Electronics for Audiophiles: Voltage and Current (Video)

[curly747]

Thanks @amirm
Interesting and useful for knowing what you need to switch out power supplies

 

[srkbear]

No, it is right for this type of video and context. Touch a high voltage source and you risk electrocution. Touch a low voltage source and you are fine. Touch a high current/low voltage source, and again, you are fine. Anyway this is a side comment so not sure how it became the core of your criticism.

I think he made a good point for a remedial discussion of voltage and current; being mindful of caution around undischarged filter caps, in an audience far more likely to peek under the hood than the average person, is to me an essential disclaimer. I think his was simply a good point to add to your already superb work, and he got quite a few likes. You got many more on yours—I don’t think you were at risk of being upstaged.

As for it being the primary focus of his criticism, I have a native German husband and I’m accustomed to German syntax causing similar misunderstandings when translated to English. I took his comment as him simply offering an omitted point he felt strongly about.

Either way, I’ve always been taught that it’s a sign of character and leadership to graciously accept constructive criticism and to approach feedback as a potential gift—especially when you’re the one setting the tone. I would have thought no less of your very helpful and appreciated video if you had just responded with “good point, thanks”.

 

[Holmz]

This is what we are taught today.

^This^, and the fact there are already many YT videos on electricity and electronics, makes it seem like a bit of a waste of time relative to staying exclusively on topic with the review of Audio gear.

So my opinion on it seems like it is in the minority here.

 

[srkbear]

From that basic point it goes that a little voltage applied directly on flesh (very low resistance) being exposed through a cut in the skin (high resistance) could certainly kill you.

Since high voltages can overcome the resistance skin have, the general idea people do remember is only high voltages are dangerous.

From a medical standpoint, there are innumerable factors that contribute to the type and degree of injury when the body is exposed to electrical current. Electrical injuries are subclassified into three discrete categories—1. The direct effect that electrical current has on body tissues/organs (eg the heart); 2. Conversion of electrical energy into thermal injury (burns), and 3. Blunt mechanical injury as a result of muscular spasm (fractures, falls).

There are any number of contributory factors that influence the type of electrical injury that can occur. DC current tends to cause a single contraction that throws the body from the source—these injuries are most likely to lead to mechanical trauma or cardiac arrest. AC current tends to cause tetany from repetitive muscle contractions and may lead to the patient being inextricable from the source, due to a hand grasp most commonly.

The frequency of the current determines how many contractions occur in any given period, and even low voltage, high current/high frequency shocks can paralyze respiratory muscles and cause suffocation, cause ventricular fibrillation at lower frequencies, or lead to fatal spinal fractures if the current is high enough and prolonged.

Obviously there are other factors pertaining to the degree of injury, particularly the differences in impedance/resistance of damp vs dry skin—dry skin has an impedance of around 100,000 ohms, whereas damp skin can drop as low as 2500 ohms. It’s actually the high resistance tissues and organs that suffer the most thermal damage, as they generate the most heat—low resistance damp skin forms a conduit for the current to disseminate throughout the body, and cook the organs with higher resistance.

There are many more complexities involved here, but in medicine, the primary determinant of morbidity and lethality in electrical injuries is current—period, full stop. It is a myth that low voltages are benign, and for the purposes of this discussion and audience, any equivocation over the voltage/current debate is superfluous—although Tomtoo is indeed correct that current is far more of a lethal determinant than voltage, any charge that is not treated with caution and precaution can be dangerous, and the bottom line is don’t mess around with opening an amp unless you know what you’re doing.

 

[kongwee]

A story that I have told long time ago.

I had a couple of friends from Israel when I was finished my EE degree. I was sitting with them overjoyed that this was our last semester before graduating. I noticed that they were not so happy. I asked why? They said that when they got their degree they would go home. There, people would bring them their broken TVs and Radios. Despite getting a 4 year degree, they had no idea how either worked let alone know how to repair them!

There is a massive gap between fundamentals and application. My goal with these videos is the latter.

