dac to your O2 in the future via rcas. But you still could always use the standard 3.5 mm jack with any other dac if you had a cable adaptor (rca to 3.5 mm) so again no real need for rca jacks anywhere on these if you haven't got other equipment you're akreadybpkanning to hook up. 

The engravings are just black and white. There's a video somewhere on YouTube or the jdslabs website of an engraving. It's simply engraving on the black top cover of the O2 or odac. I decided to choose 2 images that were black and white as I thought if the images had a bucket load of different colours it may not have done up as well. 

Do a google images search and you'll get some ideas. 

I have an odac on sale in the ckassifieds. If you have a look at that posting you'll see my odac's image.


----------



## Meremoth

thecrow said:


> The headphone adaptor would be fine. Sound would be fine.
> 
> With the separate odac you also get the choice of rca connections out rather than 3.5mm. I would just leave it with the standard 3.5mm.
> 
> ...


 
  
 WOW!  That engraving is screwing fantastic!  Way better than what I was thinking.  I love "Rikki Don't Lose That Number"!  
 I would purchase that from you if I wasn't super OCD about buying used things.  
 Out of curiosity, why are you selling it? 

  
 So the RCA outputs for the DAC offer no improvement in quality vs. 3.5mm?  
  
  
 Thanks.


----------



## thecrow

i upgraded my dac. And then my amp. 

I bought an arcam irdac at a good price second hand which suits me and my headphones. the timing was just right - I had been looking for that dac and the guy I bought it from was upgrading to the next level too. 

I used to be careful about second hand stuff initially too. Just be a little cautious. Here you'll find reviews on most sellers. That helps. And quite often you'll notice they may have bought the equipment off someone else from here so you can even go back to the classified when they were first selling it. 

also one thing I've learnt here is you can get many positive recommendations and reviews on something but nothing beats hearing what you're thinking of buying - you probably found that in choosing your headphones. 

Having said that....I have found, for me, the odac is a fair/ok dac for its price but the O2 is a great neutral/transparent dac well priced too. I'd recommend it to my own mother easily.

If I was looking for an amp around that price I would look at buying the O2 again. The only reason I haven't put that in the classifieds yet is I might keep it as a back up. Probably not though.


----------



## Meremoth

thecrow said:


> i upgraded my dac. And then my amp.
> 
> I bought an arcam irdac at a good price second hand which suits me and my headphones. the timing was just right - I had been looking for that dac and the guy I bought it from was upgrading to the next level too.
> 
> ...


 
  
@thecrow
  
 Little confused about the sentence, "Having said that....I have found, for me, the odac is a fair/ok dac for its price but the O2 is a great neutral/transparent dac well priced too. I'd recommend it to my own mother easily."

 You said the O2 is a great neutral/transparent DAC, but I thought the O2 was an amp?  Are you saying the O2 is an awesome amp, but the ODAC is only decent?


----------



## thecrow

meremoth said:


> @thecrow
> 
> 
> Little confused about the sentence, "Having said that....I have found, for me, the odac is a fair/ok dac for its price but the O2 is a great neutral/transparent dac well priced too. I'd recommend it to my own mother easily."
> ...




I wrote "having said that" as I just wrote before that to essentially take opinions with a grain of salt. 

As others have said nothing here is as good as people make it out to be and never as bad as they say either. Views all have some preferences or are tainted with personal biases. norhing beats having a listen yourself. 

My opinion is the O2 is very good. If I was in the same position gain I would buy the O2 (on its own merits) and then buy the Odac (Almost by default) to make the pigeon pair. I'd still be happy with that combo. If I just wanted a dac I'd probably look around and compare others to the Odac and spend another 2 weeks of constant reading here to make a decision. 

I found the Odac to be quite similar to the dac in my fiio x5. So quite reasonable and fair. 

Odac 7/10
O2 9/10

As a combo 8/10. 

A great combo at a good price.


----------



## Meremoth

thecrow said:


> I wrote "having said that" as I just wrote before that to essentially take opinions with a grain of salt.
> 
> As others have said nothing here is as good as people make it out to be and never as bad as they say either. Views all have some preferences or are tainted with personal biases. norhing beats having a listen yourself.
> 
> ...


 
  
 Whatever I get, I pretty much want it to be neutral and transparent for the most part.  Not that I don't like some color, but I want the color to come from my headphones and not my amp or DAC.
  
 With that being said, is there another DAC, in the price range of the ODAC, that would suit my needs/wants and would go great with the O2 and TH-900?  

 As of now I'm pretty set on the O2, ODAC, and TH-900's, but I'm always open to suggestions.
  
 Thanks again.


----------



## thecrow

There's also the Schiit magni and modi. I read they are very similar. Some say the odac is a little more natural on the upper end. 

I would go the O2 and pair it with the odac. But have a read of the others and see what you think. 

If you go the schiit modi dac then I believe you need to go to the next highest gain settings option as the powerbout of the modi is a little less than the odac. You can confirm those option with jdslabs at the end. 

My choice at that price point would simply be the 02 and odac. 

I upgraded to a $600 dac and $1000 and got a meatier sound with broader soundstage. But the odac and O2 were a great comparison to those (like a younger brother) at their prices of about 1/4 of those. Great value for $400

Good luck and have fun.


----------



## Meremoth

thecrow said:


> There's also the Schiit magni and modi. I read they are very similar. Some say the odac is a little more natural on the upper end.
> 
> I would go the O2 and pair it with the odac. But have a read of the others and see what you think.
> 
> ...


 
  
 What gave you the broader soundstage?  Your new DAC?  What's specifically different about your new DAC, compared to the ODAC, that increased your soundstage?  Does your upgraded amp have anything to do with the wider soundstage?  If so, same question, specifically what's the different between the O2 and your new amp that would 'cause this?
  
 Meatier sound?  Does the meatier sound come from coloration that your new amp and DAC add, or are there specific technical details that are different resulting in a broader soundstage (and by broader, do you also mean broader and better, or just broader and subjectively different)?  
  
 Thanks, bro.


----------



## thecrow

meremoth said:


> What gave you the broader soundstage?  Your new DAC?  What's specifically different about your new DAC, compared to the ODAC, that increased your soundstage?  Does your upgraded amp have anything to do with the wider soundstage?  If so, same question, specifically what's the different between the O2 and your new amp that would 'cause this?
> 
> Meatier sound?  Does the meatier sound come from coloration that your new amp and DAC add, or are there specific technical details that are different resulting in a broader soundstage (and by broader, do you also mean broader and better, or just broader and subjectively different)?
> 
> Thanks, bro.




The new dac has more clarity and precision. Look up the review on whathifi on the irdac. 

The amp has more power so that resulted in more vibrancy and definition. Bottom end is more solid. Everything is richer. Still transparent. 

Maybe think of it as high def tv picture. Richer. Deeper. More defined. All that kind of stuff. 

Read any review on the Burson audio soloist. 

Good luck with everything


----------



## Meremoth

thecrow said:


> The new dac has more clarity and precision. Look up the review on whathifi on the irdac.
> 
> The amp has more power so that resulted in more vibrancy and definition. Bottom end is more solid. Everything is richer. Still transparent.
> 
> ...


 
  
 Awesome, thanks for the response, crow.  
  
 I've heard tons of good things about the Soloist.  Not sure I'm ready to spend $1k on an amp, despite dropping that much on headphones, lol.  I'll still read what you suggested, though; might be something I'll pick up a couple years from now.  But going from onboard sound to O2+ODAC should keep me fairly content for awhile to come, or at least I hope so.


----------



## thecrow

I'm not suggesting you should buy it. Im just loving it. 
You'll have your own preferences as you go.


----------



## Takeanidea

I have an Odac 02 combo that i won at a headfi meet. I tend to use it without mains as a Dac going into my Fidelity AudioHPA 200 SE.
It's pretty good in it's own right but I'm afraid i don't have the TH900. I use the Alpha Dogs and HD800S on it. I'll have another listen to the 02 Odac and tell you.


----------



## Meremoth

thecrow said:


> I'm not suggesting you should buy it. Im just loving it.
> You'll have your own preferences as you go.


 
  
 Well, I still appreciate your opinion.  Actually was looking at the Conductor for awhile, but once I read more about the O2+ODAC, I decided that was probably the best bet for my very first headphone amp and DAC.  
  
 For easy to drive headphones (like the AD900X and TH900), how much of an upgrade would the Conductor be vs O2+ODAC in your opinion?
  
 I've already forgotten, did you say you had a pair of TH-900's?  
  


takeanidea said:


> I have an Odac 02 combo that i won at a headfi meet. I tend to use it without mains as a Dac going into my Fidelity AudioHPA 200 SE.
> It's pretty good in it's own right but I'm afraid i don't have the TH900. I use the Alpha Dogs and HD800S on it. I'll have another listen to the 02 Odac and tell you.


 
  
 Awesome, thanks.  I'll be here.


----------



## thecrow

Correct. Great bet for your first. 

Hd800s are mine. 

After you get to know your headphones, and what you like and what you're after then go the next step when ready. 

Enjoy what you have. Enjoy. Don't get caught up in always looking for equipment. I know did that for a while. 

I have not heard the conductor (the dac). Just the amp part (more or less in the soloist). Sort out your headphones and what you like and then look for dacs and Amps to best suit. Read the appropriate threads, PM a few people that have what you are thinking of and listen to gear when you can. 

No rush. 

For me when I'm thinking of spending $2000 on amp and dac, let alone $1000 in better be what I'm looking for and bang for buck. 

You may even change headphone preferences. 

Who knows? But yes a great first bet. 

It was like my first decent headphones - the athm50x s - what I call "gateway headphones". Beware and have fun!!!!


----------



## Takeanidea

The O2 ODac has had an hour or so of headtime this morning through my HD800s listening to a variety of acoustic pop and rock tracks mainly from the 80s recorded from vinyl.
  
 It runs these 300 OHM phones on normal gain between halfway and 60% on the volume in a quiet room. I switched between the 02 and my HPA 200 SE halfway through each song and all testing was done without any science.
  
 There was sparkle and low end impact through the 02 ; through the HPA the instruments sounded more realistic , the sound had more air , the bass had more feel. The HPA 200 SE was almost impossible to volume match to the 02 because the sound was fuller.
  
 The HPA 200 SE was a limited edition run done by Fidelity Audio (I was the first to have this done) and this represents £850 of headphone amp, so it's not surprising it outperforms the O2. So....it's worth listening to lots of units before you make the plunge.


----------



## thecrow

takeanidea said:


> The O2 ODac has had an hour or so of headtime this morning through my HD800s listening to a variety of acoustic pop and rock tracks mainly from the 80s recorded from vinyl.
> 
> It runs these 300 OHM phones on normal gain between halfway and 60% on the volume in a quiet room. I switched between the 02 and my HPA 200 SE halfway through each song and all testing was done without any science.
> 
> ...


I found that with my soloist. 

O2 was good. A little bit of tweaking on the eq helped to Season it to ones preferences. 

Then along came my Soloist (at 4 times the price). No need for an eq. And richer. 

But hey..... That's with hd800s too. 

I would still enjoy my hd800s with the O2. But now I enjoy them more.

$1000 v $250

Great on a budget.


----------



## upstateguy

thecrow said:


> meremoth said:
> 
> 
> > What gave you the broader soundstage?  Your new DAC?  What's specifically different about your new DAC, compared to the ODAC, that increased your soundstage?  Does your upgraded amp have anything to do with the wider soundstage?  If so, same question, specifically what's the different between the O2 and your new amp that would 'cause this?
> ...


 
  
 For what it's worth, you can't get more transparent than transparent and the O2 combo measures really transparent. 
  
 The deeper and richer sound you speak of is nothing more than coloration.
  


takeanidea said:


> The O2 ODac has had an hour or so of headtime this morning through my HD800s listening to a variety of acoustic pop and rock tracks mainly from the 80s recorded from vinyl.
> 
> It runs these 300 OHM phones on normal gain between halfway and 60% on the volume in a quiet room. I switched between the 02 and my HPA 200 SE halfway through each song and all testing was done without any science.
> 
> ...


 
  
 When compared with the O2 combo, a fuller sound with more bass is the hallmark of added coloration.
  
 Edit: how did you try to volume match?


----------



## Takeanidea

I wish my ears would be content with paper measurements. My wallet would be a lot better off with an ipod and a set of er4ps


----------



## upstateguy

takeanidea said:


> I wish my ears would be content with paper measurements. My wallet would be a lot better off with an ipod and a set of er4ps


 
  
 I'd be willing to bet that your ears, with in their capacities, completely agree with paper measurements.
  
 Btw, it is perfectly alright to prefer a bass boost over neutral.  Just don't confuse coloration with neutral.


----------



## Takeanidea

You're right, life would be boring if it wasn't in colour. I'm easily confused too. Thank goodness we have facts and figures to prove the point. If only it were that easy.......


----------



## upstateguy

takeanidea said:


> You're right, life would be boring if it wasn't in colour. I'm easily confused too. *Thank goodness we have facts and figures to prove the point. *If only it were that easy.......


 
  
 +1
  
 You're absolutely right.  It's a good thing that *measurement devices are not susceptible* to the *cognitive  biases* people are.
  
 If you're willing to be really honest, you'd have to admit that you don't hear the same thing from the same gear all the time. 
  
 There are so many factors that influence how and what you perceive you're hearing on a daily and day to day basis.  Emotion, mood, fatigue, expectation, time of day, barometric pressure etc...


----------



## Takeanidea

I'm glad I've got cognitive bias. It helps me enjoy my music more. Happy listening


----------



## upstateguy

takeanidea said:


> I'm glad I've got cognitive bias. It helps me enjoy my music more. Happy listening


 
  
 The problem with cognitive bias is that it's not reliable.  One time it might help you enjoy your music and another time it may work the other way.  Anyway, it's only a hobby!


----------



## Draulius

Am I right to think that the HD600 would be one of the best headphones for the ODAC+O2 combo due to its neutrality?


----------



## dazzerfong

draulius said:


> Am I right to think that the HD600 would be one of the best headphones for the ODAC+O2 combo due to its neutrality?


 
 The best headphone for the ODAC+O2 would be one whose sound signature you already love, since it does practically nothing to the sound. If you so happen to like the HD600's sound, then yes, it'll be the best for you.


----------



## SodaBoy

upstateguy said:


> +1
> 
> You're absolutely right.  It's a good thing that *measurement devices are not susceptible* to the *cognitive  biases* people are.
> 
> ...


 

 Agreed mate. I would add that auditory memory is also quite short, as I recall it lasts only about 3-4 seconds and even then only vaguely. As a result AB testing must necessarily be quick during transitions, and listening impressions should be reinforced with objective measurement.


----------



## AlanU

dazzerfong said:


> The best headphone for the ODAC+O2 would be one whose sound signature you already love, since it does practically nothing to the sound. If you so happen to like the HD600's sound, then yes, it'll be the best for you.


 
  
 Not sure if it's that simple. The headphones is last in the chain before it hits your ears. The source and amp can greatly effect the collective combo in the chain of events. I ran my concero Hd, Burson da160 and space tech labs tube dac with my 02 objective and the "sound" was worlds apart different using the same headphones. Also adding a grant fidelity tube buffer with black treasure CV181 tubes changes the sound as well.
  
 The human ear can take neutral as boring and not very engaging. This is where you can colourize the source to be more musical. Source also plays a critical role in how it presents the music as it's converted from digital to analog. As you may know not all dac's sound the same.  I must also mention how the music was mastered as well. 
  
 I personally would not use the ODAC but it comes down to personal preference. I'll have to say I could happily use my objective 02 amp connected to my Space tech tube dac and super rectifier (similar setup to the woo WA5 LE minus amp section) and leave my Burson Virtuoso alone  in the dark turned "off". The sound quality I get with this combo with inexpensive objective 02 amp is incredible. 
  
 However imo the 02 amp's probably well paired to a warmer headphone.


----------



## dazzerfong

alanu said:


> Not sure if it's that simple. The headphones is last in the chain before it hits your ears. The source and amp can greatly effect the collective combo in the chain of events. I ran my concero Hd, Burson da160 and space tech labs tube dac with my 02 objective and the "sound" was worlds apart different using the same headphones. Also adding a grant fidelity tube buffer with black treasure CV181 tubes changes the sound as well.
> 
> The human ear can take neutral as boring and not very engaging. This is where you can colourize the source to be more musical. Source also plays a critical role in how it presents the music as it's converted from digital to analog. As you may know not all dac's sound the same.  I must also mention how the music was mastered as well.
> 
> ...


 
 Well, then your ears are very different from mine, because to me, the O2 does nothing but make it go louder. Other amps may or may not colour your source. That being said, if you don't want absolute neutral, why not get another pair of headphones that have the sound you want, rather than messing around with amps? You'll be doing yourself a much greater service if you do that.
  
 Problem about your statement on DAC's in general is that DAC's aren't _meant_ to colour the source. They're meant to take your PCM signal, then churn out an analog signal accordingly. You might have bass boost or whatnot, but the overall point isn't to deviate from the intended signal. Amps also try to achieve linearity, but tube amps can't manage this as well as solid-state devices, hence the different sound. 
  
 If you like the O2 amp with warmer headphones, that means you like (_gasp_) warm headphones!


----------



## castleofargh

alanu said:


> dazzerfong said:
> 
> 
> > The best headphone for the ODAC+O2 would be one whose sound signature you already love, since it does practically nothing to the sound. If you so happen to like the HD600's sound, then yes, it'll be the best for you.
> ...


 

 so your point against the O2 being transparent is that it is transparent. of course not everybody will like a neutral transparent sound, but what was said above is still true, if you really like the sound of one headphone, then you will like it with the O2 because nothing with change much.
 your preference for another source just shows that you like the sound of the headphone altered in a certain way. nothing wrong with that, but what @dazzerfong wrote still stands IMO.


----------



## AlanU

dazzerfong said:


> Well, then your ears are very different from mine, because to me, the O2 does nothing but make it go louder. Other amps may or may not colour your source. That being said, if you don't want absolute neutral, why not get another pair of headphones that have the sound you want, rather than messing around with amps? You'll be doing yourself a much greater service if you do that.
> 
> Problem about your statement on DAC's in general is that DAC's aren't _meant_ to colour the source. They're meant to take your PCM signal, then churn out an analog signal accordingly. You might have bass boost or whatnot, but the overall point isn't to deviate from the intended signal. Amps also try to achieve linearity, but tube amps can't manage this as well as solid-state devices, hence the different sound.
> 
> If you like the O2 amp with warmer headphones, that means you like (_gasp_) warm headphones!


 
  
 If you listen to many dacs you'll find that most will have a signature house sound. This is the reason there are so many different DAC's on the market. If they were all successful in producing a so called "neutral" sound there would be no point buying a $5000 dac over the "attempted" neutral sound of the odac. Most DAC's do a good job converting digital to analog but I guess it's not really that simple if sound quality is imperative.
  
 Collectively everything matters. The 02 amp does a great job "making it louder". The point of tubes is to add pleasant distortion and overtones/harmonics solid state cannot produce (lost in translation as it was analog converted to digital in the studio) for the purpose of making it appealing to the human ear as natural (not hyper detailed). Tubes are not for everyone.....However I can make my tube dac sound solid state very easily by removing my tube rectifier with a solid state diode full rectifier replacement.  
  
 As a hobby I'm building the headphone rig and will add more headphones to the mix .  If I use a Stello u3 for a usb/spdif converter or using my Concero HD as a usb/spdif this changes the sound signature with the identical dac. I do not know how much you dabble or experience you have but every component changes the overall sound at your transducer headphone. Headphones colour the music with their house sound so this also becomes more of a synergy match of components.
  
 I can make my Hd800 extremely full bodied and warm by swapping tubes on my dac setup. I can also make my HD650's "less" laid back by using different tubes on my dac/super rectifier. However i also can buy new headphones to take on a different sound signature. 
  
 My headphone rig is still substantially cheaper than my "power conditioning" of my 2 channel. So to put this into perspective I put more emphasis on my 2 channel.
  
 "gasp" warm headphones is probably incorrect in term.  I should have said a transducer not so bright. This is why I tame my hd800 with tubes. The ODAC does NOT provide a long note decay compared to a tube component. The last time I heard an ODAC it does NOT reproduce natural organic note decay from string instruments. Being "neutral" still is not the true representation of real life music that enters your ear. There is a reason why there is a draw to analog vinyl and tube equipment these days. Substantial money has to be spent on a dac to produce "vinyl" sound from a solid state device.


----------



## AlanU

castleofargh said:


> so your point against the O2 being transparent is that it is transparent. of course not everybody will like a neutral transparent sound, but what was said above is still true, if you really like the sound of one headphone, then you will like it with the O2 because nothing with change much.
> your preference for another source just shows that you like the sound of the headphone altered in a certain way. nothing wrong with that, but what @dazzerfong wrote still stands IMO.


 
  
 The price of the 02 is so inexpensive that it's worth a try to anyone interested in the headphone world. I'd be certain anyone listening to the 02 amp blindfolded would be amazed as you change source from dac to dac. It truly is a clean amplifier. 
  
 Changing headphones will make a huge difference in sound signature without a doubt. However there are many folks in the audio world that change dacs and preamps to manipulate the sound they want in their system.  There is not "Law" in how one's hobby is enjoyed 
  
 Dazzer is correct but only 1 variation in the vast choices in an audio rig. 
  
 If music is mastered and presents a very analytical sound this can possibly be fatiguing over a period of time. Extreme neutral sound can be both a blessing and a curse LOL!! I guess the ultimate goal is to appreciate and enjoy music and not analyze it  
  
 I guess this is where there is no right or wrong purchasing headphones to colour the music or tubes manipulating the source for adding the harmonics lost in translation. Colour is colour regardless where it's been added. I dont know many folks appreciating ultimate neutral sound praying that it's mastered in a musical manner. This all comes down to personal preference. 
  
 A partially ear damaged musician may appreciated a beyerdynamics headphone that presents brighter headphones. Again individuals ears is the judge.......


----------



## dazzerfong

alanu said:


> If you listen to many dacs you'll find that most will have a signature house sound. This is the reason there are so many different DAC's on the market. If they were all successful in producing a so called "neutral" sound there would be no point buying a $5000 dac over the "attempted" neutral sound of the odac. Most DAC's do a good job converting digital to analog but I guess it's not really that simple if sound quality is imperative.
> 
> Collectively everything matters. The 02 amp does a great job "making it louder". The point of tubes is to add pleasant distortion and overtones/harmonics solid state cannot produce (lost in translation as it was analog converted to digital in the studio) for the purpose of making it appealing to the human ear as natural (not hyper detailed). Tubes are not for everyone.....However I can make my tube dac sound solid state very easily by removing my tube rectifier with a solid state diode full rectifier replacement.
> 
> ...


 
 Yes, that's all fine and dandy, but you're missing the point of the O2/ODAC: it's to simply provide a sound that's as unaltered as one could get. So while it's true tubes provide a different sound due to different harmonics (easily visible in square wave tests), that's not the point of the O2/ODAC. If you think that 'organic note decay' is better with other DAC's, more power to you. But it's an addition to the source in the end, which is contrary to the point of the O2/ODAC.
  
 I've listened to quite a few DAC's though, and I struggle to hear the difference _unless there are additional 'bass-boost' filters_. Maybe I lack the golden ears that you have, but the whole point of DAC's isn't to alter the sound, but to provide the best (ie. accurate) conversion of digital to analog. Anything else is contrary to the point of an ideal DAC. That being said, if you don't like that, fair enough.


----------



## Draulius

I am looking to buy an O2+ODAC Combo. I noticed both JDS Labs and Mayflower Electronics manufacture one. The latter boasts a "Revision B" version with supposedly improved measurements and lower price. Of course if it were both better and cheaper I think there would be far more people purchasing it, so I'm curious.
  
 Is there any reason NOT to get the Mayflower Electronics O2+ODAC Combo (Rev. B) over the JDS Labs one?

 Thanks!


----------



## chuck8403

draulius said:


> I am looking to buy an O2+ODAC Combo. I noticed both JDS Labs and Mayflower Electronics manufacture one. The latter boasts a "Revision B" version with supposedly improved measurements and lower price. Of course if it were both better and cheaper I think there would be far more people purchasing it, so I'm curious.
> 
> Is there any reason NOT to get the Mayflower Electronics O2+ODAC Combo (Rev. B) over the JDS Labs one?
> 
> Thanks!


 

 I have one from both. They work the same and I believe both are now Rev. B. You may want to compare options and decide where you want the power port, location of the input and size of the headphone jack.


----------



## pearljam50000

Geek Out V2 vs O2/ODAC Rev B should be interesting


----------



## Draulius

chuck8403 said:


> I have one from both. They work the same and I believe both are now Rev. B. You may want to compare options and decide where you want the power port, location of the input and size of the headphone jack.


 
 Both are now Rev. B? Is there anything confirming this or should I toss JDS Labs an e-mail to make sure?


----------



## chuck8403

draulius said:


> Both are now Rev. B? Is there anything confirming this or should I toss JDS Labs an e-mail to make sure?


 

 Confirmed.
  
 http://blog.jdslabs.com


----------



## Draulius

Should I go for a front or rear mounted power jack? I'm not exactly sure which would be more convenient.


----------



## K_19

draulius said:


> Should I go for a front or rear mounted power jack? I'm not exactly sure which would be more convenient.




If you are going to use it mainly stationary then it should definitely go in the back, you'd ideally want as less of a clutter in the front as possible. I'd also suggest for any inputs/outputs to go in the back as well, if possible...

Front power jack and inputs/outputs made sense in a trans/portable O2 standalone setup as it made for more easier connection with various portable sources, but in a combo unit which you can't really use portably (as the ODAC takes up the battery space), it makes absolutely no sense to keep them in the front... that's unless you just really need to save money, but rear power jack option at least is so cheap that you're not really saving much there anyway (rear RCA's meanwhile can be a bit more costly).


----------



## SnufsHeadphone

Hey guys, I've got a few questions cuz I'm considering buying the o2 + oDac combo device to use with my laptop in order to hook 'em up to my Denon D5000's. 

 The first one concerns the configuration in Windows 8.1. I've read all kinds off stuff about WASAPI and ASIO for supposed 'bit perfect' output to USB. I currently use VLC to play all my files, basically only mp3 320 44.1khz and flac 16 bit 44.1khz.
 Should I install anything in order to provide a better digital source for the oDac? Is the vlc decoding sub-par compared to eg. foobar2000? Do I need foobar with WASAPI or asio4all etc...?

 Secondly, I'd like to know if there's any difference in performance when rear mounting the AC inlet? Couldn't find it.

 Lastly, how does the oDac part perform in combination with the rear mounted RCA's?


----------



## thecrow

snufsheadphone said:


> Hey guys, I've got a few questions cuz I'm considering buying the o2 + oDac combo device to use with my laptop in order to hook 'em up to my Denon D5000's.
> 
> 
> The first one concerns the configuration in Windows 8.1. I've read all kinds off stuff about WASAPI and ASIO for supposed 'bit perfect' output to USB. I currently use VLC to play all my files, basically only mp3 320 44.1khz and flac 16 bit 44.1khz.
> ...


According to John at jds labs, and others, the rca's make no audible difference. It's just about convenience.


----------



## AlanU

dazzerfong said:


> Yes, that's all fine and dandy, but you're missing the point of the O2/ODAC: it's to simply provide a sound that's as unaltered as one could get. So while it's true tubes provide a different sound due to different harmonics (easily visible in square wave tests), that's not the point of the O2/ODAC. If you think that 'organic note decay' is better with other DAC's, more power to you. But it's an addition to the source in the end, which is contrary to the point of the O2/ODAC.
> 
> I've listened to quite a few DAC's though, and I struggle to hear the difference _unless there are additional 'bass-boost' filters_. Maybe I lack the golden ears that you have, but the whole point of DAC's isn't to alter the sound, but to provide the best (ie. accurate) conversion of digital to analog. Anything else is contrary to the point of an ideal DAC. That being said, if you don't like that, fair enough.


 
 Dazzer, why so testy?
  
 Your extremely fortunate to hear very little audible differences between DAC's. If you listen to a pianist and then throw on a pair of headphones with an excellent recording with the ODAC as the source it is NOT a true representation of this "unaltered" sound your so defending regardless how well the music was mastered in the studio.  The sound you will have with the ODAC will have a shorter tail and "thinner body" and lack the longer tail "organic note decay" compared to higher end solid state dac's and tubes. Since you've never done such a comparison you truly have no basis to compare. It's not a matter of *"more power to me"*. If you've done an a/b comparison it would be very apparent. This is where I can see you've never dabbled in vinyl or tubes or more capable solid state dac's. 
  
 The Odac works fine but what does "unaltered" mean?? True to the mastered recording?  portray layers well defined? what kind of soundstage?  what you fail to hear is your benefit in the decent performing odac. There is a reason why folks move up the line in DAC's. It's not a matter of "sticking the nose up high" for prestige. It comes down to synergy and what provides a enjoyable musical experience that is non fatiguing. 
  
 At the end of the day it comes down to synergy. The headphones can paint colours to the music. Ideally the dac should be "text book perfect" but what you will find is  they will all have some characteristic  of some form of "house sound" who ever designs the solid state dac. Go ahead and borrow a Nad m51, Concero HD, Moon 300d or MK2, wyred4sound dac mk2 and you'll find they will all sound different with your 02/dac combo. 
  
 What's the difference between a dac that accentuates high/low
  
 OR
  
 changing headphones that are bright and bass heavy?? Note decay is something a transducer cannot randomly output unless the source or preamp attempts to provide natural representation of intimate vocals or strings etc. At the end of the day it's a matter of enjoying the hobby. No rules where you can add colour to the music.  If you want neutral and proclaim the ODAC as the ultimate "unaltering " source  why do you own so many headphones??????? Your still manipulating what the mastered source that was suppose to present to your ears....yet you own so many headphones. 
  
 If your into electronica this will be less critical but if your listening to jazz vocals and strings.......you cannot compare an Odac to other much pricier DAC offerings. 
  
 I can see your defending your gear but try to be more open minded.  The 02 amp is quite a trick pony for such a small package. IMO i find the components like the headphone jack, 3.5mm stereo source connector (RCA to 3.5mm jack on the earlier version) is not the highest in quality but it works. The amp has alot of clean neutral power. 
  
 Like I mentioned before I'd be just as happy using my 02 objective amp with tube dac/super rectifier and push my Burson virtuoso aside.  For the money I think the 02 provides ALOT for the money. As for the Odac......there's a tonne of other dac's out there.


----------



## JacobLee89

alanu said:


> Dazzer, why so testy?
> 
> Your extremely fortunate to hear very little audible differences between DAC's. If you listen to a pianist and then throw on a pair of headphones with an excellent recording with the ODAC as the source it is NOT a true representation of this "unaltered" sound your so defending regardless how well the music was mastered in the studio.  The sound you will have with the ODAC will have a shorter tail and "thinner body" and lack the longer tail "organic note decay" compared to higher end solid state dac's and tubes. Since you've never done such a comparison you truly have no basis to compare. It's not a matter of *"more power to me"*. If you've done an a/b comparison it would be very apparent. This is where I can see you've never dabbled in vinyl or tubes or more capable solid state dac's.
> 
> ...


 
  
 Now I've come across two different opinions: one of that the DAC being the least important link in the chain (as long as it does it well) up until you reach the $1k mark. As I've also read that bumping yourself up from an ODAC to an uber Bifrost (both upgrades) gives you very very slight audible improvement for quintuple the amount. This side also says that the AMP plays a far more important part in synergy with the headphones. Literally piling their heiarchy as thus: Headphones > Amp > DAC.
  
 The second are on the solid ground that even a $100 difference is a night and day difference, and is just as important as the headphones themselves.
  
 The middle ground doesn't seem to appear.
  
 So my one question would be: by pricier, how much pricier are we talking about? I've seen the same amount of reviews saying that the ODAC is just as good as the benchmark DAC 1, than the reviews saying otherwise.


----------



## James-uk

jacoblee89 said:


> Now I've come across two different opinions: one of that the DAC being the least important link in the chain (as long as it does it well) up until you reach the $1k mark. As I've also read that bumping yourself up from an ODAC to an uber Bifrost (both upgrades) gives you very very slight audible improvement for quintuple the amount. This side also says that the AMP plays a far more important part in synergy with the headphones. Literally piling their heiarchy as thus: Headphones > Amp > DAC.
> 
> The second are on the solid ground that even a $100 difference is a night and day difference, and is just as important as the headphones themselves.
> 
> ...




I own O2/odac combo and benchmark dac1 usb. They sound identical with my HD800 . The benchmark just brings dual headphone outs / optical in/ can be used with iphone as source. But for pure SQ THEY ARE IDENTICAL . Both completely transparent . If there was one moment that convinced me of transparency is was seeing these 2 completely different boxes of electronics sounding EXACTLY the same . It showed me that if it measures well it will sound the same regardless of price/ components /looks/ make / model etc. transparent is transparent and odac / O2 achieve this at a low cost .


----------



## sanakimpro

james-uk said:


> I own O2/odac combo and benchmark dac1 usb. They sound identical with my HD800 . The benchmark just brings dual headphone outs / optical in/ can be used with iphone as source. But for pure SQ THEY ARE IDENTICAL . Both completely transparent . If there was one moment that convinced me of transparency is was seeing these 2 completely different boxes of electronics sounding EXACTLY the same . It showed me that if it measures well it will sound the same regardless of price/ components /looks/ make / model etc. transparent is transparent and odac / O2 achieve this at a low cost .


 
 Thanks! My wallet thanks you.


----------



## James-uk

atoniolin said:


> Thanks! My wallet thanks you.




My wallet learnt the hard way. Glad to help someone else out


----------



## JacobLee89

james-uk said:


> I own O2/odac combo and benchmark dac1 usb. They sound identical with my HD800 . The benchmark just brings dual headphone outs / optical in/ can be used with iphone as source. But for pure SQ THEY ARE IDENTICAL . Both completely transparent . If there was one moment that convinced me of transparency is was seeing these 2 completely different boxes of electronics sounding EXACTLY the same . It showed me that if it measures well it will sound the same regardless of price/ components /looks/ make / model etc. transparent is transparent and odac / O2 achieve this at a low cost .


 
  
 Thanks for your clafication, I have always itched a bit for some DAC upgradetitus but have been reading a collection of contradicting points of views. Another consideration for myself is that I purely use USB as a source, therefore I cannot help but see additional input choices (TOSLINK etc.) as unnecessary addition to cost, which seems to happen often on many of the higher priced DAC offerings.
  
 For now I am using an ODAC and an amp (DIY SeNNator Project) filtered specifically to balance out the HD650, and it's a sound signature that I enjoy thoroughly. The O2 I have, I now use with a modded pair of T50RP's, it's uncanny how well the O2 works with those headphones.
  
 My wallet can rest a bit longer.. For now..


----------



## thecrow

No No No.
  
 i try to not get (too much) caught up in hype. and hoping not to sound like a tosser..............
  
 i have recently used the odac and o2 - i have no problem with either of them and particularly really like the value in the o2 - i think it's a fantastic buy
  
  
 however i also recently bought a used irdac which sells for about 2-3 times the price of the odac and their is a distinct difference between the irdac and the odac.
  
 they are not the same - if that is what is being implied here.
  
 (the odac sells for about $220 AUD and the irdac sells for $600)
  
  
 this does not make the odac any less in value for money but since buying the irdac the odac has been packed up (and is in fact in the classifieds)
  
 there is no necessity to upgrade from the odac but if you find a dac that suits you and your equipment at the right price there could well be a reason to upgrade when the timing is right
  
 with my hd800 the soundstage is more open and the sound is fuller/richer - no doubt about it
  
  
 btw i am not one that subscribes to "sorry for your wallet" thinking but i'm one who looks for bang for buck within a budget (well.....usually a bit more than my budget)
  
 cheers
 peter


----------



## James-uk

thecrow said:


> No No No.
> 
> i try to not get (too much) caught up in hype. and hoping not to sound like a tosser..............
> 
> ...




That dac is changing the sound somehow or you are imagining it. Maybe both. Either way, Which ever you think or decide sounds best will give you more enjoyment regardless.


----------



## thecrow

Yes. It's changing the sound. 
And I enjoy it for it.


----------



## AlanU

jacoblee89 said:


> Now I've come across two different opinions: one of that the DAC being the least important link in the chain (as long as it does it well) up until you reach the $1k mark. As I've also read that bumping yourself up from an ODAC to an uber Bifrost (both upgrades) gives you very very slight audible improvement for quintuple the amount. This side also says that the AMP plays a far more important part in synergy with the headphones. Literally piling their heiarchy as thus: Headphones > Amp > DAC.
> 
> The second are on the solid ground that even a $100 difference is a night and day difference, and is just as important as the headphones themselves.
> 
> ...


 
  
 The headphones is the most colourized component in the "mix".  This is where I would say has the most weight in the change in sound. That being said the 02 amp is quite remarkable regardless of price. When I bought my Burson Virtuoso I didn't think the amplification was a big deal. However the Burson amp presented a slightly more smooth refined sound coming from the same dac I was using (Burson DA160).  
  
 What I do find is that even in the $1000 price range of DAC's they all present in a different way. This is much more evident with a 2 channel because the "sound stage" and layers must fill the room.  I tested a my Audio Engine D1 DAC on my 2 channel and it was very "thin" which lacked body.  My Burson DA160 was noticeably better and more natural sounding especially with music with string instruments. However it was still lacking richness in body. This is not warmth I'm discussing. The body of the music still seems lacking. My Concero Hd was an insane hyper detailed extremely FAST dac but still did not have the organic long note decay you would hear in real life when it comes to piano.  The sound stage was also massive and almost artificial like my HD800. I spent aprox $3000+ on my tube dac with separate rectifier cct / power supply and my jaw dropped. Female vocals have never sounded so engaging with holographic realism that is not preset with the solid state cct's in my other DAC's. Listening to an ocean "meditation" music I find my tube dac completely utterly "real" while the other dac's I own provide the sound of waves with extreme detail with lack of engagement and natural sounds we hear in real life at the beach waterfront.
  
 I do find the 02 amp has been freakishly amazing compared to my amp section of my Burson Virtuoso. Souce is extremely important. I can see how some dac's can sound the same but if you throw on a wyrd4sound dac mk2 and Odac you'll probably notice that the wyred4sound dac is much more exciting and faster but IMO at the cost of long duration listening fatigue. Howerver it does come down to synergy too. Using my concero HD I can tolerate music longer with my hd650 but with my hd800 my ears would bleed with too much hyper detail.  
  
 I started with my AudioEngine D1 and it then became a serious quest for natural real sound. The most difficult part of SQ is the subjective discussion and impression. However "note decay" is something very evident that is either "there" or "not".  This is where music genre also makes a huge difference in how people subjectively compare things. Female vocals and strings instruments/trumpet and orchestra is something you can really start to hear a huge difference in "engagement". My electronica/ R&B  I can listen to my audio engine D1 all day long.


----------



## KeithEmo

dazzerfong said:


> Yes, that's all fine and dandy, but you're missing the point of the O2/ODAC: it's to simply provide a sound that's as unaltered as one could get. So while it's true tubes provide a different sound due to different harmonics (easily visible in square wave tests), that's not the point of the O2/ODAC. If you think that 'organic note decay' is better with other DAC's, more power to you. But it's an addition to the source in the end, which is contrary to the point of the O2/ODAC.
> 
> I've listened to quite a few DAC's though, and I struggle to hear the difference _unless there are additional 'bass-boost' filters_. Maybe I lack the golden ears that you have, but the whole point of DAC's isn't to alter the sound, but to provide the best (ie. accurate) conversion of digital to analog. Anything else is contrary to the point of an ideal DAC. That being said, if you don't like that, fair enough.


 
  
 Perhaps I should restate a point here that sort of gets lost in the shuffle.
  
 It's true that some DACs (and other equipment) are deliberately "voiced" to sound different from their competitors, and things like tube buffers usually add an easily audible coloration, but the differences between DACs that are really designed to sound neutral are _VERY_ subtle. These differences are often _MUCH LESS AUDIBLE_ than the differences between speakers, or between headphones, or between room treatments. (The fact that you "struggle to hear them" probably means that you shouldn't bother.)
  
 In audiophile land it's very easy to become obsessed with some particular flaw or shortcoming of a certain component - and to expend unreasonable amounts of time and money to correct that tiny flaw - when those resources could have made a much bigger difference somewhere else.
  
 A humorous analogy comes to mind. Imagine you and a friend walk into a room, decked out with oriental tapestries and rugs, in a variety of colors that clash widely - purple, red, green. The air is filled with smoke so you can barely see, and the smoke smells like it's probably not tobacco. There's loud music blaring, and a monkey in the corner is throwing fruit at you. (Think Indiana Jones meets I Dream of Jeannie....). You notice your friend standing in front of a small shelf on the wall, which is occupied by two six inch high vases - both sort of fancy looking. He indicates one of the vases and comments: "It's driving me nuts; the vase on the left is 18th century, and belongs in a museum, and the one on the right is a cheap 19th century knockoff; how can someone put them next to each other like that? It's just wrong."   Is he wrong? No; it's just a matter of focus and perspective.


----------



## AlanU

jacoblee89 said:


> Thanks for your clafication, I have always itched a bit for some DAC upgradetitus but have been reading a collection of contradicting points of views. Another consideration for myself is that I purely use USB as a source, therefore I cannot help but see additional input choices (TOSLINK etc.) as unnecessary addition to cost, which seems to happen often on many of the higher priced DAC offerings.
> 
> For now I am using an ODAC and an amp (DIY SeNNator Project) filtered specifically to balance out the HD650, and it's a sound signature that I enjoy thoroughly. The O2 I have, I now use with a modded pair of T50RP's, it's uncanny how well the O2 works with those headphones.
> 
> My wallet can rest a bit longer.. For now..


 
  
 Upgraditis is a bad thing but when the time comes you will have an uphill battle to make it a quest to find a dac that really satisfies your ears.  As far as the 02 objective amp is concerned....its scary good !! 
  
 The only reason I bought a new Burson Virtuoso was that I wanted a clean up my clutter on my desk witha chunk of aluminum. I use my onboard dac but I run it through a grant fidelity tube buffer.  That sound "good enough" for my headphone rig for now but it's not even remotely close to my Space Tech Labs tube dac with super rectifier. 
  
 If you look at the higher end Woo amps you'll see that they put the two units as a system. This separate unit provides much better SQ because there is two independant power supplies. My setup i am using 2 tubes for the rectifier cct.
  
 If your able to hear a difference between dac's you'll start to become more eager to find what your after. More lush mids? deeper lows? refined highs?  The mids is the sweet spot for many and this is where it can be "full" yet not too heavy. The ODAC is thinner in the mids but if you've never done an A/B comparison you may know where it lack until you do so. 
  
 Sure it's simple to say a dac is suppose to represent neutral. Sadly this is not the case from dac to dac. However the reason why many search for "synergy" is because they want to manipulate the "accurate source" and massage the music with a nice preamp and amp. 
  
 I approach my music with a tube dac source and then clean amplification with my two channel setup.  For my headphones I simply use a tube buffer with my burson virtuoso. Next thing will be a new set of headphones.  I have the first gen 02 jds objective so the front cable clutter was the reason I purchased a new amp. If it was gen two I would have held back on the purchase.


----------



## Draulius

I see the ODAC/O2 Combo advertised a lot with the DT880's being shown. I'm guessing there's a reason for this, and that the DT880's make a pretty good pairing?


----------



## sanakimpro

draulius said:


> I see the ODAC/O2 Combo advertised a lot with the DT880's being shown. I'm guessing there's a reason for this, and that the DT880's make a pretty good pairing?


 
 Well, I have exactly that pairing and it sounds great to my ears! With the DT 880s, it brings our the details in songs which I never knew were there even after listening repeatedly in the past. They don't seem to hide micro or macro details but present it there for you. 
  
 With the HD 600 and O2/ODAC, it brings a smoother sound with macro details being pulled forward and I enjoy it a lot and while micro details are present but you need to watch out for them. 
 It's like if you know its there, you can hear it, but if you didn't you might just pass over it without noticing.
  
 I'm sorry for a lack of a better way to describe them.

 In both cases, with the O2/ODAC at least my mind is at ease knowing that it's 'transparent' enough to give a fair comparison. And that, IMO, is what my amp and DAC should do. Either way, I love both the DT 880 and HD 600 on my O2/ODAC.


----------



## Draulius

atoniolin said:


> Well, I have exactly that pairing and it sounds great to my ears! With the DT 880s, it brings our the details in songs which I never knew were there even after listening repeatedly in the past. They don't seem to hide micro or macro details but present it there for you.
> 
> With the HD 600 and O2/ODAC, it brings a smoother sound with macro details being pulled forward and I enjoy it a lot and while micro details are present but you need to watch out for them.
> It's like if you know its there, you can hear it, but if you didn't you might just pass over it without noticing.
> ...


 
 I hear the HD600's are more open than the DT880's. Maybe that's why it's easier to miss micro details when listening to them?


----------



## JacobLee89

draulius said:


> I see the ODAC/O2 Combo advertised a lot with the DT880's being shown. I'm guessing there's a reason for this, and that the DT880's make a pretty good pairing?


 
  
 You definitely can't go wrong with an ODAC/O2 as a starting amp/DAC combo


----------



## sanakimpro

draulius said:


> I hear the HD600's are more open than the DT880's. Maybe that's why it's easier to miss micro details when listening to them?


 
 Technically DT 880s are semi-open, but I don't really notice a difference in sound stage size though. 
 Again, my comment is nothing bad about the HD 600. I still like it's different presentation. IMO more recently recorded pop songs target the macro details anyway. 
 But.. we might be derailing from the O2/ODAC subject  Sorry on my part.


----------



## Draulius

What kind of USB cable does the O2/ODAC Combo come with and need? Is it USB to Micro/Mini USB, or something else?

 Thanks.


----------



## sanakimpro

draulius said:


> What kind of USB cable does the O2/ODAC Combo come with and need? Is it USB to Micro USB, or something else?
> 
> Thanks.


 
 With mine from Epiphany Acoustics, it comes with USB to Mini USB.
 The EHP-O2Di model (O2 / ODAC combo) also has two rear RCA jacks which function as input/output.
 And of course it came with a AC-AC converter (wallwart).
  
 check it out here: http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/


----------



## JacobLee89

draulius said:


> What kind of USB cable does the O2/ODAC Combo come with and need? Is it USB to Micro USB, or something else?
> 
> Thanks.


 
  
 It comes with it's own cable bundled with the ODAC. That you don't have to worry about.
  
 If you're buying the O2 and ODAC as separate unites you will need a 3.5mm interconnect, or RCA to 3.5mm or Dual phono RCA depending on the type you bought.
  
 If you're buying the O2/ODAC combo unit, you only need the usb cable that came with it, and the wallwart.
  
 Of course, just as important: your headphones.


----------



## inseconds99

Am I crazy to consider getting the O2+oDac for HD800's? Tons of talk about how there is no "synergy" with the headphones and this dac/amp. Would I be better off with a modi 2uber and a vali or valhalla 2?


----------



## Draulius

jacoblee89 said:


> It comes with it's own cable bundled with the ODAC. That you don't have to worry about.
> 
> If you're buying the O2 and ODAC as separate unites you will need a 3.5mm interconnect, or RCA to 3.5mm or Dual phono RCA depending on the type you bought.
> 
> ...


 
  
 I was thinking about possibly getting a better cable for it though. That's why I was curious about what kind of USB cable it is. What kind of connectors are on each end? Is it a basic USB to USB, or USB to Micro/Mini USB? And yes I am getting the combo.


----------



## sanakimpro

draulius said:


> I was thinking about possibly getting a better cable for it though. That's why I was curious about what kind of USB cable it is. What kind of connectors are on each end? Is it a basic USB to USB, or USB to Micro/Mini USB? And yes I am getting the combo.


 
 Yes, in my case it is a typical one. The stock cable works fine and I think as long as I don't hear noise with mine, I'm okay.


----------



## sanakimpro

inseconds99 said:


> Am I crazy to consider getting the O2+oDac for HD800's? Tons of talk about how there is no "synergy" with the headphones and this dac/amp. Would I be better off with a modi 2uber and a vali or valhalla 2?


 
 I'm sorry but I can't help you with that. I have heard the HD 800 with the O2/ODAC for an hour.  And I'd say I liked the presentation. I'm not sure about 'synergy' with other amps though. I have only heard the T1 with other amps other than the O2/ODAC (Burson da-160, rudistor nx-03, A20 by beyer), and I still keep my O2/ODAC. IMO, it wasn't worth the upgrade fee. 
  
 Do let us know what you decide on, as I am considering a Valhalla 2 or LD to try the tube experience.


----------



## AlanU

inseconds99 said:


> Am I crazy to consider getting the O2+oDac for HD800's? Tons of talk about how there is no "synergy" with the headphones and this dac/amp. Would I be better off with a modi 2uber and a vali or valhalla 2?


 
  
 As far as amplification goes I'd say the 02 will do a fantastic job. If there is money to be spent I'd suggest spending a good budget on the dac. 
  
 What music genre do you typically listen to?
  
 The HD800's probably would appreciate some "body" from the source. Or some meaty harmonics from a tube amp. Many ways to approach this....... I've never auditioned the schiit products but I'd imagine the Hd800's would appreciate some high frequency roll of with tubes. Not sure if the schiit products really roll off the lows and high's like a tube amps from Woo.
  
 Cosmetically speaking I think the stack you can get from the schitt line (which ever you choose) is much more appealing with a tad better feel of quality.
  
 However I'd rather put more money towards the dac and run an inexpensive magni2 or 02 amp. Then later on decide what would be a good upgrade from there.


----------



## pearljam50000

Any O2 vs Asgard 2 comparison?


----------



## JacobLee89

draulius said:


> I was thinking about possibly getting a better cable for it though. That's why I was curious about what kind of USB cable it is. What kind of connectors are on each end? Is it a basic USB to USB, or USB to Micro/Mini USB? And yes I am getting the combo.


 
  
 To prevent confusion there's a huge difference between Micro, and Mini USB.
  

  
 The ODAC uses the Mini-USB plug socket.
  
 As for noise isolation, you could fare better by getting a powered USB hub instead of an audiophile grade USB cable. It would be cheaper.


----------



## AlanU

jacoblee89 said:


> To prevent confusion there's a huge difference between Micro, and Mini USB.
> 
> 
> 
> ...


 
 Uptone audio's usb REGEN seems to be an extremely interesting product.... I'll get one soon...


----------



## rick900

My sennheiser HD700 Headphones have a 6.3mm cable will using a 6.3mm to 3.5mm Grado cable reduce sound quality at all using the combo version?


----------



## inseconds99

rick900 said:


> My sennheiser HD700 Headphones have a 6.3mm cable will using a 6.3mm to 3.5mm Grado cable reduce sound quality at all using the combo version?




No


----------



## MrMateoHead

Isn't the headphone the biggest "wild card" in the chain of sound reproduction? Aside from the quality of the recording, I generally follow the simple rule of "want different sound get different speaker". But then again I lack $1,000s of dollars to experiment with different equipment choices.


----------



## James-uk

if you want the HD800 to sound exactly like the HD800 then the O2 /odac does that perfectly. If you want to somehow change the HD800 sound to suit a preference then it's open season, it's the Wild West , it's anyone's game and good luck to you and your wallet. Alternatively there is EQ . Ignore the Luddites that are stuck in the 70s and remember software is better than the hardware now so EQ IS the best/most accurate way to change/ alter/ improve/ the sound etc. more options exist than ever to achieve a perfect sound to you. My preference at the minute is iPhone as source(convenient) benchmark dac1 (because it accepts iPhone as source) into HD650(because it just sounds right most of the time without EQ to ME) my most accurate headphone is definately HD800 which sounds perfect from either odac/O2 or benchmark dac1. My taste however sways toward HD650 at the moment . Nobody can decide anyone else's taste for them but they can say without doubt that the O2/odac is perfectly transparent . The only decision to make therefore is which headphone is best and do I use EQ to 'correct ' that headphone to my taste .


----------



## dazzerfong

alanu said:


> Dazzer, why so testy?
> 
> Your extremely fortunate to hear very little audible differences between DAC's. If you listen to a pianist and then throw on a pair of headphones with an excellent recording with the ODAC as the source it is NOT a true representation of this "unaltered" sound your so defending regardless how well the music was mastered in the studio.  The sound you will have with the ODAC will have a shorter tail and "thinner body" and lack the longer tail "organic note decay" compared to higher end solid state dac's and tubes. Since you've never done such a comparison you truly have no basis to compare. It's not a matter of *"more power to me"*. If you've done an a/b comparison it would be very apparent. This is where I can see you've never dabbled in vinyl or tubes or more capable solid state dac's.
> 
> ...


 
A lot of theories and suppositions are thrown around. Like I said, if you don't like the ODAC, more power to you. I don't care what you like.
  
The problem with your theory on the pianist playing is that you're assuming your mic is perfect and so are the million variables out there. They're not, so your argument falls flat. Let's just agree to disagree on the impact here rather than you acting all high and mighty with your strawman argument of saying I'm defending my gear. If you don't like it, fine, but don't describe what it is for everyone else. The whole point of the ODAC/O2 is the minimise colouring as much as possible _of the source_. Some may like it, others may not. You find it unnatural: nothing wrong with that, but the problem with you saying that it's inaccurate because it doesn't alter anything is wrong.
  
For the record, I also have a WA7. I like it alongside the O2/ODAC, but I'll be damned if there's a huge difference between them. After all, I don't have golden ears like you do.
  
 I'll concede: no point ruining this thread over different philosophical approaches.


----------



## WilliamLeonhart

Has anyone tried the new Jds odac that no longer has nwaguy's name on it? Is it any better than the old one?


----------



## AlanU

Dazzer,
  
 When it comes to instrument note decay we can all hear this with our own personal ears in a lounge or concert. If you can recreate this note decay  with a dac in your living room with loud speakers or on a couch with headphones it becomes once again engaging. What you hear in real life and having it recreated in your "gear" is quite evident. 
  
 The word "neutral" is used in a very loose term. Hard to determine this "unaltering" because every "can" you own will paint a different colour to the music. We judge the sound quality as a collective system. At least I would imagine most hobbyists do not analyze with great detail the sound of headphones in a scientific manner.... unless your using HP to master an album. This is where you'd want very neutral sound with studio non musical monitors or very neutral headphones. 
  
 We all have a different approach in how we build our system's synergy.  In this hobby each and every headphone paints a totally different picture and in most cases far from neutral. 
  
 Throw on a pair of AKG 702, K612 pro and K812 and they all sound extremely different and to my ears have little "house sound" resemblance on the same exact amp/dac combo.
  
 I guess you can discuss things as you please. The bottom line is the collective group of components to achieve the synergy that is pleasing to our ears. There is absolutely NO rule in how you want to create this synergy by colouring source (house sound of different manufacturers dac's)  or changing the headphones. In the Hifi two channel world it's not uncommon for a person to buy the best dac they can afford and pair it with a tube preamp and solid state amp. Again no "rule" of how a hobbyist approaches his audio nirvana.
  
 Since the system is daisy chained to one another there will always be a weak link. 
  
 I would probably say if a hobbyist wanted to spend 1-2 grand on "upgraditis" urges - 2 things would come to mind for noticeable SQ differences. 
  
 1) New headphones !! changing the transducer will colour the music in the most drastic way.
 2)  New DAC.  I would probably say the DAC would be a tad more noticeable in SQ more than swapping from solid state amp to solid state amp (different case with many tube amps though). 
  
 Keep the Objective amp because it does a very good job in clean amplification but there is more refined smoother amplification offerings out there. No doubt there is a point of diminishing returns and finances is no business but for the hobbyist's pocket/budget. 
  
 The warm veil of the HD650 IMO has great synergy with the raw power of the 02 amp. This is an example of how the intimate HD650 can benefit from the 02 amp. In some cases using an extremely lush tube amp can possibly create a heavy syrupy sound. However the higher end tube amp you'd be able to roll tubes to create the sound you like.
  
 Many ways to skin a cat..... getting back to the topic of 02 and Odac I'd say it's a good combo. However the objective amp is more along the lines of  an "excellent" performer. As far as odac is concerned musical engagement I'd look elsewhere if your wanting intimate vocals and realistic note decay but at the cost of more $$$ for a dac.  I'd imagine you cannot recreate note decay in the headphones/speakers if it's not present in the source or preamp. You certainly will not get it from a solid state 02 amp.


----------



## castleofargh

williamleonhart said:


> Has anyone tried the new Jds odac that no longer has nwaguy's name on it? Is it any better than the old one?


 
 you have all the information you need here http://blog.jdslabs.com/?p=1003
 my perception of it was that I didn't need to "upgrade" as transparent is good enough for me.


----------



## JacobLee89

alanu said:


> Uptone audio's usb REGEN seems to be an extremely interesting product.... I'll get one soon...


 
  
 Almost twice the price of our forum's DIY alternative: the Doodlebug. Which makes me wonder about impedance matching at USB level. First time I've heard of this.
  
 Also I find it interesting that you call the HD650 being "Warm veiled". I would call it warm and veiled, but I feel that the warmth and the veil are distinct enough to be separate, definable characteristics of their own. I've also heard that the HD650 favors voltage over current, which I don't quite understand why, and I imagine that the O2 is just one of those amps that is capable of providing a bit of both. However, going into the HD650 thread you'll see just as many interesting viewpoints on this lovely oddball of a headphone.
  
 Back onto topic though. It would be interesting however, to see if there are any audible improvements by linking the USB REGEN to an ODAC. I can imagine very little audible improvements, but I am open to surprises.


----------



## castleofargh

jacoblee89 said:


> alanu said:
> 
> 
> > Uptone audio's usb REGEN seems to be an extremely interesting product.... I'll get one soon...
> ...


 

 for the hd650 favoring voltage over current, it's simply that it represents a 300ohm or more load. it's the same with any high impedance headphone the hd650 is nothing special on its own.
  
 about all the crap to improve usb, if people are really concerned about how good usb can be, then they wouldn't use usb in the first place. get a soundcard and a dac with a nice coax or some optical stuff, that's how you improve usb IMO.
 now back to the odac, I have never heard noises from sources with it, when I did on some of the other DACs I got in my hands(cheap stuff for the most). so while it's nothing scientific, it's good enough for me to believe I don't need to "improve" my usb.
 now if you go on the shiit topics, you see that several people heard noises, and using a wyrd or any nonsense stuff like that does seem to improve on noise for most of those cases.
 I read it as bad computer usb(try to get an usb card for 20$, or if voltage is the problem, get a powered hub also for about 20$), or as the DAC being crap(change DAC instead of trying to turn a donkey into a race horse). on the shiit topic they prefer to read is as amazing wyrd.
 take your pick, in a sense everybody's right.


----------



## sanakimpro

castleofargh said:


> for the hd650 favoring voltage over current, it's simply that it represents a 300ohm or more load. it's the same with any high impedance headphone the hd650 is nothing special on its own.
> 
> about all the crap to improve usb, if people are really concerned about how good usb can be, then they wouldn't use usb in the first place. get a soundcard and a dac with a nice coax or some optical stuff, that's how you improve usb IMO.
> now back to the odac, I have never heard noises from sources with it, when I did on some of the other DACs I got in my hands(cheap stuff for the most). so while it's nothing scientific, it's good enough for me to believe I don't need to "improve" my usb.
> ...


 
 I agree with you. I have never had any noise from the ODAC/O2 combo with any USBs. Once, there was no sound at all, but that turned out to be a shorted/burnt USB cable. Replacing it with another spare resolved the issue.


----------



## sanakimpro

james-uk said:


> if you want the HD800 to sound exactly like the HD800 then the O2 /odac does that perfectly. If you want to somehow change the HD800 sound to suit a preference then it's open season, it's the Wild West , it's anyone's game and good luck to you and your wallet. Alternatively there is EQ . Ignore the Luddites that are stuck in the 70s and remember software is better than the hardware now so EQ IS the best/most accurate way to change/ alter/ improve/ the sound etc. more options exist than ever to achieve a perfect sound to you. My preference at the minute is iPhone as source(convenient) benchmark dac1 (because it accepts iPhone as source) into HD650(because it just sounds right most of the time without EQ to ME) my most accurate headphone is definately HD800 which sounds perfect from either odac/O2 or benchmark dac1. My taste however sways toward HD650 at the moment . Nobody can decide anyone else's taste for them but they can say without doubt that the O2/odac is perfectly transparent . The only decision to make therefore is which headphone is best and do I use EQ to 'correct ' that headphone to my taste .


 
 I like and agree with your view. My approach is to keep the O2/ODAC and keep trying different headphones. It eliminates the need to worry about up-link / chain variables since I *assume* that the O2/ODAC is perfectly transparent (read the measurements by the designer and other enthusiasts).
  
 Especially as a student, but one who really enjoys his music, I can't say how much money this approach has saved me.


----------



## JacobLee89

castleofargh said:


> for the hd650 favoring voltage over current, it's simply that it represents a 300ohm or more load. it's the same with any high impedance headphone the hd650 is nothing special on its own.
> 
> about all the crap to improve usb, if people are really concerned about how good usb can be, then they wouldn't use usb in the first place. get a soundcard and a dac with a nice coax or some optical stuff, that's how you improve usb IMO.
> now back to the odac, I have never heard noises from sources with it, when I did on some of the other DACs I got in my hands(cheap stuff for the most). so while it's nothing scientific, it's good enough for me to believe I don't need to "improve" my usb.
> ...


 
  
 Eh. My next DAC might as well be a DIY one. DIYAH has some very fun looking projects anyhow.
 It's surprising how much use blu-tac has in soldering.


----------



## AlanU

atoniolin said:


> I agree with you. I have never had any noise from the ODAC/O2 combo with any USBs. Once, there was no sound at all, but that turned out to be a shorted/burnt USB cable. Replacing it with another spare resolved the issue.


 
  
 I basically use an inexpensive well rated Belkin Gold usb cable for both my 2 channel and headphone rig.
  
 I do however don't see a problem buying a "regen" for the sake of entertainment in this hobby.   
  
 Since I own the 02 amp with a 9volt in the unit I do assume there is more potential for less noise due to having an extremely clean DC source as I unplug my wallwart from the equation. Wallwarts are not really known to produce clean DC compared to a battery.
  
 For a while I was using my April Music stello u3 as a USB/spdif converter and that box literally made the sound "smoother/tubey" which at first threw me off. However using the Stello u3 to feed my DA160 Burson dac  > 02 objective amp the overall synergy was amazingly excellent. If I used my Concero HD as a USB/Spdif converter it suddenly became extremely neutral and almost on the side of cool but increased sound stage and more detail.
  
 Thing about this audio world is that the entertainment of searching for better SQ is at the cost of thinning the wallet. However every hobby seems to eat $$


----------



## KeithEmo

alanu said:


> I basically use an inexpensive well rated Belkin Gold usb cable for both my 2 channel and headphone rig.
> 
> I do however don't see a problem buying a "regen" for the sake of entertainment in this hobby.
> 
> ...


 
  
 A battery is not only cleaner than most line-powered power supplies, but with a battery you also avoid the potential for power supply ground noise, and minimize the chance of certain other types of ground loops.
  
 How adding a USB-to-S/PDIF converter to a DAC affects the sound depends mostly on the design of the DAC itself. If the DACs USB input is really good, then adding a converter with an equally good USB input won't help a bit. However, if your DAC is sensitive to jitter on its USB input (which many, especially older ones, are), then adding a converter that is less so can make a huge improvement. The purpose of the outboard converter is to correct a weakness in the DAC, so the results you get will depend on whether your DAC has that weakness to begin with and, if so, how well the outboard converter corrects it. (And there are a few converters out there that aren't themselves very good.)
  
 Also note that some "converters" also perform other alterations to the signal - like upsampling (which I personally prefer to avoid).
  
 However, you do need to be aware that some modern DACs have _BETTER_ USB inputs than some converters - in which case adding the converter may actually degrade their performance.


----------



## JacobLee89

Sometimes it feels like a discussion on electronics, and it's an amazing experience to see so many facets that surrounds this seemingly amorphous hobby.
  
 Would batteries suffer from voltage fluctuation once they fall below a certain capacity?


----------



## jseaber

jacoblee89 said:


> Sometimes it feels like a discussion on electronics, and it's an amazing experience to see so many facets that surrounds this seemingly amorphous hobby.
> 
> Would batteries suffer from voltage fluctuation once they fall below a certain capacity?


 
  
 Voltage will fluctuate from any source, given a change in current. In other words, voltage can fluctuate even from a full battery. 
  
 Designers expect power supply voltage changes. We add filters to ensure adequate ripple rejection at the amplifier


----------



## Draulius

I just got my ODAC/O2 in the mail. I set it up using the provided cable and power jack, then plugged my headphones in. I restarted my computer and went into my sound settings to make sure everything is in working order, which it should be. But when I play any audio it only comes out on one side of the headphones, the left. I checked the balance settings but both L and R are at 100.
  
 Anyone know what the issue might be?


----------



## sanakimpro

draulius said:


> I just got my ODAC/O2 in the mail. I set it up using the provided cable and power jack, then plugged my headphones in. I restarted my computer and went into my sound settings to make sure everything is in working order, which it should be. But when I play any audio it only comes out on one side of the headphones, the left. I checked the balance settings but both L and R are at 100.
> 
> Anyone know what the issue might be?


 
 Perhaps your TRRS connector is not compatible with the O2/ODAC? I use the two ring ones and they're ok.
 Else, perhaps contact the manufacturer and get a replacement, I guess.


----------



## Draulius

atoniolin said:


> Perhaps your TRRS connector is not compatible with the O2/ODAC? I use the two ring ones and they're ok.
> Else, perhaps contact the manufacturer and get a replacement, I guess.


 
 I'm connecting with a AD700 using its stock cable (3.5mm). It worked on the Schiit Fulla so I'm not sure why it wouldn't work with this. I did e-mail their support however.


----------



## sanakimpro

draulius said:


> I'm connecting with a AD700 using its stock cable (3.5mm). It worked on the Schiit Fulla so I'm not sure why it wouldn't work with this. I did e-mail their support however.


 
 Hmm, my friend experienced that with his Sony MDR 1RNC (3 rings at the jack), but solved it by wiggling the jack a but outward. Perhaps you can try that and see if that fixes it temporarily?
 Cheers!


----------



## KeithEmo

jseaber said:


> Voltage will fluctuate from any source, given a change in current. In other words, voltage can fluctuate even from a full battery.
> 
> Designers expect power supply voltage changes. We add filters to ensure adequate ripple rejection at the amplifier


 
  
 Exactly.
  
 And batteries can even produce noise - in the form of random hiss type noise.
  
 However, batteries pretty well never generate hum.... 
	

	
	
		
		

		
		
	


	



 And, since a battery doesn't require any sort of electrical connection "to the grid", it is the perfect "floating" supply.
 (Although that's not to say that a battery operated headphone amp or phono preamp can't pick up hum directly through the air or through it's interconnects.)
  
 Also, different types and capacities of batteries vary widely in terms of their output impedance.
 (AAA or 9V alkaline batteries aren't especially low in impedance, but some rechargeable LiIon ones are quite good, and small lead-acid cells are usually good.)


----------



## castleofargh

draulius said:


> atoniolin said:
> 
> 
> > Perhaps your TRRS connector is not compatible with the O2/ODAC? I use the two ring ones and they're ok.
> ...


 

 don't you have other headphones/IEMs, usually we all have at least some crap ear buds that came with some DAPs or cellphones. that way you can know for a fact if the problem comes from the DAC and send it back for repair/change.


----------



## Draulius

castleofargh said:


> don't you have other headphones/IEMs, usually we all have at least some crap ear buds that came with some DAPs or cellphones. that way you can know for a fact if the problem comes from the DAC and send it back for repair/change.


 
 It is a problem with the DAC. They are already sending a replacement.


----------



## Draulius

Is there any downside to having a 1/4in output on the ODAC/O2, like 1/4in adapters adding distortion?


----------



## chuck8403

draulius said:


> Is there any downside to having a 1/4in output on the ODAC/O2, like 1/4in adapters adding distortion?


 
 I personally don't believe that it adds any distortion. The 1/4" adapters stick out less than the 1/8" adapters.


----------



## adydula

No. Not really...
  
 A.


----------



## Draulius

Was thinking about using an adapter and connecting to a 1/4 in jack for extra sturdiness, instead of the traditional 3.5mm. Should I go for it?


----------



## inseconds99

draulius said:


> Was thinking about using an adapter and connecting to a 1/4 in jack for extra sturdiness, instead of the traditional 3.5mm. Should I go for it?


 
 Yes


----------



## dtmhtk

draulius said:


> Was thinking about using an adapter and connecting to a 1/4 in jack for extra sturdiness, instead of the traditional 3.5mm. Should I go for it?


 

 I would personally buy a Grado Mini Adaptor because I think it's easier to adapt down than up. However, it depends on how many headphones you have with quarter inch jack.


----------



## chuck8403

dtmhtk said:


>


 
 Agree with this adapter. I use the Sennheiser version.


----------



## Draulius

dtmhtk said:


> I would personally buy a Grado Mini Adaptor because I think it's easier to adapt down than up. However, it depends on how many headphones you have with quarter inch jack.


 
  
 None, I would be changing to a 1/4 in jack just for a sturdier connection. The only headphones I have are 3.5in native. I have an adapter for every one that I would have to use.


----------



## diamondears

I've read way back a comparison of portable amps with the O2 as the reference. Which portable amp came closest or equal to the O2? Anybody remembers?


----------



## headwhacker

diamondears said:


> I've read way back a comparison of portable amps with the O2 as the reference. Which portable amp came closest or equal to the O2? Anybody remembers?




If you are talking about the comparison published on inearmatters.net, I think the leckerton amp is the closest.


----------



## Draulius

Is it normal for an O2/ODAC Combo to make a popping sound through the headphones when the power button is pressed?


----------



## diamondears

headwhacker said:


> If you are talking about the comparison published on inearmatters.net, I think the leckerton amp is the closest.


 Thanks. Yeah I think that's it. Do you agree?


----------



## headwhacker

diamondears said:


> Thanks. Yeah I think that's it. Do you agree?




Yeah I sold all my portable amps except for the UHA-6S MKII.


----------



## HotIce

draulius said:


> Is it normal for an O2/ODAC Combo to make a popping sound through he headphones when the power button is pressed?



 

The O2 circuitry has no protection for that, so yes, it is expected.
Other amps, like the E12 (or the C5 mega clone of it) just as example, have delayed activation relays to protect against that.
No "pop" in the headphone, but little "click" in the amp.


----------



## MrMateoHead

draulius said:


> I just got my ODAC/O2 in the mail. I set it up using the provided cable and power jack, then plugged my headphones in. I restarted my computer and went into my sound settings to make sure everything is in working order, which it should be. But when I play any audio it only comes out on one side of the headphones, the left. I checked the balance settings but both L and R are at 100.
> 
> Anyone know what the issue might be?


 

 wiggle the connectors gently (at input / output) and then try the headphone itself. If that don't work disconnect and re-connect. If that don't work, try other 3.5mm cables / headphones.
  
 I find the 3.5mm connectors are a little cheap and I often have the L channel cut out and have to give mine a little wiggle every now and again.


----------



## sanakimpro

Does anyone have the O2/ODAC combo and the portable O2 (with batteries)? Is there a difference in the power output ? I recall reading that the gain on O2 with batteries is limited by the maximum voltage of the batteries.
  
 Currently with the O2/ODAC driving my beyer T1 on 2.5x gain, the dial is usually at 12 o'clock or 1 o'clock, and 3 o'clock on softer tracks (recorded in 1990s? like my Queen's Greatest Hits 1993 Remaster).
  
 Will the O2 with batteries still drive the beyer T1 (or HD 600, DT 990/600) properly?
 Thank you.


----------



## JacobLee89

atoniolin said:


> Does anyone have the O2/ODAC combo and the portable O2 (with batteries)? Is there a difference in the power output ? I recall reading that the gain on O2 with batteries is limited by the maximum voltage of the batteries.
> 
> Currently with the O2/ODAC driving my beyer T1 on 2.5x gain, the dial is usually at 12 o'clock or 1 o'clock, and 3 o'clock on softer tracks (recorded in 1990s? like my Queen's Greatest Hits 1993 Remaster).
> 
> ...


 
  
 The O2 in itself is still in the same casing as the O2/ODAC combo. The difference here is that the ODAC chip takes the place of the dual 9V battery placements.
  
 The two 9V batteries should give you more or less the same performance as it would plugged into a wall. Don't expect a long battery span though.


----------



## raoultrifan

atoniolin said:


> Does anyone have the O2/ODAC combo and the portable O2 (with batteries)? Is there a difference in the power output ? I recall reading that the gain on O2 with batteries is limited by the maximum voltage of the batteries.


 
 Hello,
  
 4.5V is max. output of O2 running on batteries, so should be enough to drive your T1.
  
 No matter the voltage of O2 (power adapter or batteries), the volume will remain unchanged, just distortions might increase if gain is set below 2.5X or input source voltage is much higher than 2V.
  
 Regards.


----------



## Thad-E-Ginathom

upstateguy said:


> The problem with cognitive bias is that it's not reliable.  One time it might help you enjoy your music and another time it may work the other way.  Anyway, it's only a hobby!


 
  
_Only a hobby?_
  
 I take my cognitive biases seriously. _Very_ seriously.


----------



## deaconblues

I just built myself an O2 with ODAC rev B, and I'm very happy with it.  It's just as capable of powering my HD600 as my M^3, but at the same time, it can also run IEMs with a totally quiet background.  I really appreciate its very neutral presentation.  The O2+ODAC simply takes a recording and tells it like it is.
  
 Actually, I built two O2s at the same time.  I put an ODAC in one for use as a desktop amp, and I configured the other one as a portable.  So now, I have a tiny desktop DAC/amp and a huge portable amp.  I actually regret making the second O2.  I should have paid more attention to how big it was.  Sure, it sounds fantastic, but I don't see myself carrying it around for portable use.


----------



## WilliamLeonhart

Leave 1 at work then. I'm still wondering if there's any way to make a O2+ODAC portable enough for mobile use...
  
 Does the ODAC rev B support USB OTG too? I have never seen anyone build a ODAC to use as the external DAC from their Androids


----------



## deaconblues

williamleonhart said:


> Leave 1 at work then. I'm still wondering if there's any way to make a O2+ODAC portable enough for mobile use...
> 
> Does the ODAC rev B support USB OTG too? I have never seen anyone build a ODAC to use as the external DAC from their Androids


 

 It doesn't work when I hook it up directly to my Android phone (the Oneplus One), but it works if I connect it to the phone via a USB hub.  The phone provides power to both the hub & DAC.  I don't need to use a separate power source.


----------



## JacobLee89

deaconblues said:


> It doesn't work when I hook it up directly to my Android phone (the Oneplus One), but it works if I connect it to the phone via a USB hub.  The phone provides power to both the hub & DAC.  I don't need to use a separate power source.


 
  
 Which probably means that the chipset on the DAC wasn't designed for phone use.
  
 I have a Fiio e18 and it has a switch that allows you to select between PC input and Phone input.
  
 Guess it's a price thing.


----------



## WilliamLeonhart

deaconblues said:


> It doesn't work when I hook it up directly to my Android phone (the Oneplus One), but it works if I connect it to the phone via a USB hub.  The phone provides power to both the hub & DAC.  I don't need to use a separate power source.


 
 I'm curious. Can you post a picture? So this means you can use the ODAC as the lineout for the phone?


----------



## castleofargh

deaconblues said:


> williamleonhart said:
> 
> 
> > Leave 1 at work then. I'm still wondering if there's any way to make a O2+ODAC portable enough for mobile use...
> ...


 
 is your direct connection to the phone done with an otg cable/adapter? or did you try with a random usb cable?


----------



## rick900

Anyone know if Epiphany Acoustics are shipping them with the revB board? I tried emailing them but its been a week with no reply?


----------



## Draulius

Can this power the DT880 600 Ohms quite well?


----------



## James-uk

rick900 said:


> Anyone know if Epiphany Acoustics are shipping them with the revB board? I tried emailing them but its been a week with no reply?




Yes they are. I received my ehp-o2di last week and it contains the Rev b. Even shows up on the dac list as odac revb on my MacBook Air.


----------



## rick900

james-uk said:


> Yes they are. I received my ehp-o2di last week and it contains the Rev b. Even shows up on the dac list as odac revb on my MacBook Air.


 
 Many thanks, placing my order now.


----------



## raoultrifan

draulius said:


> Can this power the DT880 600 Ohms quite well?


 
 Yes, it can power DT880/600ohms if you use a power adapter and not the batteries. Also, I strongly advise you to use a different gain resistor; something between 3.5X - 4.5X might be OK. For gains of 5X or higher you should replace the first stage opamp with something like LME49720, , LME49860, LM4562, OPA2227, MUSES02 etc.


----------



## JacobLee89

raoultrifan said:


> Yes, it can power DT880/600ohms if you use a power adapter and not the batteries. Also, I strongly advise you to use a different gain resistor; something between 3.5X - 4.5X might be OK. For gains of 5X or higher you should replace the first stage opamp with something like LME49720, , LME49860, LM4562, OPA2227, MUSES02 etc.


 
  
 That's where ADGR's output booster board comes in.


----------



## KeithEmo

atoniolin said:


> I like and agree with your view. My approach is to keep the O2/ODAC and keep trying different headphones. It eliminates the need to worry about up-link / chain variables since I *assume* that the O2/ODAC is perfectly transparent (read the measurements by the designer and other enthusiasts).
> 
> Especially as a student, but one who really enjoys his music, I can't say how much money this approach has saved me.


 
  
 That is an excellent modus operandi.....
  
 The differences in sound between various headphones are going to be _MUCH_ more obvious that the differences between headphone amps (at least if you're talking about neutral sounding solid state ones). And, while trying lots of headphones can be a bit expensive, find yourself a local headphone meet and you can try a good selection for free and see which ones you like before you buy them.


----------



## raoultrifan

jacoblee89 said:


> That's where ADGR's output booster board comes in.


 

 You're definitely right about this, Jacob. 
  
 Anyway, 7-8V is enough to drive DT880/600ohms and this can be achieved with a gain of 3.5-4.5X on O2.
  
 Note: When driving high impedance headphones with O2 the buffer/output stage opamps might get a bit warm (almost hot I'd say, something between 50-60C); same applies for the input stage opamp. Small heat-sinks (dedicated for opamps or DIY from regular aluminum staples) and double-side thermal conductive tape or Arctic Alumina Thermal Adhesive will resolve this.


----------



## deaconblues

castleofargh said:


> is your direct connection to the phone done with an otg cable/adapter? or did you try with a random usb cable?


 
  
  


williamleonhart said:


> I'm curious. Can you post a picture? So this means you can use the ODAC as the lineout for the phone?


 

 It works when I do Phone > OTG adapter > USB cable > USB hub > USB cable > ODAC
 A direct connection from Phone > OTG adapter > USB cable > ODAC does not work for me.
 This is not the case for all DACs.  I also have a y1 DAC, and it works perfectly well on my phone without having to hide behind a hub.
 My phone (Oneplus One) supports DAC output without needing any additional apps.


----------



## castleofargh

deaconblues said:


> It works when I do Phone > OTG adapter > USB cable > USB hub > USB cable > ODAC
> A direct connection from Phone > OTG adapter > USB cable > ODAC does not work for me.
> This is not the case for all DACs.  I also have a y1 DAC, and it works perfectly well on my phone without having to hide behind a hub.
> My phone (Oneplus One) supports DAC output without needing any additional apps.


 

 that's so weird. the hub is powered only by the phone yet that changes something. maybe the phone messes up something when it identifies the peripheral?
  wow. mind blown, I have no idea why this happens(of course it makes me twice as curious to find the answer).


----------



## deaconblues

I think the phone refuses to power the DAC if it asks for more current than what the phone's software allows.  Using the hub tricks the phone into providing power.  There is an article offering a more detailed explanation at JDS Labs http://blog.jdslabs.com/?p=838


----------



## sanakimpro

From what I've read on JDS's website, the ODAC Rev B has fixed reliability issues and 16/88.2kHz compatibility. My unit from Epiphany Acoustics bought last December has no problems at this stage like the USB issue, etc.
  
 Is there any audible difference between the O2/ODAC rev B with the original O2/ODAC?
  
 Thank you!


----------



## diamondears

draulius said:


> Is it normal for an O2/ODAC Combo to make a popping sound through the headphones when the power button is pressed?







mrmateohead said:


> wiggle the connectors gently (at input / output) and then try the headphone itself. If that don't work disconnect and re-connect. If that don't work, try other 3.5mm cables / headphones.
> 
> I find the 3.5mm connectors are a little cheap and I often have the L channel cut out and have to give mine a little wiggle every now and again.




My oldest O2 have this. I have to wiggle the connectors to resume sound. I found out that the problem is the thin wire (what's this for?) looped around the screw at the bottom of the O2. I suppose the screws loosened a little and the wire got unlooped on the screw. I just loosened the screws, re-looped the thin wire and made sure it got trapped by the screw. 

If this is your problem, it might solve both your issues.


----------



## WilliamLeonhart

deaconblues said:


> It works when I do Phone > OTG adapter > USB cable > USB hub > USB cable > ODAC
> A direct connection from Phone > OTG adapter > USB cable > ODAC does not work for me.
> This is not the case for all DACs.  I also have a y1 DAC, and it works perfectly well on my phone without having to hide behind a hub.
> My phone (Oneplus One) supports DAC output without needing any additional apps.


 
 Well at least it workds... But that's too cumbersome and (for me) defeats the purpose of connecting the DAC to the Phone


----------



## xxxfbsxxx

williamleonhart said:


> Well at least it workds... But that's too cumbersome and (for me) defeats the purpose of connecting the DAC to the Phone


 
 then use this http://www.ebay.com.au/itm/321540091516?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT 
 or try ebay with keyword "OTG injection power adapter"


----------



## MrMateoHead

diamondears said:


> My oldest O2 have this. I have to wiggle the connectors to resume sound. I found out that the problem is the thin wire (what's this for?) looped around the screw at the bottom of the O2. I suppose the screws loosened a little and the wire got unlooped on the screw. I just loosened the screws, re-looped the thin wire and made sure it got trapped by the screw.
> 
> If this is your problem, it might solve both your issues.


 

 Wow thank you for sharing this - I will pop open the case later on and see what I find. It would be great to get rid of my little "channel drop" issue as I adore this amp.


----------



## MrMateoHead

diamondears said:


> My oldest O2 have this. I have to wiggle the connectors to resume sound. I found out that the problem is the thin wire (what's this for?) looped around the screw at the bottom of the O2. I suppose the screws loosened a little and the wire got unlooped on the screw. I just loosened the screws, re-looped the thin wire and made sure it got trapped by the screw.
> 
> If this is your problem, it might solve both your issues.


 
 #1 Here is the small thin wire (sry my camera sux - a lot)
  
  
  
 Hard to make out, but this screw hole was obviously ground out - the small thin wire must be a chassis ground for the input connector.

  
 And for those that have not taken apart an O2 before, here is the 1/16 allen key for putting the volume knob back on. Make sure you allow a smidge of space between it and the faceplate, when I didn't, they ground together a bit. Also, I found that keep ALL screws loose until you had each screw started was a good idea, otherwise, they were not going in easy / straight.

  
 I didn't try THAT hard to place the wire onto the bare metal, bending it only slightly for better contact when the plate went back on. So far, it appears to have done the trick though - I've played with the input connector and, to my surprise, no channel cut outs. Unfortunately I noticed during this process that one of my batteries latches on to its connector well, and the other is quite loose. Seems a piece of foam or some sort of spacer might've been a good idea for these as the batteries may dislodge slightly when dropped. Later I'll probably shove some foam I have kicking around in there to provide a little support - unless someone tells me not to. Thanks Diamondears!


----------



## deaconblues

That little wire loop is just for connecting the amp's ground to the case in order to help reduce the chances of electrical noise.  I don't see how it could affect connectivity with the headphones and/or input jack.  The most likely scenario is that the cheapo jacks on the O2 are worn out.  This is especially likely if you are using a solid 1/4" to 3.5mm adapter.  That puts a lot of stress on the headphone jack.  I've ruined 3.5mm jacks with those things before.
  
 I'm currently using a Sennheiser 1/4" to 3.5mm adapter, which has a short length of wire between the 1/4" input and the 3.5mm output.  Hopefully this will never stress the headphone jack enough to cause connection problems.  If my headphone jack ever starts acting up, I'm gonna do some surgery and replace it with a  1/4" jack.


----------



## MrMateoHead

deaconblues said:


> That little wire loop is just for connecting the amp's ground to the case in order to help reduce the chances of electrical noise.  I don't see how it could affect connectivity with the headphones and/or input jack.  *The most likely scenario is that the cheapo jacks on the O2 are worn out.*  This is especially likely if you are using a solid 1/4" to 3.5mm adapter.  That puts a lot of stress on the headphone jack.  I've ruined 3.5mm jacks with those things before.
> 
> I'm currently using a Sennheiser 1/4" to 3.5mm adapter, which has a short length of wire between the 1/4" input and the 3.5mm output.  Hopefully this will never stress the headphone jack enough to cause connection problems.  If my headphone jack ever starts acting up, I'm gonna do some surgery and replace it with a  1/4" jack.


 
 No likely for me as I've only owned mine for about 2 years and rarely mess with the input or even switch out my headphones.


----------



## WilliamLeonhart

xxxfbsxxx said:


> then use this http://www.ebay.com.au/itm/321540091516?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
> or try ebay with keyword "OTG injection power adapter"


 
 THANKS! It's cheap too, seems great for my Nexus 7!
  
 But I'm using an iPhone too...


----------



## rick900

Hi guys bit confused here I ordered the o2/odac rev b combo and there is no usb port at all on the unit for the cable it came with, am I right in saying I have been sent only the amplifier? 
  
  
  
 http://imgur.com/sRmaCbV


----------



## schmalgausen

rick900 said:


> Hi guys bit confused here I ordered the o2/odac rev b combo and there is no usb port for the cable it came with, am I right in saying I have been sent only the amplifier?
> 
> 
> 
> http://imgur.com/sRmaCbV


 
  
 Try to search it on the backpanel.


----------



## rick900

schmalgausen said:


> Try to search it on the backpanel.


 
 There is nothing on the back so I am guessing I got sent only the amp?
  
 http://imgur.com/vElXryC


----------



## WilliamLeonhart

I think it's pretty clear. Have you tried contacting JDS yet?


----------



## rick900

williamleonhart said:


> I think it's pretty clear. Have you tried contacting JDS yet?


 
 Yeah.


----------



## schmalgausen

rick900 said:


> There is nothing on the back so I am guessing I got sent only the amp?
> 
> http://imgur.com/vElXryC


 
 99% there is no ODAC inside. Its USB socket exdends beyond the panel.


----------



## deaconblues

There should be a usb port on the back of the unit.  If there is no usb port, then there is either no odac.... or they accidentally installed a rear plate with no cutout for the usb port.


----------



## castleofargh

inputs are so 2014.


----------



## jseaber

williamleonhart said:


> I think it's pretty clear. Have you tried contacting JDS yet?


 
  
 The image does appear to be an O2, rather than O2+ODAC. It does not appear to be a JDS assembly.


----------



## K_19

That unit is an Epiphany Acoustics Model and not JDS Labs, and it is definitely the amp only model as it says EHP-O2. Their O2/ODAC model is called EHP-O2Di I believe.


----------



## sanakimpro

k_19 said:


> That unit is an Epiphany Acoustics Model and not JDS Labs, and it is definitely the amp only model as it says EHP-O2. Their O2/ODAC model is called EHP-O2Di I believe.


 
 Yes, I agree. I own the EHP O2-Di (O2/ODAC) with the original ODAC and on the front panel, there is a cursive 'EHP-O2Di'. According to the imgur picture, it is definitely the O2.
  
 In that case, I'd try to contact Oliver from Epiphany Acoustics by going to Contact on Epiphany Acoustics' website:
  
 http://epiphany-acoustics.co.uk/contact-us/ 
  
 (or drop his Headfi acc a message?) 
  
 Cheers. I've been using the EHP-O2Di without problems to power anything from ER4s to DT 990, 600 Ohm and it drives them effortlessly!


----------



## rick900

atoniolin said:


> Yes, I agree. I own the EHP O2-Di (O2/ODAC) with the original ODAC and on the front panel, there is a cursive 'EHP-O2Di'. According to the imgur picture, it is definitely the O2.
> 
> In that case, I'd try to contact Oliver from Epiphany Acoustics by going to Contact on Epiphany Acoustics' website:
> 
> ...


 
 Hi what is his username on here because I am not getting any response through email?


----------



## sanakimpro

I think it's this one: http://www.head-fi.org/u/277285/epiphany-oliver
  
 I just browsed the O2 forums and found it.


----------



## walbum4262

I'm thinking about getting the O2 as an amp for my aune t1 as I just got myself a pair of alpha primes that is measured at 47 ohm I think it was. And in the alpha prime thread people talk about them liking a good amp.

So my question is What would be the optimal gain selection be ? The standard 2,5x-6,5x ?


----------



## Draulius

When the volume control on my ODAC/O2 combo is very low (And I mean extremely low, maybe the first couple centimeters or so) most of the sound only comes out of the right speaker. Anyone know if this is normal?


----------



## K_19

draulius said:


> When the volume control on my ODAC/O2 combo is very low (And I mean extremely low, maybe the first centimeter or so) most of the sound only comes out of the right speaker. Anyone know if this is normal?




Perfectly normal for pretty much all amps of this price range actually. This is an issue with all potentiators in general unless you go with amps with stepped attenuators, which have perfect volume matching throughout.


----------



## thecrow

walbum4262 said:


> I'm thinking about getting the O2 as an amp for my aune t1 as I just got myself a pair of alpha primes that is measured at 47 ohm I think it was. And in the alpha prime thread people talk about them liking a good amp.
> 
> So my question is What would be the optimal gain selection be ? The standard 2,5x-6,5x ?




I had a similar question when I bought my Odac and O2 from Jdslabs. 

John told me that the gain options should primarily come down to the voltage of the dac/source. For the Odac tgey recommend the 1x/3.5x option. You can see a little info on the Jdslabs website when you customise your Odac and your at tge stage of choosing the gain option. There's a little write up there. 

However to confirm just email John at Jdslabs. His customer service is great. 

And if you're looking to buy from them don't forget about the free engraving they do.


----------



## Draulius

Which headphones would be a better choice for this DAC/Amp, the AKG K712 Pro or Audio-Technica ATH-AD2000?
  
 I'm guessing it's the former since people say it benefits more from an amp, and it's less sensitive so you get more room on the volume control. Am I right to think this?
  
 Not that either would sound bad with it, but I can only pick one.


----------



## JacobLee89

draulius said:


> Which headphones would be a better choice for this DAC/Amp, the AKG K712 Pro or Audio-Technica ATH-AD2000?
> 
> I'm guessing it's the former since people say it benefits more from an amp, and it's less sensitive so you get more room on the volume control. Am I right to think this?
> 
> Not that either would sound bad with it, but I can only pick one.


 
  
 The O2 is a very "plain" amp, but does this "plain" in the best possible way for such a price point. So the question is more of what type of sound are you looking for?
  
 As for sensitivity, do you mean how much power it requires? I ask this because the K712's are known to be pretty power hungry. If we're going by impedence, the K712's are 62 Ohms whereas the AD2000 are 40 Ohms. Lower resistance generally means higher sensitivity.
  
 That doesn't mean much since mine are HD650's, which are 300 Ohms, and still gets stupid loud at 12' oclock, with x1 gain on the O2.
  
 However, if you could only pick one. Go for the K712's , they work well across a variety of music.
  
 I would recommend trying other headphones out first before making such a decision. are there any local stores around where you can audition headphones?


----------



## AlanU

draulius said:


> Which headphones would be a better choice for this DAC/Amp, the AKG K712 Pro or Audio-Technica ATH-AD2000?
> 
> I'm guessing it's the former since people say it benefits more from an amp, and it's less sensitive so you get more room on the volume control. Am I right to think this?
> 
> Not that either would sound bad with it, but I can only pick one.


 
 The 02 amp can very likely comfortably run majority of the headphones on the market. So it can easily cause most to become hearing impaired as far as volume is concerned 
  
 Headphones are so incredibly personal that you must audition. Also bring along the music genre you prefer. Also note short duration auditions will not easily indicate if you'll have ear fatigue.  These are just some things to make a note of .......
  
 To my ears in general  I found the K712's over emphasizing the bass and treble. The mids were lost between the two. I do prefer the softer laid back presentation of the Hd650's. Ear fatigue is something you must really consider. However it all depends on your personal taste. 
  
 This amp is not forgiving so if your source is bad the 02 amp will reveal it. If your headphones have the characteristics of being bright the 02 amplifier will gladly pierce your ears. 
  
 The odac simply does the no frills conversion so it does it's task.  
  
 test the amp/dac combo with as many HP and determine the sound signature you like. As far as volume is concerned you will have little problems in that category.


----------



## wildwood88

Hi guys, I just bought hd600. My music source is basically from iPad Air 2 spotify premium. My question is do I need o2+ odac or just o2 amp is enough? I really no clue right now


----------



## HotIce

I don't think ODAC can decode the encrypted digital audio coming off an iPad Air 2 (one of my setups is like yours - iPad Air 2 with Spotify Premium).
I let the Wolfson DAC emit the line out via lightning to 30 pin cable, and feed that to an E12.


----------



## wildwood88

So u mean when you using iPad Air 2, u set with the Wolfson+E12 rattan O2 amp?


----------



## HotIce

The Wolfson is the DAC IC the lightning to 30 pin cable uses.


----------



## Draulius

jacoblee89 said:


> The O2 is a very "plain" amp, but does this "plain" in the best possible way for such a price point. So the question is more of what type of sound are you looking for?
> 
> As for sensitivity, do you mean how much power it requires? I ask this because the K712's are known to be pretty power hungry. If we're going by impedence, the K712's are 62 Ohms whereas the AD2000 are 40 Ohms. Lower resistance generally means higher sensitivity.
> 
> ...


 
  
 I've read that the Audio-Technica AD2000's color the sound quite a bit. I don't like headphones that are too colored because it can make them sacrifice compatibility with certain music. I'd like a more natural sound signature, but with a good soundstage, useful for music and movies. And it sounded like the K712 Pro would be best for this. I've heard about the highs being shrill with certain amps, the O2 may be one of them, but that it usually goes away after burn-in.
  
 I've used AD700's for years, which is considered a bright headphone, so I'd be surprised if I find these headphones fatiguing.


----------



## WilliamLeonhart

The shrills on my friend's K702 and Q701 never went away after burn in... AKG leans on being cold and analytical, and the O2 is too "plain" for me to enjoy with those cans. In fact I don't like those cans at all.

And these AKGs are really hard to drive... I've found them to be very amp-picky. My O2 doesn't do the job. However my (DIY) O2 is config-ed to be low-gain, I believe. I'm mostly using it with low-imp cans like Grado and ATH ADs.


----------



## AlanU

williamleonhart said:


> The shrills on my friend's K702 and Q701 never went away after burn in... AKG leans on being cold and analytical, and the O2 is too "plain" for me to enjoy with those cans. In fact I don't like those cans at all.
> 
> And these AKGs are really hard to drive... I've found them to be very amp-picky. My O2 doesn't do the job. However my (DIY) O2 is config-ed to be low-gain, I believe. I'm mostly using it with low-imp cans like Grado and ATH ADs.


 
 k812 is on my short list. Much more musical than my hd800 and more open than my hd650. 
  
 If you throw a tube amp at the akg headphones that'll tame those k702's / Q701's. Synergy is what  is the quest for musical enjoyment. This is a good example of how revealing 02 can pose a problem in matching components and headphones for musical bliss with NO ear fatigue.


----------



## Draulius

williamleonhart said:


> The shrills on my friend's K702 and Q701 never went away after burn in... AKG leans on being cold and analytical, and the O2 is too "plain" for me to enjoy with those cans. In fact I don't like those cans at all.
> 
> And these AKGs are really hard to drive... I've found them to be very amp-picky. My O2 doesn't do the job. However my (DIY) O2 is config-ed to be low-gain, I believe. I'm mostly using it with low-imp cans like Grado and ATH ADs.


 
 What kind of amp did you use for those headphones that had the shrill?


----------



## AlanU

draulius said:


> What kind of amp did you use for those headphones that had the shrill?


 
 I know this question isn't directed to me but I've tested  the k712, Q701 and k612  and I was using  Bellari HA540 and tidal music stream. It was a setup at a local headphone shop. They all presented high pitch using a class A tube amp. Then I did a bad thing and put on a pair of K812's. There was a world of a difference compared to the other 3. Granted it's worth the substantial $$$ for those HP in the AKG line.So far those are the only AKG I'd consider for open headphones.
  
 shrill wise I'd probably point fingers at the HP and DAC. The designer of the DAC can artificially increase sound stage and accentuate the high's and low's in cct design. The amp probably has the least  effect's on shrill. However whatever is in the chain of events has a cause/effect.


----------



## KeithEmo

alanu said:


> I know this question isn't directed to me but I've tested  the k712, Q701 and k612  and I was using  Bellari HA540 and tidal music stream. It was a setup at a local headphone shop. They all presented high pitch using a class A tube amp. Then I did a bad thing and put on a pair of K812's. There was a world of a difference compared to the other 3. Granted it's worth the substantial $$$ for those HP in the AKG line.So far those are the only AKG I'd consider for open headphones.
> 
> shrill wise I'd probably point fingers at the HP and DAC. The designer of the DAC can artificially increase sound stage and accentuate the high's and low's in cct design. The amp probably has the least  effect's on shrill. However whatever is in the chain of events has a cause/effect.


 
  
 I tend to disagree with your comment about the tube amp. Tube amps are specifically noted for changing the character of the sound you pass through them (much more so than solid state amps). And, in general, tube amps tend to "smooth the sound" and so to "remove shrillness" - at least to a degree. Therefore, I would expect the tube amp to "de-emphasize any shrillness that may be present in the headphones you're listening to".
  
 If you find a lot of AKG phones a little harsh or shrill, you might want to try a different brand - like HiFiMan's (planars tend to sound smoother and the opposite of shrill).
  
 Considering the relative costs, it probably makes more sense to select a set of headphones you like to begin with, than to select a set you don't entirely like, then go hunting for an amp that will alter them into something you do like


----------



## AlanU

keithemo said:


> I tend to disagree with your comment about the tube amp. Tube amps are specifically noted for changing the character of the sound you pass through them (much more so than solid state amps). And, in general, tube amps tend to "smooth the sound" and so to "remove shrillness" - at least to a degree. Therefore, I would expect the tube amp to "de-emphasize any shrillness that may be present in the headphones you're listening to".
> 
> If you find a lot of AKG phones a little harsh or shrill, you might want to try a different brand - like HiFiMan's (planars tend to sound smoother and the opposite of shrill).
> 
> Considering the relative costs, it probably makes more sense to select a set of headphones you like to begin with, than to select a set you don't entirely like, then go hunting for an amp that will alter them into something you do like


 
 Sorry I should have elaborated.
  
 I was getting the fatiguing highs while using the Class A amplifier. I should have stated that this is due to the Headphones and NOT the amp.
  
 I'm fully aware and appreciate the tube "roll off of freq" and change of holographic soundstage using tubes.
  
 Your logic makes full sense.


----------



## WilliamLeonhart

draulius said:


> What kind of amp did you use for those headphones that had the shrill?


 
 The DAC was either Aune T1 with stock tubes or ODAC. 
  
 The amp was some sort of DIY solid-state.
  
 I also remember listening to the K701 via a solid state amp that didn't give the shrill (based on exteriors alone I guess it was the LD MK5), but still it was way too cold and dry for my taste. Perhaps in term of cold-ness and dry-ness, I think the AKGs are only second to the DT880s.


----------



## MrMateoHead

keithemo said:


> I tend to disagree with your comment about the tube amp. Tube amps are specifically noted for changing the character of the sound you pass through them (much more so than solid state amps). And, in general, tube amps tend to "smooth the sound" and so to "remove shrillness" - at least to a degree. Therefore, I would expect the tube amp to "de-emphasize any shrillness that may be present in the headphones you're listening to".
> 
> *If you find a lot of AKG phones a little harsh or shrill, you might want to try a different brand - like HiFiMan's (planars tend to sound smoother and the opposite of shrill).*
> 
> Considering the relative costs, it probably makes more sense to select a set of headphones you like to begin with, than to select a set you don't entirely like, then go hunting for an amp that will alter them into something you do like


 
 As an owner of O2 / ODAC / HE-400s (velour or modded pads), I should note that any "shrilliness" or harshness/thinness to the sound is typically related much more to the recording than to the equipment in question, in my experience over a couple years. The setup is very unforgiving and the HE-400s "treble" seems to be one of the main "controversies" for users, some finding it a little peaked and others finding it harsh or sibilant. Any issue with treble (and I tend to think ringing is the main problem) almost disappears when using the velour earpads (which improve the sound a lot but change the overall character a bit, with bass that is less warm).
  
 I haven't hear other Hifiman phones, but I assume the 5XX series and 400i's are probably a lot smoother with the same great speed.


----------



## Irenicus87

Would the O2+ODAC be a significant improvement over the Asus Xonar Essence STX? In other words, would it be worth it? Or would it be better to get a standalone amp instead because the STX dac may be good enough?


----------



## castleofargh

irenicus87 said:


> Would the O2+ODAC be a significant improvement over the Asus Xonar Essence STX? In other words, would it be worth it? Or would it be better to get a standalone amp instead because the STX dac may be good enough?


 

 depends on what headphone you use. the STX measures pretty well if I remember the right model (ST is the basic stuff and STX the better one right?).
 when I was looking into it, I think I gave up because the output impedance was 10ohm and I have a bunch of IEMs. but else everything seemed fine for most situations on that soundcard, even the power output.


----------



## Irenicus87

castleofargh said:


> depends on what headphone you use.


