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In Reply to: RE: Using toroid AC mains tranny for output transformer question??? posted by grhughes on July 01, 2012 at 05:44:04
I have used 50VA units before as SE output transformers either parallel feed or using a secondary fed with a high impedence to offset DC in the primary . 230:6+6 can be used with secondaries in series in place of a 3k TX in parafeed or 230:9+9 can be used as a 5K unit if a secondary is used as offset winding . What limits the useability is the primary inductance and saturation , so best to use low Ra valves and use for low power applications . 50VA units have a good 25H in the primary , it is unlikely that 70/100V matching transformers will exhibit anything like this (or have top end as extended as toroids)
Al
Follow Ups:
Al,Have you measured any matching transformers, or done an A/B comparison with a toroid of the same turns ratio?
I think wer're, obviously, talking parafeed here...
Edits: 07/02/12
I only have some 1w/5w matching transformers . The 5W tap works out approx 2k with 2H primary inductance (no DC) . These are small , the top end is nice and extended although these do fall apart under 100Hz .
Al
Ideally I would like to replicate the Raven output stage using 5687 as per Lynn Olsen. Or applying B+ to the CT of the primary so it has to tolerate Dc in the primary. The Sowter tranny is just kind of expensive, but I may have to use it. Thanks, Ray
"The gift of imagination is a gift of the Gods imparted to a few who receive innumerable kicks in the a$$ their entire life." Le Corbusier (Charles-Édouard Jeanneret)
You can get speaker matching transformers online
from companies like Atlas Sound.Radio Shack also has
one for 10 bucks but it's online only.I would not
spend too much money at first because you want to
make sure the transformer will work for what you
want it to do.If the results are good then you can
spend more money for a higher quality transformer.
Regards,
Swanson
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