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110vAC to 240vAC for Amps - Any Step Down Transformer users?

Discussion in 'Amps and Cabs [BG]' started by Cúl-Báire, Jun 13, 2005.

  1. Well I'm not far off securing a deal on a great condition 800RB, finally... Anyways
    after contacting Gallien Krueger, they said the amp is not convertable to
    220/240vAC used in Australia (these amps arent available in OZ) but recomended the use of a step down transformer- claiming that it will work fine.

    I was just wondering, is there anyone here from Europe or Australia or anywhere else for that matter uses a Step Down transformer at all on their US made 110vAC amps? This topic, or atleast the conversion topic has come up a few times, so is there anyone out here in a situation like me?

  2. I know someone who used a stepdown transformer with no problems, it was a proper one that cost about £80 i think, and was fairly big (uk voltage is also 240v)

    I know my svt II was originally from the US (has to use 110v printed on the back of the chassis), but i opened up the top cover and one of the transformers had be changed, dunno if you could get a tech to do that to your 800RB
  3. bmc


    Nov 15, 2003
    Curious about the answer from GK.

    A couple of years ago, I wrote them about converting my MB150 head from 110 to 230 and it wasn't an issue. I just can't find the the email to pass along to you. Now, it could the heads are very different and you can't make the change.

    Using a power transformer is a small manageable pain in the butt. It's an extra piece of gear to lug around. Just be sure you very clearly mark which end to plug into. Easy to cook things.
  4. +10000

    A transformer works both ways. Just as it takes your 220 volts and converts it to 110 v for your amplifier, it will also take your 220 v and convert it to 440 v if you plug it in backwards.

    Think of it like a voltage multiplier. Going one way it divides by 2, going the other way would multiply by 2 as well.

    Make sure it handles the max power requirements of the amp. NOT THE MAX RATED SPEAKER OUTPUT POWER!!!!

    A 100W amp requires significantly more power than 100W from the wall. Check the AC fuse/circuit breaker, NOT THE SPEAKER PROTECTION FUSE. That's amperage. Multiply that by the voltage to get wattage.

    110v with a 10A fuse = 1100 W. Make sure your transformer will handle more than that. NOte: It will pull 220v with 5 A (also 1100W ) from your wall socket. So if the transformer is fused at the input side, its fuse (for 220v) will be 1/2 that of the fuse on the amp (for 110v). Same wattage cause the voltage is doubled.

  5. Depends on the model and if they have used a multi-tap mains input transformer - if they have not then you would need to get another transformer - really too much hassle unless you as are really into working on this stuff.

    I an awaiting the arrival of a 110v SWR which will have to run on 240V here in Libya I have a transformer awaiting, but plan to rewire the input transformer - fortunately for me, this model can be done and the customer support people at SWR sent me the appropriate witring diagrams.

    We shall see!

  6. Interesting- I know some of GK's amps are, and some aren't- I could get a tech to change the transformer over while it's here- but the cost would be quiet high, as these amps are not distributed here- as thy didnt pass Australian CE standards. SPare parts would be hard to come by no doubt.

    Looking at wattage ratings- I know the Gallien Krueger 700RB II requires 575w at peak power- and 210w at average power on a 110/60hz circuit. I have contacted GK about the ratings for the 800RB, but they are yet to get back to me- I cant see it being much more than that, porbably due to it being an older amp- less efficient.
  7. I used one here in 240v NZ for quite a while to run a 110V SWR 350x. Never had any issues.

    I originally thought there would be a better solution - however the transformer on the SWR was not tapped, and I couldn't find anyone who was willing to have a go at re-winding the transformer.

    As other people have said, an external step-down transformer can be quite heavy & annoying... but I had room to mount it in the rack of the rack case, so it worked out ok.
    edit: I even found a pic:


    However, due to the size to the transformer you need, imho it is not a very practical solution for anything much bigger than a 300W amp (your tolerance for carrying extra bulky, heavy pieces of equipment may vary :D )
  8. BassDemon


    May 18, 2004
    I used one with my Sansamp RBI which was 110v

    I got one from Dick Smith for $50

    Make sure that the step down transformer you get can keep up with the maximum wattage draw of your amp.

