PHONOGRAPH PRIMER

There are two "tracks" cut into a stereophonic record, corresponding to the two channels in a stereo signal. The groove for channel 1 is cut into the depth of the record and it makes the needle move up and down. The second is cut into the walls of the record groove and forces the needle to move from side to side. The record stylus is the little piece of diamond coated metal that rides in the groove. It is mounted on a small metal shaft. This tiny shaft sits in a rubber ring and continues into the cartridge. In the cartridge are two small magnetic coils. Each coil has two wires that come out of it. These correspond to the four pins you see on the back of a cartridge.

When the needles ride into the groove it moves up and down and side to side at the same time. This make the metal shat of the stylus vibrate. When the shaft vibrates up and down it creates a small magnetic filed in the first coil which makes a small current. The side to side vibration does the same in the second coil ( or second part of the coil if it's one coil). These two small currents travel to the back of the cartridge, along the wires in the tone arm and out the back of the turntable. That's the basic unprocessed stereo signal

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No power ever comes to the tone arm assembly. It is independent of the rest of the electronics in the turntable and can be replaced at will. The whole sound generation part of playing a record starts out by creating current off the record with the needle and cartridge. Think of your cartridge as a small generator.

This is why you get sound even if the motor of the turntable is off and you move the record. You are not generating power by spinning the record.

Unfortunately this whole process of reproducing audio using a stylus on a piece of vinyl isn't as sonically accurate as everyone would like it to be. The signal actually has to be modified to properly be pressed as a groove in the record. And when you play the record back it gets modified again by as special circuit in your phono pre-amp. To sound like the original recording. This is pretty much the same idea as using dolby noise reduction when recording and playing back a tape. Keep in mind the actual process is very different. This process is called RIAA equalisation

RIAA EQUALIZATION

The signal (1) gets recorded onto to a master tape (2). This tape goes through RIAA equalisation (3) and that's what is printed onto the record. when the record (4) is played back a little circuit in the phono pre-amp re-eqs the signal (5) and the result sounds almost identical to the original recording. This is what you will hear(6).

Ironically what most people consider to be warmth in a record is usually due to defects in the lower frequencies. Most engineers agree that there is always a marging for low end error when mixing down a track for vinyl. Although who's gonna complain about a little extra bass..?

different things affect the quality of the signal on vinyl. The type of vinyl is a big one to whatch out for. In dance music it's no secrets that the best pressings are usually German, British and French. These countries have huge markets and great local technology in the music industry. They comonly press using the purest vinyl and press deeper into thicker vinyl. This technique gives a louder and better signal.

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ique gives a louder and better signal.

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