49

That's a "DC pop". A sound engineer dies somewhere every time you make one! simulate this circuit – Schematic created using CircuitLab Figure 1. Amplifier output and disconnected speaker. Amplifiers fed from a single-rail supply hold their output at 1/2 supply when quiet. If the speaker was connected directly to the amplifier output there would be a ...


31

The "buzz" is almost certainly RF pickup. This can be the mains (low frequency, 50/60/100/120Hz, unlikely in this scenario given a phone is involved) or rectification of the carrier frequency of the phone - remember how old tape players would make a "duh duh, duh duh" sound whenever a text message is received. Human bodies are conductive. When your skin is ...


20

When you put something to your ear reproducing standard stereo recordings, you don't want a flat frequency response because the head-related transfer function that normally comes into play for a sound source much further away looks very different when the source is against your ear. Let me quote you a couple of paragraphs from a book: Of all the ...


16

"Exactly like when a charged object is discharged and it needs some time to charge up again." That is exactly what you are hearing. The output is AC-coupled through a capacitor to the headphones to block any DC component of the signal. With the headphones first unplugged the capacitor had one side open circuit so it stays discharged. When you plug in the ...


16

"Can an electrolytic capacitor withstand 0.1V reverse polarity?" If you query e.g. technical documents of a well known manufacturer like vishay: Reverse Voltage UrevA reverse polarity of up to 1.5 V is permissible. https://www.vishay.com/docs/25001/alucapsintroroederstein.pdf Edit: German Wikipedia states, a reverse voltage should not be applied ...


13

The main fact, in my opinion, is that noise is heard only in right channel. First thing comes to mind is issue with grounding. But then both channels would receive the noise. Second - the source of this noise. You must try another headphones to see if noise is caused by headphones or is emitted by the source device. Third, reposition your phone to the ...


9

Headphones (without microphone) only use the 3 pin (stereo) type jack and these are all wired the same. The assignment for the 3 left/right/ground conductors is standard. The different standards relate to the 4th connection on headsets (with microphone). On an incompatible device, this is either unused or grounded. So there is no "lucky draw" otherwise ...


9

My guess is that there is a break in the insulation of the right earbud and that electrical hum from your body is flowing into the noise cancellation amplifier. Try wrapping the bud in cling film and see if that stops the buzz.


8

Yes, aluminum electrolytic capacitors (which is the kind you have) are fine with a bit of reverse voltage. A fraction of a volt is definitely not a problem. Edit to incorporate comment: Aluminum electrolytic capacitors are made with two aluminum plates with a conductive liquid electrolyte (and a separator) between them. The actual dielectric is a thin Al2O3 ...


6

@Transistor is right, however there is a tiny subtlety here... Jack connectors short everything to ground when you plug them in. When you slide it in, the various metal bits of the jack and the plug make contact in every possible combination before the jack finally settles into position. There's a little buzz when the tip of the jack is inserted I would ...


6

The two large capacitors are acting as AC coupling capacitors. A capacitor in series with a signal acts as a high pass filter (if you're curious about that, look into the impedance model of capacitors). Basically, the smaller the value of the capacitor, the higher the cutoff frequency and so more of the low frequency signal (in this case, the audio bass) is ...


6

Adding resistance in parallel will not attenuate the signal. It will draw more current from the amplifier output, however, and if the resistance is low enough will cause current limiting. This would be likely to cause audible distortion and generate harmonics which would be detrimental to young ears. Series resistance is the way to go but due to the ...


6

If you have a multimeter available, you can put it into AC voltage measurement mode and try to measure between the different metallic objects. Note that you should only touch the objects with the probe, not with your skin when measuring. For example, touch one probe to the keyboard and other probe to some metal part on the phone. If you find a ~60 volt (for ...


6

There are several problems with your design: The Op-amps you use on the input are typically not DC biased. You have no isolation capacitors on your input and no resistor to ground to supply a Gnd reference ...the +ve input is simply floating. The internal schematic for the NE5532 shows that the inputs are in fact the Bases of the first differential pair....


5

Wire color isn't standard. Never trust wire color. Always use a continuity tester to find which wire goes to which conductor.


