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Topic: What does a secondary headphone amp do exactly? (Read 27175 times) previous topic - next topic
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What does a secondary headphone amp do exactly?

I have a question about headphone amplifiers and what they are supposed to do. Now many professional sources like manufactures say it amplifies the sound, making it louder. But many "audiophiles" claim that you need it for better quality sound which is independent of loudness, and they use a lot of subjective terms to describe that loudness.

I plugged a 300ohm headphone into the Microsoft zune, which is said to "work best with headphones 32ohms and under".

I tried the device with the stock earbuds, a 50ohm headphone and a 600 ohm headphone.

The earbuds were loud enough at volume 8, the 555 achieves the same kind of loudness (to my ears) at volume 11, and the 300ohm is also loud enough at volume 14. Ofcourse they all sound "different" as they have different frequency responses and different sized drivers etc... But the Hd600 really sounded fine at a high volume setting, I can hear the bass, different voices in the music, the voice separation was clear with each voice clearly heard on its own.

Now I know that it wastes more battery pushing the volume up so high, but still, does an amplifier just amplify the signal? Because the 300ohm headphone sounded fine with the zune.

What does a secondary headphone amp do exactly?

Reply #1 –
Quote from: HTS on
I have a question about headphone amplifiers and what they are supposed to do. Now many professional sources like manufactures say it amplifies the sound, making it louder. But many "audiophiles" claim that you need it for better quality sound which is independent of loudness, and they use a lot of subjective terms to describe that loudness.

I plugged a 300ohm headphone into the Microsoft zune, which is said to "work best with headphones 32ohms and under".

I tried the device with the stock earbuds, a 50ohm headphone and a 600 ohm headphone.

The earbuds were loud enough at volume 8, the 555 achieves the same kind of loudness (to my ears) at volume 11, and the 300ohm is also loud enough at volume 14. Ofcourse they all sound "different" as they have different frequency responses and different sized drivers etc... But the Hd600 really sounded fine at a high volume setting, I can hear the bass, different voices in the music, the voice separation was clear with each voice clearly heard on its own.

Now I know that it wastes more battery pushing the volume up so high, but still, does an amplifier just amplify the signal? Because the 300ohm headphone sounded fine with the zune.


Does turning up the volume so that you can enjoy the music *waste* battery power? No!!!  Your enjoyment is the purpose of the device. If you don't have enough battery life to please you, there are probably options - for example my portable recorder can be powered via its USB port, and there is a cheap device by Everready that will use 2 AA batteries to extend it operating time.

Does an amplifier just amplify the signal? Yes, at least on a good day.

The final arbiter of what is enjoyable to you, is *you*. If you find that your Zune gets loud enough and sounds good with high impedance phones, then ignore those who ponitificate on such things and enjoy!

What does a secondary headphone amp do exactly?

Reply #2 –
Quote from: HTS on
Now I know that it wastes more battery pushing the volume up so high, but still, does an amplifier just amplify the signal? Because the 300ohm headphone sounded fine with the zune.

Turning up the volume to match the 300 ohm headphones does not necessarily increase battery consumption. Because the higher impedance headphones place less load on the output circuit, it is possible that there is less battery usage rather than more, It all depends on the efficiency of the headphones and the design of the amplifier circuit.

What does a secondary headphone amp do exactly?

Reply #3 –
The point of an headphone amplifier is not to make the signal louder, but they can generally do that too if the source level is too low.  Typical line level signal is about 2V which is would be way loud for many headphones.

The main function from "audiophile" point of view is that they drive headphones much better than built-in headphone outputs.  Portable ones have to make compromises for power consumption and size, but full size class-A amplifiers are clear improvement, how big depends on headphones.

When trying a dedicated amplifier the benefits may not be obvious at first, but once you get accustomed to the sound you may not want to back.  At least that happened to me, and I use headphone amplifiers for everything but portable use.  For portable players with IEMs I find the benefit so small or non-existent that it is not worth the added bulk.
Teemu

What does a secondary headphone amp do exactly?

