Saturday, 14 May 2011

Guidelines for Buying Headphones

Something I seem to get asked a lot is, "What headphones are good for <insert price>?"

That's not an easy question to answer, thanks to a number of reasons.  I'm also reluctant to give direct recommendations due to the fact that a lot about headphones (quality, sound, value) is subjective.  What I find good, someone else may find not so good.

With that in mind, I want to go through a few points which will hopefully help you to make your own, informed decision.  Here are some of the things you should consider when looking for headphones.

Style of Music
This is possibly the most obvious point, but one that should be covered.  Not all headphones are created equal, and by that I mean they have different sound signatures (a fancy phrase for the tone they impart onto the music).  You are probably aware of the fact that headphones and speakers all have different sounds, and may have put it down to a difference in quality, but it's most often, simply down to how they respond at certain frequencies.

We can put headphones into two basic categories (there are more, but we are going to keep it simple for now).  Those are neutral, and coloured.  Neutral, as the name suggests, presents the music as close as reasonably possible to the original recording.  It's difficult to make and tune neutral headphones due to various factors, so you do have a degree of variance between them.  Not all neutral headphones sound exactly alike.

As for coloured, this basically describes any headphones or speakers that add their own tone to the music.  The most common example of coloured headphones are those that boost bass, but it can also describe non-neutral behaviour in other frequencies, such boosting high frequencies which gives an impression of greater clarity.

We can determine for ourselves which headphones are neutral or coloured simply by checking their frequency response graph.

Here is a frequency response graph for 4 popular headphones.  These graphs are generated by playing a standard frequency sweep through the headphones and measuring the output.  What the graph shows us is that although the same frequency sweep is played through all the headphones, the output can vary a lot.

In a perfect world, neutral headphones would have a straight line at 0dBr, right across the frequency spectrum.  However in practice this is extremely difficult, and even the $1400 Sennheiser HD800 can't produce a completely flat line.  Generally, anything +/-5db relative to 0db would be considered neutral, and anything significantly higher or lower than that would indicate that the headphones either have a coloured sound or weakness.  As we can see, given the +/-5db rule of thumb, the HD800 do amazingly well, staying within that range for most of the frequencies.  The K701 do well too, but in comparison to the HD800, it appears that bass and highs are a little under represented (but when you consider there is a $1100 price difference, they don't do bad at all).

Moving on, we can see the Sony MDR-V700, which are sold as DJ headphones, have the weakest bass response of them all, and is lacking in the high frequencies/treble department.  Ordinarily that would stand out to me as a weakness of the headphones, but given that they are designed to be used in clubs, and support up to 3000mw of power, I wonder if they were purposely tuned this way so they can be played at high volumes without piercing treble or ear rattling bass.  For DJ headphones they are fit for purpose, but I wouldn't suggest these to any budding audiophiles (talking from first hand experience).

Conversely we can see that the Sony MDR-XB700 apply a large boost of +15 in the bass range.  That much of a bias into one frequency range means that it works superb for certain styles of music (notably hip hop or drum and bass), but potentially not so well for others.  The boost tapers off at around 250-300Hz which is the usual cutoff frequency for subwoofers, so it's obvious what these headphones were tuned for.  The only downside with this much of a boost is that it may leave some low male vocals sounding a little muddy.  While these don't appear to boost the high frequencies (in fact it's just below 0db), in comparison to most other headphones, it would sound as though they do since a lot of headphones tend to fall off to around -10db in the 10kHz+ range.

As the graph shows, the AKG K701 and Sennheiser HD800 are neutral headphones, whereas the Sony MDR-XB700 are coloured since they intentionally boost the bass.  Coloured headphones are typically a lot more popular than neutral headphones as it's easier to notice a difference in tone between two headphones than it is to notice the quality difference between two that have similar frequency responses.  To notice the quality difference between two high quality headphones, you would need an equally high quality source, but the difference between neutral and coloured headphones can be noticed on practically any output.

Protip: Coloured headphones work well on cheap players/output as their bass/treble boost can offset the rolloff associated with portable devices/underpowered amplifiers.  See this for more detail.

That alone makes it easier to differentiate between them.  Coloured headphones also give a false sense of quality.  What happens when you go from a neutral headphone to one that boosts the bass and treble by +5db?  You will easily notice the improved bass, and the extra high frequency response will give the impression of extra clarity.  Then move to headphones that boost by +10db and you have the same issue again.  The +10 boosted headphones will have even more bass and sound even more detailed than the last pair.

These kind of headphones are likely to grab your attention at first which is not something that happens when using neutral headphones.  As such, these headphones are popular and thanks to their artificial boosting of the frequencies, can leave neutral headphones sounding dull or flat in comparison.  That's not to say coloured headphones are bad or no good, but they serve a different purpose from neutral headphones.  My personal preference is to listen to music as it was intended to sound in the studio, but if you are a bass head, then that's cool too.

