Saturday, February 14, 2009

RT Articles: Tubes and vinyl: two utterly obsolete technologies that refuse to die

All of my previous articles in this magazine have been about relatively cutting edge technologies. Now, I'm going to talk about something a little older.

People often ask me, "I've heard audiophiles say that vinyl records sound better than CDs" or "Why do some guitar amplifiers use tubes?" I want to explain this to you.

Vinyl records are still alive and kicking for reasons mostly other than sound quality. DJs in the rap and hip hop music genres rely on record scratching, the art of manipulating records, which is enhanced by the use of direct-drive (motor built into the platter) turntables with a special felt "slip" mat, pitch control (for "beat matching") and a little mixer known as a fader box between the two tables. Most of the time, sound quality isn't a huge factor, and most gear is made specifically for DJing, although the Technics SL-1200, the industry standard DJ table was originally intended for Hi-Fi use.

Audiophiles and collectors
There's another little niche group that's after something else: the sound. Audiophiles have been claiming vinyl's superiority since the CD was introduced in the early 80s. The argument, at first was valid. The first generation of CD players produced incredibly brittle and irritating sound, due to the fact that they didn't dither, or smooth the output after it was converted to analog. Basically, a sine wave (which sould look perfectly "round") would look like a stair case. After the 2nd and 3rd generations, most CD players fixed this problem for good, and the audio coming out of a CD player is almost identical to the master recording.

CDs have flat (even) frequency response from 0hz-22.05 KHZ (below and above the limits of human hearing), immeasurable amounts of speed deviation (wow & flutter), infinite separation from left to right channels (no bleedthrough onto the other channel), etc. Basically, it's the ideal music medium, so why do some people insist on vinyl?

The process of cutting and playing back a record induces various types of distortion into the audio, namely harmonic distortion - faint multiples of the fundamental frequencies, giving a kind of "warm" sound. This is why audiophiles like it so much. A record sounds more "alive" than the master recording. Mind you, this comes from added distortion, rather than scientific superiority. There are two other sound factors which contribute to vinyl's sound. The first is crosstalk. A cartridge (stylus and pickup), because of it's inherent physical limitations, will pick up, say the left channel in the right channel, only it's quieter and out of phase (electrically opposite of the original). This actually creates a kind of "3-D" sound which is also more pleasing to the ear. The second is how they mastered the record compared to the CD version. In the early 80s, a lot of masters used the LP master tapes, which were intentionally very bright (treble heavy) to compensate for elements in the LP cutting process. An LP master played straight (or on a CD) sounds terrible, but usually sounded "just right" on an LP. Another factor is compression. In today's world of iPods and on the go music, popular music often has a small dynamic range (loud to soft ratio), while music from 30 years ago had a considerably higher dynamic range. Some times, when an album is re-mastered onto CD, the engineers use compression, which some people (like me) don't like. I want to hear the album the way it was originally intended, not a modern interpretation of what it should sound like.

Side note: there's only one area where an LP is scientifically superior. Frequency response. LPs (with a really good cartridge) can hold frequencies from ~20HZ-76KHZ (more than 3x the limit of human hearing [20KHZ]). In the 1970s, the industry tried to promote a quadraphonic system called CD-4, which put information for left and right rear channels into ultrasonic frequencies, and could be played back by a special decoder box and special stylus.

The Vacuum Tube was outmoded in most applications by the transistor in the 50s and 60s, and for good reason. Tubes were large, inefficient, required high voltages and large transformers, had to be replaced (sometimes frequently) and generated lots of heat.

For audio applications, solid state amplifiers are far superior (technically, anyway). The first few generations of solid state amps had problems, but most gear from the 70s onwards is pretty problem free. Tubes, however have a quality, kind of like vinyl records, that keeps them alive: harmonic distortion. Tubes create considerable amounts of odd order harmonic distortion, creating a "warm" sound, and also "soft clip." Clipping is a phenomena which happens when too much signal is applied to an amplifier. A transistor amplifier simply hits it's peak output and can't go any further, creating a hard, gritty and irritating sound. A tube amplifier on the other hand, has a little give, and will create a rounder clips (see figure). This has a warmer, less harsh sound.

Knowing these two things, it's pretty easy to see why guitarists like tubes. Back in the 1950s, some blues musicians started cranking up their tube amps until they started clipping. The result was a kind of crunchy, edgy sound. We know it today as "overdrive," "fuzz" or "distortion." Eventually, companies started making guitar amps with a gain circuit you could intentionally overdrive, then adjust the output of the overdrive, so you didn't have to run the amp full blast. Tube amps became a staple of blues and rock guitar. Solid state amplifiers were really pushed by the industry in the 70s, to the rejection of many. While some styles in the 80s and beyond relied on solid state hard clipping sound, many mid to high end amps are still tube based, and lower end amps with Digital Signal Processing (DSP) tube eimulation are common. Some mostly solid state amps have a tube circut, and tube stage pedals are also common.

Some groups of audiophiles are also into tubed gear. Most like the added "warm" sound, and are certainly willing to pay for it. Some people are also into high efficiency systems, running only run 1 watt amplifiers and using giant horn style speakers, while most tube lovers have moderate power systems). Often, these tube people use vintage 50s and 60s gear, such as early McIntosh and Marantz equipment.

In the audio production realm, microphones and pre-amp/compressors will sometimes use a tube stage, if desirable. Microphones with tube stages are often used for pianos and sound really good on male vocals.

There are also some UHF TV transmitters, microwave ovens and other specialized applications where tubes are still in use today, mostly where transistor amps don't work well. The Most common type of tube of all is the Cathode Ray Tube (CRT), which are still commonly used in TVs and computer monitors everywhere, although they are being replaced by LCD and other thin display technologies.

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