From: stoatgobbler@minasmorgul.demon.co.uk   
      
   Jasen Betts wrote:   
   > On 2009-02-21, Stoatgobbler  wrote:   
   >> Hi there,   
   >>   
   >> I'm building a JL Hood hifi amplifier and to construct the power   
   >> supplies I've mounted two toroidal transformers in a case, one on top of   
   >> the other. Each toroid has two secondary windings which I'm going to use   
   >> to create two separate, independent, regulated +22v - 0 - -22v power   
   >> supplies. To make these power supplies truly independent (and to reduce   
   >> the chances of earth loop hum) I've "lifted" each power supply 0v common   
   >> from the chassis earth via 60ohm resistors.   
   >>   
   >> On testing the power supplies I've noticed that the greater the current   
   >> I pull out of each power supply the greater the potential difference   
   >> that appears across the 60ohm resistor (chassis earth to power supply 0v   
   >> line). when I pull 1.1A from the power supply then I have nearly 17v   
   >> across the 60ohm resistor. This voltage does not seem to vary with   
   >> raising the upper toroidal away from the lower so I don't think the size   
   >> of this voltage is to do with interactions between the two (but would   
   >> stand to be corrected).   
   >>   
   >> I've never "played" with this, I did expect a voltage across it (due to   
   >> eddy currents within the transformer normally "lost" in heating the iron   
   >> core in a conventional E I type transformer?) but I thought toroidals   
   >> minimised this and the voltages resulting from this would be   
   >> nominal....17v across 60ohm is not nominal.   
   >>   
   >> Is this normal or is something going on?   
   >   
   > somethings going on.   
   >   
   > AC or DC ?   
   > frequency?   
   >   
   >> Any advice or comments would be appreciated.   
   >   
   > can't make any usefull guesses without knowing what it was and what   
   > you've done to it.   
   >   
   >   
   Two toroidal transformers, both inputs 250vac 50hz, both outputs +/-   
   37vdc (no load) regulated to +/-22vdc with a 0v centre. Simple power   
   supply, split rail regulated, circuit is here >   
   http://www.tcaas.btinternet.co.uk/jlhlm3x7cb.htm   
      
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