On Tue, 19 Jun 2007 12:20:33 +0100, Nick Gorham
wrote:

Andy Evans wrote:
Sounds like this is for a preamp, and in this case Phil is right on
the button. A couple of toroids back to back are perfect. If you use
230 to 12v and 12v to 230 you can not only take 12v AC for the heaters
but also rectify it to -15vDC for a constant current sink if you're
using a differential pair. But allow for enough current capacity and
seperate the toroids to allow for some cooling - be careful to check
the result for overheating.



Yep, I have done that myself, but don't expect to get exactly 230v out
again, it will have two sets of copper losses.

Also, helpful though the idea is, I think the Maplin/Danbury TX's will
be cheaper than two toroids.

I don't think exact voltages are going to be any kind of an issue for
this project. He is setting currents to measure noise figure - if the
volts are a bit wrong he may lose some headroom, but I think they will
be "adequate" whatever he does.

d

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