by Fred Krock, KQED
Revised June 16, 2000
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At one time most of the music and recorded effects used in broadcasting came from disc recordings. Even though most recorded music on the air today comes from CD’s, from time to time you may need to play analog disc recordings. Occasionally you may have to dub sound from a record to use in a news or public affairs program. Many stations still have extensive libraries of phonograph records slowly deteriorating in a back room. We’ll look at how to play, clean, and preserve those funny round sources of sound.
Some of the types of recordings you may encounter are:
In addition there are recommended methods of Record Washing and after they're dry, Disc Storage and Handling
Records have been equalized to produce a higher signal-to-noise ratio, but what does this mean in practical terms? A section about Record Equalization will explain.
Can you repair Off-Center Records? (quick answer: yes)
What are the types of pickups? AKA "needles"
How do you cleaning dirty styli? How do you know when to Replace Styli? And what's the correct amount of Tracking Force and Anti-Skating Force you should use on your Turntable?
Most 78-rpm records pressed before about 1946 used shellac as a binder to hold the record together. Other ingredients included filler and carbon black for color. Pure shellac is very brittle. Filler makes the records harder, stronger, and cheaper. Some materials used for filler included finely ground clay and wood fiber. Background noise would increase with increasing amounts of filler. Some record labels would use more filler in their popular music records than in classical music records. In general RCA records used less filler than Columbia. English records typically used less filler than RCA.
During World War II shellac was in very short supply since most came from parts of the world occupied by Japan. Old records were ground up, labels and all, and recycled to press new records.
Alcohol is a solvent for shellac. You must be very careful that record cleaning fluids used on shellac records do not contain any alcohol.
Radio stations often kept a bottle of water in the control room. If a record were very noisy, a little water sprinkled on the surface would lubricate the playback and cut down on the surface noise. One of the first records I played on the air as a beginning broadcaster was noisy. I grabbed a bottle of alcohol by mistake and dissolved all the grooves before the record finished playing.
Badly warped records can be flattened. Any dirt on the surface may be pushed into the surface during flattening increasing noise. Clean the record. Put it between two pieces of ¼ inch plate glass. Prop the glass horizontally over a 100-watt light bulb. In several hours heat from the light bulb will soften the record enough for it to flatten. Shellac is thermosetting, hard when cold, soft when hot.
Recommended playback stylus for 78-rpm records is 3 mils (thousandths of an inch) radius of curvature at the tip. The rule of thumb is that the playback stylus has twice the radius of the cutter stylus used to make the record. The larger radius of the playback stylus prevents it from skating on the bottom of the groove increasing distortion and noise. Some enthusiasts maintain a collection of different radius styli and experiment to get the best sound from old records. This probably is overkill for broadcast use.
Micro-groove long playing records were introduced in 1947. They used a cutter stylus tip radius of .25 mils. Recording studios soon discovered that LP cutter styli made satisfactory 78-rpm records. Rather than stock two separate types of cutter styli, they simply cut everything with an LP cutter. You will find that a number of 78-rpm records and transcriptions cut after about 1947 will play with an LP playback stylus. A record with a lot of wear caused by a 3 mil stylus often will play like new with an LP stylus if it were cut with an LP cutter. If the record was cut with a standard groove cutter, sound will be very noisy with noticeable distortion when played with an LP playback stylus.
A hard base is covered with a thick coat of nitrocellulose lacquer. Professional recording discs used aluminum as the base. Discs made for home use often used cardboard for a base.
Often these discs erroneously are called "acetates." Why this erroneous name came into use can only be guessed. Perhaps it was because the word "nitrate" had a bad reputation. Explosive gun cotton is nitrocellulose. Cellulose nitrate movie film would burn almost explosively and required special handling. Amateur photographic safety film used cellulose acetate to avoid the problems of nitrate film. Thus the word "acetate" may have become a euphemism for cellulose nitrate lacquer.
Originally phonograph records were recorded on beeswax master discs. They could not be played until they were processed and a record was pressed. Instantaneous records could be played as soon as they came off the recording lathe, thus the name.
Recording on wax caused many problems not found with the instantaneous blanks that eventually replaced wax for recording master discs. A master record never was played before processing even when cut on an instantaneous blank.
