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Guitarist Abroad - Is a Step Down Transformer Enough?

Discussion in 'Shock Brother's DIY Amps' started by Gaijinloco, Apr 17, 2021.

  1. Gaijinloco

    Gaijinloco TDPRI Member

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    Hi Everyone,

    I got a VOX AC4-HW1 recently, and about a week later found out that I'd gotten a job overseas in the Middle East. They run on standard British 240v 50Hz current. I really don't want to leave my new amp in storage and buy a new one, but is there anything I need to worry about for my amp running on 120v 50hz through a step-down transformer instead of 120v 60Hz?

    I found a few great products for frequency converters, but unfortunately they are the same price as the amp itself!
     
  2. Paul-T

    Paul-T Tele-Holic

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    Is your supply 120V 60Hz? There's no issue moving from 50Hz to 60Hz although I have read there are issues moving from 60Hz to 50 - in the latter case there are apparently more energy losses in the transformer due to the lower frequency.
     
  3. Gaijinloco

    Gaijinloco TDPRI Member

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    That's the rub. It is about $80 to get a 240v to 120v step-down transformer, but to get a voltage converter is about $600 minimum.

    The Step Down Transformer doesn't change the frequency from 50Hz to 60Hz, so the amp would be running on 120v 50Hz
     
  4. Paul-T

    Paul-T Tele-Holic

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    Please explain... your Vox is 240V 50Hz. What's the supply you're moving to?

    If your supply is 120V you have a step up, not down (ie you are converting 120V to 240V), so you will either have 240V 50Hz or 240V 60Hz at your amp, either is fine .

    THe converse, running on 50Hz with an appliance designed for 60Hz can cause problems (ie a US amp in the UK) but not often... but an appliance designed for 50Hz should be fine on 60hz. It's moving to a lower frequency that increases energy losses in the transformer.

    Do tell if I've misunderstood.

    edit: when you said "they run" do you meant that's the supply as opposed to what the Vox runs on?

    In which case, using 120V 50Hz for the amp as opposed to 120V 60Hz will very probabyl be fine. Just keep an eye on it. THere can be energy losses (ie the PT will get hotter) but most power transformers should have enough of a margin where they're fine.
     
    Last edited: Apr 17, 2021
  5. dogmeat

    dogmeat Friend of Leo's

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    I would replace the transformer in the amp. there must be a tranny made for 240v 50cycle. they usually have a connection to turn it back to 120V as well. I would contact Hammond, they make a lot of x-formers. great quality and decent price

    2 pi FL is the formula for inductive reactance. what it means is that as frequency goes up, the effective resistance goes up. and vis a vis.
     
    Last edited: Apr 17, 2021
  6. maj34

    maj34 Tele-Holic

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    Assuming you have the the 240V/50Hz version and want to run it on 120V/60Hz.

    As Dogmeat said, ideally, replace the transformer.

    But also, with a stepdown transformer, as others have said, you'll have 120V/50Hz. Won't be a problem IMO.
     
  7. Paul-T

    Paul-T Tele-Holic

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    Moving to a higher frequency = no problem

    Moving to a lower frequency = usually no problem.

    My 1954 5C1 champ has been running at 50hz (with a stepdown transformer to take UK 240V down to 120V) for the last 30 years and still seems happy.
     
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  8. Peegoo

    Peegoo Poster Extraordinaire

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  9. Gaijinloco

    Gaijinloco TDPRI Member

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    Thanks everyone, I appreciate all of your input.

    In this case, I have an American spec. amplifier designed for 120v/60Hz Primary. I am in a country with British spec power grid, so 240v / 50Hz. I am using a Step-down transformer pretty much exactly like Peegoo's link to take the 240v/50Hz mains voltage down to 120v/50Hz instead of the specified 120v/60Hz. I have some equipment that I picked up when I was living in Japan that was 100v/ 50Hz or 60Hz. I knew that I should have become an electrical engineer instead of a linguist.

    I just want to make sure I'm not damaging the amp over time. It is a Vox AC4-HW1. Here is the other issue, I haven't been able to find a VOX AC4-HW1 Power transformer for 240V/50Hz Primary anywhere. I know that the model is sold in the UK, but I've been scouring the internet for a replacement transformer, and nothing. I don't know if that means that the amp has taps for 120v as well as 220/230/240 or not.
     
