Class D Amps?

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Class D Amps?

Romana
I have read here that class D amps are very bad regarding ES. But at what distance are they ´safe´or should they not be had at all for es people. I think there are a difference also between a 30w small class d amp and a 300w class d amp.
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Re: Class D Amps?

NoRadiationForYou
Why are they bad?
Amir Borenstein
www.norad4u.com
www.4EHSByEHS.com
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Re: Class D Amps?

Marc Martin
Administrator
Class D amps are bad for ES people because they use pulse-width modulation to reduce power requirements.   I couldn't even stand to use a 25 watt Class D amp, but I have no problem with a 75 watt Class A amp (which has no power savings at all).  Class B amps are fine too, it's just the Class D and Class T amps that should be avoided.

Marc

 
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Re: Class D Amps?

Marc Martin
Administrator
It's basically the same reason that one shouldn't use dimmer switches, which turn lights on & off very rapidly, generating high frequency square waves.

Or why one shouldn't use a switching power supply.

Or an LED monitor with a flickering backlight.

From Wikipedia:
"A class-D amplifier or switching amplifier is an electronic amplifier in which the amplifying devices operate as electronic switches, and not as linear gain devices as in other amplifiers. They are rapidly switching back and forth between the supply rails, being fed by a modulator using pulse width, pulse density, or related techniques to encode the audio input into a pulse train."
 
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Re: Class D Amps?

Romana
At what frequencies do these amps emit radiaton/magnetism?
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Re: Class D Amps?

Marc Martin
Administrator
On October 23, "Romana [via ES]" <[hidden email]> wrote:
> At what frequencies do these amps emit radiaton/magnetism?

Someone would have to measure them, but if you look it up on the Internet:

   "Class-D amplifier must operate at quite high frequencies, in the 100KHz to 1MHz range"

From:
  http://sound.whsites.net/articles/pwm.htm

Marc
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Re: Class D Amps?

Romana
Ok thanks. Somehow I don´t trust everything I read. In this case they may have "sideeffects" emitting on other frequencies also - I think.
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Re: Class D Amps?

Marc Martin
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In reply to this post by Marc Martin
Although, searching on Google, I do see some results for "Ultra Low EMI Class D Amplifier", so there may be exceptions to the rule.  


 
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Re: Class D Amps?

Arctic Coast
In reply to this post by Marc Martin
75watt Classs A amp..wow.Those are for specially inclined :)
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Re: Class D Amps?

Marc Martin
Administrator
On October 23, "Arctic Coast [via ES]" <[hidden email]> wrote:
> 75watt Classs A amp..wow.Those are for specially inclined :)

I guess it's actually 85 watts, but yes, it was expensive.   But doesn't seem to bother me, ES wise -- it gets hot, though:

  https://hometheaterhifi.com/volume_10_4/creek-5350-integrated-amplifier-10-2003.html

Marc
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Re: Class D Amps?

Marc Martin
Administrator
Oh, and I see from that article that my 85 watt amp is really "Class AB", not "Class A".  So not that impressive, after all.  :-)  But still doesn't use pulse-width modulation, like the more modern amp designs.

Unfortunately, as time moves forwards, almost everything will become Class D, so one will have to either use old Class AB amps, or find a Class D amp that doesn't put out so much electromagnetic interference.
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Re: Class D Amps?

Arctic Coast
Nice toroidal in that Creek :)
Of course,you always have the old stuff to fall back on:
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Re: Class D Amps?

Romana
What can be done so the body better tolerate the emf from class D amps? Same as for other emf fields?
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Re: Class D Amps?

Marc Martin
Administrator
On October 23, "Romana [via ES]" <[hidden email]> wrote:
> What can be done so the body better tolerate the emf from class D amps? Same
> as for other emf fields?

Well, that would be the usual stuff that's discussed on groups like this... distance, shielding, protection devices, detox, nutrition, etc

Although for something like this, I think I'd just buy a different amp.

Marc