[CraftyClown]

Hi all,
 
I'd be grateful if someone could explain the science behind something for me?
 
I often see people saying that an amp or DAP can drive headphones to a sufficient volume without clipping, however these headphones aren't sounding as good as they should.
 
Is there something to this? and if so what is the problem?

 

[sonitus mirus]

Probably won't find a better explanation of the science outlined in layman's terms.
 
http://tinyurl.com/7x6uabs

 

[CraftyClown]

  Probably won't find a better explanation of the science outlined in layman's terms.
 
http://tinyurl.com/7x6uabs

 
Ok, so if I'm understanding what I read there correctly then power is not a factor, providing you are able to drive the headphones to a sufficient volume?
 
I was having a discussion regarding headphones not sounding right with a particular DAP, despite the volume being adequate, on another thread and I was a little confused by some of the comments. Do they make sense?
 
"Well "sufficient power" is the key words here. Many amps may not have sufficient power but still can make a can sound loud"
 
"it's not just about the volume to drive headphones loud.  You have different drivers: balanced armatures, dynamic (small IEM and larger ones used in full size, electrostatic, planar magnetic, and others.  All of these drivers/transducers have different spec and require sources with different characteristics to sound their best.  IEMs are usually less demanding and we can use them with smartphone and many portable daps.  But when you start getting into higher impedance full size cans or planar magnetic drivers you need beefier amp (higher voltage/current) to drive them to their full potential."

 

[zareliman]

I'll try to answer briefly.

It depends on the music you are listening to. Usually records from before the 90's, classical music, acoustic and jazz are highly dynamic. More dynamics means higher standard deviation from the average loudness. This means when you have an 85 dB SPL average you might be having peaks at much higher dB, so that's when sometimes the source will clip if the source is not capable of providing power for that peak. Usually digital sources such as phones or cheap DAPs don't really produce digital amplification (they range from -90 to 0 db) so they won't really clip in this kinds of situations, they just will not sound very loud on average (so that the loud peaks don't saturate the sources). In this case sufficient volume is sufficient for the average but it might not be enough for the loud peaks.

Most post-90's records mastered for redbook CD, specially popular and mainstream music has much lower dynamics allegedly to avoid this kind of issues. Music with lower dynamics has low standard deviation, which means the peaks don't deviate much from the average loudness and you don't really get this much louder peaks that need that extra punch. This dynamic compression allows to digitally amplify the average loudness without saturating on the peaks, which allows the source to produce much higher average loudness without clipping on the peaks (because there's practically no notorious peaks). In this case sufficient volume is indeed sufficient.

 

[CraftyClown]

I'll try to answer briefly.


It depends on the music you are listening to. Usually records from before the 90's, classical music, acoustic and jazz are highly dynamic. More dynamics means higher standard deviation from the average loudness. This means when you have an 85 dB SPL average you might be having peaks at much higher dB, so that's when sometimes the source will clip if the source is not capable of providing power for that peak. Usually digital sources such as phones or cheap DAPs don't really produce digital amplification (they range from -90 to 0 db) so they won't really clip in this kinds of situations, they just will not sound very loud on average (so that the loud peaks don't saturate the sources). In this case sufficient volume is sufficient for the average but it might not be enough for the loud peaks.


Most post-90's records mastered for redbook CD, specially popular and mainstream music has much lower dynamics allegedly to avoid this kind of issues. Music with lower dynamics has low standard deviation, which means the peaks don't deviate much from the average loudness and you don't really get this much louder peaks that need that extra punch. This dynamic compression allows to digitally amplify the average loudness without saturating on the peaks, which allows the source to produce much higher average loudness without clipping on the peaks (because there's practically no notorious peaks). In this case sufficient volume is indeed sufficient.

Thanks that's fascinating. So if I understand you correctly this shouldn't be an issue with a decent high powered DAP or amp then?

 

[castleofargh]

basically when you tell an audiophile to talk about amps, he will answer "power". most people don't understand amp designs and don't understand basic electricity like the interactions with a given load. in short they don't have a clue and you shouldn't even care about what they say.
now those same people always have an opinion on which sounded better and that's natural. even I have personal taste. but if they simply said "I preferred this one but I don't know why", then they wouldn't look like expert audiophiles now would they?
ask how they came to their opinion, and most likely you'll know why you shouldn't care about their opinion. the method is as important as the conclusion and most audiophiles have no method.
 
of course loud isn't everything, for example there is a reason why we get amps max power @1%THD into a given load instead of just being fine with max power. thinking that how loud it goes is all we need, is the same nonsense as thinking we can explain how something sounds with frequency response alone. it's a great information, but sound is still more than 1 variable. knowing that we go loud enough or that we get enough power(which is correlated once you're set on a given headphone) will help know that the system can work as intended, but it doesn't tell us about fidelity or taste. 
 for power, if the load(headphone) is known, and the loudness is known, then you have a pretty good idea of the power used. for those not clear about electrical behaviors with a load in series, think about the almost ok water analogy for current and voltage. 

