[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]

  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]

  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]

  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!

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]

  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!

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]

  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]

  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]

 
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]

   
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]

  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?