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Filaments DC or AC?
Filaments DC or AC?
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View Poll Results: What do you prefer for heating AC or DC?
AC 38 38.78%
DC 60 61.22%
Voters: 98. You may not vote on this poll

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Old 27th May 2018, 11:24 AM   #1
merlin el mago is offline merlin el mago
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Question Filaments DC or AC?

Filaments DC or AC?
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Old 27th May 2018, 11:31 AM   #2
kodabmx is offline kodabmx  Canada
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I usually use DC, mostly because I usually use an SMPS for the heaters... However, I also built a cheap amp using "junkbox" parts that used AC heaters and there was no audible difference (no hum).
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Old 27th May 2018, 12:37 PM   #3
KatieandDad is offline KatieandDad  United Kingdom
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I could never discern any audible difference but you have to be careful with layout of the high current heater wiring.
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Old 27th May 2018, 12:51 PM   #4
lcsaszar is offline lcsaszar  Hungary
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Low impedance heating voltage source -> AC
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Old 27th May 2018, 01:18 PM   #5
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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If the valves are not faulty, AC is the best source, with a null adjustment for minimum hum, (if any).
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Old 27th May 2018, 01:31 PM   #6
DF96 is offline DF96  England
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AC, in almost all circumstances.
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Old 27th May 2018, 01:57 PM   #7
merlin el mago is offline merlin el mago
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Subjectively speaking AC heaters sounds more direct & fast but I didn't compared with the same schematic.
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Old 27th May 2018, 02:06 PM   #8
merlin el mago is offline merlin el mago
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It's for attached schematic of headphone amp?
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Old 27th May 2018, 03:11 PM   #9
kevinkr is offline kevinkr  United States
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Filaments DC or AC?
AC heating should be fine for this application, but make sure to twist the heater wiring and route it away from everything else, if the filament winding is not center tapped create an artificial one with a pair of 100 ohm resistors in series across the heater winding, and ground the point between the resistors.

I use DC heating in phono stages and any DHT based amplifier circuitry, and some line stage circuitry.
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Old 27th May 2018, 03:57 PM   #10
Lingwendil is offline Lingwendil  United States
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Filaments DC or AC?
I like AC heating whenever I can use it, save for phono/RIAA and super low level DAC I/V types of circuits, or the occasional musical instrument amplifier use. I only deviate if DC will be easier to implement, such as if you are already using low level DC for other circuitry and it's easier to simply use that, which can improve regulator performance by pulling more current anyway.
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