Reply #4 –
Quote from: Arnold B. Krueger on
Quote from: HTS on
I have a question about headphone amplifiers and what they are supposed to do. Now many professional sources like manufactures say it amplifies the sound, making it louder. But many "audiophiles" claim that you need it for better quality sound which is independent of loudness, and they use a lot of subjective terms to describe that loudness.

I plugged a 300ohm headphone into the Microsoft zune, which is said to "work best with headphones 32ohms and under".

I tried the device with the stock earbuds, a 50ohm headphone and a 600 ohm headphone.

The earbuds were loud enough at volume 8, the 555 achieves the same kind of loudness (to my ears) at volume 11, and the 300ohm is also loud enough at volume 14. Ofcourse they all sound "different" as they have different frequency responses and different sized drivers etc... But the Hd600 really sounded fine at a high volume setting, I can hear the bass, different voices in the music, the voice separation was clear with each voice clearly heard on its own.

Now I know that it wastes more battery pushing the volume up so high, but still, does an amplifier just amplify the signal? Because the 300ohm headphone sounded fine with the zune.


Does turning up the volume so that you can enjoy the music *waste* battery power? No!!!  Your enjoyment is the purpose of the device. If you don't have enough battery life to please you, there are probably options - for example my portable recorder can be powered via its USB port, and there is a cheap device by Everready that will use 2 AA batteries to extend it operating time.

Does an amplifier just amplify the signal? Yes, at least on a good day.

The final arbiter of what is enjoyable to you, is *you*. If you find that your Zune gets loud enough and sounds good with high impedance phones, then ignore those who ponitificate on such things and enjoy!

Alright I might have said "use" instead of "waste".

It's not just what I find enjoyable, but I want to know what is an amplifier scientifically designed to do.

Quote
Turning up the volume to match the 300 ohm headphones does not necessarily increase battery consumption. Because the higher impedance headphones place less load on the output circuit, it is possible that there is less battery usage rather than more, It all depends on the efficiency of the headphones and the design of the amplifier circuit.

Good to know, thanks.

What does a secondary headphone amp do exactly?

Reply #5 –
Quote from: tot on
The main function from "audiophile" point of view is that they drive headphones much better than built-in headphone outputs.

That's the question, in what sense?

What does a secondary headphone amp do exactly?

Reply #6 –
Quote from: tot on
The main function from "audiophile" point of view is that they drive headphones much better than built-in headphone outputs.  Portable ones have to make compromises for power consumption and size, but full size class-A amplifiers are clear improvement, how big depends on headphones.


Yes, and the same can be said of "audiophile" fuses and power cables.  Do a volume matched blind test comparing the amp built into your portable device to a dedicated headphone amp.  Then come back and make your claim.

You know what you'll likely find with regards to "sound quality?" after a volume matched blind test?  A dedicated "audiophile" amp does little other than drain your wallet.  Some portable devices have a slight bass rolloff (RMAA verified) with low impedance headphones and this can addressed by an amp, but the bass rolloff may be so slight as to be a non-issue.

So many people claim dedicated headphone amps improve the "sound quality" of headphones, but when you ask them to demonstrate it using objective measures or even in a blind test, you end up with a lot of subjective mumbo-jumbo.

What does a secondary headphone amp do exactly?

Reply #7 –
Quote from: tot on
When trying a dedicated amplifier the benefits may not be obvious at first, but once you get accustomed to the sound you may not want to back.

Anecdotal subjectivity; not exactly a TOS #8 friendly.

What does a secondary headphone amp do exactly?

Reply #8 –
So what does the official specs for the resistance of headphones supported mean anyways? Because I have a sound card and the zune, both were supposed to run headphones not higher than 32ohms, buy both runs 50 and 300 ohm headphones fine if you just turn up the volume. In fact they are more than adequate since I still am short of their maximum volume even for the 300 ohm headphone.

What does a secondary headphone amp do exactly?

