AUDIOCLINIC (Q and A) (Jun. 1975)

by Joseph Giovanelli

Recording Directly onto Discs

Q. In the January, 1974, issue of AUDIO, page 8, there is a reference to the "direct disc method." Please explain how the method is accomplished and compare it to the normal way in which discs are cut.

-Scott C. Lewis, La Feria, Texas

A. Most disc recordings nowadays start as tape recordings. The use of tape offers conveniences, such as editing, which were not available when recordings were made directly onto discs. (Before tape equipment was in common use, all recording was made directly onto master discs.) When recording directly onto discs in the earlier days of the art, a mistake meant that the disc was wasted, and that the performance would have to be started from the beginning. Further, today's recording techniques make it possible for one performer to play several instruments because of a technique known as "over-dubbing." This is practical only by way of special tape machines which can hold 16 or even 24 tracks, recorded on a tape which is two inches wide, rather than the quarter-inch tape widths we use on home type, open reel tape recorders.

Some claim, however, that, if we use today's cutting systems, it is possible to make direct disc recordings which are better than those made under similar conditions many years ago, when the 78 rpm disc was king.

Forgetting about editing problems and over-dubbing possibilities, recording directly onto a disc, rather than making the original on tape and then dubbing that tape onto a disc, saves a copying step. Each copying step, no matter how good it may be, still produces some losses. The copy is not quite as good as the original.

In summary, recording directly onto a master disc can produce a recording which has more "transparency," more a feeling of "being there." However, any musical or technical mistakes cannot be corrected.

Further, if something happens to the master disc, the entire process would have to be repeated. This means that the performers would have to be rehired. With today's high costs, this would make a re-recording a very expensive matter.

Frequency Ranges of Voices and Instruments

Q. What are the frequencies of musical sounds which singers and orchestral instrumentalists can produce?

- Louis Goldfarb, New York, N.Y.

A. The frequency range covered by a vocalist or instrumentalist depends in great part on the skill of the performer, as well as on the type of voice.

Therefore the information here is only approximate.

The so-called "high C" sung by a soprano is just a bit above 1,000 Hz.

Her lowest note is two octaves lower, around 250 Hz. The singer won't generally be capable of producing much vocal power at this lower frequency.

An alto might have a range from 175 to 700 Hz. A tenor can sing over the range of frequencies between 125 and 500 Hz. A bass can sing from about 85 to 350 Hz.

The organ covers a much wider range of frequencies. Its pedal tones start at 32 Hz, and some organs even go down another octave to 16 Hz, though it takes 32-foot pipe to do this. The highest fundamental tones of the organ go up beyond 4 kHz.

The lowest tone produced by the bass viol is 41 Hz, while its highest is about 250 Hz. I've heard skilled jazz bassists produce even higher notes.

The violin and trumpet cover a frequency range from about 190 Hz to 1 kHz or higher.

Note that the frequencies mentioned above are all fundamentals. All musical tones have harmonics (overtones) which contribute a great deal to the timbre, or distinctive sound quality of the various voices or instruments. These harmonics are multiples which may go as high as eight or nine times the basic frequency.

Adding Capacitance to Phono Pickup

Q. My problem is finding the right phono cartridge for my turntable, Technics SL-1100A, which has a low capacitive load of 165 pF for the entire unit, including the cable and the internal arm wiring. I want to use Shure V-15 type III or Ortofon M-15E Super phono cartridge with it, but they should be used with a relatively high capacitive load. I prefer not buying a stereo/4-channel cartridge to solve my problem.

I do not know the input capacitance of my preamplifier. Can I increase the total capacitance somewhat to obtain the flattest overall response from these cartridges? What would be the effect on the overall response if I use these cartridges with such a low capacitive load?

-Robert Chang, Ithaca, N.Y.

A. Let us assume that you require, say, 400 pF to obtain flat response from the cartridge you purchase. To do this you must add capacitance to the system input. The amount of capacitance already in the preamplifier input is very low, and may for this purpose be ignored. In your case you would need to add 235 pF to bring the total up to 400 pF. The simplest way to accomplish this is to open up your amplifier and solder in a capacitor or group of capacitors which equals this value, across the terminals of each phono input jack.

The added capacitance can be readily removed if you change cartridges later.

If there is room in the amplifier and if you have the needed patience and test equipment, you can solder in adjustable trimmer capacitors so that you can adjust their effective capacitance to get the flattest possible frequency response for any particular cartridge.

( Audio magazine, Jun. 1975, JOSEPH GIOVANELLI)

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