 
 Sennheiser HD 800.
  
 And yes, I know many here are gonna tell me I need a dac+amp for ~2000$ but I can't afford that at this time, so I'm looking for something cheaper like O2+ODAC to have a decent sound until I can get higher end dac+amp. The STX doesn't really do it, I mean it's okay at the mid impedence setting, but just lacks substance and also sounds somewhat harsh in the treble, not sure if that comes from the amp or dac. Also please don't tell me to get other (cheaper) headphones, that's out of the question.


----------



## dazzerfong

irenicus87 said:


> Sennheiser HD 800.
> 
> And yes, I know many here are gonna tell me I need a dac+amp for ~2000$ but I can't afford that at this time, so I'm looking for something cheaper like O2+ODAC to have a decent sound until I can get higher end dac+amp. The STX doesn't really do it, I mean it's okay at the mid impedence setting, but just lacks substance and also sounds somewhat harsh in the treble, not sure if that comes from the amp or dac. Also please don't tell me to get other (cheaper) headphones, that's out of the question.


 
 If you want to tame the HD800's brightness, the O2/ODAC would be the opposite of what you'd want: perhaps a tube amp for the tubey mellow sound. If, however, you like the sound to be clean and unadulterated, the O2/ODAC is your guy.


----------



## Bibo

irenicus87 said:


> Would the O2+ODAC be a significant improvement over the Asus Xonar Essence STX? In other words, would it be worth it? Or would it be better to get a standalone amp instead because the STX dac may be good enough?


 
 The dac of the STX is good, no need not replace it with an ODAC IMO. I use a Titanium HD as dac together with an O2 amp and i am very satisfied. But my headphones are all much warmer sounding than HD800s. So I would look for a warmer sounding amp and keep the STX for now if I were you.


----------



## Irenicus87

dazzerfong said:


> If you want to tame the HD800's brightness


 
 No, that's not what I meant. I love their basic sound signature, else I wouldn't have bought them. I sampled them in 2 different stores previously and they didn't have that harshness like with the STX there. One had the Yamaha AS 700 (no headphone amp) and one had the Lehmann Audio Linear, which was much better. Is the latter considered neutral or warm? Seemed neutral to me. I definitely don't want to color the sound.
  
 Generally, what would be more important to improve the sound? Dac or amp? According Bibo and also other people on here, the STX dac is quite good, so maybe I'll start with just an external amp and later get an external dac. Good idea?


----------



## AlanU

irenicus87 said:


> No, that's not what I meant. I love their basic sound signature, else I wouldn't have bought them. I sampled them in 2 different stores previously and they didn't have that harshness like with the STX there. One had the Yamaha AS 700 (no headphone amp) and one had the Lehmann Audio Linear, which was much better. Is the latter considered neutral or warm? Seemed neutral to me. I definitely don't want to color the sound.
> 
> Generally, what would be more important to improve the sound? Dac or amp? According Bibo and also other people on here, the STX dac is quite good, so maybe I'll start with just an external amp and later get an external dac. Good idea?


 
  
 Source is always king. I'd concentrate of a good dac and hope the amplifier does it's job in somewhat neutral amplification.
  
 The 02 amp does a great job especially at it's price point.
  
 In the $2000 CDN  dollar range I have yet to hear a sweet MIDS/ meaty DAC that provides holographic realistic sound when I compare it to my space tech labs tube DAC.
  
 I'm quite sensitive to shrill and high's and my HD800's did acceptably well with my burson da160 with 02 amp. Adding my Grant fidelity tube buffer made a smoother presentation that with added realistic "meat" to the mids that made female jazz vocals much better in SQ. My approach was that the 02 dac can pretty well run most headphones on the market and it amplifies my manipulated "source".
  
 What I love about the HD800's is that it's a great headphone that I can manipulate. When I experimented by adding my tube dac with additional rectifier unit to my 02 dac the sound quality was unreal. If I wanted more grunt and tighter bass I'd simply swap my tube buffer to a 6550 or kt66. If i wanted sublime vocals I'd use a 6L6GC tube. The sound quality with this inexpensive 02 amp shocked me. Removing the 02 amp from the equation and just using the amp section in my Burson Virtuoso was slightly better but no where near the $2000 price tag of the Burson. By swapping tubes you are NOT limited in manipulating the sound.....unless you want to own a handful of solid state dac's. IMO no solid state dac can excel in every music genre. Tube configurations you can drastically change the sound by rolling tubes. 
  
 People can read the forums and drink koolaid all day long. You must experiment to satisfy your ears.
  
 In my particular setup I would have used my $1000 burson da160, Grant fidelity tube buffer and 02 amp and had absolutely incredible enjoyment. I really dislike most solid state dac's (aprox $2000 +) presentation in music but that's my preference.
  
 I would not buy new amp until your extremely happy with your source.


----------



## Irenicus87

AlanU, thanks for the input, but how would I change the dac but still use the amp with the STX card? I doubt that's possible. So either I replace both or only the amp by something external.
  
 edit: I guess you meant the O2+ODAC
  
 And anyway, I basically only came for a simple answer to the question whether the O2+ODAC is better than the STX (both as dac and amp), anyone here who has compared them?


----------



## castleofargh

your card seems to measure just fine and should already be mostly transparent if not totally so. trying to improve on transparent may not be audible be it on DAC or amp part. just check that you get enough power from your soundcard for the hd800 and that's about it.
 what AlanU is explaining is more about coloring the sound than going for high fidelity. his system might very well measure worst than your soundcard because of that. not saying it's bad or wrong, just that he talks about getting closer to his taste, not closer to fidelity.


----------



## AlanU

irenicus87 said:


> AlanU, thanks for the input, but how would I change the dac but still use the amp with the STX card? I doubt that's possible. So either I replace both or only the amp by something external.


 
 I'm not familiar with the STX card. There is always excitement when purchasing gear. 
  
 If I made a far fetched assumption I'd imagine just buying a single 02 amp with your onboard pci DAC would sound decent.  The DAC world seems to have similar good sound characteristic in the the sub $1000+ mark. Dac's are extremely personal.
  
 Generally speaking I almost find most sabre dac chips have a sound signature that does not suite my music genre. The sweet mids seems thin.
  
 I've heard decent realistic meaty vocals with the inexpensive Bellari ha540 amp. It sounds decent with added colour to the music. The Bellari took the edge off of the high's but of course there's always better out there.
  
 Test  your headphones with as many amps/dacs as you can. Even my Burson Virtuoso 1793 dac i prefer to  listen to it through my tube buffer to add meat to the vocals. I'd rather manipulate the source and run a solid state amp. I will be buying another tube dac down the road and possibly buy a woo tube amp. To be honest my tube buffer with vintage sylvania's 6sn7 is making my current burson combo extremely pleasing. Without a lie the 02 amp is equally as good. Only when I use my Space tech tube dac with super rectifier  I top the performance.
  
 Specs of components is not the "end all be all". The human ear can determine what sounds "natural" and "just right" even though some information is lost in the translation. Speaking to musician friends they look at this hyper detail dac's unrealistic. Stuff we discuss/debate on headfi is quite opposite to a musician playing live music. Natural sound in a venue is "real'. This is where I feel just listening to music that just "sounds right" to your ears is basically quest we simply need to find......not hearing every single details of the ventilation fan or toe tap in a recording. I find too much detail actually a distraction. Again.....everyone is different.


----------



## AlanU

castleofargh said:


> your card seems to measure just fine and should already be mostly transparent if not totally so. trying to improve on transparent may not be audible be it on DAC or amp part. just check that you get enough power from your soundcard for the hd800 and that's about it.
> what AlanU is explaining is more about coloring the sound than going for high fidelity. his system might very well measure worst than your soundcard because of that. not saying it's bad or wrong, just that he talks about getting closer to his taste, not closer to fidelity.


 
 so very true regarding colouring the sound.
  
 When a person purchases a dac they are basically seeking a colourized interpretation of what the "designer" provides in a finished product. I wont even get into cabling as an addition to change sound signature 
  
 Dacs can sound close to one another but I often find that one will "sound" different to our human ear.
  
 Regardless of 2 channel or headphones we are all seeking pleasing sound to our ears. That is in fact looking for media translated to analog music to your ears. This is all colourized to a certain extent and also how the music is mastered.
  
 With my 2 channel and my tube dac setup I cant transform my system to sound perfect for classic rock, piano, strings, accapella, electronica fast beat to female jazz vocals. With a solid state dac you cannot roll of the highs and provide meaty vocals then suddenly change the "house sound" to meet upbeat fast precise beats for electronica. This where I'm quite surprised my Totem Earth speakers can do well in a wide variety of music. It can be fast and with tubes I can lay back the music with finesse. My totem forests could not match the speed of some electronica. But this is why I've been looking for a solid state dac to match more of the electronica side of my music even though swapping to kt66 or 6550 tubes can keep up with electronica. 
  
 I find the HD800's an extremely versatile headphone in that I can lay it back or make it perform dynamically. This is where the source can be an "equalizer" in how you want to translate the music. The soundstage is quite large with the Hd800 but with tubes i can almost create an HD650 sound signature just by swapping tubes. The Hd650 does have an intimate smaller sound stage with heavy tones. Oddly I cannot get the meaty vocals from an hd650 using a Concero sabre HD dac even though the HD650 is a rich lush sounding headphone.
  
  My 02 amp does a good job in amplifying the source. This is where I manipulate the source to match the timbre of the music. Seems human ears love overtones and compression. I'm always looking for something pleasing to my ears........


----------



## KeithEmo

alanu said:


> so very true regarding colouring the sound.
> 
> When a person purchases a dac they are basically seeking a colourized interpretation of what the "designer" provides in a finished product. I wont even get into cabling as an addition to change sound signature
> 
> ...


 
  
 I don't disagree with anything you've said - but I do think you're totally ignoring another option.... plain old digital editing. What you're doing is essentially establishing a collection of "EQ presets" (each of your separate pieces of equipment creates a certain set of colorations). It seems to me that buying a new piece of equipment "every time you want to add a preset" is the long - and expensive - way around. With a digital editor, you can do the same thing, except that you can have an unlimited number of options, and pretty much an unlimited amount of control over each. In fact, you can set a general EQ in your player for all 'electronica' songs, and a different one for "vocals" - or you can adjust certain favorites individually - and simply save the edited copy to play next time.
  
 Assuming your goal is to create a pleasant set of colorations, it seems to me that a relatively simple and economical product like Izotope Ozone gives you more flexibility and options than a whole warehouse full of different DAcs and amps - and for a lot less money.
  
 (Of course, that would eliminate the fun of playing with the equipment)


----------



## upstateguy

keithemo said:


> I don't disagree with anything you've said - but I do think you're totally ignoring another option....* plain old digital editing*. What you're doing is essentially *establishing a collection of "EQ presets" *(each of your separate pieces of equipment creates a certain set of colorations). It seems to me that buying a new piece of equipment "every time you want to add a preset" is the long - and expensive - way around. With a digital editor, you can do the same thing, except that you can have an unlimited number of options, and pretty much an unlimited amount of control over each. In fact, you can set a general EQ in your player for all 'electronica' songs, and a different one for "vocals" - or you can adjust certain favorites individually - and simply save the edited copy to play next time.
> 
> Assuming your goal is to create a pleasant set of colorations, it seems to me that a relatively simple and economical product like Izotope Ozone gives you more flexibility and options than a whole warehouse full of different DAcs and amps - and for a lot less money.
> 
> (Of course, that would eliminate the fun of playing with the equipment)


 
  
 +1  EQing. 
  
 Why not start with the foobar plugins and equalizer, saving each equalizer preset as you go. 
  
 In no time at all you will have a colorized setting that suits your taste for any music you want to listen to and the best thing about it is that you can uncheck the "equalizer enabled" box any time you want and hear the difference your EQ has made, or, turn it off and listen to the sound of your headphone with uncolored music.
  
 And you can do this with the card you have without spending any money at all.
  
 Edit to say:  (Of course, that would eliminate the fun of buying and playing with the equipment)


----------



## Bibo

castleofargh said:


> your card seems to measure just fine and should already be mostly transparent if not totally so. trying to improve on transparent may not be audible be it on DAC or amp part. *just check that you get enough power from your soundcard for the hd800 and that's about it.*
> what AlanU is explaining is more about coloring the sound than going for high fidelity. his system might very well measure worst than your soundcard because of that. not saying it's bad or wrong, just that he talks about getting closer to his taste, not closer to fidelity.


 
 I think this may be the point. The headphone amp actually is a single chip (TI6120A2). It can put out 189mW max into 300 Ohms IIRC. The HD800 can take up to 500mW.
 The DAC chip (TI Burr Brown PCM1792A) is used in high-end dacs >$1000 like the Antelope Zodiac or the Luxman DA200.
 So maybe you should try a dedicated amp first with the stx as dac. You can always get a dac too if the amp alone does not do the trick. You would need the amp anyways if you go for an external dac.


----------



## HotIce

102db/Vrms @ 500mW is almost certain deafness.
500mW is the top power handling for the HD 800.


----------



## Bibo

I did not want to say that it does not get loud enough in general. But the HD800 have an impedance reaching from about 300 Ohms in the treble region up to more than 600 Ohms at 100Hz. An amp must be able to handle this. And a less powerful amp that is near its limits might not be able to reach the desired volume at 600 Ohms while it does at 300 Ohms at the same time. And what you get then is a HD800 with a harsh treble.
But I am just guessing, I neither own the STX nor the HD800s.


----------



## castleofargh

bibo said:


> I did not want to say that it does not get loud enough in general. But the HD800 have an impedance reaching from about 300 Ohms in the treble region up to more than 600 Ohms at 100Hz. An amp must be able to handle this. And a less powerful amp that is near its limits might not be able to reach the desired volume at 600 Ohms while it does at 300 Ohms at the same time. And what you get then is a HD800 with a harsh treble.
> But I am just guessing, I neither own the STX nor the HD800s.


 
 it's late and I'm a little drunk, but I still feel like I should disagree with most of this.
 I don't know how the soundcard behaves into 600ohm, but in theory, we go with 10ohm into 300ohm and then 10ohm into 600 at other frequencies. the difference in loudness won't be much with that damping ratio, and wouldn't more power be actually needed into the 300ohm part of the frequencies from more current?


----------



## Bibo

castleofargh said:


> it's late and I'm a little drunk, but I still feel like I should disagree with most of this.
> I don't know how the soundcard behaves into 600ohm, but in theory, we go with 10ohm into 300ohm and then 10ohm into 600 at other frequencies. the difference in loudness won't be much with that damping ratio, and wouldn't more power be actually needed into the 300ohm part of the frequencies from more current?


 
 As I said I am just guessing and I am no expert by any means. Actually I learned the technics behind headphone audio from people like you here on head-fi. So what I say now also might be BS...
 But if you where right in this case wouldn't it  be easier then to drive headphones the higher their impedance is???
 I do not know if Ohm's law applies here but if it does than you get half the current if you double the resistance and keep the voltage constant. And you need double the voltage to get the same current.


----------



## dazzerfong

bibo said:


> As I said I am just guessing and I am no expert by any means. Actually I learned the technics behind headphone audio from people like you here on head-fi. So what I say now also might be BS...
> But if you where right in this case wouldn't it  be easier then to drive headphones the higher their impedance is???
> I do not know if Ohm's law applies here but if it does than you get half the current if you double the resistance and keep the voltage constant. And you need double the voltage to get the same current.


 
 Impedance governs voltage division only. Basically, when you deliver power to headphones, you need sufficient current _and_ voltage to drive headphones. Hence the sensitivity measurement: x dB/mW, with mW being a function of voltage multiplied by current. Once you pass the impedance part, all the headphone cares about is the power.


----------



## WilliamLeonhart

Sold my DIY O2+ODAC (made from boards from JDS) the other day, since it was, well, ugly. Today I went to buy the "EHP-O2Di" from Epiphany, which is practically the O2+ODAC rev B, thinking (and secretly hoping) it would sound as good as my old one.
  
 I was in for a surprise.
  
 My PS500 (with Grado G cushs) always sound a bit too bassy, its mids a bit too recessed for my liking. In face, since the PS500 was not designed with G cushs in mind, sometimes it makes the singer sounds like they're covering a bit of their noses. With the new Epiphany O2+ODAC, these flaws almost completely disappreared. On most songs, the vocals sound very natural. The bass has become very clean and punchy. 
  
 I have not spent much time with my new O2+ODAC, but I can say that it is a huge improvement from my old one. 30 or 40%, perhaps. It could be the build quality, or it could be the new ODAC. Anyway I'm very happy now.


----------



## JacobLee89

williamleonhart said:


> Sold my DIY O2+ODAC (made from boards from JDS) the other day, since it was, well, ugly. Today I went to buy the "EHP-O2Di" from Epiphany, which is practically the O2+ODAC rev B, thinking (and secretly hoping) it would sound as good as my old one.
> 
> I was in for a surprise.
> 
> ...


 
  
 Almost sounds like you had USB issues, considering that the ODAC Rev.b is designed to improve upon it's USB interface moreso than the choice of DAC chip.


----------



## KeithEmo

jacoblee89 said:


> Almost sounds like you had USB issues, considering that the ODAC Rev.b is designed to improve upon it's USB interface moreso than the choice of DAC chip.


 
  
 A difference in sound could definitely be USB-related. The original 0DAC _DIDN'T_ have an async USB input; presumably the logic was that, since the Sabre DAC chip they used had internal jitter reduction, it wasn't necessary to tightly control jitter at the USB input itself. NwAvGuy mentions in his original description of the original 0DAC that he thinks async USB is unnecessary, even though "with adaptive USB the jitter will depend on the PC or other source". (With an async USB input, the DAC clocks the data from the computer, and so the jitter present on the input depends solely on how good a job the DAC does, and should be immune to things like differences in cables and USB ports. With an adaptive USB input, the jitter at the input depends on various things - including the jitter at the PC itself, and even the quality of the USB cable itself - all of which _CAN_ affect the audio quality.)  
  
 However, the new RevB version of the 0DAC no longer uses the Sabre DAC, so presumably it is now necessary to do a better job of avoiding jitter at the input (I don't think the new TI DAC they use has jitter reduction internally like the Sabre). I don't know if the new version is still adaptive USB, or if they've moved up to async - since they don't seem to mention it either way on the spec sheet.


----------



## WilliamLeonhart

I don't know much on technical details, so I just suppose any problems with my old ODAC (which was minimum, actually) only came from the lousy DIY build quality. In fact throughout my time with that one, I never had jitter or noises from the DAC.


----------



## Thenewguy007

Can someone help?
 I'm getting so many different suggestions & reviews that I can't seem to get a straight answer.
  

 Looking for a amp, maily for my Sennheiser HD600 (also for Fidelio X1 & a AD700).
 Is the O2 powerful enough to drive it?
 Is the O2 a step down from the Asgard 2 amp or equal to it?
   
People have told me yes & no to both questions.

 They also mentioned the Aune T1 mk2 & Little Dot Mk3 will blow away the O2 for amp use.
 Would that be a fair assessment?


----------



## headwhacker

thenewguy007 said:


> Can someone help?
> I'm getting so many different suggestions & reviews that I can't seem to get a straight answer.
> 
> 
> ...


 
  
 It's confusing isn't it? That's the problem with this hobby. People have different "OPINION" about the same things. There are usually 2 camps/school of thought with regards to selecting an amp to drive a particular headphone.
  
 1. Subjective/play it by ear - compare 2 amps by listening with each using your choice of headphone. People judge which amp is more powerful by the position of the volume knob. Then there's the individual's personal perception (e.g. tigher/bigger bass). Then select the amp which pairs/sounds better based on that perceptions.
  
 2. Objective/measurements - Look at the specs (provided the specs published are accurate) or take basic measurements ( like voltage ouput, current etc) and calcluate the SPL in dB (how loud the amp can drive the headphone without distortion). Now, this is a bit tricky different people have different perception on how loud is loud enough. But the generally accepted max level is 120dB (threshhold of pain). Anything louder than that is considered bad. At this level our ears should only be exposed very briefly.
  
 Now, if option 2 makes sense to you then O2 is powerful enough for all the cans mentioned above. However, if you believe option 1 is the way to go then there is no other way than to go out and try it yourself first before you make any purchase. Subjective opinions are very personal and what you hear does not necessarily means the same thing to me.
  
 Sorry if this makes you more confused.


----------



## Bibo

thenewguy007 said:


> They also mentioned the Aune T1 mk2 & Little Dot Mk3 will blow away the O2 for amp use.
> Would that be a fair assessment?


 
 This may only be true for use with the Sennheisers. The Fidelio X1s will need an amp with a low output impedance as they easily become uncontrolled and boomy in the lower frequencies if the output impedance of the amp is too high (See: Impedance mismatch, low damping factor).
 The mentioned amps are both tube amps with higher output impedance.
  
 The 02 works very well for me with the X1s and it is by far powerful enough, even at 1x gain.


----------



## Thenewguy007

Do the O2 have enough power to drive the HD600 or would they still be lacking compared to amps at the same price range?
 I heard people say the Magi2 have more power thus drive the HD600 better.


----------



## upstateguy

thenewguy007 said:


> Can someone help?
> I'm getting so many different suggestions & reviews that I can't seem to get a straight answer.
> 
> 
> ...


 
  
  


thenewguy007 said:


> Do the O2 have enough power to drive the HD600 or would they still be lacking compared to amps at the same price range?
> I heard people say the Magi2 have more power thus drive the HD600 better.


 
  
 the O2 is cheap and transparent.  It has more than enough power to drive 701s, 600s, 650s, 880s and T-1s.  just get one and start from there.


----------



## Danpyre

Does the O2 get hot at all? I'm l going to attempt the 3D print it, and use some kind of plastic. Is that a horrible, horrible idea?


----------



## WilliamLeonhart

I have some bad news. Very bad news.
  
 The other day I was sharing my impression on the O2Di from Epiphany. I couldn't be any happier with it.

  
 However yesterday I found out that my O2Di has some problems. Perhaps I should list it out for the sake of easier reading:
 - With ODAC on (USB plugged in): From the forward Output port (see the pic above) which is from the O2, I suppose, it gives perfect sound quality with hi-gain OFF.
 - However with hi-gain on (still feeding from the integrated ODAC), the sound has a lot of jitter. Small popping noise, especially when the bass is decaying.
 - ODAC only (unplugged the power and use the RCA as output): the bass is muddy and extended unaturally. It also has a bit of jitter, but not as severe as above.
 - O2 only (power plugged, RCA input) with hi-gain ON or OFF: no jitter at all.
  
 Can anyone here please speculate the problem for me? I can't send this unit to the UK right now, and the most perplexing thing is that some function of it is still working well.


----------



## WilliamLeonhart

danpyre said:


> Does the O2 get hot at all? I'm l going to attempt the 3D print it, and use some kind of plastic. Is that a horrible, horrible idea?


 
 From my experience with my previous O2 (DIY from JDS boards), it does get a bit hot, but nothing too bad. I think it was around 30 - 40 degrees celsius.


----------



## headwhacker

williamleonhart said:


> I have some bad news. Very bad news.
> 
> The other day I was sharing my impression on the O2Di from Epiphany. I couldn't be any happier with it.
> 
> ...




How much is the gain on high? The rev 2 ODAC has a higher output (2.1Vrms).


----------



## diamondears

O2 clips when total resulting gain exceeds 7V. This is why they recommend 1x/3.5x gains...perfect for 2V DACs.


----------



## WilliamLeonhart

According to the specs:
 http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/
  
 Hi-gain is just 3.3X. Meaning they're not over 7V yet.
  
 Also the RCA out (from ODAC) has bad bass quality and jitters (clipping?).
  
 However when I plug my tube amp (the LD I+ with JAN 6AK5 tubes or Mullards CV4010) into the O2 line out , the sound is just fine.


----------



## jseaber

williamleonhart said:


> According to the specs:
> http://epiphany-acoustics.co.uk/products-page/dacs/ehp-o2di-desktop-headphone-amplifierdac-3/
> 
> Hi-gain is just 3.3X. Meaning they're not over 7V yet.
> ...


 
  
 Not sure what you mean by "jitter" here (maybe clipping)? We've had the chance to inspect wiring for all manufacturers, and each has their own method. You're most likely experiencing double-loading of the amp or DAC. Check with the manufacturer and they should be able to clarify how to properly connect equipment for their specific configuration.


----------



## K_19

williamleonhart said:


> I have some bad news. Very bad news.
> 
> The other day I was sharing my impression on the O2Di from Epiphany. I couldn't be any happier with it.
> 
> ...


 
  
 Not sure what you mean by "Jitter", there's no consensus at all on what Jitter actually sounds like... I'm guessing you mean clipping.
  
 If so, you may want to contact Epiphany and make sure if it really is their NEW version; if it is clipping at high gain then it's very possible that you may have the_ older _version of this unit which came with 1x low gain and *5x* *high gain* by default.


----------



## HotIce

Never liked the O2 volume potenziometer after the VAS stage, and never will.
You can be listening music at 60db, and have clipping on it, because the hard coded gain of the VAS stage is not right, or it was right, but the source output level changed.
Whereas, in saner audio circuitry design, you are lead to clipping in a much smoother fashion, and with that typically happening at pretty high sound pressure levels (unless amps are under-powered WRT speakers).


----------



## jseaber

hotice said:


> Never liked the O2 volume potenziometer after the VAS stage, and never will.
> You can be listening music at 60db, and have clipping on it, because the hard coded gain of the VAS stage is not right, or it was right, but the source output level changed.
> Whereas, in saner audio circuitry design, you are lead to clipping in a much smoother fashion, and with that typically happening at pretty high sound pressure levels (unless amps are under-powered WRT speakers).


 
  
 Yes, O2 is best paired with a known source voltage and proper gain, so that clipping cannot occur. O2+ODAC @ 1.0/3.3x gain is a reliable combination.


----------



## WilliamLeonhart

Hi,
  
 Thank you all for your replies. Once again head-fi has proved itself as the most helpful community that I've ever joined.
  
 I remember having the tech specs sheet in the box, but if my memory proves to be right then the gain number is not provided in the sheet. I have not received Epiphany's reply to my question (sent via their Contact Us page). I should send them an email or a Facebook message.
  
 Regarding the "jitters" on my O2Di, they are actually small and continuous popping sound. On Gunshot by Lykke Li (the vid below), it is most severe during the chorus. It does NOT happen constantly, on certain songs or certain passages it's barely noticeable.
  
 The previous owner said that they were shipped to Vietnam in April. So I can't tell if my model is O2Di with ODAC rev B or the original. I was under the impression that O2Di is with the rev B one, but I was wrong. The previous owner also seems to have purchased the default option (he doesn't seem to know much about gain when I talk about it).
  
 Anyway, the problem happens even on my 120-ohm K612, so I don't know if it's clipping or not. Also, the RCA output is rather dismal (bass too soupy, tiny popping noise also happens) when connected to my Little Dot I+ with JAN 6AK5 tubes (also on low gain).


----------



## K_19

williamleonhart said:


> Hi,
> 
> Thank you all for your replies. Once again head-fi has proved itself as the most helpful community that I've ever joined.
> 
> ...




  
 I'm quite confident in that case that your combo unit probably has the Epiphany's old default gain of 1x and 5x. I do know for sure that their change in default gain setting was a very, very recent thing, I'm quite sure it was still that was as late as March/April as I recall I was checking their pages at the time.
  
 If you want to find out what your DAC revision is you can probably dig deeper through your media player's source options or the control panel to find out what that is. The old chip is the ESS9023 chip and the newer one would be the PCM (5102A?) chip.


----------



## WilliamLeonhart

This is the tech specs. there's no gain specification


----------



## WilliamLeonhart

k_19 said:


> I'm quite confident in that case that your combo unit probably has the Epiphany's old default gain of 1x and 5x. I do know for sure that their change in default gain setting was a very, very recent thing, I'm quite sure it was still that was as late as March/April as I recall I was checking their pages at the time.
> 
> If you want to find out what your DAC revision is you can probably dig deeper through your media player's source options or the control panel to find out what that is. The old chip is the ESS9023 chip and the newer one would be the PCM (5102A?) chip.


 
 Thanks. Actually the DAC revision is not quite important anymore, but the jitters really bug me. Pardon my ignorance, but at 5x gain, will my O2Di _always_ suffer from clipping? Will the impedance of the phones play any role in preventing?


----------



## dazzerfong

williamleonhart said:


> Thanks. Actually the DAC revision is not quite important anymore, but the jitters really bug me. Pardon my ignorance, but at 5x gain, will my O2Di _always_ suffer from clipping? Will the impedance of the phones play any role in preventing?


 
 Unfortunately, no: the output is already clipped. Having a higher impedance just scales the voltage down all linearly, clipped or otherwise. You can try soldering a new resistor on the board so the gain is 3x or whatnot.
  
 However, you can try turning down the volume from your source: that way, your DAC won't output as many volts into your amp.


----------



## raoultrifan

danpyre said:


> Does the O2 get hot at all? I'm l going to attempt the 3D print it, and use some kind of plastic. Is that a horrible, horrible idea?


 
 Hi there, 
  
 I strongly recommend you to get a decent aluminium case, most of all because the case should be properly grounded and it acts like a shield.
  
 Regards, 
 Raul.


----------



## WilliamLeonhart

dazzerfong said:


> However, you can try turning down the volume from your source: that way, your DAC won't output as many volts into your amp.


 
 Wow I didn't think of this. How stupid of me.
  
 I will report the result in a few hours. Thanks for all your advice.


----------



## dazzerfong

williamleonhart said:


> Wow I didn't think of this. How stupid of me.
> 
> I will report the result in a few hours. Thanks for all your advice.




Don't sweat it mate: hope it turns out all good for you!


----------



## diamondears

williamleonhart said:


> Thanks. Actually the DAC revision is not quite important anymore, but the jitters really bug me. Pardon my ignorance, but at 5x gain, will my O2Di _always_ suffer from clipping? Will the impedance of the phones play any role in preventing?


Why do you need a high gain btw?


----------



## diamondears

williamleonhart said:


> Wow I didn't think of this. How stupid of me.
> 
> I will report the result in a few hours. Thanks for all your advice.



Many sources gives up bits when you turn the volume down.


----------



## WilliamLeonhart

diamondears said:


> Why do you need a high gain btw?


 
 For the K612. I'm under the impression that the K612 sounds more open on high gain than on 1X. In the past I had the K601 as well, and my old DIY O2 drives it better on 3.5X.
  
 If high gain _always_ makes the ODAC + O2 clips, then why did Epiphany create it that way... I'm buffled. I remember JDS' O2 also has hi-gain options. How could the O2 drives the HD650 if not on high gains?


----------



## headwhacker

diamondears said:


> Many sources gives up bits when you turn the volume down.


 
  
 I think the ES9023 uses 32 bits internally for volume control. Then it should not afffect anything other than raising the noise floor. which way too low to be descernible.


----------



## dazzerfong

diamondears said:


> Many sources gives up bits when you turn the volume down.


 
 Yep, but unless you're on XP, you're fine as your OS will output a 32-bit signal. Noise floor will raise, of course, but who cares when it's inaudible to begin with?


----------



## diamondears

williamleonhart said:


> For the K612. I'm under the impression that the K612 sounds more open on high gain than on 1X. In the past I had the K601 as well, and my old DIY O2 drives it better on 3.5X.
> 
> If high gain _always_ makes the ODAC + O2 clips, then why did Epiphany create it that way... I'm buffled. I remember JDS' O2 also has hi-gain options. How could the O2 drives the HD650 if not on high gains?


 
  
 2Vrms (most DACs) x 3.5x gain=7Vrms is a LOT, unless your headphone is the HiFiMAN HE-6.
  
 The high gain is very useful for sources with low output, such as iPhone and other mobiles which has more or less 1Vrms...so 6.5x gain is perfect for them.
  
 IMHO, if the HP specs demands only the low gain, yet the sound changes using the high gain option, the output impedance varied. Some amps lower the gain by increasing output impedance, which, as we know, tweaks the SQ; this is why the high gain sounds better in this case (lower output impedance).


----------



## WilliamLeonhart

Now I'm wondering WHY Epiphany (and other companies) would integrate the ODAC and O2 this way... Also, when I put the JDS ODAC and O2 boards into the same unit, it didn't have this problem. 
  
 Why
  
 Oh
  
 Why
  
 Could be just a faulty unit, though.


----------



## Danpyre

raoultrifan said:


> Hi there,
> 
> I strongly recommend you to get a decent aluminium case, most of all because the case should be properly grounded and it acts like a shield.
> 
> ...



Darn XD
I'm going to see if I can start DIY audio, so I was seeing how cheaply I could get away with it.
Thanks.


----------



## castleofargh

williamleonhart said:


> Now I'm wondering WHY Epiphany (and other companies) would integrate the ODAC and O2 this way... Also, when I put the JDS ODAC and O2 boards into the same unit, it didn't have this problem.
> 
> Why
> 
> ...


 

 it has been answered like 15times at least in that very topic. it's of course explained on nwavguy's blog too. the gain setting is by default to adapt to the source on this amp(portable stuff often deliver 1V or less, while home systems usually have DACs in the 2 to 3V max), not so much to adapt to the headphone. you're most likely responsible for your clipping because you're using a setting you have no reason to use.
 if you can't bother to learn how to use your system looking up the specs of each components(something I really can understand), then just go with the rule of thumb saying that the lowest gain is more suitable unless you need to go louder.


----------



## castleofargh

danpyre said:


> raoultrifan said:
> 
> 
> > Hi there,
> ...


 

 how much the amp will heat up depends entirely on the headphone that will be used. in most cases it does not get warm TBH, but depending on the headphone that can happen.


----------



## MrMateoHead

I have that lykke Li Song - I will run it through audacity later to check for clipping IN THE TRACK. I hear clicks and pops through O2/HE-400s and once thought one or the other was exploding. Nope.
  
 You may have merely noticed a recording-level flaw.
  
 OK screw waiting, I put it in and, yup, the track has some clipping in it, particularly around the 2:30-3 minute mark in the R channel. I've seen worse but that there might be enough to hear a some unpleasant noises. Too bad, because like a lot of CDs, she was one of my recent favorites.


----------



## WilliamLeonhart

Guys I've never been in love with headfi as I am right now! It's all fine after I turn the volume on Windows to 45%. I feel that I need to update my audio knowledge immediately, so perhaps I'll spend more time on the nwaguy blog right now


----------



## castleofargh

williamleonhart said:


> Guys I've never been in love with headfi as I am right now! It's all fine after I turn the volume on Windows to 45%. I feel that I need to update my audio knowledge immediately, so perhaps I'll spend more time on the nwaguy blog right now


 

 looking that on my laptop, 45% is -11.8db(I changed the unit with a right clic like a boss ^_^)
 now switching from 1X to 3.3X that's about +10.4db. you see where I'm going here? 
	

	
	
		
		

		
			




  
  
@jseaber while trying to look for some specs on the revB in case lehoang was somehow reaching the limits with the K612. after all that thing seems a little horrible to drive, worst than an audeze http://www.innerfidelity.com/images/AKGK612.pdf  I noticed that on the rev B combo dac/amp you still give the same power output with different loads as nwavguy(for 33 and 150ohm at least), except that the default gain values are now different.
 I'm very aware that you're doing epiphany's customer service when you try to help here, but because you're always so reliable, we now count on you for everything ^_^.
  
 oh well, akg writes:  Max. Input Power 200 mW  on the specs of the k612... does that mean the headphone summons armageddon in a wild explosion after we pass 115db with it? @lehoang15tuoi how about selling that headphone?  that would solve a bunch of problems. (ok I know the way out, I'm leaving now... bubye..)


----------



## Danpyre

Would it work if I made the bottom of the case metal, but the rest of it some kind of plastic?


----------



## jseaber

castleofargh said:


> looking that on my laptop, 45% is -11.8db(I changed the unit with a right clic like a boss ^_^)
> now switching from 1X to 3.3X that's about +10.4db. you see where I'm going here?
> 
> 
> ...


 
  
 Gain of 1.0/3.3x is slightly rounded (try to find resistors that give exactly 7.0/2.1=3.33x gain). Actual gain is slightly higher.
  
 Also, the O2 amplifier specifications are published separately from the DAC. It's possible to reach published Max Power = 613mW at 32 ohms with an O2+ODAC RevB:
  
 P = ((gain*Vsource)^2) / 32 = (3.3*2.1*3.3*2.1)/32= 1500 mW...
  
 O2 is current limited here, so max power is unchanged at ~600mW.
  
 Max output is about 7.0VRMS from O2+ODAC, yielding:
  
 Max power @ 600 ohm = 82 mW
 Max power @ 150 ohm = 327 mW
  
 O2 can achieve 7-8% more voltage with slightly higher gain, or stronger analog input. This is a small amount since volume increase are perceived on a logarithmic scale.
  
 AKG K612 Pros are rated 92 dB/mW @ 120 ohm. Tyll's measurements show about 90dB/mW, so slightly more demanding than AKG's own spec.


----------



## castleofargh

oh yeah, I didn't think current was the limiting factor and stayed focused on voltage and power alone for some reason. that sure explains it all, thanks you for the clean explanation.


----------



## diamondears

williamleonhart said:


> Guys I've never been in love with headfi as I am right now! It's all fine after I turn the volume on Windows to 45%. I feel that I need to update my audio knowledge immediately, so perhaps I'll spend more time on the nwaguy blog right now



Your K612 doesn't get loud enough using 1x gain?


----------



## WilliamLeonhart

It does, at 1 or 2 o' clock. I'm just under the impression that the soundstage gets bigger on hi-gain.
  
@castleofargh Nah I'm starting to love it. With tubes these shine!


----------



## raoultrifan

castleofargh said:


> how much the amp will heat up depends entirely on the headphone that will be used. in most cases it does not get warm TBH, but depending on the headphone that can happen.


 
  
 With case open mosfets are heating up around 60C, also NJM4556 buffers have around 50C when listening to normal levels on 32ohms headphones. When using high impedance headphone even the 2207 is a bit hot (at most 50C). Placing small heatsink on every opamp will decrease temp with more than 5C; I did that myself and I can recommend you to do that if you want to cool down your opamps. Unfortunately, I was unable to add heatsinks to mosfets because lack of space. 
  
 Not so high temps here, but when placed inside a plastic case opamps and mosfets temps will be at least 10C higher. Most likely some small halls drilled into the plastic case will help moving the airflow a little bit.


----------



## adydula

The mosfets operate in switch mode and don't generate any heat.
  
 Are you sure your not referring to the voltage regulators?
  
 A.


----------



## HotIce

Switching mode? Are we looking at the same schematic?


----------



## KeithEmo

diamondears said:


> Many sources gives up bits when you turn the volume down.


 
  
_ALL_ sources reduce the number of bits if you use the source itself to turn down the volume.
 (To turn down the level you make the numbers smaller; smaller numbers are smaller and so use less bits.)
  
 However, the Sabre's internal 32 bit digital volume control won't do this (at least not at normal levels).
 Many DACs also have digitally controlled analog volume controls (not on the DAC chip itself).
  
 However, in both of these cases, that will only help if the source can "talk" to the DAC and use that better volume control.
 Unless they specifically say otherwise, the source device has no way to _USE_ the better volume control in the DAC.
_DO NOT_ assume this to be the case unless the manufacturer of your DAC _SPECIFICALLY _says that it is with the particular player you're using. (It's also possible for a USB DAC to "co-opt" the Windows system volume control, in which case the software volume control will be disabled and the better one in the DAC will be used no matter what player you use. However, if that's the case, they _WILL_ tell you - since it's an important feature.)


----------



## Viscera

I'm about to buy either the HD600 or the HD650 soon, will these work out well with this combo?
  
 Though I'm a bit concerned when I read that this combo is not as good as the Shiit stack, is it only because it´s cheaper than 02/Odac for US customers or is the Shiit stack audibly superior?
  
  
 A forum member on a local forum puts these together from DIY for 240$ (shipping included). Is it a fair price?


----------



## castleofargh

viscera said:


> I'm about to buy either the HD600 or the HD650 soon, will these work out well with this combo?
> 
> Though I'm a bit concerned when I read that this combo is not as good as the Shiit stack, is it only because it´s cheaper than 02/Odac for US customers or is the Shiit stack audibly superior?
> 
> ...


 

 or is shiit a very active sponsor of the forum and marketing is working well? 
	

	
	
		
		

		
		
	


	



 TBH both choices will work fine and have plenty of power to drive a hd600/650 pretty darn loud. so there isn't really a bad answer to your problem.


----------



## Danpyre

The O2 is a little superior to the Magni in all but power.


----------



## headwhacker

viscera said:


> I'm about to buy either the HD600 or the HD650 soon, will these work out well with this combo?
> 
> Though I'm a bit concerned when I read that this combo is not as good as the Shiit stack, is it only because it´s cheaper than 02/Odac for US customers or is the Shiit stack audibly superior?
> 
> ...


 
  
 $240 for an O2/ODAC combo is a fair price. Considering it cost a little bit more when you get it from the main distributors. But consider the skills of the guy doing the DIY. Not to mention the proper tools to test everything out after the build is done.
  
 I could have gone DIY myself but the lack of testing tools is what made me choose to buy it from the big guys. I know that one can build an O2+ODAC combo equipped with just a multimeter for testing. But my soldering skill are not quite as good and I might end up spending more due to busted parts.


----------



## AlanU

viscera said:


> I'm about to buy either the HD600 or the HD650 soon, will these work out well with this combo?
> 
> Though I'm a bit concerned when I read that this combo is not as good as the Shiit stack, is it only because it´s cheaper than 02/Odac for US customers or is the Shiit stack audibly superior?
> 
> ...


 
  
 In this audio realm cosmetics also plays a role in this audio market. 
  
 I own the early gen jds 02 amp. The sound quality was great but I also wanted something more cosmetically pleasing. 
  
 For the cost of the inexpensive objective amp I cannot complain because of the great sound. The Schiit product is definitely more pleasing to the eyes if your wanting a nice looking desk mount. 
  
 I'd suggest settling for a decent affordable amp but try to put more money into a higher quality dac. 
  
 I've run my tube dac/super rectifier (aprox $3000 setup)  with my objective amp and it was incredibly pleasing. That setup I could listen for hours and hours with no fatigue. Using the same inexpensive JDS amp with my Concero HD  was not even remotely close to the SQ I received from my tube dac.  Putting audio "ego" aside I would be quite certain that most would not be able to easily hear a difference in using a cheap JDS amplifier vs a much more $$$ amp when used with excellent source material and higher end dac.


----------



## diamondears

williamleonhart said:


> It does, at 1 or 2 o' clock. I'm just under the impression that the soundstage gets bigger on hi-gain.
> 
> @castleofargh
> Nah I'm starting to love it. With tubes these shine!



I'm under the impression that the sound will open up more if volume is at 2-3 o'clock. Remember that volume is a resistor. 



alanu said:


> In this audio realm cosmetics also plays a role in this audio market.
> 
> I own the early gen jds 02 amp. The sound quality was great but I also wanted something more cosmetically pleasing.
> 
> ...



+1.


----------



## Julo

Hi there !

I just found out about this thread (and this forum actually) and made myself an account to explain my situation and see if any of you guys can enlighten me !!

I'm quite interested in audio but don't know a great deal about electronics so feel free to talk to me with simplified terms if possible !!

I own a Yamaha MCR-N560 at home and a pair of Sennheiser Momentum, I have some CDs that I listen to but also listen to music through my computer and Spotify a lot. A few month ago I had an issue with my PC sound card so I bought a creative X-Fi USB sound card, which if I'm correct works as a DAC and amp. So my current set up is my PC connected to the creative x-fi going to my stereo system from a RCA out to the aux in on the Yamaha.

So what I'm wondering is (sorry I'm bring terrible at going straight to the point): if I switched the creative for the ODAC, would I hear a noticeable sonic difference that is worth the money (through the stereo system speakers and/or headphones)?

I'm also wondering whether I would need the DAC+Amp combo or just the DAC? If I was to plug my PC into the DAC and then the DAC to my stereo, then the amp from the Yamaha would be used right ? And if I want to listen to music on headphones I would have to plug them into the stereo system? But then is there any advantage of using the O2 amp instead of the stereo system amp ?

Sorry once again I know this is a bit of a messy post but I'm not really used to being on forums ! Hope someone can help, cheers !!


----------



## JacobLee89

julo said:


> Hi there !
> 
> I just found out about this thread (and this forum actually) and made myself an account to explain my situation and see if any of you guys can enlighten me !!
> 
> ...


 
  
 The O2 amp is a very very plain sound signature amp, that does this "plain'ness" in - probably - the best possible way in it's price range. It won't do anything different than most other amps, just very well (balanced-like sound, and almost invisible quiet noise floor). You already have a YAMAHA for an amp, it's already good enough.
  
 The ODAC is also of similar philosophy, so you'll have to ask yourself this question:
  
*Do you have any notable noise?*
  
 For example, any humming/beeping/whirring sounds that do not belong on the music you listen to (sometimes when my processor is doing some hard processing I hear some extremely faint beeping when I'm plugged into the onboard sound card).
  
 If you do, then you will benefit from an ODAC, since it has been designed (now updated to work even better on this front) to isolate noise from the PC's internals. Changing amps won't do anything to interference from the PC.
  
 If you do not, then you are perfectly fine as you have an already capable sound system.
  
 If you have tonnes of money, then what I said is potentially irrelevant.....


----------



## 214324

Though don't take that "plain" as a negative. A good amp and/or DAC should be transparent. The only nuances in sound should be by your headphone selection (or EQ that you've applied).


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## Julo

Many thanks for the quick reply guys !

With my current set up I don't have any noise problem, I think the creative x-fi does a pretty good job.

I guess what I was wondering about really was the difference I would perceive between different DACs.
The set up I have works fine and I'm happy with it, but I was wondering if going for another DAC could improve the sound, if a better, "more plain" DAC would give me a better, more high fidelity sound ?

But I kinda feel like I wouldn't really notice any difference between the creative and the ODAC (or really slim one) and that could be wasted money...


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## Bibo

julo said:


> So what I'm wondering is (sorry I'm bring terrible at going straight to the point): if I switched the creative for the ODAC, would I hear a noticeable sonic difference that is worth the money (through the stereo system speakers and/or headphones)?


 
  Which X-Fi USB do you have? If it was the X-Fi HD, it would already have a decent dac so you might not get a real benefit of buying an ODAC. The X-Fi Surround 5.1 pro USB is somewhat inferior. But in both cases you could also try using the built in dac of your Yamaha and bypass the X-Fi´s dac by connecting one the X-Fi´s digital outs to the corresponding digital in of yor Yamaha and see if it makes a difference.
  
 Quote:
  


> I'm also wondering whether I would need the DAC+Amp combo or just the DAC? If I was to plug my PC into the DAC and then the DAC to my stereo, then the amp from the Yamaha would be used right ? And if I want to listen to music on headphones I would have to plug them into the stereo system?


 
 There are special desktop versions of O2/ODAC or single O2 with RCA outputs avaible where you could connect your Yamaha to.
 You could also buy ODAC and O2 separately and connect the RCA out of the ODAC via Y-cable with both the O2 and your Yamaha.


> But then is there any advantage of using the O2 amp instead of the stereo system amp ?


 
 Depends on how good the headphone out of Yamaha actually is


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## castleofargh

julo said:


> Many thanks for the quick reply guys !
> 
> With my current set up I don't have any noise problem, I think the creative x-fi does a pretty good job.
> 
> ...


 

 I'll go with my favorite saying: if you don't have a problem, don't go looking for a solution.
	

	
	
		
		

		
			




 there is magic in music, but not so much in devices.


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## AlanU

julo said:


> I guess what I was wondering about really was the difference I would perceive between different DACs.
> The set up I have works fine and I'm happy with it, but I was wondering if going for another DAC could improve the sound, if a better, "more plain" DAC would give me a better, more high fidelity sound ?
> 
> But I kinda feel like I wouldn't really notice any difference between the creative and the ODAC (or really slim one) and that could be wasted money...


 
 If you buy an objective amp and using your current dac configuration you may be underwhelmed or happy. 
  
 Your source is very critical with any amp you'll ever purchase in your adventures in audio. Your subjective ears can easily determine if your going to be happy with your source when you use an objective amp.
  
 Once you start to do comparisons between different dac's you'll hear differences. 
  
 If you listen to string instruments/piano  you'll hear a longer tail in note decay using higher end dac's or when using tube gear. This may possibly be the music being hit with the gear's "colour" and "characteristics". However the difference in "engagement" will be black and white for realistic presentation. Of course the coloured sound from you headphones will also add to this "enjoyment".  
  
 I'd definitely suggest the objective amp. As far as dac is concerned you mileage will vary as you critically analyze your current dac.


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## Julo

Bibo I use the X-fi HD USB !

Just to make sure I understand how it works:
When you plug your laptop or cellphone straight into the stereo system aux in, you're using the PC/phone's DAC right ? And having the PC go through the X-fi allows sound to go through a better quality DAC ?

But then if I plug the X-fi's digital out to the Yamaha's digital in, I'll only be using the PC to "provide" the source but then the sound will be "made" by the Yamaha's DAC and amp is that right ?

That could be a cool test to make to see if I can hear a difference between the two DACs !

castleofargh you're very right about that ! It's just that everytime I hear or read about some piece of gear I'm wondering how it could affect my system and whether or not it would improve it.. That's annoying really haha

I'm very pleased with the Yamaha MCR-N560, it's just that since I started using Spotify more intensively I read about DACs and how important they are when you play music from your laptop, and I just want to make sure I'm using the stereo to its potential and not compromising the sound with a not so good DAC for instance !


----------



## AlanU

> I'm very pleased with the Yamaha MCR-N560, it's just that since I started using Spotify more intensively I read about DACs and how important they are when you play music from your laptop, and I just want to make sure I'm using the stereo to its potential and not compromising the sound with a not so good DAC for instance !


 
  
 Typically mini stereo systems do not put much emphasis on the headphone amp section. 
  
 There is alot of thing happening in the chain of events. Your  X-fi HD USB should have rca out. Using RCA cables you can use that for your "aux" . This way your simply amplifier analog signal so your bypassing the yamaha dac.
  
 There is alot of "Magic" going on in components synergy. The DAC is absolutely critical in the translation of digital to analog signal. This is where there's alot of things going on in the chain of events. If your amplification is not up to the task your "magic" will also be lost. Resolution of your speakers / headphones will also be the final transducer to your ears. 
  
 Pure speculation but I would imagine there would be a difference between your X-fi dac and Odac. I would think both of those units would do a decent job in digital conversion.  
  
 When I change my dac with my Objective amplifier the difference between my $1000 burson da160, $850 Concero HD and my $3000 Space tech lab tube dac with super rectifier  is like 3 entirely different worlds. My jaw still drops when I use my tube dac and 02 objective amp.  If I would rate SQ in a subjective manner it would be my tube dac > burson da160 > Concero HD. 
  
 There is always emphasis on "neutral" "neutral" and "neutral" sound but as every human ear is different the typical human somehow appreciates compression, overtones and harmonics. 
  
 Every headphone adds colour to the music so in most cases  system synergy plays a major role in the final sound quality "subjectively speaking". 
  
 If your happy with your current setup just be prepared to get upgraditis as you audition different gear. This hobby is evil and can be addictive.


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## Julo

AlanU thanks for helping man !

I think there are lots of things to take into consideration also. I'm 21 years old still studying and live in a flat (which is why I went for a micro-chain). To be honest I didn't know about the ODAC two days ago, I just watched a video about it on YouTube and the idea of a really transparent sounding DAC/amp seemed appealing and it is in a budget I could afford. But the DAC/amp combo is still around the 260€ to get it shipped to France where I live. That's something I would be ready to pay if I knew I was going to enjoy it in my everyday listening experience but I don't want to spend this money on something unnecessary on the other hand !

I've never had the chance to listen to music through a really nice set up (by that I mean tube DAC like you have and great amp etc), I'm sure I'd be blown away by the result, and hopefully someday if I live in a house I can have a nice music room with a great set up.

But I think I need to be realistic about how much of a difference the ODAC would make on my current set up. 

I'd like to have your thoughts about it, but my guess is in an A/B comparison I would notice the difference between my set up as it is and the ODAC, but maybe outside of that it wouldn't really be something I would notice as better sounding?

If the difference is only going to be subjective and not really one option actually delivering better sound than the other, then spending 260€ without being able to try it beforehand might be a bit risky...


----------



## AlanU

julo said:


> @AlanU thanks for helping man !
> 
> I think there are lots of things to take into consideration also. I'm 21 years old still studying and live in a flat (which is why I went for a micro-chain). To be honest I didn't know about the ODAC two days ago, I just watched a video about it on YouTube and the idea of a really transparent sounding DAC/amp seemed appealing and it is in a budget I could afford. But the DAC/amp combo is still around the 260€ to get it shipped to France where I live. That's something I would be ready to pay if I knew I was going to enjoy it in my everyday listening experience but I don't want to spend this money on something unnecessary on the other hand !
> 
> ...


 
  
 Please be sensible and just feed your yamaha by using RCA cables from your current x-fi DAC. Set your yamaha to "AUX".  
  
 Talking about audio over the internet can be confusing.  Trust your ears and if your currently happy with the sound your getting with your yamaha rig ....stick with it. 
  
 Try to go to your local "Brick 'n Mortar" shop where you can audition gear. For the price of the Objective amplifier it's quite amazing how inexpensive components from an electronics store can be compiled into something very good. The amplification is just as good as my Burson Virtuoso (again I was floored how incredibly clean and neutral amplification of this inexpensive amp). As long as you feed a good source to the amp..... scary good for cheap!!
  
 As long as your amplifier is up to the task in feeding the headphones I'd spend your beans on a different pair of headphones or higher end DAC. For the price of 260 pounds your better off buying used gear locally IMO. 
  
 New headphones will impact the sound in a big way.  The DAC will also have a large change in sound signature. I've listened to the objective amp/dac combo and it's fine and works well. I'm not that excited about the odac but it does the task of digital conversion. My inexpensive Audioengine D1 dac (feeds my A2 Audioengine speakers for my home PC)  does similar mundane task of converting digital as well. For the amount of $$$ you'd spend on a "shipped 02/odac combo" I'd suggest buying a used higher end set of headphones for more dramatic "change". Again my speculation is your current dac will not be inferior to an odac. 
  
 Audio is all about "subjective". Your appreciation of certain characteristics of sound  is very personal and individual. The inexpensive Schiit Magni2 or Vali will work well as you feed it with a nice source. 
  
 Methodically choose components as your "studies" is more critical than buying audio gear


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## Julo

AlanU I reckon this is what I needed to hear !
It's something that I can't really help doing, every once in a while I'll just start thinking about gear and getting new stuff and I start convincing myself I need it even though I was very happy with what I had in the first place.. Annoying me !!

I'm just gonna stick with what I have right now, my Yamaha system does a very nice job, I'm also very pleased with the Sennheiser Momentum headphones I own. I guess later on when I'll be able to afford the even "nicer" pieces of gear I'll start really looking into what DAC I want to use with what amp and what speakers etc.. But for now I guess I'm good to go !

Many thanks for helping out mate, it's really nice having such places to just have a chat about gear and get help from people ! Cheers for taking the time ☺


----------



## AlanU

julo said:


> @AlanU I reckon this is what I needed to hear !
> It's something that I can't really help doing, every once in a while I'll just start thinking about gear and getting new stuff and I start convincing myself I need it even though I was very happy with what I had in the first place.. Annoying me !!
> 
> I'm just gonna stick with what I have right now, my Yamaha system does a very nice job, I'm also very pleased with the Sennheiser Momentum headphones I own. I guess later on when I'll be able to afford the even "nicer" pieces of gear I'll start really looking into what DAC I want to use with what amp and what speakers etc.. But for now I guess I'm good to go !
> ...


 
  
 At this moment the biggest impact in sound would be to buy a different set of headphones. I'm just assuming your Yamaha is feeding your current Momentum headphones with ease since they are more of a mobile headphone (18 ohms) . The resolution of your headphones may not benefit in a large scale if you spend alot of $$$ on a new DAC. Getting different headphones will be a different flavor in sound as long as your pleased with your current dac/amp setup. 
  
 If you listen to music at a reasonable volume level and your not surpassing well over 50% on the volume knob and not clipping you may be fine with other headphones that are harder to drive. If your a BASS head into electronica you'll probably hear little difference on certain music genre's. However if your into female jazz vocals, piano, string instruments you will probably be able to pin point the difference alot more as you swap dacs/amp. 
  
 Try your yamaha in "aux" mode as you feed it with your dac via RCA cables. Tell us your findings. 
  
 On a budget the inexpensive schiit amps or 02 amp will deliver clean power to your headphones. If your wanting more organic natural sound you should be getting the sound signature most from your headphones and DAC. 
  
 I do like tubes as it adds harmonics to the music....yes it adds pleasant distortion that most human ears appreciate. Listening to music is subjective and I find tube gear to be much more engaging with realism.  Whichever way you look at audio gear heads there is typically one component that will add colour to the music. This neutral "amp/dac" sounds fantastic but in the end somewhere in the chain is making subjective ears happy. I personally do not know many friends loving dead on "flat" neutral sound using studio monitors (used in mastering) for a chillout session in relaxing.  All headphone companies colour their sound with a signature "house sound" or specific unique sound to the model of the headphone. 
  
 I love my tube dac setup and manipulate the source by rolling/changing tubes. In the 2 channel world some use neutral high end dacs and colour the sound with a tube preamp and powerful neutral solid state amp. Some use a neutral DAC and colour the sound with a tube amplifier (customize subjective sound swapping tubes).
  
 The beauty of the objective amp/odac is that it's an inexpensive system that delivers neutral sound.  The Odac is doing  a decent job in it's task. If per say you own an objective amp already I'd suggest getting the best dac possible within your budget to maximize sound quality. I'm not into playing with equalizers so I'd resort to finding headphones that works well with the music genre I listen too. 
  
 Again... my jds 02 amp really surprised me in how well is performed as I fed it with excellent source. With my tube dac I found the sound to be extremely natural and organic with my hd650 and Hd800. Of course I can step up the sweet mids by using different headphones or buying a tube amp. This stuff never ends. The difference between my Burson Virtuoso and 02 amp using my tube dac is so subtle it's not funny...... source is everything since the 02 amp is very good in performing it's task.


----------



## Julo

AlanU Having the Creative x-fi connected to the Yamaha through the aux in with RCA cables is how I have it set currently. From what I've been told earlier, plugging the X-fi to the Yamaha through Audio optical would let me use the Yamaha's DAC instead of the DAC from the X-fi ? Could that be interesting to try ??

When I'm not playing music through the Yamaha's speakers I usually plug my headphones in the Creative's headphones out, maybe I should try plugging the headphones in the Yamaha's out to see if I can hear a difference.

I think it could be a good thing to wait, and when I have a nice budget to dedicate to audio I'll take the time to try and compare gear and see what kind of DAC I want to use and see if I want a clean amp or one that adds a colour and everything.. I went with a mini chain for the convenience of having everything in one piece of gear in the first place, and as far as I know the Yamaha I own does a really nice job amongst mini chains and it was the one I preferred over the other ones I tried (some Denon, Pioneer etc).

And same for the Momentum headphones ! Basically I bought the gear I liked the most within the budget I had, and right now I don't have more money to put into and I'm still happy with everything so that should do for a while ! 

What I was wondering about when I first wrote here was whether the creative x-fi could be a "weak point" in my set up and if an DAC upgrade could improve the result but I think the ODAC wouldn't really represent an upgraded, just something different (and I'm not even sure I'd hear a difference).

BTW, do you know anything about the Apogee Groove ? Does it have the same kind of plain and transparent philosophy as the Objective gear or does it have its own sound features ? Just wondering about it !


----------



## AlanU

julo said:


> @AlanU Having the Creative x-fi connected to the Yamaha through the aux in with RCA cables is how I have it set currently. From what I've been told earlier, plugging the X-fi to the Yamaha through Audio optical would let me use the Yamaha's DAC instead of the DAC from the X-fi ? Could that be interesting to try ??
> 
> When I'm not playing music through the Yamaha's speakers I usually plug my headphones in the Creative's headphones out, maybe I should try plugging the headphones in the Yamaha's out to see if I can hear a difference.
> 
> ...


 
  
 Sorry I was under the impression that you were using the yamaha headphone out and using the dac to feed the yamaha. 
  
 I would hold out as long as you can on any gear purchase. As you go up the ladder in gear you gain refinements and much improved SQ. Enjoy your current gear and build a dedicated headphone rig down the road to max out SQ for headphones.
  
 IMO most dac's will sound different from one another even when the same DAC chipset is used. The ESS sabre chipset seems to have a very strong character sound that seems to have a house sound in many dacs.
  
 The Dac seems to be the weakest link in most cases. Perhaps it's all about meeting our expectations to make happy subjective ears.  The unfortunate thing is higher end dac's cost alot of $$$$    
  
 I've been concerned about my previous comments comparing my Burson Virtuoso and Jds amp.  I did that comparison when my burson was virtually fresh out of the box. I just did an A/B comparison between my objective amp and Burson Virtuoso (now with more hours of breakin' time). Using the Burson internal DAC  via Grant Fidelity vacuum tube processor  feeding the 02 amp I find the JDS amp to sound less refined and edgy/raw. Using the Burson Amplification section while getting conditioned from my Grant fidelity vacuum tube processor the Burson sounds smoother. My previous comments were based on my fresh brand new Burson amp. I'll still comment by saying the 02 amp is a great amp for the inexpensive cost.
  
 I'm entertaining the idea of buying an amp from Garage1217 for fun.
  
 http://www.garage1217.com/garage1217_diy_tube_headphone_amplifiers_013.htm
  
 You can buy an assembled one. So many toys out there


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## jring

williamleonhart said:


> From my experience with my previous O2 (DIY from JDS boards), it does get a bit hot, but nothing too bad. I think it was around 30 - 40 degrees celsius.


 
  
 But a 3D printed case is still a bad idea since the metal case with the ground wire provides electrical shielding. So unless one can 3D print with a conductive material, it's not such a great idea.
  
 Joachim


----------



## KeithEmo

I agree entirely. The single thing that influences the sound of your system the most is the headphones (or speakers). It goes far beyond the idea that upgrading to a more expensive one will be better; while two expensive (and neutral) amps will sound pretty similar, even two very expensive and "good" "accurate" pairs of headphones will sound quite different; and often even different models by the same company; (and sometimes even different "generations" of the _same_ model). You will also find that certain headphones tend to emphasize the differences in your other electronics, like DACs, while others tend to "gloss over them" or make them less apparent. (And some headphones seem to "work well with anything" while others only seem to work their best with certain other equipment.
  
 I would also add that, much like speakers, headphones are one of those places where you really can often get a significant improvement by spending more money (percentage wise). If you have a $50 pair of headphones, and a $50 headphone amp, you'd probably be much better off moving up to a $100 amp and a $300 pair of headphones, than keeping your $50 cans and buying a $350 amp in hopes of some sort of "magical transformation".
  
 You should also be aware that, while most neutral amps sound more or less the same (no surprise there), since tube amps are designed to add some coloration, there are often much larger differences between them. Some may in fact sound rather neutral, while others, like the Schiit Lyr, add a more noticeable "tubey" sound signature. Therefore, especially with tube amps, you really should try to listen to one - with your model and brand of headphones - before spending a lot of money. (And also, hyperbole aside, in most cases the differences between different tube amps will be far greater than the differences between different tubes in a given amp.)
  
  
 Quote:


alanu said:


> At this moment the biggest impact in sound would be to buy a different set of headphones. I'm just assuming your Yamaha is feeding your current Momentum headphones with ease since they are more of a mobile headphone (18 ohms) . The resolution of your headphones may not benefit in a large scale if you spend alot of $$$ on a new DAC. Getting different headphones will be a different flavor in sound as long as your pleased with your current dac/amp setup.
> 
> If you listen to music at a reasonable volume level and your not surpassing well over 50% on the volume knob and not clipping you may be fine with other headphones that are harder to drive. If your a BASS head into electronica you'll probably hear little difference on certain music genre's. However if your into female jazz vocals, piano, string instruments you will probably be able to pin point the difference alot more as you swap dacs/amp.
> 
> ...


----------



## adydula

I cant agree more!
  
 Alex


----------



## BrettMatthews

Quick question for those that are running an O2/ODAC (mine is a version 1 ODA made by mayflower) with their HE-400, when I have fubar volume set to 100% and Windows volume set to 100% the amp is set very low ( only at about 15%), is this normal?


----------



## adydula

There is a poll going on over diyAudio on how you use your O2....
  
http://www.diyaudio.com/forums/headphone-systems/277532-do-you-use-your-o2-desktop-portable-both.html
  
 Alex


----------



## rs0cal

I just hopped on the massdrop deal for the o2 amp.
  
 Do you guys think the amp will be a good pairing for the Audeze El-8 headphone (open model). Its a planar with low impedance at 30ohms


----------



## adydula

I used my O2 with LCD2's with no issues worked well. If the impedance and sensitivity are close you will be fine.
  
 Alex


----------



## riverlethe

keithemo said:


>


 
  
 What about the Lyr gives it a "tubey" sound?  It's claimed to have a flat frequency response and low distortion.


----------



## KeithEmo

riverlethe said:


> What about the Lyr gives it a "tubey" sound?  It's claimed to have a flat frequency response and low distortion.


 
  
 (Let me start by saying that I've heard the Lyr "version 1" - and had one to listen to for several weeks - but I've been told that the Lyr 2 sounds "less tubey". I also have no doubt whatsoever that it meets or exceeds the quoted specs.)
  
 The difference in sound between tube and solid state equipment is somewhat difficult to quantify. There are some obvious things that affect tube power amps - like lower damping and the phase shift and other phase issues due to the output transformers. There are also the much higher levels of second harmonic distortion, which give much of the distinctive sound to low-feedback triode amps. However, neither of these really applies to the Lyr. And the overload characteristics of tubes are way different - but that shouldn't matter if you aren't overloading them.
  
 I've never met anyone who's done an actual study about which aspects of the differences are the ones that are audible, but most people agree that their is a pretty major difference. (For that matter, assuming the product can meet those specs with a variety of tubes, then how can rolling tubes make a difference either?) I've always assumed it is a combination of certain things like distortion spectra being more audible than many people believe, and of (maybe) some time/phase effects of how tubes operate that don't necessarily show up on standard steady-state measurements. Quite possibly it's various combinations of several things.
  
 (I have no doubt that, if you were to put the Lyr on our AP tester, you would be able to see obvious differences between it and equivalent solid-state design in terms of distortion and frequency response.  However, I suspect that they would all be at levels that you wouldn't "expect" to be audible.)
  
 From an engineering difference, I can even tell you what aspects of the circuitry alter the sound.... for example, choice of grid and plate resistor value and type (carbon or metal film) alter the sound, and the operating points you choose (plate voltage and steady state plate current) make a big difference, as well as the choices you make with some other circuit operating points.
  
 From a product engineering point of view, the "situation" is pretty simple. Because of the higher voltages involved, and the need for heater power, and the cost of tubes themselves, it costs more to design and produce a product that uses tubes and, from the perspective of standard specs like frequency response and distortion, tubes don't perform as well as solid state in many ways. Therefore, to put it bluntly, unless you like the pretty glowing lights, you'd be foolish to sell or buy a tube product unless you specifically hear a difference - and find it pleasing. (Which means that, for a company selling a tube product, it makes little sense to try and minimize the things that make it sound different from an easier-to-make solid state equivalent.)
  
 In the case of Schiit's products..... if you want tube sound, then buy Lyr..... if you want a similar product, but with a more neutral sound, then you should be looking at Asgard 2.


----------



## riverlethe

keithemo said:


> (Let me start by saying that I've heard the Lyr "version 1" - and had one to listen to for several weeks - but I've been told that the Lyr 2 sounds "less tubey". I also have no doubt whatsoever that it meets or exceeds the quoted specs.)
> 
> The difference in sound between tube and solid state equipment is somewhat difficult to quantify. There are some obvious things that affect tube power amps - like lower damping and the phase shift and other phase issues due to the output transformers. There are also the much higher levels of second harmonic distortion, which give much of the distinctive sound to low-feedback triode amps. However, neither of these really applies to the Lyr. And the overload characteristics of tubes are way different - but that shouldn't matter if you aren't overloading them.
> 
> ...


 
  
 Thanks for the in-depth response!
  
 Assuming both tube and ss amps are under the threshold of "audible" distortions, etc., that we can measure, how do we know which one actually sounds more "neutral?"  Could there be some other characteristic that we're not measuring?  This, of course, assumes that it's not just sighted bias...


----------



## KeithEmo

riverlethe said:


> Thanks for the in-depth response!
> 
> Assuming both tube and ss amps are under the threshold of "audible" distortions, etc., that we can measure, how do we know which one actually sounds more "neutral?"  Could there be some other characteristic that we're not measuring?  This, of course, assumes that it's not just sighted bias...


 
  
 With devices like DACs this can be quite complicated, however it's pretty simple with an amplifier. A neutral amplifier is simply "a straight wire with gain" - it should take the input signal and do nothing to it other than increase the level. So, if your amplifier has a gain of 20x, and you take it's output and put it through a simple resistor voltage divider that reduces it by 20x, it should sound _EXACTLY_ the same as the input signal. (And you can compare them electrically to confirm this - or you can simply subtract one from the other and see if you end up with silence like you're supposed to...)
  
 As the simplest example, let's assume your source is a DAC, and you have a preamp with two line level inputs, and you want to make the test with your headphone amp set to a gain of x20. Take the output of your DAC, and run it through a passive stereo splitter. Connect one set of outputs from the splitter directly to one input on your preamp, and the other to the input of your headphone amp. Now, build a passive voltage divider using two very high quality resistors of appropriate values, connect the output of your headphone amplifier to your voltage divider, and connect the output of the voltage divider to the other input on your preamp. You now have one "copy" of your source signal going straight to your preamp, and one copy going through the headphone amp, being boosted by 20x by the headphone amp, then being reduced by 20x by the voltage divider, and finally going to the other input on the preamp. Assuming that the headphone amp is really neutral, then you should hear no difference when you switch between those two inputs on the preamp. (And, even if you didn't get the gain or the voltage divider just right, you should be able to adjust the gain on the headphone amp for "a good null" at some setting.)
  
 Note:
  
 1) You can use the level control on the headphone amp to adjust the gain very carefully. If it is truly neutral, then you should be able to find a "perfect" setting where it really does sound identical to the wire. (We're confirming that the headphone amp really is "a straight wire with gain" by cancelling out the gain and confirming that it now sounds like "just a straight wire".)
  
 2) Even really high quality small signal resistors cost less than $1 each - and you only need four of them - and high quality resistors won't change the sound.
  
 3) A passive splitter is simply one input plug connected directly to two output plugs using a piece of wire (avoid fancy ones with transformers), and so won't change the sound either.
  
 4) This will work just fine, and it doesn't matter if your preamp, amp, or speakers, have some coloration - as long as they don't have so much coloration that it completely obscures the results - since all you're listening for is a _difference_ of any kind.
  
 There are lots of variations on this. If the level control on your headphone amp has sufficient range, and your preamp has a tape monitor loop, you can simply connect the headphone amp in the tape monitor loop. If you set it so its gain is exactly one, you should be able to find a point where you can't hear any difference between when it's "in" and when it's "out"... if it's really neutral. There are also fancier ways in which you can connect the input and output that will allow you to hear the difference between them - in which case, if it's really neutral, you should be able to "null" the difference so there's nothing left.
  
 This test will tell you for certain if your amp is not neutral. However, if the output impedance of the headphone amplifier will react with the input impedance of your headphones if it's too high, but won't interact with the high input impedance of a typical preamp, so it's still possible that an amp could "pass" this test, and sound neutral with a preamp, and still NOT be neutral with some headphones. (But, if it isn't neutral when you connect it to the easy load of a preamp input, no way will it be neutral when connected to headphones.)
  
 Now, if you don't want to go to all that trouble, there is a slightly less accurate way that is much easier - but depends somewhat more on logic. Since "neutral" is a very specific thing, if you have two or more amps that sound different, then either one of them isn't neutral, or neither of them is neutral. Likewise, if a tube amp sounds different with each of five different brands of tubes in it, then, at the very most, it _might_ actually be neutral with at most one of them. So, if you listen to a dozen amps, and five of them sound pretty much the same, but the other five all sound different, you can guess that there's a pretty good chance that the five that sound similar also sound pretty close to neutral, and that none of the five that sound very different is likely to be the sole one that is neutral.
  
 As for "characteristics we're not measuring" - that's also always a possibility - but you can eliminate it by the "difference test".


----------



## riverlethe

i don't have any tube amplifiers on hand or even a soldering iron, but I'm skeptical that they actually DO sound any different, if the following conditions are met:

"There are some obvious things that affect tube power amps - like lower damping and the phase shift and other phase issues due to the output transformers. There are also the much higher levels of second harmonic distortion, which give much of the distinctive sound to low-feedback triode amps. However, neither of these really applies to the Lyr. And the overload characteristics of tubes are way different - but that shouldn't matter if you aren't overloading them."


----------



## Danpyre

riverlethe said:


> i don't have any tube amplifiers on hand or even a soldering iron, but I'm skeptical that they actually DO sound any different, if the following conditions are met:
> 
> "There are some obvious things that affect tube power amps - like lower damping and the phase shift and other phase issues due to the output transformers. There are also the much higher levels of second harmonic distortion, which give much of the distinctive sound to low-feedback triode amps. However, neither of these really applies to the Lyr. And the overload characteristics of tubes are way different - but that shouldn't matter if you aren't overloading them."



If it uses tubes, it won't be as technically accurate as the best Solid State at that price. Now, it can sound better, or even more natural depending on your headphone, tubes and amp, but won't be as technically accurate.


----------



## riverlethe

danpyre said:


> If it uses tubes, it won't be as technically accurate as the best Solid State at that price. Now, it can sound better, or even more natural depending on your headphone, tubes and amp, but won't be as technically accurate.




My question is whether it's technically "bad" enough to be audibly different. Eg., the Schiit amps have low output impedance, low THD and a flat frequency response, at least into a high impedance load...


----------



## KeithEmo

riverlethe said:


> i don't have any tube amplifiers on hand or even a soldering iron, but I'm skeptical that they actually DO sound any different, if the following conditions are met:
> 
> "There are some obvious things that affect tube power amps - like lower damping and the phase shift and other phase issues due to the output transformers. There are also the much higher levels of second harmonic distortion, which give much of the distinctive sound to low-feedback triode amps. However, neither of these really applies to the Lyr. And the overload characteristics of tubes are way different - but that shouldn't matter if you aren't overloading them."


 
  
 You really should listen to a few tube power amps and compare them for yourself. While I've certainly heard a few tube preamps that sound relatively uncolored, even to the point where it isn't obvious that they do in fact use tubes, I've never heard a tube power amp of any topology where it isn't obvious that you are, in fact, listening to tubes. And, from a purely product perspective, since tubes are somewhat more difficult to design for these days, and their need for a high voltage power supply increases the cost of building tube designs, and the tubes themselves cost more, there would be very little reason to produce tube products unless they sounded different. (If they really sounded the same, then it would be easier and cheaper to not bother, and to stick with solid state designs.)


----------



## riverlethe

keithemo said:


> You really should listen to a few tube power amps and compare them for yourself. While I've certainly heard a few tube preamps that sound relatively uncolored, even to the point where it isn't obvious that they do in fact use tubes, I've never heard a tube power amp of any topology where it isn't obvious that you are, in fact, listening to tubes. And, from a purely product perspective, since tubes are somewhat more difficult to design for these days, and their need for a high voltage power supply increases the cost of building tube designs, and the tubes themselves cost more, there would be very little reason to produce tube products unless they sounded different. (If they really sounded the same, then it would be easier and cheaper to not bother, and to stick with solid state designs.)


 

 It's not hard to imagine a scenario where expectation bias, aesthetic preference and nostalgia for the industrial era, etc., creates a market.​
  
 But yes, I'm hoping to hear my friend's Little Dot soon.  I'm still curious as to what kinds of distortion correlate to a "smoother" sound or increased soundstage, etc.  Doesn't being out of phase "compress" a soundstage?


----------



## Danpyre

riverlethe said:


> My question is whether it's technically "bad" enough to be audibly different. Eg., the Schiit amps have low output impedance, low THD and a flat frequency response, at least into a high impedance load...



Yes, it's nearly always audible, unless you're comparing it to a solid state that's trying to sound tubey.


----------



## riverlethe

danpyre said:


> Yes, it's nearly always audible, unless you're comparing it to a solid state that's trying to sound tubey.




And how do you make it sound "tubey" without some kind of DSP?


----------



## Danpyre

riverlethe said:


> danpyre said:
> 
> 
> > Yes, it's nearly always audible, unless you're comparing it to a solid state that's trying to sound tubey.
> ...



Probably by changing the way it's tuned, and using some custom components to introduce elements such as distortion.


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## castleofargh

the natural misbehavior state of SS amps doesn't sound nice, that's the main difference with most tubes, tubes can suck a lot and still sound rather euphonic or at least soft. you can use the wrong amp with wrong gain for a transducer and clip the hell out of the amp, that may still sound "interesting" on some tubes. it would be clear as day that you messed up on a SS amp.
 also I can't help but think that many of the tube lovers are just looking for something that rolls off the trebles, there are a lot of tube amp with reasonably good distortion specs that should not sound so much like a typical old time tube at all, yet people don't seem to reject those.
 of course there is also the very serious possibility that people start to feel softness and tube sound as soon as they see a tube, and a tube glowing at the top of a fully SS amp would please them just the same. ^_^
 placebo can be very powerful.
  
 wouldn't a good old impulse response from "nice sounding" tube amp convolved while using a transparent SS amp be the ideal way to the tube sound? or are there drawbacks to convolution? I tend to be satisfied with only using EQ and some crossfeed on headphones, but I'm only me.


----------



## KeithEmo

riverlethe said:


> It's not hard to imagine a scenario where expectation bias, aesthetic preference and nostalgia for the industrial era, etc., creates a market.​
> 
> But yes, I'm hoping to hear my friend's Little Dot soon.  I'm still curious as to what kinds of distortion correlate to a "smoother" sound or increased soundstage, etc.  Doesn't being out of phase "compress" a soundstage?


 
  
 You're thinking of phase as a binary choice (in phase / out of phase); when you have one channel "out of phase", like when you connect the wires backwards on one speaker, what you actually have is all frequencies out of phase by an equal 180 degrees between the channels. This causes sounds with long wavelengths that are common to both channels (bass) to cancel out, which is why the bass goes away, and in general messes with our direction perception at higher frequencies. The usual effect is that things sound very odd, you can't locate where anything is, and sounds that should be located in the center sound almost the opposite - like they're _NOT_ in the center, but you can't figure out exactly where they _ARE_. (it usually doesn't "compress" the sound stage; rather the opposite, it sort of shreds it.)
  
 The reason that this happens is that our brains use the phase relationship between a given sound in the two channels as one of the important cues for determining location. If the phase shifts between channels are somewhat less than 180 degrees, or if the amounts of signal involved aren't equal, and if they vary with frequency, you can produce all sorts of alterations in the perceived sound stage. (This is how all of those cool "surround synthesizers" work - by carefully faking the phase shifts normally caused by differences in source location to trick your brain into hearing sounds coming from different locations. Differences in amplitude are one major cue, and the next most important one is differences in phase.) One common (and simple) trick is to take _just a little bit_ of the left and right channel, invert the phase of each, and add back into the other channel. Doing this with a small fraction of the entire signal tends to make the sound stage seem wider and "push" some sounds "out past the left and right speakers". Doing it selectively with only certain frequencies, or varying it by frequency, tends to "spread out" the sound stage (this is the technology behind the Carver Sonic Holography process - among many others).
  
 While doing this in a carefully controlled fashion can produce specific results, simply randomly shifting various frequencies can sort of "swirl the sound stage around", in sometimes interesting ways - which is why, when you apply a matrix decoder (which is mostly phase-based), to stereo sound, it often creates "synthetic surround" - because the phase shifts used by the decoder interact with the phase differences in the original recording to produce shifts in the perceived sound stage. (The decoder "decodes" the random phase shifts in the source material as if they were actually information encoded there.) However, when something like an output transformer, or a too-small coupling capacitor, introduces some frequency-dependent phase shift, the result can be a sort of subtle rearrangement of the sound stage.
  
 Many tube devices, some more than others, also tend to produce a lot of second harmonic distortion. (If you can't hear the distortion, then it doesn't matter which harmonics you aren't hearing; however, if there is enough distortion to hear, the different harmonics produce different audible results.) Third harmonic distortion, which solid state amps tend to produce a lot of when they clip, sounds harsh. Second harmonic distortion sounds more mellow. When there's significant second harmonic distortion at midrange frequencies, it can actually make vocals seem clearer and more intelligible; and adding second harmonics at higher frequencies makes them seem to have "more sparkle"; and adding second harmonics to very low bass, especially in situations where the speakers or amp can't produce enough of the primary frequency involved, will make it sound like there's more bass. (Notice how all this coincides with the terms people often use to describe the way tube equipment sounds.)
  
 Most tube devices also have what's called "a monotonic distortion curve" - which is uncommon in solid state devices. What this means is simply that the distortion increases more or less linearly with loudness (the louder you play it the more distortion you get). Solid state equipment usually does _NOT_ act like this. In a typical piece of solid state equipment, the distortion remains inaudible low at all low to normal volume levels then, at some specific point, jumps up suddenly as you approach clipping. Interestingly, our brains usually associate distortion with "loudness" (which is why a 1 watt table radio can seem to be sooooo loud).
  
 Now, remembering this, think about what happens when you play a typical 15 watt single ended triode amplifier and an "equivalent" solid state amp. The triode amp puts out 1 watt @ 1% THD and 10 watts at 10% THD; the solid state amp puts out 1 watt @ 0.005% THD and 10 watts at, perhaps, 0.01% THD. Because the distortion produced by the triode is audible, and becomes more audible at higher levels, it tends to exaggerate the loudness difference between them. (Even though the actual difference in loudness between 1 watt and 10 watts is a fixed, the _perceived_ difference between 1w/1% and 10w/10% is greater than the perceived difference between 1w/0.005% and 10w/0.01%; because the higher distortion at 10 watts makes it seem proportionally louder than it really is; this makes the music you're playing sound "more dynamic" on the tube amp because, even though the dynamic range measures the same, we perceive it as being greater.) This is almost certainly why many people "hear" low powered tube amps as "sounding more powerful" than their ratings would suggest - it's a sort of "psychoacoustic dynamic range expander".
  
 (Note that, while both of these effects may sound pleasant, and may even improve the listening experience for some people, they are technically inaccuracies - aka distortion. Incidentally, there are several pieces of studio equipment, and plugins for modern DAWs, that allow you to deliberately add or "inject" second harmonic distortion, used for deliberately producing the effect I described.)


----------



## riverlethe

Very interesting and informative post! Thanks! 

I'm still skeptical about second-order harmonics, at least in the context of headphone amplifiers. 300ohm Sennheisers take what, 200-300mw to reach rock concert levels? The flagship HD800's are only rated to withstand 500mw. It would have to be a pretty under-powered headphone amp to have significant distortion at that level, right? (I'm not saying clipping doesn't happen with solid-state mobile devices or computer interfaces, but this is Head-fi...)

Edit: The Little Dot Mk III claims 0.15% THD at 80mW. That's around 115 dB for the HD800, if my math is right.

Is there an easy way to measure phase-variation vs frequency? It sounds like I would be more interested in something like an SPL Phonitor. 

How easy is it to inject second-order harmonics and phase alteration into a solid state design?


----------



## castleofargh

riverlethe said:


> Very interesting and informative post! Thanks!
> 
> I'm still skeptical about second-order harmonics, at least in the context of headphone amplifiers. 300ohm Sennheisers take what, 200-300mw to reach rock concert levels? The flagship HD800's are only rated to withstand 500mw. It would have to be a pretty under-powered headphone amp to have significant distortion at that level, right? (I'm not saying clipping doesn't happen with solid-state mobile devices or computer interfaces, but this is Head-fi...)
> 
> ...


 
 http://www.sengpielaudio.com/calculator-thd.htm
 it gives you the maximum value in db, below the original signal(so below the actual music). you remove that value to the actual loudness of the signal, and that's how loud the distortions can be. I wouldn't count on 0.01db precision for those stuff, also you never know if the quoted distortion is a tiny little spike in the bass where it won't really change much to the sound, or a wide spread carnage over frequencies. but you get a small sense of resolution.


----------



## TsukiNick

Do you guys think the O2 or the Magni is a better value for the money?  The magni has more power although I'd never really push it past 11 o'clock unless I was listening to some poorly leveled video on youtube.  I'll probably get the O2 for $70 or I might just spend extra and get a Magni 2.  I want a headphone amp with more usable range without having to run my Audio through a Schiit Sys as a finer volume control/attenuator.  And the new Magni has gain control and of course so does the O2.  Also I hate moving my amplifier from my desk to my bed (It's only a few feet away but I'm a lazy person.)


----------



## KeithEmo

riverlethe said:


> Very interesting and informative post! Thanks!
> 
> I'm still skeptical about second-order harmonics, at least in the context of headphone amplifiers. 300ohm Sennheisers take what, 200-300mw to reach rock concert levels? The flagship HD800's are only rated to withstand 500mw. It would have to be a pretty under-powered headphone amp to have significant distortion at that level, right? (I'm not saying clipping doesn't happen with solid-state mobile devices or computer interfaces, but this is Head-fi...)
> 
> ...


 
  
 The answer is - it depends. If you look at the distortion curves for most solid state power amplifiers, you will find that, somewhere above "zero", they start out pretty low, remain low until somewhere near clipping, and then rise suddenly as they near clipping. However, if you look down near zero, you will see that distortion curve start to rise again on many amplifiers, because of things like minute amounts of noise and crossover notch distortion that only become a significant part of the signal at very low levels. (So some solid state amps have the highest distortion at very high levels and at very low levels - where you would be using them with headphones.) Now, for most tube amps, while they typically have a distortion curve that rises more or less linearly with power at higher levels, many never actually drop to very low levels of distortion at any level, and some may even rise at lower levels. (So a tube amp that is 0.15% THD at 80 mW could be 0.15% at 5 mW, or it could be 0.05% at 5 mW, or it could be 1% at 5 mW - there's no way to really tell without seeing the actual measurements.)
  
 Remember that most headphone amps are designed to deliver very little power. (And a 500 mW amplifier delivering 100 mW is working just as hard as a 500 watt amplifier delivering 125 watts.) 
  
 The Phonitor uses deliberate phase shift and frequency-dependent channel mixing to simulate the sound of speakers in a room via headphones - so someone in a studio can hear what their mix would sound like through speakers - but using headphones. It is not intended to add distortion or coloration in the conventional sense.
  
 To answer your question: It's relatively easy to deliberately cause phase shift - and to deliberately produce second harmonic distortion and add it back into the signal (using solid state electronics, or using software, as with many of the editor plugins which do it). Some devices that do so use actual tubes, others use solid state circuits designed to mimic the electrical characteristics of tubes, and still other use software running on a DSP processor to do it mathematically.) Some editor plugins even simulate the sound of several specific tubes (you get to pick which tube number to simulate, how hard to drive it, how heavily to load it, how much to overload it, etc.)


----------



## riverlethe

tsukinick said:


> Do you guys think the O2 or the Magni is a better value for the money?  The magni has more power although I'd never really push it past 11 o'clock unless I was listening to some poorly leveled video on youtube.  I'll probably get the O2 for $70 or I might just spend extra and get a Magni 2.  I want a headphone amp with more usable range without having to run my Audio through a Schiit Sys as a finer volume control/attenuator.  And the new Magni has gain control and of course so does the O2.  Also I hate moving my amplifier from my desk to my bed (It's only a few feet away but I'm a lazy person.)


 

 I briefly had a Magni 2 and thought it sounded horrible, but that is a subjective impression, so take it FWIW.  The O2 just has a really awkward design.  It's not sure if it's a desktop or a portable amp, and you have to pay extra to put the inputs in logical places.  I'd recommend seeing if you can find a Dacport somewhere.
  
 Edit: I think the O2 is a safer bet if you're only choosing between those two.


----------



## riverlethe

castleofargh said:


> http://www.sengpielaudio.com/calculator-thd.htm
> it gives you the maximum value in db, below the original signal(so below the actual music). you remove that value to the actual loudness of the signal, and that's how loud the distortions can be. I wouldn't count on 0.01db precision for those stuff, also you never know if the quoted distortion is a tiny little spike in the bass where it won't really change much to the sound, or a wide spread carnage over frequencies. but you get a small sense of resolution.


 
  
 Yep, that's what I used.  While 0.15% looks really high for a modern amplifier, the commonly accepted threshold of audibility for THD is around 1% (-40dB).  Other forms of distortion, such as IMD and crossover distortion are far more objectionable.  An amp can have low THD and still sound horrible.


----------



## riverlethe

keithemo said:


> The answer is - it depends. If you look at the distortion curves for most solid state power amplifiers, you will find that, somewhere above "zero", they start out pretty low, remain low until somewhere near clipping, and then rise suddenly as they near clipping. However, if you look down near zero, you will see that distortion curve start to rise again on many amplifiers, because of things like minute amounts of noise and crossover notch distortion that only become a significant part of the signal at very low levels. (So some solid state amps have the highest distortion at very high levels and at very low levels - where you would be using them with headphones.) Now, for most tube amps, while they typically have a distortion curve that rises more or less linearly with power at higher levels, many never actually drop to very low levels of distortion at any level, and some may even rise at lower levels. (So a tube amp that is 0.15% THD at 80 mW could be 0.15% at 5 mW, or it could be 0.05% at 5 mW, or it could be 1% at 5 mW - there's no way to really tell without seeing the actual measurements.)
> 
> Remember that most headphone amps are designed to deliver very little power. (And a 500 mW amplifier delivering 100 mW is working just as hard as a 500 watt amplifier delivering 125 watts.)
> 
> ...


 

 I realize that you're a "member of the trade," but are you able to give an example of a tube headphone amp with THD that rises to or exceeds 1% at a "normal" listening level?  Do you agree that this is a good threshold of audibility?  I'd be willing to grant that it might be lower for headphones, but I think -50dB or less is stretching it.


----------



## KeithEmo

riverlethe said:


> I realize that you're a "member of the trade," but are you able to give an example of a tube headphone amp with THD that rises to or exceeds 1% at a "normal" listening level?  Do you agree that this is a good threshold of audibility?  I'd be willing to grant that it might be lower for headphones, but I think -50dB or less is stretching it.


 
  
 Honestly, I'm really not supposed to talk about specific brands... besides which, I'm really more of a fan of solid state amps, so I don't know that much about individual current tube models in detail anyway. However, considering the fact that many tube headphone amps are transformerless, and most small tubes aren't capable of delivering very much current when connected directly to a load, I suspect that many may have much higher distortion than you might think.... and their distortion is going to vary considerably depending on the impedance and efficiency of the headphones you connect them to.
  
 As far as "thresholds of audibility", that is a much stickier question than you might think. I would definitely agree that 1%, or even a a little more, would be the threshold above which an amp would sound "obviously distorted". However, I've certainly heard amps with far lower distortion than that which still had distinctive "sound signatures" - which leads me to say that amounts of certain types of distortion far below that _MAY_ still be audible under some circumstances. There's a distinct difference between "the amount of distortion which makes the signal sound distorted" and "the amount of distortion that may impart a slight 'sonic signature'". The other thing is that there are all sorts of different types of distortion - and each sounds different... (With a given signal, and a given device, 1% second harmonic would probably be inaudible, or even slightly pleasant, while 1% third harmonic would be quite annoying, 1% of the seventh harmonic would be far worse, and even 0.1% of a totally unrelated tone - which also qualifies as distortion - would be very obvious and very annoying.) You could probably get me to take a bet that anything less than about 0.01% of almost any harmonic distortion would almost certainly be inaudible but, beyond that, it really depends on a lot of things.....
  
 (Generalizations can often be too general.... You wouldn't even taste 1% sawdust in your breakfast cereal, but 1% cyanide would be enough to wipe out your entire block.)


----------



## HotIce

These are a set of good articles WRT distortion types and their audibility studies:

http://www.audioholics.com/room-acoustics/human-hearing-amplitude-sensitivity-part-1
http://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2
http://www.audioholics.com/room-acoustics/human-hearing-distortion-audibility-part-3
http://www.audioholics.com/room-acoustics/human-hearing-reprise-part-4

http://www.axiomaudio.com/distortion


----------



## riverlethe

Thenks. I think that's where j got my 1% THD figure. 

Of particular interest is Cheever's paper, mentioned in the distortion article:

http://next-tube.com/articles/Cheever/cheever.pdf

He mentions transient IMD and how it only appears in feedback amplifiers.


----------



## Pingupenguins

Wow, good read. Lots of good objective info unlike some of the other amp threads. However, this is the O2 we're talking about. hahaha.
  
 I definitely think the O2 runs under the small footprint desktop amp category. Which would work great for my cluttered desk due to space constraints. Anyone know if the O2 is only made by JDS labs? I've always been a bit hard pressed to find another O2 manufacturer and it seems via JDS blogs that there are only 2 or so companies with the schematics for the amp.


----------



## Bibo

pingupenguins said:


> Wow, good read. Lots of good objective info unlike some of the other amp threads. However, this is the O2 we're talking about. hahaha.
> 
> I definitely think the O2 runs under the small footprint desktop amp category. Which would work great for my cluttered desk due to space constraints. Anyone know if the O2 is only made by JDS labs? I've always been a bit hard pressed to find another O2 manufacturer and it seems via JDS blogs that there are only 2 or so companies with the schematics for the amp.


 

*US*
  
 Mayflower Electronics: https://www.mayflowerelectronics.com/product-category/headphone-amplifiers/
  
*Europe*
  
 Epipany Acoustics: http://epiphany-acoustics.co.uk/products-page/
 Head´n Hifi Walter: http://www.headnhifi.com/


----------



## riverlethe

Does anyone know if there are TIMD specs for the O2?


----------



## mcnordst

Hello!
 I have a distortion problem. I have now tried different wiring solutions for my O2 + ODAC setup but I always hear distortion when using the ODAC's signal (line level out) to my receiver. I want to have the possibility to use the ODAC's signal straight from my computer via USB to my stereo amplifier, but unless I turn on the power of the O2 I get massive distortion. I tried to disconnect the ODAC completely and noticed there was no distortion i.e. no problem with the ODAC itself.
 Does anyone else experience the same problem and if, how have you fixed it? Or is the only solution to have the O2 and ODAC separate or always turn on the power of the O2? That sucks...


----------



## castleofargh

mcnordst said:


> Hello!
> I have a distortion problem. I have now tried different wiring solutions for my O2 + ODAC setup but I always hear distortion when using the ODAC's signal (line level out) to my receiver. I want to have the possibility to use the ODAC's signal straight from my computer via USB to my stereo amplifier, but unless I turn on the power of the O2 I get massive distortion. I tried to disconnect the ODAC completely and noticed there was no distortion i.e. no problem with the ODAC itself.
> Does anyone else experience the same problem and if, how have you fixed it? Or is the only solution to have the O2 and ODAC separate or always turn on the power of the O2? That sucks...


 

 nope, I often use the line out/line in plug and never had a problem with the O2 powered off. the only time it becomes a problem is when using that plug as a line input for the O2 while still having the USB active(need to remove the usb and it's normal, else I'm sending 2 signals to the amp at the same time). but in your configuration, never had any kind of trouble.
 maybe a silly idea, but are the distortions still there if you lower the volume on the computer a little? would be pretty surprising, but maybe it's your receiver clipping? (wild goose hunt right there!)


----------



## KeithEmo

castleofargh said:


> nope, I often use the line out/line in plug and never had a problem with the O2 powered off. the only time it becomes a problem is when using that plug as a line input for the O2 while still having the USB active(need to remove the usb and it's normal, else I'm sending 2 signals to the amp at the same time). but in your configuration, never had any kind of trouble.
> maybe a silly idea, but are the distortions still there if you lower the volume on the computer a little? would be pretty surprising, but maybe it's your receiver clipping? (wild goose hunt right there!)


 
  
 With some circuitry, the input becomes a non-linear load when the circuit is not powered, which will introduce distortion when other devices try to drive that load. So, if the output of your 0DAC is trying to drive both the input of the O2 and your receiver, the input of the O2 may in fact distort the signal when it is off. If your setup allows it, arranging the connections so the output of the 0DAC goes straight to the receiver, but adding a small value resistor (2.2k) in series with the input of the O2, may prevent it's input from affecting the signal between the 0DAC and the receiver.


----------



## bracko

I have been considering O2 for my HE-400i (35 Ohm, 93 dB) and Fidelio X2 (30 Ohm, 100 dB). Should I go with the standard gain or should I customize the gain? I mostly use my CD-player and turntable as a source. Thanks for your help.


----------



## Bibo

Low gain should by 1x for the Fidelios.


High gain depends on the output voltage of your source. Source output voltage * gain should be < 7V


----------



## bracko

bibo said:


> Low gain should by 1x for the Fidelios.
> High gain depends on the output voltage of your source. Source output voltage * gain should be < 7V


 
 Thanks. Source output voltage is at the most 2 V (CD player). That probably means that 1x/2,5x or 1x/3x would be nice.


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## Bibo

3x or even 3.3x would be the best decision if you plan to connect more demanding headphones in the future. 3.3x would be the maximum if the source puts out 2.1V like the ODAC rev. B does for example.


----------



## deaconblues

mcnordst said:


> Hello!
> I have a distortion problem. I have now tried different wiring solutions for my O2 + ODAC setup but I always hear distortion when using the ODAC's signal (line level out) to my receiver. I want to have the possibility to use the ODAC's signal straight from my computer via USB to my stereo amplifier, but unless I turn on the power of the O2 I get massive distortion. I tried to disconnect the ODAC completely and noticed there was no distortion i.e. no problem with the ODAC itself.
> Does anyone else experience the same problem and if, how have you fixed it? Or is the only solution to have the O2 and ODAC separate or always turn on the power of the O2? That sucks...


 
 What's your O2+ODAC's configuration?  Does it have the separate line out from the ODAC in the back or does the O2's line-in do double duty as input and output?
  
 If it has separate line in and line out, the O2 should disconnect the ODAC when you plug a cable into the line-in jack.  Just connect the line-out to your amp and plug some cable into the line-in.  It doesn't even have to be connected to anything on the other end.  This should allow you to use the ODAC without turning on the O2. 
  
 If you have the double duty line-in + line-out (or if you have separate jacks but it wasn't properly configured) then this won't work.


----------



## diamondears

keithemo said:


> _ALL_ sources reduce the number of bits if you use the source itself to turn down the volume.
> (To turn down the level you make the numbers smaller; smaller numbers are smaller and so use less bits.)
> 
> However, the Sabre's internal 32 bit digital volume control won't do this (at least not at normal levels).
> ...



Keith, so if I'm using the iPhone as source/DAC/amp, its always better to use an external amp, assuming the ext amp is completely transparent? I always hear the iPhone 6+ to always sound better when I use the FiiO E06.


----------



## castleofargh

diamondears said:


> keithemo said:
> 
> 
> > _ALL_ sources reduce the number of bits if you use the source itself to turn down the volume.
> ...


 

 pretty safe to say that your preference has no relation to bit depth.


----------



## KeithEmo

diamondears said:


> Keith, so if I'm using the iPhone as source/DAC/amp, its always better to use an external amp, assuming the ext amp is completely transparent? I always hear the iPhone 6+ to always sound better when I use the FiiO E06.


 
  
 In general: Yes.
  
 Any phone is going to be limited in terms of how much voltage and current it can deliver to headphones - both simply because the manufacturer is unlikely to want to spend the money to design and include a really good quality headphone amp, and because, even beyond that, doing so will generally either shorten battery life drastically, or force them to include a bigger battery - which will make the entire device bigger and heavier (because more powerful amps use more battery power). It wouldn't be impossible to include a really good headphone amp in a phone - but nobody's done it yet. (Note, however, that some are a lot better than others.)
  
 However, the headphones themselves have a lot to do with that question. A pair of headphones that were specifically designed to work well with amplifiers that are subject to those limitations will work a lot better with a portable device like a phone. (In other words, if you get a headphone that was specifically designed to be very efficient, and to be driven by a limited voltage, then it's going to work much better with a source device that has those limitations - like a phone.)
  
 (You need to check out all the options.... It might make sense to spend money on a pair of headphones that are designed to work well with your phone than to spend the money on an amp so that you can get better performance from headphones that weren't designed with that specific goal in mind. There are several current models of headphones that are specifically designed to be used with phones and other portable devices - and which work pretty well with them.)


----------



## mcnordst

deaconblues said:


> What's your O2+ODAC's configuration?  Does it have the separate line out from the ODAC in the back or does the O2's line-in do double duty as input and output?
> 
> If it has separate line in and line out, the O2 should disconnect the ODAC when you plug a cable into the line-in jack.  Just connect the line-out to your amp and plug some cable into the line-in.  It doesn't even have to be connected to anything on the other end.  This should allow you to use the ODAC without turning on the O2.
> 
> If you have the double duty line-in + line-out (or if you have separate jacks but it wasn't properly configured) then this won't work.




Hi, thanks for the reply. I have a separate rear output. The trick with an extra cable/plug worked, no distortion! 

Still feel it is a work around to carry an extra cable along, maybe I could add a switch to the rear panel that disconnects the odac from o2.


----------



## Movezig

I'm thinking about going this route with my HE400. Anyone have extended use this setup on the 400's?


----------



## diamondears

keithemo said:


> In general: Yes.
> 
> Any phone is going to be limited in terms of how much voltage and current it can deliver to headphones - both simply because the manufacturer is unlikely to want to spend the money to design and include a really good quality headphone amp, and because, even beyond that, doing so will generally either shorten battery life drastically, or force them to include a bigger battery - which will make the entire device bigger and heavier (because more powerful amps use more battery power). It wouldn't be impossible to include a really good headphone amp in a phone - but nobody's done it yet. (Note, however, that some are a lot better than others.)
> 
> ...