A paper doesn't mean much. Many get the paper just for career. I was working an intern for switch gear company. The boss said many engineer doesn't know how to repair TV, fridge.....etc it is not their interest to do such thing. They are not that curious how these stuff works. I know a repairman doesn't has any degree, he fix audiophile gear for his entire life. He doesn't need any drawing to figure out what wrong with the gear. I have studied EE too and doesn't know how to fix them. Anything wrong just change the whole PCB board. It could be just one IC chip or diode fault, but I ask the whole board change as it is under warranty. Those not under warranty just pass to repairman.

 

[srkbear]

But can you name 5 non binary genders?, can you do the floss dance? do you get Simp money?
Maybe we shuld stop the low ball boomer vs. gen-z humor.

Education and knowledge is as easily and freely available like never before in history but somehow that's not making "us" smarter

Some of us are able to handle learning about non-binary genders and rigorous fields of academic study simultaneously—and I hardly see equanimity between learning how to respect others’ gender identities and whatever a floss dance is. Speaking as someone who provides gender affirming care as part of my position as a faculty member in infectious diseases and HIV Medicine, I am inclined to wince at that choice of example.

This whole line of discussion, implying that students in universities today are frivolous nitwits only preoccupied with vacuous memes, compared to us rigorously pragmatic Gen Xer’s, is a larf. The EE students today are exposed to the same curriculum as they were in the eighties, plus 35 years of advancements—and those of us who were in college in the eighties/nineties have the same number of beer bong photos and memories of glow in the dark ceiling stars surrounded by clouds of weed with “The Wall” playing as college kids do today.

There’s nothing new under the sun, folks.

 

[Jimster480]

Some of us are able to handle learning about non-binary genders and rigorous fields of academic study simultaneously—and I hardly see equanimity between learning how to respect others’ gender identities and whatever a floss dance is. Speaking as someone who provides gender affirming care as part of my position as a faculty member in infectious diseases and HIV Medicine, I am inclined to wince at that choice of example.

This whole line of discussion, implying that students in universities today are frivolous nitwits only preoccupied with vacuous memes, compared to us rigorously pragmatic Gen Xer’s, is a larf. The EE students today are exposed to the same curriculum as they were in the eighties, plus 35 years of advancements—and those of us who were in college in the eighties/nineties have the same number of beer bong photos and memories of glow in the dark ceiling stars surrounded by clouds of weed with “The Wall” playing as college kids do today.

There’s nothing new under the sun, folks.

Except it is actually reality. Those graduating mostly know nothing. those going to college mostly know nothing.
I rarely have good customer experiences anymore in my businesses. Most people are very ignorant and entitled. They think everything is free, and don't even know how to use what they are looking to purchase. Most cannot read and as such support tickets and emails are useless. They want a "step by step video tutorial" because even something as simple as opening an exe is too complicated for these people.
It has become a very slippery slope over the past years in regards to this. Most younger people can only name YT influencers and other "famous" people. They have no idea about any basic life facts, they cannot read and think for themselves.... they have no logic, no math skills, no comprehension skills, almost nothing. Most cannot use a computer, many cannot drive or don't plan to... they just want to sit around and watch netflix and video games (watching video games wasn't even a thing 10 years ago and now watching is bigger than playing itself)..... A scary world indeed.
Not to say that literally nobody knows anything, but the majority are not the ones capable of even the smallest tasks of today.

 

[srkbear]

Except it is actually reality. Those graduating mostly know nothing. those going to college mostly know nothing.
I rarely have good customer experiences anymore in my businesses. Most people are very ignorant and entitled. They think everything is free, and don't even know how to use what they are looking to purchase. Most cannot read and as such support tickets and emails are useless. They want a "step by step video tutorial" because even something as simple as opening an exe is too complicated for these people.
It has become a very slippery slope over the past years in regards to this. Most younger people can only name YT influencers and other "famous" people. They have no idea about any basic life facts, they cannot read and think for themselves.... they have no logic, no math skills, no comprehension skills, almost nothing. Most cannot use a computer, many cannot drive or don't plan to... they just want to sit around and watch netflix and video games (watching video games wasn't even a thing 10 years ago and now watching is bigger than playing itself)..... A scary world indeed.
Not to say that literally nobody knows anything, but the majority are not the ones capable of even the smallest tasks of today.

