Yes, that's correct, but

Posted by Maxamillion (A) on April 26, 2010 at 05:36:13

In Reply to: I'm easily confused.... posted by rwiley on April 25, 2010 at 21:51:56:

only well above the corner frequencies of both capacitors. There is a frequency dependence that needs to be taken into account. That is why I measured 32 ohms in my test setup (in the post above) instead of the calculated 25.5 ohms (51/2) - the 0.39uF cap still had a significant impedance to the test signal at the 10kHz test frequency. At a higher frequency it would have measured 25.5ohms.
What that shows is that the impedance will vary non linearly with frequency in a multiple parallel RC network - at audio frequencies it will be very large, then it will decrease to that of the resistor in series with the largest cap in the filter as the largest cap passes its corner frequency. Impedance should be stable for a range of frequencies, then it will begin to decrease non-linearly as the second cap begins to pass the RF, then it will decrease again as the third cap begins to pass the RF signal, and so on. Add to that the fact that somewhere in there the caps will reach their resonant frequency and the impedance will then increase again. It becomes quite complicated to figure out what impedance the filter is presenting at any particular frequency.

All that said, folks here do report good results with the parallel networks, so maybe sometimes we can analyze ourselves to death. It's the age-old struggle between the theorist and the experimentalist - and the best approach probably lies somewhere in the middle...

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Follow Ups Full Thread

Topic - Characteristic Impedance and RC Filters - Maxamillion 11:04:37 04/23/10 (17)

RE: Just use a resistor. - rick_m 14:10:20 04/24/10 (0)

Yes, but... - Al Sekela 14:40:56 04/23/10 (13)

Yes about those Parallel Networks... - Maxamillion 07:11:52 04/24/10 (11)

Procrustes' Bed - Al Sekela 15:32:56 04/24/10 (8)

I'm easily confused.... - rwiley 21:51:56 04/25/10 (7)

Yes, that's correct, but - Maxamillion 05:36:13 04/26/10 (6)

I've had good results with... - rwiley 08:00:30 04/26/10 (1)

RE: I've had good results with... - Maxamillion 13:31:47 04/26/10 (0)

Without the theory, in practice - bartc 06:15:09 04/26/10 (3)

Thanks, Bart. Have you tried... - Maxamillion 07:35:05 04/26/10 (2)

Yes, Max, I tried that too - bartc 07:41:29 04/26/10 (1)

I will try multiple combos - Maxamillion 08:30:32 04/26/10 (0)

That is a nature of capacitors after all... - Tweekeng 13:21:15 04/24/10 (1)

RE: That is a nature of capacitors after all... - Maxamillion 13:50:38 04/24/10 (0)

RE: Yes, but... - Maxamillion 19:31:40 04/23/10 (0)

Applies only to R-C filters on SPEAKER cables - bartc 11:22:38 04/23/10 (1)

RE: Applies only to R-C filters on SPEAKER cables - Jack D II 13:14:30 04/27/10 (0)

Follow Ups

Yes, that's correct, but - Maxamillion 05:36:13 04/26/10 (6)

I've had good results with... - rwiley 08:00:30 04/26/10 (1)

RE: I've had good results with... - Maxamillion 13:31:47 04/26/10 (0)

Without the theory, in practice - bartc 06:15:09 04/26/10 (3)

Thanks, Bart. Have you tried... - Maxamillion 07:35:05 04/26/10 (2)

Yes, Max, I tried that too - bartc 07:41:29 04/26/10 (1)

I will try multiple combos - Maxamillion 08:30:32 04/26/10 (0)

Yes, that's correct, but

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