Keith meant to ask if full bits is always better sounding than less bits, like going full bits and use analog volume control. So I use an external amp so I can always max out the digital volume and use full bits.


----------



## lucasseijikc

Would the O2 Amp + ODAC be a nice pair to the AKG K702s?
  
 I am considering buying an amp/DAC to substitute my FiiO E10 and saw that the O2 Amp + ODAC is quite famous around the audiophile community.
  
 I really like the sound to be the most neutral/analytical as possible. Would this amp/DAC be a nice substitution for my FiiO E10
  
 Thanks in advance.


----------



## raoultrifan

Yes, final sound will be quite neutral. You'll need a gain of about 2.5X for O2 to drive them properly.


----------



## lucasseijikc

raoultrifan said:


> Yes, final sound will be quite neutral. You'll need a gain of about 2.5X for O2 to drive them properly.


 

 Thank you, raoultrifan!
  
 As my next amp/DAC, I'm taking a look at a few options:
 - Objective2 + ODAC;
 - Matrix M-Stage HPA-3U;
 - Magni 2 + Modi 2.
  
 I will be using them to listen to my AKG K702, Shure SRH840, Superlux HD668B and, in the future, maybe the Beyerdynamic T1 or the AKG K812.
 I also plan on buying the Woo Audio WA7 Fireflies in the future, as an all around headphone amp/DAC.
  
 Of the 3 options listed above, which one do you think would be the most neutral and the best all around?


----------



## raoultrifan

O2 is neutral by it's nature, but let's wait for the owners of Matrix and Magni2 to speak up.
 From specs and reviews I see Matrix and Modi2 are quite powerful, in case you're dreaming of driving planars in the future.


----------



## lucasseijikc

Thanks again, raoultrifan!
  
 I've read a couple of reviews on the Matrix M-Stage HPA-3U and they both said it pairs really well with the AKG K812 and the Sennheiser HD800, so I'm guessing it is quite powerful (not that these two headphones are power hungry) and if it can drive these properly, it can drive some other high-end headphones.
 They also said that it has a dead silent background and a slightly warm sound signature, which I didn't quite appreciate, but  I can always mod it if I don't feel comfortable with it.
  
 Anyway, I really appreciate your help, raoultrifan! Thank you so much!


----------



## adydula

O2 can drive 98% of headphones that are out there to ear splitting levels, Their are exceptions like the more inefficient headphones like the HIFI mans etc
  
 People forget what the design criteria was for the O2, Its not n amp that was designed to drive all headphones out there.
  
 98% of what's out there is pretty good.
  
 And the cost to do so is peanuts compared to other amps.
  
 I drove K701;s with the O2 with no problems.
  
 Alex


----------



## lucasseijikc

But can the O2 drive 98% of the headphones properly? Does it make the headphones sound like they actually should sound?
  
 I've heard that the O2 can make the headphones sound like the respective headphones, not adding any sort of color to the sound, which I think is pretty good, but does it do that to all the headphones that are plugged in it?
  
 If so, the O2 is quite amazing!


----------



## headwhacker

lucasseijikc said:


> But can the O2 drive 98% of the headphones properly? Does it make the headphones sound like they actually should sound?
> 
> I've heard that the O2 can make the headphones sound like the respective headphones, not adding any sort of color to the sound, which I think is pretty good, but does it do that to all the headphones that are plugged in it?
> 
> If so, the O2 is quite amazing!




It can drive anything from HIfiman except HE-6.


----------



## KeithEmo

diamondears said:


> Keith meant to ask if full bits is always better sounding than less bits, like going full bits and use analog volume control. So I use an external amp so I can always max out the digital volume and use full bits.


 
  
 In theory it's always best to keep the digital side of things at full resolution - which means not reducing the bit depth. In practice, while that's technically always true, it makes a lot more difference in some situations than others. For example, the digital volume control in the Sabre DACs has extra resolution which it can use to avoid rounding errors which often occur with "simple" digital volume controls. This allows the internal digital volume control to work over a certain range without seriously degrading the audio quality. However, with digital volume controls that lack that feature, the sound quality will degrade as you reduce the level.
  
 The "trick" is that how that affects you will depend on your other equipment. For example, if your digital volume is set to maximum level at normal listening levels, then you won't notice the loss of quality when you turn it down very much - because, since you're lowering the audio level at the same time as you're lowering the resolution of the signal, the loss of resolution will be less audible. However, if your digital volume control is at 10% when you're at a normal listening level because the analog amp you have it connected to has a lot of gain, then it will probably sound noticeably degraded, and will get noticeably worse as you lower the level even further.
  
 But yes, optimally, it is always _BEST_ to use a digitally controlled analog volume control if you have one available - and leave the digital control at 100%.


----------



## MrMateoHead

movezig said:


> I'm thinking about going this route with my HE400. Anyone have extended use this setup on the 400's?


 

 I have been using O2/ODAC and HE-400s for years. I have found no real shortcoming and they both sound excellent for their part. The HE-400s are quite unforgiving so the quality of your recordings will matter somewhat to the "final" sound. I hear snaps, crackles, and pops from time to time from clipped recordings (of which so much pop is these days). If you want a more "forgiving" setup, I would recommend a different headphone.
  
 I've not needed more power than the O2 can provide, and in any case, the HE-400s are not really up to concert level SPL anyway.


----------



## adydula

The whole idea behind the O2 was to design an amp that had absolutely world class stellar objective specifications for the least cost.
  
 It wasn't designed to be pretty or versatile or a desktop unit.
  
 Being perfectly flat and with a very low output impedance it provides an amp that just amplifies the signal so you can indeed tell what your headphones "sound" like.
  
 So the answer is yes!
  
 and the O2 is quite amazing for what it is.
  
 Alex


----------



## Movezig

mrmateohead said:


> I have been using O2/ODAC and HE-400s for years. I have found no real shortcoming and they both sound excellent for their part. The HE-400s are quite unforgiving so the quality of your recordings will matter somewhat to the "final" sound. I hear snaps, crackles, and pops from time to time from clipped recordings (of which so much pop is these days). If you want a more "forgiving" setup, I would recommend a different headphone.
> 
> I've not needed more power than the O2 can provide, and in any case, the HE-400s are not really up to concert level SPL anyway.


 
  
 Thanks for the reply! It's either going to be the O2 or magni2/modi


----------



## upstateguy

adydula said:


> The whole idea behind the O2 was to design an amp that had absolutely world class stellar objective specifications for the least cost.
> 
> It wasn't designed to be pretty or versatile or a desktop unit.
> 
> ...


 
  
 What is it?
  
  


movezig said:


> mrmateohead said:
> 
> 
> > I have been using O2/ODAC and HE-400s for years. I have found no real shortcoming and they both sound excellent for their part. The HE-400s are quite unforgiving so the quality of your recordings will matter somewhat to the "final" sound. I hear snaps, crackles, and pops from time to time from clipped recordings (of which so much pop is these days). If you want a more "forgiving" setup, I would recommend a different headphone.
> ...


 
  
 Forum Brainwashing.....


----------



## Movezig

upstateguy said:


> What is it?
> 
> 
> 
> Forum Brainwashing.....


 
  
 Care to elaborate?


----------



## upstateguy

movezig said:


> <snip>
> 
> Care to elaborate?


 
 PM


----------



## bracko

upstateguy said:


> PM


 
 I believe that it would be fair to give an elaboration to the above post to everyone actually. People who visit this forum may have similar questions in mind


----------



## adydula

Hmmmmm....must be the truth patrol is on parade.
  
 What is it: A low cost linear amp that is about as good as it gets audibly for most human beings audio transducers.
  
 That's of course unless you believe more dollars buys you more perfection.
  
 A.


----------



## MrMateoHead

I guess since part of that post focused on "forum brainwashing" was apparently directed at me, I feel I should respond in some way. Having been in the unique position of owning both an HE-400 and an O2/ODAC for years, and listening to it daily, I felt I was in a position to provide advice to a person seeking some. The majority of my posts, I believe, are tempered to provide "real" advice - I want real value for my hard-earned dollars, and would never recommend a product I don't truly like or that seemed to be poor quality.
  
 I'd have personally never found the O2 or the HE-400s without this forum, and so color me brainwashed, but I was happy to risk a few dollars on what I believe are small businesses. My decision making process is not just "skin deep", sir.
  
 While Soren Kierkegaard makes a wonderful point, I am at a loss as to how his 19th century religious philosophies are applicable to an Internet forum focused on bringing lover's of certain commercial products together. But his warnings are well-heeded. If you are in possession of facts that I am not, please enlighten me, or all of us. I too wish for knowledge to set me free from my prejudices and ignorance.


----------



## adydula

All I know is I have this amp in more than one flavor and several others...they all are pretty good...the O2 is a low cost great amp that allows many the ability to be able to listen to music at a very affordable price point.
  
 We all have opinions for sure....
  
 Having the hardware and gone thru many listening and A/B sessions you cant go wrong with an O2 amp.
 All I can say is what I have personally heard and experienced first hand...and take whatever others say with a grain of salt...
  
 I don't need any Sorens or whoever to tell me what I have actually experienced....
  
 A.


----------



## upstateguy

adydula said:


> Hmmmmm....must be the truth patrol is on parade.
> 
> What is it: A low cost linear amp that is about as good as it gets audibly for most human beings audio transducers.
> 
> ...


 
 are you a member of the truth patrol?


----------



## upstateguy

mrmateohead said:


> I guess since part of that post focused on "forum brainwashing" was apparently directed at me, I feel I should respond in some way. Having been in the unique position of owning both an HE-400 and an O2/ODAC for years, and listening to it daily, I felt I was in a position to provide advice to a person seeking some. The majority of my posts, I believe, are tempered to provide "real" advice - I want real value for my hard-earned dollars, and would never recommend a product I don't truly like or that seemed to be poor quality.
> 
> I'd have personally never found the O2 or the HE-400s without this forum, and so color me brainwashed, but I was happy to risk a few dollars on what I believe are small businesses. My decision making process is not just "skin deep", sir.
> 
> While Soren Kierkegaard makes a wonderful point, I am at a loss as to how his 19th century religious philosophies are applicable to an Internet forum focused on bringing lover's of certain commercial products together. But his warnings are well-heeded. If you are in possession of facts that I am not, please enlighten me, or all of us. I too wish for knowledge to set me free from my prejudices and ignorance.


 

 apologies if you thought the post was aimed at you.  It wasn't.
  
 Regarding your choice of the O2.  It seems you refused to believe what wasn't true and embraced what was.
  
 Too bad nwav was banned.  But he left us with more than just food for thought.


----------



## adydula

Nope not me, no truth patrol here, just what my electrical engineering background, a pile of headamps, headphones, and personal experience..thats my truth...
  
 You believe what you want and I will believe what I want......you want sonic perfection...go for it but I learned along time ago it doesn't exist.
  
 but the O2 is a step in the right direction....
  
 A.


----------



## upstateguy

adydula said:


> Nope not me, no truth patrol here, just what my electrical engineering background, a pile of headamps, headphones, and personal experience..thats my truth...
> 
> *You believe what you want and I will believe what I want**.....*.you want sonic perfection...go for it but I learned along time ago it doesn't exist.
> 
> ...


 
  
 I think we're on the same page.


----------



## adydula

Ditto!


----------



## diamondears

keithemo said:


> In theory it's always best to keep the digital side of things at full resolution - which means not reducing the bit depth. In practice, while that's technically always true, it makes a lot more difference in some situations than others. For example, the digital volume control in the Sabre DACs has extra resolution which it can use to avoid rounding errors which often occur with "simple" digital volume controls. This allows the internal digital volume control to work over a certain range without seriously degrading the audio quality. However, with digital volume controls that lack that feature, the sound quality will degrade as you reduce the level.
> 
> The "trick" is that how that affects you will depend on your other equipment. For example, if your digital volume is set to maximum level at normal listening levels, then you won't notice the loss of quality when you turn it down very much - because, since you're lowering the audio level at the same time as you're lowering the resolution of the signal, the loss of resolution will be less audible. However, if your digital volume control is at 10% when you're at a normal listening level because the analog amp you have it connected to has a lot of gain, then it will probably sound noticeably degraded, and will get noticeably worse as you lower the level even further.
> 
> But yes, optimally, it is always _BEST_ to use a digitally controlled analog volume control if you have one available - and leave the digital control at 100%.



Is the iPhone 6 Plus' amp analog but digitally controlled? No way due to soace constraints?


----------



## Francisk

Does anybody here have any experience with the Audeze LCD-X pairing with the JDS Labs O2 amp? Please share your honest opinion. I'm actually looking into getting the O2 amp. Thanks in advance for your sharing.


----------



## KeithEmo

diamondears said:


> Is the iPhone 6 Plus' amp analog but digitally controlled? No way due to soace constraints?


 
  
 I would assume that it's just a simple digital volume control (mainly because they don't say otherwise). These days space per-se is rarely a concern with high-volume products. (Our Emotiva products use a separate digitally controlled analog ladder network volume control IC, which takes up about a square inch of board space, but a volume phone manufacturer could do the same thing with a chip that was a few mm square, or have that functionality included in one of their other custom audio chips.) It's just slightly simpler to connect the output of an ordinary DAC to an ordinary analog amplifier, rather than include the extra part, and most people wouldn't notice - or care about - the difference.
  
 Also, because it's something that's commonly useful, many popular headphone amp chips these days include a built-in digital volume control. (So, for anyone who does want to use an off-the-shelf part, that's the easiest way to do it.)


----------



## Luckbad

I feel like this amp/dac combo is one everyone should try on their journey.
  
 The upgrade path, in my mind, is something like: PA2V2 -> Fiio E10k -> ODAC w/ O2 or Magni/Modi -> Expensive
  
 I've had my O2 for about a year and just recently upgraded it to include the ODAC Rev B (I didn't like the previous ODAC because it sounded grainy to me. The new one sounds great).
  
 The improvement was enough that I now have spent far more money upgrading to a better DAC and ordered a Cavalli Liquid Carbon.
  
 Man... yeah, it's crazy. Now I've gotta offload as much gear as I can to afford what I already bought. Audiophilia Nervosa strikes hard.


----------



## Packdemon

So, I recently replaced my O2 amp board in my O2 + ODAC combo. It's not working, so I'm assuming that I soldered the wires from the ODAC in the wrong order on the O2 amp's contact points. I can't find any clear non-blurry pictures online, so is there anyone out there who could take up-close pictures of the inside of their O2 + ODAC with clear shots of the ODAC's wires and ones of where they lead to on the O2 amp?


----------



## UNOE

Anyone know a amp as clear and transparent as o2 but with more power and little more punch that is less than $300?  Just looking for amp only.


----------



## Luckbad

If you were looking slightly higher in price I'd try to sell you my Vorzuge. Very good with an insane bass switch. Selling it because I ordered a Liquid Carbon.

I'd recommend the Cayin C5 on the cheaper end. Super clear, portable, gain switch, and bass switch. The main weakness is that you can't keep it plugged in when in use, which is the reason I sold mine (I needed a desktop amp).

The Leckerton UHA-6S.MKII is supposed to be great but seems to always be out of stock.

The Geek Out is a decent option, but you might have to find a used V2 to stay under $300.


----------



## HotIce

unoe said:


> Anyone know a amp as clear and transparent as o2 but with more power and little more punch that is less than $300?  Just looking for amp only.



 

FIIO E12 (much cheaper than $300) or iBasso PB2 (a little over $300).
Which HP are you driving that needs more power than the O2?


----------



## UNOE

hotice said:


> unoe said:
> 
> 
> > Anyone know a amp as clear and transparent as o2 but with more power and little more punch that is less than $300?  Just looking for amp only.
> ...




I have Alpha Dogs that don't seem to punch that well compaired to o2. They sound okay on Vali. But my momuntum 1's hiss to much on Vali. I want a amp that can drive both Alpha Dogs and Momentums and sell Vali and o2.


----------



## Draulius

Would I need to use high gain if I get a pair of 400i's?


----------



## MrMateoHead

draulius said:


> Would I need to use high gain if I get a pair of 400i's?


 

 You only need high gain if your source is about 1V or less.


----------



## thejammonster

Just unboxed my HD 650's and, while they do sound nice, I was expecting them to sound considerably better than my PC 363D headset.  I'm currently just using my PC motherboard which has a built-in amp for up to 600 ohms but it doesn't really get as loud as I would have thought.  I was looking at the JDS Labs O2+ODAC for a decent option.  Would that do a good job of really powering these headphones or am I out of luck due to the open-back design?  The sound is great (and was on the PC 363D's as well) but I feel like I need one more notch on the volume knob that isn't there.  I think I could easily get the sound I want from closed-back headphones but I don't like the feeling of pressure that they put on my ears and prefer open-back headphones by far.  Thanks for any input on my admittedly stupid question; I just don't want to drop ~$300 on an amp with no appreciable difference.


----------



## MrMateoHead

thejammonster said:


> Just unboxed my HD 650's and, while they do sound nice, I was expecting them to sound considerably better than my PC 363D headset. * I'm currently just using my PC motherboard which has a built-in amp for up to 600 ohms but it doesn't really get as loud as I would have thought*.  I was looking at the JDS Labs O2+ODAC for a decent option.  Would that do a good job of really powering these headphones or am I out of luck due to the open-back design?  *The sound is great (and was on the PC 363D's as well) but I feel like I need one more notch on the volume knob that isn't there*.  I think I could easily get the sound I want from closed-back headphones but I don't like the feeling of pressure that they put on my ears and prefer open-back headphones by far.  Thanks for any input on my admittedly stupid question; I just don't want to drop ~$300 on an amp with no appreciable difference.


 
 Hi There -
  
 What is your PC Soundcard? If it is rated to 600 Ohms, is there a hardware or switch or software switch you need to toggle to switch it to
 "high impedance" mode? I might check that out first.
  
 Also, you can get the standalone O2 for about $130 - you don't need to spring for the O2/ODAC if you like your PC's soundcard. You can get an ODAC later if you want a slightly better DAC. For the money, I highly doubt you will find more than a handful of other amps that sound nearly as good (the O2 is really a great amp IMO). Also, it should easily provide that extra volume notch to which you refer. I'd note that, with my higher-impedance HD 595s (rated 50 Ohm but they swing to 200), the O2 tightened up the sound a lot and bass was much improved.
  
 So, I am quite confident that you will hear a difference, and a good one.


----------



## Luckbad

The Objective 2 / ODAC Rev B is a solid choice. If you want to save a lot of money and just get a taste, I'd recommend a PA2V2. It was my intro to amps.

I've been meaning to sell that cheap to help a new Head-Fier start their journey. Let me know if you want it.


----------



## HotIce

The PA2V2 runs on two AA batteries, so if he complains about lack of power, than is not going to provide enough voltage swing for him.
The O2 is much better in that field, even more so if fed with outlet power.


----------



## Luckbad

I ran my HD650s on the PA2V2 for a good year before I got the O2, and it runs them quite well for an entry level amp. The O2 pushes them better, and better amps push them better still. The 650s scale really well.


----------



## thejammonster

I actually ordered the O2 Amp+ODAC yesterday after some replies to my same question on the HD 650 thread.  Regarding the current PC setup - I don't have a dedicated soundcard, just an MSI Z87M Gaming motherboard.  I didn't get it because of the headphone amp but it is listed as a feature.  Obviously all amps are not created equal but I didn't realize how true that would be!  I'll post my thoughts on the O2 after it arrives later this week.


----------



## UntilThen

HD650 powered by o2+odac was how I started off with head-fi. It was thoroughly enjoyable for 2 months until I bought a tube amp, the Darkvoice 336se. Still using the o2+odac as dac, the Darkvoice gave the hd650 a warm and lushness that makes you want to listen to music for hours. This is the magic of tubes. Once you've tasted it's goodness there's no turning back.


----------



## bracko

draulius said:


> Would I need to use high gain if I get a pair of 400i's?


 
 I use my HE-400i on 1x gain. I have 1x/3x on my amp. It works great.


----------



## MrMateoHead

thejammonster said:


> I actually ordered the O2 Amp+ODAC yesterday after some replies to my same question on the HD 650 thread.  Regarding the current PC setup - I don't have a dedicated soundcard, just an MSI Z87M Gaming motherboard.  I didn't get it because of the headphone amp but it is listed as a feature.  Obviously all amps are not created equal but I didn't realize how true that would be!  I'll post my thoughts on the O2 after it arrives later this week.


 

 Your board is really nice. Your headphone amp is the TI OPA1652. It is rated 2 mA per channel, so at 1 V that is approximately 4 mWs total. That is actually quite a lot of power, but won't hold a candle to the O2 unless the chip is getting much better voltage (I couldn't find detailed info). Supposedly, the HD650s need about 0.13mWs to reach 90 dB, so your board could probably do it with a little headroom (but the dynamic range of the stuff you listen to will still matter). In any case my guess would be that you have a great sound card, but not really a powerhouse of a headphone amp (though I'd love to try it out myself).
  
 Feed an O2 the line out and you will be loving it - just shut off all the ancillary soundblaster junk. I hated the "crystallizer."


----------



## thejammonster

mrmateohead said:


> Your board is really nice. Your headphone amp is the TI OPA1652. It is rated 2 mA per channel, so at 1 V that is approximately 4 mWs total. That is actually quite a lot of power, but won't hold a candle to the O2 unless the chip is getting much better voltage (I couldn't find detailed info). Supposedly, the HD650s need about 0.13mWs to reach 90 dB, so your board could probably do it with a little headroom (but the dynamic range of the stuff you listen to will still matter). In any case my guess would be that you have a great sound card, but not really a powerhouse of a headphone amp (though I'd love to try it out myself).
> 
> Feed an O2 the line out and you will be loving it - just shut off all the ancillary soundblaster junk. I hated the "crystallizer."


 
  
 Interesting info.  I've got a new motherboard on the way (new PC build) - MSI Z170A Gaming M9 ACK.  They make excellent boards and I've built my last 3 PCs with them.  Here is the info I can find from the product page:
  
 3x headphone amp (type not listed, possibly a similar TI chip?)
 ESS SABRE ES9018K2M DAC
 C-Media 6632A audio codec chip (32-bit/384kHz)
 Chemi-Con caps
 Nahimic Sound Technology (I think this is a Sound Blaster equivalent)
  
 I'm not sure if the detailed info you found is out there yet as this board was just officially released today, but if you can find it I would love to know.  My O2 is still on the way and I don't plan on this motherboard replacing it but it is pretty cool to see the push for high-end audio.  On-board audio used to be a joke compared to a dedicated sound card!


----------



## HotIce

mrmateohead said:


> Your board is really nice. Your headphone amp is the TI OPA1652. It is rated 2 mA per channel, so at 1 V that is approximately 4 mWs total. That is actually quite a lot of power, but won't hold a candle to the O2 unless the chip is getting much better voltage (I couldn't find detailed info). Supposedly, the HD650s need about 0.13mWs to reach 90 dB, so your board could probably do it with a little headroom (but the dynamic range of the stuff you listen to will still matter). In any case my guess would be that you have a great sound card, but not really a powerhouse of a headphone amp (though I'd love to try it out myself).
> 
> Feed an O2 the line out and you will be loving it - just shut off all the ancillary soundblaster junk. I hated the "crystallizer."



 

The 2mA is the rated quiescent (opamp consumption with no load) current. Sustained max is about 30mA.


----------



## MrMateoHead

thejammonster said:


> Interesting info.  I've got a new motherboard on the way (new PC build) - MSI Z170A Gaming M9 ACK.  They make excellent boards and I've built my last 3 PCs with them.  Here is the info I can find from the product page:
> 
> 3x headphone amp (type not listed, possibly a similar TI chip?)
> ESS SABRE ES9018K2M DAC
> ...


 

 That board is actually a beast - I love MSI's stuff. I've never seen an ESS DAC used in a motherboard also - that is quite amazing. The headphone amp looks to be the same TI 1652 - but with 3 of them included, that provides either 6 channels of amplification, or maybe just 1 running in series or parallel?. Unclear. Without knowing what sort of voltage they are getting, I can't guess at the power it will produce. All the parts are great parts, but we don't really know how they perform because we don't know how well they are implemented.
  
 I seem to recall, but could not find, that the TI chips usually have 10 Ohm output impedance, which is their worst aspect - they are going to work best with headphones rated from 80 ohms on up (and new headphones are coming out daily in the 30 ohm range). It would need to produce over 100 mWs to best the O2, and 100 mWs would already be orders of magnitude more than the HD 650 requires.
  
 But I have little doubt that the soundcard section should provide high quality, if not better quality, than a lot of people's AV receivers / Headphone DACs. For this board, assuming it was low-noise ("hiss free") - I would assume you might want only a better amp.
  
 I also did just learn that a lot of Pre-Amp stages in AV receivers use similar parts all the way up to the $3,000 mark, yet they all do not measure the same, that is for sure. We all need good parts, AND good design. Wish I was an electrical engineer!


----------



## MrMateoHead

hotice said:


> mrmateohead said:
> 
> 
> > Your board is really nice. Your headphone amp is the TI OPA1652. It is rated 2 mA per channel, so at 1 V that is approximately 4 mWs total. That is actually quite a lot of power, but won't hold a candle to the O2 unless the chip is getting much better voltage (I couldn't find detailed info). Supposedly, the HD650s need about 0.13mWs to reach 90 dB, so your board could probably do it with a little headroom (but the dynamic range of the stuff you listen to will still matter). In any case my guess would be that you have a great sound card, but not really a powerhouse of a headphone amp (though I'd love to try it out myself).
> ...


 

 Thank you for the correction - so would that be 30 mA total, or 30 mA per channel? I would think per channel. Do you know what the typical, actual power output might be on a mother board? For some reason I assumed the supply voltage wouldn't be greater than 12V, and more likely +- 5 V


----------



## thejammonster

mrmateohead said:


> Thank you for the correction - so would that be 30 mA total, or 30 mA per channel? I would think per channel. Do you know what the typical, actual power output might be on a mother board? For some reason I assumed the supply voltage wouldn't be greater than 12V, and more likely +- 5 V


 
  
 MSI's website seems to indicate 5V.


----------



## thejammonster

mrmateohead said:


> But I have little doubt that the soundcard section should provide high quality, if not better quality, than a lot of people's AV receivers / Headphone DACs. For this board, assuming it was low-noise ("hiss free") - I would assume you might want only a better amp.


 
  
 I ordered the JDS Labs O2 Amp+ODAC and had a rear dedicated 3.5mm line-out added since it was only $3.  Am I correct that this should bypass the ODAC and have the O2 acting as only an amp and my motherboard as the DAC?  If so, best $3 I've spent in a while!


----------



## Takeanidea

If it's anything like my Epiphany it will; I don't even plug my o2/odac into the mains I just plug my headphone amp in


----------



## Bibo

thejammonster said:


> I ordered the JDS Labs O2 Amp+ODAC and had a rear dedicated 3.5mm line-out added since it was only $3.  Am I correct that this should bypass the ODAC and have the O2 acting as only an amp and my motherboard as the DAC?  If so, best $3 I've spent in a while!


 
 Overriding the ODAC and using only the O2 is always possible via the front 3,5mm port. on additional rear output you can connect another amp and use only the ODAC


----------



## thejammonster

bibo said:


> Overriding the ODAC and using only the O2 is always possible via the front 3,5mm port. on additional rear output you can connect another amp and use only the ODAC


 
  
 Thanks, I had it backwards.  After re-reading the website I had confused input/output.
  
 "The front, right 3.5mm jack on O2+ODAC provides shared functionality: analog input to the amplifier, and paralleled ODAC line output."
  
 'analog input to the amplifier' is the key here.


----------



## Bibo

With the additional port you can use in and output simutanously. The $3 are still a good investment, espcially if you plan to use powered desktop speakers like I do.


----------



## HotIce

mrmateohead said:


> Thank you for the correction - so would that be 30 mA total, or 30 mA per channel? I would think per channel. Do you know what the typical, actual power output might be on a mother board? For some reason I assumed the supply voltage wouldn't be greater than 12V, and more likely +- 5 V



 
It's 30mA per opamp (per channel, at least - configurations like the O2 has parallel opamps per channel, which would double the max current throughput).
Hard to say if HP amp rails runs at 12v or 5v. The former is what I would use, but not sure they did.


----------



## MrMateoHead

hotice said:


> mrmateohead said:
> 
> 
> > Thank you for the correction - so would that be 30 mA total, or 30 mA per channel? I would think per channel. Do you know what the typical, actual power output might be on a mother board? For some reason I assumed the supply voltage wouldn't be greater than 12V, and more likely +- 5 V
> ...


 

 So assuming a 5 V max power, we have a range of maybe 2 mWs to 150 mWs per channel though at an unknown impedance (output as well an input).


----------



## Packdemon

Can you take an up-close pictures of the inside of your O2 + ODAC with clear shots of the ODAC's wires and ones of where they lead to on the O2 amp? Please I need this as a reference.


----------



## Efterlade

Would this amp be good to power Beyers?


----------



## Packdemon

efterlade said:


> Would this amp be good to power Beyers?


 
  
 Yes


----------



## adydula

Absolutely.....


----------



## jring

packdemon said:


> Can you take an up-close pictures of the inside of your O2 + ODAC with clear shots of the ODAC's wires and ones of where they lead to on the O2 amp? Please I need this as a reference.


 
  
 Please google odac may update and choose the first result. This leads to the designer's blog which I'm not allowed to link to - not sure if using his nick is ok again... we used to call him Voldemort for quite a time...
  
 Joachim


----------



## riverlethe

So, anyone do a subjective comparison between the original ODAC and Rev. B yet?


----------



## thejammonster

Wanted to post some quick thoughts after some time with the HD 650s and an O2+ODAC.
  
 HD 650 - Extremely uncomfortable, I feel like my head is in a vice clamp wearing these.  The ear cups aren't deep enough so my ears are smushed up against the inner foam.  They sound good but the bass isn't great.  Overall they don't have enough bass for my personal taste.  They don't sound weak or flat or anything; I just realized I prefer a more bass-heavy listening experience.  
  
 O2+ODAC - Didn't make much of a difference over my PC other than being able to raise the volume over what the PC could output.  It would be much more useful with a lower power source like a cell phone, so this may live on my desk at work.
  
 Below are the bassier options I came up with looking through the forums:
  
 Beyerdynamic DT 990 Pro 250 ohm (what do the variations in ohms offer?)
 HiFiMan RE-400 (what is the difference in the vanilla, 'i' and 'S' variants?)
 Philips Fidelio X2
 Ultrasone Pro 2900 (hadn't heard of this brand before but they seem decent)
  
 If anyone has thoughts or experience with these or something I may have missed please let me know.  I don't want to hijack this thread with other models so feel free to PM me!


----------



## riverlethe

What kind of PC do you have that can output enough power for the HD650's?  I think the Xonar STX can handle it, but that's all that comes to mind at the moment.


----------



## thejammonster

riverlethe said:


> What kind of PC do you have that can output enough power for the HD650's?  I think the Xonar STX can handle it, but that's all that comes to mind at the moment.




MSI Z87 motherboard (see about a week ago in this thread). Most of the higher end MSI boards have dedicated power and headphone amps rated for up to 600 ohms.


----------



## riverlethe

thejammonster said:


> MSI Z87 motherboard (see about a week ago in this thread). Most of the higher end MSI boards have dedicated power and headphone amps rated for up to 600 ohms.


 

 "Up to 600 ohms" is a weird specification.  It's like saying you can drive a line input.  Contrary to popular misinformation, higher-impedance loads are in fact EASIER to drive, though they may require more voltage to reach the desired volume level.  At any rate, if you don't hear any noise, you have sufficient volume and you're satisfied with the PC "interface," you probably don't need a headphone amp.


----------



## thejammonster

riverlethe said:


> "Up to 600 ohms" is a weird specification.  It's like saying you can drive a line input.  Contrary to popular misinformation, higher-impedance loads are in fact EASIER to drive, though they may require more voltage to reach the desired volume level.  At any rate, if you don't hear any noise, you have sufficient volume and you're satisfied with the PC "interface," you probably don't need a headphone amp.


 
  
 I'm with you.  I don't claim to understand the electrical engineering side of things.  I think MSI assumes most people don't understand it, either, which is why they market it like that.  Anyway, I'm not able to get enough volume out of the motherboard which is why I went with an amp.  For that purpose, it works great.  I think I may need to look at hardware equalizers, though.  The software EQ I tried did a fairly poor job.


----------



## riverlethe

What program are you using for playback? Foobar2000 and Jriver Media Center have pretty good built-in equalizers.


----------



## thejammonster

I tried software called Equalizer APO which EQs the audio device (output to O2+ODAC) for all playback, instead of being specific to the audio player.  I will give Foobar2000 a shot to see if it is better.


----------



## bolmeteus

Behringer UCA202 is the way to go if you're on a very tight budget. Differences should be quite minimal vs the E10,ODAC.


----------



## riverlethe

thejammonster said:


> I tried software called Equalizer APO which EQs the audio device (output to O2+ODAC) for all playback, instead of being specific to the audio player.  I will give Foobar2000 a shot to see if it is better.


 

 A graphic equalizer might be a little easier to tweak in real-time.​
  
 Back to the 600 ohm thing...  I guess it's not a very meaningful spec if it couldn't handle your fairly sensitive 300 ohm Sennheisers!  The Xonar is capable of ear-splitting levels with mine, so this may be another option to consider.
  
 Edit: Actually, are you sure you're not missing a gain setting on your Z87's onboard audio?  The Xonar has three gain settings: +0dB, +12dB and +18dB.


----------



## WilliamLeonhart

riverlethe said:


> "Up to 600 ohms" is a weird specification.  It's like saying you can drive a line input.  Contrary to popular misinformation, higher-impedance loads are in fact EASIER to drive, though they may require more voltage to reach the desired volume level.  At any rate, if you don't hear any noise, you have sufficient volume and you're satisfied with the PC "interface," you probably don't need a headphone amp.


 
 By "easier" you mean "no noise"?
  
 Actually I don't really understand the meaning of impedance (and sensitivity). It seems that headphones with low sensitivity are harder to drive than low-imp cans. I can still get comfortable volume for the HD600 on my Macbook.


----------



## headwhacker

williamleonhart said:


> By "easier" you mean "no noise"?
> 
> Actually I don't really understand the meaning of impedance (and sensitivity). *It seems that headphones with low sensitivity are harder to drive than low-imp cans*. I can still get comfortable volume for the HD600 on my Macbook.


 
  
 sensitivity is not impedance and vice versa. So you can't get anything by comparing them. But combined together when comparing 2 headphones will tell how much power the headphone will need which helps in selecting an amp.
  
 Try to remember Ohm's law. (V = IR) Impedance in itself doesn't mean anything. Sensitivity tells you how much power/voltage the headphone requires to reach an sound pressure level (SPL).
  
 In this context easier to drive  just implies high impedance load only needs small amount of current to reach a certain power level. Voltage determines the volume level. Low sensitivity load will require more power and depending on the impedance will need either more current or voltage.
  
 High impedance needs more voltage and low impedance will demand more current.


----------



## WilliamLeonhart

Thanks for the explanation.
  
 I've found a website that tries to explain it further, in which they list a fomula:
power_sensitivity + 20*LOG(SQRT(1000/R)) = voltage_sensitivity

 http://benchmarkmedia.com/blogs/news/14017381-headphone-impedance-and-sensitivity
  
 From my understanding, "voltage sensitivity" seems to be the most complete index of how easy a pair of headphones can be driven.
  
 From the calculation above, the 325is and the hd650 seems to be quite equal in terms of "easiness to drive", just that the hd650 requires more voltage due to higher impedance.
 I've done the calculation myself and found that AKG x70x trio has voltage sensitivity around 106, which explains why they are notoriously hard to drive.


----------



## dazzerfong

williamleonhart said:


> Thanks for the explanation.
> 
> I've found a website that tries to explain it further, in which they list a fomula:
> power_sensitivity + 20*LOG(SQRT(1000/R)) = voltage_sensitivity
> ...


 

 Somewhat: you need roughly the same amount of watts, but the HD650 requires ​less amperes than the 325i. Some amps suffer from the lack of amperes, but others excel at it, so while it's easy to say 'less volts = harder', it's a bit more complicated than that. 
  
 Take the HE6 for example: lots of power (watts), not a lot of volts (relatively) but a healthy chunk of amps. This can be attributed to low-sensitivity and low-impedance. To drive it to 110 dB, you need 4.7 V RMS and 133 mA, or 447 mW. Compare this to the HD650's 2 mW to reach 110 dB, or 2.2 V RMS and 0.9 mA.  See that huge difference in terms of current? Voltage-wise, roughly double: current, more than 100 times.
  
 ​What's worse, most devices tend to be current-limited to prevent your amp from frying your headphones, or frying itself. Hence why the HE6 is notoriously hard to drive.

 Check out here for more info: nwavguy.blogspot.com/2011/09/more-power.html


----------



## Solrighal

Hi folks,
  
 I'm using an ODAC and my player is JRMC19. Can anyone tell me what sample rates I should be using in JRMC to get the best from the ODAC?
  
 On the Output Format page in JRMC's settings I have two coloumns, input & output. The output column has a drop-down menu for each input value & I'm unsure how to set this up. Here's a pic of the options I see..
  

  
 Many thanks in advance for any help or advice you folks can provide.


----------



## WilliamLeonhart

From what I know it actually depends on your source file. For example if it's mp3 then 44100 always.
  
 Actually on the ODAC I'm not sure if a change in bit depth or sample rates will actually make a noticeable change in sound quality.


----------



## riverlethe

You will have to downsample anything above 96kHz to 96kHz. Do you have the new ODAC or the original? The new version supports 88.1kHz.


----------



## MrMateoHead

williamleonhart said:


> From what I know it actually depends on your source file. For example if it's mp3 then 44100 always.
> 
> *Actually on the ODAC I'm not sure if a change in bit depth or sample rates will actually make a noticeable change in sound quality.*


 
  
 It has actually been shown that the ODAC set to run at 96 kHz has higher distortion when and if you are playing back a file of lesser quality (like 48 kHz or 44.1 kHz). The upsampling in Windows seems to add noise.
  
 It is audible? I don't think so - I keep mine pegged at 96 kHz anyway since it will sound better when gaming / watching a movie.


----------



## Solrighal

Thanks guys. I have the original version and only really use FLAC. I don't have much high res yet but I'm working on it. I guess I'll just leave it at its default settings the. Thanks again.


----------



## KeithEmo

In general, it's best to let the music play at its original sample rate - because any sort of resampling will cause some slight (whether audible or not) change. Therefore, for all the sample rates up to the maximum one the 0DAC supports, you're best off leaving them set to "leave as original"; only use the resampling option to resample rates above the top one supported by the 0DAC (and set those to resample to the top rate it does support).
  
  
 Quote:


solrighal said:


> Hi folks,
> 
> I'm using an ODAC and my player is JRMC19. Can anyone tell me what sample rates I should be using in JRMC to get the best from the ODAC?
> 
> ...


----------



## Solrighal

Thanks guys. I have the original version and only really use FLAC. I don't have much high res yet but I'm working on it. I guess I'll just leave it at its default settings. Thanks again.


----------



## JamesBr

riverlethe said:


> You will have to downsample anything above 96kHz to 96kHz. Do you have the new ODAC or the original? The new version supports 88.1kHz.


 
 +1


----------



## Sam21

Sorry folks, I have a question:
  
 How do I make the JDS Labs O2 work without batteries and only with the AC adapter ? I took the batteries out some time ago but the unit wouldn't turn on without the batteries !


----------



## lucasseijikc

Good night, folks!
  
  
 I was checking the different assemblers of the Objective2/ODac and started to wonder:
  
 Is there any major difference between the distinct O2s, ODacs and O2+ODacs from different assemblers (JDS Labs, Mayflower Audio, Epiphany Acoustics and etc)?
 If yes, what is it? Does it affect the sound quality?
  
  
 Thank you in advance!
  
  
 Lucas Seiji K. C.


----------



## jseaber

sam21 said:


> Sorry folks, I have a question:
> 
> How do I make the JDS Labs O2 work without batteries and only with the AC adapter ? I took the batteries out some time ago but the unit wouldn't turn on without the batteries !


 
  
 O2 should always operate from its AC adapter, whether batteries are connected or not. Perhaps your AC adapter has failed. Feel free to call/email for assistance.


----------



## Sam21

thank you for letting me know, I will try to take out the batteries tomorrow,


----------



## Packdemon

My O2+ODAC has recently begun making a hissing sound (aside from the normal sound floor) when music is playing, and whenever I paused my music I still hear the same hissing sound for about 7 more seconds before it disappears. Same thing happens with all of my other headphones when connected with my O2+ODAC. Does anyone know how to salve this issue, or even know what the cause is?


----------



## raoultrifan

While O2 is hissing, disconnect the ODAC and check if hissing has gone.


----------



## riverlethe

Which version of the ODAC is it? The DAC could be muting after a few seconds of no playback.


----------



## Packdemon

I have the 02 + ODAC combo, so every time that I want to disconnect the ODAC separately from the O2 I would to desolder it out. But, just in case I miss understood you, if I pullout the usb connected from my computer to the O2 + ODAC then yes all audio stops as would be expected. 
  
 It's RevB.
  
 Now, I am getting another weird issue, whem my computer volume is set to 0 and the O2+ODAC isn't I still hear audio.


----------



## raoultrifan

So, is it from the O2 and from ODAC you're saying?
  
 Is the ground wire from the volume pot. still there? You know, that wire from ground of potentiometer and chassis that grounds the pot. circuit.


----------



## Packdemon

raoultrifan said:


> So, is it from the O2 and from ODAC you're saying?
> 
> Is the ground wire from the volume pot. still there? You know, that wire from ground of potentiometer and chassis that grounds the pot. circuit.


 
 Yup, it's still there, but I've always debated it's effectiveness considering that the chassis has rubber feet preventing it from making direct uninsulated contact with my desk. I currently have the metal frame of my desk ground to my wall outlet, maybe I should connect the ground from my ground solder point on the pcb to the metal frame of desk using solder and a thin wire that can stick out from in between the front panel and the chassis. Or, would that just just be unnecessary and taking things too far?
  
 Just to be sure, you are talking about this, right?


----------



## BrettMatthews

Today I removed R19 and R23 to turn my standard 2.5 / 6.5 gain setting O2 amp into a 1 / 2.5 low gain setting amp and find it is much better for my HE-400. I am actually in the middle of the volume range on the amp now (where it was designed to be used), where are before I was only using about 1/4 of the dial.
  
 I had been searching to see how the 1x gain option would work with a headphone like the HE-400 and didn't find anything so I just wanted to say that it does work very well, you are actually able to use some of the volume adjustment now. I believe this is the gain setting that is best used for the HE-400, I am no expert but to my ears this is the best. Plus the lower the gain the better.


----------



## raoultrifan

Yes Packdemon, that's the ground wire I was speaking about. The case is made from aluminium and without proper grounding it may catch RF interferences and transmit them over to your circuit PCB. Some OPAMPs might work better if RFI are shielded.  Just be sure the PCB ground is connected to the mettal chassis fo your O2/ODAC (feel free to measure the voltage between ground and chassis, just in case a short circuit was done somewhere).


----------



## Draulius

Would I be able to use half of the volume dial without it getting too loud with either the HD650 and HE400i?


----------



## raoultrifan

Draulius, that really depends on the gain you choose on your O2 headamp. Also, half of volume dial means about 15% of max. volume for logharitmic potentiometers, so turning O2's pot to 12 o'clock is about 15% of max. volume. 
  
 I strongly recommend you to modify your O2's gain as follow:
 - 1X or 1.5X for low gain
 - 2.5X or 3X for high gain (at most 3.5X if you're sure your DAC will never output more than 2V RMS). With a gain of 3X you should be able to drive these 2 headphones very well and the volume pot will most likely stay between 1-2 o'clock for resonable output levels.
  
 My O2 has 1.5X/3.5X low/high gains and I'm quite pleased with this setting (input opamp was changed to LME49720 and will be changed again with MUSES8820 soon).


----------



## castleofargh

yeah it also clearly depends on what you define as too loud ^_^.
 my "too loud" is normal listening level for many people I know. I have a hd650 and my O2, gain 1X at about 9 o clock and don't touch it(I found that magic place where it's close to the loudness I wanted and also has low channel imbalance, any move on either sides and I get like +0.3db channel imbalance).
 it is in practice loud enough for me listening to music and watching TV shows on the computer without having to turn it up unless we're talking about some utube videos sometimes that are recorded with really low volume level(but then if I really want to listen to it I just switch to another DAC. notmoving that volume setting on the O2!!!!!^_^).
 so in my case 50% is too loud with the hd650 most of the time with the computer @ 100%, and I would need to lower the computer volume digitally by a good margin. but again, I insist on this, my "too loud" isn't a world wide reference level.
  
  
 also I'm talking about using the O2 that gives about 2V, you could very well use a portable gear with only 1V and be 6db down compared to my use. or have a desktop DAC that reached up to 3V and be even louder.
 I know I'm not helping, but those are all real possibilities to factor in.


----------



## Packdemon

castleofargh said:


> yeah it also clearly depends on what you define as too loud ^_^.
> my "too loud" is normal listening level for many people I know. I have a hd650 and my O2, gain 1X at about 9 o clock and don't touch it(I found that magic place where it's close to the loudness I wanted and also has low channel imbalance, any move on either sides and I get like +0.3db channel imbalance).
> it is in practice loud enough for me listening to music and watching TV shows on the computer without having to turn it up unless we're talking about some utube videos sometimes that are recorded with really low volume level(but then if I really want to listen to it I just switch to another DAC. notmoving that volume setting on the O2!!!!!^_^).
> so in my case 50% is too loud with the hd650 most of the time with the computer @ 100%, and I would need to lower the computer volume digitally by a good margin. but again, I insist on this, my "too loud" isn't a world wide reference level.
> ...


 
 That's a pretty sick avatar. I just watch the episode.


----------



## raoultrifan

castleofargh, are you totally positive that your O2 has a gain of 1X while you listen to HD650/300ohms headphones?
 I'm asking you that because if your input source is having around 2V RMS, with O2 at 1X gain and volume pot at 9 o'clock, then your output levels are about 0.2-0.25 volts RMS; that corresponds to an output power of about 0.0002mW. Honestly, with a gain of 1X I use the volume pot at 11-12 o'clock with my AKG 550 which are quite sensitive 32ohms headphones.
  
 I again recommend a gain between 2.5X and 3.5X for Senheiser 650 headphones, because you need at least 2V RMS to drive them properly (105-110dB) and around 3V RMS to drive them a bit louder (110-115dB). Also, you need some power reserve for high dynamic music or for low volume recordings (classic music is usually -2dB or -3dB quiter than pop/rock music).
  
 More details you can find here:
 - http://www.head-fi.org/t/476345/headphone-sensitivity-power-requirements-compared
 - https://www.hydrogenaud.io/forums/index.php?showtopic=100405


----------



## dazzerfong

raoultrifan said:


> castleofargh, are you totally positive that your O2 has a gain of 1X while you listen to HD650/300ohms headphones?
> I'm asking you that because if your input source is having around 2V RMS, with O2 at 1X gain and volume pot at 9 o'clock, then your output levels are about 0.2-0.25 volts RMS; that corresponds to an output power of about 0.0002mW. Honestly, with a gain of 1X I use the volume pot at 11-12 o'clock with my AKG 550 which are quite sensitive 32ohms headphones.
> 
> I again recommend a gain between 2.5X and 3.5X for Senheiser 650 headphones, because you need at least 2V RMS to drive them properly (105-110dB) and around 3V RMS to drive them a bit louder (110-115dB). Also, you need some power reserve for high dynamic music or for low volume recordings (classic music is usually -2dB or -3dB quiter than pop/rock music).
> ...




650's have a sensitivity of 103 dB/V RMS: if your derived voltage of 0.2V, that means he's listening at approximately 91 dB RMS. 100+ dB is - very- loud.


----------



## raoultrifan

nwavguy recommends on his blog a 3X gain for HD650 headphones when used with USB DAC, but also a gain of 5X for 300-600 ohms headphones. Max. SPL of 115dB would be very loud, but not 100dB! A shotgun has 140dB after all.
  
 If you need to hear all details from your music then you need to have music peaks up to 105-110dB on your headphones (I am speaking here about maximum SPL and not about continuously or average music SPL! Continuous or average SPL would probably be around 95-100dB).
  
 Myself I'm listening to a level having peaks to around 95dB in the morning or during the night (really quite environment) and peaks around 100-115dB in the evening (noisy environment). Sometimes I'm listening to max. peaks between 110-115dB for few minutes only (at most 1 track). Last audiometry test I did a couple of years ago and doctor said I am perfectly fine for my age. 
  
 nwavguy says that HD650 needs around 3.6V RMS to get a max. peak SPL of 114dB and I believe him. Also, a correct setup for a headamp would be between 115dB and 120dB when volume pot is to the max. for a 2V RMS input source (that means average music of around 105-110dB with volume to the max., depending on music type and dynamic). Anyway, most of our music sources are having at most 2V RMS peaks, so a gain of 3X looks quite resonable for a 300 ohms headphones.
  
*NOTE*: For our safety here's a guideline we should all read first when setting max. gain of our O2 headamp, based on headphones used: http://www.dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/.


----------



## dazzerfong

raoultrifan said:


> nwavguy recommends on his blog a 3X gain for HD650 headphones when used with USB DAC, but also a gain of 5X for 300-600 ohms headphones. Max. SPL of 115dB would be very loud, but not 100dB! A shotgun has 140dB after all.
> 
> If you need to hear all details from your music then you need to have music peaks up to 105-110dB on your headphones (I am speaking here about maximum SPL and not about continuously or average music SPL! Continuous or average SPL would probably be around 95-100dB).
> 
> ...


 
 While nwavguy is a fan of headroom (there's nothing wrong with that), you're misinterpreting what he said: he said if you want the headroom of 114 dB, use those gain settings. He never advocated using it at those volumes daily.​
  
 Oh, and 100 dB -is- loud, especially for headphone listening. No way about it. Just because you think it's fine doesn't make it so in general.


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## raoultrifan

Thanks dazzerfong for your thoughts, but I believe we're a bit offtopic now...sorry for that 
  
 Getting back to initial question of Draulius ("Would I be able to use half of the volume dial without it getting too loud with either the HD650 and HE400i?") my answer remains the same: setting 1X or 1.5X for low gain and 2.5X or 3X for high gain will make O2 to handle HD650 and HE400i very well.
  
 Happy listening!


----------



## dazzerfong

raoultrifan said:


> Thanks dazzerfong for your thoughts, but I believe we're a bit offtopic now...sorry for that
> 
> Getting back to initial question of Draulius ("Would I be able to use half of the volume dial without it getting too loud with either the HD650 and HE400i?") my answer remains the same: setting 1X or 1.5X for low gain and 2.5X or 3X for high gain will make O2 to handle HD650 and HE400i very well.
> 
> Happy listening!


 

 Agreed on those points: I'm tempted to knock-out some resistors as my O2 came preconfigured with 2.5x and 6.5x gain, and I practically never use 6.5x, and I'm forced to use 20% of Windows volume to the ODAC else I'm using only like 25% of the pot (this is with a HD700).​


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## raoultrifan

Please, do not ever use 6.5X with regular USB DACs or other normal home sources that outputs 2V RMS! 6.5 x 2V = 13V so your O2 will clipp and your ears will get blown away in 1 second! NLM2068D distorts signal when used with a gain of 6.5X anyway and lowering the volume from Windows means loosing dynamic and adding noise.
  
 I have a small kid around and I can't afford a 6.5X setting on my O2. He's pressing all the buttons from the house, especially while I'm listening music. 
  
 3.5X should be max. gain for O2, if used with regular gear (home USB DACs): 3.5 x 2V RMS = 7V RMS, which is almost max. voltage swing from O2.
  
 Feel free to cut the wire from your 6.5 resistors and that will make it 1X instead of 6.5X, so no need to solder anything else. This way you'll convert your O2 from 2.5X/6.5X into a 2.5X/1X in no time.


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## dazzerfong

raoultrifan said:


> Please, do not ever use 6.5X with regular USB DACs or other normal home sources that outputs 2V RMS! 6.5 x 2V = 13V so your O2 will clipp and your ears will get blown away in 1 second! NLM2068D distorts signal when used with a gain of 6.5X anyway and lowering the volume from Windows means loosing dynamic and adding noise.
> 
> I have a small kid around and I can't afford a 6.5X setting on my O2. He's pressing all the buttons from the house, especially while I'm listening music.
> 
> ...


 

 That's why I set the Windows audio output to only 20%. Besides, the amp's hidden away in my desk, so meh. The 6.5x helps with the phone at times because the internal amp is so damn weak, but I rarely use it anyway.​
  
 And no, lowering volume in Windows does -not- lose dynamic range. It used to in XP, but since Vista onwards, audio was handled in a 32-bit environment ensuring that no dynamic range was lost. Read here: http://www.head-fi.org/t/671220/effective-number-of-bits-or-why-you-have-to-keep-software-at-full-volume-is-nonsense


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## castleofargh

raoultrifan said:


> castleofargh, are you totally positive that your O2 has a gain of 1X while you listen to HD650/300ohms headphones?
> I'm asking you that because if your input source is having around 2V RMS, with O2 at 1X gain and volume pot at 9 o'clock, then your output levels are about 0.2-0.25 volts RMS; that corresponds to an output power of about 0.0002mW. Honestly, with a gain of 1X I use the volume pot at 11-12 o'clock with my AKG 550 which are quite sensitive 32ohms headphones.
> 
> I again recommend a gain between 2.5X and 3.5X for Senheiser 650 headphones, because you need at least 2V RMS to drive them properly (105-110dB) and around 3V RMS to drive them a bit louder (110-115dB). Also, you need some power reserve for high dynamic music or for low volume recordings (classic music is usually -2dB or -3dB quiter than pop/rock music).
> ...


 

 well I never cared to look up until now ^_^, but doing some very lousy check I end up with about 163mv and that's with a 1khz test tone at -3db(in case those 3 db matter).
 so that should get me around 87db @1khz on the hd650 if I'm not wrong. and 90db with our 3db for the test tone not being full scale ^_^.
 it's so nice when numbers happen to fall about right.
 now I probably go even lower as I use replay gain and such, so yup I'm on the quiet side of music.
 and sure that's not how the audiophile willing to listen "like he's really at the concert", will use his hd650. but I'm not that guy at all, and I use earplugs when I go see someone live, else I have to leave after a few minutes.
 but I warned about my very loud not necessarily being everyone else's "too loud".
  
  
 now if I had no way to check for channel imbalance I would most likely try to go a little past half of the volume knob as an attempt to limit the risks, that's indeed a very rational option, just output to 24bit to use the extra room for digital volume and all is well. but where I am right now it's close to the loudness I like to use, and I measure about 0.06db difference between left and right, so I'm mighty happy with that result(it took me like 10mn of going back and forth trying to find that damn spot and switching plugs to measure left then right where it would be the most balanced). I could get good balance in the 2 o clock area, but it's very much too loud for any practical use for me (the hd650 being the lowest sensitivity gear I own).


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## MrMateoHead

dazzerfong said:


> Agreed on those points: I'm tempted to knock-out some resistors as my O2 came preconfigured with 2.5x and 6.5x gain, and I practically never use 6.5x, and I'm forced to use 20% of Windows volume to the ODAC else I'm using only like 25% of the pot (this is with a HD700).​


 

 When using my PSB's the O2 is way, way too powerful at 2.5X.
  
 I drop windows volume to 80-90. I set the O2 to around 9 O'Clock as others mention, to ensure that the channels are not perceptibly out of balance.
  
 Because I usually use WMP or Foobar, I drop the WMP volume slider to about 10-20 (whilst system volume is still high). If using Foobar, I will use the Easy EQ parabolic or Built-in EQs to drop the global gain down however much I need to to have some play in the dial.
  
 I am seriously contemplating cutting resistors to drop to 1X / 2.5X but just haven't bothered to just yet - just because the PSBs are too damn efficient doesn't mean 6.5X hasn't been useful before . . .


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## BrettMatthews

mrmateohead said:


> When using my PSB's the O2 is way, way too powerful at 2.5X.
> 
> I drop windows volume to 80-90. I set the O2 to around 9 O'Clock as others mention, to ensure that the channels are not perceptibly out of balance.
> 
> ...




I changed my 6.5 gain setting to 1 and have been very happy for my HE-400. I was worried that it was going to be too little power but I am only around half on the amp with my computer output at max. If you aren't using the 6.5 at all I would recommend changing it to 1.


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## MrMateoHead

brettmatthews said:


> I changed my 6.5 gain setting to 1 and have been very happy for my HE-400. I was worried that it was going to be too little power but I am only around half on the amp with my computer output at max. If you aren't using the 6.5 at all I would recommend changing it to 1.


 

 Thanks for the vote - I think I probably will go ahead and perform the surgery before too long.


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## raoultrifan

@dazzerfong - We all know very well that digitaly lowering volume of your DAC means we're actually loosing dynamic (http://www.thewelltemperedcomputer.com/Intro/SQ/VolumeControl.htm), also SNR and THD are increasing. I understand that Windows 32-bits resolution means a lot for our small ears that can "only" resolve a dynamic of 120dB which is about 20 bits of audio resolution, but:
 - every electrical component from our soundcards (transformer, transistor, internal DAC, OPAMPs, resistors etc.) introduces a small amount of noise expressed in nV/Hz and this is measurable with any decent scope;
 - the sum of all soundcard's components noise will give us the final THD+noise;
 - digitaly lowering DAC's volume from Windows to 20% will not lower your soundcard's noise, it will just lower input music's volume and that means you're loosing soundcard's dynamic and you're increasing THD+noise! This is why I recommend you to change the gain from 6.5X to a lower value and use 100% of Windows volume.
 Best dynamic out of your DAC is when output volume is at max., so every dB counts here. Try doing a RMAA on your soundcard + O2 headamp with Windows volume to the max. and O2 gain at 1X and compare results with another RMAA with Windows volume at 20% and O2's gain at 6.5X; you'll be surprized to realize how a -100dB soundcard will become a -90dB one or even worse.
  
 @castleofargh - I'm glad you're happy with O2 at 1X gain and volume pot. at 9 o'clock while listening to HD650.
  
 @MrMateoHead - PSB are 32ohms, so 1X gain should be more than enough to drive them decently. It's great that you modified the gain from 6.5X to 1X, like I suggested; this is what I did myself a couple of years ago when I realized 6.5X is useless for me.


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## dazzerfong

raoultrifan said:


> @dazzerfong - We all know very well that digitaly lowering volume of your DAC means we're actually loosing dynamic (http://www.thewelltemperedcomputer.com/Intro/SQ/VolumeControl.htm), also SNR and THD are increasing. I understand that Windows 32-bits resolution means a lot for our small ears that can "only" resolve a dynamic of 120dB which is about 20 bits of audio resolution, but:
> - every electrical component from our soundcards (transformer, transistor, internal DAC, OPAMPs, resistors etc.) introduces a small amount of noise expressed in nV/Hz and this is measurable with any decent scope;
> - the sum of all soundcard's components noise will give us the final THD+noise;
> - digitaly lowering DAC's volume from Windows to 20% will not lower your soundcard's noise, it will just lower input music's volume and that means you're loosing soundcard's dynamic and you're increasing THD+noise! This is why I recommend you to change the gain from 6.5X to a lower value and use 100% of Windows volume.
> ...


 

 Obviously the dynamic range is best when it's 100% volume, but if it's not, you're losing, what, 20dB​ of dynamic range? Like I care if the noise floor is -90dB vs -60 dB: either way, I still can't hear it. As long as it's audibly transparent, it doesn't matter. If you actually read the article you linked, by using a DAC with enough bits, the noise increase is so minimal it doesn't matter. Which is precisely why you should output 24-bit audio to the ODAC.
  
 And no, our ears do not have a fixed dynamic range. To go from 0 dB to 120 dB will blow our ears, especially when you add background noise on top.


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## raoultrifan

You're not loosing so much, you're right, especially for 24-bit audio, but what about 16-bit redbooks? This is Head-Fi and every dB counts, right? 
  
 http://hyperphysics.phy-astr.gsu.edu/hbase/sound/earsens.html


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## castleofargh

I came to the conclusion that basic theory is great help as general guideline, and when convenient we should always try to follow it. but often life isn't so kind and we end up with compromises.
  
  I guess the right question is to determine if one of the choices can have audible consequences. and IMO only channel imbalance is really at risk here. hiss is pretty much a non issue on the O2, dynamic range or linearity on something like an odac also are very fine. so almost everything is in practice, ok to do with little chances of being audibly different.
 channel imbalance potentially being more audible than the rest because it concerns even the loudest signals.


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## dazzerfong

raoultrifan said:


> You're not loosing so much, you're right, especially for 24-bit audio, but what about 16-bit redbooks? This is Head-Fi and every dB counts, right?
> 
> http://hyperphysics.phy-astr.gsu.edu/hbase/sound/earsens.html


 

 In terms of that, it makes no difference if the file is 24-bit or 16-bit. Hell, the principle still applies if it's 8-bit music file: after all, the encoder is just padding with zeros and shifting everything to make up a 32/24-bit file.. And yes, our ears can hear between 0 dB to 130 dB (at least before pain kicks in), but no: that doesn't mean we listen to music like that. I'll be surprised if there's even music with a dynamic range greater than 60 dB (except perhaps Mahler).​
  
 I'd like to nuke the 6.5x gain, but I usually use it for my phone where the output is weak. I usually use 2.5x.


  


castleofargh said:


> I came to the conclusion that basic theory is great help as general guideline, and when convenient we should always try to follow it. but often life isn't so kind and we end up with compromises.
> 
> I guess the right question is to determine if one of the choices can have audible consequences. and IMO only channel imbalance is really at risk here. hiss is pretty much a non issue on the O2, dynamic range or linearity on something like an odac also are very fine. so almost everything is in practice, ok to do with little chances of being audibly different.
> channel imbalance potentially being more audible than the rest because it concerns even the loudest signals.


 

 Agreed: in the beginning, I was so damn confused what people needed amps for, considering that I could just plug my HD700's into my computer output. However, I realised that by taking the pot to less than unity and dialing back the audio on Windows, I can achieve a sweet spot where noise was minimised yet the range was usable.​


----------



## KeithEmo

dazzerfong said:


> Obviously the dynamic range is best when it's 100% volume, but if it's not, you're losing, what, 20dB​ of dynamic range? Like I care if the noise floor is -90dB vs -60 dB: either way, I still can't hear it. As long as it's audibly transparent, it doesn't matter. If you actually read the article you linked, by using a DAC with enough bits, the noise increase is so minimal it doesn't matter. Which is precisely why you should output 24-bit audio to the ODAC.
> 
> And no, our ears do not have a fixed dynamic range. To go from 0 dB to 120 dB will blow our ears, especially when you add background noise on top.


 
  
 You might convince me that you might not hear the difference between a S/N of 90 dB and 120 dB (and I don't recall ever being annoyed by the actual noise floor on a CD), but I remember when cassettes and open reel tapes were in the 60 dB to 70 dB S/N range, and I remember the background hiss being quite audible - and quite annoying.
  
 If you play a 16 bit file, then reduce its volume "digitally", _WITHOUT CHANGING THE WORD LENGTH_, then you will end up reducing the resolution audibly. So, if you play a 16/44k audio file in Windows, and turn the level down to "25%" using the Windows volume control, you will then have a 14 bit file.... In order to avoid this, some "good" digital volume controls may in fact "upscale" your 16/44k file to 24/44k before applying the level adjustment, which is what most good audio editing software programs do (and the digital volume controls in things like Sabre DACs). However, the basic controls in Windows do _NOT_ do this...
  
 You're also assuming that the noise floor is "pure noise", which it should be if the file was properly authored, and dithered. However, some files aren't properly authored and, if the digital noise floor hasn't been properly dithered, then the noise floor may not be "nice smooth white noise". (Depending on the situation, undithered digital "noise floor" can contain various audio artifacts, which make it rather more unpleasant sounding than smooth white noise. This doesn't matter if it is truly inaudible but, if the noise floor is just barely audible, can make it much more annoying.)


----------



## dazzerfong

keithemo said:


> You might convince me that you might not hear the difference between a S/N of 90 dB and 120 dB (and I don't recall ever being annoyed by the actual noise floor on a CD), but I remember when cassettes and open reel tapes were in the 60 dB to 70 dB S/N range, and I remember the background hiss being quite audible - and quite annoying.
> 
> If you play a 16 bit file, then reduce its volume "digitally", _WITHOUT CHANGING THE WORD LENGTH_, then you will end up reducing the resolution audibly. So, if you play a 16/44k audio file in Windows, and turn the level down to "25%" using the Windows volume control, you will then have a 14 bit file.... In order to avoid this, some "good" digital volume controls may in fact "upscale" your 16/44k file to 24/44k before applying the level adjustment, which is what most good audio editing software programs do (and the digital volume controls in things like Sabre DACs). However, the basic controls in Windows do _NOT_ do this...
> 
> You're also assuming that the noise floor is "pure noise", which it should be if the file was properly authored, and dithered. However, some files aren't properly authored and, if the digital noise floor hasn't been properly dithered, then the noise floor may not be "nice smooth white noise". (Depending on the situation, undithered digital "noise floor" can contain various audio artifacts, which make it rather more unpleasant sounding than smooth white noise. This doesn't matter if it is truly inaudible but, if the noise floor is just barely audible, can make it much more annoying.)




Errr, Windows does adjust the stack to 32-bit for processing then outputs 24 bits. Like I said, for XP it was a problem: not in newer Windows. 

http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/

Also, my maths was wrong: it's closer to losing put around 10 dB when my volume is at 10%.


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## castleofargh

when in properties level blablah, you can right click on the number to switch it from db to % (at least in win7). 
  
 @keith, wouldn't just setting windows to 24bit avoid that? I really don't know anything about win volume, I always let it maxed out and use foobar to set the volume with the output set in wasapi at 24bit. so I never cared to try and check .


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## KeithEmo

dazzerfong said:


> Errr, Windows does adjust the stack to 32-bit for processing then outputs 24 bits. Like I said, for XP it was a problem: not in newer Windows.
> 
> http://blog.szynalski.com/2009/11/17/an-audiophiles-look-at-the-audio-stack-in-windows-vista-and-7/
> 
> Also, my maths was wrong: it's closer to losing put around 10 dB when my volume is at 10%.


 
  
 I believe you're correct, which should obviate that single large issue in Windows 7 and up. However, you're still "trusting" Windows to manipulate bits. Converting word length upwards, for example from 16 bits to 32 bits, is a lossless process (you pad the LSBs with zeros), but mixing signals, changing levels, and then reducing the word length of the result are all non-lossless processes which can potentially affect audio quality. Unfortunately, while it's simple to test for an output signal being "bit-perfect", it's not so simple to confirm whether a signal which is known to _NOT_ be bit-perfect is "audibly equal" or not. Therefore, you are trusting Windows to "do it right", which many audiophiles aren't prepared to do. 
  
 There are also still "scaling issues" when the digital audio is converted back to analog again.
  
 Lets assume you have a 24 bit DAC which has a 100 dB S/N and outputs a 1 V RMS signal. (Note that this means that your "24 bit DAC" is really only resolving something like 18 bits - because bits 19 through 24 produce output that falls below the noise floor.) Assuming that your amplifier produces full output with a 1 V input signal, this should work out well, because a full-scale signal on the DAC will produce a full-scale output from the amp.
  
 However, now let's assume that your 24 bit DAC, with the 100 dB S/N ratio, puts out 10 V RMS with a full scale signal (the amp remains the same). Now let's assume that, in order to prevent things from overloading, you reduce the level of the signal 10x (20 dB) using a "perfect" digital volume control. The analog output of the DAC will now be 20 dB lower, and so will "line up" with the input sensitivity of the amp; however, since the noise floor of the DACs output will be the same, your DAC will now have an "effective S/N" of only 80 dB (you've "perfectly" reduced its maximum output by 10x, but the noise floor remains the same, so the S/N is reduced). 
  
 The basic problem is that, in real life, a 24 bit DAC is USUALLY not really resolving 24 bits. Most DACs have a low enough noise floor to convert a 16 bit signal and give you 'the full benefit of all 16 bits". However, let's start with a 16 bit signal, and reduce its level by a factor of 16 - which means that we'll convert it to 24 bits, then divide the resulting numbers all by 16. By doing this, we will in fact have a 24 bit file that contains all the original information, but reduced in level by 16x. However, our 16 bits of real information, which used to reside in "bits 1 through 16 - counting from MSB", is now in "bits 5 through 20 - counting from the MSB".... and, if our DAC can only really resolve 19 or 20 bits, then the lowest few bits will now be lost in the noise and distortion floor of the DAC. (Whereas, before our "perfect volume reduction", they were quite a few dB above it.)  
  
 (And, before someone suggests that "we can reduce the volume using 32 bit precision, then convert the result back to 16 bits afterwards to preserve the dynamic range of the DAC" I'll remind you that, if we do that, we're right back where we started from - with a 16 bit signal that runs the DAC to full scale output - and is too loud for the input of the amp. If you follow the entire signal chain you'll realize that using even a perfect digital volume control to lower the output of a DAC to match the input sensitivity of the amplifier, _AS A PROCESS_, isn't perfect anyway. For best sound quality, you really want to scale things so tat the scale of the analog output of the DAC matches the input sensitivity of the amp. )


----------



## dazzerfong

keithemo said:


> I believe you're correct, which should obviate that single large issue in Windows 7 and up. However, you're still "trusting" Windows to manipulate bits. Converting word length upwards, for example from 16 bits to 32 bits, is a lossless process (you pad the LSBs with zeros), but mixing signals, changing levels, and then reducing the word length of the result are all non-lossless processes which can potentially affect audio quality. Unfortunately, while it's simple to test for an output signal being "bit-perfect", it's not so simple to confirm whether a signal which is known to _NOT_ be bit-perfect is "audibly equal" or not. Therefore, you are trusting Windows to "do it right", which many audiophiles aren't prepared to do.
> 
> There are also still "scaling issues" when the digital audio is converted back to analog again.
> 
> ...




Personally, I care more about whether or not I could actually here the noise rather than whether or not it's bit perfect or not. But to each their own: however, do not obfuscate the issue to suit your agenda. Audiophiles aren't exactly the best technical lot, so I'd trust Windows more than appeal to snake-oil specialists who profit exactly from this type of fear-mongering. 

The fact remains, using digital control is more than fine for most scenarios, unless you're setting the volume to 1% and letting your amp actually amplify: in that scenario, of course you'd have a stupidly crap SNR.

However, you are right in saying that if you want bit perfect, go 100% volume: however, you'd also need something like ASIO or WASAPI to prevent the mixer from potentially messing up the mixing. 

On a side not, considering you're using V RMS, shouldn't the SNR be lower by 10 dB?


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## KeithEmo

dazzerfong said:


> Personally, I care more about whether or not I could actually here the noise rather than whether or not it's bit perfect or not. But to each their own: however, do not obfuscate the issue to suit your agenda. Audiophiles aren't exactly the best technical lot, so I'd trust Windows more than appeal to snake-oil specialists who profit exactly from this type of fear-mongering.
> 
> The fact remains, using digital control is more than fine for most scenarios, unless you're setting the volume to 1% and letting your amp actually amplify: in that scenario, of course you'd have a stupidly crap SNR.
> 
> ...


 
  
 I'm inclined to agree with you - that what concerns me most is whether I can hear something or not. However, if we're discussing "agendas", then let's talk about yours as well. Most audiophiles I know _DO_ use WASAPI - and they use it specifically because it's the only way to prevent Windows from "messing up the audio" by altering the sample rate of their files without permission if they happen to have files recorded at different sample rates. Whether you happen to agree that stuff like that matters or not, the fact remains that other people do in fact care about it, and many of them probably would like to know that they're throwing away any benefit they imagined they were buying by spending extra for a 24 bit file instead of a 16 bit one if they turn that digital volume control down to 5%.
  
 Considering that Microsoft chose to automatically alter the sample rate of any file you play in Windows that happens to be recorded at any sample rate other than the default setting (with good reasons from a programming standpoint), and that the settings necessary to avoid this are not the default (WASAPI), I'm not especially inclined to believe that the programming choices they make in Windows are "best" or even "good" from an audiophile perspective. However, I do agree that they can probably program a basic digital volume control without screwing it up. I also personally agree with you that the "bit reduction effects" of using a digital volume control - in moderation - are usually inaudible. (But I also find it significant that, once you're using WASAPI, that digital volume control is about the only thing you can do to forfeit the bit-perfect performance that you presumably chose WASAPI to ensure. I would have much preferred to see a setting in Windows named "bit-perfect" that locked out all signal modifications since, in technical terms, maintaining a bit-perfect data path is about the only way to know with certainty that no processing has occurred which will reduce the audible quality of the digital audio you're playing.
  
 And, since most people choose the 0DAC _because_ of its excellent technical performance, it seems only reasonable that they might like to know that they will be compromising that performance - at least to a degree - if they use that digital volume control. (And saying that is no more "fear mongering" then it is to suggest that, if you don't lock your front door, there is at least the possibility that someone will wander in.)
  
 The "technically proper" way to correct the situation if you have a DAC that has an output level that is too high for the input of the amplifier you're connecting it to is to reduce the analog output level of the DAC, or reduce the gain of the amp, so that they "line up". This will maintain the best S/N, and also allow you to use the level control on the amp near the top of its range, where analog potentiometers track the best. In the context of a DAC and separate headphone amp, where the output of the DAC is very high, and so forces you to have the level control on the amp way down at the bottom, the simple solution is to put a passive attenuator between them. (You can make one for about $2, or buy really pretty commercial ones for $10 or $20.) Or, if you're comfortable performing very minor modifications, you can simply change the resistors in the amp that control its gain (we're talking two 50 cent resistors there).
  
 On that side note.... When you calculate or measure S/N, you are comparing two measured values, and the result is a ratio; as long as both
 values are measured the same way, it doesn't matter which way you choose. The same holds true for relative differences; for example, if I reduce the maximum signal level by half, and the noise floor remains the same, then the S/N will be reduced by "50%" - expressed in dB - regardless of whether both levels were originally measured in peak or RMS. (The only area where you need to be careful is when comparing dissimilar numbers, such as comparing a maximum output level of 2 VRMS from a CD player, with the size of an LSB step, to determine "the overall S/N" due to the 16 bit word length. In that case, the LSB step noise - the voltage step caused by turning one bit on and off - would actually be peak-peak. You can also run into unusual values if your noise itself is unusual... but that's because the "standard" ratio between RMS values and peak values is only specified for a sine wave; if you have very spiky noise, for example, the RMS value could be a much smaller percentage of the peak value than it would be for a sine wave. However, still, if you're measuring the same noise signal, using the same method, then all that counts is the ratio between the readings.)


----------



## dazzerfong

keithemo said:


> I'm inclined to agree with you - that what concerns me most is whether I can hear something or not. However, if we're discussing "agendas", then let's talk about yours as well. Most audiophiles I know _DO_ use WASAPI - and they use it specifically because it's the only way to prevent Windows from "messing up the audio" by altering the sample rate of their files without permission if they happen to have files recorded at different sample rates. Whether you happen to agree that stuff like that matters or not, the fact remains that other people do in fact care about it, and many of them probably would like to know that they're throwing away any benefit they imagined they were buying by spending extra for a 24 bit file instead of a 16 bit one if they turn that digital volume control down to 5%.
> 
> Considering that Microsoft chose to automatically alter the sample rate of any file you play in Windows that happens to be recorded at any sample rate other than the default setting (with good reasons from a programming standpoint), and that the settings necessary to avoid this are not the default (WASAPI), I'm not especially inclined to believe that the programming choices they make in Windows are "best" or even "good" from an audiophile perspective. However, I do agree that they can probably program a basic digital volume control without screwing it up. I also personally agree with you that the "bit reduction effects" of using a digital volume control - in moderation - are usually inaudible. (But I also find it significant that, once you're using WASAPI, that digital volume control is about the only thing you can do to forfeit the bit-perfect performance that you presumably chose WASAPI to ensure. I would have much preferred to see a setting in Windows named "bit-perfect" that locked out all signal modifications since, in technical terms, maintaining a bit-perfect data path is about the only way to know with certainty that no processing has occurred which will reduce the audible quality of the digital audio you're playing.
> 
> ...


 

 Of course whether or not people are using WASAPI matters or not: they want to maintain bit-perfection. Whether or not it matters as much as they claim is a totally different matter which I'm not willing to get into here, as it's another topic for another time. However, I'm willing to accept one reasoning for WASAPI: its exclusive mode. The 'technically proper' way of using an attenuator is perhaps the best compromise to please both sides of the camp, or just splicing in new resistors.
  
 Your history of using completely terrible analogies continues . No, a more appropriate analogy (but still flawed) would be to use octane 98 fuel rather than regular fuel on the off-chance that it might've been that much of an inch better. The bad part of that analogy is that you pay more for octane 98, and you don't here (well, not really).

 And yes, I know SNR is a ratio: you didn't address my question at all. Why is it -20 dB rather than -10 dB? Is it because SNR is a measure of the power domain rather than amplitude?


----------



## castleofargh

dazzerfong said:


> And yes, I know SNR is a ratio: you didn't address my question at all. Why is it -20 dB rather than -10 dB? Is it because SNR is a measure of the power domain rather than amplitude?


 
 his example is to reduce a 10V DAC to 1V, the gain in db will be 20log(1/10) = -20db , the unit for the voltage doesn't matter already at this point, it's canceled by the ratio.
  
 I would argue with the values given as example, because 10volts for a DAC output is a little unrealistic as far as I know. but the logic behind the example does stand.


----------



## KeithEmo

dazzerfong said:


> And yes, I know SNR is a ratio: you didn't address my question at all. Why is it -20 dB rather than -10 dB? Is it because SNR is a measure of the power domain rather than amplitude?


 
  
 Actually, the whole calculation was done in voltage.
  
 In binary numbers, each bit is 1/2 the value of the one above it, and twice the value of the one below it.
 This means that one bit equates to 6 dB - in volts.
 So, when you reduce the overall resolution available by one bit, while keeping the noise floor the same,
 you are halving the dynamic range, and so reducing it by 6 dB.
 So a 16 bit CD file has a maximum dynamic range of 96 dB (16 bits x 6 dB per bit).
 And, if you reduce the available resolution by three bits, you reduce that by 18 dB.
  
 I assumed, because of the physical noise floor of the DAC being around 100 dB, you would lose between three and four bits of real resolution - which rounds to somewhere around 20 dB.
  
 The realities of what is audible are actually also slightly more complicated. For one thing, on any well mastered CD, there will only be 15 bits of audio data - because the LSB will have been "sacrificed" to dither to provide a smoother and more pleasant noise floor, and probably some noise shaping. And, on the other side of things, depending on the circumstances, sounds at a level one or two bits _BELOW_ the noise floor may in fact still be audible - but it depends heavily on the character of those sounds and how long they persist.
  
 (The value of a single bit, as being twice the one below it and half the one above it, is always specified in voltage.)
 If you look at what's actually happening electrically, the dB's used for power and voltage are the same.
 If you raise the voltage by 6 dB, that means you double it.
 And, if you double the _POWER_, you raise it by 3 dB.
 However, if you double the voltage (+6 dB) into a given load you are quadrupling the power into that load (also the same +6 dB).
 Therefore, the same measured numbers do give you the same dB ratio no matter which way you do it.
 (The difference in notation is there because power varies as the square of the voltage.)
  
  
 My point, without digging into the math in detail, was that a DAC with a S/N of 96 dB has just enough dynamic range to deliver everything recorded in a 16 bit audio file without clipping the loudest parts or losing the quietest ones below the noise floor. If you lower that resolution by one or two bits, by reducing the volume with a digital volume control, then you reduce the level of everything equally, which means that the lowest few bits will end up being below the noise floor.


----------



## dazzerfong

keithemo said:


> Actually, the whole calculation was done in voltage.
> 
> In binary numbers, each bit is 1/2 the value of the one above it, and twice the value of the one below it.
> This means that one bit equates to 6 dB - in volts.
> ...


 

 Cheers for the maths mate. I always mix up power and amplitude, and thus 3 dB or 6 dB.​
  
 For all those still curious about how the ODAC performs in 24-bit mode while undergoing digital volume control, I'm fairly sure his site had a breakdown of it somewhere.


----------



## Nec3

Is there such thing as opamp rolling for the O2?


----------



## raoultrifan

Ya Nec3, why not? 
  
 Try LME49720 in 1'st stage or OPA2227. Also, MUSES8820 and MUSES02 should work very well.
 Check AGDR's posts from diyaudio as well, you'll be amazed what can be done with this little O2 headamp.
  
 Cheers!


----------



## Nec3

raoultrifan said:


> Ya Nec3, why not?
> 
> Try LME49720 in 1'st stage or OPA2227. Also, MUSES8820 and MUSES02 should work very well.
> Check AGDR's posts from diyaudio as well, you'll be amazed what can be done with this little O2 headamp.
> ...


 
 Thanks for the quick reply!

 Originally when I got my O2, it came with JRC4556AD's (C001A), but then one channel blew so JDS Labs sent me JRC4556AD (E005A). Though they relieved some sibilance with my AKG Q701's, it sounds too flat for me now to enjoy. Eventually I went off into tubes and now my tube amp is dying. Welp.
  
 If I went for the LME49720, which part of the amp is considered the 1st stage?
  
 Are there any such opamps that have a "V shaped" sound signature? Sorry if I misunderstand opamp rolling for tube rolling.


----------



## Kwangsun

I have a question. I have a HIFIDIY ESS ES9023 USB DAC + Fiio E9 combo on my desk. Would it make sense for me to buy the ODAC+O2? Seems odd to drop so much clams on an amp+dac when I have a dac that has similar specs as the ODAC and an amp that isn't utter junk. The E9 isn't THAT great an amp though I'll admit.


----------



## raoultrifan

Nec3, I was referring to NJM2068, the OPAMP dealing with voltage amplification. OPA2227 or LME49720 should work just fine, also MUSES8820 or MUSES02.
  
 In case you want to swap the 2 x NJM4556 output buffers, then this is a bit more complicated. You can swap them with LME49720 or LME49860, but these will only drive 64-600ohms headphones.


----------



## raoultrifan

kwangsun said:


> I have a question. I have a HIFIDIY ESS ES9023 USB DAC + Fiio E9 combo on my desk. Would it make sense for me to buy the ODAC+O2? Seems odd to drop so much clams on an amp+dac when I have a dac that has similar specs as the ODAC and an amp that isn't utter junk. The E9 isn't THAT great an amp though I'll admit.


 
  
 Kwangsun, I would say that ODAC sounds better than HIFIDIY 9023 DAC. As for the Fiio E9 vs. O2, feel free to read Nwavguy's headamps compare webpage; I would say that that O2 is top notch at this price tag and Fiio E9 is not even close. You can also check Tyll's reviews and tests with many other headphone amplifiers; http://www.head-fi.org/t/670889/tyll-hersten-innerfidelitys-21-amp-measurements for details.


----------



## Kwangsun

Yeah, even I know that the E9 isn't a great amplifier. Thanks for the link!


----------



## Nec3

raoultrifan said:


> Nec3, I was referring to NJM2068, the OPAMP dealing with voltage amplification. OPA2227 or LME49720 should work just fine, also MUSES8820 or MUSES02.
> 
> In case you want to swap the 2 x NJM4556 output buffers, then this is a bit more complicated. You can swap them with LME49720 or LME49860, but these will only drive 64-600ohms headphones.


 


 I went ahead for the LME49720HA (+ Adapter). I don't think the Muses02's price was justifiable for me


----------



## Nec3

It took me a while to realize that the O2+ODac truly is the most boring combo ever.
 It's not that it's bad, it's just (like advertised), dead neutral. Can I use the word neutral? It's -/+0.1db across the 20hz/20khz board.
  
 It can certainly drive my Q701's at 63ohms at something like 400mW (when the Q's are rated for 200mW).
*but I would like to reiterate the Q701 + ODAC/O2 is a boring combo, but I love it.*

 Why? I don't know, the same reason I love the ER4S.


agdr said:


> ....*The O2 designer noted in his blog that the LME49720 was similar to the NJM2068, with the major downside just being it was more expensive*........
> [Shortened quote for space-sake, sorry if I took your quoted quote out of context]


 

 Let's just hope NWAVGuy is wrong in my case.


----------



## MrMateoHead

nec3 said:


> It took me a while to realize that the O2+ODac truly is the most boring combo ever.
> It's not that it's bad, it's just (like advertised), dead neutral. Can I use the word neutral? It's -/+0.1db across the 20hz/20khz board.
> 
> It can certainly drive my Q701's at 63ohms at something like 400mW (when the Q's are rated for 200mW).
> ...


 

 I'm glad you like the boring combo, but in all honestly, are you sure it ain't yo headphones that are boring? The flatter I get my sound, the more amazing it becomes . . . . just sayin'. But if you really wanted to save some money, I'd skip the ODAC for now and just enjoy having a proper beastly little O2 amp. I always felt the ODAC was only that last "10%" of fidelity I've been enjoying for awhile now.
  
 FYI I am half responding to this post because I have a new monitor with a mostly "flat" gamma response of 2.2, 90-100% sRGB color and fairly even lighting - I can't imagine asking for "oversaturation" and extra "backlight bleed" or IPS glow or whatever. Causes eye fatigue, you know, plus it isn't true to the images. Wonder why audio is so different to so many.


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## 329161

Does the o2 + odac rival the sound from the oppo ha1 by any chance? Man that thing blew me away.


----------



## Nec3

mrmateohead said:


> I'm glad you like the boring combo, but in all honestly, are you sure it ain't yo headphones that are boring? The flatter I get my sound, the more amazing it becomes . . . . just sayin'. But if you really wanted to save some money, I'd skip the ODAC for now and just enjoy having a proper beastly little O2 amp. I always felt the ODAC was only that last "10%" of fidelity I've been enjoying for awhile now.
> 
> FYI I am half responding to this post because I have a new monitor with a mostly "flat" gamma response of 2.2, 90-100% sRGB color and fairly even lighting - I can't imagine asking for "oversaturation" and extra "backlight bleed" or IPS glow or whatever. Causes eye fatigue, you know, plus it isn't true to the images. Wonder why audio is so different to so many.


 
 The problem for me is that the Q701 is very dry with the O2+ODAC. Notes don't tend to last very long (specifically the bass), so that's why I preferred the analogue tubes that somehow compensated for this. So even though the ER4S is supposed to be compensated for the Harman Target Response Curve, it still somehow has the perfect timbre and balance for overall enjoyment; which is "flat"
  
 I somewhat realized that of course, the music is what make or breaks the final rating. Great masterings tend to compliment the ODAC+O2/Q701 Combo, but the average masterings leaves satisfactory enjoyment.
  
 Unfortunately tube amps in my experience don't have the greatest durability so I'm switching back to full solid state.
  
 The ODAC is the only DAC I have, other than the FiiO X5... I'll try that combo when I get home.


----------



## JyNadaril

If the gain settings are defaulted to 2.5x and 6.5x, is it possible to change it to 1x and 3.5x? How would do you do it if you can?


----------



## raoultrifan

It has been written for several times on this forum on how to modify gain on O2, also on nwavguy's blog.
  
 There are 2 resistors you need to change, actually for gain of 1x you just need to unplug 1 resistor, but for for the gain of 3.5x you need to change the other resistor. I suggest you check nwavguy's blog for more details; there you'll see the schematic and it will be quite easy for you to understand it. (sorry I can't provide you with a direct link, but nwavguy has been banned on head-fi and we're not allowed to provide you links or copy-paste from his blog).
  
 Cheers!


----------



## Bibo

Sorry for nitpickking, but there are actually two resistors for each gain setting. So he has to remove the two resistors for low gain and change the ones for high gain.
 If 1x/2,5x is acceptable, only the two resistors for high gain have to be removed. I did that with my O2.
  
 Edit: You will also get to the desired result if you remove only one resistor for low gain and change one resistor high gain. So it is totally correct what raoultrifan wrote. Many apologies.


----------



## jseaber

jynadaril said:


> If the gain settings are defaulted to 2.5x and 6.5x, is it possible to change it to 1x and 3.5x? How would do you do it if you can?


 
 Medium Gain, 1.0 and 3.5x
  R17 and R21 = NONE
  R19 and R23 = 604 Ω


----------



## Draulius

Should I get the 250 Ohm or 600 Ohm version of a headphone for this DACAMP? I like to stay at 1x gain whenever possible.


----------



## HaVoC-28

draulius said:


> Should I get the 250 Ohm or 600 Ohm version of a headphone for this DACAMP? I like to stay at 1x gain whenever possible.


 
  
 Both of them will work on O²/ODAC . (seams you are talking about Beyers ...) . Peraphs on some very quiet records you will have to switch to 2.5/3X gain with the 600 ohms version (depend on how loud you listen) .


----------



## jring

havoc-28 said:


> Both of them will work on O²/ODAC . (seams you are talking about Beyers ...) . Peraphs on some very quiet records you will have to switch to 2.5/3X gain with the 600 ohms version (depend on how loud you listen) .


 
  
 If the question was about beyers, the 600 ohm version is usually the best - although the difference is not that big. So if you don't plan mobile use, get 600 ohms.
  
 Joachim


----------



## rs0cal

Hey guys! The o2 is my first amp so I was wondering if someone is kind enough to help me out.
  
 I definitely wanna protect myself from hearing damage. I am using Audirvana with the O2. From the picture shown, is it safe to leave the Audirvana's volume at 0dB and the O2 low gain at 9 o' clock?


----------



## raoultrifan

Hi Rs0cal,
  
 With Audirvana at 0dB (full volume) you'll probably attack the O2 with at most 2V RMS; having O2's volume at 9 o'clock (that would be about 20-22% of max. volume turn) when gain is 1X, that means the output voltage would probably be around 4%-6% of 2V RMS (volume pot. is logarithmic), so...something between 0.08-0.12 V RMS, quite safe I would say, even for IEMs.


----------



## wolfram

Just got in on the massdrop for O2+ODAC RevB for what seems to be a pretty good price, would be my first amp & DAC at the same time. Wondering if I made the right choice, got a M50 & SE215 for now but thinking of going high-end soon. Heard the HE-6 are hard to drive, is it possible to drive them with this combo?


----------



## dazzerfong

wolfram said:


> Just got in on the massdrop for O2+ODAC RevB for what seems to be a pretty good price, would be my first amp & DAC at the same time. Wondering if I made the right choice, got a M50 & SE215 for now but thinking of going high-end soon. Heard the HE-6 are hard to drive, is it possible to drive them with this combo?


 
 The designer of this amp actually used the HE-6 as a criteria for driving difficult headphones! So yes, it's more than possible to drive the combo.


----------



## wolfram

dazzerfong said:


> The designer of this amp actually used the HE-6 as a criteria for driving difficult headphones! So yes, it's more than possible to drive the combo.


 

 Awesome! Though I've heard conflicting reports, so maybe I'd go for the LCD-2 or T1 instead. Either way can't wait to try it out, now I just have to deal with the wait... Mid-Late Dec


----------



## raoultrifan

Hifiman recommends EF5 (2 watts.channel) or EF6 (5 watts per channel) to correctly drive HE6 headphones. Most likely their 83.5dB low sensitivity is responsable of this.  You'll actually not feed HE6 with so much power at once, but usually planars need the right voltage/amperage ratio to be driven correctly. Usually tubes or J-FET diamond buffers can do that properly, but I doubt that 2 paralleled NJM4556 can do it perfectly, especially for the HE6 planars, despite the fact that O2 has enough voltage and current to drive them.
  
 You can also read http://www.head-fi.org/products/hifiman-he-6-planar-headphone for more details.
  
 http://www.6moons.com/audioreviews/hifiman2/1.html might help too. ("The HE-6 prototype needs to see 5 to 6 watts into 60 ohms." Based on a purely resistive calculation, this would equate to an amp rated at 50wpc into 8 ohms [...])
  
 Perhaps the much more easy to drive Hifiman like HE400, HE400s, HE400i, HE500 and also HE560 would be a better choice for O2 to drive them decently.
  
 As for the LCD-2 headphones, why would you want to pay 1.000 USD for a pair of 15 Watts headphones to be driven by a 100 USD 0.7 Watts amplifier? It's not all about max. power of the amplifier, just read Tyll's reviews and tests about these planar headphones and about decent headphone amplifiers prior to spend a lot of money on planar headphones. Try not spending on a headphone more than twice the price of your combo, because it doesn't worth it, unless you intend to upgrade your DAC/amp soon.
  
 Regards!


----------



## wolfram

raoultrifan said:


> Hifiman recommends EF5 (2 watts.channel) or EF6 (5 watts per channel) to correctly drive HE6 headphones. Most likely their 83.5dB low sensitivity is responsable of this.  You'll actually not feed HE6 with so much power at once, but usually planars need the right voltage/amperage ratio to be driven correctly. Usually tubes or J-FET diamond buffers can do that properly, but I doubt that 2 paralleled NJM4556 can do it perfectly, especially for the HE6 planars, despite the fact that O2 has enough voltage and current to drive them.
> 
> You can also read http://www.head-fi.org/products/hifiman-he-6-planar-headphone for more details.
> 
> ...


 
 Thanks for heads-up! This is why it's such a great community, way more knowlegable people helping beginners out. Plan was to actually get either the HD800 / LCD 2 / T1 / HE-6 first and the FiiO X5ii, hoping for a decent-ish semi-portable setup. Later on, I'd get a desktop amp that can power speakers and headphones. Any thoughts, especially now I'm getting the O2+ODAC?


----------



## dazzerfong

raoultrifan said:


> Hifiman recommends EF5 (2 watts.channel) or EF6 (5 watts per channel) to correctly drive HE6 headphones. Most likely their 83.5dB low sensitivity is responsable of this.  You'll actually not feed HE6 with so much power at once, but usually planars need the right voltage/amperage ratio to be driven correctly. Usually tubes or J-FET diamond buffers can do that properly, but I doubt that 2 paralleled NJM4556 can do it perfectly, especially for the HE6 planars, despite the fact that O2 has enough voltage and current to drive them.
> 
> You can also read http://www.head-fi.org/products/hifiman-he-6-planar-headphone for more details.
> 
> ...


 
 Of course Hifiman is going to recommend their own amplifiers for it: it's called business! I find it interesting, though, what your rationale is behind:

_....but usually planars need the right voltage/amperage ratio to be driven correctly. Usually tubes or J-FET diamond buffers can do that properly, but I doubt that 2 paralleled NJM4556 can do it perfectly, especially for the HE6 planars, despite the fact that O2 has enough voltage and current to drive them._
  
 If it can supply enough voltage and current, and provide more than decent distortion figures and slew rates, what's the problem with it? The prototype might've needed 5W to go loud, but at 5W, the production one could go up to ~120 dB.


----------



## raoultrifan

dazzerfong said:


> Of course Hifiman is going to recommend their own amplifiers for it: it's called business! I find it interesting, though, what your rationale is behind:
> 
> _....but usually planars need the right voltage/amperage ratio to be driven correctly. Usually tubes or J-FET diamond buffers can do that properly, but I doubt that 2 paralleled NJM4556 can do it perfectly, especially for the HE6 planars, despite the fact that O2 has enough voltage and current to drive them._
> 
> If it can supply enough voltage and current, and provide more than decent distortion figures and slew rates, what's the problem with it? The prototype might've needed 5W to go loud, but at 5W, the production one could go up to ~120 dB.


 
 I got to this conclusion after analyzing schematics and specs from some Stax and Hifiman amplifiers and also based on Hi-Fi magazine reviews and recommendations. I hope I'll be able to buy Hifiman560 or AlphaDogs pretty soon, then I'll give'em a try on my ODAC/O2, but I'm quite sure will be driven correctly.
  
 http://www.theabsolutesound.com/articles/a-survey-of-six-high-end-headphones/?page=3 - "The HE-6 offers a neutral tonal balance, exceptional transient speed, extremely high resolution, plus a quality of musical “soulfulness.” The HE-6 comes ever so close to matching the resolution of Audeze’s more expensive LCD3 and does so while offering what some consider even more accurate overall timbre. Remember, though, that the HE-6 is extremely sensitive to and demanding of associated electronics. When pushed by inadequate amps the HE-6 can sound bright, edgy, and ill at ease, but with appropriate amps the headphone’s sonic persona changes, becoming powerful, masterful, engaging, and at times downright majestic. Hint: To ensure “known good” results, try powering the HE-6 with HiFiMAN’s beefy, high-output EF6 amp."
  
 So, it's not all about if O2 has the power to drive HE-6, it's mostly on how O2 will pair with HE-6.


----------



## rs0cal

raoultrifan said:


> Hi Rs0cal,
> 
> With Audirvana at 0dB (full volume) you'll probably attack the O2 with at most 2V RMS; having O2's volume at 9 o'clock (that would be about 20-22% of max. volume turn) when gain is 1X, that means the output voltage would probably be around 4%-6% of 2V RMS (volume pot. is logarithmic), so...something between 0.08-0.12 V RMS, quite safe I would say, even for IEMs.


 
  
 Should I also lower the volume to something like -4.0 dB if I am going to be using high gain too? I'm afraid i might blow out the speakers if I leave it at 0dB.
  
 I am using an Audeze El-8 and I find that being a low-impedance planar, they just dont provide enough power for me at times on low gain?
  
 EDIT: Nevermind, I was able to research a little bit further into this. I am assuming that 0dB is fine for the source volume on low gain and should be lowered for high gain to prevent chances of clippings.


----------



## dazzerfong

raoultrifan said:


> http://www.theabsolutesound.com/articles/a-survey-of-six-high-end-headphones/?page=3 - "The HE-6 offers a neutral tonal balance, exceptional transient speed, extremely high resolution, plus a quality of musical “soulfulness.” The HE-6 comes ever so close to matching the resolution of Audeze’s more expensive LCD3 and does so while offering what some consider even more accurate overall timbre. Remember, though, that the HE-6 is extremely sensitive to and demanding of associated electronics. When pushed by inadequate amps the HE-6 can sound bright, edgy, and ill at ease, but with appropriate amps the headphone’s sonic persona changes, becoming powerful, masterful, engaging, and at times downright majestic. Hint: To ensure “known good” results, try powering the HE-6 with HiFiMAN’s beefy, high-output EF6 amp."


 
 Not a fan of The Absolute Sound, but I suppose to each their own. I've yet to try an amp that really changes the characteristics of headphones. It's a shame they don't say what amps sounded wrong with it so people can have an opportunity to see if they're exaggerating or not. I'll defer to your expertise though, as I have no experience with the HE-6: only the Sennheiser HD's and AKGK700 series.

 It's a good thing the creator of the amp isn't here, because he'd scream "DBT them, volume-match it".


----------



## gikigill

The HE-6 has been tested at 73db of sensitivity so take official figures with a huge pinch of salt. I have tried them on 5w/ch and they sound thin and harsh and when powered by a 110w\ch they suddenly perked up, the bass became very tactile, very visceral.


----------



## HaVoC-28

raoultrifan said:


> As for the LCD-2 headphones, why would you want to pay 1.000 USD for a pair of 15 Watts headphones to be driven by a 100 USD 0.7 Watts amplifier? It's not all about max. power of the amplifier, just read Tyll's reviews and tests about these planar headphones and about decent headphone amplifiers prior to spend a lot of money on planar headphones. Try not spending on a headphone more than twice the price of your combo, because it doesn't worth it, unless you intend to upgrade your DAC/amp soon.
> 
> Regards!


 
  
 You put the money where it matter the most => the Headphone . Not all planar are so power hungry ... O² will not be a problem for the Current line from Audeze . if people don't like the pairing it's another story .


----------



## Takeanidea

raoultrifan said:


> I got to this conclusion after analyzing schematics and specs from some Stax and Hifiman amplifiers and also based on Hi-Fi magazine reviews and recommendations. I hope I'll be able to buy Hifiman560 or AlphaDogs pretty soon, then I'll give'em a try on my ODAC/O2, but I'm quite sure will be driven correctly.
> 
> http://www.theabsolutesound.com/articles/a-survey-of-six-high-end-headphones/?page=3 - "The HE-6 offers a neutral tonal balance, exceptional transient speed, extremely high resolution, plus a quality of musical “soulfulness.” The HE-6 comes ever so close to matching the resolution of Audeze’s more expensive LCD3 and does so while offering what some consider even more accurate overall timbre. Remember, though, that the HE-6 is extremely sensitive to and demanding of associated electronics. When pushed by inadequate amps the HE-6 can sound bright, edgy, and ill at ease, but with appropriate amps the headphone’s sonic persona changes, becoming powerful, masterful, engaging, and at times downright majestic. Hint: To ensure “known good” results, try powering the HE-6 with HiFiMAN’s beefy, high-output EF6 amp."
> 
> So, it's not all about if O2 has the power to drive HE-6, it's mostly on how O2 will pair with HE-6.


 
 The Alpha Dogs work beautifully with the 02/Odac. The He-6's need something special.


----------



## wes1099

I just built an O2 amp, and the left channel is louder than the right by a significant amount. Anyone know why? I tested it on both gain levels with multiple pairs of headphones and it still happens.


----------



## raoultrifan

Follow the original schematic and measure all resistors from gain (you can also measure all resistors from all circuit). Perhaps one resistor is having the wrong value.
 Can you lower the volume source and use the potentiometer to the max? Maybe the pot is defective...who knows?


----------



## raoultrifan

Wes1099, have you checked R17 & R19 & R21 & R23 if correct values? Also  R12 & R13 and R14 & R20 and R3 & R7 and R16 & R22 worth to be checked too. Just be 110% sure all of these resistors have to correct values, as per nwavguy's schematic.


----------



## wes1099

raoultrifan said:


> Wes1099, have you checked R17 & R19 & R21 & R23 if correct values? Also  R12 & R13 and R14 & R20 and R3 & R7 and R16 & R22 worth to be checked too. Just be 110% sure all of these resistors have to correct values, as per nwavguy's schematic.


