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-   -   What power amplifiers emit little or no electromagnetic radiation? (https://www.diyaudio.com/forums/everything-else/359196-power-amplifiers-emit-little-electromagnetic-radiation.html)

CowCat 24th August 2020 10:47 AM

What power amplifiers emit little or no electromagnetic radiation?
 
Class D amp chipsets emit electromagnetic radiation at pulse width modulation frequencies. My class D amp emits electromagnetic radiation at frequencies that my portable AM radio can pick up.

Higher quality switch mode power supplies may have built-in dirty electricity suppression. But, a linear power supply is generally a safer option for not creating dirty electricity in house wires. Dirty electricity in house wires becomes electromagnetic radiation penetrating several feet into rooms.

Thus, I reached a conclusion that I want a class AB amplifier with a linear power supply.
As far as I know, Dayton APA150 is an affordable class AB amplifier with a built-in linear power supply.

Is Dayton APA150 going to be a fine choice for me?
Does anyone know a good affordable class AB amp with a linear power supply?
Or, does anyone recommend a good power amplifier that emits little or no electromagnetic radiation?

edbarx 24th August 2020 11:35 AM

Have you ever tried to tune a short wave transmitting antenna? I remember a friend who is a radio amateur tuning a huge antenna made of wires on his roof. This was about fourty years ago. He had to try several times to tune his antenna so that the radiated energy was optimal. The wires were long, in fact, several meters long.

I am writing this, because, for efficient radio wave transmission the wiring must have the correct geometry and size to favour electromagnetic radiation. The antenna must resonate at the transmission frequency. This cannot happen at very short wire lengths compared to the wavelength of electronic waves in a wire/antenna.

If electromagnetic radiation is emitted by an audio amplifier, it is only a very very small insignificant amount of energy.

JMFahey 24th August 2020 11:40 AM

Any non switching type amplifier using a non switching type power supply will emit very low levels of electromagnetic radiation at the frequencies which worry you.
Worst case, standard diodes in the power supply will emit some switching noise at harmonics of mains frequency, but bypass capacitors and faster diodes tend to take care of that, bet the power supply section includes some data on that.
The power amp you chose is good, there are many others offering similar performance.

That said, Class D amplifiers are very usable, but require placing them in a suitably shielded enclosure and taking care with wiring.

CowCat 24th August 2020 12:16 PM

Quote:

Originally Posted by edbarx (https://www.diyaudio.com/forums/everything-else/359196-power-amplifiers-emit-little-electromagnetic-radiation-post6318544.html#post6318544)
Have you ever tried to tune a short wave transmitting antenna? I remember a friend who is a radio amateur tuning a huge antenna made of wires on his roof. This was about fourty years ago. He had to try several times to tune his antenna so that the radiated energy was optimal. The wires were long, in fact, several meters long.

I am writing this, because, for efficient radio wave transmission the wiring must have the correct geometry and size to favour electromagnetic radiation. The antenna must resonate at the transmission frequency. This cannot happen at very short wire lengths compared to the wavelength of electronic waves in a wire/antenna.

If electromagnetic radiation is emitted by an audio amplifier, it is only a very very small insignificant amount of energy.

The problem is proximity to the sources. If you are sitting next to an amp, you still get substantial amount of electromagnetic radiation even though it is enclosed in a metal case.

My portable AM radio picks up quite a bit of electromagnetic radiation at PWM frequencies of TPA3251 chipset when I sit next to the amp. I sit next to the amp because the amp has the volume knob.

Even electromagnetic radiation from wired keyboards can be problematic because your fingers are right on top of them. Some wired keyboards emit very little EMF because they don't have fancy functionalities that require more sophisticated processors which in turn emit more EMF. As far as I know, simplest wired mechanical keyboards emit least amount of EMF. I'm going to buy iKBC CD87 because it doesn't have LEDs and doesn't have fancy features like keyboard macro. It is the minimalist mechanical keyboard I was looking for.

Portable AM radios can sniff low frequency EMF from electronics very well.

