Sound Science Forum Moderator
- Jul 2, 2011
This topic is my attempt at answering that question without having to rocket science so that my mother can get a meaning out of it. and hopefully you guys too.Spoiler: You're not deaf, and I'm not a golden ear.(well that's a bummer)
I measured the volume level out of 2 DAPs in different situations using trueRTA(free software). I could have used something much more detailed like a fancy spectrum of the frequency response, or RMAA the DAPs(well I did, if at some point it feels relevant, but I don't think it is for the subject). or I could have simplified to the extreme with a simple VU meter. I thought this was good enough to show my point about hiss and why some get it and other think they don't.
So here is one of my DAPs playing a 1khz tone plugged back to the computer through a focusrite. Nothing high end, nothing is fully calibrated(the 0db signal is set at 0.35v, far from testing ideal fullscale stuff), as all I want is to show changes, I only took care of keeping everything identical and thus set things up for the worst device in the worst situation. and that's about it. I'm a noob with noob gears.
let me sing you the song of my people!
You can clearly see(if you click on the picture...) my nice 1khz test tone reaching -3db, that's the “music” I'm playing(because I'm an objectivist I only have playlists of test tones, like all subjectivist can tell you), and the next thing is way below at almost -78db. So if I think of it as listening to music, I would have my music at normal loudness up there, and all the crap that isn't music, would be at least 78db quieter, as good as non existent when it comes to hearing it.
but that's with my DAP set very loud compared to what I use with my IEMs, and plugged directly into the recording device so the DAP has an easy job of driving the load. So this is in no way a realistic situation. :'(
Here is a more realistic situation, that's the loudness I really set when listening to music with my 300ohm IEMs etyKids
Playing the 1khz tone shows to be -47db loud. Compared to the more flattering graph before, the crap in the trebles didn't really go down with the music, so now it's like the garbage is closer. With the treble crap reaching -81.39db that means I got crap sound only 81.39-47=34.39db below my music.
We don't know where it is, maybe the noise is a single point at 19khz and I wouldn't notice it if it was as loud as the music(my hearing is ok up to 16.5khz). But still it's coming dangerously close to the playing music and looks bad when we put it in perspective with the high resolution DAP marketing propaganda.
In this graphs I have now set the DAP at the loudness I usually use when listening to my IE80 . they are very sensitive IEMs and when I notice some background noise on a DAP it's often with those:
Because the IE80 are more sensitive than the etyKid IEM, to get the same perceived loudness in my ears, I need to lower the volume level of my DAP. logic!
but what if some of the background noise doesn't go down with the volume level like on the very DAP I used up till now? then it's like the noise is louder again.
The 1khz "music" in my example is now 63-47= about 16db quieter, and it sounds like the background noise is 16db louder in my ears because of the IE80's higher sensitivity. 10db louder feels like double the loudness, so no wonder I notice background noises a lot more on the IE80 than on the etyKids. the background crap is now real close to my music.
And there you have it, we could use the same DAP, but simply because you're not using an IEM as sensitive as mine, you may never get bothered by any form of hiss in the background of your music.
And that why some notice a hiss and some don't, as simple as that. it's only a matter of how sensitive your IEM can be. so the obvious solution against a DAP that hisses is to avoid buying very sensitive IEMs!
You can now stop reading and complain that I wasted your time with a badly done experiment, the original question has been answered with concrete visual example.
Or if you really have nothing to do because your torrent didn't finish downloading, then you can stay, it's free:
The graphs below are to show how from one DAP to another the noise floor might not be the same, and why I often use an external amp not for power, but to clear up the background a little.
here is another DAP, this time with a 8ohm resistor to simulate the load(it was just too clean without the 8ohm load ^_^), so I'm not being nice with that poor DAP. But nowadays many high end IEMs can go as low as 8ohm, and the 20 or 30ohm written on the specs are only the impedance at 1khz.
You can see there is crap everywhere, but rather low, so that's a pretty nice result for a consumer DAP.
Now another DAP that doesn't take the 8ohm in with the same dignity:
for the same output setting, you see the 4khz(remember I'm only using a 1Khz test tone, there is no music at 4khz) is about 10db(feels twice as loud) louder than the noise from the previous DAP. and even though the low frequencies are super clean, I tell you I'm hearing a clear hiss on this one with my IE80 when it's more subtle using the previous DAP.
I call those stuff noise, but it could as well be harmonic distortions, I have no real way to know just measuring the amplitude of the signal like I did. but whatever it is, if I can hear it, it's garbage!
So with some IEMs, that DAP hisses too much for me and I'm annoyed. and here is what I do, I plug in my external amp, and at least for this very dubious reading, it's not too hard to recognize progress:
I see external amps as a great solution for some noises, but don't get me wrong, to need a solution, you first need a problem. It's really no fun to carry a brick around if the DAP alone already sounds clean and has enough power for our IEM/headphone. and in some cases, the amp might just hiss more than the DAP.
and there you go, I hope some who didn't understand why people complain about hiss from a DAP, now understand why it can be real without them hearing any. and I also hope that it may give some practical solution to those who are annoyed by some hissing DAP. lower sensitivity IEM, or amp.