the pipe is the headphone, the amp is the water tank. a really bad amp is when the pipe isn't the limiting factor(bad impedance ratio, low current...).  most modern headphones and amps should work in an "impedance bridging" system where the diameter of the pipe should be way smaller than the diameter of the water tank. that is to say the impedance of the headphone should be way bigger than the impedance of the amp. once that is assured, it's pretty obvious that the current flow will be strongly limited by the headphone and not by the amp, the impedance is more or less stable, so what's left to care about is voltage/loudness.
 obviously if you start driving a 50ohm headphone with a 120ohm amp, then it's a whole other game as you're now using a pipe larger than the water tank ^_^.  but when you do what you're supposed to do and keep a good damping ratio, then enough voltage is often the same thing as enough power as long as you don't get into clipping or mad distortions(thus the @1%THD for power into a load being a nice extra information).
 
 
different loads will have different needs, and some amp designs will not behave as well with all loads. but there are reasons for that, and just saying it needs more power to look like we know stuff is like saying I eat baguette because I'm french. it looks legit, and in fact often enough it will be true, but obviously sometimes it was a croissant and you look like a fool when you call my croissant a baguette.
 
 
 
now if you'll excuse me, I have my meeting with the Analogy Anonymous. I want to stop using it's just so hard!!!!

 

[CraftyClown]

  basically when you tell an audiophile to talk about amps, he will answer "power". most people don't understand amp designs and don't understand basic electricity like the interactions with a given load. in short they don't have a clue and you shouldn't even care about what they say.
now those same people always have an opinion on which sounded better and that's natural. even I have personal taste. but if they simply said "I preferred this one but I don't know why", then they wouldn't look like expert audiophiles now would they?
ask how they came to their opinion, and most likely you'll know why you shouldn't care about their opinion. the method is as important as the conclusion and most audiophiles have no method.
 
of course loud isn't everything, for example there is a reason why we get amps max power @1%THD into a given load instead of just being fine with max power. thinking that how loud it goes is all we need, is the same nonsense as thinking we can explain how something sounds with frequency response alone. it's a great information, but sound is still more than 1 variable. knowing that we go loud enough or that we get enough power(which is correlated once you're set on a given headphone) will help know that the system can work as intended, but it doesn't tell us about fidelity or taste. 
 for power, if the load(headphone) is known, and the loudness is known, then you have a pretty good idea of the power used. for those not clear about electrical behaviors with a load in series, think about the almost ok water analogy for current and voltage. 

the pipe is the headphone, the amp is the water tank. a really bad amp is when the pipe isn't the limiting factor(bad impedance ratio, low current...).  most modern headphones and amps should work in an "impedance bridging" system where the diameter of the pipe should be way smaller than the diameter of the water tank. that is to say the impedance of the headphone should be way bigger than the impedance of the amp. once that is assured, it's pretty obvious that the current flow will be strongly limited by the headphone and not by the amp, the impedance is more or less stable, so what's left to care about is voltage/loudness.
 obviously if you start driving a 50ohm headphone with a 120ohm amp, then it's a whole other game as you're now using a pipe larger than the water tank ^_^.  but when you do what you're supposed to do and keep a good damping ratio, then enough voltage is often the same thing as enough power as long as you don't get into clipping or mad distortions(thus the @1%THD for power into a load being a nice extra information).
 
 
different loads will have different needs, and some amp designs will not behave as well with all loads. but there are reasons for that, and just saying it needs more power to look like we know stuff is like saying I eat baguette because I'm french. it looks legit, and in fact often enough it will be true, but obviously sometimes it was a croissant and you look like a fool when you call my croissant a baguette.
 
 
 
now if you'll excuse me, I have my meeting with the Analogy Anonymous. I want to stop using it's just so hard!!!!

 
Ha ha, those were some great analogies. Especially the baguette one! 
 
So the particular combo in question that instigated this conversation was the Lotoo Paw Gold which is 500mw per channel into 32 ohms and the Sennheiser HD800s which have an impedance of 300 ohms. Would this kind of pairing potentially warrant these kind of comments regarding the headphones not sounding right?