Instantaneous record grooves are much softer than vinyl or shellac pressings. Every time the record is played the grooves will be deformed a little bit. Instantaneous recordings are good for only a few extremely high quality playbacks. However, they were good for hundreds of plays when used for jingles, liners, commercials, and the like in radio stations.
In the late 1930’s Columbia records started making safety recordings of all recording sessions on the outside of 16 inch transcription discs. These instantaneous safety recordings were stored and never played unless the record manufacturing plant accidentally destroyed the 78-rpm master disc. Then they were used to dub a new master.
When Columbia records introduced the long playing record in 1947, virtually all of the current Columbia catalog was available on these safety discs. They were used to make almost the entire Columbia catalog available on long playing records. This gave Columbia a huge advantage over competitors who had to start from scratch recording for LP records. Early Columbia LP records give an idea of the high quality sound possible from instantaneous recordings.
You may find instantaneous recordings in micro-groove or standard groove format. The label should tell how it was recorded.
Chips cut from instantaneous discs burn readily. When the chip is picked up from the disc with a vacuum system, it is collected in a tank of water. Many studios would store chip in water until it could be removed from the premises.
Lacquer coated instantaneous recording discs were introduced in 1935 by the Presto Recording Corporation. They replaced extremely noisy embossed aluminum blanks for instantaneous recording.
During World War II and again during the Korean dispute most aluminum was allocated to war production. Recording discs were made using glass about 1/16 inch thick for a base. They were known as "glassies." The resulting discs were very fragile. A hard look was enough to break one. If you ever have to play one, be very careful putting it on the turntable. Bumping it against the spindle is enough to shatter it. I found that out the hard way.
Glassies look superficially like aluminum base discs. The word "glass" usually appears near the center with the manufacturer’s trademark. Most studios would rubber stamp labels with "glass" in large red letters.
When new aluminum was not available, disc manufacturers would buy used blanks to recycle. Typically they paid ten cents each for twelve-inch blanks. If the shipment weighed over one hundred pounds, the manufacturer would pay freight. Needless to say, checks paying for used blanks rarely made their way to station management.
At one time most radio stations could cut instantaneous discs. Most stations used Presto lathes. Cost for a lathe was just under $600 (about 1/3 of the cost of a new car to put price in perspective). Typically a station would have two lathes sharing a common amplifier that switched between the two lathes.
Use of instantaneous recordings in broadcasting for complete programs ended around 1949 when good quality low price tape recorders became available (anyone remember the Magnecord PT-6?). Use for spots and theme music mostly ended about 1958 when tape cart machines came onto the market.
Another familiar name, Scully, made better quality recording lathes.
Presto also offered a line of tape recorders. They were not successful. One unit had two transports sharing a common amplifier with a selector switch similar to the recording lathes. If you would like to learn more about Presto and its products, go to http://www.televar.com/grshome/Presto.htm.
Since both long playing (LP) and 45-rpm records use identical size grooves, we’ll discuss them together. LP records revolve at 33/13 rpm.
LP and 45 rpm records are pressed on vinylite. Actually it’s a witches' brew of polyvinyl chloride plastic, dye, plasticizer, and a lot of other probably carcinogenic things. Some record manufacturers even used filler similar to those used in shellac records to produce a harder surface and to reduce cost. A few 78-rpm records were pressed on vinyl.
Early Columbia 45’s were pressed on polystyrene. They became noisy after a few plays. They developed severe back cue burn. Radio station release discs were pressed on vinyl.
Although PVC plastic was invented in the 1920’s it was not used very much for consumer release until LP records. Early phonograph pickups had tracking forces too high for vinyl discs.
Vinylite is very stable. LP records made in 1947 are playable today. They probably will be playable 50 years from now if stored properly. The plasticizer used in vinylite is reported to evaporate very slowly; old records probably are slightly more brittle than when new. This should not cause any problems if modern, low tracking-force pickups are used to play them.
Alcohol is reported to leach out plasticizer. Cleaning fluids containing alcohol probably are not a good idea although they have been used widely in the past.
A stylus designed for long playing records must be used. Original LP styli were conical with 1.5 mil tip radius. Elliptical and other complex shape styli were shown to give better high frequency response with lower distortion. They still are available.
