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Originally Posted by PaRaNoId  freq(Hz?) = 1 / (2pi(R?)(C?) |
yes, algebraically manipulated to 2pi(R)(freq)=1/C
or, C = 1/2pi(R)(f)
R in this case could be either or both resistance and input impedance. We sometimes use R and Z (impedance) interchangeably when the other factors of impedance are miniscule and relatively benign, such as in this case.
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1-pin#1 (ground/shield) goes through in this line-level, balanced circuit
2- these will be strictly operated at line level, going into a 20-30k ohms input
3- there will be identical ratings on capacitors on pins 2 and 3 (hot and cold)
each cap will be 2 times the value we get in the below equation for "C"
4- there should be a resistor of some type b/w pin 2 and 3
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1 yes
2 yes- but knowing the input impedance eases the calculation,
3 yes - as explained by Ulysses above, both are twice the calculated value, and both ratings are the same.
4 Yes and No. I've always thought of there being a "shunt" resistor across the lines, but thinking about it now, it would seem that the shunt resistor is really just a "load" of some sort. This means that we can forgo the extra resistor since the input impedance is the load.
Yes- if the input impedance is unkown, and you're trying to calculate R to make the total equivalent (extra resistor and the input impedance/resistance combined) the closest to the desired or specified input impedance.
Since there is no real easy way to determine exactly what the input impedance/resistance is, one uses a higher value resistor from 2 to 3 than the expected input impedance in order to make the equivalent resistance close enough to the desired/specified resistance/impedance.
No- if you don't care about trying to alter the input impedance, or you accept the specified impedance as your R value, then simply forgo the extra resistor and use the two caps of doubled value that we determine from the calculations.
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now..... this is what is completely killing me.....
what is "R" going to be? Is it expressed in ohms?
Is R the resistor value? Is R a value derived from eight other not-quite known factors, or is it simply 20,000 (ohms)? This is the element that i don't get. Ethan's layout looks good to me but it doesn't give me enough to find an R value considering the diagram shows an R1, R2, R22K, R and has unexplained numbers by the resistors.
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R is synonymous with both resistance, as when the load is purely resistive, but also with equivalent impedance, expressed in Z, but as for our case we're using Z as if it was a purely resistive load.
Impedance is really a combination of three things: resistance, inductance and capacitance. Since the input inductance and capacitance are relatively miniscule, we simply forget they are part of the equation and just use the input resistance value (20-30kΩ) and call it impedance.
Yes. R is the resistance value. Here we've been combining the guestimated R value with the input impedance by another formula, the formula for parallel resistance.
1/Rtotal = 1/R1 + 1/R2 ...+ 1/R (so and so)
it happens to be just like the capacitance formula used above..
1/Ctotal = 1/C1 + 1/C2 ...+ 1/C (so and so)
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What is C going to be expressed in? and what are my two caps going to be rated? and how to i say that and write it on paper I know i suck for asking someone else to do the math but im just trying to get a ball park estimate and not sure if im applying the info correctly.
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Capacitance (C) is expressed in some amount of Farads
For this case, your circuit will require caps in nano farad range. Thats 1x10^-9 or 0.000000(000).
As for voltage, line level at odBu is somewhere around .775 volts, so a 5v rating or higher should suffice.
Its alright to ask for help. I've learned a lot about the subject from thinking and calculating it myself with the help from those above.
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Also....If price/time is no option, would certain brands/grades/types of caps and resistors improve/color the sound?  |
I can't offer suggestions as per the sound of a capacitor compared to another, but I can offer the offered values.
Looks like your stuck with two 150 nano (.15uf), capacitors or your choosing. Some type of film cap. Voltage ratings won't be a problem.
Here's a couple, but like I said, I can't speak on quality or characteristics.
WIMA WIMA