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Coupling Caps

post #1 of 5
8/27/04 at 9:33pm
Thread Starter 
What do these do?

I know that there are some in my power amp, and that better ones would improve the sound, but what is it that the coupling caps are actually doing?

Thanks to any and all,

Mark
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post #2 of 5
8/28/04 at 8:10am
Coupling capacitors remove the DC component from an audio signal, which you want to be AC. If the input has DC offset, that offset is amplified by the full gain of the amplifier to give a much larger DC offset at the output which can harm the speakers. Also, in single ended designs the output has half the supply voltage present at the output as DC, so the capacitor there is essential otherwise you'd fry your equipment... Also, the coupling cap will determine the bass roll off frequency, so if you're going to replace them, get the largest value in your chosen series that will fit.

g
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post #3 of 5
8/28/04 at 8:43am
Thread Starter 
Thanks for the "what they do" explanation.

Your comment about sizes interests me - I have a Teac Tripath amp, and am having the coupling caps replaced.

Do you mean that if say a 2.2 is the spec, that if a 3.0 will fit to use it?

Mark

PS - suggestion on brands? Auricap, Musicap...
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post #4 of 5
8/28/04 at 6:24pm
I used Sonicaps made my Sonicraft for restoring my H.H. Scott LK-48 (222c). They are said to be just about as good as Auricaps, but at a fraction of the price. I replaced 10 .1uF 600V caps and 4 .022 uF 600V caps in my amp, and it only cost about $75 with shipping. They are a good option for a lesser price without compromising the performance. Their site is http://www.gr-research.com/SoniCap.htm . Hope that helps!

-Dan
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post #5 of 5
8/28/04 at 7:23pm
I can't advise on specific caps as I don't have much experience in this area, but you'll have to see how much space you have to play with. The difference between 2.2uF and 3uF will be small at the input to the amp, as the resistor in the R-C network will likely dominate. Say the resistor going to ground is 1M ohms, the rolloff freq. for 2.2uF would be .07Hz, and for the 3uF it would be .05Hz; I challenge you to hear the difference. On the output however, it is the capacitor which is like to dominate, especially at lower C values. Btw, the formula is:

f = 1/(2(pi)*R*C)

For the output of an amp, R is equal to the impedance of the speaker

g
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