Orientation of E-I core OPT and toroidal power transformer - diyAudio
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Old 23rd December 2009, 08:32 PM   #1
tomchr is offline tomchr  United States
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Default Orientation of E-I core OPT and toroidal power transformer

Folks,

Eventually, I will get to try this in the lab, but I figured I could give myself a head start by asking out loud:

With a toroidal power transformer and regular E-I core OPT's, what is the preferred orientation of the OPT's with respect to the toroid?

My current thinking is to have the toroid 'above deck' and the OPT's 'below deck' to save space. The 'deck' is 1/16" (1.6 mm) aluminum. While the leakage fields from a toroid typically are pretty low, they're not zero. I'd still think I should be able to achieve some form of optimal placement that would eliminate any hum. But where to start...

Any input?

And happy Festivus everybody.

~Tom
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Old 23rd December 2009, 08:53 PM   #2
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The easiest way (requires no thinking) appears to be a simple measuremet. Power up the toroid and measure the induced emf in the EI while repositioning.
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Old 26th December 2009, 08:25 PM   #3
tomchr is offline tomchr  United States
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I was secretly hoping that someone had already done the experiment or analysis and was willing to share his/her results...

~Tom
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Old 26th December 2009, 09:05 PM   #4
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No serious experiment, but I have built an amp that is "backwards" from your proposed design. The toroidal power transformer is below the deck, nearly under the OPT's which are on the top of the deck. I used this layout because I painted the OPT's gloss black, but the Antek toroid is ugly unless I found a pretty box or can to put it in. This was a "zero budget" amp, built with parts that I already had.

Pictures are in post #189 in this thread. The amp had been tested, then disassembled, then all of the finishing and painting was done, then partially reassembled when the pictures were taken. The deck is 1/16 inch aluminum.


http://www.diyaudio.com/forums/tubes...ghlight=Simple
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Old 27th December 2009, 05:02 AM   #5
tomchr is offline tomchr  United States
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George,

Nice woodwork on the Simple P-P! I'm trying to do something similar for the chassis for my Spud, though, I'm using walnut wood. Nice stuff. But my woodworking skills are nowhere near yours. It'll be decent, but I expect the mitered corners to have a couple of gaps as my miter saw apparently was set up for 45.5 degrees and not 45 degrees. Oh, well. Live and learn.

I'm curious to hear what your conclusions are for the Simple P-P as far as noise/hum goes.

I'm using an Antek 1T250 for power transformer and the matching CA-100 steel pot for it. Those pots are quite stout - it probably weighs as much as the transformer. Unfortunately, there'll be a 1 mm gap between the deck and the pot so the pot doesn't form a shorted turn on the transformer. And the pot has a couple of notches (about 1/8" deep) to allow the wires to come out. I'm hoping I can fill the gap and cover those notches with a gasket of some sort. I'll be running the wires through the deck (1/16" aluminum) and cover everything with the pot. It should be pretty decent...

~Tom
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