Changing country voltages - Step down Transformer Question

[WebMentor]

Hi,
I'm in Australia and am thinking about a getting a Blackheart Little Giant amp head from the USA as the price for this in Aust is insane

In the USA you can buy a new Blackheart head and cab for $300 US
They have just been released in Australia at $809 AU (that's $752 US)
No way I'm paying that much as I could buy a decent AX84 kit for less

My Question: If I did get a Blackheart from the USA to use it I would have to get a step down voltage transformer (240v to 120v) and want to know what you think about mounting the SD transformer inside the head?
Can anyone foresee any problems such as unwanted noise etc?

Cheers,
Nigel

[Enzo]

I see the problem as fit. Check the dimensions of such a step-down. Where would you put it? it will have to be at least as large as the power transformer.

ANy chance the amp already has a multitap primary?

[WebMentor]

Hi Enzo,
I sent an email to Loud Technologies (the makers of Blackheart) asking that exact question about a multitap primary but never got a reply.
I also asked someone on eBay US who was selling mod parts for it if the prinary transformer had different tappings and they replied that it didn't and that if I would need to change both the primary and output transformers to make it suitable to use with 240v.
Seems a lot simpler (and cheaper) to use a step down transformer
Physical size of the step down transformer is an issue but it should be smaller as it won't be multitaped on the secondary so as long as it covers the overall load it should be good to go inside.
Any idea of the total wattage that the small blackheart would draw?
I'm thinking a 50w step down transformer will fit as the blackheart can't draw that much current can it?
Might get squeezy if 120w or 250w is required.

Thanks for your reply.
Cheers,
Nigel

[tubeswell]

Hi Enzo,
they replied that I would need to change both the primary and output transformers to make it suitable to use with 240v.

Nigel

Seems odd that you just can't get a PT customwound with a 240V 50Hz primary and the right secondaries? (Or are they closely guarding their little secrets about the secondary specs?) You could probably guess the VA ratings for the secondaries - whats the schematic look like? (- Time to put my Jack Darr reading into action.)

What's the story with needing a different OT as well? (Sounds most unusual - is the OT connected directly to the mains in some way? Or is someone there is telling you fibs.)

[WebMentor]

I agree as even with my limited knowledge it didn't make sense that the output transformer should need to be changed.
I'm still trying to find a circuit dia and am waiting on some emails.
BTW - The Blackheart is basically an Epiphone Valve Junior with all the mods already done.

[Steve Conner]

The Valve Jr. amps, and their many alter egos (Grainger, Harley-Benton etc) are all made in China in the same factory, and sold worldwide. So I imagine the PTs will be international types that can handle either 120 or 240V. The Blackheart stuff is probably made in the same factory too.

So like Enzo says, yes it probably has a multitap primary, and even if it doesn't you can probably pick up a new transformer easily, assuming it shares parts with the Valve Jr.

Or why don't you just import a Blackheart from the UK/Europe instead of the US? They're all 230V. Thomann in Germany have the head for the equivalent of about US$230, and they'll be in music stores here in the UK soon.

Anyone who says the O.T. needs replaced for a change in line voltage is talking out of their extension jack.

[Enzo]

The size of the transformer is not due to the taps, it is the iron needed for the amouint of power it will handle. Every ounce of power that the thing needs goes through this step down. So it needs to handle as much as the existing power tranny. Plus there will be inefficiencies, and you will want some headroom. If the amp needs 50 watts, you don't want a 50 watt transformer. Would you drive your car all over town revved up to the red line? I wouldn't either. Likewise I would not run 50 watts through a 50 watt tranny.

Changing the OT is silly. I recall a schematic once for some mainstream OEM, and they spec'd all the secondary fuses at half current for the 240v models. I called them, and the guy verified that yes, the secondaries were the same voltage on either version, but could not get through to him that the fuses would not change then.

The mains draw has to be printed on the unit, ask someone who has one to look. It would be near where the mains power comes in, and it will be spec'd in watts. If the factory has a spec sheet, it ought to be on that. For example, I have an SVT sitting next to me burning in, and it says 300w output by the speaker jacks, and 480 watts mians draw. Actually, nowdays they like to say "VA" instead of watts. (volt-amps)

[WebMentor]

I've found a manual for the combo Blackheart and it draws 45VA.
Looks like the 120w step down transformer would suit but as you have allready pointed out it's rather large and fitting it internally in the head would be a head ache

As has been suggested I should just buy one from the UK so the voltage would be right for Aust 240v.
I've searched Google for a supplier in the UK but as yet haven't found one (probably not released there yet) so I might just have to go to plan B.

Plan B is to build an AX84 kit amp or make use an old 1940's PA amp that I have (photos of the amp are in the vintage amp forum).

Thank you all for your input and suggestions - you are a wonderful community
Cheers,
Nigel