If you listen to certain types of music (such as hip hop or drum and bass as mentioned earlier), then coloured headphones may suit your requirements.  If you listen to a wide range of stuff and only want to invest in one pair of headphones, a neutral setup will serve well as a jack of all trades.  The great thing about headphones is that they are small enough to own multiple pairs, so you may decide to go for one of each and alternate depending on what you are listening to.

Source Quality
As I touched on before in previous posts, your source quality is critically important.  There's really no point in spending $1400 on some Sennheiser HD800 if you intend to run them off your onboard laptop audio or iPod.  Your output will simply be way better than your input and your source will cripple the performance of the headphones.

Budget according to the quality of your setup if you don't intend to upgrade your audio.  If you have onboard audio for example, then I'd advise spending $150 maximum.  If you have a high end soundcard, then feel free to splash out a little more (let's say up to $250).  If you still really want to spend a decent amount (over $300 for example) on a certain pair of headphones, consider buying a DAC first (or an amp if you already have a high end soundcard like the X-Fi Titanium).  It makes the initial cost of upgrading expensive, but a high quality DAC is a long term investment and will out live numerous pairs of headphones.

A common mistake, and something I can speak about from experience, is that people think they can buy good quality headphones and expect significantly better sound.  While high quality headphones will provide an improvement, they will potentially show you the flaws in your source too.  I originally bought the AKG K701 and intended to run them from my laptop audio (insert laughter here).  I thought that at $320, they would be good enough for me to not care about the pitfalls of onboard audio, or that I would be so impressed with the quality over my old Sony V700, that I wouldn't notice any flaws.

That of course wasn't the case, and I soon got the upgrade bug.  The audio quality was obviously improved from the Sony V700, but the onboard amp lacked the power to properly drive the headphones, not to mention the poor quality of the DAC.  I wanted to see what these headphoneswere actually capable of, so I went down the path of a seperate headphone amplifier and DAC.

Audio is a two way deal.  Input is equally as important as output, so with this in mind, I'd recommend splitting your budget.  I would suggest spending as much on a combined amp/DAC as you would the headphones.  For example if you have a budget of $400, rather than spend that much on a single pair of headphones to use with onboard laptop audio, split the budget and buy a DAC too.  It's a case of striking a balance since you are more likely to get better quality from a very good source with very good headphones, than a poor source with excellent headphones.

You may decide to split your budget dead in half, or something like $150/$250 for example (incidentally, $400 gets you a nice Maverick D1 and AKG K601 combo, which Findns can personally vouch for).  I would advise biasing your budget split toward the amp/DAC as they are long term, and headphones come and go.

More information on the hardware side of audio quality and upgrading can be found in my previous post on amps and DACs

While I am on the subject of source quality, let's talk briefly about the music itself.  Once you make the move to high quality audio, you may be left feeling that your 128kbps youtube rips don't quite cut it anymore.  Joking aside, MP3 is an aging standard, and what was good enough for lossy compression 10 years ago, is poor now.  Consider using at least 320kbps mp3, or better yet, AAC or FLAC.  FLAC is a lossless compression method that retains all the quality of the original recording, but reduces filesize using similar algorithms to zip and rar, but specially tuned for audio.  Typically it reduces the original bitrate of 1411kbps to around 900-1000kbps.

AAC deserves a special mention as it is the successor to MP3 and is rather impressive.  It is said to be around 30% more efficient than MP3 at the same bitrates, and in an encoding test I performed, I found that 226kbps AAC retained more high frequencies than 320kbps MP3.

So if we consider that 226kbps AAC is better than 320kbps MP3, then how good would AAC sound at 320kbps?  Even if 320k AAC isn't enough for you, you will be happy to know that AAC goes all the way up to 448kbps for CD audio, and I'd challenge anyone to tell the difference between the source and the AAC in a blind listening test.  I'm confident it simply can't be done, especially if you consider that for most people, AAC reaches transparency at around 200-250kbps.  I back this statement as I personally find it difficult to find any differences even with my gear.  Watch this space for a listening test in the future.

AAC also supports multi channel, a range of bit depths and sample rates, and rather than being stuck at a fixed highest bitrate like MP3, it can scale depending on the input.  I recently encoded a track from SACD (24 bit, 96kHz) which ended up at 2009kbps, so you don't need to worry that your high resolution sources will suffer from a maximum bitrate.  AAC is here to stay for a while.

Moving on to the software side of things, I want to talk about a couple of things that affect the audio quality.  These are quite important to get right, because they impact the audio before it is even sent to your sound card or DAC.

