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F5X -- the EUVL Approach
F5X -- the EUVL Approach
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Old 18th December 2014, 08:17 AM   #871
marconi118 is offline marconi118  Germany
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Join Date: Mar 2008
can I use passive virtual ground? what would be the max value of the 2 resistors?

What feedback configuration will be the most stable and have the less THD?

H connected to ground

Pass H lifted from the ground

X lifted from ground (in this case only the gate resistor of the input will go to the virtual ground ?)


with P3 on each side to try null out 3rd harmonic?
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Old 18th December 2014, 01:12 PM   #872
EUVL is offline EUVL  Europe
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H & X lifted are the same, and marginally better with distortion.
Grounded X is most stable. But it is then essentially 2x Singled Ended F5.

P3 will NOT null 3rd Harmonics. Nothing will.

I already told you how I would use a single 40V supply.
I have not changed my mind, but you are welcome to experiment anyway you like.
And always welcome to come back and tell us your results.


Patrick
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Old 18th December 2014, 02:01 PM   #873
marconi118 is offline marconi118  Germany
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is P3 needed for the X lifted config?

Will it help a bit n reducing THD?



Will experiment and report on it.


does the 220ohm resistor from output to ground improve symmetry?
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Old 18th December 2014, 02:13 PM   #874
EUVL is offline EUVL  Europe
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P3 has no use in F5X if you match your NN & PP devices properly.
The intrinsic symmetry of the F5X will cancel even harmonics.

The 220R at the output provide a Gnd reference for the output.
You may also argue that it is unnecessary theoretically.

Try to understand the circuit, and perhaps do some simulation first.
Getting simple answers from me does not help you to understand how it works.


Patrick
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Old 9th January 2015, 08:21 PM   #875
marconi118 is offline marconi118  Germany
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thanks a lot for help, then I will still try to find a centre tapped transformer.


Another question,
Can I use 2 J74gr in parallel with equal Idss of the K170 ?

Maybe the gm of it will be higher than the K170, then I need to follow your degenerating trick.

But in this case how to calculate the value of the extra source resistor? and what should be the Idss of the 2 combined J74gr? still 0.8mA more then the K170? or even more?

This is difficult for me to calculate... it is over my skills.

this info could help others to build F5 with j47gr still available on the market
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Old 9th January 2015, 09:06 PM   #876
EUVL is offline EUVL  Europe
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You can use 2K170GR together with 2J74GR with matched Idss.


Patrick
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Old 10th January 2015, 11:03 AM   #877
marconi118 is offline marconi118  Germany
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but I have k170BL to combine with j74GR
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Old 20th October 2015, 07:48 PM   #878
EUVL is offline EUVL  Europe
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Join Date: Oct 2003
For completeness, here an active replacement for 2SK1530/2SJ201 -- 3x FQP3N30/FQP3P20 in parallel.
True complementary.

http://www.diyaudio.com/forums/pass-...ml#post4489384


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