C1 in META42 value?
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finleyville

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I just realized that I accidently ordered 0.1uF Orange Drops for C1. Is this enough or do I need to reorder 0.47uF?
 
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morsel

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In my opinion .1µF is ususally grossly inadequate, but it depends upon the value of R2. This is discussed on the META42 part selection advice page right at the top:

http://www.tangentsoft.net/audio/meta42/advice.html

I think the -3db point should be 1Hz or less, some people feel it should be lower still. Realize that even if you are only 1db down at 10Hz you are still affecting the phase as well as the amplitude of bass signals way into the audio range. For tight, accurate bass, you need the lowest corner frequency you can get.

My amp uses a 4.7µF polycarbonate film C1 and a 1M R2. Plugging that into the formula Fo=1/(2PiRC) the resulting corner frequency is .034Hz, plenty low for my purposes.

If you know your sources are free of DC you can omit the coupling caps completely, for superior sound. C1 is only there to protect your headphones from destructive DC levels.
 
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finleyville

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Well, if I use those 0.1uF for C1 and a 1M for R2, I should get around 1.59 Hz. Now I figure that I'll probably get a rolloff somewhere in the 20's Hz region and a phase shift higher than that. But is the capacitance high enough for block DC voltage? I am a little unclear of how it accomplishes this. Thanks.
 
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morsel

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Since a capacitor is two metal plates in close proximity separated by an insulator, it will not conduct DC. The capacitance has nothing to do with it.

The Art of Electronics is really worthwhile reading, btw. I encourage you to read more about electronics if you are going to build stuff like headphone amps.
 
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finleyville

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Most of the components I do understand their basic construction and function. Now their utilization in circuits and how they accomplish their tasks is another thing altogether.
 
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tangent

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I think you're all right with 0.1uF if you use a 1M R2. But for what it's worth, if you did convince yourself that you needed a 0.47uF Orange Drop 715P, I would caution you that these things are positively huge -- thicker than a man's thumb, and nearly as long! They can be made to fit, but it's rather tricky.
 
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finleyville

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Nah, the 0.1uF's are already on their way. I listed my complete parts list here.

Let me know please if you see anything amiss...
 
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