    The Sansamp being a pre-amp only drew a max or 5 or 10w (I forget which)

    The GK will likely draw a lot more. If your transformer is not up to the task you may damage the amp, transformer or both.

    N.B - in NZ and Australia it's not possible to plug the transformer in the wrong way around. The plugs are a different shape to American mains plugs.

  9. Thanx for the picture, and feed back Jemetch, very helpfull, and the picture just confirmed what I had planned on doing also. I had planned to get the smallest transformer posable- while still maintaining the correct rating- and build it into the back of a rack case for my head. to make it easyier to transprot arround etc...

    The GK is 300w Main/ Low Channel / 100w Biamp High Channel, so it's not all that big really- not an SWR 750x or something... So a smaller transformer should do.

  10. No problem. Us 240v'ers have got to stick together. :p

    I got the transformer from JayCar... I'm sure they will have exactly the same one in the Aussie stores.
  11. teleharmonium


    Dec 2, 2003
    I use step up transformers in the USA for UK made guitar amps, same principle. The main thing to understand is that you need to have a big enough transformer for the power consumption of your amp, not the output wattage. I have no idea how many watts are consumed by solid state amps, but you should be able to find that out in your documentation or online. The small to medium sized tube amps I use need about 250 watts minimum apiece (for amps that output between 5 and 50 watts), I only use 500w xformers. They weigh about 30 or 40 pounds. I would think ss amps would need considerably less.
  12. my peavey firebass is 1200 watts consumption, 700 watt output (2 ohm)

    where as my svt II tube amp is about 1000 watt consumption and 300 watt output, fair difference in ratio!
  13. Paulotron


    Jun 5, 2005
    sorry to dig up an old thread, but the fact its this old shows at least i looked for an answer first(even if i missed it):spit:

    I have a US(live in the UK) SVT-3 pro and the manual doesnt state what wattage it requires. I've used a 100w tranformer with no problems with US BBE's and Tech-21's, but as they were pre amps i dont know if the same transformers will suffice for this head. Any help is greatly appreciated.

    Many Thanks
  14. Paulo- you should look into having the transformer changed - the SVT transformers are multitap - meaning that a fairly competent electro techie can switch a few wires over (converting it from parallel to series) and having it run like clockwork on 230v.

    I actually have a schematic kicking around if you need it. they're pretty easy to google. The last page of the schem has the transformer voltage configurations.
  15. BassMonstrum


    Mar 7, 2008
    I stumbled across this thread because I'm one step closer to ordering a GK800rb from the US and I live in Norway.

    I used to have an SVT3-PRO years ago which I bought in NYC. Had to use it with a HUGE transformer... weighed almost as mush as the amp itself. I was 19 at the time and it was my first real amp... funny I should learn about tech 10 years after.
  16. murphy


    May 5, 2004
    Toronto, Canada
    Why not just pick an amp that has internal jumpers.
    My old Eden WT400 and 800 had them,
    I think my Markbass amps have it too.
    Keep it simple
  17. One Drop

    One Drop

    Oct 10, 2004
    Swiss Alps
    Some old SVTs have dual voltage transformers and some don't. My 72 doesn't so I use a 1000w fused step-down transformer. It only weighs about a kilo.

    Most recent class D and switching power amps seem to be useable at both voltages.
  18. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    You may not have had to..... all of the SVT-XXXX amplifiers were universal 100-240V for many years. All that was required was to change the position of some wires on a plug-board.

    If the unit was VERY early, it is possible it was US only.

    On vintage '70's SVT, there WERE units with dual voltage, and ones without.

    Very easy to check, a US-only transformer from any company will have 2 mains wires only. If it has more, it is probably suitable for at least two voltages, depending on how it is made.
  19. Do this for your 800RB and keep the old trans in case you need to switch back.
    Polar Audio

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