# DAC+amp for noise cancelling headphones?



## AlliumPorrum

I was just thinking that since noise cancelling headphones always have more or less active components on the signal path, does any portable dac+amp combination such as Oppo HA-2 actually make much difference from the sound quality point of view? Or does that active NC- part kind of a "hide" all possible sound quality benefits, that non-NC headphones would reveal?
  
 And of course I'm talking about wired ones, not wireless ;=)
  
 All experiences on DAC/amp + NC combinations are more than welcome!


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## Music Alchemist

I owned the QC15 (Bose QuietComfort 15) and experienced some rather unexpected things over the years.
  

The sound changed slightly depending on battery type and charge level.
The sound changed a bit more depending on source components. (DAP, amp, DAC)
The sound improved dramatically when switching from the stock cables to normal headphone cables like the V-MODA Audio Only Cable. This is due to the fact that the stock cables have electronics that interfere with the signal. I had to wrap toilet paper around the connector shell to get the cable to stay put. Also noticed that the right-left channels were switched, due to the active circuitry of the headphones and how the stock cables normally interact with them.
  
 Anyway, there's no real point getting expensive gear for NC 'phones. Only makes sense if you have high-end headphones too. For what it's worth, I have also read about other NC models changing more significantly with different amps and so on.


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## AlliumPorrum

Thanks MA!
  
 I currently have AKG NS490's which are quite good sounding ones IMO, but actually I'm thinking of upgrading for Sennheiser Momentum Wirelesses, which should be pretty much the highest end of NC models. And of course, I would use them wired ;=)


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## Music Alchemist

Just a thought: what do you need the noise cancelling for? I ask because passive noise isolation could be all you need for most situations, and in that case, you could get headphones with better sound quality. If you do need NC, the Bose QC25 is the best for that. It also has active and passive modes, in which case an amp and/or DAC may improve the sound.


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## ClieOS

As you / OP said, active noise cancelling headphone has its own active components, which is fundamentally an amp section of its own. Driving it with another amp is basically just double amping, meaning the power of the first amp will be mostly wasted (as more accurately, the first amp isn't 'driving' the second amp at all), except for making everything louder. A DAC might benefit you, but only in the situation where the DAC itself has better SQ than whatever source you are using previously. Getting a better source will bring just as good a result.


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## AlliumPorrum

music alchemist said:


> Just a thought: what do you need the noise cancelling for? I ask because passive noise isolation could be all you need for most situations, and in that case, you could get headphones with better sound quality. If you do need NC, the Bose QC25 is the best for that. It also has active and passive modes, in which case an amp and/or DAC may improve the sound.


 

 Well I travel quite a lot, and I also like to use NC headphones on a low level while driving a car on a highway. So I do not want to totally isolate myself from the outer world. Actually I can hear outside sounds better with NC on, since static background noise is reduced.
  
 And in my opinion Bose's sound quality is far away from Momentum's, or even quite much cheaper AKG NC490's.


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## AlliumPorrum

clieos said:


> As you / OP said, active noise cancelling headphone has its own active components, which is fundamentally an amp section of its own. Driving it with another amp is basically just double amping, meaning the power of the first amp will be mostly wasted (as more accurately, the first amp isn't 'driving' the second amp at all), except for making everything louder. A DAC might benefit you, but only in the situation where the DAC itself has better SQ than whatever source you are using previously. Getting a better source will bring just as good a result.


 
  
 Well that was exactly what I was thinking of, just wasn't sure if it really is so.
  
 My current source is iPhone 5S which should have a decent DAC, but surely it is not an a level of better portable DAC's.
  
 Just to be sure; have you ClieOS tested any NC headphones with some dac+amp combination?


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## ClieOS

alliumporrum said:


> Well that was exactly what I was thinking of, just wasn't sure if it really is so.
> 
> My current source is iPhone 5S which should have a decent DAC, but surely it is not an a level of better portable DAC's.
> 
> Just to be sure; have you ClieOS tested any NC headphones with some dac+amp combination?


 
  
 Don't really own any decent ANC headphone to speak of, as the only one I have is an ANC earbud that is quite old. Pretty much giving up on ANC since none of them is anywhere near as isolating as my trusty ER4S.


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## AlliumPorrum

But is that NC section actually like "amplifier", or could it be more like "equalizer" without any amplification? I mean, at least AKG and Sennheiser sound pretty much the same both on active and passive modes, and there isn't much difference on the level either. So I *think* that the power that makes the drivers move could actually be coming from the source, not from the headphone's active section itself. And if this is the case, a better amp might do some good for the sound quality. But I really don't know...
  
 Again, real life experiences are highly appreciated!


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## ClieOS

alliumporrum said:


> But is that NC section actually like "amplifier", or could it be more like "equalizer" without any amplification? I mean, at least AKG and Sennheiser sound pretty much the same both on active and passive modes, and there isn't much difference on the level either. So I *think* that the power that makes the drivers move could actually be coming from the source, not from the headphone's active section itself. And if this is the case, a better amp might do some good for the sound quality. But I really don't know...
> 
> Again, real life experiences are highly appreciated!


