I need help with build my F3

ak4396 · 23rd January 2009, 01:27 PM

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:

ak4396 · 23rd January 2009, 06:38 PM

LS

ak4396 · 23rd January 2009, 06:38 PM

SP

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.

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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23rd January 2009, 06:51 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	When you say the greater the swing, do you mean greater gain and/or maximum output? This is normal and intended.

26th January 2009, 02:31 PM	#5
ak4396 diyAudio Member Join Date: Feb 2008	Sorry, I mean oscillation not swing. When I turn the P2 < ca.3k (R18 + P2 < 4,5k) the F3 start to oscillate.

30th January 2009, 01:54 AM	#6
Nelson Pass The one and only Join Date: Mar 2001	At what approximate frequency does it oscillate?

30th January 2009, 06:50 AM	#7
ak4396 diyAudio Member Join Date: Feb 2008	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.

30th January 2009, 08:51 PM	#8
Nelson Pass The one and only Join Date: Mar 2001	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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