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Can we agree headphone amplifiers are solved?

thewas

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Actually audio electronics like Hifi amps were already solved in the 70s where already implementations existed with far better measurements than any hearing threshold (thus transparent) so I find it weird that such is questioned even today when a smartphone has more computing power then all supercomputers of that time.

Ok, after the end of the hifi boom in the late 80s most serious big R&D companies left the game and the market was partially taken over by small boutique "highend" crap but the measurements of some great $99 amps show its no magic to get transparent measurements and sound in the for today's technology laughable audio region up to 20 kHz when for example we have DSPs which calculate millions of pixels several times a second.
 

bobbooo

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It's not possible for an amplifier to have high IMD yet low THD, as it's the same mechanism that creates both, non linearity of transfer function. Ditto with other non-linearities, they show up on a single sine wave, or if they don't, then there aren't any.

S

I've seen some evidence of a not entirely monotonic correlation between THD and IMD, e.g. the Topping DX7 and DX7s (admittedly these are DACs not amps):

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As can be seen here, the DX7 has higher average and peak THD than the DX7s, yet the latter has higher IMD. I still think it's possible other nonlinearities may be missed by the standard test tone suites.
 

bobbooo

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There are no “highly complex waveforms of a music signal”, only lots and lots of sine waves piled atop one another.

Yep, 'highly complex waveform' is synonymous with 'superposition of lots and lots of very different sine waves', so just replace that in my comment if you like, but I don't think it changes the possibility that there could be nonlinearites in a device that produce distortion of a large superposition of unequally frequency-spaced sine waves of different amplitudes (music), yet do not manifest in distortion of single (THD), two (IMD), or a relatively small number of equally-spaced, equal amplitude sine waves (multitone test).
 
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phoenixdogfan

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Recently there has been multiple headphones amps challenging the THX AAA 789 for top notch performance, some surpassing it, and at lower prices. It seems that many different companies had figured out how to make completely transparent headphone amps even without THX circuitry. Maybe it's time to call it quits? Why keep develop new amps?

And another thing – what does this means for power amplifiers? Why don't we see SINAD of 120 in those? It seems that for lower power and voltage, perfect linear amplification is easily achievable. What are the limiting factors to scaling this performance to the voltages and wattages of speaker amplifiers?
Now just make speaker amplifiers at the same level of performance with comparably low levels of cost.
 

bobbooo

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Others have addressed the 1st paragraph.

So for the 2nd, yes you would need the exact speaker in the identical room to reproduce exactly what the sound engineer heard. Which isn't practical. If recording mastering guys ever use an acceptably high fidelity speaker you would be close to only needing an equally high fidelity speaker yourself for playback. We aren't quite there and may never be. Plus room effects, etc. etc.

The intent of the artist etc is mostly a myth. Artists generally don't sit around listening to the mastering results and sign off on them. It happens, but it isn't normal. They often don't even have a say about it.

So considering all that the signal is all we have to go by, and fidelity to that at least until you reach the speakers is as far as you can go currently.

By 'artist' I am including the mastering engineer - they are part of the refinement of the 'art' that is the music. Basically the last person to make any changes to the final master before it's released is the culmination in a long chain of creation, that of course includes the composers and performers before them. Aiming for any artistic intent prior to that final stage would just be guesswork. And yes, to do all this properly would require the long overdue standardization of studios and monitors at the production end, and speakers matching the response of those monitors at the reproduction end (room EQ can help with environment differences). You might not get a perfect match, but just a simple approximate frequency response match would be way better than the mess we have now. Anyway, enough off-topic.
 

Blumlein 88

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I've seen some evidence of a not entirely monotonic correlation between THD and IMD, e.g. the Topping DX7 and DX7s (admittedly these are DACs not amps):

index.php


index.php


As can be seen here, the DX7 has higher average and peak THD than the DX7s, yet the latter has higher IMD. I still think it's possible other nonlinearities may be missed by the standard test tone suites.
I think if the other version of IMD testing (using twin tones close together and equal amplitude) were used you would not see such an anomaly.
 

bigjacko

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It isn't, this is an electrical parameter of a multichannel (more than one) system. It does not alter FR (linearity) or add new content (non-linearity).
What exactly is the effect of crosstalk if it does not add anything to the music?
 

solderdude

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I've seen some evidence of a not entirely monotonic correlation between THD and IMD, e.g. the Topping DX7 and DX7s (admittedly these are DACs not amps):

index.php


index.php


As can be seen here, the DX7 has higher average and peak THD than the DX7s, yet the latter has higher IMD. I still think it's possible other nonlinearities may be missed by the standard test tone suites.

This is a DAC. We are talking about amplifiers. Have you found similar plots for amplifiers ?
besides also in DACs this non linearity is not missed using test tones. It is clear to see in the plots.
Why would there be distortions using music that would be missed using multitones for instance. What is so special about music ?
Music, just like test tones is just a voltage changing level over time. The difference with music is that it isn't as easy to analyze as there is no pattern.
Nulling can do this but as explained a couple of time there are disadvantages to this method.

but I don't think ....
It's fine to suspect or think or reason that music is special in some way. It would be better if you presented some actual evidence of this.
Evidence not being Df or sighted listening tests as these have more issues than measurements using artificial and defined test signals.