I agree with some of this, although I think you are speaking in absolutes ahd your perceptions are anecdotal. But my main objection to the post (and perhaps where I should have left it) was the use of learning how to treat gender non-conforming people with dignity and respect as comparable to the other inanities he invoked in his analogy. Sorry if I got carried away from there.

 

[dlaloum]

Excellent - nice and simple - covers the basics as relevant to audio.

Thank you!

 

[fastfreddy666]

There is an exception but I have to admit it's not audio related. Fast cell phone / laptop chargers (modern ones) work differently than traditional PSUs
to make thinks confusing there are two quick load standards. Quick Charge (Qualcomm) and USB power delivery (open standard). newer versions of QC and PD (4 and higher in case of QC) are compatible. Thermal management (go figure) is also mandatory in newer adapters. The adapters and phones have special circuitry which senses the device capabilities and the USB-C cable used.

For example I have a Huawei super charger (40 watt max) that can output (DC of course) 5V 2A / 9V 2A and 10V / 3A. In the beginning of the charge cycle it uses a higher voltage and this will charge your phone faster. When the phone is about 80% charged it lowers the voltage and the charging is significantly slower. The phone gets rather warm when I charge my phone

My Mi charger for my laptop (65 watts) is even more powerful 5V 3A / 9V 3A / 12V 3A / 15 3A / 20V / 3,25A.

Can you charge your older phone with one of those things? Yes you probably can it won't charge any faster. To be on the safe side use the charger that came with your phone.

Also (newer) power supplies in modern pc / audio equipment with internal PSUs don't have a 110V/220V switch on the back. This is because the things are equipped with a technology called Active power Correction (not to be confused with Passive power correction). Some people call this voltage conversion but this is only one function of an APFC. Don't use a 220V adapter (on a 220V outlet) on a 110V device. This will fry your device almost certainly.

But everything Amirm said in the the video still holds true. This is just supplementary information. To be safe it's not a bad idea to check your equipment anyway. Usually it's stated on the back. My monitor speakers say 100-240 volt input this means it has an APFC build in.

I recently touched the live wire of a 220V outlet. It hurts like hell but it was very short so i survived. Don't try this at home. It can potentially kill you especially if you have a heart condition (Arrhythmias and Myocardial damage are no joke)

I loved the video. Keep up the good work.


I could babble on and on how this technically works but KISS (keep it simple stupid)

 

[diaolodoro]

At first I thought the video was a bit too basic and I wanted more advanced videos, but after reading the comments here I realized Amir's video was PERFECT.

About the debate voltage vs current you need to realize that if you have to give a general advice to people who don't fully understand electricity, then you should warn them about high voltage. Professional electricians mostly care about the high voltage and that's why there are only signs like "Danger - High Voltage" and not "high current".
A good analogy is High Voltage/Current => Guns/Bullets. Nobody cares about plain bullets unless their loaded into a gun and the general advice should be stay away from guns/high voltage. Saying "it's actually the current/bullet that kills you" is way more misleading for the general public, even though it's true.

For example, a single 18650 lithium battery can provide close to 30A which is considered somewhat high current. If someone learned that it's the current that kills and it only takes 0.5A to kill you, people could be terrified of 3.7V batteries. And we certainly don't need "Danger - High Current" stickers for batteries, because there's no danger (to human bodies at least).

So, to people who criticized the video as misleading or oversimplified, I completely disagree with you. This isn't about our knowledge, but the advice we're giving to the general public. If we have to give advice to a person who doesn't fully understand the subject, we shouldn't complicate things with current, voltage, human resistance, duration, humidity, grounding, AC frequency or the resilience of electricity on different parts of the human body. I think this subject should not be restated by Amir and the effects of electricity to the human body is irrelevant to the audio community.
Just stay away from high voltage if you don't know what you're doing.

