Voltage / Charge pump Question

[coxter]

Hi I saw this article on GeoFex.com regarding the charge pump. Where a 9V battery can be charged to produce up to 33V+

Just wondering if I can get to have a 105V+ from a 27V source, i.e, 3 x 9Vs; directly replacing the 9V with 3 batteries.

Or would I have to use 3 of the 33V+ circuits to get 99V+

Whichever the case I just need a high voltage.

[coxter]

Oh heres the link:

http://www.geofex.com/circuits/+9_to_33.htm

[Paul Perry (Frostwave)]

Those charge pump chips have a fairly low maximum input voltage, unfortunately. One thing that may be worth looking at (if the current is sufficient for your purpose) is the high voltage generator in the flash circuit in disposable cameras (sometimes you get a bunch from surplus). Oscillator & tiny step up transformer.
There are ready made DC/DC converter modules as well, but that's going to be a few bucks.

[Sir H C]

Yeah, the ICs have a maximum voltage and that would definitely exceed it.  When you get up that high in voltage, transformers or inductors is the general way.

[coxter]

So i guess it means I'll have to use 3 of the combination to get me 99V then.

[coxter]

Actually the problem is that I understand how a transformer works but I just totally have no idea how to hook it up

LoL, and most of all very afraid of killing myself by hooking it up to the mains.

[John Lyons]

Transformers are the way to go. DOn't be afraid of high voltage. The warnings are reall but the fact is that if you pay attention you will be fine.
Look for "back to back transformer" info. Goes like this wall voltage>120 to 12v transformer>12v to 120 volts same transformer but turned backwards. not you have 120volts to work with! The first trasnsformerisolates your from the high AC voltage (think safety)and the second transformer ups the voltage from 12 to 120. Now go build something!

PS you can get dirt cheap transformers from thrift stores as most phones us 12v supplies. The bigger the Ma of the transformer the larger the current and more tubes etc you can power. Tapping off the output of the first transformer will give you the 12v for the tubes filaments.

John

[coxter]

Well actually I do have a transformer right now. I bought a 9V one.

But I totally dont know how it works. I mean what each pin does.

My transformer is labelled "3VA, 9V-0-9V" So is it a back to back one?

Its got 6 pins, 3 aside, One side going 9V-0-9V, and the other side going 230-115 and can't figure out the last one, its too muffled.

Can you/anyone explain to me what those pins do, or at least how to connect them.

I know that it'll be better to use a 12V one for tube-based stuff, but I just happen to have a 9V one, so lets just pretend its 12V alright? :wink:

[John Lyons]

Let's back up a minute.
What are you trying to build here?

A back to back transformer is two tansformers. One running "normally" from wall voltage to 12v, 9v..etc The second  transformer is connected to that first ones 12v secondary so the first transformers 12v is upped to 120v. The first transformer is just isolating the supply from the wall voltage as a safety measure.

Transformers are either "step down" or "step up".
From the wall voltage through the transformer to 12v is step down, which is what a wall wart dodes. Takes 120vac and turns it into 12vac etc. Then there are two diodes which turn the AC into DC, then a large capacitor which filters the DC to a more pure DC. ( After the diodes have a little AC on them so the cap smoothes out the AC ripple. )

You should be able to find the information for your transformer from a datasheet. Just look up the # nformation  from where you ordered it and look up the datasheet which will have a diagram.

John

[coxter]

Oh oh Okay thanx for straightening up. was a little dreamy LoL its 2am here.

I think i got a single step down one. Probably can only use it as a psu for pedalboards.