 

[castleofargh]

500mw into 32ohm is a meaningless information for the hd800s, so IDK. anybody with that DAP and a 300ohm resistor could try and RMAA or whatever depending on the gears they have, to see if there are obvious limitations into such a load.
but from experience people really love to call the hd800 hard to drive when most of them simply don't like it. but then the hd800 is known as the best dynamic driver headphone, so saying you don't like it is like admitting you don't like good sound or some other elitist BS. instead many people just throw all kinds of sources and amps at it until some combo ruins and EQ the sound enough to feel good. then they'll talk about how hard the hd800 is to "drive correctly".

 
as long as you don't remove subjectivity, you can't know if it's ever actually a power problem. electricity is not subjective.

 

[Samueru Sama]

  Hi all,
 
I'd be grateful if someone could explain the science behind something for me?
 
I often see people saying that an amp or DAP can drive headphones to a sufficient volume without clipping, however these headphones aren't sounding as good as they should.
 
Is there something to this? and if so what is the problem?

 
High output impedance and or small output coupling capacitors are the most common source of problems.
 
Listen to these: https://mega.nz/#!sUgxzRgS!JLTybF_ElfTmROh6pzDngcP8wJoRqA2Sm2V5fZxq-BA
 
That motherboard has terribly small output coupling capacitors, even with a 320 Ohm completely resistive load there's a noticeable loss of sub-bass, and the 32 Ohm one directly sounds terrible, that's because the output caps with the load create a RC high pass filter. And remember that is a completely resistive load, with a reactive load there are more issues. Here's a good explanation: http://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html.
 
By the way you also have to make sure that the thing is really able to output enough power for your headphones, the Lotoo Paw Gold doesn't output 500 mWrms at 32 Ohm.
 

 

 
 
500 mWrms @32 Ohm = 4 Vrms. The thing is already clipping before reaching 3 Vrms.
 
http://reference-audio-analyzer.pro/report/amp/lotoo-paw-gold.php

 

[spruce music]

  basically when you tell an audiophile to talk about amps, he will answer "power". most people don't understand amp designs and don't understand basic electricity like the interactions with a given load. in short they don't have a clue and you shouldn't even care about what they say.
now those same people always have an opinion on which sounded better and that's natural. even I have personal taste. but if they simply said "I preferred this one but I don't know why", then they wouldn't look like expert audiophiles now would they?
ask how they came to their opinion, and most likely you'll know why you shouldn't care about their opinion. the method is as important as the conclusion and most audiophiles have no method.
 
of course loud isn't everything, for example there is a reason why we get amps max power @1%THD into a given load instead of just being fine with max power. thinking that how loud it goes is all we need, is the same nonsense as thinking we can explain how something sounds with frequency response alone. it's a great information, but sound is still more than 1 variable. knowing that we go loud enough or that we get enough power(which is correlated once you're set on a given headphone) will help know that the system can work as intended, but it doesn't tell us about fidelity or taste. 
 for power, if the load(headphone) is known, and the loudness is known, then you have a pretty good idea of the power used. for those not clear about electrical behaviors with a load in series, think about the almost ok water analogy for current and voltage. 

the pipe is the headphone, the amp is the water tank. a really bad amp is when the pipe isn't the limiting factor(bad impedance ratio, low current...).  most modern headphones and amps should work in an "impedance bridging" system where the diameter of the pipe should be way smaller than the diameter of the water tank. that is to say the impedance of the headphone should be way bigger than the impedance of the amp. once that is assured, it's pretty obvious that the current flow will be strongly limited by the headphone and not by the amp, the impedance is more or less stable, so what's left to care about is voltage/loudness.
 obviously if you start driving a 50ohm headphone with a 120ohm amp, then it's a whole other game as you're now using a pipe larger than the water tank ^_^.  but when you do what you're supposed to do and keep a good damping ratio, then enough voltage is often the same thing as enough power as long as you don't get into clipping or mad distortions(thus the @1%THD for power into a load being a nice extra information).
 
 
different loads will have different needs, and some amp designs will not behave as well with all loads. but there are reasons for that, and just saying it needs more power to look like we know stuff is like saying I eat baguette because I'm french. it looks legit, and in fact often enough it will be true, but obviously sometimes it was a croissant and you look like a fool when you call my croissant a baguette.
 
 
 
now if you'll excuse me, I have my meeting with the Analogy Anonymous. I want to stop using it's just so hard!!!!

Yeah, analogies are so misleading......................except when they aren't.  I think yours is case when they aren't misleading.  Good post.

 

[zareliman]

Thanks that's fascinating. So if I understand you correctly this shouldn't be an issue with a decent high powered DAP or amp then?

AFAIK, usually DAPs or DACs should not clip if the source is the untouched record (and the record is a proper one) even at full volume.
If the amp is integrated it will take the 2V output from the DAC and do whatever, in that case clipping is also unlikely.