 

[Ken Tajalli]

For example, a single 18650 lithium battery can provide close to 30A which is considered somewhat high current. If someone learned that it's the current that kills and it only takes 0.5A to kill you, people could be terrified of 3.7V batteries. And we certainly don't need "Danger - High Current" stickers for batteries, because there's no danger (to human bodies at least).

Good one!

 

[tomtoo]

At first I thought the video was a bit too basic and I wanted more advanced videos, but after reading the comments here I realized Amir's video was PERFECT.

About the debate voltage vs current you need to realize that if you have to give a general advice to people who don't fully understand electricity, then you should warn them about high voltage. Professional electricians mostly care about the high voltage and that's why there are only signs like "Danger - High Voltage" and not "high current".
A good analogy is High Voltage/Current => Guns/Bullets. Nobody cares about plain bullets unless their loaded into a gun and the general advice should be stay away from guns/high voltage. Saying "it's actually the current/bullet that kills you" is way more misleading for the general public, even though it's true.

For example, a single 18650 lithium battery can provide close to 30A which is considered somewhat high current. If someone learned that it's the current that kills and it only takes 0.5A to kill you, people could be terrified of 3.7V batteries. And we certainly don't need "Danger - High Current" stickers for batteries, because there's no danger (to human bodies at least).

So, to people who criticized the video as misleading or oversimplified, I completely disagree with you. This isn't about our knowledge, but the advice we're giving to the general public. If we have to give advice to a person who doesn't fully understand the subject, we shouldn't complicate things with current, voltage, human resistance, duration, humidity, grounding, AC frequency or the resilience of electricity on different parts of the human body. I think this subject should not be restated by Amir and the effects of electricity to the human body is irrelevant to the audio community.
Just stay away from high voltage if you don't know what you're doing.

Thats exactly the way hifi myths did grow. To explain it the right way is to complicated. Explain it the easy way, even its not exactly right. Iam not a fan of things like this. Explain it the right way, or dont talk about it. And its the wrong way to say its the voltage that kills you. Yes the right way would be a littel harder to explain. But it would be the right way and not the wrong way.
Even on the yt channel there is complaining about it. So now tell that the people that complaining on yt are wrong? No they are right, that short way @amirm used is the wrong way. Its easy to give you a circuit where you can thouch 2kv absolutly save. Now you can argument in hifi devices its not that way, what armir does, thats ok. But its still wrong that the voltage kills you. Dont explain things wrong, just couse its so easy and the outcome fits the purpose. Wrong explained is wrong explained what ever the outcome is. If this would be on a xyz hifi site i would just smile. But its ASR and Amir is a EE. And thats the point where i stop to smile. Like i said 2 or 3 sentence more and it would be right.How it is, its just wrong.

 

[Audiofire]

DC current tends to cause a single contraction that throws the body from the source—these injuries are most likely to lead to mechanical trauma or cardiac arrest. AC current tends to cause tetany from repetitive muscle contractions and may lead to the patient being inextricable from the source, due to a hand grasp most commonly.

This isn't about our knowledge, but the advice we're giving to the general public. If we have to give advice to a person who doesn't fully understand the subject, we shouldn't complicate things with current, voltage, human resistance, duration, humidity, grounding, AC frequency or the resilience of electricity on different parts of the human body. I think this subject should not be restated by Amir and the effects of electricity to the human body is irrelevant to the audio community.

