Virtual Heater Center Tap? Actual Heater Center Tap? Both?

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TimDude
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Virtual Heater Center Tap? Actual Heater Center Tap? Both?

Post by TimDude »

I recently built an ODS #124. I realized the transformer I originally ordered didn't have enough voltage (320V), so I ordered a new one (340V). My first transformer didn't have a center tap for the heater wires so I did what the ODS #124 schematic originally called for and I put in the 120 Ohm resistors. My new transformer has a heater center tap.
So here's my question: should I...
A. Use the virtual center taps and wrap the actual center tap.
B. Use the actual center tap and throw away the 120 Ohm resistors.
C. Use both.
I've been searching the internet, and the most I can seem to find is that C is not the correct answer, but even that isn't entirely clear. I'm not sure why one answer would be better than another, or if there is a consensus on the matter. If there's a reason I should go one way or another, please let me know, but a simple "A", "B", "C" response will suffice as well.
For the record, I currently have both hooked up. I only played it for a few minutes last night. I didn't turn it up loud. It sounded okay. Hopefully I didn't break anything.

Sorry if this is a topic that has been covered many times before!

Thanks in advance for your replies!
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bepone
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Re: Virtual Heater Center Tap? Actual Heater Center Tap? Both?

Post by bepone »

A)

but nothing bad will happen with B)
C) is wrong cause you have two paths to the gnd
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ViperDoc
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Re: Virtual Heater Center Tap? Actual Heater Center Tap? Both?

Post by ViperDoc »

The only difference between using the factory heater supply CT vs. using a artificial CT with two resistors to ground is either A) how matched the resistors are in value, or B) how matched the two halves of the heater winding are. Likely more hair splitting than is practical, but some builders default to two 1% resistors on a bet they will match more closely than the transformer windings for better symmetry on both sides. Not sure if you could hear the difference, but there you have it.
Just plug it in, man.
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bepone
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Re: Virtual Heater Center Tap? Actual Heater Center Tap? Both?

Post by bepone »

for A) resistors doesnt need to be matched, specially not 1% . because minimum of humm is never on half between them.. so the best is humdinger pot, and it will not be in medium position :P
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