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-as of [30 APRIL 2024]–
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*AKA* –>
“capacitor microphone”
“electro-static microphone”
(as ‘capacitors’ were historically called ‘condensers’)
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*BRANDS* –>
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-the condenser microphone was invented at ‘bell labs’ in 1916 by “e. c. wente”-
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(here, the ‘diaphragm’ acts as one plate of a ‘capacitor’, and the vibrations produce ‘changes’ in the ‘distance’ between the ‘plates’)
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(there are 2 types, depending on the method of extracting the ‘audio signal’ from the ‘transducer’…)
*DC-biased microphones*
*radio frequency (RF)*
*aka ‘high frequency’ (HF)*
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(with a DC-biased microphone, the plates are biased with a fixed charge (Q))
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(the voltage maintained across the capacitor plates changes with the vibrations in the air, according to the ‘capacitance equation’ (C = Q⁄V),
where Q = charge in ‘coulombs’,
C = ‘capacitance’ in ‘farads’
and V = potential difference in ‘volts’
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(the capacitance of the plates is inversely proportional to the distance between them for a parallel-plate capacitor)
(the assembly of fixed and movable plates is called an “element” or “capsule”)
(a nearly constant charge is maintained on the ‘capacitor’)
(as the ‘capacitance’ changes, the charge across the ‘capacitor’ does change very slightly, but at audible frequencies it is sensibly constant’)
(the ‘capacitance’ of the capsule (around 5 to 100 pF) and the value of the ‘bias resistor’ (100 MΩ to tens of GΩ) form a filter that is high-pass for the audio signal, and low-pass for the bias voltage)
(note that the time constant of an ‘RC circuit’ equals the product of the ‘resistance’ and ‘capacitance’)
(within the time-frame of the ‘capacitance change’ (as much as 50 ms at 20 Hz audio signal), the charge is practically constant and the voltage across the capacitor changes instantaneously to reflect the change in ‘capacitance’)
(the voltage across the ‘capacitor’ varies above and below the ‘bias voltage’)
(the ‘voltage difference’ between the ‘bias’ and the ‘capacitor’ is seen across the ‘series resistor’)
(the voltage across the ‘resistor’ is amplified for performance or recording)
(in most cases, the electronics in the microphone itself contribute no voltage gain as the voltage differential is quite significant, up to several volts for high sound levels)
(since this is a very high impedance circuit, current gain only is usually needed, with the ‘voltage’ remaining constant)
(“RF condenser microphones” use a comparatively low ‘RF voltage’, generated by a ‘low-noise oscillator’)
(the signal from the ‘oscillator’ may either be ‘amplitude’ modulated by the ‘capacitance changes’ produced by the sound waves moving the ‘capsule diaphragm’, or the ‘capsule’ may be part of a ‘resonant circuit’ that modulates the frequency of the ‘oscillator signal’)
(‘demodulation’ yields a low-noise ‘audio frequency signal’ with a very low ‘source impedance’)
(the absence of a high ‘bias voltage’ permits the use of a ‘diaphragm’ with looser tension, which may be used to achieve wider frequency response due to higher ‘compliance’)
(the RF biasing process results in a lower electrical impedance capsule, a useful by-product of which is that RF condenser microphones can be operated in damp weather conditions that could create problems in DC-biased microphones with contaminated insulating surfaces)
(the sennheiser “MKH” series of microphones use the ‘RF biasing technique’)
(‘condenser microphoness’ span the range from ‘telephone transmitters’ through inexpensive ‘karaoke microphones’ to high-fidelity ‘recording microphones’)
(they generally produce a high-quality audio signal and are now the popular choice in laboratory and recording studio applications)
(the inherent suitability of this technology is due to the very small mass that must be moved by the incident sound wave, unlike other microphone types that require the sound wave to do more work)
(they require a power source, provided either via microphone inputs on equipment as ‘phantom power’ or from a small battery)
(‘power’ is necessary for establishing the ‘capacitor plate voltage’, and is also needed to power the microphone electronics (‘impedance conversion’ in the case of ‘electret’ and ‘DC-polarized’ microphones, ‘demodulation’ or ‘detection’ in the case of ‘RF/HF microphones’))
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*’condenser microphones’ are also available with 2 diaphragms that can be electrically connected to provide a range of ‘polar patterns’, such as…*
‘cardioid’
‘omni=directional’
‘figure-eight’
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(it is also possible to vary the pattern continuously with some microphones, for example the ‘Røde NT2000’ or ‘CAD M179’)
(a ‘valve microphone’ is a ‘condenser microphone’ that uses a ‘vacuum tube’ (aka ‘valve’) amplifier)
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(they remain popular with enthusiasts of ‘tube sound’)
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*👨🔬🕵️♀️🙇♀️*SKETCHES*🙇♂️👩🔬🕵️♂️*
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👈👈👈☜*“MICROPHONE CLASSIFICATIONS”* ☞ 👉👉👉
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💕💝💖💓🖤💙🖤💙🖤💙🖤❤️💚💛🧡❣️💞💔💘❣️🧡💛💚❤️🖤💜🖤💙🖤💙🖤💗💖💝💘
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*🌈✨ *TABLE OF CONTENTS* ✨🌷*
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🔥🔥🔥🔥🔥🔥🔥*we won the war* 🔥🔥🔥🔥🔥🔥🔥