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Old 3rd July 2014, 10:01 PM   #21
6L6 is offline 6L6  United States
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...and after playing with P3 on the F5T and BA-3, I can say that personally, tuning for minimum THD does not sound the best to me.
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Old 3rd July 2014, 10:03 PM   #22
Zen Mod is offline Zen Mod  Serbia
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thus , interesting choice for Rs ,up and down
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Old 3rd July 2014, 10:54 PM   #23
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Quote:
Originally Posted by AudioSan View Post
maybe move the inner transistor 40mm closer to the transformer, for more effective use of the sinks?
For clarification, for inner transistor you mean Q1 ? And by mean transformator you mean Jensen or toroid ?

Didiet
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Old 3rd July 2014, 10:55 PM   #24
rayma is offline rayma  United States
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Originally Posted by Nelson Pass View Post
You are welcome to put more current through them, but any noise is not going to make it
through the 10K + 1,000 uF RC filter, and if it did it would be taken down another 20 dB
or so by feedback.

Yes, I was mostly concerned about the soft voltage regulation with such low current. The gate bias voltage would drift around somewhat with power supply variations. Maybe 3 series red LEDs could be used in place of the zeners?
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Old 3rd July 2014, 10:56 PM   #25
Zen Mod is offline Zen Mod  Serbia
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yup

he meant Q1 closer to Jensen
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Old 3rd July 2014, 11:01 PM   #26
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Originally Posted by didiet78 View Post
For clarification, for inner transistor you mean Q1 ? And by mean transformator you mean Jensen or toroid ?

Didiet
yes. Q1. and Jensen transformer.
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Old 3rd July 2014, 11:19 PM   #27
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Moving Q1 and R12.
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File Type: png F6 Super long Rev01.png (164.6 KB, 673 views)
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Old 3rd July 2014, 11:28 PM   #28
6L6 is offline 6L6  United States
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Didiet - I like it.
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Old 4th July 2014, 12:22 AM   #29
PKI is offline PKI  United States
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I would move the trace for the Q2 gate resistor (R12) to the top of the board, so you don't need to bite a piece of the source trace. You can easily do it in the center of the board, nothing on the bottom layer there.

Ok, I see the difficulties, but give it a though! :-)
1) Move Gate traces on the top?
2) Make a turn around 7 and 8 pin of the input transformer to put that gate trace above. Does it make any sense? (Still at work... brain is melting) ))

Last edited by PKI; 4th July 2014 at 12:29 AM. Reason: opened my eyes wider :-)
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Old 4th July 2014, 02:09 AM   #30
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Originally Posted by 6L6 View Post
...and after playing with P3 on the F5T and BA-3, I can say that personally, tuning for minimum THD does not sound the best to me.
Just curious. Did it sound best (to you) when you adjusted P3 to emphasize the second over the 3rd harmonic? Did you find any advantage of adjusting P3 over initial settings, with equal resistance on each side as best you could measure?

Steve
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