    Last edited: Apr 18, 2021
  10. ghostchord

    ghostchord Tele-Meister

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    It's very unlikely an amp runs on AC power. So there's some sort of power supply inside the amp and as long as you bring the voltage down you should be fine. There's like a transformer inside your amp followed by a rectifier and then some filtering caps, something like:
    upload_2021-4-17_23-26-31.png
    A different frequency basically means somewhat different ripple on that rectified voltage, generally the filter portion is going to be knocking off all the higher frequencies, so your filter would be designed for 60Hz but now it's gonna get 50Hz. I would guess that would make little difference. As you are saying the transformer inside the amp might already have taps for 240...

    Make sure the step down transformer you're getting has enough juice to drive your amp...

    If you want to know for sure, ask the manufacturer.
     
  11. El Marin

    El Marin Friend of Leo's

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    I wouldn't bother.

    Many friends of mine play US amps with a cheap and "normal" and buy it everywhere step down (or up) transformer. My grandparents decades ago had a frizzer made in the US that needed another step down. I am talking about Spain, Portugal and UK

    Nobody ever new anything about frequencies

    Just plug it and play the damn thing

    Or get an EU current specs amp and sell it when leaving
     
  12. Gaijinloco

    Gaijinloco TDPRI Member

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    I am running it off of a 500w Step-Down transformer. The amp has a 45w power consumption, which I'm sure might be higher when it is first turned on.

    What has surprised me is that I haven't found a drop-in 240v power transformer for the AC44-HW1 model, which is why I'm speculating that it might be one transformer with multiple taps. I've been emailing basically anyone with a pulse and an interest in amps, in addition to the Korg USA/ Japan / Middle East folks.
     
  13. Gaijinloco

    Gaijinloco TDPRI Member

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    Not a bad plan. I am in a fairly small country in the Middle East though, and I can't pick up anything from the UAE without going through a month of quarantine between coming and going right now. This wouldn't be a problem if things were normal.
     
  14. Paul-T

    Paul-T Tele-Holic

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    I used to think exactly that but apparently there's another issue. THe EMF produced by a transformer varies with frquency; transformers designed for 60Hz are a tiny bit more efficient with slightly less energy loss so are made a little smaller. They might produce a bit more heat working at 50Hz.

    I have seen people say it's a serious issue but I don't believe it... I am sure Leo Fender put a cheap small transformer in my Fender Champ and there's been no issue, nor have I heard of anyone else with a US spec vintage Fender amp in the UK switching frequency as well as voltage. So I'm certain the OP will be OK.
     
    Last edited: Apr 18, 2021
  15. ghostchord

    ghostchord Tele-Meister

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    Interesting. TIL that efficiency in transformers does decrease with frequency: https://electronics.stackexchange.com/questions/144329/transformer-size-vs-frequency

    Another effect that can matter is core saturation (where basically the magnetization reach its limit): https://en.wikipedia.org/wiki/Saturation_(magnetic) and https://www.electricalengineering.x...pens-in-transformer-and-what-are-its-effects/ ... this might mean you don't want to dial it to 11.

    These things are typically designed with enough margin so likely it's not going to be a problem.
     
  16. Wyatt

    Wyatt Tele-Afflicted

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    Just buy and install a new 240v/50hz PT. Save the original for when you move back. A 60hz doesn’t have a large enough core to handle 50hz – current draw will be 20% higher, the core will over saturate, run hot, and can even physically pulverize itself. Read up on magnetic flux and eddy currents. Touring musicians quickly learned that 50hz killed American amps.

    It’s surprising, and irresponsible, how many people on an amp board don’t know how 60/50hz works and are giving bad advice that can damage another users amp. Operating an amp should not come down to what the odds are thay it will run safely.
     
  17. Dacious

    Dacious Poster Extraordinaire

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    I wouldn't sweat it. Marshall makes 1 amp with a voltage selector switch worldwide. I've brought 3 110volt amps from the US and used ordinary stepdown with them here in Australia.

    I had an export Vibrolux with switchable 240 volt transformer identical inboard to the US model. Australia uses 230/50hz.

    Vox is a British company. An AC4 is extremely unlikely to pull too much current.
     
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  18. The Ballzz

    The Ballzz Tele-Afflicted

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    Absolutely correct! Although, had you read the whole thread, the OP @Gaijinloco mentioned searching for an appropriate replacement power transformer and/or information as to whether or not there are provisions for these voltage/frequency discrepancies already designed into the amp and existing PT. This would seem a wise move on the manufacturer's part.

    Now, given that Jim Marshall was known for being nearly as "frugal" as Leo Fender, and that he chose to use multiple tap power transformers instead of sourcing a wide variety of single primary units to deal with global differences, tells me that this was likely the most cost effective way to address the issue!

    Just Transformin'
    Gene
     
  19. Paul-T

    Paul-T Tele-Holic

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    The service manual only shows one transformer as far as I can see, not variants for different voltages (unlike the TV).
     

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