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Old 21st September 2012, 07:24 PM   #21
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ok would a small DC battery with a super fast on and off switch (like 60 times a second) to convert it to AC and then hooked to a transformer would it possibly create enough voltage to power a small tube amp? because in my other post it easily lights up a 120 volt lamp
or even a florescent light bulb (the swirly ones)
just DONT touch those two ends of the plug at the same time! (ouch thats like sticking your fingers in a light bulb socket!)
and plus who knows how many volts it is
it could be even higher than 200 volts!
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Old 21st September 2012, 07:58 PM   #22
Pano is offline Pano  United States
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Um, yes. It's called an inverter circuit. You can buy them for cars. In the good old days they were mechanical and used to get high voltages out of car batteries for radios and even the spark.

How is that safer than plugging into the wall?
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Old 21st September 2012, 08:18 PM   #23
DF96 is offline DF96  England
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(ouch thats like sticking your fingers in a light bulb socket!
No, a power socket is much worse because of the low impedance so a greater current can flow. Either can kill you, but a power socket is a bit more certain.
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Old 24th September 2012, 11:38 PM   #24
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well still the voltage could easily be enough to shock the heck out of you either way still dangerous
but i need some way to power a tube like in a tube ampliflier
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Old 25th September 2012, 02:01 AM   #25
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A fast description of how a triode works.

- A heater element heats the cathode to a high temperature.
- The cathode then emits electrons.
- The anode (usually called the plate) has a high positive DC voltage applied to it from the power supply.
- The negative voltage at the grid (negative with respect to the Cathode) controls the amount of electrons flowing from the Cathode to the Plate.


However, rather than using electron flow - most people in electronics use conventional current.
Saying that electrons flow in one direction - amounts to the same thing as saying that positive charge flows
in the opposite direction. So conventional current flows from positive to negative.

In a certain region of operation of a tube - the change in current is nearly proportional to the change in Grid voltage.
So in this region the tube is almost a linear device.

So the bottom line with a tube - the current flowing from the plate to the cathode is controlled by the voltage on the Grid.



Most tubes require a plate voltage of 100 Vdc or more - which can be lethal.
So I absolutely do not recommend this for someone starting out.

There were a few tubes made for automotive radios - These only need a 12 Vdc plate voltage.
But these tubes are getting more difficult to find - especially 6gm8's.

For a beginner who wants to built right away - maybe find a preamp kit that uses jFET's.
A jFET is similar to a tube in that the current is controlled by a voltage.
.
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Old 25th September 2012, 02:08 AM   #26
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that sure makes more sense to me than a transistor ever will
at one of my friends house I found a massive load of small tubes like the ones you've described they were all just lying around on the ground and most of them look really clean besides the dirt that was on them.
maybe next time I go to my friends house I will see if I can pick up a couple of them.
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Old 25th September 2012, 02:30 AM   #27
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Originally Posted by realflow100 View Post
that sure makes more sense to me than a transistor ever will
at one of my friends house I found a massive load of small tubes like the ones you've described they were all just lying around on the ground and most of them look really clean besides the dirt that was on them.
maybe next time I go to my friends house I will see if I can pick up a couple of them.
Interesting bit of info - in the 19th century, scientists couldn't understand why
light could propagate through a vacuum - but sound couldn't.
and it was these experiments that lead to all sorts of devices that used vacuum ... such as the vacuum tube.

North American part numbers, for common signal tubes, used in Audio are

12ax7, 12at7, 12au7

6sn7, and all the variations of a 6dj8 or 6922
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Old 25th September 2012, 03:17 AM   #28
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"RealFlow".......Hi !! It really sounds like you need to read some books about Basic Electronics. Answering your questions...which are sound & valid questions by the way....It is very frustrating to answer these questions when it seems you have no basic knowledge of electricity...let alone electronics (The manipulation of electricity). It's almost like trying to walk on quicksand.....read up on the basics...get onto some solid ground to walk on as it were. We have all been there, everyone of us....there's an extreme very few who can jump right in the middle. You need a foundation before you can build a house. OK?


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