5

I'll assume your jack is a stereo one, like on this picture: Cable shield goes to ground (see pic) and left/right signal wires go to the two smaller lugs.


5

Searching for a format specification starting with the manufacturer of the product: From the vendor you mentioned Onkyo is offering the ES-HF300 with a 6N oxygen-free copper cable encased in clear elastomer, providing almost perfect conductivity while keeping touch noise to a minimum. Gold-plated MMCX connectors and mini-stereo plug reflect the highest ...


4

The simple answer is that a flat frequency response system constructed with op-amps to correct the driver response will necessarily have a very un-flat phase response in the pass band. This non-flatness means component frequencies of transient sounds become unevenly delayed, resulting in a subtle transient distortion which prevents proper sound component ...


4

Here is something that seems to meet your specs: C1 AC-couples the signal so that it can have any DC offset inside the circuit we like. D1 and D2 rectify the input signal to its peak voltage, minus the drop of the two Schottky diodes. C2 holds the value between peaks. Q1 is a voltage-controlled current sink. The LED D3 is then driven by that current. ...


4

I've worked on countless consumer products, and I've never seen a "kill" circuit that intentionally causes the product to fail after some specified period or event. However, consumer products are designed for a certain lifetime, with a certain number of failures in that lifetime being acceptable. That's just a reality of the reliability of components. ...


4

The ability to measure something, with your phone app for instance, makes it far easier to worry about it. Consider the mass experiment that is being done now, has been ongoing for the past few decades, of people all over the world (billions?) wearing headphones. They will have similar exposure to low value DC magnetic fields. There is another population, ...


4

You are mixing things up. When the specification says 90 dB per milli watt it is referring to a sound pressure level of 90 decibels being produced close to your ear and you cannot imply any measure of power efficiency at all.


3

It sounds like there may be a bad connection within the control button box. When pressing the button(s), the pressure re-establishes the connection.


3

There is no 100% sure answer to your question. Because we (and maybe you?) don't know exactly what microphone you are talking about and how it is wired. There is more than one convention for wiring microphones to TRS 3.5mm plugs. I would first try connecting just the tip of the mic connector to "Microphone" ring on the iPhone. And if that doesn't work, I ...


3

Looks like R2 needs to be higher. The Android specs call for minimum of 1K from mic to ground. Your 1K resistor is right at the limit. An example is given for a microphone with a 5K DC resistance. So, use a larger R2, and proportionally larger R1. (R2=5K, R1=100K)


3

You have several choices: Get a chip that can drive 8 Ω. Put a buffer between the D/A and the headphones. This buffer must then be able to drive a 8 Ω load. The D/A only sees the input impedance of the buffer. Use headphones with 16 Ω or more impdance. Put a 1.4:1 audio transformer between the D/A and the headphones. The D/A output ...


3

It's a socket for a 4-pole jack as used on mobile phones. On the PJ-W27B2-06D (leftmost version) you have Tip: speaker left. Pin 2. Ring 1: speaker right. Pin 3. Ring 2: Mic or ground Pin 6. Sleeve: ground or Mic. Pin 1. Pins 4 and 5 allow audio through to internal speaker, for example, if the jack is unplugged. If you don't need the mic line then ...


3

Modern headphones are often 30 ohms per channel, some high-end ones can be 600 ohms per channel. So this 62 ohms falls within that range so I do not see why you could not drive them with almost any headphone output. The maximum signal will very likely be determined by the distortion the headphones introduce. Having said that, most portable devices with a ...


3

Acoustic power (measured in Watt) or sound instensity (measured in Watt/m^2) can be compared logarithmically via the bel (B) although the 1/10th of the unit is commonly used, the decibel (dB). So 65 dB (6.5 B) is [6.5 - 1.5 = 5] 10^5 times the acoustic power and sound intensity, respectively, of 15 dB (1.5 B), i.e. 100,000 times as high. Since work is power ...


3

I find that cyanoacrylate glue (Krazy Glue, Super Glue) works well for securing cables in strain releifs, Ideally I push the cable into the plug too far, glue the bit that sticks in and then pull it back to the correct location.


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