I measured the values of each resistor before I soldered them on, but I can check them again. I have tried changing the volume of the source and turning the pot up and down but it did not change anything. The JDS labs support guy suggested that I install the 3.5mm jack instead of the 1/4 inch jack to see if that changes anything. 

Sent from my LG-D850 using Tapatalk


----------



## wes1099

I just realized, it might not be that the left channel is louder than the right, it might be that the right channel simply lacks the low-mid and low frequencies, but the upper mids and highs are there.  I measured each resistor and they all measured the way they should except for 2. R8 measured 235Kohm when it should measure ~270Kohm like R4, R5, and R24. Then, R25 measures 0.4Mohm when it should measure 1.5Mohm. My measurements are probably not 100% accurate, but they should be close.


----------



## wes1099

lol I figured it out. I had a bad wire on the 1/4inch headphone jack...


----------



## raoultrifan

I'm glad you did resolved it!
  
 Anyway, what about R8 and R25? Are you sure are not the correct values? If so, you should probably replace those with the correct values resistors.


----------



## wes1099

raoultrifan said:


> I'm glad you did resolved it!
> 
> Anyway, what about R8 and R25? Are you sure are not the correct values? If so, you should probably replace those with the correct values resistors.


 
 I am not sure my multimeter is reading them correctly. I will measure with a different multimeter later and see if they need to be replaced.


----------



## adydula

Did u measure them in the circuit or out of the circuit??
  
 A.


----------



## KeithEmo

If you measure a resistor in-circuit, it's quite possible and even likely that you will get an INCORRECT value. (Depending on the circuitry involved, and your meter, it's also possible to damage the circuitry itself.) Some meters have what's called a "low power ohms scale" - if so, then using this would make it more likely that you would get correct readings, and less likely that you would damage something, but it's still not a great idea to measure resistors in-circuit unless you specifically know that it's OK in the particular device you're testing.
  
 Quote:


adydula said:


> Did u measure them in the circuit or out of the circuit??
> 
> A.


----------



## KeithEmo

dazzerfong said:


> Of course Hifiman is going to recommend their own amplifiers for it: it's called business! I find it interesting, though, what your rationale is behind:
> 
> _....but usually planars need the right voltage/amperage ratio to be driven correctly. Usually tubes or J-FET diamond buffers can do that properly, but I doubt that 2 paralleled NJM4556 can do it perfectly, especially for the HE6 planars, despite the fact that O2 has enough voltage and current to drive them._
> 
> If it can supply enough voltage and current, and provide more than decent distortion figures and slew rates, what's the problem with it? The prototype might've needed 5W to go loud, but at 5W, the production one could go up to ~120 dB.


 
  
 Exactly.... a lot of people seem to be confused about the relationship between voltage, current, and power.
  
 When you see something like "the impedance is 50 ohms and it needs 2 watts to reach 110 dB", what you need to do is to calculate the voltage and current it would take to produce 2 watts _INTO THAT LOAD_, and, if the amp can deliver _BOTH ENOUGH VOLTAGE AND ENOUGH CURRENT_ to reach that level, then it should be fine.
  
 Remember that most amps have both a voltage limit and a current limit. For example, let's assume I run both a "speaker" amp and a headphone amp using a single 4556 op amp off of a +/- 15V power supply. The 15V power rails limit both to about 8V RMS. However, if the speaker amp is rated to work into 4 ohms, then it can deliver about 2 Amps (2000 mA), while a single 4556 op amp is rated for about 70 mA. If you do the calculations, you will find that, into a pair of 150 ohm headphones, both will deliver the _SAME_ amount of power - because the power will be limited by their output voltage (a pair of 150 ohm headphones will only draw about 50 mA at 8 VRMS; which both the speaker amp and the op amp can deliver easily). However, into an 8 ohm load, the speaker amp can deliver 8 watts, while the 4556 op amp will deliver less than 40 mW (because its 70 mA current limit limits it to delivering that much power into 8 Ohms).
  
 The upshot of all this is that.....
  
  - With regular headphones (low to medium impedance, high efficiency), most headphone amps can deliver both enough voltage and enough current to get them to run plenty loudly and sound very good. (They'll get loud and sound good.)
  
 - With high impedance headphones (150 ohms, 300 ohms, 600 ohms), most headphone amps can deliver plenty of current, but many amps that run on lower voltage rails can't deliver enough voltage. (They'll sound great but may not get very loud, and you may be able to clip the amp at relatively low output levels, although there's a good chance you'll peg the volume control and it may just not get very loud).
  
 - With low efficiency planars (usually low to medium impedance), most amplifiers would deliver plenty of voltage, but you often need a "speaker amp" or a specially designed headphone amp to deliver enough CURRENT to drive them satisfactorily. (And a headphone amp that can't deliver enough current will sound fine at very low levels, but will clip very easily.) Headphone amps that use op amps like the 4556 will NOT deliver enough current to run low efficiency planars.
  
 - High efficiency planars have pretty much the same requirements as regular headphones.
  
 You also need to consider that the ratings you see on op amps are usually "absolute maximums". An NJM4556 is rated to put out about 70 mA, which means that two paralleled ones could could put out at most 140 mA (if they don't share exactly it could be somewhat less). However, they will probably produce more distortion at current levels near that than they do at lower levels, so they may not sound good at all if you run them near their limits (this will depend on the individual op amp, and on other aspects of the overall design).


----------



## wes1099

adydula said:


> Did u measure them in the circuit or out of the circuit??
> 
> A.


 
  
  


keithemo said:


> If you measure a resistor in-circuit, it's quite possible and even likely that you will get an INCORRECT value. (Depending on the circuitry involved, and your meter, it's also possible to damage the circuitry itself.) Some meters have what's called a "low power ohms scale" - if so, then using this would make it more likely that you would get correct readings, and less likely that you would damage something, but it's still not a great idea to measure resistors in-circuit unless you specifically know that it's OK in the particular device you're testing.


 
 I measured them all before I soldered them to the PCB, then I measured them on the PCB without power applied to it.


----------



## aka180

So I've seen mixed reactions to this question: is the popping sound when shutting down the O2 harmful? One of mine gives a slight click while the other gives a healthy pow! I generally unplug my cans before pressing the power. I've done the suggested tests and voltage relays seem good. I've also checked dc voltage at the output terminals and it peaks at 0.6v when turning on or off. From what I understand, this should ok. How can I be sure that it's OK to leave my headphones connected when powering off?


----------



## raoultrifan

I never had a problem with this clicking/popping DC on my headphones. What headphones are you talking about, please?


----------



## wes1099

aka180 said:


> So I've seen mixed reactions to this question: is the popping sound when shutting down the O2 harmful? One of mine gives a slight click while the other gives a healthy pow! I generally unplug my cans before pressing the power. I've done the suggested tests and voltage relays seem good. I've also checked dc voltage at the output terminals and it peaks at 0.6v when turning on or off. From what I understand, this should ok. How can I be sure that it's OK to leave my headphones connected when powering off?


 
  
  


raoultrifan said:


> I never had a problem with this clicking/popping DC on my headphones. What headphones are you talking about, please?


 
 I get the slightest popping sound about 5% of the time when I turn on my O2. Although, mine is so quiet that you have to listen carefully for it.


----------



## Bananaheadlin

Does anyone have any experience with the standalone ODAC plugged in with the computer? I have it hooked up with my Audioengine A2 desktop speakers, but the ODAC makes everything too loud. My system sound is always somewhere between 10 - 15, and music player around 50%. If I turn the A2 down too low, then the volume distribution between the speakers will be unbalanced. Anyone have any experience with this?


----------



## aka180

raoultrifan said:


> I never had a problem with this clicking/popping DC on my headphones. What headphones are you talking about, please?



I'm using Beyerdynamic dt990 premium 250 ohm and sennheiser ie80. The popping is irrelevant of the volume setting.


----------



## Francisk

I always switch on my O2 or any other amp for that matter, before plugging in my headphone.


----------



## HaVoC-28

I don't , my O² will celebrate his third year next month and it didn't harm any of my headphones 
	

	
	
		
		

		
			





.
  
 There is a little hump when switching off but nohting to bother with .


----------



## MrMateoHead

bananaheadlin said:


> Does anyone have any experience with the standalone ODAC plugged in with the computer? I have it hooked up with my Audioengine A2 desktop speakers, but the ODAC makes everything too loud. My system sound is always somewhere between 10 - 15, and music player around 50%. If I turn the A2 down too low, then the volume distribution between the speakers will be unbalanced. Anyone have any experience with this?


 
  
 Sounds mainly like the 2V output of the ODAC is too much for the A2's internal amps to handle (they are optimized for 1V or so?). Are you using the RCA or 3.5mm inputs? Not that it should make a difference, but you never really know.
  
 1) I'd start by setting the A2 to wherever their balanced output is, then 2) use the music player to cut volume to reasonable levels. If I still couldn't get a good volume range, I'd 3) start trimming the windows volume down.


----------



## Bananaheadlin

I'm using the 3.5mm inputs. My music player is currently set at 50%, and Windows at 10%. It works great, but the only problem is that my web browser (and other programs such as Cortana) become much louder, because my speaker volumes are usually set to play my music at a comfortable volume, which is only outputting at 50% from the music player.  
	

	
	
		
		

		
		
	


	




 Any there any other (software or hardware) solutions that might work for this?


----------



## Psalmanazar

My ODAC+O2 combo is clipping with dynamically mastered recordings on my HD 650s both 1x and 3.5x gain with foobar outputting in WASAPI or ASIO in exclusive mode at 24-bit. It does not clip at even louder volumes in DirectSound but the DirectSound imaging is so much worse. The windows volume control still affects the DAC but this shouldn't be the cause of the clipping. Any possible solutions?


----------



## castleofargh

psalmanazar said:


> My ODAC+O2 combo is clipping with dynamically mastered recordings on my HD 650s both 1x and 3.5x gain with foobar outputting in WASAPI or ASIO in exclusive mode at 24-bit. It does not clip at even louder volumes in DirectSound but the DirectSound imaging is so much worse. The windows volume control still affects the DAC but this shouldn't be the cause of the clipping. Any possible solutions?


 

 sure it's clipping and not some freezes of sort from the computer, or some conflicts with another application trying to use the device? I can't think of something that would have a reason to clip in wasapi and not with directsound.
  
 random stuff to look up, but shouldn't fit your situation if I understood it correctly:
 is there a volume threshold making the clipping come or go? test both in foobar and on the O2.
 you have the "prevent clipping according to peaks" choice in foobar?
 remove all EQ or DSPs to check if they could be responsible for clipping or distortions.
 asio would be asio4all, the best way to use it is to uninstall it, IMO.
 wasapi, I never noticed a difference, but I would guess push is the proper method for the odac. should also not matter, but maybe try changing the buffer value for wasapy.


----------



## bolmeteus

How does the ODAC perform against the Behringer UCA202 DAC. What are the sonic differences? Thank you!


----------



## raoultrifan

nwavguy, the developer of ODAC, has an article on his blog with extensive tests done to UCA202 interface. Feel free to read his thoughts and compare specs and graphs from UCA202 with ODAC.
  
 Basically, looks like UCA202 is the best bung for the buck, especially at this price.


----------



## bolmeteus

raoultrifan said:


> nwavguy, the developer of ODAC, has an article on his blog with extensive tests done to UCA202 interface. Feel free to read his thoughts and compare specs and graphs from UCA202 with ODAC.
> 
> Basically, looks like UCA202 is the best bung for the buck, especially at this price.


this is probably stupid of me to not know new guy developed the ODAC, I did not read his excellent review on the uca202 completely.. Going there now!! 
I have the uca202 and it is mind blowing for the price.


----------



## B-Rayn

Would the O2 amp be a good match for a dap like the Fiio X5ii?  I am new to headphone amps and am finding mixed reviews. Some say an O2 amp may not be noticeable others say it will increase clarity.
 Or does it just depend on headphones used?


----------



## Nec3

b-rayn said:


> Would the O2 amp be a good match for a dap like the Fiio X5ii?  I am new to headphone amps and am finding mixed reviews. Some say an O2 amp may not be noticeable others say it will increase clarity.
> Or does it just depend on headphones used?


 
  
 I don't have any experience with the 2nd gen X5, however I would say that my X5 1st gen would sound pretty much the same when I use them alone compared to using it with an O2. 

 Some headphones benefit from more power being pushed into my headphones. For example I get a bit more treble when pushing more power into the Q701's with an O2, which of course leads me into thinking that the sound is clearer.

 Try and see if your headphone is listed here and use the impedance vs frequency graph option: http://www.headphone.com/pages/build-a-graph


----------



## B-Rayn

nec3 said:


> I don't have any experience with the 2nd gen X5, however I would say that my X5 1st gen would sound pretty much the same when I use them alone compared to using it with an O2.
> 
> Some headphones benefit from more power being pushed into my headphones. For example I get a bit more treble when pushing more power into the Q701's with an O2, which of course leads me into thinking that the sound is clearer.
> 
> Try and see if your headphone is listed here and use the impedance vs frequency graph option: http://www.headphone.com/pages/build-a-graph


 
 Thanks very much for the reply and help.


----------



## Psalmanazar

WASAPI push mode and nothing else in the surge protector but my Thinkpad and the O2 wart prevents the O2 from clipping the ODAC.. Everything else but DirectSound clips. Strange.


----------



## MrMateoHead

psalmanazar said:


> WASAPI push mode and nothing else in the surge protector but my Thinkpad and the O2 wart prevents the O2 from clipping the ODAC.. Everything else but DirectSound clips. Strange.


 
 I would try using different media players - does it clip when using Windows Media Player as well? How about VLC?
  
 Are you 100% positive that the recordings you are listening to don't clip? (You can use something like Audacity to take a look). I couldn't stand the grating, "etched" sounding new Grimes CD at first, through virtually any speaker I own. I am getting over it because I still like the music, but album level clipping is an issue over and above DAC or AMP clipping. Worth it to check, and be sure!


----------



## Psalmanazar

mrmateohead said:


> I would try using different media players - does it clip when using Windows Media Player as well? How about VLC?
> 
> Are you 100% positive that the recordings you are listening to don't clip? (You can use something like Audacity to take a look). I couldn't stand the grating, "etched" sounding new Grimes CD at first, through virtually any speaker I own. I am getting over it because I still like the music, but album level clipping is an issue over and above DAC or AMP clipping. Worth it to check, and be sure!


 
 There was no red in Audacity. I wasn't listening to smashed crap when I noticed it. I noticed the clipping on a -2 peak, 11 db of dynamic range, -20 RMS average keyboard track listening on HD 650s. I just tried it with "event mode" with some 5 db of dynamic range pop, -.05 peaks and yeah no clipping on my HD 25s as it doesn't have to be amplified as much but it clipped with dynamic classical music and 80s metal.

 It's not the player, it's the output from the ODAC (powered from a USB port) clipping the O2 amp due to poor opamp design choices from nwavguy. He stuck the volume pot between the stages. It clips even on 1x gain sometimes. Then you have JDS Labs poor choice of letting the windows volume slider control the volume (power) to the ODAC despite that potentially allowing it to clip the O2 as they didn't set the firmware in the ODAC to bypass that when the DAC is set in exclusive mode with the standard drivers (ASIO and WASAPI) that bypass the Windows DirectSound mixer/resampler. This clipping is different from dirty USB power making the bus-powered ODAC not sound very good. This is the same clipping that comes up in 6.5x on the O2 when that gain setting is used with a normal 2 volt source like the ODAC.


----------



## MrMateoHead

psalmanazar said:


> There was no red in Audacity. I wasn't listening to smashed crap when I noticed it. I noticed the clipping on a -2 peak, 11 db of dynamic range, -20 RMS average keyboard track listening on HD 650s. I just tried it with "event mode" with some 5 db of dynamic range pop, -.05 peaks and yeah no clipping on my HD 25s as it doesn't have to be amplified as much but it clipped with dynamic classical music and 80s metal.
> 
> It's not the player, it's the output from the ODAC (powered from a USB port) clipping the O2 amp due to poor opamp design choices from nwavguy. He stuck the volume pot between the stages. It clips even on 1x gain sometimes. Then you have JDS Labs poor choice of letting the windows volume slider control the volume (power) to the ODAC despite that potentially allowing it to clip the O2 as they didn't set the firmware in the ODAC to bypass that when the DAC is set in exclusive mode with the standard drivers (ASIO and WASAPI) that bypass the Windows DirectSound mixer/resampler. This clipping is different from dirty USB power making the bus-powered ODAC not sound very good. This is the same clipping that comes up in 6.5x on the O2 when that gain setting is used with a normal 2 volt source like the ODAC.


 
 I've never heard the O2 clip at less than 6.5X gain and 2V in on any quality of recording. To claim that it is clipping at unity gain doesn't make any sense. There is static / popping when using the volume knob, that is typical.
  
 Are you using this thing from your Thinkpad? Are there other devices sharing the USB bus? Tried a different USB port or device yet? It sounds almost like it is a power issue, or even a defect.


----------



## Psalmanazar

mrmateohead said:


> I've never heard the O2 clip at less than 6.5X gain and 2V in on any quality of recording. To claim that it is clipping at unity gain doesn't make any sense. There is static / popping when using the volume knob, that is typical.
> 
> Are you using this thing from your Thinkpad? Are there other devices sharing the USB bus? Tried a different USB port or device yet? It sounds almost like it is a power issue, or even a defect.


 
 No other devices were on the bus. The DAC was performing well except for causing the O2 to clip. DirectSound makes the ODAC sound like a bad crossfeed plugin but wasn't clipping the O2. It's very easy to clip the O2. All of this is due to poor design choices.


----------



## HaVoC-28

psalmanazar said:


> No other devices were on the bus. The DAC was performing well except for causing the O2 to clip. DirectSound makes the ODAC sound like a bad crossfeed plugin but wasn't clipping the O2. It's very easy to clip the O2. All of this is due to poor design choices.


 

 So you are the first one here that come with clipping issue at unity gain and claim that the problem come from the O2 disign 
	

	
	
		
		

		
			





 . Sometimes there is deffective unites or wrong assembly like a resistance that is not correct etc etc .
  
 Then at witch stage the O² clips , with witch recordings to see if the issue is easy to reproduce  with any o² , cause if this is a disign defect it will be easy to reproduce .


----------



## Psalmanazar

Well it's the poor driver implementation of the JDS Labs ODAC clipping the O2. ASIO and WASAPI event mode really shouldn't be clipping it in situations where WASAPI push doesn't and that clipping in situations where DirectSound doesn't. Nothing was posted about the various driver issues so I thought it best to share for consumers' future benefit.

 Everyone knows nwavguy made the poor choice of sticking the potentiometer between the stages to lower the noise floor of the O2 and that the ODAC is bus-powered.


----------



## HaVoC-28

psalmanazar said:


> Well it's the poor driver implementation of the JDS Labs ODAC clipping the O2. ASIO and WASAPI event mode really shouldn't be clipping it in situations where WASAPI push doesn't and that clipping in situations where DirectSound doesn't. Nothing was posted about the various driver issues so I thought it best to share for consumers' future benefit.
> 
> Everyone knows nwavguy made the poor choice of sticking the potentiometer between the stages to lower the noise floor of the O2 and the the ODAC is bus-powered.


 
  
 The O²/ODAC are more than 3 years old now : / , and no one would have discovered O² clipping at 1x yet ? . Yes there is a clipping issue that happen only  when you exceed  7 v . At 1X with ODAC providing around 2.03v you can't possibly get it to Clip .
  
 Something is clearly wrong with your combo or somewhere else  .


----------



## castleofargh

psalmanazar said:


> There was no red in Audacity. I wasn't listening to smashed crap when I noticed it. I noticed the clipping on a -2 peak, 11 db of dynamic range, -20 RMS average keyboard track listening on HD 650s. I just tried it with "event mode" with some 5 db of dynamic range pop, -.05 peaks and yeah no clipping on my HD 25s as it doesn't have to be amplified as much but it clipped with dynamic classical music and 80s metal.
> It's not the player, it's the output from the ODAC (powered from a USB port) clipping the O2 amp due to poor opamp design choices from nwavguy. He stuck the volume pot between the stages. It clips even on 1x gain sometimes. Then you have JDS Labs poor choice of letting the windows volume slider control the volume (power) to the ODAC despite that potentially allowing it to clip the O2 as they didn't set the firmware in the ODAC to bypass that when the DAC is set in exclusive mode with the standard drivers (ASIO and WASAPI) that bypass the Windows DirectSound mixer/resampler. This clipping is different from dirty USB power making the bus-powered ODAC not sound very good. This is the same clipping that comes up in 6.5x on the O2 when that gain setting is used with a normal 2 volt source like the ODAC.


 
 makes little sense to me.
 the DAC won't clip unless the track is clipped on the digital level before being sent to the DAC. when the digital value for te signal reaches 0db, the odac will output about 2V. there is no way it will try or be able to output more, and no reason why 2V would be too much.
 then the O2 could be clipped if another DAC was used with a higher max voltage, and some unfortunate choices of gain for a given headphone, but again you're in a situation that cannot make it happen with a working ODAC/O2 and hd650. that's what I used for a few years now and I can't imagine a way to make it clip that wouldn't come directly from me messing up with the signal on the computer(pushing an EQ up without adjusting the global gain or anything that would be a digital clipping and would as such sound clipped on any source).
  
 so you either do something very wrong on the computer side of things and you've decided to blame the ODAC/O2/nwavguy for what is 100% your misuse of something, or you have a damaged ODAC/O2. but the "nwavguy failed design" part is BS and has nothing to do with your situation.


----------



## MrMateoHead

psalmanazar said:


> No other devices were on the bus. The DAC was performing well except for causing the O2 to clip. DirectSound makes the ODAC sound like a bad crossfeed plugin but wasn't clipping the O2. It's very easy to clip the O2. All of this is due to poor design choices.


 

 The fact that the Audio File is not clipped does not prove the absence of square waves, which may have resulted from an overloaded microphone during the recording process, or EQing problems, and so on. In that case the "clipping" is passed through the ODAC, Amp and headphone.
  
 It isn't clear that the headphones are not clipping as well, or distorting, given that they are the part of the signal chain with the highest distortion and some kind of SPL limit. Loose connections can also sound like clipping, and the inputs of the O2 / headphone cables surrounding me need a little "wiggle" once in awhile. In fact there is a chassis grounded wire hanging off the input that I had to re-seat to restore "buggy connections". I would check that, too.
  
 Finally, when I upgraded to Windows 10, it broke my Realtek audio and various other drivers. I had audio through the ODAC but nothing else. Uninstalling / reinstalling drivers was required.
  
 I hope you find a solution, or Opamps that work for you.


----------



## Psalmanazar

Blame who you want. JDS Labs for lack of driver testing or Nwavguy for making the problem possible. JDS Labs believing that ASIO and WASAPI are non-standard drivers is ridiculous.
  
 I spent most of my free time Thursday through Saturday ruling out other variables such as USB cables, headphones, and recordings while solving a problem that shouldn't have arisen to begin with. I'm done. The end.


----------



## raoultrifan

psalmanazar said:


> Well it's the poor driver implementation of the JDS Labs ODAC clipping the O2. ASIO and WASAPI event mode really shouldn't be clipping it in situations where WASAPI push doesn't and that clipping in situations where DirectSound doesn't. Nothing was posted about the various driver issues so I thought it best to share for consumers' future benefit.
> 
> Everyone knows nwavguy made the poor choice of sticking the potentiometer between the stages to lower the noise floor of the O2 and that the ODAC is bus-powered.


 
  
 Hi, 
  
 AFAIK there's no driver implemented by JDS, instead ODAC is using OS native driver, which should be perfect I'd say.
  
 As for nwavguy's design, he choose to have the potentiometer between voltage input stage and output buffer instead having it placed before voltage input stage, because the noise-floor would be greatly decreased this way. In case you have a problem with the noise when rotating the potentiometer dial (only when playing the music), then feel free to change it with a Bournes and/or change the 50K resistors as well (for details, find agdr audio webpage or contact him directly here on Head-Fi).
  
 Anyway, placing the potentiometer the way nwavguy did makes this headamp one of a kind into audiophile world, mostly because it's dead silent! And for a 59USD kit that's a steal. 
  
 ODAC is bus powered, like probably all of the existing Tenor7022/ESS9023 implementations (anyway, ODAC has a noise reduction circuit on +5V USB input). It's very cheap and sounds great, that's what it matters after all, so there's no reason to pay for a dedicated +5V PSU to power this chip. If you want, feel free to buy Schiit Wyrd or something else similar and let us know how audio improves here with ODAC. Anyway, ASUS Essence One, TEAC UD-501 and many other DACs are having their USB converter chip powered directly from the USB bus as well.
  
 Regards!
  
 L.E.: http://firev1.blogspot.ro/2014/11/schiit-wyrd-does-it-work.html - shows a little bit of improvement for the Tenor 7022 USB chip. Also, Wyrd is also powering the ESS9023 chip as well, so at least theoretically sound should get improved a bit, especially on noisy USB computer ports.


----------



## bada bing

psalmanazar said:


> Blame who you want. JDS Labs for lack of driver testing or Nwavguy for making the problem possible. JDS Labs believing that ASIO and WASAPI are non-standard drivers is ridiculous.
> 
> I spent most of my free time Thursday through Saturday ruling out other variables such as USB cables, headphones, and recordings while solving a problem that shouldn't have arisen to begin with. I'm done. The end.


 
 What are you using to power the O2 ?
  
 I wouldn't go so far as to call it a defect, but the O2's has unusual clipping that depends on rail voltage and input signal voltage.
 If you are sure you are clipping in the amp section, you have rails running too low for the input and gain. That is the only way the 
 O2 clips and it is rather odd behavior. I'd check the rails in the amp, something is amiss.
  
 The O2 is an interesting design and it is easy to get really good performance from it as long as you understand the design trade offs.
 JMO, but I am surprised that it has become as widely adopted as it has, because the design trade offs make it a bit prone
 to having issues with under informed users operating it outside of its design parameters. What you are describing isn't outside
 the design unless you are operating it with defective/dead batteries or there is a problem in the wall wart / psu section.


----------



## Takeanidea

I sold my O2/Odac but I still consider to be right up there with the very best of small form Dac/Amps and anyone who has bought one well done and anyone who is thiking about getting one- get one! You cannot go wrong


----------



## adydula

I have stopped trying to help people that just dont understand the O2 design and clipping....there are so many folks that just will never understand circuit design especially with the O2.....Its been  around for a long time now and many, many people like what it does and do understand the why's of its design points and how good of an amp it is.....
  
 Back to the music....happy clipping to you all!
  
 Alex
 :>)


----------



## marios_mar

Can the O2+ODAC combo work completely just with USB power?


----------



## adydula

Nope....the dac is powered via USB, the amp need an AC to AC walwart or batteries.
  
 A.


----------



## Meremoth

Which company's version of the O2/ODAC do you guys prefer?  I did extensive research on the O2/ODAC a couple years ago, and I think I was going to go with JDS Labs, but since time has passed I was wondering if anything has changed that I should know about?  
  
 Just purchased the Fostex TH-0XX, and I have no amp or dac - and after lots of past research I determined the O2/ODAC is what I want, I just need to know where I should purchase it from (I live in the US).  If there is no clear winner, any subjective opinions about where I should purchase it is very much appreciated.  Thanks.
  
 Edit:  Also, it doesn't have to be the all-in-one combo, it can be the separate units as well.  I think I was planning on getting separate units in case I ever wanted to mix-and-match with other amps or dacs, but I'm open to suggestions.  
  
 Edit #2:  Just read that there's a Rev B version of the ODAC from JDS Labs...  should that be of any concern to me?  Thanks.


----------



## adydula

I would go with the JDS Labs just because of their good customer service....nothing has really changed with the O2, the ODAC is a t REV B.
  
 I have both and have done side by side comparisons...I dont hear any real work differences at all.
  
 That said if you buying one now get the rev b it has some improvements in certain situations with USB connectivity that might benefit you, not sonically but with less probability of latency, pops, clicks etc...if you google search this you can read the details.
  
 I have three rev a's and never have had any of the issues that rev b is supposed to address. Over 7 different pc's.
  
 Alex


----------



## Psalmanazar

JDS Labs has the best customer service and the ODAC rev B is a totally different DAC from the original ODAC. It's USB chipset actually has ASIO drivers though. If you get separates, you might as well not get the ODAC and O2 and go with another brand or product to not deal with USB bus and battery power.


----------



## Meremoth

psalmanazar said:


> JDS Labs has the best customer service and the ODAC rev B is a totally different DAC from the original ODAC. It's USB chipset actually has ASIO drivers though. If you get separates, you might as well not get the ODAC and O2 and go with another brand or product to not deal with USB bus and battery power.


 
 Does the standalone O2 run only on battery power?  And if so, is the disadvantage with it being battery powered and not AC is that the battery powered version would have lower supply voltage, thus making the O2+ODAC combo superior in terms of maximum output power?  
  
 I don't have any amps or dacs to mix and match with the O2 and ODAC anyway, so perhaps I will just get the all-in-one box instead of separate units.


----------



## adydula

http://blog.jdslabs.com/?p=1003
  
 JDS Labs has a very nice write up of the Rev B and all its stuff....
  
 Alex


----------



## raoultrifan

O2 runs on both internal batteries and AC outlet as well. If used with internal batteries then indeed max. power will slightly decrease from a max. of 7V to about 5V, but you can find all the info needed on nwavguy's blog.
  
 If you'll get the combo, I believe you'll loose the batteries from inside. If you'll get the "2-piece" O2 + ODAC, then you may get the battery version of O2, just in case you'll need it sometimes (I haven't really used it much, honestly).


----------



## Psalmanazar

meremoth said:


> Does the standalone O2 run only on battery power?  And if so, is the disadvantage with it being battery powered and not AC is that the battery powered version would have lower supply voltage, thus making the O2+ODAC combo superior in terms of maximum output power?
> 
> I don't have any amps or dacs to mix and match with the O2 and ODAC anyway, so perhaps I will just get the all-in-one box instead of separate units.


 
 No. The O2 does have issues with clipping when the battery runs out. It has issues with clipping in general due to the volume pot being between the stages. Why would you want a desktop amp that uses a battery? The O2 doesn't have that much power in general for planars. If you want enough power to drive planars and use DSPs plugins like good equalizers (The O2 isn't powerful enough to drive the HD 650 if you use Sonarworks for example), enough power to drive everything that doesn't require a speaker amp like the HE-6, look at the Schiit Magni/Modi 2 Uber stack. The Magni 2 uber is more powerful and has RCA pass throughs while the Modi 2 Uber is mains instead of USB powered and has additional non-USB inputs compared to the non-Uber ones. The O2 and ODAC aren't the best bang for buck anymore even if you build them yourself. The Schiit stack is better and cheaper while if price is your only concern and you're not driving insensitive planars, the Monoprice Desktop Amp is under a hundred bucks and comes stock with all the O2's "extra features" you have to pay more for with such as RCA pass through jacks, a full size headphone jack, and a rear AC adapter port. It's not very difficult to design a better, more powerful, and more functional amp than the O2.

 Edit: Apparently yes it does have reduced output voltage on battery power according to the earlier poster above me.


----------



## adydula

"It's not very difficult to design a better, more powerful, and more functional amp than the O2."
  
 Really......
  
 A.


----------



## HaVoC-28

adydula said:


> "It's not very difficult to design a better, more powerful, and more functional amp than the O2."
> 
> Really......
> 
> A.


 
  
 He had a bad experience (Clipping)  with O²/ODAC ... And didn't tried to know if it was a faulty unit or not,  blaming O² being a bad disign and returned it and jumped to Schiit Stack .
  
 Because Clipping with an HD650 ... 
	

	
	
		
		

		
			





 unless mismatch Gain or defective unit i don't see how at safe listening levels .
  
 But well the Schiit Stack is also a safe bet for a first DAC/AMP he can't go wrong with either choice , and i would have also been upset if i had a defective product ...


----------



## Meremoth

psalmanazar said:


> No. The O2 does have issues with clipping when the battery runs out. It has issues with clipping in general due to the volume pot being between the stages. Why would you want a desktop amp that uses a battery? The O2 doesn't have that much power in general for planars. If you want enough power to drive planars and use DSPs plugins like good equalizers (The O2 isn't powerful enough to drive the HD 650 if you use Sonarworks for example), enough power to drive everything that doesn't require a speaker amp like the HE-6, look at the Schiit Magni/Modi 2 Uber stack. The Magni 2 uber is more powerful and has RCA pass throughs while the Modi 2 Uber is mains instead of USB powered and has additional non-USB inputs compared to the non-Uber ones. The O2 and ODAC aren't the best bang for buck anymore even if you build them yourself. The Schiit stack is better and cheaper while if price is your only concern and you're not driving insensitive planars, the Monoprice Desktop Amp is under a hundred bucks and comes stock with all the O2's "extra features" you have to pay more for with such as RCA pass through jacks, a full size headphone jack, and a rear AC adapter port. It's not very difficult to design a better, more powerful, and more functional amp than the O2.
> 
> Edit: Apparently yes it does have reduced output voltage on battery power according to the earlier poster above me.


 
  
 The only headphones I have are the ATH-AD700's and the ATH-AD900X's, and the TH-0XX's I have ordered.  And I have no idea how to use correctly use equalizers.    
  
 Is the Schiit Magni/Modi 2 Uber stack considered "neutral" sounding?  I don't currently have any external amp or DAC, so for my first amp and DAC I want something considered to be neutral sounding so I know what the headphones sound like as is instead of being colored by external devices.  Perhaps the next time I purchase an amp and dac I'll go for something more colored, but for now I just want something transparent.
  
 if you consider the Schiit stack neutral while also being superior to the O2+ODAC, then perhaps I should just go for the Schiit stack?  Are there no advantages the O2+ODAC would have over the Schiit stack?  
  
 If anyone else has opinions on my current O2+ODAC vs. Schiit Stack situation, please feel free to chime in, I can use all the advice I can get.


----------



## HaVoC-28

Also Modi 2  + O² , it will work too 
	

	
	
		
		

		
		
	


	




  . Or Modi 2 Uber if you need spdif Input . But With Modi 2 as DAC , as the max Output power is 1.5v , Gains should be something like 1.5X for low gain , and 4.5X for High Gain .


----------



## Meremoth

havoc-28 said:


> Also Modi 2  + O² , it will work too


 
  
 What's your opinion about the pros and cons of the Modi 2 + O2 vs. the Schiit stack vs. the O2+ODAC combo for my situation?   (I'm not worried about price)


----------



## Psalmanazar

havoc-28 said:


> He had a bad experience (Clipping)  with O²/ODAC ... And didn't tried to know if it was a faulty unit or not,  blaming O² being a bad disign and returned it and jumped to Schiit Stack .
> 
> Because Clipping with an HD650 ...
> 
> ...


 
 I didn't return it. It was a problem with standard but unsupported APIs by the USB controller in the original ODAC causing the combo to stutter and clip randomly. The O2 is flawed by design in certain ways and locked by the license. It's very easy to clip if you enable DSPs outputting to the HD 600/650 even at 3.3x gain or with unmastered, quiet home recordings. No realistic listening levels of music is safe with long term exposure. Most recordings are mixed at 80-90 db spl averages. Instruments are loud and musicians are deaf.
  


meremoth said:


> The only headphones I have are the ATH-AD700's and the ATH-AD900X's, and the TH-0XX's I have ordered.  And I have no idea how to use correctly use equalizers.
> 
> Is the Schiit Magni/Modi 2 Uber stack considered "neutral" sounding?  I don't currently have any external amp or DAC, so for my first amp and DAC I want something considered to be neutral sounding so I know what the headphones sound like as is instead of being colored by external devices.  Perhaps the next time I purchase an amp and dac I'll go for something more colored, but for now I just want something transparent.
> 
> ...


 
 The ODAC+O2 is an all in one so it's easier to transport around. It's not a good portable solution though. Nwavguy designed, measured, and christened them as "objectively neutral".


----------



## HaVoC-28

meremoth said:


> What's your opinion about the pros and cons of the Modi 2 + O2 vs. the Schiit stack vs. the O2+ODAC combo for my situation?


 
  
 O²/ODAC (separate units , always better )
  ODAC pros : output Voltage : 2.0v (same as standard redbook CD player output voltage) ,  USB auto Powered   .  Minus : More expensive or no spdif inputs .
 O² :  Can run from batteries if needed , so you go anywhere with a laptop , that will power your DAC and use the O² from batteries (it don't hapens many times but ...) . ODAC + O² => Objective combo (if you like combos) .  Will drive most of the Headphones out their just fine , also adjustable Gain , for very sensitive IEMs you can use 1X gain or even 0.5X . .  Cons : Less power that Magni so maybe some rare planars may not go loud enough for some very quiet recordings depending on how loud you listen music ... but your audio technicas or coming TH 0XX will not have this problem .
 For both : Objectively mesured etc ...
  
  
 Schiit Stack ,  
 Modi 2 pros : cheaper than the ODAC , Modi 2 Uber : Spdif Input , cons for both : 1.5 V out (but not a real problem) , no USB powered (if that matter) .
 Magni 2 : Pro : more powerfull output , cons : can't run on batteries if needed .
 Cool looking Combo .
 Peraphs don't have all the measurements reports that the objective combo have but ...


psalmanazar said:


> I didn't return it. It was a problem with standard but unsupported APIs by the USB controller in the original ODAC causing the combo to stutter and clip randomly. The O2 is flawed by design in certain ways and locked by the license. It's very easy to clip if you enable DSPs outputting to the HD 600/650 even at 3.3x gain or with unmastered, quiet home recordings. No realistic listening levels of music is safe with long term exposure. Most recordings are mixed at 80-90 db spl averages. Instruments are loud and musicians are deaf.


 
  
 Well , i use my HD6X0 mostly on 1X gain and without any DSP effects , and don't need more than 2.5X gain for some very quiet records that i have in my collection .  The FSA Sptifire HD that i use as DAC deliver about 2.015v at max output , so for listening music with foobar on wasapi output , i can't get my HD6X0 clipp .
  
 But hey , if the schiit stack does the djob for you , the better ^^ .


----------



## Meremoth

So I read a review that said he thought the modi was "neutral to lean" and that the Magni was "a good reference for a neutral amp".  So that raises the question of Magni Uber + ODAC; would that work?  
  
  
 In your own personal opinions, if your only pair of headphones were the Fostex TH-0XX's (and source is Win 7 PC with realtek audio) and someone held a gun to your head and told you to pick the best choice for those headphones, would you choose Magi + ODAC, Modi + O2, Magni + Modi, or O2 + ODAC?  (all the Schiit stuff will be the "Uber" versions).
  
  
 Edit:  Should I stress out about which combo is the most neutral/transparent, or are all these considered to be fairly neutral?   
  
  
 TL;DR - Someone please make this decision for me.


----------



## castleofargh

psalmanazar said:


> havoc-28 said:
> 
> 
> > He had a bad experience (Clipping)  with O²/ODAC ... And didn't tried to know if it was a faulty unit or not,  blaming O² being a bad disign and returned it and jumped to Schiit Stack .
> ...


 
 almost everybody here has been telling you odac/o2+hd650 has no problem, some of them knowing enough to build amps by themselves.
 I've had one for 2 or 3years now and it's still my source of choice anytime I measure something, that's how reliable this dac/amp combo has been for me.
 nwavguy actually used the hd650 as reference many times when posting about the odac/O2. for the O2 we know all about how it's made, we know the max voltage, how we should set the gain settings(if you don't, blame yourself not the amp), and many more things unavailable/unclear on other amps.  despite that, you show your massive expertise of having one problem doing something still unclear(but obviously wrong), to decide you know better than all those guys and blame the O2 for being flawed...
	

	
	
		
		

		
		
	


	



  
  how you go from a problem with an API to blaming an amp makes no sense whatsoever of course. the license point... IDK what to say, 99% of amps have more license locks than an O2. and et's be honest here, if what you want to do is modify an O2 for your own use, who's going to stop you? the licence is to stop people from selling crap under the name odac/O2, that's all.
  
   at one time you talked about asio when the odac has no asio driver(at least the first version), is it what you mean with API and usb controller? then DSPs, if you clip your signal because of a DSP it's100% clipped at the computer level, and 100% your own fault for not lowering the digital gain before that DSP. then you talk about gain problem in the amp... when the amp has 2 gain settings and the gain value can be changed by any noob DIYer to whatever you need. how about you stop shooting randomly trying to put some nonsense blame on this device? if you don't like the odac or the O2, don't use them. no need to lie and make up reasons.


----------



## Meremoth

I'm just going to assume I won't be able to tell a sound quality difference between whatever combo of Magni Uber, Modi Uber, O2, and ODAC I end up choosing.  Taking into consideration that all the options I've listed here are considered mostly "neutral" and "transparent", and seeing how the TH-0XX's seem to be a more "neutral" sounding pair of headphones than the TH-600 and TH-900, perhaps I should just forget about worrying about this and just focus on the features.  
  
 If my assumption is correct, then I should go for the Schiit Uber stack, yeah?  I mean because it has more features than the O2 and ODAC, correct?  
  
 Dear Lord, please give me the strength to make this decision today before I lose my sanity.


----------



## xb4iris

Anyone managed to get the Objective2 more musical with some OpAmp rolling. I know that defeats the purpose, but the transparency gets to me sometimes, especially on high emphasized headphones. The neutrality and power are awesome, but the idea of some coloration does give my mind pause sometimes when listening to music I used to enjoy when simply using my Asus Xonar headphone jack. For example my Superlux HD668Bs used to shine on my Xonar and have now become treble rockets! LOL! May be the missing Odac, using the same Xonar as a Dac at the moment.
  
 Someone did recommend 2x OPA2132PA and AD823AN OpAmps, but I'm pretty warry about rolling if the negative affects out-way the positives.
  
 Any ideas?


----------



## Psalmanazar

castleofargh said:


> almost everybody here has been telling you odac/o2+hd650 has no problem, some of them knowing enough to build amps by themselves.
> I've had one for 2 or 3years now and it's still my source of choice anytime I measure something, that's how reliable this dac/amp combo has been for me.
> nwavguy actually used the hd650 as reference many times when posting about the odac/O2. for the O2 we know all about how it's made, we know the max voltage, how we should set the gain settings(if you don't, blame yourself not the amp), and many more things unavailable/unclear on other amps.  despite that, you show your massive expertise of having one problem doing something still unclear(but obviously wrong), to decide you know better than all those guys and blame the O2 for being flawed...
> 
> ...


 
 I described perfectly well what I was doing in my last post. The ASIO and WASAPI Event mode protocols cause the ODAC to clip and stutter no matter how large the buffer as its USB chipset (the Tenor TE7022) does not support them, even with generic drivers such as ASIO4ALL. Most ODAC users bought a dongle to bypass their computers' built in Realtek chip and don't care about bypassing the Windows DirectSound mixer to achieve even more neutral and perceptively better sound quality.
  
 The O2 also easily clips with my HD 650 and recording-dependent preference for VST plugins. Most good DSPs lower the volume to prevent clipping of the signal or have anticlipping options that you are well advised to check. I have problems getting enough volume without clipping with Sonarworks and various low-pass filters I have set up for listening to poor recordings I like. That users can so easily clip the amp is a design flaw. If the O2 stayed a DIY project that wasn't marketed to consumers as a direct competitor to others' discrete solutions this wouldn't be a flaw. Unfortunately Nwavguy built his "Objective" brand by directly attacking other manufacturers' amplifiers and their design flaws from the beginning and designing his own flawed but "bang for buck" amp that was competitive at the time for new users. Many are still convinced by his marketing, someone asked about power output, and I told my experience.


----------



## Psalmanazar

meremoth said:


> I'm just going to assume I won't be able to tell a sound quality difference between whatever combo of Magni Uber, Modi Uber, O2, and ODAC I end up choosing.  Taking into consideration that all the options I've listed here are considered mostly "neutral" and "transparent", and seeing how the TH-0XX's seem to be a more "neutral" sounding pair of headphones than the TH-600 and TH-900, perhaps I should just forget about worrying about this and just focus on the features.
> 
> If my assumption is correct, then I should go for the Schiit Uber stack, yeah?  I mean because it has more features than the O2 and ODAC, correct?
> 
> Dear Lord, please give me the strength to make this decision today before I lose my sanity.


 
 The Ubers are both mains powered and have ASIO drivers for Windows. Unless you're going to carry it around the house all the time, get the Schiits. The PYSST RCA cables they sell are very convenient too.


xb4iris said:


> Anyone managed to get the Objective2 more musical with some OpAmp rolling. I know that defeats the purpose, but the transparency gets to me sometimes, especially on high emphasized headphones. The neutrality and power are awesome, but the idea of some coloration does give my mind pause sometimes when listening to music I used to enjoy when simply using my Asus Xonar headphone jack. For example my Superlux HD668Bs used to shine on my Xonar and have now become treble rockets! LOL! May be the missing Odac, using the same Xonar as a Dac at the moment.
> 
> Someone did recommend 2x OPA2132PA and AD823AN OpAmps, but I'm pretty warry about rolling if the negative affects out-way the positives.
> 
> Any ideas?


 

 Why not just use an equalizer or get a pair of headphones without treble problems? If you don't like the flaws of your transducer with a certain amp, then just don't use the O2 with the Superlux. My O2 does no favors to my HD 25's treble issues.


----------



## Meremoth

psalmanazar said:


> The Ubers are both mains powered and have ASIO drivers for Windows. Unless you're going to carry it around the house all the time, get the Schiits. The PYSST RCA cables they sell are very convenient too.


 
  
  
 I was recommend this:  https://introprose.myshopify.com/collections/frontpage/products/rca-crossconnect-for-schiit-Stack
  
 It's the same price as these:  http://schiit.com/products/pyst-cables
  
 I don't know anything about either.  Would one have any sound quality advantage over the other?  Or any pros and cons between the two products?  
  
 Edit:  I'll also need this to connect to my PC, right?
  
 http://www.monoprice.com/Product?c_id=102&cp_id=10218&cs_id=1021817&p_id=9767&seq=1&format=2


----------



## xb4iris

psalmanazar said:


> The Ubers are both mains powered and have ASIO drivers for Windows. Unless you're going to carry it around the house all the time, get the Schiits. The PYSST RCA cables they sell are very convenient too.
> 
> Why not just use an equalizer or get a pair of headphones without treble problems? If you don't like the flaws of your transducer with a certain amp, then just don't use the O2 with the Superlux. My O2 does no favors to my HD 25's treble issues.


 
  
 Me an equalizers don't click. I become obsessive compulsive. Change it on every track. Trust me, it gets scary! Opamps seem to cure diseases easier, like it did with my Asus Soundcard back in the day. Never used a EQ again, but I get yah!


----------



## Psalmanazar

xb4iris said:


> Me an equalizers don't click. I become obsessive compulsive. Change it on every track. Trust me, it gets scary! Opamps seem to cure diseases easier, like it did with my Asus Soundcard back in the day. Never used a EQ again, but I get yah!


 
 I have custom parametric equalizers set up for the L and R channels of certain extremely poor recordings as the high hat is only in one! It's a pain so I probably will pick up a slightly rolled off in the treble amp to use for some of them.


----------



## xb4iris

psalmanazar said:


> I have custom parametric equalizers set up for the L and R channels of certain extremely poor recordings as the high hat is only in one! It's a pain so I probably will pick up a slightly rolled off in the treble amp to use for some of them.


 
  
 I did that with APO once upon a time when I got this amp, but I chop and change headphones, so it gets irritating! Never had to do this with my Xonar! That rolled off the highs very well on its own, obviously at a quality cost, but it was easy. I could live my life without obsession. I even left the house on one or two occasions. LOL!


----------



## Meremoth

I would have the same problem as xb4iris and become obsessive about the EQ.  I would never reach satisfaction because I would know I could always test it a little more, and even if I did reach the most optimal levels for my ears, I'd still would be convinced I could tweek it a little more...  I mean, heck, look at all I'm going through right now just to find some sort of serenity for my ever doubting, ever questioning, ever anxious mind.  At least I got the headphones ordered.


----------



## castleofargh

> Originally Posted by *Psalmanazar* /img/forum/go_quote.gif
> 
> I described perfectly well what I was doing in my last post. The ASIO and WASAPI Event mode protocols cause the ODAC to clip and stutter no matter how large the buffer as its USB chipset (the Tenor TE7022) does not support them, even with generic drivers such as ASIO4ALL. Most ODAC users bought a dongle to bypass their computers' built in Realtek chip and don't care about bypassing the Windows DirectSound mixer to achieve even more neutral and perceptively better sound quality.
> 
> The O2 also easily clips with my HD 650 and recording-dependent preference for VST plugins. Most good DSPs lower the volume to prevent clipping of the signal or have anticlipping options that you are well advised to check. I have problems getting enough volume without clipping with Sonarworks and various low-pass filters I have set up for listening to poor recordings I like. That users can so easily clip the amp is a design flaw. If the O2 stayed a DIY project that wasn't marketed to consumers as a direct competitor to others' discrete solutions this wouldn't be a flaw. Unfortunately Nwavguy built his "Objective" brand by directly attacking other manufacturers' amplifiers and their design flaws from the beginning and designing his own flawed but "bang for buck" amp that was competitive at the time for new users. Many are still convinced by his marketing, someone asked about power output, and I told my experience.


 
 ok so that I understand.
 wasapi event AFAIK is to let the DAC handle the traffic of packets. odac not even being async or anything is unlikely to have any use for this. just use wasapi push (if on latest versions you may  have to disable event as it's now the default setting).
 asio4all isn't asio. I've only had very poor experiences with it and would rather use good old kernel streaming as is than asio4all. if you use a DAC that has real asio drivers provided, then by all means go for asio, but I don't advise asio4all, ever.
 try wasapi push and see if you still have troubles.
  
  
 about clipping,  I really don't get what you're talking about. I can use the odac with the computer output maxed out(windows and foobar) and I don't get clipping. and the extreme situation, the o2 maxed out and gain 2.5X(I have 1X and 2.5) with the hd650, and still get no clipping going as loud on the computer as I can possibly stand. so again, your device has a problem, or you fail to set your computer properly. but it's not an odac/o2 problem as I have it have a hd650 and don't have your problem. yet you keep saying it's the odac/o2 that are flawed...
  
 and if you clip something digitally with a DSP then how is it the amp's problem? I'm using some crossfeed and EQ at all time and I never have any trouble as long as I deal with the gain correctly.
 all the problems I've come accross were some really unstable VSTs, some problematic chainings where one VST could only work at a given samplerate or stuff like that, or when I try to do stuff that require too much resources for my poor old laptop(like using the best settings possible in equilibrium).
 but none of those have anything to do with the DAC and amp used.
  


xb4iris said:


> psalmanazar said:
> 
> 
> > The Ubers are both mains powered and have ASIO drivers for Windows. Unless you're going to carry it around the house all the time, get the Schiits. The PYSST RCA cables they sell are very convenient too.
> ...


 
 can't force you against your will, but what you're really looking for is probably inside a few DSPs and/or a nice EQ. try something like TB isone (free trial). I don't use this because I'm fine with a great EQ and a little crosfeed alone, but this is a kind of all-in-one, that lets you test a lot of ways to alter the sound while never really ruining it. and it's certainly less random than waiting for some component changes to result in the sound you like. you would need to be super patient or super lucky to get your beloved sound that way. not saying it can't happen, but it's the long hard path you're taking.
 and if you prefer to put your music in the hand of someone else instead of becoming obsessed with all the settings, you can indeed use something like sonawork or any stuff using measured headphones to simulate a certain sound. the choices are reduced to what they have measured or estimated to sound good. maybe a better option for the obsessive minds and those not too confident they can use an EQ properly? (I'm not trolling, it's actualy very hard to master the use of an EQ, and requires a lot of work at first)


----------



## Meremoth

castleofargh said:


> can't force you against your will, but what you're really looking for is probably inside a few DSPs and/or a nice EQ. try something like TB isone (free trial). I don't use this because I'm fine with a great EQ and a little crosfeed alone, but this is a kind of all-in-one, that lets you test a lot of ways to alter the sound while never really ruining it. and it's certainly less random than waiting for some component changes to result in the sound you like. you would need to be super patient or super lucky to get your beloved sound that way. not saying it can't happen, but it's the long hard path you're taking.
> and if you prefer to put your music in the hand of someone else instead of becoming obsessed with all the settings, you can indeed use something like sonawork or any stuff using measured headphones to simulate a certain sound. the choices are reduced to what they have measured or estimated to sound good. maybe a better option for the obsessive minds and those not too confident they can use an EQ properly? (I'm not trolling, it's actualy very hard to master the use of an EQ, and requires a lot of work at first)


 
  
  
 That's some good information.  I think it's difficult for people with stable/calm minds to empathize with someone that literally takes time every morning to decide which sock is better for his right foot or left foot when he knows they're not right or left specific, lol, yes that's my dumb butt I'm referring to, and even though I find it ridiculous and even laugh at it, I still can't help myself but do it, even though I don't want to.  Yes, I'm fairly insane in the membrane, but the information you provided showed sympathy, and that's all we can ask for.  
  
 I didn't want xb4iris to feel all alone with in his EQ anxiety.


----------



## xb4iris

castleofargh said:


> ok so that I understand.
> wasapi event AFAIK is to let the DAC handle the traffic of packets. odac not even being async or anything is unlikely to have any use for this. just use wasapi push (if on latest versions you may  have to disable event as it's now the default setting).
> asio4all isn't asio. I've only had very poor experiences with it and would rather use good old kernel streaming as is than asio4all. if you use a DAC that has real asio drivers provided, then by all means go for asio, but I don't advise asio4all, ever.
> try wasapi push and see if you still have troubles.
> ...


 
  
 It's an art! I get yah! Some people can handle it, others can't. It takes a enormous amount of patience, and I liked using it back in the day when WinAmp was a staple and gaming headset were the bees knees in my life. Good headphones made my life complicated. Quality drowns us of ignorance and the safety it provides. I generally swap between three headphones every day for different things, so a profile based EQ system would be great with a fast swap mechanism. Haven't found one like that, but I'm check your recommendations out. You never know if something suits my ideals. All EQ's these days are complicated to use, even a master like you has to remember the days when selecting 'rock' or 'dance' in the EQ was enough. I miss those days sometimes. All I want is some life to return to the music, but it may be my wax acting up!


----------



## castleofargh

xb4iris said:


> It's an art! I get yah! Some people can handle it, others can't. It takes a enormous amount of patience, and I liked using it back in the day when WinAmp was a staple and gaming headset were the bees knees in my life. Good headphones made my life complicated. Quality drowns us of ignorance and the safety it provides. I generally swap between three headphones every day for different things, so a profile based EQ system would be great with a fast swap mechanism. Haven't found one like that, but I'm check your recommendations out. You never know if something suits my ideals. All EQ's these days are complicated to use, even a master like you has to remember the days when selecting 'rock' or 'dance' in the EQ was enough. I miss those days sometimes. All I want is some life to return to the music, but it may be my wax acting up!


 
 eheh, I wish I was an EQ master. I'm way better than I was last year that's for sure. but won't next year's castleofargh laugh at my actual EQ handling? a likely answer is yes ^_^.
 I'm slowly getting better at it but I'm no sound engineer, that much is a certainty.




  
  
 sorry for the off topic.


----------



## adydula

If a recording is not well mastered, Eq'ing isnt going to make it better.....
  
 99% of clipping is due to people using a higher than needed gain setting....
  
 I have a ODA with clipping LED's set up with comparators and I never clip until I play at absurd gain levels, very high volumes with music that has high reply gain.
  
 There is no need to go this high with heaphones. If you are your going to go deaf over time!!!
  
 A.


----------



## castleofargh

adydula said:


> If a recording is not well mastered, Eq'ing isnt going to make it better.....
> 
> 99% of clipping is due to people using a higher than needed gain setting....
> 
> ...


 

 you say that like headphones are all flat.


----------



## Psalmanazar

@castleofargh
  
 Through trial and error I figured out the best settings for optimal sound quality for the original ODAC earlier this month

 1. Windows: For out the ODAC disable all enhancements, set 24-bit 44.1 kHz output (or whatever sample rate you will be listening to). The ODAC can't entirely bypass DirectSound (the windows volume control is still enabled) due to true exclusive mode not being enabled in the firmware but we can get around the resampler. Do not make the ODAC the default device and remember to mute the built in soundcard along with all open programs. This will ensure that only Foobar is outputting through the ODAC and no other audio streams are mixed in. Since exclusive mode is not enabled in the firmware of the ODAC, Windows volume control will still be in effect. DirectSound will still be floating the 16-bit PCM output to 32-bit and dithering it back to 24-bit. At least you have avoided the horrible DirectSound resampler with it's ridiculous high end roll-off though. See: http://archimago.blogspot.com/2015/11/measurements-windows-10-audio-stack.html
  
 2. foobar preference, output WASAPI push in 24-bit if you want to use foobar's volume control too for some reason. Under Advanced -> Playback -> WASAPI check high priority.
  
 I'm not even sure the DirectSound ditherer isn't terrible either. My Modi 2 Uber in DirectSound sounded comparable to the ODAC in DirectSound/WASAPI when ABed and somewhat level matched with an Iphone app. With WASAPI event and exclusive checked or using the Cmedia ASIO drivers Schiit supplies, the M2U leapfrogged over the ODAC with regards to instrument separation and treble resolution while also being a little louder than with DirectSound (the amp had to be turned down to be somewhat level matched with the phone app). API support and proper driver implementation might be more important than measurements or whatever DAC is used. I'm not sure how an ODAC rev B vs. M2U would turn out but if the ASIO drivers for the rev. B's USB chipset are actually supported, I suspect it would be closer.
  
 You have it backwards: the VST plugins lower the overall volume on the computer side or have anti-clipping settings you should definitely check that lower the amplitude. Thus you need additional amplification from the amp and the O2 needs to be used in 3.something x gain with the HD 650, sometimes towards 3 o clock for a reasonable volume. The combo just didn't have enough juice to use Sonarworks with already rather quiet recordings. Making the O2 clip the peaks from the output from the ODAC isn't so difficult.


----------



## adydula

No, not hardly all cans arent flat for sure...
  
 If material isnt well mastered  and stuff that is not at the levels via mic'ing, eq'ing during the mastering stage....all the eq'ing in the world wont fix that....garbage in garbage out....
  
 I spend lots of time looking for well recorded, well mastered material that will sound great on most modern headphones....without the need for eq'ing....if you want to muck with eq'ing, create super special custom eq profiles for individual channels and or songs well sir have at it...
  
 Life is to short for me to muck with that when its not needed.
  
 A.


----------



## dazzerfong

psalmanazar said:


> @castleofargh
> 
> Through trial and error I figured out the best settings for optimal sound quality for the original ODAC earlier this month
> 
> ...


 
 About the first one, I'm using Musicbee w/ WASAPI built-in to it and it works just fine with no clipping and running in exclusive mode too.


----------



## xb4iris

psalmanazar said:


> @castleofargh
> 
> Through trial and error I figured out the best settings for optimal sound quality for the original ODAC earlier this month
> 
> ...


 
  
 That's a nice setup, like the other dude I use Musicbee, but you can replicate most of those settings in there with some addons, just like in Foobar!
  
 I like it when people write about their setups. It gives us mere mortals some incentive. I'm gonna give the steps a go when I get the Odac, because I'm still using my Xonar as a dac, and it does pretty well with ASIO. But I'm really interested in comparing the two dacs when Odac gets here.
  
 Thanks again.


----------



## BrettMatthews

psalmanazar said:


> @castleofargh
> 
> Through trial and error I figured out the best settings for optimal sound quality for the original ODAC earlier this month
> 
> ...


 
 Your plugins must be lowering the volume a lot as my HD600's with my ODA on 1x gain are normally at less than 50% (with windows and foobar at 100%).


----------



## HaVoC-28

Again , another headphone on my inventory that the O² drive perfectly fine : HE-560 . (1X Gain and - 10 dB on Foobar , 12o clock for the volume pot) . I don't know why i was expecting that it woulnd't be the case , peraphs read to much BS about orthos "requirements" .
  
 Almost all headphone i have tried to plug on O² = Happy listening , the few that i didn't like was just headphones that i simply didn't like at all 
	

	
	
		
		

		
			





 .


----------



## Peti

I was wondering if the new JDS Elements uses the O2 for amplification? Maybe my memonry plays tricks on me but I remember that's the case? Does the O2/ODAC have anything in common with the Element?


----------



## shonoob

How do the O2 + Odac, and 'the element' also from JDS labs compare?\
  
 Looking for a neutral amp/dac to power my LCD-X's for mixing/mastering purposes.


----------



## raoultrifan

peti said:


> Does the O2/ODAC have anything in common with the Element?


 
 I don't really think so, at least not the headamp part. Also, case and look&feel is quite different as well. O2/ODAC is not really portable, is more like...transportable (I've heard that on this thread actually).


----------



## Draulius

I know this is a shot in the dark but have any O2+ODAC owners listened to the new Aune X1S and been able to compare the sound?


----------



## Alchemist007

Is there anyway to make the O2+ODAC the default device ONLY when powered on while connected to a computer? I want to use my speakers during normal use and have the amp only work when powered on. The only way I'm able to use both is by setting the amp as the default device and unplugging it from the USB when I want to use the speakers, but that can be a hassle.


----------



## castleofargh

alchemist007 said:


> Is there anyway to make the O2+ODAC the default device ONLY when powered on while connected to a computer? I want to use my speakers during normal use and have the amp only work when powered on. The only way I'm able to use both is by setting the amp as the default device and unplugging it from the USB when I want to use the speakers, but that can be a hassle.


 
 no because what you turn ON is only the amp, the DAC is powered by the USB.
 I use SSD(set sound device) to switch the audio output.  depending on what you want to do and what OS you use, another software might be better. but solutions do exist.


----------



## dazzerfong

alchemist007 said:


> Is there anyway to make the O2+ODAC the default device ONLY when powered on while connected to a computer? I want to use my speakers during normal use and have the amp only work when powered on. The only way I'm able to use both is by setting the amp as the default device and unplugging it from the USB when I want to use the speakers, but that can be a hassle.


 
 Yes if you're on Windows, at least. Right-click your speaker icon, then choose Playback Devices. Right click on your ODAC, then select 'Set as Default Device'. That way, if you unplug your ODAC, it'll revert to your speakers, but if you connect the ODAC again, it automatically sets back to your ODAC. I'm running the same thing on my computers.


----------



## Alchemist007

Damn, thanks anyways.


----------



## Alchemist007

Sorry for double post, but thought it would be worth bumping to let people know I found this program: https://code.google.com/p/audioswitch/
  
 Basically can switch the playback device with a hotkey, the next best thing to auto-detect as can be!


----------



## castleofargh

I didn't think about mentioning keyboard shorcuts sorry.
 I've been using launchy for years (to steal one of the good ideas of mac UI ^_^), where you pretty much type the first letters of any application of folder or whatever to get it recognized(so a shortcut to everything really). for that reason SSD.exe made more sense to me because once you can create a shortcut, launchy can recognize it as an independent software and start it. so in effect I'm using alt+space then O enter,  for the odac and alt+space, S enter for speakers ^_^.  I tried 2 other exe that had shortcuts, but one would pass through all my outputs even the virtual ones or hdmi(super annoying) the other could do a selected switch but the shortcut was a problem for me while under photoshop(first world problem) ^_^.
  
 that's why I said that depending on your needs and OS there might be better than my suggestion. anyway it's cool if you have found a convenient solution.


----------



## bruiselee

Hi, 
Im thinking of getting a second hand o2 amp, but from what I see most sellers have the 110v version. 
Is the way to make it work for 230v region just to buy a 230v power supply? 

Can I find these easily at the local electronics store?


----------



## Alchemist007

castleofargh said:


> I didn't think about mentioning keyboard shorcuts sorry.
> I've been using launchy for years (to steal one of the good ideas of mac UI ^_^), where you pretty much type the first letters of any application of folder or whatever to get it recognized(so a shortcut to everything really). for that reason SSD.exe made more sense to me because once you can create a shortcut, launchy can recognize it as an independent software and start it. so in effect I'm using alt+space then O enter,  for the odac and alt+space, S enter for speakers ^_^.  I tried 2 other exe that had shortcuts, but one would pass through all my outputs even the virtual ones or hdmi(super annoying) the other could do a selected switch but the shortcut was a problem for me while under photoshop(first world problem) ^_^.
> 
> that's why I said that depending on your needs and OS there might be better than my suggestion. anyway it's cool if you have found a convenient solution.


 
  
 Yeah I'm on Win7, so it's working fine for that. Customizable hotkeys are nice (and number of inputs...I use ctrl + shift + z but you can use more), and you can change the trey icon color depending on which device is currently in use. I use default black for speakers and magenta for the dac.


----------



## xb4iris

I'm no tech guru or DIY guy, but interested in looking under the hood of the Objective2 just to educate myself a bit on its inner workings. Any idea how to take this thing apart? I see four screws on either end, but what will be the best way to get the shell off? Looks like either the front or back needs to pop, that right?


----------



## raoultrifan

In case you have the basic version of O2, without any backside connectors like power plug or RCA in/out, then I believe you can just remove the 4-screws from the front side and gently grab the front side with the internal PCB.
  
 Also, if you only have the mini-USB from ODAC on the back side, perhaps this is how it should look after removal of front side and PCB:
 ​ (image taken from here: https://www.techpowerup.com/reviews/JDSLabs/O2_ODAC/images/naked.jpg)
  
  
 In case you do have some plugs on the back side (power plug or RCA or anything else) perhaps you need to get rid of all the 8 screws and take out both front & back sides. Take care of volume pot knob, that you may need to take out that knob and remove the screw nut as well, depending of what version of O2 you might have. Also, take care of backside RCA plugs screw nuts as well.


----------



## xb4iris

Thanks. My JDS O2 has the RCA and power on the back end, so thinking the best way in is the back, but need to first get the volume knob and 6.3 jack screwed off. No idea how to unscrew either. Think the 6.3 jack just needs to be unscrewed, but the knob is


raoultrifan said:


> In case you have the basic version of O2, without any backside connectors like power plug or RCA in/out, then I believe you can just remove the 4-screws from the front side and gently grab the front side with the internal PCB.
> 
> Also, if you only have the mini-USB from ODAC on the back side, perhaps this is how it should look after removal of front side and PCB:
> ​ (image taken from here: https://www.techpowerup.com/reviews/JDSLabs/O2_ODAC/images/naked.jpg)
> ...


 
  
 Thanks. My JDS O2 has the RCA and power on the back end, so thinking the best way in is the back, but need to first get the volume knob and 6.3 jack screwed off. No idea how to unscrew either. Think the 6.3 jack just needs to be unscrewed, but the knob is confusing and I really don't wanna break it. Any ideas.


----------



## cityle

xb4iris said:


> Thanks. My JDS O2 has the RCA and power on the back end, so thinking the best way in is the back, but need to first get the volume knob and 6.3 jack screwed off. No idea how to unscrew either. Think the 6.3 jack just needs to be unscrewed, but the knob is
> 
> Thanks. My JDS O2 has the RCA and power on the back end, so thinking the best way in is the back, but need to first get the volume knob and 6.3 jack screwed off. No idea how to unscrew either. Think the 6.3 jack just needs to be unscrewed, but the knob is confusing and I really don't wanna break it. Any ideas.


 
 You need a 1/16 hex key to remove the knob. I was looking for the same thing yesterday. Someone in this thread already post about it but I don't remember which page it was. "edit: I've just discovered that you can go directly to the post where was a picture"

 http://www.head-fi.org/t/616331/o2-amp-odac/4410#post_11662697


----------



## xb4iris

cityle said:


> You need a 1/16 hex key to remove the knob. I was looking for the same thing yesterday. Someone in this thread already post about it but I don't remember which page it was. "edit: I've just discovered that you can go directly to the post where was a picture"
> 
> http://www.head-fi.org/t/616331/o2-amp-odac/4410#post_11662697


 

  So you have to allen key it on and off. So thats what the hole is for. Dumb me. Thanks so much for the info, its gonna help a ton. Will do that when I get my Odac.


----------



## Aradea

havoc-28 said:


> Again , another headphone on my inventory that the O² drive perfectly fine : HE-560 . (1X Gain and - 10 dB on Foobar , 12o clock for the volume pot) . I don't know why i was expecting that it woulnd't be the case , peraphs read to much BS about orthos "requirements" .
> 
> Almost all headphone i have tried to plug on O² = Happy listening , the few that i didn't like was just headphones that i simply didn't like at all  .




Wow! Did not expect that at all..


----------



## xb4iris

Dam 6.3mm jack attachment came off when plugging my new headphones in today. Although it always felt a bit flimsy, I just thought that was the way it was supposed to be. Can't get the the attachment back on now. Put it back on slightly, and there's no sound coming through any of my headphones now. No idea what to do next.
  
 Any ideas?
  
 Was planning on opening this thing at some point, but dam, I didn't want to be forced to do it.


----------



## raoultrifan

Sorry, but I don't follow you. Do you think you ould take a picture with this issue?


----------



## xb4iris

raoultrifan said:


> Sorry, but I don't follow you. Do you think you ould take a picture with this issue?


 
  
 Hey, figured out that one of the connections on the jack box inside decided to break. Gonna solder it back on and that should fix it up. Scary stuff when things break for no reason. Thanks for the response though. May have needed you.


----------



## raoultrifan

Who knows, maybe it was a cold/bad soldering after all...might happen. Good luck and take care!


----------



## marts30

Anyone know why I can't run my O2 and my AUNE T1 at the same time (separately)? My Aune gets a playback error if the O2 is connected via USB... if I unplug it it works fine.
  
 edit: seems it was my Focusrite 2i4 interface being plugged into a USB 3 port that caused the issue.


----------



## WilliamLeonhart

Guy in my country found a way to produce the ODAC and O2 at $75 each... Would be brain-dead not to buy one!


----------



## Aradea

williamleonhart said:


> Guy in my country found a way to produce the ODAC and O2 at $75 each... Would be brain-dead not to buy one!



Where do you live?


----------



## WilliamLeonhart

In Hanoi, Vietnam. Will definitely give a pic of it when I'm home and get one


----------



## adydula

Ever wonder what an inverting version of the O2 might have been or sound like?
  
 I am, listening to one right now!
  
 http://www.diyaudio.com/forums/headphone-systems/279414-inverting-version-nwavguy-o2-headphone-amp-vs-original-thd-n.html
  
 Alex


----------



## raoultrifan

Thanks Alex,
  
 Looks like AGDR did it again. 
  
 In case you do have an A/B testing box, please do some A/B compare between regular O2 and inverting O2. It might be interesting finding out if any audible differences while playing music through.
  
 Cheers,
 Raul.


----------



## adydula

Yes AGDR has done it again!
  
 I had the pleasure of him sending me a unit to audition....and it drove me nuts to hear it....
  
 It was sooooo good I had to have one...and waited for him to complete ver 3.6 of the pc board.
  
 I finished it two days ago, my build that is.....
  
 Here is my build exerience and will post the AB with the original O2 soon:
  
 http://www.head-fi.org/t/793384/an-inverting-version-of-the-nwavguy-o2-headphone-amp-vs-the-original-diy-at-its-best#post_12217726
  
 Alex
  
 Note its playing without a case. Thats on order and a nice engraved faceplate....


----------



## adydula

One of the rubs that the O2 has had is the voltage rails and its easy to clip if your not careful with the gain...this inverting type of O2 doesnt have this exposure compared to the O2. It has a clipping detect circuit and LED.
  
 Real 15vdc +/- rails!
  
 Alex


----------



## raoultrifan

Already read entire diyaudio thread and I've seen the schematic and PCB layout.
  
 Thanks,
 Raul.


----------



## HotIce

Given that the new schematic has some major departure from the original O2, I would have went ahead and dropped the silly pot-in-the-middle design, and got rid of the potential hidden VAS stage clipping even at 2100 hours volume levels. But I guess that is arguably the only major distinctive feature left from the O2 
The +-15V rails will be very welcome by high Z headphone users, but it will mean higher power dissipation on the buffer OPamps, for lower Z headphones.


----------



## adydula

The pot in the middle is a 5K pot vs a 10K pot:
  
 * 5K pot vs the 10K in the O2, combined with a lower 24.9K ground return resistor (5x the pot to prevent loading) vs. 40.2K in the O2, to lower Johnson noise.  A 5K works here because the LME49880 gain chip is THD+N specified down to a 600 ohm load.  The NJM2068 in the O2 is only good for a 2K load.  The coupling cap here is bumped up to 4.7uf vs. 2.2uF in the O2 to keep the frequency response the same with the lower value of ground return resistors.
  
 Alex


----------



## HotIce

The issue with the pot after the VAS, is that you really cannot control the swing the VAS will be working on. It will be entirely dependent on the input device line out level.
So you either have to have the VAS to work very conservatively at lower gains (and hence lose potential swing), or you will end up playing a very dangerous game with clipping.
It also makes the amp very dependent on the device you will be plugging in.
Say you find the magical/optimal setup for device A with xV RMS output. Plugging device B with yV RMS line out might get you into a completely different area.
It is a very counter intuitive listening experience, to get into the clipping area, at very low volume levels.
IMHO, given that modern OPamps have very low noise floors (given decent PCB design and surrounding components selection), I see little to no justification in paying the price the pot-after-VAS design imposes.

This is why I always thought a design like The Wire (nothing special or Nobel winning - just an OPamp VAS plus diamond buffer within feedback loop, with volume pot before the VAS) is simpler in the imposed constraints, and pretty silent from a noise POV (I have built a couple for friends based on that design - also at least the E12, which I own, and the C5, use essentially the same schematic).


----------



## raoultrifan

HotIce, the pot after VAS is the main idea of O2 amplifier.  This is why it can achieve such a low noise, especially when pot is not to the max., though while playing music this means a bit of noise when turning the pot knob.
  
 As for the clipping part, just forget about original JRC/NJM2068 and replace it with another bi-polar OPAMP from TI like 5532, 4562, 49720 or from MUSES like 8820, 02 etc. There will be no clipping for gains up to 3.5-4X.
  
 In case you need something like 5X or even more, that means to increase the voltage to +/-15V by changing power regulators (need to check AGDR's posts first). Also, to drive planars you'll need to parallel a couple more of the 4556 output buffers (stacking additional 2 x 4556 should be enough) and by doing the above steps will get a cheap and quite decent headamp being able to output 9-10V/280-300mA for each channel.
  
 Anyway, diyaudio forum and especially AGDR could help us more in case we have questions.
  
 Thanks!


----------



## adydula

Ok guys I spoke with AGDR and here are his inputs to this design issue and how and why he did what he did in this amp:
  
 Everything that the original designer said in his blog about having the pot in the middle applies to this inverting version.  
  
 "i cant post any links to the source, if u want them PM me."
  
_“The gain stage is where most of the noise comes from. If the volume control is __after__ the gain stage reducing the volume also reduces the noise with it. In a single stage design, with the volume control at the input, you get all the noise all the time at any volume setting. With the volume control at the input you also amplify the Johnson Noise of the volume control itself which, in many headphone amps, dominates the overall noise. So there are huge noise improvements to having a second stage with the volume control __between__ them.”_
  
 I’ve taken that one step further, as with the ODA, by using the current drive capability of the gain stage chip to drive a pot with a smaller value (5K here, 1K in the ODA) than the input impedance (10K) for lower Johnson noise.  The original designer couldn’t do that in the O2 because the NJM2068 can only drive down to 2K, which is the 10K pot in parallel with the 1.5K feedback resistor.  The LME49880 in this one is good for 600 ohms at low THD, same as the LME49990’s in the ODA.
  
 In the section 2-11 below that under “location” (of the volume control) he says something interesting at directly applies to this inverting version of the O2 headamp:
  
_“See 2-3 above for why the volume control is best positioned between the two stages rather than before the input/gain stage. The main downside to the “volume control in the middle” approach is it’s easier to overload the gain stage which always runs wide open. The O2 has a gain switch to address this problem but it’s something those altering the default gain settings should be aware of. See: Gain Stage Overload. *A compromise is a “split gain” design where you divide up the gain between two sections but this requires the output stage, in a 2 stage amp, be capable of gain (many buffers are not) and usually requires additional components taking up board space.*”_
  
 Well the inverting O2 is exactly the “split gain” setup he mentions (his sentence that I’ve made bold). J  The input stage is either 0.75x or 1.87x, while the output stage is 1.33x.  The slight reduction in negative feedback in the output stage, due to having gain, that he mentions is a non-issue here because the chip involved (OPA2140) is so much better (higher open loop gain) than the older NJM455A.  The NJM4556A has Av = 100dB typical from the datasheet, while the much newer OPA2140 has Av = 126dB.  It can afford to loose a little and still come out ahead on negative feedback. J  He is right, the BUF634 in the inverting O2 isn’t itself capable of voltage gain, so it is looped with the OPA2140 to provide gain, lower DC output offset, and lower THD. And he was also right about the increased parts count, hence me having to go to the B5 case which is 1 inch wider.  The case also allowed more front panel stuff like the 1/4” jack and input select switch.
  
 Like he says the one big downside with the pot in the middle is clipping (and not being aware of it).  The inverting O2 solves the clipping problem in two ways by (1) using higher voltage rails for 3V of more peak headroom to decrease the chances of clipping and (2) the clipping indicator on both stages since they both have gain now.  So if it does clip, you will know now.
  
  
 I can attest with listening to 2 separate builds that I have not heard or seen any clipping like I have with the O2 and the ODA I have  not heard or had the clipping detect led indicate clipping. I am using both high and low impedance cans and cant get the volume loud enough to witness any clipping without blowing out my eardrums!!! LOL.....
  
 So to me this a great improvement over the original O2.....but with smart gain settings and understanding what your doing will keep clipping down to zero even with the O2. But the inverting amp helps protect the uninformed from clipping...
  
 Alex


----------



## HotIce

raoultrifan said:


> HotIce, the pot after VAS is the main idea of O2 amplifier.  This is why it can achieve such a low noise, especially when pot is not to the max., though while playing music this means a bit of noise when turning the pot knob.
> 
> 
> 
> ...



 
Changing OPamps does not solve the clipping issue.
Say that, just for example, given rails at +-VR, the VAS can emit an undistorted 8V RMS signal.
Say also that your current input source has a 1.2V RMS line out. You can in theory fine tune the VAS gain to 6.66x, and have both undistorted VAS output, and full utilization of the VAS voltage swing.
Now you plug a different DAC, with 1V RMS out, and you will be leaving on the floor, 15+% of swing.
Similarly, you plug a DAC with 1.5V RMS line out, and you will be having clipping out of the VAS stage.

But from the email above, I noticed that he now offloaded 1.33x of gain, to the output stage, which make things better, by putting clipping behavior back into the user hands via an easily user accessible and tunable pot, instead of coarse grained gain switches.
As for the noise, I already outlined my thought. With todays OPamps, unless you pick El Cheapo resistors and capacitors, and/or screw up PCB layout, it is fairly difficult to produce noisy HP amplifiers.


----------



## raoultrifan

I totally trust you HotIce, but I just don't understand right now how O2 can clip if the input signal would be 2V and gain 3.5X.
 AFAIK O2 is only clipping when gains are too high for input stage OPAMP to handle and this is why NJM2068 can be replaced for gains higher than 3.5X, but I'll investigate this further so I can get a better understanding of what you told me. Anyway, till now I had never heard O2 clipping unless a gain of 5-6.5X was used and trust me, my ears are OK.


----------



## adydula

The neat thing is that we have access to a real electrical engineer that has supported the DIY community for years and has in all of my interactions with him has gone way out of his way to help explain and understand what this amp does and how it works....when he is incorrect or discovers an error he is the first to admit it in a positive fashion.
  
 AGDR really enjoys exploring and designing circuits, he is one of the few people I have met that has a good handle on audio and design. A great positive asset where there are a lot of what I call appliance operators who just turn knobs and really dont understand whats happening. This is not meant to be a negative against people just many folks just want to listen and not understand...thats ok to, But for the few that really want to understand and learn having an AGDR resource around to bounce things off of is a good thing.
  
 If you have any postive ideas about making this or the Original O2 a better amp, I know AGDR will be glad to listen and help over at diyaudio.
  
 Alex


----------



## raoultrifan

hotice said:


> Say that, just for example, given rails at +-VR, the VAS can emit an undistorted 8V RMS signal.
> Say also that your current input source has a 1.2V RMS line out. You can in theory fine tune the VAS gain to 6.66x, and have both undistorted VAS output, and full utilization of the VAS voltage swing.
> Now you plug a different DAC, with 1V RMS out, and you will be leaving on the floor, 15+% of swing.
> Similarly, you plug a DAC with 1.5V RMS line out, and you will be having clipping out of the VAS stage.


 
  
 I believe now I understand the clipping issue you're telling me about, but nwavguy had this explained on his blog, if I remember correctly. Anyway, adjusting max. gain based on VAS max. output voltage (for a max. THD of 1% should be OK, I'd say) for 2V input signal should perhaps resolve this clipping possibility.
  
 For such a good price/quality ratio O2 has, I believe we can all live with a max. gain of 3.5X or we can start modding it.


----------



## adydula

The ODA amp has two clipping leds, tied to both +/- rails.
  
 It has 4 gain settings via a selectable pot.
  
 1x 2x 4x 8x and u can change as well...
  
 At unity gain and 2x gain settings most everything in my music collection never clips at normal listening levels.
  
 If I change the gain to 4x....and play "hot" recording the clipping leds light up a lot.
  
 If I set the gain on my O2's to a similar 4X setting I can hear this clipping....but the O2 has no clipping indicators.
  
 The music that clips easliy at a 4X gain setting seem to be those that are -10db or greater in replay gain...makes sense to me.
  
 So to me having lower gains and an indicator that helps tell me if I am clipping or not is a good thing!
  
 Alex
  
 Note all my dacs are 2+ volts or just a little higher.....nothing less than this.


----------



## HotIce

OK, I took a look at the schematic. He actually added even a buffer (BUF634) on top of the usual OPamp, in the current section (now with gain).
But the second stage, as it is, has a gain which depends on the pot position, whose value is now affecting the feedback ratio.
Moving the pot towards high values not only highers the ratio of the input signal, but also lower the resistance between the LME49880 output, and the OPA2140 input (which in turns highers the gain of the OPA2140 stage).
The clipping detector has (at least in the version of the schematic PDF I have found in that page), the zeners mounted in the wrong polarity (unless he really wants to detect clip at ~0.65V off the rails - instead of the 3.3V zener saturation value).
Also, some electrolytic capacitors are mounted with the wrong polarity (C39 and C41 for example), but he is likely going to notice that when he does the PCB 
Me that like simplicity, I would have dropped the LME49880 stage altogether (or use that instead of the OPA2140), use a normal non inverting OPA2140 stage, bump its gain to 4..6x, drop the clipping detector which would have no more use at that point, and save some $$ in components, power consumption, and PCB real estate 
But sometimes when you like to fiddle with electronics for hobby, the simplest path is not the one giving more satisfaction. I have found myself falling in that trap time to time.


----------



## adydula

C39 and C41 are not electrolytic caps?
  
 A.


----------



## HotIce

The symbols on the schematic PDF are that of polarized capacitors. Could be just wrong symbol selection.
Looking at their (low) capacity, it is very likely they are not polarized capacitors indeed.


----------



## adydula

I just soldered all those caps in and they are NOT electrolytics.....film caps...bypass
  
 Your correct on the zeners!
  
 I will PM you.
  
 A.


----------



## internaught

This thread has been pretty active lately and I can't keep up with the stuff you guys are talking about. I have been contemplating buying this amp/dac combo directly from JDS Labs to drive my MadDog headphones. Would you guys recommend -not- doing that?


----------



## adydula

JDS makes fine O2 products.
  
 Alex


----------



## raoultrifan

internaught said:


> This thread has been pretty active lately and I can't keep up with the stuff you guys are talking about. I have been contemplating buying this amp/dac combo directly from JDS Labs to drive my MadDog headphones. Would you guys recommend -not- doing that?


 
  
 Hi, 
  
 I believe http://linustechtips.com/main/topic/102501-mayflower-electronics-o2odac-combo-fostex-t50rp-v1-in-depth-review/ and http://www.head-fi.org/t/686489/mrspeakers-alpha-dog-review-and-comparison-with-hd600-and-k701 should help you out.
  
 Anyway, those drivers support up to 3W of power, but I don't really understand why would someone need so much power for 50ohms/98dB-SPL headphones (2x60mW should suffice for a SPL of 115dB). In case you'll ever need to upgrade to higher-end planars, perhaps you'll need to choose a more powerful amplifier, but for T50RP/MadDogs/AlphaDogs ODAC/O2 combo should be more than enough.


----------



## adydula

More than enough power!! 
  
 A.


----------



## adydula

Inverting O2 type amp going into case!
  
 http://www.head-fi.org/t/793384/an-inverting-version-of-the-o2-headphone-amp-vs-the-original-diy-at-its-best
  
  
 A.


----------



## LouisLoh

My O2 amp is suddenly acting up. It produces a pulsing tone/noise at about 600bpm when powered on (even when not plugged into a DAC). Anyone has any idea what this could mean?


----------



## HaVoC-28

louisloh said:


> My O2 amp is suddenly acting up. It produces a pulsing tone/noise at about 600bpm when powered on (even when not plugged into a DAC). Anyone has any idea what this could mean?


 
  
 Hum does your O² have Internal Batteries ?  I got something similar only when batteries were runing low , but yours can be defective after charge / decharge cycles ?


----------



## LouisLoh

havoc-28 said:


> Hum does your O² have Internal Batteries ?  I got something similar only when batteries were runing low , but yours can be defective after charge / decharge cycles ?


 

 Yes they do. I'll leave the charger in over the night and report back tomorrow. Thank you!


----------



## adydula

Just take them out and run on AC and see...
  
 Alex


----------



## LouisLoh

adydula said:


> Just take them out and run on AC and see...
> 
> Alex


 
  
 Hi Alex,
  
 I've taken the batteries out and they don't run with just the AC plugged in. Am I missing something really obvious?
  


havoc-28 said:


> Hum does your O² have Internal Batteries ?  I got something similar only when batteries were runing low , but yours can be defective after charge / decharge cycle


 
 Unfortunately the noise is still present. Should I bother getting new batteries?


----------



## adydula

Hmmm,
  
 Thats odd to me.
  
 I have 2 O2's,
  
 They both run without batteries when powered up by using the AC to AC wallwort.....
  
 Did you build your O2 or buy from a commercial retailer?
  
 If you bought it from a retailer, contact them about not running on AC?
  
 Did you get a AC to AC adapter?
  
 Alex


----------



## LouisLoh

adydula said:


> Hmmm,
> 
> Thats odd to me.
> 
> ...


 
  
 I bought it from a commercial retailer and I am using an AC-AC adapter.


----------



## MrMateoHead

I get a similar noise but only when the batteries are essentially drained. When I plug in the wall wart, all is well.
  
 When I opened up my O2 to fix the ground wire to stop the annoying staticky noise on the input jack, I noticed one of my batteries was too loose. The other is snapped right in, but I had to put a little cardboard in the housing to prop the poorly seated battery.
  
 Ever since that time, I swear the battery life has been a bit shorter, but that could be my own paranoia. But it did make me wonder if 1 of the batteries might be bad or going bad. Can the O2 run on a single battery? Can it make that noise if the connection isn't solid?


----------



## LouisLoh

mrmateohead said:


> I get a similar noise but only when the batteries are essentially drained. When I plug in the wall wart, all is well.
> 
> When I opened up my O2 to fix the ground wire to stop the annoying staticky noise on the input jack, I noticed one of my batteries was too loose. The other is snapped right in, but I had to put a little cardboard in the housing to prop the poorly seated battery.
> 
> Ever since that time, I swear the battery life has been a bit shorter, but that could be my own paranoia. But it did make me wonder if 1 of the batteries might be bad or going bad. Can the O2 run on a single battery? Can it make that noise if the connection isn't solid?


 

 I tried running it on 1 battery. Wouldn't work. I also rechecked the battery connections several times, to no avail.


----------



## adydula

The O2 should run without batteries using the AC to AC walwort....if it doesnt you have other issues.
  
 Please check this out if you havent already. If it works with AC only with no noise, hum, oscillation then its the batteries I would guess.
  
 Wont run on one battery, replace them and see what happens.
  
 Alex


----------



## gargani

Can I connect from the tape output jacks on my stereo reciever to the o2?. The owners manual specifies the tape out as 150mv output and 2.5kohms impedance.


----------



## Nec3

Spoiler: My initial messy post



I used to use a tube amp that had tubes that costed me $75, plus rhodium plated Q701 silver cables that costed $100.
After my tube amp died and the jacks on the Q701 cables decided to fall apart (literally!), I decided to go back to my ODAC/O2 and stock cables.
 I'm using this $20 (Texas Instruments LME 49720HA) solution with the Q701's stock cables and this combination gave me the same result compared to my previous overpriced upgrade.

 The treble is smooth but more detailed, the 2khz spike in the Q701's are smoothed out, mids seem to be faster and warmer and sweeter.
 The overall sound is wetter, not bad for a $20 side-grade. Although sub-bass took its' toll and there's a bit less extension.

 I should note that all the differences I mentioned above are just tonal to my ears. It's not a night and day difference unless if you're someone like me who has spent over 2 years with a single headphone and source.


 Good mids + highs but iffy bass. = German Telefunken Vacuum Tubes = TI LME 49720HA
 Good bass + intimacy = Russian Voskhod Vacuum Tubes = NJR NJM4556

 In a nutshell: I went in a COMPLETE CIRCLE, except with solid state!


----------



## ck2323

Does the Mayflower Objective2 + ODAC Rev. B Combo have the ability to use the dac only with an external amp?


----------



## lvince95

ck2323 said:


> Does the Mayflower Objective2 + ODAC Rev. B Combo have the ability to use the dac only with an external amp?


 

 Yes it does of course. I would rather go with JDS though, their customer service and quality control is much better than Mayflower's.


----------



## WilliamLeonhart

ck2323 said:


> Does the Mayflower Objective2 + ODAC Rev. B Combo have the ability to use the dac only with an external amp?


 
 Yes it does. My old one had RCA outputs at the back.
  
 But, same as lvine, I think you should go with JDS. My Mayflower O2 ODAC combo had 5x gain and clipped a lot. The new version only has 3.3x gain but if given a choice I'd go with JDS. I owned a diy combo made from JDS boards and even that sounded better than the Mayflower one.


----------



## ck2323

lvince95 said:


> Yes it does of course. I would rather go with JDS though, their customer service and quality control is much better than Mayflower's.


 
  


williamleonhart said:


> Yes it does. My old one had RCA outputs at the back.
> 
> But, same as lvine, I think you should go with JDS. My Mayflower O2 ODAC combo had 5x gain and clipped a lot. The new version only has 3.3x gain but if given a choice I'd go with JDS. I owned a diy combo made from JDS boards and even that sounded better than the Mayflower one.


 
 Thanks for the replies guys! Looks like the JDS will be the one I get. How exactly does the DAC only mode work? Through the RCA ports?


----------



## WilliamLeonhart

ck2323 said:


> Thanks for the replies guys! Looks like the JDS will be the one I get. How exactly does the DAC only mode work? Through the RCA ports?


 
 You can plug external amp into the headphone-in port of the O2... That port has double functions.
  
 Or you may buy the amp and DAC separately. One of my friends told me the ODAC will output better signal when not attached onto the board of the O2, but I'm not sure how many percent of truth is there in that.


----------



## ck2323

williamleonhart said:


> You can plug external amp into the headphone-in port of the O2... That port has double functions.
> 
> Or you may buy the amp and DAC separately. One of my friends told me the ODAC will output better signal when not attached onto the board of the O2, but I'm not sure how many percent of truth is there in that.


 
 Huh...that's interesting. I didnt think about that.


----------



## Hammy

I'm not a fan of starting new threads for the sake of it, so I'll post these ramblings here.
  
 Need someone to talk me out of getting the O2+ODAC to replace my FiiO E10K, which is what currently powers my Fidelio X2.  It'd work out at about 3x the price of the E10K and I'm unsure it would provide a noticeable increase in sound quality.
  
 DISCLAIMER: I'm not a headphone collector, can't hear above 15khz, 90% of my listening is TV/movies, and I have trouble noticing a difference from onboard ALC892 compared to the E10K.
  
 Talk me down!
  
 EDIT: I only just discovered that both the E10K and ODAC RevB share the same PCM5102A chip.


----------



## Psalmanazar

hammy said:


> I'm not a fan of starting new threads for the sake of it, so I'll post these ramblings here.
> 
> Need someone to talk me out of getting the O2+ODAC to replace my FiiO E10K, which is what currently powers my Fidelio X2.  It'd work out at about 3x the price of the E10K and I'm unsure it would provide a noticeable increase in sound quality.
> 
> ...


 
 Save your money and don't worry about it until you get new headphones or listen to more music. A case of beer or bottle of liquor would be a more enjoyable purchase for you now. You know it to be true!


----------



## Nec3

hammy said:


> I'm not a fan of starting new threads for the sake of it, so I'll post these ramblings here.
> 
> Need someone to talk me out of getting the O2+ODAC to replace my FiiO E10K, which is what currently powers my Fidelio X2.  It'd work out at about 3x the price of the E10K and I'm unsure it would provide a noticeable increase in sound quality.
> 
> ...


 

 I'm sorry sir, I'll probably do the opposite.

 My condolences to your wallet.


----------



## Hammy

psalmanazar said:


> Save your money and don't worry about it until you get new headphones or listen to more music. A case of beer or bottle of liquor would be a more enjoyable purchase for you now. You know it to be true!


 
  
 I do suspect this to be true, but I bought the E10K specifically for the HD598 and now suspect the synergy (is that a thing? ) with the X2 may not be the best.
  


nec3 said:


> I'm sorry sir, I'll probably do the opposite.
> 
> My condolences to your wallet.


 
  
 I can be swayed either way at the moment, although finding out they share the same DAC chip was kind of worrying.  I'm assuming the amp is much more powerful in the O2 and the ODAC implements things better on the DAC side, but I kind of suspect I'd be mostly paying for numbers on a sheet rather than lovely feelings coming in my ears.


----------



## lvince95

hammy said:


> I do suspect this to be true, but I bought the E10K specifically for the HD598 and now suspect the synergy (is that a thing? ) with the X2 may not be the best.
> 
> 
> I can be swayed either way at the moment, although finding out they share the same DAC chip was kind of worrying.  I'm assuming the amp is much more powerful in the O2 and the ODAC implements things better on the DAC side, but I kind of suspect I'd be mostly paying for numbers on a sheet rather than lovely feelings coming in my ears.


 

 The X2 doesn't scale at all. The E10K is enough.
  
 Source: Didn't notice much of a difference from my MBP Retina vs the O2+ODAC when I had the X2.


----------



## raoultrifan

I had some time to spare with my beloved O2 this weekend, so while trying to find what's my O2's max. non-clipping output voltage I was able to get a decent output voltage of 7.4V RMS (with dummy load of 500ohms resistors + original Beyers cable serialized, instead of headphones) before starting to clip and without any sort of strange spikes or oscillations.
  
 So, while my 3 years old kid was spilling water inside a power stripe's outlet (thank's God of the 30mA differential safety) and he was unscrewing all the screws from a wooden IKEA chair (for all these screws I applied a 10-12nM of torque when I built this chair; I had no idea that kids today have such a force to unscrew'em) I did few mods during this weekend:
 - 1) Changed the gain resistors from infinite/1Kohm (corresponding to 1X/2.5X) to 2.5Kohm/516ohms (corresponding to 1.6X/3.78X). I did some "custom resistors" of about 516ohms by serializing 274ohms + 242ohms resistors that I had in stock; this corresponds to a real gain of about 3.78X and an output voltage of about 7.3V RMS (a bit less than max. non-clipping voltage of 7.4V RMS, just to be sure clippings will never occur when ODAC is connected, even with loud and highly compressed music). Perhaps some of you might still say that a gain of 3.78X is too much and voltage gain will clip, but with my ODAC XL connected to O2 and 0dB sinewaves applied (taken from audiocheck.net) there's no clipping at all. Looks like my ODAC can output 1.921V RMS when sinewaves are applied; I have tried 20Hz, 32Hz, 1KHz, 16KHz, 20KHz and I get no clipping, no roll-offs, no oscillations, no strange FFT harmonics, no THD >0.1% (checked with my PicoScope 2204A).
  
​  
 - 2) Added 2 x 1uF film capacitors immediately after the 2 regulating diodes from power input plug. These 2 caps should decrease any possible noise coming from the mains.
​  
 - 3) Added 2 x 10uF/25V AVX tantalums on output regulators, to further decrease the ripple.
 - 4) Added 2 x 47uF/35V Nichicon KA and 2 x WIMA 0.1uF/100V for decoupling the input stage OPAMP (LME49720).
 - 5) Added 2 x 47uF/35V Nichicon KA for each of the 2 output buffers for decoupling purposes (NJM4556A).
​  
  
*Did I gained anything?*
 - Besides a lot of fun, I was able to decrease ripple & noise from 2.3mV p-p to 0.747mV p-p, measured directly on each regulator output and also on OPAMPs +/-V rails. That's a good ripple decrease, though it should probably not be noticed on headphones out, because O2's OPAMPs already have a good ripple reduction inside (PSRR & CMRR of about 90-100dB).
 - Soundstage increased a little bit, though this is a subjective impression that I'm going to test it soon by A/B'ing.
 - OPAMPs rolling should be easier now with additional decoupling caps used.
  
*Note*: The tested O2 has LME49720 on input stage and 2 x NJM4556A as buffers. All 3 OPAMPs have heatsinks on top, glued with Arctic Alumina compound. There are 2 power plugs in front and back, 2 headphone jack: 3.5mm and 6.3mm on front and RCA outputs on the back. I'm also using original 9V/300mAh batteries and original 15V/500mAh power adapter.
  
*P.S.*: Looks like the way I arranged one of tantalums was not good, because I couldn't close the case, so I need to move it a few mm away from the edge of the PCB.

 ​  ​  ​  ​


----------



## MrMateoHead

hammy said:


> I'm not a fan of starting new threads for the sake of it, so I'll post these ramblings here.
> 
> Need someone to talk me out of getting the O2+ODAC to replace my FiiO E10K, which is what currently powers my Fidelio X2.  It'd work out at about 3x the price of the E10K and I'm unsure it would provide a noticeable increase in sound quality.
> 
> ...


 
  
 You don't need more power, and your headphone performance will not improve appreciably on the new setup. That should be sufficient. If anything, you'll be annoyed unless you stayed on unity gain / 2.5x because you can barely twist the dang volume knob out of its channel-imbalance range.
  
 Unless you can't routinely playback your program materials at a volume you want, or can hear a difference between your available DACs, you would be straight up wasting your money.
  
 When and if you start listening to more music, and in particular get headphones with big impedance swings or that are inefficient, you will be glad to have the O2's power. Until then, you are just fantasizing about everything being "better" because you spent more and have more power. Its not true.
  
 What started you on the path to upgrading your Amp/DAC in the first place? Because I can tell you that in my experience so far, low-impedance headphones with mild impedance swings do not improve drastically going from mediocre to "awesome" amps. If you want a different sound, it is best to look for new cans!


----------



## Hammy

mrmateohead said:


> You don't need more power, and your headphone performance will not improve appreciably on the new setup. That should be sufficient. If anything, you'll be annoyed unless you stayed on unity gain / 2.5x because you can barely twist the dang volume knob out of its channel-imbalance range.
> 
> Unless you can't routinely playback your program materials at a volume you want, or can hear a difference between your available DACs, you would be straight up wasting your money.
> 
> ...


 
  
 Yes, if I had gone down this path it would have been the 1 / 2.5x gain settings for me.  I am not trying not to "fantasize", I'm just looking for opinions from more knowledgable people than myself.
  
 I appreciate you have not experienced low-impedance headphones scaling well, but some owners of the X2 have the opposite opinion, and I simply wanted to investigate whether there were better options out there for me than the E10K. 
  
 I'm very happy with the volume levels from the E10K, and thanks to you guys I think I've been brought back from the edge of the abyss... for now.


----------



## lvince95

hammy said:


> Yes, if I had gone down this path it would have been the 1 / 2.5x gain settings for me.  I am not trying not to "fantasize", I'm just looking for opinions from more knowledgable people than myself.
> 
> I appreciate you have not experienced low-impedance headphones scaling well, but some owners of the X2 have the opposite opinion, and I simply wanted to investigate whether there were better options out there for me than the E10K.
> 
> I'm very happy with the volume levels from the E10K, and thanks to you guys I think I've been brought back from the edge of the abyss... for now.




As long as you have a clean source (which the E10K provides), it's enough for the X2 really. 

Alternavely you could always get the O2+ODAC to remove your doubts and regret it at the same time :S


----------



## Alec246

I have a ODAC already. Just got the amazing HD600. I wonder if getting the O2 for AMP is the best move now, or should I focus on a better DAC+AMP combo. What do you guys think?


----------



## cityle

alec246 said:


> I have a ODAC already. Just got the amazing HD600. I wonder if getting the O2 for AMP is the best move now, or should I focus on a better DAC+AMP combo. What do you guys think?


 
 I would strongly recomment to have an amp with the HD600 if you don't have already an amp (you know, it's a 300 ohms phones). I've read good comments on pairing the HD600 with the O2, but you may want to do some more investigation. Personnaly, I would go for the O2 and the odac as I have this setup and I love it and I want the less coloration possible.


----------



## Alchemist007

What are the O2+ODAC's limits or how would you determine them? Would they run an LCD-4 and why or why not? Just an educational question, I don't have the $$ for such a headphone!


----------



## MrMateoHead

alchemist007 said:


> What are the O2+ODAC's limits or how would you determine them? Would they run an LCD-4 and why or why not? Just an educational question, I don't have the $$ for such a headphone!


