Aiyima A07 Max Amplifier Review

[Trekkis]

Hi Trekkis.

No one is 'silent' about the testing and implementation of the TPA3255 chip and certainly not TEXAS INSTRUMENTS.

If you want to know more about this chip and understand better, I invite you to do some GOOGLE searches with this document ->

View attachment 419102

Hi, But I have in mind tests performed by reviewers. No one is showing this.

@Guddu,
I can provide later waveform screens. For the moment from simple scope, as currently I do not have access to better one, but on better ones (Like 12bit Siglent) output was the same.

 

[ICIETDIYEUR]

I don't really understand the meaning of your 'approach' Trekkis...

Do you want to demonstrate:
- that the TPA3255 chip is bad compared to others ?
- that some 'manufacturers' implement it less well than others ?
- other amps than in class D give better results ?
- that you have solutions that no one had thought of before ?

Please help me to understand better.

 

[Trekkis]

Hi.

It is well known that the higher the PWM frequency, the better.
Indeed, many have noticed that this 'ripple' decreases by more than half, going from 450KHZ to 600KHZ (e.g. DiyAudio forum).
It is the PWM frequency that is used in the amplifiers that get the best SINAD.

Hi, It's interesting that frequency is related with amplitude, I wouldn't expect that. But even more there is quality difference between aiyima and fosi here. As ayiyma has 400khz and three times higher amplitude than fosi with 600khz. So this in some way confirms that fosi is better.

Btw, the lowest distorsion is in my case in fosi mc 101. There is below 0.2V distorsion with much more flat amplitude (not sine in this case, so scope can not calculate frequency).

The worst one in this aspect from my measurmets is aiyima 07 max.

 

[Trekkis]

I don't really understand the meaning of your 'approach' Trekkis...

Do you want to demonstrate:
- that the TPA3255 chip is bad compared to others ?
- that some 'manufacturers' implement it less well than others ?
- other amps than in class D give better results ?
- that you have solutions that no one had thought of before ?

Please help me to understand better.

I simply want to understand topic, and why such effect is not included in measurments and reviews (and comparisons) when is very significantly visible on output. Maybe I do not know something, maybe explanation is very easy and this effect should be ignored. I would like to know.

Te easiest one is that this is not audible - but as I wrote, mosts measured parameters are. But they are indication of device quality. Or maybe my interpretation is in some way wrong? Logically, it should be better to have device with lower distorsion, in this case especially when some one is using lower volumes. On lower volumes it's even hard to recognize wave it's so distorted...

Chip is the same. Difference looks as matter of quality of manufacturer.

Class AB and A do not have this effect from very definition. They do not use PWM.

 

[ICIETDIYEUR]

The circuits must already be properly implemented

TI advised an 'addendum' for the TPA3255 regarding its use but without detailing it.
It's not a mistake on their part but I think that at their level it wasn't useful because it's so 'obvious' but yet NO ONE does it.
Maybe they didn't understand or thought it was useless because they think they know better than TI...

More than explanations, I offer you small diagrams that will make you better understand what I am trying to explain to you ->

I will let you experiment and make measurements.

Let's not forget that each component present on the circuit will generate 'noise' and especially the POWER SUPPLY

 

[antcollinet]

Keying one from terms used to describe pwm process used to create sound in class D. Class D is working simply using pulses (something like dsd), this is pulse modulation method. These pulses should be filtered on output (kind of like pcm is filtered on dac output) and quality of filters are part of quality of device.

It can be seen using any oscilloscope, that output wave is still very distorted on lower volumes (effect is not visible on higher volumes, and it is depended from used ps voltage, also quality of used ps is directly visible within wave output) by not fully filtered pulses. Ayiyma has three time worse distorsion than fosi. Aiyima has 1V constant sine wave about 400khz, fosi has 0,3V wave about 600khz. This separate wave is directly distorting real audio wave.

Yes, I'm aware that those are ultrasonic and in practice something not directly Audible, but most measured parameters are not directly audible.
This one is huge (very huge on low volume levels) distorsion directly included within output waveform, and indication of quality of components. Differences between devices is significant. So it's strange for me, why tests are silent about this?

