So there are more that think the same 
It is you against the world it seems Never mind, stubbornness is a true virtue as it shapes a bond between souls alike !
Let's go back to the subject. The OP is very quiet. When words are sparse a schematic and/or pictures would help.
* I requested a thread title change to "Filament DC power supply for 2 valves".
It is you against the world it seems Never mind, stubbornness is a true virtue as it shapes a bond between souls alike !Let's go back to the subject. The OP is very quiet. When words are sparse a schematic and/or pictures would help.
* I requested a thread title change to "Filament DC power supply for 2 valves".
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title changed.
What is the problem using DC ? For the tubes/valves themselves it does not matter much as long as they heat up. That AC was standard for decades also does not say much as rectifiers once were bulky and expensive. Nowadays good silicon is cheap and small.
Some features of both AC and DC:
DC: Soft start, longer tube life, filament voltage independent of mains voltage, less hum, less pickup of unwanted signals, more complex, more expensive, not standard....
AC: direct start, shorter tube life, filament voltage dependent of mains voltage, careful twisted wiring needed, simple, cheap, standard ....
Some features of both AC and DC:
DC: Soft start, longer tube life, filament voltage independent of mains voltage, less hum, less pickup of unwanted signals, more complex, more expensive, not standard....
AC: direct start, shorter tube life, filament voltage dependent of mains voltage, careful twisted wiring needed, simple, cheap, standard ....
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"Soft start" and "filament voltage independent of mains voltage" are give aways that I meant regulated DC. It would not make sense to use unregulated DC as many advantages are gone then. Should be clear as OP mentioned wanting to use 78XX and I suggested using Schottky diodes and LDO regs for a 12V AC to 12V DC conversion without too many Watts going up in the air for no reason. We don't do poor PSU arrangements in DIY audio so let's forget about buzz. If it would buzz one would think that a solution would be sought and found. With 12V and just 175 mA it all seems relatively simple.
You are not telling me that I am succinct in my writing, are you ?
On second thoughts I think I do know what causes the reluctance of many tube guys against using DC for filaments. There is no tube in it.
You are not telling me that I am succinct in my writing, are you ?
On second thoughts I think I do know what causes the reluctance of many tube guys against using DC for filaments. There is no tube in it.
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FWIW non native speakers (in any language, not just English) in general use the cultured, gramatically accurate form of it, because that's what's taught (and for good reason), you must know the rules first, break them later if you wish and at your own risk.
In this case both Russian and Chinese learnt the same ... Cambridge or Oxford approved, by the way , or by "British Council".
While common English people, "on the street" , will speak anything but.
There's a lot of "daily use" words which happily live in the grey area between "Queen's English" and slang.
It used to be "BBC English" too but no more
One problem of "daily use English" is that it varies a lot, not only among Countries but even Cities ... even Boroughs!!!!
Or in the exact same place (job/school/office) by speaker social class or origin.
Or plain age.
While posting on an International access Forum such as this one, gramatically correct English will cause the least misunderstandings.
Just one silly example:
"tranny" may mean any of these 3 things (and probably more):
or
or even
To boot, in a Forum where possibly dangerous electrical voltages can be used, or simply misconnecting something may cause heavy damage (at least financially) , being redundant explaining/describing something is an asset, not a liability.
In this case both Russian and Chinese learnt the same ... Cambridge or Oxford approved, by the way
, or by "British Council".While common English people, "on the street" , will speak anything but.
There's a lot of "daily use" words which happily live in the grey area between "Queen's English" and slang.
It used to be "BBC English" too but no more
One problem of "daily use English" is that it varies a lot, not only among Countries but even Cities ... even Boroughs!!!!
Or in the exact same place (job/school/office) by speaker social class or origin.
Or plain age.
While posting on an International access Forum such as this one, gramatically correct English will cause the least misunderstandings.
Just one silly example:
"tranny" may mean any of these 3 things (and probably more):
An externally hosted image should be here but it was not working when we last tested it.
or
or even
An externally hosted image should be here but it was not working when we last tested it.
To boot, in a Forum where possibly dangerous electrical voltages can be used, or simply misconnecting something may cause heavy damage (at least financially) , being redundant explaining/describing something is an asset, not a liability.
What is the problem with using DC for the heaters?
I regularly make things which will run from a 9 volt AC supply. This is rectified to give 12v DC for heaters and also drives a small mains transformer wired backwards to step it up for the HT supply.
This is for ECC series valves with series heater connections.
Steve.
I regularly make things which will run from a 9 volt AC supply. This is rectified to give 12v DC for heaters and also drives a small mains transformer wired backwards to step it up for the HT supply.
This is for ECC series valves with series heater connections.
Steve.
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Cant draw circyit diagram until im on the desktop but it is a follows.
12Vac to diode and smoothing capacitor to give `dc` supply.
Then transistor with 13 v zener on base. Emitter will be at 12.3 v which will be supply for the heaters in series. The npn transistor will be fully on so collector at 12.5v and connected to the dc supply.
Question is if the simple half wave rectified supply has enough voltage overhead, i think if transformer is of sufficient va, it should do it (proof is when i build circuit)
Valves are 6j1 or equivalent. Heater is 6.3 v at 175 ma.
For reason stated earlier stated i like the idea of constant current which what ive described is not.
12Vac to diode and smoothing capacitor to give `dc` supply.
Then transistor with 13 v zener on base. Emitter will be at 12.3 v which will be supply for the heaters in series. The npn transistor will be fully on so collector at 12.5v and connected to the dc supply.
Question is if the simple half wave rectified supply has enough voltage overhead, i think if transformer is of sufficient va, it should do it (proof is when i build circuit)
Valves are 6j1 or equivalent. Heater is 6.3 v at 175 ma.
For reason stated earlier stated i like the idea of constant current which what ive described is not.
how many tube failures due to open filaments have you seen?
i have been doing tubes for lots of years now and haven't seen one...
but shattered glass due to carelessness, many...
i say do not worry too much....just do it and then tell us what you find...
you will be wise after that...
extra parts and so extra costs and time....if that matters to any builder...
Constant current is not necessary but use it if it makes you feel better. As the tubes filaments will be connected in series you can easily measure the current at start up and also the nominal current on DC. I think soft starting the filament current has more merits.
Filament current was the important parameter with so called "television tubes" that had all filaments connected in series straight to the mains voltage. Tubes like PCC88 etc. The ECC88 variant was meant for 6.3V filament voltage.
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Resistance at temperature would be 36 ohm, i measure 11 ohm when cold, that would be 0.5 amp initially.
Cost of additional components is not an issue.
The answers to my q. would be answered with a couple of breadboarded circuits. I am most curious as to how long for operating temp ehen current is throttled by constant current source.
Thanks to all who took time to reply.
Cost of additional components is not an issue.
The answers to my q. would be answered with a couple of breadboarded circuits. I am most curious as to how long for operating temp ehen current is throttled by constant current source.
Thanks to all who took time to reply.
That would be 16V - 6.3V = 9.7V with 2 x 0.175A. So 9.7 x 0.35 = 3.4W. So 3.4W loss in heat (dissipated by the regulator).....Hefty heatsink needs and totally unnecessary. My 2 cents.
As said before, with soft start (often just 1 capacitor extra) there is no need to worry about inrush current. When the voltage is right worrying about the nominal current is being afraid of the bogeyman.
As said before, with soft start (often just 1 capacitor extra) there is no need to worry about inrush current. When the voltage is right worrying about the nominal current is being afraid of the bogeyman.
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