CowCat 24th August 2020 12:31 PM

Quote:

Originally Posted by JMFahey (https://www.diyaudio.com/forums/everything-else/359196-power-amplifiers-emit-little-electromagnetic-radiation-post6318548.html#post6318548)
Any non switching type amplifier using a non switching type power supply will emit very low levels of electromagnetic radiation at the frequencies which worry you.
Worst case, standard diodes in the power supply will emit some switching noise at harmonics of mains frequency, but bypass capacitors and faster diodes tend to take care of that, bet the power supply section includes some data on that.
The power amp you chose is good, there are many others offering similar performance.

That said, Class D amplifiers are very usable, but require placing them in a suitably shielded enclosure and taking care with wiring.

I guess you mean Dayton APA150 is going to induce far less electromagnetic radiation than TPA3251/TPA3255 amps.

Dayton APA150 user manual doesn't say much about power supply.

Quote:

Key features of the APA150 include high current discrete power transistors (used in premium amp designs), a hefty toroidal power supply transformer, low-noise forced air cooling, a fully adjustable and defeatable electronic 50-150 Hz low-pass filter, extensive heat sinks to extend the amplifier life, and complete protection against shorting and thermal overload. Additional features found on the APA150 include full-range line-level outputs, gold-plated 5-way binding posts that accept up to 8 AWG wire, gold-plated stereo line-level inputs and outputs, user-selectable input voltage of 120/230V

nigelwright7557 24th August 2020 03:50 PM

the path between around mosfets and output filter on class d must be as short as possible to minimise radiation.
on some amps i have noticed residual carrier on the speaker output which is bad.

JMFahey 24th August 2020 04:59 PM

Quote:

Originally Posted by CowCat (https://www.diyaudio.com/forums/everything-else/359196-power-amplifiers-emit-little-electromagnetic-radiation-post6318589.html#post6318589)
I guess you mean Dayton APA150 is going to induce far less electromagnetic radiation than TPA3251/TPA3255 amps.

In principle yes

Quote:

Dayton APA150 user manual doesn't say much about power supply.
It says enough :)
Quote:

a hefty toroidal power supply transformer
That means a conventional power supply and not a switching one.

See it this way: a Class AB amplifier deals with 20Hz>20kHz Audio and only when/if driven by such a program.

A Class D amplifier is producing full blast hundreds of kHz all of the time, whether amplifying Audio or not.

It can be adequately shielded, of course, in fact commercial equipment is required to meet certain emission standards.

amplidude 24th August 2020 07:24 PM

Don't go for tripath ta3020 then

H713 11th September 2020 11:51 PM

Quote:

Originally Posted by CowCat (https://www.diyaudio.com/forums/everything-else/359196-power-amplifiers-emit-little-electromagnetic-radiation-post6318577.html#post6318577)
The problem is proximity to the sources. If you are sitting next to an amp, you still get substantial amount of electromagnetic radiation even though it is enclosed in a metal case.

My portable AM radio picks up quite a bit of electromagnetic radiation at PWM frequencies of TPA3251 chipset when I sit next to the amp. I sit next to the amp because the amp has the volume knob.

Even electromagnetic radiation from wired keyboards can be problematic because your fingers are right on top of them. Some wired keyboards emit very little EMF because they don't have fancy functionalities that require more sophisticated processors which in turn emit more EMF. As far as I know, simplest wired mechanical keyboards emit least amount of EMF. I'm going to buy iKBC CD87 because it doesn't have LEDs and doesn't have fancy features like keyboard macro. It is the minimalist mechanical keyboard I was looking for.

Portable AM radios can sniff low frequency EMF from electronics very well.

Can I ask why you're so worried about it? Do you have a bunch of very sensitive equipment around with single-ended inputs?

jjasniew 12th September 2020 02:09 AM

>I sit next to the amp because the amp has the volume knob.

How hard would it be to "Hifi ALPS 100KA motor potentiometer remote volume control diy preamp board" off ebay or elsewhere?

With most forms of radiation, distance away from it is your friend. If the amp is over there and you're over here - but still can control it - that's an effective solution. I'd think...

I power my class D amps with linear power supplies. I've no idea what they radiate, as I've never taken an AM receiver to try and find out as you have.

IMHO, we live in an RF saturated environment these days, compared to when I was a kid.

I wonder what my two routers "do" RF EMI wise - with the 100Mb AC line link boxes I have connecting them, 3 active cell phones / PC computers in the house; I dont stand right in front of the microwave while its operating waiting for it to finish...


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