Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on January 21, 2016, 03:50:39 am
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Looking for 6BQ6 amp schematic I've found this
(http://i.imgur.com/HZlkucu.gif)
What is happening there ?? Those cathodes are connected to the OT secondary ........ ???????
Someone understand this configuration ??
I foud it on this page, but there are no info about the schematic
http://www.pcad-ok.com/saup/saup13/saup13-1.htm (http://www.pcad-ok.com/saup/saup13/saup13-1.htm)
Franco
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What is happening there ?? Those cathodes are connected to the OT secondary ........ ?
It's just cathode feedback ("CFB") with the feedback winding drawn on the "secondary side", the OPT really does not care where the winding is located - since it's always in the magnetic path anyway. But commonly, the CFB winding is drawn on the "primary side" to denote its function.
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just cathode feedback
I can *sorta* see that, since the taps are at the *ends* of the windings - where the tubes would see outta phase signals, but, why ground the 4ohm tap?, wouldn't that *float* the zero tap asymmetrically??
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I should amend my earlier post, in this particular amplifier, the OPT does not have a dedicated CFB winding - to save money no doubt - so the designer just used the secondary/speaker output taps for the job. The 4 Ohm tap is grounded, because it is exactly half way between 16 Ohm and Com (or 0), so by grounding it, it serves as a center tap to allow symmetrical cathode feedback for each half of the push-pull output pair.
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Thanks Jazbo8
What you say remembers to me some schematics from Menno Van Der Veen I've seen long time ago
(http://i.imgur.com/LS0UNFA.gif)
Thanks again
Franco