Reply #9 –
Quote from: HTS on
So what does the official specs for the resistance of headphones supported mean anyways? Because I have a sound card and the zune, both were supposed to run headphones not higher than 32ohms, buy both runs 50 and 300 ohm headphones fine if you just turn up the volume. In fact they are more than adequate since I still am short of their maximum volume even for the 300 ohm headphone.


If somebody has told you you shouldn't be using a headphone with an impedance higher than 32 ohms, they are wrong.  You can run just about any headphone from any portable player or sound card without ill effect.  I've even read discussions where people said the output impedance and headphone impedance should be exactly the same otherwise it leads to amplifier overheating and damage.  What rubbish.

The following statement depends on the amp and headphones being used, but I've found that as a general rule of thumb the headphone jack impedance should be lower than the headphone impedance.  I base this statement on RMAA tests I've run on a bunch of different eqiupment.  If it's not, you can get some interesting deviations from a flat frequency response.  Not all these deviations are bad as recently I found a slightly (IMHO) bass anemic headphone sound better on an amp that was boosting the bass (RMAA verified).

What does a secondary headphone amp do exactly?

Reply #10 –
Quote from: HTS on
Now I know that it wastes more battery pushing the volume up so high, but still, does an amplifier just amplify the signal? Because the 300ohm headphone sounded fine with the zune.


Pio2001 posted at http://www.head-fi.org/forums/f133/headpho...one-abx-429619/  (referenced from the thread on AV Receivers http://www.hydrogenaudio.org/forums/index....=73054&hl=) some RMAA tests that show a headphone amp having a flatter response curve than some integrated amps with certain headphones attached. OTOH, the maximum variation with the integrated amps was +/- 1.5 dB.

I suspect, then, that there is, in at least some cases, enough of a measurable difference to enable headphone amp makers to claim they do more than just amplify the signal; but not enough of a difference for most people to hear, most of the time (really, Barnum-land: not enough for all people to hear most of the time, and most people to hear all of the time: but Pio2001 could ABX at least the most obvious differences).

What does a secondary headphone amp do exactly?

Reply #11 –
Quote from: MichaelW on
Quote from: HTS on
Now I know that it wastes more battery pushing the volume up so high, but still, does an amplifier just amplify the signal? Because the 300ohm headphone sounded fine with the zune.


Pio2001 posted at http://www.head-fi.org/forums/f133/headpho...one-abx-429619/  (referenced from the thread on AV Receivers http://www.hydrogenaudio.org/forums/index....=73054&hl=) some RMAA tests that show a headphone amp having a flatter response curve than some integrated amps with certain headphones attached. OTOH, the maximum variation with the integrated amps was +/- 1.5 dB.

I suspect, then, that there is, in at least some cases, enough of a measurable difference to enable headphone amp makers to claim they do more than just amplify the signal; but not enough of a difference for most people to hear, most of the time (really, Barnum-land: not enough for all people to hear most of the time, and most people to hear all of the time: but Pio2001 could ABX at least the most obvious differences).

Well, I'm not sure how good were the integrated amplifiers used in the test, what are they integrated into? How do they compare to the amplifiers in today's MP3 players like the Ipod and the Zune?

Also, does the flatter response have anything to do with the additional "energy" fed by a high classed amp, or just that the amps were made out of better materials thus having lower distortion? Like less hiss and artifacts?

I can't really understand that report very well.

What does a secondary headphone amp do exactly?

Reply #12 –
Quote from: odigg on
Quote from: HTS on
So what does the official specs for the resistance of headphones supported mean anyways? Because I have a sound card and the zune, both were supposed to run headphones not higher than 32ohms, buy both runs 50 and 300 ohm headphones fine if you just turn up the volume. In fact they are more than adequate since I still am short of their maximum volume even for the 300 ohm headphone.


The following statement depends on the amp and headphones being used, but I've found that as a general rule of thumb the headphone jack impedance should be lower than the headphone impedance. 

The Sennheiser HD600 is at 300ohms, the Zune's headphone jack can't possibly have an impedance above that right?

What does a secondary headphone amp do exactly?

