psu to heater on 4 el34 tubes???

wuffer · 14th December 2005, 06:51 PM

im building an amp on 4 el 34 tubes in parallel push pull and 1 ecc82 pr channel..
almost got all the parts so dont tell me its a bad project..

someone told me that its not good to put the 4 el34 heaters in serie??

is that correct???

kevinkr · 14th December 2005, 07:09 PM

I think the issue that might arise relates to the relatively uncontrolled warmup characteristic of the EL34 filament. Running 4 of them in series would require a voltage of 25.2V and depending on the thermal time constant of each tube's filament/cathode structure the voltage across the filaments may not divide equally during warm up and possibly during operation as well. One really simple way around this if you must run a series string is to operate them with a constant current source set to 1.5A, otherwise it is probably better to just run them in parallel - the only issue here is sizing the wiring to handle 6A rms which really shouldn't be a problem.

I had a marantz amplifier which used 6AU4 rectifiers with the filaments in series, and I had to very carefully select them so that when warm the voltage across each filament was equal. Incidentally when I got the amplifier (a model 2) one of the problems was a 6AU4 with an open filament.

Kevin

wuffer · 14th December 2005, 07:20 PM

parallel.. that would mean if i have one transformer on 2*6v and 2*3333ma and parallel the 2 sec windings it could be used???

dhaen · 14th December 2005, 08:09 PM

If you have 2 equal heater windings it is easier to divide the circuit into 2 (L and R?) and supply half from each.

wuffer · 14th December 2005, 08:12 PM

yes i thought of that...
that would be 6,3V and 3A each

navin · 15th December 2005, 06:10 AM

Quote:

Originally posted by kevinkr
...One really simple way around this if you must run a series string is to operate them with a constant current source set to 1.5A, otherwise it is probably better to just run them in parallel - the only issue here is sizing the wiring to handle 6A rms which really shouldn't be a problem.
Kevin

what about a series / parallel config? You'd need 3A but 13.2V?

Quote:

Originally posted by wuffer
yes i thought of that...
that would be 6,3V and 3A each

or 6.3V and 6A for one. I see no problems with 6.3V / 6A. Should there be?

wuffer · 15th December 2005, 09:15 AM

i think im going for 2 6.3v 3a pr amp...

i have a 2*24vac 3,6 can i use that transformer with a Lm350 to get the voltage i need???

wuffer · 15th December 2005, 08:55 PM

thanks for your help..
now im come to this conclussion that it should be right the first time..
so im going to look at some transformers that are made for tubes.. they cost a little more but maybe its the best

so i need to power heater on one ecc82 and 4 el34 in parallel and need high power for the ecc82..

is there one transformer with sec windings that fit???

14th December 2005, 06:51 PM	#1
wuffer diyAudio Member Join Date: Feb 2004 Location: denmark	psu to heater on 4 el34 tubes??? im building an amp on 4 el 34 tubes in parallel push pull and 1 ecc82 pr channel.. almost got all the parts so dont tell me its a bad project.. someone told me that its not good to put the 4 el34 heaters in serie?? is that correct???

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14th December 2005, 07:09 PM	#2
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	I think the issue that might arise relates to the relatively uncontrolled warmup characteristic of the EL34 filament. Running 4 of them in series would require a voltage of 25.2V and depending on the thermal time constant of each tube's filament/cathode structure the voltage across the filaments may not divide equally during warm up and possibly during operation as well. One really simple way around this if you must run a series string is to operate them with a constant current source set to 1.5A, otherwise it is probably better to just run them in parallel - the only issue here is sizing the wiring to handle 6A rms which really shouldn't be a problem. I had a marantz amplifier which used 6AU4 rectifiers with the filaments in series, and I had to very carefully select them so that when warm the voltage across each filament was equal. Incidentally when I got the amplifier (a model 2) one of the problems was a 6AU4 with an open filament. Kevin

14th December 2005, 07:20 PM	#3
wuffer diyAudio Member Join Date: Feb 2004 Location: denmark	parallel.. that would mean if i have one transformer on 26v and 23333ma and parallel the 2 sec windings it could be used???

14th December 2005, 08:09 PM	#4
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	If you have 2 equal heater windings it is easier to divide the circuit into 2 (L and R?) and supply half from each.

14th December 2005, 08:12 PM	#5
wuffer diyAudio Member Join Date: Feb 2004 Location: denmark	yes i thought of that... that would be 6,3V and 3A each

15th December 2005, 09:15 AM	#7
wuffer diyAudio Member Join Date: Feb 2004 Location: denmark	i think im going for 2 6.3v 3a pr amp... i have a 2*24vac 3,6 can i use that transformer with a Lm350 to get the voltage i need???

15th December 2005, 08:55 PM	#8
wuffer diyAudio Member Join Date: Feb 2004 Location: denmark	thanks for your help.. now im come to this conclussion that it should be right the first time.. so im going to look at some transformers that are made for tubes.. they cost a little more but maybe its the best so i need to power heater on one ecc82 and 4 el34 in parallel and need high power for the ecc82.. is there one transformer with sec windings that fit???

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