 

 Data on the O2 is already on the Internet and is easy to find. The max output is around a half-watt (500-700 mWs) at around 50 Ohms. At very low distortion, it pretty reliably supplies 100-200 mWs but I am working off memory so don't hold me to that.
  
 The "limit" IMO is all about how loud you are trying to go, as determined by the efficiency of the headphone and the available low-distortion power. Given that even some of the most inefficient phones can put out well over 90 dB with 1 little mW (or indeed more like 100 dB), the O2 is more than enough power for most cans played back at non-ear destroying levels. That would be true of any amp with similar power on tap.
  
 The LCD-4 claims efficiency of 100 dB / 1 mW. 100 dB is well into ear-damage range. But to get to concert like levels, you would need about 10 times that power or 10 mWs. Just because the thing is rated to survive 15 watts doesn't mean I'd attempt that on my head! Sheesh. Audeze claims that "optimal" power is in the 1-4 watt range, which may be true. But just on the basis of power-for-spl that would seem like complete and total overkill. But to be fair, depending on the type of recording and the maximum dynamic range of said recording, more or less power may be needed than that first fraction of a mW. Ditto if your source to the amp is "weak" (1 V or less). In fact, that is why, for example, classical music (or a movie) tends to need "more power" than pop. The wider swings of the music require the amplifier to supply more peak power during crescendos and so on.
  
 It is a good idea to consider the ability of any speaker to playback high levels with low distortion or compression (say less than 10%). The speaker is more likely the "limiting factor" in terms of sound quality - not necessarily the amp. Many can handle high power but my ears tell me that I am going from enjoyment to congestion / pain when SPL starts to average more than about 80 dB. I like to listen closer to 60-70 dB most days anyhow. But I'd be surprised if the LCD-4, or any headphone for that matter, could playback 120 dB or more full-range without being totally distorted.
  
 Hope that feeds your curiosity!


----------



## jimbop54

After reading all the great reviews, I bought an O2/ODAC and then discovered that I can't use it directly with my iphone or ipad. So now I have a powered USB hub and and the extra power and connection cables littering my desk, when I was expecting that this would be nice 1-box system.
  
 Is this common with other dacs/amps? Are there any other solutions?
  
 JD


----------



## WilliamLeonhart

jimbop54 said:


> After reading all the great reviews, I bought an O2/ODAC and then discovered that I can't use it directly with my iphone or ipad. So now I have a powered USB hub and and the extra power and connection cables littering my desk, when I was expecting that this would be nice 1-box system.
> 
> Is this common with other dacs/amps? Are there any other solutions?
> 
> JD


 
 From what I know, yes it is in most cases. With a very few exceptions (the Cayin C6, also it's very meh), you'll almost always have to buy at least the Camera Kit for iPhone/iPad. The JDS C5D requires it, for example. If you're luckier, the DAC/amp passed "MFI" certification by Apple, so you'll only need a Lighting-usb cable.
 Then, if the DAC require more power, you'll have to buy a hub too. Which is the case with the ODAC (notice that the O2 has nothing to do here).
  
 But anyway the O2 ODAC sounds definitely better than all the other DAC/amp in the price range, if neutral, accurate sound is what you're after. It's a matter of convenience vs. SQ, you see.


----------



## adydula

Hey Guys/Gals....I finally completed my inverting O2 type headphone amplifier, its in the final case, new engraved front panel from Front Panel Express and using an ODAC.
  
 If your interested check it out, many pix etc:
  
 http://www.head-fi.org/t/793384/an-inverting-version-of-the-o2-headphone-amp-vs-the-original-diy-at-its-best/15#post_12287235
  
 Alex


----------



## LiquidDan

This was a great read, thanks for the report


----------



## Deaj

Interesting read MrMateoHead - thanks for posting this.  

I've owned an Objective 2 for about 18 months or so - standard layout (all I/O, power, and control of front panel.I just finished updating it to have a 1/4" headphone Jack, 3.5mm input Jack removed, power input moved to the back panel, and RCA inputs installed on rear channel. I much prefer havingthese connectors mounted to the chassis. 

I was recently looking into buying an ODAC. Since I'd already been looking into a portable DAC/Amp I landed on the JDS Labs C5d with th analog input to the amp changed out for a DAC-only output. This provides me with a dedicated (O)DAC at my desktop and a low profile self powered DAC/Amp to use with my Android phone on the go. I couldn't be more pleased for the value and performance on the go and at my workstation!


----------



## adydula

LiquidDan,
  
 Thanks!
  
 This amp is very hard to get to clip the way its designed, low gain, higher voltage.....never see the clipping light come on at all.
  
 Alex


----------



## bobel2007

Hello O2/ODAC owners!
  
 I have a problem with my Epiphany O2D (O2+ODAC), I'm getting audible hiss in the right channel, I thought I got rid of it yesterday by simply changing the USB port in which I plug the ODAC with another one on my MacBook, and that seemed to do the trick, as I couldn't hear it after that. Today I started listening with my CAL! and there was no hissing, but it suddenly came back as soon as I changed to my Grado, and now it's present again. Anyone having this problem?


----------



## lvince95

Selling my JDS Labs O2+ODAC if anyone's interested


----------



## xb4iris

Have the Objective2 and Odac Rev B and am wondering whether anyone has found a valid solution to bit perfect audio using this setup. I read about the clipping issues with ASIO, but I am getting a similar, less severe problem with WASABI on MusicBee. Not much of a Foobar2000 fan, as I do not like the way it manages its library as apposed to MusicBee and its WASABI was great when I was previously using my ASUS Xonar STX. So stuck with DirectSound.
  
 Any ideas on how to improve things. Music does not clip all the time, just when seeking I experience a slight delay and clip effect, which is annoying. My IRQ setup seems to include all my USB ports, which means the Odac is sharing the protocol with other power munching devices on all ports. 
  
 Seems some of you folks have tested and tampered, and wondering whether anyone has found a bit perfect solution for the Rev 2 Odac yet?


----------



## adydula

I run a bitperfect setup with JRiver and Foobar2000.
  
 WASAPI, event driven.
  
 What comes in goes out with no resampling etc..
  
 I am not familiar with MusicBee.
  
 In JRiver there is a indicator that turns blue when BItperfect state is working,
  
 Alex


----------



## adydula

I found this for you....This guy was using MusicBee and Win10:
  
 I solved my problem but for the sake of others that may have the same problem I'll answer my own question.
  
 The hard part is finding control panel in Windows 10, which turns out to be easily done with the keyboard shortcut.
  
 1) Press WIN+X (windows key and the X key) to open the "power menu"
 2) Select "control panel" from the list
 3) Select "sound" from the control panel that opened up.
 4) Highlight the entry that represents your external DAC device. (Note: It has to be connected to show up in the list)
 5) With your device highlighted click "properties" (A new box with 4 tabs will open)
 6)On the "Levels" tab make sure the volume and L&R balance are all set to 100%
 7)On the "Enhancements" tab make sure "disable all enhancements" is checked. (This should uncheck everything else)
 8) On the "Advanced" tab make sure "allow applications to take exclusive control of this device" is unchecked! both boxes under "exclusive mode" are checked.
 9) Click 'apply" then click "OK" to close the window.
 10) Restart your computer and enjoy the greatly improved sound! (Assuming you had to change any settings above)
  
 This made a huge difference on my setup and I highly recommend you check yours!


----------



## xb4iris

adydula said:


> I run a bitperfect setup with JRiver and Foobar2000.
> 
> WASAPI, event driven.
> 
> ...


 
  
 Thanks. I haven't tried JRiver. May give it a go now. May also give Foobar2000 another go too, hoping I can find the kind of customization I need this time.
  


adydula said:


> I found this for you....This guy was using MusicBee and Win10:
> 
> I solved my problem but for the sake of others that may have the same problem I'll answer my own question.
> 
> ...


 
   
I'm on Windows 7, but this sounds like an interesting line of view to approach, because maybe exclusivity can be enabled in a similar fashion as well. Great advise and a few breadcrumbs to follow! Thanks.


----------



## adydula

You might also look at JDS Labs instructions for the O2 and ODAC I believe that they have directions on how to set up their stuff as well.
  
 JRiver is not FREE. It has a great interface for viewing on large screen tv's or displays, many things in it for audio and video.
  
 I use Foobar as well and its really easy to set up once you learn where the "stuff" is hidden!! LOL.
  
 Also with Foobar you might have to download plugins and install to get WASPI etc...and these additional steps sometimes can be confusing, especially where to go to change settings etc once the plugins are installed.
  
 Having your source or knowing what it is ie 44.1Khz/16bit and setting up the Operating System as in the above instructions to match this sample/but rate and use exclusive access along with the same stuff in the player....all leads to bitperfect...
  
 Source ---OS----Player Software-----Dac------->
  
 But remember even in bitperfect what goes in comes out or is played as recorded and mastered....even the crappy stuff!
  
 Alex


----------



## xb4iris

adydula said:


> You might also look at JDS Labs instructions for the O2 and ODAC I believe that they have directions on how to set up their stuff as well.
> 
> JRiver is not FREE. It has a great interface for viewing on large screen tv's or displays, many things in it for audio and video.
> 
> ...


 
  
 JDS has instructions which anyone who has used a computer already knows. LOL!
  
 Yeah, I'm trying the free version of JRiver. Foobar2000 has always done well with audio quality for me, but the interface, although highly customisable, has never been my cup of tea, even after many hours of tinkering. I'll try again though, see if I can figure it out this time around.
  
 My source is 24 bit 48 Khz Flac files, so that's what I've set it to. In my testing I could never hear the difference between DirectSound and Wasabi, but ASIO definitely had a slight improvement. Apparently DirectSound is wasabi without exclusive mode enabled, or that just in MusicBee.
  
 Cannot make my mind up just yet, but looking forward to tinkering for the hell of it.


----------



## WilliamLeonhart

While we're on the topic of players do you guys also find that foobar outputs a thinner (and perhaps more accurate) sound than iTunes? I started with iTunes but have been using foobar almost exclusively since my library grew out out iTunes' perfomance limits.


----------



## Montecristo

Is there any sound difference to the element?


----------



## Wepeel6

I get some random clicks and pops whenever I press stop in foobar when it's playing music and in MPC-HC when playing video. This doesn't happen when I pause, only stopping. Is this normal for the ODAC? I haven't tried this with any other software because I don't use anything else.


----------



## WilliamLeonhart

wepeel6 said:


> I get some random clicks and pops whenever I press stop in foobar when it's playing music and in MPC-HC when playing video. This doesn't happen when I pause, only stopping. Is this normal for the ODAC? I haven't tried this with any other software because I don't use anything else.


 
 My ODAC has a similar problems. When I start a song in foobar when another is still playing, I could hear the click. I tried everything and it still happens. Not that it always does, but it's still annoying.


----------



## Wepeel6

williamleonhart said:


> My ODAC has a similar problems. When I start a song in foobar when another is still playing, I could hear the click. I tried everything and it still happens. Not that it always does, but it's still annoying.


 
 I get that sometimes too, switching tracks mid-song. But the click is the most consistent when stopping the audio as I said before, when the audio stream gets shut off I guess.


----------



## raoultrifan

I had this issue when I used some ASIO drivers from a different soundcard and also when using ASIO4ALL. I stoped using ASIO and got back to WASAPI (event or push) and everything's fine now, at least in Windows 7 64-bit + Foobar.
  
 What OS version are you using? Also, are you using ASIO, WASAPI, Direct Sound? Is this happening in Foobar as well?


----------



## adydula

Never had this issue, use WASAPI event driven.
 You have to donwload the plugin and install and configure.
  
 A.


----------



## Wepeel6

raoultrifan said:


> I had this issue when I used some ASIO drivers from a different soundcard and also when using ASIO4ALL. I stoped using ASIO and got back to WASAPI (event or push) and everything's fine now, at least in Windows 7 64-bit + Foobar.
> 
> What OS version are you using? Also, are you using ASIO, WASAPI, Direct Sound? Is this happening in Foobar as well?


 
 I'm using Windows 7 64-bit and DirectSound, I tried using WASAPI in both event and push but it didn't fix anything.


----------



## raoultrifan

Can you please try Foobar and/or JRiver? It may be player related after all.
  
 It may also help changing priority from Normal to High in Windows Task Manager.


----------



## Wepeel6

raoultrifan said:


> Can you please try Foobar and/or JRiver? It may be player related after all.
> 
> It may also help changing priority from Normal to High in Windows Task Manager.


 
 Foobar2000 is what I'm using and high process priority doesn't help either. I found another thread about ODAC clicks but none of the suggestions in that thread helped me and the issue seems to be a bit different from what I'm having. I'm currently using my O2 with a Modi 2 without problems.


----------



## WilliamLeonhart

From what I remember using iTunes did help. I don't bother much about it now. Right now I'm using the ODAC in wasapi push mode, changed the buffer to maximum but it didn't help.

Oh and setting fadein and fadeout a few hundred ms seems to help.


----------



## castleofargh

wepeel6 said:


> williamleonhart said:
> 
> 
> > My ODAC has a similar problems. When I start a song in foobar when another is still playing, I could hear the click. I tried everything and it still happens. Not that it always does, but it's still annoying.
> ...


 
  
 if it's about what feels like a little static discharge that happens sometimes in one ear (not always the same)when you stop or change track, using my hd650, my mouse when I click to stop foobar from playing is making a louder physical noise than what I'm talking about. 
	

	
	
		
		

		
			




 it's something that doesn't exist when simply playing music, so I don't see how this is a problem? I mean you press stop and get a little noise. ok, but you stopped the music!!!!!! doesn't it mean that you stopped listening? just take the headphone OFF your head before pressing pause if that's such a big deal. if I turn OFF any amp I have, I will get a louder noise than what I'm talking about. forcing most DAC to change resolution tends to make a bigger noise than that.
  
 what's fun is that if pause doesn't make the noise, then why are you using stop? 
	

	
	
		
		

		
		
	


	




  I always thought I was a noise maniac, but I admit I've now found my master. ^_^


----------



## raoultrifan

wepeel6 said:


> Foobar2000 is what I'm using and high process priority doesn't help either. I found another thread about ODAC clicks but none of the suggestions in that thread helped me and the issue seems to be a bit different from what I'm having. I'm currently using my O2 with a Modi 2 without problems.


 
 Hi, 
  
 It would be interesting to find out if on a different computer your ODAC manifests the same issue, on the same Windows version.
 Also, an USB stick with Ubuntu-live and your ODAC connected to might help; if on ALSA or PULSE there will be the same clicks, then ODAC might be defective I'd say. 
  
 Btw, what about using ASIO4ALL for a quick test? Maybe it could help. Also, what about using jRiver, do you have the same issue?
  
 Thanks!
  
 P.S.: I have these clicks on my ASUS Essence One DAC when seeking and when start/stop/pause are involved, but not very annoying and only when using ASIO; on WASAPI everything is smooth. Also, when using ASIO and seeking a lot playback locks for about 10 seconds then I get a Foobar error (sort like "your soundcard stops responding") and I need to press play again to make it works again. I really think this is drivers/software related issue, perhaps the same for your ODAC.


----------



## Wepeel6

castleofargh said:


> if it's about what feels like a little static discharge that happens sometimes in one ear (not always the same)when you stop or change track, using my hd650, my mouse when I click to stop foobar from playing is making a louder physical noise than what I'm talking about.
> 
> 
> 
> ...


 
 It's not a very big issue but it was very noticeable and made me wonder if it's normal. 
  
  


raoultrifan said:


> Hi,
> 
> It would be interesting to find out if on a different computer your ODAC manifests the same issue, on the same Windows version.
> Also, an USB stick with Ubuntu-live and your ODAC connected to might help; if on ALSA or PULSE there will be the same clicks, then ODAC might be defective I'd say.
> ...


 
 I'll try to hunt down another computer to test it on. I'm starting to suspect it's simply the way the ODAC was designed and/or the way it interacts with my particular PC, but we'll see if I can get my hands on another PC.


----------



## adydula

Is it rev a or rev b?
  
 A.


----------



## Wepeel6

adydula said:


> Is it rev a or rev b?
> 
> A.


 
 It's a revB.


----------



## raoultrifan

wepeel6 said:


> It's a revB.


 
  
 Oh...sorry, but I have no experience on rev B yet. 
 I was only reffering to rev. A. Thanks Alex for making a point here.


----------



## xb4iris

Clicks are present here as well. Rev B model too.
  
 I have however kinda got used to it by now, as it doesn't happen all that often. From what I have read, it could be an IRQ conflict between the USB port being used and other power sapping devices. This could be the case with my situation, as all my USB ports share IRQs with other devices which are essential to the system. Sadly, I have no idea how to prove this or remedy the issue.


----------



## xb4iris

So, in theory, there is no way to get rid of the power surge 'clicking' sound you hear when stopping music?
  
 I get this sound when stopping a video, exiting an app in which music or video is playing, and exiting a game. It's pretty annoying.


----------



## jseaber

xb4iris said:


> So, in theory, there is no way to get rid of the power surge 'clicking' sound you hear when stopping music?
> 
> I get this sound when stopping a video, exiting an app in which music or video is playing, and exiting a game. It's pretty annoying.


 
  
 So far, I'm unable to reproduce this behavior on multiple PCs. Foobar's default Output settings define a 1000ms buffer and 100ms fade in, fade out. iTunes also behaves as expected, as well as various apps and Win7 and Win10 sounds. OS X is also okay.
  
 The PCM5102A's zero-detect function enters self-mute after 21ms @ 48kHz, or 10.5ms @ 96kHz. Mute mode is apparent in measurement (DAC's noise floor reaches our analyzer's noise floor), and I've never noticed transients during analysis. From TI's datasheet:
  


> *9.3.2.3 Zero Data Detect*
> The PCM510xA has a zero-data detect function. When the device detects continuous zero data, it enters a full
> analog mute condition. The PCM510xA counts zero data over 1024 LRCKs (21ms @ 48kHz) before setting
> analog mute.
> ...


 
  
 Please PM the following and I'll look for patterns:
  

Your media player and any non-default settings
OS
DAC drivers you are currently using
DAC drivers you have previously used
When does this sound occur on your system?


----------



## gargani

Hi all
  
 I have a question, maybe someone can answer. I recently purchased a jds labs o2. I use it with the ac adapter plugged in all the time. Can I leave it powered on all the time, or should Iturn it off when I'm not using it?


----------



## raoultrifan

You can leave it ON, but I recommend you to turn it OFF to save some power and to increase O2's capacitors life.


----------



## gargani

raoultrifan said:


> You can leave it ON, but I recommend you to turn it OFF to save some power and to increase O2's capacitors life.


 
 Thanks raoultrifan,  I'll turn it off when not in use.


----------



## Zankes

I bought this amp/dac. It will arrive probably next week, but honestly I feel little worried about it as people say it's outdated and there have been released greater products since. People praise it for being neutral and many say this is great, because it doesn't color the headphones and has more than enough power, but yet it bothers me that people say it's low quality and I should have bought this which costs twice more or say neutral thing is bad for some reason. I don't understand
  
 Would be great if someone could chip in and tell me how does this compare to current products and maybe something which is similar price range and higher level..
  
 I eventually try this out latest in 7 days anyways, but some comparing will be great. I just feel that should I have bought something else or are people selling me snake oil


----------



## adydula

Zankes....the O2 is a wonderful amp and just because its inexpensive does'nt mean it is a bad amp for headphpones!
  
 Its not outdated!! Who ever tells you that is smoking something...
  
 The amp was designed to give the best performance with the least cost.....and it does this very well. Sonically its pretty much a straight wire with gain. what you put into it comes out unaltered...just amplified.
  
 The switches are not the best in the world as are the pushbuttons, and it may not win any beauty contests....but the switches and parts will last
 thousands of on/off cycles and then some.
  
 For the cost, it delivers just what the designer said it would...totally transparent, flat freq response, just marvelous.
  
 Yes there are other amps as good and much more costly, but sonically if your honest in doing real AB comparisons it works as well and better that amps costing much much more.,,.,
  
 If you want a real heavy case with 1/4" thick aluminum case, stepped attenuator pots etc this is not that amp! If you want all kinds of lights abnd dials this is not that amp..its simple, close to perfect for what its designed for.....
  
 No snake oil here,...
  
 Enjoy!
 Alex


----------



## Zankes

adydula said:


> Zankes....the O2 is a wonderful amp and just because its inexpensive does'nt mean it is a bad amp for headphpones!
> 
> Its not outdated!! Who ever tells you that is smoking something...
> 
> ...


 
 I think you made me feel better about my purchase, thanks. Worst thing I read was someone said odac sounds the as if you put your hand in front of your mouth and try to sing.
  
 I bought this http://www.headnhifi.com/OBJ_O2_ODAC_digital2
  
 Silver with black volume button, because I requested it.
  
 Originally I was looking to pay way more, but then I heard HD600 in shop and had decided these are right for me. Tried out also HD700,650, 800 etc. Then I considered Audio-GD NFB11, but I felt like there was no point paying double the price for literally stuff which I feel like I don't need. I just don't understand the haters.


----------



## Nec3

I'm confused, comparing the max output, does this mean the E12 is more powerful than the O2? What makes the O2 more powerful than the E12? Voltage? 


Spoiler: Nevermind, found out the E12 is more powerful under less resistance.




 E12 Specs
Frequency Response: 20Hz – 20kHz
SNR: over 110dB (A weighted)
Crosstalk: over 65dB
Gain: 0dB (low) and 16dB (high)
THD: Less than 0.005%
Max output: 600mW (16ohm), 880mW (32ohm), 160mW (300ohm)
Recommended Headphone Impedance: 16 – 300ohm
Input Impedance: 5kohm
Battery Life: over 12 hours
Recharging Time: less the 3 hours with 5V, 2A.
Selectable Bass EQ and Crossfeed
 
[size=20.007px]_O2 SPECS_​[/size]  [size=17.03px]_AMPLIFIER PERFORMANCE_[/size] 
Frequency Response+/-0.1 dB (20Hz-20kHz)​THD 1 Khz 150 Ohms0.0016%​IMD CCIF 15 Ohms0.001%​IMD SMPTE0.002%​Noise (ref 400 mV)-105 dB​Max Output (33 Ohms)613 mW​Max Output (150 Ohms)355 mW​Max Output (600 Ohms)88 mW​Output Impedance0.54 ohms​Crosstalk (15 ohms)-65 dB​Channel Balance (50% volume)0.6 dB​Battery Run Time6-8 Hours
  ​


----------



## HotIce

Under battery power, the E12 is more powerful. The O2 is fed by dual 9v batteries (which go to about 8.6v under load, and fully charged), whereas the E12, through charge pumps, has +-11.2v rails.


----------



## riverlethe

Voltage is right, though I'd be interested to see the E12's distortion vs the O2 with a 32ohm load.


----------



## MrMateoHead

Any comparisons done between the O2 and the similarly measuring Headamp GS-X?
  
 Just curious as to how the O2 stacks up!


----------



## raoultrifan

I believe Headamp GS-X is in a different price league and is also fully balanced and more powerful as well.
 Or perhaps are you referring to a different Pico amplifier?


----------



## WilliamLeonhart

jseaber said:


> So far, I'm unable to reproduce this behavior on multiple PCs. Foobar's default Output settings define a 1000ms buffer and 100ms fade in, fade out. iTunes also behaves as expected, as well as various apps and Win7 and Win10 sounds. OS X is also okay.
> 
> The PCM5102A's zero-detect function enters self-mute after 21ms @ 48kHz, or 10.5ms @ 96kHz. Mute mode is apparent in measurement (DAC's noise floor reaches our analyzer's noise floor), and I've never noticed transients during analysis. From TI's datasheet:
> 
> ...


 
 In my experience adding fade in and fade out drastically reduce the clicking. Please try removing them from your Foobar and see if the "tsk" sound happens. It happens both when I use DS and wasabi.
 Strangely I don't remember having the same trouble on iTunes.


----------



## MrMateoHead

raoultrifan said:


> I believe Headamp GS-X is in a different price league and is also fully balanced and more powerful as well.
> Or perhaps are you referring to a different Pico amplifier?


 

 Actually I am asking about the more powerful, more expensive amp (GS-X) versus the O2. Aside from the fact that the GS-X could, in theory, deliver higher SPL to a headphone capable of higher SPL, I am curious as to whether it would sound similar to the O2 - fast, black, with great extension.
  
 I know that is isn't typical to place products of dissimilar prices into direct comparison, but then again I am always curious as to whether the $7 bottle of wine is "as good" as the $100 bottle! My guess is that the two amps measure so alike that they wouldn't sound very different at all - I see that the O2 has a lower noise floor, but the GS-X has excellent crosstalk, for example. Any reason they shouldn't sound alike?
  
 Us poor people (me) like to think our O2 is giving us a top performance for the money!


----------



## raoultrifan

I would also be interesting is anyone can share opinions about GS-X.
  
 BTW, with 2 x O2 amplifiers we might probably get a nice balanced headamp. Too bad I don't have 2 x O2s to give it a try/test.


----------



## HotIce

riverlethe said:


> Voltage is right, though I'd be interested to see the E12's distortion vs the O2 with a 32ohm load.



 
My take, at the power level you get on 32Ohms, your ears become much less linear (if not damaged) than the amp will.


----------



## Zankes

I have to say this odac is fricking awesome. Sounds really good


----------



## WilliamLeonhart

mrmateohead said:


> Actually I am asking about the more powerful, more expensive amp (GS-X) versus the O2. Aside from the fact that the GS-X could, in theory, deliver higher SPL to a headphone capable of higher SPL, I am curious as to whether it would sound similar to the O2 - fast, black, with great extension.
> 
> I know that is isn't typical to place products of dissimilar prices into direct comparison, but then again I am always curious as to whether the $7 bottle of wine is "as good" as the $100 bottle! My guess is that the two amps measure so alike that they wouldn't sound very different at all - I see that the O2 has a lower noise floor, but the GS-X has excellent crosstalk, for example. Any reason they shouldn't sound alike?
> 
> Us poor people (me) like to think our O2 is giving us a top performance for the money!


 
 Better or worse depends on perspectives, but I can say that if you're seeking neutral, clear sound then I've only seen amps/DAC definitely above 700 USD that can "beat" the O2+ODAC. That's almost 3 times the price.


----------



## MrMateoHead

williamleonhart said:


> Better or worse depends on perspectives, but I can say that if you're seeking neutral, clear sound then I've only seen amps/DAC definitely above 700 USD that can "beat" the O2+ODAC. That's almost 3 times the price.


 

 Which models are you referring to? Sometimes it is interesting that "price level" rather than some other attribute (power / sound quality) seems to be the way we all organize our determinations of where "better" should be. I can honestly say that, aside from better aesthetics, I haven't come across a headphone amp since the O2 that really seemed like a genuinely good deal. IMO, high power and useful features should be available for $200 or less, unless someone can explain how getting low-distortion milliwatts is just as hard/simple as getting low-distortion watts.
  
 For car audio, the old $1 dollar / watt is usually a good indication of a good amp (then again I've rarely spent more than about $200). For home theater forget it - the amps are pretty much the "same" until you spend up to and north of $600 (80-100 watts/channel, no real low impedance drive) - what you get for your money are features / better room correction. About $600-$1000 for better DACs and Amps (where some "high current" power seems truly available).
  
 I get that headphones are hot right now, but jeez, the value equation is all over the place.


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## KeithEmo

The short answer there is that, from a technical engineering point of view, it's not at all difficult to design a low powered amplifier with very low distortion, low noise, and excellent frequency response - and it doesn't require expensive or exotic parts. Now, it is true that the design requirements are _different_ than they are for a speaker amplifier, which means that some engineers may not be used to designing that sort of amplifier.
  
 However, I think that the main reason is simply that it's a new niche market. (Until recently headphone outputs were an afterthought, and "high end headphone amplifiers" largely didn't exist.) To me it's also obvious that, to a point, the price is "riding" on the price of headphones themselves. Back when "an expensive headphone" was a Koss Pro4aa for $49, nobody would have bought a $1000 amplifier to go with it; now that we have multi-thousand-dollar headphones, it makes sense that people are willing to consider spending similar amounts of money for the electronics to go with them.
  
 Now, to be fair, designing a new product and bringing it to market is expensive - and, the fewer you hope to sell, the bigger part of that development cost each customer is going to have to pay - that's just basic economics. (I could build you a really nice headphone amp with $20 worth of electronics - and about twice that for a case and knob - but it would take thousands of dollars worth of design time to work out the annoying little details, like making sure the board fits in the case, and that the knob turns, and to make sure that it actually does sound good.) And, also to be fair, some of the more expensive designs do in fact use some very expensive parts - and I'll leave it to you to figure out, in each case, whether those parts contribute to better audio performance, or a better "story" for the marketing brochures, or a more luxurious feel for the product (and don't doubt that's also an important "product feature").
  
 (It's also true that some headphones are more demanding, while others sound just fine on less capable electronics.... and some headphones are downright quirky, and so only really sound good on electronics designed to work well with their particular quirks.... and that part of the design process can be a bit of an art - and, if so, then you don't price a painting based on the cost of the canvas and the paint. Personally, though, I think I'd just rather avoid the really quirky ones.)
  
 Incidentally, if you want to see what - minimally - goes into a quite good headphone amplifier, attached is a data sheet for the Texas Instruments BUF634 high-current buffer amplifier chip, which makes an excellent headphone amplifier... you'll find the schematic for making one at the bottom of the first page - and you can check the prices for yourself 
	

	
	
		
		

		
			




  
 http://www.ti.com/lit/ds/symlink/buf634.pdf
  
 Quote:


mrmateohead said:


> Which models are you referring to? Sometimes it is interesting that "price level" rather than some other attribute (power / sound quality) seems to be the way we all organize our determinations of where "better" should be. I can honestly say that, aside from better aesthetics, I haven't come across a headphone amp since the O2 that really seemed like a genuinely good deal. IMO, high power and useful features should be available for $200 or less, unless someone can explain how getting low-distortion milliwatts is just as hard/simple as getting low-distortion watts.
> 
> For car audio, the old $1 dollar / watt is usually a good indication of a good amp (then again I've rarely spent more than about $200). For home theater forget it - the amps are pretty much the "same" until you spend up to and north of $600 (80-100 watts/channel, no real low impedance drive) - what you get for your money are features / better room correction. About $600-$1000 for better DACs and Amps (where some "high current" power seems truly available).
> 
> I get that headphones are hot right now, but jeez, the value equation is all over the place.


----------



## WilliamLeonhart

mrmateohead said:


> Which models are you referring to? Sometimes it is interesting that "price level" rather than some other attribute (power / sound quality) seems to be the way we all organize our determinations of where "better" should be. I can honestly say that, aside from better aesthetics, I haven't come across a headphone amp since the O2 that really seemed like a genuinely good deal. IMO, high power and useful features should be available for $200 or less, unless someone can explain how getting low-distortion milliwatts is just as hard/simple as getting low-distortion watts.
> 
> For car audio, the old $1 dollar / watt is usually a good indication of a good amp (then again I've rarely spent more than about $200). For home theater forget it - the amps are pretty much the "same" until you spend up to and north of $600 (80-100 watts/channel, no real low impedance drive) - what you get for your money are features / better room correction. About $600-$1000 for better DACs and Amps (where some "high current" power seems truly available).
> 
> I get that headphones are hot right now, but jeez, the value equation is all over the place.


 
 The Aune S16, paired with a solid-state amp that unfortunately I could not remember the name of. And no, I don't think that price equals quality, since I'd definitely take the O2+ODAC rather than _any _Fiio, iBasso or NuForce models. And yep I agree with you that the O2+ODAC offers arguably the best price/performance in the industry, especially considering that some guy in my country managed to produce these 2 at around $75 each. 
 However in the past I've tried a integrated dac/amp that cost around $60 that offers around 90% of what the JDS O2+ODAC can bring, also made by the O2+ODAC guy I mentioned above. With open source designs it's very possible for people (especially people in China and neighboring countries) to drastically cut costs and maintain similar quality. The DIY guys in my country definitely learns a thing or two from nwavguy.


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## adydula

There is only one other amp that I would think of to give you more power and versatility and thats the desktop version type that AGDR has implemented...I have built one and tested with many other amps...its about a $300 + DIY and is not a beginners project. There are only 4 or 5 of these in existance....absolutley stellar amp.
  
 Alex


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## pocahontas

Hi guys, i'm new and i got some questions. Who have a good gaming motherboard with shield iem protection,ALC1150 codecs and can compare to his o2+odac combo setup objectivly?
 Does it sound really better? Have a nice day  (quote my post for better sav )


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## Zankes

pocahontas said:


> Hi guys, i'm new and i got some questions. Who have a good gaming motherboard with shield iem protection,ALC1150 codecs and can compare to his o2+odac combo setup objectivly?
> Does it sound really better? Have a nice day  (quote my post for better sav )


 
 I have ALC887 which is probably low tier one and it sounds terrible. Odac is way better sounding like worth the money.
  
 ALC1150 might be better sounding, but I am having hard time believing that it would compare to dedicated amp/dac.
  
 Just my 2cents and I am guessing here


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## pocahontas

Hi Zankes. But the question is, did your motherboard had an integrated amp & shields protection to counter parasites? It's a very important detail in this equation, don't you think?
 No mater the DAC, even an integrated ODAC, or a more expensive one (500dollars DAC), in a motherboard like any ALC realtek codec DAC, would sound terrible too 
  
 Have a nice day Zankes, really want you to answere back to me. Any one else too  Even more if you match the description of my upper post (ALC1150, shields protection and an integrated amp on it vs ODAC).
  
 Back to an other question: Lots of people compare high end soundcard like the STX II vs the ODAC+O2. In the end, i think the DAC are basicaly the same quality.
 But the integrated amp of the STX is not very good. Good for some headphone but bad for low impedance ones if i'm not mistaken. And people just say over it "drivers sucks and even with protections, it's still in a "dangerous" place and can not stop every parasites.
  
 But if the STX II which does have better specs than the ALC1150 is the "same" in regard of the DAC, i do think (logicaly) that's the ODAC is better than the ALC1150..(??).
  
 And an other thing bother me a lot, i'm sorry for not knowing so much on this subject, but an integrated codecs and a sound card does have a SNB value.
 A very "marketed" value. The best integrated onboard is at this optimal performance "115db SNR" and for the soundcard it's never more than 124 if i'm not mistaken.
 But this value... i don't see it on the ODAC or Schiit equivalent dac product? WHERE is the "Signal-to-noise ratio" of a DAC? is it the equivalent of the "Dynamic Range (A-Weighted)" you can find on odac specs? but the ODAC revb is "> 112 dB" so it's inferior to an optimal integrated onboard dac and it's even more the same for the soundcard


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## adydula

Sometimes we forget looking at specs that many of these "specs" are into areas of human inaudibility or not discernable in most any way. The O2 and ODAC were designed to have specs,if thats your thing, that
are basically what we call a 'don't care"...any better specs at these limits are well...just that better numbers.

I do a lot of AB'ing in blind testing and the differences in the actual sound based on specs alone is very hard to tell in controlled environment.

That said I often can tell differences that over time change as well, depending on the mood I am in, time of day, and amount of cold beer consumed!

Alex


----------



## pocahontas

adydula said:


> Sometimes we forget looking at specs that many of these "specs" are into areas of human inaudibility or not discernable in most any way. The O2 and ODAC were designed to have specs,if thats your thing, that
> are basically what we call a 'don't care"...any better specs at these limits are well...just that better numbers.
> 
> I do a lot of AB'ing in blind testing and the differences in the actual sound based on specs alone is very hard to tell in controlled environment.
> ...


 

 Hi, so by your logic, you really tried and sow no difference between an odac and a ALC1150? best regard


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## adydula

I have listened to an mobo with alc 1150 and have several ODACS, I doubt you would notice any real world difference.
  
 A.


----------



## raoultrifan

Hello, 
  
 I did a complete test with the new solid-state BURSON V5-D op-amps in my Objective2 headphone amplifier. Everyone knows that O2 sounds very good "by default": it has a dark background, sounds quite neutral and doesn't emphasis treble nor bass, so I didn't expected much improvement over original sound, though I was hoping to get a little bit of a bigger sound-stage.


  
 Headphones used for this test were Dr. Beats Solo 2 (32 ohms), AKG K701 (62 ohms), Beyerdynamic DT880 (600 ohms) and DAC used was ASUS Essence One MKii MUSES.
  
 All music used for this test was FLAC:
 - Chesky Records - The Ultimate Demonstration Disk
 - Ultimate Demo Disk
 - Super Audio Check
 - Legendary Sound (LS3/5A)
 - The Nordic Sound - 2L Audiophile Reference Recordings
 - Ayre - Katie Mahan Collection
 - Head-Fi And HDtracks - Open Your Ears (2010)
  
 What am I comparing these BURSON op-amps with? Well, I already have MUSES8820 in my O2's VAS right now and I'm quite pleased because I found MUSES sound being a little bit more  spacious and cleaner than the original NJM2608. As output buffers I have NJM4556A, original O2's paralleled buffers.
  
*Test with SS V5-D in Voltage Amplification Stage (VAS):*

 - Sound is definitely more detailed with V5 then with MUSES8820, especially when cymbals are involved...hmmm, I didn't expected that. Details in cymbals were immediately noticed, without feeling any increase in trebles, so the same neutral sound but more detailed and with much better sound accuracy; now cymbals sound like I'm on the scene.
 - Women voices are very clear and "mild" even when singing loud, not fatiguing at all. Also Kenny Roger's saxophone sounds better in every way, like a delicate immersion into the music. I am sensitive to saxophone and to women yelling, especially when DT880 are used, so BURSON V5 is really helping me here with their sound.
 - Bass sounds about the same as MUSES to me, noting has changed I'd say. I tried "Chesky - Percussion Test" and also "Ultimate Demo Disk - Percussion" and I couldn't realize any differences; I got the same fast and powerful bass, especially with my K701 headphones.
  
*Test with SS V5-D as output buffers:*

 - I was unable to get any noticeable differences between the original NJM4556A op-amps and BURSON V5-D, though scene might get increasing a little bit, but not much to make a difference.
 - As O2's output buffers are directly connected to headphones, DC-output voltage of SS V5 op-amps might be a little bit higher for low impedance headphones (see V5's datasheet). For 60 ohms or higher impedance I don't see any concern here.
  
*PROS:*
 - Upgrading Objective2's VAS op-amp with solid-state V5-D from BURSON will get you the same neutral, natural, clean and balanced sound, but with more details in sound and with increased sound-stage.
  
*CONS:*
 - Price, especially comparing with O2's MSRP.
 - Size, because you'll definitely need a taller case like B4-080 model or some DYI case made of acrylic or anything else (3D printer perhaps?). 
  
_*Note 1:* BURSON V5-D op-amps were both tested for any possible oscillations or strange harmonics by using Pico-Scope. Nothing strange was found, of course, feel free to check attached screenshot._

  
_*Note 2*: V5's temperatures during this test were between 43-49C in free air/open case (24C room temperature), depending on the volume uses. IR thermometer was used to read the temps._
  
_*Note 3*: Many thanks to BURSON for providing me those 2 dual solid-state op-amps to do this test!_


----------



## pocahontas

adydula said:


> I have listened to an mobo with alc 1150 and have several ODACS, I doubt you would notice any real world difference.
> 
> A.


 
 Ok, so they are no audible differences between a well implemented mobo with shields and the last DAC available than casual DAC like ODAC or the schiit one on the market.
 Thanks you, you certainly saved me some money.
 But if you have the chance to try it, did you do it with an very good headpone? because i'm planning on getting an AKG k712 (or lower) and i don't know if my integrated amp will support it.
 Best regard


----------



## adydula

Be careful painting with a broad brush.....your asking about a DAC. Which indeed may not have much of a sonic difference from the ODAC and others...but your headphones need electrcial energy to move the transducers in them to make analog sound!

This translates into power, voltage, current, impedance etc...

The dac may be very good or inaudible in the chain, but if your headphones and the amp part of your mobo, laptop or pc sound card, apple etc....may not have what it takes to drive your headphones.

People buy headphones plug them in stuff and start wondering if it will sound better with other stuff....and the buying and trying starts....

The best thing is to try them with what you have and if they sound great fine, then find a friend or go to an audio show and try your headphones in other gear and make your decisions.

Good Luck!

A.


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## pocahontas

Hi dude. I don't have friend and headphone store with AKG stuff to try it out. And they certainly doesn't have o2...
 And like i said, i say it very kindly, you are part of the people who say "go try it and see". But i can't have a straight answere with specs comparaisons to prove it  Because it's still a max 450 euros investement for a O2(150 all gift) plus the headphone (330 for me). I can't buy o2 from amazon so if i buy directly on mayflowers or JBL, i will pay return package like 20euros or more to get a refund...
  
  
 I think more and more to just forget about all of this. Wait like max 5 years and replace my pc with a very high end motherboard that will certainly kill every 250 dollars DAC/AMP ore more here  I say certainly because high end motherboard today may already does it (i asked a guy with the lastest msi card on the 1151 market and he said it was exactly like the o2/odac stuff, very clean and powerfull). It would be maybe better to save up for this. Better investment than investing in an industry product that is going down (motherboard will kill progressivly music store concerning the dac/amp stuff).
 Only the Headphone industry will be bigger


----------



## raoultrifan

Hi pocahontas, 
  
 I believe Alex was only trying to help here. As a general rule, you should need to listen to equipment before buying, because there's a risk involved here. Most people find O2 as being a decent headphone amplifier, so either you trust all that head-fiers, either you'll need to find a way to test it.
  
 I have a friend with https://www.asus.com/Motherboards/RAMPAGE_IV_BLACK_EDITION/specifications/ :
 - Cirrus Logic® CS4398 DAC: 120 dB SNR, -107 dB THD+N (Max. 192 kHz/ 24 -bit)
 - TI 6120A2 high fidelity headphone amplifier
 - WIMA® film capacitors
 - ELNA® premium audio capacitors
 - High-fidelity audio OP AMP(s)
 - Differential circuit design
 - NEC TOKIN UC2 audio relay
  
 He never used the on-board for analog playback, he's just using the digital outputs, instead he bought a Phoebus and now he's having ASUS Essence One MUSES Mkii (like I have). For example in A/B tests the internal amplifier from Essence One is on pair with O2 amplifier when AKG K550 or AKG K701 are used.
  
 I will speak again with my friend if he agrees to let me do an A/B test between his onboard and my O2 amplifier, using AKG K701 as headphones (his workstation has about 50 kg, so it's complicated to access the motherboard soundcard plugs if are on the backside).
  
 Meantime you may read these to help deciding:
 - https://www.reddit.com/r/headphones/comments/2i8wsm/need_help_deciding_objective2_amp_gain_for_k712s/
 - http://www.head-fi.org/t/721058/hd-600-or-akg-k712-with-the-odac-o2
  
 Cheers, 
 Raul.


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## adydula

Thanks...its not as black and white as people would like it to be.....
  
 I had AKG 702's for a year or so across many amps and dacs....sold them for T90's....
  
 I never have really even considered using PC dac or amp sections for serious listening...but things do change.
  
 I spend 32 years working for a LARGE PC Company and know most of the sound stuff was really el cheopo and less than stellar in 
 specs and performance....and the specs didnt tell the whole story.....
  
 I go go on for a long time on this.
  
 Alex


----------



## derbigpr

pocahontas said:


> Hi dude. I don't have friend and headphone store with AKG stuff to try it out. And they certainly doesn't have o2...
> And like i said, i say it very kindly, you are part of the people who say "go try it and see". But i can't have a straight answere with specs comparaisons to prove it  Because it's still a max 450 euros investement for a O2(150 all gift) plus the headphone (330 for me). I can't buy o2 from amazon so if i buy directly on mayflowers or JBL, i will pay return package like 20euros or more to get a refund...
> 
> 
> ...


 
  
  
 Sorry but you are wrong. The best motherboards today have sound cards on them comparable to 50-60 dollar aftermarket cards. The same will be true in the future, motherboards will never reach the level of sound quality that separate audio components will have, for very obvious reasons.  Making a good sounding audio product is far more difficult than just throwing together a lot of good quality parts that have good specs. Also, the measurements that are used on spec sheets today (freq response, thd, snr, etc.) have very little to do with actual sound quality and perceived sound. You can't just say "oh look, this motherboard has 120 dB SNR, must be better than that 2000 dollar DAC that has 115 dB SNR). They just describe a very, very small portion of the sound that a device produces, and sadly, 99% of people who are in this hobby don't understand what those measurements mean and how they translate to actual sound, and how little they actually tell you about the sound. On top of that, those measurements are good enough to not have an audible effect in most equipment nowadays, which tells you that there are many other factors that you don't get measurements of that have a big effect on the sound. One of the reasons why O2 amp measures better than many high end amps, but actually sound clearly inferior to them. O2 was specifically designed to measure well in those few areas and then use those measurements as a means of marketing and advertising. It's still not a bad amp for the money, but it's highly overrated by those people who give too much credit to those few numbers on paper. The same "trick", if you will, is used by manufacturers of motherboards with "high end" integrated soundcards. Measures good, doesn't mean it sounds good. It's like judging cars strictly by how much horsepower they have.


----------



## pocahontas

derbigpr said:


> Sorry but you are wrong. The best motherboards today have sound cards on them comparable to 50-60 dollar aftermarket cards.


 

 Hi, so if you are right, then can you please give me a good comparaisons's numbers of the specs between the ALC1150 and the ODAC revb or Schiit in optimal situation?
 Because at this point, i can only bielieve you but i can't put my trust. You just can't get the words of any one as granted.
 It's like in the old days when white people talked about the bible to illiterate people...
 I have not the skill to compare and the money to spend to compare. Only thing i have is a bit of time for asking people that know the answere and can give it to me freely(talking about internet) 
  
 Here you can find on the page the ODAC REV B specs:
 https://www.jdslabs.com/products/46/standalone-odac-rev-b/
  
 And here for exemple, the ALC1150 specs:
 http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=28&Level=5&Conn=4&ProdID=328


----------



## derbigpr

pocahontas said:


> Hi, so if you are right, then can you please give me a good comparaisons's numbers of the specs between the ALC1150 and the ODAC revb or Schiit in optimal situation?
> Because at this point, i can only bielieve you but i can't trust. You just can't get the words of any one as granted.


 

 Go get an electrical engineering degree then we'll talk. 
  
 In the meantime, you can listen to one of the best engineers and experts in the world in this field who has been designing the best audio measurement equipment in the world for many, many years. Might change your mind about comparing audio equipment just based on some specs on paper that only tell you half of the story.
 https://www.youtube.com/watch?v=2V6YN-mshmY


----------



## MrMateoHead

pocahontas said:


> Hi dude. I don't have friend and headphone store with AKG stuff to try it out. And they certainly doesn't have o2...
> And like i said, i say it very kindly, you are part of the people who say "go try it and see". But i can't have a straight answere with specs comparaisons to prove it  Because it's still a max 450 euros investement for a O2(150 all gift) plus the headphone (330 for me). I can't buy o2 from amazon so if i buy directly on mayflowers or JBL, i will pay return package like 20euros or more to get a refund...
> 
> I think more and more to just forget about all of this. Wait like max 5 years and replace my pc with a very high end motherboard that will certainly kill every 250 dollars DAC/AMP ore more here  I say certainly because high end motherboard today may already does it (i asked a guy with the lastest msi card on the 1151 market and he said it was exactly like the o2/odac stuff, very clean and powerfull). It would be maybe better to save up for this. Better investment than investing in an industry product that is going down (motherboard will kill progressivly music store concerning the dac/amp stuff).
> Only the Headphone industry will be bigger


 
  
 Hi Pocahontas. I wanted an 1150 chipset when I bought my new computer, but I settled for the ALC 892 chipset to save some money. That said, My chipset came with "premium ELNA" caps and boasts a SNR of over 90 dB at all outputs (DAC and headphones - the threshold, I thought, for "inaudibility"). It has no dedicated TI Headphone amp, which in every case I have checked, has a very high output impedance of 10 Ohms. Hence, it should work best with headphones with an impedance of 80 ohms or more. Like with other computer chipsets, I don't know how it is typically implemented, or what power it can put out at difference impedances. I have no idea what the distortion profile looks like (because, measuring distortion at one frequency does not give you the whole picture, and never will. Lots of amps are "clean" at 1 khz but "noisy" at 5-20 khz, critical treble areas).
  
 Based on specs alone, the 892 should output 1V to an amp (a little low but adequate for all my gear). It claims 1.1V RMS @ 32 Ohms for headphone output, with an output impedance of 2 Ohms, making it suitable, in theory, for 16 ohm or higher headphones. With 5 mA of current,it may put out 5 milliwatts or so. 10-100 mWs would be a lot better in terms of working for more headphones, but even 5 is technically "a lot".
  
 Does that beat the ODAC, or the O2? The short answer is, no it does not. There is audible "hiss" in my chipset, compared to the "black" background of my O2/ODAC. DAC-to-DAC, IMO, the Realtek sounds great, but softer or less "detailed" than the Sabre chip in the ODAC. Everytime I go back to the ODAC, I am getting a better listening experience. Is that just because 2V is greater than 1V? Is it because the SNR of the ODAC is higher than the ALC 892? Probably, but also the Sabre probably just has better filters (e.g. is a better design). Do the Intel Core i3 and Core i7s perform the same, clock for clock? No. Do you need an i7?
  
 On the amp side, while 1 mW can get you 90-100+ decibels on a lot of headphones, in reality and so far, the Realtek fails to make the headphones I use regularly sound their best. My HE-400s (~90 dB sensitivity, 50 Ohms) and my Sennheiser HD595s (50 Ohm impedance with big 200 Ohm swings) sound a lot better on the O2 than on any other headphone jack I have (my Yamaha AV receiver included). Only my PSBs (30 ohm-ish) seem to sound very similar whether powered by my computer or my O2/ODAC. They are very efficient, and have a very flat impedance measurement, suggesting they are quite easy to drive so power is not the critical limiting factor. The HE-400s have a flat impedance curve, and should be easy to drive, but clearly having more power brought out the best in them (something I wouldn't have noticed based on specs alone). You may hate me saying it, but, yes, it was "dat bass" that was most clearly extending deeper and punching harder.
  
 Oh by the way, some of my music sounds horrible, because the quality of the recording is horrible. No DAC or Amp can change that.
  
 You can dismiss my thoughts because I do not have the 1150, and indeed if I did the comparison would likely be harder to make. In my opinion, until computer chipsets combine very good DAC performance WITH very good amp performance (e.g. near 0 output impedance, low distortion power of about a half-watt or so), they will not replace my O2 / ODAC. As a pure signal pass-on, the Realtek is good nuff' and I use the optical digital like to feed my receiver, a role it does perfectly. I use the ODAC to feed a small 2 channel amp (which, again, sounds better than the Realtek). But the ODAC doesn't do 192 khz audio, and can't pass on a 5.1 surround signal etc. which makes me glad to have a computer chipset that handles all that stuff natively.
  
 IF you have to go all the way to an 1150/1151 chipset to get O2/ODAC quality, and so are buying "overclocking" gaming motherboards for $150-$200 bucks or whatever to get that chipset, and don't plan to overclock / game etc., then you are still wasting your money. 
	

	
	
		
		

		
			





 I paid like $70 bucks for my mobo, passed on all the high-end nonsense and overclocking features and dumped the savings into an amp that is almost guaranteed to rock whatever headphones I want, not just the ones that spec right. So there!
  
 I would be the first to recommend that you listen to your headphones on your computer and if you like it, good, great, nothing to see here, save your money. I used my HD595s for 3 years on a laptop and a desktop, always finding them "good, not great". They I bought better headphones. Then I NEEDED an amp. Then, after all that, I realized the HD595s sounded almost like a different headphone on the O2. IMO DACs are "10%" of the performance you buy. Headphones are 70-80%. An amp, speaker depending, can be very high value or very low value.


----------



## derbigpr

pocahontas said:


> Hi, so if you are right, then can you please give me a good comparaisons's numbers of the specs between the ALC1150 and the ODAC revb or Schiit in optimal situation?
> Because at this point, i can only bielieve you but i can't put my trust. You just can't get the words of any one as granted.
> It's like in the old days when white people talked about the bible to illiterate people...
> I have not the skill to compare and the money to spend to compare. Only thing i have is a bit of time for asking people that know the answere and can give it to me freely(talking about internet)
> ...


 
  
 The only way to tell what's better is to listen to it. As I've said already, once you reach a certain level of "objective" or "technical" performance in areas that are measured and listed on the spec sheets, you reach a point where improving those specs can but DOES NOT guarantee you'll get a better subjective sound, because at that point, other aspects start to matter too. And the point is, a vast majority of well designed audio products at all price ranges today have reached that level in those specific measurements, that's why you won't find massive differences in those few measurements specs between 200 dollar portable DAC's and some high end DAC's, but you will hear a difference because of other factors that you can't read out of the spec sheets. To put it into an example, if you compare two cars, one has 200hp and the other 400hp, and they weigh about the same, the 400hp one will be obviously faster. But if you have two cars, one that has 900hp, other has 950hp, and they weigh about the same, then you can't say the 950 hp one will be faster, because at that point other factors come into play and have a much bigger effect, torque, is is rwd or awd, where the engine is, aerodynamics, gearing, tire width and compound, even a slightly wrong tire pressure can decide the faster car. And then you can start comparing other things, because one 950hp car might be the Mclaren P1, and the other might be a tuned up Subaru Impreza that's built for drag racing, which brings you to a conclusion that two things that looked so similar when you read the first two specs, are actually totally different. The same is true for audio measurements, they only tell you such a small part of the story, but people assume they tell you everything. You have to keep in mind that those specs you see on the boxes of products have been put there because they're simple enough for an average person to sort of understand, but mainly for marketing reasons, because manufacturers know about the psychology of buyers, and they know that many people associate higher numbers with better quality, a lot of them even say "higher value is better" next to measurements, Asus does that for example, as if you're gonna hear a difference between 115 and 118 dB SNR,  0,05% THD and 0,02% THD and 5-30000 or 2-50000hz frequency response, but if you see two products that cost the same, and you can't decide which to get, guess which one most people will pick.  Also, you have to keep in mind that the way an amp for example measures in a lab using synthetic tests is not necessarily how it will perform. It's one thing to measure a frequency response or distortion levels while using sweeps or simple tones, and it's a different thing to perform the same when actually playing music, which is far more complex than just a single 1khz tone at 90db for example. Not to mention that those specs also depends on which country the product comes from and which standards were used to measure the performance.


----------



## derbigpr

mrmateohead said:


> *I would be the first to recommend that you listen to your headphones on your computer and if you like it, good, great, nothing to see here, save your money.* I used my HD595s for 3 years on a laptop and a desktop, always finding them "good, not great". They I bought better headphones. Then I NEEDED an amp. Then, after all that, I realized the HD595s sounded almost like a different headphone on the O2. IMO DACs are "10%" of the performance you buy. Headphones are 70-80%. An amp, speaker depending, can be very high value or very low value.


 
  
 Yes that is very true, and it's a mistake a lot of people who are new in this hobby make.


----------



## raoultrifan

derbigpr said:


> One of the reasons why O2 amp measures better than many high end amps, but actually sound clearly inferior to them. O2 was specifically designed to measure well in those few areas and then use those measurements as a means of marketing and advertising. It's still not a bad amp for the money, but it's highly overrated by those people who give too much credit to those few numbers on paper. The same "trick", if you will, is used by manufacturers of motherboards with "high end" integrated soundcards. Measures good, doesn't mean it sounds good. It's like judging cars strictly by how much horsepower they have.


 
  
 I actually paid around 60 EUR for my O2 DIY kit, so I think O2 it's really a bargain for every frugal audiophile. Well, with all the upgrades I did, now I probably got to a total of about 75 EUR (WIMA caps & tantalums for decoupling, RCAs + back power + 6.3mm Neutrik plugs etc.).
  
 Many thanks for the Youtube movie! I'm totally with you when saying that one amplifier that measures better than a second one may actually sound worse when A/B'ing, but one thing's for sure: if an amp measures really bad, then it's impossible to sound good, that's for sure and by "measures bad" I mean noise worse than -95dB, output linearity worse than +/-0.5 dB across audio band, THD worse than 0.5% for solid-states and worse than 5% for tubes etc. Though, I had a DIY amp few years ago that was oscillating and was having a noise of around -80dB between 2MHz - 4MHz and sound was quite OK, because between 20-20.000 Hz amp was measuring pretty well. 
  
 To be honest, I don't think O2 is "highly overrated" for it's price tag, because when A/B'ing between my O2 and the internal headamp from Essence One MUSES I was unable to discern any noticeable differences with my AKG K550, AKG K701 and Beyerdynamic DT880 headphones. Perhaps with other headphones like Senheiser HD 800 I should get an advantage for the headamp inside Essence One, but I don't own these headphones right now. (Essence One is using the same schematic published by TI in LME49600 datasheet, which is about the same as "the wire" headamp). I had also compared O2 with a LME49720+TA6120A2 amplifier and also with a LME49720+BUF634 amplifier and sound was about the same to my ears. One amp I have that sounds way much better than O2 and this is my Matrix M-Stage HPA-3B that has a much better soundstage and instruments separation, but we're already speaking of a much higher price tag here.
  
 Regards, 
 Raul.


----------



## pocahontas

derbigpr said:


> The only way to tell what's better is to listen to it. As I've said already, once you reach a certain level of "objective" or "technical" performance in areas that are measured and listed on the spec sheets, you reach a point where improving those specs can but DOES NOT guarantee you'll get a better subjective sound, because at that point, other aspects stat to matter far more. To put it into an example, if you compare two cars, one has 200hp and the other 400hp, and they weigh about the same, the 400hp one will be obviously faster. But if you have two cars, one that has 900hp, other has 950hp, and the weigh about the same, then you can't say the 950 hp one will be faster, because at that point even a slightly wrong tire pressure can decide the faster car. And then you can start comparing other things, because one 950hp car might be the Mclaren P1, and the other might be a tuned up Subaru Impreza that's built for drag racing.


 

 I commented your last but i will start speaking about your first comment. I felt it like a "haughty" response to my post.
  
 First, you didn't answere my question. You basicaly said to some one you didn't know over the internet to "go learn it yourself" instead of helping him? Isn't it the complete opposite of what a community is and by a more global logic "internet" ? You used an old trick to elude my question.
 As for an exemple, you are some one talking maybe to Einstein(who i'm not) and you just say without even watching him "Man, look at your orthography... your theory is not even worth reading". It's not revelent. It doesn't bring anything on the table and you are sadly simply avoiding the question by masquerading me as a cute,
 but stupid monkey...
  
 And i don't want to be rude as some one who doesn't know a lot about this subject but i found it funny that you doesn't keep your "defence line" about the subject. First you say that 2016 high end motherboard have the onboard sound quality of a 50 dollars soundcard. Secondly, you come to me saying that it's just a matter of a "level of objectivity and technicality". So, you are basicaly saying the opposite.
 I'm sorry but you are condracting yourself there 
  
 EDIT: many other posts to read on this topic


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## pocahontas

Hi MrMateoHead :) Thx you for your answere.
  
 As you said, you paid a low end motherboard with an older chipset to save up money. Then you use the difference in money you savec on better materials.
 But at first, because it's a low end motherboard, it had certainly not very high quality concerning the sound part. Now basicaly every motherboard coming up with the ALC1150 does have a minimum of shield protection.
  
 What you said is still interesting but you compared a low end motherboard sound with an older chipset versus an external product. An odac in your motherboard should sound as worse i think.
 Here, we are with a good motherboard with shield protection, really better chipset and an integrated amp over the top. It can't really be compared 
  
 Hi raoultrifan
  
 I believe more in the O2 than the DAC coming with it  For the price, it outperform high price AMP and it was it's primary objective !


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## raoultrifan

After all, someone traded an expensive Chord Hugo for an ALC1150 motherboard here http://www.head-fi.org/t/685163/a-researched-question-about-realtek-1150-vs-sound-card/15#post_11038456, so perhaps you could be OK with this all-in-one solution after all, though I would still recommend you to buy an external DAC & headamp, not only because I consider it a good price/quality ratio, but you also need to take in consideration that an external DAC & headamp may be unplugged and installed on many other computers as well.
  
 Also, some people here http://hardforum.com/threads/alc1150-vs-usb-dedicated-asus-xonar-u7.1853931/ thinks that ASUS U7 may sound better than 2 motherboards using ALC1150 codec, but I tell you for sure that U7 is no better than ODAC+O2 in terms of high fidelity or output power (I own U7 and did A/B test between U7 and O2).


----------



## adydula

I have done many BLIND AB tests with the o2 and other amps....and almost all the time I cant and other folks cant tell the difference when they dont know whats behind the curtain, but as soon as they see and can play with the volume controls they all of a sudden become sonic experts and see to be able to  tell the "difference with same stuff they just were fooled by!!
  
 Subjective analysis is hard to quantify!! 
  
 You can spend a lot of money and get good sound and you can spend very little money and get good sound....name your poison...
  
 The O2 is and will be one of the best amps ever made for 98% of headphones...
  
 A.


----------



## MrMateoHead

pocahontas said:


> Hi MrMateoHead :) Thx you for your answere.
> 
> As you said, you paid a low end motherboard with an older chipset to save up money. Then you use the difference in money you savec on better materials.
> But at first, because it's a low end motherboard, it had certainly not very high quality concerning the sound part. Now basicaly every motherboard coming up with the ALC1150 does have a minimum of shield protection.
> ...


 
 Well, in my experience, even for an older chipset, it is a very good one. Best I've owned so far, and I used to rock a Soubdblaster X-Fi with gold-plated jacks, baby. The quality of the motherboard is top notch, but like any "do all" product, its overall cost structure undoubtedly and rightfully prioritizes the audio section far less than, say, the CPU regulators. The lack of "shielding" might be irrelevant depending on its implementation, something neither of us can "decode" on the basis of specs. It may be performing as well as it can, it may not be. Arguing that the ODAC would sound "as worse" as my Realtek chipset were it attached to my motherboard is speculative and assumptive on your part, and in any case irrelevant as you have been asserting that you are trying to make a decision on opinion alone. I don't assume that integrated vs. separate gets an "automatic" performance bonus. IMO, the ODAC in the one form you can have one, wins. Even despite all that "dirty" and jittery USB power I feed it. 
	

	
	
		
		

		
			




  
 If you are looking for confirmation of your existing biases, Toms Hardware ran an article awhile back that tried Blind Testing between 4 different DAC/AMPs (one was the Realtek 889, also a better ASUS Xonar, and O2, and a Benchmark). There the two testers concluded that anything more than $2 (the cost of the Realtek chip) was about buying features, not differentiated performance. This conclusion is drawn after realizing that, in blind testing, they could not reliably differentiate between the products. The test utilized the Sennheiser HD 800s and the AKG 550s, neither of which I own. Neither of which I would care to own, either.
  
 One issue I have is that, despite not being able to reliably tell the products apart, they did claim somewhat to reliably pick out, or even prefer, the ALC 889 or Asus STX. Also both headphones require only a fraction of a mW to reach very high SPL, and based on professional reviews, both the HD 800 and AKG 550s are not necessarily well received as "reference" headphones (Katz over at Innerfidelity recently eviscerated the 550s). At the end of reading the test, I both agreed with the reviewers, and disagreed. After all, if you can somewhat reliably "hear" the Realtek chipsets, but the rest sound identical, is it possible that it is the other products that in fact perform to a level wherein differences become effectively inaudible? It is possible that the grating treble of each headphone sounds better when "softened" by the Realtek chipset? Hmm . . .
  
 In any case, I would tend to agree that most of us can make due with a modern computer and be perfectly satisfied. It is ridiculous that some DACs and Amps cost thousands of dollars. But then again one probably shouldn't do authoritative "blind tests" without some intimate familiarity with their existing speakers and recordings, since the point is to really see if the amp/DAC are making a difference. To some extent you need to know what to listen for. If you fall under the category of "untrained" and "passive" listener, none of this stuff matters.
  
 But as a way of circling back around, I feel you should hear someone state that you are right, the ALC 1150/1151 is awesome, I wish I had it instead of my ALC 892, which is probably audibly identical despite inferior specs, no shielding, and a lack of a dedicated amp section. Maybe I could hear the difference, maybe I couldn't. For now, my experience is clear, and the $130 O2 was a reasonable investment - way more reasonable than an external soundcard (which would still leave me needing a little more power) or a multi-thousand dollar solution.


----------



## pocahontas

MrMateoHead  :)
  
 Yes i know that when i said that the "ODAC would certainly sound as worse than a realtek ALC without shield protection" was a "maybe" 
 But it seem that it's a very commom pratric in audiophile community to make assumption with nothing to back it up  My bad.
  
 I do think the real issue with this forum and his overall community in general over the internet, is that there are too few people with enough experiences or even internet reviewers to answere to this question. Every body have the best mid game products and nobody really speak about it clearly. It's a "convenient dark".
 To have a minimum of back up, you have to be a real gamer with audiophile stuff and it's rare...
 Many people know the old realtek, many know about soundcards and external stuff but very few people are at the same time "real gamer" and "audiophile".
  
 Well, i can assume nobody have the answere or want to share it  I do think my run into the audiophile world will stop a moment.
 I'm not having bad time with my sound atm so why bothering with it? At least my run with DAC is arriving to and end. Will maybe concider buying an akg with an o2... or not. I will just think about some thing else ^^
 The best thing to do is wait a few years when i will have to change my motherboard and i will ask this question again.
 Integrated stuff will be even better, GPU and CPU will have very good fine engraving...
  
  
 Nevertheless, i thanks you all for the time you spend with me.
  
 Have a nice day in your enchanting world


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## MonoOno

pocahontas said:


> Hi guys, i'm new and i got some questions. Who have a good gaming motherboard with shield iem protection,ALC1150 codecs and can compare to his o2+odac combo setup objectivly?
> Does it sound really better? Have a nice day  (quote my post for better sav )


 
 I went out of my way to get a motherboard with ALC1150 and settled on a X99 ASRock Extreme 4. I tested it on a O2+ODAC combo and Schiit amp via 3.5mm to RCA and I was not impressed. The DAC on the combo blew it out of the water. There was really no comparison at all IMO and I was really let down as I though motherboard audio had come long way and was especially hopeful after reading reviews on how good the audio was on these new motherboards. My plan was to get rid of the O2+DAC if I could not hear much of difference and just rely on the motherboards DAC with my Schiit but the difference was just too apparent and I could not do it to myself or my headphones.


----------



## pocahontas

monoono said:


> I went out of my way to get a motherboard with ALC1150 and settled on a X99 ASRock Extreme 4. I tested it on a O2+ODAC combo and Schiit amp via 3.5mm to RCA and I was not impressed. The DAC on the combo blew it out of the water. There was really no comparison at all IMO and I was really let down as I though motherboard audio had come long way and was especially hopeful after reading reviews on how good the audio was on these new motherboards. My plan was to get rid of the O2+DAC if I could not hear much of difference and just rely on the motherboards DAC with my Schiit but the difference was just too apparent and I could not do it to myself or my headphones.


 

 Hi, you tried a well set motherboard (shield, amp...) with the ALC1150 and you were not impressed. But the O2+ODAC was way better?
 I heard good review of the Purity Sound™ system...


----------



## Zankes

Without contributing much I think external option is better. Pc components get old so fast while u can easily move the external option to your new system.


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## pocahontas

zankes said:


> Without contributing much I think external option is better. Pc components get old so fast while u can easily move the external option to your new system.


 

 If you are a pc gamer, it's not necessary true. You have to change your computer like every 4-5 years if you are a normal consumer.
 And in this lapse of time, motherboard evolve and it's even more true now since the motherboard manufacture are puting a BIG EFFORT concerning the sound implementation.
  
 Depending on the stuff you already have, investing now in a o2+odac or equivalent will maybe not be "worth it" for a very long time (or already is  )


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## riverlethe

One thing to consider: You will only have to buy an ODAC once, whereas every motherboard you buy in the future, you will have to go to extra trouble and expense to make sure it's audio performance is adequate. I have an Asus motherboard with an ALC892 interface, and the noise performance is simply abysmal - around 80db to 85db SNR. Sure, I probably could have bought a more expensive motherboard, but if my only concern is audio performance, why bother?


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## riverlethe

Also, the ODAC is much more versatile. Plug it into your iPhone to achieve a reference quality line output.


----------



## thekorsen

Hi,
 I recently purchased a DIY O2 off the trade forum here and was met with audio hell. The unit has to be defective as the bass is completely distorted and flabby compared to my Schiit Vali. Putting it on high gain makes the issue even worse, which makes me suspect the issue has something to do with output impedance. From a quick inspection of the board, it seems like (aside from some some sub-par soldering with excess flux left ever where) one of the resistors right below the batteries is chipped with burn marks and a group of solders near the front of the board seem like they could be shorting. But with malfunctioning output impedance in mind, is there any other part of the port that would be particularly suspect?


----------



## MrMateoHead

pocahontas said:


> MrMateoHead  :)
> 
> 1) Yes i know that when i said that the "ODAC would certainly sound as worse than a realtek ALC without shield protection" was a "maybe"  But it seem that it's a very commom pratric in audiophile community to make assumption with nothing to back it up  My bad.
> 
> ...


 
 I will go point to point with you once more, but clearly this is venturing off-topic at this point.
  
 1) It is good that you recognized your own "maybe" was bogus from the get-go - but why bring it up then? It must also be a common practice for non-"audiophiles" to make bogus claims with nothing to back it up - for example, that a modern motherboard sounds better than some low-cost dedicated equipment. The irony is that I've studied this stuff enough and been around long enough to a) make the same claim and b) reject it on the basis of living with both integrated sound solutions, and dedicated "separates". The O2 wins, hands down. The ODAC is bettder, hands down. IF I were only gaming, perhaps no need to upgrade, but I happen to love music so much I felt like investing a little more. If you can't hear the difference, then I envy you. But there are "subjective" differences to driving different cars, using different monitors, or using different cameras, or even lightbulbs that will always make the "murky" practice of combining objective data and subjective experience a murky area. Probably only industry insiders have access to the data that really drive the "value equation", but I am not one, and I don't know any. So I have to gamble my choices like everyone else. But I say that maybe you should consider proving to us why the 1150 is better, and back that up somehow to show me how I was "duped". Please support your argument with real-world examples, data presentation, and a selection of headphones at different price points. Can't do it? Neither can I. Oh well.
  
 2) My problem with the Internet is that there is too much garbage information, or not enough information that is actually critical of what it is analyzing. It costs money to review gear, and one mustn't anger the sponsors when they are the source of the product. If you want something approaching "independent 3rd party", I suggest you consider Consumer Reports. Unfortunately, the flow of new products is too fast, and the flow of reviews too minimal. What is more, they've both liked headphones I like, and loved headphones I hate - hmm. Your admitted lack of experience, knowledge and $$$ can be overcome only by you, not us. I do suggest you put some trust into others as you shop around, trust in the "Internet" at places like Amazon where customer feedback is ample at times, and consider that leading brands get into the lead for a reason (and no, it isn't always because they just spend more on marketing). The ancillary to that is that there are small companies, with very good products, that have few employees and a minimal marketing budget. That does not preclude them from being worth your hard-earned money. Caveat Emptor. Were it only a perfect world.
  
 3) I am a real gamer and an "audiophile", and 90% of the time I let my dirt-cheap 10 year old Yamaha receiver and cheap-o pioneer speakers pump out the sounds - not my headphones (and I vary from a 2.1 to a 5.1 setup depending on my mood). Perhaps I "drank the kool aid" or perhaps my tastes have changed over the years, but the Pioneers are good to the point I that I have no desire to try to upgrade - I am far more aware of the effect of "the room" than I used to be, and know that spending 10x as much wouldn't stop the windows from rattling or the 30 hz tone from drowning out, well, everything else at times. 
	

	
	
		
		

		
		
	


	




 BTW I also build my own computers and have overclocked (and overclocking is, generally, a waste of time). The only area worth "wasting" money right now is on SSDs - the speed boost is immediately noticeable, period. I've built them for $400, and for $1300. I would never spend more than $2000, and could b**** endlessly about the way in which the Intel monopoly destroys value for all of us (my first gamer rig was an AMD that crushed my friend's Pentium 4).
  
 4) The answer was, the O2/ODAC is better than the Realtek ALC 1150. I with I could provide you with measurements to back that statement up, but I don't have thousands of dollars of measuring equipment and I am not sure the specs alone would make it obvious. What I know is that ESS is on top of their game right now, featured in lots of high end gear, 2V out is better than 1V out, and 200-500 mWs offers a lot more headroom than a typical sound card. Were we talking about, say, AV receivers, my product searches would conclude that I probably need to spend $600-$1000 to get the features and power I think are worthwhile, while you might be better off looking for a soundbar or something, which sounds great but won't really compete with my "dedicated" 5.2 setup in overall output and fidelity.
  
 5) I think its sad that standards shift so quickly that the $1000 you sink into a computer today cannot meaningfully be re-invested into a new computer in a future. New socket = new mobo, new RAM = new mobo etc. etc. There is no more difficult money pit than staying on top of PC Gaming (I know this, I am a PC Gamer). That said, not EVERYONE should spend $300 on a GPU, but if you're serious and want to play on HIGH, you have to. Period. But man, I miss the days of being able to just upgrade once in awhile, without basically rebuilding from the Mobo-up.
   
Yet you think we're crazy for spending $250-$300 on a sick little Amp and DAC for our sick headphones. HA. To each their own. Good luck to you and enjoy that 1150! I sorta knew there was no convincing you from the get-go but I am a sucker for a good argument.


----------



## raoultrifan

thekorsen said:


> Hi,
> I recently purchased a DIY O2 off the trade forum here and was met with audio hell. The unit has to be defective as the bass is completely distorted and flabby compared to my Schiit Vali. Putting it on high gain makes the issue even worse, which makes me suspect the issue has something to do with output impedance. From a quick inspection of the board, it seems like (aside from some some sub-par soldering with excess flux left ever where) one of the resistors right below the batteries is chipped with burn marks and a group of solders near the front of the board seem like they could be shorting. But with malfunctioning output impedance in mind, is there any other part of the port that would be particularly suspect?


 
 Hi, 
  
 Can you please do some decent macro pictures to affected area? We can compare affected area with O2's schematic and perhaps will get somewhere.
  
 You can also ask the same question on diyaudio forum in Home > Forums > Amplifiers > Headphone Systems > The Objective2 (O2) Headphone Amp DIY Project, in case we can't help you here.
  
 Thanks, 
 Raul.


----------



## pocahontas

mrmateohead said:


>


 
 Hi, i appreciate the time you took to write it up for me.
  
 Like i said, audio is really not my territory so i can't compete with you guys. I don't understand the most part of specs and i'm not rich enough and with the ability to try it out propely.
 With your own world you said "ALC1150 even with good implementation and a proper amp don't win versus a the O2+ODAC". Like i said, you don't have the equipement to back it up but you engaged your soul by saying it is the true. But sadly i heard the complete opposite from people looking "internetably" (lol) honest too".
  
 So, the best way is just to basicaly try it out and see by yourself. Better? not better? placebo or not? matter of tast or measurement to back it up? it's a mic mac 
  
 I completly agree about your statement over informatic, and technology in general, being versatil and one of the worst investement as a customer you could do. The strategy is to upgrade at the right time : it have to be worth the new technology improvement like (new gravure for cpu and gpu 16mn or lower for exemple) and if you actualy need it for your consommation. The next step is making 4K a standard like the 1080 now.
 What the point to paying extra money on some thing you will not use or barely use. It's like buying a 4K 3D projector with "streaming" quality on it 
 Lately, the last "good" investement i did was on a G sync monitor. It's will be new standard (the principe, not the g sync nvidia propriety) that will improve over time...
  
 But now as some one who tried good ALC1150 motherboard, does the AMP can support demanding AKG? by supporting, i want to say  "as good but maybe not better than the o2" ? Because i know that ipod can run it too  But not at their full performance (hopefully   ).
 It will certainly be the only question where i can have a straight answere 
  
 Have a good day wherever you leave


----------



## adydula

To answer that tell us what the specs of the ALC stuff your interested in?

 What is it output impedance?
 What it its power out at various impedances?
  
 What is the sensitivity of your headphones?
  
 There are formulas over at DIY audio that will tell you depending on your amp specs and headphone sensitivity if the amp will be able to provide enough power
 to work well with your headphones.
  
 A.


----------



## MrMateoHead

The only specs I can get on the ALC 1150 are:
  
 1.1 Vrms into 1 32 Ohm load.
  
 Output impedance of 2 Ohms.
  
 The AKG K550s have a measured impedance of 35 Ohm or higher.
  
 SO, assuming the 1150 is implemented according to spec, power output is about 34 mWs into a 35 Ohm load, which should be enough to drive the AKGs to ear damaging levels.
  
 But, it is not clear if that voltage holds constant at any other impedance loads (current limitations?)
  
 Thus if the headphones are loud with your cellphone, a tablet, or an Mp3 player (which typically are in the 1V range, probably), you would probably be satisfied. But, alas, I know this only in theory, since there is not enough objective information from which to estimate the adequacy of the pairing. Where my PSBs require slightly less power to reach 90 dB (0.06 mW vs. 0.09 mW), I'd guess that any device such as the 1150 with 1.1V rms or more would be enough power. I would assume that only the headphone jack, as labeled, provides the power estimated and meets the spec'd 96 dB of dynamic range and -75 db THD (about 0.02%??). The other jacks might be high output impedance, less powerful etc. Who knows?
  
 Just to be sure, I plugged my PSBs into my Nexus for you. Very similar load, very similar theoretical power. Sounds great with classical playing, except for a lot of hiss at the "cranked" levels 
	

	
	
		
		

		
		
	


	




. Of course, you'd better stick with high-efficiency dynamics with relatively flat impedance curves for best results. Those high-swing curves will want more voltage than you theoretically might have.


----------



## thekorsen

raoultrifan said:


> Hi,
> 
> Can you please do some decent macro pictures to affected area? We can compare affected area with O2's schematic and perhaps will get somewhere.
> 
> ...


 
 Hi Raul,
 I did my best to capture the area of interest, as well of the whole unit itself for reference. I'll be sure to take your advice and head to diyaudio later to ask that community if we can't sort it out here. Also, note this unit was modded for a 1/4 '' plug, with the plug squeezed over the bottom right area of the board. This is why I suspect it is taped there, to make sure the plug doesn't accidentally short anything.
  
 Top view:
  

  
  
 Bottom view:
  

  
  
 Potentially damaged areas:
  

  
 -Ryan


----------



## raoultrifan

pocahontas said:


> [...] Like i said, you don't have the equipement to back it up but you engaged your soul by saying it is the true. But sadly i heard the complete opposite from people looking "internetably" (lol) honest too".
> 
> So, the best way is just to basicaly try it out and see by yourself. Better? not better? placebo or not? matter of tast or measurement to back it up? it's a mic mac
> [...]
> ...


 
 Hi pocahontas, 
  
 I only trust 2 things in audio world:
 - 1'st would be measurements done carefully with dedicated equipment that should proves that DAC+AMP are not oscillating and are within acceptable "audiophile" parameters;
 - 2'nd would be A/B and blind A/B tests done by at least 2 persons with decent hearing (A/B tests done either between 2 identical DACs/AMPs, either by using a "reference" system to compare with and write down all noticed differences).
  
 What you need right now is to find someone having both ODAC+O2 and ALC1155 motherboard to do this A/B test I was speaking above (though I believe in one of my links provided in an earlier post there was someone on another forum that already compared that).
  
 Also, just by looking at ALC1155 specs from the datasheet and comparing with ODAC doesn't really proves anything because ODAC and O2 measurements were done at RCA/outputs plugs with scopes and AP Precision equipment, but "some motherboard manufacturer" will only tell you the spces provided by the ALC1155 itself in the datasheet and not the actual measurements done at RCA/outputs or headphone plugs. It's hard for me to believe that a manufacturer will perfectly implement a great audiophile DAC & headamp inside a "usually very noisy" computer case and powered from a "usually very noisy" switching power supply (try searching over Internet about computer PSU noisy and ripple). So, yes your computer PSU is going to influence a lot your motherboard DAC's sound, unless you're spending a lot of money on a high-end PSU with decent ripple & noise figures...and usually most people is swapping computers at every 3-5 years to get most of price/performance ratio, so perhaps would be wiser to invest in external DAC/amps.
  
 Have a great day yourself, 
 Raul.


----------



## pocahontas

raoultrifan said:


>


 
  
 Hello. Well i think we will never really know for sure. "The truth is out there" my friend 
  
 Have a great day too.
  
 ps: if some one have a solid reponse to provide, just quote one of my post so i know


----------



## jseaber

thekorsen said:


> Hi Raul,
> I did my best to capture the area of interest, as well of the whole unit itself for reference. I'll be sure to take your advice and head to diyaudio later to ask that community if we can't sort it out here. Also, note this unit was modded for a 1/4 '' plug, with the plug squeezed over the bottom right area of the board. This is why I suspect it is taped there, to make sure the plug doesn't accidentally short anything.
> 
> Top view:
> ...


 
  
 FWIW - That type of flux residue requires cleaning. Its presence often interferes with circuit behavior.


----------



## raoultrifan

thekorsen said:


> Hi Raul,
> I did my best to capture the area of interest, as well of the whole unit itself for reference. I'll be sure to take your advice and head to diyaudio later to ask that community if we can't sort it out here. Also, note this unit was modded for a 1/4 '' plug, with the plug squeezed over the bottom right area of the board. This is why I suspect it is taped there, to make sure the plug doesn't accidentally short anything.
> 
> Top view:
> ...


 
 Do I see something wrong with R16 & R22 resistors? I believe someone tried to modify the low-pass filter or something. I would recommend you change R16 & R22 with original values from BOM and also to double check values for C19 & C20 caps.
  
 Also, I suggest using a magnifier glass to check for cold-soldering around affected area (the big resistor from the other picture).


----------



## MrMateoHead

pocahontas said:


> ps: if some one have a solid reponse to provide, just quote one of my post so i know


 
 I just gave you one on pg 334.
  
*In short, and "in theory" (because the specs are largely incomplete so only Realtek's incomplete specs are in use here), the 1150 should adequately power your AKG 550s. That would be true of any headphone with similarly flat impedance fixed at about 32-35 Ohms, and with low power requirements (under 1/10th of 1 mW)*. I would not stray far from those "specs", but then again you can't know what the real impedance curve looks like without independent testers so you have to trust their measurements - even if you don't want to.
  
*As to whether the 1150 chipset actually provides 115 dB of SNR, a -75 THD (0.02% distortion) and 96 dB of dynamic range AT the headphone jack is unknown without professional testing of the actual computer / motherboard*. IF those are the "best case" specifications, than poor implementation can only make them worse from there. Where the audio section is largely an "afterthought", there are too many variables and not enough specs to guess whether, even if perfectly implemented, the chipset will deliver its theoretical best-case performance.
  
 My present chipset, as implemented inside my existing computer (the 892), is close to being relatively indistinguishable, but it has audible hiss and bass/treble roll-off / softness and low power which is the surest way I know it is not as good as my O2. I need to use more demanding headphones to make that assertion (easy - I own some). "Any amp played within its limits" will sound the same. Maybe. But different headphones have different efficiency and impedance curves, and will respond not only objectively but subjectively different to low power (e.g. one sounds "louder"/"better" the other "hisses" more/less / lacks bass). Sorry to disagree with your Internet, but you have a lot more to learn.
  
*My PSB's are very similar to the AKG's in terms of impedance and efficiency, and can play loud with my phone, tablet, and computer, so that is a "proxy" for guessing that a setup such as yours will work just fine*. In fact, in the past I've argued quite clearly that, unlike my other headphones, I'd likely be claiming that amps are a "waste of money" were the PSBs my only headphones. Not true anymore - I've seen where having dedicated equipment is a big plus. Again, sorry about your Internet.
  
 As others point out, the "noisiness" of your audio environment will relate to other parts in use, and the power supply, shielding etc. may or may not matter. It also dawned on me that all integrated onboard audio is probably limited to around 3.3V peak-to-peak to power I think, which will never be enough for the most demanding headphones. Dedicated cards and/or external solutions will continue to have more ideal operating conditions and can potentially supply more power IF they are designed to do so.
  
 So to provide a more solid (educated) response, "*Yes*".


----------



## WilliamLeonhart

Can anyone here that has tried the ODAC revB please give me an A-B comparison? I've already got the revA but currently has a deal for the revB, and I don't know if the difference (if any) will be worth it.


----------



## 214324

williamleonhart said:


> Can anyone here that has tried the ODAC revB please give me an A-B comparison? I've already got the revA but currently has a deal for the revB, and I don't know if the difference (if any) will be worth it.


 
 There really shouldn't be any audible difference.
  
 If the numbers difference really makes you feel that uncomfortable go ahead and buy it.
  
 I'd say get a Rev B ONLY if you switch sources very often and don't want to run into the distortion issue over certain USB connections found on the Rev A. Details here:
  
 http://blog.jdslabs.com/?p=1003
  
 Also straight from JDSLabs themselves:
  


> Minor performance improvements (audibly equivalent)


----------



## deaconblues

williamleonhart said:


> Can anyone here that has tried the ODAC revB please give me an A-B comparison? I've already got the revA but currently has a deal for the revB, and I don't know if the difference (if any) will be worth it.



RevA had compatibility problems with a very small percentage of motherboards. Its power regulation would become unstable and cause severe distortion. RevB was made to fix this problem. If you don't have this problem, there is no reason to replace your odac. Even if you have the problem, it can be fixed by connecting the odac to a USB hub instead of directly to the computer.


----------



## serman005

deaconblues said:


> RevA had compatibility problems with a very small percentage of motherboards. Its power regulation would become unstable and cause severe distortion. RevB was made to fix this problem. If you don't have this problem, there is no reason to replace your odac. Even if you have the problem, it can be fixed by connecting the odac to a USB hub instead of directly to the computer.


 

 Good to know.


----------



## WilliamLeonhart

This is great. I'd stay with my trusted revA then.


----------



## adydula

Absolutely no sonic difference...I have several and if you have a Rev A there is no need for a B.
  
 A.


----------



## riverlethe

williamleonhart said:


> Can anyone here that has tried the ODAC revB please give me an A-B comparison? I've already got the revA but currently has a deal for the revB, and I don't know if the difference (if any) will be worth it.




RevB does have the advantage of being able to run straight from, eg., an iPhone battery without the use of a powered hub.


----------



## WilliamLeonhart

riverlethe said:


> RevB does have the advantage of being able to run straight from, eg., an iPhone battery without the use of a powered hub.


 
 Thanks for the info.


----------



## gab840

Guys my o2 amp power supply just got blown away with huge sound and after that my o2 amp is not working
I was not present in the room when it blowed up and the upper cover of power supply was blown away 
I used mY ifi ican power supply , with it is getting power on but are not able to produce any sound. What can i do to check whats wrong ?


----------



## deaconblues

Does your ican power supply output DC voltage?
 The O2 need an AC power supply.


----------



## raoultrifan

220 mA is not enough for the O2, sorry about that. 
  
 You could try measuring FETs and power regulators, maybe you'll find the broken piece with ease. Also, might worth trying to see if op-amps are good or not, but I honestly doubt op-amps might break so easy with FETs protection...hmmm...
  
 Good luck!


----------



## deaconblues

220mA should be enough.
 The BOM even suggested a 12vAC 200mA power supply.  That's what I use on the O2s I built, and I've never experienced any explosions .
  
 That having been said, I guess it wouldn't hurt to increase his headroom a little bit.  JDS labs uses a 15vAC 500mA supply.  The O2 definitely wouldn't push that supply to its limits.


----------



## Peti

Hi all,
  
 I'm wondering if anyone can tell me the exact name of the usb cable for the O2/ODAC? I want to get something way shorter from the internet and after some research I found that USB Male A to Mini B 5-pin Data Cable would be the size I need?
  
 Anyone can confirm that?
  
 Thank You all!


----------



## thekorsen

peti said:


> Hi all,
> 
> I'm wondering if anyone can tell me the exact name of the usb cable for the O2/ODAC? I want to get something way shorter from the internet and after some research I found that USB Male A to Mini B 5-pin Data Cable would be the size I need?
> 
> ...


 
 If it hasn't changed since the Rev A, the cable you described is correct. This is the cable I bought for when I wanted a shorter one. Its the smallest one I could find (6'') at the time that had a good rep. If you want something longer this monoprice one at 1.5' should do the trick.


----------



## Peti

Thank you. I am actually looking for something really short, like 10cm. Found this one:
  
 http://www.amazon.com/System-S-angled-cable-adapter-charge/dp/B00Z6TV496/ref=sr_1_24?s=pc&ie=UTF8&qid=1457655516&sr=1-24&keywords=usb+mini+cable+10cm
  
 Been thinking to give a shot to these high end usb cables but they all kinda long and there's so much BS going on around them...dunno...
  
 If you guys know any mini usb cables around 10 cm (3-4 inches) would be appreiated if you shared on here.
  
 Piece


----------



## raoultrifan

deaconblues said:


> 220mA should be enough.
> The BOM even suggested a 12vAC 200mA power supply.  That's what I use on the O2s I built, and I've never experienced any explosions .
> 
> That having been said, I guess it wouldn't hurt to increase his headroom a little bit.  JDS labs uses a 15vAC 500mA supply.  The O2 definitely wouldn't push that supply to its limits.


 
 http://o2amp.wikia.com/wiki/Power_Adapters - 200mA is minimum. AFAIK I have 500mA in my O2.
 Anyway I wonder why why the transformer got burned and what other components got defective because of this.


----------



## cityle

peti said:


> Thank you. I am actually looking for something really short, like 10cm. Found this one:
> 
> http://www.amazon.com/System-S-angled-cable-adapter-charge/dp/B00Z6TV496/ref=sr_1_24?s=pc&ie=UTF8&qid=1457655516&sr=1-24&keywords=usb+mini+cable+10cm
> 
> ...


 

 Any decent USB cable will do the job. Just maybe add a ferrite choke like I've done as NwAvGuy mentionned that there was some measurable improvement. http://nwavguy.blogspot.ca/2012/04/odac-released.html?showComment=1334803522234#c4272810052548519926


----------



## Peti

Thank you for all the advices but I just made up my mind right now that instead of spending on aftermarket usb cables I do an upgrade towards another amp/dac and put my O2/ODAC in the classifieds. It breaks my heart to see it go but I have a hunch the upgrade will make me even happier!
  
 http://www.head-fi.org/t/801361/upgraded-o2-odac-shipping-included
  
 It was a nice journey with NWAVGUY in the past 1,5 years, and who knows, I might turn back to it later. Thank You O2/ODAC!!


----------



## Alchemist007

I'm trying to hook up my O2/ODAC to my home theater's receiver and just use the ODAC line out to the RCA on my receiver. This is in an effort to experiment with some music I have on my PC using the ODAC but with a different amp. Question is, the line-out is 3.5mm...so would I buy something like this to hook it up to the RCA input on the receiver? http://www.amazon.com/Cable-Matters-Plated-3-5mm-Stereo/dp/B00ESM3EIQ/ref=sr_1_4?ie=UTF8&qid=1458580682&sr=8-4&keywords=3.5mm+to+rca
  
 The receiver is a Sony STR-K665P if it matters.


----------



## raoultrifan

I believe this cable adapter should work just fine in your setup, in either VIDEO or DVD inputs.


----------



## gargani

alchemist007 said:


> I'm trying to hook up my O2/ODAC to my home theater's receiver and just use the ODAC line out to the RCA on my receiver. This is in an effort to experiment with some music I have on my PC using the ODAC but with a different amp. Question is, the line-out is 3.5mm...so would I buy something like this to hook it up to the RCA input on the receiver? http://www.amazon.com/Cable-Matters-Plated-3-5mm-Stereo/dp/B00ESM3EIQ/ref=sr_1_4?ie=UTF8&qid=1458580682&sr=8-4&keywords=3.5mm+to+rca
> 
> The receiver is a Sony STR-K665P if it matters.


 
 Alchemist007; I use a cable like that to connect my TV's 3.5mm output to my receivers RCA inputs. I also use a cable like that to go from my receiver's RCA outputs to the objective 2's 3.5mm input. Works in both cases.


----------



## Alchemist007

Good to know it's multipurpose.


----------



## riverlethe

Is there any reason to prefer the O2 over the Magni 2 at this point?


----------



## Alchemist007

I've heard someone say that provided enough power, any two solid state amps should sound similar if they're both claiming to be transparent.


----------



## riverlethe

alchemist007 said:


> I've heard someone say that provided enough power, any two solid state amps should sound similar if they're both claiming to be transparent.


 
  
 Right, so why buy the more expensive and/or uglier one with less features?


----------



## upstateguy

riverlethe said:


> Is there any reason to prefer the O2 over the Magni 2 at this point?


 
  
 Well if it measures as well as an O2 what's the point of Schitt's other amps?  Different flavor offerings?


----------



## riverlethe

upstateguy said:


> Well if it measures as well as an O2 what's the point of Schitt's other amps?  Different flavor offerings?




Fair question. Bigger knobs? 

I don't know if it measures as well, but I haven't seen anything to suggest that it fails to be "transparent," and it has significantly more power.


----------



## upstateguy

riverlethe said:


> upstateguy said:
> 
> 
> > Well if it measures as well as an O2 what's the point of Schitt's other amps?  Different flavor offerings?
> ...


 
  
 I suppose, if you have really hard to drive headphones... but that's probably the exception rather than the rule.
  
 I suppose another reason could be more features like an additional input and a preamp line out.


----------



## MrMateoHead

riverlethe said:


> Right, so why buy the more expensive and/or uglier one with less features?


 

 You mean you don't want selectable gain, and you don't mind the sight of a 3.5 mm to RCA adapter hanging off the back?
  
 If I put the O2 into an aluminum case and stuck an Apple logo on it, would you think it was the end-all be-all of amps?
  
 Just sayin'


----------



## riverlethe

mrmateohead said:


> You mean you don't want selectable gain, and you don't mind the sight of a 3.5 mm to RCA adapter hanging off the back?
> 
> If I put the O2 into an aluminum case and stuck an Apple logo on it, would you think it was the end-all be-all of amps?
> 
> Just sayin'




Magni 2 has had selectable gain for over a year now. Do you mean a hideous adapter like this (assuming your source has 3.5mm outputs)?

http://www.amazon.com/Mediabridge-3-5mm-Male-2-Male-Adapter/dp/B004YDUZ22/ref=sr_1_15?ie=UTF8&qid=1458913012&sr=8-15&keywords=3.5mm+rca

O2 would still be lacking volume-controlled preamp outputs.


----------



## MrMateoHead

riverlethe said:


> Magni 2 has had selectable gain for over a year now. Do you mean a hideous adapter like this (assuming your source has 3.5mm outputs)?
> 
> http://www.amazon.com/Mediabridge-3-5mm-Male-2-Male-Adapter/dp/B004YDUZ22/ref=sr_1_15?ie=UTF8&qid=1458913012&sr=8-15&keywords=3.5mm+rca
> 
> O2 would still be lacking volume-controlled preamp outputs.


 

 I still don't like the volume knob, or the power and gain switches on the back. RCA inputs are just wrong considering the purpose of the device and the likelihood of being connected to a phone, computer, etc.
  
 But that's just me - I drank the O2 koolaid a long time ago, and it was gooooood. The Magni offers nothing really other than more power, and the SQ has been deemed different, and it didn't seem to be different in a good way. Plus the O2 can now be quite extensively customized - not too shabby.


----------



## riverlethe

mrmateohead said:


> I still don't like the volume knob, or the power and gain switches on the back. RCA inputs are just wrong considering the purpose of the device and the likelihood of being connected to a phone, computer, etc.
> 
> But that's just me - I drank the O2 koolaid a long time ago, and it was gooooood. The Magni offers nothing really other than more power, and the SQ has been deemed different, and it didn't seem to be different in a good way. Plus the O2 can now be quite extensively customized - not too shabby.




The 1/4" headphone jack and RCA I/O on the Magni suggest to me that it is meant more for desktop use. I personally don't see the point of something as powerful as an O2 for portable use. I just carry IEM's, which don't require an external amp. Apple fixed their output-coupling capacitor bass roll-off issue a long time ago. 

I'm not saying there's anything wrong with the O2/ODAC - it's just getting a bit long in the tooth and seems overpriced (ODAC especially) given the current marketplace. 

I share your annoyance with the volume knob placement on Schiit's amps.


----------



## Bruch

I too have been using the Burson V5-D in the Voltage Amplification Stage of the JDS Labs O2 Amp on Raul recommendations and can verify that it does indeed make a significant and noticeable improvement to the sound quality. Music is less veiled, more detailed without sacrificing any bass.
  
 The only problem is that I had to drill a hole in the case of the O2 through which the V5 rises, declaring its presence for all to see. Personally I quite like it!


----------



## raoultrifan

I'm glad you love the sound of SS V5-dual, thanks!
  
 There's no need for drilling holes, you could try taking out the batteries and use something like this: http://www.digikey.com/product-search/en?mpart=299-93-308-10-001000&v=54 or you can just replace existing O2 case with a taller version like this one: http://www.boxenclosures.com/category/product_details.html?product__id=240050. Just double check the size before ordering, just in case I might be wrong (I don't have the time to do this "mod" right now, so my O2 is still open case.  ).
  
 To be honest I didn't expected to sound so good this V5, especially that in the past I rolled the original JRC2608 with JRC2114, LME49720, OPA2134, OPA1652, MUSES01, MUSES8820 etc. and I couldn't really say there was a definitely improvement in sound output (it was something, but nothing to be able to write on papers/forums). But when I used SS V5-dual I noticed the details and musicality coming out from these little BURSONs, quite an improvement for my small O2 I'd say. 
  
 Also, in case you have a very sensitive headset you can use (carefully) O2's highest gain and max. volume (nothing connected on inputs!) and you'll realize that background noise is even lower with BURSON V5 than when using other op-amps like for example LME49720.


----------



## Schmidter

What is the difference between a digital an analog version?


----------



## riverlethe

Oh dear, Nwavguy must be spinning in his virtual grave. Care to post some measurements?


----------



## raoultrifan

riverlethe, I know the feeling, trust me.  I usually don't trust people when tell me that changing op-amps will change the sound, but sometimes A/B tests and also scope's measurements tells the contrary.
  
 I've also read nwavguy's entire blog myself for several times (even the comments sections) and I totally understand how O2 works and what a great job nwavguy did. Also, if you look at my previous posts about what I've did to my O2 you'll realize that I did a couple of more improvements in the past, not only op-amp rolling (of course, who looks for real O2 upgrades will need to check AGDR's work from diyaudio forum).
  
 I was only using my PicoScope to check for any possible oscillations and to measure voltage output for several audio signals taken from audiocheck.net (at least 10 wave forms at around -3dB each, between 20-20.000Hz, dummy load resistive & capacitive was used). Output signal is completely flat and no strange FFT harmonics could be seen no matter of the op-amp used (well, with some op-amps I could see an increase in THD but only when output voltage gets close to 7V RMS, but that's another story).
  
 Two things I need to point out here:
 - most op-amps have been created for "general use" and only few of them are really created "for audio use"
 - V5 is completely solid-state with perfectly matched transistors and 0.5% film resistors and has been created with VAS and LPF stages in mind
 - VoltageAmplificationStage and LowPassFilter are the stages where the sound could and will get changed inside an amplifier; adding I/V stage for a DAC as well. Output buffers might also the influence sound as well, but usually LM4562/LME49720 if correctly decoupled should be OK for most audiophiles, even in A/B tests, though some people found real differences when rolling output buffers (I'm not the one of them yet).
  
 In O2 sound is created inside the first op-amp, because the output buffer is acting like a blind audio repeater. We all know the limitations of NJM4556, still sound is not changed there, actually the sound could be changed in the voltage amplification stage, so NJM2068 is the op-amp from where the sound actually comes from. So, replacing this one with a real solid-state device like V5-dual from BURSON might be a real upgrade for some of us, especially for mod-ers and DIY-ers.


----------



## upstateguy

raoultrifan said:


> <snip>
> So, replacing this one with a real solid-state device like V5-dual from BURSON *might * be a real upgrade for some of us, especially for mod-ers and DIY-ers.


 
  
 Sounds cool, time for some measurement comparisons.


----------



## adydula

AGDR's work on the booster board, ODA, and recently the non-inverting format has taken this concept forward to be sure. I have built all three and they all are stellar.
  
 Alex


----------



## riverlethe

Can someone explain the difference between "general use" and "audio use?"


----------



## raoultrifan

upstateguy said:


> Sounds cool, time for some measurement comparisons.


 
 I'll copy-paste from my above post, hope you don't mind:
 "I was only using my PicoScope to check for any possible oscillations and to measure voltage output for several audio signals taken from audiocheck.net (at least 10 wave forms at around -3dB each, between 20-20.000Hz, dummy load resistive & capacitive was used). Output signal is completely flat and no strange FFT harmonics could be seen no matter of the op-amp used (well, with some op-amps I could see an increase in THD but only when output voltage gets close to 7V RMS, but that's another story)."


riverlethe said:


> Can someone explain the difference between "general use" and "audio use?"


 
 Well, we're already on topic, but a lot of op-amps are designed for audio, video and telecommunications purpose. Some manufacturers are re-branding some of these op-amps as being "for audio use" after several tests (stability, audio quality etc.). I personally like the OPA SoundPlus series, but I found better replacement form them in some configurations (MUSES01 in I/V stage and BURSON V5 or MUSES02 in LPF and VAS stages).
  
 Everyone has ears to A/B test them all.


----------



## upstateguy

raoultrifan said:


> upstateguy said:
> 
> 
> > Quote:
> ...


 
  
 So now I'm not sure what you're saying. 
  
 Did you say you didn't notice any measurement differences regardless which op-amp was used?
  
 If measurement differences, which relate to audibility, are not there, why could this be called an *upgrade*?  <just asking>


----------



## raoultrifan

Hi upstateguy, 
  
 I couldn't see any differences on my tests, exactly. Perhaps RMAA or ARTA tests may reveal some small improvements in IMD, THD and noise, but I don't have access to a sound-card having a decent analog input, sorry. 
  
