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Why parafeed?
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=77793&th=18942#msg_77793
Steve]]>steve f2013-09-08T03:02:54-00:00Re: Why parafeed?
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=77794&th=18942#msg_77794
gofar992013-09-08T19:23:21-00:00Re: Why parafeed?
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=77856&th=18942#msg_77856
steve f2013-09-15T00:11:59-00:00Re: Why parafeed?
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=86325&th=18942#msg_86325
]]>Zohanna2017-10-14T21:57:02-00:00Re: Why parafeed?
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=87874&th=18942#msg_87874
Parallel feed (parafeed) has the DC passing through a separate inductor from B+ voltage to plate of the output tube. There is a DC blocking capacitor to the output transformer. Since there is no DC passing through the output transformer no gap is required in the transformer core so the transformer can be smaller and cheaper.
See https://www.tubecad.com/2014/09/blog0308.htm for further explanations. ]]>hudelson22018-04-25T02:04:45-00:00Re: Why parafeed?
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=93795&th=18942#msg_93795
page 519 sheds some light on the subject of parafeed operation.
"In all cases when making use of any resonance effects involving the inductance of the transformer primary, it is important to remember that this is a variable quantity. Not only are there considerable variations from one transformer to another, but there are large variations of inductance caused by the a.c. input voltage.
The series resonant circuit presents a low impedance to the valve at the resonant frequency, thus tending to cause serious distortion, particularly when the valve is being operated at a fairly high level. For these reasons the resonance method is not used in good design."
For ease of understanding for newbies, the inductance varies with power/spl, the load line varies, and the low frequency resonance frequency varies, the bass varies with loudness.