Playing 45 rpm records on broadcast turntables caused real problems trying to keep them cued when slipping them before starting. One major broadcaster, Westinghouse, decreed that no 45’s would be played at their stations.
A special cue disc was developed to play 45 rpm records on broadcast turntables. It resembled a very thick 12-inch record with a depression to hold the 45. It could be handled like a regular record or transcription allowing a good slip start of a 45.
Transcription discs date back to the early days of broadcasting. They may be up to 16 inches in diameter. The large discs require a longer tone arm than used for 12 inch and smaller discs. They use slightly finer grooves than 78-rpm records and revolve at 33 1/3 rpm. Specified transcription playback stylus tip radius is 2.5 mils compared with 3 mils for 78-rpm records. If a transcription disc was recorded after 1947, you may get better results using an LP playback stylus.
Origin of the 33 1/3 rpm speed for transcriptions is unknown. One story that makes sense is that it was an outgrowth of the Vitaphone talking picture system. Vitaphone, an early type of sound motion pictures, used a phonograph record synchronized to a movie projector.
According to the story, the developers of Vitaphone determined that a record 16 inches in diameter revolving at 35 rpm would be satisfactory to hold the sound of one reel of movie film. When they used stock gears to drive a turntable from a shaft in the projector, the turntable revolved at 33 1/3 rpm.
Transcriptions may be pressed or may be instantaneous recordings. Transcription discs were pressed on vinyl from the beginning. They may be recorded laterally or vertically. They may be recorded with the groove starting at the outside like conventional records or they may be recorded with the groove starting inside at the label. Inside-out transcriptions usually note the fact on the label. Start with the tone arm next to the label and they will play like any other transcription.
Continuous recording time for a 16-inch transcription disc is fifteen minutes. A thirty-minute program would require two discs. Often the first half of the program would be recorded outside-in. The second half would be recorded inside-out.
Sound from a transcription disc gradually deteriorates as the pickup gets closer to the label. The segue from disc one to disc two in the middle of a half-hour program is made with the pickups next to the label on both discs. This avoids the change in sound quality that would result during a segue from the inside of a disc to the outside of the next disc.
You may find a lot of instantaneous transcription discs that are recorded inside-out. This was done to avoid having to "chase the chip" while recording. The cutter stylus cuts a lacquer chip from the surface of the recording blank that resembles a heavy, wavy, black thread.
When cutting a disc, the resulting chip naturally throws toward the inside. You could cut a whole disc inside-out without having to remove the chip. Recording engineers have been known to be lazy. Outside-in recording required removing the chip as it was thrown. Otherwise you have a danger of the chip fouling the cutter.
If you cut across the chip, the cutter head would lift from the disc. The best result would be a noise on the recording or a record that would mis-track. The worst result would be a destroyed cutter stylus (I’ve broken my share).
Cutter styli were made from synthetic sapphire. Diamond was too brittle. Lifetime usually was twelve to fifteen hours of recording time before they needed to be re-sharpened.
This micro-groove format was used for talking books and for some records made to play in Chrysler Corporation automobiles. In autos the format was an underwhelming success. Dub them revolving at 33 1/3 rpm on reel–to-reel tape at 15 ips and play back at 7.5 ips. (Anyone remember tape recording?)
Old Edison recordings were vertical, rather than lateral. The groove modulates up and down rather than from side to side. Another name is hill and dale recording. Associated Transcription Service discs were released in the vertical format until the end in the 1950’s. You don’t need to get a vintage RCA or Western Electric pickup to play a vertical recording. Use any standard stereo pickup with an appropriate 2.5 mil stylus. Reverse the phase of one channel and mix together the left and right channels. Result is an instant vertical pickup.
Most disc recordings use pre-emphasis (high frequency boost) resembling that used in FM broadcasting. This requires matching de-emphasis in playback. Disc recordings also have a crossover frequency from constant width to constant velocity recording varying from about 500 Hz to 1200 Hz. In playback frequencies below the crossover frequency need to be boosted. This complex frequency response curve used in disc recording is known as equalization.
