So when my equipment breaks which one of these little doohickeys do I need to replace? 
The broken one 
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Way back in a previous life I used to do board and component level repairs on cell phones. I was component level certified on NEC, Motorola and Oki cell phones, board level for everything else.
Not that I knew what I was doing but I could follow directions and troubleshoot appropriately. But the MOST IMPORTANT thing with all this crap is having the proper tools and test equipment. Otherwise you might as well be using a hammer to try and repair crap.
I still dream about the PACE workstation I had access to, you could easily make mm sized welds and hot air remove smd chips etc. I miss that beautiful hunk of aluminum with the red led numbers. 
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Should we be expecting Maze Frame Electronics MasterClass ads on YouTube now?
I am a hobby tinkerer, not an electronics engineer. 
Part 2
Components in Circuit
Warning: Voltages above 30V are dangerous.
(With enough effort, a sweaty teashirt and car battery can kill, different story 
)
Important tools
When working with or near electronics, there are some important and some nice to have tools.
-
Multimeter - Resistance, Voltage, Current, sometimes Capacitance and Temperature measurement device in one. Way better than one of those glowing screw drivers at determining if a circuit is live (as in: Can make you dead).
-
Size 1 Philips Head - Gets you into most devices, like your multimeter when you blew a fuse because you set it to mA when dealing with A.
Insulated ones are nice, sometimes donât get into tight spots. Only take stuff apart that is unplugged! -
Replacement Fuses for your Multimeter - No shame in taking the thing apart to replace a blown fuse. Never buy just one! And avoid the glass tube ones. Under extreme fault conditions (= shit hitting the fan), the wire evaporates coating the glas making it conductive causing a minor explosion.
-
Soldering Iron - No need to own a Weller Rework Station when you solder two cables back into their plugs a year. Workable soldering irons can be had for 20 bucks.
I saw people do this: The shiny end gets HOT! Do Not Touch That!
Optional Tools
-
Known Working USB charger - When troubleshooting a phone not charging, having a known good USB charger (and cable) on hand helps a ton. Can also use your multimeter to determine if the wall socket has power.
-
Flashlight - For that extra bit of light
-
Magnifying glass & Inspection mirror - For small and tight spots
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Grounding wrist strap - For ease of mind when dealing with expensive electronics. In Europe, most sockets have a grounding pin or grounding springs to clamp to. Alternatively a water tap or plugged in computer (not a notebook) also work as grounding points.
Toaster Timer
While you could use a bimetal strip and screw to do heat-based timing or a microcontroller there is also a super simple analog circuit to achieve the same.
Note: Do not implement this 1:1 as I âjust wingedâ this circuit from what I remember building.
Operating principle:
The 5V supply charges the Capacitor C1 via the Variable Resistor R1, when C1 reaches 4V, the Zener-Diode U1 allowes the Transistor Q1 to pass current through the LED.
R2 and R3 are to protect the Transistor or LED against too high currents.
The reset switch discharges the capacitor reseting the timer.
Blinking Lights
Very common circuit is to have two LEDs blinking. Running of a 9V battery and built from 10 components, it just blinks back and forth.
Operating Principle:
The capacitor C1 controlls the state of Transistor TR2 and vice versa. A Transistor turning on means it discharges its Capacitor turning the âopposingâ Transistor off.
In other words: This is an astable multi vibrator, no state is stable and it has multiple states.
Circuit design and build guide source
Ohms Law
Ohms law is simple: Resistance = Voltage / Current
This simple formula by applying simple maths can be made into two variations:
- Voltage = Current * Resistance
- Current = Voltage / Resistance
You may ask why this is such a big deal.
Picture this: Your multimeter does only measure current and voltage. How do you determine the resistance of your headphones?
Take a AA (or AAA) battery (which can be yanked from a flashlight or remote), measure its voltage and write it down.
Now touch the tip of your headphone jack to the battery, then use the test leads of your multimeter to complete the circuit in current mode.
You end up with a voltage (about 1.3V) and a current (anything from about 0.3A down to 0.002A). And just like that, you know the resistance of your headphones!
Basic Soldering Guide
- Clean workplace, preferably a piece of wood to protect the table (or carpet)
- Clean Tip = Good Tip - Donât use your soldering iron to shrink heatshrink, please!
- Flux is your friend. That small puff of smoke when touching the solder to the iron is what makes the joint work. You can also dunk blank cable ends into flux or use a syringe to apply some to the PCB you are working on.
- Heat the parts you want to solder, then touch the solder to the joint.
- Let the joint cool on its own. No blowing on it or drenching it in the sink.
Is my solder job good?
What does your multimeter say?
Resistances greater than 0.1 Ohm (idealy 0 Ohm) are reason for concern.
How does it look?
It should be a clean shiny surface surrounding the wire or pin comletly without being a massive ball of metal.
