• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Electronics for Audiophiles: Voltage and Current (Video)

Audiofire

Senior Member
Forum Donor
Joined
Feb 8, 2022
Messages
485
Likes
227
Location
Denmark
1659425918920.png


1659425948313.png


1659426010664.png


1659426052945.png
Source: Vladimír Kůla & Michal Kříž. INTRODUCTION TO ELECTRICAL ENGINEERING. CTU PUBLISHING HOUSE.
 
Last edited:
Joined
Jul 31, 2022
Messages
31
Likes
13
I have an amp that can do 26V@8A max. and that is able to deliver 1.6 ohm @26V@8A = 416W max. (2xMA12070@PTBL@400W supply)

My speakers are KEF LS50 Meta. As they have been reviewed by Amir, I know that they are rather "heavy loads" that will pull down to 3.2 ohm (83db sensitivity) and not only for short bursts, but for a quite a while. Officially they are marketed as 8 ohm speakers tho.

Questions:
a) Since my speakers go to 3.2ohm, I consider them heavily current-dependend and not very voltage-dependend (they are extraordinarily open/transparent with vocals and high tones anyways)
b) If I would swap my amp with one that does:

26V @8A @1.6ohm -> 48V @7.1A @2ohm

Would I even benefit from that considering the new amp could do more voltage, but slightly less current?
Would I even hear a difference?
Would the newer amp play louder vocals, but "miss out" on the base at some point, whereas the old amp would not "sag" and go a full "1:1 ratio" down to the very last drop of its 26V?
 

Lambda

Major Contributor
Joined
Mar 22, 2020
Messages
1,775
Likes
1,512
I consider them heavily current-dependend and not very voltage-dependend (they are extraordinarily open/transparent with vocals and high tones anyways)
this is all not how it works.

Even on the absolute basic level the speaker "pulls" the current and the amp feeds voltage. it is a voltage source. the speker is a load.
You can only multiply Volts and Amps if they are in phase. they are not with speakers. that's the difference between VA and Watts.

Your Power supply current can't be directly translated to speaker current (especially with class d).

How do you know the amp your using now has not enough power? is it clipping?
 
Joined
Jul 31, 2022
Messages
31
Likes
13
How do you know the amp your using now has not enough power? is it clipping?
No, in fact it feels very powerful. Never made it beyond 70% of max volume before my brains got blown out, since I am in a small room about 5x3m. Never heard any clipping.

If I am correct, I'd be getting a maximum of 3.2ohm@26V = 211.25W (from possible [email protected] = 422.25W) out of this amp with my speakers. That is halfed by the two channels, so I could expect this amp to deliver a maximum of 105,625W @3.2ohm per channel. KEF says the speakers are rated for 100W, but they also say they are quote: "8ohm(3.5ohm)" hence I am not sure if they take 8 or 3.5ohm as a pairing for that 100W. If they pair it with 8ohm they could take 200W@4ohm and therefore 211,25W @3.2ohm.

There is an active version of the LS50 Meta using a D-Class 200W driver for the base and a 80W AB-class for the tweeter. Therefore I figure they must be linking the 100W to 8ohm and I could run my speakers with double the power. Am I being correct so far?

The question is, would I benefit from it?
 

sofrep811

Active Member
Joined
Jun 4, 2016
Messages
253
Likes
319
Listened to this while sitting around avoiding 100 degree weather. Really helped me. Thanks.
 

Spkrdctr

Major Contributor
Joined
Apr 22, 2021
Messages
2,184
Likes
2,899
No, in fact it feels very powerful. Never made it beyond 70% of max volume before my brains got blown out, since I am in a small room about 5x3m. Never heard any clipping.

The question is, would I benefit from it?
The quick answer is no. If it plays as loud as you want without the volume knob turned all the way up you are pretty good to go. As a consumer and not an engineer you have to use what reasonably works. If you have some headroom, you will be ok. A light bit of clipping is inaudible. Or, you can say I will buy a very big powerful amp and then never have to ever buy a new one until this one breaks from old age. It is your money. But, from what you have explained you do not "need" to spend the money. But, this is audio so need is never the issue, it is always a "want". So, it is up to you to decide what you want. You can get GOBS (technical term) of power with the new Class D stuff. Let us know what you do! Good Luck.
 