Pre-emphasis in phonograph records provides the same advantage it does in FM broadcasting, a higher signal to noise (S/N) ratio. It evolved almost by accident. The first phonographs were acoustical. High frequency response of acoustical phonographs had a natural roll-off caused by the mass of the reproducer. Early electrical recordings boosted high frequency response to sound better on acoustical phonographs.
Phonograph records have a maximum level limit as absolute as digital recordings. The modulation level must never be so high that a groove is cut into the adjacent groove. A record with this defect never will play back properly.
Cutter heads normally produce what is called constant velocity recordings. A 1000 Hz signal will produce a wider groove excursion than a 2000 Hz signal of the same electrical amplitude because the 1000 Hz signal has a longer period. To prevent low frequency signals from causing the groove to cut into an adjacent groove, recording levels must be reduced degrading S/N ratio.
To allow higher modulation levels and to reduce low frequency playback tracking problems, frequency response below an arbitrary crossover frequency is reduced with a 6 dB per octave slope. Often the physical construction of a cutter head determined the crossover frequency. A 100 Hz signal will produce the same width groove excursion as a 200 Hz signal. This is constant width recording. Playback response must be boosted 6 dB per octave below the crossover frequency to get a flat overall response.
Almost all stereo recordings use RIAA equalization. Stereo pre-amps are built to match. We can’t begin to list all the different equalization curves used in mono recordings. I have seen high-end mono record pre-amps with as many as ten different switchable playback curves.
Over the years many different equalization curves were used in making records. Often record labels used their own proprietary equalization curves. Mastering engineers sometimes applied their own private tweaks to recordings (usually to make the record sound better on a lousy quality phonograph).
Radius equalization is another form of equalization occasionally encountered. Radius equalization was not common but you may occasionally encounter an example. RCA "Dynagroove" records used radius equalization.
As the pickup gets closer to the inside of a record, the speed of the surface passing the stylus gets slower. Wavelengths get shorter. High frequency response of playback is reduced especially with a large tip radius playback stylus. To compensate for this, high frequency response was boosted during recording as the cutter got closer to the center. To my ear this usually produced an unacceptable increase in distortion.
Frequency response of cutter heads could change with temperature. The damping material used in constructing a cutter head frequently determined the crossover frequency. Cutter heads require a lot of power. Usually a cutter head would get warmer while cutting a record. Unfortunately, characteristics of the damping material would change with change in temperature altering the frequency response of cutter heads.
RCA solved this problem in one cutter head by designing it to operate at an elevated temperature. A thermostatically controlled heater kept the temperature constant no matter how much heat was coming from the cutter head coils. You had to warm it up for fifteen minutes before starting to record.
Frequency response could be affected during record manufacturing. Metal reproductions of the record surface must be polished to reduce noise. If the technicians are not careful, high frequencies could be polished off by accident. High frequency response is one of the first things noted when checking a test pressing prior to a production run of records.
In general most mono LP recordings fall close to one of two different equalization standards, NAB or AES. The AES curve requires less de-emphasis than does NAB. Most transcriptions used the NAB curve although, as usual, RCA marched to the beat of a different drummer. The RCA orthacoustic curve is closer to the AES curve but with a higher crossover frequency (requiring more bass boost). Late 78-rpm records usually use equalization similar to LP records. On early 78-rpm electrical recordings all bets are off. Sometimes the frequency response of the record was the result of the design of the cutter head used.
Fortunately the RIAA stereo record curve provides a good starting point for playing back most records. Use good quality monitor speakers and a high quality equalizer. You may be surprised by the high quality sound even on very old records.
Record equalization is a very complex subject. If you want to know more, see some of the innumerable papers published by the AES many years ago. If you want to know more about record manufacturing, the http://www.audio-restoration.com/pressing.htm site has an excellent, concise summary.
Occasionally you may encounter an off-center record pressing that produces unacceptable wow during playback. The location of the center pin of a master recording is lost during the manufacturing process. Each stamper, the die used in pressing records, must be centered before being installed in the press. Occasionally someone will goof resulting in an off-center pressing. Sometimes you will find a record with one side centered and the other side off-center. 45-rpm records were pressed with a conventional small center hole. Then they were run through a punch to create the large hole.
