switch for 120v to 240v

[Curranproducer]

I have an amp I am building that I want to be able to switch from 120v to 240v so I can tour it in Europe and asia. What kind of switch do I need for this? what would the specs be?

[Reeltarded]

A dual primary power transformer.. oh wait.. a multiple primary power transformer and a single pole switch that is around double the current rating as your mains fuse and has as many throws as the transformer has primaries.

100/120/220/240.. what else? I think that has it.

[Curranproducer]

ok GREAT!!!! i have a classic tone PT for this amp, so this is SUPER to hear!!!

[Reeltarded]

It has multiple primary connections? Some don't. Most don't.

I opt for external step transformers because then I have power for everything.

[rp]

If your transformer has one common then discreet taps for each voltage you can use use simple switch btwn 120/240. If it's got a bunch of series/parallel connections for the voltages, like a Hammond 300, done to keep the size down, then you're out of luck with a switch, maybe if you wrap your mind around it and only need 120/240 you could make it work. Not sure about the MC but on a Hammond 300 I just did it like this:

Unless you tour a lot it's pretty easy to just solder the jumpers in and out.

[martin manning]

For Classic Tone or any other transformers with dual primaries for 120/240VAC this simple DPDT switch will work.

[rp]

BTW I would use something like this, no idea where I got it. If I used something with a bat, I'd mount it on top of the chassis or on the side if there's room, somewhere so that it can't get accidentally switched and so that you'd have to at least take the back panel off to work it. Hitting 120 in 240 land would be way bad.

Or I'd use the Marshall flush selector that you can get easily.

[Curranproducer]

I do tour quite a bit so I need to definitely get that happening, and the pic of the switch is truly the way to go so nothing gets bumped and ruined!!! thanks for all of the great help and info!!! loving the site for sure!!!! you guys are super duper helpful!!!

[tubeswell]

Another design consideration you may want to consider; 230V 50hZ mains PTs need to be bigger (all other things being equal) than 115V 60hZ mains PTs, because the former have a greater amount of magnetising current in the core etc. PTs that are too small heat up and die more quickly.

Compare the red and the blue sine waves in the following graph - The area underneath each function curve is the amount of power in each case.

[img:750:430]http://upload.wikimedia.org/wikipedia/c ... Hz.svg.png[/img]

[VacuumVoodoo]

Another design consideration you may want to consider; 230V 50hZ mains PTs need to be bigger (all other things being equal) than 115V 60hZ mains PTs, because the former have a greater amount of magnetising current in the core etc. PTs that are too small heat up and die

Which is why you should check manufacturers data sheet for the transformer you intend to use. It should specify operation from 47Hz to 63Hz which is required to comply with the IEC norms. If it's not specified - don't assume anything.

[rp]

http://www.tubesandmore.com/products/S-HM100

[JazzGuitarGimp]

You should also consider fuses: if your amplifier requires a 2A fuse @ 120V, then you should use a 1A fuse @ 240V.

[Reeltarded]

And if by Asia you mean Japan you'll be needing 100v/50Hz.

[martin manning]

You should also consider fuses: if your amplifier requires a 2A fuse @ 120V, then you should use a 1A fuse @ 240V.

[Phil_S]

BTW I would use something like this, no idea where I got it.

That voltage selector is usually found in computers. I'd want to check it to see if it is rated for enough Amps.