Voltage for the Valvecaster?

[Ell]

I made a Valvecaster ages ago and I normally run it at 12 volts. I use it as a Clean Boost and it does the job nicely.

At the moment I'm building a pedal board and I'm currently looking at Power Supplies. The Fuel Tank Jr has caught my eye since it's considerably cheaper than the Pedal Power 2+ and it has 5 isolated 9v outputs. Is it very important that the Valvecaster gets 12 volts? It's kind of a matter of either getting a different power supply altogether (like the Artec SPB-8) so that I can run it at 12 volts, or I could just leave the Valvecaster at home and build yet another clean boost.

I live in London, so a lot of American power supplies aren't available to me, or cost far too much.

[Renegadrian]

Altough the tube won't noticeably suffer of heater starving, it can kill it slowly - basically it will never work at the right potential - after all, they are called 12**7 cause that's the heater voltage they need - maybe you want to try a 9**7, which is basically the same with the different heater voltage needs.
Maybe you can go with an internal voltage doubler (max1044 or a 555) so you get +-17V for the plates and 12V with a 7812 for the heaters...

[Ell]

Altough the tube won't noticeably suffer of heater starving, it can kill it slowly - basically it will never work at the right potential - after all, they are called 12**7 cause that's the heater voltage they need - maybe you want to try a 9**7, which is basically the same with the different heater voltage needs.
Maybe you can go with an internal voltage doubler (max1044 or a 555) so you get +-17V for the plates and 12V with a 7812 for the heaters...

I hadn't even thought about a 9au7. It doesn't look like they are too expensive either, so I might buy one and see how it sounds (I'm guessing it'll just have less headroom).

My mind has wondered over to the BBE Supa-Charger now. The 12 volt outputs are 100mA. Do you think this is enough juice for the Valvecaster? I'm pretty sure it's not.

[Renegadrian]

Yeah you can find one for cheap, I bought one thru Evilbay and made a 9v Valvy - indeed there is a little less headroom...
There you have to make your choice - a dedicated 12V WWart or go with 9V???

As you can read in the tube datasheet, they need more than 100mA for the heaters - so no, 100mA aren't enough...
it seems that 500mA get you in the safe territory...

[rogerinIowa]

Altough the tube won't noticeably suffer of heater starving, it can kill it slowly - basically it will never work at the right potential - after all, they are called 12**7 cause that's the heater voltage they need - maybe you want to try a 9**7, which is basically the same with the different heater voltage needs.
Maybe you can go with an internal voltage doubler (max1044 or a 555) so you get +-17V for the plates and 12V with a 7812 for the heaters...

I hadn't even thought about a 9au7. It doesn't look like they are too expensive either, so I might buy one and see how it sounds (I'm guessing it'll just have less headroom).

My has wondered over to the BBE Supa-Charger now. The 12 volt outputs are 100mA. Do you think this is enough juice for the Valvecaster? I'm pretty sure it's not.

renagadrian could you take a moment to clarify which pins of the 12au7 are which as far as "plates" and "heaters"  ?
I am new to tubes

[Renegadrian]

Sure! 
Have a look at this...


Plates are 1 and 6
Grids are 2 and 7
Cathodes are 3 and 8
Heaters are 4 and 5 - 9 is the middle heater, usually we didn't use it in our projects...

[Ell]

Right, thanks Renegadrian. Looks like I'll just be taking the Valvecaster off the board 

So I'll be making another volume boost to go at the end of my chain, any favourites of yours? So far I have a Stratoblaster in my guitar, and then an LPB1 & LPB2 combo pedal at the start of my chain. I prefer the Stratoblaster to the LPB twins since they are very bassy, but sometimes that's a good thing. Both the Stratoblaster and the LPB's distort a bit too soon, whereas I liked the Valvecaster for it's cleanness, but i'm guessing that's just because it's 12 volts. So yeah, any favourites of yours? Or should I just make another cheap Stratoblaster and run it at 12 volts.

[Renegadrian]

Glad I can help!  
I have a Stratoblaster inside on of my axes, and it sounds good thru a Valvy - But the booster I like the most and the one I suggest you is the Tillman - it gives a slight boost but doesn't alter the sound completely.
And yeah the LPBs are known to be more on the bass side, altough some guys (Rick?!  ) seem to like it (more than me...) - I'd say, play a little with the Stratoblaster but yeah build a Tillman!!! You won't regret it...

edit

I usually put the boosters before the Valvy, but I guess the Tillman should boost in a good way if after.

[slacker]

Right, thanks Renegadrian. Looks like I'll just be taking the Valvecaster off the board 

Why? just get it its own power supply, you don't need anything fancy just a bog standard 12volt wallwart will do the job, just make sure it can provide more than say 300ma, and it will be fine. You've probably got something suitable lying round the house somewhere

[frequencycentral]

slacker's right - you should keep it, just with it's own power supply. I doubt a 12AU7 in a Valvecaster circuit draws even 200ma, the heater draws 150ma @ 12 volts, the plates just a few ma together.

Renegadrian's right too - consider using a 9AU7 in your Valvecaster, run it at 9 volts, and use a MAX1044 charge pump to deliver a higher plate voltage, you'll be really pleased with the results - tubes start to 'hot up' once you pump 30 - 40 volts into them. Be aware though the the current requirement for a 9AU7 is considerably higher than a 12AU7 (225ma). Even then, the thing will still draw less than 300ma altogether.