 
  
 No, it has to be an amp to work, so to speak on a technical standpoint. ANC circuit isn't very hard to build as it is basically an amp with reversed phase and careful volume control (well, maybe a good mic or some FR compensation as well). The mic picks up the external noise and sends it to the amp, then the amp / ANC circuit creates a reversed phase signal, mixes it to the music and sends it to the headphone drivers. The drivers play both the music signal+reverse phase noise together, where the reverse phase noise signal cancels the actual noise that penetrates the headphone housing. The only thing here is to control how loud the reverse phase signal is so that the right amount is reproduced by the driver to cancel the noise totally inside the earcup. Too little and you won't have enough noise cancellation, too much then the reverse phased noise becomes the dominant noise itself. This part however can be done in a lab with a dummy head. That being said, a simple amp circuit can actually be tweaked into an ANC circuit quite easily. The only difficult part is to create the reverse phase signal with the right amount and frequency. A really fancy ANC, like those from Etymotic, uses an MCU to accurately create the desired reverse phase signal, but it still needs an amp to actually drive the driver itself.
  
 Also, any time you put an active circuit between the driver and an amp, the driver only 'see' the last component. This is because active circuit, such an ANC, usually has high input impedance that will turn the source into more or less a 'pure voltage' source, meaning only voltage is delivered to the active circuit, where current isn't. Since there isn't much current sending from the source to the circuit, the source is technically not 'driving' the circuit - and since nothing is driving the circuit per se, the only thing that actually driving the driver is the active circuit itself. It is not a 1 + 1 = 2 relationship.


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## AlliumPorrum

Thanks ClieOS, great explanation!
  
 But let's approach this from other point of view... If I turn the noise cancellation off, it should be so that only the source is driving the headphones. So the quality of the source's dac + amp pretty much defines the sound quality given. And as I said, at least AKG and Sennheiser seem to be sounding pretty much the same regardless if NC is on or off (and also so with different sources), i.e. their NC section is quite transparent from the SQ point of view. So; when you most likely can hear the difference between good and bad source when NC is turned off, and IF the NC section is transparent enough, shouldn't the sound quality improvement be heard on active mode also?
  
 I don't know if my thinking is totally messed up since I'm not an expert at all, I'm just trying to understand things ;=)


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## Music Alchemist

Concerning amps...I don't know the technical stuff. All I know is that some people insist that using an amp with their NC headphones improves the sound, even though the headphones already have a built-in amp. There are many impressions out there. I'm not saying they are true or untrue. In my own experience, amps did change the sound somewhat. But if you are going to bother investing in an amp and such, you might as well get better (normal) headphones.
  


alliumporrum said:


> Well I travel quite a lot, and I also like to use NC headphones on a low level while driving a car on a highway. So I do not want to totally isolate myself from the outer world. Actually I can hear outside sounds better with NC on, since static background noise is reduced.
> 
> And in my opinion Bose's sound quality is far away from Momentum's, or even quite much cheaper AKG NC490's.


 
  
 Which country do you live in? In mine, it's illegal (and dangerous) to drive while wearing headphones.
  
 I only mentioned Bose because the NC is the best. If you want better sound quality, I would avoid NC altogether.


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## AlliumPorrum

> Which country do you live in? In mine, it's illegal (and dangerous) to drive while wearing headphones.
> I only mentioned Bose because the NC is the best. If you want better sound quality, I would avoid NC altogether.


 
  
 I live in Finland, and in here it's not illegal to drive with headphones. In fact it is illegal to use mobile phone while driving without a hands free set, and it does not matter if you use in-ear in one of your ears or over-ear for both ears :=) Anyway, I would never use headphones and listen for music when driving in city, but I don't see any problems when going for hours on a quiet highway.
  
 Yeah, Bose's NC is easily the best one. But as I said, I don't like their sound quality at all. In my opinion Sennheiser Momentum Wirelesses do match any 200-300USD/EUR non-NC headphones on sound quality, so that's not a problem anymore. And of course I will listen for dac/amp before buying it, but I just thought that it would be nice to hear other experiences also before ordering them.


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## Music Alchemist

alliumporrum said:


> In my opinion Sennheiser Momentum Wirelesses do match any 200-300USD/EUR non-NC headphones on sound quality, so that's not a problem anymore. And of course I will listen for dac/amp before buying it, but I just thought that it would be nice to hear other experiences also before ordering them.


 
  
 You want opinions on other headphones? Because most people here with enough experience will tell you that there are many headphones in that price range with better sound quality than the Sennheiser MOMENTUM. A few examples:
  
 beyerdynamic DT 880 Edition 600 Ω
 Focal Spirit Professional
 Sennheiser HD 600
 Sennheiser HD 650
 Yamaha HPH-MT220
  
 Okay, some of those are open, not portable, and out of that price range, but even those can be found for under $300 on the used market.


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## AlliumPorrum

Thanks again MA, but as the title hints, I would like to hear experiences on "DAC+amp for noise cancelling headphones" ;=)


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## Music Alchemist

alliumporrum said:


> Thanks again MA, but as the title hints, I would like to hear experiences on "DAC+amp for noise cancelling headphones" ;=)


 
  
 Is this only to use in your car while driving?
  
 I perceived differences between the FiiO E6, Magni 2 Uber + Modi 2, and iPod classic with the QC15. Can't prove that, though.


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## AlliumPorrum

music alchemist said:


> Is this only to use in your car while driving?
> 
> I perceived differences between the FiiO E6, Magni 2 Uber + Modi 2, and iPod classic with the QC15. Can't prove that, though.


 
  
 Mostly yes, but also in trains and while flying. But nice to hear that you have heard some differences also with NC, gives hope for my tests also :=)


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## Music Alchemist

alliumporrum said:


> Mostly yes, but also in trains and while flying. But nice to hear that you have heard some differences also with NC, gives hope for my tests also :=)


 
  
 They were only very minor differences, and could have just been my imagination. With most headphones, I didn't even hear a difference between the Schiit stack and my laptop. You'll just have to test it out yourself to see whether you hear a difference.


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