[Chrome147]

While researching for a DAC/Amp, I came across a lot of new measurements and specifications that I have no idea what they mean, but after going through others' discussions, I kinda have a rough idea of what I need to know to shop for a suitable one.
 
Please correct me if I'm wrong: To know whether an amp is enough to drive a pair of headphone, I need to look at the power handling capacity of the headphone and the power output of the amp, e.g. the Beyerdynamic T1 has a power handling capacity (does this mean power requirement?) of 300mW @ 600 ohms, so that means it requires an amp that delivers at least 300mW @ 600 ohm load to drive it? Is that right?
 
So that means the Sennheiser HDVD800 (480mW @ 600 ohms), Schiit Mjolnir 2 (425mW @ 600 ohms), and WooAudio WA22 (700mW @ 600 ohms) will all be sufficient to drive the T1 right? Other than the power output, are there other specifications relevant to the compatibility with headphones?
 
Also, I don't understand the term "power handling capacity" as it implies it cannot handle anymore than the suggested number, like if the amp delivers a higher number than the "power handling capacity" will it damage the headphone?
 
Next, people talk about matching impedance of the amp and headphone, what does this mean? The HDVD800 has an output impedance of 16 ohms and the Mjolnir 2 has an output impedance of 1 ohm (high gain) / 0.3 ohms (low gain), what does it mean in terms of headphone compatibility? Does that number just mean minimum headphone impedance?
 
At first I wanted the HDVD800 because it has 2 XLR-4 outputs and 2 1/4" outputs, but then I read that the HDVD800 is only suitable for high impedance headphone? Why? Shouldn't it be fine as long as the headphones are over 16 ohms?
 
I'm after an DAC/Amp that is flexible, meaning I can pair it with headphones with any impedance, is the Schiit Mjolnir 2 the best choice out of the these amplifiers? If I want a DAC/Amp combo, are there other choices that are as flexible as the Mjolnir 2? My only other criterion is that it has at least one XLR-4 headphone connection.
 
Thanks for your time.

 

[Me x3]

  While researching for a DAC/Amp, I came across a lot of new measurements and specifications that I have no idea what they mean, but after going through others' discussions, I kinda have a rough idea of what I need to know to shop for a suitable one.
 
Please correct me if I'm wrong: To know whether an amp is enough to drive a pair of headphone, I need to look at the power handling capacity of the headphone and the power output of the amp, e.g. the Beyerdynamic T1 has a power handling capacity (does this mean power requirement?) of 300mW @ 600 ohms, so that means it requires an amp that delivers at least 300mW @ 600 ohm load to drive it? Is that right?
 
So that means the Sennheiser HDVD800 (480mW @ 600 ohms), Schiit Mjolnir 2 (425mW @ 600 ohms), and WooAudio WA22 (700mW @ 600 ohms) will all be sufficient to drive the T1 right? Other than the power output, are there other specifications relevant to the compatibility with headphones?
 
Also, I don't understand the term "power handling capacity" as it implies it cannot handle anymore than the suggested number, like if the amp delivers a higher number than the "power handling capacity" will it damage the headphone?
 
Next, people talk about matching impedance of the amp and headphone, what does this mean? The HDVD800 has an output impedance of 16 ohms and the Mjolnir 2 has an output impedance of 1 ohm (high gain) / 0.3 ohms (low gain), what does it mean in terms of headphone compatibility? Does that number just mean minimum headphone impedance?
 
At first I wanted the HDVD800 because it has 2 XLR-4 outputs and 2 1/4" outputs, but then I read that the HDVD800 is only suitable for high impedance headphone? Why? Shouldn't it be fine as long as the headphones are over 16 ohms?
 
I'm after an DAC/Amp that is flexible, meaning I can pair it with headphones with any impedance, is the Schiit Mjolnir 2 the best choice out of the these amplifiers? If I want a DAC/Amp combo, are there other choices that are as flexible as the Mjolnir 2? My only other criterion is that it has at least one XLR-4 headphone connection.
 
Thanks for your time.