To play an off-center pressing, first you must enlarge the center hole. A hand reamer is the preferred tool. Move the record around on the turntable until the grooves are centered, then play it. Remember after you enlarge the center hole, that record never can be played normally again. A few turntables allow removing the spindle to avoid reaming the record center hole.
Occasionally you may encounter a record with a lateral warp. Most of the record is centered but part of it is off center. I have observed this defect only on 78-rpm records. Probably this defect occurred when the still soft record was removed from the press. I don’t know of any cure for this problem. Perhaps one of the digital pitch correction programs could help, but I’ve never tried it.
Unless a record is tightly sealed in a plastic envelope, it will collect dust, dirt, and general crud that can make it noisy on playback. Playing a dirty record can cause a permanent increase in noise level. Even a virgin record may have a mold release compound on the surface that can cause noise on playback.
At the very least a record should be dry brushed before playing to remove any dust. Special brushes for this purpose are available from the discdoc web site listed below or from sources listed at http://www.audio-restoration.com/sources.htm. Don’t forget the hyphen in that URL.
Unless the record is brushed properly, it can become charged with static electricity and attract more dust than is wiped off. Conductive brushes are sold to minimize this problem. Wiping with a barely damp cloth usually will minimize the problem if you don’t have a special brush.
For best results records should be washed before playing. After washing records, be careful never to touch the grooves.
Plain old soap and water usually will do a good job. Old Edison records are affected by water and must be dry brushed only. (BEWARE: Keep soap and water away from the label. Some inks and some paper surfaces are not waterproof.) First rinse the record with tap water. Apply a mild detergent solution with a paintbrush (I suggest one ounce of hand dishwashing detergent in about a quart of water). Use the ends of the bristles to scrub the grooves. Rinse the record with tap water. If your tap water is soft enough that it does not leave water spots on glassware, you may stop here. Otherwise follow with a rinse of distilled water. Let the record dry, then play it. Noisy old 78-rpm records may give better results if played back while wet. Check that water won’t damage your pickup.
Several manufacturers offer record cleaning solutions and supplies. One such vendor can be found on the Internet at http://discdoc.com. I do not have any first hand experience with these products. I found accurate information on this web site with none of the voodoo science frequently found in audiophile circles.
Several record cleaning machines were sold at one time. The Rolls Royce of record cleaning machines is the one designed by Keith Monks. Brand name is Syantific (sic) Audio Record Cleaning Machine. About forty years ago they sold for over $1,000. The Rolls Royce analogy is accurate since they were made in England.
Lovers of British automobiles will appreciate the Lucas windshield washer fluid pump used to apply cleaning solution to the record. The Lucas pump applied a special cleaning solution to the record as it revolved on a turntable. A brush scrubbed inside the groves. Then an arm resembling a tone arm swept across the record vacuuming up the cleaning solution. A spool slowly fed out thread that was sucked up together with the used cleaning solution. The thread provided a final wipe of the record and kept the nozzle from rubbing on the record surface. One side of a 12-inch LP record could be cleaned in about one minute. The record was ready to play as soon as it came off the machine.
The cleaning fluid for vinyl records included alcohol to promote faster drying. Some people today claim that alcohol should not be used on vinyl records because it leaches out plasticizer.
A different cleaning fluid was made for shellac records that did not include alcohol. You always had to be careful not to use a vinyl cleaning solution on shellac records.
If you have to clean a lot of records, you might keep on the lookout for one of these machines. They do an excellent, fast job. I understand that they bring very fancy prices from record enthusiasts. A new improved version of the Monks machine is now available advertised for $3975. See http://www.audio-restoration.com/monks5.htm. I do not have any first hand experience with this company.
VPI Industries, Inc. made a similar machine in this country. It was not as rugged as the Monks machine. I never made a comparison test to see which machine did a better job.
Unless you want to pay exorbitant prices for phono pickups, your best bet is: Shure Incorporated (formerly Shure Brothers) of Evanston Illinois. Shure continues to manufacture and support pickups in several price levels. Shure pickups sound good. Some models are very rugged. (You may have to make a compromise between sound and durability for broadcast use.) Very few dealers stock pickups or replacement styli these days. You’ll probably have to contact one of the Shure representatives listed on the Shure web site. Go to http://www.shure.com for more information.
