> i have never seen NP bigger then 440.
DigiKey has 6,800uFd 35V NP.
I have designed a mike-amp where that was a limiting factor. The gain-set resistor should be under 100 ohms, and must vary more than 100:1, which leads to a minimum value of about 1 ohm. It also should be DC-blocked, yes has no predictable DC, so it has to be NP. Is this design "impossible"? With the 6,800uFd NP it is just-reasonable. Bass limit is higher than 20Hz at the highest gain, but that actually works out well with typical sources and studios. The lowest-gain settings are above the 100 ohm goal, but that isn't a serious problem.
> calls for a 14839 uF cap.
Two of the 6,800uFd in parallel puts you in the ballpark for I think about $13.
> I went to another calculater and got 8.38 uF which makes much more sense.
Yes, be suspicious of incredible answers. Check your math. Look at the situation several different ways. 10,000uFd is about 1 ohm at the bottom of the audio band and much less than 1 ohm at higher frequencies: can you possibly be working at such insanely low impedances? Seems unlikely. If you are, can you really build it? In my super-low resistance gain-set scheme, fractional-ohm parasitics in the wiring and switch really screw-up the results.
I don't know if 8.38uFd is the right answer, but 14,000uFd is probably a wrong answer, or the right number for the wrong solution to the problem.
Remember if two approaches give two answers, at leat one is wrong, but maybe BOTH are wrong.
DigiKey has 6,800uFd 35V NP.
I have designed a mike-amp where that was a limiting factor. The gain-set resistor should be under 100 ohms, and must vary more than 100:1, which leads to a minimum value of about 1 ohm. It also should be DC-blocked, yes has no predictable DC, so it has to be NP. Is this design "impossible"? With the 6,800uFd NP it is just-reasonable. Bass limit is higher than 20Hz at the highest gain, but that actually works out well with typical sources and studios. The lowest-gain settings are above the 100 ohm goal, but that isn't a serious problem.
> calls for a 14839 uF cap.
Two of the 6,800uFd in parallel puts you in the ballpark for I think about $13.
> I went to another calculater and got 8.38 uF which makes much more sense.
Yes, be suspicious of incredible answers. Check your math. Look at the situation several different ways. 10,000uFd is about 1 ohm at the bottom of the audio band and much less than 1 ohm at higher frequencies: can you possibly be working at such insanely low impedances? Seems unlikely. If you are, can you really build it? In my super-low resistance gain-set scheme, fractional-ohm parasitics in the wiring and switch really screw-up the results.
I don't know if 8.38uFd is the right answer, but 14,000uFd is probably a wrong answer, or the right number for the wrong solution to the problem.
Remember if two approaches give two answers, at leat one is wrong, but maybe BOTH are wrong.
> Got a part number for that?
jeez, I knew someone would ask.
http://digikey.com
Put "6,800" in the Search-box, you don't get any cap.
Put "6800" in the Search-box, you get many things including "200 capacitors".
Click that, highlight "6800uF" and "Bi-Polar", Apply Filters.
Bingo. Digi-Key Part Number P1151-ND
I wuz wrong. It is only 6 volt, and only $2.44.
Indeed, at Bi-Polar 35V, DigiKey only has up to 470uFd, P1194-ND. They are only $1.08 each and cheaper for 10, so you could parallel-up a 4,700uFd 35V NP cap for $7.72. I found one listing for Black Gate 4,700uF 35V non-polar and it shows $120. So neglecting any special magic in a Black Gate, in effect you do 20 minutes soldering for a $112 savings, $336/hour, which is a fine labor-rate.
jeez, I knew someone would ask.
http://digikey.com
Put "6,800" in the Search-box, you don't get any cap.
Put "6800" in the Search-box, you get many things including "200 capacitors".
Click that, highlight "6800uF" and "Bi-Polar", Apply Filters.
Bingo. Digi-Key Part Number P1151-ND
I wuz wrong. It is only 6 volt, and only $2.44.