Power handling capacity (often max input power) is typically the highest power you can feed the headphone with without damaging the drivers. Anyway this is very tricky since same power at different frequencies make the headphone behave quite different and in some cases you might damage your drivers causing an over excurssion (bass tones) before reaching the stated power handling capacity.
 
What you need to know is the headphone's sensitivity. You can find it on provided specs or you can check innerfidelity measurments
http://www.innerfidelity.com/headphone-measurements
(Bottom right hand corner)
 
Let's use the T1 SN 3964 as an example:
 
According to Innerfidelity Data Sheet:
Power Needed for 90dB SPL ...................................... 0.28 mW
 
The simple rule:
Double the power ------------> Add 3dB
 
0.28mW ................ 90dB
0.56mW ................ 93dB
1.12mW ................ 96dB
2.24mW ................ 99dB
4.48mW ................ 102dB
8.96mW ................ 105dB
 
If you normally listen to music at moderate/healthy, almost too loud from time to time, you are done with 8.96mW @ 600 Ohm
If you want extra room, and that really means extra most of the times (in the sense that you are not going to use it because it's too loud and not fun/healthy) then you can keep doing the same thing "Double the power ------------> Add 3dB"
 
17.92mW ................ 108dB
35.84mW ................ 111dB
71.68mW ................ 114dB
 
For reference, normal listening level is 70-80dB average depending on the recording
Under these conditions, the loudest peaks on certain recordings might hit 95-100dB.
 
So, 20mW into 600 Ohm is a very safe mark to drive the T1 properly.
 
------------------------------------------------------------------------------------------------------------------------------
 
If the amplifier's output impedance is not much lower than the headphone's impedance, the sound will be coloured in the shape of the headphone's impedance vs frequency plot (pink trace on innerfidelity datasheet).
 
In the case of the T1, if you drive them with an amplifier with (say) 200 Ohm output impedance, you'll get a boost in the mid-bass where the impedance is higher.
 
A very simplistic general rule, if the headphone's impedance is 8 times higher than the amplifier's output impedance you won't hear any colouration (the amplifier will behave flat).
 
The output impedance on the HDVD800 is low for 600 Ohm T1 or 300 Ohm Sennheiser, but not that low for 62 Ohm AKG or 35 Ohm Fidelio X2. So it's flat for T1 and HD800 but not that flat for AKG or Fidelio.
 
The effects of relatively high output impedance are very subtle or even inaudibles on planar magnetic headphones with perfectly flat impedance vs frequency plot, for the simple reason that equalization in the shape of the headphone's impedance means no equalization in that case (flat headphone impedance)
 
So, yeah... That's all you need to know.
What's your main headphone?

 

[MindsMirror]

The power handling capacity tells you how much power the headphone can handle before it could be damaged, but that does not necessarily tell you how much power it needs. If the headphone would be damaged, your ears are likely to be damaged as well, so you probably don't need that much power. The Beyerdynamic T1 spec sheet says that at 300mW the headphone would produce 126dB which is very loud, you should not need that much power. I'd say a conservative estimate for the volume that you might need for very dynamic music would be 115dB, which is about 10 times less power, or 30mW for the T1.
 
The spec you normally use to figure out how much power is needed is the sensitivity and impedance. The calculations can get a little complicated, so you can use an online calculator where you can plug in all the numbers. That one I linked gave about 20mW as the required power.
 
Using an amp with higher output capability would only damage your headphone if you turned it up that loud. Leave the amp at a reasonable volume for listening and it wont damage anything.
 
Output impedance should ideally be zero, or as low as possible. It can tell you how much of the amp's output will be lost. For example, if your amp had a 600 Ohm output impedance and you used it with a 600 Ohm headphone, half the amp's output will be lost due to the output impedance. It the output impedance were zero, nothing would be lost. Most people recommend having an output impedance at least 8 times less than the headphone impedance, so the losses will be minimal. Since the HDVD800 has 16 Ohm output impedance, if you go by the 1/8th rule you should use it with a headphone with at least 128 Ohms impedance. With that in mind, the Mjolnir 2 is probably the one you should get, because it will also work well with low impedance headphones.

