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Topic: External DACs/amps vs. onboard audio: when do they matter? (Read 351 times) previous topic - next topic
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External DACs/amps vs. onboard audio: when do they matter?

For some time now, my understanding of digital audio has been something like this: near-perfect DACs are now so cheap that they're in virtually everything, from your motherboard to your smartphone. If you plug your headphones in and you get an adequate volume, and the noise level is low enough to be tolerable to you, then that's that, the sound quality you're getting is transparent and you don't need anything more to "drive" your cans regardless of what anybody might have to say about thousand-dollar external solutions.

Is my understanding incorrect? Beyond the production of adequate volume and the elimination of noise from interference (onboard audio often gets plenty of interference from the motherboard itself, for example), is there any advantage to using an external DAC and amp, assuming the only thing you're interested in is transparent audio through a pair of headphones?

Re: External DACs/amps vs. onboard audio: when do they matter?

Reply #1
For some time now, my understanding of digital audio has been something like this: near-perfect DACs are now so cheap that they're in virtually everything, from your motherboard to your smartphone.

Almost all commercial DACs are far better than almost all commercially available music is mastered for.  But the DAC is just the interface between the digital part of your system and the analog.  The fact that even cheap DACs are absurdly good doesn't mean the analog bits they're hooked into are any good.  Quality varies, particularly when you look at the ability to drive lower impedance loads like headphones.

is there any advantage to using an external DAC and amp, assuming the only thing you're interested in is transparent audio through a pair of headphones?

There is no particular advantage to an external DAC/amp as opposed to any other type, but if you have a motherboard with noisy output, an external DAC is a cheap way to fix that problem, especially if you don't want a whole sound card.  An external amp can less often be useful as well if you have very low impedance or very low sensitivity headphones. 

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

Re: External DACs/amps vs. onboard audio: when do they matter?

Reply #2
So, it seems like one of the primary concerns is output impedance vs. headphone impedance.

As an example, an iPhone output is 5 ohms. Earpods are 40 ohms. This, seemingly, is more than enough of a ratio to eliminate any potential problems with distortion due to output impedance being too high for low-impedance phones.

And in such a case, for high-impedance phones, say the HD800 (my daily drivers—oh, I guess that turns out to be a pun) at 300 ohms, the issue is not potential distortion, but inadequate amplification. I have some hearing problems and I have very little tolerance for loud sounds, so I tend to listen to music at around 70dB, perhaps a touch more if I'm feeling adventurous. Anything more than that hurts my ears.

If I connect my HD800s to my iPhone, I can crank the volume and actually get just over my preferred listening level. Adequate volume. There's a very small amount of noise just because it's an iPhone output, but it's still quite low and certainly inaudible while music is being played—the recordings themselves often have far more noise than that.

In the case of connecting cans like that to a tiny little DAC/amp setup as seen in a device like an iPhone, what other potential concerns are there in terms of sound quality? Is there, say, something about the amp's frequency response that means the signal just isn't going to be as good compared to a dedicated amp with nicer analogue components?

Re: External DACs/amps vs. onboard audio: when do they matter?

Reply #3
In the case of connecting cans like that to a tiny little DAC/amp setup as seen in a device like an iPhone, what other potential concerns are there in terms of sound quality?

If volume, noise floor and output impedance are all more than adequate there likely aren't any other concerns. 

Is there, say, something about the amp's frequency response that means the signal just isn't going to be as good compared to a dedicated amp with nicer analogue components?

Frequency response can be off if the amp's output impedance is too high, but if that isn't the case, then you don't have to worry about frequency response.

 
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