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Old 11th February 2012, 10:27 PM   #11861
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While you here
what would be the efect of using mosfets with Ciss of about 2500 pf on F5
they came in TO3P packs which current wise is nice?

also dumb.....
o YEAH

Last edited by Bksabath; 11th February 2012 at 10:33 PM.
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Old 11th February 2012, 10:31 PM   #11862
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Quote:
Originally Posted by UKToecutter View Post
Has anyone considered using FQA36P15 and FQA28N15?

Would they be suitable replacements for output devices?

Andy
Those ones
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Old 11th February 2012, 10:38 PM   #11863
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Quote:
Originally Posted by Bksabath View Post
While you here
what would be the efect of using mosfets with Ciss of about 2500 pf on F5
they came in TO3P packs which current wise is nice?

also dumb.....
o YEAH
just turn on your own dumbness , and co-relate Ciss vs. xconductance vs. No. of needed mosfets vs. max allowable dissipation per device

piece of cake
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Old 11th February 2012, 10:50 PM   #11864
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Yeah if one just had a clue of what all tose things with big words mean it would not have to ask dumb questions.

Xcnductance may go avay with more gain on decent pre but capacitance may trow spanner in to works.

Me prety good with spanners
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Old 11th February 2012, 10:59 PM   #11865
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by Bksabath View Post
.....

Xcnductance may go avay with more gain on decent pre
.....
nope

you need to observe F5 in isolation

xconductance , considering OLG vs. CLG vs. feedback

generally-if you lack in xconductance of output sage , or if you have higher than desired capacitance of output stage , you can partially compensate that with increase of xconductance of input stage ...... and way to do that is to double No. of input Jfets
or just use 2SJ74P and 2SK170P ; all problems will be solved
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Last edited by Zen Mod; 11th February 2012 at 11:01 PM.
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Old 11th February 2012, 11:12 PM   #11866
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Quote:
Originally Posted by Bksabath View Post
the efect of using mosfets with Ciss of about 2500 pF on F5
Ciss = Cgs + Cgd. Crss = Cgd.
Ever wondered why the P-channel is mounted with it's source to the positive rail, and the N-channel with the source to negative rail ?
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Old 11th February 2012, 11:31 PM   #11867
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Tanks Zen and Jaco
will have to ponder about that for a while (was looking for smiley with smoke comming out of head as it would be most apropiate LOADS of SMOKE).
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Old 12th February 2012, 06:47 AM   #11868
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Speaker return sees heavy currents causing voltage drops on its path that are not welcome on the input ground.
No need of a speaker return on the pcb. Can be wired at main star ground, leaving input ground clean.
At least separate ouptut ground path from input ground path.
Same for qround side of decoupling caps. Not clean. They need to have their own path to ground.


Quote:
I don't think miliampere would cause problems
look at current flowing through R7, R8, R3 when output is near positive rail.

Last edited by bobodioulasso; 12th February 2012 at 07:05 AM.
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Old 12th February 2012, 07:44 AM   #11869
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Hi people!
I need schematic and PCB for this F5 audio amplifier!
Thank you all for help
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Old 12th February 2012, 07:52 AM   #11870
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Chchyong
Your layout deserved a deeper looking at.

It'is very nice all in all.

Formula 22
Google "Firstwatt"
And search for Cviller's blog on Diyaudio
All is there.

Last edited by bobodioulasso; 12th February 2012 at 07:55 AM.
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