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Old 14th January 2013, 02:25 PM   #1
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Default Use only half of OPT secondary?

I've built a headphone amp with pencil tubes and use tiny OPT with CT secondary (2500:400+400 turns). It sounds much better when 32-ohm headphones are connected between one side and CT rather than between the two sides (reflects 1.25K to the tube with 400:2500 turn ratio).
The question is whether I can leave one half of the secondary unloaded (B+ is only 29V and output tube is 1p24p @approx 4.5 mA) or should I connect some resistor across it and what value would be best (32 Ohm to equal the other side, or not relevant)
The amp was playing for several hours with one half of the secondary open with no ill effects and I also tried connecting CT and unused side with 47Ohm, which reduces the volume but no audible distortion is added.
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Old 14th January 2013, 02:28 PM   #2
TheGimp is offline TheGimp  United States
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You can leave it open. This is the same as putting an 8 ohm speaker on a multi-tap output with 4/8/16 ohm taps.
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Old 14th January 2013, 03:08 PM   #3
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Thanks, Gimp
Very simple answer once you think of it properly
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