D’ sound

AUDIOFILE - Val A. Villanueva (The Philippine Star) - September 11, 2015 - 10:00am

When I do critical listening to audition audio gadgets or review music, I cocoon myself in the comfort of my listening room. There, I spend long hours dissecting each musical passage. If needed, I go through the whole process again and again, just to make sure that my ears picked up the flaws and the pluses of recreated sound.

My listening room, built from ground up, took more than eight years of tuning, replacing gadgets and accessories; and building the right room acoustics to make the sound being played back as accurate as possible. I have completely stopped the upgrades two years ago, satisfied that what I have now is a system which can give me a precise appreciation of what I am listening to.

For many years, I have shunned the “the new kid on the block” amplifier or what sound design engineers called Class D amplifier or amp. I dismissed it as another epic fail. I listened to one or two brands three years ago, and I must admit I hated the way they reproduced an otherwise magnificent recording.

What is Class D amp?

You may be aware of audio amplifier classes, such as Class A, B and AB, or what we know as linear amps. Simply put, the power of ratings of these amps are only as good as half of them, with the rest lost to heat. So if you have a 200-watt amp, chances are the other half of its power is lost as heat.

But really, who cares about such wastage if the amps are able to accurately reproduce music? For years, many audiophiles in the Philippines have been unmindful of the astronomical electricity rates they pay to Meralco as long as they are satisfied with what they’ve been hearing.

A friend of mine, well aware that my system is built around a tri-amp configuration, recently lent me three Class D amps (RSA-F33EX, rated 120 watts in 4 ohms and 60 watts in 8 ohms) from Spec Corporation. I plugged them into my system, and instantly liked what I heard.

Rebecca Pidgeon, Chesky Records’ prized recording artist, is undeniably at the top of audiophiles’ list of musical greats. Crossing Scottish folk and modern pop, her angelic voice easily endears her to legion of music enthusiasts. I first came across her musical genius in her 1994 debut album “The Raven.” Since then, I have become one of her avid followers. Her crystalline vocal quality has become the door through which music lovers pass to become audiophiles.

A singer and songwriter, Rebecca grabs you with her crisp song interpretation and trenchant storylines. To me, “The Raven” is many things at the same time: it is reflective, contemporary, intimate and witty.  Without doubt, it was Rebecca’s lilting and expressive musical persona in the album that has kindled the fire in audiophiles’ hearts. The audiophile classic Spanish Harlem is the apex of the “The Raven.” The song is so warm and tender that those who care for and adore someone would easily identify with it.

The Spec amps were able to flawlessly recreate each musical passage in “The Raven” album. However, I feel that the effect was a tad colder than what my tube amps could do. Listening to the same album with my tube amps would unfailingly give me goose bumps all over. But if you’re into clean or clinical sound, then, the Spec is just right for you.

I also played Patricia Barber’s “Night Club” album to test the Spec’s dynamics and timber. The amps effortlessly delivered. The piano in Patricia Barber’s Bye Bye Blackbird was uncolored and natural! High frequencies sounded clean, with minimal exaggeration. Low frequencies were tight, controlled and extended. With the Spec driving your speakers, you can achieve acceptable dynamics. 

I must admit that Class D amps have leapt tenfold in technological advancement. It’s a given that they are power-efficient: all its rated power goes to pumping music out of your transducers. 

Theoretical power efficiency of class-D amplifiers is 100 percent.  All of the power supplied to it is delivered to the load; none is turned to heat. This is because an ideal switch in its ON state would conduct all the current without voltage loss across it. Hence, no heat would dissipate. When the switch is in the OFF state, there would be full supply voltage across it with no leak current flowing through it. Again, no heat would be dispelled.

The amplifying devices (or transistors) in a class-D amp are usually MOSFETs, which operate as electronic switches, instead of as linear gain devices like those in other amps. They may not be ideal switches, but real-world power MOSFETs commonly have practical efficiencies well over 90 percent. In contrast, linear AB-class amplifiers are always operated with both current flowing through and voltage standing across the power devices.

The sound of Spec amps owe a lot to the individual parts of low-pass filter in the final stage of the amplifier. I was told that the capacitor and the coil employed for the low-pass filter were custom-ordered after careful listening tests. They guarantee the excellent musical sound of RSA-F33EX / RSA-M3EX / RSA-V1EX. Above all, many custom hermetic seal paper-oil filled capacitors are employed in the low-pass filter and snubber circuit of RSA-F33EX because of the natural and vivid character of the sound only those old type capacitors have. These paper-oil filed capacitors have been supplied to the aerospace industry for the past half-century, and meet the strict military (MIL) standards for getting the highest reliability.

This year, Class D amps may have come of age. Certainly, they’re worth a try.

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For comments and suggestions, please email me at audioglow@yahoo.com.


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