Please be aware that I have made a technical article about safety tips with professional references:
"DC tends to cause a single muscle contraction that prevents the hand from letting go of the circuit. The 50 or 60 Hz cycle of AC gives a chance to repel the hand away from the current, but the cyclical muscle contractions can be severely damaging. Currents around the let-go threshold are very painful and will help an individual with voluntarily moving the hand or other inflicted body part away immediately. A safe AC threshold for when muscle contractions are inextricable is 15.5 mA (milliamperes) for men, and 10.2 mA for women. An equivalent DC threshold is 18.13 mA for men, and 12.0 mA for women. The difference stems from the sensitivity of nervous systems and the extent of muscle development. 12 V are a safe threshold and is used for batteries. 24 VAC (volts AC) and 50 VDC (volts DC) are safe under normal, dry conditions."

Servicing Safety and Replacement of Electrolytic Capacitors

Health Hazards "The limited energy in capacitors (E = (1/2) C V²) restricts the duration of the shock, even if there are no circuit breakers to trip. The shock current will be limited by the body resistance, and the duration of the shock will be characterized by the time constant (τ = R C)...

www.audiosciencereview.com

 

[tomtoo]

But peace, its just when a kid asks why a bird can sit on a high voltage line?
I think its better to explain its the current trough the body that kills not the voltage.

 

[diaolodoro]

Thats exactly the way hifi myths did grow. To explain it the right way is to complicated. Explain it the easy way, even its not exactly right. Iam not a fan of things like this. Explain it the right way, or dont talk about it. And its the wrong way to say its the voltage that kills you. Yes the right way would be a littel harder to explain. But it would be the right way and not the wrong way.
Even on the yt channel there is complaining about it. So now tell that the people that complaining on yt are wrong? No they are right, that short way @amirm used is the wrong way. Its easy to give you a circuit where you can thouch 2kv absolutly save. Now you can argument in hifi devices its not that way, what armir does, thats ok. But its still wrong that the voltage kills you. Dont explain things wrong, just couse its so easy and the outcome fits the purpose. Wrong explained is wrong explained what ever the outcome is. If this would be on a xyz hifi site i would just smile. But its ASR and Amir is a EE. And thats the point where i stop to smile. Like i said 2 or 3 sentence more and it would be right.How it is, its just wrong.

I don't recall hearing Amir saying it's the voltage that kills you (I'm not going to rewatch the video), but I think he warned about the dangers of high voltage just like I did. So if that's the case, nothing said was wrong. If Amir said "it's the voltage that kills", then yes, that would be a wrong statement. If that wasn't the case then I respectfully disagree with you and whatever comments are on youtube. Back to the gun/bullet analogy, imagine a cop seeing someone with a gun and saying "well, it could be an unloaded gun and since only bullets kill people then it might be ok".

 

[Ken Tajalli]

I think poor Amir has just about got the feedback he asked for, and perhaps regretting the endeavour!
136 137 posts (I think I am responsible for 3 including this one), arguing on finer points of dying from electric shock!
If you are killed off, you wouldn't care if it was the voltage, the current, your barefoot on a tiled-floor or your sheer stupidity to have fingered something you didn't know much about!
You are dead . . . .

 

[Dmitri]

Thanks Amir!

As you stated many times...your video was to be considered overview of general principles...not an all encompassing treatise on the subject. Truth, not all of us learn and comprehend in the same fashion. My mind does not collect and retain information in the same way as an accomplished EE’s might. I am not lacking in intelligence, but, and with respect to those who are a bit critical of the simplicity and hence potential inaccuracy of your explanation, your video helps me understand the concepts in a basic enough way to build upon and integrate them with further concepts that I hope you will add to this series in the future. My understanding will likely happen via intuitive jumps as opposed to the linear thinking required of a more scientifically honed mind. There’s a lot of us out there...the ones that shined in English Lit but struggled in Calculus...who reveled in Sociology but were traumatized by Physics and Chemistry. You remember us? We helped rewrite some of your English Composition papers while you helped walk us through mathematical formulae. ; )

Many different minds here...and a lot of brilliant ones at that, whose knowledge far exceeds my own, but ASR needs provide a place for all or else it fails in its primary mission to expose a level of truth in audio via the demonstrated use of scientific principle. Your video helps bridge the knowledge gap.

