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Has anyone used this TPA3251 amplifier?

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You could use a cheap TV dongle and some free software to get a much more quantitative assessment of the radio frequency levels in your house - search for RTL-SDR for details. Compatible dongles start at ~$15. This will let you put the different levels of RF at different frequencies, and at different distances from things, into perspective.

Thanks for information. I hope it won't take much time to set up RTL-SDR. It may be suitable for far field measurement.
But, I don't know whether it's good for near-field measurement. Low frequency signals from household appliances are near-field signals.
 

somebodyelse

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Don't we all live in areas of AM/FM radiation, since that is how radios/tuners pick up their signal? How much worse is the tda3251 compared to what is already being transmitted?
It'll be very dependent on whether the manufacturer has bothered to minimise radiated emissions. My guess is it won't be any worse than radio stations unless you're very close to it, or live a long way from any transmitters, but I haven't checked. I would be amazed if it approached levels proven to be harmful - the TV stick's rf input would be well into overload by then.
 

LiloLee

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AM from 1906 and FM from 1933, if there was any adverse effects science would have shown it by now. I think we have far more lethal things to worry about that radio waves.
 
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AM from 1906 and FM from 1933, if there was any adverse effects science would have shown it by now. I think we have far more lethal things to worry about that radio waves.

Telecommunication industry has tried very very hard to ridicule and censor scientists who raise concerns about any kind of EMF.
They also hire a lot of keyboard warriors to spread misinformation and ridicule and discredit EMF researches.
For decades, tobacco industry also stated cigarette absolutely doesn't cause lung cancer. Tobacco industry called people who link cigarette and lung cancer conspiracy theorists.

Watch https://www.corbettreport.com/the-crisis-of-science/ for more details on widespread corruptions among scientists.

Unless you are already a part of EMF communities, it's very unlikely for you to hear any warnings about EMF.
EMF researches are still suppressed very hard in mainstream institutions and mainstream media.

Do you think radio industry wanted people to know about dangers of EMF from radio stations? If people knew, they would have repelled radio stations.

I'm saying that there has been global censorship campaign for more than 100 years.

There have been global censorship campaigns for a lot of things. Unless you are looking for censored videos and censored books, you don't even know that there are censorship campaigns directed by powerful special interest groups. If you want to find censored materials, join research communities. My research group talks about health, money, relationship, censorship, conspiracy theories, etc, ... There are even censored books about making money because those books were too effective at teaching money making to be allowed to exist in bookstores.

I've already read about various diseases including cancer caused by long-term exposure to electromagnetic radiation between 10khz and 30mhz radiated by household appliances and dirty electricity in house wires.

My rule of thumb is to minimize EMF except infrared and visible light. Even visible light can be harmful if you look at blue light at night because blue light decreases melatonin at night. I use a software blue light filter on my computer that kicks in at night. Flickering visible light can also cause epilepsy. But, visible light is generally safe if you avoid flickers and blue light at night time.
 
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LiloLee

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Any links to actual papers on the dangersof EMF? I would genuinely like to read some.
 
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Any links to actual papers on the dangersof EMF? I would genuinely like to read some.
 

somebodyelse

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You may have linked to a paper you didn't intend to - instead of being a paper on male breast cancer it links to 'Occupational exposure to low frequency magnetic fields and dementia: a case-control study' which concludes 'Our study does not support a strong association between occupational exposure to low-frequency magnetic fields and dementia. Further studies should consider the relationship between blue-collar work and the late development of dementia.'

Unfortunately the papers themselves are mostly paywalled, so most of us will have to settle for the abstracts. From looking through a number of the 'similar articles' links at the NIH site I'm not going to start worrying - there's some equivocal evidence of an increased relative risk, but the absolute risk remains below that of many everyday activities that we consider 'safe.' A lot of the papers are looking at mains frequency magnetic fields which will be worse from the linear PSU you prefer.
 
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You may have linked to a paper you didn't intend to - instead of being a paper on male breast cancer it links to 'Occupational exposure to low frequency magnetic fields and dementia: a case-control study' which concludes 'Our study does not support a strong association between occupational exposure to low-frequency magnetic fields and dementia. Further studies should consider the relationship between blue-collar work and the late development of dementia.'