 

[Chrome147]

  Power handling capacity (often max input power) is typically the highest power you can feed the headphone with without damaging the drivers. Anyway this is very tricky since same power at different frequencies make the headphone behave quite different and in some cases you might damage your drivers causing an over excurssion (bass tones) before reaching the stated power handling capacity.
 
What you need to know is the headphone's sensitivity. You can find it on provided specs or you can check innerfidelity measurments
http://www.innerfidelity.com/headphone-measurements
(Bottom right hand corner)
 
Let's use the T1 SN 3964 as an example:
 
According to Innerfidelity Data Sheet:
Power Needed for 90dB SPL ...................................... 0.28 mW
 
The simple rule:
Double the power ------------> Add 3dB
 
0.28mW ................ 90dB
0.56mW ................ 93dB
1.12mW ................ 96dB
2.24mW ................ 99dB
4.48mW ................ 102dB
8.96mW ................ 105dB
 
If you normally listen to music at moderate/healthy, almost too loud from time to time, you are done with 8.96mW @ 600 Ohm
If you want extra room, and that really means extra most of the times (in the sense that you are not going to use it because it's too loud and not fun/healthy) then you can keep doing the same thing "Double the power ------------> Add 3dB"
 
17.92mW ................ 108dB
35.84mW ................ 111dB
71.68mW ................ 114dB
 
For reference, normal listening level is 70-80dB average depending on the recording
Under these conditions, the loudest peaks on certain recordings might hit 95-100dB.
 
So, 20mW into 600 Ohm is a very safe mark to drive the T1 properly.
 
------------------------------------------------------------------------------------------------------------------------------
 
If the amplifier's output impedance is not much lower than the headphone's impedance, the sound will be coloured in the shape of the headphone's impedance vs frequency plot (pink trace on innerfidelity datasheet).
 
In the case of the T1, if you drive them with an amplifier with (say) 200 Ohm output impedance, you'll get a boost in the mid-bass where the impedance is higher.
 
A very simplistic general rule, if the headphone's impedance is 8 times higher than the amplifier's output impedance you won't hear any colouration (the amplifier will behave flat).
 
The output impedance on the HDVD800 is low for 600 Ohm T1 or 300 Ohm Sennheiser, but not that low for 62 Ohm AKG or 35 Ohm Fidelio X2. So it's flat for T1 and HD800 but not that flat for AKG or Fidelio.
 
The effects of relatively high output impedance are very subtle or even inaudibles on planar magnetic headphones with perfectly flat impedance vs frequency plot, for the simple reason that equalization in the shape of the headphone's impedance means no equalization in that case (flat headphone impedance)
 
So, yeah... That's all you need to know.
What's your main headphone?

 
Thanks for the detailed explanation, that's a very useful equation. I don't have any headphones that require an amplifier at the moment, but I just bought a pair of DT 990 600 ohm version, so I'm looking for an amp for that but I also want one that's flexible so I don't have to change the amp if I get another pair of headphone in the future.
 
So going by the same process (I assume the numbers are same as the DT 880 since there is no information for the DT 990 both on the Beyer website and InnerFidelity), it goes like:
 
0.43mW - 90dB
0.86mW - 93dB
1.72mW - 96dB
3.44mW - 99dB
6.88mW - 102dB
13.76mW - 105dB
27.52mW - 108dB
55.04mW - 111dB
111.08mW - 114dB
 
So anything that outputs more than 55mW into 600 ohm should be plenty enough to drive the DT 990 right?
 
Also, the Schiit Mjolnir 2 outputs:
 
Maximum Power, 32 ohms: 8.0W RMS per channel
Maximum Power, 50 ohms: 5.0W RMS per channel
Maximum Power, 300 ohms: 850mW RMS per channel
Maximum Power, 600 ohms: 425mW RMS per channel
 
Is that through the XLR or 1/4" connector? Since the OPPO HA-1 provides separate numbers for both connections, which connection type is the Mjolnir 2 referring to?
 
