# Tag Info

28

Although you could do this whole thing with just an amplifier and a microcontroller (Arduino), as far as I can see, you want the analog option. I have tried to create a circuit that outputs the voice level on the microphone. The range is from 0V to 4V. However, you can upgrade it easily to 0V to 5V by just changing the OP-AMP. Now, let's go into it; First ...

22

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 customers for cash cows. The exact same cap on Digikey is less than 1€ (unit price - it doesn't have the same product code: MAL214651101E3, but this is just a ...

18

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 sound only when the hand is on the volume knob, otherwise there is no sound." If this is the case, then I'd suspect a bad contact perhaps at the pot wiper, or a ...

16

This is the data I can share with you after having run my own set of experiments and having search (extensively) through the Web for other people's real hands-on tests. I have discarded / omitted the data which I have been unable to reproduce: The impedance of the standard Apple miniature hands-free microphone, the one integrated with the headphones they ...

16

A contact microphone is basically an accelerometer. It does not require any air for its operation.

14

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 does not produce a voltage offset at the output of the opamp. But in this case, the effective DC resistance on the inverting input is only 1k||100k = 990Ω,...

14

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 first big difference is the internal compensation capacitor inside the LM324 op-amp (shown with a red box around it). This compensation will ensure that with ...

14

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 4V through the jacks on the left side. You could use a battery pack with 3 normal AA or C cells in series. That's the easiest way, and will probably sound ...

13

The resistor is needed so that your bypass capacitors have an R with which to form an RC filter. The 22 uF and 0.1 uF capacitors do not effectively remove voltage noise from the 2.2 kOhm resistor because they are in parallel with it. But when the 100 ohm is added, then there is suddenly a voltage divider, the bottom leg of which is bypassed by the ...

13

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 semiconductors, both bi-polar and JFET, and these are often the best choice for an input stage, possibly using an IC for the later gain and output stages. Among ...

11

I work for Analog Devices, who makes MEMS microphones. I have written an application note to describe how to use a MEMS microphone in a circuit that was originally designed to use electret mics. Along with the MEMS mic, it requires a few additional passive components to remove the bias from the signal and provide a dc supply to the mic's Vdd pin. https://www....

11

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 LM393 on it, and is advertised as a sound detector. It has an active low output, which matches the capabilties of the LM393 - the LM393 can only pull down. It ...

11

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 Figure 2. A schematic showing the potentiometer arrangement. As the wiper (2) is adjusted from (1) to (3) the volume goes from zero to maximum. If pressing on ...

10

The circuit is okay (not ideal for quality but it will work), but there's one small issue if you want to feed the output to your Arduino. As shown, the output will swing below ground (i.e. it will be biased at 0V) and your Arduinos analog input will only accept positive voltages. The output with the above circuit will be something like this: If your ...

10

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 good idea. When the circuit is powered up the left side of the capacitors will lift to, maybe, 24 V (depending on the load presented by the mic) and the right ...

10

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 compact form, here is what Vishay supplies on how to choose their caps. I made a small filtering in Digikey, and concluded that a fair comparison would be 142 RHS, ...

10

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 (meaning it may clip at high level one way or the other depending on the capsule sensitivity and actual sound pressure level) and the distortion is relatively ...

9

As far as I understood, you are trying to make some kind of a sound level detector, which will let you detect if there is a sound with a certain volume or not. You can do this with minor changes to the schematic you have. But before that, you should understand the circuit. Let's break that circuit down. First of all the part with the microphone. R1 is for ...

9

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, depending on how much current it draws. You say you want 2.5 V, but not at what impedance the mic wants to see. I'll use a target of 3 kΩ, which most ...

8

Better make R2 switchable or variable with 1k being the upper limit. But the basic approach is probably OK. Speaker signals are relatively high voltage and relatively low impedance (meaning they can deliver a lot of current). What that means depends on the speaker; anything from a couple of volts and a fraction of an amp (total power 0.25 watts or so) for ...

8

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 check polarity with a multimeter. Here, from a Panasonic Datasheet, is a typical arrangement: The two diagrams you show are equivalent, one is just drawn ...

8

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 power supply decoupling, or signal DC blocking, and what makes a capacitor good at one specific use does not make it good at another use. So you have to be more ...

8

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 have much of leakage and seems fully functional, see Fig.2-2, with little degradation (see Fig.2-3).

8

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: - $$20\cdot log_{10}(6000)$$ And this is 75.56 dB hence, an SPL of 94 dB (at 0.5 m) reduces to 18.44 dB (at 3 km). This assumes a perfect scenario with no ...

7

You seem to be on the right track. It does take a lot of discrete components to do this sort of thing. You may not believe me, but using op-amps may make all of this simpler and smaller. I'm sure you can find even more specific ICs that do more of what you need in a smaller package. I bet there's an IC out there that does exactly what you need. However, you ...

7

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 the 1 kohm resistor will make the input impedance very low and significantly distort the signal from the microphone. With the 1 kohm resistor I've added, the ...

6

I would approach this as two problems, generating a sine wave, and making a balanced line driver. Other answers have covered the sine wave generator, and it's an easy thing to research, and I have nothing to add there. However, I'll say some things about the differential line driver. As some others have said, the canonical way to do this is with a ...

6

Yes, it will probably work just fine. You just need to eliminate R1, since a dynamic microphone doesn't need a DC bias.

6

I know it's old, but may still interest someone. With a piezo contact mic, you may want to also connect two diodes allowing current to go from ground to mic output and from mic output to vcc. Under normal conditions there is not voltage over them, but a piezo can create some serious voltage spikes if hit, and this will protect your amp / arduino, so excess ...

Only top voted, non community-wiki answers of a minimum length are eligible