It’s time for the show
AUDIOFILE - Val A. Villanueva (The Philippine Star) - November 12, 2016 - 12:00am

The Philippine STAR and AudioFile are again collaborating in this year’s November Hi-Fi Show to showcase the best of locally made audio system.

Like previous exhibits, all electronics and transducers are locally handcrafted.

The show will be held on Nov. 12 and 13 at the Dusit Thani Hotel Makati from 10 a.m. to 6 p.m. You can visit us at room 417 to experience that elusive sound magic which we promise to deliver. Entrance, as always, is free.

Unlike past years, however, we’ll be featuring what could probably be the first amplifier to be successfully DIYed in the Philippines. This is something we are truly proud of, since many have tried but failed to build one.

Our main offering for the 2016 November Hi-Fi Show is the 6C33 OTL or transformer-less amplifier. OTL is a subset of vacuum tube audio power amplifier topologies. Output transformers (OPT) have been a fixture in conventional amplifiers for linearity and fidelity. The transformers we grew up with rely on OPTs to couple the amplifier’s output stage to the loudspeaker.

The single biggest factor that controls the sound of any tube power amp is the OPT. Having a correctly built OPT ensures a vibrant-sounding stereo system. In any tubed amplifiers, OPT is the lifeline. Build it right, and you’ll get an excellent-sounding amplifier.

Some believe that tube components are what make or break the sound quality of an amplifier. But tubes can be procured effortlessly. New production tubes and those new-old-stocks populate the audio marketplace. Audiophiles call it tube rolling. If they can’t get the sound right in a particular brand of vacuum tube, all they have to do is to replace them to get the musical flavor that fits their sound preference. To quote Tim de Paravicini, the maker of the legendary Luxman MB3045: “It is all about the topology and the output transformer” … or so it seems.

Why then will we be taking the risk of building an amp sans its transformer?

Tony Tecson, who built our transformer-less amp, says: “The output transformer is easily the single most expensive part of any tube power amp. You need the irons in the OPT to transfer energy: that is, from the output tubes to the speakers. Since the impedances involved are not the same — tubes being of high impedance and speakers of low impedances — OPTs therefore are mandatory. To avoid low frequency saturation, the irons or the core have to be massive. But making the core massive increases leakage inductance, so high frequencies are severely attenuated. In other words, the OPT is also the chink in the tube power amp’s armor.”

Tony explains that doing away with the OPT altogether means avoiding these pitfalls. “This is why I built a 6C33C power amp capable of 25 watts into an 8-ohm speaker and about 40 watts into 4-ohm speakers. Since there are no OPTs, the amplifier is now lighter, frequency response is better, and all frequencies get amplified equal. This amp grows 350 watts at idle, and about 400 watts at full power.”

Our pre-amplifier and phono stage, on the other hand, have been conceived and constructed by Erik Flores. His Isabel pre-amplification system needs no further proof of how excellent its sound is. Through years of participating in the Hi-Show, Erik has proven his worth as an expert DIYer.

Our speaker system, built by the ever-reliable Larry Roxas, is a three-way configuration using Altec 414 woofers, Altec 802G mid-compression drivers with modified Le Cleach horns and EV T35 tweeters. The whole transducer system is seamlessly linked by a crossover in the first order slope, or 6db per octave. The speaker cabinet can either be used as bass reflex or open baffle.

No other acoustician can approximate the work of Tony Rodriguez. He will again treat the hotel’s music-hostile room environment to match our system’s sound quality.

The audio rack is specially designed by Boy Bustamante using exotic hardwood.

Our cables and inter-connects were designed and fabricated by audio stalwart Cal Cano, while overall room tuning will be done by John Alegre, one of our team’s mainstays.

Of course, our participation in this year’s Hi-Fi show’s staging will not be possible without the supervision and direction of environmentalist Mandy Mariño, and mining executive Antonio “Buboy” Sarte. Another highlight of our exhibit is Mandy’s linear-tracking tonearm on a Garrard 301 turntable, which will be the subject of my future column.

* * *

For comments or questions, please e-mail me at audioglow@yahoo.com.

 

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