[wje]

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I'm currently testing the Desktop version of the O2 that I just finish building with a friend and it sound the same as the portable version. The only differences is the taller case and input/output & volume control mounted on the back/front plate.
 
I'm definitely going to look at the upcoming ODA / ODAC combo.  

 

Simon, You're playing with all the fun gear.  I still need to order a black knob from you too.
 
 
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Well I was driving my HE-5LEs which need about 9-10'O clock-ish amplification. For my Denons I don't go past 9'O clock on the dial.

That's essentially where I play my HE-5LEs, too.  Often, I've thought that I should be opting for a better amp for the HE-5LE headphones.  However, it's not all too often that I use the O2 amp with them, as I mostly use the Sansui Vintage receiver to juice 'em.
 

 

[stv014]

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Thanks again. So even if I am on AC and if I use a higher gain it's going to clip in that case because it's only OK up and till 7 Vrms. So I've got to use it in low gain and AC power to avoid any clipping whilst at home at least.

Yes, the default 6.5x high gain mode would clip a 2.1 Vrms input even from AC power.
 

 

[mikeaj]

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Is this the new design from Voldemort, or is it just the same O2 with different mounting locations for everything?

Most probably the old design with custom mounting locations, since (1) the new design hasn't been released yet and (2) somebody who already has the new design would not be looking at the "upcoming ODA / ODAC combo."
 
 
I'm starting to wonder if the O2 couldn't have had three gain settings:  high, low, and none.  Are there any kind of through-hole six-pole switches with three settings?  You wouldn't even have to connect two of the poles to anything, since an open circuit is how you get no gain.  It wouldn't require any more resistors than there currently are.  The gain settings are a little more important than for some other amps because of the position of the volume control, so greater flexibility would have been nice.  I mean, two settings is enough for me, but it's less convenient for somebody without extra resistors or a soldering iron, or who don't know what's going on.

 

[Digital-Pride]

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Thanks again. So even if I am on AC and if I use a higher gain it's going to clip in that case because it's only OK up and till 7 Vrms. So I've got to use it in low gain and AC power to avoid any clipping whilst at home at least.
 

To put it in even simpler terms, on AC power the O2 can handle sources up to 2.8 Vrms on low gain, 1.8 Vrms on battery power.  High gain is really more for low powered sources like portable players.

 

[Grev]

 
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Most probably the old design with custom mounting locations, since (1) the new design hasn't been released yet and (2) somebody who already has the new design would not be looking at the "upcoming ODA / ODAC combo."
 
 
I'm starting to wonder if the O2 couldn't have had three gain settings:  high, low, and none.  Are there any kind of through-hole six-pole switches with three settings?  You wouldn't even have to connect two of the poles to anything, since an open circuit is how you get no gain.  It wouldn't require any more resistors than there currently are.  The gain settings are a little more important than for some other amps because of the position of the volume control, so greater flexibility would have been nice.  I mean, two settings is enough for me, but it's less convenient for somebody without extra resistors or a soldering iron, or who don't know what's going on.

I got two O2 units from John at JDSLabs, one with 1x/3x gain and the other at the default 2.5x/6.5x gain, the 1x gain is driving all of my low resistance headphones already from my CLAS, LOD(iDevice) and Clip+.

 

[vkvedam]

An update from my side. Tried using the UE attenuator at the input and it didn't work. So I've got to use it on AC if used with my DAC. Or else change the gain to 1x.

 

[Crazy*Carl]

Can anyone compare the O2 to their computers onboard sound?
 
I mean take your headphones, plug them into the computer and do some listening.  Then run the PC -> O2 -> headphones and listen and post a comparison.  Thanks!

 

[Digital-Pride]

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Can anyone compare the O2 to their computers onboard sound?
 
I mean take your headphones, plug them into the computer and do some listening.  Then run the PC -> O2 -> headphones and listen and post a comparison.  Thanks!

My laptop's headphone out ha lowest noise of all the PCs in my house, so I'll do some extended listening tomorrow and report back on my findings.  Unfortunately I won't able to do any blind testing, but I think I can at least get a tangible sense of any real improvement if there is one.

 

[Naim.F.C]

Comparing PC/Mac > headphone with PC/Mac > O2 > Headphone will yield pretty much exactly the same sound quality. Reason for this is because the PC/Mac's motherboard or soundcard already carries out amplification, so all you'd be doing is amplifying an already pre-amplified sound.
 