You could start with proving this by building an actual analog null tester which has different but not the same challenges as a digital null tester.
So you know I already did such about 30 years ago and till this day still believe that measurements using artificial signals has advantages over nulling and disadvantages. Measurements are enough. What is lacking is the knowledge of the general public in how to interpret all of those measurements and perhaps a basic grasp of audibility levels.

Nulling is a great method but you need to listen to it, amplified and not amplified in order to assess whether or not the null is detrimental to the sound.
 
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Hipper

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So for the 2nd, yes you would need the exact speaker in the identical room to reproduce exactly what the sound engineer heard. Which isn't practical. If recording mastering guys ever use an acceptably high fidelity speaker you would be close to only needing an equally high fidelity speaker yourself for playback. We aren't quite there and may never be. Plus room effects, etc. etc.

In theory anyway, something like the Smyth Realiser or similar software (e.g. Out of Your Head) could do this for headphones.
 

sergeauckland

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In theory anyway, something like the Smyth Realiser or similar software (e.g. Out of Your Head) could do this for headphones.
I hadn't heard of 'Out of your Head' so I've just tried their demo, and sadly, it didn't work for me at all. It was still all in the plane of my head, although sounded wider than just the normal head width. I certainly didn't get any impression of listening to 'speakers in front. No surround effects either on the 5.1 tracks.

But then, I've never managed to hear surround with Ambisonics on headphones when the BBC broadcast the proms and some other music programmes that way. I haven't heard the Smyth Realiser, maybe that's better.

S.
 

JohnYang1997

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IMO Headphone amp is close to "solved". More about ground related, lower noise and better performance (more power) with just SE not replying on BAL output.
DAC is still in progress. When we see no weird tones in FFT, extremely low noise (very low noise even when playing at max volume). One day we will see sub -123dB thd+n under 300usd.
ADC is not yet started, we gotta find a way to push it to the same performance as dac first then surpass performance of current dac offerings.
Then there's DSP integration. There's very limited products with superb digital and analogue performance has DSP functionality and those that have DSP functionalities either performance in ADDA is poor or are very expensive.
 

MSTARK

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IMO Headphone amp is close to "solved". More about ground related, lower noise and better performance (more power) with just SE not replying on BAL output.
DAC is still in progress. When we see no weird tones in FFT, extremely low noise (very low noise even when playing at max volume). One day we will see sub -123dB thd+n under 300usd.
ADC is not yet started, we gotta find a way to push it to the same performance as dac first then surpass performance of current dac offerings.
Then there's DSP integration. There's very limited products with superb digital and analogue performance has DSP functionality and those that have DSP functionalities either performance in ADDA is poor or are very expensive.
Totally agree with this statement.
 

MSTARK

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@JohnYang1997
I have a question for you.
Is it possible with today’s technology to implement DSP processing to include or set profiles for various headphones? Of cause, in customer level products.
If so, where would this application be more practical to implement, amplifier or a DAC?
 

solderdude

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For SE headphone amps I would argue that the electronics is factors more 'solved' than 3-wire headphone cables which, in itself, again is factors more solved than transducers.

Low noise is possible, low distortion is possible, PCB layout and PS is also possible to do well, output power for headphones also is no problem but of course all of the above at the same time is a challenge.

Then there is the question what one considers 'solved', a matter of defining thresholds for 'solved'.
Is solved not visible on specified test equipment ? Is solved below certain (estalished) thresholds ?
 
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Fluffy

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ADC is not yet started, we gotta find a way to push it to the same performance as dac first then surpass performance of current dac offerings.
What are you basing this on? Amir doesn't really measure professional ADC devices. In ASR all I've seen are cheap interfaces. In the professional market you have digital recorders with far better quality.
 

solderdude

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@JohnYang1997
I have a question for you.
Is it possible with today’s technology to implement DSP processing to include or set profiles for various headphones? Of cause, in customer level products.
If so, where would this application be more practical to implement, amplifier or a DAC?

The way forward to this is to build a better miniDSP ears and calibrate the headphone(s) one owns through this device which then applies EQ.
This basically is what the miniDSP was designed to do. The idea is good, the implementation can be improved. I reckon it needs be affordable.
Using a large database won't cover all headphones and would need to be updated with new models coming out.
So measuring is the only logical way.

Caveats: Positioning headphones on the test rig can give substantially incorrect compensation. You could average multiple test runs. Then again it is no guarantee you will get 'perfect sound' but most likely it will be closer than doing nothing.
 

JohnYang1997

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What are you basing this on? Amir doesn't really measure professional ADC devices. In ASR all I've seen are cheap interfaces. In the professional market you have digital recorders with far better quality.

Name one that's cheaper than adi2pro but better performance?
 

JohnYang1997

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@JohnYang1997
I have a question for you.
Is it possible with today’s technology to implement DSP processing to include or set profiles for various headphones? Of cause, in customer level products.
If so, where would this application be more practical to implement, amplifier or a DAC?
Doing this is trivial stuff. But what's more important is the versatility of the framework and how much the error of the individual headphones and individual ears affect the result. It would be better to design a protocol or process that leads you to the target rather than just blindly implementing a profile.
 
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