230V single primary toroid in a 115V country - diyAudio
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Old 8th February 2011, 05:06 AM   #1
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Default 230V single primary toroid in a 115V country

Hi,

I could not find the exact answer to the following question and do not want to mess up with my PSU's wiring given the dangers involved.

I have a 300VA 230V 2 x 18V toroidal transformer like this one from the UK:

0300218 : 300VA 230V 2 x 18V toroidal transformer

I am living in a 115V country and am in the process of building a PSU with a single rectifier bridge for both channels exactly like this one: Mick Feuerbacher Audio Projects

As I understand if I connect the above transformer in a 115V country it will give half the power (ie 150VA 2x9V), but my question is: would it be possible to wire the twin secondary windings in a way that the outcome becomes: 150VA 2x18? This would be great as it would be enough for my project.

Thanks in advace.

Antonio

Last edited by A Sanchez; 8th February 2011 at 05:14 AM.
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Old 8th February 2011, 05:57 AM   #2
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You would need a stepup transformer. Otherwise you only get 2x9.

Of course you could rewind it; use half the primary turns with larger wire size by 3 gauges.
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Old 8th February 2011, 06:29 AM   #3
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The options do exist but it would be easier and cheaper to buy the correct transformer and sell your one.
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Old 10th February 2011, 05:12 AM   #4
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Hi,

Thanks very much for your comments.

My problem is that, where I am living at the moment (Mexico City), there are no many options regarding quality transformers (and certainly not as good as my UK toroid). So, I was hoping I could use my toroid by wiring differently the secondaries in order to get half the Va(300 to 150) but getting same 18V on the secondaries.

In terms of step up transformers my only reasonable priced option would be one that handles only 50 watts (the bigger ones are big, bulky, noisy and very expensive). Since I am not intending to play at high volumes may be the 50 watts one would be enough. I'll try it and will report back.

Regards

Antonio
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Old 10th February 2011, 05:41 AM   #5
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Just make sure you don't overheat the little transformer and start a fire or something.
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Old 10th February 2011, 06:35 AM   #6
AEIOU is offline AEIOU  United States
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They can ship you one, Mexico isn't that far from the U.S. Just look for whatever you need on the internet, eBay, Avel-Lindberg, etc, and ask how much they will charge for shipping it to you in Mexico.
Transformers and Power Converters From Avel Lindberg, Inc.


Quote:
Originally Posted by A Sanchez View Post
Hi,

Thanks very much for your comments.

My problem is that, where I am living at the moment (Mexico City), there are no many options regarding quality transformers (and certainly not as good as my UK toroid). So, I was hoping I could use my toroid by wiring differently the secondaries in order to get half the Va(300 to 150) but getting same 18V on the secondaries.

In terms of step up transformers my only reasonable priced option would be one that handles only 50 watts (the bigger ones are big, bulky, noisy and very expensive). Since I am not intending to play at high volumes may be the 50 watts one would be enough. I'll try it and will report back.

Regards

Antonio
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Old 10th February 2011, 01:48 PM   #7
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You could put the secondaries in series and half wave rectify.
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Old 10th February 2011, 02:13 PM   #8
kevinkr is offline kevinkr  United States
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Antek based in New Jersey sells very good, and very inexpensive toroids. (Chinese made)

What you want is an Antek AN-3218 or AS-3218 (with electro-static shield) which will run you the princely sum of $36 to $40 + S&H to Mexico City depending on model..

Here: Antek - AN-3218

OR

Shielded version: Antek - AS-3218

I have been using this brand for about 5yrs now, and have purchased something like 8 transformers from them so far. I'm completely pleased with their performance. Since one with an electro-static shield is stocked I would personally go for this slightly more expensive option as it will reduce coupling of line born EMI into your amplifier circuitry.
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Last edited by kevinkr; 10th February 2011 at 02:16 PM.
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Old 10th February 2011, 11:51 PM   #9
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Thanks to you all.

Wow Kevin! that's a great price and even with delivery costs it will be worth buying it in the US. Thanks

Regards

Antonio
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