Headphone amplifier

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Headphone amplifier

Postposted on Thu Mar 26, 2009 1:14 pm

So... what's the point?
What is the improvement using them?

I've tried reading the wikipedia article on headphone amplifiers, but all I've ended up with was some weird stuff about impedance and some gibberish that never reached my brain. Can someone explain it in plain English?
I've been contemplating buying some sort of headphone amplifier for whatever's sake once my "to buy" software list is exhausted and I designate more attention to hardware items.

I'd rather if this didn't turn into an advertising thread of 42-carat gold amplifiers that cost your next sibling's life, or 3 thousand dollar Stax electrojizzamafiggle 'phones, or a discussion of anything beyond elementary physics.
I would also advise you to stay away from comments like "it makes it sound warmer" or "sound gets cleaner" or things like that, because I'm interested in neither the thermometer readings you get from next to your speakers, nor how much coffee and cherry juice stains make sound "unclean", so please phrase clearly. I'd really appreciate if someone could explain where the extra audio definition comes from, where it materialises (how to discern it), and why it's there in the first place.

Thanks in advance.
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 1:40 pm

The socket on the mp3 player that you would usually plug your headphones into provides the correct voltages but doesn't provide much current. If you have small earbuds, that would be fine, but larger headphones pull too much current from the feeble Ipod socket. The result is clipping: it's that picture of a waveform that has the peaks cut off because the Ipod hasn't the power to drive the headphones at those high or low frequencies.

I think a simple way to put is... the headphone amp is pretty much a voltage buffer. The Ipod socket would need to provide a tiny tiny current, which means it can provide the perfectly correct voltages (the voltage is the actual signal/music) The amp would then back up that signal with all the current that the headphones need. Amps can also mutliply the voltage a few times if you would like (increase volume), but mainly the amp provides all the current necessary for large headphones so that the weak ipod socket doesn't get stressed and start distorting the sound.

You can also add various frequency filters on it to amplify base or treble and such. It's most fun to build.
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 1:48 pm

lol @ your comments about subjective audiophile-esque review words.

What are you using to drive headphones right now, and what are the headphones?
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 1:52 pm

Basically, the headphone output amplifier on most devices is a very cheap, low quality component. Typically, it will have a difficult time driving the higher impedance of high-quality headphones. It will still work, but the sound quality will suffer, especially the bass.

You can think of it like the difference between the speaker amplifier in your typical cheapo boombox and the amplifier in a real hi-fi amp. If you plug REAL hi-fi speakers into the boombox, it's going to sound bad because the crappy boombox amp can't handle the impedance or the current demands. It will still work, but the sound quality will suffer, and the bass will sound like crap.

A headphone amp solves this problem by making it easier for the crappy device's output amplifier to supply a signal (by giving it an easy-to-drive impedance), and then amplifying that signal properly with high-quality components.
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 1:59 pm

Meadows wrote:I would also advise you to stay away from comments like "it makes it sound warmer" or "sound gets cleaner" or things like that, because I'm interested in neither the thermometer readings you get from next to your speakers, nor how much coffee and cherry juice stains make sound "unclean", so please phrase clearly.
You really shouldn't have an objection to the bolded text, unless you have an objection to using words in accordance with their appropriate definition.
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 2:06 pm

I don't own any sort of portable music player. I only indulge in such entertainment at home.
In addition, I would never ever buy anything from Apple, especially not an iPod.

I'm more interested in why it's supposedly an advantage over, say, your generic output jack connector that's on your sound card or whatnot.
Now that I mention that, it would also be nice to figure out why the "big" jack plug my headphones originally shipped with are better (Sennheiser HD 555, with a "smallifier" adaptor provided as well). So in short, what are the advantages of headphone amps and big jack connections when we're talking about a desktop PC environment?

nerdrage wrote:Basically, the headphone output amplifier on most devices is a very cheap, low quality component. Typically, it will have a difficult time driving the higher impedance of high-quality headphones. It will still work, but the sound quality will suffer, especially the bass.

You can think of it like the difference between the speaker amplifier in your typical cheapo boombox and the amplifier in a real hi-fi amp. If you plug REAL hi-fi speakers into the boombox, it's going to sound bad because the crappy boombox amp can't handle the impedance or the current demands. It will still work, but the sound quality will suffer, and the bass will sound like crap.

A headphone amp solves this problem by presenting the crappy device's output stage with an easy to drive impedance, and then amplifying the signal with high-quality components.

Thanks. That explains some, particularly why the above headphones have a less grating sound low-end. Though frankly, it never was bothersome, let alone show-stopping.

mattsteg wrote:You really shouldn't have an objection to the bolded text, unless you have an objection to using words in accordance with their appropriate definition.

