Really, how quiet IS a toroidal transformer?

[Praying_V]

Hi everyone,
I started a project months ago, and I think its really time to finish it.  Its a mic preamp & compressor in one enclosure.  I need + - 15V, so I built a power supply using a toroidal transformer.  Before I go through all the trouble of designing & drilling an enclosure though, I'm wondering how far I need to get the toroidal from the two circuits, to ensure a quiet build.  Is there a certain axis on which I must mount the toroidal (and power supply PCB), in relation to the two circuit boards??

[Minion]

A Torriodal Transformer will emit less of a Magnetic field and has better noise rejection and better regulation, That being said they do still emit a magnetic field and if put to close to your curcuit it can inject some noise....I would suggest that you put the transformer as far away from curcuit in the chassis as possible....If there isn"t a lot of Room in the chassis and can"t put it far away you can shield the transformer with a Piece of metal or even put the Transformer in an old Tuna can (make sure you isolate it from the transformer so it doesn"t touch the transformer ot eh metal Fasening bolt) , If you can mount the transformer on it"s side that would also help as the magnetic field is emited from the windings so there is a dead area at the top and bottom of the Transformer....

I have used both toroids and EI transformers in Mic preamps and both worked equaly well ,I end up useign EI Xformers more often that mot because they are cheaper and eisier to find in Low Va rateings.....

Also remember that you will need +48v if you are going to have phantom power for condenser mics ,and a Good regulated supply is a must for mic preamps...

Cheers

[ubersam]

...If there isn"t a lot of Room in the chassis and can"t put it far away you can shield the transformer with a Piece of metal...

Or, use mu-metal sheets to contain the EMF. I did  this to a Furman voltage regulator that I use in my rack. Not the cheapest solution but it works. You can check here for more info: http://www.lessemf.com/guidelines.pdf