[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]

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.

 
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]

 
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]

  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 . . .

 
 
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]

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]

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]

  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]

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]

Yes I listen to classical as well.

What specific song and album? I'll buy it and listen for myself.

 

[Xenophon]

   
 
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]

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.
 

 
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]

  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.