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For the general case of complex impedance, the load voltage is maximal at . I believe this must be mentioned. Leokor ( talk) 02:57, 12 February 2013 (UTC)
I moved this to impedance bridging since it gives this idea that it is the "opposite" of impedance matching, but the term "voltage bridging" i think is more common.
Also they are not opposites really. One maximizes power and one maximizes voltage. Not opposites.
Also to differentiate it from a bridged amplifier, in which two positive outputs are inverted from each other and used to drive a load in a floating type configuration. not the same thing.
Also I am going to keep editing these. - Omegatron 20:54, Jun 23, 2004 (UTC)
Moved from Talk:Impedance matching — Omegatron 19:51, 13 April 2007 (UTC)
Is this an acccepted term in the industry?-- Light current 03:29, 16 December 2006 (UTC)
It's not actually made up, but it's not commonly referred to by name:
"High-impedance bridging" might actually be a better term? — Omegatron 19:14, 5 January 2007 (UTC)
Here is a book that mentions "bridging" vs "matching".
http://books.google.com/books?id=wBlRtAlKPFsC&dq=%22impedance+bridging%22&q=bridging#search — Omegatron 19:50, 13 April 2007 (UTC)
"It is a bridging connection if the second device does not appreciably load the previous device." Which is the "second" device? The load or the source? How is "previous" defined here? I'm pretty sure that this means that the source does not appreciably load the load device, but this language could be clearer. Steve carlson 23:27, 9 March 2007 (UTC)
The connection between an amplifier and speaker is not an instance of impedance bridging. Amplifiers are current sources.
The reason why a low output impedance is desired is for two reasons: damping, which is an electro-mechanical effect, and maximum power transfer to the speaker.
The purpose of this connection is not to pass along a signal to the speaker with minimal voltage drop, but to drop current into the speaker while dissipating as little heat as possible in the amplifier and controlling the speaker's motion. — Preceding unsigned comment added by 192.139.122.42 ( talk) 23:46, 2 June 2011 (UTC)
I'm just pointing out that the Rod Elliot reference now 404's. I found this article. http://sound.whsites.net/impedanc.htm but am not sure if it's equivalent. — Preceding unsigned comment added by Petergcook ( talk • contribs) 00:52, 28 November 2016 (UTC)
The section "Maximizing power transfer given a fixed source impedance" belongs better in Impedance_matching#Power_transfer. Can I or can someone else just cut and paste it there, and just keep the first sentence or so here? Em3rgent0rdr ( talk) 05:23, 25 May 2022 (UTC)
When a load is connected across a parallel transmission line, that load is bridged, regardless of its impedance. If one side of the transmission line is ground, or the environment, the load is still bridged regardless of the impedance. Bridging is a real thing. The power company, the gas company, and the water company all use it. Roman viaducts use it. Irrigation water distribution uses it. Trees use it to distribute nutrients. Impedance bridging seems to be a less general term. The only cited sources are from the audio engineering community.
It has never been about efficiency. It is about convenience. We use it because it is available, and it works. If you only know the output impedance of a source, then you know nothing about its internal power dissipation. If the source is truly a voltage source, then maximum efficiency is approached with a near infinite load impedance. A synchronous generator probably well modeled this way. If the source is actually a current source, then maximum efficiency is approached with a near zero load. If the source internally is a voltage driving a voltage divider, then maximum efficiency is neither near infinite nor near zero. This model would apply to a battery with self-discharge leakage. Audio amplifiers are complicated and difficult to generalize. The whole efficiency discussion only applies in a mathematically hypothetical case. Again, it is not about efficiency. If you want the best efficiency to the electric system, then just shut the whole thing off.
The first sentence of Impedance matching § Loudspeaker amplifiers reads:
Audio amplifiers typically do not match impedances, but provide an output impedance that is lower than the load impedance (such as < 0.1 ohm in typical semiconductor amplifiers), for improved speaker damping.
So it seems that that entire section should just be cut from that article and pasted into this article. Maybe just leave a note saying that and linking to its new location in Impedance bridging.
