As you guys all know, I have had my fair share of headphone amplifiers (and headphones), and there is one thing that repeatedly seems to come back to haunt me.
It is my opinion that if you own an amplifier like mine (which has a built in headphone socket), and a similarly specced source component to what I use, I think that cheap headphone amps are a waste of money, and even the more expensive ones, which will undoubtedly be better than the headphone socket of a Rotel amp, are probably well down the road of diminishing returns anyway.
OK, for some people, a headphone amp is essential, since their kit may not include a headphone socket (amp), or it might, but may well be underpowered (CD player), and for those people, a headphone amp, for headphone listening, will be essential.
However, if like me, you have an amplifier with a pretty good headphone output, with certain headphones there is virtually no point whatsoever in a headphone amp. However, with others there may be more of a need.
This is what I have found:-
1. Lower impedance headphones tend to seem to take more advantage of headphone amps than higher impedance ones. The reason for this is to do with the output impedance of the headphone jack. The output impedance on a typical headphone amp will be close to 0 ohms. When you plug in a set of headphones, the impedance of the headphones contributes to the overall impedance in the "chain". So, for example, its clear to see that 0+32 ohm's = 32 ohms is probably a good thing for most headphones. However, take an integrated amp, which due to the resistor based design, has an output impedance of 220 ohms at the jack, this will more severely affect the sound. However, if you plug 250 or 300 (or even 600) ohm headphones into the jack, although they are still affected, it seems to affect them far less. Without being an expert in electronics, this has universally seemed to be the case in my experience. For example, the headphones that sounded distinctly disadvantaged on my Rotel were the Sony MDR-CD3000, CD1700, AKG K240 and K271 Studio headphones. All of these headphones are 55 ohms or less. Pretty much all of the other headphones were at least 250 ohms, and there seemed to be much less difference between the integrated and a headphone amp in these cases.
2. Having said all that in point 1, it does not always follow that a low impedance headphone will sound bad out of an integrated. I firmly believe that some headphones were designed to be used in such a scenario. Whether that be by design or by the headphones sonic signature, some such headphones will sound better driven by an integrated amp regardless. Examples of headphones I believe were specifically designed for use with integrated amps are Beyerdynamics, the DT831, DT931, DT660 and DT860. All of these headphones are designed to be driven by the INDUSTRY STANDARD output impedance of 120 ohms, and not 0 ohms as most headphones seem to be.
3. Going back to a bit in point 2, the headphones tonality can often dictate whether it'll sound any good on an integrated amplifier or not. Again this may or may not be by design. I personally find that the best headphones to use on integrated amps are definitely on the brighter side of neutral, and not too bassy. This is because when you raise the resistance of the output jack, it tends to have the effect of "warming" the sound, and increasing the perceived power of the bass, and decreasing brightness. With all this in mind, I'd say you wont go far wrong if you choose a headphone that has a highish impedance and a bright sound with not too exagerrated bass as standard for use with an integrated amp. Although you should audition because as I say it doesnt always follow for a low imp. can to sound bad on an integrated, the DT660 and DT860 are good examples of this. Grado also tends to sound quite good in this context. However, I WOULD SERIOUSLY avoid the temptation to go with warm headphones with an integrated amp, as the result tends not to be too involving (read dull).
So, whether one considers a headphone amp should be dictated firstly by whether you have a jack to use already. If not, then obviously there is little choice. However, if one does have an amp with a headphone jack, I'd seriously question the need for one. I think the source is clearly the most important factor here, unless you have an output jack that sounds like total arse. If you have a jack to use, and you dont wish to spend too much cash, then consider a headphone suitable for use in such circumstances. I'd say the performance split was about 60% headphone, 30% source and 10% amp.
Naturally if you want every last drop of performance, and money is no object, then by all means go for an amp, as the best amps will undeniably make some difference, but folks, dont go buying a headphone amp if you already have a good quality jack and expect a huge improvement, because you simply wont get one. My advice to you would be to get down a shop, and audition a number of budget amps like the Creek, Rega, X-Can. If you feel they make a big difference, then be confident in your purchase. However, try not to kid yourself, see it objectively, and if you dont feel there is a big improvement, dont bother. I have found out the hard way, but I will be glad if this thread at least makes people consider carefully their purchase, before doing what I did and wasting good money.
Now, a few words about the Rega Ear vs my Rotel RA-01. The Rega seems to be *slightly* cleaner sounding, but really there is very little in it to all intents and purposes. The Rega is probably a tad more detailed, and definitely brighter. The Rega has a fairly leanish, but fast bass. The Rotel seems to have a lot more slam in the bass, and certainly is no less fun. Actually, a word on headphone bass. Tight bass in headphones IMO can make it sound a touch too clinical, and a bit of overhang gives a slightly more "speaker" like presentation, IMO. Also, the Rotel is a bit warmer, so although it gives slightly less detail, its ultimately a touch less fatiguing.
On that note, I feel like I do not enjoy my music any less using the Rotel amplifier than the Rega. I am not saying that the Rega (or indeed my old Corda HA-1, Perreaux SXH1, X-Can v3 etc) were bad amps, just that as a bang for buck hifi component, they rate as one of the worst VFM "upgrades" for me, which have only ever really sounded different rather than better.
HTHs someone.
