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I am wanting to build a small valve foot pedal for guitar. Would it be possible to run the plate off mains 240vac 50hz?

The tube is maxed at 300v but can run as low as 100v. http://pdf1.alldatasheet.com/datasheet-pdf/view/121279/GEC/12AX7.html

Re-design7 years ago
YOU MUST USE AN ISOLATION TRANSFORMER.
YOU MUST USE AN ISOLATION TRANSFORMER!
YOU MUST USE AN ISOLATION TRANSFORMER!!

Otherwise you could die and take some of the other people with you.  Running electronic equipment off the mains without an isolation transformer is very dangerous.

You can make an isolation transformer by connecting the secondaries of two transformers that are exactly alike.  240 input to one becomes safer 240 on the other side. 

Now that I've got your attention on the safety of this,  you can run the tube on 240 volts.  It must be d/c though so you'll have to rectify it.  And you'll need a 12V transformer for the filament.

Where is your schematic for this guitar effect pedal?  Can you post a link?

If you've not done some tube work before on proven diagrams, now is not the time to strike out on your own.  There are too many ways to make a mistake and working with high voltages any mistake can be deadly.

Go to this website and search "isolation transformer".  This site is concerned mainly with old radios, amps and test equipment.  Old radios work on high voltages, sometimes had little thought to safety and these guys have been working on them for lots of years and are still alive.  It's a great place to pick up information that you will be needing.

Good luck, and don't you dare touch that bare wire to see if it shocks you.
NachoMahma7 years ago
.  In addition to Re-design's isolation transformer, I would recommend using a GFCI / GFI / ALCI / RCD / RCCB on all circuits to instruments, amps, and effects.