Thank you again. I look forward to further installments!

 

[srkbear]

Please be aware that I have made a technical article about safety tips with professional references:
"DC tends to cause a single muscle contraction that prevents the hand from letting go of the circuit. The 50 or 60 Hz cycle of AC gives a chance to repel the hand away from the current, but the cyclical muscle contractions can be severely damaging. Currents around the let-go threshold are very painful and will help an individual with voluntarily moving the hand or other inflicted body part away immediately. A safe AC threshold for when muscle contractions are inextricable is 15.5 mA (milliamperes) for men, and 10.2 mA for women. An equivalent DC threshold is 18.13 mA for men, and 12.0 mA for women. The difference stems from the sensitivity of nervous systems and the extent of muscle development. 12 V are a safe threshold and is used for batteries. 24 VAC (volts AC) and 50 VDC (volts DC) are safe under normal, dry conditions."

Servicing Safety and Replacement of Electrolytic Capacitors

Health Hazards "The limited energy in capacitors (E = (1/2) C V²) restricts the duration of the shock, even if there are no circuit breakers to trip. The shock current will be limited by the body resistance, and the duration of the shock will be characterized by the time constant (τ = R C)...

www.audiosciencereview.com

Thanks, although you either misquoted me or spoke incorrectly—DC current typically causes a single muscle contraction that throws one from the source of the shock; AC current is what prevents a hand from letting go. May I ask what discipline you’re writing this technical article from?

 

[srkbear]

At first I thought the video was a bit too basic and I wanted more advanced videos, but after reading the comments here I realized Amir's video was PERFECT.

About the debate voltage vs current you need to realize that if you have to give a general advice to people who don't fully understand electricity, then you should warn them about high voltage. Professional electricians mostly care about the high voltage and that's why there are only signs like "Danger - High Voltage" and not "high current".
A good analogy is High Voltage/Current => Guns/Bullets. Nobody cares about plain bullets unless their loaded into a gun and the general advice should be stay away from guns/high voltage. Saying "it's actually the current/bullet that kills you" is way more misleading for the general public, even though it's true.

For example, a single 18650 lithium battery can provide close to 30A which is considered somewhat high current. If someone learned that it's the current that kills and it only takes 0.5A to kill you, people could be terrified of 3.7V batteries. And we certainly don't need "Danger - High Current" stickers for batteries, because there's no danger (to human bodies at least).

So, to people who criticized the video as misleading or oversimplified, I completely disagree with you. This isn't about our knowledge, but the advice we're giving to the general public. If we have to give advice to a person who doesn't fully understand the subject, we shouldn't complicate things with current, voltage, human resistance, duration, humidity, grounding, AC frequency or the resilience of electricity on different parts of the human body. I think this subject should not be restated by Amir and the effects of electricity to the human body is irrelevant to the audio community.
Just stay away from high voltage if you don't know what you're doing.

Welcome to the forum (sincerely)!

But do stop furthering this bit of apocrypha about voltage being the primary risk in electrical injuries—I don’t know what is taught in engineering forums, but those of us in the medical field who deal with the consequences can assure you that although voltage does play a role in fatal outcomes from electrocution injuries, current is the factor that correlates with morbidity and mortality.

Moderate to low voltages applied to low resistance tissues at high currents are lethal, while implantable defibrillators hit you with 6,000 volts at low currents for a fraction of a second and you’re A-OK.

Despite some debate about the worthiness of this topic for Amir’s primer, based on some of the answers I’ve seen here I’m concerned that quite a few folks might do well to go back to the basics on this one, or at least stop offering advice.

PS Your battery analogy was a poor one and a gross oversimplification of the science at work here. At this point I’m going to let this one go, because since you’re all still here, clearly you’re not putting yourself at substantial risks. But for the first time since I’ve been on this forum I’m the one speaking from a position of authority for a change, and folks are still convinced that their EE degrees grant them a medical license. I’m at the learned helplessness stage, you just can’t cut through the crap on here sometimes