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The World of Audio Restoration
Graham Newton

What is Audio Restoration?

It's something like the restoration of an old art masterpiece except I work on sound recordings, instead of visual images. It could be anything from a favorite piece of music to an "audio letter" sent home to a loved one during wartime. In short, just about anything audible, that has ever been recorded, on any medium, at any time.

With the Compact Disc so widely accepted, many people no longer have the means to play an LP phonograph record, let alone your grandfathers 78ís!... and much of that music effectively is lost, except to collectors like ourselves... most will likely never be re-issued on CD...

Phonograph recordings have been with us since just before the turn of the century, and up until the 1950ís, most were very fragile and easily damaged... and if you dropped one, it would almost surely shatter into small fragments. Even something THAT seriously damaged can be restored, although the process is VERY time consuming, and as you would expect, expensive.

Many of the steps discussed here are subtle, resulting in small improvements. Listening on good quality studio monitors, however, each step reveals the improvement, and the whole becomes a striking improvement over the original condition. Still, nobody can make a "silk purse from a sowís ear"... if it isnít in the grooves, it canít be made to magically appear.

How is it Done?

The process of restoration begins with a careful cleaning to remove all the dirt, dust, fingerprints and other contaminants that have accumulated over the years. Did you know that old 78ís could actually go moldy? They can, and particularly where the discs have been stored in a damp basement. The mold "feeds" on the shellac content in old 78's, an organic compound, it actually comes from an insect found in India... the Lac bug! Simply put, dirty records sound bad, even when played with the correct stylus, and for average 78ís a selection of three stylus sizes 2.0 mil, 2.5 mil and 3.3 mil conical shapes will do for 90 percent of the cases.

There are so many "old wives tales" about how to clean your records that a few words about it may be in order. Purity of the cleaning solutions is a MUST, so purchase a jug of distilled water from the local pharmacy to use for mixing and rinsing. Ordinary tap water contains a variety of minerals, and you DONíT want to leave them on your disc after cleaning it. Among sound archivists, the Keith Monks Record Cleaning Machine is considered to be the best available, but at roughly CA $5,000 it is beyond what most of us can afford. My "manual" cleaning method takes much longer, but works just as well, and will let you spend what you save on more records. Most of us like THAT idea!

For dry cleaning of dusty records, a stiff short bristle brush can be used to get off most of the surface material and a good part of what has gotten into the grooves.

Wet cleaning is generally considered to be the best way to ensure a completely clean record, and hereís how to do it with minimum risk to your treasures. A flat velvet brush is used to get into the bottom of the grooves and get the dirt out. An easily available surfactant is Kodak Photo-Flo 200 and it is diluted in water to the tune of between 5 to 20 ml in 250 ml of distilled water. (The higher amount produces more sudsing!) In some really bad cases, a few drops of liquid dishwashing detergent can be added to the mix. Always bring the solution to the disc by amply "wetting" the velvet brush, and scrub until the surface looks "soapy". This will loosen the dirt and cause the fluid to flow in an even film without breaking up into droplets on the surface of the record. The now dirty fluid can be sopped up with a piece of white quilted kitchen toweling, always wiping with the grooves, never across them. Using a thoroughly rinsed velvet brush, saturate it with distilled water, and again scrub the disc surface. You should now see the water "beading" into droplets. The disc is wiped off again with toweling. Allow it to air dry, and voilal... A really clean disc, ready to transfer.

Subsequent dusting of the disc can be done dry with a red "duster" brush which has a more coarsely distributed fibre than the black brush.

Now play your cleaned disc. Sounds better, doesnít it! Most of the bad clicks and pops caused by dirt will be gone. A sum and difference matrix allows me to pull out all the unwanted vertical noise on a lateral recorded disc, or all the lateral noise on a vertical disc, like an Edison. Now, with some sharp low frequency filtering it is possible to get rid of most of the "thump" noises that seem to plague some early 78's. Adding some careful equalization can help to reduce the mechanical resonances of acoustic recordings and vastly improve the sound of most electrical recordings.

Next, comes the real charm. The heavyweight of the restoration process is the CEDAR processing used to remove most of the remaining clicks and pops crackle and hiss... it is simply a VERY big, VERY fast, high power computer system, where dirty audio is fed into the CEDAR boxes and clean audio comes out. This all happens in real time, that is, the actual playing time of the music! A few gouges may remain that will need to be removed by editing in a digital workstation, but that pretty much does it.

There are many other facets of restoration, such as the "pitching" of an old recording to ensure that you are playing it back at the correct speed. Remember, the music should be heard in the same key as it was played! EDISON discs, for example, donít play at 78 rpm... they are about a half tone low at that speed and need to be played at about 80 rpm. On some early discs, the speed actually varies from the beginning of a side to the end of the same side,creating some real challenges for "pitching" of these records, particularly in a symphonic work where side joins are necessary. A digital metronome, such as those made by Seiko, can continuously "play" actual notes of the musical scale and this is an invaluable aid to "getting it right".

This has been only a brief outline of what I do to restore old records for CD producers throughout the world. Next time you buy a CD of restored old recordings, and see a credit for "Noise Reduction Processing by Graham Newton", you'll have a pic- ture in your mind of just what went into that work.


Surfactant: Kodak Photo-Flo 200,
Catalog No. 146-4502 (4 fl ounces - 118 ml, cost about $5.00).
Available at photo stores with darkroom supplies

Measuring cup: 1 fluid ounce (30 ml)
(available at most pharmacies, cost under $1.00)

Velvet Brushes: Lagniappe Chemicals Ltd.
P.O. Box 37066
St. Louis, Missouri 63141 U.S.A.
(314) 205-1388