Just can’t get enough

Can a stereo system function without a pre-amplifier? This is the common question I get from readers who are just starting to build their own two-channel sound system and may be confused by the heated online arguments between pragmatists who profess it is an essential part of the musical chain and the purists who believe it is not.

For the benefit of beginners who have just recently discovered my “AudioFile” column. a pre-amplifier (preamp) is the gadget placed in between music sources (CD players, turntables, musical streamers, among other modern day music sources) and the amplifier. The preamp decodes minute electrical signals from these sources to audible levels for further amplification or processing by the amplifier(s) before music comes out of the loudspeakers. Technically, the preamp ups voltage gain — from 10 millivolts to 1 volt — without the crucial current gain. It is the power amplifier that does the job to drive loudspeakers.

Purists insist that putting another chain between music sources and amplifiers affects the integrity of the sound system. They would rather opt for the straight path where they believe music signals can travel unobstructed.

Most amplifiers give out about 26-28dB gain. Some are closer to the “–teens” (i.e., 16, 17, etc.), while others give out over 30dB. Most, if not all, have gains in the upper 20s. If you are satisfied with the audibility level of the sound produced by your system, or more importantly if you already have a passive gadget that can take care of volume control and switching, then you probably do not need a preamp.

Do I have a preamp in my system? Yes! And I am pleased to report that my Isabelle preamp has just been upgraded by its designer, Jose Erik Flores, to Mark II. Does my preamp degrade sound quality? Absolutely not! In fact I have never been happier with the result and could never get enough of the robust musicality that it has added into my system. Before this upgrade, I thought that I had already reached the pinnacle of sound success. I have never been so happy and fortunate to be mistaken!

This is not to say that the purists are wrong. I guess, in everything, it still boils down to a person’s personal taste or preference. Different strokes for different folks!

I’m not at odds with those who believe that a preamp is no longer necessary with modern-day music sources. But consider this: most power amps are not designed with suitable gain to keep in step with all conditions or environments. A typical power amp is designed with an input sensitivity of 0.775Vrms to 1Vrms in for full output. A standard CD player has a fixed output of 2Vrms, and on the disc it gives out 2Vpk. In this situation, the amp can only be driven to full output if the disc was recorded at the maximum level of 3dB. This rarely happens, though.

In most cases, gain can only reach within -10 to -12dB of full level, giving the system good enough safety threshold and to avoid clipping the A/D converter resulting in sound distortion. A 100W amp could only effectively give you as little as 10W at full volume!

Now back to the technical specs of the Mark II: gain: 26 dB; frequency response: 6Hz to >1 MHz; output impedance: under 10 ohms; tube complements: 4 x 407A, 1 x 5U4G and tube rectified with second-order choke capacitor filter.

Erik, my favorite local audio designer who created my Isabelle preamp, called me a few months ago to ask if I was interested in upgrading his creation for a minimal cost. Before Isabelle, I had the Conrad Johnson PV3, Audible Modulus, among other branded preamps available in the market. I settled on the Isabelle in 2007, and became a happy camper since then. Well-meaning audio friends have sent me many branded preamps to audition in my music room, but none even came close to the sonics of my Isabelle. Erik said that other Isabelle users, like my bosom friends Saint Luke’s urologist Dr. Randy Barba and lawyer Dante Pamintuan, had their preamps upgraded. I made a quick visit to Randy’s place for a listening session, and was, right then and there, convinced.

People who know Erik will not be surprised to hear that his life revolves around audio. He was born into this hobby. “My recollection of childhood,” Eric reveals, “is listening to Sinatra, Ella, Sara, Perry Como, Tony Bennett, George Shearing, Cal Tjader, Joe Loco, Eddie Cano, Dave Brubeck, Chopin, Ravel, Puccini, Tchaikovsky, Verdi and many more. I listened to them on tube-based amplifiers (EL 34 or a KT 88) on my dad’s Lenco Turntable and Lowther speakers.”

Erik received an aeronautics degree and worked as an air traffic controller before leaving for the US a few years ago. There, he worked as a technician for several telecommunications companies before working as a systems designer for AT&T where he honed his skills in building and designing tube electronics. He came home to devote more time to his passion for audio.

As I have said in my previous columns, I strive to maintain a system that reproduces sound precisely as it was recorded. With the Mark II, that is exactly what I get. In my small music room at home, I am transported to whatever venue my favorite musical artists are performing in. And now, I’m bowled over by its capacity to even reproduce sound in all its theatrical magnificence — and I just can’t get enough.

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For comments or questions, please e-mail me at audioglow@yahoo.com or at vphl@hotmail.com. You can also visit www.wiredstate.com for quick answers to your audio concerns.