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Given poor SINAD of headphones, how big of a difference can an AMP make?

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Headphones have very poor SINAD. Even the best measuring ones have around 0.1% THD+N, which is 60 dB SINAD.

A concrete example. Let's take the Stax SR-009, with ~0.1% THD+N.

https://www.stereophile.com/content...09-sr-007-sr-507-sr-404-ltd-sr-404-and-sr-003

The Stax SRM-311 has 0.005147 THD+N.

https://www.audiosciencereview.com/...-headphone-amplifier-review-comparison.17161/

A difference between 0.1% and 0.105147% (the headphone + amp added together) THD+N is 0.4 dB. Is that an audible difference?

If the amp had 100 dB sinad, the difference would only be 0.1 dB.

In other words, isn't the headphone such a big bottleneck that chasing after 100+ dB SINAD of amplifiers is an overkill?

What is the smallest difference between two dB values that is still audible?
 

MRC01

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... What is the smallest difference between two dB values that is still audible?
Depends on the frequency content of the sound, but under ideal conditions the smallest discernable difference is about 0.2 to 0.5 dB. However, comparing 2 different levels of distortion, both near minimum audible thresholds, is not ideal conditions and will likely require bigger differences to be audible.

This is further complicated by the fact that our sensitivity to distortion is also frequency dependent. So 2 amps with the same SINAD are not necessarily the same, because the frequency spectrum of the distortion & noise may not be the same.

However, when taking SINAD of the amp remember to use the SINAD under actual listening levels. The published SINAD is typically taken at max volume which nobody uses when listening. Most good headphone amps having SINAD above 100 dB, have SINAD roughly in the low to mid 80 dB range at 50 mV.

Note: overall your question is relevant, because of masking. A higher level of noise or distortion can mask a lower level one, to the point that even if the lower level one is audible alone it becomes inaudible or masked in the presence of the louder one. Whether masking happens also depends in part on the frequency content of the noise/distortions being detected.

PS: all that said, if you have highly sensitive headphones, the SINAD limitations of the amp may become audible. In this case you'll be using the lower range of the volume knob, where its SINAD (and channel balance) are worst, and may become audible when listening to music having wide dynamic range. That is, you could hear noise or hiss during the quietest parts.
 
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preload

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Headphones have very poor SINAD. Even the best measuring ones have around 0.1% THD+N, which is 60 dB SINAD.
...
A difference between 0.1% and 0.105147% (the headphone + amp added together) THD+N is 0.4 dB. Is that an audible difference?

Are you asking whether someone could differentiate between -60dB SINAD vs. -59.6dB SINAD? Because I think you have your answer.
 

amirm

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If an amp runs out of power, it will easily create distortion that dwarfs the headphone. So you still need an excellent/powerful amp even if you ignore its SINAD. And while at it, might as well get one with low distortion and noise. And oh, noise can also be audible as the headphone doesn't generate any on its own.
 

RayDunzl

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With headphones, I notice all kinds of varying studio noise levels on TV programming that I'd almost never notice while listening through speakers.

So, I'd say there is some reason to ensure a quiet baseline for reproduction with headphones.
 
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J
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If an amp runs out of power, it will easily create distortion that dwarfs the headphone. So you still need an excellent/powerful amp even if you ignore its SINAD. And while at it, might as well get one with low distortion and noise. And oh, noise can also be audible as the headphone doesn't generate any on its own.


Yes, I'm saying that something like the 99$ Atom should be completely audibly transparent for any headphone it has enough power to drive.
 

MRC01

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... If an amp runs out of power, it will easily create distortion that dwarfs the headphone. So you still need an excellent/powerful amp even if you ignore its SINAD. ...
That's true, but it seems unlikely. Most headphone amps have enough power to drive most headphones to levels loud enough for our ears to distort and cause hearing damage.

For example, it takes only about 0.64 V and 5.7 mW of power to drive my LCD-2F headphones to 105 dB SPL. Anybody who listens that loud is likely to to damage his hearing over time. Yet this level of voltage and power level is nowhere near taxing most of the amps reviewed here. My ears will distort long before most of the amps reviewed here get anywhere close to their power limits. Of course there are exceptions like the HE-6 headphones which are very insensitive and need a lot more power.

IME, the headphone amp limitation that is more likely to be audible, is low level noise & channel imbalance at low volume settings, when using sensitive headphones.

Yes, I'm saying that something like the 99$ Atom should be completely audibly transparent for any headphone it has enough power to drive.
That sounds right to me. However, I can hear a slight channel imbalance on my JDS Atom at low volume levels. This happens only occasionally when listening to music that is recorded "hot" requiring me to turn down the volume.
 

amirm

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Yes, I'm saying that something like the 99$ Atom should be completely audibly transparent for any headphone it has enough power to drive.
For sure. The Atom is superb. The only issue with it is the plastic case which some people don't like.
 

Robin L

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I just got the Philips X2HR headphones. This would be an example of a headphone that has audible distortion in the treble. There's a spike of distortion around 5k [about 1%], coinciding with with a peak at the same frequency. My guess is that it's a resonance, ringing. It is somewhat more noticeable using the Topping E/L 30 combo than it is on my cheap little Fiio DAP, the M3K. I can filter out some of that distortion, but there is a signature hardness and forward quality of sound even when the Philips headphones are EQ-ed. On the other hand, the DAP is a little soft sounding [what would one expect for $69?]. The Philips headphones were designed with portable devices in mind, so they're easy to drive with plenty of bass even with low power sources like my DAP. I've also got Drop 6XX headphones, they don't play comfortably with portable devices, have very little distortion in the treble. I can hear the 6XX's lack of distortion using the Topping gear, can't really tell with the DAP. I'd say a low distortion DAC/amp combo with some grunt is necessary to get the most out of the Drop 6XXs.
 

Joachim Herbert

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With headphones, I notice all kinds of varying studio noise levels on TV programming that I'd almost never notice while listening through speakers.

This is even more pronounced with closed headphones, as they attenuate ambient noise that is present most of the time. Also decent headphones typically show lower distortions throughout trhan audible band than speakers do.
 
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