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Old 28th September 2010, 10:13 PM   #1
diyAudio Member
Join Date: Apr 2007
Default screen tap on OPT

Please excuse my inexperience with output transformers.

General question:
With regards to a single ended OPT with multiple primaries, could one of the primaries be used as a screen tap?

Specific question:
I have OPT with 0 2.5k 4k 7k 10k primaries (and 0 4 8 16 secondaries).
If I use the 7K for B+, can the 2.5K tap be used as a 35% (2.5/7) screen tap?

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Old 29th September 2010, 10:26 AM   #2
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
If the transformer is of a suitably high quality, with very tight coupling between the primary sections. Otherwise you get HF phase shifts and your output stage may turn into an oscillator. You can run pentode-mode into any old transformer, but UL demands high quality (which probably means an OPT designed for this purpose).
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