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 3rd October 2012, 01:52 PM #2211 kasey197 The Dastardly Dad of Three diyAudio Member   Join Date: Sep 2009 If the parasitic capacitance is a major issue as you suspect, then you could use two separate transformers for the two halves to prove the point either way, esp as you have two of the jensens already... Just my 2 cents ...
lhquam
diyAudio Member

Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
If two transformers are used in the way shown in the F6 Conceptual Schematic, there is still a problem. The AC voltages between the secondaries and the primaries are different. The top trafo has (Gain-1)*Vin AC voltage. The bottom trafo was -Vin AC voltage. If the Gain is chosen to be one, then the interwinding currents will cancel, otherwise they will not.

Quote:
 Originally Posted by kasey197 If the parasitic capacitance is a major issue as you suspect, then you could use two separate transformers for the two halves to prove the point either way, esp as you have two of the jensens already... Just my 2 cents ...

lhquam
diyAudio Member

Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
The sweet spot?

If the "spare" transformer winding is connected to a resistor divider generating (approx) Vout*(Gain-1)/Gain as shown in the schematic below, the interwinding parasitic currents are nulled.

I used a potentiometer to adjust the resistor divider ratio and generated the following harmonic distortion sweeps with slightly different adjustments of the Zen amount pot.

If you want to add more 2nd harmonic, use the Zen amount pot to increase it.
Attached Images
 F6-txmod-2-cleaned-sch.jpg (68.7 KB, 432 views) F6-PCB2-Rs0R12-Gain-5-Txmod2.jpg (152.9 KB, 426 views) F6-PCB2-Rs0R12-Gain-5-Txmod2c.jpg (156.8 KB, 400 views)

 3rd October 2012, 05:42 PM #2214 Zen Mod   Official Court Jester diyAudio Member     Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain I like that mid pic regarding parasitic cap. of winding - moi thinks that we are splitting da hair can you hear difference ? __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
 3rd October 2012, 06:44 PM #2215 BudP   diyAudio Member     Join Date: Feb 2007 Location: upper left crust, united snakes Zen, consider the 3.5k to 90k multiplication factor provided by the core, to any irregularity in the B Field transform from antenna to antenna up through 3.5 kHz. Then consider that it is physically impossible to wind quadfiller and keep all wires where they should lay. You can get a bifillar winding to couple perfectly, or very nearly so. You cannot say the same for four wires, wound into a narrow winding well, guided by either delicate fingers or uncontrollable mechanical traverse. The graphs shown will sound different, if for no other reason than where the differences are in the FR. Contemplate the differences heard between two drivers, one with an uncorrected initial 4 ms response and one with a 4 ms response corrected with manic spots. __________________ "You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
 3rd October 2012, 06:59 PM #2216 lhquam   diyAudio Member   Join Date: Mar 2010 Location: Olalla, Oregon: Land of the 100 Valleys In post #2213 I forgot to mention that the graphs were NOT from simulations, but actual measurements.
 3rd October 2012, 08:22 PM #2217 generg   diyAudio Member     Join Date: Jul 2009 Location: Near Frankfurt I can confirm by experiment today that the Zen Pot is a fine way to trim distortion level and spectra even in the case of feedback with Mufollowers like SIT2 (NFB) and J2 (FB) the link again... L'Amp: A simple SIT Amp __________________ and the First Wtt is......a really First Class PSS Idea
 3rd October 2012, 08:45 PM #2218 Nelson Pass   The one and only     Join Date: Mar 2001 You are overlooking another location for trimming the cancellation, which is resistance across the secondary coils. Typical values would be on the order of 200 ohms or more.
 3rd October 2012, 09:02 PM #2219 generg   diyAudio Member     Join Date: Jul 2009 Location: Near Frankfurt Mostly I have no overlook.... especially in the case of F6. Still fixed on J2 and Mikes SIT amp I confess. Thanks for the hint...... __________________ and the First Wtt is......a really First Class PSS Idea
lhquam
diyAudio Member

Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
I briefly experimented with that in the early days of my Teaser-6 build, but other parameters were too far from the "sweet spot" at the time to detect an improvement. I will experiment with it again.

Quote:
 Originally Posted by Nelson Pass You are overlooking another location for trimming the cancellation, which is resistance across the secondary coils. Typical values would be on the order of 200 ohms or more.

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