eraos
Local Spiderman
bigwillz24 said:
the formula is 1/(2*pi*f*C), i think. so.. uh,
1/(2*pi*100*(2*10^-3))
came to like .796
I don't know what the fuck i'm doing either.
Edit: is that mF micro or milli?
reshp1
New member
Yeah, that's the right formula. The 3db cutoff frequency of that circuit (low pass filter) is essentially when the reactance of the capacitor becomes equal in magnitude to the resistance of the resistor.
bigwillz24
Well-known member
Ok this is the formula I got...
Xc= 1/2*pi*f*C
I think I'm on the right track but I'm not sure what "C" is...
I came up with 795.7747155
my "m" = micro farat which may be whats wrong I don't know.
Xc= 1/2*pi*f*C
I think I'm on the right track but I'm not sure what "C" is...
I came up with 795.7747155
my "m" = micro farat which may be whats wrong I don't know.
eraos
Local Spiderman
bigwillz24 said:
yeah, if you use micro, you'll get 795.
MadAudio
Damned if I do
Ummm, I was told that there'd be no math at this website.... 
eraos
Local Spiderman
MadAudio said:Ummm, I was told that there'd be no math at this website....
I've spent the last week trying to teach myself about circuits and shit, so I'm trying to put it to some use.
bigwillz24
Well-known member
Another question... Should I be rounding off my answers?
bigwillz24
Well-known member
Thanks by the way only 29 more of these to go...
C
cpl_crud
New member
Yes, by all means round off your answers. Never, ever have an answer that has more significant figures than the least significant number used in your calculations...
As a "qualified" scientist (i've avtually got a degree in that...) I can say this:
Stay the hell away from LRC circuitry!
Well, kinda. It's one of those "can I master at home?" questions. Sure, you can do it if you try, but you'll be missing a lot unless you practice a lot.
The forumlaue in this thread, whilst technically correct, are only looking at one half of what's actually happening. There's a while world of imaginary numbers and hurt right there.
What you're also ignoring is the phase shift inherant in CR, LR and LRC curcuits. WOuld love to stay and chat more about hte topic but I've got a conference to run... friggin work...
As a "qualified" scientist (i've avtually got a degree in that...) I can say this:
Stay the hell away from LRC circuitry!
Well, kinda. It's one of those "can I master at home?" questions. Sure, you can do it if you try, but you'll be missing a lot unless you practice a lot.
The forumlaue in this thread, whilst technically correct, are only looking at one half of what's actually happening. There's a while world of imaginary numbers and hurt right there.
What you're also ignoring is the phase shift inherant in CR, LR and LRC curcuits. WOuld love to stay and chat more about hte topic but I've got a conference to run... friggin work...
bigwillz24
Well-known member
Z = R + jXl -jXc
I think....
I wrote it in my uncomprehendable notes.
I think....
I wrote it in my uncomprehendable notes.
Hugo H
New member
and as an engineer I've gotta say that in the real world there's always +/- tolerances involved in any component. but you knew that 
bigwillz24
Well-known member
OK heres a differant type problem with the same circuit...
Calculate the voltage at e out when R = 270 Ohms and E in = 12 V
Calculate the voltage at e out when R = 270 Ohms and E in = 12 V
bigwillz24
Well-known member
I would use E = I x R correct?
C
cpl_crud
New member
Z = R + jXl -jXc
Yeah, it's something like that (i've "misplaced" my memory of the exact formulae- I'm a firm believer of deriving things from first principals)
However, this totally neglects the fact taht this is a complex function.
Becuase you've got an oscillating supply, and a phase/frequency dependant component (the capicitor) you've got to factor in that little i (you know, the sqrt(-1) fellow).
If you ignore the complex part, then you get these simple equations like Z = R + jXl - jXc, which I think comes from something like Z = R + jcis(fl) + 1/jcis(fc) or some crap like that. If you're doing simple electronics for homework, then the equations you're loooking at will be fine.
If, however, you want to use this in the design of audio gear, then you cannot ignore the complex part of this equation, as it deals with phase shifts etc. This is one of the reasons that most frequency-dependant analouge resistors (EQs, HPF/LPFs) rarely go above +/-24dB / octave, as the phase shifitng becomes uncontrollable.
It's also why expensive EQs sound better, they don't taint the phase so much as cheap ones that jsut have simple vRLC or RLvC cuircits
Once again, duty calls, so I must away, however if this thread is still alive I'll fire up the brain and write out some lengthy, dry RLC posts if you want...
Yeah, it's something like that (i've "misplaced" my memory of the exact formulae- I'm a firm believer of deriving things from first principals)
However, this totally neglects the fact taht this is a complex function.
Becuase you've got an oscillating supply, and a phase/frequency dependant component (the capicitor) you've got to factor in that little i (you know, the sqrt(-1) fellow).
If you ignore the complex part, then you get these simple equations like Z = R + jXl - jXc, which I think comes from something like Z = R + jcis(fl) + 1/jcis(fc) or some crap like that. If you're doing simple electronics for homework, then the equations you're loooking at will be fine.
If, however, you want to use this in the design of audio gear, then you cannot ignore the complex part of this equation, as it deals with phase shifts etc. This is one of the reasons that most frequency-dependant analouge resistors (EQs, HPF/LPFs) rarely go above +/-24dB / octave, as the phase shifitng becomes uncontrollable.
It's also why expensive EQs sound better, they don't taint the phase so much as cheap ones that jsut have simple vRLC or RLvC cuircits
Once again, duty calls, so I must away, however if this thread is still alive I'll fire up the brain and write out some lengthy, dry RLC posts if you want...
Hugo H
New member
cpl_crud said:
ignore all that - he's imagining things
B
boingoman
New member
cpl_crud said:
I don't believe this is accurate. Many eqs, even cheap ones, will display basically the same phase characteristics as their more-expensive counterparts when producing the same curve. A cheap eq may ring more, or be noisier, or have sloppy tolerances regarding filter width or the like, but the amount of phase shift in a cheap eq is basically the same as an expensive one, from what I've seen.
mshilarious
Banned
boingoman said:
I was unaware that analog EQs could manage to EQ without phase shift. Digital EQs can do the linear-phase bit.
B
boingoman
New member
mshilarious said:
I'm just saying the phase shift in a cheap eq will be basically the same as in an expensive one, if they are used to make the same curve. They kind of have to be, by definition. If they exhibit different phase shift, the curve would be different. I'm talking about the actual curve produced, not front panel settings. Two eqs may sound different with the same front panel settings, but that doesn't have much to do with the phase shift induced to make a specific curve. They may also sound different making the same curve, but again that is not because of differences in phase shift.
mshilarious
Banned
boingoman said:
And I was agreeing with you
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