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Old 16th April 2012, 09:27 PM   #731
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Next thing he says is he still wants balanced out for duck with shot wing.
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Old 23rd April 2012, 01:33 PM   #732
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So, I've been trying to keep up with this thread but, I have a question I don't remember anyone discussing.
What cap is everyone using for C1 & C2? I don't find many "Audiophile" types that fit the footprint of the DiyAudio store board? It needs to be 13mm or less Dia. The B.O.M. specifies 1000u 25V but no mfg, model etc.etc. I'm not sure how low a voltage you can go there but, under normal conditions 10V or 16V would be safe? Gotta think about that somemore?
Any comments? Suggestions? Thanks
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Old 23rd April 2012, 01:42 PM   #733
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I used Elna 50v. WAY too big. Cant remember if they have smaller varities. Also tried Nichicon, but didnt notice a lot of difference. I am considering smaller Elnas or cerafine for final build.
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Old 23rd April 2012, 01:50 PM   #734
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Yes, I have 1000u 50V silmics and their a littlle big for the board. I do have a 2200 25V Rubycon Low ESR (Black Gate mfg'r) that almost fits. I also have a few 470 in Silmic and Cerafine @ 16V I may try???
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Old 23rd April 2012, 03:00 PM   #735
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Quote:
Originally Posted by flg View Post
What cap is everyone using for C1 & C2? I don't find many "Audiophile" types that fit the footprint of the DiyAudio store board?
its in series with power supply

why would you need it to better than the supply caps



I will use the new compact brown Panasonic FR type

105 degr, long life, high ripple current, low ESR

what else counts
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Old 23rd April 2012, 04:35 PM   #736
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Quote:
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its in series with power supply

why would you need it to better than the supply caps
The power supply, under certain conditions, may apppear totally across one component. What might that be 50V??? I don't see an expected condition where that might happen with C1 & C2 in this circuit though. But, all those unexpected things are hard to imagine. We ussually think of normal operation, and not necessarily start-up or shut down or hi-cup on-off behaviour etc. etc.???

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I will use the new compact brown Panasonic FR type

105 degr, long life, high ripple current, low ESR

what else counts
Well, ESL is also important but, when it comes to caps, some people think they hear all kinds of stuff that's wrong but, sometimes no stuff, depending on the cap, the dialectric etc. I'm not sayin anything new here. But, we want that cap to be totally inert as it deals with the input signal as a short to Power supply, AC gnd. In other words, the cap is invisible to AC and imparts no non-linearities on the F.E. signal being passed to the output FETs. 1000uF is only available in electrolytic, which have a questionable audiophile performance. However, there is a Silmic looking cap in N.P.'s pic of his board. What's that cap???
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Last edited by flg; 23rd April 2012 at 04:38 PM.
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Old 23rd April 2012, 04:49 PM   #737
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....... as it deals with the input signal as a short to Power supply, AC gnd.
its in paralel with bias pot, which is basicly a resistor
wouldnt the pot 'take over'
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Old 23rd April 2012, 06:11 PM   #738
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There is a Silmic II Elna cap that is 16 MM diameter 1000uF 25 volts. Digikey P/N is 604-1059-ND.
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Old 23rd April 2012, 06:37 PM   #739
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The signal's current variation see's the 100 ohm and then the C||500 pot. But, the C||Pot has the Xc of the cap dominating. Probably equal to a 250 pot at 2Hz. Above 2 Hz it's impeadance is a closer to a short cicuit to the power supply. But it blocks the DC needed to help bias the ouput FETs. That DC is added to the 100 ohm DC drop to form the output stage bias. Adjust the 500 ohm pot controls the DC but at audio freq.s does nothing (we hope).
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Old 23rd April 2012, 06:44 PM   #740
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Try to put two 16mm caps on that footprint and they probably won't fit. they will hit each other and the pots.
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