Ok, *why* do I need a headphone amp for HD650?

Discussion in 'Computer Audio' started by alfbaxter, Aug 10, 2010.
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  1. Hybrys
    Yes, volume was matched for me, to 0.1 dB.  (Tested with equipment In my former theatre)

    No EQs for the testing, but I did use both of their EQs extensively in normal listening  I preferred the Clip+ for everything but the sound...  But the sound wasn't far off of the S9.  The S9 is basically better at everything but the highs, where it matches the Clip.  The S9 also had some neat EQ effects but most of them added a bit of noticable distortion before they were even half way up.  (The DSP effects, not the regular EQ.)  The Clip was simple and brilliant, where as the S9 was more full featured.
  2. AlfBaxter
    Thanks for your replies. The Prelude opamp for the front l/r line out is LM4562NA. There is no problem at all with volume, it is easily loud enough and I can't turn it above 60% most of the time without pain. I don't know what the current output is, but I do know it's 5V rms. One reason I was sceptical about the M-Stage is that it has an OPA2134, which I understand is not as good as the one on the Prelude. If such an amp can really improve the way my HD650 sound compared to my current setup, then it must be something else that is going to make the difference.
    Incidentally, I just listened to Brilliant Corners, and I do hear a little harshness in the cymbals, and quite a bit of muddiness in the bass. I would previously have put that down to the recording, but perhaps not...
    Any more views on what an amp can do that my soundcard can't?
    Well your LM4562NA opamp is a used in a line driver circuit.  Used for (you guessed it) driving line level devices such as amplifiers.  This is also why many soundcard feature can amps now because line outputs cannot properly drive high impedance headphones.
    If you try a can amp vs just a line out on a high impedance set you should easily notice the difference.  Nobody is talking about buying a $2000 amp or other exageration people use to try and prove their views.  You can buy reasonable amps for great prices...If you think you need one.
  4. AlfBaxter
    @ROBSCIX: You say that line outputs can't properly drive high impedance cans. I guess there must be some truth in that, but why can't they? Like I said, the line out of my Prelude easily gets my Senns *loud* enough - sorry if I'm being ignorant, but what else is there to driving them?
    I think I may buy an M-Stage just to see, since I'm not totally happy with the sound I'm getting and it does seem to have some symptoms that many associate with lack of an amp. As one poster said, I can always sell it on here if I can't tell the difference.


    Simply put, Impedance can be seen as a opposition to current in the signal so if your output doesn't have the power to drive these cans you may get reasonable volume but you will notice lack of bass and other sonic aspects.  The Prelude is not designed to drive high impedance cans.  Don't take my word for it.  See if you ucan get your hands on a can amp and test for yourself.  Make sure what you buy can be returned, this way your not out any money.
  6. AlfBaxter
    Thanks again to all who posted. For anyone who's interested and doesn't already know this, I did a little more research based on some of your replies and it seems the real issue with my soundcard is high output impedance compared to the impedance of my headphones.
    Damping factor (as I understand it, the ability of an amplifier to control resonance in a loudspeaker) = load impedance / output impedance, and higher is better. I don't know about the Prelude but the line out impedance of the Auzen Forte is 330 Ohm, which means (assuming the Prelude line out is more or less the same) that I currently have a damping factor of less than 1 with my HD650 (300 Ohm). Output impedance of the M-Stage is 5 Ohm, giving a DF of 60. What's interesting is that poor speaker damping shows up as poorly defined, muddy bass, which is the main gripe I have with my current setup. I found a pretty decent explanation here: http://www.crownaudio.com/pdf/amps/damping_factor.pdf.
    Edit: There's also a coupling effect with high output impedance amps, if the headphones have a non-uniform impedance curve (which the HD650 do - higher impedance at low frequencies). The available voltage is divided between output and load, based on relative impedances. If the impedance of the load and output are close, then changes in the load impedance will produce significant changes in the voltage divided with the load, altering frequency response so that it matches the impedance curve. So (again, as I understand it, which may not be so well), The fact that the HD650's impedance peaks at the low end means you will get artificially pronounced bass if it is used with a high output impedance source. This effect is obviously much less if the output impedance is much lower than the load. More info here: http://www.avguide.com/blog/why-headphone-amps-sound-different-frequency-responseimpedance-issues.
    Sounds convincing to me! Anyway I've decided to buy an M-Stage, and will let you know if I can tell the difference.
    Yes, as was mentioned the cards outputs are meant for driving a line level device.
    It is a combination of the cards outputs and your cans input.  You need a device in between to power the headphone properly or as I said, you will get poor bass..etc
    Hope this helps
  8. FallenAngel Contributor
    LM4562 is quite a nice line driver capable of going down to 600 Ohms (as per datasheet)... but toss a pair of 32 Ohm Grados at it and it sounds like crap.  Personal results/preference may vary for 300 Ohm Sennheiser, 600 Ohm BeyerDynamic or AKG.
  9. drews

    Sorry, but not true.  When I started with this hobby I suspected and hoped that that this was the case but it just isn't.  Even swapping op amps in a cmoy has an obvious effect on the sound.  If you actually a/b some amps and can't detect any difference with decent phones I guess you're lucky since that will save you some cash but equating amp choices with cable choices is not really valid IMHO...
  10. nullstring
    I hate when people like JxK come around and spout their opinions as facts.
    It completely junks these threads and drives everyone off into a spiralling argument and in the end the topic is not usually satisfied.
  11. Currawong Contributor
    Not to say one can't enjoy listening with cheap gear, but this is worth reading and considering. Quite a few people have said they are fine with the HD-650s out of the STX.  Nothing wrong with that.
  12. freestyler
    Even my asus xonar d1 could drive the hd650 to higher than needed volume.
    Volume does not mean anything at all.
    Sound was flat, uninteresting, no character and overall a "blob of sound".
    With the essence ST the dynamics were much improved. Every time a drum "hits you" you want to bang your head like when you are in a live. 
    I only use the hd650's like once every 10 days (rest time i use a headset senn pc160, because most of the time on my pc i spend on gaming-voip)
    But when i use them i always have a big smile on my face for the whole duration. (hours)
    For all the above you need high quality recordings else do not bother at all.
  13. Satellite_6
    My 650s sound perfectly OK plugged straight into my Cowon but they sound better when using i7 -> EF2A -> HD 650s. . .
  14. Phelonious Ponk


    Of course terms like "harsh" and "boom" represent the fuzziest kind of subjectivism and what I think they mean might not match your ideas, but "Brilliant Corners" is pretty well-recorded, and the cymbals and bass sound good on my systems. So I would guess your 650s aren't getting enough juice. What else can an amp do? All those things that amps do -- lower distortion, lower noise, better channel separation, faster transient response. If the amp in question has a DAC in it, it can get all of the analog audio stages out of the noisy environment of your computer. An amp can do a lot of good things. Do watch out for the audiophile voodoo and extremely diminishing returns, though. The difference between an underpowered headphone jack and well-designed $200 amp, or even the headphone section of a good receiver, can be very noticeable. The difference between that and a $2,000 amp? Incremental if audible. That's not to say that it always gets you nothing, or even that it's not worth it. But the first few hundred bucks, spent right, gets you the lion's share of the goodness.
    P's mantra: Only buy with a liberal return policy. Audition blind. Send back everything that doesn't clearly earn its keep.
  15. maverickronin

    You'd need to have soundproofed listening room or something to do that with the HD650s.  They will get pretty harsh at quite moderate volumes if they don't have enough juice.
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