Reply #13 –
Quote from: HTS on
Quote from: odigg on
Quote from: HTS on
So what does the official specs for the resistance of headphones supported mean anyways? Because I have a sound card and the zune, both were supposed to run headphones not higher than 32ohms, buy both runs 50 and 300 ohm headphones fine if you just turn up the volume. In fact they are more than adequate since I still am short of their maximum volume even for the 300 ohm headphone.


The following statement depends on the amp and headphones being used, but I've found that as a general rule of thumb the headphone jack impedance should be lower than the headphone impedance. 

The Sennheiser HD600 is at 300ohms, the Zune's headphone jack can't possibly have an impedance above that right?


Hi HTS. Let me make these points very clear regarding high impedance phones.

1. The only potential problem with using higher impedance phones on your Zune (or any other player for that matter) is that in theory you may not get enough volume control to achieve desired loudness. If you are still getting plenty of volume range to cover your full music collection then, no matter how high the impedance, there is no problem.

2. Pushing the volume control higher to achieve the same listening volume on higher impedance phones does NOT waste power and may very well do the exact opposite! ( That is, reduce the power consumption. ) A typical class B or class AB output stage would use less power to drive a high impedance load at closer to rail to rail level than it would to drive the same power into a lower impedance load. Your pre-existing intuition here is completely wrong (but don't feel bad about it because most people would think the same thing.  )

BTW. In the above I'm not making any claims about whether high-Z verus low-Z phones construction gives any intrinsic sonic advantage. I dont know if your low-Z phones sound  better or worse than the high-Z ones when both are driven from a suitable amplifier. All I'm saying that if you like the sound of the High-Z ones on a good amplifier then there is no reason not to use them on the Zune (no matter how high is the impedance) as long as you can get enough volume.

What does a secondary headphone amp do exactly?

Reply #14 –
Quote from: uart on
Quote from: HTS on
Quote from: odigg on
Quote from: HTS on
So what does the official specs for the resistance of headphones supported mean anyways? Because I have a sound card and the zune, both were supposed to run headphones not higher than 32ohms, buy both runs 50 and 300 ohm headphones fine if you just turn up the volume. In fact they are more than adequate since I still am short of their maximum volume even for the 300 ohm headphone.


The following statement depends on the amp and headphones being used, but I've found that as a general rule of thumb the headphone jack impedance should be lower than the headphone impedance. 

The Sennheiser HD600 is at 300ohms, the Zune's headphone jack can't possibly have an impedance above that right?


Hi HTS. Let me make these points very clear regarding high impedance phones.

1. The only potential problem with using higher impedance phones on your Zune (or any other player for that matter) is that in theory you may not get enough volume control to achieve desired loudness. If you are still getting plenty of volume range to cover your full music collection then, no matter how high the impedance, there is no problem.

So the "audiophile" amps sounding a little more neutral vs the integrated amps, is not because of the difference in the headphones' impedance, but because of the amps themselves right? Like a low impedance headphone of 32 ohms will benefit equally from an "audiophile" amp than a 300ohm headphone? So if the Zune sounds a little "off" (I'm not saying that it does) with the high impedance headphones, the problem here is independent of the impedance of the headphone?

Because I did listen to the same headphone on a sound card that can power 600ohm headphones. And it sounded very alike on the zune and on that sound card, in tracks where the bass was bloated, on both sources it was the same. And where the bass was tight and clear, on both sources it was the same.

Thanks for clearing that up!

What does a secondary headphone amp do exactly?

Reply #15 –
Quote from: HTS on
So if the Zune sounds a little "off" (I'm not saying that it does) with the high impedance headphones, the problem here is independent of the impedance of the headphone?

Because I did listen to the same headphone on a sound card that can power 600ohm headphones. And it sounded very alike on the zune and on that sound card, in tracks where the bass was bloated, on both sources it was the same. And where the bass was tight and clear, on both sources it was the same.



Yeah if the Zune can provide the volume then it can drive the phones. In some sense Hi-Z phones are easier for the device to drive than low-Z. There's just one caveat on this that I should have mentioned above. You do have to be careful that you're not clipping (the voltage) if the phones are too higher impedance. Basically you just need to be sure that at the very loudest transients of your music (or very loudest plus a bit more for testing purposes) that you don't get any noticeable distortion - if you do then it might be clipping. Other than that high impedance phones will generally reduce the amplifier distortion due to their lower current requirements.

