1:1 quadrifilar wiring

[Winston OBoogie]

Indeed: too much negative impedance turns the circuit into an oscillator.

Hehe, yep.

 

[Tubetec]

Quadrifilar 1:1 sounds dicey to do right  , dual bobbin on a UI core seems to offer better capacitive balance and better values of induced noise for a simpler winding topology ,

Is it not feed forward turns your circuit into an Oscillator? negative impedence is a concept I've had trouble trying to visualise .

 

[Winston OBoogie]

Is it not feed forward turns your circuit into an Oscillator? negative impedence is a concept I've had trouble trying to visualise .

Negative impedance does sound a bit like parallel universe stuff     
Using the simpler unbalanced drive drawing from the Lundahl pdf , think of the sense R as being the source of current positive feedback .  As long as this +tve fb loop gain is less than unity in reference to the normal negative feedback loop, it won't oscillate.  Which is why I said best to err on the low side if in doubt. 

 

[Winston OBoogie]

Reading back, it occurred to me that my explanation above is very possibly a sh*te one and I've not cleared anything up at all.  It'll have to do until another comes along as it's now gone 3 a.m. and I'm about to put this glass of Maker's Mark down...  my neck and then going to bed. 

 

[Tubetec]

I get the unbalanced drive bit , I can clearly see how a dual coiled choke can balance its capacitance to way less than a single coil between ground and signal+, I can measure it with an LCR and see the pair of windings in series amount to a tiny fraction of the capacitance of either measured seperately , Ive certainly seen crumby layout turn what looks like normal circuits into Cap'n foldbacks  ;D ,even the purple feedback wire in a Marshall is pickey about how it finds its way back to the phase invertor, on one or two troublesome specimens Ive replaced said unscreened purple wire with single core screened to good effect.Makersmark is indeed a fine supeen, carefull with that axe eugene 

 

[Winston OBoogie]

Makersmark is indeed a fine supeen, carefull with that axe eugene 

Had to google to remind me where the reference was from:  Pink Floyd.  Nice one

 

[abbey road d enfer]

Quadrifilar 1:1 sounds dicey to do right  , dual bobbin on a UI core seems to offer better capacitive balance and better values of induced noise for a simpler winding topology ,

Quadfilar yields very high coupling coefficient, thus very small leakage, hence very good HF response.
It does not seem too difficult. I had three winders making them for me; no one complained, they all seem to consider it a normal job.