Tube pedal transformers...

[pott]

Hey everyone! I just registered here after having had a stupid idea for a very simple tube pedal which I'm really trying to go forward with...
The idea is a pedal with 2 12AX7s (though I could only use 1, not sure yet) with only a drive, tone and level knob. The first side would simply be a clean boost, the second would use the 3 next triodes for an OD. The idea is that the level control would control the first channel (as the boost level), but also work on the second channel as the overall level of the pedal.
Secondly, my main concern is about the transformer. I don't want it to run on 9V, because I'd have NO IDEA on how to transform those 9V into 200 for the tubes... So I'd need a primary of 230V (Europe) and 2 secondaries of 6.3V/300mA and 200/6mA though obviously, it could go as high as 300V for higher headroom and clarity. The transformer used in the Matchless Hotbox (which is similar to my design) is a Hammond 269EX but I can't find them in any European online stores. I couldn't find any other transformers with the figures I want either... would anyone be able to advise me on what they're using, or even if possible on how to run the tube on battery/9V?

Thanks a lot!

[bancika]

Did you try at tubetown.de?
If there's company nearby that does toroid transformers you could get one. They should be cheaper than hammond and better as well.
The other solution is to get two 12V transformers and wire them back to back. First one will convert 220->12V for heaters and second will convert 12V back to 220V, then you rectify it and get about 300V.
Be carefull with HV!!!

[pott]

Eh I didn't think of that! Good point, thanks! Is that how most tube pedals are made then, with 2 small back to back transformers? I'll see if I can find some of those 12V and see how big they are. Tubes are safely ran at 12V instead of 6.3?

[The Tone God]

Don't take this as a jab at yourself but as a typical safety warning that is made around here. If you are asking these types of questions I don't think you are ready to work with high voltage circuits yet.

Andrew

[pott]

Well I already rebiased my tube amp without any problems... Maybe it's not safe, but in the lack of teacher/mentor around here, it's the only way for me to learn: by trial and error. Though hopefully not error. I'm not studying electronics and it's too late now for me to change, so I gotta try by asking around. I should probably buy a book, but all I could find were way too specialized compared to what I wanted to do... All the knowledge I gathered is from amp books so far.

[bancika]

Well, my first electronic project was firefly tube amp, made with absolutely no previouse knowledge or expirience. Just be cautios all the time...

[PaulC]

start off with a 12.6vac wallwort.  Run that into a common 12.6vac fil tranny wired backwards (going into the secondary side).  This will make the tranny act like a step-up tranny.  In the states the trick is done running 12vac into 6.3vac because of our lower line voltage.  What will happen is you now have a 230vac line isolated voltage to rectifiy and filter for your high B+ supply. 

Then you can tap off of the original 12.6vac wallwort to give you other voltages for the pedal.  You can take a tap off of it and rect/filter it to give you a DC heater supply for the tubes, and you can also tap off of it to give you a + - supply to power any opamps and other SS stuff. 

This is done alot in some pro tube pedals.

Later, PaulC

[The Tone God]

Maybe it's not safe, but in the lack of teacher/mentor around here, it's the only way for me to learn: by trial and error. Though hopefully not error.

My main concern is that an "error" may cause you the inability to learn...perminantly. I'm not saying don't try the project but more take alittle more time to learn before attempting it.

...so I gotta try by asking around.

By all means ask away. You can't get hurt by that. There are some other tube amp related forums you can visit to help like Ampage, 18watt, AX84, etc. I'm sure that will help you along as there is not that much HV work done around here.

Andrew

[pott]

Thanks everyone. I've also actually built my own tube amp and a pedal. Buildinga tube pedal just seems like the next step  But yeah... unfortunately, I'm a student, and in Europe. It's hard for me to get the part, to find someone who knows what he's talking about, and pretty much anything.
What's a wallwart..? Is that an American thing? I'll check it out and see if they have them here, thanks!

[bancika]

Where do you live?
I'm in same situation, just I live in Serbia which makes things even harder.
Wall wart means this
One idea I have: I'd like to build some tube pedal also, and I have one unfinished multi power supply project. At the moment it gives few 9VDC and 12VDC regulated and filtered outputs, but I'll put bipolar +-12V and 300V for tube pedals also. So it will just need two cables (one for High and one for Low) voltage going from power supply box to tube pedal. Other pedals will be powered with 9V outputs. I'll put everything inside old PC power supply unit I have around. So inside tube pedal I'll have only circuit with no chance of getting hum caused by proximity of AC to signal wires. And it will be more space for actual pedal.

[d95err]

Checkout the small and cheap Electro Harmonix toroid trafo that Aron sells:
http://www.diystompboxes.com/cart

You can input 12V AC and get 230V AC out. Perfect for a tube pedal or preamp. The heaters can run on 12V AC instead of 6.3V if you connect them in series (that's what the "12" in 12AX7 is for anyway...).

2 channels and 4 gain stages is certainly not "simple"; it's a very complex design. If you are new to tube electronics, I'd suggest simplifying the project idea a bit. It may be best to start off with a tried and tested project before trying to design your own. Tube pedals are very sensitive to noice, hum and oscillation, so it's very important to get the layout right.

Good luck with the project!

[bancika]

Since you live in Europe it's better to get it from www.banzaieffects.com, shipping will be less and it's the same transformer as hoffman's. Damn, if I got a dollar every time I recommended Banzai

[Desperado]

You got a guy in Novi Sad he is making very good transformers for me, power and output transformers.