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Old 22nd November 2001, 07:44 AM   #21
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I'm missing a 3.3uF Cap,
can't find one thats not polar anywhere
is that cap important?
or can I replace it with a 10K resistor to provide impedance?
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Old 22nd November 2001, 02:13 PM   #22
paulb is offline paulb  Canada
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The cap isolates any DC offset from getting into the amp. You can't substitute a resistor.
You can parallel smaller values to get a larger one.
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Old 23rd November 2001, 01:25 AM   #23
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I'll see if I can find anything
Is the diagram at ESP wrong?
the 3.3uF is a non-polar
while for the rest of his designs, the input cap is usually polar EC
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Old 23rd November 2001, 01:32 AM   #24
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Also, I have 2.2uF ECs from the 20W/channel amp
can I just use them instead?
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Old 23rd November 2001, 05:09 AM   #25
paulb is offline paulb  Canada
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The input capacitor and the input resistor form a high-pass filter that cuts out DC and low frequencies. This filter's "half-power" frequency is 1 / (2 * PI * R * C).
Punching in the numbers, I get 3.3 Hz with a 2.2 uF cap (R=22K). Anything frequency BELOW this will be reduced in volume by the filter. I think even a 1 uF cap would be fine ( = 7 Hz), unless maybe it's a subwoofer amp.
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Old 23rd November 2001, 05:27 AM   #26
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Wow, that was a very timely response
thanks alot Paulb... was about to go out in the rain to get some more caps.
Polar ones would be fine right?
but I'll go find Mylar ones, heard EC caps might reduce sound quality
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