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Powering DHT Filaments
Powering DHT Filaments
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Old 2nd October 2017, 06:28 PM   #1
zesak is offline zesak
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Default Powering DHT Filaments

I plan to use a battery to power the filaments of 3 ck5676 dhc tubes.

Do I need 3 separate batteries, each floating on top of cathode of each tube separately, or
can I connect one battery across all filaments (assuming that battery can provide 3x120mA needed) ?
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Old 2nd October 2017, 07:19 PM   #2
Matt BH is offline Matt BH  United Kingdom
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It depends on your circuit. If your using filament bias then separate batteries will be needed.

They only have a 100hr life though. The datasheet says it is because the filaments don't last. I would try starving the filaments to see if it increases life. Don't expect them to last long though. They were designed for push to talk radios and proximity fuses so never needed a long life.

Cheers
Matt
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Old 2nd October 2017, 08:26 PM   #3
zesak is offline zesak
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I guess the one battery solution is only possible with all of the cathodes connected to ground, correct ?
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Old 2nd October 2017, 08:36 PM   #4
andyjevans is offline andyjevans  United Kingdom
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Quote:
Originally Posted by Matt BH View Post

They only have a 100hr life though. The datasheet says it is because the filaments don't last. I would try starving the filaments to see if it increases life. Don't expect them to last long though. They were designed for push to talk radios and proximity fuses so never needed a long life.

Cheers
Matt
Exactly. I tried a bunch of these wire ended small tubes and they didn't last at all. Plus the batteries - I used lead acid - ran down and needed constant recharging. As they lost the charge it would screw up the sound as well. I still have a bunch and I'm open to ludicrously small offers for them.
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Old 2nd October 2017, 09:35 PM   #5
Matt BH is offline Matt BH  United Kingdom
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I hoped you would come in on this thread Andy. You gave me the CK5676 I have several years ago when I bought a pair of Beard output transformers from you.

At the time I had not tried DH valves and you said try these little things. You warned me the that they don't last but it got me hooked. Cheers

I now have a GM70 SE amp that sees winter use and have been playing with 4P1L for a while.

Good times and of course you were right about DH valves.

Cheers
Matt
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Old 2nd October 2017, 09:48 PM   #6
Matt BH is offline Matt BH  United Kingdom
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Zesak, yes if all filaments are at 0V then one battery will be fine.

They don't last long and using batteries is a pain but it is a very rewarding experiment.

What are you planning on doing with them, care to share your ideas or a schematic?

Cheers
Matt
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Old 3rd October 2017, 03:20 PM   #7
zesak is offline zesak
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Actually I planned on buying some russian subminiature low filament current dhts. In the meantime I managed to find 3 of those 5676s in my junk pile so I figured I would try to figure out this whole filament stuff mess with them first before I buy the russian ones.
This is my first attempt with dht so i figured battery for filaments and dc to dc converter for plates would do.

Anyone can comment on their experience with longevity and quality of the 1J (1ZH) tubes like 1j24,29,30 etc. ?
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Old 3rd October 2017, 08:06 PM   #8
andyjevans is offline andyjevans  United Kingdom
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Why not stick to established and great sounding tubes like 4P1L and 2P29L which are still cheap and available? Plenty of build instructions and schematics on this site.
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Old 3rd October 2017, 09:03 PM   #9
zesak is offline zesak
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my preference/requirements are low filament current, low plate voltage and flex leads

i plan on using these in preamp app
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Old 3rd October 2017, 09:32 PM   #10
sser2 is offline sser2  United States
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Default Because it becomes boring.

4P1L here, 4P1L there, 4P1L everywhere...

1Ж24Б is a very interesting tube. It is one of the uniquely Russian rod pentodes. These tubes were developed in late 60s and have no Western analogs. In place of conventional electrodes there are rods, arranged in a way that they form electron beams and focus them on anodes. Rod pentodes have several advantages as audio tubes:

1. g2 currents are much lower than in conventional pentodes. This allows variable negative feedback from plate to g2. By connecting plate and screen through resistors, mu can be varied from 20 to 180. With straight connection, mu=20, Rp=20 K at 70 V and 1.5 mA.

2. Extremely thrifty directly heated filament: 1.5 V 13 mA, perfect for battery heating.

3. Virtually no microphonics, which is a plague of DHT voltage amplifier tubes.

4. Service life: at least 5,000 h (compared to 100 h of 5676).

Last edited by sser2; 3rd October 2017 at 09:56 PM.
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