Attempting to do impedance matching to achieve the goal of maximum power transfer to a speaker does have a significant downside of burning a lot of heat in the resistance of the output impedance.
There is a lot of material copied from copyrighted sources in the notes. Does this exceed fair use? Constant314 ( talk) 04:00, 17 June 2022 (UTC)
There is a question that this page doesn't address, which is if large ratios are good, then why do mic preamps input impedance only go to about 10x of typical low impedance mics Why not use the same very high input impedance of line or pickup inputs. I found this explanation in https://www.soundonsound.com/techniques/understanding-impedance that there would be too much noise from resistors, which maybe could be paraphrased into this page:
"Typically, most microphones therefore have an output impedance of 150-200Ω, and most preamplifier inputs offer an input impedance of between 1.5kΩ and 3kΩ — on the limit of the 'ten times higher' rule of thumb I mentioned earlier. It is a good idea to keep the input impedance of mic amps relatively low (at least compared to typical line inputs) since resistors generate noise when current flows through them; the higher the resistance the greater the noise. Since the signal level from microphones is relatively weak, a lot of gain is generally required, amplifying the resistor noise along the way. This is the reason why mic preamp specs should quote the source impedance when providing the Equivalent Input Noise (EIN) measurement; the lower the source impedance, the lower the noise will be. A good EIN figure can be achieved for the spec sheet by measuring the input stage with a 50Ω source impedance. However, this noise figure will be totally unrealisable with a real-world 200Ω microphone!"
And regarding why it is crucial for guitar inputs to be very high:
"If the input has too low an impedance, the most noticeable effect will be a loss of high end — in fact, even using guitar cables with too high a capacitance can audibly reduce high frequencies"
And in a follow up article https://www.soundonsound.com/sound-advice/q-do-i-need-think-about-matching-mic-and-preamp-impedances says both "In fact, there can be benefits in using a higher input impedance to reduce the source loading even more" than 10x, though also talks about sometimes people like the coloration from using lower input impedances. Em3rgent0rdr ( talk) 06:45, 17 June 2022 (UTC)
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For the general case of complex impedance, the load voltage is maximal at . I believe this must be mentioned. Leokor ( talk) 02:57, 12 February 2013 (UTC)
I moved this to impedance bridging since it gives this idea that it is the "opposite" of impedance matching, but the term "voltage bridging" i think is more common.
Also they are not opposites really. One maximizes power and one maximizes voltage. Not opposites.
Also to differentiate it from a bridged amplifier, in which two positive outputs are inverted from each other and used to drive a load in a floating type configuration. not the same thing.
Also I am going to keep editing these. - Omegatron 20:54, Jun 23, 2004 (UTC)
Moved from Talk:Impedance matching — Omegatron 19:51, 13 April 2007 (UTC)
Is this an acccepted term in the industry?-- Light current 03:29, 16 December 2006 (UTC)
It's not actually made up, but it's not commonly referred to by name:
"High-impedance bridging" might actually be a better term? — Omegatron 19:14, 5 January 2007 (UTC)
Here is a book that mentions "bridging" vs "matching".
http://books.google.com/books?id=wBlRtAlKPFsC&dq=%22impedance+bridging%22&q=bridging#search — Omegatron 19:50, 13 April 2007 (UTC)
"It is a bridging connection if the second device does not appreciably load the previous device." Which is the "second" device? The load or the source? How is "previous" defined here? I'm pretty sure that this means that the source does not appreciably load the load device, but this language could be clearer. Steve carlson 23:27, 9 March 2007 (UTC)
The connection between an amplifier and speaker is not an instance of impedance bridging. Amplifiers are current sources.
The reason why a low output impedance is desired is for two reasons: damping, which is an electro-mechanical effect, and maximum power transfer to the speaker.
