Lexicon Transformer

Electronic component that functions like a Transformer. In the case of the transformer, the focus is usually on the transfer of information, whereas in the case of the transformer, the focus is on the transfer of energy. In some fields, the two terms are used synonymously.

For information on how a transformer works, see the web links below.

Today, transformers are relatively rarely found in audio equipment. A distinction is made between different areas of application, each of which requires its own type of transformer:

LF audio transformers

Microphone transformers

These transformers can be found in the input of a microphone preamplifier. Because of the relatively high price of such a transformer, and its mechanical size, this solution is reserved for higher quality equipment. The advantages of a transformer in this application are:

• Good common mode rejection, providing good immunity to noise signal coupling into the microphone cable.
• Possibility of impedance matching between microphone and preamplifier, allowing low noise to be achieved. This impedance matching is particularly important for the very low impedance ribbon microphones, in which corresponding transformers are therefore directly installed. The impedance matching is done by a corresponding ratio of the number of turns between the primary and the secondary side.
• Simple possibility of phantom powering the microphone via a center tap of a transformer winding.
• Galvanic isolation

MC phono transformers

These transformers are used to match an MC pickup system to a preamplifier for MM pickups. As with microphone transformers, the impedance and level matching is done via an appropriate turns ratio.

Output transformers in tube amplifiers

Most tube amplifiers have a relatively high output voltage due to their design and require a relatively high impedance load. This is a poor match for a typical speaker, which is low impedance. For impedance matching a transformer is used, which also keeps potentially lethal voltages away from the speaker terminals due to its galvanic isolation.

In this case, of course, it is not only a matter of transmitting information, but also, depending on the amplifier, of transmitting some energy to operate the loudspeaker. Accordingly, output transformers of considerable size and weight are offered.

Transistor amplifiers have lower output voltages that directly match the loudspeakers used, so no transformer is required.

Loudspeaker transformers

These are used especially in ELA technology (100V technology), and largely correspond to the output transformers of tube amplifiers. However, they are not built into the amplifier, but into the loudspeaker. This facilitates the parallel operation of many loudspeakers on one amplifier.

Isolating and balancing transformers

Here the galvanic separation of the signal is in the foreground, an impedance matching does not happen. The turns ratio is usually 1:1. Such transformers are sometimes found at inputs or outputs of devices, to make the transmission via cable independent of the ground level of the device. This is an effective way to avoid ground loops. External transformers can also be found for this purpose, which can be looped into cable connections.

DI transformers

These transformers are used in event technology to feed the electrical signal from an electric musical instrument directly into the microphone input of a mixing console (DI = Direct Injection), instead of picking up the signal via microphone. Again, this is especially a matter of impedance matching, since the impedances of instruments may be very different from those of a microphone. In addition, galvanic isolation is helpful for suppressing hum interference.

Branch transformer (splitter)

This type of transformer has two or more secondary windings, so that an input signal can be distributed impedance-correct on several galvanically separated ways. This is used, for example, in event technology when a signal is to be distributed to several mixing consoles (front-of-house, monitor, OB van).

Digital audio transformers

These transformers can be used with digital audio interfaces (AES/EBU, S/P-DIF, etc.) to achieve galvanic isolation. Compared to LF transformers, the size and therefore the price is quite small. Some special forms allow impedance matching between different transmission standards.

See also

• Wikipedia article: transformer, transformer.