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ak4396 23rd January 2009 01:27 PM

I need help with build my F3
2 Attachment(s)

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.


The PCB:

ak4396 23rd January 2009 06:38 PM

2 Attachment(s)

ak4396 23rd January 2009 06:38 PM

2 Attachment(s)

Nelson Pass 23rd January 2009 06:51 PM

When you say the greater the swing, do you mean greater gain and/or
maximum output? This is normal and intended.


ak4396 26th January 2009 02:31 PM

Sorry, I mean oscillation not swing.

When I turn the P2 < ca.3k (R18 + P2 < 4,5k) the F3 start to oscillate.

Nelson Pass 30th January 2009 01:54 AM

At what approximate frequency does it oscillate?


ak4396 30th January 2009 06:50 AM

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. :cloud9:

Nelson Pass 30th January 2009 08:51 PM

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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