Tube life question

woody · 29th March 2003, 01:53 AM

I am thinking of building a OTL amp. My question is how long
can I expect a 6as7ga to live if asked to handel 100 ma at 100v.
Or how much longer would it live if asked to only handel 70 ma at
100v?

Thanks

bob12345678

fdegrove · 29th March 2003, 02:07 AM

Hi,

Does starving yourself to death help?

Sch3mat1c · 29th March 2003, 02:36 AM

Try one at 300mA, 200V. After that one goes, try stepping down the voltage and/or current a little and try again... After that one goes......

Tim

Brett · 29th March 2003, 03:47 AM

Steve Bench has a report on his site where he's tallied lots of data and related it to the type of filament and their power, versus the cathode current. Not definitive, but gives an idea.

http://members.aol.com/sbench/heater.html

Sch3mat1c · 29th March 2003, 04:43 AM

Someone here should conduct a test. Grab a box of say, 12AU7s, 6V6s, 6L6s, a type of sweep tube, and some 6080s or 6AS7s and see how long they last for each rating.
Unfortunately, this could take a *long* time to get the data.

BTW, I heard that unipotential coated cathodes can do like, 200mA/W at saturation. So in theory, a 6CD6 could pull 3 amperes of cathode current! Of course, screen and grid voltages would have to be through the roof...

Tim

EC8010 · 29th March 2003, 06:20 AM

Provided that you stay within all the manufacturer's ratings, valves last forever. I say this because DIY amplifiers are generally made obsolete by their owner/builder thinking up a new idea long before the valves wear out.

fdegrove · 30th March 2003, 12:48 AM

Hi,

Quote:

Provided that you stay within all the manufacturer's ratings, valves last forever.

Proviso: you take the low side, not the hot side of specs.

For instance: run a 12.6 heater at 12 V and just make sure it can draw it's required current which I feel is more important than the voltage rating, never overdo the ratings or you'll see transonductance figures of the tube vannish within a few minutes.

Cheers,

/Forever.

SHiFTY · 31st March 2003, 10:23 AM

Quote:

Provided that you stay within all the manufacturer's ratings, valves last forever. I say this because DIY amplifiers are generally made obsolete by their owner/builder thinking up a new idea long before the valves wear out.

Are you saying we're ever so slightly insane?

EC8010 · 31st March 2003, 02:10 PM

Quote:

Originally posted by ShiFtY
Are you saying we're ever so slightly insane?

Never. I am sure that we all operate a policy of constant improvement on our products driven by a vigourous research initiative, supported by a vigilant purchasing department, and backed by distaff-led industrial design.

(Translation: I've thought of this great new idea for a valve I couldn't resist on eBay, and I've promised to make it look nicer this time.)

robbie · 31st March 2003, 02:17 PM

where you are coming from..

think its a male 'thang'

29th March 2003, 01:53 AM	#1
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	Tube life question I am thinking of building a OTL amp. My question is how long can I expect a 6as7ga to live if asked to handel 100 ma at 100v. Or how much longer would it live if asked to only handel 70 ma at 100v? Thanks bob12345678

29th March 2003, 02:07 AM	#2
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	I AM BAD. Hi, Does starving yourself to death help? __________________ Frank

29th March 2003, 06:20 AM	#6
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Valves last forever! Provided that you stay within all the manufacturer's ratings, valves last forever. I say this because DIY amplifiers are generally made obsolete by their owner/builder thinking up a new idea long before the valves wear out. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

31st March 2003, 02:17 PM	#10
robbie diyAudio Member Join Date: Mar 2003 Location: south coast	i so know where you are coming from.. think its a male 'thang'

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29th March 2003, 02:36 AM	#3
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Try one at 300mA, 200V. After that one goes, try stepping down the voltage and/or current a little and try again... After that one goes...... Tim

29th March 2003, 03:47 AM	#4
Brett diyAudio Member Join Date: Jan 2002	Steve Bench has a report on his site where he's tallied lots of data and related it to the type of filament and their power, versus the cathode current. Not definitive, but gives an idea. http://members.aol.com/sbench/heater.html

29th March 2003, 04:43 AM	#5
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Someone here should conduct a test. Grab a box of say, 12AU7s, 6V6s, 6L6s, a type of sweep tube, and some 6080s or 6AS7s and see how long they last for each rating. Unfortunately, this could take a long time to get the data. BTW, I heard that unipotential coated cathodes can do like, 200mA/W at saturation. So in theory, a 6CD6 could pull 3 amperes of cathode current! Of course, screen and grid voltages would have to be through the roof... Tim

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