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Is there any objective way to determine whether the Apple dongle is capable of powering a headphone to 100% capability?

tigerapostle

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It would be good to be able to recommend the Apple dongle to people seeking an amplifier, but I can't always do it in good faith without knowing of a way to determine objectively whether it has sufficient power for their hedphones. People often the use impedance rating of the headphones to determine the suitability, but presumably it is also a factor of other things such as sensitivity.

I have ample volume on my DT770/80, but searching the internet resulting in 50% of people saying that it's sufficient and 50% saying it's insufficient.
 

JSmith

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Hello and welcome to ASR. :)

Unsure if you have seen this yet;
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JSmith
 

DVDdoug

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The DT770 specs say 105dB, but it doesn't give a power or voltage. I assume that's sensitivity at 1mW...

The Apple dongle can put-out 1V RMS, and at 80 Ohms, that's 12.5mW (if I did the math correctly).

That's about 11dB more than 1mW so if my assumption is correct, that's about 116dB SPL.

The headphone specs also say it can handle 100mW so you can't max it out... (That would be +20dB so 125dB SPL.)

People often the use impedance rating of the headphones to determine the suitability, but presumably it is also a factor of other things such as sensitivity.
Impedance is a clue but you really need to know the sensitivity. Impedance and resistance are "the resistance to current flow" so at lower impedance you get more current and more power, given the same voltage. Half the impedance gives you twice the power (watts or milliwatts). So higher impedance headphones tend to need more voltage. But that's electrical power and different headphones have different efficiency.
 
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tigerapostle

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Yes i have seen that (but haven't read many pages deep into the thread), and a few other measurements of the dongle. I'm just unsure of what factors can be used to say confidently that the dongle is sufficient.

This website seems to indicate that the voltage required is relative to the sensitivity of the headphones, and that current draw is relative to the impedance. Based off that, the DT770/80 requires 1.9V and 12.9mA to be powered with sufficient headroom. If I'm reading that correctly then the Apple dongle would be woefully underpowered at 1V
 
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tigerapostle

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The DT770 specs say 105dB, but it doesn't give a power or voltage. I assume that's sensitivity at 1mW...

I don't see an actual sensitivity rating given, but the manual and website say "nominal SPL" 96db. 11db over 96 would be 107, which is still enough to explode my head.

I remember reading on a forum somewhere that high impedance headphones are intended to work on high voltage amps (4V?), which used to be used, and are still in use in studios. This again implies a correlation between impedance and amplifier voltage, although the previously linked website correlates voltage to sensitivity

edit: here it is said that "u need higher gain and higher output voltage for high impedance headphones", which might imply that at there might be a cutoff point in impedance where the 1V dongle is insufficient

Due to my limited understanding of this stuff, I'm only really reading it at a superficial level
 
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NTK

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The Apple dongle doesn't clip at max volume setting. (I.e. It outputs digital full scale at max volume setting without clipping.) It can output 1 Vrms at 33 ohms or above. If it is loud enough, you are all good.
 

pablolie

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It would be good to be able to recommend the Apple dongle to people seeking an amplifier, but I can't always do it in good faith without knowing of a way to determine objectively whether it has sufficient power for their hedphones. People often the use impedance rating of the headphones to determine the suitability, but presumably it is also a factor of other things such as sensitivity.

I have ample volume on my DT770/80, but searching the internet resulting in 50% of people saying that it's sufficient and 50% saying it's insufficient.
Do you mean driving +90dB? Who cares - it will just destroy your hearing mid term. It never ceases to amaze me so many are so obsessed about driving headphones to hearing damage levels...
 

b7676

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Beyers are generally current eaters. 300-600mW@300ohm is more like it. Topping L tier, but more is better for having ample gain for quieter content. This is if you want to simulate standing around the real amp cabinet, cymbal crash, piano, etc. The cans also need something like the objective EQ going to lower audible distortion.
 
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oleg87

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Volume preferences are enormously significant with respect to whether an amp is "enough". It's probably the case that 120dB peak SPL is enough for any reasonable person for any reasonable purpose, but for my needs, even 95dB peak SPL would be more than enough, and that's about a 320x difference in power.
 
