[Tassie Devil]

I can only see two situations where head amps are essential -
 
1. When the DAP has insufficient output to drive the headphones to the required sound level (could be due to a weak DAP internal amp or to inefficient cans)
 
2. When there are severe synergy differences (maybe because of impedance problems) causing AQ to be reduced.
 
Apart from these I fail to see the use of a head amp for analog input.  It is taking the AQ output from the DAP, amplifying and processing it, so I cannot understand how it could ever yield better AQ than direct from the DAP.  The old GIGO applies so the amp could not be expected to improve AQ unless situation 2 above exists .  The best it can do is not further corrupt the analog signal.
 
Now if we are taking the digital out of a DAP then I can see an external DAC/amp combo could yield impressive improvement.  But as I understand it few DAPs offer the digital out option so most portable head amps are being used with analog input.  So it is in that context of analog input to amps I fail to see any benefit.
 
Please note I'm not trolling here and the above is my genuine conclusion after having sampled and used both a Fio Mont Blanc A12 and a Headstage 5.  But please do not fire back at me those amps are crap and I should have tried XYZ as it yields incredible and most impressive results.  Instead give me a rational explanation why spending hundreds of dollars on an analog input can improve the AQ.  To this old mind all it does is empty the pocket and increase the weight and complexity of the portable player.
 
FOOTNOTE:  
 
The players involved in arriving at my opinion are SONY A17, SONY A25, SONY ZX100 (and please let us avoid a similar accusation that these are crap and I would hear headphone amp differences with other DAPs.  If headphone amps improved AQ then I should hear a difference with the SONY ZX100/Sennheiser HD800 combo)
 
The headphones are AKG 702, Sennheiser HS598, two Sennheiser HD600, HiFiMan 400S and Sennheiser HD800 (yes, with an aftermarket balanced cable butchered to be unbalanced and a 3.5mm plug silver soldered in - that headphone is far superior to the others and really does show up AQ differences, if they exist that is!)

 

[DougD]

On some players, on analog OUT you have a choice of a line-out signal, which bypasses the DAP's internal amplifier. So in that case, you *could* definitely have better SQ by using an external portable head amp rather than the DAP's own amp.
 
But with the quality improvement of both DAPs and designed-for-portable-use headphones in the past 10 years, I think the market for portable head amps is a little puddle that is drying up quickly. With just a little care in choosing a DAP (or even a cellphone like the LG V10) and a matching headphone, there's absolutely no need for 99% of people to deal with the inconvenience of an additional box to carry around. 

 

[Jackson 6]

They have their plus and minus points. The bad? They make your in ears redundant and make just dap and in ears sound  second  class, on the plus side they transform the SQ of your dap and existing headphones, but  make it impractical for bike rides etc.

 

[GRUMPYOLDGUY]

Well, all portable headphone amplifiers use an analog input. Whether an external DAC is driving the amplifier or the DAC inside the DAP is driving the amplifier is somewhat irrelevant to your question.

Point 1 is that a lot of the AQ will depend on the DAC and the DSP chain leading up to it. So you're right in the sense that a large part of audio quality comes from somewhere other than the amplifier.

Point 2 is that the amplifier is not as insignificant as you might think. AQ is perceptive more than objective. The measurements we take tell us a lot about the objective characteristics, but not the perceptive. An example of this is tube amplifiers. Objectively they have more noise and distortion than an equivalent SS amplifiers, however many people perceive that distortion to be appealing. Amplifiers in general will have different transfer characteristics that may improve perceived quality, or, at the very least, listening experience.

Point 3 is the utilitarian point that some headphones simply may just require a more powerful output than what your DAP is capable of driving.




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[hylas512]

I would agree with the three points the poster above made, especially the point about needing more power. Before I had a nice pair of IEMs, my devices usually didn't provide my headphones with enough volume. I don't do much portable listening, but I have been surprised at some of the results from some portable amps I've sampled from friends.

 

[Tassie Devil]

Well, all portable headphone amplifiers use an analog input. Whether an external DAC is driving the amplifier or the DAC inside the DAP is driving the amplifier is somewhat irrelevant to your question.

Point 1 is that a lot of the AQ will depend on the DAC and the DSP chain leading up to it. So you're right in the sense that a large part of audio quality comes from somewhere other than the amplifier.

