A transformer is an electrical device that allows an AC input signal to produce a related AC output signal without the input and output being physically connected together. The transformer offers several advantages in coupling signals from one circuit to another. A transformer is considered large, heavy, and expensive but it continues to be the most effective solution in many audio applications. Audio transformers improve sound quality by removing interference from audio signals. Audio transformer is generally encased in a magnetic shield which is filled with an epoxy resin that provides insulation, protects the windings, and prevents vibration of the core material. Some audio transformers do not have a center tap, while other devices have a center tap in only the primary side, only the secondary side, or in both the primary and secondary sides. Transformers can be manufactured with multiple primary or secondary windings.
The two types of audio transformers are step up/ step down transformers and unity 1.1 transformers. The basic use of step up transformer is signal level compatibility, and impedance compatibility. Use of unity1.1 transformers are DC blocking, radio frequency interference and ground lift. In step up transformer, the primary and secondary have a different number of windings, thus they have different impedances. A unity transformer allows an audio signal to pass unmodified from the primary to the secondary while blocking DC voltage and radio frequency interference (RFI). Pros of audio transformer is to match impedances, to increase or decrease signal level by up to 25 db. While unity 1:1 transformer is used to increase signal level by more than 25 db. Audio transformer is used in audio devices like microphones, speakers, tape drives to transmit voice and sound signals. The transformers have wide frequency bandwidth, low distortion and noise suppression.
Audio transformers are recognized as wide band transformers. The services that are related to audio transformers are current sense transformers, gate drive transformers, RF transformers, signal transformers, switch mode transformers and telecom transformers. Current sense transformers are used to detect and measure current. Gate drive transformers are used in applications such as switching power supplies. RF transformers transfer energy from one circuit to another by electromagnetic induction. Signal transformers transfer information from one circuit to another by electromagnetic induction. Switch mode transformers are generally used mainly in switching power supplies and DC-DC converters. Telecom transformers are used in applications which require high bandwidths and fast switching speeds.
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