What step-down transformer for US to UK?

Bill

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Hi,

Completely non-technical person here!

I'm planning to bring my old Fender amps from California to London. Is it totally safe to run them using a step-down transformer?

If so, what transformer do you recommend or features look for?

Price isn't an issue, quality is. I'd like it to have at least two us-style sockets so I can run two amps at once. This would be almost solely for home use. And I don't know if I need to have it adapt to the different frequency here. I'd assume that's not an issue with amps, though I read of at least one transformer that can do that if necessary.

My amps include late tweed Princetons, a silverface Princeton Reverb, a Rivera-era Super Champ, a '66 Deluxe Reverb, a '78 70-watt Pro Reverb, a 40's Leilani, etc.

Thanks for any help!
 

Rich_S

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An auto transformer might be cheaper than an actual step-down transformer. Auto transformers don't have independent windings, so they don't provide isolation. That makes them less expensive and you don't need isolation here, you just need voltage reduction. They also provide completely variable output voltage, so you could tweak the output to whatever voltage the amps really want.

It's not an exact science, but I would recommend a unit that can provide output current equal to the sum of your two largest amps, times a fudge factor of about 2. This makes sure you have enough capacity that the voltage won't sag when you hit it hard.

So, let's say the Deluxe and the Pro together can put out almost 100 watts. Tube amps are inefficient, so they draw 3-4 times that from the wall, so say 350 watts are needed. I'd buy an auto transformer in the 750 VA range. Even 1 kVA wouldn't be out of line.

Make sure you get one rated for 50 Hz.

And once you figure out the working range of the dial, I'd screw a couple of little rubber feet to the front of the thing, to keep you from accidentally turning the voltage outside the range of 100-130 volts. Hate to accidentally bump the knob up to 10 and fry those amps with 230.
 
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Jon Snell

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I have found that RS or Farnell supply a good range. No account, just a credit/debit card is needed for RS, Farnell require a trade account. Easilly set up on their main web site.

You will not be using them all at the same time so look on the model plate at the rear of the cabinet. There will be the maximum wattage drawn. Choose a 230 - 110 Auto transformer of equal Wattage.
If the plate states 270Watts, try and find a 300V/A transformer something like https://uk.rs-online.com/web/p/autotransformers/3101162/ or https://uk.rs-online.com/web/p/autotransformers/3288067/ if you can fix it in the cabinet https://uk.rs-online.com/web/p/toroidal-transformers/1233991/
If you have not got the knowledge for a safe job, there are many professionals in the UK that will be willing to help including myself if you fancy a trip to the coast.

I hope that helps.
 
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Gazza74

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Hi,

Completely non-technical person here!

I'm planning to bring my old Fender amps from California to London. Is it totally safe to run them using a step-down transformer?

If so, what transformer do you recommend or features look for?

Price isn't an issue, quality is. I'd like it to have at least two us-style sockets so I can run two amps at once. This would be almost solely for home use. And I don't know if I need to have it adapt to the different frequency here. I'd assume that's not an issue with amps, though I read of at least one transformer that can do that if necessary.

My amps include late tweed Princetons, a silverface Princeton Reverb, a Rivera-era Super Champ, a '66 Deluxe Reverb, a '78 70-watt Pro Reverb, a 40's Leilani, etc.

Thanks for any help!
Welcome to the U.K. ! I went through the same experience 3 years ago. For home use I bought this unit made by mercury magnets.

IMG_5587.JPG
 
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voskarp

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Be sure to use one that keeps the amps properly grounded (assuming that they do have a three prong cord to start with, right?)!
 
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Gazza74

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I hope youre not using this unit with a 20 watt tube amp or more.
40 watters pull up to 180 watts your unit is 100:D

So... For a 40 watt you need around 200 watt unit to be on the safe side
Fair question.... I have a 15w fender super champ tube hybrid amp and a 30w fender acoustasonic solid state that I use with it.
 

metalicaster

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A long shot, but I'd look up the specs for your amp's power transformer. Many of them have multiple taps to allow for configuration for different markets. It could just be a case of moving a couple wires to make it work on 240 or 120.
 

Bill

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Wouldn't that be a step UP transformer?

I'm taking a US amp that expects 110 volts and plugging it into a UK wall that delivers 230 volts. So I assume I want to step down the voltage from 230 to 110.

But maybe I have this wrong?
 

Rich_S

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It bears repeating: guitar amplifiers are inefficient beasts. They draw substantially more power from the wall than their rated output power to the speakers. For tube amps, figure their draw is 3-4 times the rated output. For solid-state, it's more like 2-3.
 

knavel

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I'm close to the point where I've lived longer in a 230v world than the 110v world I grew up in. It's important to heed the advice above about sufficient power in a step down transformer for your amp, i.e., not some thing that just plugs into a wall socket. You need something that looks like a Neumann U47 power supply.

In my decades I've never had a problem with my step down transformers a single time, be they the Chinese junk ones I bought in LA before I moved here and was much in your current mindset, or the stuff I got when I got here.

Rather, where I had real issues has always been with grounding (or earthing as they say here). I got to the point where I just bought a wireless unit and that was that.

If you are coming here to the UK to gig and get stuck, just contact me. I have a 62 Tremolux and a 65 Epiphone Comet (15watt) that I've changed the power transformers on (because they were fried when I got them). Also the only original 230w amp I own, a 64 Vox AC4, the quietest amp ever made. The rest of my amps are still 117v.
 

Bill

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If you are coming here to the UK to gig and get stuck, just contact me.

Actually, I live in London and have for the past decade. My amps are still in storage in the states though. I'm hoping to bring them out to London next year.

But thank you kindly for the offer!
 




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