Masteregg, dearest of all my friends, I didn't mean it that way. All is well if people say that sound gets cleaner, clearer, more crystaline, genuine, alkaline or anything, so long as they explain it in meaningful English terms, such as talking about frequency curve deltas, altered low- or high limits, or even if the behaviour of the magnet drivers is changed. I'm not interested in grand royal adjectives, because I'm expecting them - I pretty much know that all people above entry-level audiophiles will invariably have a headphone amp as well. I'm just interested in the hows and why's.
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 2:28 pm

Think about it this way:
The impedance of headphones (or speakers for that matter) could be thought of how much power it takes for any given volume. A pair 4-ohm headphones will be louder than a pair of 16-ohm headphones given the same output. Generally, the bigger the physical diaphragm that needs to be moved correlates to the higher impedance. The upside is that the higher impedance headphones are generally of better audio quality.
When you look at most mp3 players, the amount of power that they can output is fairly limited, and as you get to the max volume, the audio quality drops (due to clipping as said above as well as other factors).
So, in short, having a headphone amplifier lets you keep high-quality out of the player while letting the amplifier do the amplifying and giving you the capability for higher-power output. Most media players will quote a spec of the output power, and the higher-impedance headphones might not be loud enough to listen to at that output power. (or the top 10% of the "volume" will give way to degraded audio quality).
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 2:38 pm

Dan (www.dansdata.com) has reviewed a decent share of headphones and amps over the years. He's always honest about whether a product sucks or is worth the money. He doesn't buy into the "if it costs a fortune it must be good" mindset, like the people who buy CD stabilizers and thousand-dollar wood volume knobs. You can always trust him to provide an honest opinion.
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Re: Headphone amplifier

Postposted on Thu Mar 26, 2009 3:41 pm

Dan's Data +1. I was going to say, go to a store, bring your headphones and some very familiar recordings, and experiment with a few amps. You can go on eBay, as Dan's suggests, and just pick up a little Cmoy amp-in-a-mint-tin. If you're a little handy with a soldering iron, you can even make one yourself.

As far as sound cards, most of them you buy nowadays have some sort of decent quality headphone amp built into it. The Asus Xonars (the Essence especially) do, as do most of the Auzentech X-Fi clones as well.

Since you've forbade us from expounding the auditory virtues of using an external headphone amplifier in terms of whack-o language, I'll say a good amp just might knock your socks off.
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Re: Headphone amplifier

Postposted on Fri Mar 27, 2009 4:30 am

drsauced wrote:Since you've forbade us from expounding the auditory virtues of using an external headphone amplifier in terms of whack-o language, I'll say a good amp just might knock your socks off.

I think his opening warning forbade the use of sock-knocking.
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Re: Headphone amplifier

Postposted on Fri Mar 27, 2009 4:36 am

drsauced wrote:Since you've forbade us from expounding the auditory virtues of using an external headphone amplifier in terms of whack-o language, I'll say a good amp just might knock your socks off.

I wrote:All is well if people say that sound gets cleaner, clearer, more crystaline, genuine, alkaline or anything, so long as they explain it in meaningful English terms, such as talking about frequency curve deltas, altered low- or high limits, or even if the behaviour of the magnet drivers is changed. I'm not interested in grand royal adjectives, because I'm expecting them - I pretty much know that all people above entry-level audiophiles will invariably have a headphone amp as well. I'm just interested in the hows and why's.

Thankfully, got most of the hows and why's explained to me already. I've also read some old Dan's reviews, so I'm slowly beginning to form a clue.
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Re: Headphone amplifier

Postposted on Fri Mar 27, 2009 4:53 am

Bottom line is: if you use some good cans and/or push the volume up, your sound quality will be a lot better with a proper headphone amp.
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Re: Headphone amplifier

Postposted on Fri Mar 27, 2009 4:55 am

morphine wrote:Bottom line is: if you use some good cans and/or push the volume up, your sound quality will be a lot better with a proper headphone amp.

That's what I wanted to know. I don't like investing in anything (especially audio stuff due to the related community) without being sure that it brings some absolutely noticeable difference.
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Re: Headphone amplifier

Postposted on Mon Mar 30, 2009 4:49 am

drsauced wrote:As far as sound cards, most of them you buy nowadays have some sort of decent quality headphone amp built into it. The Asus Xonars (the Essence especially) do, as do most of the Auzentech X-Fi clones as well.

After looking into the issue, I wouldn't say "most of them".
There are only two models in the expansive Xonar repertoire that have one, the Xonar Essence STX and its tiny cousin, the external Xonar U1 that was designed with laptops in mind. And of the two, only the Essence has a real amplifier, the U1 couldn't drive a Sennheiser HD 280 to save its life.

I don't know about the X-Fis, but I don't want one.

