Since the tape has a certain amount of noise built in, the basic quandry is to get the signal as hot as possible to be louder than the Amnesia - New 7th Music - Tape Two - Variable (Cassette) but not distorted due to tape saturation. To really understand what is going on, we need to look at three factors that are normally hidden from the user-- tape bias, equalization, and Amnesia - New 7th Music - Tape Two - Variable (Cassette). All analog tape is recorded with a high frequency AC bias added to the signal to reduce distortion.
Changing the amount of bias has several effects on the result. As bias is increased, the level of the output increases up to a point, then falls off again. This effect is more pronounced at high frequency than at hz, so the overall frequency response changes. Also, as bias increases, distortion decreases, and then begins to creep back in. By the time distortion bottoms out, the signal level has usually peaked and fallen 1. The tightness of the distortion curve depends on the brand of tape-- some require a very precise bias adjustment to give best distortion, others are more forgiving.
Bias is one of the things that is changed when you set the deck for type I or type II tape. This is often automatic, keyed by a cutout on the cassette shell but if it is not, you must get it right for good sound.
Many cassette decks allow the user to make a small adjustment in the bias level, Amnesia - New 7th Music - Tape Two - Variable (Cassette). Generally this is used to trim up the high frequency response-- increasing bias reduces the highs. Since bias is just a very high frequency signal, it is possible for the highest partials of the music to act as additional bias and paradoxically reduce the high frequency response. The Dolby HX PRO feature is a circuit that compensates for this, adusting the amount of bias according to the spectral content of the recorded signal.
As a hedge against noise, the signal recorded on the tape has a high frequency emphasis. When played, the electronics reduce the high end to normal level, effectively filtering the tape noise.
For standard cassette tape this emphasis starts at about 1 khz . With premium tape, Amnesia - New 7th Music - Tape Two - Variable (Cassette) is quieter, the emphasis is moved up an octave  so that the highs will not hit saturation so soon. Noise reduction systems are an elaboration on the equalization concept. There are two basic types of noise reduction, each with a series of variations. In the dbx system, the signal is compressed by when recorded, and then expanded upon playback.
This definitely reduces noise by 20 or 30 dB and also prevents distortion, but it can have two bad side effects. Sometimes you can hear the noise "pumping" especially on bass tracksand if there is any loss of high frequency signal during the recording, common enough in cassettes the decoding will not be accurate. DBX type II addresses the second problem by keying only on the mid band signal. This is usually all right, but material that is principally high or low may be distorted because it is read as no signal during encoding and amplified.
The best feature of DBX is that unrecorded sections of tape are silent on playback, so it is popular on multi-track decks. The down side is that a DBX encoded tape sounds horrible if played without decoding.
The dolby systems also compress upon recording and expand during playback, but they do this within restricted frequency bands:. Type A was the original professional Dolby system. It is still in use, but is being replaced by SRa more sophisticated design.
Both of these are too expensive to consider for cassettes. Type B was the first cassette noise reduction system. It gives a 10 dB reduction in hiss, which effectively cuts the noise in half. Almost every cassette deck made includes Dolby B. Type C came along aboutand gives more extreme reduction, along with some features to make adjustment of the deck less critical. The overall noise reduction is about 20 dB.
The latest flavor of Dolby is type S. It is only available on Amnesia - New 7th Music - Tape Two - Variable (Cassette) price decks, but does a very good job of quieting the tape. Probably the best feature of Dolby is that B and C encoded tapes are usable without decoding. The high frequency response will not be right, but the sound is not too awful. As a matter of fact, playing an unencoded tape with type B decoding will sound quiet, and lots of decks don't have much in the way of high frequency anyway.
The cassette can now be inserted and played in a cassette player. Take out the tape and allow to cool. The glue that binds the oxide to the plastic of the tape should be rejoined and improve sound quality.
Gently pull out the tape from the cassette casing with your finger until there is room to place a pen underneath. Place the pen underneath and continue to pull out until you reach the damaged portion of tape. Cut out the entire section of damaged tape. Cut the tape straight to create a clean join for re-forming.
Join the two remaining sections of tape with the sticky tape. The two sections should overlap about a millimeter. Wrap the sticky tape all the way around the two sections, and press Amnesia - New 7th Music - Tape Two - Variable (Cassette) together.
Wind the tape back in the cassette using the method in Section 1. Nicole Carlin is a registered yoga teacher. By: Nicole Carlin Updated September 15,
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