Description of Audio Transformers

Like most other transformer products, audio transformers consist of two or more magnetically coupled coils of wire, usually wound around a magnetic core. They are distinguished from other transformer types by being adapted and characterized for use at frequencies across all or a significant portion of the human audible range spanning roughly 20 Hz to 20 kHz, and are used for isolation and transformation of information in analog format, as contrasted with transformers designed for transmission of information encoded using a digital signaling protocol. Examples include output transformers for vacuum tube amplifiers and voice coupling transformers for traditional telecom applications.

What is Audio Transformers

Audio Transformers are electromagnetic devices that transmit and modify input electromagnetic signals into output signals via inductive coupling. They isolate an input circuit from an output circuit and filter signals; operating on the audible band of the frequency spectrum (20Hz to 20kHz). As such they can have applications in the input stage (microphones), output stage (loudspeakers), as well as coupling and impedance matching of amplifiers. In all cases, the frequency response, primary and secondary impedances and power capabilities all need to be considered.

Materials and Structure

A transformer is an electrical device which allows an input signal (such as an audio signal or voltage) to produce an output signal or voltage without the input side and output side being physically connected to each other. This coupling is achieved by having two (or more) wire coils (called windings) of insulated copper wire wound around a soft magnetic iron core. Audio transformers are typically composed of copper wire windings around a steel or nickel-iron alloy core. Each core material transmits electromagnetic signals differently. Steel has a higher degree of hysteresis (magnetic signal lag), making it better for lower frequency transfer. The higher permeability of nickel makes it ideal for transmitting higher frequencies. The windings around the core determine the impedance level, which increases, decreases, or maintains the signal level as it passes through the transformer.