The first thing I want to talk about, and the one that can have the most bearing on quality are equalisers.  In my opinion, equalizers don't have a place in high quality audio.  When I was a kid, I was under the impression that CDs were simply mastered to sound a bit flat so that they didn't sound overly bright or bassy on different setups.  Now that I have got a good quality setup, I realise that it wasn't the CDs that were made to sound flat, it was simply my audio gear that made them sound that way.

Consider recording studios.  We know that they spend insane amounts of money on high quality headphones and monitor speakers.  These are designed to be as neutral and realistic as possible, and the recording is mixed and levels adjusted, according to how it sounds coming from their speakers/headphones.  In order to hear what they heard in the studio, we also need a high quality, neutral setup and equalizers have no place in obtaining this goal.

Disabling EQ and any other sound processing is especially important when using a DAC.  EQ alters the audio levels (and in turn the quality) before it's even sent to the DAC, so the DAC is then forced to deal with pre-processed audio which will give sub optimal results.  How can the DAC accurately decode the audio if the contents have been changed before hand?

Another, more detrimental effect of equalisation is clipping and distortion which can occur when the level of a frequency range is already close to zero, but is equalised to an extent that would ordinarily cause the level to go positive.  For example let's take a bass range that is already at -5db.  If we add 10db to that in an equaliser, it will cause it to clip since the audio cannot go above 0db.

There are two methods of equalisation.  One is to boost the frequencies requested by the user, which can often lead to distortion (such as the example I just gave, and the awful EQ on the iPod).  The other method is to reduce the amplitude of the other frequencies, so the higest level of boost actually becomes neutral, and anything lower than that is effectively a decrease.  In the second method, adding 10db to the bass frequencies would leave the bass range at -5db to prevent clipping, but all other frequencies would be dropped by -10db to create the effective 10db bass boost over the rest of the frequencies.

Some media players with fixed EQ levels already do this, for example if the maximum you can boost a range by is +15db, then you will find that all the frequencies are already at -15db when the EQ is flat to prevent boosting causing clipping.  The only downside to this method is that the volume levels are lower.

If neutral sound isn't your kind of thing and you would prefer coloured sound, then it's generally better to achieve the type of sound you want through careful choice of amplifier and headphones, rather than using an equaliser.

Finally I want to mention media players and codecs.  As far as lossless codecs go, your choice of media player isn't that important, but for lossy codecs such as MP3 and AAC, there can be slight differences in quality due to the accuracy of the decoding.  Fortunately most media players have a choice of plugins (such as Winamp) or software like Windows Media Player which uses the directshow framework and has a huge choice of decoders available.

Windows Vista also introduced a new audio API called WASAPI.  In short this is ideal for DACs because it bypasses any OS processing of the sound and allows bit perfect transport.  Also of interest is a feature called exclusive mode renderer.  While audio is playing using WASAPI in exclusive mode, all other sounds are suppressed, so that means you can listen to music and not be bothered by system sounds, or audio from websites as you browse.  Foobar 2000 has WASAPI built into it, and it is available in Winamp via a third party plugin from Maiko, although at the time of writing, Maiko's exclusive mode renderer is incomplete and somewhat buggy.

As you are looking round for headphones, you will no doubt encounter some specifications.  Although they aren't critically important, they can give us some clues and other useful information.  Here are the specifications for the K701 which I will use as an example.

Headphone Type: Open
Headphones tend to come in two types; open and closed, which refers to the back of the unit.  Closed headphones have a solid back and open are usually some form of mesh.  Open headphones tend to offer the better sound quality of the two and generally sound more natural (I also feel that closed back headphones cause a little reverb from the sound rebounding off the outer case).  Unfortunately, open back headphones typically don't have the same kind of bass punch that closed types have.

Open back headphones tend to be more comfortable for long use and your ears don't get stuffy since the air can get to them.  The main down side to open headphones though, is that they leak a lot of noise, and also noise can get in easily which makes them poor for outdoor use.  Although there isn't anything wrong with the bass reproduction on open back headphones, they can sometimes lack a bit of the punch that closed types offer.  In my opinion, open headphones, despite their downsides, are still better than closed.

Frequency Range: 10Hz - 39.8kHz
This tells up the lowest and highest frequencies the headphones can produce, however there are a couple of things to note about frequency ranges and why they aren't as important as you might think.  The first is that for CD audio, the normal frequency range tops out at 22.05kHz (although digital audio is sampled at 44.1kHz, the nyquist/effective frequency is half of that).  The second is that the average range of hearing for a human is 20Hz to 20kHz.  That makes the fact that these headphones go to 39.8kHz largely irrelevant when talking about CD audio since there are no frequencies higher than 22.05kHz, and most people can't hear above 20kHz anyway.  If you are buying your setup to listen to CD audio, then you should be fine as long as your headphones cover 20Hz to 22kHz.  The only thing I could say about headphones with such a high frequency response is that if offers a bit of overhead, so that you know if it can do 39.8kHz, then it won't struggle at 22.05kHz at all, compared to headphones that top out at 22kHz.

