Impedance bridging

bridging
In electronics, especially audio and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance.wikipedia
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Impedance matching

matching networkimpedance matchmatching
A different configuration is an impedance matching connection in which the source and load impedances are either equal or complex conjugates.
An alternative to impedance matching is impedance bridging, in which the load impedance is chosen to be much larger than the source impedance and maximizing voltage transfer, rather than power, is the goal.

DI unit

direct injectiondirect boxDI
In the cases of devices with very high output impedances, such as with a guitar or a high-Z mic, a DI box can be used to convert the high output impedances to a lower impedance so as to not require the receiving device to have outrageously high input impedance and thus suffer drawbacks such as increased noise pickup with long cable runs.
The DI performs level matching, balancing, and either active buffering or passive impedance matching/impedance bridging to minimize unwanted noise, distortion, and ground loops.

Input impedance

load impedanceinput resistanceload resistance
When the output of a device (consisting of the voltage source V S and output impedance Z S in illustration) is connected to the input of another device (the load impedance Z L in the illustration), it is a bridging connection if the input impedance of the load device is much greater than (typically at least ten times) the output impedance of the source device. In audio amplifier specifications, the input impedance of modern op-amp circuits (and many old vacuum tube circuits) is often naturally much higher than the signal source.
This is called impedance bridging.

Electrical impedance

impedanceimpedancescomplex impedance
In electronics, especially audio and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance.
Impedance bridging

Line level

line-levelline inline out
This situation is typically encountered in line or mic level connections where the source device (such as the line-out of an audio player or the output of a microphone) has a fixed output impedance which cannot be changed.
Instead, line level circuits use the impedance bridging principle,

Output impedance

source impedanceoutput resistancesource resistance
When the output of a device (consisting of the voltage source V S and output impedance Z S in illustration) is connected to the input of another device (the load impedance Z L in the illustration), it is a bridging connection if the input impedance of the load device is much greater than (typically at least ten times) the output impedance of the source device.
This is called impedance bridging or voltage bridging.

Damping factor

damping
When driving transducers (especially loudspeakers) the output impedance is often described by a ratio, the damping factor, DF, which is:
When the effect is small, it is called voltage bridging.

Sound

audiosound wavesound waves
In electronics, especially audio and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance.

Sound recording and reproduction

recordingrecordedrecordings
In electronics, especially audio and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance.

Electrical connector

connectorconnectorselectrical connection
In electronics, especially audio and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance.

Power (physics)

powermechanical powerpower output
In cases where only the source impedance can be varied, minimizing the source impedance serves to maximize the power delivered to the load.

Complex conjugate

complex conjugationconjugateconjugation
A different configuration is an impedance matching connection in which the source and load impedances are either equal or complex conjugates.

Voltage source

voltageconstant voltageideal voltage source
When the output of a device (consisting of the voltage source V S and output impedance Z S in illustration) is connected to the input of another device (the load impedance Z L in the illustration), it is a bridging connection if the input impedance of the load device is much greater than (typically at least ten times) the output impedance of the source device.

Microphone

microphonescondenser microphonedynamic microphone
This situation is typically encountered in line or mic level connections where the source device (such as the line-out of an audio player or the output of a microphone) has a fixed output impedance which cannot be changed.

Balanced audio

balancedunbalancedbalanced audio connector
In such cases, the DI box is placed close to the source device (such as the guitar and mic), and any long cables are attached to the output of the DI box (which usually also converts unbalanced signals to balanced signals to further increase noise immunity).

Ohm

Ωohms
In such cases, the impedance of the loudspeaker is fixed (a typical value being 8Ω), so to deliver the maximum power to the speaker, the output impedance of the amplifier should be as small as possible (ideally zero).

Noise (electronics)

noiseelectronic noiseelectrical noise
Possibly increased environmental noise pickup (since the combined parallel impedance of Z S and Z L increases slightly and makes it easier for stray noise to drive the signal node). (The impedance will be dominated by the source, though, which is still small in a bridging connection.)

Maximum power transfer theorem

maximum power theoremMaximum powermaximize the power transfer
(See Maximum power transfer theorem.) The only typical audio application where power delivery (as opposed to voltage delivery) is important is the situation mentioned above of an amplifier driving a loudspeaker.

Antenna (radio)

antennaantennasradio antenna
The matched impedance situation is encountered much more in non-audio-related situations, for example in antenna design where the impedance at the antenna terminals takes on a set value due to requirements in its geometry.

Radio frequency

RFradio frequenciesradio-frequency
Such cases frequently arise in RF circuits, where transmission line effects also dictate impedance matching.

Transmission line

transmission linestransmissionbalanced transmission line
Such cases frequently arise in RF circuits, where transmission line effects also dictate impedance matching. Such a configuration serves to either prevent reflections when transmission lines are involved, or to maximize power delivered to the load given an unchangeable source impedance.

Operational amplifier

op-ampop ampoperational amplifiers
In audio amplifier specifications, the input impedance of modern op-amp circuits (and many old vacuum tube circuits) is often naturally much higher than the signal source.

Vacuum tube

vacuum tubestubethermionic valve
In audio amplifier specifications, the input impedance of modern op-amp circuits (and many old vacuum tube circuits) is often naturally much higher than the signal source.

Negative feedback

negative feedback loopnegative-feedbacknegative
While voltage-drives to speakers (reducing back-EMF from the speaker), i.e. high damping factors, are generally taken as a good design goal, there are some engineers who advocate low-nfb power amplifiers with damping factors closer to unity or find high Damping Factors have little effect, such as a mere 0.35 dB difference in real-life results between a high (100) and medium (20) Damping Factor.

Bridging

In electronics, using a low source impedance to drive a large load impedance for maximum voltage transfer, called impedance bridging