Audio transformer - Revision history

Brad Johnson at 17:12, 12 April 2018

2018-04-12T17:12:54Z

Brad Johnson at 17:12, 12 April 2018

2018-04-12T17:12:24Z

Brad Johnson at 23:48, 3 August 2017

2017-08-03T23:48:27Z

Brad Johnson at 00:04, 3 August 2017

2017-08-03T00:04:29Z

Brad Johnson at 00:03, 3 August 2017

2017-08-03T00:03:43Z

Brad Johnson: Created page with "==Overview== The term "Audio transformer" is used to describe a form of signal transformer used in audio applications. With few exceptions, these transformers co..."

2017-08-02T23:53:43Z

Created page with "==Overview== The term "<nowiki>Audio transformer</nowiki>" is used to describe a form of signal transformer used in audio applications. With few exceptions, these transformers co..."

New page

==Overview==
The term "<nowiki>Audio transformer</nowiki>" is used to describe a form of signal transformer used in audio applications. With few exceptions, these transformers consist of two “coils” of insulated wire wrapped around a common ferrous (steel) core. The coils are electrically isolated by the insulation, and can only transfer the signal from the primary (input) coil to the secondary (output) coil by electromagnetic coupling.
This quality and the inductance of the coils allow the transformer to provide electrical isolation between the primary and the secondary for non-audio signals such as [[DC]] and [[RF]].

==History==
Before audio electronics were developed that worked on power supplies with both "plus" and "minus" voltages; some method was needed to isolate the DC voltages required for audio circuits operating on "single-ended" DC power from different stages of the circuitry and from devices connected to the input and output. In many cases; "coupling capacitors" were used to allow the AC (audio signal) to pass while "blocking" the DC. In some cases, transformers could also serve this function; and provided other useful functions such as [[impedance]] and level matching.
Special audio transformers made [[Balanced]] audio transmission possible. Please see [[balanced]] for more details.
==Basics==
Audio transformers are low-power signal devices optimized for transmission of wide-frequency [[AC]] signals, typically with very low distortion. Exceptions include transformers for voice communication with the associated reduced requirements for frequency bandwidth and quality.

This differs from more common power transformers where the main concern is efficiency.

Another quality important to audio is related to efficiency; insertion loss. Even with a 1:1 turns ratio there may be some loss of signal level due to insertion loss.

The number of times the coil of wire is wrapped around the ferrous core is referred to the “turns.” Depending on the application, the number of turns in the primary and secondary may be the same or different. This is typically referred to as the “turns ratio.” In this discussion, it is assumed that the term “voltage” refers to an AC voltage because transformers do not allow DC voltages to pass between input and output.

For pure isolation, it is not unusual for the ratio of the number of turns in the primary and secondary to be 1:1. This means the signal voltage will be the same on the output as the input.
In other cases, it can be desirable to use a different turns ration for level matching or impedance matching. For example, if a transformer has a turns ratio of 2:1, the voltage of the output will be one-half the input voltage. A typical application for this would be converting a balance audio signal to an unbalanced audio signal.
===Analog===
In analog circuitry, the transformer transmits the audio signal from primary to secondary, so signal quality is directly related to the transformer quality. This results in high quality audio transformers being relatively expensive, and in the case of output transformers, relatively large.
===Digital===
Transformers used in digital audio transmission are, strictly speaking, not audio transformers. They are “impulse” or signal transformers with limited bandwidth optimized for very high frequencies. By dramatically limiting the “low frequency” response of this type of transformer, excellent AC power line frequency rejection can be accomplished at the same time as DC isolation. Limiting response at frequencies higher than the desired signal frequencies decreases very high frequency interference which can increase [[jitter]] in transmission between digital audio devices.

[[Category:Terminology]]
[[Category:Analog interconnects]]
[[Category:Digital interconnects]]

@@ Line 4: / Line 4: @@
 ==History==
-Before audio electronics were developed that operated on [[bipolar]] power supplies; some method was needed to isolate the DC [[voltages]] required for audio circuits operating on [[single-ended]] DC power from different stages of the circuitry and from devices connected to the input and output. In many cases; "coupling capacitors" were used to allow the [[AC]] (audio signal) to pass while blocking the DC. In some cases, transformers could also serve this function; and provided other useful functions such as [[impedance]] and level matching.
+Before audio electronics were developed that operated on [[bipolar]] power supplies; some method was needed to isolate the DC [[voltage]]s required for audio circuits operating on [[single-ended]] DC power from different stages of the circuitry and from devices connected to the input and output. In many cases; "coupling capacitors" were used to allow the [[AC]] (audio signal) to pass while blocking the DC. In some cases, transformers could also serve this function; and provided other useful functions such as [[impedance]] and level matching.
 Special audio transformers made Balanced audio transmission possible. Please see [[balanced]] for more details.
 ==Basics==