To get a proper real world account of sound quality differences, what you need to be comparing is the PC/Mac's direct headphone jack with a source that bypasses its own amplifier when connected to an amp such as the O2, for example PC/Mac > Headphones vs iPhone/iPod > LOD > O2 > Headphones. Only then could you guage the difference.
 
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Can anyone compare the O2 to their computers onboard sound?
 
I mean take your headphones, plug them into the computer and do some listening.  Then run the PC -> O2 -> headphones and listen and post a comparison.  Thanks!

 
 

 

[MikeW]

That's not really true, while most soundcards have an op-amp output stage. It's typically very weak, often times less then 2.0v. And very limited ability to drive headphones, especially difficult to drive ones. So yes, you are "Double amping" the amp still can have a large effect on sound output.
 
Plug in some HE6 to your sound card and see what happends

 
this is why some higher end soundcards have a completely separate jack for headphones, as it's typically a more proper amp for them.

 

[Naim.F.C]

Whilst true, I was referring to bog standard in-built motherboard sound cards which I believe is what Carl uses? Naturally better sound cards will have different levels of performance. For example, on my PC I have an Asus Xonar Essence and it sounds a lot better than headphones straight out of my Macbook Pro, but even then, you have to use one of the other outputs in order to bypass it's own amplification otherwise you essentially get a similar sort of sound despite using a different amp connected to it and still providing further amplification.
 
On a side note, my Macbook Pro actually sounds worse than the sound straight out of my iPhone 4S! But for reference, when using my Macbook to one of my other amps and then to my headphones, the sound signature itself is almost exactly the same as direct from the Macbook. It's as if the pre-amplified sonics carry through to the amp. Certainly doesn't sound very good. I quite dislike the sound straight out of the Macbook.
 
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That's not really true, while most soundcards have an op-amp output stage. It's typically very weak, often times less then 2.0v. And very limited ability to drive headphones, especially difficult to drive ones. So yes, you are "Double amping" the amp still can have a large effect on sound output.
 
Plug in some HE6 to your sound card and see what happends

 
this is why some higher end soundcards have a completely separate jack for headphones, as it's typically a more proper amp for them.

 

 

[mikeaj]

It's not just volume.  You can easily improve performance by double amping, particularly if the limiting factor is the amplifier and not the D/A behind it.  Here's a few shots from an RMAA run I did a long while back, using 32 ohm headphones at 1V output.  This isn't the first time I posted some of these.
 
    
IMD SMPTE (7 kHz and 60 Hz test tones), THD (1 kHz test tone), crosstalk
 
White lines are double amped (sound card to O2 to headphones/sound card).  Green is single amped (sound card to headphones/sound card).  Note that the measurements are very much limited by the A/D on the cheap sound card.  Still I imagine both the input and output are better than most onboard sound, since those tend to sit on noisy motherboards, not too far from a lot of I/O and CPU and maybe even GPU VRMs.
 
It's a whole lot easier for an amplifier to drive something like 10 kohms than something like 32 ohms, as you can see above.  

 

[Crazy*Carl]

I have listened to Xonar Essence and it sounded the exact same as onboard.  Only difference was it could get my headphones ridiculously loud instead of just insanely loud.
 
Also, I know from blind testing that amping a HD580 with a powerful headphone amp (10V output) has little or no affect on the sound compared to my PC.  I remain skeptical that the O2 would do any better.  Most people here will dispute that, yet I am the only one to show actual test results.  What does that tell you?  Audio is alot more objective than we make it out to be here, but no one wants to admit that, especially the companies that make all this crap.  Maybe other headphones really do benefit, I don't know.  But I wager to bet that its grossly exaggerated based on what I have read and heard.

 

[mikeaj]

High-impedance headphones like HD 580 are easy loads and should generally do pretty well with anything that has enough volume for it.  I wouldn't be surprised at minimal differences with reasonably competent sources, maybe even differences below audibility.  It's different for lower-impedance headphones, depending.  It's especially true if you have impedance interaction issues and get a significantly different FR because one source has high output impedance.  Aside from that and some other cases, most everybody is probably exaggerating about differences, overemphasizing small details, or just hearing what they want to hear.
 
Personally, I can say that typical 1V sources are clearly not enough for 100 dB SPL / 1V headphones on classical music, so I got something more powerful.  Also there's less noise when using IEMs.  Aside from that, I wouldn't attest to anything more personally, particularly without first doing the comparisons blind.

 

[uelover]

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Did you diy those cables yourself? I am still trying to find a RCA-3.5mm cable. Not sure which to get. There are iChord, QED, Oyaide, etc.