Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: acheld on May 20, 2021, 01:01:12 pm
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Very basic question. I am building a 5F6A using Doug's schematic and board. No mods.
I just noticed that the Hammond 290DX PT I purchased has a wired heater center tap. Of course, Doug's board has the artificial center tap with 100r resistors.
Is there an advantage (or disadvantage) to using the wired center tap vs the artificial center tap? LOL, the one thing I do know is to not use both, so I won't do that.
My inclination is to tape off the center tap wire, and use the artificial CT per the schematic, but I am not sure which would be better in the long run.
I'm looking for a rock stable amp with clean tone -- it won't be pushed hard.
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I asked this same question last year when building my first amp. AA1164. My upgraded transformer came with a CT. Schematic called for artificial. Sadly, I cannot find the thread.
You’ll get different opinions from guys here. Either works. Just don’t do both. :)
I wound up using the supplied CT in my transformer and skipped the 100R resistors. Resulted in a very quiet amp.
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Here it is
https://el34world.com/Forum/index.php?topic=26016.msg283094#msg283094
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Why would you use an artificial CT when the PT has a filament CT...?
What is a filament CT is for..., ground for the filaments, why is it there..., to ground the filaments, why is a artificial CT used..., because the PT has no filament CT. :icon_biggrin:
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1% balancing resistors can provide a more accurate balance than a CT of a winding on a winding of only a few turns.
But humdingers reveal that the lowest noise might rarely occur with a perfect balance.
My current view is that a positive VDC elevation offers the best option; using a CT if available, balancing resistors if not. On the basis that having a 0V terminal in very close proximity to the output valve anode is an invitation to tracking / arcing between socket terminals 2 & 3.