Looking at the value proposition here, I might just save some dough for a "real" Xonar instead of a similarly priced headphone amp, if only to experience their general silky goodness and ASIO support/performance. Pity they don't support 88.2 kHz ASIO, though. Or maybe they do, but it's just not listed. I'm hoping it's the latter.
Thanks for the heads-up, if this thing works out, I won't have to eye an external amp again, unless for some reason I'd want to use multiple headphones.
Actually, I believe it's not available in Europe yet and sold out everywhere else (unless I'm wrong), so that gives me a lot of time to ponder and count money.
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Re: Headphone amplifier

Postposted on Fri Apr 03, 2009 10:47 pm

I'm late to the discussion, I know, but I thought the following may be useful info to some.

One of the "features", if you will, of all PC-based audio is that there are no negative voltages with which to work. We have +3.3, +5, and +12V in abundance, but the -5 and -12 rails are all but gone (and were never all that useful anyway). Think about what this means for audio. Audio is AC, which means that in order to push AND pull speaker cones (or headphone diaphragms) back and forth, you have to have a voltage that rises above and drops BELOW some idle point. In a regular home stereo amplifier this is done by using a center-tapped transformer in the power supply to generate +35V (for example), ground, and -35V. The speaker outputs sit at 0V until some music is played, and then the output swings positive and negative in response to the source content.

Well, in PC audio, you can't have the outputs sit at 0V when idle, because there'd be no way to go negative (since there's no negative rail). So what happens in PC audio is that line and headphone outputs are all biased at the midpoint of the +5 rail, or 2.5V. Signals that place the diaphragm closer to your ear are between 2.5V and 5V, and signals that place the diaphragm farther from your ear are between 2.5V and 0V. As they say in the fashion world, 2.5 is the new zero. But since you can't feed 2.5V DC to headphones or other amplifier inputs, there are capacitors between the sound card's output op-amps and the actual output connectors so as to block the DC. The AC passes through mostly unmolested.

But only mostly, and this is one of the big differences between what you usually find on onboard audio and a well-made sound card. Space is limited and precious on motherboards, and there are at least six analog ouputs to be concerned with. Putting six capacitors of the type that would sound best would take a fair amount of PCB area (and would cost about 10x in parts), so the motherboard manufacturers typically use very small, high-ESR, polarized electrolytic caps to do the blocking. They do a great job of blocking, but they can degrade the sound significantly.

Quality sound cards get around this by providing better op-amps driving the outputs, and far better capacitors blocking the DC. For headphone outputs in particular, the op-amps used are capable of current levels that can wiggle a physical diaphragm wihout breaking a sweat.

Like PC audio, external headphone amps are generally powered by single-rail supplies (using AA batteries to produce 3V, for instance), but often use internal converters to generate a higher voltage so as to allow the use of lower-noise op-amps and greater voltage swing. Instead of having a 1.5V bias point, for instance, they may boost the 3V to 12V and have a 6V (half of 12) bias point.
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Re: Headphone amplifier

Postposted on Fri Apr 03, 2009 11:29 pm

Time to bring back boards with audiophile pretensions, like the AOpen AX4B with its 6922 pre-amp tube and massive coupling capacitors.
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Re: Headphone amplifier

Postposted on Sat Apr 04, 2009 8:14 am

Captain Ned wrote:Time to bring back boards with audiophile pretensions, like the AOpen AX4B with its 6922 pre-amp tube and massive coupling capacitors.

The thing that really cracked me up about that one was the fact that they were still using a Realtek codec...
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Re: Headphone amplifier

Postposted on Sat Apr 04, 2009 11:44 am

just brew it! wrote:
Captain Ned wrote:Time to bring back boards with audiophile pretensions, like the AOpen AX4B with its 6922 pre-amp tube and massive coupling capacitors.

The thing that really cracked me up about that one was the fact that they were still using a Realtek codec...


True, I looked at that and thought, 'doesn't VIA have something that would do better here?' Then I hoped that maybe someone would throw something like that on a soundcard... which I've yet seen.

But let me throw this out there- my last motherboard and my current one both have more than sufficient onboard audio solutions- I can't tell the difference between the two of them, one ADI the other Realtek, or my old Audigy 2 ZS I have lying around. I wonder then, if the Realtek codec would be just fine supplying the processing/sampling and the DAC, if the circuit layouts were clean? I know well amplified s*** is still s***, but I think that something like this would even work today, even with a Realtek, ADI or Crystal solution.
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Re: Headphone amplifier

Postposted on Sat Apr 04, 2009 1:01 pm

Realtek is certainly better than they used to be, and PCB layout plays a big part. Of the current onboard audio vendors, I'd probably trust ADI the most (ADI's PC audio codec business was recently acquired by Conexant, so strictly speaking they are actually Conexant codecs now).
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Re: Headphone amplifier