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FYI on the soldering, above 400 MHz good solder joints are even harder and look closest to the middle OK solder joint (with the rare through hole). Why? Parasitic values start messing with circuits. The #1 way to cut down a parasitic inductance is keep all your via and solder joints as SMALL as possible.
Keep it up @MazeFrame!
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This post here is mainly to bump this thread up a bit. Also shows you what lightning does to your electronics:
Next regular post in this here will be Multimeter, Measuring basics and Safety
Part 3
Multimeter basics
Warning: Voltages above 30V are dangerous.
Introduction
A good multimeter does not have to cost a fortune. If you need one twice a year, donât shell out $200.
I would recommend to buy one with detachable leads so you can hook up the right probe for the right job.
Most cheap multimeters have 3 settings:
- Voltage
- Current
- Resistance (included Continuity)
Other functions you may find:
- Diode Test
- Capacitance (hit & miss in my experience)
- Inductance (Multimeter â Inductance meter, very different devices)
- Temperature (using a thermocouple, often with an adapter)
- Frequency Counter (hit & miss in my experience)
- Transistor tester (what for? Donât you have a datasheet?)
- Max/Min Function
- Hold (Flukes Auto-Hold is
) - Backlight
- Range Adjust
Measureing
Range selection
When your meter does not do this automatically, you select the range that includes the highest value you expect.
Note that when measureing current, the inrush current may be a lot higher than current while the load is running.
To throw all beginners into the deep end, welcome to the bastard meter from hell:
90V is the outer one.
20V is the center scale.
For 10A, you have to take the same scale as 20V, but divide by 2. And the 1A scale is the inner one, divided by 10. Donât laugh, I have seen this in the wild!
The only good feature of this example piece is the fact it requires you to plug the probes from Black&Blue for volts to Green&Black for Amps.
There are meters that shutter the incorrect ports so you donât blow up fuses (Gossen Metrawatt does this on a lot of their meters).
Do yourself a favour, buy a good meter.
Probing
Do get good results, you need good contact. The manual probes will often be âgood enoughâ for resistances or finding if there is voltage presend. For everything beyond that, you want alligator clamps, screw terminals, 4mm hookups, etc.
That way your fingers (and body) donât skew the results or put your heart and lungs into the line of fire.
When Probing arround >30V, use shielded test leads like the ones below. Only use 1 hand to hold the probes, the other hand holds the meter.
â Honestly though, use clamps/plugs to hook up and donât even touch whatever you measure.
Correct Meter Positioning
Current (A) - Your meter will be in series with the load. In this example, a light bulb.
This is also how you measure resistance, capacitance, etc. Just without the battey in circuit.
Voltage (V) - Your meter will be in parallel with the load.
Urgent Advice: After EVERY use, plug the leads back to measure volts.
That way you will not blow up your meter or the fuses inside it by accident.
Purchase advice
You want a True-RMS (= TRMS) meter, simply because these types of meter can measure AC.
The measurement leads should have guards so your fingers donât slip into the danger zone.
Fluke TL 75 for example:
Analogue vs Digital
I find analog meters to be way too much hassle. The neelde is never readable, accuracy is at the mercy of correctly positioning the meter and there are multiple scales of which you have to read the right one.
Buy a digital meter and you are set, even when holding the meter at wierd angles.
Autorange vs Manual
Do you want to think about the highest value you could see?
Do you want to step through the ranges until you get a usefull measurement?
Are you mad?
Answered any of the above questions with yes, then get a Manual one. All the normal people, save yourself the hassle and get an auto-ranging one.
Brands that wonât blow up in your face:
- Fluke (expensive!, except the Fluke 101 which lacks current measuring)
- Gossen-Metrawatt (The DM41 is nice and not overly expensive)
Misc Advice
Help! My meter does not measure amps!
â Have you checked you got the test leads plugged in correctly?
â Correct range selected?
â Still nope? You blew a fuse. Time to open the battery cover (or the entire meter) and replace it
Fuses
You want ceramic fuses in all your devices, especially the multimeter you have in your hand.
The good ones are filled with a fine sand that will take up the metal vapour under extreme fault conditions interrupting the current flow. Glas fuses may cover their insides in metal, which will then conduct making them explode.
Video showcasing fuses under fault conditions
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Anyone interested in nearly 25 Minutes of electronics nerdery?
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Part 4
Understanding Power Supplies
Introduction
Most equipment runs on less than grid voltage (110 to 240V, depending where you live). In order to not make itself explode, most electronic devices use a power supply of sorts.
The idea is to turn whatever comes in into the desired voltage(s) while keeping EMI from the grid out and EMI caused by internal happenings inside.
Linear Power Supplies
These are the more traditional PSUs. Efficiency is not great, size and weight are bad. They donât introduce more ripple to the power though.