Just to summarize the main issues.

- Low-Z phones place higher current demands on your device while hi-Z phones place higher voltage demands.

- The higher current demand of low-Z phones can increase the distortion levels of your devices output stage. In particular (for devices with AC coupled outputs) low-Z phones might strain the output coupling capacitor a bit which can increase low frequency distortion and impair the low end frequency response.

- The higher voltage demand of hi-Z phones generally doesn't increase distortion levels, except for the caveat mentioned above if the output level gets pushed too close to clipping.

- As Hi-Z phones use less current they may place less drain on your battery (though it's probably too smaller effect to make much noticeable difference).

- Both hi-Z and low-Z phone might (or might not) benefit from a good headphone amplifier, but for different reasons. Typically low-Z phones will benefit most from the amplifier, but generally only where the devices inbuilt amplifier is a bit wimpy on available drive current. Hi-Z phones will usually only benefit from an added amplifier where the existing device is not providing enough output voltage swing and you're suffering from either a lack of volume or from clipping under transient volume extremes.

What does a secondary headphone amp do exactly?

Reply #16 –
Quote from: HTS on
The Sennheiser HD600 is at 300ohms, the Zune's headphone jack can't possibly have an impedance above that right?


Unless the Zune designers were on some drug they made it, the output impedance is probably a lot closer to 0 than 300.  Just to support your listening to a HD600 on a Zune, I listen to a DT880 (250 ohms) connected straight to a Nokia phone.

Even if the impedance of a headphone jack is higher than the headphone, it's not automatically a problem.  It is a question of the headphone and the particular amp.  Depending on the headphone impedance curve and particular output impedance of the amp, there might be a shift in the frequency response.  In layman terms, you might have a boosted or attenuated bass, treble, or whatever else depending on the particular headphone you are using.

I've played with this myself.  Sometimes the frequency response change makes the headphone sound "a little off."  Sometimes the boost can be somewhat dramatic and you'll hear distortion.  At least in one case, I found the altered frequency response to actually be more enjoyable.  If you look at Pio2001's test and graph (linked in MichaelW's post) the frequency response of the DT880 is altered a bit depending on the output impedance (not given) of the amps, although my current speculation is the Project amp has the lowest output impedance and the Marantz the highest.  The deviations from a flat FR are measurable and maybe blind testable, but I wonder what would happen if somebody had the project box in one room and the Marantz in another and compared the two by walking between rooms.  I suspect the time required to move from room to room would blur the audible memory enough so it ended up sounding the same.

Notice they also tested pair of 16 ohm creative IEMs.  If somebody showed me that graph, told me nothing else, and asked me to blind test the differences between amps, I'd laugh and walk away.  In this case the impedance of the speaker amps is probably (my speculation) quite a bit higher than 16 ohms so my "output impedance of headphone should be higher than headphone jack impedance" rule of thumb falls flat on it's face.

If the output jack impedance is near 0, the frequency response is typically flat or near flat with just about any headphone.  It really doesn't take much to have a headphone amp with a low impedance output.  Even a Cmoy ($50 on ebay) can do this.

What does a secondary headphone amp do exactly?

Reply #17 –
Quote from: uart on
2. Pushing the volume control higher to achieve the same listening volume on higher impedance phones does NOT waste power and may very well do the exact opposite! ( That is, reduce the power consumption. )


No it definitely uses more power at higher volumes.  You can verify this easily enough with an ammeter and a regulated powersupply.    Of course, the higher impedance of the headphones can also save power too, so its a tradeoff. 

Quote from: uart on
A typical class B or class AB output stage ...


Cass AB on a DAP?  The battery would be dead in no time

Modern DACs use much more efficient designs then that.