Equalizers, RG, DSPs and other stuff can eventually push digital clipping.
Multi stage amplification (notably using a preamp and then a separate power amp) is where problems begin because if the input is higher than 2V, then the power amp at full gain might not be able to amplify that voltage. AFAIK amps gain is rated for a 2V input, so 4x gain would yield 8V signal. This doesn't mean the same 4x gain amp will be able to produce 16V from a 4V input.

 

[pinnahertz]

 
AFAIK, usually DAPs or DACs should not clip if the source is the untouched record (and the record is a proper one) even at full volume.
If the amp is integrated it will take the 2V output from the DAC and do whatever, in that case clipping is also unlikely.

Equalizers, RG, DSPs and other stuff can eventually push digital clipping.
Multi stage amplification (notably using a preamp and then a separate power amp) is where problems begin because if the input is higher than 2V, then the power amp at full gain might not be able to amplify that voltage. AFAIK amps gain is rated for a 2V input, so 4x gain would yield 8V signal. This doesn't mean the same 4x gain amp will be able to produce 16V from a 4V input.

It's a power supply voltage issue.  If the DAP or DAC is meant to run or charge on USB power, that's single pole 5V.  Without some internal voltage multiplier (often a noise source), the maximum RMS voltage you can ever get is just under 2V (actually about 1.7V), and that assumes you can peak at the full supply rails (usually not).  If the system can run on a higher supply voltage, and you have a means of doing that cleanly, you can clip at much higher voltages.  Back in the day when I designed stuff we ran bipolar 15V supply rails, and clipped well above 8V rms.  Today's lower supply voltages dictate maximum output before clipping...all stages.   With a DSP EQ you have to scale gain anyway, because most music will hit a peak within a few dB of 0dBFS.  If you apply gain EQ digitally there must be scaling applied or you can go above 0dBFS quite easily.  
 
The only places you'll ever see 16V is a pro-audio balanced line output or a power amp. 

 

[Joe Bloggs]

By the way you also have to make sure that the thing is really able to output enough power for your headphones, the Lotoo Paw Gold doesn't output 500 mWrms at 32 Ohm.








500 mWrms @32 Ohm = 4 Vrms. The thing is already clipping before reaching 3 Vrms.

http://reference-audio-analyzer.pro/report/amp/lotoo-paw-gold.php

Well with the HD800 being rated for 102dB/V, 2Vrms is still good for 102+6dB = 108dB, which is still plenty loud for most situations. And again most people's complaints of the HD800's sound have nothing to do with the driving power available behind them. For example they'd say that the bass sounds weak or loose even though the impedance of the HD800 peaks at the bass and for a given variable load headphone the frequencies at which the impedance peaks are easiest to drive. Lack of understanding of amp / headphone interaction will lead most of those same people to cite said low frequency impedance peak as the reason for the loose / weak bass they hear. Heck they claim loose / weak bass as the result of any kind of underdriving when statistically underdriving headphones says nothing either way about frequency response changes, as illustrated by this sample argument and my rebuttal:

Often, when underpowering a headphone, the first thing to go is the bass. It might be boomy, loose, or non-existent. I think there's a whole lot of people out there underpowering their headphones.

When underpowering a headphone all the signal peaks simply get rounded out or lopped off as the case may be--this is not a frequency-selective process.

From top to bottom, frequency plots of the effects of hard clipping and soft clipping respectively carried out on sample music material:



The amount of clipping here is 4-5 dBs from the original peaks of the music, and just beginning to be audible. In either case the effect on overall frequency response is negligible, more like a boost to both the subbass and high treble in the case of hard clipping or a general attenuation in the case of soft clipping.

Distortion is most audible as... distortion--that buzzing, crackling sound that is easily audible at high levels of distortion. At low levels, when it is not easily audible, it does not introduce a mysterious loss of bass.

castleofargh made good analogies of how power does and does not relate to driving a pair of headphones properly. Here's a simpler analogy to how much sense it makes to always ask for more power from a given amp: http://tvtropes.org/pmwiki/pmwiki.php/Main/TimTaylorTechnology

To make things more fun, amplification problems are often the LAST thing I look at when faced with a sound quality problem but the FIRST thing for most anybody else around here. :rolleyes:

 

[castleofargh]

 axiom: knowledge is power.
so it's only logical that people with no electrical understanding would wish for more power as a way to compensate.  but I don't know if that axiom applies to electrical devices? maybe I should get more power to make sure.

 

[pinnahertz]

   axiom: knowledge is power.
so it's only logical that people with no electrical understanding would wish for more power as a way to compensate.  but I don't know if that axiom applies to electrical devices? maybe I should get more power to make sure.

My highest power amp is still pretty stupid.  It's so dumb, all it does is take whatever I give it and amplify it.   Maybe knowledge is power, but power isn't knowledge?