THD: <1%
THD, or Total Harmonic Distortion gives us information about how the headphone perform at high volumes.  Basically, it is how the driver is able to respond under a load.  A high THD will usually cause popping, cracking or general distortion in how the music sounds.  Needless to say, you want this to be as low as possible.

Impendance: 62 ohms
Impendance is one of the more useful specifications as it gives us a clue about how easy or hard it is to drive the headphones.  Headphones for portable devices tend to be 16 or 24 ohms, and the higher the rating, the more power you need to get the same volume levels.  In other words, the K701 at 62 ohms are a lot quieter than my V700 at 24 ohms when using them on my mobile phone.  I would say that anything over 60 ohms benefits from an amplifier, and anything under may get away with using the stock output.  High quality headphones that have low levels of hiss usually have high impendance as a result, so don't assume that high impendance is a bad thing.

Max Power Input: 200mw
This simply tells us the maximum milliwattage the headphones can handle without damage.  This is usually not of much interest since at the maximum power ratings for most headphones, it would be so loud it would be uncomfortable, and damage your hearing.  Some headphones such as the Sony V700 and XB700 handle up to 3000mw (3 watts), which is probably two or three times louder than most laptop speakers.  It should also be noted the the power your amp can deliver to the headphones depends on their impendance.  The Yulong A100 for example can provide 1000mw at 33ohms at full volume, but drops to 343mw at 50ohms.

Efficiency: 105dB/V (99.8dB/mW)
Also known as Sound Pressure Level or sensitivity, this is a measure of how loud the headphones are at a given input level.  This can also be a bit confusing due to the fact that manufacturers measure this in different ways.  Sennheiser and AKG tend to use dB/V, where most other companies use dB/mW.  You can convert dB/V to dB/mW with the following formula.  Just change dB/V to the value supplied in the specifications and paste this in google search.

By comparison, the Sony XB700 have 106dB/mW compared to the K701's 99.8dB/mW.  This is probably owing to the differences in impendance more than anything else.

Suggestions should come later.

Saturday, 7 May 2011

Headphone Amps and DACs

Shortly after I bought the AKG K701 as an upgrade from my dying Sony MDR-V700, I started looking around at ways of improving the audio quality from my laptop.  I had it in my mind that I wanted a new soundcard (which in my case would have been USB since it's a laptop) plus a seperate amp.  Soundcard output levels are much the same, so the K701 would have sounded just as quiet on a top end soundcard as onboard.

I spent some time looking around, trying to find an external soundcard that was at least as good as the X-Fi Elite Pro that I had in my last desktop computer but to no avail.  All the USB soundcards I found were low end.  As I was looking around, I came across threads with posters suggesting DACs instead.  After a bit of research I found the right DAC for me.

I'm lucky enough to hang around with a bunch of cool people that love music and appreciate quality too, so I'm going to explain a little about headphone amplifiers and DACs, and why they are a better alternative than sound cards.

An amplifier simply increases the volume of an input signal.  The features can vary between amps but they all serve the same basic purpose - to take a low power input signal and turn it into something powerful enough to move drivers and in turn, air.  Standalone amplifiers should only be considered if you have a good source, since an amplifier does no decoding of any sort (it just amplifies an analog signal).  In general, you'd only buy a standalone amplifier if you have a seperates hifi system with good quality RCA outputs, or a very high end sound card with RCA out.

The thing to remember is that you get out what you put in.  That means if you connect a low quality laptop audio out to the amp, you will get low quality laptop audio out, but just at higher volumes.  Similarly if you connected a cassette player to your amp, you will get the same hissing, low quality sound.  You may notice a small improvement simply due to the fact the amp has more power, which will usually present itself as slightly fuller bass.

So if your source is high quality and already has a headphone out, why would you buy a seperate amp?  There are a few reasons.  The first and most common reason is that some headphones require more power to drive than others.  This is a result of their resistance (impendance), measured in ohms.  My Sony V700 are 24 ohms and were loud enough for me not to max out the volume on my old laptop.  The AKG K701 on the other hand, are 62 ohms and because of the extra resistance, require more voltage to reach the same listening levels.  With the AKG I could max out the volume level on my laptop and still be left wanting a little more.  The K601 are even more power hungry at 120 ohms and would sound relatively quiet on most headphone out jacks.

The other reason is that headphone outputs in most devices always leave something to be desired.  Portable devices such as the iPod are specifically designed with headphone output, but the limited power of the player and often compromised circuit design due to cost and space means you can get bass rolloff.  Fortunately, you can buy portable headphone amps if it bothers you that much.