Joined
Jul 31, 2022
Messages
31
Likes
13
If it plays as loud as you want without the volume knob turned all the way up you are pretty good to go.
There is an old saying in the hifi world claiming that a more powerful amp will sound fuller/heavier even on the same volume output compared to a less powerful one. But I believe this to be coming from older Class-D amps of which had insufficient ability to run high currents, resulting in a fading out baseline with rising the volume, thus becoming a "thin sound".
The KEF LS50 Meta will move their woofers visibly when being pushed on certain deep base tracks. Very few tracks will make them even start to move around 55-60% of volume.
As Amir stated in his video-review, once you can see the woofers on the LS50 Metas move and seperate from the tweeter, the base will start to distort slightly and even more when you push it further. Therefore I figure they cannot take any more current reasonably. But this is leaving a very important question. Since those speakers are already among the most demanding speakers one could buy at nowaday markets and since my "little" ~100W@4ohm amplifier is being able to push them to woofer seperation quite early, why would anyone even need more power than ~26V@8A other than with very exotic or very big tower speakers?
 

Holmz

Major Contributor
Joined
Oct 3, 2021
Messages
2,011
Likes
1,233
Location
Australia

If I am correct, I'd be getting a maximum of 3.2ohm@26V = 211.25W (from possible [email protected] = 422.25W) out of this amp with my speakers. That is halfed by the two channels, so I could expect this amp to deliver a maximum of 105,625W @3.2ohm per channel. KEF says the speakers are rated for 100W, but they also say they are quote: "8ohm(3.5ohm)" hence I am not sure if they take 8 or 3.5ohm as a pairing for that 100W. If they pair it with 8ohm they could take 200W@4ohm and therefore 211,25W @3.2ohm.

How do you go from 3.2 ohms to 1.6 ohms? Are you connecting two speakers to one channel?

Secondly the 3.2 ohms is probably DC resistance. But the speakers also have inductance, so that gets one towards 4 ohms with frequencies /= zero Hz.



There is an active version of the LS50 Meta using a D-Class 200W driver for the base and a 80W AB-class for the tweeter. Therefore I figure they must be linking the 100W to 8ohm and I could run my speakers with double the power. Am I being correct so far?

In an active speaker, I am not sure you would need any external amplifier.
 
Joined
Jul 31, 2022
Messages
31
Likes
13
How do you go from 3.2 ohms to 1.6 ohms? Are you connecting two speakers to one channel?
No. My speakers go to 3.2ohm. The amp could in theory go down to 1.6ohm, but there is no speaker I know of other than subwoofers going that low. However, since it can go down this low means that there is plenty of headroom left in the base. Hence, I do not get the feeling of sound becoming "thin" on louder volumes as I probably (maybe) would get with a smaller amp running in BTL instead of PBTL. Running my amp in PBTL means it can do twice the current, but about the same or just slightly more Voltage. However, most of this power is wasted, since I will never plug a speaker to it that will demand such current. Nonetheless it is nice to have that headroom.
In an active speaker, I am not sure you would need any external amplifier.
This is the active version of the LS50 Meta, it is called "LS 50 Wireless II" and it does have 1x200W D-Class and 1x80W AB-Class installed. Basically it is the same speaker just with an amplifier and a DAC with DSP installed. Therefore I figured the passive LS50 Meta could take similar or nearly similar power from an external amp.
 

Gord

Member
Joined
Jul 17, 2022
Messages
5
Likes
3
Good stuff, I definitely find these kinds of posts super useful.

I am starting a new educational series on simple but essential engineering concepts/lingo we use in discussing audio products. This is the introductory video on voltage, current and power supplies:


Please give feedback as to whether you find this type of video useful and I will make more of them.

Thanks.
Thanks, Amir. Please keep them coming!
 
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
44,174
Likes
231,820
Location
Seattle Area
Thanks, Amir. Please keep them coming!
Will do. Statistics though for the video shows it to have below average viewership. Maybe I have to find a clickbait title to go with them! :)
 

DonH56

Master Contributor
Technical Expert
Forum Donor
Joined
Mar 15, 2016
Messages
7,757
Likes
16,318
Location
Monument, CO
"Shocking video! See it here first!"
 

changster

Member
Joined
May 6, 2022
Messages
96
Likes
110
Location
Taipei
Will do. Statistics though for the video shows it to have below average viewership. Maybe I have to find a clickbait title to go with them! :)

Of course videos of “This $5000 cable doesn’t do anything!” videos would be watched more! People love mythbuster HiFi videos.
 