Point 2 is that the amplifier is not as insignificant as you might think. AQ is perceptive more than objective. The measurements we take tell us a lot about the objective characteristics, but not the perceptive. An example of this is tube amplifiers. Objectively they have more noise and distortion than an equivalent SS amplifiers, however many people perceive that distortion to be appealing. Amplifiers in general will have different transfer characteristics that may improve perceived quality, or, at the very least, listening experience.

Point 3 is the utilitarian point that some headphones simply may just require a more powerful output than what your DAP is capable of driving.




Sent from my E5803 using Tapatalk

 
Not sure I understand what you are saying Grump.  Surely the input to an external DAC is digital, not analog so surely it would be relevant to my original question?
 
You quote tube amplifiers being preferred by some because their distortion is preferred.  If that is what a user prefers then no argument such an external amp would suit but in general terms I still stand by my argument that no external amplifier, accepting the analog input from the DAP, can improve the quality of the AQ.  But if you mean it alters it to be more appealing because of added distortions then of course it is worthwhile for that person.  To my old mind (also gets quite grumpy at times) it seems an odd situation to pay hundreds of dollars for something that not only adds weight to the DAP package but also adds distortion. But then the world is full of people with odd tastes, me included.

 
And as I said in the first post, an amplifier is justified if the DAP output is insufficient to drive the desired headphone to a satisfactory SPL.  But apart from that I remain unconvinced they are necessary.  In general an added amp goes against the KISS principle.  The more items there are in the AQ chain, the more likely there will be a weaker link.

 

[GRUMPYOLDGUY]

Well, all portable headphone amplifiers use an analog input. Whether an external DAC is driving the amplifier or the DAC inside the DAP is driving the amplifier is somewhat irrelevant to your question.

Point 1 is that a lot of the AQ will depend on the DAC and the DSP chain leading up to it. So you're right in the sense that a large part of audio quality comes from somewhere other than the amplifier.

Point 2 is that the amplifier is not as insignificant as you might think. AQ is perceptive more than objective. The measurements we take tell us a lot about the objective characteristics, but not the perceptive. An example of this is tube amplifiers. Objectively they have more noise and distortion than an equivalent SS amplifiers, however many people perceive that distortion to be appealing. Amplifiers in general will have different transfer characteristics that may improve perceived quality, or, at the very least, listening experience.

Point 3 is the utilitarian point that some headphones simply may just require a more powerful output than what your DAP is capable of driving.




Sent from my E5803 using Tapatalk

 
Not sure I understand what you are saying Grump.  Surely the input to an external DAC is digital, not analog so surely it would be relevant to my original question?
 
You quote tube amplifiers being preferred by some because their distortion is preferred.  If that is what a user prefers then no argument such an external amp would suit but in general terms I still stand by my argument that no external amplifier, accepting the analog input from the DAP, can improve the quality of the AQ.  But if you mean it alters it to be more appealing because of added distortions then of course it is worthwhile for that person.  To my old mind (also gets quite grumpy at times) it seems an odd situation to pay hundreds of dollars for something that not only adds weight to the DAP package but also adds distortion. But then the world is full of people with odd tastes, me included.

 
And as I said in the first post, an amplifier is justified if the DAP output is insufficient to drive the desired headphone to a satisfactory SPL.  But apart from that I remain unconvinced they are necessary.  In general an added amp goes against the KISS principle.  The more items there are in the AQ chain, the more likely there will be a weaker link.

You asked about amplifiers, not DACs. The amplifier section comes after the DAC and is strictly analog. And of course an amplifier (like the ALO Rx) is strictly an amplifier and has no digital component at all. The only point I was trying to make with that statement was that when you said "most portable head amps are being used with analog input", it's kind of a tautology... All portable amplifiers use an analog input. In the context of this discussion, only DACs use a digital input.

I'm inclined to agree with you that, in practice, driving an amplifier directly from the amplified output of the DAP will not yield improvements to AQ. That said, it is possible to get improvements in theory. For example a filter on the front end of an amp to remove switching and EMI noise. Because the amp would be in a separate housing it would be less prone to picking up switching noise again. I don't know of any available products off hand that do this though.

Now, I think that if you took an analog preamp output from the DAP and ran that through an amplifier, you could achieve substantially and noticably better performance through an external amplifier. The amp stages in portables are limited by space/size and power consumption. It inherently limits the design of the amplifier section inside the portable.

