Hey all,

I am racking up a Mic pre project and need a power transformer for my
PSU. I need a 20-0-20 secondary and a 120V primary which will fit in a
1U space. What is the best type to get as to not interfering with other
electronics? It does not need to be high current as it will only supply
two mic pre's and phantom (total of around 100mA).

Thanks for the input,
Brian

Brian Allen wrote:

Hey all,

I am racking up a Mic pre project and need a power transformer for my
PSU. I need a 20-0-20 secondary and a 120V primary which will fit in a
1U space. What is the best type to get as to not interfering with other
electronics? It does not need to be high current as it will only supply
two mic pre's and phantom (total of around 100mA).

Toroidal transformers offer quite low radiated flux compared to EI
laminated types.

The best performance I've seen regarding radiated flux is from R-core
types. Unfortunately I think they're only available to special order. The
more recent O cores may be even better.


Graham

"Brian Allen" wrote ...
I am racking up a Mic pre project and need a power transformer for my PSU.
I need a 20-0-20 secondary and a 120V primary which will fit in a 1U
space. What is the best type to get as to not interfering with other
electronics? It does not need to be high current as it will only supply
two mic pre's and phantom (total of around 100mA).

There appear to be several options available from DigiKey. Both
torrodial and "flat-pack" E/I core. With such modest power
requirements, it should be easy to find something that will fit in 1 RU .

Brian Allen wrote:

I am racking up a Mic pre project and need a power transformer for my
PSU. I need a 20-0-20 secondary and a 120V primary which will fit in a
1U space. What is the best type to get as to not interfering with other
electronics? It does not need to be high current as it will only supply
two mic pre's and phantom (total of around 100mA).

Look at the Talema toroids. They make a series with 24V secondaries,
which Digi-Key carries. Low magnetic leakage, excellent noise filtering.
Flat.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Sat, 09 Oct 2004 15:28:32 GMT, Brian Allen
wrote:

Hey all,

I am racking up a Mic pre project and need a power transformer for my
PSU. I need a 20-0-20 secondary and a 120V primary which will fit in a
1U space. What is the best type to get as to not interfering with other
electronics? It does not need to be high current as it will only supply
two mic pre's and phantom (total of around 100mA).

Thanks for the input,
Brian

Use a toroidal transformer for low radiation.

for example:

Hammond 182F18 (2 x 18V, 0.84 A) or 182F22 (2 x 22V, 0.68A). Both are
15VA, dual secondary, 1.25 in. high by 3.2 in. diameter toroids.
http://www.hammondmfg.com/182.htm
Available from Digi-Key and Allied.

Mike T.