 What I was trying to say in my previous posts is that some op-amps just sound better than others without measuring better (check datasheet of MUSES02 and compare it with LME49720's datasheet for example). A better channel separation inside the op-amp will increase sound-stage and depth, FET-input op-amps may sound better than BJT-input op-amps (read about odd-order harmonics on OPA604 datasheet) etc.
  
 To my ears BURSON SS V5-dual when used in voltage amplification stage (first op-amp) sounds definitely better in my Objective2 headamp than other op-amps tested (NJM2608, LME49720, MUSES8820 etc.). Usually solid-state devices sound better than op-amp devices.
  
 Regards, 
 Raul.


----------



## Blarzor

Hey guys, can you help me what gain settings to get on my O2 that I'm ordering in near future? I'm buying O2 only, without ODAC. I will be using my interface Focusrite Scarlett 2i4 which has 1.46 volts output on its DAC.
  
 So basically, I'm getting ATH-R70X headphones, which according to reviews require optimal 5V or 7V for pop/classical. Does that mean that my recommended minimum gain should be 3,4x on O2 (5V : 1,46V = 3,4x?). Is this how you calculate it?
  
 Can you guys suggest me the gain settings before I buy O2?


----------



## raoultrifan

I would go with 1-1.5X as lowest gain and 3-3.5X as highest gain, if you have this setup available for buying. Now, this really depends on your headset used.


----------



## Ver7o

Hello good ppl.
  
 I'm thinking of getting O2+ODAC combo for my setup and for any future setups. So my current setup are powered studio monitors and HD598 cans. So my thinking here is that with this combo I can make my setup futureproof if I ever decide on harder to drive cans or passive speakers.
  
 Now my questions are;
 - how would 1x gain work with powered speakers?
 - does 1x actually mean there is no amplification of the output signal (pre-amp option)?
 - has anyone tried powering passive speakers with this combo (on 3.3x gain?)
  
 Thank you for any kind of answers.


----------



## Blarzor

@raoultrifan My headphone use will be for mixing first and enjoyable listening second (gothic rock, progressive rock, classic rock)


----------



## raoultrifan

ver7o said:


> Now my questions are;
> - how would 1x gain work with powered speakers?
> - does 1x actually mean there is no amplification of the output signal (pre-amp option)?
> - has anyone tried powering passive speakers with this combo (on 3.3x gain?)
> ...


 
 I'm not sure I understand your questions, sorry. Shouldn't you use ODAC to power the amped-speakers?
  
 There's also an ODAC/O2 combo that has RCA out so I believe that might suit better for you: http://www.headnhifi.com/amplifiers/OBJ_O2_ODAC_digital2 (I don't know how Walter did connected both O2 input and RCA outputs, but feel free to ask him; I had my ODAC modded with a small switch to switch between O2 input and RCA outputs).
  


blarzor said:


> @raoultrifan My headphone use will be for mixing first and enjoyable listening second (gothic rock, progressive rock, classic rock)


 
  
 I believe 1-1.5X for lowest gain setting and 3-3.5X for the highest setting should suffice, but that depends on the headphones you'd like to use. In your case to get the max. power available out of your O2 means to use the gain of 5X that translates in about 7.3V RMS for your Scarlett DAC (though, something around 4.8-4.9X would be recommended to prevent clipping).
  
 You need to calculate yourself the RMS voltage needed for your headphones and carefully choose desired gains. Headphones manufacturer's specs or Innerfidelity and something like http://www.digizoid.com/headphones-power.html might help you out.


----------



## Blarzor

raoultrifan said:


> I believe 1-1.5X for lowest gain setting and 3-3.5X for the highest setting should suffice, but that depends on the headphones you'd like to use. In your case to get the max. power available out of your O2 means to use the gain of 5X that translates in about 7.3V RMS for your Scarlett DAC (though, something around 4.8-4.9X would be recommended to prevent clipping).
> 
> You need to calculate yourself the RMS voltage needed for your headphones and carefully choose desired gains. Headphones manufacturer's specs or Innerfidelity and something like http://www.digizoid.com/headphones-power.html might help you out.


 
  
 I'm buying Audio Technica R70x which has impedance of 470 ohms and 99 dB sensitivity, I don't know if that is 99db SPL/mW or SPL/V though :/
  
 http://www.audio-technica.com/cms/headphones/f39784ce643a82e6/index.html


----------



## raoultrifan

Blarzor, you should probably aim for the 4.8-5X for the max. gain. The lowest gain feel free to choose it between 1.5-2.5X, depending on your thoughts (future headphones perhaps?).
  
*Note*: Read the "Loudness" chapter from here: http://www.head-fi.org/t/765004/audio-technica-ath-r70x-in-depth-review-impressions#post_11565945, it's an interesting review that also proves that R70x could be driven with a headamp able to deliver between 5-7V RMS (though the reviewer claims that even an iBasso DX90 that has a maximum output voltage of 2.69 Vrms could do the job with R70x).


----------



## Blarzor

raoultrifan said:


> Blarzor, you should probably aim for the 4.8-5X for the max. gain. The lowest gain feel free to choose it between 1.5-2.5X, depending on your thoughts (future headphones perhaps?).
> 
> *Note*: Read the "Loudness" chapter from here: http://www.head-fi.org/t/765004/audio-technica-ath-r70x-in-depth-review-impressions#post_11565945, it's an interesting review that also proves that R70x could be driven with a headamp able to deliver between 5-7V RMS (though the reviewer claims that even an iBasso DX90 that has a maximum output voltage of 2.69 Vrms could do the job with R70x).


 
  
 Thanks for all the help. I learned to do the calculations overnight with the help of NwAvGuy's blog, I calculated the amount of gain I need, but the only thing I still don't understand is the concept of excess gain.
  
 I used these tools:
 http://www.digizoid.com/headphones-power.html
 http://www.sengpielaudio.com/calculator-gainloss.htm
  
 My calculations for R70x are the following:
  
 To reach 110dB with my DAC (or Source as called in the article which outputs 1.46V), I need gain of 1,66x. To reach 100dB with my DAC, I need gain of 0,52x. To reach 115dB with my DAC I need gain of 2,96x.
 Now, I don't really understand the excess gain, if I add 3db (excess gain) to the 2,96x (which translates into 9.43dB) I get 12.43dB which translates to 4.18x.
  
 I mean, I got all the calculations going on, I just don't know what's the difference between looking at 115dB minimum gain calculation with added excess gain.
  
 Also, does having let's say 1.5x minimum gain value translate into reaching maximum 110db when my volume button is all the way to the end up? Is this how it works?


----------



## Fingerling

Hi,
  
 I didn't find the answer to my question by searching the thread.
  
 I have a O2+ODAC with RCA output: is it capable of driving my Eltax Monitor III?
  
 Thanks


----------



## WilliamLeonhart

fingerling said:


> Hi,
> 
> I didn't find the answer to my question by searching the thread.
> 
> ...


 
 No they're for headphones. But you can try using the O2 as pre-amp.


----------



## Fingerling

williamleonhart said:


> No they're for headphones. But you can try using the O2 as pre-amp.


 

 OK but why? What happens if I try (I ask before because I don't want to move my Eltax for nothing)?
  
 So the RCA output are for active speakers only? Or as a tiny pre-amp (but what is the point?)?


----------



## castleofargh

fingerling said:


> williamleonhart said:
> 
> 
> > No they're for headphones. But you can try using the O2 as pre-amp.
> ...


 

 headphones will typically be in the 16 to 600ohm area, and those in the 16ohm area will most likely be IEMs with very high sensitivity needing very very little power. 5mW will get most IEMs pretty loud.
 while speakers are at least in theory dancing in the 4 to 8ohm area, while needing a lot of power. usually a few W.
 different amps for different needs.


----------



## Fingerling

castleofargh said:


> headphones will typically be in the 16 to 600ohm area, and those in the 16ohm area will most likely be IEMs with very high sensitivity needing very very little power. 5mW will get most IEMs pretty loud.
> while speakers are at least in theory dancing in the 4 to 8ohm area, while needing a lot of power. usually a few W.
> different amps for different needs.


 

 Thanks. So if i plug the bananas from my pair of Eltax, no sound at all? Someone has tried with passive speakers?


----------



## MrMateoHead

fingerling said:


> Thanks. So if i plug the bananas from my pair of Eltax, no sound at all? Someone has tried with passive speakers?


 

 Don't do it.


----------



## Fingerling

That doesn't tell me what happens if I do.


----------



## maheeinfy

What is the general soung signature of O2? 
Bright? Warm? flat?


----------



## adydula

You want to damage your amp???
 A.


----------



## maheeinfy

maheeinfy said:


> What is the general soung signature of O2?
> Bright? Warm? flat?


 
 anyone?


----------



## Peti

Absolutely neutral. The only thing it does that it amplifies the signal without any kind of added flavor whatsoever. Dead clean. Don't expect any kind of coloration. Same goes with the ODAC. I'm selling my combo now but they served really well me in the past 1,5 yrs. You get value for your money I think.


maheeinfy said:


> anyone?


----------



## pinkfloydhomer

Is there an audible difference between ODAC and ODAC rev. b?


----------



## WilliamLeonhart

peti said:


> Absolutely neutral. The only thing it does that it amplifies the signal without any kind of added flavor whatsoever. Dead clean. Don't expect any kind of coloration. Same goes with the ODAC. I'm selling my combo now but they served really well me in the past 1,5 yrs. You get value for your money I think.


 
 This I can agree 100%. When you plug your headphones into the O2 ODAC you're gonna hear the "vanilla" sound of your headphones.


pinkfloydhomer said:


> Is there an audible difference between ODAC and ODAC rev. b?


 
 No. If my memory serves me well even JDS or Yoyodyne confirmed that somewhere.


----------



## pocahontas

I heard there is not. If you already have the first edition, it's totaly a wast of money.


----------



## hidehide

Just ordered myself a JDS O2 amp to power my LCD-3 thru Macbook Pro Retina in the meantime. Going to get Schiit Gungnir multibit + Mjolnir 2 combo later when I move to a bigger place.
 I asked the customer rep whether I should get the O2 or O2+ODAC combo. Surprisingly, he told me that the Macbook Pro Retina has a reputation DAC and he suggest me to skip the ODAC and just get the amp. Very great customer service experience. Hope I will enjoy it when it arrives.


----------



## WilliamLeonhart

hidehide said:


> Just ordered myself a JDS O2 amp to power my LCD-3 thru Macbook Pro Retina in the meantime. Going to get Schiit Gungnir multibit + Mjolnir 2 combo later when I move to a bigger place.
> I asked the customer rep whether I should get the O2 or O2+ODAC combo. Surprisingly, he told me that the Macbook Pro Retina has a reputation DAC and he suggest me to skip the ODAC and just get the amp. Very great customer service experience. Hope I will enjoy it when it arrives.


 
 Oh my...
  
 Definitely buy the ODAC as soon as you can. Even though I no longer keep it, the ODAC is still one of my best purchase ever.


----------



## polyrhythm66

hello,
  
 is there a shop in Europe that sells this product?


----------



## bracko

polyrhythm66 said:


> hello,
> 
> is there a shop in Europe that sells this product?


 
 Head 'n' hifi in Switzerland are the best:
  
http://www.headnhifi.com/


----------



## drteming

After playing around with a Lehmann clone, I revisited my O2 amp and decided to do a complete rebuild.  Got a new PCB from JDS labs and spent some time on Mouser.  The Vishay-Dale resistors on the power supply and management circuits are total overkill, but I like the little brown sausages.  The electrolytic caps are Panasonic FR and FM's.  I'm running 1.1x and 4x gain.  I know I can just leave the 15K resistor out and get 1x gain, but I can't stand the empty space.  The 1.1x gain is perfect for my AKG K7XX and the 4x gain works well with the DT900 600 ohm.  I got a NE5532 in the gain stage op amp in the picture, but I stuck in an OPA2107 I had lying around (no instability or distortion, can't really tell a difference truthfully, but it make me feel warm and fuzzy so why not?).


----------



## hidehide

I wonder would there be any SQ benefit if I'm running it on 1.0x gain against just plugging it in the headphone jack?


----------



## cityle

hidehide said:


> I wonder would there be any SQ benefit if I'm running it on 1.0x gain against just plugging it in the headphone jack?



In my case, using the O2 with 1.0x with the ath-ad900x had improve the sound, giving a relief to the bass that was not there before. But I guess it depends as always of what you're using as the source, crappy laptop vs top-end gaming/workstation motherboard.


----------



## MrMateoHead

Hey all -
  
 Having a problem with my ODAC for the first time. Crackling / Static, Hissing sounds - not good. At first I thought some noise may have gotten into my signal chain, but when I plugged in my realtek line - the noise was all gone.
  
 Wiggling, trying new USB jacks, different cables didn't matter. Not sure what might be up. I could've sworn I heard the noise coming from a separate speaker / AV receiver, but that was probably just some Mp3 clipping.
  
 Any ideas? I opened up the device and nothing looks blackened / damaged. Everything seems tight and normal. If I have time later I may try plugging it into my laptop to see if the problem definitely moves with the ODAC.


----------



## schmalgausen

Have you tried to connect it to another PC?


----------



## MrMateoHead

schmalgausen said:


> Have you tried to connect it to another PC?


 
  
 Yes - I just connected it to my Laptop. After installing the ODAC automatically, it was at first noise free.
  
 Then, after playing some music for a few minutes, I stopped playback, and cranked volume on the amp.
  
 Seems the slightest jiggle of the ODAC brought back the "noise" I'm hearing.
  
 What does this indicate? I am on Windows 10 on both machines
  
 The ODAC has performed flawlessly on the problem computer for a year or two thus far, and I've never switched the port in use. Now, I'm having problems.


----------



## MrMateoHead

As an update, my ODAC is "behaving" recently. Disconnecting / Plugging it back in seems to have helped. Any slight disturbance may bring back the noise so I have simply left it alone for a day and cranked up the jams.
  
 Still, I am curious to hear from others that may have had issues in the past. Could it be weak / cheap connector ports? Some issue with the USB interface? The ODAC ain't cheap but I don't know of a better DAC if this one gives up the ghost.


----------



## sanakimpro

mrmateohead said:


> As an update, my ODAC is "behaving" recently. Disconnecting / Plugging it back in seems to have helped. Any slight disturbance may bring back the noise so I have simply left it alone for a day and cranked up the jams.
> 
> Still, I am curious to hear from others that may have had issues in the past. Could it be weak / cheap connector ports? Some issue with the USB interface? The ODAC ain't cheap but I don't know of a better DAC if this one gives up the ghost.


 
 I've used the O2/ODAC combo for almost 2 years. 
  
 My best guess is that the noise heard even when a song is playing is 50 Hz noise coupling through.
  
 I realized this issue is common especially when the ODAC power adapter is connected to the same socket as the PC.
  
 When I run into the trouble mentioned, either a PC restart or USB unplug / replug fixes the issue. I think unplugging and replugging forces the USB controller to reset and resolves the issue. Besides that, no issue with the ODAC/O2.
  
 Cheers, Shu.


----------



## MrMateoHead

atoniolin said:


> I've used the O2/ODAC combo for almost 2 years.
> 
> My best guess is that the noise heard even when a song is playing is 50 Hz noise coupling through.
> 
> ...


 

 Thanks for sharing.
  
 To be clear, I seem to hear a "tearing" static, or very low-level statickyness. It is similar to the sound of clipping, but as if it were occurring over much more than a millisecond or so. The big giveaway is when nothing is playing of course, and the "tearing" static can be heard as I turn the volume up much higher.
  
 I'll have to assume that it has something to do with the USB ports at this time. Technology . . . .


----------



## WilliamLeonhart

Could be that some components on the board is loose. Happened to mine a long time ago but it was easily fixed. Would be great if you could find a DIY guy to help you out.


----------



## sanakimpro

mrmateohead said:


> Thanks for sharing.
> 
> To be clear, I seem to hear a "tearing" static, or very low-level statickyness. It is similar to the sound of clipping, but as if it were occurring over much more than a millisecond or so. The big giveaway is when nothing is playing of course, and the "tearing" static can be heard as I turn the volume up much higher.
> 
> I'll have to assume that it has something to do with the USB ports at this time. Technology . . . .


 
 Yes, I hear that static too. If I try to play a song, I notice the bass is messed up and during quieter passages, the static is there.


----------



## MrMateoHead

atoniolin said:


> Yes, I hear that static too. If I try to play a song, I notice the bass is messed up and during quieter passages, the static is there.


 

 As the static reminds me of clipping - either too much power, or too little, the investigation has continued. I have yet a new theory.
  
 The only device that has changed in recent months is my mouse - I retired a Logitech for a MS mouse. I have 2 USB 2.0 ports (keyboard and mouse), and 4 USB 3.0 ports (2 in the front of the machine, 2 in the rear). ALL ports demonstrate the noise with the keyboard/mouse no USB 2.0 ports, and with the ODAC on any of the 3.0 ports.
  
 I deleted the USB drivers and manually rebooted the machine and it automatically re-installed the same USB drivers. No dice.
  
 I tried going into power settings to shut off the selective USB Suspend "feature". That also failed.
  
 So I poked around Device Manager to see what devices were showing up under what USB paths. No matter where I plug in, the ODAC as well as an input device seem to show up under a "USB composite device", along with an "USB input device". So, it appears as if the ODAC shares with the mouse, while the Keyboard gets its own port. Then, I have the two front 3.0 ports, which I think are shared and I typically only use them for HDDs and other memory devices. They appear to be not in use, which is true.
  
 Anyway, I once again moved the ODAC back to its original, seemingly trouble-free port. Then I moved the mouse from the USB 2.0 port to the other rear USB 3.0 port. So far so good, the ODAC is back to "behaving" normally. I am not at all sure if the USB 2.0 ports are "shared" with the USB 3.0 ports or if they have independent paths. But it would seem that switching mice may have caused a problem - perhaps starving the ODAC of power. I don't know as I've had success followed by a return of the bad noises. We'll see!


----------



## sanakimpro

mrmateohead said:


> As the static reminds me of clipping - either too much power, or too little, the investigation has continued. I have yet a new theory.
> 
> The only device that has changed in recent months is my mouse - I retired a Logitech for a MS mouse. I have 2 USB 2.0 ports (keyboard and mouse), and 4 USB 3.0 ports (2 in the front of the machine, 2 in the rear). ALL ports demonstrate the noise with the keyboard/mouse no USB 2.0 ports, and with the ODAC on any of the 3.0 ports.
> 
> ...


 
 Great snooping! My current laptop hasn't given me any trouble with ODAC clipping/noise issues, so I can't do much more. If it ain't broke, huh? 
  
 Hopefully things work out for you.


----------



## WilliamLeonhart

mrmateohead said:


> As the static reminds me of clipping - either too much power, or too little, the investigation has continued. I have yet a new theory.
> 
> The only device that has changed in recent months is my mouse - I retired a Logitech for a MS mouse. I have 2 USB 2.0 ports (keyboard and mouse), and 4 USB 3.0 ports (2 in the front of the machine, 2 in the rear). ALL ports demonstrate the noise with the keyboard/mouse no USB 2.0 ports, and with the ODAC on any of the 3.0 ports.
> 
> ...


 
 That seems like a valid theory to me. AFAIK the mainboard have different chipsets for USB2.0 and USB3.0


----------



## MrMateoHead

williamleonhart said:


> That seems like a valid theory to me. AFAIK the mainboard have different chipsets for USB2.0 and USB3.0


 

 Indeed - I need to revise the theory as my prior post was written sloppily.
  
 So, 2 USB 3.0 ports, front, connected to the MB header.
  
 4 USB 3.0 ports, rear.
 2 USB 2.0 ports, rear.
  
 So far, keeping the ODAC on its original USB 3.0 port, and connecting the "new" mouse to the adjacent USB 3.0 port, with a keyboard attached to the USB 2.0 port has seemed to be a solution to my problem, which is that the ODAC is producing a constant clipping / static that increases with volume. Since this has been working, I have not bothered to investigate further.
  
 When I had left both the mouse and keyboard attached to the USB 2.0 ports, with the ODAC on any of the remaining USB 3.0 ports, I would hear static / clipping.
  
 But then it dawned on me that I had heard the issue on my laptop, which has 2 USB 2.0 ports + 1 eSata / USB combo port. It also runs Windows 10. The ODAC was misbehaving on that computer as well, which had me thinking there was something wrong with my ODAC.
  
 It also dawned on me that Windows 10 has been buggy since I first started using it months ago (e.g., the mysterious 'self-booting' computer bug, the need to uninstall/reinstall drivers to get them to work). I'm willing to bet that there is something going on with their USB drivers, but I can't "control" which drivers are in use as Windows is now auto-updating, using "generic" drivers and so forth. I could, if I detect an issue again, try to uninstall the generic 2.0 drivers or the 3.0 driver but of course I lose my mouse and keyboard lol. I will monitor this problem but miss the days of windows 7 when everything just worked as it should.


----------



## Nachash

Which gains should I use for the K701?


----------



## jimbop54

Can the Burson V5-D op amps be installed in the JDS labs O2/ODac combo?


----------



## drteming

jimbop54 said:


> Can the Burson V5-D op amps be installed in the JDS labs O2/ODac combo?


 
  
 It's a DIP-8 package so it should fit and the specs seem fine. Physically, you won't be able to get it back in its original case as the Burson is 29mm tall, which is as tall as the entire case.  Also the O2 is a dual stage design with one gain opamp (NJM2068) and 2 output opamps (NJM4556), so you are looking at 3 at $70 per pop.  The O2 was designed around opamps.  If you want a discrete amp, just get a discrete amp.


----------



## WilliamLeonhart

WOW I DID NOT KNOW THE O2 USED OPAMP
  
 This changes everything!


----------



## schmalgausen

Have anyone compared ODAC with HiFiME products?


----------



## WilliamLeonhart

schmalgausen said:


> Have anyone compared ODAC with HiFiME products?


 
 Did. Big nope. If you won't get to 350/400 USD then the ODAC is best sound you can have.


----------



## Rado2

nachash said:


> Which gains should I use for the K701?


 

 This depend on your input level.
  
 If your input level (source) is 2.1V RMS (like in the ODAC combo) you should not go over x3.33 gain (if I remember O2 tops near 7V).
 For your K701, which are 105dB/V this mean... 115dB I think... Anyway, its enough to overload your ears or even burn the phones (they are rated 200mW).
  
 If your source is low, like 0.775V you have to increase the gain correspondingly. If you buy O2 from store, they can help you decide.
  
 Very common setup is to have 1 and 3.33 gain I think. I see this on many places and mine is like that too.
  
 For example I have HD700 which are harder to drive than k701, and my source is the ODAC, I use only the x1 gain and very, very rare turn over the half of the knob.


----------



## raoultrifan

Hi, 
  
 My ODAC has 1.92 V RMS @ 1 KHz, measured with my scope, in case it helps.
  
 Cheers!


----------



## rizzotti91

Hello, I've a question about the O2. If I buy the "mobile version", can I use it plugged in the power source? If yes, will the battery deteriorate?


----------



## Jiexi

rizzotti91 said:


> Hello, I've a question about the O2. If I buy the "mobile version", can I use it plugged in the power source? If yes, will the battery deteriorate?


 
 Yes, and yes. You can't avoid battery degradation. Battery should be replaceable, so no worries.


----------



## barontan2418

Hi. Just wondering if the O2 has any built in protection to cut off charging when the batteries are fully charged. Reason I'm asking is I accidentally left the charger in overnight and the batteries were flat today when I tried using the amp? And batteries are not that old.


----------



## Jiexi

barontan2418 said:


> Hi. Just wondering if the O2 has any built in protection to cut off charging when the batteries are fully charged. Reason I'm asking is I accidentally left the charger in overnight and the batteries were flat today when I tried using the amp? And batteries are not that old.




Battery charge protection circuits are pretty standard. Were you charging from a wall port? It almost sounds like you were charging with an usb battery, the usb battery ran out of charge, and started draining power back from the O2.


----------



## barontan2418

jiexi said:


> Battery charge protection circuits are pretty standard. Were you charging from a wall port? It almost sounds like you were charging with an usb battery, the usb battery ran out of charge, and started draining power back from the O2.



Hi. No I was charging using the normal AC adapter from the mains. Giving it another go now. Thanks for your reply.


----------



## WilliamLeonhart

Does anyone here roll opamps on the Objective2? From what I understand, it seems that the U2 opamp won't affect sound quality, the U3 and U4 opamp will be used for low-gain and the U1 will be activated in high-gain. Is it true? If not, please correct me. Cheers.


----------



## raoultrifan

Many of us swapped opamps in O2, so feel free to search inside this thread about it. Now, depending on what you need to gain, the original opamps are the best price/value possible and they also have a very good THD and a very low-noise, so by using the original opamps you can be sure that O2's background will be really "dark".
  
 For me, using Burson SS V5 in voltage amplification stage improved soundstage, details and musicality (http://www.head-fi.org/t/616331/o2-amp-odac/4965#post_12382477), but I did some other mods to my O2 as well (http://www.head-fi.org/t/616331/o2-amp-odac/4905#post_12282731).


----------



## WilliamLeonhart

raoultrifan said:


> Many of us swapped opamps in O2, so feel free to search inside this thread about it. Now, depending on what you need to gain, the original opamps are the best price/value possible and they also have a very good THD and a very low-noise, so by using the original opamps you can be sure that O2's background will be really "dark".
> 
> For me, using Burson SS V5 in voltage amplification stage improved soundstage, details and musicality (http://www.head-fi.org/t/616331/o2-amp-odac/4965#post_12382477), but I did some other mods to my O2 as well (http://www.head-fi.org/t/616331/o2-amp-odac/4905#post_12282731).


 
  
 Thanks for the tips.
 Right now my O2 look like this: 

 I have not tried switching the V5i to voltage gain yet, so I don't know how great it can improve the sound. But so far I'm enjoying this special "Burson O2" greatly. One certain thing that can be praised is the bass. My K7xx sound much fuller than before and on some songs it can reach basshead levels. Details retrieval is good and soundstage is spacious. The inherent "dry" trait of the O2 is no where to be found, although the change is actually subtle.


----------



## raoultrifan

It looks great, now you need to find a way to fit all these opamps inside the original case. Maybe 90 degrees angled adaptor for the SS V5 opamp? You should leave the SS V5 in VAS, as I really don't think V5i would sound better than SS V5, at least not in this scenario. 
  
 Also, max. power output would be a little bit lower with V5i in buffer stage, at least when low-impedance headphones are be used.


----------



## WilliamLeonhart

Pardon my very limited knowledge on this, but how would I know which opamp will be more suitable for low/high impedance headphones? And while we're at it, how will sensitivity factor in this?


----------



## thuNDa

hey guys, don't wanna hold back this mod i did to my O2(desktop version). 
	

	
	
		
		

		
			




  
 It's a meier crossfeed filter with bypass and high/low switch:
  

  

  
  
 I mainly use the "high" setting, which brings relaxed listening to another level, even with 60's stereo recordings.


----------



## MrMateoHead

Still no solution to my crackling, distorting ODAC
  
 After the problem had gone away for a brief period, it returned with a vengeance. I did a round of driver deletions / updating and nothing is working.
  
 Is there a reason that Windows 10 should have broken my ODAC, or is it possible the thing is failing?
  
 I did notice that a Driver for Intel(R) USB 3.0 eXtensible Host Controller 1.0 (MSFT) was installed on 3/28/2016. It is version 10.0.10586.212. I can't roll the driver back, and re-installing it did not help. I have a feeling this "automatic update" might've been my culprit. 
  
 I could use some help - I miss my ODAC!


----------



## raoultrifan

williamleonhart said:


> Pardon my very limited knowledge on this, but how would I know which opamp will be more suitable for low/high impedance headphones? And while we're at it, how will sensitivity factor in this?




The original NJR/JRC4556 opamps can deal with 150mA per channel while being paralleled. If you don't intend to use 32-50 ohms planar headphones you should be fine with the V5i in output buffer stage. Anyway, it worth checking if V5i opamps are warm or hot after 1-2 hours of intensive listening.


----------



## WilliamLeonhart

All of my headphones are dynamic. So far I have not found any problems with the v5i serving as buffers. However it's worth noting that when no headphones are connected to the amp and it's on, the two opamps would heat up dramatically.


----------



## raoultrifan

Get a scope and check for oscillations, O2's designer stated on his blog that some opamps may oscillate. If you can't get a scope I suggest you to replace V5i from output buffer with original 4556 opamps and keep the SS V5 dual in VAS.

I've tested myself with a scope the SS V5 dual in VAS and I had no oscillations; also, sound was more detailed and more spacious.


----------



## cityle

I don't have any problem on my side with Windows 10. But did you tried to switch the usb cable of place betweens usb 3.0 and 2.0 usb ports?


----------



## MrMateoHead

cityle said:


> I don't have any problem on my side with Windows 10. But did you tried to switch the usb cable of place betweens usb 3.0 and 2.0 usb ports?


 

 Ya - The problem follows all the ports, 2.0 to 3.0. I've tried different USB cables as well.
  
 A recent update by Windows brought the version of the USB host to (Intel) 10.0.14393.0
  
 I had tried the ODAC on a different computer with the same result. I has performed flawlessly until recently. Only the L Channel seems affected. Do these things ever fail or something? Mine is only about 2 years old.


----------



## adydula

I would think the ODAC would last for a very long time....but stuff happens...would have to be some kind of voltage surge, but thats rare here....if the odac was dropped or some kind of mechanical damage...could be just a bad solder joint that over age if "cracked' might have oxidized and is causing this wierd failure. You need to get a second ODAC to see if it works to rule out anything else for sure...
  
 Alex


----------



## MrMateoHead

The only way I can get a second ODAC is to buy a second ODAC, and that would be a last resort.
  
 I heard the crackling on a laptop I have kicking around as well, but I will try my brothers to see if I get better luck.


----------



## WilliamLeonhart

I sold my first ODAC to a fellow local audiophile and the first thing he did was to break the black thingy on the lower right in the picture (that is marked "L100"). Some how a part of it got sliced off. He told me he heard crackling sound as well. 
 So accidents can happen and have happened some where. If the crackling was not consistent, I'd suspect it is due to clipping or overflown buffer. But that doesn't seme to be the case in your problem.


----------



## tkddans

mrmateohead said:


> The only way I can get a second ODAC is to buy a second ODAC, and that would be a last resort.
> 
> I heard the crackling on a laptop I have kicking around as well, but I will try my brothers to see if I get better luck.


 
 Do you think it's a usb connection issue? What if you tried Schiit's Wyrd? $100 is a pretty steep price to pay for troubleshooting a $250 device, but you can return the Wyrd within 15 days or keep it anyway since it can help prevent future USB issues if they come up.
  
 And some people claim Wyrd improves the sound, I guess. I have one and don't notice a difference but oh well.


----------



## jseaber

mrmateohead said:


> The only way I can get a second ODAC is to buy a second ODAC, and that would be a last resort.
> 
> I heard the crackling on a laptop I have kicking around as well, but I will try my brothers to see if I get better luck.


 
  
 Sorry in advance if this was already shared earlier. Are you listening to an ODAC, or ODAC RevB?
  
 PM your order # and I can help out. The ES9023 is known to fail on up to 1% of the original ODACs, confirmed by ESS Q/C. We've repaired all brought to our attention.


----------



## MrMateoHead

tkddans said:


> Do you think it's a usb connection issue? What if you tried Schiit's Wyrd? $100 is a pretty steep price to pay for troubleshooting a $250 device, but you can return the Wyrd within 15 days or keep it anyway since it can help prevent future USB issues if they come up.
> 
> And some people claim Wyrd improves the sound, I guess. I have one and don't notice a difference but oh well.


 
  
 What baffles me is that the device has worked flawlessly on my computer until after I switched to Win 10, which has been buggy, no doubt (I re-installed Realtek audio and networking after the upgrade as both weren't working).
  
 I thought I had "fixed" the problem by deleting / reinstalling the USB driver and I went ahead and attacked some others as well. The problem subsided, and then returned. My laptop recently had a major update and I tried the ODAC on it - exact same issue. Static / noise in the L Channel, which can be drowned out with volume to a point but is always there. Unless I have developed a major USB-Audio specific bug on two computers at approximately the same time, I suspect a hardware fault.


----------



## MrMateoHead

jseaber said:


> Sorry in advance if this was already shared earlier. Are you listening to an ODAC, or ODAC RevB?
> 
> PM your order # and I can help out. The ES9023 is known to fail on up to 1% of the original ODACs, confirmed by ESS Q/C. We've repaired all brought to our attention.


 

 Thanks John - I'll find the order and PM.


----------



## raoultrifan

Hi guys, will just copy-paste my thoughts from http://www.head-fi.org/t/784790/burson-supreme-sound-audio-v5-opa-d-v5-opa-s-review/120#post_12800983, in case you're interested in getting all the "juice" from our beloved Objective2 headamp.
  
 Hope you remember my post regarding O2 and SS V5-dual from here: http://www.head-fi.org/t/784790/burson-supreme-sound-audio-v5-opa-d-v5-opa-s-review/90#post_12384936. I did some "wiring" this evening and I was able o fit the Burson beast inside the O2, but I needed to remove the batteries (didn't needed anyway).
 ​ 
​​
  
 Gosh, sound is amazing and I can't believe that I am actually recommending an op-amp that costs about 50% the price of the O2. Anyway, the Objective2 headamp sounds three times the money it costs, perhaps this is why so many people is still purchasing it and with a Burson V5-dual placed in Voltage Amplification stage I get an increased soundstage and more details on top of a neutral sound.
  
 P.S.: Hope you'll be able to find a 90 degree adapter, because doing this wiring inside O2's case might get you into troubles if you're not paying attention!


----------



## WilliamLeonhart

raoultrifan said:


> Hi guys, will just copy-paste my thoughts from http://www.head-fi.org/t/784790/burson-supreme-sound-audio-v5-opa-d-v5-opa-s-review/120#post_12800983, in case you're interested in getting all the "juice" from our beloved Objective2 headamp.
> 
> Hope you remember my post regarding O2 and SS V5-dual from here: http://www.head-fi.org/t/784790/burson-supreme-sound-audio-v5-opa-d-v5-opa-s-review/90#post_12384936. I did some "wiring" this evening and I was able o fit the Burson beast inside the O2, but I needed to remove the batteries (didn't needed anyway).
> ​
> ...


 
 Hey Raoul,
 High-five from Singapore!


----------



## raoultrifan

I've seen your mod recently and I love it! You should probably buy a taller case to accomodate the new op-amps.
BTW, don't try Hifiman planars unless you can measure output opamps temps in "real time". I've seen a couple of people here on Head-Fi with "exploded" NJM4556 when high power was used to drive planars.
Also, can you please measure DC output voltage?

Regards,
Raul.


----------



## dukefx

raoultrifan said:


> I can't believe that I am actually recommending an op-amp that costs about 50% the price of the O2.


 
 50% more than the O2 you mean. It's about 180$ unless I was looking in the wrong place.


----------



## raoultrifan

You could check BURSON's website, I see it's about 70 USD each V5 dual. If you look further to eBay you can find a pair of V5 duals at the price of about 83 USD + shipping from DE (most likely samples from BURSON).
  
 P.S.: My "modded" O2 should cost over 150 USD, because it has back power plug, 6.3mm + 3.5mm output headphone plugs, RCA gold plated plugs for input etc. So, it deserves a V5 dual I'd say.


----------



## dukefx

I have the swiss desktop version with power and RCA inputs/outputs at the back and no battery slots, but I'm not a big fan of wires.
  
 As for the price: you are right, it's 85$ directly from Burson incl. shipping.


----------



## raoultrifan

I'm not a fan of wires myself, buy this is why I was using my scope, to test if there are some oscillations or any other suspicious signals (I couldn't find anything suspicious, so I closed O2's case with the BURSON SS V5 dual inside).
  
 Anywyay, now I'm waiting for the V5i to get'em shiped so I can test one in O2's VAS. I've seen headfiers saying that the sound is about the same as SS V5. Also, V5i is cheaper than the original V5, so for low-heigt cases this should be a very good choice for audiophiles/modders .


----------



## dukefx

According to reviewers the V5i has an inferior sound stage compared to the V5, but I'm still quite curious.


----------



## raoultrifan

http://www.head-fi.org/products/burson-audio-supreme-sound-opamp-v5i - some say it's about the same sound as V5, some say soundstage is better for the V5, but I really believe it depends on what DAC/amp you're using to do the test. I'm looking further to receive my V5i and give'em a spin, though I'm pretty sure it will be very difficult for me to get the differences between V5 and V5i in my setup.


----------



## Sunrider6

Hi there,
  
 I have just finished building my O2 amp, as well as putting my Odac in there, using the "method 2", that consist of cutting 2 traces of the input jack, to be able to still use the input jack of the O2.
 I bought the full kit, as well as the Odac, from www.headnhifi.com. (really good service, I highly recommend buying from them !). 
 (It was my first DIY project ^_^)
  
 It work really great, but I have a "small" issue with it.
 I have a "hum" noise when I put my fingers on the aluminum closure.
 Hopefully, when I don't lay my fingers on it, it's stay silent. Same if I only use the volume knob, silent. 
  
 Is there something I can do about this issue ?


----------



## raoultrifan

Hello, 
  
 I also bought my ODAC and my O2 kit from Walter and I was happy with my purchase. I recommend you to triple-check if you cut the correct wires and if the aluminum case is correclty connected to GND plane. Also, you may try grounding the pot knob as well; just use a decent ohm-meter to check if correclty grounded.
  
 Regards, 
 Raul.


----------



## Sunrider6

I didn't connected the aluminum case to the GND plane at all, so maybe it's the issue ^_^
 I will try it in a couple of hours or tomorrow.
  
 Thank you for trying to help, it's appreciated


----------



## raoultrifan

Taken from  https://www.jdslabs.com/products/34/machined-objective2-front-panel/ :
  
 "Attach ground wire to input jack of Objective2 PCB.
 Attach front panel to enclosure. Securely wrap ground wire between front panel and case."
  
 More details from the original O2's blog: "_If you hear hum with the O2 running on AC power make sure the case is grounded as documented in the next section"._
  
 Good luck, 
 Raul.


----------



## escalibur

Is anyone of you having such an issue with ODAC O2 RevB and Sennheiser HD650s where ''high gain' setting is causing some strange noise even at 9 o'clock setting?
  
 For example in this song:
  

  
 Another sample (during chorus' drum bass hits)
  
 https://open.spotify.com/track/0LbaxqqbUVE1kANizaaL0F (Official music video has some thunder effects so I didn't link a YouTube video for this one)
  
 I've tested with Spotify and some other songs too. Same issue. Low gain setting is not causing this but I'm still not sure is this more of a 'feature' than an actual problem?
  
 ps. I didn't had this issue with my previous combo Audinst HUD-mx1.


----------



## bada bing

Likely your amp is clipping. It is a well known design trade off of the O2. Either you need a source with less voltage swing or use low gain. The O2 clips from too high an input voltage for the gain used, not from the volume output.


----------



## thuNDa

@escalibur
  
 try setting the digital volume lower to 50% or so(either in windows, or in the player), and see if the problem persists.
 If no = see post above, if yes = something else is going on.


----------



## MrMateoHead

escalibur said:


>


 
 Escalibur -
  
 WHAT is the source going in to the O2, and what gain settings does it have? (2.5X or 6.5X) or is it (1X and 3.3X)? Or is it (1X or 2.5X)?
  
 IF you are using a 2V source, you are not supposed to use more than a 3X gain. 6.5X is for sources with 1V or less. If you use a source with 2V or more and high gain in excess of 3X, you are most definitely clipping. That would be normal, for mismatching gain / input voltage. 
	

	
	
		
		

		
			





 If it is not making bad noises at 2.5X, that is the setting I would use - save high gain for your MP3 player or phone.
  
 BTW it can also sometimes be that you are hearing clipping in the recording itself. I haven't listened to Contiuum in awhile, but it sounds the same embedded in the recording as it does on the electronics.
  
 My understanding is that the ODAC rev B has slightly higher output volage - 2.1V vs. 2.0V for the original ODAC.


----------



## escalibur

thunda said:


> @escalibur
> 
> try setting the digital volume lower to 50% or so(either in windows, or in the player), and see if the problem persists.
> If no = see post above, if yes = something else is going on.


 
  
 Thanks for the idea. I've tested and no noise at all.
  


mrmateohead said:


> Escalibur -
> 
> WHAT is the source going in to the O2, and what gain settings does it have? (2.5X or 6.5X) or is it (1X and 3.3X)? Or is it (1X or 2.5X)?
> 
> ...


 
  
  
 The source is my motherboard Asus Ranger VII with USB 3.0 (Intel controller). I'm using Windows 10 64bit with disabled all sound enhancements, 24/96k and volume at 100%.
  
 For playing music mostly Spotify Premium but that should be good enough in this case.
  
  
 Continuum can indeed be tricky for this testing because some songs definitely have some mixed noise or whatever effects in them.


----------



## MrMateoHead

escalibur said:


> Thanks for the idea. I've tested and no noise at all.
> 
> The source is my motherboard Asus Ranger VII with USB 3.0 (Intel controller). I'm using Windows 10 64bit with disabled all sound enhancements, 24/96k and volume at 100%.
> 
> ...


 
  
 Hi there - Contiuum looked "clean" under audacity, even in Mp3, so that can't be the noise you were hearing. Unless the noise is a feature of the music (probably is!), it is coming from something else. Better to see if you can find other recordings that either definitely use static sources (like Hip Hop), or are definitely pristine (like some Jazz or classical recording) to compare results. Just because the file isn't clipped when I look at it (usually from excess compression), doesn't mean that some waveforms in there aren't clipped.
  
 Most Motherboards do not, I think, put out more than about 1V, so your source is "weak" in the sense that 2V is the typical standard in the Audio world. That said, the original O2 was designed to be optimized for a 2V source at no more than 2.5X gain. So, with a 2.1V source, anything beyond 2.5X would definitely be enough to clip it, I would think. Anyway you could plug the motherboard straight into the O2 to listen for the noise. My guess is you wouldn't be able to clip the amp, but you might not hear the static either, unless the fidelity of the motherboard was good.
  
 But I've confused myself - you are using the O2 / ODAC rev B correct? If that is the case the Motherboard Audio outputs aren't relevant since the ODAC rev B is handling the audio feed.


----------



## escalibur

mrmateohead said:


> Hi there - Contiuum looked "clean" under audacity, even in Mp3, so that can't be the noise you were hearing. Unless the noise is a feature of the music (probably is!), it is coming from something else. Better to see if you can find other recordings that either definitely use static sources (like Hip Hop), or are definitely pristine (like some Jazz or classical recording) to compare results. Just because the file isn't clipped when I look at it (usually from excess compression), doesn't mean that some waveforms in there aren't clipped.
> 
> Most Motherboards do not, I think, put out more than about 1V, so your source is "weak" in the sense that 2V is the typical standard in the Audio world. That said, the original O2 was designed to be optimized for a 2V source at no more than 2.5X gain. So, with a 2.1V source, anything beyond 2.5X would definitely be enough to clip it, I would think. Anyway you could plug the motherboard straight into the O2 to listen for the noise. My guess is you wouldn't be able to clip the amp, but you might not hear the static either, unless the fidelity of the motherboard was good.
> 
> But I've confused myself - you are using the O2 / ODAC rev B correct? If that is the case the Motherboard Audio outputs aren't relevant since the ODAC rev B is handling the audio feed.


 
  
  
 Thanks for the analysis. Yes I'm using RevB and it is plugged straight into my MB to USB 3.0 port. Intel's controller which should be the best if not the best available in my case. I'm using Windows 10 native USB drivers because I'm not sure are there any better versions even available.
  
 I will try to find some hip hop music to test this even more. So far John Mayer's and Carrie Underwood's songs definitely caused some noise on my cans. :/
  
 I will test even with this song. It has some quite 'scary' bass tracks.


----------



## MrMateoHead

escalibur said:


> Thanks for the analysis. Yes I'm using RevB and it is plugged straight into my MB to USB 3.0 port. Intel's controller which should be the best if not the best available in my case. I'm using Windows 10 native USB drivers because I'm not sure are there any better versions even available.
> 
> I will try to find some hip hop music to test this even more. So far John Mayer's and Carrie Underwood's songs definitely caused some noise on my cans. :/
> 
> I will test even with this song. It has some quite 'scary' bass tracks.


 
  
 OK that helps. Frankly, I think you are clipping the O2 by running 2.1V into it + High Gain. Any reason you feel the need to run your headphones that way? FYI 9 O'Clock is a tad low on the dial - running lower gain, you avoid clipping + can definitely get out of possible channel imbalance territory on the volume dial.
  
 In short use low gain!


----------



## WilliamLeonhart

escalibur said:


>


 
 I would concur with the others that this is caused by clipping. Had it on my old Mayflower O2 ODAC. It's a very lousy decision to build into the product something that you (should) know would cause trouble. So yes it's a "feature" that will result a bug.
 Can you specify what make is your O2 ODAC and what is the hi-low gain setting (2.5x/6.5x?) I think the O2 would clip at around 3.5x when driving demanding cans. IMO none of the O2 builds I tried could drive the HD650/HD600 effectively. My first one is only 1x/3x and on hi-gain the volume was not adequate.


----------



## castleofargh

williamleonhart said:


> escalibur said:
> 
> 
> >
> ...


 
  I measure about 0.2Vrms at the output of my O2 right now and that's fine for me while I use replay gain on my music. that gets me at close to 80db more or less at 1khz on my hd650. I get digital peaks around -10/-12db for most songs from replay gain with my settings(not all songs obviously, but it's often in that ballpark for digital peaks with my settings). I know that I'm not a loud listener, when it's late and quiet at night I'm around 50-60db loud and I enjoy that. still, with replay gain, I can get close to 100db with my music on gain 1 and the pot maxed out on the hd650. that's loud for me, I would need to be drunk and screaming the song out of my lungs to justify louder personally. but then again if I was drunk I probably wouldn't care to piss off the neighbors with my speakers instead of using my headphone.
	

	
	
		
		

		
		
	


	



 and gain 3X is close to +10db added to whatever I just talked about up until now, that's about twice as loud.
 so my hypothesis for your volume not being adequate with the 3X gain, is that your computer never was at maxed output for some reason, or that you might want to start worrying about your ears. I would expect most people to be very fine with gain 1 on the hd650.


----------



## WilliamLeonhart

I never measured mine so I can't know for sure, but I can be sure that my computer was at max volume (why would I touch the volume there?) and it wasn't just me that could not get enough volume from the o2+odac driving hd600/hd650. Gave it to a few friends that own the Senns and they all said the same. So it could be that I remember the wrong gain level on that one O2 (it was diy). But even with some O2 that could give enough volume, the sound was disappointing, in comparison to the Lovely Cube for example. The sound has every trace of bad synergy, like bass that don't have oomph or trebels that is very dull. Not to say that the o2 odac is bad because I stick with them for years before moving onto the $500 price range this last winter, but I think it's not the omnipotent amp/dac that people would want to believe. Anyway now I do have another diy O2 with upgraded opamps to try, but I have not laid my hands on another hd600 yet


----------



## dukefx

Almost every HD600 reviewer complains about the lack of (sub)bass and sluggish speed. Of course there isn't much oomph. Don't blame the amp for that. As far as I know the HD600s are fairly easy to drive. Anything providing more juice than a standard onboard soundcard should do the trick.


----------



## escalibur

mrmateohead said:


> Any reason you feel the need to run your headphones that way?


 
  
 Mostly out of curiousity is this 'normal' behaviour of my ODAC and HD650s or not. I can live with low gain setting just fine. I don't go over 12 almost at any point. Sometimes when I hear some crazy good song I might give them a shot at 1-2 or too but I couldn't stand that loudness for any longer.


----------



## MrMateoHead

escalibur said:


> Mostly out of curiousity is this 'normal' behaviour of my ODAC and HD650s or not. I can live with low gain setting just fine. I don't go over 12 almost at any point. Sometimes when I hear some crazy good song I might give them a shot at 1-2 or too but I couldn't stand that loudness for any longer.


 
 I see! 
	

	
	
		
		

		
		
	


	



  
 Playing around is certainly a good way to learn. I find that my O2 at 2.5X is TOO MUCH for my more sensitive headphones (I can barely stand 9 O'Clock). My much less efficient HE-400s live around 9-1 O'Clock depending on song, mood, and so on.
  
 That said, I haven't yet had the nerve to chop the gain down to 1.0X / 2.5X, which would probably be a lot better for a wide range of very efficient / moderately efficient headphones.
  
 Anyway - in the future don't intentionally clip your amps! You risk damage to them or your speakers. Enjoy the O2, it is a great little amp.


----------



## Nachash

mrmateohead said:


> You risk damage to them or your speakers.


 
 Worse, your ears


----------



## WilliamLeonhart

dukefx said:


> Almost every HD600 reviewer complains about the lack of (sub)bass and sluggish speed. Of course there isn't much oomph. Don't blame the amp for that. As far as I know the HD600s are fairly easy to drive. Anything providing more juice than a standard onboard soundcard should do the trick.


nah. I can hear the difference between a well amped HD600 and a not-so-well amped HD600. Just because you have enough volume doesn't mean the cans are being driven to their full potential. After all there's a reason people pay a few hundred bucks to buy an amp for headphones like the ad2000 or the grado ps1000


----------



## adydula

I beg to differ.....I would like to do a blind AB test with you ......I have done many and its very humbling when you cant reliably tell the difference between a $100 good amp and a $1000 good amp.
 Alex


----------



## dukefx

williamleonhart said:


> nah. I can hear the difference between a well amped HD600 and a not-so-well amped HD600. Just because you have enough volume doesn't mean the cans are being driven to their full potential. After all there's a reason people pay a few hundred bucks to buy an amp for headphones like the ad2000 or the grado ps1000


  

 So, you are saying that a Schiit Vali, Apogee Duet, Schiit Lyr 2, Woo Audio WA6, uDAC, Beyerdynamic A1, Sansa Clip+, LH Labs Pulse Infinity etc. etc. etc. can't drive them properly? Those are just the ones from reviewers who bothered to mention their amp. They all complained about the lack of (sub)bass. Some of these are quite pricey. In case of the O2 you only pay for parts and assembly. No marketing and no research costs to cover. Take your own amp for example. The DIY clone costs roughly 150$, the original Lehmann not-so-linear-as-they-claim amp costs a hell of a lot more.


----------



## WilliamLeonhart

Obviously no. I wasn't meaning to say that the amps you listed can't drive the hd600 fully. In fact I have not heard all of them. What I was trying to say is plain and simple: 





williamleonhart said:


> nah.* I can hear the difference between a well amped HD600 and a not-so-well amped HD600. Just because you have enough volume doesn't mean the cans are being driven to their full potential. *After all there's a reason people pay a few hundred bucks to buy an amp for headphones like the ad2000 or the grado ps1000




And I would like to disagree here is that the odac and o2 aren't the omnipotent amp/dac people would like them to be. Yes they are great but there's a difference when you use the Lehmann not-so-linear and the o2 to drive cans like hd600 and hd650. Homestly though the hd600 remains the hd600 in any circumstance (hen the lack of sub bass you mentioned), if you have actually heard all those amps you listed you would know it will sound at least a bit different on each amp, especially on tube amps. There will be a different when you used a Mullard tube as opposed to a GE JAN on tube amps. 

Would you like to say that just because the Macbook gives you enough volume on the hd600 then it's "easy to drive" and thus there's no need to buy amps like Vali2 or WA6 too? At all? Then what's the point of the O2? If the O2 is so omnipotent, why are all the amp makers still in business?


----------



## thuNDa

It's not like those amps(with their 5 Watt or w/e max. power) which are supposed to drive the HD650 to their full potential, will bring more volts/ampere/watt into the headphones once you dial down the vol. pot to the desirable listening volume.
 So what "drives" them then?


----------



## dukefx

Let me try to explain what's happening here. You have a slightly bassy amp and you combine it with headphones that slightly lack bass and you get -1 +1 = 0. Tadaaaaa! With the O2 it's -1 + 0 = -1.
  
 I will agree with you that the O2 and ODAC aren't the creme de la creme. The O2 has 2 known minor issues and it won't drive the absolute hardest to drive headphones, but all amps have their flaws. The ODAC doesn't support anything above 24bit/96kHz for compatibility reasons (not that I'd have anything higher than that, most of the time it's 16 bit 44kHz or 48kHz), but the combo is relatively cheap for what it provides.


----------



## headwhacker

williamleonhart said:


> Obviously no. I wasn't meaning to say that the amps you listed can't drive the hd600 fully. In fact I have not heard all of them. What I was trying to say is plain and simple:
> And I would like to disagree here is that the odac and o2 aren't the omnipotent amp/dac people would like them to be. Yes they are great but there's a difference when you use the Lehmann not-so-linear and the o2 to drive cans like hd600 and hd650. Homestly though the hd600 remains the hd600 in any circumstance (hen the lack of sub bass you mentioned), if you have actually heard all those amps you listed you would know it will sound at least a bit different on each amp, especially on tube amps. There will be a different when you used a Mullard tube as opposed to a GE JAN on tube amps.
> 
> Would you like to say that just because the Macbook gives you enough volume on the hd600 then it's "easy to drive" and thus there's no need to buy amps like Vali2 or WA6 too? At all? Then what's the point of the O2? If the O2 is so omnipotent, why are all the amp makers still in business?


 
  
 How do you quantify driving a can to "full potential"? just because you like how it sound with one amp doesn't mean other amps is inadequate to drive the particular can. For all we know it's just your personal bias/preference with that particular amp and has nothing to do with the actual ability of the amp to drive a can.


----------



## headwhacker

dukefx said:


> Let me try to explain what's happening here. You have a slightly bassy amp and you combine it with headphones that slightly lack bass and you get -1 +1 = 0. Tadaaaaa! With the O2 it's -1 + 0 = -1.
> 
> I will agree with you that the O2 and ODAC aren't the creme de la creme. The O2 has 2 known minor issues and it won't drive the absolute hardest to drive headphones, but all amps have their flaws. The ODAC doesn't support anything above 24bit/96kHz for compatibility reasons (not that I'd have anything higher than that, most of the time it's 16 bit 44kHz or 48kHz), but the combo is relatively cheap for what it provides.


 
  
 So you are like referring to an amp like a hardware eq?
  
 What exactly minor issues you are referring to?


----------



## dukefx

headwhacker said:


> So you are like referring to an amp like a hardware eq?
> 
> What exactly minor issues you are referring to?


 
 Well, some amps tend to have a sound signature of their own, call it flavor if you like. It's not exactly like an EQ.
  
 Minor flaws: Stereo imbalance when the knob is almost at min. The other being the input voltage, you gotta be careful with that. It can't handle more than 2.8V and you have to adjust your gain resistors accordingly. There is no circuit that does that for you.


----------



## headwhacker

dukefx said:


> Well, some amps tend to have a sound signature of their own, call it flavor if you like. It's not exactly like an EQ.
> 
> Minor flaws: Stereo imbalance when the knob is almost at min. The other being the input voltage, you gotta be careful with that. It can't handle more than 2.8V and you have to adjust your gain resistors accordingly. There is no circuit that does that for you.


 
  
 Call it a flavor, signature or whatever but it's still what eq does. Remember, O2 was designed to be a wire with gain amp. Or call it flavorless. What you hear is very close if not exactly how the source sounds like from a particular headphone.
  
 Being a DIY amp I fail to see why you consider it as a flaw. True not everyone wants the option but. this is actually a plus. If you read the designers blog the original prototype doesn't have a gain switch. So it's up to you to match the resistors with the output of your source.
  
 In the end having a gain switch allows you to consider at least 2 sources to maximize O2's output. I have 2 O2s with 4 different gain settings to accomodate any source I have and not to worry about clipping.


----------



## dukefx

One O2 is enough for me


----------



## adydula

Some of you guys are absolutely silly...some of you have forgotten the original design goal of the O2 and the ODAC. Design an amp with low cost, least amount of parts, parts that dont cost a zillion dollars, and with meaningful specs that when met are a giant step towards a device that is totally transparent. It can drive 98 of the headphones out there with authority. It met its design goals well. Minor issues with very low pot imbalance is a 'nit'. 
  
 I have AB it with 6 + watt amps and with tube and a wide variety of botique amps costing a whole lot more that an assembled O2.
 None sound any better than the oiriginal O2. When I do an AB test, blind!! The people that think they can hear vast differences are humbled more often than not.
  
 That said if you feel the need to spend lots of money for a 1/4 thick aluminum chassis, big heavy power supplies etc have at it...
 Its your money,
  
 If you are trying to add bass to a set of transducers that can not reproduce that bass, your really trying to do something IMO that ie really well kind of "stupid". An amp should add nothing to the input signal, but some amps not well designed do alter the signal to some extent. This to me is not good at all. It violates the totally transparent design goals of the O2. 
  
 WIth so many variables in the playback chain, I dont want an amp that adds anything to the input signal, This way I can better evaluate the source material and the playback of the transducers.
  
 I would rather have an amp that is neutral than chase an amp that might affect the sound in my headphones because of a design issue with them..
  
 A.


----------



## headwhacker

adydula said:


> *I would rather have an amp that is neutral than chase an amp that might affect the sound in my headphones because of a design issue with them..*
> 
> A.


 
  
 I don't understand why some people need multiple amps with one headphone. I would rather have a single amp/DAC and have multiple headphones/transducers.


----------



## upstateguy

williamleonhart said:


> nah. I can hear the difference between a well amped HD600 and a not-so-well amped HD600. Just because you have enough volume doesn't mean the cans are being driven to their full potential. *After all there's a reason people pay a few hundred bucks to buy an amp for headphones like the ad2000 or the grado ps1000*


 
  
 Sure there's a reason.


----------



## WilliamLeonhart

The thing is I'm not against the O2 or the fact that it's transparent. Or neutral. 

But how would you define "transparent"? I could hear a fuller sound from the HD600 driven by HDV800 or idsd micro, Chord Mojo, Grace m9xx than by the O2. Practically every solid state would use the world "neutral" because it's a buzz word that every "audiophile" (wannabe) loves to hear. 

Sure the O2 is transparent. It's not as colored as tube amp. So if you want to hear transparent the O2 is a good choice for a cheap price. I don't dispute that, so don't say as if I want the O2 to add some bass just so it sounds "well amped" to me. 

Now there's a lot of solid state, "neutral" sounding amps that are going to sound different than the O2 when driving the HD600. Tell me is it silly you consider one of them the benchmark and the other colors the sound? The O2 sounds thin in some cases. Is that "coloring"? Is clipping "affecting the sound"?

And this is from a guy with 4 amps (incl the integrated amps on my DAC) and at the moment, 8 pairs of headphones. Whatever it is, I can be sure that my old Mayflower O2 will clip on high gain. And another of my O2 (brought the board from Jds) could not drive the hd600 adequately- when I say "adequately", I was refering to the sound on my idsd micro and m9xx. The volume at max was not louder than my Macbook Pro. 

And if we can move past the transparent thing, IMO it's stupid to assert that an amp should or should not add anything to the sound. If a transducer "can't " produce some bass then why is it present on, say, a tube amp or the c5d with bass boost on? And it's MY personal liking, why shouldn't I like tube amp just because "neutral" is always the hottest thing in audio?


----------



## raoultrifan

Alex, I totally agree with you and everyone here knows that O2 is a great neutral amp that can drive most headphones out there for a decent amount of money. It's just some people likes the sound a bit coloured or warmer or a bit of more bassy or detailed or maybe an increased soundstage and this is why in A/B tests some of them might find the O2 being a bit to...clinical perhaps or not pairing perfectly with some headphones.
  
 I find my O2 an amp that can be used as reference without any worries for all the headphones I have, but I will not stop trying some of AGDR's mods or swapping the inside opamps, even if there will be not much of a difference between the original O2 and the modded one. Not all of us are hearing the same way (audiograms can prove this) and not everyone of us can perceive the same no. of harmonics, this is why we're called "individuals". Imagine that from a group of 4 individuals (between 30 to 40 years old) I was the only one perceiving an ultrasound insects device from one of my neighbour's house. 
  
*Note*: It has been technically proved that a BJT-input opamp will generate greater odd-order harmonics than a FET-input opamp and audio experts say that human ear likes FET's even-order harmonics better; also, our human memory is around 4KHz so an amp that generates a 2'nd order or 3'rd order harmonic higher with 0.5dB around 4KHz might help for some people; they'll probably say that the mids are clearer and voices are upfront. So indeed, by swapping the opamps or by A/B-ing between different headamps our ears might get some unknown pleasant audio differences, which is perfectly normal, even if on a scope or RMAA tests we can prove that audio signal that comes from signal generators are about identical with its output, just we can't really prove that there're the same number and intensity of harmonics. And there's always placebo effect in some cases, of course. 
  
*P.S.*: BTW, please allow me to make a joke: If we decide here that a 100 USD headamp is an end-game then the audio industry might die soon. Also, this might cease existence of Head-Fi forum and then we're all going to miss all of this fun, right? 
  
*L.E.*: "To the human ear, odd-order harmonics have long been identified as sounding more unpleasant than even-order harmonics. FETs, like vacuum tubes, have a square-law I-V transfer function which is more linear than the exponential transfer function of a bipolar transistor. As a direct result of this square-law characteristic, FETs produce predominantly even-order harmonics" - OPA604 datasheet


----------



## raoultrifan

> [...] And this is from a guy with 4 amps (incl the integrated amps on my DAC) and at the moment, 8 pairs of headphones. Whatever it is, I can be sure that my old Mayflower O2 will clip on high gain. And another of my O2 (brought the board from Jds) could not drive the hd600 adequately- when I say "adequately", I was refering to the sound on my idsd micro and m9xx. The volume at max was not louder than my Macbook Pro.[...]


 
  
 I'm about sure this might be a gain choice issue. Could you please post here what gain settings are you using for both of your O2's?
  
 Thanks!


----------



## HotIce

raoultrifan said:


> I find my O2 an amp that can be used as reference without any worries for all the headphones I have, but I will not stop trying some of AGDR's mods or swapping the inside opamps, even if there will be not much of a difference between the original O2 and the modded one. Not all of us are hearing the same way (audiograms can prove this) and not everyone of us can perceive the same no. of harmonics, this is why we're called "individuals". Imagine that from a group of 4 individuals (between 30 to 40 years old) I was the only one perceiving an ultrasound insects device from one of my neighbour's house.
> 
> *Note*: It has been technically proved that a BJT-input opamp will generate greater odd-order harmonics than a FET-input opamp and audio experts say that human ear likes FET's even-order harmonics better; also, our human memory is around 4KHz so an amp that generates a 2'nd order or 3'rd order harmonic higher with 0.5dB around 4KHz might help for some people; they'll probably say that the mids are clearer and voices are upfront. So indeed, by swapping the opamps or by A/B-ing between different headamps our ears might get some unknown pleasant audio differences, which is perfectly normal, even if on a scope or RMAA tests we can prove that audio signal that comes from signal generators are about identical with its output, just we can't really prove that there're the same number and intensity of harmonics. And there's always placebo effect in some cases, of course.


 
  
 So, what you are basically saying, is that even if an oscilloscope FFT might not show signs of differences between input and output, your ears are actually able to tell them apart?
 Gigi, the oscilloscope right next to me, would like to challenge that 
	

	
	
		
		

		
			




 Unless of course, you have want to introduce the  concept of "dark sound" to the snake oil science, as some some of dark matter/energy.


----------



## raoultrifan

I like the name of Gigi for your scope. 
  
 What I wrote there is not snake oil at all, but I'm pretty sure we could all find enough data on the Internet about 2'nd order and 3'rd order harmonics (most opamps have it on their datasheets). Also, an opamp that is oscillationg may sound better than the one that's running stable and that's because of the harmonics it's inducing into the final sound (you can find many posts here on HeadFi about oscillating opamps that sound so great); have no idea why some people likes lots of harmonics, but from the posts I was reading looks like it's a true fact.
  
 What I was actually trying to say in my previous post is that different schematics of headamps may sound different, no matter what RMAA or a scope can read.
  
 P.S.: Class A amplifiers should have the lowest harmonics ever and this is why most audiophilles rates these amps so high. Who is really able to find the differences between an A-class amp and a AB-class amp in a ABX test it's another question, but perhpas we're already off-topic a bit.


----------



## adydula

Ha!
  
 Now I would not want to take the fun out of buying and trying new stuff in the search for audio nirvana!
  
 Thats why I have built many amps and have compared them to my ears...and the O2 holds its own!
  
 When I hear the O2 sounds thin, the first thing comes to mind is your source or source material is probably the culprit, a recording that is "thin" or poorly mastered. If the O2 or any amp is neutral
 then garbage in garbage out and add to that a set of cans that have issues its made more an issue, but its not the O2 amp.
  
 Is clipping affecting the sound?? Where do I begin? 
  
 It sure is!!! 
  
 and the answer is: Dont do that!!
  
 At least I hope people will look at this objectively at least in "some ways" and not be duped or at least take the time to understand the hobby in a bit more detail....glittering genearalities often
 lead us astray!!
  
 All the best
 Alex


----------



## adydula

I think many folks think Class A is the best because it sounds better than saying I have a Class F amp!!! lol...99% most likely have not a clue what a Class A amp really is...or AB or etc..
  
 The good old blind test I do humbles the best of them!
  
 Alex


----------



## MrMateoHead

adydula said:


> *WIth so many variables in the playback chain*, I dont want an amp that adds anything to the input signal, This way I can better evaluate the source material and the playback of the transducers.


 
  
 Basically, this. It took an O2, an ODAC, and some planar headphones to reveal to me one of the most important variables of all - the recording itself. Not to mention all THOSE electronics + the venue used in producing the recording for $X dollars or $XX dollars. That said, it'd be interesting to see if 2 different systems played with the same speakers could "fool" a microphone into believing that each record was played back more or less identically. Even with my anatomically varied ears, and yours, controlling for everything we could I suspect we'd not notice much, if any difference between 2 controlled setups.
  
 Of course with my favorite listening devices all utilizing difference DACs, different Amps, and different levels of DSP intervention (some, none, or near complete), it is impossible for me to decide on which part of the signal chain is most influencing my listening outcome (but it is usually the speakers, period). The same issues pop up on the video side, btw, when reviewers talk about "blacker blacks" and "richer contrast". In a side-by-side comparison such differences can be stark - but to me mostly only when we are comparing totally different technologies (e.g. LCD to OLED, IPS to TN to VA). In the speaker world, frequency response aside, Planars seem very different from dynamics despite attempting to do the same thing - reproduce sounds. But note those differences are far from the level of amps, discs, or DACs, which are all designed to transfer signal from a source medium to an end point, preferably not degrading it on the way.
  
 That is why I am now tending to assume that the electronics are about 10% and the speakers are 90% of the sound I get to hear - complete with their performance (SPL and Distortion) determining how "good" those watts or those DACs appear to be. But I have to say, absent a blind test, and likely because of DSP, I swear that my new AV Receiver sounds totally different than my old one - and that somehow the speakers connected went from sounding "good" if a little "polite", to sounding detailed and dynamic. But I still wonder where the big "bass" is from my towers (does my amp have lots of voltage but no current? Do I need more power to "play the bass"?).  The point is, my towers aren't THAT great bass-wise, always a bit "soft" to my ears. They need a sub-woofer, they need a crossover point far higher than I personally could accept at first (90-100 hz). They will never be Revels. But set them up right, and I would pit them against anything in a blind test and expect them to keep up just fine within the limits of reason.
  
 BTW I'd note that some amps with frequency response problems, like these Sony AVRs I've been reading about, apparently have a weird shelving response - 1 dB down in the bass, 1 db up in the treble. The difference is slight, but it is there and maybe some people might notice it with the right recording (a flaw, I would think, not a feature).
  
 The O2 is a great amp for what it is, no question about it. If there is one thing I love, it is inexpensive, useful, entertaining electronics!


----------



## adydula

I have to agree with most of your statements, MrMateoHead...the transducer and source material have a HUGE influence on the outcome. Unless the amp is really a poor design, most amps play rather well, some have more higher or lower noise floors etc..but for the most part its your headphones and source material.
  
 Some folks chase cables, tubes, power supplies, boutique caps, and all the rest. The little O2 just does and when u run off of PURE DC (that's batteries for those in Rio Linda) lol...all those power supply arguments just vanish...poof! 
  
 But I like most like stuff and have a bunch of amps here, but they all sound pretty much the "same"....imagine that?
  
 Alex


----------



## MrMateoHead

I figure the main reason my new AVR seems so much "better" is that a) it has about 50% more power than the old one (potentially twice as much power if I could actually measure it) b) my relatively inefficient speakers needed more headroom c) the new amp is objectively "cleaner" d) the DAC in the old AVR is 10 years old and probably doesn't come close to the same SNR of the new one. Not to mention, I can play back HD movies in all their uncompressed glory.
  
 Then of course there is the build-in "room correction", which is really a slew of actual crossover points I can choose (the old AVR was 90hz or nothing), time-alignment (sometimes useful, sometimes not that useful). Then there is the 9-band or whatever EQ that can be set for each channel independently - hmm. The big one is the standing-wave "tweak", which does magic with the bass for the most part. I'm shocked that I actually don't mind it with music or movies. In a nutshell, I am ready to get a measurement microphone as I can at last, if I want, take some measurements and see if I can further improve things in the critical 20hz-500hz area (screw the rest, room correction clearly more about good bass correction, IMO - not "flat" bass, just bass - most of the room mode). Its nice that the 30-40hz mode in my room no longer rattles the window until I choose to set the volume too high.
  
 The O2 is nothing more than the equivalent of that super-clean, affordable, 100 Wpc amp. I finally get why the 100Wpc rating is sort of the "gold" standard - for one thing, it'll take 1,000 watts to truly reach the next level and not a lot of speakers can even take kind of power that anyway. When it comes down to it, 100 Wpc is a reasonable target for driving any speaker to deafening levels without immediately destroying it. 
	

	
	
		
		

		
		
	


	



  
 When my O2 dies, assuming it ever does, I think I'll just get another O2. I haven't seen anything else come out that really challenges it.


----------



## upstateguy

adydula said:


> I have to agree with most of your statements, MrMateoHead...the transducer and source material have a HUGE influence on the outcome. Unless the amp is really a poor design, most amps play rather well, some have more higher or lower noise floors etc..but for the most part its your headphones and source material.
> 
> Some folks chase cables, tubes, power supplies, boutique caps, and all the rest. The little O2 just does and when u run off of PURE DC (that's batteries for those in Rio Linda) lol...all those power supply arguments just vanish...poof!
> 
> ...


 
  
 I Agree, but the operative words are *"pretty much"* the same.  I think the truth is that if you listen carefully with resolving headphones some sound different. 
  
 Of the amps I use most often, an M^3 with OPA 637/627 chips, and a Woo3 with a Cetron 7236 power tube and two Jan-Philips 6922s, strangely enough share a similar sound signature, while my O2 and GS-1 share another.  The differences being a greater resolution with the O2 and GS-1 and a warmer sound from the M^3 and Woo3, which in direct comparison had the effect of making the O2 and GS-1 sound on the lean side.  I can clearly remember being acclimated to the sound of the M^3 and Woo3 before I got the GS-1 and remarking to myself after listening to the GS-1 for the !st time, "where did the bass go"?  As I got used to the crystal clear sound of the GS-1 I realized that the other two amps were slightly colored and what I was hearing from the GS-1 was as close to a wire with gain as I was going to get.
  
 When I got the O2, I compared it to my other amps and decided that I wouldn't want to try to blind test it against the GS-1.
  
 So there you have it.  I guess most amps sound pretty much the same but if you listen carefully that is not always the case.
  
 This of course is my opinion and YMMV.
  
 I don't like to go to the trouble of testing stuff anymore, but if I get in the mood I'll make some DiffMaker files from the amps.  It'll be interesting to see what the DiffMaker turns up and how it compares with my perceptions..


----------



## adydula

_Its _good to see folks out there that have good common sense!!
  
 Happy Listening!!
  
 Alex


----------



## mikkelmmk93

So have anyone here tried and had succes with modding the O2 amp to have lexx than 1x gain?
 I am asking because my DIY CIEM's are so sensitive that I can barely touch the volume even at 1x gain.


----------



## dukefx

Could you specify source voltage?


----------



## mikkelmmk93

I'm using the ODAC


----------



## jseaber

mikkelmmk93 said:


> So have anyone here tried and had succes with modding the O2 amp to have lexx than 1x gain?
> I am asking because my DIY CIEM's are so sensitive that I can barely touch the volume even at 1x gain.


 
  
 Yes, gain below 1.0x is possible by increasing the input attenuation resistors. However, this compromises noise performance at high gain.


----------



## thuNDa

Quote: 





mikkelmmk93 said:


> So have anyone here tried and had succes with modding the O2 amp to have lexx than 1x gain?
> I am asking because my DIY CIEM's are so sensitive that I can barely touch the volume even at 1x gain.


 

 the formular in the implemention of the O2 is: gain = "R2" / "R1" *+1*
 So no matter to what you change the resistors responsible for the gain, there is always the "+1" left.
 There would be an easy way to add an input signal attenuator with 4 resistors, if you had an O2 with RCA inputs(to do this with the 3.5mm inputjack, it could get ugly).
  
 ...just lower the volume of the ODAC within your OS. 
	

	
	
		
		

		
		
	


	




 
  
 EDIT: oh ye, there are already attenuation resistors in the O2, but they also affect the high frequency filter.
  
 How about changing "R20" from 10K to 330Ohm?
  
 this would reduce the signal from ~1V to ~0.5V(given that R3 is 274Ohm).


----------



## dukefx

2/2.1V is indeed quite high for earbuds. I'm not even sure why you need an amp for those. -3kOhm (yes, minus) resistors could do the trick for ~0.5x gain. Jokes aside I'd do what thuNDa suggested adjust the volume digitally or grab a secondary potmeter (cable with volume control and such).


----------



## HotIce

You better not divide before the VAS, but after, adding a series resistor before the pot.
 Noise figures will rejoy for that.


----------



## castleofargh

hotice said:


> You better not divide before the VAS, but after, adding a series resistor before the pot.
> Noise figures will rejoy for that.


 

 if background noise was an issue on the O2 I could understand, but given how clean it is, I really don't see a problem to using the volume on the computer. I'm probably rank in the top 10 of the noise obsessed annoying grumpy whiner, headfi's world championship edition(I believe I'm number 2 but I don't wanna brag), and yet I can't notice a thing even when I have foobar set at -25db.
 in fact channel imbalance being a way more significant and audible problem to me, I have found a position at low volume on the O2 pot where the channel balance is very good(using a multimeter), and I stick to that while only adjusting the volume level digitally.
 if it really sounded different/bad, I would look into physical modifications or another amp, but it just doesn't(at least to me on my system).


----------



## mikkelmmk93

jseaber said:


> Yes, gain below 1.0x is possible by increasing the input attenuation resistors. However, this compromises noise performance at high gain.


 
 Thanks - at how much gain?
 All my earphones atm are quite sensitive so I would in no way need more than 2.5X gain.


----------



## thuNDa

The most elegant way would be to change R14 and R20 to something lower than 10K IMHO.
 The lower this resistor, the more signal gets shunt to ground, while the resistor(R3/R7, i guess standard value was 100 Ohm) which the signal has to pass, which is responsible for noise, can be left untouched.
 The filter characteristics still work too:


----------



## jseaber

mikkelmmk93 said:


> Thanks - at how much gain?
> All my earphones atm are quite sensitive so I would in no way need more than 2.5X gain.


 
  
 Thunda's answer is correct. You can uses a resistor divider calculator to determine signal strength, relative to the input signal.


----------



## wes1099

If I wanted to use the odac with an iPhone, could I just chop off the USB end if a lightning cable and replace it with a mini USB connector? Is there anything special in the cck adapter people usually use to do this?


----------



## HotIce

castleofargh said:


> if background noise was an issue on the O2 I could understand, but given how clean it is, I really don't see a problem to using the volume on the computer. I'm probably rank in the top 10 of the noise obsessed annoying grumpy whiner, headfi's world championship edition(I believe I'm number 2 but I don't wanna brag), and yet I can't notice a thing even when I have foobar set at -25db.
> in fact channel imbalance being a way more significant and audible problem to me, I have found a position at low volume on the O2 pot where the channel balance is very good(using a multimeter), and I stick to that while only adjusting the volume level digitally.
> if it really sounded different/bad, I would look into physical modifications or another amp, but it just doesn't(at least to me on my system).


 
 Given that the main reason of the really weird design (VAS which runs at full gain, with pot follower - which means you can get clipping even when listening at 30dB) was to reduce noise, scaling signal before the VAS, aside from being a fairly bad decision from a design POV, would probably make the original author twitch a little.


----------



## castleofargh

hotice said:


> Given that the main reason of the really weird design (VAS which runs at full gain, with pot follower - which means you can get clipping even when listening at 30dB) was to reduce noise, scaling signal before the VAS, aside from being a fairly bad decision from a design POV, would probably make the original author twitch a little.


 
 eheh. I was talking about easy practical solution, not about getting the lowest measurable noise. in practice nowadays I don't use the O2 with IEMs except to measure them. because I don't use IEMs in my room when I have headphones, but also because of the volume knob. but if we get into soldering solutions, then I'm sure we can also get a great pot instead with good balance further down. I wasn't saying my answer was the best answer, or the answer. but it's the easy one and it still sounds audibly clean to me.


----------



## HotIce

Oh, sorry, I misunderstood your post


----------



## mikkelmmk93

thunda said:


> The most elegant way would be to change R14 and R20 to something lower than 10K IMHO.
> The lower this resistor, the more signal gets shunt to ground, while the resistor(R3/R7, i guess standard value was 100 Ohm) which the signal has to pass, which is responsible for noise, can be left untouched.
> The filter characteristics still work too:


 
  
  


jseaber said:


> Thunda's answer is correct. You can uses a resistor divider calculator to determine signal strength, relative to the input signal.


 
 Thanks you two.
 If I ever get around to doing it I will return with my findings 
 I'm guessing that if I shunt the signal down to 0.5X gaing, then my other gain config of 2.5x would be 1.25x instead?


----------



## adydula

I have played with lowering the impedance of the O2 to "0" ohms by replacing the two 4556 op amps with the AGDR O2 Booster board that uses 827's...with this booster board you get the ability to remove the 4 "1" ohm output resistors and have a zero ohm impedance....
  
 I also have been listening and doing blind AB tests and with lower impedance headphones you can hear differences...
  
 The booster board doesnt seem to affect the noise levels that are real world discernable at real work listening levels.
  
 Check it out:  http://www.audiocircle.com/index.php?topic=142513.0
  

 Version 3.5
  
 Alex


----------



## dukefx

I've seen it quite a while back on diyaudio. Waste of 100 bucks, but that's just my opinion.


----------



## adydula

Only cost me $45 to build and at I can make a real judgement as to if its garbage or not. People who dont have the stuff in their possession can only comment from afar. You can waste a lot of bucks on NOS tubes, boutique caps etc...but the booster board doenst harm the O2 in anyway that I can "hear" and adds things that are meaningful to lots of folks. That said its your money spend as you like.
  
  Benefits:

Nearly twice the current output capability on peaks, 250mA vs. 140mA per channel on a stock O2 Headphone Amplifier. Why this matters
Nearly zero (50 microvolt) DC output offset voltage, vs. typically 3000uV (60x more) for the stock O2.
Zero turn-on or turn-off thumps due to an included headphone relay circuit
Doubles the slew rate to 6V/uS, and 20V/uS if the NJM2068 gain chip is replaced by 2x LME49990 adapter
Power rail clamp diodes.  This is an important O2 ommision - some versions of the 7912 voltage regulator have been known to fail to start up into some load conditions (in general, not just the O2)         without a rail clamp diode.
Lower input-resistance induced distortion.  Many op-amps have a little-known problem of distortion being caused by higher levels of series resistance on their inputs.  The NJM4556A is believed to have this problem.  The OPA827 and OPA140 FET-input op-amps used in the O2  Booster Board have been desgined by TI to specifically reduce this problem.
Adds 2 LEDs that show when the power management mosfets in the O2 are on.  Helps if any O2 troubleshooting is ever required, to see immediately if both power supply rails are OK.
Allows for true zero ohm output vs. 0.5 ohm for the stock O2 Headphone Amplifier.  Lower amplifier output resistance means a better damping factor.
THD and noise figures of the chips, per the datasheets, slightly beat (better) the O2's stock NJM4556A

 Whether any of these mean anything to listeners is a subjective guess, but to me I had to listen for myself to determine that they do indeed.
  
 Alex


----------



## dukefx

All I'm seeing here is taking a nice car and turning it into some Mad Max style war machine and talking about those spikes on the rims, the flamethrower on the roof, the harpoon gun on the hood and you are supposed to take that car to Walmart to get some milk. That's the best I can do to describe why I don't see any benefit without being too technical and writing a 20 page essay.


----------



## adydula

Duke if your happy and content with the O2 as is great! I have several of the here....enjoy!
  
 Have to go now and head to Walmart for some "skim" milk! 
  
 Taking my Z06.
  
 LOL...
  
 Alex


----------



## dukefx

Well, at least you had a good laugh and I didn't have to preach. Win/Win


----------



## adydula

Wait until I put 1688's into an O2!
  
 A.


----------



## dukefx

I see you already did and you are still using the 2068Ds.


----------



## adydula

Hmm are you stalking me? (LOL)...
  
 http://www.diyaudio.com/forums/headphone-systems/193977-objective2-o2-headphone-amp-diy-project-477.html
  
 http://www.ti.com/product/OPA1688
  

  
 Simple Circuit:


----------



## dukefx

Haha, no, but it's one of those few diyaudio threads I'm keeping my eye on.


----------



## adydula

Thats a good thing, AGDR is a pretty nice person and has helped me and many others often in unseen ways. He was one of the people back in the nwavuy days that had many good technical interactions with him. AGDR really likes to tinker and get the most out of circuits and I have been able to build a bunch of amps based on his designs. All of them are really good performers.
  
 Most of his stuff is centered around better parts with lower noise floors etc..,.whether we can really heard the differences with our human transducers will always be open to debate.
  
 For the most part they all sound pretty good comapred with the O2 and other amps. Some have IMO a definite "sound", especially when listening to my Bottlehead Crack to these derivitives.
  
 Its nothing like having them all in a room to see for yourself...then wonder why I spent all this money in the first place!! Ha!
  
 All the best
 Alex


----------



## raoultrifan

Hi Alex, 
  
 I really like your mod, but I'm worried about how the OPA1688 will handle output power under 32 ohms or even lower impedance headphones, because despite having the same mA output I see from the datasheet that can only handle 50mW/32ohms before clipping; for 2 paralleled opamp this would be 100mW/32ohms, so about 6 times less power than original 4556 opamps (please correct me if I'm wrong).
  
 I will most likely purchase a couple of OPA1688 opamps soon, because I'm very interested in final results, but meanwhile do you think you could please test output power of your modded O2 with OPA1688 as output buffer for 32ohms output resistance? Also, if you could somehow measure OPA1688 die temperature while doing this test it would be perfect.
  
 Thank you very much, 
 Raul.


----------



## adydula

Thats a great question and concern!
  
 The only headphones I have used so far are 250 ohm T90's I have several low impedance cans and will test. I also am querying a few folks that have a good engineering level of understandings as well. I have a thermocouple as well. I did do the simple hot finger test the other day and they are not warm at all...
  
 Stay tuned!
 Alex


----------



## HotIce

raoultrifan said:


> Hi Alex,
> 
> I really like your mod, but I'm worried about how the OPA1688 will handle output power under 32 ohms or even lower impedance headphones, because despite having the same mA output I see from the datasheet that can only handle 50mW/32ohms before clipping; for 2 paralleled opamp this would be 100mW/32ohms, so about 6 times less power than original 4556 opamps (please correct me if I'm wrong).
> 
> ...


 
  
 Where have you seen that it can handle only 50mW on 32 Ohm?
 Max output power depends on thermal characteristics, load Z, and power rails voltage.
 I have never seen opamps data sheets reporting max power on load, w/out specifying the rails voltage.
 From a quick look, the mention 50mW in two places, but nothing mean in such places, that that's the IC max output power.
 There are conflicting design choices where you design a linear amp.
 If you jack up power rails, you get better handling of high Z loads, but high thermal profile on low Z loads.
 If you lower the rail voltages, you get better thermal profiles at low Z, but clipping when driving high Z loads.
 This is why amps like the iFi iDSD, have a switch to change.
 Some other amps (IIRC Carver, and possibly others) had also developed dynamic power rails which were driven on output voltage.


----------



## adydula

FYI....after 1 hour of playing at VERY high levels the temps on the 1688s are 93 deg F. or approx 32 deg C.
  
 I hear no distortion at all.
  
 Alex


----------



## raoultrifan

Well, it's written in the main page from TI website for OPA1688 product: http://www.ti.com/product/OPA1688: _"THD+N, 50 mW, 32 Ω, 1 kHz, –109 dB"_ and also on datasheet first paragraph: http://www.ti.com/lit/ds/symlink/opa1688.pdf.
  
 Although, after reading a bit the datasheet I realise that this may be the power for +/- 5V only: 
_10.2.1 Design Requirements_
_The design requirements are:_
_• Supply voltage: 10 V (±5 V)_
_• Headphone loads: 16 Ω to 600 Ω_
_• THD+N: > 100 dB (1-kHz fundamental, 1 VRMS in 32 Ω, 22.4-kHz measurement bandwidth)_
_• Output power (before clipping): 50 mW into 32 Ω_
  
 So, let's wait for Alex or somebody else to do some measurements.


----------



## raoultrifan

adydula said:


> FYI....after 1 hour of playing at VERY high levels the temps on the 1688s are 93 deg F. or approx 32 deg C.
> 
> I hear no distortion at all.
> 
> Alex


 
 Well, that's great news Alex, that makes me wanting to purchase these 1688 pretty soon.


----------



## HotIce

raoultrifan said:


> Well, it's written in the main page from TI website for OPA1688 product: http://www.ti.com/product/OPA1688: _"THD+N, 50 mW, 32 Ω, 1 kHz, –109 dB"_ and also on datasheet first paragraph: http://www.ti.com/lit/ds/symlink/opa1688.pdf.
> 
> Although, after reading a bit the datasheet I realise that this may be the power for +/- 5V only:
> _10.2.1 Design Requirements_
> ...


 
  
 That is not the spec of the IC. That is the spec of the sample circuit fed with +-5V.


----------



## raoultrifan

hotice said:


> Max output power depends on thermal characteristics, load Z, and power rails voltage.
> I have never seen opamps data sheets reporting max power on load, w/out specifying the rails voltage.


 
  
 I believe figure no. 9 might provide us some data: http://www.ti.com/lit/ds/symlink/opa1688.pdf, page no. 11. For 75mA there's about 20V p-p that would be about 7V RMS, so it's about the same output power as the NJM4556, just package size is smaller and this is why I was wondering about power dissipation and temperature.
  
 AFAIK many opamps are providing max. TDP, for example for NJM4556 would be 700mW for the DIP8 package only (perhaps an absolut max). Also, for NJM4556 max power dissipation at +/-15V would be somewhere between 270-360mW, so looks like NWAV engineer had enough data about this opamp to build the output buffer.


----------



## raoultrifan

hotice said:


> That is not the spec of the IC. That is the spec of the sample circuit fed with +-5V.


 
 That's exactly what I said after in my previous post.
  
 Thank you!


----------



## HotIce

To figure out max power, if the spec does not clearly spell it, you need to consider that while the IC is providing Vo to a load Zo, hence emitting a Vo^2/Zo output power on the load, it is dissipating (V-Vo)*Vo/Zo power in the drivers.
 Where V is the rail voltage.
 Once you have that, once you have the maximum IC silicon temperature, and the silicon to air (unless heatsink is provided) thermal resistance, you can figure out if you can afford to dissipate such power while being within the max temperature range.


----------



## raoultrifan

I believe this can be easily tested with a dummy 32ohms resistor and a IR thermometer or some contact thermometer (or just use carefully the fingers).
  
 I'll probably purchase a pair of these soon, because AGDR had did some great tests with 1688 on diyaudio.


----------



## adydula

I spoke to AGDR and here are his comments"
  
   The OPA1688 can do way more than 50mW into 32ohms (before clipping) with higher chip source voltages, like the +/-12Vdc in the O2 if running on AC. 
  
 An OPA1688 should be pretty much equivalent to a NJM4556A in terms of power dissipation.  A person might ask how can that be, given the NJM4556A is a DIP-8 package, while the OPA1688 is smaller surface mount SOIC-8 package?  The answer is the dramatically reduced idle (quiescent) current of the newer OPA1688 part.  The Iq of the OPA1688 is just 1.8mA max per amplifier, 3.6mA total, vs a whopping 12mA maximum total for the older NJM4556A.  That means the about half of the NJM4556A’s package power dissipation is taken up just dissipating its own idle current!  At +/-12V (12V – (-12V) * 12mA = 288mW.  So although the OPA1688’s package is smaller, it has a lot more dissipation “room” left for the signal.
  
 Alex


----------



## adydula

There is a concern with chip oscillation depending on the capacitance of the load...I dont hear anything but its indeed a possible issue. The O2 circuit and TI's recommendation circuit is different...so putting the 1688 into the o2 is taking a chance with oscillations, but the o'scope traces over at DIY by mlackey look good...but again at what capacitance?
  
 If I hear anything more I will add to the thread...
  
 Aled


----------



## HotIce

adydula said:


> I spoke to AGDR and here are his comments"
> 
> The OPA1688 can do way more than 50mW into 32ohms (before clipping) with higher chip source voltages, like the +/-12Vdc in the O2 if running on AC.
> 
> ...


 
  
 If the extra current of the NJMs is drivers bias current, like 99% probability is, the argument above is not quite correct.
 Think about a class A amp, where power dissipated by drivers actually lowers with load (if you keep operation under the class A range).
 IOW, the output power and the idle one, do not sum up in the thermal output.
 In a very crude form (which is incorrect, among other things, because it does not account rail voltages for PO), if PI is idle power, and PO is output power, dissipated power is more like max(PI, PO), more than PI+PO.


----------



## adydula

This am I soldered a pair of 1nf caps across the outputs with the 1688's in the O2 to see if I could get it to oscillate and it did not. Temps were the same...and I was able to place the stock 4556's back in and compare somewhat. The issue when changing out parts and the time it takes from one setup to another may affect my opinion subjectively....I like to do blind AB testing to leave the bias part out.
  
 That said, I thought there was a improvement using the 1688's playing several demo tracks with really well recorded bass it seems the 1688s version is indeed better in my humble mind IMO.
  
 I guess I could keep increasing the capacitance to see where it oscillates but for me with 35 ohm and 250 headphones there seems to be no issues that I am concerned with now.
  
 Alex


----------



## thuNDa

thunda said:


> The most elegant way would be to change R14 and R20 to something lower than 10K IMHO.
> The lower this resistor, the more signal gets shunt to ground, while the resistor(R3/R7, i guess standard value was 100 Ohm) which the signal has to pass, which is responsible for noise, can be left untouched.
> The filter characteristics still work too:


 

 I must correct myself:
  
 It's generally not a good idea to attenuate by decreasing R14 / R20 if someone wants less than effectively 1x gain, because those resistors determine the input impedance of the O2.
 In my example you would lower the input impedance from 10K to only 100 Ohm for "0.5x gain".


----------



## adydula

I recently built AGDR's O2 Booster board with 827's and you can remove or short out the output resistors and have "0" ohm output imedance!!
  
 Alex


----------



## Arkady Duntov

Does agdr still sell his (her?) pre-assembled ODAs? My amp died this week.


----------



## adydula

Its a "him"....send him a pm directly over at diyaudio.com.
 I know he is a bit out of pocket due to some personal issues, but hopes to be back soon, dec? 
  
 Oh forgot....agdraudio.com
 He has contact info there as well.
  
 Alex


----------



## chimney189

Very interesting thread here. I wonder what happened to the designer of this little beast?
  
 I have a question to anyone who might know: would the 02 + ODAC be able to power ALPHA PRIMES?


----------



## raoultrifan

Definitely yes! More details about the drivers here: http://www.fostexinternational.com/docs/products/RP-Series.shtml#content-3-tab-tab.
 Also, feel free to search on HeadFi or Google some reviews related to Alpha Prime and amplifiers compatibility.


----------



## gkanai

I haven't looked over the whole thread recently but does anyone know if there is a 100-240V power source for the O2? I have the 100V one, but now live in a 220V country, and travel sometimes to the US, where mains is 120V. I'd pay for a larger power source if it could work globally.


----------



## dukefx

Why not get one for Europe and one for the US? The wall sockets don't match anyways.


----------



## Arkady Duntov

adydula said:


> Its a "him"....send him a pm directly over at diyaudio.com.
> I know he is a bit out of pocket due to some personal issues, but hopes to be back soon, dec?


 
  
 I decided to buy, after reading most of this thread and quite a bit of a few others, a DAC+amp now and perhaps get an ODA later. In doing so, I had to ignore innumerable posts with topics like "it's good for a small device" and "need to spend at least $3,000 to get a good amp." The one that looked the best in price _and_ performance was JDS Labs' ODAC+O2 combo.
  
 I had one problem. When I attached it to a USB2 hub, Windows7 recognized it and "installed" drivers. However, the ODAC never showed up under Sound>Playback devices. When I attached it directly to a USB2 port on the PC, everything worked as planned.
  
 So far, with about 16 hours of listening time, I find the ODAC (rev B) and O2 provide great sound. I think I made the right choice for me.


----------



## castleofargh

not helping sorry, but for the anecdote, my main use is on an old laptop with usb2 and usb3 ports on one side, and 2 usb 2 on the other.
 the usb2 on one side comes from a separate card(not the motherboard), and is the only port where I could use the crappy amazon powered hub I bought. I don't know why, I tried all kinds of drivers, old and new, flashed the bios tweaked all the settings I could find about usb(energy saving stuff and the likes). only one out of 4 usb ports let me use DACs and ADCs plugged in the hub.
  
 with an older hub, it wouldn't plug&play with the scarlet 2i2, but if I were to boot with everything already plugged, then it would show as an output(and input in this case). windowzzz is magical, sometimes it's black magic.


----------



## raoultrifan

arkady duntov said:


> [...]
> 
> I had one problem. When I attached it to a USB2 hub, Windows7 recognized it and "installed" drivers. However, the ODAC never showed up under Sound>Playback devices. When I attached it directly to a USB2 port on the PC, everything worked as planned.
> 
> [...]


 
  
 Just use one of the backside USB ports from your desktop (you need to use an USB port directly soldered onto the motherboard, no internal wires!); in case you're using a laptop as source, use an USB port not close to power plug.
  
 Enjoy you new sound!


----------



## Rado2

Just to mention, that some computers have dedicated USB ports for audio or other purposes. I was quite surprised for example that my motherboard came with two of such, for which the manual (and the engineers staff) said are specially though over for clean power and data supply. I have no idea how true is that, but I ran from there my O2+DAC and USB Microphone.


----------



## dukefx

Do a RMAA test to find. I haven't had the pleasure of testing such USB port myself, but I highly doubt it'd anywhere close to a linear power supply.


----------



## raoultrifan

Try finding a good scope and measure AC ripple and noise on the +5V for that USB port.
  
 Thank you!


----------



## chongky

Will the O2 amp clip at loud volume for dynamic music like classical? I have a SMSL M8 DAC which has an output level of 2.15 Vrms, dynamic range: > 125dB, SNR: > 126dB. My headphones is the Beyerdynamic T90, impedance 250 ohm, sensitivity 102 dB SPL at 500 Hz at 1 mW. I plan to listen at the 1.0x gain.
  
 I'm not a math guy and I wonder if listening to classical music Redbook CDs (mainly symphonic) my T90s will distort at high (but not ear-deafening) volume.


----------



## raoultrifan

It all depends on the gain setting used. Feel free to search within this thread, because there are lot of people explaining the correct gain calculation.
  
 From what I know, max. output voltage for the O2 would be around 7.3V RMS, so if you'll devide this to 2.15 you'll get the max gain for your setup of 3.39X. That being said, I can strongly recommend you the highest gain setting of 3X and the lowest gain setting between 1X and 1.5X, depending on the headphones used.


----------



## chongky

Thank you for your speedy reply. I found a site after searching this thread:
  
 http://www.digizoid.com/headphones-power.html
  
 So I keyed in the impedance (250 ohms) and sensitivity (102 dB SPL/mW) of my T90, which in turn showed it requires ~ 4 Vrms to output to ear-splitting levels, i.e. 120 dB.
  
 Which means it's more than loud enough, and still below the distortion inducing level of .7.3V RMS. Which means it ought not distort either at 1x or 3.3x gain (according to your calculations)?
  
 Correct me if I'm wrong.


----------



## raoultrifan

There will be no distortions for gains up to 3X, no worries here; just be sure not to setup the gain to 3.5X or more, because 3.5x2.15=7.525 V RMS and the internal gain stage will start clipping. I recommend you MUSES8820 for your gain stage, to replace NJM2068, but only if you intend to start modding (most likely between the 2 opamps there's an inaudible difference for most people).
  
 I strongly recommend you to read how much you can from this thread because you'll find many answers and thoughts.
  
 Regards,
 Raul.


----------



## adydula

I have several O2's and T90's....I hae gains from 1x to 6.5x and no issues at all at 1.0x or "unity" gain. The O2 will work fine with your T90's, which are my favorite cans over many, many others even those costing more!
  
 Enjoy
 Alex


----------



## chongky

adydula said:


> I have several O2's and T90's....I hae gains from 1x to 6.5x and no issues at all at 1.0x or "unity" gain. The O2 will work fine with your T90's, which are my favorite cans over many, many others even those costing more!
> 
> Enjoy
> Alex


 
  
 Thanks - that is really assuring. My O2 will take a while to arrive due to the Black Friday traffic but I'm sure it and the T90s will be a great pairing!


----------



## dukefx

My newest addition finally arrived. Had to replace 2 caps to make it fit.


----------



## dukefx

I joined the OPA1688 club. The difference is subtle, but noticeable. Don't even ask how I managed to fit them in.


----------



## raoultrifan

Guys, please stop teasing me!
 I really have no time to do this mod right now and every post like this one makes me have nightmares. 
  
 P.S.: Nice one dukefx, any chance on an A/B test?


----------



## dukefx

Haha, here's no way I'm gonna remove the one next to the TRS socket unless I absolutely have to. I had to remove the spacers and shorten the pins, then stuff it under the cables.
 Alternatively I could have gotten Browndog adapters, but I'm not gonna pay 12$ shipping for something that costs 6$ total and weighs close to nothing, lets not mention that it's the slowest possible shipping method.
  
 I found these on ebay from a greek guy, which means fast shipping within the EU (arrived in about a week). I also ordered rounded pins, but I couldn't have shortened those like these ones as they have those thicker parts which are pretty much mandatory spacers. Something to keep in mind if your O2 is as crowded as mine. The OPAs came directly from TI. Packaging was total overkill XD

  
 As for the sound, don't expect much improvement over the 4556s, but it's noticeable.


----------



## adydula

Been there done that!! lol...1688's great specs, use these in several amps with great success.....the OP Amp thread on this site and over at DIYaudio....several folks have done this and the TI design engineer frequents the discussion over there for this IC.
  
 Compared to original O2 A/B several times....hard to really tell any difference...bass is solid.


----------



## adydula

Note the small boards I got from Mouser, they fit real well and no issues mounting in my O2 at all. Pins worked well,
 A.


----------



## dukefx

Small boards? They are way bigger than mine.


----------



## adydula

Yes they are a bit larger, you can file them down a little, but unlike your O2 mine is bone stock except for this minor mod...I have several O2's for comparing etc....I did build a AGDR O2 Booster Board and it to me IMO makes the biggest difference in sound...
  
 For a Desktop version of the O2 that "never" was AGDR has a "ODA" and I built one of these last year, another stellar amp with tons of current for driving most evey can out there..(note "most"). 
  
 AGDR has started a website for those that want to ply around with his mods and designs....he also has a "super" Cmoy with 1688's one single and one with a dual circuit....really inexpensive and fun to build up..
  
 Ok dont mean to hijack this thread!!
  
 Back to the your normal O2 + DAC channel!
  
 Alex


----------



## dukefx

I honestly can't imagine the booster board making a bigger difference than whatever you have for U1. The OPA1688s are hardly noticeable. In some tracks I can't hear any difference, in others I feel slightly more control. The booster board should be no different, if anything I imagine it'd be worse as it defies 2 of the golden rules of designing amps. Yes, I know, you will defend it to the end. Have you even tried anything else other than the stock 2068D?


----------



## adydula

I wont defend it to the end...but it works and works well considering. I dont think it hurts anything.
 It is an attempt to make thing "better" by using better spec'd parts, more current if needed etc...the engineering side of it vs the esoteric side of my uber blue 8 guage cables are so cool (lol)... 
  
 Statement of Benefits....true or false from the author. 
  
 The O2 Booster Board provides several benefits:



 
Nearly twice the current output capability on peaks, 250mA vs. 140mA per channel on a stock O2 Headphone Amplifier.
Why this matters
Nearly zero (50 microvolt) DC output offset voltage, vs. typically 3000uV (60x more) for the stock O2.
Zero turn-on or turn-off thumps due to an included headphone relay circuit
Doubles the slew rate to 6V/uS, and 20V/uS if the NJM2068 gain chip is replaced by 2x LME49990 adapter
Power rail clamp diodes.  This is an important O2 ommision - some versions of the 7912 voltage regulator have been
known to fail to start up into some load conditions (in general, not just the O2) without a rail clamp diode.
Lower input-resistance induced distortion.  Many op-amps have a little-known problem of distortion being caused
by higher levels of series resistance on their inputs.  The NJM4556A is believed to have this problem.  
The OPA827 and OPA140 FET-input op-amps used in the O2  Booster Board have been desgined by TI to
specifically reduce this problem.
Adds 2 LEDs that show when the power management mosfets in the O2 are on.  
Helps if any O2 troubleshooting is ever required, to see immediately if both power supply rails are OK.
Allows for true zero ohm output vs. 0.5 ohm for the stock O2 Headphone Amplifier.  Lower amplifier output
resistance means a better damping factor.
THD and noise figures of the chips, per the datasheets, slightly beat (better) the O2's stock NJM4556A

  
 I have AB this mod with a stock O2 for many days, I am drawn to the Booster Board version, but I honestly
 do not think I can really hear any differences other than the ole it sounds better to me!!
  
