Mylar cap polarity - Help [message #9047] |
Wed, 29 June 2005 17:12 ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
colinhester
Messages: 1349 Registered: May 2009 Location: NE Arkansas
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Illuminati (3rd Degree) |
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Just some 10uF 400VDC mylar caps and there are no polarity markings. How do I tell which end is which? I contacted the seller and he was not quite sure either and emailed the mfg......Colin
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Re: Mylar cap polarity - Help? [message #9050 is a reply to message #9048] |
Wed, 29 June 2005 21:50 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Poindexter
Messages: 108 Registered: May 2009
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Viscount |
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What about the outer foil / inner foil thing? You know anything about this? When I use nonpolarized caps, I just make sure that they are (channel-to-channel) oriented the same; I send the signal down the print on the outside, presuming that they are manufactured consistently. I am presuming presumptuously? Heh, Poinz
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Re: Mylar cap polarity - Help [message #9051 is a reply to message #9049] |
Wed, 29 June 2005 22:09 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Steve
Messages: 83 Registered: May 2009
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Viscount |
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Hi Colin, Some manufacturers specify which way to connect the cap, while others don't. I know one brand that outer wraps the caps randomly, so it is an individual cap situation. Mylars may not be that critical as there sonic signature is usually fairly strong. ![](http://www.audioroundtable.com/emoticons/smiley.gif) Take care. Steve
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Re: Mylar cap polarity - Help [message #9052 is a reply to message #9051] |
Thu, 30 June 2005 10:24 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Thermionic
Messages: 208 Registered: May 2009
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Master |
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Which direction the cap is installed won't make a difference in the sound, but which way it's installed WILL make a difference in how much noise can be coupled into the cap, which will of course indeed make a difference in sound. Always connect the outside foil to the lowest impedance, not the lowest voltage as many recommend. Voltage has nothing to do with it, it's the lowest *impedance* that you want! That'll most always be the plate of the first stage, versus the control grid of the second stage. The control grid is an extremely high impedance itself, with (usually) a bare minimum of 100K all the way up to a 1 Meg resistor to ground. OTOH, the impedance of the first driver stage (which is the product of the internal plate resistance in parallel with the load resistor), will most always be much lower. Even a very high plate resistance triode like a 12AX7 will only have about 40K output Z when the cathode resistor is bypassed, unbypassed still less than 70K depending on the cathode resistor value. So, the outside foil goes to that side for the best electrostatic shielding. Thermionic
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Re: Mylar cap polarity - Help [message #9053 is a reply to message #9052] |
Thu, 30 June 2005 11:11 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Steve
Messages: 83 Registered: May 2009
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Viscount |
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Yes, it can make a sonic difference/sound, depending on the quality of the cap and quality of the components. A low value capacitor, say 0.05uf is generallly more critical in respect to the outer foil vs a higher value cap, say 2.0uf. The outer foil should be to the lower Z for sure if the cap is small. Good shielding and design will minimize or eliminate noise, interference problems to begin with. Take care. ![](http://www.audioroundtable.com/emoticons/smiley.gif) Steve
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