Indeed, at Bi-Polar 35V, DigiKey only has up to 470uFd, P1194-ND. They are only $1.08 each and cheaper for 10, so you could parallel-up a 4,700uFd 35V NP cap for $7.72. I found one listing for Black Gate 4,700uF 35V non-polar and it shows $120. So neglecting any special magic in a Black Gate, in effect you do 20 minutes soldering for a $112 savings, $336/hour, which is a fine labor-rate.
PRR said:
It was to build a zobel for a passive x-over. One online calculator is on crack because the other two gave me nearly identical answers.
http://www.apicsllc.com/apics/Misc/filter2.html#TOP this one gave me the 14k cap zobel with a 8.3 ohm resistor.
http://www.mhsoft.nl/spk_calc.asp and this guy and a formula and a calculator gave me nearly identical 7.78 or 8.1 cap results with approx 8 ohm resistor.
So the top site has been removed from my bookmarks just in case
Go ahead and enter 6.5 RE and .61 Le and see what you get. Tell me that someone has a different formula and that the top link is for designing anti gravity units or something.
Everything should be in mH for the un initiated DAMN the british and their superior reading ability. 
> enter 6.5 RE and .61 Le and see what you get
I never saw a ~8Ω speaker with 0.6 Henries of inductance.
One milliHenry is more typical. Maybe you mean 0.61 mH? Or 0.000,61 H?
>> It would seem that you did not enter Le in Henries!
> BAHH ! ! How am i supposed to know that?
It clearly says "Henries" next to the box.
In fact if you read the Instructions instead of skipping to the pictures, it says:
Inductor value(s) are given in thousands of a Henry (mH).
For the Zobel circuit, enter inductance in Henries (not mH).
I don't trust a programmer to write the right units, but I will try it his way and see what I get.
> Everything should be in mH for the un initiated
I agree that, since this is clearly a SPEAKER calculator and mentions 4 ohm speakers, and uses mH elsewhere, it would be more obvious and convenient, less error-prone, to use mH here. But I didn't write it, I didn't pay for it to be written, I'm glad it was written even if it isn't "exactly how I would like it".
Also: it is JavaScript and you can modify it yourself. (For personal fun only: don't share your hack of ApICS LLC's work without permission!) View Source gets everything including the math, save it to your machine. Find the Zobel script, the equations are fairly clear, including a number with a lot of zeros in it. Take 3 zeros out of that, change the instructions and the label on the Le box, and open it in your browser. Looks like this (I didn't bother grabbing the images):
> in the US, where all sorts of weird old imperial units pop up all over the place
I have a room-acoustic calculator, scaled to a specific old concert hall, with input in milli-furlongs, output in micro-fortnights.
I never saw a ~8Ω speaker with 0.6 Henries of inductance.
One milliHenry is more typical. Maybe you mean 0.61 mH? Or 0.000,61 H?
>> It would seem that you did not enter Le in Henries!
> BAHH ! ! How am i supposed to know that?
It clearly says "Henries" next to the box.
In fact if you read the Instructions instead of skipping to the pictures, it says:
Inductor value(s) are given in thousands of a Henry (mH).
For the Zobel circuit, enter inductance in Henries (not mH).
I don't trust a programmer to write the right units, but I will try it his way and see what I get.
> Everything should be in mH for the un initiated
I agree that, since this is clearly a SPEAKER calculator and mentions 4 ohm speakers, and uses mH elsewhere, it would be more obvious and convenient, less error-prone, to use mH here. But I didn't write it, I didn't pay for it to be written, I'm glad it was written even if it isn't "exactly how I would like it".
Also: it is JavaScript and you can modify it yourself. (For personal fun only: don't share your hack of ApICS LLC's work without permission!) View Source gets everything including the math, save it to your machine. Find the Zobel script, the equations are fairly clear, including a number with a lot of zeros in it. Take 3 zeros out of that, change the instructions and the label on the Le box, and open it in your browser. Looks like this (I didn't bother grabbing the images):
An externally hosted image should be here but it was not working when we last tested it.
> in the US, where all sorts of weird old imperial units pop up all over the place
I have a room-acoustic calculator, scaled to a specific old concert hall, with input in milli-furlongs, output in micro-fortnights.
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