Postposted on Sat Apr 04, 2009 1:29 pm

Personally, I think Realtek gets a mostly undeserved bad rap. Because they provide the lowest-cost solution they're often coupled with the lowest-cost, worst-case implementations, the combination of which can lead to some truly crap sound. The specs on their mainstream parts are good enough for most listening as long as the associated parts and layout are up to snuff. My DFI motherboards used Realtek codecs on their audio modules and I didn't hear any of the noise that I'm getting now on a much newer Gigabyte motherboard which uses a Realtek part with marginally better specs.
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Re: Headphone amplifier

Postposted on Sat Apr 04, 2009 2:41 pm

Asus and DFI seem to do a reasonably good job with their onboard audio. MSI (and Gigabyte, apparently) not so much.
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Re: Headphone amplifier

Postposted on Sat Apr 04, 2009 11:19 pm

just brew it! wrote:Asus and DFI seem to do a reasonably good job with their onboard audio. MSI (and Gigabyte, apparently) not so much.

FWIW, I kicked my Audigy 2 ZS Pro to the curb due to the Realtek implementation on my Gigabyte 965P-DS3 being more than good enough (at least better than what I got from Creative).
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Re: Headphone amplifier

Postposted on Sat Apr 04, 2009 11:32 pm

morphine wrote:
just brew it! wrote:Asus and DFI seem to do a reasonably good job with their onboard audio. MSI (and Gigabyte, apparently) not so much.

FWIW, I kicked my Audigy 2 ZS Pro to the curb due to the Realtek implementation on my Gigabyte 965P-DS3 being more than good enough (at least better than what I got from Creative).


The Realtek on my P45-DS3L is great, and the ADI that was on it's own riser on my dead P5N32E-SLI was great as well.
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Re: Headphone amplifier

Postposted on Sun Apr 19, 2009 12:28 am

sluggo wrote:Personally, I think Realtek gets a mostly undeserved bad rap. Because they provide the lowest-cost solution they're often coupled with the lowest-cost, worst-case implementations, the combination of which can lead to some truly crap sound. The specs on their mainstream parts are good enough for most listening as long as the associated parts and layout are up to snuff. My DFI motherboards used Realtek codecs on their audio modules and I didn't hear any of the noise that I'm getting now on a much newer Gigabyte motherboard which uses a Realtek part with marginally better specs.

I wouldn't know about their recent stuff, but the last RealTek board where I tried to use the onboard a few years ago was smearing the high frequency range in a fashion that sounded like a badly encoded mp3. That doesn't come from a bad board implementation; it comes from a bad codec implementation. I'm glad to hear they've improved since then, but IMO they earned their reputation fairly.

Also, re: your earlier comments, have you actually tested the voltage coming from a PC headphone jack? There's nothing to prevent a soundcard manufacturer from using a DC-to-DC switching converter to obtain acceptable output swing.
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Re: Headphone amplifier

Postposted on Sun Apr 19, 2009 12:49 am

ludi wrote:I wouldn't know about their recent stuff, but the last RealTek board where I tried to use the onboard a few years ago was smearing the high frequency range in a fashion that sounded like a badly encoded mp3. That doesn't come from a bad board implementation; it comes from a bad codec implementation. I'm glad to hear they've improved since then, but IMO they earned their reputation fairly.

Also, re: your earlier comments, have you actually tested the voltage coming from a PC headphone jack? There's nothing to prevent a soundcard manufacturer from using a DC-to-DC switching converter to obtain acceptable output swing.


I remember some ALC650 based stuff that was terrible- but the ones shipping on today's boards I have a hard time finding fault in, taking account of their on-board nature. Even as a hard-core believer in discrete audio for a long time, I can't bring myself to purchase a sound card today, as I have no budget for high end headphones nor do I want to give up the simplicity and versatility that Realtek implementations offer, even over their discrete (Creative) competition.
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Re: Headphone amplifier

Postposted on Sun Apr 19, 2009 1:47 am

ludi wrote:Also, re: your earlier comments, have you actually tested the voltage coming from a PC headphone jack? There's nothing to prevent a soundcard manufacturer from using a DC-to-DC switching converter to obtain acceptable output swing.

Nothing but cost. Anyway, there's no need to do any DC/DC as you have access to +12V should you so desire.

I've haven't tested every card made, but I've designed/tested/reviewed many. Consumer line-level output is 1V RMS full-scale. If you go higher than that you risk clipping the inputs of the next stage, which would be bad. So 5V is plenty.

The soundcards that offer a "line/headphone" output don't change output voltage for headphones, they just use an output that can drive a 32 Ohm load. Most of the newer codecs have this on-board so external op-amps are not required.
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