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Old 25th May 2005, 03:10 PM   #1
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Default CD player output caps - calculations

I am about to upgrade the stock electrolytics on the output of my player. They are 220uF Nichicon Muse, bypassed with 0.47uF MKP caps. I think to replace them with 3-4uF (>4uF are too expensive for my budget) film and foil Multicaps without additional bypass. The problem is that I don't know how to calculate whether ~3-4uF is enough capacitance to avoid audible bass roll-off. My tube amp next to the player has about 50k input impedance. If 3-4uF is not enough I could buy 10-15uF lower grade metallized polypropylene Multicaps instead.

Does anybody could help me to calculate the output caps value? Thanks in advance.
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Old 25th May 2005, 03:52 PM   #2
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The cutoff frequency fc of a first order low pass is given by

fc = 1 / (2 * Pi * R * C)

If you rearrange the formula you can calculate C

C = 1 / (2 * Pi * R * fc)

Assuming that fc should be 5Hz max. your Cap must have at least 636nF. 3 to 4F should be sufficiant for your player.
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Old 26th May 2005, 08:24 PM   #3
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If the pre-amp has input caps, why do you need output caps in the CD player? Aren't they redundant?
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Old 27th May 2005, 06:17 AM   #4
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My pre-amp doesn't have input caps.
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Old 28th May 2005, 09:32 AM   #5
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Check resistor value to ground in the CD-player.
This should be from output to ground somewhere after the capacitor.
Often this is 10k or similar. In my experience this is not good.
Dont know why they are doing this. 100k is a lot better.
Not only can you use a smaller, better quality capacitor, but it also improves sound quality in terms of dynamics, headroom etc.

If you want no influence from Fc on frequency response, Fc should be around 1/10 of the lowest frequency you want to reproduce .
So if you want 30Hz with no roll-off go for 3Hz as Fc etc.

MultiCap RTX are very good but fairly expensive. Mundorf silver capacitor might be very good, but I havent tried them.

For those so inclined Black Gate migth work, but they have some high frequency coloration or something. Sanyo SEP seems good, but I havent listened to them yet for more than a couple of hours.
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Old 28th May 2005, 02:37 PM   #6
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Any body tried bypassing the Black Gate or Tonerex with small value silvered mica? (I know, it sounds like silver!). There could be worse things.
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