NwAvGuy

The rules of thumb about "60% of maximum volume for 60 minutes" and "if you can't hear your surroundings, it's too loud" are nonsense. Dangerous volume settings depend on a headphone's sensitivity, the output device power, the headphone's isolation ability, and the recording. These parameters vary. Wildly.

A well-fitting isolating IEM can slice off 25dB of noise, more than enough to (mostly) eliminate background conversation noise at any location short of a hip restaurant. These IEMs tend to be so sensitive that they become earsplitting at a tiny fraction of the maximum output volume, way less than 60%.

Learn approximate dB levels of various sounds, compare various noise with a meter (even an uncalibrated app will give you a ballpark idea of what you're dealing with), and listen to music at an average 65dB or less (this will obviously vary with dynamic range of your music; occasional 80-85dB peaks won't kill your hearing).

One trip to a dance club or rock concert without earplugs (100-110dB on average in my experience, 120+ has been known to happen) will do more hearing damage in a few minutes than a lot of headphone listening while working. I'm pretty sure the busy street near my home routinely hits a 90dB average at rush hour, solidly in the danger zone compared to reasonable headphone use.

Edit: To learn more, read the following:

- http://www.rane.com/pdf/old/note100.pdf

- http://nwavguy.blogspot.com/2011/09/more-power.html

> I noticed a difference in clarity using Audio-Technica ATH-M50s and Beyerdynamic DT 990 250Ω. Specifically, the Beyerdynamics could be driven "good enough" for me with the iPhone SE jack, but I wasn't happy with how they sounded on the Lightning dongle.

Scientifically speaking, it should be noted that the adapter performs exceedingly well to the point of audible transparency[1]. You are not going to hear the distortion components as they lie below 90 dB.

The fact of the matter is that your ears simply cannot be trusted, not when it comes to discerning differences in DACs and amps. There is a beautiful read[2] that illustrates this by NwAvGuy, it's worth checking out even for non-audiophile.

And Xiph's Digital Show and Tell[3] (again, a must-read) tells us that the 44kHz of the dongle is more than enough for audible transparency to humans.

The differences you hear are likely due to incorrectly matched volumes. If you volume-match to a fraction of a decibel, you probably would not be able to tell the difference in a blind test. There are other potential differences like a different impedance etc but these should only effect a very small subset of IEMs, let alone your headphones.

[1]: https://www.kenrockwell.com/apple/lightning-adapter-audio-quality.htm

[2]: http://nwavguy.blogspot.com/2012/04/what-we-hear.html

[3]: https://wiki.xiph.org/Videos/Digital_Show_and_Tell

>16 bit enough

It is so believed (although there's a lack of supporting evidence, and knowledge that human hearing has excellent dynamic range), but only as long as the mastering work was well done. 24bit allows for much less destructive human error and is very welcome. Much more so than absurdly high sample rates (96KHz, reproducing sounds up to 48KHz as per Niquist), which are of dubious value.

>my sennheiser hd600s are 300Ω

At some frequencies. At some others, it's more like 600Ω. Impedance is seldom stable across the frequency range in headphones.

Amplifier design should account for this and still provide enough power[0].

Output impedance of headphone jacks should be low enough (1:10 is commonly cited, which means <2Ω in practice as 20-30Ω headphones are very common) relative to the low end of the headphone impedance range, in order to prevent the impairment of frequency response.

>Not -all- onboard cards suck of course

But most do. The design of audio circuitry in motherboards doesn't get that much attention. None of my motherboards have good sound. Flaws vary. Some are lowpassed (greedy anti-aliasing filter). Some are noisy. Most have excessive output impedance (typically more than 6Ω, and at times higher than 15Ω). None can output enough power[0] for hd600 (my favourite pair).

[0]: https://nwavguy.blogspot.com/2011/09/more-power.html

I greatly respect NwAvGuy and agree with almost everything he says, but I think in practical terms that's a slightly over-simplified perspective. Look how inaccurate even these headphones are [1], arguably the best or one of the best ever made.

Getting the inaccuracies to be the right inaccuracies is quite subtle and very important in my opinion. See for example this review of his [2] and in particular the paragraph near the end:

>AN EQ EXPERIMENT: I tried using highly configurable parametric EQ to tweak my Denon D2000s to be similarly forgiving and I failed. When I filter out equivalent amounts of sibilance and harshness with the Denons, more of the music is gone and the result sounds veiled and artificial. The HD 650, to my ears, somehow works more like polarized sunglasses. They largely remove what I don’t want while revealing more of what’s left. It’s not just a simple frequency response difference. My objective side wants to pin down what’s going on but I don’t have a full explanation besides the HD 650’s lack of distortion.

[1] http://www.innerfidelity.com/images/StaxSR009.pdf
[2] http://nwavguy.blogspot.co.uk/2011/06/sennheiser-hd-650.html

The root is that at some point (late 20th century) the cheap wine became as good as the good wine. So the key differentiating metric for most of the space turned from performance to marketing. The high-end got pushed into the stratosphere (I'll never own a pair of electrostats) and everything else is good enough (hopefully, sometimes there is incompetence).

So if it's all good enough for the mass market then the audiophiles need to look in the mirror and ask what they're after. Some will say a mystical, ethereal experience. Some will say total control over the signal chain from outside the body to inside. These are orthogonal wants crammed into a single market.

The second path is harder, but it at least the end result is some form of truth. Very few engineers want to devote themselves to a pointless crusade for a tiny market of consumer goods. There's better things to do on the weekend. However, when they do it's special.

http://nwavguy.blogspot.com/

Section 2-29 of:

http://nwavguy.blogspot.com/2011/07/o2-design-process.html

And the entire article at:

http://nwavguy.blogspot.com/2011/05/virtual-grounds-3-channel-amps.html

Its easy to make something that amplifies, but he's trying to make something that provides specs maybe 10x to 10000x better than human hearing can detect, which is much harder. You can build something that outputs 0.1% THD and you won't be able to hear it, but he wants (wanted?) to build to 0.001% THD and he's got the rather expensive test equipment required to prove it.

JDS labs sells a PCB for less than the cost of shipping (you'll spend more on UPS than on the board) or a full parts kit for $60. This has been around for years and I've been tempted but haven't built one. I just checked JDS and its still in production and in stock. Being CC- licensed there are probably other places to get PCBs and kits.