Unfortunately the papers themselves are mostly paywalled, so most of us will have to settle for the abstracts. From looking through a number of the 'similar articles' links at the NIH site I'm not going to start worrying - there's some equivocal evidence of an increased relative risk, but the absolute risk remains below that of many everyday activities that we consider 'safe.' A lot of the papers are looking at mains frequency magnetic fields which will be worse from the linear PSU you prefer.

It is https://pubmed.ncbi.nlm.nih.gov/15202128/
Three cases of male breast cancer were diagnosed among a small group of men who worked in a basement office of a multi-story office building. This office was adjacent to an electrical switchgear room which generated high magnetic fields in their work space. The risk of male breast cancer in this group was increased about 100-fold

There are lots of papers funded by telecom companies. If you are just starting your journey, it's better for you to start with books and documentaries. For each topic that I research, I read papers after watching a documentary.

Linear PSU consumes a bit more power than SMPS, but it's not much. Unless there are wiring errors in your house, a slight bit of increase in electricity consumption by using Dayton APA150 is not going to increase magnetic field much. Dayton APA150 is not a monster GPU that consumes at least 200W during heavy gaming sessions. Even 500W doesn't increase magnetic field much if your house is wired well without errors. I have ME3830B which measures electric field and magnetic field.

Unless there are wiring errors in your house, magnetic field mostly comes from motors and rotating metal parts. When your car runs fast, rotating metal parts create stronger magnetic field. Unless you have an EMF meter like ME3830B, you cannot know.

So, I don't worry that Class AB amps will create strong magnetic fields that affect my body. I am worried about electromagnetic radiation at PWM frequencies from class D amps because I sit next to an amp. According to my portable AM radio, there's quite a bit of electromagnetic radiation from my TPA3251 amp when I sit next to it.
 
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Tangband

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All this can be solved with this product. Its the reason Allo:s tpa3118 design measures so well. The ripple is about 1 mV. Im gonna test Aiyima A04 tpa 3251 with a smps 30 v 6 A supply and this capacitance multiplier and report the result later.
https://www.audiophonics.fr/en/sing...cer-for-allo-volt-or-class-d-amp-p-11436.html
889A48AB-1657-45C3-86E9-F03A3C417BE9.jpeg
 
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All this can be solved with this product. Its the reason Allo:s tpa3118 design measures so well. The ripple is about 1 mV. Im gonna test Aiyima A04 tpa 3251 with a smps 30 v 6 A supply and this capacitance multiplier and report the result later.
https://www.audiophonics.fr/en/sing...cer-for-allo-volt-or-class-d-amp-p-11436.htmlView attachment 80853

That's basically a capacitive dirty electricity filter.
While I like it, it reduces dirty electricity from SMPS, not electromagnetic radiation at PWM frequencies from class D amp chips.
Reducing dirty electricity is good, but class D amp chips are going to produce electromagnetic radiation.

If you really want to reduce dirty electricity, you may look into attaching a common mode choke to an SMPS.

If you are at least 2 meters away from a class D amp inside a metal case, electromagnetic radiation at PWM frequencies may not be a problem.
 
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frabor

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For a while, I was looking for a TPA3255 amplifier end product that works out of the box. I stopped looking because all TPA3255 end products had bluetooth chipset which can add noise to audio.
I found a proper prospect by searching aliexpress.com for TPA3251.
  • AIYIMA TPA3251 amplifier
    • It doesn't have bluetooth connectivity.
    • It recommends 32V 5A adapter.
    • In a product picture, I see a pair of 35V capacitors. I don't know whether 35V capacitors can endure 32V power in the long run.
  • 32V 5A Adapter
I suspect this combination is better than TPA3116, TPA3250, and TDA7498E amps.
Although there are a few positive feedbacks, I don't know whether it will sound correctly and last long.
Has anyone used this or something like this?
Most of the info below cames from the diyaudio thread of the aiyima 04

Opamps look counterfeit, but they are on sockets, I would change them for mouser originals ne5532. Some ppl there like the opa1656 but you need to solder in a dip adapter.

24 volts should be the higher voltage used as the the caps are 32 V and it will be too close to the ratings. This is a low cost chinese electronics, so assume that some of the components may be fake and or ratings overstated.

