Headphone amps, external power supplies: what difference do they make?, was: "First post here, Hi." Options

[1096bimu]

Ever since I was told that it is possible to tell 320kbps CBR from loseless, I've had some interest in hi-fi, and that was a few years ago. Today, I use an ASUS Xonar Essance sound card and an AKG Q701 headphone. I am pretty confident that it sounds better than all the cheaper alternatives I've had before, and I am quite proud of my own ability to eliminate biases without blind testing (because of lack of equipment). However, 320kbps MP3 is still transparent to me. The absolute best I can do is tell 128kbps, and it is extremely difficult as I have to go through the samples multiple times to try and spot one or two obvious distortions, and tell from that. If I couldn't find any than they sound identical to me. I have read through many of the FAQs, compilation of test results and older posts so I know this isn't uncommon and isn't what I am worried about. I keep everything loseless even though I can't tell the difference because I don't have that many music, only a few gigs which isn't a problem for today's mobile devices (exported selected few from CD images).

The biggest problem is I keep running into this claim that headphone amps are supposed to make ginormous differences, especially with the AKG Q701. Some people say there is more difference with the K701 but aren't they identical except the colors? Of course nobody could show any blind test results and they are nothing more than testimonies. I am not a hard core audiophile I don't have any audiophile friends so it's not possible so it is not possible for me to try out stand alone amps. It just seems to me that many of these audiophiles believe in some kind of mystical superiority of external boxes. You gotta have an external DAC, and an external amp and you have to connect them together. I mean today they are just intergraded circuits why do they have to be external? The Xonar Essance says "Headphone amp card" and it does have an amplifier chip as well as those small ones that you can swap out and everything, so What's the difference?
In fact, I tried the Q701 on my cell phone, iPad, on-board intergraded audio, and even an iPod shuffle. They sound slightly worse I would say, the difference is quite subtle when compared to the Xonar. And I could not tell any difference between my phone, iPad and iPod shuffle.

I've also heard that you have to use an external power supply (it has a port that plugs into the computer power supply) for the Xonar to "bring out its full potential". Again, what's the difference? are computer power supplies not stabilized? I guess I also count as an overclocker so I know how voltages in the computer are set to two or three digits after the decimal, it is really sensitive stuff. I mean maybe the computer with its variable power requirement will destabilize the power source, but I don't listen to music while playing games or anything, I leave the computer idle for that. Also being a fairly high-end spec, the -12V power supply has a capacity of 650W (for 12V alone) , isn't that enough head room for small fluctuations?

[DVDdoug]

The biggest problem is I keep running into this claim that headphone amps are supposed to make ginormous differences, especially with the AKG Q701. Some people say there is more difference with the K701 but aren't they identical except the colors? Of course nobody could show any blind test results and they are nothing more than testimonies. I am not a hard core audiophile I don't have any audiophile friends so it's not possible so it is not possible for me to try out stand alone amps. It just seems to me that many of these audiophiles believe in some kind of mystical superiority of external boxes.

Sometimes a headphone amp can make a difference. But, there is a TON on nonsense in the audiophile community and in audiophile marketing.

The parts to build a good headphone amp (or put one on a soundcard or motherboard) are not expensive. But, when you manufacture & distribute specialty items in small quanties, the costs go up. A nice cabinet also adds to the cost. So, an nice headphone amp could legitimately sell for a couple-hundred dollars, even if it doesn't sound any better than your average-good soundcard (or cheaper headphone amp). Plus, audiophiles are generally more-attracted to higher-price items.

Basically, there are 3 kinds of potential defects or differences in sound reproduction:
Noise, distortion, and frequency response variations. So, if you read something like, "This amp has weak bass", or "This soundcard is noisy", that's engineering & scientific terminology and I'd tend to trust it. But, when someone says, "This headphone has more detail", I don't know what that really means, and I'm not sure anybody knows what it means in scientific terms or specifications.

If you are hearing noise in your headphones, you'll probably benefit from an external DAC & headphone amp (or from a better soundcard).


Otherwise, here's why a headphone amp can sometimes be an improvement:
Impedance - Headphone impedance varies over the frequency spectrum, that's perfectly normal and acceptable and the impedance curve is different with every headphone. Bit if the souce impedance of your soundcard (or headphone amp) is high (say, close to the headphone impedance), the variations in headphone-impedance interact with the soundcard's impedance and you get variations in frequency response (not acceptable). I think it's usually a bump in the bass or mid-bass, but like I said every headpone is different. Technically, these frequency variations degrade the audio reproduction and it's not performing as designed or as specified. But, the frequency variations (such as an increase in bass) could actually heard as an improvement.

With high impedance headphones (i.e. 600 Ohms) this isn't an issue, and you won't get different frequency response from different soundcards or headphone amps (assuming no actual defects).

Most headphone amplifiers should have low impedance, so this shouldn't be an issue. It might not be an issue with most soundcards either, but a "line output" could be higher impedance.

What complicates this is that the output impedance specs are not always clear... The specs for the headphone amp might say "32 Ohms", but that's usually the (minimum) recomended headphone impedance, not the internal impedance of the headphone amp itself, which is hopefully much lower. (The goal is not to "match" the impedance. With headphone amps & power amps, the amp shoud have much lower internal output-impedance than the actual load.)

Voltage - If you are not getting enough volume without distortion, a headphone amp will generally help because they are usually designed for higher-voltage output than an average sooundcard.

Voltage is also related to impedance... A higher impedance headphone (i.e. 600 Ohm) requires more voltage to get the same power (milliwatts) and loudness as a lower impedance headphone.

I've also heard that you have to use an external power supply (it has a port that plugs into the computer power supply) for the Xonar to "bring out its full potential".

This could be a voltage issue. I don't remember if there is +/- 12V on the PCI bus. I would assume so because they used to have +/-12V RS-232 ports on I/O cards, but I don't know for sure.

This post has been edited by DVDdoug: Dec 7 2012, 03:20

[Nessuno]

But, when someone says, "This headphone has more detail", I don't know what that really means, and I'm not sure anybody knows what it means in scientific terms or specifications.

Better impulse response, maybe?