Quote from: uart on
BTW. In the above I'm not making any claims about whether high-Z verus low-Z phones construction gives any intrinsic sonic advantage. I dont know if your low-Z phones sound  better or worse than the high-Z ones when both are driven from a suitable amplifier. All I'm saying that if you like the sound of the High-Z ones on a good amplifier then there is no reason not to use them on the Zune (no matter how high is the impedance) as long as you can get enough volume.


Its usually pretty safe to assume that higher == better for a DAP.  RMAA tests as a function of impedance are a lot of fun on most devices:

http://rmaa.elektrokrishna.com/Comparisons...%2048%20Ohm.htm

Note that as the impedance approaches line out, the frequency response approaches being good

Just don't go too high that you get stuck needing an amp!

What does a secondary headphone amp do exactly?

Reply #18 –
Quote from: HTS on
So the "audiophile" amps sounding a little more neutral vs the integrated amps, is not because of the difference in the headphones' impedance, but because of the amps themselves right?


Its mostly because audiophiles aren't the brightest people when it comes to audio.

Quote from: HTS on
Like a low impedance headphone of 32 ohms will benefit equally from an "audiophile" amp than a 300ohm headphone?


No.  If you have low impedance headphones, and a DAP with a crappy DAC/Amp, it may have trouble driving them.

In this situation, I'd buy a DAP that didn't have crappy output.  But you can also buy an amp too.

Quote from: HTS on
So if the Zune sounds a little "off" (I'm not saying that it does) with the high impedance headphones, the problem here is independent of the impedance of the headphone?


It won't sound off with high impedance, but it may sound quieter. 

What does a secondary headphone amp do exactly?

Reply #19 –
Quote from: uart on
- The higher current demand of low-Z phones can increase the distortion levels of your devices output stage. In particular (for devices with AC coupled outputs) low-Z phones might strain the output coupling capacitor a bit which can increase low frequency distortion and impair the low end frequency response.


Replacing the output coupling capacitors in a device, that suffers from low end roll-off with low impedance phones, like some iPod models do, would be much more portable while having the same quality as a good additional amp. Does anybody have links to sites that document such mods for iPods & Co.?

What does a secondary headphone amp do exactly?

Reply #20 –
Quote from: uart on
- The higher current demand of low-Z phones can increase the distortion levels of your devices output stage. In particular (for devices with AC coupled outputs) low-Z phones might strain the output coupling capacitor a bit which can increase low frequency distortion and impair the low end frequency response.


Yes but I suggest you actually perform a volume matched test before running out to get an amplifier.  A lot of people use "facts" like the above to justify the purchase and existence of expensive portable amplifiers.  Myself, I used the bass rolloff and measurements of an RMAA graph to justify buying a dedicated amplifier for the Denons.  Yet, when I actually did a volume matched test using an A/B switch, I found the differences were quite small.  In truth, I probably only heard them because I had an A/B switch and could almost instantaneous switch between the internal amp in the PMP and a headphone amp.  Had there been even a 2 second gap between the switching, I'm not confident in passing a blind test.

This is why I value volume matched tests.  You can use measurements to justify just about any purchase (-80db of stereo crosstalk is better than -77!), but these differences may range from minor to inaudible.

Quote
So the "audiophile" amps sounding a little more neutral vs the integrated amps, is not because of the difference in the headphones' impedance, but because of the amps themselves right?


If you are talking about speaker versus many dedicated solid-state (no tubes) headphone amps, the sound differences are typically from a combination of the headphone impedance and speaker amp headphone jack output impedance.  As far as the differences between all the dedicated amps on Head-Fi, I'll propose those differences are mostly between the listeners ears.

What does a secondary headphone amp do exactly?

Reply #21 –
Quote from: Mike Giacomelli on
Quote from: uart on
A typical class B or class AB output stage ...


Cass AB on a DAP?  The battery would be dead in no time  Modern DACs use much more efficient designs then that.


