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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, 05:00 PM   #21
kevinkr is offline kevinkr  United States
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Filaments DC or AC?
Always nice when things work as expected..
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Old 27th May 2018, 05:49 PM   #22
Wavebourn is offline Wavebourn  United States
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Filaments DC or AC?
Quote:
Originally Posted by Gopher View Post
So why do some people swear by regulated DC powered heaters? Are they hearing something different to those who prefer AC heating?
Regulated DC is too cheap today to ignore it's advantages, even when they are not so audible.
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Old 27th May 2018, 08:58 PM   #23
DF96 is offline DF96  England
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But regulated DC contains several 'newbie traps':
1. the transformer needs more VA than AC heaters (maybe at least 2x)
2. the (voltage) regulator needs to cope with cold heaters without doing a current/temperature foldback and shutting down
3. current regulation avoids '2' but can mean slower warm up
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Old 27th May 2018, 09:11 PM   #24
kevinkr is offline kevinkr  United States
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Filaments DC or AC?
I'll add to that in that badly done DC is almost always worse from a noise/buzz perspective because of the dv/dt of that sawtooth riding on top of the DC. (drop out etc)
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Old 27th May 2018, 09:58 PM   #25
Hearinspace is online now Hearinspace  Canada
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Filaments DC or AC?
Quote:
Originally Posted by merlin el mago View Post
Filaments DC or AC?
Thinking over a reply I realize it could sound judgemental or contentious , which I don't feel so please take this as a friendly reply.

You've been around for a while , know a lot, so it's hard for me not to wonder why you're actually asking the question. You've made it clear by your comment that you ascribe a positive sonic difference to AC heating, so why the doubt in this case?

I don't really disagree with the answers above but the engineer's fast cut to the finish to me carries the danger of shorting out exploration. I'll thump my personal bible and put in that everything makes a difference and you just have to decide what you care about. I can't imagine not breadboarding the circuit and trying different stuff.

You've indicated that you have heard a difference between AC and DC so it might not be unreasonable to think you could also hear a difference between different types of DC circuit - unregulated, voltage regulated, current regulated, etc. There are posts by some who have switched from one dc supply to another and commented on what they heard. These days, notably Rod Coleman's regulators get high billing.

Which one do you like the sound of , or is the difference so small that it's not worth the financial cost, space allocation, or level of complexity, etc. . . . .

To me , it's not a question you can really answer without trying different things, and by then you know the answer without having to ask.

Anyway, just some thoughts.
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Old 27th May 2018, 10:05 PM   #26
6A3sUMMER is offline 6A3sUMMER  United States
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Why do you have a 3.3 Meg resistor across the bias battery?
Did you calculate the life of the battery with about 1.1uA current?
For a 10mA hour battery that is about 9090 hours (about 1.04 years).
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Old 27th May 2018, 10:19 PM   #27
kevinkr is offline kevinkr  United States
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Filaments DC or AC?
The capacitor most likely is not required as well. (You can't reaonably make it large enough for it to have a meaningful effect) This is my least favorite form of battery bias right after sticking a battery in the cathode circuit. I've tried a number of variations, the batteries are not perfect either and some of them markedly color the sound (sometimes to a measurable extent at least in so far as distortion is concerned).

I use battery bias a lot in phono stages as the two or three people who read my threads will have noticed.
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Old 27th May 2018, 10:24 PM   #28
gabdx is offline gabdx  Canada
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Electrons wear the heater in one way in DC heaters. The sound becomes tiresome with lots of harmonics in DC pre-amps or amps.

Only place acceptable is in phono stages.
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Old 27th May 2018, 11:33 PM   #29
twystd is offline twystd  United States
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There is a lot of rhetoric on the subject. Like most subjects simple questions like this often get simple answers sometimes based on supposition. AC filament supplies are very simple and don't vary much. DC filaments are another story, so hard to make generalizations about them. AC may be fine for the last stage in a power amp, especially if paired with relatively inefficient speakers, however if you are using them with highly efficient speakers, or in earlier stages in a an amplifier chain, maybe not so much.

I had a single ended 300B amp driving 96dB speakers, the amp had simple DC filaments on the 300Bs The DC filament supply I was using on the amp at first was a just a simple CRC supply using cheap electrolytics and a good power resistor. In an attempt to improve the sonics of the amp, I then built a second DC supply. The second supply had high quality electrolytics and used a CLC topology employing a large high quality vintage Chicago potted filament choke. That 2nd DC supply was a BIG improvement.

I decided to A/B the new DC supply with an AC supply. I made a second AC supply, I could balance the hum with a balance pot to get the hum to acceptable levels, and could switch the two supplies back and forth on the fly with a DPDT switch. Myself and others thought the DC supply sounded livelier than the AC supply. The Rod Coleman filament supplies I expect would sound even better than my CLC supply, but I've never tried one. I always wanted to, but never seemed to get the time and money together to give them a shot, but others rave about them.

I'm one of the few who has bothered to build a better than average DC supply, and actually A/Bd it instantly with an AC filament supply in the same amp/system. This really allowed me to explore the generalizations on the subject. My conclusions are that a typical cheap CRC DC supply will not sound as good as AC, however a more sophisticated DC supply may beat AC.

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Old 28th May 2018, 01:58 AM   #30
AquaTarkus is offline AquaTarkus  Canada
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I always use AC heaters with DC elevation, including in my commercial designs. I get no noise problems, even in high gain guitar amps.
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