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Old 23rd January 2009, 01:27 PM   #1
ak4396 is offline ak4396  Germany
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Default I need help with build my F3

Hello,

first sorry for my bad English.

When I adjust the Aleph CCS to 50% ,ca.3,3KOhm for R18 + P2 in Original, and greater the F3 swing. I think I did some wrong in my Layout. Can anybody help me?

I made my own PCB for the F3 because I want learn.

Thanks

The PCB:
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Old 23rd January 2009, 06:38 PM   #2
ak4396 is offline ak4396  Germany
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LS
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Old 23rd January 2009, 06:38 PM   #3
ak4396 is offline ak4396  Germany
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SP
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Old 23rd January 2009, 06:51 PM   #4
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When you say the greater the swing, do you mean greater gain and/or
maximum output? This is normal and intended.

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Old 26th January 2009, 02:31 PM   #5
ak4396 is offline ak4396  Germany
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Sorry, I mean oscillation not swing.

When I turn the P2 < ca.3k (R18 + P2 < 4,5k) the F3 start to oscillate.
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Old 30th January 2009, 01:54 AM   #6
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At what approximate frequency does it oscillate?

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Old 30th January 2009, 06:50 AM   #7
ak4396 is offline ak4396  Germany
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I tried a Capacitor between the B and C of the NPN-transistor in the CCS.
With out this C it oscillates at about 200 kHz and with 1nF at 25 kHz (Aleph CCS at 50%).
With 4,7nF the F3 is completely stabile no meter where the P2 stay.
But the bandwidth gets down.
I think I make a new Layout like Peter Daniel.

Can I change the values of the Feedback Resistors 9k to 6,19k and 47k to 31,6k to increase a little bit the bandwidth with out Problems? I think my pre amp will do this (200Ohm output impedance).

With the Aleph CCS at about 10% (no oscillation) it sounds very good. I hope I can hear the F3 with 50% Aleph as soon as possible.
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Old 30th January 2009, 08:51 PM   #8
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I see that your C19 at .1uf is lower than the 10uf in ZV9. Perhaps
you should try the higher value.

Alternatively try a CE cap instead of a CB cap.

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