@@ Line 4: / Line 4: @@
 ==History==
-Before audio electronics were developed that worked on power supplies with both "plus" and "minus" voltages; some method was needed to isolate the DC voltages required for audio circuits operating on "single-ended" DC power from different stages of the circuitry and from devices connected to the input and output. In many cases; "coupling capacitors" were used to allow the AC (audio signal) to pass while "blocking" the DC. In some cases, transformers could also serve this function; and provided other useful functions such as [[impedance]] and level matching.
+Before audio electronics were developed that operated on [[bipolar]] power supplies; some method was needed to isolate the DC [[voltages]] required for audio circuits operating on [[single-ended]] DC power from different stages of the circuitry and from devices connected to the input and output. In many cases; "coupling capacitors" were used to allow the [[AC]] (audio signal) to pass while blocking the DC. In some cases, transformers could also serve this function; and provided other useful functions such as [[impedance]] and level matching.
-Special audio transformers made [[Balanced]] audio transmission possible. Please see [[balanced]] for more details.
+Special audio transformers made Balanced audio transmission possible. Please see [[balanced]] for more details.
 ==Basics==
 Audio transformers are low-power signal devices optimized for transmission of wide-frequency [[AC]] signals, typically with very low distortion. Exceptions include transformers for voice communication with the associated reduced requirements for frequency bandwidth and quality.
@@ Line 13: / Line 13: @@
 Another quality important to audio is related to efficiency; insertion loss. Even with a 1:1 turns ratio there may be some loss of signal level due to insertion loss.
-The number of times the coil of wire is wrapped around the ferrous core is referred to the “turns.” Depending on the application, the number of turns in the primary and secondary may be the same or different. This is typically referred to as the “turns ratio.” In this discussion, it is assumed that the term “voltage” refers to an AC voltage because transformers do not allow DC voltages to pass between input and output.
+The number of times the coil of wire is wrapped around the ferrous core is referred to as the “turns.” Depending on the application, the number of turns in the primary and secondary may be the same or different. This is typically referred to as the “turns ratio.” In this discussion, it is assumed that the term [[voltage]] refers to an AC voltage because transformers do not allow DC voltages to pass between input and output.
 For pure isolation, it is not unusual for the ratio of the number of turns in the primary and secondary to be 1:1. This means the signal voltage will be the same on the output as the input.
@@ Line 20: / Line 20: @@
 In analog circuitry, the transformer transmits the audio signal from primary to secondary, so signal quality is directly related to the transformer quality. This results in high quality audio transformers being relatively expensive, and in the case of output transformers, relatively large.
 ===Digital Signal Transformer===
-Transformers used in digital audio transmission are, strictly speaking, not audio transformers. They are “impulse” or signal transformers with limited bandwidth optimized for very high frequencies. By dramatically limiting the “low frequency” response of this type of transformer, excellent AC power line frequency rejection can be accomplished at the same time as DC isolation. Limiting response at frequencies higher than the desired signal frequencies decreases very high frequency interference which can increase [[jitter]] in transmission between digital audio devices.
+Transformers used in [[digital audio]] transmission are, strictly speaking, not audio transformers. They are “impulse” or signal transformers with limited bandwidth optimized for very high frequencies. By dramatically limiting the low frequency response of this type of transformer, excellent AC power line frequency rejection can be accomplished at the same time as DC isolation. Limiting response at frequencies higher than the desired signal frequencies decreases very high frequency interference which can increase [[jitter]] in transmission between digital audio devices.
 For more information on transformers, [https://en.wikipedia.org/wiki/Transformer_types click here]

@@ Line 17: / Line 17: @@
 For pure isolation, it is not unusual for the ratio of the number of turns in the primary and secondary to be 1:1. This means the signal voltage will be the same on the output as the input.
 In other cases, it can be desirable to use a different turns ration for level matching or impedance matching. For example, if a transformer has a turns ratio of 2:1, the voltage of the output will be one-half the input voltage. A typical application for this would be converting a balance audio signal to an unbalanced audio signal.
-===Analog===
+===Analog Audio Transformer===
 In analog circuitry, the transformer transmits the audio signal from primary to secondary, so signal quality is directly related to the transformer quality. This results in high quality audio transformers being relatively expensive, and in the case of output transformers, relatively large.
-===Digital===
+===Digital Signal Transformer===
 Transformers used in digital audio transmission are, strictly speaking, not audio transformers. They are “impulse” or signal transformers with limited bandwidth optimized for very high frequencies. By dramatically limiting the “low frequency” response of this type of transformer, excellent AC power line frequency rejection can be accomplished at the same time as DC isolation. Limiting response at frequencies higher than the desired signal frequencies decreases very high frequency interference which can increase [[jitter]] in transmission between digital audio devices.

@@ Line 22: / Line 22: @@
 Transformers used in digital audio transmission are, strictly speaking, not audio transformers. They are “impulse” or signal transformers with limited bandwidth optimized for very high frequencies. By dramatically limiting the “low frequency” response of this type of transformer, excellent AC power line frequency rejection can be accomplished at the same time as DC isolation. Limiting response at frequencies higher than the desired signal frequencies decreases very high frequency interference which can increase [[jitter]] in transmission between digital audio devices.
-For more information, [https://en.wikipedia.org/wiki/Transformer_types click here]
+For more information on transformers, [https://en.wikipedia.org/wiki/Transformer_types click here]
 [[Category:Terminology]]
 [[Category:Analog interconnects]]
 [[Category:Digital interconnects]]