Information About Turntables and Needles

This page is intended to provide basic phonograph information and provide general knowledge about turntables.

It is the Creation of db electronics who is a reseller of replacement needles and who would appreciate considering them if you are looking for a replacement needle or stylus.

Before we begin I'll take up the subject of materials used for needles, Diamond is always used in Magnetic Cartridges( which we cover later) and Sapphire is often used as the "second" side of a flip over needle in ceramic cartridges( also discussed later).

Diamond needles last longer, sapphire needles wear out sooner. Sometimes it is possible to provide a sapphire needle at the lowest cost for replacement needles, but generally Diamond needles are always used in modern turntables.

Since Turntables and Needles are used to play Records that is the first subject we need to know something about

The three most common are: 33 1/3 RPM 12 inch records, known as "Albums" or "LP's" LP meaning "Long Play"

45 RPM 7 inch Records known as "Singles" or "45's"

78 RPM 10 inch Records usually just known as "78's".

There are records with combinations of these sizes and speeds, such as 45 RPM 12 inch records, and there are also records recorded at the slowest of standard speeds which is 16 RPM, but outside of custom transcription recordings, virtually all commercially produced records require only one of two standard needle sizes for playback.

Both 33 1/3 RPM and 45 RPM Records use the same needle for playback, you sometimes see early records of this type with the "Microgroove" designation, which was a way to alert the user that they were not 78's but had a smaller groove size.

78 RPM Records require a different size of needle for playback, it is wider than the needle used for 33/45 RPM Records

If you attempt to use a needle intended for 78 RPM records on 33/45 Records it often will skim across the surface because it is too wide to fit into the narrow grooves of the LP "Microgroove" records

And if you attempt to play a 78 with a LP needle it goes straight to the bottom of the groove just barely picking up the groove wall where the music is recorded, mostly playing back the dirt at the bottom of the groove. If you hear someone playing a 78 record and most of what you hear is hiss and noise with a little thin sounding music in the background, they are using an LP needle to play a 78 record. With the right needle 78's can sound pretty good. A lot better than most people would expect from such an "old" technology.

If you are ordering a replacement needle it is important to specify that you want to be able to playback 78 RPM records as most replacements are for the LP records only.

Next is Cartridges, which is what the needle fits into and what creates the electrical signal which then creates the sound from the speakers

The two most common types of Cartridges are Ceramic (or crystal) and Magnetic

The needle in both cases is fitted to the end of a small rod ( metal and plastic are both used) which then connects to the cartridge.

The rod itself usually is attached to a molded piece of plastic which then attaches to the cartridge body , although some insert the rod directly into the cartridge without using a holder of any kind..

There are an endless variety of these molded plastic pieces, and is what creates the biggest headache in determining a correct replacement needle, all "needles" (that being the part that touches the record) are basically alike, it is the mounting that varies..

For Ceramic Cartridges the "Flip Over" molded piece is widely used, originally intended to allow a LP needle to be on one side and a 78 needle on the other side.

The method of coupling the movement of the rod as it is vibrated by the record groove wall and then into the cartridge is through a mechanical device known as the "yoke". The rod itself sits in the middle of the yoke and is kept centered and held at an angle so that it wouldn't collapse upwards away from the record. The yoke is often is made of rubber and prone to breaking, here's a set of pictures showing the yoke as it should look and one that is broken. If you are replacing a needle in a ceramic cartridge you should look carefully at the yoke in your cartridge, if it is damaged a new needle won't help restore the sound.

For Magnetic Cartridges the molded piece can be almost any imaginable shape

The method of coupling the vibration created by the groove wall for magnetic cartrifges is usually without mechanical contact. Using either a magnet that moves within a coiled wire or a piece of iron that moves within a magnetic field the signal is transfered into the electrical circuit of the cartridge.

Without the advantage of the direct mechanical coupling that the "yoke" provides the ceramic cartidges there is an inherant loss of signal level in magnetic cartridges.

For that reason the magnetic cartidges require a "preamp" to reach the same volume level as a Cd player or tape deck.

Most hi-fi components in the past included a "phono" input , if you are the owner of a recent product it might not have a "Phono" input in which case you will need an external preamp for your turntable.

Tonearms and Cartridge Mounting

Tonearms intended for use with a Ceramic Cartridge can mount the cartridge using a single screw, two screws, or sometimes are glued in place at the end of the tonearm

These tonearms often do have a crude adjustment for tracking force ( the downward pressure that the needle exerts on the record) but it rarely needs adjustment, it is set at the factory. The tracking force for ceramic cartridges usually is higher than that of magnetic cartridges, often being on the order of 3 to 5 grams, but can be as low as one gram.

Tonearms intended for use with Magnetic Cartridges Generally Fall into two categories, half ( 1/2) Inch Mount and "P" Mount, also known as T4P

Half Inch Mount Tonearms Use a Holder at the end with two holes spaced 1/2 inch apart in what is known as the "Headshell" which often has the ability to be removed from the end of the tonearm itself

These tonearms are intended to accept a wide variety of Brands and Styles so the Tracking Force "MUST BE ADJUSTED"

Tonearms Intended for use with a "P" Mount Cartridge Simply Have an Opening at the end of the tonearm into which the Cartridge is inserted

The beauty of this design is that the Cartridge is simple to install and the tracking Force is fixed by the T4P specification so that adjustment is unnecessary..

Types of Needles and Styli for Magnetic Cartridges

This subject gets a bit complicated, but i'll make it as simple as possible, I'll be using the term "stylus or styli" from now on, but you can substitute "needle" for stylus , they are both used to describe the part that actually touches the record surface.

All Styli have the same width according to the type of record they are intended to play. i.e. LP/Microgroove vs 78's

The width has to be precise in order to fit the groove, but how the stylus contacts the actual groove wall is where the fun begins.

The simplest form is known as "spherical" or "conical" meaning that it is shaped in the form of a cone being perfectly round on all sides that reach into the record groove.

The other form of stylus is known as "elliptical" , which means that it has been shaped so that the part that touches the groove wall is narrower than the width. What that does is to provide a smaller contact area that can then trace the variations in the groove wall (the recorded music information ) much more accurately at all frequencies and also fit itself into smaller and smaller variations in the groove wall ( which gets smaller as the frequency goes higher ) extending the high frequency response.

The drawback to this is that the force exerted on the record is now focused on a smaller area, which can create more wear on the record as it is played.

The sound quality of the elliptical is better, but depending on the quality of your stereo in some cases you might not hear the difference and the spherical stylus has response to around 15 KHz which is pretty good.

 

This Page is from : db electronics, Knoxville,Tenn 865-588-9532

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