 Alex
  
 PS: The one item I do like is the ability to have a true zero ohm for those that want to try.....


----------



## dukefx

Why do you keep copy/pasting that? I think everyone who's interested in the O2 knows about it, and you probably posted it no further than 2 pages back. Anyways, the OPAs should do roughly the same thing sound wise as the booster board for literally peanuts (otherwise I wouldn't have bothered with it), on top of that it won't increase thermal noise, nor the amount of components. I think I already said it, but I'll say it again: the booster board is too damn expensive for what it does. It's a definite no for me.
  
 You still didn't answer my question: did you even try to replace U1? It's the one that can make a hell of a difference.


----------



## adydula

Gee Duke I didint know I was under interrrogation! Sorry about pasting the above "stuff" once again...some folks dont back browse. If the booster board is too expensive for you great...for many of us we like to play and the cost of this mod is not that expensive....but hey its YOUR money,.
  
 There are alot of theoritical benefits of the booster board, whether you agree or disagee or hear anything at all...
  
 oh and YES I have changed U1
  
 Ok back to my cave....have a nice Merry Christmas!!
  
 A.


----------



## dukefx

Oh, no you don't! No going back to your cave for you, Mister!  It's not expensive for me, it's expensive for what you get: audibly close to nothing. I've spent a lot of money on various upgrades, for example the Burson and Sparkos opamps, but they are worth it, especially the Sparkos. I've spent 98€ on a power supply + 38$ (which is really cheap) on a custom made silver plated and teflon coated Y cable for my ODAC... money well spent. Spending money on something that may or may not improve (or worse may decrease) SQ is not really my thing.
  
 Back to the interrogation: what opamps did you try?


----------



## adydula

Muse...only 78x more expensive that the original 2068.....worth it?? You decide.
  
 Heck u can build a booster board for the cost people spend on Burson and other ooompa loomp goodies....parts listed on agdrs cost spreadsheet is $57....not that expensive. But if it doesnt do anything for you then i understand where your coming from....
  
 another post just for the kiddies:
  
  
Replace the U1 gain chip witth the ($47!) MUSES02 chip. The NJM2068 gain chip that NwAvGuy used in the O2 headphone amp is really pretty good, as he showed by tests in his blog. Good enough that relatively few chips would yield any substantial improvements in measured numbers.   One chip to consider is also made by that same company, New Japan Radio, the MUSES02 available at Mouser as part #513-MUSES02 for a whopping $47 vs. just $0.60 for the original chip. There really is nothing in the MUSES01 datasheet numbers that jumps out at being a big significant improvement over the NJM2068, certainly not worth 78x the cost. The slew rate is 5V/uS but again with the NJM4556A output chips in place you still won't exceed 3V/uS. The MUSES02 is written up by NJR as their "flagship" audio chip with "excellent sound". I've read one posted review of the chip (an amp other than the O2) where the person was claiming a noticable sonic improvement. So there you go - for the "how it sounds vs. measurements" audiophiles out there, here is a chip to try and see what you personally think. 
  
 all the best, this was written from deep inside my cave...."echo, echo...."
  
 A.


----------



## dukefx

Last time you said 40$ for the booster board if you solder it yourself in reply to my ~100$ (not including shipping to Europe and customs). As for the opamp I trust my gut feeling and it tells me to stay away from the MUSES0X. The Burson and Sparkos opamps on the other hand use topologies that have proven themselves. There are a lot of really great solid state amps on diyaudio with the same or similar designs. I'm gonna stick to the Sparkos, it has cleaner bass and sounds so damn realistic and natural. The Burson is a bit more musical, almost as if it was a tiny bit V shaped, but there's listening fatigue on the long run, in the O2 at least.


----------



## adydula

Inflation....and  I got a GREAT deal on parts!!
  
 Its too bad your in a different part of the world,,,I would like to sit you down and do a blind test with you to see how
 well those op amp derivatives really work...many a man has been humbled.
  
 A,


----------



## Nec3

Is there a reason why certain groups hate the O2? I've never really owned higher priced dac/amps and those who have alternative setups such as ADG NFB-11's state they hate the sound of the JDS Labs ODAC/O2 combo. There's actual disgust when they hear people have the HD600 and pair it with the combo, to me it sounds fine...


----------



## raoultrifan

Never heard someone really hating the ODAC/O2 combo (fell free to copy-paste the comment here, if possible), I mean really...for this price it's quite a decent setup. It's neutral and can drive most headphones out there, so don't see any complains.
  
 Of course that much more expensive setups might have a better soundstage and better micro-details too, but like I said before: for its price range the ODAC/O2 setup is really good.


----------



## U-3C

nec3 said:


> Is there a reason why certain groups hate the O2? I've never really owned higher priced dac/amps and those who have alternative setups such as ADG NFB-11's state they hate the sound of the JDS Labs ODAC/O2 combo. There's actual disgust when they hear people have the HD600 and pair it with the combo, to me it sounds fine...




Just people with different preferences. Amps sound different, just like how headphones sound different, and people actually buy headphones that sounds different because of different preferences *gasp!* Same for their other setups. The best method is to try it out yourself, as a person who imposes their preferences on you may result in very terrible purchases (I made the mistake of recommending something I loved to a friend. He ended up hating it so much that I bought it off him. because I loved it that much and he hated it that much). For example, the guy who designed the O2 used his HD600 as reference to design what he believes is the affordable yet closest to "ideal" amp out there. There are, of course people who need to have xyz tube amp in order to stay alive when wearing the headphones, which is their standard of "ideal." Nothing wrong with the amps. Just different.


----------



## castleofargh

raoultrifan said:


> Never heard someone really hating the ODAC/O2 combo (fell free to copy-paste the comment here, if possible), I mean really...for this price it's quite a decent setup. It's neutral and can drive most headphones out there, so don't see any complains.
> 
> Of course that much more expensive setups might have a better soundstage and better micro-details too, but like I said before: for its price range the ODAC/O2 setup is really good.


 

 you're clearly missing out on what headfi's appreciation topics have to offer.
 my favorite being the guy who complains that the O2 distorts like crazy because he never got the purpose of the gain switch.
 but most really talk about sound they like and aren't after any sort of transparency(even if they don't know it). it's the eternal misuse of personal taste to judge objective performances. not much we can do about that. "I prefer the sound, so it must be superior!" you know like how my pringles are so superior to vegetables.
 oh I got one who said it sounded bad because the ODAC had pre-ringing(perhaps the only guy with an actual objective information). one of my toys does minimum phase and I've never been able to tell them apart(and the FR roll off is too high for me to notice that with my hearing), but maybe some people can?
  
  
  
 now as you said, there are better DACs and better amps out there even from an objective perspective, but it's still a challenge to get one at the cost of the Odac/O2.


----------



## dukefx

nec3 said:


> Is there a reason why certain groups hate the O2? I've never really owned higher priced dac/amps and those who have alternative setups such as ADG NFB-11's state they hate the sound of the JDS Labs ODAC/O2 combo. There's actual disgust when they hear people have the HD600 and pair it with the combo, to me it sounds fine...


 
 People with HD600s aren't fond of the O2 because it has flat frequency response and shows how bad the HD600 actually are. Measurements show the HD600 starting at -15db and it only reaches 0db at around 95Hz meaning it has close to no bass and the O2 won't compensate for this flaw. This is why they prefer V shaped tube amps. I've read plenty of comments here how their Little Dots and various Lehmann clones are so much better, and most of them were HD600/650 owners. There  are also a lot of false statements floating around how the O2 doesn't provide enough current. I can't comment on the JDS Labs O2s, mine isn't from them and I have no idea what people complain about. You are the first to mention it.


----------



## headwhacker

nec3 said:


> Is there a reason why certain groups hate the O2? I've never really owned higher priced dac/amps and those who have alternative setups such as ADG NFB-11's state they hate the sound of the JDS Labs ODAC/O2 combo. There's actual disgust when they hear people have the HD600 and pair it with the combo, to me it sounds fine...


 
 If it sounds fine to you already, why do you let other people bother you? After all, aren't most people always say around here to only trust your ears?
  
 There is no single product which has 100% approval rating. Of course there are some that are popular because a lot of people talk about it. But not everyone who likes the same product like them for the same reason.
  
 I would say that most people who disliked O2/ODAC are those they don't understand the product and why it came to be.


----------



## Nec3

dukefx said:


> People with HD600s aren't fond of the O2 because it has flat frequency response and shows how bad the HD600 actually are. Measurements show the HD600 starting at -15db and it only reaches 0db at around 95Hz meaning it has close to no bass and the O2 won't compensate for this flaw. This is why they prefer V shaped tube amps. I've read plenty of comments here how their Little Dots and various Lehmann clones are so much better, and most of them were HD600/650 owners. There  are also a lot of false statements floating around how the O2 doesn't provide enough current. I can't comment on the JDS Labs O2s, mine isn't from them and I have no idea what people complain about. You are the first to mention it.


 
   
 Pretty insightful actually, thanks 
  
 Quote:


raoultrifan said:


> Never heard someone really hating the ODAC/O2 combo (fell free to copy-paste the comment here, if possible), I mean really...for this price it's quite a decent setup. It's neutral and can drive most headphones out there, so don't see any complains.
> 
> Of course that much more expensive setups might have a better soundstage and better micro-details too, but like I said before: for its price range the ODAC/O2 setup is really good.


 


  
  
 Mentioning the ODAC/O2 is pretty much forbidden there. lol.


----------



## KeithEmo

I think you will find that the fellow who invented the 0DAC ("he whose name shall not be mentioned") offended a lot of people.....
 and that's why nobody talks about his creations here....       
	

	
	
		
		

		
			




  
 Quote:


> Mentioning the ODAC/O2 is pretty much forbidden there. lol.


----------



## mindbomb

I think I know what this is about. So nwavguy made some enemies if you recall, like nuforce, schiit, and AMB. If fans of one of these products happened to become tastemakers, they could get easily get the ball rolling on some o2 hate.
  
 The other thing is that laypeople aren't great at gauging headphone amp performance. The o2 did a lot of measurements with a punishing 15 ohm load and measured noise at a very low voltage or distortion at near max power output levels and using thd+n instead of just thd, rather than cherry picking for the best numbers. So people might not appreciate that the o2 probably outperforms the amps that they assume are better than it. This is also not helped by the fact that nwavguy was big on the idea of transparency, which can be perceived as a crutch for low performing amps (as an excuse to why it doesn't have better performance).
  
 With the odac, I do think the distortion and jitter performance could be a little better. Jdslabs recently released the ol dac, and I suspect it is better.


----------



## adydula

There are 352 posts in this thread on the O2 and ODAC combo....as long as we keep the designer out of the picture and speak to the amp and dac headfi IMO has allowed this one of a kind. revolutionary low cost high performing piece of headphone gear to be discussed ad-naseum.
  
 I have two of them at the moment and several "modded" ones as well....they all hold up to many others costing more very, very well....people who are new dont know or forger the original design concept or ignore it and compare it at approx $100 to amps costing alot more.
  
 We all know there are other amps that are great and cost more....many are more versatile and have much better mechanical switches etc..but for what the O2 is, a very transparent, straight wire with gain, this amp has weathered the storms of headphone mani for sure.
  
 I think many headphone addicts have or have had an O2 and or an ODAC and can attest to its performance...
  
 Alex
  
 Note as far as JDS labs and its ODAC and having better distortion and jitter specs I would let JDS speak to this. The original was REV A. and now its a REV B. but it was for some usb connectivity issues....the specs are "better" but IMO its so far in the weeds that it doesnt really matter at all...I have compared rev A + rev B many times and I hear no difference at all. Increases in measureable performance at these levels dont necessairly mean you will hear any differences....


----------



## sammaher1

Love the O2+ODAC


----------



## sammaher1

It has a nice exterior, and you can add in batteries if you're savy enough.


----------



## MrMateoHead

I have no real qualms with the O2 other than I probably needed to replace the batteries after about a year or two. The thing may have had one battery "go bad" in the sense that it seems to lose charge faster than I remember.
  
 That and the ODAC has some problems, I went through a series of repairs and finally a replacement, and hear little static "pops" and "clips" once in awhile that let me know it too will probably die. JDS Labs was IMMENSELY helpful in this regard, and other than paying some shipping costs, kept at it until I was back to "normal". From that process I learned that the ODAC Rev B. was also intended to be more reliable, not just a little "cleaner".
  
 I use the ODAC as a source to my bookshelf speakers all the time, and it sounds almost as detailed as the newer AKM in my Onkyo Receiver (damn that thing is good).
  
 When someone puts out a superior combo at about $100-$200 I'll consider it. Until then, this has to be one of the best values in audio that I know of right now.


----------



## raoultrifan

mrmateohead said:


> From that process I learned that the ODAC Rev B. was also intended to be more reliable, not just a little "cleaner" + DSD support.


 
  
 What do you mean by DSD support, please?


----------



## U-3C

raoultrifan said:


> What do you mean by DSD support, please?




Yeah, I was wondering. Never heard of the Rev. B featuring DSD support.


----------



## MrMateoHead

raoultrifan said:


> What do you mean by DSD support, please?


 

 Oops - I had mis-remembered a spec. It doesn't have DSD support.


----------



## U-3C

Curious about the new Objective Line ODAC.

I really want optical in. Not really a common case, I know, which is why the original designer didn't bother with implementing it in, but I'm happy that there is finally an option for people like me. ^_^

Now, if only it has a mic in...

Mayflower Electronics hinted that they will be releasing a new product quite some time ago, and it's basically an ODAC with new features, including optical in and a mic in. Other features have not been unannounced, but those two features are all that I wished that the original ODAC had. Surprised that JDS Labs is the first one to release their new line. Curious about that the Mayflower team can throw out.


----------



## Nec3

u-3c said:


> Curious about the new Objective Line ODAC.
> 
> I really want optical in. Not really a common case, I know, which is why the original designer didn't bother with implementing it in, but I'm happy that there is finally an option for people like me. ^_^
> 
> ...


 
  
 I think the optical in and mic in should have been featured with the JDS Element. I would have been sold on mic-in, since my motherboard's mic-in on my motherboard is pretty noisy.


----------



## jseaber

u-3c said:


> Curious about the new Objective Line ODAC.
> 
> I really want optical in. Not really a common case, I know, which is why the original designer didn't bother with implementing it in, but I'm happy that there is finally an option for people like me. ^_^
> 
> ...


 
  
 The "ODAC with new features" was as a collaboration led by JDS Labs. All Objective retailers were involved in early 2016. Unfortunately, it failed to reach beta testing due to technical limitations
  


nec3 said:


> I think the optical in and mic in should have been featured with the JDS Element. I would have been sold on mic-in, since my motherboard's mic-in on my motherboard is pretty noisy.


 
  
 Thanks for the feedback!


----------



## Nec3

jseaber said:


> The "ODAC with new features" was as a collaboration led by JDS Labs. All Objective retailers were involved in early 2016. Unfortunately, it failed to reach beta testing due to technical limitations
> 
> 
> Thanks for the feedback!


 
  
 I might sound like a spoiled kid but I also think the JDS Labs Element could have also included a bass boost option from the C421 portable amp. 
  
 Right now I've yet to recommend anyone the JDS Element since there are so many competitive options out there on the market for 350USD _(stated on the website as of January 9th, 2017)_, and I currently don't see a reason to not recommend the JDS Labs ODAC/O2 instead which is very flexible, compact and does what it needs to do. I still use my odac/o2 because instead of spending $300 to change a sound signature in the amp portion, I could swap in a Muses02 or LME49720HA (w/ adapter) to do that for me. With the C421 I could just flip a switch and be happy with a change in sound.
  


jseaber said:


> Spoiler: Snipped to conserve space
> 
> 
> 
> ...


 
 I bolded and underlined that statement there. Now I'm no engineer, but I'm an end user. I like pushing buttons where I can see it and buttons can most definitely be an aesthetic. 
  
 However as a former visual arts photographer and currently part of the IT field, minimalism is starting to fade out and people like seeing simple yet powerful options in front of them where they can control/see it. I also think putting buttons in the front could definitely open up some space.


----------



## Naim.F.C

Where is NwAVGuy? I really want him to come back and finish his desktop amp version, ideally with balanced outputs too. Though from what I can remember reading, he seemed to dismiss balanced as actually offering sonic benefits of any kind.


----------



## adydula

AGDR's ODA design....I have built one:
  
 http://www.audiocircle.com/index.php?topic=125353.0
  
 http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda.html
  
 Alex


----------



## U-3C

jseaber said:


> The "ODAC with new features" was as a collaboration led by JDS Labs. All Objective retailers were involved in early 2016. Unfortunately, it failed to reach beta testing due to technical limitations


 
  
 Ah, I see. I'm sorry the project was unsuccessful. 
	

	
	
		
		

		
			




  
 Wish you guys best of luck with whatever else you are working on though! o(^_^)b


----------



## jseaber

u-3c said:


> Ah, I see. I'm sorry the project was unsuccessful.
> 
> 
> 
> ...


 
  
 That's the nature of development! O2 was unable to support the power requirements of the DAC, so it needed to stand on its own. The group was only interested in producing an amp/DAC combo. Thus, we launched OL DAC independently using the core circuitry.
  
 There's little reason for Standalone ODAC to exist at this point.


----------



## adydula

There is finally an independent set of O2 measurements at:
  
 http://www.neurochrome.com/o2-headphone-amp/
  
 http://www.diyaudio.com/forums/headphone-systems/302852-o2-measurements-review.html
  
 You can take a look and see how it measures objectively from an engineer who has an analyzer to do it correctly.
  
 The person is an engineer and has designed a high end headphone amp and is selling it as well.
  
 To make this up and above board the engineer states this in his article.
  
 Alex


----------



## U-3C

adydula said:


> There is finally an independent set of O2 measurements at:
> 
> http://www.neurochrome.com/o2-headphone-amp/
> 
> ...




Nice!


----------



## Jimster480

So I'm a bit of a newbie in regards to dedicated desktop Amps but this ODAC design is actually built by a couple companies based on specifications which were developed (scientifically?) by someone who used to be on this forum?

 Sorry if I am incorrect, but this is what I have gathered from reading about this. One of my audiophile friends has one from mayflower and tells me it punches far above its price class in quality sound reproduction.


----------



## dukefx

adydula said:


> There is finally an independent set of O2 measurements at:
> 
> http://www.neurochrome.com/o2-headphone-amp/
> 
> ...


 
 And yet again a H6X0 has been used for testing. People who complain about not getting an "out of your head" experience obviously have the wrong headphones. My K712 pairs exceptionally well with my modded O2 and I doubt anything other than DSP (or maybe a highly overpriced pair of HD800) could beat the sound stage while still providing the necessary amount on the lower end. His only valid point is the power management circuitry.


----------



## jologskyblues

Noticed the author just conveniently disregarded the design goals of the O2 plus used different reference points for the measurements to magnify the spikes. Even his subjective evaluation showed his bias because he didn't do blind testing. Not surprised since he's probably promoting his own product. 


Sent from my iPad using Tapatalk


----------



## adydula

Those are fair comments. 
  
 His evaluation is still accurate, I agree blind testing is the only way to see if you can really tell objectively if there are any real world differences. But this has been a matter of debate for years....dont want to go there.
  
 And Yes the design goal had a cost factor in mind as well...
  
 Still its nice to know what the analyzer states good or bad...it doesnt make the O2 sound any worse or any better...its still a good amp at a great price.
  
 Alex


----------



## Naim.F.C

It also seemed like a lot of emphasis was placed on performance out of battery usage. Not really fair. Any comparisons to other powered amps etc ought to be on a like for like basis. I also agree that blind testing is the only way forward. 

Only after blind testing did I realise the O2 actually offers the same level of sonic performance as the Violectric V200 and Meier Concerto. It doesn't sound exactly the same as the V200, but that's because the V200 is ever so slightly coloured, whilst the O2 is dead neutral.


----------



## Arkady Duntov

jimster480 said:


> So I'm a bit of a newbie in regards to dedicated desktop Amps but this ODAC design is actually built by a couple companies based on specifications which were developed (scientifically?) by someone who used to be on this forum?
> 
> 
> Sorry if I am incorrect, but this is what I have gathered from reading about this. One of my audiophile friends has one from mayflower and tells me it punches far above its price class in quality sound reproduction.




No, you're correct...except his amp is the Objective2 (O2) and his DAC is the ODAC. I got mine from JDS Labs. It sounds great and I'm quite happy.


----------



## Jimster480

arkady duntov said:


> No, you're correct...except his amp is the Objective2 (O2) and his DAC is the ODAC. I got mine from JDS Labs. It sounds great and I'm quite happy.


 

 So the O2 amp is different? Because the design only is for the ODAC itself right? Or is it for both because when I looked at JDS labs it looked the same as the O2


----------



## adydula

The O2 amp is the "O2" amp.
  
 The ODAC is the "ODAC".
  
 Both are totally standalone and can be used separately or together.
  
 Vendors that sell the O2, and ODAC separately and some have put the two in the same case etc...
  
 I believe JDS sells a O2 and a O2 + ODAC Rev B, as well as a bunch of other stuff.
  
 Alex


----------



## Jimster480

adydula said:


> The O2 amp is the "O2" amp.
> 
> The ODAC is the "ODAC".
> 
> ...


 

 Ah alright that makes sense.
 They are both designed by the same guy right? These are "his specs" as I have seen some sites tout am I correct?


----------



## adydula

You should go over to his blog site and do some reading.....
  
 Alex


----------



## U-3C

adydula said:


> You should go over to his blog site and do some reading.....
> 
> Alex




Just due to the nature of said blog, make that..."a lot of reading."


----------



## Jimster480

u-3c said:


> Just due to the nature of said blog, make that..."a lot of reading."


 

 Where is that?


----------



## Arkady Duntov

jimster480 said:


> Where is that?




He's banned here but use Google to search for 'NwAvGuy'.


----------



## dukefx

Or RocketScientist on diyaudio


----------



## Arkady Duntov

dukefx said:


> Or RocketScientist on diyaudio




Thanks. I didn't know that.


----------



## MrMateoHead

adydula said:


> There is finally an independent set of O2 measurements at:
> 
> http://www.neurochrome.com/o2-headphone-amp/
> 
> ...


 
  
 Wow - Its great to see such a detailed and somewhat "critical" review of the O2. Thanks for the links.
  
 The "dramatic rise" in THD at higher output powers is basically true of any amp - they all have their "sweet spots", and they also sound like s*** when playing out of their performance envelope. That said I've never turned my volume knob much past noon using HE-400s, which are my least efficient headphones. I'm pretty sure I've never clipped a home or car amp either, since I generally can't stand it when the volume starts to hit 80 dB and beyond. So, I try real hard not to worry when an amp distorts at maximum volume and beyond. I'm actually quite impressed that the O2 provides essentially all its usable/rated power at less than 0.01%. That's better than most home AV receivers I read about.
  
 But it would be nice if someone can explain to me why I should or should not care about intermodulation distortion. That and it would be nice to see the result when on AC power, since I'd venture that MOST O2 users stay plugged in, like me!
  
 I've never thought that the O2 was the end-all be-all amp for headphones in the world, but I certainly don't feel that other amps will be a resounding unimpeachable improvement over an O2 playing within its performance envelope with normal headphones at reasonable (e..g 60-80 dB) volumes. Call me jaded - I just seek out the power I think my speakers need to hit a SPL in my room, then add 3-10dB if I can afford it! If you want to change the sound, you start by changing the speakers, IMO. That said I can't lie, at least in the case of AV receivers, I convinced myself that an Onkyo amp sounds "lean", my old Yamaha a little "warm". Don't know why, and don't know if I'd still think so in a blind / controlled test.
  
 I can say I've heard the battery-drain "pulsing" - its bad, and with no low battery indicator, the first time I heard it I thought I'd broken something. Then again I tend to leave mine plugged in, going on battery once in awhile for the sake of cycling them. Considering how expensive most "audiophile" headphone amps are these days, I happily accept that flaw since the price is reasonable.


----------



## turkayguner

Hello guys,
  
 How does the combo do with a Shure SE846? Currently I prefer the iPad mini 4, iPhone 5s and Macbook Air's plain headphone out over my Apogee ONE, which makes me sad. I love the Apogee ONE's recording audio features so much, and its portability. Mainly, the bass was so problematic when I pair my SE846 (also my ATHM50x) with Apogee ONE, I was not sure why and digged up the internet. Found that the output impedance of an amp is very important to match the impedance of the headphone. Those articles etc led me here to the O2/ODAC thread. I need your opinions before I make my purchase.


----------



## adydula

Mr MateoHead...
  
 Just an FYI...you can follow the discussion with Tom the designer of the HP1 amp over at DIY in the headphone section.
  
 Also AGDR might send his O2 Booster Board out for a similar analysis...
  
 You can ask Tom directly about the IMD concern as well....
  
 Alex


----------



## Jimster480

turkayguner said:


> Hello guys,
> 
> How does the combo do with a Shure SE846? Currently I prefer the iPad mini 4, iPhone 5s and Macbook Air's plain headphone out over my Apogee ONE, which makes me sad. I love the Apogee ONE's recording audio features so much, and its portability. Mainly, the bass was so problematic when I pair my SE846 (also my ATHM50x) with Apogee ONE, I was not sure why and digged up the internet. Found that the output impedance of an amp is very important to match the impedance of the headphone. Those articles etc led me here to the O2/ODAC thread. I need your opinions before I make my purchase.


 

 Depends on how much you are willing to spend? The FiiO K1 is quite good for a low price if you just want to try out something better.
 But this ODAC/AMP is one of the best rated things on this page and multiple Audiophile friends of mine have recommended it to me as its price/Sound Quality ratio is astounding.


----------



## turkayguner

I will buy the ODAC and the O2 seperately. But which gain setup do I need for my headphones? I have HD650 (300 ohms), ATHM50x (38 ohms) and Shure SE846 (9 ohms). "1x - 2.5x" or "1x - 3.5x" or "1x - 6.5x" ?


----------



## turkayguner

jimster480 said:


> Depends on how much you are willing to spend? The FiiO K1 is quite good for a low price if you just want to try out something better.
> But this ODAC/AMP is one of the best rated things on this page and multiple Audiophile friends of mine have recommended it to me as its price/Sound Quality ratio is astounding.


 
 I do not want something just a tad better, I want the best for the money. The best for my current headphones actually.


----------



## U-3C

turkayguner said:


> I will buy the ODAC and the O2 seperately. But which gain setup do I need for my headphones? I have HD650 (300 ohms), ATHM50x (38 ohms) and Shure SE846 (9 ohms). "1x - 2.5x" or "1x - 3.5x" or "1x - 6.5x" ?


 as low as possible for comfortable listening levels.


----------



## HotIce

u-3c said:


> as low as possible for comfortable listening levels.


 
  
 Yeah, given the nature of the circuitry, I'd pick a gain level which let your volume potenziometer position to be around 1200 ... 1300 position, at your normal listening SPL.


----------



## Jimster480

turkayguner said:


> I do not want something just a tad better, I want the best for the money. The best for my current headphones actually.


 

 So how much are you willing to spend then?
 Because ODAC is like $280, if you want to spend that then pick one up.
 I don't think you get a better "bang for the buck" setup


----------



## U-3C

jimster480 said:


> So how much are you willing to spend then?
> 
> Because ODAC is like $280, if you want to spend that then pick one up.
> 
> I don't think you get a better "bang for the buck" setup




"Bang for buck" it's so subjective though.

Many argue the Cord Mojo is the best bang for buck. Many argue the m902 is the best value you can get. Some claim xyz brand new sub 100 dollar dac amp combo is the newest bang for buck. The next day the same person will claim a tube amp from eBay changes everything and is better then any thousands dollar well respected setup that is always talked about on Head-Fi. Meanwhile, here I am, firmly believing that good onboard and dsp offers way more value then any of those.

Choose between my ghetto setup and a free focal utopia with good knows what paired with it, and I'll choose my dsp every time.

Figure out what you want, then find a setup that achieves it out comes close to it with the least amount of money. That's the most bang for buck for you and you only.


----------



## turkayguner

hotice said:


> Yeah, given the nature of the circuitry, I'd pick a gain level which let your volume potenziometer position to be around 1200 ... 1300 position, at your normal listening SPL.


 
  


u-3c said:


> as low as possible for comfortable listening levels.


 
  
 So.. Which setup will be enough for the headphones I'd stated? I cannot demo that is why I'm asking it here.


----------



## castleofargh

hotice said:


> u-3c said:
> 
> 
> > as low as possible for comfortable listening levels.
> ...


 

 not going to happen on the O2. even 1X gain is already fairly loud for the hd650 at 12 o'clock if we count a 2V DAC output(at least I never use it that loud, but I'm the quiet listening type). and the shure will be like 20db louder.
  the se846 is an abomination when it comes to specs, sensitive IEM with the impedance of a speaker, stupid. at the very least crosstalk will end up ugly on almost any amp(not that it's necessarily audible or annoying though). the good thing about the O2 is the low noise floor and fairly low impedance, both variables could become a problem with that IEMs. the bad thing is that it will be hard to avoid channel imbalance at normal loudness, even on 1X.
  
 IMO almost any desktop amps including the O2 are very fine for the hd650 (most of the guys in the 650's topic don't agree but they usually don't have a clue what objective reality means). as for the shure, maybe with a way to measure each channel (multimeter?) and fool around until he gets lucky? works fairly well on my O2 in most cases.
  I personally have a uha760(negative gain, low noise, digital control of the volume for good channel matching at all time) for sensitive IEMs that cause trouble with my DAPs, but it's not exactly cheap. and I use the O2 for my hd650 like a fool who doesn't like music
	

	
	
		
		

		
			





. I have no idea if it's the "best" choice, or the best bang for the buck, it's what I ended up being comfortable with.
  
  @Turk we almost always lack the measurements that would let us give you a clear objective answer as to which is the best. even when we have have all the measurements we want, what if an amp has a little more channel imbalance, but a little less distortions than another amp? how do we decide which is the better amp? IMO, when you pick something and don't have too many things making you mad about it, that's when you've found the best device for yourself. but trying is still a necessary step.


----------



## Jimster480

u-3c said:


> "Bang for buck" it's so subjective though.
> 
> Many argue the Cord Mojo is the best bang for buck. Many argue the m902 is the best value you can get. Some claim xyz brand new sub 100 dollar dac amp combo is the newest bang for buck. The next day the same person will claim a tube amp from eBay changes everything and is better then any thousands dollar well respected setup that is always talked about on Head-Fi. Meanwhile, here I am, firmly believing that good onboard and dsp offers way more value then any of those.
> 
> ...


 

 Depends on how much buck you have.
 Chord Mojo is highly rated but For a desktop DAC/Amp the O2Dac is really a great value for what has been called "reference quality" audio and the ability to drive basically any headphones on the planet.
 If SQ is what you want all my research suggests that this is what to buy.
  
 Now if you are in the Entry level you can get a FiiO K1 (as I did) and it works great for alot of lower priced Cans/IEM's upto anything really with 100imped and it does sound pretty good overall (especially for the price) with a wide soundstage and decent instrument separation.


----------



## dukefx

turkayguner said:


> I will buy the ODAC and the O2 seperately. But which gain setup do I need for my headphones? I have HD650 (300 ohms), ATHM50x (38 ohms) and Shure SE846 (9 ohms). "1x - 2.5x" or "1x - 3.5x" or "1x - 6.5x" ?


 
 No resistors for low gain and 649 Ohm (680 if you need something more common) resistors for high gain. That will get you a bit more than 3x gain which is the max it can handle with the ODAC as input.


----------



## HotIce

castleofargh said:


> not going to happen on the O2. even 1X gain is already fairly loud for the hd650 at 12 o'clock if we count a 2V DAC output(at least I never use it that loud, but I'm the quiet listening type). and the shure will be like 20db louder.


 
  
 But that is fine. If you are at 1x with 2V input, given the O2 p2p swing potential, you are far away from clipping.
 The risk with the O2 circuitry is the contrary. Where high gain settings can lead to clipping even at 40dB SPL listening sessions.
 So the rule should state like "Use the minimum gain setting which allows you to listen music at the closest volume position of 1200"


----------



## jologskyblues

My headphones have 32 Ohm impedance and 101 dB sensitivity while my DAC has a 2.25Vrms line out voltage. Most modern mastered music gets pretty loud at just above 9 o'clock on the volume dial with only 1x gain on the O2.


----------



## castleofargh

hotice said:


> castleofargh said:
> 
> 
> > not going to happen on the O2. even 1X gain is already fairly loud for the hd650 at 12 o'clock if we count a 2V DAC output(at least I never use it that loud, but I'm the quiet listening type). and the shure will be like 20db louder.
> ...


 
 I was just answering your post. there isn't really a gain where normal listening level will be at 12 ot 13 o'clock with the hd650(unless you really like loud music). even unity gain is pretty loud (clearly too loud for me and I use replay gain and -5db for my EQ).  of course the se846 is going to be 20db louder so it's just not an option without massive digital attenuation.


----------



## turkayguner

castleofargh said:


> ..the bad thing is that it will be hard to avoid channel imbalance at normal loudness, even on 1X.


 
  
 There is a short volume control cable in the SE846 package. May it solve that channel imbalance issue without sacrificing any quality from the digital domain?


----------



## AverageGuyNC

I'm new and first off bought a mayflower o2/dac and hifiman he400i (which I like that combo) and also got a Fostex th900 which I won on ebay and I am wondering how good the o2 should be with the Fostex? And is there another amp that people really like with either of these headphones if I ever decide to upgrade? thx!


----------



## Jimster480

averageguync said:


> I'm new and first off bought a mayflower o2/dac and hifiman he400i (which I like that combo) and also got a Fostex th900 which I won on ebay and I am wondering how good the o2 should be with the Fostex? And is there another amp that people really like with either of these headphones if I ever decide to upgrade? thx!


 

 My friend has a O2/DAC and he uses it for all of his headphones. He said it is almost of reference quality for the price and really can't be beat unless you go into the high end tiers and that the amp itself is good enough to drive basically any pair of headphones period.


----------



## AverageGuyNC

​Oh, so the O2/DAC is probably as good or better SQ wise as the Jotunheim? Ok, well that makes me feel better then! Thanks for the reply


----------



## U-3C

averageguync said:


> ​Oh, so the O2/DAC is probably as good or better SQ wise as the Jotunheim? Ok, well that makes me feel better then! Thanks for the reply




Now way of knowing that as we don't know what sounds you like.


----------



## Jimster480

averageguync said:


> ​Oh, so the O2/DAC is probably as good or better SQ wise as the Jotunheim? Ok, well that makes me feel better then! Thanks for the reply


 

 No problem!
  
 I will say that the SChiit products do look very good and I plan on getting a Schiit stack myself but probably will also end up with an O2/DAC due to how good it is for the price range.


----------



## turkayguner

Guys, I need some recommendations for the engraving. I am considering two different engravings for the amp and the dac. I would appreciate any ideas. Thanks!


----------



## U-3C

turkayguner said:


> Guys, I need some recommendations for the engraving. I am considering two different engravings for the amp and the dac. I would appreciate any ideas. Thanks!




What do you like? 

No really, anything or types of things you are considering to put on your o2? Anything you really don't want to put on your o2?

Some put emotional scenes from shows that they love, some put album covers, logos, famous people, artwork, text, anything that resonates with them that they like. Maybe some picture of food or a cat meme? A headphone picture? Cars? Architecture? Picasso? Cover of book you like? Batman vs Superman symbol?


----------



## AverageGuyNC

u-3c said:


> Now way of knowing that as we don't know what sounds you like.




I'm starting our so I'm not that sure either? I like good detail where u can hear all the different vocals and instruments. And I like plenty of bass (warm sound I think it's referred to?). But to me good Sq is good Sq, bad would be stuff like lots of hiss and 
distortion or "muddy" sounding


----------



## Jimster480

averageguync said:


> I'm starting our so I'm not that sure either? I like good detail where u can hear all the different vocals and instruments. And I like plenty of bass (warm sound I think it's referred to?). But to me good Sq is good Sq, bad would be stuff like lots of hiss and
> distortion or "muddy" sounding


 

 Do you need headphones and an audio stack? Or just an audio stack?


----------



## AverageGuyNC

So far I have hifiman he400i and fostex th900. The fostex were purchased off ebay with a 4 pin xlr. I've ordered a viablue 1/4 inch connector to swap out to use on my o2. The jotunheim has an xlr out that would work with the way they are now. So I think I'm going to put a $15 connector on there and use the o2 rather than spend $500 on a jotunheim since fostex still have factory cables so it wouldn't even be balanced. Even though it's using the balanced out. Am I right? 

I'm not even sure the o2 would sound better or worse than jotunheim with a regular connection (not balanced?) But the mjolnir has xlr and has tube so I've had a hard time making my mind up


----------



## AverageGuyNC

jimster480 said:


> Do you need headphones and an audio stack? Or just an audio stack?




Have fostex th900 and o2/dac. How good would that sound? Any amp within 500-600$ that would be better with it?


----------



## Jimster480

averageguync said:


> Have fostex th900 and o2/dac. How good would that sound? Any amp within 500-600$ that would be better with it?


 

 I honestly don't think so.
 Unless you want to go to one of the new multibit Schiit stacks w/ a new amp or just use the O2 Amp. Its a great amp with enough power to run basically any headphones with great fidelity.
  
 The Multibit DAC's from Schiit might be better than ODAC but I haven't tested side by side as I have neither set yet but should have one or both soon enough.
  
 From what I have read comparatively the o2/dac is really a great value and hard to beat unless you are spending atleast twice that.
  
 Now I think that the Modi Multibit + Magni does come close for about $80 more (possibly better, would have to test side by side) but overall Tube amps change the sound and tubes can be expensive in their own right. If you want reference quality audio (as it was intended to be) the stack you already have is hard to beat!


----------



## AverageGuyNC

OK so how much difference does a good dac make, like the bifrost? And I'm not really an audiophile. I mainly watch a decent amount of music videos on YouTube and watch dvd's on my computer and I figure it's worth spending money on nice headphones and amp/dac since my old $50 pair that ran off the pc have lasted me 15 years and still going so I think I can get good value out of these premium ones! I have music streaming on Amazon prime that I've considered using now with good headphones.

 Is Amazon music streaming or even YouTube decent quality or just average?


----------



## jseaber

averageguync said:


> OK so how much difference does a good dac make, like the bifrost? And I'm not really an audiophile. I mainly watch a decent amount of music videos on YouTube and watch dvd's on my computer and I figure it's worth spending money on nice headphones and amp/dac since my old $50 pair that ran off the pc have lasted me 15 years and still going so I think I can get good value out of these premium ones! I have music streaming on Amazon prime that I've considered using now with good headphones.
> 
> Is Amazon music streaming or even YouTube decent quality or just average?




Find headphones you enjoy first. This is the most important decision. 

Add an amplifier if the headphones you choose need a boost. 

Only consider a DAC if your PC or DAP is audibly noisy. DACs contribute the least to overall audio quality, compared to headphones and amplifiers.


----------



## Jimster480

jseaber said:


> Find headphones you enjoy first. This is the most important decision.
> 
> Add an amplifier if the headphones you choose need a boost.
> 
> Only consider a DAC if your PC or DAP is audibly noisy. DACs contribute the least to overall audio quality, compared to headphones and amplifiers.


 

 Basically this!
  
 If your PC has poor audio quality there are a number of cheap options to significantly improve it.
  
 The only time I would disagree is if he wouldn't be able to tell if headphones actually need more power (many people cannot) in which case a decent amp should be first and then test headphones with it.


averageguync said:


> OK so how much difference does a good dac make, like the bifrost? And I'm not really an audiophile. I mainly watch a decent amount of music videos on YouTube and watch dvd's on my computer and I figure it's worth spending money on nice headphones and amp/dac since my old $50 pair that ran off the pc have lasted me 15 years and still going so I think I can get good value out of these premium ones! I have music streaming on Amazon prime that I've considered using now with good headphones.
> 
> Is Amazon music streaming or even YouTube decent quality or just average?


 
  
 If you are just streaming amazon + youtube I wouldn't worry too much. Like jseaber said you would benefit more from an amp if the headphones you choose require one.
  
 Now if you wanted to go out and get a ODAC/AMP then that would be more than what you would need overall and should last you a long time with great quality.


----------



## AverageGuyNC

jseaber said:


> Find headphones you enjoy first. This is the most important decision.
> 
> Add an amplifier if the headphones you choose need a boost.
> 
> Only consider a DAC if your PC or DAP is audibly noisy. DACs contribute the least to overall audio quality, compared to headphones and amplifiers.




I got a Hifiman he400i and O2/DAC a month ago and really like it.

 I won an auction on ebay and bought Fostex th900. They sound like it would be a perfect fit for me in reviews I read sound wise plus I wanted closed back. I just need to swap out the plug since the guy put XLR on it and I can only use 1/4 or 1/8 inch plugs. 

I'm just wondering if o2+dac would be a great fit for the Fostex or if I should consider upgrading one or both or other ideas for "end game" like should I even consider getting new USB or power cord etc? Not wanting to change wire on the headphones at this time.


----------



## AverageGuyNC

jimster480 said:


> Basically this!
> 
> If your PC has poor audio quality there are a number of cheap options to significantly improve it.
> 
> ...




Well read my reply to him but I have an o2-amp-odac and good headphones. Should I even consider swapping USB cable or power wire maybe? I don't mind spending money if there is decent value there but don't want to just spend it to feel cool haha


----------



## Jimster480

averageguync said:


> Well read my reply to him but I have an o2-amp-odac and good headphones. Should I even consider swapping USB cable or power wire maybe? I don't mind spending money if there is decent value there but don't want to just spend it to feel cool haha


 

 Depends on what power supply you have. People have reported good gains with many DAC/AMP's with Linear power supplies or higher quality power supplies.

 if you already have a good linear PSU then don't worry about switching it up and just keep your current setup. Usually headphone cables make very little difference unless you have one with some insane impedance.


----------



## AverageGuyNC

jimster480 said:


> Depends on what power supply you have. People have reported good gains with many DAC/AMP's with Linear power supplies or higher quality power supplies.
> 
> 
> if you already have a good linear PSU then don't worry about switching it up and just keep your current setup. Usually headphone cables make very little difference unless you have one with some insane impedance.




I just have the power cord that came with it. It's a mayflower o2 with built in dac. I've seen some power cords for hundreds and some for thousands of dollars but I wouldn't spend more than $30 - 40 for one since I only paid 240 for it to start with. I'm not having a problem with distortion that I am able to notice but who knows, could it make a noticeable difference? And I'm considering getting a power brick that helps filter static and power spikes too.


----------



## Jimster480

averageguync said:


> I just have the power cord that came with it. It's a mayflower o2 with built in dac. I've seen some power cords for hundreds and some for thousands of dollars but I wouldn't spend more than $30 - 40 for one since I only paid 240 for it to start with. I'm not having a problem with distortion that I am able to notice but who knows, could it make a noticeable difference? And I'm considering getting a power brick that helps filter static and power spikes too.


 

 Nah I mean you don't need anything too fancy. And don't buy fancy power cords, only the physical adapter is really going to make any difference.
 I'm not sure how good the stock one is or what the next tier is either.


----------



## Nitreb

jimster480 said:


> averageguync said:
> 
> 
> > I just have the power cord that came with it. It's a mayflower o2 with built in dac. I've seen some power cords for hundreds and some for thousands of dollars but I wouldn't spend more than $30 - 40 for one since I only paid 240 for it to start with. I'm not having a problem with distortion that I am able to notice but who knows, could it make a noticeable difference? And I'm considering getting a power brick that helps filter static and power spikes too.
> ...


 

 I have the stock wallwart (a Triad PSU) JDS sells with their O2 and it's fine - no need to spend hundred or thousands of dollars for another one.


----------



## dukefx

It wouldn't make much sense anyways. It's an AC adapter. Filtering is done inside the O2, so if you want a PSU upgrade you need to do some serious work. The DAC is USB powered, so it's a lot easier to fiddle with and there are a lot of options.


----------



## Jimster480

nitreb said:


> I have the stock wallwart (a Triad PSU) JDS sells with their O2 and it's fine - no need to spend hundred or thousands of dollars for another one.


 

 No I wouldn't spend hundreds or thousands, but I have seen some high quality linear PSU's for $50 or so. So one of those MIGHT be a worthwhile upgrade, but I can't say for sure.


----------



## AverageGuyNC

In what way? A better usb cord or inside the 02/DAC? (It's a combo with both in same case.) So the regular power cord isn't worth messing with? Thx


----------



## AverageGuyNC

dukefx said:


> It wouldn't make much sense anyways. It's an AC adapter. Filtering is done inside the O2, so if you want a PSU upgrade you need to do some serious work. The DAC is USB powered, so it's a lot easier to fiddle with and there are a lot of options.







jimster480 said:


> No I wouldn't spend hundreds or thousands, but I have seen some high quality linear PSU's for $50 or so. So one of those MIGHT be a worthwhile upgrade, but I can't say for sure.




U mean the PSU that's inside it? Swapping out some of the internals? I was originally meaning if any of the cords (power or usb) would be worth while upgrading? But if that's a good option, then I'm curious! What about brand names or where to get them from? Thx!


----------



## AverageGuyNC

nitreb said:


> I have the stock wallwart (a Triad PSU) JDS sells with their O2 and it's fine - no need to spend hundred or thousands of dollars for another one.


 

My o2/dac is from mayflower but I assume both have decent power cords? Or are u saying JDS offers an upgraded one that is better than stock like mine?


----------



## dukefx

No matter what you got, they need to pick from parts approved by NwAvGuy. They won't sell you anything that won't perform well. The only thing they have no control over is your USB power which may affect the DAC.


----------



## AverageGuyNC

dukefx said:


> No matter what you got, they need to pick from parts approved by NwAvGuy. They won't sell you anything that won't perform well. The only thing they have no control over is your USB power which may affect the DAC.




So change the usb cord?


----------



## Jimster480

If it is USB powered then there is little you can do other than get a powered USB hub with good power output and plug it into that hub instead of into the motherboard directly.


----------



## dukefx

Yup, either powered hub (might not be better), an isolator or a linear PSU with custom Y cable, but it's hardly worth the trouble, I can tell you that, unless you have some junkbucket from the stone ages. ODAC rev. B isn't as picky as its predecessor. 
 The only things really worth tampering with are the opamps in the O2. There's plenty of info here a few pages back and in the DIY section's opamp thread.


----------



## AverageGuyNC

dukefx said:


> Yup, either powered hub (might not be better), an isolator or a linear PSU with custom Y cable, but it's hardly worth the trouble, I can tell you that, unless you have some junkbucket from the stone ages. ODAC rev. B isn't as picky as its predecessor.
> The only things really worth tampering with are the opamps in the O2. There's plenty of info here a few pages back and in the DIY section's opamp thread.




OK will search for "upgrade opamps"? I'll try that thanks! And have u messed with power conditioners? There was a monster mp pro 2000 ($100) and a Furman one ($80) and pyco ($50) on amazon. I run my amp, computer and ps4 off one brick so was considering one but didn't plan on spending more than $100 unless there was an actual need for it. But they have a Belkin one that has some filtration for less than $25. Is there a good thread on power conditioners?


----------



## AverageGuyNC

jimster480 said:


> If it is USB powered then there is little you can do other than get a powered USB hub with good power output and plug it into that hub instead of into the motherboard directly.




Interesting idea hmmm.. and yeah it's a rev b just got it last month


----------



## Jimster480

dukefx said:


> Yup, either powered hub (might not be better), an isolator or a linear PSU with custom Y cable, but it's hardly worth the trouble, I can tell you that, unless you have some junkbucket from the stone ages. ODAC rev. B isn't as picky as its predecessor.
> The only things really worth tampering with are the opamps in the O2. There's plenty of info here a few pages back and in the DIY section's opamp thread.


 

 Yea those custom cables lol they can get pricey, but I have read that there are guys on this forum who make them quite cheaply.
  
 Technically I could make one myself (as could he) with some wire strippers a connector and some time.
  
 I can tell you that USB power is certainly not linear.


----------



## AverageGuyNC

Well update.... My month old O2 stopped working. Computer won't even recognize a device anymore. Sent it back for repairs. I knew I took a little gamble when it says "refurbished" but only lasting a month? It still has 10 year warranty but I asked if they could send me a different unit but they didn't say. Now the wait...


----------



## Jimster480

averageguync said:


> Well update.... My month old O2 stopped working. Computer won't even recognize a device anymore. Sent it back for repairs. I knew I took a little gamble when it says "refurbished" but only lasting a month? It still has 10 year warranty but I asked if they could send me a different unit but they didn't say. Now the wait...


 

 Ouch, that really sucks man.
  
 Make sure also that your computer doesn't have any USB fuse problems.
 i've seen this happen before too.


----------



## AverageGuyNC

jimster480 said:


> Ouch, that really sucks man.
> 
> Make sure also that your computer doesn't have any USB fuse problems.
> 
> i've seen this happen before too.




Hmm. Well I tried it on another computer and it would not recognize it at all either so I really think it's the dac. And my computer has usb ports on front and back and it wouldn't work on any of them. Well I'm thinking about getting something else incase of more problems but not sure yet.


----------



## Jimster480

averageguync said:


> Hmm. Well I tried it on another computer and it would not recognize it at all either so I really think it's the dac. And my computer has usb ports on front and back and it wouldn't work on any of them. Well I'm thinking about getting something else incase of more problems but not sure yet.


 

 How much did you pay for refurb?


----------



## dukefx

jimster480 said:


> dukefx said:
> 
> 
> > Yup, either powered hub (might not be better), an isolator or a linear PSU with custom Y cable, but it's hardly worth the trouble, I can tell you that, unless you have some junkbucket from the stone ages. ODAC rev. B isn't as picky as its predecessor.
> ...


 
 It can go from 5$ all the way to the stars, it all depends on how much you believe in cable voodoo XD
 Personally, I don't spend much on cables. OFC with proper shielding and gold/silver plated pure metal connectors tend to do it for me. That's 50$ tops for a cable.


----------



## Nitreb

averageguync said:


> nitreb said:
> 
> 
> > I have the stock wallwart (a Triad PSU) JDS sells with their O2 and it's fine - no need to spend hundred or thousands of dollars for another one.
> ...


 

 I bought my O2 from JDS about 3-4 years ago. As far as I recall, there was a wallwart for the North American market, and one for the European market. They didn,t offer any basic/premium options.


----------



## Jimster480

dukefx said:


> It can go from 5$ all the way to the stars, it all depends on how much you believe in cable voodoo XD
> Personally, I don't spend much on cables. OFC with proper shielding and gold/silver plated pure metal connectors tend to do it for me. That's 50$ tops for a cable.


 

 Yea honestly cable's dont matter that much. As long as you have a good one it literally won't make an actual difference.


----------



## Arkady Duntov

jimster480 said:


> Yea honestly cable's dont matter that much. As long as you have a good one it literally won't make an actual difference.




There really isn't any point attempting to "upgrade" an ODAC or O2 without identifying a specific problem in the unit which requires correction. It's not as if any defects have been identified in the designs.


----------



## AverageGuyNC

arkady duntov said:


> There really isn't any point attempting to "upgrade" an ODAC or O2 without identifying a specific problem in the unit which requires correction. It's not as if any defects have been identified in the designs.




No "problem", just wasn't sure if there were cheap upgrades that might make a noticeable improvement. I have seen lots of expensive power wire upgrades and this and that, etc (tho I'm sure they're for way higher priced DACs as well).


----------



## Jimster480

averageguync said:


> No "problem", just wasn't sure if there were cheap upgrades that might make a noticeable improvement. I have seen lots of expensive power wire upgrades and this and that, etc (tho I'm sure they're for way higher priced DACs as well).


 

 Yea most of those are snake oil I tell you.
  
 There are few upgrades which really make differences, but often they are power supplies especially with lower cost units that have crappy non-linear PSU's.


----------



## AverageGuyNC

​Yeah,I've seen 2k plus power cables and just cant see how the value could be there. Maybe a few hundred on a high end amp, but I read that there were $4,000 ones out there. It blows my mind and not even sure on the most expensive power cable is.. Just wonder if a reasonably priced one could benefit the ordinary guys out there with regular stuff


----------



## AverageGuyNC

​Refub was $240 and the reg one was 285. saves $45 and comes with same 10 yr warranty. And I figure both could have problems. I've been considering getting something higher up and hold one to this as backup maybe. but some say it will be as good as most under $1,000 so not sure if going for, say, a chord mojo would be worth it? heard good things about both really


----------



## Jimster480

averageguync said:


> ​Refub was $240 and the reg one was 285. saves $45 and comes with same 10 yr warranty. And I figure both could have problems. I've been considering getting something higher up and hold one to this as backup maybe. but some say it will be as good as most under $1,000 so not sure if going for, say, a chord mojo would be worth it? heard good things about both really



To be honest I don't think that the chord Mojo would be much better. The only thing I can really think that might be better would be one of the schiit multi-bit DAC. Because those take a completely different path in decoding audio and many people have said that they are much better than the Delta Sigma approach found in mostly everything else. Even the Mojo uses a Delta Sigma style approach with its fpga. So I think it for regular audio products objective2 is really as good as you're going to get.


----------



## jologskyblues

dukefx said:


> It can go from 5$ all the way to the stars, it all depends on how much you believe in cable voodoo XD
> Personally, I don't spend much on cables. OFC with proper shielding and gold/silver plated pure metal connectors tend to do it for me. That's 50$ tops for a cable.


 

 I agree. Particularly for USB cables, those don't have to be expensive but it's very important that the data and power wires in the cable are properly isolated or shielded from each other as any interference between the two may cause audible and measurable noise/distortion.


----------



## AverageGuyNC

jimster480 said:


> To be honest I don't think that the chord Mojo would be much better. The only thing I can really think that might be better would be one of the schiit multi-bit DAC. Because those take a completely different path in decoding audio and many people have said that they are much better than the Delta Sigma approach found in mostly everything else. Even the Mojo uses a Delta Sigma style approach with its fpga. So I think it for regular audio products objective2 is really as good as you're going to get.




So the Multibit option is the way to go for sure? I have not read much comparison yet on that but I've looked at it vs gungnir and doesn't seem to be a $400 difference unless going balanced. 

I have been considering getting it ($600) with a burson soloist ($400). Should I spend more on a DAC than the amp? One person said to spend the most on the headphones and amp and to cheap out on the dac was best? This would be to go with a Hifiman he400i and Fostex th900. There was a convincing review on here by sumofallparts saying how good the th900+burson solist was. Would that combo be good for $1,000?


----------



## Jimster480

averageguync said:


> So the Multibit option is the way to go for sure? I have not read much comparison yet on that but I've looked at it vs gungnir and doesn't seem to be a $400 difference unless going balanced.
> 
> I have been considering getting it ($600) with a burson soloist ($400). Should I spend more on a DAC than the amp? One person said to spend the most on the headphones and amp and to cheap out on the dac was best? This would be to go with a Hifiman he400i and Fostex th900. There was a convincing review on here by sumofallparts saying how good the th900+burson solist was. Would that combo be good for $1,000?


 

 Now that they have Modi Multibit you can literally get a Multibit DAC for $250.
  
 Personally i think that can't be beat at that price.
  
 Magni is $99, or you could use your O2DAC's Amplifier stage only since you already have it. meaning you could get a better DAC for $250 only.
  
 I wouldn't go crazy on the higher end setups unless you have some really really high end refined cans with some serious power requirements.


----------



## AverageGuyNC

jologskyblues said:


> I agree. Particularly for USB cables, those don't have to be expensive but it's very important that the data and power wires the cable are properly isolated or shielded from each other as any interference between the two may cause audible and measurable noise/distortion.




Well the power cable runs from the back of the o2-amp-odac to the power brick and the usb cable goes to the front and hooks on my computer. I saw audio quest usb cable for 30-40$ and gold plated Belkin that looked good quality for $10. So worth $10 or no.


----------



## jologskyblues

averageguync said:


> Well the power cable runs from the back of the o2-amp-odac to the power brick and the usb cable goes to the front and hooks on my computer. I saw audio quest usb cable for 30-40$ and gold plated Belkin that looked good quality for $10. So worth $10 or no.


 

 Among those I've tried with my USB-powered DAC, the AudioQuest Forest, HP printer USB cable and QED Performance Graphite seem to all have poor data and power line isolation. Monoprice, Analysis Plus USB 2.0 and Wireworld Ultraviolet offer good isolation and quality.
  
 BTW, shorter cable lengths are more ideal.


----------



## AverageGuyNC

jimster480 said:


> Now that they have Modi Multibit you can literally get a Multibit DAC for $250.
> 
> Personally i think that can't be beat at that price.
> 
> ...




Yeah the o2-amp-odac has enough to power it OK I think, but do you think the higher end DAC (bifrost multibit vs Magni Multibit) would help with sensitive, high quality th900 hp?


----------



## AverageGuyNC

jologskyblues said:


> Among those I've tried with my USB-powered DAC, the AudioQuest Forest, HP printer USB cable and QED Performance Graphite seem to all have poor data and power line isolation. Monoprice, Analysis Plus USB 2.0 and Wireworld Ultraviolet offer good isolation and quality.
> 
> BTW, shorter cable lengths are more ideal.




Thanks, I've been a Mono price fan for or a while now, will look there


----------



## Jimster480

averageguync said:


> Yeah the o2-amp-odac has enough to power it OK I think, but do you think the higher end DAC (bifrost multibit vs Magni Multibit) would help with sensitive, high quality th900 hp?


 

 No I don't think that it would be better.
 Magni is also a Amp and Bifrost is a DAC.
  
 Bifrost and Modi have the same DAC chips inside of them, the only difference is the power supply + upgradability.
  
 personally I am going to try out Modi Multibit first and then see if I want to invest in a higher end multibit later on.


----------



## AverageGuyNC

jimster480 said:


> No I don't think that it would be better.
> Magni is also a Amp and Bifrost is a DAC.
> 
> Bifrost and Modi have the same DAC chips inside of them, the only difference is the power supply + upgradability.
> ...




Yeah meant Modi, you are right. Well, they allow returns and I even think they suggest getting two different items and just returning the one we don't want so that's my next idea. May get the burson and audition it too! (Amazon has a great return policy if I don't care for it). 

Think I have a plan now! I appreciate all the ideas


----------



## Jimster480

averageguync said:


> Yeah meant Modi, you are right. Well, they allow returns and I even think they suggest getting two different items and just returning the one we don't want so that's my next idea. May get the burson and audition it too! (Amazon has a great return policy if I don't care for it).
> 
> Think I have a plan now! I appreciate all the ideas


 

 No problem man, happy listening!


----------



## dukefx

You guys really lost me here with the multibit talk. Most DS DACs are multibit (including the ODAC). Instead of 1 switch they usually have about 3-6 (good luck getting that info from their datasheets). 1 bit DACs are rather uncommon nowadays. It's pretty much DS vs old school R2R, or simply explained a few switches vs lots of resistors.


----------



## AverageGuyNC

dukefx said:


> You guys really lost me here with the multibit talk. Most DS DACs are multibit (including the ODAC). Instead of 1 switch they usually have about 3-6 (good luck getting that info from their datasheets). 1 bit DACs are rather uncommon nowadays. It's pretty much DS vs old school R2R, or simply explained a few switches vs lots of resistors.


 

I'm kinda new but look at schiit audio's site and you have the option to get delta Sigma dacs, or multibit for more money.


----------



## Jimster480

dukefx said:


> You guys really lost me here with the multibit talk. Most DS DACs are multibit (including the ODAC). Instead of 1 switch they usually have about 3-6 (good luck getting that info from their datasheets). 1 bit DACs are rather uncommon nowadays. It's pretty much DS vs old school R2R, or simply explained a few switches vs lots of resistors.


 

 Multibit in what we were talking about a R2R actual full ladder DAC's processing a full 16-21 bits simultaneously.
  
 I know that the ODAC uses a TI DAC with advanced segment Delta-sigma processing. So does the FiiO K1 (infact they use the same DAC).


----------



## dukefx

Why not simple use DS or R2R instead. Multibit is such an outdated term as it refers to anything but 1 bit which includes all R2Rs and most DSs.


----------



## AverageGuyNC

dukefx said:


> Why not simple use DS or R2R instead. Multibit is such an outdated term as it refers to anything but 1 bit which includes all R2Rs and most DSs.




It sounds fancy and let's them charge more?


----------



## dukefx

They will charge more anyways. An R2R is expensive by design and not necessarily better, this is why it's a dying breed. There are pros and cons for both, some swear by DS, some by R2R, but R2Rs will die out sooner or later. There's also a good thread about this in the sound science section, but we are really going off topic here.


----------



## Jimster480

averageguync said:


> It sounds fancy and let's them charge more?


 

 Nah this is just what they decided to use.

 its their nomenclature, I don't really see a problem with it. 
  
 Their stuff has good reviews and the company seems very honest.


----------



## Jimster480

dukefx said:


> They will charge more anyways. An R2R is expensive by design and not necessarily better, this is why it's a dying breed. There are pros and cons for both, some swear by DS, some by R2R, but R2Rs will die out sooner or later. There's also a good thread about this in the sound science section, but we are really going off topic here.


 

 I have read quite a bit into that thread and nothing conclusive is there. Mostly its just people arguing about satire and post content.
 From a technical perspective R2R should be better as D/S is approximating, it also makes sense why every DAC company has a "signature" sound if the DAC's run algorithms vs direct processing audio.
  
 But yes its a more expensive design that also isn't very portable due to its enormous (by comparison) power usage. Something that they did find out in that thread though is that the current ways to measure audio output aren't really capable of actually measuring performance in music or at different frequencies.
  
 But there is no other standard which was produced, nor any other testing methods which would allow us to effectively compare different products side by side.


----------



## castleofargh

jimster480 said:


> I have read quite a bit into that thread and nothing conclusive is there. Mostly its just people arguing about satire and post content.
> *From a technical perspective R2R should be better as D/S is approximating*, it also makes sense why every DAC company has a "signature" sound if the DAC's run algorithms vs direct processing audio.
> 
> But yes its a more expensive design that also isn't very portable due to its enormous (by comparison) power usage. Something that they did find out in that thread though is that the current ways to measure audio output aren't really capable of actually measuring performance in music or at different frequencies.
> ...


 
 to this day I haven't seen clear evidence of this so you must know something I don't.
 R2R isn't approximating? you think each resistor used for the conversion is exactly at the desired value? ^_^  you think that analog music expects the signal to hold a discrete value all the way to the next sample? ^_^
 don't fall for marketing. in both designs it's a mess where filters(and noise shaping for DS) come to save the day. 
 also let's not forget how you can find the same DS chip in 30$ DACs and in 2000$ DACs and they won't measure the same. it would be really misleading to dumb down the quality of a DAC to 1 chipset type.
  
 I also don't get why the multibit name came out to define R2R? as dukefx mentioned, for many years now DS dacs have used more than one bit. the chip in the Odac isn't one bit as far as I know. in fact even DSD DACs dealing with 1bit signal, tend to use more than one bit nowadays.I guess R2R feels old(for good reason) so it needed some little rebranding to appeal to people again.
 the audio industry has already given up on R2R, I don't know if there are still R2R chips designed for the purpose of audio anymore? but then again it's exactly the kind of reason that would make some audiophiles desire R2R. "can't have it? I want one!". ^_^ not a very technical reason.
 as for Shiit, I remember Baldr saying(I'm paraphrasing) that making DS was boring because all you had to do was follow the manufacturer's advice. also not too sure how technical that reason is 
	

	
	
		
		

		
			





.
  
  
 now about measurements, there are logical limitations, when a DAC has better linearity but a little more noise(like it could happen with DS vs R2R), it's apples and oranges. how do we design a measurement technique to tell which has superior fidelity?
 the other problem is that we're ultimately interfacing with music subjectively. so if we try 2 devices and prefer the one that measures worst, then we want to believe that the wrong thing was measured. it could be so, but there is also the very likely possibility that my personal taste isn't a fidelity measurement tool.
  
  
 I'm not off topic, I said Odac.. twice now ^_^.   sorry


----------



## AverageGuyNC

jimster480 said:


> Nah this is just what they decided to use.
> 
> 
> its their nomenclature, I don't really see a problem with it.
> ...




Yeah I'm just kidding around. I wish I had something good to add but I'm not familiar with R2R or DS or whatever and didn't bother to look it up. I'm sure they thought it sounded best and went with it.

Another question. Do you think it's best to go with something like jotunheim over burson or O2 because it will power the th900 to basically their max (around 1800mw] if it has same or less distortion level? And would burson be too high at 3 ohm output for a 25 ohm headphone? I have heard several recommend it tho so maybe it's just about right?


----------



## Jimster480

averageguync said:


> Yeah I'm just kidding around. I wish I had something good to add but I'm not familiar with R2R or DS or whatever and didn't bother to look it up. I'm sure they thought it sounded best and went with it.
> 
> Another question. Do you think it's best to go with something like jotunheim over burson or O2 because it will power the th900 to basically their max (around 1800mw] if it has same or less distortion level? And would burson be too high at 3 ohm output for a 25 ohm headphone? I have heard several recommend it tho so maybe it's just about right?


 
 If you really want to listen at max?
 I mean I guess im not really the person to ask about this since Amp's aren't my specialty. But its all about the power draw vs your listening levels.
 Some Amps are too strong for headphones causing them to be too loud.


----------



## AverageGuyNC

Its being able to get to see what they can do i guess. like I had a pair of Senn 598 Cs that I returned but when hooked up to the O2, they got so loud when I turned them up it was unbearable. but the he400i on some songs wont go as loud as I want unless I turn the gain up. I know they are not quit as efficient as the th900 but I want to make sure I can power all well. I like to listen to them pretty loud some, but not always.


----------



## AverageGuyNC

And off subject but i saw a marantz hd dac1 for $600 on ebay and I thought those were supposed to be terrific amp/dac right? I know they go for $800 normally


----------



## Jimster480

averageguync said:


> And off subject but i saw a marantz hd dac1 for $600 on ebay and I thought those were supposed to be terrific amp/dac right? I know they go for $800 normally


 

 Personally from a technical aspect I don't think it would be any better or even as good as the ODAC/AMP.

 The only thing I have actual faith in being better is a Schiit Multibit DAC just from the technical prospects of R2R decoding.
  
 Otherwise after all the articles I have read I don't think that DAC's do that much overall. I think its more about the AMP itself and the analog stages and if it can really power your headphones.
  
 But in many blind tests I have found not only on this forum but in other places around the net, most people couldn't tell a Benchmark DAC2 from an Asus Xonar or a Chord Mojo from a FiiO E17k or even a Xonar from a O2DAC, etc.
 And this is with a good pair of headphones, so I believe that really the sound quality has to be quite comparable amongst most offerings and honestly over the years I have found that speakers/headphones make so much more of a difference than the player as long as their is ample power.
  
 Its found actually that the most difference is noted because of volume, one output may have slightly more volume than another one and therefore sounds "better". But in volume matched blind testing, it proved as I said that many components both high end and "low end" could not be told apart.


----------



## AverageGuyNC

jimster480 said:


> Personally from a technical aspect I don't think it would be any better or even as good as the ODAC/AMP.
> 
> 
> The only thing I have actual faith in being better is a Schiit Multibit DAC just from the technical prospects of R2R decoding.
> ...




I've wondered about that and heard similar stuff. The burson and jotunheim have significant more power but the o2 really should push the th900 great as sensitive as it is. 

And I emailed schiit asking about Modi vs Bifrost both in multidac and they said that for the money, yeah the Modi Multibit is probably better if you were not worried about upgrading. They do think multidac is the way to go though.


----------



## Jimster480

averageguync said:


> I've wondered about that and heard similar stuff. The burson and jotunheim have significant more power but the o2 really should push the th900 great as sensitive as it is.
> 
> And I emailed schiit asking about Modi vs Bifrost both in multidac and they said that for the money, yeah the Modi Multibit is probably better if you were not worried about upgrading. They do think multidac is the way to go though.


 

 Yea I mean personally compared to anything D/S it will just be better.
 If you look at the Texas Instruments website the highest end DAC they sell is actually for car audio and its $12.
 The "high end" Burr Brown DAC's are $3-8 lol....
 The K1 uses a DAC that is like $2.70 and it sounds great, and the K1 has the same DAC as the ODAC Rev. B.
 Same thing with the ESS Sabre it costs upto around $25 depending on the version it seems. But its harder to find the 1000 unit counts, so I would be willing to bet its much cheaper in large quantities.
  
 But then again TI is a much larger company and doesn't need the revenue from DAC's the way that ESS does.


----------



## dukefx

Prices are hardly indicators of SQ, especially in the case of TI. For example they sell top notch opamps for peanuts and vice versa. There are "high-end audio" opamps that cost 20 something $ and are mediocre at best. The K1 doesn't use the same DAC as the ODAC. The K1 has the old version while the ODAC has the much newer "A" version.


----------



## AverageGuyNC

​And people will pay a premium for stuff that is hand built in small batches with high end or rare materials, assuming the quality is good as well. Some will pay $2,000-5,000 for one like that, knowing the SQ is going to be on par with many $1,000-1,500 that were more massively built. Same as many will pass over a Mercedes or Corvette to get a Hand built Austin Martin that is probably no more luxurious or faster and costs even more. And then you could bring up Some exotics that aren't even reliable and wayyyy over priced but go for so much because they remain popular and supply is so limited... But if I were rich, I might go for them as well.


----------



## Jimster480

dukefx said:


> Prices are hardly indicators of SQ, especially in the case of TI. For example they sell top notch opamps for peanuts and vice versa. There are "high-end audio" opamps that cost 20 something $ and are mediocre at best. The K1 doesn't use the same DAC as the ODAC. The K1 has the old version while the ODAC has the much newer "A" version.


 

 Yes i know but the specs are virtually the same just the ODAC's one is slightly better. Either way this proves that its possible to make high end components for low cost once it gets to production.
  
 But I know what you mean that price of chips isn't an indiciator, especially for TI.
  
 But what I am saying is that audio companies sell DAC's for thousands with $2 chips in them and the overall cost of building it is somewhere like $30-100.
 Looking over many of the offerings especially from big brands, it seems that in many ways you are paying for brand.
  
 Now don't get me wrong the K1 isn't as good as an ODAC, but the components inside are very good for the price and it sounds really nice considering its very modest price tag. I honestly have to set it at 25% volume in windows and then i usually end up reducing the volume in spotify too because it has so much power to drive my triples and my RP-HD10's.


----------



## dukefx

The thousand dollar DACs surely cost more than 100$ (if we are talking about respectable companies). Rule of thumb for products of such quality/fidelity is usually about 600% of components. This covers research, marketing and labor with plenty of profit left. The reason for the O2 and ODAC being so cheap is the creative commons license. Basically we are talking about 600-800$ per piece if they were commercial. On top of that they utilize components of "good enough" quality. No overkill, no voodoo, no snake oil.


----------



## rizzotti91

Hi, I'm evaluating to switch from my Xonar U7 to an ODAC. I will connect to it my Logitec Z-2300 and, when I need cans, an Objective 2 with the JVC HA-SZ1000.
 Actually, when I play videogames, I activate the virtual surround from the Xonar Dolby panel, but if I switch to the ODAC which software could I use for virtual surrounding? I read good opinions about the Razer software. Any suggestes? Thank you


----------



## maheeinfy

I got the O2 from JDSLabs with inbuilt battery. This battery seems to be the most inefficient cell ever made
  
 I charge it for like 6hrs and it lasts may be an hour, with my easy-to-drive Grados. 
  
 Is this an issue?


----------



## jseaber

maheeinfy said:


> I got the O2 from JDSLabs with inbuilt battery. This battery seems to be the most inefficient cell ever made
> 
> I charge it for like 6hrs and it lasts may be an hour, with my easy-to-drive Grados.
> 
> Is this an issue?




Please check the instructions guide: charge for at least 20 hours!

The Tenergy 9Vs are one of the top rated cells on the market. Just make sure to charge as instructed.


----------



## maheeinfy

jseaber said:


> Please check the instructions guide: charge for at least 20 hours!
> 
> The Tenergy 9Vs are one of the top rated cells on the market. Just make sure to charge as instructed.



Thanks!
May i know how long its supposed to last after 20hrs of recharge?


----------



## jseaber

Run time varies with your listening style and headphones. Average run time is about 6 hours on a full charge.


----------



## dr3wd4wg

Is there any benefit to purchasing an OL DAC and an Objective2 separately versus buying the O2+ODAC revB combo?


----------



## kiler

I dont think there is any benefit, if anything you will lose a compact form factor


----------



## dukefx

Yes, there is. More room for tinkering and also the ability to keep one and replace the other with something else.


----------



## jseaber

dr3wd4wg said:


> Is there any benefit to purchasing an OL DAC and an Objective2 separately versus buying the O2+ODAC revB combo?


 
  


kiler said:


> I dont think there is any benefit, if anything you will lose a compact form factor


 
  
 None?!
  
 ODAC is powered by USB, which is its only input.
  
 OL DAC accepts optical (TOSLINK) and USB input, and is powered by an AC adapter, so it has no reliance on the USB 5V rail. OL DAC exceeds every specification of ODAC, some by an order of magnitude, although both are considered transparent.


----------



## Faber65

jseaber said:


> dr3wd4wg said:
> 
> 
> > Is there any benefit to purchasing an OL DAC and an Objective2 separately versus buying the O2+ODAC revB combo?
> ...




The OL DAC is very transparent indeed. 
And the Toslink optical input does allow to use a coax connection as well (with an adapter).


----------



## leeperry

So what's the story with the RCA input at the back of the desktop O2 on massdrop? Some crappy wires going from the PCB front minijack eh? ^^


----------



## raoultrifan

I don't think they're crappy, after all it's the same output impedance. Two crossed copper wires (or shielded) should be perfectly fine I'd say.
  
 Also, I believe the RCA version has no jack input at all, unless there's a button involved to select the source.


----------



## dukefx

Mine has a 6.3mm, a 3.5mm and 2 pairs of RCAs and no switch. Basically use whichever suits you best. I'm using the RCAs.


----------



## leeperry

But did you open it? Got cheapo wires going from the PCB front to the back of the enclosure?


----------



## dukefx

Mine's modded, ofc I opened it. Wires are standard copper twisted pairs, but even if they were some "cheapo" garbage there'd be 0 difference.


----------



## raoultrifan

leeperry said:


> But did you open it? Got cheapo wires going from the PCB front to the back of the enclosure?


 
 Nope, but I've seen some pics around this forum. Anyway, mine is DIY; I've added myself 2xRCA gold-plated plugs and a small metallic switch. Cables were shielded and I have no hum or additional noise.


----------



## leeperry

dukefx said:


> Mine's modded, ofc I opened it. Wires are standard copper twisted pairs, but even if they were some "cheapo" garbage there'd be 0 difference.


 
  
 Sweet, thanks! So cables don't matter but opamps do even though nwadude said they wouldn't, am I getting this right? 
	

	
	
		
		

		
			




  
 So it's indeed a ghetto RCA output, BTW is there an explanation of the role of each opamp please?
  
 I'm getting a RevA O2+DAC mayflower, hopefully opamps will be rollable too.


----------



## raoultrifan

Feel free to replace the cheap wires with better cables with a decent shield. At least in theory cross-talk could decrease.
  
 First opamp is the Voltage Amplification Stage, the other 2 opamps are paralleled and used as output buffers...hope this helps.


----------



## dukefx

I don't think NwAvGuy ever said that opamps do not matter. As far as I can recall it was more about price/performance and drawing a line where "better" opamps wouldn't result in an audible improvement.
  
 As for the roles: the one next to the potmeter (2068 by default) amplifies voltage. The pair operated in parallel on the side is the output and supplies your headphones with the juice required. The 4th has nothing to do with the sound, it's for the battery and overall protection.


----------



## leeperry

Fair enough, what he said is "*CAN I UPGRADE THE OP AMPS?* You _could_, but it would be a waste of money and might degrade the performance. I tested nearly two dozen op amps and the O2 is optimized for the op amps that proved best."
  
OK sounds good thanks, I got a whole bunch of LME49990, ADA4627 gizmos to roll but apparently my revA mayflower comes with 1X/3.3X gain and that seems very very low, oh well I don't expect much so I can't be disappointed I guess. I also got a spare 2A 16VAC PSU that sounds great on Mimby, can't hurt ^^


----------



## dukefx

The proper statement would be _I tested nearly two dozen op amps and the O2 is optimized for the op amps that proved best *from what I had at hand.*_ 
  
  
Gain depends on your input. 1/3.3x is excellent for a 2.1V input (ODAC). 3.3x is actually a tiny bit more than it can safely handle. Mine's at 1/3.2x and I don't really need the gain button. If you use a >1V onboard soundcard output with hungry headphones it's low indeed.


----------



## leeperry

MStage sounds best in many ppl's experiences with 10X gain, I would use Mimby and ODAC but I bet its ancient Tenor/9023 chips won't make me too happy
	

	
	
		
		

		
			




  
 Anyone tried that O2 booster board? http://www.agdraudio.com/o2%20booster%20board.html


----------



## dukefx

No, but Alex will storm in and tell you all about it XD I'm happy with the OPA1688s.


----------



## ostewart

I posted my review up of the Head "n" HiFi desktop kit: https://www.head-fi.org/showcase/head-n-hifi-objective2-desktop-version.22677/reviews#review-19254


----------



## adydula

I have two O2's, one with OPA 1688's and one with AGDR's booster board that has 827's installed plus a few other things.
I also have a bone stock O2 and have done many listening tests..and they all sound pretty much the same.

I dont think that 99% of people would be able to tell any real world differences in the sound ....

I am down to only 9 head and three dacs, I switch back and forth every few days and each time the amp being put into use
sounds really good for a few days.....lol.

Alex


----------



## leeperry

Well AGDR main sales argument is that distortion is much lower when you start listening at 120dBA 

Any internal pics of the masdrop units around? I guess the desktop version is using some crappy wires to reach the back jacks and some ghetto kludge for the 6.35mm HO?


----------



## Jimster480

dukefx said:


> The proper statement would be _I tested nearly two dozen op amps and the O2 is optimized for the op amps that proved best *from what I had at hand.*_
> 
> 
> Gain depends on your input. 1/3.3x is excellent for a 2.1V input (ODAC). 3.3x is actually a tiny bit more than it can safely handle. Mine's at 1/3.2x and I don't really need the gain button. If you use a >1V onboard soundcard output with hungry headphones it's low indeed.



I feel the same way. I just leave it on 1x most of the time and its fine!


----------



## UNOE

If I have (2.5x / 6.5x) gain unit.  Can I just remove the 6.5x resistors to have (2.5x / 1.0x)?  Or do you have to remove the 2.5x to get 1.0x.

http://www.jdslabs.com/pdf/O2_LowGain.pdf


----------



## dukefx

Whichever pair you remove will turn to 1.0x.


----------



## Arkady Duntov

dukefx said:


> Whichever pair you remove will turn to 1.0x.



+1

Removing one pair changes the gains to 1.0/2.5x and removing the other pair changes to the gains to 1.0/6.5x. I checked with JDS a long time ago, and they'll do the removal for a relatively small fee. (My ODAC+O2 is from JDS.)


----------



## Jimster480

Arkady Duntov said:


> +1
> 
> Removing one pair changes the gains to 1.0/2.5x and removing the other pair changes to the gains to 1.0/6.5x. I checked with JDS a long time ago, and they'll do the removal for a relatively small fee. (My ODAC+O2 is from JDS.)


Yep I did custom gain at build time. Its def worth for lower impedance headphones. I use my o2 all day every day now.


----------



## UNOE

Arkady Duntov said:


> +1
> 
> Removing one pair changes the gains to 1.0/2.5x and removing the other pair changes to the gains to 1.0/6.5x. I checked with JDS a long time ago, and they'll do the removal for a relatively small fee. (My ODAC+O2 is from JDS.)


So it is a yes to my question "Can I just remove the 6.5x resistors to have (2.5x / 1.0x)?"


----------



## UNOE

Should I solder or just clip.


----------



## cityle

UNOE said:


> So it is a yes to my question "Can I just remove the 6.5x resistors to have (2.5x / 1.0x)?"


Yes, just clipped one end of the two 6.5x resistors and you will have a 2.5x/1.0x


----------



## BenF

Something weird - when O2 is about to run out of battery, if I unplug and replug the input, instead of music, I hear very strong repeating noise, that hurts my ears.
Unplugging/replugging headphones/DAC doesn't help.
What does help, is attaching AC adapter.
Has anyone experienced this? Is it normal?

From http://nwavguy.blogspot.co.il/2011/07/o2-headphone-amp.html
*LOW BATTERY HEADPHONE PROTECTION:* A significant problem with dual battery designs is what happens if one battery dies first or becomes disconnected. Under those conditions the amp could destroy your headphones with DC. The O2 uses, as far as I know, a novel approach to solving this problem. It shuts the entire amplifier down when either or both batteries start to get low or if one battery becomes disconnected. This not only prevents harmful DC at the output, it also helps protect the rechargeable batteries from being damaged by cell reversal. So with the O2 there’s _zero_ worry about the batteries. You can safely listen until it shuts itself off.


----------



## Nitreb

BenF said:


> Something weird - when O2 is about to run out of battery, if I unplug and replug the input, instead of music, I hear very strong repeating noise, that hurts my ears.
> Unplugging/replugging headphones/DAC doesn't help.
> What does help, is attaching AC adapter.
> Has anyone experienced this? Is it normal?
> ...



It happened to me on a few occasions. The amp shuts down automatically when the battery power gets low, as it's supposed to do, but if you don't recharge the batteries and power on the amp again, the problem you describe above will appear. In my case, it was a loud repeating clicking noise in my Grado GS1000. It seems that as the batteries continue to discharge, the protection circuit stops working and you get that noise, which may be CD current feeding into the headphones. So now, when the amp shuts down because the batteries get low, I recharge immediately. I've read somewhere, I don't remember where, that this was a design flaw of the O2 protection circuit.


----------



## UNOE

Clipping worked perfect got 1x and 6.5x now.  I clipped the wrong end but that okay.  1x will be my go to 95% of the time.  The o2 background is so quite.  I like o2 amp better than Mojo with my BA IEMs.  That was surprising.  Mojo has slight noise.  I don't listen to music loud.  So o2 dead silent with really low playing well sealed CIEM's the o2 is great for this application.  I'm still using the mojo DAC.  If you have BA IEM's I would get a o2 over Magini 3.


----------



## BenF

Nitreb said:


> It happened to me on a few occasions. The amp shuts down automatically when the battery power gets low, as it's supposed to do, but if you don't recharge the batteries and power on the amp again, the problem you describe above will appear. In my case, it was a loud repeating clicking noise in my Grado GS1000. It seems that as the batteries continue to discharge, the protection circuit stops working and you get that noise, which may be CD current feeding into the headphones. So now, when the amp shuts down because the batteries get low, I recharge immediately. I've read somewhere, I don't remember where, that this was a design flaw of the O2 protection circuit.


In my scenario, the amp wasn't powered down - the problem happened while it was still on.


----------



## Anarion

Joined in Massdrop drop earlier for desktop variant Objective 2 (O2) amp. Even with shipping it was ~90 €. Even with VAT it's still a nice price.


----------



## BenF (Nov 27, 2017)

Can O2 (1.0/3.3X) power Sennheiser HD700?


----------



## Arkady Duntov

BenF said:


> Can O2 (1.0/3.3X) power Sennheiser HD700?



Works great on the HD650 and AKG 7XX. Unless the 700 is much less efficient than the 650, you'd have no problem.


----------



## Jimster480

BenF said:


> Can O2 (1.0/3.3X) power Sennheiser HD700?


This all depends on the volume with which you want to listen to it.
The o2 doesn't have much power for a HD650 for example as it has a high impedance and the o2's amp isn't the best for high impedance headphones.


----------



## headwhacker

Jimster480 said:


> This all depends on the volume with which you want to listen to it.
> The o2 doesn't have much power for a HD650 for example as it has a high impedance and the o2's amp isn't the best for high impedance headphones.


How much power do you think HD650 needs? And how much power does O2 can output?


----------



## headwhacker

BenF said:


> Can O2 (1.0/3.3X) power Sennheiser HD700?


what is the source you are using? How much output does your source have? If it has at least 2Vrms then the 3.3x gain option should be good enough. But if your source is week. Say around 1 Vrms. You need a higher gain option to tap into the max power output of O2.


----------



## MagR

The O2 should be able to power these easily. The HD600's I have are impedance 300 ohms with sensitivity 97dbl. The HD700 are impedance 150 ohms with sensitivity 105dbl. Assuming the sensitivity is measured the same (there are two versions I have come across) these are easier to drive. I run my HD 600's at 2x gain on my amp and rarely need to go above halfway on the volume. You might get them to work fine on your 1x gain setting but if not the higher gain should be ample.

However I am using the ODAC also. This DAC outputs 2V but if you are using a weaker source that affects the overall position.

The O2 is generally fine with high impedance headphones. I also own the Beyerdynamic DT880 600 ohm and the O2 drives it well at my 3.5x gain.


----------



## headwhacker (Nov 28, 2017)

O2 can go as high at 7Vrms output. Gain settings must be carefully selected depending on your source output to maximize the output. The original 2.5x/6.5x combo is good for 1Vrms output such as the iPod classic lineout or very hot source nearining 3.0Vrms output.

The standard redbook at 2.0Vrms and most modern DAPs lineout at 1.5Vrms on high impedance cans will either sound too soft with 2.5x gain or clip with 6.5x.

If you have such sources, having a 3.3x gain is ideal. This is the reason why the 1x/3.3x gain option is offered by O2 sellers.


----------



## raoultrifan

Jimster480 said:


> This all depends on the volume with which you want to listen to it.
> The o2 doesn't have much power for a HD650 for example as it has a high impedance and the o2's amp isn't the best for high impedance headphones.



The engineer who built the O2 has an in-depth review about HD650 headphones and he said that @ 2V RMS these headphones sound loud enough. Imagine that O2 has about 7.3 V RMS just before clipping, so with a 1.5-2.5X gain on O2 amplifier, the HD650 should be driven very well.

For example, my DT880 600-ohms are driven perfectly by my O2 amplifier.


----------



## BenF

headwhacker said:


> what is the source you are using? How much output does your source have? If it has at least 2Vrms then the 3.3x gain option should be good enough. But if your source is week. Say around 1 Vrms. You need a higher gain option to tap into the max power output of O2.


My favorite DAC is 1VRMS DAC (HA-2), but most of my DACs are 2VRMS


----------



## headwhacker

BenF said:


> My favorite DAC is 1VRMS DAC (HA-2), but most of my DACs are 2VRMS


Looks like the default 2.5x/6.5x is ideal for you. Your can is not that hard to drive and having a 5vrms to 6.5Vrms output is more than enough. Unless your headphone collection ranges from the most sensitive iems to less efficient/high impedance then the 1x/3.3x option is the way to go.


----------



## BenF

headwhacker said:


> Looks like the default 2.5x/6.5x is ideal for you. Your can is not that hard to drive and having a 5vrms to 6.5Vrms output is more than enough. Unless your headphone collection ranges from the most sensitive iems to less efficient/high impedance then the 1x/3.3x option is the way to go.


I already have 1/3.3x, just wanted to know if HD700 will sound good with it.


----------



## Arkady Duntov

BenF said:


> I already have 1/3.3x, just wanted to know if HD700 will sound good with it.



What do you have in mind when you says "sound good?"

* The ODAC and O2 are transparent and will faithfully reproduce the signal they're given without coloration. Some people, including me, think this is good; some don't.

* At 3.3x gain, the O2 will produce a strong-enough signal to make the HD650 (and K7XX) louder than I can stand. The HD700 is apparently more sensitive ('efficient') than the 650, so it should be even louder (if loudness is what you're after.)


----------



## BenF

Arkady Duntov said:


> What do you have in mind when you says "sound good?"
> 
> * The ODAC and O2 are transparent and will faithfully reproduce the signal they're given without coloration. Some people, including me, think this is good; some don't.
> 
> * At 3.3x gain, the O2 will produce a strong-enough signal to make the HD650 (and K7XX) louder than I can stand. The HD700 is apparently more sensitive ('efficient') than the 650, so it should be even louder (if loudness is what you're after.)


Loudness is the least of my worries, I want to know if HD700 can sound its best out of O2, or is it a bad/mediocre pairing.


----------



## Arkady Duntov

BenF said:


> Loudness is the least of my worries, I want to know if HD700 can sound its best out of O2, or is it a bad/mediocre pairing.



I've used my ODAC+O2, extensively, with the Sennheiser HD650, Beyerdynamic T70, AKG K7XX, Grado PS1000e, and a number of IEMs including my new Westone W80. I find it to be excellent and recommend it wholeheartedly. As I wrote before, it's a neutral combo and that's what I was after when I bought it. In my opinion, it wouldn't be bad or even mediocre.

However, some listeners want, for example, a V-shaped sound, or hardware bass-boost, or the kind of coloration produced by tube amplifiers. If this is what you're after, I don't think the O2 is your best choice.

Disclaimer: I have no experience with the HD700.


----------



## UNOE

Is it possible to blow the amps gain?  I let a co worker borrow the amp and he said he turned it almost all the way up on 6X.  I never used 6x so I don't know how it should sound.  But 6x sounds distorted now even on very low settings.  1x seems the same as it was before.


----------



## raoultrifan

Well, voltage amplification stage could have higher distortions if 6X gain is used with input sources > 1V RMS. Maybe you could lower your input source volume or try using the 1X gain settings.


----------



## UNOE

I'm using the mojo to feed it.  If I lower the mojo out it sounds find at 6x.  So I think its safe to say its not broke its just mojo out is two high at 6x.  Does everyone else get distortion at 6x with mojo line out settings ?


----------



## Jimster480

UNOE said:


> I'm using the mojo to feed it.  If I lower the mojo out it sounds find at 6x.  So I think its safe to say its not broke its just mojo out is two high at 6x.  Does everyone else get distortion at 6x with mojo line out settings ?


The mojo doesn't have a static line out? Its a variable voltage line out?


----------



## Arkady Duntov

UNOE said:


> I'm using the mojo to feed it.  If I lower the mojo out it sounds find at 6x.  So I think its safe to say its not broke its just mojo out is two high at 6x.  Does everyone else get distortion at 6x with mojo line out settings ?



Apparently, the default line-out voltage of the Mojo is 3V, which I think is too high, but it can be changed to 1.9V. 2.0V is the "standard", if such a thing exists.



UNOE said:


> Does everyone else get distortion at 6x with mojo line out settings ?



May I ask why you aren't using the Mojo as an amplifier?


----------



## UNOE

Arkady Duntov said:


> Apparently, the default line-out voltage of the Mojo is 3V, which I think is too high, but it can be changed to 1.9V. 2.0V is the "standard", if such a thing exists.
> 
> 
> 
> May I ask why you aren't using the Mojo as an amplifier?


You mean DAC?  I'm using the Mojo as a DAC with o2.  Mojo amp is good with almost everything I have.  But Mojo amp has slight hiss on my sensitive IEMs.  The BA iem sound better through o2 amp at lower volumes than Mojo.


----------



## Jimster480

UNOE said:


> You mean DAC?  I'm using the Mojo as a DAC with o2.  Mojo amp is good with almost everything I have.  But Mojo amp has slight hiss on my sensitive IEMs.  The BA iem sound better through o2 amp at lower volumes than Mojo.


The o2 really seems to be THE AMP for low impedance loads!


----------



## Arkady Duntov

UNOE said:


> You mean DAC?  I'm using the Mojo as a DAC with o2.  Mojo amp is good with almost everything I have.  But Mojo amp has slight hiss on my sensitive IEMs.  The BA iem sound better through o2 amp at lower volumes than Mojo.



Sorry, that makes sense. I read on another web site that the Mojo's output voltage can be reduced to 1.9V. That's what I'd do.

Additionally, the lack of noise (including hiss) is another reason I like the O2.


----------



## UNOE

Jimster480 said:


> The o2 really seems to be THE AMP for low impedance loads!


I really don't think most people listen to volumes as low as me.


----------



## headwhacker (Nov 28, 2017)

UNOE said:


> I'm using the mojo to feed it.  If I lower the mojo out it sounds find at 6x.  So I think its safe to say its not broke its just mojo out is two high at 6x.  Does everyone else get distortion at 6x with mojo line out settings ?



Like @Arkady Duntov mentioned why are you using O2 when you already have Mojo which by itself alone can drive a wide range of headphone. I think most people do not understand gain and how it affects the output if it is not properly matched with the input. 6x used with the Mojo's 3Vrms output is supposed to be 18Vrms output which is well beyond the max output voltage of O2 @7Vrms. Even at the lowest volume pot position it is most likely reached clipping. Then dealing with channel imbalance common for analog volume pot. So, yes you are easily getting a distortion. All O2 will behave the same. If you must insist using O2 with Mojo, 1x gain is all you need. The other option should not be more than 2x.



Jimster480 said:


> The o2 really seems to be THE AMP for low impedance loads!


Please stop. You need to understand first or at least revisit what you have learned about how amplifiers work. It's just not helping and worse, misleads a lot of people including yourself.


----------



## UNOE

headwhacker said:


> Like @Arkady Duntov mentioned why are you using O2 when you already have Mojo which by itself alone can drive a wide range of headphone. I think most people do not understand gain and how it affects the output if it is not properly matched with the input. 6x used with the Mojo's 3Vrms output is supposed to be 18Vrms output which is well beyond the max output voltage of O2 @7Vrms. Even at the lowest volume pot position it is most likely reached clipping. Then dealing with channel imbalance common for analog volume pot. So, yes you are easily getting a distortion. All O2 will behave the same. If you must insist using O2 with Mojo, 1x gain is all you need. The other option should not be more than 2x..



You can go back and read what I said of your confused.  I said I don't use 6x.  I was trying to see if it was normal distorted.  My co worker borrowed my o2 and turned it all the way up at 6x gain.  I didn't expect him to do that.  I tried the 6x gain after making sure nothing was damaged with mojo and then noticed it was distorted so asked the question I asked.
And yes I do like o2 at low volume with my sensitive IEM's I said I only like o2 with the IEM at low volume (my IEM seal really well so only little volume is needed).  Otherwise mojo for everything else.  And yes my Mojo does hiss with IEM slightly with nothing playing.  I can't make out any hiss at all on any other headphone except the BA driver IEMs.
The reason I asked the question I asked is cause I never used 6x gain since I bought it so don't know if it was distorted before I let me co worker borrow it.


----------



## headwhacker

UNOE said:


> You can go back and read what I said of your confused.  I said I don't use 6x.  I was trying to see if it was normal distorted.  My co worker borrowed my o2 and turned it all the way up at 6x gain.  I didn't expect him to do that.  I tried the 6x gain after making sure nothing was damaged with mojo and then noticed it was distorted so asked the question I asked.
> And yes I do like o2 at low volume with my sensitive IEM's I said I only like o2 with the IEM at low volume (my IEM seal really well so only little volume is needed).  Otherwise mojo for everything else.  And yes my Mojo does hiss with IEM slightly with nothing playing.  I can't make out any hiss at all on any other headphone except the BA driver IEMs.
> The reason I asked the question I asked is cause I never used 6x gain since I bought it so don't know if it was distorted before I let me co worker borrow it.



I'm not referring to you directly as confused. But for most people who used O2 and wonder why they hear distortion. Your coworker being one I suppose. Like I said, 6x with Mojo is distorted as expected. It does not take Mojo to distort O2. Even with weaker source like Fiio or iBasso DAPs line out can easily distort O2 and 6x.


----------



## Jimster480

UNOE said:


> I really don't think most people listen to volumes as low as me.


I listen at about 11 on my 02 with 1 X gain.  so I would say that I listen at a pretty low volume.


----------



## raoultrifan

6X gain is for input sources having an output voltage of about 1V RMS (mobile phones for example). Voltage amplification stage from inside the O2 will clip if:
"input source" x "gain" > 7.3 V RMS.

If your source if delivering a max. of 2V RMS and you're using the 6X gain at the O2 then sound will be heavily distorted, no matter O2's volume potentiometer.

Unless you really need to feed the O2 with 1V RMS signals, I strongly advise everyone to lower the 6X gain to somewhere around 2.5-3.5X, depending on the playback sources you have around the house.


----------



## joasjoas (Nov 29, 2017)

¿El JDS O2 + ODAC rev B tiene problemas para mover 600 ohmios? por ejemplo, alrededor de 990 dt? 2.5X  6.5X


----------



## UNOE

raoultrifan said:


> 6X gain is for input sources having an output voltage of about 1V RMS (mobile phones for example). Voltage amplification stage from inside the O2 will clip if:
> "input source" x "gain" > 7.3 V RMS.
> 
> If your source if delivering a max. of 2V RMS and you're using the 6X gain at the O2 then sound will be heavily distorted, no matter O2's volume potentiometer.
> ...


Very helpful.  I acidently clipped the 2.5x gain to get 1x.  I meant to cut 6x to have both 1.x and 2.5x.  But now I have 1x and 6x.  I will try to resolder at 2x gain.
Actually I have a question about that spreadsheet says "SFR16S0001501FR500 - Metal Film Resistors - Through Hole 1/2watt 1.5Kohms 1%" will give you 2x gain.  Is there a recommended resister for 1.5x gain?  Nothing on the spreadsheet is lower than 2x.


----------



## raoultrifan

joasjoas said:


> Will the JDS O2 + ODAC rev B have problems to move 600 ohm? for example about 990 dt?


https://www.head-fi.org/threads/o2-amp-odac.616331/page-363#post-13878914



UNOE said:


> [...] Is there a recommended resister for 1.5x gain?  Nothing on the spreadsheet is lower than 2x.


Everything's written in the o2-details page, just search after gain resistors. Also, the BOM has enough defined resistors. We're not allowed to post anything here about that, so you need to dive deep into by reading designer's website, sorry.


----------



## dukefx

You need 3K for 1.5x gain


----------



## Arkady Duntov

joasjoas said:


> ¿El JDS O2 + ODAC rev B tiene problemas para mover 600 ohmios? por ejemplo, alrededor de 990 dt? 2.5X  6.5X



The ability of an amplifier to drive a headphone is more a function of its _sensitivity_ rather than its _impedance_. The O2 should work just fine with 600Ω Beyerdynamic models.

You might have better luck using English here.


----------



## Anarion (Dec 2, 2017)

Jimster480 said:


> I listen at about 11 on my 02 with 1 X gain.  so I would say that I listen at a pretty low volume.


I use 2% volume from Windows using Sound Blaster Zx line out when not using volume pot (I have HD 595). Anything higher is unbearable for me. I can go up to 10% with volume pot around 66% (though, even at 100% that pot lowers the volume).

I bought the 1x & 3,3x gain version from Massdrop. I try how the volume control works with HD 595 but I plan to upgrade to something else that's not so unbearably sensitive. How on earth can people even use HD 595 without volume pot?


----------



## HeroXLazer

AAAAAAAAAA. I screwed it up again. I bought an O2 DIY kit from JDSLAB, along with the ODAC, etc. I screwed the first PCB up. Then, I ordered another PCB. I assembled it yesterday. At first, it turned on, but there was a thudding sound in the headphones, but now the LED isn't even lighting up. At least now I have a new show piece...


----------



## DJ The Rocket (Dec 13, 2017)

HeroXLazer said:


> At first, it turned on, but there was a thudding sound in the headphones, but now the LED isn't even lighting up



Well, the standard question here is did you follow the designer's testing procedure? Sounds like a no, because if you had I can't imaging you would have missed this.

The fact that the LED isn't turning on is a major clue here. The LED is actually an integral part of the power management circuit, so if it's not turning on of course it isn't going to work right.

Your o2 is likely fixable. Maybe it's something easy like a loose connection on the LED itself, but who the hell knows without actually testing things? It might be a pain if everything is already soldered in place (you'll understand why when you see the tests you're going to run).

An expert is just someone who knows all the ways there are to foul something up. Try to take this as another step toward becoming an expert: you learned a new mistake, so there's one less way for things to go wrong next time.

Always familiarize yourself with all steps involved--including the test procedure--BEFORE soldering the first resistor! Then, don't take shortcuts! Fouling up the first PCB should be a clue that you're not ready to step off the beaten path yet, which is fine. Very, very few people are, I think.

There is TONS of info about problems just like this one no further than the first page of google search results. This is the most well documented DIY build in audio, but it's on you to take advantage.


----------



## DJ The Rocket

mikeaj said:


> When the designer decided upon the default gains, it was envisioned (maybe in some sort of distorted fantasy land?) that most people using the O2 would be DIYers making one for themselves and thus setting the gains for themselves, and/or people were going to use this thick large palm-sized amp as a portable / transportable and primarily use portable sources like iPods and phones with weaker outputs that need more gain to reach the same levels. On the other hand, you could call it some kind of modesty (har har?) in not expecting the O2 to be as big a success as it is now among non-DIY users.



Hehehe, there's so much great stuff in these old posts...


----------



## HeroXLazer

DJ The Rocket said:


> Well, the standard question here is did you follow the designer's testing procedure? Sounds like a no, because if you had I can't imaging you would have missed this.
> 
> The fact that the LED isn't turning on is a major clue here. The LED is actually an integral part of the power management circuit, so if it's not turning on of course it isn't going to work right.
> 
> ...


I figured that I burned out the power adapter. I emailed the JDSLabs guys and asked, they said it's most likely the voltage regulators, so I replaced them, and I'm waiting for a new power supply adapter.