Raindog123

Major Contributor
Joined
Oct 23, 2020
Messages
1,599
Likes
3,554
Location
Melbourne, FL, USA
1) To be dangerous to a human, a certain (a) level and (b) amount (duration) of _current_ needs to flow through critical internal organs (like heart and/or certain nerves).

2) Yes, due to a relatively high impedance of a human body (and of certain organs/parts — eg, skin — more than others) a _low-voltage_ electric source usually would not produce enough current to be dangerous/harmful (yes, per the basic Ohm’s Law). [However, under certain circumstances it can be — eg, electrodes directly attached to a heart, cuts in the skin, etc.)

3) However, a _high-voltage_ source might not always be dangerous either. It would depend on the amount (!) of the charge available at the source: If it is a “sustained“ (lasting) source of high voltage, then it is definitely dangerous and potentially fatal — as a high current will get generated to flow through the body’s internals. Yet, if it’s a [very] high voltage but a low capacity source, the quick (“transient”) discharge it can generate will only flow through the body surface due to (a) the “skin effect” (field distribution) and (b) capacitance and inductance of our body — irrelevant for sustained DC currents, but defining the electric charge distribution of a transient AC burst. [And this is why we can easily survive multi-kilovolt voltages of various “static” discharges, vandergraaf generators, and even lightnings — while with huge voltages, there is simply not enough charge to penetrate deep/long enough into the body to kill us…]
 

OCA

Addicted to Fun and Learning
Forum Donor
Joined
Feb 2, 2020
Messages
628
Likes
456
Location
Germany
I am starting a new educational series on simple but essential engineering concepts/lingo we use in discussing audio products. This is the introductory video on voltage, current and power supplies:


Please give feedback as to whether you find this type of video useful and I will make more of them.

Thanks.
Dear Amir,

I'd really like to know your opinion about the role of conductors on transferring energy based on the information below:


Could this be proof that may be it's not all snake oil with expensive cables or there's some science behind cable risers? Will the effect of conductance reflect in your measurements and thus is negligible?

I'll only be convinced if you're convinced
 

pma

Major Contributor
Joined
Feb 23, 2019
Messages
4,514
Likes
10,538
Location
Prague
I'd really like to know your opinion about the role of conductors on transferring energy based on the information below:
You have to distinguish between propagation speed of information (electromagnetic field along the wire) which is usually at 60% - 70% of speed of light and slow motion of electrons inside the conductor - conduction current of electrons.
 
  • Like
Reactions: OCA

OCA

Addicted to Fun and Learning
Forum Donor
Joined
Feb 2, 2020
Messages
628
Likes
456
Location
Germany
You have to distinguish between propagation speed of information (electromagnetic field along the wire) which is usually at 60% - 70% of speed of light and slow motion of electrons inside the conductor - conduction current of electrons.
So, if I understand your explanation correctly what matters for audio is the high speed transfer of information through the electromagnetic field along the wire which is not affected by the conduction of the wire.
 

Holmz

Major Contributor
Joined
Oct 3, 2021
Messages
2,011
Likes
1,233
Location
Australia

I'd really like to know your opinion about the role of conductors on transferring energy based on the information below:

Maybe just remove the cables and see if the energy transfers at all?
(That should give us an idea whether the conductors are playing a role or not.)


Franklin, Faraday and others, noted that the electric field is zero at the surface of the conductor. So the magic that was in that video, is stuff that has been known since Faraday and Maxwell, and is more physics based than something I would be trusting a cable manufacturer to be depended upon knowing.
 
  • Like
Reactions: OCA

OCA

Addicted to Fun and Learning
Forum Donor
Joined
Feb 2, 2020
Messages
628
Likes
456
Location
Germany
Maybe just remove the cables and see if the energy transfers at all?
(That should give us an idea whether the conductors are playing a role or not.)


Franklin, Faraday and others, noted that the electric field is zero at the surface of the conductor. So the magic that was in that video, is stuff that has been known since Faraday and Maxwell, and is more physics based than something I would be trusting a cable manufacturer to be depended upon knowing.
 
Top Bottom