I wonder why the 9AU7 isn't used more, considering that it's 9 volt heater requirement really lends itself to stompboxes. But I've gone the other way, I run all my stompboxes from 12 volts, basically because it's such a tube-heater-friendly voltage.

[Ell]

Glad I can help!  
I have a Stratoblaster inside on of my axes, and it sounds good thru a Valvy - But the booster I like the most and the one I suggest you is the Tillman - it gives a slight boost but doesn't alter the sound completely.
And yeah the LPBs are known to be more on the bass side, altough some guys (Rick?!  ) seem to like it (more than me...) - I'd say, play a little with the Stratoblaster but yeah build a Tillman!!! You won't regret it...

edit

I usually put the boosters before the Valvy, but I guess the Tillman should boost in a good way if after.

Right, I'm eager to hear what the Tillman sounds like now. I'm gonna give it a go! I've found a layout in the gallery so I might even finish it today. Cheers.

Why? just get it its own power supply, you don't need anything fancy just a bog standard 12volt wallwart will do the job, just make sure it can provide more than say 300ma, and it will be fine. You've probably got something suitable lying round the house somewhere

At the moment I'm using this power supply ( http://www.maplin.co.uk/Module.aspx?ModuleNo=32754 ) for the Valvecaster, but it's huge! I suppose I could buy a supply with a lower current, but I'd kinda prefer have everything on my board plugged into the same unit - just for ease sake.

slacker's right - you should keep it, just with it's own power supply. I doubt a 12AU7 in a Valvecaster circuit draws even 200ma, the heater draws 150ma @ 12 volts, the plates just a few ma together.

Renegadrian's right too - consider using a 9AU7 in your Valvecaster, run it at 9 volts, and use a MAX1044 charge pump to deliver a higher plate voltage, you'll be really pleased with the results - tubes start to 'hot up' once you pump 30 - 40 volts into them. Be aware though the the current requirement for a 9AU7 is considerably higher than a 12AU7 (225ma). Even then, the thing will still draw less than 300ma altogether.

I wonder why the 9AU7 isn't used more, considering that it's 9 volt heater requirement really lends itself to stompboxes. But I've gone the other way, I run all my stompboxes from 12 volts, basically because it's such a tube-heater-friendly voltage.

I've never used a charge pump before. Would it be easy to just throw it in the circuit and get some results, or is it a large modification?

[Renegadrian]

There's the max1044 doubler/tripler, or google for the 555 doubler/tripler - quite easy to build and the parts count's low!

[frequencycentral]

I've never used a charge pump before. Would it be easy to just throw it in the circuit and get some results, or is it a large modification?

Very easy.

Have a look at this for the technical aspect: http://www.geofex.com/circuits/+9_to_33.htm

I'd recommend the charge pump part of this circuit (the seperate small schematic at the bottom left): http://www.diystompboxes.com/smfforum/index.php?topic=77636.0

Here's a layout that will get you 80 volts for 12 volts, or a little less from 9 volts: http://www.diystompboxes.com/smfforum/index.php?topic=74729.0

[Ell]

So if I stuck with the 12AU7, but did use the charge pump, what voltage would you recommend I boost it to for the plates? And I'm assuming I keep the voltage going to the heaters at 12 volts, right?

[Renegadrian]

I believe that everything above the incoming voltage gives more headroom - I think you start to have quite a difference at 3 times the voltage, while still if you just double it it's not bad at all, just not so pronounced...
I tried mine at 50V and got good results - haven't got the link handy, but I suggest you to search for the VOLTAGE MULTIPLIERS FOR OUR TUBE PROJECTS thread - you'll find some there...And yeah, heaters stay at 12V

[Ell]

I believe that everything above the incoming voltage gives more headroom - I think you start to have quite a difference at 3 times the voltage, while still if you just double it it's not bad at all, just not so pronounced...
I tried mine at 50V and got good results - haven't got the link handy, but I suggest you to search for the VOLTAGE MULTIPLIERS FOR OUR TUBE PROJECTS thread - you'll find some there...And yeah, heaters stay at 12V

So really there's no set in stone requirement? There's no ideal number is there, and no values will damage the valve?
I'm pretty sure I can add the layout in http://www.diystompboxes.com/smfforum/index.php?topic=74729.0 to my pedal without any problems, and I saw somewhere else which bit needs to be added again and again in order to go from 25 to 33 and up and up.

Thanks a lot guys, i'll let you know how it goes when I get around to doing it. By the way, at what point does the voltage become dangerous?

[Renegadrian]

Every tube has it own requirements - there are some good sites with all the tube listed, I love this one
http://www.nj7p.org/Tube4.php?index=1
So you can read every tube specifics, and voltage limits...While the 12**7 family has got a high voltage plate limit, some subminis have lower maximum voltages...
As for the danger, I know that the voltage is not the main thing - it's the current...You may find a lot of advices/warnings on tube oriented diy sites...

[Ell]

Thanks a lot Adriano, Rick and Ian. This has been an insightful thread.

[frequencycentral]

  BTW, the MAX1044 power supply is totally safe even at 80 volts - though I guess it would tingle if you stuck your tongue in it.........

[bassmannate]

That's the beautiful thing about tubes. They're so flexible! You really can do quite a bit with them and not have any issues!