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14

It is conceptually possible to induce magnetic interference at audio frequency in an electrically shielded cable, which is not so much possible at higher frequencies due to the shields becoming opaque for magnetic fields. You just can't ignore magnetic fields at audio frequencies. Normal conductors usually used for shields (aluminum/copper) will not shield ...


7

There's no reason to think the shielding has a monotonic impedance. There are parasitic inductances and capacitances lurking in the cable so it would be expected that there are impedance peaks and valleys. It could just be the cable designers bothered to make the impedance low at video frequencies and so audio frequencies fall into a region of high impedance....


5

From direct experience (adding shielding to a mixing desk which was modified to include a build in mains PSU), to shield magnetic signals (like mains transformers) at 50Hz and LF harmonics thereof, you need SIGNIFICANT mass of ferrous material. We actually bought mu-metal and did use it but the best turned out to be big chunks of pig iron scavenged from the ...


4

Here is a datasheet. You cannot re-program this device- it is one-time programmable only. This was a magnificent improvement from the mask-programmed parts we had to source prior to OTP EPROM availability, at least for prototypes and small quantities. The mask-programmed parts had a large minimum order quantity, significant lead time, and mask charges, and ...


3

Thanks to @tobalt for pointing out that the other end of the cable is open. For the same results to apply when there is a receiver, the receiver has to have a high-z input (normal for audio) and there can't be a ground loop (maybe the transmitter is on battery). I will attempt to explain what happens in that case. We can estimate the fields surrounding it ...


3

Conductive plastic is generally the best choice for most audio doings. It has lower noise then the carbon track parts and (usually) better rotational life then the cemrets, note that power dissipation is also lower. Temperature coefficient is a weak point, but usually for audio you are in a ratiometric situation anyway. The trick as ever is to NOT run DC ...


2

A typical smart phone only has a microphone input. You are limited to the signal levels that a typical microphone would produce. The basic limits are: AC only. Microphone inputs aren't made to deal with DC. Frequency range up to about 20 kHz. Microphone inputs are only intended for use with audio signals. Low voltage input signals only. Microphones only ...


2

A guess: There's a substantial voltage difference between the ceiling electricity network and the outlets available on the floor. Any system which is connected to both systems will be electrocuted. That needs nothing more than they are taken from different phases of building's main 3-phase system. Shouldn't power supplies be isolated? Yes, but for practical ...


2

The cheap cable in the video is constructed like this: There is an insulated wire in the center, loosely wrapped with "shield" copper threads. Since these are not braided, and there is no foil, there are a lot of holes in the "shield". Also copper costs money, so the number of threads is in proportion to the price. Cheaper cable have ...


2

I've seen this question before... It depends how much your coil looks like a loudspeaker. If its DC resistance is above a few ohms, then it's a reasonable approximation of a 4 ohms loudspeaker, whose DC resistance is usually around 3 ohms. In this case an audio amp rated for 4 ohms will work fine. You can use an audio amp from the pawn shop, or a kit from ...


2

My simple AC-DC converter contains bridge rectifier, 3x 3300uF capacitor and 1x 100nF Total overkill. Your TL072 can under no circumstances even draw enough current to load the 3330 µF significantly. Very likely, using 1 µF with lower ESR and lower leakage would have been better. More isn't always better! I would need few 10 000 uF capacitors Not true. ...


2

It has nothing to do with Microchip... the part you link is apparently only available as BGA. The part is from a manufacturer called Zuhai Jie Li. See this: Indentifying a JL chip in a Bluetooth. It might be a proprietary part.


1

To answer the question, stereo headphones, when connecting both left and right in parallel as a load for GPIO output pin, is too much load and this causes the MCU to draw too much current and supply voltage may drop too much so the MCU resets or browns out. The IO pins are rated for about 10mA when used at 3.3V. This is about a load of 330 ohms or higher. A ...


1

A Helmholtz coil would require a current source rather than voltage source. The output voltage of the audio amplifier is proportional to the signal input voltage. What you would need is an amplifier whom output current is proportional to the input voltage - voltage controlled current source. This can be done with an operational amplifier, but you should know ...


1

It's easy enough provided the two items can be matched up. Obviously, you need an amp that goes down to 10 Hz. Not many audio amps do that, so check the specs very carefully. More technically, the output of the generator must also be electrically matched to the input of the amp. For example the amp may have an impedance of 1 kΩ and require an input of 100 mV ...


1

The limit will be the loading by the cable capacitances. You can amass 10s of nF of load capacitance if you use many long cables. This would be like a load of only a few 100 Ohm at 20kHz and the opamp will eventually not be able to drive this due to the lack of output current capabilities, producing distortion.


1

Most power relays require a minimum current ("wetting current") to remove oxidation from contacts. For low level signals there is very low current so these relays will cause problems. You should use a signal relay that doesn't need wetting current, for example sealed reed or Omron G6K. There is always some crosstalk between the coil and contacts, ...


1

Hum is generally not an issue, at least not from the relay. You do want to select a sealed relay designed for signal switching. Larger unsealed relays (like the ones used on old Revox tape machines) eventually have problems due to oxide on the contacts. Omron G6 series is one typical type used.


1

Look for good low current performance .Power relays are more reliable with some minimum current .If the current is really small and you are below the arc voltage then the contact may appear open when its supposed to be closed .Old cars had points .The first transistor assisted ignition circuits used the points to drive the base of a power BJT .The needed ...


1

The relay should actually be one of the most robust things in the circuit. Make sure the coil is DC and not AC which could inject 60Hz noise. The only real issue you might have to worry about would be one signal bleeding into the other--I'm pretty sure there is no spec on relays for this. However, most relay contacts have pretty sizable air gaps (lots of ...


1

simulate this circuit – Schematic created using CircuitLab Figure 1. A simple example circuit. It's a common feature on microcontrollers and other devices that there is a low powered sleep mode. Notice in Figure 1 that the battery is permanently connected to V+ but the on-off switch only signals to the device whether to be on or off. Switching off will ...


1

This depends a bit on where/how you want to insert the potentiometer but generally is a bad idea for passive pickups. The moment you get more than a few kOhm in series with a pickup, you will damp its resonance a lot making the sound very dull. Single coils are especially susceptible to this. The same goes for less than about 200 kOhm in parallel to a pickup,...


1

It happened to me once. The spacing was ok, but the legs were too think. It was not 1 layer PCB (so no drilling) and did not want to mount anything to the cap lead (the circuit was visible behind plexiglass). I just filed some material off.


1

On a single sided pcb, with non plated through holes, if the pads are large enough you can simply drill to enlarge the holes a bit. Make sure you drill from the copper side then through the PCB, not the other way around, as that could lift the pads out from the pcb.


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