Hi Jeff,

I just wanted to add my two cents to the pending case, Vinyl v. CD, et al. I work in a sound studio and have followed the debate amongst engineers and audiophiles for a while. Oddly enough, audiophiles often spend far more money on far sillier things than the engineers who record the material the philes are listening to. I have yet to see or read about a studio that uses separate $200/meter-pair wires braided around hollow PVC cores for each driver (bi-amped or even tri-amped) in their monitor speakers. But I digress.

In the early recording industry, in order to overcome some of the limitations in the bandwidth that can practically be achieved by various recording mediums and/or equipment, various equalization curves were used and standardized. For example, the Dolby Noise Reduction circuitry on a cassette tape enhances the high frequencies prior to recording so that the signal to noise ratio in the range of inherent tape hiss is greater. Upon playback, the highs of the total off-tape signal are reduced by a corresponding amount, lower the noise to a less distracting level and lowering the signal to it's original amplitude.

Records are just as subject to these limitations as any medium. In order to work around similar limitations, signals are processed prior to cutting the master stamping die for a record. The standard by which record masters are processed is the RIAA Equalization Curve (Recording Industry Association of America). Interestingly enough, different speed records actually had different curves associated with them, but for general purpose 33 1/3 RPM's from 1960 to the present, this curve applies. Bass frequencies are attenuated (-6dB/octave from 500Hz to 50Hz) to limit the physical travel of the needle and to limit groove width. Thinner grooves = more grooves, more play time per record. High frequencies are also accentuated (+6dB/octave from 2120Hz to 10KHz) for purposes similar to that of the DNR curve on tape: the higher the signal level going in, the lower the noise level can be pushed coming out. Even without dust and scratches to worry about, the minute surface characteristics of the vinyl itself lends some noise to the extremely low signal level contained on a record. Also consider that a record is stamped from a master, in a physical process that introduces some (albeit very) minor variation from copy to copy. Generational loss is a real concern for any analog replication method and something digital encoding is virtually free from. Thus is is easy to see that the relationship of an analog signal to the groove on a vinyl record is nearly as distant as that of a signal from a CD. Vinyl certainly does NOT provide an "exact mirror" of the original signal.

Let's consider curves again: RIAA equalization and the learning curve of new technology. Early CD's were made from existing analog tape masters. (These masters are often recorded at very high speeds on broad tape, so their contribution to the overall loss of quality is relatively minor.) Remember that these masters have already had the RIAA curve applied to them in the mixing and mastering process. When encoded to CD, the curve was often left in place. Since this equalization was reversed in the circuitry of phonograph preamplifiers, but not in the design of CD D/A converters, the playback of CD's sounded harsh. They lacked some of the chest-thumping bass and had very distracting sibilants. Everyone immediately assumed that the digital medium, with it's harsh one-to-zero transitions was at fault for the. Not to say that early D/A designs couldn't stand some improvement, but especially with noise shaping circuitry and various forms of oversampling, current CD's produced by professional engineers* and artists played on current machines do stand well against any analog source. We'll not get into comparing the carefully tuned acoustics of good studios to the haphazard setup of all but the most die hard audiophiles private listening rooms.

*Do NOT consider the 'professionally' produced pop music scene as a reference source however! These engineers tend to overdrive the medium, no matter what it may be. For example, any Ricky Martin song I have ever seen (the waveform of) looks almost like a modulated square wave! But we are only human, and even such notable audiophile fav's such as Rebecca Pidgeon's beautiful The Raven CD can have flaws (there is a slight clipping on one song of this album).

And just to add one more issue into the fray. Error correction. By now many of us know that there is error correction incorporated into the signal stream on a CD. This allows the player to ignore and fill in the gaps left by dust and scratches. We all also know that record have no such correction. Dust and scratches are the thorn in any avid vinyl proponents side. Unless a record is opened, stored and played in a clean room, handled with exquisite care and gently spun 'round upon the finest of turntables, their sound will degrade. Actually, their sound may degrade simply by dragging a hard needle across their surface, as is required to hear them in the first place. For practicality, durability, portability (in-dash phono players never quite made it), AND audio quality, CD can and do hold their own. While analog tapes and records played through tube amps can and do have definite appeal - both nostalgic and tonal - and excellent quality under the right circumstances, it is important to recognize that digital does not equal dismal.

Chris Rakoczy
D&K Sound Services Inc


Add'l sources:

http://www.vadlyd.dk/English/Transferring.html
http://www.glass-ware.com/audiogadgets/AG_RIAA_Eq_Networks_Design.html
http://www.sweetwater.com/insync/word.php?find=RIAAEqualization
 

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