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tigerapostle

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Do you mean driving +90dB? Who cares - it will just destroy your hearing mid term. It never ceases to amaze me so many are so obsessed about driving headphones to hearing damage levels...
It's worth understanding that this topic isn't about me worrying whether the dongle can power my headphones. It's about whether there is an objective measure that can be applied used to determine whether a specific amp is capable of fully powering headphones. I'm just using my headphones as an example, because they're the only model I've used with an Apple dongle.

It seems like it should be possible to use known measurements of a model of headphones and apply it to known measurements of an amp and determine compatibility. If someone posts "I have X headphone, what amp should I buy?" It would be nice to be able to confidently say "the Apple dongle is all you could ever need because your headphones are X,Y,Z and the apple dongle is A, B, C". Instead, the comment section always devolves into "no, it can't be used because the headphones are Xohm", "even if it's loud enough, that doesn't mean it's fully powered" and various other subjective statements or assumptions

FWIW, people usually aim for headroom well above the constant listening volume, and presumably the goal is to get an amp that can reach the rare peaks
 
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oleg87

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Instead, the comment section always devolves into "no, it can't be used because the headphones are Xohm", "even if it's loud enough, that doesn't mean it's fully powered" and various other subjective statements or assumptions
Frankly it's hard to think of an internet audio-related topic more awash in misinformation and confusion than headphone amplifier requirements.

If you know your required peak volume, and have reliable/comprehensive enough measurements of both amp and headphone, it's an objective question of whether the amp will get you there without audible distortion.
 

MaxwellsEq

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I think your question has been answered, but not necessarily in one post!

1. Sensitivity is key. For a fixed amplifier output, a very sensitive headphone may deafen the listener, a very insensitive headphone may be too quiet.
2. If you know the impedance, you know how much voltage swing is needed (high impedance headphones) or current swing is needed (low impedance headphones) to generate a fixed power.
3. There is no guaranteed correlation between impedance and sensitivity. You need both bits of information.
4. People experience different "coupling" from different headphones which may mean that they perceived loudness differently
5. Different frequency-amplitude responses can make a sound source seem louder

With enough data, it should be possible to objectively indicate whether an amp is sufficient, but often the data is in short supply or is inconsistent.
 
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tigerapostle

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Amirm has done measurements of both the Apple dongle and Beyerdynamic dt990/250. In it he includes a graph indicating that it needs 704mV to reach 94db due to being very insensitive, and says "You better have a very high performance headphone amplifier that can drive its high impedance and provide the required power:" Due to the high impedance and large impedance swing, he says the amp needs a very low impedance.

This gives me the weird contradiction, that his dongle measurements show it at 1V with an output impedance of 0.9ohm. Does this mean that the dongle meets its requirements for a "very high performance amplifier"?

If I'm following DVDdoug properly, I can determine that a DT880/250 draws 4mW from the dongle (w=v^2/r), and thus is able to provide a 6db boost over its sensitivity of 96db@1mw (102db). Does this mean that the dongle can happily power a dt990 linearly to 102db headroom?
 
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Dazerdoreal

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I didnt read the topic too carefully, but are you looking for something like this?
 

oleg87

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Amirm has done measurements of both the Apple dongle and Beyerdynamic dt990/250. In it he includes a graph indicating that it needs 704mV to reach 94db due to being very insensitive, and says "You better have a very high performance headphone amplifier that can drive its high impedance and provide the required power:" Due to the high impedance and large impedance swing, he says the amp needs a very low impedance.

This gives me the weird contradiction, that his dongle measurements show it at 1V with an output impedance of 0.9ohm. Does this mean that the dongle meets its requirements for a "very high performance amplifier"?

If I'm following DVDdoug properly, I can determine that a DT880/250 draws 4mW from the dongle (w=v^2/r), and thus is able to provide a 6db boost over its sensitivity of 96db@1mw (102db). Does this mean that the dongle can happily power a dt990 linearly to 102db headroom?
Well, these are two different metrics. The amp’s output impedance is a measure of how much its output sags as the load demands more current. Low is better, and the apple dongle is good in this regard. But it has a limited output level to begin with. What’s important here depends on your headphone. For IEMs for example, power is usually a total non-issue, but multi-driver ones can be very sensitive to output impedance.
 