The purpose of this connection is not to pass along a signal to the speaker with minimal voltage drop, but to drop current into the speaker while dissipating as little heat as possible in the amplifier and controlling the speaker's motion. — Preceding unsigned comment added by 192.139.122.42 ( talk) 23:46, 2 June 2011 (UTC)
I'm just pointing out that the Rod Elliot reference now 404's. I found this article. http://sound.whsites.net/impedanc.htm but am not sure if it's equivalent. — Preceding unsigned comment added by Petergcook ( talk • contribs) 00:52, 28 November 2016 (UTC)
The section "Maximizing power transfer given a fixed source impedance" belongs better in Impedance_matching#Power_transfer. Can I or can someone else just cut and paste it there, and just keep the first sentence or so here? Em3rgent0rdr ( talk) 05:23, 25 May 2022 (UTC)
When a load is connected across a parallel transmission line, that load is bridged, regardless of its impedance. If one side of the transmission line is ground, or the environment, the load is still bridged regardless of the impedance. Bridging is a real thing. The power company, the gas company, and the water company all use it. Roman viaducts use it. Irrigation water distribution uses it. Trees use it to distribute nutrients. Impedance bridging seems to be a less general term. The only cited sources are from the audio engineering community.
It has never been about efficiency. It is about convenience. We use it because it is available, and it works. If you only know the output impedance of a source, then you know nothing about its internal power dissipation. If the source is truly a voltage source, then maximum efficiency is approached with a near infinite load impedance. A synchronous generator probably well modeled this way. If the source is actually a current source, then maximum efficiency is approached with a near zero load. If the source internally is a voltage driving a voltage divider, then maximum efficiency is neither near infinite nor near zero. This model would apply to a battery with self-discharge leakage. Audio amplifiers are complicated and difficult to generalize. The whole efficiency discussion only applies in a mathematically hypothetical case. Again, it is not about efficiency. If you want the best efficiency to the electric system, then just shut the whole thing off.
The first sentence of Impedance matching § Loudspeaker amplifiers reads:
Audio amplifiers typically do not match impedances, but provide an output impedance that is lower than the load impedance (such as < 0.1 ohm in typical semiconductor amplifiers), for improved speaker damping.
So it seems that that entire section should just be cut from that article and pasted into this article. Maybe just leave a note saying that and linking to its new location in Impedance bridging.
Attempting to do impedance matching to achieve the goal of maximum power transfer to a speaker does have a significant downside of burning a lot of heat in the resistance of the output impedance.
There is a lot of material copied from copyrighted sources in the notes. Does this exceed fair use? Constant314 ( talk) 04:00, 17 June 2022 (UTC)
There is a question that this page doesn't address, which is if large ratios are good, then why do mic preamps input impedance only go to about 10x of typical low impedance mics Why not use the same very high input impedance of line or pickup inputs. I found this explanation in https://www.soundonsound.com/techniques/understanding-impedance that there would be too much noise from resistors, which maybe could be paraphrased into this page:
"Typically, most microphones therefore have an output impedance of 150-200Ω, and most preamplifier inputs offer an input impedance of between 1.5kΩ and 3kΩ — on the limit of the 'ten times higher' rule of thumb I mentioned earlier. It is a good idea to keep the input impedance of mic amps relatively low (at least compared to typical line inputs) since resistors generate noise when current flows through them; the higher the resistance the greater the noise. Since the signal level from microphones is relatively weak, a lot of gain is generally required, amplifying the resistor noise along the way. This is the reason why mic preamp specs should quote the source impedance when providing the Equivalent Input Noise (EIN) measurement; the lower the source impedance, the lower the noise will be. A good EIN figure can be achieved for the spec sheet by measuring the input stage with a 50Ω source impedance. However, this noise figure will be totally unrealisable with a real-world 200Ω microphone!"
And regarding why it is crucial for guitar inputs to be very high:
"If the input has too low an impedance, the most noticeable effect will be a loss of high end — in fact, even using guitar cables with too high a capacitance can audibly reduce high frequencies"
And in a follow up article https://www.soundonsound.com/sound-advice/q-do-i-need-think-about-matching-mic-and-preamp-impedances says both "In fact, there can be benefits in using a higher input impedance to reduce the source loading even more" than 10x, though also talks about sometimes people like the coloration from using lower input impedances. Em3rgent0rdr ( talk) 06:45, 17 June 2022 (UTC)