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#1
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Double primary windings in SE output transformers
Is it possible to prevent pre saturation of a SE output transformer by
adding an identical primary winding which has a steady DC flowing in opposite with the original primary? What is the disadvantages of it other than higher cost? Any successful project made? |
#2
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"·à¤l¤f" Is it possible to prevent pre saturation of a SE output transformer by adding an identical primary winding which has a steady DC flowing in opposite with the original primary? What is the disadvantages of it other than higher cost? ** How do you intend DC current be passed through the extra winding ?? From a PSU or a battery ?? That would place a hard short on the winding and since all windings on the same core are magnetically coupled that shorts out the tranny. If you did it with a tube set up as a current source - then PP operation is just a tiny step away. Maybe it could be done with a large, suitably gapped, iron core inductor in series with the winding - bit like another SE tranny - but why bother ? .......... Phil |
#3
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Here's a forum thread on the exact topic.
http://geek.scorpiorising.ca/cgi-bin...m=10896598 61 -- Gregg t3h g33k "Ratings are for transistors....tubes have guidelines" http://geek.scorpiorising.ca |
#4
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"·à¤l¤f" wrote: Is it possible to prevent pre saturation of a SE output transformer by adding an identical primary winding which has a steady DC flowing in opposite with the original primary? The extra winding will need to be equal turns to the P winding, and take up a lot of room, and it will need a CCS feed which is capable of standing the B+ voltage and the 200 vrms signal swings. But if the anode current is 70mA, and P to S OPT turn ratio was 25:1, then 25 x 0.07A = 1.75 amps could be sent through the secondary from a CCS using SS devices. But since the sec has some DCR of say 0.2ohms, then 0.35DV appears at the sec, which makes a DC current in the speakers, so cap coupling with 10,000 uF is needed to the speakers. What a hassle! After going to all that trouble, there would be only a marginal thd improvment. at mainly lower F, since the tube thd dominates the thd. If you don't want DC in the OPT core, use a para feed choke to get the DC to the tube anode, using a choke at least as big as the SE OPT, and then cap couple a normal PP output transformer from the anode, which can be set up as an auto transformer with P in series with S and the S grounded. Patrick Turner. What is the disadvantages of it other than higher cost? Any successful project made? |
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