What about miniature tubes?

[mnordbye]

I'm searching for different types of tubes, which easily can be used in pedal related circuits, and where to buy them. I'm looking for the small kind of tubes (preferably).

Also, what tubes, or kind of tubes, works well at 9V?

I've seen the Valvecaster, and all the deriviates, which makes me wanna design something myself, with mini tubes!

[sickbend]

the sub mini 6111 comes to mind as does the 6112 submini tubes and the 5676 submini tubes to look um up on ebay  

http://stores.ebay.com/Townsend-Tube-Works_W0QQfrsrcZ1QQfsubZ14212008QQtZkm section is labled stomp box tubes

[mnordbye]

the sub mini 6111 comes to mind as does the 6112 submini tubes and the 5676 submini tubes to look um up on ebay  

http://stores.ebay.com/Townsend-Tube-Works_W0QQfrsrcZ1QQfsubZ14212008QQtZkm section is labled stomp box tubes

Quite a selection they've got! Seems like a good place to get some of those dwarf-tubes..

Another question.. Many of these require the 6.3V filament. I guess i can use the same biasing as with pedals, to drop from 9V to 6,3V with a trimpot?

Any other issues i must tend?

[sickbend]

some of them are 1.5 volts id use a double a battery for the heaters im thinking a center tapped 12 volt transformer could be used to supply the 6 volts for the heaters or an adjustable regulator to bring down the voltage for the heaters via a dc jack 

[sean k]

http://www.mif.pg.gda.pl/homepages/frank/sheets/137/6/6112.pdf

Heres the data sheet for the 6112

http://www.storm-software.co.yu/diy/

which I got from this page.

Sub mini's are just like big tubes except they are much smaller... so they could be put into various bombs and missiles in WW2 as part of the guidance systems... well not guidance so much as proximity... anyways they were designed for war kinda stuff.

Anyways, like a regular tube, the filament requirements are not a bias thing, like the 4.5V on opamps, but a set of heaters that when heated expel a whole bunch of free electrons that become the audio signal. That means the heater voltage and current requirements are pretty much written in stone, and usually on a different winding of the PT than the power for the circuit.

Thats not to say you have to power then from a different winding on a transformer but its what usually happens.

Tubes are a totally different kettle of fish to transistors and  like diesels and two strokes are different from four stoke gasoline engines. Basically the same to acheive the same kind of output but different in how they go about acheiving that output.

So the plate, grid and cathode, of a tube, are analogous to the collector, base and emitter of a npn transistor and basically use the same connections. Plate to power, grid to 0 volts and cathode biased positive a little above ground but the heaters are what makes it all happen even if they don't actually play a part in the signal processing itself.

They are kinda like the LED's we use to show us our FX is turned on. They use a whole bunch of current at a much lower voltage than the rest of the circuit and if they aren't put in the right way, as regards the power supply and it's grounding, they can add noise we don't want on the signal.

Just read up some on tubes and you'll soon get it. I could go on about LED's as light emitting diodes being somewhat similar to heaters as electron emitting devices but it'd just get silly and move too far away from what you've asked to be answered.

[Zben3129]

Compared to stompboxes, the filaments draw tons of current (150mA all the way to 1A+), so setting filament voltage with a trimpot (or a pot for that matter) is a no-go, as you could never get enough current from a normal voltage divider. You could use a 6v AC supply, 6v DC supply, and with some tubes a 12v AC or DC supply. Any supply over the heater voltage can be made to work with a dropping resistor, whose value and wattage can be easily calculated.

Zach

[mnordbye]

I appreciate your comments, Sean! It get's easier when you can compare the pinout of a transistor with the ones on a tube. If i got it right, i understand it's the same as firing up a transistor, except you also have to provide the heaters with it's prescribed voltage (6,3V, 1,5V or whatever...), so they can get moving! That sounds about right?

So, what i then wanna know is how i can supply the heaters with the voltage required, in the easiest way possible. Or even the most practical way. It would be nice to not need to use anything other than a 9V adapter. Does that sound doable?

Thanks for the replies so far!

EDIT: If i understand you correct, Zach, if i needed, let's say 6,3V at the heaters, and i'm using a 9V adapter, would it be plausible to use something like a zener diode to drop the voltage from 9 to ~6,3? And does it need to be 6,3V accurately, if that's the case?

Like this: http://www.banzaieffects.com/2-7V-Zener-Diode-0-5W-pr-16457.html

[Zben3129]

Common comparison is N-CHAN JFET to a triode as well.

As for how they work, the heaters heat up the cathode to the point where electrons "shed" off of it and these are pulled across the vacuum of the tube to the plate (anode) which is always at a more positive voltage by design. This is a simple diode tube. Add the grid, and you have a triode (think 12ax7). Signal is applied to the grid, which is then amplified dependant on this flow of electrons across the tube. The grids job is to make sure electrons don't fall back to the cathode (grid is always more negative to cathode by design).

Zach

[mnordbye]

I posted a link to a Zener diode in the last post. Do you think that putting that between the 9V source and the heaters will work, and generate the 6,3V required?

[Renegadrian]

You can use a 12V source (regulate it with a 7812 if you like), then apply 6v to the heaters thru a 7806 - that's what I did for my Triode Triode experiment

[Minion]

If you know the current draw of the fillament and the source voltage you can calculate the required resistor needed to drop the source voltage to the needed fillament voltage...It is the same calculation used when figureing out how to Power a LED from a Voltage higher than the LED Voltage.....

So for a 6v heater from a 9v supply at 150ma you will need a 22 ohm 1w resistor.....

[mnordbye]

Okey, so it's as easy as using a 1 watt resistor? What's the exact calculation phrase?

[Minion]

Since I suck at Math I simply use the LED Voltage calculator.....

http://led.linear1.org/1led.wiz


Just put in yer source Voltage ,then the heater Voltage and then the heater current....

[mnordbye]

Thanks! Now that makes real sense to me. I've learned a lot tonight, thanks guys!

[frequencycentral]

Lots of submini tube info here: http://www.diystompboxes.com/smfforum/index.php?topic=71381.0