OPPO HA-1:
 

Specification	Condition	XLR Input - Balanced Output	RCA Input - 6.35 mm Output
Maximum Output Power (Per Channel)	Into 600 Ohm	2400 mW	600 mW
Into 32 Ohm	3000 mW	3500 mW
Rated Output Power (Per Channel)	Into 600 Ohm	800 mW	200 mW
Into 32 Ohm	2000 mW	500 mW

 
One last thing, what's the difference between maximum and rated power output? Is the rated output power closer to real life usage? Thanks.

 

[Chrome147]

  The power handling capacity tells you how much power the headphone can handle before it could be damaged, but that does not necessarily tell you how much power it needs. If the headphone would be damaged, your ears are likely to be damaged as well, so you probably don't need that much power. The Beyerdynamic T1 spec sheet says that at 300mW the headphone would produce 126dB which is very loud, you should not need that much power. I'd say a conservative estimate for the volume that you might need for very dynamic music would be 115dB, which is about 10 times less power, or 30mW for the T1.
 
The spec you normally use to figure out how much power is needed is the sensitivity and impedance. The calculations can get a little complicated, so you can use an online calculator where you can plug in all the numbers. That one I linked gave about 20mW as the required power.
 
Using an amp with higher output capability would only damage your headphone if you turned it up that loud. Leave the amp at a reasonable volume for listening and it wont damage anything.
 
Output impedance should ideally be zero, or as low as possible. It can tell you how much of the amp's output will be lost. For example, if your amp had a 600 Ohm output impedance and you used it with a 600 Ohm headphone, half the amp's output will be lost due to the output impedance. It the output impedance were zero, nothing would be lost. Most people recommend having an output impedance at least 8 times less than the headphone impedance, so the losses will be minimal. Since the HDVD800 has 16 Ohm output impedance, if you go by the 1/8th rule you should use it with a headphone with at least 128 Ohms impedance. With that in mind, the Mjolnir 2 is probably the one you should get, because it will also work well with low impedance headphones.

 
Thanks for the explanation as well. So if I use the Mjolnir 2 which outputs 425mW into 600 ohms, to drive the T1 which can only handle 100mW of power, it will not damage it unless I turn the volumn knob up to a ridiculous level. That makes things a lot easier 

 
The explanation on output impedance is also very clear, I get it now, thanks!

 

[Me x3]

   
Thanks for the detailed explanation, that's a very useful equation. I don't have any headphones that require an amplifier at the moment, but I just bought a pair of DT 990 600 ohm version, so I'm looking for an amp for that but I also want one that's flexible so I don't have to change the amp if I get another pair of headphone in the future.
 
So going by the same process (I assume the numbers are same as the DT 880 since there is no information for the DT 990 both on the Beyer website and InnerFidelity), it goes like:
 
0.43mW - 90dB
0.86mW - 93dB
1.72mW - 96dB
3.44mW - 99dB
6.88mW - 102dB
13.76mW - 105dB
27.52mW - 108dB
55.04mW - 111dB
111.08mW - 114dB
 
So anything that outputs more than 55mW into 600 ohm should be plenty enough to drive the DT 990 right?
 
Also, the Schiit Mjolnir 2 outputs:
 
Maximum Power, 32 ohms: 8.0W RMS per channel
Maximum Power, 50 ohms: 5.0W RMS per channel
Maximum Power, 300 ohms: 850mW RMS per channel
Maximum Power, 600 ohms: 425mW RMS per channel
 
Is that through the XLR or 1/4" connector? Since the OPPO HA-1 provides separate numbers for both connections, which connection type is the Mjolnir 2 referring to?
 
OPPO HA-1:
 

Specification	Condition	XLR Input - Balanced Output	RCA Input - 6.35 mm Output
Maximum Output Power (Per Channel)	Into 600 Ohm	2400 mW	600 mW
Into 32 Ohm	3000 mW	3500 mW
Rated Output Power (Per Channel)	Into 600 Ohm	800 mW	200 mW
Into 32 Ohm	2000 mW	500 mW

 
One last thing, what's the difference between maximum and rated power output? Is the rated output power closer to real life usage? Thanks.