Hi Mike, do most DAPs use class D output stages to increase efficiency? I wouldn't have thought the current drain of a class A-B stage would have been all that bad when only driving earbuds. Anyway even with a class-D output the power demands should not increase with Hi-Z phones. A class D amplifier should consume no more power when suppling a given output power level to a high impedance load (albeit at a higher volume setting level) than it would to supply the same output power to a low impedance load. Why would the efficiency of a class-D be reduced when driving a higher impedance load? If anything I would have thought it would still be slightly better due to lower I^2_R losses.


Quote
Replacing the output coupling capacitors in a device, that suffers from low end roll-off with low impedance phones, like some iPod models do, would be much more portable while having the same quality as a good additional amp. Does anybody have links to sites that document such mods for iPods & Co.?


Hi rpp3ro and odigg. I have to admit that most of my experience (and interest) here is not with DAP's but with sound cards and motherboard audio output stages. Here in RMAA tests I've found that onboard audio in particular can suffer a lot at low frequencies (roll off and added distortion) when low impedance phones are connected.

What does a secondary headphone amp do exactly?

Reply #22 –
File Edit Options Buffers YASnippet Tools Help
Quote from: odigg on
So many people claim dedicated headphone amps improve the "sound
quality" of headphones, but when you ask them to demonstrate it using
objective measures or even in a blind test, you end up with a lot of
subjective mumbo-jumbo.

I don't see how passing a blind test helps to determine "sound quality", it would only show
that there is audible difference.  I have a portable amplifier that sounds tad bright and hence
possible to identify, but to say it is better would still be subjective mumbo-jumbo.
Teemu

What does a secondary headphone amp do exactly?

Reply #23 –
Quote from: uart on
Quote from: Mike Giacomelli on
Quote from: uart on
A typical class B or class AB output stage ...


Cass AB on a DAP?  The battery would be dead in no time  Modern DACs use much more efficient designs then that.


Hi Mike, do most DAPs use class D output stages to increase efficiency? I wouldn't have thought the current drain of a class A-B stage would have been all that bad when only driving earbuds.


SOCs are sold on cost and power consumption more then anything.  Even a few mW of added power consumption cannot be tolerated when the entire system is running on << 70-100 mW.  On many systems, the amp can use nearly as much power as the CPU core.  It makes little sense to spend a fortune on a high end low power CMOS process then throw away the benefits on an inefficient amp.

Quote from: uart on
Anyway even with a class-D output the power demands should not increase with Hi-Z phones. A class D amplifier should consume no more power when suppling a given output power level to a high impedance load (albeit at a higher volume setting level) than it would to supply the same output power to a low impedance load. Why would the efficiency of a class-D be reduced when driving a higher impedance load? If anything I would have thought it would still be slightly better due to lower I^2_R losses.


See the next couple sentences after the ones you quoted in my above post

What does a secondary headphone amp do exactly?

Reply #24 –
Quote from: tot on
I don't see how passing a blind test helps to determine "sound quality", it would only show
that there is audible difference.  I have a portable amplifier that sounds tad bright and hence
possible to identify, but to say it is better would still be subjective mumbo-jumbo.


Many people claim, as you have in your previous post, that using a dedicated headphone amp improves the "sound quality" when compared to a headphone plugged straight into a headphone jack.  That would indicate to me that there is a sonic difference between the two pieces of hardware (a dedicated headphone amp versus a built in headphone jack).  If a such a sonic difference exists, it should be verifiable in a volume matched blind test.  You made the following claims in your first post.

1. The main function from "audiophile" point of view is that they drive headphones much better than built-in headphone outputs.
2. Portable ones have to make compromises for power consumption and size, but full size class-A amplifiers are clear improvement, how big depends on headphones
3. When trying a dedicated amplifier the benefits may not be obvious at first, but once you get accustomed to the sound you may not want to back.

From my reading of your posts, you made comments alluding to improved "sound quality" when using a headphone amp.  This would indicate a sonic difference.  According to TOS8, the burden falls on you to demonstrate this difference using the terms in TOS8.

Yes, you did not specifically say "sound quality" but I assumed it was implicit.  I may have done this in error so let me say you really claimed a difference in "sound quality" rather than an improvement. But you have made a claim to a sonic difference and this such a difference should be verifiable in a blind test.