OK - you are talking about switching frequency leaking out into the output wave form. As you say, at 20x the maximum audible frequency - inaudble and not much to worry about.

 

[Trekkis]

I do not see clear response above.
Regarding psu this is something what I wrote few posts ago. If someone is thinking which psu to choose, not voltage is most important but quality. Bad psu is directly visible on output similary as keying is. And difference is big.

 

[antcollinet]

and why such effect is not included in measurments and reviews (and comparisons) when is very significantly visible on output.

Becuase it is a fundamental characteristic of class D designs, that has no impact on the audio quality. No need to measure - exactly as there are no measurements of distortion components outside of a 45kHz band.

You call it a quality difference. Arguably if it has no impact on quality then it is not.

 

[Trekkis]

OK - you are talking about switching frequency leaking out into the output wave form. As you say, at 20x the maximum audible frequency - inaudble and not much to worry about.

But isn't this indication of device quality? Kind of Engineering craftsmanship? As I mentioned, difference in many measured parameters are pure Theoretical. So why ommit this one?

It's hard to believe that such huge distorsion within output wave do not have audible impact effect in any way.

There is a reason, why many peoples prefer fosi sound that aiyima sound, despite the same components.

 

[antcollinet]

Let's not forget that each component present on the circuit will generate 'noise' and especially the POWER SUPPLY

All of which - if it gets to the output of the amp is measurable - and is measured.

 

[antcollinet]

But isn't this indication of device quality? As I mentioned, difference in many measured parameters are pure Theoretical. So why ommit this one?

Why?

Quality is a measure (fundamentally) as to how well something meets the needs of the customer. If something doesn't impact the customer - either through performance or reliability - then it is not a quality metric.

 

[Trekkis]

Why?

Quality is a measure (fundamentally) as to how well something meets the needs of the customer. If something doesn't impact the customer - either through performance or reliability - then it is not a quality metric.

Because you can non not be fully sure if something in fact do not have any audible impact for anyone, there is too many dependencies in audio. Especially when real listeners are in fact choosing between two usually product in with lower distorsion. May be coincidence but maybe is not?

Distorsion is distorsion, the goal of the product is to produce output as close as possible to provided input. More distorted output is cleary further away from the expected effect and goal.

 

[antcollinet]

Because you can non not be fully sure if something in fact do not have any audible impact for anyone,

There is no human who can hear anything close to 400KHz, or even 1/10th of that, and there is no speaker that will reproduce it, if even if they could. You are looking at a non issue.

Oh, and it is not distortion - it is noise.

 

[doug s.]

....There is a reason, why many peoples prefer fosi sound that aiyima sound, despite the same components.

this is patently false. there are hardly any, (if any?), people(s?) who prefer the sound of either fosi over aiyima. almost all choose one amp over the other due to aesthetics, or slightly different feature implementation. it's pretty-much unanimous that both brands offer similar, if not identical, outstanding performance. please stop spreading misinformation.

doug s.

 

[Guddu]

There is a reason, why many peoples prefer fosi sound that aiyima sound, despite the same components.

Don't mind me saying but there isn’t any Aiyima sound or Fosi sound, they both have decent/good/better products with different chips and designs.
There are many factors, other than same components, like amplifier size, heat dissipation, looks etc. helping making the decision.

 

[Trekkis]

There is no human who can hear anything close to 400KHz, or even 1/10th of that, and there is no speaker that will reproduce it, if even if they could. You are looking at a non issue.

Oh, and it is not distortion - it is noise.

Not frequency is problem here but amplitude. This is 1V! Where input from dac is 2V on max volume. Often a lot lower when volume is regulated before dac. This 1V signal can be even larger in amplitude than input signal! On lower volumes wave is so distorted that it's not even wave but some abstract form, one big mess. This is not noise (noise would be some lot lower than base signal and within audible range), this is absurdly huge distorsion, equal or higher than input. I have impression that some people may entairly dont realize What 1V amplitude mean in relation to input. No way that this do not affect sound in any way. Output wave simply is uncomparably better created as a whole in case of device with lower keying. This is day and night difference from wave fidelity Point of view.