I hope that helps.



Sent from my E5803 using a highly trained, special forces carrier pigeon

 

[Tassie Devil]

You asked about amplifiers, not DACs. The amplifier section comes after the DAC and is strictly analog. And of course an amplifier (like the ALO Rx) is strictly an amplifier and has no digital component at all. The only point I was trying to make with that statement was that when you said "most portable head amps are being used with analog input", it's kind of a tautology... All portable amplifiers use an analog input. In the context of this discussion, only DACs use a digital input.

I'm inclined to agree with you that, in practice, driving an amplifier directly from the amplified output of the DAP will not yield improvements to AQ. That said, it is possible to get improvements in theory. For example a filter on the front end of an amp to remove switching and EMI noise. Because the amp would be in a separate housing it would be less prone to picking up switching noise again. I don't know of any available products off hand that do this though.

Now, I think that if you took an analog preamp output from the DAP and ran that through an amplifier, you could achieve substantially and noticably better performance through an external amplifier. The amp stages in portables are limited by space/size and power consumption. It inherently limits the design of the amplifier section inside the portable.

I hope that helps.



Sent from my E5803 using a highly trained, special forces carrier pigeon

I see we are not really on opposite sides of the fence.
 
I wondered about bypassing the DAP amp with line out so purchased an adaptor for the SONY ZX100 to do just that.  I experimented feeding the signal from the DAP via the headphone socket (using the internal amp) and via the adaptor (line out) but could detect no difference.  The feed was into a high quality Luxman integrated amp and to high quality Dali speakers.
 
Now it could be that these old ears are too tired to be able to detect subtle differences, or that the Luxman amp/speakers were not good enough to reproduce them but the bottom line for me was it was wasted effort if I could not hear improvement.  And my ears, although deficient is high frequency sensitivity, are not insensitive to AQ and differences in headphones and AQ in general can be clearly detected.
 
So I'm not sure what conclusion (except of no advantage to me) can be drawn.  Even if only line out, the internal DAC is used and presumably some of the internal amplification circuitry although all of the (much of it ghastly) sound modification circuitry is most certainly avoided.  I'm suspecting that the latest crop of high quality DAPs have miniaturized circuitry down to a fine art with the DACs and amps used being of very high quality. 
 
I've been guilty of it and suspect our problem is we always have the feeling at the back of our mind that items are built to a price and we are clever enough to improve the AQ.  So the conclusion fort me is that no, I'm not clever enough to improve on what the SONY ZX100 offers.  And I should add, the AQ from it IS better, although it is only subtle, than the SONY A25 & SONY A17 also here.

 

[GRUMPYOLDGUY]

I hear you on that. I noticed a lot of contention around here on improvements vs. audible improvements.

As an engineer, I don't really care if I can hear the difference as long as I can measure it. If I can get an extra dB of gain, or an extra 10Hz of 3dB bandwidth, or a few dB of SNR... I want (read: need) it. Your mileage will definitely vary regarding what you hear.

I've definitely noticed a huge difference in some equipment and substantially less of a difference. I think many others have also.

But yes, definitely agree a second amplifier in the chain almost always will not yield improvements over just the first amp.

Sent from my E5803 using a highly trained, special forces carrier pigeon

 

[Tassie Devil]

I hear you on that. I noticed a lot of contention around here on improvements vs. audible improvements.

As an engineer, I don't really care if I can hear the difference as long as I can measurement. If I can extra dB of gain, or a 10Hz of 3dB bandwidth, or a few dB of SNR... I want (read: need) it. Your mileage will definitely vary regarding what you hear.

I've definitely noticed a huge difference in some equipment and substantially less of a difference. I think many others have also.

But yes, definitely agree a second amplifier in the chain almost always will not yield improvements over just the first amp.

Sent from my E5803 using a highly trained, special forces carrier pigeon

 LOL, I like your high-tech method of communication.

  You are obviously keeping that bird updated with the latest software to keep it nice and warm.

 

[GRUMPYOLDGUY]

Unfortuately "auto correct" absolutely butchered it. Fixed it though.

 

[Tassie Devil]

Unfortuately "auto correct" absolutely butchered it. Fixed it though.

Have you tried this APP?
https://itunes.apple.com/au/app/dont-let-pigeon-run-this-app!/id459749670?mt=8