I guess Bentsnake's universe is about to reach its end.
Magnetic field lines around parallel conductors carrying equal currents flowing in opposite directions cancel everywhere outside of the conductors and add everywhere between them. If the inside loop area can be made small, then the total magnetic flux, and therefore the inductance, will also be small.
Magnetic field lines around parallel conductors carrying equal currents flowing in opposite directions cancel everywhere outside of the conductors and add everywhere between them. If the inside loop area can be made small, then the total magnetic flux, and therefore the inductance, will also be small.
You need to learn the topic. Until you do, you will continue with some very bad understandings.
Not to worry. In order to have an intellectual discussion on electromagnetic theory, there needs to be two with the knowledge. Attempting to explain this to you is like one hand clapping.
I have. At work, we had to inspect over 50 thousand internally built chassis as a result of one failure. A potted module consistent with a calix style unit failed internally and caused an input hot to output ground short. Because the widget at the far end was low level high gain instrumentation, ground loops were avoided by allowing the plumbing it was attached onto to serve as the safety ground. A problem arose when a tech disconnected the pipe at two ends, it floated, the tech received current. This was equipment designed and built by experienced techs.
Your solenoidal example is incorrect, as was pointed out by others.
Perhaps you should learn the topic first.
I suspect no amount of reality will change his universe.
Thanks for trying.
edit: my moniker is the magfield intensity between coaxial cylinders with currents in opposing directions. Of course, outside it's zero, it's 1/r between, and it's zero within the internal cylinder.. A consequence of symmetry and lack of sources within the center cylinder. In general, there is no magnetic field inside a cylindrical wall carrying current.
jn
Last edited:
Actually this single statement explains much. "...or whatever you want to call it."? C'mon.
If you call induction a flux field (they are not the same thing), then how is anybody going to know what you're talking about? Then as a side issue, do you know yourself?
In technical fields it's critical to use correct terms. But sadly, these forums are littered with the opposite. Which is why you read so much of...
"I thought you meant..."
"Oh no, I meant..."
"Then you must have meant to say..."
"No, I really wanted to say..."
And on it goes. Part of it is probably due the idea that this is a speed-typing forum, but as often as not it seems to be just plain sloppy thinking. Perhaps the same sloppy thinking that leads to so many suppositions being put forward as axioms.
If you don't know, typing a single word into Google brings up a definition of that word. This applies also to many or most technical terms. I just thought somebody might like to know that.
.
bentsnake,
build your amps, i say build it, test it and learn from it....
otherwise you end up as someone who liked talking but ends up building nothing....
show us what you have done, like i always say, a build up amp tells a lot more than
drawings can ever tell....
blah-blah all you want, but please go and build something....
this thread is about building an amp that is safe, and does not hum.....
you can have both, but you have to start building it....
build your amps, i say build it, test it and learn from it....
otherwise you end up as someone who liked talking but ends up building nothing....
show us what you have done, like i always say, a build up amp tells a lot more than
drawings can ever tell....
blah-blah all you want, but please go and build something....
this thread is about building an amp that is safe, and does not hum.....
you can have both, but you have to start building it....
Wow, you're really gonna call people out on what they know like that? What is your problem bentsnake? Oh wait, BentSnake or... BS for short! Now I get it!
We can tell that is what you try to do to counterpoint what everyone's advice to you is.
Have you soldered anything yet on your chipamp project or you didn't have time yet cause you're in here breaking everyone's balls who are trying to help you?
Any idea what was the cause of that fail? I hope the tech wasn't badly injured.
^ in relation to this, i use double bay nylon bobbins whenever i can find them....no way for the primary of the traffo to touch the secondary nor the chassis....
and bentsnake, if you are not sold to the idea of twisting wires of power leads, then do it untwisted, but do something and not argue...
no one can stop you if you do not want to twist your wires....
and bentsnake, if you are not sold to the idea of twisting wires of power leads, then do it untwisted, but do something and not argue...
no one can stop you if you do not want to twist your wires....
Would that be like this pic, (I did not show the 100nF ceramics, just the electrolytic bypass caps) -a 1st order low pass? If so, what frequency should I shoot for for the cutoff frequency? I was messing around with an online calculator and I noticed that the resistance of the wire/PCB traces to the bypass cap must make it's own snubber with the cap anyway around 50000Hz or somewhere in that area. Is this right? Will this snubber affect the higher frequency ceramics in any way?
Attachments
I don't try to calculate a frequency. Probably because I can't and possibly because I would not know what to do with the answer.