----------



## Anarion (Dec 19, 2017)

I just received the Massdrop Objective 2 amp but unfortunately I don't have adapter for that power adapter. However, I do have different one (the right one). I assume it would be just fine to use that one? Also that thing that came with the amp seems to be really, REALLY weak. 220mA?! Also the quality is rather questionable...


----------



## Oscar-HiFi

Anarion said:


> I just received the Massdrop Objective 2 amp but unfortunately I don't have adapter for that power adapter. However, I do have different one (the right one). I assume it would be just fine to use that one? Also that thing that came with the amp seems to be really, REALLY weak. 220mA?! Also the quality is rather questionable...



The O2 needs a 14-20V power brick... https://www.jdslabs.com/products/147/us-15vac-power-adpater-for-O2/
That's what the JDS Labs website says: "Power: Battery or 14-20VAC"


----------



## Anarion (Dec 19, 2017)

Oscar-HiFi said:


> The O2 needs a 14-20V power brick... https://www.jdslabs.com/products/147/us-15vac-power-adpater-for-O2/
> That's what the JDS Labs website says: "Power: Battery or 14-20VAC"


Massdrop gives 12VAC adapter (the left one) with it, so I'd assume that their adapter (12VAC) would work. I need to do some searching...


----------



## dukefx




----------



## Anarion (Dec 19, 2017)

Blaah... I guess I'll just order one from JDS: https://www.jdslabs.com/products/73/g-e-z-15vac-adapter-for-o2/

EDIT:
Actually... Look like I can get basically the same thing from Germany ~20 € with shipping.


----------



## mindbomb

The massdrop power supply is unregulated, so it does end up being higher voltage in practice.


----------



## Anarion

mindbomb said:


> The massdrop power supply is unregulated, so it does end up being higher voltage in practice.


Yeah, I just read some Massdrop comments and noticed that. It's funny, their adapter is 240V 60Hz A plug. Where that combination is even a thing? In any case I ordered this: http://www.headnhifi.com/power-supply-15v-ac It should do the job.


----------



## dukefx

That's the one I posted


----------



## Anarion

dukefx said:


> That's the one I posted


Spec wise at least - might be the same though, that would be good.


----------



## Arkady Duntov

Anarion said:


> Spec wise at least - might be the same though, that would be good.



A few years ago, JDS shipped an AC-AC adapter which delivered 12V. There was some discussion, in this thread I think, which said that 12V might be insufficient for some loads, so I bought a 20V adapter. Later I read that the excess power from that adapter would just be wasted as heat.

The O2 I bought from them this year has a 12V adapter. It works fine for the IEMs and AKG 7XX which which I 've used it.


----------



## jseaber

Arkady Duntov said:


> A few years ago, JDS shipped an AC-AC adapter which delivered 12V. There was some discussion, in this thread I think, which said that 12V might be insufficient for some loads, so I bought a 20V adapter. Later I read that the excess power from that adapter would just be wasted as heat.
> 
> The O2 I bought from them this year has a 12V adapter. It works fine for the IEMs and AKG 7XX which which I 've used it.



We've only shipped *15VAC, 500mA* transformers since at least 2014, if not longer:
https://www.jdslabs.com/products/147/15vac-power-adapter/

Triad P/N WAU12-200 was a 12VAC, 200mA adapter originally recommended by NwAvGuy in 2011. It was acceptable under light loads. Voltage dips into unacceptable territory from 100-110VAC outlets. We've long since abandoned this part.


----------



## Arkady Duntov

jseaber said:


> We've only shipped *15VAC, 500mA* transformers since at least 2014, if not longer:
> https://www.jdslabs.com/products/147/15vac-power-adapter/
> 
> Triad P/N WAU12-200 was a 12VAC, 200mA adapter originally recommended by NwAvGuy in 2011. It was acceptable under light loads. Voltage dips into unacceptable territory from 100-110VAC outlets. We've long since abandoned this part.



Obviously, I misread the markings on my newer adapter. It's clearly 15VAC, 500mA as you noted.

I must have purchased my first O2 in 2012 or 2013. It was one with the "silver-colored" face plate.


----------



## Anarion (Jan 7, 2018)

The adapter arrived two days ago (it's beyond me how priority air mail from Germany can take this long - it was shipped on 20.12.2017). It's the same one as sold by JDS.

When it comes to sound I think it's no contest. I keep using AE-5 as an amp too when using my desktop.


----------



## ostewart

Anarion said:


> The adapter arrived two days ago (it's beyond me how priority air mail from Germany can take this long - it was shipped on 20.12.2017). It's the same one as sold by JDS.
> 
> When it comes to sound I think it's no contest. I keep using AE-5 as an amp too when using my desktop.



Enjoy your O2, still love mine for reference purposes  otherwise I mainly use my Keces S3


----------



## Anarion

ostewart said:


> Enjoy your O2, still love mine for reference purposes  otherwise I mainly use my Keces S3


It can be handy when using portable devices as source. Just to clear possible confusion: AE-5 is _noticeably _better and the advantage in soundstage is drastic. The difference is actually quite big which is surprising. Makes me wonder whether or not Massdrop cut corners... That being said, on paper AE-5's headphone out is better and it seems to be the case in practice too.


----------



## Arkady Duntov

Anarion said:


> It can be handy when using portable devices as source. Just to clear possible confusion: AE-5 is _noticeably _better and the advantage in soundstage is drastic. The difference is actually quite big which is surprising. Makes me wonder whether or not Massdrop cut corners... That being said, on paper AE-5's headphone out is better and it seems to be the case in practice too.



Would you post the paper result comparison for the O2 and AE-5 showing the noticeably [i.e., audibly] better output and drastic improvement in soundstage?

Thanks.


----------



## DJ The Rocket (Jan 8, 2018)

Anarion said:


> Makes me wonder whether or not Massdrop cut corners



This isn't possible in the way that you mean. Maybe the enclosure is really cheap or something, but the specs to build one are exact. When I put one together a couple weeks ago I even looked for ways to substitute cheaper components. It turns out that NwAvGuy did that for us already. There aren't any corners to cut as long as everything is in spec, and if they aren't in spec then you didn't buy an o2, which would have consequences that would require a lawyer to explain. Personally I think the chances of that are effectively zero.

Do you have a multimeter? You can open yours up and follow the testing procedure lined out online. It's really easy (presuming you know how to use your MM already) and it will put any concerns to bed with finality.

I obviously can't have any idea what you're hearing, but have you perused NwAvGuy's subjective vs objective post recently?



Anarion said:


> AE-5 is _noticeably _better



No, it is not. You are absolutely wrong here. The AE-5 is different, and therefore not transparent. You may very well like it a million times more, that's perfectly okay. But please don't represent your value judgment as universal truth.


----------



## Anarion (Jan 9, 2018)

Arkady Duntov said:


> Would you post the paper result comparison for the O2 and AE-5 showing the noticeably [i.e., audibly] better output and drastic improvement in soundstage?
> 
> Thanks.


Make your own conclusions (no idea how accurate this is): http://reference-audio-analyzer.pro/en/report/amp/creative-sound-blaster-ae-5.php

I can only think that the stereo crosstalk is the main issue.


Creative doesn't mention other specs for the headphone than 0.0009% THD+N, 116dB SNR and 1 Ω output Impedance. They say the following about the amp:


> The on-board headphone amplifier is custom-built using discrete transistors and
> audiophile-grade WIMA® film/foil capacitors in a dual-amp design to satisfy the
> most demanding needs of today’s intense games and high-resolution audio.
> Experience the difference of a discrete dual-amp design as each audio channel is individually amplified
> ...





DJ The Rocket said:


> This isn't possible in the way that you mean. Maybe the enclosure is really cheap or something, but the specs to build one are exact. When I put one together a couple weeks ago I even looked for ways to substitute cheaper components. It turns out that NwAvGuy did that for us already. There aren't any corners to cut as long as everything is in spec, and if they aren't in spec then you didn't buy an o2, which would have consequences that would require a lawyer to explain. Personally I think the chances of that are effectively zero.
> 
> Do you have a multimeter? You can open yours up and follow the testing procedure lined out online. It's really easy (presuming you know how to use your MM already) and it will put any concerns to bed with finality.
> 
> ...


In this case I trust my ears and how the unit I have here sounds. Some kind of defect is always possible or it just doesn't play well with ridiculously efficient and sensitive headphones like HD 595. Even potato would power it to dangerous levels (the main problem is the output impedance).


----------



## JakeJack_2008 (Jan 9, 2018)

Hi,

I've got the JDS Labs O2 amp as a standalone unit which I had bought in Feb 2013.
I have just bought a new Tenergy 9V NiMH Battery 2PK and would like to replace the old batteries
( which were installed in Feb 2013 by JDS Labs).
Since this is the first time that I am planning to install the new batteries I would like to know
what screwdrivers  I need to unscrew
- the volume knob
- the front panel


Are there any hints with pics on this site which would guide me through the process?

Thanx,

JJ


P.S.
I am also a proud owner of the JDS Labs ODAC (2013).


----------



## DJ The Rocket

Anarion said:


> Make your own conclusions (no idea how accurate this is): http://reference-audio-analyzer.pro/en/report/amp/creative-sound-blaster-ae-5.php
> 
> I can only think that the stereo crosstalk is the main issue.
> 
> ...



Two things here: at first glance that link with the ae-5 measurements looks good, but did they also measure the o2? I couldn't find it, and comparing measurements across websites is not valid without a specific reason to believe the tests were equivalent. What o2 measurements are you comparing to? 

And I'm sorry, but did you really say you "trust your ears" here? I don't know if you're trolling or being serious, but in case you're serious, what makes you think this is a valid area to apply subjective sighted listening impressions? Even if we assume your AE-5 measurements are comparable with, say, the JDS Labs O2 measurements, what makes you so sure the difference is audible in the first place?


----------



## Arkady Duntov

DJ The Rocket said:


> And I'm sorry, but did you really say you "trust your ears" here? I don't know if you're trolling or being serious, but in case you're serious, what makes you think this is a valid area to apply subjective sighted listening impressions? Even if we assume your AE-5 measurements are comparable with, say, the JDS Labs O2 measurements, what makes you so sure the difference is audible in the first place?



While I agree with your conclusions, I don't think it's at all worthwhile to disagree with an "I trust my ears" statement; this is, in my opinion, intended to be a final conclusion which is not amenable to argument or correction.


----------



## DJ The Rocket

@Arkady Duntov In any other forum I would agree with you, effective discussion about most products wouldn't be possible otherwise. But when discussing the O2 or ODAC I think it's fair to use different standards. I think it's fair to say the objective approach is inherent to the very soul of the o2.

I can see where a reasonable person might or might not agree with me on that though.


----------



## Nitreb

From what I can see on my own O2, you'll need a small Allen key (the hexagonal type, in metric presumably) for the volume knob, and a Phillips screwdriver (the "+" type) of suitable size for the casing. There's also the ground cable you'll have to take care of. I think it's behind the front panel, right corner.



JakeJack_2008 said:


> Hi,
> 
> I've got the JDS Labs O2 amp as a standalone unit which I had bought in Feb 2013.
> I have just bought a new Tenergy 9V NiMH Battery 2PK and would like to replace the old batteries
> ...


----------



## DJ The Rocket (Jan 9, 2018)

Nitreb said:


> There's also the ground cable you'll have to take care of. I think it's behind the front panel, right corner.



Just in case anyone needs clarification, by "take care of" the ground wire, I think he means loosen it so that the board can slide out. It took me a while to understand that part, but FWIW everything he said is correct.

It also gives me an idea: I'm using a cut component lead for the ground like everyone else probably, but now I'm thinking it'll be worth the effort to switch to a wire with enough slack to let the board slide out just enough to access the batteries without needing to worry about the front panel. I'm surprised I haven't read about anyone doing that in any of the build threads I read, but lots of people must have done it that way

I made mine bone-standard, but after using it for a few weeks I have a list of customizations I mean to do. Besides the ground wire, the front panel power jack bugs me _way_ more than I expected. It makes the front look so horribly cluttered. I may do away with the gain switch as well, 2.5x is perfect for me already. Then I'm going to pull the headphone jack and replace it with a switched jack, to be connected to rear RCA jacks. That way the RCA level will be adjustable with the volume pot, and they'll switch off when headphones are inserted. The power and RCA cables will need to be given enough slack to let the board slide out of course, that detail sounds dangerously easy to forget about. 

The O2 works really well in a preamp role, the alps pot I used is really clean, and I got to choose one with a linear taper that I like. I was not a fan of the front-loaded curve used on the Magni 3 pot. I thought the Magni 3 sounded great for my headphones that the o2 isn't powerful enough to drive well, but it's just not as clean sounding, which only really became apparent to me using it as a preamp.


----------



## Anarion (Jan 10, 2018)

DJ The Rocket said:


> Two things here: at first glance that link with the ae-5 measurements looks good, but did they also measure the o2? I couldn't find it, and comparing measurements across websites is not valid without a specific reason to believe the tests were equivalent. What o2 measurements are you comparing to?
> 
> And I'm sorry, but did you really say you "trust your ears" here? I don't know if you're trolling or being serious, but in case you're serious, what makes you think this is a valid area to apply subjective sighted listening impressions? Even if we assume your AE-5 measurements are comparable with, say, the JDS Labs O2 measurements, *what makes you so sure the difference is audible in the first place?*


The fact that I have both here and I can hear them by myself. You, on the other hand, don't.

I can make my conclusion based on what I actually hear. I wouldn't be so quickly to accuse other people trolls just because you think that O2 is the best sounding, flawless amp on this whole planet. It's not possible to compare measurements made by different tests but you can see some pattern and then I can try validation those with my own ears. Finally, if you have both you can just hear them by yourself.

The difference is definitely there. Soundstage is airier and wider on AE-5 and I'd definitely give the detail advantage to AE-5 too because it affect separation too.

I didn't expect this. It's somewhat similar situation than with Zx - the headphone amp noticeably neutered the soundstage and fine detail. That's not the case with AE-5 so I guess the individually amped channels makes the difference.

Also if you wonder about my hearing, I can hear grasshoppers just fine - even when there's other noises around.

Heck, I could do the testing myself but the problem is that the ADCs that I have available would be bottleneck.


----------



## MrMateoHead

Anarion said:


> The fact that I have both here and I can hear them by myself. You, on the other hand, don't.
> 
> I can make my conclusion based on what I actually hear. I wouldn't be so quickly to accuse other people trolls just because you think that O2 is the best sounding, flawless amp on this whole planet. It's not possible to compare measurements made by different tests but you can see some pattern and then I can try validation those with my own ears. Finally, if you have both you can just hear them by yourself.
> 
> ...




You can trust your own ears, but I don't have to. 

A proper subjectivist would simply have claimed that they preferred the sound of the AE-5 to the O2, then make some claim like, "because the soundstage was better" and "separation" was superior to particular listening tastes, environment, and recording choices. Note that evaluating the DACs is probably as important to the actual amplification sections themselves, since they aren't the same.

I am not saying I disagree with your conclusion so much as I would say that I always wish, in these cases, some actual investigation could be conducted. There is not enough data on the AE-5 for me to determine if it provided superior dynamic range, even lower distortion etc.  But its great to see soundblaster taking headphone users seriously. And I am sure I would probably like it also.

In my experience something like adding an ODAC to the O2 sounded superior relative to my laptop. The difference wasn't great, but I am sure it would be measurable, and had I the equipment, I would measure it.


----------



## Arkady Duntov

Anarion said:


> I can make my conclusion based on what I actually hear. I wouldn't be so quickly to accuse other people trolls just because you think that O2 is the best sounding, flawless amp on this whole planet. It's not possible to compare measurements made by different tests but you can see some pattern and then I can try validation those with my own ears. Finally, if you have both you can just hear them by yourself.
> 
> The fact that I have both here and I can hear them by myself. You, on the other hand, don't.



Personal attacks, by anyone, are certainly unwelcome here.


Anarion said:


> The difference is definitely there. Soundstage is airier and wider on AE-5 and I'd definitely give the detail advantage to AE-5 too because it affect separation too.



It's possible that distortion on the AE-5 sounds like a "detail advantage" and "it [affects] separation too." I don't think this has been disputed or even that it's worth disputing.


----------



## Nitreb

DJ The Rocket said:


> Just in case anyone needs clarification, by "take care of" the ground wire, I think he means loosen it so that the board can slide out. It took me a while to understand that part, but FWIW everything he said is correct.
> 
> It also gives me an idea: I'm using a cut component lead for the ground like everyone else probably, but now I'm thinking it'll be worth the effort to switch to a wire with enough slack to let the board slide out just enough to access the batteries without needing to worry about the front panel. I'm surprised I haven't read about anyone doing that in any of the build threads I read, but lots of people must have done it that way
> 
> ...



Here's what the ground wire should look on a standard-build O2:


----------



## Anarion (Jan 11, 2018)

MrMateoHead said:


> You can trust your own ears, but I don't have to.
> 
> A proper subjectivist would simply have claimed that they preferred the sound of the AE-5 to the O2, then make some claim like, "because the soundstage was better" and "separation" was superior to particular listening tastes, environment, and recording choices. Note that evaluating the DACs is probably as important to the actual amplification sections themselves, since they aren't the same.
> 
> ...


Here's are some measurements just to see if my ears work correctly. I wanted to know if these reflect what I actually hear. The DAC on AE-5 is ESS ES9016K2M SABRE32 Ultra.

Full specs of test system:
Intel Core i7-3770K & Thermalright True Spirit | ASUS P8Z77-V | Corsair AX760 | Define R4 | 4x4GB G.SKILL RipjawsX 1600MHz | EVGA GeForce GTX 1070 GAMING ACX 3.0 | Creative Sound BlasterX AE-5 | Samsung 830 128GB & 3x HDD = 5TB | Windows 10 Pro x64

Method:
ASIO playback and record. Main volume was set to 94% to avoid clipping (about 1dB headroom). Line out was 100%. Direct HP mode was used for AE-5 while Direct mode was used for Objective 2.




Things to note: SoundCore3D chip's ADC is the limiting factor for AE-5 and it's pretty safe to assume that AE-5 has even larger advantage in dynamic range and noise level. Not for Objective 2 amp though. Noise level, dynamic range and stereo crosstalk do not fit within the error margin and the AE-5 advantage is rather large. Those basically explain the difference in soundstage and everything really.


----------



## raoultrifan

Hello, 

Seems a very good soundcard this AE-5, which is really good for all of us, because raising the bar for such products is very helpful, especially regarding the SNR and the power output for headphones.

However, I remember I did some measurements myself few years ago to my O2 amplifier and I got a bit over 110dB of SNR (default NJM2068 or LME49720 on the input stage, can't remember now); I believe I used 2V RMS sine-waves on the input. O2 is the quietest headphone amplifier I've ever heard, but it can be annoying when paired with neutral and narrow-stage headphones, mostly because of it's sound neutrality (some call it "clinical sound"), but also because it's scene is above average, so some might prefer other amplifiers in their setup. Although, O2 concept is one of the best ever and the fact that I built it myself from scratch increased my love for O2 a lot (subjective, I know). I'm using it with the ODAC and a pair of Beats Solo 2 nearby my bed, just in case I fell like listening some music before sleeping. 

Best, 
Raul.


----------



## DJ The Rocket

Anarion said:


> AE-5 and I'd definitely give the detail advantage to



What do you mean by this? Details (or lack thereof) don't have anything to do with the amplifier, provided the amp meets certain minimum thresholds for noise, distortion, or less likely, slew rate, etc. One amp is going to have precisely the same detail as the next. 

Often, certain kinds of treble distortion can be perceived as being "more detailed," but that's not true detail. Again, there's nothing wrong with enjoying this kind of distortion more than transparency. I personally consider anything that decreases transparency a flaw. 




Anarion said:


> Also if you wonder about my hearing, I can hear grasshoppers just fine - even when there's other noises around.



Okay. That's neat? This is a really, really strange thing to say. From the context I think I know what you're trying to prove, and I'm trying really hard not to sound condescending here and I don't think I'm going to succeed, but the fact that you think this example means anything demonstrates that you don't understand how hearing perception works. Maybe someone else with better tact can break down exactly why?


----------



## MrMateoHead

Anarion said:


> Here's are some measurements just to see if my ears work correctly. I wanted to know if these reflect what I actually hear. The DAC on AE-5 is ESS ES9016K2M SABRE32 Ultra.
> 
> Full specs of test system:
> Intel Core i7-3770K & Thermalright True Spirit | ASUS P8Z77-V | Corsair AX760 | Define R4 | 4x4GB G.SKILL RipjawsX 1600MHz | EVGA GeForce GTX 1070 GAMING ACX 3.0 | Creative Sound BlasterX AE-5 | Samsung 830 128GB & 3x HDD = 5TB | Windows 10 Pro x64
> ...



What is direct HP mode? What is "directo Mode"? What was the source for the O2 measurements? The amp should be showing approximately 115 dBA for the noise level. The creator claimed upwards of 130 dBA at full output. With an ODAC hooked up my guess is it would drop to about 103 dbA with up to 115 dB dynamic range limited by the ODAC, not the amp. Worst case crosstalk is about 65 dBA and best case is about 95 dBA impedance / signal depending. Did you build the O2 yourself? Something looks off with these values.


----------



## Arkady Duntov

MrMateoHead said:


> Did you build the O2 yourself? Something looks off with these values.



One thing I didn't recall while responding is that the OP said his O2 was from Massdrop and questioned whether they had "cut corners." That could be an important point.


----------



## DJ The Rocket (Jan 11, 2018)

Arkady Duntov said:


> One thing I didn't recall while responding is that the OP said his O2 was from Massdrop and questioned whether they had "cut corners." That could be an important point.



Far, far more likely than "cut corners" is an innocent mistake, like ESD killing a FET or a manufacturing defect in a component, or something like that. It's uncommon but it does happen. It would be unspeakably stupid to intentionally do something like that on what's possibly the most well documented headphone amp that's ever been designed.

Technically the problem would be with whoever Massdrop contracted anyway, not massdrop themselves, though they're who you would deal with. It's not like MD manufactures anything in-house. I also have to think Massdrop would take this very seriously if it was the case. They should take any defective product seriously, regardless of fault


----------



## Oscar-HiFi

DJ The Rocket said:


> Far, far more likely than "cut corners" is an innocent mistake, like ESD killing a FET or a manufacturing defect in a component, or something like that. It's uncommon but it does happen. It would be unspeakably stupid to intentionally do something like that on what's possibly the most well documented headphone amp that's ever been designed.
> 
> Technically the problem would be with whoever Massdrop contracted anyway, not massdrop themselves, though they're who you would deal with. It's not like MD manufactures anything in-house. I also have to think Massdrop would take this very seriously if it was the case. They should take any defective product seriously, regardless of fault



I do recall a picture of a power supply that came with the massdrop units, it was 12v...


----------



## Anarion (Jan 12, 2018)

Oscar-HiFi said:


> I do recall a picture of a power supply that came with the massdrop units, it was 12v...


I'm not using that. I use the G.E.Z. 15V AC adapter (same as this). Highly doubt that it's the problem. The thing that came with Massdrop is _definitely _junk.




The one that Massdrop bundled is on the left (ignore the right one).

It's entirely possible that this is the so called "Monday unit". It's also possible that O2 just isn't quite one par with AE-5. At the very least I don't think there's any reason to believe that O2 should spank AE-5 (or the other way around). In any case though, the measurements line up with how it actually sounds (for what ever reason).




MrMateoHead said:


> What is direct HP mode? What is "directo Mode"? What was the source for the O2 measurements? The amp should be showing approximately 115 dBA for the noise level. The creator claimed upwards of 130 dBA at full output. With an ODAC hooked up my guess is it would drop to about 103 dbA with up to 115 dB dynamic range limited by the ODAC, not the amp. Worst case crosstalk is about 65 dBA and best case is about 95 dBA impedance / signal depending. Did you build the O2 yourself? Something looks off with these values.


This is the Massdrop pre-built Objective 2 amp. Source for Objective 2 was Creative Sound BlasterX AE-5 (line out). Direct mode means that the Sound Core3D chips was bypassed and the audio went straight to the DAC. On paper ODAC is worse than the line out on AE-5 so it shouldn't make a difference for the better.



DJ The Rocket said:


> What do you mean by this? Details (or lack thereof) don't have anything to do with the amplifier, provided the amp meets certain minimum thresholds for noise, distortion, or less likely, slew rate, etc. One amp is going to have precisely the same detail as the next.
> 
> Often, certain kinds of treble distortion can be perceived as being "more detailed," but that's not true detail. Again, there's nothing wrong with enjoying this kind of distortion more than transparency. I personally consider anything that decreases transparency a flaw.


"More detailed" is a combination of things. Dynamic range and crosstalk all play a role. I consider more accurate soundstage and better dynamic range as "detail". Dynamic range difference may play even larger role once you start lowering the volume (to something that you actually use for listening).


DJ The Rocket said:


> Okay. That's neat? This is a really, really strange thing to say


In case you though that I have a hearing problem. Considering the way you started writing... You started out rather hostile and condescending. How do you think people will respond?


----------



## MrMateoHead (Jan 12, 2018)

Basically, my hunch is that you should seek another O2 before subjectively OR objectively concluding that the Soundblaster AE-5 is superior - and that its superiority is plainly audible.

To prove that, I would seek out a neutral 3rd party, and A/B the amp+DAC for them. It won't conclude WHY the AE-5 is better (could be the amp, the dac, or some combo of the two), but if it is the users preference the majority of the time, it is probably a winner, period.

I tried this exercise with some really good speakers separated by $400 in price (full retail), and coax vs. "regular" drivers / alignment. Set up and volume matched to 1 dB (for a listening level of about 65-70 dB+ peaks at about 6 feet). Source was Laptop using an ODAC and FLAC recordings. Trust me, 70 dB or so average SPL is basically plenty loud for music listening - any louder would start to be uncomfortable and glare (a little about myself, I think most concerts sound like s*** because they are just too loud, my ears can't take it). I did sighted listening while the "blind" person did the A/B listening. 

After three days, I hate to admit it, the more expensive speaker won. Apart from its advantages NOT in play (superior horizontal and vertical response), I suspect the slightly better bass extension and weight (it measured noticeably better around 45-65 hz) contributed to it sounding "bigger" and more powerful. Personally, I felt that the added depth (e.g. transparency) of the more expensive speaker, when it was apparent on some recordings, was just undeniable. Then again, I must say the cheap, $100 speakers were demonstrably awesome. They lacked for nothing in the room, and were in some cases almost preferable - almost. I've never heard them sound that good and I suspect the "liveliness" of the room helped the high frequency response a tad.

No I didn't test Maximum SPL or push volume to concert levels to see which speaker fell apart first - that just isn't my "90%" rule - _how does it sound, when 90% of the time you aren't cranking it to death?_

Anyway the bottom line was you do sometimes get what you pay for (when both products are from companies that obviously care about real performance). BUT given that the "winner" cost, technically, several times more, I wouldn't recommend them to someone that didn't have money to burn, because the gains just weren't THAT great. Absent an A/B test, you wouldn't feel you were missing out at all. After averaging the response of each speaker from several positions, I discovered the measured extremely similarly - that is, great speakers DO probably measure somewhat alike. With tonal balance almost the same, this was a great way to see if lower distortion, larger cabinets etc. make a difference.


----------



## Anarion (Jan 12, 2018)

It would be nice to test another O2 but that's not possible. I also tried different 3,5mm to RCA cable just to rule that out - no improvement. This particular unit that I have here definitely doesn't perform that well. It would be nice if someone with O2 and AE-5 could test.

My O2 is the 1x & 3,3x gain version. I've used the low gain option. AE-5 has three gain settings and I used the low gain one which also seems to be 1x gain (since both produced the same volume, give or take 0,5 dB).

It's annoying that often the sound in movie theatres is often so loud that you actually hear things more clearly once you plug your fingers in your ears. I bet that would apply to concerts too. I can't handle loud sound very well at all and I use rather low volume levels myself. No one ever complains about leakage when I use open cans. HD 595's are rather pain in the backside because they are so sensitive. With O2 I have to turn the volume knob around 33% (in low gain) while PC's master volume is at 10%... If I'd plug them directly in the card I'd have to use something around 2-4%.


----------



## MrMateoHead

The reality is that most headphones require, at most, just a few mWs of power to CRANK. when 1 mW can yield 90-100 dB, frankly, the power requirement is too low to justify a dedicated amp. That is why, frankly, most of my midrange cans sound just fine on a modern smartphone. Its the higher impedance stuff that gets tricky.

The only headphone which definitely needed the O2 was the HE-400s I own, which I playback at close to noon-1 pm when I am really feeling crazy. My Old 595s benefited from the amp a bit but still sounded about the same.

Here's what I would like to have. A volume knob that steps up the power in fractions of a mW for about half the travel. Then one that scales from that mW to hundreds of mWs over the next 6-9 hours for the insensitive cans. I'm sure it would be bizarre, but at least it might add some flexibility. 

To use my O2 with my PSBs, I raise the knob until I am just clear of the L/R channel imbalance area, about 9 O'clock, and then use windows volume control from about 20-50. Luckily I detect no loss of fidelity even if it is there. Thats it. Then just strap in the best source I have available.


----------



## DJ The Rocket

Anarion said:


> "More detailed" is a combination of things. Dynamic range and crosstalk all play a role. I consider more accurate soundstage and better dynamic range as "detail". Dynamic range difference may play even larger role once you start lowering the volume (to something that you actually use for listening).



Ah, so we're using different definitions for the word "detail." How lovely that audio doesn't have any sort of standardization about what words mean. No wonder this hobby is such a mess, we can't even communicate without defining terms at the beginning of every post. 

I always thought that every 101-level college course was mostly just to teach the basic vocabulary of the field, otherwise the more advanced courses wouldn't make any sense to anyone. Somebody--anybody--should put together a standardized glossary of terms for describing audio, and then we'd need a critical mass of people to follow it and people with more tact than me to nudge everyone else to get them on board too. It doesn't matter if we use your conception of detail or mine or anyone else's, everyone will adjust eventually.


----------



## DJ The Rocket

Oscar-HiFi said:


> I do recall a picture of a power supply that came with the massdrop units, it was 12v...



I wonder what it actually measures at. I use a reterminated "16V" linear supply from Schiit, and it measured 19.5V, just barely within o2 spec.


----------



## Arkady Duntov

DJ The Rocket said:


> Far, far more likely than "cut corners" is an innocent mistake, like ESD killing a FET or a manufacturing defect in a component, or something like that. It's uncommon but it does happen. It would be unspeakably stupid to intentionally do something like that on what's possibly the most well documented headphone amp that's ever been designed.
> 
> Technically the problem would be with whoever Massdrop contracted anyway, not massdrop themselves, though they're who you would deal with. It's not like MD manufactures anything in-house. I also have to think Massdrop would take this very seriously if it was the case. They should take any defective product seriously, regardless of fault



Your conclusions are some I failed to make and I agree with you.

Another mistake I made was to attribute the differences encountered by the OP to problems in the AE-5; while it's possible I was correct, that isn't the only reasonable deduction.


----------



## Anarion (Jan 13, 2018)

DJ The Rocket said:


> I wonder what it actually measures at. I use a reterminated "16V" linear supply from Schiit, and it measured 19.5V, just barely within o2 spec.


It's an 12VAC unregulated power adapter. Someone measured it at and it seems to drop below 14V while other tested that it's just above 14V. Somewhat questionable decision from Massdrop to bundle that adapter with it. There are likely cases where it's not in within spec for O2.



MrMateoHead said:


> The reality is that most headphones require, at most, just a few mWs of power to CRANK. when 1 mW can yield 90-100 dB, frankly, the power requirement is too low to justify a dedicated amp. That is why, frankly, most of my midrange cans sound just fine on a modern smartphone. Its the higher impedance stuff that gets tricky.
> 
> The only headphone which definitely needed the O2 was the HE-400s I own, which I playback at close to noon-1 pm when I am really feeling crazy. My Old 595s benefited from the amp a bit but still sounded about the same.
> 
> ...


The irony is that, HD 595 for example, doesn't need amplification (gain) at all quite the opposite. Why they sound better with amp (assuming that the amp has low output impedance) is the fact that they work better with low output impedance. HD 595 sound a bit boomy and sloppy when plugged to line out directly for that reason.

Some amps have pretty significant gain even in the low gain mode and might be a really bad thing for sensitive headphones because they would be just too loud. Degain options would be perfect for some headphones.


----------



## DJ The Rocket

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?


----------



## Nitreb

DJ The Rocket said:


> 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?



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


----------



## DJ The Rocket

Nitreb said:


> 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

DJ The Rocket said:


> 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

Architeuthis said:


> 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

DJ The Rocket said:


> 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.


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## Nitreb

Architeuthis said:


> 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.


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## 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.


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## MrMateoHead

Heitosj said:


> 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.


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## 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

MrMateoHead said:


> 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

DJ The Rocket said:


> @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

Heitosj said:


> 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

MrMateoHead said:


> 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


----------



## Detectit

Got the O2 for a month now. It's a good amp. 

Yes it's quiet 
Yes it's reference with no change to the sound. 
And i came to the conclusion for myself an amp must have some coloration. 

Almost sold the O2. But gave it a second change with opamp rolling.

OPA2228PA and the OPA2134. And the amp came alive....

Bass is deeper more present and the cimbles highs are clearer.

Thats the way I like it. An upgrade of a few dollars but a good one.


----------



## raoultrifan

So, you replaced the original NJM/JRC2068 with OPA2228PA or with OPA2134?


----------



## Detectit

raoultrifan said:


> So, you replaced the original NJM/JRC2068 with OPA2228PA or with OPA2134?



Only the U11 slot with OPA2228PA
And U3/4 with OPA2134


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## raoultrifan

Detectit said:


> [...]
> And U3/4 with OPA2134



I wouldn't do that, honestly. You're cutting in half the output power and you're also not in line with designer's recommendations (please read his blog before replacing the output opamps). However, OPA2134 is just not designed to work as headphones output buffer, so I strongly suggest you to remove it. You might find more answers from this entire forum, but also from diyaudio (lot of EE info in there too).


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## Detectit (Mar 1, 2018)

raoultrifan said:


> I wouldn't do that, honestly. You're cutting in half the output power and you're also not in line with designer's recommendations (please read his blog before replacing the output opamps). However, OPA2134 is just not designed to work as headphones output buffer, so I strongly suggest you to remove it. You might find more answers from this entire forum, but also from diyaudio (lot of EE info in there too).



But if it sound right  It's okay i guess? I don't have the idea it sucks a lot of power down? Maybe a little but not much.

And yes the designer didn't meant it that way. But i think reference equals lifeless to me.

BTW I have searched the forum yesterday and there weren't any results. Thought I post it.
But now there are.... Guess the search function was broken. 
I will read up.


----------



## 439598

My o2 is measuring different DC voltages on the negative and positive rail, with a 12V AC supply it reads -15V and +12V DC, is this a problem?


----------



## raoultrifan

Yes. Please measure again.


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## 439598 (Mar 9, 2018)

still getting that,  there is also 24V AC on positive rail, 0V AC on negative rail.

there isnt any op amps in or extra caps


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## 439598 (Mar 9, 2018)

measuring directly from the voltage regulator's outputs shows +12V DC and +24V AC on U5 but +0.6V DC and 0V AC on U6... is this totally wrong?


----------



## raoultrifan

Just measure between GND and opams V-/+ both rails, also between GND and batteries + & -.


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## raoultrifan

Here's an already uploaded picture on Head-Fi: 







Try measuring the voltage on C8, C9 or C17 and C18, reference with GND, of course.
Though, what is the issue, actually?


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## 439598 (Mar 10, 2018)

I noticed strange problems after adding additional caps, some occasional fluttering and booming in the bass. on MC7912 negative regulator output there is just 0.6v but it should be -12V, this faulty regulator has probably been the cause of the sound quality issues all along. the extra caps must have caused the unregulated negative rail to increase in voltage even more, probably past the op amp max -18V. edit: or the caps will only increase voltage without a load so maybe not


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## raoultrifan

Are you referring to https://www.head-fi.org/threads/obj...mpressions-thread.704804/page-5#post-14078842? Please triple-check of short circuit. I got 2 x 4.700uF/50V huge Nichicon caps in parallel to existing 470uF/35V caps and AC ripple remains constant, hence I left the original caps only. AGDR had a comprehensive post, most likely on diyaudio forum about that and he also proved that adding more caps will not improve the ripple in no way; instead, cutting the PCB traces between the 2 caps (not the GND, just the rails) and adding 2x1 ohms resistors will decrease the already very low ripple (however, first 2 caps need to get changed from 35V to 50V).

Usually, when adding more and more caps to a power rail or to bypass opamp rails you might expect to pre and/or post ringing. This may also cause oscillations to some power regulator. In this case, also the 2 FETs might get into issues, so please revert what you've done and see if O2 works fine after that.

You need to measure the voltages around C6 and C7 (reference to GND), but also around C8, C9 or C17 and C18. Also, measure the voltage across C10.

Usually, if a rail fail, then all DC goes to the headphones, so I doubt you're having an entire rail defective.

P.S.: If you really-really want to add more caps, get some WIMA MKP100-200nF) and add then on the bottom of the PCB between V+GND and V-/GND to bypass each opamp (at least the 4556 ones). Additionally, you could add tantalums too, because they can handle the ripple very well and can also fit between the PCB and the O2's aluminium case.


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## JakeJack_2008 (Mar 14, 2018)

jseaber said:


> We've only shipped *15VAC, 500mA* transformers since at least 2014, if not longer:
> https://www.jdslabs.com/products/147/15vac-power-adapter/
> 
> Triad P/N WAU12-200 was a 12VAC, 200mA adapter originally recommended by NwAvGuy in 2011. It was acceptable under light loads. Voltage dips into unacceptable territory from 100-110VAC outlets. We've long since abandoned this part.




Hi, I have bought both the Triad P/N WAU12-200 - 12VAC, 200mA  and the current one *15VAC, 500mA* from you for using in the *USA.*
Not having golden ears, I do not hear any difference in sound quality while using either of them with my  Beyerdynamic DT 880 (*250* *Ohm*; 2005 Edition)  headphones.
Are my ears missing something here?


----------



## jseaber

JakeJack_2008 said:


> Hi, I have bought both the Triad P/N WAU12-200 - 12VAC, 200mA  and the current one *15VAC, 500mA* from you for using in the *USA.*
> Not having golden ears, I do not hear any difference in sound quality while using either of them with my  Beyerdynamic DT 880 (*250* *Ohm*; 2005 Edition)  headphones.
> Are my ears missing something here?



No, the difference is unlikely to be noticed except under extreme conditions.


----------



## 439598

Isnt the other function of those caps to reserve power for the amp?

once I have a replacement mc7912 ill record the output to see if theres any difference, and compare to digital waveform to see which is more accurate.


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## JakeJack_2008 (Mar 15, 2018)

jseaber said:


> No, the difference is unlikely to be noticed except under extreme conditions.



Thank you very much.
So, certainly teenagers _with _or without _golden ears_, or even audiophiles, would not hear any difference.

By the way, I have forgotten to mention my setup:
_laptop _(Windows 10) ----> ODAC ----> O2 ----> Beyerdynamic DT 880 (*250 *Ohm)



On another matter.
Last week I did replace two Tenergy 9V batteries in my JDS Labs O2 (Feb. 2013) amp.
I suppose that those batteries were installed by JDS Labs in late 2012 or early 2013.
After more than 5 (five)  years of usage, the old batteries did not leak, were not corroded or rusty, etc.
and above all,  surprisingly *still  *performed 'quite' well.
Outside, the old batteries looked like new - very clean.  Obviously I don't know how they changed inside,
over the period of 5 years .


----------



## Zouka

Has anyone upgraded from this to something else and found it to be a worthy upgrade?

I've been using the ODAC/O2 for years now and since I will be getting a Focal Clear soon I think I'm up for a DAC upgrade too.


----------



## BenF

Zouka said:


> Has anyone upgraded from this to something else and found it to be a worthy upgrade?
> 
> I've been using the ODAC/O2 for years now and since I will be getting a Focal Clear soon I think I'm up for a DAC upgrade too.


Oppo HA-2/HA-2SE has a DAC that sounds better to me.
I liked it with Elear, TH900MK2 and AB-1266.
O2 is unsurpassable though.


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## Arkady Duntov

Zouka said:


> I've been using the ODAC/O2 for years now and since I will be getting a Focal Clear soon I think I'm up for a DAC upgrade too.



May I ask why you find the ODAC to be insufficient?


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## WilliamLeonhart (Apr 11, 2018)

I would say the m9xx, the Mojo or the iDSD Micro. Those were the first that proved to me the O2 ODAC wasn’t everything. What I remember was cleaner, overally more detailed sound, especially in the trebles. Also no more problems with ASIO buffers. That being said, these were still my first “proper” amp/DAC and I’m still using the ODAC for my computer speakers.


----------



## raoultrifan

I have the ODAC A revision, the first one and it's the noisiest from all the DACs I have. Not that I can actually hear that noise while listening to regular music, but when I get my O2 at max. gain and full volume (no music playing!) I can hear the noise with 16-ohms IEMs, but also with AKG K550 and Beats Solo2. In order of background noise from highest-to-lowest from the RCA output I got this: ODAC > ROLAND UA-M10 > ASUS Essence One MKii Muses > BURSON PLAY = ASUS U7 (Essence One and PLAY are heavily modded; U7 has a much lower output volume, so not the best way to compare it with the other DACs).

Also, my ODAC rev. A has a lot of noise around 500kHz, inaudible of course, but I don't care...it's still there and it shouldn't be. I strongly suggest you to get the ODAC rev. B or the OL version or the SDAC, so don't buy the ODAC rev. A.


----------



## WilliamLeonhart

raoultrifan said:


> I have the ODAC A revision, the first one and it's the noisiest from all the DACs I have. Not that I can actually hear that noise while listening to regular music, but when I get my O2 at max. gain and full volume (no music playing!) I can hear the noise with 16-ohms IEMs, but also with AKG K550 and Beats Solo2. In order of background noise from highest-to-lowest from the RCA output I got this: ODAC > ROLAND UA-M10 > ASUS Essence One MKii Muses > BURSON PLAY = ASUS U7 (Essence One and PLAY are heavily modded; U7 has a much lower output volume, so not the best way to compare it with the other DACs).
> 
> Also, my ODAC rev. A has a lot of noise around 500kHz, inaudible of course, but I don't care...it's still there and it shouldn't be. I strongly suggest you to get the ODAC rev. B or the OL version or the SDAC, so don't buy the ODAC rev. A.


That's right, the revB is much more refined.

It should also be noted that some O2 does suffer from clipping at high gains. I owned 3 different versions of it and the 2nd one, made by Mayflower, had that issue at 3.5x. Obviously 1.5x was more than enough for every headphones I used with the O2.


----------



## raoultrifan

I know about the clipping and this is occurring only when feeding it with loud music. Swapping the NJM2068 with a different op-amp might help a bit, though the output stage will start clipping soon as well. Everything is documented on O2's building "datasheet" and measurements. However, I still find it the cleanest amp I've ever heard and completely flat.


----------



## MrMateoHead

raoultrifan said:


> I know about the clipping and this is occurring only when feeding it with loud music. Swapping the NJM2068 with a different op-amp might help a bit, though the output stage will start clipping soon as well. Everything is documented on O2's building "datasheet" and measurements. However, I still find it the cleanest amp I've ever heard and completely flat.



Not to be defensive or anything, but are you sure the clipping your hear is from the O2 / ODAC and not the recording itself? The combo has always been revealing enough to make recorded clipping audible through a pair of sensitive headphones (like planars). Tons of my music, whether CD or not, clips. It is often audible if I listen for it. Like Beck, attached. I don't hate Mp3s because they "sound bad" - I hate them because when the album has no headroom Mp3s will push near-clipping into clipping. And then consumers PAY for it! 

I don't think I ever heard noise from my ODAC that wasn't in the end indicative of a failed / failing ODAC unit. The Rev B is supposedly more reliable, I'm sure it sounds great.


----------



## castleofargh

MrMateoHead said:


> Not to be defensive or anything, but are you sure the clipping your hear is from the O2 / ODAC and not the recording itself? The combo has always been revealing enough to make recorded clipping audible through a pair of sensitive headphones (like planars). Tons of my music, whether CD or not, clips. It is often audible if I listen for it. Like Beck, attached. I don't hate Mp3s because they "sound bad" - I hate them because when the album has no headroom Mp3s will push near-clipping into clipping. And then consumers PAY for it!
> 
> I don't think I ever heard noise from my ODAC that wasn't in the end indicative of a failed / failing ODAC unit. The Rev B is supposedly more reliable, I'm sure it sounds great.


it's a matter of signal input. originally the gain switch was for when the source was a super weak portable device with a line out at sometimes not even 0.5V. so you would multiply that by 3 or 6 with the gain setting and still be well within the maximum voltage the amp can output into whatever load. 6*0.5V that's 3V. of course the O2 can deal with that.
but if you have a DAC sending a signal at 2 or 3V and you still ask the amp to multiply that value by 3 or 6 times, now we might get in trouble. ^_^

but it was never intended in the design to use high gain and high voltage input at the same time. that just ends up being a misuse of a function for weak lines out.


----------



## raoultrifan

I think WilliamLeonhart was referring to the distortions made by high-gain use for the VAS opamp, NJM2068. This has been explained by the designer, so it's a limitation that can be resolved by using a NE5532, LM4562 or a similar opamp. However, for most of us a max. gain between 3-3.5X will suffice, so I don't really see this as being a limitation, but more a...specification.

Like I said it for several times, O2 is a great amplifier and given the very low noise and flat bandwidth I consider it a reference amplifier. I'm using the OPA1652 in VAS for now with MUSES8920 in output buffer and I'm enjoying every second of music out of it.


----------



## WilliamLeonhart

Did you hear a difference in sound signature when rolling op-amp though? I had both the 8920 and 8820 and I couldn’t hear any difference compared to the NJM at all. The Burson and the Sparko brought about just a tiny bit of change (could be my imagination). So I think nwAV didn’t design the O2 for opamp rolling. On the cMoy or the Burson Play for example, you’d hear it right away


----------



## raoultrifan

No, couldn't fell anything, after all it's damned flat line in bandwidth response (tested with sine and square wave signals). 
The only advantage of the MUSES8920 in output stage would be lower DC-output, especially if you want to modify the high-pass filter (the trade-off resistor/cap). I think I posted some details and pics around this forum recently...just can't find this info now.


----------



## 439598

got something new to try. I found replacing the 2068 for anything else never sounded right. The OPA1612 or LM49720/LM4562 preserve much more detail but they dont really sound good, its not obvious and you will probably like the extra detail at first (if you can hear it) but after a while its gets fatiguing. The best choice for U1 is actually nothing at all. with some solid core copper either link the input and outputs of the U1's socket or get a new turned pin socket and link the input and outputs pins and use that to 'roll' this little adapter like an op amp (dont link the power rails by accident, check the pinout carefully).

This removes all gain options. its more neutral and accurate than any op amp, the volume was slightly lower compared to 1X gain with an op amp. it was the complete opposite experience to rolling op amps, it sounded flat and boring at first, i was used to the subtle colouration of the op amps, but it just keeps growing on me.

for output stage the OPA1612 is untouchable, I have been listening for weeks now comparing over and over and Im totalyl confident in this. if you think the current is an issue I bought an R2R11 and prefer the O2 amp with OPA1612 in 90% of the time. the OPA1612 is cutting edge with those distortion levels, discreet designs can not compare in neutrality and detail


----------



## Double-A

Hey guys, I'm thinking about using an Aune T1se as the DAC for my just-purchased 600-ohm DT 880s and an O2 for my amp. The Aune will have to wait a little bit because it is a little pricey for my humble means, but I can purchase the O2 now.

Which version would be a better match for my setup? The JDS Labs version, the Massdrop version, or (if there is one) a third version? I could save a little money by going with the Massdrop version, but if the extra money buys me something slightly nicer, then maybe I'll go with JDS Labs. What do you guys think? Does there seem to be a general consensus in this thread about which version is the best?

Thank you,
Alec


----------



## ostewart

JDS Labs have been producing the O2 for years, and their customer support is the best in the business. Always been a pleasure dealing with them.

Also JDS Labs is now available in the UK from Hifiheadphones, along with being on Amazon


----------



## Arkady Duntov

Double-A said:


> Hey guys, I'm thinking about using an Aune T1se as the DAC for my just-purchased 600-ohm DT 880s and an O2 for my amp. The Aune will have to wait a little bit because it is a little pricey for my humble means, but I can purchase the O2 now.
> 
> Which version would be a better match for my setup? The JDS Labs version, the Massdrop version, or (if there is one) a third version? I could save a little money by going with the Massdrop version, but if the extra money buys me something slightly nicer, then maybe I'll go with JDS Labs. What do you guys think? Does there seem to be a general consensus in this thread about which version is the best?
> Alec



I've had excellent customer service from JDS Labs, just like @ostewart said. Plus, JDS himself posts here.

Have you considered the JDS' ODAC+O2 combo? Both the O2 and ODAC are neutral,  the O2 has 0.54Ω output impedance so that it can better control more headphones, and it's less expensive than the Aune. I'm completely satisfied with the sound and operation of mine. BUT:: I haven't heard the Aune.


----------



## ostewart

Arkady Duntov said:


> I've had excellent customer service from JDS Labs, just like @ostewart said. Plus, JDS himself posts here.
> 
> Have you considered the JDS' ODAC+O2 combo? Both the O2 and ODAC are neutral,  the O2 has 0.54Ω output impedance so that it can better control more headphones, and it's less expensive than the Aune. I'm completely satisfied with the sound and operation of mine. BUT:: I haven't heard the Aune.



For roughly the same price, if you have the desk space, JDS Labs OL DAC + O2 would be my choice over the O2+ODAC combo.


----------



## Arkady Duntov

ostewart said:


> For roughly the same price, if you have the desk space, JDS Labs OL DAC + O2 would be my choice over the O2+ODAC combo.



The only thing about the OL DAC which made me not consider it for my office was the wall-wart. Otherwise, it looked quite good.


----------



## ostewart

Arkady Duntov said:


> The only thing about the OL DAC which made me not consider it for my office was the wall-wart. Otherwise, it looked quite good.



Yeah fair point, it does need an extra socket  

I have the OL DAC, Subjective3 + O2 stack, at home that is.

At work I have the Topping D30 + A30 as I'm not as worried about it being a pure reference system.


----------



## Double-A (May 21, 2018)

Arkady Duntov said:


> Have you considered the JDS' ODAC+O2 combo?


The reason why I want to go with the Aune is that it is a tube DAC and I want to get a taste of that "tube magic" that I hear members rave about on this website. I know that tubes are associated with followers of the subjective philosophy and, thus, could be considered antithetical to what the O2 is trying to accomplish, but, from reading on the Aune T1's thread here on Head-Fi, there seem to be several people who have paired the two products together and liked the result.

Thank you for your recommendations, @ostewart and @Arkady Duntov , I will be going with JDS Labs.


----------



## MrMateoHead

There was an article online recently suggesting that "2nd order distortion" makes good amps sound great - since apparently even-order distortion is pleasant and odd-order distortion is not. It would be fun to find a way to test that hypothesis on my own, but for the article a dedicated piece of hardware was used. Of all the amps, they seemed to hate the O2 the most, for some reason, but I am sure the reason is that they believe that negative feedback ruins amps even if it makes them measure clean.

ANYWAY if you go with the O2 combo to save some $$$, I would stick with the ODAC revision B - it should be more bulletproof reliable. 

The OLDAC probably sounds lovely - I have the AKM4490 in another audio device and it sounds great, or at least, no worse than the ESS in the ODAC. Sometimes I think the AKM is ultimately a bit more detailed and "musical" but I don't even know what I mean by that! It is good that the OLDAC has a dedicated plug-in adapter - you avoid all the issues with USB power that way, and you won't be "computer bound" if you decide to use it in a stereo stack instead. But sure . . . one more outlet!


----------



## Arkady Duntov

Double-A said:


> The reason why I want to go with the Aune is that it is a tube DAC and I want to get a taste of that "tube magic" that I hear members rave about on this website. I know that tubes are associated with followers of the subjective philosophy and, thus, could be considered antithetical to what the O2 is trying to accomplish, but, from reading on the Aune T1's thread here on Head-Fi, there seem to be several people who have paired the two products together and liked the result.



Does the Aune T1se have an analog (tube) DAC? If so, your plan sounds good.

If not, maybe you'll want an ODAC, OL DAC, ODAC+O2, or OL DAC+O2, and later replace it (them) with the analog Aune T1se. I don't know if this fits your plan.

P.S. I'm an objectivist.


----------



## Double-A

MrMateoHead said:


> There was an article online recently suggesting that "2nd order distortion" makes good amps sound great - since apparently even-order distortion is pleasant and odd-order distortion is not.


What does this mean? If it is too hard to explain more simply, don't worry about it.



MrMateoHead said:


> ANYWAY if you go with the O2 combo to save some $$$, I would stick with the ODAC revision B - it should be more bulletproof reliable.


Compared to the OL DAC, you're saying? Or compared to the T1se?



Arkady Duntov said:


> Does the Aune T1se have an analog (tube) DAC?


From what I read from the product thread, the product has a DAC chip, a solid state amplifier, and a "tube buffer". I assume this just means that the sound passes through the tube before it reaches the amplifier.


----------



## MrMateoHead

What I mean is that the distribution of harmonic distortion and its so-called "masking" effects might be subjectively pleasing to some, or all listeners of an amp. Amp distortion might create some "character" that is subjectively pleasing. Solid state amps with low THD sometimes get there with a lot of negative feedback, and that negative feedback suppresses 2nd and 3rd order distortion, which some claim sounds a lot better than the higher-order distortion that remains or is placed in line with the lower-order distortion after lots of negative feedback is applied.

Do I believe this stuff? I'm very skeptical. For one, the transducer / speaker is usually the object in the signal chain with the highest distortion, significantly higher than a clean amp. If the "harsh, cold, analytical" high order distortion of an amp like the O2 is even a problem, how am I supposed to hear it when its level is far below the level generated by the headphone? How do I hear it when I am not actually pushing the amp hard enough for some distortion to appear? Naw mean? At what listening level would any distortion be great to listen to? 60 dB? 70 dB? Don't say 80 dB - that's almost too loud for me.

That said, people seem to love tube amps and Samsung was making some "hybrid" amps for home theater stuff I played with in a store. So there are reasons / a "market" for this stuff. Not to mention, a lot of modern music uses effects like actually distorting guitars or straight up synthesizes beats that sound like a 15 inch subwoofer bottoming out so "distorted sound" has a place in our lives even at the level of recordings.   

As for the ODAC rev B, I recommend that over the ODAC rev A (the first version). Rev A sounds fantastic but as I learned from JDS are ultimately not as reliable as they could have been - my original one failed after a year or two but John hooked me up with repairs and eventually a replacement, which was beyond fair (I will definitely buy from JDS again). They tend to start crackling / having channel dropouts at some point. The OL DAC is a different product and uses a different (and awesome) DAC so I'd have to hear both to know which I really liked more. The nice thing about the ODAC is that it is setup to run straight off a computer USB like a little sound card and uses the 3.5mm jack which is ubiquitous. 

I love the integrated O2/ODAC but after experiencing problems with my ODAC, I am glad I went with separate units. Its nice to have the flexibility of mixing/matching separates, and when something blows up, its easier to trouble-shoot. I also like switching around from my Onkyo to iPad to O2 and so on to see if anything changes.


----------



## raoultrifan

We should only hear the original sound produced by the studio, not artefacts/harmonics introduced by our audio equipment. This is why Benchmark was able to lower the 2nd and 3rd harmonics under -120dB, because they are looking for the pure original sound: 
	

	
	
		
		

		
			





Source: https://hometheaterhifi.com/reviews...ac3-dx-recording-mastering-studio-dac-review/


----------



## MrMateoHead

That is a nice flat line. 

When you read the reviews of "high end" (e.g. ridiculously expensive amps), the distortion is often not the same across frequencies. Notably, the midrange-treble areas may be the area where you see rising distortion at power (though, typically, max power or high power so your ears would already be bleeding out). I've sometimes wondered if that is why some amps sound a little "hard". Just because it looks clean at 1K doesn't mean it is at all drive levels. Then again I tend to think that I reach the limits of driver distortion before I ever reach the limits of amps / preamps.

Note, I am really more of an objectivist / enthusiast. Just sayin'.


----------



## damart81

Plus on the combo as well


----------



## Oscar-HiFi

My personal Objective stack (OL DAC + O2 Desktop version) doing it's thing in the office today. Headphone demo and we have run out of O2 + ODAC combos so I brought my stack in from home.


----------



## overhaze

On advice I'm going to copy and paste a post I made elsewhere on the forum. Looking for advice on whether I have a ground loop. Also I accidentally used DirectSound for the direct connection test but I re-tested it with MME and the results are identical.



Hello

I'm looking to for help interpreting some RMAA results from an odac+O2 combo connected to one of my computers. I can't judge whether I am looking at an actual ground loop between my computer and the odac or one between the odac and my PCs line-in. Some large screenshots incoming. 

This is what I get with a direct connection to my pc
	

	
	
		
		

		
			





And this is what I get with a hifimediy USB ground isolator






Also since I had one lying around here is what a direct USB connection to the pc looks like using a Behringer HD400 Hum destroyer instead of a standard audio cable






And here is the mess I get if I combine the Hd400 and the USB isolator


----------



## raoultrifan

Why don't you power the O2 from internal batteries? There will be no ground loop at all.

Also, O2 is powered from a transformer, so it's already isolated from mains, which is a good thing. However, try using a laptop...see if it measures better.

Have you tried listening with sensitive cans if there's an audible noise coming from O2 while connected to ODAC? Of course...no music playing.


----------



## overhaze

raoultrifan said:


> Why don't you power the O2 from internal batteries? There will be no ground loop at all.
> 
> Also, O2 is powered from a transformer, so it's already isolated from mains, which is a good thing. However, try using a laptop...see if it measures better.
> 
> Have you tried listening with sensitive cans if there's an audible noise coming from O2 while connected to ODAC? Of course...no music playing.



Its a combo unit so battery power isn't an option. I would say the most sensitive headphones I own are my Nighthawks, they are incredibly easy to drive. No hiss. I suppose I could dig out the IEMs that came with my phone.


----------



## raoultrifan

Sometimes RMAA tests are not conclusive, the 50/60Hz could get induced into the RCA cables with no reason and might compromise the results. Also, there are many other reasons that RMAA might be not the best way to measure the SNR or dynamics.

I would say that if no noise could be heard you should be fine with the O2/ODAC combo.


----------



## overhaze

Question about the hifimediy isolator and the odac. Is the 200mA its putting out enough to run the odac without audio degradation and is the 45 nanoseconds of added jitter within the range the odac can compensate for?


----------



## adydula

I measured the current draw years ago and it was less than 50 ma.

Alex


----------



## wariwaro (Oct 25, 2018)

Hi, I was searching a power supply for the O2, and I've found a relatively cheap adapter here in my country (I'm from Spain and the adapter costs less than 10€), it's an european AC adapter, it has an output of 15V 400mA AC, 6VA... but there is something about this adapter that makes me wonder if it's suitable;
In the adapter, there is a sticker that has the symbol of: Safety isolating transformer for toys. (It has the form kinda of a train or a car).

Could this adapter work for the O2? Or maybe should I just go with one of the well known adapters for O2 without risks?

Can you help me please guys?

Ty!


----------



## raoultrifan

http://www.jdslabs.com/O2_poweradapters.php

Some pictures might be more helpful, but 15VAC/400mA sound OK.

The thing with the toys protection looks like advertising to me. After all such an AC/AC transformer will provide isolation from the  230V mains.


----------



## wariwaro

Oh, thank you, I'll upload an image of the power supply then!


----------



## raoultrifan

Looks fine to me: http://www.spelektroniikka.fi/kuvat/A20920G.pdf. Hope the plug will fit fine too.


----------



## grig

Boys is out there any real alternative to the O2 budget friendly and on the portable side more or less like the O2 ? In case no anyone than can help to find and buy all the components to build an O2 ?


----------



## WilliamLeonhart

grig said:


> Boys is out there any real alternative to the O2 budget friendly and on the portable side more or less like the O2 ? In case no anyone than can help to find and buy all the components to build an O2 ?


Closest I can think of is the JDS C5D. If you want to build yourself a (somewhat) portable O2+ODAC (it's possible), you can start with buying the O2 and ODAC boards from JDS too


----------



## grig

WilliamLeonhart said:


> Closest I can think of is the JDS C5D. If you want to build yourself a (somewhat) portable O2+ODAC (it's possible), you can start with buying the O2 and ODAC boards from JDS too


jds is not exactly budget friendly, not to mention that i have to add import fees and shipping cost all the way to australia. when i was counting to source all the parts from third parties and save a lot by doing so...


----------



## MrMateoHead

grig said:


> jds is not exactly budget friendly, not to mention that i have to add import fees and shipping cost all the way to australia. when i was counting to source all the parts from third parties and save a lot by doing so...



How Much Power do you need? 

There are products from Fiio that may also work just fine and they are not that costly. IF you can go without portability, there are good options that are affordable. The Schiit Fulla is about $100, AMP+DAC, for example. Not SUPER powerful, but more than enough for "normal" headphones. 

What headphones are you using? Depending on their sensitivity / impedance etc. you may be better off using a good smartphone/computer on the run, and add a decent desktop setup at home. After all, the outside world can have a really poor signal to noise ratio.


----------



## grig

MrMateoHead said:


> How Much Power do you need?
> 
> There are products from Fiio that may also work just fine and they are not that costly. IF you can go without portability, there are good options that are affordable. The Schiit Fulla is about $100, AMP+DAC, for example. Not SUPER powerful, but more than enough for "normal" headphones.
> 
> What headphones are you using? Depending on their sensitivity / impedance etc. you may be better off using a good smartphone/computer on the run, and add a decent desktop setup at home. After all, the outside world can have a really poor signal to noise ratio.


My dac at the moment is FiiO x5 III Gen, but i will add soon an SMSL Su-8 or a Topping D50. The headphones that i use most are the DT 1990 Pro, in general i need at least the power of an O2 or more just keep things more future proof. The important thing is a good amp that makes the music to shine sounding as best as possible. Now the O2 is very good amp i use to own the little own.... But perhaps out there in the china market i can find something as good but cheap, perhaps an Smsl SAP 2 could do the trick...?!


----------



## raoultrifan

You could get only the PCB from overseas, then the BOM for O2 can be ordered later from a local dealer (Digikey, Mouser, Arrow etc.); latest BOM is available on developer's website, but also on AGDR's website as well.


----------



## raoultrifan

grig said:


> My dac at the moment is FiiO x5 III Gen, but i will add soon an SMSL Su-8 or a Topping D50. The headphones that i use most are the DT 1990 Pro, in general i need at least the power of an O2 or more just keep things more future proof. The important thing is a good amp that makes the music to shine sounding as best as possible. Now the O2 is very good amp i use to own the little own.... But perhaps out there in the china market i can find something as good but cheap, perhaps an Smsl SAP 2 could do the trick...?!


I would vote for Topping DX7s combo DAC/headamp, as it measures about perfect. If not, get the D50 and an external headamp.


----------



## grig

raoultrifan said:


> You could get only the PCB from overseas, then the BOM for O2 can be ordered later from a local dealer (Digikey, Mouser, Arrow etc.); latest BOM is available on developer's website, but also on AGDR's website as well.


i think i can get the pcb on ebay, quick and easy


----------



## Martijn W

I purchased this version as an occasion.

Very VERY good design. This thing sounds flawless to me.


----------



## raoultrifan

From Stephan I was also purchased my O2 and ODAC too, great service indeed.


----------



## overhaze

Would this be a suitable replacement power supply for the O2?

https://www.amazon.co.uk/gp/product/B00472TO6S/ref=ox_sc_saved_title_10?smid=AUMXTTCB9ZXTY&psc=1


----------



## adydula (Jan 12, 2019)

No....the 02 calls for 14 - 20 VAC supply.

JDS Labs sells a 15vac 500mw Eurpoean adapter for $15.99 I believe.


----------



## overhaze

adydula said:


> No....the 02 calls for 14 - 20 VAC supply.


Darn it. Finding one is proving quite difficult.


----------



## adydula

https://mayflowerelectronics.com/220-240v-power-supply-for-objective2/


----------



## overhaze

Well thats handy! Thanks!


----------



## overhaze

Does that ASIO driver still work? I installed it and it isn't detecting the odac.


----------



## JakeJack_2008

My 7-year old ODAC is  *as dead as a door-nail*
as was Old Marley  in  'A Christmas Carol'.

PS.1
What is _life expectancy _of the ODAC (or the O2 amp)?


P.S. 2
I have the O2 and ODAC as two separate units from JDS Labs.
Everything is quiet, no hiss, buzz, or _any kind_ of sound.
Therefore,  I suspect that  my  7-year old ODAC is *as dead as a door-nail*
and _not_ the O2 amp run on baterries or plugged into an AC outlet.

What shall I do? How to check it? Should I send  just my ODAC back to JDS Labs?


----------



## raoultrifan

Sorry to hear that.

First, you need to identify which device is broken, so try ODAC in a different amplifier.
Also, get an audio cable from your computer soundcard to your O2 and test this one as well.

If ODAC is completely dead, then you could probably double check the USB and audio plugs for intermittent connectivity (cold joints or some pins broken); use a magnifier glass too.

If O2 is dead, you might also try searching for cold joints or broken pins on the both input and output plugs, but you might also swap the final opamps (for a simple test only, you could use LME49720 if you can't find NJM4556).

Good luck!


----------



## JakeJack_2008 (Mar 10, 2020)

raoultrifan said:


> Sorry to hear that.
> 
> First, you need to identify which device is broken, so try ODAC in a different amplifier.
> Also, get an audio cable from your computer soundcard to your O2 and test this one as well.
> ...



Thanx.
I will follow your suggestions.
Incidentally I've found this:

here
*iPhone Not Charging? Clean Your Lightning Port*

and

*What to Do When Your iPhone or iPad Isn’t Charging Properly
( … Check Your Charging Block, Inspect Your Cable)*


----------



## MrMateoHead

JakeJack_2008 said:


> My 7-year old ODAC is  *as dead as a door-nail*
> as was Old Marley  in  'A Christmas Carol'.
> 
> PS.1
> ...



My O2 is going strong after, I don't know, 5 years or something? The original batteries are shot but it runs off the adapter just fine. Solid-state electronics usually are rock solid when and if they don't blow up early in their lives. I have AV receivers and other audio gadgets that are over a decade old at this point that still work great. 

I did lose the ODAC however, and am on my second one (JDS was awesome about trying to diagnose/fix it, and ultimately gave me a new one). It lasted several years but gradually I began to hear some "static" and eventually it just blew a channel out. 

John at JDS seems to know that the original ODAC might have some / or a design flaw that may shorten its life.

IF the ODAC is dead (and I wouldn't be surprised, given my experience), I'd heartily recommend a purchase from JDS Labs again - the service has been top notch. BUT I would look to get an ODAC Revision B or one of their other DAC offerings. I'm sure they would sound awesome. They have some new affordable amps as well that look very interesting and spec great.


----------



## jdowne04

Do you guys think buying a Modi 3 and Magni Heresy would be a worthy upgrade from the Objective 2+Odac Rev b? I would be using these with mostly AKG cans such as the K712 Pro and K7XX


----------



## raoultrifan (Mar 30, 2020)

Modi 3 and Heresy are newer and both measure very well, especially the Heresy that also has a bigger output power.
However, for the AKG headphones you are using I don't think in an A/B test, conducted correctly, you will hear any differences.


----------



## matti621

The O2 is the worst sounding amp I listened to. Is that your impression as well? Which amps did you contrast it with and liked better at the same price class? I had a $90 Chinese HA5000 clone which sounded a lot better.


----------



## raoultrifan

matti621 said:


> The O2 is the worst sounding amp I listened to.


Either your O2 is broken, either you never read real reviews and measurements that prove that this headamp is a very good one. It has a SINAD higher than 100dB, so it's completely transparent and it works with a huge amount of headphones. Check diyaudio forum for more technical details, but also for the measurements and thoughts on neurochrome webpage.

P.S.: A bad amp is the one who introduces unwanted harmonics and SINAD is below 90dB or it has treble or bass roll-off etc.


----------



## descloud

matti621 said:


> The O2 is the worst sounding amp I listened to. Is that your impression as well? Which amps did you contrast it with and liked better at the same price class? I had a $90 Chinese HA5000 clone which sounded a lot better.


I'd agree with raoultrifan's comments.   I see one of the possible scenarios with what you're experiencing:

Your O2 is defective, introducing unwanted distortion, channel imbalance, or artifacts in the record you're listening to
Your source or DAC is not transparent and does not output the necessary voltage to reach the volume you're adjusting with the O2 amp - introducing distortion to the songs you're listening to
You don't like how the HD600 reveals certain parts of a recording since the O2 amp is transparent - causing you to blame the amp for being transparent about your source
You're sensitive to certain frequencies that the HD600's frequency response generates which the O2 amp (a transparent amp) reveals - causing you to describe how the amp sounds the "worst"
So either you have a defective unit, your DAC/source is the weak link of being non-transparent and terrible performing objectively, or you just don't like a transparent amplifier output.


----------



## matti621 (Jun 20, 2020)

descloud said:


> I'd agree with raoultrifan's comments.   I see one of the possible scenarios with what you're experiencing:
> 
> Your O2 is defective, introducing unwanted distortion, channel imbalance, or artifacts in the record you're listening to
> Your source or DAC is not transparent and does not output the necessary voltage to reach the volume you're adjusting with the O2 amp - introducing distortion to the songs you're listening to
> ...


If the O2 was defective or the cans had a peak I'd be able to tell from listening to test recordings and AB'ing.
I'd agree with you the O2 transparency was at fault if I didn't own a very transparent very analytical set - Dac1->T1.
It also wouldn't make sense the BHC sounded so much better despite measuring very well as well.


----------



## adydula

Sounding better is a very subjective topic....


----------



## 439598

matti621 said:


> The O2 is the worst sounding amp I listened to. Is that your impression as well? Which amps did you contrast it with and liked better at the same price class? I had a $90 Chinese HA5000 clone which sounded a lot better.


yes, I have not found a better example of ''measures good, sounds bad'' than O2 Amp.
With modifications, like bypassing NJM2068 gain stage completely and replacing NJM4556 with OPA1622, the sound can be improved somewhat, and it should measure better, not worse, if done right. Unfortunately the power supply is also to blame for the poor sound quality... you'd basically be scrapping the entire original design to get something decent sounding.
If that HA5000 clone is really class A then any Class AB buffer like these op amps are not gonna sound great in comparison.

It's ironic that the *Objective*2 of all amps is the one that causes most people to realise measurements (at least the current methodology) cant tell full picture of the way something will sound.
And it's confusing that there are some many people who still believe its transparent, If you listen to at least one more amp that measures as well as or better than the O2 it should be obvious there is an audible difference in measurably transparent gear.


----------



## adydula

wow.....really?


----------



## matti621 (Jun 20, 2020)

Acke said:


> yes, I have not found a better example of ''measures good, sounds bad'' than O2 Amp.
> With modifications, like bypassing NJM2068 gain stage completely and replacing NJM4556 with OPA1622, the sound can be improved somewhat, and it should measure better, not worse, if done right. Unfortunately the power supply is also to blame for the poor sound quality... you'd basically be scrapping the entire original design to get something decent sounding.
> If that HA5000 clone is really class A then any Class AB buffer like these op amps are not gonna sound great in comparison.




You put it a lot better than I ever could, I wish there was a way to give you 10 'likes' or at least buy you a beer.



> It's ironic that the *Objective*2 of all amps is the one that causes most people to realise measurements (at least the current methodology) cant tell full picture of the way something will sound.
> And it's confusing that there are some many people who still believe its transparent, If you listen to at least one more amp that measures as well as or better than the O2 it should be obvious there is an audible difference in measurably transparent gear.


I sometimes think nawguy or whatever was the creator's nickname started that project to double-irony troll the hi-fi community.

That said, which amp costing the same or less would you pick instead?


----------



## adydula (Jun 20, 2020)

The idea was to NOT sound at all....

..and he did this to troll the retail overpriced audio manufacturers..

...your free to buy anyones stuff.

but the whole excercise was to produce a low cost, decent amp.

And thousands of folks bough, built and think differently...

All opinions and experiences are valid.


----------



## Relaxasaurus

I don't know guys I'm testing all of these and for the money the O2 is top notch.






For the naysayers what other amps at this price point where you thinking?


----------



## matti621

Relaxasaurus said:


> For the naysayers what other amps at this price point where you thinking?


Chinese brands. Some use the same Texas Instruments chips.


----------



## adydula (Jun 20, 2020)

I have 20 head amps here...and doing blind testing....many folks have a real hard time identifying amps from one another...

When a person picks out the O2, and not the $600 amp they sometimes dont like this!!!


----------



## adydula

Lots of chi-fi stuff uses el crapo parts....


----------



## matti621

adydula said:


> Lots of chi-fi stuff uses el crapo parts....


And lots of gringo-fi charges X10 for nothing but the brand


----------



## 439598

adydula said:


> Lots of chi-fi stuff uses el crapo parts....


thats just a stereotype, even some ridiculously cheap no-name chinese kits I bought from ebay had genuine, high quality parts. Ive found cheaper parts in my headnhifi O2.
Any of the proper chinese brands (Topping, SMSL etc.) use top quality parts.
Just cos you pay more doesnt mean you get better quality.

@matti621 about good amps, cant really say as the best amps I've used are diy and havent bothered with commercial ones again, its so much cheaper to DIY and you have full control over parts etc. I was considering the magni 3 at one point,  design wise it looks like a really good amp for the price.

Do you have a link to the HA5000 kit u bought?


----------



## matti621

Acke said:


> cant really say as the best amps I've used are diy and havent bothered with commercial ones again, its so much cheaper to DIY and you have full control over parts etc


So which SS kit amp would you say sounds as good as the BHC?



Acke said:


> Do you have a link to the HA5000 kit u bought?


It wasn't a kit, it was a ready made clone for $90 including shipping...


----------



## 439598

matti621 said:


> So which SS kit amp would you say sounds as good as the BHC?
> 
> 
> It wasn't a kit, it was a ready made clone for $90 including shipping...


what is a BHC? 
I havent built anything from a complete kit, and most of it was only based loosely on different schematics. There was 'DCA headphone amp' you could buy the PCB or pre-built a while back, but there is a very good chance the HA5000 is a better and less expensive amp than that.


----------



## matti621

Acke said:


> what is a BHC?


BHC = Bottlehead Crack (+Speedball). The kit is $430. Sounds very tubish and colored but it also has a sound like nothing else I heard.


----------



## adydula

Well I doubt you could tell if the parts were indeed genuine as many are duped!

The Magni 3+ is an excellent amp as well as the IC Magni Hersey...and it does have GOOD parts...and excellent service and support. And you dont have to wonder about cheap-fi anything....all for a paltry $99....beat that ch-fi man.

Also its funny to me that a BHC would sound "tubush"!! It is a tube amp?

:>)


----------



## 439598 (Jun 20, 2020)

matti621 said:


> BHC = Bottlehead Crack (+Speedball). The kit is $430. Sounds very tubish and colored but it also has a sound like nothing else I heard.


ah ok, I have only tried a cathode follower tube amp circuit, similar to non-sb crack, but i wasnt a fan, too much distortion.
I have heard very good things about this DHT tube amp, buts its very advanced and expensive project


----------



## 439598

Unless the parts are such good fakes that they are completely visually identical to the guarateed genuine ones Ive gotten from mouser then I dont think so.
I have gotten fake parts many times, usually capacitors, you can spot them a mile away.


----------



## adydula

Well a mile away is quite a distance!!

:>)


----------



## 439598

adydula said:


> Well a mile away is quite a distance!!
> 
> :>)


yes i use binoculars


----------



## descloud

matti621 said:


> If the O2 was defective or the cans had a peak I'd be able to tell from listening to test recordings and AB'ing.
> I'd agree with you the O2 transparency was at fault if I didn't own a very transparent very analytical set - Dac1->T1.


I'm not sure about that.  I haven't seen measurements of the Benchmark DAC1 headphone output, but the DAC doesn't appear to be as transparent as excellently performing DACs nowadays from these measurements: https://www.audiosciencereview.com/...-measurements-of-benchmark-dac1-usb-dac.3708/

So I don't completely agree with your statement that it's a very transparent set with that comparison.  You haven't mentioned your source to your O2 amp either so there's other variables that haven't been taken into account.

Also, is the T1 in the chain you described the Beyerdynamic T1 headphones?



matti621 said:


> It also wouldn't make sense the BHC sounded so much better despite measuring very well as well.



What you find as "sounded better" and what I find "sounded better" is personal preference.  So there's nothing to "make sense" from there, since you preferred the tube sound from the BHC than the solid state transparent amp to your HD600.  And there's nothing wrong with that, but there's no logic to preference.

I also can't tell how well the BHC measures, given that it introduces second or third harmonic distortion to the output.  I haven't been able to find measurements for it.

But you find that better sounding, so its great that it works out for you!


----------



## rvalero

I have this setup

PC -  usb ODAC RCA - Grado RA1 (9v batteries) and it sounds far better than my soundcard and give grados headphones a better sound im very happy with it

Greetings


----------



## adydula

The BHC measures not that well at all.

BUT

Its been around for years, thousands of them out here, I have one as well...

For high impedance headphones like the Senn's HD600 and HD800, one would be hard pressed to find a better pairing regardless of any measurment concerns..

Numbers are not everything..especially for tube addicts...


----------



## castleofargh

The O2 isn't a youngster anymore, but I'd just point out that the user needs to pay attention to the DAC's voltage and possibly the amp's gain setting setting. Within the group of people who didn't just dislike the O2 but stated over the years that it sounded horrible, quite few were sending well above 2V into the amp while on high gain, and distorting the hell out of the signal. In case of doubt, just lower the digital level sent to the DAC a good deal, adjust the amp and check if the sound is still "bad".

The O2 served me very well for years. Both for testing and listening. I only put it aside a few months ago because since I got the Realizer A16 I just used the headphone out in it and really stopped caring about audio gears in general, but I keep the Odac/O2 around for consistency in my cheapo IEM measurements. 

beyond that, if made properly and used properly it's still not what the user likes(for whatever reason, audio or not), then there's an entire world of other and often younger amps out there.


----------



## gargani

castleofargh said:


> The O2 isn't a youngster anymore, but I'd just point out that the user needs to pay attention to the DAC's voltage and possibly the amp's gain setting setting. Within the group of people who didn't just dislike the O2 but stated over the years that it sounded horrible, quite few were sending well above 2V into the amp while on high gain, and distorting the hell out of the signal. In case of doubt, just lower the digital level sent to the DAC a good deal, adjust the amp and check if the sound is still "bad".
> 
> The O2 served me very well for years. Both for testing and listening. I only put it aside a few months ago because since I got the Realizer A16 I just used the headphone out in it and really stopped caring about audio gears in general, but I keep the Odac/O2 around for consistency in my cheapo IEM measurements.
> 
> beyond that, if made properly and used properly it's still not what the user likes(for whatever reason, audio or not), then there's an entire world of other and often younger amps out there.


I have a magni 3 and an o2. I've compared them back to back. If there is a difference in sound, It's subtle enough that I can't hear the difference.


----------



## adydula

gargani said:


> I have a magni 3 and an o2. I've compared them back to back. If there is a difference in sound, It's subtle enough that I can't hear the difference.


There ya go...my point exactly!

I have torn apart lots of amps, including $1K + and thoes $100-$500 Chi-FI amps....and let me tell you besides the worry about crappy parts and comonents, which there are many. The overall quality
inside if often very, very apparent. From poor soldering, crappy wiring, safety grounding issues etc...

And when your chi-fi amp goes south its a several week and month back and forth from over there to over here...

When there are so many really great amps and dacs made in the USA its a no bariner for me....

A.


----------



## 439598

adydula said:


> There ya go...my point exactly!
> 
> I have torn apart lots of amps, including $1K + and thoes $100-$500 Chi-FI amps....and let me tell you besides the worry about crappy parts and comonents, which there are many. The overall quality
> inside if often very, very apparent. From poor soldering, crappy wiring, safety grounding issues etc...
> ...



It sounds like you opened a LOT of ''chi-fi'' amps. How about you name 3 of them, so we know what to look out for??

AudioGD use shady capacitors. This british brand called Nover that you cant seem to buy anymore and have basically no info (if it ever existed to begin with), either they are some counterfeits stealing the brand or these are old stock.
Electrolytic capacitors have a limited lifespan, they will still work after many decades but their performance will be severly degraded and the older they get the more likely they are to fail.
If they are counterfeits that doesnt necessarily mean they are bad capacitors, could just be a fancy wrapping on standard cheap cap, anyway AGD is the only main chinese brand I would agree about quality concerns, their customer service system is worryingly primitive and I think their stuff is probably overhyped with how polarised people are about them.


Fiio, Topping, SMSL, Monoprice(?), Gustard - all build top quality products, as good any american or european brands. Which sound the best is a different discussion entirely.


----------



## adydula

Well,

Counterfiets IMO are illegal and just wrong when people go out of there way to steal someones else's work or prodcut. Period.
Thats "my" feeling on that one.

Ususally the electrolytic knock offs, have inferior dielectric material and chemicals, doping that dont last very long compared to the "real" thing...they often short or partially short causing all kinds of issues. Seveal major pc vendors had these cap issues for years....but the chi-fi guys often use these less than stellar, lack of any real QC on the parts blindly....and couple that with poor soldering and crappy point to point wiring makes me cringe...

BUT hey its your money..take a look at your Ch-fi stuff and if it meets your standards, great , enjoy the gear...just beware.

Not all ch-fi stuff is bad, but lots of the el cheopp ebay stuff, low cost stuff is not to be trusted....again thats my experience and opinion. 

In the end it your choice, and buy what you want. I just buy stuff from honest vendors that have a good track record. On Ebay you need to be careful what you buy....

Alex


----------



## 439598 (Jun 22, 2020)

adydula said:


> Well,
> 
> Counterfiets IMO are illegal and just wrong when people go out of there way to steal someones else's work or prodcut. Period.
> Thats "my" feeling on that one.
> ...


If we are just talking about the unbranded chinese ebay stuff then I agree, its 50/50 on the quality of what you get.
They are good for DIY, where you can buy them for next to nothing and improve them with modding where needed without spending much.

Ali express is miles better than ebay for these sort of things, their refund policies and item specific feedback kind of the force the sellers not to sell junk (in fact there is a ton of really cool stuff on there you wont find in other places)


----------



## adydula

Agree its hit or miss, I just dont like buying crap from overseas and having to muck with it when there is so much other good stuff to play with....DIY is fun and understand the aspect of that, I have a dozen DIY projects here and most are done with parts from Digikey and Mouser etc...Some from diyaudio, some homebrew stuff with my own pcbs..but when a company like Schitt comes out with a $99 high quality amp...well...

I have built several O2 derivitives with a fellow called AGDR over at Diyaudio...O2 booster boards, inverting and non inverting types...lots of fun, all sold now.

The attraction to DIY has always been for me to build an amp thats as good as one costing much more...but with the $99 great stuff out there thats a thing of the past for me.


----------



## matti621

Dano91 said:


> Not really, in fact voltage requirement is depended only on headphone's sensitivity which doesn't necessarily correlates with hp's impedance curve. Look here: http://doctorhead.ru/upload/iblock/efd/fr.png
> At 500 Hz it has higher sensitivity than on 1 kHz despite being higher impedance on 500 Hz.
> 
> In worst case they measured sensitivity of 96 dB/V and at best 109.9 dB/V. Which means that for playing 110 dB you would need 5.01 V in worst case and 1.01 V in best case and in average it's 3.13 V. O2 amp max output is 7.15 V, but exact number depends on used source and gain.
> ...


Thanks for the explanation. Finally someone explains it well.


----------



## schmalgausen

Hi all,

I have noticed that drop combo described as Rear RCA input/output:

- USB and RCA only: DAC is active, and RCA is set as output (amp is unpowered)
- Power brick and RCA only: DAC is bypassed and RCA is set as input for amp (DAC is unpowered)
- Power brick, USB, and RCA: DAC is active, RCA is set as additional input for amp

I wonder if I can use ODAC 1/8" output jack as input with disconnected USB in my DIY O2+ODAC combo? Does it affect sound quality?

Sorry for electronics nub question.


----------



## BenF

schmalgausen said:


> Hi all,
> 
> I have noticed that drop combo described as Rear RCA input/output:
> 
> ...


Sure, you can do this with 3.5mm -> RCA adapter, sound quality will be as great as ODAC + O2 (which I have).


----------



## Starbound

I got an O2/ODAC amp last month and I have been very impressed by it. I use it to drive HD580 and MDR-7506 headphones. The MDR-7506 is very easy to drive, but it seems to also benefit from using it with the Objective2/ODAC, it sounds cleaner and more controlled.

This is am amazing amp, very clear and with no discernible noise!

I just got an old Austria-made K240 Monitor (the 600 ohm model). Will the O2 be enough to drive it? According to the notorious vlogger Zeos it is almost as hard to drive as an HE-6, though I take Zeos's opinions with a grain of salt (he is very entertaining but sometimes I think he is too sensationalistic).

My O2 has the 2.5x / 6.5x gain and I use it on AC power. I have a TRIAD 1000mAh, which is recommended for cans with high power demands.

What is the most power-hungry headphones an Objective 2 amp can drive with this power supply, in your opinion?


----------



## gargani

Starbound said:


> I got an O2/ODAC amp last month and I have been very impressed by it. I use it to drive HD580 and MDR-7506 headphones. The MDR-7506 is very easy to drive, but it seems to also benefit from using it with the Objective2/ODAC, it sounds cleaner and more controlled.
> 
> This is am amazing amp, very clear and with no discernible noise!
> 
> ...


My Objective 2 can power my 600 Ohm Beyer dt990 pemium headphones. With low gain I set it at 3 o'clock. With high gain I set it at 12 o'clock.

I owned the Austrian-made k240m for years before they finally gave up the ghost. I used them with my Yamaha receiver, at the time.


----------



## Starbound

gargani said:


> My Objective 2 can power my 600 Ohm Beyer dt990 pemium headphones. With low gain I set it at 3 o'clock. With high gain I set it at 12 o'clock.
> 
> I owned the Austrian-made k240m for years before they finally gave up the ghost. I used them with my Yamaha receiver, at the time.


Thank you for the reference point. I believe for some reason the old K240 600 ohm cans tend to be harder to drive than more modern headphones at the same impedance.

I also hear a lot of good stuff about the K240M getting paired with old receivers. What music did you use the K240M to listen? I can't wait to get mine and give them a try. They will be the oldest headphones I have ever listened to, and the classic K240 models have a sort of mystique surrounding them.


----------



## Starbound

adydula said:


> There ya go...my point exactly!
> 
> I have torn apart lots of amps, including $1K + and thoes $100-$500 Chi-FI amps....and let me tell you besides the worry about crappy parts and comonents, which there are many. The overall quality
> inside if often very, very apparent. From poor soldering, crappy wiring, safety grounding issues etc...
> ...


Interesting you say this, and although it might be a hasty generalization, I think there must be some truth to it in many cases. Did you hear about the Topping L30 issues?


----------



## gargani (Mar 16, 2021)

Starbound said:


> Thank you for the reference point. I believe for some reason the old K240 600 ohm cans tend to be harder to drive than more modern headphones at the same impedance.
> 
> I also hear a lot of good stuff about the K240M getting paired with old receivers. What music did you use the K240M to listen? I can't wait to get mine and give them a try. They will be the oldest headphones I have ever listened to, and the classic K240 models have a sort of mystique surrounding them.


It was about 20 years ago that they gave up the ghost; so I have no idea how they would stand up to headphones today.
I listened to what is now classic rock and early prog rock. Also I never owned a headphone amp at the time.
It would be interesting to know how you make out with the objective 02 and how you think about them as compared to the other headphones you mentioned.


----------



## raoultrifan (Mar 17, 2021)

Starbound said:


> I believe for some reason the old K240 600 ohm cans tend to be harder to drive than more modern headphones at the same impedance.


Everything is related to basic math here: AKG K240 has a sensitivity of 104 dB SPL/V @ 1 kHz and according to Digizoid we have this:

�

Listening LoudnessVoltage NeededCurrent NeededPower NeededSafe85 dB SPL0.11 Vrms0.18 mA0.02 mWModerate100 dB SPL0.63 Vrms1.05 mA0.66 mWFairly Loud110 dB SPL2 Vrms3.33 mA6.67 mWVery Loud115 dB SPL3.55 Vrms5.92 mA21 mWPainful120 dB SPL6.31 Vrms10.52 mA66.36 mW

Given that O2 has a max. output power of about 7.3 V RMS, I see no problems driving K240.

My DT880 has a lower sensitivity and O2 will not drive them to full power, but I can still get acceptable dB levels to my ears.



Starbound said:


> I also hear a lot of good stuff about the K240M getting paired with old receivers.


Probably folks thinking that a simple resistors added to speakers output will make 600-Ohms headphones sound "better". I would ignore them and use a dedicated headamp with a low output impedance (even if the 1/8-rule will not matter to our 600-Ohms headset, you never know when you'll pair a 16-Ohms headset with that amp).


----------



## Starbound

gargani said:


> It was about 20 years ago that they gave up the ghost; so I have no idea how they would stand up to headphones today.
> I listened to what is now classic rock and early prog rock. Also I never owned a headphone amp at the time.
> It would be interesting to know how you make out with the objective 02 and how you think about them as compared to the other headphones you mentioned.


Yes, I will post about my experience with them. I really look forward to getting them, they will be my first AKG headphone. I remember eons ago when I was a very young child hearing music at some friends of my parents in their stereo on some AKG headphones, I believe an AKG K240 Sextett. Fond memories!


----------



## Starbound

raoultrifan said:


> Everything is related to basic math here: AKG K240 has a sensitivity of 104 dB SPL/V @ 1 kHz and according to Digizoid we have this:
> 
> �
> 
> ...


That Digizoid tool is awesome, thanks. I ran the calculation again at 600 ohms, 92dB/mW (the sensitivity of the vintage K240 Monitor is reported to be between 92 and 95 dB/mW) and the results are still good enough, as I tend to listen to music at a very moderate volume.







I don't plan on getting low impedance headphones and I don't like IEMs, but one of the many things I like about the O2 is its low output impedance.

BTW, doesn't having a source with low output impedance also result in better performance with cans that have very non-linear impedances with respect to frequency?

For whatever reason, I have noticed quite an improvement with my MDR7506 through my O2/ODAC vs through other sources. That could be in part to the ODAC being cleaner, but I think there might be something else going on, maybe the low output impedance in the O2 making the headphone more controlled?


----------



## raoultrifan

Starbound said:


> BTW, doesn't having a source with low output impedance also result in better performance with cans that have very non-linear impedances with respect to frequency?


I don't see a correlation between source's output impedance and headamp's output impedance. However, a low output impedance is usually providing a cleaner signal and with a lower noise & interference (well, at least theoretically and only if using long interconnects).


----------



## Starbound

raoultrifan said:


> I don't see a correlation between source's output impedance and headamp's output impedance. However, a low output impedance is usually providing a cleaner signal and with a lower noise & interference (well, at least theoretically and only if using long interconnects).


I see, thanks. I was under the impression that it was the O2's low output impedance which made it a good match for headphones of very different impedances (and I assume, would also make it a better amp for headphones with very nonlinear impedance vs frequency graphs).


----------



## raoultrifan

Bu "source" I meant ODAC, not O2. Indeed, O2's low output impedance will make it compatible with most headphones, even with 8-Ohms ones.


----------



## Starbound

raoultrifan said:


> Bu "source" I meant ODAC, not O2. Indeed, O2's low output impedance will make it compatible with most headphones, even with 8-Ohms ones.


I see where the misunderstanding was. And just for a final clarification, this is why in theory the O2 would be a more neutral amp with headphones that have impedance/frequency curves which are non linear, is this correct?


----------



## raoultrifan

Usually headphones do not vary much their impedance while playing music, as speakers do, so I don't think neutrality of a headamp is much related to this. Instead, frequency response tested with several impedances across audibile bandwidth will be more helpful here.

More probably, the O2 is neutral because it has a rather low output impedance and is able to drive, with +/- 0.1 dB freq. linearity, all headsets between 16 to 600 Ohms.


----------



## Starbound

raoultrifan said:


> Usually headphones do not vary much their impedance while playing music, as speakers do, so I don't think neutrality of a headamp is much related to this. Instead, frequency response tested with several impedances across audibile bandwidth will be more helpful here.
> 
> More probably, the O2 is neutral because it has a rather low output impedance and is able to drive, with +/- 0.1 dB freq. linearity, all headsets between 16 to 600 Ohms.


I think I was misunderstanding. Every headphone has a non-linear impedance to frequency curve, but some move than others. My understanding was that because of this, if a headphone has an output impedance that is relatively high, it can cause frequencies where a specific headphone has a peak in the impedance/frequency curve to not be represented correctly. But now that I think about it it I see this doesn't make sense, because in these sense higher impedance actually is not a problem. It's more a matter of the amp being able to produce enough power even at frequencies where there is a peak in the impedance.

So yeah, I get what you are saying there, thanks.


----------



## raoultrifan (Mar 26, 2021)

On speakers the impedance across audible bandwidth is usually between 3...5 Ohms to 20...25 Ohms, depending on the frequency, so it's varying with at least 500% between min. and max. On headsets the differences are usually below 10% between min. and max., but of course, it depends from one headphone to another.

Not sure this is related to your question, but low impedance headphones might not have the best bass response under some circumstances, especially when the output impedance of the headamp is higher than 1/8 of headphone's impedance.

In case of O2, people and measurements are calling it neutral due to its ability of driving headphones of different impedances with an almost perfect frequency response. Well, electronic engineering advanced a lot in the past years, so most of today headamps are neutral and trying to not alter the input signal at all. So, best bet when buying a headamp is mostly related to THD+N, output noise (in uV RMS), price and warranty (period and who's paying the shipping back and forth).


----------



## SuperFlyEDSguy (May 16, 2022)

cubusmybro said:


> I am trying to remove the volume knob so I can put a faceplate on my O2. If anyone could help I would greatly appreciate it because I have no idea.  Thanks


I know this is a ridiculously old post, but I actually ran into the very same issue today, literally almost a decade later. I guess that says a lot about the quality of these little amps as they’re still being used in 2022 and even sold band-new. Mine is the Drop variety, BTW. Basically, I wanted to swap the knob out as both of the rubber o-rings have worn-out, cracked, and finally snapped off. This little detail makes it quite a bit more difficult to turn as there is nothing else grippy on such a tiny knob to begin with. I purchased the Black Aluminum Knob by Taiss as sold through JDS Labs for my replacement as it’s (a) far beefier and easier to grasp onto, (b) has no rubber components at all, and (c) actually has a dial marker, something my OEM knob never came with! I am actually curious why Drop’s version of the O2 Amp does not have a dial markers as they make it significantly easier to see exactly where your volume level is currently set at — Hmmm 🤔 — Anyhow, regarding my upgraded knob, not bad for $5 when considering that I was placing an order with JDS anyways!

So, even after completely unscrewing the Allen screw, it still wouldn’t budge and of course I was using a fair amount of force considering an Alps Pot should be able to take a bit of abuse. I was still not overdoing it as those Alps Pots are not invincible, but won’t break even half as easy as the stuff coming out of China in mass these days. Well, after trying a few ideas something finally hit me — to use a couple of small drops of oil — that’s right, any kind of oil designed for lubricating should work, but I used a couple of drops of Wahl Clipper Blade Oil as that’s what I had handy. The Wahl oil also has a dropper top so you won’t make a mess like you would when spraying a can of WD-40, something I would highly advise against when working near electronic components! A very small and targeted amount of such oil should do the trick, and it did!

Here’s the procedure:

Always completely remove the Allen screw from the current knob.


If the knob still cannot be removed from the Pot shaft with a fair amount of force, place 1 to 2 full drops of oil into the screw hole while allowing the oil to penetrate before applying a second drop. You will clearly see the oil level go down, but keep in mind that oil is viscous and may take a couple of minutes to work. Additionally, be careful that no oil works it’s way too far back into the O2 Amp itself.


Periodically wiggle the knob as your applying the oil, e.g. wiggle it a bit after the screw hole fills with the first drop, wait a minute and wiggle it again as the oil level is going down, subsequently wait another minute and wiggle again after the first drop has completely penetrated, you get the idea! You may just get lucky and it will easily wiggle at this point off as it did for me, otherwise repeat the procedure with a second drop. _(Note: You could also use the faceplate to help distribute greater pressure a bit more equally in an attempt to remove the knob, but be careful not to apply too much pressure as you could bend the faceplate or worse!)_


If after a couple of drops of oil and several attempts at wiggling off the knob don’t prove successful, simply let it sit for a while as the oil will continue to penetrate. You could consider another drop of oil, but prop the O2 Amp in such a way that the oil will not drip back into the device if you do. I really don’t think it should take this much work for anyone, but I am nevertheless listing the steps that I would take. Whatever you do, I would avoid using heat or direct flame to ‘help’ the oil penetrate! Heat may work great to loosen parts in a mechanical setting, but I would absolutely urge you to avoid this method in an electrical setting! _(BTW, Yes! Soldering does get extremely hot, but such heat is highly targeted, quick to cool, and the proximal components are built for heat at those specific locations, e.g. the leads.)_


Finally, once the old knob is removed, visually inspect the Pot and remove any excess oil from the shaft with isopropyl alcohol wipes. Once the shaft has been thoroughly cleaned of any remaining oil and/or debris, ensure the alcohol has completely dried, and install the replacement knob. Don’t forget to use a new Allen screw when installing the replacement knob.
That’s the procedure, and yes, I didn’t ‘have to’ be so wordy, but I wanted the instructions to be crystal clear. Just to cover my behind, this procedure is to be done at your own risk, and I am not to be held liable for any mistakes, errors, omissions, or the like. Please, only attempt those repairs that you are comfortable with or that you understand may cause additional damage if done incorrectly.

With all that said, it’s time for me to peace out ✌️


----------



## Starbound

SuperFlyEDSguy said:


> I know this is a ridiculously old post, but I actually ran into the very same issue today, literally almost a decade later. I guess that says a lot about the quality of these little amps as they’re still being used in 2022 and even sold band-new. Mine is the Drop variety, BTW. Basically, I wanted to swap the knob out as both of the rubber o-rings have worn-out, cracked, and finally snapped off. This little detail makes it quite a bit more difficult to turn as there is nothing else grippy on such a tiny knob to begin with. I purchased the Black Aluminum Knob by Taiss as sold through JDS Labs for my replacement as it’s (a) far beefier and easier to grasp onto, (b) has no rubber components at all, and (c) actually has a dial marker, something my OEM knob never came with! I am actually curious why Drop’s version of the O2 Amp does not have a dial markers as they make it significantly easier to see exactly where your volume level is currently set at — Hmmm 🤔 — Anyhow, regarding my upgraded knob, not bad for $5 when considering that I was placing an order with JDS anyways!
> 
> So, even after completely unscrewing the Allen screw, it still wouldn’t budge and of course I was using a fair amount of force considering an Alps Pot should be able to take a bit of abuse. I was still not overdoing it as those Alps Pots are not invincible, but won’t break even half as easy as the stuff coming out of China in mass these days. Well, after trying a few ideas something finally hit me — to use a couple of small drops of oil — that’s right, any kind of oil designed for lubricating should work, but I used a couple of drops of Wahl Clipper Blade Oil as that’s what I had handy. The Wahl oil also has a dropper top so you won’t make a mess like you would when spraying a can of WD-40, something I would highly advise against when working near electronic components! A very small and targeted amount of such oil should do the trick, and it did!
> 
> ...


Is there anything WD40 can't do? Last night I wanted to fry some sardines and I had run out of oil. Guess what? WD40 to the rescue.

I used the WD40 to losen the stuck lock of my pantry to get some oil. 

Anyway, talking about removing stuff... I was planning on removing the 9V batteries from my JDS Labs O2, and I was wondering if there is something I should be aware of before I open the unit. Are the batteries hooked with a holder, or are they glued? If so, should I get a hair drier to soften the glue, or should I use WD40 again?


----------



## HeatFan12

After 9 years in storage, I brought her out last night.  Still going strong and spankin' all the headphones I throw at her with clarity and detail.  I still have the different face plates and a volume knob.

Cheers!!!


----------



## garlicky

HeatFan12 said:


> After 9 years in storage, I brought her out last night.  Still going strong and spankin' all the headphones I throw at her with clarity and detail.  I still have the different face plates and a volume knob.
> 
> Cheers!!!


Where did you get the faceplate and the red knobs from? Also what do you use to clean the amp itself? It looks brand new and shiny in the picture.


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## schmalgausen

garlicky said:


> Where did you get the faceplate and the red knobs from? Also what do you use to clean the amp itself? It looks brand new and shiny in the picture.


Head ‘n’ HiFi was selling them years ago.


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## garlicky

schmalgausen said:


> Head ‘n’ HiFi was selling them years ago.


OK thanks


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## HeatFan12

garlicky said:


> Where did you get the faceplate and the red knobs from? Also what do you use to clean the amp itself? It looks brand new and shiny in the picture.



I purchased mine from Mayflower Electronics.  They had all the various accessories.

Thanks!  I clean all my equipment with screen cleaner then store in plastic containers with lids.  Keeps them looking new.


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## garlicky

HeatFan12 said:


> I purchased mine from Mayflower Electronics.  They had all the various accessories.
> 
> Thanks!  I clean all my equipment with screen cleaner then store in plastic containers with lids.  Keeps them looking new.


Thanks for the reply.
 My o2 was from jds labs but I heard mayflower electronics also sold them. Good to know they have all of the accessories.
OK screen cleaner, I'll try that.


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