What are hard to find are replacement cartridge shells for tone arms. Every manufacturer seemed to use a different design. Guard your cartridge shells carefully.
The stylus tip always should be vertical to the record. This is especially important when playing stereo records. Many cartridge shells will slip in the tone arm allowing the cartridge to twist sideways. Bouncing a pickup on a revolving turntable can bend the stylus armature causing mis-alignment of the stylus. Check regularly that the stylus is vertical with respect to the record and correct it if needed.
Most phono pickups today are one of two different types: moving coil and variable reluctance. In the first type a coil moves in a magnetic field to induce a voltage. Disadvantages are low level output, higher moving mass, and occasional failure of the flexible lead connecting to the coil.
In a variable reluctance pickup the coil is wound around the magnet and a piece of iron moves in a magnetic gap to vary the magnetic field and induce voltage in the coil. Disadvantage is the problem of keeping trash steel out of the gap.
The GE pickup was the most popular of the variable reluctance pickups. In the early 1950’s a person usually could tell which radio stations were using GE pickups because they sounded better on the air. GE made a professional version of the pickup that had a lower impedance than the consumer version. It was used with a passive equalizer to plug into a regular console microphone input. The professional version had a shiny chrome plated shell rather than the satin finish used on the consumer version. Some tweaks were very proud of their professional GE pickups. In reality they didn’t work as well as the consumer version because the lower impedance gave a lower output level.
Over the years many other types of pickups have been used. Some of them are:
The Weathers pickup was supplied only with the Weathers tone arm that was made of balsa wood. The wooden tone arm was very light and had almost no resonances. Weathers made a longer version of the arm for playing 16 inch transcriptions.
The Weathers pickup sounded superb. Tracking forces were extremely low. Efforts were made to sell the Weathers system to broadcast stations. A problem that never was solved was that the discriminator had to be tuned for minimum distortion frequently. Changes in temperature or humidity changed the capacitance of the wire connecting the pickup enough to change the frequency of the oscillator.
Zenith used both capacitance and strain gauge pickups in consumer record players.
If you play dirty records, dirt, lint, and other fuzzy stuff will collect around the stylus. Eventually enough can collect to cause mistracking and audible distortion. Check the stylus tip from time to time. Special little brushes for stylus cleaning were sold at one time. A toothbrush usually will do the job. Brush gently in same direction as the record revolves past the stylus.
You should use the pickup manufacturer’s recommended tracking force whenever possible. A stylus pressure gauge is a low cost, invaluable tool. If a record is warped, you can try flattening it as suggested in the 78-rpm record section of this article. The same technique will work on either shellac or vinylite records.
If the record won’t track properly, try putting a coin on top of the pickup. Start with a penny then work your way up as needed. In my experience most pickups will tolerate tracking forces much higher than recommended. In the old days in radio stations, operators sometimes would write the size of coin needed to play a record on the label. Has anyone seen a 50-cent piece recently?
The geometry of a tone arm in relation to the rotating record creates a force on the stylus in the direction of the center of a record. This is known as skating force. In theory skating force can introduce distortion into the record playback. Some tone arms were equipped with small weights attached to the tone arm with a plastic thread to counteract skating force.
I never could hear any sound improvement using anti-skating weights. Without the weights if the stylus encountered a bad spot in a record, it tended to skip into the next groove and keep playing. With anti-skating weights, the stylus would not skip over the problem spot and the record would sit there and repeat all day or until the announcer woke up.
The points of contact between a playback stylus and a record groove are microscopically small. Although tracking forces with modern pickups are very low, they still translate into many thousands of pounds per square inch because the point of contact is so small. This pressure will wear flat spots even on diamond tip styli. (At one time cheaper sapphire tip styli were sold but they wore out so fast that use of diamond tips became universal.)
The old rule of thumb was that the life of a diamond tip stylus was one thousand hours playing time. Dealers frequently had microscopes sitting on a counter so customers could examine their styli for wear. I seriously doubt that very many customers ever had the slightest idea what to look for in the microscope.
Fortunately a very simple test exists for stylus wear. It doesn’t require a microscope or any other tools. Take your stylus into a room with a single point light source such as a naked light bulb. Also you can use sunlight coming through a window into a darkened room.
