22 votes
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Normal capacitor vs. audio capacitor

Let's forget about audio for now and try to find where the price difference lies in the specific products you mentioned, first. Main reason: the ebay seller of the Vishay cap seems to mistake his ...
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  • 15.5k
18 votes
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Why would this microphone only work while touching the volume control?

If it is a grounding issue, touching it could change the amount of hum, buzz or interference. However you say "It only works if you keep your hand on the volume knob" which I interpret as "there is ...
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  • 57.7k
17 votes
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Does a pickup microphone work in space (vacuum)?

A contact microphone is basically an accelerometer. It does not require any air for its operation.
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  • 164k
15 votes
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Use of 100K ohm resistor along with 0.1uF capacitor?

The resistor is there to provide a DC path for the input bias current of the opamp. It is normally selected to be the same as the DC resistance connected to the other input, so that the bias current ...
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  • 164k
15 votes

Can a comparator (LM393) be used as an amplifier?

Take a look at the basic schematics of the internals shown in the data sheets for the LM324 (regular op-amp) and LM393 (comparator) respectively: - The input stages are both pretty similar but the ...
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  • 380k
14 votes
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Using a microphone from the 1930s

A quick look at the Radio Museum pictures and descriptions makes it look like it ought to be fairly easy to hook up. Here is the picture of the connections from the Radio Museum: You provide it with ...
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  • 57.7k
13 votes
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Low-noise amplification of microphone signals, tubes or chips?

In outline, it depends on the signal source, i.e. the type of microphone. There are some very low noise vacuum tubes. There are some low noise IC amplifiers, but not many. There are also discrete ...
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  • 65.8k
11 votes

Can a comparator (LM393) be used as an amplifier?

The LM393 modules you see advertised on eBay aren't microphone amplifiers as such. They are advertised as sound detection modules, which deliver a (more or less) digital ouput. That module has an ...
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  • 57.7k
11 votes

Why would this microphone only work while touching the volume control?

Repair questions are off-topic on this site so let's make it an education question. Figure 1. Potentiometer terminals 1, 2 and 3. simulate this circuit – Schematic created using CircuitLab ...
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  • 159k
10 votes
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Will this phantom power circuit work?

The second schematic is right. The first has polarity the wrong way around and a dead short across the signal lines. You've also got the polarity wrong on the LM386 so be careful! The Zeners are a ...
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  • 159k
10 votes

Normal capacitor vs. audio capacitor

I was curious, because I have the feeling that a component being "audio" is partly driven by belief, but in so many cases there are underlying reasons for that belief to be sensible. In the most ...
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10 votes
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Why is the collector feedback bias popular in electret-mic preamp circuits?

Most of the hobbyist circuits you find by googling are crap originating from dubious tinkering and then copied from each other. The bias level of this circuit is not very predictable from BJT to BJT (...
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9 votes
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Phantom Power supply for Electret mic

You have roughly the right idea, but you should use a resistor divider instead of a single resistor to bring down the voltage. With your setup, the microphone is still subjected to high voltage, ...
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9 votes
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Can I connect multiple electret microphones for better gain?

I am a technician at a boutique mic company. I like to build electret mics in my spare time. You can increase sensitivity, gain, and signal to noise ratio by running multiple electrets in PARALLEL-...
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8 votes
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Do electret microphones have polarity?

Yes, they have polarity and it has to be right to work- the output needs to be biased positive with respect to the ground terminal. The ground/GND terminal should be common with the case, so you can ...
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8 votes

Normal capacitor vs. audio capacitor

Question: what kind of difference is there between such a capacitor, for "audio applications" First "audio application" doesn't mean anything. A capacitor can serve many different uses, for example ...
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  • 57.7k
8 votes
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Why is the electrolytic capacitor not polarity sensitive?

An aluminum electrolytic will handle a reverse polarity of about 1 volt or so. The cap probably never sees anything near that. This appnote from Nichicon shows that under 1V the capacitors don't ...
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  • 2,177
8 votes
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Acoustic localization

Does that sound reasonable? Or am I missing something? Theoretically SPL halves with a doubling of distance so, the extra attenuation over the distance range of 0.5 metres to 3000 metres becomes: - $...
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  • 380k
8 votes
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Are microphones with flatter frequency response charts better at picking up frequencies?

In general, the frequency-measurement would be quite accurate even with a low-quality microphone. This would only be affected by the accuracy of the clock used to control the sampling in the analog-to-...
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  • 716
7 votes
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Why does cable length matter so much when source is high impedance?

The problem is the cable's capacitance, which is proportional to its length. This capacitance works in conjunction with the high source impedance of the microphone to create a low-pass filter that can ...
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  • 164k
7 votes
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What is the best preamplifier circuit for electret condenser microphone?

Add a resistor in series with the 100 uF capacitor across R3 as shown below: - Without that resistor there is nothing that defines the AC gain of the amplifier and the effect of the 100 uF without ...
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  • 380k
7 votes
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Anti-eavesdropping Electronics?

Eavesdropping microphones can be jammed by overloading them with ultrasonic sound waves. The microphone and the front end analog circuitry, when overloaded, can generate noise in the audible frequency ...
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  • 2,995
6 votes
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Output from amplifier is clipping

You might need to look for rail to Rail op-amps if the output of op-amp is expected to be close to supply voltage. Below spec is from datasheet of LM358 op-amp which tells that the difference can be ...
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  • 8,971
6 votes

Can a comparator (LM393) be used as an amplifier?

A comparator lacks compensation so, in general, it cannot be stabilized to act as an amplifier at unity gain easily, if at all, depending on the internal construction. However, in the particular ...
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6 votes
Accepted

Why does my electret microphone amplifying and filtering circuit output so much noise?

There are a number of problems with this circuit: The input to the reference is not filtered. R5 and R4 make half the supply voltage, but also transfer half of whatever noise is on the supply. ...
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6 votes

Filter circuit in Microphone

Most of those capacitors aren't in filters that are intended to influence the frequency response of the microphone. C17, C16 and R12A, R12B,R13A,R13B are there to provide a clean and stable DC ...
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  • 57.7k
6 votes

Does a pickup microphone work in space (vacuum)?

if it is mounted on the same surface with the same vibrations, it in theory should measure nothing. When sound waves propagate through solid material, it's not just the whole rigid object shaking ...
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  • 2,285
6 votes
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Why LME49710 does not perform at least as good as LM358 for audio mic op-amp?

I suspect it is honking somewhere ultrasonic! The 49710 is an excellent part, but it is FAST (~50MHz GBP), where the '358 barely manages 1MHz GBP. Layout will be a LOT more important with the faster ...
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  • 16.1k
6 votes

Using a microphone from the 1930s

It's a carbon microphone, apparently designed to work off of it's own or a separate 4V power source, and with an isolation transformer. Even back in the day they were known for mediocre sound, but ...
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  • 35.9k
6 votes
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Mic amplifier noise

You might want to consider these things: - Without the input resistor the 220 nF has an impedance of 723 ohms and this means that your mid band gain (1 kHz) is 150,000/723 = 207. At 10 kHz the gain ...
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  • 380k

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