Tube filaments in series?

Klimon · 6th April 2007, 06:41 PM

Dear tube-lover,

Is it detrimental for tubes of same type and make to wire their heaters in series (e.g. to suit two 6.3V tubes with a 12.5 supply)? I know some tubes have a certain affix indicating their suitability for heaters connected in series, what about your average tube?

Cheers --- Simon

Alain Dupont · 6th April 2007, 06:47 PM

Klimon,

Go for it, without any problems, but make sure you replace the tubes in pairs...

Regards,

Alain.

crispycircuit · 6th April 2007, 06:56 PM

Scott integrateds wired 4 12ax7s in series and powered them with DC. Only the very early Scotts used AC on their heaters. Also the Dyna PAS preamps use a higher voltage DC and series the heaters... It works fine.....

Eli Duttman · 6th April 2007, 06:58 PM

I agree with Alain. You should be fine using a pair of tubes from the same production run.

Controlled heater warm up time is important in lengthy strings of dissimilar types rated for the same heater current. None of the heaters get overvoltaged.

Johan Potgieter · 6th April 2007, 09:19 PM

Supporting this - best way to get dc on heaters with proper filtering (low current, high voltage). One must just watch the maximum heater-cathode voltage rating if several are used in series.

mach1 · 7th April 2007, 03:22 AM

Some of the odd-voltage variants of common tubes have controlled heater warm up characterisitcs (usually around 11 secs) specially made for series wiring.

You can sometimes get 3V filament versions for a song and series heat them from a regular 6.3V tap.

pm

cliffforrest · 7th April 2007, 07:12 AM

Some of us are old enough to remember directly heated TV sets.

All the tube heaters strung together in series across the mains.

No mains transformer

and live chassis

Great fun!

Klimon · 7th April 2007, 09:16 AM

That's a clear answer, and luckily the one that opens possibilities!

Thanx,
Simon

6th April 2007, 06:41 PM	#1
Klimon diyAudio Member Join Date: Apr 2005 Location: Leuven	Tube filaments in series? Dear tube-lover, Is it detrimental for tubes of same type and make to wire their heaters in series (e.g. to suit two 6.3V tubes with a 12.5 supply)? I know some tubes have a certain affix indicating their suitability for heaters connected in series, what about your average tube? Cheers --- Simon

6th April 2007, 06:47 PM	#2
Alain Dupont diyAudio Member Join Date: Sep 2003 Location: Paris - France	Klimon, Go for it, without any problems, but make sure you replace the tubes in pairs... Regards, Alain. __________________ Did live about 10 years in Canada Back to France since the 1st February 2007.

6th April 2007, 06:56 PM	#3
crispycircuit diyAudio Member Join Date: Feb 2007 Location: Near Buffalo NY USA	Scott integrateds wired 4 12ax7s in series and powered them with DC. Only the very early Scotts used AC on their heaters. Also the Dyna PAS preamps use a higher voltage DC and series the heaters... It works fine..... __________________ The stuff you don't know always humbles us.........

6th April 2007, 06:58 PM	#4
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	I agree with Alain. You should be fine using a pair of tubes from the same production run. Controlled heater warm up time is important in lengthy strings of dissimilar types rated for the same heater current. None of the heaters get overvoltaged. __________________ Eli D.

7th April 2007, 03:22 AM	#6
mach1 diyAudio Member Join Date: Sep 2004 Location: Brisvegas	Some of the odd-voltage variants of common tubes have controlled heater warm up characterisitcs (usually around 11 secs) specially made for series wiring. You can sometimes get 3V filament versions for a song and series heat them from a regular 6.3V tap. pm __________________ Au rutti wop-bop-a-loom-bop-a-boom-bam-boom - Richard Penniman


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6th April 2007, 09:19 PM	#5
Johan Potgieter diyAudio Member Join Date: May 2005 Location: Pretoria, South Africa	Supporting this - best way to get dc on heaters with proper filtering (low current, high voltage). One must just watch the maximum heater-cathode voltage rating if several are used in series.

7th April 2007, 07:12 AM	#7
cliffforrest diyAudio Member Join Date: Sep 2004 Location: UK	Some of us are old enough to remember directly heated TV sets. All the tube heaters strung together in series across the mains. No mains transformer and live chassis Great fun!

7th April 2007, 09:16 AM	#8
Klimon diyAudio Member Join Date: Apr 2005 Location: Leuven	That's a clear answer, and luckily the one that opens possibilities! Thanx, Simon

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