Putting the incomming AC from the grid into a transformers primary winding will give you an electrically isolated voltage. Depending on the ratio between primary and secondary, a lower, equal or higher voltage than incomming.
Depending on the transformer, you now have a lower voltage AC.
By using 4 diodes in the following arrangement, you can now turn your AC into choppy DC.
After the rectifier, you probably want to add some capacitors to smooth out the choppy DC. Some additional filtering using chokes to catch higher frequencies that passed through the primary transformer could not hurt either.
Now it is time to hand our almost desired DC to a linear regulator (or several of them).
Due to their working principle, they reduce the remaining ripple even further and provide a clean stable DC for your circuit to work with.
As a block diagramm, a linear PSU looks like this:
Source
Pros and Cons of Linear PSUs
| Pro | Cons |
|---|---|
| Simple Circuit | Inefficent, Linear Regulators are by design inefficent |
| Reliable, this is largely because of their simplicity | Size/Weight, due to how transformers behave, the low frequency requires âbig copperâ |
| Low Noise, the only ânoiseâ they produce is the 50/60 Hz from the grid (or double that after the rectifier) |
Switch Mode Power Supplies
What if instead of having the transformer first, you had the rectifier first?
That is exactly what a Switch Mode Supply does.
Step 1 is to rectify the incomming AC doubling its voltage in respect to Ground. They also put a filter stage here because the next stage produces nasty EMI that canât make its way to the grid.
Now comes a switching element like a MOSFET. This will be used to run the transformer at the frequency we want and only when we want. Keep this in mind for later.
After the switching element followes the transformer. As we can run it at any frequency we want, it can be relatively small and the winding ratio does not matter as much (it still is important).
After this transformer, we need a diode and some filtering including some capacitors (donât need them nearly as big as in a linear supply due to the high frequency of the transformer) and an inductor to keep EMI in check.
Resonant Switch Supplies
These PSUs are a relatively recent development as they require very fast switching components. Their claim to fame is very high efficency upwards of 90% achieved by switching at the zero-crossings of the incomming sine wave.
So instead of a âdumbâ passive diode rectifier, these PSUs have active rectifiers (there are reverse protection diodes in the MOSFETs, different topic).
I could not find a graphic with the wave forms for each stage plotted. 
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Some âapplied electronicsâ:
I feel like I may need to introduce you to old fashioned spice that COULD show you waveforms of that system quite easily.
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I could certainly rig up a schematic and simulate one.
Question is if that is not beyond the scope of a beginners electronics thread.
I even kicked out capacitive dropers from the PSU post to keep it relevant to audio gear.
Hi guys, this is an interesting thread tbh.
I study electrical engineering, just gotta pass the calculus 1 and the first semester is doneâŠ
But i was just wonderingâŠ
How do the components of hybrid or multi-driver IEMs work?
Are the crossovers just systems of small capacitors and inductors?
Do they have to put resistors in front of lower impedance transducers?
Sooo many questions, not many people to answerâŠ
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Damn successful first semester. Congrats.
Could be. MLCCâs exist in surprising capacities. Not sure about Ferrite beads.
There are probably some IEMs in clear enough cases to get an idea what is going on.
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To not derail the GL2000 thread, I brought you here 
Looking for a simple answer to a simple question, that may sound right.
Problem is two fold:
-
Depending on the inner workings on the amp (I wrote an overview of all but the Op-Amp based ones here), you may have a linear power to load impedance, except for two power spikes into 50 and 200 Ohm.
-
Voice coils, Ribbons and Planar drivers do not present a linear impedance. In fact, the impedance may be a mountain range similar to the frequency response.
Example:
Source
Donât get me wrong, guestimating the SPL an amp can get out of a speaker/headphone using a spreadsheet is perfectly valid.
As you said yourself, loud â quality
The Correct-ish Method
I have tried to measure power into a headphone.
Setup was less than ideal as I had a lot of probe leads dangling around acting as antennas, I have no LCR-meter on hand to verify AC-characteristics of the precision resistor I had in series with the drivers and the Oscilloscope I have on loan is a bit slow on the FFT.
The results were as expected: Shite
Learned a lot in trying though.
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I wasnât trying to give the most scientific answer here. To be fair, most members of this forum donât even know what a OHM is. I find that if you give really complicated answers here, people eyes just glaze over and they ignore your post. Iâm not saying youâre wrong. I was giving an easy method that could help those that think that Loud = Good.
This community found a good balance between objective and subjective audiophilia.
And as tubes are somewhat popular on here (most OTL tube amps donât play well with low impedance headphones), I think most people here know what resistance (and by extension, impedance) is.
Then word it in a way that is understandable?
If my answer relied on pretending to be the smartest person in the room, then I would reconsider the wording of said answer.
Except I did word my original post in an easier to understand way. You came in and complicated it and thought you were smarter by replying in the 101 thread. You literally just did the thing you said you donât do.