Take a look at this image.  This is a 40Hz square wave.  This is a tough test for an amplifier, because it requires it to drive to full voltage, hold it for a short while then back in the opposite direction.

Here we have the iPod 15GB playing back the 40Hz square wave.  On the left is with no headphones connected, and to the right is with the standard Apple headphones

As you can see, unloaded the iPod does a fine job of playing the file accurately, but once load is applied the internal amp runs out of steam and cannot sustain the voltage for the required time.  You have to wonder that if such a difference is seen here, that what kind of difference it will make to your music if signals are being distorted like this?  As mentioned earlier, this specific problem is typically recognised as thin bass.  Now you can see why bass boosting headphones and equalizers are so popular.  They are a workaround for poor amp design.  I can only presume this effect is magnified when using larger, more powerful headphones.

That is the benefit of a dedicated headphone amplifier.  The better design and having its own power supply means it can better sustain the voltages required of it, rather than falling off like weak internal amps.  Even for portable amps there is still a benefit because the amp has it's own battery rather than sharing a power source with the iPod or phone.

Some people use headphone jacks on stereo amplifiers, but since these are designed to drive speakers primarily, the headphone output is usually secondary.  There's nothing to say that the headphone output on a £500 stereo amp is going to be better than that of a £200 headphone amp, in fact it's likely to be the opposite.  As important as good amplification is, you also need a quality source, which brings me on to the next section:

A DAC is a Digital to Analog Converter.  Its job is to turn digital signals into analog, which is then passed on to the amplifer and then to the speakers/headphones.  DAC chips can be found in any digital music device and they come in all kinds of sizes and specifications.  DAC chips are found in CD players for example, which is why you can plug those directly into an amp (since the digital signal has already been converted to analog).  A DAC alone does not provide a suitable signal for driving speakers or headphones, so the signal must pass through amplification first.

For the most part, when I refer to a DAC, I'm talking about an external device that pretty much does the same job as a soundcard.  They are usually available with USB connections, require no special drivers and work perfectly fine on Windows, Mac and Linux.  All that's required is that you change your audio output in the control panel to the DAC.

The vast majority of USB DACs have a built in amplifier and headphone output, but it is possible to buy standalone DACs in which case a standalone amp must also be used.

Using an external/USB DAC bypasses any existing audio hardware, so it's an ideal solution for getting away from poor quality and noisy internal DACs.  Another advantage is since they are seperate from the computer, they are less likely to pick up interference from power supplies the other circuitry (eg WLAN card).  The DAC chips used in the external DAC device are generally a lot better quality than those found in sound cards too.

If you are reading this post, then it's probably because you want to buy some decent quality headphones or upgrade your computer audio.  Although the most common usage for a DAC is to use as an external soundcard via USB, most of them also come equipped with Coax, Optical and AES inputs which means you can use them in a variety of other ways.  Combine that with the RCA outputs and you've got a device with a lot of potential in a seperates system.

A DAC can be used in such a way to turn a cheap DVD player into an audiophile grade CD player.  How you ask?  The trick is in using the optical output.  By using the optical out, you bypass the DAC stage in the DVD player, and the digital audio is sent to your external DAC and converted to analog.  Connect the RCA outputs to a speaker or headphone amp and enjoy the quality.  You can also use an external DAC to play computer audio through your hifi; simply connect the PC to the DAC with USB or optical, and the RCA out to your stereo amp.

When buying a DAC, you should aim for the highest quality you can afford.  The amplification can come later, or on most models, there is a built in headphone amp.  Good quality source is important, and as I explained earlier, there's no point cutting corners getting a low spec DAC that will show noise at high volumes.  A source should also be completely neutral and transparent.

With regard to connecting the DAC to your computer, you usually have a choice of USB or optical (at least on Vaio and Macbook laptops).  Optical is almost always the better connection, and I'd suggest you go with that.  My experience with Windows 7 is that I could not choose 16 bit output to the DAC (16 bit being the bit depth CD audio uses), so the OS only gave me the choice of 24 bit at 44.1, 48 and 96kHz, which meant the bit depth was upsampled before it was sent to the DAC.  That's not a problem in itself, but most DACs upsample the source anyway, so it's just a pointless process which can be avoided with using optical since you can set 16 bit, 44.1kHz.

Another advantage with optical is that there is no electrical connection between the computer and the DAC.  This means less chance of interference.  I found that when using the D100 and A100 with my laptop plugged into the mains that I would get a lot of interference, and it was really quite noticable.  I ordered an optical cable and just like that it cured the problem.  I'm not sure how interference was transmitted via USB, but according to my experience, it can happen.

