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Old 14th August 2012, 10:39 AM   #11
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Have you got Ci fitted that is on your circuit ?
Yes Ci is fitted.

Beside of changing the gain of the amp, do i have the option to change Rin from 1K to 0,5 in order to increase the input sensitivity?
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Old 14th August 2012, 10:57 AM   #12
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Altering the 1K Rin won't make any audible difference. Levels have to change a lot for our ears to notice, far more than tweaking that 1K will make.

Again on practical matters...

Ci will probably need to be increased in value to compensate for the lower value of the feedback resistor. Unless you have something oversized in there anyway. Not doing so will cause the bass response to roll off that bit earlier. So doubling the value would make sense.
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Old 14th August 2012, 09:10 PM   #13
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if i remember correctly, i believe i used the values suggested by the chematic.
ci = 110 μf non polar for the woofer channels.
ci= 10 μf for the tweeter channels.

what values you suggest?
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Old 15th August 2012, 05:25 AM   #14
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I like the MooseFet preamp from Classic Valve Design, available as just a board, or with some parts. I have IRF510 fets on mine.
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Old 15th August 2012, 06:40 AM   #15
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by zakman35 View Post
if i remember correctly, i believe i used the values suggested by the chematic.
ci = 110 μf non polar for the woofer channels.
ci= 10 μf for the tweeter channels.

what values you suggest?
Go to the next preferred values, so that's 220uf (two 470uf's to make bi-polar) and 22uf (or two 47uf for bi-polar).
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Old 16th August 2012, 06:26 AM   #16
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Ok, thanks.
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Old 17th August 2012, 07:57 AM   #17
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One more question,
how important is the quality of the caps at this position and what caps do you suggest me to use?
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Old 17th August 2012, 08:37 AM   #18
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CI (NFB cap) is a cap at the inverting input and that is exactly as important as any other input cap. This is a good spot to test drive a couple of different options and to try a tiny bypass cap all for the purpose of finding out what you like best.
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Old 17th August 2012, 08:54 AM   #19
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Can you give a place to start?

Nichicon Muse for instance would be an option?
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Old 17th August 2012, 09:41 AM   #20
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Standard commercial/industrial grade electrolytics works well in this location.
But if you make the electrolytic value too low, then it can have avoidable voltage across it and that voltage gives rise to avoidable distortions.

Make the cap big enough and you don't need fancy priced capacitors.
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