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Amp Question
have recently ordered a pair of Sennhieser HD 558 Headphones. I want to know if I need an amp with my current set up. I have a Creative Labs Sound Blaster X-Fi Xtreme Audio sound card and a 650 watt power supply if that even matters.
(I put this in the wrong category initially sorry about that)

  • saratoga
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Amp Question
Reply #1
Those are fairly high impedance headphones with good sensitivity, so you would generally not need to amp them.  No idea if that creative card is any good though.

Amp Question
Reply #2
Those are fairly high impedance headphones with good sensitivity, so you would generally not need to amp them.  No idea if that creative card is any good though.

They're decent I blew my computer budget on my CPU and GPU so I had to get a card in the $ 40-50 range.

  • saratoga
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Amp Question
Reply #3
They're decent I blew my computer budget on my CPU and GPU so I had to get a card in the $ 40-50 range.


You probably should have just not got a card.

Amp Question
Reply #4
Those are fairly high impedance headphones with good sensitivity, so you would generally not need to amp them.  No idea if that creative card is any good though.

They're decent I blew my computer budget on my CPU and GPU so I had to get a card in the $ 40-50 range.

What about if I connected them to my TV would I need an amp then?

  • saratoga
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Amp Question
Reply #5
Those are fairly high impedance headphones with good sensitivity, so you would generally not need to amp them.  No idea if that creative card is any good though.

They're decent I blew my computer budget on my CPU and GPU so I had to get a card in the $ 40-50 range.

What about if I connected them to my TV would I need an amp then?


Absolutely not.  Powered devices will never require an amp, they have a built in one.

Generally speaking, if you have to ask if you need an amp, you probably are in a use case where an amp will not be required.

Amp Question
Reply #6
Those are fairly high impedance headphones with good sensitivity, so you would generally not need to amp them.  No idea if that creative card is any good though.

They're decent I blew my computer budget on my CPU and GPU so I had to get a card in the $ 40-50 range.

What about if I connected them to my TV would I need an amp then?


Absolutely not.  Powered devices will never require an amp, they have a built in one.

Generally speaking, if you have to ask if you need an amp, you probably are in a use case where an amp will not be required.

Thanks man!

  • skamp
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  • Developer
Amp Question
Reply #7
I hate to sound like a broken record (I'm already annoying myself as I type this), but you're going to need a fairly low output impedance with those (<6Ω, ideally), or they won't sound like they're supposed to (the HD 558's have a huge impedance spike at 100 Hz). You might need a headphone amplifier with low output impedance if your X-Fi's impedance is too high (I have no idea of its actual value, it could be anything).

http://graphs.headphone.com/graphCompare.p...phID%5B%5D=2861
  • Last Edit: 29 April, 2013, 05:30:39 AM by skamp
See my profile for measurements, tools and recommendations.

  • pdq
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Amp Question
Reply #8
I hate to sound like a broken record (I'm already annoying myself as I type this), but you're going to need a fairly low output impedance with those (<6?, ideally), or they won't sound like they're supposed to (the HD 558's have a huge impedance spike at 100 Hz). You might need a headphone amplifier with low output impedance if your X-Fi's impedance is too high (I have no idea of its actual value, it could be anything).

http://graphs.headphone.com/graphCompare.p...phID%5B%5D=2861

Uhmmm... Why would a spike of HIGH impedance need a LOW output impedance amplifier?

Amp Question
Reply #9
I hate to sound like a broken record (I'm already annoying myself as I type this), but you're going to need a fairly low output impedance with those (<6?, ideally), or they won't sound like they're supposed to (the HD 558's have a huge impedance spike at 100 Hz). You might need a headphone amplifier with low output impedance if your X-Fi's impedance is too high (I have no idea of its actual value, it could be anything).

http://graphs.headphone.com/graphCompare.p...phID%5B%5D=2861

Uhmmm... Why would a spike of HIGH impedance need a LOW output impedance amplifier?



Good question. The fact that the overall curve stays above about 50 ohms eases the source impedance requirements on the amp.  If you set your goals on amp source impedance goals based on the minimum impedance the maximum impedance can go to the moon and it is handled.

A load that stays above 50 ohms can have low coloration with an amp with a source impedance of  like 1 ohm, but a load that goes down under 16 ohms may have audible coloration with the same amp.

  • skamp
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  • Developer
Amp Question
Reply #10
Uhmmm... Why would a spike of HIGH impedance need a LOW output impedance amplifier?


You need to aim for the lowest impedance. Though, I did some math, and the FR variation that I've come up with, with 22? and 75? output impedance values as real-world examples, isn't nearly as bad as I thought (assuming a 1V source):

22? output impedance:
50 / (50 + 22) = 0.694V
275 / (275 + 22) = 0.926V
20 * log10(0.926 / 0.694) = 2.5dB

75? output impedance:
50 / (75 + 50) = 0.4V
275 / (275 + 75) = 0.786V
20 * log10(0.786 / 0.4) = 5.87dB

So essentially, you'll get or more or less pronounced bass boost (though I'm not sure how it would sound / feel, in practice).

