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Welcome to the latest GoldenEar newsletter. In this issue, we're diving into technology with a focus on amplifier types. We start with a quick summary of the different types of audio amplifier technologies available in today's audio equipment. Then we follow that up with some detail on Class D amplifiers and how digital amplifiers, like the ones used in GoldenEar Subs and powered Triton Towers work.

In Sandy's Place, Sandy shares one of his recent concert experiences: The musical genius of The Beach Boys' Brian Wilson, for the Pet Sounds 50th Anniversary Tour performance at the Beacon Theater in NYC last fall.

As always, we hope you'll find this stuff interesting and informative. And don't forget, we truly value your thoughts and feedback concerning these newsletters. Shoot us an e-mail at info@goldenear.com and let us know what you're thinking.

Happy listening,

The GoldenEar Team
Does Your Amplifier Have Class?
  
Courtesy of OhmArt

Over the eons Audiophiles have been subjected to any number of questionable "tweaks" claiming to make dramatic improvements in the sound quality of their systems. Who among us can forget green marker pen to be applied on CD disc edges? A personal favorite of ours was spawned by a major high end audio magazine reviewer who claimed that shining a flashlight on the tweeter in her speakers changed their sound. Ah, Houdini would have been proud. 

But that's not to say that there aren't sonic differences in component parts of audio systems, with speakers being perhaps the easiest to detect but certainly not the only component to affect the sound of your system. When it comes to amplifiers there's pretty universal agreement that they can and do sound different too. So we thought a broad overview of amplifier types in general might be interesting and even helpful to all you GoldenEar audio aficionados out there.


Advanced Technology Switching Amplifiers
 
 
A Typical 400 watt Class D Amplifier (compare this to the Class A/B amp image)
 
 
Pulse Width Modulation - PWM
 
Before our discussion of Class D amplifiers, a little background is needed. "Pulse Width Modulation" (PWM) encodes information onto a pulsing signal (also known as a carrier signal). The average value voltage (and current) fed to the (in our case, the loudspeaker) is controlled by turning a switch between the amplifier's power supply and the load on and off at a fast rate. The longer the switch is on compared to the off periods, the higher the total power supplied to the load.
 
The PWM switching frequency has to be much higher than what would affect the load (the device that uses the power), which is to say that the resultant waveform perceived by the load must be as smooth as possible. The rate (or frequency) at which the power supply must switch can vary greatly depending on load and application, for example switching has to be done several times a minute in an electric stove; 120Hz in a lamp dimmer; between a few kilohertz (kHz), to tens of kHz for a motor drive; and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies. The main advantage of PWM is that power loss in the switching devices is very low, making for very high efficiency.

Class D and PWM 

Class D amplifiers are based on the PWM principle as they produce a PWM equivalent of the analog input signal which is fed to the loudspeaker using a suitable high quality filter network that blocks the high frequency carrier signal and recovers the amplified original audio signal. These amplifiers are characterized by very good efficiency figures (≥ 90%) and compact size/light weight for large power outputs. For a few decades, industrial and military PWM amplifiers have been in common use, often for driving servo motors. Field-gradient coils in medical MRI machines are driven by relatively high-power PWM amplifiers too.

Sandy's Place - Brian Wilson: American Musical Genius
Sandy with New Triton Three at CES 2012

I suppose that most of you know, from previous postings, that I am a big Beach Boys fan. Oh yes, I listen mainly to jazz and you can find me on many evenings sitting in THE chair, listening to the disharmonious musical ravings of
John ColtraneAlbert Ayler and the like. But then, on some more mellow occasions, I relax and listen to the more sonorous harmonies of the Beach Boys, and that musical virtuoso,  Brian Wilson .

I grew up musically in the 1960s, and my musical taste was quite varied, from Motown R&B, to the Beatles to the aforesaid Beach Boys. Many were the nights that I listened in bed to my little Spica transistor radio (one of the very first) to Cousin Brucie. Those were the days that I could recite by heart the top 50 singles in the USA. And foremost among my favorites were the Beach Boys.
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