[KeithEmo]

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]

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]

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.)

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]

  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]

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]

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]

  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