The only downside to using optical is if you switch between speakers and the DAC a lot.  Generally it means going into the control panel and setting the optical or speakers as the default device.
Protip: Right click the speaker tray icon and choose playback devices

This can get quite annoying.  During my time using USB, I set the DAC as the default device so it would take precedence when connected, but when disconnected Windows would fall back and use the speakers.  Unfortunately it seems that the OS has no knowledge of devices being connected to the optical, but that can also work in your favour since it means you can disconnect it without your media player exploding or that annoying hardware disconnected sound/notification.

Buying an Amplifier or DAC
Now that you have an idea of what amplifiers and DACs do, it's time to look at some of the options.  As mentioned in my previous post, I own the Yulong A100 amp and D100 DAC, so I'm happy to vouch for those and answer any questions if you are interested.  Here's a short list of gear that's worth looking into.

Stand Alone Amplifiers
These have no DAC section and are intended to boost the level of good quality sources.  These should be used in combination with a DAC, or some other high quality source.

Matrix M-Stage
Price: $220 excluding shipping
Input: 2x Stereo RCA
Output: 1x Stereo RCA, 1x 6.3mm Headphone
Where to buy: Shenzhen Audio Store (official outlet)
Review: Project86 at head-fi
The Matrix M-Stage is a great amp for the money.  It was hard for me to choose between the M-Stage and the Yulong A100, but the neutrality of the A100 was what won me over.  Project86 has described the M-Stage as the darker sounding of the two and comments that the M-Stage has a little more low end.  This amp is quite popular with fellow K701 owners for that fact.  Despite its low price, it's essentially a clone of the Lehman Black Cube Linear, which retails at £600 ($985).  This amp has a very good reputation and I'd be happy to suggest it. 

Yulong A100
Price: $330 excluding shipping
Input: 1x Stereo RCA
Output: 2x 6.3mm Headphone
Where to buy: Shenzhen Audio Store (official outlet)
Review: Project86 at head-fi
The Yulong A100 isn't cheap, but it features top of the range opamps.  The only thing I feel lets it down is the lack of inputs.  Sound quality is excellent.  An ideal amp if you have a stand alone DAC, but if you already have something like the Yulong D100, the amp in that is good enough for most people not to notice much difference.  It largely depends on your headphones, so bear that in mind.  See this post for more of my impressions.

Combined Amplifier/DAC
These are the best way to get started in high quality audio, and some of them are good enough that you will not even feel the need to upgrade.  If you want to jump straight in to a seperate amp/DAC system, look at standalone DACs so you are not paying for a headphone amp section that won't even be used.

FiiO E7 (Portable Amp/DAC)
Price: $100 excluding shipping
Input: 1x USB, 1x 3.5mm Line In
Output: 2x 3.5mm Headphone
Where to buy: FiiO
Review: Misc E7 Reviews
This is a great little portable unit.  Not only will it amplify the output from your phone or portable audio player, but it also has 2 headphone out jacks meaning you can share with a friend.  What's more is that it also doubles up as a DAC.  Obviously, the DAC section isn't going to be as good quality as the rest of the choices here, and neither is the amplifier, but at $100 can you really complain?  Decent signal to noise ratio (>100db) but probably not enough to notice a difference from a decent onboard soundcard. 

Maverick Audio D1
Price: $200 excluding shipping
Input: 1x USB, 1x Coax, 1x Optical, 1x Stereo RCA, 1x 6.3mm Line In
Output: 2x Stereo RC, 1x 6.3mm Headphone
Where to buy: Maverick-Audio
Review: Maverick D1 Condensed FAQ
This unit is the definition of bang for buck.  At only $200 it has more inputs and outputs than more expensive models, and features a very powerful amplifier which can deliver up to 300mw at 600ohms - more than enough to ruin your headphones and your hearing.  You can also upgrade it by replacing the  opamps, which is a feature you rarely see.  Be sure to check the review link above for tons of information.

Matrix Cube DAC
Price: $300 excluding shipping
Input: 1x USB, 1x Optical, 1x Stereo RCA, 1x BNC
Output: 1x Stereo RC, 1x Coax
Where to buy: Tam's Audio
Review: Project86 at head-fi
The Matrix Cube was one of my first choices for DAC, before I learned of the Yulong D100.  My intention was to buy the Matrix Cube and pair it with the Matrix M-Stage.  While not as fully featured as the Maverick D1, it's assumed that with less features and a higher cost, that it has been invested in the audio quality, which is why we are here to begin with.  If this is in your budget, be sure to check out Project86's excellent reviews.  The cube has a decent SNR at 109db and a wide soundstage.

