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  • LC3
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Questions about DAC and headphones for hardware upgrade
Hi, I'm new here.  I came here at the recommendation of somebody who said this is a good place for audio info that's free of snake oil.

I'll tell you about my current system and what my goals are, then I'll ask my questions.

I'm using my computer as my audio system.  I haven't gotten into music servers or any of that.  It's basically CDs and CD rips being played through my Sony MDR-V6 headphones.  I'm going to get stereo speakers soon.  When I got into it, I focused on improving the source - I got the highest-quality masterings of the albums I want in my collection.  I've gotten pretty far with that and am ready to get better headphones.  My MDR-V6 sound great, but I'd like to try open headphones.  The Beyerdynamic DT880 seems like a good choice for my price range (around $200).  I'd like a headphone amp to get them sounding their best, which is where my questions start.

1. Output impedance - I've been reading that a headphone amp's output impedance should be no more than 1/8 of the headphone's impedance.  There seems to be some debate about this, or at least suggestions that it's more a rule of thumb depending on other properties of the amp-headphone combination.  I've also read that a higher output impedance offers protection from electrical mishaps that could damage the headphones.  I'd like to know more about this output impedance topic before I get into the habit of considering high output impedance a disqualifier or low output impedance a feature.

2. DACs - Are they all the same at this point, or are some better than others?  In other words, are Burr Browns and Wolfsons better than the DAC in my ALC662 onboard audio?  If so, what makes them better?  One possible answer that caught my attention is jitter, but I don't know the category of DACs, if any, in which jitter is likely to be an issue.

3. EMI - My PC has a very minimal and efficient APU with the stock cooler; the case has one large, slow-turning fan; and I have one SSD and one HDD.  No video card.  I built it with the goal of minimal power and overall efficiency.  Is EMI likely to be an issue in a setup like this?

These questions arose while I was researching the ASUS Xonar STX II as a possible upgrade.  From what I've read so far, the DAC seems to be outstanding (again, if there's any difference at this point).  It also has the EMI shield (if that's an issue).  My biggest questions are about the headphone amp.  Its output impedance is 10Ω.  Is that a problem for my MDR-V6 at 63Ω?  The second question is about how the card handles gain.  I've read that it isn't "proper" gain, but some alternate adjustment.  Is that alternate adjustment inferior, or an equally valid way of solving the problem?

If the STX II isn't the right way to go, I've been thinking of a few other options.  But I'll leave it at the STX II for now, just for the sake of addressing my questions in terms of this first option.

Thanks!  
  • Last Edit: 15 June, 2017, 01:41:42 PM by LC3

  • saratoga
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Re: Questions about DAC and headphones for hardware upgrade
Reply #1
1. Output impedance - I've been reading that a headphone amp's output impedance should be no more than 1/8 of the headphone's impedance.  There seems to be some debate about this, or at least suggestions that it's more a rule of thumb depending on other properties of the amp-headphone combination.  I've also read that a higher output impedance offers protection from electrical mishaps that could damage the headphones.  I'd like to know more about this output impedance topic before I get into the habit of considering high output impedance a disqualifier or low output impedance a feature.

https://en.wikipedia.org/wiki/Headphones#Electrical_characteristics

Lower is better, but super low doesn't make much difference. Higher impedance shouldn't offer any more protection unless the amp is really bad since these devices will all have current limiters anyway.

2. DACs - Are they all the same at this point, or are some better than others?  In other words, are Burr Browns and Wolfsons better than the DAC in my ALC662 onboard audio?

Brand name is meaningless, and the actual model number is only a little better.  You have to look at the performance of the individual product, not the marketing.  There isn't much difference though unless you're looking at very low quality devices.  Cheap has gotten surprisingly good, especially if you're using CDs and therefore limited to 16 bit.  Everything will do that.

If so, what makes them better?

Noise floor mainly, how well the device decouples external noise from its output.  This won't matter much though for 16 bit audio.  Also the internal amp if you plan on using it. 

3. EMI - My PC has a very minimal and efficient APU with the stock cooler; the case has one large, slow-turning fan; and I have one SSD and one HDD.  No video card.  I built it with the goal of minimal power and overall efficiency.  Is EMI likely to be an issue in a setup like this?

EMI is what people blame when they buy bad equipment or wire it wrong and hear a ground loop.  It isn't something you should be worrying about other than when you worry about buying reasonable quality equipment and connecting it correctly.

These questions arose while I was researching the ASUS Xonar STX II as a possible upgrade.  From what I've read so far, the DAC seems to be outstanding (again, if there's any difference at this point).  It also has the EMI shield (if that's an issue).  My biggest questions are about the headphone amp.  Its output impedance is 10Ω.  Is that a problem for my MDR-V6 at 63Ω?  The second question is about how the card handles gain.  I've read that it isn't "proper" gain, but some alternate adjustment.  Is that alternate adjustment inferior, or an equally valid way of solving the problem?

You mean it doesn't have analog volume control?  That might be annoying if you're using high sensitivity headphones and don't plan to use an external amp with volume control. 

