You can think of the ambient light as a DC signal, while the proposed f.o. circuitry only responds to AC.
It seems to me that as described the circuit could pickup/send both electrical and f.o. signals, therefore easy to do a side-by-side comparison of the results.
edit: Although the diaphragm optimized for one probably won't be optimized for the other...
It seems to me that as described the circuit could pickup/send both electrical and f.o. signals, therefore easy to do a side-by-side comparison of the results.
edit: Although the diaphragm optimized for one probably won't be optimized for the other...
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The question was too broad.
It depend of what kind of device (FET or BJT), thermal resistance, quiescent current etc...
As an example, the variation of the quiescent current of a BJT Vs temp depends of the way it is used.
For an emitter feedback, it is an order of 15% for 40°. It seems enormous, but, it will be compensated by the feedback or error correction (if any).
The real difference ? You can have an idea, looking at the distortion curve of your amp at various output power, they include the same temp variation.
In your example, you double the voltage, so you X4 the power of half a period while 0 for the other.
The difference introduced by offset will be mainly in the harmonic figure, because less symetry so more percent of even-order harmonics in the total harmonic distortion.
Nothing to worry, i believe, when your amp is < 0.005% ?
Note that Class D amps will ask-you: "What are-you talking about ?"
????? What?
I could have sworn I mentioned CM relates to THD production.... especially in asymmetrical topologies, in particular. And, that tests using asym waveforms have a CM component to them to deal with. Thus, whats the CMR... doesnt anyone care about this aspect of amp design. You should. Thx-RNM
Noise of the light emitter ? Noise of the receptor ? How did they analyses the membrane displacement ?
Digital ? You need a line of 36mm for 1000000 pixels in the actual density of photosites in the best photo captors. For 120db of dynamic (in the nature) and 1db step (not enough).
Analog ? How ?
One thing is for sure, we could get rid of the inertia of a moving coil , like in electrostatic capsules. And if captor is digital, get rid of any analog problems, and converters, yes.
Those are for industrial applications. I was wondering because couldn't recall seeing a review in the recording magazines.There are several makers -- try OPTIMIC by Optoacoustics. One of the leaders.
You guys get out much? Out of your box? It's well into the 21st century. I may be an old geezer But I'll never be that old ! try to keep up. -RNM
About mikes, there are some omni-directional Electrets capsules, with very flat response curves and a diameter of 5 millimeters.
Glued on the branches of my glasses, above the ears, i used them to record ambiances for movies, without nobody can notice.
Kinda very good "Stereo natural head" recordings
Glued on the branches of my glasses, above the ears, i used them to record ambiances for movies, without nobody can notice.
Kinda very good "Stereo natural head" recordings
Actually common mode issues are basic to non-inverting amplifiers. In a non-inverting amp both if the differential inputs are moving with the input signal, the feedback terminal following the input as closely as possible. Inverting amps do not have this issue and tend to have less distortion for that reason. Asymmetry of the waveform has little to do with this issue.
The microphone is not for any one appl. These are low distortion, wide bandwith mics.... not any less suitable than "measurement" mics cannot be used for recording music. Try them and learn. -RNM
Asym has everything to do with CM signal source to be dealt with. CM signals do no Only come from rfi/emi/60Hz pickup/grounding. Other issue is how does amp do with CM signals -- CMR? Need to test it or SIM it. Thx-RNM
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Well in your defense you did qualify your statements with the words "pretty much". I wasn't suggesting that the use of photons and optical detectors was unfeasible, just that a sweeping generalization about photonic techniques eliminating "noise, amps..." is simplistic and not, on the face of it, guaranteed of superior performance.
The optical detectors will require preamps with their own noise issues. Using more light will help to a point. Being able to remote the electronics may be useful in specific circumstances.
" Why arent more using them and developing them further for more recording appl? Why, why, why?"
Why aren't people using them? Perhaps because they don't work as well, are more cumbersome, require more power? The fact is that, already, the thermomechanical noise of diaphragms and the Brownian motion noise of room temperature air is in excess of the contributions of the best JFET preamps --- and we're not even talking about other ambient noise in the best studios.
There is a prevalent notion that there is something about using light that somehow trumps other electronic approaches. And indeed there are powerful benefits with photonics in certain cases, but the techniques have their own subtleties and tradeoffs. Try to get good signal-to-noise out of an optocoupler for example. It is nontrivial.
I had a look to the Optoacoustics site.
Imagine, a mike manufacturer with NO DATA.
They show somewhere a captor witch is just a piece of acrylic... so it has to be sensible to ambient light variation ? hum, what about the 50 or 60 hz from neon tubes ?
No response curve, no directivity curve, no available dynamic nbr, no signal to noise ratio nbr , no distortion percents, not a word on the technology used, digital or analog...
I figure we have made a misunderstanding, they produce micro lights...
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t is more serious on the Sennheiser site.
Polar pattern: omni-directional
Optical fiber: multimode 200/230 µm
Frequency response: 20 Hz to 40 kHz (±6 dB)
Sensitivity: 15 mV/Pa
S/N related to 1 Pa sound pressure: > 50 dB(A)
Maximum sound pressure: 134dB
Amplification: infinitely variable in the range; +/-15 dB, switchable in steps 0 dB, +20 dB, +40 dB
AF output level: 15 mV/Pa (potentiometer in mid position, switch set to 0dB)
Output impedance: approx. 330 ohms asymmetrical, 660 ohms symmetrical
Current consumption: 120 mA
Operating temperature range - microphone: -10°C to +70°C; central unit: 0°C to 40°C __________________
Polar pattern: omni-directional
Optical fiber: multimode 200/230 µm
Frequency response: 20 Hz to 40 kHz (±6 dB)
Sensitivity: 15 mV/Pa
S/N related to 1 Pa sound pressure: > 50 dB(A)
Maximum sound pressure: 134dB
Amplification: infinitely variable in the range; +/-15 dB, switchable in steps 0 dB, +20 dB, +40 dB
AF output level: 15 mV/Pa (potentiometer in mid position, switch set to 0dB)
Output impedance: approx. 330 ohms asymmetrical, 660 ohms symmetrical
Current consumption: 120 mA
Operating temperature range - microphone: -10°C to +70°C; central unit: 0°C to 40°C __________________
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