 

[Trekkis]

this is patently false. there are hardly any, (if any?), people(s?) who prefer the sound of either fosi over aiyima. almost all choose one amp over the other due to aesthetics, or slightly different feature implementation. it's pretty-much unanimous that both brands offer similar, if not identical, outstanding performance. please stop spreading misinformation.

doug s.

There are many. Even when aiyima has a lot better feature set and price. V3 do not have mono mode, aiyima has. Aiyima is a lot cheaper (coincidence?). There are no Significant factors in form, size etc, but aiyima has also a lot better connectors. Still, after direct comparison fosi is usually choosed, ever despite features and price difference. Besides, check surveys above this and v3 threads. There is no need to look far away to find opinion examples.

 

[Joe Smith]

Not frequency is problem here but amplitude. This is 1V! Where input from dac is 2V on max volume. Often a lot lower when volume is regulated before dac. This 1V signal can be even larger in amplitude than input signal! On lower volumes wave is so distorted that it's not even wave but some abstract form, one big mess. This is not noise (noise would be some lot lower than base signal and within audible range), this is absurdly huge distorsion, equal or higher than input. I have impression that some people may entairly dont realize What 1V amplitude mean in relation to input. No way that this do not affect sound in any way. Output wave simply is uncomparably better created as a whole in case of device with lower keying. This is day and night difference from wave fidelity Point of view.

Sorry to say, but the A07 MAX does just fine for me at low volumes and there is no appreciable difference from the Fosi V3.

If you have any actual measurements or graphs, please feel free to share. If there is as much of a problem as you claim, it should be audible, and it's simply not.

 

[antcollinet]

Not frequency is problem here but amplitude. This is 1V!

I suspect you are measuring that incorrectly. The largest switching frequency residual I've seen in published measurements when I've looked is -20dB - others were -60 and -80.

Even at -20, that would be 0nly 0.2V and that was from a pro amp (crowne) which are not renowned for their stellar clean performance. At -60 or -80, you are at the mV level or lower.


But even if it were at 1V - it is still of no consequence either to the speaker (whose inductance will basically block any current at that frequency - and whose voice coils couldn't move at that frequency in any case) or your ears, which even if 400kHz were transmitted in the air, there is nothing in your ear that can respond to it.

 

[Trekkis]

I suspect you are measuring that incorrectly. The largest switching frequency residual I've seen in published measurements when I've looked is -20dB - others were -60 and -80.

Even at -20, that would be 0nly 0.2V and that was from a pro amp (crowne) which are not renowned for their stellar clean performance. At -60 or -80, you are at the mV level or lower.


But even if it were at 1V - it is still of no consequence either to the speaker (whose inductance will basically block any current at that frequency - and whose voice coils couldn't move at that frequency in any case) or your ears, which even if 400kHz were transmitted in the air, there is nothing in your ear that can respond to it.

And how such simplest value can be measured incorrectly? In what way error can be introduced? In case when dac voltage is presented exactly in pair with specification (about 2V), also measured power supplies have also correct reading? (32v = 32v, 48V = 48V, etc). So on what base amp voltage could be any way incorrect, multiplied In this case? Also when output amp voltage on max volume is also in pair with expectation?

As I said, problem has nothing to do with speakers and high frequencies but with quality of output waveform. Ears definietly are Sensitive to quality of generated waveform, even subtle distorsions like generated by jitter or power supply can be audible. And this one is very distorted.

Ok, so response is that this is not audible. I do not believe fully in such response as there is real difference in sound for this reason on another. It is not the same.

I expected this, But as I stated many times this do not explain for me why such measurment is not included in tests, as most of them ale below threshold of audibility anyway. Tests should show all aspect of the gear, also factors indicating the quality of the components. Quality of aiyama components looks worse, even if difference is below audible level. Audible or not, tests should inform about that.