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Old 20th December 2005, 07:05 PM   #1
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Question why toroidail?

Hi!!!

what is the diference between normal transformers and toroidal trasnformers? is there any advantage?

I'm asking this because in Argentina i cant find any place to buy a 24+24 toroidal. I can only find 12V toroidals for 12V lamps.

maybe i can use 4x12v toroidal to make 2x24v. is that worth? or just buy an old "EI" transformer?
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Old 20th December 2005, 07:38 PM   #2
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From what I gather a toroidal transformer emitts much less flux which affects the audio.
Plus I think the eddy current is also lower.
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Old 20th December 2005, 07:43 PM   #3
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Smaller magnetic field (leakage), better VA and regulation for same size.
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Old 21st December 2005, 01:51 AM   #4
Tweeker is offline Tweeker  United States
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EI pluses- lower bandwith, far more tolerance for DC offset. One way to deal with the flux is just have it a couple feet from the amp.
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Old 21st December 2005, 02:01 AM   #5
jcx is offline jcx  United States
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toroidal is really used because they are the cheapest per VA due to more efficient use of materials + investment in auto-winding

EI give better isolation from the line due to lower pri-sec parasitic C, they do have higher leakage flux, but is easily "short circuited" by cheap iron such as tin can stock or even galvanized sheet - some high end manufacturers put EI pwr xfmrs in drawn cylindrical cans to to get superior performance while avoiding questions from those brainwashed by toroidal="hi tech" hype
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Old 21st December 2005, 02:09 AM   #6
AJT is offline AJT  Philippines
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imho, you miss nothing if you just used EI's...
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Old 21st December 2005, 02:50 AM   #7
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EIs have lower inrush

Badly made EIs tend to vibrate and buzz audibly
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Old 21st December 2005, 03:28 AM   #8
AJT is offline AJT  Philippines
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Quote:
Badly made EIs tend to vibrate and buzz audibly
something that is easily cured!

Click the image to open in full size.
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Old 21st December 2005, 12:26 PM   #9
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thanks to all!! I only hope that my next EI trans. fit into my case. I will make 4xLM3886 chip amp + 1 dual LM3886(bridged). I dont know how much VA's should be the trans. can you help me?

70W x 4 + 100W = 380W of audio output

500va? 600va?
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Old 21st December 2005, 02:26 PM   #10
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A good rule of thumb is VA = 2 x output RMS
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