Yulong D100
Price: $450 excluding shipping
Input: 1x USB, 1x Optical, 1x Coax, 1x AES
Output: 1x Stereo RCA, 2 x XLR
Where to buy: Shenzhen Audio Store (official)
Review: Project86 at head-fi
I eventually decided to go for the D100 based on the strength of Project86's review.  The most expensive amp/DAC combo here, but also has the highest SNR at over 120db.  An excellent all in one unit.  The DAC section is highly praised and the internal amp is comparable (but slightly lacking) to the Matrix M-Stage.
To quote Project86, "I find the Yulong amp to be very neutral and transparent sounding. I've owned various models in the $1,000+ range including Benchmark DAC1, Grace Design M902, and Lavry DA10. This Yulong competes well with those units and is even superior to some of them in certain aspects. The headphone amp, while not quite on the level of the DAC section, is still quite good, and you'd need to spend a significant amount of money on a standalone amp to get much improvement."

Tuesday, 3 May 2011

My Audio Gear

Since music is something I enjoy a lot (even moreso after rediscovering it thanks to a certain series), I thought I'd post my current setup which will serve as a reference for some later posts.  There is quite a bit of interest in the K701 headphones in particular, and I also think an amp/DAC is something everyone should have if they appreciate music and quality.  DACs in general are way better than soundcards, but I'll save that for another, DAC specific post.

AKG K701
The K701 are my default headphones.  They were expensive at £200 (currently the equivalent of $330) but perform very well.  They are often compared to more expensive models which makes me feel like they are good value.  That said, you can't simply buy these headphones and expect everything to sound amazing.  Just like you need a good amp to drive powerful, expensive speakers, you need a good headphone amp to drive powerful, expensive headphones.  After all, it's the same concept just on a smaller scale.  Think about the Sennheiser HD800.  At £1000, would you expect a laptop soundcard to drive those to the same potential as some £10 headphones?  No.  Source quality must improve with output quality.

Initially I was a little dissapointed.  I felt that the highs were a little less pronounced than my Sony MDR-V700, and that they also lacked bass (it should be noted that I didn't have an amp or a DAC at that time).  It may have been that my source wasn't very good (pretty awful laptop audio...), but it might also have been that the K701 require quite a long burn in time.  Some people dispute burn in and some swear by it.  My opinion is that anything mechanical can improve or degrade with time/wear.  We are all familiar with the concept that things wear with age such as car clutches, brakes and hard disk drives, but with speakers and headphones it is believed that sound quality improves with wear up to a point.  The theory is that the material the driver is made from becomes worn and more flexible with use and can operate more freely.  Of course I don't believe in burn in for things like solid state amplifiers or processors.

Now I feel that there is no comparison between my K701 and V700.  The K701 simply has better soundstage, bass and treble.  Is that a result of burn in?  Or is it the case that with a much better source it's easier to tell the difference between the headphones?  Could be a bit of both I expect.

The K701 are impressive but discreet.  At no point have I put these on and thought, "WOW".  Well that's not exactly true because I'm somewhat impressed everytime I put them on, but what I mean is that the sound doesn't jump out at you.  These headphones are designed to be neutral and accurate, so with a good source, music should sound somewhat like it was intended to (since studios invest crazy amounts of money in high quality, neutral output).  The thing is not everyone appreciates the neutrality as we have become so used to hearing music with bass boost, equalizers and subwoofers.  The thing is these exist only because of shortfalls in driver ability/design.  If you have an accurate, high quality driver, why would you need to boost the bass or treble?

In fact boosting bass is one of the easiest ways to sell headphones, since it's the easiest thing for a listener to pick up on.  Why waste time developing and tuning drivers that can accurately represent frequencies over 16kHz if few people can hear it?  Unfortunately your average person doesn't appreciate the neutrality of these headphones, and compared to "consumer" headphones like Beats by Dre which boost low frequencies, the K701 will naturally sound flat in comparison (since you automatically feel that more is better).

The only drawback to the K701 is the fact that to get the most out of them you need a decent source and an amp.  That's not to say they are so power hungry that you can't use them in normal headphone sockets as is the common misconception.  You can, just the maximum volume is not as high as I'd have liked it to be, and you are more likely to get bass rolloff with stock soundcard/portable player amps than a dedicated headphone amp.

They also leak a lot of noise.  The noise coming out of the back of them is loud enough for my sister to identify what I'm listenting too... In another room.  The noise leakage is owing to their open back design.  Open back makes them a lot more comfortable for long use as you don't find your ears getting hot and sweaty (plus the cloth earpads as opposed to leather help with this too).  The sound is a lot more natural and doesn't have the usual "closed in" feeling that headphones usually have, but one of the other downsides to open back is that bass doesn't quite have the same level of impact.  It's strange, drums sound amazingly real and can rattle your eardrums, but you seem to lack the ear ticking sensation of air being forced down that you get from closed back designs.  If bass is really that much of a big deal for you though, there are plenty of headphones designed for that purpose (such as the Sony XB700).

