Cap. at the output on bridged no DC - Page 2 - diyAudio
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Old 11th November 2003, 12:29 AM   #11
avenger is offline avenger  United States
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HEHE, you got it Portuguese people rule...I just finished my new amp, an I tried the capacitor at the output, 2200 mfd 25 vdc, in series with the chocke and, I had 1.2 mV initially but after the cap was in the circuit DC offset became "0" null, no voltage at all and there was absolutelly no alteration on the sound quality whatsoever, it sounded the same, my next project will be to parallel one more amp and use the cap. at the output and see what happens..I can almost predict it..can't wait. I will post the results
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Old 11th November 2003, 12:59 AM   #12
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couldn't that badly reverse bias the cap?
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Old 11th November 2003, 01:20 AM   #13
avenger is offline avenger  United States
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well, the dc offset will either be positive or negative in relation to ground, I placed my cap with the negative lead out to the speaker terminal.....I don't remember if the dc voltage I measured was pos.or neg.....should've payed some attention. Everything worked great. Should that dc offset voltage be + or -? In theory what should it be?
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Old 11th November 2003, 02:55 AM   #14
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no, i mean when the AC wave output swings from 0 to -10V or so, the cap becomes reversed biased.
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Old 11th November 2003, 03:31 AM   #15
avenger is offline avenger  United States
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Yea I see what you mean, but if you look at it the same thing happens on the input capacitor right? Capacitors are basically used to block DC and let AC flow through, in this case audio is AC.
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Old 11th November 2003, 04:00 AM   #16
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yeah, i follow that, but still the cap becomes reversed biased on the negative cycle in a split supply. in a single supply the cap is always forward biased because the signal is at an artefical ground of aobut Vcc/2. in a split supply the voltage can swing negative and the cap can thus become reversed biased.
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Old 11th November 2003, 02:47 PM   #17
GregGC is offline GregGC  Canada
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That's why I was going to suggest: Just use single supply voltage instead +/- (simpler power supply too). Bias the +In with the 1/2 of the total voltage and use the output cap if you like it with it.

Greg
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Old 11th November 2003, 02:56 PM   #18
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Quote:
Originally posted by theChris
yeah, i follow that, but still the cap becomes reversed biased on the negative cycle in a split supply. in a single supply the cap is always forward biased because the signal is at an artefical ground of aobut Vcc/2. in a split supply the voltage can swing negative and the cap can thus become reversed biased.

Are we still taking about a bridge? Then, if the left bridge is at +V, and the right bridge at -V, the left side of the cap is + wrt to right side. And vice versa. So, the cap really must be non-polarized.

If we are talking single, non-bridged amp, yeah I agree.

Jan Didden
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Old 11th November 2003, 04:39 PM   #19
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Quote:
Originally posted by janneman



Are we still taking about a bridge? Then, if the left bridge is at +V, and the right bridge at -V, the left side of the cap is + wrt to right side. And vice versa. So, the cap really must be non-polarized.

If we are talking single, non-bridged amp, yeah I agree.

Jan Didden

AC analysis, not DC. bridged or not the cap will reverse bias on half of the cycle. in both cases the cap becomes reverse biased and begins conduction.
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Old 11th November 2003, 05:39 PM   #20
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Huh? If the bridge is properly balanced, there is no DC across the cap, right? Only AC, from the AC load current through the cap AC impedance.

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