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Old 12th January 2018, 02:59 PM   #4321
6L6 is offline 6L6  United States
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F4 power amplifier
BA-3 output stage holds the bias circuit a little differently, look at C1 and the diodes and where the gian stage drives it.

The Output buffers you ask about are all essentially identical - they are IRF240/9240 push pull followers. Followers don't impart much signature at all to the circuit. Which means they will all sound very similar, and that sound will pretty much be like whatever you drive them with.
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Old 12th January 2018, 03:05 PM   #4322
marconi118 is offline marconi118  Germany
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Refering to the BA PP output and gain stage I don't understand your explanation about C1

It seems the same as F4 and M2fig4.jpg

Output_Push-pull.jpg
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Old 12th January 2018, 03:36 PM   #4323
wdecho is offline wdecho  United States
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Quote:
Originally Posted by marconi118 View Post
Refering to the BA PP output and gain stage I don't understand your explanation about C1

It seems the same as F4 and M2Attachment 656383

Attachment 656384
From the Firstwatt BA-3 article.

http://www.firstwatt.com/pdf/art_ba_3.pdf

Coming off the Drain of Q1 is the loading network of R6, C1 and P1, and there is a
comparable network of R7, C2, and P2 attached to the Drain of Q2. R6 clearly sets the AC
load for Q1, but the DC requirements to bias up Mosfet Q3 are higher than that, so P1 in
parallel with C1 provides a higher resistance value below about 0.5 Hz, and gives the
approximately 3 volt DC drop required to bias the Mosfets
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Old 12th January 2018, 03:43 PM   #4324
marconi118 is offline marconi118  Germany
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I am referring to the BA output stage vs the F4 and M2

The BA-3 gain stage is cap coupled to the output stage has nothing to do with bias and ground reference
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Old 12th January 2018, 04:07 PM   #4325
marconi118 is offline marconi118  Germany
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any substitute for input Jfets? as they are only buffer, some lower transconductance jfets could still give good performance
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Old 12th January 2018, 04:13 PM   #4326
Zen Mod is offline Zen Mod  Serbia
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F4 power amplifier
why asking same thing in more than one thread ?

somebody will answer
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Old 12th January 2018, 04:15 PM   #4327
luvdunhill is offline luvdunhill  United States
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Quote:
Originally Posted by Zen Mod View Post
why asking same thing in more than one thread ?

somebody will answer


But... Can it drive a F4?
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Old 12th January 2018, 05:48 PM   #4328
Nelson Pass is offline Nelson Pass  United States
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Quote:
Originally Posted by marconi118 View Post
any substitute for input Jfets? as they are only buffer, some lower transconductance jfets could still give good performance
You can remove them entirely if your source has a reasonably low
output impedance.
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Old 16th January 2018, 03:48 PM   #4329
marconi118 is offline marconi118  Germany
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my source has 10K output impedance
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Old 16th January 2018, 05:46 PM   #4330
Nelson Pass is offline Nelson Pass  United States
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Then you need the Jfets. The raw F4 output stage is OK up to about 1K source.
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