Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: orson on January 09, 2015, 01:59:55 AM
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I have several NOS 6080s lying around here and want to do some tube rolling to find the right match for my ears.
As the tubes are mostly unused they will need some burn in time.
Thats why the idea of a separate burn in station came up to my mind.
As I understand it should be as simple as that:
-> powerline -> fuse -> switch -> transformer to 6 volts AC -> tube socket (or 2 sockets parallel)
Does that work or did I miss something?
And how much current does each 6080 draw? About 2,5A? If so the power needed would be around 15VA per tube, so a 25VA transformer would be fine for one tube?
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Orson,
Yes, 2.5A is right. Just in case you need more data here is a link to it:
http://tdsl.duncanamps.com/show.php?des=6080
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I asked the same question a while back and without having any B+ present for the tube to start conducting it wouldn't really do anything for burn in. It would however help the getter to remove any gas inside the tube if that was an issue.
You need 2.5amps for a 6080 or 2.4amps for a 6AS7G, but it will peak to almost 3amps on cold startup so take that into account.
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Thanks for the fast replies.
So that was the point I missed. I read that there does not need to be an (audio-) input signal present and therefore completely forgot about the B+.
That means the solution would be one heater circuit with 6,3 volts AC (max. 3 amps) and one B+ circuit with 130 volts DC.
Basically a reduced version of the Crack PS (see attachment).
Is the filter stage with R1 and C1 needed for this purpose?
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Orson,
Depending on whether or not you have extra 220uF caps you might want a CRC filter with the bleeder after the second cap.
As for cold heater inrush, all heater transformer makers know that there is a cold inrush. They design for it.
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You could just leave each tube in your Crack running overnight.
Otherwise, your power supply will give the necessary voltages to cook in a 6080.
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I've left my Crack running 24/7 for over a week with ITunes playing on shuffle a couple of times now with no ill effects.
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Yeah, you are right. I burn in the tubes over night. At first I was a bit afraid of running the Crack alone but having it on the last days for 10 hours proved that it runs stable at a constant temperature.
The circuit needed is nearly half the Crack. That makes only sense if one has the parts needed in his drawer.
But thanks for sharing your thoughts.
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I will admit to being a little paranoid about leaving it running overnight the first time so I placed a fire sensor on the shelf above and slept soundly ;)
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Yeah, you are right. I burn in the tubes over night. At first I was a bit afraid of running the Crack alone but having it on the last days for 10 hours proved that it runs stable at a constant temperature.
The circuit needed is nearly half the Crack. That makes only sense if one has the parts needed in his drawer.
But thanks for sharing your thoughts.
Thats why i never built one, by the time your done you might as well add a few sockets and call it an amp. Just plug em in and use them..
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Thanks for the fast replies.
So that was the point I missed. I read that there does not need to be an (audio-) input signal present and therefore completely forgot about the B+.
That means the solution would be one heater circuit with 6,3 volts AC (max. 3 amps) and one B+ circuit with 130 volts DC.
Basically a reduced version of the Crack PS (see attachment).
Is the filter stage with R1 and C1 needed for this purpose?
Don't forget to have a cathode resistor! The point is to have a substantial bot controlled current through the tube. No filter would be needed.