 
Yes, 55mW is plenty of power for DT990 600 Ohm.
In real life you'll be using less than 15mW.
 
I guess the specs for Mjolnir 2 are referred to balanced output. You can try asking in the Mjolnir 2 thread.
 
Rated often means under certain conditions but can't help with the Oppo since there's not much info.
 
Despite the power thing, I strongly suggest reading about amplifiers sound signature (tilt) that's what make a difference in real life.
Schiit, Violectric, Bryston, Burson, Matrix, JDS Labs all of them sound slightly different and all of them will drive most headphones just fine (the extra power is useless)
Try to pick one that's a good match for your preferences and current/future headphones.
 
The only headphone that needs serious power is the Hifiman HE-6

 

[Chrome147]

   
Yes, 55mW is plenty of power for DT990 600 Ohm.
In real life you'll be using less than 15mW.
 
I guess the specs for Mjolnir 2 are referred to balanced output. You can try asking in the Mjolnir 2 thread.
 
Rated often means under certain conditions but can't help with the Oppo since there's not much info.
 
Despite the power thing, I strongly suggest reading about amplifiers sound signature (tilt) that's what make a difference in real life.
Schiit, Violectric, Bryston, Burson, Matrix, JDS Labs all of them sound slightly different and all of them will drive most headphones just fine (the extra power is useless)
Try to pick one that's a good match for your preferences and current/future headphones.
 
The only headphone that needs serious power is the Hifiman HE-6

 
Thanks! Regarding sound signature, I originally wanted the HDVD800 because it's neutral and uncoloured according to reviews, but it lacks flexibility as it doesn't go well with low impedance headphones. I do want to try out different high end headphones in the future, such as the T1, HD800, HE-6, but also want the flexibility to use low impedance headphones with the amp. I will research more on the sound signature of different brands.
 
Just have another question, to benefit from balanced output, do you also need a balanced input source? How do you achieve that with a PC (without a high end audiophile grade sound card)? Since the USB connection would be unbalanced? Does balanced output/unbalanced input still sound better than unbalanced output/unbalanced input? Should I even bother looking for an amp with a balanced headphone jack if I'm only using it with a computer?

 

[Me x3]

   
Thanks! Regarding sound signature, I originally wanted the HDVD800 because it's neutral and uncoloured according to reviews, but it lacks flexibility as it doesn't go well with low impedance headphones. I do want to try out different high end headphones in the future, such as the T1, HD800, HE-6, but also want the flexibility to use low impedance headphones with the amp. I will research more on the sound signature of different brands.
 
Just have another question, to benefit from balanced output, do you also need a balanced input source? How do you achieve that with a PC (without a high end audiophile grade sound card)? Since the USB connection would be unbalanced? Does balanced output/unbalanced input still sound better than unbalanced output/unbalanced input? Should I even bother looking for an amp with a balanced headphone jack if I'm only using it with a computer?

 
Balanced output is not necessarily better, it's just a different, more complex approach with pros and cons from a design point of view. So the phrase "benefit from balanced..." is relative.
Normally you would want a balanced DAC like the Gungnir (or Yggdrasil) to feed a balanced amplifier like the Mjolnir 2. Nothing wrong about using Gungnir or Yggdrasil via USB.

 

[Chrome147]

   
Balanced output is not necessarily better, it's just a different, more complex approach with pros and cons from a design point of view. So the phrase "benefit from balanced..." is relative.
Normally you would want a balanced DAC like the Gungnir (or Yggdrasil) to feed a balanced amplifier like the Mjolnir 2. Nothing wrong about using Gungnir or Yggdrasil via USB.

 
Is that the same case with all-in-one USB DAC/Amp, like the OPPO HA-1 and HDVD800?

 

[Me x3]

   
Is that the same case with all-in-one USB DAC/Amp, like the OPPO HA-1 and HDVD800?

Yes, both should work just fine via USB.