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Old 3rd April 2011, 07:49 PM   #1
tinitus is offline tinitus  Europe
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Default OPT with cathode feedback

hey, I remember a thread with members debating this
but can't find it

and that noone produce those trafos anymore

well, Amplimo makes them now
and holds the patent too

if some could link to that thread, I will remove this one
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Old 3rd April 2011, 08:06 PM   #2
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You jay use an ordinary transformer with 4 and 16 Ohm secondaries for push-pull cathode feedback.
For SE cathode feedback any secondary may be used.
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Old 3rd April 2011, 08:09 PM   #3
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Cathode feedback windings are NOT new. Whatever patent Amplimo holds is not on that concept.

Amplimo and Plitron (Canada) are "joined at the hip". Plitron builds Vanderveen designed toroidal trafos. Descriptions of Plitron's tube O/P trafos, including those with CFB windings, can be found here
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Old 3rd April 2011, 08:43 PM   #4
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Its really not new, I have seen cathode feedback design in Russian magazine published back in 1958.

Vintage amps like Sansui AU-111 and Quad II are examples of cathode feedback. McIntosh unity coupled is actually a 50% cathode feedback (invented in 1936).

Below you can see draft assembly of PP amp with CFB trafos of my own design

Click the image to open in full size.
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Old 4th April 2011, 11:43 PM   #5
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great, thanks

magic word, cathode feedback

hope you don't I 'corrected' the thread title
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Old 5th April 2011, 03:29 PM   #6
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how about this one ?
Attached Images
File Type: jpg C3g - KT120 PSE IT Garter.JPG (49.7 KB, 437 views)
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Old 5th April 2011, 05:03 PM   #7
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oh, and with the 'desired' UL tap for driver tube
suddenly figured that out, after long osmosis
maybe

not sure about specs on trafos

well, lots of
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File Type: jpg C3g - KT120 PSE IT Garter rev.JPG (48.7 KB, 409 views)
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Old 5th April 2011, 10:26 PM   #8
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hmm, maybe anode phase splitter choke for driver tube

and 'added' trafo for cathode and garter bias
due to current, sutrely not an interstage
but how about a toroid power trafo
not a CT, but double symmetric windings
though all primary, wouldnt they also work ok as 2x primary and 2x secondary
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Old 9th April 2011, 03:09 AM   #9
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interesting Crowhurst amp

original DIY 'kit' from 1957-1960
curcuit and setup explained in detail

http://www.audioxpress.com/magsdirx/...0crowhurst.pdf
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Old 9th April 2011, 03:31 AM   #10
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Or just use a circlotron output stage. Two OTs for the Twin versus two power supplies for the Circlo.
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