Remember from your high school physics class that the angle of reflection will equal the angle of incidence. Hold the stylus where you will be able to see any reflection from the tip of that point-source light. Slowly revolve the stylus looking at the area that contacts the groove walls. A flat spot will reflect a lot more light than will the curved surface of a new stylus. If you see a sudden flash of light from the tip, the stylus has a flat spot and should be replaced.
You should replace the entire stylus assembly if possible. Some vendors will replace just the tip on your stylus. If you are passionately in love with a pickup that uses a stylus that no longer is manufactured, this may be your only option. You can find links to these services on the web site http://www.audio-restoration.com/sources.htm.
A stylus assembly reduced to its simplest element is a spring. All springs have resonant frequencies. The stylus designer will try to reduce all resonant frequencies or to change the resonant frequency to one that causes no harm. One way to minimize resonance is to use a rubbery damping material. Viscaloy is the trade name for one substance that was used commonly.
Damping materials can change characteristics with use and age. Even with a new tip an old stylus may not perform as well as a new one. A stylus that has been on the shelf for a long time may not sound as good as one manufactured recently. That’s why I prefer to use a fresh new stylus whenever possible.
The most common turntables found in radio stations today are Technics models such as the
SP-10 MKII. The good news is that they tend to last forever. The bad news is that Technics does not support them very well.
What don’t last forever are the electrolytic capacitors in the power supply. Every five years or so you should replace all the electrolytic capacitors in the power supply.
Another thing which fails is the neon light that illuminates the stroboscopic markings on the edge of the platter. Technics cannot supply a replacement. I haven’t researched it, but a stock neon lamp might be used to replace the original.
This neon lamp doesn’t really tell you very much that is useful. It does not tell you that the turntable is revolving at the correct speed. All it tells you is that the turntable motor is synchronized with the amplifier driving it. If you lose synch, your ears will tell you much faster than the lamp. If you want to check speed accuracy, you need to use a separate strobe disc.
If you keep the turntable clean inside, the motor bearings clean and oiled, and replace power supply capacitors regularly, the Technics turntables should keep revolving for a long time.
If you’re using old broadcast turntables such as QRK, RCA, Fairchild, or EMT, you’re on your own for spare parts. You can find links to new turntable suppliers with prices up to $3500 on the audio restoration web site.
Records must be stored vertically. Never stack records horizontally. Pressure from above can force dust and dirt into the record surface. If a shelf is not full so that records lean at an angle, fill the empty space with cardboard so records are vertical. Records stored at an angle can become warped.
Records should be stored in separate sleeves. The audio-restoration web site mentioned earlier has links with suppliers. An LP jacket without the original internal sleeve is not satisfactory. Some archives rotate records ¼ turn every year to minimize cold flow problems.
Storage room temperatures always should be reasonable low. An attic definitely is not the place to store records. Store records away from sunlight. A record left in the sun can warp.
A basement probably is not a good idea either. High humidity can cause deterioration of cardboard and paper protecting the records. I have seen mildew growing on instantaneous records.
You want to protect your records from dust, dirt, and chemical fumes. You don’t need semi-conductor manufacturing clean room standards, but the cleaner the better.
Diesel fuel in the vicinity of records is not a good idea. You don’t want to store them near a standby generator. Diesel fuel evaporates and then deposits sticky gum on nearby things.
Never touch the grooves of a record. Fingerprints can etch the surface of vinyl records and can cause dust to adhere. If you are doing a lot of work with records, get some lightweight cotton gloves from a photo supply store. Even when wearing gloves, avoid touching the grooves whenever possible.
Your hands should be clean and dry while handling records. This is not the time to be eating a greaseburger from the nearest fast food emporium.
If you are not wearing gloves, handle records only by the edge. You can remove records from jackets by putting fingers on the label without touching the grooves and pushing the record against the palm of your hand. If this description doesn’t make sense, get some old timer to show you the proper technique.
Work with records only in clean, dust free areas. Never set records where any liquid could be spilled on them. Keep them in their storage sleeves at all times except when they are being played.
Cover turntables when not in use to minimize dust collecting. Vacuum turntables and turntable pads frequently. You’d be surprised how much dust and dirt will collect in a turntable pad.
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