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Old 13th January 2013, 03:57 PM   #3431
Zen Mod is offline Zen Mod  Serbia
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Default Pa sent me F7 Teaser for ya .......



joking , off course

here's quick draw of Sony Vfet complementary F6 concept

time for another public disgrace of Mighty ZM



I'm not going to try it in next ...... 6 months ......... or even later

disclaimer - my main spks are 16 Ohms , so for my needs everything is relaxed , regarding OLG , CLG ,NFB,yukyuk

edit : recommended reading , needed for circuit calc : https://dl.dropbox.com/u/20665608/SONY%20VFET%20AES.rar , tnx to RK R

dunno how long it will be there , so down it

editedit : for sorta useful logic for circ calc , see Pa's BA3 article ; scroll down to my comment , where I done all work , decrypting differences between explanation and schm nomenclature
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Last edited by Zen Mod; 13th January 2013 at 04:07 PM.
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Old 13th January 2013, 04:47 PM   #3432
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Quote:
Originally Posted by Zen Mod View Post


joking , off course

here's quick draw of Sony Vfet complementary F6 concept

time for another public disgrace of Mighty ZM


Thanks Zen Mod for the valuable schematic and info. Best regards.

Last edited by Antoinel; 13th January 2013 at 05:16 PM.
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Old 13th January 2013, 04:47 PM   #3433
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fuuugly

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Old 13th January 2013, 05:16 PM   #3434
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thanks ZM
much for me to chew on
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Old 13th January 2013, 05:28 PM   #3435
Zen Mod is offline Zen Mod  Serbia
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not much for chewing

just look at it in blocks - front same as in F6 , bottom out same , upper out flipped

biasing for bottom - depletion , keeping gate well below source
biasing for top - depletion , keeping gate well above source ( aaargh! I wanna P type toobz !!)

floating bias supply for top , floating bias supply for bottom - each made of 28Vac winding going to Graetz,small cap , then rest - made of small Jfet pushing 10-15mA to TL431 shunt reg , then simple resistive divider for establishing proper bias

luckily - they're saying that Sony VFets are pretty well behaving regarding tempco , so no need for further complication

whatever - as every concept , it needs verification in praxis
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Old 13th January 2013, 05:44 PM   #3436
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not much for you to chew on

for me an entire different story

thanks for the breakdown
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Old 14th January 2013, 10:33 AM   #3437
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back to normal F6 at the moment....!

I just do my second run with the F6 using Permaneders boards....

At the moment I have heavy k2 about 20 -14 db over k3. I already tried different SS pairs.

At the first tries I got only 0,035% THD/1W/8Ohm, I changed later the upper and lower SS and THD went down to 0,012%, very nice!

But why? I thought the circuit is purely symmetric.... why does the place influence so heavy the THD?

May be the circuit is not 100% symmetric because the pots are separate for bias and offset and not like in F5 both pots care for bias and offset equally.....

Next step I have to look if the persistant k2 dominance is coming from an input J-Fets mismatch......
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Old 14th January 2013, 10:55 AM   #3438
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Quote:
Originally Posted by generg View Post
......
May be the circuit is not 100% symmetric because the pots are separate for bias and offset and not like in F5 both pots care for bias and offset equally...........
correct , and not correct

facts :
1. xformer windings are quadrifilar ; that means somewhat highish capacitance between them
2.lower secondary is sort of sitting on lower rail potential all the time , while
3. upper secondary is floating with output potential ;

result: that (2 vs. 3) , and fact that upper biasing net is really using it's bootstrap function , is really introducing capacitance issue in game

whatever - as Pa said - that's not an issue if you are aware of it - sonic results of F6 are confirming that

our beta testing guys ( you know who you are ) already gave us primary info about that ; with your chip about flipping places of SS , we know more



edit: it's much easier to be clever (fart) post hoc ; being clever and make a hoc is where men are different from boyz

your truly , Mighty Boy ZM

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Last edited by Zen Mod; 14th January 2013 at 11:01 AM.
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Old 14th January 2013, 11:54 AM   #3439
generg is offline generg  Germany
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THX very much Zen Mod!

And to understand you 10% more i add this.....!

"In the design and analysis of experiments, post-hoc analysis (from Latin post hoc, "after this") consists of looking at the data—after the experiment has concluded—for patterns that were not specified a priori. It is sometimes called by critics data dredging to evoke the sense that the more one looks the more likely something will be found. More subtly, each time a pattern in the data is considered, a statistical test is effectively performed."

BTW why do you want to take a complementary pair of SITs and no two SK82? Many of us may have at home....
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Old 14th January 2013, 12:17 PM   #3440
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because I have ( well , not exactly "I" , but Bata Bane - he acquired them for rejuvenating his Papa's TA-5650) leftovers - 2+2 pairs ;

whatever - it's easy to accommodate biasing scheme for complementary , taking care of Pa's arrangement (upper ref. to gnd) ; I would still go to both biasing circs based on floating supplies , it's easier to grasp

as I said - it's easy to be smart post hoc
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