There are two versions of the board, black and green. Seems all they are labeled with tilear. Black is the preferred one as it has better brand caps among other differences. The green is the one available now.

As improvement, supply caps are being changed, for equivalent rating panasonic or other brand names , 24 v and I believe 3500 uf) and for Wurth chockes following stated TI values from the reference board. They seem to fit but they leads are thicker. Most of the 32V caps will not fit the case.

I have done the upgrade of the ne5532 to mouser originals. Regarding all other mods, there is no mesurent performed other than the subjective praise of the modder. It would be great if a modded unit would be tested, and one of the posters at diyaudio was thinking about sending it here, but I have no idea if it has happened bit not.
 

Tangband

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Most of the info below cames from the diyaudio thread of the aiyima 04

Opamps look counterfeit, but they are on sockets, I would change them for mouser originals ne5532. Some ppl there like the opa1656 but you need to solder in a dip adapter.

24 volts should be the higher voltage used as the the caps are 32 V and it will be too close to the ratings. This is a low cost chinese electronics, so assume that some of the components may be fake and or ratings overstated.

There are two versions of the board, black and green. Seems all they are labeled with tilear. Black is the preferred one as it has better brand caps among other differences. The green is the one available now.

As improvement, supply caps are being changed, for equivalent rating panasonic or other brand names , 24 v and I believe 3500 uf) and for Wurth chockes following stated TI values from the reference board. They seem to fit but they leads are thicker. Most of the 32V caps will not fit the case.

I have done the upgrade of the ne5532 to mouser originals. Regarding all other mods, there is no mesurent performed other than the subjective praise of the modder. It would be great if a modded unit would be tested, and one of the posters at diyaudio was thinking about sending it here, but I have no idea if it has happened bit not.

Breaking news. I have sent the original ne5532 from my Aiyima a04 amplifier to an amplifier engineer for investigation and the results are like this:
The ne5532 that is inside the Aiyima amplifier is NOT a fake IC.

A genuin ne5532 was compared to a Aiyima ne5532 and a lm4562.
The two ne5532 where performing exactly the same and the lm4562 is only a tiny bit better. https://www.faktiskt.io/phpBB3/viewtopic.php?f=9&t=70688&start=300
61DAA277-47AD-41F7-BF91-59939AF4BF7B.jpeg
 

AIYIMA

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Breaking news. I have sent the original ne5532 from my Aiyima a04 amplifier to an amplifier engineer for investigation and the results are like this:
The ne5532 that is inside the Aiyima amplifier is NOT a fake IC.

A genuin ne5532 was compared to a Aiyima ne5532 and a lm4562.
The two ne5532 where performing exactly the same and the lm4562 is only a tiny bit better. https://www.faktiskt.io/phpBB3/viewtopic.php?f=9&t=70688&start=300
View attachment 88124
Now we can provide the service to change NE5532 to LM4562 on AIYIMA A04 & A07.
If anyone need the service, please tell me.
 

Ralferator

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Breaking news. I have sent the original ne5532 from my Aiyima a04 amplifier to an amplifier engineer for investigation and the results are like this:
The ne5532 that is inside the Aiyima amplifier is NOT a fake IC.

A genuin ne5532 was compared to a Aiyima ne5532 and a lm4562.
The two ne5532 where performing exactly the same and the lm4562 is only a tiny bit better. https://www.faktiskt.io/phpBB3/viewtopic.php?f=9&t=70688&start=300
View attachment 88124
I can't imagine it is possible to hear a difference - not even for bats
 

Tangband

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I can't imagine it is possible to hear a difference - not even for bats
The measurements shows almost nothing in difference, but the sound is a bit better with lm4562, believe it or not.
 

perchman

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Hi all. been following various class D threads with interest. Having been a lifelong fan of class A and A/B amps i recently tried a Crown XLS 1002 and was very surprised at how good it sounded, my only criticism would be the limited sound stage and imaging which seems fairly common the the class D topology. Anyhow in the search for a great value class d i have just ordered a pair of the Aiyima 04. Has anyone tried bridging these to run one unit per speaker? TIA
 

Tangband

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How would you describe the difference? Did you make a blind test?
Slightly cleaner sound, and more dynamic . No, but the sound difference is obvious.
 
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