One sensation that I haven't quite got used to yet is that some music sounds dull.  By that I mean the high frequencies appear to lack treble, and it makes me tempted to fiddle with the EQ, which is something I have left on flat ever since buying the K701.  If you are going to EQ, then there's no point buying neutral headphones in my opinion.  This dull sounding treble is certainly not a shortfall with the headphones (although it feels like it at the time).  Switching to a better mastered track reveals just what they are capable of, so bear that in mind.  You get out what you put in, and you can really notice the difference in recording quality and mastering between artists and tracks.

Yulong D100 DAC
Finding an amp and DAC to suit me was the hardest part.  Initially I intended to buy a combined amp/DAC for £200, which after some thought I decided to split it and budget £100 for a DAC and £200 for an amp.  I couldn't find anything that appealed to me, but I happened to come across the Yulong D100 at and a very nice review by project86.  I wanted to avoid buying an all in one unit, because I'd rather have had a dedicated DAC and a dedicated amp, but it turns out the Yulong D100 had an excellent DAC and a very good amp, and was within what I wanted to spend at £320.

The Yulong D100 is a very nice unit.  The DAC section is very highly praised and the amp is surprisingly good (uses the same OPA2134 opamp as the Matrix M-Stage, which is a clone of the £600 Lehman Black Cube Linear).  Unfortunately it has no analog inputs, so you can't plug an RCA source into it and use its headphone amp.  It's strictly for digital input (Coax, USB, Optical, AES) but has balanced outputs and standard RCA out so you can use it as part of a seperate system (eg connect a DVD player to the DAC via optical and the DAC to your amp).

The D100 has 2 headphone out sockets.  They are intended for different impendances, and I find the high impendance output is best for the K701.  I feel that some of the dynamics are lost when using the low impendance output, but I don't think this is going to be a problem for low impendance headphones (32 ohm or lower).

There are also 2 sound modes.  The first is flat, unaltered sound and the second mode reduces frequencies 16kHz and above by -3db.  The effect is actually not that easy to notice, but it was intended to be used with headphones that are heavy on treble.  I never felt the need to use the second sound mode.

Overall it's a great DAC and amp combo and I'm happy to suggest it.  Like with most things though, there's an element of diminishing returns.  By that I mean you could probably pick up the excellent Mavrick D1.  At $200 it's less than half the price, but I don't think the difference in sound quality will be that much between them.  The Yulong D100 is excellent quality, but value or bang for buck wise, you can probably do better.

Yulong A100 Headphone Amp
I had always had it in my mind that I wanted a seperate amp to go with my DAC to make the best of what I've got (since although the amp in the D100 DAC is great, it didn't do the DAC section justice).  One amp that kept popping up was the Matrix M-Stage, which is a component for component clone of the Lehmann Black Cube Linear and cost 1/3 of the price (Chinese, how do they work?).

I lurked around on the forums for a bit trying to gather information to make an educated decision which was when I learned that Yulong were making a dedicated headphone amp to match their DAC.  This amp is quite impressive.  At first I found it hard to tell the difference (from listening to the D100 one day and the A100 another) but if you match the volume levels and switch between them while playing something, the D100 sounds somewhat flat in comparison (which is impressive because the D100 never sounded flat to begin with).  The A100 feels like it has more detail, and is more lifelike.  Drums really do sound like drums, cymbals are more apparent and aren't hidden in the mix of everything going on, but I do find the improvement varies depending on the source and type of music.

Great sources benefit more than average ones rather than it seeming like an improvement across the board.  I attribute this to the amp and DAC combination just being detailed and neutral rather than the A100 adding anything or boosting any frequencies over the D100's own amp.

The A100 amp cost me £240.  It's a nice unit and it matches the D100 DAC (with some slight design differences, looks like the volume pot and circuit board is higher up in this one).  The RCA jacks are notably better quality than on the D100, but unfortunately it does not have balanced input which is weird considering the D100 DAC had balanced output.  The one downside to this amp is that it only has one pair of RCA in and no other inputs.  I suspect this was a decision made to keep costs down, because internally they use the highest spec opamps currently available, the OPA627B.  If you enter that in google shopping, you will see that amps using those opamps usually cost thousands of pounds.

The headphone jacks are also higher quality and the fit is quite snug.  At first I was worried that it would scratch the gold plating off of the K701 jack, but they seem to have become less tight over time.  It's a class A amp and it does generate more heat than the D100, so Yulong drilled some holes in the top to allow it to cool.

Overall that brings my K701/D100/A100 combo to an eye watering £760 ($1250).  Would I have spent that much in one go?  I doubt it.  This was the result of upgrading a bit at a time.  Like most things however, there is a case of diminishing returns which I may also discuss later.  In other words performance/price.  While the Yulong D100 DAC is more than double the price of the Maverick D1, the quality doesn't icrease linearly with price