  • LC3
  • [*]
Re: Questions about DAC and headphones for hardware upgrade
Reply #2
You mean it doesn't have analog volume control?  That might be annoying if you're using high sensitivity headphones and don't plan to use an external amp with volume control.
It doesn't have analog volume control, but that is a separate issue.  I was asking about the STX II's software adjustment for different levels of headphone impedance.  In the control center software, it lets you choose four settings:

IEM or for 16~32 ohms headsets
Normal Gain or for <64 ohms headsets
High Gain or for 64~300 ohms headsets
Extra High Gain or for 300~600 ohms headsets

Back to the lack of physical volume control, that is a good point.  That alone might tip the decision toward staying with my onboard DAC and getting a desktop headphone amp.  The Schiit Magni 2 Uber seems like a good budget choice, but I'm unsure whether its quality (including longevity) lives up to its marketing.

  • saratoga
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Re: Questions about DAC and headphones for hardware upgrade
Reply #3
You mean it doesn't have analog volume control?  That might be annoying if you're using high sensitivity headphones and don't plan to use an external amp with volume control.

It doesn't have analog volume control, but that is a separate issue.  I was asking about the STX II's software adjustment for different levels of headphone impedance.

One does not adjust gain for impedance (only sensitivity), so I'm not sure what that option would even do. 

Re: Questions about DAC and headphones for hardware upgrade
Reply #4

1. Output impedance - I've been reading that a headphone amp's output impedance should be no more than 1/8 of the headphone's impedance. 

True.

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There seems to be some debate about this, or at least suggestions that it's more a rule of thumb depending on other properties of the amp-headphone combination. 

IMO there is no possible reasonable debate about the requirement that the source impedance of any amplifier be on the order of 8-10 times the load impedance, or even lower.  The issue is frequency response. Most loads have natural variations with frequency, and unless the source impedance is sufficiently low, there will be additional unintentional frequency response variations.

There is no reasonable technical reason for compromising this issue.

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I've also read that a higher output impedance offers protection from electrical mishaps that could damage the headphones.

That's very wrong-headed. There are other ways to protect the load that don't necessarily compromise frequency response.

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2. DACs - Are they all the same at this point, or are some better than others?

From an audibility standpoint, any reasonable DAC can be sonically blameless.

As always, if you want to be a slave of numbers for the sake of numbers, some DACs have better numbers than others.  And, if you mess up the system design and adjustment, you can paint yourself into a corner where all but a premium DAC is too noisy.

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In other words, are Burr Browns and Wolfsons better than the DAC in my ALC662 onboard audio?

Depends which BB's and W's you are talking about.  Not all DACs of a given brand are the same. Not even close.

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If so, what makes them better?

A DAC is well-defined in terms of its frequency response or bandwidth, and dynamic range or noise and distortion.


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One possible answer that caught my attention is jitter, but I don't know the category of DACs, if any, in which jitter is likely to be an issue.

Jitter in digital gear is generally a red herring. Notice that you hear very little about jitter in LPs and analog tape where audible jitter is almost imposible to eliminate, and the obsession with jitter in digital gear, where it almost always several orders of magnitude below audibility.

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3. EMI - My PC has a very minimal and efficient APU with the stock cooler; the case has one large, slow-turning fan; and I have one SSD and one HDD.  No video card.  I built it with the goal of minimal power and overall efficiency.  Is EMI likely to be an issue in a setup like this?

Your PC has a video card or you would be running it blind. The video card's function is either built onto the motherboard or there is a GPU in the same chip case as the CPU.

In terms of the items you mention, there is insufficient information to make a reliable determination of EMI.  I understand that the most likely cause of unmanageable EMI is one big honking video card, that probably cost you megabucks.  But even that may be moot.

Quote
These questions arose while I was researching the ASUS Xonar STX II as a possible upgrade.  From what I've read so far, the DAC seems to be outstanding (again, if there's any difference at this point).  It also has the EMI shield (if that's an issue).  My biggest questions are about the headphone amp.  Its output impedance is 10Ω.  Is that a problem for my MDR-V6 at 63Ω?  The second question is about how the card handles gain.  I've read that it isn't "proper" gain, but some alternate adjustment.  Is that alternate adjustment inferior, or an equally valid way of solving the problem?

10 ohm output impedance strikes me as being excessively HIGH. Might work with the headphones you have today, but what if you upgrade?  The best solution to a headphone jack with too high of a source impedance is an outboard headphone amp with a low source impedance.  These can be had for under $30. FIIO and M-Audio are possible brand names to investigate.
  • Last Edit: 15 June, 2017, 11:14:24 PM by Arnold B. Krueger

  • DVDdoug
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Re: Questions about DAC and headphones for hardware upgrade
Reply #5
Output impedance specs can be tricky.    Often the manufacturer doesn't publish an output impedance spec, and sometimes when they do, they are specifying the minimum headphone impedance, not the impedance of the DAC/headphone amp.

That's also true with power amps...   An amplifier rated at 4 or 8 Ohms will actually have a much lower output impedance... It's just rated to drive 4 or 8 Ohm speakers.     You'll never see an output impedance spec for an amp but sometimes you'll see damping factor.