Got a link to a back to back one? Or a picture? cos I'll be going down to my hardware store tmr. so i can pick one out

[brett]

Hi
Whoa!  If you are building anything capable of powering the common types of tubes, you are definately building something capable of killing yourself, your family, the dog...you get the idea.
OK.  Now that the "heads up" concerning safety is over, here's what you can do:

As suggested above, for a power supply for low-current at valve voltages, almost everyone will want to use *two* small transformers "back-to-back".  If you've got a 9V, you'll probably want another 9V or a 6V to complement it. 
A well-known example of back-to-back transformers is in the Real McTube.  It is a good idea to read eveything you can about the power supply in this circuit.  It steps 120V to 12V and 12V to 120V.  For this circuit, I changed things a bit to increase the headroom and to account for my local voltage (240V) by using two 12V transformers and a resistor to step 240V to 12V, 12V to 9V (via resistor losses), and 9V to 180V.
Depending on what you want to do with the tube(s), you might be able to get away with quite small transformers.  The high value plate resistors in the McTube allows for a very small step-up transformer.  However, the step-down transformer will usually have to produce at least 300mA output to power one heater and the step-up transformer.

If you would like more assistance from the forum it would be useful if you could describe your project in more detail.  And feel free to ask questions.
cheers  

[Minion]

There are some Low voltage/Low current Tubes that are suitable for audio applications so you don"t necessarilly have to use a Tube with a Plate voltage of 120v+ in an audio circuit....

I have recently started working with some Sub-Mini Tubes with quite good results....I have been useing some 6418 Sub mini Power amp pentode tubes in Pedal circuits and Preamp circuits and get a very Good Tubey sound...These tubes only need a 1.25v Fillament Voltage and between 15v and 30v Plate voltage and only require about 10mA per tube and the tubes are extremely small at about the size of a small Capacitor (about 1in High and 1/4 in wide)....

also instead of useing a bulky Output transformer for controlling the output impedance I use Fets or Transistors or even an Opamp which can be easilly run on the available Voltages for the Tubes.....

Just something to look in to....

[coxter]

I just got back from my regular trip to the hardware store and couldn't find any back to back trannys.
So I bought 2 x 12V ones... Just in case

And I also can't find any online, cause I dont know whats the correct name for it.
Tried searching for 'back to back transformers" in the forum and on google. Can't find anything.

I got to Hammond's website though.

http://www.hammondmfg.com/claspg.htm

Can someone pick out which one is the 220-12V-220 Back to back one for me ?
I'll for very grateful

[John Lyons]

There is no single back to back trasformer. Back to back is two separate transformers. One running forwards and one running bacKwards.
This is why the two used together is called back to back.
WHat you nheed is two 12v transformers as you now have.

One thing you may want to look at is the low voltage tubes That Minion mentioned above. Also look for sopht amps or something like that. Low voltage tube circuits...

John

[coxter]

Oh... ROFL... Thats why there was some sort of a communication gap in the few previous post.

Alright Alright, I understand now. LoL. Quite unappealing isn't it? To have 2 trannies busting out of the enclosure.

Thanx for being so paitent by the way.

Yeah, I managed to check out the new Seymour Duncan tube driver, OMG, the tone is wicked.

[brett]

Hi
a tube that I've spent some time messing with is the 12U7.  Some people call it a 12AX7 designed to work at 12V    ....but it isn't  .
It works at 12V but only gives a gain of about 4.  It takes a bit to overload it, too.  I've used it in this configuration:
op-amp with gain of 10 ---> first triode   ----> second triode
Using heater and plate voltages of 13.2V works ok (they were designed for cars).
However, don't expect a high-gain 12AX7 sound.  In my current configuration (both triodes with a 47k plate resistor and 4.7k cathode) the tone is quite mild.  There's also some problem by which driving it really hard results in a loss of gain that takes a short time to dissipate (about a second?).  Maybe the grid is accumulating charge and I need to reduce the grid resistor?

Anyway, these tubes can be got second hand for about $5, and datasheets are available, so anybody who's thinking about low voltage tubes could give them a go.
cheers

[Paul Perry (Frostwave)]

To have 2 trannies busting out of the enclosure.

You don't need to have them BOTH in the enclosure.
I would have one as a plug pack (wall wart) and the other as a small uncased transformer inside the effect box.

[coxter]

I've found it.  those two in one transformers.

Check out the 269EX by hammond. It provides a 6.3V filament voltage. LoL.

I bought like so many, - 3 , trannies... argh...