The power supply cable has impedance, partly resistance and partly inductance.
The RC makes a single pole filter.
The LC makes to 2pole filter.
You end up with a weird version of a 3pole filter.
What would you work out from that if you had the frequency answer?
But your diagram is not right.
The two electros need to connect to each other with a smallish loop area and shortish loop length.
When you analyse the output current loop you find that at high frequencies most of it returns direct to the electros and only a tiny bit goes back to the PSU Zero Volts.
When you add in the HF decoupling and look at VHF currents and include a Zobel which only pass HF and VHF, you will see that almost no VHF curent returns to the PSU and little goes to the electros. Almost all of it returns to the HF decoupling ground. Since this is VHF, it becomes absolutely necessary to keep the loop lengths and loop areas ultra short/small.
The power supply cable has impedance, partly resistance and partly inductance.
The RC makes a single pole filter.
The LC makes to 2pole filter.
You end up with a weird version of a 3pole filter.
What would you work out from that if you had the frequency answer?
But your diagram is not right.
The two electros need to connect to each other with a smallish loop area and shortish loop length.
When you analyse the output current loop you find that at high frequencies most of it returns direct to the electros and only a tiny bit goes back to the PSU Zero Volts.
When you add in the HF decoupling and look at VHF currents and include a Zobel which only pass HF and VHF, you will see that almost no VHF curent returns to the PSU and little goes to the electros. Almost all of it returns to the HF decoupling ground. Since this is VHF, it becomes absolutely necessary to keep the loop lengths and loop areas ultra short/small.
Last edited:
For this exact reason it has always bothered me that the bypass caps are given their own ground return back to the main star. Rationally I want to return them directly to the 'ground end' of the load, then run a wire from there back to the main star. I would love to hear a good explanation for doing the former!
That should bother you, since it's completely wrong. The whole point of a "bypass cap" is to bypass the circuit inductance,
not to add even more inductance with a long wire. When you see every ground wire in the circuit run to a single "star ground,"
it is not possible for it to function as well as it should.
Last edited:
Hmm, then at the risk of showing my ignorance, coudl someone explain why I see this arrangement advised by Doug Self for grounding an amplifier, and not the second version?
EDIT: Looking at it, I suppose it is because the load is so remote that the ground wire leading to the output terminal must be considered an extension of the load impedance.
Attachments
Last edited:
I think the significant question is, "Bypass what?" There are some pretty wild tales along this line, but broadly speaking the object is to shunt anything in the power lines that's not pure DC to ground.
From the National data sheet for the LM1875, paragraphs and some punctuation added by me.
"...to eliminate possible oscillations all op amps and power op amps should have their supply leads bypassed with low-inductance capacitors having short leads and located close to the package terminals. Inadequate power supply bypassing will manifest itself by a low frequency oscillation known as “motorboating,” or by high frequency instabilities.
"These instabilities can be eliminated through multiple bypassing utilizing a large tantalum or electrolytic capacitor (10 µF or larger), which is used to absorb low frequency variations, and a small ceramic capacitor (0.1 µF) to prevent any high frequency feedback through the power supply lines.
"...all sorts of problems can arise from improper grounding, which again can be avoided by returning all grounds separately to a common point. Without isolating the ground signals, and returning the grounds to a common point, ground loops may occur.
"...When designing a layout, it is important to return the load ground, the output compensation ground, and the low level (feedback and input) grounds to the circuit board common ground point through separate paths. Otherwise, large currents flowing along a ground conductor will generate voltages on the conductor which can effectively act as signals at the input, resulting in high frequency oscillation or excessive distortion."
In a postscript, I really shouldn't say it, but I'm weak. If you can believe a capacitor can somehow bypass inductance...well, you have my admiration.
.
my rule of thumb, look at what posters have actually accomplished by way of finished amps....if they talk and talk but has nothing to show for it, then you know who to ignore....
^should be from the 1980 AUDIO handbook by national semiconductor....
in the manual they say, a ground is a ground, is a ground and a ground...
any ground point should be zero volts, but when two ground points are of different potential, then ground loops will happen...
this is what we should look for in our circuit layouts, if there is a possibility of this happening, then we should break it....
in the manual they say, a ground is a ground, is a ground and a ground...
any ground point should be zero volts, but when two ground points are of different potential, then ground loops will happen...
this is what we should look for in our circuit layouts, if there is a possibility of this happening, then we should break it....
- Status
- Not open for further replies.