Source: http://nwavguy.blogspot.com/2011/02/headph...-impedance.html
See my profile for measurements, tools and recommendations.

  • saratoga
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Amp Question
Reply #11
Uhmmm... Why would a spike of HIGH impedance need a LOW output impedance amplifier?


You need to aim for the lowest impedance.


I think his point is that the lowest impedance is about 60 ohms, which is still quite high, therefore there isn't much need for a low output impedance amp. 

That said, a lot of PCI cards have awful headphone output, so who knows if that Creative card works ok.  Dedicated sound cards can be less noisy than onboard, but in practice they rarely have better headphones amps and sometimes are even worse. 

  • skamp
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  • Developer
Amp Question
Reply #12
Well, the output impedance is rarely published by the manufacturer, so it could be perfect (<1Ω) or it could be insanely high (75Ω for my laptop, >100Ω for my Nexus 7). Best to measure it yourself (here's how I do it, it's actually pretty easy).
See my profile for measurements, tools and recommendations.

  • saratoga
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Amp Question
Reply #13
It is infuriating that no reviewer ever bothers to measure it.  Theres a Russian and a Chinese site out there somewhere that actually bothered to measure a few devices, and they're all almost uniformly awful.  Even many highend devices are 50+ ohm.  My assumption is the older and low end devices are probably not any better. 

I guess the reasoning is that most people buy sound cards to work with speakers, not headphones while people who care about headphones like to buy external devices for whatever reason.  Still, its annoying that you can spend 100+ on a dedicated sound card and get worse performance than some onboard devices.

  • Case
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  • Developer (Donating)
Amp Question
Reply #14
I measured some time ago output impedance of most of my sound cards. Here's a list if someone cares:
Asus Xonar Phoebus ROG control box headphone output: 10 Ω
Asus Xonar Phoebus ROG front speaker output: 94 Ω
Sound Blaster X-Fi Titanium: 32 Ω
Sound Blaster X-Fi HD USB: 32 Ω
Sound Blaster X-Fi Surround 5.1 Pro USB: 10.0 Ω
Sound Blaster Recon3D USB: 0.8 Ω
Sound Blaster Tactic3D Sigma USB: 0.8 Ω
Audioengine D1 USB: 9.5 Ω

Amp Question
Reply #15
Well, the output impedance is rarely published by the manufacturer, so it could be perfect (<1?) or it could be insanely high (75? for my laptop, >100? for my Nexus 7). Best to measure it yourself (here's how I do it, it's actually pretty easy).

Would the FiiO E11 do the trick? I am sure I need an amp they are really quiet and when I play some games even if I increase my volume to 100 I cant hear the game well.
  • Last Edit: 02 May, 2013, 11:59:35 PM by TheChaosofCreation

Amp Question
Reply #16
Well, the output impedance is rarely published by the manufacturer, so it could be perfect (<1?) or it could be insanely high (75? for my laptop, >100? for my Nexus 7). Best to measure it yourself (here's how I do it, it's actually pretty easy).

Would the FiiO E11 do the trick? I am sure I need an amp they are really quiet and when I play some games even if I increase my volume to 100 I cant hear the game well.



Look here:

http://nwavguy.blogspot.com/2011/11/fiio-e11-amp.html

He finds Zout = 0.5 ohms, which should be just fine.

If you have not done so, you might want to read the whole review...

  • skamp
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  • Developer
Amp Question
Reply #17
Note this particular part of the review:

Quote
That means it’s impossible to use it as a regular desktop amp as the battery will end up dead and you can’t listen to it while it’s charging.
See my profile for measurements, tools and recommendations.

Amp Question
Reply #18
Note this particular part of the review:

Quote
That means it’s impossible to use it as a regular desktop amp as the battery will end up dead and you can’t listen to it while it’s charging.




The good news for me is that the E5 has no such issue.

Amp Question
Reply #19
Well, the output impedance is rarely published by the manufacturer, so it could be perfect (<1?) or it could be insanely high (75? for my laptop, >100? for my Nexus 7). Best to measure it yourself (here's how I do it, it's actually pretty easy).

Would the FiiO E11 do the trick? I am sure I need an amp they are really quiet and when I play some games even if I increase my volume to 100 I cant hear the game well.



Look here:

http://nwavguy.blogspot.com/2011/11/fiio-e11-amp.html

He finds Zout = 0.5 ohms, which should be just fine.

If you have not done so, you might want to read the whole review...

Can you listen to the E6 while charging?