NTK

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Amirm has done measurements of both the Apple dongle and Beyerdynamic dt990/250. In it he includes a graph indicating that it needs 704mV to reach 94db due to being very insensitive, and says "You better have a very high performance headphone amplifier that can drive its high impedance and provide the required power:" Due to the high impedance and large impedance swing, he says the amp needs a very low impedance.

This gives me the weird contradiction, that his dongle measurements show it at 1V with an output impedance of 0.9ohm. Does this mean that the dongle meets its requirements for a "very high performance amplifier"?
The issue with the Apple dongle is its output capacity (0.5 Vrms max output for the EU version, 1 Vrms for others, with loads of >33 ohms). If this output capacity is sufficient, it meets every requirement to be called a "a very high performance amplifier".
If I'm following DVDdoug properly, I can determine that a DT880/250 draws 4mW from the dongle (w=v^2/r), and thus is able to provide a 6db boost over its sensitivity of 96db@1mw (102db). Does this mean that the dongle can happily power a dt990 linearly to 102db headroom?
Per Amir's measurement, the DT990/250 needs 0.7 Vrms to reach 94 dBSPL. The non-EU version of the Apple dongle only gives a 3 dB headroom ( = 20log10(1.0/0.7) ), meaning it can only produce a max 97 dBSPL with the DT990/250. (The EU version cannot output 0.7 V and will max out at <94 dBSPL.)
 

staticV3

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@tigerapostle the DT 770 Pro 80Ω has a sensitivity of 107dB/Vrms (SSN measured it at 106.8dB here).

The A2049 Apple dongle can output 1.0Vrms into an 80Ω load, meaning it can drive the DT770 Pro 80Ω to 107dB SPL Peak.

Depending on the audio files that you're listening to and how you're transmitting those files to the dongle, the real-world, average SPL will be some dB below that.

For example, the files that I listen to tend to be mastered to -0.5dBFS with peaks that are 15dB above the average volume, and I can transmit those files 1:1 with software like UAPP or foobar2000.
Ergo, with the A2049 I could drive the DT 770 Pro 80Ω to 107-0.5-15=91.5dB SPL AVG.

My preferred listening volume is about 65dB SPL AVG, so this setup would be capable of more than six times my usual volume.

Others may not be aware of the A2049's volume limiter that's present on Android, or they may listen to files with higher crest factor, lower dBFS Peak, or both, or they may just be used to higher SPLs, which can explain why some people say that the A2049 does not get loud enough.
 
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DanielT

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Keep in mind that the Apple dongle sold in Europe is considerably weaker than the normal version.
It applies within the EU zone. Booster brake created according to EU directives. Nope, I'm not kidding. Buy directly from countries outside the EU, if you're lucky they send the non-braked variant.

I, who live in an EU country, bought the Apple dongle and tested it on an Android product. Nope it didn't work at all. Very poor amplification.:oops:

Note that my testing is all on Windows. I attempted to test on my Samsung S8+ and got odd results. Using both Google dongles, all they did was route the not so good sound of the internal DAC through the dongle (???). With Apple dongle I got music but level was very low. So if you plan to use the Apple dongle on an Android phone, you should do some compatibility testing.

Edit:
Adroid - Apple Dongle - 30 W Yamaha receiver. Then, when I tested with a 30 W receiver, the volume control was turned almost to maximum to get a normal listening volume. With a CD player without an Apple dongle and the same listening volume, maybe like 30% on the volume control.
(nope, I'm not exaggerating)

This receiver:

"Input sensitivity: 2.5mV (MM), 120mV (DIN), 120mV (line)"

Edit 2.
Having said that. A dac that costs as much as a pizza. Not much to say really. Buy one and try it.:)
 
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solderdude

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It would be good to be able to recommend the Apple dongle to people seeking an amplifier, but I can't always do it in good faith without knowing of a way to determine objectively whether it has sufficient power for their hedphones. People often the use impedance rating of the headphones to determine the suitability, but presumably it is also a factor of other things such as sensitivity.

I have ample volume on my DT770/80, but searching the internet resulting in 50% of people saying that it's sufficient and 50% saying it's insufficient.

When you do not play loud it is sufficient. So music at levels you can endure for an hour or more enjoying music.
When you want it to play impressively loud it will not cut the mustard.

So... depending on how loud you want to go the dongle is suitable or not.
 
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